Passive imaging with pulsed ultrasound insonations

Previously, passive cavitation imaging has been described in the context of continuous-wave high-intensity focused ultrasound thermal ablation. However, the technique has potential use as a feedback mechanism for pulsed-wave therapies, such as ultrasound-mediated drug delivery. In this paper, results of experiments and simulations are reported to demonstrate the feasibility of passive cavitation imaging using pulsed ultrasound insonations and how the images depend on pulsed ultrasound parameters. The passive cavitation images were formed from channel data that was beamformed in the frequency domain. Experiments were performed in an invitro flow phantom with an experimental echo contrast agent, echogenic liposomes, as cavitation nuclei. It was found that the pulse duration and envelope have minimal impact on the image resolution achieved. The passive cavitation image amplitude scales linearly with the cavitation emission energy. Cavitation images for both stable and inertial cavitation can be obtained from the same received data set.     

Microgel,nanogel and hydrogel–hydrogel semi-IPN composites for biomedical applications: synthesis and characterization

Quaternary ammonium salt hydrogels from a cationic monomer, (3-acrylamidopropyl)-trimethylammonium chloride (APTMACl), in a variety sizes such as bulk, micro- and nano- has been prepared. The synthesis of micro- and nanogels were carried out in the microenvironment of water-in-oil microemulsions using two types of surfactants, namely, L-α- phosphatidylcholine (lecithin) and dioctyl sulfosuccinate sodium salt (AOT). Additionally, hydrogel–hydrogel composite semi-interpenetrating polymer networks (semi-IPN) was synthesized by dispersing previously prepared micro/nanogel into neutral monomers such as acrylamide (AAm) or 2-hydroxylethyl methcarylate (HEMA) before network formation. Hydrogel swelling and pH response behaviors have been investigated for bulk gels. Morphology, structure, and size of nano-, micro- and bulk materials were explored utilizing transmission electron microcopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). It was confirmed with gel electrophoresis that completely charged nanogel form a strong complex with DNA.     

Synthesis of Acylacetylenes from α-Diazo-β-Hydroxylcarbonyl Compounds

A facile synthesis of α-diazo-β-hydroxy ketones and esters by the condensation of aldehydes or ketones with acyldiazomethanes was reported recently.² Exposure of the trifunctional compounds to boron trifluoride in ether-acetonitrile solution leads to acylacetylenes. Thus substances 1 and 3 were converted readily into acetylenes 2 and 4 respectively.³ This makes available a simple two-step procedure for the synthesis of conjugated acetylenic carbonyl compounds.     

Polymer microsphere and polymer-ferrite nanocomposite preparation by precipitation from water-in-oil microemulsions

 A simple method to encapsulate intramicellar solutes (enzymes, nanoparticles) in polymer microspheres is described. The method involves dissolving a polymer in a minimum amount of solvent. The polymer solution is then added to a large volume of a nonsolvent system containing bis(2-ethylhexyl)sulfo-succinate (AOT) reversed micelles. Immediate precipitation of the dissolved polymer takes place. The precipitation results in the formation of stable microparticles ∼0.1–1 μm in diameter. There is a direct correlation between the internal voidage of the particles and the water content of the micelles. Precipitation also leads to encapsulation of intramicellar solutes, resulting in the formation of microspherical composites. Received: 18 February 1997 Accepted: 30 April 1997     

DNA vaccine containing the mycobacterial hsp65 gene prevented insulitis in MLD-STZ diabetes

Background  

Our group previously demonstrated that a DNA plasmid encoding the mycobacterial 65-kDa heat shock protein (DNA-HSP65) displayed prophylactic and therapeutic effect in a mice model for tuberculosis. This protection was attributed to induction of a strong cellular immunity against HSP65. As specific immunity to HSP60 family has been detected in arthritis, multiple sclerosis and diabetes, the vaccination procedure with DNA-HSP65 could induce a cross-reactive immune response that could trigger or worsen these autoimmune diseases.     

Induced moment magnetism in TbAsO4: Constant coupling approximation

The constant-coupling approximation (CCA) is applied to the Ising model with a transverse field which is then used to study the induced-moment magnetism in TbAsO₄. We first show that in contrast to previous work, the CCA is valid throughout the entire temperature range; there exist no anomalies at low temperatures. A comparison of the phase boundaries in the Δ (transverse field)-T plane as predicted by the molecular-field approximation (MFA), CCA, and the high temperature series expansion (HTE), shows that the CCA predicts a transition temperature which is much closer to the HTE value for all Δ. The temperature dependence of the sublattice magnetization is also shown for the CCA and the MFA. A fitting to the experimentally observed energy level splitting is shown for TbAsO₄. By using a single parameter, the exchange integral, a good agreement is found between the theory and the experiment for the whole range of temperature.     

Energy transfer in linear chain manganese salts: Emission spectra of CsMnBr3, RbMnBr3 and CsMnI3 crystals doped with Er3+

The luminescence spectra of CsMnBr₃, RbMnBr₃ and CsMnI₃ crystals doped with Er³⁺ have been investigated in the 10–300 K temperature range. These linear chain manganese salts behave as “pseudo” one-dimensional antiferromagnets. The temperature dependence of luminescence from the doped materials indicates a rapid thermally activated transfer of excitation energy from the Mn²⁺ ions of the bulk crystal to the Er³⁺ impurity centers. Analysis of the data suggests that energy migration occurs by two distinct processes with activation barriers of: 200 and 500 cm^?1 for CsMnBr₃, 180 and 500 cm^?1 for RbMnBr₃ and 300 and 650 cm^?1 for CsMnI₃. The behavior of CsMn_xCd_1-xBr₃ crystals containing Er³⁺ clearly indicates that the process with the higher activation barrier corresponds to two- or three-dimensional exciton migration.     

Human liver glycogen phosphorylase inhibitors bind at a new allosteric site

Background: Glycogen phosphorylases catalyze the breakdown of glycogen to glucose-1-phosphate for glycolysis. Maintaining control of blood glucose levels is critical in minimizing the debilitating effects of diabetes, making liver glycogen phosphorylase a potential therapeutic target.Results: The binding site in human liver glycogen phosphorylase (HLGP) for a class of promising antidiabetic agents was identified crystallographically. The site is novel and functions allosterically by stabilizing the inactive conformation of HLGP. The initial view of the complex revealed key structural information and inspired the design of a new class of inhibitors which bind with nanomolar affinity and whose crystal structure is also described. Conclusions: We have identified the binding site of a new class of allosteric HLGP inhibitors. The crystal structure revealed the details of inhibitor binding, led to the design of a new class of compounds, and should accelerate efforts to develop therapeutically relevant molecules for the treatment of diabetes.