Self-similar dynamics of bacterial chemotaxis

Colonies of bacteria grown on thin agar plate exhibit fractal patterns as a result of adaptation to their environments. The bacterial colony pattern formation is regulated crucially by chemotaxis, the movement of cells along a chemical concentration gradient. Here, the dynamics of pattern formation in bacterial colony is investigated theoretically through a continuum model that considers chemotaxis. In the case of the gradient sensed by the bacterium is nearly uniform, the bacterial colony patterns are self-similar, which they look the same at every scale. The scaling law of the bacterial colony growth has been revealed explicitly. Chemotaxis biases the movement of bacterial population in colony trend toward the chemical attractant. Moreover, the bacterial colonies evolve long time as the traveling wave with sharp front.Comment: 4 pages, 3 figures, accepted by Phys. Rev. E (Brief Report

Weak localization and spin splitting in inversion layers on p-type InAs

We report on the magnetoconductivity of quasi two-dimensional electron systems in inversion layers on p-type InAs single crystals. In low magnetic fields pronounced features of weak localization and antilocalization are observed. They are almost perfectly described by the theory of Iordanskii, Lyanda-Geller and Pikus. This allows us to determine the spin splitting and the Rashba parameter of the ground electric subband as a function of the electron density.Comment: Accepted for publication in Phys. Rev. B, 4 page

Conical Singular Solutions in (2+1)-Dimensional Gravity Employing the ADM Canonical Formalism

Topological solutions in the (2+1)-dimensional Einstein theory of gravity are studied within the ADM canonical formalism. It is found that a conical singularity appears in the closed de Sitter universe solution as a topological defect in the case of the Einstein theory with a cosmological constant. Quantum effects on the conical singularity are studied using the de Broglie-Bohm interpretation. Finite quantum tunneling effects are obtained for the closed de Sitter universe, while no quantum effects are obtained for an open universe.Comment: 15 pages, 3 figure

True polar wander driven by late-stage volcanism and the distribution of paleopolar deposits on Mars

The areal centroids of the youngest polar deposits on Mars are offset from those of adjacent paleopolar deposits by 5-10 degrees. We test the hypothesis that the offset is the result of true polar wander (TPW), the motion of the solid surface with respect to the spin axis, caused by a mass redistribution within or on the surface of Mars. In particular, we consider TPW driven by late-stage volcanism during the late Hesperian to Amazonian. There is observational and qualitative support for this hypothesis: in both North and South, observed offsets lie close to a great circle 90 degrees from Tharsis, as expected for polar wander after Tharsis formed. We calculate the magnitude and direction of TPW produced by mapped late-stage lavas for a range of lithospheric thicknesses, lava thicknesses, eruption histories, and prior polar wander events. If Tharsis formed close to the equator, the stabilizing effect of a fossil rotational bulge located close to the equator leads to predicted TPW of <2 degrees, too small to account for observed offsets. If, however, Tharsis formed far from the equator, late-stage TPW driven by low-latitude, late-stage volcanism would be 6-33 degrees, similar to that inferred from the location of paleopolar deposits. 4.4+/-1.3x10^19 kg of young erupted lava can account for the offset of the Dorsa Argentea Formation from the present-day south rotation pole. This mass is consistent with prior mapping-based estimates and would imply a mass release of CO2 by volcanic degassing similar to that in the atmosphere at the present time. The South Polar Layered Deposits are offset from the spin axis in the opposite sense to the other paleopolar deposits. This can be explained by an additional contribution from a plume beneath Elysium. We conclude with a list of observational tests of the TPW hypothesis.Comment: Accepted by Earth and Planetary Science Letters. 3 tables, 8 figure

The role of the phosphopantetheinyltransferase enzyme, PswP, in the biosynthesis of antimicrobial secondary metabolites by <em>Serratia marcescens </em>Db10

Phosphopantetheinyltransferase (PPTase) enzymes fulfil essential roles in primary and secondary metabolism in prokaryotes, archaea and eukaryotes. PPTase enzymes catalyse the essential modification of the carrier protein domain of fatty acid synthases, polyketide synthases (PKSs) and non-ribosomal peptide synthetases (NRPSs). In bacteria and fungi, NRPS and PKS enzymes are often responsible for the biosynthesis of secondary metabolites with clinically relevant properties; these secondary metabolites include a variety of antimicrobial peptides. We have previously shown that in the Gram-negative bacterium Serratia marcescens Db10, the PPTase enzyme PswP is essential for the biosynthesis of an NRPS-PKS dependent antibiotic called althiomycin. In this work we utilize bioinformatic analyses to classify PswP as belonging to the F/KES subfamily of Sfp type PPTases and to putatively identify additional NRPS substrates of PswP, in addition to the althiomycin NRPS-PKS, in Ser. marcescens Db10. We show that PswP is required for the production of three diffusible metabolites by this organism, each possessing antimicrobial activity against Staphylococcus aureus. Genetic analyses identify the three metabolites as althiomycin, serrawettin W2 and an as-yet-uncharacterized siderophore, which may be related to enterobactin. Our results highlight the use of an individual PPTase enzyme in multiple biosynthetic pathways, each contributing to the ability of Ser. marcescens to inhibit competitor bacteria by the production of antimicrobial secondary metabolites

Flat rotation curves in Chern-Simons modified gravity

We investigate the spacetime of a slowly rotating black hole in the Chern-Simons modified gravity. The long range feature of frame-dragging effect under the Chern-Simon gravity well explains the flat rotation curves of galaxies which is a central evidence of dark matter. Our solution provides a different scenario of rotating space from Goedel's solution.Comment: 4 pages, Accepted for publication in Phys. Rev.

Does care at a cardiac arrest centre improve outcome after out-of-hospital cardiac arrest? - A systematic review

Aim: To perform a systematic review to answer 'In adults with attempted resuscitation after non-traumatic cardiac arrest does care at a specialised cardiac arrest centre (CAC) compared to care in a healthcare facility not designated as a specialised cardiac arrest centre improve patient outcomes?' Methods: The PRISMA guidelines were followed. We searched bibliographic databases (Embase, MEDLINE and the Cochrane Library (CENTRAL)) from inception to 1st August 2018. Randomised controlled trials (RCTs) and non-randomised studies were eligible for inclusion. Two reviewers independently scrutinized studies for relevance, extracted data and assessed quality of studies. Risk of bias of studies and quality of evidence were assessed using ROBINS-I tool and GRADEpro respectively. Primary outcomes were survival to 30 days with favourable neurological outcomes and survival to hospital discharge with favourable neurological outcomes. Secondary outcomes were survival to 30 days, survival to hospital discharge and return of spontaneous circulation (ROSC) post-hospital arrival for patients with ongoing resuscitation. This systematic review was registered in PROSPERO (CRD 42018093369) Results: We included data from 17 observational studies on out-of-hospital cardiac arrest (OHCA) patients in meta-analyses. Overall, the certainty of evidence was very low. Pooling data from only adjusted analyses, care at CAC was not associated with increased likelihood of survival to 30 days with favourable neurological outcome (OR 2.92, 95% CI 0.68-12.48) and survival to 30 days (OR 2.14, 95% CI 0.73-6.29) compared to care at other hospitals. Whereas patients cared for at CACs had improved survival to hospital discharge with favourable neurological outcomes (OR 2.22, 95% CI 1.74-2.84) and survival to hospital discharge (OR 1.85, 95% CI 1.46-2.34). Conclusions: Very low certainty of evidence suggests that post-cardiac arrest care at CACs is associated with improved outcomes at hospital discharge. There remains a need for high quality data to fully elucidate the impact of CACs.Peer reviewe

Quantum transport theory for nanostructures with Rashba spin-orbital interaction

We report on a general theory for analyzing quantum transport through devices in the Metal-QD-Metal configuration where QD is a quantum dot or the device scattering region which contains Rashba spin-orbital and electron-electron interactions. The metal leads may or may not be ferromagnetic, they are assumed to weakly couple to the QD region. Our theory is formulated by second quantizing the Rashba spin-orbital interaction in spectral space (instead of real space), and quantum transport is then analyzed within the Keldysh nonequilibrium Green's function formalism. The Rashba interaction causes two main effects to the Hamiltonian: (i) it gives rise to an extra spin-dependent phase factor in the coupling matrix elements between the leads and the QD; (ii) it gives rise to an inter-level spin-flip term but forbids any intra-level spin-flips. Our formalism provides a starting point for analyzing many quantum transport issues where spin-orbital effects are important. As an example, we investigate transport properties of a Aharnov-Bohm ring in which a QD having Rashba spin-orbital and e-e interactions is located in one arm of the ring. A substantial spin-polarized conductance or current emerges in this device due to a combined effect of a magnetic flux and the Rashba interaction. The direction and strength of the spin-polarization are shown to be controllable by both the magnetic flux and a gate voltage.Comment: 12 pages, 8 figure

Impact of Dental Diseases on Quality-Adjusted Life Expectancy in US Adults

Comparing the burden of dental conditions to other health outcomes provides useful insight for public policy. We aimed to estimate quality-adjusted life expectancy (QALE) loss due to dental conditions in the US adult population. Social inequalities in QALE loss by dental conditions were also examined. Data from 3 cross-sectional waves of the National Health and Nutrition Examination Survey (NHANES waves 2001 to 2002, 2003 to 2004, and 2011 to 2012) were pooled and analyzed. The average age of study participants (n = 9,445) was 48.4 y. Disutility scores were derived from self-rated health and the numbers of physically unhealthy days, mentally unhealthy days, and days with activity limitation, employing a previously published algorithm. The associations between the disutility scores and the numbers of decayed teeth, missing teeth, and periodontitis were examined by multiple linear regression stratified by age groups (20–39, 40–59, and ≥60 y), adjusted for other covariates (age, sex, wave fixed effect, educational attainment, smoking, and diabetes). The QALE loss due to dental conditions at the age of 20 was estimated using life tables. Decayed and missing teeth, but not periodontitis, were associated with a larger disutility score. The coefficient for decayed teeth was larger among the older population, whereas that of missing teeth was smaller among them. The estimated QALE loss was 0.43 y (95% confidence interval [CI], 0.28–0.59), which reached 5.3% of QALE loss (8.15 y; 95% CI, 8.03–8.27) due to overall morbidity. There were clear social gradients in QALE loss by dental conditions across the life course, and people with high school or less education had 0.32 y larger QALE loss in total compared with people with college or more education. This study suggests that improvements in people’s dental health may yield substantial gains in population health and well-being. The necessity of more comprehensive public health strategies is highlighted