116 research outputs found
Electricity storage requirements to support the transition towards high renewable penetration levels: Application to the Greek power system
This paper investigates the electricity storage requirements to support the
transition towards a high renewable energy source (RES) penetration in a
cost-optimal manner. The achieved reduction of renewable energy curtailments
and the decrease in the total generation cost of the system are quantified
against a counterfactual scenario without storage. A methodology is presented
to determine the optimum mix of short- and medium-duration storage needed to
support system operation at increased RES penetration levels, using the mixed
integer linear programming mathematical optimization. The Greek power system
serves as a realistic study case, in its planned development for the year 2030,
with a targeted annual RES energy penetration in the order of 60%. Li-ion
batteries and pumped-hydro are selected as the representative technologies to
include in the storage mix, assuming energy-to-power ratios of up to 6 hours
for the former and 10 hours for the latter. It is shown that the introduction
of a suitable mixture of storage facilities may improve renewable energy
integration and, at the same time, reduce system cost to the extent that
entirely compensates for the full cost of storage, thus allowing for a net
economic benefit for the system. The optimum storage portfolio for the study
case system and the targeted RES penetration level combines 2-h batteries and
6-h pumped-hydro stations, with an aggregate capacity of new facilities between
1250 MW and 1750 MW, on top of the existing 700 MW of open-loop pumped hydro
plants. The optimum storage requirements vary with the targeted RES penetration
and with the balance of RES technologies in the generation mix, particularly
the level of PV integration.Comment: 28 pages, 19 figure
On a system of difference equations having exponential terms
In this paper we study the asymptotic behavior of the positive solutions of a cyclic system of the following difference equations:
\begin{align*}
x^{(i)}_{n+1}&=a_ix_n^{(i+1)}+b_i x^{(i)}_{n-1}e^{{-x^{(i+1)}_n}},\qquad
i=1,2,\ldots, m-1,\\
x^{(m)}_{n+1}&=a_mx^{(1)}_n+b_m x^{(m)}_{n-1}e^{{-x^{(1)}_n}},
\end{align*}
where , and , are positive constants and the initial values , are positive numbers
A comprehensive review of electricity storage applications in island systems
Electricity storage is crucial for power systems to achieve higher levels of
renewable energy penetration. This is especially significant for
non-interconnected island (NII) systems, which are electrically isolated and
vulnerable to the fluctuations of intermittent renewable generation. This paper
comprehensively reviews existing literature on electricity storage in island
systems, documenting relevant storage applications worldwide and emphasizing
the role of storage in transitioning NII towards a fossil-fuel-independent
electricity sector. On this topic, the literature review indicates that the
implementation of storage is a prerequisite for attaining renewable penetration
rates of over 50% due to the amplified requirements for system flexibility and
renewable energy arbitrage. The analysis also identifies potential storage
services and classifies applicable storage architectures for islands. Amongst
the available storage designs, two have emerged as particularly important for
further investigation; standalone, centrally managed storage stations and
storage combined with renewables to form a hybrid plant that operates
indivisibly in the market. For each design, the operating principles,
remuneration schemes, investment feasibility, and applications discussed in the
literature are presented in-depth, while possible implementation barriers are
acknowledged. The literature on hybrid power plants mainly focuses on
wind-powered pumped-hydro stations. However, recently, PV-powered battery-based
hybrid plants have gained momentum due to the decreasing cost of Li-ion
technology. On the other hand, standalone storage establishments rely heavily
on battery technology and are mainly used to provide flexibility to the island
grid. Nevertheless, these investments often suffer from insufficient
remunerating frameworks, making it challenging for storage projects to be
financially secure.Comment: 55 pages, 10 figure
Excessive weight gain after remission of depression in a schizophrenic patient treated with risperidone: case report
BACKGROUND: The use of atypical antipsychotics in schizophrenic patients has been associated with a risk of weight gain. Similarly, recovery from depression is often followed by improved appetite, greater food intake and potential increase in weight. CASE PRESENTATION: A Caucasian 33-year-old schizophrenic female patient was being treated with 6 mg/day of risperidone and 15 mg/day of clorazepate. She developed depressive symptomatology and 40 mg/day of fluoxetine was gradually added to her treatment regimen for about 9 months. After the remission of depression, and the discontinuation of fluoxetine, she experienced an increase in appetite and subsequently excessive weight gain of 52 kg. Re-administration of fluoxetine did not reverse the situation. The patient developed diabetes mellitus, which was successfully controlled with metformin 1700 mg/day. The addition at first of orlistat 360 mg/day and later of topiramate 200 mg/day has helped her to lose a significant part of the weight gained (30 kg). CONCLUSION: The case suggests a probable association between the remission of depressive symptomatology and weight gain in a schizophrenic patient
Preparation of polycaprolactone nanoparticles via supercritical carbon dioxide extraction of emulsions
Polycaprolactone (PCL) nanoparticles were produced via supercritical fluid extraction of emulsions (SFEE) using supercritical carbon dioxide (scCO2). The efficiency of the scCO2 extraction was investigated and compared to that of solvent extraction at atmospheric pressure. The effects of process parameters including polymer concentration (0.6–10% w/w in acetone), surfactant concentration (0.07 and 0.14% w/w) and polymer-to-surfactant weight ratio (1:1–16:1 w/w) on the particle size and surface morphology were also investigated. Spherical PCL nanoparticles with mean particle sizes between 190 and 350 nm were obtained depending on the polymer concentration, which was the most important factor where increase in the particle size was directly related to total polymer content in the formulation. Nanoparticles produced were analysed using dynamic light scattering and scanning electron microscopy. The results indicated that SFEE can be applied for the preparation of PCL nanoparticles without agglomeration and in a comparatively short duration of only 1 h
Insomnia and its correlates in a representative sample of the Greek population
<p>Abstract</p> <p>Background</p> <p>Insomnia is a major public health concern affecting about 10% of the general population in its chronic form. Furthermore, epidemiological surveys demonstrate that poor sleep and sleep dissatisfaction are even more frequent problems (10-48%) in the community. This is the first report on the prevalence of insomnia in Greece, a southeastern European country which differs in several socio-cultural and climatic aspects from the rest of European Community members. Data obtained from a national household survey (n = 1005) were used to assess the relationship between insomnia symptoms and a variety of sociodemographic variables, life habits, and health-related factors.</p> <p>Methods</p> <p>A self-administered questionnaire with questions pertaining to general health and related issues was given to the participants. The Short Form-36 (Mental Health subscale), the Athens Insomnia Scale (AIS) as a measure of insomnia-related symptoms, and the International Physical Activity Questionnaire (IPAQ) were also used for the assessment.</p> <p>Results</p> <p>The prevalence of insomnia in the total sample was 25.3% (n = 254); insomnia was more frequent in women than men (30.7% vs. 19.5%) and increased with age. Multiple regression analysis revealed a significant association of insomnia with low socio-economical status and educational level, physical inactivity, existence of a chronic physical or mental disease and increased number of hospitalizations in the previous year.</p> <p>Conclusions</p> <p>The present study confirms most findings reported from other developed countries around the world regarding the high prevalence of insomnia problems in the general population and their association with several sociodemographic and health-related predisposing factors. These results further indicate the need for more active interventions on the part of physicians who should suspect and specifically ask about such symptoms.</p
An unusual case of bacillary angiomatosis in the oral cavity of an AIDS patient who had no concomitant tegumentary lesions – case report and review
ABSTRACT Bacillary angiomatosis (BA) is an angioproliferative disease of immunocompromised patients that usually presents as vascular tumors in the skin and subcutaneous tissues. It is caused by chronic infections with either Bartonella henselae or B. quintana. Oral cavity BA is exceedingly rare and even rarer without simultaneous cutaneous disease. We report herein the case of a 51-year-old HIV-infected man who presented severe odynophagia and an eroded lesion on the hard palate that progressed to an oronasal fistula. No cutaneous lesions were recorded. Doxycycline led to complete resolution. To the best of our knowledge, only six previous cases of oral BA without tegumentary disease have been previously reported and none of them progressed to fistula
The Annotation, Mapping, Expression and Network (AMEN) suite of tools for molecular systems biology
<p>Abstract</p> <p>Background</p> <p>High-throughput genome biological experiments yield large and multifaceted datasets that require flexible and user-friendly analysis tools to facilitate their interpretation by life scientists. Many solutions currently exist, but they are often limited to specific steps in the complex process of data management and analysis and some require extensive informatics skills to be installed and run efficiently.</p> <p>Results</p> <p>We developed the Annotation, Mapping, Expression and Network (AMEN) software as a stand-alone, unified suite of tools that enables biological and medical researchers with basic bioinformatics training to manage and explore genome annotation, chromosomal mapping, protein-protein interaction, expression profiling and proteomics data. The current version provides modules for (i) uploading and pre-processing data from microarray expression profiling experiments, (ii) detecting groups of significantly co-expressed genes, and (iii) searching for enrichment of functional annotations within those groups. Moreover, the user interface is designed to simultaneously visualize several types of data such as protein-protein interaction networks in conjunction with expression profiles and cellular co-localization patterns. We have successfully applied the program to interpret expression profiling data from budding yeast, rodents and human.</p> <p>Conclusion</p> <p>AMEN is an innovative solution for molecular systems biological data analysis freely available under the GNU license. The program is available via a website at the Sourceforge portal which includes a user guide with concrete examples, links to external databases and helpful comments to implement additional functionalities. We emphasize that AMEN will continue to be developed and maintained by our laboratory because it has proven to be extremely useful for our genome biological research program.</p
Heterogeneity of pollen food allergy syndrome in seven Southern European countries: The @IT.2020 multicenter study
Background Pollen food allergy syndrome (PFAS) is a frequently underdiagnosed disease due to diverse triggers, clinical presentations, and test results. This is especially relevant in geographic areas with a broad spectrum of pollen sensitization, such as Southern Europe. Objectives To elucidate similarities and differences of PFAS in nine Southern European centers and identify associated characteristics and unique markers of PFAS. Methods As part of the @IT.2020 Multicenter Study, 815 patients with seasonal allergic rhinitis (SAR), aged 10-60 years, were recruited in seven countries. They completed questionnaires regarding SAR, comorbidities, family history, and PFAS, and underwent skin prick testing (SPT) and serum IgE testing. Results Of the 815 patients, 167 (20.5%) reported PFAS reactions. Most commonly, eliciting foods were kiwi (58, 34.7%), peach (43, 25.7%), and melon (26, 15.6%). Reported reactions were mostly local (216/319, 67.7%), occurring within 5 min of contact with elicitors (209/319, 65.5%). Associated characteristics included positive IgE to at least one panallergen (profilin, PR-10, or nsLTP) (p = 0.007), maternal PFAS (OR: 3.716, p = 0.026), and asthma (OR: 1.752, p = 0.073). Between centers, heterogeneity in prevalence (Marseille: 7.5% vs. Rome: 41.4%, p < 0.001) and of clinical characteristics was apparent. Cypress played a limited role, with only 1/22 SPT mono-sensitized patients reporting a food reaction (p < 0.073). Conclusions PFAS is a frequent comorbidity in Southern European SAR patients. Significant heterogeneity of clinical characteristics in PFAS patients among the centers was observed and may be related to the different pollen sensitization patterns in each geographic area. IgE to panallergen(s), maternal PFAS, and asthma could be PFAS-associated characteristics
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