388 research outputs found

    Depression in Belgian first-year university students: A longitudinal study of self-definition, interpersonal relatedness, mentalizing, and integration

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    Despite evidence of increasing prevalence of depression in university students, few studies investigated how depression evolves over the first months at university. We investigate severity of depression among first-year university students during their first semester at university, and whether it was associated with impairments in personality, mentalizing (or reflective functioning) and social and academic integration. Participants in this two-wave prospective study were 377 Belgian first-year students in 2018 and 2019. Results showed that maladaptive interpersonal relatedness and self-definition at the start of the first semester (T1) were prospectively associated with increases in the prevalence and severity of depression at the end of the semester (T2). Uncertainty, but not certainty, with regard to mentalizing was positively associated with severity of depression at T2 and mediated the association between personality dimensions and severity of depression. The implications of these findings for depression prevention and intervention strategies in first-year university students are discussed

    An ultrasound evaluation of the relationship between changes in the lumbar perimuscular layer and Body Mass Index in people with non-specific lower back pain

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    BACKGROUND Mechanisms underlying non-specific lower back pain are still poorly understood. In an ultrasound-based study, Langevin et al. [1] found differences in the lumbar connective tissue structures in people with non-specific lower back pain (LBP) compared to people without (no-LBP). The aim of this study is to extend the work of Langevin and colleagues, and evaluate the relationship between the lumbar perimuscular layer and Body Mass Index (BMI) in LBP and no-LBP people. METHODS This study is a cross-sectional study design. Ultrasound imaging was used to investigate the echogenicity and thickness of the lumbar perimuscular layer in 45 participants (31 LBP, 14 no-LBP). The outcome measures were the thickness and echogenicity of the lumbar perimuscular layer. Longitudinal B-Mode ultrasound images were taken bi-laterally on an area 2 cm lateral to the midpoint between the spinous processes of L2-3,at a frequency of 18MHz, depth of 3 cm, (EsoateMyLab 25Gold, Firenze, Italy) using a 4 cm linear probe (Esaote LA435, Firenze, Italy) . Images were converted to grey-scale in Matlab (Mathworks, USA). The borders of the perimuscular layer were identified by a blinded investigator. Thickness was calculated in pixels and echogenicity as the average grey-scale value. Data was analysed using ANCOVA and linear regression. RESULTS The LBP and no-LBP groups did not significantly differ in age, sex, BMI or level of physical activity. Age (r= .452, p =.002) and BMI (r= .374, p =.013) showed significant positive correlations with perimuscular thickness, but not with perimuscular echogenicity. BMI significantly predicted perimuscular thickness (ANCOVA: p = .016), whereas group membership did not (ANCOVA:p=.168). Perimuscular echogenicity could be significantly predicted only by considering the interaction between group membership and BMI. The interaction between BMI and group membership accounted for 16% of the observed changes in perimuscular echogenicity (ANCOVA:p=.006). The interaction arose because in the no-LBP group, echogenicity significantly decreased as BMI increased (Regression:p = .005). In contrast, there was no systematic relationship between perimuscular echogenicity and BMI in the LBP group (Regression:p = .391). CONCLUSIONS Measurements of echogenicity can only be accounted for by considering group membership (LBP and no-LBP) and BMI values jointly. The relationship between BMI and echogenicity (negative correlation) in the no-LBP group is not found in participants with LBP. Possible causes, which require further investigation, include: sub-failure, changes in movement patterns, chronic inflammation, fibrosis, and/or fatty tissue infiltration

    Simulations of Solid-on-Solid Models of Spreading of Viscous Droplets

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    We have studied the dynamics of spreading of viscous non-volatile fluids on surfaces by MC simulations of SOS models. We have concentrated on the complete wetting regime, with surface diffusion barriers neglected for simplicity. First, we have performed simulations for the standard SOS model. Formation of a single precursor layer, and a density profile with a spherical cap shaped center surrounded by Gaussian tails can be reproduced with this model. Dynamical layering (DL), however, only occurs with a very strongly attractive van der Waals type of substrate potential. To more realistically describe the spreading of viscous liquid droplets, we introduce a modified SOS model. In the new model, tendency for DL and the effect of the surface potential are in part embedded into the dynamics of the model. This allows a relatively simple description of the spreading under different conditions, with a temperature like parameter which strongly influences the droplet morphologies. Both rounded droplet shapes and DL can easily be reproduced with the model. Furthermore, the precursor width increases proportional to the square root of time, in accordance with experimental observations. PACS: 68.10.Gw, 05.70.Ln, 61.20.Ja.Comment: to appear in Physica A (1994), standard LaTex, 20 page

    Carbon Capture and Storage

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    Emissions of carbon dioxide, the most important long-lived anthropogenic greenhouse gas, can be reduced by Carbon Capture and Storage (CCS). CCS involves the integration of four elements: CO 2 capture, compression of the CO2 from a gas to a liquid or a denser gas, transportation of pressurized CO 2 from the point of capture to the storage location, and isolation from the atmosphere by storage in deep underground rock formations. Considering full life-cycle emissions, CCS technology can reduce 65–85% of CO2 emissions from fossil fuel combustion from stationary sources, although greater reductions may be possible if low emission technologies are applied to activities beyond the plant boundary, such as fuel transportation. CCS is applicable to many stationary CO2 sources, including the power generation, refining, building materials, and the industrial sector. The recent emphasis on the use of CCS primarily to reduce emissions from coal-fired electricity production is too narrow a vision for CCS. Interest in CCS is growing rapidly around the world. Over the past decade there has been a remarkable increase in interest and investment in CCS. Whereas a decade ago, there was only one operating CCS project and little industry or government investment in R&D, and no financial incentives to promote CCS. In 2010, numerous projects of various sizes are active, including at least five large-scale full CCS projects. In 2015, it is expected that 15 large-scale, full-chain CCS projects will be running. Governments and industry have committed over USD 26 billion for R&D, scale-up and deployment. The technology for CCS is available today, but significant improvements are needed to support widespread deployment. Technology advances are needed primarily to reduce the cost of capture and increase confidence in storage security. Demonstration projects are needed to address issues of process integration between CO2 capture and product generation, for instance in power, cement and steel production, obtain cost and performance data, and for industry where capture is more mature to gain needed operational experience. Large-scale storage projects in saline aquifers are needed to address issues of site characterization and site selection, capacity assessment, risk management and monitoring. Successful experiences from five ongoing projects demonstrate that, at least on this limited scale, CCS can be safe and effective for reducing emissions. Five commercial-scale CCS projects are operational today with over 35 million tonnes of CO2 captured and stored since 1996. Observations from commercial storage projects, commercial enhanced oil recovery projects, engineered and natural analogues as well as theoretical considerations, models, and laboratory experiments suggest that appropriately selected and managed geological storage reservoirs are very likely to retain nearly all the injected CO2 for very long times, more than long enough to provide benefits for the intended purpose of CCS. Significant scale-up compared to existing CCS activities will be needed to achieve large reductions in CO2 emissions. A 5- to 10-fold scale-up in the size of individual projects is needed to capture and store emissions from a typical coal-fired power plant (500 to 1000 MW). A thousand fold scale-up in size of today’s CCS enterprise would be needed to reduce emissions by billions of tonnes per year (Gt/yr). The technical potential of CCS on a global level is promising, but on a regional level is differentiated. The primary technical limitation for CCS is storage capacity. Much more work needs to be done to realistically assess storage capacity on a worldwide, regional basis and sub-regional basis. Worldwide storage capacity estimation is improving but more experience is needed. Estimates for oil and gas reservoirs are about 1000 GtCO2, saline aquifers are estimated to have a capacity ranging from about 4000 to 23,000 GtCO2. However, there is still considerable debate about how much storage capacity actually exists, particularly in saline aquifers. Research, geological assessments and, most importantly, commercial-scale demonstration projects will be needed to improve confidence in capacity estimates. Costs and energy requirements for capture are high. Estimated costs for CCS vary widely, depending on the application (e.g. gas clean-up vs. electricity generation), the type of fuel, capture technology, and assumptions about the baseline technology. For example, with today’s technology, CCS would increase cost of generating electricity by 50–100%. In this case, capital costs and parasitic energy requirements of 15–30% are the major cost drivers. Research is underway to lower costs and energy requirements. Early demonstration projects are likely to cost more. The combination of high cost and low or absent incentives for large-scale deployment are a major factor limiting the widespread use of CCS. Due to high costs, CCS will not take place without strong incentives to limit CO2 emissions. Certainty about the policy and regulatory regimes will be crucial for obtaining access to capital to build these multi-billion dollar projects. Environmental risks of CCS appear manageable, but regulations are needed. Regulation needs to ensure due diligence over the lifecycle of the project, but should, most importantly, also govern site selection, operating guidelines, monitoring and closure of a storage facility. Experience so far has shown that local resistance to CO2 storage projects may appear and can lead to cancellation of planned CCS projects. Inhabitants of the areas around geological storage sites often have concerns about the safety and effectiveness of CCS. More CCS projects are needed to establish a convincing safety record. Early engagement of communities in project design and site selection as well as credible communication can help ease resistance. Environmental organisations sometimes see CCS as a distraction from a sustainable energy future. Social, economic, policy and political factors may limit deployment of CCS if not adequately addressed. Critical issues include ownership of underground pore space (primarily an issue in the US); long-term liability and stewardship; GHG accounting approaches and ve rification; and regulatory oversight regimes. Governments and the private sector are making significant progress on all of these issues. Government support to lower barriers for early deployments is needed to encourage private sector adoption. Developing countries will need support for technology access, lowering the cost of CCS, developing workforce capacity and training regulators for permitting, monitoring and oversight. CCS combined with biomass can lead to negative emissions . Such technologies are likely to be needed to achieve atmospheric stabilization of CO2 and may provide an additional incentive for CCS adoption

    Spreading of a Macroscopic Lattice Gas

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    We present a simple mechanical model for dynamic wetting phenomena. Metallic balls spread along a periodically corrugated surface simulating molecules of liquid advancing along a solid substrate. A vertical stack of balls mimics a liquid droplet. Stochastic motion of the balls, driven by mechanical vibration of the corrugated surface, induces diffusional motion. Simple theoretical estimates are introduced and agree with the results of the analog experiments, with numerical simulation, and with experimental data for microscopic spreading dynamics.Comment: 19 pages, LaTeX, 9 Postscript figures, to be published in Phy. Rev. E (September,1966

    Force-velocity relation and density profiles for biased diffusion in an adsorbed monolayer

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    In this paper, which completes our earlier short publication [Phys. Rev. Lett. 84, 511 (2000)], we study dynamics of a hard-core tracer particle (TP) performing a biased random walk in an adsorbed monolayer, composed of mobile hard-core particles undergoing continuous exchanges with a vapor phase. In terms of an approximate approach, based on the decoupling of the third-order correlation functions, we obtain the density profiles of the monolayer particles around the TP and derive the force-velocity relation, determining the TP terminal velocity, V_{tr}, as the function of the magnitude of external bias and other system's parameters. Asymptotic forms of the monolayer particles density profiles at large separations from the TP, and behavior of V_{tr} in the limit of small external bias are found explicitly.Comment: Latex, 31 pages, 3 figure

    Controversies in ureteroscopy: lasers, scopes, ureteral access sheaths, practice patterns and beyond

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    Ureteroscopy has become an increasingly popular surgical intervention for conditions such as urinary stone disease. As new technologies and techniques become available, debate regarding their proper use has risen. This includes the role of single use ureteroscopes, optimal laser for stone lithotripsy, basketing versus dusting, the impact of ureteral access sheath, the need for safety guidewire, fluoroscopy free URS, imaging and follow up practices are all areas which have generated a lot of debate. This review serves to evaluate each of these issues and provide a balanced conclusion to guide the clinician in their practice

    Scaling up climate finance in the context of Covid-19: A science-based call for financial decision-makers

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    The sooner we act, the lower the risks of climate change and the higher the synergies between climate action and other societal benefits. That is a clear conclusion from the IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels. Financing a rapid transition to achieve the Paris Agreement goals requires significantly more investment and investment in a different set of low emission, climate resilient assets. The Covid-19 crisis increases the imperative to scale up climate action before these goals are out of reach. In particular, it is critical to increase the ability of developing countries to realize their climate ambitions in the context of the pandemic without increasing their debt burden.This new report, Scaling up climate finance in the context of Covid-19, aims to help financial decision-makers to align finance with sustainable development, accelerating the transition to a net-zero, climate resilient economy, based on the latest scientific findings and policy developments. It proposes four sets of actions to support developing countries in achieving this transition.This report aims to help financial decision-makers to align finance with sustainable development, accelerating the transition to a net-zero, climate resilient economy, based on the latest scientific findings and policy developments. It proposes four interventions to achieve this objective in the context of Covid-19

    Estimating damages from price-fixing: the value of transaction data

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    We use a unique private data set of about 340,000 invoice positions from 36 smaller and larger customers of German cement producers to study the value of such transaction data for an estimation of cartel damages. In particular, we investigate, first, how structural break analysis can be used to identify the exact end of the cartel agreement and, second, how an application of before-and-after approaches to estimate the price overcharge can benefit from such rich data sets. We conclude that transaction data allows such a detailed assessment of the cartel and its impact on direct customers that its regular application in private antitrust cases is desired as long as data collection and preparation procedures are not prohibitively expensive

    A microscopic model for thin film spreading

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    A microscopic, driven lattice gas model is proposed for the dynamics and spatio-temporal fluctuations of the precursor film observed in spreading experiments. Matter is transported both by holes and particles, and the distribution of each can be described by driven diffusion with a moving boundary. This picture leads to a stochastic partial differential equation for the shape of the boundary, which agrees with the simulations of the lattice gas. Preliminary results for flow in a thermal gradient are discussed.Comment: 4 pages, 3 figures. Submitte
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