4,024 research outputs found
Chemosensitivity of human tumor clonogenic cells simultaneously assayed in agar diffusion chambers and in a two-layer agar culture system
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Factors affecting expansion success of bird populations in human-transformed environments: the marsh harrier Circus aeruginosus in the Ebro Valley
No full text[eng] Change in species geographic ranges is a natural phenomenon, but the rate and magnitude of such change has significantly increased due to anthropogenic causes. The rate at which a population spreads/contracts through space is a function of the rates of population growth and dispersal, coupled with density-dependence. Human-induced environmental changes can lead to variation in density-independent components of local birth or death rates through deterministic process (e.g. impoverishment/increase of habitat and food resources), thus pushing populations toward positive/negative growth. Moreover, spatial range constraints, such as dispersal, and density-dependence may also limit population growth and range expansion, beyond environmental characteristics. The main goal of this thesis is to explore the role played by ecological factors such as habitat and food availability, spatial range constraints and density-dependence in the expansion of a species through human-transformed environments. For this purpose, I use as a study model an expanding population of the marsh harrier living in an agricultural landscape of the Ebro Valley (northeastern peninsular Spain). Results obtained in this thesis suggest that environmental factors, sociability, dispersal constraints and density-dependent mechanisms may play an important role in the distribution of a species. Marsh harrier breeding numbers had been greatly reduced in previous decades (1960-1980) mainly due to organochlorine pesticides, drainage of wetlands and direct persecution. Thus, at least part of their increase in recent decades may represent population recovery following reductions in organochlorine use and direct persecution. However, the species may also have benefited from the spread of human-made structures such as artificial ponds and reservoirs related to agricultural intensification, for breeding and from their surrounding herbaceous crops for hunting. At a local scale, individual variation in density-dependence for productivity and settlement patterns may have favoured dispersal of some individuals to new empty habitat patches, while others aggregated around traditional areas. However, at a large scale (i.e., across peninsular Spain), the breeding population of marsh harriers seems to be spatially constricted beyond environmental variables. This result indicates that potential habitat for marsh harriers still exists for further expansions in the Iberian Peninsula (at least at the spatial resolution of our analyses, which does not allow us to consider smaller scale processes that may restrict the species distribution such as local food abundances or pesticides). Potential consequences of this expansion for other species should be considered in order to properly conserve biodiversity in a world of change.[cat] En aquesta tesi s’analitza el paper que desenvolupen factors ecològics com l’hàbitat i la disponibilitat d’aliments, les limitacions espacials i la denso-dependència en l’expansió d’una espècie en ambients transformats per l’home. S’utilitza com a model d’estudi l’arpella Circus aeruginosus en una zona agrícola de la Península Ibèrica, a la part oriental de la Vall de l’Ebre. Els resultats d’aquesta tesi indiquen que tant els factors ambientals, de sociabilitat, les limitacions dispersives i els mecanismes de denso-depèndecia poden jugar un paper important en la distribució d’una espècie. La població d’arpella s’havia reduït en dècades anteriors (1960-0980) degut principalment a l’assecament i contaminació de les zones humides on criava, a l’ús de pesticides i a la persecució directa per part de l’home. Si bé, part de l’augment que la població ha experimentat en els darrers anys podria ser degut a la recuperació de la seva població després de la reducció en l’ús d’organoclorats i en la seva persecució per part d l’home, l’espècie també s’hauria beneficiat en els darrers anys de l’increment d’estructures artificials, com embassaments i basses de reg artificials relacionades amb l’agricultura, e l’espècie utilitza per nidificar i dels cultius herbacis del voltant per caçar. A escala local, la variació individual en els efectes de la denso-dependència en la productivitat i patrons d’assentament, podrien haver afavorit la dispersió d’alguns individus a noves localitats buides, mentre altres individus amb una resposta diferent a la densitat s’agregaven al voltant de zones ja ocupades. A escala de la Península Ibèrica, l’àrea de distribució de l’arpella encara es veuria limitada, per factors espacials diferents al clima i al tipus d’hàbitat, indicant que encara hi hauria hàbitat potencial per a l’espècie (com a mínim a la resolució espacial de les nostres anàlisi, que no permeten considerar processos a escala local). Les possibles conseqüències de l’expansió d’aquesta i altres espècies haurien de ser considerades per tal de conservar adequadament la biodiversitat en l’actual escenari de canvi global
The Fishery Value of Salt Marsh Restoration Projects
No full textpgs. 37-50We assessed the benefits of different wetland restoration techniques for fishery resources by comparing habitat complexity, fishery support, and construction costs among five salt marsh restoration projects in Galveston Bay, Texas. The restoration projects included marsh terracing at Galveston Island State Park (GISPT) and Pierce Marsh Preserve (PMPT), mound construction at Jumbile Cove (JC), and marsh island construction north of Galveston Island along Interstate Highway 45 at 1-45 East Marsh (I45EM) and I-45 West Marsh (I45WM). The projects were located in shallow estuarine waters and used bottom sediments or upland soils to construct intertidal areas that were planted with smooth cordgrass Spartina alterniflora. We used a Geographic Information System (GIS) and high-resolution aerial photography to classify areas into land (marsh vegetation) and water and applied fishery density models to assess fishery support. These models were developed to describe fine-scale distribution patterns for brown shrimp Farfantepenaeus aztecus, white shrimp Litopenaeus setiferus, and blue crab Callinectes sapidus across shallow estuarine habitat types (emergent marsh and shallow open water) of the Galveston Bay estuary. Restoration sites ranged in size from 6.9 ha (I45EM) to 68.2 ha (GISPT). Construction costs ranged from 74,200 (I45EM). Costs standardized to 1 ha for comparison among projects were 11,875 (JC), 8,771 (PMPT), and $5,310 (GISPT). The I45WM project contained the greatest percentage of marsh vegetation (68%), whereas the two terracing projects had the smallest percentage (PMPT = 18%, GISPT = 19%). More of the constructed marsh in the terracing projects, however, was vegetated marsh edge (located within 1 m of the marsh shoreline) than in other projects (PMPT = 29%, GISPT = 25%, I45EM = 20%, JC = 11%, I45WM = 9%), and this habitat type supports the greatest densities of fishery species. Based on our modeling analysis, overall fishery support was greatest for the two 1-45 projects, followed by the PMPT terracing project. Estimates of standing crop (number of animals) standardized to 1 ha ranged between 22,246-30,863 for brown shrimp, 21,773-33,139 for white shrimp, and 17,240-24,927 for blue crab. The two terracing projects and I45EM had higher fishery-benefit:cost ratios (ratio of standardized net fishery value to standardized project cost) than the other projects. Although marsh terraces composed of small cells supported the highest nekton populations, terraces constructed of medium cells were more cost-effective than terraces composed of either small or large cells. Based on our modeling results, all five restored sites supported relatively high populations of fishery species compared to prerestoration conditions. However, restoration sites did not support populations equivalent to a reference marsh system. Restoration projects should maximize the area of marsh vegetation and create a high degree of water-marsh interspersion to provide the most benefit for fishery species.http://gbic.tamug.edu/request.ht
Movement of microphytobenthos and sediment between mudflats and salt marsh during spring tides
No full textThe movement of sediment and associated microphytobenthos (MPB) between the upper mudflat and salt marsh in a macrotidal estuary was investigated by comparing the variability of benthic chlorophyll a (Chl. a) and suspended Chl. a during flood and ebb spring tides during the 2015 super moon event. Sampling was carried out for four days in August and September. Flood tide water carried significantly higher amounts of Chl. a from the mudflat transition zone onto the salt marsh compared to the amount of leaving the salt marsh during ebb tides. Suspended solid loads, suspended Chl. a concentrations, and diatom species composition provided evidence that resuspended mudflat sediments containing biofilm material was transferred onto the salt marsh by flood tide. Significant negative correlations between sediment Chl. a concentrations on the upper mudflat transition zone and Chl. a concentrations in flood tide water indicated biostabilisation of sediments by biofilms reducing sediment resuspension. Mean wind speed had a significant positive effect on resuspending Chl. a from the salt marsh sediment surface into the ebb tide (p < 0.001). The amount of Chl. a being resuspended in flood and ebb tidal waters was significantly correlated with MPB biomass on the sediment surface on the mudflat and salt marsh, respectively. Resuspended diatoms over the mudflat during high tide shared a total of 54.3 % similar species with diatoms recorded in flood tidal water over the salt marsh. Diatom taxa characteristic of salt marsh assemblages, and some deposited diatom taxa were resuspended and carried off the salt marsh during ebb tide. Resuspension of Chl. a in both flood and ebb waters was significantly controlled by the tidal range (both significant at p < 0.001). During spring tides, there was a net movement of characteristic MPB mudflat diatom taxa and sediment from the adjacent mudflat to the salt marsh, contributing to the accumulation of material within vegetated marshes during summer months
Distribution of Aquatic Macro-Fauna in a Marsh on West Galveston Bay, Texas and Possible Effects Thereon Resulting From Impoundments for Shrimp Culture
No full text-A survey was conducted to identify the macro-fauna of a marsh adjacent to West Galveston Bay, Texas. The factors affecting their distribution were studied for evaluation of changes which might result from large areas of marsh being impounded for shrimp culture. Results indicate that construction of large-scale impoundments for shrimp culture, at the expense of removing flooded grasslands, would alter the physical features of the marsh and reduce habitats suitable for year-round survival of the stable macro-fauna. In addition, competitor and predator control in these ponds would require the removal of all aquatic macro-fauna other than shrimp. The impact of these changes on the total marsh ecosystem is not known but should be considered and studied in detail before ponds are constructed. Conceivably, marsh areas could be managed so as to insure a reasonable amount of habitat for the stable macro-fauna while allowing ample lands for shrimp culture. (TAMU-SG abstract)http://gbic.tamug.edu/request.ht
Distribution of Aquatic Macro-Fauna in a Marsh on West Galveston Bay, Texas and Possible Effects Thereon Resulting From Impoundments for Shrimp Culture
No full text-A survey was conducted to identify the macro-fauna of a marsh adjacent to West Galveston Bay, Texas. The factors affecting their distribution were studied for evaluation of changes which might result from large areas of marsh being impounded for shrimp culture. Results indicate that construction of large-scale impoundments for shrimp culture, at the expense of removing flooded grasslands, would alter the physical features of the marsh and reduce habitats suitable for year-round survival of the stable macro-fauna. In addition, competitor and predator control in these ponds would require the removal of all aquatic macro-fauna other than shrimp. The impact of these changes on the total marsh ecosystem is not known but should be considered and studied in detail before ponds are constructed. Conceivably, marsh areas could be managed so as to insure a reasonable amount of habitat for the stable macro-fauna while allowing ample lands for shrimp culture. (TAMU-SG abstract)http://gbic.tamug.edu/request.ht
Perancangan Sistem Informasi Pengelola Barang/Inventaris Di Jc Komp
No full textInventory information system is a system used to enter inventory data into the database, so that there are no errors in input, output data, and reporting based on the desired data. based on surveys and interviews with jc comp personnel, information was obtained that the existing system in the jc comp warehouse section is still manual. therefore, the system that will be created by the author is the result of a replication of the existing system in the jc comp warehouse section. in addition to the process of input and output of goods, this information system is also equipped with features for creating data reports, input and output of goods, and searching for goods data by item name. with the inventory information system is expected to be useful for the warehouse parts jc comp. By implementing this system in the jc comp warehouse, it is hoped that it can reduce errors that may occur. this system is also expected to further speed up the process of input, output, and report generation, which in turn will help the jc comp warehouseSistem Informasi Persediaan Barang adalah sebuah sistem yang digunakan untuk memasukkan data-data persediaan barang ke dalam database, sehinggga tidak terjadi kesalahan dalam input, output data, dan pembuatan laporan berdasarkan data yang diinginkan. Berdasarkan survey dan wawancara dengan bagian personalia Jc Komp, didapatkan informasi bahwa sistem yang ada dibagian gudang Jc Komp masih manual. Oleh karena itu, sistem yang akan dibuat oleh penulis adalah hasil replikasi dari sistem yang telah ada dibagian gudang Jc Comp. Selain proses input dan output barang, pada sistem informasi ini juga dilengkapi fitur pembuatan laporan data, input, dan output barang, dan pencarian data barang berdasarkan nama barang. Dengan adanya Sistem Informasi persediaan barang ini diharapkan dapat bermanfaat bagi bagian gudang Jc Komp. Dengan diterapkannya sistem ini pada bagian gudang Jc Comp, maka diharapkan dapat mengurangi kesalahan-kesalahan yang mungkin terjadi. Sistem ini juga diharapkan dapat lebih mempercepat proses input, output, dan pembuatan laporan yang pada akhirnya dapat membantu bagian gudang Jc Komp
Policy networks in British government
No full textPolicy is not made in the electoral arena or in the gladiatorial confrontations of Parliament, but in the netherworld of committees, civil servants, professions, and interest groups.This collection explores the private world of public policy. It provides a survey of the literature on the concept of policy networks and demonstrates its importance for understanding specific policy areas. The case studies cover policy-making in agriculture, civil nuclear power, youth employment, smoking, heart disease, sea defences, information technology, and exchange rate policy. Finally the editors attempt an overall assessment of the utility of the concept, focusing on such questions as why networks change, which interests dominate and benefit from networks, and the consequences of the present system for representative democracy.To describe policy networks is not to condone political oligopoly. Britain has witnessed the substitution of private government for public accountability. The analysis of policy networks draws attention to this erosion of representative democracy and exposes the private government of Britain to public gaze
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