204 research outputs found
Triply mixed coverings of arbitrary base curves : quasimodularity, quantum curves and a mysterious topological recursions
Simple Hurwitz numbers are classical invariants in enumerative geometry counting branched morphisms between Riemann surfaces with fixed ramification data. In recent years, several modifications of this notion for genus 0 base curves have appeared in the literature. Among them are so-called monotone Hurwitz numbers, which are related to the HarishâChandraâItzyksonâZuber integral in random matrix theory and strictly monotone Hurwitz numbers which enumerate certain Grothendieck dessins dâenfants. We generalise the notion of Hurwitz numbers to interpolations between simple, monotone and strictly monotone Hurwitz numbers for arbitrary genera and any number of arbitrary but fixed ramification profiles. This yields generalisations of several results known for Hurwitz numbers. When the target surface is of genus one, we show that the generating series of these interpolated Hurwitz numbers are quasimodular forms. In the case that all ramification is simple, we refine this result by writing this series as a sum of quasimodular forms corresponding to tropical covers weighted by GromovâWitten invariants. Moreover, we derive a quantum curve for monotone and Grothendieck dessins dâenfants Hurwitz numbers for arbitrary genera and one arbitrary but fixed ramification profile. Thus, we obtain spectral curves via the semi-classical limit as input data for the ChekhovâEynardâOrantin (CEO) topological recursion. Astonishingly, we find that the CEO topological recursion for the genus 1 spectral curve of the strictly monotone Hurwitz numbers computes the monotone Hurwitz numbers in genus 0. Thus, we give a new proof that monotone Hurwitz numbers satisfy CEO topological recursion. This points to an unknown relation between those enumerative invariants. Finally, specializing to target surface â1, we find recursions for monotone and Grothendieck dessins dâenfants double Hurwitz numbers, which enables the computation of the respective Hurwitz numbers for any genera with one arbitrary but fixed ramification profile
Climate change adaptation in agriculture; the use of multi-scale modelling and stakeholder participation in the Netherlands
Abstract about a research project to develop a methodology to assess adaptation of agriculture to climatic and socio-economic changes at multiple scales, with a first application in the Province of Flevoland, the Netherlands
Use of organic inputs by arable farmers in six agro-ecological zones across Europe: Drivers and barriers
Soil organic matter (SOM) in agricultural soils builds up via â among others - the use of organic inputs such as straw, compost, farmyard manure or the cultivation of green manures or cover crops. SOM has benefits for long-term soil fertility and can provide ecosystem services. Farmer behaviour is however known to be motivated by a larger number of factors. Using the theory of planned behaviour, we aimed to disentangle these factors. We addressed the following research question: What are currently the main drivers and barriers for arable farmers in Europe to use organic inputs? Our study focuses on six agro-ecological zones in four European countries (Austria, Flanders [Belgium], Italy and the Netherlands) and four practices (straw incorporation, green manure or cover crops, compost and farmyard manure). In a first step, relevant factors were identified for each practice with farmers using 5 to ten semi-structured interviews per agro-ecological zone. In a second step, the relevance of these factors was quantified and they were classified as either drivers or barriers in a large scale farm survey with 1263 farmers. In the semi-structured interviews, 110 factors that influenced farmer decisions to use an organic input were identified. In the larger farm survey, 60% of the factors included were evaluated as drivers, while 40% were evaluated as barriers for the use of organic inputs. Major drivers to use organic inputs were related to the perceived effects on soil quality (such as improved soil structure or reduced erosion) and the positive influence from social referents (such as fellow farmers or agricultural advisors). Major barriers to use organic inputs were financial (increased costs or foregone income) and perceived effects on crop protection (such as increased weeds, pests and diseases, or increased pesticide use). Our study shows that motivating farmers to use organic inputs requires specific guidance on how to adapt cultivation practices to reduce weeds, pests and diseases for specific soil types, weather conditions, and crops. In addition, more research is needed on the long-term financial consequences of using organic inputs
Nitrogen fertiliser replacement values for organic amendments appear to increase with N application rates
Nitrogen (N) supply from organic amendments [such as farmyard manure (FYM), slurries or crop residues] to crops is commonly expressed in the amendmentâs Nitrogen Fertiliser Replacement Value (NFRV). Values for NFRV can be determined by comparison of crop yield or N uptake in amended plots against mineral fertiliser-only plots. NFRV is then defined as the amount of mineral fertiliser N saved when using organic amendment-N (kg/kg), while attaining the same crop yield. Factors known to affect NFRV are crop type cultivated, soil type, manuring history and method or time of application. We investigated whether long-term NFRV depends on N application rates. Using data from eight long term experiments in Europe, values of NFRV at low total N supply were compared with values of NFRV at high total N supply. Our findings show that FYM has a significant higher NFRV value at high total N supply than at low total N supply (1.12 vs. 0.53, p = 0.04). For the other amendment types investigated, NFRV was also higher at high total N supply than at low total N supply, but sample sizes were too small or variations too large to detect significant differences. Farmers in Europe usually operate at high rates of total N applied. If fertiliser supplements are based on NFRV of the manure estimated at low total N supply, N fertiliser requirements might be overestimated. This might lead to overuse of N, lower N use efficiency and larger losses of N to the environment
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Sustainable development goal 2: improved targets and indicators for agriculture and food security
The pursuit of global food security and agricultural sustainability, the dual aim of the
second Sustainable Development Goal (SDG-2), requires urgent and concerted action
from developing and developed countries. This, in turn, depends on clear and
universally applicable targets and indicators which are partially lacking. The novel and
complex nature of the SDGs poses further challenges to their implementation on the
ground, especially in the face of interlinkages across SDG objectives and scales. Here
we review the existing SDG-2 indicators, propose improvements to facilitate their
operationalization and illustrate their practical implementation in Nigeria, Brazil and the
Netherlands. This exercise provides insights into the concrete actions needed to
achieve SDG-2 across contrasting development contexts and highlights the challenges
of addressing the links between targets and indicators within and beyond SDG-2.
Ultimately, it underscores the need for integrated policies and reveals opportunities to
leverage the fulfillment of SDG-2 worldwide
Analysing urban heat island patterns and simulating potential future changes
Climate change is interpreted as one of the most serious environmental problems for the 21st century. Changes in climate are now generally accepted. However, the rate of change has spatial characteristics and is highly uncertain. The Himalaya is experiencing abrupt change; so vulnerability and adaptation studies have become crucial. This pilot study presents initial findings of the research project entitled âHuman Ecological Implications of Climate Change in the Himalaya.â A study of climate change perceptions, vulnerability, and adaptation strategies of farming communities of the cool-wet temperate (Lumle) and the hot-wet sub-tropical (Meghauli) villages in Central Nepal was conducted. The findings are derived from the analysis of temperature and precipitation data of last 40 years, and primary data collected in September 2012. Focus Group Discussions, Key Informant Interviews, and Historical Timeline Calender were applied. The changes perceived by the communities are fairly consistent with the meteorological observations and are challenging the sustainability of social-ecological systems and communitiesâ livelihoods. Farming communities have adopted some strategies to minimize the vulnerability. But the adopted strategies have produced both negative and positive results. Strategies like flood control, shifting crop calendars, occupational changes and labour migrations have produced positive results in livelihood security. Occupational changes and labour migration have negatively impacted local agro-ecology and agricultural economies. Early-harvesting strategies to reduce losses from hailstorm have reduced the food and fodder security. Lack of irrigation for rice-seedlings is severely affecting the efficacy of shifting the rice-transplantation calendar. Conclusions suggest that while farmers have practiced strategies to better management of farms, livelihood sustainabilities are reaching thresholds due to the changing conditions.Rishikesh Pandey, Douglas K Bardsle
Self-Reported Functional Status as Predictor of Observed Functional Capacity in Subjects with Early Osteoarthritis of the Hip and Knee: A Diagnostic Study in the CHECK Cohort
Objectives Patients with hip or knee osteoarthritis (OA) may experience functional limitations in work settings. In the Cohort Hip and Cohort Knee study (CHECK) physical function was both self-reported and measured performance-based, using Functional Capacity Evaluation (FCE). Relations between self-reported scores on SF-36 and WOMAC (Western Ontario and McMaster Arthritis Index, function scales) and FCE performance were studied, and their diagnostic value for clinicians in predicting observed physical work limitations was assessed. Methods Ninety-two subjects scored physical function on SF-36 (scale 0â100, 100 indicating the best health level) and WOMAC (scale 0â68, 68 indicates maximum restriction) and performed the FCE. Correlations were calculated between all scores. Cross-tables were constructed using both questionnaires as diagnostic tests to identify work limitations. Subjects lifting <22.5 kg on the FCE-test âlifting-lowâ were labeled as having physical work limitations. Diagnostic aspects at different cut-off scores for both questionnaires were analysed. Results Statistically significant correlations (Spearmanâs Ď 0.34â0.49) were found between questionnaire scores and lifting and carrying tests. Results of a diagnostic cross-table with cut-off point <60 on SF-36 âphysical functioningâ were: sensitivity 0.34, specificity 0.97 and positive predictive value (PV+) 0.95. Cut-off point âĽ21 on WOMAC âfunctionâ resulted in sensitivity 0.51, specificity 0.88 and PV+ 0.88. Conclusion Low self-reported function scores on SF-36 and WOMAC diagnosed subjects with limitations on the FCE. However, high scores did not guarantee performance without physical work limitations. These results are specific to the tested persons with early OA, in populations with a different prevalence of limitations, different diagnostic values will be found. FCE may be indicated to help clinicians to assess actual work capacity
Allocation to highly sensitized patients based on acceptable mismatches results in low rejection rates comparable to non-sensitized patients
Whereas regular allocation avoids unacceptable mismatches on the donor organ, allocation to highly sensitized patients within the Eurotransplant Acceptable Mismatch (AM) program is based on the patient's HLA phenotype plus acceptable antigens. These are HLA antigens to which the patient never made antibodies, determined by extensive laboratory testing. AM patients have superior long-term graft survival compared to highly sensitized patients in regular allocation. Here, we questioned whether the AM program also results in lower rejection rates. From the PROCARE cohort, consisting of all Dutch kidney transplants 1995-2005, we selected deceased donor single transplants with minimum one HLA mismatch and determined the cumulative 6-month rejection incidence for patients in AM or regular allocation. Additionally, we determined the effect of minimal matching criteria of one HLA-B plus one HLA-DR, or two HLA-DR antigens on rejection incidence. AM patients showed significantly lower rejection rates than highly immunized patients in regular allocation, comparable to non-sensitized patients, independent of other risk factors for rejection. Contrasting to highly sensitized patients in regular allocation, minimal matching criteria did not affect rejection rates in AM patients. Allocation based on acceptable antigens leads to relatively low risk transplants for highly sensitized patients with rejection rates similar to non-immunized individuals. This article is protected by copyright. All rights reserved.</p
Development of a conceptual framework for integrated analysis and assessment of agricultural systems in SEAMLESS-IF
The report is divided into two parts. The first part describes basic concepts of systems analysis, sustainability and sustainable development, and integrated assessment and modelling that are potentially relevant for the present project. It further reviews the role of indicator, models, scenarios and case studies for impact assessments and provides information about possible technical solutions together with a general introduction into participatory methods including the communication of knowledge. The second part of the report describes the conceptual basis that is proposed for SEAMLESS-IF to enable integrated analysis and assessment of agricultural systems. Three levels of conceptualisation are distinguished and refer to: 1. delineation of the theoretical framework for analysis and assessment. 2. specification of the procedure (workflow) for analysis and assessment. 3. model formulatio
Evaluation of spelt germplasm for polyphenol oxidase activity and aluminium resistance
Kidney transplantation is the best treatment option for patients with end-stage renal failure. At present, approximately 800 Dutch patients are registered on the active waiting list of Eurotransplant. The waiting time in the Netherlands for a kidney from a deceased donor is on average between 3 and 4years. During this period, patients are fully dependent on dialysis, which replaces only partly the renal function, whereas the quality of life is limited. Mortality among patients on the waiting list is high. In order to increase the number of kidney donors, several initiatives have been undertaken by the Dutch Kidney Foundation including national calls for donor registration and providing information on organ donation and kidney transplantation. The aim of the national PROCARE consortium is to develop improved matching algorithms that will lead to a prolonged survival of transplanted donor kidneys and a reduced HLA immunization. The latter will positively affect the waiting time for a retransplantation. The present algorithm for allocation is among others based on matching for HLA antigens, which were originally defined by antibodies using serological typing techniques. However, several studies suggest that this algorithm needs adaptation and that other immune parameters which are currently not included may assist in improving graft survival rates. We will employ a multicenter-based evaluation on 5429 patients transplanted between 1995 and 2005 in the Netherlands. The association between key clinical endpoints and selected laboratory defined parameters will be examined, including Luminex-defined HLA antibody specificities, T and B cell epitopes recognized on the mismatched HLA antigens, non-HLA antibodies, and also polymorphisms in complement and Fc receptors functionally associated with effector functions of anti-graft antibodies. From these data, key parameters determining the success of kidney transplantation will be identified which will lead to the identification of additional parameters to be included in future matching algorithms aiming to extend survival of transplanted kidneys and to diminish HLA immunization. Computer simulation studies will reveal the number of patients having a direct benefit from improved matching, the effect on shortening of the waiting list, and the decrease in waiting time
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