15,176 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
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
Multi-Qubit Gates in Arrays Coupled by 'Always On' Interactions
Recently there has been interest in the idea of quantum computing without
control of the physical interactions between component qubits. This is highly
appealing since the 'switching' of such interactions is a principal difficulty
in creating real devices. It has been established that one can employ 'always
on' interactions in a one-dimensional Heisenberg chain, provided that one can
tune the Zeeman energies of the individual (pseudo-)spins. It is important to
generalize this scheme to higher dimensional networks, since a real device
would probably be of that kind. Such generalisations have been proposed, but
only at the severe cost that the efficiency of qubit storage must *fall*. Here
we propose the use of multi-qubit gates within such higher-dimensional arrays,
finding a novel three-qubit gate that can in fact increase the efficiency
beyond the linear model. Thus we are able to propose higher dimensional
networks that can constitute a better embodiment of the 'always on' concept - a
substantial step toward bringing this novel concept to full fruition.Comment: 20 pages in preprint format, inc. 3 figures. This version has fixed
typos and printer-friendly figures, and is to appear in NJ
Differential Interleukin-2 Transcription Kinetics Render Mouse but Not Human T Cells Vulnerable to Splicing Inhibition Early after Activation
T cells are nodal players in the adaptive immune response against pathogens and malignant cells. Alternative splicing plays a crucial role in T cell activation, which is analyzed mainly at later time points upon stimulation. Here we have discovered a 2-h time window early after stimulation where optimal splicing efficiency or, more generally, gene expression efficiency is crucial for successful T cell activation. Reducing the splicing efficiency at 4 to 6 h poststimulation significantly impaired murine T cell activation, which was dependent on the expression dynamics of the Egr1-Nab2-interleukin-2 (IL-2) pathway. This time window overlaps the time of peak IL-2 de novo transcription, which, we suggest, represents a permissive time window in which decreased splicing (or transcription) efficiency reduces mature IL-2 production, thereby hampering murine T cell activation. Notably, the distinct expression kinetics of the Egr1-Nab2-IL-2 pathway between mouse and human render human T cells refractory to this vulnerability. We propose that the rational temporal modulation of splicing or transcription during peak de novo expression of key effectors can be used to fine-tune stimulation-dependent biological outcomes. Our data also show that critical consideration is required when extrapolating mouse data to the human system in basic and translational research
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