Endogenous driving and synchronization in cardiac and uterine virtual tissues: bifurcations and local coupling

Cardiac and uterine muscle cells and tissue can be either autorhythmic or excitable. These behaviours exchange stability at bifurcations produced by changes in parameters, which if spatially localized can produce an ectopic pacemaking focus. The effects of these parameters on cell dynamics have been identified and quantified using continuation algorithms and by numerical solutions of virtual cells. The ability of a compact pacemaker to drive the surrounding excitable tissues depends on both the size of the pacemaker and the strength of electrotonic coupling between cells within, between, and outside the pacemaking region. We investigate an ectopic pacemaker surrounded by normal excitable tissue. Cell-cell coupling is simulated by the diffusion coefficient for voltage. For uniformly coupled tissues, the behaviour of the hybrid tissue can take one of the three forms: (i) the surrounding tissue electrotonically suppresses the pacemaker; (ii) depressed rate oscillatory activity in the pacemaker but no propagation; and (iii) pacemaker driving propagations into the excitable region. However, real tissues are heterogeneous with spatial changes in cell-cell coupling. In the gravid uterus during early pregnancy, cells are weakly coupled, with the cell-cell coupling increasing during late pregnancy, allowing synchronous contractions during labour. These effects are investigated for a caricature uterine tissue by allowing both excitability and diffusion coefficient to vary stochastically with space, and for cardiac tissues by spatial gradients in the diffusion coefficient.     

FGF-23 is associated with cardiac troponin T and mortality in hemodialysis patients

Fibroblast growth factor 23 (FGF-23) is elevated in patients with end-stage kidney disease and has been linked with mortality, vascular calcification, markers of bone turnover, and left ventricular hypertrophy. In this cohort study, we determined the correlates of FGF-23 (including cardiac troponin T [cTNT]) and determined its association with mortality over 3.5 years of follow-up in 103 prevalent hemodialysis patients. Mean age was 61.2 (15.5) and the mean dialysis vintage was 4.19 years (4.6). The median (interquartile range) FGF-23 was 1259 (491, 2885) RU/mL. Independent predictors (estimate standard error) of log-transformed FGF-23 concentrations included phosphorus (0.75 [0.237], P = 0.002) and cardiac troponin T (1.04 [0.41], P = 0.01). There were 57 deaths. In the fully adjusted model, the significant predictors of mortality included age and albumin. The independent association between FGF-23 and cTNT is a novel finding. Whether this relationship supports the possibility that a downstream effect of dysregulated phosphorous homeostasis may be enhanced cardiac remodeling requires further study.     

Correlation between the magnetic imaging of cobalt nanoconstrictions and their magnetoresistance response

Scanning transmission x-ray microscopy (STXM) and magnetoresistance (MR) measurements are used to investigate the magnetic behavior of a nanoconstriction joining two micrometric electrodes (a pad and a wire). The reversal of the magnetization under variable external static magnetic fields is imaged. By means of a detailed analysis of the STXM images at the nanocontact area, the MR is calculated, based on diffusive anisotropic-MR. This MR agrees well with that obtained from electrical transport measurements, allowing a direct correlation between the MR signal and the magnetic reversal of the system. The magnetization behavior depends on the sample thickness and constriction dimensions. In 40 nm-thick samples, with 20 × 175 nm(2) contact areas, the magnetization at the two sides of the constriction forms a net angle of 90°, with a progressive evolution of the magnetization structure between the electrodes during switching. The MR in those cases has a more peaked shape than with 20 nm-thick electrodes and 10 × 80 nm(2) contact areas, where the magnetization forms 180° between them, with a wide domain wall pinned at the constriction. As a consequence of this configuration, a plateau in the MR is observed for about 20 Oe.     

The spatial dimensions of neighbourhood: how older people define it

This paper seeks to develop our understanding of neighbourhood boundaries, as defined by older people. Using interview and mapping methods, research revealed the significance of three factors ? built-form pattern, spatial distribution of the social networks and personal attributes ? as contributing to how older people define their neighbourhood boundaries. Research findings highlighted discrepancies between residents’ perceived neighbourhood boundaries and the statistical unit used as the neighbourhood proxy in most neighbourhood-related research. The findings suggested that the statistical information about the neighbourhood effects on older people does not necessarily reflect the lived experience of older people in their perceived neighbourhood.     

A new critical heat flux correlation for vertical water flow through multiple thin rectangular channels

A critical heat flux (CHF) study of the vertical up-flow of water through multiple thin rectangular channels was conducted. Pressures varied from 89.8 to 115 kPa, inlet temperatures from 291 to 306 K, and mass fluxes from 9.5 to 39 kg m^?2 s^?1. Electrical resistance heaters embedded in aluminum provided a uniform heat flux. A more universal and robust CHF correlation based on the geometry of the Advanced Test Reactor at Idaho National Laboratory was developed. This new CHF correlation predicts 126 data points from this and three previous studies within an error of ±8.5% with a 95% confidence.     

Evaluation of a novel radiopacifiying agent on the physical properties of surgical spineplex<Superscript>®</Superscript>

Polymethlylmethacrylate (PMMA) is the most frequently used cement for percutaneous vertebroplasty and kyphoplasty. To aid visualisation during surgery cements are doped with radiopacifying agents such as Barium sulphate (Ba₂SO₄) or Zirconium Dioxide (ZiO₂). Mounting research suggests that these agents may impair the biocompatibility of the cements. However, incorporating an alternative radiopacifier agent with excellent biocompatibility would be a significant step forward. Bioactive radiopaque glasses incorporating elements such as strontium (Sr) and zinc (Zn), known to have beneficial and therapeutic effects on bone, are of great interest in this respect. In this study, the Ba₂SO₄ of the commercially available Spineplex^® was incrementally replaced with a radiopaque therapeutic glass composition. The resulting effects on cement setting time, peak isotherm, ultimate compressive strength, Young’s modulus (up to 30 days cement maturation) and radiopacity were evaluated. The substitution lead to an increase in cement setting time from 13.1 mins for Spineplex^® to 16.6–18.3 mins for the glass substituted cements. The peak exotherm during curing was reduced from 74°C for Spineplex^® to a minimum of 51°C for the fully substituted cement, indicating that reduced thermal necrosis in the in vivo setting is likely with these materials. Ultimate compressive strength and Young’s modulus of each formulation showed no significant deterioration due to the substitution. Finally, the radiopacity of the substituted cements were reduced by up to a maximum of 18% in comparison to the control. However, the experimental formulations still maintained radiopacity equivalent to several millimetres of aluminium. As such the substituted cements had substantial equivalence to the Spineplex^® control. In order to assess the clinical relevance of these findings further investigation is warranted.     

Criterion validity of the Holden Psychological Screening Inventory Social Symptomatology Scale in a prison sample.

The 36-item, self-report Holden Psychological Screening Inventory (HPSI; R. R. Holden, 1996) and the Psychopathy Checklist–Revised (PCL–R; R. D. Hare, 1991) were administered to 214 male, adult prison inmates in Canadian federal correctional facilities. The 12-item HPSI Social Symptomatology scale, a measure of antisocial behavior, demonstrated a large effect size in significantly differentiating between PCL–R-identified psychopaths and nonpsychopaths. HPSI scales not theoretically related to psychopathic behavior showed no such significant effects. Findings are interpreted as supporting the criterion validity of the Social Symptomatology scale and suggest that this brief, self-report screen has research and clinical merit. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Psychologists in medical schools: Comment.

Comments on the article by S. Williams and J. L. Kohout (see record 1999-10642-004) which presented data from a large survey of psychologists employed by medical schools and concluded that there is a growing marginalization of the psychologists' role in medical schools. The authors note that it is unfortunate that Williams and Kohout based their conclusions on limited evidence from their own survey and disregarded preexisting literature. The authors discuss methodological similarities and differences between their own survey conducted in 1994 and the survey of Williams and Kohout that have direct bearing on the interpretation of the results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)