An Application of 3-D Kinematical Conservation Laws: Propagation of a 3-D Wavefront

Three-dimensional (3-D) kinematical conservation laws (KCL) are equations of evolution of a propagating surface Omega(t) in three space dimensions. We start with a brief review of the 3-D KCL system and mention some of its properties relevant to this paper. The 3-D KCL, a system of six conservation laws, is an underdetermined system to which we add an energy transport equation for a small amplitude 3-D nonlinear wavefront propagating in a polytropic gas in a uniform state and at rest. We call the enlarged system of 3-D KCL with the energy transport equation equations of weakly nonlinear ray theory (WNLRT). We highlight some interesting properties of the eigenstructure of the equations of WNLRT, but the main aim of this paper is to test the numerical efficacy of this system of seven conservation laws. We take several initial shapes for a nonlinear wavefront with a suitable amplitude distribution on it and let it evolve according to the 3-D WNLRT. The 3-D WNLRT is a weakly hyperbolic 7 x 7 system that is highly nonlinear. Here we use the staggered Lax-Friedrichs and Nessyahu-Tadmor central schemes and have obtained some very interesting shapes of the wavefronts. We find the 3-D KCL to be suitable for solving many complex problems for which there presently seems to be no other method capable of giving such physically realistic features.

Optimal infinite-horizon feedback laws for a general class of constrained discrete-time systems: stability and moving-horizon approximations

Stability results are given for a class of feedback systems arising from the regulation of time-varying discrete-time systems using optimal infinite-horizon and moving-horizon feedback laws. The class is characterized by joint constraints on the state and the control, a general nonlinear cost function and nonlinear equations of motion possessing two special properties. It is shown that weak conditions on the cost function and the constraints are sufficient to guarantee uniform asymptotic stability of both the optimal infinite-horizon and movinghorizon feedback systems. The infinite-horizon cost associated with the moving-horizon feedback law approaches the optimal infinite-horizon cost as the moving horizon is extended.

Eigenvalues of kinematical conservation laws (KCL) based 3-D weakly nonlinear ray theory (WNLRT)

System of kinematical conservation laws (KCL) govern evolution of a curve in a plane or a surface in space, even if the curve or the surface has singularities on it. In our recent publication K. R. Arun, P. Prasad, 3-D kinematical conservation laws (KCL): evolution of a surface in R-3-in particular propagation of a nonlinear wavefront, Wave Motion 46 (2009) 293-311] we have developed a mathematical theory to study the successive positions and geometry of a 3-D weakly nonlinear wavefront by adding an energy transport equation to KCL. The 7 x 7 system of equations of this KCL based 3-D weakly nonlinear ray theory (WNLRT) is quite complex and explicit expressions for its two nonzero eigenvalues could not be obtained before. In this short note, we use two different methods: (i) the equivalence of KCL and ray equations and (ii) the transformation of surface coordinates, to derive the same exact expressions for these eigenvalues. The explicit expressions for nonzero eigenvalues are important also for checking stability of any numerical scheme to solve 3-D WNLRT. (C) 2010 Elsevier Inc. All rights reserved.

Dietary aspects of cow's milk allergy in young children

Cow s milk allergy (CMA) affects about 2-6% of infants and young children. Environmental factors during early life are suggested to play a role in the development of allergic diseases. One of these factors is likely to be maternal diet during pregnancy and lactation. The association between maternal diet and development of CMA in offspring is not well known, but diet could contain factors that facilitate development of tolerance. After an established food allergy, another issue is gaining tolerance towards an antigen that causes symptoms. The strictness of the elimination depends on the individual level of tolerance. This study aimed at validating a questionnaire used to inquire about food allergies in children, at researching associations between maternal diet during pregnancy and lactation and subsequent development of cow s milk allergy in the offspring, and at evaluating the degree of adherence to a therapeutic elimination diet of children with CMA and factors associated with the adherence and age of recovery. These research questions were addressed in a prospective birth cohort born between 1997 and 2004 at the Tampere and Oulu University Hospitals. Altogether 6753 children of the Diabetes Prediction and Prevention (DIPP) Nutrition cohort were investigated. Questionnaires regarding allergic diseases are often used in studies without validation. High-quality valid tools are therefore needed. Two validation studies were conducted here: one by comparing parentally reported food allergies with information gathered from patient records of 1122 children, and the other one by comparing parentally reported CMA with information in the reimbursement records of special infant formulae in the registers of the Social Insurance Institution for 6753 children. Both of these studies showed that the questionnaire works well and is a valid tool for measuring food allergies in children. In the first validation study, Cohen s kappa values were within 0.71-0.88 for CMA, 0.74-0.82 for cereal allergy, and 0.66-0.86 for any reported food allergy. In the second validation study, the kappa value was 0.79, sensitivity 0.958, and specificity 0.965 for reported and diagnosed CMA. To investigate the associations between maternal diet during pregnancy and lactation and CMA in offspring, 6288 children were studied. Maternal diet during pregnancy (8th month) and lactation (3rd month) was assessed by a validated, 181-item semi-quantitative food frequency questionnaire (FFQ), and as an endpoint register-based information on diagnosed CMA was obtained from the Social Insurance Institution and complemented with parental reports of CMA in their children. The associations between maternal food consumption and CMA in offspring were analyzed by logistic regression comparing the highest and lowest quarters with two middle quarters of consumption and adjusted for several potential confounding factors. High maternal intake of milk products (OR 0.56, 95% CI 0.37-0.86 p = 0.002) was associated with a lower risk of CMA in offspring. When stratified according to maternal allergic rhinitis or asthma, a protective association of high use of milk products with CMA was seen in children of allergy-free mothers (OR 0.30, 95% CI 0.13 - 0.69, p < 0.001), but not in children of allergic mothers. Moreover, low maternal consumption of fish during pregnancy was associated with a higher risk of CMA in children of mothers with allergic rhinitis or asthma (OR 1.47, 95% CI 0.96 - 2.27 for the lowest quarter, p = 0.043). In children of nonallergic mothers, this association was not seen. Maternal diet during lactation was not associated with CMA in offspring, apart from an inverse association between citrus and kiwi fruit consumption and CMA. These results imply that maternal diet during pregnancy may contain factors protective against CMA in offspring, more so than maternal diet during lactation. These results need to be confirmed in other studies before giving recommendations to the public. To evaluate the degree of adherence to a therapeutic elimination diet in children with diagnosed CMA, food records of 267 children were studied. Subsequent food records were examined to assess the age at reintroduction of milk products to the child s diet. Nine of ten families adhered to the elimination diet of the child with extreme accuracy. Older and monosensitized children had more often small amounts of cow s milk protein in their diet (p < 0.001 for both). Adherence to the diet was not related to any other sociodemographic factor studied or to the age at reintroduction of milk products to the diet. Low intakes of vitamin D, calcium, and riboflavin are of concern in children following a cow s milk-free diet. In summary, we found that the questionnaires used in the DIPP study are valid in investigating CMA in young children; that there are associations between maternal diet during pregnancy and lactation and the development of CMA in offspring; and that the therapeutic elimination diet in children with diagnosed CMA is rigorously adhered to.

Control of Agent Swarms using Generalized Centroidal Cyclic Pursuit Laws

One of the major tasks in swarm intelligence is to design decentralized but homogenoeus strategies to enable controlling the behaviour of swarms of agents. It has been shown in the literature that the point of convergence and motion of a swarm of autonomous mobile agents can be controlled by using cyclic pursuit laws. In cyclic pursuit, there exists a predefined cyclic connection between agents and each agent pursues the next agent in the cycle. In this paper we generalize this idea to a case where an agent pursues a point which is the weighted average of the positions of the remaining agents. This point correspond to a particular pursuit sequence. Using this concept of centroidal cyclic pursuit, the behavior of the agents is analyzed such that, by suitably selecting the agents' gain, the rendezvous point of the agents can be controlled, directed linear motion of the agents can be achieved, and the trajectories of the agents can be changed by switching between the pursuit sequences keeping some of the behaviors of the agents invariant. Simulation experiments are given to support the analytical proofs.

Making Music, Making Muslims : A Case Study of Islamic Hip Hop and the Discursive Construction of Muslim Identities on the Internet

Hip-hopin juuret juontavat 1970-luvulle Yhdysvaltoihin, mutta hip-hop-kulttuuri ja musiikkityyli ovat sen jälkeen levinneet ympäri maailmaa osana globalisaatiokehitystä. Myös monet nuoret muslimit tekevät nykyään hip-hop-musiikkia, ja yhä useampi tuo myös sanoituksiinsa vaikutteita Islamista ja elämästään muslimina. Musiikin asema on islamissa varsin kiistelty, eikä sitä ole selvästi sallittu (halal) tai kielletty (haram) muslimeilta. Muslimien tekemää hip-hoppia on toistaiseksi tutkittu hyvin vähän. Tutkielmassa tarkastellaan diskurssianalyysin keinoin, miten tapaustutkimuksena toimivalla muslimhiphop.com-internetsivustolla argumentoidaan ja konstruoidaan käsityksiä muslimi-identiteetistä. Teoreettisena ja analyyttisenä viitekehyksenä toimii sosiaalikonstruktivistinen näkemys identiteetistä kontekstisidonnaisena sekä puheessa ja teksteissä diskursiivisesti rakentuvana. Tutkielma kyseenalaistaa aiempien tutkimusten oletuksen hip-hopista vaikutuksiltaan yksinomaan positiivisena muslimi-identiteetille sekä muslimeja yhdentävänä tekijänä. Aineisto on kerätty edellä mainitulta sivustolta syksyn 2010 ja kevään 2011 aikana, josta analyysiin on rajattu vain itse sivusto ja sen hip-hoppia käsittelevät osiot. Sivusto ja sen perustaja ovat yhdysvaltalaisia, mutta sivustolla esiteltävien artistien tausta on hyvin monikulttuurinen. Moni on myös maahanmuuttajana nykyisessä kotimaassaan. Aineistossa esiintyviä teemoja ja diskursseja eritellään ja analysoidaan tutkielmassa lainauksien avulla. Sivuston periaatteissa ja artistien esillepääsyn kriteereissä määritellään tarkasti asennoituminen Islamin ja musiikin yhdistämiseen: mikäli sanoitukset ja artistit noudattavat Islamin oppeja, on muslimin sallittua tehdä ja kuunnella tällaista musiikkia. Islam-aiheisen hip-hopin perustellaan olevan ennen kaikkea vaihtoehto valtavirran hip-hopille, jota konstruoidaan aineistossa moraalisesti arveluttavaksi. Hip-hopille sekä muslimeille sallittuja ja kiellettyjä elementtejä erottelevan halal-haram-diskurssin ohella aineistosta nousee esiin opetusdiskurssi. Muslimien tekemän hip-hopin perustellaan edistävän Islamin opettamista erityisesti nuorille muslimeille ja siten vahvistavan positiivista muslimi-identiteettiä. Myös positiivisen muutoksen diskurssia käytetään aineistossa runsaasti liittyen mm. muslimiyhteisöihin sekä muslimeihin kohdistuviin taloudellisiin ja sosiaalipoliittisiin epäkohtiin ja stereotypioihin; musiikin sisältöä ja sen tekemistä perustellaan sen voimalla muuttaa asioita parempaan suuntaan. Monet muslimiartistit kamppailevat yhdistääkseen toisaalta Islamin ja taiteellisen luovuuden ja ilmaisuvapauden, toisaalta menestyäkseen kaupallisesti unohtamatta uskonnollista vakaumustaan. Monilla heistä hip-hop on ollut vahvasti läsnä kasvuympäristössä, mutta sen yhdistäminen Islamin periaatteisiin aiheuttaa kysymyksiä ja kyseenalaistuksia oman musiikillisen ja uskonnollisen identiteetin muodosta ja sisällöstä. Aineiston perusteella monet muslimiartistit ja Islam-aiheista hip-hoppia kuuntelevat muslimit joutuvat jatkuvasti puolustamaan musiikkia siihen kielteisesti suhtautuville muslimeille sekä ei-muslimeille, jotka vierastavat sen uskonnollisuutta. Muslimi-identiteettiä neuvotellaan jatkuvasti, ja se näyttäytyy aineistossa moniulotteisena ja tilanteisesti rakentuvana. Avainsanat: Muslimit, Islam, hip-hop, identiteetti, Internet, diskurssi, diskurssianalyysi

Dietary habits and obesity: the role of emotional and cognitive factors

In post-industrialised societies, food is more plentiful, accessible and palatable than ever before and technological development has reduced the need for physical activity. Consequently, the prevalence of obesity is increasing, which is problematic as obesity is related to a number of diseases. Various psychological and social factors have an important influence on dietary habits and the development of obesity in the current food-rich and sedentary environments. The present study concentrates on the associations of emotional and cognitive factors with dietary intake and obesity as well as on the role these factors play in socioeconomic disparities in diet. Many people cognitively restrict their food intake to prevent weight gain or to lose weight, but research on whether restrained eating is a useful weight control strategy has produced conflicting findings. With respect to emotional factors, the evidence is accumulating that depressive symptoms are related to less healthy dietary intake and obesity, but the mechanisms explaining these associations remain unclear. Furthermore, it is not fully understood why socioeconomically disadvantaged individuals tend to have unhealthier dietary habits and the motives underlying food choices (e.g., price and health) could be relevant in this respect. The specific aims of the study were to examine 1) whether obesity status and dieting history moderate the associations of restrained eating with overeating tendencies, self-control and obesity indicators; 2) whether the associations of depressive symptoms with unhealthier dietary intake and obesity are attributable to a tendency for emotional eating and a low level of physical activity self-efficacy; and 3) whether the absolute or relative importance of food choice motives (health, pleasure, convenience, price, familiarity and ethicality) contribute to the socioeconomic disparities in dietary habits. The study was based on a large population-based sample of Finnish adults: the participants were men (N=2325) and women (N=2699) aged 25-74 who took part in the DILGOM (Dietary, Lifestyle and Genetic Determinants of Obesity and Metabolic Syndrome) sub-study of the National FINRISK Study 2007. The participants weight, height, waist circumference and body fat percentage were measured in a health examination. Psychological eating styles (the Three-Factor Eating Questionnaire-R18), food choice motives (a shortened version of the Food Choice Questionnaire), depressive symptoms (the Center for Epidemiological Studies Depression Scale) and self-control (the Brief Self-Control Scale) were measured with pre-existing questionnaires. A validated food frequency questionnaire was used to assess the average consumption of sweet and non-sweet energy-dense foods and vegetables/fruit. Self-reported total years of education and gross household income were used as indicators of socioeconomic position. The results indicated that 1) restrained eating was related to a lower body mass index, waist circumference, emotional eating and uncontrolled eating, and to a higher self-control in obese participants and current/past dieters. In contrast, the associations were the opposite in normal weight individuals and those who had never dieted. Thus, restrained eating may be related to better weight control among obese individuals and those with dieting experiences, while among others it may function as an indicator of problems with eating and an attempt to solve them. 2) Emotional eating and depressive symptoms were both related to less healthy dietary intake, and the greater consumption of energy-dense sweet foods among participants with elevated depressive symptoms was attributable to the susceptibility for emotional eating. In addition, emotional eating and physical activity self-efficacy were both important in explaining the positive association between depressive symptoms and obesity. 3) The lower vegetable/fruit intake and higher energy-dense food intake among individuals with a low socioeconomic position were partly explained by the higher priority they placed on price and familiarity and the lower priority they gave to health motives in their daily food choices. In conclusion, although policy interventions to change the obesogenic nature of the current environment are definitely needed, knowledge of the factors that hinder or facilitate people s ability to cope with the food-rich environment is also necessary. This study implies that more emphasis should be placed on various psychological and social factors in weight control programmes and interventions.

Stable carbon isotope ratios in Asian elephant collagen: implications for dietary studies

Stable carbon isotope ratios in bone collagen have been used in a variety of dietary studies in modern and fossil animals, including humans. Inherent in the stable isotope technique is the assumption that the isotopic signature is a reflection of the diet and is persistent in collagen because this is a relatively inert protein. Carbon isotope analyses of bones from a southern Indian population of Asian elephant (Elephas maximus), a long-lived mammal that alternates seasonally between a predominantly C3 (browse) and C4 (grass) plant diet, showed two patterns that have important implications for dietary interpretation based on isotopic studies. Relative to the quantity of the two plant types consumed on average, the ?13C signal in collagen indicated that more carbon was incorporated from C3 plants, possibly due to their higher protein contribution. There was a much greater variance in ?13C values of collagen in sub-adult (range -10.5� to-22.7�, variance=14.51) compared to adult animals (range -16.0� to -20.3�, variance=1.85) pointing to high collagen turnover rates and non-persistent isotopic signatures in younger, growing animals. It thus seems important to correct for any significant relative differences in nutritive value of food types and also consider the age of an animal before drawing definite conclusions about its diet from isotope ratios.

Limit Laws for Coverage in Backbone-Sensor Networks

We study the coverage in sensor networks having two types of nodes, sensor and backbone nodes. Each sensor is capable of transmitting information over relatively small distances. The backbone nodes collect information from the sensors. This information is processed and communicated over an ad-hoc network formed by the backbone nodes,which are capable of transmitting over much larger distances. We consider two modes of deployment of sensors, one a Poisson-Poisson cluster model and the other a dependently-thinned Poisson point process. We deduce limit laws for functionals of vacancy in both models using properties of association for random measures.

Universality of scaling laws in correlation between velocity and shear stress in turbulent boundary layers

In this study, we analyse simultaneous measurements (at 50 Hz) of velocity at several heights and shear stress at the surface made during the Utah field campaign for the presence of ranges of scales, where distinct scale-to-scale interactions between velocity and shear stress can be identified. We find that our results are similar to those obtained in a previous study [Venugopal et al., 2003] (contrary to the claim in V2003, that the scaling relations might be dependent on Reynolds number) where wind tunnel measurements of velocity and shear stress were analysed. We use a wavelet-based scale-to-scale cross-correlation to detect three ranges of scales of interaction between velocity and shear stress, namely, (a) inertial subrange, where the correlation is negligible; (b) energy production range, where the correlation follows a logarithmic law; and (c) for scales larger than the boundary layer height, the correlation reaches a plateau.