Agriculture, environment and food security in the context of rice

Agriculture requires inputs, which can be found within the system or need to be supplied from outside. The latter, referred to as the ‘Green Revolution’ in the 1950s and developed as the high external input agriculture, has spread over the world as a solution to the food crisis that arose due to World War II. The drive embraced a special package including high- yielding crop varieties, inorganic fertilizer, agro- chemicals and farm machineries. As a result, farmers in many developing countries began to practice mono-cropping with high external inputs. This has turned traditional ecological agriculture into environmentally destructive food production systems, which provided huge amounts of produce causing serious environmental damage. During the ‘Green Revolution’ traditional crop varieties were replaced by high-yielding new improved varieties, which had higher yield potential. However, natural pest resistance of these high-yielding varieties was generally poor, while nutritive requirements were high. Increased use of pesticides and chemical fertilizer is a matter of concern. Some of the issues and problems due to indiscriminate use of pesticides are: a) pest resistance; b) pest resurgence; c) health hazards; d) environmental pollution; and e) lower profits to farmers. Extensive use of chemical fertilizer has created environment issues such as nitrate leaching, release of greenhouse gases and eutrophication of inland water bodies. Millennium development goals earmark the eradication of extreme poverty and hunger, while ensuring environmental sustainability. This dispels the concept of achieving food security in any country through the adoption of high external input agriculture. Sri Lanka remains vulnerable to natural disasters such as floods, droughts, cyclones, landslides, epidemics etc., causing substantial threats to the food security situation of the country. Challenges posed by external factors due to globalization and open- economic policies have directed the country’s agriculture to move away from self- reliance. This situation demands a firm and perfect policy for the country’s agriculture. Furthermore, present agriculture does not show any indication of sustainability as it has ignored the centuries-old wisdom of traditional agriculture. Farmers’ dependency mentality evolved due to modern agriculture and government policies, which dealt with agriculture from time to time. This should be gradually replaced by developing farmers’ self- confidence, selfmotivation and empowerment. There is a great potential to increase productivity in Sri Lanka as only 40 % of the average potential for grain yield was achieved in different ecological and hydrological regimes. By narrowing this gap between actual and potential yield, Sri Lanka will not only increase productivity but also increase the competitive advantage for rice with other countries in the region. The experiences of the present productivity improvement program of the Department of Agriculture (DOA) have clearly shown that the average yield could be increased. In achieving food security in the country, a major set back in the development process is that institutional linkage among agencies responsible for water, land, agriculture and environment is very weak, and they work in isolation, setting their own targets. The need is felt for the immediate formulation of a firm policy to implement a sustainable agricultural production program in the country in order to ensure the food security in Sri Lanka.Length: pp.47-56RiceFood securityFarming systems

Power computation for the triboelectric nanogenerator

We consider, from a mathematical perspective, the power generated by a contact-mode triboelectric nanogenerator, an energy harvesting device that has been well studied recently. We encapsulate the behaviour of the device in a differential equation, which although linear and of first order, has periodic coefficients, leading to some interesting mathematical problems. In studying these, we derive approximate forms for the mean power generated and the current waveforms, and describe a procedure for computing the Fourier coefficients for the current, enabling us to show how the power is distributed over the harmonics. Comparisons with accurate numerics validate our analysis

Sequential fixed-width confidence bands for kernel regression estimation

We consider a random design model based on independent and identically distributed (iid) pairs of observations (Xi, Yi), where the regression function m(x) is given by m(x) = E(Yi|Xi = x) with one independent variable. In a nonparametric setting the aim is to produce a reasonable approximation to the unknown function m(x) when we have no precise information about the form of the true density, f(x) of X. We describe an estimation procedure of non-parametric regression model at a given point by some appropriately constructed fixed-width (2d) confidence interval with the confidence coefficient of at least 1&minus;. Here, d(&gt; 0) and 2 (0, 1) are two preassigned values. Fixed-width confidence intervals are developed using both Nadaraya-Watson and local linear kernel estimators of nonparametric regression with data-driven bandwidths. The sample size was optimized using the purely and two-stage sequential procedure together with asymptotic properties of the Nadaraya-Watson and local linear estimators. A large scale simulation study was performed to compare their coverage accuracy. The numerical results indicate that the confidence bands based on the local linear estimator have the best performance than those constructed by using Nadaraya-Watson estimator. However both estimators are shown to have asymptotically correct coverage properties.<br /

Atomic Fluorine Beam Etching Of Silicon And Related Materials

A 1 eV neutral atomic fluorine beam has been shown to produce etch rates in silicon as high as 1 µm/min. Using a CaF 2 resist layer we fabricated 120 µm-deep by 1 µm-wide trenches (aspect ratio 120:1) in silicon with little sidewall taper (slopes of about 1000:1) or aspect-ratio dependent etching effects. Achieving such anisotropic etching suggests that the scattered species do not contribute significantly to sidewall etching under the conditions of this experiment. We estimate that the ultimate depth attainable for a 1 µm-wide trench is about 250 µm and that the critical parameter for attaining a trench of a certain depth is the aspect ratio. Our observations and analysis suggest that this etching technique can be used to fabricate trenches on a nanoscale level while maintaining high aspect ratios of 100 or greater. JVST_web.doc 09/12/99

Estimating process capability index Cpm using a bootstrap sequential sampling procedure

Construction of a confidence interval for process capability index CPM is often based on a normal approximation with fixed sample size. In this article, we describe a different approach in constructing a fixed-width confidence interval for process capability index CPM with a preassigned accuracy by using a combination of bootstrap and sequential sampling schemes. The optimal sample size required to achieve a preassigned confidence level is obtained using both two-stage and modified two-stage sequential procedures. The procedure developed is also validated using an extensive simulation study.<br /

Utilization of a deoxynucleoside diphosphate substrate by HIV reverse transcriptase

Background: Deoxynucleoside triphosphates (dNTPs) are the normal substrates for DNA sysnthesis is catalyzed by polymerases such as HIV-1 reverse transcriptase (RT). However, substantial amounts of deoxynucleoside diphosphates (dNDPs) are also present in the cell. Use of dNDPs in HIV-1 DNA sysnthesis could have significant implications for the efficacy of nucleoside RT inhibitors such as AZT which are first line therapeutics fro treatment of HIV infection. Our earlier work on HIV-1 reverse transcriptase (RT) suggested that the interaction between the γ phosphate of the incoming dNTP and RT residue K65 in the active site is not essential for dNTP insertion, implying that this polymerase may be able to insert dNPs in addition to dNTPs. Methodology/Principal Findings: We examined the ability of recombinant wild type (wt) and mutant RTs with substitutions at residue K65 to utilize a dNDP substrate in primer extension reactions. We found that wild type HIV-1 RT indeed catalyzes incorporation of dNDP substrates whereas RT with mutations of residue K645 were unable to catalyze this reaction. Wild type HIV-1 RT also catalyzed the reverse reaction, inorganic phosphate-dependent phosphorolysis. Nucleotide-mediated phosphorolytic removal of chain-terminating 3′-terminal nucleoside inhibitors such as AZT forms the basis of HIV-1 resistance to such drugs, and this removal is enhanced by thymidine analog mutations (TAMs). We found that both wt and TAM-containing RTs were able to catalyze Pi-mediated phosphorolysis of 3′-terminal AZT at physiological levels of Pi with an efficacy similar to that for ATP-dependent AZT-excision. Conclusion: We have identified two new catalytic function of HIV-1 RT, the use of dNDPs as substrates for DNA synthesis, and the use of Pi as substrate for phosphorolytic removal of primer 3′-terminal nucleotides. The ability to insert dNDPs has been documented for only one other DNA polymerase The RB69 DNA polymerase and the reverse reaction employing inorganic phosphate has not been documented for any DNA polymerase. Importantly, our results show that Pi-mediated phosphorolysis can contribute to AZT resistance and indicates that factors that influence HIV resistance to AZT are more complex than previously appreciated. © 2008 Garforth et al

Land use-based participatory assessment of ecosystem services for ecological restoration in village tank cascade systems of Sri Lanka

Village Tank Cascade System (VTCS) landscapes in the dry zone of Sri Lanka provide multiple ecosystem services (ESs) and benefits to local communities, sustaining the productivity of their land use systems (LUSs). However, there is a lack of adequate scientific research on the ESs of LUSs, despite the recent land use changes that have greatly impacted the provisioning of ESs. Collection of baseline ESs data is a pre-requisite for decision making on ESs-based ecological restoration and management of the VTCS. Thus, this study aimed at assessing ESs of the Mahakanumulla VTCS (MVTCS) located in the Anuradhapura district of Sri Lanka by using a participatory approach involving the integration of local knowledge, expert judgements and LUSs attribute data to assess the ESs. The methodology was designed to integrate the biodiversity and land degradation status of LUSs in a way that is directly linked with the supply of ESs. The study identified twenty-four ESs of the MVTCS based on community perceptions. The identified ESs were assessed as a function of LUSs to develop an ecosystem service supply (ESS) and demand (ESD) matrix model. The results reveal that the current overall ESD for regulating and supporting ESs is higher than the ESS capacity of MVTCS. The assessment also revealed that land degradation and biodiversity deterioration reduce the capacity to provide ESs. Downstream LUSs of the meso-catchment were found to be more vulnerable to degradation and insufficient to provide ESs. Further, the study established that ESs in the MVTCS are generated through direct species-based and biophysical-based providers. In addition, it emerged that social and cultural engagements also played an important role in association with both providers to generate certain types of ESs. Therefore, it can be concluded that VTCS ecological restoration depends on the extent to which integrated effort addresses the levels of ecological complexity, as well as the social engagement of communities and stakeholders. The results of this study provide a scientific basis that can inform future land use decision making and practices that are applicable to successful ESs-based ecological restoration and management of the VTCSs in the dry zone of Sri Lanka

A new direct detection electron scattering experiment to search for the X17 particle

A new electron scattering experiment (E12-21-003) to verify and understand the nature of hidden sector particles, with particular emphasis on the so-called X17 particle, has been approved at Jefferson Lab. The search for these particles is motivated by new hidden sector models introduced to account for a variety of experimental and observational puzzles: excess in $e^+e^-$ pairs observed in multiple nuclear transitions, the 4.2$\sigma$ disagreement between experiments and the standard model prediction for the muon anomalous magnetic moment, and the small-scale structure puzzle in cosmological simulations. The aforementioned X17 particle has been hypothesized to account for the excess in $e^+e^-$ pairs observed from the $^8$Be M1, $^4$He M0, and, most recently, $^{12}$C E1 nuclear transitions to their ground states observed by the ATOMKI group. This experiment will use a high resolution electromagnetic calorimeter to search for or set new limits on the production rate of the X17 and other hidden sector particles in the $3 - 60$ MeV mass range via their $e^+e^-$ decay (or $\gamma\gamma$ decay with limited tracking). In these models, the $1 - 100$ MeV mass range is particularly well-motivated and the lower part of this range still remains unexplored. Our proposed direct detection experiment will use a magnetic-spectrometer-free setup (the PRad apparatus) to detect all three final state particles in the visible decay of a hidden sector particle for an effective control of the background and will cover the proposed mass range in a single setting. The use of the well-demonstrated PRad setup allows for an essentially ready-to-run and uniquely cost-effective search for hidden sector particles in the $3 - 60$ MeV mass range with a sensitivity of 8.9$\times$10$^{-8}$ - 5.8$\times$10$^{-9}$ to $\epsilon^2$, the square of the kinetic mixing interaction constant between hidden and visible sectors.Comment: 6 pages, 7 figures. arXiv admin note: substantial text overlap with arXiv:2108.1327

COMPARISON OF ENVIRONMENTAL RICHNESS IN NATURAL FOREST AND HOMEGARDENS A CASE STUDY FROM NACHCHADUWA CATCHMENT

An attempt was made to develop an assessment indicator combining the most importantparameters which decide the environmental richness of a plant community. Stratalcoverage, species richness and plant density were included in the following formula todescribe the environmental richness as:ER = S. / (KL NL + KM NM + Ks Ns), Where ER is environmental richness, K is acoefficient to represent stratal coverage and N is the number of plants per 100 sq.m forlarge (L), medium (M) and small (S) canopy types and S is the number of species per 100sq. m.A plant composition survey was carried out in a selected forest block of 25 m x 25 m atPaindikulama in the Nachchaduwa watershed in 1997 to assess the environmental richnessin natural forest. A comparison was then made with results obtained from a previoushomegarden survey conducted in the same watershed.During the survey 31 plant species were identified and the total number of plants surveyedwas 1360. The average plant density was 218 per 100 m2. Environmental richness of thisforest block was found as high as 108 whereas the value for homegardens has ranged from0.7 to 34.7. Results also revealed that the contribution made to environmental richnesswas higher (75%) by small canopy plants compared to large (3%) and medium (22%)categories. This may be due to the selective felling of large trees and subsequentemergence of small plants in the exposed patches. Results conclude that man madehomegardens could only achieve about one third of the environmental richness of naturalforest.