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201.
202.
A survey is given on fluid-dynamic effects caused by the structure and properties of biological surfaces. It is demonstrated
that the results of investigations aiming at technological applications can also provide insights into biophysical phenomena.
Techniques are described both for reducing wall shear stresses and for controlling boundary-layer separation. (a) Wall shear
stress reduction was investigated experimentally for various riblet surfaces including a shark skin replica. The latter consists
of 800 plastic model scales with compliant anchoring. Hairy surfaces are also considered, and surfaces in which the no-slip
condition is modified. Self-cleaning surfaces such as that of lotus leaves represent an interesting option to avoid fluid-dynamic
deterioration by the agglomeration of dirt. An example of technological implementation is discussed for riblets in long-range
commercial aircraft. (b) Separation control is also an important issue in biology. After a few brief comments on vortex generators,
the mechanism of separation control by bird feathers is described in detail. Self-activated movable flaps (=artificial bird
feathers) represent a high-lift system enhancing the maximum lift of airfoils by about 20%. This is achieved without perceivable
deleterious effects under cruise conditions. Finally, flight experiments on an aircraft with laminar wing and movable flaps
are presented. 相似文献
203.
IntroductionTheprocessofmunicipalsolidwaste(MSW)isoneofthemostseriousissuesintermsofenvironmentalprotection.ProcessingofMSWwithoutfurtherdisastrouscontaminationcanbeachievedonlyinmodernizedmeasures,suchasincineratingandenergygeneratingconcurrently(Shen… 相似文献
204.
IntroductionChengdu KunmingRailwayLineislocatedonthemountainregionofsouthwesternChina .Therearealotofdebrisflowgulliesspreadingbesidethisrailwayline .Onsummer,thedebrisflowoftenburstsandthreatensthesafetyoftherailwaytransportation.In 1981,alarge scaledebris… 相似文献
205.
Three cases of unusual chromosomal mosaicism are reported for which the cytogenetic data show inconsistent findings between CVS and AC or fetal tissue, and which cannot be explained simply by non-disjunction. For case 1, in CVS the karyotype was 46,XY, whereas lymphocytes and fibroblasts revealed 69,XXY. DNA fingerprinting indicated one paternal and two maternal chromosome sets, the latter most probably due to omission of maternal meiosis II. For case 2, in CVS mos 46,XX/47,XX,+mar de novo was observed. Amniotic fluid cells had the karyotype 46,XX. The origin of the marker chromosome might be explained by at least two events of unknown order (a somatic chromosome/chromatid deletion and non-disjunction of the homologous chromosome). In case 3 (CVS: mos 46,XY/46,XY,19q+ de novo; amniotic fluid cells, lymphocytes, and fibroblasts: 46,XY), the surplus of chromosome material in 19q+ might be explained on the basis of a somatic translocation. The idea of a chimera is less convincing, as the mosaic finding is restricted to one tissue. Furthermore, there was no hint of a vanishing twin. Hitherto, no case of structural chromosome mosaicism in CVS has been reconfirmed in fetal tissues. 相似文献
206.
A. G. W. Hunter M.D. 《黑龙江环境通报》1987,7(6):433-441
Three hundred and fifty-four women who underwent midtrimester genetic amniocentesis were matched for age, parity, indication, and smoking history, with an equivalent number of women who had declined the procedure, for the purpose of comparing the neonatal respiratory status of their offspring. There was no evidence that the infants exposed to genetic amniocentesis were compromised. 相似文献
207.
Diana W. Bianchi MD Gretchen K. Zickwolf Melissa C. Yih Alan F. Flint Ossie H. Geifman Marlena S. Erikson John M. Williams 《黑龙江环境通报》1993,13(4):293-300
Fetal nucleated erythrocytes (NRBC) in maternal blood are a non-invasive source of fetal DNA for prenatal genetic screening. We compared the effectiveness of three monoclonal antibodies for the separation of fetal cells from maternal blood by flow sorting. Mononuclear blood cells from 49 healthy pregnant women were incubated with antibody to CD 71, CD 36, and/or glycophorin A (GPA), employed singly or in combination with each other. These monoclonal antibodies recognize surface antigens on haematopoietic precursor cells. Successful isolation of fetal cells was defined as detection of Y chromosomal sequences in maternal blood from women carrying male fetuses, with absence of Y sequences when female fetuses were carried. Thus, gender prediction accuracy was used as a measure of fetal cell separation. Using anti-CD 71 to isolate fetal cells, gender prediction was 57 per cent correct; with anti-CD 36, it was 88 per cent correct. Anti-GPA, an erythrocyte-specific antigen, used alone or in combination with anti-CD 71 or 36, improved gender prediction to 100 per cent. We conclude that antibody to GPA improves the retrieval of fetal NRBC from maternal blood, permitting genetic analysis by the polymerase chain reaction. 相似文献
208.
209.
镉胁迫下大豆中镉的分布状况及其籽粒品质 总被引:18,自引:1,他引:18
溶液培养中0.5μmol·L-1镉胁迫浓度下,大豆表现出轻微受害症状,籽粒减产25 . 7%,而籽粒中粗脂肪和粗蛋白含量变化不大.镉在大豆中的积累分布状况为根>叶>籽>油,比例为32.100:1.690:1.000:0.003.大豆籽粒含镉4.89mg/kg,超过了国家环境标准规定的最高容许量.而大豆粗脂肪中含镉仅0.015mg/kg,远低于国家食品环境卫生标准.豆粕中含镉6.17mg/kg,表明大豆籽粒中的镉主要存在于粗蛋白和淀粉中. 相似文献
210.
While true mosaicism occurs in only 0–25 per cent of genetic amniocenteses, nearly 2–5 per cent of amniotic fluid cell cultures contain a second cell line. In the common practice of prenatal diagnosis, an aberrant cell line confined to a single colony is usually disregarded. We present a case of mosaic trisomy 14 which was not detected on initial chromosome analysis. At birth, multiple malformations were apparent. Newborn cytogenetic studies revealed mosaicism [46,XX/46,XX,-14,+i(14q)] with an isochromosome 14 in 37 per cent of lymphocytes. Additional cells from the initial amniotic fluid culture were analysed post-delivery and the isochromosome 14 identified in only one of 12 total colonies. This case illustrates two important lessons in prenatal diagnosis. First, amniotic fluid cell cultures may not accurately reflect the relative distribution of the normal and abnormal cell lines within a mosaic fetus. Second, while it is generally reasonable to disregard mosaicism confined to a single colony, this policy will, on rare occasion, result in diagnostic error. This should be taken into consideration, particularly when dealing with autosomal trisomies potentially compatible with livebirth. 相似文献