Quantum Monte Carlo study of a resonant Bose-Fermi mixture.

We study a resonant Bose-Fermi mixture at zero temperature by using the fixed-node diffusion Monte Carlo method. We explore the system from weak to strong boson-fermion interaction, for different concentrations of the bosons relative to the fermion component. We focus on the case where the boson density n(B) is smaller than the fermion density n(F), for which a first-order quantum phase transition is found from a state with condensed bosons immersed in a Fermi sea, to a Fermi-Fermi mixture of composite fermions and unpaired fermions. We obtain the equation of state and the phase diagram, and we find that the region of phase separation shrinks to zero for vanishing n(B).

Density and spin response of a strongly interacting Fermi gas in the attractive and quasirepulsive regime.

Recent experimental advances in ultracold Fermi gases allow for exploring response functions under different dynamical conditions. In particular, the issue of obtaining a "quasirepulsive" regime starting from a Fermi gas with an attractive interparticle interaction while avoiding the formation of the two-body bound state is currently debated. Here, we provide a calculation of the density and spin response for a wide range of temperature and coupling both in the attractive and quasirepulsive regime, whereby the system is assumed to evolve nonadiabatically toward the "upper branch" of the Fermi gas. A comparison is made with the available experimental data for these two quantities.

Repeated inhalation of crack-cocaine affects spermatogenesis in young and adult mice.

To investigate the effects of repeated crack-cocaine inhalation on spermatogenesis of pubertal and mature Balb/c mice, ten young (Y(ex)) and ten adult (A(ex)) Balb/c mice were exposed to the smoke from 5 g of crack with 57.7% of pure cocaine in an inhalation chamber, 5 days/week for 2 months. The young (Y(c)) and adult (A(c)) control animals (n = 10) were kept in a specially built and controlled animal house facility. The morphologic analysis of both testes of all animals included the analysis of quantitative and qualitative histologic parameters to assess the effect of crack-cocaine on spermatogenesis and Leydig cells. Apoptosis was determined by immunolabeling with caspase-3 antibodies. Compared to the Y(c) animals, Y(ex) animals showed a significant reduction in the number of stage VII tubules per testis (p = 0.02), Sertoli cells (p < 0.001) and elongated spermatids (p = 0.001). Comparisons between the Y(ex) and A(ex) groups identified a significant reduction in the number of Sertoli cells (p < 0.001) and round spermatids (p < 0.001) in the Y(ex) group and a significant increase in apoptotic Leydig cells (p = 0.04) in the A(ex) group. The experimental results indicate that crack-cocaine smoke inhalation induced spermatogenesis disruption in chronically exposed mice, particularly in pubertal mice.

Evolution of the normal state of a strongly interacting Fermi gas from a pseudogap phase to a molecular Bose gas.

Wave-vector resolved radio frequency spectroscopy data for an ultracold trapped Fermi gas are reported for several couplings at T(c), and extensively analyzed in terms of a pairing-fluctuation theory. We map the evolution of a strongly interacting Fermi gas from the pseudogap phase into a fully gapped molecular Bose gas as a function of the interaction strength, which is marked by a rapid disappearance of a remnant Fermi surface in the single-particle dispersion. We also show that our theory of a pseudogap phase is consistent with a recent experimental observation as well as with quantum Monte Carlo data of thermodynamic quantities of a unitary Fermi gas above T(c).

Penile anthropometry in systemic lupus erythematosus patients.

The aim of this study was to evaluate penile anthropometry in systemic lupus erythematosus (SLE) patients compared with healthy controls and the possible relevant pubertal, clinical, hormonal and treatment factors that could influence penile dimensions. Twenty-five consecutive SLE patients were assessed by urological examination, sexual function, testicular ultrasound, hormones, sperm analysis, genetic analysis, clinical features and treatment. The control group included 25 age-matched healthy males. SLE patients had a lower median penis length and circumference [8 (7.5-10) vs. 10 (8-13) cm, p = 0.0001; 8 (7-10) vs. 10 (7-11) cm, p = 0.001; respectively], lower median testicular volume by right and left Prader [15 (10-25) vs. 20 (12-25) ml, p = 0.003; 15 (10-25) vs. 20 (12-25) ml, p = 0.006; respectively], higher median of follicle-stimulating hormone [5.8 (2.1-25) vs. 3.3 (1.9-9) IU/l, p = 0.002] and lower morning total testosterone levels (28% vs. 0%, p = 0.009) compared with controls. In spite of that, erectile dysfunction was not observed in patients or controls. Analyses of lupus patients revealed that the median penis circumference was lower in patients with disease onset before first ejaculation compared with those with disease onset after first ejaculation [7.8 (7-10) vs. 9.0 (7.5-10) cm, p = 0.026]. No differences were observed in the median penile anthropometry regarding sexual dysfunction (p = 0.610), lower morning total testosterone levels (p = 0.662), oligo/azoospermia (p = 0.705), SLE Disease Activity Index ≥ 4 (p = 0.562), Systemic Lupus International Collaborating Clinics/ACR Damage Index ≥ 1 (p = 0.478), prednisone cumulative dose (p = 0.789) and intravenous cyclophosphamide therapy (p = 0.754). Klinefelters syndrome (46XY/47XXY) was diagnosed in one (4%) SLE patient with decreased penile size whereas Y-chromosomal microdeletions was absent in all of them. In conclusion, we have identified reduced penile dimensions in SLE patients with no deleterious effect in erectile function. Disease onset before first ejaculation seems to affect penis development in pre-pubertal lupus.

Simulating disordered quantum Ising chains via dense and sparse restricted Boltzmann machines.

In recent years, generative artificial neural networks based on restricted Boltzmann machines (RBMs) have been successfully employed as accurate and flexible variational wave functions for clean quantum many-body systems. In this article, we explore their use in simulations of disordered quantum Ising chains. The standard dense RBM with all-to-all interlayer connectivity is not particularly appropriate for large disordered systems, since in such systems one cannot exploit translational invariance to reduce the amount of parameters to be optimized. To circumvent this problem, we implement sparse RBMs, whereby the visible spins are connected only to a subset of local hidden neurons, thus reducing the amount of parameters. We assess the performance of sparse RBMs as a function of the range of the allowed connections, and we compare it with that of dense RBMs. Benchmark results are provided for two sign-problem-free Hamiltonians, namely pure and random quantum Ising chains. The RBM Ansätzes are trained using the unsupervised learning scheme based on projective quantum Monte Carlo (PQMC) algorithms. We find that the sparse connectivity facilitates the training process and allows sparse RBMs to outperform their dense counterparts. Furthermore, the use of sparse RBMs as guiding functions for PQMC simulations allows us to perform PQMC simulations at a reduced computational cost, avoiding possible biases due to finite random-walker populations. We obtain unbiased predictions for the ground-state energies and the magnetization profiles with fixed boundary conditions, at the ferromagnetic quantum critical point. The magnetization profiles agree with the Fisher-de Gennes scaling relation for conformally invariant systems, including the scaling dimension predicted by the renormalization-group analysis.

Supervised machine learning of ultracold atoms with speckle disorder.

We analyze how accurately supervised machine learning techniques can predict the lowest energy levels of one-dimensional noninteracting ultracold atoms subject to the correlated disorder due to an optical speckle field. Deep neural networks with different numbers of hidden layers and neurons per layer are trained on large sets of instances of the speckle field, whose energy levels have been preventively determined via a high-order finite difference technique. The Fourier components of the speckle field are used as the feature vector to represent the speckle-field instances. A comprehensive analysis of the details that determine the possible success of supervised machine learning tasks, namely the depth and the width of the neural network, the size of the training set, and the magnitude of the regularization parameter, is presented. It is found that ground state energies of previously unseen instances can be predicted with an essentially negligible error given a computationally feasible number of training instances. First and second excited state energies can be predicted too, albeit with slightly lower accuracy and using more layers of hidden neurons. We also find that a three-layer neural network is remarkably resilient to Gaussian noise added to the training-set data (up to 10% noise level), suggesting that cold-atom quantum simulators could be used to train artificial neural networks.

Self-learning projective quantum Monte Carlo simulations guided by restricted Boltzmann machines.

The projective quantum Monte Carlo (PQMC) algorithms are among the most powerful computational techniques to simulate the ground-state properties of quantum many-body systems. However, they are efficient only if a sufficiently accurate trial wave function is used to guide the simulation. In the standard approach, this guiding wave function is obtained in a separate simulation that performs a variational minimization. Here we show how to perform PQMC simulations guided by an adaptive wave function based on a restricted Boltzmann machine. This adaptive wave function is optimized along the PQMC simulation via unsupervised machine learning, avoiding the need of a separate variational optimization. As a byproduct, this technique provides an accurate ansatz for the ground-state wave function, which is obtained by minimizing the Kullback-Leibler divergence with respect to the PQMC samples, rather than by minimizing the energy expectation value as in standard variational optimizations. The high accuracy of this self-learning PQMC technique is demonstrated for a paradigmatic sign-problem-free model, namely, the ferromagnetic quantum Ising chain, showing very precise agreement with the predictions of the Jordan-Wigner theory and of loop quantum Monte Carlo simulations performed in the low-temperature limit.

Josephson effect throughout the BCS-BEC crossover.

We study the stationary Josephson effect for neutral fermions across the BCS-BEC (Bose-Einstein condensate) crossover, by solving numerically the Bogoliubov-de Gennes equations at zero temperature. The Josephson current is found to be considerably enhanced for all barriers at about unitarity. For vanishing barrier, the Josephson critical current approaches the Landau limiting value which, depending on the coupling, is determined by either pair-breaking or sound-mode excitations. In the coupling range from the BCS limit to unitarity, a procedure is proposed to extract the pairing gap from the Landau limiting current.

Microclimate influence on mineral and metabolic profiles of grape berries.

The grape berry microclimate is known to influence berry quality. The effects of the light exposure of grape berry clusters on the composition of berry tissues were studied on the "Merlot" variety grown in a vineyard in Bordeaux, France. The light exposure of the fruiting zone was modified using different intensities of leaf removal, cluster position relative to azimuth, and berry position in the cluster. Light exposures were identified and classified by in situ measurements of berry temperatures. Berries were sampled at maturity (>19 Brix) for determination of skin and/or pulp chemical and metabolic profiles based on (1) chemical and physicochemical measurement of minerals (N, P, K, Ca, Mg), (2) untargeted 1H NMR metabolic fingerprints, and HPLC targeted analyses of (3) amino acids and (4) phenolics. Each profile defined by partial least-square discriminant analysis allowed us to discriminate berries from different light exposure. Discriminant compounds between shaded and light-exposed berries were quercetin-3-glucoside, kaempferol-3-glucoside, myricetin-3-glucoside, and isorhamnetin-3-glucoside for the phenolics, histidine, valine, GABA, alanine, and arginine for the amino acids, and malate for the organic acids. Capacities of the different profiling techniques to discriminate berries were compared. Although the proportion of explained variance from the 1H NMR fingerprint was lower compared to that of chemical measurements, NMR spectroscopy allowed us to identify lit and shaded berries. Light exposure of berries increased the skin and pulp flavonols, histidine and valine contents, and reduced the organic acids, GABA, and alanine contents. All the targeted and nontargeted analytical data sets used made it possible to discriminate sun-exposed and shaded berries. The skin phenolics pattern was the most discriminating and allowed us to sort sun from shade berries. These metabolite classes can be used to qualify berries collected in an undetermined environment. The physiological significance of light and temperature effects on berry composition is discussed.

Radionuclide imaging of the synthetic smooth muscle cell phenotype in experimental atherosclerotic lesions.

Although the exact mechanisms of atherogenesis have not yet been elaborated, it is believed to be an inflammatory immunological response of the injured intima. The molecules and cells involved in this inflammatory response may provide specific targets for the development of novel diagnostic modalities. The present review deals with use of antibodies specific for the neoantigens of the vascular smooth muscle cells of the transformed synthetic phenotype for the detection of atherosclerotic lesions, as well as the potential use of the upregulation of the purinoceptors as indicators of the phenotypic transformation of these cells. In addition to the recognition of atherosclerotic lesions, such a strategy may also help identify accelerated proliferating smooth muscle cells associated with postangioplastic restenosis. © 1996, Elsevier Science Inc. (Trends Cardiovasc Med 1996;6:226-232).

Characterization of the reinjection thallium image.

The 201TI image after reinjection was characterized by analysis of stress and reinjection data acquired in 204 consecutive patients undergoing planar 201TI cardiac stress tests. In an additional 63 patients, redistribution data were also acquired to determine the effect of washout on the final reinjection image. Maximum count densities for the myocardium, lung and liver were measured, and the ratios between the stress and redistribution and the stress and reinjection sets of data were calculated. In patients with < 5% probability of coronary artery disease (CAD) ("normal" group), the reinjection image was typified by less myocardial activity (initial/reinjection = 1.22), slightly less lung activity (initial/reinjection = 1.05) and greater hepatic activity compared to the initial postexercise image. In male patients with > 5% probability of CAD, peak myocardial activity after reinjection was affected by the following variables: the interval between stress and reinjection, the amount of the initial dose and the 201TI scan results (normal 201TI study: initial/reinjection = 1.16; abnormal = 1.06; p < 0.009). Myocardial activity after reinjection was linearly related to myocardial activity after redistribution (r = 0.82). There was no significant influence by those variables in the 76 women who were studied. In conclusion, myocardial 201TI was decreased after reinjection in normal patients. The results indicate that there is an increased likelihood of underlying CAD in male patients undergoing exercise stress tests when 201TI myocardial activity on reinjection is greater than on the initial image.

Cardiac blood-pool scintigraphy in rats and hamsters: comparison of five radiopharmaceuticals and three pinhole collimator apertures.

Preclinical evaluation of cardiac drugs may require evaluation of cardiac function in intact animals. To optimize the quality of radionuclide measurements of ventricular function in small animals, a comparison was made of gated blood-pool scans recorded with five blood-pool radiopharmaceuticals (99mTc-labeled human polyclonal IgG, 99mTc-human serum albumin labeled by two methods, and red blood cells radiolabeled with 99mTc via in vivo and in vitro methods) in rats and three pinhole apertures in hamsters. The quality of the radiopharmaceuticals was evaluated by comparing count density ratios (LV/BACKGROUND and LV/LIVER) and ejection fractions recorded with each agent. The edge definition of the left ventricle and count rate performance of the 1-, 2-, and 3-mm apertures was evaluated in hamsters. In general, the images obtained with the radiolabeled cells were superior to those obtained with the labeled proteins and no significant differences between the protein preparations were detected. Left ventricular ejection fractions calculated with all five radiopharmaceuticals were not significantly different. The best quality images were obtained with the 1-mm pinhole collimator. Ejection fraction and acquisition time were inversely related to aperture size. A good compromise between resolution and sensitivity was obtained with the 2-mm pinhole collimator.

Assessment of myocardial viability after thallium-201 reinjection or rest-redistribution imaging: a multicenter study. The Italian Group of Nuclear Cardiology.

UNLABELLED: To establish the real nature of 201Tl defects in the assessment of myocardial viability (e.g., fixed versus reversible), 201Tl reinjection was evaluated in a multicenter trial involving 402 consecutive patients with ischemic heart disease and exercise 201Tl defects. METHODS: Twelve hospitals, using the same type of gamma camera and computer software, adopted one of the two most widely used reinjection protocols. In 230 patients (Group A), reinjection was performed immediately after stress-redistribution planar imaging; in 172 patients (Group B), reinjection was performed on a separate day and followed by rest-redistribution imaging. The images were interpreted by three blinded observers in a core laboratory on a five-point qualitative scale; the reproducibility in visual scoring was excellent. RESULTS: Groups A and B had a similar prevalence of myocardial segments with abnormal uptake at stress (39%, 40%), as well as with reversible (16%, 17%), partially reversible (21%, 19%) and irreversible (63%, 64%) defects at redistribution. After reinjection, 201Tl uptake improved in 27% and 36% of both partially reversible and irreversible defects in Groups A and B. No differences were found when comparing early and delayed reinjection imaging in Group B. CONCLUSION: This study confirms the validity of 201Tl reinjection in a large, unselected population, but the discordance with stress/redistribution is less than has been previously reported for both 201Tl reinjection protocols, the prevalence of improved segments after reinjection was higher with the separate day approach.

Evaluation of myocardial infarct size before and after reperfusion: dual-tracer imaging with radiolabeled antimyosin antibody.

UNLABELLED: Antimyosin antibody is a specific marker of myocardial necrosis that is based on the loss of integrity of the sarcolemmal membrane. Because antimyosin can be labeled with several different radiotracers, gamma imaging performed with antimyosin labeled with two different radionuclides can be used to quantify infarct size before and after an intervention such as reperfusion. METHODS: Twelve open-chested anesthetized dogs were evaluated both at the end of 1.5 hr of occlusion of the left anterior descending coronary artery and following reperfusion. Antimyosin Fab radiolabeled with either 123I or 111In was injected by intracoronary administration over 3 min at the end of the occlusion interval, and the coronary sinus was drained continuously for 7 min to prevent recirculation of the antibody. One hour after reperfusion, a second injection of antimyosin Fab (labeled with a different isotope from the first) was administered as before. Six dogs were given intracoronary trifluoperazine (150 micrograms/kg of body weight) simultaneously with reperfusion, and another six dogs received saline as the control. The infarct size in grams before and after reperfusion was assessed by antimyosin antibody uptake in ex vivo images of 1-cm thick slices of the hearts. The mean infarct sizes before (W1) and after (W2) reperfusion were then calculated as the percent of infarcted myocardium/ventricular myocardial mass. RESULTS: There was a significant increase in the mean percent infarct size after reperfusion in the control group (W2 = 16.73 +/- 4.0, W1 = 14.92 +/- 3.88; p = 0.029). The mean infarct size was uniformly smaller with trifluoperazine intervention (W2 = 12.33 +/- 2.03, W1 = 16.34 +/- 2.78; p = 0.004). The difference between the mean change in the infarct sizes in the two groups was highly significant (p = 0.002). CONCLUSION: Dual imaging of the extent of myocardial necrosis before and after an intervention (reperfusion) in the same animal demonstrated the utility of antimyosin imaging to document changes in the extent of necrosis.

Assessment of myocardial viability by radionuclide imaging.

The differentiation of viable from non viable myocardium is a key issue in the current era of revascularization. Several methods have been used to assess myocardial viability. The radionuclide detection of dysfunctional but viable myocardium depends upon the use of radiotracers whose uptake and trapping are related to presence and amount of living cells. The choice of the diagnostic technique to be applied in clinical practice depends on accuracy of the method and availability of resources. SPECT imaging with TI-201 and Tc-99m-myocardial perfusion tracers are widely available diagnostic tools. Several studies have documented their reliability to detect myocardial segments which may improve in both perfusion and function after revascularization. Positron emission tomography after injection of glucose analogues is a more sophisticated and accurate technology to detect viability, whose utilization is at present limited to few centers due to its high cost. Therefore an accurate selection of patients requiring viability studies is needed in order to identify the most appropriate diagnostic test.

[Multidimensional diagnosis in general medicine. Comparative study of the use of various instruments]. / La diagnosi multidimensionale in medicina generale. Studio comparativo sull'uso di alcuni strumenti.

This study was performed to test three instruments for functional status assessment in General Practice: the Dartmouth Coop Charts (COOP Charts), the Functional Status Questionnaire (FSQ) and the Duke University Health Profile (DUHP). All the instruments covered a score of functional aspects in physical, mental and social areas, providing a multidimensional measure of health status. We used these three instruments, validated by international studies, to acquire information concerning their feasibility and acceptability among patients from rural communities needing primary care and to test their validity in differentiating between patient subgroups. The COOP Charts, the FSQ and the DUHP were administered by physicians respectively to 98, 100 and 97 patients, waiting for a visit in the ambulatories of their General Practitioner. Answers relating to each instrument were analyzed according to sex, age and education of patients. All the instruments seemed to be feasible and acceptable, but only the COOP Charts and the FSQ were able to discriminate between different sex, age and scolarity groups. Taking into account the need to elaborate answers according to a formula when using the FSQ, we concluded that the best instrument for General Practice to provide a multidimensional measure of health status seems to be the COOP Charts.