Optical Manipulation of Bipolarons in a System with Nonlinear Electron-Phonon Coupling.

We investigate full quantum mechanical evolution of two electrons nonlinearly coupled to quantum phonons and simulate the dynamical response of the system subject to a short spatially uniform optical pulse that couples to dipole-active vibrational modes. Nonlinear electron-phonon coupling can either soften or stiffen the phonon frequency in the presence of electron density. In the former case, an external optical pulse tuned just below the phonon frequency generates attraction between electrons and leads to a long-lived bound state even after the optical pulse is switched off. It originates from a dynamical modification of the self-trapping potential that induces a metastable state. By increasing the pulse frequency, the attractive electron-electron interaction changes to repulsive. Two sequential optical pulses with different frequencies can switch between attractive and repulsive interaction. Finally, we show that the pulse-induced binding of electrons is shown to be efficient also for weakly dispersive optical phonons, in the presence anharmonic phonon spectrum and in two dimensions.

Transition to the Haldane phase driven by electron-electron correlations.

One of the most famous quantum systems with topological properties, the spin [Formula: see text] antiferromagnetic Heisenberg chain, is well-known to display exotic [Formula: see text] edge states. However, this spin model has not been analyzed from the more general perspective of strongly correlated systems varying the electron-electron interaction strength. Here, we report the investigation of the emergence of the Haldane edge in a system of interacting electrons - the two-orbital Hubbard model-with increasing repulsion strength U and Hund interaction JH. We show that interactions not only form the magnetic moments but also form a topologically nontrivial fermionic many-body ground-state with zero-energy edge states. Specifically, upon increasing the strength of the Hubbard repulsion and Hund exchange, we identify a sharp transition point separating topologically trivial and nontrivial ground-states. Surprisingly, such a behaviour appears already at rather small values of the interaction, in a regime where the magnetic moments are barely developed.

Restoring Ergodicity in a Strongly Disordered Interacting Chain.

We consider a chain of interacting fermions with random disorder that was intensively studied in the context of many-body localization. We show that only a small fraction of the two-body interaction represents a true local perturbation to the Anderson insulator. While this true perturbation is nonzero at any finite disorder strength W, it decreases with increasing W. This establishes a view that the strongly disordered system should be viewed as a weakly perturbed integrable model, i.e., a weakly perturbed Anderson insulator. As a consequence, the latter can hardly be distinguished from a strictly integrable system in finite-size calculations at large W. We then introduce a rescaled model in which the true perturbation is of the same order of magnitude as the other terms of the Hamiltonian, and show that the system remains ergodic at arbitrary large disorder.

Interaction-induced topological phase transition and Majorana edge states in low-dimensional orbital-selective Mott insulators.

Topological phases of matter are among the most intriguing research directions in Condensed Matter Physics. It is known that superconductivity induced on a topological insulator's surface can lead to exotic Majorana modes, the main ingredient of many proposed quantum computation schemes. In this context, the iron-based high critical temperature superconductors are a promising platform to host such an exotic phenomenon in real condensed-matter compounds. The Coulomb interaction is commonly believed to be vital for the magnetic and superconducting properties of these systems. This work bridges these two perspectives and shows that the Coulomb interaction can also drive a canonical superconductor with orbital degrees of freedom into the topological state. Namely, we show that above a critical value of the Hubbard interaction the system simultaneously develops spiral spin order, a highly unusual triplet amplitude in superconductivity, and, remarkably, Majorana fermions at the edges of the system.

Effects of Osteopathic Manual Therapy on Hyperinflation in Patients with Chronic Obstructive Pulmonary Disease: A Randomized Cross-Over Study.

Osteopathic manual therapy (OMT) may reduce hyperinflation in patients with chronic obstructive pulmonary disease (COPD) by improving breathing mechanics. The aim of the study was to evaluate the immediate effects of OMT on hyperinflation in stable COPD patients with forced expired volume in 1 s (FEV1) <50% predicted. Nineteen COPD patients of the median age 68 (IQR 63-72) years and the median FEV1 39.8 (IQR 33.4-46.6) % predicted were enrolled into the study. For the first session, patients were randomly assigned to either OMT or sham therapy. During the second session, the two groups of patients were crossed over. Pulmonary function and dyspnea were compared before and after both procedures. Neither pulmonary function nor dyspnea differed significantly before and after OMT or sham procedures. However, 36.7% and 47.4% patients achieved the minimally important difference for residual volume (RV) reduction after both OMT and sham therapy, respectively. Responders to OMT had a greater median (IQR) baseline sense of dyspnea compared to non-responders, assessed on a visual analog scale, of 7.0 (4.5-7.0) vs. 3.0 (0.0-5.0), p = 0.040, respectively. Although OMT did not have an immediate effect on hyperinflation or dyspnea, a subgroup experienced a reduction in RV following OMT and sham therapy. Future studies are needed to identify the characteristics of responders.

Einstein Relation for a Driven Disordered Quantum Chain in the Subdiffusive Regime.

A quantum particle propagates subdiffusively on a strongly disordered chain when it is coupled to itinerant hard-core bosons. We establish a generalized Einstein relation (GER) that relates such subdiffusive spread to an unusual time-dependent drift velocity, which appears as a consequence of a constant electric field. We show that GER remains valid much beyond the regime of the linear response. Qualitatively, it holds true up to strongest drivings when the nonlinear field effects lead to the Stark-like localization. Numerical calculations based on full quantum evolution are substantiated by much simpler rate equations for the boson-assisted transitions between localized Anderson states.

Eigenvalue statistics of reduced density matrix during driving and relaxation.

We study a subsystem of an isolated one-dimensional correlated metal when it is driven by a steady electric field or when it relaxes after driving. We obtain numerically exact reduced density matrix ρ for subsystems which are sufficiently large to give significant eigenvalue statistics and spectra of log(ρ). We show that both for generic as well as for the integrable model, the statistics follows the universality of Gaussian unitary and orthogonal ensembles for driven and equilibrium systems, respectively. Moreover, the spectra of modestly driven subsystems are well described by the Gibbs thermal distribution with the entropy determined by the time-dependent energy only.

Nonequilibrium propagation and decay of a bound pair in driven t-J models.

We perform an accurate time-dependent numerical study of an out-of-equilibrium response of a bound state within t-J systems on a two-leg ladder and a square lattice. We show that the bound hole pair decays with the onset of finite steady current if both mechanisms for binding and the dissipation share matching degrees of freedom. Moreover, by investigating the mechanism of decay on the square lattice we find that the dynamics is governed by the decay in the direction perpendicular to the electric field, leading to much shorter decay times in comparison to the ladder where such dynamics is topologically restricted.

Nonequilibrium quantum dynamics of a charge carrier doped into a Mott insulator.

We study real-time dynamics of a charge carrier introduced into an undoped Mott insulator propagating under a constant electric field F on the t-J ladder and a square lattice. We calculate the quasistationary current. In both systems an adiabatic regime is observed followed by a positive differential resistivity (PDR) at moderate fields where the carrier mobility is determined. Quantitative differences between the ladder and two-dimensional (2D) systems emerge when at large fields both systems enter the negative differential resistivity (NDR) regime. In the ladder system Bloch-like oscillations prevail, while in two dimensions the current remains finite, proportional to 1/F. The crossover between the PDR and NDR in two dimensions is accompanied by a change of the spatial structure of the propagating spin polaron.

Current in Hubbard rings manipulated via magnetic flux.

We study currents in a quantum ring threaded by a magnetic flux which is varied in an arbitrary way from an initial constant value φ(1) at time t(1) to a final constant value φ(2) at time t(2). We analyze how the induced currents for t > t(2) can be controlled by the rate of flux variation [Formula: see text]. The dynamics of electrons in the ring is described using the Hubbard and the extended Hubbard models. In the Hubbard model with infinite on-site repulsion the current for t > t(2) is shown to be independent of the flux variation before t(2) and is fully determined by a solution of the initial equilibrium problem and by the value φ(2) of the flux. For intermediate values of the interaction strength the current displays regular or irregular time oscillations and the amplitude of oscillations is sensitive to the rate of the flux changing [Formula: see text]: slow changes of the flux result in small amplitudes of the current oscillations and vice versa. We demonstrate that the time dependence of the induced current bears information on electronic correlations. Our results have important implications for not only mesoscopic rings but also the designing of quantum motors built out of ring-shaped optical lattices.

Ising t-J model close to half filling: a Monte Carlo study.

Within the recently proposed doped-carrier representation of the projected lattice electron operators we derive a full Ising version of the t-J model. This model possesses the global discrete Z(2) symmetry as a maximal spin symmetry of the Hamiltonian at any values of the coupling constants, t and J. In contrast, in the spin anisotropic limit of the t-J model, usually referred to as the t-J(z) model, the global SU(2) invariance is fully restored at J(z) = 0, so that only the spin-spin interaction has in this model the true Ising form. We discuss a relationship between these two models and the standard isotropic t-J model. We show that the low-energy quasiparticles in all three models share qualitatively similar properties at low doping and small values of J/t. The main advantage of the proposed Ising t-J model over the t-J(z) one is that the former allows for the unbiased Monte Carlo calculations on large clusters of up to 10(3) sites. Within this model we discuss in detail the destruction of the antiferromagnetic (AF) order by doping as well as the interplay between the AF order and hole mobility. We also discuss the effect of the exchange interaction and that of the next-nearest-neighbour hoppings on the destruction of the AF order at finite doping. We show that the short-range AF order is observed in a wide range of temperatures and dopings, much beyond the boundaries of the AF phase. We explicitly demonstrate that the local no-double-occupancy constraint plays the dominant role in destroying the magnetic order at finite doping. Finally, a role of inhomogeneities is discussed.

Dynamical bimodality in equilibrium monostable systems.

General features of the stochastic dynamics of classical systems approaching a thermodynamic equilibrium Gibbs state are studied via the numerical analysis of time-dependent solutions of the Fokker-Planck equation for an overdamped particle in various monostable potentials. A large class of initial states can dynamically bifurcate during its time evolution into bimodal transient states, which in turn wear off when approaching the long-time regime. Suitable quantifiers characterizing this transient dynamical bimodality, such as its lifetime, the positions of maxima, and the time-dependent well depth of the probability distribution, are analyzed. Some potential applications are pointed out that make use of this interesting principle which is based on an appropriately chosen initial preparation procedure.

Breast cancer predisposing alleles in Poland.

Mutant alleles of several genes in the DNA repair pathway have been found to predispose women to breast cancer. From a public health perspective, the importance of a given allele in a population is determined by the frequency of the allele and by the relative risk of breast cancer that it confers. In Poland founder alleles of the BRCA1, CHEK2 and NBS1 genes have been associated with an increased risk of breast cancer, but the relative contribution of each of these alleles to the overall breast cancer burden has not yet been determined. We screened 2012 unselected cases of breast cancer and 4000 population controls for 7 different mutations in these genes. Overall, a mutation was found in 12% of the cases and in 6% of the controls. Mutations in BRCA1 and CHEK2 contributed in approximately equal measure to the burden of breast cancer in Poland. A BRCA1 mutation was present in 3% of the cases. The missense BRCA1 mutation C61G was associated with a higher odds ratio for breast cancer (OR=15) than were either of the truncating BRCA1 mutations 4153delA (OR=2.0) and 5382insC (OR=6.2). In contrast, a higher odds ratio was seen for truncating CHEK2 mutations (OR=2.1) than for the missense mutation I157T (OR=1.4). This study suggests that cancer risks may be specific for particular alleles of a susceptibility gene and that these different risks should be taken into account by genetic counselors.

NOD2 variants and the risk of malignant melanoma.

Both hereditary and environmental factors are important in the aetiology of malignant melanoma. Among the risk factors for malignant melanoma are immunodeficiency and immunosuppression. The recently identified NOD2 gene is involved in the regulation of immune function through activation of the transcription factor nuclear factor-kappaB (NF-kappaB). Three common NOD2 mutations -- 3020insC, G908R and R702W -- have been shown to be associated with chronic inflammatory disease such as Crohn's disease, the 3020insC also with human malignancy colorectal cancer. We examined the frequency of the NOD2 variants in 424 patients with malignant melanoma and 649 controls. The 3020insC mutation was present in 6.9% of unselected cases and 7% of the controls (odds ratio (OR) 1.0; P not significant). The mutation was present in 6.8% of 162 cases diagnosed under the age of 50 and in 7.1% of cases diagnosed after the age of 50. A mutation was present in the index case in 5% of 40 familial melanomas (OR 0.7; P not significant). There were no statistically significant differences between prevalence of G908R and R702W in malignant melanoma patients and controls. In conclusion, the three common NOD2 mutations are not associated with increased risk of development of malignant melanoma.

CHEK2 is a multiorgan cancer susceptibility gene.

A single founder allele of the CHEK2 gene has been associated with predisposition to breast and prostate cancer in North America and Europe. The CHEK2 protein participates in the DNA damage response in many cell types and is therefore a good candidate for a multisite cancer susceptibility gene. Three founder alleles are present in Poland. Two of these result in a truncated CHEK2 protein, and the other is a missense substitution of an isoleucine for a threonine. We ascertained the prevalence of each of these alleles in 4,008 cancer cases and 4,000 controls, all from Poland. The majority of the common cancer sites were represented. Positive associations with protein-truncating alleles were seen for cancers of the thyroid (odds ratio [OR] 4.9; P=.0006), breast (OR 2.2; P=.02), and prostate (OR 2.2; P=.04). The missense variant I157T was associated with an increased risk of breast cancer (OR 1.4; P=.02), colon cancer (OR 2.0; P=.001), kidney cancer (OR 2.1; P=.0006), prostate cancer (OR 1.7; P=.002), and thyroid cancer (OR 1.9; P=.04). The range of cancers associated with mutations of the CHEK2 gene may be much greater than previously thought.

NBS1 is a prostate cancer susceptibility gene.

To evaluate whether an inactivating mutation in the gene for the Nijmegen breakage syndrome (NBS1) plays a role in the etiology of prostate cancer, we compared the prevalence of the 657del5 NBS1 founder allele in 56 patients with familial prostate cancer, 305 patients with nonfamilial prostate cancer, and 1500 control subjects from Poland. Loss of heterozygosity analysis also was performed on DNA samples isolated from 17 microdissected prostate cancers, including 8 from carriers of the 657del5 mutation. The NBS1 founder mutation was present in 5 of 56 (9%) patients with familial prostate cancer (odds ratio, 16; P < 0.0001), 7 of 305 (2.2%) patients with nonfamilial prostate cancer (odds ratio, 3.9; P = 0.01), and 9 of 1500 control subjects (0.6%). The wild-type NBS1 allele was lost in seven of eight prostate tumors from carriers of the 657del5 allele, but loss of heterozygosity was seen in only one of nine tumors from noncarriers (P = 0.003). These findings suggest that heterozygous carriers of the NBS1 founder mutation exhibit increased susceptibility to prostate cancer and that the cancers that develop in the prostates of carriers are functionally homozygous for the mutation.

Multiple metastases of carcinoma basocellulare into spinal column.

Basal cell carcinoma presents a relatively low potential and local malignancy and very slow growth giving only occasionally metastatic spreading. The frequency of occurrence of metastatic dissemination is estimated in the literature depending on examined population from 0.028% to 0.55%. Metastases are most often found in lymph nodes, lungs bones and internal organs: liver, spleen, kidneys, adrenal glands, pleura and the peritoneum. Authors present a case of a 69-years old female with an extensive basal cell carcinoma of the head convexity, infiltrating the subcutaneous tissue, periostium, bone and dura mater, giving distant metastases to other bone and soft tissue structures of a thoracic spine, which was confirmed by biopsy and histopathological findings of neoplasm tissue in spine. The primary lesion was successfully treated surgically. Despite administered radiotherapy of metastases in spine, progress of the disease during 1-year period was observed. The patient was alive with metastatic tumours present at last follow-up. Basing on the review of the literature and our case report we can distinguish following factors which may increase the risk of occurrence of basal cell carcinoma metastases: the great extent of the primary lesion, deep penetration to stromal tissue, blood and lymph vessel invasion, long history of tumour occurrence and the presence of metatypia in histopathological findings. The above-mentioned case fulfils the criteria of carcinoma basocellulare metastases proposed by Latters and Kessel and may be included to the general registration list of this cancer in the world.

[The usefulness of intraoperative high-frequency doppler flowmetry in surgeries for intracranial aneurysms]. / Przydatnosc sródoperacyjnego aparatu dopplerowskiego wysokiej czestotliwosci w operacjach tetniaków tetnic mózgowych.

The flowmeter enables estimation of blood flow velocity changes in small calibre arteries. The authors examined blood flow velocity patterns in the vessels during aneurysm operations and blood flow velocity and its disturbances inside aneurysm. Evaluation technique, technical data of the flowmeter use are described and the characteristics of the blood flow velocity picture in cerebral arteries obtained by this method is presented. The presented method enables a very precise estimation of blood flow velocity and detection of changes in flow patterns. The method may become very helpful in identification of the vessels in other types of cerebral surgery.

Prevalence of low back pain among physical therapists in Edmonton, Canada.

Questionnaires were sent to 462 physical therapists in Edmonton, Canada, to determine the prevalence of work-related low back pain (LBP) and to characterize those who reported pain. Of the 311 (67.3%) valid questionnaires returned. 49.2% reported back pain due to work. The occurrence rates of work-related LBP among physical therapists in Edmonton was higher than that of the general population reported in Canada (27%), Great Britain (27%), and the United States (26-29%). There was no significant difference (p < or = 0.05) between those with and without work-related LBP. The initial onset of work-related LBP frequently occurred within the first 5 years of practice as a physical therapist, and before the age of 30. Hospitals and private practices were the most prevalent work settings in which injury occurred. Patient handling, bending, stooping, lifting, carrying, pushing, and pulling were the commonly described activities causing precipitation of injury. The severity of back discomfort had been sufficient to require 13.7% of therapists to stop their work. Despite LBP, 35.3% of the pain sufferers continued to work. Over half (55.4%) of the respondents with current work-related LBP demonstrated little or no disability.