Nucleation and growth of potassium dihydrogen phosphate crystals in silica gels

Kinetic studies on nucleation and growth of potassium dihydrogen phosphate crystals in silica gels show that the rate-determining process for the growth of these crystals in silica gels is diffusion. Morphology, microhardness and perfection of gel grown crystals are also reported.     

Impression management versus intrapsychic explanations in social psychology: A useful dichotomy?

Impression management refers to the behavioral strategies that people use to create desired social images or identities. The current status of impression management explanations in social psychology is discussed, and it is argued that the common practice of referring to impression management theory is misleading. Many potential theories of impression management exist, each based on distinct assumptions. Methodological strategies that investigators have used to distinguish between impression management and intrapsychic explanations for a variety of research findings are reviewed. Although empirical confrontations between impression management and intrapsychic explanations have stimulated innovative research, there are serious limits on the discriminability of the 2 classes of explanation. Possible conceptual frameworks are discussed for integrating the psychological processes described by both impression management and intrapsychic explanations. (60 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Measuring distribution in distributed representations

The concept of distribution is often encountered in neural network architectures without any formal quantification. A method of quantifying the amount of distribution present in the hidden layer representations of a feed-forward network with binary inputs is described.     

Nutrition education for student community volunteers: a comparative study of two different communication methods

BACKGROUND: Nutrition education for student volunteers can enhance their skills, and they can act as change agents in the community. There is a dearth of data from India on the effectiveness of different communication tools in providing nutrition education to student volunteers. OBJECTIVE: This study aims to examine the comparative effectiveness of two different methods of communication--lectures in the classroom aided by print material, and a televised version of a local folk-dance form--for providing nutrition education to student community volunteers in a South Indian state. METHODS: Interventions were conducted during two mega-camps of student volunteers (camps 1 and 2) with 70 and 137 participants, respectively. Their knowledge levels were tested at baseline. Camp 1 received the lecture intervention and camp 2 the televised folk-dance intervention. Knowledge scores were measured before and after the intervention in each camp, and the two camps were compared for significant improvements in knowledge. RESULTS: At baseline, the knowledge levels of students in both camps were comparable. Significant improvement in knowledge was observed in both camps after intervention (p < .05). Although there was no significant difference between the camps in improvement in knowledge, a significant difference was observed when only the positive increments (improvement over baseline) were compared. CONCLUSIONS: The televised version of the folk-dance form was better in bringing about positive increment.     

Electron beam-induced thickening of the protective oxide layer around Fe nanoparticles

There are many circumstances in science where the process of measuring the properties of a system alters the system. An imaging process can exert an inadvertent effect on the object being observed. Consequently, what we observe does not necessarily represent what had been present before the observation. Normally, this effect can be ignored if the consequence of such a change is believed not to be significant. The expansion of nanostructured materials has made high-resolution transmission electron microscopy one of the indispensable tools for probing the characteristics of nanomaterials. Modification of nanoparticles by the electron beam during their imaging has been widely noticed and this is generally believed to be due to electron beam-induced heating effect, defect formation in the particles, charging of the particle, or excitation of surrounding gases. However, an explicit experimental identification of which process dominates is often very hard to establish. We report the thickening of native oxide layer on iron nanoparticle under electron beam irradiation. Based on atomic level imaging, electron diffraction, and computer simulation, we have direct evidence that the protecting oxide layer formed on Fe nanoparticle at room temperature in air or oxygen continues to grow during an electron beam bombardment in the vacuum system typical of most TEM systems. Typically, the oxide layer increases from approximately 3 to approximately 6 nm following approximately 1h electron beam exposure typically with an electron flux of 7 x 10(5)nm(-2)s(-1) and an vacuum of approximately 3 x 10(-5)Pa. Partial illumination of a nanoparticle and observation of the shell thickening conclusively demonstrates that many of the mechanisms postulated to explain such processes are not occurring to a significant extent. The observed growth is not related to the electron beam-induced heating of the nanoparticle, or residual oxygen ionization, or establishment of an electrical field, rather it is related to electron beam-facilitated mass transport across the oxide layer (a defect-related process). The growth follows a parabolic growth law.     

A Photoclick Hydrogel for Enhanced Single‐Cell Immunoblotting

Advances in single‐cell immunoblotting assays, which facilitate the exploration of cell‐to‐cell variation that affects biological systems from cancer development to stem cell biology, have attracted much attention. A tetrazole‐functionalized photoclick hydrogel is reported for single‐cell proteomic analysis. The gel serves as a molecular sieving matrix for sodium dodecyl sulfate–polyacrylamide gel electrophoresis and a protein immobilization scaffold for in‐gel immunoblotting. Upon a very short time (60 s) of long‐wavelength ultraviolet irradiation, it can effectively capture the electrophoretically separated proteins in the gel for the subsequent in situ antibody incubation. As a proof of concept, its performance is demonstrated in profiling cell‐to‐cell variations of P‐glycoprotein expression in GES‐1/MGC803 cell lines treated with different drugs. Combined with single‐cell immunoblotting method, employing this photoactive gel enables the monitoring simultaneously in ≈2000 individual cells of subtle protein expression level changes that may be concealed using conventional techniques. The proposed gel has the advantages of excellent electrophoretic separation ability, high protein photoimmobilization efficiency, low autofluorescence, and it can be used as a promising photoactive polyacrylamide gel for in‐gel/in situ capillary and microfluidic immunoblotting assays, especially for developing novel single cell immunoblotting methods.     

Analyzing the efficiency of nanostructured Sm3+- and Gd3+-doped TiO2 and constructing DSSCs using efficacious photoanodes

The rare earth elements, gadolinium and samarium, are doped with TiO₂ by hydrothermal synthesis technique to study the photoconversion performance of a photoanode in a dye-sensitized solar cell (DSSC). The obtained materials are subjected to the characterizations XRD, HR-TEM, UV–Vis spectroscopy, and XPS. DSSCs are fabricated using N719 dye, redox electrolyte, and platinum counter electrode. Charge-transfer ability was investigated using electrochemical impedance spectroscopy (EIS) on DSSCs. The efficiencies of DSSCs are influenced by the electron transport within the TiO₂–dye–electrolyte system. After the fabrication and simulation, among the two, Gd³⁺-doped TiO₂ gives the desired outcomes and higher efficiency (5.542%) than the pure and Sm³⁺-doped TiO₂ and thus it proves to be a superior solar cell anode material.

     

2D van der Waals Heterojunction of Organic and Inorganic Monolayers for High Responsivity Phototransistors

Van der Waals (vdW) heterostructures composing of organic molecules with inorganic 2D crystals open the door to fabricate various promising hybrid devices. Here, a fully ordered organic self-assembled monolayer (SAM) to construct hybrid organic–inorganic vdW heterojunction phototransistors for highly sensitive light detection is used. The heterojunctions, formed by layering MoS₂ monolayer crystals onto organic [12-(benzo[b]benzo[4,5]thieno[2,3-d]thiophen-2-yl)dodecyl)]phosphonic acid SAM, are characterized by Raman and photoluminescence spectroscopy as well as Kelvin probe force microscopy. Remarkably, this vdW heterojunction transistor exhibits a superior photoresponsivity of 475 A W⁻¹ and enhanced external quantum efficiency of 1.45 × 10⁵%, as well as an extremely low dark photocurrent in the pA range. This work demonstrates that hybridizing SAM with 2D materials can be a promising strategy for fabricating diversified optoelectronic devices with unique properties.     

Identification of Two Sex Pheromone Components of the Potato Aphid, Macrosiphum euphorbiae (Thomas)

Females of the potato aphid Macrosiphum euphorbiae exhibit typical calling behavior, with virgin female oviparae raising their back legs off the substrate to release sex pheromone from glands on the tibia. Airborne collections from calling oviparae were analyzed by GC and GC-MS to determine if, like the majority of aphids examined to date, they produced (1R,4aS,7S,7aR)-nepetalactol (1) and (4aS,7S,7aR)-nepetalactone (2). Both components were present and produced in ratios that varied with age from 4:1 to 2:1. The relative stereochemical configurations of these components were determined by GC-coinjection of the aphid-derived sample with synthetic standards on both HP-1 and DB-Wax GC columns. The absolute stereochemical configuration of the nepetalactol (determined from approximately 15 microg of material in an air entrainment sample) was determined as (1R,4aS,7S,7aR)-1 by derivatization of the aphid sample with (S)-(+)-alpha-methoxy-alpha-(trifluoromethyl)phenylacetyl chloride (Mosher's acid chloride) to generate a diastereoisomer that was compared to synthetic samples by NMR spectroscopy and GC. In bioassays in the wind tunnel, M. euphorbiae males responded to potato plants with oviparae but not to unattacked plants or those infested with parthenogenetically reproducing apterae. In no-choice laboratory bioassays, the same level of male response was observed to virgins and to the 3:1-5:1 synthetic blends of nepetalactol (1):nepetalactone (2). However, the time taken to reach the source was significantly less to virgin females than to the synthetic pheromone blends. In all cases, males walked rather than flew to the source. Males showed lower responses to a 1:1 synthetic mixture and did not respond to either of the components when presented alone. Under field conditions, few M. euphorbiae males were captured in traps baited with different ratios of the synthetic pheromone. Possible reasons for the different responses under laboratory and field conditions are discussed.