305 research outputs found
Between Poisson and GUE statistics: Role of the Breit-Wigner width
We consider the spectral statistics of the superposition of a random diagonal
matrix and a GUE matrix. By means of two alternative superanalytic approaches,
the coset method and the graded eigenvalue method, we derive the two-level
correlation function and the number variance . The graded
eigenvalue approach leads to an expression for which is valid for all
values of the parameter governing the strength of the GUE admixture
on the unfolded scale. A new twofold integration representation is found which
can be easily evaluated numerically. For the Breit-Wigner width
measured in units of the mean level spacing is much larger than
unity. In this limit, closed analytical expression for and
can be derived by (i) evaluating the double integral
perturbatively or (ii) an ab initio perturbative calculation employing the
coset method. The instructive comparison between both approaches reveals that
random fluctuations of manifest themselves in modifications of the
spectral statistics. The energy scale which determines the deviation of the
statistical properties from GUE behavior is given by . This is
rigorously shown and discussed in great detail. The Breit-Wigner
width itself governs the approach to the Poisson limit for . Our
analytical findings are confirmed by numerical simulations of an ensemble of
matrices, which demonstrate the universal validity of our
results after proper unfolding.Comment: 25 pages, revtex, 5 figures, Postscript file also available at
http://germania.ups-tlse.fr/frah
Occupant-oriented demand response with multi-zone thermal building control
In future energy systems with high shares of renewable energy sources, the electricity demand of buildings has to react to the fluctuating electricity generation in view of stability. As buildings consume one-third of global energy and almost half of this energy accounts for Heating, Ventilation, and Air Conditioning (HVAC) systems, HVAC are suitable for shifting their electricity consumption in time. To this end, intelligent control strategies are necessary as the conventional control of HVAC is not optimized for the actual demand of occupants and the current situation in the electricity grid. In this paper, we present the novel multi-zone controller Price Storage Control (PSC) that not only considers room-individual Occupantsâ Thermal Satisfaction (OTS), but also the available energy storage, and energy prices. The main feature of PSC is that it does not need a building model or forecasts of future demands to derive the control actions for multiple rooms in a building. For comparison, we use an ideal, error-free Model Predictive Control (MPC), a heuristic control approach from the literature (PC), and a conventional hysteresis-based two-point control as upper and lower benchmarks. We evaluate the four controllers in a multi-zone environment for heating a building in winter and consider two different scenarios that differ in how much the permitted temperatures vary. In addition, we compare the impact of model parameters with high and low thermal capacitance. The results show that PSC strongly outperforms the conventional control approach and PC in both scenarios and for both parameters concerning the electricity costs and OTS. For high capacitance, it leads to 22 % costs reduction while the ideal MPC achieves cost reductions of more than 39 %. Considering that PSC does not need any building model or forecast, as opposed to MPC, the results support the suitability of our developed control strategy for controlling HVAC systems in future energy systems
Occupant-Oriented Demand Response with Room-Individual Building Control
In future energy systems with high shares of renewable energy sources, the
electricity demand of buildings has to react to the fluctuating electricity
generation in view of stability. As buildings consume one-third of global
energy and almost half of this energy accounts for Heating, Ventilation, and
Air Conditioning (HVAC) systems, HVAC are suitable for shifting their
electricity consumption in time. To this end, intelligent control strategies
are necessary as the conventional control of HVAC is not optimized for the
actual demand of occupants and the current situation in the electricity grid.
In this paper, we present the novel multi-zone controller Price Storage Control
(PSC) that not only considers room-individual Occupants' Thermal Satisfaction
(OTS), but also the available energy storage, and energy prices. The main
feature of PSC is that it does not need a building model or forecasts of future
demands to derive the control actions for multiple rooms in a building. For
comparison, we use an ideal, error-free Model Predictive Control (MPC), a
simplified variant without storage consideration (PC), and a conventional
hysteresis-based two-point control. We evaluate the four controllers in a
multi-zone environment for heating a building in winter and consider two
different scenarios that differ in how much the permitted temperatures vary. In
addition, we compare the impact of model parameters with high and low thermal
capacitance. The results show that PSC strongly outperforms the conventional
control approach in both scenarios and for both parameters. For high
capacitance, it leads to 22 % costs reduction while the ideal MPC achieves cost
reductions of more than 39 %. Considering that PSC does not need any building
model or forecast, as opposed to MPC, the results support the suitability of
our developed control strategy for controlling HVAC systems in future energy
systems.Comment: Paper revisio
The Microbiota Profile in Inflamed and Non-Inflamed Ileal Pouch-Anal Anastomosis
The objective was to determine the bacterial composition in inflamed and non-inflamed pouches for comparison to the microbiota of healthy individuals. Pouch patients and healthy individuals were included between November 2017 and June 2019 at the Department of Gastrointestinal Surgery, Aalborg University Hospital, Denmark. A faecal sample was collected from all participants for microbiota analysis using 16S rRNA amplicon sequencing. Overall, 38 participants were included in the study. Eleven patients with a normally functioning pouch, 9 patients with chronic pouchitis, 6 patients with familial adenomatous polyposis, and 12 healthy individuals. Patients with chronic pouchitis had overall lower microbial diversity and richness compared to patients with a normal pouch function (p < 0.001 and p = 0.009) and healthy individuals (p < 0.001 and p < 0.001). No significant difference was found between patients with familial adenomatous polyposis and chronic pouchitis (microbial diversity p = 0.39 and richness p = 0.78). Several taxa from the family Enterobacteriaceae, especially genus Escherichia, were associated primarily with patients with chronic pouchitis, while taxa from the genus Bacteroides primarily were associated with healthy individuals and patients with a normally functioning pouch. Finally, a microbial composition gradient could be established from healthy individuals through patients with normal pouch function and familial adenomatous polyposis to patients with chronic pouchitis
Expression of human AID in yeast induces mutations in context similar to the context of somatic hypermutation at G-C pairs in immunoglobulin genes
BACKGROUND: Antibody genes are diversified by somatic hypermutation (SHM), gene conversion and class-switch recombination. All three processes are initiated by the activation-induced deaminase (AID). According to a DNA deamination model of SHM, AID converts cytosine to uracil in DNA sequences. The initial deamination of cytosine leads to mutation and recombination in pathways involving replication, DNA mismatch repair and possibly base excision repair. The DNA sequence context of mutation hotspots at G-C pairs during SHM is DGYW/WRCH (G-C is a hotspot position, R = A/G, Y = T/C, W = A/T, D = A/G/T). RESULTS: To investigate the mechanisms of AID-induced mutagenesis in a model system, we studied the genetic consequences of AID expression in yeast. We constructed a yeast vector with an artificially synthesized human AID gene insert using codons common to highly expressed yeast genes. We found that expression of the artificial hAIDSc gene was moderately mutagenic in a wild-type strain and highly mutagenic in an ung1 uracil-DNA glycosylase-deficient strain. A majority of mutations were at G-C pairs. In the ung1 strain, C-G to T-A transitions were found almost exclusively, while a mixture of transitions with 12% transversions was characteristic in the wild-type strain. In the ung1 strain mutations that could have originated from deamination of the transcribed stand were found more frequently. In the wild-type strain, the strand bias was reversed. DGYW/WRCH motifs were preferential sites of mutations. CONCLUSION: The results are consistent with the hypothesis that AID-mediated deamination of DNA is a major cause of mutations at G-C base pairs in immunoglobulin genes during SHM. The sequence contexts of mutations in yeast induced by AID and those of somatic mutations at G-C pairs in immunoglobulin genes are significantly similar. This indicates that the intrinsic substrate specificity of AID itself is a primary determinant of mutational hotspots at G-C base pairs during SHM
Case Report: Plasticity in Central Sensory Finger Representation and Touch Perception After Microsurgical Reconstruction of Infraclavicular Brachial Plexus Injury
After brachial plexus injury (BPI), early microsurgery aims at facilitating reconnection of the severed peripheral nerves with their orphan muscles and sensory receptors and thereby reestablishing communication with the brain. In order to investigate this sensory recovery, here we combined functional magnetic resonance imaging (fMRI) and tactile psychophysics in a patient who suffered a sharp, incomplete amputation of the dominant hand at the axilla level. To determine somatosensory detection and discomfort thresholds as well as sensory accuracy for fingers of both the intact and affected hand, we used electrotactile stimulation in the framework of a mislocalization test. Additionally, tactile stimulation was performed in the MRI scanner in order to determine the cortical organization of the possibly affected primary somatosensory cortex. The patient was able to detect electrotactile stimulation in 4 of the 5 fingertips (D1, D2, D4, D5), and in the middle phalanx in D3 indicating some innervation. The detection and discomfort threshold were considerably higher at the affected side than at the intact side, with higher detection and discomfort thresholds for the affected side. The discrimination accuracy was rather low at the affected side, with stimulation of D1/D2/D3/D4/D5 eliciting most commonly a sensation at D4/D1/D3/D2/D5, respectively. The neuroimaging data showed a mediolateral succession from D2 to D5 to D1 to D4 (no activation was observed for D3). These results indicate a successful regrowth of the peripheral nerve fibers from the axilla to four fingertips. The data suggest that some of the fibers have switched location in the process and there is a beginning of cortical reorganization in the primary somatosensory cortex, possibly resulting from a re-education of the brain due to conflicting information (touch vs. vision)
Classical Spin Clusters: Integrability and Dynamical Properties
A pair of exchangeâcoupled classical spins with biaxial exchange and singleâsite anisotropy represents a Hamiltonian system with two degrees of freedom for which the integrability question is nontrivial. We have found that such a system is completely integrable if the model parameters satisfy a certain condition. For the integrable cases, the second integral of the motion (in addition to the Hamiltonian), which guarantees integrability, is determined explicitly. It can be reconstructed numerically by means of time averages of dynamical variables over all trajectories. In the nonintegrable cases, the existence of the time averages is still guaranteed, but they no longer define an analytic invariant, and their determination is subject to longâtime anomalies. Our numerical calculation of time averages for two lines of initial conditions reveals a number of interesting features of such nonanalytic invariants
Induced pluripotent stem cells and cerebral organoids from the critically endangered Sumatran rhinoceros
Less than 80 Sumatran rhinos (SR, Dicerorhinus sumatrensis) are left on earth. Habitat loss and limited breeding possibilities are the greatest threats to the species and lead to a continuous population decline. To stop the erosion of genetic diversity, reintroduction of genetic material is indispensable. However, as the propagation rate of captive breeding is far too low, innovative technologies have to be developed. Induced pluripotent stem cells (iPSCs) are a powerful tool to fight extinction. They give rise to each cell within the body including gametes and provide a unique modality to preserve genetic material across time. Additionally, they enable studying species-specific developmental processes.
Here, we generate iPSCs from the last male Malaysian SR Kertam, who died in 2019, and characterize them comprehensively. Differentiation in cells of the three germ layers and cerebral organoids demonstrate their high quality and great potential for supporting the rescue of this critically endangered species
New Types of Off-Diagonal Long Range Order in Spin-Chains
We discuss new possibilities for Off-Diagonal Long Range Order (ODLRO) in
spin chains involving operators which add or delete sites from the chain. For
the Heisenberg and Inverse Square Exchange models we give strong numerical
evidence for the hidden ODLRO conjectured by Anderson \cite{pwa_conj}. We find
a similar ODLRO for the XY model (or equivalently for free fermions in one
spatial dimension) which we can demonstrate rigorously, as well as numerically.
A connection to the singlet pair correlations in one dimensional models of
interacting electrons is made and briefly discussed.Comment: 13 pages, Revtex v3.0, 2 PostScript figures include
Nucleation and Growth of the Superconducting Phase in the Presence of a Current
We study the localized stationary solutions of the one-dimensional
time-dependent Ginzburg-Landau equations in the presence of a current. These
threshold perturbations separate undercritical perturbations which return to
the normal phase from overcritical perturbations which lead to the
superconducting phase. Careful numerical work in the small-current limit shows
that the amplitude of these solutions is exponentially small in the current; we
provide an approximate analysis which captures this behavior. As the current is
increased toward the stall current J*, the width of these solutions diverges
resulting in widely separated normal-superconducting interfaces. We map out
numerically the dependence of J* on u (a parameter characterizing the material)
and use asymptotic analysis to derive the behaviors for large u (J* ~ u^-1/4)
and small u (J -> J_c, the critical deparing current), which agree with the
numerical work in these regimes. For currents other than J* the interface
moves, and in this case we study the interface velocity as a function of u and
J. We find that the velocities are bounded both as J -> 0 and as J -> J_c,
contrary to previous claims.Comment: 13 pages, 10 figures, Revte
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