Self-sustained clusters and ergodicity breaking in spin models

Self-sustained spin clusters are analytically linked to ergodicity breaking in fully connected Ising and Sherrington-Kirkpatick (SK) models, relating the less understood spin space to the well understood state space. This correspondence is established through the absence of clusters in the paramagnetic phase, the presence of one dominant cluster in the Ising ferromagnet, and the formation of nontrivial clusters in SK spin glass. Yet unobserved phenomena are also revealed such as a first order phase transition in cluster sizes in the SK ferromagnet. The method could be adapted to investigate other spin models

From the physics of interacting polymers to optimizing routes on the London Underground

Optimizing paths on networks is crucial for many applications, ranging from subway traffic to Internet communication. Because global path optimization that takes account of all path choices simultaneously is computationally hard, most existing routing algorithms optimize paths individually, thus providing suboptimal solutions. We use the physics of interacting polymers and disordered systems to analyze macroscopic properties of generic path optimization problems and derive a simple, principled, generic, and distributed routing algorithm capable of considering all individual path choices simultaneously. We demonstrate the efficacy of the algorithm by applying it to: (i) random graphs resembling Internet overlay networks, (ii) travel on the London Underground network based on Oyster card data, and (iii ) the global airport network. Analytically derived macroscopic properties give rise to insightful new routing phenomena, including phase transitions and scaling laws, that facilitate better understanding of the appropriate operational regimes and their limitations, which are difficult to obtain otherwise

Coverage versus supply cost in facility location:physics of frustrated spin systems

A comprehensive coverage is crucial for communication, supply, and transportation networks, yet it is limited by the requirement of extensive infrastructure and heavy energy consumption. Here, we draw an analogy between spins in antiferromagnet and outlets in supply networks, and apply techniques from the studies of disordered systems to elucidate the effects of balancing the coverage and supply costs on the network behavior. A readily applicable, coverage optimization algorithm is derived. Simulation results show that magnetized and antiferromagnetic domains emerge and coexist to balance the need for coverage and energy saving. The scaling of parameters with system size agrees with the continuum approximation in two dimensions and the tree approximation in random graphs. Due to frustration caused by the competition between coverage and supply cost, a transition between easy and hard computation regimes is observed. We further suggest a local expansion approach to greatly simplify the message updates which shed light on simplifications in other problems

Entropy inflection and invisible low-energy states: Defensive alliance example

Lower temperature leads to a higher probability of visiting low-energy states. This intuitive belief underlies most physics-inspired strategies for addressing hard optimization problems. For instance, the popular simulated annealing (SA) dynamics is expected to approach a ground state if the temperature is lowered appropriately. Here, we demonstrate that this belief is not always justified. Specifically, we employ the cavity method to analyze the minimum strong defensive alliance problem and discover a bifurcation in the solution space, induced by an inflection point in the entropy-energy profile. While easily accessible configurations are associated with the lower-free-energy branch, the low-energy configurations are associated with the higher-free-energy branch within the same temperature range. There is a discontinuous phase transition between the high-energy configurations and the ground states, which generally cannot be followed by SA. We introduce an energy-clamping strategy to obtain superior solutions by following the higher-free-energy branch, overcoming the limitations of SA

Elevated plasma TGF-β1 levels in patients with chronic obstructive pulmonary disease

SummaryBackgroundTransforming growth factor-β1 (TGF-β1), a multifunctional cytokine, has been implicated to be responsible for the increased deposition of extracellular matrix in the airways, and increased submucosal collagen expression in chronic obstructive pulmonary disease (COPD). We determined plasma TGF-β1 levels in patients with COPD and explored its association with common functional polymorphisms of TGF-β1 gene at C-509T and T869C in the development of COPD in a case–control study.MethodsStable COPD patients who were ever smokers, and age and pack-years smoked matched healthy controls (n = 205 in each group) were recruited for measurement of plasma TGF-β1 levels using commercially available ELISA kit, and genotyped at C-509T and T869C functional polymorphisms of TGF-β1 gene using polymerase chain reaction and restriction fragment length polymorphism (PCR–RFLP).ResultsCOPD patients had significantly elevated plasma TGF-β1 levels in comparison to healthy controls irrespective of the genotypes. Allele frequencies and genotype distributions at both polymorphic sites were not different among COPD patients or controls. TGF-β1 levels were inversely correlated (Pearson's correlation analysis) with FEV1 (% predicted) (p < 0.001) and FVC (% predicted) (p < 0.001).ConclusionThe findings of elevated plasma TGF-β1 levels in patients with COPD suggest that TGF-β1 may play a role in COPD pathogenesis. The C-509T and T869C functional polymorphisms of TGF-β1 gene do not represent a genetic predisposition to COPD susceptibility in Hong Kong Chinese patients

Networking - A Statistical Physics Perspective

Efficient networking has a substantial economic and societal impact in a broad range of areas including transportation systems, wired and wireless communications and a range of Internet applications. As transportation and communication networks become increasingly more complex, the ever increasing demand for congestion control, higher traffic capacity, quality of service, robustness and reduced energy consumption require new tools and methods to meet these conflicting requirements. The new methodology should serve for gaining better understanding of the properties of networking systems at the macroscopic level, as well as for the development of new principled optimization and management algorithms at the microscopic level. Methods of statistical physics seem best placed to provide new approaches as they have been developed specifically to deal with non-linear large scale systems. This paper aims at presenting an overview of tools and methods that have been developed within the statistical physics community and that can be readily applied to address the emerging problems in networking. These include diffusion processes, methods from disordered systems and polymer physics, probabilistic inference, which have direct relevance to network routing, file and frequency distribution, the exploration of network structures and vulnerability, and various other practical networking applications.Comment: (Review article) 71 pages, 14 figure

Early rheumatoid arthritis is characterized by a distinct and transient synovial fluid cytokine profile of T cell and stromal cell origin

Pathological processes involved in the initiation of rheumatoid synovitis remain unclear. We undertook the present study to identify immune and stromal processes that are present soon after the clinical onset of rheumatoid arthritis ( RA) by assessing a panel of T cell, macrophage, and stromal cell related cytokines and chemokines in the synovial fluid of patients with early synovitis. Synovial fluid was aspirated from inflamed joints of patients with inflammatory arthritis of duration 3 months or less, whose outcomes were subsequently determined by follow up. For comparison, synovial fluid was aspirated from patients with acute crystal arthritis, established RA and osteoarthritis. Rheumatoid factor activity was blocked in the synovial fluid samples, and a panel of 23 cytokines and chemokines measured using a multiplex based system. Patients with early inflammatory arthritis who subsequently developed RA had a distinct but transient synovial fluid cytokine profile. The levels of a range of T cell, macrophage and stromal cell related cytokines ( e. g. IL-2, IL-4, IL-13, IL-17, IL-15, basic fibroblast growth factor and epidermal growth factor) were significantly elevated in these patients within 3 months after symptom onset, as compared with early arthritis patients who did not develop RA. In addition, this profile was no longer present in established RA. In contrast, patients with non-rheumatoid persistent synovitis exhibited elevated levels of interferon-gamma at initiation. Early synovitis destined to develop into RA is thus characterized by a distinct and transient synovial fluid cytokine profile. The cytokines present in the early rheumatoid lesion suggest that this response is likely to influence the microenvironment required for persistent RA

Leaders in Social Networks, the Delicious Case

Finding pertinent information is not limited to search engines. Online communities can amplify the influence of a small number of power users for the benefit of all other users. Users' information foraging in depth and breadth can be greatly enhanced by choosing suitable leaders. For instance in delicious.com, users subscribe to leaders' collection which lead to a deeper and wider reach not achievable with search engines. To consolidate such collective search, it is essential to utilize the leadership topology and identify influential users. Google's PageRank, as a successful search algorithm in the World Wide Web, turns out to be less effective in networks of people. We thus devise an adaptive and parameter-free algorithm, the LeaderRank, to quantify user influence. We show that LeaderRank outperforms PageRank in terms of ranking effectiveness, as well as robustness against manipulations and noisy data. These results suggest that leaders who are aware of their clout may reinforce the development of social networks, and thus the power of collective search

Embryonic Lethality in Mice Lacking the Nuclear Factor of Activated T Cells 5 Protein Due to Impaired Cardiac Development and Function

Nuclear factor of activated T cells 5 protein (NFAT5) is thought to be important for cellular adaptation to osmotic stress by regulating the transcription of genes responsible for the synthesis or transport of organic osmolytes. It is also thought to play a role in immune function, myogenesis and cancer invasion. To better understand the function of NFAT5, we developed NFAT5 gene knockout mice. Homozygous NFAT5 null (NFAT5−/−) mouse embryos failed to develop normally and died after 14.5 days of embryonic development (E14.5). The embryos showed peripheral edema, and abnormal heart development as indicated by thinner ventricular wall and reduced cell density at the compact and trabecular areas of myocardium. This is associated with reduced level of proliferating cell nuclear antigen and increased caspase-3 in these tissues. Cardiomyocytes from E14.5 NFAT5−/− embryos showed a significant reduction of beating rate and abnormal Ca2+ signaling profile as a consequence of reduced sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) and ryanodine receptor (RyR) expressions. Expression of NFAT5 target genes, such as HSP 70 and SMIT were reduced in NFAT5−/− cardiomyocytes. Our findings demonstrated an essential role of NFAT5 in cardiac development and Ca2+ signaling. Cardiac failure is most likely responsible for the peripheral edema and death of NFAT5−/− embryos at E14.5 days

Mindfulness Awareness Is Associated With a Lower Risk of Anxiety and Depressive Symptoms in Older Adults With Neurocognitive Disorders

Background: Apart from depressive disorders, there are great interests in adopting mindfulness based interventions (MBIs) for other mental health conditions. Depression and anxiety are common in people with neurocognitive disorders (NCD). The potential of MBIs as an adjuvant treatment in this cognitively at-risk group should be further explored. Objectives: The current study explored the association between depression and anxiety symptoms with dispositional mindfulness in older adults, and if same association stays in the context of cognitive impairment. Methods: The Hong Kong Mental Morbidity Survey for Older People (MMSOP) is an ongoing epidemiology study of the prevalence of neurocognitive and mental disorders in adults aged 60 years or over in Hong Kong. MMSOP evaluated cognitive function, psychiatric symptoms (Clinical Interview Schedule-revised, CIS-R), chronic physical disease burden, psychosocial support, and resilience factors, including dispositional mindfulness as measured by the Mindful Attention Awareness Scale (MAAS). We analyzed the impact of MAAS on CIS-R and potential moderation effects of mindfulness. Results: In March 2021, 1,218 community dwelling participants completed assessments. The mean age of the sample is 69.0 (SD 6.9) years. Eight hundred and two participants (65.7%) were not demented (CDR 0) and 391 (32%) and 25 (2%) were categorized as having mild NCD (CDR 0.5) and major NCD (CDR 1 or more), respectively. One hundred forty-three (11.7%) satisfied ICD-10 criteria for anxiety or depressive disorder as measured by CIS-R. Linear regression analysis showed that female gender, CIRS, and MAAS scores were significant factors associated with CIS-R scores. MAAS scores moderated and attenuated the impact CIRS on CIS-R (adjusted R2 = 0.447, p < 0.001). MAAS scores remained as significant moderator for CIRS in patients with NCD (CDR ≥ 0.5) (adjusted R2 = 0.33, p < 0.001). Conclusion: Interim findings of the MMSOP suggested that dispositional mindfulness is associated with lower level of mood symptoms in community dwelling older adults in Hong Kong. The interaction effects further suggested that high mindful awareness may reduce the adverse effects of chronic physical morbidity on mental health. The observation stayed in the participants with cognitive impairment. We should further explore MBIs as a non-pharmacological treatment for in older adults at-risk of physical morbidity and cognitive decline