Studying quasars at the highest redshifts can constrain models of galaxy and black hole formation, and it also probes the intergalactic medium in the early universe. Optical surveys have to date ...discovered more than 60 quasars up to z Asymptotically = to 6.4, a limit set by the use of the z-band and CCD detectors. Only one z gap 6.4 quasar has been discovered, namely the z = 7.08 quasar ULAS J1120+0641, using near-infrared imaging. Here we report the discovery of three new z gap 6.4 quasars in 332 deg super(2) of the Visible and Infrared Survey Telescope for Astronomy Kilo-degree Infrared Galaxy (VIKING) survey, thus extending the number from 1 to 4. The newly discovered quasars have redshifts of z = 6.60, 6.75, and 6.89. The absolute magnitudes are between -26.0 and -25.5, 0.6-1.1 mag fainter than ULAS J1120+0641. Near-infrared spectroscopy revealed the Mg II emission line in all three objects. The quasars are powered by black holes with masses of ~(1-2) x 10 super(9) M sub(middot in circle). In our probed redshift range of 6.44 < z < 7.44 we can set a lower limit on the space density of supermassive black holes of rho(M sub(BH) > 10 super(9) M sub(middot in circle)) > 1.1 x 10 super(-9) Mpc super(-3). The discovery of three quasars in our survey area is consistent with the z = 6 quasar luminosity function when extrapolated to z ~ 7. We do not find evidence for a steeper decline in the space density of quasars with increasing redshift from z = 6 to z = 7.
The VLT Survey Telescope ATLAS Shanks, T.; Metcalfe, N.; Chehade, B. ...
Monthly notices of the Royal Astronomical Society,
08/2015, Letnik:
451, Številka:
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Journal Article
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The VLT Survey Telescope ATLAS survey is an optical ugriz survey aiming to cover ≈4700 deg2 of the southern sky to similar depths as the Sloan Digital Sky Survey (SDSS). From reduced images and ...object catalogues provided by the Cambridge Astronomical Surveys Unit, we first find that the median seeing ranges from 0.8 arcsec FWHM (full width at half-maximum) in i to 1.0 arcsec in u, significantly better than the 1.2–1.5 arcsec seeing for SDSS. The 5σ mag limit for stellar sources is r
AB
= 22.7 and in all bands these limits are at least as faint as SDSS. SDSS and ATLAS are more equivalent for galaxy photometry except in the z band where ATLAS has significantly higher throughput. We have improved the original ESO magnitude zero-points by comparing m < 16 star magnitudes with the AAVSO Photometric All-Sky Survey in gri, also extrapolating into u and z, resulting in zero-points accurate to ≈ ± 0.02 mag. We finally compare star and galaxy number counts in a 250 deg2 area with SDSS and other count data and find good agreement. ATLAS data products can be retrieved from the ESO Science Archive, while support for survey science analyses is provided by the OmegaCAM Science Archive, operated by the Wide-Field Astronomy Unit in Edinburgh.
We present the results of our first year of quasar search in the ongoing ESO public Kilo-Degree Survey (KiDS) and VISTA Kilo-Degree Infrared Galaxy (VIKING) surveys. These surveys are among the ...deeper wide-field surveys that can be used to uncover large numbers of z ~ 6 quasars. This allows us to probe a more common population of z ~ 6 quasars that is fainter than the well-studied quasars from the main Sloan Digital Sky Survey. From this first set of combined survey catalogues covering ~250 deg... we selected point sources down to Z = 22 that had a very red i - Z (i - Z > 2.2) colour. After follow-up imaging and spectroscopy, we discovered four new quasars in the redshift range 5.8 < z < 6.0. The absolute magnitudes at a rest-frame wavelength of 1450 ... are between -26.6 < M... < -24.4, confirming that we can find quasars fainter than M*, which at z = 6 has been estimated to be between M* = -25.1 and M* = -27.6. The discovery of four quasars in 250 deg... of survey data is consistent with predictions based on the z ... 6 quasar luminosity function. We discuss various ways to push the candidate selection to fainter magnitudes and we expect to find about 30 new quasars down to an absolute magnitude of M... = -24. Studying this homogeneously selected faint quasar population will be important to gain insight into the onset of the co-evolution of the black holes and their stellar hosts. (ProQuest: ... denotes formulae/symbols omitted.)
The metabolic actions of storage fungi and other microorganisms can cause spoilage and post-harvest losses in agricultural commodities, including flaxseed. These microbial contaminants are oxidized ...with hydroxyl radicals that are efficiently generated when ozone, hydrogen peroxide (H
2
O
2
) and ultraviolet (UV) light react in an advanced oxidative process (AOP). The present work explores what we believe is the first application of an AOP technology to reduce mould on whole brown and yellow flaxseed. The impact of AOP on storage and quality parameters was assessed by measuring the fatty acid value (FAV), germination rate, moisture content (MC) and visible mould growth after 12 weeks of storage at 30°C and 75% relative humidity (RH). Under these conditions, the yellow decontaminated flaxseed showed a 31% decrease in the number of seeds with visible mould without any adverse effect on germination rate, FAV and MC. In contrast, the same AOP treatment created an insignificant decrease in mould in stored brown flaxseed, at the cost of decreasing the germination rate and increasing FAV. The adverse effects of AOP on brown flaxseed were not readily apparent but became measurable after storage. Moreover, Fourier transform infrared (FTIR) spectroscopy was utilized to explore the rationale behind the different reactions of flaxseed varieties to AOP. The corresponding results indicated that the tolerance of yellow flaxseed to AOP might be related to its richness in olefins. The authors believe that technologies that harness advanced oxidative processes open new horizons in decontamination beyond ozone alone and towards increasing the shelf life of various agri-food products.
Background The National Cancer Institute of Canada Clinical Trials Group CO.17 study showed that patients with advanced colorectal cancer had improved overall survival when cetuximab, an epidermal ...growth factor receptor–targeting antibody, was given in addition to best supportive care. We conducted a cost-effectiveness analysis using prospectively collected resource utilization and health utility data for patients in the CO.17 study who received cetuximab plus best supportive care (N = 283) or best supportive care alone (N = 274). Methods Direct medical resource utilization data were collected, including medications, physician visits, toxicity management, blood products, emergency department visits, and hospitalizations. Mean survival times for the study arms were calculated for the entire population and for the subset of patients with wild-type KRAS tumors over an 18- to 19-month period. All costs were presented in 2007 Canadian dollars. One-way and probabilistic sensitivity analysis was used to determine the robustness of the results. Cost-effectiveness acceptability curves were determined. The 95% confidence intervals (CIs) for the incremental cost-effectiveness ratios and the incremental cost–utility ratios were estimated by use of a nonparametric bootstrapping method (with 1000 iterations). Results For the entire study population, the mean improvement in overall and quality-adjusted survival with cetuximab was 0.12 years and 0.08 quality-adjusted life-years (QALYs), respectively. The incremental cost with cetuximab compared with best supportive care was $23 969. The incremental cost-effectiveness ratio was $199 742 per life-year gained (95% CI = $125 973 to $652 492 per life-year gained) and the incremental cost–utility ratio was $299 613 per QALY gained (95% CI = $187 440 to $898 201 per QALY gained). For patients with wild-type KRAS tumors, the incremental cost with cetuximab was $33 617 and mean gains in overall and quality-adjusted survival were 0.28 years and 0.18 QALYs, respectively. The incremental cost-effectiveness ratio was $120 061 per life-year gained (95% CI = $88 679 to $207 075 per life-year gained) and the incremental cost–utility ratio was $186 761 per QALY gained (95% CI = $130 326 to $334 940 per QALY gained). In a sensitivity analysis, cetuximab cost and patient survival were the only variables that influenced cost-effectiveness. Conclusions The incremental cost-effectiveness ratio of cetuximab over best supportive care alone in unselected advanced colorectal cancer patients is high and sensitive to drug cost. Incremental cost-effectiveness ratios were lower when the analysis was limited to patients with wild-type KRAS tumors.
We present a new redshift survey, the 2dF Quasar Dark Energy Survey pilot (2QDESp), which consists of ...10 000 quasars from ...150 deg^sup 2^ of the southern sky, based on VST-ATLAS imaging and ...2dF/AAOmega spectroscopy. Combining our optical photometry with the WISE (W1,W2) bands we can select essentially contamination free quasar samples with 0.8 < z < 2.5 and g < 20.5. At fainter magnitudes, optical UVX selection is still required to reach our g ... 22.5 limit. Using both these techniques we observed quasar redshifts at sky densities up to 90 deg^sup -2^. By comparing 2QDESp with other surveys (SDSS, 2QZ and 2SLAQ) we find that quasar clustering is approximately luminosity independent, with results for all four surveys consistent with a correlation scale of r^sub 0^ = 6.1 ± 0.1 h^sup -1^ Mpc, despite their decade range in luminosity. We find a significant redshift dependence of clustering, particularly when BOSS data with r^sub 0^ = 7.3 ± 0.1 h^sup -1^ Mpc are included at z ... 2.4. All quasars remain consistent with having a single host halo mass of ...2 ± 1 x 10^sup 12^ h^sup -1^ M... This result implies that either quasars do not radiate at a fixed fraction of the Eddington luminosity or AGN black hole and dark matter halo masses are weakly correlated. No significant evidence is found to support fainter, X-ray selected quasars at low redshift having larger halo masses as predicted by the 'hot halo' mode AGN model of Fanidakis et al. (2013). Finally, although the combined quasar sample reaches an effective volume as large as that of the original SDSS LRG sample, we do not detect the BAO feature in these data. (ProQuest: ... denotes formulae/symbols omitted.)
SUMMARY
The purpose of this study was to assess the oncological outcomes of a large multicenter series of left thoracoabdominal esophagectomies, and compare these to the more widely utilized ...Ivor–Lewis esophagectomy. With ethics approval and an established study protocol, anonymized data from five centers were merged into a structured database. The study exposure was operative approach (ILE or LTE). The primary outcome measure was time to death. Secondary outcome measures included time to tumor recurrence, positive surgical resection margins, lymph node yield, postoperative death, and hospital length of stay. Cox proportional hazards models provided hazard ratios (HR) with 95% confidence intervals (CI) adjusting for age, pathological tumor stage, tumor grade, lymphovascular invasion, and neoadjuvant treatment. Among 1228 patients (598 ILE; 630 LTE), most (86%) had adenocarcinoma (AC) and were male (81%). Comparing ILE and LTE for AC patients, no difference was seen in terms of time to death (HR 0.904 95%CI 0.749–1.1090) or time to recurrence (HR 0.973 95%CI 0.768–1.232). The risk of a positive resection margin was also similar (OR 1.022 95%CI 0.731–1.429). Median lymph node yield did not differ between approaches (LTE 21; ILE 21; P = 0.426). In-hospital mortality was 2.4%, significantly lower in the LTE group (LTE 1.3%; ILE 3.6%; P = 0.004). Median hospital stay was 11 days in the LTE group and 14 days in the ILE group (P < 0.0001). In conclusion, this is the largest series of left thoracoabdominal esophagectomies to be submitted for publication and the only one to compare two different transthoracic esophagectomy strategies. It demonstrates oncological equivalence between operative approaches but possible short- term advantages to the left thoracoabdominal esophagectomy.
Aim
Transanal total mesorectal excision (TaTME) offers a promising alternative to the standard surgical abdominopelvic approach for rectal cancer. The aim of this study was to report a two‐centre ...experience of this technique, focusing on the short‐term and oncological outcome.
Method
From May 2013 to May 2015, 40 selected patients with histologically proven rectal adenocarcinoma underwent TaTME in two institutions and were prospectively entered on an online international registry.
Results
Forty patients (80% men, mean body mass index 27.4 kg/m2) requiring TME underwent TaTME. Procedures included low anterior resection (n = 31), abdominoperineal excision (n = 7) and proctocolectomy (n = 2). A minimally invasive approach was attempted in all cases, with three conversions. The mean operation time was 368 min and 16 patients (40%) had a synchronous abdominal and transanal approach. There was no mortality and 16 postoperative complications occurred, of which 68.8% were minor. The median length of stay was 7.5 (3–92) days. A complete or near‐complete TME specimen was delivered in 39 (97.5%) cases with a mean number of 20 lymph nodes harvested. R0 resection was achieved in 38 (95%) patients. After a median follow‐up of 10.7 months, there were no local recurrences and six (15%) patients had developed distant metastases.
Conclusion
TaTME appears to be feasible, safe and reproducible, without compromising the oncological principles of rectal cancer surgery. It is an attractive option for patients for whom laparoscopy is likely to be particularly difficult. These encouraging results should encourage larger studies with assessment of long‐term function and the oncological outcome.
The European Southern Observatory's (ESO) Visible and Infrared Survey Telescope for Astronomy (VISTA) is a 4-m class survey telescope for wide-field near-infrared imaging. VISTA is currently running ...a suite of six public surveys, which will shortly deliver their first Europe wide public data releases to ESO. The VISTA Kilo-degree Infrared Galaxy survey (VIKING) forms a natural intermediate between current wide shallow and deeper more concentrated surveys, by targeting two patches totalling 1500 deg2 in the Northern and Southern hemispheres with measured 5σ limiting depths of Z≃ 22.4, Y≃ 21.4, J≃ 20.9, H≃ 19.9 and K
s≃ 19.3 (Vega). This architecture forms an ideal working parameter space for the discovery of a significant sample of 6.5 ≤ z ≤ 7.5 quasars. In the first data release, priority has been placed on small areas encompassing a number of fields well sampled at many wavelengths, thereby optimizing science gains and synergy whilst ensuring a timely release of the first products. For rare object searches, e.g. high-z quasars, this policy is not ideal since photometric selection strategies generally evolve considerably with the acquisition of data. Without a reasonably representative data set sampling many directions on the sky, it is not clear how a rare object search can be conducted in a highly complete and efficient manner.
In this paper, we alleviate this problem by supplementing initial data with a realistic model of the spatial, luminosity and colour distributions of sources known to heavily contaminate photometric quasar selection spaces, namely dwarf stars of spectral types M, L and T. We use this model along with a subset of available data to investigate contamination of quasar selection space by cool stars and galaxies and lay down a set of benchmark selection constraints that limit contamination to reasonable levels whilst maintaining high completeness as a function of both magnitude and redshift. We review recent follow-up imaging of the first VIKING high-z quasar candidates and find that the results lend considerable support for the choice of selection constraints. The methods outlined here are also applicable to rare object searches in a number of other ongoing and forthcoming projects.
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