bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential Secretion of Satiety Hormones With Progression of Obesity in JCR:LA‐corpulent Rats
Authors: Parnell Jill A. , Reimer Raylene A.
Published: January 2008

Objective: To characterize the gastrointestinal tract at the onset and in well‐established obesity.

Methods and Procedures: Lean (+/?) and obese (cp/cp) male JCR:LA‐cp rats lacking a functional leptin receptor were killed at 3.5 weeks and 9 months of age and plasma concentrations of satiety hormones determined. The small intestine, colon, and stomach were measured, weighed, and mRNA levels of satiety genes quantified.

Results: At the onset of obesity, obese rats had greater intestine, colon, and liver mass when adjusted for body weight compared to lean rats. Conversely, adult rats with established obesity had lower intestine and colon mass and length after adjustment for body weight. Early changes in gene expression included decreased ghrelin mRNA levels in stomach and increased peptide YY (PYY) mRNA levels in duodenum of young obese rats. After massive accumulation of adipose tissue had occurred, adult obese rats had increased proglucagon and ghrelin mRNA expression in the proximal intestine. In the distal small intestine, obese rats had lower proglucagon, ghrelin, and PYY mRNA levels. Finally, at the onset and in well‐established obesity, obese rats had higher plasma insulin, amylin, glucagon like peptide‐1 (GLP‐1), and PYY, a finding, with the exception of insulin, unique to this model. Plasma total ghrelin levels were significantly lower at the onset of obesity and established obesity compared to the lean rats.

Discussion: Several defects are manifested in the obese gut early on in the disease before the accumulation of large excesses of body fat and represent potential targets for early intervention in obesity.
Meal‐related Changes in Ghrelin, Peptide YY, and Appetite in Normal Weight and Overweight Children
Authors: Lomenick Jefferson P. , Clasey Jody L. , Anderson James W.
Published: January 2008

Objective: Ghrelin and peptide YY (PYY) are two gut hormones that have effects on appetite. Our objectives were to characterize the patterns of secretion of these hormones in response to feeding in school‐age children and determine whether there were differences between normal weight (NW) and overweight (OW) subjects.

Methods and Procedures: This was a cross‐sectional study at one tertiary care center. Subjects were 7‐ to 11‐year‐old healthy NW and OW volunteers recruited from local advertisements. Following an overnight fast, the subjects were given a standardized breakfast and lunch and had nine hourly blood samples for total ghrelin and total PYY. We assessed whether ghrelin and PYY levels changed from the preprandial to postprandial state and corresponded to reported hunger/satiety.

Results: Hunger ratings were similar between the two groups throughout the study period. Ghrelin was not suppressed after eating, did not rise prior to the next meal, and did not correspond to hunger ratings in either group. PYY increased postprandially and decreased preprandially in the NW group, but OW children exhibited this pattern for only part of the day. PYY levels incompletely corresponded to reported satiety in the OW group.

Discussion: Mixed meal consumption had little effect on ghrelin secretion and a variable effect on PYY secretion in young children in our study. Differences that were observed between the groups do not suggest that an abnormality in their secretion contributes to the development of obesity.
The Taq1B‐variant in the Cholesteryl Ester–Transfer Protein Gene and the Risk of Metabolic Syndrome
Authors: Sandhofer Anton , Tatarczyk Tobias , Laimer Markus , Ritsch Andreas , Kaser Susanne , Paulweber Bernhard , Ebenbichler Christoph F. , Patsch Josef R.
Published: January 2008

The metabolic syndrome is associated with low high‐density lipoprotein–cholesterol (HDL‐C) and decreased low‐density lipoprotein (LDL) particle size. The Taq1B‐polymorphism in the cholesteryl ester–transfer protein (CETP)‐gene influences HDL‐C, CETP concentration, and LDL‐size. We investigated the effect of the Taq1B‐polymorphism on the risk of the metabolic syndrome in 1,503 participants (973 men, 530 women) of the Salzburg Atherosclerosis Prevention program in subjects at High Individual Risk study. CETP concentration was determined in a subgroup (n = 486) by an enzyme‐linked immunosorbent assay. Prevalence of the metabolic syndrome was 16.7% (18.5% in men, 13.5% in women). The Taq1B‐polymorphism influenced significantly CETP concentrations, HDL‐C levels, and LDL‐size (P < 0.001 for all). The relative risk of the metabolic syndrome was reduced by 32% (odds ratio (OR) 0.68 (95% CI: 0.51–0.89), P = 0.005) in carriers of the B2 variant. This risk reduction persisted after adjustment for age and sex (OR 0.69 (0.53–0.92), P = 0.01) and after further adjustment for body mass index, waist‐to‐hip ratio, blood pressure, insulin resistance (IR), HDL‐C, and triglycerides (TGs) (OR 0.43 (0.26–0.72), P = 0.001). Furthermore, the risk reduction was more pronounced in men than in women. We conclude that CETP plays an important role in the metabolic syndrome, possibly involving novel functions of CETP.
Use of Dietary Supplements for Weight Loss in the United States: Results of a National Survey
Authors: Pillitteri Janine L. , Shiffman Saul , Rohay Jeffrey M. , Harkins Andrea M. , Burton Steven L. , Wadden Thomas A.
Published: January 2008

We examined dietary supplement use for weight loss and perceptions about safety, efficacy, and regulatory oversight of these products. A random digit‐dialed telephone survey was conducted in 2005–2006, with a representative sample of 3,500 US adults. The survey assessed the beliefs and practices related to weight control. Outcome measures included the prevalence of dietary supplement use for weight reduction, demographic profile of supplement users, and knowledge about safety, efficacy, and regulation of dietary supplements. Of the adults who made a serious weight‐loss attempt (n = 1,444), 33.9% reported ever using a dietary supplement for weight loss. Supplement use was more common among women (44.9%) vs. men (19.8%); those aged 25–34; African Americans (48.7%) or Hispanics (41.6%) vs. whites (31.2%); less educated (38.4% high school degree or less vs. 31.1% some college or more); lower income households (41.8% made <$40K vs. 30.3% made ≥$40K); obese (40.7%) vs. overweight (29.1%); those who made more lifetime weight‐loss attempts (42.0% made ≥3 vs. 22.1% made <3); and those who used more weight‐loss methods (48.2% used ≥4 vs. 25.2% used <4). Many users and non‐users of dietary supplements had misperceptions about these products—many believed they are evaluated for safety and efficacy by the Food and Drug Administration (FDA) before marketing, and that dietary supplements are safer than over‐the‐counter (OTC) or prescription medications. Use of dietary supplements for weight loss is common. More information about dietary supplements is necessary to correct misperceptions and encourage the use of safe and effective weight‐loss methods.
IAAT, Catecholamines, and Parity in African‐American and European‐American Women
Authors: Blaudeau Tamilane E. , Hunter Gary R. , St‐Onge Marie‐Pierre , Gower Barbara A. , Roy Jane L.P. , Bryan David R. , Zuckerman Paul A. , Darnell Betty E.
Published: January 2008

Objective: We have recently reported that parous European‐American (EA) women have disproportionately more intra‐abdominal adipose tissue (IAAT) than their nulliparous counterparts. Mediating mechanisms for IAAT accumulation remain unknown; however, some evidence suggests a possible catecholamine link. The objective of this study was to determine whether the IAAT‐parity relationship found in EA women exists in African‐American (AA) women and to determine whether catecholamines play a mediating role.

Methods and Procedures: Subjects included 44 EA and 47 AA premenopausal women. Free‐living physical activity by doubly labeled water (activity‐related time equivalent (ARTE)), body composition (air plethysmography, computed tomography), and 24‐h fractionated urinary catecholamines were measured.

Results: Repeated measures ANOVA revealed parous EA and AA women had significantly higher IAAT than their nulliparous counterparts (100.1 ± 28.5 and 76.2 ± 34.8 cm2 vs. 75.9 ± 29.1 and 59.6 ± 15.0 cm2). In AA women and nulliparous women, 24‐h urinary dopamine was significantly higher (AA parous 260.8 ± 88; EA parous 197.2 ± 78.8; AA nulliparous 376.5 ± 81; EA nulliparous 289.6 ± 62). Multiple regression analysis for modeling IAAT indicated that race, parity, dopamine, ARTE, and VO2max were all significant and independent contributors to the model (Unstandardized βs: race −32.6 ± 7.4; parity (number of births) 10.0 ± 3.4; 24‐h urinary dopamine 0.08 ± 0.04; ARTE (min/day) −0.09 ± 0.04; VO2max (ml/kg/min) −2.8 ± 1.0).

Discussion: Independent of the potential confounders: age, race, percent body fat, IAAT, 24‐h fractionated urinary catecholamines, physical activity, and VO2max, parous EA and AA women had more IAAT than their nulliparous counterparts. Of the catecholamines, dopamine was found to be significantly lower in parous women and higher in AA's. Dopamine, however, did not explain racial or parity differences in IAAT.
Influence of Age on the Association of Retinol‐binding Protein 4 With Metabolic Syndrome
Authors: Gavi Shai , Qurashi Saima , Stuart Louise M. , Lau Raymond , Melendez Mark M. , Mynarcik Dennis C. , McNurlan Margaret A. , Gelato Marie C.
Published: January 2008

Objective: The relationships of retinol‐binding protein 4 (RBP4) with insulin sensitivity and body fat distribution have been investigated in a few recent studies with conflicting results. This may have been due to differences in ages of the subjects in the different studies. The aim of this study was to investigate whether the association of RBP4 and insulin sensitivity and percent trunk fat are influenced by age.

Methods and Procedures: Cross‐sectional analyses of 48 young subjects and 55 elderly subjects. Insulin sensitivity was determined by a hyperinsulinemic–euglycemic clamp. Body fat distribution was determined by a dual‐energy X‐ray absorptiometry (DXA).

Results: In the young subjects, RBP4 levels were associated with insulin sensitivity (r = −0.30, P = 0.04), percent trunk fat (r = 0.54, P < 0.001), triglycerides (r = 0.44, P = 0.003), low‐density lipoprotein (r = 0.38, P = 0.01). In contrast, in the elderly subjects there was no correlation between RBP4 levels and insulin sensitivity (r = −0.18, P = 0.20), percent trunk fat (r = 0.00, P = 0.10), triglycerides (r = 0.25, P = 0.10), and low‐density lipoprotein (r = −0.11, P = 0.47).

Discussion: The associations of RBP4 with insulin sensitivity, percent trunk fat, and lipid levels are influenced by age.
Socioeconomic Status and Adiposity in Childhood: A Systematic Review of Cross‐sectional Studies 1990–2005
Authors: Shrewsbury Vanessa , Wardle Jane
Published: January 2008

Background: Sobal and Stunkard's review (1989) of 34 studies from developed countries published after 1941, found inconsistent relationships between socioeconomic status (SES) and childhood adiposity. Inverse associations (36%), no associations (38%), and positive associations (26%) were found in similar proportions. In view of the trends in pediatric obesity, the relationship between SES and adiposity may have changed.

Objective: To describe the cross‐sectional association between SES and adiposity in school‐age children from western developed countries in epidemiological studies since 1989.

Methods and Procedures: PubMed database was searched to identify potentially relevant publications. Epidemiological studies from western developed countries presenting cross‐sectional data on the bivariate association between an SES indicator and objectively measured adiposity in childhood (5–18 years), carried out after 1989 were included. SES indicators included parental education, parental occupation, family income, composite SES, and neighborhood SES.

Results: Forty‐five studies satisfied the review criteria. SES was inversely associated with adiposity in 19 studies (42%), there was no association in 12 studies (27%), and in 14 studies (31%) there was a mixture of no associations and inverse associations across subgroups. No positive SES‐adiposity associations were seen in unadjusted analyses. With parental education as the SES indicator, inverse associations with adiposity were found in 15 of 20 studies (75%).

Discussion: Research carried out within the past 15 years finds that associations between SES and adiposity in children are predominately inverse, and positive associations have all but disappeared. Research is needed to understand the mechanisms through which parental social class influences childhood adiposity.
Effects of Exercise on Adiponectin: A Systematic Review
Authors: Simpson Kylie A. , Singh Maria A. Fiatarone
Published: January 2008

Secreted from white adipose tissue, circulating concentrations of adiponectin are reduced in the presence of metabolic and cardiovascular disease such as obesity and type 2 diabetes. The aim of this systematic review is to assess the body of evidence critically for the effects of exercise on adiponectin levels. Literature searches using the Medline, CINAHL, Cochrane Controlled Trials registry, EMBASE, and SportDiscus databases were conducted from 1966 to September 2006 using keywords pertaining to “adiponectin” and “exercise.” Thirty‐three trials met the inclusion criteria. Study designs consisted of 5 cross‐sectional studies, 7 trials of acute exercise, 11 uncontrolled trials, 2 non‐randomized controlled trials, and 8 randomized controlled trials (RCTs). Exercise of varying prescription has been shown to increase serum adiponectin in 38% of RCTs, demonstrating small‐to‐moderate effect sizes (ESs). One study reported a dose–response effect of resistance training intensity and the augmentation of adiponectin. Inconsistent support in the literature exists for increasing adiponectin levels after short‐term exposure to robust aerobic or resistance training of moderate‐to‐high intensities. Particular attention should be directed toward high‐risk cohorts, in whom augmentation of the anti‐inflammatory cytokine adiponectin may assume critical importance.
BMI vs. Waist Circumference for Identifying Vascular Risk
Authors: Freiberg Matthew S. , Pencina Michael J. , D'Agostino Ralph B. , Lanier Katherine , Wilson Peter W.F. , Vasan Ramachandran S.
Published: January 2008

Objective: Current guidelines recommend measurement of both BMI and waist circumference (WC) in individuals with BMI between 25.0 and 34.9 kg/m2. We investigated the relative contributions of BMI and WC toward identifying risk of adverse vascular events in a community‐based sample.

Methods and Procedures: We evaluated Framingham Study participants (n = 4,195 person‐examinations, 53% women) using pooled logistic regression to assess the incremental prognostic utility of WC in predicting risk of a first cardiovascular disease (CVD) event in the three BMI categories (normal, <25 kg/m2; overweight, 25 to <30 kg/m2; obese, ≥30 kg/m2) and to assess the incremental prognostic utility of BMI and WC separately for predicting risk of a first cardiovascular event.

Results: On follow‐up (16 years), 430 participants (158 women) had experienced a first CVD event. In overweight women, but not in overweight men, larger WC was found to be an independent predictor of CVD incidence, longitudinally (in women, multivariable‐adjusted odds ratio (OR) per s.d. increment in WC 1.86, 95% confidence interval (CI) = 1.03–3.36, P = 0.04; in men adjusted OR per s.d. increment in WC 0.91, 95% CI 0.60–1.38, P = 0.66). In obese individuals and in those with normal BMI, WC was not associated independently with incident CVD. When BMI and WC were analyzed separately for predicting risk of a first cardiovascular event, the c statistics associated with the multivariable CVD models incorporating BMI vs. WC were nearly identical in men and women.

Discussion: Knowledge of WC aids identification of vascular risk among overweight women. Among normal weight or obese women and men (regardless of BMI category) WC did not appear to substantially add to prediction of risk of vascular events.
Adiponectin and Leptin in African Americans
Authors: Considine Robert V. , Premkumar Ahalya , Reynolds James C. , Sebring Nancy G. , Ricks Madia , Sumner Anne E.
Published: January 2008

Objective: African Americans (AAs) have less visceral and more subcutaneous fat than whites, thus the relationship of adiponectin and leptin to body fat and insulin sensitivity in AA may be different from that in whites.

Methods and Procedures: Sixty‐nine non‐diabetic AA (37 men and 32 women), aged 33 ± 1 year participated. The percent fat was determined by dual‐energy X‐ray absorptiometry, abdominal visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) volume by computerized tomography (CT), and insulin sensitivity by homeostasis model assessment (HOMA).

Results: VAT was greater in men (1,619 ± 177 cm3 vs. 1,022 ± 149 cm3; P = 0.01); women had a higher percentage of body fat (34.1 ± 1.4 vs. 24.0 ± 1.2; P < 0.0001), adiponectin (15.8 ± 1.2 μg/ml vs. 10.4 ± 0.8 μg/ml; P = 0.0004) and leptin (23.2 ± 15.8 ng/ml vs. 9.2 ± 7.2 ng/ml; P < 0.0001). SAT and HOMA did not differ because of the sex. Adiponectin negatively correlated with VAT (r = −0.41, P < 0.05) in men, and with VAT (r = −0.55, P < 0.01), and SAT (r = −0.35, P < 0.05) in women. Adiponectin negatively correlated with HOMA in men (r = −0.38, P < 0.05) and women (r = −0.44, P < 0.05). In multiple regression, sex (P = 0.02), HOMA (P = 0.03) and VAT (P = 0.003) were significant predictors of adiponectin (adj R 2 = 0.38, P < 0.0001). Leptin positively correlated with VAT, SAT, percent fat and HOMA in men (r = 0.79, r = 0.86, r = 0.89, and r = 0.53; P < 0.001) and women (r = 0.62, r = 0.75, r = 0.83, and r = 0.55; P < 0.01). In multiple regression VAT (P = 0.04), percent body fat (P < 0.0001) and sex (P = 0.01), but not HOMA were significant predictors of serum leptin (adj R 2= 0.82, P < 0.0001).

Discussion: The relationship of adiponectin and leptin to body fat content and distribution in AA is dependent on sex. Although VAT and insulin sensitivity are significant determinants of adiponectin, VAT and percent body fat determine leptin.
Enhanced Effects of 1,25(OH)2D3 Plus Genistein on Adipogenesis and Apoptosis in 3T3‐L1 Adipocytes
Authors: Rayalam Srujana , Della‐Fera Mary Anne , Ambati Suresh , Yang Jeong‐Yeh , Park Hea Jin , Baile Clifton A.
Published: January 2008

Objective: To investigate the ability of 1,25(OH)2D3 (D) and genistein (G), alone and in combination, to inhibit adipogenesis and induce apoptosis in 3T3‐L1 adipocytes.

Methods and Procedures: 3T3‐L1 preadipocytes and mature adipocytes were incubated with various concentrations of D and G, alone and in combination, for 48 h. Viability was determined using the Cell Titer 96 Aqueous One Solution Cell Proliferation Assay. Post‐confluent preadipocytes were incubated with D and G for up to 6 days during adipogenesis and lipid content was quantified by Nile Red dye; apoptosis was quantified by measurement of single‐stranded DNA. Expression of adipocyte‐specific proteins and VDR was analyzed by western blotting.

Results: Combining D and G did not cause an enhanced effect on cell viability in either preadipocytes or mature adipocytes. In maturing preadipocytes, D at 0.5 nmol/l (D0.5) increased apoptosis by 47 ± 10.25% (P < 0.05) and inhibited lipid accumulation by 28 ± 10% (P < 0.001), while G at 25 μmol/l (G25) had no significant effect. However, D+G caused an enhanced apoptosis by 136 ± 12.6% (P < 0.001) and enhanced inhibition of lipid accumulation by 82.46 ± 2.95% (P < 0.001). Similarly, D0.5 alone decreased adipose‐specific gene 422 (aP2) expression to 34.2 ± 2.3% and increased VDR expression levels by 41.8 ± 11% (P < 0.001), but G25 showed no effect. However, D0.5+G25 decreased aP2 expression to 52 ± 4.2% (P < 0.05) and increased VDR expression levels by 131 ± 14.5% (P < 0.0001).

Discussion: These findings suggest that combining 1,25(OH)2D3 with genistein results in an enhanced inhibition of lipid accumulation and induction of apoptosis in maturing 3T3‐L1 preadipocytes.
Assessing Body Composition With DXA and Bioimpedance: Effects of Obesity, Physical Activity, and Age
Authors: Völgyi Eszter , Tylavsky Frances A. , Lyytikäinen Arja , Suominen Harri , Alén Markku , Cheng Sulin
Published: January 2008

Objective: This study evaluated to what extent dual‐energy X‐ray absorptiometry (DXA) and two types of bioimpedance analysis (BIA) yield similar results for body fat mass (FM) in men and women with different levels of obesity and physical activity (PA).

Methods and Procedures: The study population consisted of 37–81‐year‐old Finnish people (82 men and 86 women). FM% was estimated using DXA (GE Lunar Prodigy) and two BIA devices (InBody (720) and Tanita BC 418 MA). Subjects were divided into normal, overweight, and obese groups on the basis of clinical cutoff points of BMI, and into low PA (LPA) and high PA (HPA) groups. Agreement between the devices was calculated by using the Bland–Altman analysis.

Results: Compared to DXA, both BIA devices provided on average 2–6% lower values for FM% in normal BMI men, in women in all BMI categories, and in both genders in both HPA and LPA groups. In obese men, the differences were smaller. The two BIA devices provided similar means for groups. Differences between the two BIA devices with increasing FM% were a result of the InBody (720) not including age in their algorithm for estimating body composition.

Discussion: BIA methods provided systematically lower values for FM than DXA. However, the differences depend on gender and body weight status pointing out the importance of considering these when identifying people with excess FM.
SIK2 Can be Activated by Deprivation of Nutrition and It Inhibits Expression of Lipogenic Genes in Adipocytes
Authors: Du Jing , Chen Qiu , Takemori Hiroshi , Xu Haiyan
Published: January 2008

Objective: Determine the biological function of SIK2 in 3T3‐L1 adipocytes.

Methods and Procedures: 3T3‐L1 adipocytes were treated with serum‐free, serum/glucose‐free, or complete Dulbecco's Modified Eagle's Medium (DMEM) for 15 min, or 10 µg/ml oligomycin in serum‐free DMEM for 15 min, or different doses of 5‐amino‐4‐imidazolecarboxamide (AICAR) for different periods of time in serum‐free DMEM. After treatment, SIK2 kinase activity was measured by examining phosphorylation of a peptide substrate. SIK2 was overexpressed and knocked down in 3T3‐L1 CAR adipocytes using adenovirus‐mediated gene transfer for the assessment of lipogenic gene expression and triglyceride content. Electroporation was used to transiently transfect 3T3‐L1 adipocytes with fatty acid synthase (FAS) promoter‐driven luciferase construct to evaluate the effect of SIK2 on FAS transcription.

Results: In 3T3‐L1 adipocytes, SIK2 can be activated by nutrient deprivation, inhibition of ATP synthesis, and treatment of AICAR. Overexpression of SIK2 repressed the expression of lipogenic genes, including FAS, acetyl CoA carboxylase 2 (ACC2), and stearoyl CoA desaturase 1 (SCD1), and reduced triglyceride content. Reduction of endogenous SIK2 expression through RNA interference increased the expression of FAS, ACC2, and SCD1. This effect is independent of adenosine monophosphate–activated protein kinase (AMPK) since neither phosphorylation state nor protein level of AMPKα1 and AMPKα2 was affected by SIK2 overexpression. SIK2 inhibits the expression of FAS‐promoter driven luciferase reporter gene, and this effect can be reversed by overexpression of constitutively active sterol regulatory element binding protein–1 (SREBP‐1). Furthermore, SIK2 also reduces the nuclear translocation of endogenous SREBP‐1.

Discussion: Our results support a role for SIK2 in adipocyte energy metabolism. SIK2 may function similarly to AMPK for turning off lipogenesis in low‐energy state.
Differential expression and regulation of myristoylated alanine‐rich C kinase substrate (MARCKS) in the hippocampus of C57/BL6J and DBA/2J mice
Authors: McNamara Robert K. , Vasquez Patricia A. , Mathe Aleksander A. , Lenox Robert H.
Published: February 2008

The myristoylated alanine‐rich C kinase substrate (MARCKS) is a major protein kinase C (PKC) substrate in brain that binds the inner surface of the plasma membrane, calmodulin, and cross‐links filamentous actin, all in a PKC phosphorylation‐reversible manner. MARCKS has been implicated in hippocampal‐dependent learning and long‐term potentiation (LTP). Previous studies have shown DBA/2 mice to exhibit poor spatial/contextual learning, impaired hippocampal LTP, and hippocampal mossy fiber hypoplasia, as well as reduced hippocampal PKC activity and expression relative to C57BL/6 mice. In the present study, we assessed the expression (mRNA and protein) and subcellular distribution (membrane and cytolsol) of MARCKS in the hippocampus and frontal cortex of C57BL/6 and DBA/2 mice using quantitative western blotting. In the hippocampus, total MARCKS mRNA and protein levels in C57BL/6J mice were significantly lower (∼45%) compared with DBA/2J mice, and MARCKS protein was observed predominantly in the cytosolic fraction. MARCKS expression in frontal cortex did not differ significantly between strains. To examine the dynamic regulation of MARCKS subcellular distribution, mice from each strain were subjected to 60 min restraint stress and MARCKS subcellular distribution was determined 24 h later. Restraint stress resulted in a significant reduction in membrane MARCKS expression in C57BL/6J hippocampus but not in the DBA/2J hippocampus despite similar stress‐induced increases in serum corticosterone. Restraint stress did not affect cytosolic or total MARCKS levels in either strain. Similarly, restraint stress (30 min) in rats also induced a significant reduction in membrane MARCKS, but not total or cytosolic MARCKS, in the hippocampus but not in frontal cortex. In rats, chronic lithium treatment prior to stress exposure reduced hippocampal MARCKS expression but did not affect the stress‐induced reduction in membrane MARCKS. Collectively these data demonstrate higher resting levels of MARCKS in the hippocampus of DBA/2J mice compared to C57BL/6J mice, and that acute stress leads to a long‐term reduction in membrane MARCKS expression in C57BL/6J mice and rats but not in DBA/2J mice. These strain differences in hippocampal MARCKS expression and subcellular translocation following stress may contribute to the differences in behaviors requiring hippocampal plasticity observed between these strains.
Low pressure and high power rf sources for negative hydrogen ions for fusion applications (ITER neutral beam injection) (invited)
Authors: Fantz U. , Franzen P. , Kraus W. , Falter H. D. , Berger M. , Christ-Koch S. , Fröschle M. , Gutser R. , Heinemann B. , Martens C. , McNeely P. , Riedl R. , Speth E. , Wünderlich D.
Published: January 2008

The international fusion experiment ITER requires for the plasma heating and current drive a neutral beam injection system based on negative hydrogen ion sources at 0.3Pa. The ion source must deliver a current of 40A D− for up to 1h with an accelerated current density of 200A∕m2 and a ratio of coextracted electrons to ions below 1. The extraction area is 0.2m2 from an aperture array with an envelope of 1.5×0.6m2. A high power rf-driven negative ion source has been successfully developed at the Max-Planck Institute for Plasma Physics (IPP) at three test facilities in parallel. Current densities of 330 and 230A∕m2 have been achieved for hydrogen and deuterium, respectively, at a pressure of 0.3Pa and an electron/ion ratio below 1 for a small extraction area (0.007m2) and short pulses (<4s). In the long pulse experiment, equipped with an extraction area of 0.02m2, the pulse length has been extended to 3600s. A large rf source, with the width and half the height of the ITER source but without extraction system, is intended to demonstrate the size scaling and plasma homogeneity of rf ion sources. The source operates routinely now. First results on plasma homogeneity obtained from optical emission spectroscopy and Langmuir probes are very promising. Based on the success of the IPP development program, the high power rf-driven negative ion source has been chosen recently for the ITER beam systems in the ITER design review process.
Electron cyclotron resonance charge breeder ion source simulation by MCBC and GEM
Authors: Kim J. S. , Zhao L. , Cluggish B. P. , Bogatu I. N. , Pardo R.
Published: February 2008

Numerical simulation results by the GEM and MCBC codes are presented, along with a comparison with experiments for beam capture dynamics and parameter studies of charge state distribution (CSD) of electron cyclotron resonance charge breeder ion sources. First, steady state plasma profiles are presented by GEM with respect to key experimental parameters such as rf power and gas pressure. As rf power increases, electron density increases by a small amount and electron energy by a large amount. The central electrostatic potential dip also increased. Next, MCBC is used to trace injected beam ions to obtain beam capture profiles. Using the captured ion profiles, GEM obtains a CSD of beam ions. As backscattering can be significant, capturing the ions near the center of the device enhances the CSD. The effect of rf power on the beam CSD is mainly due to different steady states plasmas. Example cases are presented assuming that the beam ions are small enough not to affect the plasma.
RCNP polarized He3 ion source
Authors: Tanaka M. , Takahashi Y. , Shimoda T. , Yosoi M. , Takahisa K. , Plis Yu. A.
Published: January 2008

We have developed a polarized He3 ion source named “SEPIS” (spin-exchange polarized ion source) at RCNP, and Department of Physics, Osaka Univeristy. The SEPIS uses a large spin-exchange cross section, σse, and a small electron capture cross section,σec, for the He+3+Rb system theoretically expected at low He+3 incident energies. The validity of SEPIS was experimentally proven by observing the He+3 nuclear polarization as a function of the incident He+3 energy.
Large magnetic entropy change and low hysteresis loss in the Nd- and Co-doped La(Fe,Si)13 compounds
Authors: Shen Jun , Li Yang-Xian , Zhang Jian , Gao Bo , Hu Feng-Xia , Zhang Hong-Wei , Chen Yun-Zhong , Rong Chuan-Bing , Sun Ji-Rong
Published: January 2008

The effect of Nd and Co substitution on magnetic entropy changes and hysteresis losses has been investigated for the cubic NaZn13-type LaFe13−xSix compounds. Partially replacing La with Nd leads to a decrease of the Curie temperature TC and an increase of the magnetic entropy change ΔS. Substitution of Co for Fe in La0.7Nd0.3Fe10.5Si1.5 can adjust TC to around room temperature. A large ΔS of 15J∕KgK at TC=280K for a field change from 0to5T and a small hysteresis loss close to zero near TC have been obtained in La0.7Nd0.3Fe10.7Co0.8Si1.5. The Co-doped NaZn13-type LaNdFeSi compounds may be a suitable candidate for magnetic refrigerant near room temperature.
Contribution of the surface plasmon resonance to optical and magneto-optical properties of a Bi:YIG-Au nanostructure
Authors: Fujikawa R. , Baryshev A. V. , Kim J. , Uchida H. , Inoue M.
Published: January 2008

We have studied the optical and magneto-optical properties of bismuth-substituted yttrium iron garnet (Bi:YIG) films with Au nanoparticles dispersed on their top surfaces. These structures exhibit surface plasmon resonances due to light coupling to Au nanoparticles, showing, for any direction of polarization of the incoming light beam, an absorption band in the spectral range of 500–750nm. For transmitted light beams with the plasmon-resonant wavelengths, the plane of polarization rotates slightly when the structure is not magnetized. Polarization-resolved transmission spectra show that this rotation is due to anisotropy of light propagation through the array of Au nanoparticles. For the structure comprising the 90-nm-thick Bi:YIG film and the array of Au nanoparticles of several tens of nanometers, the Faraday rotation angle enhances as compared with that for the original Bi:YIG film of the same thickness.
Chemically selective gas-induced spin polarization changes in ultrathin fcc Co films
Authors: Kopper K. P. , Küpper D. , Reeve R. , Mitrelias T. , Bland J. A. C.
Published: January 2008

The influence of submonolayer quantities of O and N adsorbed on ultrathin Co∕Cu(001) films as a function of Co thickness has been studied using spin polarized secondary electron spectroscopy. The gaseous adsorbate was prepared by depositing Co on (2×22)R45°-O and c(2×2)-N reconstructed Cu(001) utilizing surfactant effects to reproducibly control quantity. Adsorbed quantities were monitored by Auger electron spectroscopy and surface reconstructions by low energy electron diffraction. The secondary electron spin polarization increases with the Co film thickness, following an exponential law, and the chemical interaction between the adsorbate and the Co reduces polarization to (98±2)% in the case of O and (84±3)% in the case of N compared to the uncovered substrate. For both, the onset of ferromagnetism is suppressed by approximately 1 ML. The effects on polarization and the onset of ferromagnetism are attributed to the partial cancellation of the magnetic moment in the Co layer adjacent to the adsorbate. The estimated reduction in moment is comparable to the results of theoretical predictions.
Micromagnetic analysis of current driven domain wall motion in nanostrips with perpendicular magnetic anisotropy
Authors: Fukami S. , Suzuki T. , Ohshima N. , Nagahara K. , Ishiwata N.
Published: January 2008

Current driven domain wall motion in nanostrips with perpendicular magnetic anisotropy was analyzed by using micromagnetic simulation. The threshold current density of perpendicular anisotropy strips in adiabatic approximation was much smaller than that of in-plane anisotropy strips, and it reduced with thickness reduction. The differences originate from the differences in domain wall width and hard-axis anisotropy. Also, the threshold current density of perpendicular anisotropy strips required to depin from a pinning site was quite small although the threshold field of the strips was sufficiently large relative to those of in-plane anisotropy strips.
Investigation of negative coercivity in one layer formation of soft and hard magnetic materials
Authors: Tho Luu Van , Kim Cheol Gi , Kim Chong Oh
Published: January 2008

A single layer consists of CoFe soft and LaCoFeO hard magnetic materials was deposited using the cosputtering method. Microstructure analysis of the layer demonstrated that CoFe particles were surrounded by a LaCoFeO shell and the ratio of the thicknesses was dependent on the amount of La and on the O2∕(Ar+O2) gas flow ratio used during sputtering. When the O2∕(Ar+O2) gas flow ratio was increased from 7% to 13%, coercivity (Hc) along the hard axis decreased from 11.3Oe at 7% to −9.1Oe at 11%. At a gas flow ratio of 13%, the coercivity increased to 11.7Oe. The results of the present study show that negative coercivity Hc<0 is caused by interactions between two single domains of soft and hard magnetic materials. This interaction was modeled and described in detail using an extension of Heisenberg’s model to the case of two domains. The results of the present study, demonstrating the conditions required to obtain negative Hc, can be applied to other pairs of soft-hard magnetic materials.
Spin-wave excitations in arrays of asymmetric ferromagnetic nanorings
Authors: Nguyen T. M. , Cottam M. G.
Published: January 2008

Calculations are reported for the spin-wave excitations in asymmetric ferromagnetic nanorings using a Hamiltonian-based formalism. Both the exchange and dipole-dipole interactions are included, as well as an external magnetic field and single-ion anisotropy. The equilibrium configurations of the nanorings are found by minimizing numerically the energy functional with respect to the spin orientation. Depending on the geometry, particularly the degree of asymmetry and the in-plane applied magnetic field, the nanorings can be in a vortex, onion, or other inhomogeneous state. Spin-dependent Green’s functions are calculated to deduce the dispersion spectra and the mode profiles of the spin waves, and the dependence of the spin-wave properties on the asymmetry factor is studied. The effects of inter-ring dipolar coupling on the spin-wave spectrum are also investigated by considering small arrays (e.g., a 3×3 square array) of nanorings.
Evaluation of minority-carrier diffusion length in n-type β-FeSi2 single crystals by electron-beam-induced current
Authors: Ootsuka Teruhisa , Suemasu Takashi , Chen Jun , Sekiguchi Takashi
Published: January 2008

We have evaluated the diffusion length of minority carriers (holes) in single-crystalline n-type β-FeSi2 bulk grown by chemical vapor transport by means of electron-beam-induced current (EBIC) technique in the edge-scan configuration. The EBIC line-scan data showed a clear exponential dependence of distance from the Al electrode. The diffusion length was estimated to be 20μm at room temperature, and increased upon high-temperature annealing, reaching approximately 30μm after annealing at 800°C for 8h. This result explained the improvement of photoresponsivity in the Al∕n-β-FeSi2 Schottky diodes by high-temperature annealing.
Surface magnetic polaritons in ferromagnetic and antiferromagnetic cylindrical tubes
Authors: Das T. K. , Cottam M. G.
Published: January 2008

A theory is developed for the localized surface magnetic polaritons in hollow magnetic cylinders or tubes, in the presence of a longitudinal applied field. This involves solving for the dynamical response using the nondiagonal susceptibility tensor for a ferromagnet or antiferromagnet in Maxwell’s equations, with electromagnetic boundary conditions at the inner and outer tube surfaces. Results for wires and antiwires are deduced as limiting cases of this geometry. As the outer radius is increased, the surface polariton branches near the light line are reduced in frequency and the localization properties are modified due to strong retardation effects. Numerical applications are made to yttrium iron garnet and MnF2 materials.
Volume dependent magnetism in zinc-blende MnX (X=N,P,As,Sb,Bi) compounds
Authors: Sanyal B. , Eriksson O.
Published: January 2008

Half-metallic ferromagnets are promising candidates for use in spintronic devices. In order to investigate the complex magnetism of such systems, we have studied the magnetic interactions in zinc-blende MnX (X=N,P,As,Bi,Sb) systems as a function of volume by ab initio density functional calculations. The calculated Heisenberg pair-exchange parameters show a strong volume dependence resulting in the transition from a metallic to a half-metallic behavior for certain systems. As a result, in MnAs, the calculated Curie temperatures, obtained from Monte Carlo simulations using ab initio exchange parameters and a classical Heisenberg Hamiltonian, increase with an increase in volume. Calculations of self-consistent noncollinear spin configurations indicate that spins deviate strongly from collinear ordering for low volumes whereas they align in a collinear ferromagnetic fashion for high volumes.
Structure, magnetism, and magnetocaloric properties of MnFeP1−xSix compounds
Authors: Cam Thanh D. T. , Brück E. , Trung N. T. , Klaasse J. C. P. , Buschow K. H. J. , Ou Z. Q. , Tegus O. , Caron L.
Published: January 2008

Mn Fe P 1 − x Si x compounds with x=0.10,0.20,0.24,0.28,…,0.80,1 were prepared by high-energy ball milling and solid-state reaction. The structural, magnetic, and magnetocaloric properties are investigated as a function of temperature and magnetic field. X-ray diffraction studies show that the samples in the range from x=0.28 to 0.64 adopt the hexagonal Fe2P-type structure with a small amount of second phase which increases with increasing Si content. The samples with lower Si content show the orthorhombic Co2P-type structure. Magnetic measurements show that the paramagnetic-ferromagnetic transition temperatures range from 214to377K. Of much importance is the fact that these compounds do not contain any toxic components and exhibit excellent magnetocaloric properties.
Gain-induced switching in metal-dielectric-metal plasmonic waveguides
Authors: Yu Zongfu , Veronis Georgios , Fan Shanhui , Brongersma Mark L.
Published: January 2008

The authors show that the incorporation of gain media in only a selected device area can annul the effect of material loss and enhance the performance of loss-limited plasmonic devices. In addition, they demonstrate that optical gain provides a mechanism for on/off switching in metal-dielectric-metal (MDM) plasmonic waveguides. The proposed gain-assisted plasmonic switch consists of a subwavelength MDM plasmonic waveguide side coupled to a cavity filled with semiconductor material. They show that the principle of operation of such gain-assisted plasmonic devices can be explained using a temporal coupled-mode theory.
Controlled focused electron beam-induced etching for the fabrication of sub-beam-size nanoholes
Authors: Miyazoe Hiroyuki , Utke Ivo , Michler Johann , Terashima Kazuo
Published: January 2008

Sub-beam-size focused electron beam-induced etching of amorphous carbon membranes was achieved. The size of the tungsten filament generated electron beam was determined from the in situ stage current monitoring and verified by knife edge measurements. The in situ time resolved stage current measurements as an end point detection allowed the fabrication of nanoholes with a diameter of sub-20nm, corresponding to 20%–40% of the full width at half maximum of the incident beam.
Influence of phonon scattering on the performance of p-i-n band-to-band tunneling transistors
Authors: Koswatta Siyuranga O. , Lundstrom Mark S. , Nikonov Dmitri E.
Published: January 2008

Power dissipation has become a major obstacle in performance scaling of modern integrated circuits and has spurred the search for devices operating at lower voltage swing. In this letter, we study p-i-n band-to-band tunneling field effect transistors taking semiconducting carbon nanotubes as the channel material. The on current of these devices is mainly limited by the tunneling barrier properties, and phonon-scattering has only a moderate effect. We show, however, that the off current is limited by phonon absorption assisted tunneling, and thus is strongly temperature dependent. Subthreshold swings below the 60mV∕decade conventional limit can be readily achieved even at room temperature. Interestingly, although subthreshold swing degrades due to the effects of phonon scattering, it remains low under practical biasing conditions.
Optical spin manipulation of electrically pumped vertical-cavity surface-emitting lasers
Authors: Hövel S. , Bischoff A. , Gerhardt N. C. , Hofmann M. R. , Ackemann T. , Kroner A. , Michalzik R.
Published: January 2008

We analyze the potential for the spin manipulation of vertical-cavity surface-emitting lasers (VCSELs) by operating them electrically and injecting additional spin-polarized carriers by polarized optical excitation. The output polarization of the VCSELs can be easily controlled by the spin orientation of the optically injected carriers when the injection current does not exceed the threshold current.
Two-photon absorption in ZnSe and ZnSe∕ZnS core/shell quantum structures
Authors: Lad Amit D. , Kiran P. Prem , More Deepak , Kumar G. Ravindra , Mahamuni Shailaja
Published: January 2008

The third order nonlinear optical properties of two different sized ZnSe and ZnSe∕ZnS quantum dots (QDs) are investigated. The nonlinear absorption is measured at 806nm using Ti:sapphire 100fs laser pulses in an open aperture Z-scan setup. Two-photon absorption (2PA) is found to be dominant in core and core shell QDs. 2PA cross section is enhanced by three orders of magnitude compared bulk ZnSe. 2PA cross section is observed to increase with reduction in QD diameter, due to strong confinement effect. ZnSe∕ZnS QDs exhibit higher 2PA cross section compared with corresponding ZnSe QDs, indicating better passivation of the QD surface.
Thermal stress analysis of a Nd:YVO4 laser medium end pumped by a Gaussian beam
Authors: Huai Xiulan , Li Zhigang
Published: January 2008

The heat conduction and the thermal stress problems in an orthotropic Nd:YVO4 laser medium end pumped by a Gaussian beam are modeled and analytically solved. The three-dimensional temperature expression is derived via an integral transform method, and the thermal stress field is deduced by Airy’s thermal stress function method, utilizing said three-dimensional temperature expression, based on the plain-strain assumption. The results indicate that the orthotropic thermal properties have significant influence on the thermal strain pattern, but have less effect on the thermal stress profile in the absence of external forces.
Transient electromagnetically induced transparency in self-assembled quantum dots
Authors: Marcinkevičius S. , Gushterov A. , Reithmaier J. P.
Published: January 2008

A coherent absorption dip in pump-probe experiment performed on a ten layer optically thin InGaAs∕GaAs quantum dot (QD) structure has been observed. Measurements performed for different wavelengths, polarizations, pulse widths, and temperatures allow assigning the dip to electromagnetically induced transparency (EIT). The EIT scheme is based on coupling of excitons with different spins in asymmetric QDs. Using spectrally narrow pulses, detrimental effect of the inhomogeneous broadening is reduced since only the QDs with transitions resonant with the pulse wavelength are addressed and participate in the EIT. The effect has been observed at temperatures up to 140K.
Valence band structure of AlN probed by photoluminescence
Authors: Sedhain A. , Lin J. Y. , Jiang H. X.
Published: January 2008

Deep ultraviolet photoluminescence (PL) was employed to probe the valence band structure of AlN epilayers grown by metal organic chemical vapor deposition on c-plane sapphire substrates. At 10K, in addition to the dominant emission peak at 6.050eV polarized in the E∥c direction, we observed two additional emission peaks at 6.249 and 6.262eV polarized in the E⊥c direction. These two emission lines are assigned to the recombination of free excitons related to the B and C valence bands. A more comprehensive picture of the valence band structure of AlN is thus directly obtained from the PL measurements.
High resolution vacuum scanning thermal microscopy of HfO2 and SiO2
Authors: Hinz M. , Marti O. , Gotsmann B. , Lantz M. A. , Dürig U.
Published: January 2008

We present scanning thermal microscopy (SThM) measurements on a sample consisting of regions of 3nm thick HfO2 film and 2nm thick SiO2 on a silicon substrate. The experiments were preformed in high vacuum conditions using microfabricated silicon cantilevers with sharp heatable tips, facilitating the unprecedented achievement of a lateral SThM image resolution of 25nm. In addition, the heat transfer through the tip to the sample was investigated using approach curves and used to determine the thermal conductivity of the 3nm thick HfO2 layer.
Amine-capped silicon quantum dots
Authors: Li Q. S. , Zhang R. Q. , Lee S. T. , Niehaus T. A. , Frauenheim Th.
Published: February 2008

Water-soluble photoluminescent (PL) silicon quantum dots (SiQDs) can be obtained by surface modification with small organic molecules, while still leaving some sites uncovered by the employed organic molecules due to steric repulsion. Using a density-functional tight-binding method, we show the possibility of fully capping surface of SiQDs by amine, which is more effective in protecting the surface against oxidation. The presence of amine not only reduces the optical gaps but also results in a significant enhancement of absorbance and fluorescence. Moreover, the amine-capped SiQDs are expected to be water soluble and PL stable, and thus could be used as biological sensors.