442 research outputs found

    Wave function mapping conditions in Open Quantum Dots structures

    Get PDF
    We discuss the minimal conditions for wave function spectroscopy, in which resonant tunneling is the measurement tool. Two systems are addressed: resonant tunneling diodes, as a toy model, and open quantum dots. The toy model is used to analyze the crucial tunning between the necessary resolution in current-voltage characteristics and the breakdown of the wave functions probing potentials into a level splitting characteristic of double quantum wells. The present results establish a parameter region where the wavefunction spectroscopy by resonant tunneling could be achieved. In the case of open quantum dots, a breakdown of the mapping condition is related to a change into a double quantum dot structure induced by the local probing potential. The analogy between the toy model and open quantum dots show that a precise control over shape and extention of the potential probes is irrelevant for wave function mapping. Moreover, the present system is a realization of a tunable Fano system in the wave function mapping regime.Comment: 6 pages, 6 figure

    Productividad y caracteres morfolĂłgicos de hĂ­bridos de maĂ­z forrajero

    Get PDF
    In orden to evaluate the yield of dry matter and the relationship of the morphological components among plants of forage corn hybrids in Tecali of Herrera, Puebla, Mexico. 10 experimental trilinear hybrids, two simple hybrids, a criollo and the HS-2 commercial hybrid were studied. Plant material was sown at random in plots of four rows of 80 cm wide and 40 m long with four repetitions, depositing 7 cm deep one seed every 20 cm. A dossage of 160-60 -00 (N-P-K) was applied. Irrigation was applied every fifteen days. Ten plants were harvested in complete competition in the center of each plot in the physiological state of 1/3 milk line. The variables yield of green matter (YGM), yield of dry matter (YDM), plant height (PH), number of corn (NC), number of leaves (NL), stem diameter (SD) and the relationships leaf:plant (L:P), stem:plant (S:P) and corn:plant (C:P), under a completely random design were measured. The HT-1 presented the highest YGM, YDM and HP. YGM and YDM were influenced to a certain extent by the PH, SD when presenting considerable positive correlations near or above 0.50. The S:P is greatly affected in a negative way to the C:P by showing a very high negative correlation.El objetivo fue evaluar el rendimiento de materia seca y la relación de los componentes morfológicos de plantas de maíz forrajero en Tecali de Herrera, Puebla, México. Se evaluaron 10 híbridos trilineales, dos híbridos simples, un criollo y el híbrido comercial HS-2. Se sembraron en parcelas de cuatro surcos de 80 cm ancho y 40 m largo con cuatro repeticiones, depositando una semilla cada 20 cm a 7 cm de profundidad. Se fertilizó con 160-60-00 (N-P-K). Los riegos se aplicaron cada quince días. Se cosecharon 10 plantas en competencia completa en el centro de cada parcela en el estado fisiológico de 1/3 de línea de leche. Se midió el rendimiento de materia verde (RMV) y seca (RMS), altura de planta (AP), número de elotes (NE), número de hojas (NH), diámetro del tallo (DT) y las relaciones hoja:planta (H:P), tallo:planta (T:P) y elote:planta (E:P), bajo un diseño completamente al azar. El genotipo HT-1 presentó las medias más altas para las variables RMV, RMS y AP. RMV y RMS fueron influenciados por las variables AP, DT y NH al presentar correlaciones positivas cercanas a 0.50. El NE tuvo influencia en una menor T:P al presentar una correlación negativa considerable por arriba de 0.50. La T:P afectó grandemente en forma negativa a la E:P al mostrar una correlación negativa muy alt

    Routine computed tomography after recent operative exploration for penetrating trauma

    Get PDF
    BACKGROUND Patients with penetrating trauma who cannot be stabilized undergo operative intervention without preoperative imaging. In such cases, postoperative imaging may reveal additional injuries not identified during the initial operative exploration. The purpose of this study is to explore the utility of postoperative CT imaging in the setting of penetrating trauma. METHODS This was a retrospective analysis of patients with penetrating trauma treated at an urban Level 1 trauma center between 2010 and 2015. Patients were included if they underwent an emergent laparotomy without preoperative imaging. Patients were excluded if they had prior imaging or concomitant blunt injury. For the purposes of this study, occult injury was defined as a CT scan finding not mentioned in the first operative report. Descriptive statistics were used to compare patient characteristics who had received imaging immediately postoperatively with those who had not. RESULTS During the 5-year study period, 328 patients who had a laparotomy for penetrating trauma over the study period, 225 patients met the inclusion criteria. Seventy-three (32%) patients underwent CT scanning immediately postoperatively with occult injuries identified in 38 (52%) patients. The most frequent occult injuries were orthopedic (20 of 43) and genitourinary (9 of 43). Importantly, 10 (26%) of the 38 patients required an intervention for these occult injuries. Those selected for immediate postoperative imaging were more likely to have sustained gunshot wounds and were significantly more severely injured (higher Injury Severity Score and longer length of hospital stay) when compared to patients who did not receive immediate imaging. CONCLUSION We recommend the use of immediate postoperative CT after emergent laparotomy especially when there is a high index of suspicion for spine or genitourinary injuries and in patients who have sustained ballistic penetrating injuries. LEVEL OF EVIDENCE Therapeutic/care management, level IV diagnostic tests or criteria, level IV

    Secondary Beam Monitors for the NuMI Facility at FNAL

    Get PDF
    The Neutrinos at the Main Injector (NuMI) facility is a conventional neutrino beam which produces muon neutrinos by focusing a beam of mesons into a long evacuated decay volume. We have built four arrays of ionization chambers to monitor the position and intensity of the hadron and muon beams associated with neutrino production at locations downstream of the decay volume. This article describes the chambers' construction, calibration, and commissioning in the beam.Comment: Accepted for publication in Nucl. Instr. Meth.

    New 1-aryl-3-substituted propanol derivatives as antimalarial agents

    Get PDF
    This paper describes the synthesis and in vitro antimalarial activity against a P. falciparum 3D7 strain of some new 1-aryl-3-substituted propanol derivatives. Twelve of the tested compounds showed an IC50 lower than 1 ÎĽM. These compounds were also tested for cytotoxicity in murine J774 macrophages. The most active compounds were evaluated for in vivo activity against P. berghei in a 4-day suppressive test. Compound 12 inhibited more than 50% of parasite growth at a dose of 50 mg/kg/day. In addition, an FBIT test was performed to measure the ability to inhibit ferriprotoporphyrin biocrystallization. This data indicates that 1-aryl-3-substituted propanol derivatives hold promise as a new therapeutic option for the treatment of malaria

    Neutron cross-sections for advanced nuclear systems : The n-TOF project at CERN

    Get PDF
    © Owned by the authors, published by EDP Sciences, 2014 This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly citedThe study of neutron-induced reactions is of high relevance in a wide variety of fields, ranging from stellar nucleosynthesis and fundamental nuclear physics to applications of nuclear technology. In nuclear energy, high accuracy neutron data are needed for the development of Generation IV fast reactors and accelerator driven systems, these last aimed specifically at nuclear waste incineration, as well as for research on innovative fuel cycles. In this context, a high luminosity Neutron Time Of Flight facility, n-TOF, is operating at CERN since more than a decade, with the aim of providing new, high accuracy and high resolution neutron cross-sections. Thanks to the features of the neutron beam, a rich experimental program relevant to nuclear technology has been carried out so far. The program will be further expanded in the near future, thanks in particular to a new high-flux experimental area, now under construction.Peer reviewedFinal Published versio

    238U(n, Îł) reaction cross section measurement with C 6D6 detectors at the n-TOF CERN facility

    Get PDF
    This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly citedThe radiative capture cross section of 238U is very important for the developing of new reactor technologies and the safety of existing ones. Here the preliminary results of the 238U(n,Îł) cross section measurement performed at n-TOF with C6D6 scintillation detectors are presented, paying particular attention to data reduction and background subtraction.Peer reviewe

    High accuracy 234U(n,f) cross section in the resonance energy region

    Get PDF
    New results are presented of the 234U neutron-induced fission cross section, obtained with high accuracy in the resonance region by means of two methods using the 235U(n,f) as reference. The recent evaluation of the 235U(n,f) obtained with SAMMY by L. C. Leal et al. (these Proceedings), based on previous n-TOF data [1], has been used to calculate the 234U(n,f) cross section through the 234U/235U ratio, being here compared with the results obtained by using the n-TOF neutron flux

    The nucleosynthesis of heavy elements in Stars : The key isotope 25Mg

    Get PDF
    This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly citedWe have measured the radiative neutron-capture cross section and the total neutron-induced cross section of one of the most important isotopes for the s process, the 25Mg. The measurements have been carried out at the neutron time-of-flight facilities n-TOF at CERN (Switzerland) and GELINA installed at the EC-JRC-IRMM (Belgium). The cross sections as a function of neutron energy have been measured up to approximately 300 keV, covering the energy region of interest to the s process. The data analysis is ongoing and preliminary results show the potential relevance for the s process.Peer reviewe

    Time-of-flight and activation experiments on 147Pm and 171Tm for astrophysics

    Get PDF
    The neutron capture cross section of several key unstable isotopes acting as branching points in the s-process are crucial for stellar nucleosynthesis studies, but they are very challenging to measure due to the difficult production of sufficient sample material, the high activity of the resulting samples, and the actual (n,Îł) measurement, for which high neutron fluxes and effective background rejection capabilities are required. As part of a new program to measure some of these important branching points, radioactive targets of 147Pm and 171Tm have been produced by irradiation of stable isotopes at the ILL high flux reactor. Neutron capture on 146Nd and 170Er at the reactor was followed by beta decay and the resulting matrix was purified via radiochemical separation at PSI. The radioactive targets have been used for time-of-flight measurements at the CERN n-TOF facility using the 19 and 185 m beam lines during 2014 and 2015. The capture cascades were detected using a set of four C6D6 scintillators, allowing to observe the associated neutron capture resonances. The results presented in this work are the first ever determination of the resonance capture cross section of 147Pm and 171Tm. Activation experiments on the same 147Pm and 171Tm targets with a high-intensity 30 keV quasi-Maxwellian flux of neutrons will be performed using the SARAF accelerator and the Liquid-Lithium Target (LiLiT) in order to extract the corresponding Maxwellian Average Cross Section (MACS). The status of these experiments and preliminary results will be presented and discussed as well
    • …
    corecore