The performance of Schottky diodes as far-infrared modulators

We analyze the performance as a terahertz-frequency modulator of a small-area Schottky diode mounted in a corner-cube antenna. The analysis includes the effects of carrier inertia and dielectric relaxation as modeled by Champlin and Eisenstein (1978). It also includes the effect of the vanishing of the depletion region above the flat-band potential, as modeled by Crowe and Mattauch (1986). Our baseline calculation refers to a 1.4 μm diameter diode (Univ. of Virginia batch no. 1E12) operated at a carrier frequency of 2.52 THz and a modulation frequency of 8 GHz, as was used in the experiments of Watson, Grossman, and Phillips (1988). The effects on reflectivity modulation, and therefore on sideband-generation efficiency, of varying the diode parameters are investigated. Our conclusions are: A) For all realistic diode parameters, the phase modulation completely dominates the amplitude modulation. B) Performance is degraded well below the plasma frequency in the undepleted epilayer due to the presence of a second resonance, caused by the interaction of the barrier capacitance and the effective inductance due to carrier inertia, C) The effects of varying the antenna impedance, temperature, diode substrate size, and Schottky barrier height over realistic ranges are small. D) An improvement in single-sideband conversion efficiency of approximately 20 db may be obtained by increasing the epilayer doping and simultaneously reducing the diode radius.     

Chemical and Isotopic Tracer Evaluation of Water Mixing and Evaporation in a Dammed Texas River During Drought

The interaction between drought and river regulation is monitored to better understand river flow mixing, evaporation and surface‐groundwater exchange in changing regional climates and in increasingly regulated waterways. This study compared Brazos River stable isotope (δ¹⁸O and δD) and electrical conductivity values with reservoir, creek and aquifer samples in the Brazos watershed, the largest watershed in Texas. The combination of tributaries, rainfall and the Brazos River Alluvium Aquifer, on the one hand, and the Lake Whitney reservoir, on the other hand, represent endmembers of dilute run‐off water and evaporated saline water, respectively. A simple isotope mixing model that uses monthly river discharge, Lake Whitney discharge, historical monthly precipitation δ¹⁸O and pan evaporation accurately reconstructs river δ¹⁸O (±0.5‰ on average). Data and isotope balance modelling support continued evaporation of ¹⁸O‐enriched Lake Whitney water as it flows downstream, although the most evaporation took place in Lake Whitney. The difference between river and precipitation δ¹⁸O, or Δ¹⁸O_RIV‐_PPT, here a measurement of degree of evaporation, ranged from ?0.1‰ for a small creek, to 1.7‰ for the Brazos River, to at least 2.7‰ in Lake Whitney. This study indicates that drought in regulated rivers may enhance reservoir discharge dominance in river flows during peak drought conditions when combined run‐off and baseflow dominance would be expected in a similar undammed river. Copyright © 2016 John Wiley & Sons, Ltd.     

Lead stabilizers and alternatives in wire & cable and geomembranes

Lead replacement heat stabilizers have made considerable inroads in areas where water resistance is not significant, primarily in wire jackets and insulations not for wet locations. In areas where short-term moisture resistance is required, such as with flexible cord insulation and electrical tapes, nonlead products are either in use or under development. In those areas where long-term water resistance is needed, as with geomembranes and many wire insulations, despite much experimentation, commercial products are not in use as yet in the United States. The factors involved are discussed.     

Analysis of the interaction between the dendritic conductance density and activated area in modulating alpha-motoneuron EPSP: statistical computer model

Five reconstructed alpha-motoneurons (MNs) are simulated under physiological and morphological realistic parameters. We compare the resulting excitatory postsynaptic potential (EPSP) of models, containing voltage-dependent channels on the dendrites, with the EPSP of a passive MN and an active soma and axon model. In our simulations, we apply three different distribution functions of the voltage-dependent channels on the dendrites: a step function (ST) with uniform spatial dispersion; an exponential decay (ED) function, with proximal to the soma high-density location; and an exponential rise (ER) with distally located conductance density. In all cases, the synaptic inputs are located as a gaussian function on the dendrites. Our simulations lead to eight key observations. (1) The presence of the voltage-dependent channels conductance (g(Active)) in the dendrites is vital for obtaining EPSP peak boosting. (2) The mean EPSP peaks of the ST, ER, and ED distributions are similar when the ranges of G (total conductance) are equal. (3) EPSP peak increases monotonically when the magnitude of g(Na_step) (maximal g(Na) at a particular run) is increased. (4) EPSP kinetics parameters were differentially affected; time integral was decreased monotonically with increased g(Na_step), but the rate of rise (the decay time was not analyzed) does not show clear relations. (5) The total G can be elevated by increasing the number of active dendrites; however, only a small active area of the dendritic tree is sufficient to get the maximal boosting. (6) The sometimes large variations in the parameters values for identical G depend on the g(Na_step) and active dendritic area. (7) High g(Na_step) in a few dendrites is more efficient in amplifying the EPSP peak than low g(Na_step) in many dendrites. (8) The EPSP peak is approximately linear with respect to the MNs' R(N) (input resistance).     

3D Printing Thermally Stable High-Performance Polymers Based on a Dual Curing Mechanism

High-performance polymers are an important class of materials that are used in challenging conditions, such as in aerospace applications. Until now, 3D printing based on stereolithography processes can not be performed due to a lack of suitable materials. There is report on new materials and printing compositions that enable 3D printing of objects having extremely high thermal resistance, with Tg of 283 °C and excellent mechanical properties. The printing is performed by a low-cost Digital Light Processing printer, and the formulation is based on a dual-cure mechanism, photo, and thermal process. The main components are a molecule that has both epoxy and acrylate groups, alkylated melamine that enables a high degree of crosslinking, and a soluble precursor of silica. The resulting objects are made of hybrid materials, in which the silicon is present in the polymeric backbone and partly as silica enforcement particles.     

Cancer pain management in developing countries: a mosaic of complex issues resulting in inadequate analgesia

OBJECTIVE: To determine the prevalence of suicidal ideation and the symptomatic profile as well as to identify the sociodemographic characteristics highlighting female adolescents with the highest scores on suicidal ideation in adolescents living in Mexico City: students and suicidal patients. MATERIAL AND METHODS: A cross-sectional and ex-post-facto study was carried out in order to analyze information from two samples: 1,712 junior and junior high school women students (representative student sample in Mexico City), and 30 adolescents inpatient hospitalized for her suicide attempts (clinical sample). RESULTS: Prevalence of presence as well as persistence of suicidal ideation were higher in the clinical sample, nevertheless 11.8% of the school sample had everyone of the symptoms in a range of 1 to 7 days. The most persistent of the ideation symptoms was: "My family would be better if I were dead"; and in the clinical sample it was "I thought about killing myself". Finally, the sociodemographic characteristics that best matched the student girls having the highest scores in suicidal ideation were: to be on junior high school, to get low grades, to acknowledge school performance as bad and to have interrupted her studies. The characteristics that highlight the girls with a first attempt were analyzed in the clinic sample in comparison with those ones with two or more attempts. It was significant that girls in the second group were living only with one parent and they thought in the last attempt that their dead would be possible or certain. CONCLUSIONS: The prevalence of suicidal ideation was important in the school sample. If it is considered that this psychological construct has a strong association with suicidal attempt, and multiple suicide conduct, then is a priority to detect adolescents in risk and to make preventive efforts, considering the sociodemographic characteristics that configurate in risk for suicidal ideation.     

Nutritional regulation of the activities of lipogenic enzymes of rat liver and brown adipose tissue

Nutrition-induced effects on the activity of enzymes of lipogenesis, fatty acid synthase (FAS: EC 2.3.1.85), ATP citrate lyase (ACL: EC 4.1.3.8), malic enzyme (ME; EC 1.1.1.40), glucose-6-phosphate dehydrogenase (G6PDH: EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (PGDH; EC 1.1.1.44) were investigated in liver and interscapular brown adipose tissue (BAT) of rats. The lipogenic enzymes could be grouped into two categories according to their response to dietary manipulations: FAS and ACL, both key enzymes of lipogenesis, responded fast and strongly to dietary manipulations. ME, G6PDH and PGDH, enzymes which also contribute to metabolic pathways other than lipogenesis, responded in a more sustained and less pronounced fashion. Feed deprivation caused the specific activities of lipogenic enzymes to decline several-fold. Refeeding of previously fasted (up to 3 days) animals increased the activities dramatically (10-to 25-fold) to far above pre-fasting levels ("overshoot"). Repetition of the fasting/refeeding regimen increasingly impaired the ability of both tissues to synthesize overshooting enzyme activities in the subsequent refeeding period. The fasting-induced decline of the activities was prevented when sugars were provided to the animals via drinking water. The sugars displayed different effectivities: sucrose = glucose > fructose > maltose > > lactose. Sugars as the sole nutrient after fasting were also able to induce overshooting enzyme activities. Again, activities of FAS and ACL responded in a more pronounced fashion than the other three enzymes. Transition from feeding one diet to feeding a new diet of different composition led to adaptation of the lipogenic enzyme activities to levels characteristic for the new diet. Replacing a low-carbohydrate with a high-carbohydrate diet proceeded with major alterations of enzyme activities. This process of attaining a new level took up to 20 days and involved pronounced oscillations of the specific activities. In contrast, when a high-carbohydrate diet was replaced with another diet. particular one high in fat, transition to new enzyme activities was completed within 2-3 days and proceeded without oscillations. All dietary manipulations caused more pronounced responses in young (35d-old) than in adult (180d-old) animals.     

Surgical salvage after radiation for laryngeal cancer

From January, 1962, through December, 1973, 1,084 patients with cancer of the intrinsic larynx were treated at the Mayo Clinic. Of the 1,084 patients, 136 were retreated after radiation therapy failed to cure their cancer (105 glottic, 30 supraglottic, and one subglottic cancers). Recurrence of glottic cancer was generally recognized later than recurrences in the supraglottic area; likewise, glottic cancers were more advanced at recurrence than supraglottic growths. When feasible, conservation surgery was carried out on both glottic and supraglottic growths. Unfortunately, many growths were too advanced for conservation surgery by the time recurrence was recognized. The concept of "radiate-and-watch" for early glottic and supraglottic cancers is designed to save larynges. The concept is not supported by this study.     

A randomized controlled trial of home care: clinical outcome for five surgical procedures

The clinical function of patients receiving home care after five surgical procedures was assessed. Hospital patients who normally would have received minimal nursing care at the end of their hospital stay were randomly assigned to an experimental home-care group or a control group who were discharged from hospital after the normal length of stay. Comprisons of "untoward events" (discomfort, infection, delayed healing, or complications) are reported for the two groups in five surgical categories (varicose vein stripping, herniorrhaphy, cholecystectomy, anal and rectal operations and abdominal hysterectomy) where the home-care program operated efficientyl. No apparent differences in the rates of untoward events were noted between hospital and home-care groups. It is concluded that home care should be considered for reasons other than clinical function, such as socio-economic functioning, the wishes of the patient, or more efficient use of hospital space.