Nonlinear photonic crystals near the supercollimation point

We uncover a strong coupling between nonlinearity and diffraction in a photonic crystal at the supercollimation point. We show this is modeled by a nonlinear diffraction term in a nonlinear schroedinger type equation, in which the properties of solitons are investigated. Linear stability analysis shows solitons are stable in an existence domain that obeys the Vakhitov-Kolokolov criterium. In addition, we investigate the influence of the nonlinear diffraction on soliton collision scenarios.Comment: 16 pages, 3 figures, being published in Optics Letter

Adding a reward increases the reinforcing value of fruit

Adolescents' snack choices could be altered by increasing the reinforcing value (RV) of healthy snacks compared with unhealthy snacks. This study assessed whether the RV of fruit increased by linking it to a reward and if this increased RV was comparable with the RV of unhealthy snacks alone. Moderation effects of sex, hunger, BMI z-scores and sensitivity to reward were also explored. The RV of snacks was assessed in a sample of 165 adolescents (15.1 (SD 1.5) years, 39.4% boys and 17.4% overweight) using a computerised food reinforcement task. Adolescents obtained points for snacks through mouse clicks (responses) following progressive ratio schedules of increasing response requirements. Participants were (computer) randomised to three experimental groups (1: 1: 1): fruit (n 53), fruit + reward (n 60) or unhealthy snacks (n 69). The RV was evaluated as total number of responses and breakpoint (schedule of terminating food reinforcement task). Multilevel regression analyses (total number of responses) and Cox's proportional hazard regression models (breakpoint) were used. The total number of responses made were not different between fruit + reward and fruit (b -473; 95% CI -1152, 205, P=0.17) or unhealthy snacks (b 410; 95% CI -222, 1043, P = 0.20). The breakpoint was slightly higher for fruit than fruit + reward (HR 1.34; 95% CI 1.00, 1.79, P=0.050), whereas no difference between unhealthy snacks and fruit + reward (HR 0.86; 95% CI 0.62, 1.18, P=0.34) was observed. No indication of moderation was found. Offering rewards slightly increases the RV of fruit and may be a promising strategy to increase healthy food choices. Future studies should however, explore if other rewards, could reach larger effect sizes

Sensitivity to reward and adolescents’ unhealthy snacking and drinking behavior: the role of hedonic eating styles and availability

Background: Although previous research found a positive association between sensitivity to reward (SR) and adolescents' unhealthy snacking and drinking behavior, mechanisms explaining these associations remain to be explored. The present study will therefore examine whether the associations between SR and unhealthy snack and/or sugar-sweetened beverage (SSB) intake are mediated by external and/or emotional eating and if this mediation is moderated by availability at home or at school. Methods: Cross-sectional data on snacking, availability of snacks at home and at school, SR (BAS drive scale) and external and emotional eating (Dutch eating behavior questionnaire) of Flemish adolescents (n = 1104, mean age = 14.7 +/- 0.8 years; 51 % boys; 18.0 % overweight) in 20 schools spread across Flanders were collected. Moderated mediation analyses were conducted using generalized structural equation modeling in three steps: (1) direct association between SR and unhealthy snack or SSB intake, (2) mediation of either external or emotional eating and (3) interaction of home or school availability and emotional or external eating. Results: Partial mediation of external eating (a*b = 0.69, p < 0.05) and of emotional eating (a*b = 0.92, p < 0.01) in the relation between SR and intake of unhealthy snacks was found (step 2). The relation between SR and SSB intake was not mediated by external or emotional eating (step 2). No moderation effects of home or school availability were found (step 3). Conclusion: Our findings indicate that the association between SR and the consumption of unhealthy snacks is partially explained by external and emotional eating in a population-based sample of adolescents irrespective of the home or school availability of these foods

Use of fitness and nutrition apps : associations with body mass index, snacking, and drinking habits in adolescents

Background: Efforts to improve snacking and drinking habits are needed to promote a healthy body mass index (BMI) in adolescents. Although commercial fitness and nutrition mobile phone apps are widely used, little is known regarding their potential to improve health behaviors, especially in adolescents. In addition, evidence on the mechanisms through which such fitness and nutrition apps influence behavior is lacking. Objectives: This study assessed whether the use of commercial fitness or nutrition apps was associated with a lower BMI and healthier snacking and drinking habits in adolescents. Additionally, it explored if perceived behavioral control to eat healthy; attitudes to eat healthy for the good taste of healthy foods, for overall health or for appearance; social norm on healthy eating and social support to eat healthy mediated the associations between the frequency of use of fitness or nutrition apps and BMI, the healthy snack, and beverage ratio. Methods: Cross-sectional self-reported data on snack and beverage consumption, healthy eating determinants, and fitness and nutrition app use of adolescents (N=889; mean age 14.7 years, SD 0.8; 54.8% [481/878] boys; 18.1% [145/803] overweight) were collected in a representative sample of 20 schools in Flanders, Belgium. Height and weight were measured by the researchers. The healthy snack ratio and the healthy beverage ratio were calculated as follows: gram healthy snacks or beverages/(gram healthy snacks or beverages+ gram unhealthy snacks or beverages) x100. Multilevel regression and structural equation modeling were used to analyze the proposed associations and to explore multiple mediation. Results: A total of 27.6% (245/889) of the adolescents used fitness, nutrition apps or both. Frequency of using nutrition apps was positively associated with a higher healthy beverage ratio (b=2.96 [1.11], P=.008) and a higher body mass index z-scores (zBMI; b=0.13 [0.05], P=.008. A significant interaction was found between the frequency of using nutrition and for the zBMI (b=-0.03 [0.02], P=.04) and the healthy snack ratio (b=-0.84 [0.37], P=.03). Attitude to eat healthy for appearance mediated both the fitness app use frequency-zBMI (a x b=0.02 [0.01], P=.02) and the nutrition app use frequency-zBMI (a x b= 0.04 [0.01], P=.001) associations. No mediation was observed for the associations between the frequency of use of fitness or nutrition apps and the healthy snack or beverage ratio. Conclusions: Commercial fitness and nutrition apps show some association with healthier eating behaviors and BMI in adolescents. However, effective behavior change techniques should be included to affect key determinants of healthy eating

On the association of common and rare genetic variation influencing body mass index: a combined SNP and CNV analysis

Background As the architecture of complex traits incorporates a widening spectrum of genetic variation, analyses integrating common and rare variation are needed. Body mass index (BMI) represents a model trait, since common variation shows robust association but accounts for a fraction of the heritability. A combined analysis of single nucleotide polymorphisms (SNP) and copy number variation (CNV) was performed using 1850 European and 498 African-Americans from the Study of Addiction: Genetics and Environment. Genetic risk sum scores (GRSS) were constructed using 32 BMI-validated SNPs and aggregate-risk methods were compared: count versus weighted and proxy versus imputation. Results The weighted SNP-GRSS constructed from imputed probabilities of risk alleles performed best and was highly associated with BMI (p = 4.3×10−16) accounting for 3% of the phenotypic variance. In addition to BMI-validated SNPs, common and rare BMI/obesity-associated CNVs were identified from the literature. Of the 84 CNVs previously reported, only 21-kilobase deletions on 16p12.3 showed evidence for association with BMI (p = 0.003, frequency = 16.9%), with two CNVs nominally associated with class II obesity, 1p36.1 duplications (OR = 3.1, p = 0.009, frequency 1.2%) and 5q13.2 deletions (OR = 1.5, p = 0.048, frequency 7.7%). All other CNVs, individually and in aggregate, were not associated with BMI or obesity. The combined model, including covariates, SNP-GRSS, and 16p12.3 deletion accounted for 11.5% of phenotypic variance in BMI (3.2% from genetic effects). Models significantly predicted obesity classification with maximum discriminative ability for morbid-obesity (p = 3.15×10−18). Conclusion Results show that incorporating validated effect sizes and allelic probabilities improve prediction algorithms. Although rare-CNVs did not account for significant phenotypic variation, results provide a framework for integrated analyses

Cross-reactivity between HLA-A2-restricted FLU-M1:58–66 and HIV p17 GAG:77–85 epitopes in HIV-infected and uninfected individuals

BACKGROUND: The matrix protein of the influenza A virus and the matrix and capsid proteins of the human immunodeficiency virus (HIV) share striking structural similarities which may have evolutionary and biological significance. These similarities led us to hypothesize the existence of cross-reactivity between HLA-A2-restricted FLU-M1:58–66 and HIV-1 p17 GAG:77–85 epitopes. METHODS: The hypothesis that these two epitopes are cross-reactive was tested by determining the presence and extent of FLU/GAG immune cross-reactivity in lymphocytes from HIV-seropositive and seronegative HLA-A2(+ )donors by cytotoxicity assays and tetramer analyses. Moreover, the molecular basis for FLU/GAG cross-reactivity in HIV-seropositive and seronegative donors was studied by comparing lymphocyte-derived cDNA sequences corresponding to the TCR-β variable regions, in order to determine whether stimulation of lymphocytes with either peptide results in the expansion of identical T-cell clonotypes. RESULTS: Here, we report evidence of cross-reactivity between FLU-M1:58–66 and HIV-1 p17 GAG:77–85 epitopes following in vitro stimulation of PBMC derived from either HIV-seropositive or seronegative HLA-A2(+ )donors as determined by cytotoxicity assays, tetramer analyses, and molecular clonotyping. CONCLUSION: These results suggest that immunity to the matrix protein of the influenza virus may drive a specific immune response to an HLA-A2-restricted HIV gag epitope in HIV-infected and uninfected donors vaccinated against influenza

A method for determining venous contribution to BOLD contrast sensory activation

While BOLD contrast reflects haemodynamic changes within capillaries serving neural tissue, it also has a venous component. Studies that have determined the relation of large blood vessels to the activation map indicate that veins are the source of the largest response, and the most delayed in time. It would be informative if the location of these large veins could be extracted from the properties of the functional responses, since vessels are not visible in BOLD contrast images. The present study describes a method for investigating whether measures taken from the functional response can reliably predict vein location, or at least be useful in down-weighting the venous contribution to the activation response, and illustrates this method using data from one subject. We combined fMRI at 3 Tesla with high-resolution anatomical imaging and MR venography to test whether the intrinsic properties of activation time courses corresponded to tissue type. Measures were taken from a gamma fit to the functional response. Mean magnitude showed a significant effect of tissue type (P veins ≈ grey matter > white matter. Mean delays displayed the same ranking across tissue types (P grey matter. However, measures for all tissue types were distributed across an overlapping range. A logistic regression model correctly discriminated 72% of the veins from grey matter in the absence of independent information of macroscopic vessels (ROC=0.72). Whilst tissue classification was not perfect for this subject, weighting the T contrast by the predicted probabilities materially reduced the venous component to the activation map

Marine Pollution in the Caribbean: Not a Minute to Waste

The economic prosperity and sustainable development of the Wider Caribbean Region (WCR), and in particular Small Island Developing States (SIDS), greatly depend on the wealth of resources provided by the oceans. The marine ecosystems of the Caribbean provide food, livelihoods, and income to millions of people through fisheries, tourism, coastal protection, transportation, and resilience to climate change. In 2017, gross revenues from marine and coastal tourism alone were estimated to total US$57 billion. Building a sustainable ocean economy — the Blue Economy — through better and more effective use of marine resources holds enormous potential for income growth, community development, environmental protection, and poverty reduction

S28 peptidases: lessons from a seemingly 'dysfunctional' family of two

<p>Abstract</p> <p>A recent paper in <it>BMC Structural Biology </it>reports the crystal structure of human prolylcarboxypeptidase (PRCP), one of the two members of the S28 peptidase family. Comparison of the substrate-binding site of PRCP with that of its family partner, dipeptidyl dipeptidase 7 (DPP7), helps to explain the different enzymatic activities of these structurally similar proteins, and also reveals a novel apparent charge-relay system in PRCP involving the active-site catalytic histidine.</p> <p>See research article: <url>http://www.biomedcentral.com/1472-6807/10/16/</url></p> <p>Commentary</p> <p>The S28 serine peptidase family is something of an enzymatic odd couple. While showing low sequence similarity to all proteins except each other, the two known family members appear to be at odds functionally; one, prolylcarboxypeptidase (PRCP), is a carboxypeptidase that cleaves single hydrophobic residues from the carboxyl termini of proteins that end with a Pro-X motif (where X is any hydrophobic amino acid), while the other, human dipeptidyl peptidase (DPP7), is an aminopeptidase that cleaves amino-terminal X-Pro dipeptides. The structural basis of this orthogonal specificity would undoubtedly be interesting, and a recent report in <it>BMC Structural Biology </it>from the Merck Global Structural Biology group (Soisson <it>et al</it>. <abbrgrp><abbr bid="B1">1</abbr></abbrgrp>) has now met that expectation. In addition they reveal a new wrinkle to the iconic catalytic triad common to most serine hydrolases.</p> <p>The practical pharmaceutical interest in both these enzymes as potential drug targets is at present speculative. PRCP can inactivate a number of peptide hormones, such as angiotensin II, III and prekallikrein, implicating a role for the enzyme in hypertension, tissue proliferation and smooth-muscle growth. These properties suggest that this enzyme may well be a useful target for hypertension and anti-inflammatory therapy <abbrgrp><abbr bid="B2">2</abbr></abbrgrp>. Another (non-S28 family) dipeptidyl dipeptidase (DPP4) is a major drug target in type 2 diabetes, and Merck has already developed a successful inhibitor of DPP4, the anti-hyperglycemic drug sitagliptin, for the treatment of type 2 diabetes. The DPP enzymes are rich in biological functions and other drug targets emerging from the group are possible <abbrgrp><abbr bid="B3">3</abbr></abbrgrp>.</p

A damage model based on failure threshold weakening

A variety of studies have modeled the physics of material deformation and damage as examples of generalized phase transitions, involving either critical phenomena or spinodal nucleation. Here we study a model for frictional sliding with long range interactions and recurrent damage that is parameterized by a process of damage and partial healing during sliding. We introduce a failure threshold weakening parameter into the cellular-automaton slider-block model which allows blocks to fail at a reduced failure threshold for all subsequent failures during an event. We show that a critical point is reached beyond which the probability of a system-wide event scales with this weakening parameter. We provide a mapping to the percolation transition, and show that the values of the scaling exponents approach the values for mean-field percolation (spinodal nucleation) as lattice size $L$ is increased for fixed $R$. We also examine the effect of the weakening parameter on the frequency-magnitude scaling relationship and the ergodic behavior of the model