558 research outputs found
The Globular Cluster Systems in the Coma Ellipticals. II: Metallicity Distribution and Radial Structure in NGC 4874, and Implications for Galaxy Formation
Deep HST/WFPC2 (V,I) photometry is used to investigate the globular cluster
system (GCS) in NGC 4874, the central cD galaxy of the Coma cluster. The
luminosity function of the clusters displays its normal Gaussian-like shape and
turnover level. Other features of the system are surprising: the GCS is (a)
spatially extended, with core radius r_c = 22 kpc, (b) entirely metal-poor (a
narrow, unimodal metallicity distribution with mean [Fe/H] = -1.5), and (c)
modestly populated, with specific frequency S_N = 3.7 +- 0.5. We suggest on the
basis of some simple models that as much as half of this galaxy might have
accreted from low-mass satellites, but no single one of the three classic modes
of galaxy formation (accretion, disk mergers, in situ formation) can supply a
fully satisfactory formation picture. Even when they are used in combination,
strong challenges to these models remain. The principal anomaly in this GCS is
essentially the complete lack of metal-rich clusters. If these were present in
normal (M87-like) numbers in addition to the metal-poor ones that are already
there, then the GCS in total would more closely resemble what we see in many
other giant E galaxies.Comment: 27 pp. with 9 Figures. Astrophys.J. 533, in press (April 10, 2000
Plasma sarcosine does not distinguish early and advanced stages of prostate cancer
Introduction. Diagnosis of prostate cancer by prostate specific antigen (PSA) is error-prone and cannot distinguish benign prostatic hyperplasia (BPH) from malignant disease, nor identify aggressive and indolent types.
Methods. We determined serum sarcosine (N-methylglycine) in 328 cancer patients by gas chromatography (GC)/mass spectroscopy (MS) and searched for correlations with early (stage T1/T2) and advanced (stage T3/T4) disease.
Results. Serum sarcosine of male control patients ranged from 1.7 ”mol/l to 4.8 ”mol/l. In prostate cancer patients, sarcosine ranged from 2.8 ”mol/l to 20.1 ”mol/l. Expressed as the sarcosine/alanine ratio, serum control values were 9.4±5.5x10-3 (mean±SD) compared with 21.6±9.0; 28.5±16.6; 22.7±7.7 and 22.2±11.0 for patients diagnosed with T1, T2, T3 and T4 prostate tumours, respectively. The small differences between T1, T2, T3 and T4 patients were not statistically significant (p=0.51). However, the conventional PSA marker significantly correlated with T stage in these patients (r=0.63;
Arsenic in Soils and Forages from Poultry Litter-Amended Pastures
In regions of concentrated poultry production, poultry litter (PL) that contains significant quantities of trace elements is commonly surface-applied to pastures at high levels over multiple years. This study examined the effect of long-term applications of PL on soil concentrations of arsenic (As), copper (Cu), Zinc (Zn), and the uptake of these elements by bermuda grass grown on Cecil (well-drained) and Sedgefield (somewhat poorly-drained) soils. The results showed that concentrations of As, Cu, and Zn in soils that had received surface-applied PL over a 14-year period were significantly greater than untreated soil at 0â2.5 and 2.5â7.5 cm depths. However, the levels were well below the USEPA loading limits established for municipal biosolids. Arsenic fractionation showed that concentrations of all As fractions were significantly greater in PL-amended soils compared to untreated soils at 0â2.5 and 2.5â7.5 cm depths. The residual fraction was the predominant form of As in all soils. The water-soluble and NaHCO3-associated As were only 2% of the total As. Significant differences were found in concentrations of these trace elements and phosphorus (P) in forage from PL-amended soils compared to that in untreated plots. The concentrations of Cu, Zn, As, and P were significantly greater in forage from Sedgefield amended soil compared to Cecil soil, but were in all cases below levels of environmental concern
A calibration method for broad-bandwidth cavity enhanced absorption spectroscopy performed with supercontinuum radiation
An efficient calibration method has been developed for broad-bandwidth cavity enhanced absorption spectroscopy. The calibration is performed using phase shift cavity ring-down spectroscopy, which is conveniently implemented through use of an acousto-optic tunable filter (AOTF). The AOTF permits a narrowband portion of the SC spectrum to be scanned over the full high-reflectivity bandwidth of the cavity mirrors. After calibration the AOTF is switched off and broad-bandwidth CEAS can be performed with the same light source without any loss of alignment to the set-up. We demonstrate the merits of the method by probing transitions of oxygen molecules O-2 and collisional pairs of oxygen molecules (O-2)(2) in the visible spectral range
Identification of 2,4-Disubstituted Imidazopyridines as Hemozoin Formation Inhibitors with Fast-Killing Kinetics and In Vivo Efficacy in the Plasmodium falciparum NSG Mouse Model
A series of 2,4-disubstituted imidazopyridines, originating from a SoftFocus Kinase library, was identified from a high throughput phenotypic screen against the human malaria parasite Plasmodium falciparum. Hit compounds showed moderate asexual blood stage activity. During lead optimization, several issues were flagged such as cross-resistance against the multidrug-resistant K1 strain, in vitro cytotoxicity, and cardiotoxicity and were addressed through structureâactivity and structureâproperty relationship studies. Pharmacokinetic properties were assessed in mice for compounds showing desirable in vitro activity, a selectivity window over cytotoxicity, and microsomal metabolic stability. Frontrunner compound 37 showed good exposure in mice combined with good in vitro activity against the malaria parasite, which translated into in vivo efficacy in the P. falciparum NOD-scid IL-2RÎłnull (NSG) mouse model. Preliminary mechanistic studies suggest inhibition of hemozoin formation as a contributing mode of action
âReal interestâ? Understanding the 2018 Agreement to Prevent Unregulated High Seas Fisheries in the Central Arctic Ocean
Analysis of a recovery process: Dwingelose Heide revisited
The recovery process of a Dutch heathland after fire is investigated. The study area, 12 m x 20 m, has been surveyed yearly between 1963 and 1993. Previous work has shown that a stationary Markov chain models the observed recovery process well. However, the Markov model fails to capture an important observation, the existence of a phase structure. The process begins deterministically, but small random (non-Markov) effects accumulate through time and at some point the process suddenly becomes noisy. Here we make use of the spatial information contained in vegetation maps to examine dynamics at a fine spatial scale. We find that the phases observed at a large spatial scale separate themselves out distinctly at finer spatial scales. This spatial information allows us to investigate hypotheses about the mechanisms governing deterministic versus noisy vegetation dynamics
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