Tunneling into a two-dimensional electron system in a strong magnetic field

We investigate the properties of the one-electron Green's function in an interacting two-dimensional electron system in a strong magnetic field, which describes an electron tunneling into such a system. From finite-size diagonalization, we find that its spectral weight is suppressed near zero energy, reaches a maximum at an energy of about $0.2e^{2}/\epsilon l_{c}$, and decays exponentially at higher energies. We propose a theoretical model to account for the low-energy behavior. For the case of Coulomb interactions between the electrons, at even-denominator filling factors such as $\nu=1/2$, we predict that the spectral weight varies as $e^{-\omega_0/|\omega|}$, for $\omega\rightarrow 0$

Secretion of Hepatitis C Virus Envelope Glycoproteins Depends on Assembly of Apolipoprotein B Positive Lipoproteins

The density of circulating hepatitis C virus (HCV) particles in the blood of chronically infected patients is very heterogeneous. The very low density of some particles has been attributed to an association of the virus with apolipoprotein B (apoB) positive and triglyceride rich lipoproteins (TRL) likely resulting in hybrid lipoproteins known as lipo-viro-particles (LVP) containing the viral envelope glycoproteins E1 and E2, capsid and viral RNA. The specific infectivity of these particles has been shown to be higher than the infectivity of particles of higher density. The nature of the association of HCV particles with lipoproteins remains elusive and the role of apolipoproteins in the synthesis and assembly of the viral particles is unknown. The human intestinal Caco-2 cell line differentiates in vitro into polarized and apoB secreting cells during asymmetric culture on porous filters. By using this cell culture system, cells stably expressing E1 and E2 secreted the glycoproteins into the basal culture medium after one week of differentiation concomitantly with TRL secretion. Secreted glycoproteins were only detected in apoB containing density fractions. The E1–E2 and apoB containing particles were unique complexes bearing the envelope glycoproteins at their surface since apoB could be co-immunoprecipitated with E2-specific antibodies. Envelope protein secretion was reduced by inhibiting the lipidation of apoB with an inhibitor of the microsomal triglyceride transfer protein. HCV glycoproteins were similarly secreted in association with TRL from the human liver cell line HepG2 but not by Huh-7 and Huh-7.5 hepatoma cells that proved deficient for lipoprotein assembly. These data indicate that HCV envelope glycoproteins have the intrinsic capacity to utilize apoB synthesis and lipoprotein assembly machinery even in the absence of the other HCV proteins. A model for LVP assembly is proposed

Lipid droplets: a classic organelle with new outfits

Lipid droplets are depots of neutral lipids that exist virtually in any kind of cell. Recent studies have revealed that the lipid droplet is not a mere lipid blob, but a major contributor not only to lipid homeostasis but also to diverse cellular functions. Because of the unique structure as well as the functional importance in relation to obesity, steatosis, and other prevailing diseases, the lipid droplet is now reborn as a brand new organelle, attracting interests from researchers of many disciplines

Facilitating and Disinhibiting Prosocial Behaviors: The Nonlinear Interaction of Trait Perspective Taking and Trait Personal Distress on Volunteering

Prior theorists and researchers have suggested that multiplicative models of prosocial behavior may account for weak and inconsistent relations between traits and prosocial behaviors. This study examined the multiplicative relations of trait personal distress, trait sympathy, and trait perspective taking on prosocial behaviors. Nonlinear, 2-way interactions were hypothesized, such that as trait personal distress decreased from moderate to low levels, and trait perspective taking or trait sympathy increased, volunteering would increase. One hundred and eighty-two undergraduate students completed a battery of trait measures that included trait perspective taking, trait sympathy, and trait personal distress. Approximately 6 weeks later, the students were given an opportunity to volunteer for a charity organization. Results indicated that there was a nonlinear multiplicative effect of trait perspective taking and trait personal distress on volunteering. Discussion focused on the implications of nonlinear, multiplicative trait models of prosocial behaviors

Selecting Advanced Software Technology in Two Small Manufacturing Enterprises

Small manufacturing enterprises (SMEs) face a number of challenges when selecting and implementing advanced manufacturing technologies. These challenges may include the lack of awareness of the specific technologies and commercial products available, the lack of ability to select the appropriate product, and the lack of skill sets needed to utilize the selection techniques. This paper documents the actual process and benefits of advanced software technologies adoption by two SMEs. Considerations for defining requirements and selecting a software product are described. This note explains the issues involved for SMEs, presents methods they can use, and provides artifacts used in this documented case

Deficiency of acyl CoA:cholesterol acyltransferase 2 prevents atherosclerosis in apolipoprotein E-deficient mice

Deficiency of acyl CoA:cholesterol acyltransferase 2 (ACAT2) in mice results in a reduction in cholesterol ester synthesis in the small intestine and liver, which in turn limits intestinal cholesterol absorption, hepatic cholesterol gallstone formation, and the accumulation of cholesterol esters in the plasma lipoproteins. Here we examined the contribution of ACAT2-derived cholesterol esters to atherosclerosis by crossing ACAT2-deficient (ACAT2(–/–)) mice with apolipoprotein (apo) E-deficient (ApoE(–/–)) mice, an atherosclerosis-susceptible strain that has impaired apoE-mediated clearance of apoB-containing lipoproteins. ACAT2(–/–) ApoE(–/–) mice and ACAT2(+/+) ApoE(–/–) (control) mice had similar elevations of plasma apoB and total plasma lipids; however, the lipid cores of the apoB-containing lipoproteins in ACAT2(–/–) ApoE(–/–) mice contained primarily triglycerides rather than cholesterol esters. At 30 wk of age, only the control mice had significant atherosclerosis, which was nearly absent in ACAT2(–/–) ApoE(–/–) mice. ACAT2 deficiency in the apoE-deficient background also led to a compensatory increase in the activity of lecithin/cholesterol acyltransferase, the major plasma cholesterol esterification enzyme, which increased high-density lipoprotein cholesterol esters. Our results demonstrate the crucial role of ACAT2-derived cholesterol esters in the development of atherosclerosis in mice and suggest that triglyceride-rich apoB-containing lipoproteins are not as atherogenic as those containing cholesterol esters. Our results also support the rationale of pharmacological inhibition of ACAT2 as a therapy for atherosclerosis