Polarons by translationally invariant diagrammatic perturbation theory

The structure of the translationally-invariant diagrammatic perturbation theory for one polaron is examined on the 1D discrete lattice described by the Holstein Hamiltonian. The latter is characterized by the electron hopping t, the phonon frequency ω_0 and the electron-phonon coupling g. It is shown that the polaron localization (and translation) properties are contained in the electron propagator of one electron, intermittently added to the lattice, and/or in the phonon correlation function with one electron permanently present in the lattice. The order by order analysis in g/ω_0 shows that the expansion of the irreducible electron self-energy corresponds to the expansion of the phonon correlation function, rather than of the irreducible phonon self-energy. The range of polaronic correlations is determined in this way. For small t/ω_0 and already to the second order g/ω_0 small, the electron-lattice correlation becomes very short ranged, i.e. the polaron is already localized to one site, although the overall translational symmetry remains unbroken. For large t/ω0, the second order result is meaningful up to large g/ω_0 ≈ (t/ω_0)^\frac14, where it becomes degenerate with the results for the large adiabatic Holstein polaron. This suggests that the translationally invariant perturbation theory crosses then over smoothly, without symmetry breaking, into the adiabatic, continuous quantum limit, as rigorously demonstrated in the companion paper. Thus the quantum theory of the large adiabatic Holstein polaron provides a simple, instructive example of the quantum crossover which replaces the behavior in the quantum critical point

Obesity Moderates the Effects of Motivational Interviewing Treatment Outcomes in Fibromyalgia

Objective: Obesity is a common comorbid condition among patients with fibromyalgia (FM). Our objective was to assess if obesity moderates the treatment benefits of exercise-based motivational interviewing (MI) for FM. Methods: This is a secondary data analysis of a completed clinical trial of 198 FM patients who were randomized to receive either MI or attention control (AC). Using body mass index (BMI) to divide participants into obese (BMI >=30 kg/m2) and non-obese (BMI <30 kg m2) groups, mixed linear models were used to determine interaction between treatment arms and obesity status with regards to the primary outcome of global FM symptom severity (Fibromyalgia Impact Questionnaire, FIQ). Secondary measures included pain intensity (Brief Pain Inventory, BPI), 6-minute walk test, and self-reported physical activity (Community Health Activities Model Program for Seniors). Results: Of the 198 participants, 91 (46%) were non-obese and 107 (54%) were obese. On global FM symptom severity (FIQ), the interaction between treatment arms and obesity status was significant (P=0.02). In the non-obese group, MI was associated with a greater improvement in FIQ than AC. In the obese group, MI participants reported less improvement in FIQ compared to AC. The interaction analysis was also significant for BPI pain intensity (P=0.01), but not for the walk test and self-reported physical activity. Discussion: This is the first study to show that obesity negatively affects the treatment efficacy of MI in patients with FM. Our findings suggest that exercise-based MI may be more effective if initiated after weight loss is achieved

Neurodevelopmental Outcomes at Two Years of Age for Premature Infants Diagnosed With Neonatal Obstructive Sleep Apnea

STUDY OBJECTIVES: Neurocognitive deficits have been shown in school-aged children with sleep apnea. The effect of obstructive sleep apnea (OSA) on the neurodevelopmental outcome of preterm infants is unknown. METHODS: A retrospective chart review was performed for all preterm infants ( 1 event/h. Regression analyses were performed to find a relationship between PSG parameters and cognitive, language, and motor scores. RESULTS: Fifteen patients (males: n = 10) were eligible for the study. Median postmenstrual age at the time of the PSG was 41 weeks (37-46). Median AHI for the cohort was 17.4 events/h (2.2-41.3). Median cognitive, language, and motor scores were 90 (65-125), 89 (65-121), and 91 (61-112), respectively. Mean end-tidal CO2 (median 47 mm Hg [25-60]) negatively correlated with cognitive scores (P = .01) but did not significantly correlate with language or motor scores. AHI was not associated with cognitive, language, or motor scores. CONCLUSIONS: The median score for cognitive, language, and motor scores for preterm infants with neonatal OSA were within one standard deviation of the published norm. Mean end-tidal CO2, independent of AHI, may serve as a biomarker for predicting poor cognitive outcome in preterm infants with neonatal OSA

Factors associated with survival during high frequency oscillatory ventilation in children

Our aim is to determine indicators of survival in children with severe hypoxic respiratory failure (HRF) after transition to high-frequency oscillatory ventilation (HFOV). Single-center retrospective examination of children with HRF transitioned to HFOV. Blood gases and ventilator settings 24 hours prior to and 48 hours after HFOV in survivors and nonsurvivors were evaluated. Sixty-two children with mean age of 7 years and mean weight of 26 kg were included with an observed mortality of 29%. Mean airway pressures (Paw), oxygenation index (OI), arterial oxygen partial pressure (PaO2)/fraction of inspired oxygen (FiO2) (P/F) ratio, pH, bicarbonate, and arterial carbon dioxide partial pressure were similar prior to HFOV in survivors and nonsurvivors. During HFOV, mean OI and P/F ratio improved in both groups with an average Paw increase of ∼10 cm H2O. Survivors had lower OI than nonsurvivors (21 ± 0.9 vs. 26.5 ± 2.2; p 200. Survivors had higher pH than nonsurvivors at 36 hours (7.40 ± 0.01 vs. 7.32 ± 0.02; p < 0.05), higher bicarbonate levels (27.1 ± 0.7 vs. 23.9 ± 1.3 mEq/L), and similar arterial carbon dioxide partial pressure with less oscillatory support (i.e., hertz and amplitude). Inhaled nitric oxide was used in 53% of patients with improvements in oxygenation but with no effect on mortality. HFOV improves oxygenation in children with severe HRF. Nonsurvivors can be distinguished from survivors at 24 to 36 hours during HFOV by higher OI, metabolic acidosis, and higher oscillatory support. These data may assist in prognostication or timing of initiating alternative therapies, such as extracorporeal membrane oxygenation

Embedding a Carbon Nanotube across the Diameter of a Solid State Nanopore

A fabrication method for positioning and embedding a single-walled carbon nanotube (SWNT) across the diameter of a solid state nanopore is presented. Chemical vapor deposition (CVD) is used to grow SWNTs over arrays of focused ion beam (FIB) milled pores in a thin silicon nitride membrane. This typically yields at least one pore whose diameter is centrally crossed by a SWNT. The final diameter of the FIB pore is adjusted to create a nanopore of any desired diameter by atomic layer deposition, simultaneously embedding and insulating the SWNT everywhere but in the region that crosses the diameter of the final nanopore, where it remains pristine and bare. This nanotube-articulated nanopore is an important step towards the realization of a new type of detector for biomolecule sensing and electronic characterization, including DNA sequencing.Engineering and Applied SciencesMolecular and Cellular BiologyPhysic

Production and decay of the neutral top-pion in high energy e+e−e^{+}e^{-} colliders

We study the production and decay of the neutral top-pion $\pi_{t}^{0}$ predicted by topcolor-assisted technicolor(TC2) theory. Our results show that, except the dominant decay modes $b\bar{b}$, $\bar{t}c$ and $gg$, the $\pi_{t}^{0}$ can also decay into $\gamma\gamma$ and $Z \gamma$ modes. It can be significantly produced at high energy $e^{+}e^{-}$ collider(LC) experiments via the processes $e^{+}e^{-}\to \pi_{t}^{0}\gamma$ and $e^{+}e^{-}\to Z\pi_{t}^{0}$. We further calculate the production cross sections of the processes $e^{+}e^{-}\to\gamma\pi_{t}^{0}\to\gamma\bar{t}c$ and $e^{+}e^{-}\to Z\pi_{t}^{0}\to Z\bar{t}c$. We find that the signatures of the neutral top-pion $\pi_{t}^{0}$ can be detected via these processes.Comment: Latex file, 13 Pages, 6 eps figures. to be published in Phys.Rev.

Commercials, careers and culture: travelling salesmen in Britain 1890s-1930s

Within the lower middle-class, British commercial travellers established a strong fraternal culture before 1914. This article examines their interwar experiences in terms of income, careers, and associational culture. It demonstrates how internal labour markets operated, identifies the ways in which commercial travellers interpreted their role, and explores their social and political attitudes

Pseudo-Goldstone Boson Effects in Top-Antitop Productions at High Energy Hadron Colliders and Testing Technicolor Models

We study the top quark pair production process p+p(anti-p)-->top+antitop in various kinds of technicolor (TC) models at the Fermilab Tevatron Run II and the CERN LHC. The s-channel neutral pseudo-Goldstone bosons (PGB's) contribute dominately to the production amplitudes from its coupling to the gluons through the triangle loops of techniquarks and the top quark. Cross sections in different TC models with s-channel PGB contributions are calculated. It is shown that the PGB effects can be experimentally tested and different TC models under consideration can be distinguished at the LHC. Therefore, the p+p-->top+antitop process at the LHC provides feasible tests of the TC models.Comment: 10 pages in RevTex and 4 PS-files for the figures. Paramemter range is changed, and some references are added. Version for publication in Phys. Rev.

Electronic Raman scattering in a multiband model for cuprate superconductors

Charge-charge, current-current and Raman correlation functions are derived in a consistent way using the unified response theory. The theory is based on the improved description of the conduction electron coupling to the external electromagnetic fields, distinguishing further the direct and indirect (assisted) scattering on the quasi-static disorder. The two scattering channels are distinguished in terms of the energy and momentum conservation laws. The theory is illustrated on the Emery three-band model for the normal state of the underdoped high-$T_c$ cuprates which includes the incoherent electron scattering on the disorder associated with the quasi-static fluctuations around the static antiferromagnetic (AF) ordering. It is shown, for the first time consistently, that the incoherent indirect processes dominate the low-frequency part of the Raman spectra, while the long-range screening which is dynamic removes the long-range forces in the $A_{1g}$ channel. In the mid-infrared frequency range the coherent AF processes are dominant. In contrast to the nonresonant $B_{1g}$ response, which is large by itself, the resonant interband transitions enhance both the $A_{1g}$ and $B_{1g}$ Raman spectra to comparable values, in good agreement with experimental observation. It is further argued that the AF correlations give rise to the mid-infrared peak in the $B_{1g}$ Raman spectrum, accompanied by a similar peak in the optical conductivity. The doping behavior of these peaks is shown to be correlated with the linear doping dependence of the Hall number, as observed in all underdoped high-$T_c$ compounds.Comment: 18 pages, 14 figures; to appear in Phys. Rev.

The polymer phase of the TDAE-C60_{60} organic ferromagnet

The high-pressure Electron Spin Resonance (ESR) measurements were preformed on TDAE-C$_{60}$ single crystals and stability of the polymeric phase was established in the $P - T$ parameter space. At 7 kbar the system undergoes a ferromagnetic to paramagnetic phase transition due to the pressure-induced polymerization. The polymeric phase remains stable after the pressure release. The depolymerization of the pressure-induced phase was observed at the temperature of 520 K. Below room temperature, the polymeric phase behaves as a simple Curie-type insulator with one unpaired electron spin per chemical formula. The TDAE$^+$ donor-related unpaired electron spins, formerly ESR-silent, become active above the temperature of 320 K and the Curie-Weiss behavior is re-established.Comment: Submitted to Phys. Rev.