97 research outputs found
Diagonalization of a bosonic quadratic form using CCM: Application on a system with two interpenetrating square lattice antiferromagnets
While the diagonalization of a quadratic bosonic form can always be done
using a Bogoliubov transformation, the practical implementation for systems
with a large number of different bosons is a tedious analytical task. Here we
use the coupled cluster method (CCM) to exactly diagonalise such complicated
quadratic forms. This yields to a straightforward algorithm which can easily be
implemented using computer algebra even for a large number of different bosons.
We apply this method on a Heisenberg system with two interpenetrating square
lattice antiferromagnets, which is a model for the quasi 2D antiferromagnet
Ba_2Cu_3O_4Cl_2. Using a four-magnon spin wave approximation we get a
complicated Hamiltonian with four different bosons, which is treated with CCM.
Results are presented for magnetic ground state correlations.Comment: 4 pages, 2 Postscript figures, to be published in acta physica
polonica A (European Conference 'Physics of Magnetism 99'
On the nodal structure of nonlinear stationary waves on star graphs
We consider stationary waves on nonlinear quantum star graphs, i.e., solutions to the stationary (cubic) nonlinear Schrödinger equation on a metric star graph with Kirchhoff matching conditions at the centre. We prove the existence of solutions that vanish at the centre of the star and classify them according to the nodal structure on each edge (i.e., the number of nodal domains or nodal points that the solution has on each edge). We discuss the relevance of these solutions in more applied settings as starting points for numerical calculations of spectral curves and put our results into the wider context of nodal counting, such as the classic Sturm oscillation theorem
How do microbiota associated with an invasive seaweed vary across scales?
Communities are shaped by scale dependent processes. To study the diversity and variation of microbial communities across scales, the invasive and widespread seaweed Agarophyton vermiculophyllum presents a unique opportunity. We characterized pro‐ and eukaryotic communities associated with this holobiont across its known distribution range, which stretches over the northern hemisphere. Our data reveal that community composition and diversity in the holobiont vary at local but also larger geographic scales. While processes acting at the local scale (i.e., within population) are the main structuring drivers of associated microbial communities, changes in community composition also depend on processes acting at larger geographic scales. Interestingly, the largest analysed scale (i.e., native and non‐native ranges) explained variation in the prevalence of predicted functional groups, which could suggest a functional shift in microbiota occurred over the course of the invasion process. While high variability in microbiota at the local scale supports A. vermiculophyllum to be a generalist host, we also identified a number of core taxa. These geographically independent holobiont members imply that cointroduction of specific microbiota may have additionally promoted the invasion process
Dirofilaria repens Infection and Concomitant Meningoencephalitis
Dirofilaria repens, a filarial nematode of dogs and other carnivores, can accidentally infect humans. Clinical symptoms are usually restricted to a subcutaneous nodule containing a single infertile parasite. Here, we report a case of D. repens infection with a subcutaneous gravid worm and the patient’s concomitant meningoencephalitis and aphasia
Mid-infrared GaSb-based resonant tunneling diode photodetectors for gas sensing applications
The authors are grateful for financial support by the BMBF via the national project HIRT (FKZ:13XP5003A).We present resonant tunneling diode-photodetectors (RTD-PDs) with GaAs0.15Sb0.85/AlAs0.1Sb0.9 double barrier structures combined with an additional quaternary Ga0.64In0.36As0.33Sb0.67 absorption layer covering the fingerprint absorption lines of various gases in the mid-infrared wavelength spectral region. The absorption layer cut-off wavelength is determined to be 3.5 µm and the RTD-PDs show peak-to-valley current ratios up to 4.3 with peak current densities of 12 A/cm-2.The incorporation of the quaternary absorption layer enables the RTD-PD to be sensitive to illumination with light up to the absorption lines of HCl at 3395 nm. At this wavelength, the detector shows a responsivity of 6.3 mA/W. At the absorption lines of CO2 and CO at 2004 nm and 2330 nm respectively, the RTD-PD reaches responsivities up to 0.97 A/W. Thus RTD-PDs pave the way towards high sensitive mid-infrared detectors that can be utilized in tunable laser absorption spectroscopy.PostprintPeer reviewe
3D capture, processing, display, and perception with digital holography: results from a European-funded project
“Digital holography for 3D and 4D real-world objects’ capture, processing,
and display” (acronym “Real 3D”) is a research project funded under the Information
and Communication Technologies theme of the European Commission’s Seventh Framework Programme, and brings together nine participants from academia and industry (see
www.digitalholography.eu). This three-year project contributes to a long-term effort to
facilitate the greater presence of digital holography in the three-dimensional capture and
display markets. At the end of its third year, the aims and results of the project are summarized
Substance P Saliva Reduction Predicts Pharyngeal Dysphagia in Parkinson's Disease
Introduction: Although patients with Parkinson's disease (PD) often suffer from oropharyngeal dysphagia, knowledge about the underlying pathophysiological mechanisms is limited. Substance P (SP) is a localization-independent neurotransmitter of the entire nervous system. Reduced levels of SP were found in saliva of patients with impaired cough reflex and in advanced stages of PD. The aim of the study was to investigate SP in PD patients in order to gain further insights into the underlying pathophysiology of PD-related dysphagia and to evaluate the potential of SP as a biomarker for early dysphagia.Methods: Flexible endoscopic evaluation of swallowing (FEES) was used to objectively assess pharyngeal swallowing function. From a cohort of 105 consecutive PD patients 20 subjects were recruited: in 10 of them pharyngeal dysphagia was excluded by FEES, the other 10 subjects showed signs of early pharyngeal dysphagia defined as hypopharyngeal sensory deficit with mild to moderate vallecular residues after swallowing solid consistencies. Analysis of the Substance P level in saliva of the 20 included PD patients was performed in the clinical on state condition by ELISA-type immunoassay. Significant differences were calculated by using the Mann-Whitney test.Results: Twenty PD patients with a mean age of 69.5 ± 12.5 years (8 female) were included in the study. No significant differences were found regarding gender, age, UPDRS III, Hoehn and Yahr stage, disease duration, and Levodopa equivalent dose between the non-dysphagic and dysphagic subjects. Dysphagia was mainly characterized by unrecognized residues in the valleculae without any aspiration risk for all of the tested consistencies in FEES and was thereby scored as mild in all cases. Saliva SP concentrations were significantly lower in PD patients with pharyngeal dysphagia compared to those with a normal pharyngeal swallowing function (9,644 vs. 17,591 pg/mL; p = 0.001).Conclusion: Reduced saliva SP concentrations may predict early pharyngeal swallowing dysfunction in PD patients. This finding supports the hypothesis that an impaired SP mediated neurotransmission has a significant impact for the development of dysphagia in PD patients. Larger studies are needed to confirm SP as a clinical useful biomarker for early detection of PD-related dysphagia
Resource Partitioning between Bacteria, Fungi, and Protists in the Detritusphere of an Agricultural Soil
The flow of plant-derived carbon in soil is a key component of global carbon cycling. Conceptual models of trophic carbon fluxes in soil have assumed separate bacterial and fungal energy channels in the detritusphere, controlled by both substrate complexity and recalcitrance. However, detailed understanding of the key populations involved and niche-partitioning between them is limited. Here, a microcosm experiment was performed to trace the flow of detritusphere C from substrate analogs (glucose, cellulose) and plant biomass amendments (maize leaves, roots) in an agricultural soil. Carbon flow was traced by rRNA stable isotope probing and amplicon sequencing across three microbial kingdoms. Distinct lineages within the Actinobacteria, Bacteroidetes, Gammaproteobacteria, Basidiomycota, Ascomycota as well as Peronosporomycetes were identified as important primary substrate consumers. A dynamic succession of primary consumers was observed especially in the cellulose treatments, but also in plant amendments over time. While intra-kingdom niche partitioning was clearly observed, distinct bacterial and fungal energy channels were not apparent. Furthermore, while the diversity of primary substrate consumers did not notably increase with substrate complexity, consumer succession and secondary trophic links to bacterivorous and fungivorous microbes resulted in increased food web complexity in the more recalcitrant substrates. This suggests that rather than substrate-defined energy channels, consumer succession as well as intra- and inter-kingdom cross-feeding should be considered as mechanisms supporting food web complexity in the detritusphere
Social Value Orientation, Expectations, and Cooperation in Social Dilemmas:A Meta-analysis
Interdependent situations are pervasive in human life. In these situations, it is essential to form expectations
about the others’ behaviour to adapt one’s own behaviour to increase mutual outcomes and avoid exploitation. Social
value orientation, which describes the dispositional weights individuals attach to their own and to another person’s
outcome, predicts these expectations of cooperation in social dilemmas—an interdependent situation involving a
conflict of interests. Yet, scientific evidence is inconclusive about the exact differences in expectations between
prosocials, individualists, and competitors. The present meta-analytic results show that, relative to proselfs (individualists
and competitors), prosocials expect more cooperation from others in social dilemmas, whereas individualists
and competitors do not significantly differ in their expectations. The importance of these expectations in the decision
process is further highlighted by the finding that they partially mediate the well-established relation between social
value orientation and cooperative behaviour in social dilemmas. In fact, even proselfs are more likely to cooperate
when they expect their partner to cooperate
- …