Rice Starch Diversity: Effects on Structural,Morphological, Thermal,and Physicochemical Properties—A Review

Abstract: Rice starch is one of the major cereal starches with novel functional properties. Significant progress has been made in recent years on the characterization of rice starches separated from different rice cultivars. Studies have revealed that the molecular structure and functional properties are affected by rice germplasm, isolation procedure, climate, agronomic conditions, and grain development. Morphological studies (microscopy and particle size analysis) have reflected significant differences among rice starch granule shapes (polyhedral, irregular) and in granule size (2 to 7 μm). Nonwaxy and long‐grain rice starches show greater variation in granular size than the waxy starches. Rice starch granules are smaller than other cereal starches with amylose contents varying from virtually amylose‐free in waxy to about 35% in nonwaxy and long‐grain rice starches. Amylose content appears to be the major factor controlling almost all physicochemical properties of rice starch due to its influence on pasting, gelatinization, retrogradation, syneresis, and other functional properties. Waxy rice starches have high swelling and solubility parameters, and larger relative crystallinity values than nonwaxy and long‐grain starches. However, nonwaxy rice starches have a higher gelatinization temperature than the waxy and long‐grain starches. The bland taste, nonallergenicity, and smooth, creamy, and spreadable characteristics of rice starch make it unique and valuable in food and pharmaceutical applications. This review provides recent information on the variation in the molecular structure and functional properties of different rice starches.     

Molecular Mechanisms of Nitric Oxide (NO) Signaling and Reactive Oxygen Species (ROS) Homeostasis during Abiotic Stresses in Plants

Abiotic stressors, such as drought, heavy metals, and high salinity, are causing huge crop losses worldwide. These abiotic stressors are expected to become more extreme, less predictable, and more widespread in the near future. With the rapidly growing human population and changing global climate conditions, it is critical to prevent global crop losses to meet the increasing demand for food and other crop products. The reactive gaseous signaling molecule nitric oxide (NO) is involved in numerous plant developmental processes as well as plant responses to various abiotic stresses through its interactions with various molecules. Together, these interactions lead to the homeostasis of reactive oxygen species (ROS), proline and glutathione biosynthesis, post-translational modifications such as S-nitrosylation, and modulation of gene and protein expression. Exogenous application of various NO donors positively mitigates the negative effects of various abiotic stressors. In view of the multidimensional role of this signaling molecule, research over the past decade has investigated its potential in alleviating the deleterious effects of various abiotic stressors, particularly in ROS homeostasis. In this review, we highlight the recent molecular and physiological advances that provide insights into the functional role of NO in mediating various abiotic stress responses in plants.     

Hydrogen bubble flotation of silica

In this study the flotation recovery of silica using air, and molecular and electrolytically-generated hydrogen was investigated. For comparison of air and molecular hydrogen recoveries, a laboratory Denver, type D12, flotation machine was used. For both gases, pH of the suspension, gas flow rate, concentration of collector and frother, solids concentration, particle size and speed of impeller were kept constant. Almost identical recoveries were obtained for both gases, suggesting that gas composition played no significant role in silica flotation. Electroflotation experiments were carried out using 12.6 μm mean diameter silica particles. While fine particles had very poor recovery in the Denver cell, greater than 70% recoveries were achieved in the electroflotation cell. This was thought to be the result of the very small (less than 40 μm) bubbles generated by the electroflotation process. A population-balance model, incorporating the hydrogen generation process, supported the conclusion that increased recovery for electroflotation, for very fine silica particles at least, was attributed to the reduced bubble size and not by the composition of the gas.     

Development of maintainability index for mechanical systems

A procedure based on a digraph and matrix method is developed for evaluation of maintainability index of mechanical systems. Features which characterize or ease in maintenance of a system are identified and are called the maintainability attributes. Consideration of these attributes and their interrelations are rudiment in evaluating the index. This is modeled in terms of a Maintainability Attributes Digraph for the system. Nodes in the digraph represent these attributes and their interrelations are represented by the edges. The digraph is represented by one-to-one matrix for development of a maintainability expression, which is characteristic of the system. A Variable Maintainability Attributes Facilitation Permanent Matrix is defined to develop maintainability expression (VPF-m) which is also useful in comparing two systems. Maintainability Index of the system is obtained from the permanent of the matrix or from the maintainability expression by substituting numerical values of the attributes and their interrelations. A higher value of the index implies good maintainability of the system. The ideal value of maintainability index (I_mi) is also obtained from the matrix expression, which is useful in assessing relative maintainability, I_r, of the system alternative. The procedure is useful in design and development of maintainable systems. A step by step procedure for evaluation of maintainability index is also suggested and is illustrated by means of an example.     

Millimeter‐wave antenna with wide‐scan angle radiation characteristics for MIMO applications

A three‐element quasi Yagi‐Uda antenna array with printed metamaterial surface generated from the array of uniplanar capacitively loaded loop (CLL) unit‐cells printed on the substrate operating in the band 25‐30 GHz is proposed. The metamaterial surface is configured to provide a high‐refractive index to tilt the electromagnetic (EM) beam from the two dipole antennas placed opposite to each other. The metamaterial region focuses the rays from the dipole antenna and hence increases the gain of the individual antennas by about 5 dBi. The antenna elements are printed on a 10 mil substrate with a center to center separation of about 0.5 λ ₀ at 28 GHz. The three‐element antenna covers 25‐30 GHz band with measured return loss of 10 dB and isolation greater than 15 dB between all the three ports. The measured gain of about 11 dBi is achieved for all the antenna elements. The three antenna elements radiate in three different directions and cover a radiation scan angle of 64°.     

Geometrical Modeling of Scattering Environment for Highways in Umbrella Cell Based MIMO Communication Systems

In this paper, we develop a three-dimensional (3D) eccentricity-based cylindrical geometrical channel model for nonisotropic multiple-input-multiple-output (MIMO) communication systems under umbrella macrocellular environment. We use elliptic cylindrical geometry to model the scattering phenomenon in streets, canyons and highways. The scattering objects like, high-rise building, trees and vegetation that lie along the roadside premises are modeled by the height of an elliptical cylinder. The proposed channel model targets fast moving vehicles on the highways in an umbrella-cell of cellular communication networks. We assume that both ends of the communication link are equipped with multiple antenna arrays, where, mobile-station antenna height is lower than base-station antenna. Utilizing the proposed MIMO communication channel model, we obtain closed-form expressions for the space–time correlation function among the MIMO antenna elements. The obtained theoretical expressions are plotted and analyzed for different values of channel parameters. Finally, we compare the proposed model with the existing models in the literature and prove that our model can be deduced to the existing two-dimensional and 3D channel models.     

Maintainability design and evaluation of mechanical systems based on tribology

Maintainability of mechanical systems based on tribology is suggested and evaluated in this paper. Tribo-features of mechanical systems, which characterise maintainability are identified and are modelled in terms of tribo-maintainability digraph. The nodes in the digraph represent the tribo-features and edges represent the degree of influence among the features. A matrix, one to one representation of the digraph, is defined to develop system maintainability expression (SPF-t) based on the tribology. It is also useful in comparing the various design alternatives from tribo-maintainability point of view. Maintainability is evaluated from the tribo-maintainability index, obtained from SPF-t (i.e. permanent of the matrix) by substituting the numerical values of the features and their interdependence. A higher value of the index implies better maintainability of the systems. The proposed methodology also guides designers in enhancing the maintainability of a system by appropriately incorporating tribo-features. An example to illustrate the methodology is also presented.     

Compact frequency reconfigurable triple band notched monopole antenna for ultrawideband applications

A compact ultra‐wideband (UWB) reconfigurable microstrip fed monopole antenna having size of 0.22 λ₀ × 0.28 λ₀ × 0.005 λ₀ with switchable frequency bands is presented. Triple band notched characteristics are achieved by inserting two stubs at top of radiator and one slot in between the radiator and microstrip feed line. Proposed antenna achieves reconfigurability with three PIN diodes at strategic positions to obtain eight different operational modes. In one of the operational modes, antenna operates in the entire UWB (3‐14 GHz) with fractional bandwidth of 127.5%. Two stubs are used to notch two frequency bands worldwide interoperability for microwave access (3.3‐3.6 GHz/WiMAX) and C‐band (3.7‐4.2 GHz). T‐shaped slot is also inserted to notch wireless local area network (5.725‐5.825 GHz/WLAN) frequency band. Proper biasing of PIN diodes is done by using suitable chip inductors and capacitors. Proposed antenna exhibits stable radiation patterns with average gain of around 3 dBi. Simulation and measurement results are in good agreement. Proposed antenna is suitable for on‐demand band rejection of parasitic bands coexisting in UWB.