64 research outputs found
Analysis and Assembling of Network Structure in Mutualistic Systems
It has been observed that mutualistic bipartite networks have a nested
structure of interactions. In addition, the degree distributions associated
with the two guilds involved in such networks (e.g. plants & pollinators or
plants & seed dispersers) approximately follow a truncated power law. We show
that nestedness and truncated power law distributions are intimately linked,
and that any biological reasons for such truncation are superimposed to finite
size effects . We further explore the internal organization of bipartite
networks by developing a self-organizing network model (SNM) that reproduces
empirical observations of pollination systems of widely different sizes. Since
the only inputs to the SNM are numbers of plant and animal species, and their
interactions (i.e., no data on local abundance of the interacting species are
needed), we suggest that the well-known association between species frequency
of interaction and species degree is a consequence rather than a cause, of the
observed network structure.Comment: J. of. Theor. Biology, in pres
Strategy updating rules and strategy distributions in dynamical multiagent systems
In the evolutionary version of the minority game, agents update their
strategies (gene-value ) in order to improve their performance. Motivated by
recent intriguing results obtained for prize-to-fine ratios which are smaller
than unity, we explore the system's dynamics with a strategy updating rule of
the form (). We find that the strategy
distribution depends strongly on the values of the prize-to-fine ratio , the
length scale , and the type of boundary condition used. We show that
these parameters determine the amplitude and frequency of the the temporal
oscillations observed in the gene space. These regular oscillations are shown
to be the main factor which determines the strategy distribution of the
population. In addition, we find that agents characterized by
(a coin-tossing strategy) have the best chances of survival at asymptotically
long times, regardless of the value of and the boundary conditions
used.Comment: 4 pages, 7 figure
Tuberculous Peritonitis Presenting Acute Recurrent Pancreatitis
Tuberculosis (TB), one of the oldest diseases known to affect humans, is a major cause of death worldwide. TB is still a major problem in Indonesia. This disease, which is caused by bacteria of the Mycobacterium tuberculosis, usually affects the lungs, although other organs are involved in up to one- third of cases. Approximately 95% cases of TB and 98% death because of TB occur in developing country. Gastrointestinal tuberculosis is uncommon, making up 3.5% of extrapulmonary cases in the United States. This kind of TB may involve gastrointestinal tract, peritoneal, lymph nodes, or solid intraabdominal organs (viscera). A 17 years old male admitted to hospital with TB peritonitis presenting unusual clinical manifestation. At the first admission patients was diagnosed with acute pancreatitis based on elevation of amylase and lipase level up to 285 and 2,046 U/L and after finishing further examination, patients suffered from tuberculous peritonitis which based on literature manifested some gastrointestinal disorders. Diagnostic confirmation was accomplished by conducting serum-ascites albumin gradient (SAAG) of < 1.1 g/dL, peritoneal thickening and the presence of ascites with fine mobile septations on ultrasound, positive polymerase chain reaction (PCR) TB from ascitic fluid. Patients received conventional antitubercular therapy for 12 months of rifampicin, isoniazid, pyrazinamide, and ethambutol. The addition of corticosteroids for the first two or three months of treatment may reduce the incidence of late complications arising from adhesive disease, such as small bowel obstruction
Abdominal Tuberculosis: Diagnostic and Management Problems
Abdominal tuberculosis, as one of the manifestations of extrapulmonary tuberculosis, may involve gastrointestinal tract, peritoneum, mesenteric lymph nodes, liver, and also spleen. Most patients have constitutional symptoms of fever, pain, diarrhea, constipation, alternating constipation and diarrhea, weight loss, anorexia and malaise. It also has an insidious course without any specific laboratory, radiological or clinical findings and makes it difficult to diagnosis. Anti tuberculosis treatments with initiation phase for 2 months and continue with continuation phase for 7 months is effective. Steroids may be used to reduce acute inflammation and limit delayed fibrotic complications. We report a male patient with abdominal tuberculosis involving peritoneum, liver, colon, paraaorta lymph nodes, and spleen, which at first suggested as a Malignancy. Drug induced hepatitis due to anti tuberculosis drug during treatment was emerged and substituted with other regimen. After given anti tuberculosis treatment and steroid as adjunctive treatment, the clinical condition of patient was improved
First-order transition features of the 3D bimodal random-field Ising model
Two numerical strategies based on the Wang-Landau and Lee entropic sampling
schemes are implemented to investigate the first-order transition features of
the 3D bimodal () random-field Ising model at the strong disorder
regime. We consider simple cubic lattices with linear sizes in the range
and simulate the system for two values of the disorder strength:
and . The nature of the transition is elucidated by applying the
Lee-Kosterlitz free-energy barrier method. Our results indicate that, despite
the strong first-order-like characteristics, the transition remains continuous,
in disagreement with the early mean-field theory prediction of a tricritical
point at high values of the random-field.Comment: 19 pages, 6 figures, slightly extended version as accepted for
publicatio
Scaling in a Nonconservative Earthquake Model of Self-Organised Criticality
We numerically investigate the Olami-Feder-Christensen model for earthquakes
in order to characterise its scaling behaviour. We show that ordinary finite
size scaling in the model is violated due to global, system wide events.
Nevertheless we find that subsystems of linear dimension small compared to the
overall system size obey finite (subsystem) size scaling, with universal
critical coefficients, for the earthquake events localised within the
subsystem. We provide evidence, moreover, that large earthquakes responsible
for breaking finite size scaling are initiated predominantly near the boundary.Comment: 6 pages, 6 figures, to be published in Phys. Rev. E; references
sorted correctl
Simulation study of the inhomogeneous Olami-Feder-Christensen model of earthquakes
Statistical properties of the inhomogeneous version of the
Olami-Feder-Christensen (OFC) model of earthquakes is investigated by numerical
simulations. The spatial inhomogeneity is assumed to be dynamical. Critical
features found in the original homogeneous OFC model, e.g., the
Gutenberg-Richter law and the Omori law are often weakened or suppressed in the
presence of inhomogeneity, whereas the characteristic features found in the
original homogeneous OFC model, e.g., the near-periodic recurrence of large
events and the asperity-like phenomena persist.Comment: Shortened from the first version. To appear in European Physical
Journal
Elucidation of chiral Recognition mechanism of alpha-amino acids using ligand exchange high performance liquid chromatography
Ligand exchange HPLC technique was applied to resolve chiral separation of aliphatic side chain aminoacid racemates. Chiral selector was copper L-phenylalaninate (II) and the results showed the elution of D enantiomer followed by L form. Considering the 3-point interaction concept, a mechanism of chiral recognition was proposed, in which no change of configuration would follow the formation of pseudo-homochiral and heterochiral complexes. To prove the reliability of this mechanism, the trans configuration of homochiral complex had to be more stable than the cis form, which was confirmed by DFT-B3LYP calculation in gas phase. The infrared frequencies were also calculated and the comparison with the subtracted and deconvoluted spectrum of the in-solution complex also pointed to the presence of the trans diasteroisomer
Early cytotoxic effects of ochratoxin A in rat liver: a morphological, biochemical and molecular study
We characterized the overall early effect of chronic ochratoxin A (OTA) treatment on rat liver, analyzing different aspects related to: (i) fibrosis, by measuring collagen content and turnover, and alpha-smooth muscle actin (alphaSMA); (ii) oxidative stress and stress response, by analyzing protein carbonylation, superoxide dismutase (SOD) and heat shock protein (HSP70) gene expression; (iii) the possible tumor promoter effect, evaluating cadherin and connexin (CX) mRNA levels. Light microscopy analysis showed no histological differences in OTA-treated and control (CT) rats. Collagen content, determined by computer analysis of Sirius red-stained liver sections, was similar in both groups. In liver homogenates COL-I, COL-III, TIMP-1 and TGF-beta1 mRNA levels and alphaSMA were unaffected by OTA. Matrix metalloproteinase (MMP)-1, MMP-2 and MMP-9 protein levels were also similar in the two groups. Protein carbonylation, a marker of severe oxidative stress, was not evident in the homogenates of OTA-treated livers; superoxide dismutase (SOD) mRNA tended to be lower and HSP70 was strongly down-regulated. OTA reduced E-cadherin and DSC-2 transcription, and down-regulated liver CX26, CX32 and CX43. In conclusion, these in vivo results show that OTA-induced liver injury involves a reduction in the ability to counterbalance oxidative stress, maybe leading to altered gap junction intercellular communication and loss of cell adhesion and polarity. This suggests that mild oxidative damage might be a key factor, in combination with other cytotoxic effects, in triggering the promotion of liver tumors after exposure to OTA
Sperm protein 17 is expressed in human nervous system tumours
BACKGROUND: Human sperm protein 17 (Sp17) is a highly conserved protein that was originally isolated from a rabbit epididymal sperm membrane and testis membrane pellet. It has recently been included in the cancer/testis (CT) antigen family, and shown to be expressed in multiple myeloma and ovarian cancer. We investigated its immunolocalisation in specimens of nervous system (NS) malignancies, in order to establish its usefulness as a target for tumour-vaccine strategies. METHODS: The expression of Sp17 was assessed by means of a standardised immunohistochemical procedure [(mAb/antigen) MF1/Sp17] in formalin-fixed and paraffin embedded surgical specimens of NS malignancies, including 28 neuroectodermal primary tumours (6 astrocytomas, 16 glioblastoma multiforme, 5 oligodendrogliomas, and 1 ependymoma), 25 meningeal tumours, and five peripheral nerve sheath tumours (4 schwannomas, and 1 neurofibroma),. RESULTS: A number of neuroectodermal (21%) and meningeal tumours (4%) were found heterogeneously immunopositive for Sp17. None of the peripheral nerve sheath tumours was immunopositive for Sp17. The expression pattern was heterogeneous in all of the positive samples, and did not correlate with the degree of malignancy. CONCLUSION: The frequency of expression and non-uniform cell distribution of Sp17 suggest that it cannot be used as a unique immunotherapeutic target in NS cancer. However, our results do show the immunolocalisation of Sp17 in a proportion of NS tumour cells, but not in their non-pathological counterparts. The emerging complex function of Sp17 makes further studies necessary to clarify the link between it and immunopositive cells
- âŠ