bluuebunny/crossref_metadata_2025 huggingface dataset:
An experiment in numerical prediction in equatorial latitudes
Authors: Krishnamurti T. N.
Published: February 2007

A short‐range prediction experiment is performed to study the dynamical structure of the tropical atmosphere in equatorial latitudes. The initial field includes the intertropical convergence zone and associated disturbances over the western Pacific Ocean during March 1965. A complete initial state is constructed using a consistent balanced system of equations. The procedure involves construction of pressure, temperature and vertical motion distributions starting from the rotational part of the observed wind field. It is shown that this procedure, the validity of which assumes a small Rossby number, does not yield a realistic field of vertical motion.

A short‐range prediction with a multi‐level prediction model yields some interesting solutions in the vicinity of the intertropical convergence zone. During the first 18 hours of prediction there occurs an adjustment of the motion and the mass field, with gravity‐inertia oscillations.

An important feature of the model is a parameterization of cumulus convection as a function of the largescale moisture convergence. The role of cumulus scale heating in the vicinity of the intertropical convergence zone is investigated and it is shown that during the adjustment process a convergence zone forms which exhibits a strong coupling with the zone of frictional vertical rising motion and the field of computed cloud cover. The formation of this feature appears to represent the numerical simulation of a tropical storm.
The energy formula in a moving reference frame
Authors: Betts A. K. , McIlveen J. F. R.
Published: February 2007

The energy formula quoted by Green, Ludlam and McIlveen (1966) requires an additional term if it refers to a frame moving over the Earth's surface. The correction is derived for steady motion of the frame and tested observationally. The error incurred by ignoring the motion of a weather system is discussed.
Unsteady wind‐driven ocean currents
Authors: Lighthill M. J.
Published: February 2007

The linear theory of unsteady wind‐driven currents in a horizontally stratified ocean is reviewed in general and applied in detail to the northern part of the Indian Ocean, for several reasons the most suitable area for comparison with observed current changes. The ocean is predicted to respond to the onset of the Southwest Monsoon principally in two modes as far as vertical distribution of current is concerned; to a somewhat lesser extent in the barotropic mode with uniform distribution, and to a somewhat greater extent in the first baroclinic mode with current distribution roughly as in Fig. 1, concentrated predominantly in the uppermost 200 m.

Calculations for a zonal distribution of winds, which rather rapidly make a reversal of direction and increase of strength somewhat north of the Equator characteristic of monsoon onset, predict that the barotropic and baroclinic modes are both propagated to the west at comparable speeds of the order of 1 m s−1; the marked contrast here with other oceans (in the comparability of speeds) is given particularly detailed study. When the associated patterns of current flux reach the coast of East Africa, they become concentrated into the Somali current, which flows northward along the coast only during the Northern Hemisphere summer (after monsoon onset) but during that time is comparable in volume flow (about 5 × 107 m3 s−1) to other western boundary currents such as the Gulf Stream.

Theory indicates one month (of which two‐thirds is needed for propagation of current patterns and one‐third for their concentration into a boundary current) as the characteristic time scale for formation of the Somali current, in contra‐distinction to the ‘decades’ predicted by the same type of theory for the Gulf Stream (Veronis and Stommel 1956). The flow is calculated to reach 40 per cent of a typical maximum value (observed in August) within a month of monsoon onset (May). The linear theory predicts the current as extending as far north as 6°N, but non‐linear terms are generally found in computational studies (Bryan 1963; Veronis 1966) to bring about some ‘inertial overshoot’ in concentrated boundary currents, which may explain why the current does not in fact separate until about 9°N. In the non‐equatorial oceans, however, non‐linear effects are expected to be much greater.
The influence of vertical variation of zonal wind on the response curve in atmospheric oscillations
Authors: Giwa F. B. A.
Published: February 2007

The Earth is treated as a flat non‐rotating plane across which tidal forces sweep from east to west. It is shown that one effect of zonal wind variation is to replace the constant quantity σ0, (iσ0 = δ/δt) by another quantity σ which varies as the zonal wind. This results in an ‘effective equivalent depth’ whose value varies with the wind.

It is also shown that the effect of westerlies is to reduce the values of resonant equivalent depths while easterlies increase them. The inclusion of zonal wind gives a better value of magnification to explain the lunar tide than does the classical theory.
On the representativeness of mean ozone distributions
Authors: Pittock A. B.
Published: February 2007

On the basis of total ozone, Umkehr data and ozone soundings with Mast‐Brewer sondes at Aspendale, it is shown that the systematic effect of selectivity in the days on which Umkehr observations are made may be as large as 10 to 35 per cent of the annual mean content of layers 2 and 3. This selectivity effect varies with time, and is reasonably explained in terms of a correlation between ozone content in the lower stratosphere and cloudiness. Caution with regard to the use of Umkehr‐derived mean ozone distributions in climatological studies is therefore urged, and the need for further research is pointed out. The statistical limitations of mean distributions derived from ozone‐sonde flights are also discussed, with particular reference to quasi‐periodic influences.
The electrostatic forces on charged ice crystals separated by small distances in an electric field
Authors: Latham J. , Saunders C. P. R.
Published: February 2007

Measurements have been made, using a precision balance, of the electrostatic forces exerted on scaled‐up metallic models of cloud droplets and, particularly, ice crystals, as a function of their charges, configurations and proximity to a second model, together with the strength of the electric field E in which they were situated and the angle θ between the direction of the field and the line of centres of the models.

It was found that the electrostatic forces on metallic spheres agreed closely with those calculated from the equation of Davis (1964). The forces on irregularly shaped uncharged metallic models of ice crystals were generally larger than those on spheres of equivalent volume to the crystals by a factor γ which was shown to be independent of E and θ and, in general, extremely insensitive to the separation over the range of conditions studied.

The measured values of γ, together with the values of the equivalent radius Re of a crystal, deduced directly from its volume, were incorporated into a modified form of Davis' equations which should be useful in computations of the collision efficiencies of uncharged ice crystals.
Ice particles in maritime clouds near Tasmania
Authors: Mossop S. C. , Ono A. , Wishart E. R.
Published: February 2007

An instrumented aircraft was used to sample particles in the upper regions of small supercooled cumulus clouds in maritime air off the Tasmanian coast in May 1968. 114 clouds were studied on nine days, and it was found on average that clouds had a 50 per cent chance of containing ice particles when a summit temperature of about − 8°C was reached. Not only cloud temperature but also cloud width had a profound effect on whether ice particles were found.

The cloud summit temperature at which ice particles first reached detectable concentrations in narrow clouds on a particular day was related to the ice nucleus concentration as measured in a cloud chamber, being, in general, highest on days of high ice nucleus concentration. However, in some glaciated clouds ice crystal concentrations of the order of 100 1−1 were found. These were greater by a factor of ∼ 104 than the estimated number of active ice nuclei. The process of multiplication of ice crystals may be associated with the riming of ice particles. Riming was assisted by the presence of large droplets, up to drizzle size, in these clouds. Multiplication of the number of ice crystals by a factor of 10 took place in about 8 minutes.

The various stages in the glaciation process are described.
Estimates of kinetic energy over the Indian monsoon trough zone
Authors: Anjaneyulu T. S. S.
Published: February 2007

Averaged radiosonde/rawin/pibal data for July and August have been used to study the kinetic energy budget of the troposphere over a quasi‐elliptical area containing the Indian monsoon trough.

Incoming and outgoing kinetic energy fluxes have been evaluated. The computations show that the export of kinetic energy from the monsoon ellipse is about 57 × 106 Joules day−1. This export takes place in the upper troposphere, mostly above 300 mb.

Production of kinetic energy occurs mainly in the upper troposphere in the southern periphery of the huge quasi‐static South Asiatic ridge in the upper troposphere.
Observations of the eddy fluxes of heat and vapour over the sea
Authors: Warner J.
Published: February 2007

The results are reported of 61 observations of eddy fluxes of heat and vapour at different heights above the sea surface in the trade wind régime off the eastern Australian coast at latitude 16.51°S. The flux gradients were found to be consistent with observed temporal changes in temperature and mixing ratio as the air moved over the sea. The measured fluxes were found to agree with those calculated by bulk aerodynamic methods on the assumption of a 2°C sea‐air temperature difference. The evaporation rate deduced from the vapour flux measurements is about 7 mm day −1.
The geostrophic drag coefficient and the ‘effective’ roughness length
Authors: Fiedler F. , Panofsky H. A.
Published: February 2007

An ‘effective’ roughness length is defined for use over heterogeneous terrain as the roughness length which homogeneous terrain would have to give the correct surface stress over a given area. A method is suggested to compute geostrophic drag coefficient, wind‐contour angle and surface heat flux, given this roughness length, latitude, geostrophic wind speed and insolation or ground‐air temperature differences.
A scheme for kinematic estimate of large‐scale vertical motion with an upper‐air network
Authors: Kung E. C.
Published: February 2007

A scheme for kinematic estimate of the vertical p‐velocity ω is designed under the presumption that the profiles should converge to a near zero value at the top of the atmosphere without being so required when a sensitive balance between the analysis scheme and data disposition is achieved. The scheme provides a range of eight degrees of optimization in estimating the divergence through the order of polynomial representation of the wind field, the treatment of missing wind data, and the space smoothing of the divergence.

The scheme is applied to synoptic wind observations from the upper‐air network over North America. The computed ω profiles and patterns of vertical motion field obtained from those profiles appear to support the proposition. It is indicated that the field of kinematic ω so computed through the depth of atmosphere will be useful in the study of large‐scale atmospheric dynamics.
The dry‐line of Northern India and its role in cumulonimbus convection
Authors: Weston K. J.
Published: February 2007

An interesting feature of the flow pattern over India during the premonsoon months ‐ a frontal surface separating a shallow, warm moist layer from a deeper, hot, very dry layer ‐ is studied in some detail. In particular, its role in the development of severe cumulonimbus over north‐east India is investigated. Routine observations are insufficient to resolve many of the features of this ‘dry‐line’ and a simple dynamical model is constructed which suggests an interface in the form of a step with a height (Zi*) dependent upon the pressure gradient in the moist air (A = 1/ρ ∂p/∂x), surface drag coefficient (CD) and Coriolis parameter (f), given by the expression Zi* = 4/15 A CD/f2. An extension of the model to include a frictional stress variable with height suggests a circulation within the shallow moist layer which, together with solar heating, would be likely to lead to cumulus and cumulonimbus development near the edge of the moist air; this is observed on satellite photographs.
Flooding of Venice: Phenomenology and prediction of the Adriatic storm surge
Authors: Robinson A. R. , Tomasin A. , Artegiani A.
Published: February 2007

Since both observations and theory indicate weak dissipation, a frictionless one‐dimensional model elucidates the dynamics of the surge and is used to hindcast and forecast. Wind over the shallow northern Adriatic dominates the forcing. The relative phases of the astronomical tide, the storm tide, and the preexisting seiche determines flooding. Good real time predictions are now in progress.
A numerical study of the nocturnal atmospheric boundary layer
Authors: Delage Yves
Published: February 2007

The evolution of the structure of the atmospheric boundary layer during the cooling phase of the diurnal cycle is studied with the help of a one‐dimensional numerical model. The model uses a turbulent energy equation for the determination of the eddy exchange coefficients, which also involve the local value of the Monin‐Obukhov length. The surface temperature is prescribed as a function of time and the geostrophic wind is held constant. Results are presented in nondimensional form and cover a wide range of possible values for the external parameters. After several hours of cooling the inversion layer is found to reach a maximum depth, which depends strongly upon the magnitude of the geostrophic wind and, to a lesser extent, on the cooling rate of the ground surface.
The information content of remote measurements of atmospheric temperature by satellite infra‐red radiometry and optimum radiometer configurations
Authors: Peckham G.
Published: February 2007

Infra‐red radiometry from an earth satellite is becoming an important technique for the determination of the three‐dimensional temperature structure of the atmosphere on a global scale. In this paper a quantitative expression for the information content of the data from a temperature sounding radiometer is derived. A simple model for the 15 μm CO2 absorption band is used to find radiometer configurations which give maximum information. The spectral bandwidths corresponding to these optimum configurations are considerably broader than those specified in the past for radiometers of this type. The technique of selective chopping in which the radiometer contains absorbing cells filled with CO2 is shown to make a significant increase in the information content.
A field study of the turbulent fluxes of heat, water vapour and momentum at a ‘typical’ agricultural site
Authors: Högström Ulf
Published: February 2007

An extensive set of measurements of turbulent fluxes of sensible heat, water vapour and momentum together with mean profiles of temperature, water vapour and wind speed at a ‘non‐ideal’ agricultural site in southern Sweden have been analysed in terms of the Monin‐Obukhov similarity theory. The fluxes of sensible heat, H, and water vapour, E, have been determined with the eddy correlation method, the accuracy of H + ELv being c. Φ 12% according to comparison with net radiation minus ground heat flux. The momentum flux has been determined from low level wind measurements, with a stability dependent ‘skin friction method’.

During stationary conditions with winds from ‘undisturbed’ directions (extensive forest areas more than 3 km distant) and unstable stratification, the data for dimensionless wind and temperature gradients, Φm and ϕh, respectively, are well described by the expressions put forward by Businger et al. (1971), with von Kàrmàn's constant, k = 0.35. The corresponding dimensionless water vapour gradient, Φe, is shown also to follow similarity during these conditions (although exhibiting larger scatter than the two other plots), coinciding with Φh for strong instability but approaching Φm= 1.35 Φh, at neutrality.

For stable stratification the dimensionless profiles do not follow similarity in this study, nor do cases with winds from a 700 m distant forest nor non‐stationary cases, as might be expected.

A combined energy balance and gradient approach is shown to give good results not only for the ‘ideal’, unstable case but also for non‐stationary conditions and for conditions with winds from the ‘disturbed’ direction. With temperature and humidity differences measured between 0.5 and 1.14 m above ground and with Φe/Φh = 1.35 there is no systematic difference between measured and calculated fluxes, the accuracy in an individual calculated flux being better than 20%. For the stable case it is shown that the flux of sensible heat can be determined with good accuracy with the flux‐gradient method, using data from the 0.5 ‐ 1.14 m layer. The water vapour flux is obtained with good accuracy as a residual term from the energy balance equation.
The temperature structure of the Southern Hemisphere stratosphere August – October 1971
Authors: Harwood R. S.
Published: February 2007

The temperature field in the Southern Hemisphere stratosphere from 100 to 1mb during August to October 1971 is described using observations from the Selective Chopper Radiometer on the Nimbus IV spacecraft.

Zonal and monthly mean wind fields for September and October 1971 deduced from these temperatures are presented and the behaviour of the zonal temperature waves with wavenumbers 1, 2 and 3 is discussed. The largest amplitudes of wavenumbers 1 and 2 in the horizontal coincide broadly with the maximum westerlies. The amplitudes of wavenumber 2 are generally smaller at around 20mb than above or below. The amplitudes of both waves are small north of 30°S.

Wavenumber 1 exhibits little vertical coherence throughout August and September. In October, however, the slope of the wave with height is much less variable, in spite of a slow eastward movement in early October and a westward movement in late October.

Wavenumber 2 travelled eastwards with a fairly uniform rate of approximately 15·5° longitude per day between 15 August and 7 October but less uniformly at other times. Changes in wave amplitude at strato‐pause levels are associated with comparable changes near the tropopause. A maximum of wavenumber 2 amplitude on 26 September 1971 is associated with falling ZPE in the lower stratosphere and rising ZPE in the higher stratosphere. The dominant contribution to the eddy available potential energy is in the lower stratosphere.

In the low stratosphere there is an inverse relationship in zonal and eddy available potential energies, rises in one form being associated with falls in the other. This inverse relationship is not well marked in the high stratosphere.
Production of ice crystals by riming in slightly supercooled cumulus
Authors: Mason B. J.
Published: February 2007

It is shown that ice‐crystal concentrations of order 10/litre may be produced in clouds limited to the −8°C level if growing pellets of soft hail release splinters at the rates recently observed in laboratory experiments by Hallett and Mossop (1974) and provided that these splinters can continue to grow in at least three successive thermals over a period of about 1 1/2 hours.
A two‐dimensional mean circulation model for the atmosphere below 80km
Authors: Harwood R. S. , Pyle J. A.
Published: February 2007

The paper sets out the detailed formulation of a numerical model whose purpose is the study of the interactions of dynamics, photochemistry and radiation in the stratosphere and mesosphere. Two integrations of the model for 900 days are described in which many features of the atmosphere are reproduced but with important differences of detail.

The dependent variables are zonal means of the relevant meteorological quantities, held as functions of time, latitude and height (log pressure) with a resolution of μ/19 in latitude and 0.5 in pressure scale height.

Eddy fluxes of heat and matter are treated by large‐scale diffusion coefficients. This treatment is not applicable to momentum fluxes: these are currently specified from observations made mainly from the selective chopper radiometer on the Nimbus V spacecraft.

Radiative coolings due to CO2and O3emission are computed from simplified expressions which are essentially cooling‐to‐space approximations with emissivities obtained by curve‐fitting against the results of more elaborate treatments. Absorption of solar radiation by ozone is obtained from tabulations of absorption against ozone amount traversed. Radiation and latent heat release in the troposphere are specified climatologically.

The photochemistry in the integrations described here is the classical ozone scheme but, with a view to investigating possible stratospheric pollution problems, integrations have been performed with the inclusion of reactions involving nitrogen and hydrogen compounds. These will be described in a later paper.
The assignment of Rainfall stations into homogeneous groups: An application of principal component analysis
Authors: Dyer T. G. J.
Published: February 2007

The calculation of eigenvectors has been used to describe annual precipitation totals over an area of large extent. Rotation of the eigenvectors brought about further clarification of the system of recording stations. By noting the eigenvector of most importance to each station, delimitation of an area was made possible. Reduction in records, a necessary prelude to our future work on forecasting models, was obtained by discarding those stations most closely related to eigenvectors whose eigenvalue was less than 0·6.
Low‐level air flow circulation over the Arabian Sea during the summer monsoon as deduced from satellite‐tracked superpressure balloons. Part I—Balloon trajectories
Authors: Cadet Daniel , Ovarlez Henri
Published: February 2007

During the northern summer of 1975, 45 superpressure constant‐level balloons were released from the Seychelles Islands (4.7°S 55.5°E) for flight at 955mb (500m), 910mb (1000m) and 860mb (1500m) within the tropical boundary layer. The balloons were located by the Random Access Measurement System (RAMS) of the Nimbus‐6 satellite. This spacecraft also operated as a data relay system and collected pressure measurements performed by transducers carried by the balloons. The mean lifetime of the balloons was about 4–5 days, some of them lasting more than 8 days. Low‐level Lagrangian air trajectories in the southwesterly flow over the Arabian Sea are presented. They show the drastic changes in the airflow direction over the southwestern Arabian Sea associated with high or low activity periods of the monsoon over the western coast of India. During the first period of the experiment, the airflow over the southwestern Arabian Sea joins the low‐level jet flowing to the east of the Somali coast. This change, due to intense convective activity near Somalia, can be associated with a break in the monsoon activity. During the second period the air joins the Bay of Bengal branch of the monsoon over the southwest coast of India. Before the end of July a complete reversal of the winds over the Seychelles Islands is observed and some balloons drift towards Madagascar. During the third period the air flow over the Arabian Sea resumes a southwesterly direction and at the beginning of August it seems to join again the Bay of Bengal branch of the monsoon.

Thus this experiment shows that low‐level ballooning can be used to map air currents over vast unsurveyed areas of the oceans.
Eddy flux measurements above a pine forest
Authors: Moore C. J.
Published: February 2007

Estimates of sensible and latent heat flux measured above a Pinus radiata forest plantation, 11km north of Mt Gambier in South Australia, by eddy‐correlation instrumentation, were found to satisfy the forest energy budget to within 20% provided the mean windspeed was greater than about 2ms−1. In lighter winds these two fluxes were severely underestimated. A study of the higher windspeed data when the forest canopy was externally dry and transpiration the only water loss, gave a Bowen ratio of 0.8 ± 0.1 during the day, with a diurnal trend similar to that for shorter vegetation types. In these conditions the hourly change in canopy heat storage was a significant component of the energy budget. When the canopy was wet from intercepted rainfall, the Bowen ratio was generally less than 0.3 and often negative. Incoming sensible heat and a cooling canopy provided energy for evaporation when the net radiation was low or negative.
Baroclinic instability in the summer mesosphere
Authors: Simmons A. J.
Published: February 2007

Baroclinic instability is examined in idealized models of the summer circulation of the upper stratosphere and mesosphere. For all but possibly the fastest rate of thermal dissipation, results suggest the development of disturbances which have zonal wavelengths around 5000 km and which move with westerly phase speeds between 5 and 10 m−1 relative to an easterly maximum. Their periods relative to the ground are close to one day. the vertical scale of perturbation velocities is some 15 km. Temperatures exhibit a shorter vertical scale of about 5 km or less.
Hydropeaking impact on a riparian ground beetle community
Authors: Looy Kris Van , Jochems Hans , Vanacker Stijn , Lommelen Els
Published: February 2007

The Common Meuse reach is strongly influenced by the operation of a hydropower plant at the upstream weir of Lixhe, especially during periods of low flow. Ecologically based in‐stream flow requirements and fluctuation thresholds have already been determined for this reach by reconstruction of the natural discharge course from historic and actual reference conditions. Nevertheless, more evidence from the present biota at risk has been demanded. This study therefore attempts to define boundary conditions for the low flow regime from the analysis of riparian ground beetles in this river reach. To achieve this, reference conditions for the hydroregime aspects of flow variation were determined. Then, using the habitat templet approach, the hydropeaking pressure was related to biological quality elements. Finally, after detecting the impact on the specific gravel bar ground beetles, thresholds and boundary conditions were determined for the hydropeaking pressure in peak velocity. Copyright © 2007 John Wiley & Sons, Ltd.
Creating value in the face of declining performance: firm strategies and organizational recovery
Authors: Morrow J. L. , Sirmon David G. , Hitt Michael A. , Holcomb Tim R.
Published: February 2007

Firms that have failed to meet the performance expectations of investors must seek new ways of creating value or face the loss of financial support. Using resource‐based arguments, we find that valuable and difficult‐to‐imitate strategies that recombine the firm's existing stock of resources to create new products, processes, or technologies have a positive effect on organizational recovery as measured by investors' expectations. Similarly, acquiring new resources through mergers or acquisitions also has positive effects on investors' expectations. In contrast, valuable and difficult‐to‐imitate strategies that provide the firm with access to new resources through alliances or joint ventures do not affect investors' expectations of performance. We also find that taking actions that are not valuable and difficult‐to‐imitate either have no effect on performance or may lead to further performance declines. Lastly, our results show that valuable and difficult‐to‐imitate strategic actions that use existing resources in new ways contribute the most to organizational recovery. Copyright © 2007 John Wiley & Sons, Ltd.
Reproductive behaviour in three Navarrese villages (eighteenth to twentieth centuries)
Authors: BARRICARTE JESÚS J. SÁNCHEZ
Published: February 2007

This article presents the results of the family reconstitution carried out in three villages in the Spanish province of Navarre, covering a period from the late seventeenth century to 1994. This set of data from over 300 years comprises one of the longest family reconstitution projects in Spain, and means that the present study is based on a major database consisting of over 110,000 entries which can be used to explore various aspects of the demography. In this study I present the evolution of several indicators of fertility, all of which are aspects that can help us to reflect on a phenomenon that has long been known, but which is still not fully understood: the demographic transition. The microfocus of family reconstitution has enabled us to question numerous assumptions about the time when the fall in the birth rate began, the irrational or unconscious nature of reproduction in the pretransitional phase and the strategies employed by couples to have smaller families.
First Farmers: the Origins of Agricultural Societies, by Peter Bellwood. Malden (MA): Blackwell, 2005; ISBN 0-631-20565-9 hardback £60; ISBN 0-631-20566-7 paperback £17.99, xix+360 pp., 59 figs., 3 tables
Authors: Bellwood Peter , Gamble Clive , Le Blanc Steven A. , Pluciennik Mark , Richards Martin , Terrell John Edward
Published: February 2007

There can be no doubt that Peter Bellwood's First Farmers is a major new statement which presents a robustly expressed solution to one of those classic problems which provides a benchmark for theorization and justifies archaeology as a field. But agreement stops there. Few academic books published recently have evoked such highly charged reactions. On the one hand, First Farmers has impressed many critics, reached audiences far afield from traditional archaeological readerships, and garnered major book awards from professional bodies such as the Society for American Archaeology. On the other hand, it has been subjected to a level of concerted criticism rare in the academic world. As the reviews below show, it has clearly hit a nerve; the gloves are off.

First Farmers polarizes scholars in complex ways. Much recent work on agricultural origins, particularly in Europe, has had a strongly indigenist and particularistic tone, averse to mass movements of peoples and ‘grand narratives’ in general. But even advocates of grand narrative in general may take exception to Bellwood's ‘language dispersals’ thesis. Similarly, the very attempt to bring together linguistic, genetic and archaeological data in an account of the past is controversial to some, but even those who aspire to this kind of interdisciplinary synthesis rarely agree on how it can be carried out.

Neither the book nor its critics here are likely to be the last word on the subject. But whether one agrees with it or not, First Farmers is a welcome addition to the agricultural origins scene, which, at least in Europe, has been evolving over the last two decades towards a sort of eclectic middle-ground consensus in which difference of opinion is accommodated by eschewing bold generalization.
Isolation and initial culture of porcine inner cell masses derived fromin vitro-produced blastocysts
Authors: Kim H-S. , Son H-Y. , Kim S. , Lee G-S. , Park C-H. , Kang S-K. , Lee B-C. , Hwang W-S. , Lee C-K.
Published: February 2007

The present study was conducted to isolate and culture inner cell mass (ICM) primarily derived fromin vitro-produced blastocysts and to develop the culture conditions for the ICM cells. In Experiment 1, immunosurgically isolated ICMs of blastocysts derived fromin vitrofertilization (IVF), somatic cell nuclear transfer (SCNT) or parthenogenetic activation (PA) were seeded onto STO cells. Primary colonies from each isolated ICM were formed with a ratio of 28.9, 30.0 and 4.9%, respectively. In Experiment 2, blastocysts collected from IVF were directly seeded onto a feeder layer with or without zona pellucida (ZP), or were subjected to ICM isolation by immunosurgery. Primary colonies were formed in 36.8% of isolated ICMs and 19.4% in intact blastocysts without ZP. In Experiment 3, ICMs from IVF blastocysts were seeded onto STO cells, mouse embryonic fibroblast (MEF) or porcine uterine epithelial cells (PUEC). On STO and MEF cells, 34.5 and 22.2% of primary colonies were formed, respectively. However, no primary colony was formed on the PUEC or in feeder-free condition. In Experiment 4, ICMs from IVF blastocysts were cultured in DMEM + Ham's F10 (D/H medium), DMEM + NCSU-23 (D/N medium) or DMEM alone. When D/H medium or D/N medium was used, 21.7 or 44.4% of primary colony were formed, respectively, while no primary colony was formed in DMEM alone. These cells showed alkaline phosphatase activity and could be maintained for up to five passages. In suspension culture, cells formed embryoid bodies. These results demonstrate that porcine ICM could be isolated and cultured primarily fromin vitro-produced blastocysts with a suitable culture system.
Trends in food availability determined by the Food and Agriculture Organization's food balance sheets in Mediterranean Europe in comparison with other European areas
Authors: Balanza Rafael , García-Lorda Pilar , Pérez-Rodrigo Carmen , Aranceta Javier , Bonet Mònica Bulló , Salas-Salvadó Jordi
Published: February 2007

Objective

The aims of this study were to assess the changes that have occurred in food patterns in Europe over the last 40 years based on food availability data and to compare the stability of the traditional Mediterranean diet in the south of Europe in this period.

Design

An ecological study carried out on the basis of Food and Agriculture Organization food balance sheets for three geographical areas of Europe (Mediterranean, north and east) over two time periods: 1961–1963 and 1998–2000. The average availability of total energy, energy provided from macronutrients and food groups was calculated for each area and each period studied.

Results

Over the last 40 years total energy availability and energy availability from lipids have increased considerably in the three European areas, while the percentage of energy from carbohydrates has fallen. The greatest changes have occurred in Mediterranean Europe, with an increase of 20.1% in total energy availability, an increase of 48.1% in energy availability from lipids and a fall of 20.5% from carbohydrates. Moreover, Mediterranean Europe showed a significant fall in the energy supplied by cereals (29.9%) and wine (55.2%), while the contribution of milk (77.8%) and dairy products (23.6%) increased.

Conclusions

The results of this study suggest that European Mediterranean countries should take nutrition policy action to maintain their traditional healthy food pattern, with a cultural added value. This implies actions at all levels, including raising awareness of consumers, collaboration with the food sector and a call to set the agenda of the concerned politicians and stakeholders.
Secular trends in the association of socio-economic position with self-reported dietary attributes and biomarkers in the US population: National Health and Nutrition Examination Survey (NHANES) 1971–1975 to NHANES 1999–2002
Authors: Kant Ashima K , Graubard Barry I
Published: February 2007

Objective

Recent reports suggest persistence of health disparities related to socio-economic position (SEP). To understand if diet may be a contributor to these trends, we examined secular trends in the association of diet and indicators of SEP from 1971–1975 to 1999–2002.

Design

We used data from the National Health and Nutrition Examination Surveys (NHANES) I (1971–1975), II (1976–1980), III (1988–1994) and 1999–2002 to examine the independent associations of poverty income ratio (PIR) and education with diet and biomarkers of diet and disease in 25–74-year-olds (n = 36 600). We used logistic and linear regression methods to adjust for multiple covariates and survey design to examine these associations.

Results

A large PIR differential in the likelihood of reporting a fruit or all five food groups and vitamin C intake, and an education differential in likelihood of obesity and carbohydrate intake, was noted in 1971–1975 but narrowed in 1999–2002 (P < 0.007). The positive association of education with intake of a fruit, vegetable or all five food groups, vitamins A and C, calcium and potassium intake remained unchanged across surveys (P < 0.001). Similarly, the positive association of PIR with the amount of foods and intakes of energy and potassium remained unchanged over three decades (P < 0.001). The education and the PIR differential in energy density, and the PIR differential in the likelihood of obesity, persisted over the period of the four surveys (P < 0.001).

Conclusions

Persistence of unfavourable dietary and biomarker profiles in Americans with low income and education suggests continued need for improvement in the quality of diets of these high-risk groups.
The mass multiplet in Penning trap ion cyclotron resonance mass spectroscopy
Authors: Barlow S. E.
Published: February 2007

A model for the behavior of closely spaced masses—the “mass multiplet”—in a Penning trap mass spectrometer is developed. The model shows how these species separate from each other (or not) following resonant excitation, and gives quantitative criteria for mass separation. More surprisingly, the model shows the species tend to drift to different mean cyclotron radii. This latter effect undoubtedly plays a role in the problem of abundance determinations in Penning trap mass spectrometers.
Purely dipolar versus dipolar-exchange modes in cylindrical nanorods
Authors: Puszkarski H. , Krawczyk M. , Lévy J.-C. S.
Published: February 2007

Properties of purely dipolar and dipolar-exchange modes in finite circular rods are investigated numerically, with the sample static magnetization assumed to be uniform and parallel to the rod axis; we study magnetic excitations propagating along this direction. In particular, we demonstrate size-exchange effects induced by modifying the rod aspect ratio (the diameter to length ratio) and the strength of the exchange coupling. Untypical groups of purely dipolar modes are shown to occur in smooth rods: bulk-dead modes, characterized by a dead-amplitude region inside the rod, and comb modes, in which a nearly “dead” region is found at the sample borders, while numerous (“comb-like”) oscillations take place in the bulk. These two mode groups fade to disappear when the sample geometry evolves toward the thin-film one, or when the exchange becomes dominant. The existence of these untypical modes is related to local demagnetizing field profile nonhomogeneity, particularly to two edge wells found in the field profile. The bulk-dead modes are low-frequency modes confined to the well regions only (and therefore double-degenerated), while modes with higher frequency values (subjected to an interference within the barrier) become fast-oscillating comb modes. When the contribution of the exchange grows to prevail, the “dipolar” nonhomogeneity becomes negligible with respect to the total (exchange and dipolar) energy, and only the typically exchange-related bulk and surface modes are found to subsist.
Quantum dynamical semigroups for finite and infinite Bose systems
Authors: Blanchard Ph. , Hellmich M. , Ługiewicz P. , Olkiewicz R.
Published: February 2007

A new class of quasifree quantum Markov semigroups on C*-algebras of canonical commutation relations is introduced and discussed. Two applications to decoherence in the Heisenberg representation are given. In the first one the dynamical semigroup which leads to the appearance of decoherence induced superselection rules corresponding to the boundary conditions of a quantum particle in a finite interval is considered. The second example analyzes the possibility of the transition from infinite systems to systems with a finite number of degrees of freedom.
Blue light emitting diodes based on fluorescent CdSe∕ZnS nanocrystals
Authors: Rizzo Aurora , Li Yanqin , Kudera Stefan , Della Sala Fabio , Zanella Marco , Parak Wolfgang J. , Cingolani Roberto , Manna Liberato , Gigli Giuseppe
Published: February 2007

The authors report on the blue electroluminescence from CdSe∕ZnS core/shell nanocrystals prepared from ultrasmall, magic size CdSe clusters that have a diameter of less than 2nm. The light emitting device consists of an active layer of nanocrystals blended with 4,4′,N,N′- diphenylcarbazole and an evaporated electron transporting/hole blocking layer made of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline. A blue, stable electroluminescence at 485nm from the hybrid device was observed, in good agreement with the photoluminescence spectra of a solid film of the same nanocrystals used for the device.
How does the coupling of secondary and tertiary interactions control the folding of helical macromolecules?
Authors: Varshney Vikas , Carri Gustavo A.
Published: February 2007

The authors study how the simultaneous presence of short-range secondary and long-range tertiary interactions controls the folding and collapse behavior of a helical macromolecule. The secondary interactions stabilize the helical conformation of the chain, while the tertiary interactions govern its overall three-dimensional shape. The authors have carried out Monte Carlo simulations to study the effect of chain length on the folding and collapse behavior of the chain. They have calculated state diagrams for four chain lengths and found that the physics is very rich with a plethora of stable conformational states. In addition to the helix-coil and coil-globule transitions, their model describes the coupling between them which takes place at low temperatures. Under these conditions, their model predicts a cascade of continuous, conformational transitions between states with an increase in the strength of the tertiary interactions. During each transition the chain shrinks, i.e., collapses, in a rapid and specific manner. In addition, the number of the transitions increases with increasing chain length. They have also found that the low-temperature regions of the state diagram between the transition lines cannot be associated with specific structures of the chain, but rather, with ensembles of various configurations of the chain with similar characteristics. Based on these results the authors propose a mechanism for the folding and collapse of helical macromolecules which is further supported by the analysis of configurational, configurational, and thermodynamic properties of the chain.
Nonlinear wave modulation in a quantum magnetoplasma
Authors: Misra Amar P. , Bhowmik Chandan
Published: February 2007

Amplitude modulation of ion-acoustic waves (IAW) in a magnetized electron-ion quantum plasma is investigated. For this purpose, a three-dimensional (3D) quantum magnetohydrodynamic model is considered in the limit of small mass ratio of the charged particles. By using the standard reductive perturbation technique, a 3D nonlinear Schrödinger equation containing the magnetic field and the quantum effects is derived. The importance of quantum corrections is described through a nondimensional parameter H which is proportional to quantum diffraction effects. Some important and new modulational instability criteria of 3D IAW, quite distinct from the classical one, are obtained and analyzed.
Complex excitonic recombination kinetics in ZnO: Capture, relaxation, and recombination from steady state
Authors: Bertram F. , Christen J. , Dadgar A. , Krost A.
Published: February 2007

The kinetics of relaxation and recombination processes of excitons in an epitaxial-grown thick ZnO layer has been examined using time-resolved cathodoluminescence. The unique feature of this technique allows the full analysis of excitation from thermal equilibrium into true steady state and the relaxation back into thermal equilibrium. The luminescence at 5K is characterized by a rich structure of excitonic lines: XA, I1, I2, I6, I8, and I9 as well as the excited states I6*, I8*, and I9* are clearly resolved. The efficient capture of the free excitons by impurities is directly visualized during the onset as well as the decay. This capture feeds the neutral impurity bound excitons I8 and I9, the initial decay of which becomes delayed. The ionized impurity bound excitons I1 and I2 exhibit a very fast initial decay due to the carrier capture by the impurities followed by a persistent, significantly slower nonexponential component.
Self-generated in-plane superlattice in relaxed epitaxial La0.67Sr0.33MnO3 films
Authors: Zhou T. F. , Li G. , Li X. G. , Jin S. W. , Wu W. B.
Published: February 2007

The strain relaxation and its effect on the in-plane superlattice formation of epitaxial La0.67Sr0.33MnO3 (LSMO) thin films on the (LaAlO3)0.3(Sr2AlTaO6)0.7 (001) [LSAT (001)] substrates were investigated as a function of film thickness by x-ray diffraction. Rocking curves and reciprocal space mappings around (002) and (103) reflections reveal that the film with a thickness above 27nm is almost fully relaxed and has a modulated superlattice structure. The recovery of the pseudocubic angle of LSMO resulting from the relaxation of the shear strain introduced by the growth of rhombohedral LSMO on cubic LSAT was suggested to be the origin of the superlattice structure.
Influence of the electron beam on electromigration measurements within a scanning electron microscope
Authors: Stahlmecke B. , Dumpich G.
Published: February 2007

In situ electromigration studies on polycrystalline gold nanowires are performed using a high resolution scanning electron microscope. Simultaneously, the resistance of the gold nanowires is recorded during current stressing. The nanowires are prepared by electron beam lithography (EBL) and subsequent thermal evaporation of gold onto the resist mask. In a further EBL-process contact leads are attached to the gold nanowires to determine resistance changes of better than 5×10−4. The authors observe small resistance oscillations which occur during the scanning process. They show that these oscillations are due to the scanning process of the electron beam rather than founded on periodic changes of the void morphology.
Process-dependent defects in Si∕HfO2∕Mo gate oxide heterostructures
Authors: Walsh S. , Fang L. , Schaeffer J. K. , Weisbrod E. , Brillson L. J.
Published: February 2007

The authors have used low energy electron-excited nanoscale-depth-resolved spectroscopy to probe the bulk and interface defect states of ultrathin Mo∕HfO2∕Si with conventional process sequences. Multiple deep level emissions are evident below the 5.9eV HfO2 near band edge, including three associated with HfO2 oxygen vacancies in different charge states predicted theoretically. Defects resembling SiO2-related nonbonding oxygen hole centers and positively charged O vacancies increase with depth within the 4nm HfO2 film suggesting Hf silicate formation at the HfO2∕Si interface. These states vary dramatically between process sequences and can be understood in terms of known reactions at HfO2–Si interfaces.
Single order x-ray diffraction with binary sinusoidal transmission grating
Authors: Cao L. F. , Förster E. , Fuhrmann A. , Wang C. K. , Kuang L. Y. , Liu S. Y. , Ding Y. K.
Published: February 2007

All existing x-ray dispersive devices including crystals, multilayers and diffraction gratings generate spectra in multiple orders. In this letter the authors describe how an axis symmetrically distributed sinusoidal-shaped aperture with binary transmittance values can be used to disperse x rays and with a superior diffraction pattern where, along its symmetry axis, all higher-order diffractions can be effectively suppressed. Hence this sophisticated dispersive element generates pure soft x-ray spectra in the first diffraction order, free from interference from higher diffraction orders.