Abstract
We report on a sensitive infrared search for disks around isolated young planetary-mass objects (PMOs) in the NGC 1333 cluster, by stacking 70 Spitzer/IRAC frames at 3.6 and 4.5
μ
m. Our ...coadded images go >2.3 mag deeper than single-epoch frames, and cover 50 brown dwarfs, 15 of which have M9 or later spectral types. Spectral types >M9 correspond to masses in the giant-planet domain, i.e., near or below the deuterium-burning limit of 0.015
M
⊙
. Five of the 12 PMOs show definitive evidence of excess, implying a disk fraction of 42%, albeit with a large statistical uncertainty given the small sample. Comparing with measurements for higher-mass objects, the disk fraction does not decline substantially with decreasing mass in the substellar domain, consistent with previous findings. Thus, free-floating PMOs have the potential to form their own miniature planetary systems. We note that only one of the six lowest-mass objects in NGC 1333, with spectral type L0 or later, has a confirmed disk. Reviewing the literature, we find that the lowest-mass free-floating objects with firm disk detections have masses ∼0.01
M
⊙
(or ∼10
M
Jup
). It is not clear yet whether even lower-mass objects harbor disks. If not, it may indicate that ∼10
M
Jup
is the lower-mass limit for objects that form like stars. Our disk-detection experiment on deep Spitzer images paves the way for studies with JWST at longer wavelengths and higher sensitivity, which will further explore disk prevalence and formation of free-floating PMOs.
In this study we compare consumer brand loyalty in online and traditional shopping environments for over 100 brands in 19 grocery product categories. The online purchase data come from a large ...traditional grocery retailer that also operates an online store for its products. The offline data corresponds to the exact same brands and categories bought in traditional stores by a panel of homes operated by ACNielsen for purchases made in the same city and over the same time period. We compare the observed loyalty with a baseline model, a new segmented Dirichlet model, which has latent classes for brand choice and provides a very accurate model for purchase behavior. The results show that observed brand loyalty for high market share brands bought online is significantly greater than expected, with the reverse result for small share brands. In contrast, in the traditional shopping environment, the difference between observed and predicted brand loyalty is not related to brand share.
Naturally occurring gas hydrates are established as an abundant reserve of natural gas. Production initiatives raised challenges such as low production rate, freezing problems, water, and sand ...production along with geomechanical concerns. Recent studies suggest that fracturing the sediment can significantly improve the conductivity and productivity of such reserves. This study is an initiative to verify the suitability of conventionally used polymer (guar) for fracturing at extremely low temperatures along with the integration of widely available gas hydrate inhibitors for efficient stimulation. Established inhibitors such as NaCl, CaCl2 and KCl were introduced to linear and crosslinked gels to study their compatibility with the reference guar-based gels. The inhibitor integrated linear gel samples demonstrated similar performance trends to that of the reference gel establishing their compatibility with the polymer, whereas the inhibitor integrated crosslinked samples displayed deswelling nature. The low concentration inhibitor integrated linear gel samples performed superior to the reference gel whereas the high concentration sample inhibited the swelling performance of the polymer. Both the reference and inhibitor integrated linear gel samples gradually disintegrated after 48 h leaving behind soft cloudy residue, whereas the inhibitor integrated crosslinked samples rapidly released water and contracted into a solid residue which can cause serious flow related disruptions during operations and apparently damage the conductivity of the sediment for long term. This study delivers crucial understanding on how various salts interact with guar polymers at low temperatures and whether their presence can be a boon or bane during the design of a fracturing fluid.
•Low temperature fracturing of hydrate-bearing sediments for improved gas recovery.•Integration of hydrate inhibitors with conventional gelling polymer used in hydraulic fracturing.•Inhibitor integrated linear gel samples demonstrated good integrity during tests.•Inhibitor integrated low concentration samples performed superiorly.•Inhibitor integrated crosslinked gels prone to deswelling and residue formation.
The over dependence on fossil fuels for human energy requirements together with the resultant adverse environmental effects in the form of greenhouse gas discharges has redirected our attention ...towards renewable energy sources. Researchers have identified hydrogen, a non-carbonaceous energy source holding the capacity to substitute fossil fuels, as a viable fuel option that has the potential to be generated utilizing eco-friendly techniques. Studies have identified underground sites that are operational or have the potential to be used for hydrogen storage. Shale formations, characterized by their low permeability, offer promising opportunities for underground hydrogen storage. These formations require stimulation techniques to generate flow channels. Pumping frac-fluid into these formations at high pressure induces fractures in them and the engineered fractures are supported by the proppants injected along with the fluid. Propped fractures form a vital conduit in unconventional gas reservoirs, which are a potential medium for storage of hydrogen. Cryogenic fracturing is an innovative approach that aims to enhance and broaden the capabilities of conventional hydraulic fracturing processes. The transmission and settlement of proppants are influenced by certain critical aspects including their density, size and volume fraction and fluid velocity, which are investigated in this contribution. This study incorporates water and cryogenic fluids like liquid nitrogen (LN2) and liquid helium (LHe) as fracturing fluids. The primary objective of this effort is to analyze proppant transportation phenomenon and the key influential factors in LN2 and LHe. The proppant volume fraction contour, equilibrium dune level (EqDL) and dune height (EqDH) data are illustrated in this research for better understanding of proppant migration. It was observed that when the fracturing fluid is given a higher velocity, the proppant grains experience increased drag force, causing them to penetrate deeper into the fracture. The desired range of proppant volume fraction for improved grain transmission was determined as 0.45 to 0.50 and the critical proppant density that significantly affected the EqDL as 187.2839 lb/ft3.
•Fracturing of impermeable formations for enhanced underground hydrogen storage.•Eulerian-Granular model for studying the proppant bearing ability of cryogenic fluids.•Desired proppant volume fraction range for improved grain transmission is 0.45–0.50•Higher fluid velocity enables better proppant transportation.•Cryo-fluids carry low-diameter, low-density proppants deeper into the fractures.
Iron overload in the Asian community Lok, Chun Yu; Merryweather-Clarke, Alison T.; Viprakasit, Vip ...
Blood,
07/2009, Letnik:
114, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Hereditary hemochromatosis is an iron overload disorder that can lead to the impairment of multiple organs and is caused by mutations in one or more different genes. Type 1 hemochromatosis is the ...most common form of the disease and results from mutations in the HFE gene. Juvenile hemochromatosis (JH) is the most severe form, usually caused by mutations in hemojuvelin (HJV) or hepcidin (HAMP). The autosomal dominant form of the disease, type 4, is due to mutations in the SLC40A1 gene, which encodes for ferroportin (FPN). Hereditary hemochromatosis is commonly found in populations of European origin. By contrast, hemochromatosis in Asia is rare and less well understood and can be masked by the presence of iron deficiency and secondary iron overload from thalassemia. Here, we provide a comprehensive report of hemochromatosis in a group of patients of Asian origin. We have identified novel mutations in HJV, HAMP, and SLC40A1 in countries not normally associated with hereditary hemochromatosis (Pakistan, Bangladesh, Sri Lanka, and Thailand). Our family studies show a high degree of consanguinity, highlighting the increased risk of iron overload in many countries of the developing world and in countries in which there are large immigrant populations from these regions.
In recent years hundreds of high-profile ‘free speech’ incidents have rocked US college campuses. Jordan Peterson, Ben Shapiro, Ann Coulter and other right-wing speakers have faced considerable ...protest, with many being disinvited from speaking. These incidents are widely circulated as examples of the academy’s intolerance towards conservative views. But this response is not the spontaneous outrage of the liberal colleges. There is a darker element manufacturing the crisis, funded by political operatives, and designed to achieve specific political outcomes. If you follow the money, at the heart of the issue lies the infamous and ultra-libertarian Koch donor network. Grooming extremist celebrities, funding media platforms that promote these controversies, developing legal organizations to sue universities and corrupting legislators, the influence of the Koch network runs deep. We need to abandon the ‘campus free speech’ narrative and instead follow the money if we ever want to root out this dangerous network from our universities.
Well productivity in the Asmari carbonate formation of southwest Iran has decreased in recent years as a result of production issues. The production rate must be maintained below 1500 STB/day to ...prevent water coning. In this study, a gas lift well is modeled using data from one of the producing wells of this field. Nodal analysis is performed using lift-gas injection rates and wellhead pressures at different reservoir pressures and water cut conditions to optimize production. Economic aspects are considered to optimize the artificial gas injection rates at different tubing head pressures and water cut conditions. Increasing the lift-gas injection rate from 0.4 MMscf/day to 1 MMscf/day enhances the oil production rate by 37.71% and 43.89% for 10% and 30% water cut conditions, respectively. Gas injection rates of 5.2 MMscf/day and 5.4 MMscf/day are determined to be economically optimal for 30% water cut with tubing head pressures of 260 psig and 270 psig, respectively.
Hydraulic fracturing, a highly efficient well-stimulation technique, can be utilised to significantly increase production from unconventional low-permeability rocks like shale. This is achieved ...through creating fractures in the formation by injecting a solution of water, sand, and chemicals. These fractures may make it easier for the hydrocarbons to enter the wellbore. Proppant is essential in the hydraulic fracturing technique since it is employed to maintain the fractures open. Therefore, the movement and placement of the proppant are crucial elements that determine the conductivity and efficiency of the propped fracture. In this study, the efficacy of water and liquid nitrogen (LN) as fracturing fluids is examined. In order to analyse elucidate the factors controlling the phenomenon of proppant transportation, volume percent of sand (proppant), proppant density, fluid viscosity, fluid velocity, and proppant diameter have been examined in this study. The concepts of proppant volume fraction (V.F.) contour, equilibrium dune height (EDH, in mm) and equilibrium dune level (EDL, in %) have been established in this study. Water was observed to have higher proppant carrying capacity than LN. The developed model was validated against published information. Reduction in proppant density was found to have a significant impact on its placement. Major findings of this study shall assist in comprehending the proppant movement and placement during the course of fracturing and ultimately in improving the job performance.
When compared to Waterfall, the Agile Methodology has been a boon for technical teams to develop and deliver software solutions. For Business teams, this transformation has not been as smooth or ...accepted. The research attempted to identify some challenges and what factors affect Agile Transformation by performing research with the Project Management Institute (PMI); PMI Kentuckiana Chapter.Because it is not known what experiences members of the PMI Kentuckiana Chapter have had with the successful implementation of Agile software solutions during Agile Transformation from Waterfall. It is also not known the potential challenges of Agile software implementation associated with Agile Transformation, two research questions have been developed; RQ1: What Business-oriented challenges do PMI members describe during an Agile Transformation? RQ2: What Successful Criteria have PMI members identified for Business resources to employ to improve their chances of success during an Agile Transformation? The research design selected for the research was a qualitative research method. The research plan was structured to answer questions related to the targeted organizations' members through several qualitative instruments. The instruments were two sets of interviews and one focus group. The research used a Descriptive Exploratory Research Design. Exploratory research allowed the research to look at specific phenomenon related to Agile Transformation.Each instrument was designed to work with five participants who have been recruited from the membership roster of the organization. After the completion of the data capture process, the analysis process used followed the Braun & Clarke six-step thematic analysis process. These steps include Familiarization with data through review; Preliminary codes; Pattern Creation; Review themes: Define and name themes from instruments for Triangulation; and produce report.
O presente projeto de dissertação, intitulado como Melhoria de Práticas de Gestão de Projetos numa Empresa de Gestão Ambiental, foi desenvolvido no âmbito do curso de Mestrado de Gestão de Projetos ...de Engenharia, da Universidade do Minho. Perante as necessidades das organizações se destacarem e crescerem num mercado cada vez mais competitivo, onde a capacidade de resposta no tempo certo e com qualidade é cada vez mais importante, as vantagens da utilização das boas praticas de gestão de projetos torna-se cada vez mais evidente. A implementação de melhorias das práticas de gestão de projetos tem sido um fator preponderante para o sucesso das organizações. Este trabalho de dissertação foi desenvolvido na empresa Ecofirma. É uma empresa ligada ao ramo ambiental, tendo sido abordado o caso particular de um projeto de abastecimento de água.O objetivo principal desta dissertação de mestrado foi propor boas praticas de gestão de projetos com enfoque no departamento de produção e apresentar propostas que visam melhorar os processos internos e a gestão de projetos. Para tal, foram consideradas estratégias para simplificar os processos, melhorar a gestão da informação, comunicação, organização e gestão dos projetos. Estas propostas basearam-se nas diferentes áreas de conhecimento do PMBOK® Guide.Partindo do diagnóstico inicial, foram apresentadas propostas de alteração ao nível da aprendizagem operacional e dos processos e técnicas da gestão de projetos. Destaca-se a necessidade de maior envolvimento de colaboradores, melhor organização de atividades de manutenção e definição de competências e responsabilidades. Foram ainda apresentadas propostas diversas para a criação de ferramentas de apoio à gestão de projetos com apresentação de templates específicos exemplificados para o caso do projeto de abastecimento de água, sendo ainda referida a importância da criação da figura do gestor de projeto.
PDF
