Observation of the baryonic decay B \uaf 0 \u2192 \u39bc+ p \uaf K-K+

We report the observation of the baryonic decay B\uaf0\u2192\u39bc+p\uafK-K+ using a data sample of 471 7106 BB\uaf pairs produced in e+e- annihilations at s=10.58GeV. This data sample was recorded with the BABAR detector at the PEP-II storage ring at SLAC. We find B(B\uaf0\u2192\u39bc+p\uafK-K+)=(2.5\ub10.4(stat)\ub10.2(syst)\ub10.6B(\u39bc+)) 710-5, where the uncertainties are statistical, systematic, and due to the uncertainty of the \u39bc+\u2192pK-\u3c0+ branching fraction, respectively. The result has a significance corresponding to 5.0 standard deviations, including all uncertainties. For the resonant decay B\uaf0\u2192\u39bc+p\uaf\u3c6, we determine the upper limit B(B\uaf0\u2192\u39bc+p\uaf\u3c6)<1.2 710-5 at 90% confidence level

Search for Darkonium in e+e- Collisions

Collider searches for dark sectors, new particles interacting only feebly with ordinary matter, have largely focused on identifying signatures of new mediators, leaving much of dark sector structures unexplored. In particular, the existence of dark matter bound states (darkonia) remains to be investigated. This possibility could arise in a simple model in which a dark photon (A0 ) is light enough to generate an attractive force between dark fermions. We report herein a search for a JPC ¼ 1−− darkonium state, the ϒD, produced in the reaction eþe− → γϒD, ϒD → A0 A0 A0 , where the dark photons subsequently decay into pairs of leptons or pions, using 514 fb−1 of data collected with the BABAR detector. No significant signal is observed, and we set bounds on the γ − A0 kinetic mixing as a function of the dark sector coupling constant for 0.001 < mA0 < 3.16 GeV and 0.05 < mϒD < 9.5 GeV.publishedVersio

Use of biguanides and the risk of colorectal cancer: a register-based cohort study

Observational studies have shown conflicting results on the potential protecting effect of biguanide use with the risk of colorectal neoplasms. In addition, the cellular mechanism can either support or oppose biguanides influence on colorectal carcinoma. Our objective was to evaluate the association between biguanide use and colorectal carcinoma. A population-based cohort study using healthcare data from the Danish National database (1996-2007), was conducted. Oral antidiabetic drug users (n = 177,281) were matched 1:3 with a population-based reference group. Cox proportional hazard models estimated hazard ratios (HRs) of colorectal carcinoma. Stratification was performed to analyse the risk of colorectal cancer in current biguanide users. Two sub-analyses were performed, to investigate the risk of colorectal cancer associated with discontinuous and prolonged use of biguanides. Instead of a protective effect, we found that current biguanide users had a 1.2-fold increased risk of colorectal cancer (HR = 1.19, 95% CI = 1.08-1.30) as compared with the non-diabetes reference group. Prolonged use was not inversely associated with colorectal cancer either. When studying colorectal risk with biguanides, the underlying T2DM should be taken into account since a 1.3-1.6-fold increased risk was found in oral antidiabetic drug users compared to controls unexposed to diabetic medication. This study could not detect a protective effect of biguanide use with colorectal cancer. Therefore, this study does not support a further investigation of the effectiveness of biguanides to prevent colorectal carcinoma in clinical studies

Neoproterozoic cap carbonates: a critical appraisal of existing models and the plumeworld hypothesis

Evidence for glaciation during the mid-late Neoproterozoic is widespread on Earth, reflecting three or more ice ages between 730 Ma and 580 Ma. Of these, the late Neoproterozoic Marinoan glaciation of approximately 635 Ma stands out because of its ubiquitous association with a characteristic, microcrystalline cap dolostone that drapes glacially influenced rock units worldwide. The Marinoan glaciation is also peculiar in that evidence for low altitude glaciation at equatorial latitudes is compelling. Three models have been proposed linking abrupt deglaciation with this global carbonate precipitation event: (i) overturn of an anoxic deep ocean; (ii) catastrophically accelerated rates of chemical weathering because of supergreenhouse conditions following global glaciation (Snowball Earth Hypothesis); and (iii) massive release of carbonate alkalinity from destabilized methane clathrates. All three models invoke extreme alkalinity fluxes into seawater during deglaciation but none explains how such alkalinity excess from point sources could be distributed homogeneously around the globe. In addition, none explains the consistent sequence of precipitation events observed within cap carbonate successions, specifically: (i) the global blanketing of carbonate powder in shallow marine environments during deglaciation; (ii) widespread and disruptive precipitation of dolomite cement; followed by (iii) localized barite precipitation and seafloor cementation by aragonite. The conceptual model presented here proposes that low latitude deglaciation was so massive and abrupt that the resultant meltwater plume could extend worldwide, physically separating the surface and deep ocean reservoirs for ≥103 years. It is proposed that cap dolostones formed primarily by microbially mediated precipitation of carbonate whitings during algal blooms within this low salinity plumeworld rather than by abiotic precipitation from normal salinity seawater. Many of the disruption features that are characteristic of cap dolostones can be explained by microbially mediated, early diagenetic dolomitization and cementation. The re-initiation of whole ocean circulation degassed CO2 into the atmosphere in areas of upwelling, triggering localized, abiotic CaCO3 precipitation in the form of aragonite fans that overlie cap dolostones in NW Canada and Namibia. The highly oxygenated shallow marine environments of the glacial and post-glacial Neoproterozoic world provided consistently favourable conditions for the evolutionary development of animals and other oxygenophiles