Large area high efficiency broad bandwidth 800 nm dielectric gratings for high energy laser pulse compression.

We have demonstrated broad bandwidth large area (229 mm x 114 mm) multilayer dielectric diffraction gratings for the efficient compression of high energy 800 nm laser pulses at high average power. The gratings are etched in the top layers of an aperiodic (Nb0.5Ta0.5)2O5-SiO2 multilayer coating deposited by ion beam sputtering. The mean efficiency of the grating across the area is better than 97% at the center wavelength and remains above 96% at wavelengths between 820 nm and 780 nm. The gratings were used to compress 5.5 J pulses from a Ti:sapphire laser with an efficiency above 80 percent.

(7)Li NMR and two-dimensional exchange study of lithium dynamics in monoclinic Li(3)V(2)(PO(4))(3).

High-resolution solid-state (7)Li NMR was used to characterize the structure and dynamics of lithium ion transport in monoclinic Li(3)V(2)(PO(4))(3). Under fast magic-angle spinning (MAS) conditions (25 kHz), three resonances are clearly resolved and assigned to the three unique crystallographic sites. This assignment is based on the Fermi-contact delocalization interaction between the unpaired d-electrons at the vanadium centers and the lithium ions. One-dimensional variable-temperature NMR and two-dimensional exchange spectroscopy (EXSY) are used to probe Li mobility between the three sites. Very fast exchange, on the microsecond time scale, was observed for the Li hopping processes. Activation energies are determined and correlated to structural properties including interatomic Li distances and Li-O bottleneck sizes.

The Baby Friendly Hospital Initiative and breast feeding rates in Scotland.

OBJECTIVE: To examine the effect of the Baby Friendly Hospital Initiative on breast feeding rates in Scotland. DESIGN: Observational study using an annual survey of progress towards the WHO/UNICEF Baby Friendly Hospital Initiative and routinely collected breast feeding rates gathered on the Guthrie Inborn Errors Screening card at 7 days of postnatal age. SETTING: Scotland, UK, population 5.1 million, with about 53 000 births a year. PARTICIPANTS: All 33 maternity units with over 50 births per annum and 464,246 infants born in Scotland between 1995 and 2002. MAIN OUTCOME MEASURES: Baby Friendly status of each maternity unit at the time of an infant's birth: certificate of commitment, UK standard award, and breast feeding at 7 days postnatal age. RESULTS: Babies born in a hospital with the UK Baby Friendly Hospital Initiative standard award were 28% (p<0.001) more likely to be exclusively breast fed at 7 days of postnatal age than those born in other maternity units after adjustment for mother's age, deprivation, hospital size, and year of birth. From 1995, breast feeding rates had increased significantly faster in hospitals with Baby Friendly status by 2002: 11.39% (95% confidence interval 10.35 to 12.43) v 7.97% (95% confidence interval 7.21 to 8.73). CONCLUSION: Being born in a hospital that held the award increased the chance of being breast fed. All maternity units should be encouraged to undertake the significant strategic and practical changes required to achieve UK Baby Friendly Hospital Initiative standard status.

Stacking efficiency of diselenadiazolyl pi-dimers. Consequences for electronic structure and transport properties.

The preparation and crystal structure of 5-cyanofuran-2-[1,2,3,5-diselenadiazolyl], [RCN(2)Se(2)] (R = 5-cyanofuran), is reported. Crystal data for C(6)H(2)ON(3)Se(2): monoclinic, space group P2(1), a = 7.1121(7), b= 20.541(2), c =20.923(2) A, beta = 99.785(1) degrees, Z = 16. The crystal structure consists of diselenadiazolyl pi-dimer stacks running parallel to the x direction; the asymmetric unit consists of four pi-dimer units. The dimers are aligned into snakelike ribbons along the y direction, with consecutive dimers linked by head-to-tail CN-Se contacts. Each pi-dimer stack is bordered by two out-of-register stacks, but most interstack Se-Se contacts lie outside the van der Waals separation. Along the pi-dimer stacks, the intradimer Se-Se distances range from 3.183(10) to 3.294(1) A, and the interdimer Se-Se distances range from 3.826(1) to 3.945(1) A. Like other pi-dimer stacked diselenadiazolyls, [C(6)H(2)ON(3)Se(2)](2) is diamagnetic over the temperature range 4-380K. Variable temperature single-crystal conductivity measurements reveal a room-temperature conductivity near 10(-5) S cm(-1) and provide a calculated band gap of 0.72 eV. The structural results and transport properties are interpreted in the light of Extended Hückel band structure calculations.

Alkynylcyclohexanol chairs and twist-boats: Co(2)(CO)(6) as a conformational switch.

Treatment of 1-[axial]-(trimethylsilylethynyl)cyclohexan-1-ol with dicobalt octacarbonyl results in a conformational ring flip such that the bulky dicobalt-alkyne cluster moiety now occupies the favored equatorial site. However, when a 4-tert-butyl substituent is present, the coordinated alkynyl group retains its original axial or equatorial position. Complexation of trans-[diaxial]-1,4-bis(triphenylsilylethynyl)cyclohexane-1,4-diol brings about a chair-to-chair conformational inversion such that both cluster fragments now occupy equatorial sites. In contrast, cis-1,4-bis(triphenylsilylethynyl)cyclohexane-1,4-diol reacts with Co(2)(CO)(8) to yield the twist-boat conformer in which the two axial hydroxy substituents exhibit intra-molecular hydrogen bonding. Likewise, the corresponding reaction of cis-1,4-bis(trimethylsilylethynyl)cyclohexane-1,4-diol with Co(2)(CO)(8) leads to a twist-boat, but in this case, the molecules are linked through inter-molecular hydrogen bonds. Eight of these cobalt clusters have been characterized by X-ray crystallography, and the potential use of twist-boats in synthesis is discussed.

Benzo[2,1-c:3,4-c']bis(1,2,3-thiaselenazole) (BSe) and its charge trasfer chemistry. Crystal and electronic structure of [BSe]3[ClO4]2.

The S-Se-N-based heterocycle benzo[2,1-c:3,4-c']bis(1,2,3-thiaselenazole) (BSe) can be prepared by the condensation of 1,4-diaminobenzene-2,3-dithiol with selenium tetrachloride. Crystals of this compound are not isomorphous with the related benzo[2,1-c:3,4-c']bis(1,2,3-dithiazole) (BT); a structure is adopted that allows for more extensive intermolecular Se- - -Se contacts. Electro-oxidation of BSe in the presence of [n-Bu4N][ClO4] affords metallic green needles of the charge transfer salt [BSe]3[ClO4]2, which exhibit a pressed pellet conductivity sigma(RT) = 10(-1) S cm(-1). The crystal structure of [BSe]3[ClO4]2 consists of slipped pi-stacks based on the triple-decker closed shell [BSe]3(2+) building block. The packing is analogous to that found for the charge transfer salt [BT]3[FSO3]2, for which sigma(RT) = 10(-2) S cm(-1). Extended Hückel band structure calculations on these two (sulfur- and selenium-based) 3:2 salts reveal more extensive intermolecular interactions in the selenium compound. As a result, the latter has a more two-dimensional electronic structure. Crystal data for Se2S2N2C6H2, a = 4.103(2) A, b = 12.159(2) A, c = 16.171(2) A, orthorhombic, Pbnm, Z = 4. Crystal data for Se6S6N6C18H6Cl2O4, a =17.00(1) A, b = 18.36(1) A, c = 10.679(4) A, 110.27(3), monoclinic, C2/c, Z = 4.

Breastfeeding rates are increasing in Scotland.

OBJECTIVE: To measure the change in prevalence of breastfeeding between 1990/1991 and 1997/1998 in Scotland, using information collected on Guthrie cards when newborn infants are about seven days old. DESIGN: Analysis, by geographic postcode area, health board and maternity unit, for babies born in 1990/1991 and 1997/1998. For 1997, maternity unit and health board breastfeeding rates were also compared after standardisation for maternal age, deprivation and age of infant. SETTING: Scotland. SUBJECTS: 131,759 babies born in 1990/1991 and 118,055 in 1997/1998. RESULTS: In 1990/1991, 46,949 (35.6%) were breastfed as were 49,615 (42.0%) in 1997/1998, an increase of 6.4% (95% CI 6.0, 6.8) over eight years. A 3.8% increase remained after adjustment for change in maternal age. Maternity units with the Baby Friendly award improved 8.1% (95% CI 7.0, 9.2) compared with those with a certificate of commitment 6.1% (95% CI 5.2, 7.0). Other units improved 2.2% (95% C1 1.6, 2.8) no more than estimates due to increase in maternal age. Standardised rates were higher on the East Coast of Scotland 111 (109, 112) than the West or Central Regions 97 (96, 99). CONCLUSION: Breastfeeding has increased over eight years in Scotland. Less than half can be explained by demographic change in maternal age. However present breastfeeding targets are unlikely to be met. Maternity units should be urged to participate fully in the UNICEF U.K. Baby Friendly Initiative. Effective interventions prior to pregnancy are required so that more young men and women want their babies to be breastfed.

Monitoring breastfeeding rates and setting local targets: the Glasgow experience.

OBJECTIVE: The objective was to provide baseline data on infant feeding intention and practice in Glasgow. DESIGN: Information was collected from a prospective cohort of women who booked for maternity care in Glasgow during the months November 1995 and May 1996. Figures on feeding intention and practice were collected at five points from maternity booking until six weeks postnatal age. SETTING: Women were recruited at the four maternity units in Glasgow. Follow-up information was collected at birth, discharge from the maternity hospital at four days, and then at 12 days at home by the community midwife, and finally at six weeks by the health visitor. SUBJECTS: One thousand seven hundred and ninety two women were recruited at maternity booking. Breastfeeding information was available at birth for 1723, at discharge for 1743, at 12 days for 1513, and at six weeks for 1394. Multiple logistic regression determined maternal and infant factors predicting feeding intention and duration. RESULTS: At booking 50% planned to breastfeed. Fifty percent breastfed at birth; by four days the rate had dropped to 42%, by 12 days to 36% and by six weeks to 27%. Five factors: deprivation score, maternal age, parity, maternal smoking and previous breastfeeding experience independently predicted feeding intention. Maternal factors explained differences in breastfeeding rates between the four hospitals. CONCLUSION: Original breastfeeding targets for Glasgow have been revised to take account of local circumstances. An alternative method using routinely collected data is needed to monitor progress.

Fabrication of large-aperture lightweight diffractive lenses for use in space.

We describe the advantages of using diffractive (Fresnel) lenses on thin membranes over conventional optics for, among others, future space telescope projects. Fabrication methods are presented for lenses on two types of freestanding membrane up to 50 cm in size. The first is a Fresnel lens etched into a thin (380-microm) glass sheet, and the second is an approximately 50-microm-thick polymer membrane containing a Fresnel lens made by replication process from a specially made fused-silica master. We show optical performance analysis of all the lenses that are fabricated, including a diffraction-limited Airy spot from a 20-m- focal-length membrane lens in a diffractive telescope system.

Breastfeeding in Scotland--statistical sources.

INTRODUCTION: The health benefits of breastfeeding for babies and mothers are increasingly recognised. In Scotland, a national breastfeeding target has been set and national policies commend the promotion and support of breastfeeding. In order to set realistic local breastfeeding targets, and to evaluate success in increasing the initiation and duration of breastfeeding, Health Boards need accurate local data on breastfeeding rates. OBJECTIVE: To examine existing Scottish sources of routinely collected data on infant feeding intention and practice, and to make recommendations for the future collection, dissemination and quality of such data. METHODS: Information on Scottish infant feeding data was collected from published sources and from personnel responsible for infant feeding data within larger infant and child health data sets. Data for Glasgow were analysed for completeness. RESULTS: Four major sources of routinely collected data exist, one of which provides national figures only. The other three collect local data on feeding intention and practice at a variety of stages from pregnancy to baby's age 8/9 months. Whilst some data are available locally, there is no routine dissemination of data at all stages throughout Scotland. The quality and completeness of data require further investigation. CONCLUSIONS: Attention should be given to developing the use of existing routinely collected sources of data to provide regular, reliable information on local breastfeeding rates to assist the monitoring and implementation of local breastfeeding strategies. A small group of health professionals, health information staff and researchers should be convened by ISD to pursue this task.

Petawatt laser pulses.

We have developed a hybrid Ti:sapphire-Nd:glass laser system that produces more than 1500 TW (1.5 PW) of peak power. The system produces 660 J of power in a compressed 440+/-20 fs pulse by use of 94-cm master diffraction gratings. Focusing to an irradiance of >7x10(20) W/cm (2) is achieved by use of a Cassegrainian focusing system employing a plasma mirror.

Prenatal diagnosis and follow-up of 14 cases of unilateral ventriculomegaly.

OBJECTIVE: To report prospectively the prenatal diagnosis, management and outcome of 14 cases of unilateral ventriculomegaly. METHODS: Fourteen fetuses were diagnosed as having one ventricle of > or = 10 mm, as measured at the level of the atrium. RESULTS: In ten cases, the scan showed mild unilateral ventriculomegaly with an atrium width between 11 and 13 mm and this remained stable up to term. Eight of these fetuses had a magnetic resonance imaging scan in utero between 32 and 34 weeks of gestation which confirmed the diagnosis of mild ventriculomegaly without other brain abnormalities and showed a normal cortical mantle. No obvious cause was found and the outcome was normal in all cases. In four cases, the unilateral ventriculomegaly evolved rapidly with an atrium width up to 20-25 mm. Causes included atresia of the foramen of Monro, toxoplasmosis, brain atrophy and Weaver syndrome. Three underwent termination of pregnancy and the postmortem examination confirmed the diagnosis. The baby with brain atrophy and schizencephaly had a ventriculoperitoneal shunt placed at 1 month of age and has severe developmental delay at 9 months. CONCLUSION: The prognosis of unilateral ventriculomegaly is uncertain. Examination of both ventricles during the anomaly scan should be performed, as should ultrasound follow-up of these cases up to the end of the third trimester. Fetuses with an isolated, mild, stable unilateral ventriculomegaly seem to have a favourable neurological outcome. However, fetuses with rapidly evolving unilateral ventriculomegaly or cases associated with other brain abnormalities may have a poor neurological outcome.

Multiscale, multifunction diffractive structures wet etched into fused silica for high-laser damage threshold applications.

We combined functionalities of two diffractive optics with almost 100x lateral and vertical scale-length difference onto a single fused-silica surface. Fine-scale (2-mum-period) gratings for beam sampling were printed in photoresist by interference lithography and transferred to the substrate by a hydrofluoric acid etch. Subsequently, 115-mum-linewidth stairstep gratings for color separation at focus were proximity printed and wet etched in a two-mask process. Line shapes of the lamellar sampling grating are remarkably preserved following etching of the much deeper color separation grating structures with this nominally isotropic etch process. Model simulations of isotropic etching of topographical features show good agreement with the measured shape evolution of the sampling grating profiles, and the simulations reveal the sensitivity of the final feature shape to its initial aspect ratio. As a rule of thumb, lamellar grating profiles can be etched approximately 0.08A(-2) times their modulation depth, where A is their initial aspect ratio (height/width), before they evolve into a cusplike shape and begin to lose height.

Cholinesterase. Its significance in anaesthetic practice.

Plasma cholinesterase is an enzyme which has importance to the anaesthetist primarily for its role in the metabolism of suxamethonium, although other anaesthetic related drugs that this enzyme metabolises are also increasingly important. In this article we review current thoughts on the function, profile and chemistry of plasma cholinesterase. Causes of variations in the activity of the enzyme are described and the basis of genetic variations is explained.

High-efficiency fused-silica transmission gratings.

We describe the design, fabrication, and performance of high-efficiency transmission gratings fabricated in bulk fused silica for use in high-power ultraviolet laser systems. The gratings exhibit a diffraction efficiency of 94% in order m=-1 and a damage threshold greater than 13>J/cm( 2) for 3-ns pulses at 351 nm. Model calculations and experimental measurements are in good agreement.

125-TW Ti:sapphire/Nd:glass laser system.

We have demonstrated a Ti:sapphire/Nd:glass laser system that produces up to 51 J of energy in 395-fs pulses (125TW). Focusing at f/3 to a 2.5-times diffraction-limited spot results in a peak irradiance greater than 10(20) W/cm(2) . Our 40-cm-diameter gold diffraction gratings have a damage threshold of 0.42 J/cm(2) for 320-fs pulses.