bluuebunny/crossref_metadata_2025 huggingface dataset:
The coreless winter at Scott Base, Antarctica
Authors: Thompson D. C.
Published: February 2007

The temporary early‐winter reversal of the downward trend in monthly mean surface air temperatures, which has been noted for other stations in the Ross Sea – South Pole region, is a particularly marked and persistent feature at Scott Base. An examination of temperature records shows that this reversal in the trend is probably due to a more frequent destruction of the low‐level surface inversion in these months, rather than a temporary increase in the level of warm air advection into the region.
The polar low as a baroclinic disturbance
Authors: Harrold T. W. , Browning K. A.
Published: February 2007

This paper describes the three dimensional airflow and precipitation within small ‘polar’ depressions which sometimes cross Britain during northerly outbreaks and which in winter can be responsible for heavy snowfalls. The data used in the study consist of Doppler and conventional radar information, together with routine synoptic data and sequential radiosonde ascents from the radar station. Three dimensional airflow was derived from the radiosonde data assuming that wet bulb potential temperature was conserved. Horizontal and vertical air velocities were also derived from the Doppler radar measurements.

Previous knowledge of polar lows is meagre; they are generally thought to be shallow features resulting from enhanced convection within cold air flowing over a warm sea. However, the well‐developed polar low which is the main subject of this paper is shown to have been an essentially baroclinic disturbance. Although enhanced small‐scale convection occurred in one sector, the main area of widespread precipitation associated with the polar low was produced not by small‐scale convective overturning but rather by slantwise convection within a narrow tongue of air ascending steadily at about 10 cm s−1.

The speed of travel and short wavelength (900 km) of the polar low in this study are consistent with its having formed in a region of enhanced baroclinicity within the polar air below 850 mb rather than in the major baroclinic zone bounding the polar air mass. Considerable low‐level baroclinicity within the polar air is also shown to have been present during the formation of other intense polar lows.
A theoretical study of cup and vane anemometers ‐ Part II
Authors: Ramachandran S.
Published: February 2007

The differential equation for cup and vane anemometers, developed earlier (Ramachandran 1969) is checked by comparing the computed overestimations of mean values in sinusoidally fluctuating winds with the experimental results of Deacon (1951). The equation predicts an overestimation of low frequency components in winds containing more than one sinusoidal component.

Results from direct measurements are compared with those obtained from compensated data, using an approximate compensation technique.

The logarithmic power spectra obtained from compensated data show peaked shapes arising out of the removal of the nonlinear overestimation of response at the low frequencies.
Eigenvector representations of Northern Hemispheric fields
Authors: Craddock J. M. , Flintoff Susan
Published: February 2007

The best eigenvector representations of Northern Hemispheric fields of the height of the 1,000 mb surface and the 1,000‐500 mb thickness are compared with those previously found for the 500 mb surface. It is shown that the use of the first 50 eigenvectors of the 500 mb fields, for all three types of field, produces a representation which is only marginally inferior to that obtainable by using three different sets of eigenvectors.
Generalizations of the Richardson criterion for the onset of atmospheric turbulence
Authors: Hines C. O.
Published: February 2007

The energetics of air‐parcel interchange are examined for the case in which the atmospheric potential temperature θ and background wind U are continuous but otherwise arbitrarily varying in space, and in which the direction of U is free from constraint. Interchange along a single s‐axis, inclined at angle α to the vertical, is shown to be energetically feasible if

where g is the gravitational acceleration. This condition, which is in general far less stringent than that imposed by the standard Richardson criterion, is suggested as a condition portending the onset of anisotropic turbulence. An isotropic interchange throughout a sphere is shown to be energetically feasible if

where the z co‐ordinate of the Cartesian x, y, z system is directed upward. This condition, which is in general somewhat less stringent than that imposed by the elementary Richardson criterion, may well portend the occurrence of isotropic turbulence. An outer time scale for the turbulence is estimated in each case, and its relevance to the occurrence of turbulence is discussed for the case when the background parameters of the system change with time.
Ice crystal concentrations in cumulus and stratocumulus clouds
Authors: Mossop S. C. , Cottis R. E. , Bartlett B. M.
Published: February 2007

Concentrations of ice crystals of the order of 100 l−1 were found in some of the cumulus clouds sampled on four different days over or near the Australian mainland. These concentrations were 102 to 104 times higher than those of the ice nuclei present. The clouds had summit temperatures no colder than −13°C.

Penetrations of shallow stratocumulus clouds with similar top temperatures showed that ice particle enhancement was much less important in these clouds, a factor of 10 being the upper limit.

This difference in glaciation behaviour is considered in the light of differences in measured drop spectra, the stratocumuli having much narrower drop size distributions than the cumuli.

Of all the suggested mechanisms by which the number of ice crystals could be enhanced, the evidence presented here favours the production of secondary ice crystals when ice particles grow by riming.
Electric field recovery after lightning as the response of the conducting atmosphere to a field change
Authors: Illingworth A. J.
Published: February 2007

Computations are presented to show that the rearrangement of space charge existing in the fair weather conductivity profile of the atmosphere can explain the observed rapid recovery of electric field after a lightning flash without invoking a core of high conductivity within the cloud or charge at the cloud boundary. An exponential conductivity profile accurately accounts for the first second of observed recoveries at the ground, predicting increasingly rapid recoveries at greater distances. The whole of the rapid recoveries observed above clouds is also explained, but the suggestion that recoveries become even more rapid at higher altitudes remains to be verified by observation.

The conductivity near the ground is less than that given by the exponential profile, and if the model is restricted to include only the clear air above the cloud, the complete recovery curve at all distances on the ground is explained, while recoveries above the cloud are unaffected. The slight but significant deviations from the exponential form of distant recoveries observed on the ground are also accurately forecast.

The simple Coulomb field of a regenerated charge within the cloud cannot result in more rapid recoveries after distant discharges than after close ones.
Aerosol and solar radiation in Britain
Authors: Unsworth M. H. , Monteith J. L.
Published: February 2007

The irradiance of the solar beam was measured on cloudless days at Sutton Bonington in the English Midlands and at sites in north‐west Scotland. Total and diffuse fluxes were also measured on some days. An attenuation coefficient for aerosol τa was defined by

relating the measured flux at normal incidence S(τa) to the flux calculated for a dust‐free atmosphere when the air mass number is m. Changes of τa from day to day were related to changes of air mass origin; local sources of aerosol were relatively unimportant. In maritime air, τa ranged from 0.05 to 0.15, and in continental air, from 0.1 to 0.5. In a tropical maritime air mass, τa decreased from 0.13 at sea level to 0.07 at 1,340 m.

The fraction of (ultra‐violet + visible) to total radiation was (0.54 – 0.28 τa) and the ratio of diffuse to total radiation (m < 2) was (0.1 + 0.7 τa). The ratio of total scattering to absorption by aerosol decreased from 4 at m = 1.1 to 0.5 at m = 2.

Mean monthly values of τa at four Meteorological Office stations were calculated from records of solar radiation and hours of sunshine and corresponding values of total and diffuse flux were tabulated for ‘isolated’, ‘rural’ and ‘urban’ sites.
A synoptic climatology of satellite observed cloud vortices over the Southern Hemisphere
Authors: Streten N. A. , Troup A. J.
Published: February 2007

A classification scheme for satellite observed cloud vortices is used to assess some general features of the behaviour of Southern Hemisphere depressions. From coincident conventional observations the mean variation of surface pressure and upper level geopotential anomaly near the centre of, and in west‐east cross‐section through an extratropical vortex is determined in relation to its age. Data are obtained on the geographical variation of occurrence of vortex type, duration, and frequency of change between development stages. The percentage of vortices developing without a pre‐existing cloud band is found to be greater at higher latitudes but, in general, over 50 per cent of developments occur in this way.

Persistent maxima of early vortex development are found in the western South Atlantic and in the central South Pacific, both regions extending into lower latitudes than elsewhere in the hemisphere. Two less prominent maxima are located in the central Indian Ocean, and south of Australia. Generalized vortex track and speed data are obtained, and several areas of high frequency of termination of depression track are observed at high latitudes near the Antarctic coast.

In total, the observations tend to point to a circulation pattern having a high frequency of major long wave troughs east of the Andes, and in the central Pacific, with a further frequent trough more variable in space and time being located between the central Indian Ocean and the longitude of the Great Australian Bight.
Geostrophic drag and heat transfer relations for the atmospheric boundary layer
Authors: Arya S. P. S.
Published: February 2007

The empirical determinations of the similarity functions of geostrophic drag and heat transfer relations by Zilitinkevich and Chalikov (1968) and by Clarke (1970a, b) indicate large disparities between their results, raising serious doubts on the universality of these relations. Some reasons for these large differences are investigated by reanalysing the available data from the two sites (O'Neill in Nebraska, U.S.A., and Hay in New South Wales, Australia) in the same format, using the best available flux‐profile relations and reasonable criteria for the selection of suitable runs. Although there is still considerable (but, much less than in previous studies) scatter of data points, when plotted in the similarity framework, we find no significant differences in the results of two sites. Thus a large part of the above noted disparities must have been spurious, probably caused by different ways of determining surface fluxes and of defining external variables by the previous investigators.

Our empirical results are compared with those obtained from recent theoretical models for both stable and unstable boundary layers. Having fitted some third degree polynomials through the same, nomograms are obtained for geostrophic drag and heat transfer coefficients and also for the surface cross‐isobaric angle as functions of dimensionless parameters defined in terms of easily measured ‘external’ variables. These show expected trends with stability.
Comparison of evaporation measurements using different methods
Authors: Grant D. R.
Published: February 2007

During the 1971 growing season continuous measurements were made (with some breaks in the record due to instrumental faults) of the evaporation from barley using five methods:

Bowen ratio method;

aerodynamic method;

use of the energy balance equation and the aerodynamic heat flux to obtain evaporation as the residue (for convenience called the energy balance method);

a weighing lysimeter; and

a neutron moisture meter.

In this paper some estimates are made of the error expected from each method and the results of the measurements are presented. It is shown that the energy balance method is almost as good as the Bowen ratio method and has the advantage of not requiring humidity measurements.
Variation of the sea surface drag coefficient with wind speed
Authors: Smith S. D. , Banke E. G.
Published: February 2007

Eddy correlation measurements of wind turbulence obtained at a sand spit on Sable Island, Nova Scotia, in winds ranging from gentle breeze to strong gale force agree with other recent measurements over water. There is a significant increase in the drag coefficient with wind speed which is well described by the equation of Charnock (1955). The heat transfer coefficient is slightly lower than the drag coefficient.
Forecasting of vertical temperature profiles in the atmosphere during nocturnal radiation inversions from air temperature trend at screen height
Authors: Anfossi D. , Bacci P. , Longhetto A.
Published: February 2007

A theoretical model for vertical distribution of air temperature in lower layers during night‐time calm periods has been developed by modifying some boundary conditions of the classical Brunt's model, on the ground of a more realistic behaviour of low atmosphere.

The model allows the vertical temperature profile to be deduced from screen data records and it fits with experimental data collected from a meteorological tower better than the classical model.

Radiative heat exchange is assumed to play the principal role, with diffusion thermal coefficient constant with height and time; previous work has shown that such an assumption holds true in the Po Valley air flow, when sky is cloudless and winds are light.
Wind profile relationships from the ‘wangara’ experiment
Authors: Hicks B. B.
Published: February 2007

From over 1000 half‐hour observations of near‐surface wind profiles at Hay, NSW, more than 500 high quality sets of data are selected. In unstable conditions, these closely confirm previous analyses and suggest near equality between z/L and Ri. The data are well described by either the KEYPS relationship (Panofsky) or that of Businger: ϕM = (1–16z/L)−1/4. In stable conditions, a log‐linear formulation (ϕM = 1+az/L) is found to give an adequate description of the wind profile up to z/L ≃ 0.5, with some evidence for a slight variation in α between the values 4.0 at neutral and about 6 when z/L ≃ 0.2. The average value of α between these limits is found to be 5.0±0.2.

In conditions of very high stablity, a linear profile (du/dz = cu*/(kL)) is suggested above the height z ≃ 10L. In the transition region between the log‐linear and linear profile regimes, the log‐linear formulation appears to tend towards a purely logarithmic law as stability increases. There is no evidence for any sudden change in behaviour, nor is there any suggestion that a purely logarithmic relationship is ever attained as an average situation. The value of c in the purely linear relationship is found to be between 0.4 and 0.9. The data also indicate that in extremely stable conditions (L ≃ 50cm) the dimensionless gradients of heat and of momentum may differ by about a factor of two, with ϕH being the larger.

The roughness length of the site used is found to be 1.2±0.1 mm, considerably less than the values appropriate to earlier experiments performed in the same general area. There is some evidence for an increase in z0 with decreasing wind speed (reaching about 3 mm when the wind at 1 m is about 1 ms−1), in accord with Deacon's hypothesis concerning the form drag of roughness elements. From the point of view of applying a low‐level drag coefficient in order to estimate friction velocities, the errors arising from the change in roughness length are sometimes comparable to those resulting from stability effects.

Not surprisingly, the data show that in slightly stable conditions dewfall was low, whereas in extremely stable situations dewfall accounted for most of the heat loss from the air.

The data used here form part of a much larger body of information obtained during 1967 and known as the ‘Wangara’ experiment.
Spatial and temporal variations of the Southern Oscillation
Authors: Trenberth K. E.
Published: February 2007

The Southern Oscillation is an important mode of operation of the atmosphere. Several indices of the Southern Oscillation have been recognized, but for many purposes an index that gives a continuous, homogeneous time series is required. Phase differences between various areas complicate the definition of a simple index but weighted values of seasonal surface pressure at Darwin and Tahiti seem suitable for reference purposes. Time series of short period correlation coefficients prove useful for revealing temporal variations in the character and amplitude of the Southern Oscillation and reveal times when it is not very prominent. Lag relationships are determined and used to indicate some aspects of the circulation near times of phase reversal of the oscillation.

Spectral analysis showed most variance to be in the range of 2 to 10 year periodicities, and cross spectral calculations further indicated that only for the 2–10 year range, and mainly for the 3–6 year range, of periodicities is there large‐scale coherence and out‐of‐phase relationships between stations in the South Pacific and Darwin. This defines the time scale of the Southern Oscillation.

The Southern Oscillation is not confined to tropical and subtropical latitudes but is clearly linked to mid‐latitude systems and long waves in the westerlies. East‐west circulations coupling the South Pacific Convergence Zone and the South Pacific high also appear to play an important role in the Southern Oscillation.
Longitudinal analysis of the relation between moderate long‐term stress and health
Authors: Öhman Lena , Bergdahl Jan , Nyberg Lars , Nilsson Lars‐Göran
Published: February 2007

The main goal of the present work was to longitudinally examine consequences of long‐term moderately elevated levels of stress for various health outcomes. To address this issue, data covering 10 years was used from the ongoing Swedish population‐based prospective Betula Study. Based on the ratings on a validated self‐reported stress scale, matched subsamples between 40 and 65 years of age were divided into a high (n = 137) and low (n = 211) stress group. The reported incidence of cardiovascular, diabetes, psychiatric, tumour and musculoskeletal diseases was assessed 5 and 10 years after baseline (baseline = 1993–1995) without contaminating effects of past health history. The incidence of diseases 5 years after baseline assessment showed no differences between the groups. After 10 years, there was a significantly higher incidence of psychiatric diseases, mainly depression in the high‐stress group as well as a significant effect for tumours, although the number of cases was low. Although moderately elevated stress level may have a possible impact on psychiatric diseases especially depression and some tumours, it seems that prolonged moderate stress does not appear to be harmful to other stress‐related diseases. Copyright © 2007 John Wiley & Sons, Ltd.
Why do firms both make and buy? An investigation of concurrent sourcing
Authors: Parmigiani Anne
Published: February 2007

Transaction cost economics, neoclassical economics, and the firm capabilities literatures propose theories of the firm that typically depict firm boundaries determined by a dichotomous choice: the makeorbuy decision. However, none of these theories presents a satisfying explanation as to why firms would concurrently source, i.e., simultaneously makeandbuy the same good. This study combines these organizational economics theories and compares when firms make, buy, and concurrently source through surveying small manufacturing firms. Support was shown for aspects of all three theories, with evidence indicating that concurrent sourcing is a distinctly different choice, rather existing along a make/buy continuum. Copyright © 2007 John Wiley & Sons, Ltd.
Low‐cost wireless sensor networks for remote cardiac patients monitoring applications
Authors: Hu Fei , Jiang Meng , Xiao Yang
Published: February 2007

One of today's most pressing matters in medical care is response time to patients in need. Scope of this research is to suggest a solution that would help reduce response time in emergency situations utilizing technologies of wireless sensor networks. The enhanced power efficiency, minimized production cost, condensed physical layout, and reduced wired connections present a much more proficient and simplified approach to the continuous monitoring of patients' physiological status. The proposed sensor network system is composed of wearable vital sign sensors and a workstation monitor. The wearable platforms are to be distributed to patients of concern. The wearable platforms can provide continuous electrocardiogram (ECG) monitoring by measuring electrical potentials between various points of the body using a galvanometer. They will then relay the ECG signals wirelessly to the workstation monitor. In addition to displaying the data, the workstation will also perform signal wavelet transformation for ECG characteristic extractions. Copyright © 2007 John Wiley & Sons, Ltd.
Load balance and energy efficient data gathering in wireless sensor networks
Authors: Mandala Devendar , Du Xiaojiang , Dai Fei , You Chao
Published: February 2007

Many data‐gathering protocols for wireless sensor networks use clustering technology for prolonging network lifetime. Cluster‐based protocols reduce the total energy consumption via data aggregation and balance energy consumption via clusterhead rotation. However, most existing protocols focus on load balance within each cluster. The energy consumption of the entire network is still unbalanced and this uneven energy dissipation can significantly reduce network lifetime. We propose an even energy dissipation protocol (EEDP) for efficient cluster‐based data gathering in wireless sensor networks. In EEDP, sensor data are forwarded to the base station (BS) via multiple chains of clusterheads. Each chain uses a rotation scheme to balance energy consumption among clusterheads and avoid the formation of a hot spot. We developed efficient algorithms to organize clusterheads into multiple chains, such that the traffic load is evenly distributed among different chains. Analysis and simulation results show that EEDP achieves better load balance than several existing protocols and significantly increases network lifetime. Copyright © 2007 John Wiley & Sons, Ltd.
Parenting styles, coping strategies, and the expression of homesickness
Authors: Nijhof Karin S. , Engels Rutger C.M.E.
Published: February 2007

The present study examined the role of parenting styles in the experience and expression of homesickness, and the way of coping with the feelings involved. Using a sample of 670 first year college and university students, aged 16 to 25, we tested three hypotheses: (1) authoritarian, permissive as well as uninvolved parenting are associated with the experience of homesickness, contrary to students with authoritative parents who are less likely to have feelings of homesickness; (2) students with authoritarian, permissive or uninvolved parents show their homesickness by internalizing and externalizing problems; and (3) students raised by authoritative or permissive parents use more effective coping strategies to deal with homesickness. Results indicated that students raised by authoritative and permissive parents experienced more homesickness with stronger feelings of homesickness than students raised by authoritarian or uninvolved parents. However, they hardly express homesickness by internalizing or externalizing problems when they use effective ways of coping, namely support‐seeking and/or problem‐solving. Students with parents endorsing an authoritarian or uninvolved parenting style, on the other hand, showed more internalizing and externalizing problems in reaction to feelings of homesickness. They also use less effective coping strategies. The results revealed the importance of a loving and accepting home environment for the development and expression of homesickness, as well as the importance of the way in which students learn to cope with their problems.
Nordic retirement contracts and the economic situation of widows
Authors: MORING BEATRICE
Published: February 2007

The aim of this article is to explore the economic status and the quality of life of widows in the Nordic past, based on the evidence contained in retirement contracts. Analysis of these contracts also shows the ways in which, and when, land and the authority invested in the headship of the household were transferred between generations in the Nordic countryside. After the early eighteenth century, retirement contracts became more detailed but these should be viewed not as a sign of tension between the retirees and their successors but as a family insurance strategy designed to protect the interests of younger siblings of the heir and his or her old parents, particularly if there was a danger of the property being acquired by a non-relative. Both the retirement contracts made by couples and those made by a widow alone generally guaranteed them an adequate standard of living in retirement. Widows were assured of an adequately heated room of their own, more generous provision of food than was available to many families, clothing and the right to continue to work, for example at spinning and milking, but to be excused heavy labour. However, when the land was to be retained by the family, in many cases there was no intention of establishing a separate household.
An urban–rural comparison of the prevalence of the metabolic syndrome in Eastern China
Authors: Weng Xiaoping , Liu Youxue , Ma Jiemin , Wang Wenjuan , Yang Gonghuan , Caballero Benjamin
Published: February 2007

Objective

To assess the impact of urbanisation on the prevalence of the metabolic syndrome in Chinese adults.

Design

As part of a community-based cross-sectional survey conducted in 2002, a sample from rural and urban populations in East China was obtained. The metabolic syndrome is defined by the National Cholesterol Education Program Adult Treatment Panel III criteria (ATP III) and the modified ATP III, which recommended a lower waist circumference cut-off for Asians.

Setting

Field sites in Jiangxi and Anhui provinces and the Jing'an District of Shanghai, China.

Subjects

A total of 529 non-pregnant, non-lactating urban and rural adults, aged 20–64 years without diagnosed diabetes.

Results

Dwelling in urban areas was associated with higher dietary fat intake and slightly lower total energy intake, and with significantly lower occupational physical activity. Using the ATP III criteria, the prevalence of the metabolic syndrome was significantly higher for urban than rural men (12.7 vs. 1.7%, P < 0.001), and was similar between urban and rural women (10.1 vs. 9.7%, P = 0.17). These urban–rural differences were greatly enhanced when the modified ATP III criteria for the syndrome were used, for men (34.3 vs. 2.7%, P < 0.01) and women (24.1 vs. 11.4%, P = 0.07). The Asian waist circumference cut-offs (90 and 80 cm for men and women, respectively) had a better combination of sensitivity and specificity in identifying other metabolic disorders, which included high glucose, high blood pressure, high triglycerides and low high-density lipoprotein cholesterol, for this population.

Conclusion

For the Chinese population, urban dwelling was associated with higher prevalence of the metabolic syndrome, especially in men.
Diet and overweight and obesity in populations of African origin: Cameroon, Jamaica and the UK
Authors: Jackson M , Walker S , Cruickshank JK , Sharma S , Cade J , Mbanya J-C , Younger N , Forrester TF , Wilks R
Published: February 2007

Objectives

To determine the relationship of diet to overweight and obesity among populations of African origin.

Design and setting

Cross-sectional data were obtained from adults aged 25–74 years in rural Cameroon (n = 686), urban Cameroon (n = 975), Jamaica (n = 924) and Afro-Caribbeans in the UK (n = 257). Dietary data were collected using food-frequency questionnaires specifically designed for each site. Body mass index (BMI) was used as a measure of overweight.

Results

The expected gradient in the distribution of overweight across sites was seen in females (rural Cameroon, 9.5%; urban Cameroon, 47.1%; Jamaica, 63.8%; UK, 71.6%); however, among males overweight was less prevalent in Jamaica (22.0%) than urban Cameroon (36.3%). In developing countries increased risks of overweight (BMI ≥ 25 kg m− 2) were influenced by higher energy (urban Cameroonian men) and protein (Jamaican women) intakes. No dietary variables were associated with obesity (BMI ≥ 30 kg m− 2) in Cameroon or Jamaica. In the UK, energy intakes were inversely related with overweight whereas increased risks of being overweight were associated with higher protein (men) and fat (women) intakes. Similarly, whereas higher protein and fat intakes in UK men and women were associated with obesity, carbohydrate intakes were associated with decreased risks of obesity in men.

Conclusions

Diet and overweight were associated in the UK but few dietary variables were related to overweight in Jamaica and the Cameroon. These findings suggest that associations between diet and overweight/obesity are not generalisable among populations.
Predictors of misreporting in an elderly population: the ‘Quality of life after 65’ study
Authors: Bazelmans C , Matthys C , De Henauw S , Dramaix M , Kornitzer M , De Backer G , Levêque A
Published: February 2007

Objectives

To evaluate the prevalence and identify some predictors of misreporting in an elderly Belgian population and to assess the effect of underreporting on estimated intakes of macronutrients and foods.

Design

A 1-day food record was completed by 2083 adult men and women aged 65 years or more. Individuals whose energy intake was lower than 0.90 × BMR (basal metabolic rate) were defined as underreporters. Overreporting was defined as energy intake greater than 2 × BMR.

Results

Underreporting and overreporting occurred in 13.6% and 7.9% of food records, respectively. Results from logistic regression models indicated that gender and body mass index (BMI) were predictors of misreporting. Whereas women were more likely to underreport energy intake, the prevalence of overreporting was higher in men. Underreporting was more prevalent among obese people and overreporting more prevalent in normal-weight subjects. Smoking status and education level did not predict underreporting; however, overreporting was more likely to occur in more highly educated subjects. A cultural difference in reporting of nutrient intakes was also found, with the percentage of underreporters being higher among Walloons compared with Flemish.

Conclusion

BMI seemed to be one of the most important factors in misreporting. This calls for special attention when dietary surveys are performed on obese or lean people.
Challenges in obtaining reliable measurements of point rainfall
Authors: Sieck Lisa C. , Burges Stephen J. , Steiner Matthias
Published: February 2007

Extensive data recorded from storm systems passing over the well‐instrumented 21.4 km2 Goodwin Creek watershed in northern Mississippi are used to highlight uncertainties associated with the measurement of surface rainfall, focusing on data quality control, gauge calibration, out‐of‐level gauge orifices, and wind effects on rain gauge catch. Assessment of the wind effect on gauge catch is central to the presented analyses, including an in‐depth evaluation of a recent technique for estimating the rainfall undercatch by means of wind and raindrop size information. Our findings emphasize that quantification of the wind effect on rain gauge catch is difficult because of uncertainties associated with measuring rainfall, drop size distribution, and the wind at gauge rim height. On the basis of our evaluation the sophisticated wind effect correction technique that makes use of raindrop size and wind information is much less effective than traditional methods based on rainfall rate and wind observations alone.
Modelling the surface and subsurface Martian radiation environment: Implications for astrobiology
Authors: Dartnell L. R. , Desorgher L. , Ward J. M. , Coates A. J.
Published: February 2007

The damaging effect of ionising radiation on cellular structure is one of the prime limiting factors on the survival of life in potential astrobiological habitats. Here we model the propagation of solar energetic protons and galactic cosmic ray particles through the Martian atmosphere and three different surface scenarios: dry regolith, water ice, and regolith with layered permafrost. Particle energy spectra and absorbed radiation dose are determined for the surface and at regular depths underground, allowing the calculation of microbial survival times. Bacteria or spores held dormant by freezing conditions cannot metabolise and become inactivated by accumulating radiation damage. We find that at 2 m depth, the reach of the ExoMars drill, a population of radioresistant cells would need to have reanimated within the last 450,000 years to still be viable. Recovery of viable cells cryopreserved within the putative Cerberus pack‐ice requires a drill depth of at least 7.5 m.
Numerical modeling of poorly sorted depositional turbidity currents
Authors: Huang H. , Imran J. , Pirmez C.
Published: February 2007

The characteristics of poorly sorted turbidity currents are investigated by numerical simulation. A multiphase approach is utilized to express the mass and momentum conservation equations for the bulk fluid. The Exner equation for multiple size classes of sediment is solved for the evolution of the bottom boundary. The model is applied to simulate experiments on poorly sorted gravity currents and reproduced the vertical structures of velocity, sediment concentration of individual size class and the total deposition depth satisfactorily. The numerical simulation further reveals that the normalized vertical profiles of concentration of all size classes coincide at the position where the maximum longitudinal velocity occurs. Below this position, in the logarithmic velocity region, all concentration profiles are upwardly convex and coarser particle size classes are of larger concentration; above it, in the exponentially decaying velocity region, all concentration curves are upwardly concave and finer particle size classes are of higher concentration. The model also predicts that the position of maximum longitudinal velocity corresponds to a region of low turbulent kinetic energy. The model has also been applied to study three‐dimensional poorly sorted depositional turbidity currents debouching from a straight channel into a horizontal unconfined area. Model results reveal the levee and channel building process in which the channel bed slope aggrades at a faster rate than that in the overbank area. The simulation also shows that the contour of mean size of deposited sediment is closely related to the contour of deposit thickness, and elongated somewhat in the flow direction.
Minimal dynamic model for electron-temperature-gradient turbulence
Authors: Peng X. D. , Tang C. J. , Qiu X. M.
Published: February 2007

The dynamical system for the toroidal electron-temperature-gradient (ETG) driven turbulence is investigated. Employing the low-order-truncation approximation, a set of coupling equations is derived to describe the minimal dynamic model for the ETG turbulence. Numerical simulation results show that there exist complex dynamical bifurcation behaviors in that turbulence. The onset of an electric local mode brings about the low to high (H) mode transition or the H to the barrier-localized/edge-localized mode (BLM/ELM) transition for the confinement in a tokamak. An interesting result is the onset of a magnetic local mode in the ETG turbulence system. It leads to the H to the magnetic high mode transition or the BLM/ELM to the magnetic BLM/ELM transition.
The effect of transverse wave vector and magnetic fields on resonant tunneling times in double-barrier structures
Authors: Wang Hongmei , Zhang Yafei , Xu Huaizhe
Published: February 2007

The effect of transverse wave vector and magnetic fields on resonant tunneling times in double-barrier structures, which is significant but has been frequently omitted in previous theoretical methods, has been reported in this paper. The analytical expressions of the longitudinal energies of quasibound levels (LEQBL) and the lifetimes of quasibound levels (LQBL) in symmetrical double-barrier (SDB) structures have been derived as a function of transverse wave vector and longitudinal magnetic fields perpendicular to interfaces. Based on our derived analytical expressions, the LEQBL and LQBL dependence upon transverse wave vector and longitudinal magnetic fields has been explored numerically for a SDB structure. Model calculations show that the LEQBL decrease monotonically and the LQBL shorten with increasing transverse wave vector, and each original LEQBL splits to a series of sub-LEQBL which shift nearly linearly toward the well bottom and the lifetimes of quasibound level series (LQBLS) shorten with increasing Landau-level indices and magnetic fields.
Instabilities and solitary structures in plasmas with ion beams: Linear theory and Vlasov simulations
Authors: Silin I. , Sydora R. , Sauer K.
Published: February 2007

The instabilities and solitons in plasmas with cold and relatively weak (nb∕ne⩽0.1) sonic (vb∼vs) ion beams are investigated by linear perturbation theory and Vlasov-Poisson simulations. The properties of beams and plasmas under consideration are comparable to those observed in the solar wind and in the Earth auroral zone near 1 RE. It is found that in the nonlinear phase, after the saturation of the unstable waves, the subsonic rarefactive and supersonic compressional solitary structures can be formed. Their propagation velocities are slightly below or above the ion sound velocity vs, lengths are of the order of 20–50 electron Debye lengths λDe, amplitudes δn∕n∼0.03–0.3 and eϕ∕(κBTe)∼0.01–0.1.
A pulsed electron gun for ultrafast electron diffraction at surfaces
Authors: Janzen A. , Krenzer B. , Heinz O. , Zhou P. , Thien D. , Hanisch A. , Meyer zu Heringdorf F.-J. , von der Linde D. , Horn von Hoegen M.
Published: February 2007

The construction of a pulsed electron gun for ultrafast reflection high-energy electron diffraction experiments at surfaces is reported. Special emphasis is placed on the characterization of the electron source: a photocathode, consisting of a 10 nm thin Au film deposited onto a sapphire substrate. Electron pulses are generated by the illumination of the film with ultraviolet laser pulses of femtosecond duration. The photoelectrons are emitted homogeneously across the photocathode with an energy distribution of 0.1 eV width. After leaving the Au film, the electrons are accelerated to kinetic energies of up to 15 keV. Focusing is accomplished by an electrostatic lens. The temporal resolution of the experiment is determined by the probing time of the electrons traveling across the surface which is about 30 ps. However, the duration of the electron pulses can be reduced to less than 6 ps.
Studies on the formation of large amplitude kinetic Alfvén wave solitons and double layers in plasmas
Authors: Devi N. , Gogoi R. , Das G. C. , Roychoudhury R.
Published: February 2007

A two fluid model has been employed to study the oblique propagation of solitary kinetic Alfvén waves. Formation of solitary waves and double layers is observed. Amplitude, width (in the case of solitons), and thickness (in the case of double layers) of the nonlinear structures are studied in some detail. Wider solitary structures are found to exist for oblique propagation nearer to the magnetic field direction.
Electronic states and photoexcitation processes of titanium dioxide nanoparticle films dip coated from aqueous Degussa P25 photocatalyst suspension
Authors: Yang Jihua , Warren David S. , Gordon Keith C. , McQuillan A. James
Published: February 2007

The electronic properties of titanium dioxide (TiO2) nanocrystalline films, which were prepared by dip coating from Degussa P25 photocatalyst aqueous suspension, have been investigated by surface photovoltage spectroscopy (SPS). As indicated by the positive contact potential difference (CPD) change in the sub-band-gap region, SPS shows that the molecularly adsorbed H2O in the freshly prepared P25 film creates an empty electron state, which is distributed within 0.79eV below the conduction band edge, and acts as an electron trap and carrier recombination center. With film aging or under a drying atmosphere, the H2O-associated state diminishes, and the occupied electron state due to molecularly adsorbed oxygen, lying within 1.06eV above the valence band edge, is identified by the reversed polarity of the CPD change in the sub-band-gap region. This information is important in developing a better understanding of real photocatalyst behavior.
Ultrasonic torsional guided wave sensor for flow front monitoring inside molds
Authors: Visvanathan Karthik , Balasubramaniam Krishnan
Published: February 2007

Measuring the extent of flow of viscous fluids inside opaque molds has been a very important parameter in determining the quality of products in the manufacturing process such as injection molding and resin transfer molding. Hence, in this article, an ultrasonic torsional guided wave sensor has been discussed for monitoring the movement of flow front during filling of resins in opaque molds. A pair of piezoelectric normal shear transducers were used for generating and receiving the fundamental ultrasonic torsional guided wave mode in thin copper wires. The torsional mode was excited at one end of the wire, while the flowing viscous fluid progressively wet the other free end of the wire. The time of flight of the transient reflections of this fundamental mode from the air-fluid interface, where the wire enters the resin, was used to measure the position of the fluid flow front. Experiments were conducted on four fluids with different viscosity values. Two postprocessing algorithms were developed for enhancing the transient reflected signal and for suppressing the unwanted stationary signals. The algorithms were tested for cases where the reflected signals showed a poor signal to noise ratio.
Room-temperature oxygen sensitivity of ZnS nanobelts
Authors: Liu Y. G. , Feng P. , Xue X. Y. , Shi S. L. , Fu X. Q. , Wang C. , Wang Y. G. , Wang T. H.
Published: February 2007

Room-temperature oxygen sensing is realized from individual ZnS nanobelts. Under UV illumination the current through ZnS nanobelt increases from 0.265to2.26nA as the oxygen pressure decreases from 1×105to3×10−3Pa. The conductance of ZnS nanobelt exhibits a logarithmic dependence on oxygen pressure, which is in agreement with theoretical prediction. The sensing is based on the enhanced modulation of ZnS nanobelts conductance by adsorbed oxygen under illumination. These results demonstrate an approach to in situ precisely detect oxygen at room temperature.
Spin-valve phototransistor
Authors: Huang Biqin , Altfeder Igor , Appelbaum Ian
Published: February 2007

The spin-valve phototransistor is a semiconductor-ferromagnetic metal multilayer-semiconductor transistor operated by photoexciting hot electrons in the emitter semiconductor into a Schottky collector. This device uses an ultra-high vacuum-bonded float zone Si/multilayer/n-InP structure. To distinguish the emitter interband-excited component of collector current from base/collector internal photoemission, a lock-in spectroscopy sensitive only to the magnetocurrent is used. The experimental results indicate a pathway to improve the magnetocurrent of a related device, the spin-valve photodiode, by increasing the fraction of hot electron current that travels through both layers of the ferromagnetic spin valve and demonstrate that hot electrons photogenerated in one semiconductor can be collected by another through a thin ferromagnetic multilayer.
Evidence for long-living charge carriers in electrically biased low-temperature-grown GaAs photoconductive switches
Authors: Loata Gabriel C. , Löffler Torsten , Roskos Hartmut G.
Published: February 2007

Low-temperature-grown GaAs continues to be one of the most important materials of ultrafast optoelectronics. Little is known, however, about the recombination dynamics of photogenerated charge carriers under the influence of an applied electric field, and it has remained unclear to what extent biased photoswitches exhibit field screening effects. Here, the authors investigate the screening in biased few-micrometer-sized photoconductive gaps quantitatively and find that it can amount to tens of percent of the applied field. They find that a subgroup of the photogenerated carriers recombines on an unexpectedly long excitation-density-dependent time scale of nanoseconds to tens of nanoseconds.
γ
-
Ga
2
O
3
quantum dots with visible blue-green light emission property
Authors: Chen Tao , Tang Kaibin
Published: February 2007

Visible blue-green light emission metastable γ-Ga2O3 quantum dots were prepared, and the light emission is clearly visible to the naked eyes. The UV-visible spectra present a blueshift phenomenon of the absorption edge as the particle sizes decrease; the fitted result of UV-visible data by Tauc function shows that the as-prepared γ-Ga2O3 is a wide-band-gap semiconductor with a direct band gap structure. The photoluminescence spectra show the evidence of quantum confinement and a blueshift when the crystal sizes decrease.
Efficient switching of Rashba spin splitting in wide modulation-doped quantum wells
Authors: Gvozdić D. M. , Ekenberg U.
Published: February 2007

The authors demonstrate that the size of the electric-field-induced Rashba spin splitting in an 80nm wide modulation-doped InGaSb quantum well can depend strongly on the spatial variation of the electric field. In a slightly asymmetric quantum well it can be an order of magnitude stronger than for the average uniform electric field. For even smaller asymmetry spin subbands can have wave functions and/or expectation values of the spin direction that are completely changed as the in-plane wave vector varies. The Dresselhaus effect [Phys. Rev. 100, 580 (1955)] can give an anticrossing at which the spin rapidly flips.
Age, growth and maturity of the roundel skate, Raja texana, from the Gulf of Mexico, USA
Authors: Sulikowski James A. , Irvine Sarah B. , DeValerio Kate C. , Carlson John K.
Published: February 2007

The roundel skate (Raja texana) inhabits near-shore waters throughout the Gulf of Mexico. Despite such a wide distribution, very little is known about its biology. In order to gain insight into the life history of this species, the age, growth and maturity of 231 skates ranging in size from 277 to 630-mm total length (TL) were examined. Based on vertebral band counts, the oldest age estimates obtained were 8 years for males and 9 for females, which corresponded to 495-mm TL and 630-mm TL respectively. Age-bias plots and coefficient of variation suggested that our ageing method represents a non-biased and precise approach to age assessment. Marginal increment and edge analyses suggested that growth bands are formed annually with a distinct trend of increasing growth at the beginning of March. Back calculations suggested a birth size of 113–118-mm TL. Observed and back-calculated length-at-age data were used to assess growth with four different models, including the von Bertalanffy (VBGM), von Bertalanffy with size at birth (VB with L
0), Gompertz and Francis models. Male and female growth was significantly different. The VBGM and the Francis model produced similar results and provided the best fit. Curves fitted with observed and back-calculated data suggested slightly faster growth than curves fitted with only observed data. Maturity occurred at 444-mm TL and 4.95 years for males, whereas females matured at 537-mm TL and 5.8 years.