bluuebunny/crossref_metadata_2025 huggingface dataset:
Linking environmental heterogeneity and reproductive success at single-cell resolution
Authors: Remus-Emsermann Mitja N P , Leveau Johan H J
Published: October 2009

Individual-based microbial ecology (IBME) is a developing field of study in need of experimental tools to quantify the individual experience and performance of microorganisms in their natural habitats. We describe here the conception and application of a single-cell bioreporter approach with broad utility in IBME. It is based on the dilution of stable green fluorescent protein (GFP) in dividing bacteria. In the absence of de novo synthesis, GFP fluorescence of a daughter cell approximates half of that of its mother, from which follows that the fluorescence of a progeny cell is a quantitative measure for the reproductive success of its ancestor. To test this concept, we exposed GFP-filled bacteria to different degrees of environmental heterogeneity and assessed how this affected individual cells by the analysis of GFP content in their progeny. Reporter bacteria growing in rich medium in a shaking flask showed no variation in reproductive success, confirming that life in a broth is experienced much the same from one bacterium to the next. In contrast, when reporter bacteria were released onto plant leaf surfaces, representing a microscopically heterogeneous environment, clear intrapopulation differences in reproductive success were observed. Such variation suggests that individual cells in the founding population experienced different growth-permitting conditions, resulting in unequal contributions of individual bacteria to future offspring and population sizes. Being able to assess population changes bottom-up rather than top-down, the bioreporter offers opportunities to quantify single-cell competitive and facilitative interactions, assess the role of chance events in individual survivorship and reveal causes that underlie individual-based environmental heterogeneity.
Interactions between gut microbiota, host genetics and diet relevant to development of metabolic syndromes in mice
Authors: Zhang Chenhong , Zhang Menghui , Wang Shengyue , Han Ruijun , Cao Youfang , Hua Weiying , Mao Yuejian , Zhang Xiaojun , Pang Xiaoyan , Wei Chaochun , Zhao Guoping , Chen Yan , Zhao Liping
Published: October 2009

Both genetic variations and diet-disrupted gut microbiota can predispose animals to metabolic syndromes (MS). This study assessed the relative contributions of host genetics and diet in shaping the gut microbiota and modulating MS-relevant phenotypes in mice. Together with its wild-type (Wt) counterpart, the Apoa-I knockout mouse, which has impaired glucose tolerance (IGT) and increased body fat, was fed a high-fat diet (HFD) or normal chow (NC) diet for 25 weeks. DNA fingerprinting and bar-coded pyrosequencing of 16S rRNA genes were used to profile gut microbiota structures and to identify the key population changes relevant to MS development by Partial Least Square Discriminate Analysis. Diet changes explained 57% of the total structural variation in gut microbiota, whereas genetic mutation accounted for no more than 12%. All three groups with IGT had significantly different gut microbiota relative to healthy Wt/NC-fed animals. In all, 65 species-level phylotypes were identified as key members with differential responses to changes in diet, genotype and MS phenotype. Most notably, gut barrier-protecting Bifidobacterium spp. were nearly absent in all animals on HFD, regardless of genotype. Sulphate-reducing, endotoxin-producing bacteria of the family, Desulfovibrionaceae, were enhanced in all animals with IGT, most significantly in the Wt/HFD group, which had the highest calorie intake and the most serious MS phenotypes. Thus, diet has a dominating role in shaping gut microbiota and changes of some key populations may transform the gut microbiota of Wt animals into a pathogen-like entity relevant to development of MS, despite a complete host genome.
A Preliminary Candidate Genotype–Intermediate Phenotype Study of Satiation and Gastric Motor Function in Obesity
Authors: Papathanasopoulos Athanasios , Camilleri Michael , Carlson Paula J. , Vella Adrian , Nord Sara J. Linker , Burton Duane D. , Odunsi Suwebatu T. , Zinsmeister Alan R.
Published: October 2009

Stomach motility contributes significantly to fullness sensation while eating and cessation of food intake in humans. Genes controlling adrenergic and serotonergic mechanisms (ADRA2A, GNB3, and SLC6A4) affect gastric emptying (GE), volume (GV), and satiation. Fat mass and obesity‐associated gene (FTO) is linked with satiety. Our aim was to examine the association of these candidate genes with stomach functions that signal postprandial fullness: GE, GV, and maximum tolerated volume (MTV). These biomarkers constitute a component of the intermediate phenotype of satiation. A total of 62 overweight or obese participants underwent genotyping of the candidate genes, and validated measurements of GE of solids and liquids by scintigraphy, fasting and postprandial change in GV by SPECT (single photon emission computed tomography), and MTV by nutrient drink test. These markers of satiation were compared for 38 genetic variants in ADRA2A, ADR2C, ADRB3, uncoupling protein (UCP)‐2 and ‐3, GNB3, FTO, and SLC6A4 using a recessive model of inheritance. ADRA2A, ADR2C, UCP‐3, GNB3, and FTO loci were significantly associated with the intermediate phenotype markers of satiation: ADR2C (Ins‐Del322_325) with accelerated GE; GNB3 (rs1047776) with delayed GE; ADRA2A (rs491589 and rs553668) and GNB3 (rs2269355, rs10849527, and rs3759348) with decreased postprandial GV; ADRA2A (rs3750625) and GNB3 (rs4963517 and rs1129649) with increased postprandial GV; UCP‐3 (rs1685356) with increased MTV, and FTO (rs9939609) decreased MTV. Genetic susceptibility to postprandial satiation can be identified through intermediate phenotype markers. With independent validation, these markers may guide patient selection of weight‐loss therapies directed at gastric motor functions.
The Role of Adolescent Behaviors in the Female–Male Disparity in Obesity Incidence in US Black and White Young Adults
Authors: Robinson Whitney R. , Stevens June , Kaufman Jay S. , Gordon‐Larsen Penny
Published: October 2009

In the United States, black women are at much greater risk for obesity than black men. We explored whether adolescent behaviors (family dinners, hours of television, playing sports with mother, playing sports with father, bouts of physical activity) were associated with gender disparity in 6‐year obesity incidence in young adulthood. We used data from the nationally representative National Longitudinal Study of Adolescent Health to examine adolescent behaviors in nonimmigrant black (n = 1,503) and white (n = 4,452) youths in 1994–95 (aged 11–19 years) and 1995–96 (aged 12–20). We assessed gender disparity in obesity incidence (female incidence minus male incidence) during young adulthood (2001–02; aged 18–26). Standardized gender disparities were calculated using race‐ and gender‐stratified, covariate‐adjusted logistic regression models in which males and females were set to the same distributions of adolescent behaviors. In adolescence, black females reported less leisure‐time physical activity and lower likelihood of playing sports with either parent compared with black males. Setting adolescent behaviors equal for black males and females did not reduce the estimated gender disparity in obesity incidence (nonstandardized: 9.8 percentage points (95% confidence interval (CI): 4.5, 15.1); fully standardized: 10.2 percentage points (5.2, 15.2)). There was little gender disparity in whites before or after adjustments. To our knowledge, this is the first study to examine to what extent behavioral differences during adolescence might account for gender disparity in obesity incidence in black young adults. Male‐female differences in these adolescent behaviors did not appear to underlie the gender gap in young adult obesity.
Postabsorptive VLDL‐TG Fatty Acid Storage in Adipose Tissue in Lean and Obese Women
Authors: Nellemann Birgitte , Gormsen Lars C. , Christiansen Jens S. , Jensen Michael D. , Nielsen Søren
Published: October 2009

Adipose tissue lipoprotein lipase (LPL) is a necessary enzyme for storage of very‐low‐density lipoprotein–triglyceride (VLDL‐TG), but whether it is a rate‐determining step is unknown. To test this hypothesis we included 10 upper‐body obese (UBO), 11 lower‐body obese (LBO), and 8 lean women. We infused ex vivo‐labeled VLDL‐14C‐TG and then performed adipose tissue biopsies to understand the relationship between VLDL‐TG storage and LPL activity in femoral and upper‐body subcutaneous fat. Both fractional tracer storage and rate of storage of the VLDL‐TG tracer were evaluated. VLDL‐TG storage was also examined as a function of regional adipose tissue blood flow (ATBF), insulin, VLDL‐TG turnover, regional fat mass, fat‐free mass (FFM), and fat cell size. LPL activity per adipocyte was significantly greater in obese than lean women but not significantly different per gram lipid. Both VLDL‐TG fractional tracer storage per kg lipid and VLDL‐TG storage rate per kg lipid were similar in abdominal and femoral fat in all three groups and were not significantly different between groups. Multiple regression analysis identified FFM and femoral fat mass as significant independent predictors of VLDL‐TG fractional tracer storage and insulin as a significant predictor of VLDL‐TG fatty acid storage rate. LPL activity, ATBF, and VLDL‐TG turnover did not predict VLDL‐TG storage. We conclude that lower FFM and greater plasma insulin are associated with greater VLDL‐TG deposition in abdominal subcutaneous and femoral fat. Greater femoral fat mass signals greater femoral VLDL‐TG storage. We suggest that the differences in VLDL‐TG storage in abdominal and femoral fat that occur with progressive obesity are regulated through mechanisms other than LPL activity.
Adaptations in Mitochondrial Function Parallel, but Fail to Rescue, the Transition to Severe Hyperglycemia and Hyperinsulinemia: A Study in Zucker Diabetic Fatty Rats
Authors: Lenaers Ellen , De Feyter Henk M. , Hoeks Joris , Schrauwen Patrick , Schaart Gert , Nabben Miranda , Nicolay Klaas , Prompers Jeanine J. , Hesselink Matthijs K.C.
Published: October 2009

Cross‐sectional human studies have associated mitochondrial dysfunction to type 2 diabetes. We chose Zucker diabetic fatty (ZDF) rats as a model of progressive insulin resistance to examine whether intrinsic mitochondrial defects are required for development of type 2 diabetes. Muscle mitochondrial function was examined in 6‐, 12‐, and 19‐week‐old ZDF (fa/fa) and fa/+ control rats (n = 8–10 per group) using respirometry with pyruvate, glutamate, and palmitoyl‐CoA as substrates. Six‐week‐old normoglycemic–hyperinsulinemic fa/fa rats had reduced mitochondrial fat oxidative capacity. Adenosine diphosphate (ADP)‐driven state 3 and carbonyl cyanide p‐trifluoromethoxyphenylhydrazone (FCCP)‐stimulated state uncoupled (state u) respiration on palmitoyl‐CoA were lower compared to controls (62.3 ± 9.5 vs. 119.1 ± 13.8 and 87.8 ± 13.3 vs. 141.9 ± 14.3 nmol O2/mg/min.). Pyruvate oxidation in 6‐week‐old fa/fa rats was similar to controls. Remarkably, reduced fat oxidative capacity in 6‐week‐old fa/fa rats was compensated for by an adaptive increase in intrinsic mitochondrial function at week 12, which could not be maintained toward week 19 (140.9 ± 11.2 and 57.7 ± 9.8 nmol O2/mg/min, weeks 12 and 19, respectively), whereas hyperglycemia had developed (13.5 ± 0.6 and 16.1 ± 0.3 mmol/l, weeks 12 and 19, respectively). This mitochondrial adaptation failed to rescue the progressive development of insulin resistance in fa/fa rats. The transition of prediabetes state toward advanced hyperglycemia and hyperinsulinemia was accompanied by a blunted increase in uncoupling protein‐3 (UCP3). Thus, in ZDF rats insulin resistance develops progressively in the absence of mitochondrial dysfunction. In fact, improved mitochondrial capacity in hyperinsulinemic hyperglycemic rats does not rescue the progression toward advanced stages of insulin resistance.
IPO8 and FBXL10: New Reference Genes for Gene Expression Studies in Human Adipose Tissue
Authors: del Pozo Carmen Hurtado , Calvo Rosa M. , Vesperinas‐García Gregorio , Gómez‐Ambrosi Javier , Frühbeck Gema , Corripio‐Sánchez Ramón , Rubio Miguel A. , Obregon Maria‐Jesus
Published: October 2009

Housekeeping genes frequently used in gene expression studies are highly regulated in human adipose tissue. To ensure a correct interpretation of results, it is critical to select appropriate reference genes. Subcutaneous (SC) and omental (OM) adipose tissue expression was analyzed from lean and obese subjects using whole genome complementary DNA (cDNA) microarrays to identify stably expressed genes and commercial TaqMan low density arrays (LDAs), with 16 common control genes. The best candidate gene from microarrays analysis was F‐box and leucine‐rich repeat protein‐10 (FBXL10) (fold‐change 10−3 P < 0.01), an ubiquitous nucleolar protein evolutionarily conserved. Hypoxanthine phosphoribosyltransferase 1 (HPRT1) and importin 8 (IPO8), were the best reference genes among the 16 genes in the LDAs with coefficient of variation (CV) of 4.51 and 4.55%, respectively. However, when the LDAs data were further analyzed by the geNorm and NormFinder softwares, IPO8, a nuclear protein mediating import of proteins, was the first and the third better reference gene, respectively. IPO8 and FBXL10 were further validated by real‐time PCR in additional OM and SC fat samples and primary cultured preadipocytes. According to their CV, IPO8 resulted more suitable than FBXL10 in both adipose tissue depots and SC preadipocytes, whereas FBXL10 performed better than IPO8 in OM cultured preadipocytes. Both genes expression levels did not change throughout adipogenesis. Thus, we provide clear evidence that IPO8 and FBXL10 are good candidates to use as reference genes in gene expression studies in human OM and SC adipose tissues as well as differentiated primary preadipocytes.
Obesity‐related Polymorphisms and Their Associations With the Ability to Regulate Fat Oxidation in Obese Europeans: The NUGENOB Study
Authors: Corpeleijn Eva , Petersen Liselotte , Holst Claus , Saris Wim H. , Astrup Arne , Langin Dominique , MacDonald Ian , Martinez J. Alfredo , Oppert Jean‐Michel , Polak Jan , Pedersen Oluf , Froguel Philippe , Arner Peter , Sørensen Thorkild I.A. , Blaak Ellen E.
Published: October 2009

Both obesity and insulin resistance have been related to low fat oxidation rates, which may be genetically determined. The association between variation in fat oxidation rates among obese subjects and genotype was studied for 42 common single‐nucleotide polymorphisms (SNPs) in 26 candidate genes for fat oxidation, insulin resistance, and obesity, including FTO. Energy expenditure (EE) and fat oxidation were measured with indirect calorimetry during fasting and 3 h after a high fat load containing 95 energy% of fat (60% saturated fat, energy content 50% of estimated resting EE) in 722 obese subjects (541 women, 181 men) from 8 European centers. After adjustment for center and gender, −178 A>C CD36 (rs2232169) (P = 0.02), −22510 C>G SLC6A14 (women, rs2011162) (P = 0.03), and T690S C>G PCSK1 (rs6235) (P = 0.02) were related to a reduced fat oxidation, whereas 17 C>G SREBF1 (17 C>G) (P = 0.01) was related to increased fat oxidation in the fasting state. The ability to increase fat oxidation after a high fat load was increased in subjects with −174 G>C IL6 (rs1800795) (P = 0.01). Effect sizes range from 1.1 to 3.1% differences in fat oxidation (expressed as % of EE). FTO rs9939609 was not related to fat oxidation. At the same time, the results are not adjusted for multiple testing, thus none of the associations can be considered statistically significant. The results should therefore only be considered as leads to new hypotheses about effects of specific genetic polymorphisms on fasting and postprandial fat oxidation.
Common PCSK1 Haplotypes Are Associated With Obesity in the Chinese Population
Authors: Chang Yi‐Cheng , Chiu Yen‐Feng , Shih Kuang‐Chung , Lin Ming‐Wei , Sheu Wayne Huey‐Herng , Donlon Timothy , Curb Jess David , Jou Yuh‐Shan , Chang Tien‐Jyun , Li Hung‐Yuan , Chuang Lee‐Ming
Published: October 2009

Prohormone convertase subtilisin/kexin type 1 (PCSK1) genetic polymorphisms have recently been associated with obesity in European populations. This study aimed to examine whether common PCSK1 genetic variation is associated with obesity and related metabolic phenotypes in the Chinese population. We genotyped nine common tag single‐nucleotide polymorphisms (tagSNP) of the PCSK1 gene in 1,094 subjects of Chinese origin from the Stanford Asia‐Pacific Program for Hypertension and Insulin Resistance (SAPPHIRe) family study. One SNP in the PCSK1 gene (rs155971) were nominally associated with risk of obesity in the SAPPHIRe cohort (P = 0.01). A common protective haplotype was associated with reduced risk of obesity (23.79% vs. 32.89%, P = 0.01) and smaller waist circumference (81.71 ± 10.22 vs. 84.75 ± 10.48 cm, P = 0.02). Another common haplotype was significantly associated with increased risk of obesity (37.07% vs. 23.84%, P = 0.005). The global P value for haplotype association with obesity was 0.02. We also identified a suggestive association of another PCSK1 SNP (rs3811951) with fasting glucose, fasting insulin, homeostasis model assessment of insulin resistance (HOMAIR), triglycerides, and high‐density lipoprotein cholesterol (P = 0.05, 0.003, 0.001, 0.04, and 0.04, respectively). These data indicate common PCSK1 genetic variants are associated with obesity in the Chinese population.
Effect of Genetic Variation in the Human Fatty Acid Synthase Gene (FASN) on Obesity and Fat Depot‐Specific mRNA Expression
Authors: Schleinitz Dorit , Klöting Nora , Körner Antje , Berndt Janin , Reichenbächer Marlene , Tönjes Anke , Ruschke Karen , Böttcher Yvonne , Dietrich Kerstin , Enigk Beate , Filz Matthias , Schön Michael R. , Jenkner Jost , Kiess Wieland , Stumvoll Michael , Blüher Matthias , Kovacs Peter
Published: October 2009

Inhibition of fatty acid synthase (FASN) induces a rapid decline in fat stores in mice, suggesting a role for this enzyme in energy homeostasis. To investigate the potential role of FASN in the pathophysiology of human obesity, the FASN gene was sequenced in 48 German whites. Thirty‐five single‐nucleotide polymorphisms (SNPs) were identified. Eight SNPs representative for their linkage disequilibrium groups and the Val1483Ile (rs2228305) substitution were genotyped for subsequent association analyses in 1,311 adults from Germany. Further, the tagging SNPs were genotyped also in German childhood cohorts (738 schoolchildren, 205 obese children). Effects of genetic variation on FASN mRNA expression in visceral and subcutaneous adipose tissue from a subgroup of 172 subjects were analyzed. Several polymorphisms in the FASN (rs62078748, rs2229422, rs2229425, and rs17848939) were nominally associated with obesity in case–control studies including 446 obese subjects (BMI ≥30 kg/m2) and 389 lean controls (BMI ≤25 kg/m2) (adjusted P < 0.05). The strongest significant effect was found for rs2229422 (P = 1.3 × 10−5 adjusted for age, sex, type 2 diabetes status), which was supported by associations with BMI, waist‐to‐hip ratio (WHR), fasting plasma insulin and glucose infusion rate (adjusted P < 0.05). Subjects with the Val1483Ile substitution appeared to be protected against obesity. In addition, rs17848939 was nominally significantly associated with the ratio of visceral/subcutaneous FASN mRNA expression (adjusted P = 0.04). No effect of genetic variation in FASN on obesity was found in children. In conclusion, our data indicate a role of FASN genetic variation in susceptibility to obesity in adults.
Retrospective Reports of Child Feeding Practices, Current Eating Behaviors, and BMI in College Students
Authors: Galloway Amy T. , Farrow Claire V. , Martz Denise M.
Published: October 2009

Research concerning child feeding practices has focused on children and adolescents, and little is known about how feeding practices used in childhood relate to eating behaviors and weight status in early adulthood. We assessed college students' and their parents' retrospective reports of child feeding practices used when the students were in middle childhood. We also assessed the college students' current reports of their eating behaviors using the Dutch Eating Behavior Questionnaire (DEBQ) and the Intuitive Eating Scale (IES), and measured their current BMI. Results showed that college students' and their parents' reports about previous parental use of child feeding practices were not correlated. Parent reports of their own use of child feeding practices were more related to students' eating behaviors and BMI than were students' recollections about feeding practices used by their parents. An analysis of gender effects showed that there were positive correlations between parental child feeding practices, BMI, and emotional eating for female students. These relationships did not exist for male students. The results suggest that child feeding practices recollected by parents are linked to the development of emotional eating and weight status of women in early adulthood.
Evidence of Shared Genetic Effects Between Pre‐ and Postobesity Epidemic BMI Levels
Authors: Martin Lisa J. , Woo Jessica G. , Morrison John A.
Published: October 2009

United States has experienced a widespread obesity epidemic. However, it is unclear whether the obesogenic environment has uncovered genes previously unimportant in adiposity or whether genes influencing obesity are the same before and after the obesity epidemic. The objective of this study was to test whether BMI pre‐ and postobesity epidemic would be controlled by shared genetic effects. A 25–30‐year follow‐up of parents and children who participated in the National Institutes of Health–National Heart, Lung, and Blood Institute Lipid Research Clinics (LRC) Princeton School Study, 1973–1976, were followed up in 1999–2004 in the Princeton Follow‐up Study (PFS). Heritability of BMI and genetic correlations between pre‐epidemic BMI and BMI z‐scores in adolescents and postobesity epidemic BMI were calculated. Even though they had similar ages, offspring had higher BMI in PFS than their parents in LRC (28.5 ± 6.6 vs. 26.1 ± 4.4, P < 0.0001). BMI measurements in offspring were strongly heritable (BMILRC: h2 = 0.78 ± 0.17; BMI z‐scoreLRC: h2 = 0.61 ± 0.16; BMIPFS: h2 = 0.64 ± 0.16, all P ≤ 0.0001). Further, the change of BMI exhibited a high heritability (h2 = 0.51 ± 0.18, P = 0.003). Bivariate analysis of BMI in LRC and PFS showed significant genetic correlation (0.70 ± 0.16, P = 0.005), whereas the environmental correlation was not significant (0.36 ± 0.17). Although the obesogenic environment may have changed between the 1970s and 2000s, many of the same genes are likely to be involved in establishing genetic susceptibility to obesity. Furthermore, shared genetic effects survive the period of the transition from adolescence to adulthood.
Physical Activity and Reduced Intra‐abdominal Fat in Midlife African‐American and White Women
Authors: Dugan Sheila A. , Everson‐Rose Susan A. , Karavolos Kelly , Avery Elizabeth F. , Wesley Deidre E. , Powell Lynda H.
Published: October 2009

The purpose of our study was to determine whether self‐reported physical activity (PA), including recreational, household, and exercise activities, is associated with intra‐abdominal fat (IAF) in community‐dwelling white and black midlife women. We performed a cross‐sectional study of 369 women from the Chicago site of the Study of Women's Health Across the Nation (SWAN) ancillary study, the SWAN Fat Patterning Study. PA level was the independent variable, and IAF, assessed by computerized tomography (CT) scan, was the dependent variable. Measures were obtained at SWAN Fat Patterning Baseline visit between August 2002 and December 2005. Linear regression models explored the association between PA and IAF. The first model included IAF as the outcome and total score PA as the main predictor, adjusting for total percent fat mass, age, and ethnicity. The second model included education, parity, sex hormone–binding globulin (SHBG) level, and depressive symptoms, measured by Center for Epidemiological Studies‐Depression (CES‐D) scale. Each 1‐point higher total PA score was associated with a 4.0 cm2 lower amount of IAF (P = 0.004), independent of total percent fat mass, age, ethnicity, SHBG level, educational level, CES‐D, and parity. Associations did not differ between white and black women. This study demonstrates a significant negative association between PA and IAF independent of multiple covariates in midlife women. Our findings suggest that motivating white and black women to increase PA during midlife may lessen IAF, which may have a positive impact on subsequent development of diabetes and cardiovascular disease.
Mg doping of thermochromic VO2 films enhances the optical transmittance and decreases the metal-insulator transition temperature
Authors: Mlyuka N. R. , Niklasson G. A. , Granqvist C. G.
Published: October 2009

Thermochromic films of MgxV1−xO2 were made by reactive dc magnetron sputtering onto heated glass. The metal-insulator transition temperature decreased by ∼3 K/at. %Mg, while the optical transmittance increased concomitantly. Specifically, the transmittance of visible light and of solar radiation was enhanced by ∼10% when the Mg content was ∼7 at. %. Our results point at the usefulness of these films for energy efficient fenestration.
In situ probing of electromechanical properties of an individual ZnO nanobelt
Authors: Asthana Anjana , Momeni Kasra , Prasad Abhishek , Yap Yoke Khin , Yassar Reza Shahbazian
Published: October 2009

We report here, an investigation on electrical and structural-microstructural properties of an individual ZnO nanobelt via in situ transmission electron microscopy using an atomic force microscopy (AFM) system. The I-V characteristics of the ZnO nanobelt, just in contact with the AFM tip indicates the insulating behavior, however, it behaves like a semiconductor under applied stress. Analysis of the high resolution lattice images and the corresponding electron diffraction patterns shows that each ZnO nanobelt is a single crystalline, having wurtzite hexagonal structure (a=0.324 nm, c=0.520 66 nm) with a general growth direction of [101¯0].
Size-dependent polymorphism in HfO2 nanotubes and nanoscale thin films
Authors: Shandalov Michael , McIntyre Paul C.
Published: October 2009

Many metal oxides exhibit size-dependent phase transitions among multiple polymorphs. In this work, the microstructure and crystallinity of ultrathin HfO2 films and utrathin-wall nanotubes were investigated by high-resolution electron microscopy and electron diffraction after high-temperature annealing. Nanotubes were formed by atomic layer deposition of HfO2 on epitaxial Ge ⟨111⟩ nanowire arrays on Si (111) substrates followed by selective etching of the Ge wires. A size-dependent phase transition sequence from amorphous (a-HfO2) to tetragonal (t-HfO2) and from tetragonal to monoclinic (m-HfO2) phase was observed with increasing film and nanotube wall thickness. These results are analyzed in light of recent predictions of surface energy-driven phase transitions in nanoscale fluorite-structure oxides.
Simulation of the effect of viscosity on jet penetration into a single cavitating bubble
Authors: Minsier V. , De Wilde J. , Proost J.
Published: October 2009

The dynamics of a cavitating bubble in a viscous liquid near a solid surface is numerically calculated. In the model, the two dimensional axisymmetric Navier–Stokes equations are solved for both the compressible gas phase and the incompressible liquid phase on a fixed Cartesian grid. The bubble-liquid interface is tracked by the Volume Of Fluid method. Our numerical model, which explicitly takes into account the liquid viscosity, is first validated against available experimental data from the literature on single laser-induced bubble collapse near a solid surface. Next, the time evolution of the jet front velocity of penetrating jets has been calculated for different values of the viscosity as a function of the so-called stand-off parameter γ, the latter being characteristic of the distance separating the initial bubble center from the solid surface. Finally, from these data, the maximum jet front velocity has been calculated. Good agreement was obtained with experimental data. Our numerical calculations further predict a maximum in the evolution of the maximum jet front velocity as a function of γ, the magnitude and position of which decrease with increasing liquid viscosity. Before the maximum, increasing the viscosity gives rise to a strongly diverging maximum jet front velocity with decreasing γ.
Rheology and phase behavior of dense casein micelle dispersions
Authors: Bouchoux A. , Debbou B. , Gésan-Guiziou G. , Famelart M.-H. , Doublier J.-L. , Cabane B.
Published: October 2009

Casein micelle dispersions have been concentrated through osmotic stress and examined through rheological experiments. In conditions where the casein micelles are separated from each other, i.e., below random-close packing, the dispersions have exactly the flow and dynamic properties of the polydisperse hard-sphere fluid, demonstrating that the micelles interact only through excluded volume effects in this regime. These interactions cause the viscosity and the elastic modulus to increase by three orders of magnitude approaching the concentration of random-close packing estimated at Cmax≈178 g/l. Above Cmax, the dispersions progressively turn into “gels” (i.e., soft solids) as C increases, with elastic moduli G′ that are nearly frequency independent. In this second regime, the micelles deform and/or deswell as C increases, and the resistance to deformation results from the formation of bonds between micelles combined with the intrinsic mechanical resistance of the micelles. The variation in G′ with C is then very similar to that observed with concentrated emulsions where the resistance to deformation originates from a set of membranes that separate the droplets. As in the case of emulsions, the G′ values at high frequency are also nearly identical to the osmotic pressures required to compress the casein dispersions. The rheology of sodium caseinate dispersions in which the caseins are not structured into micelles is also reported. Such dispersions have the behavior of associative polymer solutions at all the concentrations investigated, further confirming the importance of structure in determining the rheological properties of casein micelle systems.
Structural and magnetic properties of the molecular beam epitaxy grown MnSb layers on GaAs substrates
Authors: Lawniczak-Jablonska Krystyna , Wolska Anna , Bak-Misiuk Jadwiga , Dynowska Elzbieta , Romanowski Przemyslaw , Domagala Jaroslaw Z. , Minikayev Roman , Wasik Dariusz , Klepka Marcin T. , Sadowski Janusz , Barcz Adam , Dluzewski Piotr , Kret Sławomir , Twardowski Andrzej , Kamińska Maria , Persson Andreas , Arvanitis Dimitri , Holub-Krappe Elisabeth , Kwiatkowski Adam
Published: October 2009

The structural and magnetic properties of MnSb layers grown on two differently oriented GaAs substrates are reported. The MnSb compounds grow nonhomogenously both on GaAs(111)B and on GaAs(100) substrates. In x-ray diffraction studies the formation of two epitaxial domains is observed depending on the crystallographic orientation of the substrate. The observed diffusion of Ga atoms from the substrate to the layers results in the formation of an additional Mn-rich cubic phase of GaMnSb. In the case of the (100) oriented substrate, the diffusion of Mn into the substrate was additionally found. Traces of other phases were also noticed. The complex morphology of the layers is found to influence their magnetic properties. Magnetic force microscopy images revealed an inhomogenous distribution of the magnetic force gradient on the surface and the formation of magnetic domains in the samples. X-ray absorption studies of the chemical bonding and local atomic structure around Mn atoms confirmed high structural and chemical disorder in the samples. The chemical bonding of the dominating fraction of Mn atoms is found, however, similar to that in the reference MnSb powder. The x-ray magnetic circular dichroism measurements reveal an enhanced orbital moment and a reduced spin moment, which is most likely caused by the presence of different phases and a Mn-rich surface in the investigated samples.
Accurate noise projection for reduced stochastic epidemic models
Authors: Forgoston Eric , Billings Lora , Schwartz Ira B.
Published: October 2009

We consider a stochastic susceptible-exposed-infected-recovered (SEIR) epidemiological model. Through the use of a normal form coordinate transform, we are able to analytically derive the stochastic center manifold along with the associated, reduced set of stochastic evolution equations. The transformation correctly projects both the dynamics and the noise onto the center manifold. Therefore, the solution of this reduced stochastic dynamical system yields excellent agreement, both in amplitude and phase, with the solution of the original stochastic system for a temporal scale that is orders of magnitude longer than the typical relaxation time. This new method allows for improved time series prediction of the number of infectious cases when modeling the spread of disease in a population. Numerical solutions of the fluctuations of the SEIR model are considered in the infinite population limit using a Langevin equation approach, as well as in a finite population simulated as a Markov process.
Tuning of photonic crystal cavities by controlled removal of locally infiltrated water
Authors: Intonti Francesca , Vignolini Silvia , Riboli Francesco , Zani Margherita , Wiersma Diederik S. , Balet Laurent , Li Lianhe H. , Francardi Marco , Gerardino Annamaria , Fiore Andrea , Gurioli Massimo
Published: October 2009

We present a spectral tuning mechanism of photonic crystal microcavities based on microfluidics. The microinfiltration with water of one or few cavity holes and its subsequent controlled evaporation allow us to tune the cavity resonances in a spectral range larger than 20 nm, with subnanometer accuracy, and we also observe that the addition of water in the microcavity region improves its quality factor Q.
Time-resolved imaging of the laser forward transfer of liquids
Authors: Duocastella M. , Fernández-Pradas J. M. , Morenza J. L. , Serra P.
Published: October 2009

Time-resolved imaging is carried out to study the dynamics of the laser-induced forward transfer of an aqueous solution at different laser fluences. The transfer mechanisms are elucidated, and directly correlated with the material deposited at the analyzed irradiation conditions. It is found that there exists a fluence range in which regular and well-defined droplets are deposited. In this case, laser pulse energy absorption results in the formation of a plasma, which expansion originates a cavitation bubble in the liquid. After the further expansion and collapse of the bubble, a long and uniform jet is developed, which advances at a constant velocity until it reaches the receptor substrate. On the other hand, for lower fluences no material is deposited. In this case, although a jet can be also generated, it recoils before reaching the substrate. For higher fluences, splashing is observed on the receptor substrate due to the bursting of the cavitation bubble. Finally, a discussion of the possible mechanisms which lead to such singular dynamics is also provided.
Apparatus and method for investigation of energy consumption of microwave assisted drying systems
Authors: Göllei Attila , Vass András , Magyar Attila , Pallai Elisabeth
Published: October 2009

Convective, hot air drying by itself is relatively efficient for removing water from the surface environment of agricultural seed products. However, moving internal moisture to the surface needs rather a long time, as a rule. The major research aim of the authors was to decrease the processing time and processing costs, to improve the quality of the dried product, and to increase drying efficiency. For this reason their research activities focused on the development of a special drying apparatus and a method suitable for measuring of energy conditions in a hybrid (microwave and convective) dryer. Experimental investigations were made with moistened wheat as model material. Experiments were carried out in microwave, convective and hybrid drying systems. The microwave drying alone was more efficient than the convective method. The lowest energy consumption and shortest drying time were obtained by the use of a hybrid method in which the waste energy of magnetron was utilized and the temperature was controlled. In this way, it was possible to keep the temperature of the dried product at a constant and safe value and to considerably decrease the energy consumption.
Compact shell solitons in K field theories
Authors: Adam C. , Klimas P. , Sánchez-Guillén J. , Wereszczyński A.
Published: October 2009

Some models providing shell-shaped static solutions with compact support (compactons) in 3+1 and 4+1 dimensions are introduced, and the corresponding exact solutions are calculated analytically. These solutions turn out to be topological solitons and may be classified as maps S3→S3 and suspended Hopf maps, respectively. The Lagrangian of these models is given by a scalar field with a nonstandard kinetic term (K field) coupled to a pure Skyrme term restricted to S2, rised to the appropriate power to avoid the Derrick scaling argument. Further, the existence of infinitely many exact shell solitons is explained using the generalized integrability approach. Finally, similar models allowing for nontopological compactons of the ball type in 3+1 dimensions are briefly discussed.
Dielectric elastomer membranes undergoing inhomogeneous deformation
Authors: He Tianhu , Zhao Xuanhe , Suo Zhigang
Published: October 2009

Dielectric elastomers are capable of large deformation subject to an electric voltage and are promising for use as actuators, sensors, and generators. Because of large deformation, nonlinear equations of states, and diverse modes of failure, modeling the process of electromechanical transduction has been challenging. This paper studies a membrane of a dielectric elastomer deformed into an out-of-plane axisymmetric shape, a configuration used in a family of commercial devices known as the universal muscle actuators. The kinematics of deformation and charging, together with thermodynamics, leads to equations that govern the state of equilibrium. Numerical results indicate that the field in the membrane can be very inhomogeneous, and that the membrane is susceptible to several modes of failure, including electrical breakdown, loss of tension, and rupture by stretch. Care is needed in the design to balance the requirements of averting various modes of failure while using the material efficiently.
An oxide thermal rectifier
Authors: Kobayashi W. , Teraoka Y. , Terasaki I.
Published: October 2009

We have experimentally demonstrated thermal rectification as bulk effect. According to a theoretical design of a thermal rectifier, we have prepared an oxide thermal rectifier made of two cobalt oxides with different thermal conductivities, and have made an experimental system to detect the thermal rectification. The rectifying coefficient of the device is found to be 1.43, which is in good agreement with the numerical calculation.
A scattering model for surface-textured thin films
Authors: Jäger Klaus , Zeman Miro
Published: October 2009

We present a mathematical model that relates the surface morphology of randomly surface-textured thin films with the intensity distribution of scattered light. The model is based on the first order Born approximation [see e.g., M. Born and E. Wolf, Principles of Optics, 7th ed. (Cambridge University Press, Cambridge, England, 1999)] and on Fraunhofer scattering. Scattering data of four transparent conductive oxide films with different surface textures were used to validate the model and good agreement between the experimental and calculated intensity distribution was obtained.
Pulsed-laser printing of organic thin-film transistors
Authors: Rapp Ludovic , Diallo Abdou Karim , Alloncle Anne Patricia , Videlot-Ackermann Christine , Fages Frédéric , Delaporte Philippe
Published: October 2009

Organic thin-film transistors have been fabricated using laser-induced forward transfer as spatially resolved laser-printing method. Using this technique, source and drain electrodes were deposited from silver nanoparticle ink and the copper phthalocyanine (CuPc) was used to form the active layer. Both kinds of materials were transferred from a donor substrate onto a receiver substrate upon irradiation with laser pulses in the picosecond regime. The latter substrate formed the gate and the dielectric of the transistor. Electrical characterizations showed that the transistors are fully operative, showing well-defined linear and saturation regimes in the I-V curves.
Microwave absorption in YBa2Cu3O7−δ-manganite superlattices
Authors: Gierłowski P. , Werner-Malento K. , Przysłupski P. , van der Beek C. J.
Published: October 2009

We report on results of direct microwave absorption measurements of Re1−xBxMnO3/YBa2Cu3O7−δ half metal/d-wave superconductor superlattices (where Re–La and Pr) and (B–Sr and Ca) for microwave frequencies in the range from 9 to 20 GHz. The measurements of the entire heterostructure were performed mostly at temperatures below the superconducting transition. The obtained results strongly depend on the microwave frequency and can be qualitatively described within the theoretical model of high-frequency properties of Josephson junctions with a ferromagnetic barrier proposed by Takahashi et al. [Phys. Rev. Lett. 99, 057003 (2007)].
Direct contact mechanism of Ohmic metallization to AlGaN/GaN heterostructures via Ohmic area recess etching
Authors: Wang Liang , Kim Dong-Hyun , Adesida Ilesanmi
Published: October 2009

The effects of recess etching of the Ohmic contact area on the performance of Ti/Al/Mo/Au metallization and its interfacial reactions with AlGaN/AlN/GaN epilayers were investigated. The best Ohmic contact performances of 0.31, 0.41, and 0.26 Ω mm for three epilayers from two different sources were obtained only when the two-dimensional electron gas (2DEG) channels were completely removed under the Ohmic contact metallization. This is due to the direct sideway contact made by the electrode to the 2DEG around the edges of the active-layer mesas or pads; this is believed to be a more efficient carrier transport mechanism than tunneling through the AlGaN barrier.
Magnetothermal instability of plasmas in a horizontal magnetic field
Authors: Ren Haijun , Wu Zhengwei , Cao Jintao , Chu Paul K.
Published: October 2009

The linear buoyancy instability in a magnetized plasma, generally referred to as magnetothermal instability (MTI), is investigated by considering anisotropic heat conduction. The external magnetic field is assumed to be horizontal and background heat flux is not taken into account. The general dispersion relationship of the convective instability is derived. The growth rate of the MTI in fixed boundary condition is presented and discussed. The effect of density spacial gradient on the MTI is investigated. The magnetic field is shown to suppress the MTI and even quench the instability when the magnetic field is strong enough. Under the standard Wentzel–Kramaers–Brillouin approximation, our results could be simplified to a brief form reported by one previous paper [E. Quataert, Astrophys. J. 673, 758 (2008)].
Mg doping and its effect on the semipolar GaN(112¯2) growth kinetics
Authors: Lahourcade L. , Pernot J. , Wirthmüller A. , Chauvat M. P. , Ruterana P. , Laufer A. , Eickhoff M. , Monroy E.
Published: October 2009

We report the effect of Mg doping on the growth kinetics of semipolar GaN(112¯2) synthesized by plasma-assisted molecular-beam epitaxy. Mg tends to segregate on the surface, inhibiting the formation of the self-regulated Ga film which is used as a surfactant for the growth of undoped and Si-doped GaN(112¯2). We observe an enhancement of Mg incorporation in GaN(112¯2) compared to GaN(0001). Typical structural defects or polarity inversion domains found in Mg-doped GaN(0001) were not observed for the semipolar films investigated in the present study.
Local and global properties of mixtures in one-dimensional systems. II. Exact results for the Kirkwood–Buff integrals
Authors: Ben-Naim Arieh , Santos Andrés
Published: October 2009

The Kirkwood–Buff integrals for two-component mixtures in one-dimensional systems are calculated directly. The results are applied to square-well particles and found to agree with those obtained by the inversion of the Kirkwood–Buff theory of solutions.
Response modes of a flexible filament in the wake of a cylinder in a flowing soap film
Authors: Jia Lai-Bing , Yin Xie-Zhen
Published: October 2009

Flow induced vibrations are observed in many engineering applications. A flexible body located in the wake of an obstacle is usually forced to vibrate by the periodic vortices shedding from the obstacle. Here we focus on the response of the flexible body in the wake. Soap film tunnels are used to provide two-dimensional flow. Cylinders and flexible filaments are employed as obstacles and flexible bodies, respectively. The filaments exhibit lock-in behavior to the wake. Three response modes are found by changing the distance between the filaments and cylinders. The observations are illuminated in terms of waving plate theory.
Impact of Sn/Zn ratio on the gate bias and temperature-induced instability of Zn-In-Sn-O thin film transistors
Authors: Ryu Min Ki , Yang Shinhyuk , Park Sang-Hee Ko , Hwang Chi-Sun , Jeong Jae Kyeong
Published: October 2009

We investigated the effect of the Sn/Zn ratio in the amorphous Zn-In-Sn-O (ZITO) system on the gate voltage stress-induced stability of the resulting thin film transistors (TFTs). The device stability of the TFTs with a composition channel of Zn:In:Sn=0.35:0.20:0.45 (device C) was dramatically improved, while those of the devices with Zn:In:Sn=0.45:0.20:0.35 and 0.40:0.20:0.40 suffered from deep level trap creation in the channel and charge trapping, respectively. The stability enhancement of device C can be attributed to its having the lowest total trap density, which was corroborated by the superior temperature stability of the subthreshold current region in the temperature range from 298 to 398 K. Therefore, the Sn atoms are believed to act as a stabilizer of the amorphous ZITO network, which is similar to the role of Ga in the In-Ga-Zn-O system.
Chaos in a cylinder wake due to forcing at the Strouhal frequency
Authors: Perdikaris Paris G. , Kaiktsis Lambros , Triantafyllou George S.
Published: October 2009

In this letter we show that a cylinder oscillating harmonically in line with an incoming flow at a frequency equal to the natural frequency of vortex shedding induces for certain amplitudes of oscillation a chaotic state in the flow, characterized by an aperiodic lift force. The result is obtained through numerical simulation of the Navier–Stokes equations for two-dimensional flow. The chaos is attributed to the competition between two modes: the natural mode of the wake and the mode forced by the moving cylinder, which have entirely different spatial structures.
Estimating the viscoelastic moduli of a complex fluid from observation of Brownian motion
Authors: Felderhof B. U.
Published: October 2009

A procedure is proposed to estimate the viscoelastic properties of a complex fluid from the behavior of the velocity autocorrelation function of a suspended Brownian particle in a limited range of time. The procedure is tested for a model complex fluid with given frequency-dependent shear viscosity. It turns out that the procedure can provide a rather accurate prediction of the viscoelastic properties of the fluid on the basis of experimental data on the velocity autocorrelation function of the Brownian particle in the range of time where it turns negative.