Highly Coupled Seven-Core Fiber for Ratiometric Anti-Phase Sensing.

A ratiometric fiber optic temperature sensor based on a highly coupled seven-core fiber (SCF) is proposed and experimentally demonstrated. A theoretical analysis of the SCF's sinusoidal spectral response in transmission configuration is presented. The proposed sensor comprises two SCF devices exhibiting anti-phase transmission spectra. Simple fabrication of the devices is shown by just splicing a segment of a 2 cm long SCF between two single-mode fibers (SMFs). The sensor proved to be robust against light source fluctuations, as a standard deviation of 0.2% was registered in the ratiometric measurements when the light source varied by 12%. Its low-cost detection system (two photodetectors) and the range of temperature detection (25 °C to 400 °C) make it a very attractive and promising device for real industrial applications.

Extended axial irradiances: Barker rings.

For extending focal depth we employ a set of transparent concentric rings, which are coded with the Barker sequences of length L. At the neighborhood of the paraxial focal plane, these transparent masks generate an axial uniform distribution, which is modulated with sinusoidal variations. For imaging applications, one can extend focal depth if the Barker length is congruent to unity modulo 4. And, for optical trapping, a bottle neck irradiance distribution is generated if the Barker length is congruent to three modulo 4.

In-Line Mach-Zehnder Interferometers Based on a Capillary Hollow-Core Fiber Using Vernier Effect for a Highly Sensitive Temperature Sensor.

In this paper, we propose a highly sensitive temperature sensor based on two cascaded Mach-Zehnder interferometers (MZIs) that work using the Vernier effect. The all-fiber MZIs were assembled by splicing a segment of capillary hollow-core fiber (CHCF) between two sections of multimode fibers (MMFs). This cascaded configuration exhibits a temperature sensitivity of 1.964 nm/°C in a range from 10 to 70 °C, which is ~67.03 times higher than the sensitivity of the single MZI. Moreover, this device exhibits a high-temperature resolution of 0.0153 °C. A numerical analysis was carried out to estimate the devices' temperature sensitivity and calculate the magnification of the sensitivity produced by the Vernier effect. The numerical results have an excellent agreement with the experimental results and provide a better insight into the working principle of the MZI devices. The sensor's performance, small size, and easy fabrication make us believe that it is an attractive candidate for temperature measurement in biological applications.

Sensitivity Enhancement of Curvature Fiber Sensor Based on Polymer-Coated Capillary Hollow-Core Fiber.

In this paper, we propose and experimentally demonstrate a simple technique to enhance the curvature sensitivity of a bending fiber optic sensor based on anti-resonant reflecting optical waveguide (ARROW) guidance. The sensing structure is assembled by splicing a segment of capillary hollow-core fiber (CHCF) between two single-mode fibers (SMF), and the device is set on a steel sheet for measuring different curvatures. Without any surface treatment, the ARROW sensor exhibits a curvature sensitivity of 1.6 dB/m-1 in a curvature range from 0 to 2.14 m-1. By carefully coating half of the CHCF length with polydimethylsiloxane (PDMS), the curvature sensitivity of the ARROW sensor is enhanced to -5.62 dB/m-1, as well as an increment in the curvature range (from 0 to 2.68 m-1). Moreover, the covered device exhibits a low-temperature sensitivity (0.038 dB/°C), meaning that temperature fluctuations do not compromise the bending fiber optic sensor operation. The ARROW sensor fabricated with this technique has high sensitivity and a wide range for curvature measurements, with the advantage that the technique is cost-effective and easy to implement. All these features make this technique appealing for real sensing applications, such as structural health monitoring.

All-Fiber Measurement of Surface Tension Using a Two-Hole Fiber.

An all-fiber approach is presented to measure surface tension. The experimental realization relies on the use of a specialty fiber, a so-called two-hole fiber (THF), which serves a two-fold purpose: providing a capillary channel to produce bubbles while having the means to measure the power reflected at the end facet of the fiber core. We demonstrate that provided a controlled injection of gas into the hollow channels of the THF, surface tension measurements are possible by simply tracking the Fresnel reflection at the distal end of the THF. Our results show that the characteristic times involved in the bubble formation process, from where the surface tension of the liquids under test is retrieved, can be measured from the train of pulses generated by the continuous formation and detachment of bubbles.

Laser-Induced Deposition of Carbon Nanotubes in Fiber Optic Tips of MMI Devices.

The integration of carbon nanotubes (CNTs) into optical fibers allows the application of their unique properties in robust and versatile devices. Here, we present a laser-induced technique to obtain the deposition of CNTs onto the fiber optics tips of multimode interference (MMI) devices. An MMI device is constructed by splicing a section of no-core fiber (NCF) to a single-mode fiber (SMF). The tip of the MMI device is immersed into a liquid solution of CNTs and laser light is launched into the MMI device. CNTs solutions using water and methanol as solvents were tested. In addition, the use of a polymer dispersant polyvinylpyrrolidone (PVP) in the CNTs solutions was also studied. We found that the laser-induced deposition of CNTs performed in water-based solutions generates non-uniform deposits. On the other hand, the laser-induced deposition performed with methanol solutions generates uniform deposits over the fiber tip when no PVP is used and deposition at the center of the fiber when PVP is present in the CNTs solution. The results show the crucial role of the solvent on the spatial features of the laser-induced deposition process. Finally, we register and study the reflection spectra of the as-fabricated CNTs deposited MMI devices.

Pseudo-random masks for angular alignment.

We present an alignment technique that exploits angular correlations by employing a pair of masks, which encode in an angular format pseudo-random sequences. The angular correlator generates peaked irradiance distributions on-axis, provided that the elements of the pair are aligned. Otherwise, the on-axis irradiance distribution decreases to a minimum value. Since the proposed angular correlator is independent of the lateral magnification, it is useful for testing the performance of varifocal lenses. A merit function describes the tolerance to focus errors associated with the location of a small size detector. We use linearly polarized films for showing that the technique also works well with broad band light.

Optical fiber temperature sensor based on a microcavity with polymer overlay.

An ultracompact, cost-effective, and highly accurate fiber optic temperature sensor is proposed and demonstrated. The sensing head consists of Fabry-Perot microcavity formed by an internal mirror made of a thin titanium dioxide (TiO2) film and a microscopic segment of single-mode fiber covered with Poly(dimethylsiloxane) (PDMS). Due to the high thermo-optic coefficient of PDMS the reflectance of the fiber-PDMS interface varies strongly with temperature which in turn modifies the amplitude of the interference pattern. To quantify the changes of the latter we monitored the visibility of the interference pattern and analyzed it by means of the fast Fourier transform. Our sensor exhibits linear response, high sensitivity, and response time of 14 seconds. We believe that the microscopic dimensions along with the performance of the sensor here presented makes it appealing for sensing temperature in PDMS microfluidic circuits or in biological applications.

Highly Sensitive Liquid Core Temperature Sensor Based on Multimode Interference Effects.

A novel fiber optic temperature sensor based on a liquid-core multimode interference device is demonstrated. The advantage of such structure is that the thermo-optic coefficient (TOC) of the liquid is at least one order of magnitude larger than that of silica and this, combined with the fact that the TOC of silica and the liquid have opposite signs, provides a liquid-core multimode fiber (MMF) highly sensitive to temperature. Since the refractive index of the liquid can be easily modified, this allows us to control the modal properties of the liquid-core MMF at will and the sensor sensitivity can be easily tuned by selecting the refractive index of the liquid in the core of the device. The maximum sensitivity measured in our experiments is 20 nm/°C in the low-temperature regime up to 60 °C. To the best of our knowledge, to date, this is the largest sensitivity reported for fiber-based MMI temperature sensors.

Oxygen Isotope and Fluorine Impurity Signatures during the Conversion of Uranium Ore Concentrates to Nuclear Fuel.

Within the front end of the nuclear fuel cycle, many processes impart forensic signatures. Oxygen-stable isotopes (δ18O values) of uranium-bearing materials have been theorized to provide the processing and geolocational signatures of interdicted materials. However, this signature has been minimally utilized due to a limited understanding of how oxygen isotopes are influenced during uranium processing. This study explores oxygen isotope exchange and fractionation between magnesium diuranate (MDU), ammonium diuranate (ADU), and uranyl fluoride (UO2F2) with steam (water vapor) during their reduction to UOx. The MDU was precipitated from two water sources, one enriched and one depleted in 18O. The UO2F2 was precipitated from a single water source and either directly reduced or converted to ADU prior to reduction. All MDU, ADU, and UO2F2 were reduced to UOx in a 10% hydrogen/90% nitrogen atmosphere that was dry or included steam. Powder X-ray diffraction (p-XRD) was used to verify the composition of materials after reduction as mixtures of primarily U3O8, U4O9, and UO2 with trace magnesium and fluorine phases in UOx from MDU and UO2F2, respectively. The bulk oxygen isotope composition of UOx from MDU was analyzed using fluorination to remove the lattice-bound oxygen, and then O2 was subsequently analyzed with isotope ratio mass spectrometry (IRMS). The oxygen isotope compositions of the ADU, UO2F2, and the resulting UOx were analyzed by large geometry secondary ion mass spectrometry (LG-SIMS). When reduced with steam, the MDU, ADU, and UO2F2 experienced significant oxygen isotope exchange, and the resulting δ18O values of UOx approached the values of the steam. When reduced without steam, the δ18O values of converted ADU, U3O8, and UOx products remained similar to those of the UO2F2 starting material. LG-SIMS isotope mapping of F impurity abundances and distributions showed that direct steam-assisted reduction from UO2F2 significantly removed F impurities while dry reduction from UO2F2 led to the formation of UOx that was enhanced in F impurities. In addition, when UO2F2 was processed via precipitation to ADU and calcination to U3O8, F impurities were largely removed, and reductions to UOx with and without steam each had low F impurities. Overall, these findings show promise for combining multiple signatures to predict the process history during the conversion of uranium ore concentrates to nuclear fuel.

A highly sensitive fiber optic sensor based on two-core fiber for refractive index measurement.

A simple and compact fiber optic sensor based on a two-core fiber is demonstrated for high-performance measurements of refractive indices (RI) of liquids. In order to demonstrate the suitability of the proposed sensor to perform high-sensitivity sensing in a variety of applications, the sensor has been used to measure the RI of binary liquid mixtures. Such measurements can accurately determine the salinity of salt water solutions, and detect the water content of adulterated alcoholic beverages. The largest sensitivity of the RI sensor that has been experimentally demonstrated is 3,119 nm per Refractive Index Units (RIU) for the RI range from 1.3160 to 1.3943. On the other hand, our results suggest that the sensitivity can be enhanced up to 3485.67 nm/RIU approximately for the same RI range.

The Kv1.3 channel blocker Vm24 enhances muscle glucose transporter 4 mobilization but does not reduce body-weight gain in diet-induced obese male rats.

AIMS: Voltage-gated potassium channels 1.3 (Kv1.3) can be targeted to reduce diet-induced obesity and insulin resistance in mice. Since species-specific differences in Kv1.3 expression and pharmacology have been observed, we tested the effect of Vm24, a high-affinity specific blocker of Kv1.3 channels from Vaejovis mexicanus smithi, on body weight (BW), glucose tolerance and insulin resistance in diet-induced obese rats. MATERIALS AND METHODS: Young adult male Wistar rats were switched to a high-fat/high-fructose (HFF) diet. Eighteen days later animals were divided in two groups: vehicle and Vm24 group. Subcutaneous injections were applied every other day until sacrifice 2months later. An additional cohort was maintained on standard chow. KEY FINDINGS: The HFF diet promoted obesity. Treatment with Vm24 did not alter various metabolic parameters such as food intake, BW gain, visceral white adipose tissue mass, adipocyte diameter, serum glucose, leptin and thyroid hormone concentrations, brown adipose tissue mass or uncoupling protein-1 expression, and insulin tolerance. Vm24 did reduce basal and glucose-stimulated serum insulin concentrations, serum C-peptide concentration, increased QUICKI, and tended to lower HOMA-IR. Vm24 treatment did not change the activation of insulin receptor substrate-1, but enhanced protein-kinase B activation and membrane glucose-transporter 4 (GLUT4) protein levels in skeletal muscle. SIGNIFICANCE: In conclusion, in male rats, long-term blockade of Kv1.3 channels with Vm24 does not reduce weight gain and visceral adiposity induced by HFF diet; instead, it reduces serum insulin concentration, and enhances GLUT4 mobilization in skeletal muscle.

Segmentation of Coronary Angiograms Using Gabor Filters and Boltzmann Univariate Marginal Distribution Algorithm.

This paper presents a novel method for improving the training step of the single-scale Gabor filters by using the Boltzmann univariate marginal distribution algorithm (BUMDA) in X-ray angiograms. Since the single-scale Gabor filters (SSG) are governed by three parameters, the optimal selection of the SSG parameters is highly desirable in order to maximize the detection performance of coronary arteries while reducing the computational time. To obtain the best set of parameters for the SSG, the area (Az ) under the receiver operating characteristic curve is used as fitness function. Moreover, to classify vessel and nonvessel pixels from the Gabor filter response, the interclass variance thresholding method has been adopted. The experimental results using the proposed method obtained the highest detection rate with Az = 0.9502 over a training set of 40 images and Az = 0.9583 with a test set of 40 images. In addition, the experimental results of vessel segmentation provided an accuracy of 0.944 with the test set of angiograms.

Purification of a specific inhibitor of pyroglutamyl aminopeptidase II from the marine annelide Hermodice carunculata. in vivo effects in rodent brain.

An inhibitor of the metallo-ectoenzyme, pyroglutamyl aminopeptidase II (PPII), a thyrotropin releasing hormone-specific peptidase, was identified by screening extracts from marine species of the Cuban coast-line belonging to the phylla Chordata, Echinodermata, Annelida, Mollusca, Cnidaria, Porifera, Chlorophyta and Magnoliophyta. Isolation of the inhibitor (HcPI), from the marine annelide Hermodice carunculata, was achieved by trichloroacetic acid treatment of the aqueous extract, followed by ion-exchange chromatography on DEAE Sephacel, gel filtration on Sephadex G-25 and reverse phase-HPLC. HcPI had a small apparent molecular weight (below 1000 Da) and was not a peptide. It inhibited rat PPII (a membrane preparation with 8.5mg protein/ml) with an apparent K(i) of 51 nM. HcPI did not inhibit serine (trypsin, chymotrypsin, elastase and dipeptidyl aminopeptidase IV), cysteine (papain, bromelain and pyroglutamyl aminopeptidase I), aspartic (pepsin and recombinant human immunodeficiency virus 1 protease (HIV1-PR)) nor other metallo proteinases (collagenase, gelatinase, angiotensin converting enzyme, aminopeptidase N and carboxypeptidase A). HcPI was non-toxic and active in vivo. Intraperitoneal injection of HcPI reduced mouse pituitary and brain PPII activity. Potency of the effect was higher in hypophysis and hypothalamus than in other brain regions. Intrathecal administration to male rats reduced PPII activity in the spinal cord. In conclusion we have identified a specific inhibitor of PPII that is the first M1 family zinc metallo-peptidase inhibitor isolated from marine invertebrates. It may be useful for elucidating the in vivo role of PPII in the pituitary and central nervous system.

Thyrotropin-releasing hormone regulates the diurnal variation of pyroglutamyl aminopeptidase II activity in the male rat adenohypophysis.

OBJECTIVE: Thyrotropin-releasing hormone (TRH) is inactivated in the extracellular compartment by pyroglutamyl aminopeptidase II (PPII), a narrow specificity ectopeptidase present in the brain and in the lactotrophs of the adenohypophysis. TRH and various hypothalamic/paracrine agents regulate the activity of PPII on the surface of adenohypophyseal cells in primary culture. The activity of the hypothalamic-pituitary-thyroid axis presents circadian variations including an increase of serum thyrotropin levels in the early hours of the day. The purpose of this study was to determine whether adenohypophyseal PPII activity fluctuates during the daytime in the male rat and the role of TRH in these regulatory events in vivo. RESULTS: Adenohypophyseal PPII specific activity and mRNA levels presented diurnal variations. A decrease in specific activity occurred with a minimum between 0930 and 1130 h, associated with increased serum thyrotropin levels. PPII mRNA levels were lowest at 0800 h. Intraperitoneal injection at 0800 or 1000 h of [3-Me-His(2)]-TRH, a potent agonist of the TRH receptor, reduced PPII specific activity at 30 min post-injection which was followed by a return to basal levels at 2 h. A second phase of decrease occurred between 4 and 8 h post-injection. Intravenous injection of a TRH-immune serum induced, at 2 h post-injection, an increase in adenohypophyseal PPII specific activity, which lasted up to 6 h. CONCLUSIONS: Adenohypophyseal PPII activity and mRNA levels fluctuate during the day; TRH down-regulates PPII activity in vivo, contributing to some of these variations. These new findings, and previous data, suggest that adenohypophyseal PPII activity varies in distinct physiological events, in response to endocrine and hypothalamic/paracrine factors, potentially modulating responses to TRH.

Voluntary exercise adapts the hypothalamus-pituitary-thyroid axis in male rats.

The hypothalamic-pituitary thyroid (HPT) axis modulates energy homeostasis. Its activity decreases in conditions of negative energy balance but the effects of chronic exercise on the axis are controversial and unknown at hypothalamic level. Wistar male rats were exposed for up to 14 days to voluntary wheel running (WR), or pair-feeding (PF; 18% food restriction), or to repeated restraint (RR), a mild stressor. WR and RR diminished food intake; body weight gain decreased in the 3 experimental groups, but WAT mass and serum leptin more intensely in the WR group. WR, but not RR, produced a delayed inhibition of central markers of HPT axis activity. At day 14, in WR rats paraventricular nucleus-pro-TRH mRNA and serum TSH levels decreased, anterior pituitary TRH-receptor 1 mRNA levels increased, but serum thyroid hormone levels were unaltered, which is consistent with decreased secretion of TRH and clearance of thyroid hormones. A similar pattern was observed if WR animals were euthanized during their activity phase. In contrast, in PF animals the profound drop of HPT axis activity included decreased serum T3 levels and hepatic deiodinase 1 activity; these changes were correlated with an intense increase in serum corticosterone levels. WR effects on HPT axis were not associated with changes in the activity of the hypothalamic-pituitary adrenal axis, but correlated positively with serum leptin levels. These data demonstrate that voluntary WR adapts the status of the HPT axis, through pathways that are distinct from those observed during food restriction or repeated stress.

The systemic inhibition of nitric oxide production rapidly regulates TRH mRNA concentration in the paraventricular nucleus of the hypothalamus and serum TSH concentration. Studies in control and cold-stressed rats.

Neurons of the paraventricular nuclei of the hypothalamus (PVN) that synthesize the peptide thyrotropin releasing hormone (TRH) control energy homeostasis. Identifying the circuits which regulate these neurons is critical to fully understand integration of metabolic information and the mechanisms that set thyroid hormone levels. We tested the hypothesis that nitric oxide (NO) acutely controls PVN TRH expression and thyrotropin (TSH) secretion by the anterior pituitary. The subcutaneous treatment of rats with N(G)-nitro-L-arginine methyl ester (L-NAME), an inhibitor of NO synthases, enhanced PVN TRH mRNA and medio-basal hypothalamic TRH levels, and reduced serum TSH concentration. Analysis of the effect of a NO donor in primary cultures of hypothalamic or anterior pituitary cells suggested that the effect of NO includes a direct action on hypothalamic neurons. The cold stress-induced increase in TSH release was inhibited by sc L-NAME. Therefore, production of NO may control the activity of the hypothalamus-pituitary-thyroid axis.

La importancia de la leptospirosis humana en México: detección de anticuerpos antileptospira en una población de donadores de sangre / The importance of human leptospirosis in Mexico: detection of antileptospira antibodies in a population o blood donors

La detección de anticuerpos específicos en suero se ha utilizado como prueba diagnóstica para leptospirosis humana. En el hombre, la presencia de anticuerpos solamente se puede deber a un proceso infeccioso, ya que no existen vacunas que estimulen al sistema inmune para la producción de éstos. En el presente estudio de analizaron 206 sueros de adultos donadores de sangre, con la técnica de aglutinación microscópica contra siete serovariedades de Leptospira interrogans. El 7 por ciento de los sueros fueron positivos. La distribución de éstos por serovariedad fue la siguiente: shermani 53 por ciento, canicola 33 por ciento, pyrogenes 20 por ciento, pomona 13 por ciento e icterohaemorrhagiae 6 por ciento. El grupo etario con mayor frecuencia de seropositividad fue el de 20 a 39 años. Los resultados encontrados en individuos asintomáticos muestran que la leptospirosis en México es una zoonosis más frecuente de lo se sospecha