Spiral-wave Dynamics Depends Sensitively on nhomogeneities in Mathematical Models of Ventricular Tissue

Every sixth death in industrialised countries occurs because of cardiac arrhythmias like ventricular tachycardia (VT) and ventricular fibrillation (VF). There is growing consensus that VT is associated with an unbroken spiral wave of electrical activation on cardiac tissue but VF with broken waves, spiral turbulence, spatiotemporal chaos and rapid, irregular activation. Thus spiral-wave activity in cardiac tissue has been studied extensively. Nevertheless many aspects of such spiral dynamics remain elusive because of the intrinsically high-dimensional nature of the cardiac-dynamical system. In particular, the role of tissue heterogeneities in the stability of cardiac spiral waves is still being investigated. Experiments with conduction blocks in cardiac tissue yield a variety of results: some suggest that blocks can eliminate VF partially or completely, leading to VT or quiescence, but others show that VF is unaffected by obstacles. We propose theoretically that this variety of results is a natural manifestation of a fractal boundary that must separate the basins of the attractors associated, respectively, with VF and VT. We substantiate this with extensive numerical studies of Panfilov and Luo-Rudy I models, where we show that the suppression of VF depends sensitively on the position, size, and nature of the inhomogeneity.Comment: 9 pages, 5 figures

The Exotic Barium Bismuthates

We review the remarkable properties, including superconductivity, charge-density-wave ordering, and metal-insulator transitions, of lead- and potassium-doped barium bismuthate. We discuss some of the early theoretical studies of these systems. Our recent theoretical work, on the negative-U\/, extended-Hubbard model for these systems, is also described. Both the large- and intermediate-U\/ regimes of this model are examined, using mean-field and random-phase approximations, particularly with a view to fitting various experimental properties of these bismuthates. On the basis of our studies, we point out possibilities for exotic physics in these systems. We also emphasize the different consequences of electronic and phonon-mediated mechanisms for the negative U.\/ We show that, for an electronic mechanism, the \secin \,\,phases of these bismuthates must be unique, with their transport properties {\it dominated by charge $\pm 2e$ Cooperon bound states}. This can explain the observed difference between the optical and transport gaps. We propose other experimental tests for this novel mechanism of charge transport and comment on the effects of disorder.Comment: UUencoded LaTex file, 122 pages, figures available on request To appear in Int. J. Mod. Phys. B as a review articl

Nonequilibrium Phase Transitions in a Driven Sandpile Model

We construct a driven sandpile slope model and study it by numerical simulations in one dimension. The model is specified by a threshold slope \sigma_c\/, a parameter \alpha\/, governing the local current-slope relation (beyond threshold), and $j_{\rm in}$, the mean input current of sand. A nonequilibrium phase diagram is obtained in the \alpha\, -\, j_{\rm in}\/ plane. We find an infinity of phases, characterized by different mean slopes and separated by continuous or first-order boundaries, some of which we obtain analytically. Extensions to two dimensions are discussed.Comment: 11 pages, RevTeX (preprint format), 4 figures available upon requs

Pengaruh Penyiangan Dan Suhu Penyimpanan Terhadap Mutu Kimiawi, Mikrobiologis Dan Organoleptik Ikan Tongkol (Auxis Tharzard, Lac)

Ikan tongkol merupakan salah satu bahan pangan yang dikonsumsi masyarakat dan jika dibiarkanpada suhu kamar, maka terjadi proses penurunan mutu menjadi busuk. Ikan yang sudah mengalami prosespembusukan, bila dikonsumsi dapat menimbulkan keracunan (Histamine fish poisoning). Keracunan inidisebabkan oleh kontaminasi bakteri pathogen dengan dekarboksilasi asam amino histidin oleh enzimhistidin dekarboksilase menghasilkan histamin. Bakteri ini banyak terdapat pada anggota tubuh manusiayang tidak higienis, kotoran/tinja, isi Perut ikan, insang serta peralatan yang tidak bersih.Penelitian eksperimental dengan pola faktorial, yaitu faktor P adalah faktor penyiangan dengan 2 taraf,tanpa penyiangan dan penyiangan, sedangkan faktor T adalah suhu penyimpanan dengan 3 taraf yaitu suhupenyimpanan 30oC, 15oC dan 0oC.Analisis statistik terhadap mutu kimiawi seperti kadar histamin, kadar total volatil bases (TVB) dantrimetilamin (TMA) menunjukkan perbedaan nyata (P<0,05) pada pengaruh penyiangan dan suhupenyimpanan. Terjadi peningkatan kadar histamin, kadar TVB dan TMA selama penelitian. Selamapenelitian terjadi peningkatan jumlah koloni bakteri, jumlah Coliform, kecuali bakteri Vibrioparahaemolyticus negatif. Perlakuan penyiangan dan suhu penyimpanan 0oC memiliki mutu kimiawi,mikrobiologis terbaik sampai hari ke 10 serta masih diterima panelis.Hubungan antara kadar histamin dengan jumlah bakteri mempunyai hubungan sangat kuat, ditunjukkandengan nilai r ? 0,7 kecuali kadar histamin dengan waktu memiliki hubungan agak lemah r ? 0,5.Keamanan ikan tongkol dengan penerapan teknologi tepat guna berupa tanpa penyiangan danpenyiangan pada suhu 30oC hanya aman untuk dikonsumsi sampai hari ke 0. Perlakuan tanpa penyiangandan suhu penyimpanan 15oC aman sampai hari ke 4, sedangkan dengan penyiangan aman sampai hari ke 6.Untuk perlakuan tanpa penyiangan dan penyiangan dengan suhu penyimpanan 0oC aman sampai hari ke 10

Morphologic and histological differentiation of gubernaculum in female fetus: a cadaveric study

Background: In both male and female fetuses inguinal canal development entails a complex sequence of anatomic events involving the gubernaculum and processus vaginalis. Much has been written about the embryological development of the genital system, particularly the male genital system and the descent of the testes from the abdominal cavity into the scrotum. In this process, the gubernaculum plays a relevant although still unclear role. Despite all the studies that have been performed, controversy still exists in this anatomical region.Methods: Twenty round ligaments of uterus were dissected from female fetuses and microscopic structure was studied under light microscope using haematoxylin and eosin stain. The specimens were collected from female fetuses (8wks-26wks). One male fetus was also dissected.Results: Gubernaculum plays a crucial role in the development of the inguinal region. The gubernaculum is directly associated with the migration of the testis through the inguinal canal and probably to the scrotum; but the inguinal canal is present before testicular descent and females have both an inguinal canal and gubernaculum, although the ovaries do not migrate through the abdominal wall.Conclusions: In this anatomical region, and despite all the studies that have been performed, controversy still exists. This article attempts to study the morphology and histology and the differentiation of the gubernaculum with age.

Comparison of Anterior Chamber Depth Measurements from the Galilei Dual Scheimpflug Analyzer with IOLMaster

Purpose. To compare anterior chamber depth (ACD), representing the distance between the anterior corneal surface and anterior lens surface measurements between the Galilei Dual Scheimpflug Analyzer and the IOLMaster. Methods. A retrospective review of 65 individual patient eyes with normal anterior segments, and no prior ocular surgery was performed. Patients underwent ACD measurements with both devices during the same session by a trained examiner. Interdevice agreement was evaluated using paired two-tailed t-tests, Pearson correlation coefficient, and Bland-Altman analysis. Results. The mean ± standard deviation (SD) ACD for the Galilei and IOLMaster was 3.37 ± 0.36 mm (range from 2.62 to 4.13) and 3.25 ± 0.38 mm (range from 2.34 to 3.92), respectively (Pearson correlation coefficient = 0.96). ACD mean difference was 0.12 mm (P < 0.0001); 95% limits of agreement was from −0.09 to 0.34. The Galilei measured slightly longer ACD values than the IOLMaster. There was no relationship between axial length and interdevice difference. Conclusion. ACD measurements correlate well between the Galilei and IOLMaster, with Galilei values on average 0.12 mm longer than the IOLMaster

Gunnery Surface Target

The functional and technical requirements of the Gunnery surface target for Naval firing practice are given. The design evolved, and the raw materials required for its various components are described and discussed in detail. The target designed can with stand the sea state of seven in all operating conditions while being towed at a speed of 15 knots in a wind speed of 25 knots. It is visible upto a distance of 18 km and has radar responsive characteristics upto 22 km

A Super-Fast Distributed Algorithm for Bipartite Metric Facility Location

The \textit{facility location} problem consists of a set of \textit{facilities} $\mathcal{F}$, a set of \textit{clients} $\mathcal{C}$, an \textit{opening cost} $f_i$ associated with each facility $x_i$, and a \textit{connection cost} $D(x_i,y_j)$ between each facility $x_i$ and client $y_j$. The goal is to find a subset of facilities to \textit{open}, and to connect each client to an open facility, so as to minimize the total facility opening costs plus connection costs. This paper presents the first expected-sub-logarithmic-round distributed O(1)-approximation algorithm in the $\mathcal{CONGEST}$ model for the \textit{metric} facility location problem on the complete bipartite network with parts $\mathcal{F}$ and $\mathcal{C}$. Our algorithm has an expected running time of $O((\log \log n)^3)$ rounds, where $n = |\mathcal{F}| + |\mathcal{C}|$. This result can be viewed as a continuation of our recent work (ICALP 2012) in which we presented the first sub-logarithmic-round distributed O(1)-approximation algorithm for metric facility location on a \textit{clique} network. The bipartite setting presents several new challenges not present in the problem on a clique network. We present two new techniques to overcome these challenges. (i) In order to deal with the problem of not being able to choose appropriate probabilities (due to lack of adequate knowledge), we design an algorithm that performs a random walk over a probability space and analyze the progress our algorithm makes as the random walk proceeds. (ii) In order to deal with a problem of quickly disseminating a collection of messages, possibly containing many duplicates, over the bipartite network, we design a probabilistic hashing scheme that delivers all of the messages in expected-$O(\log \log n)$ rounds.Comment: 22 pages. This is the full version of a paper that appeared in DISC 201

Finding Independent Sets in Unions of Perfect Graphs

The maximum independent set problem (MaxIS) on general graphs is known to be NP-hard to approximate within a factor of $n^{1-epsilon}$, for any $epsilon > 0$. However, there are many ``easy" classes of graphs on which the problem can be solved in polynomial time. In this context, an interesting question is that of computing the maximum independent set in a graph that can be expressed as the union of a small number of graphs from an easy class. The MaxIS problem has been studied on unions of interval graphs and chordal graphs. We study the MaxIS problem on unions of perfect graphs (which generalize the above two classes). We present an $O(sqrt{n})$-approximation algorithm when the input graph is the union of two perfect graphs. We also show that the MaxIS problem on unions of two comparability graphs (a subclass of perfect graphs) cannot be approximated within any constant factor