bluuebunny/crossref_metadata_2025 huggingface dataset:
Noncommutative gauge theories on $ \mathbb{R}_{\theta}^2 $ as matrix models
Authors: Martinetti Pierre , Vitale Patrizia , Wallet Jean-Christophe
Published: September 2013

Abstract

We study a class of noncommutative gauge theory models on 2-dimensional Moyal space from the viewpoint of matrix models and explore some related properties. Expanding the action around symmetric vacua generates non local matrix models with polynomial interaction terms. For a particular vacuum, we can invert the kinetic operator which is related to a Jacobi operator. The resulting propagator can be expressed in terms of Chebyschev polynomials of second kind. We show that non vanishing correlations exist at large separations. General considerations on the kinetic operators stemming from the other class of symmetric vacua, indicate that only one class of symmetric vacua should lead to fast decaying propagators. The quantum stability of the vacuum is briefly discussed.
Anatomical causes of female infertility and their management
Authors: Abrao Mauricio S. , Muzii Ludovico , Marana Riccardo
Published: September 2013

The main female anatomical causes of infertility include post‐infectious tubal damage, endometriosis, and congenital/acquired uterine anomalies. Congenital (septate uterus) and acquired (myomas and synechiae) diseases of the uterus may lead to infertility, pregnancy loss, and other obstetric complications. Pelvic inflammatory disease represents the most common cause of tubal damage. Surgery still remains an important option for tubal factor infertility, with results in terms of reproductive outcome that compare favorably with those of in vitro fertilization. Endometriosis is a common gynecologic condition affecting women of reproductive age, which can cause pain and infertility. The cause of infertility associated with endometriosis remains elusive, suggesting a multifactorial mechanism involving immunologic, genetic, and environmental factors. Despite the high prevalence of endometriosis, the exact mechanisms of its pathogenesis are unknown. Specific combinations of medical, surgical, and psychological treatments can ameliorate the quality of life of women with endometriosis. In the majority of cases, surgical treatment of endometriosis has promoted significant increases in fertilization rates. There are obvious associations between endometriosis and the immune system, and future strategies to treat endometriosis might be based on immunologic concepts.
Glucose uptake by the brain on chronic high-protein weight-loss diets with either moderate or low amounts of carbohydrate
Authors: Lobley Gerald E. , Johnstone Alexandra M. , Fyfe Claire , Horgan Graham W. , Holtrop Grietje , Bremner David M. , Broom Iain , Schweiger Lutz , Welch Andy
Published: September 2013

Previous work has shown that hunger and food intake are lower in individuals on high-protein (HP) diets when combined with low carbohydrate (LC) intakes rather than with moderate carbohydrate (MC) intakes and where a more ketogenic state occurs. The aim of the present study was to investigate whether the difference between HPLC and HPMC diets was associated with changes in glucose and ketone body metabolism, particularly within key areas of the brain involved in appetite control. A total of twelve men, mean BMI 34·9 kg/m2, took part in a randomised cross-over trial, with two 4-week periods when isoenergetic fixed-intake diets (8·3 MJ/d) were given, with 30 % of the energy being given as protein and either (1) a very LC (22 g/d; HPLC) or (2) a MC (182 g/d; HPMC) intake. An18fluoro-deoxyglucose positron emission tomography scan of the brain was conducted at the end of each dietary intervention period, following an overnight fast (n4) or 4 h after consumption of a test meal (n8). On the next day, whole-body ketone and glucose metabolism was quantified using [1,2,3,4-13C]acetoacetate, [2,4-13C]3-hydroxybutyrate and [6,6-2H2]glucose. The composite hunger score was 14 % lower (P= 0·013) for the HPLC dietary intervention than for the HPMC diet. Whole-body ketone flux was approximately 4-fold greater for the HPLC dietary intervention than for the HPMC diet (P< 0·001). The 9-fold difference in carbohydrate intakes between the HPLC and HPMC dietary interventions led to a 5 % lower supply of glucose to the brain. Despite this, the uptake of glucose by the fifty-four regions of the brain analysed remained similar for the two dietary interventions. In conclusion, differences in the composite hunger score observed for the two dietary interventions are not associated with the use of alternative fuels by the brain.
Salt, fruit and vegetable consumption and blood pressure development: a longitudinal investigation in healthy children
Authors: Shi Lijie , Krupp Danika , Remer Thomas
Published: September 2013

Low salt intake and high fruit and vegetable intake (FVI) have been shown to reduce blood pressure (BP) in adults. Longitudinal data on the independent effect of both FVI and salt intake on BP in healthy normotensive children are not available yet. In the present study, we aimed to characterise the concomitant influence of salt intake and FVI on BP development throughout childhood and adolescence. We examined 435 healthy subjects, for whom at least three repeated measurements of BP had been taken and who had provided 24 h urine samples and 3 d weighed dietary records between 4 and 18 years of age. BP was measured using a mercury sphygmomanometer (Mercuro 300, WelchAllyn) and salt intake was determined based on 24 h Na excretion. The intra-individual change in salt intake was almost significantly associated with the change in systolic BP (SBP, P= 0·06) and marginally (P= 0·09) with that in diastolic BP (DBP) in puberty, but not in pre-puberty. A 1 g/d increase in salt intake was associated with a 0·2 mmHg increase in SBP. In pre-puberty, but not in puberty, differences in FVI between children predicted between-person variations in SBP and DBP (P= 0·03). Corresponding findings were obtained for 24 h K excretion (a urinary indicator for FVI). A 100 g/d lower FVI was related to a 0·4 mmHg higher BP value. In conclusion, in healthy children and adolescents with BP in the low-normal range, both salt intake and FVI may already start to influence BP, although at a small magnitude. The potential importance of establishing healthy eating habits in childhood for later BP development emphasises the role of higher FVI and lower salt intake in the prevention of hypertension in the long run.
Abelian Semigroups of Matrices on ℂnand Hypercyclicity
Authors: Ayadi Adlene , Marzougui Habib
Published: September 2013

We give a complete characterization of a hypercyclic abelian semigroup of matrices on ℂn. For finitely generated semigroups, this characterization is explicit and it is used to determine the minimal number of matrices in normal form over ℂ that form a hypercyclic abelian semigroup on ℂn. In particular, we show that no abelian semigroup generated bynmatrices on ℂncan be hypercyclic.
The potential role of fruit and vegetables in aspects of psychological well-being: a review of the literature and future directions
Authors: Rooney Ciara , McKinley Michelle C. , Woodside Jayne V.
Published: September 2013

The objective of the present paper was to review the literature investigating the potential relationship between fruit and vegetables (FV) and psychological well-being. The rising prevalence of mental ill health is causing considerable societal burden. Inexpensive and effective strategies are therefore required to improve the psychological well-being of the population, and to reduce the negative impact of mental health problems. A growing body of literature suggests that dietary intake may have the potential to influence psychological well-being. For example, studies have suggested that particular dietary constituents, including vitamins and minerals, might be beneficial to psychological health. However, in order to better reflect normal dietary intake, health-based research has increasingly begun to focus on whole foods and dietary patterns, rather than individual nutrients. One food group that has received increasing attention with regard to psychological health is FV. This is probably a result of the strong evidence base, which exists in relation to their protective association with a number of chronic diseases, as well as the fact that they are a rich source of some of the nutrients which have been linked to psychological health. While some promising findings exist with regards to FV intake and psychological well-being, overall, results are inconsistent. Possible reasons for this, such as methodological issues related to study design and the measurement of psychological well-being and FV intake, are discussed within this review. Based on the predominantly observational nature of existing literature, the present paper concludes that future well-designed randomised controlled trials are required to investigate the relationship further.
PUFA-derived endocannabinoids: an overview
Authors: Cascio Maria Grazia
Published: September 2013

Following on from the discovery of cannabinoid receptors, of their endogenous agonists (endocannabinoids) and of the biosynthetic and metabolic enzymes of the endocannabinoids, significant progress has been made towards the understanding of the role of the endocannabinoid system in both physiological and pathological conditions. Endocannabinoids are mainly n-6 long-chain PUFA (LCPUFA) derivatives that are synthesised by neuronal cells and inactivated via a two-step process that begins with their transport from the extracellular to the intracellular space and culminates in their intracellular degradation by hydrolysis or oxidation. Although the enzymes responsible for the biosynthesis and metabolism of endocannabinoids have been well characterised, the processes involved in their cellular uptake are still a subject of debate. Moreover, little is yet known about the roles of endocannabinoids derived from n-3 LCPUFA such as EPA and DHA. Here, I provide an overview of what is currently known about the mechanisms for the biosynthesis and inactivation of endocannabinoids, together with a brief analysis of the involvement of the endocannabinoids in both food intake and obesity. Owing to limited space, recent reviews will be often cited instead of original papers.
Low host specificity in species-rich assemblages of xylem- and phloem-feeding herbivores (Auchenorrhyncha) in a New Guinea lowland rain forest
Authors: Dem Francesca F. , Stewart Alan J.A. , Gibson Amos , Weiblen George D. , Novotny Vojtech
Published: September 2013

We documented one of the most species-rich assemblages of tropical rain-forest Auchenorrhyncha, comprising 402 phloem- and xylem-feeding species, by sampling adults from forest vegetation. Further, we reared 106 species from larvae sampled on 14 plant species. Both xylem- and phloem-feeding guilds exhibited wide host-plant ranges, as 74% of species fed on more than one plant family. In comparison, using data extracted from the temperate-zone literature, phloem-feeders exhibited lower host specificity in Papua New Guinea than in Germany, because in Papua New Guinea they were dominated by generalist Fulgoroidea while in Germany by specialist Membracoidea. The similarity of Auchenorrhyncha assemblages from different plant species was unrelated to the phylogenetic distance between their hosts. Host specificity, abundance and species composition of Auchenorrhyncha assemblages were unrelated to the optimum of their host plant species on succession gradient from secondary to primary forest. Higher host specificity did not lead to greater species richness in Auchenorrhyncha assemblages feeding on different plant species, but the number of species feeding on a particular plant species was a strong predictor of the Auchenorrhyncha abundance on that plant. These patterns suggest that Auchenorrhyncha assemblages on these plant species are not saturated with species and determined by division of limited resources among competitors, but instead are dependent on the number of colonizers from the regional species pool.
Asymmetric pollen transfer and reproductive success of the hawkmoth-pollinated distylous tree Palicourea tetragona (Rubiaceae) at La Selva, Costa Rica
Authors: Martén-Rodríguez Silvana , Muñoz-Gamboa Paola , Delgado-Dávila Ruth , Quesada Mauricio
Published: September 2013

Distyly is a floral polymorphism that presumably evolved to facilitate cross-pollination and to prevent sexual interference. However, pollen transfer is often asymmetric, with one floral morph acting as a pollen donor and the other as a pollen recipient. We evaluated the association between floral morphology, pollinator visitation and effectiveness on patterns of pollen transfer in distylous Palicourea tetragona at La Selva Biological Station in Costa Rica. To assess floral variation we measured corolla, pistil and stamen traits from 66 plants. We quantified pollinator visitation and efficiency on 56 individuals and counted pollen loads on stigmas of flowers observed for 1 h. We determined fruit set 2 mo later and assessed between-morph variation in pollen transfer and female reproductive success. Floral variation was mostly consistent with a typical distylous system; however, there was overlap in the stigma heights of pin and thrum individuals in the study population. Primary pollinators were two species of hawkmoths that visited both morphs at a frequency of 2 visits per flower h−1. The mean number of pollen grains deposited on stigmas was 89 for pin and 153 for thrum individuals. However, loads of illegitimate pollen were higher on stigmas of thrum individuals, while loads of legitimate pollen were higher on stigmas of pin individuals. Consistently, fruit set was higher in pin (31%) than in thrum individuals (22%). High deposition of illegitimate pollen, in addition to the lower female reproductive success in the thrum morph reveal that distyly in P. tetragona does not always prevent sexual interference. We suggest that in long and narrow tubular flowers, like those of P. tetragona, stigma clogging by deposition of self- or same-morph pollen may reduce legitimate fertilization of ovules causing the observed asymmetric fruit set.
A survey of different approaches to support in argumentation systems
Authors: Cohen Andrea , Gottifredi Sebastian , García Alejandro J. , Simari Guillermo R.
Published: September 2013

In the last decades, most works in the literature have been devoted to study argumentation formalisms that focus on a defeat relation among arguments. Recently, the study of a support relation between arguments regained attention among researchers; the bulk of the research has been centered on the study of support within the context of abstract argumentation by considering support as an explicit interaction between arguments. However, there exist other approaches that take support into account in a different setting. This article surveys several interpretations of the notion of support as proposed in the literature, such as deductive support, necessary support, evidential support, subargument, and backing, among others. The aim is to provide a comprehensive study where similarities and differences among these interpretations are highlighted, as well as discuss how they are addressed by different argumentation formalisms.
Relationships between tree species diversity and above-ground biomass in Central African rainforests: implications for REDD
Authors: DAY MICHAEL , BALDAUF CRISTINA , RUTISHAUSER ERVAN , SUNDERLAND TERRY C. H.
Published: September 2013

Tropical forests are both important stores of carbon and among the most biodiverse ecosystems on the planet. Reducing emissions from deforestation and degradation (REDD) schemes are designed to mitigate the impacts of climate change, by conserving tropical forests threatened by deforestation or degradation. REDD schemes also have the potential to contribute significantly to biodiversity conservation efforts within tropical forests, however biodiversity conservation and carbon sequestration need to be aligned more closely for this potential to be realized. This paper analyses the relationship between tree species diversity and above-ground biomass (AGB) derived from 1-ha tree plots in Central African rainforests. There was a weakly significant correlation between tree biomass and tree species diversity (r = 0.21, p = 0.03), and a significantly higher mean species diversity in plots with larger AGB estimates (M = 44.38 species in the top eight plots, compared to M = 35.22 in the lower eight plots). In these Central African plots, the relationship between tree species diversity and AGB appeared to be highly variable; nonetheless, high species diversity may often be related to higher biomass and, in such cases, REDD schemes may enhance biodiversity by targeting species diverse forests.
Estimation of the sensitivity of environmental sampling for detection ofSalmonellain commercial layer flocks post-introduction of national control programmes
Authors: ARNOLD M. E. , MARTELLI F. , MCLAREN I. , DAVIES R. H.
Published: September 2013

A key element of national control programmes (NCPs) forSalmonellain commercial laying flocks, introduced across the European Union, is the identification of infected flocks and holdings through statutory sampling. It is therefore important to know the sensitivity of the sampling methods, in order to design effective and efficient surveillance forSalmonella. However, improvedSalmonellacontrol in response to the NCP may have influenced key factors that determine the sensitivity of the sampling methods used to detectSalmonellain NCPs. Therefore the aim of this study was to compare estimates of the sensitivity of the sampling methods using data collected before and after the introduction of the NCP, using Bayesian methods. There was a large reduction in the sensitivity of dust in non-cage flocks between the pre-NCP studies (81% of samples positive in positive flocks) and post-NCP studies (10% of samples positive in positive flocks), leading to the conclusion that sampling dust is not recommended for detection ofSalmonellain non-cage flocks. However, cage dust (43% of samples positive in positive flocks) was found to be more sensitive than cage faeces (29% of samples positive in positive flocks). To have a high probability of detection, several NCP-style samples need to be used. For confirmation ofSalmonella, five NCP faecal samples for cage flocks, and three NCP faecal boot swab samples for non-cage flocks would be required to have the equivalent sensitivity of the EU baseline survey method, which was estimated to have an 87% and 75% sensitivity to detectSalmonellaat a 5% within-flock prevalence in cage and non-cage flocks, respectively.
MICROPRODUCTION FUNCTIONS WITH UNIQUE COEFFICIENTS AND ERRORS: A RECONSIDERATION AND RESPECIFICATION
Authors: Swamy P.A.V.B. , Tavlas G.S. , Hall S.G.
Published: September 2013

Estimated microproduction functions confront two major problems—those of (1) unknown functional forms and (2) the measurement of capital independent of the distribution of output among the factors of production. The latter problem has emerged unresolved from the earlier Cambridge capital controversy. In the presence of these two problems, all specifications of microproduction functions have involved nonunique coefficients and error terms. We provide a method of deriving time-varying coefficients that produces unique coefficients and error terms. Specifically, we respecify the microproduction function in such a way that its coefficients are the sums of (i) the appropriate partial derivatives and (ii) exact representations of excluded-variable biases. By decomposing the total coefficients, we obtain the unique coefficients and a unique error term. Our treatment of heterogeneous capital is not subject to the criticisms of that concept that emerged during the Cambridge controversy.
Knowledge, attitudes and behaviour of Greek adults towards salt consumption: a Hellenic Food Authority project
Authors: Marakis Georgios , Tsigarida Eirini , Mila Spyridoula , Panagiotakos Demosthenes B
Published: September 2013

Objective

To investigate the knowledge, attitudes and behaviour of Greek adults towards salt as well as their differences with respect to gender, age and level of education.

Design

Cross-sectional, observational survey.

Setting

Voluntary participation to a telephone interview, using a seventeen-item questionnaire.

Subjects

Greek adults aged over 25 years (n 3609), nationally representative according to age, gender and geographical distribution of the Greek population, were interviewed.

Results

More women of all age groups compared with men reported adding salt during cooking (P < 0·001), while less reported adding salt on the plate (P < 0·001). Also, more women believed that salt added during cooking was the main source of salt in the diet (P < 0·001). Participants aged 25–34, 35–44 and 45–54 years old had better knowledge of the harmful effects of salt on health compared with the 55+ years age group (P = 0·002, P = 0·001, P < 0·001, respectively); respondents in the aforementioned age groups also knew that children should consume less salt than adults compared with 55+ years age group (P = 0·004, P < 0·001, P < 0·001, respectively). Respondents with secondary and higher educational status were more likely to avoid consumption of processed foods (P < 0·001) and to check the nutrition information on food packaging as compared with respondents having basic education status (P < 0·001).

Conclusions

Awareness needs to be raised regarding salt recommendations for adults and children, sources of sodium in the diet and adding less salt during cooking, as well as reading food labels. Future campaigns for salt reduction should consider gender, age and level of education differences regarding knowledge, attitudes and behaviour towards salt.
Relative validity of a semi-quantitative FFQ in 3-year-old Polish children
Authors: Sochacka-Tatara Elżbieta , Pac Agnieszka
Published: September 2013

Objectives

The aim of the study was to assess the relative validity of a semi-quantitative FFQ (SFFQ) which measures the usual dietary intake of 3-year-old children.

Design

The children's daily dietary intake was measured using the SFFQ. The average intake of three 24 h dietary recalls (24hDR) was calculated as a reference method. Wilcoxon's rank test and Spearman's rank-correlation coefficient were used to compare nutrient intakes assessed by both methods. The level of agreement between the SFFQ and the repeated 24hDR was determined by the Bland–Altman method. To assess the agreement in quartile distribution, the weighted kappa coefficient (κw) was used.

Setting

Krakow, Poland.

Subjects

One hundred and forty-three 3-year-old children and their mothers, participants of a prospective cohort study.

Results

Overall, the SFFQ overestimated energy and nutrient intakes compared with the repeated 24hDR. The median correlation coefficient for energy and nutrient intakes was 0·456, with higher results for Ca, P and riboflavin. Although theκwvalue showed only slight to fair agreement between the two methods, about 75 % of the children were classified into the same or adjacent quartile and the level of agreement assessed by the Bland–Altman method for most of the nutrients investigated was good.

Conclusions

The study indicated that the SFFQ might be a useful tool to assess dietary intakes of nutrients by small children, especially for ranking them according their nutrient intake.
THE ZELEZNIKOW PROBLEM ON A CLASS OF ADDITIVELY IDEMPOTENT SEMIRINGS
Authors: SHAO YONG , CRVENKOVIĆ SINIŠA , MITROVIĆ MELANIJA
Published: September 2013

A semiring is a set$S$with two binary operations$+ $and$\cdot $such that both the additive reduct${S}_{+ } $and the multiplicative reduct${S}_{\bullet } $are semigroups which satisfy the distributive laws. If$R$is a ring, then, following Chaptal [‘Anneaux dont le demi-groupe multiplicatif est inverse’,C. R. Acad. Sci. Paris Ser. A–B 262(1966), 274–277],${R}_{\bullet } $is a union of groups if and only if${R}_{\bullet } $is an inverse semigroup if and only if${R}_{\bullet } $is a Clifford semigroup. In Zeleznikow [‘Regular semirings’,Semigroup Forum 23(1981), 119–136], it is proved that if$R$is a regular ring then${R}_{\bullet } $is orthodox if and only if${R}_{\bullet } $is a union of groups if and only if${R}_{\bullet } $is an inverse semigroup if and only if${R}_{\bullet } $is a Clifford semigroup. The latter result, also known as Zeleznikow’s theorem, does not hold in general even for semirings$S$with${S}_{+ } $a semilattice Zeleznikow [‘Regular semirings’,Semigroup Forum 23(1981), 119–136]. The Zeleznikow problem on a certain class of semirings involves finding condition(s) such that Zeleznikow’s theorem holds on that class. The main objective of this paper is to solve the Zeleznikow problem for those semirings$S$for which${S}_{+ } $is a semilattice.
Relationship Quality among Swiss Women in Opposite-Sex Versus Same-Sex Romantic Relationships
Authors: Meuwly Nathalie , Feinstein Brian A. , Davila Joanne , Nuñez David Garcia , Bodenmann Guy
Published: September 2013

Romantic relationship quality is an important factor for well-being. Most research on romantic relationships is based on heterosexual couples, but studies of different types of dyads showed that relationship functioning among same-sex couples is similar to that among heterosexual couples. However, a few studies suggest that lesbian partners are better communicators and more satisfied in their romantic relationships. The present study aimed to replicate these findings with a sample of Swiss couples, as most of the previous studies have been based on US-American samples. Eighty-two women who were currently in a romantic relationship with either a male or a female partner completed an online questionnaire about their relationship functioning. Compared to heterosexual women, lesbian women reported receiving better support from and experiencing less conflict with their female partners. They also showed a trend toward being more satisfied in their relationship. The study supports the notion that, relative to heterosexual couples, the quality of support and conflict interactions may be enhanced in female same-sex couples.
Vascular Aspects of Cognitive Impairment and Dementia
Authors: Wiesmann Maximilian , Kiliaan Amanda J , Claassen Jurgen AHR
Published: September 2013

Hypertension and stroke are highly prevalent risk factors for cognitive impairment and dementia. Alzheimer's disease (AD) and vascular dementia (VaD) are the most common forms of dementia, and both conditions are preceded by a stage of cognitive impairment. Stroke is a major risk factor for the development of vascular cognitive impairment (VCI) and VaD; however, stroke may also predispose to AD. Hypertension is a major risk factor for stroke, thus linking hypertension to VCI and VaD, but hypertension is also an important risk factor for AD. Reducing these two major, but modifiable, risk factors—hypertension and stroke—could be a successful strategy for reducing the public health burden of cognitive impairment and dementia. Intake of long-chain omega-3 polyunsaturated fatty acids (LC-n3-FA) and the manipulation of factors involved in the renin-angiotensin system (e.g. angiotensin II or angiotensin-converting enzyme) have been shown to reduce the risk of developing hypertension and stroke, thereby reducing dementia risk. This paper will review the research conducted on the relationship between hypertension, stroke, and dementia and also on the impact of LC-n3-FA or antihypertensive treatments on risk factors for VCI, VaD, and AD.
An Integrated Population Pharmacokinetic Meta‐Analysis of Propofol in Morbidly Obese and Nonobese Adults, Adolescents, and Children
Authors: Diepstraten J , Chidambaran V , Sadhasivam S , Blussé van Oud‐Alblas HJ , Inge T , van Ramshorst B , van Dongen EPA , Vinks AA , Knibbe CAJ
Published: September 2013

This study describes a population pharmacokinetic meta‐analysis of propofol to characterize the influence of body size measures and age in morbidly obese and nonobese adults, adolescents, and children. Sixty morbidly obese and nonobese adult patients (55–167 kg; 21–79 years) and 34 morbidly obese and nonobese adolescents and children (37–184 kg; 9–20 years) were included. The results show that clearance increased with total body weight in an allometric function while age was found to influence clearance in a bilinear fashion with two distinct slopes, reflecting an initial increase and subsequent decrease as a result of aging. Using these two functions, the influence of both (over)weight and age on propofol clearance was well characterized, which may provide a basis for dosing across this diverse group of patients.

CPT: Pharmacometrics & Systems Pharmacology (2013) 2, e73; doi:10.1038/psp.2013.47; advance online publication 11 September 2013
The air–water interface determines the outcome of seeding during amyloidogenesis
Authors: Trigg Ben J. , Lee Chiu Fan , Vaux David J. , Jean Létitia
Published: September 2013

Amyloid formation is a hallmark of protein misfolding diseases (e.g. Type II diabetes mellitus). The energetically unfavourable nucleation step of amyloidogenesis can be accelerated by seeding, during which pre-formed aggregates act as templates for monomer recruitment. Hydrophobic–hydrophilic interfaces [e.g. AWI (air–water interface)] can also catalyse amyloidogenesis due to the surfactant properties of amyloidogenic polypeptides. Using thioflavin T fluorescence and electron microscopy, we demonstrate that the outcome of seeding on human islet amyloid polypeptide amyloidogenesis is dependent upon whether the AWI is present or absent and is dictated by seed type. Seeding significantly inhibits (with AWI) or promotes (without AWI) plateau height compared with seedless controls; with short fibrils being more efficient seeds than their longer counterparts. Moreover, promotion of nucleation by increasing monomer concentrations can only be observed in the absence of an AWI. Using biophysical modelling, we suggest that a possible explanation for our results may reside in lateral interactions between seeds and monomers determining the fibril mass formed in seeded reactions at steady-state. Our results suggest that in vivo hydrophobic–hydrophilic interfaces (e.g. the presence of membranes and their turnover rate) may dictate the outcome of seeding during amyloidogenesis and that factors affecting the size of the pre-aggregate may be important.
Assessment of the contribution of NAD(P)H-dependent quinone oxidoreductase 1 (NQO1) to the reduction of vitamin K in wild-type and NQO1-deficient mice
Authors: Ingram Brian O. , Turbyfill Jared L. , Bledsoe Peggy J. , Jaiswal Anil K. , Stafford Darrel W.
Published: September 2013

NQO1 [NAD(P)H quinone oxidoreductase 1; also known as DT-diaphorase] is a cytosolic enzyme that catalyses the two-electron reduction of various quinones including vitamin K. The enzyme may play a role in vitamin K metabolism by reducing vitamin K to vitamin K hydroquinone for utilization in the post-translational γ-glutamyl carboxylation reactions required by several proteins involved in blood coagulation. The aim of the present study was to assess the contribution of NQO1 to vitamin K reduction and haemostasis in an in vivo model. We examined the contribution of NQO1 to haemostasis by examining survival rates in mice poisoned with the anticoagulant warfarin. Supraphysiological amounts of vitamin K sufficiently reversed the effects of warfarin in both wild-type and NQO1-deficient mice. Additionally, vitamin K reductase activities distinct from VKOR (vitamin K epoxide reductase) and NQO1 were measured in vitro from both wild-type and NQO1-defecient mice. The results of the present study suggest that NQO1 does not play a major role in the production of vitamin K hydroquinone and supports the existence of multiple vitamin K reduction pathways. The properties of a NAD(P)H-dependent vitamin K reductase different from NQO1 are described.
Cognitive and Linguistic Sources of Variance in 2-Year-Olds' Speech-Sound Discrimination: A Preliminary Investigation
Authors: Lalonde Kaylah , Holt Rachael Frush
Published: September 2013

Purpose

This preliminary investigation explored potential cognitive and linguistic sources of variance in 2-year-olds' speech-sound discrimination by using the toddler change/no-change procedure and examined whether modifications would result in a procedure that can be used consistently with younger 2-year-olds.

Method

Twenty typically developing 2-year-olds completed the newly modified toddler change/no-change procedure. Behavioral tests and parent report questionnaires were used to measure several cognitive and linguistic constructs. Stepwise linear regression was used to relate discrimination sensitivity to the cognitive and linguistic measures. In addition, discrimination results from the current experiment were compared with those from 2-year-old children tested in a previous experiment.

Results

Receptive vocabulary and working memory explained 56.6% of variance in discrimination performance. Performance was not different on the modified toddler change/no-change procedure used in the current experiment from in a previous investigation, which used the original version of the procedure.

Conclusions

The relationship between speech discrimination and receptive vocabulary and working memory provides further evidence that the procedure is sensitive to the strength of perceptual representations. The role for working memory might also suggest that there are specific subject-related, nonsensory factors limiting the applicability of the procedure to children who have not reached the necessary levels of cognitive and linguistic development.
Age Differences in Speech Motor Performance on a Novel Speech Task
Authors: Sadagopan Neeraja , Smith Anne
Published: September 2013

Purpose

The study was aimed at characterizing age-related changes in speech motor performance on a nonword repetition task as a function of practice and nonword length and complexity.

Method

Nonword repetition accuracy, lip aperture coordination, and nonword production durations were assessed on 2 consecutive days for 16 young and 16 elderly participants for the production of 6 novel nonwords increasing in length and complexity.

Results

The effect of age on the ability to accurately and rapidly repeat long, complex nonwords was significant. However, the authors found no differences between the speech motor coordinative patterns of young and elderly adults. Further, the authors demonstrated age- and nonword-specific within- and between-session gains in speech motor performance.

Conclusions

The authors speculate that cognitive, sensory, and motor factors interact in complex ways in elderly individuals to produce individual differences in nonword repetition ability at the levels of both behavioral and speech motor performance.
Preterm and Term Infants' Perception of Temporally Coordinated Syllable–Object Pairings: Implications for Lexical Development
Authors: Gogate Lakshmi , Maganti Madhavilatha , Perenyi Agnes
Published: September 2013

Purpose

This experimental study examined term infants (n= 34) and low-risk near-term preterm infants (gestational age 32–36 weeks) at 2 months chronological age (n= 34) and corrected age (n=16). The study investigated whether the preterm infants presented with a delay in their sensitivity to synchronous syllable–object pairings when compared with term infants.

Method

First, infants were habituated to a single syllable, [tah] or [gah], spoken in synchrony with the motions of 1 of 4 toy objects, a crab, a porcupine, a star, or a lamb chop. Next, the infants received 2 syllable- and 2 object-change test trials, counterbalanced for order.

Results

After factoring out differential looking time during habituation, the study found that preterm infants showed attenuated looks to the change in the object and the change in the syllable relative to term infants.

Conclusions

These findings suggest that even near-term preterm infants present with a delay in their sensitivity to synchrony in syllable–object pairings relative to term infants. Given the important role that synchrony plays in word mapping at 6–9 months, this early delay in sensitivity to synchrony might be an indicator of word mapping delays found in older preterm infants.
Necessary and sufficient conditions to the transitivity in simultaneous stabilisation of time‐varying systems
Authors: Liu Liu , Lu Yufeng
Published: September 2013

In this study, the authors study the transmission problem in simultaneous stabilisation of discrete time‐varying systems in the frame work of nest algebra. The necessary and sufficient conditions are developed for the transitivity and strong transitivity in simultaneous stabilisation, respectively. Some criterions for these two properties are established in terms of singly strong representations of only one or two given plants but not all. Finally, the authors give parameterisations of simultaneous stabilisers when the properties of transitivity hold.
A numerical study of the effects of superhydrophobic surface on skin-friction drag in turbulent channel flow
Authors: Park Hyunwook , Park Hyungmin , Kim John
Published: September 2013

Superhydrophobic surfaces have attracted much attention lately as they present the possibility of achieving a substantial skin-friction drag reduction in turbulent flows. In this paper, the effects of a superhydrophobic surface, consisting of microgrates aligned in the flow direction, on skin-friction drag in turbulent flows were investigated through direct numerical simulation of turbulent channel flows. The superhydrophobic surface was modeled through a shear-free boundary condition on the air-water interface. Dependence of the effective slip length and resulting skin-friction drag on Reynolds number and surface geometry was examined. In laminar flows, the effective slip length depended on surface geometry only, independent of Reynolds number, consistent with an existing analysis. In turbulent flows, the effective slip length was a function of Reynolds number, indicating its dependence on flow conditions near the surface. The resulting drag reduction was much larger in turbulent flows than in laminar flows, and near-wall turbulence structures were significantly modified, suggesting that indirect effects resulting from modified turbulence structures played a more significant role in reducing drag in turbulent flows than the direct effect of the slip, which led to a modest drag reduction in laminar flows. It was found that the drag reduction in turbulent flows was well correlated with the effective slip length normalized by viscous wall units.
Improvement of the photocatalytic properties of TiO2 by (Fe+Mo) co-doping—A possible way to retard the recombination process
Authors: Guo Junbo , Gan Zhanghua , Lu Zhihong , Liu Jing , Xi Jingjing , Wan Yang , Le Lin , Liu Hailin , Shi Jing , Xiong Rui
Published: September 2013

Low visible light absorption and high charge carrier recombination rate are two main disadvantages of TiO2 as a photocatalyst which severely limit its practical applications. To overcome the problems, Fe mono-doped and (Fe+Mo) co-doped TiO2 were synthesized and studied. It was found that (Fe+Mo) co-doping can further increase the visible absorption and improve the photocatalytic property of TiO2 compared with Fe mono-doping; Fe mono-doping improves the photocatalytic property of TiO2 only at very low doping level (Fe concentration less than 1.0%), while by co-doping a small amount of Mo with Fe, the effective doping concentration of Fe can be pushed to a higher level and the photocatalytic property of TiO2 can be further improved. Photoluminescence spectra indicated that Mo dopant may play a role in retarding the recombination process when co-doped into TiO2 with Fe. The mechanism behind was discussed. It was suggested that doping a small amount of Mo into Fe-TiO2 might be an efficient way to further improve the photocatalytic property of Fe-TiO2 without losing its photocatalytic specificity.
Protein fibrillation due to elongation and fragmentation of initially appeared fibrils: A simple kinetic model
Authors: Kashchiev Dimo
Published: September 2013

The assembly of various proteins into fibrillar aggregates is an important phenomenon with wide implications ranging from human disease to nanoscience. Employing a new model, we analyze the kinetics of protein fibrillation in the case when the process occurs by elongation of initially appeared fibrils which multiply solely by fragmentation, because fibril nucleation is negligible. Owing to its simplicity, our model leads to mathematically friendly and physically clear formulas for the time dependence of the fibrillation degree and for a number of experimental observables such as the maximum fibrillation rate, the fibrillation lag time, and the half-fibrillation time. These formulas provide a mechanistic insight into the kinetics of fragmentation-affected fibrillation of proteins. We confront theory with experiment and find that our model allows a good global description of a large dataset [W.-F. Xue, S. W. Homans, and S. E. Radford, Proc. Natl. Acad. Sci. U.S.A. 105, 8926 (2008)]10.1073/pnas.0711664105 for the fibrillation kinetics of beta-2 microglobulin. Our analysis leads to new methods for experimental determination of the fibril solubility, elongation rate constant, and nucleation rate from data for the time course of protein fibrillation.
Stable negative ions and shape resonances in a series of organic molecules
Authors: Gallup G. A.
Published: September 2013

We report on the theoretical determination of low-lying shape resonances in a selected set of seven molecules. The finite element discrete model method is used and the absolute differences between calculated and experimental values, where known, are ⪅0.15 eV for the resonances lowest in energy. Difficulties expected with the higher calculated values are discussed. This article reports results for ortho-benzyne, benzene, naphthalene, anthracene, styrene, formamide, and acetamide. Comparisons are made with a few other calculations, again where available.
Photochromic cycle of 2′-hydroxyacetophenone azine studied by absorption and emission spectroscopy in different solvents
Authors: Filipczak Katarzyna , Karolczak Jerzy , Lipkowski Pawel , Filarowski Aleksander , Ziółek Marcin
Published: September 2013

This paper reports on the investigations of the synthesized di-(o-hydroxyaryl ketoimine) compound by the steady state absorption and emission techniques as well as picosecond time resolved emission and femtosecond transient absorption methods in different solvents. The results of the experimental observation have been supported by the theoretical DFT and TD-DFT calculations. The theoretical data have revealed the completed influence of the environmental polarity on particular conformers of studied compound. Dependencies between the activation rate constant and polarizability function as well as Kamlet-Abbond-Taft hydrogen-bonding parameter have been obtained in different solvent. The mechanism of photodynamic changes of di-(o-hydroxyaryl ketoimine) is presented.
The role of available sites in the activity of lattice gases with geometric constraints
Authors: Strobl Jonathan R. , Harrington David A.
Published: September 2013

The activity in lattice-gas systems with geometric constraints is shown to be the ratio of the number of particles to the number of available sites. The key role of sites available for occupation is emphasized. Available sites may be different for different species and are not necessarily just unoccupied sites. Location-specific or non-local constraints are allowed. An analytical expression for the number of available sites is given for the hard-hexagon model. The utility of an expression for available sites is illustrated for the non-trivial case of a mixed Langmuir/hard-hexagon adsorption system, where the influence of the Langmuir adsorbates on the hard-hexagon phase transition is investigated. The dependence on available sites indicates how to extend these results to the kinetic regime and simulations of kinetic voltammograms for the hard-hexagon model are given as an example.
Interplay between crystallization and glass transition in binary Lennard-Jones mixtures
Authors: Banerjee Atreyee , Chakrabarty Suman , Bhattacharyya Sarika Maitra
Published: September 2013

In this work we explore the interplay between crystallization and glass transition in different binary mixtures by changing their inter-species interaction length and also the composition. We find that only those systems which form bcc crystal in the equimolar mixture and whose global structure for larger xA (xA = 0.6, where xA is the mole fraction of the bigger particles) is a mixed fcc + bcc phase, do not crystallize at this higher composition. However, the systems whose equimolar structure is a variant of fcc (NaCl type crystal) and whose global structure at larger xA is a mixed NaCl + fcc phase, crystallize easily to this mixed structure. We find that the stability against crystallization of this “bcc zone” is due to the frustration between the locally preferred structure (LPS) and the mixed bcc + fcc crystal. Our study suggests that when the global structure is a mixed crystal where a single species contributes to both the crystal forms and where the two crystal forms have large difference in some order parameter related to that species then this induces frustration between the LPS and the global structure. This frustration makes the systems good glass former. When xA is further increased (0.70 ⩽ xA < 0.90) the systems show a tendency towards mixed fcc crystal formation. However, the “bcc zone” even for this higher composition is found to be sitting at the bottom of a V shaped phase diagram formed by two different variants of the fcc crystal structure, leading to its stability against crystallization.
Microwave surface waves supported by a tapered geometry metasurface
Authors: Brock Elizabeth M. G. , Hibbins Alastair P.
Published: September 2013

Spatial dependent reduction of a surface wave's group velocity is demonstrated in the microwave regime across a metasurface comprised linear array of rectangular cavities. We manipulate the surface wave dispersion through variation in cavity width to provide a spatially dependent modal index. The mode is slowed and trapped at different positions along the metasurface. This “slow-light” phenomenon is observed via local electric-field and phase measurements. The latter is shown to provide a more accurate identification of the trapping location. We discuss the reflectivity of the mode close to this point and explore the excitation of higher order surface modes.
Dynamics of a deformable active particle under shear flow
Authors: Tarama Mitsusuke , Menzel Andreas M. , ten Hagen Borge , Wittkowski Raphael , Ohta Takao , Löwen Hartmut
Published: September 2013

The motion of a deformable active particle in linear shear flow is explored theoretically. Based on symmetry considerations, we propose coupled nonlinear dynamical equations for the particle position, velocity, deformation, and rotation. In our model, both, passive rotations induced by the shear flow as well as active spinning motions, are taken into account. Our equations reduce to known models in the two limits of vanishing shear flow and vanishing particle deformability. For varied shear rate and particle propulsion speed, we solve the equations numerically in two spatial dimensions and obtain a manifold of different dynamical modes including active straight motion, periodic motions, motions on undulated cycloids, winding motions, as well as quasi-periodic and chaotic motions induced at high shear rates. The types of motion are distinguished by different characteristics in the real-space trajectories and in the dynamical behavior of the particle orientation and its deformation. Our predictions can be verified in experiments on self-propelled droplets exposed to a linear shear flow.