Some Results On Convex Greedy Embedding Conjecture for 3-Connected Planar Graphs

A greedy embedding of a graph $G = (V,E)$ into a metric space $(X,d)$ is a function $x : V(G) \to X$ such that in the embedding for every pair of non-adjacent vertices $x(s), x(t)$ there exists another vertex $x(u)$ adjacent to $x(s)$ which is closer to $x(t)$ than $x(s)$. This notion of greedy embedding was defined by Papadimitriou and Ratajczak (Theor. Comput. Sci. 2005), where authors conjectured that every 3-connected planar graph has a greedy embedding (possibly planar and convex) in the Euclidean plane. Recently, greedy embedding conjecture has been proved by Leighton and Moitra (FOCS 2008). However, their algorithm do not result in a drawing that is planar and convex for all 3-connected planar graph in the Euclidean plane. In this work we consider the planar convex greedy embedding conjecture and make some progress. We derive a new characterization of planar convex greedy embedding that given a 3-connected planar graph $G = (V,E)$, an embedding x: V \to \bbbr^2 of $G$ is a planar convex greedy embedding if and only if, in the embedding $x$, weight of the maximum weight spanning tree ($T$) and weight of the minimum weight spanning tree (\func{MST}) satisfies \WT(T)/\WT(\func{MST}) \leq (\card{V}-1)^{1 - \delta}, for some $0 < \delta \leq 1$.Comment: 19 pages, A short version of this paper has been accepted for presentation in FCT 2009 - 17th International Symposium on Fundamentals of Computation Theor

Structural insights into Clostridium perfringens delta toxin pore formation

Clostridium perfringens Delta toxin is one of the three hemolysin-like proteins produced by C. perfringens type C and possibly type B strains. One of the others, NetB, has been shown to be the major cause of Avian Nectrotic Enteritis, which following the reduction in use of antibiotics as growth promoters, has become an emerging disease of industrial poultry. Delta toxin itself is cytotoxic to the wide range of human and animal macrophages and platelets that present GM2 ganglioside on their membranes. It has sequence similarity with Staphylococcus aureus β-pore forming toxins and is expected to heptamerize and form pores in the lipid bilayer of host cell membranes. Nevertheless, its exact mode of action remains undetermined. Here we report the 2.4 Å crystal structure of monomeric Delta toxin. The superposition of this structure with the structure of the phospholipid-bound F component of S. aureus leucocidin (LukF) revealed that the glycerol molecules bound to Delta toxin and the phospholipids in LukF are accommodated in the same hydrophobic clefts, corresponding to where the toxin is expected to latch onto the membrane, though the binding sites show significant differences. From structure-based sequence alignment with the known structure of staphylococcal α-hemolysin, a model of the Delta toxin pore form has been built. Using electron microscopy, we have validated our model and characterized the Delta toxin pore on liposomes. These results highlight both similarities and differences in the mechanism of Delta toxin (and by extension NetB) cytotoxicity from that of the staphylococcal pore-forming toxins

Confluence up to Garbage

No abstract available

Voronoi Drawings of Trees

This paper investigates the following problem: Given a tree T, can we find a set of points in the plane such that the Voronoi diagram of this set of points is a drawing of T? We study trees that can be drawn as Voronoi diagrams both in the Euclidean and in the Manhattan metric. Characterizations of drawable trees are given and different drawing algorithms that take into account additional geometric constraints are presented

Dietary patterns associated with fall-related fracture in elderly Japanese: a population based prospective study

<p>Abstract</p> <p>Background</p> <p>Diet is considered an important factor for bone health, but is composed of a wide variety of foods containing complex combinations of nutrients. Therefore we investigated the relationship between dietary patterns and fall-related fractures in the elderly.</p> <p>Methods</p> <p>We designed a population-based prospective survey of 1178 elderly people in Japan in 2002. Dietary intake was assessed with a 75-item food frequency questionnaire (FFQ), from which dietary patterns were created by factor analysis from 27 food groups. The frequency of fall-related fracture was investigated based on insurance claim records from 2002 until 2006. The relationship between the incidence of fall-related fracture and modifiable factors, including dietary patterns, were examined. The Cox proportional hazards regression model was used to examine the relationships between dietary patterns and incidence of fall-related fracture with adjustment for age, gender, Body Mass Index (BMI) and energy intake.</p> <p>Results</p> <p>Among 877 participants who agreed to a 4 year follow-up, 28 suffered from a fall-related fracture. Three dietary patterns were identified: mainly vegetable, mainly meat and mainly traditional Japanese. The moderately confirmed (see statistical methods) groups with a Meat pattern showed a reduced risk of fall-related fracture (Hazard ratio = 0.36, 95% CI = 0.13 - 0.94) after adjustment for age, gender, BMI and energy intake. The Vegetable pattern showed a significant risk increase (Hazard ratio = 2.67, 95% CI = 1.03 - 6.90) after adjustment for age, gender and BMI. The Traditional Japanese pattern had no relationship to the risk of fall-related fracture.</p> <p>Conclusions</p> <p>The results of this study have the potential to reduce fall-related fracture risk in elderly Japanese. The results should be interpreted in light of the overall low meat intake of the Japanese population.</p

Zaštitno djelovanje selenija protiv prekomjerne ekspresije apoptotskih gena povezanih s karcinomom u štakora izloženih o-krezolu

Cresols are monomethyl derivatives of phenol frequently used as solvents and intermediates in the production of disinfectants, fragrances, pesticides, dyes, and explosives, which is probably why they are widely distributed in the environment. General population may be exposed to cresols mainly through inhalation of contaminated air. In this study we evaluated the toxicological effects of o-cresol on differential gene expression profile of rat liver and prostate. Experiments were conducted on 80 male rats, 60 of which were exposed to o-cresol (1.5 g kg-1, 5 g kg-1, or 15 g kg-1) through feed for 8 weeks. Three groups of rats were supplemented with 0.1 mg kg-1 selenium (Se, in the form of, sodium selenite) in addition to o-cresol to evaluate its effectiveness against o-cresol toxicity. Control group received neither o-cresol nor Se, while one group received Se alone. Survival was similar between the exposed and control animals. Rats exposed to 15 g kg-1 of o-cresol showed a 16 % loss in body weight by the end of the study, which may have been related to o-cresol making feed unpalatable at this concentration. Liver and prostate tissue samples were collected at the end of the treatment. mRNA analysis revealed that apoptotic genes (CYP3A, COX-2, PPARγ, BAX, BCL2, AKT-1, and PKCα) related to cancer were up-regulated in liver and prostate tissues isolated from groups exposed to 5 g kg-1 and 15 g kg-1 o-cresol in comparison to control. Changes in gene expression profile were prevented when rats were supplemented with Se. The exact mechanisms underlying its protective effect remain to be clarified by future studies.Krezoli su monometilni derivati fenola koji se često rabe kao otapala te kao posrednici u proizvodnji dezinfekcijskih sredstava, mirisa, pesticida, boja i eksploziva. Otuda i njihova rasprostranjenost u okolišu. Opća je populacija izložena krezolima uglavnom putem zraka. U ovome se toksikološkom istraživanju ocijenilo djelovanje o-krezola, jednoga od tri krezolova izomera, na ekspresiju gena u tkivima jetre i prostate mužjaka štakora. Istraživanje je provedeno na 80 mužjaka, od kojih je 60 tijekom osam tjedana bilo izloženo o-krezolu (1,5 g kg-1, 5 g kg-1, odnosno 15 g kg-1) preko krmiva. Tri skupine štakora primale su uz o-krezol nadomjestak selenija u dozi od 0.1 mg kg-1 (Se, u obliku natrijeva selenita) radi ocjene njegove djelotvornosti protiv toksičnosti o-krezola. Kontrolna skupina nije primala ni o-krezol ni Se, dok je jedna skupina primala samo Se. Preživljenje je bilo podjednako u svih skupina životinja. Štakori izloženi najvišoj dozi o-krezola (15 g kg-1) imali su 16 % manju tjelesnu masu od kontrolne skupine na kraju ispitivanja, što može biti povezano s lošim okusom krmiva zbog primjese visoke doze o-krezola. S istekom osmotjednoga izlaganja o-krezolu životinje su eutanazirane te su prikupljeni uzorci tkiva jetre i prostate. Analiza m-RNA pokazala je značajno povišenu ekspresiju apoptotskih gena CYP3A, COX-2, PPARγ, BAX, BCL2, AKT-1 i PKCα, koji su povezani s nastankom karcinoma u skupinama štakora izloženim o-krezolu (5 g kg-1 i 15 g kg-1 u odnosu na kontrolu. Ova je prekomjerna ekspresija poništena u štakora koji su primali selenij. Još nisu jasni mehanizmi iza ovoga zaštitnog djelovanja, na što će odgovoriti buduća istraživanja

Tumour antigen expression in hepatocellular carcinoma in a low-endemic western area

Background: Identification of tumour antigens is crucial for the development of vaccination strategies against hepatocellular carcinoma (HCC). Most studies come from eastern-Asia, where hepatitis-B is the main cause of HCC. However, tumour antigen expression is poorly studied in low-endemic, western areas where the aetiology of HCC differs. Methods: We constructed tissue microarrays from resected HCC tissue of 133 patients. Expression of a comprehensive panel of cancer-testis (MAGE-A1, MAGE-A3/4, MAGE-A10, MAGE-C1, MAGE-C2, NY-ESO-1, SSX-2, sperm protein 17), onco-fetal (AFP, Glypican-3) and overexpressed tumour antigens (Annexin-A2, Wilms tumor-1, Survivin, Midkine, MUC-1) was determined by immunohistochemistry. Results: A higher prevalence of MAGE antigens was observed in patients with hepatitis-B. Patients with expression of more tumour antigens in general had better HCC-specific survival (P=0.022). The four tumour antigens with high expression in HCC and no, or weak, expression in surrounding tumour-free-liver tissue, were Annexin-A2, GPC-3, MAGE-C1 and MAGE-C2, expressed in 90, 39, 17 and 20% of HCCs, respectively. Ninety-five percent of HCCs expressed at least one of these four tumour antigens. Interestingly, GPC-3 was associated with SALL-4 expression (P=0.001), an oncofetal transcription factor highly expressed in embryonal stem cells. SALL-4 and GPC-3 expression levels were correlated with vascular invasion, poor differentiation and higher AFP levels before surgery. Moreover, patients who co-expressed higher levels of both GPC-3 and SALL-4 had worse HCC-specific survival (P=0.018). Conclusions: We describe a panel of four tumour antigens with excellent coverage and good tumour specificity in a western area, low-endemic for hepatitis-B. The association between GPC-3 and SALL-4 is a novel finding and suggests that GPC-3 targeting may specifically attack the tumour stem-cell compartment

Histone H4 Lys 20 Monomethylation of the CENP-A Nucleosome Is Essential for Kinetochore Assembly

SummaryIn vertebrate cells, centromeres are specified epigenetically through the deposition of the centromere-specific histone CENP-A. Following CENP-A deposition, additional proteins are assembled on centromeric chromatin. However, it remains unknown whether additional epigenetic features of centromeric chromatin are required for kinetochore assembly. Here, we used ChIP-seq analysis to examine centromere-specific histone modifications at chicken centromeres, which lack highly repetitive sequences. We found that H4K20 monomethylation (H4K20me1) is enriched at centromeres. Immunofluorescence and biochemical analyses revealed that H4K20me1 is present at all centromeres in chicken and human cells. Based on immunoprecipitation data, H4K20me1 occurs primarily on the histone H4 that is assembled as part of the CENP-A nucleosome following deposition of CENP-A into centromeres. Targeting the H4K20me1-specific demethylase PHF8 to centromeres reduces the level of H4K20me1 at centromeres and results in kinetochore assembly defects. We conclude that H4K20me1 modification of CENP-A nucleosomes contributes to functional kinetochore assembly

Low-Temperature Continuous Flow Synthesis of Metal Ammonium Phosphates

The synthesis of the high performance inorganic materials essential to the quality of modern day life is hindered by traditionalist attitudes and reliance on outdated methods such as batch syntheses. While continuous flow methods have been extensively adopted in pharmaceutical circles, they remain largely unexplored for the preparation of inorganic compounds, despite higher efficiency, safety and versatility. In this publication, we demonstrate a step-change for the synthesis of metal ammonium phosphates through conversion of the extant batch process to a low-temperature continuous regime, exhibiting a tenfold increase in throughput combined with a significant decrease in particle size