Distributed detection of hydrogen and deuterium diffusion into a single-mode optical fiber with chirped-pulse phase-sensitive optical time-domain reflectometry.

For some infrastructures such as oil and gas extraction boreholes or radioactive waste repositories, where distributed optical fiber sensors are employed to grant the safety of the facilities, the presence of gas species such as hydrogen or deuterium is one of the most relevant parameters to monitor. The possibility of employing the same kind of sensors for this purpose is of special interest, reducing the cost by employing a single interrogator, able to measure multiple parameters by simply employing adequate sensing fibers. To meet this goal, we present here a chemical sensor based on chirped-pulse phase-sensitive optical time-domain reflectometry (CP-φOTDR), which is able to detect these species while they diffuse into the silica fiber. The ability of chirped-pulse φOTDR to measure a change in refractive index with sensitivity around 10-8 has allowed determining hydrogen concentration with accuracy on the order of 10-3 mol/m3 and spatial resolution ∼6 m. Another experiment provides an indirect measurement of the solubility of deuterium in a standard telecom-grade optical fiber, which is found to be around 1.47×1024 m3/bar.

Morphological changes of the internal carotid artery: prevalence and characteristics. A clinical and ultrasonographic study in a series of 19 804 patients over 25 years old.

BACKGROUND AND PURPOSE: Morphological changes of the internal carotid arteries (McICA) are frequently found during cervical ultrasound studies. However, the etiology of McICA remains controversial. During this study, the prevalence and demographic characteristics of McICA, such as kinking, coiling or looping identified by Doppler ultrasound, were analysed and its relationship with vascular risk factors and stroke was assessed. METHODS: A retrospective study was performed by analysing 19 804 patients who were subjected to cervical ultrasonographic study between January 2000 and June 2012. The data were statistically analysed with SPSS® 20 and a multivariate logistic regression was performed. Statistical significance was accepted for P < 0.05 and 95% confidence intervals (CIs) were used. RESULTS: Morphological changes of the internal carotid arteries were present in 2678 patients (13.5%) and were unilateral in 61.6% of these cases. Carotid kinking was found in 80% of the patients, coiling in 16% and looping in 1%. In multivariate analysis, the presence of McICA was related to older groups (1.04; 95% CI, 1.04-1.05; P < 0.01), female gender (1.78; 95% CI, 1.64-1.94; P < 0.01), patients with hyperlipidemia (1.28; 95% CI, 1.17-1.40; P < 0.01), carotid thickness (1.22; 95% CI, 1.13-1.33; P < 0.01) and cardiac or cardioembolic disease (1.11; 95% CI, 1.01-1.21; P = 0.02). The results of this study indicate that kinking in the carotid artery was associated with ipsilateral cerebral ischemic events (1.43; 95% CI, 1.040-1.958; P < 0.05). CONCLUSION: Morphological changes of the internal carotid arteries were associated with aging, female gender and patients with hyperlipidemia, hypertension, diabetes and heart disease. Kinking was associated with ipsilateral cerebral ischemia.

Real time dynamic strain monitoring of optical links using the backreflection of live PSK data.

A major cause of faults in optical communication links is related to unintentional third party intrusions (normally related to civil/agricultural works) causing fiber breaks or cable damage. These intrusions could be anticipated and avoided by monitoring the dynamic strain recorded along the cable. In this work, a novel technique is proposed to implement real-time distributed strain sensing in parallel with an operating optical communication channel. The technique relies on monitoring the Rayleigh backscattered light from optical communication data transmitted using standard modulation formats. The system is treated as a phase-sensitive OTDR (ΦOTDR) using random and non-periodical non-return-to-zero (NRZ) phase-shift keying (PSK) pulse coding. An I/Q detection unit allows for a full (amplitude, phase and polarization) characterization of the backscattered optical signal, thus achieving a fully linear system in terms of ΦOTDR trace coding/decoding. The technique can be used with different modulation formats, and operation using 4 Gbaud single-polarization dual PSK and 4 Gbaud dual-polarization quadrature PSK is demonstrated. As a proof of concept, distributed sensing of dynamic strain with a sampling of 125 kHz and a spatial resolution of 2.5 cm (set by the bit size) over 500 m is demonstrated for applied sinusoidal strain signals of 500 Hz. The limitations and possibilities for improvement of the technique are also discussed.

Single-shot distributed temperature and strain tracking using direct detection phase-sensitive OTDR with chirped pulses.

So far, the optical pulses used in phase-sensitive OTDR (ΦOTDR) were typically engineered so as to have a constant phase along the pulse. In this work, it is demonstrated that by acting on the phase profile of the optical pulses, it is possible to introduce important conceptual and practical changes to the traditional ΦOTDR operation, thus opening a door for new possibilities which are yet to be explored. Using a ΦOTDR with linearly chirped pulses and direct detection, the distributed measurement of temperature/strain changes from trace to trace, with 1mK/4nε resolution, is theoreticaly and experimentaly demonstrated. The measurand resolution and sensitivity can be tuned by acting on the pulse chirp profile. The technique does not require a frequency sweep, thus greatly decreasing the measurement time and complexity of the system, while maintaining the potential for metric spatial resolutions over tens of kilometers as in conventional ΦOTDR. The technique allows for measurements at kHz rates, while maintaining reliability over several hours.

Gastrenterocolite em lactentes. / Gastroenteritis in infants

Os autores estudaram 66 lactentes com gastroenterocolite. Analisam aspectos nutricionais por ocasicao do internamento e da alta, etiologicos, tempo medico de duracao da diarreia e de internamento, patologia associadas mais frequentes e comentarios sobre tratamento. Mais de 80% tinham de 0-6 meses de vida. A grande maioria piora de seu estado nutricional durante o quadro diarreico. O grau de nutricao inicial nao alterou o tempo medio de duracao dos sintomas. Sindrome anemica e moniliase foram as patologias associadas mais frequentemente encontradas. Os pacientes que receberam antibioticoterapia apresentaram um tempo medio de duracao da diarreia maior do que casos que nao receberam aquela medicacao

The influence of diazepam on the dosage of muscel-relaxants during anaesthesia.

The literature on anaesthesiological studies performed to investigate a possible sparing effect of diazepam on the dosage of muscle-relaxants during anaesthesia is reviewed. Despite some conflicting results it can be concluded that diazepam exerts such an effect, thus allowing between 8 and 30% of the amounts of muscle-relaxants, depending on the type of anesthesia used, to be spared. This conclusion is also supported by the results of pharmacological studies in animals, using the head drop method. The mechanism of this effect is discussed on the basis of the relevant published pharmacological evidence from "in vitro" studies and from both animal and human "in vivo" studies. From these reports it is concluded that diazepam, at therapeutic doses, does not act on neuromuscular transmission and that this sparing effect does not result from direct pharmacological interaction with neuromuscular blocking agents. Some studies indicate a minimal action of the product on the skeletal muscle fibre, but this also is not related to the sparing effect. It is furthermore concluded that his sparing effect of diazepam on the dosage of muscle-relaxants during anesthesia is due to a summation of muscle-relaxant actions exerted at different levels of the nervous system, those of diazepam being mainly exerted at the spinal and brainstem level and consisting in inhibition of polysynaptic reflex activity, enhancement of presynaptic inhibition, and depression of gamma-motoneuron activity.