Topologically protected subdiffusive transport in two-dimensional fermionic wires

The conductance at the band edges of one-dimensional fermionic wires, with $N$ sites, has been shown to have subdiffusive $(1/N^2)$ behavior. We investigate this issue in two-dimensional fermionic wires described by a hopping model on an $N_x\times N_y$ rectangular lattice comprised of vertical chains with a Hermitian intra-chain and inter-chain hopping matrices given by $H_0$ and $H_1$, respectively. We study particle transport using the non-equilibrium Green's function formalism, and show that the asymptotic behavior of the conductance, $T(\omega)$, at the Fermi level $\omega$, is controlled by the spectrum of a dimensionless matrix $A(\omega)=(-\omega+H_0)H_1^{-1}$. This gives three simple conditions on the spectrum of $A(\omega)$ for observing ballistic, subdiffusive, and exponentially decaying $T(\omega)$ with respect to $N_x$. We show that certain eigenvalues of $A(\omega)$ give rise to subdiffusive contributions in the conductance, and correspond to the band edges of the isolated wire. We demonstrate that the condition for observing the subdiffusive behavior can be satisfied if $A(\omega)$ has nontrivial topology. In that case, a transition from ballistic behavior to subdiffusive behavior of the conductance is observed as the hopping parameters are tuned within the topological regime. We argue that at the transition point, different behaviors of the conductance can arise as the trivial bulk bands of $A(\omega)$ also contribute subdiffusively. We illustrate our findings in a simple model by numerically computing the variation of the conductance with $N_x$. Our numerical results indicate a different subdiffusive behavior ($1/N_x^3$) of the conductance at the transition point. We find the numerical results in good agreement with the theoretical predictions.Comment: 12 pages and 6 figure

Quantized two terminal conductance, edge states and current patterns in an open geometry 2-dimensional Chern insulator

The quantization of the two terminal conductance in 2D topological systems is justified by the Landauer-Buttiker (LB) theory that assumes perfect point contacts between the leads and the sample. We examine this assumption in a microscopic model of a Chern insulator connected to leads, using the nonequilibrium Greens function formalism. We find that the currents are localized both in the leads and in the insulator and enter and exit the insulator only near the corners. The contact details do not matter and a perfect point contact is emergent, thus justifying the LB theory. The quantized two-terminal conductance shows interesting finite-size effects and dependence on system-reservoir coupling.Comment: 11 pages, 10 figure

Road traffic injuries in Rawalpindi city, Pakistan.

Data on road traffic accident (RTA) injuries and their outcome are scarce in Pakistan. This study assessed patterns of RTA injuries reported in Rawalpindi city using standard surveillance methods. All RTA injury patients presenting to emergency departments of 3 tertiary care facilities from July 2007 to June 2008 were included. RTA injuries (n = 19 828) accounted for 31.7% of all injuries. Among children aged 0-14 years females suffered twice as many RTA injuries as males (21.3% versus 11.4%), whereas this trend reversed for the age group 15-24 years (41.9% versus 21.7%). One-fifth of injuries were either fractures or concussion. Severity and outcome of injuries were worse for the age group 45 years and older. For every road traffic death in Rawalpindi city, 29 more people were hospitalized and 177 more received emergency department care. These results suggest the need for better RTA injury surveillance to identify preventive and control measures for the increasingly high road disease burden in this city

Yang-Lee Zeros of Certain Antiferromagnetic Models

We revisit the somewhat less studied problem of Yang-Lee zeros of the Ising antiferromagnet. For this purpose, we study two models, the nearest-neighbor model on a square lattice, and the more tractable mean-field model corresponding to infinite-ranged coupling between all sites. In the high-temperature limit, we show that the logarithm of the Yang-Lee zeros can be written as a series in half odd integer powers of the inverse temperature, $k$, with the leading term $\sim k^{1/2}$. This result is true in any dimension and for arbitrary lattices. We also show that the coefficients of the expansion satisfy simple identities (akin to sum rules) for the nearest-neighbor case. These new identities are verified numerically by computing the exact partition function for a 2D square lattice of size $16\times16$. For the mean-field model, we write down the partition function (termed the mean-field polynomials) for the ferromagnetic (FM) and antiferromagnetic (AFM) cases, and derive from them the mean-field equations. We analytically show that at high temperatures the zeros of the AFM mean-field polynomial scale as $\sim k^{1/2}$ as well. Using a simple numerical method, we find the roots lie on certain curves (the root curves), in the thermodynamic limit for the mean-field polynomials for the AFM case as well as for the FM one. Our results show a new root curve, that was not found earlier. Our results also clearly illustrate the phase transition expected for the FM and AFM cases, in the language of Yang-Lee zeros. Moreover, for the AFM case, we observe that the root curves separate two distinct phases of zero and non-zero complex staggered magnetization, and thus depict a complex phase boundary

Differences in Reporting of Violence and Deliberate Self Harm Related Injuries to Health and Police Authorities, Rawalpindi, Pakistan

Background: The aim of study was to assess differences in reporting of violence and deliberate self harm (DSH) related injuries to police and emergency department (ED) in an urban town of Pakistan. Methods/Principal Findings: Study setting was Rawalpindi city of 1.6 million inhabitants. Incidences of violence and DSH related injuries and deaths were estimated from record linkage of police and ED data. These were then compared to reported figures in both datasets. All persons reporting violence and DSH related injury to the police station, the public hospital\u27s ED, or both in Rawalpindi city from July 1, 2007 to June 30, 2008 were included. In Rawalpindi city, 1 016 intentional injury victims reported to police whereas 3 012 reported to ED. Comparing violence related fatality estimates (N = 56, 95% CI: 46–64), police reported 75.0% and ED reported 42.8% of them. Comparing violence related injury estimates (N = 7 990, 95% CI: 7 322–8 565), police reported 12.1% and ED reported 33.2% of them. Comparing DSH related fatality estimates (N = 17, 95% CI: 4–30), police reported 17.7% and ED reported 47.1% of them. Comparing DSH related injury estimates (N = 809, 95% CI: 101–1 516), police reported 0.5% and ED reported 39.9% of them. Conclusion: In Rawalpindi city, police records were more likely to be complete for violence related deaths as compared to injuries due to same mechanism. As compared to ED, police reported DSH related injuries and deaths far less than those due to other types of violence

Formation of chitosan nanoparticles to encapsulate krill oil (Euphausia superba) for application as a dietary supplement

Encapsulation of krill oil (KO), a rich source of eicosapentanoic (EPA) and docosahexanoic acid (DHA) was carried out in chitosan-TPP (tripolyphosphate) nanoparticles using a newly developed two-step process (i.e, formation of emulsion and later electrostatic interaction of chitosan with TPP). The encapsulation of KO in chitosan nanoparticles (CSNPs) was confirmed by using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Thermo gravimetric analysis (TGA) techniques. Loading capacity (LC) and encapsulation efficiency (EE) of the obtained particles were about 9 – 25 and 33 – 59 % respectively, when the initial KO content was in the ratio of 0.25 – 1.25 g/g of Chitosan. Bulk KO showed less protection to oxidation and showed more formation of hydroperoxides during first week as noted by FTIR. However, KO loaded CSNPs showed better prevention of KO towards oxidation with less hydroperoxide formation even after two weeks of storage at elevated temperature (45 oC). The obtained KO-loaded CSNPs were irregular in shape with an average particle diameter of < 130 nm as observed by SEM. The results obtained confirmed the suitability of the emulsion and later electrostatic interaction of CS with TPP for the formation of KO loaded CSNPs with greater EE & LC, which will enhance their usage in the Food and Pharmaceutical industrie

Medicinal plants with gastroprotective potential

Peptic ulcer disease (PUD) is a main source of morbidity and mortality worldwide. It is characterized by erosions in mucosal linings of stomach and duodenum. Non-steroidal anti-inflammatory drugs (NSAIDs) and Helicobacter pylori are mainly responsible for peptic ulcer disease. Histamine receptor blockers and proton pump inhibitors are most prominent therapies in the treatment of peptic ulcer. However, severe adverse effects of NSAIDs have been reported. Therefore, focus is now diverted towards herbal formulations of medicinal plants for the treatment of ulcer. Plants contain different phytoconstituents which are responsible for increasing defensive mechanisms of body against peptic ulcer. The current review focuses on the commonly used gastroprotective plants as antiulcer agents.