Visual thresholds measured with color video monitors

We describe the types of threshold measurement that can be made by using a circular test spot whose colorimetric, temporal, and spatial parameters can be varied. Examples are given of the application of a number of these tests to studies of normal and clinical vision.     

Increased blood pressure later in life may be associated with perinatal n−3 fatty acid deficiency

Hypertension is a major risk factor for cardiovascular and cerebrovascular disease. Previous work in both animals and humans with high blood pressure has demonstrated the antihypertensive effects of n−3 polyunsaturated fatty acids (PUFA), although it is not known whether these nutrients are effective in preventing hypertension. The predominant n−3 PUFA in the mammalian nervous system, docosahexaenoic acid (DHA), is deposited into synaptic membranes at a high rate during the perinatal period, and recent observations indicate that the perinatal environment is important for the normal development of blood pressure control. This study investigated the importance of perinatal n−3 PUFA supply in the control of blood pressure in adult Sprague-Dawley rats. Pregnant rat dams were fed semisynthetic diets that were either deficient in (DEF) or supplemented with (CON) n−3 PUFA. Offspring were fed the same diets as their mothers until 9 wk; then, half of the rats from each group were crossed over to the opposite diet, creating four groups, i.e., CON-CON; CON-DEF; DEF-DEF, DEF-CON. Mean arterial blood pressures (MAP) were measured directly, at 33 wk of age, by cannulation of the femoral artery. The phospholipid fatty acid profile of the hypothalamic region was determined by capillary gas-liquid chromatography. The tissue phospholipid fatty acid profile reflected the diet that the rats were consuming at the time of testing. Both groups receiving DEF after 9 wk of age (i.e., DEF-DEF and CON-DEF) had similar profiles with a reduction in DHA levels of 30%, compared with rats receiving CON (i.e., CON-CON and DEF-CON). DEF-DEF rats had significantly raised MAP compared with all other groups, with differences as great as 17 mm Hg. DEF-CON rats had raised MAP compared with CON-CON rats, and DEF-DEF rats had higher MAP than CON-DEF rats, despite the fact that their respective fatty acid profiles were not different. These findings indicate that inadequate levels of DHA in the perinatal period are associated with altered blood pressure control in later life. The way in which these long-term effects are produced remains to be elucidated.     

An approach to simulate the motion of spherical and non-spherical fuel particles in combustion chambers

The objective of this paper is to identify a numerical method to simulate motion of a packed or fluidized bed of fuel particles in combustion chambers, such as a grate furnace and a rotary kiln. Therefore, the various numerical methods applied in the areas of granular matter and molecular dynamics were reviewed extensively. As a result, a time driven approach was found to be suited for the numerical simulation of particle motion in combustion chambers. Furthermore, this method can also be employed to moving boundaries which are required for the present application e.g. travelling grate. The method works in a Lagrangian frame of reference, which uses the position and orientation of particles as independent variables. These are obtained by time integration of the three-dimensional dynamics equations derived from the classical Newtonian approach for each particle. This includes the keeping track of all forces and momentums acting on each particle at every time step. Viscoelastic contact forces include normal and tangential components with viscoelastic models for energy dissipation and friction. The particle shapes are approximated by spheres and ellipsoids with a varying size and ratio of the semi-axis accounting for the variety of particle geometries in a combustion chamber. For these shapes the overlap of particles during contact is expressed by a polynomial of 4th order in the two-dimensional case and a polynomial of 6th order in the three-dimensional case. A new algorithm to detect two-dimensional elliptical particle contact with sufficient accuracy was developed. It is based on a sequence of coordinate transformations and has demonstrated its reliability in numerous applications. Finally, the method was applied to simulate the motion of spherical and elliptical particles in a rectangular enclosure, on a travelling grate, and in a rotary kiln. Received: 16 November 2001     

Experimental and numerical evaluation of the transport behaviour of a moving fuel bed on a forward acting grate

The objective of this study is to evaluate experimentally and numerically the transport behaviour of a moving bed on a forward acting grate. Therefore, the grate was operated with expanded clay and wood chips without combustion. Frequency and amplitude of the grate bars and feed rate were subject to change. Experimental findings showed that large particles have shorter residence times than small particles which is due to segregation on the grate. Additionally, the experiments indicated that increased frequencies of the grate bars lead to reduced residence times whereas the amplitude had no significant effect. The motion of a packed bed e.g., its particles was described numerically by the discrete element method (DEM). Thus, detailed data on all the particle’s paths and velocities are available. These data were used within the mean velocity method (MVM) and the tracking method (TM) to estimate the residence time of a packed bed. Both methods confirmed the dependency of the residence time on particle size, however, better predictions were obtained by the Tracking Method. The mean residence times varies from 40 to 120 min depending on the particle size. B. Peters is an Academic visitor to the Lituanian Energy Institute.     

The districts of Lithuania with low heat demand density: A chance for the integration of straw biomass

District heating sector is one of the most important sectors of Lithuanian energy industry. Consequently, low-cost bioenergy sources could play an important role in developing biofuels based on the so-called second-generation feedstock and decentralized energy supply for remote rural areas with low heat demand density. The present amount of biomass straw is already considerable in Lithuania but the potential is even much higher. It is assumed that the share of firewood in the balance of RES will decrease significantly – from 86.7% in 2009 to 55% in 2020 and future decisions on the acceptability of new substitutes must be found. The most important factors that could hasten the diffusion of straw combustion technologies for heat-only boilers (HOBs) in order to contribute to a local fuel and low-emission energy infrastructure are political issues, reduction in existing technical thresholds, market and economic conditions, international cooperation activity, and broad experience through wood residue combustion.The collected data indicated that under conditions in Lithuania, biomass straw combustion is prospective mainly to be used for heat production in small and medium scale units of 0.6–5.0 MW_th capacity as well as in large scale installations where multi-biomass strategies are foreseen.     

Simulation of the normal impact of randomly shaped quasi-spherical particles

The paper reports the modelling of randomly shaped particles. An emphasis is placed on the illustration of random properties of particles, using simulations with a controlled probability distribution for the depth of the surface profile. The randomly-shaped quasi-spherical particles were described by applying a multi-sphere approximation and a statistical evaluation technique, and the surface of the particles was approximated using randomly located overlapping subspheres. The concept of statistically similar particles, i.e., particles characterised by having a similar probability distribution for the depth of the surface profile, was employed for these purposes, and an original method involving the application of a stochastic optimisation was developed. The optimization method was demonstrated by generating statistically similar particles. The contact behaviour was investigated by simulating a random particle impact against a wall, using the discrete element method. It was observed that statistically similar particles did not show statistically similar contact characteristics. The results of this study suggested that the refinement of the multi-sphere model (achieved by increasing the number of subspheres) was non-unique, not only in a deterministic context but also in statistical context, and that this subject requires further investigation.     

Cardiac and visual responses to moving stimuli presented either successively or simultaneously to the central and peripheral visual fields in 4-month-old infants.

Measured cardiac and visual orienting responses as indices of attention in 41 4-mo-old infants. Two stimulus situations were used. In the 1st situation, the presentation of a peripheral stimulus followed the offset of a central fixation stimulus. In the 2nd situation, the peripheral stimulus came on while the central fixation stimulus was on. Each stimulus comprised a horizontal black and white bar pattern. Corneal reflection was used to monitor infant gaze. The visual-response measure confirmed that with simultaneous presentation the probability of orienting to the peripheral stimulus decreased. The extent of this reduction was determined by the speed difference between the central and peripheral stimuli. The cardiac data indicate that on the trials in which the peripheral stimulus did not elicit lateral eye/head movements the stimulus was still being detected. Thus, cardiac change can reflect attentional processes without evidence of somatic orienting. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Decontamination of Zincate Solutions Using Calcium Hydroxide in a Fluidised Bed Reactor

This article deals with the decontamination and utilisation of waste water. The effectiveness and conditions for the removal of Zn(II) from diluted alkali zinc electroplating bath solutions in flow-rate regime have been investigated. A cheap and simple decontamination route is proposed using the fluidised bed reactor with Ca(OH)₂. The advantage of this method is that up to 98% of Zn(II) can be precipitated as a fine crystalline recyclable material—CaZn₂ (OH) ₆ 2H₂O with small amount of ZnO. The industrial scheme of this process using lime is proposed.     

含贵金属废催化剂的分析

介绍了含贵金属废催化剂的工业分析方法,包括试金和湿法浸出分析法及其优缺点,详细地讨论了分析过程中的三级质量控制,包括方法质量控制、样品质量控制及仪器质量控制.给出了试金分析及湿法浸出分析原则流程图.