A k-out-of-n reliability system with an unreliable server and phase type repairs and services: the (N, T) policy

In this paper we study a k-out-of-n reliability system in which a single unreliable server maintains n identical components. The reliability system is studied under the (N,T) policy. An idle server takes a vacation for a random amount of time T and then attends to any failed component waiting in line upon completion of the vacation. The vacationing server is recalled instantaneously upon the failure of the Nth component. The failure times of the components are assumed to follow an exponential distribution. The server is subject to failure with failure times exponentially distributed. Repair times of the component, fixing times of the server, and vacationing times of the server are assumed to be of phase type. Using matrix-analytic methods we perform steady state analysis of this model. Time spent by a failed component in service, total time in the repair facility, vacation time of the server, non-vacation time of the server, and time until failure of the system are all shown to be of phase type. Several performance measures are evaluated. Illustrative numerical examples are presented

Some remarks on the hyperelliptic moduli of genus 3

In 1967, Shioda \cite{Shi1} determined the ring of invariants of binary octavics and their syzygies using the symbolic method. We discover that the syzygies determined in \cite{Shi1} are incorrect. In this paper, we compute the correct equations among the invariants of the binary octavics and give necessary and sufficient conditions for two genus 3 hyperelliptic curves to be isomorphic over an algebraically closed field $k$, $\ch k \neq 2, 3, 5, 7$. For the first time, an explicit equation of the hyperelliptic moduli for genus 3 is computed in terms of absolute invariants.Comment: arXiv admin note: text overlap with arXiv:1209.044

New limit for the half-life of double beta decay of 94^{94}Zr to the first excited state of 94^{94}Mo

Neutrinoless Double Beta Decay is a phenomenon of fundamental interest in particle physics. The decay rates of double beta decay transitions to the excited states can provide input for Nuclear Transition Matrix Element calculations for the relevant two neutrino double beta decay process. It can be useful as supplementary information for the calculation of Nuclear Transition Matrix Element for the neutrinoless double beta decay process. In the present work, double beta decay of $^{94}$Zr to the $2^{+}_{1}$ excited state of $^{94}$Mo at 871.1 keV is studied using a low background $\sim$ 230 cm$^3$ HPGe detector. No evidence of this decay was found with a 232 g.y exposure of natural Zirconium. The lower half-life limit obtained for the double beta decay of $\rm^{94}Zr$ to the $2^{+}_{1}$ excited state of $\rm^{94}Mo$ is $T_{1/2} (0\nu + 2\nu)> 3.4 \times 10^{19}$ y at 90% C.L., an improvement by a factor of $\sim$ 4 over the existing experimental limit at 90\% C.L. The sensitivity is estimated to be $T_{1/2} (0\nu + 2\nu) > 2.0\times10^{19}$ y at 90% C.L. using the Feldman-Cousins method.Comment: 11 pages, 7 figures, Accepted in Eur. Phys. J.

Susceptibility baselines for the invasive mealybugs Phenacoccus manihoti and Paracoccus marginatus (Hemiptera: Pseudococcidae) in cassava ecosystem against selected neonicotinoid insecticides

In recent years, an invasive cassava mealybug Phenacoccus manihoti has been threatening cassava cultivation alongside another invasive papaya mealybug Paracoccus marginatus which invaded the country more than a decade ago. In order to evaluate their responses against the commonly used neonicotinoid insecticides: thiamethoxam 25 WG and imidacloprid 17.8 SL,  acute toxicity experiments to determine the susceptibility baselines in populations of two invasive mealybugs in the cassava agro-ecosystem, namely, cassava mealybug P. manihoti and papaya mealybug P. marginatus were performed upto 15 generations. A systemic uptake method was used for the bioassay. The LC50 values of thiamethoxam for F1 generation were 3.298 ppm whereas it was 1.066 ppm for F15 in cassava mealybug. The LC50 values of F1 generation were 2.014 ppm and that of F15 generation was 1.384 ppm when tested with imidacloprid. In the case of papaya mealybug, the LC50 values ranged from 6.138 ppm (F1) to 2.503 ppm (F15) for thiamethoxam and 7.457 ppm (F1) to 3.231 ppm (F15) for imidacloprid. All the susceptibility indices calculated were less than threefold. The rate of resistance development was negative in all cases showing that none of the tested populations harboured any resistance without insecticidal selection pressure. Tentative discriminating doses were fixed for both chemicals with the help of LC95 values obtained from the bioassay experiments, namely five ppm for both thiamethoxam and imidacloprid in the case of cassava mealybug and 10 ppm and 15 ppm, respectively, for thiamethoxam and imidacloprid in the case of papaya mealybug.          

Randomized trial of two different conditioning regimens for bone marrow transplantation in thalassemia - the role of busulfan pharmacokinetics in determining outcome

In total, 94 patients with homozygous beta thalassemia were randomized to two different conditioning regimens: busulfan 600 mg/m2+cyclophosphamide 200 mg/kg or busulfan 16 mg/kg+cyclophosphamide 200 mg/kg and antilymphocyte globulin (47 in each group), for bone marrow transplantation, to see whether increased myeloablation or increased immunosuppression would reduce rejection. Busulfan pharmacokinetics in determining outcome was evaluated. There was no significant difference in engraftment, graft-versus-host disease, rejection, and overall and disease-free survival in the two groups. Systemic exposure to busulfan was significantly higher in the 600 mg/m2 group, but in both groups there was a wide interindividual variation in the busulfan kinetics. Six patients rejected the graft, two in the busulfan 600 mg group and four in busulfan 16 mg group (P=0.677 CI -0.17, 0.07), but in five patients (pharmacokinetic data not available in one patient) who rejected the graft busulfan first dose trough level (Cmin-1) was below 150 ng/ml while it was above this level in the 66 of 68 patients with successful engraftment (P0.001). This randomized trial shows that rejection is influenced by busulfan levels and suggests that monitoring of busulfan levels and dose adjustment based on first-dose kinetics may reduce the risk of rejection

ASSOCIATION OF SERUM URIC ACID AND LIPID PROFILE IN TYPE 2 DIABETIC PATIENTS WITH AND WITHOUT DIABETIC RETINOPATHY

Objectives: Diabetic retinopathy (DR) is one of the microvascular complications in type 2 diabetes (T2D).  Elevated serum uric acid (SUA) has been shown to play a significant role in diabetic neuropathy and nephropathy but there is little information on retinopathy. Therefore, the present study was aimed to investigate the SUA and lipid profile in T2D patients with and without DR and the association between SUA and severity of DR.Methods: The study was conducted in the ophthalmology OPD at Sri Lakshmi Narayana Institute of Medical Sciences. The presence of T2D was confirmed by investigating fasting blood glucose level (normal limit < 110 mg/dl) in all the individuals. DR was examined by detailed dilated fundoscopic examination. Based on the fundus examination, patients were divided in to diabetes with signs of DR and those without signs of DR. Age and sex matched healthy were taken as controls. Fasting blood sugar, SUA and lipid profile were investigated for these groups. Results: The study found elevated SUA and abnormal lipid profile in DR group when compared to non-DR and control groups. We also found the significant association between SUA and severity of DR particularly in males.Conclusion: We found a significant association between SUA and severity of DR in T2D patients. Further studies with large sample size are needed to establish the role of elevated SUA and the mechanism involved in the pathogenesis of retinopathy in diabetic patients. Regular measurements of SUA level could be advised to the diabetic patients for the early management

Site-specific fluorescence dynamics in an RNA 'thermometer' reveals the role of ribosome binding in its temperature-sensitive switch function

RNA thermometers control the translation of several heat shock and virulence genes by their temperature-sensitive structural transitions. Changes in the structure and dynamics of MiniROSE RNA, which regulates translation in the temperature range of 20–45°C, were studied by site specifically replacing seven adenine residues with the fluorescent analog, 2-aminopurine (2-AP), one at a time. Dynamic fluorescence observables of 2-AP-labeled RNAs were compared in their free versus ribosome-bound states for the first time. Noticeably, position dependence of fluorescence observables, which was prominent at 20°C, was persistent even at 45°C, suggesting the persistence of structural integrity up to 45°C. Interestingly, position-dependent dispersion of fluorescence lifetime and quenching constant at 45°C was ablated in ribosome-bound state, when compared to those at 20°C, underscoring loss of structural integrity at 45°C, in ribosome-bound RNA. Significant increase in the value of mean lifetime for 2-AP corresponding to Shine–Dalgarno sequences, when the temperature was raised from 20 to 45°C, to values seen in the presence of urea at 45°C was a strong indicator of melting of the 3D structure of MiniROSE RNA at 45°C, only when it was ribosome bound. Taken all together, we propose a model where we invoke that ribosome binding of the RNA thermometer critically regulates temperature sensing functions in MiniROSE RNA

Liquid Xenon Detectors for Positron Emission Tomography

PET is a functional imaging technique based on detection of annihilation photons following beta decay producing positrons. In this paper, we present the concept of a new PET system for preclinical applications consisting of a ring of twelve time projection chambers filled with liquid xenon viewed by avalanche photodiodes. Simultaneous measurement of ionization charge and scintillation light leads to a significant improvement to spatial resolution, image quality, and sensitivity. Simulated performance shows that an energy resolution of <10% (FWHM) and a sensitivity of 15% are achievable. First tests with a prototype TPC indicate position resolution <1 mm (FWHM).Comment: Paper presented at the International Nuclear Physics Conference, Vancouver, Canada, 201