Ground-state properties of weakly bound helium-alkali trimers

Weakly bound triatomic molecules consisting of two helium atoms and one alkali metal atom are studied by means of the diffusion Monte Carlo method. We determined the stability of 4He2A, 4He3HeA, and 3He2A, where A is one of the alkali atoms Li, Na, K, Rb, or Cs. Some of the trimers with 3He are predicted to be self-bound for the first time, but this is observed to be dependent on the He–A interaction potential model. In addition to the ground-state energy of the trimers, we determined their density, radial, and angular distributions. Many of them are spatially very extended, which qualifies them as quantum halo statesPostprint (author's final draft

Quantum Particles Constrained on Cylindrical Surfaces with Non-constant Diameter

We present a theoretical formulation of the one-electron problem constrained on the surface of a cylindrical tubule with varying diameter. Because of the cylindrical symmetry, we may reduce the problem to a one-dimensional equation for each angular momentum quantum number $m$ along the cylindrical axis. The geometrical properties of the surface determine the electronic structures through the geometry dependent term in the equation. Magnetic fields parallel to the axis can readily be incorporated. Our formulation is applied to simple examples such as the catenoid and the sinusoidal tubules. The existence of bound states as well as the band structures, which are induced geometrically, for these surfaces are shown. To show that the electronic structures can be altered significantly by applying a magnetic field, Aharonov-Bohm effects in these examples are demonstrated.Comment: 7 pages, 7 figures, submitted to J. Phys. Soc. Jp

Effective polyethylenimine-mediated gene transfer into human endothelial cells

Background The major advantage in choosing non‐viral vectors such as cationic polymers for in vitro and in vivo transfection is their higher biosafety than viral ones. Among the cationic polymers, polyethylenimines (PEIs) are promising molecules for gene delivery to a variety of cells. Efficient transfection of primary endothelial cells using PEIs could be regarded as an interesting strategy of treatment in some ischemic cardiovascular diseases. Methods Efficacies of a 22‐kDa linear PEI (L‐PEI) and its glucose‐grafted derivative (L‐PEI‐Glc4) were compared for gene transfer into human umbilical vein endothelial cells (HUVEC) using the reporter gene luciferase. Cells were incubated for 2, 4 and 24 h with PEI/DNA complexes made in 150 mM sodium chloride (NaCl) or in 5% glucose solution. Luciferase activity was measured 24 h after the onset of transfection. The effects of low (2%) and high (30%) concentrations of serum on transfection efficacy were assessed as well. We then studied the intracellular fate of the PEI/DNA complexes labelled with the DNA intercalator YOYO‐1 using flow cytometry analysis (FACS) and confocal microscopy. Results PEI/DNA complexes formed in NaCl led to a higher transfection efficacy than those made in glucose. The optimal formulation, depending on the incubation time and the presence of serum in the medium, was obtained using DNA complexed to L‐PEI‐Glc4 and incubated for 4 h with the cells. This condition led to 50% fluorescent cells after GFP transfection. A high serum concentration diminished the L‐PEI associated toxicity but decreased L‐PEI‐Glc4 transfection efficiency. FACS analysis using both vectors showed that almost 90% of the cells had internalized the DNA complexes. Confocal microscopic observations showed a fast attachment of the complexes to the cell surface followed by inclusion into vesicles that migrated to the perinuclear region. Conclusions In this work, we defined the optimal conditions for gene delivery in HUVEC. These conditions were obtained when using derivatives L‐PEI and L‐PEI‐Glc4 complexed with DNA in 150 mM NaCl and added to cells for 2 and 4 h, respectively. Cellular trafficking of the complexes suggested that cell entry was not a limiting factor for gene delivery using PEI. This study underlined the interest in PEIs as efficient vectors for gene transfer into human endothelial cells

Gauge field for edge state in graphene

By considering the continuous model for graphene, we analytically study a special gauge field for the edge state. The gauge field explains the properties of the edge state such as the existence only on the zigzag edge, the partial appearance in the $k$-space, and the energy position around the Fermi energy. It is demonstrated utilizing the gauge field that the edge state is robust for surface reconstruction, and the next nearest-neighbor interaction which breaks the particle-hole symmetry stabilizes the edge state.Comment: 9 pages, 5 figure

Antibacterial and cytotoxic activities of naphthoquinone pigments from Onosma visianii Clem

In this study, the antibacterial and cytotoxic activities of isolated compounds from the roots of Onosma visianii were investigated. By using different chromatographic techniques and appropriate spectroscopic methods, the seven naphthoquinones were described: deoxyshikonin (1), isobutyrylshikonin (2), α-methylbutyrylshikonin (3), acetylshikonin (4), ß-hydroxyisovalerylshikonin (5), 5,8-O-dimethyl isobutyrylshikonin (6) and 5,8-O-dimethyl deoxyshikonin (7). Among the tested compounds, 3 and 4 exhibited the highest antibacterial activities toward all tested bacterial species (MIC50 and MIC90 for gram positive bacteria: 6.40 µg/mL-12.79 µg/mL and 6.82 µg/mL-13.60 µg/mL, respectively; for gram negative bacteria: 4.27 µg/mL-8.53 µg/mL and 4.77 µg/mL-9.54 µg/mL, respectively). Also, naphthoquinones 3 and 4 exhibited strong cytotoxic activity against MDA-MB-231 cells (IC50 values 86.0 µg/mL and 80.2 µg/mL, respectively), while compounds 1, 3, 4 and 5 significantly decreased viability of HCT116 cells (IC50 values of 97.8 µg/mL, 15.2 µg/mL, 24.6 µg/mL and 30.9 µg/mL, respectively). Our results indicated that all tested naphthoquinone pigments are potential candidates for clinical uses as antibacterial and cytotoxic agents

Orbital Kondo effect in carbon nanotubes

Progress in the fabrication of nanometer-scale electronic devices is opening new opportunities to uncover the deepest aspects of the Kondo effect, one of the paradigmatic phenomena in the physics of strongly correlated electrons. Artificial single-impurity Kondo systems have been realized in various nanostructures, including semiconductor quantum dots, carbon nanotubes and individual molecules. The Kondo effect is usually regarded as a spin-related phenomenon, namely the coherent exchange of the spin between a localized state and a Fermi sea of electrons. In principle, however, the role of the spin could be replaced by other degrees of freedom, such as an orbital quantum number. Here we demonstrate that the unique electronic structure of carbon nanotubes enables the observation of a purely orbital Kondo effect. We use a magnetic field to tune spin-polarized states into orbital degeneracy and conclude that the orbital quantum number is conserved during tunneling. When orbital and spin degeneracies are simultaneously present, we observe a strongly enhanced Kondo effect, with a multiple splitting of the Kondo resonance at finite field and predicted to obey a so-called SU(4) symmetry.Comment: 26 pages, including 4+2 figure

Simulation of an SEIR infectious disease model on the dynamic contact network of conference attendees

The spread of infectious diseases crucially depends on the pattern of contacts among individuals. Knowledge of these patterns is thus essential to inform models and computational efforts. Few empirical studies are however available that provide estimates of the number and duration of contacts among social groups. Moreover, their space and time resolution are limited, so that data is not explicit at the person-to-person level, and the dynamical aspect of the contacts is disregarded. Here, we want to assess the role of data-driven dynamic contact patterns among individuals, and in particular of their temporal aspects, in shaping the spread of a simulated epidemic in the population. We consider high resolution data of face-to-face interactions between the attendees of a conference, obtained from the deployment of an infrastructure based on Radio Frequency Identification (RFID) devices that assess mutual face-to-face proximity. The spread of epidemics along these interactions is simulated through an SEIR model, using both the dynamical network of contacts defined by the collected data, and two aggregated versions of such network, in order to assess the role of the data temporal aspects. We show that, on the timescales considered, an aggregated network taking into account the daily duration of contacts is a good approximation to the full resolution network, whereas a homogeneous representation which retains only the topology of the contact network fails in reproducing the size of the epidemic. These results have important implications in understanding the level of detail needed to correctly inform computational models for the study and management of real epidemics

The impact of delays to admission from the emergency department on inpatient outcomes

<p>Abstract</p> <p>Background</p> <p>We sought to determine the impact of delays to admission from the Emergency Department (ED) on inpatient length of stay (LOS), and IP cost.</p> <p>Methods</p> <p>We conducted a retrospective analysis of 13,460 adult (≥ 18 yrs) ED visits between April 1 2006 and March 30 2007 at a tertiary care teaching hospital with two ED sites in which the mode of disposition was admission to ICU, surgery or inpatient wards. We defined ED Admission Delay as ED time to decision to admit > 12 hours. The primary outcomes were IP LOS, and total IP cost.</p> <p>Results</p> <p>Approximately 11.6% (n = 1558) of admitted patients experienced admission delay. In multivariate analysis we found that admission delay was associated with 12.4% longer IP LOS (95% CI 6.6% - 18.5%) and 11.0% greater total IP cost (6.0% - 16.4%). We estimated the cumulative impact of delay on all delayed patients as an additional 2,183 inpatient days and an increase in IP cost of $2,109,173 at the study institution.</p> <p>Conclusions</p> <p>Delays to admission from the ED are associated with increased IP LOS and IP cost. Improving patient flow through the ED may reduce hospital costs and improve quality of care. There may be a business case for investments to reduce emergency department admission delays.</p