1,366 research outputs found

    Differential miRNA expression profiling reveals miR-205-3p to be a potential radiosensitizer for low- dose ionizing radiation in DLD-1 cells

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    Indexación: Scopus.Departamento de Oncología Básico-Clínica, Facultad de Medicina, Universidad de Chile, Santiago, Chile 2Comisión Chilena de Energía Nuclear, Santiago, Chile 3Center for Research and Applications in Plasma Physics and Pulsed Power, P4, Chile 4Departamento de Ciencias Físicas, Universidad Andres Bello, Santiago, Chile 5Centro de Investigación y Tratamiento del Cáncer, Facultad de Medicina, Universidad de Chile, Santiago, Chile 6Current Address: Center of Excellence in Precision Medicine, Pfizer, Chile. on IR responsive modeling. This work was supported by Anillo grant ACT1115 and ACT172101, PIA Program, CONICYT; the Chilean doctoral fellowship 21130246Enhanced radiosensitivity at low doses of ionizing radiation (IR) (0.2 to 0.6 Gy) has been reported in several cell lines. This phenomenon, known as low doses hyperradiosensitivity (LDHRS), appears as an opportunity to decrease toxicity of radiotherapy and to enhance the effects of chemotherapy. However, the effect of low single doses IR on cell death is subtle and the mechanism underlying LDHRS has not been clearly explained, limiting the utility of LDHRS for clinical applications. To understand the mechanisms responsible for cell death induced by low-dose IR, LDHRS was evaluated in DLD-1 human colorectal cancer cells and the expression of 80 microRNAs (miRNAs) was assessed by qPCR array. Our results show that DLD-1 cells display an early DNA damage response and apoptotic cell death when exposed to 0.6 Gy. miRNA expression profiling identified 3 over-expressed (miR-205-3p, miR-1 and miR-133b) and 2 downregulated miRNAs (miR-122-5p, and miR-134-5p) upon exposure to 0.6 Gy. This miRNA profile differed from the one in cells exposed to high-dose IR (12 Gy), supporting a distinct low-dose radiation-induced cell death mechanism. Expression of a mimetic miR- 205-3p, the most overexpressed miRNA in cells exposed to 0.6 Gy, induced apoptotic cell death and, more importantly, increased LDHRS in DLD-1 cells. Thus, we propose miR-205-3p as a potential radiosensitizer to low-dose IR. © Andaur et al.http://www.oncotarget.com/index.php?journal=oncotarget&page=article&op=view&path[]=25405&path[]=7956

    Pulsed x-rays dose measurements from a hundred joules plasma focus device

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    Indexación: Scopus.Present work is aimed to perform dosimetric measurements to characterize dosis obtained from pulsed x-rays emitted from a hundred joules plasma focus device PF-400J using thermoluminescent dosimeters (TLD-100). Two dosimeter arrays (containing 21 dosimeters in each) were used. One of the arrays was kept inside the PF-400J vacuum chamber and other outside the vacuum chamber, simultaneously. It was found that dosis obtained from the inside array (∼200.7 mGy) were hundred times larger than the outside array (∼1.1 mGy) for hundred pulses of x-rays. Later, the vacuum window of PF-400J, which was made of 1 mm aluminum, was replaced by a plastic window and a similar dosimeter array was kept outside the chamber over the plastic window. With this arrangement, the obtained doses (100 pulses of x-rays) were of the same order of magnitude (∼106 mGy) as it was inside the vacuum chamber. Later, a lead piece was inserted inside the hollow anode of PF-400J, which increased dose (∼250 mGy) per hundred pulses of x-ray outside the vacuum chamber using plastic vacuum window. Our results suggest that PF-400J could be a useful device to study low dose pulsed radiation effects on cancer cell lines in in vitro experiments. © Published under licence by IOP Publishing Ltd.The work is supported by grant ACT-1115, CONICYT, Chile.https://iopscience.iop.org/article/10.1088/1742-6596/1043/1/01204

    DATOS SOBRE LA FLORA Y COROLOGIA ALGAL DEL LITORAL DE MURCIA (SE DE ESPAÑA)

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    The coast of Murcia has been increased with 23 taxa of benthic marine algae. Among them the following are specially interesting in the corology of the Spanish Mediterranean: Naccaria wiggii (Tumer) Endlicher, Helminthora stackhousei (Clemente) Cremades et Pérez-Cirera, Polysiphonia adriatica Schiffn., Polysiphonia Elongate (Hudson) Sprengel, Laurencia pelagosae (Schiffn.) Ercegovic, Elachista jlaccida (Dillwyn) Areschoug, Cystoseira platyclada Sauvageau and Enteromorpha simplex (Vinograd.) Koeman et Van den Hoek.Se incrementa el conocimiento algal del litoral de Murcia en 23 taxones de algas marinas. De ellas son especialmente interesantes en la corología de las aguas mediterráneas españolas las siguientes: Naccaria wiggii (Tumer) Endlicher, Helminthora stackhousei (Clemente) Cremades et Pérez-Cirera, Polysiphonia adriatica Schiffn., Polysiphonia elongata (Hudson) Sprengel, Laurencia pelagosae (Schiffn.) Ercegovic, Elachista jlaccida (Dillwyn) Areschoug, Cystoseira platyclada Sauvageau y Enteromorpha simples (Vinograd.) Koeman et Van den Hoek

    Analysis of Deterioration in a Plasma Focus Device

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    Indexación: Scopus.The Plasma Focus (PF) is a kind of dense transient plasmas in with high-pulsed voltage. To produce devices for eld application it is necessary to obtain PF equipment able to operate for a long period of time. Thus, a reliability analysis is indispensable. In this work a reliability analysis program for plasma focus devices is presented. The program considers a criticality analysis using Failure Modes and Effects Criticality Analysis (FMECA) to identify the most important failure modes of the system. Said failure modes are studied operating the Plasma Focus for many cycles, obtaining from them the characteristic curves of V(t) and İ(t). Feature Extraction (FE) techniques are applied to obtain a list of parameters that correlate to the degrading process. Furthermore, Machine Learning tools are used to learn from the obtained data, linking the changes in these parameters during its life cycle to the decay of the system in hope for future implementation of a predictive maintenance system and a reference for data analysis and prediction in PFs. The study was applied to a portable plasma focus device operated at 2 joules of stored energy. © Published under licence by IOP Publishing Ltd.The work is supported by IAEA CRP contract 20370 and by grant ACT-1115, CONICYT, Chile.https://iopscience.iop.org/article/10.1088/1742-6596/1043/1/01204

    Hundred joules plasma focus device as a potential pulsed source for in vitro cancer cell irradiation

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    Indexación: Web of Science; Scopus.Plasma focus devices may arise as useful source to perform experiments aimed to study the effects of pulsed radiation on human cells in vitro. In the present work, a table top hundred joules plasma focus device, namely "PF-400J", was adapted to irradiate colorectal cancer cell line, DLD-1. For pulsed x-rays, the doses (energy absorbed per unit mass, measured in Gy) were measured using thermoluminescence detectors (TLD-100 dosimeters). The neutron fluence and the average energy were used to estimate the pulsed neutron doses. Fifty pulses of x-rays (0.12 Gy) and fifty pulses of neutrons (3.5 μGy) were used to irradiate the cancer cells. Irradiation-induced DNA damage and cell death were assessed at different time points after irradiation. Cell death was observed using pulsed neutron irradiation, at ultralow doses. Our results indicate that the PF-400J can be used for in vitro assessment of the effect of pulsed radiation in cancer cell research.http://recursosbiblioteca.unab.cl:2296/doi/pdf/10.1063/1.499465

    Study of the photon strength functions and level density in the gamma decay of the n + 234U reaction

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    The accurate calculations of neutron-induced reaction cross sections are relevant for many nuclear applications. The photon strength functions and nuclear level densities are essential inputs for such calculations. These quantities for 235U are studied using the measurement of the gamma de-excitation cascades in radiative capture on 234U with the Total Absorption Calorimeter at n_TOF at CERN. This segmented 4π gamma calorimeter is designed to detect gamma rays emitted from the nucleus with high efficiency. This experiment provides information on gamma multiplicity and gamma spectra that can be compared with numerical simulations. The code diceboxc is used to simulate the gamma cascades while geant4 is used for the simulation of the interaction of these gammas with the TAC materials. Available models and their parameters are being tested using the present data. Some preliminary results of this ongoing study are presented and discussed

    The MobyDick Project: A Mobile Heterogeneous All-IP Architecture

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    Proceedings of Advanced Technologies, Applications and Market Strategies for 3G (ATAMS 2001). Cracow, Poland: 17-20 June, 2001.This paper presents the current stage of an IP-based architecture for heterogeneous environments, covering UMTS-like W-CDMA wireless access technology, wireless and wired LANs, that is being developed under the aegis of the IST Moby Dick project. This architecture treats all transmission capabilities as basic physical and data-link layers, and attempts to replace all higher-level tasks by IP-based strategies. The proposed architecture incorporates aspects of mobile-IPv6, fast handover, AAA-control, and Quality of Service. The architecture allows for an optimised control on the radio link layer resources. The Moby dick architecture is currently under refinement for implementation on field trials. The services planned for trials are data transfer and voice-over-IP.Publicad

    Influence of electrode geometry on X-ray emission, plasma inductance, voltage, and current derivative signals obtained from a plasma focus device

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    Indexación ScopusPlasma focus devices have been investigated as a pulsed radiation source. Different studies have shown that the shape of the anode affects strongly the plasma dynamic and X-ray emission that takes place in plasma focus devices. In the present work, a hybrid-type plasma focus device (6 μF, 16 ± 1 kV), named PF-2kJ, is operated at various pressures of hydrogen gas with five cylindrical anodes of the same lengths but different in shapes, without cathode bars. The effect of cathode bars on various electric parameters is studied for the anode that has the maximum X-ray emission. The electrical signals of Rogowski coil (current derivative), voltage divider (voltage at the anode), and photomultiplier tubes (X-rays) were analyzed for all the anodes. Inductance and the voltage at the time of the pinch were derived from the measured voltage and current derivative signals. The X-ray dose measurements were performed using thermoluminescent dosimeters (TLD-100). The PF-2kJ performance is not the best while using the cathode bars. Our results show that by changing the anode shape just over the insulator sleeve the plasma focus devices can be switched between close energies stored in the capacitor bank. © 2021 The Authorshttps://www-sciencedirect-com.recursosbiblioteca.unab.cl/science/article/pii/S2211379721001832?via%3Dihu

    Low energy excitations of double quantum dots in the lowest Landau level regime

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    We study the spectrum and magnetic properties of double quantum dots in the lowest Landau level for different values of the hopping and Zeeman parameters by means of exact diagonalization techniques in systems of N=6 and N=7 electrons and filling factor close to 2. We compare our results with those obtained in double quantum layers and single quantum dots. The Kohn theorem is also discussed.Comment: 23 pages, 4 figures, 1 table; references added; journal versio

    Graphene Synthesis Using a CVD Reactor and a Discontinuous Feed of Gas Precursor at Atmospheric Pressure

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    The present work shows a new method in order to cost-effectively achieve the synthesis of graphene by Chemical Vapor Deposition (CVD). Unlike most usual processes, where precursors such as argon, H2, CH4, and high purity copper foil are used, the proposed method has replaced the previous ones by N2, N2 (90%) : H2 (10%), C2H2, and electrolytic copper (technical grade) since the use of industrialized precursors helps reduce production costs. On the other hand, the process was modified from a continuous flow system with vacuum to a discontinuous one at atmospheric pressure, eliminating the use of vacuum pump. In addition, this modification optimized the consumption of gases, which reduced the waste and the emission of pollutant gases into the atmosphere. Graphene films were grown under different gas flowrates and temperatures. Then, the obtained material was characterized by TEM, Raman spectroscopy, and AFM, confirming the presence of few graphene layers. In brief, the growth time was reduced to six minutes with acetylene as a carbon precursor at 1000°C and at atmospheric pressure, with a flow rate of 30 sccm. Finally, the reported conditions can be used for the synthesis of good quality graphene films in industrial applications
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