Dark matter within high surface brightness spiral galaxies

We present results from a detailed dynamical analysis of five high surface brightness, late type spirals, studied with the aim to quantify the luminous-to-dark matter ratio inside their optical radii. The galaxies' stellar light distribution and gas kinematics have been observed and compared to hydrodynamic gas simulations, which predict the 2D gas dynamics arising in response to empirical gravitational potentials, which are combinations of differing stellar disk and dark halo contributions. The gravitational potential of the stellar disk was derived from near-infrared photometry, color-corrected to constant (M/L); the dark halo was modelled by an isothermal sphere with a core. Hydrodynamic gas simulations were performed for each galaxy for a sequence of five different mass fractions of the stellar disk and for a wide range of spiral pattern speeds. These two parameters mainly determine the modelled gas distribution and kinematics. The agreement between the non-axisymmetric part of the simulated and observed gas kinematics permitted us to conclude that the galaxies with the highest rotation velocities tend to possess near-maximal stellar disks. In less massive galaxies, with v_max<200 km/s, the mass of the dark halo at least equals the stellar mass within 2-3 R_disk. The simulated gas morphology provides a powerful tool to determine the dominant spiral pattern speed. The corotation radius for all galaxies was found to be constant at R_corotation ~ 3 R_disk and encloses the strong part of the stellar spiral in all cases.Comment: 28 pages, 7 figures; to appear in the Astrophysical Journal, Vol. 586, March 200

Effect of rapidly resorbable bone substitute materials on the temporal expression of the osteoblastic phenotype \u3cem\u3ein vitro\u3c/em\u3e

Ideally, bioactive ceramics for use in alveolar ridge augmentation should possess the ability to activate bone formation and, thus, cause the differentiation of osteoprogenitor cells into osteoblasts at their surfaces. Therefore, in order to evaluate the osteogenic potential of novel bone substitute materials, it is important to examine their effect on osteoblastic differentiation. This study examines the effect of rapidly resorbable calcium–alkali– orthophosphates on osteoblastic phenotype expression and compares this behavior to that of ß-tricalcium phosphate (TCP) and bioactive glass 45S5. Test materials were three materials (denominated GB14, GB9, GB9/25) with a crystalline phase Ca2KNa(PO4)2 and with a small amorphous portion containing either magnesium potassium phosphate (GB14) or silica phosphate (GB9 and GB9/25, which also contains Ca2P2O7); and a material with a novel crystalline phase Ca10[K/Na](PO4)7 (material denominated 352i). SaOS-2 human bone cells were grown on the substrata for 3, 7, 14, and 21 days, counted, and probed for an array of osteogenic markers. GB9 had the greatest stimulatory effect on osteoblastic proliferation and differentiation, suggesting that this material possesses the highest potency to enhance osteogenesis. GB14 and 352i supported osteoblast differentiation to the same or a higher degree than TCP, whereas, similar to bioactive glass 45S5, GB9/25 displayed a greater stimulatory effect on osteoblastic phenotype expression, indicating that GB9/25 is also an excellent material for promoting osteogenesis

Office-Based Preventive Dental Program and Statewide Trends in Dental Caries

To evaluate the impact of a North Carolina Medicaid preventive dentistry program in primary care medical offices (Into the Mouths of Babes Program [IMBP]) on decayed, missing, and filled teeth (dmft) of kindergarten students statewide and in schools with a large proportion of students from low-income families

Effects of Physician-Based Preventive Oral Health Services on Dental Caries

Most Medicaid programs reimburse nondental providers for preventive dental services. We estimate the impact of comprehensive preventive oral health services (POHS) on dental caries among kindergarten students, hypothesizing improved oral health among students with medical visits with POHS

Gross and net production during the spring bloom along the Western Antarctic Peninsula

Author Posting. © The Author(s), 2014. This is the author's version of the work. It is posted here by permission of New Phytologist Trust for personal use, not for redistribution. The definitive version was published in New Phytologist 205 (2015): 182-191, doi:10.1111/nph.13125.This study explores some of the physiological mechanisms responsible for high productivity near the shelf in the Western Antarctic Peninsula despite a short growing season and cold temperature. We measured gross and net primary production at Palmer Station during the summer 2012/2013 via three different techniques: 1) incubation with H218O; 2) incubation with 14CO2; and 3) in situ measurements of O2/Ar and triple oxygen isotope. Additional laboratory experiments were performed with the psychrophilic diatom Fragilariopsis cylindrus. During the spring bloom, which accounted for more than half of the seasonal gross production at Palmer Station, the ratio of net to gross production reached a maximum greater than ~60%, among the highest ever reported. The use of multiple-techniques showed that these high ratios resulted from low heterotrophic respiration and very low daylight autotrophic respiration. Laboratory experiments revealed a similar ratio of net to gross O2 production in F.cylindrus and provided the first experimental evidence for an important level of cyclic electron flow (CEF) in this organism. The low ratio of community respiration to gross primary production observed during the bloom at Palmer Station may be characteristic of high latitude coastal ecosystems and partially supported by a very active CEF in psychrophilic phytoplankton.This study was supported by funds from the US National Science Foundation (Award numbers 1040965 and 1043593). Funding to PDT was provided by the Natural Science and Engineering Research Council of Canada

The Gas Content in Galactic Disks: Correlation with Kinematics

We consider the relationship between the total HI mass in late-type galaxies and the kinematic properties of their disks. The mass $M_HI$ for galaxies with a wide variety of properties, from dwarf dIrr galaxies with active star formation to giant low-brightness galaxies, is shown to correlate with the product $V_c R_0$ ($V_c$ is the rotational velocity, and $R_0$ is the radial photometric disks scale length), which characterizes the specific angular momentum of the disk. This relationship, along with the anticorrelation between the relative mass of HI in a galaxy and $V_c$, can be explained in terms of the previously made assumption that the gas density in the disks of most galaxies is maintained at a level close to the threshold (marginal) stability of a gaseous layer to local gravitational perturbations. In this case, the regulation mechanism of the star formation rate associated with the growth of local gravitational instability in the gaseous layer must play a crucial role in the evolution of the gas content in the galactic disk.Comment: revised version to appear in Astronomy Letters, 8 pages, 5 EPS figure