Distribution-based CFAR detectors in SAR images

1. INTRODUCTION Many researches have been made on automatic target recognition (ATR) from SAR images in the past few years. Lincoln Laboratory has developed a complete, end-to-end ATR system[1-4]. The whole system inclu- des three stages: detection (or prescreening), discri- mination and classification. In the detection stage, a two-parameter CFAR (constant false alarm rate) detector is used as a prescreener to select candidate targets in an SAR image on the basis of local brightne…     

Flow and heat transfer behaviour of nanofluids in microchannels

Flow and heat transfer of aqueous based silica and alumina nanofluids in microchannels were experimentally investigated. The measured friction factors were higher than conventional model predictions at low Reynolds numbers particularly with high nanoparticle concentrations. A decrease in the friction factor was observed with increasing Reynolds number, possibly due to the augmentation of nanoparticle aggregate shape arising from fluid shear and alteration of local nanoparticle concentration and nanofluid viscosity. Augmentation of the silica nanoparticle morphology by fluid shear may also have affected the friction factor due to possible formation of a core/shell structure of the particles. Measured thermal conductivities of the silica nanofluids were in approximate agreement with the Maxwell-Crosser model, whereas the alumina nanofluids only showed slight enhancements. Enhanced convective heat transfer was observed for both nanofluids, relative to their base fluids (water), at low particle concentrations. Heat transfer enhancement increased with increasing Reynolds number and microchannel hydraulic diameter. However, the majority of experiments showed a larger increase in pumping power requirements relative to heat transfer enhancements, which may hinder the industrial uptake of the nanofluids, particularly in confined environments, such as Micro Electro-Mechanical Systems (MEMS).     

Exome sequencing of liver fluke-associated cholangiocarcinoma

Opisthorchis viverrini-related cholangiocarcinoma (CCA), a fatal bile duct cancer, is a major public health concern in areas endemic for this parasite. We report here whole-exome sequencing of eight O. viverrini-related tumors and matched normal tissue. We identified and validated 206 somatic mutations in 187 genes using Sanger sequencing and selected 15 genes for mutation prevalence screening in an additional 46 individuals with CCA (cases). In addition to the known cancer-related genes TP53 (mutated in 44.4% of cases), KRAS (16.7%) and SMAD4 (16.7%), we identified somatic mutations in 10 newly implicated genes in 14.8-3.7% of cases. These included inactivating mutations in MLL3 (in 14.8% of cases), ROBO2 (9.3%), RNF43 (9.3%) and PEG3 (5.6%), and activating mutations in the GNAS oncogene (9.3%). These genes have functions that can be broadly grouped into three biological classes: (i) deactivation of histone modifiers, (ii) activation of G protein signaling and (iii) loss of genome stability. This study provides insight into the mutational landscape contributing to O. viverrini-related CCA.     

两种赤潮藻对温度、氮、磷营养的反应及活体荧光特性的研究

在实验室分批培养条件下,研究了温度及氮磷营养元素对两种赤潮藻增殖的影响,发现海洋原甲藻(Prorocentrum micans)要求的温度较低,其生长最适温度为23℃,生长温度上限在33℃至34℃之间;微小角毛藻(Chaetoceras minutissmus)的生长最适温度约为30℃,生长温度上限在41℃与44℃之间。氮磷缺乏使两种藻的增殖受阻,生长周期缩短,且缺氮比缺磷的影响大,测定表明两种藻的荧光激发光谱的高峰位置都在580nm附近,而荧光发射光谱的峰位为675nm.DCMU能引起两种藻活体荧光的增益,海洋原甲藻的增益荧光比率(F_D/F_X)为2.5,角毛藻的荧光比率较低,通常小于2.0。     

Long-term sensory deprivation prevents dendritic spine loss in primary somatosensory cortex

A substantial decrease in the number of synapses occurs in the mammalian brain from the late postnatal period until the end of life. Although experience plays an important role in modifying synaptic connectivity, its effect on this nearly lifelong synapse loss remains unknown. Here we used transcranial two-photon microscopy to visualize postsynaptic dendritic spines in layer I of the barrel cortex in transgenic mice expressing yellow fluorescent protein. We show that in young adolescent mice, long-term sensory deprivation through whisker trimming prevents net spine loss by preferentially reducing the rate of ongoing spine elimination, not by increasing the rate of spine formation. This effect of deprivation diminishes as animals mature but still persists in adulthood. Restoring sensory experience after adolescent deprivation accelerates spine elimination. Similar to sensory manipulation, the rate of spine elimination decreases after chronic blockade of NMDA (N-methyl-D-aspartate) receptors with the antagonist MK801, and accelerates after drug withdrawal. These studies of spine dynamics in the primary somatosensory cortex suggest that experience plays an important role in the net loss of synapses over most of an animal's lifespan, particularly during adolescence.     

Review of galactic and extragalactic searches for class I methanol masers

Class I methanol masers are important tools for investigations of star formation throughout the Universe. Recently, a series of surveys for class I methanol masers at the 95 GHz transition toward samples of young stellar objects have been undertaken. These surveys have resulted in the detection of about 200 new class I methanol masers and combined with previous increased the number of known observations they have class I methanol masers in our Galaxy to ~400. From analysis of the relationship between class I methanol maser emission and associated astrophysical objects, it has been shown that the intensity of the class I methanol maser emission is closely correlated with the properties of the 1.1 mm Bolocam Galactic Plane Survey （BGPS） dust continuum sources and outflow properties. This further supports the hypothesis that class I methanol masers are collisionally pumped and excited in shocked regions. Based on these observations, it can be inferred that the BGPS catalog is likely to provide more reliable samples for targeting further class I methanol maser searches. A new survey for class I methanol masers toward a larger size sample of BGPS sources to test this is currently underway. The prospects for detecting class I methanol megamasers in extragalactic sources is discussed, and observations constituting the first sensitive search have been proposed.     

脑卒中临床医生手册脑卒中病人护理临床指南

脑卒中是一种突然起病的脑血液循环障碍性疾病,临床表现以猝然昏倒、不省人事或突然发生口眼歪斜、半身不遂、言语不清、智力障碍为主要特征。脑卒中是老年人重要的死亡或致残原因,在人口老龄化趋势日益加速的情况下,脑卒中的危害性亦日益突出,因此,脑卒中的防治已成为卫生工作中的一项重要课题,越来越引起医学界的重视。而在实际生活中,许多脑卒中病人最开始就诊时,接诊的可能并不是神经专科医生,所以对脑卒中的治疗措施难免有些生疏。     

角毛藻（Chaetoceras SP．）热胁迫机理的活体调制叶绿素荧光研究

采用脉冲调制荧光仪（ＰＡＭ）研究了热胁迫下海洋硅藻角毛藻（ＣｈａｅｔｏｃｅｒａｓＳＰ．）的调制叶绿素荧光动力学，分析了各项荧光参数的变化，结果发现该藻基础荧光（Ｆｏ）的骤升温度（Ｔｃ）为３９．５℃．当温度上升至４５℃时Ｆｖ／Ｆｍ比率及最大可变荧光（Ｆｖ）ｓ显著下降，表明光系统Ⅱ受损害．同时非光化猝灭ｑＮ增大，推测是Ｃａｌｖｉｎ循环受阻．用氧电极法测定光合放氧，确定该藻的光合光饱和点在３００～４００μｍｏｌ／ｍ２·Ｓ－１，更高的光强会引起光抑制，在４５℃热胁迫４０ｍｉｎ后其光合放氧才完全停止，结果表明角毛藻具有较高的耐热能力．