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M. Hill 《Cellular and molecular life sciences : CMLS》1957,13(10):395-396
Zusammenfassung Das morphologische Bild der Sekretion des Histamins und der Mukopolysaccharide vom Hyaluronattypus wird in den Mastzellen festgestellt. Die Histaminsekretion äussert sich im Verlust der metachromatischen Eigenschaften mancher Mastzellgranula und in der dadurch auftretenden Wabenstruktur der Mastzellen selbst, während die Sekretion der Mukopolysaccharide durch die intrazelluläre Änderung der Färbbarkeit der Granula und ihre darauffolgende Ausschüttung aus dem Zytoplasma der Mastzellen charakterisiert ist. 相似文献
74.
Schliekelman et al. have provided a model to quantify the speed at which HIV-resistance haplotypes can become enriched in a susceptible population through a delay in the onset of AIDS, permitting greater lifetime reproduction and the selection of AIDS-delaying haplotypes. But we question their conclusion that there could be a rapid evolution of resistance to AIDS onset in some African populations if the current HIV epidemic persists, as this depends on an untested assumption: that variant forms of the chemokine-receptor-5 (CCR5) gene impart selective advantages or disadvantages in Africa that are comparable to those reported for African Americans. Here we test this premise in a large Ugandan population, and find that CCR5 variants are not associated with HIV/AIDS disease risk in Africa--the origin and centre of the current AIDS pandemic. This gene may therefore not be subject to rapid evolutionary change as a result of the HIV epidemic in Africa. 相似文献
75.
TSLP promotes interleukin-3-independent basophil haematopoiesis and type 2 inflammation 总被引:1,自引:0,他引:1
76.
Chan J Alegre TP Safavi-Naeini AH Hill JT Krause A Gröblacher S Aspelmeyer M Painter O 《Nature》2011,478(7367):89-92
The simple mechanical oscillator, canonically consisting of a coupled mass-spring system, is used in a wide variety of sensitive measurements, including the detection of weak forces and small masses. On the one hand, a classical oscillator has a well-defined amplitude of motion; a quantum oscillator, on the other hand, has a lowest-energy state, or ground state, with a finite-amplitude uncertainty corresponding to zero-point motion. On the macroscopic scale of our everyday experience, owing to interactions with its highly fluctuating thermal environment a mechanical oscillator is filled with many energy quanta and its quantum nature is all but hidden. Recently, in experiments performed at temperatures of a few hundredths of a kelvin, engineered nanomechanical resonators coupled to electrical circuits have been measured to be oscillating in their quantum ground state. These experiments, in addition to providing a glimpse into the underlying quantum behaviour of mesoscopic systems consisting of billions of atoms, represent the initial steps towards the use of mechanical devices as tools for quantum metrology or as a means of coupling hybrid quantum systems. Here we report the development of a coupled, nanoscale optical and mechanical resonator formed in a silicon microchip, in which radiation pressure from a laser is used to cool the mechanical motion down to its quantum ground state (reaching an average phonon occupancy number of 0.85 ± 0.08). This cooling is realized at an environmental temperature of 20?K, roughly one thousand times larger than in previous experiments and paves the way for optical control of mesoscale mechanical oscillators in the quantum regime. 相似文献
77.
Solutions for a cultivated planet 总被引:61,自引:0,他引:61
Foley JA Ramankutty N Brauman KA Cassidy ES Gerber JS Johnston M Mueller ND O'Connell C Ray DK West PC Balzer C Bennett EM Carpenter SR Hill J Monfreda C Polasky S Rockström J Sheehan J Siebert S Tilman D Zaks DP 《Nature》2011,478(7369):337-342
Increasing population and consumption are placing unprecedented demands on agriculture and natural resources. Today, approximately a billion people are chronically malnourished while our agricultural systems are concurrently degrading land, water, biodiversity and climate on a global scale. To meet the world's future food security and sustainability needs, food production must grow substantially while, at the same time, agriculture's environmental footprint must shrink dramatically. Here we analyse solutions to this dilemma, showing that tremendous progress could be made by halting agricultural expansion, closing 'yield gaps' on underperforming lands, increasing cropping efficiency, shifting diets and reducing waste. Together, these strategies could double food production while greatly reducing the environmental impacts of agriculture. 相似文献
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本书被公认为是有关模拟与数字电子学线路设计的权威性教课书与参考书。本书第一版出版后即在世界范围销售了12.5万册,并且被翻译成8种文字。作者通过实际使用的方法来革命化电子学的教学,即将基本定律、经验方法与窍门相结合,在很大程度上采取非数学处理,鼓励线路直觉、奇思妙想以及线路数值与性能的简单计算。第二版是经过彻底修改与更新的,完全重写有关微计算机和微处理器的章节,通过对有关数字电子学、运算放大器与精确设计和构建技术的具体修订,来回应电子学中极其危险的变化步伐。第二版对每一张表格都做了修订,还增加了许多新的表格。本书的第一作者是美国哈佛大学的物理教授,第二作者是Rowland科学研究所的电气工程主任,他曾在哈佛大学设计了一百多种电子科学仪器。 相似文献
80.
The process of segmentation, in which the developing embryo is divided into repetitive structures along its antero-posterior (A-P) axis, as a means of organizing and coordinating the body plan is found in a wide range of organisms. In Drosophila, homoeotic genes are involved in all levels of segmental organization and in determining segment identity. The roles of these genes in segmentation have been found mainly by mutational studies, but also by in situ hybridization, which has shown their domains of expression. In contrast to Drosophila, however, embryonic expression of homoeobox-containing genes in vertebrate organisms has not been found to follow a segmental pattern. Vertebrate segmentation can be clearly seen in the mesodermal somites, but repetitive morphological structures in the central nervous system (neuromeres) have only recently been shown to have developmental significance. Neuromeres in the hindbrain (rhombomeres) have been defined as segmental units by their pattern of nerve formation in the developing chick and by the alternating expression of Krox-20, a gene encoding a zinc-finger DNA-binding protein, in the 9.5-day-old mouse. Here we report that a mouse homoeobox-containing gene, Hox-2.9, is expressed in a segment-specific manner in the developing mouse hindbrain. This expression is in a region which is flanked by the regions of expression of Krox-20, and is precisely contained within a single neuromere, rhombomere 4. 相似文献