Experimental evaluation of transition rate of sapphire crystal for thermal and fast neutrons using MNSR vertical neutron beam line.

Using a perfect single crystal as a neutron filter allows us to have a thermal neutron beam with almost no background of fast neutrons. Single crystals of Al2O3 (sapphire) have proven to be effective filters for fast neutrons and are incorporated into neutron instruments. The present work would experimentally investigate c-axis neutron transmission rate by using different crystal thicknesses. In fact, the optimal thickness for sapphire filter is the one that maximizes the transmission of low energy neutrons and minimizes the transmission of fast neutrons, if there is no significant decrease in thermal neutron flux. In addition, neutron-filtering power of a-axis and c-axis sapphire crystals were compared with each other using different tests on a 2.5 cm slab of the sapphire crystals. The experimental tests were carried out by means of the available neutron flux top of the vertical neutron beam line of the Isfahan Miniature Neutron Source Reactor (MNSR) in two methods of foil activation and flux monitoring. In addition, the thermal and fast neutron dose rate reduction was discussed by using different thicknesses of the c-axis crystal.

Neutronic feasibility study of using a multipurpose MNSR for BNCT, NR, and NAA.

In this study, the conceptual design of a multipurpose research reactor for boron neutron capture therapy (BNCT), neutron radiography (NR) and neutron activation analysis (NAA) applications has been performed. Specifically, a suitable epithermal neutron flux (φEpi) of about 1×109 (n.cm-2.s-1) for BNCT and high quality thermal neutron flux (φTh) of above 1×106 (n.cm-2.s-1)for NR are carried out based on our LEU reactor core designing. The UO2 fuel with density of 10.5 g/cm3 and enrichment of 12.4% is applied as an appropriate LEU fuel. The reactor safety is assured by designing the safety control rod system with two banks. A fission converter facility (FCF) consists of 19 fuel rods of UO2 is used to increase φEpi for BNCT treatment. Furthermore, a unique thermal column of heavy water is used to increase φTh for NR purpose. Four internal irradiation sites, two external irradiation sites, and one large thermal column irradiation site are considered at the reactor which can be used for NAA application. The results of neutronic calculations show that the reactor meets the neutronic design limits for a low power research reactor.

Designing a new graphite illuminator for imaging facility of INUS to improve neutron beam uniformity and intensity.

A cylindrical graphite illuminator with a thickness of 6.5 cm and diameter of 18 cm was installed inside the collimator of INUS (Instalatie de Neutronografie UScata) neutron imaging facility in the past. The graphite illuminator is usually utilized inside the collimator of neutron imaging facility to provide an intense and approximately uniform beam of neutrons at the outlet of collimator. With the mentioned existing illuminator in INUS imaging facility, the thermal neutron flux at the exit of collimator was measured 7.2 × 104 n/cm2/s. Also the obtained neutron beam profile in this facility shows that it is not completely uniform at the imaging screen and the intensity of neutrons at the top and bottom of beam profile are not the same. Hence, in this paper a new graphite illuminator is proposed to improve the neutron beam characteristics in INUS imaging facility. Monte Carlo N-Particle (MCNP) code was implemented in this study for evaluating the proposed illuminator. The shape of proposed illuminator is a cylinder whose one side is inclined. Three quality factors of thermal neutron intensity, thermal neutron beam uniformity and gamma radiation dose rate were used to evaluate performance of the new illuminator. In order to obtain optimum illuminator shape, three effective parameters of thickness, angle of inclined side and position of the illuminator inside the collimator were investigated in this research. The investigation was carried out on thicknesses in the range of 5 to 25 cm with a step of 5 cm, angles in the range of 10 to 60° with a step of 10° and positions of -5, 0 and 5 cm with respect to center of reactor core. After investigating and interpolating the results, it was found that the proposed illuminator with a thickness of 10 cm, angle of 54.5° and position of 0 can produce a uniform beam profile, increase the thermal neutron intensity up to 7.1% and also decrease the neutron to gamma ratio up to 5% in comparison with the existing one.

Rolled-up SiO x /SiN x microtubes with an enhanced quality factor for sensitive solvent sensing.

The microtubes made through rolling-up of strain-engineered nanomembranes have received growing research attention after their first invention due to the technology's high flexibility, integrability, and versatility. These rolled-up microtubes have been used for a variety of device applications including sensors, batteries and transistors, among others. This paper reports the development of highly sensitive whispering-gallery mode (WGM) chemical sensors based on rolled-up microtube optical microcavities (RUM-OCs). For the first time, such microcavities were batch fabricated through rolling-up of plasma-enhanced chemical vapor deposition (PECVD)-synthesized SiO x /SiN x bilayer nanomembranes, which have better optical properties than the conventional electron-beam-deposited SiO/SiO2 bilayers. Benefiting from the high refractive index (RI) of PECVD-deposited SiN x , our RUM-OC shows an enhanced quality factor of 880 that is much higher than that (50) of a SiO/SiO2 RUM-OC with the same dimensions. The developed RUM-OC is used for sensitive WGM solvent sensing, and demonstrate a limit of detection of 10-4 refractive index unit (RIU), which is 10 times lower than that (10-3 RIU) of a SiO/SiO2 RUM-OC.

Simulation of a complete X-ray digital radiographic system for industrial applications.

Simulating X-ray images is of great importance in industry and medicine. Using such simulation permits us to optimize parameters which affect image's quality without the limitations of an experimental procedure. This study revolves around a novel methodology to simulate a complete industrial X-ray digital radiographic system composed of an X-ray tube and a computed radiography (CR) image plate using Monte Carlo N Particle eXtended (MCNPX) code. In the process of our research, an industrial X-ray tube with maximum voltage of 300 kV and current of 5 mA was simulated. A 3-layer uniform plate including a polymer overcoat layer, a phosphor layer and a polycarbonate backing layer was also defined and simulated as the CR imaging plate. To model the image formation in the image plate, at first the absorbed dose was calculated in each pixel inside the phosphor layer of CR imaging plate using the mesh tally in MCNPX code and then was converted to gray value using a mathematical relationship determined in a separate procedure. To validate the simulation results, an experimental setup was designed and the images of two step wedges created out of aluminum and steel were captured by the experiments and compared with the simulations. The results show that the simulated images are in good agreement with the experimental ones demonstrating the ability of the proposed methodology for simulating an industrial X-ray imaging system.

Three-fold Symmetric Doping Mechanism in GaAs Nanowires.

A new dopant incorporation mechanism in Ga-assisted GaAs nanowires grown by molecular beam epitaxy is reported. Off-axis electron holography revealed that p-type Be dopants introduced in situ during molecular beam epitaxy growth of the nanowires were distributed inhomogeneously in the nanowire cross-section, perpendicular to the growth direction. The active dopants showed a remarkable azimuthal distribution along the (111)B flat top of the nanowires, which is attributed to preferred incorporation along 3-fold symmetric truncated facets under the Ga droplet. A diffusion model is presented to explain the unique radial and azimuthal variation of the active dopants in the GaAs nanowires.

Methods of Ga droplet consumption for improved GaAs nanowire solar cell efficiency.

We describe methods of Ga droplet consumption in Ga-assisted GaAs nanowires, and their impact on the crystal structure at the tip of nanowires. Droplets are consumed under different group V flux conditions and the resulting tip crystal structure is examined by transmission electron microscopy. The use of GaAsP marker layers provides insight into the behavior of the Ga droplet during different droplet consumption conditions. Lower group V droplet supersaturations lead to a pure zincblende stacking-fault-free tip crystal structure, which improved the performance of a nanowire-based photovoltaic device.

Adenosine A1 receptor modifies P53 expression and apoptosis in breast cancer cell line Mcf-7.

BACKGROUND: Breast cancer cells over-express the adenosine receptor A1 and in most of these cells, P53 gene is a wild type. Because of this finding and relationship between A1 receptor and cell apoptosis and proliferation, this study aimed to determine the effect of agonist and antagonist of A1 receptor on cell apoptosis and proliferation and recognize the relationship between this receptor and P53 expression. METHODS: We used a Real-Time PCR test for measuring expression of p53 gene also flow cytometry assay for apoptotic and survival cell rate after treatment of MCF-7 cells with A1 receptor agonist CPA (N6-Cyclopentyladenosine) and A1 receptor antagonist DPCPX (1,3-dipropyl-8-cyclopentylxanthine) in 24,48 and 72 hours. RESULTS: Our flow cytometry findings indicate that DPCPX significantly induces apoptosis in MCF-7. Also the expression of P53 becomes upregulated with time of DPCPX treatment. CPA treatment increased the survival cell rate and down-regulated this apoptosis-relevant gene P53 (p > 0.05). CONCLUSION: DPCPX can induce P53 expression which consequently promotes the cell apoptosis in MCF-7. Therefore, DPCPX could be used as an anti-cancer agent (Tab. 1, Fig. 3, Ref. 5).

Aluminum nitride nanowire light emitting diodes: Breaking the fundamental bottleneck of deep ultraviolet light sources.

Despite broad interest in aluminum gallium nitride (AlGaN) optoelectronic devices for deep ultraviolet (DUV) applications, the performance of conventional Al(Ga)N planar devices drastically decays when approaching the AlN end, including low internal quantum efficiencies (IQEs) and high device operation voltages. Here we show that these challenges can be addressed by utilizing nitrogen (N) polar Al(Ga)N nanowires grown directly on Si substrate. By carefully tuning the synthesis conditions, a record IQE of 80% can be realized with N-polar AlN nanowires, which is nearly ten times higher compared to high quality planar AlN. The first 210 nm emitting AlN nanowire light emitting diodes (LEDs) were achieved, with a turn on voltage of about 6 V, which is significantly lower than the commonly observed 20 - 40 V. This can be ascribed to both efficient Mg doping by controlling the nanowire growth rate and N-polarity induced internal electrical field that favors hole injection. In the end, high performance N-polar AlGaN nanowire LEDs with emission wavelengths covering the UV-B/C bands were also demonstrated.

Quantification of allospecific and nonspecific corneal endothelial cell damage after corneal transplantation.

PURPOSE: To investigate the effect of host immunity (allospecific) and surgical manipulation (non-allospecific) on corneal endothelial cells (CECs) in corneal transplantation. METHODS: Draining lymph nodes and grafted C57BL/6 corneas were harvested from syngeneic recipients, allograft acceptors, and allograft rejectors (BALB/c) 1, 3, and 8 weeks after transplantation. We analyzed CEC apoptosis using an ex vivo cornea-in-the-cup assay, and visualized cell-to-cell junctions using immunohistochemical staining (ZO-1). Automatic cell analysis using Confoscan software was used to measure CEC density as well as changes in CEC morphology by quantifying the coefficient of variation in cell size (polymegethism) and shape (pleomorphism). RESULTS: The cornea-in-the-cup assay showed that allogeneic acceptor T cells and to an even greater extent rejector T cells (but not syngeneic T cells) induced CEC apoptosis. CEC density after corneal transplantation was significantly reduced in allogeneic acceptors compared with syngeneic grafts (P<0.001), and CEC density was even further reduced in the allo-rejector group compared with the allo-acceptor group. Allogeneic grafts showed a greater increase in the coefficient of variation in cell size (polymegethism) when compared with syngeneic grafts 1 week after transplantation (P=P<0.001). However, pleomorphism was not significantly different between syngeneic and allo-acceptor grafts, indicating that polymegethism (but not pleomorphism or cell density) is a sensitive indicator of the effect of alloimmunity on CECs. CONCLUSIONS: Our data demonstrate that host alloimmunity rather than surgical manipulation alone is the major cause of CEC damage in corneal transplantation, and such morphologic changes of CECs can be detected before the clinically visible onset of allograft rejection.

Thermally controlled coupling of a rolled-up microtube integrated with a waveguide on a silicon electronic-photonic integrated circuit.

We report on the first experimental demonstration of the thermal control of coupling strength between a rolled-up microtube and a waveguide on a silicon electronic-photonic integrated circuit. The microtubes are fabricated by selectively releasing a coherently strained GaAs/InGaAs heterostructure bilayer. The fabricated microtubes are then integrated with silicon waveguides using an abruptly tapered fiber probe. By tuning the gap between the microtube and the waveguide using localized heaters, the microtube-waveguide evanescent coupling is effectively controlled. With heating, the extinction ratio of a microtube whispering-gallery mode changes over an 18 dB range, while the resonant wavelength remains approximately unchanged. Utilizing this dynamic thermal tuning effect, we realize coupling modulation of the microtube integrated with the silicon waveguide at 2 kHz with a heater voltage swing of 0-6 V.

Effects of disulfiram on apoptosis in PANC-1 human pancreatic cancer cell line.

Pancreatic carcinoma is currently considered as a rapidly progressive and fatal disease, and is typically diagnosed late in its natural course. It is characterized by a poor diagnosis and lack of response to conventional therapy. Recent studies have suggested that disulfiram (DSF), a member of the dithiocarbamate family, may have antitumor activity. This study aimed to evaluate the in vitro effect of DSF on apoptosis in human pancreatic cancerous cell line (PANC-1). PANC-1 cells were cultured and treated with DSF at doses of 5, 10, 13 µM for 24 h and apoptosis was measured. Methylation specific PCR (MS-PCR) and real-time quantitative PCR were carried out to detect the methylation pattern and to estimate the mRNA expression levels of RASSF1A, p21 and Bax. MS-PCR analysis demonstrated that no unmethylated band was apeared in PANC-1 cell line after DSF treatments. The real-time quantitative PCR results showed no significant mRNA expression for RASSF1A (p>0.05); whereas p21 and Bax expression were significantly (p<0.01) enhanced after treatment with DSF. The results of the current study indicated that DSF can induce appoptosis in PANC-1 through p21 and Bax pathway but not through RASSF1A.

Assessment of lead and cadmium levels in frequently used cosmetic products in Iran.

This study aims to investigate the content of lead and cadmium in most frequently used brands of cosmetic products (lipstick and eye shadow) in Iran. Fifty samples of lipstick (5 colors in 7 brands) and eye shadow (3 colors in 5 brands) were selected taken from large cosmetic stores in Isfahan (Iran) and lead and cadmium of them were analyzed. The results showed that the concentration of lead and cadmium in the lipsticks was within the range of 0.08-5.2 µ g/g and 4.08-60.20 µ g/g, respectively. The eye shadow samples had a lead level of 0.85-6.90 µ g/g and a cadmium level of 1.54-55.59 µ g/g. The content range of the heavy metals in the eye shadows was higher than that of the lipsticks. There was significant difference between the average of the lead content in the different brands of the lipsticks and eye shadows. Thus, the continuous use of these cosmetics can increase the absorption of heavy metals, especially Cd and Pb, in the body when swallowing lipsticks or through dermal cosmetic absorption. The effects of heavy metals such as lead can be harmful, especially for pregnant women and children. Therefore, effort must be made to inform the users and the general public about the harmful consequences of cosmetics.

The apoptotic effects of sirtuin1 inhibitor on the MCF-7 and MRC-5 cell lines.

Sirtuin1 (SIRT1) is an enzyme that deacetylates histones and several nonhistone proteins including p53 during stress and plays an important role in the survival of tumor cells. Hereby, this study describes the potency of salermide as a SIRT1 inhibitor to induce apoptosis in the MCF-7 and MRC-5 cell lines. MCF7 and MRC-5 cell lines were cultured in RPMI-1640 and treated with or without salermide at concentration of 80.56 µmol/L, based on the half-maximal inhibitory concentration (IC50) index at different times (24, 48 and72 h). The IC50 value was established for the salermide in MCF-7. The percentage of apoptotic cells was measured by flow cytometry. Real-time quantitative RT-PCR was performed to estimate the mRNA expression of sirtuin1 in MCF-7 and MRC-5 with salermide at different times. ELISA and Bradford protein techniques were used to detect endogenous levels of total and acetylated p53 protein generated in MCF-7 and MRC-5 cells. Our findings indicated that salermide can induce apoptosis in MCF-7 significantly more effective than MRC-5 cells. We showed that the expression of SIRT1 was dramatically down-regulated by increasing the time of salermide treatment in MCF-7 but not MRC-5 and that the acetylated and total p53 protein levels were increased more in MCF-7 than MRC-5. Salermide, by decreasing the expression of sirtuin1 gene, can induce acetylation of P53 protein and consequently induce significant cell death in MCF-7 that was well tolerated in MRC-5.

Characterization of azimuthal and longitudinal modes in rolled-up InGaAs/GaAs microtubes at telecom wavelengths.

We report on theoretical and experimental investigation of azimuthal and longitudinal modes in rolled-up microtubes at telecom wavelengths. These microtubes are fabricated by selectively releasing a coherently strained InGaAs/GaAs bilayer. We apply planar waveguide method and a quasi-potential model to analyze the azimuthal and longitudinal modes in the microtubes near 1550 nm. Then we demonstrate these modes in transmission spectrum by evanescent light coupling. The experimental observations agree well with the calculated results. Surface-scattering-induced mode splitting is also observed in both transmission and reflection spectra at ~1600 nm. The mode splitting is in essence the non-degeneracy of clockwise and counter-clockwise whispering-gallery modes of the microtubes. This study is significant for understanding the physics of modes in microtubes and other microcavities with three-dimensional optical confinement, as well as for potential applications such as microtube-based photonic integrated devices and sensing purposes.

Evaluation of chemical and microbiological quality in 21 brands of Iranian bottled drinking waters in 2012: a comparison study on label and real contents.

The purpose of this study was to evaluate and compare chemical and microbiological quality of the 21 Iranian bottled drinking waters reported on manufacturer's labeling and standards in 2012. Samples were analyzed for chemical properties K(+), F(-), SO4 (2-), Cl(-), Mg(2+), Ca(2+), and pH. Total and fecal coliform and heterotrophic plate counts of selected samples were analyzed by MPN and HPC tests, respectively, for three months. Finally, the labeled and real contents of the samples were compared. Potassium and sulfate ions about 43 and 52 percent of studied sample contents had values higher than label amounts, respectively. Ca(2+), Cl(-) ions, and pH were about 71, 48, and 67 percent, respectively, less than label values. Total and fecal coliforms had negative results. The mean concentrations and standard deviations for K(+), Cl(-), pH, Ca(2+), Mg(2+), SO4 (2-), and HPC were 1.13 ± 1.06, 16.39 ± 31.97, 6.6 ± 0.7, 28.35 ± 10.34, 86.58 ± 33.21, 24.17 ± 17.30 mg/L, and 16855 ± 25603 cfu/mL, respectively. Thus, there is possibility of microorganisms' growth in favorite conditions in bottled water. It was imperative to assess the public health risks in bottled water in Iran.

Epidemiological features of human brucellosis in central Iran, 2006-2011.

OBJECTIVES: Brucellosis is still one of the most challenging issues for health and the economy in many developing countries such as Iran. This study investigated the epidemiological features of brucellosis in Isfahan province in central Iran. STUDY DESIGN: This retrospective descriptive study was planned to determine the epidemiological features of brucellosis in central Iran, as this is one of the most endemic areas in the country. METHODS: Data collection was performed using epidemiological questionnaires from the private and public sectors over a 4-year period (2006-2009). RESULTS: In total, 1996 cases of brucellosis were reported. The incidence of brucellosis decreased from 17.1/100,000 in 2006 to 8.2/100,000 in 2009. The male:female ratio was 2.1, and the disease was most common in individuals aged 15-20 years. Sixty-eight percent of cases were from rural areas, and the animal contact rate was 81% in rural cases and 61% in urban cases. Raw milk was the most commonly consumed dairy product, consumed by 37% of cases. CONCLUSIONS: Health-related interventions need to empower communities at risk, especially young men and adult women in the western districts of Isfahan province. Public health promotion is needed for control of risk factors in these areas.