Thermopower of the Hubbard model: Effects of multiple orbitals and magnetic fields in the atomic limit

We consider strongly-correlated systems described by the multi-orbital Hubbard model in the atomic limit and obtain exact expressions for the chemical potential and thermopower. We show that these expressions reduce to the Heikes formula in the appropriate limits ($k_BT \gg U$) and ($k_BT \ll U$) and obtain the full temperature dependence in between these regimes. We also investigate the effect of a magnetic field introduced through a Zeeman term and observe that the thermopower of the multi-orbital Hubbard model displays spikes as a function of magnetic field at certain special values of the field. This effect might be observable in experiments for materials with a large magnetic coupling.Comment: 8 pages, 4 figures Typos in eqns. 3 and 4 and reference 17 correcte

Computation efficiency of master-slave processors in multitasking applications: a performance analysis

Examines the computational efficiency of the master slave Multiple processor architectures system by considering a system consisting of a master M and p slave processors. The system performance is found by modelling it as a Markov process and a new method presented for computing the steady-state performance by dividing the state space into an interior and boundary space. The throughput of the system is then compared with that of a cost equivalent single processor using different values for the well-known Grosch parameter. It is demonstrated that the system is computationally efficient only for a sufficiently large number of jobs

Regular fractions of mixed factorials with maximum estimation capacity

We use a finite projective geometric approach to investigate the issue of maximum estimation capacity in regular fractions of mixed factorials, recognizing the fact that not all two-factor interactions may have equal importance in such a set-up. Our results provide further statistical justification for the popular criterion of minimum aberration as applied to mixed factorials.published_or_final_versio

Active immunization by a dengue virus-induced cytokine

Dengue type 2 virus (DV)-induced cytotoxic factor (CF) is capable of reproducing various pathological lesions in mice that are seen in human dengue. The present study was undertaken to investigate the protective effect of active immunization of mice with CF, Mice were immunized with 5 μ g of CF and prevention of CF-induced increase in capillary permeability and damage to the blood brain barrier were studied at weekly intervals, up to 48 weeks, by challenging with 3 μ g of CF, Maximum protection against increase in capillary permeability and damage to the blood-brain barrier was observed in week 4 after immunization. A breakthrough in the protection occurred with higher doses of CF in a dose-dependent manner. Challenge with a lethal intracerebral (i.e.) dose of DV showed significantly prolonged mean survival time and delayed onset of symptoms of sickness in the immunized mice compared with the normal mice, but the titre of the virus in the brain was similar in the two groups. On i.p. challenge with the virus the protection against damage to the blood-brain barrier was 86± 7% at week 4 and 17± 4% at week 26 after immunization. Sera obtained from the immunized mice showed the presence of CF-specific antibodies by ELISA, Western blot, and by neutralization of the cytotoxic activity of CF in vitro. The present study describes successful prevention of a cytokine-induced pathology by specific active immunization

Understanding the nature of electronic effective mass in double-doped SrTiO3_{3}

We present an approach to tune the effective mass in an oxide semiconductor by a double doping mechanism. We demonstrate this in a model oxide system Sr$_{1-x}$La$_x$TiO$_{3-\delta}$, where we can tune the effective mass ranging from 6--20$\mathrm{m_e}$ as a function of filling or carrier concentration and the scattering mechanism, which are dependent on the chosen lanthanum and oxygen vacancy concentrations. The effective mass values were calculated from the Boltzmann transport equation using the measured transport properties of thin films of Sr$_{1-x}$La$_x$TiO$_{3-\delta}$. Our method, which shows that the effective mass decreases with carrier concentration, provides a means for understanding the nature of transport processes in oxides, which typically have large effective mass and low electron mobility, contrary to the tradional high mobility semiconductors.Comment: 5 pages with 4 figure

Cytotoxic factor in dengue haemorrhagic fever

Objective: Cytotoxic factor is a unique pathogenesis-associated cytokine that is produced in mice (mCF) and man (hCF) during dengue virus infection. This study was undertaken to investigate the prevalence of hCF and its relationship to the duration and severity of the illness, and to ascertain its role, if any, in the pathogenesis of dengue fever (DF) and dengue haemorrhagic fever (DHF). Methods: Peripheral venous blood was collected from the patients of various grades and on different days after the onset of clinical illness. Sera were collected from a total of 333 cases, and analysed for the presence of hCF by inhibition ELISA and dot blot tests. Result: The positivity for hCF was 100% in cases of DHF grades III and IV, while overall positivity was seen in 295 out of 333 (88%) cases studied. Sera collected from the 1st to the 20th day of illness were positive for hCF. This was not seen at later periods. A majority of cases (52%) were below 15 years of age and peak positivity of 96% was noticed in the age-group of 11-15 years. The mean inhibition value of the ELISA was lowest (40 ± 8%) in cases of DF and was highest (70 ± 10%) in DHF grade IV, and the peak titres were found on the first 4 days of the illness. Conclusion: The findings show the presence of hCF in the majority of cases. It is detectable up to the 20th day of illness and may suggest an association of higher levels of hCF with the onset and severity of the illness

A non destructive method to detect the incipient fault in rolling element bearing

It is essential to have prior warning of incipient fault (s) in any critical equipment occurring due to vibration. Vibration monitoring is good nondestructive technique to detect the fault of machines at an early stage. Capturing vibration signature of machines at slow speed is a difficult task due to impact of low energy, mostly absorbed by the structural path and falls much below the cut off frequency of the normally available accelerometer. To resolve the issue, a systematic proce-dure has been developed. It has the facility to break the signal in different level, envelope capturing and finally convert to frequency spectrum. The system has been tested under various operating condition that suits to industry to diagnose the problem of bearing. The method can predict the problem very well at its inception

Dynamical thermal response functions for strongly correlated one-dimensional systems: Hubbard and spinless fermion t-V model

In this paper, we study the thermal response functions for two one-dimensional models, namely, the Hubbard and spinless fermion t-V model, respectively. By exactly diagonalizing finite sized systems, we calculate dynamical, electrical, thermoelectrical, and thermal conductivities via the Kubo formalism [J. Phys. Soc. Jpn. 12, 570 (1957)]. The thermopower (Seebeck coefficient), Lorenz number, and dimensionless figure of merit are then constructed, which are quantities of great interest to the physics community both theoretically and experimentally. We also geometrically frustrate these systems and destroy integrability by the inclusion of a second-neighbor hop in the kinetic energy operator. These frustrated systems are shown to have enhanced thermopower and Lorenz number at intermediate and low temperatures