On effects of regular S=1 dilution of S=1/2 antiferromagnetic Heisenberg chains by a quantum Monte Carlo simulation

The effects of regular S=1 dilution of S=1/2 isotropic antiferromagnetic chain are investigated by the quantum Monte Carlo loop/cluster algorithm. Our numerical results show that there are two kinds of ground-state phases which alternate with the variation of $S^1=1$ concentration. When the effective spin of a unit cell is half-integer, the ground state is ferrimagnetic with gapless energy spectrum and the magnetism becomes weaker with decreasing of the $S^1$ concentration $\rho = 1/M$. While it is integer, a non-magnetic ground state with gaped spectrum emerges and the gap gradually becomes narrowed as fitted by a relation of $\Delta \approx 1.25\sqrt{\rho}$.Comment: 6 pages, 9 figure

Unscented Particle Smoother and its Application to Transfer Alignment of Airborne Distributed POS

This paper deals with the problem of state estimation for the transfer alignment of airborne distributed position and orientation system (distributed POS). For a nonlinear system, especially with large initial attitude errors, the performance of linear estimation methods will degrade. In this paper a nonlinear smoothing algorithm called the unscented particle smoother (UPS) is proposed and utilized in the off-line transfer alignment of airborne distributed POS. In this algorithm, the measurements are first processed by the forward unscented particle filter (UPF) and then a backward smoother is used to achieve the improved solution. The performance of this algorithm is compared with that of a similar smoother known as the Unscented Rauch-Tung-Striebel Smoother. The simulation results show that the UPS effectively improves the estimation accuracy and this work offers a new off-line transfer alignment approach of distributed POS for multi-antenna synthetic aperture radar and other airborne earth observation tasks

Cross-inhibition to heterologous foot-and-mouth disease virus infection induced by RNA interference targeting the conserved regions of viral genome

AbstractRNA interference (RNAi) is the process by which double-stranded RNA (dsRNA) directs sequence-specific degradation of messenger RNA in animal and plant cells. In mammalian cells, RNAi can be triggered by 21–23 nucleotide duplexes of small interfering RNA (siRNA). Strategies to inhibit RNA virus multiplication based on the use of siRNAs have to consider the high genetic polymorphism exhibited by this group of virus. Here we described a significant cross-inhibition of foot-and-mouth disease (FMD) virus (FMDV) replication in BHK-21 cells by siRNAs targeted to various conserved regions (5′NCR, VP4, VPg, POL, and 3′NCR) of the viral genome. The results showed that siRNAs generated in vitro by human recombinant dicer enzyme gave an inhibition of 10- to 1000-fold in virus yield of both homologous (HKN/2002) and heterologous (CHA/99) isolates of FMDV serotype O at 48 h post-infection (hpi). The inhibition extended to at least 6 days post-infection. For serotype Asia1, the virus yield in YNBS/58-infected cells examined at 12, 24, and 48 hpi decreased by ∼10-fold in cells pretreated with HKN/2002-specific siRNAs, but there was no significant decrease at 60 hpi. The inhibition was specific to FMDV replication, as no reduction was observed in virus yield of pseudorabies virus, an unrelated virus. Moreover, we also demonstrated an enhanced viral suppression could be achieved in BHK-21 cells with siRNA transfection after an infection had been established. These results suggested that siRNAs directed to several conserved regions of the FMDV genome could inhibit FMDV replication in a cross-resistance manner, providing a strategy candidate to treat high genetic variability of FMDV

Evaluation of Neck Lymph Node Metastasis on Contrast-Enhanced Ultrasound: An Animal Study

Objectives To assess the performance of contrast-enhanced ultrasound (CEUS) intended to differentiate hyperplastic from malignant neck lymph nodes in an animal model. Methods Twenty-four New Zealand rabbits were randomly divided into two groups: neck lymph node metastasis group (12 rabbits) and reactive hyperplastic lymph node group (12 rabbits). Tongue VX2 carcinoma with cervical lymph node metastasis was induced in 12 rabbits by injecting VX2 carcinoma suspension into the left tongue submucosa. Hyperplastic neck lymph nodes were induced by injecting egg yolk in the submandibular region of the rabbits in hyperplastic group. CEUS were performed in both groups before and after intravenous administration of SonoVue. The site, number, echogenicity, longitudinal and transverse nodal dimensions, patterns of enhancement of the neck lymph nodes were observed and recorded. Results In both groups only one lymph node was found in the left (tumor) side of the neck. CEUS found 12 of 12 metastatic lymph nodes in metastasis group, and diagnosed 11 of 12 lymph nodes as metastatic. Histopathologic analysis revealed metastatic lesions in all 12 rabbits, each with one lymph node, and all 12 lymph nodes in hyperplastic group is inflammation lymph nodes. All 12 cases in the hyperplastic group showed centripetal homogeneous enhancement while in the metastasis group one case showed centripetal homogeneous enhancement, three cases showed centrifugal heterogeneous enhancement, and eight cases showed diffused heterogeneous enhancement. Only one lymph node was dissected on the left side of the neck in each rabbit in both groups. Conclusion CEUS can play a role in discriminating metastatic from hyperplastic lymph nodes in head and neck carcinoma

Numerical studies on supersonic spray combustion in high-temperature shear flows in a scramjet combustor

Numerical simulation is applied to detail the combustion characteristics of n-decane sprays in highly compressible vortices formed in a supersonic mixing layer. The multi-phase reacting flow is modeled, in which the shear flow is solved Eulerianly by means of direct numerical simulation, and the motions of individual sub-grid point-mass fuel droplets are tracked Lagrangianly. Spray combustion behaviors are studied under different ambient pressures. Results indicate that ignition kernels are formed at high-strain vortex braids, where the scalar dissipation rates are high. The flame kernels are then strongly strained, associated with the rotation of the shearing vortex, and propagate to envelop the local vortex. It is observed that the flammable mixtures entrained in the vortex are burned from the edge to the core of the vortex until the reactants are completely consumed. As the ambient pressure increases, the high-temperature region expands so that the behaviors of spray flames are strongly changed. An overall analysis of the combustion field indicates that the time-averaged temperature increases, and the fluctuating pressure decreases, resulting in a more stable spray combustion under higher pressures, primarily due to the acceleration of the chemical reaction

Attenuated Salmonella choleraesuis-mediated RNAi targeted to conserved regions against foot-and-mouth disease virus in guinea pigs and swine

In this study, specific sequences within three genes (3D, VP4 and 2B) of the foot-and-mouth disease virus (FMDV) genome were determined to be effective RNAi targets. These sequences are highly conserved among different serotype viruses based on sequence analysis. Small interfering RNA (siRNA)-expressing plasmids (p3D-NT19, p3D-NT56, pVP4-NT19, pVP4-NT65 and p2B-NT25) were constructed to express siRNA targeting 3D, VP4 and 2B, respectively. The antiviral potential of these siRNA for various FMDV isolates was investigated in baby hamster kidney (BHK-21) cells and suckling mice. The results show that these siRNA inhibited virus yield 10- to 300-fold for different FMDV isolates of serotype O and serotype Asia I at 48 h post infection in BHK-21 cells compared to control cells. In suckling mice, p3D-NT56 and p2B-NT25 delayed the death of mice. Twenty percent to 40% of the animals that received a single siRNA dose survived 5 days post infection with serotype O or serotype Asia I. We used an attenuated Salmonella choleraesuis (C500) vaccine strain, to carry the plasmid that expresses siRNA directed against the polymerase gene 3D (p3D-NT56) of FMDV. We used guinea pigs to evaluate the inhibitory effects of recombinant S. cho (p3D-NT56/S. cho) on FMDV infection. The results show that 80% of guinea pigs inoculated with 109 CFU of p3D-NT56/S. cho and challenged 36 h later with 50 ID50 of homologous FMDV were protected. We also measured the antiviral activity of p3D-NT56/S. cho in swine. The results indicate that 100% of the animals treated with 5 × 109 CFU of p3D-NT56/S. cho were protected in 9 days