6,833 research outputs found
Projections for future radiocarbon content in dissolved inorganic carbon in hardwater lakes: a retrospective approach
Inland water bodies contain significant amounts of carbon in the form of dissolved inorganic carbon (DIC) derived from a mixture of modern atmospheric and pre-aged sources, which needs to be considered in radiocarbon-based dating and natural isotope tracer studies. While reservoir effects in hardwater lakes are generally considered to be constant through time, a comparison of recent and historical DI14C data from 2013 and 1969 for Lake Constance reveals that this is not a valid assumption. We hypothesize that changes in atmospheric carbon contributions to lake water DIC have taken place due to anthropogenically forced eutrophication in the 20th century. A return to more oligotrophic conditions in the lake led to reoxygenation and enhanced terrigenous organic matter remineralization, contributing to lake water DIC. Such comparisons using DI14C measurements from different points in time enable nonlinear changes in lake water DIC source and signature to be disentangled from concurrent anthropogenically induced changes in atmospheric 14C. In the future, coeval changes in lake dynamics due to climate change are expected to further perturb these balances. Depending on the scenario, Lake Constance DI14C is projected to decrease from the 2013 measured value of 0.856 Fm to 0.54–0.62 Fm by the end of the century
Compatibility of phenomenological dipole cross sections with the Balitsky-Kovchegov equation
Phenomenological models of the dipole cross section that enters in the
description of for instance deep inelastic scattering at very high energies
have had considerable success in describing the available small-x data in both
the saturation region and the so-called extended geometric scaling (EGS)
region. We investigate to what extent such models are compatible with the
numerical solutions of the Balitsky-Kovchegov (BK) equation which is expected
to describe the nonlinear evolution in x of the dipole cross section in these
momentum regions. We find that in the EGS region the BK equation yields results
that are qualitatively different from those of phenomenological studies. In
particular, geometric scaling around the saturation scale is only obtained at
asymptotic rapidities. We find that in this limit, the anomalous dimension
\gamma(r,x) of phenomenological models approaches a limiting function that is
universal for a large range of initial conditions. At the saturation scale,
this function equals approximately 0.44, in contrast to the value 0.628
commonly used in the models. We further investigate the dependence of these
results on the starting distribution, the small-r limit of the anomalous
dimension for fixed rapidities and the x-dependence of the saturation scale.Comment: 14 pages, 8 figures. Extensive revisions, several new results, plots,
references and conclusions added; to appear in Phys.Rev.
Functional consequences of sphingomyelinase-induced changes in erythrocyte membrane structure.
Inflammation enhances the secretion of sphingomyelinases (SMases). SMases catalyze the hydrolysis of sphingomyelin into phosphocholine and ceramide. In erythrocytes, ceramide formation leads to exposure of the removal signal phosphatidylserine (PS), creating a potential link between SMase activity and anemia of inflammation. Therefore, we studied the effects of SMase on various pathophysiologically relevant parameters of erythrocyte homeostasis. Time-lapse confocal microscopy revealed a SMase-induced transition from the discoid to a spherical shape, followed by PS exposure, and finally loss of cytoplasmic content. Also, SMase treatment resulted in ceramide-associated alterations in membrane-cytoskeleton interactions and membrane organization, including microdomain formation. Furthermore, we observed increases in membrane fragility, vesiculation and invagination, and large protein clusters. These changes were associated with enhanced erythrocyte retention in a spleen-mimicking model. Erythrocyte storage under blood bank conditions and during physiological aging increased the sensitivity to SMase. A low SMase activity already induced morphological and structural changes, demonstrating the potential of SMase to disturb erythrocyte homeostasis. Our analyses provide a comprehensive picture in which ceramide-induced changes in membrane microdomain organization disrupt the membrane-cytoskeleton interaction and membrane integrity, leading to vesiculation, reduced deformability, and finally loss of erythrocyte content. Understanding these processes is highly relevant for understanding anemia during chronic inflammation, especially in critically ill patients receiving blood transfusions
Petrogenic organic carbon retention in terrestrial basins: a case study from perialpine Lake Constance
Inland waters play a major role in the global carbon cycle, with particulate organic carbon (POC) burial in terrestrial wetlands surpassing that in ocean sediments. Lake Constance, the second largest lake at the periphery of the European Alps, receives POC sourced from both aquatic and terrestrial productivity as well as petrogenic OC (OCpetro) from bedrock erosion. Distinguishing POC inputs to lake sediments is key to assessing carbon flux and fate as reworked OCpetro represents neither a net sink of atmospheric CO2 nor source of O2. New stable and radiocarbon isotopic data indicate that 11 (9–12) Gg/yr of OCpetro is buried in Lake Constance with underlying sediments on average containing 0.3 (0.25–0.33) wt% OCpetro. Extrapolation of these results suggests that 27 TgOCpetro/yr (12–54 TgOC/yr) could be subject to temporary geological storage in lakes globally, which is comparable to estimates of 43−25+61 TgOCpetro/yr delivered to the ocean by rivers (Galy et al., 2015). More studies are needed to quantify OCpetro burial in inland sedimentary reservoirs in order to accurately account for atmospheric carbon sequestration in terrestrial basins
An exploration of the experiences and utility of functional electrical stimulation for foot drop in people with multiple sclerosis
Purpose: Functional electrical stimulation (FES) is effective in improving walking in people with multiple sclerosis (MS) with foot drop. There is limited research exploring people’s experiences of using this device. This study aims to explore the utility, efficacy, acceptability, and impact on daily life of the device in people with MS.
Methods: An interpretative phenomenological approach was employed. Ten participants who had used FES for 12 months were interviewed. Transcripts were analysed, and emergent themes identified.
Results: Nine participants continued to use the device. Three relevant super-ordinate themes were identified; impact of functional electrical stimulation, sticking with functional electrical stimulation, and autonomy and control. Participants reported challenges using the device; however, all reported positive physical and psychological benefits. Intrinsic and external influences such as; access to professional help, the influence of others, an individual’s ability to adapt, and experiences using the device, influenced their decisions to continue with the device. A thematic model of these factors was developed.
Conclusions: This study has contributed to our understanding of people with MS experiences of using the device and will help inform prescribing decisions and support the continued, appropriate use of FES over the longer term
A Lindley-type equation arising from a carousel problem
Abstract: In this paper we consider a system with two carousels operated by one picker. The items to be picked are randomly located on the carousels and the pick times follow a phasetype distribution. The picker alternates between the two carousels, picking one item at a time. Important performance characteristics are the waiting time of the picker and the throughput of the two carousels. The waiting time of the picker satisfies an equation very similar to Lindley’s equation for the waiting time in the P H/U/1 queue. Although the latter equation has no simple solution, it appears that the one for the waiting time of the picker can be solved explicitly. Furthermore, it is well known that the mean waiting time in the P H/U/1 queue depends on to the complete inter-arrival time distribution, but numerical results show that, for the carousel system, the mean waiting time and throughput are rather insensitive to the pick-time distribution
Характеристика экономических отношений на финансовом рынке Украины
Розглянуто проблеми, особливості функціонування та взаємодії учасників фінансового ринку України. Обґрунтовано наявність внутрішніх фінансових джерел формування ресурсного потенціалу вітчизняних банків, доведено їх пріоритетність для країни порівняно із зовнішніми джерелами. Окреслено причини, що зумовлюють дефіцит ресурсного потенціалу в банківській системі України.
Ключові слова: заощадження, нагромадження, банки, економічне зростання, посередники, фінансовий ринок, ресурси, трансформація, інвестиційний потенціал.Рассмотрены проблемы, особенности функционирования и взаимодействия участников финансового рынка Украины. Обосновано наличие внутренних финансовых источников формирования ресурсного потенциала отечественных банков, доказана их приоритетность для страны по сравнению с внешними источниками. Очерчены причины, которые предопределяют дефицит ресурсного потенциала в банковской системе Украины.
Ключевые слова: сбережения, накопления, банки, экономический рост, посредники, финансовый рынок, ресурсы, трансформация, инвестиционный потенциал.The present paper examines topical problems related to the specific aspects of economic relations in the financial market of Ukraine. The relevance and selection of the theme stem from the fact that financial market as a specific organization form of cash flows takes a leading place in the economic mechanism of market economy. Agents of this market are engaged in a whole range of complex economic relations which in their turn play a key role in securing a dynamic and sustainable economic growth of a country. Development of the financial market and creation of adequate flexible and adaptive economic relations between its players are critical for Ukraine. This is explained by specific aspects of the economic system formation and reforming, which are related to undergoing an intersystem transformation stage. The indicated circumstances predetermined the goal and objectives of the study pursued, which come to examination of economic relations in the financial market of Ukraine, identification of the interaction specificity of various financial intermediaries in the accumulation process of idle cash and its transformation into the investment capital of national economy. Based on the results of the analysis conducted, it is established that unlike countries with developed financial systems, where the majority of institutional participants of the capital market are proportionally developed, it is the banking sector that dominates in Ukraine and has a determinant role in financing the economic development of the state. The availability of domestic financial resources for forming the resource potential of banks is substantiated, and their priority versus external resources for Ukraine is proved. The comparison of gross savings and gross capital formation allowed identifying certain problems as to transformation of the former into investment resources in Ukraine. The paper outlines some causes of a poor resource potential of national banking institutions.
Keywords: savings, accumulation, banks, economic growth, intermediaries, financial market, resources, transformation, investment potential
Telematics-based technology and the development of road condition trends from cloud-sourced data
Road related telematics encompasses a combination of road transportation, in-vehicle electronics and telecommunications. It is continuously evolving in terms of complexity and diversity, and contains high volumes of sensor data. Telematics-based technology is mainly used for the recovery of hijacked/stolen vehicles, insurance purposes and vehicle fleet monitoring and management. In this paper, it is demonstrated that telematics-based technology may offer capabilities in terms of predicting road condition. This is based on a project where some simple statistical analysis techniques were used to interpret existing data originating from standard vehicle telematics units. The paper mainly evaluates the z-direction (up / down) acceleration for a few different vehicle types and x-direction (lateral), y-direction (longitudinal) and z-direction acceleration for the identification of road anomalies/defects. Roads are currently monitored using Class 1 profilometers, which provides a detailed but relatively costly indication of road condition. The use of vehicle telematics may provide a more cost-effective solution to monitor a wider road network and on a continuous basis, albeit on a Class 3 profilometer level. Telematics units are currently installed in numerous vehicle types throughout South Africa, and this paper focuses on achieving a reliable Class 3, real-time response-type measurement which can be used as a screening device and which is able to accurately produce an indication of road roughness, as well as major road distresses. This may assist in ensuring that agencies without direct access to funding for Class 1 road condition data may be able to obtain an indication of their road network conditions. It also contributes towards the safety and comfort of road users.Paper presented at the 34th Annual Southern African Transport Conference 6-9 July 2015 "Working Together to Deliver - Sakha Sonke", CSIR International Convention Centre, Pretoria, South Africa.The Minister of Transport, South AfricaTransportation Research Board of the US
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