Importance of linking inertia and frequency response procurement: the Great Britain case

In order to decarbonise the electricity sector, the future Great Britain (GB) power system will be largely dominated by non-synchronous renewables. This will cause low levels of inertia, a key parameter that could lead to frequency deterioration. Therefore, the requirement for ancillary services that contain frequency deviations will increase significantly, particularly given the increase in size of the largest possible loss with the commissioning of large nuclear plants in the near future. In this paper, an inertia-dependent Stochastic Unit Commitment (SUC) model is used to illustrate the benefits of linking inertia and frequency response provision in low-inertia systems. We demonstrate that the cost of procuring ancillary services in GB could increase by 165% if the level of inertia is not explicitly considered when procuring frequency response. These results highlight the need to re-think the structure of ancillary-services markets, which in GB are nowadays held one month ahead of delivery

Stochastic co-optimisation of energy, frequency and carbon services considering flexible nuclear power plants

Data availability: No data was used for the research described in the article.Integration of high levels of non-synchronous Renewable Energy Sources (RES) and nuclear power plant will play a vital role in decarbonising the electricity grid of Great Britain (GB). However, the uncertainties associated with RES may increase the risk of grid frequency deterioration, which will increase the requirement for the provision of ancillary services such as inertia and Frequency Response (FR). Furthermore, nuclear power plants typically have lower operational flexibility due to limited load following capabilities and the ability to provide FR services, which will not only lead to high system operation cost but also present a potential barrier to reach the net-zero emissions target cost-effectively by reducing the utilisation of RES. A potential solution to mitigate these challenges consists of incorporating thermal energy storage and secondary steam rankine cycle into the nuclear power plant, effectively resulting in a Flexible Nuclear Power Plant (FNPP) configuration. Therefore, this paper proposes a novel ancillary services constrained stochastic unit commitment model, which optimises the simultaneous provision of energy production, synchronised inertia and primary FR from conventional power plants and FNPP, enhanced FR from wind, whilst explicitly considering the uncertainties associated with wind generation using the quantile-based scenario tree method. The effectiveness of the proposed model is demonstrated through several case studies conducted on the 2030 GB power system. The results explore the economic savings and carbon emissions cost reductions obtained from simultaneous co-optimisation of FNPP and the provision of FR services provided by FNPP and wind.This work was supported by the UK EPSRC project: ‘Integrated Development of Low-Carbon Energy Systems (IDLES): A Whole-System Paradigm for Creating a National Strategy’ (project code: EP/R045518/ 1)

Increasing efficiency of perovskite solar cells using low concentrating photovoltaic systems

This is the final version. Available from Royal Society of Chemistry via the DOI in this record. Perovskite solar cell (PSC) technology is the flag bearer for the future of photovoltaics allowing unlimited possibilities for its application. This technology is currently limited by issues related to its scale-up, stability and the composition of the materials used in its preparation. Using small sized solar cells with higher efficiency under solar concentration is gaining traction as a methodology for scaling up this technology and broadening its applications. However, this has only been reported in devices with size <1 mm2 neglecting the series resistance of the device. Here, we report the performance of a 9 mm2 PSC at varying solar concentration levels and correlate it with the series resistance of the solar cell. The n–i–p structured device using a triple cation perovskite absorber with a mesoporous titanium oxide/SnO2 layer as the electron transporting layer and Spiro-OMeTAD as the hole transporting material achieved a peak efficiency of 21.6% under 1.78 Suns as compared to the 21% obtained under 1 Sun (1000W m−2) and AM1.5G. We further boosted the power output up to 15.88 mW under 10.7 Suns compared to the 1.88 mW obtained under 1 Sun; however this results in an actual efficiency drop of the PSC owing to the device series resistance. Further, we investigated the impact of the increasing solar cell temperature at higher concentration levels and identified the influence of series resistance on the performance of the PSC. Our work identifies the potential of concentrating photovoltaics and highlights the challenges and makes recommendations for future development.EPSRCEuropean Union's Horizon 202

Advances in research on the use of biochar in soil for remediation: a review

Purpose: Soil contamination mainly from human activities remains a major environmental problem in the contemporary world. Significant work has been undertaken to position biochar as a readily-available material useful for the management of contaminants in various environmental media notably soil. Here, we review the increasing research on the use of biochar in soil for the remediation of some organic and inorganic contaminants.  Materials and methods: Bibliometric analysis was carried out within the past 10 years to determine the increasing trend in research related to biochar in soil for contaminant remediation. Five exemplar contaminants were reviewed in both laboratory and field-based studies. These included two inorganic (i.e., As and Pb) and three organic classes (i.e., sulfamethoxazole, atrazine, and PAHs). The contaminants were selected based on bibliometric data and as representatives of their various contaminant classes. For example, As and Pb are potentially toxic elements (anionic and cationic, respectively), while sulfamethoxazole, atrazine, and PAHs represent antibiotics, herbicides, and hydrocarbons, respectively.  Results and discussion: The interaction between biochar and contaminants in soil is largely driven by biochar precursor material and pyrolysis temperature as well as some characteristics of the contaminants such as octanol-water partition coefficient (KOW) and polarity. The structural and chemical characteristics of biochar in turn determine the major sorption mechanisms and define biochar’s suitability for contaminant sorption. Based on the reviewed literature, a soil treatment plan is suggested to guide the application of biochar in various soil types (paddy soils, brownfield, and mine soils) at different pH levels (4–5.5) and contaminant concentrations ( 50 mg kg−1).  Conclusions: Research on biochar has grown over the years with significant focus on its properties, and how these affect biochar’s ability to immobilize organic and inorganic contaminants in soil. Few of these studies have been field-based. More studies with greater focus on field-based soil remediation are therefore required to fully understand the behavior of biochar under natural circumstances. Other recommendations are made aimed at stimulating future research in areas where significant knowledge gaps exist

Reverse Myocardial Remodeling Following Valve Repair in Patients With Chronic Severe Primary Degenerative Mitral Regurgitation

OBJECTIVES: The aims of this study were to quantify preoperative myocardial fibrosis using late gadolinium enhancement (LGE), extracellular volume fraction (ECV%), and indexed extracellular volume (iECV) on cardiac magnetic resonance; determine whether this varies following surgery; and examine the impact on postoperative outcomes. BACKGROUND: Myocardial fibrosis complicates chronic severe primary mitral regurgitation and is associated with left ventricular dilatation and dysfunction. It is not known if this nonischemic fibrosis is reversible following surgery or if it affects ventricular remodeling and patient outcomes. METHODS: A multicenter prospective study was conducted among 104 subjects with primary mitral regurgitation undergoing mitral valve repair. Cardiac magnetic resonance and cardiopulmonary exercise stress testing were performed preoperatively and ≥6 months after surgery. Symptoms were assessed using the Minnesota Living With Heart Failure Questionnaire. RESULTS: Mitral valve repair was performed for Class 2a indications in 65 patients and Class 1 indications in 39 patients. Ninety-three patients were followed up at 8.8 months (interquartile range: 7.4 months-10.6 months). Following surgery, there were significant reductions in both ECV% (from 27.4% to 26.6%; P = 0.027) and iECV (from 17.9 to 15.4 mL/m2; P < 0.001), but the incidence of LGE was unchanged. Neither preoperative ECV% nor LGE affected postoperative function, but iECV predicted left ventricular end-systolic volume index (β = 1.04; 95% CI: 0.49 to 1.58; P < 0.001) and left ventricular ejection fraction (β = -0.61; 95% CI: -1.05 to -0.18; P = 0.006). Patients with above-median iECV of ≥17.6 mL/m2 had significantly larger postoperative values of left ventricular end-systolic volume index (30.5 ± 12.7 mL/m2 vs 23.9 ± 8.0 mL/m2; P = 0.003), an association that remained significant in subcohort analyses of patients in New York Heart Association functional class I. CONCLUSIONS: Mitral valve surgery results in reductions in ECV% and iECV, which are surrogates of diffuse myocardial fibrosis, and preoperative iECV predicts the degree of postoperative remodeling irrespective of symptoms. (The Role of Myocardial Fibrosis in Degenerative Mitral Regurgitation; NCT02355418)

Gastrointestinal stromal tumour and hypoglycemia in a Fjord pony: Case report

<p>Abstract</p> <p>Background</p> <p>Neoplasia may cause hypoglycemia in different species including the horse, but hypoglycemia has not previously been reported in the horse associated with gastrointestinal stromal tumours.</p> <p>Case presentation</p> <p>A case of a gastrointestinal stromal tumour in a Fjord pony with severe recurrent hypoglycemia is presented. The mechanism causing the hypoglycemia was not established.</p> <p>Conclusion</p> <p>This case indicates that a gastrointestinal stromal tumour may cause hypoglycemia also in the horse.</p

Geriatric patients' expectations of their physicians: findings from a tertiary care hospital in Pakistan

<p>Abstract</p> <p>Background</p> <p>Geriatric health is a neglected and under-explored area internationally and in Pakistan. We aimed to ascertain the expectations of the geriatric patients from their physicians and the factors associated with patient satisfaction in this particular age bracket.</p> <p>Methods</p> <p>A cross-sectional survey was carried out at a tertiary care teaching hospital in Karachi, Pakistan. Data collection was carried out via face-to-face interviews based on structured, pre-tested questionnaires. All consenting individuals aged 65 years or above were recruited into the study. Convenience sampling was used to draw the sample. The data was analyzed using SPSS version 16. Geriatric patient's expectations from physicians were elicited using a set of 11 questions that were graded on a scale of 1-3 where 1 = not important, 2 = important, 3 = very important.</p> <p>Results</p> <p>Three hundred and eighty geriatric patients were interviewed. The response rate of this study was 89.8%. The mean age of the respondents was 73.4 ± 6.8 years. Two hundred and forty eight respondents (65.3%) were female. Diabetes mellitus (53.7%), hypertension (59.5%), arthritis (40.5%) and renal disease (32.1%) were common ailments among geriatric patients. More than 50% of the patients were visiting their physicians once every two to three months. Discussing treatment options and letting patients make the final decision (79.2%), prescribing minimum possible medications (84.5%), physician's holistic knowledge about the spectrum of care issues for geriatric patients (79.2%), being given a realistic but optimistic picture of future health by physicians (85.5%) were ranked as very important expectations by patients from their physicians. Cumulative household income (p = 0.005), most important health complaint (p = 0.01) and frequency of experiencing health complaint (p < 0.001) emerged as independent predictors of the satisfaction of geriatric patients from care provided by physicians.</p> <p>Conclusion</p> <p>We have documented the expectations of the geriatric patients from their physicians in a developing country. Physicians belonging to all disciplines should keep these expectations in mind during clinical encounters with geriatric patients.</p

Cerebrospinal fluid findings in adults with acute Lyme neuroborreliosis

Presence of BB-specific antibodies in the cerebrospinal fluid (CSF) with evidence of their intrathecal production in conjunction with the white cell count in the CSF and typical clinical symptoms is the traditional diagnostic gold standard of Lyme neuroborreliosis (LNB). Few data are available on the CSF lactate concentration in European adults with the diagnosis of acute LNB. The objective of the study was to investigate the CSF changes during acute LNB. Routine CSF parameters [leukocyte count, protein, lactate and albumin concentrations, CSF/serum quotients of albumin (QAlb), IgG, IgA and IgM, and oligoclonal IgG bands] and the Borrelia burgdorferi (BB)-specific antibody index were retrospectively studied in relation to the clinical presentation in patients diagnosed with acute LNB. A total of 118 patients with LNB were categorized into the following groups according to their symptoms at presentation; group 1: polyradiculoneuritis (Bannwarth’s syndrome), group 2: isolated facial palsy and group 3: predominantly meningitic course of the disease. In addition to the CSF of patients with acute LNB, CSF of 19 patients with viral meningitis (VM) and 3 with neurolues (NL) were analyzed. There were 97 patients classified with definite LNB, and 21 as probable LNB. Neck stiffness and fever were reported by 15.3% of patients. Most of these patients were younger than 50 years. Polyradiculoneuritis was frequently found in patients older than 50 years. Lymphopleocytosis was found in all patients. Only 5 patients had a CSF lactate ≥3.5 mmol/l, and the mean CSF lactate level was not elevated (2.1 ± 0.6 mmol/l). The patients with definite LNB had significantly higher lactate levels than patients with probable LNB. Elevated lactate levels were accompanied by fever and headache. In the Reiber nomograms, intrathecal immunoglobulin synthesis was found for IgM in 70.2% followed by IgG in 19.5%. Isoelectric focussing detected an intrathecal IgG synthesis in 83 patients (70.3%). Elevated BB AIs in the CSF were found in 97 patients (82.2%). Patients with VM showed lower CSF protein concentration and CSF/serum quotients of albumin than LNB patients. In acute LNB, all patients had elevated cerebrospinal fluid (CSF) leukocyte counts. In contrast to infections by other bacteria, CSF lactate was lower than 3.5 mmol/l in all but 5 patients. The CSF findings did not differ between polyradiculoneuritis, facial palsy, and meningitis. The CSF in LNB patients strongly differed from CSF in VM patients with respect to protein concentration and the CSF/serum albumin quotient

Severe loss of mechanical efficiency in COVID‐19 patients

Background: There is limited information about the impact of coronavirus disease (COVID-19) on the muscular dysfunction, despite the generalized weakness and fatigue that patients report after overcoming the acute phase of the infection. This study aimed to detect impaired muscle efficiency by evaluating delta efficiency (DE) in patients with COVID-19 compared with subjects with chronic obstructive pulmonary disease (COPD), ischaemic heart disease (IHD), and control group (CG). Methods: A total of 60 participants were assigned to four experimental groups: COVID-19, COPD, IHD, and CG (n = 15 each group). Incremental exercise tests in a cycle ergometer were performed to obtain peak oxygen uptake (VO2 peak). DE was obtained from the end of the first workload to the power output where the respiratory exchange ratio was 1. Results: A lower DE was detected in patients with COVID-19 and COPD compared with those in CG (P ≤ 0.033). However, no significant differences were observed among the experimental groups with diseases (P > 0.05). Lower VO2 peak, peak ventilation, peak power output, and total exercise time were observed in the groups with diseases than in the CG (P < 0.05). A higher VO2 , ventilation, and power output were detected in the CG compared with those in the groups with diseases at the first and second ventilatory threshold (P < 0.05). A higher power output was detected in the IHD group compared with those in the COVID-19 and COPD groups (P < 0.05) at the first and second ventilatory thresholds and when the respiratory exchange ratio was 1. A significant correlation (P < 0.001) was found between the VO2 peak and DE and between the peak power output and DE (P < 0.001). Conclusions: Patients with COVID-19 showed marked mechanical inefficiency similar to that observed in COPD and IHD patients. Patients with COVID-19 and COPD showed a significant decrease in power output compared to IHD during pedalling despite having similar response in VO2 at each intensity. Resistance training should be considered during the early phase of rehabilitation