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排序方式: 共有765条查询结果,搜索用时 0 毫秒
91.
High structure or so‐called conductive carbon blacks (CCBs) constitute the major family of conductive additives. They enable one to make polymers permanently conductive at “low” to “very low” loadings, for technical applications involving, e.g., the transport of energy, protection against arcing or discharge. Designing conductive parts requires certain know‐how, as many parameters influence the final electrical conductivity, and many other requirements have to be fulfilled. This paper highlights the impact of the carbon black (CB) type and loading, the polymer type, and the compounding conditions on the conductive, mechanical, dispersion, and flow properties of various plastics compounds. The study especially positions a unique family of low surface area (LSA) CCBs, suggests means to make conductive parts with compounding and transformation ease, and points out that more conductive additive does not automatically give the best overall performance. J. VINYL. ADDIT. TECHNOL., 12:14–18, 2006. © 2006 Society of Plastics Engineers 相似文献
92.
1. Pregnant Wistar rats were treated orally with a single dose of 100 microg 3,3',4,4'-tetrachlorobiphenyl (PCB 77)/kg b.w. or 10 microg 3,3',4,4',5 pentachlorobiphenyl (PCB 126)/kg b.w. on day 15 of pregnancy. The control rats received peanut oil at the same day. Developmental landmarks were assessed in all offspring rats and reproductive effects of PCB 77 and PCB 126 on male offspring were studied on postnatal day 65 (at puberty) and on postnatal day 140 (at adulthood). 2. The ano-genital distance as well as the ratio ano-genital distance to body length was reduced in male pups of the PCB 126 group and the age at vaginal opening was significantly delayed in the female pups. 3. Testis, brain weights and daily sperm production were permanently increased and seminal vesicle weights were decreased in male offspring of the PCB 77 group. In male rats of PCB 126 group, the brain weights were permanently increased and ventral prostate weights permanently reduced. In both PCB groups, however, serum testosterone concentration was reduced only at adulthood. Additionally, the male rats of the PCB 126 group showed alterations in sexual behavior. In these rats the number of mounts with intromissions was significantly increased. 4. The results of this study show that PCB 126 elicits some TCDD-like reproductive effects after in utero exposure, while the reproductive effects of in utero exposure to PCB 77 on male offspring may be attributed to the neonatal hypothyroidism induced by the substance during early fetal development. Further studies using multiple doses and providing thyroid hormone data will be necessary to support this hypothesis. 相似文献
93.
Based on the dispersion model rather than on the conventional pluf-flow model, a method of predicting the transient behaviour of parallel and counterflow heat exchangers is developed, whereby the effects of shell-side flow maldistribution and the finite heat capacities of both fluids, tube bundle and shell are considered. The final solution has been obtained by numerical inversion of the Laplace transform, to determine the transient responses to arbitrary inlet temperature variations. The experiment was carried out in a one pass tube heat exchanger. The comparison between therotical and experimental results is presented and the feasibility of this method is discussed. 相似文献
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97.
Wilfried H. Eppendorfer 《Journal of the science of food and agriculture》1977,28(7):607-614
In experiments with increasing applications of nitrogen to ryegrass, red clover and lucerne grown in pots, freeze-dried plant material with widely varying N-content was obtained. Increasing N-concentrations were associated with increasing nitrate contents which proportionally decreased the concentrations (g/16 g total-N) of all amino acids. Expressed as g amino acid/16 g total-N minus NO3-N, concentrations of all amino acids were closely similar at different N-levels. Differences between the three species ' amino acid composition were negligible except for a lower concentration of lysine in the crude protein of ryegrass and of methionine + cystine in the crude protein of clover and lucerne. In feeding experiments with rats increasing total-N concentrations were generally associated with higher true digestibilities of the crude protein of ryegrass, red clover and lucerne, but slightly lower biological values, especially in red clover. Net crude protein utilisation was increased by increasing total-N concentration in ryegrass, decreased in red clover and unchanged in lucerne. When ranked according to the nutritional value of the crude protein, ryegrass comes first, lucerne second and red clover last. Addition of synthetic methionine to ryegrass and lucerne improved their biological values by 30 and 47% respectively. 相似文献
98.
Wilfried H. Eppendorfer 《Journal of the science of food and agriculture》1977,28(2):152-156
In experiments with increasing applications of nitrogen to oats and rye grown in pots, grain with widely varying N-content was obtained. In rye increasing N-concentrations were associated with decreases in the protein of lysine and several other amino acids including threonine, tryptophan, methionine and cystine, whereas glutamic acid, proline and phenylalanine increased. In oat protein the amino acid composition was less affected by increasing N-content in grain. Concentrations of most essential amino acids were higher in oat than in rye protein, especially at high N-levels. The ratio lysine + arginine/proline was higher in oat than in rye protein and did not, as in rye, decrease with increasing N-concentration. Lysine as a percentage of dry matter increased up to the highest N-level in both cereals. In rat feeding experiments true digestibility of the protein of oats and rye increased to the same extent with increasing N-concentration in grain, whereas the biological value of the protein decreased considerably in rye but only slightly in oats. Net protein utilisation decreased with increasing N-content in rye but increased in oats. 相似文献
99.
Impaired nasal breathing has been reported to cause changes in human head posture. The aim of this study was to assess whether there was any relationship between nasorespiratory function and variables of head posture in 58 young adults. The pressure flow technique was used to measure airflow rate and oral/nasal pressure and to calculate the smallest cross-sectional area of the nasal airway. A natural head position roentgenocephalogram was used to measure the craniovertical angulation (NSL/VER), craniocervical angulation (NSL/OPT), and cervical spine inclination (OPT/HOR). The results showed a trend toward enlarged craniocervical angulation and forward inclination of the cervical spine in subjects with a relatively large nasal cross-sectional area. Though the general opinion on the effects of reduced upper airway size on head posture is opposite, these results are an experimental confirmation of the theoretically expected mechanism that leads to increased head extension in obstructed subjects. 相似文献
100.
Wilfried Pestemer und Werner Mannt 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1980,171(4):272-277
Zusammenfassung Die Rückstandssituation von 14 herbiciden Wirkstoffen (Alachlor, Chloridazon, Chlorpropham, Chloroxuron, Chlorthal-methyl, Desmetryn, Lenacil, Linuron, Methabenzthiazuron, Monolinuron, Napropamid, Pendimethalin, Phenmedipham und Terbutryn) in 6 Küchenkräutern (Borretsch, Dill, Kerbel, Kresse, Pimpinelle und Sauerampfer) wird erläutert anhand von Rückstandsdaten aus Freilandversuchen (2 Vegetationsperioden), die in zwei Laboratorien ermittelt wurden. Die Methoden werden schematisch beschrieben sowie Bestimmungsgrenzen und Wiederfindungsraten für beide Laboratorien angegeben.
Herbicide residues in some herbs
Summary Residue occurrence is discussed with use of 14 herbicides (Alachlor, Chloridazone, Chlorpropham, Chloroxuron, Chlorthal-methyl, Desmetryne, Lenacil, Linuron, Methabenzthiazuron, Monolinuron, Napropamide, Pendimethalin, Phenmedipham and Terbutryne) on 6 herbs (borage, dill, garden-chervil, garden cress, anise and sorrel) in the light of residue analyses (from field trials over two seasons with analyses carried out in two laboratories). The methods are outlined; limits of the determinations and recoveries are given.相似文献