Ultrasound imaging of the carpal tunnel during median nerve compression

Median nerve (MN) compression is a recognized component of carpal tunnel syndrome (CTS). In order to document compressive changes in the MN during hand activity, the carpal tunnel was imaged with neuromuscular ultrasound (NMUS). Ten patients with CTS and five normal controls underwent NMUS of the MN at rest and during dynamic stress testing (DST). DST maneuvers involve sustained isometric flexion of the distal phalanges of the first three digits. During DST in the CTS patients, NMUS demonstrated MN compression between the contracting thenar muscles ventrally and the taut flexor tendons dorsally. The mean MN diameter decreased nearly 40%, with focal narrowing in the mid-distal carpal canal. Normal controls demonstrated no MN compression and a tendency towards MN enlargement, with an average diameter increase of 17%. Observing the pathologic mechanism of MN injury during common prehensile hand movements could help better understand how to treat and prevent CTS

Long Range Forces from Pseudoscalar Exchange

Using dispersion theoretic techniques, we consider coherent long range forces arising from double pseudoscalar exchange among fermions. We find that Yukawa type coupling leads to $1/r^3$ spin independent attractive potentials whereas derivative coupling renders $1/r^5$ spin independent repulsive potentials.Comment: 27 pages, REVTeX, 3 figures included using epsfi

Relativistic and QED corrections to the 2pσu(υ=1)2p\sigma_{u}(\upsilon = 1) vibrational state of the H2+H^{+}_{2} molecular ion

Relativistic and QED corrections to the recently discovered first vibrational $2p\sigma_u$ state are presented. This state has an extremely small nonrelativistic binding energy $E_B=1.085045252(1)\times10^{-9}$ a.u. Its wave functions has a maximum at $R\approx100$ a.u. and extends up to several hundreds. It is shown that this state does not disappear if higher order relativistic and QED corrections, including the Casimir--Polder effect, are taken into account

Constraints on Light Pseudoscalars Implied by Tests of the Gravitational Inverse-Square Law

The exchange of light pseudoscalars between fermions leads to a spin-independent potential in order g^4, where g is the Yukawa pseudoscalar-fermion coupling constant. This potential gives rise to detectable violations of both the weak equivalence principle (WEP) and the gravitational inverse-square law (ISL), even if g is quite small. We show that when previously derived WEP constraints are combined with those arisingfrom ISL tests, a direct experimental limit on the Yukawa coupling of light pseudoscalars to neutrons can be inferred for the first time (g_n^2/4pi < 1.6 \times 10^-7), along with a new (and significantly improved) limit on the coupling of light pseudoscalars to protons.Comment: 12 pages, Revtex, with 1 Postscript figure (submitted to Physical Review Letters

How to obtain a covariant Breit type equation from relativistic Constraint Theory

It is shown that, by an appropriate modification of the structure of the interaction potential, the Breit equation can be incorporated into a set of two compatible manifestly covariant wave equations, derived from the general rules of Constraint Theory. The complementary equation to the covariant Breit type equation determines the evolution law in the relative time variable. The interaction potential can be systematically calculated in perturbation theory from Feynman diagrams. The normalization condition of the Breit wave function is determined. The wave equation is reduced, for general classes of potential, to a single Pauli-Schr\"odinger type equation. As an application of the covariant Breit type equation, we exhibit massless pseudoscalar bound state solutions, corresponding to a particular class of confining potentials.Comment: 20 pages, Late

Quantum Electrodynamics of the Helium Atom

Using singlet S states of the helium atom as an example, I describe precise calculation of energy levels in few-electron atoms. In particular, a complete set of effective operators is derived which generates O(m*alpha^6) relativistic and radiative corrections to the Schr"odinger energy. Average values of these operators can be calculated using a variational Schr"odinger wave function.Comment: 23 pages, revte

The Standard Model in Strong Fields: Electroweak Radiative Corrections for Highly Charged Ions

Electroweak radiative corrections to the matrix elements $<ns_{1/2}|{\hat H}_{PNC}|n'p_{1/2}>$ are calculated for highly charged hydrogenlike ions. These matrix elements constitute the basis for the description of the most parity nonconserving (PNC) processes in atomic physics. The operator ${\hat H}_{PNC}$ represents the parity nonconserving relativistic effective atomic Hamiltonian at the tree level. The deviation of these calculations from the calculations valid for the momentum transfer $q^{2}=0$ demonstrates the effect of the strong field, characterized by the momentum transfer $q^{2}=m_{e}^{2}$ ($m_{e}$ is the electron mass). This allows for a test of the Standard Model in the presence of strong fields in experiments with highly charged ions.Comment: 27 LaTex page

The Schroedinger Problem, Levy Processes Noise in Relativistic Quantum Mechanics

The main purpose of the paper is an essentially probabilistic analysis of relativistic quantum mechanics. It is based on the assumption that whenever probability distributions arise, there exists a stochastic process that is either responsible for temporal evolution of a given measure or preserves the measure in the stationary case. Our departure point is the so-called Schr\"{o}dinger problem of probabilistic evolution, which provides for a unique Markov stochastic interpolation between any given pair of boundary probability densities for a process covering a fixed, finite duration of time, provided we have decided a priori what kind of primordial dynamical semigroup transition mechanism is involved. In the nonrelativistic theory, including quantum mechanics, Feyman-Kac-like kernels are the building blocks for suitable transition probability densities of the process. In the standard "free" case (Feynman-Kac potential equal to zero) the familiar Wiener noise is recovered. In the framework of the Schr\"{o}dinger problem, the "free noise" can also be extended to any infinitely divisible probability law, as covered by the L\'{e}vy-Khintchine formula. Since the relativistic Hamiltonians $|\nabla |$ and $\sqrt {-\triangle +m^2}-m$ are known to generate such laws, we focus on them for the analysis of probabilistic phenomena, which are shown to be associated with the relativistic wave (D'Alembert) and matter-wave (Klein-Gordon) equations, respectively. We show that such stochastic processes exist and are spatial jump processes. In general, in the presence of external potentials, they do not share the Markov property, except for stationary situations. A concrete example of the pseudodifferential Cauchy-Schr\"{o}dinger evolution is analyzed in detail. The relativistic covariance of related waveComment: Latex fil

Block of NMDA receptor channels by endogenous neurosteroids: implications for the agonist induced conformational states of the channel vestibule

N-methyl-D-aspartate receptors (NMDARs) mediate synaptic plasticity, and their dysfunction is implicated in multiple brain disorders. NMDARs can be allosterically modulated by numerous compounds, including endogenous neurosteroid pregnanolone sulfate. Here, we identify the molecular basis of the use-dependent and voltage-independent inhibitory effect of neurosteroids on NMDAR responses. The site of action is located at the extracellular vestibule of the receptor's ion channel pore and is accessible after receptor activation. Mutations in the extracellular vestibule in the SYTANLAAF motif disrupt the inhibitory effect of negatively charged steroids. In contrast, positively charged steroids inhibit mutated NMDAR responses in a voltage-dependent manner. These results, in combination with molecular modeling, characterize structure details of the open configuration of the NMDAR channel. Our results provide a unique opportunity for the development of new therapeutic neurosteroid-based ligands to treat diseases associated with dysfunction of the glutamate system

Relativistic Calculation of two-Electron one-Photon and Hypersatellite Transition Energies for 12≤Z≤3012\leq Z\leq30 Elements

Energies of two-electron one-photon transitions from initial double K-hole states were computed using the Dirac-Fock model. The transition energies of competing processes, the K$\alpha$ hypersatellites, were also computed. The results are compared to experiment and to other theoretical calculations.Comment: accepted versio