Neutron time-of-flight detectors (nTOF) used at Sandia's Z-Machine.

Neutron time-of-flight (nTOF) detectors have been used on Sandia National Laboratories' Z-Machine for inertial confinement fusion and magnetized liner fusion experiments to infer physics parameters including the apparent fuel-ion temperature, neutron yield, the magnetic-radius product (BR), and the liner rho-r. Single-paddle, dual-paddle, and co-axial scintillation nTOF detectors are used in axial lines-of-sight (LOS) and LOS that are 12° from the midplane. Detector fabrication, characterization, and calibration are discussed.

Temperature effects on the conductance, spin-valley polarization and tunneling magnetoresistance of single magnetic silicene junctions.

Magnetic silicene junctions are versatile structures with spin-valley polarization and magnetoresistive capabilities. Here, we investigate the temperature effects on the transport properties of single magnetic silicene junctions. We use the transfer matrix method and the Landauer-Büttiker formalism to calculate the transmittance, conductance, spin-valley polarization and tunneling magnetoresistance. We studied the case for T = 0 K, finding the specific parameters where the spin-valley polarization and the tunneling magnetoresistance reach optimized values. Regarding the temperature effects, we find that its impact is not the same on the different transport properties. In the case of the conductance, depending on the spin-valley configuration the resonant peaks disappear at different temperatures. The spin polarization persists at a considerable value up to T=80 K, contrary to the valley polarization which is more susceptible to the temperature effects. In addition, a stepwise spin-valley polarization can be achieved at low temperature. The tunneling magnetoresistance is attenuated considerably as the temperature rises, decreasing more than two orders of magnitude after T=20 K. These findings indicate that in order to preserve the spin-valley polarization and magnetoresistive capabilities of magnetic silicene junctions is fundamental to modulate the temperature adequately.

Electronic cloaking of confined states in phosphorene junctions.

We study the electronic transport of armchair (AC) and zigzag (ZZ) gated phosphorene junctions. We find confined states for both direction-dependent phosphorene junctions. In the case of AC junctions confined states are reflected in the transmission properties as Fabry-Pérot resonances at normal and oblique incidence. In the case of ZZ junctions confined states are invisible at normal incidence, resulting in a null transmission. At oblique incidence Fabry-Pérot resonances are presented in the transmission as in the case of AC junctions. This invisibility or electronic cloaking is related to the highly direction-dependent pseudospin texture of the charge carriers in phosphorene. Electronic cloaking is also manifested as a series of singular peaks in the conductance and as inverted peaks in the Seebeck coefficient. The characteristics of electronic cloaking are also susceptible to the modulation of the phosphorene bandgap and an external magnetic field. So, electronic cloaking in phosphorene junctions in principle could be tested through transport, thermoelectric or magnetotransport measurements.

Enhancement of the thermoelectric properties in bilayer graphene structures induced by Fano resonances.

Fano resonances of bilayer graphene could be attractive for thermoelectric devices. The special profile presented by such resonances could significantly enhance the thermoelectric properties. In this work, we study the thermoelectric properties of bilayer graphene single and double barrier structures. The barrier structures are typically supported by a substrate and encapsulated by protecting layers, reducing considerably the phonon thermal transport. So, we will focus on the electronic contribution to the thermal transport. The charge carriers are described as massive chiral particles through an effective Dirac-like Hamiltonian. The Hybrid matrix method and the Landauer-Büttiker formalism are implemented to obtain the transmission, transport and thermoelectric properties. The temperature dependence of the Seebeck coefficient, the power factor, the figure of merit and the efficiency is analyzed for gapless single and double barriers. We find that the charge neutrality point and the system resonances shape the thermoelectric response. In the case of single barriers, the low-temperature thermoelectric response is dominated by the charge neutrality point, while the high-temperature response is determined by the Fano resonances. In the case of double barriers, Breit-Wigner resonances dominate the thermoelectric properties at low temperatures, while Fano and hybrid resonances become preponderant as the temperature rises. The values for the figure of merit are close to two for single barriers and above three for double barriers. The system resonances also allows us to optimize the output power and the efficiency at low and high temperatures. By computing the density of states, we also corroborate that the improvement of the thermoelectric properties is related to the accumulation of electron states. Our findings indicate that bilayer graphene barrier structures can be used to improve the response of thermoelectric devices.

Association between dental hygiene, gingivitis and overweight or the risk of overweight in primary teeth of 4- and 5-year-old preschoolers in México.

OBJECTIVE: To determine the association between dental hygiene, gingivitis and overweight or the risk of overweight according to body mass index (BMI). METHODS: A cross-sectional study was performed with 1527 preschoolers. The children were divided into 4 groups: (i) absence of visible plaque and normal weight; (ii) absence of visible plaque and risk of overweight or overweight; (iii) presence of visible plaque and normal weight; and (iv) presence of visible plaque and risk of overweight or overweight. The clinical parameters evaluated were as follows: body mass index, degree of urban marginalization, dental caries, the simplified oral hygiene index and gingival status. Bivariate analysis and multivariate binary logistic regression models were used to identify associations between variables. RESULTS: The highest mean of gingivitis (0.28) was observed in the groups with visible plaque with normal weight and with overweight and risk of overweight. The presence of visible plaque and risk of overweight or overweight were positively associated (P = .0001) with the mean of gingivitis (OR = 8.28, 95% CI = 3.30-19.8). The absence of visible plaque and risk of overweight or overweight (P = .0001) were also positively associated with the presence of gingivitis (OR = 2.44, 95% CI = 0.68-8.06). This is after both models were adjusted by gender and degree of marginalization. CONCLUSIONS: The professionals should develop interdisciplinary approaches to (i) propose appropriate interventions to improve oral health in overweight preschoolers; and (ii) propose interventions to decrease the overweight with the possibility of also reducing its association with gingivitis.

Development of a reusable and sustainable biocatalyst by immobilization of soybean peroxidase onto magnetic adsorbent.

In this work we synthesized an activated carbon/magnetite composite by a simple co-precipitation method. The activated carbon (AC) was synthesized from the solid waste obtained in the extraction process of the peroxidase enzyme and the magnetic composite was used as support for the immobilization of soybean peroxidase (SP). After the determination of the optimal immobilization parameters, a 100% yield was achieved under the following conditions: support:enzyme proportion of 1.0:0.05 g, equilibration time of 7 h, pH 3.0 (citrate buffer phosphate 0.1 mol L-1) and temperature of 50 °C. The determination of pH to the point of zero charge was also done to assist in the understanding of the immobilization process at different pH values. Several characterization techniques were used, such as thermogravimetric analysis, elemental analysis composition, X-ray powder diffraction, Fourier transform infrared spectroscopy and Scanning electron microscopy. The biocatalyst presented excellent operational stability and was reused for 11 consecutive cycles. The magnetic properties inserted in the AC contributed to the removal of the biocatalyst from the reaction medium without interfering in the adsorptive characteristics of the AC. Thus, the activated carbon/magnetite composite can be applied to different research fields with high performance.

Fano resonances in bilayer graphene superlattices.

In this work, we address the ubiquitous phenomenon of Fano resonances in bilayer graphene. We consider that this phenomenon is as exotic as other phenomena in graphene because it can arise without an external extended states source or elaborate nano designs. However, there are not theoretical and/or experimental studies that report the impact of Fano resonances on the transport properties. Here, we carry out a systematic assessment of the contribution of the Fano resonances on the transport properties of bilayer graphene superlattices. Specifically, we find that by changing the number of periods, adjusting the barriers height as well as modifying the barriers and wells width it is possible to identify the contribution of Fano resonances on the conductance. Particularly, the coupling of Fano resonances with the intrinsic minibands of the superlattice gives rise to specific and identifiable changes in the conductance. Moreover, by reducing the angular range for the computation of the transport properties it is possible to obtain conductance curves with line-shapes quite similar to the Fano profile and the coupling profile between Fano resonance and miniband states. In fact, these conductance features could serve as unequivocal characteristic of the existence of Fano resonances in bilayer graphene.

Evaluation of four designs of short implants placed in atrophic areas with reduced bone height: a three-year, retrospective, clinical and radiographic study.

The aim of the present study was to evaluate retrospectively the clinical and radiographic behaviour of four commercially-available short implants with different macrodesigns and microdesigns in areas in which the height of the bone was reduced. We took into account the success and survival, peri-implant crestal bone loss, and the level of probing at which the gum bled. Patients were included if they had been given one or more short implants (≤8.5mm long) in the posterior jaws at least three years earlier. Three hundred and ninety-one short implants were placed in 170 subjects, and were divided in four groups based on the brand of implant. The implants were evaluated one, two, and three years after they had been inserted. Short implants had a three-year survival and success rate of 90% in all groups, and bone loss was acceptable after three years with no significant differences between them. These results support the use of short implants as an effective and safe treatment. However, within the limitations of this study, the design of the implant does seem to influence the behaviour of peri-implant bone at the crestal level.

Two-dimensional self-assembly of benzotriazole on an inert substrate.

The ultra-high vacuum (UHV) room temperature adsorption of benzotriazole (BTAH), a well-known corrosion inhibitor for copper, has been investigated on the pristine Au(111) surface using a combination of surface sensitive techniques. The dimensionality of the molecule is reduced from the 3D crystal structure to a 2-dimensional surface confinement, which induces the formation of hydrogen bonded 1-dimensional molecular chains consisting of alternating pro-S and pro-R enantiomers mainly. The 0-dimensional system is characteristic of gas-phase BTAH, which undergoes a tautomeric equilibrium, with consequences for the resulting adsorbed species. The balance between hydrogen bonding, inter-chain van der Waals interactions and surface-molecule interactions, and the correlation with the dimensionality of the system, are discussed in light of the experimental results and a computational description of the observed features.

[Breast Cancer Survival: Clinical andPathological Prognostic Factors Analysis]. / Supervivencia de pacientes con cáncer de mama. Análisis por factores pronóstico, clínicos y patológicos.

Background: Breast cancer is the leading cause of cancer death in women in Mexico, is a heterogeneous disease, and knowledge of prognostic factors are critical in making treatment decisions. Objetive: determine the overall survival (OS) and disease-free survival (DFS) at 5 years, analyzed by risk groups. Material and methods: Patients diagnosed with breast treated at the Institute of Breast Diseases FUCAM from July 2005 to December 2014 were included. Simple frequencies were used for analysis of the general characteristics, and 5- year OS and DFS were analyzed using Kaplan-Meier curves. A subset analysis of the clinical stage and comparing survival in those patients diagnosed by mammography screening program was performed. Results: 4,902 patients with breast cancer were included, general clinical and pathological features are described and 3,762 patients were included for analysis of 5-year OS and DFS. The average age at diagnosis was 53.7 years; 13.3% were <40 years, which deleteriously reflects on the supervivencia global 76 vs 84% in >40. At diagnosis predominated locally advanced stages (45%), OS and DFS at 5 years was 96.8 ± 0.6% and 93.4%±0.9 respectively for early stages, 74.6 ± 1.7% and 68.7 ± 2% for locally advanced and 35.9 ± 5.1% and 37.4 ± 10.3% for metastatic tumors. Women diagnosed in the screening program had significantly better OS and DFS compared with symptomatic patients (95 and 93% vs 79 and 77%). For biological subtypes, OS and DFS was 89 and 84% for luminal, 81 and 81% for luminal Her +, 74 and 78% for pure Her 2, and 69 and 73% for triple negative. Conclusion: Knowledge of the prognostic factors that affect survival of patients with breast cancer is essential for categorizing risk groups and to individualize treatment in order to improve life expectancy.

A technique for verifying the input response function of neutron time-of-flight scintillation detectors using cosmic rays.

An accurate interpretation of DD or DT fusion neutron time-of-flight (nTOF) signals from current mode detectors employed at the Z-facility at Sandia National Laboratories requires that the instrument response functions (IRF's) be deconvolved from the measured nTOF signals. A calibration facility that produces detectable sub-ns radiation pulses is typically used to measure the IRF of such detectors. This work, however, reports on a simple method that utilizes cosmic radiation to measure the IRF of nTOF detectors, operated in pulse-counting mode. The characterizing metrics reported here are the throughput delay and full-width-at-half-maximum. This simple approach yields consistent IRF results with the same detectors calibrated in 2007 at a LINAC bremsstrahlung accelerator (Idaho State University). In particular, the IRF metrics from these two approaches and their dependence on the photomultipliers bias agree to within a few per cent. This information may thus be used to verify if the IRF for a given nTOF detector employed at Z has changed since its original current-mode calibration and warrants re-measurement.

Predicting the sensitivity of the beryllium/scintillator layer neutron detector using Monte Carlo and experimental response functions.

A methodology for obtaining empirical curves relating absolute measured scintillation light output to beta energy deposited is presented. Output signals were measured from thin plastic scintillator using NIST traceable beta and gamma sources and MCNP5 was used to model the energy deposition from each source. Combining the experimental and calculated results gives the desired empirical relationships. To validate, the sensitivity of a beryllium/scintillator-layer neutron activation detector was predicted and then exposed to a known neutron fluence from a Deuterium-Deuterium fusion plasma (DD). The predicted and the measured sensitivity were in statistical agreement.

Pulmonary hypertension due to acute respiratory distress syndrome

Our aims were to describe the prevalence of pulmonary hypertension in patients with acute respiratory distress syndrome (ARDS), to characterize their hemodynamic cardiopulmonary profiles, and to correlate these parameters with outcome. All consecutive patients over 16 years of age who were in the intensive care unit with a diagnosis of ARDS and an in situ pulmonary artery catheter for hemodynamic monitoring were studied. Pulmonary hypertension was diagnosed when the mean pulmonary artery pressure was >25 mmHg at rest with a pulmonary artery occlusion pressure or left atrial pressure <15 mmHg. During the study period, 30 of 402 critically ill patients (7.46%) who were admitted to the ICU fulfilled the criteria for ARDS. Of the 30 patients with ARDS, 14 met the criteria for pulmonary hypertension, a prevalence of 46.6% (95% CI; 28-66%). The most common cause of ARDS was pneumonia (56.3%). The overall mortality was 36.6% and was similar in patients with and without pulmonary hypertension. Differences in patients' hemodynamic profiles were influenced by the presence of pulmonary hypertension. The levels of positive end-expiratory pressure and peak pressure were higher in patients with pulmonary hypertension, and the PaCO2 was higher in those who died. The level of airway pressure seemed to influence the onset of pulmonary hypertension. Survival was determined by the severity of organ failure at admission to the intensive care unit.

Pulmonary hypertension due to acute respiratory distress syndrome.

Our aims were to describe the prevalence of pulmonary hypertension in patients with acute respiratory distress syndrome (ARDS), to characterize their hemodynamic cardiopulmonary profiles, and to correlate these parameters with outcome. All consecutive patients over 16 years of age who were in the intensive care unit with a diagnosis of ARDS and an in situ pulmonary artery catheter for hemodynamic monitoring were studied. Pulmonary hypertension was diagnosed when the mean pulmonary artery pressure was >25 mmHg at rest with a pulmonary artery occlusion pressure or left atrial pressure <15 mmHg. During the study period, 30 of 402 critically ill patients (7.46%) who were admitted to the ICU fulfilled the criteria for ARDS. Of the 30 patients with ARDS, 14 met the criteria for pulmonary hypertension, a prevalence of 46.6% (95% CI; 28-66%). The most common cause of ARDS was pneumonia (56.3%). The overall mortality was 36.6% and was similar in patients with and without pulmonary hypertension. Differences in patients' hemodynamic profiles were influenced by the presence of pulmonary hypertension. The levels of positive end-expiratory pressure and peak pressure were higher in patients with pulmonary hypertension, and the PaCO2 was higher in those who died. The level of airway pressure seemed to influence the onset of pulmonary hypertension. Survival was determined by the severity of organ failure at admission to the intensive care unit.

Fusion-neutron-yield, activation measurements at the Z accelerator: design, analysis, and sensitivity.

We present a general methodology to determine the diagnostic sensitivity that is directly applicable to neutron-activation diagnostics fielded on a wide variety of neutron-producing experiments, which include inertial-confinement fusion (ICF), dense plasma focus, and ion beam-driven concepts. This approach includes a combination of several effects: (1) non-isotropic neutron emission; (2) the 1/r(2) decrease in neutron fluence in the activation material; (3) the spatially distributed neutron scattering, attenuation, and energy losses due to the fielding environment and activation material itself; and (4) temporally varying neutron emission. As an example, we describe the copper-activation diagnostic used to measure secondary deuterium-tritium fusion-neutron yields on ICF experiments conducted on the pulsed-power Z Accelerator at Sandia National Laboratories. Using this methodology along with results from absolute calibrations and Monte Carlo simulations, we find that for the diagnostic configuration on Z, the diagnostic sensitivity is 0.037% ± 17% counts/neutron per cm(2) and is ∼ 40% less sensitive than it would be in an ideal geometry due to neutron attenuation, scattering, and energy-loss effects.