The oscillatory distribution of distances in random tries

We investigate \Delta_n, the distance between randomly selected pairs of nodes among n keys in a random trie, which is a kind of digital tree. Analytical techniques, such as the Mellin transform and an excursion between poissonization and depoissonization, capture small fluctuations in the mean and variance of these random distances. The mean increases logarithmically in the number of keys, but curiously enough the variance remains O(1), as n\to\infty. It is demonstrated that the centered random variable \Delta_n^*=\Delta_n-\lfloor2\log_2n\rfloor does not have a limit distribution, but rather oscillates between two distributions.Comment: Published at http://dx.doi.org/10.1214/105051605000000106 in the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

Competition of copper, lead, and cadmium adsorption to goethite

Competition of copper, lead, and cadmium adsorption on goethite depends on metal ion and oxide surface characteristics. Goethite was characterized via X-ray diffraction, potentiometric titrations, site density determination, particle size analysis, and optical microscopy. In this thesis, a hypothesis was tested that electronegativity is the most important factor in metal affinities and adsorption competition to goethite. Metal affinity and site density for the goethite surface were assessed by performing adsorption edges and isotherms. Based on the results of these experiments, competition studies were designed to observe adsorption and displacement of the competing metals by limiting the number of available sites on the oxide surface. Adsorption competition was studied by conducting competition isotherms in two-metal and three-metal systems, where the temperature and pH were maintained constant. Competing metals of equivalent, below saturation, concentrations were introduced in solution in alternative orders as well as simultaneously. In adsorption edges, ionic strength was varied and no changes were observed in the amount of metal adsorbed, suggesting that copper, lead, and cadmium were specifically adsorbed on goethite. Metal affinity and capacity for the goethite surface were found to increase with metal electronegativity:Cu\u3ePb\u3eCd. Neutrally charged hydrolysis products of metal ions were found to slightly decrease metal affinities for goethite. Goethite posses distinct types of sites with varying affinities for adsorbates. In addition to the sites used by heavy metals (Cu, Pb, and Cd), strontium, apparently binds to another group of, possibly lower energy sites. Modeling of copper, lead, and cadmium adsorption and competition was best described with a two-site Langmuir isotherm. From the equilibrium constants obtained from the two-site Langmuir model, more electronegative species were preferably adsorbed over less electronegative species on the high affinity sites of goethite. However, lead showed higher affinity than copper for the low energy sites. In Cu and Cd competition studies, cadmium was completely displaced. In the Pb and Cd studies, lead displaced cadmium from the sites it required. Because sites were not limited in this experiment, unoccupied ones were then filled with cadmium. During Cu and Pb as well as Pb, Cu, and Cd competition studies, copper preferably adsorbed over lead to the high energy sites, whereas lead showed greater affinity for the lower energy sites. During Pb, Cu and Cd competition studies, cadmium was completely desorbed. Furthermore, during the same competition study, the hydrolysis product Cu(OH)2(aq) decreased copper adsorption on goethite where only 30% of this species was adsorbed. The two-site Langmuir model worked well with Cu and Cd competition and Pb and Cd competition, but it was not able to predict the Cu and Pb and the Cu, Pb, and Cd systems\u27 results. The findings from this thesis suggest that electronegativity is an important factor in adsorption competition of pollutants on high affinity sites on the goethite surface. However, lead showed higher affinity than copper for the low energy sites. This study confirms that adsorption competition plays a crucial role in contaminant mobility in the environment

What determines ageing of the transplanted liver?

AbstractBackgroundLiver transplantation is used to treat patients with irreversible liver failure from a variety of causes. Long‐term survival has been reported, particularly in the paediatric population, with graft survival longer than 20 years now possible. The goal for paediatric liver transplantation is to increase the longevity of grafts to match the normal life expectancy of the child. This paper reviews the literature on the current understanding of ageing of the liver and biomarkers that may predict long‐term survival or aid in utilization of organs.MethodsScientific papers published from 1950 to 2013 were sought and extracted from the MEDLINE, PubMed and University of Melbourne databases.ResultsHepatocytes appear resistant to the ageing process, but are affected by both replicative senescence and stress‐related senescence. These processes may be exacerbated by the act of transplantation. The most studied biomarkers are telomeres and SMP‐30.ConclusionThere are many factors that play a role in the ageing of the liver. Further studies into biomarkers of ageing and their relationship to the chronological age of the liver are required to aid in predicting long‐term graft survival and utilization of organs

Analysis of Steiner subtrees of Random Trees for Traceroute Algorithms

We consider in this paper the problem of discovering, via a traceroute algorithm, the topology of a network, whose graph is spanned by an infinite branching process. A subset of nodes is selected according to some criterion. As a measure of efficiency of the algorithm, the Steiner distance of the selected nodes, i.e. the size of the spanning sub-tree of these nodes, is investigated. For the selection of nodes, two criteria are considered: A node is randomly selected with a probability, which is either independent of the depth of the node (uniform model) or else in the depth biased model, is exponentially decaying with respect to its depth. The limiting behavior the size of the discovered subtree is investigated for both models

Levels of physical dependence on tobacco among adolescent smokers in Cyprus

PURPOSE: The purpose of this study is to assess tobacco dependence among Cypriot adolescents and examine its association to cigarette consumption and attitudes towards smoking. METHODS: The current study used cross-sectional data from the 2011 Cyprus Global Youth Tobacco Survey which adopted multistage cluster sampling methods to select adolescents registered in middle and high schools in Cyprus. Tobacco use, physical dependence on tobacco, and attitudes towards tobacco use were measured in 187 adolescents aged 13-18years old who reported that they had smoked at least once in the preceding 30 days. Physical dependence was assessed using the Levels of Physical Dependence scale. RESULTS: Physical dependence was present in 86% of the adolescent smokers. The mean latency to needing among smokers in the highest dependence group was 101h. Significant associations were observed between physical dependence and the perceived difficulty in quitting (OR=13.1, 95% CI: 4.0, 43.0) as well as the expectation to continue smoking for the next five years (OR=3.3, 95% CI: 1.3, 8.4). Significant associations were also observed between physical dependence and the number of smoking days per month, daily smoking, daily cigarette consumption, lifetime cigarette consumption, and perceived difficulty in abstaining from smoking for one week. CONCLUSIONS: Physical dependence provides a symptom-based approach to assess dependence and it is a strong predictor of adolescents\u27 perceptions of their ability to quit or to refrain from smoking for a week. Physical dependence on tobacco was highly prevalent among adolescent smokers in Cyprus and it was associated with greater perceived difficulty in quitting. Interventions targeting adolescent smoking must account for the high prevalence of physical dependence

Randomization Technique, Allocation Concealment, Masking, And Susceptibility Of Trials To Selection Bias

It is widely believed that baseline imbalances in randomized clinical trials must necessarily be random. Yet even among masked randomized trials conducted with allocation concealment, there are mechanisms by which patients with specific covariates may be selected for inclusion into a particular treatment group. This selection bias would force imbalance in those covariates, measured or unmeasured, that are used for the patient selection. Unfortunately, few trials provide adequate information to determine even if there was allocation concealment, how the randomization was conducted, and how successful the masking may have been, let alone if selection bias was adequately controlle d. In this article we reinforce the message that allocation details should be presented in full. We also facilitate such reporting by identifying and clarifying the role of specific reportable design features. Because the designs that eliminate all selection bias are rarely feasible in practice, our development has important implications for not only the implementation, but also the reporting and interpretation, of randomized clinical trials

Microvascular Architecture of Hepatic Metastases in a Mouse Model

Development of effective treatment for hepatic metastases can be initiated by a better understanding of tumour vasculature and blood supply. This study was designed to characterise the microvascular architecture of hepatic metastases and observe the source of contributory blood supply from the host. Metastases were induced in mice by an intrasplenic injection of colon carcinoma cells (106 cells/ml.) Vascularization of tumours was studied over a three week period by scanning electron microscopy of microvascular corrosion casts. Metastatic liver involvement was observed initially within a week post induction, as areas approximately 100 μm in diameter not perfused by the casting resin. On histology these spaces corresponded to tumour cell aggregates. The following weeks highlighted the angiogenesis phase of these tumours as they received a vascular supply from adjacent hepatic sinusoids. Direct sinusoidal supply of metastases was maintained throughout tumour growth. At the tumour periphery most sinusoids were compressed to form a sheath demarcating the tumour from the hepatic vasculature. No direct supply from the hepatic artery or the portal vein was observed. Dilated vessels termed vascular lakes dominated the complex microvascular architecture of the tumours, most tapering as they traversed towards the periphery. Four vascular branching patterns could be identified as true loops, bifurcations and trifurcations, spirals and capillary networks. The most significant observation in this study was the direct sinusoidal supply of metastases, together with the vascular lakes and the peripheral sinusoidal sheaths of the tumour microculature

Rectal budesonide and mesalamine formulations in active ulcerative proctosigmoiditis: efficacy, tolerance, and treatment approach

Ulcerative colitis (UC) is an immune-mediated disease of the colon that is characterized by diffuse and continuous inflammation contiguous from the rectum. Half of UC patients have inflammation limited to the distal colon (proctitis or proctosigmoiditis) that primarily causes symptoms of bloody diarrhea and urgency. Mild-to-moderate distal UC can be effectively treated with topical formulations (rectal suppositories, enemas, or foam) of mesalamine or steroids to reduce mucosal inflammation and alleviate symptoms. Enemas or foam formulations adequately reach up to the splenic flexure, have a minimal side-effect profile, and induce remission alone or in combination with systemic immunosuppressive therapy. Herein, we compare the efficacy, cost, patient tolerance, and side-effect profiles of steroid and mesalamine rectal formulations in distal UC. Patients with distal mild-to-moderate UC have a remission rate of approximately 75% (NNT =2) after treatment for 6 weeks with mesalamine enemas. Rectal budesonide foam induces remission in 41.2% of patients with mild-to-moderate active distal UC compared to 24% of patient treated with placebo (NNT =5). However, rectal budesonide has better patient tolerance profile compared to enema formulations. Despite its favorable efficacy, safety, and cost profiles, patients and physicians significantly underuse topical treatments for treating distal colitis. This necessitates improved patient education and physician familiarity regarding the indications, effectiveness, and potential financial and tolerability barriers in using rectal formulations

Effects of a community-based intervention package on postnatal care seeking behavior in rural Bangladesh: a cluster-randomized controlled trial

Background: Community-based Postnatal Care (PNC) initiatives have been found to improve maternal and neonatal health. Objectives: This paper aims at evaluating the effectiveness of a Community-Based Intervention Package in providing ‘limited’ PNC services by Community Support Systems (CmSS) and in increasing maternal PNC visits from Skilled Healthcare Providers (SHPs) in rural Bangladesh as well as identifying the predictors of maternal PNC from SHPs. Methods: A cluster-randomized controlled trial was employed where 6 clusters (each with an average population of about 28,000) of Narsingdi District were randomly assigned to the intervention and the comparison group. Sample sizes for pre- and post-intervention were 675 and 702, respectively, collected in June 2010 and December 2011, respectively, from mothers with a recent live birth. Logistic regression was used in examining the main outcomes and the predictors of maternal PNC from SHPs. Results: The coverage of ‘limited’ PNC services by the CmSS members to the mothers did not increase significantly (p=0.25), nor did the maternal PNC from SHPs (p=0.11). Both delivery at a Healthcare Facility and delivery by SHPs increased the odds of taking at least one PNC from SHPs 10-fold with 95% confidence intervals of 4.52-24.04 (p Conclusion: This intervention was found to be effective neither in providing limited PNC services by the CmSS members, nor in increasing maternal PNC from SHPs in our study. Further research with proper monitoring and sufficient number of clusters is recommended

Targeting the angiotensin II type 2 receptor (AT2R) in colorectal liver metastases

BACKGROUND: Blockade of the angiotensin (ANG) II type 1 receptor (AT1R) inhibits tumour growth in several cancers, including colorectal cancer (CRC) liver metastases. While AT1R blockade has been extensively studied, the potential of targeting the antagonistically acting AT2R in cancer has not been investigated. This study examined the effect of AT2R activation with the agonist CGP42112A in a mouse model of CRC liver metastases. RESULTS: In vitro, mouse CRC cell (MoCR) proliferation was inhibited by treatment with CGP42112A in a dose dependent manner while apoptosis was increased. Immunofluorescent staining for key signalling and secondary messengers, PLA2 and iNOS, were also increased by CGP42112A treatment in vitro. Immunohistochemical staining for proliferation (PCNA) and the apoptosis (active caspase 3) markers confirmed a CGP42112A-associated inhibition of proliferation and induction of apoptosis of mouse CRC cells (MoCR) in vivo. However, angiogenesis and vascular endothelial growth factor (VEGF) appeared to be increased by CGP42112A treatment in vivo. This increase in VEGF secretion by MoCRs was confirmed in vitro. Despite this apparent pro-angiogenic effect, a syngenic orthotopic mouse model of CRC liver metastases showed a reduction in liver to body weight ratio, an indication of tumour burden, following CGP42112A treatment compared to untreated controls. CONCLUSIONS: These results suggest that AT2R activation might provide a novel target to inhibit tumour growth. Its potential to stimulate angiogenesis could be compensated by combination with anti-angiogenic agents