Magnetic trapping of neutrons

Accurate measurement of the lifetime of the neutron (which is unstable to beta decay) is important for understanding the weak nuclear force and the creation of matter during the Big Bang. Previous measurements of the neutron lifetime have mainly been limited by certain systematic errors; however, these could in principle be avoided by performing measurements on neutrons stored in a magnetic trap. Neutral-particle and charged-particle traps are widely used for studying both composite and elementary particles, because they allow long interaction times and isolation of particles from perturbing environments. Here we report the magnetic trapping of neutrons. The trapping region is filled with superfluid 4He, which is used to load neutrons into the trap and as a scintillator to detect their decay. Neutrons in the trap have a lifetime of 750(+330)(-200) seconds, mainly limited by their beta decay rather than trap losses. Our experiment verifies theoretical predictions regarding the loading process and magnetic trapping of neutrons. Further refinement of this method should lead to improved precision in the neutron lifetime measurement.     

The duration of antigen receptor signalling determines CD4+ versus CD8+ T-cell lineage fate

Signals elicited by binding of the T-cell antigen receptor and the CD4/CD8 co-receptor to major histocompatibility complex (MHC) molecules control the generation of CD4+ (helper) or CD8+ (cytotoxic) T cells from thymic precursors that initially express both co-receptor proteins. These precursors have unique, clonally distributed T-cell receptors with unpredictable specificity for the self-MHC molecules involved in this differentiation process. However, the mature T cells that emerge express only the CD4 (MHC class II-binding) or CD8 (MHC class I-binding) co-receptor that complements the MHC class-specificity of the T-cell receptor. How this matching of co-receptor-defined lineage and T-cell-receptor specificity is achieved remains unknown, as does whether signalling by the T-cell receptors, co-receptors and/or general cell-fate regulators such as Notch-1 contributes to initial lineage choice, to subsequent differentiation processes or to both. Here we show that the CD4 versus CD8 lineage fate of immature thymocytes is controlled by the co-receptor-influenced duration of initial T-cell receptor-dependent signalling. Notch-1 does not appear to be essential for this fate determination, but it is selectively required for CD8+ T-cell maturation after commitment directed by T-cell receptors. This indicates that the signals constraining CD4 versus CD8 lineage decisions are distinct from those that support subsequent differentiation events such as silencing of co-receptor loci.     

把力学扩展到思维：心理学和经济学的力学基础

本书阐述现代理性力学的数学原理在人工智能中的应用并发展成精确的智力模型，这种阐述可以帮助读者把思维理解为力学系统。该系统显示出真实的、非隐喻的力、惯性和运动。作者用力学术语分析了诱导、论证、学习和通告过程。这些分析为心理学和经济学提供了有限合理性的新特征，为力学提供新型的材料，这些材料显示出不同思维类型的本构运动学和动力学特性，也为哲学提供结合离散和连续力学量的杂交系统的严格理论。描述人体的物理科学和描述人类思维的心理科学合成的力学重整体（reintegration）将为传统的哲学和现代的计算问题打开技术分析的新途径。     

Hydatellaceae identified as a new branch near the base of the angiosperm phylogenetic tree

Although the relationship of angiosperms to other seed plants remains controversial, great progress has been made in identifying the earliest extant splits in flowering-plant phylogeny, with the discovery that the New Caledonian shrub Amborella trichopoda, the water lilies (Nymphaeales), and the woody Austrobaileyales constitute a basal grade of lines that diverged before the main radiation in the clade. By focusing attention on these ancient lines, this finding has re-written our understanding of angiosperm structural and reproductive biology, physiology, ecology and taxonomy. The discovery of a new basal lineage would lead to further re-evaluation of the initial angiosperm radiation, but would also be unexpected, as nearly all of the approximately 460 flowering-plant families have been surveyed in molecular studies. Here we show that Hydatellaceae, a small family of dwarf aquatics that were formerly interpreted as monocots, are instead a highly modified and previously unrecognized ancient lineage of angiosperms. Molecular phylogenetic analyses of multiple plastid genes and associated noncoding regions from the two genera of Hydatellaceae identify this overlooked family as the sister group of Nymphaeales. This surprising result is further corroborated by evidence from the nuclear gene phytochrome C (PHYC), and by numerous morphological characters. This indicates that water lilies are part of a larger lineage that evolved more extreme and diverse modifications for life in an aquatic habitat than previously recognized.     

Vision. Realignment of cones after cataract removal

Through unique observations of an adult case of bilateral congenital cataract removal, we have found evidence that retinal photoreceptors will swiftly realign towards the brightest regions in the pupils of the eye. Cones may be phototropic, actively orientating themselves towards light like sunflowers in a field.     

Liver monoamine oxidase in normal and regeneratingDiemictylus viridescens

Résumé L'oxydase monoamine se trouve sous une forme active dans le foie d'un urodèle adulte capable d'activité normale et régénératrice. Au cours des deux premières heures qui suivent l'amputation d'un membre antérieur, on peut noter une augmentation appréciable de l'activité de l'oxydase monoamine. Cette augmentation indique que la tension physiologique produite par l'amputation rend actifs dans le foie les précurseurs de l'oxydase monoamine qui peuvent, à leur tour, stimuler un métabolisme plus rapide et augmenter la quantité des catécholamines qui circulent.     

The origin of tourniquet shock-induced cardiovascular failure in exogenous hyperthyroidism

Zusammenfassung Die Veränderung des endogenen Catecholamin-Gehaltes des Herzens hyperthyroider Ratten hebt die Schockempfindlichkeit der Tiere nicht auf.     

Histamine-induced hypotension modified by H1 and H2 antagonists in the monkey (Macaca mulatta)

Summary Blocking H₂ receptors with burimamide in the dose used (20 mg/kg) approximately doubles the amount) of histamine needed to produced the same effect as seen when H₁ antagonists (chlorpheniramine or mepyramine) are used alone. TheK ₂ ratios for chlorpheniramine-chlorpheniramine plus burimamide are 117–204 and for mepyramine-mepyramine phus burimamide are 200–478. H₁ and H₂ receptors, in the monkey, when stimulated, both cause cardiovascular responses in the same direction.