12,904 research outputs found

    Stability mapping of bipartite tight-binding graphs with losses and gain: PT{\cal PT}-symmetry and beyond

    Full text link
    We consider bipartite tight-binding graphs composed by NN nodes split into two sets of equal size: one set containing nodes with on-site loss, the other set having nodes with on-site gain. The nodes are connected randomly with probability pp. We give a rationale for the relevance of such "throttle/brake" coupled systems (physically open systems) to grasp the stability issues of complex networks in areas such as biochemistry, neurons or economy, for which their modelling in terms of non-hermitian Hamiltonians is still in infancy. Specifically, we measure the connectivity between the two sets with the parameter α\alpha, which is the ratio of current adjacent pairs over the total number of possible adjacent pairs between the sets. For general undirected-graph setups, the non-hermitian Hamiltonian H(γ,α,N)H(\gamma,\alpha,N) of this model presents pseudo-Hermiticity, where γ\gamma is the loss/gain strength. However, we show that for a given graph setup H(γ,α,N)H(\gamma,\alpha,N) becomes PT{\cal PT}-symmetric. In both scenarios (pseudo-Hermiticity and PT{\cal PT}-symmetric), depending on the parameter combination, the spectra of H(γ,α,N)H(\gamma,\alpha,N) can be real even when it is non-hermitian. Thus, we numerically characterize the average fractions of real and imaginary eigenvalues of H(γ,α,N)H(\gamma,\alpha,N) as a function of the parameter set {γ,α,N}\{\gamma,\alpha,N\}. We demonstrate, for both setups, that there is a well defined sector of the γα\gamma\alpha-plane (which grows with NN) where the spectrum of H(γ,α,N)H(\gamma,\alpha,N) is predominantly real.Comment: 10 pages, 9 figure

    Spectral and localization properties of random bipartite graphs

    Get PDF
    Bipartite graphs are often found to represent the connectivity between the components of many systems such as ecosystems. A bipartite graph is a set of nn nodes that is decomposed into two disjoint subsets, having mm and nmn-m vertices each, such that there are no adjacent vertices within the same set. The connectivity between both sets, which is the relevant quantity in terms of connections, can be quantified by a parameter α[0,1]\alpha\in[0,1] that equals the ratio of existent adjacent pairs over the total number of possible adjacent pairs. Here, we study the spectral and localization properties of such random bipartite graphs. Specifically, within a Random Matrix Theory (RMT) approach, we identify a scaling parameter ξξ(n,m,α)\xi\equiv\xi(n,m,\alpha) that fixes the localization properties of the eigenvectors of the adjacency matrices of random bipartite graphs. We also show that, when ξ10\xi10) the eigenvectors are localized (extended), whereas the localization--to--delocalization transition occurs in the interval 1/10<ξ<101/10<\xi<10. Finally, given the potential applications of our findings, we round off the study by demonstrating that for fixed ξ\xi, the spectral properties of our graph model are also universal.Comment: 17 pages, 10 figure

    Towards an easy-to-use D.S.P

    Get PDF
    The use of digital signal processors is not yet commonly widespread despite their obvious advantages . In this paper we present a certain number of ideas helping case their use. These ideas have been put to work by conceiving the architecture of a processor which is both optimal and easy to use .L'utilisation des processeurs de signaux n'est pas encore très courante, en dépit des avantages qu'ils procurent . Nous présentons ici un certain nombre de réflexions menées dans le sens d'une plus grande facilité d'utilisation de ces processeurs . Ces réflexions ont été concrétisées dans l'élaboration d'une architecture de processeur, à la fois optimisée et d'utilisation aisée

    A comparison of drinking behavior using a harmonized methodology (Liq.In 7) in six countries

    Get PDF
    Purpose: To assess drinking occasions (volume and type) according to consumption with food in or outside meals, and location, for six countries. Methods: A total of 10, 521 participants aged 4–65 years from Argentina, Brazil, China, Indonesia, Mexico and Uruguay completed a validated 7-day fluid intake record. For each drinking event, the volume consumed, the fluid type, the location of intake, and whether the drink was accompanied by food (meal or snack) or not, was recorded. Results: Similar drinking behaviors were found in Mexico and Argentina; fluid intake during meals was 48 and 45% of total fluid intake (TFI), respectively. In Brazil (55%), Indonesia (58%) and China (66%) most fluid was consumed without food. In Uruguay, 34% of TFI was with a main meal, 31% with food between meals and 35% without food. Indonesia had the highest median (25–75th percentile) TFI; 2520 (1750–3347) mL/day, and China the lowest 1138 (818–3347) mL/day. Water was consumed with meals for 37% of Chinese and 87% of Indonesian participants, while the four Latin-American American countries showed a preference for sweet drinks; 54% in Mexico, 67% in Brazil, 55% in Argentina and 59% in Uruguay. Diversity in fluid type was noted when drinking with food between meals. Apart from China, most drinking occasions (> 75%) occurred at home. Conclusions: Three distinct drinking behaviors were identified, namely, drinking with meals, drinking as a stand-alone activity, and a type of ‘grazing’ (i.e., frequent drinks throughout the day) behavior. Most drinking occasions occurred at home

    Fluid intake of Latin American children and adolescents: results of four 2016 LIQ.IN 7 National Cross-Sectional Surveys

    Get PDF
    Purpose: The primary aim of this survey was to report total fluid intake (TFI) and different fluid types for children (4–9 years) and adolescents (10–17 years) in Mexico, Brazil, Argentina and Uruguay. The second aim was to compare TFI with the adequate intake (AI) of water from fluids as recommended by the USA Institute of Medicine. Methods: Data were collected using a validated liquid intake 7-day record (Liq.In7). Participants’ characteristics, including age, sex and anthropometric measurements were recorded. Results: A total of 733 children and 933 adolescents were recruited. Over 75% of children in Uruguay met the IOM’s recommended intake. Fewer children in Argentina (64–72%) and Brazil (41–50%) obtained AI and the lowest values were recorded in Mexico (33–44%), where 16% of boys and 14% girls drank 50% or less of the AI. More adolescents in Argentina (42%) met the AIs than other countries; the lowest was in Mexico (28%). Children and adolescents in Mexico and Argentina drank more sugar sweetened beverages than water. Conclusions: Large numbers of children and adolescents did not meet AI recommendations for TFI, raising concerns about their hydration status and potential effects on mental and physical well-being. Given the negative effects on children’s health, the levels of SSB consumption are worrying

    Model-free Rheo-AFM probes the viscoelasticity of tunable DNA soft colloids

    Get PDF
    Atomic force microscopy rheological measurements (Rheo‐AFM) of the linear viscoelastic properties of single, charged colloids having a star‐like architecture with a hard core and an extended, deformable double‐stranded DNA (dsDNA) corona dispersed in aqueous saline solutions are reported. This is achieved by analyzing indentation and relaxation experiments performed on individual colloidal particles by means of a novel model‐free Fourier transform method that allows a direct evaluation of the frequency‐dependent linear viscoelastic moduli of the system under investigation. The method provides results that are consistent with those obtained via a conventional fitting procedure of the force‐relaxation curves based on a modified Maxwell model. The outcomes show a pronounced softening of the dsDNA colloids, which is described by an exponential decay of both the Young's and the storage modulus as a function of the salt concentration within the dispersing medium. The strong softening is related to a critical reduction of the size of the dsDNA corona, down to ≈70% of its size in a salt‐free solution. This can be correlated to significant topological changes of the dense star‐like polyelectrolyte forming the corona, which are induced by variations in the density profile of the counterions. Similarly, a significant reduction of the stiffness is obtained by increasing the length of the dsDNA chains, which we attribute to a reduction of the DNA density in the outer region of the corona

    Assessment of nutritional status and bone health in neurologically impaired children: a challenge in pediatric clinical practice

    Get PDF
    NTRODUCTION: neurologically impaired children frequently experience nutritional disorders and bone health complications. Our aim was firstly to analyze a method to interpret bone mineral density (BMD) accurately in neurologically impaired children. Secondly, to determine its relationship with the nutritional status and micronutrient levels in order to identify which factors are associated with low BMD. METHODS: a observational multicenter study was conducted in children with moderate-to-severe neurological impairment. Data collected included: medical records, anthropometric measures, hematologic and biochemical evaluation. BMD was measured with Dual-energy X-ray absorptiometry and z-scores were calculated adjusting for sex and chronological age. Secondly, BMD z-scores were calculated applying height age (age at which the child's height would be in 2nd percentile) instead of chronological age. RESULTS: fifty-two children were included (aged 4-16 years). Seventeen patients (32.7%) received feeding by gastrostomy tube. Height and BMI z-score were below 2SD in 64% and 31% of patients respectively, with normal mid upper arm circumference and skinfold thickness measurements. Low vitamin-D levels were found in 42% of cases. 50% of patients evidenced low BMD when calculated for chronological age, whereas only 34.5% showed BMD z-score <-2 when calculated for height age. No correlation was observed between BMD and vitamin-D levels, weight and height z-scores or age when BMD was calculated applying height age. CONCLUSIONS: the prevalence of low BMD is high in neurologically impaired children, and it is probably multifactorial. In these children, we suggest adjusting BMD for height age, in order not to over diagnose low BMD

    Fluid intake of children, adolescents and adults in Indonesia: results of the 2016 Liq.In7 national cross-sectional survey

    Get PDF
    Purpose: To report daily total fluid intake (TFI) and fluid types in Indonesia according to age, sex, socio-economic status (SES) and geographic region, and compare TFI with the Indonesian adequate fluid intake (AI) recommendations. Methods: Data were collected in 32 cities over nine regions from children (4–9 years, n = 388), adolescents, (10–17 years, n = 478) and adults (18–65 years, n = 2778) using a fluid intake 7-day record (Liq.In7); socio-economic status was also recorded. The 7-day mean TFIs were compared with the AI of water set by the Ministry of Health of the Republic of Indonesia. Results: Total median fluid intakes for all age groups exceeded 2000 mL/day. At population level, TFI was associated with household income (P &lt; 0.001), education (P &lt; 0.001) and Indonesian geographical regions (P &lt; 0.001). More than 67% of participants met the AI of water from fluids. A higher percentage of children and adolescents met the AI (78 and 80%, respectively), compared with adults (72%). Drinking water was the main contributor to TFI in all age groups (76–81%). Sugar-sweetened beverages (SSB) were consumed by 62% children, 72% adolescents and 61% of adults. An SSB intake = 1 serving per day was observed for 24% children, 41% adolescents and 33% adults. Conclusions: A high percentage of the population drank enough to meet the AI of water from fluids. Water was the most frequently consumed drink; however, many participants consumed at least one serving of SSB per day. This study provides data to help direct targeted intervention programs

    Fluid intake of Latin American adults: results of four 2016 Liq.In7 national cross-sectional surveys

    Get PDF
    Purpose: To report total fluid intake (TFI) and the intake of different fluid types in adults (= 18 years old) from Mexico, Argentina, Brazil and Uruguay. To compare intakes between countries and with recommended adequate intake (AI) of water from fluids. Methods: Cross-sectional data were collected using a validated liquid intake 7-day record (Liq.In7) in populations from Argentina (n = 1089), Brazil (n = 477), Mexico (n = 1677) and Uruguay (n = 554). Population characteristics, including age, gender, body mass index and socioeconomic level were recorded. Mean TFI was compared with the AI of water from fluids set by the USA Institute of Medicine. Results: The lowest TFI was recorded in Mexican women (1748 mL/day) and the highest in Argentinean men (2318 mL/day). Median daily TFI was significantly different between countries; Uruguay and Argentina had higher values than Mexico and Brazil. In the former, plain water contributed to only 25% of TFI, the remainder being predominantly from hot beverages. Approximately, a third of adults did not drink enough fluid to meet the recommended AI. High SSB consumption was reported, which was significantly different between countries (p &lt; 0.05), the highest being in Mexico (median 25–75th percentiles): 531 (300–895 mL/day. Conclusions: This survey highlights the need to increase water consumption and reduce SSB intake in this region to avoid potential associated health risks. These findings may be useful information in monitoring public health policy strategies

    Fluid intake in urban China: results of the 2016 Liq.In 7 national cross-sectional surveys

    Get PDF
    Purpose: To describe total fluid intake (TFI) and types of fluid consumed in urban China by age, gender, regions and city socioeconomic status relative to the adequate intakes (AI) set by the Chinese Nutrition Society. Methods: In 2016, participants aged 4–9, 10–17 and 18–55 years were recruited via a door-to-door approach in 27 cities in China. In total, 2233 participants were included. The volumes and sources of TFI were collected using the Liq.In7 record, assisted by a photographic booklet of standard fluid containers. Results: The mean daily TFI among children, adolescents and adults were 966, 1177 and 1387 mL, respectively. In each age group, TFI was significantly higher in male vs female (981 vs 949, 1240 vs 1113, 1442 vs 1332; mL). Approximately 45, 36 and 28% of children, adolescents and adults reached the AI. Although plain water was the highest contributor to TFI, the contribution of sugar sweetened beverages (SSB) was ranked in the top three together with water and milk and derivatives. Approximately 27, 48 and 47% of children, adolescents and adults consumed more than one serving of SSB per day, respectively. Conclusions: A relatively large proportion of participants did not drink enough to meet the AI in urban China. Many children, adolescents and adults consumed more than one serving of SSB per day. A majority of children, adolescents and adults in the study population do not meet both quantitative and qualitative fluid intake requirements, and signal socioeconomic disparities