Application of spectral gamma and magnetic susceptibility in a As bearing loessic aquifer, Argentina

Application of Natural Gamma Spectroscopy (NGS) borehole logging and magnetic susceptibility (χ) on aquifer samples are compared with the identified mineralogy and trace elemental analyses. Acceptable correlation between ICP analyses (K and Th) and NGS signals has been found. However, some observed discrepancies on them could be related to the different exploratory volumes of each technique. Magnetic Susceptibility measurements present better correlations between the superparamagnetic signal (χdf) and As contents, probably linked to the pedogenetic origin of such particles

Factores que influyen en la elección de las carreras de pedagogía en Colombia

Resumen El presente trabajo tiene como objetivo identificar los factores que influyen sobre las motivaciones, la satisfacción y expectativas en torno al ejercicio profesional en estudiantes de las facultades de Educación y ciclos complementarios de Escuelas Normales Superiores (ENS) en Colombia, tomando caso de estudio la región Caribe de este país. Para ello, se aplicó un estudio de tipo cuantitativo, cuya muestra estuvo integrada por 805 estudiantes de programas afines a los antes mencionados, quienes estuvieron a cargo del diligenciamiento de una encuesta orientada a la medición de los factores que influyen en la elección de estos estudios, de acuerdo con la escala FIT-choice (Factors Influencing Teaching choice), desarrollado por Watt y Richardson (2007). Los resultados obtenidos no solo nos permiten establecer un perfil socioeducativo de los futuros maestros analizados en este trabajo; sino también, facilitan la identificación de los factores vinculados a los principales tipos de motivaciones que tienen mayor peso, al momento de elegir carreras relacionadas con la Pedagogía; siendo las motivaciones de tipo altruistas e intrínsecas las más valoradas por los estudiantes encuestados. Las motivaciones extrínsecas, relacionadas con el salario y la conciliación, por ejemplo, tuvieron una valoración menor, con la excepción del factor relacionado con la seguridad del trabajo. La satisfacción de la elección es elevada pese al bajo salario, la falta de estatus social y una alta disuasión social.This paper aims to identify the factors that influence motivation, satisfaction and expectations about the professional practices among students in education colleges and postsecondary education colleges in Colombia, studying the case of the Caribbean region, based on a quantitative study with 805 students linked with the programs mentioned above, who were in charge of measuring the factors that influence the selection of teaching careers, according to the FIT-choice scale (Factors Influencing Teaching choice), developed by Watt and Richardson (2007). Findings not only allow us to establish a socio-educational profile of future teachers analyzed in this work, but also help us to identify factors linked to the main types of motivations that mostly affect the choice of education careers. In this case, the altruistic and intrinsic motivations are the most valued by respondents, compared with extrinsic motivations, related to salary and time for family, for example, whose valuation was lower. Satisfaction with choice is well valued despite low salaries, lack of social status and high social dissuasion

Paleolandscape reconstruction and interplay of controlling factors of an Eocene pedogenically-modified distal volcaniclastic succession in Patagonia

The middle Eocene Koluel-Kaike Formation, located in the San Jorge Basin, Patagonia, Argentina, is a strongly pedogenically modified succession associated with volcaniclastic input in an aggrading distal eolian-dominated fluvial system, located ∼400 km downwind of the Eocene Andean volcanic arc. The coordinated study of sediments and paleosols of this unit allows (1) reconstruction of environmental conditions and landscape evolution, and (2) determination of the interplay of the main forcing factors in the evolution of the Kokuel-Kaike Formation. The landscape reconstruction attests to the existence of a loessic rolling plain drained by a subordinate fluvial system, composed of both unconfined and confined flows, with locally ponded areas. Over these, thick stacked cumulative paleo-Ultisols and vertic paleo-Ultisols developed with scarce simple and stacked compound vitric Entisols analogues and compound Inceptisols equivalents. This high-resolution sedimentological-pedological analysis of the Kokuel-Kaike Formation indicates that the interplay between episodic volcaniclastic supply and cyclic climate controlled landscape evolution and soil development.Fil: Raigemborn, María Sol. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; ArgentinaFil: Beilinson, Elisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; ArgentinaFil: Krause, Javier Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; ArgentinaFil: Varela, Augusto Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; ArgentinaFil: Bellosi, Eduardo Sergio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; ArgentinaFil: Matheos, Sergio Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; ArgentinaFil: Sosa, Numa Nahuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentin

Influence of the dwell time in the polarization hysteresis of polymer electrolyte membrane fuel cells

The extent of the cell voltage hysteresis observed in polarization curves of PEM fuel cells and the origins causing this effect are investigated by performing experimental polarization curves with different dwell times for a 50 cm2 PEM fuel cell. Electrochemical Impedance Spectroscopy measurements are carried out in order to determine the relative contributions of the different polarizations (ohmic, activation, and concentration polarization). Equivalent circuits were obtained from the impedance spectra, where the interpretation of the circuit parameters enabled the analysis of the origin and extent of the cell voltage hysteresis. It was identified that the cause of the cell voltage hysteresis is actually dominated by the changes in the concentration polarization at low current densities, and by the changes in the activation polarization at high current densities. The cell ohmic resistance (and consequently the membrane hydration) presents a minor effect on the cell voltage hysteresis. The effect of the dwell time in the cell voltage hysteresis (with values ranging from 15 to 25 mV) presents a mixed trend, with an initial decrease for increasing dwell times from 120 to 600 s, and a later increase and a final almost constant hysteresis for longer dwell times

Preoperative chemoradiation and intra-operative radiotherapy for pancreatic carcinoma

In recent years, preoperative chemoradiation has received growing interest for the treatment of locally advanced pancreatic cancer. In an attempt to improve resectability and disease control, we used preoperative radiation therapy and concomitant 5-fluorouracil in a combined modality therapy protocol. The aim of the study was to evaluate definitive results in terms of toxicity, response and clinical outcome

External Beam Radiotherapy Plus 24-Hour Continuous Infusion of Gemcitabine in Unresectable Pancreatic Carcinoma: Long-Term Results of a Phase II Study

Purpose: To evaluate the efficacy of gemcitabine-based chemoradiation (CT-RT) in treating patients (pts) affected by locally advanced pancreatic cancers (LAPC). Methods and Materials: Weekly gemcitabine (100 mg/m2) was given as a 24-hour infusion during the course of three-dimensional radiotherapy (50.4 Gy to the tumor, 39.6 Gy to the nodes). After CT-RT, pts received five cycles of sequential chemotherapy with gemcitabine (1000 mg/m2; 1, 8, q21). Response rate was assessed according to World Health Organization criteria 6 weeks after the end of CT-RT. Local control (LC), time to progression (TTP), metastases-free survival (MFS), and overall survival (OS) were analyzed by the Kaplan Meier method. Results: Forty pts (male/female 22/18; median age 62 years, range, 36-76) were treated from 2000 to 2005. The majority had T4 tumour (n = 34, 85%), six pts (15%) had T3 tumour. Sixteen pts (40%) were node positive at diagnosis. Grade 3-4 acute toxicity was observed in 21 pts (52.5%). Thirty pts (75%) completed the treatment schedule. A clinical response was achieved in 12 pts (30%). With a median follow-up of 76 months (range, 32-98), 2-year LC was 39.6% (median, 12 months), 2-year TTP was 18.4% (median, 10 months), and 2-year MFS was 29.7% (median, 10 months). Two-year OS (25%; median, 15.5 months) compared with our previous study on 5-fluorouracil-based CT-RT (2.8%) was significantly improved (p <0.001). Conclusions: Gemcitabine CT-RT seems correlated with improved outcomes. Healthier patients who are likely to complete the treatment schedule may benefit most from this therapy. \ua9 2010 Elsevier Inc. All rights reserved

Application of a practical method for the isocenter point in vivo dosimetry by a transit signal

This work reports the results of the application of a practical method to determine the in vivo dose at the isocenter point, Diso, of brain thorax and pelvic treatments using a transit signal St. The use of a stable detector for the measurement of the signal St (obtained by the x-ray beam transmitted through the patient) reduces many of the disadvantages associated with the use of solid-state detectors positioned on the patient as their periodic recalibration, and their positioning is time consuming. The method makes use of a set of correlation functions, obtained by the ratio between St and the mid-plane dose value, Dm, in standard water-equivalent phantoms, both determined along the beam central axis. The in vivo measurement of Diso required the determination of the water-equivalent thickness of the patient along the beam central axis by the treatment planning system that uses the electron densities supplied by calibrated Hounsfield numbers of the computed tomography scanner. This way it is, therefore, possible to compare Diso with the stated doses, D iso,TPS, generally used by the treatment planning system for the determination of the monitor units. The method was applied in five Italian centers that used beams of 6 MV, 10 MV, 15 MV x-rays and 60Co \u3b3-rays. In particular, in four centers small ion-chambers were positioned below the patient and used for the St measurement. In only one center, the St signals were obtained directly by the central pixels of an EPID (electronic portal imaging device) equipped with commercial software that enabled its use as a stable detector. In the four centers where an ion-chamber was positioned on the EPID, 60 pelvic treatments were followed for two fields, an anterior-posterior or a posterior-anterior irradiation and a lateral-lateral irradiation. Moreover, ten brain tumors were checked for a lateral-lateral irradiation, and five lung tumors carried out with three irradiations with different gantry angles were followed. One center used the EPID as a detector for the St measurement and five pelvic treatments with six fields (many with oblique incidence) were followed. These last results are reported together with those obtained in the same center during a pilot study on ten pelvic treatments carried out by four orthogonal fields. The tolerance/action levels for every radiotherapy fraction were 4% and 5% for the brain (symmetric inhomogeneities) and thorax/pelvic (asymmetric inhomogeneities) irradiations, respectively. This way the variations between the total measured and prescribed doses at the isocenter point in five fractions were well within 2% for the brain treatment, and 4% for thorax/pelvic treatments. Only 4 out of 90 patients needed new replanning, 2 patients of which needed a new CT scan. \ua9 2007 IOP Publishing Ltd

Preoperative chemoradiation and intra-operative radiotherapy for pancreatic carcinoma

In recent years, preoperative chemoradiation has received growing interest for the treatment of locally advanced pancreatic cancer. In an attempt to improve resectability and disease control, we used preoperative radiation therapy and concomitant 5-fluorouracil in a combined modality therapy protocol. The aim of the study was to evaluate definitive results in terms of toxicity, response and clinical outcome. MATERIAL AND METHODS: Twenty-eight patients with unresectable (cT4, 19 patients) or resectable (cT3, 9 patients) nonmetastatic pancreatic tumors received radiotherapy (39.6 Gy) plus 5-fluorouracil (continuous infusion, days 1-4 at 1000 mg/m(2)/day). After 4 weeks, patients were evaluated for surgical resection. In 9 resected patients, electron-beam intra-operative radiotherapy (10 Gy) was given before reconstruction. Thereafter, in resected patients, adjuvant chemotherapy was prescribed. RESULTS: During chemoradiation, 1 patient (3.6%) developed grade 3 acute gastrointestinal toxicity and 2 patients (7.1%) developed grade 3 hematological toxicity. Three of 19 patients with unresectable tumors had tumor downstaging (15.8%). Two patients showed partial response (response rate, 7.1%; 95% CI, 0.2-25.3) and 4 patients (14.3%) had minimal tumor response. Four patients (14.3%) showed progressive disease after chemoradiation. One postoperative death was recorded. The median survival time was 11.3 months (20.5 and 9.0 months in resected and unresected patients, respectively). Only one local failure was recorded in 8 patients resected with negative margins. CONCLUSIONS: Although the response rate is still low, our preliminary results suggest that preoperative 5-fluorouracil chemoradiation is well tolerated and may result in tumor downstaging. Delivery of intra-operative radiotherapy seems to be associated with a low rate of local recurrences

Intraoperative radiation therapy in resected pancreatic carcinoma: long-term analysis.

PURPOSE: The combination of external radiotherapy (RT) plus intraoperative radiotherapy (IORT) in patients with pancreatic cancer is still debated. This study presents long-term results (minimum follow-up, 102 months) for 26 patients undergoing integrated adjuvant RT (external RT+IORT). METHODS AND MATERIALS: From 1990 to 1995, a total of 17 patients with pancreatic cancer underwent IORT (10 Gy) and postoperative external RT (50.4 Gy). Preoperative "flash" RT was included for the last 9 patients. The liver and pancreatic head received 5 Gy (two 2.5-Gy fractions) the day before surgery. In the subsequent period (1996-1998), 9 patients underwent preoperative concomitant chemoradiation (39.6 Gy) with 5-fluorouracil, IORT (10 Gy), and adjuvant chemotherapy. RESULTS: Preoperative chemoradiation was completed in all patients, whereas postoperative therapy was completed in 13 of 17 patients. All 26 patients underwent pancreatectomy (25 R0 and one R1 resections). One patient died of postoperative complications (3.8%) not related to IORT. The 9 patients undergoing concomitant chemoradiation were candidates for adjuvant chemotherapy; however, only 4 of 9 underwent adjuvant chemotherapy. At last follow-up, 4 patients (15.4%) were alive and disease free. Disease recurrence was documented in 20 patients (76.9%). Sixteen patients (61.5%) showed distant metastasis, and 5 patients (19.2%) showed local recurrence. The incidence of local recurrence in R0 patients was 4 of 25 (16.0%). The overall 5-year survival rate was 15.4%. There was significant correlation with overall survival of tumor diameter (p=0.019). CONCLUSIONS: The incidence of local recurrence in this long follow-up series (19.2%) was definitely less than that reported in other studies of adjuvant RT (approximately 50%), suggesting a positive impact on local control of integrated adjuvant RT (IORT+external RT)