Clouds and Chemistry Ultracool Dwarf Atmospheric Properties from Optical and Infrared Color
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Clouds and Chemistry:Ultracool Dwarf Atmospheric Properties from Optical and Infrared Colors Mark S.Marley 1,S.Seager 2,D.Saumon 3,Katharina Lodders 4,Andrew S.Ackerman 1,Richard S.Freedman 1,Xiaohui Fan 2ABSTRACT The optical and infrared colors of L and T dwarfs are sensitive to cloud sedi-mentation and chemical equilibrium processes in their atmospheres.The i ′?z ′vs.J ?K color-color diagram provides a window into diverse atmospheric pro-cesses mainly because di?erent chemical processes govern each color,and cloud opacity largely a?ects J ?K but not i ′?z ′.Using theoretical atmosphere mod-els that include for the ?rst time a self-consistent treatment of cloud formation,we present an interpretation of the i ′?z ′vs.J ?K color trends of known L and T dwarfs.We ?nd that the i ′?z ′color is extremely sensitive to chemi-cal equilibrium assumptions:chemical equilibrium models accounting for cloud sedimentation predict redder i ′?z ′colors—by up to 2magnitudes—than mod-els that neglect sedimentation.We explore the previously known J ?K color trends where objects ?rst become redder,then bluer with decreasing e?ective temperature.Only models that include sedimentation of condensates are able to reproduce these trends.We ?nd that the exact track of a cooling brown dwarf in J ?K (and i ′?z ′)is very sensitive to the details of clouds,in particular to the e?ciency of sedimentation of condensates in its atmosphere.We also ?nd that clouds still a?ect the strength of the J ,H ,and K band ?uxes of even the coolest T dwarfs.In addition,we predict the locus in the i ′?z ′vs.J ?K color-color
diagram of brown dwarfs cooler than yet discovered.
Subject headings:stars:atmospheres —stars:low-mass,brown dwarfs
1.Introduction
The Sloan Digital Sky Survey(SDSS)and the2-Micron All Sky Survey(2MASS)have both had great success in discovering L and T type ultracool dwarfs.The colors of these objects provide insight into the processes operating in their atmospheres.In the SDSS system,all such objects are uniquely red in i′?z′.L dwarfs are red in the2MASS J?K s color(1≤J?K s≤2)while the cooler T dwarfs like Gliese229B are bluer(J?K s<0.5) (Kirkpatrick et al.1999;Burgasser et al.1999;Burgasser et al.2000).While the mechanisms responsible for the J?K s and the i′?z′colors of the L and T dwarfs are generally understood, there has yet been no single theory that self-consistently describes the evolution of ultracool dwarfs5in this color space.
Because of their intrinsic faintness,moderate to high resolution spectroscopy may not be performed on all of the ultracool dwarfs discovered by these surveys.Thus analyses of ultracool dwarf colors could be essential to provide information on their physical properties. We have explored the utility of a number of i′,z′,J,H,and K color-color diagrams for constraining physical properties and?nd the i′?z′vs.J?K diagram particularly interesting. First,these are essentially the colors in which SDSS and2MASS discover ultracool dwarfs6. Second,alkali metals dominate the i′?z′colors while H2O and CH4absorption bands and cloud physics control the J?K colors.Over the pressure and temperature ranges of interest, the chemical pathways of alkali metals and H2O/CH4/CO are not strongly coupled,thus this particular color-color diagram re?ects a remarkably diverse set of chemical e?ects.
In this paper we describe how clouds and the chemistry of carbon,oxygen and alkali elements(mainly potassium)control the2MASS and SDSS colors used to discover ultracool dwarfs,and we explore the potential of the i′?z′vs.J?K color-color diagram as a tool to deduce the physical characteristics of dwarfs and the physics of their atmospheres.We also predict the colors of very cool brown dwarfs,those with e?ective temperatures T e?～<700K, which are yet to be discovered.
2.Color Trends
Ultracool dwarfs are notoriously di?erent from blackbodies of the same e?ective tem-perature.Figure1shows the i′?z′vs.J?K colors for observed SDSS L and T dwarfs (Strauss et al.1999;Fan et al.2000;Leggett et al.2000;Tsvetanov et al.2000;Geballe et al.2001a).The ultracool dwarfs are spread out over several magnitudes in both i′?z′and J?K.In addition,they are located in very di?erent parts of this diagram.
Blackbodies become redder in all colors with decreasing T e?as the Planck peak shifts redward;a temperature sequence of blackbody emitters in Figure1would follow a diagonal line cutting from blue to red through the extreme upper left corner of the color-color diagram. Ultracool dwarfs,however,are subject to a more complex set of in?uences and?rst become redder and then bluer in J?K as they age and cool.The initial reddening arises as progressively larger amounts of condensates are found in the visible atmospheres in the T e?range from～2000to～1400K.At lower e?ective temperatures J?K turns blueward because in the cooler brown dwarfs the cloud base(and thus most of the cloud opacity)falls below the photosphere(Marley2000;Ackerman&Marley2001;Tsuji2001;Allard et al. 2001),leaving the visible atmosphere relatively clear of condensates.In the absence of clouds, opacities such as water,methane,and pressure-induced absorption by molecular hydrogen act to rapidly close the K band infrared window as T e?falls,resulting in increasingly blue J?K.
In the optical,known ultracool dwarfs become redder with decreasing T e?.This trend is produced by the growing importance of the0.59μm Na I and0.77μm K I resonance doublets (Tsuji,Ohnaka&Aoki1999;Burrows,Marley,&Sharp2000)with decreasing T e?;as the dwarf cools,the gradual disappearance of TiO and cloud opacity leaves a progressively more transparent atmosphere at optical wavelengths.The K I resonance doublet is centered on the i′band while the z′band is only a?ected by the far red wing,producing very red i′?z′colors(Fig.2).We predict below that this trend should reverse in objects with lower T e?than have yet been observed.
Brown dwarfs with T e?and infrared colors intermediate between the coolest and reddest L dwarfs and the much cooler and bluer T dwarfs like Gl229B were initially thought to be rare since2MASS found few of them(Kirkpatrick et al.2000).T dwarfs with1100～ 3.Model Atmospheres To model the colors of solar metallicity L and T dwarfs we employ the radiative-convective equilibrium atmosphere model of Marley et al.(1996;further described in Burrows et al.1997).The model has been updated to self-consistently include both alkali opacities as described in Burrows et al.(2000)and the precipating clouds of Ackerman&Marley (2001).The treatment of the clouds and the chemistry is described further below. High resolution spectra are computed from these atmosphere models(temperature pro-?le and cloud structure)with a spectral synthesis code(Saumon et al.2000;Geballe et al.2001b).In the high-resolution spectra,the non-isotropic scattering by dust particles is mapped onto an equivalent isotropic scattering problem following the prescription given in Chamberlain&Hunten(1987).Theoretical colors in turn are calculated from the high resolution synthetic spectra.For J and K colors we use the Mauna Kea Observatory(MKO) Near Infrared System(Simons&Tokunaga2001;Tokunaga,Simons&Vacca2001)and for SDSS the i′and z′?lter functions and the AB magnitude system(Fukugita et al.1996). 3.1.Cloud Model For the radiative transfer calculations the clouds are assumed to be horizontally homo-geneous and are modeled following the approach developed by Ackerman&Marley(2001). This approach assumes a steady state in which the upward transport of gas and condensate by turbulent mixing is balanced by the downward transport of condensate by sedimentation. In convective regions the turbulent mixing in the model is determined by the convective heat ?ux,and in radiative regions the mixing is determined by a minimum eddy di?usion coe?-cient,a prescribed parameter that characterizes such processes as breaking buoyancy waves. The sedimentation(or precipitation)in the model is determined by the condensate mass, the convective velocity,and f rain,an adjustable parameter that describes the e?ciency of sedimentation relative to the turbulent mixing.Physically,f rain represents the combined ef-fects of unresolved dynamical and microphysical details such as the skewness of atmospheric circulations and the abundance of condensation https://www.wendangku.net/doc/bb18625900.html,rger values of f rain correspond to greater precipitation and hence thinner clouds.Note that the base of a cloud is?xed at the lowest level where the partial pressure of a condensible exceeds its saturation vapor pressure. Hence,any precipitation that falls through the base of a cloud is assumed to evaporate,re-turning its mass to the reservoir of vapor below the cloud.Precipitation through cloud base does not annihilate the cloud;instead the(steady-state)cloud is continually replenished by condensation in updrafts from below,as in long-lived terrestrial clouds. The value of f rain and the pro?le of turbulent mixing together determine the pro?le of condensate mass in the clouds;by assuming that the cloud particle sizes follow a lognormal distribution in a manner consistent with the turbulent mixing and sedimentation,the model also calculates a vertical pro?le of cloud opacity.Ackerman&Marley(2001)?nd that their model best?ts the observations of condensate scale height,particle size,and optical depth in Jupiter’s ammonia cloud deck with a value of f rain=3. The cloud structure and atmosphere temperature pro?les are solved to converge simul-taneously and self-consistently by the atmosphere code.As the atmospheric temperature structure as a function of pressure,T(P),is adjusted by the convergence algorithm,a new cloud pro?le is computed following Ackerman&Marley(2001).In the course of the cal-culation of a single temperature-pressure pro?le for a speci?ed T e?and gravity g,many hundreds of trial T(P)and associated cloud pro?les are computed.An atmospheric struc-ture is not considered acceptable unless both the temperature structure and the cloud model have simultaneously and self-consistently converged7. In this work we include only Fe,MgSiO3(representing both Mg2SiO4and MgSiO3), and H2O as condensates.Other species(e.g.Al2O3)either condense below the optically thick Fe cloud or are relatively insigni?cant opacity sources(see Marley2000).For example, in the T e?=2000K model the Al2O3cloud falls in a region of the atmosphere that is already opaque.The additional opacity arising from the cloud does not alter the adiabatic temperature pro?le.The overlying silicate and iron clouds play a far more important role. For hotter cases where silicates do not condense,Al2O3is more important. Figure3presents several of our temperature-pressure pro?les for T e?=2000and1300 K.For each T e?a cloud free and two cloudy models are shown.Our cloud free models are computed with the same set of assumptions for chemical equilibrium as are our cloudy models (condensed species are segregated by settling and no longer interact with the gas),but with all cloud opacity removed to isolate the e?ect of the clouds(see§3.2for comparison with the models of Allard et al.(2001)).Condensation equilibrium curves establish the cloud base level for each pro?le.Two T e?=1300K pro?les from Tsuji(2001)are also shown. For the T e?=2000K models silicate and iron grains form above the radiative-convective boundary and their in?uence on the radiative temperature pro?le is apparent.The cloudy models are substantially warmer than the equivalent cloud free case.As expected,the(op-tically and physically)thicker f rain=3cloud produces an even greater thermal perturbation than the case with more e?cient sedimentation(f rain=5). In the case of the1300K cloudy models,the cloud base is located within the convective region.The temperature pro?le within this region is set by the adiabatic lapse rate.Since the cloud simply adds to the(already high)opacity and the thermal pro?le is controlled by the adiabatic lapse rate,perturbations along the atmospheric thermal pro?le comparable to the hotter case are not seen.The clouds do play a role in raising the top of the convection zone above what it would be in the otherwise identical cloud free case by adding opacity above the cloud-free radiative-convective boundary.Above the cloudy radiative-convective boundary the cloud-top opacity is su?cient to keep the radiative portions of the atmosphere warmer than in the cloud-free case. The entropy at the radiative-convective boundary controls the adiabat upon which the deeper atmosphere—and consequently the entire interior of the ultracool dwarf—resides (Burrows et al.1997).The cloudier the upper atmosphere(smaller f rain),the hotter the interior.The interior structure at a?xed e?ective temperature and the amount of energy which must be radiated away to cool the entire dwarf to a lower e?ective temperature are thus a?ected by even small di?erences in cloud opacity.Hence di?erent cloud structure assumptions produce di?erent cooling histories.We plan to explore such e?ects in a future work. Di?erent assumptions regarding the cloud models result in very di?erent thermal pro-?les.For example the cloud free model from Tsuji(2001)shown in Figure3is quite similar to our own result for the same g and T e?.Also shown is a model from Tsuji(2001)(Tsuji’s case B)in which there is no removal of condensates from the atmosphere above the cloud base.In this case the greenhouse heating of the atmosphere by the abundant dust far exceeds what our cloudy models with sedimentation predict.The upper atmosphere in this T e?=1300K case reaches temperatures as high as those found in our cloudiest T e?=2000K case.This example dramatically highlights the important role sedimentation plays in moderating what would otherwise be an overpowering role of dust in controlling the temperature-pressure pro-?le of the atmosphere.Chabrier et al.(2000)discuss the dissociation of water occuring in the atmospheres of their hot,dusty no-sedimentation cases(their‘DUSTY’models).The large dissociation fractions in those models are simply driven by the lack of any sedimentation and thus represent particularly extreme–and likely unphysical–cases.Although not shown in Figure3for the sake of clarity,Tsuji(2000)also presents a‘uni?ed’model in which the top of the cloud is simply terminated at an arbitrary temperature.Such a model produces little to no heating in the atmosphere above the cloud top and substantial heating below the cloud top(comparable to our f rain=5case for T e?=1300K).Ultimately only detailed ?tting of observed spectra and colors will distinguish between all such possibilities. 3.2.Chemical Equilibrium Model The calculation of chemical equilibrium in an atmosphere is dependent upon the as-sumptions made regarding the fate of condensates.In a gravitational?eld,atmospheric constituents that condense tend to fall.If the condensate is liquid water meteorologists term it rain.We consider two di?erent chemical equilibrium models.In the?rst case there is no sedimentation of condensates.For this we use the baseline model from Burrows and Sharp (1999;hereafter BS99).In the second case we treat sedimentation with the cloud conden-sation model developed by Lewis(1969)for Jovian planets and used by Fegley and Lodders (1996),Lodders(1999),and Lodders and Fegley(2001)for brown dwarfs. Note that there is a slight inconsistency between the vertical distribution of condensates in the chemical equilibrium model(using the vertical pro?le described by Lewis(1969))and the radiative transfer cloud model(using the model of Ackerman&Marley(2001)).However, the vertical condensate pro?les with moderate values of f rain are similar to those predicted by the Lewis model.See Ackerman&Marley(2001)for more details. For the purposes of comparison,we have also computed a sequence of cloud free models. In these models,the presence of condensates is taken into account in the calculation of the chemical equilibrium but the opacity of condensates is ignored in the calculation of radiative transfer.These models di?er from the‘COND’models of Allard et al.(2001).In the Allard et al.models the chemical equilibrium always assumes the presence of grains even if they are not included in the radiative transfer. 4.The Optical-IR Color-Color Diagram Figure1shows a temperature sequence of ultracool dwarf models in the i′?z′vs. J?K color-color diagram.Models are plotted for a?xed surface gravity of1000m s?2, corresponding roughly to a mass of35Jupiter masses(M J).Note that the surface gravity, g,of a given object increases as it contracts and cools,so for a given object the cooling track will follow a slightly di?erent path.Evolution paths for ultracool dwarfs of di?erent masses,however,are almost degenerate in the color-color diagram because the temperature at which optical depth2/3is reached as a function of wavelength depends only weakly on the gravity.All surface gravities very nearly overlap in the i′?z′vs.J?K color-color diagram.So although T e?may be estimated,there is no unique(T e?,g)solution for given i′?z′and J?K colors. The i′?z′vs.J?K color-color diagram is very sensitive to T e?because of the disparate chemistry governing the two colors.The alkali metal chemistry for the observed ultracool dwarfs shown in Figure1mostly consists of neutral K being depleted into molecules and solids.This process(see Lodders1999for a complete discussion)is not strongly coupled to the C/H/O chemistry that controls CO,CH4and H2O partitioning.At even lower tem-peratures,K disappears into chloride and hydroxide gases but the alkali chemistry is still only weakly coupled to the C,H,and O chemistry.As a result dwarfs at di?erent T e?are well separated in this color-color diagram.There is no degeneracy for di?erent T e?as found in most other color-color combinations(e.g.H?K s vs.J?H,J?K s vs.I?J(see Kirkpatrick et al.2000and Tsuji2001)). 4.1.Clouds The behavior of a cloud layer as a function of T e?is of primary astrophysical interest. Qualitatively,the base of the cloud occurs where the(T,P)structure of the atmosphere crosses the condensation curve of the major condensates(silicate and iron at high tem-peratures,and water at lower temperatures).A cloud deck forms with a vertical pro?le determined by the cloud model.Because in the region of interest the condensation tem-perature of relevant substances increases weakly with pressure,the base of the cloud layer occurs at a nearly constant(but slowly increasing)temperature as T e?decreases.On the other hand,the temperature of the photosphere is approximately T e?.It follows that as T e?decreases,the cloud layer gradually disappears below the observable level of the atmosphere. This phenomenon has been discussed by several authors(Chabrier et al.2000;Marley2000; Allard et al.2001;Tsuji2001). The opacity of the gas in ultracool dwarfs is dominated by molecular bands and varies strongly with wavelength.In contrast Mie scattering by large particles produces a nearly grey cloud opacity.Thus the above discussion is somewhat simplistic since the concept of photosphere is not well de?ned in these objects.While continuum opacities ensure that the photosphere corresponds approximately to a?xed physical level in normal stars,in brown dwarfs the visible and near-infrared spectrum can probe a range of depths of up to6pressure scale heights(Saumon et al.2000).This range provides an opportunity to observationally probe the vertical structure of brown dwarf atmospheres. The gradual disappearance of the cloud layer below the“photosphere”as T e?decreases is illustrated in Figure4where the curves show the level in the atmosphere where the =2/3.Here,vertical position in the atmosphere is indicated by the local optical depthτ ν temperature.Three cases are shown with T e?=500,1000,and1500K from top to bottom, respectively.A pair of curves is shown for each model;one showing the photosphere(where optical depth2/3is reached)determined by gas opacity only and one for the nearly grey cloud opacity only.For the upper pair of curves(T e?=500K),the deep silicate and iron cloud “photosphere”lies below(at higher temperature)the gas photosphere at all wavelengths, implying that the cloud layer remains essentially invisible and has little e?ect on the emergent spectrum.In the lower pair of curves(T e?=1500K),the cloud becomes opaque well above the gas photosphere in the J,H,and K bands.The cloud layer is therefore observable in these three bandpasses(but not at other wavelengths)and the spectral energy distribution is strongly a?ected by the presence of the cloud. Figure4clearly shows that the cloud layer disappears below the observable atmosphere over a range of e?ective temperatures,depending on the bandpass of observation.For example,the cloud becomes invisible in the K band for T e?～<1400K but remains detectable in the J band down to T e?～800K.The Ackerman&Marley cloud model with f rain=5 implies that the spectra of all known T dwarfs are a?ected by clouds. Observationally,one of the most revealing features in the i′?z′vs.J?K color-color diagram shown in Figure1is the reddening in J?K of the L dwarfs that is not present in the T dwarfs.This di?erence in J?K trajectory results from the presence of condensates throughout the photosphere of the L dwarfs but not in the late T dwarfs.The blackbody-like condensate emission pushes L dwarfs to the red in J?K,despite the tug of water opacity towards the blue.This e?ect of condensate opacity is best illustrated by comparing the cloud free models and the cloudy models in Figure1a.The cloud free L dwarf models show a continuous blueward trend in J?K with decreasing T e?—because of increasing H2O and pressure-induced H2absorption—in contradiction with the redward trend of the L dwarf data.The cloudy models on the other hand,generally match the redward trend in J?K of the L dwarf data. The progressively redder J?K colors of L dwarfs has been noted before(e.g.Kirkpatrick et al.1999;Martin et al.1999;Fan et al.2000;Leggett et al.2001;Tsuji2001)and demonstrated by spectral?tting to be caused by the appearance of more and more silicate condensates in the cooling ultracool dwarf atmospheres(e.g Leggett,Allard,&Hauschildt 1998;Burrows,Marley&Sharp2000;Chabrier et al.2000;Marley2000).However models in which there is no settling of the condensates(Chabrier et al.2000)produce colors, particularly for the later L dwarfs,that are much too red.For example the dusty model of Chabrier et al.predicts that a1Gyr old50M J brown dwarf with T e?=1424K will have J?K=3.9.In fact the reddest L-dwarfs have J?K≈2.2(see Fig.4of Leggett et al. 2001).Our models with f rain=3peak at J?K～1.8for T e?=1400K.The muted J?K colors of the reddest L dwarfs provide strong evidence of condensate sedimentation. A second revealing feature in the i′?z′vs.J?K color-color diagram is the transition between the L and early T dwarfs that begins as a blueward turnover in J?K in the latest L dwarfs(Leggett et al.2001).As the condensates sink below the visible atmosphere,their blackbody e?ect is removed,halting the redward J?K progression.As molecular opacities (H2,H2O,and later CH4)become predominant,their greater absorption at K band initiates the turn in J?K to the blue.This turnover occurs when the cloud layer is no longer visible in the K band(see Fig.4).An important issue has been the temperature range over which the L to T transition occurs(e.g.Reid et al.2001).The model T e?at which the turnover begins,as well as the maximum value of J?K,depend on the sedimentation parameter f rain. Of the models shown in Figure1,f rain=3comes closest to matching the observed turnover in J?K.Smaller values of f rain produce thicker,more massive clouds and somewhat lower values may better?t the peak J?K at the turnover.The cloud tops remain in view in the J and K bands down to cooler T e?.This J?K blueward turnover likely will be better characterized by future SDSS discoveries,and the data will be essential for understanding cloud properties in ultracool dwarfs. At some lower T e?(～800K for f rain=5)the base of the condensate cloud base is below the visible photosphere.However,the tops of the silicate clouds might still be limiting the depths from which?ux emerges in the water and methane windows,thus accounting for the di?culty all cloud free models have had in correctly reproducing the ratio of the?ux emerging from within and without of the water bands(Allard et al.1996;Marley et al. 1996;Tsuji et al.1996;Saumon et al.2000;Geballe et al.2001b). 4.2.Alkali Metal Chemistry The i′and z′band?uxes are diagnostic of alkali metal chemistry,mainly because they measure the core and the wing of the K I resonance doublet,respectively.In T dwarfs,the red wing of the doublet is detected up to200nm from the line core(Burrows et al.2000). Figure2shows the i′and z′?lters superimposed on two di?erent model spectra.The i′?lter is centered on the K I doublet core and the z′?lter probes the far red wing.The ultracool dwarf colors become redder in i′?z′for decreasing T e?because these?lters probe the Wien tail of the Planck function and the K I doublet gets stronger.The gradual disappearance of TiO and cloud opacity as T e?decreases leaves behind a nearly transparent atmosphere at wavelengths below1μm(Figure4)and reveals the K I doublet in all its pressure-broadened splendor.At low T e?(～700K)the i′?z′redward trend halts as K I is depleted into KCl and the doublet weakens. Given the dependence of the i′?z′color on the K I resonance doublet,this color provides a stringent test for chemical equilibrium models.The two curves in Figure1b show colors computed with and without the assumption of condensate sedimentation in the chemical equilibrium calculation.There is a substantial di?erence—of2magnitudes —in i′?z′at e?ective temperatures where the K I line is prominent(～800K).The major di?erence between the two approaches is that at temperatures below1400K,the monatomic K abundance(hence the opacity)is greatly reduced under the assumption of no sedimentation(BS99)compared to the assumption of sedimentation(Lodders1999).A comparison of spectra computed under both assumptions is shown in Figure2.The e?ect on the i′?z′color is rather dramatic and the models without sedimentation turn blueward well before the model that includes sedimentation,as shown in Figure1. Because the SDSS T-dwarfs are only marginally detected in i′band,errorbars for those objects shown in Figure1are substantial.The trends in T-dwarf data shown in the?gure are generally closer to the sedimentation chemistry models,but more and better i′-band detections are required to fully support this conclusion. The two di?erent assumptions used to model chemical equilibrium of gas and conden-sates give such di?erent results that they are worth discussing in more detail.The two models depend on the physical setting(see Lodders1999;Lodders&Fegley2001).In the no-sedimentation case condensates remain in local equilibrium with the gas.In cooler re-gions,the high temperature(primary)condensates react with the upper atmospheric gas to form secondary condensates via gas-solid https://www.wendangku.net/doc/bb18625900.html,plete chemical equilibrium exists between all phases in this no-sedimentation case.BS99term this case the“no rainout”approach.Their approach(also employed by e.g.Chabrier et al.2000;Allard et al.2001) implies that alkali elements such as Na and K condense into alkali feldspar((Na,K)AlSi3O8) after a long sequence of primary condensate reactions with the gas.The net e?ect in this no-sedimentation case is that the gaseous atomic K and Na become depleted in the atmosphere once alkali feldspar condenses. As described in detail by Lodders(1999)and Lodders&Fegley(2001),however,this approach does not apply to ultracool dwarf and giant planet atmospheres because a gravity ?eld is acting on condensates.The primary condensates are sequestered by sedimentation into a cloud and are not available for gas-solid reactions in the atmosphere above the cloud layer as the dwarf cools.These cloud condensation models have been used successfully for over30years in the planetary community(Lewis1969,Barshay&Lewis1978,Fegley& Lodders1994)and were recently termed“rainout”by BS99.We prefer to use the term ‘sedimentation’because‘rainout’could be interpretted as implying complete removal.In the sedimentation case,elements such as Al and Ca condense at greater depth and are consequently absent in the overlying atmosphere.Thus alkali feldspar cannot form,and Na and K remain in the gas phase.Only when a brown dwarf is much older and cooler (T e?～700K)are atmospheric temperatures low enough for monatomic Na and K to convert into chloride and hydroxide gases.At even lower temperatures Na and K condense into Na2S and KCl(see also the discussions in Lodders(1999)and Burrows et al.(2000)). The i′?z′color is sensitive to pressure broadening of the K I doublet.The exceptionally strong pressure broadening a?ecting the0.59μm Na I and the0.77μm K I resonance doublets in T dwarfs stretches the current theories of line broadening beyond their limit of validity. These lines are modeled with a far wing exponential cuto?exp?(qh?ν/kT)where q is an undetermined parameter of order unity8.A detailed discussion is given in Burrows et al. (2000),as are?ts of the optical spectra of Gl229B and SDSS1624+00.With abundances determined from the sedimentation chemistry of Lodders(1999),we have obtained good?ts of the optical spectra of Gl229B and Gl570D with q=1(Geballe et al.2001b).The i′?z′color changes by as much as0.4mag for models computed with q=0.5and q=1. Disentangling the line broadening parameters from other i′?z′color e?ects will likely come from?tting high resolution spectra. 4.3.The Coolest Brown Dwarfs The coolest brown dwarf known with a reliable determination of its e?ective temperature is Gl570D with T e?～800K(Geballe et al.2001b).Cooler brown dwarfs are expected to enter a new regime in the i′?z′vs.J?K color space than those discovered so far.Brown dwarfs with T e?<～600K are expected to have water clouds forming in the upper atmosphere. Just as the subsidence of silicate clouds below the photosphere causes a turnover in colors, the appearance of water clouds in the upper reaches of low-T e?atmospheres could have dramatic e?ects on the colors. At a relatively cool e?ective temperature(～600K),as K I disappears into KCl,the i′?z′color reaches a maximum and turns blueward as suggested by the coolest objects in Figure1.The formation of signi?cant(τ>0.1)water clouds below T e?～500K(depending on g)halts and may eventually reverse the blueward march in J?K with decreasing T e?because the water cloud acts like a blackbody,redistributing the?ux to the blackbody peak. The models presented here may underestimate the size of the redward turn in J?K.Smaller particles than the～20to30μm predicted by the cloud model would arise for smaller values of the unconstrained stratospheric eddy di?usion coe?cient and would produce more cloud opacity for T e?≤500K.Such objects will be very faint at z′and will be di?cult to detect with SDSS.Nevertheless,the number density of brown dwarfs suggests that a few such objects could be detected by SIRTF(Mart′?n et al.2001). 5.Discussion The i′?z′vs.J?K color-color diagram reveals the importance of precipitating con-densation clouds in controlling the colors of the L dwarfs and the transition between L and T dwarfs,and will complement high resolution spectroscopy(Gri?th&Yelle2000;Geballe et al.2001a)to reveal the nature of condensation chemistry in these atmospheres. Most previous and current ultracool dwarf models(e.g.Allard et al.1996;Marley et al.1996;Tsuji et al.1996;Burrows et al.1997;Chabrier et al.2000;Allard et al.2001) considered either the case in which condensates remain suspended in the atmosphere or considered them to be absent from the photosphere due to sedimentation.In contrast Marley (2000)and Tsuji(2001)considered cloud decks con?ned to some fraction of a pressure scale height.The Marley and Tsuji models,although including no cloud physics,were both able to produce a red to blue transition in J?K.By including for the?rst time a self-consistent treatment of cloud physics,we demonstrate that sedimentation processes in clouds result in model J?K colors that are much less red—by up to2.5magnitudes—than models with no sedimentation(Chabrier et al.2000).Sedimentation controls the cloud vertical extent and is responsible for the observed turnover in J?K with decreasing e?ective temperature.The model further predicts that the spectra and colors of even the coolest known T dwarfs are in?uenced by clouds. Furthermore our atmosphere model is the?rst to compute particle sizes simultaneously and self-consistently with the thermal pro?le.Both Allard et al.(2001)and Tsuji(2001) assume a?xed,submicron,particle size distribution derived from interstellar medium dust grains.Allard et al.correctly point out that as long as the particle size is smaller than the wavelength of light,Rayleigh scattering dominates the opacities and the exact size dis-tribution of particles has little e?ect on the opacities.They also argue that particle sizes larger than100μm are implausible because they would break up(terrestrial raindrops and billiard-ball sized hailstones bely this assertion).Our model predicts silicate and iron par-ticle sizes between10–100μm.Such large particles are Mie,not Rayleigh,scatterers in the near-infrared and possess a completely di?erent spectral opacity(see Figure3in Marley (2000))than the submicron particles assumed by other groups. The models,however,do not provide a perfect?t to the available data.As noted in section4.1,the peak model J?K(1.8)is not quite as red as the peak observed value(2.2).L dwarfs with the largest J?K range in i′?z′from2.5to3.0.At the J?K peak the f rain=3 model predicts i′?z′=2.1.This discrepancy may arise from the large uncertainty in the alkali pressure broadening.The value of f rain which comes closest to matching the peak in J?K(observationally an L5or L6object,Leggett et al.2001)does so at a model e?ective temperature of1400K.This is slightly cooler than the range expected for such an object (see Burgasser et al.2001).Of greater concern is that this model then moves too slowly to the blue.The earliest T dwarfs have J?K～1.3(Leggett et al.2001).The f rain=3 model reaches this point at T e?=1000K which is certainly too cool.Hence it appears that di?erent values of f rain are required for the early to mid L dwarfs(a Jupiter-like f rain～3) and the latest L’s and the T dwarfs(f rain～5or larger)Alternatively Ackerman&Marley (2001)have suggested that holes might preferentially appear in the cloud decks of later type L dwarfs as the clouds begin to form within the convective region of the atmosphere.Bright, relatively blue cloud-free?ux emerging from the holes may help hasten the L to T transition in J?K.If this is the case a complete description of the disk-averaged emitted?ux would by necessity include both relatively cloudy and clear regions. The optical i′?z′color is strongly a?ected by the presence of monatomic potassium and modeling this color relies on the treatment of the alkali condensation chemistry.Chem-ical equilibrium models not accounting for sedimentation of condensates result in lower KI abundances because potassium is removed from the gas by alkali-feldspar at higher temper-atures.Hence the no-sedimentation models yield up to two magnitudes bluer i′?z′colors than models where sedimentation of condensates is taken into account.This is because the sedimentation of high temperature condensates prevents alkali feldspar from forming and K I abundances are higher until monatomic K is converted into KCl gas and KCl condensa-tion sets in at lower temperatures.Improved brown dwarf i′?z′colors will reveal which treatment of the equilibrium chemistry in brown dwarf atmospheres is correct.Since the best-?tting cloud model predicts that cloud particles are not lofted much above the cloud base,the sedimentation chemistry is likely most appropriate,in agreement with physically based expectations.A complete test of this hypothesis,however,requires more accurate photometry since brown dwarfs are usually not detected in i′band by the SDSS survey.The follow up photometry is in progress. It is now clear that the interpretation of objects from the warmest L dwarfs to the the coolest T dwarfs requires an understanding of cloud formation in ultracool dwarf atmo-spheres.Indeed more complex models,motivated perhaps by time resolved photometry and spectroscopy,will be needed to address many fundamental issues.There is no question that what some have termed the?eld of‘astrometeorology’is still in its infancy. We thank Adam Burrows for use of the results from his chemical equilibrium model and alkali gas opacity table.We thank the anonymous reviewers who provided many helpful comments which markedly improved the presentation of this paper.M.M.acknowledges support from NASA grants NAG2-6007and NAG5-8919and NSF grants AST-9624878and AST-0086288.S.S.is supported by the W.M.Keck Foundation,and work by K.L.and D.S. is supported by NSF grant AST-0086487and NASA grant NAG54988,respectively. REFERENCES Ackerman,A.&Marley,M.2001ApJ,556,872 Allard,F.,Hauschildt,P.H.,Bara?e,I.,&Chabrier,G.1996,ApJ,465,L123 Allard,F.et al.2001,MNRAS,in press,arXiv:astro-ph/0104256 Barshay,S.S.&Lewis,J.S.1978,Icarus,33,593 Burgasser,A.J.et al.1999,ApJ,522,L65 Burgasser,A.J.et al.2000,AJ,120,1100 Burrows,A.et al.1997,ApJ,491,856 Burrows,A.,Marley,M.S.,&Sharp,C.M.2000,ApJ,531,438 Burrows,A.,&Sharp,C.M.1999,ApJ,512,843(BS99) Chabrier,G.,Bara?e,I.,Allard,F.,&Hauschildt,P.2000,ApJ,542,464 Chamberlain,J.W.&Hunten,D.M.1987,Orlando FL Academic Press Inc International Geophysics Series,36 Fan,X.et al.2000,AJ,119,928 Fegley,B.J.&Lodders,K.1994,Icarus,110,117 Fegley,B.J.&Lodders,K.1996,ApJ,472,L37 Fukugita,M.,Ichikawa,T.,Gunn,J.E.,Doi,M.,Shimasaku,K.,&Schneider,D.P.1996, AJ,111,1748 Geballe,T.et al.ApJ,in press,arXiv:astro-ph/0108443 Geballe,T.R.,Saumon,D.,Leggett,S.K.,Knapp,G.R.,Marley,M.S.,&Lodders,K. 2001b,ApJ,556,373 Gri?th,C.&Yelle,R.2000,ApJ,532,L59 Kirkpatrick,J.D.et al.1999,ApJ,519,802 Kirkpatrick,J.D.,Reid,I.N,Liebert,J.,Gizis,J.E.,Burgasser,A.J.,Monet,D.G.,Dahn, C.C.,Nelson,B,&Williams,R.J.2000,ApJ120,447 Leggett,S.K.,Allard,F.,&Hauschildt,P.H.1998,ApJ,509,836 Legget,S.K.et al.2000,ApJ,536,L35 Lewis,J.S.1969,Icarus,10,365 Lodders,K.1999,ApJ,519,793 Lodders,K.&Fegley,B.2001,Icarus,in press Marley,M.2000,From Giant Planets to Cool Stars,ASP Conference Series,Vol.212.Edited by C.A.Gri?th and M.S.Marley.(San Francisco:ASP),p.152 Marley,M.S.,Saumon,D.,Guillot,T.,Freedman,R.S.,Hubbard,W.B.,Burrows,A.,& Lunine,J.I.1996,Science,272,1919 Mart′in,E.L.,Delfosse,X.,Basri,G.,Goldman,B.,Forveille,T.,&Zapatero Osorio,M.R. 1999,AJ,118,2466 Mart′in,E.L.,Brandner,W.,Jewitt,D.C.,Simon,T.,Wainscoat,R.,Connelley,M.,Marley, M.,&Gelino,C.2001,PASP,113,529 Reid,N.et al.ApJ,in press Saumon,D.,Geballe,T.R.,Leggett,S.K.,Marley,M.S.,Freedman,R.S.,Lodders,K., Fegley,B.,&Sengupta,S.K.2000,ApJ,541,374 Simons,D.&Tokunaga,A.2001,PASP,in press,arXiv:astro-ph/0110594 Strauss,M.et al.1999,ApJ,522,L61 Tokunaga,A.,Simons,D.,&Vacca W.2001,PASP,in press arXiv:astro-ph/0110593 Tsuji,T.,Ohnaka,K.,Aoki,W.,&Nakajima,T.1996,A&A,308,L29 Tsuji,T.,Ohnaka,K.,&Aoki,W.1999,ApJ,520,L119 Tsuji,T.2001,in press,arXiv:astro-ph/0103395 Tsvetanov,Z.I.et al.2000,L61 Fig.1.—i′?z′J?K(MKO system)color-color for L(triangles)and T(circles)dwarfs(Strauss et al.1999;Fan et al.2000;Legett et al.2000;Tsvetanvo et al.2000;Leggett et al.2001;Geballe et al.2001a).Plotted SDSS magnitudes have been converted to the AB system while the MKO magnitudes are in the Vega system.Lower limits are denoted by arrows.The lines show our theoretical models computed in the same systems with the symbols representing T e?steps of100K in the T e?range2000K–400K.Panel(a) shows the results of cloudy models(dashed and dotted lines with f rain=3and5,respectively) and cloud free models(solid line)for g=1000m s?2.Panel(b)shows cloud free models with g=1000m s?2.The solid line shows models with the sedimentation chemical equilibrium model by Lodders and the dotted line are models using the BS99chemical equilibrium model with no condensate sedimentation.See§3and§4for details.The anomalous data point at i′?z′=2.44,J?K=0.01represents SDSSJ020742.83+000056.2. Fig.2.—SDSS r′,i′,and z′transmission curves(dotted lines from left to right,respectively) superimposed on brown dwarf model spectra.The i′?ux is controlled by the K I doublet line core and the z′?ux by the K I doublet wing.These cloud free synthetic spectra with T e?=1000K and g=1000m s?2are computed with the chemical abundances of BS99(i.e. no sedimentation assumed;upper curve)and of Lodders(with condensate sedimentation; 50010001500200025003000 21 -1 -2 -3 Fig.3.—Radiative-convective equilibrium atmosphere models for g =1000m s ?2.For two values of T e?solid lines illustrate self-consistent temperature pro?les calculated for the case of no cloud opacity (nc)and rainfall e?ciency factor f rain =3and 5(Ackerman &Marley 2001).Lines are labelled for the 2000K case.For 1300K the sequence of curves is the same.Triangles denote convective-radiative zone boundaries;the deepest region of the atmosphere is always convective.Dotted lines show 1300K models by Tsuji (2001)without condensation (left curve)and with condensation but no sedimentation (right curve).Dashed lines show the condensation curves of enstatite and iron. Fig.4.—Visibility of the cloud layer in brown dwarfs as a function of T e?.The curves show =2/3),indicated by the temperature in the atmosphere,as the depth of the photosphere(τ ν a function of wavelength.The abcissa is essentially a brightness temperature.Three models with g=1000m s?2and f rain=5are shown,from top to bottom T e?=500,1000(dotted), and1500K,respectively.Two curves are shown for each model,one showing the photosphere due to gas opacity only,and one due to cloud opacity only.The latter is very?at,due to the nearly grey cloud opacity,and shows the level where the cloud becomes optically thick. At wavelengths longer than shown here,the cloud remains below the photosphere for all models.Bandpasses for several?lters are indicated along the bottom of the?gure. 脱发的主要症状是头发油腻，如同擦油一样，亦有焦枯发蓬，缺乏光泽，有淡黄色鳞屑固着难脱，或灰白色鳞屑飞扬，自觉瘙痒。若是男性脱发，主要是前头与头顶部，前额的发际与鬓角往上移，前头与顶部的头发稀疏、变黄、变软，终使额顶部一片光秃或有些茸毛；女性脱发在头顶部，头发变成稀疏，但不会完全成片的脱落。 中医学认为本病有两种原因：一是血热风燥，血热偏胜，耗伤阴血，血虎生风，更伤阴血，阴血不能上至巅顶濡养毛根，毛根干涸，或发虚脱落；二是脾胃湿热，脾虚运化无力，加之恣食肥甘厚味，伤胃损脾，致使湿热上蒸巅顶，侵蚀发根，发根渐被腐蚀，头发则表现粘腻而脱落。 有关治疗脱发的偏方、秘方主要如下: [方一] 柏枝(干药)、椒仁、半夏各90克。将药加水500毫升，煎至250毫升，入蜜少许，再煎1--2沸。用时人生姜汁少许，调匀，擦无发处，每日2次。 [方二] 白矾、郁金各等分。将白矾、郁金制成丸，每次4--5克，每日2次。 [方三] 食盐15克。将食盐加入1500毫升温开水，搅拌均匀，洗头，每周1--2次。 此法长期应用，可防止脱发。 [方四] 榧子3枚，胡桃2个，侧柏叶30克。将药共捣浸雪水梳头，其发水不脱落，而且光润。 本方尤适用于肾虚型脱发。 [方五] 侧柏叶若干。将柏叶阴干研细，以春油浸之。每戟蘸刷头，头发长出后，用猪胆汁人汤洗头。 本方尤适用于妇女脱发。 [方六] 车前草200克，米酷适量。将车前草全草焙成炭，浸入米醋，一周后用该药醋外涂患处，每日2--3次。[方七] 黑牛胆1个，槐豆适量。将槐豆装入有胆汁的牛胆内装满，浸透槐豆即可，内服。每次9克，每日3次。[方八] 侧柏叶240克(焙干)，当归(全身)120克。将药共研为末(忌铁器)，水糊为丸，如梧桐子大。每服50--70丸，早、晚各1服，用黄酒或盐汤送下。 [方九] 芝麻花、鸡冠花各60克，樟脑1．5克，白酒500克。将芝麻花，鸡冠花撕碎。然后浸泡人酒内密封，15日后过滤、再将樟脑人药酒中，使之溶化，备用。以药棉蘸药酒，涂搽脱发区，每日搽3--4次。 本方尤适用于神经性脱发。 [方十] 芝麻梗、清明柳(清明节采的柳枝嫩叶)各90--120克。煎汤洗发，并摩擦头皮，连用1--7日。 本方尤适用于脂溢性脱发。 [方十一] 猪苦胆1个。将猪苦胆汁倒入半面盆温水中，搅拌后洗头或洗患处，把油脂状鳞屑清除干净，再用清水冲洗，每日1次。 本方尤适用于脂溢性脱发。 [方十二] 活蜈蚣3条。将活蜈蚣用菜油浸3--4日，先取生木片汤洗发，洗后，以蜈蚣油涂头至愈止。 [方十三] 代赭石。将代赭石研为细面，每日早、晚各服3克，白天水送服，连服2--3个月。 [方十四] 枸杞子15克，大米50克。将枸杞子、大米洗净，放砂锅中煮成粥，食用。 [方十五] 何首乌30克，大米50克，冰糖适量。将何首乌放人砂锅中煎取浓汁后去药渣，然后放人大米和冰糖，将米煮成粥即成，食用。 本方尤适用于脱发久不愈。 [方十六] 野蔷薇嫩枝100克。猢狲姜50克。将药水煎百沸，取汁刷头。 本方尤适用于病后脱发。 哥特式建筑赏析 哥特式建筑是11世纪下半叶起源于法国，13～15世纪流行于欧洲的一种建筑风格。主要见于天主教堂，也影响到世俗建筑。哥特式建筑以其高超的技术和艺术成就，在建筑史上占有重要地位。最负著名的哥特式建筑有巴黎圣母大教堂、意大利米兰大教堂、德国科隆大教堂、英国威斯敏斯特大教堂 （一）哥特式建筑的历史背景 自公元12世纪到公元15世纪，城市已成为各个封建王国的政治、宗教、经济和文化中心，这一时期兴起了封建社会大发展的产物——哥特式艺术。 其开始于建筑方面，而后才追件波及到雕刻和绘画。它发展的重点是从追求建筑的效果而转向绘画的效果：早期哥特式雕刻和绘画都是巨大建筑的一部分，而晚期的建筑和雕刻则追求片面装饰性的效果，不再追求结实和简洁的处理。 哥特式建筑（Gothic architecture）是以法国为中心发展起来的。在12—15世纪，城市手工业和商业行会相当发达，城市内实行一定程度的民主政体，市民们以极高的热情建造教堂，以此相互争胜来表现自己的城市。另外，当时教堂已不再是纯属宗教性建筑物，它已成为城市公共生活的中心，成为市民大会堂，公共礼堂，甚至可用作市场和剧场。在宗教节日时，教堂往往成为热闹的赛会场地。 确切说，开始于1140-1144年间路易七世的长玺官苏热重修圣德尼教堂之时。圣德尼教堂表明了一种新的建筑风格，这种风格从本质上区别于罗马式建筑：首先，后者有着结实而厚重的墙壁，而前者具有轻盈、纤细的结构。罗马式的教堂建有沉重的拱顶，其稳定性取决于足够厚实的墙壁，以支撑各种各样的压力和应力。其次在罗马式建筑中，窗户总是很小，而现在，窗户的尺寸大大增加，允许空前规模的采用彩色玻璃画。第三，圣德尼教堂的片面遵循了带有呈放射分布的礼拜堂的后堂回廊式型制，但这些礼拜堂不再像早先建筑那样呈孤立的单元。 （二）哥特式建筑的技术成就 哥特式建筑所显示的技术成就，我们可以从两个方面具体地感受到。首先是外部造型。哥特式建筑特别是教堂，外观的基本特征是高而直，其典型构图是一对高耸的尖塔，中间夹着中厅的山墙，在山墙檐头的栏杆、大门洞上设置了一列布有雕像的凹龛，把整个立面横联系起来，在中央的栏杆和凹龛之间是象征天堂的圆形玫瑰窗。西立面作为教堂的入口，有三座门洞，门洞内都有几层线脚，线脚上刻着成串的圣像。所有墙体上均由垂直线条统贯，一切造型部位和装饰细部都以尖拱、尖券、尖顶为合成要素，所有的拱券都是尖尖的，所有门洞上的山花、凹龛上的华盖、扶壁上的脊边都是尖耸的，所有的塔、扶壁和墙垣上端都冠以直刺苍穹的小尖顶。与此同时，建筑的立面越往上划分越为细巧，形体和装饰越见玲珑。这一切，都使整个教堂充满了一种超俗脱凡，腾跃迁升的动感与气势。这种气势将基督教的“天国理想”表现得生动、具体，也显示出中世纪高超的建筑技 生姜烧水治------大量掉头发有奇效 1 看到一篇帖子说头发稀少或者掉头发的姐妹有什么办法因为我的秘方太有效就另开帖子说明首先，我老婆以前就头发稀少，头上成块的没头发，还掉头发。后来在湖南遇见一个老中医，开了一个方子，吃了后头发开始长，也不咋掉了，而且开始长新头发，非常有效，后来把这方子告诉身边掉头发，头发少的朋友，用了都说有效。关键是这个方子非常便宜，呵呵！开始公布，一共是3种药：鱼肝油，胱氨酸，维生素B6。都是一块多一瓶，都是一天3次，按着瓶上说明吃几片去吃，记住，3瓶一块吃，不要断。效果绝对好，比可贵的其他药有效得多。 2-煮生姜水洗头治疗脱发。我洗了两次，效果非常好。不但治疗了脱发，连头皮屑都治好了~ 本人被头皮屑困扰多年，曾用了，采乐，什么霸王洗发水。。根本不管用，想不到被2块生姜给治好了就是把生姜切小,放在锅里加水小火煮,煮到汤汁变得黄黄的有浓烈姜味溢出就可以使用了..用姜水抹在头皮上就可以了~ 等它自然干掉,可洗可不洗，一周一两次。还有就是可以喝红枣黄芪汤。也是生发的。电热壶烧开水的 时候把姜切好放进去。 3-我就是看了那个生姜水洗头发的帖子后试了一下，到现在已经洗过3次了，头发多没多我没看不出来，但是控制脱发的效果是很明显，以前每次洗头头发都掉一大把，现在好了很多。头发也有点光泽了，而且蓬松了，哈哈。具体方法：大润发买的生姜（嫩的），切了大约20~30片，放大半锅水一起煮，煮啊煮，一直煮直到水的颜色很黄，并且整个屋子弥漫着姜的味道，我用的电磁炉，160度火，半小时左右。然后，我用买豆浆机时赠的那个滤网把姜水过滤，等姜水冷却成温水就可以洗啦，我是直接就把自己脑袋泡进去了，不是说一定要泡到头皮么，不过TZ们千万别把姜水弄到脸尤其是眼睛上，很疼。我是每隔1天洗1次。 4-我的头发三大症状：症状一：头皮屑很多，多到什么地步？刚洗完头，一下午时间久又长出来了，很且很大块~ 我都有心理疾病了，比如有人站在我身后，我就很紧张，恐怕被人看到我有头皮屑。每次出门之前，必问我老公，让他看看我有没有头皮。症状二：我头发很容易油，但是又很干！是真的，又油又干。症状三：最近1，2年开始掉头发，本来我头发很多，很且很粗的。最近一两年，我洗头的时候，发现头发掉的很多~~ 然后，我一照镜子发现， 引言 什么是哥特式风格呢？哥特式风格史于歌特复兴时期，最早起源于日耳曼部族，它是以贵族奢侈糜烂的生活为原型，将各种极尽奢侈的小装饰品用于打造整个建筑。建筑多以流畅的线条，瑰丽的图案，精致的雕刻等为主要设计手法，从而打造出一种颇受欢迎的建筑。那么哥特式建筑特点是什么呢？哥特式建筑的主要特点是运用宗教的笔法，将现实主义的特色倾情展现，可运用夸张的手法，将贵族生活的奢侈与糜烂都展现了出来。其描绘的具体手法有：尖形拱门、尖塔高耸、、尖肋拱顶、飞扶壁、修长的束柱、大窗户及花窗玻璃等。最负著名的哥特式建筑代表作有巴黎圣母大教堂，德国科隆大教堂，意大利米兰大教堂，英国威斯敏斯特大教堂等。 前言 哥特式建筑艺术和文艺复兴时期教堂建筑都是某种文化的综合体现,虽然是抽象的,但又是具体的,可以感受的。在不同的时代背景下,社会传统,宗教信仰,自然条件等方面均表现不同的特点。成为某个时代,民族的标志,也成为一种特有的文化语言。哥特式建筑是11世纪下半叶起源于法国，13～15世纪流行于欧洲的一种建筑风格。主要见于天主教堂，也影响到世俗建筑。哥特式建筑以其高超的技术和艺术成就，在建筑史上占有重要地位当代的哥特文化是一种在很多国家都存在的亚文化种类。比起同时期其他流行文化,哥特亚文化存在的时间要长得多,并且仍在向着多元化发展。当代的哥特文化伴随 着音乐、美学和时尚的体验于一身。哥特音乐流派众多。通常来说这一类的乐队倾向于凄惨、神秘声音的演绎并打扮成产生同样视觉效果的外表,在服饰中大量使用黑色并且加入化妆和发型。90年代,维多利亚时尚的复兴流行于哥特圈中,哥特迷们从19世纪中期的哥特复兴和维多利亚文化更加病态的其他方方面面汲取了大量灵感。哥特文化影响了不同的艺术家,不止是音乐家还有画家和摄影师。他们的作品的创作动机建立在神秘主义,病态和浪漫主义之上。本文以哥特艺术的复兴为索引,讨论欧洲中世纪教堂的艺术衰败之后,哥特艺术以亚文化的形式渗透到音乐和视觉领域的价值所 生发秘方大全 1-看到一篇帖子说头发稀少或者掉头发的姐妹有什么办法因为我的秘方太有效就另开帖子说明首先，我老婆以前就头发稀少，头上成块的没头发，还掉头发。后来在湖南遇见一个老中医，开了一个方子，吃了后头发开始长，也不咋掉了，而且开始长新头发，非常有效，后来把这方子告诉身边掉头发，头发少的朋友，用了都说有效。关键是这个方子非常便宜，呵呵！开始公布，一共是3种药：鱼肝油，胱氨酸，维生素B6。都是一块多一瓶，都是一天3次，按着瓶上说明吃几片去吃，记住，3瓶一块吃，不要断。效果绝对好，比可贵的其他药有效得多。 2-煮生姜水洗头治疗脱发。我洗了两次，效果非常好。不但治疗了脱发，连头皮屑都治好了~ 本人被头皮屑困扰多年，曾用名贵牌子洗发水根本不管用，想不到被2块生姜给治好了就是把生姜切小,放在锅里加水小火煮,煮到汤汁变得黄黄的有浓烈姜味溢出就可以使用了..用姜水抹在头皮上就可以了~ 等它自然干掉,可洗可不洗，一周一两次。还有就是可以喝红枣黄芪汤。也是生发的。电热壶烧开水的时候把姜切好放进去。 3-我就是看了那个生姜水洗头发的帖子后试了一下，到现在已经洗过3次了，头发多没多我没看不出来，但是控制脱发的效果是很明显，以前每次洗头头发都掉一大把，现在好了很多。头发也有点光泽了，而且蓬松了，哈哈。具体方法：大润发买的生姜（嫩的），切了大约20~30片，放大半锅水一起煮，煮啊煮，一直煮直到水的颜色很黄， 并且整个屋子弥漫着姜的味道，我用的电磁炉，160度火，半小时左右。然后，我用买豆浆机时赠的那个滤网把姜水过滤，等姜水冷却成温水就可以洗啦，我是直接就把自己脑袋泡进去了，不是说一定要泡到头皮么，不过你们千万别把姜水弄到脸尤其是眼睛上，很疼。我是每隔1天洗1次。 4-我的头发三大症状：症状一：头皮屑很多，多到什么地步？刚洗完头，一下午时间久又长出来了，很且很大块~ 我都有心理 近二十年来国外学者对于哥特式建筑的研究综述 中世纪时期是欧洲历史转折的关键时刻，艺术在这一阶段呈现出多姿多彩的面貌。多种流派在相互竞争中得到交融，共同组成了中世纪灿烂辉煌的艺术发展史。而哥特艺术作为中世纪欧洲艺术最重要的组成部分之一，同样也是西文明重要的组成部分之一，其在艺术史中的地位是不言而喻的。其中的佼佼者哥特式建筑，以其高超的技艺和独特的艺术形式理所应当的成为横扫欧洲、风靡一时的建筑风格，凸现 出来。它广泛的流行于13到15世纪的欧洲，成为基督教最具代表性的载体，深刻地反映了欧洲中世纪的社会生活、宗教信仰、审美意识等面发展、变化的在原因。哥特建筑是哥特艺术的核心部分，它的发展历程实际上就是中世纪历史视觉上的呈现。研究哥特建筑的发展历程及其在欧洲艺术史、建筑史中的地位与影响不仅对于深入认识欧洲的宗教传统拥有十分重要的意义，在此基础上，更有助于我们了解西社会文化思潮与审美观念的变迁。由于关于此问题面的研究，国学者的著述实属有限，在中文的出版物中很难寻找到直接的学术参考，故下面的综述主要以国外学者的研究为主，辅之国期刊中可见的短暂论述资料。 一.哥特文化的起源及其在中世纪的地位 在建筑史的普遍意义中，“中世纪”主要是指公元4世纪至公元13世纪的一千年左右，而历史往往将这一时期称为“黑暗时代”。但正如志毅指出的：“在人们看来是一个黑暗时期的中世纪，在建筑艺术面却有着很高的美学价值。”《世界艺术史?建筑卷》（志毅著，东出版社，2003.2，第73页）的确，“哥特式”建筑的价值早已超过了建筑艺术本身，成为了中世纪的精神象征，影响了中世纪的审美，更 影响了今天我们对建筑的理解和对审美的体验。它充满诗意与结构的奇异之花正是 生姜种植技术／方法／管理－山东平度生姜基地 http://hi.baidu .com/sdmmw 2007-11-06 19:17 生姜种植与管理 一、选地 选择土层深厚、疏松肥沃、排灌方便的沙质土地种植，忌连作。 二、整地和施基肥 播种前亩施农家肥1000－1500公斤、钙镁磷肥50公斤、复合肥20公斤作基肥，施后要充分犁翻耙匀。分畦开沟，每畦宽1米，畦高20公分，并在畦面横开播种沟。 三、种姜处理和播种 播种前先将姜种置于阳光下晒2天，然后用2%福尔马林浸种消毒6－8小时（注意消毒后要用清水洗干净），或用农用链霉素浸种消毒6－7个小时。播种适期为3月初至4月中旬，播种规格一般为株行距0.25米×0.4米，每亩播种姜块3500－4000个。 四、田间管理 1、适时追肥。苗期追肥以轻、淡肥为主；以后重追肥两次，第一次是在6月上旬至7月上旬，此时是孙姜旺长期，是生姜的吸肥高峰期，亩追施复合肥20公斤、尿素10公斤；第二次是在9月上旬－10月上旬，此时是生姜块茎迅速膨大期，亩追施复合肥30公斤、氯化钾10公斤。 2、适当遮荫覆盖。夏季气温高、日照强，对生姜越夏极为不利，做好遮荫覆盖十分必要。可在畦边间套种玉米、大豆等作物或搭棚遮荫。同时在姜行间覆盖稻草，减少地面辐射，增加土壤湿度。 3、水分管理。生姜整个生长期间必须保持土壤湿润，干旱时要求灌“跑马水”，畦沟渍水时要及时排清。 五、病虫害防治 （1）防治姜瘟：播种前选用无病种姜，做好种姜消毒。发病初期喷施农用链霉素或叶青双或波尔多液，每隔15天喷一次，共喷3－4次。重病株要及时挖除烧毁，并在姜穴撒石灰消毒。 （2）防治炭疽病：炭伏(苯醚.咪鲜胺)。 （3）防治条螟：在发生期用敌百虫＋杀虫威防治。 生姜种植月历表 4月气温稳定在15℃以上，地温16℃以上即可露地播种，最好根据各地情况播种，一般适期为清明至谷雨，在这段时间内，以早播较好。每块姜重50~80克，具1~2个壮芽，用250~500毫克/升的乙烯利浸种15分钟后，采用平摆法播种，单行栽植，株距18~24厘米，每亩2500~4000株，亩用种量150~250公斤。播后盖一层薄土，然后用堆肥、厩肥等盖姜种，最后覆草保温。幼苗期一般不施肥水。 5月从5月上旬开始，即可为姜苗遮荫，可采用搭架遮阴，或地面覆草遮阴，或间作遮阴或盖黑色地膜遮阴等多种形式。姜地要随时清沟沥水，严防渍水烂姜。 加强中耕除草，化学除草可用25%的除草醚可湿性粉剂，采用喷雾法，每667平方米用1公斤左右，加入100公斤左右清水配成药液，于姜播种后，趁土壤湿润将药液均匀地喷在姜沟及周围地面上，倒退操作。也可用杜尔、拉索等药剂。 6月从6月初开始注意钻心虫的危害，每隔7~10天喷1次溴氰菊脂类杀螟 1-看到一篇帖子说头发稀少或者掉头发的姐妹有什么办法因为我的秘方太有 效就另开帖子说明首先，我老婆以前就头发稀少，头上成块的没头发，还掉头发。后来在湖南遇见一个老中医，开了一个方子，吃了后头发开始长，也不咋掉了，而且开始长新头发，非常有效，后来把这方子告诉身边掉头发，头发少的朋友，用了都说有效。关键是这个方子非常便宜，呵呵！开始公布，一共是3种药：鱼肝油，胱氨酸，维生素B6。都是一块多一瓶，都是一天3次，按着瓶上说明吃几片去吃，记住，3瓶一块吃，不要断。效果绝对好，比可贵的其他药有效得多。 2-煮生姜水洗头治疗脱发。我洗了两次，效果非常好。不但治疗了脱发，连头皮屑都治好了~ 本人被头皮屑困扰多年，曾用了，采乐，什么霸王洗发水。。根本不管用，想不到被2块生姜给治好了就是把生姜切小,放在锅里加水小火煮,煮到汤汁变得黄黄的有浓烈姜味溢出就可以使用了..用姜水抹在头皮上就可以了~ 等它自然干掉,可洗可不洗，一周一两次。还有就是可以喝红枣黄芪汤。也是生发的。电热壶烧开水的时候把姜切好放进去。 3-我就是看了那个生姜水洗头发的帖子后试了一下，到现在已经洗过3次了，头发多没多我没看不出来，但是控制脱发的效果是很明显，以前每次洗头头发都掉一大把，现在好了很多。头发也有点光泽了，而且蓬松了，哈哈。具体方法：大润发买的生姜（嫩的），切了大约20~30片，放大半锅水一起煮，煮啊煮，一直煮直到水的颜色很黄，并且整个屋子弥漫着姜的味道，我用的电磁炉，160度火，半小时左右。然后，我用买豆浆机时赠的那个滤网把姜水过滤，等姜水冷却成温水就可以洗啦，我是直接就把自己脑袋泡进去了，不是说一定要泡到头皮么，不过TZ们千万别把姜水弄到脸尤其是眼睛上，很疼。我是每隔1天洗1次。4-我的头发三大症状：症状一：头皮屑很多，多到什么地步？刚洗完头，一下午时间久又长出来了，很且很大块~ 我都有心理疾病了，比如有人站在我身后，我就很紧张，恐怕被人看到我有头皮屑。每次出门之前，必问我老公，让他看看我有没有头皮。症状二：我头发很容易油，但是又很干！是真的，又油又干。症状三：最近1，2年开始掉头发，本来我头发很多，很且很粗的。最近一两年，我洗头的时候，发现头发掉的很多~~ 然后，我一照镜子发现，原来很粗的头发变的很细的~~ 也许变的过程是漫长的，但是我的发现是突然的和惊人的。看了原来天涯的那个贴之后，我本来没当真，这些年来，希望太多，失望太多了~~ 。我也就是那么姑且一试而已，想不到效果是惊人的！！ 程序一，切姜块煮水，把大拇指那么大的生姜，切成四，五块。煮到水变少，变成黄色，就可以了。稍微凉会儿，否则一会烫脑袋。 程序二，我先用洗发水把头发洗一遍，我没用护发素，就把姜水倒在洗头的盆里。把脑袋放进去泡着，沾不到水的地方，用手来淋水，直到很烫的姜水变凉就可以了。（原帖是按摩，我人比较懒，我宁愿直接泡，呵呵）。别用水冲。就等干就行了。没任何味道的。到现在为止，共用了两次。第一次用完，我就立刻 生姜高产栽培技术(一) 摘要介绍了生姜高产栽培技术,主要包括选地整地、种姜处理、合理密植、田间管理、病虫害防治、采收等内容,以供种植户参考。 关键词生姜;种姜处理;合理密植;田间管理 生姜的食用部分为根茎,除了用作调味外,还有很好的药用价值1]。梅州市旅游业的兴旺,带动了客家特产“姜糖”的热销,对原料生姜的需求量也日益增加。生姜是喜温暖、耐阴湿、怕高热的作物,五华县气候非常适合姜的生长,生姜产量高,种植成本低,经济效益好。一般产量45.0~52.5t/hm2,产值4.5万元/hm2左右。最高姜田产量超过67.5t/hm2,产值达6.00~6.75万元/hm2以上。为使农民了解生姜的特性,正确掌握种植生姜的方法,确保获得高产,笔者经过多年实践研究,总结出一套高产栽培技术,现将其介绍如下。 1选地整地 生姜要求阴湿而温暖,较弱光照,适宜温度为25~32℃,田间土壤湿度以70%~80%为宜,常积水,排水不良,易感病枯死。根据这些特性,种姜时应选择地势较高、荫蔽、土层深厚、土壤疏松肥沃、水源方便、排水良好的地块。以中性或弱酸性为佳,生姜不宜连作,选地时注意避免选择前作是姜、烟草等作物的地块,以防止姜瘟病的发生2]。需轮作3年以上,可与水稻或与芋头、瓜类、豆类等轮作、间作。由于生姜的根系不发达、分布土层较浅,既不耐旱也不耐涝,为此地块要深翻、晒白,开好排水沟,起高畦种植3]。畦宽80cm,高30cm,沟宽30cm,并施足基肥,施优质农家肥30t/hm2加过磷酸钙750kg/hm2。 2种姜处理 生姜发芽适宜温度为15~18℃。10℃以下低温和湿度较大时根茎易腐烂,地上部遇霜冻即枯死,在强光下叶片易凋萎。选择无病虫害、色泽金黄、无机械损伤、有1~2个壮芽的姜块作种姜,选后用20%的草木灰液浸种30min或用1.0∶1.5∶120.0的波尔多液浸种20min进行消毒,以防治姜腐病。然后催芽,把已消毒的种姜晒2~3d,以减少水分,杀死病菌,提早发芽4]。待姜块表面水分消失和附着的泥土脱落后进行堆放,用稻草或麻袋覆盖保湿催芽,也可放进温床催芽,当姜芽长1cm或已出了3~4cm的须根时即可种植。 3合理密植 谷雨后,立夏前,当地温达到16℃时即可种植。种植时要做好合理密植,适当密植能提高生姜产量,将经催芽后的种姜掰成小块,每块重50~100g,每块留1～2个壮芽。若收老姜为主,用种量1500~2250kg/hm2,若收种姜为主,用种量多至5250~6000kg/hm2。种植时,开9～11cm深的种植沟,施入腐熟的猪牛粪混火烧泥15.0~22.5t/hm2、草木灰1500~2250kg/hm2或钾肥150~225kg/hm2。每畦种2行,要求行距10~15cm,株距20～25cm。放种时,姜芽应朝同一方向排列,便于以后回收种姜。种植以后,用细土压紧姜芽,然后覆盖稻草或芒萁草,最后再覆上1层细土,以利遮荫、保温、保湿、防草、防冻。 最佳答案 人为什么会掉头发 掉头发人人都有，不过有的人掉得多，有的人掉得少。而有些人还会一片一片地掉，最后成了秃子。这是怎么回事呢? 头发有它自己的寿命，长到一定长度，寿命到头了，它自己就老死，自然会脱落下来，这是一种正常现象。属于这种情况的掉头发，任何人都有，而且是经常的。不正常的掉头发，是因为头发的生长受到了影响的缘故。头发的生长需要营养，而营养是靠血液运送的，如果一个人长期多病，身体软弱，血气不足，身体营养很差，头发就会因缺少营养、生长不好而短命脱落。这样的人就容易掉头发，掉的也比较多。有人生过一场大病以后，头发掉得稀稀拉拉的，可能就是这个原因。人用脑过度，或者经常心事重重，烦闷，或者遇到了什么事儿，精神过于紧张，使脑子受到了很大的刺激，有时候也会影响到头发营养的供应和生长。因为人体的一切活动都是属大脑管的，大脑受了刺激，活动乱了脚步，不能正常地发挥作用，势必要使身体的营养受到刺激，出现掉头发的情况。有的人遇到什么过于激动的事，大脑受了强烈的刺激，精神很不正常，有时一夜之间头上的头发就脱掉一大片，人们说是“鬼剃头”、实际上就是这样脱掉的。 头发生长原本就有一个生长与衰老的周期，自然生理性的落发其实每天都在发生。但是也有一些掉发是病态性因素所导致。以年轻人来说，比较常见的是圆形秃，也就是俗称的“鬼剃头”，这是一种因为压力、情绪，导致一个头皮一个区块的毛发突然进入生长末期，突然掉光。这类的情况下毛发在经过治疗后，三到五个月内可以恢复生长。 掉头发的原因与营养有关，与精神紧张或突然的精神刺激也有很大关系，可查血微量元素，平时不要经常处于精神紧张状态。可在掉头发的地方经常用生姜擦一擦，可促进头发生长，饮食营养要全面，适当多吃些硬壳类食物，适当吃些黑芝麻！ 充足的睡眠 充足的睡眠可以促进皮肤及毛发正常的新陈代谢，而代谢期主要在晚上特别是晚上10时到凌晨2时之间，这一段时间睡眠充足，就可以使得毛发正常新陈代谢。反之，毛发的代谢及营养失去平衡就会脱发。 建议：尽量做到每天睡眠不少于6个小时，养成定时睡眠的习惯。注意饮食营养，常吃富含蛋白质及微量元素丰富的食品，多吃青菜、水果，少吃油腻及含糖高的食品。 避免过多的损害 染发、烫发和吹风等对头发都会造成一定的损害；染发液、烫发液对头发的影响也较大，次数多了会使头发失去光泽和弹性，甚至变黄变枯；日光中的紫外线会对头发造成损害，使头发干枯变黄；空调的暖湿风和冷风都可成为脱发和白发的原因，空气过于干燥或湿度过大对保护头发都不利。 建议：染发、烫发间隔时间至少3—6个月。夏季要避免日光的暴晒，游泳、日光浴更要注意防护。 洗头及梳头 夏季可以每周3至7次，冬季可以每周1至3次，洗头时水温不要超过40℃，与体温37℃接近。不要用脱脂性强或碱性洗发剂，因这类洗发剂的脱脂性和脱水均很强，易使头发干燥、头皮坏死。 西方建筑风格体系 ——浅析哥特式建筑的风格 哥特式建筑是流行于欧洲中世纪的一种建筑风格，以其高超的技术和艺术成就，在建筑史上占有重要地位，代表了欧洲中世纪艺术的最高成就。 哥特式起源于12世纪的法国，盛行于12—15世纪的欧洲大地，前承罗马式后肩文艺复兴。其经济和社会产生了深刻的变革，其思想、文化和艺术也达到了空前的发展。主要见于天主教堂，也影响到世俗建筑。这一时期的艺术风格，通常被称为“哥特式”风格。“哥特式”(Gothic)一词的来源颇难说清，因为“哥特”本是来自斯堪的纳维亚的野蛮游牧部落之名称。哥特人自1世纪起开始南迁，并定居多瑙河地区，但在其后漫长的岁月中并未发展出这种子高水落石出平的艺术风格。意大利著名画家拉斐尔在其给教皇利奥十世的信中首先用到“哥特式”一词，借以批评文艺复兴之前中欧及北欧的建筑样式，即把“哥特式”一词作为“野蛮”的同义语，从而将凡是从网尔卑斯山以北传来的东西都称之为“哥特式”的。此后，16世纪的意大利艺术评论家乔尔乔欧·瓦萨里把介于欧洲古代与文艺复兴之间的所有艺术都贬称为“哥特人的创作”，“哥特式”之名在艺术史上遂沿用至今。其实，哥特式艺术与哥特人并无任何联系，它乃“罗马式”艺术的更高发展，为中世纪天主教神学观念在艺术上的一种反映。 哥特式建筑总体风格特点是：空灵、纤瘦、高耸、尖峭。尖峭的形式，尖券、尖拱技术的结晶；高耸的墙体，则包含着斜撑技术、扶壁技术的功绩，体现了创造者无穷的想象力和创造力。哥特式建筑艺术实现了中世纪基督教哲学与艺术创作的完美结合，其塔形屋顶、飞扶壁结构、玫瑰花窗、柱了雕像等经典建筑特点无不体现其作为“上帝之屋”的宗教精神本质。哥特式建筑最明显的建筑风格就是高耸入云的尖顶及窗户上巨大斑斓的玻璃画。最富著名的哥特式建筑有俄罗斯圣母大教堂、意大利米兰大教堂、德国科隆大教堂、英国威斯敏斯特大教堂、法国巴黎圣母院以及凯旋门。哥特式建筑艺术不只影响着中世纪欧洲各艺术领域的发展，更影响着现今世界各艺术领域的发展趋势。 哥特式建筑的典范——科隆大教堂 说到“哥特式建筑”最容易使人联想起来的莫过于那些弥漫着中世纪风情充满着传奇色彩的哥特式大教堂。坐落在德国科隆的“科隆大教堂”，正是这样一座建筑史上的传奇，也是“哥特式建筑”最具代表性的“璀璨明珠”。科隆大教堂是科隆城的象征，是德国最大的哥特式教堂，也是世界上最著名的教堂之一，与巴黎圣母院、罗马圣彼得大教堂并称为欧洲三大教堂。2000多年前，罗马人创建了科隆城。1248年，科隆人又动于建造科隆大教堂，这个工程远比建一座城艰巨，直至1880年10月15日才完成，创造了欧洲建筑史上的奇迹。科隆大教堂是中世纪欧洲哥特式建筑艺术的代表作，被联合国教科文组织列为“世界遗产”。 歌特建筑的杰出之作——巴黎圣母院大教堂 巴黎圣母院大教堂是一座位于法国巴黎市中心、西堤岛上的教堂建筑，也是天主教巴黎总教区的主教座堂，是古老巴黎的象征。圣母院约建造于1163年到1250年间，属哥特式建筑形式，是法兰西岛地区的哥特式教堂群里面，非常具有关键代表意义的一座。始建于1163年，是巴黎大主教莫里斯?德?苏利决定兴 一、生姜生物学特性 1．生姜属姜科，根系属肉质根，不发达，一般每个姜块只能生7~9 条根，入土浅，对肥水吸收能力弱，根系分布 在土壤0~30 厘米，深度超过30 厘米无吸收能力。 2．大姜对环境条件的要求 （1）温度大姜喜温但怕高温，不耐霜，5℃以下受冻害，15~16℃以上开始萌发，生长适温在20~23℃，26℃以上生长受阻，超过35℃时可造成死亡，昼夜温差在12~15℃时茎块膨大最快。 （2）光照姜喜阴凉，不耐强光，光照强度在3~5 万雷克斯，幼苗期间需中等光照，否则易伤苗，发芽及茎块膨大 需在黑暗环境中进行。 （3）水分大姜根系浅，吸收能力弱，对水分要求严格；前期苗小吸收水份较少，湿度大，不利提高地温，易造成姜种腐烂；地面干旱，地表温度过高易造成伤苗，生产上以小水勤浇，不干地表为准；后期，地上苗生长过旺需水量大，应每隔7~10 天浇水一次。 （4）土壤大姜对土壤要求不严格，无论沙壤, 壤土,粘土均可种植大姜；土壤PH5.5~7之间均可种植。大姜根系吸收能力较弱，生产上主要收获姜块，姜块膨大对产量影响较大。对肥吸收，每生产1000 公斤姜块需 氮 4.44 公斤，五氧化二磷 1.21 公斤，氧化钾 6.96 公斤，前期需氮量较大，后期需钾量大。除此之外需钙，硼，锌量较大。 二。种植大姜栽培技术 1/品种大姜作为地理标志产品以它生长旺盛/分芽多/块茎鲜黄/肉质细嫩/辛辣味浓/产量高/深加工价值高而具称，适合我市大姜生产。 2/ 栽培时间及催芽（1）晒种根据我市气候条件，露天地膜栽培可于4 月上中旬播种，小拱棚栽培可于3 月底4 月初进行播种，大拱棚栽培可在3月20 日前后播种。中午气温达到15℃以上时（二月下旬）即可从储存窖中取出姜种晾晒。注意：时间要掌握在好天的上午10 点至下午 3 点前高温时进行，早晾晚收，晚上堆放室内，连晒2~3 天，将姜块表皮湿度晾干为止。在晒种过程中可结合喷施20%噻菌铜300 倍液消菌。 （2）困姜结合晒姜进行，每天晾晒完毕将将种姜堆放困种。 （3）选种上炕催芽前进行，选择姜块肥大/色泽鲜艳/皮色有光/质地硬/不软化/无病虫的姜块作种用。将选好的姜种进行掰分，掰后的姜块以80 克为宜（一斤姜块掰六块左右）。 （4）催芽因地制宜，我市在火炕上催芽，先在火炕上铺垫10 厘米左右麦草并压平，然后铺放姜种，铺放姜种高度以60 厘米为宜，上覆草毡或棉毡密封保温避光。温度保持在20~23℃，经25~35 天当姜芽在0.5~1.0 厘米时 （胖而壮，仅见根突起为宜）既可保护地播种。 （5）分芽将姜芽按大小分开，一般情况下按0.5 厘米以下/0.5~1.5 厘米/1.5 厘米以上尽心分级，超过 2.0 厘米幼根已长出的尽量不作种用（试验表明：0.5~1.5 厘米的姜芽种植后能使产量1000 公斤的话，0.5 以下的芽能产700公斤， 2.0 厘米以上幼根已长出的芽只能产300 公斤。）。按姜芽大小分播。 3/ 播种 （1）整地施肥前茬作物收获后，及时清除田园植株残体，带出田外集中处理，以压低病（虫）源基数。年前使用机械深翻，深 度在25cm以上。第二年 3 月上旬耙实，达到深、平、细、净、实，并按行距65~70 厘米，深度15cm.开沟。 （2）基肥施用 根据土壤肥力状况，整地前每亩撒施有机肥2500～5000kg 作基肥。开沟后每亩施生物有机肥80kg（N P K25%以 上、有机质25％以上），蓝得土壤调理剂75-100kg 、硼肥 1 kg 、锌肥 2 kg，5％丁硫克百威颗粒剂10kg, 顺沟撒施，划锄混匀待播。 （3）播种将开好姜沟的地块灌透水水，待水渗下后按株距22~25 厘米播种，播种时姜芽朝上，姜种西南向排列 （与行向成45度角），播后覆土2~3 厘米。干旱年份播后再次浇水。 （4）喷施除草剂选择40％新姜蒜草克（乙氧氟草醚加二甲戊乐灵）乳油120～150 ml/667m 2或33%施田补（二甲戊乐灵）乳油100～125 ml/667m 2兑水50～75kg 均匀喷雾。 掉头发和生发的偏方 工作紧张，压力大，很多人还没进入中年就有脱发的现象。那么，该怎么才能长保秀发浓密呢？二十五条药方子，帮助你解决脱发困扰，效果很不错哦！ 【方一】柏枝(干药)、椒仁、半夏，各90克。将药加水500毫升煎至250 毫升，入蜜少许，再煎1--2min，沸用时入生姜汁少许调匀，擦无发处每日2次。 【方二】白矾、郁金各等分，将白矾、郁金制成丸，每次4--5克，每日2次。 【方三】食盐15克，将食盐加入1500毫升温开水，搅拌均匀，洗头每周1--2次。此法长期应用可防止脱发。 【方四】榧子3枚，胡桃2个，侧柏叶30克，将药共捣浸雪水梳头，其 发水不脱落而且光润。本方尤适用于肾虚型脱发。 【方五】侧柏叶若干，将柏叶阴干研细，以春油浸之，每戟蘸刷头头发长出后用猪胆汁人汤洗头。本方尤适用于妇女脱发。 【方六】车前草200克，米酷适量，将车前草全草焙成炭，浸入米醋，一周后，用该药醋外涂患处每日2--3次。 【方七】黑牛胆1个，槐豆适量，将槐豆装入有胆汁的牛胆内，装满浸透槐豆即可，内服每次9克，每日3次。 【方八】侧柏叶240克(焙干)，当归(全身)120克，将药共研为末(忌铁器)，水糊为丸，如梧桐子大，每服50--70丸，早晚各1，服用黄酒或盐汤送下。 【方九】芝麻花、鸡冠花各60克，樟脑1.5克，白酒500克，将芝麻花、 鸡冠花撕碎，然后浸泡人酒内，密封15日后，过滤再将樟脑人药酒中，使之溶化备用，以药棉蘸药酒涂搽脱发区，每日搽3--4次。本方尤适用于神经性脱发。 【方十】芝麻梗、清明柳(清明节采的柳枝嫩叶)各90--120克，煎汤洗发，并摩擦头皮连用1--7日。本方尤适用于脂溢性脱发。 【方十一】猪苦胆1个，将猪苦胆汁倒入半面盆温水中搅拌后，洗头或洗 患处，把油脂状鳞屑清除干净，再用清水冲洗，每日1次。本方尤适用于脂溢 性脱发。 【方十二】活蜈蚣3条，将活蜈蚣用菜油浸3--4日，先取生木片汤洗发， 浅析哥特式建筑的发展与影响 【摘要】哥特式建筑是11世纪下半叶起源于法国，13世纪到15世纪流行于欧洲的一种建筑风格，以其高超的技术和艺术成就，在建筑史上占有重要地位。哥特式教堂的结构体系由石头的骨架圈和飞扶壁组成，总体的风格特点是空灵纤瘦、高耸、尖峭。那空灵的意境和垂直向上的形态是基督教精神内涵的最确切的表述，而高且直、空灵、虚幻的形象，似乎直指上苍，启示人们脱离这个苦难、充满罪恶的世界，奔赴“天国乐土”。总之哥特式建筑体现了创造者无穷的想象力和创造力，对现在的艺术设计也产生了不少的启发与影响。 【关键词】哥特式教堂建筑传统文化启发与影响 哥特式建筑是11世纪下半叶起源于法国，13世纪到15世纪流行于欧洲的一种建筑风格。自公元12世纪到公元15世纪，城市已成为各个封建王国的政治、宗教、经济和文化中心，这一时期正是哥特式艺术发展的巅峰时期。“哥特”原是指野蛮人，哥特艺术就是野蛮艺术之义，是一个贬义词，在欧洲人眼里罗马式才是正统艺术，但哥特式建筑凭借其高超的技术和艺术成就，在建筑史上占据了重要的地位。 哥特式建筑外观的基本特征是高而直，其典型构图是一对高耸的尖塔，中间夹着中厅的山墙在山墙檐头的栏杆大门洞上设置了一列布有雕像的凹形盒，把整个立面横联系起来在中央的栏杆和凹形盒之间是象征天堂的圆形玫瑰窗，与此同时建筑的立面越往上划分越为细巧，形体和装饰越见玲珑。内部空间的特点哥特式教堂的平面一般为拉丁十字形，但中厅窄而长，瘦而高，教堂内部导向天堂和祭坛的动势都很强教堂内部的结构全部裸露.近于框架式，垂直线条统率着所有部分，使空间显得极为高耸象征着对天国的憧憬。 教堂的结构体系由石头的骨架圈和飞扶壁组成。其基本单元是在一个正方形或矩形平面四角的柱子上做双圆心骨架尖券，四边和对角线上各一道，屋面石板架在券上，形成拱顶。采用这种方式，可以在不同跨度上做出矢高相同的圈，拱顶重量轻，交线分明，减少了券脚的推力，简化了施工；飞扶壁则是由侧厅外面的柱墩发券，平衡中厅拱脚的侧推力，为了增加稳定性，常在柱墩上砌有尖塔。由于采用了尖券、尖拱和飞扶壁，哥特式教堂的内部空间高旷、单纯、统一，装 种植姜的方法 姜原产东南亚的热带地区，喜欢温暖、湿润的气候，耐寒和抗旱能力较弱，那么姜要怎么种植?下面是为你整理的种植姜的方法，希望对您有用。 种植姜的方法栽培季节 一般春季播种，霜前收获。由于姜喜温暖，不耐寒、不耐霜，所以必须在温暖无霜的季节栽培。确定姜的播种期应考虑以下几个条件： ⒈根据发芽所需的温度，应在10厘米地温稳定在16℃以上时播种; ⒉根据姜的生长习性，要获得较高的产量，需有135-150天的适于姜生长的时间;根据本地的气候条件，生姜一般于惊蛰后至4月中旬播种，播种过早，地温低，发芽慢，播种过晚，则生育期缩短，降低产量。 整地施肥 姜发芽期由种姜供应营养，幼苗期生长缓慢，需肥较少，“三股杈”以后需大量养分，约占全生育期总吸收量的88%。全生育期对肥料的需求以钾肥最多，氮肥次之，磷肥较少，氮(N)、磷(P O )、钾(K O)的吸收比例为1:0.5:2。在中等肥力条件下，生产1000千克生姜产品，需吸收氮(N)5.76千克、磷(P O )2.54千克、钾(K O)11.47 千克。施肥时应根据生姜需肥规律、土壤总养分和肥料效应，按照有机肥与无机肥、基肥与追肥相结合的原则，实行平衡施肥。生姜根系细弱、分布浅，生育期长，必须施足基肥。最好在冬前深翻风化土壤，翌年春耙细耙平。结合翻地，一般每亩施腐熟有机肥3000千克、硫酸钾30千克，或每亩施有机肥复合肥800千克、普钙20千克做基施。基肥施入后进整地，可做成平畦，也可开沟待播。采用沟播，沟距为50-55厘米，沟宽25厘米，沟深10-12厘米。 播种 应选择晴暖天气播种。 优选种姜 应在前一年，从生长健壮、无病、高产的地块上选留种姜。收获后选择肥壮、芽头饱满、个头大小均匀、颜色鲜亮、无病虫、无腐烂、无损伤、未受冻的姜块做姜种贮藏。姜在播种前应先进行催芽。幼芽是幼苗生长的基础，培育壮芽是获得高产的基础。壮芽的形态特征是芽身粗壮，顶部钝圆;弱芽的形态特征是芽身细瘦，芽顶细尖。 培育壮芽 ⑴晒姜困姜 播种前1个月左右，选晴天，将姜种平铺在室外地上晾晒1-2天，夜晚收进室内防霜冻。通过晒种，可提高姜块温度，打破休眠，促进发芽，并减少姜块中的水分，防止腐烂。晒种1-2天后，再把姜块置于室内堆放3-4天，姜堆上盖上草莲，进行困姜，促进种姜内养分分解。经过2-3次反复晒姜困姜后，便可催芽。姜易受姜瘟病、炭 网友关于生发补发的实战总结（全） 生姜水煮的时候我是用20来片姜(大概直径3cm左右大小)，加大半锅水，大火熬沸了再用小火急需慢沸，熬啊熬，一直熬成恰好小半盆水，足够我洗头发用就行，这时的颜色是很浓的黄色1-看到一篇帖子说头发稀少或者掉头发的姐妹有什么办法因为我的秘方太有效就另开帖子说明首先，我老婆以前就头发稀少，头上成块的没头发，还掉头发。后来在湖南遇见一个老中医，开了一个方子，吃了后头发开始长，也不咋掉了，而且开始长新头发，非常有效，后来把这方子告诉身边掉头发，头发少的朋友，用了都说有效。关键是这个方子非常便宜，呵呵!开始公布，一共是3种药:鱼肝油，胱氨酸，维生素B6。都是一块多一瓶，都是一天3次，按着瓶上说明吃几片去吃，记住，3瓶一块吃，不要断。效果绝对好，比可贵的其他药有效得多 2-煮生姜水洗头治疗脱发。我洗了两次，效果非常好。不但治疗了脱发，连头皮屑都治好了~本人被头皮屑困扰多年，曾用了，采乐，什么霸王洗发水。根本不管用，想不到被2块生姜给治好了就是把生姜切小，放在锅里加水小火煮，煮到汤汁变得黄黄的有浓烈姜味溢出就可以使用了。用姜水抹在头皮上就可以了~等它自然干掉，可洗可不洗，一周一两次。还有就是可以喝红枣黄芪汤。也是生发的。电热壶烧开水的时候把姜切好放进去 3-我就是看了那个生姜水洗头发的帖子后试了一下，到现在已经洗过3次了，头发多没多我没看不出来，但是控制脱发的效果是很明显，以前每次洗头头发都掉一大把，现在好了很多。头发也有点光泽了，而且蓬松了，哈哈。具体方法:大润发买的生姜(嫩的)，切了大约20~30片，放大半锅水一起煮，煮啊煮，一直煮直到水的颜色很黄，并且整个屋子弥漫着姜的味道，我用的电磁炉，160度火，半小时左右。然后，我用买豆浆机时赠的那个滤网把姜水过滤，等姜水冷却成温水就可以洗啦，我是直接就把自己脑袋泡进去了，不是说一定要泡到头皮么，不过TZ们千万别把姜水弄到脸尤其是眼睛上，很疼。我是每隔1天洗1次4-我的头发三大症状: 症状一:头皮屑很多，多到什么地步?刚洗完头，一下午时间久又长出来了，很且很大块~我都有心理疾病了，比如有人站在我身后，我就很紧张，恐怕被人看到我有头皮屑。每次出门之前，必问我老公，让他看看我有没有头皮 。症状二:我头发很容易油，但是又很干!是真的，又油又干。 症状三:最近1，2年开始掉头发，本来我头发很多，很且很粗的。最近一两年，我洗头的时候，发现头发掉的很多~~然后，我一照镜子发现，原来很粗的头发变的很细的~~也许变的过程是漫长的，但是我的发现是突然的和惊人的。看了原来天涯的那个 浅析哥特式建筑的历史和发展 【论文关键词】哥特式风格教堂建筑 【论文摘要】哥特式建筑是流行于欧洲的一种建筑风格。以其高超的技术和艺术成就，在建筑史上占有重要地位。哥特式建筑总体风格特点是:空灵、纤瘦、高耸、尖峭。尖峭的形式，尖券、尖拱技术的结晶;高耸的墙体，则包含着斜撑技术、扶壁技木的功绩，体现了创造者无穷的想象力和创造力。我们学习和借鉴传统文化，也要创新传统文化，让它更灿烂辉煌。 哥特式建筑，又译作歌德式建筑，是位于罗马式建筑和文艺复兴建筑之间的，1140 年左右产生于法国的欧洲建筑风格。它由罗马式建筑发展而来，为文艺复兴建筑所继承。哥德式建筑主要用于教堂，在中世纪高峰和晚期盛行于欧洲，发源于十一世纪的法国，持续至十六世纪，哥德式建筑在当代普遍被称作“法国式”，“哥德式”一词则于文艺复兴后期出现，带有贬意。哥德式建筑的整体风格为高耸削瘦，以卓越的建筑技艺表现了神秘、哀婉、崇高的强烈情感，对后世其他艺术均有重大影响。哥德式大教堂等无价建筑艺术已列入联合国教科文组织的世界遗产，其也成了一门关于主教座堂和教堂的研究学问。十八世纪，英格兰开始了一连串的哥德复兴，蔓延至十九世纪的欧洲，并持续至二十世纪，主要影响教会与大学建筑。 哥特式建筑是11世纪下半叶起源于法国，13～15世纪流行于欧洲的一种建筑风格。主要见于天主教堂，也影响到世俗建筑。哥特式建筑以其高超的技术和艺术成就，在建筑史上占有重要地位。哥特式建筑最明显的建筑风格就是高耸入云的尖顶及窗户上巨大斑斓的玻璃画。最富著名的哥特式建筑有俄罗斯圣母大教堂、意大利米兰大教堂、德国科隆大教堂、英国威斯敏斯特大教堂、法国巴黎圣母院以及凯旋门。 哥特式建筑的特点是尖塔高耸、尖形拱门、大窗户及绘有圣经故事的花窗玻璃。在设计中利用尖肋拱顶、飞扶壁、修长的束柱，营造出轻盈修长的飞天感。新的框架结构以增加支撑顶部的力量，使整个建筑以直升线条、雄伟的外观和教堂内空阔空间，常结合镶着彩色玻璃的长窗，使教堂内产生一种浓厚的宗教气氛。 从罗曼式建筑的圆筒拱顶普遍改为尖肋拱顶，推力作用于四个拱底石上，这样拱顶的高度和跨度不再受限制，可以建得又大又高。并且尖肋拱顶也具有“向上”的视觉暗示。 飞扶壁，也称扶拱垛，是一种用来分担主墙压力的辅助设施，在罗曼式建筑中即已得到大量运用。但哥特式建筑把原本实心的、被屋顶遮盖起来的扶壁，都露在外面，称为飞扶壁。由于对教堂的高度有了进一步的要求，扶壁的作用和外观也被大大增强了。亚眠大教堂的扶拱垛有两道拱壁，以支撑来自推力点上方和下方的推力。沙特尔大教堂用横向小连拱廊增加其抗力，博韦大教堂则双进拱桥增加扶拱垛的承受力。有的在扶拱垛上又加装了尖塔改善平衡。扶拱垛上往往有繁复的装饰雕刻，轻盈美观，高耸峭拔。 哥特式建筑逐渐取消了台廊、楼廊，增加侧廊窗户的面积，直至整个教堂采用大面积排窗。这些窗户既高且大，几乎承担了墙体的功能。并应用了从阿拉伯国家学得的彩色玻璃工艺，拼组成一幅幅五颜六色的宗教故事，起到了向不识字的民众宣传教义的作用，也具有很高的艺术成就。花窗玻璃以红、蓝二色为主，蓝色象征天国，红色象征基督的鲜血。窗棂的构造工艺十分精巧繁复。细长的窗户被称为“柳叶窗”，圆形的则被称为“玫瑰窗”。花窗玻璃造就了教堂内部神秘灿烂的景象，从而改变了罗曼式建筑因采光不足而沉闷压抑的感觉，并表达了人们向往天国的内心理想。 柱子不再是简单的圆形，多根柱子合在一起，强调了垂直的线条，更加衬托了空间的高25种治疗脱发的偏方1
论文--哥特式建筑赏析
生姜烧水治------大量掉头发有奇效
论哥特式建筑艺术的特色
最新生发秘方大全
哥特式建筑的研究报告综述
生姜种植技术
关于头发稀疏和掉头发的超级秘密(我的秘方太有效)
生姜高产栽培技术(一)
最佳答案.治脱发
西方建筑风格体系(哥特式建筑风格)
大姜种植管理技术
掉头发和生发的偏方
浅析哥特式建筑的发展与影响
种植姜的方法
脱发生发的实战总结(绝对有效,求验证!)
浅析哥特式建筑的历史和发展