Spectral gradients in central cluster galaxies: further evidence of star formation in cooling flows

We have obtained radial gradients in the spectral features D4000 and Mg2 for a sample of 11 central cluster galaxies (CCGs). The new data strongly confirm the correlations between line-strength indices and the cooling flow phenomenon found in our earlier study. We find that such correlations depend on the presence and characteristics of emission lines in the inner regions of the CCGs. CCGs in cooling flow clusters exhibit a clear sequence in the D4000-Mg2 plane, with a neat segregation depending on emission-line types and blue morphology. This sequence can be modelled, using stellar population models with a normal IMF, by a recent burst of star formation. In CCGs with emission lines, the gradients in the spectral indices are flat or positive inside the emission-line regions, suggesting the presence of young stars. Outside the emission-line regions, and in cooling flow galaxies without emission lines, gradients are negative and consistent with those measured in CCGs in clusters without cooling flows and giant elliptical galaxies. Index gradients measured exclusively in the emission-line region correlate with mass deposition rate. We have also estimated the radial profiles of the mass transformed into new stars which are remarkably parallel to the radial behaviour of the mass deposition rate. A large fraction (probably most) of the cooling flow gas accreted into the emission-line region is converted into stars. We discuss the evolutionary sequence suggested by McNamara (1997), in which radio triggered star formation bursts take place several times during the lifetime of the cooling flow. This scenario is consistent with the available observations.Comment: 19 pages, 18 PostScript figures, accepted for publication in MNRA

Liquidated Damages: An Analysis of Their Use and Effectiveness

A construction company’s success and/or failure is dependent upon project completion with respect to time and budget. Failure to meet the contract completion date results in a loss of profit for owners and contractors alike. In order to help mitigate project delays, liquidated damage clauses have been included into construction contracts. Incorporating provisions within the construction contracts in the form of liquidated damages aims to help shift the financial burden when there is a failure to meet contractual obligations, hopefully offering quick compensation for delays. Unlike general or actual damages, liquidated damages are pre-defined and agreed upon prior to entering project construction. These daily monetary amounts are chargeable against finances due to the contractor. This paper will discuss the features and requirements of liquidated damages as well as define the established laws that are written on liquidated clauses. Both prime contractor and subcontractor approaches to this clause will be discussed and analyzed. Finally, this paper will examine both the usefulness and effectiveness of including liquidated damages to mitigate project delays

The Tully-Fisher relation of intermediate redshift field and cluster galaxies from Subaru spectroscopy

We have carried out spectroscopic observations in 4 cluster fields using Subaru's FOCAS multi-slit spectrograph and obtained spectra for 103 bright disk field and cluster galaxies at $0.06 \le z \le 1.20$. Seventy-seven of these show emission lines, and 33 provide reasonably-secure determinations of the galaxies' rotation velocity. The rotation velocities, luminosities, colours and emission-line properties of these galaxies are used to study the possible effects of the cluster environment on the star-formation history of the galaxies. Comparing the Tully-Fisher relations of cluster and field galaxies at similar reshifts we find no measurable difference in rest-frame $B$-band luminosity at a given rotation velocity (the formal difference is $0.18\pm0.33$mag). The colours of the cluster emission line galaxies are only marginally redder in rest-frame $B-V$ (by $0.06\pm0.04$mag) than the field galaxies in our sample. Taken at face value, these results seem to indicate that bright star-forming cluster spirals are similar to their field counterparts in their star-formation properties. However, we find that the fraction of disk galaxies with absorption-line spectra (i.e., with no current star formation) is larger in clusters than in the field by a factor of $\sim3$--5. This suggests that the cluster environment has the overall effect of switching off star formation in (at least) some spiral galaxies. To interpret these observational results, we carry out simulations of the possible effects of the cluster environment on the star-formation history of disk galaxies and thus their photometric and spectroscopic properties. Finally, we evaluate the evolution of the rest-frame absolute $B$-band magnitude per unit redshift at fixed rotation velocity.Comment: 21 pages, 13 figures, accepted for publication in MNRA

Spectral Indices in Cooling Flow Galaxies: Evidence for Star Formation

Through the study of two absorption spectral features in the optical range (Mg2 and the 4000 A break), we find evidence for star formation in the inner regions of cooling-flow galaxies. The application of simple stellar population models reveals that the measured indices are explained if a relatively small fraction of the total mass flow (5-17%) is forming new stars with a normal IMF. However, we argue that this is only a lower limit, and conclude that a large fraction of the gas accreted inside the galaxy could be forming stars. In addition, the analysis of line-strength gradients in the inner galaxy regions reveals that, in the mean, they are lower than those of normal ellipticals, and exhibit a hint of correlation with the mass accretion rate. Simultaneously, the spectral indices in the outer regions of some galaxies, with and without cooling flow, attain extremely low values, suggesting that they could be hosting star formation with an origin not related to the cooling flows.Comment: PostScript file (compressed and encoded) containing 21 page

Laser-treated electrospun fibers loaded with nano-hydroxyapatite for bone tissue engineering

Core-shell polycaprolactone/polycaprolactone (PCL/PCL) and polycaprolactone/polyvinyl acetate (PCL/PVAc) electrospun fibers loaded with synthesized nanohydroxyapatite (HAn) were lased treated to create microporosity. The prepared materials were characterized by XRD, FTIR, TEM and SEM. Uniform and randomly oriented beadless fibrous structures were obtained in all cases. Fibers diameters were in the 150–300 nm range. Needle-like HAn nanoparticles with mean diameters of 20 nm and length of approximately 150 nm were mostly encase inside the fibers. Laser treated materials present micropores with diameters in the range 70–120 µm for PCL-HAn/PCL fibers and in the 50–90 µm range for PCL-HAn/PVAC material. Only samples containing HAn presented bioactivity after incubation during 30 days in simulated body fluid. All scaffolds presented high viability, very low mortality, and human osteoblast proliferation. Biocompatibility was increased by laser treatment due to the surface and porosity modification

Effect of breed of cow and calf on recorded milk yield in a dairy ranching herd in Costa Rica

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Economic Efficiency of Rice Farmers in a Rainfed Lowland Environment Before and During the Financial Crisis

IndonesianPenelitian ini bertujuan untuk menilai efisiensi ekonomi dari petani padi lahan sawah tadah hujan sebelum dan selama krisis ekonomi di Jawa Tengah. Data yang digunakan dalam analisis adalah panel data dari 90 petani responden yang mencakup musim tanam 1997 dan 1999. Teknik analisa yang digunakan adalah analisa pendapatan dan biaya, uji beda nilai tengah, dan analisa regresi. Hasil regresi dari fungsi keuntungan menunjukkan bahwa harga gabah, pupuk dan tenaga kerja secara statistik nyata pengaruhnya terhadap keuntungan USAhatani baik pada musim hujan maupun musim kemarau. Petani secara ekonomi ternyata lebih efisien dalam memproduksi padi selama krisis dari pada sebelum krisis ekonomi. Efisiensi ekonomi pada musim hujan ternyata lebih tinggi dari pada musim kemarau karena infestasi hama dan kompetisi gulma lebih rendah serta air cukup. Efisiensi ekonomi meningkat selama krisis ekonomi seiring dengan meningkatnya harga sarana produksi terutama pupuk, herbisida dan insektisida. Efisiensi ekonomi sangat dipengaruhi oleh tingkat pendidikan, krisis ekonomi, dan musim tanam. Pengalaman USAhatani, ukuran rumah tangga, dan status penguasaan lahan tidak nyata pengaruhnya terhadap efisiensi ekonomi.EnglishThis study assessed the economic efficiency of rainfed lowland rice farmers before and during the financial crisis in Central Java. Panel data from 90 farmers were gathered by means of a structured questionnaire covering the 1997 and 1999 crop seasons. The analytical techniques employed in this study were costs and returns analysis, statistical test of means, and regression analysis. Regression results of the unit profit model showed that the prices of rough rice, fertilizer and labor were statistically significant for both the wet season and the dry season. Regardless of cropping season, the farmers were more economically efficient in producing rice during the period of financial crisis than before the financial crisis. Economic efficiency in the wet season was higher than in the dry season because of lower pest infestation and weed competition and because of sufficient water supply. Economic efficiency was significantly affected by level of education, financial crisis and cropping season. It increased during the financial crisis despite the price increase of input factors, especially fertilizer, herbicide and insecticide. During the wet season, farmers were found to be more economically efficient than in the dry season. Farming experience, household size, and tenure status did not significantly affect farmers\u27 economic efficiency

An Optical/Near-Infrared Study of Radio-Loud Quasar Environments II. Imaging Results

We use optical and near-IR imaging to examine the properties of the significant excess population of K>=19 galaxies found in the fields of 31 z=1-2 radio-loud quasars by Hall, Green & Cohen (1998). The excess occurs on two spatial scales: a component at <40'' from the quasars significant compared to the galaxy surface density at >40'' in the same fields, and a component roughly uniform to ~100'' significant compared to the galaxy surface density seen in random-field surveys in the literature. The r-K color distributions of the excess galaxy populations are indistinguishable and are significantly redder than the color distribution of the field population. The excess galaxies are consistent with being predominantly early-type galaxies at the quasar redshifts, and there is no evidence that they are associated with intervening MgII absorption systems. The average excess within 0.5 Mpc (~65'') of the quasars corresponds to Abell richness class ~0 compared to the galaxy surface density at >0.5 Mpc from the quasars, and to Abell richness class ~1.5 compared to that from the literature. We discuss the spectral energy distributions (SEDs) of galaxies in fields with data in several passbands. Most candidate quasar-associated galaxies are consistent with being 2-3 Gyr old early-types at the quasar redshifts of z~1.5. However, some objects have SEDs consistent with being 4-5 Gyr old at z~1.5, and a number of others are consistent with ~2 Gyr old but dust-reddened galaxies at the quasar redshifts. These potentially different galaxy types suggest there may be considerable dispersion in the properties of early-type cluster galaxies at z~1.5. There is also a population of galaxies whose SEDs are best modelled by background galaxies at z>2.5.Comment: Accepted to ApJ; 54 pages including 30 figures; 2 color GIF files available separately; also available from http://www.astro.utoronto.ca/~hall/thesis.htm