QUESTION:Does an advice and exercise program improve outcome for adults following distal radius fracture? DESIGN:Randomised trial with concealed allocation, assessor blinding, and intention-to-treat analysis. PARTICIPANTS:Fifty-six patients whose fracture had been managed with pins and/or cast. INTERVENTION:The experimental group received a physiotherapist-directed program of advice and exercises. The control group did not receive any physiotherapy intervention. OUTCOME MEASURES:The primary outcome was wrist extension (measured with a goniometer). Secondary outcomes were the other wrist ranges of motion (measured with a goniometer), grip strength (measured with a dynamometer), pain, and activity limitations (measured with questionnaires). These outcomes were measured initially, then three and six weeks later. Participants also rated their satisfaction with physiotherapy intervention at Week 6. RESULTS:No difference was found between groups for the primary outcome of wrist extension (mean difference 6 deg, 95% CI -3 to 14), nor for the secondary outcomes of other range of motion data and grip strength. The difference between groups for pain was -16 points out of 100 (95% CI -27 to -5) at Week 3, and -14 points (95% CI -25 to -3) points at Week 6, and for activity was -13 points out of 100 (95% CI -24 to -2) at Week 3; in favour of the experimental group. The experimental group was also more satisfied with the amount of physiotherapy intervention. CONCLUSION:An advice and exercise program provided some additional benefits over no intervention for adults following distal radius fracture.
An exact solution of the gravitational field equations is presented for a homogeneous flat Friedmann-Robertson-Walker universe filled with a causal bulk viscous fluid obeying the Zeldovich stiff equation of state and having bulk viscosity coefficient proportional to the fourth root of the energy density.
The aim of the present paper is to investigate some globally pathological features of a class of static planary symmetric exact solutions with a G6-group of motion, namely with g44 = –sinh2 (αz), by means of the null oblique geodesics and Penrose diagram. Finally, we derive general expressions for the Aµ(x, y, z)µ=1,3― components of the vector potential, satisfying the source-free Maxwell equations and the Lorentz condition, pointing out the influence of the global pathological properties on the behaviour of magnetostatic fields in such universes.
In the past five years numerous experimental studies of a wide variety of low disorder two-dimensional (2D) semiconductor systems have revealed an unexpectedly large decrease in the resistance as the temperature is lowered from T ~ 1 K, suggesting the existence of a 2D metal. Although numerous theories have been put forward to explain this metallic-like behaviour (which contradicts the expectations of one parameter scaling theory), its origins, and the question of whether it persists to T = 0, are still subjects of great debate. We present a detailed study of the influence of inversion symmetry on the B = 0 metallic behaviour in a low density GaAs hole gas close to the apparent two-dimensional metal—insulator transition. The strength of the metallic behaviour (determined by the size of the drop in resistance as T→ 0) is found to be almost independent of the electric field across the hole gas, and is predominantly determined by the magnitude of k F l at low temperatures (i.e. by the low temperature resistivity). These results suggest that the shape of the potential well and spin—orbit effects alone cannot account for the existence of metallic behaviour in low density, strongly interacting 2D systems.
The decays of a scalar particle, of either parity, into two photons or into two gravitons are evaluated. The effective interactions are of the form ? FF , ? FF ~ or ? RR ,? RR ~ ; in particular, the Higgs meson decay mode into gravitons is tiny and can be neglected.
There has been renewed interest in the physics of the so-called ‘crossover’ for current fluctuations in mesoscopic conductors, most recently involving the possibility of its appearance in the passage to the macroscopic limit. Shot noise is normally absent from solid-state conductors in the large, and its anomalous resurgence there has been ascribed to a rich interplay of drift, diffusion, and Coulomb screening. We demonstrate that essentially the same rise in shot noise occurs in a much less complex system: the Boltzmann—Drude—Lorentz model of a macroscopic, uniform gas of strictly non-interacting carriers. We conclude that the ‘anomalous crossover’ is a manifestation of simple kinetics. Poissonian carriers, if driven by a high enough field, cross the sample faster than any scattering time, thus fulfilling Schottky’s condition for ideal shot noise.
Variational ro–vibrational wave functions are calculated using an Eckart?Watson Hamiltonian, which has embedded an ab initio potential energy function. These wave functions,together with an ab initio dipole moment function,are employed to predict transition energies and absorption intensities. The radiative transition probability integrals are determined using a novel adaptation of the Harris–Engerholm–Gwinn integration scheme. The method and solution algorithm yields results in excellent agreement with previously determined experimental and theoretical electric dipole allowed transitions for the 1 A 1 ground state of H 2 O. The method has also been applied to the 1 A 1 states of the helide analogs of water, namely He 2 O 2+ and He 2 S 2+, in order to predict their ro–vibrational transition energies and absorption intensities, thereby facilitating their possible interstellar detection.
A numerical study of coupled to the dilaton field, static, spherically symmetric monopole solutions inspired by the Kaluza-Klein theory with large extra dimensions are presented. The generalized Prasad-Sommerfield solution is obtained. We show that monopole may have also the dilaton cloud configurations.
A scheme is presented for the generation of superpositions of two two-mode SU(2) coherent states of the motion for a trapped ion. In the scheme an ion is trapped in a two-dimensional isotropic harmonic potential and driven by two resonant laser beams. Under certain conditions, the motional two-mode SU(2) cat state can be generated after a conditional measurement on the internal state following the ion-laser interaction.
By describing strong interactions between hadrons via a relativistic supermultiplet scheme and regarding weak interactions as a perturbation thereof, we derive expressions for nonleptonic weak decay amplitudes in terms of constituent quark masses and CKM angles, with no other parameters. Application of this method leads to ΔI = dominance in some pseudoscalar meson decays if one scales down the couplings of heavy particles by M mass factors, in keeping with heavy quark theory expectations. However, certain B and D decay processes to kaons are badly predicted and point to substantial soft gluon renormalisation effects inW-quark interactions.
A nonlinear Schrödinger equation which governs the nonlinear interaction of the ion-acoustic wave with the quasistatic plasma slow response in a magnetised plasma is deduced. The magnetic field is assumed to be constant. It is observed that the coefficient of the nonlinear term in the derived nonlinear Schrödinger equation turns out to be complex, in contrast to the usual situation. The condition for modulational stability is derived and it is found to be somewhat different. In the final section such a condition is discussed graphically. Our NLS equation goes back to that of the unmagnetised case if wc is put to zero.
I give a brief review of the weak coupling theory of frictional drag of the coupled quantum well. I then present a theory of frictional drag based on the Kubo formalism that goes beyond weak coupling. Using the T-matrix approximation, I consider the Maki–Thompson contribution to the transconductivity and obtain a formal result for strong-coupling frictional drag in clean Fermi liquid systems. I discuss how the strong interlayer coupling could affect the temperature dependence of the drag transresistivity.
Based on the dielectric continuum model, we calculated the phonon assisted tunneling (PAT) current of general double barrier resonant tunneling structures (DBRTSs) including both symmetric and antisymmetric ones. The results indicate that the four higher frequency interface phonon modes (especially the one which peaks at either interface of the emitter barrier) dominate the PAT processes, which increase the valley current and decrease the PVR of the DBRTSs. We show that an asymmetric structure can lead to improved performance.
Comparative effects of elastic scattering by random surface inhomogeneities and bulk impurities are discussed for ultrathin quantised systems. A simple general surface collision operator is derived outside of the quantum resonance domain. Analytical and semi-analytical applications to corrugation-defined localisation and transport in various types of physical systems are presented.
Highly excited many-particle states in quantum systems (nuclei, atoms, quantum dots, spin systems, quantum computers) can be ``chaotic'' superpositions of mean-field basis states (Slater determinants, products of spin or qubit states). This is a result of the very high energy level density of many-body states which can be easily mixed by a residual interaction between particles. We consider the time dynamics of wave functions and increase of entropy in such chaotic systems. As an example we present the time evolution in a closed quantum computer. A time scale for the entropy S(t) increase is t_c =t_0/(n log_2{n}), where t_0 is the qubit ``lifetime'', n is the number of qubits, S(0)=0 and S(t_c)=1. At t << t_c the entropy is small: S= n t^2 J^2 log_2(1/t^2 J^2), where J is the inter-qubit interaction strength. At t > t_c the number of ``wrong'' states increases exponentially as 2^{S(t)} . Therefore, t_c may be interpreted as a maximal time for operation of a quantum computer, since at t > t_c one has to struggle against the second law of thermodynamics. At t >>t_c the system entropy approaches that for chaotic eigenstates.
The effect of a squeezed vacuum on the optical bistable and multistable behaviour of a system of N three-level atoms is investigated, where the quantum interference between the atomic transition paths is considered. It is shown that the squeezed vacuum can profoundly affect the output field of this system. A strong squeezed vacuum can lead to multistable behaviour, even in the case where the cooperation parameter C is so small that the input–output relationship curve is monotone in the absence of the squeezed vacuum. The optical multistability is most significant when the quantum interference is perfect. The bistability and multistability can be controlled by the squeezing photon number and the strength of the two-photon correlation.
This paper addresses sub-Poissonian electronic and photonic noise generation in semiconductor junctions. Recent theoretical and technical advances in the understanding and generation of quantum noise-suppressed ('quiet') light have emphasised the links between photonic and electronic shot noise. Shot-noise suppression and single electron-photon control through the operation of the collective and single-electron Coulomb blockade mechanisms are described.
We review recent theoretical investigations of shot-noise suppression in nondegenerate semiconductor structures surrounded by two contacts acting as thermal reservoirs. Calculations make use of an ensemble Monte Carlo simulator self-consistently coupled with a one-dimensional Poisson solver. By taking the doping of the injecting contacts and the applied voltage as variable parameters, the influence of elastic and inelastic scattering as well as of tunneling between heterostructures in the active region is investigated. In the case of a homogeneous structure at T = 300 K the transition from ballistic to diffusive transport regimes under different contact injecting statistics is analysed and discussed. Provided significant space-charge effects take place inside the active region, long-range Coulomb interaction is found to play an essential role in suppressing shot noise at applied voltages much higher than the thermal value. In the elastic diffusive regime, momentum space dimensionality is found to modify the suppression factor γ, which within numerical uncertainty takes values respectively of about ⅓, ½ and 0·7 in the 3D, 2D and 1D cases. In the inelastic diffusive regime, shot noise is suppressed to the thermal value. In the case of single and multiple barrier non-resonant heterostructures made by GaAs/AlGaAs at 77 K, the mechanism of suppression is identified in the carrier inhibition to come back to the emitter contact after having been reflected from a barrier. This condition is realised in the presence of strong inelastic scattering associated with emission of optical phonons. At increasing applied voltages for a two-barrier structure, shot noise is suppressed up to about a factor of 0·50 in close analogy with the corresponding resonant barrier-diode. For an increasing number of barriers, shot noise is found to be systematically suppressed to a more significant level by following approximately a 1/(N + 1) behaviour, N being the number of barriers. This mechanism of suppression is expected to conveniently improve the signal-to-noise ratio of these devices.
A generalised linear response theory is used to derive the dielectric function at arbitrary wave numbers k and frequencies w for interacting quantum systems. The connection to thermodynamic Green functions allows the systematic perturbative treatment going beyond RPA and treating local field corrections as well as the inclusion of collisions on the same footing. Emphasis will be on the demonstration of the formalism. Results will be presented for the three-dimensional as well as two-dimensional case of an interacting electron gas. In the long-wavelength limit, a Drude-type expression with frequency dependent relaxation time is given bridging the theories of dielectric function and electrical conductivity.
As electronic circuits get progressingly smaller to the nanometre scale, the quantum wave nature of the electrons starts to play a dominant role. It is thus possible for the devices to operate by controlling the phase of the quantum electron waves rather than the electron density as in present-day devices. This paper presents a highly accurate numerical method to treat quantum waveguides with arbitrarily complex geometry. Based on this model, a variety of quantum effects can be studied and quantified.
