Scaling near Quantum Chaos Border in Interacting Fermi Systems

The emergence of quantum chaos for interacting Fermi systems is investigated by numerical calculation of the level spacing distribution $P(s)$ as function of interaction strength $U$ and the excitation energy $\epsilon$ above the Fermi level. As $U$ increases, $P(s)$ undergoes a transition from Poissonian (nonchaotic) to Wigner-Dyson (chaotic) statistics and the transition is described by a single scaling parameter given by $Z = (U \epsilon^{\alpha}-u_0) \epsilon^{1/2\nu}$, where $u_0$ is a constant. While the exponent $\alpha$, which determines the global change of the chaos border, is indecisive within a broad range of $0.9 \sim 2.0$, finite value of $\nu$, which comes from the increase of the Fock space size with $\epsilon$, suggests that the transition becomes sharp as $\epsilon$ increases.Comment: 4 pages, 4 figures, to appear in Phys. Rev. E (Rapid Communication

Heat flux operator, current conservation and the formal Fourier's law

By revisiting previous definitions of the heat current operator, we show that one can define a heat current operator that satisfies the continuity equation for a general Hamiltonian in one dimension. This expression is useful for studying electronic, phononic and photonic energy flow in linear systems and in hybrid structures. The definition allows us to deduce the necessary conditions that result in current conservation for general-statistics systems. The discrete form of the Fourier's Law of heat conduction naturally emerges in the present definition

Prognostics health management: perspectives in engineering systems reliability prognostics

The Prognostic Health Management (PHM) has been asserting itself as the most promising methodology to enhance the effective reliability and availability of a product or system during its life-cycle conditions by detecting current and approaching failures, thus, providing mitigation of the system risks with reduced logistics and support costs. However, PHM is at an early stage of development, it also expresses some concerns about possible shortcomings of its methods, tools, metrics and standardization. These factors have been severely restricting the applicability of PHM and its adoption by the industry. This paper presents a comprehensive literature review about the PHM main general weaknesses. Exploring the research opportunities present in some recent publications, are discussed and outlined the general guide-lines for finding the answer to these issues.(undefined

A longitudinal assessment of chronic periodontitis in Australian adults

Aim: The study aimed to estimate the incidence/progression and reversal of chronic periodontitis and to identify factors associated with chronic periodontitis in Australian adults over a 12-year period. Materials and Methods: Data were obtained from the longitudinal component of the National Study of Adult Oral Health (NSAOH) in 2004–2006, and repeated data, among the same adults, in 2017–2018. NSAOH 2004–2006 was a population-based study of Australian adults aged 15+ years. The American Academy of Periodontology/European Federation of Periodontology case definitions were used, and then compared with two other case definitions. Multivariable Poisson regression models were used to estimate incidence rate ratios (IRRs) and reversal rate ratio (RRRs) of periodontitis. Results: A total of 775 dentate Australian adults had dental examinations at both times. The proportion of incidence/progression and reversal among Australian adults was 56.4% and 11.0%, respectively. Tobacco smokers presented with more than three times higher incidence (IRR: 3.32, 95% CI: 1.50–7.60) and lower reversals (RRR: 0.94, 95% CI: 0.39–0.98) than those who had never smoked. Cessation of smoking was positively associated with periodontitis reversal. The total incidence/progression was 471.7/10,000 person-years, with reversal being 107.5/10,000 person-years. The average number of teeth lost due to periodontal disease was 1.9 in 2017–2018. Being male and not having periodontal treatment were significant risk markers for the incidence/progression of periodontitis. Conclusion: Smoking is a risk factor for periodontitis. Cessation of smoking is an effective means of reducing the incidence and progression of chronic periodontitis, to reduce the risk of tooth loss, and to improve overall periodontal health.Xiangqun Ju | Gloria Mejia | Sergio Chrisopoulos | Liana Luzzi | Lisa M. Jamieso

A Longitudinal Study of Chronic Periodontitis in Two Cohorts of Community-Dwelling Elderly Australians.

Background: The study aimed to estimate and compare the incidence and progression of chronic periodontitis among two generations of older Australian adults. Methods: Data were from two population-based cohort studies of Australian older adults aged 60+ years South Australian Dental Longitudinal Studies (SADLS), SADLS I (1991–1992) and SADLS II (2013–2014). American Academy of Periodontology/the U.S. Centres for Disease Control and Prevention (CDC/AAP), and the 2018 European Federation of Periodontology classification (EFP/AAP) case definitions were used to define and calculate the incidence and progression of chronic periodontitis. Multivariable Poisson regression models were used to estimate incidence risk ratios (IRRs) of periodontitis. Results: A total 567 and 201 dentate respondents had periodontal exams in SADLS I and II, respectively. The incidence rate was greater in SADLS II than in SADLS I, approximately 200 vs. 100/1000 person years, respectively. Current smokers had more than two times higher IRRs, 2.38 (1.30–4.34) and 2.30 (1.24–4.26), than their non-smoking counterparts in the previous generation under the CDC/AAP and EFP/AAP, respectively. Conclusions: The most recent generation of older adults has greater incidence and progression of periodontitis than the previous generation. Being a current tobacco smoker was a significant risk factor for both the incidence and progression of periodontitis.Xiangqun Ju, Jane Harford, Liana Luzzi, Gloria Mejia, and Lisa M. Jamieso

Cdkn2a deficiency promotes adipose tissue browning.

Genome-wide association studies have reported that DNA polymorphisms at the CDKN2A locus modulate fasting glucose in human and contribute to type 2 diabetes (T2D) risk. Yet the causal relationship between this gene and defective energy homeostasis remains elusive. Here we sought to understand the contribution of Cdkn2a to metabolic homeostasis. We first analyzed glucose and energy homeostasis from Cdkn2a-deficient mice subjected to normal or high fat diets. Subsequently Cdkn2a-deficient primary adipose cells and human-induced pluripotent stem differentiated into adipocytes were further characterized for their capacity to promote browning of adipose tissue. Finally CDKN2A levels were studied in adipocytes from lean and obese patients. We report that Cdkn2a deficiency protects mice against high fat diet-induced obesity, increases energy expenditure and modulates adaptive thermogenesis, in addition to improving insulin sensitivity. Disruption of Cdkn2a associates with increased expression of brown-like/beige fat markers in inguinal adipose tissue and enhances respiration in primary adipose cells. Kinase activity profiling and RNA-sequencing analysis of primary adipose cells further demonstrate that Cdkn2a modulates gene networks involved in energy production and lipid metabolism, through the activation of the Protein Kinase A (PKA), PKG, PPARGC1A and PRDM16 signaling pathways, key regulators of adipocyte beiging. Importantly, CDKN2A expression is increased in adipocytes from obese compared to lean subjects. Moreover silencing CDKN2A expression during human-induced pluripotent stem cells adipogenic differentiation promoted UCP1 expression. Our results offer novel insight into brown/beige adipocyte functions, which has recently emerged as an attractive therapeutic strategy for obesity and T2D. Modulating Cdkn2a-regulated signaling cascades may be of interest for the treatment of metabolic disorders

Low energy transition in spectral statistics of 2D interactingfermions

We study the level spacing statistics $P(s)$ and eigenstate properties of spinless fermions with Coulomb interaction on a two dimensional lattice at constant filling factor and various disorder strength. In the limit of large lattice size, $P(s)$ undergoes a transition from the Poisson to the Wigner-Dyson distribution at a critical total energy independent of the number of fermions. This implies the emergence of quantum ergodicity induced by interaction and delocalization in the Hilbert space at zero temperature.Comment: revtex, 5 pages, 4 figures; new data for eigenfunctions are adde