bluuebunny/crossref_metadata_2025 huggingface dataset:
Raman and photoluminescence properties of highly Cu doped ZnO nanowires fabricated by vapor-liquid-solid process
Authors: Zhu Huichao , Iqbal Javed , Xu Hongjun , Yu Dapeng
Published: September 2008

Highly Cu doped ZnO nanowires have been fabricated by vapor-liquid-solid (VLS) process. The average concentration of Cu in the ZnO nanowires is estimated to be 6at.%. The ultrafine synthesized nanowires have diameters nearly 80nm, while their average length lies in the range of 40to90μm. Raman spectroscopy shows that the Cu doped ZnO nanowires have a typical wurtzite structure. High resolution transmission electron microscopy (HRTEM) investigations of individual nanowires demonstrate that the nanowires have single crystalline structure in which the growth direction is oriented along the c axis. Room temperature photoluminescence spectrum of as prepared nanowires shows two emissions in UV and visible regions that can be ascribed to the near band edge (NBE) transition and defects respectively, while the spectrum of the annealed nanowires exhibits a red shift in UV and a suppression in visible bands. Furthermore, the low temperature (10K) PL spectrum illustrates a novel dominant blue emission relating to the different valence states of Cu atoms in ZnO, which is explained on the basis of Dingle model.
Fast electron bremsstrahlung in axisymmetric magnetic configuration
Authors: Peysson Y. , Decker J.
Published: September 2008

The nonthermal bremsstrahlung is calculated in a plasma with arbitrary axisymmetric magnetic configuration, taking into account the relativistic angular anisotropy of the radiation cross section at high photon energies, the helical winding of the field lines on the magnetic flux surfaces, and the poloidal variation of the electron distribution function including particle trapping effects. The fast electron dynamics during current drive in tokamaks and reverse field pinches can be investigated in detail by coupling this calculation to a bounce-averaged relativistic Fokker–Planck solver, which calculates the electron distribution function. The asymmetry between high- and low-field side hard x-ray emission intensity that has been measured on the Tore-Supra tokamak [Equipe TORE SUPRA, in Proceedings of the 15th Conference on Plasma Physics and Controlled Nuclear Fusion Research, Seville (International Atomic Energy Agency, Vienna, 1995) Vol. 1, IAEA-CN-60/A1-5 (Institute of Physics, Bristol, U.K., 1995), p. 105] is explained for the first time by the role of trapped electrons. A much stronger poloidal asymmetry is predicted for the line-integrated fast electron bremsstrahlung in the poloidal plane of the Madison Symmetric Torus [R. N. Dexter et al., Fusion Tech. 19, 131 (1991)], since the helical winding of the magnetic field lines is much larger for a reverse field pinch configuration. In this case, the hard x-ray emission is no longer a flux surface quantity, which prevents local reconstructions using a standard Abel inversion, whatever the geometrical arrangement of the lines of sight.
Reversible escape from a well across a barrier by diffusion in one dimension
Authors: Felderhof B. U.
Published: September 2008

Escape by diffusion in one dimension from a parabolic well across a parabolic barrier is investigated for a range of barrier heights. The probability of occupation of the well decays at long times inversely with the square root of time due to repeated return to the well after excursion in the outer space. The amplitude of the long-time tail increases as the barrier gets lower. The time dependence of the occupation probability can be described by a phenomenological rate equation with memory term and with a source term describing the rate of return from the outer space. For moderately high barrier the rate coefficient deviates from the Kramers expression.
Evaluation of growth rate equations of three-dimensional grains using large-scale Monte Carlo simulation
Authors: Wang Hao , Liu Guoquan
Published: September 2008

Three-dimensional normal grain growth process was simulated in scale of 300×300×300 on the basis of Monte Carlo–Potts model to study topology-dependent growth rate equations for individual grains. The results show that those growth rate equations solely dependent on the grain face number (f) are not applicable for grains with face number f<8; however, Glazier’s equation [J. A. Glazier, Phys. Rev. Lett. 70, 2170 (1993)], MacPherson–Srolovitz’s topology-dependent equation [R. D. MacPherson and D. J. Srolovitz, Nature (London) 446, 1053 (2007)], and Yu–Liu’s equation [G. Q. Liu and H. B. Yu, Chin. Sci. Bull. 41, 2000 (1996)] describe the simulation data well for grains with face number f>8.
Examination of the photoinitiation processes in photopolymer materials
Authors: Gleeson Michael R. , Liu Shui , O’Duill Sean , Sheridan John T.
Published: September 2008

Holographic data storage requires multiple sequential short exposures. However, the complete exposure schedule may not necessarily occur over a short time interval. Therefore, knowledge of the temporally varying absorptive effects of photopolymer materials becomes an important factor. In this paper, the time varying absorptive effects of an acrylamide/polyvinylalcohol photopolymer material are examined. These effects are divided into three main photochemical processes, which following identification, are theoretically and experimentally examined. These processes are (i) photon absorption, (ii) photosensitizer recovery, and (iii) photosensitizer bleaching.
Fictive temperature-independent density and minimum indentation size effect in calcium aluminosilicate glass
Authors: Gross T. M. , Tomozawa M.
Published: September 2008

Using the calcium aluminosilicate system a glass was developed that exhibits fictive temperature-independent density by creating an intermediate glass between normal and anomalous glasses. Normal glass, such as soda-lime silicate glass, exhibits decreasing density with increasing fictive temperature while anomalous glass, such as silica glass, exhibits increasing density with increasing fictive temperature. This intermediate glass composition was found to exhibit the minimum indentation size effect during indentation hardness testing. It appears that the indentation size effect is correlated with a deformation-induced fictive temperature increase, which is accompanied by a density change and hardness change in the vicinity of the indentation. It is suggested from these observations that indentation size effect originates from the energy required to create interfaces and defects such as shear bands, subsurface cracks, and point defects near the indenter-specimen boundary, which accompany the volume change.
Possible origin of electronic phase separation in La0.7Ca0.3MnO3
Authors: Sagdeo P. R. , Choudhary R. J. , Phase D. M.
Published: September 2008

The effect of substrate strain on the electronic valence band structure of La0.7Ca0.3MnO3 thin films has been investigated. For this purpose La0.7Ca0.3MnO3 thin films have been simultaneously grown on SrTiO3 and LaAlO3 substrates using pulsed laser deposition technique. The chemical characterization of these samples is carried out by core level x-ray photoelectron spectroscopy and the structural characterization by x-ray diffraction. Our experiments confirm that all these samples have the same chemical composition but different strain configuration. The electronic structure of these samples is probed through valence band spectroscopy measurements on Indus-1 synchrotron x-ray source. We observe that strain has a large effect on the valence band of La0.7Ca0.3MnO3. The results are explained on the basis of change in the crystal field splitting due to Mn–O bond length.
Carrier density and quantum capacitance for semiconducting carbon nanotubes
Authors: Liang Jiale , Akinwande Deji , Wong H.-S. Philip
Published: September 2008

A full-band analytical model of the equilibrium carrier density for single-wall semiconducting carbon nanotubes (sCNTs) is presented. The carrier density, which is a fundamental property of all semiconductors, is obtained using a semiempirical method for degenerate positions of the Fermi level and shows good agreement with numerical tight-binding results. The quantum capacitance is subsequently derived from the carrier density and used to develop a C-V model with good agreement with experimental quantum capacitance measurements. An analytical model of the gate coupling function of sCNTs is also reported which relates the internal surface potential with the external applied gate voltage. The diameter temperature and Fermi level dependency, and the essential properties of carbon nanotubes device physics are captured in these analytical equations.
Spinwave propagation and coupling in magnonic waveguides
Authors: Xi Haiwen , Wang Xiaobin , Zheng Yuankai , Ryan Pat J.
Published: September 2008

In this study, we start with the Landau-Lifshitz-Gilbert equation to describe the spinwaves in magnetic medium using the linearization approach. First, the reflection and refraction behaviors of spinwaves on an interface of a nonuniform magnetic medium is investigated. The study is then extended to spinwave propagation in lossless planar magnonic waveguides. Spinwave modes have been characterized based on the magnetic properties of the waveguides. Coupling between spinwaves in the structure of double magnonic waveguides is found to be possible due to the dipole interaction of the spinwaves. The spinwave coupling and power transfer associated with it is totally dependent on the waveguide structure and properties and the spinwave modes.
Thermal diffusivity study in supported epitaxial InN thin films by the traveling-wave technique
Authors: Wei Pai-Chun , Shih Han-Chang , Chattopadhyay Surojit , Hsu Chih-Ming , Lin Fang-Sheng , Chen Kuei-Hsien , Ganguly Abhijit , Chen Li-Chyong
Published: September 2008

High-quality crystalline (c) InN thin films have been obtained via gas-source molecular beam epitaxy, using hydrazoic acid (HN3) precursor, on indium tin oxide/glass, c-sapphire, and c-GaN substrates at growth temperatures between 623 and 823 K. A systematic study of thermal diffusivity has been performed using the traveling-wave method. We report a high thermal diffusivity value of 0.55 cm2/s for a combined 1.7 μm thick InN film grown on GaN substrates not observed before. X-ray diffraction data of InN grown on GaN substrates indicated lattice shrinkage with increasing thickness of the film that supports efficient phonon propagation and resulting higher thermal diffusivity. The lattice vibrational modes expressed in the Raman spectroscopic data corroborate the diffraction results. The thickness dependence of the thermal diffusivity has been modeled to estimate a bulk value of the essential thermal property.
High mobility HfO2-based In0.53Ga0.47As n-channel metal-oxide-semiconductor field effect transistors using a germanium interfacial passivation layer
Authors: Kim Hyoung-Sub , Ok Injo , Zhu Feng , Zhang M. , Park S. , Yum J. , Zhao H. , Majhi Prashant , Garcia-Gutierrez Domingo I. , Goel Niti , Tsai W. , Gaspe C. K. , Santos M. B. , Lee Jack C.
Published: September 2008

The electrical characteristics of HfO2-based n-channel metal-oxide-semiconductor field effect transistors (MOSFETs) and metal-oxide-semiconductor capacitors (MOSCAPs) on high indium content In0.53Ga0.47As channel layers are presented. N-channel MOSFETs with a germanium (Ge) interfacial passivation layer (IPL) show maximum mobility 3186 cm2/V s from split capacitance-voltage (C-V) method and the normalized drain current (to the channel length of 1 μm) of 753 mA/mm at Vg=Vth+2 V and Vd=2 V. On the contrary, MOSFETs without a Ge IPL or with high temperature post-metal annealing (PMA) exhibit inferior characteristics. MOSCAPs on n-type In0.53Ga0.47As layers demonstrate excellent C-V characteristics including low C-V frequency dispersion and low dielectric leakage current.
Low noise superconducting single photon detectors on silicon
Authors: Dorenbos S. N. , Reiger E. M. , Perinetti U. , Zwiller V. , Zijlstra T. , Klapwijk T. M.
Published: September 2008

We have fabricated superconducting nanowire single photon detectors made of NbTiN on a silicon substrate. This type of material reduces the dark count rate by a factor of 10 compared to identical NbN detectors, enabling single photon detection with unprecedented signal to noise ratio: we report a noise equivalent power of 10−19 W Hz−1/2 at 4.2 K. The compatibility of our superconducting device with silicon enables its integration with complex structures.
Phonon control in metallic carbon nanotubes due to laser-induced defects
Authors: Kang D. , Kato K. , Kojima K. , Uchida T. , Tachibana M.
Published: September 2008

Single-walled carbon nanotubes (SWNTs) irradiated with laser were investigated by Raman spectroscopy. The intensity of D band related to defects increased with the laser irradiation. It should be noticed that the corresponding change was observed for G− peak associated with metallic SWNTs that is related to the electron-phonon coupling with Kohn anomaly. The upshift and narrowing of the G− peak occur due to the laser irradiation. The G− peak can recover the original one due to the thermal annealing. On the other hand, G band associated with semiconducting SWNTs remained unchanged even after the laser irradiation. This means that the laser-induced defects significantly affect phonons in metallic SWNTs, compared with semiconducting ones, and can control the electron-phonon coupling.
Three photon absorption in silicon for 2300–3300nm
Authors: Pearl Shaul , Rotenberg Nir , van Driel Henry M.
Published: September 2008

We measure the spectral dependence of the degenerate three photon absorption coefficient, γ, for a Si [100] wafer using 200fs pulses in the range 2300–3300nm, i.e., photon energy between half and one-third the indirect band gap. For pulses linearly polarized along the [001] crystal axis γ increases from a value of near 0cm3∕GW2 at 3300nm to a peak value of 0.035cm3∕GW2 at 2700nm before decreasing with shorter wavelength; this is consistent with the dispersion expected from allowed-allowed-allowed transitions. At 2600nm the γ value is ∼30% larger for light polarized along [011] than along [001].
Achieving high Curie temperature in (Ga,Mn)As
Authors: Wang M. , Campion R. P. , Rushforth A. W. , Edmonds K. W. , Foxon C. T. , Gallagher B. L.
Published: September 2008

We study the effects of growth temperature, Ga:As ratio, and postgrowth annealing procedure on the Curie temperature TC of (Ga,Mn)As layers grown by molecular beam epitaxy. We achieve the highest TC values for growth temperatures very close to the two-dimensional–three-dimensional phase boundary. The increase in TC, due to the removal of interstitial Mn by postgrowth annealing, is counteracted by a second process, which reduces TC and which is more effective at higher annealing temperatures. Our results show that it is necessary to optimize the growth parameters and postgrowth annealing procedure to obtain the highest TC.
Domopolitics and Disease: HIV/AIDS, Immigration, and Asylum in the UK
Authors: Ingram Alan
Published: September 2008

Geographers and others have become increasingly interested in the intersections between globalization, disease, and security, particularly in relation to ‘short-wave’ public health threats such as SARS and pandemic influenza, but ‘long-wave’ epidemics such as HIV/AIDS are also often said to raise questions of security. While a literature is emerging to analyze the politics of security in relation to global HIV/AIDS relief, in this paper I argue that it is also important analytically and politically to connect and contrast this with the ways that HIV/AIDS is politicized as a security issue in relation to immigration and asylum within Western states themselves. Drawing on literatures in governmentality, biopolitics, and security, I examine the politics of HIV/AIDS, immigration, and asylum in the UK from 1997 to 2007 with particular reference to the reactionary press coverage that influenced policy formation and judicial rulings in this period. Following the work of William Walters, I trace the emergence of a ‘domopolitical’ rationality in press reporting around HIV/AIDS in terms of a number of imaginative geographies, and suggest that these imaginative geographies are both biopolitical in a classical sense and connected with the colonial dimensions of the present. The circulation of these imaginative geographies through policy and legal developments, the dilemmas they have raised, and resistance to them from medical, civil society, and parliamentary groups are then outlined. Reflecting on the disjuncture in approaches to HIV/AIDS between the global and national spheres, I argue that while the association of HIV/AIDS and security is enhancing life chances for many it is also reducing them for people caught in the wrong place at the wrong time.
Philosophical Conceptions of Cultural Space in Russia and Japan: Comparing Nishida Kitarō and Semën Frank
Authors: Botz-Bornstein Thorsten
Published: September 2008

Jean-Luc Nancy notes that the community, since it is no absolute subject (self, will, spirit), is by its nature not inscribed in any logic metaphysics. In spite of this, or indeed because of this, Western philosophy has persistently tried to interpret the community through precisely these metaphysical terms (Nancy, 1986, page 18, La Commonauté désoevrée, Christian Bourgeois, Paris). Some thoughts about Russian and Japanese notions of community and space will show that characteristics pointed out by Nancy and Kant are binding only for societies that function within a Western intellectual framework. I want to introduce and compare the thought of Nishida Kitarō (1870–1945) and Semën L Frank (1877–1950), who develop the notions of basho and sobornost’ as alternative philosophical concepts of space. Both Nishida and Frank attempt to overcome what they consider a typically ‘Western’ idea of individual ‘I's as materialized ‘objects’. Procedures like Einfühlung or intuition are inefficient because all they do is to transform the other, from the point of view of the ‘I’, into an object. Finally, for the Eurasianist, the state organization had at its center a personal god, and the ‘symphonic personality’ of Russia-Eurasia represented a nonegoistic, communal consciousness.
Ram-Pressure Induced Star Formation in the LMC
Authors: Mastropietro Chiara , Burkert Andreas , Moore Ben
Published: September 2008

We use high-resolution n-body/SPH simulations to study the hydrodynamical interaction between the Large Magellanic Cloud and the hot halo of the Milky Way. We investigate whether the ram-pressure acting on the gaseous disk of the satellite can explain the peculiarities observed in the Hidistribution and the location of the recent star formation activity.
The Molecular Ridge Close to 30 Doradus in the Large Magellanic Cloud
Authors: Ott Jürgen , Wong Tony , Pineda Jorge L. , Hughes Annie , Muller Erik , Li Zhi-Yun , Wang Min , Staveley-Smith Lister , Fukui Yasuo , Weiß Axel , Henkel Christian , Klein Ulrich
Published: September 2008

With the ATNF Mopra telescope we are performing a survey in the 12CO(1–0) line to map the molecular gas in the Large Magellanic Cloud. For some regions we also obtained interferometric maps of the high density gas tracers HCO+ and HCN with the Australia Telescope Compact Array. Here we discuss the properties of the elongated molecular complex that stretches about 2 kpc southward from 30 Doradus. Our data suggest that the complex, which we refer to as the ‘molecular ridge’, is not a coherent feature but consists of many smaller clumps that share the same formation history. Likely triggers of molecular-cloud formation are shocks and shearing forces that are present in the surrounding south-eastern Hi overdensity region, a region influenced by strong ram pressure and tidal forces. The molecular ridge is at the western edge of the the overdensity region where a bifurcated velocity structure transitions into a single disk velocity component. We find that the 12CO(1–0) and Hi emission peaks in the molecular ridge are typically near each other but never coincide. A likely explanation is the conversion of warmer, low-opacity Hi to colder, high-opacity Hi from which H2 subsequently forms. On smaller scales we find that very dense molecular gas, as traced by interferometric HCO+ and HCN maps, is associated with star formation along shocked filaments and with rims of expanding shell-like structures, both created by feedback from massive stars.
Consequences of genetic change in farm animals on food intake and feeding behaviour
Authors: Emmans Gerry , Kyriazakis Ilias
Published: September 2008

Selection in commercial populations on aspects of output, such as for growth rate in poultry, against fatness and for growth rate in pigs, and for milk yield in cows, has had very large effects on such outputs over the past 50 years. Partly because of the cost of recording intake, there has been little or no selection for food intake or feeding behaviour. In order to predict the effects of such past, and future, selection on intake it is necessary to have some suitable theoretical framework. Intake needs to be predicted in order to make rational feeding and environmental decisions. The idea that an animal will eat ‘to meet its requirements’ has proved useful and continues to be fruitful. An important part of the idea is that the animal (genotype) can be described in a way that is sufficient for the accurate prediction of its outputs over time. Such descriptions can be combined with a set of nutritional constants to calculate requirements. There appears to have been no change in the nutritional constants under selection for output. Under such selection it is simplest to assume that changes in intake follow from the changes in output rates, so that intake changes become entirely predictable. It is suggested that other ways that have been proposed for predicting intake cannot be successful in predicting the effects of selection. Feeding behaviour is seen as being the means that the animal uses to attain its intake rather than being the means by which that intake can be predicted. Thus, the organisation of feeding behaviour can be used to predict neither intake nor the effects of selection on it.
Metabolism 2000: the emperor needs new clothes
Authors: Young Vernon R. , Ajami Alfred M.
Published: September 2008

Metabolism is one of the corner stones of nutritional science. As biology enters the post-genomic era and with functional genomics beginning to take off, we anticipate that the study of metabolism will play an increasingly important role in helping to link advances made via the reductionist paradigm, that has been so successful in molecular and cellular biology, with those emerging from observational studies in animals and human subjects. A reconstructive metabolically-focused approach offers a timely paradigm for enhancing the elegance of nutritional science. Here we give particular attention to the use of tracers as phenotyping tools and discuss the application of our metaprobe concepts with respect to some novel features of metabolism, including ‘underground metabolism’, ‘metabolic hijacking’, ‘catalytic promiscuity’ and ‘moonlighting proteins’. The opportunities for enhancing the study of metabolism by new and emerging technologies, and the importance of the interdisciplinary research enterprise are also touched upon. We conclude that: (1) the metaprobe concepts and approach, discussed herein, potentially yield a quantitative physiological (metabolic) phenotype against which to elaborate partial or focused genotypes; (2) physiological (metabolic) phenotypes which have a whole-body or kinetically-discernible inter-organ tissue-directed metabolic signature are an ideal target for this directed tracer-based definition of the ‘functional’ genotype; (3) metabolism, probed with tracer tool kits suitable for measuring rates of turnover, change and conversion, becomes in the current sociology of the ‘Net’, like AOL, Yahoo, Alta Vista, Lycos or Ask Jeeves, the portal for an exploration of the metabolic characteristics of the ‘Genomics Internet’.
Iron deficiency and iron overload: effects of diet and genes
Authors: Burke Wylie , Imperatore Giuseppina , Reyes Michelle
Published: September 2008

Like most essential nutrients, Fe needs to be maintained in the body at a defined level for optimal health, with appropriate adaptation to varying Fe needs and supply. The primary mechanism for controlling Fe level is the regulation of Fe absorption. Several different proteins have been identified as contributors to the process. Despite a complex regulatory system, Fe disorders (both Fe deficiency and Fe overload) occur. Fe deficiency is a common problem worldwide, resulting from inadequate dietary Fe and blood loss. Complications include pre-term labour, developmental delay, and impaired work efficiency. No specific genetic syndromes causing isolated Fe deficiency have been described, but animal studies and clinical observations suggest that such a relationship may be a possibility. Conversely, the known causes of Fe overload are genetic. Fe overload is less common than Fe deficiency, but can result in serious medical complications, including cirrhosis, primary liver cancer, diabetes, cardiomyopathy and arthritis. The most common and best characterized syndrome of Fe overload is hereditary haemochromatosis (HHC), an autosomal recessive disorder. Mutations in the HFE protein cause HHC, but the clinical presentation is variable. Of particular interest is the factor that some HFE genotypes appear to be associated with protection from Fe deficiency. Other genetic variants in the regulatory pathway may influence the likelihood of Fe deficiency and Fe overload. Studies of genetic variants in HFE and other regulatory proteins provide important tools for studying the biological processes in Fe regulation. This work is likely to lead to new insights into Fe disorders and potentially to new therapeutic approaches. It will not be complete, however, until coordinated study of both genetic and nutritional factors is undertaken.
The relative contribution of diet and genotype to bone development
Authors: Prentice Ann
Published: September 2008

The present review addresses the relative contribution of diet and genotype to variability in human bone growth and mineralisation in the context of the aetiology of osteoporosis. Heritability studies indicate that 60–70 % of the variability in bone mineral mass or bone mineral density (BMD) can be accounted for by genetic variation. Cross-trait analyses suggest that a proportion of this variation reflects genetic influences on bone and body size, such as height and lean body mass. Candidate-gene studies have demonstrated associations between several genetic polymorphisms and bone mineral mass but, as yet, genotype determinations have proved unhelpful in identifying individuals at increased risk of osteoporosis. Variations in diet and other environmental factors contribute 30–40 % to total phenotypic variance in bone mineral mass or BMD. Correlations between intakes of individual nutrients and BMD have been reported, but these relationships are subject to confounding due to size. However, no specific dietary factor has been identified from prospective and twin studies as making a significant contribution to environmental variability in BMD or bone loss. This finding may reflect the difficulties in quantifying environmental exposures, both current and over a lifetime. In addition, the influence of diet on bone health may depend on the genotype of the individual. Optimisation of nutrition and lifestyle remains an attractive strategy for the reduction of fracture risk, but more research is required to fully define optimal dietary requirements.
Challenges for meeting the global food and nutrient needs in the new millennium
Authors: Khush Gurdev S.
Published: September 2008

Major advances have occurred in food production during the last 30 years as a result of the adoption of ‘green revolution’ technology. The price of rice and wheat is 40 % lower than it was in the 1950s. This lower price has helped the poorer sections of society, who spend 50–60 % of their income on food. The proportion of the population in the developing world that is malnourished fell from 46·5 % in the early 1960s to 31 % in 1995. However, there are still 1·3 billion of the population who go to bed hungry every day. Deficiencies of micronutrients such as Fe, Zn and vitamin A affect millions of the population in the developing world. The world population is increasing at the rate of 1·4 %, or an increase of eighty million per year. It is estimated that we will have to produce 50 % more food grains by 2025. Various strategies for meeting this challenge exist, including the development of cereal varieties with a higher yield potential and yield stability, and farmer-friendly public policies. In order to tackle hidden hunger, efforts are underway to develop crop varieties with higher concentrations of Fe and Zn. Recently, a breakthrough has occurred in the introduction of the genes for the pathway leading to the biosynthesis of β-carotene, a precursor of vitamin A, in rice. Various conventional approaches and modern tools of biotechnology are being employed in the development of crop varieties with higher yields and higher levels of micronutrients.
Dietary effects on the microbiological safety of food
Authors: Carol McWilliam Leitch E. , Duncan Sylvia H. , Stanley Karen N. , Stewart Colin S.
Published: September 2008

The high mortality rate associated with human infections caused byEscherichia colistrains of the serotype O157:H7 has brought to public attention the importance of ruminants as reservoirs of food-borne pathogens. In addition to established examples such as salmonella, campylobacter and listeria, recent evidence is emerging of the role of food in the transmission ofHelicobacter pyloriandMycobacterium paratuberculosis. Food-borne pathogens harboured by ruminants are spread through shedding in the faeces and subsequent faecal contamination of raw food. Ruminant shedding appears to be affected by diet and, of particular concern, may be increased during fasting regimens imposed during transport to the slaughterhouse. The survival of food-borne pathogens in the ruminant gut is affected by many factors including microbe–microbe interactions, interactions involving plant metabolites and the presence of inhibitory end-product metabolites such as short-chain fatty acids. The potential importance of digesta flow and bacterial detachment in shedding of food-borne pathogens is discussed. Experimental procedures with dangerous pathogens have constraints, particularly in animal experimentation. This situation may be overcome by the use of rumen-simulating fermentors. One such system which, like the natural rumen, has a different turnover rate for solid and liquid digesta, was found to maintain rumen-like variables over an 11 d period. This system may prove useful for the study of dietary effects on food-borne pathogens.
Producing specific milks for speciality cheeses
Authors: Bertoni Giuseppe , Calamari Luigi , Grazia Maianti Maria
Published: September 2008

Protected denomination of origin (PDO) cheeses have distinctive sensorial characteristics. They can be made only from raw milk possessing specific features, which is processed through the ‘art’ of the cheesemaker. In general, the distinctive sensorial traits of PDO cheese cannot be achieved under different environmental–production conditions for two main reasons: (1) some milk features are linked to specific animal production systems; (2) cheese ripening is affected by the interaction between milk (specific) and the traditional technology applied to the transformation process (non-specific). Also, the environment for a good ripening stage can be quite specific and not reproducible. With reference to milk, factors of typicality are species and/or breed, pedo–climatic conditions, animal management system and feeding. Other factors that influence cheese quality are milk treatments, milk processing and the ripening procedures. The technology applied to most cheeses currently known as PDO utilizes only raw milk, rennet and natural lactic acid bacteria, so that milk must be, at its origin, suitable for processing. The specific milk characteristics that ensure a high success rate for PDO cheeses are high protein content and good renneting properties, appropriate fat content with appropriate fatty acid composition and the presence of chemical flavours originating from local feeds. Moreover, an appropriate microflora is also of major importance. The factors that contribute to achieving milk suitable for transformation into PDO cheese are genetics, age, lactation stage, season and climate, general management and health conditions, milking and particularly feeding, which affect nutrient availability, endocrine response and health status, and also the presence of microbes and chemical substances which enrich or reduce the milk–cheese quality. Many of these factors are regulated by the Producer Associations. However, the secret of the success of PDO cheeses is the combination of modern technology and tradition, with the objective of adapting the product to market demand, without losing specificity, originality and authenticity.
Tube feeding patients with advanced dementia: an ethical dilemma
Authors: McNamara Edel P. , Kennedy Nicholas P.
Published: September 2008

Many patients with dementia lose the ability to feed themselves in the advanced stages of the disease. Tube feeding is sometimes initiated to overcome feeding difficulties. Recent studies have questioned the appropriateness of tube feeding in these patients. There is limited research to support the benefits of enteral nutrition in patients with advanced dementia. Deciding whether to tube feed or to withhold tube feeding from a patient with dementia poses a difficult challenge, and many carers may make decisions without adequate information and with an overly hopeful view of the future clinical course. Numerous studies have examined opinions about life-sustaining treatments; many individuals do not want to be tube fed if they were to develop dementia. Results from studies examining the opinions of physicians and other health professionals regarding the use of tube feeding in these patients are conflicting. A number of factors, such as race and cultural background may affect decisions. Healthcare professionals, relatives and patients must be aware of the realistic expectations of tube feeding in patients with dementia, as it can be difficult to withdraw once it has been initiated.
Challenges to meet: food and nutrition security in the new millennium
Authors: Lipton Michael
Published: September 2008

Before about 1750 there was no substantial secular fall in protein–energy malnutrition (PEM) over large areas, nor reason to expect it. We have since learned that sufficient economic advance (poverty reduction) plus scientific advance (in medicine and food production) are achievable to eliminate mass PEM. The two advances are linked via increased demand for labour, and hence wages and employment, for those formerly too poor to afford adequate food. The extra employment income arises first from smallholder and employee food production, and later, as labour is released, from a wide range of specialised, increasingly non-farm, production, with employment income traded for food. This process eliminated mass hunger in Europe in 1750–1960. Only by 1975 had PEM in the developing world retreated to (very high) 1936–8 levels, but it fell sharply in Asia and Latin America in 1975–1990, due to unprecedented growth in staples yields, smallholder and farm employment income, and hence the poor's purchasing power over food. However, since 1990, poverty reduction has slowed (before reaching most of Africa), alongside much slower-staples yield growth, increasing water shortages, and big shifts of grain and land from man to farm animals. These trends prefigure declining progress against PEM in coming decades, unless there is renewed, employment-intensive food-staples-yield growth. That process requires reorienting crop biotechnology and water science towards the needs of small tropical farmers and their staple food crops, and shifting land towards them. Mass PEM is indeed largely due to inadequate ‘food entitlements’ by the hungry, but will not be remedied without growth in their employment, based on further advances in food-staples yields per unit land and water. Recent evidence suggests that early PEM may increase lifelong risks of infection and/or degenerative disease. This factor would increase the ‘squeeze’ on health resources in low-income countries, between the diseases of poverty and those of old age. That situation increases the need to readdress PEM by renewed progress in food production and land distribution.
The role of leptin in the transition from fetus to neonate
Authors: Mostyn A. , Keisler D. H. , Webb R. , Stephenson T. , Symonds M. E.
Published: September 2008

Leptin is a 16 kDa hormone which has been shown to have a major physiological role in the control of energy balance. Leptin is produced primarily in white adipose tissue, although there is evidence for its production in brown adipose tissue (BAT) and the placenta. BAT is critically important for the initiation of non-shivering thermogenesis in the newborn through the BAT-specific uncoupling protein (UCP), UCP1. This factor is particularly important in lambs in which levels of UCP1 peak at birth, concomitant with a rapid decline in plasma leptin levels. Our studies have examined the effect of acute and chronic administration of leptin to neonatal lambs, investigating effects on colonic temperature, UCP1 and thermogenic potential of BAT. Administration of leptin in sequential physiological doses of 10, 100 and 100 µg to neonatal lambs caused a modest increase in colonic temperature which was not observed in weight-matched vehicle-treated controls. This increase in colonic temperature was not mediated by an increase in either abundance or thermogenic potential of UCP1, as previously shown in adult rodents. UCP1 mRNA levels were 30 % lower in leptin-treated lambs, which is also contradictory to findings in adult rodents. Leptin treatment resulted in a dose-dependent rise in plasma leptin, with levels at the end of the study being almost twenty times greater in leptin-treated animals. To determine whether these findings in neonatal lambs were transient due to the complex milieu of hormones present after birth, we examined the effect of chronic leptin treatment over 6 d. Pairs of lambs were treated daily, from the second to seventh day of life with 100 µg leptin or vehicle. Colonic temperatures of leptin- and vehicle-treated animals remained similar throughout the study. UCP1 abundance was significantly lower in the leptin-treated animals, suggesting that the drop in UCP1 mRNA seen in the previous study had been translated to protein levels. In conclusion, the decline in plasma leptin levels at birth may be a signal to initiate enteral feeding. In lambs, the rapid loss of UCP1 mRNA, which occurs within the first few days of life, appears to be accelerated by leptin administration, possibly stimulating the development of white adipose tissue and generation of body heat through mechanisms other than non-shivering thermogenesis by UCP1 in BAT.
The sympathetic nervous system in white adipose tissue regulation
Authors: Vernon Rayner D.
Published: September 2008

Sympathetic stimulation has long been recognized to mobilise fatty acids from white adipose tissue. However, it is now apparent that adipose tissue is not only concerned with energy storage as fat, but is a major endocrine and secretory organ. This change has resulted from the identification of leptin as a hormone of energy balance secreted by white adipose tissue. The sympathetic system is a key regulator of leptin production in white fat. Sympathomimetic amines, cold exposure or fasting (which lead to sympathetic stimulation of white fat), decreaseobgene expression in the tissue and leptin production. On the other hand, sympathetic blockade often increases circulating leptin andobgene expression, and it is postulated that the sympathetic system has a tonic inhibitory action on leptin synthesis. In rodents this action is through stimulation of b3-adrenoceptors. The adrenal medulla (as opposed to the direct sympathetic innervation) has been thought to play only a minor role in the catecholaminergic regulation of white adipose tissue. However, in rodents responses of the leptin system to adrenergic blockade vary with the method used. Changes in leptin andobgene expression are considerably less using methods of blockade that only effect the terminal adrenergic innervation, rather than medullary secretions as well. Stimulation of the leptin system increases sympathetic activity and hence metabolic activity in many tissues. As well as leptin, other (but not all) secretions from white adipose tissue are subject to sympathetic regulation. In obesity the sympathetic sensitivity of adipose tissue is reduced and this factor may underlie the dysregulation of leptin production and other adipose tissue secretions.
New processing technologies: an overview
Authors: Gould Grahame W.
Published: September 2008

Most food-preservation techniques act by slowing down or completely inhibiting the growth of micro-organisms. Few techniques act by inactivating them. While heat remains the technique most extensively used for inactivation, there has been increasing interest recently in the development of alternative approaches in response to the desires of consumers for products which are less organoleptically and nutritionally damaged during processing and less reliant on additives than previously. The new approaches, therefore, mostly involve technologies that offer full or partial alternatives to heat for the inactivation of bacteria, yeasts and moulds. They include the application to foods of high hydrostatic pressure, high-voltage electric discharges, high-intensity laser and non-coherent light pulses, ‘manothermosonication’ (the combination of mild heating with ultrasonication and slightly-raised pressure), and high-magnetic-field pulses. In addition, a number of naturally-occurring antimicrobials, including lysozyme and low-molecular-weight products of micro-organisms are finding increasing use. High pressure is being used commercially to non-thermally pasteurize a number of foods, while the other physical procedures are in various stages of development and commercial evaluation. Possible nutritional consequences have so far been given little attention compared with microbiological ones.
Technical constraints in the development of reduced-fat bakery products
Authors: Sharp Terry
Published: September 2008

The present study was funded by the Ministry of Agriculture, Fisheries and Food, its aim being to identify the technical barriers to the development of reduced-fat alternatives for bakery products. Using National Food Survey (Ministry of Agriculture, Fisheries and Food, 1998) statistics on dietary consumption within the home, biscuits, cakes and pastries were identified as contributing significant amounts of fat to the population's dietary intake. Face-to-face interviews were conducted with contacts in the technical community of the baking industry, who were usually working in technical and new-product development functions. A discussion guide was developed to cover the main lines of enquiry. The companies selected were ingredient suppliers (eight), manufacturers (twelve) and retailers (four) and so represented each step of the food supply chain. In brief, results showed that current labelling rules were too stringent, and constrained development of reduced-fat bakery products. Products with lower fat levels are harder to make due to altered handling and processing properties. Their quality is usually poorer than standard products, particularly for flavour, texture and mouthfeel. The perception of freshness is reduced and product shelf-life may consequently be shorter. For the product developer, there are relatively few ingredients that can be used in place of fat, and knowledge of how they work is limited, which inhibits product development. There is no identifiable source of technical knowledge in this field. Consumers perceive reduced-fat bakery products to be of lower quality and are generally unwilling to pay higher prices than for standard products.
Development of antibiotic resistance and options to replace antimicrobials in animal diets
Authors: Erik Knud , Knudsen Bach
Published: September 2008

As there is a risk of developing antibiotic resistance, a number of commonly-used antimicrobial growth promoters have been banned in the EU member states. This decision has put new emphasis on using the diet to control enteric bacterial infections of pigs. Dietary carbohydrates constitute a major proportion of diets for pigs, and the carbohydrate fraction has a diverse composition, with different properties in the gastrointestinal tract, some of which are of importance to gut health. Findings from different studies indicate that dietary carbohydrate composition influences the expression of swine dysentery and infection with nematode worms after experimental challenge withBrachyspira hyodesenteriaeandOesophagostumum dentatumrespectively. In both cases the type, amount and physico-chemical properties of the carbohydrates entering the large intestine played an important role in the infection, and emerging data suggest a synergism between different porcine pathogens. There is also increasing evidence that the feed structure, which relates to the type of plant material in the diet and the way it is processed, can be used to reduceSalmonellaprevalence at the herd level. However, it should be stressed that using the diet to manage gut health is not straightforward, since the expression of a pathogen in many cases requires the presence of other components of the commensal biota.
Pregnancy as a time for dietary change?
Authors: Anderson Annie S.
Published: September 2008

It is thought that nutrition during pregnancy plays a key role in the well-being of the mother and the newborn infant, and further influences health during childhood and adulthood. Pregnancy is a time of increased nutritional requirements, but many of these requirements will be met by adaptive physiological changes that occur during gestation, with little need to alter maternal dietary intake. A modest increment of food which provides 0.8 MJ/d (above prepregnant requirements) during the third trimester is considered adequate to meet the needs of fetal and maternal growth, and to satisfy the small increase in requirements of many macro- and micronutrients. However, requirements for vitamin D and folic acid increase substantially, and should be met primarily by supplementation. Food selection may also be altered to avoid a range of food-borne diseases and toxic constituents. There are a number of psycho-social reasons why pregnancy might be considered a good time for promoting changes in dietary behaviour for the health of the wider family. However, pregnancy may be a bad time to promote dietary change if it is perceived to involve slimming, if nutritional requirements are greatest before pregnancy, or if dietary changes made are harmful. There is little evidence to support educational interventions as successful at changing dietary behaviour during pregnancy. Pregnancy may be best viewed as an opportunity for maintaining good dietary selections and for building knowledge for future action, and should not be seen as the only opportunity for promoting dietary change within the life course.