Confidence in beliefs about pain predicts expectancy effects on pain perception and anticipatory processing in right anterior insula.

Psychological factors play a major role in exacerbating chronic pain. Effective self-management of pain is often hindered by inaccurate beliefs about the nature of pain which lead to a high degree of emotional reactivity. Probabilistic models of perception state that greater confidence (certainty) in beliefs increases their influence on perception and behavior. In this study, we treat confidence as a metacognitive process dissociable from the content of belief. We hypothesized that confidence is associated with anticipatory activation of areas of the pain matrix involved with top-down modulation of pain. Healthy volunteers rated their beliefs about the emotional distress that experimental pain would cause, and separately rated their level of confidence in this belief. Confidence predicted the influence of anticipation cues on experienced pain. We measured brain activity during anticipation of pain using high-density EEG and used electromagnetic tomography to determine neural substrates of this effect. Confidence correlated with activity in right anterior insula, posterior midcingulate and inferior parietal cortices during the anticipation of pain. Activity in the right anterior insula predicted a greater influence of anticipation cues on pain perception, whereas activity in right inferior parietal cortex predicted a decreased influence of anticipatory cues. The results support probabilistic models of pain perception and suggest that confidence in beliefs is an important determinant of expectancy effects on pain perception.

Shock transmission in a coupled beam system

This paper investigates the circumstances under which high peak acceleration can occur in the internal parts of a system when subjected to impulsive driving on the outside. Motivating examples include the design of packaging for transportation of fragile items. The system is modelled in an idealised form using two beams coupled with point connections. A Rayleigh-Ritz model of such coupled beams was validated against measurements on a particular beam system, then the model was used to explore the acceleration response to impulsive driving in the time, frequency and spatial domains. This study is restricted to linear vibration response and additional mechanisms for high internal acceleration due to nonlinear effects such as internal impacts are not considered. Using Monte Carlo simulation in which the indirectly driven beam was perturbed by randomly placed point masses a wide range of system behaviour was explored. This facilitates identification of vulnerable configurations that can lead to high internal acceleration. The results from the study indicate the possibility of curve veering influencing the peak acceleration amplification. The possibility of veering within an ensemble was found to be dependent on the relative coupling strength of the modes. Understanding of the mechanism may help to avoid vulnerable cases, either by design or by preparatory vibration testing. © 2013 Elsevier Ltd.

细菌性败血症引起鲫凝血障碍的研究

以嗜水气单胞菌感染体重为70g左右的鲫并检测了感染鱼和对照鱼的血液学及播散性血管内凝血判定指标等参数。结果表明细菌性败血症病鱼严重贫血，存在明显的凝血障碍，在疾病发展过程中存在播散性血管内凝血现象，这一现象导致了病鱼全身性出血，并在疾病的病理生理过程中起了重要的作用。

凤眼莲组织培养的研究

将凤眼莲茎段培养在含６－ＢＡ１～１０ｍｇ／Ｌ的ＭＳ培养基上，光照培养，可直接分化出芽．６－ＢＡ浓度为３ｍｇ／Ｌ时，芽分化频率最高，达４６．７％．所分化的不定芽必须及时转移到低激素浓度的培养基上，才能进一步生长发育．凤眼莲幼叶和幼根外植体在上述相同培养条件下，仅能形成愈伤组织．凤眼莲再生植株必须生长在高湿度的培养环境中，液体培养明显优于固体培养．

The propagation of acoustic waves in a slowly varying duct with radially sheared axial mean flow

We consider the propagation of acoustic waves along a cylindrical duct carrying radially sheared axial mean flow, in which the duct radius is allowed to vary slowly along the axis. In previous work [A.J. Cooper & N. Peake, Journal of Fluid Mechanics 445 (2001) 207-234.] radially sheared axial mean flow with nonzero swirl in a slowly varying duct was considered, but in this paper we set the swirl to zero, thereby allowing simplification of the calculations of both the mean and unsteady flows. In this approach the acoustic wavenumber and corresponding eigenfunction are determined locally, while the wave amplitude is found by solving an evolution equation along the duct. Sample results are presented, including a case in which, perhaps surprisingly, the number of cut-on modes increases as the duct radius decreases. © 2013 Elsevier Ltd. All rights reserved.

鳜鱼的耗氧率及其池塘养殖

本文较详细地报道了鳜鱼的耗氧率和窒息点，并对鳜鱼和作其饲料的鱼同池饲养的可能性进行了探讨。结果表明，鳜鱼耗氧量和体重正相关（ｒ＝０．９９），耗氧率与体重反相关（ｒ＝－０．９７）；在水温２０℃，鱼种耗氧率约为０．１４ｍｇ／ｇ．ｈ．，成鱼约为０．１２ｍｇ／ｇ．ｈ．；耗氧量和耗氧率均与水温正相关（ｒ＝０．９０，ｒ＝０．９４），水温１３—３０℃时，体重２３０±１１．７ｇ的鳜鱼。耗氧量为１４．３１—４２．１３ｍｇ／尾。ｈ．，耗氧率为０．０５９—０．１７５ｍｇ／ｇ．ｈ．；鳜鱼耗氧率昼夜变化与家鱼相反，黄昏至凌晨是高峰

Modelling the vibration of tyre sidewalls

The dynamical behaviour of the sidewall has an important influence on tyre vibration characteristics. Nonetheless, it remains crudely represented in many existing models. The current work considers a geometrically accurate, two-dimensional, sidewall description, with a view to identifying potential shortcomings in the approximate formulations and identifying the physical characteristics that must be accounted for. First, the mean stress state under pressurisation and centrifugal loading is investigated. Finite-Element calculations show that, while the loaded sidewall shape remains close to a toroid, its in-plane tensions differ appreciably from the associated analytical solution. This is largely due to the inability of the anisotropic sidewall material to sustain significant azimuthal stress. An approximate analysis, based on the meridional tension alone, is therefore developed, and shown to yield accurate predictions. In conjunction with a set of formulae for the 'engineering constants' of the sidewall material, the approximate solutions provide a straightforward and efficient means of determining the base state for the vibration analysis. The latter is implemented via a 'waveguide' discretisation of a variational formulation. Its results show that, while the full geometrical description is necessary for a complete and reliable characterisation of the sidewall's vibrational properties, a one-dimensional approximation will often be satisfactory in practice. Meridional thickness variations only become important at higher frequencies (above 500 Hz for the example considered here), and rotational inertia effects appear to be minor at practical vehicle speeds. © 2013 Elsevier Ltd. All rights reserved.

Friction-induced vibration: Model development and comparison with large-scale experimental tests

This paper presents a comparison between theoretical predictions and experimental results from a pin-on-disc test rig exploring friction-induced vibration. The model is based on a linear stability analysis of two systems coupled by sliding contact at a single point. Predictions are compared with a large volume of measured squeal initiations that have been post-processed to extract growth rates and frequencies at the onset of squeal. Initial tests reveal the importance of including both finite contact stiffness and a velocity-dependent dynamic model for friction, giving predictions that accounted for nearly all major clusters of squeal initiations from 0 to 5 kHz. However, a large number of initiations occurred at disc mode frequencies that were not predicted with the same parameters. These frequencies proved remarkably difficult to destabilise, requiring an implausibly high coefficient of friction. An attempt has been made to estimate the dynamic friction behaviour directly from the squeal initiation data, revealing complex-valued frequency-dependent parameters for a new model of linearised dynamic friction. These new parameters readily destabilised the disc modes and provided a consistent model that could account for virtually all initiations from 0 to 15 kHz. The results suggest that instability thresholds for a wide range of squeal-type behaviour can be predicted, but they highlight the central importance of a correct understanding and accurate description of dynamic friction at the sliding interface. © 2013 Elsevier Ltd. All rights reserved.

Transient response of structures with uncertain properties to nonlinear shock loading

A method is presented to predict the transient response of a structure at the driving point following an impact or a shock loading. The displacement and the contact force are calculated solving the discrete convolution between the impulse response and the contact force itself, expressed in terms of a nonlinear Hertzian contact stiffness. Application of random point process theory allows the calculation of the impulse response function from knowledge of the modal density and the geometric characteristics of the structure only. The theory is applied to a wide range of structures and results are experimentally verified for the case of a rigid object hitting a beam, a plate, a thin and a thick cylinder and for the impact between two cylinders. The modal density of the flexural modes for a thick slender cylinder is derived analytically. Good agreement is found between experimental, simulated and published results, showing the reliability of the method for a wide range of situations including impacts and pyroshock applications. © 2013 Elsevier Ltd. All rights reserved.

DL.1微生物饲料添加剂对养殖鱼类的促长作用

<正> 微生物作为饲料添加剂有其独特的优越性,有些已投入使用,并显示了明显的效果。微生物饲料添加剂资源的开发利用已日益引起国内外科学界和产业部门的重视。本文报道的是应用DL.1菌株培养物作为饲料添加剂饲养草鱼、团头鲂试验结果及其所起的促长作用。

直链烷基苯磺酸盐在模拟水生态系统中转化和归宿的研究

用~(14)C标记直链烷基苯磺酸盐,(~(14)C-LAS),研究了在由塘泥、水草、鱼、螺蛳和溞构成的室内模拟水生态系统中,LAS的降解规律、在水生生物体内的积累分布及其与在水中降解之间的相互关系.

柄杆菌对固氮蓝藻生物量及色素的影响

柄杆菌对固氮蓝藻生物量和色素的影响研究结果表明:多态柄杆菌(Caulobacter polymorphus)017-41或新月柄杆菌(Caulobacter creseentus)CB_2的活菌、死菌及破碎细胞悬液分别与鱼腥藻(Anabaena)、念珠藻(Nostoc)不同藻珠混合培养时,试验组生长量均优于对照组;对衰老黄化的藻培养物的生长刺激作用尤为显著;试验组藻培养物的藻蓝或藻红素含量亦明显高于对照组。其作用机理尚待进一步阐明。