Resistivity scaling and critical dynamics of fully frustrated Josephson-junction arrays with on-site dissipation

We study the scaling behavior and critical dynamics of the resistive transition in Josephson-junction arrays, at f=1/2 flux quantum per plaquette, by numerical simulation of an on-site dissipation model for the dynamics. The results are compared with recent simulations using the resistively-shunted-junction model. For both models, we find that the resistivity scaling and critical dynamics of the phases are well described by the same critical temperature as for the chiral (vortex-lattice) transition, with a power-law divergent correlation length. The behavior is consistent with the single transition scenario, where phase and chiral variables order at the same temperature, but with different dynamic exponents z for phase coherence and chiral order.Comment: 17 pages, 13 figures, to appear in Phys. Rev.

Plastic shrinkage cracking of concrete - Roles of osmotic suction

Plastic shrinkage cracking of concrete occurs when the stresses arising in the concrete, due to a combination of suction and restraints of deformation such as reinforcement or formwork, equal its strength. However, three different types of suctions should be distinguished, namely total, matric and osmotic suctions. Although the total suction comprises matric and osmotic suctions, it is often used interchangeably with matric suction, with the underlying unconfirmed assumption that either the osmotic suction or its effect is negligible. In this paper, after a discussion of the pore moisture suctions and strength of unsaturated early-age concrete, experimental investigations of the suctions arising in, and the tensile strength and shear strength of, fly ash mixed with solutions of different osmotic suctions are described. It was found that osmotic suction has negligible effect on the shear and tensile strength, and hence, by inference, the inter-particle stresses in the fly ash mixture and early-age concrete. This strongly suggests that the role played by osmotic suction in the plastic shrinkage cracking of concrete is minimal and, accordingly, justifies the focus of earlier researchers on matric suction only

Dynamic Scaling of Magnetic Flux Noise Near the KTB Transition in Overdamped Josephson Junction Arrays

We have used a dc Superconducting QUantum Interference Device to measure the magnetic flux noise generated by the equilibrium vortex density fluctuations associated with the Kosterlitz-Thouless-Berezinskii (KTB) transition in an overdamped Josephson junction array. At temperatures slightly above the KTB transition temperature, the noise is white for $f<f_\xi$ and scales as $1/f$ for $f>f_\xi$. Here $f_\xi\propto\xi^{-z}$, where $\xi$ is the correlation length and $z$ is the dynamic exponent. Moreover, when all frequencies are scaled by $f_\xi$, data for different temperatures and frequencies collapse on to a single curve. In addition, we have extracted the dynamic exponent $z$ and found $z=1.98\pm0.03$.Comment: 5 pages, LaTeX (REVTeX) format, requires epsfig and amstex style files. 3 figures included. Tentatively scheduled for publication in Physical Review Letters, 18 March, 199

Fluctuation-dissipation theorem and flux noise in overdamped Josephson junction arrays

The form of the fluctuation-dissipation theorem for a resistively shunted Josephson juction array is derived with the help of the method which explicitely takes into acoount screening effects. This result is used to express the flux noise power spectrum in terms of frequency dependent sheet impedance of the array. The relation between noise amplitude and parameters of the detection coil is analysed for the simplest case of a single-loop coil.Comment: ReVTeX, 8 page

Non-equilibrium transitions in fully frustrated Josephson junction arrays

We study the effect of thermal fluctuations in a fully frustrated Josephson junction array driven by a current I larger than the apparent critical current I_c(T). We calculate numerically the behavior of the chiral order parameter of Z_2 symmetry and the transverse helicity modulus (related to the U(1) symmetry) as a function of temperature. We find that the Z_2 transition occurs at a temperature T_{Z_2}(I) which is lower than the temperature T_{U(1)}(I) for the U(1) transition. Both transitions could be observed experimentally from measurements of the longitudinal and transverse voltages.Comment: 4 pages, 4 figure

1/\omega-flux-noise and dynamical critical properties of two-dimensional XY-models

We have numerically studied the dynamic correlation functions in thermodynamic equilibrium of two-dimensional O(2)-symmetry models with either bond (RSJ) or site (TDGL) dissipation as a function of temperature T. We find that above the critical temperature the frequency dependent flux noise $S_{\Phi}(\omega)\sim \vert 1+ {(\omega/\Omega)}^2\vert^{-\alpha (T)/2}$, with $0.85\leq \alpha (TDGL)(T)\leq 0.95$ and $1.17 \leq \alpha (RSJ)(T) \leq 1.27$, while the dynamic critical exponents $z(TDGL)\sim 2.0$ and $z(RSJ)\sim 0.9$. Contrary to expectation the TDGL results are in closer agreement with the experiments in Josephson-junction arrays by Shaw et al., than those from the RSJ model. We find that these results are related to anomalous vortex diffusion through vortex clusters.Comment: 4 pages Rev-Tex, two figures in postscript. To appear In Physical Review Letter

The Epidemiology, Genetics and Future Management of Syndactyly

Syndactyly is a condition well documented in current literature due to it being the most common congenital hand defect, with a large aesthetic and functional significance

Evidence for perinatal and child health care guidelines in crisis settings: can Cochrane help?

<p>Abstract</p> <p>Background</p> <p>It is important that healthcare provided in crisis settings is based on the best available research evidence. We reviewed guidelines for child and perinatal health care in crisis situations to determine whether they were based on research evidence, whether Cochrane systematic reviews were available in the clinical areas addressed by these guidelines and whether summaries of these reviews were provided in Evidence Aid.</p> <p>Methods</p> <p>Broad internet searches were undertaken to identify relevant guidelines. Guidelines were appraised using AGREE and the clinical areas that were relevant to perinatal or child health were extracted. We searched The Cochrane Database of Systematic Reviews to identify potentially relevant reviews. For each review we determined how many trials were included, and how many were conducted in resource-limited settings.</p> <p>Results</p> <p>Six guidelines met selection criteria. None of the included guidelines were clearly based on research evidence. 198 Cochrane reviews were potentially relevant to the guidelines. These reviews predominantly addressed nutrient supplementation, breastfeeding, malaria, maternal hypertension, premature labour and prevention of HIV transmission. Most reviews included studies from developing settings. However for large portions of the guidelines, particularly health services delivery, there were no relevant reviews. Only 18 (9.1%) reviews have summaries in Evidence Aid.</p> <p>Conclusions</p> <p>We did not identify any evidence-based guidelines for perinatal and child health care in disaster settings. We found many Cochrane reviews that could contribute to the evidence-base supporting future guidelines. However there are important issues to be addressed in terms of the relevance of the available reviews and increasing the number of reviews addressing health care delivery.</p

SYNCHROTRON-BASED HIGHEST RESOLUTION FTIR SPECTROSCOPY OF AZULENE, NAPHTHALENE (C10_{10}H8_8), INDOLE (C8_{8}H6_6N) AND BIPHENYL (C12_{12}H10_{10})

Author Institution: Physical Chemistry, Eth ZUrich, Ch-8093 ZUrich, Switzerland; SWISS LIGHT SOURCE, PAUL-SCHERRER-INSTITUTE, CH-5232; Villigen, SwitzerlandGreat progress has been made in resolution ($\Delta\nu\leq 20$~MHz) and sensitivity in the field of high resolution Fourier transform infrared (FTIR) spectroscopy over the last decade \textbf{2003}, \emph{84}, 177-180.}$^,$, \textbf{2007}, \emph{8}, 1271-1281.}$^,$ in \emph{Handbook of High Resolution Spectroscopy}, Vol.~2 (Eds. M. Quack and F. Merkt), Wiley, Chicester \textbf{2011}, 965-1021.}. In particular, the use of synchrotron sources such as the Swiss Light Source (SLS) \textbf{2011}, \emph{150}, 71-99.} have overcome one of the disadvantages of high resolution FTIR spectroscopy, the problem of noise related to modest signal strength with broad band coverage from weak light sources. FTIR spectroscopy with synchrotron sources now makes it possible to investigate scientific questions of fundamental physics and astrophysics. One of the great challenges of astronomical infrared spectroscopy is the identification of the Unidentified Infrared Bands (UIBs) found in several interstellar objects. Polycyclic Aromatic Hydrocarbons (PAHs) have been proposed to be the carrier of the UIBs \textbf{2008}, \emph{46}, 289.}. For that reason we have started to investigate with our ETH-SLS interferometer the rotationally resolved FTIR spectra of the bicyclic molecules naphthalene (C$_{10}$H$_8$)$^d$ and azulene (C$_{10}$H$_8$) as a simple prototypical spectrum for a PAH infrared spectrum and of indole (C$_{8}$H$_6$N) as a prototype of a bicyclic heteroaromatic system. We have analysed in high resolution the $\nu_{46}$ band of naphthalene, the $\nu_{35}$ and $2\nu_{40}$ bands of indole as well as the $\nu_{44}$ band of azulene. We have found a coincidence between the $\nu_{46}$ fundamental of naphthalene and the UIB at 12.78~$\mu$m. A comparison of the biphenyl FTIR spectrum with the UIBs in the range 13 to 15~$\mu$m illustrates a coincidence between the UIBs at 13.6~$\mu$m and 14.2~$\mu$m with the major biphenyl bands

Stability of Coronene at high temperature and pressure

The infrared response of coronene (C24H12) under pressure and temperature conditions up to 10 GPa and 300 °C is examined in situ using a diamond anvil cell and synchrotron-source Fourier transform infrared (FTIR) spectroscopy. Coronene is a polycyclic aromatic hydrocarbon that is present in the interstellar medium and meteorites which may have contributed to the Earth’s primordial carbon budget. It appears to undergo a reversible phase transition between 2 and 3.2 GPa at ambient temperature; new intramolecular bonds in the region 840−880 cm−1 result from compression. We document the shift of spectral features to higher wavenumbers with increasing pressure but find this change suppressed by increased temperature. By investigating the stability of coronene over a range of naturally occurring conditions found in a range of environments, we assess the survival of the molecule through various terrestrial and extraterrestrial processes. Coronene has previously been shown to survive atmospheric entry during Earth accretion; this can now be extended to include survival through geological processes such as subduction and silicate melting of the rock cycle, opening the possibility of extraterrestrial coronene predating terrestrial accretion existing on Earth