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101.
Average rates of polypeptide chain elongation have been determined in cockerel liver explants on 4 successive days following an in vivo injection of 17 beta-estradiol. Incorporation of [3H]leucine by the explants is linear for at least 24 h, and the rate of protein synthesis increases significantly after estrogen injection. The explants synthesize and secrete serum albumin. B-apolipoprotein, and the phosphoprotein vitellogenin at relative rates which are similar to those reported for liver in vivo. Using this system, changes in the average rates of polypeptide chain elongation have been analyzed as a temporal sequence following a single injection of 17 beta-estradiol into cockerels. For this, average ribosome half-transit times were determined by measuring the kinetics of transfer of labeled polypeptides from polysomal-bound to released polypeptides. The data revealed a dramatic effect of estradiol on the average ribosome half-transit time with a maximum increase of 4.6-fold; however, the average size of polypeptides synthesized by explants at the peak of induction increased only 15% when compared to uninduced liver explants. These findings indicate that injection of estradiol results in large changes in the actual rates at which amino acids are added to the growing nascent polypeptide chain; that is, rates of polypeptide chain elongation. Therefore, translation-level regulation of protein synthesis in cockerel livers plays a significant part in determining the magnitude of the response to hormone stimulation. 相似文献
102.
O?2 radicals were formed in the presence of 2,5- dimethyl benzoquinone (DMBQ). The equilibrium constant of the electron transfer reaction DMBQ + O?2 ? DMBQ? + O2 was determined. From this value and from E0(DMBQ/DMBQ?) we calculated the redox potential of the couple O2/O?2, as E0 (O2/O?2) = ?0.33 V. 相似文献
103.
Ilan Shomer Pinhas Lindner Itamar Ben-Gera Rosa Vasiliver 《Journal of the science of food and agriculture》1982,33(6):565-575
The structure of potato protein precipitates formed by heat treatment or acidification of potato juice was investigated by transmission electron microscopy. Precipitates formed by heat denaturation (3 min at 100°C) consist of electron-dense particles of diameter < 300 nm, aggregated into three-dimensional open networks. Precipitates, formed by acidification to pH 3.0 and holding the acidified juice at room temperature, consist of network-like aggregates of electron-dense particles embedded in thin films which hinder the formation of a dense sediment. This structure explains the high sediment volumes which are typical of this kind of precipitate. By warming the acidified potato juice to 40°C, rapid flocculation and sedimentation of the suspended insoluble protein are observed within a few minutes and a dense sediment is finally obtained. This sediment consists mainly of the network-like aggregates of electron-dense particles and material of low electron density formed by the collapse of the films. Protein films have also been observed in precipitates of heat-denatured bovine serum albumin (BSA). High-methoxyl pectin promotes the formation of protein films on heat denaturation of potato proteins or BSA. 相似文献
104.
The relationship between the product specifications and its economic value for the manufacturer and the customer is analyzed. The aspects of the product dealt with are cost performance and its implications for pricing policy. An economic model for the manufacturer is combined with a cost/benefit analysis for the prospective customer to yield an integrative model that permits coupling of the demand and supply functions under the common denominator of performance level. It allows the manufacturer to weigh the performance attributes of the product by means of the customer evaluation and attenuates the tendency to overspecify the product. A numerical example based on data gathered on a citrus-fruit sorting robot is given. In this example the profitability frontier, where both parties make profits, is defined and calculated 相似文献
105.
Daniel Keren Ehud Rivlin Ilan Shimshoni Isaac Weiss 《Journal of Mathematical Imaging and Vision》2000,12(1):5-23
A general paradigm for recognizing 3D objects is offered, and applied to some geometric primitives (spheres, cylinders, cones, and tori). The assumption is that a curve on the surface, or a pair of intersecting curves, was measured with high accuracy (for instance, by a sensory robot). Differential invariants of the curve(s) are then used to recognize the surface. The motivation is twofold: the output of some devices is not surface range data, but such curves. Also, a considerable speedup is obtained by using curve data, as opposed to surface data which usually contains a much higher number of points.We survey global, algebraic methods for recognizing surfaces, and point out their limitations. After introducing some notions from differential geometry and elimination theory, the differential and semi-differential approaches to the problem are described, and novel invariants which are based on the curve's curvature and torsion are derived. 相似文献
106.
Scent has been well documented as having significant effects on emotion (Alaoui-Ismaili in Physiol Behav 62(4):713–720, 1997; Herz et al. in Motiv Emot 28(4):363–383, 2004), learning (Smith et al. in Percept Mot Skills 74(2):339–343, 1992; Morgan in Percept Mot Skills 83(3)(2):1227–1234, 1996), memory (Herz in Am J Psychol 110(4):489–505, 1997) and task performance (Barker et al. in Percept Mot Skills 97(3)(1):1007–1010, 2003). This paper describes an experiment in which environmentally appropriate scent was presented as an additional sensory modality
consistent with other aspects of a virtual environment called DarkCon. Subjects’ game play habits were recorded as an additional
factor for analysis. Subjects were randomly assigned to receive scent during the VE, and/or afterward during a task of recall
of the environment. It was hypothesized that scent presentation during the VE would significantly improve recall, and that
subjects who were presented with scent during the recall task, in addition to experiencing the scented VE, would perform the
best on the recall task. Skin-conductance was a significant predictor of recall, over and above experimental groups. Finally,
it was hypothesized that subjects’ game play habits would affect both their behavior in and recall of the environment. Results
are encouraging to the use of scent in virtual environments, and directions for future research are discussed.
The project described herein has been sponsored by the US Army Research, Development, and Engineering Command (RDECOM). Statements
and opinions expressed do not necessarily reflect the position or the policy of the US Government; no official endorsement
should be inferred. 相似文献
107.
The reduction rate of Cr3+ by eaq was determined, k8 = 1.7 × 1010 M?1 s?1. The reaction of Cr2+ with O2 was studied, k2 = 1.6 × 108 M?1 s?1. The spectrum of CrO2+2 was obtained both with the pulse radiolysis method and by mixing Cr2+ with excess of O2. It was shown that CrO2+2 decays slowly to yield HCrO?4. The results suggest that the reaction of Cr2+ with O2 is a two electron transfer process. 相似文献
108.
The interaction of CO2 with potassium-covered Re(001) has been investigated. This system has been studied by means of work function (Δϕ), optical second harmonic generation (SHG), and temperature-programmed desorption (TPD) measurements. Strong electronic interaction between carbon dioxide and potassium is observed upon adsorption at 90 K. This is indicated by a rapid quenching of the SHG signal of K following postadsorption of CO2, with a quenching cross section of 70 Å2. Work function change measurements are consistent with such interaction, evidenced by an undepolarization effect, namely, further decrease of the work function upon CO2 adsorption, below the minimum obtained by pure potassium. In the presence of potassium, the dissociation probability of 0.5 ML adsorbed carbon dioxide increases from 0.5 on the clean metal surface to 0.85 on 1 ML potassium-covered Re(001), information obtained from TPD measurements following heating to 1250 K. It is concluded that a K–CO2 surface compound is formed upon adsorption at 95 K on the potassium-covered surface. 相似文献
109.
Ilan Marek 《Israel journal of chemistry》2018,58(1-2):122-126
Many prominent colleagues have discussed over the years the past and future of our field and it is clear that organic chemistry had, and will continue to have, an extremely important impact on the development of our modern society and on the quality of life. 1 In this essay, I am not planning to repeat the importance of the field, the major breakthroughs that shape our discipline, as several authors of this Rosarium will certainly do it much better than me. I am rather going to express my personal opinion on a general problem that our field has to confront in our modern time and will then discuss the origin, importance and impact of organic chemistry in Israel. Finally, I will finish this Rosario by giving the words to the youngest generation of chemists that will continue to expand organic synthesis to different directions by sharing a “brainstorming” session we had in one of our weekly group meetings. 相似文献
110.