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Galaxy proto-clusters at z 2 provide a direct probe of the rapid mass assembly and galaxy growth of present day massive clusters. Because of the need of precise galaxy redshifts for density mapping and the prevalence of star formation before quenching, nearly all the proto-clusters known to date were confirmed by spectroscopy of galaxies with strong emission lines. Therefore, large emission-line galaxy surveys provide an efficient way to identify proto-clusters directly. Here we report the discovery of a large-scale structure at z = 2.44 in the HETDEX Pilot Survey. On a scale of a few tens of Mpc comoving, this structure shows a complex overdensity of Lyα emitters (LAE), which coincides with broad-band selected galaxies in the COSMOS/UltraVISTA photometric and zCOSMOS spectroscopic catalogs, as well as overdensities of intergalactic gas revealed in the Lyα absorption maps of Lee et al. (2014). We construct mock LAE catalogs to predict the cosmic evolution of this structure. We find that such an overdensity should have already broken away from the Hubble flow, and part of the structure will collapse to form a galaxy cluster with 10 14.5±0.4 M by z = 0. The structure contains a higher median stellar mass of broad-band selected galaxies, a boost of extended Lyα nebulae, and a marginal excess of active galactic nuclei relative to the field, supporting a scenario of accelerated galaxy evolution in cluster progenitors. Based on the correlation between galaxy overdensity and the z = 0 descendant halo mass calibrated in the simulation, we predict that several hundred 1.9 < z < 3.5 proto-clusters with z = 0 mass of > 10 14.5 M will be discovered in the 8.5 Gpc 3 of space surveyed by the Hobby Eberly Telescope Dark Energy Experiment.in the largest halos first, i.e., in cluster progenitors during this epoch (Kereš et al. 2005;Dekel & Birnboim 2006;Dekel et al. 2009b). The subsequent virialization on both galaxy and cluster scales in about a dynamical timescale largely erases the signatures of the aforementioned processes, placing a fundamental limit on inferences based on the largely archaeological record of cluster formation based upon near-field studies. Direct studies of cluster progenitors thus provide irreplaceable probes to understand the formation of present day massive clusters.The search for high-redshift cluster progenitors is challenging due to their lack of mature cluster signatures such as extended X-ray emission (Fassbender et al. 2011), the Sunyaev-Zel'dovich effect (Bleem et al. 2015), and the prominent galaxy red sequence (Gladders & Yee 2005;Gilbank et al. 2011). The fundamental picture of gravitational structure formation implies that the most massive collapsed objects evolved from the densest regions in the early universe on a large scale (Kravtsov & Borgani 2012, and references therein). The finding of proto-clusters requires identifying galaxy overdensities in three-dimensions using precise redshift measurements (Chiang et al. 2013b).Active star formation in cluster progenitors implies that (at least ...

BackgroundTo explore if exposures to specific heavy metals in the environment is a new risk factor of oral cancer, one of the fastest growing malignancies in Taiwan, in addition to the two established risk factors, cigarette smoking and betel quid chewing.MethodsThis is an observational study utilized the age-standardized incidence rates of oral cancer in the 316 townships and precincts of Taiwan, local prevalence rates of cigarette smoking and betel quid chewing, demographic factors, socio-economic conditions, and concentrations in farm soils of the eight kinds of heavy metal. Spatial regression and GIS (Geographic Information System) were used. The registration contained 22,083 patients, who were diagnosed with oral cancer between 1982 and 2002. The concentrations of metal in the soils were retrieved from a nation-wide survey in the 1980s.ResultsThe incidence rate of oral cancer is geographically related to the concentrations of arsenic and nickel in the patients' residential areas, with the prevalence of cigarette smoking and betel quid chewing as controlled variables.ConclusionsBeside the two established risk factors, cigarette smoking and betel quid chewing, arsenic and nickel in farm soils may be new risk factors for oral cancer. These two kinds of metal may involve in the development of oral cancer. Further studies are required to understand the pathways via which metal in the farm soils exerts its effects on human health.

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This study aimed to elucidate whether or not high-risk clusters of oral cancer (OC) incidence spatially correlate with the prevalence rates of betel quid chewing (BQC) and cigarette smoking (CS) in Taiwan. The spatial autocorrelation and potential clusters of OC incidence among the 307 townships and heavy metal content of soil throughout Taiwan were identified using the Anselin's local Moran test. Additionally, the spatial correlations among the incidence of OC, the prevalence of BQC and CS and heavy metal content of soil were determined based on a comparison of spatial clusters. High-risk OC (Moran's I = 0.638, P <0.001) clusters were located in central and eastern Taiwan, while "hot spots" of BQC and CS prevalence were located mainly in eastern Taiwan. The distributions of BQC and CS lifestyle factors (P <0.001) were spatially autocorrelated. The "hot spots" of OC largely coincided with the "hot spots" of BQC, except for the Changhua and Yunlin counties, which are located in central Taiwan. However, high soil contents of nickel and chromium (P <0.001) in central Taiwan also coincided with the high-risk areas of OC incidence. In particular, Changhua county has incurred several decades of serious heavy-metal pollution, with inhabitants living in polluted areas having high-risk exposure to these metals. Results of this study suggest that, in addition to BQC and CS, anthropogenic pollution may profoundly impact the complexity of OC aetiology in central Taiwan.