Authoritarianism, leader acceptance, and group cohesion.

An examination of the validity of the Frommian compromise between leader-centered and member-centered theories of group cohesiveness is made, using a sample of enlisted men of the Air Defense Command. The variables of authoritarianism and leader-acceptance were measured in this sample by means of Likert-type scales. The Frommian hypothesis is supported to some extent, since, as expected, under conditions of military organization, more high authoritarians than low apparently accept or idealize their formally designated leader; and, attractive force of the group is apparently stronger for high than for low scorers on the authoritarianism scale. The strong positive association between leader acceptance and group cohesion, for high authoritarians, that is expected on the Frommian hypothesis is not found. A discussion of the Frommian compromise is then made. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of Processing on Mechanical Properties of Platelet-Reinforced Mullite Composites

SiC- and Al₂O₃-platelet-reinforced mullite-matrix composites were fabricated by both conventional powder processing and a pressure filtration route with constant filtration rate. Consolidation during the pressure filtration experiment was monitored as a function of time with respect to actual pressing stages. The packing density of green bodies was strongly affected by the different processing methods. Either fracture toughness (3.2 MPa · m^1/2) or bending strength (344 MPa) increased, depending on surface conditioning of the SiC platelets. Pressure filtration was shown to decrease processing flaws in the platelet-reinforced bodies leading to substantial improvement of the mechanical properties.     

A dry electrochemical cell containing cupric chloride supported by γ-alumina

An electrochemical cell was formed by enclosing a commercial catalyst containing cupric chloride supported by γ-alumina between electrodes of copper and iron. The voltage obtained is a logarithmic function of the vapour pressure of the water sorbed by the support. Voltages of a few hundred millivolts are obtained at relative pressures between 0.1 and 0.8 and temperatures between 25 and 170°C.     

Adaptive-resolution reinforcement learning with polynomial exploration in deterministic domains

We propose a model-based learning algorithm, the Adaptive-resolution Reinforcement Learning (ARL) algorithm, that aims to solve the online, continuous state space reinforcement learning problem in a deterministic domain. Our goal is to combine adaptive-resolution approximation schemes with efficient exploration in order to obtain polynomial learning rates. The proposed algorithm uses an adaptive approximation of the optimal value function using kernel-based averaging, going from coarse to fine kernel-based representation of the state space, which enables us to use finer resolution in the “important” areas of the state space, and coarser resolution elsewhere. We consider an online learning approach, in which we discover these important areas online, using an uncertainty intervals exploration technique. In addition, we introduce an incremental variant of the ARL (IARL), which is a more practical version of the original algorithm with reduced computational complexity at each stage. Polynomial learning rates in terms of mistake bound (in a PAC framework) are established for these algorithms, under appropriate continuity assumptions.     

On Symmetry, Perspectivity, and Level-Set-Based Segmentation

We introduce a novel variational method for the extraction of objects with either bilateral or rotational symmetry in the presence of perspective distortion. Information on the symmetry axis of the object and the distorting transformation is obtained as a by--product of the segmentation process. The key idea is the use of a flip or a rotation of the image to segment as if it were another view of the object. We call this generated image the symmetrical counterpart image. We show that the symmetrical counterpart image and the source image are related by planar projective homography. This homography is determined by the unknown planar projective transformation that distorts the object symmetry. The proposed segmentation method uses a level-set-based curve evolution technique. The extraction of the object boundaries is based on the symmetry constraint and the image data. The symmetrical counterpart of the evolving level-set function provides a dynamic shape prior. It supports the segmentation by resolving possible ambiguities due to noise, clutter, occlusions, and assimilation with the background. The homography that aligns the symmetrical counterpart to the source level-set is recovered via a registration process carried out concurrently with the segmentation. Promising segmentation results of various images of approximately symmetrical objects are shown.     

Data quality and query cost in pervasive sensing systems

This research is motivated by large-scale pervasive sensing applications. We examine the benefits and costs of caching data for such applications. We propose and evaluate several approaches to querying for, and then caching data in a sensor field data server. We show that for some application requirements (i.e., when delay drives data quality), policies that emulate cache hits by computing and returning approximate values for sensor data yield a simultaneous quality improvement and cost saving. This win–win is because when system delay is sufficiently important, the benefit to both query cost and data quality achieved by using approximate values outweighs the negative impact on quality due to the approximation. In contrast, when data accuracy drives quality, a linear trade-off between query cost and data quality emerges. We also identify caching and lookup policies for which the sensor field query rate is bounded when servicing an arbitrary workload of user queries. This upper bound is achieved by having multiple user queries share the cost of a single sensor field query. Finally, we demonstrate that our results are robust to the manner in which the environment being monitored changes using models for two different sensing systems.     

Electrical and Magnetic Properties of NiZn Ferrite Prepared by Conventional and Solar Sintering

The electrical properties of polycrystalline NiZn ferrite, Zn_0.44Ni_0.38Fe_2.18O₄, were investigated by impedance spectroscopy over the frequency and temperature ranges, 5 Hz to 2 MHz and 10–600 K and by magnetic permeability measurements at room temperature. Samples were sintered in either conventional or solar furnaces followed by quenching or slow cooling to ambient temperature. Depending on processing conditions, the room‐temperature electrical resistivity of conventionally sintered samples varied by seven orders of magnitude, from 5 ohm cm for a sample quenched from 1250°C to 10 Mohm cm for a sample quenched from 400°C. These differences were attributed to variations in oxygen content of the ferrite which decreased with increasing quench temperature. Oxygen deficiency led to mixed valence of Fe in the octahedral B sites of the spinel structure and was responsible for high electronic conductivity with low activation energy at low temperatures in oxygen‐deficient samples. By contrast, in oxygen‐stoichiometric samples, Fe on the tetrahedral A sites was believed to be divalent and Fe on the octahedral B sites to be entirely trivalent. Electron hopping between A and B sites had much higher activation energy and dominated the conductivity at high temperature for all samples. Samples sintered in the solar furnace were much more conductive than ones that were slow‐cooled after conventional sintering and this is attributed to the relatively rapid cooling rate after exposure in the solar furnace, which preserved some of the oxygen deficiency present at high temperature. For the same reason, samples that were slow cooled in N₂ were also much more conductive. Solar‐sintered samples with higher density (96%) had higher real permeability than slow‐cooled, conventionally sintered ones (86%) mainly due to a combination of their lower resistivity and higher density. Resistivity seems to have a greater correlation with the imaginary permeability than density has.     

A novel sensor platform based on aptamer-conjugated polypyrrole nanotubes for label-free electrochemical protein detection

We first present a simple yet versatile strategy for the functionalization of polymer nanotubes in a controlled fashion. Carboxylic-acid-functionalized polypyrrole (CPPy) nanotubes were fabricated by using cylindrical micelle templates in a water-in-oil emulsion system, and the functional carboxyl groups were effectively incorporated into the polymer backbone during the polymerization by using pyrrole-3-carboxylic acid (P3CA) as a co-monomer without a sophisticated functionalization process. It was noteworthy that the chemical functionality of CPPy nanotubes was readily controlled in both qualitative and quantitative aspects. On the basis of the controlled functionality of CPPy nanotubes, a field-effect transistor (FET) sensor platform was constructed to detect specific biological entities by using a buffer solution as a liquid-ion gate. The CPPy nanotubes were covalently immobilized onto the microelectrode substrate to make a good electrical contact with the metal electrodes, and thrombin aptamers were bonded to the nanotube surface via covalent linkages as the molecular recognition element. The selective recognition ability of thrombin aptamers combined with the charge transport property of CPPy nanotubes enabled the direct and label-free electrical detection of thrombin proteins. Upon exposure to thrombin, the CPPy nanotube FET sensors showed a decrease in current flow, which was probably attributed to the dipole-dipole or dipole-charge interaction between thrombin proteins and the aptamer-conjugated polymer chains. Importantly, the sensor response was tuned by adjusting the chemical functionality of CPPy nanotubes. The efficacy of CPPy nanotube FET sensors was also demonstrated in human blood serum; this suggests that they may be used for practical diagnosis applications after further optimization.     

Herbal Medicine in Mexico: A Cause of Hepatotoxicity. A Critical Review

In Mexico, herbal products are commonly used as therapeutic tools. The analysis of several publications reveals that there are dozens of different herbs and herbal products used for different reasons, some of which have been implicated in causing toxic liver disease. However, methodological aspects limit the attribution of causality, and the precise incidence and clinical manifestations of herb-induced liver injury have not been well characterized. This review outlines the history of traditional herbal medicine in Mexico, critically summarizes the mechanisms and adverse effects of commonly used herbal plants, and examines the regulatory issues regarding the legal use of these products.