63 research outputs found
Induced Impacts of Climate Change on Livelihood and Migration in Upper Himalayas: A Case of Mustang, Nepal
No full textInduced Impacts of Climate Change on Livelihood and Migration in Upper Himalayas: A Case of Mustang, Nepal
No full textInvariant measures of piecewise concave dynamical systems via maximum entropy optimization method
No full textPiecewise Concave Dynamical System (PCDS) has its wide application in various science fields.
Many real-world problems can be modeled into mathematical models via PCDS. First, we let T:
[0,1] → [0,1] be a piecewise concave transformation/maps (PCDS) and study the existence of
absolutely continuous invariant measures. Then, we present a maximum entropy optimization
method for approximating densities of Piecewise Concave Maps. A numerical example will be
presented to compare the approximate densities of Piecewise Concave Maps using the maximum
entropy method and the actual densities of the Piecewise Concave Maps
Effects of irrigation rates on cotton yield as affected by soil physical properties and topography in the southern high plains
No full text© 2021 Neupane et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Lack of precipitation and groundwater for irrigation limits crop production in semi-arid regions, such as the Southern High Plains (SHP). Advanced technologies, such as variable rate irrigation (VRI), can conserve water and improve water use efficiency for sustainable agriculture. However, the adoption of VRI is hindered by the lack of on-farm research focusing on the feasibility of VRI. The objective of this study was to assess the effect of irrigation rates on cotton yield as affected by soil physical properties and topography in the Southern High Plains. This study was conducted in two fields within a 194-ha commercially managed farm in Hale County, Texas, in 2017. An irrigation treatment with three rates was implemented in a randomized complete block design with two replications as separate blocks in each field. A total of 230 composite soil samples were collected from the farm in spring 2017 and analyzed for texture. Information on apparent soil electrical conductivity (ECa), elevation, and final yield were collected from the fields. A statistical model showed that the effect of irrigation rates on cotton yield depended on its interaction with soil physical properties and topography. For example, areas with slope >2% and sand content >50% had no significant response to higher irrigation rates. This model suggests that applying irrigation amounts based on the yield response can be a basis for VRI. This study provides valuable information for site-specific irrigation to optimize crop production in fields with significant variability in soil physical properties and topography
Study Of Mercaptobenzimidazoles As Inhibitors For Copper Corrosion: Down to the Molecular Scale
No full textThe initiation of corrosion can be triggered by defects in the adsorbed layer of organic inhibitors. A detailed knowledge of the intermolecular forces between the inhibitor molecules and the interfacial bonding will be decisive to unravel the mechanisms driving the corrosion initiation. In this work, adsorbed organic layers of 2-mercapto-5-methoxybenzimidazole (SH-BimH-5OMe) and 5-amino-2-mercaptobenzimidazole (SH-BimH-5NH2) were compared regarding their performance mitigating copper corrosion. Atomic force microscopy was used to address the stability and intermolecular forces of the self-assembled monolayers, using imaging and force measurement modes. For a film formed by amino-derivative molecules, a gold-coated tip frequently picked up individual molecules (molecular fishing) in force-distance measurements. For layers of the methoxy-derivative, no fishing events were observed, pointing to a constant functional layer. X-ray photoelectron spectroscopy revealed that SH-BimH-5OMe molecules form a stronger bond with the surface and more stable SAM layers on Cu surfaces as compared to SH-BimH-5NH2 molecules. Results of computational density functional theory modeling and electrochemical corrosion tests are in line with the microscopy and spectroscopy results. In particular, with aid of computational modeling the less ordered structure of the SH-BimH-5NH2 monolayer is attributed to dual bonding ability of SH-BimH-5NH2 that can adsorb with either S or NH2 groups.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Formation of nanosized monolayer MoS2 by oxygen-assisted thinning of multilayer MoS2
No full textWe report the controllable nanosized local thinning of multi-layer (2 L and 3 L)-thickness MoS2 films down to the monolayer (1 L) thickness using the simple method of annealing in a dry oxygen atmosphere. The annealing temperature was optimized in the range of 240 °C to 270 °C for 1.5 h, and 1 L thick nanosized pits were developed on the uniform film of the 2 L and 3 L MoS2 grown using the chemical vapor deposition method. We characterized the formation of the 1 L nanosized pits using nanoscale confocal photoluminescence (PL) and Raman spectroscopy. We observed that the PL intensity increased and the Raman frequency shifted, representative of the characteristics of 1 L MoS2 films. A subsequent hydrogen treatment process was useful for removing the oxygen-induced doping effect resulting from the annealing. © 2016 Author(s)6711sciescopu
Simplistic correlations between molecular electronic properties and inhibition efficiencies: Do they really exist?
No full textThe often used simplistic correlations between molecular electronic parameters and experimentally determined corrosion inhibition efficiencies are critically evaluated for a set of 24 heterocyclic organic compounds, tested as corrosion inhibitors for copper in 3 wt.% NaCl aqueous solution. Twelve different molecular electronic descriptors—such as ionization potential, electron affinity, HOMO–LUMO gap, dipole moment—are tested and it is shown that none of them displays any noticeable correlation with the inhibition efficiency. Our results, therefore, cast serious doubt on reported correlations between such parameters and inhibition efficiency, obtained for only a few inhibitors, which are abundant in the literature. We also discuss some pros and cons of inhibition efficiency as a metric for evaluating the performance of corrosion inhibitors, and introduce a new metric termed inhibition power that uses the universal logarithmic scale and dimensionless decibel (dB) units.Team Peyman TaheriTeam Arjan Mo
Essential elements of game development : a case study EvilHuman Game
No full textThe game industries have been growing rapidly since the last decade. The main objective of this thesis was to develop a game from scratch to have a deeper look at the game development process. This thesis attempts to answer the following questions; what are the essential elements for game design, how to generate revenue through games by using different monetization models, what are the tools and software available today to create a game, what is game testing methodology and how it is implemented, and, finally, how to manage customer service. To know about whole game design process, one simple mobile game called“EvilHuman” was designed.
A fully functional game was completed using the Unity3D game engine and was published in Google Play Store to receive comments and feedbacks from the users. The game was downloaded between 100 – 500 times. The users who downloaded the game wrote reviews in Google Play Store, and the average rating was 4.6 out of 5. There were many challenges duringthe practical part of this thesis. The main challenge for this game was learning Unity3D, C# programming, game designing and modeling. However, some assets were used from the premade assets from the Unity3D asset store, which had made the design process easier.
The publishing of this game in Google Play has motivated the author to continue in the game development field because of suggestions and positive feedback, which were provided by the real users who downloaded the game and played it
BMI1 is a context-dependent tumor suppressor that is a barrier to dedifferentiation in non-small cell lung adenocarcinoma
No full textThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: Ph. D., Massachusetts Institute of Technology, Department of Biology, 2019Cataloged from student-submitted PDF version of thesis. "May 2019."Includes bibliographical references.Predictive value is expected when preclinical models of disease are used for research. However, not all models appropriately mimic the disease progression or the treatment paradigm in the clinic. This thesis addresses an epigenetic regulator, Bmi1, which acts in stem cells to maintain their proliferative and self-renewal capacity primarily through silencing of the Ink4a/Arf locus. Bmi1 has been proposed as a good therapeutic candidate in cancer because of its presumed role in maintaining tumor propagating cells (TPCs). This conclusion is based on the observed tumor suppressive effects of Bmi1 deletion in in vitro cell culture models, in vivo transplant models, and autochthonous models in which Bmi1 was absent throughout development. However, to date, no one has assessed the consequences of deleting Bmi1 in existing autochthonous tumors, to mimic patient treatment in the clinic.To accomplish this, we have generated a mouse model that allows induction of autochthonous lung adenocarcinoma, driven by oncogenic Kras and Tp53 loss (KP LUAD), and subsequent deletion of Bmi1 specifically within the tumor cells once more than half the tumors progress to grade 3 or higher. We confirmed that this model yielded Bmi1 loss that was tumor-specific and almost complete. We then aged tumor bearing mice for up to seven weeks post Bmi1 deletion to determine the impact on LUAD. Unexpectedly, Bmi1 deletion did not yield significant tumor suppression. Instead, gene expression analyses of Bmi1 deficient tumor cells revealed upregulation of a gastric gene expression program that is a known marker of lung tumor progression towards a more aggressive state in the KP LUAD model. Additionally, single cell sequencing showed that Bmi1 deficient tumors contained a higher frequency of cells that expressed previously described markers of TPCs and metastasis.We also extended these findings to colorectal cancer where we show that deletion of Bmi1 is not tumor suppressive in either in vitro organoids or orthotopic transplants. Given these findings, we conclude that deletion, or inhibition, of BMI1 in existing tumors will be ineffective for cancer treatment in the contexts examined, and potentially deleterious because it can enable acquisition of alternate differentiation states that promote tumor progression.by Rachit Neupane.Ph. D.Ph.D. Massachusetts Institute of Technology, Department of Biolog
Designing Resilient Agents Using Grammatical Evolution, Behavior Trees, and Finite Linear Temporal Logic
No full textResilience is essential for long-term autonomous agents. Swarm behaviors seen in bees, ants, birds, fish, and others are interesting because they resiliently perform complex coordinated tasks like foraging, nest-selection, flocking and escaping predators without centralized control or coordination. Conventionally, mimicking swarm behaviors with robots requires researchers to study actual behaviors, derive mathematical models, and implement these models as state machines. Since the conventional approach is time-consuming and cumbersome, this dissertation uses a grammatical evolution algorithm with Behavior Trees (BTs) to evolve behaviors that are resilient to different perturbations for foraging and nest maintenance tasks. The modular, reactive, and readable properties of BTs make it an excellent controller for implementing swarm behaviors. Our method is based on the author\u27s master\u27s thesis work on a core algorithm called Grammatical Evolution algorithm for Evolution of Swarm bEhaviors using Behavior Trees (GEESE-BT). The GEESE-BT algorithm can be used to evolve swarm behaviors for interesting multiagent problems, but the solutions require ad hoc fitness functions tailored to the specific problems. This dissertation presents the BeTr-GEESE algorithm, which replaces ad hoc fitness functions with direct feedback from the BT modules. BeTr-GEESE learns more efficiently than GEESE-BT. The modular, subtask-specific programs produced by BeTr-GEESE can be exchanged through lateral transfer to perform missions that require sequential execution of subtasks. Lateral transfer produces resilient performance in divisible and additive group tasks like foraging and nest maintenance. However, the behaviors of successful groups must exhibit temporal locality, meaning that an agent must persist in behavior long enough to perform essential functions but also means that agents cannot persist too long or evolution is too slow. A biologically inspired enhancement of using multiple genes with BeTr-GEESE allowed a fixed population of heterogeneous agents to accomplish tasks with high resilience power and efficiency. The last part of the dissertation complements the empirical approach used in designing resilient swarms using grammatical evolution. Goal specification and verification are vital to designing resilient artificial agents. Finite trace Linear Temporal Logic () is a potent way of specifying goals, but synthesizing planners that guarantee the goals are satisfied can be computationally prohibitive. This dissertation shows that goals specified using a subset of finite trace Linear Temporal Logic () can be decomposed into an equivalent BT that leads to a relaxed behavior synthesis problem in which a wide range of planners can be used to generate effective behaviors that satisfy the goal specification
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