IS THERE A CLASSICAL ANALOG OF A QUANTUM TIME-TRANSLATION MACHINE?

In a recent article [D. Suter, Phys. Rev. {\bf A 51}, 45 (1995)] Suter has claimed to present an optical implementation of the quantum time-translation machine which ``shows all the features that the general concept predicts and also allows, besides the quantum mechanical, a classical description.'' It is argued that the experiment proposed and performed by Suter does not have the features of the quantum time-translation machine and that the latter has no classical analog.Comment: 7 pages, LaTe

A new questionnaire for quick assessment of food tolerance after bariatric surgery.

BACKGROUND: Bariatric surgery is often associated with reduced food tolerance and sometimes frequent vomiting, which influence quality of life, but are not included in the overall evaluation of these procedures, notably the BAROS. Our aim was to develop a simple questionnaire to evaluate food tolerance during follow-up visits. METHODS: A one-page questionnaire including questions about overall satisfaction regarding quality of alimentation, timing of eating over the day, tolerance to several types of food, and frequency of vomiting/regurgitation was developed. A composite score was derived from this questionnaire, giving a score of 1 to 27. Validation was performed with a group of non-obese adults and a group of morbidly obese non-operated patients. Patients were administered the questionnaire at follow-up visits since January 1999. Data were collected prospectively. RESULTS: It takes 1-2 minutes to fill out the questionnaire. Food tolerance is worse in the morbidly obese population compared with non-obese adults (24.2 vs 25.2, P=0.004). Following Roux-en-Y gastric bypass, food tolerance is reduced after 3 months (21.2), but becomes comparable to that of the normal population and remains so at 1 year postoperatively. Following gastric banding, food tolerance is already significantly reduced after 3 months (22.3), and worsens continuously over time (19.03 after 7 years). In the gastric banding population, the decision to adjust the band is based at least partially on food tolerance, and the questionnaire proved helpful in that respect. CONCLUSIONS: Our new questionnaire proved very easy to use, and helpful in day-to-day practice, especially after gastric banding. It was also helpful in comparing food tolerance over time after surgery, and in comparing food tolerance between procedures. Evaluation of food tolerance should be part of the overall evaluation of the results after bariatric surgery

Serum antioxidants as predictors of the adult respiratory distress syndrome in septic patients

Adult respiratory distress syndrome (ARDS) can develop as a complication of various disorders, including sepsis, but it has not been possible to identify which of the patients at risk will develop this serious disorder. We have investigated the ability of six markers, measured sequentially in blood, to predict development of ARDS in 26 patients with sepsis. At the initial diagnosis of sepsis (6-24 h before the development of ARDS), serum manganese superoxide dismutase concentration and catalase activity were higher in the 6 patients who subsequently developed ARDS than in 20 patients who did not develop ARDS. These changes in antioxidant enzymes predicted the development of ARDS in septic patients with the same sensitivity, specificity, and efficiency as simultaneous assessments of serum lactate dehydrogenase activity and factor VIII concentration. By contrast, serum glutathione peroxidase activity and α1Pi-elastase complex concentration did not differ at the initial diagnosis of sepsis between patients who did and did not subsequently develop ARDS, and were not as effective in predicting the development of ARDS. Measurement of manganese superoxide dismutase and catalase, in addition to the other markers, should facilitate identification of patients at highest risk of ARDS and allow prospective treatment

Electron spin evolution induced by interaction with nuclei in a quantum dot

We study the decoherence of a single electron spin in an isolated quantum dot induced by hyperfine interaction with nuclei for times smaller than the nuclear spin relaxation time. The decay is caused by the spatial variation of the electron envelope wave function within the dot, leading to a non-uniform hyperfine coupling $A$. We show that the usual treatment of the problem based on the Markovian approximation is impossible because the correlation time for the nuclear magnetic field seen by the electron spin is itself determined by the flip-flop processes. The decay of the electron spin correlation function is not exponential but rather power (inverse logarithm) law-like. For polarized nuclei we find an exact solution and show that the precession amplitude and the decay behavior can be tuned by the magnetic field. The decay time is given by $\hbar N/A$, where $N$ is the number of nuclei inside the dot. The amplitude of precession, reached as a result of the decay, is finite. We show that there is a striking difference between the decoherence time for a single dot and the dephasing time for an ensemble of dots.Comment: Revtex, 11 pages, 5 figure

Laparoscopic gastric banding.

INTRODUCTION: Laparoscopic gastric banding (LGB) is currently the most popular purely restrictive bariatric operation in Europe and many other countries. It has a low operative morbidity, but is associated with a substantial late complication rate. Many late complications have been attributed to technical errors or to the learning curve. The aim of this paper is to present our results with gastric banding after the learning curve in order to disclose the true incidence of long-term complications. METHODS: LGB was introduced in our department in December 1995. Thirty patients were operated on until June 1997 using the early banding technique (band within the lesser sac), at which time the surgical technique was slightly modified in order to place the band above the lesser sac. Then another 300 patients underwent LGB using either the Lapband or the SAGB system. This report focuses on the latter patients. All the data were collected prospectively. RESULTS: The series includes 300 patients (257 women and 43 men) with a mean age of 38.3 years (19-64). The mean initial weight was 119.2 kg (57-179), initial body mass index (BMI) was 43.3 kg/m2 (21-64), and initial excess weight was 96.5% (0-191). The mean duration of surgery was 90 min, decreasing over time to a mean of 75 min for the last 50 cases. Early overall morbidity was 6.6%. Major complications occurred in 7 patients (2.3%). Excess weight loss (EWL) was at least 50% in 66% of the patients after 2 years, averaging 60%, with no substantial change until 4 years, and the BMI stabilized between 30 and 31 kg/m2. Forty-nine patients developed a total of 52 long-term complications, of which 23 (7.6%) were related only to the port or catheter. Band erosion occurred in 17 (5.6%), pouch dilatation with slippage in 8 (2.6%), and infection in 4 (1.3%) patients. Fifty-five reoperations were necessary. Twenty-five of these were related only to the port. The band was removed from 26 (9%) patients, of whom 17 were converted to Roux-en-Y gastric bypass. CONCLUSIONS: LGB gives satisfactory results in terms of weight loss in about two-thirds of the patients. Even beyond the learning curve, the long-term morbidity is not negligible, but is acceptable compared to other procedures such as vertical banded gastroplasty. Conversion to gastric bypass is possible when complications occur and can be performed when the band is removed in most cases

Paramagnetic Faraday rotation with spin-polarized ytterbium atoms

We report observation of the paramagnetic Faraday rotation of spin-polarized ytterbium (Yb) atoms. As the atomic samples, we used an atomic beam, released atoms from a magneto-optical trap (MOT), and trapped atoms in a far-off-resonant trap (FORT). Since Yb is diamagnetic and includes a spin-1/2 isotope, it is an ideal sample for the spin physics, such as quantum non-demolition measurement of spin (spin QND), for example. From the results of the rotation angle, we confirmed that the atoms were almost perfectly polarized.Comment: 8 pages, 20 figure

Essential and distinct roles for cdc42 and rac1 in the regulation of Schwann cell biology during peripheral nervous system development

During peripheral nervous system (PNS) myelination, Schwann cells must interpret extracellular cues to sense their environment and regulate their intrinsic developmental program accordingly. The pathways and mechanisms involved in this process are only partially understood. We use tissue-specific conditional gene targeting to show that members of the Rho GTPases, cdc42 and rac1, have different and essential roles in axon sorting by Schwann cells. Our results indicate that although cdc42 is required for normal Schwann cell proliferation, rac1 regulates Schwann cell process extension and stabilization, allowing efficient radial sorting of axon bundles

Influence of incommensurate dynamic charge-density wave scattering on the line shape of high-Tc_c cuprates

We show that the spectral lineshape of superconducting La$_{2-x}$Sr$_x$CuO$_4$ (LSCO) and Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (Bi2212) can be well described by the coupling of the charge carriers to collective incommensurate charge-density wave (CDW) excitations. Our results imply that besides antiferromagnetic (AF) fluctuations also low-energy CDW modes can contribute to the observed dip-hump structure in the Bi2212 photoemission spectra. In case of underdoped LSCO we propose a possible interpretation of ARPES data in terms of a grid pattern of fluctuating stripes where the charge and spin scattering directions deviate by $\alpha=\pi/4$. Within this scenario we find that the spectral intensity along $(0,0) \to (\pi,\pi)$ is strongly suppressed consistent with recent photoemission experiments. In addition the incommensurate charge-density wave scattering leads to a significant broadening of the quasiparticle-peak around $(\pi,0)$.Comment: 5 pages, 4 figure

Limits on anomalous trilinear gauge boson couplings from WW, WZ and Wgamma production in pp-bar collisions at sqrt{s}=1.96 TeV

We present final searches of the anomalous gammaWW and ZWW trilinear gauge boson couplings from WW and WZ production using lepton plus dijet final states and a combination with results from Wgamma, WW, and WZ production with leptonic final states. The analyzed data correspond to up to 8.6/fb of integrated luminosity collected by the D0 detector in pp-bar collisions at sqrt{s}=1.96 TeV. We set the most stringent limits at a hadron collider to date assuming two different relations between the anomalous coupling parameters Delta\kappa_\gamma, lambda, and Delta g_1^Z for a cutoff energy scale Lambda=2 TeV. The combined 68% C.L. limits are -0.057<Delta\kappa_\gamma<0.154, -0.015<lambda<0.028, and -0.008<Delta g_1^Z<0.054 for the LEP parameterization, and -0.007<Delta\kappa<0.081 and -0.017<lambda<0.028 for the equal couplings parameterization. We also present the most stringent limits of the W boson magnetic dipole and electric quadrupole moments.Comment: 10 pages, 5 figures, submitted to PL

Search for Higgs bosons decaying to tautau pairs in ppbar collisions at sqrt(s) = 1.96 TeV

We present a search for the production of neutral Higgs bosons decaying into tautau pairs in ppbar collisions at a center-of-mass energy of 1.96 TeV. The data, corresponding to an integrated luminosity of 5.4 fb-1, were collected by the D0 experiment at the Fermilab Tevatron Collider. We set upper limits at the 95% C.L. on the product of production cross section and branching ratio for a scalar resonance decaying into tautau pairs, and we then interpret these limits as limits on the production of Higgs bosons in the minimal supersymmetric standard model (MSSM) and as constraints in the MSSM parameter space.Comment: 7 pages, 5 figures, submitted to PL