Energy-level statistics of interacting trapped bosons

It is a well-established fact that statistical properties of energy-level spectra are the most efficient tool to characterize nonintegrable quantum systems. The statistical behavior of different systems such as complex atoms, atomic nuclei, two-dimensional Hamiltonians, quantum billiards, and noninteracting many bosons has been studied. The study of statistical properties and spectral fluctuations in interacting many-boson systems has developed interest in this direction. We are especially interested in weakly interacting trapped bosons in the context of Bose-Einstein condensation (BEC) as the energy spectrum shows a transition from a collective nature to a single-particle nature with an increase in the number of levels. However this has received less attention as it is believed that the system may exhibit Poisson-like fluctuations due to the existence of an external harmonic trap. Here we compute numerically the energy levels of the zero-temperature many-boson systems which are weakly interacting through the van der Waals potential and are confined in the three-dimensional harmonic potential. We study the nearest-neighbor spacing distribution and the spectral rigidity by unfolding the spectrum. It is found that an increase in the number of energy levels for repulsive BEC induces a transition from a Wigner-like form displaying level repulsion to the Poisson distribution for P(s). It does not follow the Gaussian orthogonal ensemble prediction. For repulsive interaction, the lower levels are correlated and manifest level-repulsion. For intermediate levels P(s) shows mixed statistics, which clearly signifies the existence of two energy scales: external trap and interatomic interaction, whereas for very high levels the trapping potential dominates, generating a Poisson distribution. Comparison with mean-field results for lower levels are also presented. For attractive BEC near the critical point we observe the Shnirelman-like peak near s = 0, which signifies the presence of a large number of quasidegenerate states.

Use of a gold microelectrode for discrimination of gunshot residues

Gunshot residues (GSR) can be used in forensic evaluations to obtain information about the type of gun and ammunition used in a crime. In this work, we present our efforts to develop a promising new method to discriminate the type of gun [four different guns were used: two handguns (0.38 revolver and 0.380 pistol) and two long-barrelled guns (12-calibre pump-action shotgun and 0.38 repeating rifle)] and ammunition (five different types: normal, semi-jacketed, full-jacketed, green, and 3T) used by a suspect. The proposed approach is based on information obtained from cyclic voltammograms recorded in solutions containing GSR collected from the hands of the shooters, using a gold microelectrode; the information was further analysed by non-supervised pattern-recognition methods [(Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA)]. In all cases (gun and ammunition discrimination), good separation among different samples in the score plots and dendrograms was achieved. (C) 2012 Elsevier B.V. All rights reserved.

Dyspeptic symptoms and delayed gastric emptying of solids in patients with inactive Crohn’s disease

Background Patients with Crohn’s disease (CD) have been shown to present dyspeptic symptoms more frequently than the general population. Some of these symptoms could be related to motility disorders to some degree. Then, we propose to investigate whether gastric emptying of solids in patients with inactive CD is delayed and to determine the relationships between gastric emptying and dyspeptic symptoms in inactive CD. Methods Twenty-six patients with inactive Crohn’s disease, as defined by a Crohn’s Disease Activity Index (CDAI) < 150, underwent a gastric emptying test by breath test using 13C octanoic acid coupled to a solid meal and answered a validated questionnaire (The Porto Alegre Dyspeptic Symptoms Questionnaire) to assess dyspeptic symptoms. Patients with scores ≥ 6 were considered to have dyspepsia. The control group was composed by 19 age- and sex-matched healthy volunteers. Results Patients with CD had a significantly longer t 1/2 and t lag (p<0.05) than the controls. CD patients with dyspepsia had significantly (p<0.05) prolonged gastric emptying when compared to patients without dyspeptic symptoms. When the individual symptom patterns were analyzed, only vomiting was significantly associated with delayed gastric emptying (p<0.05). There was no difference between the subgroups of patients with respect to gender, CDAI scores, disease location, clinical behavior (obstructive/obstructive) or previous gastrointestinal surgery. Conclusion Delayed gastric emptying in inactive Crohn’s disease patients seems to be associated with dyspeptic symptoms, particularly vomiting, even without any evidence of gastrointestinal obstruction.

Association of a probiotic to a Helicobacter pylori eradication regimen does not increase efficacy or decreases the adverse effects of the treatment: a prospective, randomized, double-blind, placebo-controlled study

Abstract Background The treatment for the eradication of Helicobacter pylori (H. pylori) is complex; full effectiveness is rarely achieved and it has many adverse effects. In developing countries, increased resistance to antibiotics and its cost make eradication more difficult. Probiotics can reduce adverse effects and improve the infection treatment efficacy. If the first-line therapy fails a second-line treatment using tetracycline, furazolidone and proton-pump inhibitors has been effective and low cost in Brazil; however it implies in a lot of adverse effects. The aim of this study was to minimize the adverse effects and increase the eradication rate applying the association of a probiotic compound to second-line therapy regimen. Methods Patients with peptic ulcer or functional dyspepsia infected by H. pylori were randomized to treatment with the furazolidone, tetracycline and lansoprazole regimen, twice a day for 7 days. In a double-blind study, patients received placebo or a probiotic compound (Lactobacillus acidophilus, Lactobacillus rhamnosus, Bifidobacterium bifidum and Streptococcus faecium) in capsules, twice a day for 30 days. A symptom questionnaire was administered in day zero, after completion of antibiotic therapy, after the probiotic use and eight weeks after the end of the treatment. Upper digestive endoscopy, histological assessment, rapid urease test and breath test were performed before and eight weeks after eradication treatment. Results One hundred and seven patients were enrolled: 21 men with active probiotic and 19 with placebo plus 34 women with active probiotic and 33 with placebo comprising a total of 55 patients with active probiotic and 52 with placebo. Fifty-one patients had peptic ulcer and 56 were diagnosed as functional dyspepsia. The per-protocol eradication rate with active probiotic was 89.8% and with placebo, 85.1% (p = 0.49); per intention to treat, 81.8% and 79.6%, respectively (p = 0.53). The rate of adverse effects at 7 days with the active probiotic was 59.3% and 71.2% with placebo (p = 0.20). At 30 days, it was 44.9% and 60.4%, respectively (p = 0.08). Conclusions The use of this probiotic compound compared to placebo in the proposed regimen in Brazilian patients with peptic ulcer or functional dyspepsia showed no significant difference in efficacy or adverse effects. Trial registration Current Controlled Trials ISRCTN04714018

Role of soluble triggering receptor expressed on myeloid cells-1 for diagnosing ventilator-associated pneumonia after cardiac surgery: an observational study

Abstract Background The diagnosis of ventilator-associated pneumonia (VAP) is a challenge, particularly after cardiac surgery. The use of biological markers of infection has been suggested to improve the accuracy of VAP diagnosis. We aimed to evaluate the usefulness of soluble triggering receptor expressed on myeloid cells (sTREM)-1 in the diagnosis of VAP following cardiac surgery. Methods This was a prospective observational cohort study of children with congenital heart disease admitted to the pediatric intensive care unit (PICU) after surgery and who remained intubated and mechanically ventilated for at least 24 hours postoperatively. VAP was defined by the 2007 Centers for Disease Control and Prevention criteria. Blood, modified bronchoalveolar lavage (mBAL) fluid and exhaled ventilator condensate (EVC) were collected daily, starting immediately after surgery until the fifth postoperative day or until extubation for measurement of sTREM-1. Results Thirty patients were included, 16 with VAP. Demographic variables, Pediatric Risk of Mortality (PRISM) and Risk Adjustment for Congenital Heart Surgery (RACHS)-1 scores, duration of surgery and length of cardiopulmonary bypass were not significantly diferent in patients with and without VAP. However, time on mechanical ventilation and length of stay in the PICU and in the hospital were significantly longer in the VAP group. Serum and mBAL fluid sTREM-1 concentrations were similar in both groups. In the VAP group, 12 of 16 patients had sTREM-1 detected in EVC, whereas it was undetectable in all but two patients in the non-VAP group over the study period (p = 0.0013) (sensitivity 0.75, specificity 0.86, positive predictive value 0.86, negative predictive value 0.75, positive likelihood ratio (LR) 5.25, negative LR 0.29). Conclusion Measurement of sTREM-1 in EVC may be useful for the diagnosis of VAP after cardiac surgery.

Biphasic positive airway pressure minimizes biological impact on lung tissue in mild acute lung injury independent of etiology

Abstract Introduction Biphasic positive airway pressure (BIVENT) is a partial support mode that employs pressure-controlled, time-cycled ventilation set at two levels of continuous positive airway pressure with unrestricted spontaneous breathing. BIVENT can modulate inspiratory effort by modifying the frequency of controlled breaths. Nevertheless, the optimal amount of inspiratory effort to improve respiratory function while minimizing ventilator-associated lung injury during partial ventilatory assistance has not been determined. Furthermore, it is unclear whether the effects of partial ventilatory support depend on acute lung injury (ALI) etiology. This study aimed to investigate the impact of spontaneous and time-cycled control breaths during BIVENT on the lung and diaphragm in experimental pulmonary (p) and extrapulmonary (exp) ALI. Methods This was a prospective, randomized, controlled experimental study of 60 adult male Wistar rats. Mild ALI was induced by Escherichia coli lipopolysaccharide either intratracheally (ALIp) or intraperitoneally (ALIexp). After 24 hours, animals were anesthetized and further randomized as follows: (1) pressure-controlled ventilation (PCV) with tidal volume (Vt) = 6 ml/kg, respiratory rate = 100 breaths/min, PEEP = 5 cmH2O, and inspiratory-to-expiratory ratio (I:E) = 1:2; or (2) BIVENT with three spontaneous and time-cycled control breath modes (100, 75, and 50 breaths/min). BIVENT was set with two levels of CPAP (Phigh = 10 cmH2O and Plow = 5 cmH2O). Inspiratory time was kept constant (Thigh = 0.3 s). Results BIVENT was associated with reduced markers of inflammation, apoptosis, fibrogenesis, and epithelial and endothelial cell damage in lung tissue in both ALI models when compared to PCV. The inspiratory effort during spontaneous breaths increased during BIVENT-50 in both ALI models. In ALIp, alveolar collapse was higher in BIVENT-100 than PCV, but decreased during BIVENT-50, and diaphragmatic injury was lower during BIVENT-50 compared to PCV and BIVENT-100. In ALIexp, alveolar collapse during BIVENT-100 and BIVENT-75 was comparable to PCV, while decreasing with BIVENT-50, and diaphragmatic injury increased during BIVENT-50. Conclusions In mild ALI, BIVENT had a lower biological impact on lung tissue compared to PCV. In contrast, the response of atelectasis and diaphragmatic injury to BIVENT differed according to the rate of spontaneous/controlled breaths and ALI etiology.

Alpha cluster structure in 16O.

The alpha cluster phenomenon in the light nuclei structure has been the subject of a longtime investigation since the proposal of the Ikeda diagrams, however the mechanism of the cluster formation is still not completely understood. In fact, if the clusters have a fairly rigid crystal-like or a gas-like structure remains an open question. The interpretation of the Hoyle state as an α condensate brought a renewed interest to this subject, in particular to resonances analogous to the Hoyle state. In this context the study of the experimental evolution of the α-cluster phenomenon through (6Li,d) transfer reactions has been performed in São Paulo. Particularly important are the regions around the nα thresholds where the α-cluster structure states are predicted. The resonant states around the 4α threshold in the nucleus 16O are the focus of the present contribution. The 12C(6Li,d)16O reaction was measured at a bombarding energy of 25.5 MeV employing the São Paulo Pelletron-Enge-Spectrograph facility and the nuclear emulsion detection technique. Resonant states above the α threshold were measured and an energy resolution of 15-30 keV allows to define states previously unresolved. The angular distributions of the absolute cross sections were determined in a range of 4-40 degree in the center of mass system and up to 17 MeV excitation energy. The upper limit for the resonance widths in the crucial region of the 4α threshold was obtained. These values revealed to be at least a factor three smaller than the ones previously reported in the literature, indicating that the α cluster structure information on this region should be revised.

Variability of neurally-adjusted ventilatory assist (nava) compared to pressure support ventilation (psv) during the weaning phase of mechanical ventilation.

Rationale: NAVA is an assisted ventilatory mode that uses the electrical activity of the diaphragm (Edi) to trigger and cycle the ventilator, and to offer inspiratory assistance in proportion to patient effort. Since Edi varies from breath to breath, airway pressure and tidal volume also vary according to the patient's breathing pattern. Our objective was to compare the variability of NAVA with PSV in mechanically ventilated patients during the weaning phase. Methods: We analyzed the data collected for a clinical trial that compares PSV and NAVA during spontaneous breathing trials using PSV, with PS of 5 cmH2O, and NAVA, with Nava level titrated to generate a peak airway pressure equivalent to PSV of 5 cmH2O (NCT01137271). We captured flow, airway pressure and Edi at 100Hz from the ventilator using a dedicated software (Servo Tracker v2, Maquet, Sweden), and processed the cycles using a MatLab (Mathworks, USA) code. The code automatically detects the tidal volume (Vt), respiratory rate (RR), Edi and Airway pressure (Paw) on a breath-by-breath basis for each ventilatory mode. We also calculated the coefficient of variation (standard deviation, SD, divided by the mean). Results: We analyzed data from eleven patients. The mean Vt was similar on both modes (370 ±70 for Nava and 347± 77 for PSV), the RR was 26±6 for Nava and 26±7 or PSV. Paw was higher for Nava than for PSV (14±1 vs 11±0.4, p=0.0033), and Edi was similar for both modes (12±8 for Nava and 11±6 for PSV). The variability of the respiratory pattern, assessed with the coefficient of variation, was larger for Nava than for PSV for the Vt ( 23%±1% vs 15%±1%, p=0.03) and Paw (17%±1% vs 1% ±0.1%, p=0.0033), but not for RR (21% ±1% vs 16% ±8%, p=0.050) or Edi (33%±14% vs 39% ±16%,p=0.07). Conclusion: The variability of the breathing pattern is high during spontaneous breathing trials independent of the ventilatory mode. This variability results in variability of airway pressure and tidal volume, which are higher on Nava than on PSV. Our results suggest that Nava better reflects the normal variability of the breathing pattern during assisted mechanical ventilation.

Spin coherent states in NMR quadrupolar system: experimental and theoretical applications

Working with nuclear magnetic resonance (NMR) in quadrupolar spin systems, in this paper we transfer the concept of atomic coherent state to the nuclear spin context, where it is referred to as pseudonuclear spin coherent state (pseudo-NSCS). Experimentally, we discuss the initialization of the pseudo- NSCSs and also their quantum control, implemented by polar and azimuthal rotations. Theoretically, we compute the geometric phases acquired by an initial pseudo-NSCS on undergoing three distinct cyclic evolutions: (i) the free evolution of the NMR quadrupolar system and, by analogy with the evolution of the NMR quadrupolar system, that of (ii) single-mode and (iii) two-mode Bose-Einstein Condensate like system. By means of these analogies, we derive, through spin angular momentum operators, results equivalent to those presented in the literature for orbital angular momentum operators. The pseudo-NSCS description is a starting point to introduce the spin squeezed state and quantum metrology into nuclear spin systems of liquid crystal or solid matter.

Classical bifurcation in a quadrupolar NMR system

The Josephson junction model is applied to the experimental implementation of classical bifurcation in a quadrupolar nuclear magnetic resonance system. There are two regimes, one linear and one nonlinear, which are implemented by the radio-frequency and the quadrupolar terms of the Hamiltonian of a spin system, respectively. These terms provide an explanation of the symmetry breaking due to bifurcation. Bifurcation depends on the coexistence of both regimes at the same time in different proportions. The experiment is performed on a lyotropic liquid crystal sample of an ordered ensemble of 133Cs nuclei with spin I = 7/2 at room temperature. Our experimental results confirm that bifurcation happens independently of the spin value and of the physical system. With this experimental spin scenario, we confirm that a quadrupolar nuclei system could be described analogously to a symmetric two-mode Bose-Einstein condensate.