Smearing effect due to the spread of a probe-particle on the Brownian motion near a perfectly reflecting boundary

Quantum fluctuations of electromagnetic vacuum are investigated in a half-space bounded by a perfectly reflecting plate by introducing a probe described by a charged wave-packet distribution in time-direction. The wave-packet distribution of the probe enables one to investigate the smearing effect upon the measured vacuum fluctuations caused by the quantum nature of the probe particle. It is shown that the wave-packet spread of the probe particle significantly influences the measured velocity dispersion of the probe. In particular, the asymptotic late-time behavior of its $z$-component, $$, for the wave-packet case is quite different from the test point-particle case ($z$ is the coordinate normal to the plate). The result for the wave-packet is \sim 1/\t^2 in the late time (\t is the measuring time), in stead of the reported late-time behavior $\sim 1/z^2$ for a point-particle probe. This result can be quite significant for further investigations on the measurement of vacuum fluctuations.Comment: 8 page

Spectral gap of segments of periodic waveguides

We consider a periodic strip in the plane and the associated quantum waveguide with Dirichlet boundary conditions. We analyse finite segments of the waveguide consisting of $L$ periodicity cells, equipped with periodic boundary conditions at the ``new'' boundaries. Our main result is that the distance between the first and second eigenvalue of such a finite segment behaves like $L^{-2}$.Comment: 3 page

Biological basis of child health 2: introduction to fertilisation, prenatal development and birth

This article is the second in a series called the biological basis of child health. It considers the period of development from fertilisation to birth, outlining the three stages of prenatal development - the germinal, embryonic and fetal stages. The article details how tissues and organs typically develop at each stage, and explains how and when deviations in development and congenital anomalies are likely to occur. It also describes some of the common congenital anomalies, their potential effects and their detection before or after birth. Information is also provided about the delivery of full-term infants, including the stages of labour

Coral symbiodinium community composition across the Belize Mesoamerican barrier reef system is influenced by host species and thermal variability

Accepted manuscrip

The Tenerife Cosmic Microwave Background Maps: Observations and First Analysis

The results of the Tenerife Cosmic Microwave Background (CMB) experiments are presented. These observations cover 5000 and 6500 square degrees on the sky at 10 and 15 GHz respectively centred around Dec.~ +35 degrees. The experiments are sensitive to multipoles l=10-30 which corresponds to the Sachs-Wolfe plateau of the CMB power spectra. The sensitivity of the results are ~31 and \~12 microK at 10 and 15 GHz respectively in a beam-size region (5 degrees FWHM). The data at 15 GHz show clear detection of structure at high Galactic latitude; the results at 10 GHz are compatible with these, but at lower significance. A likelihood analysis of the 10 and 15 GHz data at high Galactic latitude, assuming a flat CMB band power spectra gives a signal Delta T_l=30+10-8 microK (68 % C.L.). Including the possible contaminating effect due to the diffuse Galactic component, the CMB signal is Delta T_l=30+15-11 microK. These values are highly stable against the Galactic cut chosen. Assuming a Harrison-Zeldovich spectrum for the primordial fluctuations, the above values imply an expected quadrupole Q_RMS-PS=20+10-7 microK which confirms previous results from these experiments, and which are compatible with the COBE DMR.Comment: 17 pages, 7 figures. Submitted to Ap

Surfaxe: Systematic surface calculations

Surface science is key to understanding the properties of a wide range of materials for energy applications, from catalysts to solar cells to battery components. Computational modelling based on quantum mechanics is often used to calculate surface properties of materials, which in turn determine their stability and performance. The maturity of these “first-principles” methods, coupled with the huge amount of computational power accessible today, means they can now be used predictively in high-throughput screening workflows to suggest new materials for specific applications before they are synthesised. The surfaxe package provides a framework for such screening workflows, automating each stage of the process

Improved impact performance of marine sandwich panels using through-thickness reinforcement: Experimental results

This paper presents results from a test developed to simulate the water impact (slamming) loading of sandwich boat structures. A weighted elastomer ball is dropped from increasing heights onto rigidly supported panels until damage is detected. Results from this test indicate that honeycomb core sandwich panels, the most widely used material for racing yacht hulls, start to damage due to core crushing at impact energies around 550 J. Sandwich panels of the same areal weight and with the same carbon/epoxy facings but using a novel foam core reinforced in the thickness direction with pultruded carbon fibre pins, do not show signs of damage until above 1200 J impact energy. This suggests that these will offer significantly improved resistance to wave impact. Quasi-static test results cannot be used to predict impact resistance here as the crush strength of the pinned foam is more sensitive to loading rate than that of the honeycomb core