Liquid marbles.

The transport of a small amount of liquid on a solid is not a simple process, owing to the nature of the contact between the two phases. Setting a liquid droplet in motion requires non-negligible forces (because the contact-angle hysteresis generates a force opposing the motion), and often results in the deposition of liquid behind the drop. Different methods of levitation-electrostatic, electromagnetic, acoustic, or even simpler aerodynamic techniques-have been proposed to avoid this wetting problem, but all have proved to be rather cumbersome. Here we propose a simple alternative, which consists of encapsulating an aqueous liquid droplet with a hydrophobic powder. The resulting 'liquid marbles' are found to behave like a soft solid, and show dramatically reduced adhesion to a solid surface. As a result, motion can be generated using gravitational, electrical and magnetic fields. Moreover, because the viscous friction associated with motion is very small, we can achieve quick displacements of the droplets without any leaks. All of these features are of potential benefit in microfluidic applications, and also permit the study of a drop in a non-wetting situation-an issue of renewed interest following the recent achievement of super-hydrophobic substrates.     

国内大学出版社客户投诉处理工作探析

通过对中国大学出版社客户投诉处理工作的抽样调查,分析了大学出版社客户投诉处理工作中的问题以及开展这项工作的现实意义,提出了大学出版社客户投诉处理的对策。     

Infection of young Douglas-firs by dwarf mistletoe in the Southwest

Studies in several areas in Arizona and New Mexico show that dwarf mistletoe ( Arceuthobium douglasii ) is rare in young Douglas-firs growing under infected overstories. Less than 5% of the Douglas-firs under 26 years old and less than 6% of those under 1.4m tall were infected in 77 mistletoe-infested stands. Both percent infection and mean dwarf mistletoe rating of young Douglas-firs increased as tree age, height, and stand dwarf mistletoe ratings increased.     

硫酸钛为钛源制备二氧化钛的实验条件研究

实验以硫酸钛为钛源、尿素为沉淀剂、聚乙二醇600为分散剂,采用均匀沉淀法制备二氧化钛粉末。主要讨论了影响沉淀形成时间的主要因素:尿素的用量及加入方法、聚乙二醇的用量、以及水浴的温度等。实验结果表明,以硫酸钛为钛源、尿素为沉淀剂、聚乙二醇600为分散剂,采用均匀沉淀法制备二氧化钛粉末最佳反应条件为:在水浴加热343 K条件下,将尿素缓慢滴加到硫酸钛和聚乙二醇600的混合液中,硫酸钛和聚乙二醇600的混合液在磁力搅拌器搅拌时滴加尿素,用硫酸调节pH在1.5~2,保持硫酸钛、尿素和聚乙二醇600的摩尔比1∶12∶0.01。     

生化实验室在实践教学中的课程协调和管理作用

自2011年以来,为实现培养医学生动手能力、批判性思维和创新能力的教学目标,作为基础实验课程的生物化学与分子生物学实验在实验内容和课程设置方面进行了一系列的改革,循序渐进,由浅入深,同时突出小班化精英化的教育特色,最大限度地使学生受益。在整个课程的实施过程中,生物化学与分子生物学实验室作为实践课程开展的核心部门,无论是在课程准备,课程安排,还是在教学资源分配和课程内容改革中,都起到了有利的协调和管理作用,最大限度地服务于实践教学,使实验课程在良好有序的环境中发展前行。     

A very faint core-collapse supernova in M85

An anomalous transient in the early Hubble-type (S0) galaxy Messier 85 (M85) in the Virgo cluster was discovered by Kulkarni et al. on 7 January 2006 that had very low luminosity (peak absolute R-band magnitude M(R) of about -12) that was constant over more than 80 days, red colour and narrow spectral lines, which seem inconsistent with those observed in any known class of transient events. Kulkarni et al. suggest an exotic stellar merger as the possible origin. An alternative explanation is that the transient in M85 was a type II-plateau supernova of extremely low luminosity, exploding in a lenticular galaxy with residual star-forming activity. This intriguing transient might be the faintest supernova that has ever been discovered.     

Novel neurotrophic factor CDNF protects and rescues midbrain dopamine neurons in vivo

In Parkinson's disease, brain dopamine neurons degenerate most prominently in the substantia nigra. Neurotrophic factors promote survival, differentiation and maintenance of neurons in developing and adult vertebrate nervous system. The most potent neurotrophic factor for dopamine neurons described so far is the glial-cell-line-derived neurotrophic factor (GDNF). Here we have identified a conserved dopamine neurotrophic factor (CDNF) as a trophic factor for dopamine neurons. CDNF, together with its previously described vertebrate and invertebrate homologue the mesencephalic-astrocyte-derived neurotrophic factor, is a secreted protein with eight conserved cysteine residues, predicting a unique protein fold and defining a new, evolutionarily conserved protein family. CDNF (Armetl1) is expressed in several tissues of mouse and human, including the mouse embryonic and postnatal brain. In vivo, CDNF prevented the 6-hydroxydopamine (6-OHDA)-induced degeneration of dopaminergic neurons in a rat experimental model of Parkinson's disease. A single injection of CDNF before 6-OHDA delivery into the striatum significantly reduced amphetamine-induced ipsilateral turning behaviour and almost completely rescued dopaminergic tyrosine-hydroxylase-positive cells in the substantia nigra. When administered four weeks after 6-OHDA, intrastriatal injection of CDNF was able to restore the dopaminergic function and prevent the degeneration of dopaminergic neurons in substantia nigra. Thus, CDNF was at least as efficient as GDNF in both experimental settings. Our results suggest that CDNF might be beneficial for the treatment of Parkinson's disease.     

West Nile virus emergence and large-scale declines of North American bird populations

Emerging infectious diseases present a formidable challenge to the conservation of native species in the twenty-first century. Diseases caused by introduced pathogens have had large impacts on species abundances, including the American chestnut, Hawaiian bird species and many amphibians. Changes in host population sizes can lead to marked shifts in community composition and ecosystem functioning. However, identifying the impacts of an introduced disease and distinguishing it from other forces that influence population dynamics (for example, climate) is challenging and requires abundance data that extend before and after the introduction. Here we use 26 yr of Breeding Bird Survey (BBS) data to determine the impact of West Nile virus (WNV) on 20 potential avian hosts across North America. We demonstrate significant changes in population trajectories for seven species from four families that concur with a priori predictions and the spatio-temporal intensity of pathogen transmission. The American crow population declined by up to 45% since WNV arrival, and only two of the seven species with documented impact recovered to pre-WNV levels by 2005. Our findings demonstrate the potential impacts of an invasive species on a diverse faunal assemblage across broad geographical scales, and underscore the complexity of subsequent community response.