A framework for space-efficient string kernels

String kernels are typically used to compare genome-scale sequences whose length makes alignment impractical, yet their computation is based on data structures that are either space-inefficient, or incur large slowdowns. We show that a number of exact string kernels, like the $k$-mer kernel, the substrings kernels, a number of length-weighted kernels, the minimal absent words kernel, and kernels with Markovian corrections, can all be computed in $O(nd)$ time and in $o(n)$ bits of space in addition to the input, using just a $\mathtt{rangeDistinct}$ data structure on the Burrows-Wheeler transform of the input strings, which takes $O(d)$ time per element in its output. The same bounds hold for a number of measures of compositional complexity based on multiple value of $k$, like the $k$-mer profile and the $k$-th order empirical entropy, and for calibrating the value of $k$ using the data

Hydrogen Phases on the Surface of a Strongly Magnetized Neutron Star

The outermost layers of some neutron stars are likely to be dominated by hydrogen, as a result of fast gravitational settling of heavier elements. These layers directly mediate thermal radiation from the stars, and determine the characteristics of X-ray/EUV spectra. For a neutron star with surface temperature T\lo 10^6 K and magnetic field B\go 10^{12} G, various forms of hydrogen can be present in the envelope, including atom, poly-molecules, and condensed metal. We study the physical properties of different hydrogen phases on the surface of a strongly magnetized neutron star for a wide range of field strength $B$ and surface temperature $T$. Depending on the values of $B$ and $T$, the outer envelope can be either in a nondegenerate gaseous phase or in a degenerate metallic phase. For T\go 10^5 K and moderately strong magnetic field, B\lo 10^{13} G, the envelope is nondegenerate and the surface material gradually transforms into a degenerate Coulomb plasma as density increases. For higher field strength, $B>> 10^{13}$ G, there exists a first-order phase transition from the nondegenerate gaseous phase to the condensed metallic phase. The column density of saturated vapor above the metallic hydrogen decreases rapidly as the magnetic field increases or/and temperature decreases. Thus the thermal radiation can directly emerge from the degenerate metallic hydrogen surface. The characteristics of surface X-ray/EUV emission for different phases are discussed. A separate study concerning the possibility of magnetic field induced nuclear fusion of hydrogen on the neutron star surface is also presented.Comment: TeX, 35 pages including 6 postscript figures. To be published in Ap

Incidence of osteonecrosis after renal transplantation

The incidence of osteonecrosis was 24% in 248 patients who had received 262 kidney transplants 1971-1982. However, based only on patients at risk, i.e. alive with functioning transplants, the incidence at 1, 3 and 6 years was found to be 13, 27 and 36%; after six years no new cases were found. the relative increase in body-weight at 180 days was predictive as regards risk for osteonecrosis, while the cumulative dose of steroids was not. This suggests that individual sensitivity to steroids rather than the absolute cumulative dose is involved in the development of osteonecrosis

Unintended consequences of drug policies experienced by young drug users in contact with the criminal justice systems

The aim of this paper is to assess to what extent prohibitive drug policies hamper the management of drug problems from the perspective of young people who have experience with the criminal justice systems (CJS). Qualitative, in-depth interviews were carried out in six European countries (Austria, Denmark, Germany, Italy, Poland, and the UK) following a common interview guide to obtain comparative data on the life trajectories of drug experienced youth. Altogether 198 interviews with people aged 14–25 years were collected and analysed by national teams following a common coding book. Unintended consequences of drug policies for the individual and society were identified. Individual consequences included health consequences and traumatic experiences with law enforcement. Social consequences included those affecting social relations such as stigmatisation and those impacting on institutions, for example, focusing on drug use and neglecting other problems. This paper confirmed earlier research indicating unintended consequences of prohibitive drug policies but also added to the literature its cross-national perspective and use of young people narratives as a source of analyses. There are, however, policy measures available that may reduce the volume and range of unintended effects. Their implementation is crucial to reduce the array of unintended consequences of prohibitive drug policies

Spin-Dependent Cyclotron Decay Rates in Strong Magnetic Fields

Cyclotron decay and absorption rates have been well studied in the literature, focusing primarily on spectral, angular and polarization dependence. Astrophysical applications usually do not require retention of information on the electron spin state, and these are normally averaged in obtaining the requisite rates. In magnetic fields, higher order quantum processes such as Compton scattering become resonant at the cyclotron frequency and its harmonics, with the resonances being formally divergent. Such divergences are usually eliminated by accounting for the finite lifetimes of excited Landau states. This practice requires the use of spin-dependent cyclotron rates in order to obtain accurate determinations of process rates very near cyclotronic resonances, the phase space domain most relevant for certain applications to pulsar models. This paper develops previous results in the literature to obtain compact analytic expressions for cyclotron decay rates/widths in terms of a series of Legendre functions of the second kind; these expressions can be expediently used in astrophysical models. The rates are derived using two popular eigenstate formalisms, namely that due to Sokolov and Ternov, and that due to Johnson and Lippmann. These constitute two sets of eigenfunctions of the Dirac equation that diagonalize different operators, and accordingly yield different spin-dependent cyclotron rates. This paper illustrates the attractive Lorentz transformation characteristics of the Sokolov and Ternov formulation, which is another reason why it is preferable when electron spin information must be explicitly retained.Comment: 11 pages, 2 embedded figures, apjgalley format, To appear in The Astrophysical Journal, Vol 630, September 1, 2005 issu

A new measurement of K+(e4) decay and the s-wave pi-pi-scattering length a00

A sample of 400000 events from the decay K+->pi+pi-e+nu(e)(K(e4)) has been collected in experiment E865 at the Brookhaven AGS. The analysis of these data yields new measurements of the K(e4) branching ratio (4.11+-0.01+-0.11)*10**(-5)), the s-wave pi-pi scattering length a00=0.228+-0.012+-0.003, and the form factors F, G, and H of the hadronic current and their dependence on the invariant pi-pi mass

First observation of the decay K+ -> e+ nu mu+ mu-

Experiment 865 at the Brookhaven AGS has observed the decay K^+ -> e^+ nu mu^+ mu^-. The branching ratio extracted is (1.72 +/- 0.37(stat) +/- 0.17(syst) +/- 0.19(model)) x 10^{-8} where the third term in the error results from the use of a model to extrapolate into a kinematic region dominated by background.Comment: 4 pages, 6 figures, Revtex4. Correction to figure and minor text change

An Improved upper limit on the decay K^+ -> pi^+ mu^+ e^-

Based on results of a search for the lepton-family-number-violating decay $K^+ \to \pi^+\mu^+ e^-$ with data collected by experiment E865 at the Alternating Gradient Synchrotron of Brookhaven National Laboratory, we place an upper limit on the branching ratio at $2.1 \times 10^{-11}$ (90% C.L.). Combining the results with earlier E865 data and those of a previous experiment, E777, an upper limit on the branching ratio of $1.3 \times 10^{-11}$ (90% C.L.) is obtained.Comment: v2: 13 pages, submitted to the Phys. Rev. D v3: 13 pages, resubmitted to Phys. Rev. D (corrections include: a more detailed overview of the combined analysis of the available experimntal data

Methanol conversion on borocarbonitride catalysts: Identification and quantification of active sites

Borocarbonitrides (BCNs) have emerged as highly selective catalysts for the oxidative dehydrogenation (ODH) reaction. However, there is a lack of in-depth understanding of the catalytic mechanism over BCN catalysts due to the complexity of the surface oxygen functional groups. Here, BCN nanotubes with multiple active sites are synthesized for oxygen-assisted methanol conversion reaction. The catalyst shows a notable activity improvement for methanol conversion (29%) with excellent selectivity to formaldehyde (54%). Kinetic measurements indicate that carboxylic acid groups on BCN are responsible for the formation of dimethyl ether, while the redox catalysis to formaldehyde occurs on both ketonic carbonyl and boron hydroxyl (B-OH) sites. The ODH reaction pathway on the B-OH site is further revealed by in situ infrared, x-ray absorption spectra, and density functional theory. The present work provides physical-chemical insights into the functional mechanism of BCN catalysts, paving the way for further development of the underexplored nonmetallic catalytic systems