bluuebunny/crossref_metadata_2025 huggingface dataset:
Benchmarking Waste Disposal in the Egyptian Hotel Industry
Authors: Ball Stephen , Taleb Mohamed Abou
Published: August 2010

The growing environmental awareness among tourists, governments and other bodies, the sustainability of resources, waste management and the greening of hotels have resulted in waste becoming a critical issue for the industry. Waste disposal and its regulation are both important and complex in Egypt and as a result the Law 4/1994 for the Protection of the Environment was enforced. This study aimed to investigate the weight of solid waste produced by five star hotels in Cairo and to identify whether this weight complies with international standard benchmarks. Questionnaires were distributed to hotel executives responsible for monitoring waste management programmes. It was found that since 1994 hotels have started some successful waste management practices. However the weight of the waste produced by a number of hotels still exceeds the international benchmarks. A recommendation is that existing legislation needs to be amended to further both environmental and waste management practices.
Advanced modeling of electron avalanche process in polymeric dielectric voids: Simulations and experimental validation
Authors: Testa L. , Serra S. , Montanari G. C.
Published: August 2010

This paper deals with aging phenomena in polymers under electric stress. In particular, we focus our efforts on the development of a novel theoretical method accounting for the discharge process (partial discharge) in well known defects present in polymers, which are essentially tiny air gaps embedded in a polymeric matrix. Such defects are believed to act as trigger points for the partial discharges and their induced aging process. The model accounts for the amplitude as well as the energy distribution of the electrons during their motion, particularly at the time in which they impact on the polymer surface. The knowledge of the number of generated electrons and of their energy distributions is fundamental to evaluate the amount of damage caused by an avalanche on the polymer-void interface and get novel insights of the basic phenomena underlying the relevant aging processes. The calculation of such quantities would require generally the combined solution of the Boltzmann equation in the energy and space/time domains. The proposed method simplifies the problem, taking into account only the main phenomena involved in the process and provides a partial discharge (PD) model virtually free of adjustable parameters. This model is validated by an accurate experimental procedure aimed at reproducing the same conditions of the simulations and regarding air gaps embedded in polymeric dielectrics. The experimental results confirm the validity and accuracy of the proposed approach.
Visible light emission from self-catalyzed GaInP/GaP core-shell double heterostructure nanowires on silicon
Authors: Tatebayashi J. , Lin A. , Wong P. S. , Hick R. F. , Huffaker D. L.
Published: August 2010

The authors report on the formation, structural analyses, and optical properties of GaInP/GaP self-catalyzed core-shell double heterostructure nanowires (NWs) grown on Si(111) substrates. The NW growth is initiated with the formation of Ga droplets as catalysts, followed by the growth of GaP core and GaInP double heterostructure shells. Structural analyses elucidate the existence of interfaces among GaP core and GaInP double heterostructure shells. Light emissions at 640 and 800 nm are observed at 77 K from GaInP core-shell double heterostructure NWs and surface states of GaInP layers, respectively. The signal from the surface state can be mitigated via surface passivation with ammonium sulfide solution. These results will enable the realization of novel NW-based light-emitting diodes or nanolasers grown on Si substrates utilizing mature Si technologies.
Temperature dependence of luminescence characteristics of Lu2(1−x)Y2xSiO5:Ce3+ scintillator grown by the Czochralski method
Authors: Feng He , Jary Vitezslav , Mihokova Eva , Ding Dongzhou , Nikl Martin , Ren Guohao , Li Huanying , Pan Shangke , Beitlerova Alena , Kucerkova Romana
Published: August 2010

In this paper, we investigate the temperature dependence of luminescence characteristics of highly efficient cerium-doped scintillator, lutetium-yttrium orthosilicate Lu2(1−x)Y2xSiO5:Ce3+. The photoluminescence excitation and emission spectra have been measured in a broad temperature range. The temperature dependence of the Ce1 and Ce2 decay times shows the onset of decay time decrease at about 300 K. This observation demonstrates that unlike so far reported, the Ce2 center is not substantially quenched until room temperature. The 5d1 excited-state ionization of both Ce1 and Ce2 centers is studied by purely optical methods.
Remarkably low turn-on field emission in undoped, nitrogen-doped, and boron-doped graphene
Authors: Palnitkar U. A. , Kashid Ranjit V. , More Mahendra A. , Joag Dilip S. , Panchakarla L. S. , Rao C. N. R.
Published: August 2010

Field emission studies have been carried out on undoped as well as N- and B-doped graphene samples prepared by arc-discharge method in a hydrogen atmosphere. These graphene samples exhibit very low turn-on fields. N-doped graphene shows the lowest turn-on field of 0.6 V/μm, corresponding to emission current density of 10 μA/cm2. These characteristics are superior to the other types of nanomaterials reported in the literature. Furthermore, emission currents are stable over the period of more than 3 h for the graphene samples. The observed emission behavior has been explained on the basis of nanometric features of graphene and resonance tunneling phenomenon.
Mechanism of femtosecond-laser induced refractive index change in phosphate glass under a low repetition-rate regime
Authors: Little Douglas J. , Ams Martin , Dekker Peter , Marshall Graham D. , Withford Michael J.
Published: August 2010

Raman microscopy and refractive near-field profilometry were used to analyze waveguides written in Yb-doped Kigre QX glass under the low repetition-rate (noncumulative-heating) regime. It was found that femtosecond-laser induced refractive index change was due to an increase in the proportion of Q1 P-tetrahedra and the associated increase in the polarizability of the glass. The role of color center formation and removal in this process is clearly defined, phosphorous–oxygen hole centers (POHCs) and PO3− ions form as a result of P–O bonds being broken during the modification process, and the subsequent removal of POHCs give rise to the increased proportion of Q1 P-tetrahedra. This result, when compared to other studies undertaken in the cumulative-heating regime, show conclusively that the mechanism of refractive index change in a particular type of glass can be very different, depending on the irradiation conditions.
Helium cryostat for experimental study of natural turbulent convection
Authors: Urban P. , Hanzelka P. , Kralik T. , Musilova V. , Skrbek L. , Srnka A.
Published: August 2010

Published experiments on natural turbulent convection in cryogenic H4e gas show contradictory results in the values of Rayleigh number (Ra) higher than 1011. This paper describes a new helium cryostat with a cylindrical cell designed for the study of the dependence of the Nusselt number (Nu) on the Rayleigh number (up to Ra≈1015) in order to help resolve the existing controversy among published experimental results. The main part of the cryostat is a cylindrical convection cell of 300 mm in diameter and up to 300 mm in height. The cell is designed for measurement of heat transfer by natural convection at pressures ranging from 100 Pa to 250 kPa and at temperatures between 4.2 and 12 K. Parasitic heat fluxes into the convection medium are minimized by using thin sidewalls of the bottom and top parts of the cell. The exchangeable central part of the cell enables one to modify the cell geometry.
Communication: Ionization and Coulomb explosion of xenon clusters by intense, few-cycle laser pulses
Authors: Mathur D. , Rajgara F. A.
Published: August 2010

Intense, ultrashort pulses of 800 nm laser light (12 fs, ∼4 optical cycles) of peak intensity 5×1014 W cm−2 have been used to irradiate gas-phase Xen clusters (n=500–25 000) so as to induce multiple ionization and subsequent Coulomb explosion. Energy distributions of exploding ions are measured in the few-cycle domain that does not allow sufficient time for the cluster to undergo expansion due to Coulombic and hydrodynamic pressures. This results in overall dynamics that appear to be significantly different to those in the many-cycle regime. One manifestation is that the maximum ion energies are measured to be much lower than those obtained when longer pulses of the same intensity are used. Ion yields are cluster-size independent but polarization dependent in that they are significantly larger when the polarization is perpendicular to the detection axis than along it. This unexpected behavior is qualitatively rationalized in terms of a spatially anisotropic shielding effect induced by the electronic charge cloud within the cluster.
Dislocation nucleation from interacting surface corners in silicon
Authors: Li Z. , Picu R. C.
Published: August 2010

The nucleation of dislocations from sharp corners acting as stress concentration sites on a silicon (100) surface is studied by a combination of atomistic and continuum modeling. Ledges of various heights, similar to those found in microelectronic devices, are considered. In this work we focus on the effect of ledge height and of ledge-ledge elastic interaction on the activation energy for dislocation nucleation. The activation energy decreases slightly with increasing the height of the ledge and has a more pronounced, nonmonotonic variation with the distance between stress concentration sites. The effect of introducing a radius of curvature at the root of the ledge is also studied. It is concluded that even a small radius of curvature renders the nucleation process similar to that from a flat surface of same crystallographic orientation.
Detection of specific DNA using a microfluidic device featuring tethered poly(N-isopropylacrylamide) on a silicon substrate
Authors: Chen Jem-Kun , Li Jun-Yan
Published: August 2010

In this study, we grafted thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) onto a Si substrate as the medium in a microfluidic device to detect specific DNA molecules [human genomic DNA (hgDNA528), 528 bp] at extremely low concentrations (down to 2 ng/μl). After using the polymerase chain reaction to amplify the released human gDNA signal from the tethered PNIPAAm on the substrate, the amplified human gDNA molecules were characterized through agarose gel electrophoresis. The tethered PNIPAAm in the fluid device allowed the precise detection of the human gDNA.
Large internal dipole moment in InGaN/GaN quantum dots
Authors: Ostapenko Irina A. , Hönig Gerald , Kindel Christian , Rodt Sven , Strittmatter André , Hoffmann Axel , Bimberg Dieter
Published: August 2010

Direct observation of large permanent dipole moments of excitonic complexes in InGaN/GaN quantum dots is reported. Characteristic traces of spectral diffusion, observed in cathodoluminescence of InGaN/GaN quantum dots, allow deducing the magnitude of the intrinsic dipole moment. Our experimental results are in good agreement with realistic calculations of quantum dot transition energies for position-dependent external electric fields.
Cross-correlation frequency-resolved optical gating by molecular alignment for ultraviolet femtosecond pulse measurement
Authors: Lu Peifen , Liu Jia , Li Hao , Pan Haifeng , Wu Jian , Zeng Heping
Published: August 2010

We experimentally demonstrate a molecular-alignment-based cross-correlation frequency-resolved optical gating technique for ultraviolet femtosecond pulse measurement, which use laser-induced impulsive alignment of gaseous molecules as the gate function instead of the phase-matched frequency mixing process in a nonlinear crystal. The spectrogram measurements and retrieving results of the intensity and phase of the second and third harmonic pulses centered at 400 and 267 nm are presented.
Dose effects in electron beam irradiation of DNA-complex thin films
Authors: Li W. , Jones R. , Spaeth H. , Steckl A. J.
Published: August 2010

Electron beam irradiation of double-stranded DNA (dsDNA)-surfactant thin films was investigated. Irradiation caused dissociation, leading to increasing thin film solubility in water and degradation of dsDNA. These two effects produced a maximum concentration of dsDNA in aqueous solution at 400 μC/cm2 dose. These properties resulted in dual-mode resist characteristics of the DNA-surfactant films. At low dose, the DNA films functioned as positive resist while at high dose they worked as negative resist. The transition between the two regimes also occurred at 400 μC/cm2. This implies that the cross-linking process (typical for negative resists) first requires the dissociation of the DNA-surfactant complex.
Coating effect on optical resonance of plasmonic nanobowtie antenna
Authors: Lin Tzy-Rong , Chang Shu-Wei , Chuang Shun Lien , Zhang Zhaoyu , Schuck P. James
Published: August 2010

We investigate the effect of dielectric coating on the optical resonance of metallic bowtie nanoantennas, both theoretically and experimentally. The resonance wavelengths of the nanostructures measured by means of dark-field scattering spectroscopy are in excellent agreement with our theoretical calculations. The resonance wavelength is redshifted as the thickness of the coating layer increases, which is attributed to a longer effective optical path due to the larger refractive index of the coating than that of the air.
Photovoltaic characteristics of Pd doped amorphous carbon film/SiO2/Si
Authors: Ma Ming , Xue Qingzhong , Chen Huijuan , Zhou Xiaoyan , Xia Dan , Lv Cheng , Xie Jie
Published: August 2010

The Pd doped amorphous carbon (a-C:Pd) films were deposited on n-Si substrates with or without a native SiO2 layer using magnetron sputtering. The photovoltaic characteristics of the a-C:Pd/SiO2/Si and a-C:Pd/Si junctions were studied. It is found that under light illumination of 15 mW/cm2 at room temperature, the a-C:Pd/SiO2/Si solar cell fabricated at 350 °C has a high power conversion efficiency of 4.7%, which is much better than the a-C/Si junctions reported before. The enhanced conversion efficiency is ascribed to the Pd doping and the increase in sp2-bonded carbon clusters in the carbon film caused by the high temperature deposition.
Multiferroic and magnetoelectric properties of core-shell CoFe2O4@BaTiO3 nanocomposites
Authors: Raidongia Kalyan , Nag Angshuman , Sundaresan A. , Rao C. N. R.
Published: August 2010

Core-shell CoFe2O4@BaTiO3 nanoparticles and nanotubes have been prepared using a combination of solution processing and high temperature calcination. Both the core-shell nanostructures exhibit magnetic and dielectric hysteresis at room temperature and magnetoelectric effect. The dielectric constant of both the nanocomposites decreases upon application of magnetic field. The core-shell nanoparticles exhibit 1.7% change in magnetocapacitance around 134 K at 1 T, while the core-shell nanotubes show a remarkable 4.5% change in magnetocapacitance around 310 K at 2 T.
Retrieving the effective parameters of metamaterials from the single interface scattering problem
Authors: Yang J. , Sauvan C. , Paul T. , Rockstuhl C. , Lederer F. , Lalanne P.
Published: August 2010

In order to better understand when man-made structures may be considered as metamaterials with effective properties at optical frequencies, we study the scattering (reflection, transmission) of light at a single interface between a uniform half-space and a bulk metamaterial, i.e., a semi-infinite three-dimensional periodic structure. We accurately compute the scattering coefficients between plane waves and Bloch modes and test the validity of the single-Bloch-mode approximation within the metamaterial. The knowledge of the single-interface scattering coefficients allows us to propose an innovative method for deriving effective optical parameters.
Long room-temperature electron spin lifetimes in highly doped cubic GaN
Authors: Buß J. H. , Rudolph J. , Schupp T. , As D. J. , Lischka K. , Hägele D.
Published: August 2010

We report on very long electron spin relaxation times in highly n-doped bulk zincblende GaN exceeding 500 ps up to room-temperature. Time-resolved Kerr-rotation measurements show an almost temperature independent spin relaxation time between 80 and 295 K confirming an early prediction of Dyakonov and Perel for a degenerate electron gas.
The Role of Linear Alkyl and Alkoxy Side Chains in the Modulation of the Structure and Electrical Properties of Bithiophene:a Theoretical Study
Authors: Garcia Gregorio , Garzón Andrés , Granadino-Roldán José M. , Moral Mónica , Fernández-Liencres M. Paz , Navarro Amparo , Fernández-Gómez Manuel
Published: August 2010

In the present work, we have studied from a theoretical perspective the geometry and electronic properties of 2,2′-bithiophene (BT) and its derivatives 3,4′-alkyl-2,2′-bithiophene (3,4′ABT) and 3,4′-alkoxy-2,2′-bithiophene (3,4′OABT). Properties such as planarity, bond lengths, electron density, highest occupied molecular orbital → lowest unoccupied molecular orbital (HOMO → LUMO) excitation energy and π-delocalization energy, which are related to the electrical conductivity, were calculated and analyzed as a function of both the nature and length of the substituent. The oxidation process was also studied for the single-polaronic state. The ionization potential and the intramolecular reorganization energy were calculated following the semiclassical Marcus treatment. As a conclusion, the introduction of alkoxy chains in 3,4′-positions improves the electrical properties with respect to the bithiophene molecule and the corresponding alkyl derivatives.
Fire severity effects on soil organic matter from a ponderosa pine forest: a laboratory study
Authors: Hatten Jeff A. , Zabowski Darlene
Published: August 2010

This study investigated the changes in soil organic matter composition by controlling fire severity of laboratory burns on reconstructed surface soil profiles (O, A1 (0–1 cm), and A2 (1–2 cm)). Laboratory burning simulated prescribed burns that would be typical in the understorey of a ponderosa pine forest at low, moderate, and high–moderate severity levels. Soils were analysed for C, N and soil organic matter composition. Soil organic matter was fractionated into humin, humic acid, fulvic acid, soluble non‐humic materials and other hydrophobic compounds. In the O horizon, low‐, moderate‐, and high‐severity treatments consumed an increasing proportion of C and N. Carbon content of the mineral soil was unaffected by burning; however, N content of the A2 horizon decreased after the moderate‐ and high‐severity treatments, likely as a result of N volatilisation. The proportion of non‐soluble material in the O horizon increased with fire severity, whereas the proportion of humin C as total C of the A horizon decreased with fire severity. The decrease in humin was followed by an increase in the other hydrophobic compounds. The higher fire intensity experienced by the burning O horizon created recalcitrant materials while an increase in labile soil organic matter was observed in mineral soil. An increase in labile soil organic matter may cause elevated C and N mineralisation rates often seen after fire.
Experimental investigation of the physical mechanisms governing the spread of wildfires
Authors: Morandini Frédéric , Silvani Xavier
Published: August 2010

One of the objectives of the present study is to gain a deeper understanding of the heat transfer mechanisms that control the spread of wildfires. Five experimental fires were conducted in the field across plots of living vegetation. This study focussed on characterising heat transfer ahead of the flame front. The temperature and heat flux were measured at the top of the vegetation as the fire spread. The results showed the existence of two different fire spread regimes that were either dominated by radiation or governed by mixed radiant–convective heat transfer. For plume‐dominated fires, the flow strongly responds to the great buoyancy forces generated by the fire; this guides the fire plume upward. For wind‐driven fires, the flow is governed by inertial forces due to the wind, and the fire plume is greatly tilted towards unburned vegetation. The correlations of the temperature (ahead of the flame front) and wind velocity fluctuations change according to the fire regime. The longitudinal distributions of the radiant heat flux ahead of the fire front are also discussed. The data showed that neither the convective Froude number nor the Nelson convection number – used in the literature to predict fire spread regimes – reflect the observed behaviour of wind‐driven fires.
Development of post-fire crown damage mortality thresholds in ponderosa pine
Authors: Fowler James F. , Sieg Carolyn Hull , McMillin Joel , Allen Kurt K. , Negrón Jose F. , Wadleigh Linda L. , Anhold John A. , Gibson Ken E.
Published: August 2010

Previous research has shown that crown scorch volume and crown consumption volume are the major predictors of post-fire mortality in ponderosa pine. In this study, we use piecewise logistic regression models of crown scorch data from 6633 trees in five wildfires from the Intermountain West to locate a mortality threshold at 88% scorch by volume for trees with no crown consumption. For trees with >40% crown consumption volume, linear regression indicates >85% mortality, but for trees with crown consumption volume <40%, there is a statistically significant, linear relationship between increasing crown scorch and increasing probability of mortality. Analysis of an independent 600+ tree dataset from Colorado produced similar results and supports the analysis approach. Crown scorch volume (>85%), crown consumption volume (>40%), and crown consumption between 5 and 40% combined with crown scorch volume >50% mortality thresholds could be incorporated into post-fire marking guidelines for forest management goals.
Environmental determinants of lightning- v. human-induced forest fire ignitions differ in a temperate mountain region of Switzerland
Authors: Reineking Björn , Weibel Patrick , Conedera Marco , Bugmann Harald
Published: August 2010

Understanding the environmental and human determinants of forest fire ignitions is crucial for landscape management. In this study, we consider lightning- and human-induced fires separately and evaluate the relative importance of weather, forest composition and human activities on the occurrence of forest fire ignitions in the most fire-prone region of Switzerland, the Canton Ticino. Independent variables included 14 drought and fire weather indices, forest composition and human influences. Logistic regression models were used to relate these independent variables to records of forest fires over a 37-year period (1969–2005). We found large differences in the importance of environmental and human controls on forest fire ignitions between lightning- and human-induced events: lightning-induced fires occurred in a small range of weather conditions well captured by the Duff Moisture Code from the Canadian Forest Fire Weather Index System and the LandClim Drought Index, and with negligible influence of distance to human infrastructure, whereas human-induced fires occurred in a wider range of weather conditions well captured by the Angstroem and the Fosberg Fire Weather Index, mainly in deciduous forests, and strongly depending on proximity to human infrastructure. We conclude that the suitability of fire indices can vary dramatically between ignition sources, suggesting that some of these indices are useful within certain regions and fire types only. The ignition source is an important factor that needs to be taken into account by fire managers and when developing models of forest fire occurrence.
Evaluating Landsat Thematic Mapper spectral indices for estimating burn severity of the 2007 Peloponnese wildfires in Greece
Authors: Veraverbeke Sander , Verstraeten Willem W. , Lhermitte Stefaan , Goossens Rudi
Published: August 2010

A vast area (more than 100 000 ha) of forest, shrubs and agricultural land burned on the Peloponnese peninsula in Greece during the 2007 summer. Three pre- and post-fire differenced Landsat Thematic Mapper (TM)-derived spectral indices were correlated with field data of burn severity for these devastating fires. These spectral indices were the Normalised Difference Vegetation Index (NDVI), the Normalised Difference Moisture Index (NDMI) and the Normalised Burn Ratio (NBR). The field data consist of 160 Geo Composite Burn Index (GeoCBI) plots. In addition, indices were evaluated in terms of optimality. The optimality statistic is a measure for the index’s sensitivity to fire-induced vegetation depletion. Results show that the GeoCBI–dNBR (differenced NBR) approach yields a moderately high R2 = 0.65 whereas the correlation between field data and the differenced NDMI (dNDMI) and the differenced NDVI (dNDVI) was clearly lower (respectively R2 = 0.50 and R2 = 0.46). The dNBR also outperformed the dNDMI and dNDVI in terms of optimality. The resulting median dNBR optimality equalled 0.51 whereas the median dNDMI and dNDVI optimality values were respectively 0.50 and 0.40 (differences significant for P < 0.001). However, inaccuracies observed in the spectral indices approach indicate that there is room for improvement. This could imply improved preprocessing, revised index design or alternative methods.
FLIPping the kill switch
Authors: Short Ben
Published: August 2010

The amounts of different cFLIP isoforms help cells choose between life and death.
Drosophila Mtm and class II PI3K coregulate a PI(3)P pool with cortical and endolysosomal functions
Authors: Velichkova Michaella , Juan Joe , Kadandale Pavan , Jean Steve , Ribeiro Inês , Raman Vignesh , Stefan Chris , Kiger Amy A.
Published: August 2010

Reversible phosphoinositide phosphorylation provides a dynamic membrane code that balances opposing cell functions. However, in vivo regulatory relationships between specific kinases, phosphatases, and phosphoinositide subpools are not clear. We identified myotubularin (mtm), a Drosophila melanogaster MTM1/MTMR2 phosphoinositide phosphatase, as necessary and sufficient for immune cell protrusion formation and recruitment to wounds. Mtm-mediated turnover of endosomal phosphatidylinositol 3-phosphate (PI(3)P) pools generated by both class II and III phosphatidylinositol 3-kinases (Pi3K68D and Vps34, respectively) is needed to down-regulate membrane influx, promote efflux, and maintain endolysosomal homeostasis. Endocytosis, but not endolysosomal size, contributes to cortical remodeling by mtm function. We propose that Mtm-dependent regulation of an endosomal PI(3)P pool has separable consequences for endolysosomal homeostasis and cortical remodeling. Pi3K68D depletion (but not Vps34) rescues protrusion and distribution defects in mtm-deficient immune cells and restores functions in other tissues essential for viability. The broad interactions between mtm and class II Pi3K68D suggest a novel strategy for rebalancing PI(3)P-mediated cell functions in MTM-related human disease.
Model-based dissection of CD95 signaling dynamics reveals both a pro- and antiapoptotic role of c-FLIPL
Authors: Fricker Nicolai , Beaudouin Joel , Richter Petra , Eils Roland , Krammer Peter H. , Lavrik Inna N.
Published: August 2010

Cellular FADD-like interleukin-1β–converting enzyme inhibitory proteins (c-FLIPs; isoforms c-FLIP long [c-FLIPL], c-FLIP short [c-FLIPS], and c-FLIP Raji [c-FLIPR]) regulate caspase-8 activation and death receptor (DR)–induced apoptosis. In this study, using a combination of mathematical modeling, imaging, and quantitative Western blots, we present a new mathematical model describing caspase-8 activation in quantitative terms, which highlights the influence of c-FLIP proteins on this process directly at the CD95 death-inducing signaling complex. We quantitatively define how the stoichiometry of c-FLIP proteins determines sensitivity toward CD95-induced apoptosis. We show that c-FLIPL has a proapoptotic role only upon moderate expression in combination with strong receptor stimulation or in the presence of high amounts of one of the short c-FLIP isoforms, c-FLIPS or c-FLIPR. Our findings resolve the present controversial discussion on the function of c-FLIPL as a pro- or antiapoptotic protein in DR-mediated apoptosis and are important for understanding the regulation of CD95-induced apoptosis, where subtle differences in c-FLIP concentrations determine life or death of the cells.
Syndecan-3 and Notch cooperate in regulating adult myogenesis
Authors: Pisconti Addolorata , Cornelison D.D.W. , Olguín Hugo C. , Antwine Tiffany L. , Olwin Bradley B.
Published: August 2010

Skeletal muscle postnatal growth and repair depend on satellite cells and are regulated by molecular signals within the satellite cell niche. We investigated the molecular and cellular events that lead to altered myogenesis upon genetic ablation of Syndecan-3, a component of the satellite cell niche. In the absence of Syndecan-3, satellite cells stall in S phase, leading to reduced proliferation, increased cell death, delayed onset of differentiation, and markedly reduced numbers of Pax7+ satellite cells accompanied by myofiber hypertrophy and an increased number of centrally nucleated myofibers. We show that the aberrant cell cycle and impaired self-renewal of explanted Syndecan-3–null satellite cells are rescued by ectopic expression of the constitutively active Notch intracellular domain. Furthermore, we show that Syndecan-3 interacts with Notch and is required for Notch processing by ADAM17/tumor necrosis factor-α–converting enzyme (TACE) and signal transduction. Together, our data support the conclusion that Syndecan-3 and Notch cooperate in regulating homeostasis of the satellite cell population and myofiber size.
KIF17 stabilizes microtubules and contributes to epithelial morphogenesis by acting at MT plus ends with EB1 and APC
Authors: Jaulin Fanny , Kreitzer Geri
Published: August 2010

Epithelial polarization is associated with selective stabilization and reorganization of microtubule (MT) arrays. However, upstream events and downstream consequences of MT stabilization during epithelial morphogenesis are still unclear. We show that the anterograde kinesin KIF17 localizes to MT plus ends, stabilizes MTs, and affects epithelial architecture. Targeting of KIF17 to plus ends of growing MTs requires kinesin motor activity and interaction with EB1. In turn, KIF17 participates in localizing adenomatous polyposis coli (APC) to the plus ends of a subset of MTs. We found that KIF17 affects MT dynamics, polymerization rates, and MT plus end stabilization to generate posttranslationally acetylated MTs. Depletion of KIF17 from cells growing in three-dimensional matrices results in aberrant epithelial cysts that fail to generate a single central lumen and to polarize apical markers. These findings implicate KIF17 in MT stabilization events that contribute to epithelial polarization and morphogenesis.
Multicenter Study of Clostridium difficile Infection Rates from 2000 to 2006
Authors: Dubberke Erik R. , Butler Anne M. , Yokoe Deborah S. , Mayer Jeanmarie , Hota Bala , Mangino Julie E. , Khan Yosef M. , Popovich Kyle J. , Fraser Victoria J. ,   Prevention Epicenters Program from the Centers for Disease Control and Prevention
Published: August 2010

Objective.

To compare incidence rates of Clostridium difficile infection (CDI) during a 6-year period among 5 geographically diverse academic medical centers across the United States by use of recommended standardized surveillance definitions of CDI that incorporate recent information on healthcare facility (HCF) exposure.

Methods.

Data on C. difficile toxin assay results and dates of hospital admission and discharge were collected from electronic databases. Chart review was performed for patients with a positive C. difficile toxin assay result who were identified within 48 hours after hospital admission to determine whether they had any HCF exposure during the 90 days prior to their hospital admission. CDI cases, defined as any inpatient with a stool toxin assay positive for C. difficile, were categorized into 5 surveillance definitions based on recent HCF exposure. Annual CDI rates were calculated and evaluated by use of the χ2 test for trend and the χ2 summary test.

Results.

During the study period, there were significant increases in the overall incidence rates of HCF-onset, HCF-associated CDI (from 7.0 to 8.5 cases per 10,000 patient-days; P < .001); community-onset, HCF-associated CDI attributed to a study hospital (from 1.1 to 1.3 cases per 10,000 patient-days; P = .003); and community-onset, HCF-associated CDI not attributed to a study hospital (from 0.8 to 1.5 cases per 1,000 admissions overall; P < .001). For each surveillance definition of CDI, there were significant differences in the total incidence rate between HCFs.

Conclusions.

The increasing incidence rates of CDI over time and across healthcare institutions and the correlation of CDI incidence in different surveillance categories suggest that CDI may be a regional problem and not isolated to a single HCF within a community.
Platelet function defects
Authors: SIMON D. , KUNICKI T. , NUGENT D.
Published: August 2010

Summary.  Inherited defects of platelet function are a heterogeneous group of disorders that can result in bleeding symptoms ranging from mild bruising to severe mucocutaneous haemorrhage. These defects may be classified according to their effect on the various steps of platelet microthrombi formation including initiation, extension and cohesion, or based on their particular structural or functional deficiency. Platelet membrane receptor deficiencies result in the rare, but well‐characterized syndromes of defective clot initiation, such as Bernard–Soulier Syndrome. Platelet storage pool defects are the most common disorders affecting the extension phase of clot formation. Glanzmann thrombasthenia, with absent or dysfunctional αIIbβ3 receptor is the prototypical defect of the cohesion/aggregation phase of microthrombi formation. Many of these disorders share common treatments although some therapies will have greater efficacy for one patient than another and should be individualized so as to provide optimal control of symptoms. Currently much effort is being put into methods to more rapidly and accurately diagnose patients with platelet disorders and to initiate appropriate therapy and prevent life threatening bleeding.
PREPARATION OF Nα‐BOC‐Nε‐P‐BRZ‐LYSINE AND Nα‐BOC‐0‐M‐BRBZL‐TYROSINE AND THEIR USE FOR THE SOLID PHASE SYNTHESIS OF AN OCTAPEPTIDE OCCURRING IN THE HGH MOLECULE
Authors: Yamashiro Donald , Li Choh Hao
Published: August 2010

Crystalline Nα‐t‐butyloxycarbonyl‐Nε‐(p‐bromobenzyloxycarbonyl)lysine has been synthesized and employed in the solid phase synthesis of the octapeptide H‐Phe‐Lys‐Gln‐Thr‐Tyr‐Ser‐Lys‐Phe‐OH(I) which corresponds to positions 138–145 in human growth hormone. Crystalline Nα‐t‐butyloxycarbonyl‐O‐(m‐bromobenzyl)tyrosine has also been synthesized; a second synthesis of I was accomplished by use of both of these new amino acid derivatives.

All amino acids employed in this work are of the l configuration. The abbreviations used are: tlc, thin layer chromatography; TFA, trifluoroacetic acid; EtOH, absolute ethanol; DMF, dimethylformamide; Boc, Nα‐t‐butyloxycarbonyl; Z, benzyloxycarbonyl; Bzl, benzyl; HGH, human pituitary growth hormone.
CONFORMATIONAL ENERGY CALCULATIONS OF ENZYME‐SUBSTRATE INTERACTIONS. II. Computation of the Binding Energy for Substrates in the Active Site of α‐Chymotrypsin
Authors: Platzer Karen E. B. , Momany Frank A. , Scheraga Harold A.
Published: August 2010

Empirical energy calculations are carried out to study the binding of the substrates N‐acetyl‐L‐phenylalanine amide, N‐acetyl‐L‐tyrosine amide, N‐formyl‐L‐tyrosine α‐mide, and N‐acetyl‐L‐tryptophan amide to the enzyme molecule α‐chymotrypsin. As an initial probe of the active‐site surface, the low‐energy conformations of the phenylalanine substrate (see Part I) are allowed to approach the enzyme by overall rotational and translational motion until a minimum is achieved in the enzyme‐substrate interaction energy. Four regions of good binding are found near the active site, the one of lowest energy being that in which the ring is oriented in the cleft of the enzyme. This cleft binding site is the same as the binding position found by X‐ray diffraction for the virtual substrate N‐formyl‐L‐tryptophan; the other three favorable binding regions might not be detected by X‐ray analysis, possibly because they are blocked in the dimer structure of the crystalline enzyme. Further investigation of the most favorable (cleft) binding site indicates that left‐handed α‐helical backbone conformations of the substrate do not form stable enzyme‐substrate complexes, while the equatorial seven‐membered ring, as well as the right‐handed α‐helical and β and γ backbone conformations (the latter three of which commonly occur in proteins) bind well. The calculated binding energies of all four substrates correlate with experimental binding constants.
SEQUENCE COMPARISON OF HUMAN PITUITARY GROWTH HORMONE, HUMAN CHORIONIC SOMATOMAMMOTROPIN, AND OVINE PITUITARY GROWTH AND LACTOGENIC HORMONES
Authors: Bewley Thomas A. , Dixon Jonathan S. , Li Choh Hao
Published: August 2010

A comparison of the primary structure of human pituitary growth hormone, human chorionic somatomammotropin, ovine pituitary lactogenic hormone and ovine pituitary growth hormone indicates that all four molecules have evolved from a common ancestor. Ovine pituitary lactogenic hormone appears to have diverged from the other three proteins, and to have evolved independently over a relatively long period of time. Cross comparisons, intended to detect the presence of compact and mutually exclusive sequence segments that might be specifically correlated with the two types of biological activities displayed by these hormones, were unsuccessful.
REFINEMENT OF THE MOLECULAR STRUCTURE OF ACTINOMYCIN D BY ENERGY MINIMIZATION
Authors: Ponnuswamy P. K. , McGuire R. F. , Scheraga H. A.
Published: August 2010

The atomic coordinates of actinomycin D obtained by x‐ray analysis by Sobell et al. have been refined to fit a set of standard bond lengths and bond angles using a least squares procedure and a conformational energy minimization technique. The computationally refined structure shows greater similarity between the conformations of the two pentapeptide rings and an improved dyad symmetry, compared to the x‐ray structure. The refined structure is compared with NMR data and with the structure proposed by De Santis et al. The energy calculations also provide information about the conformational features of cis proline residues in polypeptide chains.
A STATISTICAL ANALYSIS OF THE AMINO ACID COMPOSITIONS OF PROTEINS
Authors: Reeck Gerald R. , Fisher Lloyd
Published: August 2010

Univariate and multivariate analyses are presented which give a descriptive statistical look at the amino acid compositions of proteins. Means, expressed in mole percent, and standard deviations are calculated using a sample of 207 proteins. The distributions of six of the 18 amino acids (Asp, Val, Met, Phe, Ile, and Leu) appear somewhat normal (Gaussian), whereas the distributions of the other 12 amino acids are judged by a chi‐squared test and the coefficients of kurtosis and skewness to not be normal. Principal component analysis has revealed the relationships among the amino acids to be quite complex: for example, to account for 70% of the variability in the data an eight dimensional space is needed. Several pairs of amino acids appear to have significant correlation coefficients, but most of the correlations do not have an obvious rationale in terms of the structures of the amino acids. The following pairs of protein sets have mean amino acid compositions that differ significantly, although no one amino acid accounts for the overall difference in any case: (eukaryotic enzymes, eukaryotic nonenzymes), (eukaryotic enzymes, prokaryotic enzymes) and (nonmicrobial enzymes, microbial enzymes).
CONFORMATIONAL ANALYSIS OF AROMATIC AMINO ACIDS BY X‐RAY CRYSTALLOGRAPHY
Authors: Cody Vivian , Duax William L. , Hauptman Herbert
Published: August 2010

A systematic analysis of 48 crystal structures of aromatic amino acids or amino acid residues with tyrosine or phenylalanine in their molecular make up reveals that there are three basic energy minimum conformations which these molecules adopt and which, in this statistical sample, can be further subdivided into subsets. These groups are bounded by the interactions of the three rotational parameters X1, X2and ø1which describe the amino acid backbone. The three major classes A, B and C are defined as the structures having the three staggered positions of X1(60°, 180° and 300°, respectively). Class B (X1= 180°) can be subdivided into two subsets B1and B2by means of the correlation between χ2and ø1. The statistical distribution of this sample (A:B:C: 23:31:46%) agrees better with the theoretical distribution from energy minimization calculations (19:36:45%) than does the distribution observed in proteins (4:29:67%). Also, it is observed that, in those structures which contain an ethyl ester, the latter maintains a fixed orientation relative to the amino acid backbone.
CHARACTERIZATION OF SOLUBILIZED CYTOCHROME P‐450
Authors: Koes M. T. , Stasiw R. O. , Forrester L. J. , Chattopadhyay S. K. , Bartung G. J. , Cowan D. , Brown H. D.
Published: August 2010

Porcine liver microsomes were subjected to digitonin, n‐butanol and sonication treatment to solubilize cytochrome P‐450 and other mixed‐function oxidation components. The best preparation achieved with 2% digitonin gave characteristic P‐450, CN‐and NO2‐ difference spectra. It was further purified by ammonium sulfate fractionation and column chromatography. Column chromatography resulted in the separation of cytochrome P‐450 subparticles from cytochrome P‐420 subparticles; both contained negligible quantities of cytochrome b5and significant amounts of ferricyanide reductase and NADPH oxidase activity.
CYCLOLS‐FORMATION FROM TRIPEPTIDE SYSTEMS AND STRUCTURE ASSIGNMENT BY CARBON‐13 NUCLEAR MAGNETIC RESONANCE
Authors: Conti F. , Lucente G. , Romeo A. , Zanotti G.
Published: August 2010

The influence of the nature of the amino acids on the cyclolization reaction, starting from linear tripeptides, has been studied. In these systems the presence of proline at the carboxyl end as well as the alkyl substitution on the other two residues have been found to be important. The utilization of 13C‐NMR spectroscopy as a direct method for detecting the cyclolic structure is reported.
STUDIES ON SILK FIBROIN. II. SEDIMENTATION COEFFICIENT DISTRIBUTION OF FIBROINS
Authors: Pandit M. W. , Rao M. S. Narasinga
Published: August 2010

The sedimentation coefficient distributions of silk fibroin samples prepared by extraction of silk fibre by boiling Na2CO3 solution for different intervals of time were determined.

Samples from 150 and 180 min extraction gave sharper distribution curves than those from 30, 60, 90 and 120 min extraction.

The s̀2corr vs (t — t0) plots for samples from 30, 60, 90 and 120 min extraction showed upward curvature indicating heterogeneity of the preparation. On the other hand, samples from 150 and 180 min extraction gave linear plots.

The molecular weight of the sample from 180 min extraction was calculated from the sedimentation coefficient and the diffusion coefficient obtained from the linear s̀2 vs (t — t0) plot. This value was in good agreement with the limiting value obtained at higher speeds of centrifugation by the Archibald method. However, it was lower than the molecular weight determined by the Archibald method at low speeds, indicating the heterogeneous nature of this sample also.
SUBTILOPEPTIDASE A CLEAVAGE IN THE CYCLIC REGION OF THE PEPTIDE ANTIBIOTIC POLYMYXIN B1
Authors: Galardy Richard E. , Bockman Richard S. , Sogn John A. , Gibbons William A. , Printz Morton P. , Craig Lyman C.
Published: August 2010

Digestion of a commercial mixture of the peptides polymyxin B1 and B2 with subtilopeptidase A yielded a peptide whose amino acid composition corresponded to the ring fragment common to both antibiotics. However, in contrast to the earlier chemical studies of Suzuki and collaborators, our high resolution nmr studies indicated that the ring had been split. Edman degradation, hydrazinolysis and exopeptidase digestion showed the rupture to have occurred between positions 8 and 9.
STUDIES ON PROTEIN MULTIMERS:
Authors: Contaxis C. C. , McAfee Don , Goodrich R. , Reithel F. J.
Published: August 2010

β‐Galactosidase from E. coli dissociates readily in commonly used buffer systems except at pH values close to the isoelectric point. Dissociation of the tetramer to the monomer does not result, per se, in a substantial change in the value of the apparent specific volume. In contrast, dissociation of very dilute protein solutions such as those produced at the meniscus in high speed sedimentation equilibrium runs, or dissociation of protein at low ionic strength, does lead to monomeric forms with a lower apparent specific volume. The ϕ2 value of the monomer formed in 90% glycerol changes markedly on transfer from aqueous buffer to 99.8% D2O. The dissociation of the tetrameric form of β‐galactosidase in aqueous buffer is minimized by 99.8% D2O.
A Model Of The Three‐Dimensional Structure Of Snake Venom Neurotoxins Based On Chemical Evidence
Authors: Ryden Lars , Gabel Detlef , Eaker David
Published: August 2010

Data, from studies of covalent structure and chemical and physico‐chemical behaviour of 27 different homologous proteins with either neurotoxic, cardiotoxic or fytic activity isolated from the venoms of elapid or hydrophid snakes have been collected from the literature. Because of their small size (60–74 amino acid residues) and their high content of disulphide bridges (4 or 5 bridges) these proteins provide an unusually favourable opportunity for trials to construct models of three‐dimensional structure from indirect chemical evidence. Such a model has been built from atomic skeleton model units for the Naja nigricollis a‐toxin, which contains 61 amino acid residues and 4 disulfide bridges.

The dizerences in amino acid sequences bet ween the proteins with neurotoxic and those with cardiotoxic or lytic activity have been used to assign certain residues as important for the general folding of the molecule and others as important for neurotoxic activity. The last‐mentioned residues are presumed to form the site that binds to the acetyl‐choline receptor.
SYMMETRICAL DISULFIDE BONDS AS S‐PROTECTING GROUPS AND THEIR CLEAVAGE BY DITHIOTHREITOL: SYNTHESIS OF OXYTOCIN WITH HIGH BIOLOGICAL ACTIVITY
Authors: Hase Satoe , Walter Roderich
Published: August 2010

Oxytocin, possessing high rat uterotonic activity(560 ± 25 U/mg)and avian vasodepressor activity(510±23 U/mg)was obtained according to the following scheme: acylation of bis(L‐tyrosyl‐L‐isoleucyl‐L‐glutaminyl‐L‐asparaginyl)‐L‐cystinyl‐bis(L‐prolyl‐L‐leucylglycinamide)with bis(tett‐butyloxycarbonyl)‐L‐cystinyl‐bis(p‐nitro‐phenyl ester);liberation of the N‐terminal amino groups of the coupling products with TFA and reduction of all disulfide bonds with dithiothreitol in aqueous medium at pH 8; separation of oxytoceine from low molecular weight compounds; followed by air oxidation of the disulfhydryl monomer to the cyclic disulfide. The protected intermediates of oxytocin were prepared according to the stepwise method of peptide synthesis in which the peptide chain was elongated by the use of N‐protected activated esters as acylating agents; the cysteine residues were introduced into the peptide as symmetrically substituted cystines.