Missing Stellar Mass in SED Fitting: Spatially Unresolved Photometry can Underestimate Galaxy Masses

We fit model spectral energy distributions to each pixel in 67 nearby (=0.0057) galaxies using broadband photometry from the Sloan Digital Sky Survey and GALEX. For each galaxy, we compare the stellar mass derived by summing the mass of each pixel to that found from fitting the entire galaxy treated as an unresolved point source. We find that, while the pixel-by-pixel and unresolved masses of galaxies with low specific star formation rates (such as ellipticals and lenticulars) are in rough agreement, the unresolved mass estimate for star-forming galaxies is systematically lower then the measurement from spatially-resolved photometry. The discrepancy is strongly correlated with sSFR, with the highest sSFRs in our sample having masses underestimated by 25% (0.12 dex) when treated as point sources. We found a simple relation to statistically correct mass estimates derived from unresolved broad-band SED fitting to the resolved mass estimates: m_{resolved} = m_{unresolved}/(-0.057log(sSFR) + 0.34) where sSFR is in units of yr^{-1}. We study the effect of varying spatial resolution by degrading the image resolution of the largest images and find a sharp decrease in the pixel-by-pixel mass estimate at a physical scale of approximately 3 kpc, which is comparable to spiral arm widths. The effects we observe are consistent with the "outshining" idea which posits that the youngest stellar populations mask more massive, older -- and thus fainter -- stellar populations. Although the presence of strong dust lanes can also lead to a drastic difference between resolved and unresolved mass estimates (up to 45% or 0.3 dex) for any individual galaxy, we found that resolving dust does not affect mass estimates on average. The strong correlation between mass discrepancy and sSFR is thus most likely due to the outshining systematic bias.Comment: 13 pages, 8 figures, accepted for publication in MNRA

Misfit landforms imposed by ill-conditioned inverse parametric problems

In the paper, we put forward a new topological taxonomy which allows to distinguish and separate multiple solutions to the ill-conditioned parametric inverse problems appearing in engineering, geophysics, medicine, etc. This taxonomy distinguishes the areas of insensitivity to parameters, called landforms of the misfit landscape, be it around minima (lowlands), maxima (uplands), or stationary points (shelves). We proved their important separability and completeness conditions. In particular, lowlands, uplands and shelves are pairwise disjoint and there are no other subsets of the positive measure in the admissible domain on which misfit function takes a constant value. The topological taxonomy is related to the second, 'local' one, which characterizes the types of ill-conditioning of the particular solutions. We hope that the proposed results will be helpful for a better and more precise formulation of the ill-conditioned inverse problems and for selecting and profiling complex optimization strategies used to solve these problems

Studies of Flexural Creep Behavior in Particleboard Under Changing Humidity Conditions

The effect of changing relative humidity, to cause simple adsorption or cyclic adsorption-desorption, on the creep behavior of particleboard, oriented particleboard, and plywood was studied. For the particular boards studied, creep response was sensitive to the highest humidity to which the boards were subjected. Behavior of both urea and phenolic resin-bonded particleboards was similar. When stressed below approximately 20% of maximum static bending strength, flexural creep was linear with stress level. An increased rate of adsorption had a smaller overall effect than the greatest humidity level to which the board was subjected. A shavings/residue-type particleboard demonstrated accelerated creep behavior above about 75% RII. Although plywood and oriented particleboard had increased creep at the higher humidity levels, there did not appear to be as definite a point where creep rate accelerated. Flexural creep behavior under a single concentrated load was qualitatively similar to that under simple flexural stress

Estimation of gastric ghrelin-positive cells activity in hyperthyroid rats.

Ghrelin is a peptide of 28 amino acids that transmits appetite related signals from peripheral organs to the brain. The main source of ghrelin is stomach. The regulation of ghrelin secretion is still unknown. The finding that fasting and food intake, respectively increase and decrease the secretion of ghrelin suggests that this hormone may be a bridge connecting somatic growth with energy metabolism and appears to play an important role in the alteration of energy homeostasis and body weight in pathophisiological conditions. The purpose of this study was the evaluation of gastric ghrelin immunoreactivity and ghrelin plasma concentration in male Wistar rats with hyperthyroidism. Experimental model of hyperthyroidism was induced by intraperitoneal injection of levothyroxine at the dose of 80 microg/kg daily over 21 days. At the end of experiment the animals were anaesthetized, blood was taken from abdominal aorta to determinate plasma ghrelin concentration by RIA and then the animals underwent resection of distal part of stomach. Immunohistochemical study were performed using monoclonal specific antybodies against ghrelin. Hyperthyroidism was a reason of increase of gastric mucosal ghrelin - immunoreactivity, accompanied by a significant decreased of ghrelin plasma concentration. Those observations may indicate, that chronic administration of L-thyroxine cause the change of ghrelin plasma concentration in rats, probably via direct influence on gastric X/A-like cells, but this effect is not responsible for hyperphagia associated with hyperthyroidism

Cannabinoids enhance gastric X/A-like cells activity.

It has been reported that cannabinoids may cause overeating in humans and in laboratory animals. Although, endogenous cannabinoids and their receptors (CB1) have been found in the hypothalamus, and recently also in gastrointestinal tract, the precise mechanism of appetite control by cannabinoids remains unknown. Recently, ghrelin--a hormone secreted mainly from the stomach X/A-like cells was proposed to be an appetite stimulating agent. The aim of this study was the evaluation of the influence of a single ip injection of a stable analogue of endogenous cannabinoid--anandamide, R-(+)-methanandamide (2.5 mg/kg) and CP 55,940 (0.25 mg/kg), an exogenous agonist of CB1 receptors, on ghrelin plasma concentration and on ghrelin immunoreactivity in the gastric mucosa of male Wistar rats. Four hours after a single injection of both cannabinoids or vehicle, the animals were anaesthetized and blood was taken from the abdominal aorta to determinate plasma ghrelin concentration by RIA. Subsequently, the animals underwent resection of distal part of stomach. Immunohistochemical study of gastric mucosa, using the EnVision method and specific monoclonal antibodies against ghrelin was performed. The intensity of ghrelin immunoreactivity in X/A-like cells was analyzed using Olympus Cell D image analysis system. The attenuation of ghrelin-immunoreactivity of gastric mucosa, after a single injection of R-(+)-methanandamide and CP 55,940 was accompanied by a significant increase of ghrelin plasma concentration. These results indicate that stimulation of appetite exerted by cannabinoids may be connected with an increase of ghrelin secretion from gastric X/A-like cells

Using the 1.6um Bump to Study Rest-frame NIR Selected Galaxies at Redshift 2

We explore the feasibility and limitations of using the 1.6um bump as a photometric redshift indicator and selection technique and use it to study the rest-frame H-band galaxy luminosity and stellar mass functions at redshift z~2. We use publicly available Spitzer/IRAC images in the GOODS fields and find that color selection in the IRAC bandpasses alone is comparable in completeness and contamination to BzK selection. We find that the shape of the 1.6um bump is robust, and photometric redshifts are not greatly affected by choice of model parameters. Comparison with spectroscopic redshifts shows photometric redshifts to be reliable. We create a rest-frame NIR selected catalog of galaxies at z~2 and construct a galaxy stellar mass function (SMF). Comparisons with other SMFs at approximately the same redshift but determined using shorter wavelengths show good agreement. This agreement suggests that selection at bluer wavelengths does not miss a significant amount of stellar mass in passive galaxies. Comparison with SMFs at other redshifts shows evidence for the downsizing scenario of galaxy evolution. We conclude by pointing out the potential for using the 1.6um technique to select high-redshift galaxies with the JWST, whose lambda > 0.6 um coverage will not be well suited to selecting galaxies using techniques that require imaging at shorter wavelengths.Comment: Accepted for publication in Ap

Activity of the thyroid parafollicular (C) cells in simple and hyperactive nodular goitre treated surgically - preliminary investigations

The aim of this study was to evaluate the significance of measuring calcitonin (CT) plasma concentrations in patients with simple and hyperthyroid goitre treated surgically. Eighty four patients who underwent operations during the years 2000-2002 were analysed. Plasma concentrations of CT were determined by commercially available radioimmunoassay on the day of hospitalisation. Elevated concentrations of CT were found in 8 patients: in 5 out of 26 (19.2%) and in 3 out of 33 (9.0%) patients with Graves’ disease and with multinodular goitre, respectively. No major differences in concentrations of CT were observed in patients with simple goitre. Postoperative morphological analysis of pathologically changed hyperactive thyroids showed the presence of enlarged C cells distributed either in small groups or even singly with weakening immunohistochemical reaction for CT. These observations may point to the possibility of a relationship between the functional state of the thyroid gland and the activity of C cells

The role of HE4 and CA125 in differentiation between malignant and non-malignant endometrial pathologies

Objectives: The aim of the study was to assess the role of HE4 and CA125 in differentiation between malignant and non-malignant endometrial pathologies. Material and methods: A retrospective study of 87 patients with endometrial pathologies was conducted. Tumor markers were assessed two weeks before surgical intervention in each subject. The final diagnosis was established on the basis of the histopathological examination of the endometrium. Results: Serum HE4 levels were significantly higher in patients with endometrial cancer (EC) as compared to non-malignant endometrial pathologies (p < 0.001), patients with stage I EC as compared to non-malignant endometrial pathologies (p < 0.001), and patients with stage Ia EC as compared to non-malignant endometrial pathologies (p = 0.003). Serum CA125 levels were not significantly different as far as these groups of patients were concerned. Both tumor markers were significantly higher in patients with stage II-III as compared to stage I EC and non-malignant endometrial pathologies (p < 0.001 for both markers). Sensitivity and specificity of HE4 at the cut-off level of 70 pmol/L for detecting endometrial malignancies were 73.08% and 85.71%, respectively. Sensitivity and specificity of CA125 at the cut-off level of 35 U/mL were 29.41% and 94.29%, respectively. The area under the curve (AUC) for HE4 was 0.875, suggesting that this marker reliably differentiates malignant from non-malignant endometrial pathologies (p < 0.001). AUC for CA125 was 0.552, suggesting that this marker does not reliably differentiate between malignant and non-malignant endometrial pathologies (p = 0.414). Conclusion: HE4, in contrast to CA125, might be a useful tool for detecting malignant endometrial pathologies