Background light adaptation of the retinal neuronal adaptive system

The behaviour of the neuronal adaptive retinal mechanisms to environmental light exposures was studied by measuring the oscillatory potentials (OPs) of the electroretinogram. Dark adapted rats were exposed to four levels of background light (BG), starting at a 'low scotopic' level of 1.43x 10(6) cd/m2, increased by steps of two log units, through 'high scotopic' -, 'low mesopic' - and finally the 'high mesopic' BG of 1.43x 10(0) cd/m2. The summed oscillatory response significantly increased as the BG intensity was raised, except at the 'high mesopic' level. The amplitudes of the a- and b-waves reduced as the BG light increased above the 'high scotopic' level. Each OP responded individually to the different BGs. O1 and O2, significantly enhanced at the 'low scotopic' BG. The amplitudes of the three later OPs increased significantly at the 'low mesopic' BG. The adaptational behaviour of the retinal oscillatory response to BG illumination was different to that of the a- and b- waves. The results indicate that the adaptational neuronal system, as reflected by the OPs, seems to be relatively robust and is separate from the slower photochemical adaptive process in the distal retina. The tentative corollary suggests the oscillatory system to play a vision-preserving role, possibly as an alert against undue depletion of the slowly regenerating visual pigment. The enhancement of the oscillatory response at the 'mesopic' illumination levels indicate both scotopic and photopic processes to contribute to neuronal adaptive activity of the retina.     

青海省卫生监督员现状调查分析

本文对青海省47个卫生行政机关,63个卫生专业机构的监督员情况进行了调查分析,我省现有监督员489人,符合《中国2000年预防保健战略目标》（以下简称《目标》）中有关专职监督员的数量按辖区人口1／万比例配备标准。省级监督员年龄偏高,地市级及具区级年龄分布呈较为理想的“三角宝塔”。省级监督员大专以上学历者占59.72%,与《目标》要求相差甚远;地市级监督员中专以上学历者为98.94%,基本符合《目标》要求;县区级监督员学历偏低,其中有7名监督员无学历。专业分布不够理想,卫生专业人员比例偏低。     

UPLC-MS背景扣除法联合代谢组学技术分析柴胡-白芍药对配伍前后化学成分变化

目的探究柴胡-白芍药对配伍前后化学成分的整体变化情况。方法 UPLC-MS背景扣除法联合代谢组学技术对柴胡-白芍配伍前后的化学成分进行整体分析,采用UPLC-MS分析柴胡、白芍及柴胡-白芍药对各8批提取物的化学成分,并用质谱背景扣除法将柴胡-白芍药对合提物的质谱数据分别扣除白芍、柴胡单提物的质谱数据得配伍后柴胡、白芍的单提物的质谱数据,将柴胡、白芍配伍后的化学成分分别与配伍前各自的化学成分进行主成分分析(PCA)、正交偏最小二乘法判别分析(OPLS-DA),分析柴胡-白芍药对组成药味柴胡、白芍配伍前后整体化学成分的变化情况。结果 UPLC-MS检测柴胡-白芍药对共提物、柴胡及白芍单提物化学成分共57个,结合文献报道指认出其中32个。多元统计结果显示,柴胡-白芍药对配伍前后柴胡中含量发生显著变化的成分有6个,鉴定其中3个成分;白芍中含量发生显著变化的成分有3个,鉴定其中2个成分。分别为柴胡中柴胡皂苷a、3″-O-乙酰化柴胡皂苷a、4″-O-乙酰化柴胡皂苷a配伍后含量降低;白芍中芍药苷、没食子酰基芍药苷或其异构体配伍后含量升高。结论从整体化学组成上比较了柴胡-白芍药对配伍前后的差异,为其配伍机制的阐释奠定了基础。     

背景信号抑制扩散加权成像对兔VX2肝移植瘤疗效评价的实验研究

目的探讨磁共振背景信号抑制扩散加权体部成像(MR DWIBS)在经肝动脉化疗栓塞术(TACE)联合静脉注射血管生成抑制剂内皮抑素(ES)治疗VX2肝移植瘤疗效评价中的作用。材料与方法荷瘤兔随机分为两组,每组8只。ES组经耳缘静脉注射ES0.7 mg.kg-1.d-1,连续应用12天;TACE+ES组经肝动脉给予超液化碘油0.2 ml/kg和阿霉素2 mg/kg,并经耳缘静脉注射内皮抑素0.7 mg.kg-1.d-1,连续应用12天。两组均于治疗前后行MR DWIBS检查,分别测量各组肿瘤组织在不同时间点的表观扩散系数(ADC),并评价DWIBS及DWIBS原始图经3D MIP重组及黑白翻转获得类PET图像的图像特征。结果 ADC值从治疗后第3天起即有变化,TACE+ES组ADC值在治疗后第3、7、13天均高于ES组并有统计学意义(P<0.05)。结论 DWIBS可以在治疗早期动态评价TACE术联合静脉注射血管生成抑制剂ES对VX2肝移植瘤的疗效。DWIBS结合ADC值的定量测量及类PET大范围成像,可以无创性活体评价药物抗肿瘤的治疗反应,为肿瘤的诊断、分期、疗效评价提供有价值的信息。     

Effects of Signal Level and Background Noise on Spectral Representations in the Auditory Nerve of the Domestic Cat

Background noise poses a significant obstacle for auditory perception, especially among individuals with hearing loss. To better understand the physiological basis of this perceptual impediment, the present study evaluated the effects of background noise on the auditory nerve representation of head-related transfer functions (HRTFs). These complex spectral shapes describe the directional filtering effects of the head and torso. When a broadband sound passes through the outer ear en route to the tympanic membrane, the HRTF alters its spectrum in a manner that establishes the perceived location of the sound source. HRTF-shaped noise shares many of the acoustic features of human speech, while communicating biologically relevant localization cues that are generalized across mammalian species. Previous studies have used parametric manipulations of random spectral shapes to elucidate HRTF coding principles at various stages of the cat’s auditory system. This study extended that body of work by examining the effects of sound level and background noise on the quality of spectral coding in the auditory nerve. When fibers were classified by their spontaneous rates, the coding properties of the more numerous low-threshold, high-spontaneous rate fibers were found to degrade at high presentation levels and in low signal-to-noise ratios. Because cats are known to maintain accurate directional hearing under these challenging listening conditions, behavioral performance may be disproportionally based on the enhanced dynamic range of the less common high-threshold, low-spontaneous rate fibers.     

Development of a low-level background gamma-ray spectrometer by KRISS

A new low-level background and high-efficiency gamma-ray spectrometric system, to be used mainly for the activity certification of natural-matrix certified reference materials (CRMs) and environmental reference materials (RMs) that has been developed on the grounds of the Korea Research Institute of Standards and Science (KRISS). The spectrometer consists of a low-background high-purity germanium detector with a relative efficiency of 120% and various shielding devices to reduce radiation background. The cabinet-shaped device made of 10 ton of shielding materials encloses the germanium detector for protection against background from natural radioactivity and neutrons. Three plates of 50-mm-thick plastic scintillation detectors on top of the passive shielding cabinet suppress cosmogenic background by detecting high-energetic cosmic muons bombarding the germanium detector. The measured background rate of the spectrometer for the energy range 50–3000 keV was 1.72 s^–1.     

表证并非六淫都有

表证是寒邪袭表，束缚卫气引起的证候，其特征性的表现是恶寒。表证的病因是寒邪，不可能因为其他的病邪而引起。表证的治疗只须根据有汗和无汗辨别中风和伤誊，分别运用桂枝汤和麻黄汤，不须辨表证的寒热。我们现在所说的其他“表证”，是其他的病邪与表证的兼挟。     

Dephased MRI.

In this work gradient dephasing is treated as a mechanism for manipulating contrast in otherwise conventional MR images. The paper provides a theoretical and experimental framework for this approach. It starts from the observation that dephasing gradients invoke a shift in k-space. From this it is inferred that the effects of in-plane and through-plane dephasing can be systematically explored in the context of any given imaging experiment by sampling k-space more widely and densely than dictated by the field of view (FOV) and the spatial resolution of the desired images. The oversampled k-space allows an ensemble of lower-resolution dephased images to be reconstructed in which the degree and direction of dephasing are determined by the off-center position of the reconstruction window. The efficacy of this approach is demonstrated for standard gradient-echo acquisitions in a phantom. The results indicate the potential of the proposed methodology for evaluating 3D image data and optimizing gradient dephasing in applications that rely on the exploitation of partial volume and susceptibility effects (e.g., tracking interventional devices and tracing magnetically labeled substances).