The rapid development of optoelectronic applications for optical-to-electrical conversion has increased the interest in graphene oxide material. Here, graphene oxide films (GOF) were used as source ...material in an infrared photodetector configuration and the temperature dependence of the electrical conductivity was studied. GOF were prepared by the double-thermal decomposition (DTD) method at 973 K, with a fixed carbonization temperature, in a pyrolysis system, under a controlled nitrogen atmosphere, over quartz substrates. Graphene oxide films were mechanically supported in a photodetector configuration on Bakelite substrates and electrically contacted with copper wires and high-purity silver paint. Morphological images from the GOF's surface were taken employing a scanning electron microscope and observed a homogeneous surface which favored the electrical contacts deposition. Vibrational characteristics were studied employing Raman spectroscopy and determined the typical graphene oxide bands. GOF were used to discuss the effect of temperature on the film's electrical conductivity. Current-voltage (I-V) curves were taken for several temperatures varying from 20 to 300 K and the electrical resistance values were obtained from 142.86 to 2.14 kΩ. The GOF electrical conductivity and bandgap energy (E
) were calculated, and it was found that when increasing temperature, the electrical conductivity increased from 30.33 to 2023.97 S/m, similar to a semiconductor material, and E
shows a nonlinear change from 0.33 to 0.12 eV, with the increasing temperature. Conduction mechanism was described mainly by three-dimensional variable range hopping (3D VRH). Additionally, measurements of voltage and electrical resistance, as a function of wavelength were considered, for a spectral range between 1300 and 3000 nm. It was evidenced that as the wavelength becomes longer, a greater number of free electrons are generated, which contributes to the electrical current. The external quantum efficiency (EQE) was determined for this proposed photodetector prototype, obtaining a value of 40%, similar to those reported for commercial semiconductor photodetectors. This study provides a groundwork for further development of graphene oxide films with high conductivity in large-scale preparation.
We describe the design and performance of the near-infrared (1.51-1.70 m), fiber-fed, multi-object (300 fibers), high resolution (R = λ/Δλ ∼ 22,500) spectrograph built for the Apache Point ...Observatory Galactic Evolution Experiment (APOGEE). APOGEE is a survey of ∼105 red giant stars that systematically sampled all Milky Way populations (bulge, disk, and halo) to study the Galaxy's chemical and kinematical history. It was part of the Sloan Digital Sky Survey III (SDSS-III) from 2011 to 2014 using the 2.5 m Sloan Foundation Telescope at Apache Point Observatory, New Mexico. The APOGEE-2 survey is now using the spectrograph as part of SDSS-IV, as well as a second spectrograph, a close copy of the first, operating at the 2.5 m du Pont Telescope at Las Campanas Observatory in Chile. Although several fiber-fed, multi-object, high resolution spectrographs have been built for visual wavelength spectroscopy, the APOGEE spectrograph is one of the first such instruments built for observations in the near-infrared. The instrument's successful development was enabled by several key innovations, including a "gang connector" to allow simultaneous connections of 300 fibers; hermetically sealed feedthroughs to allow fibers to pass through the cryostat wall continuously; the first cryogenically deployed mosaic volume phase holographic grating; and a large refractive camera that includes mono-crystalline silicon and fused silica elements with diameters as large as ∼400 mm. This paper contains a comprehensive description of all aspects of the instrument including the fiber system, optics and opto-mechanics, detector arrays, mechanics and cryogenics, instrument control, calibration system, optical performance and stability, lessons learned, and design changes for the second instrument.
•β-Carotene was encapsulated in nanoemulsions and emulsions.•Initial droplet size influenced potential biological fate of delivery systems.•Lipid digestion rate and extent increased with decreasing ...droplet size.•β-Carotene bioaccessibility increased with decreasing droplet size.
The interest in incorporating carotenoids, such as β-carotene, into foods and beverages is growing due to their potential health benefits. However, the poor water-solubility and low bioavailability of carotenoids is currently a challenge to their incorporation into many foods. The aim of this work was to study the influence of particle size on lipid digestion and β-carotene bioaccessibility using corn oil-in-water emulsions with different initial droplet diameters: large (d43≈23μm); medium (d43≈0.4μm); and small (d43≈0.2μm). There was a progressive increase in the mean particle size of all the emulsions as they passed through a simulated gastrointestinal tract (GIT) consisting of mouth, stomach, and small intestine phases, which was attributed to droplet coalescence, flocculation, and digestion. The electrical charge on all the lipid particles became highly negative after passage through the GIT due to accumulation of anionic bile salts, phospholipids, and free fatty acids at their surfaces. The rate and extent of lipid digestion increased with decreasing mean droplet diameter (small≈medium≫large), which was attributed to the increase in lipid surface area exposed to pancreatic lipase with decreasing droplet size. There was also an appreciable increase in β-carotene bioaccessibility with decreasing droplet diameter (small>medium>large). These results provide useful information for designing emulsion-based delivery systems for carotenoids for food and pharmaceutical uses.
•Lycopene bioaccessibility in tomato juice increased with addition of nanoemulsions.•Small lipid droplets gave a higher oil digestibility than larger ones.•Carotenoids were trapped in tomato ...chromoplasts during in vitro digestion.•Thermal treatment slightly increased lycopene bioaccessibility.
The use of excipient emulsions to increase the bioaccessibility of lycopene in tomato juice was studied by simulating gastrointestinal conditions. The influence of droplet diameter (d=0.17 or 19μm) and thermal treatment (90°C, 10min) on lycopene bioaccessibility was evaluated. Lycopene bioaccessibility was relatively low (<8%) in the absence of excipient emulsions due to the crystalline nature of the carotenoids and their entrapment within chromoplasts. Emulsions containing small droplets were fully digested within the small intestine phase, and led to a higher bioaccessibility (12.5%) than emulsions containing large droplets (10.0%) or emulsion-free samples (7.5%). The relatively modest increase in bioaccessibility was attributed to the high level of entrapment in crystalline form. Thermal processing did not appreciably disrupt tomato cells, and therefore only led to a slight increase in lycopene bioaccessibility. Overall, this study shows that excipient emulsions may increase the bioaccessibility of carotenoids in tomato juices.
Impaired emotion regulation may underlie exaggerated emotional reactivity in patients with obsessive compulsive disorder (OCD), yet instructed emotion regulation has never been studied in the ...disorder.
This study aimed to assess the neural correlates of emotion processing and regulation in 43 medication-free OCD patients and 38 matched healthy controls, and additionally test if these can be modulated by stimulatory (patients) and inhibitory (controls) repetitive transcranial magnetic stimulation (rTMS) over the left dorsolateral prefrontal cortex (dlPFC). Participants performed an emotion regulation task during functional magnetic resonance imaging before and after a single session of randomly assigned real or sham rTMS. Effect of group and rTMS were assessed on self-reported distress ratings and brain activity in frontal-limbic regions of interest.
Patients had higher distress ratings than controls during emotion provocation, but similar rates of distress reduction after voluntary emotion regulation. OCD patients compared with controls showed altered amygdala responsiveness during symptom provocation and diminished left dlPFC activity and frontal-amygdala connectivity during emotion regulation. Real v. sham dlPFC stimulation differentially modulated frontal-amygdala connectivity during emotion regulation in OCD patients.
We propose that the increased emotional reactivity in OCD may be due to a deficit in emotion regulation caused by a failure of cognitive control exerted by the dorsal frontal cortex. Modulatory rTMS over the left dlPFC may influence automatic emotion regulation capabilities by influencing frontal-limbic connectivity.
•Emulsions with different droplet sizes and compositions were prepared.•Long chain fatty acids and Coenzyme Q10 were encapsulated in droplets.•For digestible droplets, bioavailability increased with ...decreasing particle size.•The bioavailability of indigestible droplets was lower than digestible ones.
The influence of droplet size (d32=0.21, 0.70 or 2.2μm) and oil digestibility (corn oil versus mineral oil) on the bioavailability of a model long chain fatty acid (heptadecanoic acid) and lipophilic nutraceutical (Coenzyme Q10) was investigated using a rat feeding study. Initially, we showed that small droplets were digested more rapidly than large droplets using a simulated small intestinal model (pH stat), which was attributed to the greater surface area of lipid exposed to intestinal juices. The pH stat model also confirmed that emulsified corn oil was digestible, whereas emulsified mineral oil was indigestible. A rat feeding study showed that the bioavailability of the fatty acid and lipophilic nutraceutical in small intestinal tissues was highest when they were encapsulated within digestible oil droplets with the smallest size. This study provides important information for development of nanoemulsion-based delivery systems that increase oral bioavailability of lipophilic nutraceuticals.
► β-Carotene was encapsulated in nanoemulsions with different oil compositions. ► The long- to medium-chain triglyceride ratio in the oil phase was varied. ► Carrier oil composition strongly ...influenced β-carotene bioaccessibility. ► Higher long chain triglycerides led to higher bioaccessibility.
Diets rich in carotenoids have been correlated with a reduced risk of developing certain types of chronic diseases, but these bioactive components have low intestinal absorption due to their hydrophobic nature. The aim of this work was to study the effect of carrier oil composition (medium-chain triglyceride (MCT) to long-chain triglyceride (LCT) ratio) and total carrier oil concentration (1% or 4% w/w) on the physical stability, lipid digestibility and bioaccessibility of β-carotene-loaded nanoemulsions, using a simulated digestion process. Lipolysis led to an appreciable increase in the size and negative charge on the particles in the system. The total fraction of triacylglycerols converted to free fatty acids decreased as the percentage of LCT within the lipid phase increased, particularly for the nanoemulsions with higher fat contents. There was an increase in β-carotene bioaccessibility as the LCT within the lipid phase increased for low fat nanoemulsions, which was attributed to the increased solubilisation capacity of mixed micelles formed by LCT. β-carotene bioaccessibility showed a complex relationship on LCT content for high fat nanoemulsions, due to the opposing effects of lipid digestion and micelle solubilisation. These results may facilitate the optimisation of delivery systems for lipophilic bioactive compounds for food or pharmaceutical applications.
Lead (Pb) is a heavy metal that alters the oxidation-reduction balance, affecting reproductive health and transfer during pregnancy and lactation. However, the multigenerational impact of exposure to ...low concentrations of Pb on mammalian ovaries has not been assessed. This study evaluated general parameters, histology, redox state (RS), protein carbonylation (PC), lipid peroxidation (LP), and hormone concentrations in the ovaries of mice (CD1® ICR) of three successive generations with both unigenerational (E1) and multigenerational (E2) exposure to 0.2 ppm lead acetate through the drinking water and a control group. Body weight, food consumption, the number of born pups, and their weight after weaning were not significantly affected by Pb exposure in E1 and E2. However, the ovaries of three successive generations of the E1 group, in which only the F0 was exposed, showed alterations in the ovarian histoarchitecture, increase in follicular atresia, decrease in the number of available follicles, and a significant RS and PC elevation that were surprisingly similar to those observed in the E2 group. LP increased in the second generation of E1 and E2, while hormone concentration was not altered. This is the first demonstration that exposure to low concentration of Pb induces multigenerational histological alterations and oxidative stress in mouse ovaries, that the termination of this exposure does not ensure the safety of later generations and that the lack of modifications in general parameters may facilitate the silent development of pathologies that affect ovarian health.
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•Low Pb exposure compromises ovarian health in three successive generations.•Low Pb exposure has multigenerational effects on ovarian histoarchitecture.•Low Pb exposure has multigenerational effects in follicle count.•Low Pb exposure induces multigenerational oxidative stress in mice ovaries.
Vitamin D deficiency is prevalent in some populations leading to adverse health effects, and therefore there is a need to supplement functional foods and beverages with this important micronutrient. ...In this study, we examined the influence of the initial lipid droplet size on the in vitro bioaccessibility and in vivo absorption of vitamin D
encapsulated in oil-in-water emulsions. Changes in particle size, charge, and microstructure were measured as vitamin-loaded lipid droplets were passed through a simulated GIT (mouth, stomach, small intestine). The in vitro studies showed that smaller lipid droplets were digested more rapidly than larger ones, thereby leading to the more rapid formation of mixed micelles in the small intestine capable of solubilizing the lipophilic vitamins. This effect may account for the highest vitamin D
bioaccessibility being observed for the emulsions containing the smallest droplets. In contrast, the in vivo rat feeding studies suggested that the absorption of vitamin D
was the highest for the emulsions containing the largest droplets. The poor in vitro-in vivo correlation observed in our study may have occurred for a number of reasons: the simulated GIT did not accurately model the complexity of a real GIT; the in vivo approach used did not monitor changes in vitamin levels in the blood over time. Overall, this study suggests that particle size does influence the gastrointestinal fate of encapsulated oil-soluble vitamins, but that further work is needed to establish strong correlations between in vitro and in vivo methods.
The 'exposome' represents the accumulation of all environmental exposures across a lifetime. Top-down strategies are required to assess something this comprehensive, and could transform our ...understanding of how environmental factors affect human health. Metabolic profiling (metabonomics/metabolomics) defines an individual's metabolic phenotype, which is influenced by genotype, diet, lifestyle, health and xenobiotic exposure, and could also reveal intermediate biomarkers for disease risk that reflect adaptive response to exposure. We investigated changes in metabolism in volunteers living near a point source of environmental pollution: a closed zinc smelter with associated elevated levels of environmental cadmium.
High-resolution ¹H NMR spectroscopy (metabonomics) was used to acquire urinary metabolic profiles from 178 human volunteers. The spectral data were subjected to multivariate and univariate analysis to identify metabolites that were correlated with lifestyle or biological factors. Urinary levels of 8-oxo-deoxyguanosine were also measured, using mass spectrometry, as a marker of systemic oxidative stress.
Six urinary metabolites, either associated with mitochondrial metabolism (citrate, 3-hydroxyisovalerate, 4-deoxy-erythronic acid) or one-carbon metabolism (dimethylglycine, creatinine, creatine), were associated with cadmium exposure. In particular, citrate levels retained a significant correlation to urinary cadmium and smoking status after controlling for age and sex. Oxidative stress (as determined by urinary 8-oxo-deoxyguanosine levels) was elevated in individuals with high cadmium exposure, supporting the hypothesis that heavy metal accumulation was causing mitochondrial dysfunction.
This study shows evidence that an NMR-based metabolic profiling study in an uncontrolled human population is capable of identifying intermediate biomarkers of response to toxicants at true environmental concentrations, paving the way for exposome research.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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