Shortening of the Short Refractory Periods in Short QT Syndrome.

BACKGROUND: Diagnosis of short QT syndrome (SQTS) remains difficult in case of borderline QT values as often found in normal populations. Whether some shortening of refractory periods (RP) may help in differentiating SQTS from normal subjects is unknown. METHODS AND RESULTS: Atrial and right ventricular RP at the apex and right ventricular outflow tract as determined during standard electrophysiological study were compared between 16 SQTS patients (QTc 324±24 ms) and 15 controls with similar clinical characteristics (QTc 417±32 ms). Atrial RP were significantly shorter in SQTS compared with controls at 600- and 500-ms basic cycle lengths. Baseline ventricular RP were significantly shorter in SQTS patients than in controls, both at the apex and right ventricular outflow tract and for any cycle length. Differences remained significant for RP of any subsequent extrastimulus at any cycle length and any pacing site. A cut-off value of baseline RP <200 ms at the right ventricular outflow tract either at 600- or 500-ms cycle length had a sensitivity of 86% and a specificity of 100% for the diagnosis of SQTS. CONCLUSIONS: Patients with SQTS have shorter ventricular RP than controls, both at baseline during various cycle lengths and after premature extrastimuli. A cut-off value of 200 ms at the right ventricular outflow tract during 600- and 500-ms basic cycle length may help in detecting true SQTS from normal subjects with borderline QT values

Postural adaptations to unilateral knee joint hypomobility induced by orthosis wear during gait initiation

Abstract Balance control and whole-body progression during gait initiation (GI) involve knee-joint mobility. Single knee-joint hypomobility often occurs with aging, orthopedics or neurological conditions. The goal of the present study was to investigate the capacity of the CNS to adapt GI organization to single knee-joint hypomobility induced by the wear of an orthosis. Twenty-seven healthy adults performed a GI series on a force-plate in the following conditions: without orthosis ("control"), with knee orthosis over the swing leg ("orth-swing") and with the orthosis over the contralateral stance leg ("orth-stance"). In orth-swing, amplitude of mediolateral anticipatory postural adjustments (APAs) and step width were larger, execution phase duration longer, and anteroposterior APAs smaller than in control. In orth-stance, mediolateral APAs duration was longer, step width larger, and amplitude of anteroposterior APAs smaller than in control. Consequently, step length and progression velocity (which relate to the "motor performance") were reduced whereas stability was enhanced compared to control. Vertical force impact at foot-contact did not change across conditions, despite a smaller step length in orthosis conditions compared to control. These results show that the application of a local mechanical constraint induced profound changes in the global GI organization, altering motor performance but ensuring greater stability

Bond-charge Interaction in the extended Hubbard chain

We study the effects of bond-charge interaction (or correlated hopping) on the properties of the extended ({\it i.e.,} with both on-site ($U$) and nearest-neighbor ($V$) repulsions) Hubbard model in one dimension at half-filling. Energy gaps and correlation functions are calculated by Lanczos diagonalization on finite systems. We find that, irrespective of the sign of the bond-charge interaction, $X$, the charge--density-wave (CDW) state is more robust than the spin--density-wave (SDW) state. A small bond-charge interaction term is enough to make the differences between the CDW and SDW correlation functions much less dramatic than when $X=0$. For $X=t$ and fixed $V<2t$ ($t$ is the uncorrelated hopping integral), there is an intermediate phase between a charge ordered phase and a phase corresponding to singly-occupied sites, the nature of which we clarify: it is characterized by a succession of critical points, each of which corresponding to a different density of doubly-occupied sites. We also find an unusual slowly decaying staggered spin-density correlation function, which is suggestive of some degree of ordering. No enhancement of pairing correlations was found for any $X$ in the range examined.Comment: 10 pages, 7 PostScript figures, RevTeX 3; to appear in Phys Rev

Bronchogenic cyst excision using a robotic laparoscopic transdiaphragmatic approach

AbstractWe describe one case of a bronchopulmonary foregut malformations (BPFM) excision using robotic technology in a pediatric patient. Traditionally, surgical resection is performed using a thoracotomy or video-assisted thoracic surgery. A 12-year-old girl with a previous medical history of cough was diagnosed with a left cystic paracardiac mass. Her operation employed a transdiaphragmatic approach to remove the mass. The postoperative course was uneventful, and she was discharged after four days. The subsequent pathology concluded that the mass was a bronchogenic cyst. To the best of our knowledge, this is the first report of transdiaphragmatic laparoscopic approach and first use of robotics-platform for BPFM excision by children. We elected to use this type of procedure to decrease the postoperative morbidity associated with the thoracic approach. The robotic technology permitted surgical resection with a similar efficiency as standard thoracic or laparoscopic procedures. We hypothesized that this technology would simplify some of the technical points, decreasing any postoperative complications

Mechanism of CDW-SDW Transition in One Dimension

The phase transition between charge- and spin-density-wave (CDW, SDW) phases is studied in the one-dimensional extended Hubbard model at half-filling. We discuss whether the transition can be described by the Gaussian and the spin-gap transitions under charge-spin separation, or by a direct CDW-SDW transition. We determine these phase boundaries by level crossings of excitation spectra which are identified according to discrete symmetries of wave functions. We conclude that the Gaussian and the spin-gap transitions take place separately from weak- to intermediate-coupling region. This means that the third phase exists between the CDW and the SDW states. Our results are also consistent with those of the strong-coupling perturbative expansion and of the direct evaluation of order parameters.Comment: 5 pages(REVTeX), 5 figures(EPS), 1 table, also available from http://wwwsoc.nacsis.ac.jp/jps/jpsj/1999/p68a/p68a42/p68a42h/p68a42h.htm

Evaluating the ecological realism of plant species distribution models with ecological indicator values

Species distribution models (SDMs) are routinely applied to assess current as well as future species distributions, for example to assess impacts of future environmental change on biodiversity or to underpin conservation planning. It has been repeatedly emphasized that SDMs should be evaluated based not only on their goodness of fit to the data, but also on the realism of the modelled ecological responses. However, possibilities for the latter are hampered by limited knowledge on the true responses as well as a lack of quantitative evaluation methods. Here we compared modelled niche optima obtained from European-scale SDMs of 1,476 terrestrial vascular plant species with empirical ecological indicator values indicating the preferences of plant species for key environmental conditions. For each plant species we first fitted an ensemble SDM including three modeling techniques (GLM, GAM and BRT) and extracted niche optima for climate, soil, land use and nitrogen deposition variables with a large explanatory power for the occurrence of that species. We then compared these SDM-derived niche optima with the ecological indicator values by means of bivariate correlation analysis. We found weak to moderate correlations in the expected direction between the SDM-derived niche optima and ecological indicator values. The strongest correlation occurred between the modelled optima for growing degree days and the ecological indicator values for temperature. Correlations were weaker for SDM-derived niche optima with a more distal relationship to ecological indicator values (notably precipitation and soil moisture). Further, correlations were consistently highest for BRT, followed by GLM and GAM. Our method gives insight into the ecological realism of modelled niche optima and projected core habitats and can be used to improve SDMs by making a more informed selection of environmental variables and modeling techniques

Self-Dual Bending Theory for Vesicles

We present a self-dual bending theory that may enable a better understanding of highly nonlinear global behavior observed in biological vesicles. Adopting this topological approach for spherical vesicles of revolution allows us to describe them as frustrated sine-Gordon kinks. Finally, to illustrate an application of our results, we consider a spherical vesicle globally distorted by two polar latex beads.Comment: 10 pages, 3 figures, LaTeX2e+IOPar

Tricritical Behavior in the Extended Hubbard Chains

Phase diagrams of the one-dimensional extended Hubbard model (including nearest-neighbor interaction $V$) at half- and quarter-filling are studied by observing level crossings of excitation spectra using the exact diagonalization. This method is based on the Tomonaga-Luttinger liquid theory including logarithmic corrections which stem from the renormalization of the Umklapp- and the backward-scattering effects. Using this approach, the phase boundaries are determined with high accuracy, and then the structure of the phase diagram is clarified. At half-filling, the phase diagram consists of two Berezinskii-Kosterlitz-Thouless (BKT) transition lines and one Gaussian transition line in the charge sector, and one spin-gap transition line. This structure reflects the U(1) $\otimes$ SU(2) symmetry of the electron system. Near the $U=2V$ line, the Gaussian and the spin-gap transitions take place independently from the weak- to the intermediate-coupling region, but these two transition lines are coupled in the strong-coupling region. This result demonstrates existence of a tricritical point and a bond-charge-density-wave (BCDW) phase between charge- and spin-density-wave (CDW, SDW) phases. To clarify this mechanism of the transition, we also investigate effect of a correlated hopping term which plays a role to enlarge BCDW and bond-spin-density-wave (BSDW) phases. At quarter-filling, a similar crossover phenomenon also takes place in the large-$V$ region involving spin-gap and BKT-type metal-insulator transitions.Comment: 18 pages(REVTeX), 17 figures(EPS(color)), 3 tables, Detailed paper of JPSJ 68 (1999) 3123 (cond-mat/9903227), see also cond-mat/000341

Ultra-flat wideband single-pump Raman-enhanced parametric amplification

We experimentally optimize a single pump fiber optical parametric amplifier in terms of gain spectral bandwidth and gain variation (GV). We find that optimal performance is achieved with the pump tuned to the zero-dispersion wavelength of dispersion stable highly nonlinear fiber (HNLF). We demonstrate further improvement of parametric gain bandwidth and GV by decreasing the HNLF length. We discover that Raman and parametric gain spectra produced by the same pump may be merged together to enhance overall gain bandwidth, while keeping GV low. Consequently, we report an ultra-flat gain of 9.6±0.5 dB over a range of 111 nm (12.8 THz) on one side of the pump. Additionally, we demonstrate amplification of a 60 Gbit/s QPSK signal tuned over a portion of the available bandwidth with OSNR penalty less than 1 dB for Q2 below 14 dB