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Minimum and maximum energy for crystals of magnetic dipoles
No full textProperties of many magnetic materials consisting of dipoles depend crucially on the nature of the dipole–dipole interaction. In the present work, we study systems of magnetic dipoles where the dipoles are arranged on various types of one-dimensional, two-dimensional and three-dimensional lattices. It is assumed that we are in the regime of strong dipole moments where a classical treatment is possible. We combine a new classical numerical approach in conjuncture with an ansatz for an energy decomposition method to study the energy stability of various magnetic configurations at zero temperature for systems of dipoles ranging from small to an infinite number of particles. A careful analysis of the data in the bulk limit allows us to identify very accurate minimum and maximum energy bounds as well as ground state configurations corresponding to various types of lattices. The results suggest stabilization of a particularly interesting ground state configuration consisting of three embedded spirals for the case of a two-dimensional hexagonal lattice
An overview of and factor analytic approach to flow theory in online contexts
No full textAn overview of flow theory is presented from the literature across multiple disciplines, including information systems, ecommerce, marketing, digital gaming, user interface, management, and cultural contexts. Flow can play a pivotal role in the user experience and impact the user interaction with a site, computing device, or app. It is worthwhile to examine the effects of flow experience on users and incorporate these findings in designing engaging user experiences and interfaces in both web sites and mobile applications. To further understand these implications, the present study gave a questionnaire to 310 participants in a computer laboratory setting following an online shopping episode. The factor analysis revealed three dimensions of flow experience: control, attention focus, and cognitive enjoyment. All three dimensions had very low correlations. No gender effect on flow was found
Nonlinear integral models with delays: Recent developments and applications
No full textThe authors examine contemporary integral dynamic models of biological, environmental, and technological systems with heterogeneous components. The models contain two-dimensional control functions, nonlinearities, and delays in system inputs. The paper demonstrates the versatility of integral equations and their importance to various applications. Connections and advantages of integral and differential models are discussed. A survey of optimal control strategies for such models is provided
Removing the excuse: Using free course materials to improve student success in general studies courses
No full textFaculty and students have long complained about the prohibitive costs of textbooks. According to the National Bureau of Labor Statistics the price of textbooks has risen more than 1000 percent since the 1970s and Public Research Interest Group found that 65 percent of students have skipped purchasing a textbook because of cost. This study uses survey and grade distribution data to examine the effectiveness of a pilot program designed to increase student accessibility to textbooks as well as improve students’ academic performance. We found statistically significant impacts on early assignments and positive increases in student attitudes towards their classes
Thermal resistance of foodborne pathogens and enterococcus faecium NRRL B-2354 on inoculated pistachios
No full textProcess control validations require knowledge of the resistance of the pathogen(s) of concern to the target treatment and, in some cases, the relative resistance of surrogate organisms. Selected strains of Escherichia coli O157:H7 (five strains), Listeria monocytogenes (five strains), and Salmonella enterica (five strains) as well as Salmonella Enteritidis phage type (PT) 30 and nonpathogenic Enterococcus faecium NRRL B-2354 were inoculated separately (as individual strains) onto inshell pistachios. The thermal tolerance of each strain was compared via treatment of inoculated pistachios to hot oil (1218C) or hot water (808C) for 1 min. Survivor curves in hot oil or hot water (0.5 to 6 min, n ¼ 6 to 15) were determined for one or two of the most resistant strains of each pathogen, as well as E. faecium NRRL B-2354 and Salmonella Enteritidis PT 30, and the Weibull model was fit to the data. A pilot-scale air-impingement oven was used to compare the thermal tolerance of E. faecium NRRL B-2354 and Salmonella Enteritidis PT 30 on pistachios with or without a brining pretreatment and at either dry (no steam) or 30% humidity (v/v) oven conditions. No significant difference in the time to a 4-log reduction in hot oil or hot water was predicted for any of the strains evaluated, on the basis of the 95% confidence interval. In the pilot-scale oven, E. faecium NRRL B-2354 was more thermally resistant than Salmonella in a broad set of differing treatments, treatment times, and temperatures. Salmonella is a suitable target pathogen of concern in pistachios for thermal processes because no other pathogen tested was more thermally resistant under the conditions evaluated. E. faecium NRRL B-2354 was at least as thermally resistant as Salmonella under all conditions evaluated, making it a good potential surrogate for Salmonella on pistachios
Evaluation of atmospheric and terrestrial effects in the carbon cycle for forest and grassland ecosystems using a remote sensing and modeling approach
No full textSoil moisture (SM) and vapor pressure deficit (VPD) are key variables that affect the carbon, water, and energy cycles. Very few studies have been conducted to evaluate their impacts on site-specific ecosystems, especially in mountainous regions and plains using an integrated remote sensing and modeling approach. This study used two flux tower sites, P301 (forest–ecosystem), Prairie View A&M University (PVAMU) (grassland–ecosystem) to evaluate gross primary production (GPP), sensible heat flux (H), and latent heat flux (LE). The community land model (CLM4) and soil moisture active passive (SMAP) carbon product were employed and evaluated using the flux tower data from 2016 to 2018. From the CLM4 and SMAP estimation of GPP, the CLM4 showed better accuracy at P301, whereas SMAP performed better at PVAMU. The SMAP overestimated GPP at P301, which could be due to the coarse footprint of SMAP (9 × 9 km). CLM4 overestimated GPP during the growing season at PVAMU, which could be due to the structural and parametric uncertainties. The H at P301 showed good agreement between the CLM4 results and flux tower measurements. However, H at the PVAMU site was most likely affected by the precipitation. Moreover, at P301, VPD was effective in controlling the carbon and water fluxes (GPP and LE) with a positive partial correlation (p–value \u3c 0.05). However, at PVAMU, SM (terrestrial control) showed substantial control over the fluxes due to year-round precipitation. Overall, the results showed that the California site was affected due to low precipitation and could be vulnerable to climate change due to a reduction in SM and high VPD during the summers. In contrast, the Texas site had high SM due to frequent and intense rainfall events due to the changing climate. For the future study, a detailed analysis of SM and VPD control at regional and global scales for various land cover types is needed
Applications of remote sensing in precision agriculture: A review
No full textAgriculture provides for the most basic needs of humankind: food and fiber. The introduction of new farming techniques in the past century (e.g., during the Green Revolution) has helped agriculture keep pace with growing demands for food and other agricultural products. However, further increases in food demand, a growing population, and rising income levels are likely to put additional strain on natural resources. With growing recognition of the negative impacts of agriculture on the environment, new techniques and approaches should be able to meet future food demands while maintaining or reducing the environmental footprint of agriculture. Emerging technologies, such as geospatial technologies, Internet of Things (IoT), Big Data analysis, and artificial intelligence (AI), could be utilized to make informed management decisions aimed to increase crop production. Precision agriculture (PA) entails the application of a suite of such technologies to optimize agricultural inputs to increase agricultural production and reduce input losses. Use of remote sensing technologies for PA has increased rapidly during the past few decades. The unprecedented availability of high resolution (spatial, spectral and temporal) satellite images has promoted the use of remote sensing in many PA applications, including crop monitoring, irrigation management, nutrient application, disease and pest management, and yield prediction. In this paper, we provide an overview of remote sensing systems, techniques, and vegetation indices along with their recent (2015–2020) applications in PA. Remote-sensing-based PA technologies such as variable fertilizer rate application technology in Green Seeker and Crop Circle have already been incorporated in commercial agriculture. Use of unmanned aerial vehicles (UAVs) has increased tremendously during the last decade due to their cost-effectiveness and flexibility in obtaining the high-resolution (cm-scale) images needed for PA applications. At the same time, the availability of a large amount of satellite data has prompted researchers to explore advanced data storage and processing techniques such as cloud computing and machine learning. Given the complexity of image processing and the amount of technical knowledge and expertise needed, it is critical to explore and develop a simple yet reliable workflow for the real-time application of remote sensing in PA. Development of accurate yet easy to use, user-friendly systems is likely to result in broader adoption of remote sensing technologies in commercial and non-commercial PA applications
Parameterization of the modified water cloud model (MWCM) using normalized difference vegetation index (NDVI) for winter wheat crop: a case study from Punjab, India
No full textSoil moisture is essential for water resources management, yet accurate information of soil moisture has been a challenge. The major goal was to parametrize the Modified Water Cloud Model (MWCM). The Sentinel-1A data of winter wheat crop was collected for two weeks. Concurrently, in-situ soil moisture data was collected using Time Domain Reflectometer (TDR). A parametric scheme was used for the retrieval of the VV polarization of Sentinel-1A. The effect of NDVI as a vegetation descriptors (V1 and V2) on total VV backscatter (σ 0) was analyzed. The calibration showed NDVI has the potential to influence Water Cloud Model (WCM) and vegetation descriptors; hence it is recommended to calibrate the MWCM. The coefficient of determination (R2 = 0.83) showed a good agreement between observed and estimated soil moisture. Therefore, this approach help improve soil moisture prediction, and can be applied to determine soil moisture more accurately for winter crops, grasses, and pasture lands
The effects of dimmer controlled atmospheric pressure plasma jet to the biophysical structures of hela cells
No full textNon-thermal atmospheric pressure plasma jet (NTAPPJ) was shown as a promising tool for sterilization, treatment of chronic wounds & tumors. A portable and facile NTAPPJ system will broaden the application of plasma for many other biomedical applications. This paper demonstrates the feasibility of a customized dimmer controllable atmospheric pressure plasma jet (APPJ) in treating HeLa cells. A plasma torch was energized at 8 kVpp and 35 kHz from a neon transformer and discharged with argon gas-producing plasma plume of various gas species. The output intensity of the plasma discharge was adjusted by the voltage input from the dimmer controller circuit. Between 60 - 220 V, a different power output of the dimmer can be varied between 8.4 to 83.6 W, to generate different intensities of non-thermal APPJ (NTAPPJ). The NTAPPJ was then applied to HeLa cells for 20 sec & it was found that cells reduced their adhesion at a dimmer power \u3c 20 W but stayed viable. This progressed to observations of damaged cell body when the power was increased beyond 20 W & the cell membranes shattered when the power was up to 83.6 W. This was due to the ultraviolet rays and reactive oxygen species (ROS), that induced detrimental effects to the cells. The controllable NTAPPJ system, based on dimmer control, induced different levels of effects on the biophysical structures of cells, ranging from reduced cell spread to apoptosis and eventually cell membrane disintegration
Application of conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) polymers in potential biomedical engineering
No full textBackground: Biomedical engineering has emerged as a multidisciplinary endeavor. Biomedical engineering includes the development of new devices, processes, and systems in order to advance medical practice and health care. The specialty areas of biomedical engineering are biomaterials and tissue engineering (TE), bioinstrumentation, clinical and rehabilitation engineering. Area covered: Over the past few decades, conductive polymers have received much attention in many applications. The applications of conductive polymers are in the drug delivery system, in the construction of bioactuators, as well as in the Tissue Engineering field. Composites are produced by combining conductive polymers with other polymers or materials. Modification of conductive polymers can render these polymers to be biodegradable and biocompatible, making them very useful in TE applications. Expert opinion: Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), a biocompatible conductive polymer, is recently being researched, to be used as nano-bio interfaces for medical applications such as nucleic acid detection, controlled release of neuron growth factor, and guided cell growth. This review focuses on the recent advances of conductive polymers, specifically, PEDOT:PSS aiming towards TE, photovoltaic devices and biosensor applications