Solidification of undercooled liquids

During rapid solidification processing (RSP) the amount of liquid undercooling is an important factor in determining microstructural development by controlling phase selection during nucleation and morphological evolution during crystal growth. While undercooling is an inherent feature of many techniques of RSP, the deepest undercoolings and most controlled studies have been possible in carefully prepared fine droplet samples. From past work and recent advances in studies of nucleation kinetics it has become clear that the initiation of crystallization during RSP is governed usually by heterogeneous sites located at surfaces. With known nucleant sites, it has been possible to identify specific pathways of metastable phase formation and microstructural development in alloys. These advances have allowed for a clearer assessment of the interplay between undercooling, cooling rate and particle size statistics in structure formation. New approaches to the examination of growth processes have been developed to follow the thermal behavior and morphology in small samples in the period of rapid crystallization and recalescence. Based upon the new experimental information from these studies, useful models can be developed for the overall solidification process to include nucleation behavior, thermodynamic constraints, thermal history, growth kinetics, solute redistribution and resulting structures. From the refinement of knowledge concerning the underlying factors that govern RSP a basis is emerging for an effective alloy design and processing strategy

Retraction Note: An apoptosis-enhancing drug overcomes platinum resistance in a tumour-initiating subpopulation of ovarian cancer.

This Article has been retracted; see accompanying Retraction Note

Two stage superconducting quantum interference device amplifier in a high-Q gravitational wave transducer

We report on the total noise from an inductive motion transducer for a gravitational-wave antenna. The transducer uses a two-stage SQUID amplifier and has a noise temperature of 1.1 mK, of which 0.70 mK is due to back-action noise from the SQUID chip. The total noise includes thermal noise from the transducer mass, which has a measured Q of 2.60 X 10^6. The noise temperature exceeds the expected value of 3.5 \mu K by a factor of 200, primarily due to voltage noise at the input of the SQUID. Noise from flux trapped on the chip is found to be the most likely cause.Comment: Accepted by Applied Physics Letters tentatively scheduled for March 13, 200

Quartz crystal microbalance use in biological studies

Design, development, and applications of quartz crystal microbalance are discussed. Two types of crystals are used. One serves as reference and other senses changes in mass. Specific application to study of bacterial spores is described

Ultrafast light-induced response of photoactive yellow protein chromophore analogues

The fluorescence decays of several analogues of the photoactive yellow protein (PYP) chromophore in aqueous solution have been measured by femtosecond fluorescence up-conversion and the corresponding time-resolved fluorescence spectra have been reconstructed. The native chromophore of PYP is a thioester derivative of p-coumaric acid in its trans deprotonated form. Fluorescence kinetics are reported for a thioester phenyl analogue and for two analogues where the thioester group has been changed to amide and carboxylate groups. The kinetics are compared to those we previously reported for the analogues bearing ketone and ester groups. The fluorescence decays of the full series are found to lie in the 1–10 ps range depending on the electron-acceptor character of the substituent, in good agreement with the excited-state relaxation kinetics extracted from transient absorption measurements. Steady-state photolysis is also examined and found to depend strongly on the nature of the substituent. While it has been shown that the ultrafast light-induced response of the chromophore in PYP is controlled by the properties of the protein nanospace, the present results demonstrate that, in solution, the relaxation dynamics and pathway of the chromophore is controlled by its electron donor–acceptor structure: structures of stronger electron donor–acceptor character lead to faster decays and less photoisomerisation

Histone Deacetylase Inhibitors in Malignant Pleural Mesothelioma: Preclinical Rationale and Clinical Trials

AbstractMalignant pleural mesothelioma (MPM) is a rare and aggressive cancer of the mesothelium with only a limited range of treatment options that are largely ineffective in improving survival. Recent efforts have turned toward the analysis of specific, dysregulated biologic pathways for insight into new treatment targets. Epigenetic regulation of tumor suppressor genes through chromatin condensation and decondensation has emerged as an important mechanism that leads to tumorogenesis. A family of histone acetyltransferases and deacetylases regulates this balance, with the latter facilitating chromatin condensation, thus preventing gene transcription, resulting in the loss of heterozygosity of tumor suppressors. Inhibition of this process, coupled with a similar inhibition of nonhistone protein deacetylation, ultimately leads to the promotion of apoptosis, cell cycle arrest, and inhibition of angiogenesis. An increasing amount of preclinical data highlighting the effectiveness of histone deacetylase inhibition in MPM cell lines and mouse xenograft models has led to a number of early phase clinical trials in patients with MPM. The results of these efforts have led to a multicenter, randomized, placebo-controlled phase III study of the histone deacetylase inhibitor vorinostat in patients with advanced MPM, offering hope for a new and effective therapy in patients with this disease

A Historical Analysis of Southeast Asian Refugee Communities: Post-war Acculturation and Education in the U.S.

This analysis considers the circumstances of Southeast Asian refugee immigration following the Vietnam War as well as the political and social environment in the US upon their arrival, in order to examine the historical factors that link to their subsequent educational trends. Receptive government policies enabled these communities to survive; however, with the exception of first-wave Vietnamese refugees, their limited job skills, English language knowledge, and education upon arrival were exacerbated by overall prejudiced societal reception and the lack of an existing co-ethnic community to buffer their entry into US society. All groups have generally experienced low academic achievement except in the case of Vietnamese Americans, for whom a notable contingent demonstrates higher attainment. Implications for subsequent generations, and for research and practice, are discussed

Ambient Dried Aerogels

A method has been developed for creating aerogel using normal pressure and ambient temperatures. All spacecraft, satellites, and landers require the use of thermal insulation due to the extreme environments encountered in space and on extraterrestrial bodies. Ambient dried aerogels introduce the possibility of using aerogel as thermal insulation in a wide variety of instances where supercritically dried aerogels cannot be used. More specifically, thermoelectric devices can use ambient dried aerogel, where the advantages are in situ production using the cast-in ability of an aerogel. Previously, aerogels required supercritical conditions (high temperature and high pressure) to be dried. Ambient dried aerogels can be dried at room temperature and pressure. This allows many materials, such as plastics and certain metal alloys that cannot survive supercritical conditions, to be directly immersed in liquid aerogel precursor and then encapsulated in the final, dried aerogel. Additionally, the metalized Mylar films that could not survive the previous methods of making aerogels can survive the ambient drying technique, thus making multilayer insulation (MLI) materials possible. This results in lighter insulation material as well. Because this innovation does not require high-temperature or high-pressure drying, ambient dried aerogels are much less expensive to produce. The equipment needed to conduct supercritical drying costs many tens of thousands of dollars, and has associated running expenses for power, pressurized gasses, and maintenance. The ambient drying process also expands the size of the pieces of aerogel that can be made because a high-temperature, high-pressure system typically has internal dimensions of up to 30 cm in diameter and 60 cm in height. In the case of this innovation, the only limitation on the size of the aerogels produced would be in the ability of the solvent in the wet gel to escape from the gel network