bluuebunny/crossref_metadata_2025 huggingface dataset:
Histone H1 kinase activity in bovine oocytes following calcium stimulation
Authors: Collas Philippe , Sullivan Eddie J. , Barnes Frank L.
Published: February 2005

The influence of number of Ca2+ stimulations on the profile of histone H1 kinase activity in bovine oocytes was investigated. A Ca2+ stimulation consisted of transferring oocytes directly from culture medium to mannitol containing 100 μM Ca2+ and pulsing oocytes with a 0.2 kVcm−1, 20 μsec discharge. One, three, or six Ca2+ stimulations were given, each 22 min apart. Oocytes were frozen from 0 to 8 hr after the first stimulation at indicated time points and assayed for histone H1 kinase activity. H1 kinase activity was quantified using a densitometer and expressed as a percent of activity in nonpulsed metaphase II oocytes. Stimulating oocytes in the absence of Ca2+ in the pulsing medium did not inactivate H1 kinase. In the presence of Ca2+, however, H1 kinase was rapidly inactivated after stimulation. A single stimulation decreased H1 kinase activity to 44% ± 11% of its initial level in 1 hr. However, H1 kinase was dramatically reactivated at 2 hr after the stimulation and reached 122% ± 22% of the initial activity at 6 hr. With three stimulations, basal H1 kinase activity was 21% ± 3% and was obtained in 30 min. H1 kinase reactivation started at 4 hr after the first stimulation and level of activity reached 38% ± 15% at 8 hr. Six stimulations also led to rapid H1 kinase inactivation and to a basal activity of 14% ± 0.4%. With six stimulations, however, basal H1 kinase activity was maintained over at least 8 hr, and no reactivation occurred during this period. Basal H1 kinase activity obtained after six stimulations was similar to that of fertilized oocytes. Immunoprecipitation of p34cdc2 with an anti‐cdc2 antibody strongly suggested an identity between histone H1 kinase and maturation‐promoting factor. The data indicate that histone H1 kinase activity in oocytes could be regulated by the number of Ca2+ stimulations. A single Ca2+ stimulation led to H1 kinase inactivation, followed by reactivation of the kinase. Increasing the number of Ca2+ stimulations delayed the onset and reduced the extent of H1 kinase reactivation in the first parthenogenetic cell cycle. © 1993 Wiley‐Liss, Inc.
Differential expression of activation‐induced cytidine deaminase (AID) in nodular lymphocyte‐predominant and classical Hodgkin lymphoma
Authors: Greiner Axel , Tobollik Stephanie , Buettner Maike , Jungnickel Berit , Herrmann Kathrin , Kremmer Elisabeth , Niedobitek Gerald
Published: February 2005

Activation‐induced cytidine deaminase (AID) is indispensable for class switch recombination and somatic hypermutation of immunoglobulin genes. Expression of AID has been detected in germinal centre centroblasts and in lymphomas derived from germinal centre cells. However, in situ studies of AID expression have until now been hampered by a lack of antibodies suitable for immunohistochemistry. To overcome this problem, an AID‐specific monoclonal antibody suitable for immunohistochemical staining of formalin‐fixed, paraffin wax‐embedded tissue sections has been generated. This antibody was shown to detect AID expression in normal germinal centre B‐cells as well as in non‐Hodgkin lymphomas with a putative germinal centre origin. Using this antibody, a virtually exclusive cytoplasmic localization of AID in normal and neoplastic B‐cells is shown. Employing a combination of immunohistochemistry and AID‐specific in situ hybridization, it is demonstrated that AID is consistently expressed in the neoplastic cells of nodular lymphocyte‐predominant Hodgkin lymphoma (HLnlp) but only infrequently in classical HL (cHL). This is in keeping with the notion that tumour cells of HLnlp represent transformed germinal centre B‐cells showing evidence of somatic hypermutation. AID represents an additional marker useful in the differential diagnosis of HLnlp and cHL. Copyright © 2005 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Wavelet‐accelerated Monte Carlo sampling of polymer chains
Authors: Ismail Ahmed E. , Stephanopoulos George , Rutledge Gregory C.
Published: February 2005

We introduce a new method for coarse‐graining polymer chains, based on the wavelet transform, a multiresolution data analysis technique. This method, which assigns a cluster of particles to a coarse‐grained bead located at the center of mass of the cluster, reduces the complexity of the problem significantly by dividing the simulation into several stages, each with a small fraction of the number of beads in the overall chain. At each stage, we compute the distributions of coarse‐grained internal coordinates as well as potential functions required for subsequent simulation stages. We show that, with this wavelet‐accelerated Monte Carlo method, coarse‐grained Gaussian and self‐avoiding random walks can reproduce results obtained from atomistic simulations to a high degree of accuracy in orders of magnitude less time. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 897–910, 2005
Aspects of holography in the AdS/CFT correspondence
Authors: Sieg C.
Published: February 2005

We study quantities which are important for the realization of the holographic principle in the AdS/CFT correspondence: boundaries, geodesics and the propagators of scalar fields. They should play a role in the holographic setup in the BMN limit as well. We review the backgrounds and their relations that are relevant in the AdS/CFT correspondence and in its BMN limit. We describe the realization of the holographic principle in the AdS/CFT correspondence and summarize proposals of how to translate it in the BMN limit. We analyze the boundaries, geodesics and propagators of scalar fields in detail and observe how they behave in the limiting process from AdS5×S5to the 10‐dimensional plane wave, which is the spacetime in the BMN limit.
Characterization of deep levels in n‐GaN by combined capacitance transient techniques
Authors: Py M. A. , Zellweger Ch. , Wagner V. , Carlin J.‐F. , Buehlmann H.‐J. , Ilegems M.
Published: February 2005

Deep centers in undoped n‐GaN grown by Hydride Vapor Phase Epitaxy were characterized by Deep Level Transient Spectroscopy (DLTS), revealing four known levels with activation energies in the range 0.17–0.94 eV. Deeper levels in the bandgap were observed by photocapacitance (PHCAP) experiments. A correspondence can be established for the dominant DLTS level observed both by thermal and optical experiments, exploiting the temperature as a key parameter in PHCAP measurements. The Franck–Condon shift dF–C for this level was estimated around 0.33 eV, in close agreement with results obtained by Hacke and coworkers in a more elaborate way. The tentative assignment of most levels is discussed on the basis of literature, pointing out unsettled origins for some of them. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Terahertz investigation of high quality indium nitride epitaxial layers
Authors: Meziani Y. M. , Maleyre B. , Sadowski M. L. , Ruffenach S. , Briot O. , Knap W.
Published: February 2005

We report on the optical characterization of InN layers in the THz range and magnetic fields up to 13 T. The results are interpreted using the dielectric function formalism, with contributions of cyclotron resonance, phonons, plasmons and helicon wave excitations. We show how THz radiation transmission measurements can provide an optical contactless method of determining the quality (carrier density and momentum scattering rate) in the InN layers. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron transport properties of AlGaAs/GaAs heterostructure containing a d‐doping in the quantum well
Authors: Rekaya S. , Bouzaïene L. , Sfaxi L. , Hjiri M. , Contreras S. , Robert J. L. , Maaref H.
Published: February 2005

Electronic properties of the Si δ‐doped AlGaAs/GaAs heterostructure such as the electron density and electron mobility have been studied when the Al concentration in the vicinity to the silicon (xAl(Si)) is varied. Shubnikov–de Haas and quantum Hall effect measurements at 4.2 K have been carried out to investigate the existence of a quasi‐two‐dimensional electron gas (2DEG) in such structures. We have studied the effects of the Al concentration xAl(Si) on the electronic properties. Results show an improvement of the electron transport properties when xAl(Si) decreases. But as far as the electron mobility is concerned, a slight difference between the theoretical and experimental values was observed. The value of interface charge density (NBI) is necessary to explain the experimental mobility at low temperature. For NBI ≈ 6 × 109 cm–2, we have obtained a good agreement between the theoretical and experimental electron mobility. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Donor ionization energy in bulk GaAs for different donor concentrations and magnetic fields
Authors: Bisotto I. , Jouault B. , Raymond A. , Zawadzki W. , Strasser G.
Published: February 2005

We present the analysis of magnetotransport measurements of n‐type GaAs samples grown by MBE technique. The samples cover a wide range of donor concentrations, from 4.0 × 1014 cm–3 to 3.0 × 1016 cm–3. Experiments were performed for a wide range of temperatures and magnetic fields. The apparition of a magnetic freeze‐out for conduction electrons allows us to extract the binding energy of donors as a function of the magnetic field as well as the impurity concentration. The measured binding energies decrease as the doping level increases. This behavior is due to the overlap of the wavefunctions of neighbouring impurities which results in the formation of an impurity band. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic field effects on the near field spectra of quantum dots
Authors: Zora Anna , Simserides Constantinos , Triberis Georgios
Published: February 2005

We theoretically investigate the linear near field absorption spectra of semiconductor quantum dots under magnetic field of variable orientation. We examine if the application of the magnetic field alone is sufficient to cause – increasing the spot illuminated by the near field probe – “unexpected” features to the absorption spectra. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Assessment of layer composition and thickness in AlGaN/GaN HEMT structures by spectroscopic ellipsometry
Authors: Baeumler M. , Müller S. , Köhler K. , Wagner J.
Published: February 2005

AlGaN/GaN heterostructures for power applications, grown on sapphire substrates by metal organic vapor phase epitaxy (MOVPE) in a multiwafer reactor were analyzed by spectroscopic ellipsometry (SE). The thickness of the individual layers as well as the AlGaN bandgap energy were extracted from pseudodielectric function spectra 〈ε〉 for photon energies ranging from 2 to 5 eV. The experimental 〈ε〉 spectra were analyzed using a multilayer approach, describing the dielectric functions of the individual layers by a parametric oscillator model. The potential of the technique will be demonstrated using on‐wafer homogeneity as well as wafer‐to‐wafer variation within the same growth run in the MOVPE reactor as examples. SE was found to be capable of detecting relative variations in the Al content of 1% and the AlGaN layer thickness of 10%. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High magnetic field studies of 1/f noise in GaN/AlGaN heterostructure field effect transistors
Authors: Dyakonova N. , Rumyantsev S. L. , Shur M. S. , Meziani Y. , Pascal F. , Hoffmann A. , Fareed Q. , Hu X. , Bilenko Yu. , Gaska R. , Knap W.
Published: February 2005

The influence of strong magnetic field on the 1/f noise in AlGaN/GaN metal‐oxide‐Semiconductor heterostructure field effect transistors (MOSHFETs) has been studied. The independence of 1/f noise on the magnetic fields up to 10 T where the strong geometric magneto‐resistance has been observed, shows that the carrier number fluctuations is the dominant mechanism of the noise in these devices. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Short-term inhibition of the energy metabolism affects motility but not surface properties of sperm cells
Authors: Pascual M. L. , Cebrian-Perez J. A. , Lopez-Perez M. J. , Muiño-Blanco T.
Published: February 2005

Centrifugal countercurrent distribution (CCCD) in aqueous two-phase systems has been proven to be a useful method to study subtle surface properties of spermatozoa. The present work shows that a short-term inhibition of the energy metabolism of sperm cells effected by incubating bovine sperm cells with KCN or ouabain, did not account for changes in the cell surface properties, as assessed either by estimation of the cell viability or by CCCD analysis. However, the short-term inhibition of energy metabolism provoked a clear decrease of cell motility, suggesting that a drop of cellular ATP levels brings about a rapid decrease of motility followed by a very delayed effect on cell surface properties. The relevance of these results on the handling of sperm and on the understanding of the molecular events underlying asthenospermia is discussed.
Calcium pools, calcium entry, and cell growth
Authors: Gill Donald L. , Waldron Richard T. , Rys-Sikora Krystyna E. , Ufret-Vincenty Carmen A. , Graber Matthew N. , Favre Cécile J. , Alfonso Amparo
Published: February 2005

The Ca2+ pump and Ca2+ release functions of intracellular Ca2+ pools have been well characterized. However, the nature and identity of Ca2+ pools as well as the physiological implications of Ca2+ levels within them, have remained elusive. Ca2+ pools appear to be contained within the endoplasmic reticulum (ER); however, ER is a heterogeneous and widely distributed organelle, with numerous other functions than Ca2+ regulation. Studies described here center on trying to determine more about subcellular distribution of Ca2+ pools, the levels of Ca2+ within Ca2+ pools, and how these intraluminal Ca2+ levels may be physiologically related to ER function. Experiments utilizing in situ high resolution subcellular morphological analysis of ER loaded with ratiometric fluroescent Ca2+ dyes, indicate a wide distribution of inositol 1,4,5-trisphosphate (InsP3)-sensitive Ca2+ pools within cells, and large changes in the levels of Ca2+ within pools following InsP3-mediated Ca2+ release. Such changes in Ca2+ may be of great significance to the translation, translocation, and folding of proteins in ER, in particular with respect to the function of the now numerously described luminal Ca2+-sensitive chaperonin proteins. Studies have also focussed on the physiological role of pool Ca2+ changes with respect to cell growth. Emptying of pools using Ca2+ pump blockers can result in cells entering a stable quiescent G0-like growth state. After treatment with the irreversible pump blocker, thapsigargin, cells remain in this state until they are stimulated with essential fatty acids whereupon new pump protein is synthesized, functional Ca2+ pools return, and cells reenter the cell cycle. During the Ca2+ pool-depleted growth-arrested state, cells express a Ca2+ influx channel that is distinct from the store-operated Ca2+ influx channels activated after short-term depletion of Ca2+ pools. Overall, these studies indicate that significant changes in intraluminal ER Ca2+ do occur and that such changes appear linked to alteration of essential ER functions as well as to the cell cycle-state and the growth of cells.
An approach to literate and structured formal developments
Authors: Simons Martin , Weber Matthias
Published: February 2005

We present an approach to the literate and structured presentation of formal developments. We discuss the presentation of formal developments in a logical framework and distinguish three aspects: language-related aspects, structural aspects of proofs, and presentational aspects. We illustrate the approach by two examples: a simple mathematical proof of the Knaster-Tarski fixpoint theorem, and a formalization of the VDM development of a revision management system.
Sexual and vegetative reproduction in the aboveground part of a dioecious clonal plant, Dioscorea japonica (Dioscoreaceae)
Authors: Mizuki Inoue , Ishida Kiyoshi , Kikuzawa Kihachiro
Published: February 2005

In dioecious clonal plants, the reproductive effort required to set seeds will be responsible for the larger investment in sexual reproduction by females. If there will be a trade‐off in resource allocation between sexual and clonal reproduction, this differential sexual reproduction will lead to sexual differentiation in the relative amount of clonal reproduction. To test this prediction, we studied differences between the sexes in their phenologies and investments in sexual and vegetative reproduction (clonal reproduction by means of bulbils) with respect to ramet size in a dioecious clonal plant, Dioscorea japonica Thunb. The period of bulbil production overlapped the period during which infructescences developed. Females flowered later, produced heavier inflorescences, and fewer flowers per inflorescence than did males. Regression analysis using the size of the individual plants demonstrated that large females made smaller investments in inflorescences and larger investments in sexual reproduction than did large males. In contrast, females invested fewer resources in vegetative reproduction than did males. However, the total investments in sexual and vegetative reproduction did not differ between the sexes. These results supported our hypothesis on the sexual differentiation in sexual and clonal reproduction.
Pre- and postwar generations of rural female youth and the future of the German nation, 1871–1933
Authors: JONES ELIZABETH BRIGHT
Published: February 2005

Just before the First World War, German agricultural economists and social-welfare experts constructed a new social category – rural female youth, whose mobility provoked growing alarm. Framing rural flight in terms of gender and generation allowed experts to focus on its demographic, economic, and moral threats, and rural female youth became a target for reform. These debates presaged a wave of popular anxiety over rural female youth that expanded dramatically during the Weimar Republic. However, prewar court testimonies of runaway maids in rural Saxony suggest that some rural girls understood their mobility in terms of ‘getting ahead’, and resisted efforts to restrict their occupational, social, and spatial horizons.
Different paths to the public: European women, educational opportunity, and expertise, 1890–1930
Authors: RYAN MARYNEL
Published: February 2005

This article describes a comparison of two groups of women, one German and one French, who were able to use the expanding educational opportunities for women during the late nineteenth and early twentieth centuries to forge a new path to public influence. The comparison highlights the different socio-political and institutional contexts of Imperial Germany and Third Republic France, in order to explain the very different career patterns of women with similar research interests: national economists who trained in Berlin and lawyers who trained in Paris. Although the greater emphasis is on the German case, I explore the possibilities for (and limitations to) women's claims to public influence in both contexts.
Investigating responses to theft in early modern Wales: communities, thieves and the courts
Authors: HOWARD SHARON
Published: February 2005

This article makes use of the rich deposits of pre-trial documents in the court archives of early modern Wales, focusing on the county of Denbighshire, to investigate attitudes and responses to theft. Qualitative research on this subject tends to emphasize or privilege actively law-enforcing behaviour that led to trials; while that is the inevitable emphasis of court records, I argue that we need to examine witness testimonies more closely in order to understand responses that did not match up to the ideals of vigilance and communal responsibility. Drawing on modern criminological research, I explore ‘suspicion’ and the decision-making processes leading to various outcomes: non-action; investigation and prosecution; alternative resolutions that bypassed the courts. Finally, I explore the everyday ‘world of stolen goods’ and its social and economic rewards in local networks of reciprocal favours, gifts and alliances.
Happiness and Utility: Jeremy Bentham's Equation
Authors: BURNS J. H.
Published: February 2005

Doubts about the origin of Bentham's formula, ‘the greatest happiness of the greatest number’, were resolved by Robert Shackleton thirty years ago. Uncertainty has persisted on at least two points. (1) Why did the phrase largely disappear from Bentham's writing for three or four decades after its appearance in 1776? (2) Is it correct to argue (with David Lyons in 1973) that Bentham's principle is to be differentially interpreted as having sometimes a ‘parochial’ and sometimes a ‘universalist’ bearing? These issues are reopened here with particular reference to textual evidence overlooked in earlier discussions and contextual evidence on the development of Bentham's radicalism in the last two decades of his life. In conclusion some broader issues are raised concerning the character of Bentham's understanding of ‘happiness’ itself.
Improved model predictions of HO2 with gas to particle mass transfer rates calculated using aerosol number size distributions
Authors: Haggerstone A.‐L. , Carpenter L. J. , Carslaw N. , McFiggans G.
Published: February 2005

Hydroperoxy radical (HO2) measurements made during the second Southern Ocean Atmospheric Photochemistry Experiment (SOAPEX‐2) were used as a modeling case study to investigate the role of aerosol uptake of free radicals in remote marine boundary layer (MBL) air. The SOAPEX‐2 campaign was held at the Cape Grim Baseline Atmospheric Pollution Station on the northwestern tip of Tasmania during austral summer from 18 January to 18 February 1999. A box model based on the Master Chemical Mechanism (MCMv3) was tailored to campaign conditions. With no aerosol uptake of HO2 the model overestimated the midday (1100–1400 hours) HO2 measurements by 74–83% on two clean marine air days with HO2 measurements. Two different methods were used to simulate aerosol uptake of free radicals. The first method used a simple first‐order rate coefficient for interfacial mass transport (kinetic regime), kkin, with two treatments of the aerosol surface area, estimated from clean MBL Californian air and calculated by analysis of lognormal aerosol number versus size distributions from the first Aerosol Characterization Experiment (ACE‐1). The second method used a rate coefficient which takes into account diffusion to the surface as well as interfacial mass transport (transition regime), ktrans, integrated over most of the aerosol size range (up to 2.5 μm diameter) using aerosol number size distribution data from ACE‐1. With the simple uptake rate the model to measured overestimation of HO2 was on average 63 and 20% with uptake coefficients of 0.2 and 1, respectively. With ktrans the overestimation was 60 and 44%, respectively. These overestimations are upper limits because the calculations did not take into account the largest sea salt mode (which was not measured). An estimate of the aerosol in the largest sea salt modes was calculated and used to recalculate the values of ktrans, reducing the overestimation to 58 and 25%, respectively. The variation in the available literature values for the HO2 uptake coefficient is a large source of uncertainty in the calculated rate of uptake. Another source of uncertainty exists in the values assumed for the aerosol volume in this work. As these data did not exist for SOAPEX‐2, we calculated ktrans from ACE‐1 aerosol volume data and used a constant averaged value of ktrans; in reality there will be a significant degree of temporal variation in this parameter. Given these uncertainties, we conclude that aerosol uptake of the hydroperoxy radical (HO2) could be a significant process in clean MBL environments and its incorrect parameterization or absence in atmospheric models could contribute to overestimation of measured concentrations.
Distant origins of Arctic black carbon: A Goddard Institute for Space Studies ModelE experiment
Authors: Koch Dorothy , Hansen James
Published: February 2005

Black carbon (BC) particles, derived from incomplete combustion of fossil fuels and biomass, may have a severe impact on the sensitive Arctic climate, possibly altering the temperature profile, cloud temperature and amount, the seasonal cycle, and the tropopause level and accelerating polar ice melting. We use the Goddard Institute for Space Studies general circulation model to investigate the origins of Arctic BC by isolating various source regions and types. The model suggests that the predominant sources of Arctic soot today are from south Asia (industrial and biofuel emissions) and from biomass burning. These are the primary global sources of BC (approximately 20% and 55%, respectively, of the global emissions), and BC aerosols in these regions are readily lofted to high altitudes where they may be transported poleward. According to the model the Arctic BC optical thickness is mostly from south Asia (30%) and from biomass (28%) (with slightly more than half of biomass coming from north of 40°N); North America, Russia, and Europe each contribute 10–15%. Russia, Europe, and south Asia each contribute about 20–25% of BC to the low‐altitude springtime “Arctic haze.” In the Arctic upper troposphere/lower stratosphere during the springtime, south Asia (30–50%) and low‐latitude biomass (20–30%) are dominant, with a significant aircraft contribution (10–20%). Industrial S emissions are estimated to be weighted relatively more toward Russia and less toward south Asia (compared with BC). As a result, Russia contributes the most to Arctic sulfate optical thickness (24%); however, the south Asian contribution is also substantial (17%). Uncertainties derive from source estimates, model vertical mixing, and aerosol removal processes. Nevertheless, our results suggest that distant sources contribute more to Arctic pollution than is generally assumed.
Iron proteins of duodenal enterocytes isolated from mice with genetically and experimentally altered iron metabolism
Authors: Pountney David J. , Konijn Abraham M. , McKie Andrew T. , Peters Timothy J. , Raja Kishor B. , Salisbury Jonathan R. , Simpson Robert J.
Published: February 2005

The molecular basis for the control of iron absorption by the duodenum remains unknown; however, ferritin (Ft) and the iron status of enterocytes have been suggested as regulatory factors. We determined the iron and Ft status of duodenal enterocytes from mice with hypotransferrinaemia, a genetic defect leading to greatly enhanced iron absorption, and for comparison we also investigated mice with experimentally‐altered iron absorption. Duodenal enterocytes were isolated and analysed for Ft and non‐haem iron content and for transferrin binding (as a measure of transferrin receptor activity). RNA was extracted from the duodenal mucosa and examined for transferrin receptor and H‐ and L‐Ft mRNA levels by Northern hybridization analysis. Ft levels were elevated in enterocytes of hypotransferrinaemic mice, similar to that seen in iron dextran‐injected mice of the CD1‐strain. Enterocyte Ft levels were reduced in mice fed a diet diminished in iron, but unchanged in hypoxic mice enterocytes. Enterocytes of hypotransferrinaemic mice had normal non‐haem iron levels and transferrin binding; however, enterocytes from CD‐1 mice fed a low iron diet had increased transferrin binding and a decreased non‐haem iron content. Duodenal mRNA levels for transferrin receptor and H‐Ft were unchanged in hypotransferrinaemic mice, whereas L‐Ft was increased. We conclude from the Ft and non‐haem iron contents and transferrin binding that duodenal enterocytes from hypotransferrinaemic mice are not simply iron deficient, leading to increased expression of iron carriers proteins. Duodenal iron absorption can be enhanced in mice even when enterocyte Ft levels are raised or unchanged, suggesting that iron absorption is regulated by developmentally programmed expression of iron transporters by enterocytes.
Human G‐CSF‐mobilized CD34‐positive peripheral blood progenitor cells can stimulate allogeneic T‐cell responses: implications for graft rejection in mismatched transplantation
Authors: Van Rhee Frits , Jiang Yin‐Zheng , Vigue Faye , Kirby Martha , Mavroudis Dimitrios , Hensel Nancy F. , Agarwala Vaishali , Clave Emmanuel , Childs Richard , Raptis Anastasios , Sloand Elaine , Carter Charles , Read Elizabeth J. , Barrett John
Published: February 2005

To investigate mechanisms of stem cell graft rejection we studied the allo‐stimulatory potential of G‐CSF mobilized peripheral blood progenitor cells (PBPC). CD34+ cells were purified (> 95%) in a two‐step procedure using immunoaffinity columns for CD34 selection and T‐depletion. The capacity of CD34+ cells to stimulate allogeneic T‐cell responses was compared with other cells from the same individual. CD34+ cells induced potent proliferative responses at stimulator:responder ratios of 1:20, but were approximately 50‐fold less efficient compared to dendritic cells. Furthermore, CD34+ cells primed responses from partially matched allogeneic T cells in bulk cultures. Dual‐colour flow cytometry showed that the co‐stimulatory molecules B7.1, CD40 and ICAM‐1 were absent on resting CD34‐positive progenitor cells, but were induced during incubation with allogeneic lymphocytes due to a cytokine‐mediated effect. Up‐regulation of accessory molecules on CD34+ cells was reproduced by incubation with interferon‐γ or GM‐CSF which enhanced the allo‐stimulatory activity of CD34+ cells. Blocking studies with inhibitory antibodies suggested co‐stimulatory functions for B7.2, ICAM‐3, CD40 and LFA‐3. CD34+ cells were more efficient in inducing allogeneic T‐cell responses when compared to the unprocessed leukapheresis products. The reduced allo‐stimulatory ability of G‐CSF mobilized PBPC could be explained by the presence of CD3+4+ and CD3+8+ lymphocytes with suppressor activity. We conclude that current methods of stem cell selection for transplantation do not avoid allo‐sensitization of the recipient and that further graft manipulation with add‐back of lymphocytes or selection of subsets of CD34+ cells with reduced allo‐stimulatory ability may reduce graft rejection.
Structures of [(CO2)n(H2O)m]− (n=1–4, m=1,2) cluster anions. I. Infrared photodissociation spectroscopy
Authors: Muraoka Azusa , Inokuchi Yoshiya , Nishi Nobuyuki , Nagata Takashi
Published: February 2005

The infrared photodissociation spectra of [(CO2)n(H2O)m]− (n=1–4, m=1, 2) are measured in the 3000–3800cm−1 range. The [(CO2)n(H2O)1]− spectra are characterized by a sharp band around 3570cm−1 except for n=1; [(CO2)1(H2O)1]− does not photodissociate in the spectral range studied. The [(CO2)n(H2O)2]− (n=1, 2) species have similar spectral features with a broadband at ≈3340cm−1. A drastic change in the spectral features is observed for [(CO2)3(H2O)2]−, where sharp bands appear at 3224, 3321, 3364, 3438, and 3572cm−1. Ab initio calculations are performed at the MP2/6-311++G** level to provide structural information such as optimized structures, stabilization energies, and vibrational frequencies of the [(CO2)n(H2O)m]− species. Comparison between the experimental and theoretical results reveals rather size- and composition-specific hydration manner in [(CO2)n(H2O)m]−: (1) the incorporated H2O is bonded to either CO2− or C2O4− through two equivalent OH⋯O hydrogen bonds to form a ring structure in [(CO2)n(H2O)1]−; (2) two H2O molecules are independently bound to the O atoms of CO2− in [(CO2)n(H2O)2]− (n=1, 2); (3) a cyclic structure composed of CO2− and two H2O molecules is formed in [(CO2)3(H2O)2]−.
Excited-state decay of hydrocarbon radicals, investigated by femtosecond time-resolved photoionization: Ethyl, propargyl, and benzyl
Authors: Zierhut Matthias , Noller Bastian , Schultz Thomas , Fischer Ingo
Published: February 2005

The excited state decay of the hydrocarbon radicals ethyl, C2H5; propargyl, C3H3; and benzyl, C7H7 was investigated by femtosecond time-resolved photoionization. Radicals were generated by flash pyrolysis of n-propyl nitrite, propargyl bromide, and toluene, respectively. It is shown that the 2A′2(3s) Rydberg state of ethyl excited at 250nm decays with a time constant of 20fs. No residual signal was observed at longer delay times. For the 3B12 state of propargyl excited at 255nm a slower decay with a time constant 50±10fs was determined. The 4B22 state of benzyl excited at 255nm decays within 150±30fs.
Accelerating quantum mechanical/molecular mechanical sampling using pure molecular mechanical potential as an importance function: The case of effective fragment potential
Authors: Bandyopadhyay Pradipta
Published: February 2005

Acceleration of sampling from a quantum mechanical/effective fragment mechanical (QM/EFP) potential is explored with effective fragment potential (EFP) as an importance function. EFP, generated on the fly, is found to be an excellent choice for an importance function for a QM/EFP potential. This technique is used to find nine stationary points of a blocked amino acid with twelve waters in a semi-automated way.
Spectroscopic studies of molecular-beam epitaxially grown Cr2+-doped ZnSe thin films
Authors: Gallian A. , Fedorov V. V. , Kernal J. , Allman J. , Mirov S. B. , Dianov E. M. , Zabezhaylov A. O. , Kazakov I. P.
Published: February 2005

Cr:ZnSe thin films were grown by molecular-beam epitaxy with the long-term goal of demonstrating a route for the development of transitional-metal-doped semiconductor lasers. Photoluminescence (PL) and PL lifetime measurements of doped thin films and bulk crystals indicate that Cr is incorporated in the optically active Cr2+ state up to levels of 5×1019cm−3. The shape of PL spectra and lifetime measurements of doped thin films compares favorably with that reported for bulk samples. A microcavity formed by film interfaces is responsible for differences in spontaneous emission observed between films and bulk crystals.
Viscous versus inviscid instability of two-phase mixing layers with continuous velocity profile
Authors: Boeck Thomas , Zaleski Stéphane
Published: February 2005

We consider the temporal instability of parallel two-phase mixing layers. The viscous case is examined using a composite error-function velocity profile. The inviscid case is considered for the broken-line velocity profile, where the thickness of the boundary layer in each fluid next to the interface is chosen to match the viscous error-function profile at the interface and far away from it. Viscosity modifies the inviscid stability properties quantitatively, but we can also discern an additional unstable mode exclusively related to viscous shear. In the absence of interfacial tension, this mode dominates at large wavenumbers when the Reynolds number is sufficiently high. The various viscous modes cannot generally be attributed to either one of the phases due to mode mixing or exchange. For parameters resembling those of atomization experiments and applications, the most unstable wavelength and growthrate in the viscous case can exceed the inviscid values significantly. The viscous stability analysis also provides better agreement with recent experimental results for air and water than inviscid stability calculations.
Three-dimensional numerical simulation of receptor-mediated leukocyte adhesion to surfaces: Effects of cell deformability and viscoelasticity
Authors: Khismatullin Damir B. , Truskey George A.
Published: February 2005

Computational fluid dynamics is used to investigate the effects of cell deformability and viscoelasticity on receptor-mediated leukocyte adhesion to endothelium or a ligand coated surface in a parallel-plate flow chamber. In the three-dimensional numerical code, a leukocyte is modeled as a compound viscoelastic drop (a nucleus covered by a thick layer of cytoplasm). The nucleus, cytoplasm, and extracellular fluid are considered as Newtonian or viscoelastic liquids of high viscosity. The receptor-ligand interaction is incorporated into the code by using the spring-peeling kinetic model under the assumption that leukocyte receptors are located on the tips of cylindrical microvilli distributed over the leukocyte membrane. The code is based on the volume-of-fluid method, and the Giesekus constitutive equation is implemented in the code to capture viscoelasticity of the cytoplasm and nucleus. Numerical simulations demonstrate the formation and breakup of membrane tethers observed in vitro and suggest that the elasticity of the cytoplasm is responsible for a teardrop shape of rolling leukocytes in vivo. When viewed from the top, as normally occurs during shear flow experiments in vitro, little or no deformation occurs, a side view shows significant deformation in the contact region. We show that the leukocyte membrane can be extended and disrupted under high shear if the receptor-ligand bonds live in a stressed state for a sufficiently long time. If the shear rate is low, the leukocyte rolls along the surface. The rolling velocity of the viscoelastic cell is smaller than that of the Newtonian cell. This is due to the increased deformability of the viscoelastic cell and, as a result, the decreased torque acting on this cell.
Thermodiffusion in ferrofluids in the presence of a magnetic field
Authors: Voelker T. , Odenbach S.
Published: February 2005

Investigations were made to investigate the thermodiffusion process (Soret effect) of magnetic particles in a ferrofluid under the influence of a magnetic field. The so-called magnetic Soret effect was theoretically predicted to be two to three orders of magnitude smaller than the conventional Soret effect. In contrast, former experiments have qualitatively shown that the magnetic influence on the thermodiffusion process is much higher than the theoretical predictions for the magnetic Soret effect. However, in those experiments the influence of buoyancy and magnetic driven convection disturbed the measurement significantly. Thus it is still an open question how strong the influence of a magnetic field on thermodiffusion can be and how this influence can be explained theoretically. Therefore an experimental setup was developed which minimizes parasitic effects, simplifying the analysis of the experimental results. These results provide quantitative measures of the magnetic field dependence of the Soret effect in suspensions of magnetic nanoparticles. If this influence is taken as a magnetic Soret effect it is shown that it can even be higher than the conventional one and that its strength as well as its direction depend on the magnetic field strength and its relative alignment to the temperature gradient in the fluid.
Electron-lattice coupling in ZnFe2O4∕TiO2 nanocomposite films
Authors: Jin Yunxia , Li Guanghai , Zhang Lide
Published: February 2005

Electron-lattice (e-ph) coupling originated from the low-temperature photoluminescence in ZnFe2O4∕TiO2 nanocomposite films has been studied. The purely linear character of the e-ph coupling is shown through the Huang–Rhys model within the Franck–Condon approximation. The interfacial coupling capability between the ZnFe2O4 nanoparticles and the TiO2 host lattice is characterized by the Huang–Rhys factors (S0) and the vibrational quantum energy (ℏΩ). It is found that the Huang–Rhys factors S0 increases with increasing the content of ZnFe2O4 in the TiO2 films and the vibrational energy ℏΩ is quite in agreement with that in the infrared spectra.
Double layer formation in the expanding region of an inductively coupled electronegative plasma
Authors: Plihon N. , Corr C. S. , Chabert P.
Published: February 2005

Double-layers (DLs) were observed in the expanding region of an inductively coupled plasma with Ar–SF6 gas mixtures. No DL was observed in pure argon or SF6 fractions below a few percent. They exist over a wide range of power and pressure although they are only stable for a small window of electronegativity (typically between 8% and 13% of SF6 at 1 mTorr), becoming unstable at higher electronegativity. They seem to be formed at the boundary between the source tube and the diffusion chamber and act as an internal boundary [the amplitude being roughly 1.5(kTe∕e)] between a high electron density, high electron temperature, low electronegativity plasma upstream (in the source), and a low electron density, low electron temperature, high electronegativity plasma downstream.
Optimal energy resolution of a hemispherical analyzer with virtual entry
Authors: Zouros T. J. M. , Benis E. P.
Published: February 2005

For an ideal hemispherical deflector analyzer (HDA) utilizing a virtual entry aperture whose size is controlled by an injection lens, the “slit” and angular contributions to the overall base resolution RB are not independent, but constrained by the Helmholtz–Lagrange law. Thus, RB becomes a function of the linear lens magnification ∣ML∣ and has a minimum, RBo¯≡RB(∣ML∣o), at the optimal magnification ∣ML∣=∣ML∣o. RBo¯ and ∣ML∣o are shown to be analytic expressions of basic experimental parameters. RBo¯ is thus the ultimate resolution that can be attained in this case. The generality and simplicity of this result should be very helpful in the efficient design and performance evaluation of any modern HDA.
Reaction-dispersive proton transport model for negative bias temperature instabilities
Authors: Houssa M. , Aoulaiche M. , De Gendt S. , Groeseneken G. , Heyns M. M. , Stesmans A.
Published: February 2005

Negative bias temperature instabilities in p-channel metal-oxide-semiconductor field effect transistors are modeled by taking into account the generation of Pb0 centers at the (100)Si∕SiO2 interface, followed by the dispersive transport of protons away from the interface. It is shown that the characteristic time, oxide electric field, and temperature dependence of the threshold voltage shifts observed in these devices can be very well reproduced by the model. The general belief that the transport of positively charged species cannot explain negative bias temperature instabilities thus appears to be incorrect.
Stress effects on ferroelectric and fatigue properties of Nd- and La-doped Bi4Ti3O12 thin films
Authors: Wu Xiumei , Lu Xiaomei , Chen Aiping , Yin Yuan , Ma Jun , Li Wei , Kan Yi , Qian Dong , Zhu Jinsong
Published: February 2005

The ferroelectric properties of Bi3.15Nd0.85Ti3O12 and Bi3.25La0.75Ti3O12 thin films under applied uniaxial stress were investigated. It was observed in both films that the remnant polarization (Pr) increased with tensile stress, while it decreased with compressive stress. On the contrary, the coercive field (Ec) decreased with the stress changing from maximum compression to maximum tension. Fatigue behavior of the films was improved under either compressive or tensile stress compared with zero stress (free state). These results can be well explained in the scenario of domain reorientation under stress; however, the polarization-strain coupling mechanism could not be simply ruled out.
Parallel Solution-Phase Synthesis of Targeted Tyrphostin Libraries with Anticancer Activity
Authors: Hill Timothy A. , Sakoff Jennette A. , Robinson Phillip J. , McCluskey Adam
Published: February 2005

The combination of semi-automation, an elegant synthesis, and parallel solution-phase synthesis approaches has allowed the development of five targeted, symmetrical tyrphostin compound libraries. These libraries on average are comprised of 12 compounds. Notwithstanding this, low micromolar potent growth inhibitors against HT29 (colorectal carcinoma) and G401 (renal carcinoma) cell lines were discovered. Additionally, significant SAR data was obtained. We noted that the most potent growth inhibitory activity was consistently observed for those analogues that possessed a 2-chlorophenyl (for 10: GI50 HT29 5.5 ± 0.4 μM, GI50 G401 2.6 ± 0.4 μM; for 23: GI50 HT29 2.4 ± 0.2 μM, GI50 G401 1.9 ± 1 μM; for 34: GI50 HT29 8.8 ± 3.1 μM, GI50 G401 6.2 ± 2.9 μM; for 46: GI50 HT29 5.2 ± 0.9 μM, GI50 G401 3.7 ± 0.6 μM; for 57: GI50 HT29 4.6 ± 0.8 μM, GI50 G401 2.1 ± 0.2 μM), a 3-chlorophenyl (for 11: GI50 HT29 3.8 ± 0.7 μM, GI50 G401 1.7 ± 0.7 μM; for 48: GI50 HT29 5.9 ± 0.1 μM, GI50 G401 3.4 ± 0.6 μM; for 58: GI50 HT29 4.8 ± 0.9 μM, GI50 G401 3.4 ± 0.2 μM), or a 3-methoxyphenyl substituent (for 13: GI50 HT29 7.4 ± 3.8 μM, GI50 G401 2.8 ± 0.5 μM; for 26: GI50 HT29 4.5 ± 0.5 μM, GI50 G401 4.9 ± 1 μM; for 37: GI50 HT29 3.7 ± 0.2 μM, GI50 G401 1.6 ± 0.2 μM; for 49: GI50 HT29 3.7 ± 0.4 μM, GI50 G401 3.4 ± 0.2 μM; for 60: GI50 HT29 4.1 ± 0.6 μM, GI50 G401 1.8 ± 0.3 μM). Finally, we noted that increasing the distance between the terminal aromatic rings had only a minimal effect on the 2-, 3-chlorophenyl, and 3-methoxyphenyl analogues, but did have a favourable effect on OH, COOH, and multiply substituted analogues.
A Three-Dimensional Silver(I) Framework Assembled from Nitrilotriacetate
Authors: Chen Chun-Long , Zhang Qian , Jiang Ji-Jun , Wang Qin , Su Cheng-Yong
Published: February 2005

The reaction of AgCF3CO2 with nitrilotriacetate (NTA) yields the three-dimensional silver(i) coordination polymer {Ag3[N(CH2COO)3]}n 1 which was characterized by means of elemental analysis and IR spectroscopy as well as X-ray diffraction. The single crystal structure shows that the NTA3– anions act as unusual heptadentate 13-coordination agents and the silver(i) atoms exhibit various coordination numbers in the range 3–6.
Life history of the frog Crinia signifera in Tasmania, Australia
Authors: Lauck B.
Published: February 2005

A pitfall-trap study was used to investigate the importance of body size, age, body condition (males only), season and growth history as determinates of male and female life-history fitness traits in a population of the frog Crinia signifera. Specimens were dissected to determine physiological characteristics and skeletochronology was used to determine age. Females lived longer and attained a larger size than males by delaying sexual maturity. Most females and males attained sexual maturity after three and two years, respectively; although eggs were found in females as young as one year old. Body size (but not age) was the primary determinant of fecundity, total reproductive output (clutch mass) and oviduct mass for females. Season was the predominant influence on egg size, with smaller eggs produced in summer than in other seasons. Direct investment in male gonads (testes size) was determined by body size and also by age. This, and the fact that sexual size dimorphism in amphibians is commonly female biased, suggests that male size is not necessarily the primary determinant of male reproductive success in C. signifera. Whereas selection on reproductive traits in females is likely to act predominantly on body size, selection in males is also likely to act on survival.
Weak selection revealed by the whole-genome comparison of the X chromosome and autosomes of human and chimpanzee
Authors: Lu Jian , Wu Chung-I
Published: February 2005

The effect of weak selection driving genome evolution has attracted much attention in the last decade, but the task of measuring the strength of such selection is particularly difficult. A useful approach is to contrast the evolution of X-linked and autosomal genes in two closely related species in a whole-genome analysis. If the fitness effect of mutations is recessive, X-linked genes should evolve more rapidly than autosomal genes when the mutations are advantageous, and they should evolve more slowly than autosomal genes when the mutations are deleterious. We found synonymous substitutions on the X chromosome of human and chimpanzee to be less frequent than those on the autosomes. When calibrated against substitutions in the intergenic regions and pseudogenes to filter out the differences in the mutation rate and ancestral population size between X chromosomes and autosomes, X-linked synonymous substitutions are still 10% less frequent. At least 90% of the synonymous substitutions in human and chimpanzee are estimated to be deleterious, but the fitness effect is weaker than the effect of genetic drift. However, X-linked nonsynonymous substitutions are ≈30% more frequent than autosomal ones, suggesting the fixation of advantageous mutations that are recessive.