A Killing Disease Epidemic Among Displaced Sudanese Population Identified as Visceral Leishmaniasis.

A fatal disease epidemic affected the Bentiu area in southern Sudan and led to a mass migration of the Nuer tribe searching for treatment. The initially available information revealed a high mortality rate due to a possible occurrence of tuberculosis, malaria, enteric fever or visceral leishmaniasis (VL). Serological screening of 53 of the most severely affected patients in an enzyme-linked immunosorbent assay (ELISA) or an improved direct agglutination test (DAT) revealed positivity for VL. In 39 of those patients, diagnosis was confirmed by identification of Leishmania donovani amastigotes in lymph node or bone-marrow aspirates. In a total of 2714 patients observed, 1195 (44.0%) had clinical symptoms suggesting VL: DAT positive titers (1:3200-greater than or equal to 1:12800) were obtained in 654 (24.1%), of whom 325 were confirmed parasitologically. Forty-two VL cases died before or during treatment, giving a mortality rate of 6.4%. Among the intercurrent infections diagnosed in the VL population (654), respiratory involvements (31.7%) and malaria (10.7%) were most prevalent. With the exception of four (0.6%), all other VL patients (509) responded readily to sodium stibogluconate. The factors initiating the outbreak are discussed. Malnutrition and nomadic movements to potential VL endemic areas appeared to be the most important. HIV infection as a possible predisposition seemed remote considering the clinical and epidemiological similarity to VL occurring in East Africa, adequate humoral response in DAT, and immediate positive response to specific anti-Leishmania chemotherapy

Quenching through Dirac and semi-Dirac points in optical Lattices: Kibble-Zurek scaling for anisotropic Quantum-Critical systems

We propose that Kibble-Zurek scaling can be studied in optical lattices by creating geometries that support, Dirac, Semi-Dirac and Quadratic Band Crossings. On a Honeycomb lattice with fermions, as a staggered on-site potential is varied through zero, the system crosses the gapless Dirac points, and we show that the density of defects created scales as $1/\tau$, where $\tau$ is the inverse rate of change of the potential, in agreement with the Kibble-Zurek relation. We generalize the result for a passage through a semi-Dirac point in $d$ dimensions, in which spectrum is linear in $m$ parallel directions and quadratic in rest of the perpendicular $(d-m)$ directions. We find that the defect density is given by $1 /{\tau^{m\nu_{||}z_{||}+(d-m)\nu_{\perp}z_{\perp}}}$ where $\nu_{||}, z_{||}$ and $\nu_{\perp},z_{\perp}$ are the dynamical exponents and the correlation length exponents along the parallel and perpendicular directions, respectively. The scaling relations are also generalized to the case of non-linear quenching

Adiabatic multicritical quantum quenches: Continuously varying exponents depending on the direction of quenching

We study adiabatic quantum quenches across a quantum multicritical point (MCP) using a quenching scheme that enables the system to hit the MCP along different paths. We show that the power-law scaling of the defect density with the rate of driving depends non-trivially on the path, i.e., the exponent varies continuously with the parameter $\alpha$ that defines the path, up to a critical value $\alpha= \alpha_c$; on the other hand for $\alpha \geq \alpha_c$, the scaling exponent saturates to a constant value. We show that dynamically generated and {\it path($\alpha$)-dependent} effective critical exponents associated with the quasicritical points lying close to the MCP (on the ferromagnetic side), where the energy-gap is minimum, lead to this continuously varying exponent. The scaling relations are established using the integrable transverse XY spin chain and generalized to a MCP associated with a $d$-dimensional quantum many-body systems (not reducible to two-level systems) using adiabatic perturbation theory. We also calculate the effective {\it path-dependent} dimensional shift $d_0(\alpha)$ (or the shift in center of the impulse region) that appears in the scaling relation for special paths lying entirely in the paramagnetic phase. Numerically obtained results are in good agreement with analytical predictions.Comment: 5 pages, 4 figure

Dynamics of an inhomogeneous quantum phase transition

We argue that in a second order quantum phase transition driven by an inhomogeneous quench density of quasiparticle excitations is suppressed when velocity at which a critical point propagates across a system falls below a threshold velocity equal to the Kibble-Zurek correlation length times the energy gap at freeze-out divided by $\hbar$. This general prediction is supported by an analytic solution in the quantum Ising chain. Our results suggest, in particular, that adiabatic quantum computers can be made more adiabatic when operated in an "inhomogeneous" way.Comment: 7 pages; version to appear in a special issue of New J. Phy

Quenching across quantum critical points: role of topological patterns

We introduce a one-dimensional version of the Kitaev model consisting of spins on a two-legged ladder and characterized by Z_2 invariants on the plaquettes of the ladder. We map the model to a fermionic system and identify the topological sectors associated with different Z_2 patterns in terms of fermion occupation numbers. Within these different sectors, we investigate the effect of a linear quench across a quantum critical point. We study the dominant behavior of the system by employing a Landau-Zener-type analysis of the effective Hamiltonian in the low-energy subspace for which the effective quenching can sometimes be non-linear. We show that the quenching leads to a residual energy which scales as a power of the quenching rate, and that the power depends on the topological sectors and their symmetry properties in a non-trivial way. This behavior is consistent with the general theory of quantum quenching, but with the correlation length exponent \nu being different in different sectors.Comment: 5 pages including 2 figures; this is the published versio

Model based kinematic & dynamic simulation of 6-DOF upper-limb rehabilitation robot

Globally, a large population is suffering from motor disabilities caused by acute lesions to brain nervous system. One example is stroke, which is the third largest killer in New Zealand and the United States. Traditional manual therapy usually requires cooperative and intensive efforts from therapists and patients. Robot-assisted upper-limb rehabilitation techniques have been actively researched in the past few decades. However, limitations still exist such as inappropriate robotic modelling, mechanical design or limited Range of Motion (ROM). This paper proposes a mathematical model for a 6-Degree of Freedom (DOF) Universal Robot to be used in a rehabilitation system. This study focuses on the kinematics and dynamic analysis by using the Denavit-Hartenberg (D-H) parameters method with coordinate transformation theory. In order to simplify the computation process, Kane equation method is introduced in this paper. Simulation results show that the proposed model is correct although the fluctuation is possible to be reduced further. It concludes that the mathematical model can provide an intuitive and effective environment for designing the rehabilitation robot and planning the clinical trials

Effective Spin Quantum Phases in Systems of Trapped Ions

A system of trapped ions under the action of off--resonant standing--waves can be used to simulate a variety of quantum spin models. In this work, we describe theoretically quantum phases that can be observed in the simplest realization of this idea: quantum Ising and XY models. Our numerical calculations with the Density Matrix Renormalization Group method show that experiments with ion traps should allow one to access general properties of quantum critical systems. On the other hand, ion trap quantum spin models show a few novel features due to the peculiarities of induced effective spin--spin interactions which lead to interesting effects like long--range quantum correlations and the coexistence of different spin phases.Comment: 11 pages, 13 figure

Model based kinematic & dynamic simulation of 6-DOF upper-limb rehabilitation robot

Globally, a large population is suffering from motor disabilities caused by acute lesions to brain nervous system. One example is stroke, which is the third largest killer in New Zealand and the United States. Traditional manual therapy usually requires cooperative and intensive efforts from therapists and patients. Robot-assisted upper-limb rehabilitation techniques have been actively researched in the past few decades. However, limitations still exist such as inappropriate robotic modelling, mechanical design or limited Range of Motion (ROM). This paper proposes a mathematical model for a 6-Degree of Freedom (DOF) Universal Robot to be used in a rehabilitation system. This study focuses on the kinematics and dynamic analysis by using the Denavit-Hartenberg (D-H) parameters method with coordinate transformation theory. In order to simplify the computation process, Kane equation method is introduced in this paper. Simulation results show that the proposed model is correct although the fluctuation is possible to be reduced further. It concludes that the mathematical model can provide an intuitive and effective environment for designing the rehabilitation robot and planning the clinical trials