Analytical results for stochastically growing networks: connection to the zero range process

We introduce a stochastic model of growing networks where both, the number of new nodes which joins the network and the number of connections, vary stochastically. We provide an exact mapping between this model and zero range process, and use this mapping to derive an analytical solution of degree distribution for any given evolution rule. One can also use this mapping to infer about a possible evolution rule for a given network. We demonstrate this for protein-protein interaction (PPI) network for Saccharomyces Cerevisiae.Comment: 4+ pages, revtex, 3 eps figure

Towards goal-directed therapy of hepatorenal syndrome: we have the tools but we need the trials

Patients with cirrhosis who develop tense ascites and hepatorenal syndrome have a very high mortality and present a management challenge. Current debate stems from a lack of studies evaluating changes in effective arterial blood volume following paracentesis or targeting fluid replacement with appropriate vascular physiological measures to ensure no paracentesis-related circulatory dysfunction. The study by Umgelter and colleagues addresses a goal-directed approach to fluid management in hepatorenal syndrome and raises several mechanistic questions, the answers to which are likely to improve our understanding of the pathophysiology in hepatorenal syndrome and to guide future management

Acute-on-chronic liver failure: A new syndrome that will re-classify cirrhosis.

Acute-on-chronic liver failure (ACLF) is a recently recognized syndrome characterized by acute decompensation (AD) of cirrhosis and organ/system failure(s) (organ failure: liver, kidney, brain, coagulation, circulation and/or respiration) and extremely poor survival (28-day mortality rate 30-40%). ACLF occurs in relatively young patients. It is especially frequent in alcoholic- and untreated hepatitis B associated-cirrhosis, in addition it is related to bacterial infections and active alcoholism, although in 40% of cases no precipitating event can be identified. It may develop at any time during the course of the disease in the patient (from compensated to long-standing cirrhosis). The development of ACLF occurs in the setting of a systemic inflammation, the severity of which correlates with the number of organ failures and mortality. Systemic inflammation may cause ACLF through complex mechanisms including an exaggerated inflammatory response and systemic oxidative stress to pathogen- or danger/damage-associated molecular patterns (immunopathology) and/or alteration of tissue homeostasis to inflammation caused either by the pathogen itself or through a dysfunction of tissue tolerance. A scoring system composed of three scores (CLIF-C OFs, CLIF-C AD, and CLIF-C ACLFs) specifically designed for patients with AD, with and without ACLF, allows a step-wise algorithm for a rational indication of therapy. The management of ACLF should be carried out in enhanced or intensive care units. Current therapeutic measures comprise the treatment for associated complications, organ failures support and liver transplantation

Giant lipoma: an unusual cause of carpal tunnel syndrome

Carpal tunnel syndrome, in its idiopathic form, is an extremely common entrapment neuropathy in the clinical practice however secondary compressive causes are rare. Among secondary causes, tumors are even rarer. Although lipomas are the most common soft tissue tumor in the body, <5% of the benign tumors of the hand are lipomas. A 48-year old manual laborer man presented to us with a two-year history of numbness, tingling and burning pain in the palmar surface of the left hand and fingers along with a progressively increasing swelling in the hand and wrist. His medical history was unremarkable and no trauma episode was reported. According to the clinical examination and the result of median nerve conduction study (NCS) the diagnosis of carpal tunnel syndrome was established. Operative release of the transverse carpal ligament was subsequently performed along with excision of the lipoma using extensile open approach. Intraoperatively, median nerve and its digital branches were found to be stretched over the giant lipoma causing substantial compression to median nerve. Histopathological findings of the resected mass were consistent with lipoma. After two years the patient was pain-free without any sign of tumor recurrence. Lipomas are infrequently seen in hand and wrist, however giant lipoma as a cause of secondary carpal tunnel syndrome is even more rare, which makes this case interesting.Key words: Lipoma, carpal tunnel syndrome, median nerve, nerve compressio

Spectral analysis of Gene co-expression network of Zebrafish

We analyze the gene expression data of Zebrafish under the combined framework of complex networks and random matrix theory. The nearest neighbor spacing distribution of the corresponding matrix spectra follows random matrix predictions of Gaussian orthogonal statistics. Based on the eigenvector analysis we can divide the spectra into two parts, first part for which the eigenvector localization properties match with the random matrix theory predictions, and the second part for which they show deviation from the theory and hence are useful to understand the system dependent properties. Spectra with the localized eigenvectors can be characterized into three groups based on the eigenvalues. We explore the position of localized nodes from these different categories. Using an overlap measure, we find that the top contributing nodes in the different groups carry distinguished structural features. Furthermore, the top contributing nodes of the different localized eigenvectors corresponding to the lower eigenvalue regime form different densely connected structure well separated from each other. Preliminary biological interpretation of the genes, associated with the top contributing nodes in the localized eigenvectors, suggests that the genes corresponding to same vector share common features.Comment: 6 pages, four figures (accepted in EPL

MELD remains the best predictor of mortality in outpatients with cirrhosis and severe ascites

BACKGROUND: The Model for Endstage Liver Disease (MELD) score may put patients with severe ascites at a disadvantage because they often have a poor quality of life and high mortality despite a favourable MELD score. AIM: To develop a model that is better than the MELD score at predicting 1-year mortality among patients with cirrhosis, severe ascites and MELD ≤18. METHODS: We used data from a randomised trial (SPARe-1) of patients with cirrhosis and severe ascites to develop a model to predict 1-year mortality. We used stepwise backward elimination and Cox regression to identify the strongest predictors. Performance was assessed with the C index and the Brier score. We examined performance in an external cohort of trial participants with cirrhosis and severe ascites (SPARe-2 participants). RESULTS: We included 308 patients with a 1-year mortality of 20.4%. The final prediction model (Severe Ascites Mortality score, "SAM score") included four variables: serum bilirubin, serum sodium, history of SBP (yes or no) and diabetes (yes or no). No indicators of quality of life were included. After correction for optimism bias, the SAM and MELD scores had nearly identical predictive ability. The external validation cohort included 149 patients whose 1-year mortality was 22.4%. The MELD score performed marginally better in this cohort, partly because the effects of SBP and diabetes on mortality were much smaller in this cohort. CONCLUSION: We did not succeed in developing a prediction model that was superior to the MELD score among patients with cirrhosis and severe ascites

Spectral analysis of deformed random networks

We study spectral behavior of sparsely connected random networks under the random matrix framework. Sub-networks without any connection among them form a network having perfect community structure. As connections among the sub-networks are introduced, the spacing distribution shows a transition from the Poisson statistics to the Gaussian orthogonal ensemble statistics of random matrix theory. The eigenvalue density distribution shows a transition to the Wigner's semicircular behavior for a completely deformed network. The range for which spectral rigidity, measured by the Dyson-Mehta $\Delta_3$ statistics, follows the Gaussian orthogonal ensemble statistics depends upon the deformation of the network from the perfect community structure. The spacing distribution is particularly useful to track very slight deformations of the network from a perfect community structure, whereas the density distribution and the $\Delta_3$ statistics remain identical to the undeformed network. On the other hand the $\Delta_3$ statistics is useful for the larger deformation strengths. Finally, we analyze the spectrum of a protein-protein interaction network for Helicobacter, and compare the spectral behavior with those of the model networks.Comment: accepted for publication in Phys. Rev. E (replaced with the final version

Random matrix analysis of complex networks

We study complex networks under random matrix theory (RMT) framework. Using nearest-neighbor and next-nearest-neighbor spacing distributions we analyze the eigenvalues of adjacency matrix of various model networks, namely, random, scale-free and small-world networks. These distributions follow Gaussian orthogonal ensemble statistic of RMT. To probe long-range correlations in the eigenvalues we study spectral rigidity via $\Delta_3$ statistic of RMT as well. It follows RMT prediction of linear behavior in semi-logarithmic scale with slope being $\sim 1/\pi^2$. Random and scale-free networks follow RMT prediction for very large scale. Small-world network follows it for sufficiently large scale, but much less than the random and scale-free networks.Comment: accepted in Phys. Rev. E (replaced with the final version

New clinical and pathophysiological perspectives defining the trajectory of cirrhosis

Traditionally, the complications of cirrhosis, namely variceal bleeding, ascites and hepatic encephalopathy, were thought to result predominantly from circulatory dysfunction and altered organ perfusion arising as a result of portal hypertension. Over the past 20 years, large, international prospective studies have indicated the importance of systemic inflammation and organ immunopathology as additional determinants of organ dysfunction in cirrhosis, which not only manifests in the liver, brain, circulation and the kidneys, but also the immune system, gut, muscles, adrenal glands, reproductive organs, heart and lungs. This review provides an overview of the traditional and emerging concepts around the initiation and maintenance of organ dysfunction in cirrhosis and proposes a new paradigm based upon a better understanding of acute decompensation of cirrhosis. The interaction between the traditional concepts and the emerging perspectives remains a matter of great interest and the basis for future research