Effect of intraband Coulomb repulsion on the excitonic spin-density wave

We present a study of the magnetic ground state of a two-band model with nested electron and hole Fermi surfaces and both interband and intraband Coulomb interactions. Our aim is to understand how the excitonic spin-density-wave (ESDW) state induced by the interband Coulomb repulsion is affected by the intraband interactions. We first determine the magnetic instabilities of our model in an unbiased way by employing the random-phase approximation (RPA) to calculate the static spin susceptibility in the paramagnetic state. From this, we construct the mean-field phase diagram, demonstrating the robustness of the ESDW against the intraband interaction. We then calculate the RPA transverse spin susceptibility in the ESDW state and show that the intraband Coulomb repulsion significantly renormalizes the paramagnon line shape and suppresses the spin-wave velocity. We conclude with a discussion of the relevance of this suppression for the commensurate ESDW state of Mn-doped Cr alloys.Comment: 8 pages, 6 figure

Performance, digestive disorders and the intestinal microbiota in weaning rabbits are affected by a herbal feed additive

[EN] A herbal feed additive (Digestarom(R), containing a mixture of onion, garlic, caraway, fennel, gentian, melissa, peppermint, anise, oak bark and clove) was fed to rabbit does and kits to study its impact on performance, post-weaning digestive disorders and intestinal microbiota. Two groups of 9 doe rabbits and their offspring, after weaning, were fed a standard diet without or with the addition of 300 mg Digestarom(R)/kg diet. Forty kits from each group were weaned at 28 d of age weighing 0.614±0.005 kg. They were caged in groups of four rabbits (10 cages/treatment) and fed the same diet as their mothers for 13 d. Weight gain and feed intake of the kits fed Digestarom(R) was 18 and 14% higher, respectively, than those fed control diet (P<0.001), with no differences in the feed conversion. Rabbits were killed 13 d after weaning and 10 healthy animals from the Digestarom(R) group and 10 healthy and 10 diseased animals from the control group were dissected. Healthy rabbits fed control diet and those fed Digestarom(R) showed closer intestinal digesta dry matter, pH and volatile fatty acid (VFA) profi les, compared to diseased animals. VFA concentration in the small intestine was higher (P=0.030) in the diseased animals of the control group compared with the healthy and Digestarom(R) fed rabbits. However, no differences were observed in VFA concentration in stomach or caecum contents. The fermentation profi le of diseased animals was characterised by a higher proportion of propionic, i- and n-valeric acids in the caecal contents (P<0.001), and an increased i-butyric acid concentration in the stomach and caecum contents (P=0.014), whereas n-butyric acid was reduced (P<0.033) compared with the healthy or Digestarom(R) fed rabbits. Denaturing gradient gel electrophoresis indicated a higher caecal bacterial diversity in the control rabbits compared with kits fed Digestarom(R) (P=0.008). The reduced evenness factor (P<0.010) also indicated that the bacterial composition included more dominant species in the Digestarom(R) group. Under our experimental conditions, the tested herbal feed additive Digestarom(R) had protective effects in rabbit kits after weaning, making it an interesting alternative for establishing nutritional strategies.Krieg, R.; Vahjen, W.; Awad, W.; Sysel, M.; Kroeger, S.; Zocher, E.; Hulan, H.... (2009). Performance, digestive disorders and the intestinal microbiota in weaning rabbits are affected by a herbal feed additive. World Rabbit Science. 17(2):87-95. doi:10.4995/wrs.2009.662879517

De novo DNA methylation controls neuronal maturation during adult hippocampal neurogenesis

Adult neurogenesis enables the life-long addition of functional neurons to the hippocampus and is regulated by both cell-intrinsic molecular programs and behavioral activity. De novo DNA methylation is crucial for embryonic brain development, but its role during adult hippocampal neurogenesis has remained unknown. Here, we show that de novo DNA methylation is critical for maturation and functional integration of adult-born neurons in the mouse hippocampus. Bisulfite sequencing revealed that de novo DNA methyltransferases target neuronal enhancers and gene bodies during adult hippocampal neural stem cell differentiation, to establish neuronal methylomes and facilitate transcriptional up-regulation of neuronal genes. Inducible deletion of both de novo DNA methyltransferases Dnmt3a and Dnmt3b in adult neural stem cells did not affect proliferation or fate specification, but specifically impaired dendritic outgrowth and synaptogenesis of newborn neurons, thereby hampering their functional maturation. Consequently, abolishing de novo DNA methylation modulated activation patterns in the hippocampal circuitry and caused specific deficits in hippocampus-dependent learning and memory. Our results demonstrate that proper establishment of neuronal methylomes during adult neurogenesis is fundamental for hippocampal function

Spin-Rotation Symmetry Breaking in the Superconducting State of CuxBi2Se3

Spontaneous symmetry breaking is an important concept for understanding physics ranging from the elementary particles to states of matter. For example, the superconducting state breaks global gauge symmetry, and unconventional superconductors can break additional symmetries. In particular, spin rotational symmetry is expected to be broken in spin-triplet superconductors. However, experimental evidence for such symmetry breaking has not been conclusively obtained so far in any candidate compounds. Here, by 77Se nuclear magnetic resonance measurements, we show that spin rotation symmetry is spontaneously broken in the hexagonal plane of the electron-doped topological insulator Cu0.3Bi2Se3 below the superconducting transition temperature Tc=3.4 K. Our results not only establish spin-triplet superconductivity in this compound, but may also serve to lay a foundation for the research of topological superconductivity

Parity Breaking in Nematic Tactoids

We theoretically investigate under what conditions the director field in a spindle-shaped nematic droplet or tactoid obtains a twisted, parity-broken structure. By minimizing the sum of the bulk elastic and surface energies, we show that a twisted director field is stable if the twist and bend elastic constants are small enough compared to the splay elastic constant, but only if the droplet volume is larger than some minimum value. We furthermore show that the transition from an untwisted to a twisted director-field structure is a sharp function of the various control parameters. We predict that suspensions of rigid, rod-like particles cannot support droplets with a parity broken structure, whereas they could possibly occur in those of semi-flexible, worm-like particles.Comment: 20 pages, 9 figures, submitted to Journal of Physics: Condensed Matte

Facilities for macromolecular crystallography at the Helmholtz Zentrum Berlin

Three macromolecular crystallography MX beamlines at the Helmholtz Zentrum Berlin HZB are available for the regional, national and international structural biology user community. The state of the art synchrotron beamlines for MX BL14.1, BL14.2 and BL14.3 are located within the low section of the BESSY II electron storage ring. All beamlines are fed from a superconducting 7 T wavelength shifter insertion device. BL14.1 and BL14.2 are energy tunable in the range 5 16 keV, while BL14.3 is a fixed energy side station operated at 13.8 keV. All three beamlines are equipped with CCD detectors. BL14.1 and BL14.2 are in regular user operation providing about 200 beam days per year and about 600 user shifts to approximately 50 research groups across Europe. BL14.3 has initially been used as a test facility and was brought into regular user mode operation during the year 2010. BL14.1 has recently been upgraded with a microdiffractometer including a mini k goniometer and an automated sample changer. Additional user facilities include office space adjacent to the beamlines, a sample preparation laboratory, a biology laboratory safety level 1 and high end computing resources. In this article the instrumentation of the beamlines is described, and a summary of the experimental possibilities of the beamlines and the provided ancillary equipment for the user community is give

Exploring the Effect of Structure-Based Scaffold Hopping on the Inhibition of Coxsackievirus A24v Transduction by Pentavalent N-Acetylneuraminic Acid Conjugates

Coxsackievirus A24 variant (CVA24v) is the primary causative agent of the highly contagious eye infection designated acute hemorrhagic conjunctivitis (AHC). It is solely responsible for two pandemics and several recurring outbreaks of the disease over the last decades, thus affecting millions of individuals throughout the world. To date, no antiviral agents or vaccines are available for combating this disease, and treatment is mainly supportive. CVA24v utilizes Neu5Ac-containing glycans as attachment receptors facilitating entry into host cells. We have previously reported that pentavalent Neu5Ac conjugates based on a glucose-scaffold inhibit CVA24v infection of human corneal epithelial cells. In this study, we report on the design and synthesis of scaffold-replaced pentavalent Neu5Ac conjugates and their effect on CVA24v cell transduction and the use of cryogenic electron microscopy (cryo-EM) to study the binding of these multivalent conjugates to CVA24v. The results presented here provide insights into the development of Neu5Ac-based inhibitors of CVA24v and, most significantly, the first application of cryo-EM to study the binding of a multivalent ligand to a lectin

Husserl’s covert critique of Kant in the sixth book of Logical Investigations

In the final book of Logical Investigations from 1901, Husserl develops a theory of knowledge based on the intentional structure of consciousness. While there is some textual evidence that Husserl considered this to entail a critique of Kantian philosophy, he did not elaborate substantially on this. This paper reconstructs the covert critique of Kant’s theory of knowledge which LI contains. With respect to Kant, I discuss three core aspects of his theory of knowledge which, as Husserl’s reflections on Kant indicate, Husserl was familiar with. These are (i) the cooperation of two faculties for the justification of beliefs; (ii) the concept of a priori structures of knowledge Kant operated with; and (iii) the delivered transcendental proof of these structures. Regarding Logical Investigations, I first briefly outline the intentional structure of consciousness as presented in the fifth book and then turn to the theory of knowledge in the sixth book. I then clarify, partially on the basis of manuscripts and lecture notes, the covert critique of the three core aspects of Kant’s theory which the sixth book contains