20,177 research outputs found
The role of spinning electrons in paramagnetic phenomena
An attempt is made to explain paramagnetic phenomena without assuming the orientation of a molecule or ion in a magnetic field. Only the spin angular momentum is assumed to be responsible. A derivative of the Gurie-Langevin law and the magnetic moments of ions are given as a function of the number of electrons in an inner, incomplete shell. An explanation of Gerlach's experiments with iron and nickel vapors is attempted. An explanation of magnetomechanical experiments with ferromagne elements is given
Analysis of somatic mutations across the kinome reveals loss-of-function mutations in multiple cancer types
AbstractIn this study we use somatic cancer mutations to identify important functional residues within sets of related genes. We focus on protein kinases, a superfamily of phosphotransferases that share homologous sequences and structural motifs and have many connections to cancer. We develop several statistical tests for identifying Significantly Mutated Positions (SMPs), which are positions in an alignment with mutations that show signs of selection. We apply our methods to 21,917 mutations that map to the alignment of human kinases and identify 23 SMPs. SMPs occur throughout the alignment, with many in the important A-loop region, and others spread between the N and C lobes of the kinase domain. Since mutations are pooled across the superfamily, these positions may be important to many protein kinases. We select eleven mutations from these positions for functional validation. All eleven mutations cause a reduction or loss of function in the affected kinase. The tested mutations are from four genes, including two tumor suppressors (TGFBR1 and CHEK2) and two oncogenes (KDR and ERBB2). They also represent multiple cancer types, and include both recurrent and non-recurrent events. Many of these mutations warrant further investigation as potential cancer drivers.</jats:p
Quasilocal energy for rotating charged black hole solutions in general relativity and string theory
We explore the (non)-universality of Martinez's conjecture, originally
proposed for Kerr black holes, within and beyond general relativity. The
conjecture states that the Brown-York quasilocal energy at the outer horizon of
such a black hole reduces to twice its irreducible mass, or equivalently, to
\sqrt{A} /(2\sqrt{pi}), where `A' is its area. We first consider the charged
Kerr black hole. For such a spacetime, we calculate the quasilocal energy
within a two-surface of constant Boyer-Lindquist radius embedded in a constant
stationary-time slice. Keeping with Martinez's conjecture, at the outer horizon
this energy equals the irreducible mass. The energy is positive and
monotonically decreases to the ADM mass as the boundary-surface radius
diverges. Next we perform an analogous calculation for the quasilocal energy
for the Kerr-Sen spacetime, which corresponds to four-dimensional rotating
charged black hole solutions in heterotic string theory. The behavior of this
energy as a function of the boundary-surface radius is similar to the charged
Kerr case. However, we show that in this case it does not approach the
expression conjectured by Martinez at the horizon.Comment: 15 page
Double burden of malnutrition among urban Bengalee adolescent boys in Midnapore, West Bengal, India
Malnutrition is an important public health problem worldwide. Therefore a study was undertaken to assess the prevalence of adolescent thinness, overweight and obesity in Midnapore town, West Bengal, India. A total of 974 adolescent boys aged 10-18 years were selected following multistage cluster sampling method from three higher secondary schools. Data was collected using pretested questionnaire following standard technique. Presence of thinness was evaluated using the cut-off values of international survey as suggested by Cole et al (2007). While overweight and obesity was determine by using international cut-off values develop by Cole et al (2000) based on international surveys as recommended by IOTF. Overall the prevalence of thinness, overweight and obesity were 20.8%, 14.9% and 3.8%, respectively. This study developed age specific smooth BMI percentile values using LMS method. Moreover, the study also developed BMI cut-off values to define thinness, overweight and obesity. In conclusion, the present analyses indicated that the prevalence of adolescent undernutrition is still a major problem. In addition, there was also an emerging trend for overweight/obesity, thereby indicating a double burden of malnutrition as observed in other developing countries
Reproducing spin lattice models in strongly coupled atom-cavity systems
In an array of coupled cavities where the cavities are doped with an atomic
V-system, and the two excited levels couple to cavity photons of different
polarizations, we show how to construct various spin models employed in
characterizing phenomena in condensed matter physics, such as the spin-1/2
Ising, XX, Heisenberg, and XXZ models. The ability to construct networks of
arbitrary geometry also allows for the simulation of topological effects. By
tuning the number of excitations present, the dimension of the spin to be
simulated can be controlled, and mixtures of different spin types produced. The
facility of single-site addressing, the use of only the natural hopping photon
dynamics without external fields, and the recent experimental advances towards
strong coupling, makes the prospect of using these arrays as efficient quantum
simulators promising.Comment: 4 pages, 3 figures. v3: References adde
Bayesian Approach for Counting Experiment Statistics applied to a Neutrino Point Source Analysis
In this paper we present a model independent analysis method following
Bayesian statistics to analyse data from a generic counting experiment and
apply it to the search for neutrinos from point sources. We discuss a test
statistic defined following a Bayesian framework that will be used in the
search for a signal. In case no signal is found, we derive an upper limit
without the introduction of approximations. The Bayesian approach allows us to
obtain the full probability density function for both the background and the
signal rate. As such, we have direct access to any signal upper limit. The
upper limit derivation directly compares with a frequentist approach and is
robust in the case of low-counting observations. Furthermore, it allows also to
account for previous upper limits obtained by other analyses via the concept of
prior information without the need of the ad hoc application of trial factors.
To investigate the validity of the presented Bayesian approach, we have applied
this method to the public IceCube 40-string configuration data for 10 nearby
blazars and we have obtained a flux upper limit, which is in agreement with the
upper limits determined via a frequentist approach. Furthermore, the upper
limit obtained compares well with the previously published result of IceCube,
using the same data set.Comment: 15 pages, 7 figures, 1 tabl
- …
