TL glow curve and kinetic analysis of Na2SiO3:Pr3+ under beta radiation effect.

Ionizing radiation dosimetry with thermoluminescence (TL) materials based on silicon or glass can be interesting in its potential use in radiation monitoring as the solution to the constant looking of development of new radiation detectors. In this work, TL characteristics of sodium silicate exposed to beta radiation effects were studied. TL response beta irradiated exhibited a glow curve with two peaks centered at 398 K and 473 K. Samples showed linearity from 0.55 to 13.2 Gy. TL readings after 10 times showed a repeatability with an error of less than 1%. Remain information showed significant losses during the first 24 h, but its information was almost constant after 72 h of storage. The Tmax-Tstop method exhibited three peaks which were mathematically analyzed with a general order deconvolution finding kinetic orders close to the second order for the first peak, meanwhile the kinetic order for the second peak and third peak are close to second order. Finally, the VHR method showed anomalous TL glow curve behavior with an increasing intensity TL as the heating rate increased.

A shared accretion instability for black holes and neutron stars.

Accretion disks around compact objects are expected to enter an unstable phase at high luminosity1. One instability may occur when the radiation pressure generated by accretion modifies the disk viscosity, resulting in the cyclic depletion and refilling of the inner disk on short timescales2. Such a scenario, however, has only been quantitatively verified for a single stellar-mass black hole3-5. Although there are hints of these cycles in a few isolated cases6-10, their apparent absence in the variable emission of most bright accreting neutron stars and black holes has been a continuing puzzle11. Here we report the presence of the same multiwavelength instability around an accreting neutron star. Moreover, we show that the variability across the electromagnetic spectrum-from radio to X-ray-of both black holes and neutron stars at high accretion rates can be explained consistently if the accretion disks are unstable, producing relativistic ejections during transitions that deplete or refill the inner disk. Such a new association allows us to identify the main physical components responsible for the fast multiwavelength variability of highly accreting compact objects.

Thermoluminescent studies of GdAlO3 powders.

The increasing use of thermoluminescence (TL) materials as radiation detectors with application in different areas of ionizing radiation has motivated research on new materials with adequate luminescent characteristics. In this work, experimental results gadolinium aluminate (GdAlO3) analyzed by thermoluminescent phenomenon under beta irradiation effect are studied. To prepare GdAlO3 powders the coprecipitation method was used. TL glow curve and other luminescent characteristics were analyzed using an automatic Lexsig Smart TL/OSL luminescent reader. TL glow curve showed four peaks with three prominent and well-defined peaks centered at 140, 230, and 270 °C. TL response as a function of beta radiation dose was linearity in the range from 1.1 up to 44 Gy. Kinetic parameters such as activation energy (E), frequency factor (s), and order of kinetics after the deconvolution of the TL glow curve were also determined using Chen's peak shape method. Experimental results show GdAlO3 as a potential luminescent host material for TL studies.

A persistent ultraviolet outflow from an accreting neutron star binary transient.

All disc-accreting astrophysical objects produce powerful disc winds. In compact binaries containing neutron stars or black holes, accretion often takes place during violent outbursts. The main disc wind signatures during these eruptions are blue-shifted X-ray absorption lines, which are preferentially seen in disc-dominated 'soft states'1,2. By contrast, optical wind-formed lines have recently been detected in 'hard states', when a hot corona dominates the luminosity3. The relationship between these signatures is unknown, and no erupting system has as yet revealed wind-formed lines between the X-ray and optical bands, despite the many strong resonance transitions in this ultraviolet (UV) region4. Here we report that the transient neutron star binary Swift J1858.6-0814 exhibits wind-formed, blue-shifted absorption lines associated with C IV, N V and He II in time-resolved UV spectroscopy during a luminous hard state, which we interpret as a warm, moderately ionized outflow component in this state. Simultaneously observed optical lines also display transient blue-shifted absorption. Decomposing the UV data into constant and variable components, the blue-shifted absorption is associated with the former. This implies that the outflow is not associated with the luminous flares in the data. The joint presence of UV and optical wind features reveals a multi-phase and/or spatially stratified evaporative outflow from the outer disc5. This type of persistent mass loss across all accretion states has been predicted by radiation-hydrodynamic simulations6 and helps to explain the shorter-than-expected duration of outbursts7.

[Transcultural adaptation of AGRASS questionnaire to evaluate the management of heathcare risks]. / Adaptación transcultural del Questionário AGRASS para evaluar la gestión de riesgos asistenciales.

OBJECTIVE: To cross-culturally adapt the Questionário AGRASS for evaluation of healthcare risk management in health services. MATERIAL AND METHODS: The work was carried out following 5 stages: 1) initial translation to Spanish; 2) Synthesis; 3) translation back to Portuguese; 4) experts review, and 5) pretest performed in a specialized Costa Rican hospital. RESULTS: The AGRASS Questionnaire translated and adapted into Spanish has the same dimensional structure as the original, with 2 dimensions and 9 subdimensions. Thirty-nine of the 40 original items were approved (general validation index=100% per item). Its application was considered viable, with items well understood and with useful results that identify opportunities for improvement in healthcare risk management. CONCLUSIONS: The AGRASS Questionnaire is culturally adapted to the Costa Rican reality and future studies can evaluate its contribution to other hospital contexts in Ibero-American countries.

The corona contracts in a black-hole transient.

The geometry of the accretion flow around stellar-mass black holes can change on timescales of days to months1-3. When a black hole emerges from quiescence (that is, it 'turns on' after accreting material from its companion) it has a very hard (high-energy) X-ray spectrum produced by a hot corona4,5 positioned above its accretion disk, and then transitions to a soft (lower-energy) spectrum dominated by emission from the geometrically thin accretion disk, which extends to the innermost stable circular orbit6,7. Much debate persists over how this transition occurs and whether it is driven largely by a reduction in the truncation radius of the disk8,9 or by a reduction in the spatial extent of the corona10,11. Observations of X-ray reverberation lags in supermassive black-hole systems12,13 suggest that the corona is compact and that the disk extends nearly to the central black hole14,15. Observations of stellar-mass black holes, however, reveal equivalent (mass-scaled) reverberation lags that are much larger16, leading to the suggestion that the accretion disk in the hard-X-ray state of stellar-mass black holes is truncated at a few hundreds of gravitational radii from the black hole17,18. Here we report X-ray observations of the black-hole transient MAXI J1820+07019,20. We find that the reverberation time lags between the continuum-emitting corona and the irradiated accretion disk are 6 to 20 times shorter than previously seen. The timescale of the reverberation lags shortens by an order of magnitude over a period of weeks, whereas the shape of the broadened iron K emission line remains remarkably constant. This suggests a reduction in the spatial extent of the corona, rather than a change in the inner edge of the accretion disk.

[Strategies for teaching self-examination of the breast to women in reproductive age]. / Estrategias para la enseñanza del autoexamen del seno a mujeres en edad reproductiva.

OBJECTIVE: To develop an effective strategy to inform Mexican women between 12 and 47 years of age about breast cancer (BC) and train them to perform breast self-examination (BSE). MATERIAL AND METHODS: Between April, 1996 and July, 1998, two different strategies to teach BSE were designed and evaluated in Cuernavaca, State of Morelos, Mexico. These strategies included teaching materials and were based on opinions of women participating in the first stage of this study. Both strategies consisted of the presentation of a leaflet and a video. The first strategy was delivered by a public health nurse in charge of leading the session. The second one was presented by a BC survivor. This second strategy included slides and silicon breast models. These two strategies were then compared to a third one, consisting of a primary care nurse handling out a leaflet and showing a video, based on Health Secretariat's guidelines. In total, 149 women were trained. They were randomly assigned to any one of these three strategies. The effectiveness of the teaching strategies was determined by assessing the changes in the women's knowledge of BC and BSE, as well as in their ability to identify the largest number of lumps on a natural size silicon breast, before and after training. Statistical analysis included Student's t test, variance analysis, McNemar's chi 2, Pearson's chi 2, and multiple linear regression. RESULTS: With all three strategies, there was an increase of approximately 30% in women's knowledge of BC and BSE as well as in their ability to detect lumps. Although at the beginning of the training only one out of every 20 women were able to identify more than three lumps in the silicon model, by the end between 3 and 4 of every 10 women were able to do this, with values of p < 0.05. Some factors determine women's learning of both BSE and information about BC as well as their ability to identify lumps. CONCLUSIONS: Teaching BSE with any of the strategies evaluated could be included in an integral program to educate Mexican women on breast cancer prevention and early detection. The appropriate and monthly practice of BSE is linked both to a decrease in the amount of time elapsing between the identification of suspect signs and the demand for medical care, such as requesting a clinical breast examination, which entails identifying small tumors when BC is present.

[Complications of posterior capsulotomy with the Nd:YAG laser. Study of 226 cases]. / Complications de la capsulotomie postérieure au Nd:YAG laser. Etude de 226 cas.

BACKGROUND: Severe complications are classically described after capsulotomy: ocular hypertension, cystoid macular edema and secondary retinal detachment. PATIENTS AND METHODS: A series of 226 patients having sustained Nd:YAG laser (PC). Posterior capsulotomy has been studied retrospectively in order to determine the rate of early complications (24 hours after PC) and late complications (up to 6 months after the PC). RESULTS: Fifteen patients (6.6%) presented acute temporary intraocular hypertension, 2 patients (0.9%) a retinal detachment, 2 patients (0.9%) a cystoid macular edema (CME). A total number of complications of 8.4% was observed, 1.8% were heavy. CONCLUSIONS: Transient rise of intraocular pressure is seen. Prophylactic treatment with acetazolamide 500 mg (Diamox) and timolol (Timoptic) is necessary.

[Re-evaluation of the role of argon laser trabeculoplasty in therapy of glaucoma]. / Réévaluation du rôle de la trabéculoplastie au laser argon (TLA) dans la thérapie du glaucome.

BACKGROUND: The pressure lowering effect of Argon laser trabeculoplasty (ALT) has been well demonstrated in the past. Today some clinicians tend to avoid ALT perhaps because it has been used in erroneous indications. The aim of this study was to re-evaluate the usefulness of ALT and to define its indication in the treatment of glaucoma. PATIENTS AND METHODS: A collective of 81 patients treated by ALT entered in a data bank between 1989 and 1991 were analysed retrospectively, focussing on: the percentage of patients requiring trabeculectomy (TE) after ALT, the mean time from ALT to TE, the stage of disease progression at which the decision for ALT was taken and the post-ALT evolution of ocular pressure (IOP), visual field and optic disc. RESULTS: After a mean follow-up of 28 +/- 10.5 months a TE was performed in 25% of cases. It was found that in our clinical practice the decision for ALT tended to be taken at a rather late stage of disease. For the patients that did not need a TE, the mean decrease of IOP at the end of follow-up was 5.4 mm Hg and the analysis of glaucoma parameters showed that there was no significant worsening of disease. The disease progression in the group of patients that were operated was already significantly worse than the total collective before ATL was performed. CONCLUSIONS: ALT is useful in the treatment of glaucoma, as long as it is not considered as an alternative to TE and as long as the patients benefit from a strict follow-up. Advanced cases should however be operated without delay.

[Prospective study of 163 retinal detachments operated by episcleral technique (preoperative examination)]. / Etude prospective de 163 décollements de rétine opérés par technique épisclérale (examens pré-opératoires).

The predominance of retinal breaks in the superior temporal quadrant is well known. This predominance was found to be related to age and refraction (p < 0.01). The distribution of breaks plotted across the 12 meridians shows a predilection for the superior temporal quadrant and half of the inferior temporal and superior nasal one. However, in this area the distribution is irregular (p >> 0.001) with a predominance in the 10-11 and 12-1 o'clock section (if we consider the right eye). The H/T ratio (holes/tears for each case) is positive for patients under 40 years of age and becomes negative after 50 years.

Acute retinal necrosis: a result of immune dysfunction? Report of a case with subacute evolution and relapses in a patient with impaired cellular immunity.

We report an atypical case of acute retinal necrosis (ARN) with a subacute course and relapses lasting for more than 4 years in an apparently immunocompetent 71-year-old female who had been followed for 4.5 years for recurrent retinochoroidal lesions with transient exudative retinal detachments and areas of consecutive chorioretinal atrophy. The diagnosis of varicella-zoster virus (VZV)-induced ARN was finally made on the basis of anterior granulomatous uveitis, typical retinal necrosis and the detection of anti-VZV antibodies in the aqueous humor. A widespread lumbar zoster dermatitis, cutaneous anergy and depressed in vitro lymphocyte activation indicated depressed cellular immunity. Absolute and relative numbers of B lymphocytes were increased. It is suspected that depressed cellular immunity and maintained B cell function might possibly be at the origin of ARN. The protracted course of ARN in this patient also suggests that the dysregulation of the immune system has probably existed for a long time.

Aqueous humor analysis after Nd:YAG laser capsulotomy with the laser flare-cell meter.

Using the laser flare-cell meter (Kowa FC-1000), we conducted a prospective study analyzing the effect of Nd:YAG posterior capsulotomy on the quantity of aqueous particles, aqueous flare, and intraocular pressure in 65 eyes (58 patients). Aqueous particles increased at six hours, followed by flare rise which was significant at 18 hours after capsulotomy. Only 22 eyes (34%) had a significant flare rise over prelaser values. Anti-inflammatory therapy was necessary in only one patient. The mean intraocular pressure value did not rise significantly after capsulotomy. Acute intraocular hypertension (AIOHT) (> 7 mm Hg increase) occurred between three and six hours after laser therapy in 12 patients (19%), was related in time to particle rise, and always responded to a single dose of acetazolamide. Acute intraocular hypertension was strongly correlated with elevated aqueous particles (P < .0001) and somewhat correlated with flare rise (P < .036), but was not correlated with the intraocular lens position (bag or sulcus fixation). Our findings strongly suggest that trabecular meshwork clogging by debris generated by the capsulotomy is the mechanism at the origin of AIOHT.