425 research outputs found

    Multicomponent Strongly Interacting Few-Fermion Systems in One Dimension

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    The paper examines a trapped one-dimensional system of multicomponent spinless fermions that interact with a zero-range two-body potential. We show that when the repulsion between particles is very large the system can be approached analytically. To illustrate this analytical approach we consider a simple system of three distinguishable particles, which can be addressed experimentally. For this system we show that for infinite repulsion the energy spectrum is sixfold degenerate. We also show that this degeneracy is partially lifted for finitely large repulsion for which we find and describe corresponding wave functions.Comment: Paper in connection with the 22nd European Conference on Few-Body Problems in Physics, Krakow, Poland, 9-13 September 201

    A Solvable Model for Decoupling of Interacting Clusters

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    We consider M clusters of interacting particles, whose in-group interactions are arbitrary, and inter-group interactions are approximated by oscillator potentials. We show that there are masses and frequencies that decouple the in-group and inter-group degrees of freedom, which reduces the initial problem to M independent problems that describe each of the relative in-group systems. The dynamics of the M center-of-mass coordinates is described by the analytically solvable problem of M coupled harmonic oscillators. This paper derives and discusses these decoupling conditions. Furthermore, to illustrate our findings, we consider a charged impurity interacting with a ring of ions. We argue that the impurity can be used to probe the center-of-mass dynamics of the ions.Comment: Version accepted for publication in EP

    Clusters in separated tubes of tilted dipoles

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    A few-body cluster is a building block of a many-body system in a gas phase provided the temperature at most is of the order of the binding energy of this cluster. Here we illustrate this statement by considering a system of tubes filled with dipolar distinguishable particles. We calculate the partition function, which determines the probability to find a few-body cluster at a given temperature. The input for our calculations—the energies of few-body clusters—is estimated using the harmonic approximation. We first describe and demonstrate the validity of our numerical procedure. Then we discuss the results featuring melting of the zero-temperature many-body state into a gas of free particles and few-body clusters. For temperature higher than its binding energy threshold, the dimers overwhelmingly dominate the ensemble, where the remaining probability is in free particles. At very high temperatures free (harmonic oscillator trap-bound) particle dominance is eventually reached. This structure evolution appears both for one and two particles in each layer providing crucial information about the behavior of ultracold dipolar gases. The investigation addresses the transition region between few- and many-body physics as a function of temperature using a system of ten dipoles in five tubes

    Interplay between solid state microstructure and photophysics for poly(9,9-dioctylfluorene) within oriented polyethylene hosts

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    We present a study of isotropic and uniaxially oriented binary blend films comprising ≤1 wt % of the conjugated polymer poly(9,9‐dioctylfluorene) (PFO) dispersed in both ultra‐high molecular weight (UHMW) and linear‐low‐density (LLD) polyethylene (PE). Polarized absorption, fluorescence and Raman spectroscopy, scanning electron microscopy, and X‐ray diffraction are used to characterize the samples before and after tensile deformation. Results show that blend films can be prepared with PFO chains adopting a combination of several distinct molecular conformations, namely glassy, crystalline, and the so‐called β‐phase, which directly influences the resulting optical properties. Both PFO concentration and drawing temperature strongly affect the alignment of PFO chains during the tensile drawing of the blend films. In both PE hosts, crystallization of PFO takes place during drawing; the resulting ordered chains show optimal optical anisotropy. Our results clarify the PFO microstructure in oriented blends with PE and the processing conditions required for achieving the maximal optical anisotropy.ISSN:0887-6266ISSN:0098-1273ISSN:1099-048

    Feeding Ecology of Coryphaenoides rupestris from the Mid-Atlantic Ridge

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    The Macrourid fish roundnose grenadier, Coryphaenoides rupestris, is one of the most common benthopelagic fishes on the northern mid-Atlantic Ridge. The ecology of the species is comparatively well studied in continental slope waters of the North Atlantic, but not on the mid-Atlantic Ridge, which is a central mid-ocean area of its distribution. In total, 166 specimens from the RV G.O. Sars cruise in July 2004 were examined. The diet mainly comprised cephalopods, pelagic shrimps and fish. Pelagic and benthopelagic copepods were the most numerous prey, but did not contribute much on a weight basis. Cephalopods were by far the most important prey of the small grenadiers, while shrimps and fish became increasingly significant with increasing size. Previous studies from other areas have also found pelagic prey to be important, but in contrast to this study, cephalopods were generally of less importance. The study was an element of more wide-ranging food-web studies of the mid-Atlantic Ridge macro- and megafauna communities within the international MAR-ECO project

    Interactive Multiple Object Tracking (iMOT)

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    We introduce a new task for exploring the relationship between action and attention. In this interactive multiple object tracking (iMOT) task, implemented as an iPad app, participants were presented with a display of multiple, visually identical disks which moved independently. The task was to prevent any collisions during a fixed duration. Participants could perturb object trajectories via the touchscreen. In Experiment 1, we used a staircase procedure to measure the ability to control moving objects. Object speed was set to 1°/s. On average participants could control 8.4 items without collision. Individual control strategies were quite variable, but did not predict overall performance. In Experiment 2, we compared iMOT with standard MOT performance using identical displays. Object speed was set to 2°/s. Participants could reliably control more objects (M = 6.6) than they could track (M = 4.0), but performance in the two tasks was positively correlated. In Experiment 3, we used a dual-task design. Compared to single-task baseline, iMOT performance decreased and MOT performance increased when the two tasks had to be completed together. Overall, these findings suggest: 1) There is a clear limit to the number of items that can be simultaneously controlled, for a given speed and display density; 2) participants can control more items than they can track; 3) task-relevant action appears not to disrupt MOT performance in the current experimental context

    Optimum air feed locations on medical waste incineration rotary kiln by computational fluid dynamics (CFD)

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    Twenty-four tons of medical waste is combusted every day in Istanbul. The plant is operated by ISTAÇ AŞ and combustor type is rotary kiln. The air was being fed manually along with the waste being introduced to the kiln. This case caused some problems regarding the combustion efficiency. The administration staff decided to open holes to supply air to the combustor. In this study, CFD was utilized in order to determine the optimum places for air inlets. Flow geometry of the air was prepared and then meshed for calculations. k-ε turbulence model was utilized in the calculations. Four air inlet pipes were placed on the edges of the circular inlet area. Different locations were tested. When the air was fed from the top, waste could not completely contact with the air. Additionally, different inlet angles were tested from zero degrees to thirty degrees. The degree of the inlet did not much change the combustion characteristics inside the kiln. Piping holes were burrowed from the bottom at zero degree angle

    Batı Karadeniz Bölgesinde anormal servikal sitoloji risk faktörleri ve sağlık sigortasının önemi

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    Objective: To evaluate the prevalence of abnormal cervical cytological findings in the Western Black Sea Region and investigate an association between socio-demographic risk factors and the presence of cytological abnormalities. Material and Method: The reports of 11,539 cervical smears diagnosed according to Bethesda System 2001 version in the Pathology Department between January 2011 and December 2012 were reviewed retrospectively from the hospital records and cytopathology reports. Repeated smear results, unsatisfactory smear results, patients with known gynecologic malignancy history, smear results of patients with hysterectomy and smear results of patients whose socio-demographic information could not be obtained were excluded from the evaluation. The results of 7,740 patients who met the criteria for the study were evaluated. Results: The prevalence of cervical cytological abnormalities was 1.8 % in general. The prevalence rates for atypical squamous cells with undetermined significance (ASC-US), atypical squamous cells, cannot exclude a high-grade squamous intraepithelial lesion (ASC-H), low-grade squamous intraepithelial lesions (LSIL), high-grade squamous intraepithelial lesions (HSIL), and atypical glandular cells (AGC) were 1.16%, 0.11%, 0.29%, 0.15%, and 0.03% respectively. The prevalence of cytologically diagnosed cervical invasive neoplasia was 0.025%. Advanced age, low education level (primary school or less) and not having health insurance were found as to be risk factors for preinvasive and invasive lesions. Women who had a high school education and previously had a smear test had decreased risk for developing preinvasive and invasive lesions. Conclusion: This study shows prevalence of abnormal cervical cytology findings and associoted risk factors in the Western Black Sea Region of Turkey. The most important risk factor was identified as not having health insurance
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