The effect of ultrasound treatment on the particle-size of Wyoming bentonite in aqueous suspensions

Aqueous suspensions of Na-montmorillonite (1.80 and 0.60 wt%) were aged for three months and were sonicated for different times. Statistical parameters related to volume were determined from particle-size distributions obtained by Laser Shadow Analysis. After a long ultrasound treatment the concentrated suspension showed a gradual increase of the largest particles and of the mean and median particles, as well as a decrease of the percentage of particles with diameters under 1.5 μm. The dilute suspension, on the other hand, showed a decrease of the largest particles and of the mean and median particles, and an increase of the percentage of particles with diameters under 1.5 μm. In the dilute suspension sonication resulted in the formation of small swollen particles by the delamination of large swollen tactoids. In the concentrated suspension the swelling of the clay was not complete during the three months aging period. As a result of the ultrasound treatment tactoids were delaminated and the swelling of the clay particles became more efficient.     

A nutrient-sensing pathway regulates leptin gene expression in muscle and fat

Leptin, the protein encoded by the obese (ob) gene, is synthesized and released in response to increased energy storage in adipose tissue. However, it is still not known how incoming energy is sensed and transduced into increased expression of the ob gene. The hexosamine biosynthetic pathway is a cellular 'sensor' of energy availability and mediates the effects of glucose on the expression of several gene products. Here we provide evidence for rapid activation of ob gene expression in skeletal muscle by glucosamine. Increased tissue concentrations of the end product of the hexosamine biosynthetic pathway, UDP-N-acetylglucosamine (UDP-GlcNAc), result in rapid and marked increases in leptin messenger RNA and protein levels (although these levels were much lower than those in fat). Plasma leptin levels and leptin mRNA and protein levels in adipose tissue also increase. Most important, stimulation of leptin synthesis is reproduced by either hyperglycaemia or hyperlipidaemia, which also increase tissue levels of UDP-N-acetylglucosamine in conscious rodents. Finally, incubation of 3T3-L1 pre-adipocytes and L6 myocytes with glucosamine rapidly induces ob gene expression. Our findings are the first evidence of inducible leptin expression in skeletal muscle and unveil an important biochemical link between increased availability of nutrients and leptin expression.     

Atrial-Synchronized Demand Heart Pacing

A universal heart pacing method is proposed, making use of the atrial-synchronized and demand operation modes. The system includes an ECG-sensing network for control of the pacing action. Special logic design provides for processing the P- and QRS-waves in two parallel channels.     

Fast Pass-Transistor Simulation for Custom MOS Circuits

This approach uses the Yorktown Simulation Engine to bridge the gap between electrical and gate-level simulators. It is well-suited to fault simulation and design verification.     

Splits in the self following immigration: An adaptive defense or a pathological reaction?

This study examines the extent to which splits in the sense of self following immigration can be seen to be an adaptive defense, allowing the self time to adapt and adjust to a new reality or rather a pathological reaction to the trauma of migration. In-depth interviews were conducted with 68 emerging adult immigrants in Israel from the Former Soviet Union around sense of self and the immigration experience. One year following the first interview, levels of functioning were assessed. Results showed that attempts to resolve splits (self/object) early after immigration led to an initially lower level of psychological symptoms, but one year later to an increased level of symptoms, suggesting that attempts of precocious resolution are likely to lead to subsequent adaptation difficulties. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Combinatorial Library of Lipid Nanoparticles for RNA Delivery to Leukocytes

Lipid nanoparticles (LNPs) are the most advanced nonviral platforms for small interfering RNA (siRNA) delivery that are clinically approved. These LNPs, based on ionizable lipids, are found in the liver and are now gaining much attention in the field of RNA therapeutics. The previous generation of ionizable lipids varies in linker moieties, which greatly influences in vivo gene silencing efficiency. Here novel ionizable amino lipids based on the linker moieties such as hydrazine, hydroxylamine, and ethanolamine are designed and synthesized. These lipids are formulated into LNPs and screened for their efficiency to deliver siRNAs into leukocytes, which are among the hardest to transfect cell types. Two potent lipids based on their in vitro gene silencing efficiencies are also identified. These lipids are further evaluated for their biodistribution profile, efficient gene silencing, liver toxicity, and potential immune activation in mice. A robust gene silencing is also found in primary lymphocytes when one of these lipids is formulated into LNPs with a pan leukocyte selective targeting agent (β₇ integrin). Taken together, these lipids have the potential to open new avenues in delivering RNAs into leukocytes.     

Coordinated motion planning for two independent robots

We present anO(n ²) algorithm for planning a coordinated collision-free motion of two independent robot systems of certain kinds, each having two degrees of freedom, which move in the plane amidst polygonal obstacles having a total ofn corners. We exemplify our technique in the case of two planar Stanford arms, but also discuss the case of two discs or convex translating objects. The algorithm improves previous algorithms for this kind of problems, and can be extended to a fairly simple general technique for obtaining efficient coordinated motion planning algorithms.     

Ab initio modeling of Al adsorption on CaF2 surfaces

Ab initio simulations of the adsorption of Al atoms on CaF₂ (0 0 1) and (1 1 1) surfaces have been performed for supercells with 7 different atomic configurations, using density functional theory. For (1 1 1) surfaces, a repulsive interaction was observed for most configurations, while a weak attraction was obtained when the Al atom was placed above F atoms. For the Ca-terminated (0 0 1) surface, the adsorption energy was about 5 times larger, whereas for the F-terminated (0 0 1) surface it was about 20 times greater. The comparative analysis indicates that the (0 0 1) surfaces are reactive and have a strong Al adatom bonding (chemisorption), especially for the F-terminated substrate. On the contrary, the (1 1 1) plane may be considered as non-reactive (physisorption), having a weak bonding of the Al adatom above the F site.