bluuebunny/crossref_metadata_2025 huggingface dataset:
Pyrolysis of Pb(Zr05Ti05)O3 Precursors: Avoiding Lead Partitioning
Authors: Polli Andrew D. , Lange Fred F.
Published: April 2005

Three different chemical precursor routes were investigated to synthesize Pb(Zr05Ti05)O3: mixing hexanoates, acetate complexing of alkoxides, and the synthesis of a mixed alkoxide by the reaction of titanium alkoxide and zirconium alkoxide with lead acetate. For each, elemental Pb and PbO were the first crystalline phase observed during pyrolysis conditions that involved rapid heating (e.g., to 400°C). The formation of Pb (and PbO) could be avoided by first heattreating hydrolyzed, mixed alkoxide precursor powders at 300°C for 1 h. This treatment was not effective for the two other precursors. It is concluded that both the carbonaceous content of the precursor (lowest for the hydrolyzed, mixed alkoxides) and the rate of hydrocarbon release during pyrolysis are critical to avoid the formation of elemental Pb during pyrolysis.
Determination of Short‐Crack Toughness Curves
Authors: Smith Stanley M. , Scattergood Ronald O.
Published: April 2005

Measurements of indentation crack length vs applied bend stress were used to develop a new method of analysis for determining short‐crack toughness curves. Three glass‐ceramics and a polycrystalline alumina were used as prototype test materials. Crack‐shape effects were incorporated into the analysis. The magnitude of the residual‐stress factor can be determined independently from the experimental data using the methodology. In contrast to other test methods using indentation precracks, calibration constants or reference materials are not required for obtaining absolute values of the toughness. Good agreement with conventional toughness values reported for the long‐crack limit was obtained for the different materials tested.
Crack Branching in All‐Oxide Ceramic Composites
Authors: Lu Tian Jian
Published: April 2005

The existence of oxidation embrittlement in previously developed ceramic‐matrix composite (CMC) systems at intermediate temperatures (500–900°C) has motivated the development of all‐oxide CMCs. Studies of the damage tolerance of an all‐oxide CMC suggest that it relies on distributing fiber bundles heterogeneously in a porous matrix with a thin matrix‐only region surrounding each bundle. For such composites, loading in the direction of the fibers causes cracks to first commence in the fiber bundles, breaching both the matrix and fibers within each bundle. These fiber‐bundle cracks then branch in the matrix‐rich region, parallel to the load, forming stable H‐shaped cracks. The mechanics behind one mechanism controlling the competition between branching and continued extension of a preexistent fiber‐bundle crack in a unidirectional all‐oxide CMC are provided in this paper. Both plane‐strain and axisymmetric cases are studied using an integral equation method as well as a numerical method based on finite elements. With no elastic mismatch assumed between the fiber and matrix, a single nondimensional combination, EΩ/σ∞, emerges as the key parameter that governs the tendency of the crack to branch (where E is Young's modulus, Ω is the thermal misfit strain between the fiber bundle and matrix, and σ∞ is the stress applied parallel to the fiber axis). Quantitative estimates of the conditions under which the branching of the bundle crack is favored are presented.
Predicting the impact of livestock grazing on birds using foraging height data
Authors: MARTIN TARA G. , POSSINGHAM HUGH P.
Published: April 2005

Habitat structure is a major determinant of bird species diversity. One process by which habitat structure is altered is livestock grazing, the most extensive land use across most continents. While the impacts of grazing on vegetation have received much attention, the effects on avifauna are less well known.

Predictions of the impact of grazing on Australian woodland and riparian bird assemblages were formulated. We used available information on the vegetation strata utilized by each species for foraging and the strata most affected by grazing.

We compared predictions based on foraging height preferences with differences in bird density in grassy eucalypt woodland and riparian habitats subject to three levels of grazing. We found that foraging height preference was a good predictor of species’ susceptibility to grazing. Birds exhibited both monotonic and non‐monotonic responses to grazing, with the majority of bird species declining with increasing grazing pressure.

Synthesis and applications. Existing information on foraging behaviour can be used to make predictions of the impact of any threat on birds where that threat alters habitat structure. While the approach is simple, it is a point of departure for more complex predictive models, and avoids the circularity of post hoc interpretation of impact data. This approach can be used to guide management decisions where landscapes are in a state of transition and species conservation is a priority.
Stating mechanisms and refining criteria for ecologically successful river restoration: a comment on Palmer et al. (2005)
Authors: JANSSON R. , BACKX H. , BOULTON A. J. , DIXON M. , DUDGEON D. , HUGHES F. M. R. , NAKAMURA K. , STANLEY E. H. , TOCKNER K.
Published: April 2005

To encourage more project assessment and reporting of restoration outcomes, Palmer et al. (2005) propose five criteria for assessing the ecological success of river restoration. They also suggest that these criteria should help to clarify which activities should qualify for ecological restoration funding and facilitate consistency about what constitutes an ecologically successful restoration project.

We critique the five criteria and agree they all merit inclusion in an assessment of successful river restoration. However, the practical application of measuring self‐sustainability (resilience) following restoration is potentially problematic and an explicit timeframe is needed to evaluate the results of the restoration.

A sixth criterion is proposed that encourages specific hypotheses and/or a conceptual model of the ecological mechanisms by which the proposed activities will achieve their target. This would enhance our understanding of the mechanisms at play for successful river restoration, and provide a more powerful deductive framework likely to lead to appropriate practices that can be applied across rivers. To explore the potential practical applicability of these six criteria, we applied them to a recently published example of river restoration to ascertain its ecological success.

Synthesis and applications. We agree with the criteria proposed by Palmer et al. (2005), although the problems of measuring resilience and defining a timeline for recovery should be addressed. We suggest strengthening the deductive framework of restoration projects by formulating some sort of conceptual model. This step could involve scientists, and be a useful way of involving science more explicitly in restoration activities. Agreed‐upon criteria for successful restoration will greatly facilitate evaluation of river ecosystem recovery at the critical broader scales where our knowledge is still limited.
Genetic variation and evolution of Polaskia chichipe (Cactaceae) under domestication in the Tehuacán Valley, central Mexico
Authors: OTERO‐ARNAIZ ADRIANA , CASAS ALEJANDRO , HAMRICK JAMES L. , CRUSE‐SANDERS JENNIFER
Published: April 2005

Polaskia chichipe is a columnar cactus under artificial selection in central Mexico because of its edible fruits. Our study explored the effect of human manipulation on levels and distribution of genetic variation in wild, silviculturally managed and cultivated sympatric populations. Total genetic variation, estimated in nine populations with five microsatellite loci, was HT = 0.658 ± 0.026 SE, which was mainly distributed within populations (HS = 0.646) with low differentiation among them (FST = 0.015). Fixation index (FIS) in all populations was positive, indicating a deficit of heterozygous individuals with respect to Hardy–Weinberg expectations. When populations were pooled by management type, the highest expected heterozygosity (HE = 0.631 ± 0.031 SE) and the lowest fixation index (FIS = 0.07) were observed in wild populations, followed by cultivated populations (HE = 0.56 ± 0.03 SE, FIS = 0.14), whereas the lowest variation was found in silviculturally managed populations (HE = 0.51 ± 0.05 SE, FIS = 0.17). Low differentiation among populations under different management types (FST 0.005, P < 0.04) was observed. A pattern of migration among neighbouring populations, suggested from isolation by distance (r2 = 0.314, P < 0.01), may have contributed to homogenizing populations and counteracting the effects of artificial selection. P. chichipe, used and managed for at least 700 generations, shows morphological differentiation, changes in breeding system and seed germination patterns associated with human management, with only slight genetic differences detected by neutral markers.
Dispersal and phylogeography of the agamid lizardAmphibolurus nobbiin fragmented and continuous habitat
Authors: DRISCOLL D. A. , HARDY C. M.
Published: April 2005

Approximately 90% of native vegetation has been cleared for agriculture in central New South Wales, Australia. Habitat loss has reduced and fragmented populations of the agamid lizardAmphibolurus nobbi. We compared genetic structure of populations of this species in an unmodified landscape with those from small nature reserves and linear remnants in farming areas. We ask: Is there evidence for reduced dispersal and population fragmentation among farm populations? Using 2008 bp mtDNA sequences and allozyme electrophoresis, we found that small populations in farming areas had as much genetic variation as populations in nature reserves. Application of nested clade analysis (NCA) indicated isolation‐by‐distance effects among populations from uncleared areas, but not among populations within farming locations. The genetic evidence therefore implied a high level of migration in the cleared landscapes. High dispersal after fragmentation may have resulted from either a burst of movement at the time of land clearing with dragons from many sources finding refuge in a few remnants, or from ongoing rapid dispersal through unsuitable habitat. A phylogeny based on mtDNA revealed thatA. nobbipopulations in the study area are deeply divided into two reciprocally monophyletic groups. Although we did not sample the entire species range, one of these evolutionarily significant units was only detected in remnant vegetation in the agricultural landscape. Therefore, a substantial subclade of this species may be vulnerable to extinction. Our findings emphasize that local populations of widespread species can harbour important intraspecific genetic diversity, supporting the case for maintaining widespread species throughout production landscapes.
Mitochondrial and nuclear DNA phylogeography of European grayling (Thymallus thymallus): evidence for secondary contact zones in central Europe
Authors: GUM B. , GROSS R. , KUEHN R.
Published: April 2005

Mitochondrial and microsatellite DNA markers were applied to infer the phylogeography, intraspecific diversity and dynamics of the distributional history of European grayling (Thymallus thymallus) with focus on its central and northern European distribution range. Phylogenetic and nested clade analyses revealed at least four major mtDNA lineages, which evolved in geographical isolation during the Pleistocene. These lineages should be recognized as the basic evolutionary significant units (ESUs) for grayling in central and northern Europe. In addition, and in contrast to previous work on grayling, the results of Bayesian analysis of individual admixture coefficients, two‐dimensional scaling analysis and spatial analysis of molecular variance provided evidence for a high level of admixture among major lineages in contact zones between drainages (e.g. the low mountain range of Germany), most likely resulting from glacial perturbations and ancient river connections between drainages during the Pleistocene glaciations. Even within river systems, a high level of differentiation among populations was revealed as indicated by the microsatellite data. Grayling sampled from 29 sites displayed high levels of differentiation (overall FST = 0.367), a high number of private alleles and high bootstrap support for the genetic distance‐based population clusters across 12 loci. We specifically discuss our results in context of phylogeograpic studies on other European freshwater fish species with habitat preferences similar to those of grayling. Our study shows that both large‐scale phylogeographical and detailed genetic analyses on a fine scale are mandatory for developing appropriate conservation guidelines of endangered species.
Molecular scatology as a tool to study diet: analysis of prey DNA in scats from captive Steller sea lions
Authors: DEAGLE B. E. , TOLLIT D. J. , JARMAN S. N. , HINDELL M. A. , TRITES A. W. , GALES N. J.
Published: April 2005

The DNA of prey present in animal scats may provide a valuable source of information for dietary studies. We conducted a captive feeding trial to test whether prey DNA could be reliably detected in scat samples from Steller sea lions (Eumetopias jubatus). Two sea lions were fed a diet of fish (five species) and squid (one species), and DNA was extracted from the soft component of collected scats. Most of the DNA obtained came from the predator, but prey DNA could be amplified using prey‐specific primers. The four prey species fed in consistent daily proportions throughout the trial were detected in more than 90% of the scat DNA extractions. Squid and sockeye salmon, which were fed as a relatively small percentage of the daily diet, were detected as reliably as the more abundant diet items. Prey detection was erratic in scats collected when the daily diet was fed in two meals that differed in prey composition, suggesting that prey DNA is passed in meal specific pulses. Prey items that were removed from the diet following one day of feeding were only detected in scats collected within 48 h of ingestion. Proportions of fish DNA present in eight scat samples (evaluated through the screening of clone libraries) were roughly proportional to the mass of prey items consumed, raising the possibility that DNA quantification methods could provide semi‐quantitative diet composition data. This study should be of broad interest to researchers studying diet since it highlights an approach that can accurately identify prey species and is not dependent on prey hard parts surviving digestion.
Inferring contemporary levels of gene flow and demographic history in a local population of the leaf beetle Gonioctena olivacea from mitochondrial DNA sequence variation
Authors: MARDULYN PATRICK , MILINKOVITCH MICHEL C.
Published: April 2005

We have studied mitochondrial DNA variation in a local population of the leaf beetle species Gonioctena olivacea, to check whether its apparent low dispersal behaviour affects its pattern of genetic variation at a small geographical scale. We have sampled 10 populations of G. olivacea within a rectangle of 5 × 2 km in the Belgian Ardennes, as well as five populations located approximately along a straight line of 30 km and separated by distances of 3–12 km. For each sampled individual (8–19 per population), a fragment of the mtDNA control region was polymerase chain reaction‐amplified and sequenced. Sequence data were analysed to test whether significant genetic differentiation could be detected among populations separated by such relatively short distances. The reconstructed genealogy of the mitochondrial haplotypes was also used to investigate the demographic history of these populations. Computer simulations of the evolution of populations were conducted to assess the minimum amount of gene flow that is necessary to explain the observed pattern of variation in the samples. Results show that migration among populations included in the rectangle of 5 × 2 km is substantial, and probably involves the occurrence of dispersal flights. This appears difficult to reconcile with the results of a previous ecological field study that concluded that most of this species dispersal occurs by walking. While sufficient migration to homogenize genetic diversity occurs among populations separated by distances of a few hundred metres to a few kilometres, distances greater than 5 km results in contrast in strong differentiation among populations, suggesting that migration is drastically reduced on such distances. Finally, the results of coalescent simulations suggest that the star‐like genealogy inferred from the mtDNA sequence data is fully compatible with a past demographic expansion. However, a metapopulation structure alone (without the need to invoke a population expansion event) cannot be dismissed as the cause of this star shape.
The internal anal sphincter: regulation of smooth muscle tone and relaxation
Authors: Rattan S.
Published: April 2005

Abstract  Basal tone in the internal anal sphincter (IAS) is primarily myogenic. Neurohumoral substances like angiotensin II may partially provide external signal for the basal tone in the IAS. The sphincteric relaxation on the contrary is neurogenic by activation of non‐adrenergic non‐cholinergic (NANC) nerves that release nitric oxide (NO), vasoactive intestinal polypeptide (VIP) and perhaps carbon monoxide. Because of the presence of spontaneous tone, the IAS offers an excellent model to investigate the nature of the inhibitory neurotransmission for NANC relaxation. Work from different laboratories in different species concludes that NO is the major contributor in the NANC relaxation. This may invoke the role of other inhibitory neurotransmitters such as VIP, working partly via NO. An understanding of the basic regulation of basal tone in the IAS and nature of inhibitory neurotransmission are critical in the pathophysiology and therapeutic potentials in the anorectal motility disorders.
The puborectalis muscle
Authors: Azpiroz F. , Fernandez‐fraga X. , Merletti R. , Enck P.
Published: April 2005

Abstract  The role of the levator ani and puborectalis muscle in preserving continence has been underestimated in the past, due predominantly to technical difficulties to investigate its proper function in healthy subjects, and its dysfunction as in patients with incontinence problems. This has recently been overcome by applying new investigational procedures such as a perineal dynamometer which measures the traction exerted by the levator ani on an intrarectal balloon catheter, or by multi‐electrode arrays recording the generation of motor unit action potentials from various parts of the puborectalis muscle sling via intrarectal surface electrodes. Both techniques have the potential to provide new insights into the physiology of defecation and the pathophysiology of incontinence and constipation.
The pylorus
Authors: Ramkumar D. , Schulze K. S.
Published: April 2005

Abstract  The pylorus controls the flow between a reservoir dedicated to mechanical and chemical digestion (the stomach) and a conduit dedicated to the absorption of nutrients (the intestines). The pylorus adjusts gastric outflow resistance to physiological needs. It allows the outflow of isotonic fluids yet selectively retains particles too large for delivery to the intestines and in concert with the antrum further processes them (gastric sieving). Unlike most gut sphincters, the pylorus, at least of man, maintains a patent lumen most of the time. It only intermittently becomes a tightly closed barrier that arrests all flow out of and into the stomach. The geometry of the pylorus changes dramatically from the relaxed open state to closure. Pyloric closure involves contraction of its proximal and distal muscle loops, and occlusion of its lumen by mucosal folds. Current studies that combine pressure recordings with imaging by magnetic resonance imaging or ultrasound and fluid‐mechanical analysis shed new light on the role of the pylorus in gastric emptying and digestion. Much has been learned in recent years on the innervation of the normal pylorus particularly from studies on infantile hypertrophic stenosis, and attempts are being made to treat gastroparesis by interventions on the pylorus.
Locally differentiated cryptic pigmentation in the freshwater isopod Asellus aquaticus
Authors: HARGEBY A. , STOLTZ J. , JOHANSSON J.
Published: April 2005

A repeated pattern of background colour matching in animals is an indication that pigmentation may be cryptic. Here, we examine the relationship between pigmentation of the freshwater isopod Asellus aquaticus and background darkness in 29 lakes, wetlands and ponds in Southern Sweden. The results show that Asellus pigmentation was correlated with substrate darkness across all localities. In seven localities, in which two contrasting substrate types were noted, Asellus populations were differentiated with respect to pigmentation. These findings thus provide phenomenological support for cryptic pigmentation in Asellus. Pigmentation generally increased with body size, but the relationship between pigmentation and size differed among localities, possibly as a result of differences in correlational selection on pigmentation and size. Selection thus appears to have resulted in local differentiation over a small spatial scale, even within lakes and wetlands. This differentiation is a likely cause behind elevated phenotype variation noted in localities with two substrate types, suggesting that habitat heterogeneity promotes genetic diversity.
The influence of mating system on the intensity of parent–offspring conflict in primates
Authors: LONG T. A. F.
Published: April 2005

An evolutionary conflict of interest exists between parents and their offspring over the partitioning of parental investment (PI) among siblings. When the direct fitness benefits to offspring of increased PI, outweigh the inclusive fitness costs from lost future sibling fitness, selection should favour the evolution of offspring selfishness over altruism. In theory, this conflict is heightened when females are not strictly monogamous, as current offspring should be less altruistic towards future half‐siblings than they would be towards full‐siblings. Using data collected on foetal growth rate (representing prenatal PI) in primates, I test the prediction from theory that the resolution of the parent‐offspring conflict will be closer to the offspring's evolutionary optima in polyandrous species than in more monandrous species. Using phylogenetic comparative analysis, and controlling for allometry, I show that offspring are able to obtain more PI when the probability of future full‐siblings decreases, and that this is most pronounced in taxa where there is the opportunity for direct foetal access to the maternal bloodstream. These results support the hypothesis that the resolution of prenatal PI conflict is influenced by both a species’ mating system and by its placental structure.
Habitat selection behaviour links local and regional scales in aquatic systems
Authors: Resetarits William J.
Published: April 2005

The role of habitat selection behaviour in the assembly of natural communities is an increasingly important theme in ecology. At the same time, ecologists and conservation biologists are keenly interested in scale and how processes at scales from local to regional interact to determine species distributions and patterns of biodiversity. How important is habitat selection in generating observed patterns of distribution and diversity at multiple spatial scales? In theory, habitat selection in response to interacting species can generate both positive and negative covariances among species distributions and create the potential to link processes of community assembly across multiple scales. Here I demonstrate that habitat selection by treefrogs in response to the distribution of fish predators functions at both the regional scale among localities and the local scale among patches within localities, implicating habitat selection as a critical link between local communities and the regional dynamics of metacommunities in complex landscapes.
Impact of hormone replacement therapy on microvascular function in healthy and Type 2 diabetic postmenopausal women
Authors: Gooding K. M. , MacLeod K. M. , Spyer G. , Ewings P. , Tooke J. E. , Shore A. C.
Published: April 2005

Aims  Hormone replacement therapy (HRT) has been previously reported to modulate vascular function and cardiovascular risk. Its impact on the macrocirculation has previously been explored, however, little data is available on its impact on the microcirculation. This study aimed to determine the impact of HRT on microvascular function in healthy and Type 2 diabetic postmenopausal women (n = 20 and 17, respectively).

Methods  Microvascular function was assessed by skin maximum hyperaemia, skin hyperaemic response to iontophoretically applied acetylcholine (endothelial‐dependent vasodilator) and sodium nitroprusside (endothelial‐independent vasodilator), capillary pressure and the microvascular filtration capacity. Microvascular assessments were carried out at baseline and repeated following 6 months’ oral hormone replacement therapy (1 mg oestradiol/0.5 mg norethisterone or 1 mg unopposed oestradiol for hysterectomized women).

Results  Following 6 months’ therapy there were no significant changes in microvascular assessments in the healthy women. In the diabetic women there was a reduction in the skin hyperaemic response to acetylcholine [median pretreatment peak response: 1.95 (25th, 75th centiles: 1.54, 2.30) V vs. post‐treatment peak response: 1.53 (1.30, 1.91) V (P = 0.011, Wilcoxon's signed rank test)] and sodium nitroprusside [median peak response 1.59 (1.37, 1.99) vs. 1.35 (0.92, 1.63) V (P = 0.011)] with HRT, but no other changes.

Conclusion  These data suggests that HRT does not affect microvascular function in healthy women, but adversely affects it in diabetic women. These findings may help to explain why HRT fails to provide the predicted cardiovascular protection, and raises the possibility that HRT influences microangiopathy progression in diabetic women.
11 September 2001, Counter‐terrorism, and the Human Rights Act
Authors: Gearty Conor
Published: April 2005

The attacks of 11 September 2001 and the reaction to them has been the gravest challenge to date to the Human Rights Act 1998. The Antiterrorism, Crime and Security Act 2001 has expanded the remit of the Terrorism Act 2000 and there has been a new concentration on antiterrorism by government. This article assesses the impact of human rights law on the debate about liberty and security following 11 September. It considers how the provisions of the Human Rights Act have influenced the formulation and interpretation of anti‐terrorism laws, and examines the role of the judiciary in adjudicating on disputes between the individual and the state. It ends with some general discussion about the security‐driven challenges to human rights that lie ahead.
Human Rights in the Scottish Courts
Authors: Mullen Tom , Murdoch Jim , Miller Alan , Craig Sarah
Published: April 2005

This article looks at the use made of the human rights legislation in the Scottish courts since the devolution of legislative and executive power to Scotland, based on research undertaken in all the ordinary courts, but excluding tribunals. It concludes that the incorporation of the Convention via the human rights legislation has had significant effects within the Scottish court system and on policy development without amounting to a major upheaval.
Adverse events of herbal food supplements for body weight reduction: systematic review*
Authors: Pittler M. H. , Schmidt K. , Ernst E.
Published: April 2005

Herbal weight‐loss supplements are marketed with claims of effectiveness. Our earlier systematic review identified data from double‐blind, randomized controlled trials for a number of herbal supplements. The aim of this systematic review was to assess all clinical evidence of adverse events of herbal food supplements for body weight reduction for which effectiveness data from rigorous clinical trials exist. We assessed Ephedra sinica, Garcinia cambogia, Paullinia cupana, guar gum, Plantago psyllium, Ilex paraguariensis and Pausinystalia yohimbe. Literature searches were conducted on Medline, Embase, Amed and The Cochrane Library. Data were also requested from the spontaneous reporting scheme of the World Health Organization. We hand‐searched relevant medical journals and our own files. There were no restrictions regarding the language of publication. The results show that adverse events including hepatic injury and death have been reported with the use of some herbal food supplements. For herbal ephedra and ephedrine‐containing food supplements an increased risk of psychiatric, autonomic or gastrointestinal adverse events and heart palpitations has been reported. In conclusion, adverse events are reported for a number of herbal food supplements, which are used for reducing body weight. Although the quality of the data does not justify definitive attribution of causality in most cases, the reported risks are sufficient to shift the risk–benefit balance against the use of most of the reviewed herbal weight‐loss supplements. Exceptions are Garcinia cambogia and yerba maté, which merit further investigation.
Comparison of overweight and obesity prevalence in school‐aged youth from 34 countries and their relationships with physical activity and dietary patterns
Authors: Janssen I. , Katzmarzyk P. T. , Boyce W. F. , Vereecken C. , Mulvihill C. , Roberts C. , Currie C. , Pickett W. ,   The Health Behaviour in School‐Aged Children Obesity Working Group
Published: April 2005

The purposes of this systematic review were to present and compare recent estimates of the prevalence of overweight and obesity in school‐aged youth from 34 countries and to examine associations between overweight and selected dietary and physical activity patterns. Data consisted of a cross‐sectional survey of 137 593 youth (10–16 years) from the 34 (primarily European) participating countries of the 2001–2002 Health Behaviour in School‐Aged Children Study. The prevalence of overweight and obesity was determined based on self‐reported height and weight and the international child body mass index standards. Logistic regression was employed to examine associations between overweight status with selected dietary and physical activity patterns. The two countries with the highest prevalence of overweight (pre‐obese + obese) and obese youth were Malta (25.4% and 7.9%) and the United States (25.1% and 6.8%) while the two countries with the lowest prevalence were Lithuania (5.1% and 0.4%) and Latvia (5.9% and 0.5%). Overweight and obesity prevalence was particularly high in countries located in North America, Great Britain, and south‐western Europe. Within most countries physical activity levels were lower and television viewing times were higher in overweight compared to normal weight youth. In 91% of the countries examined, the frequency of sweets intake was lower in overweight than normal weight youth. Overweight status was not associated with the intake of fruits, vegetables, and soft drinks or time spent on the computer. In conclusion, the adolescent obesity epidemic is a global issue. Increasing physical activity participation and decreasing television viewing should be the focus of strategies aimed at preventing and treating overweight and obesity in youth.
Method and structure for local emission regulation and arc prevention in field emitter arrays
Authors: Shaw Jonathan L. , Hsu David S. Y.
Published: April 2005

Field emission from air-exposed silicon and other surfaces typically occurs at energies up to several volts below the Fermi level, and the energies can change substantially during emission. We conclude this behavior results from emission from initial states in a dielectric (oxide) surface coating, and that the energies of these states change relative to the emitter Fermi level due to changing oxide state density and charge density. When emission occurs below the bulk Fermi level, energy is deposited into the emitter. In some cases this energy can be coupled to chemical bonds, creating states in the oxide and improving electron transport. If the power density deposited this way becomes excessive, oxide breakdown and arc initiation can result. Thus preventing excessive emission current at potentials more than 1–2V positive relative to the bulk Fermi level may prevent arc initiation. We propose that might be done by building a second (filter) aperture above each gate aperture in an array, and placing the aperture at a low positive voltage relative to the emitter contact. That structure creates a potential barrier for emitted electrons, which will cause those electrons emitted at excessively positive potentials to be returned to the gate electrode. A circuit element in series with the gate electrode will reduce the gate voltage, thereby limiting the current emitted at low energy. To limit or regulate the total emission current, a small resistor or other circuit element can be placed in series with the emitter, forcing the emission energy to be reduced in response to a given current.
Scanning tunneling microscopy observations of hafnium carbide thin films as a field emission material
Authors: Sato T. , Saida M. , Horikawa K. , Sasaki M. , Nagao M. , Kanemaru S. , Matsukawa T. , Itoh J. , Yamamoto S.
Published: April 2005

We have already reported superior characteristics of field emission from hafnium carbide (HfC)-coated Si field emission arrays. To clarify the microscopic feature of HfC films related to electron emission, the topograph and local work function (LWF) of the HfC film deposited on Si(100) substrates are examined in an atomic scale by using scanning tunneling microscopy (STM). From the STM/LWF images of the sputtering-cleaned film, it is revealed that the HfC film consists of grains with about 10 nm in size, and that the surface stoichiometry at the grain boundaries becomes carbon rich due to preferential sputtering after higher energy argon ion sputtering.
Field emission under extreme conditions from carbon nanopearls in a foam-like arrangement
Authors: Levesque A. , Vincent P. , Binh Vu Thien , Guillot D. , Brookes M. D.
Published: April 2005

We studied field emission properties of carbon nanopearls for application as cold cathodes in low vacuum conditions (up to 10−4Torr). The nanopearls are spherical in shape, 150 nm in diameter, and composed of both amorphous and nanocrystalline regions. The nanopearls form two-dimensional “strings” which give rise to a macroscopic three-dimensional foam-like material. For this study, we have synthesized uniform layers of nanopearls by chemical vapor deposition directly on the apex of tungsten tips and performed comparative field emission measurements under different gas pressures. We present field emission current stabilities in the μA range under nitrogen and oxygen atmosphere up to 10−4Torr, which corresponded to field emission current densities up to 1A∕cm2, and were obtained for hours with a simple “retroaction” voltage control. These results show that field emission with nanopearls is a promising way for applications requiring high current densities in high pressure environment. The long lifetime of nanopearls cathodes at high pressures is a consequence of the foam-like structure of the deposited layers of the nanopearls, leading to a self-healing process of the emission sites that were continuously destroyed by retro-ion sputtering during emission.
Uniformity measurement of electron emission from carbon nanotubes using electron-beam resist
Authors: Lee J. H. , Lee S. H. , Kim W. S. , Lee H. J. , Heo J. N. , Jeong T. W. , Choi C. H. , Kim J. M. , Park J. H. , Ha J. S. , Lee H. J. , Moon J. W. , Yoo M. A. , Nam J. W. , Cho S. H. , Yoon T. I. , Kim B. S. , Choe D. H.
Published: April 2005

The field-emission sites’ distribution was measured to monitor the emission uniformity from randomly oriented carbon-nanotube (CNT) emitters using electron-beam resists (ER). The dot-patterned CNT emitters were fabricated by screen-printing a photoimageable CNT paste on an indium doped tin oxide (ITO) coated glass plate. An ER-coated Si substrate used as an anode provides the detection of the location and amount of the electron emission from the partial number of active emission sites among many existing CNTs. The measurements were carried out with the variation of electrical fields through continuous- or pulsed-voltage applications on a diode-type configuration. Developed ER images after a similar dosage of field-emission current flow indicate that emission uniformity is improved as the electrical field is increased. This method suggests that the emission uniformity could be estimated for various conditions of emitter preparation, such as CNT type, paste composition, and dispersion process, as well as the variation of the electrical field, the existence of a resistive layer, and so on.
Ring-shaped images as a result of nonuniform field emission from capped carbon nanotubes
Authors: Filip L. D. , Nicolaescu D. , Tanemura M. , Kanemaru S. , Itoh J.
Published: April 2005

A model for electron field emission from carbon nanotubes (CNTs) has been developed and modeling results are presented. The model assumes that for high emission currents, part of the electrons behave as quasifree. As a result, the spatial confinement quantization of their states appears, the tunneling field emission taking place from these states into the vacuum. The probability of finding an electron in a small axial interval is higher close to the CNT cylindrical body, while the extraction field is higher on the CNT hemispherical tip. These two opposite trends lead to enhancement of the CNT lateral field emission for higher extraction voltages. The model outlines the possibility of inhomogeneous electron field emission for very thin CNTs at high emission levels and the appearance of peculiar ring-shaped and/or spot-shaped field emission images, in accordance to available experimental observations.
Polysilicon metal-insulator-semiconductor electron emitter
Authors: Govyadinov Alexander , Novet Thomas , Pidwerbecki David , Ramamoorthi Sriram , Smith Jim , Chen John , Otis Chuck , Neiman David , Benning Paul
Published: April 2005

The flat metal-insulator-semiconductor (MIS) electron emitter is a simple design, allowing easy manufacture. The emitters are relatively insensitive to environment, allowing them to operate in poorer vacuum conditions than are necessary for oxide thermionic or microtip field emitters. In most literature reports, MIS and metal-insulator-metal devices are limited in emission current (<0.001A∕cm2) by their low efficiencies (⪡0.1%). We have observed emission currents as high as 2–10A∕cm2 at efficiencies from 3%–10%. Our best results are from emitters comprised of 5–7.5nmgold∕15nm SiO2∕100nm polysilicon/n++ doped silicon substrate. The roles of each component of the flat emitter were investigated. The polysilicon serves a dual role: Bumps on its surface act as field-enhanced emission sites while the bulk of the film behaves as a self-adjusting ballast resistor preventing run away emission from any one emission site. The thin gold layer self-assembles into a nanomesh with >400pores∕μm2 through which electrons are emitted. Energy distribution and angular divergence of emitted electrons were measured. A coherent explanation of emission including the origination of the divergence is presented. Pros and cons of the MIS emitter and potential application are discussed.
Edge-shaped diamond field emission arrays
Authors: Takalkar R. S. , Davidson J. L. , Kang W. P. , Wisitsora-at A. , Kerns D. V.
Published: April 2005

This article presents the fabrication, characterization, and field emission behavior of edge-shaped diamond field emission arrays. Edge-shaped field emitter geometry is advantageous in the pursuit of high emission current since each edge can have a continuous multiple emission site along the edge as determined by the microstructure of the edge surface. Thus in totality an edge emitter provides significantly larger emission area and hence has the potential for larger current or transconductance for field emission devices. The edge arrays were fabricated via a mold transfer technique on a silicon substrate utilizing silicon micropatterning and etching, followed by chemical-vapor deposited diamond deposition. Arrays of micropatterned edge-shaped diamond emitters were developed and tested for field emission. Moreover, field emission characteristics were improved by further sharpening the edge apex achieving a lower turn-on field and higher emission current. Edge sharpening was achieved by introducing a silicon oxidation step in the mold fabrication process before the diamond deposition step. This oxidation process not only sharpened the edge but also served as a gate dielectric for the development of a self-aligned gated triode device.
Edge effects characterization of phase shift mask
Authors: Chua Gek Soon , Tay Cho Jui , Quan Chenggen , Lin Qunying
Published: April 2005

The demand for steadily decreasing dimensions in semiconductor devices is driving the need for increased resolution in optical lithography. The use of phase shift masks (PSMs) is among such resolution enhancement techniques. PSM are well known to show prominent diffraction effects, which cannot be described by the assumption of an infinitely thin mask (Kirchhoff approach) that is used in many commercial photolithography simulators. A correct prediction of sidelobe printability, process window and linearity of an OPC mask requires a rigorous application of diffraction theory. Optical lithography simulation employing a time-domain finite-difference (TDFD) algorithm (TEMPEST) has been used effectively to study the problem of aerial image intensity imbalance through focus with alternating phase shift masks (altPSMs). Using Geometrical Theory of Diffraction (GTD), and the solutions to canonical problems, we obtained a relationship between mask edge and disturbance in an image space. The main objective to develop useful formulations that can be readily applied to diffraction in mask technology. Rigorous analysis of diffraction effect on altPSMs using the GTD approach is discussed and results show that the effect of shifter edge angle is equivalent to that of shifter width.
Mechanism of simultaneous formation of refractory-metal free C40 and C49TiSi2 induced by Q-switched Nd:Yttrium–aluminum–garnet laser irradiation
Authors: Tan S. C. , See A. , Yu T. , Shen Z. X. , Lin J.
Published: April 2005

In this article, we demonstrate the usefulness of using a Q-switched Nd:Yttrium–aluminum–garnet laser to induce various phases of TiSi2 in 350Å of Ti layer deposited onto (100)Si substrates by varying the pulse width, τ, and energy fluence of the laser. Two sets of experiments were carried out. In the first set of experiments, τ and energy fluence of the laser are set at 0.18μs and approximately 1.5J∕cm2, respectively. The laser annealed Ti∕Si sample was then characterized using micro-Raman spectroscopy and it was found that C49TiSi2 is formed at two different temperatures. One is formed at a nonmelting temperature, 680°C, and the other formation temperature is at a high temperature of around 1975°C. A mechanism is proposed to explain the formation of C49 under these two different conditions. In addition, we also note that C40 is formed between these two temperatures. In the second set of experiments, increasing τ to 1.6μs and reducing the energy fluence to approximately 1.0J∕cm2 resulted in the formation of pure refractory C40. This refractory metal free C40 phase is confirmed with glancing angle x-ray diffraction.
Nanoimprint and nanocontact technologies using hydrogen silsesquioxane
Authors: Nakamatsu Ken-ichiro , Watanabe Keiichiro , Tone Katsuhiko , Namatsu Hideo , Matsui Shinji
Published: April 2005

Room-temperature nanoimprint lithography (RT-NIL) and nanocontact printing (RT-NCP) processes using hydrogen silsesquioxane (HSQ) are promising techniques for fabricating various nanostructure devices. We have evaluated the linewidth dependence of the HSQ imprinted depth and the baking-temperature dependence of HSQ replicated patterns after RT-NIL. We have also demonstrated an advanced bilayer resist process with HSQ as a top layer and AZ photoresist as a bottom layer; this process can be used to fabricate high-aspect resist patterns on a Si substrate for RT-NIL and RT-NCP. The etching-rate ratio of the AZ photoresist to HSQ exceeds 100 for O2 reactive-ion etching, which means the etching tolerance of the HSQ top layer is sufficient to enable its use as a mask. We have fabricated high-aspect nanostructure patterns with 100 nm linewidth and 1 μm height using RT-NIL and 150 nm linewidth and 1 μm height by using RT-NCP. Furthermore, we have successfully transferred Au electrode patterns from a mold onto HSQ resin by using the adhesion properties of HSQ.
Observation of electron emission pattern from nanosplit emitter fabricated using beam assisted process
Authors: Murakami K. , Yamasaki N. , Abo S. , Wakaya F. , Takai M.
Published: April 2005

A fabrication process of nanosplit emission sites has been developed with a minimum gap size of 12 nm using beam assisted processing. The electron emission patterns on a phosphor screen from a conventional single emitter and nanosplit emitters with various gap sizes were observed at room temperature and 77 K. The emission patterns from the conventional single emitter had a single spot at all the gate voltages. On the other hand, the emission patterns with two spots and additional spots were observed from the nanosplit emitters at gate voltages close to the turn-on voltages and the two spots became overlapped at a higher gate voltage.
Laser surface treatment of carbon nanotube cathodes for field emission displays with large diagonal size
Authors: Rochanachirapar W. , Murakami K. , Yamasaki N. , Abo S. , Wakaya F. , Takai M. , Hosono A. , Okuda S.
Published: April 2005

Excimer lasers with various wavelengths, power densities and beam profiles, have been used to irradiate to carbon nanotube-cathodes (CNT-cathodes) for field emission displays (FEDs) with large diagonal size. KrF (248 nm) and XeCl (308 nm) lasers were used with average power densities varied from 3 to 9MW∕cm2. The beam shapes of the laser beam were adjusted as a square spot of 8×8mm2 for the KrF laser and a stripe of 180×0.4mm2 for XeCl laser using a beam homogenizer. The emission characteristics of CNT-cathodes were improved after laser irradiation. The turn-on-field became as low as 0.7V∕μm and the emission current density became as high as 1.5mA∕cm2 at an applied field of 2.5V∕μm by KrF laser irradiation with a power density of 4MW∕cm2. Homogeneous emission-site distribution could be obtained by a square beam or a stripe beam processing with steps from 0.2 to 0.5 mm. The emission pattern became more homogeneous with increase in laser power density. The laser processing time for large diagonal sizes using a stripe beam of 365–200×0.4mm2 have been estimated, giving a processing time of 92–138 s for a cathode of diagonal size 60 in. with an aspect ratio of 4:3.
Field electron emission from two-dimensional electron gas
Authors: Filip V. , Nicolaescu D. , Wong H. , Nagao M. , Chu P. L.
Published: April 2005

The article presents a quantum mechanical model for the electron field emission from semiconductor surfaces covered by dielectric layers. By systematically connecting electronic wave functions at various interfaces, the model obtains in a unified manner the field emission current density from both clean and dielectric-covered semiconductor substrates. No energy quantization is imposed for the interface layer and thermodynamic nonequilibrium is allowed between the conduction electrons from the interface (accumulation) layer and those of the bulk. The model is applied to study the electron field emission from Si tips covered by ultrathin oxide layers and also to explain the resonance effects observed in field emission from Si covered by thicker dielectric layers.