IMPLEMENTACIÓN DE UNA HERRAMIENTA DE CÁLCULO DE DOSIS PARA EL IRRADIADOR PRECLÍNICO X-RAD 320.

A tool was developed that facilitates the determination of the absorbed dose in water under reference conditions (DOSAB) and a dose calculation tool (DOSREL) for the X-RAD 320 preclinical irradiator from Monte Carlo simulations using the DOSXYZnrc code a starting from a point source of isotropic radiation that emits energy spectra generated with the SpekCalc program. This tool can calculate the dose in the central radiation axis and off the axis for different beam qualities and between field sizes of 0.5 x 0.5 and 15 x 15 cm2, for simulated and non-simulated conditions. Relative depth doses and relative dose profiles were also compared for MC simulations and those calculated by linear interpolation for field sizes of 5 x 5 and 7 x 7 cm2 and beam qualities of 300 and 71 kVp and the results shown. a good concordance between both, therefore, the linear interpolation method implemented for intermediate field sizes to those simulated was validated.Se desarrolló una herramienta que facilita la determinación de la dosis absorbida en agua en condiciones de referencia (DOSAB) y una herramienta de cálculo de dosis (DOSREL) para el irradiador preclínico X-RAD 320 a partir de simulaciones Monte Carlo utilizando el código DOSXYZnrc a partir de una fuente puntual de radiación isotrópica que emite espectros de energía generados con el programa SpekCalc. Esta herramienta puede calcular la dosis en el eje central de radiación y fuera del eje para diferentes calidades de haz y entre tamaños de campo de 0,5 x 0,5 y 15 x 15 cm2, para condiciones simuladas y no simuladas. También se compararon las dosis relativas en profundidad y los perfiles de dosis relativa para las simulaciones MC y las calculadas por interpolación lineal para tamaños de campo de 5 x 5 y 7 x 7 cm2 y calidades de haz de 300 y 71 kVp y los resultados mostraron una buena concordancia entre ambos, por lo tanto, el método de interpolación lineal implementado para tamaños de campo intermedios a los simulados quedo validado

EVALUACIÓN DOSIMÉTRICA DEBIDO AL CAMBIO DE ENERGÍA EN FANTOMAS HETEROGÉNEOS.

The dosimetric dependence of the bone and lung heterogeneities with the dose in water was evaluated using two photon beam energies (300 kVp and 225 kVp) and two field sizes for the X-RAD 320 preclinical irradiator by Monte Carlo simulations using the code DOSXYZnrc from a point source of isotropic radiation that emits energy spectra generated with the SpekCalc program. This was carried out in two water phantoms to which bone and lung heterogeneities were introduced respectively and for a computational mouse phantom generated from simulations with the MOBY program. A significant increase in the dose in bone was found when photon beams of 300 and 225 kVp were used, this effect is greater as the energy decreases. This dosimetric effect, due to the presence of bone heterogeneity, was more significant compared to lung heterogeneity. Therefore, for kV photon energies in the range used in irradiating small animals, increasing the dose to bone due to the photoelectric effect could be a dosimetric concern.Se evaluó la dependencia dosimétrica de las heterogeneidades del hueso y pulmón con la dosis en agua utilizando dos energías de haces de fotones (300 kVp y 225 kVp) y dos tamaños de campo para el irradiador preclínico X-RAD 320 mediante simulaciones Monte Carlo utilizando el código DOSXYZnrc a partir de una fuente puntual de radiación isotrópica que emite espectros de energía generados con el programa SpekCalc. Esto se llevó a cabo en dos fantomas de agua al cual se le introdujeron heterogeneidades de hueso y pulmón respectivamente y para un fantoma de ratón computacional generado a partir de simulaciones con el programa MOBY. Se encontró un aumento significativo de la dosis en hueso cuando se utilizaron haces de fotones de 300 y 225 kVp, este efecto es mayor a medida que la energía disminuye. Este efecto dosimétrico, debido a la presencia de la heterogeneidad de hueso fue más significativo en comparación con la heterogeneidad de pulmón. Por lo tanto, para las energías de fotones kV del rango utilizado en la irradiación de animales pequeños, el aumento de la dosis en hueso debido al efecto fotoeléctrico podría ser una preocupación dosimétrica

MODELAMIENTO DEL IRRADIADOR PRECLÍNICO X-RAD 320 A PARTIR DE SIMULACIONES MONTE CARLO UTILIZANDO UNA FUENTE PUNTUAL

Se determinó un método para modelar el irradiador preclínico X-RAD 320 a partir de simulaciones Monte Carlo utilizando el código DOSXYZnrc a partir de una fuente puntual de radiación isotrópica que emite un espectro de energía generado con el programa SpekCalc. Las simulaciones MC dan como resultados matrices 3D de dosis por partícula, de las mismas se pueden extraer la dosis relativa en profundidad, perfiles de dosis relativa y output factors. Se utilizó un programa que emite imágenes planares de rayos X de kV para corregir los perfiles de dosis relativa por el efecto talón. Debido a la falta de datos experimentales se tuvo que validar las simulaciones MC de este trabajo con las medidas realizadas por Azimi et. al. (2014). Las congruencias de las simulaciones MC con las medidas de Azimi permiten validar la metodología empleada en este trabajo, siempre y cuando se tengan presentes las limitaciones que tiene el método empleado

CARACTERIZACIÓN DOSIMÉTRICA DEL IRRADIADOR PRECLÍNICO X-RAD 320 A PARTIR DE SIMULACIONES MONTE CARLO

Se caracterizó el irradiador preclínico X-RAD 320 a partir de simulaciones Monte Carlo utilizando el código DOSXYZnrc a partir de una fuente puntual de radiación isotrópica que emite espectros de energía generados con el programa SpekCalc. Dichas simulaciones fueron llevadas a cabo en una fantoma de agua para diferentes calidades de haz y tamaños de campo entre 0,5 x 0,5 y 15 x 15 cm2 para los cuales se obtuvieron matrices 3D de dosis. Se encontraron incertidumbres relativas asociadas a las simulaciones de hasta  1,39 % para profundidades menores a 5 cm. Los resultados obtenidos para las curvas de dosis en profundidad, perfiles de dosis y output factors para las diferentes calidades de haz corresponden al comportamiento esperado

Self-consistent model for ambipolar tunneling in quantum-well systems

We present a self-consistent approach to describe ambipolar tunneling in asymmetrical double quantum wells under steady-state excitation and extend the results to the case of tunneling from a near-surface quantum well to surface states. The results of the model compare very well with the behavior observed in photoluminescence experiments in $InGaAs/InP$ asymmetric double quantum wells and in near-surface $AlGaAs/GaAs$ single quantum wells.Comment: 10 pages, REVTeX 3.

Effect of temperature in bursting of thalamic reticular cells

Objective: To show the relation between the four parameters associated to bursting discharges of the thalamic reticular cells (TRNn): the maximum firing frequency (fmax) and the temperature at which it occurs (Tfmax), the range of temperatures defined as the full width at half maximum (∆Th) and the maximum specific low threshold calcium conductance (GT). Materials and Methods: In order to simulate the TRNn bursting activity a computational simulation model was implemented using the NEURON software, which incorporates morphological and electrophysiological data and stimuli properties closely related to reality. Results: It was found that there are nonlinear relations between the parameters. The fmax frequency follows a quadratic grow with temperature and tends asymptotically towards a limit value with the maximum calcium conductance.  In the same manner, ∆Th increases until reaching a limit value as function of fmax and GT. However, the increment per frequency unit is bigger than the increment per conductance unit. Conclusions: There were obtained four equations that model the relations between the parameters associated to bursting discharges of the TRNn in rats and other neurons with similar characteristics in different animal species

An Update of Eyeglasses-Supported Nasal–Facial Prosthetic Rehabilitation of Cancer Patients with Post-Surgical Complications: A Case Report

Featured Application: This case report aims to describe an update of the digital protocol for the fabrication of a facial prosthesis for those patients who cannot be rehabilitated with plastic surgery because of post-surgical complications after maxillofacial surgery. In detail, it describes the application of the digital protocol to a mid-facial defect. The innovation proposed is oriented to simplify the procedures and reduce the time and cost of the process, aiming to recover the quality of life of inoperable patients. This case report aims to describe novel steps in the digital design/manufacturing of facial prostheses for cancer patients with wide inoperable residual defects, with a focus on a case of a mid-facial defect. A facial scanner was used to make an impression of the post-surgical residual defect and to digitalize it. The daughter’s face scan was used for reconstructing the missing anatomy. Using 3D printing technologies, try-in prototypes were produced in silicone material. The substructure was laser melted. The final prosthesis was relined directly onto the patient’s defect. The prosthesis resulted in a very low weight and a high elasticity of the external margins. The laser-melted substructure ensured the necessary rigidity with minimum thickness

Efecto de la temperature en las descargas en ráfaga de la células del núcleo reticular del tálamo

Objective: To show the relation between the four parameters associated to bursting discharges of the thalamic reticular cells (TRNn): the maximum firing frequency (fmax) and the temperature at which it occurs (Tfmax), the range of temperatures defined as the full width at half maximum (∆Th ) and the maximum specific low threshold calcium conductance (GT). Materials and Methods: In order to simulate the TRNn bursting activity, a computational simulation model was implemented using the NEURON software, which incorporates morphological and electrophysiological data, and stimuli properties closely related to reality. Results: It was found that there are nonlinear relations between the parameters. The fmax frequency follows a quadratic growth with temperature and tends asymptotically towards a limit value with the maximum calcium conductance. In the same manner, ∆Th increases until reaching a limit value as function of fmax and GT . However, the increment per frequency unit is bigger than the increment per conductance unit. Conclusions: Four equations were obtained that model the relations between the parameters associated to bursting discharges of the TRNn in rats and other neurons with similar characteristics in different animal species

Acetylation of the HIV-1 Tat protein by p300 is important for its transcriptional activity.

AbstractThe human immunodeficiency virus 1 (HIV-1) Tat protein activates transcriptional elongation by recruiting the positive transcription elongation factor (pTEFb) complex to the TAR RNA element, which is located at the 5′ extremity of all viral transcripts [1–3]. Tat also associates in vitro and in vivo with the transcriptional coactivator p300/CBP [4–6]. This association has been proposed to recruit the histone acetyltransferase (HAT) activity of p300 to the integrated HIV-1 promoter. We have observed that the purified p300 HAT domain acetylates recombinant Tat proteins in vitro and that Tat is acetylated in vivo. The major targets of acetylation by p300 are lysine residues (Lys50 and Lys51) in the arginine-rich motif (ARM) used by Tat to bind RNA and for nuclear import. Mutation of these residues in full-length recombinant Tat blocked its acetylation in vitro. Furthermore, mutation of these lysine residues to arginine markedly decreased the synergistic activation of he HIV promoter by Tat and p300 or by Tat and cyclin T1. These results demonstrate that acetylation of Tat by p300/CBP is important for its transcriptional activation of the HIV promoter