bluuebunny/crossref_metadata_2025 huggingface dataset:
Operational and environmental stability of pentacene thin-film transistors
Authors: Kagan C. R. , Afzali A. , Graham T. O.
Published: May 2005

We report the effects of repeated stressing and environmental exposure on the operational stability of pentacene thin-film transistors (TFTs). Pentacene TFT channels were deposited by thermal evaporation and by spin coating and thermally converting soluble precursors. For a given dielectric thickness and applied voltage, pentacene TFTs with shorter channel lengths and therefore higher current densities have the largest decrease in field-effect mobility, on-current, and subthreshold slope and the largest threshold voltage shift with device cycling. Devices measured in ambient nitrogen show little degradation and devices fabricated on thinner dielectrics, operated at lower voltages with similarly high current densities in air, show reduced degradation. These results are consistent with degradation by thermal oxidation and suggest that reducing the operational power (by device scaling) and limiting channel exposure to ambient air improves device stability.
Priority of domain wall pinning during the fatigue period in bismuth titanate ferroelectric thin films
Authors: Li Wei , Chen Aiping , Lu Xiaomei , Zhu Jinsong , Wang Yening
Published: May 2005

The switching current densities of pure Bi4Ti3O12 thin films were measured during a fatigue process. The peak switching current density and switching time decrease with the increase of switching cycles, which indicates a domain wall pinning effect by defects inside thin films. Through the fitting of the switching current density using the modified Kolmogorov-Avrami theory, it is found that the percentage of two-dimensional (2D) domain growth decreases during the fatigue period, which reveals that 2D domain growth has an absolute priority to be pinned compared with one-dimensional domain growth. The mechanism of the increased activation field during the fatigue process is briefly discussed based on the domain wall pinning effect. These results are of great importance in the switching kinetics and fatigue mechanisms in ferroelectric films.
Spin-polarized transport of two-dimensional electron gas embedded in a diluted magnetic semiconductor
Authors: Yang W. , Chang Kai , Peeters F. M.
Published: May 2005

The spin-polarized transport property of a diluted magnetic semiconductor two-dimensional electron gas is investigated theoretically at low temperature. A large current polarization can be found in this system even at small magnetic fields and oscillates with increasing magnetic field while the carrier polarization is vanishingly small. The magnitude as well as the sign of the current polarization can be tuned by varying magnetic field, the electron density and the Mn concentration.
Theory of Galvano-Thermomagnetic Energy Conversion Devices. I. Generators
Authors: Harman T. C. , Honig J. M.
Published: May 2005

Using phenomenological equations in partially inverted form, the operation of galvano-thermomagnetic generators has been analyzed for six different modes of operation. The efficiency, figure of merit, and geometry optimization have been investigated. The two-dimensional temperature distribution prevailing in a device arm is also briefly analyzed. For the “longitudinal” case where heat flow and current are colinear in a transverse field, Hz, the mathematical relations conform to the standard theory, except that the transport coefficients depend on Hz. In the “transverse” case where heat flow, current, and magnetic field are mutually perpendicular, new expressions are obtained for the figure of merit and device efficiency. Furthermore, in the latter case the optimal operating conditions are those in which both device arms are made of the same material. The results are discussed in the light of some existing experimental data.
Stimulated and Fluorescent Optical Emission in Ruby from 4.2° to 300°K: Zero-Field Splitting and Mode Structure
Authors: D'Haenens I. J. , Asawa C. K.
Published: May 2005

The spectral character of the stimulated emission from ruby has been investigated; we found that the zero-field splitting (0.38 cm−1) of the A42 ground level and the cavity optical length and its reflectivity determine the spectral character of this emission. At 300°K the system is induced into oscillation in a number of cavitymodes separated by Δv̄ = (2lε12)−1, where l is the length of the resonator and ε12 is the index of refraction for the ordinary ray. At T≅80°K the Ē(2E) → ±32(A2) and the Ē(2E) → ±12(4A2) transitions were identified in the stimulated emission spectrum. Each can oscillate in an axial cavity mode (or modes) plus an off-axis mode at the center of the transition. At 4.2°K the system oscillates in off-axis modes, unless the length of the cavity l is such that it has axial resonances coincident with the transition frequencies. An analysis of the temperature dependence of the oscillation threshold for the separate transitions is presented and is compared with the observed behavior.
Fluorescence in CdS and Its Possible Use for an Optical Maser
Authors: Thomas D. G. , Hopfield J. J.
Published: May 2005

This paper discusses how the fluorescence from semiconductors might be useful in constructing an optical maser. Attention is given to the sharp line emission which occurs at low temperatures in CdS and which arises from excitons bound to impurities. Some recent experimental results are summarized which give information concerning the fluorescent efficiency and the depth to which crystals are excited using ultraviolet light for excitation. Possible maser geometries are discussed and the opportunities for using an evacuated ground state are pointed out. There appear to be several severe difficulties in the way of success. These are partly associated with the small depth of penetration of the exciting light, with the low fluorescent efficiencies available and with the inability to grow large perfect crystals with controlled impurity content. An improvement in the art of crystal growing is probably necessary before the effects described here can be expected to result in a useful optical maser.
Dendritic Crystallization of an Amorphous Alloy
Authors: Willens R. H.
Published: May 2005

A 15 at. % germanium-tellurium alloy was quenched from the melt at a rate that prevented the formation of a crystalline phase or phases. The transformation of this amorphous alloy to a crystalline state was studied by transmission electron microscopy. It was observed that the initial crystalline phase precipitates out of the amorphous matrix in the form of dendrities. The later stages of crystallization are characterized by growth of the dendrites.
Zero-Field Emission from Thermionic Hollow Cathodes
Authors: Brodie I. , Niewold A.
Published: May 2005

An examination of the theory of the thermionic hollow cathode shows that several distinct modes of zero-field emission are possible. The mode that exists in any given case depends on the relationship between a certain parameter d, which characterizes the nature of the electron cloud within the cavity, and the size of the effusion hole and the cavity dimensions. A quantitative expression is given for the conditions under which the hollow cathode can be used for a precise determination of the thermionic constants by the method of Jain and Krishnan. Under other conditions a quasi-hollow beam is obtained and a theoretical prediction of the total zero-field current from the hole was found to be in order of magnitude agreement with experimental observations. An explanation of the similarity of emissions between ‘L’ cathodes of different porosity is also given.
Dislocation Motion and Asymmetric Resonance Peaks
Authors: Baker G. S.
Published: May 2005

Asymmetries and jumps in amplitude of the resonance curves for lead are present in a region of strain amplitudes where the damping and modulus are rapidly varying with strain amplitude. This is due to the vibrations causing a change in the modulus of the specimen. This change takes place in a fraction of a second at room temperature and anneals out in a few seconds when the amplitude of vibration is reduced.
Anisotropy in the Conductivity of Hot Holes in Germanium
Authors: Gibbs W. E. K.
Published: May 2005

The anisotropy in the conductivity of p-type germanium at fields of up to 3 kV/cm has been measured at lattice temperatures of 77°K and 21°K for specimens with impurity concentrations from 3.0×1014 cm−3to 3.2×1015 cm−3. The electric field vector was found to deviate from the current vector towards the 〈111〉direction for specimens in the (110) plane and this behavior is opposite to that previously published by Sasaki et al. The anisotropy decreased with increased impurity concentration and the reduction of temperature from 77° to 21°K shifted the anisotropy-electric field curve to lower fields.
Dislocation Pinning in Copper at 4.2°K and in Stage I
Authors: Sosin A.
Published: May 2005

Pure copper samples were electron bombarded at 4.2°K. The elastic modulus was observed to rise in a typically saturating manner during irradiation. Following irradiation, the modulus was observed to increase further in the temperature range from 35° to 50°K. The modulus increase is consistent with the Cottrell-Bilby model of stress-induced diffusion to dislocations.
Solution of the Initial-Value Transport Problem for Monoenergetic Neutrons in Slab Geometry
Authors: Bowden Robert L. , Williams Clayton D.
Published: May 2005

The initial-value transport problem of monoenergetic neutrons migrating in a thin slab is solved by applying the normal-mode expansion method of Case to the results of Lehner and Wing. Fredholm integral equations are derived for the expansion coefficients. In addition, exact expressions for the eigenvalues of the problem are derived and the results of calculations are presented. The solution is shown to have properties expected from elementary diffusion theory.
Two Classes of New Conservation Laws for the Electromagnetic Field and for Other Massless Fields
Authors: Morgan Thomas A.
Published: May 2005

The existence of a class of conserved tensors Tμνα1...αnβ1...βm and the existence of a class of conserved tensor densities Vμνα1...αnβ1...βm is exhibited for the electromagnetic field. They are differential generalizations of the energy momentum tensor in the sense that they are bilinear in E and B, contain n + m derivatives and are symmetric, trace free and divergenceless on their μν pair of indices. Corresponding conserved quantities for the two-component neutrino field, linear gravitational field and indeed for all massless free fields are also exhibited.
The Invariance of the Vacuum is the Invariance of the World
Authors: Coleman Sidney
Published: May 2005

The following theorem is demonstrated: If the vacuum is invariant under the group generated by the space integral of the time component of a local vector current, then the Hamiltonian is invariant also. A similar theorem holds for the group generated by the space integral of a space component of a local axial-vector current.
Adiabatic Switching in the Schrödinger Theory of Scattering
Authors: Dollard John Day
Published: May 2005

The time-dependent Schrödinger theory of scattering is studied rigorously with the potential Vreplaced by e−ε|l|V. Sufficient conditions are given that the Møller wave-matrices Ω± be obtainable from this theory as ε → 0. The conjecture that this theory can be used to define a reasonable S-matrix when the Ω± do not exist is shown to be false for the Coulomb potential. It is remarked that the Goldberger-Gell-Mann switching procedure also breaks down in this case.
Generalized Spherical Functions for the Noncompact Rotation Groups
Authors: Fischer J. , Niederle J. , Raczka R.
Published: May 2005

Special representations of arbitrary noncompact rotation groups labeled by one independent Casimir operator are considered. The explicit construction of the corresponding generalized spherical functions is given and the properties of these representations are discussed in detail.
Direct-Product Representations of the Canonical Commutation Relations
Authors: Klauder J. R. , McKenna J. , Woods E. J.
Published: May 2005

We consider direct-product representations of the canonical commutation relations. An irreducible representation is defined on each of the incomplete direct-product spaces (IDPS) of von Neumann. We prove that two such representations are unitarily equivalent if and only if the corresponding IDPS are weakly equivalent, for which simple analytic tests exist. The matrix elements of these representations, coupled with a Friedrichs-Shapiro type of integral, fulfill group orthogonality relations. This classification into unitary equivalence classes also applies to direct-product representations of the canonical anticommutation relations.
Determination of Optical Field Correlations from Photon Counts
Authors: Mukunda N. , Jordan T. F.
Published: May 2005

It is shown that the off-diagonal matrix elements of an operator on an N-boson space are determined by diagonal matrix elements in different symmetrized product bases. The motivating application is that optical field correlations are determined by moments of the numbers of photons in different modes.
Voltage Clamp for Biological Investigations
Authors: Menninger J. R. , Snell F. M. , Spangler R. A.
Published: May 2005

A unique voltage clamp circuit for certain biological investigations, which features the provision of maintaining the clamped region at ground potential with the residual error balanced about ground, is discussed. Theoretical consideration of the circuit function indicates that the possibility of error arising from stray current pathways and loading of the electrodes is reduced by holding the clamped region close to ground. An additional secondary feedback loop, in conjunction with this circuit, reduces switching transients and other high frequency noise and allows dynamic balance of the clamped region about ground potential despite assymmetries in the experimental circuit. This circuit has been employed, using commercially available operational amplifier units, to clamp the isolated frog skin for measurement of sodium transport flux. In this application, the assembly clamped the skin to well within 1 mv, with excellent dc stability and a theoretical error of 0.1% in response to 1-msec transients.
Double Focusing Zero Dispersion Magnetic Spectrometer
Authors: Alvarez R. A. , Brown K. L. , Panofsky W. K. H. , Rockhold C. T.
Published: May 2005

A double focusing zero dispersion magnetic spectrometer has been constructed having the following properties:The spectrometer consists of two magnets, each n≅0.25, 110° deflection, 30-in. radius of curvature, bending the particles in the same sense. For the central momentum p0, the useful solid angle Ω0 is ∼0.0055 sr with a possibility of improvement to 0.01 sr. The momentum acceptance Δp is in excess of ±4% with a useful solid angle Ω of ∼0.0015 sr at the 4% points. For a point source and for the solid angles and momentum acceptances given, over 90% of the trajectories terminate within a circle of 2-in. diameter at the focal plane.
Operation of Hydrogen Bubble Chambers in High-Energy Photon Beams
Authors: Gates Duane C. , Kenney Robert W. , McPherson Donald A. , Swanson William P.
Published: May 2005

Operation of the Alvarez 4-in. hydrogen bubble chamber in a high-energy photon beam is described, the techniques employed in several modes of operation are discussed, and the corresponding bubble chamber conditions are tabulated. Reduction of electron background was accomplished by beam hardening and by using a Mylar beam-entrance window on the chamber.
Absorption of Gamma Radiation in NaI Well Crystals
Authors: Wächter M. H. , Ellett W. H. , Brownell G. L.
Published: May 2005

The results of Monte Carlo calculations on the detection and total absorption peak efficiencies of spherical NaI crystals are presented. A method of applying these data to cylindrical well crystals of arbitrary size and well geometry is described and the results are compared with experimental data. The Monte Carlo computations cover the gamma-ray energy range from 200 kev to 2 Mev and crystal radii from 1.5 to 12.0 cm. Histograms are presented of the number of Compton scattering events which a 0.662-Mev gamma ray undergoes in crystals of different sizes.
Promoting Retail Innovation: Knowledge Flows during the Emergence of Self-Service and Supermarket Retailing in Britain
Authors: Alexander Andrew , Shaw Gareth , Curth Louise
Published: May 2005

The notion of innovation underpins many studies of change within the literatures of retail management and the new retail geography. However, conceptualisation of the innovation process within retailing has remained surprisingly partial, with insufficient attention being given to the processes of knowledge management and learning within the firm. The authors illustrate the importance of such themes by reference to the key organisational and technological changes surrounding the development of self-service and supermarket retailing in Britain during the postwar years 1945–65. A conceptual framework derived from a reading of the business-management and economic geography literatures is employed to analyse the innovation transfer and related knowledge-management processes that influenced retail change during this critical period.
Placing the Environment in Migration: Environment, Economy, and Power in Ghana's Central Region
Authors: Carr Edward R
Published: May 2005

This paper examines the role of environmental change as a driver of migration, a central concern of areas of inquiry ranging from the Human Dimensions of Global Change research to population geography and development studies. Although much of the literature on the role of the environment in migration reflects a general awareness that environmental factors are but one of a suite of influences shaping migration decisionmaking, a framework within which to place social, economic, and environmental issues with regard to particular migration decisions is absent from this literature. Drawing upon recent contributions to the literature on migration, and political ecological concerns for access to and control over resources, in this paper I present a framework for placing such issues founded on a Foucauldian conceptualization of power. This framework treats environment, economy, and society as both products of and productive of social differentiation, instrumental modes of power, and resistance. These forms shape actors' understanding and negotiation of their social, economic, and environmental contexts, and therefore their migration decisionmaking. I illustrate the application of this framework through the example of three villages in Ghana's Central Region, where rural environmental and economic changes appear to have driven a complex pattern of out-migration over the past thirty-five years. This migration shows the ways in which environmental change becomes inseparable from local perceptions of economy and local politics through local manifestations of power.
Globalisation, Academic Capitalism, and the Uneven Geographies of International Journal Publishing Spaces
Authors: Paasi Anssi
Published: May 2005

Geographers have been arguing recently that the idea of what is ‘international’ in this field has been occupied by the hegemonic discourses of Anglo-American geography and journals. This paper takes this lively debate as an indicator of the global challenges facing higher education and research and provides an analysis of the changing conditions of knowledge production, characterised by internationalisation and competition. Knowledge production is governed to an increasing degree through practices based on market-like operations. The author argues that this may lead to the homogenisation of social science publication practices, which are known to be heterogeneous and context dependent. One indicator of this homogenisation is the demand for publishing in international journals that is arising in social sciences and humanities round the world. Both ‘international’ and ‘quality’ are increasingly being connected with the journals noted in the Institute of Scientific Information's (ISI) databases. Starting with an analysis of the changing conditions of knowledge production in general and in human geography in particular, the author scrutinises the spatial patterns of the international journal publishing spaces constituted by the ISI. The results show specific geographies: not only the manner in which the Anglo-American journals dominate the publishing space in science but also how the publishing spaces of the natural sciences, social sciences, and humanities are very different. The publication space of social science journals is particularly limited to the English-speaking countries, and this is especially the case with human geography.
The reintroduction, and subsequent impact, of rabbit haemorrhagic disease virus in a population of wild rabbits in south-western Australia
Authors: Bruce John S. , Twigg Laurie E.
Published: May 2005

The natural arrival of rabbit haemorrhagic disease virus (RHDV) in south-western Australia in September 1996 resulted in a reduction in rabbit numbers of ~65% (~90% morbidity, with ~72% mortality of infected rabbits). As no signs of the disease (clinical or serological) were seen over the next two years, and as rabbit numbers over the last 12-month monitoring period at the site were similar to those observed before the natural 1996 RHDV epizootic (i.e. pre-RHD), RHDV was deliberately reintroduced into this rabbit population in April 1999 (autumn). Seven RHDV-inoculated rabbits were released prior to the main breeding season when <3% of sampled rabbits (n = 118) were seropositive for RHDV antibodies. Following the deliberate release, the overall decline in rabbit numbers (68%) was comparable to that seen during the natural 1996 epizootic. However, on the basis of the observed changes in rabbit numbers, and in their serology, the impact of the deliberate RHDV release appeared to be more variable across the six trapping areas than was seen during the natural 1996 spring epizootic. The reductions in rabbit numbers on these areas 6–8 weeks after RHDV-release ranged from 55% to 90%. The serology of the surviving rabbits on the trapping areas was also variable over this period, with the proportion of seropositive rabbits ranging from 5% to 90%. Overall, only 15% of the surviving rabbit population showed evidence of recent challenge by RHDV, giving a morbidity rate of 73% 8 weeks after the release. However, over 90% of infected rabbits died. This provides further evidence that some rabbits remained un-challenged by RHDV for up to 8 weeks after its release. The variable impact of the April 1999 release may have been partially caused by the observed differences in abundance of insect vectors, and/or an apparent increase in the incidence of non-virulent RHDV in the months preceding the release.
5-Methyltetrahydrofolate and tetrahydrobiopterin can modulate electrotonically mediated endothelium-dependent vascular relaxation
Authors: Griffith Tudor M. , Chaytor Andrew T. , Bakker Linda M. , Edwards David H.
Published: May 2005

We have investigated the ability of 5-methyltetrahydrofolate (5-MTHF) and tetrahydrobiopterin (BH
4
) to modulate nitric oxide (NO)-independent vascular relaxations that are mediated by the sequential spread of endothelial hyperpolarization through the wall of the rabbit iliac artery by means of myoendothelial and homocellular smooth muscle gap junctions. Relaxations and subintimal smooth muscle hyperpolarizations evoked by cyclopiazonic acid were depressed by the gap junction inhibitor 2-aminoethoxydiphenyl borate, whose effects were prevented by 5-MTHF and BH
4
, but not by their oxidized forms folic acid and 7,8-dihydrobiopterin. Analogously, 5-MTHF and BH
4
, but not folic acid or 7,8-dihydrobiopterin, attenuated the depression of subintimal hyperpolarization by a connexin-mimetic peptide targeted against Cx37 and Cx40 (
37,40
Gap 26) and the depression of subadventitial hyperpolarization by a peptide targeted against Cx43 (
43
Gap 26), thus reflecting the known differential expression of Cx37 and Cx40 in the endothelium and Cx43 in the media of the rabbit iliac artery. The inhibitory effects of 2-aminoethoxydiphenyl borate and
37,40
Gap 26 against subintimal hyperpolarization were prevented by catalase, which destroys H
2
O
2
. 5-MTHF and BH
4
thus appear capable of modulating electrotonic signaling by means of myoendothelial and smooth muscle gap junctions by reducing oxidant stress, potentially conferring an ability to reverse the endothelial dysfunction found in disease states through mechanisms that are independent of NO.
Visualizing reaction pathways in photoactive yellow protein from nanoseconds to seconds
Authors: Ihee Hyotcherl , Rajagopal Sudarshan , Šrajer Vukica , Pahl Reinhard , Anderson Spencer , Schmidt Marius , Schotte Friedrich , Anfinrud Philip A. , Wulff Michael , Moffat Keith
Published: May 2005

Determining 3D intermediate structures during the biological action of proteins in real time under ambient conditions is essential for understanding how proteins function. Here we use time-resolved Laue crystallography to extract short-lived intermediate structures and thereby unveil signal transduction in the blue light photoreceptor photoactive yellow protein (PYP) from
Halorhodospira halophila
. By analyzing a comprehensive set of Laue data during the PYP photocycle (forty-seven time points from one nanosecond to one second), we track all atoms in PYP during its photocycle and directly observe how absorption of a blue light photon by its
p
-coumaric acid chromophore triggers a reversible photocycle. We identify a complex chemical mechanism characterized by five distinct structural intermediates. Structural changes at the chromophore in the early, red-shifted intermediates are transduced to the exterior of the protein in the late, blue-shifted intermediates through an initial “volume-conserving” isomerization of the chromophore and the progressive disruption of hydrogen bonds between the chromophore and its surrounding binding pocket. These results yield a comprehensive view of the PYP photocycle when seen in the light of previous biophysical studies on the system.
Ab initio
molecular dynamics: Concepts, recent developments, and future trends
Authors: Iftimie Radu , Minary Peter , Tuckerman Mark E.
Published: May 2005

The methodology of
ab initio
molecular dynamics, wherein finite-temperature dynamical trajectories are generated by using forces computed “on the fly” from electronic structure calculations, has had a profound influence in modern theoretical research.
Ab initio
molecular dynamics allows chemical processes in condensed phases to be studied in an accurate and unbiased manner, leading to new paradigms in the elucidation of microscopic mechanisms, rationalization of experimental data, and testable predictions of new phenomena. The purpose of this work is to give a brief introduction to the technique and to review several important recent developments in the field. Several illustrative examples showing the power of the technique have been chosen. Perspectives on future directions in the field also will be given.
Deep history impacts present-day ecology and biodiversity
Authors: Vitt Laurie J. , Pianka Eric R.
Published: May 2005

Lizards and snakes putatively arose between the early Jurassic and late Triassic; they diversified worldwide and now occupy many different ecological niches, making them ideal for testing theories on the origin of ecological traits. We propose and test the “deep history hypothesis,” which claims that differences in ecological traits among species arose early in evolutionary history of major clades, and that present-day assemblages are structured largely because of ancient, preexisting differences. We combine phylogenetic data with ecological data collected over nearly 40 years to reconstruct the evolution of dietary shifts in squamate reptiles. Data on diets of 184 lizard species in 12 families from 4 continents reveal significant dietary shifts at 6 major divergence points, reducing variation by 79.8%. The most striking dietary divergence (27.6%) occurred in the late Triassic, when Iguania and Scleroglossa split. These two clades occupy different regions of dietary niche space. Acquisition of chemical prey discrimination, jaw prehension, and wide foraging provided scleroglossans access to sedentary and hidden prey that are unavailable to iguanians. This cladogenic event may have profoundly influenced subsequent evolutionary history and diversification. We suggest the hypothesis that ancient events in squamate cladogenesis, rather than present-day competition, caused dietary shifts in major clades such that some lizard clades gained access to new resources, which in turn led to much of the biodiversity observed today.
Lower bounds for moments of
L
-functions
Authors: Rudnick Z. , Soundararajan K.
Published: May 2005

The moments of central values of families of
L
-functions have recently attracted much attention and, with the work of Keating and Snaith [(2000)
Commun. Math. Phys.
214, 57–89 and 91–110], there are now precise conjectures for their limiting values. We develop a simple method to establish lower bounds of the conjectured order of magnitude for several such families of
L
-functions. As an example we work out the case of the family of all Dirichlet
L
-functions to a prime modulus.
Chayanov revisited: A model for the economics of complex kin units
Authors: Hammel E. A.
Published: May 2005

Chayanov's model of the peasant economy is based on autarkic nuclear family households. Expansion to the more complex households and kin groups common in peasant societies shows that the sharp changes Chayanov observed in the consumer/producer ratio over the domestic cycle are smoothed by the intergenerational structure of complex households and extended kin groups. This amelioration may be retarded by competition between constituent units. Understanding the dynamics of the developmental cycle and micropolitics of domestic groups is a useful correction to Chayanov's widely used formulation, especially in developing countries where complex kin structures are common.
Inhibition of tumor growth by plant-derived mAb
Authors: Ko Kisung , Steplewski Zenon , Glogowska Magdalena , Koprowski Hilary
Published: May 2005

The tumor-associated antigen EpCAM (GA733-2) is a highly expressed target on adenocarcinoma cells, as defined by murine mAb CO17-1A. We recently developed a transgenic plant system for the safe and inexpensive production of large quantities of mAb CO17-1A as a future source of clinical-grade protein. Although the glycosylation pattern of plant-derived mAb (mAbP) CO17-1A differs considerably from that of the mammalian-derived mAb (mAbM), we show here that the biological activity of both mAbs is quite similar. mAbPheavy and light chains assembled to bind the recombinant antigen GA733-2E and specifically bound to human SW948 colorectal carcinoma cells expressing the antigen GA733-2 to the same extent as mAbM. mAbPwas as effective as mAbMCO17-1A in inhibiting tumor growth of xenotransplanted SW948 cells in nude mice. These results suggest the promise of transgenic plants as a useful alternative way to produce full-size mAb for cancer immunotherapy.
Effects of inulin-type fructans on lipid metabolism in man and in animal models
Authors: Beylot Michel
Published: May 2005

Studies in rodents show that inulin and oligofructose can reduce the plasma levels of cholesterol and triacylglycerols (TG). In addition, they can oppose TG accumulation in liver and have favourable effects on hepatic steatosis. The hypotriglyceridaemic effect is due to a reduction in hepatic re-esterification of fatty acids, but mainly in the expression and activity of liver lipogenesis, resulting in lower hepatic secretion rate of TG. This repression of lipogenesis is not observed in adipose tissue. The effect on liver lipogenesis can be explained by reduced insulin/glucose levels or by a selective exposure of the liver to increased amounts of propionic acid produced in the large intestine during fermentation of non-digestible carbohydrates. The decrease in plasma cholesterol could also be due to inhibition of cholesterol synthesis by propionic acid or to modifications in the bile acid metabolism. Studies in man yield more conflicting results with a decrease or no effects on plasma lipid levels, and, when a decrease is observed, more marked effects on TG than on cholesterol and more consistent action of inulin than of oligofructose. Besides the difference in the dose of inulin or oligofructose used, differences in metabolic status could play a role in this discrepancy between man and animals since reduction in plasma TG is observed in man mainly in a situation of increased liver lipogenesis (high-carbohydrate diet, obesity, hypertriglyceridaemia). The effects on plasma cholesterol appear also more marked in hyperlipidaemic subjects than in healthy controls, suggesting that inulin and oligofructose have beneficial effects in these types of subjects.
Inulin-type fructans and reduction in colon cancer risk: review of experimental and human data
Authors: Pool-Zobel Beatrice L.
Published: May 2005

Inulin-type fructans (β(2,1)fructans) extracted from chicory roots (Cichorium intybus) are prebiotic food ingredients, which in the gut lumen are fermented to lactic acid and SCFA. Research in experimental animal models revealed that inulin-type fructans have anticarcinogenic properties. A number of studies report the effects of inulin-type fructans on chemically induced pre-neoplastic lesions (ACF) or tumours in the colon of rats and mice. In twelve studies, there were twenty-nine individual treatment groups of which twenty-four measured aberrant crypt foci (ACF) and five measured tumours. There was a significant reduction of ACF in twenty-one of the twenty-four treatment groups and of tumour incidence in five of the five treatment groups. Higher beneficial effects were achieved by synbiotics (mixtures of probiotics and prebiotics), long-chain inulin-type fructans compared to short-chain derivatives, and feeding high-fat Western style diets. Inulin-type fructans reduced tumour incidence in APCMin mice in two of four studies and reduced growth and metastasising properties of implanted tumour cells in mice (four studies). The effects have been reported to be associated with gut flora-mediated fermentation and production of butyrate. In human cells, inulin-derived fermentation products inhibited cell growth, modulated differentiation and reduced metastasis activities. In conclusion, evidence has been accumulated that shows that inulin-type fructans and corresponding fermentation products reduced the risks for colon cancer. The involved mechanisms included the reduction of exposure to risk factors and suppression of tumour cell survival. Thus, this specific type of dietary fibre exerted both blocking agent and suppressing agent types of chemopreventive activities.
The stability of soft drinks intake from adolescence to adult age and the association between long-term consumption of soft drinks and lifestyle factors and body weight
Authors: Kvaavik Elisabeth , Andersen Lene Frost , Klepp Knut-Inge
Published: May 2005

Objectives

To investigate the tracking of sugar-sweetened, carbonated soft drinks intake from age 15 to 33 years and the association between this intake and lifestyle factors and body weight.

Design

A longitudinal study with 18–20 years of follow-up. Data about diet, physical activity, smoking and dieting were collected in 1981/1979, 1991 and 1999. Body weight and height were measured in 1981/1979 and self-reported in 1999.

Setting

Oslo, Norway.

Subjects

Four hundred and twenty-two men and women.

Results

Tracking of soft drinks intake from adolescence into early adulthood (age 25 years) and from early adulthood into later adulthood (33 years) was moderate to high, while tracking from adolescence into later adulthood was low. Comparing those reporting a high intake of soft drinks in both 1991 and 1999 with those reporting a low intake at both times, male long-term high consumers were more likely to smoke (48 vs. 21%,P= 0.002) and reported higher intakes of energy (12.2 vs. 10.2 MJ day−1,P= 0.005) and sugar (142 vs. 50 g day−1,P< 0.001) in 1999 than did long-term low consumers. Women high consumers were less likely to be physically active (14 vs. 42%,P= 0.03) and had higher sugar intake (87 vs. 41 g day−1,P< 0.001) in 1999 than did women low consumers. There were no differences in body mass index, overweight or obesity in 1999 between long-term high and low consumers.

Conclusion

In this study, stability of soft drinks intake from age 15 to 25 years and from age 25 to 33 years was moderate to high, while from age 15 to 33 years it was low. Soft drinks intake from age 25 to 33 years was associated with smoking and physical inactivity, but not with body weight.
Who eats four or more servings of fruit and vegetables per day? Multivariate classification tree analysis of data from the 1998 Survey of Lifestyle, Attitudes and Nutrition in the Republic of Ireland
Authors: Friel Sharon , Newell John , Kelleher Cecily
Published: May 2005

Objective

To identify, using the novel application of multivariate classification trees, the socio-economic, sociodemographic and health-related lifestyle behaviour profile of adults who comply with the recommended 4 or more servings per day of fruit and vegetables.

Design

Cross-sectional 1998 Survey of Lifestyle, Attitudes and Nutrition.

Setting

Community-dwelling adults aged 18 years and over on the Republic of Ireland electoral register.

Subjects

Six thousand five hundred and thirty-nine (response rate 62%) adults responded to a self-administered postal questionnaire, including a semi-quantitative food-frequency questionnaire.

Results

The most important determining factor of compliance with the fruit and vegetable dietary recommendations was gender. A complex constellation of sociodemographic and socio-economic factors emerged for males whereas the important predictors of 4 or more servings of fruit and vegetable consumption among females were strongly socio-economic in nature. A separate algorithm was run to investigate the importance of health-related lifestyle and other dietary factors on compliance with the fruit and vegetable recommendations. Following an initial split on compliance with dairy recommendations, a combination of non-dietary behaviours showed a consistent pattern of healthier options more likely to lead to compliance with fruit and vegetable recommendations. There did, however, appear to be a compensatory element between the variables, particularly around smoking, suggesting the non-existence of an exclusive lifestyle for health risk.

Conclusions

Material and structural influences matter very much for females in respect to compliance with fruit and vegetable recommendations. For males, while these factors are important they appear to be mediated through other more socially contextual-type factors. Recognition of the role that each of these factors plays in influencing dietary habits of men and women has implications for the manner in which dietary strategies and policies are developed and implemented.
Mnt–Max to Myc–Max complex switching regulates cell cycle entry
Authors: Walker William , Zhou Zi-Qiang , Ota Sara , Wynshaw-Boris Anthony , Hurlin Peter J.
Published: May 2005

The c-Myc oncoprotein is strongly induced during the G0 to S-phase transition and is an important regulator of cell cycle entry. In contrast to c-Myc, the putative Myc antagonist Mnt is maintained at a constant level during cell cycle entry. Mnt and Myc require interaction with Max for specific DNA binding at E-box sites, but have opposing transcriptional activities. Here, we show that c-Myc induction during cell cycle entry leads to a transient decrease in Mnt–Max complexes and a transient switch in the ratio of Mnt–Max to c-Myc–Max on shared target genes. Mnt overexpression suppressed cell cycle entry and cell proliferation, suggesting that the ratio of Mnt–Max to c-Myc–Max is critical for cell cycle entry. Furthermore, simultaneous Cre-Lox mediated deletion of Mnt and c-Myc in mouse embryo fibroblasts rescued the cell cycle entry and proliferative block caused by c-Myc ablation alone. These results demonstrate that Mnt-Myc antagonism plays a fundamental role in regulating cell cycle entry and proliferation.
Impairment of starvation-induced and constitutive autophagy in Atg7-deficient mice
Authors: Komatsu Masaaki , Waguri Satoshi , Ueno Takashi , Iwata Junichi , Murata Shigeo , Tanida Isei , Ezaki Junji , Mizushima Noboru , Ohsumi Yoshinori , Uchiyama Yasuo , Kominami Eiki , Tanaka Keiji , Chiba Tomoki
Published: May 2005

Autophagy is a membrane-trafficking mechanism that delivers cytoplasmic constituents into the lysosome/vacuole for bulk protein degradation. This mechanism is involved in the preservation of nutrients under starvation condition as well as the normal turnover of cytoplasmic component. Aberrant autophagy has been reported in several neurodegenerative disorders, hepatitis, and myopathies. Here, we generated conditional knockout mice of Atg7, an essential gene for autophagy in yeast. Atg7 was essential for ATG conjugation systems and autophagosome formation, amino acid supply in neonates, and starvation-induced bulk degradation of proteins and organelles in mice. Furthermore, Atg7 deficiency led to multiple cellular abnormalities, such as appearance of concentric membranous structure and deformed mitochondria, and accumulation of ubiquitin-positive aggregates. Our results indicate the important role of autophagy in starvation response and the quality control of proteins and organelles in quiescent cells.
Integrins control motile strategy through a Rho–cofilin pathway
Authors: Danen Erik H.J. , van Rheenen Jacco , Franken Willeke , Huveneers Stephan , Sonneveld Petra , Jalink Kees , Sonnenberg Arnoud
Published: May 2005

During wound healing, angiogenesis, and tumor invasion, cells often change their expression profiles of fibronectin-binding integrins. Here, we show that β1 integrins promote random migration, whereas β3 integrins promote persistent migration in the same epithelial cell background. Adhesion to fibronectin by αvβ3 supports extensive actin cytoskeletal reorganization through the actin-severing protein cofilin, resulting in a single broad lamellipod with static cell–matrix adhesions at the leading edge. Adhesion by α5β1 instead leads to the phosphorylation/inactivation of cofilin, and these cells fail to polarize their cytoskeleton but extend thin protrusions containing highly dynamic cell–matrix adhesions in multiple directions. The activity of the small GTPase RhoA is particularly high in cells adhering by α5β1, and inhibition of Rho signaling causes a switch from a β1- to a β3-associated mode of migration, whereas increased Rho activity has the opposite effect. Thus, alterations in integrin expression profiles allow cells to modulate several critical aspects of the motile machinery through Rho GTPases.
STIM1, an essential and conserved component of store-operated Ca2+ channel function
Authors: Roos Jack , DiGregorio Paul J. , Yeromin Andriy V. , Ohlsen Kari , Lioudyno Maria , Zhang Shenyuan , Safrina Olga , Kozak J. Ashot , Wagner Steven L. , Cahalan Michael D. , Veliçelebi Gönül , Stauderman Kenneth A.
Published: May 2005

Store-operated Ca2+ (SOC) channels regulate many cellular processes, but the underlying molecular components are not well defined. Using an RNA interference (RNAi)-based screen to identify genes that alter thapsigargin (TG)-dependent Ca2+ entry, we discovered a required and conserved role of Stim in SOC influx. RNAi-mediated knockdown of Stim in Drosophila S2 cells significantly reduced TG-dependent Ca2+ entry. Patch-clamp recording revealed nearly complete suppression of the Drosophila Ca2+ release-activated Ca2+ (CRAC) current that has biophysical characteristics similar to CRAC current in human T cells. Similarly, knockdown of the human homologue STIM1 significantly reduced CRAC channel activity in Jurkat T cells. RNAi-mediated knockdown of STIM1 inhibited TG- or agonist-dependent Ca2+ entry in HEK293 or SH-SY5Y cells. Conversely, overexpression of STIM1 in HEK293 cells modestly enhanced TG-induced Ca2+ entry. We propose that STIM1, a ubiquitously expressed protein that is conserved from Drosophila to mammalian cells, plays an essential role in SOC influx and may be a common component of SOC and CRAC channels.
A falsification of the thermal specialization paradigm: compensation for elevated temperatures in Antarctic fishes
Authors: Seebacher Frank , Davison William , Lowe Cara J , Franklin Craig E
Published: May 2005

Specialization to a particular environment is one of the main factors used to explain species distributions. Antarctic fishes are often cited as a classic example to illustrate the specialization process and are regarded as the archetypal stenotherms. Here we show that the Antarctic fishPagothenia borchgrevinkihas retained the capacity to compensate for chronic temperature change. By displaying astounding plasticity in cardiovascular response and metabolic control, the fishes maintained locomotory performance at elevated temperatures. Our falsification of the specialization paradigm indicates that the effect of climate change on species distribution and extinction may be overestimated by current models of global warming.
Tortuosity and objective relative accelerations in the theory of porous materials
Authors: Wilmanski Krzysztof
Published: May 2005

The aim of this work is twofold. We show the construction of an objective relative acceleration for a two-component mixture and prove that its incorporation in the momentum source requires additional terms in partial stresses and in the energy. This may be interpreted as an influence of tortuosity, in the theory of saturated poroelastic materials, and a connection of tortuosity with fluctuations of the kinetic energy on a mesoscopic level of observation. The linearization of such a model yields Biot's equations, used in poroacoustics.

We demonstrate as well, that results for the propagation of acoustic waves in saturated poroelastic media, are qualitatively similar for Biot's model, and for the simple mixture model, in which both the tortuosity and the Biot's coupling between partial stresses are neglected. It is also indicated that the coupling constant of Biot's model obtained by means of the Gassmann relation may be too large, as it leads to very small differences in the speed of propagation of the P1-wave for small and large frequencies, which contradicts the data for soils.
African endemics span the tree of songbirds (Passeri): molecular systematics of several evolutionary ‘enigmas’
Authors: Beresford P , Barker F.K , Ryan P.G , Crowe T.M
Published: May 2005

The deep divergence between the African endemic passerines Picathartidae (rockfowlPicathartesand rockjumpersChaetops, four species) and the Passerida (ca. 3500 species) suggests an older history of oscines on the African continent than has previously been assumed. In order to determine whether any additional, unexpectedly deep lineages occur in African endemic songbirds, 29 species—including 10 enigmatic focal taxa endemic to southern Africa—were added to a large nuclear sequence dataset gathered from oscine songbirds (Passeri). Phylogenetic analyses of these data resolve many long-standing questions about the affinities of these birds, not all of which were predicted by traditional approaches. The application of a molecular clock indicates that most basal divergences in Passerida occurred in the middle to late Eocene, with divergences between African and Australasian core corvoids occurring somewhat later in the early Miocene. Consistent with inferences for mammals, divergences between Malagasy endemic passerines and their mainland relatives suggests an asynchronous colonization history. This emerging phylogenetic picture reveals that relationships within Old World families are highly informative regarding the early dispersal and radiation of songbirds out of Gondwana. Future analyses will depend on improving resolution of higher-level phylogenetic relationships among these groups, and increasing the density of taxon sampling within them.