Optical and physical properties of stratospheric aerosols from balloon measurements in the visible and near-infrared domains. II. Comparison of extinction,reflectance, polarization,and counting measurements

The physical properties of stratospheric aerosols can be retrieved from optical measurements involving extinction, radiance, polarization, and counting. We present here the results of measurements from the balloonborne instruments AMON, SALOMON, and RADIBAL, and from the French Laboratoire de Météorologie Dynamique and the University of Wyoming balloonborne particle counters. A cross comparison of the measurements was made for observations of background aerosols conducted during the polar winters of February 1997 and January-February 2000 for various altitudes from 13 to 19 km. On the one band, the effective radius and the total amount of background aerosols derived from the various sets of data are similar and are in agreement with pre-Pinatubo values. On the other hand, strong discrepancies occur in the shapes of the bimodal size distributions obtained from analysis of the raw measurement of the various instruments. It seems then that the log-normal assumption cannot fully reproduce the size distribution of background aerosols. The effect ofthe presence of particular aerosols on the measurements is discussed, and a new strategy for observations is proposed.     

Lesions of Specific and Nonspecific Thalamic Nuclei Affect Prefrontal Cortex-Dependent Aspects of Spatial Working Memory.

Three studies compared lesions of specific mediodorsal (MD) and nonspecific midline/intralaminar (M/IL) and ventromedial (VM) thalamic nuclei placed to spare the anterior nuclei. Lesions of MD, M/IL, or VM impaired delayed matching trained with retractable levers, a measure of spatial memory affected by prefrontal cortical lesions. The effects of the MD lesion increased at longer retention intervals and thus appeared delay dependent. The effects of M/IL and VM lesions were delay independent. Even when combined, these lesions had no effect on varying choice radial maze delayed nonmatching, a task sensitive to hippocampal or anterior thalamic (but not prefrontal) lesions. These results demonstrate effects of MD, M/IL, and VM lesions distinct from the contributions of hippocampus or anterior thalamus to spatial memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lesions of the frontal cortex, hippocampus, and intralaminar thalamic nuclei have distinct effects on remembering in rats.

Lesions of the intralaminar thalamic nuclei (ILn), the medial wall (MW) area of prefrontal cortex, and the hippocampus were compared and found to have distinct effects on delayed matching-to-sample (DMS) and delayed non-matching-to-sample (DNMS) tasks based on different types of stimulus cues. Hippocampal lesions impaired DNMS trained in a radial arm maze but had little effect on DMS trained with retractable levers or olfactory DNMS. MW lesions affected the DMS task but had limited effects on olfactory DNMS and radial arm maze DNMS. ILn lesions resulted in a more generalized pattern of impairment for radial maze tasks and (in previous studies) for the DMS and olfactory DNMS tasks. Only the hippocampal lesion was associated with a delay-dependent impairment. It is argued that ILn lesions disrupt remembering through their effects on the recurrent, feedback pathways that link functionally related areas of the basal ganglia and cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Immunostaining of human autopsy aortas with antibodies to modified apolipoprotein B and apoprotein(a)

A systematic immunohistochemical study of different stages of atherosclerosis in human aortas was performed using several antibodies. Because oxidation of lipoproteins could be a key event in atherogenesis, an antibody against apolipoprotein B (apoB) from low-density lipoprotein (LDL) modified with the lipid peroxidation-specific aldehyde, 4-hydroxynonenal (4-HNE) (anti-4-HNE-apoB), was raised in rabbits. This antibody recognizing 4-HNE protein adducts was used in concert with an antibody to apo(a) from lipoprotein(a), considered also potentially atherogenic, as well as with an antibody and a monoclonal antibody (mAb) to apoB. Autopsy material from 12 corpses was investigated. The immunohistochemical investigation by the alkaline-phosphatase technique included control specimens regarding postmortem artifacts by autolysis and oxidation. The results from six specimens from five corpses are presented. A positive staining with the antibody to apoB but not with anti-4-HNE-apoB was seen in the normal intima. The thickened intima of early, transitional, and advanced atherosclerotic lesions and atheromata showed a predominantly extracellular staining with all antibodies and the applied mAb. To test the specificity of the staining, antibodies preadsorbed by the appropriate antigens and nonimmune sera were used, giving negative results. These findings indicated a colocalization of epitopes derived from lipid peroxidation of polyunsaturated fatty acids and epitopes specific for apoB and apo(a) during atherogenesis in humans.     

The role and uses of technologies in mathematics classrooms: Between challenge and modus Vivendi

Abstract

Drawing support from theoretical frameworks, this article analyses the role and uses of technology in the teaching of mathematics, with specific reference to the complexity of integrating technology into teaching. Four aspects are discussed here: the changes that technology brings about in classroom mathematical activity, the difficulties students encounter in solving problems in a technology‐rich environment, the evaluation of potential assignments and the creation of conditions appropriate for learning, and the difficulties faced by teachers who use technology in deciding when and how to intervene. This analysis is illustrated by examples taken primarily from dynamic geometry, but similar analyses could be conducted for computerized environments of other kinds.     

From conceptual modelling to requirements engineering

Conceptual modelling is situated in the broader view of information systems requirements engineering. Requirements Engineering (RE) explores the objectives of different stakeholders and the activities carried out by them to meet these objectives in order to derive purposeful system requirements and therefore lead to better quality systems, i.e., systems that meet the requirements of their users. Thus RE product models use concepts for modelling these instead of concepts like data, process, events, etc., used in conceptual models. Since the former are more stable than the latter, requirements engineering manages change better. The paper gives the rationale for extending traditional conceptual models and introduces some RE product models. Furthermore, in contrast to conceptual modelling, requirements engineering lays great stress on the engineering process employed. The paper introduces some RE process models and considers their effect on tool support. This revised version was published online in June 2006 with corrections to the Cover Date.     

MK-801 prevents brain lesions and delayed-nonmatching-to-sample deficits produced by pyrithiamine-induced encephalopathy in rats.

Rats were trained on a spatial delayed-nonmatching-to-sample (DNMTS) task and assigned by block randomization to 1 of 4 treatments: pyrithiamine-induced thiamine deficiency (PTD), PTD with administration of MK-801 after 12 days, control with MK-801 treatment, and control without MK-801. After 15 days of treatment followed by 21 days of recovery, the PTD rats showed significant deficits for DNMTS accuracy at retention intervals (RIs) that ranged from 3.0 sec to 15.0 sec, the RIs that produced 75% accuracy on DNMTS in staircase training, and the rate at which a novel radial arm maze task was learned. The PTD-treated rats had consistent lesions in the thalamus and the mammillary bodies. MK-801 protected rats from both behavioral deficits and brain lesions (assessed quantitatively and qualitatively) that were produced by the PTD treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Elastoplastic Solution for Soil-Pipe-Tunnel Interaction

Solutions for the problem of tunneling effects on existing pipelines are given. The solution utilizes a boundary integral formulation for describing the elastic continuum, in conjunction with a limiting force to consider relative pullout failure. The solution requires estimation of soil and pipe elastic properties, relative pipe-soil uplift capacity, and the green field soil settlement profile given in the current paper as a modified Gaussian curve. Normalized graphs for the solution are given as a function of these input parameters. The solution method is compared and evaluated against a limited number of finite-element analysis.     

Randomized self-stabilizing and space optimal leader election under arbitrary scheduler on rings

We present a randomized self-stabilizing leader election protocol and a randomized self-stabilizing token circulation protocol under an arbitrary scheduler on anonymous and unidirectional rings of any size. These protocols are space optimal. We also give a formal and complete proof of these protocols. To this end, we develop a complete model for probabilistic self-stabilizing distributed systems which clearly separates the non deterministic behavior of the scheduler from the randomized behavior of the protocol. This framework includes all the necessary tools for proving the self- stabilization of a randomized distributed system: definition of a probabilistic space and definition of the self-stabilization of a randomized protocol. We also propose a new technique of scheduler management through a self-stabilizing protocol composition (cross-over composition). Roughly speaking, we force all computations to have a fairness property under any scheduler, even under an unfair one. This work was done while Maria Gradinariu was working at LRI, Univ. Paris-Sud, CNRS.     

Is motion processing unitary?

Motion discrimination space is conventionally categorized into motion detection, speed discrimination, and direction discrimination tasks. But an ideal observer uses a unitary motion mechanism that is affected only by the noise level and the difference in speed (or displacement) between two stimuli. We tested whether human performance in the various motion tasks showed the working of a unitary mechanism or the combined outputs of more than one mechanism. We examined the whole motion discrimination space, using random dots that underwent a sudden jump or displacement. The discriminability was measured as a function of the standard and comparison displacements. Both the ideal observer model and a nonideal observer model that contains additive internal noise predict a planar response surface. When the dot motion was noiseless, the planar surface fitted well except for much higher than expected sensitivity for motion detection. This is consistent with a purely temporal mechanism that uses flicker or a purely spatial mechanism that uses the length of time-averaged streaks. It is also consistent with a Weber's law device. When motion noise was added to the displays, the planar response surface again fitted well, although the residuals showed the presence of a speed energy mechanism. We conclude that a unitary motion mechanism exists (nonideal observer model), although its performance may be supplemented by other mechanisms whose main impact is on discrimination of speeds near zero.