991 research outputs found
On the stability of polaronic superlattices in strongly coupled electron-phonon systems
We investigate the interplay of electron-phonon (EP) coupling and strong
electronic correlations in the frame of the two-dimensional (2D) Holstein t-J
model (HtJM), focusing on polaronic ordering phenomena for the quarter-filled
band case. The use of direct Lanczos diagonalization on finite lattices allows
us to include the effects of quantum phonon fluctuations in the calculation of
spin/charge structure factors and hole-phonon correlation functions. In the
adiabatic strong coupling regime we found evidence for ``self-localization'' of
polaronic carriers in a charge-modulated structure, a type of
superlattice solidification reminiscent of those observed in the nickel
perovskites .Comment: 2 pages, Latex. Submitted to Physica C, Proc. Int. Conf. on M2HTSC
Spin-resolved electron-impact ionization of lithium
Electron-impact ionization of lithium is studied using the convergent
close-coupling (CCC) method at 25.4 and 54.4 eV. Particular attention is paid
to the spin-dependence of the ionization cross sections. Convergence is found
to be more rapid for the spin asymmetries, which are in good agreement with
experiment, than for the underlying cross sections. Comparison with the recent
measured and DS3C-calculated data of Streun et al (1999) is most intriguing.
Excellent agreement is found with the measured and calculated spin asymmetries,
yet the discrepancy between the CCC and DS3C cross sections is very large
Physical Mapping of Micronutritional Genes in Wheat-rye Translocations
In rye (Secale cereale L.), there are loci on chromosome arm 5RL which give rise to increased copper (Cu)- and iron (Fe)-efficiency, respectively. Four different wheat-rye translocations each harboring a terminal segment of different size of the rye chromosome arm 5RL were identified by test crosses and Giemsa-banding: \u27T29\u27 (5AS.5RL), \u27T63\u27 (5BS.5BL-5RL), \u27Vhn\u27 (4BS.4BL-5RL) and \u27Cor\u27 (4BS.4BL-5RL). The translocation break points were detected by chromosome painting technique GISH and the sizes of the rye chromosome segments involved were determined by computer image analysis. The Cu-efficiency gene Ce was physically mapped to the terminal region of 5RL, and the genes for mugineic acid and for hydroxymugineic acid synthetases involved in the strategy II of Fe-efficiency control to two intercalary regions of 5RL. In all wheat-rye translocation lines the Ce gene is linked to the dominant hairy neck character (HaI) from rye. This morphological trait and the RFLP probe \u27WG 199\u27 as well can serve as proper markers for a marker-based large-scale selection in wheat breeding
Low Temperature Magnetic Properties of the Double Exchange Model
We study the {\it ferromagnetic} (FM) Kondo lattice model in the strong
coupling limit (double exchange (DE) model). The DE mechanism proposed by Zener
to explain ferromagnetism has unexpected properties when there is more than one
itinerant electron. We find that, in general, the many-body ground state of the
DE model is {\it not} globally FM ordered (except for special filled-shell
cases). Also, the low energy excitations of this model are distinct from spin
wave excitations in usual Heisenberg ferromagnets, which will result in unusual
dynamic magnetic properties.Comment: 5 pages, RevTeX, 5 Postscript figures include
Tissue inhibitor of matrix metalloproteinase 1 (TIMP1) controls adipogenesis in obesity in mice and in humans
Aims/hypothesis: Extracellular matrix reorganisation is a crucial step of adipocyte differentiation and is controlled by the matrix metalloproteinase-tissue inhibitor of matrix metalloproteinase (TIMP) enzyme system. We therefore sought to define the role of TIMP1 in adipogenesis and to elucidate whether upregulation of TIMP1 in obesity has direct effects on adipocyte formation. Methods: TIMP1 protein levels and mRNA were measured in lean and obese mice with a focus on levels in adipose tissue. We also analysed the effect of recombinant murine TIMP1 on adipogenesis, adipocyte size and metabolic control in vitro and in vivo. Results: TIMP1 levels were increased in the serum and adipose tissue of obese mouse models. Recombinant murine TIMP1 inhibited adipocyte differentiation in 3T3-L1 as well as in subcutaneous primary pre-adipocytes. Conversely, neutralising TIMP1 with a specific antibody enhanced adipocyte differentiation. In vivo, injection of recombinant TIMP1 in mice challenged with a high-fat diet led to enlarged adipocytes. TIMP1-treated mice developed an impaired metabolic profile with increased circulating NEFA levels, hepatic triacylglycerol accumulation and accelerated insulin resistance. Altered glucose clearance in TIMP1-injected mice was due to changes in adipose tissue glucose uptake, whereas muscle glucose clearance remained unaffected. Conclusions/interpretation: TIMP1 is a negative regulator of adipogenesis. In vivo, TIMP1 leads to enlarged adipocytes in the state of overnutrition. This might contribute to the detrimental metabolic consequences seen in TIMP1-injected mice, such as systemic fatty acid overload, hepatic lipid accumulation and insulin resistanc
Antimicrobial Finish of Polyethersulfone Membranes: Sticking PhotosensitizersâLike Marine Mussels Would Do
Biofouling is one of the most serious problems in membrane filtration systems for water treatment. An easily applicable antimicrobial finish of polyethersulfone (PES) filter membranes is shown by derivatizing an approved chlorin photosensitizer drug with adhesive ortho-catechol functionalities as known from l-3,4-dihydroxyphenylalanin (Dopa) residues of marine mussel glues. The chemical structure of the second-generation photosensitizer 5,10,15,20-tetrakis(3-hydroxyphenyl)chlorin (m-THPC) is modified by 2-iodoxybenzoic acid (IBX) oxidation, transforming the peripheric meta-phenols of m-THPC into ortho-catechols, and thus improving the adsorption properties of m-THPC derivatives onto PES material. Stable coatings are formed that preserve chlorin's capability to generate singlet oxygen under visible light illumination. The modification of one or two phenol groups out of the four m-THPC substituents leads to an optimum in the generation of active singlet oxygen, and thus the finish significantly reduces the bacterial growth of gram-negative Escherichia coli and gram-positive Micrococcus luteus on the PES membranes.Deutsche Forschungsgemeinschaft
http://dx.doi.org/10.13039/501100001659Peer Reviewe
Electron-impact ionization of atomic hydrogen at 2 eV above threshold
The convergent close-coupling method is applied to the calculation of fully
differential cross sections for ionization of atomic hydrogen by 15.6 eV
electrons. We find that even at this low energy the method is able to yield
predictive results with small uncertainty. As a consequence we suspect that the
experimental normalization at this energy is approximately a factor of two too
high.Comment: 10 page
Semiclassical model for calculating fully differential ionization cross sections of the H molecule
Fully differential cross sections are calculated for the ionization of H
by fast charged projectiles using a semiclassical model developed previously
for the ionization of atoms. The method is tested in case of 4 keV electron and
6 MeV proton projectiles. The obtained results show good agreement with the
available experimental data. Interference effects due to the two-center
character of the target are also observed and analyzed.Comment: 11 pages, 4 figure
Maternal stress, child behavior and the promotive role of older siblings
Abstract Background: In the first years of their lives, children develop the cognitive, social and emotional skills that will provide the foundations for their lifelong health and achievements. To increase their life prospects and reduce the long-term effects of early aversive conditions, it is therefore crucial to understand the risk factors that negatively affect child development and the factors that are instead beneficial. In this study, we tested (i) the effects of different social and environmental stressors on maternal stress levels, (ii) the dynamic relationship between maternal stress and child behavior problems during development, and (iii) the potential promotive (i.e. main) or protective (i.e. buffering) effect of siblings on child behavior problems during development.Methods: We used longitudinal data from 373 motherâchild pairs (188 daughters, 185 sons) from pregnancy until 10 years of age. We assessed maternal stress and child behavior problems (internalizing and externalizing) with vali-dated questionnaires, and then used linear mixed models, generalized linear mixed models and longitudinal cross-lagged models to analyze the data.Results: Our results showed that higher maternal stress levels were predicted by socio-environmental stressors (i.e. the lack of sufficient social areas in the neighborhood). Moreover, prenatal maternal stress reliably predicted the occurrence of behavior problems during childhood. Finally, the presence of older siblings had a promotive function, by reducing the likelihood that children developed externalizing problems.Conclusions: Overall, our results confirm the negative effects that maternal stress during pregnancy may have on the offspring, and suggest an important main effect of older siblings in promoting a positive child development
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