受精前卵细胞卵周腔显微注射法制备转基因动物

在医学实验动物模型、生物反应器、器官移植、禽畜活体内的基因表达调控、禽畜育种及品种改良等科学研究领域中,转基因动物技术有着广泛的应用前景[1]。目前转基因动物的制备,主要是在动物胚胎发育的不同阶段采用原核显微注射法、逆转录病毒载体法和胚胎干细胞法等技术,但...

显微组织对Ti-31合金低周疲劳性能的影响

研究了Ti-31合金的显微组织对低周疲劳性能的影响.结果表明:当应变控制在△ε/2=0.6%-1.0%,应变比R=-1时,片状组织和等轴状组织对低周疲劳性能无明显影响,当循环应变次数较低时,基本都表现为循环饱和特征;当循环周次超过100 cyc时,片状组织出现轻度循环软化.等轴状组织的Ti-31合金的过度疲劳寿命略高于片状组织,分别为758和556 cyc.

渠道底宽计算新法

使用本法可避免试算法的反复性和近似性，本法既适用于梯、矩形的过水断面也适用于复式断面。（美自词）

天台山文化研究会在天台成立

1989年5月17日至18日,值日本佛教天台宗第253代座主山田惠谛长老率80名日本僧众来天台佛陇山智者塔院参加“般若心经塔揭幕典礼”之际,浙江省第一个研究天台山文化的群众性学术团体——天台山文化研究会在天台山国清寺宣告成立.首届会员共有38人.大会通过了《天台山文化研究会章程》,选举产生了首届理事会,省、地、县30多位同志参加了成立大会.

Low cycle fatigue behavior of T4-treated Al-Zn-Mg-Cu alloys prepared by squeeze casting and gravity die casting

Gravity die casting(GC) and squeeze casting(SC) T4-treated Al-7.0Zn-2.5Mg-2.1Cu alloys were employed to investigate the microstructures,mechanical properties and low cycle fatigue(LCF) behavior.The results show that mechanical properties of SC specimens are significantly better than those of GC specimens due to less cast defects and smaller secondary dendrite arm spacing(SDAS).Excellent fatigue properties are obtained for the SC alloy compared with the GC alloy.GC and SC alloys both exhibit cyclic stabilization at low total strain amplitudes(less than 0.4%) and cyclic hardening at higher total strain amplitudes.The degree of cyclic hardening of SC samples is greater than that of GC samples.Fatigue cracks of GC samples dominantly initiate from shrinkage porosities and are easy to propagate along them,while the crack initiation sites for SC samples are slip bands,eutectic phases and inclusions at or near the free surface.

罗工柳 被“文革”抄出来的历史

解放军进北平后不久,人民银行制币局副局长王显周就来找我,让我参加人民币设计工作。他和我曾一起在《新华日报》(华北版)一起工作,知道我当时曾照着钞票刻过一外通券。刚开始我只是抱着试试看的态度,没想这一试不得了。

Microstructure and phase composition of as-cast Mg-9Er-6Y-xZn-0.6Zr alloys

The microstructure and phase composition of as-cast Mg-9Er-6Y-xZn-0.6Zr （x=1, 2, 3, 4; normal mass fraction in %） alloys were investigated. In low Zn content, aside from the major second phase of Mg24（Er, Y, Zn）5, there are a few lamellar phases that grow parallel with each other from the grain boundaries to the grain interior. With Zn content increasing, the Mg24（Er, Y, Zn）5 phase decreases, but the Mg12Zn（Y, Er） phase and lamellar phases continuously increase. When Zn content reaches 4% （normal mass fraction）, the Mg12Zn（Y, Er） phase mainly exists as large bulks, and some a-Mg grains are thoroughly penetrated by the lamellar phases. Moreover, the crystallography structures of the Mgl2Zn（Y, Er） and Mg24（Er, Y, Zn）5 phases are confirmed as 18R-type long-period stacking ordered structure and body-centred cubic structure, respectively.

UNDERSTANDING HREM IMAGES OF Al-Mn-Si ICOSAHEDRAL QUASICRYSTAL

提出了处理数字化图像的光滑算子。用它处理了Ａｌ－Ｍｎ－Ｓｉ二十面体准晶的高分辨电子显微图，处理后的图像展示了周期结构特征，由此建立了一个平面周期模型，其Ｆｏｕｒｉｅｒ变换图符合Ａｌ－Ｍｎ－Ｓｉ准晶相应的电子衍射图。

Microstructure evolution of 55Ni−23Cr−13Co nickel-based superalloy during high-temperature cyclic deformation

The cyclic deformation behavior and microstructure evolution of the 55Ni−23Cr−13Co nickel-based superalloy were studied at 750℃ under the strain amplitudes from 0.35%to 0.6%.Coffin−Manson−Basquin and Smith−Watson−Topper relationships were employed,which satisfactorily predicted the fatigue life of the alloy under various strain amplitudes.The superalloy showed an initial cyclic hardening as a result of the interaction between the dislocations and the precipitates,and following cyclic softening behavior mainly due to the shearing of theγ′phase by dislocations and dislocations recovery under all strain amplitudes.Microstructure analyses showed that the M_(23)C_(6) carbides exhibited a continuous-chain distribution at lower strain amplitudes,while they showed a discontinuous distribution at higher strain amplitudes.As the strain amplitude increased,the size of theγ′phase decreased as the consequence of repeated shearing by dislocations.Fracture mechanisms were analyzed.Under higher strain amplitudes,cavities preferred to form around grain boundaries.

Effect of Zn addition on microstructure and mechanical properties of cast Mg-Gd-Y-Zr alloys

The effects of Zn addition on the microstructure and mechanical properties of Mg.10Gd.3Y.0.6Zr(wt.%)alloys in the as-cast,solution-treated,and peak-aged conditions were investigated.Experimental results reveal that the microstructure of the as-cast alloy without Zn consists ofα-Mg and Mg24(Gd,Y)5 phases,and the alloy with 0.5 wt.%Zn consists ofα-Mg,(Mg,Zn)3(Gd,Y)and Mg24(Gd,Y,Zn)5 phases.With the addition of Zn increasing to 1 wt.%,the Mg24(Gd,Y,Zn)5 phase disappears and some needle-like stacking faults distribute along the grain boundaries.Moreover,the 18R long-period stacking ordered(LPSO)phase is observed in the as-cast alloy with 2 wt.%Zn.After solution treatment,the Mg24(Gd,Y)5 and Mg24(Gd,Y,Zn)5 eutectic phases are completely dissolved,and the(Mg,Zn)3(Gd,Y)phase,needle-like stacking faults and 18R LPSO phase all transform into 14H LPSO phase.Both the suitable volume fraction of 14H LPSO phases and the fine ellipsoidal-shapedβ′phases make the peak-aged alloy with 0.5 wt.%Zn exhibit excellent comprehensive mechanical properties and the UTS,YS and elongation are 338 MPa,201 MPa and 6.8%,respectively.

Effects of Res on proliferation and apoptosis of human cervical carcinoma cell lines C33A,SiHa and HeLa

Objective:To explore the effects of Res on the proliferation and apoptosis of human cervical cancer cell lines C33A,SiHa and HeLa.Methods:Inhibition rates by different concentrations of Res were calculated using MTT method.Apoptosis rates and cell cycles were measured and examined by flow cytometry(FCM).Morphological configuration of apoptotic cells were observed under the fluorescence microscope.Results:The growth of cancer cells was inhibited by Res of varied concentrations in a time-and dose-dependent manner(P<0.01).The cells showed characteristic apoptosis morphologic changes under fluorescence microscope.Res exerted no effects on cell cycles.Conclusion:Res inhibits the growth of cervical cell lines C33A,SiHa and HeLa by inducing cell apoptosis in a time-and dose-dependent manner.

Establishment of a Technique to PCR Detection about Follistatin Transgenic Sheep by Injection of Lentivirus

[Objective] The aim was to establish a stable detection method of lentivirus transgenic sheep at DNA level.[Method] The cotyledons,umbilical cord,tail tissue of newborn transgenic lambs and the body tissues of dead lambs were collected and used to extract DNA for PCR with primers designed for N＋D1 fragment of follistatin gene.At the same time,we detected the CMV promoter,5＇-LTR and so many other structure elements of lentiviral vector.The body tissues of dead lambs and muscle tissues of transgenic lambs in vivo were used to extract RNA for RT-PCR.[Result]The results showed that the DNA Extraction Kit was faster and more efficient than conventional method in extracting DNA and the DNA extracted with kit was easier to be amplified than that with conventional method.In order to avoid false positive caused by the interference of endogenous gene,the primers were designed for amplifying the combination of upstream of vector gene and downstream of target gene,increasing the specificity of detection.Tail tissue of newborn transgenic lambs could be used for detection and the detected results were reliable and accurate.The detection of CMV promoter,5＇-LTR and so many other structure elements of lentiviral vector provided a data support for the biological safety of transgenic animals and verify the detected results of target gene of transgenic lambs.The transcription products of RNA extracted from three of the lambs were not detected.[Conclusion] The PCR method established in our research for detecting transgenic sheep was efficient,fast and accurate.It would provide experimental basis for further detection at protein level,lay a foundation for the establishment of multi-level and systematic detection method of transgenic sheep and provide a stable technology platform for safety monitoring of transgenic sheep.

Rayleigh Wave Group Velocity Maps of East Guangdong and Its Surrounding Regions from Ambient Seismic Noise Tomography

We perform Rayleigh wave tomography in east Guangdong and its surrounding regions by applying the ambient noise method to broadband data recorded at 26 stations from Guangdong,Fujian and Jiangxi Digital Seismic Networks.Cross-correlations of verticalcomponent ambient noise data are computed in one-day segments and stacked over seven months from March to September,2011.Then Rayleigh wave group dispersion curves are measured using the frequency-time analysis method.Group velocity maps at periods from5s to 15s are inverted.The resulting group velocity maps generally show good correlation with tectonic features,reflecting the velocity variations in the shallow crust.The basin areas are clearly resolved with lower group velocities at the short periods due to thick sedimentary layers,and the mountain areas with higher group velocities due to thin sedimentary layers.The variations of group velocity on the map can draw out the distribution of basins and mountains in study areas.The geothermal field can change the group velocity obviously,and lower group velocities are always found in high geothermal areas.The velocity maps indicate that a low-velocity layer may be found in the study areas.

Early development of Grateloupia turuturu (Halymeniaceae, Rhodophyta)

Grateloupia turuturu is a commercial red alga with potential value in nutraceuticals and pharmaceuticals. To supplement information on its life history and verify whether carpospores can be used for seedling culture, early development of G. turuturu was investigated under culture conditions （27~C, 10-13 ~mol/（mZ.s） in irradiance, photoperiod 10：14 h L：D）. Three physiological stages were recognized by continuous microscopic observation： division stage, discoid crust stage, and juvenile seedling stage. At the beginning of the division stage, the carpospores developed germ tubes into which the carpospore protoplasm was evacuated, and then the carpospore protoplasm in the germ tubes began to divide continuously until discoid crusts formed. Finally, upright thalli appeared on the discoid crusts and developed into juvenile seedlings. It took about 60 days for carpospores to develop into juvenile seedlings. The growth parameters, including germination rate for carpospores and discoid crust diameter, were recorded. These results contribute more information on the life cycle, and at the same time are of great significance in the scaling-up of artificial seedling cultures of G. turuturu.

Effect of 8-Chloroadenosine on Undifferentiatied HL-60 Cell Line

Aim To study the effect of 8 chloroadenosine (8 CA)on undifferentiatied HL 60 cell line. Methods The IC 50 of cancer cell proliferation was determined using a microculture plate reader at 570 nm (MTT) and 540 nm (SRB). Morphology of HL 60 cells was observed under a scanning electron microscope and a transmission electron microscope. The differentiation of HL 60 cells was examined by nitro blue tetrazolium reduction (NBT) and acid phosphatase assay. The cycle of HL 60 cells was analyzed by flow cytometry. Results 8 CA inhibited proliferation of eight human cancer cell lines. The IC 50 ranked in the following order: KB (0 05 μmol·L -1 ) < HL 60 (0 25 μmol·L -1 ) < Bel 7402 (0 56 μmol·L -1 ) < MCF 7 (0 65 μmol·L -1 ) < HCT (0 79 μmol·L -1 ) < HeLa (0 89 μmol·L -1 ) < BGC 823 (1 149 μmol·L -1 ) < PG (2 50 μmol·L -1 ). The scanning and transmission electron microscopy showed that the microvilli of HL 60 cell surface shortened, and the shape of HL 60 cells nuclei changed to kidney shaped, horse shoe shaped and bilob ated after treatment with 8 CA. Meanwhile, 8 CA promoted NBT reduction and increased activity of acid phosphatase in HL 60 cells in a time and concentration dependent manner. Flow cytometry analysis indicated that 8 CA induced an appreciable increase of the cell population in G 1 phase with a marked reduction in S phase. Conclusion 8 CA can induce differentiation of HL 60 cells and block the cells at G 1 phase, thus inhibiting proliferation of HL 60 cells.

Effect of nano-sized Al2O3 reinforcing particles on uniaxial and high cycle fatigue behaviors of hot-forged AZ31B magnesium alloy

The effect of hot-forging process was investigated on microstructural and mechanical properties of AZ31 B alloy and AZ31 B/1.5 vol.%Al2 O3 nanocomposite under static and cycling loading. The as-cast alloy and composite were firstly subjected to a homogenization heat treatment at 450 ℃ and then an open-die forging at 450 ℃. The results indicated that the presence of reinforcing particles led to grain refinement and improvement of dynamic recrystallization. The forging process was more effective to eliminate the porosity in the cast alloy workpiece. Microhardness of the forged composite was increased by up to 80% and 16%, in comparison with those of the cast and forged alloy samples, respectively. Ultimate tensile strength and maximum tensile strain of the composite were improved by up to 45% and 23%, compared with those of the forged alloy in similar regions. These enhancements were respectively 50% and 37% in the compression test. The composite exhibited a fatigue life improvement in the region with low applied strain;however, a degradation was observed in the high applied strain region. Unlike AZ31 B samples, tensile, compressive and high cycle fatigue behaviors of the composite showed less sensitivity to the applied strain, which can be attributed to the amount of porosity in the samples before and after the hot-forging.

Mechanism and development of dip-pen nanolithography(DPN)

Dip-pen nanolithography is a new scanning probe lithography (SPL) technique based on atomic force microscopy (AFM), and now has made a great progress. The process of dip-pen lithography involves the adsorption of ink molecules on AFM tip, the formation of water meniscus, the transport of ink molecules, and diffusion of ink molecules on the substrate. More factors such as temperature, humidity, tip, scanning speed and so on will influence the process of dip-pen lithography. The paper analyzes in detail the mechanism of this technique, introduces synthetically the latest development, including electrochemical DPN, more-mode DPN, multiple DPN, multi-probe array DPN and so on. Finally, the paper describes the characteristics and the application of DPN.

Working Capital Management Programs： Yesterday, Today, Tomorrow

The paper develops a view on the history and future of working capital programs and focuses on the state of the art in four remarkable years： 1900, 1930, 1960, and 1990. In these years, an operations approach, an accounting approach, an economic approach, and a capital market approach, respectively, were prevalent. The paper shows that all of the approaches have their merits for today＇s working capital management （WCM） programs and discusses useful working capital program indicators, taking into account the cash conversion cycle （CCC） and its delineation into accounts receivables （A/R）, inventory, and accounts payables （A/P） periods. This enables the author to take step ahead to the magic year 2020. Finally, the paper discusses briefly an academic development agenda.

Debt Rating Initiations： Natural Evolution or Opportunistic Behavior？

The authors examine a firm＇s decision to begin issuing debt in public bond markets and find that it is a function of both life cycle influences and opportunistic timing. Defining life cycle factors to encompass both a firm＇s age in years and its underlying characteristics, the authors confirm that bond market participation is generally restricted to large, mature firms. Summary statistics show that finns obtain their initial bond ratings on average 9.5 years after their equity initial public offering （IPO） and 11.8 years after initiating dividend payments. Growth rates, capital expenditures, and cash flow volatility all decline as the firm accesses public debt markets, consistent with entry into the mature phase of its life cycle. With respect to opportunistic timing, it is asked whether entry into public bond markets follows strong performance （or precedes weak performance） at both the firm and market levels. At the firm level, the authors find that the debt IPO occurs following periods of strong operating performance and high excess stock returns. At the market level, entry coincides with favorable interest rates and default spreads. The benefits of careful timing result in firms receiving initial bond ratings that are stronger than what would be predicted; however, there is no evidence of abnormal numbers of downgrades for these firms in subsequent years.