Gate protective device for insulated gate field-effect transistors

Device, which protects insulated gate field-effect transistors, improves reliability through utilization of layers of conductive material on top of each alternating semiconductor material region. Separation of layers is necessary to prevent shorting out junctions between alternating regions

The Evolving Activity of the Dynamically Young Comet C/2009 P1 (Garradd)

We used the UltraViolet-Optical Telescope on board Swift to observe the dynamically young comet C/2009 P1 (Garradd) from a heliocentric distance of 3.5 AU pre-perihelion until 4.0 AU outbound. At 3.5 AU pre-perihelion, comet Garradd had one of the highest dust-to-gas ratios ever observed, matched only by comet Hale-Bopp. The evolving morphology of the dust in its coma suggests an outburst that ended around 2.2 AU pre-perihelion. Comparing slit-based measurements and observations acquired with larger fields of view indicated that between 3 AU and 2 AU pre-perihelion a significant extended source started producing water in the coma. We demonstrate that this source, which could be due to icy grains, disappeared quickly around perihelion. Water production by the nucleus may be attributed to a constantly active source of at least 75 km$^2$, estimated to be more than 20 percent of the surface. Based on our measurements, the comet lost $4x10^{11}$ kg of ice and dust during this apparition, corresponding to at most a few meters of its surface.Even though this was likely not Garradd's first passage through the inner solar system, the activity of the comet was complex and changed significantly during the time it was observed

Modest Declines in Proteome Quality Impair Hematopoietic Stem Cell Self-Renewal.

Low protein synthesis is a feature of somatic stem cells that promotes regeneration in multiple tissues. Modest increases in protein synthesis impair stem cell function, but the mechanisms by which this occurs are largely unknown. We determine that low protein synthesis within hematopoietic stem cells (HSCs) is associated with elevated proteome quality in vivo. HSCs contain less misfolded and unfolded proteins than myeloid progenitors. Increases in protein synthesis cause HSCs to accumulate misfolded and unfolded proteins. To test how proteome quality affects HSCs, we examine Aarssti/sti mice that harbor a tRNA editing defect that increases amino acid misincorporation. Aarssti/sti mice exhibit reduced HSC numbers, increased proliferation, and diminished serial reconstituting activity. Misfolded proteins overwhelm the proteasome within Aarssti/sti HSCs, which is associated with increased c-Myc abundance. Deletion of one Myc allele partially rescues serial reconstitution defects in Aarssti/sti HSCs. Thus, HSCs are dependent on low protein synthesis to maintain proteostasis, which promotes their self-renewal

Poly(β-Amino Ester)-Nanoparticle Mediated Transfection of Retinal Pigment Epithelial Cells In Vitro and In Vivo

A variety of genetic diseases in the retina, including retinitis pigmentosa and leber congenital amaurosis, might be excellent targets for gene delivery as treatment. A major challenge in non-viral gene delivery remains finding a safe and effective delivery system. Poly(beta-amino ester)s (PBAEs) have shown great potential as gene delivery reagents because they are easily synthesized and they transfect a wide variety of cell types with high efficacy in vitro. We synthesized a combinatorial library of PBAEs and evaluated them for transfection efficacy and toxicity in retinal pigment epithelial (ARPE-19) cells to identify lead polymer structures and transfection formulations. Our optimal polymer (B5-S5-E7 at 60 w/w polymer∶DNA ratio) transfected ARPE-19 cells with 44±5% transfection efficacy, significantly higher than with optimized formulations of leading commercially available reagents Lipofectamine 2000 (26±7%) and X-tremeGENE HP DNA (22±6%); (p<0.001 for both). Ten formulations exceeded 30% transfection efficacy. This high non-viral efficacy was achieved with comparable cytotoxicity (23±6%) to controls; optimized formulations of Lipofectamine 2000 and X-tremeGENE HP DNA showed 15±3% and 32±9% toxicity respectively (p>0.05 for both). Our optimal polymer was also significantly better than a gold standard polymeric transfection reagent, branched 25 kDa polyethyleneimine (PEI), which achieved only 8±1% transfection efficacy with 25±6% cytotoxicity. Subretinal injections using lyophilized GFP-PBAE nanoparticles resulted in 1.1±1×103-fold and 1.5±0.7×103-fold increased GFP expression in the retinal pigment epithelium (RPE)/choroid and neural retina respectively, compared to injection of DNA alone (p = 0.003 for RPE/choroid, p<0.001 for neural retina). The successful transfection of the RPE in vivo suggests that these nanoparticles could be used to study a number of genetic diseases in the laboratory with the potential to treat debilitating eye diseases

Ab Initio Calculation of Impurity Effects in Copper Oxide Materials

We describe a method for calculating, within density functional theory, the electronic structure associated with typical defects which substitute for Cu in the CuO2 planes of high-Tc superconducting materials. The focus is primarily on Bi2Sr2CaCu2O8, the material on which most STM measurements of impurity resonances in the superconducting state have been performed. The magnitudes of the effective potentials found for Zn, Ni and vacancies on the in-plane Cu sites in this host material are remarkably consistent with phenomenological fits of potential scattering models to STM resonance energies. The effective potential ranges are quite short, of order 1 A with weak long range tails, in contrast to some current models of extended potentials which attempt to fit STM data. For the case of Zn and Cu vacancies, the effective potentials are strongly repulsive, and states on the impurity site near the Fermi level are simply removed. The local density of states (LDOS) just above the impurity is nevertheless found to be a maximum in the case of Zn and a local minimum in case of the vacancy, in agreement with experiment. The Zn and Cu vacancy patterns are explained as due to the long-range tails of the effective impurity potential at the sample surface. The case of Ni is richer due to the Ni atom's strong hybridization with states near the Fermi level; in particular, the short range part of the potential is attractive, and the LDOS is found to vary rapidly with distance from the surface and from the impurity site. We propose that the current controversy surrounding the observed STM patterns can be resolved by properly accounting for the effective impurity potentials and wave-functions near the cuprate surface. Other aspects of the impurity states for all three species are discussed.Comment: 37 pp. pdf including figures, submitted to Phys. Rev.

Orbital Configurations and Magnetic Properties of Double-Layered Antiferromagnet Cs3_3Cu2_2Cl4_4Br3_3

We report the single-crystal X-ray analysis and magnetic properties of a new double-layered perovskite antiferromagnet, Cs$_3$Cu$_2$Cl$_4$Br$_3$. This structure is composed of Cu$_2$Cl$_4$Br$_3$ double layers with elongated CuCl$_4$Br$_2$ octahedra and is closely related to the Sr$_3$Ti$_2$O$_7$ structure. An as-grown crystal has a singlet ground state with a large excitation gap of $\Delta/k_{\rm B}\simeq 2000$ K, due to the strong antiferromagnetic interaction between the two layers. Cs$_3$Cu$_2$Cl$_4$Br$_3$ undergoes a structural phase transition at $T_{\rm s}\simeq330$ K accompanied by changes in the orbital configurations of Cu$^{2+}$ ions. Once a Cs$_3$Cu$_2$Cl$_4$Br$_3$ crystal is heated above $T_{\rm s}$, its magnetic susceptibility obeys the Curie-Weiss law with decreasing temperature even below $T_{\rm s}$ and does not exhibit anomalies at $T_{\rm s}$. This implies that in the heated crystal, the orbital state of the high-temperature phase remains unchanged below $T_{\rm s}$, and thus, this orbital state is the metastable state. The structural phase transition at $T_{\rm s}$ is characterized as an order-disorder transition of Cu$^{2+}$ orbitals.Comment: 6pages. 6figures, to appear in J. Phys. Soc. Jpn. Vol.76 No.

Water Ice and Dust in the Innermost Coma of Comet 103P/Hartley 2

On November 4th, 2010, the Deep Impact eXtended Investigation (DIXI) successfully encountered comet 103P/Hartley 2, when it was at a heliocentric distance of 1.06 AU. Spatially resolved near-IR spectra of comet Hartley 2 were acquired in the 1.05-4.83 micron wavelength range using the HRI-IR spectrometer. We present spectral maps of the inner ~10 kilometers of the coma collected 7 minutes and 23 minutes after closest approach. The extracted reflectance spectra include well-defined absorption bands near 1.5, 2.0, and 3.0 micron consistent in position, bandwidth, and shape with the presence of water ice grains. Using Hapke's radiative transfer model, we characterize the type of mixing (areal vs. intimate), relative abundance, grain size, and spatial distribution of water ice and refractories. Our modeling suggests that the dust, which dominates the innermost coma of Hartley 2 and is at a temperature of 300K, is thermally and physically decoupled from the fine-grained water ice particles, which are on the order of 1 micron in size. The strong correlation between the water ice, dust, and CO2 spatial distribution supports the concept that CO2 gas drags the water ice and dust grains from the nucleus. Once in the coma, the water ice begins subliming while the dust is in a constant outflow. The derived water ice scale-length is compatible with the lifetimes expected for 1-micron pure water ice grains at 1 AU, if velocities are near 0.5 m/s. Such velocities, about three order of magnitudes lower than the expansion velocities expected for isolated 1-micron water ice particles [Hanner, 1981; Whipple, 1951], suggest that the observed water ice grains are likely aggregates.Comment: 51 pages, 12 figures, accepted for publication in Icaru

Divergent drivers of leaf trait variation within species, among species, and among functional groups.

Understanding variation in leaf functional traits-including rates of photosynthesis and respiration and concentrations of nitrogen and phosphorus-is a fundamental challenge in plant ecophysiology. When expressed per unit leaf area, these traits typically increase with leaf mass per area (LMA) within species but are roughly independent of LMA across the global flora. LMA is determined by mass components with different biological functions, including photosynthetic mass that largely determines metabolic rates and contains most nitrogen and phosphorus, and structural mass that affects toughness and leaf lifespan (LL). A possible explanation for the contrasting trait relationships is that most LMA variation within species is associated with variation in photosynthetic mass, whereas most LMA variation across the global flora is associated with variation in structural mass. This hypothesis leads to the predictions that (i) gas exchange rates and nutrient concentrations per unit leaf area should increase strongly with LMA across species assemblages with low LL variance but should increase weakly with LMA across species assemblages with high LL variance and that (ii) controlling for LL variation should increase the strength of the above LMA relationships. We present analyses of intra- and interspecific trait variation from three tropical forest sites and interspecific analyses within functional groups in a global dataset that are consistent with the above predictions. Our analysis suggests that the qualitatively different trait relationships exhibited by different leaf assemblages can be understood by considering the degree to which photosynthetic and structural mass components contribute to LMA variation in a given assemblage

Age of Migration Differentials in Life Expectancy With Cognitive Impairment: 20-Year Findings From the Hispanic-EPESE

Background and Objectives To examine differences in life expectancy with cognitive impairment among older Mexican adults according to nativity (U.S.-born/foreign-born) and among immigrants, age of migration to the United States. Research Design and Methods This study employs 20 years of data from the Hispanic Established Populations for the Epidemiologic Study of the Elderly to estimate the proportion of life spent cognitively healthy and cognitively impaired prior to death among older Mexican adults residing in the southwestern United States. We combine age-specific mortality rates with age-specific prevalence of cognitive impairment, defined as a Mini-Mental Status Exam score of less than 21 points to calculate Sullivan-based life table models with and without cognitive impairment in later life. Results Foreign-born Mexican immigrants have longer total life expectancy and comparable cognitive healthy life expectancy regardless of gender compared to U.S.-born Mexican-Americans. However, the foreign-born spend a greater number of years after age 65 with cognitive impairment relative to their U.S.-born counterparts. Furthermore, we document an advantage in life expectancy with cognitive impairment and proportion of years after age 65 cognitively healthy among mid-life immigrant men and women relative to early- and late-life migrants. Discussion and Implications The relationship between nativity, age of migration, and life expectancy with cognitive impairment means that the foreign-born are in more need of support and time-intensive care in late life. This issue merits special attention to develop appropriate and targeted screening efforts that reduce cognitive decline for diverse subgroups of older Mexican-origin adults as they age