Reduction of Fruit Load Affects Early Fruit Growth

J.A MER.S OC.H ORT.S CI.138(4):253–262.2013.

Reduction of Fruit Load Affects Early Fruit Growth in Apple by Enhancing Carbohydrate Availability, Altering the Expression of Cell Production-related Genes,and Increasing Cell Production

Madhumita Dash1,Lisa Klima Johnson,and Anish Malladi2

Department of Horticulture,University of Georgia,1111Miller Plant Sciences,Athens,GA30602 A DDITIONAL INDEX WORDS.cell division,cell expansion,fruit size,source-sink relationship,thinning

A BSTRACT.Carbohydrate availability is a key factor determining fruit growth in apple(Malus·domestica)and other fruits.However,the molecular mechanisms regulating?eshy fruit growth in response to changes in carbohydrate availability are not well understood.In this study,carbohydrate availability was manipulated by reducing fruit load, and its effects on apple fruit growth,cell production and expansion,and the expression of genes associated with these processes was investigated.Reduction of fruit load during early fruit development led to a rapid increase in early fruit growth.The increase in fruit growth was associated with a transient increase in sorbitol and fructose concentrations and altered expression of sorbitol dehydrogenase and sucrose synthase genes.Increase in early fruit growth was mediated primarily by an increase in cell production.The aintegumenta gene,MdANT1,an AP2-domain transcription factor associated with the regulation of cell production and fruit growth,displayed an increase in expression by up to 5-fold during early fruit development in response to the reduction in fruit load.Additionally,multiple cell cycle genes positively associated with cell production such as the cyclins,MdCYCA2;1,MdCYCA2;3,MdCYCB1;1,and MdCYCB2;2,and the B-type cyclin-dependent kinases,MdCDKB1;1,MdCDKB1;2,and MdCDKB2;2,displayed higher expression by up to5-fold under reduced fruit load conditions during early fruit growth.These data indicate that carbohydrate availability affects the expression of key transcription factors and cell proliferation genes,thereby regulating cell production during early fruit growth.Several genes associated with cell expansion such as the expansins,and cobra and cobra-like genes,also displayed altered expression in response to the reduction in fruit load. The expression of three expansin genes was higher under reduced fruit load conditions at maturity,a stage at which a minor increase in cell size was apparent.Together,data from this study indicate that fruit load reduction induces changes in carbohydrate availability and metabolism,which in turn affect cell production-related mechanisms, thereby enhancing early fruit growth.

Fruit growth in apple and other fruits is greatly dependent on and often limited by carbohydrate availability(Bertin et al.,2002;Lakso et al.,1998,1999).In apple,fruit growth is sensitive to carbohydrate limitation during early(%2to3 weeks after bloom)and at late stages of fruit development (Lakso et al.,1998,1999).Early fruit development is particu-larly sensitive to carbohydrate limitation because it is often highly responsive to treatments that alter carbohydrate avail-ability(Dash et al.,2012;Dash and Malladi,2012;Gof?net et al.,1995;Link,2000;Wismer et al.,1995).Similarly,in other fruits such as tomato(Solanum lycopersicum),fruit growth is limited by carbohydrate availability during early development(Baldet et al.,2002;Bertin,2005;Bertin et al., 2002).Reduction of fruit load during early fruit development has been used to study the effects of changes in carbohydrate availability on fruit growth(Baldet et al.,2006;Bertin,2005; Bertin et al.,2002;Gof?net et al.,1995;Morandi et al.,2008). Reduction of fruit load during early fruit development may increase carbohydrate availability to other sinks,including the remaining fruit,thereby allowing for fruit growth to progress under less limiting conditions.For example,reduction of fruit load lowered the hexose:sucrose ratio and enhanced fruit growth rate in peach[Prunus persica(Morandi et al.,2008)]. Similarly in tomato,reduction of fruit load during early development altered starch and sugar content,enhanced fruit growth,and increased?nal fruit size(Prudent et al.,2010).In Rosaceae plants including apple,sorbitol and sucrose are the main translocated carbohydrates,with sorbitol constituting the majority(Bieleski,1969).A reduction of fruit load enhanced apple fruit growth(Dash and Malladi,2012;Gof?net et al., 1995),potentially by decreasing competition for these trans-located carbohydrates.

Sensitivity of the early stages of fruit development to carbohydrate availability may be attributed in large part to the extensive competition for the available photosynthetic carbohydrates among multiple sinks such as fruit and shoots (Bepete and Lakso,1998;Bertin et al.,2002;Lakso et al.,1999). This is further exacerbated by the high demand for carbohy-drates from growth-facilitating processes active during this period.In many fruits including apple,early fruit growth is associated with multiple cycles of cell production(Gillaspy et al.,1993;Malladi and Johnson,2011).Because cell pro-duction-related processes are intensive in terms of their re-quirements for energy and carbohydrates,limitation of carbohydrates during this period may severely impact their

Received for publication1May2013.Accepted for publication4June2013. We thank the staff at the Georgia Mountain Research and Education Center in Blairsville,GA,for tree maintenance and help with the fruit load reduction experiment.We thank Dr.Phil Brannen for the trees used in this study.We thank Betty Schroeder and Dr.Stanley Kays for assistance with carbohydrate measurement using gas chromatography.

1Present address:School of Forest Resources and Environmental Sciences, Michigan Technological University,Houghton,MI49931.

2Corresponding author.E-mail:malladi@https://www.wendangku.net/doc/8912196206.html,.

progression(Bepete and Lakso,1997;Dash et al.,2012;Lakso et al.,1999).In apple,fruit load reduction during early fruit development resulted in enhanced cell production(Dash and Malladi,2012;Gof?net et al.,1995).Also,the application of chemical agents that result in fruit removal(thinning)such as benzyl adenine(BA)increased fruit size by increasing the number of cells in the fruit cortex,although some of the response to BA applications may be attributed to its direct effect on promoting cell production(Wismer et al.,1995). Similarly in tomato,an increase in carbohydrate availability as a result of fruit load reduction at anthesis resulted in higher cell production(Bertin et al.,2002;Fanwoua et al.,2012;Prudent et al.,2010).Together,these studies underline the importance of cell production as a key mechanism mediating the effects of altered carbohydrate availability on early fruit growth.

Nevertheless,several studies have also reported the effects of fruit load manipulation on cell expansion during fruit growth.In apple,fruit load reduction during early fruit devel-opment resulted in a minor increase in cell size at maturity (Dash and Malladi,2012).Application of chemical thinning agents such as naphthaleneacetic acid during early fruit de-velopment enhanced?nal cell size in apple(Wismer et al., 1995).In tomato,although some studies indicated that en-hanced fruit growth resulting from fruit load reduction was associated with higher cell expansion(Bertin,2005;Bertin et al.,2003),others indicated that the effects of fruit load re-duction on cell expansion were dependent on the genotype under study(Fanwoua et al.,2012;Prudent et al.,2010).

Several studies have explored the molecular mechanisms associated with the regulation of?eshy fruit growth in response to carbohydrate availability.In tomato,reduction of fruit load before anthesis resulted in changes in the expression of several genes associated with cell proliferation during?ower develop-ment,including an increase in the expression of cell cycle genes such as B2-and D3-type cyclins and a reduction in the expression of a negative regulator of fruit size,fw2.2(Baldet et al.,2006).An analysis of changes in the tomato fruit transcriptome during the cell expansion phase(21d after anthesis),in response to a reduction in fruit load at anthesis, revealed changes in the expression of genes associated with hormone metabolism and signaling,carbohydrate metabolism, and transcriptional mechanisms(Prudent et al.,2010).How-ever,these studies did not investigate the effects of altered carbohydrate availability on molecular mechanisms regulating the progression of the cell production phase of fruit growth,the key phase of fruit development responsive to such manipula-tion.A recent study that approached this aspect in tomato indicated no signi?cant effects of fruit load reduction on the expression of three cell cycle genes at7d after anthesis(Fanwoua et al.,2012).In apple,the expression of two aintegumenta(ANT) transcription factors associated with cell production,MdANT1 and MdANT2,was enhanced during early fruit growth in response to a reduction in fruit load(Dash and Malladi, 2012).Beyond these studies,little is known regarding the genes and the mechanisms mediating changes in early fruit growth in response to carbohydrate availability,especially in apple.

The main goal of the current study was to develop an understanding of the molecular mechanisms mediating an increase in apple fruit growth in response to increased carbo-hydrate availability.A speci?c objective was to determine if a reduction in fruit load alters carbohydrate concentrations and the expression of genes associated with carbohydrate metabo-lism.An additional objective was to determine if a reduction in fruit load enhances cell production by altering the expression of key genes associated with the regulation of this process.These objectives were achieved by reducing fruit load during early fruit development and by investigating its effects on carbohy-drate metabolism,cell production and expansion,and the expression of key genes associated with these processes.

Materials and Methods

P LANT MATERIAL.Mature trees(planted in2001)of‘Golden Delicious’Smoothie(GS)growing on‘M.7a’(M.7a)root-stocks at the Mountain Research and Education Center, University of Georgia,Blairsville,were used in this study. All trees used in these studies were maintained according to commercial apple production practices.The applications of chemical thinning agents were not performed on these trees during the course of this experiment.In2010,four randomly selected GS trees were subjected to a reduced fruit load(RFL) treatment and four other trees were used as control trees(n=4). Reduction of fruit load involved the removal by hand of all fruit within a cluster except for one lateral fruit at11d after full bloom(DAFB),when fruit were%5mm in diameter.Such a reduction of fruit load at this stage has been previously shown to enhance fruit growth in GS(Dash and Malladi,2012).In comparison with the control trees,trees under the RFL treatment had3-fold lower fruit load per trunk cross-sectional area at maturity.Initially,20fruit per replicate tree were tagged for fruit diameter measurements.Because many of these fruit dropped during fruit development,fruit diameter was measured on other fruit on these trees.Fruit were randomly sampled(four or more fruit)from these trees at different stages of develop-ment and were either?xed in CRAF III?xative(0.3%chromic acid,2%acetic acid,and10%formalin;Berlyn and Miksche, 1976)for cytology or frozen in liquid N2and stored at–80°C for carbohydrate and gene expression analyses.All sampling was performed around noon.At maturity,50fruit per replicate tree were harvested and the average fruit weight(grams)was determined.

C ELL NUMBER AN

D CELL AREA MEASUREMENT.The number of cell layers within the fruit cortex and the area of the cortex cells were measured as described previously in Malladi and Johnson (2011).Brie?y,cell number was determined by counting the number of cell layers between the petal vascular trace and the epidermis.The relative cell production rate(RCPR)was determined using the cell number data using the formula: [Ln(C2)–Ln(C1)]/(T2–T1),where C1and C2are cell number at time T1and T2,respectively.The number of cells within a de?ned area(grid of known area)was determined at three regions in the fruit cortex between the petal vascular trace and the epidermis,and the average cortex cell area was calculated using these data.

RNA EXTRACTION AND C DNA SYNTHESIS.RNA extraction from?ower(0DAFB)and fruit tissues was performed using the method described in Dash and Malladi(2012).One microgram of total RNA was used for cDNA synthesis after removal of genomic DNA with DNase(Promega Corp.,Madison,WI).The synthesis of cDNA was performed in a total volume of20m L, which was subsequently diluted by6-fold with autoclaved distilled water and stored at–20°C until further analysis.

Q UANTITATIVE RT-PCR.Quantitative RT-PCR analyses were performed using the Stratagene Mx3005P real-time

PCR system(Agilent Technologies,Santa Clara,CA).One microliter of the diluted cDNA was used in a?nal reaction volume of12m L.The Veriquest SYBR Green qPCR Master Mix(2·)was used in this analysis(Affymetrix,Santa Clara, CA).The PCR conditions involved the following cycles:50°C for2min,95°C for10min,and40cycles of95°C for30s and 60°C for1min.Melt curve analyses were performed at the end of these cycles.Controls without a template were used.On rare occasions,some of these negative controls displayed ampli?-cation at very late stages of the PCR program.Primer ef?ciency was determined using LinRegPCR(Ruijter et al.,2009).All gene expression was normalized to the expression of three reference genes,MdACTIN,MdGAPDH(glyceraldehyde3-phosphate dehydrogenase),and MdUBC2[ubiquitin conjugat-ing enzyme2(Han et al.,2008)].Gene expression was calculated from the Cq values using a method involving correction for ampli?cation ef?ciency(Pfaf?,2001).The relative quantities (1/E Cq,where E is the ef?ciency of a given gene and Cq is the cycle number where the threshold?uorescence level is crossed) was normalized using the geometric mean of the relative quantities of the three reference genes.Expression of a given gene in relation to its expression in the control fruit at0DAFB is presented here.Four biological replicates were used in this analysis.The SE of the expression of a gene was determined as described by Rieu and Powers(2009).Statistical analyses were performed on log2transformed normalized relative quantity values.

A list of the genes and primer sequences used in this analysis is presented in Table1.

C ARBOHYDRATE ANALYSIS.The carbohydrates,sorbitol,su-crose,fructose,and glucose,were extracted and analyzed as their trimethylsilyl(oxime;TMS)derivatives as described by Tisza et al.(1994).Three of the four replicates from the experiment were used for the carbohydrate analysis.Multiple fruit were pooled within a replicate.Approximately0.25g of the fruit tissue was extracted in1.5mL of80%methanol containing phenyl b-D-glucoside as an internal standard.For derivatization,100m L of the extract was heated at40°C and the solvent was evaporated to dryness under a stream of nitrogen. Carbohydrates were?rst converted to their oxime derivatives by adding25m L hydroxylamine(25mgámL–1in pyridine)and heated to75°C for30min.They were subsequently converted to their TMS derivatives by the addition of70m L of N,O-bis(trimethylsilyl)tri?uoroacetamide+1%trimethylchlorosi-lane.After cooling,the oxime-TMS derivatives of the sugars were analyzed using a gas chromatograph(5890Series II; Hewlett-Packard,Palo Alto,CA)equipped with a DB5column (30m;0.32mm inner diameter).Standards were prepared by dissolving known quantities of sorbitol,sucrose,fructose, glucose,and phenyl b-D-glucoside in80%methanol followed by derivatization as described previously.

S TATISTICAL ANALYSES.All statistical analyses were per-formed using SAS(Version9.2;SAS Institute,Cary,NC)and Sigmaplot11(Systat Software,San Jose,CA).Fruit diameter, cell number,cell area,RCPR,and gene expression data were analyzed using two-way analysis of variance(factors:reduction of fruit load and time after treatment)with repeated measures. Wherever the interactions between the factors were signi?cant, the simple effects were analyzed using test of effect slices(a= 0.05).The cell number and cell area data were transformed (square root and log,respectively)before analysis to meet the normality and equal variance assumptions.For carbohydrate accumulation data,Student’s t tests were performed on data at 21DAFB and28DAFB.Fruit weight data at maturity were analyzed using the Student’s t test.

Results

R EDUCTION IN FRUIT LOAD ENHANCES FRUIT GROWTH.Early fruit growth was enhanced in response to the reduction in fruit load(Fig.1).Fruit load reduction at11DAFB led to sig-ni?cantly larger fruit diameter by21DAFB,indicating a rapid response.Fruit size continued to be larger in the RFL treatment during subsequent stages of development.In comparison with the control,fruit in the RFL treatment had%15%greater fruit diameter at maturity.The?nal fruit weight of the control fruit was168.1±3.2g,whereas that of fruit under the RFL treatment was236.3±13.4g(P=0.003).

R EDUCTION OF FRUIT LOAD INCREASES SORBITOL AND FRUCTOSE CONCENTRATIONS AND ALTERS THE EXPRESSION OF GENES ASSOCIATED WITH CARBOHYDRATE METABOLISM.At21DAFB,

sorbitol and fructose concentrations were higher by2.2-and 1.6-fold,respectively,in fruit from the RFL treatment,whereas glucose and sucrose concentrations were not signi?cantly altered(Fig.2).At28DAFB,none of the carbohydrates an-alyzed was signi?cantly different between the control and the RFL treatments.The expression of MdSDH1,one of the genes that encodes for sorbitol dehydrogenase(Nosarzewski and Archbold,2007),an enzyme involved in the conversion of sorbitol to fructose,was2.2-fold higher in fruit from the RFL treatment at18DAFB but was generally lower than in the control fruit during the rest of fruit development(Fig.3).In comparison with fruit from the RFL treatment,MdSDH2 expression was higher in the control fruit at40DAFB(1.4-fold)and at maturity(2.7-fold).The expression of a gene coding for a neutral invertase[MdNINV3(Li et al.,2012)], involved in the conversion of sucrose to fructose and glucose, did not display an interaction among the factors,reduction of fruit load,and time after treatment.The expression of MdSUSY3,coding for a sucrose synthase involved in the conversion of sucrose to fructose and uridine diphosphate (UDP)–glucose(Li et al.,2012),was higher in fruit from the RFL treatment during early fruit development at18 DAFB(%2-fold)and28DAFB(%2.7-fold)but was lower than in the control fruit during the?nal stages of fruit development.

F RUIT LOAD REDUCTION INCREASES CELL PRODUCTION DURIN

G EARLY FRUIT DEVELOPMENT.Enhanced fruit growth during early development in response to the reduction in fruit load was primarily associated with an increase in cell production in the fruit cortex(Fig.4).Fruit from the RFL treatment displayed %6%higher cell number than the control fruit by10d after treatment(21DAFB)indicating a rapid increase in cell production as a result of the reduction in fruit load.Toward the end of the cell production phase(%28DAFB),fruit from the RFL treatment had33%greater cell number than the control fruit.Fruit from the RFL treatment displayed a higher RCPR between21and28DAFB by up to3.5-fold.Cell area within the fruit cortex was slightly greater in the control fruit in compar-ison with the fruit from the RFL treatment at40DAFB(8%). However,at maturity,fruit from the RFL treatment displayed %11%higher cell area than the control fruit.These data indicate that the reduction in fruit load enhanced early fruit growth primarily by increasing cell production and enhanced cell expansion at late stages of fruit development.

E XPRESSION O

F MdANT1,A TRANSCRIPTION FACTOR ASSOCIATED WITH THE REGULATION OF FRUIT GROWTH,IS ALTERED IN RESPONSE TO THE REDUCTION IN FRUIT LOAD.Effects of the reduction in fruit load on the expression of MdANT1,an AP2-domain transcription factor,and an auxin response factor (MdARF106)associated with the regulation of fruit growth

Table1.List of genes and the primer sequences used in quantitative RT-PCR analyses of gene expression in response to reduction of fruit load in apple.

Gene Accession no.z Primer sequence(5#to3#)y MdACTIN EB127077ACCATCTGCAACTCATCCGAACCT

ACAATGCTAGGGAACACGGCTCTT MdGAPDH EB146750TGAGGGCAAGCTGAAGGGTATCTT

TCAAGTCAACCACACGGGTACTGT MdUBC2EU586200CATTTTGAAAGAGCAGTGGAGCCCT

TTGCGGTTGTCTCGTACTTTGAACG MdSDH1MDP0000932467GAGTCTTGGCGCAGATGCAGT

ACAGTCGAAGGTTACATCCACTCCATT MdSDH2MDP0000874667CATTGCCAGCAGTGCAAAGGC

GGCAATTTAAAGCACAGATCCGCG MdNINV3MDP0000186866GTACTCCATGATCCTGTCCGGAATAGT

CATACCCTTCTGGCATTCAGGCAG MdSUSY3MDP0000126946GGAAAAGAATACTGCAGCCGCACG

GAACTTCGCTGAAAGGTCCGGT

MdANT1MDP0000175309CACCAAGGTGATCGAACCTAACATCCTG

CCAATGCCGTTGAGAAGGAAGGG MdARF106MDP0000232116GAGGGGAAGCCGTTTGAGGT

GCCGTCCAAAACACCTTCAAT

MdCDKB1;1CV085424CGATTGATCTGCGTCGAGCATGTT

CGGATTCGGCCCCTTCCG

MdCDKB1;2EB138473GATTGCTCTGCGTCGAACACGTC

CCCAGGATTCGGCCCCTTTCT

MdCDKB2;1CV129014GGTAACAGAGATGCGCTCTGTAGTAGT

GAGATTGTTGAGTTGTTGAATCCTATGGA MdCDKB2;2CV086331AGAGAAGCGCTCTGTACTACTGAAGTT

AAAGCTACTTGCAAATTGTAAACACCAC MdCYCA2;1CO416185CAATTGAACACCACCGGTTGTCC

ACTCGAAGCACCTGAATGGAGG MdCYCA2;2CO722204CAATTGAACACGACTGGTTGCCT

CCTCAAACTCAAAGTACCCGAATGCAAA MdCYCA2;3CO415585GCAAGAATTACAGTTGAACACTAGTGGTT

CCGGAAAGTGTACATGTCACAGTCTCT MdCYCB1;1CN579062AGACACTCAAGCTTCACACTGGTTTC

AGCAGTGCAACAGCTCCGTG

MdCYCB1;2CV084069GTTCTGGTAACCCTTCATTCGGCA

AGAAGAGCAACCGCGCTACG

MdCYCB2;2CV628904GTGAAGGAGGTTGGACCGAATC

CAGTATACGAGCTCAGTTTCTTAGCTTCC MdKRP4CV084380GCTTGCAGAATTCGGCGATGGAAC

CTCCTCCTCCGCCTCGGA

MdKRP5CN912198CCGTCGTCGTATGACGTGGC

GCCGTCGTTGGAAGTCCGT

MdCOB1MDP0000288732GCAATCATGGATCCAGGACCCAGA

GGGTCCATCTCCTTTTGTCCGAC MdCOBL4MDP0000895592CCCTGGCTGGACTCTCGG

ACGCCACCTTTGCAGCAATTAGAA MdEXPA8;1MDP0000138500CTTCAACCTACATCTGCATGGTGTG

TCAAAGCTGCAGTGTTGGTTCCATAT MdEXPA8;2MDP0000431696GGGTCTTGCTATGAGATGAAATGTGG

CACCATTGTCGTTGGCCTGC

MdEXPA10;1MDP0000681724GGGTGCGGATCTTGCTACG

GGAGGGCGTTGTTTGGTGGA

z Genbank accession numbers or accession numbers from the Apple Genome Database(Mach,2007)are presented.

y The forward(top)and reverse(bottom)primers are presented.

were investigated (Fig.5;Dash and Malladi,2012;Devoghalaere et al.,2012).In comparison with the control fruit,MdANT1expression was 2.9-and 5.4-fold higher in fruit from the RFL treatment at 21and 24DAFB,respectively,the period when differences in cell production and fruit growth were apparent.

MdANT1expression was also higher in fruit from the RFL treatment at 133DAFB,a period when its general expression was much lower than during early fruit development.MdARF106expression did not display a signi?cant interaction between the factors,reduction of fruit load and time after treatment.

A LTERED EXPRESSION OF CELL PRODUCTION AND EXPANSION -RELATED GENES IN RESPONSE TO THE REDUCTION IN FRUIT LOAD .The expression of multiple cell cycle genes,which are positive regulators of cell production (Malladi and Johnson,2011),increased in response to the RFL treatment during early stages of fruit growth,coincident with the period of increased cell production (Fig.6).Three of the four B-type cyclin-dependent kinase (CDK )genes (MdCDKB1;1,MdCDKB1;2,and MdCDKB2;2)displayed between 1.6-and 5-fold higher ex-pression in fruit from the RFL treatment at 28DAFB.The expression of two A2-type cyclins,MdCYCA2;1and MdCYCA2;3,was also enhanced in response to a reduction in fruit load by up to 4.4-and 4-fold,respectively,during

early

Fig.1.Effect of reduction of fruit load on fruit growth in apple.Fruit load reduction was performed at 11d after full bloom.Fruit diameter was measured from bloom until fruit maturity.Error bars indicate SE (n =4).Asterisks indicate a signi?cant difference between the control and the reduced fruit load (RFL)treatments (single asterisk:P #0.05;double asterisk:P #0.005;test of effect

slices).

Fig.2.Effect of reduction of fruit load on carbohydrate concentrations in the apple fruit.Reduction of fruit load was performed at 11d after full bloom.The concentration of carbohydrates was measured in fruit from the control and the reduced fruit load (RFL)treatments at 21and 28d after full bloom.Asterisk indicates a signi?cant difference between the control and the RFL treatments (P <0.05).Error bars indicate SE (n =

3).

Fig.3.Effect of reduction of fruit load on the expression of genes associated with carbohydrate metabolism in apple.Fruit load reduction was performed at 11d after full bloom (DAFB).All expression data were normalized to the expression of three reference genes.Expression of a gene relative to its expression at 0DAFB in the control fruit is presented.For each gene,the left panel displays expression during entire fruit development,whereas the right panel displays an expanded version of the data during early fruit growth.Error bars indicate SE (n =4).Asterisks indicate a signi?cant difference between the control and the reduced fruit load (RFL)treatments (single asterisk:P #0.05;double asterisk:P #0.005;test of effect slices).The factors,reduction in fruit load and time after treatment,did not display a signi?cant interaction in case of MdNINV3.

fruit growth (21to 28DAFB).The expression of a B1-type cyclin,MdCYCB1;1,was higher at 28DAFB by 1.7-fold,whereas that of a B2-type cyclin,MdCYCB2;2,was %2-and 3-fold higher in fruit from the RFL treatment at 28and 54DAFB,respectively.Many of these genes also displayed higher expression in fruit from the RFL treatment at 133DAFB,a period when their expression was generally much lower than during early fruit development.The expression of MdKRP4(kip-related protein4),a negative regulator of cell production,was %3-fold higher in fruit from the RFL treatment at 133DAFB.The expression of MdKRP5was reduced by 1.6-fold at 24DAFB in response to the RFL treatment but was enhanced at 18(1.8-fold)and 28DAFB (2.1-fold).

The effect of reduced fruit load on the expression of several genes potentially associated with cell expansion was investi-gated.The cobra (COB )and cobra-like (COBL )genes encode glycosylphosphatidylinositol (GPI)-anchored proteins.COB genes are associated with cellulose synthesis and directional cell expansion (Roudier et al.,2005;Schindelman et al.,2001),and COBL genes are associated with cellulose deposition during secondary wall synthesis (Brown et al.,2005;Ching et al.,2006;Li et al.,2003).In tomato,two putative cobra-like genes are present within a quantitative trait locus (fw3.2)associated with the control of fruit weight (Zhang et al.,2012).The a –type expansin genes encode for proteins putatively associated with cell wall loosening (Cho and Cosgrove,2000;Sampedro and Cosgrove,2005).Reduction in fruit load de-creased MdCOB1expression by 1.7-to 2.3-fold at 24and 28DAFB (Fig.7).In contrast,the expression of MdCOBL4was up to 2.5-fold higher in fruit from the RFL treatment during early fruit development (24and 28DAFB).The expression of MdEXPA8;1was enhanced by the RFL treatment at 18DAFB (2.4-fold)but was subsequently reduced by up to 2.7-fold (21,24,and 28DAFB).MdEXPA8;2expression was higher in fruit from the RFL treatment by up to 2.2-fold during midfruit development (28and 40DAFB).MdEXPA8;1and MdEXPA8;2also displayed lower expression before maturity and higher expression at maturity in fruit from the RFL treatment.Expression of MdEXPA10;1was higher in fruit from the RFL treatment during most of fruit development by up to 4.9-fold.

Discussion

Reduction of fruit load performed at 11DAFB,during a period of initiation of intensive growth (Dash and Malladi,2012;Malladi and Hirst,2010;Malladi and Johnson,2011),resulted in a rapid increase in fruit growth by 10d after treatment and led to an increase in ?nal fruit size.These data are consistent with previous studies in apple and other fruits in which fruit load reduction enhanced fruit growth and ?nal fruit size (Bertin,2005;Dash and Malladi,2012;Gof?net et al.,1995;Morandi et al.,2008;Prudent et al.,2010).An increase in fruit growth in response to a reduction of fruit load has been shown previously to be associated with an increase in cell production in apple and other fruits (Dash and Malladi,2012;Denne,1960;Gof?net et al.,1995;Prudent et al.,2010).In the current study,increase in cell number within the fruit cortex was observed within 10d (21DAFB)after the reduction in

fruit

Fig.4.Effects of fruit load reduction on cell production and expansion in the apple fruit.Fruit load reduction was performed at 11d after full bloom.Number of cell layers in the fruit cortex,the relative cell production rate (RCPR),and the cortex cell area were determined in fruit from the control and the reduced fruit load (RFL)treatments.Error bars indicate SE (n =4).Asterisks indicate a signi?cant difference between the control and the RFL treatments (single asterisk:P #0.05;double asterisk:P #0.005;test of effect

slices).

Fig.5.Effect of a reduction of fruit load on the expression of key transcription factors associated with apple fruit growth.Reduction of fruit load was performed at 11d after full bloom (DAFB).The expression data were normalized to the expression of three reference genes.The expression of a gene in relation to its expression in the control fruit at 0DAFB is presented.For each gene,the left panel displays expression during entire fruit de-velopment and the right panel displays an expanded version of the expression data during early fruit development.Error bars indicate SE (n =4).Asterisks indicate a signi?cant difference between the control and reduced fruit load (RFL)treatments (single asterisk:P #0.05;double asterisk:P #0.005;test of effect slices).The factors,reduction of fruit load and time after treatment,did not display a signi?cant interaction for MdARF106.

load and was associated with higher RCPR until %28DAFB,indicating greater cell production during early fruit growth.This was the primary mechanism that contributed to the increase in early fruit growth.An increase in cell production may either be a result of a higher rate of cell division within proliferating cells or an increase in the proportion of pro-liferating cells in the fruit cortex.The former suggests that carbohydrate limitation during early fruit growth affects the rate of progression of proliferating cells through the mitotic cell cycle,while the latter suggests that it affects the timing of exit of the proliferating cells from the mitotic cell cycle.Further work is required to distinguish between these possibilities.

Reduction of fruit load affects the metabolite composition of fruits and these effects are dependent on the stage of fruit development (Do et al.,2010;Morandi et al.,2008;Prudent et al.,2010).In the current study,enhancement of fruit growth in response to the reduction in fruit load was associated with a transient increase in the concentrations of two key carbohy-drates during early fruit growth.Sorbitol concentrations in the fruit were rapidly increased in response to the RFL treatment by over 2-fold by 10d after treatment,suggesting that a reduction in fruit load resulted in greater partitioning of the available carbohydrates to the remaining fruit.A transient increase in MdSDH1expression was observed at 18DAFB.If an increase in sorbitol in?ux was already initiated by 18DAFB,it may trigger an increase in sorbitol de-hydrogenase levels to facilitate its conversion to fructose (Archbold,1999).This is supported by the in-crease in fructose concentration in response to the reduction in fruit load at 21DAFB by 1.6-fold.In fact,substantial sorbitol dehydroge-nase activity has been previously reported during early fruit develop-ment in apple (Nosarzewski et al.,2004).MdSDH1expression was higher in the control fruit at later stages.This may re?ect a require-ment for higher metabolism of the available sorbitol in the control fruit to meet the requirements for growth.The higher concentration of fruc-tose observed at 21DAFB may also be a result of enhanced sucrose metabolism.Sucrose imported into the fruit may be converted to fruc-tose and glucose by invertases or to fructose and UDP-glucose by sucrose synthase (Li et al.,2012).The expression of MdSUSY3,one of three potentially important SUSY genes associated with sucrose me-tabolism in the apple fruit (Li et al.,2012),was generally higher in the

RFL treatment during early fruit development.If the reduction in fruit load also increased sucrose in?ux (in addition to sorbitol)into the fruit,it may be rapidly converted by sucrose synthase,thereby con-tributing to an increase in fructose

concentration.At a relatively later stage of fruit development (28DAFB),no difference in sorbitol and fructose concentra-tions was observed,indicating that the increase in carbohydrate concentrations was transient and that they were rapidly metab-olized to meet the demands of increased fruit growth.Similarly in tomato,carbohydrate concentrations in response to a re-duction of fruit load varied during different stages of fruit development (Baldet et al.,2006;Fanwoua et al.,2012;Prudent et al.,2010).Carbohydrate availability affects cell proliferation (Baldet et al.,2002,2006;Joubes et al.,2000;Kwon and Wang,2011;

Riou-Khamlichi et al.,2000).In this study,the rapid increase in carbohydrate concentrations and their subsequent metabolism during early fruit development may promote cell production and thereby increase fruit growth.Carbohydrates may facilitate this process by providing the required energy through respira-tion to support the intensive demands of cell production.Also,carbohydrates may act more directly as signals that regulate the expression of genes,thereby promoting cell proliferation during early fruit growth.For example,sucrose regulates the expression of several cell cycle genes (Baldet et al.,2002,2006;Joubes et al.,2000;Kwon and Wang,2011;Riou-Khamlichi et al.,2000).The expression of multiple genes associated with cell pro-liferation was affected by the reduction in fruit load.The AP2-domain transcription factor,MdANT1,may modulate

fruit

Fig.6.Effect of a reduction in the fruit load on the expression of core cell cycle genes associated with cell production in the apple fruit.Fruit load reduction was performed at 11d after full bloom (DAFB).All expression data were normalized to the expression of three reference genes.Expression of a gene relative to its expression in control fruit at 0DAFB is presented.Error bars indicate SE (n =4).Asterisks indicate a signi?cant difference

between the control and the reduced fruit load (RFL)treatments (single asterisk:P #0.05;double asterisk:P #

0.005;test of effect slices).MdCDKB1;2expression was not detectable in the RFL treatment at 154DAFB.

growth by regulating cell production during apple fruit de-velopment (Dash and Malladi,2012).Expression of MdANT1was enhanced by up to 5-fold in response to increased carbohydrate availability during early fruit development (21to 24DAFB).These data are consistent with a previous study in which MdANT1expression was found to be higher under reduced fruit load conditions (Dash and Malladi,2012).Also,the expression of MdANT1was reduced in response to shading (M.Dash,L.K.Johnson,and A.Malladi,unpublished results),a treatment that reduces carbohydrate availability and fruit growth in apple (Dash et al.,2012).These data suggest that the availability of carbohydrates during early fruit development regulates MdANT1expression as a rapid and primary response.MdANT1may subsequently modulate the expression of downstream target genes associated with cell production,thereby leading to an increase in fruit growth.Cell cycle genes may potentially constitute such target genes of MdANT1.In fact,ANT and ANT-LIKE proteins are known to affect the expression of D3-type cyclins (Karlberg et al.,2011;Mizukami and Fischer,2000).

Increase in carbohydrate availability during early fruit growth was associated with coordinated changes in the expres-sion of cell cycle genes.The expression of seven genes,MdCDKB1;1,MdCDKB1;2,MdCDKB1;2,MdCYCA2;1,MdCYCA2;3,MdCYCB1;1,and MdCYCB2;2,was enhanced by the reduction in fruit load by 1.6-to 5-fold during the period of increased cell production.A2-type cyclins facilitate the progression of the cell through the G2/M phase of the cell cycle through their interaction with CDKBs (Boudolf et al.,2009).Similarly,B-type cyclins regulate the progression of the cell through the G2/M phase of the cell cycle (Inze and De Veylder,2006).These genes have been previously shown to be posi-tively associated with cell production during apple fruit growth (Malladi and Johnson,2011).These data suggest that co-ordinated increase in the expression of these cell cycle genes,in response to the reduction in fruit load,facilitates an increase in cell production.Similarly,a decrease in cell production and fruit growth in response to shading in apple fruit was associated with the altered expression of several cell cycle genes,in-cluding two A2-type cyclins (Dash et al.,2012).Together,these studies suggest that carbohydrate availability affects cell pro-duction during early apple fruit growth by altering the expres-sion of key cell cycle genes associated with the progression of cell proliferation.In tomato,reduction of fruit load before anthesis was associated with an increase in the expression of several cell cycle genes including a B-type CDK and a B2-type cyclin during ?ower development (Baldet et al.,2006).Also,carbohydrate limitation imposed through prolonged exposure to darkness decreased the expression of several cell cycle genes in tomato fruit,especially during early fruit development (Baldet et al.,2002).Hence,data from the current study,along with previous studies in other fruits,suggest that carbohydrate availability during early fruit growth affects cell proliferation by regulating the expression of genes associated with this process,thereby modulating fruit growth.

Although cell expansion was largely unaffected by the reduction in fruit load,fruit from the RFL treatment displayed slightly larger cell size at maturity.These data are consistent with a previous study with the same genotype,in which a similar increase in cell size was observed during late stages of development under reduced fruit load conditions (Dash and Malladi,2012),but not with a study on a different apple genotype,‘Empire’(Gof?net et al.,1995).The effect of fruit load reduction on cell expansion and ?nal cell size has been suggested to be genotype-dependent in tomato because it enhanced ?nal cell size in the genotype ‘Moneyberg’but not in C9d (Prudent et al.,2010).Similarly in apple,the effects of fruit load reduction on cell expansion may be genotype-dependent.Alteration of carbohydrate availability during early fruit growth can in?uence metabolite accumulation at sub-sequent stages of fruit development (Do et al.,2010).Such changes in metabolite accumulation at later stages of apple fruit development may allow for greater cell expansion.

Expression of several genes associated with cell expansion was altered by a reduction in fruit load and increased carbohy-drate availability,although such changes were not

consistently

Fig.7.Effect of a reduction in the fruit load on the expression of genes associated with cell expansion in the apple fruit.Reduction of fruit load was performed at 11d after full bloom (DAFB).The expression data were normalized to the expression of three reference genes.Expression of a gene relative to its expression at 0DAFB in the control fruit is presented.For each gene,the left panel displays data during entire fruit development,whereas the right panel displays an expanded version of the data during early fruit development.Error bars indicate SE (n =4).Asterisks indicate a signi?cant difference between the control and reduced fruit load (RFL)treatments (single asterisk:P #0.05;double asterisk:P #0.005;test of effect slices).

associated with differences in cell expansion during fruit growth.MdCOB1expression was reduced in fruit from the RFL treatment during the period when cell production was enhanced.Similarly,MdEXPA8;1displayed higher expression in the control fruit during early fruit growth(21to24DAFB).It may be likely that the developmental increase in the expression of MdCOB1and MdEXPA8;1facilitates post-mitotic cell expansion,thereby contributing to fruit growth.Higher expres-sion of these genes may be re?ective of the onset and pro-gression of post-mitotic cell expansion in the control fruit during a period when fruit from the RFL treatment display higher cell production.In fact,control fruit had slightly larger cell size at40DAFB,after the period when these genes displayed higher expression in these fruit.Conversely,the expression of MdCOBL4,MdEXPA8;2,and MdEXPA10;1was enhanced during early fruit growth in response to increased carbohydrate availability.It may be likely that these genes facilitate cell wall synthesis and maintenance associated with increased cell production during this period,roles that require further investigation.The increase in cell size at?nal stages of development in fruit from the RFL treatment was associated with enhanced expression of the three expansins studied here, suggesting their involvement in facilitating this increase in response to potential changes in metabolite composition during fruit development.

A model is proposed to explain changes in apple fruit growth in response to carbohydrate availability during early develop-ment.Availability of carbohydrates such as sorbitol and fructose may directly(as signals)or indirectly(through their metabolism)regulate the expression of key transcription factors associated with fruit growth such as MdANT1.Such transcrip-tion factors may subsequently alter the expression of facilitators of cell production such as the core cell cycle genes,thereby altering the competence for cell production and modulating early fruit growth.Furthermore,changes in the availability of carbohydrates during early fruit growth may alter the fruit metabolome at subsequent stages of development and thereby regulate cell expansion during the?nal stages of development. Transcriptome and metabolite analyses in response to altered carbohydrate availability during fruit development,particularly during the period of active cell production,may provide further insights into the molecular networks that facilitate?eshy fruit growth.

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(易错题精选)初中英语词汇辨析的单元汇编含答案解析

一、选择题 1．I’d like to________the mall because it’s crowded and noisy. A．visit B．hang out C．walk D．go off 2．That path ________ directly to my house.You won't miss it. A．leads B．forms C．repairs D．controls 3．I don’t want to go. __________, I am too tired. A．However B．And C．Besides D．But 4．Some animals carry seeds from one place to another, ________ plants can spread to new places. A．so B．or C．but D．for 5．When I as well as my cousins __________ as a volunteer in Beijing, I saw the Water Cube twice. A．were treated B．treated C．was served D．served 6．He is wearing his sunglasses to himself from the strong sunlight. A．prevent B．stop C．keep D．protect 7．When you are________, you should listen to music to cheer you up. A．shy B．afraid C．strict D．down 8．Mr. Smith gave us some________on how to improve our speaking skills. A．advice B．news C．knowledge D．information 9．World Book Day takes place ________ April 23rd every year. A．at B．in C．on 10．More and more people have realized that clear waters and green mountains are as ________ as mountain of gold and silver. A．central B．harmful C．valuable D．careful 11．We loved the food so much, ________the fish dishes. A．special B．especial C．specially D．especially 12．—Oh, my God! I have ________ five pounds after the Spring Festival. —All of the girls want to lose weight, but easier said than done. A．given up B．put on C．got on D．grown up 13．—What do you think of the performance today? —Great! ________ but a musical genius could perform so successfully. A．All B．None C．Anybody D．Everybody 14．He ________ his homework________the morning of Sunday. A．doesn’t do; on B．doesn’t do; in C．doesn’t; on 15．Maria ________ speaks Chinese because she doesn’t know much Chinese. A．seldom B．always C．often D．usually 16．In 2018, trade between China and Hungary rose by 7.5 percent, and recently on Friday companies from China and Hungary________ several cooperation (合作) agreements under the

人教版初一英语现在进行时

现在进行时 撰稿：王红艳审稿：白雪雁 【概念引入】 I. 什么是现在进行时？ 1）现在进行时表示说话时正在进行或发生的动作。 例如：I am reading a book. 我正在看书。 2）表示现阶段正在进行而说话时不一定在进行的动作。 例如：I am learning English hard these days. 这些日子我正在努力学习英语。 II. 现在进行时的标志词。 现在进行时常和now、at the moment、look、listen等连用。 【用法讲解】 I.现在进行时的结构。 现在进行时的结构是：助动词be（am，is，are）＋现在分词v-ing 现在分词的构成： 1）动词的后面直接加－ing。例如：work－working，study－studying 2）以不发音的字母e结尾的动词，先去掉字母e，再加－ing。例如：live－living 3）以重读闭音节结尾并且只有一个辅音字母的动词，先双写这个辅音字母，再加－ing。 例如：stop－stopping，swim－swimming，run－running II. 现在进行时的用法。 1）现在进行时表示说话的时候正在进行的动作，经常和now，right now，at the moment 等时间状语或者动词look，listen等连用。 例如：My father is watching TV now.我爸爸现在在看电视。 Look! My brother is playing basketball there. 看！我弟弟正在那里打篮球。 2）现在进行时可以表示目前一段时间内一直进行的动作，经常和these days，this week，at present等时间状语连用。 例如：My parents are working on a farm these days. 这些天我的父母在农场干活。 3）现在进行时还可以表示现在不断发展变化的事情，表示不断发展变化的动词有get，grow，turn，become等。 例如：The leaves are turning yellow. 树叶在变黄。 4）现在进行时还可以表示将要发生的动作，只限于动词arrive，begin，go，come，leave，fly等动词。 例如：I am coming soon. 我马上来。 Ⅲ. 现在进行时的句式变化。 肯定句式：主语+be( am, is, are)+现在分词+其它. 否定句式：主语+be(am, is, are) +not +现在分词+其它. 一般疑问句：Be(am, is, are) +主语+现在分词+其它？ 特殊疑问句：疑问词+be(am, is, are)+主语+现在分词+其它？ 对现在进行时的特殊疑问句的回答，它不可以用Yes或No直接作答，要根据实际情况回答。 Ⅳ. 现在进行时的特殊用法。 表示位置移动的动词，如：leave/ come/go/begin等用于现在进行时，表示按计划或安排近期将要进行的动作，常与表示将来的时间状语连用。 —Can you help me? 你能帮我吗？

检波器设计(完整版)概要

职业技术学院学生课程设计报告 课程名称：高频电路课程设计 专业班级：信工102 姓名： 学号：20110311202 学期：大三第一学期

目录 1课程设计题目……………………………………………2课程设计目的…………………………………………3课程设计题目描述和要求……………………………4课程设计报告内容……………………………………… 4.1二极管包络检波电路的设计……………………… 4.2同步检波器的设计……………………………5结论……………………………………………………6结束语………………………………………………………7参考书目……………………………………………………8附录………………………………………………………

摘要 振幅调制信号的解调过程称为检波。有载波振幅调制信号的包络直接 反映调制信号的变化规律，可以用二极管包络检波的方法进行检波。而抑 制载波的双边带或单边带振幅调制信号的包络不能直接反映调制信号的变 换规律，无法用包络检波进行解调，所以要采用同步检波方法。 同步检波器主要是用于对DSB和SSB信号进行解调（当然也可以用于AM）。它的特点是必须加一个与载波同频同相的恢复载波信号。外加载波信 号电压加入同步检波器的方法有两种。利用模拟乘法器的相乘原理，实现 （t）,和输入的同步 同步检波是很简单的，利用抑制载波的双边带信号V s （t），经过乘法器相乘，可得输出信号，实现了双 信号（即载波信号）V c 边带信号解调 课程设计作为高频电子线路课程的重要组成部分，目的是一方面使我们能够进一步理解课程内容，基本掌握数字系统设计和调试的方法，增加集成电路应用知识，培养我们的实际动手能力以及分析、解决问题的能力。 另一方面也可使我们更好地巩固和加深对基础知识的理解，学会设计中小型高频电子线路的方法，独立完成调试过程，增强我们理论联系实际的能力，提高电路分析和设计能力。通过实践引导我们在理论指导下有所创新，为专业课的学习和日后工程实践奠定基础。 通过设计，一方面可以加深我们的理论知识，另一方面也可以提高我们考虑问题的全面性，将理论知识上升到一个实践的阶段。

(工作分析)计数器工作原理的模式化分析

（工作分析）计数器工作原理的模式化分析

计数器工作原理的模式化分析 时序逻辑电路是《脉冲和数字电路》这门课程的重要组成部分，计数器是时序逻辑电路基础知识的实际应用，其应用领域非常广泛。计数器原理是技工学校电工电子专业学生必须重点掌握的内容，也是本课程的考核重点，更是设计计数器或其他电子器件的基础。 但近年来技校学生的文化理论基础和理解能力普遍较差，按照课件体系讲授计数器这个章节的知识，超过70%的学生听不懂。 我先后为四届学生讲授过这门课，于教学实践中摸索出壹套分析计数器的方法——模式化分析，即把分析步骤模式化，引导学生按部就班地分析计数器。用这种方法分析，我只要以其中壹种计数器（如异步二进制计数器）为例讲解，学生便能够自行分析其他计数器。 教学实践证明，用这种方法讲授计数器知识，学生比较感兴趣，觉得条理清晰，易于理解，掌握起来比较轻松。这种方法仍有壹个好处，不管是同步计数器仍是异步计数器，不管是二进制计数器仍是十进制计数器，不管是简单的计数器仍是复杂的计数器，只要套用这种方法，计数器工作原理迎刃而解。即使是平时基础很差的学生，只要记住几个步骤，依葫芦画瓢，也能把计数器原理分析出个大概来。 一、明确计数器概念 分析计数器当然要先清楚什么是计数器啦。书上的概念是：

计数器是数字系统中能累计输入脉冲个数的数字电路。我告诉学生，计数器就是这样壹种电子设备：把它放于教室门口，每个进入教室的同学均于壹个按钮上按壹下，它就能告诉你壹共有多少位同学进入教室。其中，每个同学按壹下按钮就是给这个设备壹个输入信号，N个同学就给了N个信号，这N个信号就构成计数器的输入CP脉冲，计数器要统计的就是这个CP脉冲系列的个数。当然，如果没有接译码器，计数器的输出端显示的是二进制数而非十进制数，比如有9位同学进入教室，它不显示“9”，而是显示“1001”。 随后，我简要介绍了计数器的构成和分类，且强调，计数器工作前必须先复位，即每个触发器的输出端均置零。 二、回顾基础知识 分析计数器要用到触发器的关联知识，其中JK触发器最常用，偶尔用到T触发器和D触发器。因此，介绍完计数器概念后，我不急于教学生分析其原理，而是先提问JK、T、D触发器的关联知识，包括触发器的逻辑符号、特性方程、特性表等。 由于计数器的控制单元由逻辑门电路构成，分析前仍要简要回顾壹下和、或、非等常用逻辑门电路的关联知识。另外，用模式化方法分析计数器仍要用到逻辑代数的运算方法、逻辑函数的化简方法等关联知识。 三、画出解题模板 准备工作做完了，下面进入核心部分——列出分析计数器的

boring 令人厌烦的

boring 令人厌烦的，乏味的，无聊的 tedious 乏味的，单调的，冗长的 flat 单调的，沉闷的 dull 乏味的，单调的 troublesome 令人烦恼的，讨厌的，麻烦的 tired 疲劳的，累的 bored 无聊的，无趣的，烦人的 exhausted 极其疲倦的 weary 疲劳的 bright 聪敏的，机灵的 apt 聪明的，反应敏捷的 intelligent 聪明的，有才智的 shrewd 机灵的，敏锐的，精明的（表示生意上的精明） ingenious （人，头脑）灵巧的 alert 警觉的，留神的 cute 聪明伶俐的，精明的 acute/cute acute 指的是视力，感觉的敏锐 dull 愚钝的，笨的 awkward 笨拙的，不灵巧的 absurd 荒谬的 ridiculous 可笑的，荒谬的 idiotic 白痴般的 blunt 率直的，直言不讳的 clumsy 笨拙的，粗陋的 happy 快乐的，幸福的 cheerful 欢乐的，高兴的 content 满意的，满足的 merry 欢乐的，愉快的，快乐的 pleasure 高兴，愉快，满足 enjoyment 享乐，快乐，乐趣 cheer 喝彩 applause 鼓掌，掌声 optimism 乐观，乐观主义 delight 快乐，高兴 kick 极大的乐趣 paradise 天堂，乐园 instant 立即的，即刻的 instantaneous 瞬间的，即刻的 immediate 立即的，即刻的 simultaneous 同时发生的，同时存在的，同步的punctual 严守时刻的，准时的，正点的 pick 挑选，选择 select 选择，挑选 single 选出，挑出 elect 选举，推举 vote 投票，选举 appoint 任命，委派 nominate 提名，任命 propose 提名，推荐 recommend 推荐，举荐 designate 指派，委任 delegate 委派（或选举）…为代表 install(l) 使就职，任命 ballot 使投票表决 dub 把…称为 choice 选择（权） option 选择 selection 选择，挑选 alternative 取舍，供选择的东西 favorite 特别喜爱的人（或物） inclination 爱好 preference 喜爱，偏爱，优先 observe 注意到，察觉到 perceive 认识到，意识到，理解 detect 察觉，发现 appreciate （充分）意识到，领会，体会 alert 使认识到，使意识到 awake 意识到，醒，觉醒 scent 察觉 ancient 古代的，古老的 primitive 原始的 preliminary 预备的，初步的 preliminary trial初审 primary 最初的，初级的 initial 开始的，最初的 original 起初的 former 在前的，以前的 previous 先，前 prior 在前的，优先的 beforehand 预先，事先 medieval 中世纪的，中古（时代）的preceding 在先的，在前的，前面的 senior 资格较老的，地位较高的 following 接着的，下述的 attendant 伴随的 subsequent 随后的，后来的 succeeding 以后的，随后的 consequent 作为结果（或后果）的，随之发生的 resultant 作为结果的，因而发生的therefore 因此，所以 consequently 所以，因此 then 那么，因而 thus 因此，从而 hence 因此，所以 accordingly 因此，所以，于是 thereby 因此，从而

现在进行时特殊用法展现

现在进行时特殊用法展现 现在进行时表示说话时正在进行的动作，这是我们平时接触最多的。然而除此以外，现在进行时还有以下几种用法。 1．表示“在做某事的过程中”，此时动作不一定正在发生。例如： Next I'll give you a few minutes to read the article．When you are reading，make a mark where there is a new word．现在我给你们几分钟时间读一下这篇文章。在读的过程中，在有生词的地方作以标记。 2．表示按计划、方案或安排而进行的将来的动作。在这种情况下谓语动词多为非延续性动词，如come，go， leave，move，die，start，stop，arrive等，及少数延续性动词，如spend，stay等。例如： She is leaving for Guangzhou next week．她下星期就要去广州了。 We are spending the whole summer holiday inBeijing soon．不久我们要在北京度过整个暑假。 Where are you staying in Guangzhou？在广州你打算住什么地方？ 3．与副词forever，always，constantly等连用，表示赞成、厌烦、生气等情绪。例如： She is always talking loudly in our class．她总是在我们班上吵吵嚷嚷的。（表示厌烦） She's constantly changing her mind．她老是改变主意。（表示不以为然） He is forever complaining about his job．他总是对他的工作提出抱怨。（表示厌烦） 4．teach，work，live，study等表示状态的动词使用现在进行时可表状况，与一般现在时区别不大。例如： I'm studying in No．1Middle School．我在一中学习。（相当于：I study in No．1Middle School．） My brother is working in a big factory．我哥哥在一家大工厂工作。（相当于：My brother works in a big factory．） 5．表示目前经常发生的动作，然而此时动作不一定正在进行之中。例如：

仪器原理

1.侧向测井（电流聚焦测井）采用电屏蔽方法，使主电流聚焦后水平流入地层，减小井眼和围岩影响。主电流线沿井轴径向成饼状流入地层。 2.理想的侧向测井组合是双侧向加微球形聚焦，可较准确地确定地层电阻率、冲洗带电阻率和侵入带直径，是计算地层含油饱和度、判断地层含油性的重要参数。 3.侧向测井电极系的主电极A0位于电极系中心，两端有屏蔽电极A1、A2，呈对称排列。 七侧向电极系主电极A0，屏蔽电极A1、A2，两对监督电极M1N1和M2N2；Um1＝Un1或Um2＝Un2，使主电流沿水平方向流入地层。 七侧向四个参数：①电极系长度: 210A A L =影响侧向测井的径向探测深度。电极系长度越大，探测越深；②电极距：21O O L =影响纵向分辨率。L 越小纵向分层能力越强。③分布比：L L s /0=影响电流层的形状，一般取s 为3左右较适宜。④聚焦系数：L L L q /)0(-= 1-=s q 影响电流层的形状。 双侧向电极系由9个电极组成，第二屏蔽电极A1’、A2’有着双重的作用。 4. 如何保证屏流和主电流同极性？ 用同一电流源供给屏流和主电流。屏流大于主电流，在测井过程中屏流是浮动的。所以，屏流要由平衡放大电路输出的信号加以调制后通过功率放大后加到屏蔽电极上；二是用跟踪主电流来产生屏流，或用跟踪屏流来产生主电流，这种方式用在双侧向仪器中。 5.双侧向测井仪器中，增加屏蔽电极的长度可以加大聚焦能力，而增加仪器探测深度。相反，在屏蔽电极两端设置回流电极，可使主电极和屏流流入地层的深度变浅，降低探测深度。 6.侧向测井仪器工作方式：恒流式（高阻地层），恒压式（低阻地层），自由式（1229、JSC801）和恒功率式（DLT-E ）。 恒流式：保持主电流恒定，测量主电极（通常用监督电极M1或M2代替）至远处电极N 之间的电位差U 。地层的电阻率越高测量电压信号越大，测量误差越小。 恒压式：保持主电极电位恒定，测量主电流。地层的电阻率越低测量电流信号越大，测量误差越小。 自由式：电流和电压按一定规律浮动，同时测量电流、电压两个量，可以得到较宽的测量动态范围。 恒功率式或可控功率式：测量过程中使最高和最低电阻率的两个极点保持功率（IU 乘积）不变，让测量电压和电流保持在仪器可测量的范围之内（不被限幅）。比自由式仪器有更宽的测量动态范围。 7.1229双侧向测井仪采用屏流主动式供电，即先有屏流后又主电流，用屏流来激励产生主电流。工作方式为自由式，为提高仪器测量动态范围用U2D 来控制深、浅屏流、屏压的变化幅度在于此。 频分双侧向供电式，fS = 4fD ，深、浅侧向供电频率分别为32Hz 和128Hz 。使深、浅侧向两个系统相对独立地控制和测量。

计数器原理分析及应用实例

计数器原理分析及应用实例 除了计数功能外，计数器产品还有一些附加功能，如异步复位、预置数（注意，有同步预置数和异步预置数两种。前者受时钟脉冲控制，后者不受时钟脉冲控制）、保持（注意，有保持进位和不保持进位两种）。虽然计数器产品一般只有二进制和十进制两种，有了这些附加功能，我们就可以方便地用我们可以得到的计数器来构成任意进制的计数器。下面我们举两个例子。在这两个例子中，我们分别用同步十进制加法计数器74LS160构成一个六进制计数器和一个一百进制计数器。 因为六进制计数器的有效状态有六个，而十进制计数器的有效状态有十个，所以用十进制计数器构成六进制计数器时，我们只需保留十进制计数器的六个状态即可。74LS160的十个有效状态是BCD编码的，即0000、0001、0010、0011、0100、0101、0110、0111、1000、1001[图5-1]。 图5-1 我们保留哪六个状态呢？理论上，我们保留哪六个状态都行。然而，为了使电路最简单，保留哪六个状态还是有一点讲究的。一般情况下，我们总是保留0000和1001两个状态。因为74LS160从1001变化到0000时，将在进位输出端产生一个进位脉冲，所以我们保留了0000和1001这两个状态后，我们就可以利用74LS160的进位输出端作为六进制计数器的进位输出端了。于是，六进制计数器的状态循环可以是0000、0001、0010、0011、0100和1001，也可以是0000、0101、0110、0111、1000和1001。我们不妨采用0000、0001、0010、0011、0100

和1001这六个状态。 如何让74LS160从0100状态跳到1001状态呢？我们用一个混合逻辑与非门构成一个译码器[图5.3.37b]，当74LS160的状态为0100时，与非门输出低电平，这个低电平使74LS160工作在预置数状态，当下一个时钟脉冲到来时，由于等于1001，74LS160就会预置成1001，从而我们实现了状态跳跃。 图5.3.37b用置数法将74160接成六进制计数器（置入1001） 比这个方案稍微繁琐一点的是利用74LS160的异步复位端。下面这个电路中[图5.3.34]，也有一个由混合逻辑与非门构成的译码器。 图5.3.34用置零法将74LS160接成六进制计数器

板框压滤机的工作原理

板框压滤机的工作原理 板框压滤机是由交替排列的滤板和滤框共同构成一组滤室。在滤板的表面有沟槽构造，它凸出部位是用来支撑滤布的。滤框和滤板的边角上各有通孔，组装以后可以构成一个完整的通道，能够通入洗涤水、悬浮液和引出滤液来。板和框的两侧各有把手支托在横梁的上面，由压紧装置压紧板、框。板、框之间的滤布起到密封垫片的作用。由供料泵将悬浮液压入滤室，在滤布的上面形成滤渣，直至充满了滤室。 滤液穿过滤布并沿滤板沟槽流至板框边角通道，集中排出。过滤完毕之后，可以通入清洗涤水洗涤滤渣。洗涤后，有时还通入压缩空气，除去剩余的洗涤液。随后打开压滤机卸除滤渣，清洗滤布，重新压紧板、框，开始下一工作循环。 板框压滤机主要由压紧板(活动滤板)、止推板(固定滤板)、过滤介质(滤布或滤纸等)、滤板和滤框、横梁(扁铁架)、压紧装置、集液槽等组成(参见附图)，其中的过滤介质和集液槽上由用户自备，当然也可以由上海大张过滤设备代配。 板框压滤机对于滤渣压缩性大或近于不可压缩的悬浮液都能适用。适合的悬浮液的固体颗粒浓度一般为10%以下，操作压力一般为0.3～0.6兆帕，特殊的可达3兆帕或更高。过滤面积可以随所用的板框数目增减。板框通常为正方形，滤框的内边长为 320～2000毫米，框厚为16～80毫米，过滤面积为1～1200米2。板与框用手动螺旋、电动螺旋和液压等方式压紧。板和框用木材、铸铁、铸钢、不锈钢、聚丙烯和橡胶等材料制造。 板框压滤机共有手动压紧、机械压紧和液压压紧三种形式。 手动压紧是螺旋千斤顶推动压紧板压紧；机械压紧是电动机配H型减速箱，经机架传动部件推动压紧板压紧；液压压紧是有液压站经机架上的液压缸部件推动压紧板压紧。

boring 和bored的区别

不能片面说人做主语用ed，物做主语ing ing形式是修饰引起这种感觉的人或物；ed形式是描写人或物的感受。（当然物一般是动物） 翻译的话 ing形式的词译为“令人……的”；ed形式译为“……的” boring是令人感到厌烦的；bored是厌烦的。 a boring person 能够指一个了无情趣的人，让人觉得无趣的人 a bored person 则是说这个人自己感到很无趣 1.bore 1）vt.使厌烦；挖 e.g. I'm bored with this job. 这件工作厌烦了。 The oldier bore the sharp pain in the wound with great courage. 这士兵以巨大的勇气忍受着伤口的剧烈疼痛。 2）n.令人讨厌的人（或事） e.g. It's a bore having to go out again. 外出真是讨厌。 boredom n.厌倦，无趣 e.g. in infinite boredom 极其无趣 boring n. 钻(孔) adj. 令人厌烦的(事或物） e.g. The play was boring. 这部短剧很一点意思都没有。 bored adj. 无聊的, 无趣的, 烦人的 e.g. Jack is so bored. 杰克是个没有趣的人。 2.surprising 是针对事或物感到惊奇。 surprised 则是针对人。 3.pleasant adj. 愉快的, 快乐的, 舒适的, 合意的可爱的, 举止文雅的, 活泼的滑稽的, 有趣的 (天气)晴朗的, 美好的容易相处的, 友爱的 e.g. a pleasant voice 悦耳的声音 a pleasant companion 可爱的伴侣 a pleasant time 愉快地度过时光 pleasing adj. 舒适的, 使人愉快的; 满意的; 惹人喜欢的, 可爱的 e.g. a pleasing look 使人愉快的神情 a very well mannered and pleasing young man 彬彬有礼而令人喜爱的年轻人

现在进行时_动词加ing的变化规律

现在进行时动词加ing的变化规律 1)一般情况下，直接加 -ing: 如：go—going answer—answering study—studying be—being see—seeing [注一] 和名词复数、一般现在时动词第三人称单数加-s(-es)不同， 动词末尾如为“辅音字母 + y”时，y不变，其后直接加ing。 如: study—studying fly—flying carry—carrying [注二] 动词结尾为辅音字母r时，加-ing，r在此必须发音。 如: water—watering answer—answering wear—wearing 2)以不发音的e结尾的动词，去掉e，再加ing 如：come—coming write—writing take—taking become—becoming 3)动词是闭音节的单音节词，或是以重读闭音节结尾的多音节词， 而末尾只有一个辅音字母时，这个辅音字母须双写，然后再加ing。 如：sit—sitting run—running stop—stopping begin—beginning admit—admitting forget—forgetting [注一] send，think，accept等动词虽是闭音节或以重读闭音节结尾， 但末尾有一个以上的辅音字母，因此，这个辅音字母不双写，应直接加ing。 如：sending thinking accepting 4)少数几个以-ie结尾的动词，须将ie变作y，再加ing。 如：die—dying tie—tying lie—lying躺，说谎 5)少数以-c结尾的动词变为现在分词时和过去式，须先将-c变为ck,然后再加-ing 或-ed 。 如：picnic—picnicking (picnicked) traffic—trafficking (trafficked)

二极管检波电路设计

目录 第1章二极管检波电路设计方案论证 (1) 1.1检波的定义 (1) 1.2二极管检波电路原理 (1) 1.3二极管检波电路设计的要求及技术指标 (1) 第2章对二极管检波电路各单元电路设计 (2) 2.1检波器电路设计检波器电路 (2) 2.1.1检波器电路原理及工作原理 (2) 2.1.2检波器质量指标 (3) 第3章二极管检波电路整体电路设计及仿真结果 (4) 3.1整体电路图及工作原理 (4) 3.3电路仿真图形 (4) 第4章总结 (5) 参考文献 (6) 元器件清单 (7)

第1章二极管检波电路设计方案论证 1.1检波的定义 广义的检波通常称为解调，是调制的逆过程，即从已调波提取调制信号的过程。对调幅波来说，是从它的振幅变化提取调制信号的过程；对调频波来说，是从它的频率变化提取调制信号的过程；对调相波来说，是从它的相位变化提取调制信号的过程。 狭义的检波是指从调幅波的包络提取调制信号的过程。因此，有时把这种检波称为包络检波或幅度检波。图1-20-21出了表示这种检波的原理：先让调幅波经过检波器（通常是晶体二极管），从而得到依调幅波包络变化的脉动电流，再经过一个低通滤波器滤去高频成分，就得到反映调幅波包络的调制信号 1.2二极管检波电路原理 调幅波信号是二极管检波电路的输入，由于二极管只允许单向导电，所以，如果使用的是硅管，则只有电压高于0.7V的部分可以通过二极管。 同时，由于二极管的输出端连接了一个电容，这个电容与电阻配合对二极管输出中的高频信号对地短路，使得输出信号基本上就是AM信号包络线。电容和电阻构成的这种电路功能叫做滤波。 1.3二极管检波电路设计的要求及技术指标 1．对常规调幅信号进行二极管检波解调并仿真，能够观察输入输出波形。 2．根据电路结果求出电压利用系数 3．判断设计的电路是否能够产生失真 参数：常规调幅信号调幅系数为0.5，输入信号载波频率10000HZ，载波电压100mV左右。

现在进行时用法

现在进行时 一、定义及用法： 1定义：（1）表示说话时正在进行的动作及行为。（2）表示现阶段正在进行的动作。 2基本用法： (1)现在进行时主要表示说话人的说话时刻正在进行的动作、不断重复的动作或目前这个阶段（不一定是说话时刻）正在进行的动作，如： We’re having a meeting. 我们在开会。（说话时正在进行的动作） Be quiet！The baby is sleeping.安静，孩子在睡觉。 He is teaching in a middle school. 他在一所中学教书。（目前阶段在进行的动作） (2)现在进行时表将来: 现在进行时表将来，主要表示按计划或安排要发生的动作： I’m leaving tomorrow. 我明天走。 They’re getting married next month. 他们下个月结婚。 注意：现在进行时与一般现在时均可表示将来，区别是：用现在进行时表示将来，其计划性较强，并往往暗示一种意图；而一般现在时表示将来，则其客观性较强，即通常被视为客观事实，多指按时刻表或规定要发生的情况： I’m not going out this evening. 今晚我不准备出去。 What time does the train leave？火车什么时候开？ (3)现在进行时表示感情色彩: 现在进行时有时可表示满意、称赞、惊讶、厌恶等感情色彩，通常与always，forever，constantly，continually等副词连用。比较： She’s always helping people. 她老是帮助别人。（表赞扬） She always helps others. 他总是帮助别人。（陈述一个事实） The boy is constantly lying. 这孩子老是撒谎。（表示厌恶） The boy often lies. 这孩子常撒谎。（指出缺点） 二、结构: 现在进行时常有三种句型： （1）肯定式：主语＋be＋v-ing＋其它。 如：He is mending his bike．他正在修自行车。 （2）否定式：主语＋be＋not＋v-ing＋其它。 如：He is not（isn't）mending his bike．他没在修自行车。 （3）疑问式：主要分一般疑问句和特殊疑问句两种句式。 一般疑问句：Be＋主语＋v-ing＋其它？ 如：—Is he mending his bike？他正在修自行车吗？—Yes，he is．（No，he isn't．）特殊疑问句：疑问词＋be＋主语＋v-ing＋其它？ 如：—What is he doing？他正在干什么？ 三、何时用现在进行时？ （1）以Look！或Listen！开头的句子提示我们说话时动作正在进行，应用现在进行时。 如：Look！The children are playing games over there． Listen！Who's singing in the classroom？ （2）当句子中有now（现在）时，常表示说话时动作正在进行，这时也常用现在进行时。 如：We are reading English now． （3）描述图片中的人物的动作时常用现在进行时，以示生动。 如：Look at the picture．The girl is swimming． （4）表示当前一段时间内的活动或现阶段正在进行的动作时常用现在进行时。这时常与时间状语these days，this week等连用。

各种过滤器的原理及结构资料

各种过滤器的原理及结构 株洲海润公司郑胜春（摘录） 石英砂过滤器主要用于去除水中的悬浮物。该设备与其它水处理设备配合，广泛地应用在给水净化、循环水净化污水处理等各类水处理工程中。 活性碳过滤器主要用于吸附水中游离氯（吸附力达99％），对有机物和色度也有较高的去除率。是软化、除盐系统制纯水工艺的预处理设备。滤料为活性碳。设备主要材质为碳钢防腐、玻璃钢和不锈钢等。 活性碳过滤器技术参数 过滤速度：8-10m3/h 进水浊度：≤5mg/L； 工作温度：常温工作压力：≤0.6Mpa; 反洗压缩空气量：18-25L/m2.S 滤料层高：1000-1200mm 反洗强度：4-12L/m2.S; 反冲洗时间：4-6分钟 石英砂过滤器技术参数： 1、运行参数 2、水质参数 设计滤速：8-10米/时期终水头损失：1.7米进水浊度小于15度，出水浊度小于3度。反清洗强度：4-15升/秒·平方米进水浊度小于10度，出水浊度小于2度。 冲洗历时：5-7分钟滤料：石英砂3、水压 垫层厚度：200-400毫米滤层厚度：800毫米进水水压：≥0.04Mpa 反冲洗进水水压：≥0.15Mpa 盘式过滤器原理与应用分析 工厂制水的预处理系统以前采用的是纤维过滤法，在近几年的运行过程中，这种方法暴露出许多问题：过滤效率明显下降，运行阻力增加，树脂破碎率升高，制水成本逐年上升；出现纤维扭曲，发生“粘连抱团”现象，纤维束不能垂直竖立，下移动不能复位；过滤器内部气囊破损严重，无法正常发挥松散纤维的作用。为了改善制水预处理系统的现状，转而采用盘式过滤器代替高效纤维过滤，取得了良好的效果。 一、盘式过滤器机理 1盘式过滤器的原理： 利用相邻盘片之间的沟槽纹交叉点实现对固体颗粒的拦截，运行时14组过滤头并联，在水和弹簧的压力作用下过滤滤芯的滤盘被压紧，水从盘片的端面进入，水中的颗粒杂质被压紧的盘片截留，从而起到过滤的作用。反洗时，其中一组进水阀关闭，排污阀打开，其他13组过滤单元的部分出水反向进入这组过滤单元，在反洗水压下促使碟片横向旋转和纵向颤动。滤芯盘片松开，同时反洗水沿管线方向冲向过滤盘片，导致盘片高速旋转，使截留在盘片上的杂物在离心力和水流冲洗的共同作用下脱离盘片，并经反洗水的作用排除。冲洗过程仅需十几秒钟，一个滤头反洗结束后，再对其它几组依次进行反洗。阿速德盘式过滤器又有其独到之处：旋转设计。水流进入到过滤器单元内时，沿外壳的切向进入，在过滤单元内高速旋转，没有真正进入盘式过滤器之前，系统已经将大部分的泥沙等杂质从水中分离，减轻了过滤器的负担，使其工作寿命是同类产品的10倍左右。

(易错题精选)初中英语词汇辨析的难题汇编及解析

一、选择题 1．Is this a photo of your son? He looks________ in the blue T-shirt. A．lovely B．quietly C．beautiful D．happily 2．—Jerry looks so tired. He works too hard. —He has to ________ a family of four on his own. A．offer B．support C．provide D．remain 3．— Mr. Wilson, can I ask you some questions about your speech? — Certainly, feel __________ to ask me. A．good B．patient C．free D．happy 4．Some animals carry seeds from one place to another, ________ plants can spread to new places. A．so B．or C．but D．for 5．— Can you tell us about our new teacher? —Oh, I’m sorry. I know________ about him because I haven’t seen him before. A．something B．anything C．nothing D．everything 6．—Help yourselves! The drinks are ________ me. —Thank you. You’re always so generous. A．above B．in C．on D．over 7．Gina didn’t study medicine. ________, she decided to become an actor. A．Instead B．Again C．Anyway D．Also 8．—Have you got Kathy’s________ for her concert? —Yes, I’d like to go and enjoy it. A．interview B．information C．invitation D．introduction 9．More and more people have realized that clear waters and green mountains are as ________ as mountain of gold and silver. A．central B．harmful C．valuable D．careful 10．Kangkang usually does her homework ________ it is very late at night. A．until B．when C．before D．after 11．He ________all the “No Smoking” signs and lit up a cigarette. A．requested B．attacked C．protected D．ignored 12．一Where is Mr. Brown? 一I think he's _____________ the music hall. A．on B．in C．over D．from 13．— Is your home close to the school, Tom? — No, it's a long way, but I am________ late for school because I get up early daily. A．always B．usually C．never D．sometimes 14．—Mum, I don’t want the trousers. They’re too long.

英语现在进行时用法

英语现在进行时用法 初中英语――现在进行时 1】现在进行时的构成 现在进行时由"be+v-ing"构成。be应为助动词，初学者最容易漏掉，它应与主语的人称和数保持一致。 2】现在进行时的应用 在实际运用时，现在进行时常用以下几种情况： (1)当句子中有now时，常表示动作正在进行，这时要用现在进行时。如： They are playing basketball now.现在他们正在打篮球。 (2)以look, listen开头的句子，提示我们动作正进行，这时要用现在进行时。如： Listen！She is singing an English song.听，她正在唱英语歌。 (3)表示当前一段时间或现阶段正在进行的动作，且此时有this week, these days等时间状语，这时常用现在进行时。如： We are making model planes these days.这些天我们在做飞机模型。 (4)描述图片中的人物的动作，也为了表达更生动。此时也常用现在进行时。如： Look at the picture. The children are flying kites in the park.看这幅图，那些孩子正在公园放风筝。 3】现在进行时的变化 肯定句式：主语+be( am, is, are)+现在分词+其它. 否定句式：主语+be(am, is, are) +not +现在分词+其它. 一般疑问句：Be(am, is, are) +主语+现在分词+其它？ 特殊疑问句：疑问词+be(am, is, are)+主语+现在分词+其它？ 对现在进行时的特殊疑问句的回答，它不可以用Yes或No直接作答，要根据实际情况回答。 注意事项 1.在英语中，并不是所有的动词都要使用正在进行时。例如一些表示状态和感觉的动词，一般不用进行时态，而是用现在一般时表示。例如： I hear someone singing. 我正听见有人唱歌。