Simplified theory of wideband spectra of liquid H2O and D2O (from 0 to 1000 cm(-1)) due to reorienting polar and vibrating H-bonded water molecules

A semi-phenomenological molecular model is presented, which is capable of describing with the use of analytical formulae, the wideband dielectric(1) and far-infrared spectra of ordinary and heavy water. In the model the vector of a dipole moment is presented as a sum of two components. The absolute value of the first one is constant; the second one changes harmonically with time. The key aspect of this work is consideration of FIR spectra due to the second component. In the context of the modified hybrid model presented in the work, reorientation of the dipoles in the rectangular potential well is considered, as a result of which the librational (near 700 cm (-1)) and translational (near 200 cm (-1)) absorption bands and the microwave Debye relaxation spectrum arise. It is shown that the time-dependent part of a dipole moment contributes most to the translational band, the relevant mechanism is taken to be stretching vibration of the H-bonded molecules. Previous linear-response molecular models were unsuccessful in describing this band (in heavy water) in terms of the complex dielectric permittivity. The spatial and time scales characteristic of water are estimated. (C) 2002 Elsevier Science B.V. All rights reserved.

Children's judgements about pain at age 8-10 years:do extremely low birthweight (<or = 1000 g) children differ from full birthweight peers?

Children's judgements about pain at age 8-10 years were examined comparing two groups of children who had experienced different exposure to nociceptive procedures in the neonatal period: extremely low birthweight (ELBW) <or = 1000 g (N = 47) and full birthweight (FBW) > or = 2500 g (N = 37). The 24 pictures that comprise the Pediatric Pain Inventory, depicting events in four settings: medical, recreational, daily living, and psychosocial, were used as the pain stimuli. The subjects rated pain intensity using the Color Analog Scale and pain affect using the Facial Affective Scale. Child IQ and maternal education were statistically adjusted in group comparisons. Pain intensity and pain affect related to activities of daily living and recreation were significantly higher than psychosocial and medically related pain on both scales in both groups of children. Although the two groups of children did not differ overall in their perceptions of pain intensity or affect, the ELBW children rated medical pain intensity significantly higher than psychosocial pain, unlike the FBW group. Also, duration of neonatal intensive care unit stay for the ELBW children was related to increased pain affect ratings in recreational and daily living settings. Despite altered response to pain in the early years reported by parents, on the whole at 8-10 years of age ELBW children judged pain in pictures similarly to their term peers. However, differences were evident, which suggests that studies are needed of biobehavioural reactivity to pain beyond infancy, as well as research into beliefs, attitudes, and perceptions about pain during the course of childhood in formerly ELBW children.

Language development at 3 years in pre-term children of birth weight below 1000 g

Language development at 3 years of pre-term children born below 1000 g birth weight was compared with full-term controls matched for social background. The pre-term group used less complex expressive language and showed lower receptive understanding, auditory memory and verbal reasoning. Language outcome was related to intraventricular haemorrhage but not to global indication of postnatal illness such as number of days on the ventilator. Average verbal intelligence in environmentally low risk, extremely low birth weight children is an insufficient indicator of complex language functioning.

Magma Evolution in the Primitive, Intra-oceanic Tonga Arc: Rapid Petrogenesis of Dacites at Fonualei Volcano

Fonualei is unusual amongst subaerial volcanoes in the Tonga arc because it has erupted dacitic vesicular lavas, tuffs and phreomagmatic deposits for the last 165 years. The total volume of dacite may approach 5 km(3) and overlies basal basaltic andesite and andesite lavas that are constrained to be less than a few millennia in age. All of the products are crystal-poor and formed from relatively low-viscosity magmas inferred to have had temperatures of 1100-1000 degrees C, 2-4 wt % H2O and oxygen fugacities 1-2 log units above the quartz-fayalite-magnetite buffer. Major and trace element data, along with Sr-Nd-Pb and U-Th-Ra isotope data, are used to assess competing models for the origin of the dacites. Positive correlations between Sc and Zr and Sr rule out evolution of the within-dacite compositional array by closed-system crystal fractionation of a single magma batch. An origin by partial melting of lower crustal amphibolites cannot reproduce these data trends or, arguably, any of the dacites either. Instead, we develop a model in which the dacites reflect mixing between two dacitic magmas, each the product of fractional crystallization of basaltic andesite magmas formed by different degrees of partial melting. Mixing was efficient because the two magmas had similar temperatures and viscosities. This is inferred to have occurred at shallow (2-6 km) depths beneath the volcano. U-Th-Ra disequilibria in the basaltic andesite and andesite indicate that the parental magmas had fluids added to their mantle source regions less than 8 kyr ago and that fractionation to the dacitic compositions took less than a few millennia. The 165 year eruption period for the dacites implies that mixing occurred on a similar timescale, possibly during ascent in conduits. The composition of the dacites renders them unsuitable candidates as contributors to average continental crust.

165/183 GHz FSS for the MetOp Second Generation Microwave Sounder Instrument

This paper reports the design of a Frequency Selective Surface (FSS) which simultaneously allows transmission of 175.3 – 191.3 GHz radiation and rejection from 164 - 167 GHz with a loss <0.5 dB for TE wave polarization at 45° incidence. The state-of-the art filter consists of three air spaced perforated screens with unit cells that are composed of nested resonant slots. The FSS satisfies the stringent electromagnetic performance requirements for signal demultiplexing in the quasi-optical feed train of the Microwave Sounder (MWS) instrument which is under development for the MetOp-SG mission.

One-dimensional porous La0.5Sr0.5CoO2.91 nanotubes as a highly efficient electrocatalyst for rechargeable lithium-oxygen batteries

The electrochemical performance of one-dimensional porous La_0.5Sr_0.5CoO_2.91 nanotubes as a cathode catalyst for rechargeable nonaqueous lithium-oxygen (Li-O₂) batteries is reported here for the first time. In this study, one-dimensional porous La_0.5Sr_0.5CoO_2.91 nanotubes were prepared by a simple and efficient electrospinning technique. These materials displayed an initial discharge capacity of 7205 mAh g^-1 with a plateau at around 2.66 V at a current density of 100 mA g^-1. It was found that the La_0.5Sr_0.5CoO_2.91 nanotubes promoted both oxygen reduction and oxygen evolution reactions in alkaline media and a nonaqueous electrolyte, thereby improving the energy and coulombic efficiency of the Li-O₂ batteries. The cyclability was maintained for 85 cycles without any sharp decay under a limited discharge depth of 1000 mAh g^-1, suggesting that such a bifunctional electrocatalyst is a promising candidate for the oxygen electrode in Li-O₂ batteries.