Energy dependence of the effective mass in liquid3He

The striking behavior of the specific heat of liquid³He as function of temperature at low temperatures requires the effective massm* to change rapidly with temperature; this can be translated into a rapid variation with energy,m*/m dropping from itsE=0 value to 1 over the temperature range 0.5 K. We explore this effect in a model in which the enhancement of the effective mass is due to coupling to spin fluctuations. At very lowT50 mK, the variation in specific heat results fromT ³ lnT terms. The free energy, on the other hand, does not containT ² lnT terms in its dependence on the magnetic field, implying that the susceptibility, which is essentiallym*/(1+F ₀ ^a ), also does not have such logarithmic terms. Consequently, ifm* varies with energy, so mustF ₀ ^a , so as to leave the susceptibility free of this rapid variation. The rough constancy ofm*/(1+F ₀ ^a ) seems empirically to hold to higher energies and temperatures. Ifm*/m drops, with increasing energy, to unity, the spin-fluctuation theory, which is described in terms of Landau parameters at the Fermi surface, goes over into the paramagnon theory. The rapid change with energy of the effective interactions can be understood within the framework of response theory as a shaking off of the relevant collective modes with increasing frequency of the imposed oscillations. The changes in effective interactions have consequences for the interpretation of experiments involving inelastic neutron scattering from liquid³He.Also State University of New York, Stony Brook, New York. Supported in part by U.S. D.O.E. Contract DE-AC02-76ER13001.Also University of Illinois at Urbana—Champaign. Supported in part by U.S. NSF Grant DMR 81-21273.     

Aerosol Synthesis of Inhalation Particles via a Droplet-to-Particle Method

Inhalation powders with consistent particle properties, including particle size, size distribution, and shape were produced with an aerosol synthesis method. Compared to conventional spray drying, the aerosol method provides better control of the thermal history and residence time of each droplet and product particle due to the laminar flow in the heated zone of the reactor where the droplet drying and particle formation take place. A corticosteroid, beclomethasone dipropionate, generally used for asthma treatment was chosen as a representative material to demonstrate the process. Spherical particles were produced with a droplet-to-particle method from an ethanolic precursor solution. The droplets produced with an ultrasonic nebulizer were carried to a heated zone of the reactor at 50-150°C where the solvent was evaporated and dry particles formed. The mass mean diameter of the particles were well within the respirable size range (approximately 2 μm). The geometric standard deviation (GSD) of produced particles was approximately 2. The particle surface structure varied from smooth to rough depending on the degree of particle crystallinity and was affected by the thermal history of the particle. Amorphous particles with smooth surface were most likely obtained due to the rapid evaporation of the solvent from the droplet combined with the slow diffusion of the beclomethasone dipropionate molecule. The amorphous particles were transformed slowly to crystalline particles in the open atmosphere. In addition, the particle surface structure changed from smooth to rough during storage. The process was accelerated by thermal post-annealing. However, additional heating also increased particle sintering. By optimizing the reactor parameters, and thus increasing the molecular diffusion, stable, crystalline particles were produced at 150°C.     

The effect of hydrogen in the mechanism of aluminum-induced crystallization of sputtered amorphous silicon using scanning Auger microanalysis

The metal-induced crystallization (MIC) of hydrogenated sputtered amorphous silicon (a-Si:H) using aluminum has been investigated using X-ray diffraction (XRD) and scanning Auger microanalysis (SAM). Hydrogenated, as well as non-hydrogenated, amorphous silicon (a-Si) films were sputtered on glass substrates, then capped with a thin layer of Al. Following the depositions, the samples were annealed in the temperature range 200 °C to 400 °C for varying periods of time. Crystallization of the samples was confirmed by XRD. Non-hydrogenated films started to crystallize at 350 °C. On the other hand, crystallization of the samples with the highest hydrogen (H₂) content initiated at 225 °C. Thus, the crystallization temperature is affected by the H₂ content of the a-Si. Material structure following annealing was confirmed by SAM. In this paper, a comprehensive model for MIC of a-Si is developed based on these experimental results.     

Monitoring the Synthesis and Composition Analysis of Microsilica Encapsulated Acetylacetonatocarbonyl TriphenylphosphinerhodiumCatalyst by Inductively Coupled Plasma (ICP) Techniques

A novel technique to monitor the synthesis process of encapsulated acetylacetonatocarbonyl triphenylphosphinerhodium within a microsilica nanoshell has been studied using inductively coupled plasma (ICP) techniques. Nanospheres sized around 50-100 nm were obtained and ICP was used to quantify the exact composition of rhodium, phosphorous, and silicon with differing digestion solvents. In addition, ICP was used to detect rhodium and phosphorous in the nano core-shell catalysts as a quality control procedure     

Immobilization of dendrimers on Si-C linked carboxylic acid-terminated monolayers on silicon(111)

Poly(amidoamine) dendrimers were attached to activated undecanoic acid monolayers, covalently linked to smooth silicon surfaces via Si-C bonds. The resulting ultra-thin dendrimer films were characterized by X-ray photoelectron spectroscopy (XPS), X-ray reflectometry (XR) and atomic force microscopy (AFM). XPS results suggested amide bond formation between the dendrimer and the surface carboxylic acid groups. XR yielded thicknesses of 10 Å for the alkyl region of the undecanoic acid monolayer and 12 Å for the dendrimer layer, considerably smaller than the diameter of these spherical macromolecules in solution. This was consistent with AFM images showing collapsed dendrimers on the surface. It was concluded that the deformation arose from a large number of amine groups on the surface of each dendrimer reacting efficiently with the activated surface, whereby the dendrimers can deform to fill voids while spreading over the activated surface to form a homogeneous macromolecular layer.     

A Controlled Study of a Cigarette Smoking Cessation Intervention for Adolescents in Substance Abuse Treatment.

Tobacco use is prevalent among youth with alcohol and other drug problems, yet this issue has received limited research and clinical attention. This study reports on a controlled evaluation of a cigarette smoking intervention with 54 adolescents in treatment for substance abuse, ages 13-18 (22% female). Participants were assessed at 4 time points. A greater proportion of participants in the treatment condition (n = 26) reported cessation attempts and point abstinence than did control participants (n = 28) at all time points. However, significant differences were found only for point abstinence at a 3-month follow-up. These findings provide initial support for the efficacy of a smoking cessation intervention delivered in the context of adolescent substance abuse treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Obituaries: Leo Joseph Postman (1918-2004).

Presents the obituary of Leo Joseph Postman, one of the most prolific psychologists of the last century. With over 250 publications to his credit, Postman died on April 22, 2004, of heart failure in Marblehead, Massachusetts, at the age of 85. His life and career accomplishments are discussed. Postman is best known for his interests in perception, serial learning, memory, and interference theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Teachers' and Pupils' Behavior in Large and Small Classes: A Systematic Observation Study of Pupils Aged 10 and 11 Years.

The authors examined class size effects on teacher-pupil interactions, pupil engagement, and pupil-pupil interaction. They extended previous research by recognizing the hierarchical nature of observation data and the possible influence of other variables. The study used a time sampling method involving 257 children (aged 10-11 years) in 16 small (25 or under) and 26 large (31 and over) classes. In small classes, there were more individualized task-related contacts between teacher and pupils and a more active role for pupils. These results confirmed those from earlier research on children aged 4 and 5 years. Against expectation, class size did not affect pupil on-task behavior or peer interaction. There was a moderating role for school subject and a beneficial effect of teaching assistants. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recent Advances in Pharmacotherapies for the Externalizing Disorders.

This article provides a review of various psychotropic agents employed for children and adolescents with externalizing disorders. With the exception of the stimulants, clinical use of psychotropic medications for children with externalizing disorders far exceeds the available empirical literature. Further, there are insufficient data pertaining to the safety and efficacy of most psychotropics. Studies that examine the combination of psychotherapy and pharmacotherapy are also reviewed, with particular attention to the National Institutes of Health Multimodal Treatment Study for Children with Attention-Deficit/Hyperactivity Disorder. Recommendations are made for future multimodal studies all externalizing disorders and with all psychotropics in addition to the stimulants. Future goals for research over the next decade include studies that examine treatment acceptability, adherence and satisfaction, adherence with various psychotropic agents, and ecologically valid investigations of pharmacotherapies for both symptom reduction and enhancement of functional behaviors among children and adolescents with externalizing behavioral problems. (PsycINFO Database Record (c) 2011 APA, all rights reserved)