Intrinsic ripples in graphene

The stability of two-dimensional (2D) layers and membranes is subject of a long standing theoretical debate. According to the so called Mermin-Wagner theorem, long wavelength fluctuations destroy the long-range order for 2D crystals. Similarly, 2D membranes embedded in a 3D space have a tendency to be crumpled. These dangerous fluctuations can, however, be suppressed by anharmonic coupling between bending and stretching modes making that a two-dimensional membrane can exist but should present strong height fluctuations. The discovery of graphene, the first truly 2D crystal and the recent experimental observation of ripples in freely hanging graphene makes these issues especially important. Beside the academic interest, understanding the mechanisms of stability of graphene is crucial for understanding electronic transport in this material that is attracting so much interest for its unusual Dirac spectrum and electronic properties. Here we address the nature of these height fluctuations by means of straightforward atomistic Monte Carlo simulations based on a very accurate many-body interatomic potential for carbon. We find that ripples spontaneously appear due to thermal fluctuations with a size distribution peaked around 70 \AA which is compatible with experimental findings (50-100 \AA) but not with the current understanding of stability of flexible membranes. This unexpected result seems to be due to the multiplicity of chemical bonding in carbon.Comment: 14 pages, 6 figure

Does the risk of cerebral palsy increase or decrease with increasing gestational age?

BACKGROUND: It is generally accepted that the risk of cerebral palsy decreases with increasing gestational age of live born infants. However, recent studies have shown that cerebral palsy often has prenatal antecedents including congenital malformations, vascular insults and maternal infection. Cerebral palsy is therefore better viewed as occurring among fetuses, rather than among infants. We explored the epidemiologic implications of this change in perspective. METHODS: We used recently published data from Shiga Prefecture, Japan and from North-East England to examine the pattern of gestational age-specific rates of cerebral palsy under these alternative perspectives. We first calculated gestational age-specific rates of cerebral palsy as per convention, by dividing the number of cases of cerebral palsy identified among live births within any gestational age category by the number of live births in that gestational age category. Under the alternative formulation, we calculated gestational age-specific rates of cerebral palsy by dividing the number of cases of cerebral palsy identified among live births within any gestational age category by the number of fetuses who were at risk of being born at that gestation and being afflicted with cerebral palsy. RESULTS: Under the conventional formulation, cerebral palsy rates decreased with increasing gestational age from 63.9 per 1,000 live births at <28 weeks gestation to 0.9 per 1,000 live births at 37 or more weeks gestation. When fetuses were viewed as potential candidates for cerebral palsy, cerebral palsy rates increased with increasing gestational age from 0.08 per 1,000 fetuses at risk at <28 weeks gestation to 0.9 per 1,000 fetuses at risk at 37 or more weeks gestation. CONCLUSIONS: The fetuses-at-risk approach is the appropriate epidemiologic formulation for calculating the gestational age-specific rate of cerebral palsy from a causal perspective. It shows that the risk of cerebral palsy increases as gestational duration increases. This compelling view of cerebral palsy risk may help refocus research aimed at understanding and preventing cerebral palsy

Quality of Life Changes Following Peripheral Blood Stem Cell Transplantation and Participation in a Mixed-Type, Moderate-intensity, Exercise Program

Summary:The purpose of this investigation was to evaluate the impact of undertaking peripheral blood stem cell transplantation (PBST) on quality of life (QoL), and to determine the effect of participating in a mixed-type, moderate-intensity exercise program on QoL. It was also an objective to determine the relationship between peak aerobic capacity and QoL in PBST patients. QoL was assessed via the CARES questionnaire and peak aerobic capacity by a maximal graded treadmill test, pretransplant (PI), post transplant (PII) and following a 12-week intervention period (PIII). At PII, 12 patients were divided equally into a control or exercise intervention group. Undergoing a PBST was associated with a statistically but not clinically significant decline in QoL (P<0.05). Following the intervention, exercising patients demonstrated an improved QoL when compared with pretransplant ratings (P<0.01) and nonexercising transplant patients (P<0.05). Moreover, peak aerobic capacity and QoL were correlated (P<0.05). The findings demonstrated that exercise participation following oncology treatment is associated with a reduction in the number and severity of endorsed problems, which in turn leads to improvements in global, physical and psychosocial QoL. Furthermore, a relationship between fitness and QoL exists, with those experiencing higher levels of fitness also demonstrating higher QoL.Bone Marrow Transplantation (2004) 33, 553-558. doi:10.1038/sj.bmt.1704378 Published online 12 January 200

Steady-state modulation of voltage-gated K+ channels in rat arterial smooth muscle by cyclic AMP-dependent protein kinase and protein phosphatase 2B

Voltage-gated potassium channels (Kv) are important regulators of membrane potential in vascular smooth muscle cells, which is integral to controlling intracellular Ca2+ concentration and regulating vascular tone. Previous work indicates that Kv channels can be modulated by receptor-driven alterations of cyclic AMP-dependent protein kinase (PKA) activity. Here, we demonstrate that Kv channel activity is maintained by tonic activity of PKA. Whole-cell recording was used to assess the effect of manipulating PKA signalling on Kv and ATP-dependent K+ channels of rat mesenteric artery smooth muscle cells. Application of PKA inhibitors, KT5720 or H89, caused a significant inhibition of Kv currents. Tonic PKA-mediated activation of Kv appears maximal as application of isoprenaline (a β-adrenoceptor agonist) or dibutyryl-cAMP failed to enhance Kv currents. We also show that this modulation of Kv by PKA can be reversed by protein phosphatase 2B/calcineurin (PP2B). PKA-dependent inhibition of Kv by KT5720 can be abrogated by pre-treatment with the PP2B inhibitor cyclosporin A, or inclusion of a PP2B auto-inhibitory peptide in the pipette solution. Finally, we demonstrate that tonic PKA-mediated modulation of Kv requires intact caveolae. Pre-treatment of the cells with methyl-β-cyclodextrin to deplete cellular cholesterol, or adding caveolin-scaffolding domain peptide to the pipette solution to disrupt caveolae-dependent signalling each attenuated PKA-mediated modulation of the Kv current. These findings highlight a novel, caveolae-dependent, tonic modulatory role of PKA on Kv channels providing new insight into mechanisms and the potential for pharmacological manipulation of vascular tone

A Simple Grand Unified Relation between Neutrino Mixing and Quark Mixing

It is proposed that all flavor mixing is caused by the mixing of the three quark and lepton families with vectorlike fermions in 5 + 5-bar multiplets of SU(5). This simple assumption implies that both V_{CKM} and U_{MNS} are generated by a single matrix. The entire 3-by-3 complex mass matrix of the neutrinos M_{nu} is then found to have a simple expression in terms of two complex parameters and an overall scale. Thus, all the presently unknown neutrino parameters are predicted. The best fits are for theta_{atm} less than or approximately 40 degrees. The leptonic Dirac CP phase is found to be somewhat greater than pi radians.Comment: 10 pages, 4 figures, one table. Typos correcte

A survey of individual preference for colorectal cancer screening technique

BACKGROUND: Due to the low participation in colorectal cancer screening, public preference for colorectal cancer screening modality was determined. METHODS: A cross-sectional survey was performed of healthy ambulatory adults in a pediatrics primary care office and neighboring church. Overall preference was ranked for each of four colorectal cancer screening modalities: Faecal Occult Blood, Fiberoptic Sigmoidoscopy, Barium Enema and Colonoscopy. Four additional domains of preference also were ranked: suspected discomfort, embarrassment, inconvenience and danger of each exam. RESULTS: 80 surveys were analyzed, 57 of which were received from participants who had experienced none of the screening tests. Fecal Occult Blood Testing is significantly preferred over each other screening modality in overall preference and every domain of preference, among all subjects and those who had experienced none of the tests. CONCLUSIONS: Efforts to increase public participation in colorectal cancer screening may be more effective if undertaken in the context of public perceptions of screening choices

Spontaneous Parity Violation in SUSY Strong Gauge Theory

We suggest simple models of spontaneous parity violation in supersymmetric strong gauge theory. We focus on left-right symmetric model and investigate vacuum with spontaneous parity violation. Non-perturbative effects are calculable in supersymmetric gauge theory, and we suggest two new models. The first model shows confinement, and the second model has a dual description of the theory. The left-right symmetry breaking and electroweak symmetry breaking are simultaneously occurred with the suitable energy scale hierarchy. The second model also induces spontaneous supersymmetry breaking.Comment: 14 page

Intussusception trends in Hong Kong children

OBJECTIVES: To assess trends in intussusception and to validate the coding in Hong Kong's computerised discharge information system. DESIGN: Case notes were reviewed for all children under the age of 5 years who had a discharge diagnosis indicating intussusception or a procedure indicating reduction of intussusception during the 6-year period 1 July 1997 through 30 June 2003. RESULTS: Intussusception rates for infants under 1 year of age (108/100,000) and under 5 years of age (38/100,000) were slightly higher than previous estimates (78-100/100,000 and 27-32/100,000, respectively) that used passive discharge data alone. CONCLUSIONS: Hong Kong's passive computer data systems could be used to monitor rates of intussusception after the introduction of new rotavirus vaccines, provided readmissions, inter-hospital transfers, and hospital follow-ups for the same episode are taken into account.published_or_final_versio