Monte Carlo simulation of the radiation transport in chromium compensated gallium arsenide detectors / Simulación por Monte Carlo del transporte de las radiaciones en detectores dearseniuro de galio compensado con cromo

Abstract Some results obtained with the use of Monte Carlo mathematical simulation of radiation transport in Timepix hybrid detectors based on chromium compensated gallium arsenide are presented in this contribution. The MCNPX, GEANT4, SRIM and MCCM code systems were used for this purpose. The in-depth profiles of the deposited energy by the incident photons within the sensor active volume, the shapes and dimensions of the generated charge carriers clouds for different incident energies and specific geometrical conditions were obtained and presented. The 22Ne ions ranges in the target material for two different energies and the contributions of each energy loss channel were also determined. Finally, for a selected detector irradiated with photons of different energies, the displacement cross sections for each chemical element in the active material, as well as the number of displacements per atoms produced for each atomic species were calculated.

Resumen En este trabajo se presentan algunos de los resultados obtenidos con el uso de la modelación matemática por Monte Carlo del transporte de radiación en detectores híbridos Timepix basados en el arseniuro de galio compensado con cromo. Se emplearon para este propósito los sistemas de códigos MCNPX, GEANT4, SRIM y MCCM. Fueron obtenidos los perfiles en profundidad de la energía depositada por la radiación incidente dentro del volumen activo del sensor, las formas y dimensiones de las nubes de portadores de cargas generados por fotones incidentes de diferentes energías y condiciones geométricas específicas. También se determinaron los alcances de los iones de 22Ne de dos energías diferentes en el material blanco y las contribuciones de cada canal de pérdida de energía. Finalmente, para un detector seleccionado irradiado con fotones de diferentes energías se calcularon las secciones eficaces de desplazamiento para cada elemento químico en el material activo, así como el número de desplazamientos por átomos producidos para cada especie atómica.

Ácido úrico como factor de riesgo cardiovascular / Uric acid as cardiovascular risk factor

La relación entre niveles séricos de ácido úrico y enfermedad cardiovascular es conocida desde hace tiempo. Sin embargo, ha sido en los últimos años cuando hemos encontrado creciente evidencia estableciendo el posible papel patogénico del ácido úrico en las diferentes manifestaciones de la enfermedad cardiovascular. La importancia de esta relación continúa siendo motivo de controversia y el debate sobre si debemos considerar la hiperuricemia un factor de riesgo vascular independiente o si es un mero epifenómeno de la enfermedad vascular o metabólica permanece abierto. Esta revisión pretende repasar la evidencia sobre estos aspectos y analizar las implicaciones terapéuticas que los nuevos conocimientos pudieran conllevar (AU)

The relation between uric acid serum levels and cardiovascular disease has been known for a long time. However, it has been in recent times that we have found growing evidence that establishes the possible pathogenic role of uric acid in the different manifestations of cardiovascular disease. The importance of this relation continues to be cause of controversy and the debate is still open on whether we should consider hyperuricemia as an independent vascular risk factor or if it is a mere epiphenomenon of the vascular or metabolic disease. This review aims to go over the evidence on these aspects again and to analyze the therapeutic implications that the new knowledge may involve (AU)

Dietary intervention focused on phosphate intake in hemodialysis patients with hyperphosphoremia.

BACKGROUND: Elevated serum phosphorus has been identified as a cardiovascular risk factor. This study aimed to assess the effectiveness of dietary intervention to reduce phosphorus intake and to improve the calcium-phosphorus metabolism in hemodialysis patients. DESIGN: Patients were included in a 6-month, 2-group experimental study if their previous 3-month average serum phosphorus was over 5.5 mg/dl. Patients were allocated to intensive dietary intervention or usual dietary recommendations. The clinical end-points were the multivariate-adjusted change in serum phosphorus and the number of patients who achieved serum phosphorus levels of < 5.5 mg/dl and serum phosphorus levels of < 5 mg/dl. RESULTS: 80 dialysis patients completed the study, 41 in the experimental group and 39 in the control group. After 6 months, phosphorus intake (702 ± 168 vs. 872 ± 242 mg/24 h; p = 0.002) was lower in the experimental group than in the control group, with no inter-group differences in protein-caloric intake. Serum phosphorus decreased 1.67 mg/dl in the experimental group and 0.58 mg/dl in the control group (multivariate-adjusted difference 0.93 mg/ dl; 95% CI 0.34 - 1.52; p = 0.003). Serum phosphorus < 5.5 mg/dl and serum phosphorus < 5 mg/dl were attained more frequently in the experimental group (51 vs. 18%, p = 0.002 and 31.7 vs. 15.4%, p = 0.08 respectively). CONCLUSIONS: Intensive dietary intervention focusing on phosphorus intake may be useful to reduce phosphorus retention and to improve calcium-phosphorus metabolism in hemodialysis patients.

[A pilot study on a quality improvement plan with systematic nutritional screening in patients admitted to a regional hospital]. / Estudio piloto de un plan de mejora de la calidad con cribaje nutricional sistemático de pacientes ingresados en un hospital comarcal.

OBJECTIVE: A pilot study to assess the feasibility of implementing a hospital protocol for systematic nutritional screening of admitted patients. METHOD: Descriptive cross-sectional study. Patients admitted to the Orthopedic Surgery Department of the Regional Hospital of Alcañiz were systematically included within the first 48 hours of hospitalization, from February to September of 2007. The screening methods used were the Nutritional Risk Index (NRI), the CONUT Nutritional Control system, and an indicator based on SENPE recommendations. The need for nutritional support was defined as the presence of any of the following instances: moderate to severe hyponutrition according to the NRI or CONUT methods, or hyponutrition according to the adapted SENPE recommendations. RESULTS: 36.4% of the patients assessed need nutritional support. The rate of hyponutrition according to CONUT is 13.6%, by SENPE criteria is 27.3%, and by the NRI 29.5%. The inter-method agreement is statistically significant and clinically acceptable: Kappa between NRI and CONUT 0.547, between NRI and SENPE 0.609, and between CONUT and SENPE 0.593. CONCLUSIONS: The implementation of a structured protocol for collecting the anthropometrical and biochemical parameters implicating a multidisciplinary hospital team enables identifying those patients in whom appropriate nutritional support may improve their prognosis during hospital stay.

Isthmectomy: a conservative operation for solitary nodule of the thyroid isthmus.

PURPOSE: To assess the results obtained in patients with nontoxic uninodular goiter confined to the isthmus undergoing isthmectomy. METHODS: Between April 1994 and June 2006, 330 consecutive patients with nontoxic uninodular goiter underwent thyroidectomy at our institution. In 31 patients, lesions were limited to the thyroid isthmus with evidence of benign or undetermined pathology on ultrasound-guided fine-needle aspiration biopsy. Total isthmectomy was performed. RESULTS: Preoperatively, thyroid nodules on ultrasonography were solid in 26 patients and mixed with cystic and solid components in 2. The mean size of nodules was 2.43 (+/- 0.88) cm. No intraoperative or postoperative complications occurred. Histological examination showed nodular hyperplasia in 29 cases, follicular adenoma in 1 and papillary thyroid carcinoma in 1. The patient with papillary carcinoma underwent bilateral lobectomy 7 days later. A total of 24 patients (77.4%) attended clinical visits at follow-up (mean 70,57 months). Ultrasonographic scanning revealed thyroid nodules in 17 patients, in 16 of which nodules range from one to five (0.5 to 2 cm in size) and further surgery was not indicated. One patient with a 4-cm nodule and tracheal displacement found at ultrasonography 2 years after isthmectomy had inconclusive results of FNAB. This patient was re-operated for completion thyroidectomy, which was successfully performed without technical difficulties. The detection of recurrent nodules was independent of the time elapsed since thyroid isthmectomy. CONCLUSIONS: These findings document the feasibility and efficacy of isthmectomy in solitary thyroid nodules confined to the isthmus.

[Nutrient intake and eating habits in hemodialysis patients: comparison with a model based on mediterranean diet]. / Principales déficits del consumo alimentario de los pacientes en hemodiálisis: aproximación a un modelo de alimentación saludable basado en la dieta mediterránea.

OBJECTIVES: Inadequate nutrient intake seems to be one of the most important cause of malnutrition in hemodialysis patients. The purpose of this study was to analyse their nutrient intake and eating habits, comparing food groups' intake with standard Mediterranean diet values (Healthy Diet Guide 2004, Nutrition Community Spanish Society). MATERIAL AND METHODS: There were 28 stable hemodialysis (HD) patients, 15 males and 13 females, mean age 62,9 +/- 16 years. Dietary evaluation was based on 7-day dietary recalls conducted by a single observer. We compare nutrients intake with recommended hemodialysis intake and we contrast food groups consumption with the theoretical ideal based on Mediterranean diet. RESULTS: The protein intake was 1,33 +/- 0,2 g/kg/day and the energy intake 29,5 +/- 2,1 kcal/kg/day. Carbohydrates accounted 43,1% of energy intake, proteins 19% and lipids 37,9% (55,5% monounsaturated fatty acids, 16,4% polyunsaturated fatty acids and 28,1% saturated fatty acids). Complex carbohydrates (potatoes, cereals, vegetables, fruits) and olive oil consumption was lower than that recommended to the Spanish healthy population and to the chronic hemodialysis patients. The animal protein intake (meat, fish, eggs) was correct, although excessive in red and processed meats. Results: Potatoes and cereals recommended frequency (RF) 4-6 portions/day, HD patients frequency (HDF) 4,1 portions/day; vegetables RF > 2 portions/day, HDF 1,2; fruits RF > 3 portions/day, HDF 1,3; olive oil RF 3-6 portions/day, HDF 1,5; Fish RF 3-4 portions/week, HDF 4,2; White meat RF 3-4 portions/week, HDF 1,5; Poultry RF 3-4 portions/week, HDF 2,3; Eggs RF 3-4 portions/week, HDF 3,6; Pulses RF 3-4 portions/week, HDF 1,7; Nuts RF 3-7 portions/week, HDF 0; Red meat RF occasionally, HDF 4,8 portions/week; Processed meats RF occasionally, HDF 4,6 portions/week; Sweets, snacks, soft drinks RF occasionally, HDF 1,7 portions/week; Butter, margarine, processed bakery products, biscuits RF occasionally , HDF 0,5 portions/week. CONCLUSIONS: Nutritional abnormalities are frequently found even in apparently stable patients on chronic hemodialysis. Caloric rather than protein undernutrition is the major abnormality. Inadequate caloric intake (< 35 kcal/kg/day) can lead to a negative nitrogen balance. Their eating habits are healthy and natural, but there is a deficit in slowly absorbed carbohydrates and olive oil intake (with caloric intake reduction), and an excessive consumption of red and processed meats (with saturated fats increase). The individual correction of these dietary patterns could reduce the saturated fats and increase the energy intake, obtaining a balanced diet integrated into our geographic region and culture.

Quantitative corneal anatomy in emmetropic subjects.

PURPOSE: Currently there is little information available about the corneal thickness values of healthy emmetropic subjects. Therefore, the authors decided to analyze the corneal thickness in healthy emmetropic subjects. METHODS: The authors analyzed the difference in thickness values between the thinnest corneal site and the central and paracentral cornea in 124 eyes of 124 healthy emmetropic white subjects. RESULTS: The mean difference between the thinnest site of the cornea and the thickness values obtained in the areas analyzed was as follows: 12+/-6 microm center; 140+/-19 microm superonasal; 133+/-23 microm nasal; 117+/-26 microm inferonasal; 122+/-19 microm superotemporal ; 89+/-22 microm temporal; and 99+/-29 microm inferotemporal (p<0.001; one way analysis of variance test). CONCLUSIONS: In healthy emmetropic white subjects the thinnest site of the cornea is statistically lower than the central and paracentral cornea.

[Orbscan pachymetry: differences between observers when carrying out measurements of the corneal thickness]. / Paquimetría Orbscan: diferencias entre observadores al realizar mediciones del espesor corneal.

PURPOSE: To study the corneal thickness and the inter-observer variability of corneal thickness measurements by means of Orbscan pachymetry. METHODS: We analysed the central and para-central corneal thickness of 30 subjects, whose age ranged from 19 to 38 years (mean 27.27, S.D. 5.25), with the Orbscan Topography System II (Orbscan, Inc., Salt Lake City, UT, USA). The mean of five consecutive measurements of the corneal thickness were obtained by two different observers and the results obtained were compared. RESULTS: No significant differences in mean corneal thickness between observers were found at central (p=0.749), nasal (p=0.931), supero-nasal (p=0.847), infero-nasal (p=0.930), temporal (p=0.918), supero-temporal (p=0.912) and infero-temporal (p=0.760) regions of the cornea. The maximum mean corneal thickness was found most commonly at the supero-nasal cornea (14 of 30 eyes for observer 1, and 16 of 30 eyes for observer 2). The difference between the central thickness and the maximum para-central thickness was 117 (S.D. 22) and 117 (S.D. 23) microns for observers 1 and 2 respectively (p=0.974). The difference between the central thickness and the minimum para-central thickness was 40 (S.D. 20) and 39 (S.D. 19) microns for observers 1 and 2 respectively (p=0.846). The difference between the minimum and the maximum para-central thickness was 76 (S.D. 24) and 77 (S.D. 23) microns for observers 1 and 2 respectively (p=0.895). CONCLUSIONS: Orbscan pachymetry allows central and para-central corneal studies to be carried out by different observers without any significant differences being found between them.

Corneal endothelial cell density decreases with age in emmetropic eyes.

PURPOSE: To analyze the corneal endothelial cell density in healthy adult emmetropic subjects. METHODS: We analyzed the corneal endothelial cell density of a group made up of 225 emmetropic subjects (n=225). As age-matched control groups we analyzed two other groups, one made up of myopic subjects (n=209) and the other made up of hyperopic subjects (n=203). We recorded the mean of three consecutive measurements of the corneal endothelial cell density using the Topcon SP-2000P non-contact specular microscope (Topcon Corp., Tokyo, Japan). RESULTS: The mean age was 38.6+/-11.8 years, 40.7+/-12.2 years, and 39.2+/-10.5 years for emmetropic, myopic and hyperopic subjects respectively (p=0.994). No significant differences (p=0.920) in endothelial cell density values were found between emmetropic (2985+/-245 cells/mm2), myopic (2936+/-258 cells/mm2) and hyperopic eyes (2946+/-253 cells/mm2). Lower corneal endothelial cell density values were found in older emmetropic (p<0.001), myopic (p<0.001), and hyperopic subjects (p<0.001). A significant correlation between endothelial cell density and age was found in emmetropic (r=-0.958; p<0.001), myopic (r= -0.954; p<0.001) and hyperopic subjects (r= -0.948; p<0.001). CONCLUSIONS: In healthy emmetropic subjects there is a reduction in corneal endothelial cell density with age although there are no differences in corneal endothelial cell density values between emmetropic, myopic and hyperopic subjects.

Intraobserver reproducibility of retinal nerve fiber layer measurements using scanning laser polarimetry and optical coherencetomography in normal and ocular hypertensive subjects.

PURPOSE: To evaluate quantitatively the intraobserver reproducibility of measurements of the retinal nerve fiber layer (RNFL) in healthy subjects and an ocular hypertensive population using two nerve fiber analyzers. METHODS: Sixty eyes of normal (n=30) and ocular hypertensive subjects (n=30) were consecutively recruited for this study and underwent a complete ophthalmologic examination and achromatic automated perimetry. RNFL were measured using scanning laser polarimeter (GDx-VCC) and optical coherence tomography (OCT Model 3000). Reproducibility of the RNFL measurements obtained with both nerve fiber analyzers were compared using the coefficient of variation. RESULTS: In both groups the authors found fair correlations between the two methods in all ratio and thickness parameters. The mean coefficient of variation for measurement of the variables ranged from 2.24% to 13.12% for GDx-VCC, and from 5.01% to 9.24% for OCT Model 3000. The authors could not detect any significant differences between healthy and ocular hypertensive eyes, although in normal eyes the correlations improved slightly. Nev-ertheless, the testretest correlation was slightly better for GDx-VCC than for OCT Model 3000 (5.55% and 7.11%, respectively). CONCLUSIONS: Retinal mapping software of both nerve fiber analyzers allows reproducible measurement of RNFL in both healthy subjects and ocular hypertensive eyes, and shows fair correlations and good intraobserver reproducibility. However, in our study, GDx showed a better testretest correlation. (Eur J Ophthalmol 2004; 14: 523-30).

Intraobserver reproducibility of retinal nerve fiber layer measurements using scanning laser polarimetry and optical coherence tomography in normal and ocular hypertensive subjects.

PURPOSE: To evaluate quantitatively the intraobserver reproducibility of measurements of the retinal nerve fiber layer (RNFL) in healthy subjects and an ocular hypertensive population using two nerve fiber analyzers. METHODS: Sixty eyes of normal (n=30) and ocular hypertensive subjects (n=30) were consecutively recruited for this study and underwent a complete ophthalmologic examination and achromatic automated perimetry. RNFL were measured using scanning laser polarimeter (GDx-VCC) and optical coherence tomography (OCT Model 3000). Reproducibility of the RNFL measurements obtained with both nerve fiber analyzers were compared using the coefficient of variation. RESULTS: In both groups the authors found fair correlations between the two methods in all ratio and thickness parameters. The mean coefficient of variation for measurement of the variables ranged from 2.24% to 13.12% for GDx-VCC, and from 5.01% to 9.24% for OCT Model 3000. The authors could not detect any significant differences between healthy and ocular hypertensive eyes, although in normal eyes the correlations improved slightly. Nevertheless, the test-retest correlation was slightly better for GDx-VCC than for OCT Model 3000 (5.55% and 7.11%, respectively). CONCLUSIONS: Retinal mapping software of both nerve fiber analyzers allows reproducible measurement of RNFL in both healthy subjects and ocular hypertensive eyes, and shows fair correlations and good intraobserver reproducibility. However, in our study, GDx showed a better test-retest correlation.

[Comparative clinical study of visual results between two different types of bifocal intraocular lenses]. / Estudio clínico comparativo de los resultados visuales en dos lentes intraoculares bifocales.

PURPOSE: To compare visual results after cataract surgery in patients who underwent bilateral implantation of two different types of bifocal intraocular lenses: the model 811E (Pharmacia), and the model MF4 (Ioltech). METHODS: This prospective study comprised 99 patients who underwent phacoemulsification with bifocal IOL implantation. The model 811E was implanted in forty-seven eyes of 47 patients (group I) and the model MF4 in fifty-two eyes of 52 patients (group II). Visual acuity (distance and near), complications, and adverse events were measured. The postoperative follow-up in all patients was of 6 months. Patient satisfaction was also valued using a questionnaire. RESULTS: There was no significant difference in uncorrected distance visual acuity between both groups, which was respectively 0.63 (S.D.: 0.2) for group I and 0.58 (S.D.: 0.16) for group II (p=0.17). Nonetheless a significant difference was found when measuring corrected distance visual acuity, which was 0.86 (S.D.: 0.1) for group I and 0.77 (S.D.: 0.12) for group II (p=0.01). Mean uncorrected near visual acuity was statistically better in group I: J2.00 (S.D.:1.16) in comparison with J2.48 (S.D.:0.83) for group II (p=0.021). Subjectively, both groups indicated high levels of satisfaction, without significant difference between them, being respectively 78% (group I) and 73.4% (group II). CONCLUSIONS: Our results reveal a superiority of the bifocal diffractive lens over the refractive bifocal lens for corrected distance visual acuity and distance-corrected near visual acuity. Postoperatory complications and satisfaction degree were similar for both IOL models.

Estudio clínico comparativo de los resultados visuales en dos lentes intraoculares bifocales / Comparative clinical study of visual results between two different types of bifocal intraocular lenses

Introducción: Comparar los resultados visuales tras cirugía de cataratas con implante de dos tipos de lentes intraoculares (LIO) bifocales: el modelo 811E (Pharmacia), y el modelo MF4 (Ioltech).Métodos: Para ello realizamos un estudio prospectivo en 99 pacientes intervenidos de cataratas mediante facoemulsificación con posterior implante de LIO bifocales. En 47 pacientes se implantó el modelo 811E, y en 52 pacientes se implantó el modelo MF4. Se valoraron agudezas visuales (AV) (lejos y cerca) y refracción postoperatoria tras un periodo de seguimiento de 6 meses. La satisfacción de los pacientes se evaluó mediante un cuestionario. Resultados: No se observaron diferencias entre ambos tipos de lentes al valorar la AV para lejos sin corrección, siendo 0,63 (D.E.: 0,2) para la 811E y 0,58 (D.E.: 0,16) para la MF4 (p=0,17). Por el contrario, se observaron diferencias significativas al valorar la AV media para lejos con corrección, siendo 0,86 (D.E.: 0,1) para la 811E y 0,77 (D.E.: 0,12) para la MF4 (p=0,01), y la AV media para cerca sin corrección, siendo J2,00 (D.E.: 1,16) para la 811E y J2,48 (D.E.: 0,83) para la MF4 (p=0,021). El porcentaje de satisfacción de los pacientes fue similar en ambos tipos de LIOs, siendo respectivamente del 78 por ciento (811E) y del 73,4 por ciento (MF4).Conclusiones: Nuestros resultados muestran una superioridad de las lentes difractivas bifocales sobre las lentes refractivas bifocales en la agudeza visual corregida para lejos y en la agudeza visual de cerca con la corrección de lejos. Las complicaciones postoperatorias y el grado de satisfacción fueron similares para ambos modelos (AU)

NGF and TGF-beta mRNA expression during pregnancy in a rat corneal wound healing model.

BACKGROUND: Growth factors seem to play a major role in corneal wound healing and TGF-beta seems to be associated with abnormal healing after corneal surgical procedures. Few studies have analysed the role of NGF and TGF-beta on corneal wound healing during pregnancy. The aim of the present study was to create an animal model to evaluate the expression of NGF and TGF-betas during corneal wound healing in two groups: control and pregnant rats. METHODS: Corneal mRNA for NGF and the three isoforms of TGF-beta were analysed by RT-PCR, in a time-course experiment on different days after epithelial wounding (2, 7, 14 days) in pregnant and control groups RESULTS: The results show high corneal mRNA expression for NGF and TGF-beta1 without any variation throughout the healing process or pregnancy evolution. However, we detected a different expression of corneal mRNAs for TGF-beta2 and TGF-beta3 in the control group. This data was not detected in the pregnant group. DISCUSSION: Our results suggested that pregnancy could have a relevant role on TGF-beta2 and TGF-beta3 mRNA expression during the corneal wound healing process. Additional research should be performed to corroborate these findings.