A modulation-doped heterostructure-based terahertz photoconductive antenna emitter with recessed metal contacts.

We present the implementation of an efficient terahertz (THz) photoconductive antenna (PCA) emitter design that utilizes high mobility carriers in the two-dimensional electron gas (2DEG) of a modulation-doped heterostructure (MDH). The PCA design is fabricated with recessed metal electrodes in direct contact with the 2DEG region of the MDH. We compare the performance of the MDH PCA having recessed contacts with a PCA fabricated on bulk semi-insulating GaAs, on low temperature-grown GaAs, and a MDH PCA with the contacts fabricated on the surface. By recessing the contacts, the applied bias can effectively accelerate the high-mobility carriers within the 2DEG, which increases the THz power emission by at least an order of magnitude compared to those with conventional structures. The dynamic range (62 dB) and bandwidth characteristics (3.2 THz) in the power spectrum are shown to be comparable with the reference samples. Drude-Lorentz simulations corroborate the results that the higher-mobility carriers in the MDH, increase the THz emission. The saturation characteristics were also measured via optical fluence dependence, revealing a lower saturation value compared to the reference samples. The high THz conversion efficiency of the MDH-PCA with recessed contacts at low optical power makes it an attractive candidate for THz-time domain spectroscopy systems powered by low power fiber lasers.

Associations of health literacy with diabetic foot outcomes: a systematic review and meta-analysis.

BACKGROUND: People with diabetes have low health literacy, but the role of the latter in diabetic foot disease is unclear. AIM: To determine, through a systematic review and meta-analysis, if health literacy is associated with diabetic foot disease, its risk factors, or foot care. METHODS: We searched PubMed, EMBASE, CINAHL, Web of Science, Scopus and Science Direct. All studies were screened and data extracted by two independent reviewers. Studies in English with valid and reliable measures of health literacy and published tests of association were included. Data were extracted on the associations between the outcomes and health literacy. Meta-analyses were performed using random effects models. RESULTS: Sixteen articles were included in the systematic review, with 11 in the meta-analysis. In people with inadequate health literacy, the odds of having diabetic foot disease were twice those in people with adequate health literacy, but this was not statistically significant [odds ratio 1.99 (95% CI 0.83, 4.78); two studies in 1278 participants]. There was no statistically significant difference in health literacy levels between people with and without peripheral neuropathy [standardized mean difference -0.14 (95% CI -0.47, 0.18); two studies in 399 participants]. There was no association between health literacy and foot care [correlation coefficient 0.01 (95% CI -0.07, 0.10); seven studies in 1033 participants]. CONCLUSIONS: There were insufficient data to exclude associations between health literacy and diabetic foot disease and its risk factors, but health literacy appears unlikely to have a role in foot care. The contribution of low health literacy to diabetic foot disease requires definitive assessment through robust longitudinal studies.

Spectral fitting approach for the determination of enrichment and contamination factors in mining sediments using laser-induced breakdown spectroscopy.

Monitoring of pollution index values in sediments is crucial in assessing the environmental impacts of toxic metals in a given location. These indices are typically acquired using elaborate and tedious calibration curve-dependent techniques such as (inductively coupled plasma - optical emission spectroscopy) ICP-OES and (atomic absorption spectroscopy) AAS. In this study, laser-induced breakdown spectroscopy (LIBS) was used as a simple and fast alternative method for estimating enrichment factor (EF) and contamination factor (CF) of the sediment samples obtained from selected mining sites. Quantitative analyses of three metal targets (Cd, Pb, and Zn) were done using a calibration-free LIBS method based on the Boltzmann population distribution. Both the EF and CF values calculated from classical ICP-OES method provided significantly high correspondence with the respective EF (R2 = 0.8862-0.9770, p < 0.01-0.05) and CF (R2 = 0.9454-0.9714, p < 0.01) obtained from the developed LIBS method. The intensity-based LIBS approach identified samples AC2 and CCC as the ones with the highest and lowest pollution index values, respectively. The same observation was seen using the concentration-based ICP-OES technique which showed good correlation between the two methods. The correlation results showed the potential of the curve-fitting LIBS analysis in evaluating the level of metal contamination in an area without the preparation of matrix-matched calibration curves.

Terahertz emission enhancement in semi-insulating gallium arsenide integrated with subwavelength one-dimensional metal line array.

A one-order-of-magnitude terahertz (THz) emission enhancement in the transmission geometry, over a 0.7-THz broadband range, was observed in semi-insulating gallium arsenide (SI-GaAs) integrated with a subwavelength one-dimensional metal line array (1DMLA). THz emission of the 1DMLA samples showed an intensity increase and exhibited a full-width-at-half-maximum broadening relative to the emission of the bare substrate. Improved index matching could not account for the observed phenomenon. A nonlinear dependence of the integrated THz emission intensity on the number of illuminated lines and on the pump power was observed. The actual origin of the increased THz emission is still under investigation. At present, it is attributed to extraordinary optical transmission.

Development of Resistance-Based pH Sensor Using Zinc Oxide Nanorods.

The resistance-based pH sensing capability of ZnO nanorods was presented in this study. Interdigitated finger structures of nickel/gold (Ni/Au) electrodes were fabricated on the substrates prior to the sensing material. The effect of varying electrode widths was also considered. Zinc oxide (ZnO) film, as seed layer, was deposited via spray pyrolysis, and zinc oxide nanorods (ZnO-NRs) were grown via low temperature chemical bath deposition. Resistance measurements have shown plausible difference in varying pH of a test solution. The sensor was found reasonably more appreciable in sensing acidic solutions. The electrode widths were also found to relay substantial consequence in the resistance-based sensor. The least electrode-width design has shown a significant increase in the sensitivity of the sensor, with higher initial resistance and greater range of response.

Confined photocarrier transport in InAs pyramidal quantum dots via terahertz time-domain spectroscopy.

We present experimental demonstration of photocarrier dynamics in InAs quantum dots (QDs) via terahertz (THz) time-domain spectroscopy (TDS) using two excitation wavelengths and observing the magnetic field polarity characteristics of the THz signal. The InAs QDs was grown using standard Stranski-Krastanow technique on semi-insulating GaAs substrate. Excitation pump at 800 nm- and 910 nm-wavelength were used to distinguish THz emission from the InAs/GaAs matrix and InAs respectively. THz-TDS at 800 nm pump revealed intense THz emission comparable to a bulk p-InAs. For 910 nm pump, the THz emission generally weakened and upon applying external magnetic field of opposite polarities, the THz time-domain plot exhibited anomalous phase-shifting. This was attributed to the possible current-surge associated with the permanent dipole in the QD.

Chronic eccentric cycling improves quadriceps muscle structure and maximum cycling power.

An interesting finding from eccentric exercise training interventions is the presence of muscle hypertrophy without changes in maximum concentric strength and/or power. The lack of improvements in concentric strength and/or power could be due to long lasting suppressive effects on muscle force production following eccentric training. Thus, improvements in concentric strength and/or power might not be detected until muscle tissue has recovered (e. g., several weeks post-training). We evaluated alterations in muscular structure (rectus-femoris, RF, and vastus lateralis, VL, thickness and pennation angles) and maximum concentric cycling power (Pmax) 1-week following 8-weeks of eccentric cycling training (2×/week; 5-10.5 min; 20-55% of Pmax). Pmax was assessed again at 8-weeks post-training. At 1 week post-training, RF and VL thickness increased by 24±4% and 13±2%, respectively, and RF and VL pennation angles increased by 31±4% and 13±1%, respectively (all P<0.05). Compared to pre-training values, Pmax increased by 5±1% and 9±2% at 1 and 8 weeks post-training, respectively (both P<0.05). These results demonstrate that short-duration high-intensity eccentric cycling can be a time-effective intervention for improving muscular structure and function in the lower body of healthy individuals. The larger Pmax increase detected at 8-weeks post-training implies that sufficient recovery might be necessary to fully detect changes in muscular power after eccentric cycling training.

Terahertz emission from Indium Oxide films grown on MgO substrates using sub-bandgap photon energy excitation.

Indium oxide (In2O3) films grown by thermal oxidation on MgO substrates were optically excited by femtosecond laser pulses having photon energy lower than the In2O3 bandgap. Terahertz (THz) pulse emission was observed using time domain spectroscopy. Results show that THz emission saturates at an excitation fluence of ~400 nJ/cm2. Even as two-photon absorption has been excluded, the actual emission mechanism has yet to be confirmed but is currently attributed to carriers due to weak absorption from defect levels that are driven by a strain field at the interface of the substrate and the grown film.

Improvements in multi-joint leg function following chronic eccentric exercise.

Previous authors have reported that chronic eccentric cycling facilitates greater changes in multi-joint leg function (hopping frequency, maximum jumping height) compared with concentric cycling. Our purpose was to evaluate changes in leg spring stiffness and maximum power following eccentric and concentric cycling training. Twelve individuals performed either eccentric (n=6) or concentric (n=6) cycling for 7 weeks (3 sessions/week) while training duration progressively increased. Participants performed trials of submaximal hopping, maximal counter movement jumps, and maximal concentric cycling to evaluate leg spring stiffness, maximum jumping power, and maximum concentric cycling power respectively, before and 1 week following training. Total work during training did not differ between eccentric and concentric cycling (126 ± 15-728 ± 91 kJ vs 125 ± 10-787 ± 76 kJ). Following training, eccentric cycling exhibited greater changes in k(leg) and jumping P(max) compared with CON(cyc) (10 ± 3% vs -2 ± 4% and 7 ± 2% vs -2 ± 3%, respectively, P=0.05). Alterations in CON(cyc) P(max) did not differ between ECC(cyc) (1035 ± 142 vs 1030 ± 133 W) and CON(cyc) (1072 ± 98 vs 1081 ± 85 W). These data demonstrate that eccentric cycling is an effective method for improving leg spring stiffness and maximum power during multi-joint tasks that include stretch-shortening cycles. Improvements in leg spring stiffness and maximum power would be beneficial for both aging and athletic populations.

Effect of a contusion injury on muscular force, power, work, and fatigue.

The purpose of the investigation was to compare alterations in muscular force, power, work, and fatigue following a contusion injury. We hypothesized that power and work would be more greatly reduced than isometric force due to several mechanisms that would alter the force-velocity relationship and impair activation/relaxation kinetics specific to dynamic muscle contractions. Contusion injury was administered to the gastrocnemius muscle of adult rats using the drop-mass technique. Isometric force, power during shortening (10, 25, and 40 mm/s), work produced during cyclic contractions (2 and 4 Hz), and fatigue during 60 work loops, were normalized to dry muscle mass and analyzed in control animals (n=11), as well as 1 h (n=11) and 48 h (n=9) following contusion injury. Passive work increased (30-38%) 48 h after injury compared with control (P<0.01). Isometric force, power, and work were significantly reduced by similar magnitudes 1 h (28-33%) and 48 h (28-38%) after injury compared with control (P<0.01). Fatigue index 1 h post-injury was significantly less than control (75% vs 85%; P=0.02). The observed increases in muscle hysteresis were apparently not large enough to cause greater reductions in power and work than isometric force. We conclude that isometric measures provide adequate quantification of muscular dysfunction following a contusion injury in these animals and may offer sufficient information to determine recovery status in clinical settings as well.

Wide-field functional imaging of blood flow and hemoglobin oxygen saturation in the rodent dorsal window chamber.

The rodent dorsal window chamber is a widely used in vivo model of the microvasculature. The model consists of a 1cm region of exposed microvasculature in the rodent dorsal skin that is immobilized by surgically implanted titanium frames, allowing the skin microvasculature to be visualized. We describe a detailed protocol for surgical implantation of the dorsal window chamber which enables researchers to perform the window chamber implantation surgery. We further describe subsequent wide-field functional imaging of the chamber to obtain hemodynamic information in the form of blood oxygenation and blood flow on a cm size region of interest. Optical imaging techniques, such as intravital microscopy, have been applied extensively to the dorsal window chamber to study microvascular-related disease and conditions. Due to the limited field of view of intravital microscopy, detailed hemodynamic information typically is acquired from small regions of interest, typically on the order of hundreds of µm. The wide-field imaging techniques described herein complement intravital microscopy, allowing researchers to obtain hemodynamic information at both microscopic and macroscopic spatial scales. Compared with intravital microscopy, wide-field functional imaging requires simple instrumentation, is inexpensive, and can give detailed metabolic information over a wide field of view.

Pharmacodynamics and safety of pantoprazole in neonates, preterm infants, and infants aged 1 through 11 months with a clinical diagnosis of gastroesophageal reflux disease.

BACKGROUND: Limited data on proton pump inhibitors in infants led regulatory agencies to request sponsors to conduct pediatric studies. AIM: To determine the pharmacodynamic response to pantoprazole in infants with GERD to aid the dose selection for an efficacy study. METHODS: In two open-label studies, neonates and preterm infants (study 1, ~1.2 mg/kg [high dose]) and infants 1 through 11 months (study 2, ~0.6 [low dose] or ~1.2 mg/kg [high dose]) received once-daily pantoprazole. Twenty-four-hour dual-electrode pH-metry parameters were compared between predose and steady state (≥5 days) (two-sided paired t test). Treatment was administered for ≤6 weeks. RESULTS: In studies 1 and 2, 21 and 24 patients, respectively, were enrolled for pharmacodynamic evaluation. The high dose provided similar responses in the two studies and improved these parameters significantly: mean gastric pH and percent time gastric pH > 4 increased (p < 0.05 both studies), normalized area under the curve (AUC) of gastric H(+) activity decreased (p < 0.05 study 2), and normalized AUC of esophageal H(+) activity decreased (p < 0.05 both studies). The AUC of esophageal pH < 4 decreased. Normalized AUC of esophageal H(+) activity decreased (p < 0.05 both studies), indicating refluxate pH increased, although this was not reflected in any change in mean esophageal pH or reflux index. The normalized AUC of esophageal H(+) activity was a more sensitive measure of changes in esophageal pH. CONCLUSIONS: In neonates, preterm infants, and infants aged 1 through 11 months, pantoprazole (high dose) improved pH-metry parameters after ≥5 consecutive daily doses, and was generally well tolerated for ≤6 weeks.

Role of intestinal transporters in neonatal nutrition: carbohydrates, proteins, lipids, minerals, and vitamins.

To support rapid growth and a high metabolic rate, infants require enormous amounts of nutrients. The small intestine must have the complete array of transporters that absorb the nutrients released from digested food. Failure of intestinal transporters to function properly often presents symptoms as "failure to thrive" because nutrients are not absorbed and as diarrhea because unabsorbed nutrients upset luminal osmolality or become substrates of intestinal bacteria. We enumerate the nutrients that constitute human milk and various infant milk formulas, explain their importance in neonatal nutrition, then describe for each nutrient the transporter(s) that absorbs it from the intestinal lumen into the enterocyte cytosol and from the cytosol to the portal blood. More than 100 membrane and cytosolic transporters are now thought to facilitate absorption of minerals and vitamins as well as products of digestion of the macronutrients carbohydrates, proteins, and lipids. We highlight research areas that should yield information needed to better understand the important role of these transporters during normal development.

Limitations of relaxation kinetics on muscular work.

AIM: Positive net work produced during cyclic contractions is partially limited by relaxation kinetics, which to date, have not been directly investigated. Therefore, the purpose of this investigation was to determine the influence of relaxation kinetics on cyclic work. METHODS: Soleus muscles of four cats were isolated and subjected to a series of work loops (0.5, 1, 1.5 and 2 Hz cycle frequencies) during which stimulation terminated prior to the end of the shortening phase to allow for complete muscle relaxation and matched discrete sinusoidal shortening contractions during which stimulation remained on until the completion of the shortening phase. Muscle length changes during these protocols were centred on optimum length and were performed across muscle lengths that represented walking gait. RESULTS: When muscle excursions were centred on L(o) relaxation kinetics decreased muscular work by 2.8 + or - 0.8%, 12.1 + or - 4.1%, 27.9 + or - 4.5% and 40.1 + or - 5.9% for 0.5, 1, 1.5 and 2 Hz respectively. However, relaxation kinetics did not influence muscular work when muscle excursions represented walking gait. In addition, muscular work produced at muscle lengths associated with walking gait was less than the work produced across L(o) (55.7 + or - 20.0%, 53.5 + or - 21.0%, and 50.1 + or - 22.0% for 0.5, 1 and 1.5 Hz respectively). CONCLUSION: These results imply that relaxation kinetics are an important factor that limit the ability of muscle to produce work; however, the influence of relaxation kinetics on physiological function may depend on the relation between the optimum length and natural excursion of a muscle.

Field based evidence of enhanced healthcare utilization among persons insured by micro health insurance units in Philippines.

Underutilization of healthcare is common among rural and low-income population segments in countries with lower income or inequitable income distribution. Micro health insurance units (MIUs) are created by informal sector groups because people cannot access health insurance or are dissatisfied with the programmes they can access. The policy choice to support MIUs relies on evidence that affiliation with these schemes increases healthcare utilization. This article examines new evidence of the association between affiliation with MIUs and healthcare utilization. We analyzed field data collected in 6 MIUs in the Philippines in 2002 (through a household survey encompassing 890 insured- and 1063 uninsured households). The two cohorts did not differ in demographic parameters, and differed only marginally in income and education levels, both higher amongst the insured. Insured persons reported higher hospitalization rates, higher rates of professionally-attended deliveries, lower rates of delivery at home, a higher frequency of primary-care physician encounters, a higher rate of diagnosed chronic diseases, and better drug compliance among chronically ill. Increased utilization by the insured is not due to adverse selection, judging by two facts: morbidity of the two cohorts, as assessed by a proxy indicator (the reported number of episodes of illness) did not differ; and rates of deliveries were even slightly higher among the uninsured. We conclude that MIUs in the Philippines can alleviate underutilization of heath care.

Ontogenetic development of rat intestinal bile acid transport requires thyroxine but not corticosterone.

Absorption of bile acids by the distal ileum is an essential component of the enterohepatic circulation. In neonatal rats, the appearance of the apical sodium-dependent bile acid transporter (ASBT) at 17 d of age coincides with increases in serum corticosterone and thyroxine. We tested the hypothesis that these hormones modulate ASBT expression during ileal development. Taurocholate uptake into the isolated ileum of normal 20-d-old pups exhibited saturable (K(m) = 0.52 mM, J(max) = 0.34 pmol mg/min) and nonsaturable (K(diff) = 0.015 min(-1)) components and was two to five times greater than uptake in the proximal intestine. Hypothyroid or euthyroid pups received daily thyroxine injections starting at 6 d of age. At 12 d of age, serum concentrations of thyroxine, ileal abundance of ASBT mRNA, and ileal rates of taurocholate uptake were low in hypothyroid pups that received an injection of vehicle (HT-) or thyroxine (HT+) and in euthyroid pups that received an injection of vehicle (ET-) or thyroxine (ET+). At 20 and 26 d, ileal ASBT mRNA abundance and taurocholate uptake rate remained low in HT- pups but increased dramatically in ET- and ET+ pups, paralleling the increase in serum thyroxine. Restoration of normal plasma thyroxine in HT- pups by thyroxine injections (HT+) restored normal ASBT development. Sodium-glucose co-transporter activity and mRNA expression were independent of serum thyroxine levels. Corticosterone levels were significantly lower in pups that were adrenalectomized at 10 d of age. ASBT mRNA abundance and taurocholate uptake rate increased markedly with age but were the same in adrenalectomized, sham-operated, and nonoperated pups. Hence, endogenous thyroxine but not corticosterone regulates the developmentally timed appearance of ASBT.

[Consequences of short term fluctuations of environmental temperatures in calves--Part 1: Immediate reactions of the respiratory system, the cardiovascular system, metabolism and thermal regulation]. / Die Auswirkungen kurzzeitiger Schwankungen der Umgebungstemperatur auf den Kälberorganismus--1. Mitteilung: Sofortreaktionen des respiratorischen Systems, des Herz-Kreislauf-Systems, des Stoffwechsels und des Wärmehaushaltes.

Clinically healthy calves (aged 3-6 weeks) were exposed to defined ambient temperature for 4 hours (cold: 5 degrees C, 60% humidity, n = 12; warm: 35 degrees C, 60% humidity, n = 11). During the exposure of each animal in a climatic chamber, certain parameters of lung function, respiratory mechanics, blood gas analysis, circulation, metabolism and thermal regulation were registered simultaneously in order to study immediate physiological consequences of different environmental conditions. In comparison to control calves (18-20 degrees C, 60% humidity, n = 13) an insufficient adaptation of these young calves was noticed in both cold and warm conditions. At 5 degrees C, marked changes in lung function were observed, i.e. airway constriction, pulmonary hypertension, and ventilation-perfusion-mismatching leading to hypoxemia and hypercapnia. Due to compensation by the circulatory system, a sufficient O2-consumption of the organism as well as an unchanged body temperature were maintained. At 35 degrees C, the respiratory pattern changed to panting and a higher dead space ventilation. No changes were observed in pulmonary gas exchange and blood arterialisation. Due to hyperventilation, the partial pressure for CO2 decreased in blood. Since the body temperature increased continuously, thermal regulation was insufficient. This situation would have led to animals collapsing after a period of heat stress lasting longer than 4 hours. In conclusion, young calves up to the age of 6 weeks were not able to tolerate acute changes in ambient temperature. This was true for cold conditions (5 degrees C) as well as for hot conditions (35 degrees C). The results of this study should be taken into account in order to optimise transport and farming conditions.

[Consequences of short term fluctuations of the environmental temperatures in calves--Part 2: Effects on the health status of animals within three weeks after exposure]. / Die Auswirkungen kurzzeitiger Schwankungen der Umgebungstemperatur auf den Kälberorganismus--2. Mitteilung: Auswirkungen auf die Tiergesundheit bis drei Wochen post expositionem.

The aim of the present study was to examine consequences of sudden changes in ambient temperature over a 4-hour period (see part 1 [ELMER & REINHOLD, 2002]) on respiratory health in clinically healthy calves. Therefore, the relationship between short-term changes in ambient temperature and the occurrence of clinical respiratory disease was checked over a period of 3 weeks after exposure in 10 calves exposed to 5 degrees C, in 9 calves exposed to 35 degrees C and in 8 control calves (kept at 18-20 degrees C). Within the period beginning 3 days before exposure and lasting until up to 21 days after exposure, each calf was examined clinically. Rectal temperature and respiratory rate were measured daily. All calves were euthanised on day 21 after exposure. Macroscopically visible pneumonic lesions were evaluated using a semiquantitative system. Tissue samples from tonsils, bronchi, trachea, lung and mediastinal lymph nodes were examined bacteriologically. In contrast to non-exposed control calves, severe respiratory illness was observed in individual calves of both exposed groups (5 degrees C, 35 degrees C). Significant increases in body temperature, respiratory rate and animal losses (2 calves died in the group exposed to 5 degrees C, one calf died in the group exposed to 35 degrees C) were the main clinical findings. At necropsy (3 weeks after exposure), no pneumonic lesions were observed in control calves--despite the fact that this group had the highest microbiological colonisation rates in tonsils and in large airways, i.e. trachea and bronchi, within all groups. However, variable pneumonic lung lesions were seen in remaining calves exposed to cold or warm air (5 degrees C, 35 degrees C). The microbiological examination confirmed that mainly Mycoplasma spp. were identified in the lung tissue of calves exposed to 5 degrees C while Pasteurella multocida and/or Mannheimia haemolytica were the only germs found in the lung tissue of calves exposed to 35 degrees C. The results of parts 1 and 2 of the present study related to health issues of calves should be taken into account for future legislation on animal welfare.

Intraocular pressure changes in breastfeeding

To determine changes in intraocular pressure before and after breastfeeding, 21 lactating mothers, aged 20 - 36 (mean age = 28), who delivered vaginally without complications, were studied.After instillation of topical anesthetics, the Tonopen was used to take the intraocular pressure (IOP) in millimeters Mercury (mm Hg) 1 hour prior to and immediately after breast-feeding.Three pressure readings were recorded and averaged in each determination.Using the paired T-test, a post-lactation increase in IOP of 0.6 +_ 3.1 mm Hg;(p=0.412) was noted on the right eye;an IOP increased of 2.3+_ 3.7 mm Hg;(p=0.010) was noted on the left eye.