Directed strongly walk-regular graphs

We generalize the concept of strong walk-regularity to directed graphs. We call a digraph strongly $\ell$-walk-regular with $\ell >1$ if the number of walks of length $\ell$ from a vertex to another vertex depends only on whether the two vertices are the same, adjacent, or not adjacent. This generalizes also the well-studied strongly regular digraphs and a problem posed by Hoffman. Our main tools are eigenvalue methods. The case that the adjacency matrix is diagonalizable with only real eigenvalues resembles the undirected case. We show that a digraph $\Gamma$ with only real eigenvalues whose adjacency matrix is not diagonalizable has at most two values of $\ell$ for which $\Gamma$ can be strongly $\ell$-walk-regular, and we also construct examples of such strongly walk-regular digraphs. We also consider digraphs with nonreal eigenvalues. We give such examples and characterize those digraphs $\Gamma$ for which there are infinitely many $\ell$ for which $\Gamma$ is strongly $\ell$-walk-regular

Analysis of rock burst in critical section of second part of Karaj-Tehran Water Supply Tunnel

Practical Applications and Case Studie

Seroprevalence of hepatitis B virus and its co-infection with hepatitis D virus and hepatitis C virus in Iranian adult population

Context: Hepatitis B virus (HBV) infection is one of the most prevalent public health problems worldwide (especially in developing countries). Aims: This study was carried out to determine the seroprevalence of HBV and its co-infection with hepatitis D (HDV) and C (HCV) viruses in the northeastern part of Iran. Setting and Design: A population-based cross-sectional study in Iran. Materials and Methods: As many as 1,850 subjects were explored for HBsAg. Anti-HDV and anti-HCV antibodies were assessed in HBsAg-positive cases. Statistical Analysis Used: Proportions were compared by Chi-square and Fisher's exact tests. Results: The mean age of subjects was 43.86 ± 11.2 years. The age- and sex-standardized prevalence for HBsAg positivity was 9.7%. It was higher in males than in females (OR: 1.28; 95% CI: 0.9-1.7). The risk of infection in singles was significantly higher than in married cases (OR: 2.13). Eight (5.8%) of HBsAg-positive cases were infected with HDV, and 17 (12.3%) were positive for anti-HCV antibody. Conclusion: This study demonstrates that the prevalence of HBsAg seropositivity in Golestan province of Iran is higher than the levels reported by WHO and previous studies from Iran. It is very important, especially for health providers and policy makers, to recognize the risk factors of HBV infection and its co-infection with HDV and HCV in this area and design effective preventive programs

Analysis and comparison of wheat losses in two harvesting methods

Wheat losses in John Deere 955 combine was compared between stripper header and conventional header.  Tests were conducted in a wheat field.  At first for comparison, the optimum working condition was obtained for both type of headers and then other parameters are compared. Results showed that the optimum working condition of combine with a second gear and mediate engine speed for stripper header was obtained with 75 cm for hood distance, 60 cm for header distance and 760 rmin-1 for rotor speeds.  In stripper header, the total loss of different parts of combine was under 3.5%, although these losses in conventional header reached up to 6.5% which was the highest loss for headers.  Number and weight of lost cluster in harvesting with stripper header was much less than conventional header. Keywords: wheat, stripper header, conventional header, rotor speed, los

Isolation and Molecular Characterization of a Novel Cytopathogenic Paramyxovirus from Tree Shrews

AbstractA cytopathic infectious agent was isolated from the kidneys of an apparently healthy tree shrew (Tupaia belangeri) that had been captured in the area around Bangkok. The infectivity was propagated in Tupaia fibroblast and kidney cell cultures. Paramyxovirus-like pleomorphic enveloped particles and helical nucleocapsids were observed by electron microscopy and accordingly the infectious agent was termed Tupaia paramyxovirus (TPMV). However, no serological cross-reactions were detected between TPMV and known paramyxoviruses. For the molecular characterization of TPMV an experimental strategy that allows the random-primed synthesis of relatively large cDNA molecules from viral genomic RNA was applied. Nucleotide sequence analysis of a TPMV-specific cDNA fragment (1544 bp) revealed two nonoverlapping partial open reading frames corresponding to paramyxoviral N and P transcription units. Using modified rapid amplification of cDNA ends techniques, a substantial contiguous portion of the viral genome (4065 nt) was elucidated including the complete N and P/V/C genes. The coding strategy of TPMV as well as significant amino acid sequence homologies clearly indicates an evolutionary relationship between TPMV and members of the genus Morbillivirus. Highest homologies were detected between TPMV and Hendra virus (equine morbillivirus), which recently emerged in Australia, causing outbreaks of fatal respiratory and neurological disease in horses and humans

Transport Properties in Ferromagnetic Josephson Junction between Triplet Superconductors

Charge and spin Josephson currents in a ballistic superconductor-ferromagnet-superconductor junction with spin-triplet pairing symmetry are studied using the quasiclassical Eilenberger equation. The gap vector of superconductors has an arbitrary relative angle with respect to magnetization of the ferromagnetic layer. We clarify the effects of the thickness of ferromagnetic layer and magnitude of the magnetization on the Josephson charge and spin currents. We find that 0-\pi transition can occur except for the case that the exchange field and d-vector are in nearly perpendicular configuration. We also show how spin current flows due to misorientation between the exchange field and d-vector.Comment: 6 pages, 8 figure

Effect of point-contact transparency on coherent mixing of Josephson and transport supercurrents

The influence of electron reflection on dc Josephson effect in a ballistic point contact with transport current in the banks is considered theoretically. The effect of finite transparency on the vortex-like currents near the contact and at the phase difference $\phi =\pi ,$ which has been predicted recently \cite{KOSh}, is investigated. We show that at low temperatures even a small reflection on the contact destroys the mentioned vortex-like current states, which can be restored by increasing of the temperature.Comment: 6 pages, 8 Figures, Latex Fil

Electrically switching transverse modes in high power THz quantum cascade lasers.

The design and fabrication of a high power THz quantum cascade laser (QCL), with electrically controllable transverse mode is presented. The switching of the beam pattern results in dynamic beam switching using a symmetric side current injection scheme. The angular-resolved L-I curves measurements, near-field and far-field patterns and angular-resolved lasing spectra are presented. The measurement results confirm that the quasi-TM(01) transverse mode lases first and dominates the lasing operation at lower current injection, while the quasi-TM(00) mode lases at a higher threshold current density and becomes dominant at high current injection. The near-field and far-field measurements confirm that the lasing THz beam is maneuvered by 25 degrees in emission angle, when the current density changes from 1.9 kA/cm(2) to 2.3 kA/cm(2). A two-dimension (2D) current and mode calculation provides a simple model to explain the behavior of each mode under different bias conditions

Pilot-aided estimation and equalisation of a Radio-over-Fibre system in Wideband Code Division Multiple Access

In this study, the impact of a Radio-over-Fibre (RoF) subsystem on the capacity performance of wideband code division multiple access is evaluated. This study investigates the use of pilot-aided channel estimation to compensate for the optical subsystem non-linearities for different channel conditions, estimation intervals and coding schemes. The results show that pilot-aided channel estimation is an effective method for compensating the composite impairments of the optical subsystem and the radio frequency (RF) channel. It is found that there is always a suitable pilot power level which maximises the system capacity performance regardless of coding scheme and channel condition. Also, the peak capacity is only slightly affected by a decrease in the estimation interval

Supersymmetric solutions of PT-/non-PT-symmetric and non-Hermitian Screened Coulomb potential via Hamiltonian hierarchy inspired variational method

The supersymmetric solutions of PT-symmetric and Hermitian/non-Hermitian forms of quantum systems are obtained by solving the Schrodinger equation for the Exponential-Cosine Screened Coulomb potential. The Hamiltonian hierarchy inspired variational method is used to obtain the approximate energy eigenvalues and corresponding wave functions.Comment: 13 page