• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 119
  • 54
  • 43
  • 17
  • 13
  • 8
  • 8
  • 8
  • 7
  • 7
  • 4
  • 3
  • 3
  • 2
  • 1
  • Tagged with
  • 349
  • 52
  • 48
  • 40
  • 37
  • 36
  • 31
  • 28
  • 25
  • 24
  • 24
  • 22
  • 21
  • 19
  • 19
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
131

Hidden intrusions and molybdenite mineralization beneath the Kucing Liar Skarn, Ertsberg-Grasberg Mining District, Papua, Indonesia

Trautman, Marin Cherise 05 November 2013 (has links)
The Ertsberg-Grasberg Mining District of Papua, Indonesia (Western New Guinea) hosts the Ertsberg Cu-Au Skarn, the giant Grasberg Porphyry Cu-Au deposit, and several other orebodies. Two 1700-meter-long cores beneath the Kucing Liar ore skarn (KL98-10-22) and the Grasberg Igneous Complex (KL98-10-21) contain high concentrations of vein and disseminated molybdenite. KL98-10-22, the focus of this study, intersects two previously unencountered intrusions, the “Tertiary intrusion Kucing Liar” (Tikl) and “Tertiary Pliocene intrusion” (Tpi). An intense dilatational quartz vein stockwork cuts Tikl and Ekmai Sandstone (Kkes) units, predating Tpi intrusion. Prior to these ultradeep cores, which extend almost 3 km below pre-mining surface, molybdenite was rarely observed in the district. Geochemistry and isotopic data indicate that Tikl and Tpi intrusions originated from the same large magmatic system that emplaced other ore-forming Ertsberg-Grasberg district intrusions. Magma in a lower crustal chamber was recharged at least twice, according to Sr-Nd data. Laser-ablation inductively-coupled plasma mass spectrometry of magmatic zircons yields 238U-206Pb ages between 3.40 ± 0.12 Ma (Dalam Andesite) and 2.77 ± 0.15 Ma (Ertsberg intrusion), revealing a shorter period of igneous activity than previously measured by K-Ar and Ar-Ar dating. Analyses include composite ages of 3.28 ± 0.08 Ma for Tikl and 3.18 ± 0.11 Ma for Tpi. Inherited zircon cores indicate Precambrian (mostly Proterozoic) basement. Molybdenite veining beneath the Kucing Liar Skarn and Grasberg Igneous Complex postdates stockwork veining and occurred before the 2.99 ± 0.11 Ma Kali dikes. Only one molybdenite vein was observed cutting Tpi. Molybdenites yielded ~3 Ma Re-Os ages and anomalous >4 Ma and <0.5 Ma ages; anomalous ages were not reproducible in follow-up analyses (this study). Smearing deformation of molybdenite (through fault activity) causes crystal strain, likely leading to annealing recrystallization. Recrystallization possibly redistributes daughter-product Os, resulting in anomalous ages from annealed material. Fluids with high Mo/Cu ratios (which were likely supercritical) precipitated late-stage molybdenite deep in the system. These fluids developed through magma chamber crystallization, which concentrated molybdenum in the melt as an incompatible element, and stripping of Cu from the magma chamber during hydrothermal activity. / text
132

Hidden intrusions and molybdenite mineralization beneath the Kucing Liar Skarn, Ertsberg-Grasberg Mining District, Papua, Indonesia

Trautman, Marin Cherise 05 November 2013 (has links)
The Ertsberg-Grasberg Mining District of Papua, Indonesia (Western New Guinea) hosts the Ertsberg Cu-Au Skarn, the giant Grasberg Porphyry Cu-Au deposit, and several other orebodies. Two 1700-meter-long cores beneath the Kucing Liar ore skarn (KL98-10-22) and the Grasberg Igneous Complex (KL98-10-21) contain high concentrations of vein and disseminated molybdenite. KL98-10-22, the focus of this study, intersects two previously unencountered intrusions, the “Tertiary intrusion Kucing Liar” (Tikl) and “Tertiary Pliocene intrusion” (Tpi). An intense dilatational quartz vein stockwork cuts Tikl and Ekmai Sandstone (Kkes) units, predating Tpi intrusion. Prior to these ultradeep cores, which extend almost 3 km below pre-mining surface, molybdenite was rarely observed in the district. Geochemistry and isotopic data indicate that Tikl and Tpi intrusions originated from the same large magmatic system that emplaced other ore-forming Ertsberg-Grasberg district intrusions. Magma in a lower crustal chamber was recharged at least twice, according to Sr-Nd data. Laser-ablation inductively-coupled plasma mass spectrometry of magmatic zircons yields 238U-206Pb ages between 3.40 ± 0.12 Ma (Dalam Andesite) and 2.77 ± 0.15 Ma (Ertsberg intrusion), revealing a shorter period of igneous activity than previously measured by K-Ar and Ar-Ar dating. Analyses include composite ages of 3.28 ± 0.08 Ma for Tikl and 3.18 ± 0.11 Ma for Tpi. Inherited zircon cores indicate Precambrian (mostly Proterozoic) basement. Molybdenite veining beneath the Kucing Liar Skarn and Grasberg Igneous Complex postdates stockwork veining and occurred before the 2.99 ± 0.11 Ma Kali dikes. Only one molybdenite vein was observed cutting Tpi. Molybdenites yielded ~3 Ma Re-Os ages and anomalous >4 Ma and <0.5 Ma ages; anomalous ages were not reproducible in follow-up analyses (this study). Smearing deformation of molybdenite (through fault activity) causes crystal strain, likely leading to annealing recrystallization. Recrystallization possibly redistributes daughter-product Os, resulting in anomalous ages from annealed material. Fluids with high Mo/Cu ratios (which were likely supercritical) precipitated late-stage molybdenite deep in the system. These fluids developed through magma chamber crystallization, which concentrated molybdenum in the melt as an incompatible element, and stripping of Cu from the magma chamber during hydrothermal activity. / text
133

Assessing the reproducibility of skeletal geochemistry records in Atlantic corals using Montastraea annularis coral heads from the Dry Tortugas, Florida

Stair, Kristine L 01 June 2007 (has links)
Core samples were collected in September 1995 from live coral heads of Montastraea annularis at Bird Key reef in the Dry Tortugas, Florida (24 degrees 55 minutes N, 82 degrees 92 minutes W). Four 4 mm-thick coral slabs from two cores were continuously sampled at 12 samples per year (0.025 cm per sample for Core 31, 0.023 cm per sample for Core 35). Visual inspection of X-radiographs indicates an average skeletal extension rate of about 3 mm per year in Bird Key corals. The goal of this study was to perform a replication test in Montastraea annularis by using elemental and stable isotopes from four coral slabs from two different coral heads to address the following questions: 1) how well do geochemical signals replicate within a single coral head, 2) how well do geochemical signals replicate from two different cores from the same coral head, 3) how well do geochemical signals replicate from two coral heads from the same general area, and 4) do growth effects influence the geochemistry of slow-growing corals at the Dry Tortugas? Geochemical variations versus depth and time of all coral records show strong seasonal cyclicity. Variations in d18O in the suite of Bird Key coral records replicate the best; d13C and Sr/Ca variations replicate less well. For example, differences in the mean Sr/Ca record from two different coral heads are large (0.179 mmol/mol for BK31B-BK35CC; 0.196 mmol/mol for BK31C-BK35CC; ~4 degrees C) and nearly 4 times greater than analytical precision. Therefore, caution must be exercised in interpreting Sr/Ca-SST records in Montastraea annularis. Mean differences in coral d18O for all records, on the other hand, are within analytical precision and translate to temperature differences of less than 0.5 degrees C. Robust d18O values among cores that co-vary with a significant level of agreement further point to this proxy being more reliable than Sr/Ca. Because of its skeletal complexity, drilling difficulty, and large bio-geological error for Sr/Ca, Montastraea annularis seems poorly suited for coral-based Sr/Ca-SST studies. However, the species must be studied to understand tropical Atlantic interannual-decadal scale variability, so further assessment is warranted.
134

Reconstructing 20th century SST variability in the southwest pacific: A replication study using multiple coral Sr/Ca records from New Caledonia

DeLong, Kristine L 01 June 2006 (has links)
Coral-based climate reconstructions typically have not used multiple cores from a region to capture and replicate a climate signal largely because of concerns focused on coral conservation, analytical expense, and time constraints. Coral Sr/Ca reproducibility through the 20th century was investigated using three intra-colony and three inter-colony coral records, from the reefs offshore of Amédée Island, New Caledonia. Different sampling resolutions were examined in coral Sr/Ca (fortnightly and monthly) and delta 18O (fortnightly, monthly, and seasonally) as well as similar scale subsampling of the daily in situ SST record. The mean coral Sr/Ca, delta 18O, and daily SST values do not change as a function of sampling resolution. The coral Sr/Ca signal is highly reproducible; the average absolute offset between coeval Sr/Ca determinations between any two coral Sr/Ca time series is 0.036 mmol/mol (approximately 0.65°C), which is less than twice the analytical precision of the coral Sr/Ca measurements. The stack average of the monthly coral Sr/Ca variations and monthly anomalies are significantly correlated with monthly in situ SST (r equals -0.95, -0.56, respectively) for the period 1967 to 1992 and monthly 1-degree gridded SST data product (r equals -0.95, -0.53, respectively) for the period 1900 to 1999. The coral Sr/Ca-SST reconstruction exhibits decadal-scale fluctuations that exceed those observed in the gridded SST time series, which may reflect true differences between the SST at a shallow reef site and those averaged over a 1-degree grid box or they may reflect inadequacies in the methodology used to create the gridded SST product when few observations are available. A warming trend of approximately 0.6°C is observed in the coral Sr/Ca-SST record. Monthly coral Sr/Ca records and seasonally resolved coral delta 18O record from this site share variance in the latter half of the 20th century, but not in the early 20th century, suggestive of a change in seawater delta 18O.
135

Banksektorns vägar till hållbar utveckling : Institutionalisering av CSR och miljö

Bergold, Olof, Norén, Mikael January 2008 (has links)
I banksektorn är ekonomiska frågor betydligt mer institutionaliserade än miljöfrågor som bara varit aktuella i tiotalet år. Det leder till en viss osäkerhet att hantera miljöfrågor. Banksektorn försöker via legitimitetssökande standarder, ofta med start i bankkontorens direkta miljöpåverkan, att hantera miljöfrågorna. Bankers överlägset största miljöpåverkan ligger dock i den indirekta miljöpåverkan via kreditgivning och investeringar till kunder. Banker kan inte ta hela ansvaret utan det måste delas med kunderna som måste ställa krav på bankerna att erbjuda miljöansvarstagande tjänster. Bankernas ansvar ligger i att erbjuda miljöansvarstagande tjänster och aktivt presentera och förklara dem för kunderna. Enligt omvärldsanalysen har Marginalen goda förutsättningar för att initiera ett aktivt miljöarbete. Det är stor vikt att Marginalen inte bara hanterar den direkta miljöpåverkan utan även den mer miljöbelastande indirekta påverkan. / The world´s economic development during the past 100 years has led to improvements for millions of people. But it has also led to enormous environmental problems like global warming, species extinction and loss of biodiversity. Every human being and every sector in society are responsible to solve these grave environmental problems. One of those sectors is the banking sector. At first glance, the banking sector may look like an environmentally clean sector, especially when you compare the banking sector´s direct environmental impact with for example manufacturing industries. But when you look at the banking sector´s indirect environmental impact through loans and investments, you can envision the sectors potential to steer the society towards a sustainable development. This thesis has shown this a complex matter though, since banks and their customers share responsibility to elevate environmental issues. Customers need to understand that banks indirect environmental impact is big and then put pressure on banks to provide environmental responsible services and products. Banks, on the other hand, offer quite complex services and products which mean that banks have a responsibility to explain services and products different environmental effects. Banks have handled environmental risks for a long time in credit grants, but banks are now starting to feel that customers demand for environmental products and services is on a rise. The thesis has also found out that different types of environmental standards are very important for a credible environmental work in the banking sector.
136

Structural insights into Arginine-Serine rich proteins and N-H spin-spin coupling constants

Xiang, Shengqi 28 February 2013 (has links)
No description available.
137

Changes in Cell Morphology and the Cellular Localization of Protein Kinase Dsk1 in Schizosaccharomyces pombe in Response to Butylated Hydroxyanisole

Humphries, Jacqueline T 01 January 2013 (has links)
Dsk1 is the Schizosaccharomyces pombe functional homolog of human SRPK1, an SR protein kinase that regulates localization and function of SR protein splicing factors involved in transcription, alternative splicing, and mRNA export. It has been shown that a Dsk1 deletion strain of S. pombe is sensitive to exposure to butylated hydroxyanisole (BHA), a phenol derivative commonly used as a food preservative. Little is known about how BHA interacts with cells on a functional level, although it has been shown to be cytotoxic and tumorigenic. The aims of this thesis are to study the effect of BHA on eukaryotic cells and the possible involvement of Dsk1 protein kinase in the cellular response network to BHA through the use of fluorescence microscopy. The results showed that in BHA-treated cells, Dsk1 exhibits reduced nuclear localization and increased incidence of cytoplasmic clusters as well as a series of changes in cellular morphology. These observations imply that the function of Dsk1 is altered in response to BHA, consistent with genomic data collected by the Tang Lab. Thus, this study provides a basis for a series of future studies that will reveal in more detail how BHA affects fission yeast cells, and potentially gene or protein functional homologs in human cells.
138

Roles of SR protein kinase Dsk1 and LAMMER kinase Kic1 in mRNA processing in fission yeast, Schizosaccharomyces pombe

Nurimba, Margaret 20 January 2014 (has links)
Protein kinases comprise a fundamental class of cell function regulators that modify proteins by transferring phosphate groups from a nucleoside triphosphate such as ATP to specific amino acid residues on target proteins, altering protein conformation, function, and activity. As such, protein kinases are major regulators of many biological processes, including gene expression, which consists of the transfer of hereditary information in two major processing steps, transcription of DNA into a complementary precursor RNA transcript (pre-mRNA) and its subsequent translated into protein by the ribosome, where it can then go on to perform various processes in the cell. One particular family of protein kinases, otherwise known as serine/arginine protein-specific protein kinases (SRPKs), is conserved throughout eukaryotes and has been shown to be important in regulating gene expression, yet their roles in the gene expression pathway have yet to be elucidated. SRPK are known to phosphorylate serine/arginine (SR) splicing factor proteins, which are involved in mRNA splice site recognition and recruitment of splicing machinery. Members of the LAMMER kinase subfamily of SRPKs have also been shown to be required for efficient pre-mRNA splicing and important for mediating cellular progression through the cell cycle. To determine what other roles SRPKs play in mRNA processing, it is of use to study the homologous SRPK and LAMMER kinases in fission yeast, S. pombe, Dsk1 and Kic1, respectively. S. pombe provides a genetically valuable model for studying kinase function in RNA processing as both RNA processing machinery and SRPKs are conserved through higher eukaryotes. Using a novel green fluorescent protein tagging system based on properties of the MS2 bacteriophage genome, we are able to label specific mRNA transcripts of interest and visualize their locations in the cell using fluorescence microscopy. By visualizing the mRNA trafficking patterns of intron-containing and intronless mRNA transcripts, we show for the first time that deletions of the Dsk1 and Kic1 genes result in the nuclear retention of mRNA, such that Dsk1 and Kic1 are distinctly involved in mRNA export out of the nucleus.
139

Nätverksbaserade informationssystem : Standardprotokoll ANSI Z39.50/OSI SR / Network-based information system : protocol standards ANSI Z39.50/OSI SR

Hammar, Fredrik January 1997 (has links)
This master thesis examines the development of the two earlier independent IR protocols Z39.50 and SR (Search and Retrieve, ISO 10162/10163), now Z39.50/SR, from the beginning of the 80s to 1996 and their functionality in the client/server environment. Z39.50 applications in library systems will allow easy access to information regardless of platform or location. The use of Z39.50 will create a new user environment. Almost all the library systems of the market support the Z39.50 and surprisingly the use of it in Sweden lied on a very low leve! in 1996. This thesis was followed-up by an interview and a questioner among the Swedish Z39.50 users. They could see a huge potential of development concerning the future IR process. Z39.50 will change the libraries' traditional IR structure and the behaviour of the end-users.
140

Meteoric Diagenesis of Plio-Pleistocene Reef Terraces in the Southern Dominican Republic

Hernawati, Yulaika 09 December 2011 (has links)
Four prograding reef terraces (6, 15, 30, and 50 m) have been repetitively exposed to marine and freshwater alteration during the Pliocene and Pleistocene periods. Prolonged freshwater alterations have resulted in many diagenetic overprints that obscure early diagenetic products. This study investigates the sequence of the diagenetic processes and products in the terrace deposits using five long cores and 14 short cores taken from these different reef terraces. The lithologic changes in the cores were documented for reconstruction of the original depositional frameworks prior to embarking on a diagenetic study. Both textural and geochemical changes were examined within all four different terraces in order to characterized the diagenetic history. The textural changes observed in the cores and thin sections, provided preliminary evidence of the diagenetic environment. Through the use of X-ray diffractometry, stable isotopes (C and O), and trace element data, the interpretation of the diagenetic environment can be constrained. The reef terraces were deposited as as shallowing upward units following a down-stepping carbonate sequence. The lithology of the cores is dominated by reefal facies, which consist of the back reef, reef crest, front, and fore reef facies. The exposure surfaces, observed at various depths, constrained the interpretation of early diagenetic environments (met. vadose and phreatic). Three major diagenetic environments can be characterized from the cores, these are meteoric vadose, meteoric phreatic, and dolomitizaton. These diagenetis environments produced different geochemical signatures, which can be quantified through analysis of the stable isotopes and trace elements incorporated into the cements. The different reef terraces represent different duration of exposure, with the higher terraces having been exposed longer than the lower ones. This study enables the documentation and comparison of the processes and products of the meteoric diagenesis that occurred within these different terraces. In addition, this study also constrain the early dolomitization observed in sigmoidal reef deposits. In order to further quantify the process of early dolomitization, mineralogy, isotopes C and O, trace elements, and the Sr-isotopes were examined as well.

Page generated in 0.228 seconds