Electromagnetic energy absorption patterns in subjects with common visual disorders

This article describes the analysis of electromagnetic energy absorption properties of models of the human eye with common visual disorders. The investigation addresses two types of visual disorders, namely hyperopia (or farsightedness) and myopia (or nearsightedness). Calculations were carried out using plane multilayered method with common wireless communication frequencies of 900, 1800, and 2450?MHz. The effect of wireless radiation on the eye is studied by calculation of the specific absorption rate (SAR) in three different eye models. The results of the simulations confirmed the anticipated and more complex relationship between absorption and structural variations of the eye at these frequencies.     

Electromagnetic energy absorption patterns in subjects with common visual disorders

This article describes the analysis of electromagnetic energy absorption properties of models of the human eye with common visual disorders. The investigation addresses two types of visual disorders, namely hyperopia (or farsightedness) and myopia (or nearsightedness). Calculations were carried out using plane multilayered method with common wireless communication frequencies of 900, 1800, and 2450 MHz. The effect of wireless radiation on the eye is studied by calculation of the specific absorption rate (SAR) in three different eye models. The results of the simulations confirmed the anticipated and more complex relationship between absorption and structural variations of the eye at these frequencies.     

Biodiversity correlates with regional patterns of forest litter pools

We compared litter pools of more than 1,000 forests differing in tree species diversity over a large scale in Catalonia (NE Spain). Monospecific forests always had smaller litter pools than mixed (from 2 to 5 tree species) forests. Whether there was a positive effect beyond two species mixtures depended on the species and functional identity of the dominant tree species. In sclerophyllous forests the positive effect of diversity was a step-function from one to more species. However, in conifers, litter pools increased constantly with tree diversity. The identity of the dominant tree species and functional type had also a significant effect on litter pools. For instance, forests dominated by sclerophyllous tree species had larger litter pools than forests dominated by deciduous and conifer tree species. When other forest structure parameters (i.e. tree basal area, wood production, successional stage, shrub cover and leaf area index) and environmental factors (i.e. mean annual temperature, mean annual precipitation, annual evapotranspiration and hillside position) where included in the analysis only leaf area index, basal area, wood production and mean temperature influenced litter pools positively. Our analysis emphasizes that at the regional scale, the litter compartment can be as influenced by biodiversity components as by other forest structure and climate components. In mixed forests, species and functional identity of the trees determine whether litter pools increase with tree diversity.     

Time pressure modulates electrophysiological correlates of early visual processing

Background

Reactions to sensory events sometimes require quick responses whereas at other times they require a high degree of accuracy–usually resulting in slower responses. It is important to understand whether visual processing under different response speed requirements employs different neural mechanisms.

Methodology/Principal Findings

We asked participants to classify visual patterns with different levels of detail as real-world or non-sense objects. In one condition, participants were to respond immediately, whereas in the other they responded after a delay of 1 second. As expected, participants performed more accurately in delayed response trials. This effect was pronounced for stimuli with a high level of detail. These behavioral effects were accompanied by modulations of stimulus related EEG gamma oscillations which are an electrophysiological correlate of early visual processing. In trials requiring speeded responses, early stimulus-locked oscillations discriminated real-world and non-sense objects irrespective of the level of detail. For stimuli with a higher level of detail, oscillatory power in a later time window discriminated real-world and non-sense objects irrespective of response speed requirements.

Conclusions/Significance

Thus, it seems plausible to assume that different response speed requirements trigger different dynamics of processing.     

EEG correlates of the change in information processing strategy in visual imagery

Cnanger of the spatial organization of biopotentials (spatial synchronization and disorder, spectral power and coherence) were analyzed during mental creating of visual images from two simple elements: the angle the oblique line. With the transition from the first to the fourth task, the total number of used elements increased from the number suitable for simultaneous presentation and conscious processing (less than 7 +/- 2) to a much higher number. Changes in the characteristics of the spatial organization of biopotentials associated with the increase in the number of the elements can be explained by a change in the information processing strategy, transformation of information processing strategy, i.e. the transition from the left-hemispheric successive (conscious) analyses to the right-hemispheric simultaneous (unconscious) processing. It was shown that this change in the information processing strategy was accompanied by an increase in the index of spatial disorder sensitive to complicated nonlinear processes. Subjects were divided in two groups with different forms of the reorganization of interhemispheric and fronto-occipital relationships of biopotentials. These data are interpreted in terms of different involvement of the unconscious intellectual processes of different layers (subconsciousness and superconsciousness) in the change in information processing strategy.     

Electrophysiological correlates of object location and object identity processing in spatial scenes

The ability to quickly detect changes in our surroundings has been crucial to human adaption and survival. In everyday life we often need to identify whether an object is new and if an object has changed its location. In the current event-related potential (ERP) study we investigated the electrophysiological correlates and the time course in detecting different types of changes of an objecṫs location and identity. In a delayed match-to-sample task participants had to indicate whether two consecutive scenes containing a road, a house, and two objects, were either the same or different. In six randomly intermixed conditions the second scene was identical, one of the objects had changed its identity, one of the objects had changed its location, or the objects had switched locations. The results reveal different time courses for the processing of identity and location changes in spatial scenes. Whereas location changes elicited a posterior N2 effect, indicating early mismatch detection, followed by a P3 effect reflecting post-perceptual processing, identity changes elicited an anterior N3 effect, which was delayed and functionally distinct from the N2 effect found for the location changes. The condition in which two objects switched position elicited a late ERP effect, reflected by a P3 effect similar to that obtained for the location changes. In sum, this study is the first to cohesively show different time courses for the processing of location changes, identity changes, and object switches in spatial scenes, which manifest themselves in different electrophysiological correlates.     

Consultation patterns and clinical correlates of consultation in a tertiary care setting

Background

Chronic diarrhoea is one of the most debilitating consequences of HIV infection in sub-Saharan Africa and it carries a high mortality rate. We report unexpectedly low concentrations of circulating aldosterone in 12 patients (6 men, 6 women) in the University Teaching Hospital, Lusaka, who all had diarrhoea for over one month. Changes in serum electrolytes, blood pressure, Karnofsky score and serum aldosterone concentration were being monitored during a short study of responses to saline infusion (3 litres/24 h) over 72 hours.

Findings

At baseline, 9/12 (75%) of the patients were hyponatraemic, 10/11 (91%) were hypokalaemic, and 6/12 (50%) had undetectable aldosterone concentrations. Blood pressure and Karnofsky score rose and creatinine concentration fell in response to the infusion.

Conclusion

Circulating aldosterone concentrations were inappropriately low and complicate the profound electrolyte deficiencies resulting from chronic diarrhoea. Management of these deficiencies needs to be more aggressive than is currently practised and consideration should be given to a formal clinical trial of mineralocorticoid replacement in these severely ill patients. If the inappropriately low aldosterone reflects a general adrenal failure, it may explain a considerable proportion of the high mortality seen both before and after initiation of anti-retroviral therapy.     

中国蛇类物种丰富度地理格局及其与生态因子的关系

物种丰富度地理格局成因是生态学和生物地理学研究重要目标之一。生态假说在解释物种丰富度地理格局的成因上受到广泛关注。该文基于100km×100km空间分辨率研究中国蛇类物种丰富度的地理分布格局,并结合生态假说探讨影响蛇类分布格局的因素。该研究采用主轴邻距法获得基于特征值的空域数据,并同生态因子进行多元回归分析,结果表明:(1)中国蛇类物种丰富度在经、纬度上呈现多峰分布格局,物种丰富度最高的地区位于东洋界亚热带、热带,丰富度较低的地区位于青藏高原、北方草原荒漠、黄淮平原、两湖平原及鄱阳湖平原等;(2)多元回归分析能解释56.5%的蛇类物种丰富度变化,分析得出蛇类物种丰富度格局的主要影响因子是归一化植被指数、最冷季降水量和年温差。(3)模型选择结果显示,在多元回归分析中,P<0.05的变量(归一化植被指数、最冷季降水量和年温差)组成的模型是解释蛇类物种丰富度格局的最优模型。这说明蛇类物种丰富度格局是由不同生态因子共同作用的结果。基于中国蛇类物种丰富度地理格局成因研究的复杂性,该文提出在进一步研究中,需重视各假说中影响因子的选择和人类活动的影响,并在不同空间尺度上对蛇类物种丰富度地理格局进行综合分析。     

Neural correlates of variations in event processing during learning in central nucleus of amygdala

Attention or variations in event processing help drive learning. Lesion studies have implicated the central nucleus of the amygdala (CeA) in this process, particularly when expected rewards are omitted. However, lesion studies cannot specify how information processing in CeA supports such learning. To address these questions, we recorded CeA neurons in rats performing a task in which rewards were delivered or omitted unexpectedly. We found that activity in CeA neurons increased selectively at the time of omission and declined again with learning. Increased firing correlated with CeA-inactivation sensitive measures of attention. Notably CeA neurons did not fire to the cues or in response to unexpected rewards. These results indicate that CeA contributes to learning in response to reward omission due to a specific role in signaling actual omission rather than a more general involvement in signaling expectancies, errors, or reward value.     

Environmental correlates of vegetation patterns and species richness in the northern Grampians,Victoria

Abstract Plant species cover-abundance and density data were collected for 94 sample plots across a gradient from rocky uplands to sandy outwash plains in the northern part of Grampians (Gariwerd) National Park in western Victoria. Detrended correspondence analysis (DCA) was used to identify dominant gradients in species composition. A range of static (e.g. substrate type, soil depth, microclimate indicators) and dynamic (e.g. elapsed time since last fire) environmental variables were measured. Correlations were sought between these variables and vegetation patterns including those for richness (R) and Shannon-Weiner diversity (H′). The dominant gradient of vegetation change identified by DCA separated rocky sites and sites near ephemeral streams, from well-drained, sandy sites. Secondary gradients identified time since last fire as important for sandy sites, and altitude and aspect-related microclimate for rocky sites. Diversity was highest in the first 2 years after fire but showed no further decline in older sites. Overall, R and H' were negatively correlated with soil nutrient concentrations. On sandy sites R was high, but was low on rocky sites and near streams. Within the rocky sites, R was highest on cool, moist south and east slopes, and lowest on hot, dry north and west slopes. Explanations of diversity patterns based on inhibition of competitive exclusion due to stress and recurrent disturbance best fit the results presented here.     

Haemodynamic patterns in ST-elevation myocardial infarction: incidence and correlates of elevated filling pressures

Objectives. We sought to study the incidence and clinical correlates of elevated filling pressures in ST-elevation myocardial infarction (STEMI) patients, without physical signs of heart failure and treated with primary coronary angioplasty. Background. Haemodynamic data, as measured with a Swan-Ganz catheter, are not routinely obtained in STEMI patients. At admission, low blood pressure, increased heart rate, sweating, increased respiration rate, rales, oedema, and a third heart sound are indicative of heart failure. Methods. All consecutive STEMI patients were monitored by a Swan-Ganz catheter and central venous pressure (CVP), pulmonary capillary wedge pressure (PCWP), pulmonary artery pressure (PAS) and cardiac index (CI) were measured. To investigate the clinical correlates of the haemodynamic status patients were classified according to previously defined haemodynamic criteria. Results. We studied 90 patients, aged 60.5±13.1 year, 76% were male. Mortality at 30 days was 2/90 (2.2%). Patients with impaired haemodynamics presented later and had larger myocardial infarct sizes. CVP, PCWP and PAS were above normal in 36 (40%) patients. Conclusion. A large proportion of STEMI patients without physical signs of heart failure have elevation of right- as well as left-sided cardiac filling pressures. (Neth Heart J 2007:15:95-9.)     

Phycological expertise in geological applications

Our knowledge about fossil algae has been biased for a long time towards groups with calcified tissues such as dasyclads and crustose rhodophytes. This picture has recently begun to change owing to the growing number of discoveries of silicified microbial fossils and fossil microbial endoliths. There is good evidence that both groups contain a large proportion of photosynthetic organisms, particularly algae. Silicified microbial fossils are best known from the Precambrian strata, while microbial endoliths, which apparently evolved during middle to late Precambrian times are common throughout the Phanerozoic including the present. Because of the small size of these fossils, it is possible to study and morphometrically evaluate entire populations rather than individual specimens or body fragments. Thus, we are able to approach fossil taxa using largely biological rather than strictly paleontological criteria and to apply interpretations and reconstructions of biological species. Phycologists entering this field can contribute to the interpretation of such fossils by applying comparisons with modern algae, their life cycles, cellular organization, and cell division patterns. However, they have to learn to deal with post-mortem degradation and diagenetic changes, and to recognize algal remains from mineral features that surround and often obliterate the fossils. This work is often similar to that of a detective or coroner where the use of intuition and imagination is just as dangerous as it is necessary. Detection of microfossils between and within single carbonate grains in otherwise unfossiliferous rocks can provide valuable information for applied geology including petroleum exploration.     

Prey processing in amniotes: biomechanical and behavioral patterns of food reduction

In this paper we examine the biomechanics of prey processing behavior in the amniotes. Whether amniotes swallow prey items whole or swallow highly processed slurries or boluses of food, they share a common biomechanical system where hard surfaces (teeth or beaks) are brought together on articulated jaws by the actions of adductor muscles to grasp and process food. How have amniotes modified this basic system to increase the chewing efficiency of the system? To address this question we first examine the primitive condition for prey processing representative of many of the past and present predatory amniotes. Because herbivory is expected to be related to improved prey processing in the jaws we review patterns of food processing mechanics in past and present herbivores. Herbivory has appeared numerous times in amniotes and several solutions to the task of chewing plant matter have appeared. Birds have abandoned jaw chewing in favor of a new way to chew--with the gut--so we will detour from the jaws to examine the appearance of gut chewing in the archosaurs. We will then fill in the gaps among amniote taxa with a look at some new data on patterns of prey processing behavior and jaw mechanics in lizards. Finally, we examine evolutionary patterns of amniote feeding mechanism and how correlates of chewing relate to the need to increase the efficiency of prey processing in order to facilitate increased metabolic rate and activity.     

Proteolytic processing of a protein involved in sperm-egg fusion correlates with acquisition of fertilization competence

A protein located on the surface of guinea pig sperm (PH-30) has been implicated in the process of sperm-egg fusion (Primakoff, P., H. Hyatt, and J. Tredick-Kline. 1987. J. Cell Biol. 104:141-149). In this paper we have assessed basic biochemical properties of PH-30 and have analyzed the molecular forms of PH-30 present at different stages of sperm maturation. We show the following: (a) PH-30 is an integral membrane glycoprotein; (b) it is composed of two tightly associated and immunologically distinct subunits; (c) both subunits are made as larger precursors; (d) processing of the two subunits occurs at different developmental stages; (e) the final processing step occurs in the region of the epididymis where sperm become fertilization competent; (f) processing can be mimicked in vitro; (g) processing exposes at least two new epitopes on PH-30-one of the newly exposed epitopes is recognized by a fusion-inhibitory monoclonal antibody. These results are discussed in terms of the possible role of PH-30 in mediating fusion with the egg plasma membrane.