Inverse Problems and Data Assimilation

These notes are designed with the aim of providing a clear and concise introduction to the subjects of Inverse Problems and Data Assimilation, and their inter-relations, together with citations to some relevant literature in this area. The first half of the notes is dedicated to studying the Bayesian framework for inverse problems. Techniques such as importance sampling and Markov Chain Monte Carlo (MCMC) methods are introduced; these methods have the desirable property that in the limit of an infinite number of samples they reproduce the full posterior distribution. Since it is often computationally intensive to implement these methods, especially in high dimensional problems, approximate techniques such as approximating the posterior by a Dirac or a Gaussian distribution are discussed. The second half of the notes cover data assimilation. This refers to a particular class of inverse problems in which the unknown parameter is the initial condition of a dynamical system, and in the stochastic dynamics case the subsequent states of the system, and the data comprises partial and noisy observations of that (possibly stochastic) dynamical system. We will also demonstrate that methods developed in data assimilation may be employed to study generic inverse problems, by introducing an artificial time to generate a sequence of probability measures interpolating from the prior to the posterior

A Statistical Graphical Model of the California Reservoir System

The recent California drought has highlighted the potential vulnerability of the state's water management infrastructure to multiyear dry intervals. Due to the high complexity of the network, dynamic storage changes in California reservoirs on a state-wide scale have previously been difficult to model using either traditional statistical or physical approaches. Indeed, although there is a significant line of research on exploring models for single (or a small number of) reservoirs, these approaches are not amenable to a system-wide modeling of the California reservoir network due to the spatial and hydrological heterogeneities of the system. In this work, we develop a state-wide statistical graphical model to characterize the dependencies among a collection of 55 major California reservoirs across the state; this model is defined with respect to a graph in which the nodes index reservoirs and the edges specify the relationships or dependencies between reservoirs. We obtain and validate this model in a data-driven manner based on reservoir volumes over the period 2003–2016. A key feature of our framework is a quantification of the effects of external phenomena that influence the entire reservoir network. We further characterize the degree to which physical factors (e.g., state-wide Palmer Drought Severity Index (PDSI), average temperature, snow pack) and economic factors (e.g., consumer price index, number of agricultural workers) explain these external influences. As a consequence of this analysis, we obtain a system-wide health diagnosis of the reservoir network as a function of PDSI

Identification of AFLP markers linked with cocoon weight genes in silkworm (Bombyx mori L.)

DNA markers used in assisting selection method is a safe method in breeding process, due to deletion of environmental conditions, and it is an important tool in preparing linkage map and QTLs mapping. In mulberry silkworm that is, foundation of world sericulture, its major production-economic characteristics are polygenic. In this study, we want to determine QTL(s) affecting cocoon weight trait by AFLP markers. For this reason, we used 20 selected primer combinations from among 81 primers combinations of PstI/TaqI at the level of three F2 populations including 33, 36 and 34 offsprings sample, respectively. These populations were obtained by crossing two lines of Lemon Khorasan (as maternal) and 107 (as paternal). The parental lines, F1 and F2 individuals’ DNA were extracted with phenolchloroform method. Then they were digested by two restriction enzymes (TaqI and PstI) and amplified by using of appropriate adaptors. These amplified samples are transfered on annealed 6% polyacrylamide gels. After genotyping of individuals, the linkage maps of populations were drawn by Map manager/QTX and QTL Cartographer ver.2.5 softwares. Number of total and polymorphic bands that formed to 20 primer combinations in each populations were 930, 944, 810 and 142, 171, 178 bands, respectively. Therefore polymorphic frequencies were 15.27, 18.11 and 21.97%. The obtained linkage maps were included in 16, 18 and 24 linkage groups. The total length of this linkage maps and average distance between two markers were 2186.40, 2582.50 and 2392.60 cM, and 18.37, 16.45 and 14.95 cM, respectively. The detection of QTLs numbers of cocoon weight character in each F2 populations also showed 1, 6 and 1 loci in LRS>17 (LOD > 3.7) by compound interval mapping methods, respectively

In-vitro prostate cancer biomarker detection by directed conjugation of anti-PSCA antibody to super paramagnetic iron oxide nanoparticless

Background: The main property of a successful conjugation of antibodies to nanoparticles is keeping the potency of antibody for binding the antigen, and an oriented conjugation can do that. Under such ground, this study was carried out to explore the efficiency of two conjugation methods in binding iron nanoparticles to an antibody produced against PSCA (prostate stem cell antigen) using in vitro labeling of PC3 cells. Methods: In this experimental study, we conjugated dextran-superparamagnetic iron oxide nanoparticles (dexSPIONs) to anti-PSCA antibody by two different methods, including targeting carbohydrate moieties in FC domain and the free amine group of amino acid side chains. Ultimately, Iron staining was done by anti-PSCA antibody-dexSPIONs in PC3 cells to detect antibody binding to the cells. Results: A strong blue dye was induced by iron staining in conjugated dexSPIONs on the membrane of PC3 cells by the former method than the second one. Moreover, cells treated with 20 nm diameters of dexSPIONs showed higher resolution of blue color than those treated with 100 nm nanoparticles. Conclusion: This oriented conjugation method promoted the efficiency of targeting tumor antigens, and the presence of iron particles might enhance MRI image intensity in vivo by targeting PSCA-overexpressing cells in future studies. © Iran University of Medical Sciences

A Statistical Graphical Model of the California Reservoir System

The recent California drought has highlighted the potential vulnerability of the state's water management infrastructure to multiyear dry intervals. Due to the high complexity of the network, dynamic storage changes in California reservoirs on a state-wide scale have previously been difficult to model using either traditional statistical or physical approaches. Indeed, although there is a significant line of research on exploring models for single (or a small number of) reservoirs, these approaches are not amenable to a system-wide modeling of the California reservoir network due to the spatial and hydrological heterogeneities of the system. In this work, we develop a state-wide statistical graphical model to characterize the dependencies among a collection of 55 major California reservoirs across the state; this model is defined with respect to a graph in which the nodes index reservoirs and the edges specify the relationships or dependencies between reservoirs. We obtain and validate this model in a data-driven manner based on reservoir volumes over the period 2003–2016. A key feature of our framework is a quantification of the effects of external phenomena that influence the entire reservoir network. We further characterize the degree to which physical factors (e.g., state-wide Palmer Drought Severity Index (PDSI), average temperature, snow pack) and economic factors (e.g., consumer price index, number of agricultural workers) explain these external influences. As a consequence of this analysis, we obtain a system-wide health diagnosis of the reservoir network as a function of PDSI

The genetics of salt and waterlogging tolerance in wheat (Triticum aestivum L.)

SIGLEAvailable from British Library Document Supply Centre- DSC:D062159 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Impact Of Food Aid On Smallholder Agricultural Development In Swaziland

Food aid is a widely debated development topic and such debates have given rise to the existence of two schools of thought regarding its resultant effects. The general belief is that food aid has disincentive effects, whereas the counter belief is that food aid instead comes with contributional effects to agricultural development. For the past five production seasons, cereal food aid deliveries have featured prominently in the coverage of Swaziland's maize gap following Government's appeal to the international community to assist with the impact of drought on the country's food production. This study examined whether food aid has affected agricultural production of smallholder farmers in Swaziland who ironically constitute a larger proportion of food aid beneficiaries in the occurrence of drought. The study was based on empirical evidence from a representation of 240 smallholder farming households identified from the Lowveld Cattle & Cotton and the Highveld Maize & Cattle Food Economy Zones. Data were collected using multiple stage and random sampling techniques and analysed using Chi-square, logistic regression and multiple regression. Key findings of the study reflected that there is no significant dependence between food aid and agricultural production at household level. Agricultural production is not affected by receiving food aid per se, however, the mode of distribution to beneficiaries (free food aid) remains a cause for concern as it is likely to influence production decisions of beneficiaries. Further analysis revealed that the identification criteria are inconsistent within the study area, reflecting the necessity to improve on targeting. The issue of targeting needs to be further investigated as it could give a broader picture with regards to errors of inclusion and exclusion. Such a study would be suitable to examine the efficiency of food aid in the country. It is recommended that the Government of Swaziland considers the formulation of a food security policy that will address food security issues in a wholistic manner rather than to rely on a food aid programme that is meant for short term interventions when infact the effects of drought appear to be perpetual in the country

Impact of food aid on smallholder agriculture development in Swaziland

Food aid is a widely debated development topic and such debates have given rise to the existence of two schools of thought regarding its resultant effects. The general belief is that food aid has disincentive effects, whereas the counter belief is that food aid instead comes with contributional effects to agricultural development. For the past five production seasons, cereal food aid deliveries have featured prominently in the coverage of Swaziland's maize gap following Government's appeal to the international community to assist with the impact of drought on the country's food production. This study examined whether food aid has affected agricultural production of smallholder farmers in Swaziland who ironically constitute a larger proportion of food aid beneficiaries in the occurrence of drought. The study was based on empirical evidence from a representation of 240 smallholder farming households identified from the Lowveld Cattle & Cotton and the Highveld Maize & Cattle Food Economy Zones. Data were collected using multiple stage and random sampling techniques and analysed using Chi-square, logistic regression and multiple regression. Key findings of the study reflected that there is no significant dependence between food aid and agricultural production at household level. Agricultural production is not affected by receiving food aid per se, however, the mode of distribution to beneficiaries (free food aid) remains a cause for concern as it is likely to influence production decisions of beneficiaries. Further analysis revealed that the identification criteria are inconsistent within the study area, reflecting the necessity to improve on targeting. The issue of targeting needs to be further investigated as it could give a broader picture with regards to errors of inclusion and exclusion. Such a study would be suitable to examine the efficiency of food aid in the country. It is recommended that the Government of Swaziland considers the formulation of a food security policy that will address food security issues in a wholistic manner rather than to rely on a food aid programme that is meant for short term interventions when infact the effects of drought appear to be perpetual in the country. Keywords: Food Aid, Agricultural Production, impactAJFAND Vol. 8 (2) 2008 pp. 151-16

Achieving a Fully-Flexible Virtual Network Embedding in Elastic Optical Networks

Network operators must continuously scale the capacity of their optical backbone networks to keep apace with the proliferation of bandwidth-intensive applications. Today's optical networks are designed to carry large traffic aggregates with coarse-grained resource allocation, and are not adequate for maximizing utilization of the expensive optical substrate. Elastic Optical Network (EON) is an emerging technology that facilitates flexible allocation of fiber spectrum by leveraging finer-grained channel spacing, tunable modulation formats and Forward Error Correction (FEC) overheads, and baud-rate assignment, to right size spectrum allocation to customer needs. Virtual Network Embedding (VNE) over EON has been a recent topic of interest due to its importance for 5G network slicing. However, the problem has not yet been addressed while simultaneously considering the full flexibility offered by an EON. In this paper, we present an optimization model that solves the VNE problem over EON when lightpath configurations can be chosen among a large (and practical) set of combinations of paths, modulation formats, FEC overheads and baud rates. The VNE over EON problem is solved in its splittable version, which significantly increases problem complexity, but is much more likely to return a feasible solution. Given the intractability of the optimal solution, we propose a heuristic to solve larger problem instances. Key results from extensive simulations are: (i) a fully-flexible VNE can save up to 60% spectrum resources compared to that where no flexibility is exploited, and (ii) solutions of our heuristic fall in more than 90% of the cases, within 5% of the optimal solution, while executing several orders of magnitude faster