Molecular dynamics study of the point defects in bcc uranium

Thermodynamic properties of bcc uranium with point defects are studied using ab initio molecular dynamics (MD) simulations at 1100 K. The simulations were performed with canonical ensembles of U127M1,U128M1, and U 126 M1□1 for M = □, He, Ne, Ar, Kr, Xe, Sr, Zr, I, Cs, and Pu disposed on a bcc lattice lying within a 4×4×4 cubic supercell. This work provides formation energies of substitutional, self, and solute interstitial atom defects as well as binding energies of M-□ pair defects. This work demonstrates that our computational scheme based on MD simulations gives reliable formation and binding energies of atomic defects in bcc uranium compared to conventional density functional theory calculations. The equilibrium volume, bulk modulus, and thermal expansion coefficient of pure bcc uranium obtained from our MD simulations compare very well with corresponding experimental results. The vacancy formation energy is predicted to be 0.88 eV. The experimental vacancy formation energy remains uncertain. Experimental study of the formation and binding energies of other point defects as well as the bulk modulus and thermal expansion coefficients of uranium with these defects is also not found in the literature. This work shows that point defects tend to decrease the bulk modulus and increase the thermal expansion coefficient of bcc uranium. The solute formation energies of noble gas atoms show a bearing on their size. A large solute (Xe) has a high formation energy, and vice versa. This size effect is not quite evident for the chemically reactive solutes, namely, Sr, Zr, I, Cs, and Pu. Our MD simulations further show that vacancies are the favorable point defects in bcc uranium rather than both vacancies and self interstitials as predicted by earlier calculations. The formation energies of self interstitial atoms are found to be lower than those of solute interstitial atoms, each calculated in six different basic interstitial dumbbell configurations. That is, bcc U accommodates self interstitials more easily than decay or fission gas interstitials (He, Kr, and Xe). Further, He atoms are found to have comparable formation energies in the substitutional and interstitial locations. The fission product atoms Kr and Xe prefer to occupy vacant substitutional lattice sites rather than interstitial sites. Binding energies of divacancy and solute-vacancy pairs (0.31 vs −0.69 eV for the Xe-□ pair, for instance) from our MD simulation show that nucleation and growth of fission gas bubbles are supported by a thermodynamic driving force, whereas vacancies tend to stay apart. This is in agreement with literature reporting that bcc uranium softens and swells mainly by agglomeration of noble gas bubbles

A Conflict between Self and World in Philip Roth’s Portnoy’s Complaint

This study discerns Portnoy’s Complaint by Philip Roth concerning the struggle between self and world. Roth’s protagonists want a haven of protection and stability, or a home, from which they may interpret the world meaningfully. In addition to this, they require stability and repose in the achievement of selfhood. Their home may be their static, centred self, from which they could get meaning from their surroundings. In the novel Portnoy’s Complaint , the protagonist faces external and internal and selfversus- world conflicts. It is discovered that Portnoy conflicts with his Jewish family, a microcosm of the ethnic group to which he belongs. He incorrectly feels that his ethnicity is the core reason for his alienated feelings. In addition, he is troubled by the contradiction between his moral convictions and his sexual indulgence. His difficulties remain unanswered until the novel’s conclusion, even though he begins comprehending the actual nature of his moral issue. In his exploration of the never-ending and, maybe, the insoluble issue between man and his fundamental desires, Roth delves into the simple mind of his species to bring to light the unfathomable, grotesque, and frightening realities of human drives and experiences. This skill lends his compositions a worldwide appeal that transcends ethnic and racial distinctions. All the characters in the narrative are banished from themselves and arrive in the brave new world of choice, America, representing a domestic transgression

Operator modeling in commerical aviation: Cognitive models, intelligent displays, and pilot's assistants

One of the goals of the National Aviation Safety/Automation program is to address the issue of human-centered automation in the cockpit. Human-centered automation is automation that, in the cockpit, enhances or assists the crew rather than replacing them. The Georgia Tech research program focused on this general theme, with emphasis on designing a computer-based pilot's assistant, intelligent (i.e, context-sensitive) displays, and an intelligent tutoring system for understanding and operating the autoflight system. In particular, the aids and displays were designed to enhance the crew's situational awareness of the current state of the automated flight systems and to assist the crew's situational awareness of the current state of the automated flight systems and to assist the crew in coordinating the autoflight system resources. The activities of this grant included: (1) an OFMspert to understand pilot navigation activities in a 727 class aircraft; (2) an extension of OFMspert to understand mode control in a glass cockpit, Georgia Tech Crew Activity Tracking System (GT-CATS); (3) the design of a training system to teach pilots about the vertical navigation portion of the flight management system -VNAV Tutor; and (4) a proof-of-concept display, using existing display technology, to facilitate mode awareness, particularly in situations in which controlled flight into terrain (CFIT) is a potential

Nanotubes and nanowires

Synthesis and characterization of nanotubes and nanowires constitute an important part of nanoscience since these materials are essential building units for several devices. We have prepared aligned carbon nanotube bundles and Y-junction nanotubes by the pyrolysis of appropriate organic precursors. The aligned bundles are useful for field emission display while the Y-junction nanotubes are likely to be useful as nanochips since they exhibit diode properties at the junction. By making use of carbon nanotubes, nanowires of metals, metal oxides and GaN have been obtained. Both the oxide and GaN nanowires are single crystalline. Gold nanowires exhibit plasmon bands varying markedly with the aspect ratio. GaN nanowires show excellent photoluminescence characteristics. It has been possible to synthesise nanotubes and nanowires of metal chalcogenides by employing different strategies

Prevalence of Inhibitors in Patients with Hemophilia Treated with Factor VIII or IX Transfusion in Coimbatore Medical College Hospital

INTRODUCTION: Deficiency or absence of factor VIII or factor IX causes hemophilia A and hemophilia B respectively. According to the level of factor VIII hemophilia is classified into mild, moderate and severe forms. Recent problem in treating patients with hemophilia is development of alloantibodies against factor VIII or IX, also known as inhibitors. This should be suspected if the patient is not responding to replacement of missing factor at therapeutic doses. The objective of the study was to study the prevalence of inhibitors in severe hemophilia patients by using Bethesda assay. METHODOLOGY: This was an observational study. 50 patients with severe hemophilia were selected based on their factor levels. Among them, Hemophilia A contributed to 36 patients, whereas 14 patients had Hemophilia B. Inhibitor assay was done using Bethesda assay. Inhibitor development was analyzed by comparing the various factors which influence the development of inhibitors. RESULTS AND DISCUSSION: Among the patients with severe hemophilia A, 31% had inhibitors, of which 25% had high responding inhibitors and 6% had low responding inhibitors. Among the severe hemophilia B patients, 7% had inhibitors. Small sample size may be a reason for the high prevalence noted in our study. The Mean age of patients with inhibitors and without inhibitors was 19.33 years and 23.63 years respectively. Patients with more than 30 cumulative exposure days to factor concentrates had 53% more risk of developing inhibitors. Patients who were diagnosed earlier and those with family history of inhibitors had significantly higher risk of developing inhibitors during the course of treatment. Patients with inhibitors also had a high bleeding score

Zirconia nanotubes

Hollow nanotubes of zirconia as well as of yttria-stabilized zirconia are successfully prepared by first coating the carbon nanotubes appropriately with the oxidic material and then burning off the carbon of the template

Identification of Fe and Zn Responsive Genes in Pearl Millet (Pennisetum glaucum L.) through Whole Genome Transcriptome Approach

Micronutrient malnutrition due to iron and zinc deficiencies is a serious public health problem in developing countries. In India alone, about 80% of the pregnant women and 74% of children suffer from iron and zinc deficiency. At present, knowledge of the genes controlling specific steps in the Fe and Zn pathways is still rudimentary hence studying genes of Fe and Zn density has become important. A whole genome RNA-Seq approach was carried out to understand the genes and pathways related to Fe and Zn accumulation in pearl millet. Seedlings of a high Fe and Zn grain density pearl millet inbred ICMB 1505 were exposed to four Fe and Zn stress treatments namely, –Fe –Zn, –Fe +Zn, +Fe –Zn and +Fe +Zn in hydroponics for 12 days (Figure 1). Seedlings were expressed interveinal chlorosis in the leaves due to the non-availability of Fe and Zn compared to control during the stress treatments. At that time, the leaf and root tissues in four treatments were harvested separately. Total RNA was extracted from the treated samples followed by cDNA synthesis. Illumina HiSeq 2500 platform was used to sequence the constructed cDNA libraries. Analysis of differentially expressed genes and pathways associated Fe and Zn is underway. Simultaneously, a set of 40 genotypes with variable Fe and Zn grain density were selected and tissue samples from different plant parts such as seed, flag leaf, root, stem sheath, panicles at anthesis and panicle at milky-stage were collected. RNA was extracted from the samples to validate the genes associated with Fe and Zn homeostasis. The information will be used for accelerated breeding programmes to improve the Fe and Zn density in pearl millet

Improved synthesis of carbon nanotubes with junctions and of single-walled carbon nanotubes

Pyrolysis of thiophene over nickel nanoparticles dispersed on silica is shown to yield Y-junction carbon nanotubes with smaller diameters than those obtained by the pyrolysis of organometallic-thiophene mixtures. In the presence of water vapour, the pyrolysis of organometallic-hydrocarbon mixtures yields single-walled nanotubes, as well as relatively narrow-diameter carbon nanotubes with Y-junctions. Pyrolysis of organometallic-hydrocarbon mixtures, in the absence of water vapour, only gives nanotubes with T- and Y-junctions