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E Davenas F Beauvais J Amara M Oberbaum B Robinzon A Miadonna A Tedeschi B Pomeranz P Fortner P Belon 《Nature》1988,333(6176):816-818
When human polymorphonuclear basophils, a type of white blood cell with antibodies of the immunoglobulin E (IgE) type on its surface, are exposed to anti-IgE antibodies, they release histamine from their intracellular granules and change their staining properties. The latter can be demonstrated at dilutions of anti-IgE that range from 1 x 10(2) to 1 x 10(120); over that range, there are successive peaks of degranulation from 40 to 60% of the basophils, despite the calculated absence of any anti-IgE molecules at the highest dilutions. Since dilutions need to be accompanied by vigorous shaking for the effects to be observed, transmission of the biological information could be related to the molecular organization of water. 相似文献
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Mehdi Haj Hojjatollah Mansouri Reza Vafaei Golam Reza Ebrahimi Ali Kanani 《矿物冶金与材料学报》2013,20(6):529-534
The hot compression behavior of AISI 321 austenitic stainless steel was studied at the temperatures of 950–1100℃ and the strain rates of 0.01–1 s?1 using a Baehr DIL-805 deformation dilatometer. The hot deformation equations and the relationship between hot deformation parameters were obtained. It is found that strain rate and deformation temperature significantly influence the flow stress behavior of the steel. The work hardening rate and the peak value of flow stress increase with the decrease of deformation temperature and the increase of strain rate. In addition, the activation energy of deformation (Q) is calculated as 433.343 kJ/mol. The microstructural evolution during deformation indicates that, at the temperature of 950℃ and the strain rate of 0.01 s?1, small circle-like precipitates form along grain boundaries; but at the temperatures above 950℃, the dissolution of such precipitates occurs. Energy-dispersive X-ray analyses indicate that the precipitates are complex carbides of Cr, Fe, Mn, Ni, and Ti. 相似文献
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Summary Two new syntheses of Chloramphenicol are described starting from the diastereoisomers of -phenylserinmethyl ether and cinnamyl alcohol methyl ether respectively. The configurational correlation of the diastereoisomers of -phenylserin-methyl ether with -phenylserin and chloramphenicol is discussed. A new method for transforming erythro--phenylserinol into threo--phenylserinol is described. New examples of the Neighboring group effect were studied. The sterical course of the addition of methylhypobromite to the double bond is discussed. 相似文献
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Summary By reacting dopa, -methyl- and -ethyldopa and the corresponding esters with aldehydes geminate amino-carbinols of the general formula I can be prepared. The acetylation of the adduct of -methyldopa-methylester with acetaldehyde and benzaldehyde and the resolution of the latter compound withd-tartaric acid is described. 相似文献
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Ramzi Chalghaf Walid Oueslati Marwa Ammar Hafsia Ben Rhaiem AbdesslemBen Haj Amara 《自然科学进展(英文版)》2013,23(1):23-35
This work aims at investigating the strain effect,created by varying pH solution and continuous heating cycle,on the cation exchange process in the case of Na-rich montmorillonite sample in contact with bi-ionic solution with variable concentration,saturated respectively by Co2+ and Cu2+ cations.The ionic exchange process is characterized using XRD analysis obtained through the comparison of experimental XRD patterns with calculated ones,which allowed us to determine several structural parameters related to the nature,abundance,size,position and organization of exchangeable cation and water molecule in the interlamellar space along the caxis.Indeed,the proposed theoretical models,for the stressed samples,show that the structure presents an interstratified hydration character and proves the coexistence of more than two ’’crystallite’’ specie in the structure.The perturbation types have an obvious effect on the selective exchange process for all stressed samples,where the interlayer space is characterized by the coexistence of more one exchangeable cation. 相似文献
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Expression cloning of a cocaine- and antidepressant-sensitive human noradrenaline transporter 总被引:56,自引:0,他引:56
At most synapses, chemical signalling is terminated by a rapid reaccumulation of neurotransmitter into presynaptic terminals. Uptake systems for the biogenic amines are the initial site of action for therapeutic antidepressants and drugs such as cocaine and the amphetamines. We have isolated a complementary DNA clone encoding a human noradrenaline transporter. The cDNA sequence predicts a protein of 617 amino acids, with 12-13 highly hydrophobic regions compatible with membrane-spanning domains. Expression of the cDNA clone in transfected HeLa cells indicates that noradrenaline transport activity is sodium-dependent and sensitive to selective noradrenaline transport inhibitors. Transporter RNA is localized to the brainstem and the adrenal gland. The predicted protein sequence demonstrates significant amino-acid identity with the Na+/gamma-aminobutyric acid transporter, thus identifying a new gene family for neurotransmitter transporter proteins. Analysis of its structure and function may lead to structure-based drug design for the treatment of human depression and could help determine whether transporter abnormalities underlie affective disorders. 相似文献
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The zoeal stages of Hiplyra variegata are described and illustrated for the first time. Zoea I was obtained from an ovigerous female, and the zoea II and zoea III stages were captured in the plankton (their identity was confirmed by rearing some of them from earlier stages). Comparisons are made with the only other species of the genus of which larvae are known, i.e. H. platycheir. The presence of a lateral spine on the carapace of zoea I is one of the most important characters that can be used for easy recognition of H. variegata. It is important to note that the third zoea of H. variegata has four small spines at each posterolateral margin of the carapace, in contrast to three spines in other species. 相似文献