Environmental Stress and Plants

Land plants are constantly subjected to multiple unfavorable or even adverse environmental conditions. Among them, abiotic stresses (such as salt, drought, heat, cold, heavy metals, ozone, UV radiation, and nutrient deficiencies) have detrimental effects on plant growth and productivity and are increasingly important considering the direct or indirect effects of climate change. Plants respond in many ways to abiotic stresses, from gene expression to physiology, from plant architecture to primary, and secondary metabolism. These complex changes allow plants to tolerate and/or adapt to adverse conditions. The complexity of plant response can be further influenced by the duration and intensity of stress, the plant genotype, the combination of different stresses, the exposed tissue and cell type, and the developmental stage at which plants perceive the stress. It is therefore important to understand more about how plants perceive stress conditions and how they respond and adapt (both in natural and anthropogenic environments). These concepts were the basis of the Special Issue that International Journal of Molecular Sciences expressly addressed to the relationship between environmental stresses and plants and that resulted in the publication of 5 reviews and 38 original research articles. The large participation of several authors and the good number of contributions testifies to the considerable interest that the topic currently receives in the plant science community, especially in the light of the foreseeable climate changes. Here, we briefly summarize the contributions included in the Special Issue, both original articles categorized by stress type and reviews that discuss more comprehensive responses to various stresses.     

The growth of (InGa)As quantum wells on GaAs(111)A, (211)A and (311)A substrates

The ability to grow high quality (InGa)As on the (111)A surface is essential for the production of a wide range of optoelectronic devices, but the topic has so far received little attention. What work there has been shows it to be highly problematic, reflected in the very broad photoluminescence (PL) peaks observed for GaAs:(InGa)As multiple quantum well structures. The origin of this broadening is unclear but is certainly related to the difficulty in choosing appropriate conditions for the growth of III-Vs on the (111)A surface. We have undertaken a study of the growth of (InGa)As on the GaAs(111)A, (211)A and (311)A surfaces with the goal of achieving high quality quantum well structures, the test being the ability to obtain narrow PL line widths. We have demonstrated that 80 Å 15% InGaAs(111)A single quantum wells with 12K PL peak widths of less than 8 meV can be obtained by growth at 400°C under a V:III ratio of 5:1.     

Fabrication and current-drive of SiGe/Si 'Micro-origami' epitaxial MEMS device on SOI substrate

A micromirror structure with SiGe/Si heteroepitaxial layer on a silicon-on-insulator (SOI) substrate using a 'Micro-origami' technique has been successfully fabricated. The micromirror is supported by two curved hinge structures. The device is driven by application of a current, and net angular displacements larger than 10/spl deg/ (static) and 30/spl deg/ (in resonance) were obtained. These values are comparable with or even larger than the reported values for other MEMS optical switches or beam scanning devices. The experimental results suggest that the movement is evoked by a thermal effect. The Micro-origami device has advantages of low operation voltage smaller than 2 V, and structural compatibility with the Si or SiGe LSIs.     

The past, present, and the future of underwater acoustic signalprocessing

This is a collection of articles written by members of the Underwater Acoustic Signal Processing (UASP) Technical Committee. The first article, by D. W. Tufts, deals with the history of UASP prior to 1980. In this period, initial mathematical models were developed and the first experimental investigations of underwater acoustic propagation were performed. It was also recognized during this time that there are many similarities between radar and sonar signal processing. The article by J.P. Ianniello deals with research in passive and active sonar from 1980 to the present. Work in this period included experimental verification of algorithms that had been developed in the 1960s and 1970s (e.g. for adaptive beamforming), as well as the development of new approaches, which include acoustic propagation modeling in the design of signal processing algorithms. Such processing is referred to as matched field processing. A common task in passive sonar systems is to estimate the difference in times at which different sensors receive the same signal. Time-delay estimation is a first stage that feeds into subsequent processing blocks. I. Lourtie provides a concise review of work in this field. The article by J.C. Preisig deals with underwater acoustic communications. The underwater channel has several features that make reliable communication a challenging problem. Nevertheless, progress is being made by combining results from ocean acoustic modeling, communication theory, and signal processing. The final article, by J.M.F. Moura, deals with the future of signal processing in the ocean. In addition to considering advances in detection and localization, he deals with new applications such as acoustic tomography, physical oceanography, and synthetic aperture sonar     

Supermodularity and subadditivity properties of the entropy on themajorization lattice

We prove that the entropy is a supermodular and subadditive function on the lattice of all n-dimensional probability distributions, ordered according to the partial order relation defined by majorization among vectors     

Exploiting spatial correlation features for SAR image analysis

Spatial information is of great importance in Synthetic Aperture Radar (SAR) image analysis and recently, many methods have been developed that take this feature into account. This paper deals with a supervised approach to SAR image classification that exploits spatial features within a hierarchical classification framework. In contrast to the classical approach, which makes the hypothesis about sample data independence, in the proposed method, the spatial dependence of neighboring pixels is taken into account to estimate relatively simple statistical features such as sample spatial mean and sample spatial variance, thus allowing contextual information to be easily handled. The Bhattacharyya distribution distance is used during the training phase, and the generated tree is applied during the test phase. After this, both phases are based on the proposed features. As a result, second-order statistics play a major role in the present classification problem. Experimental results on different SAR data sets are reported. It is shown that the accuracy of the proposed method is better than that of the hit classifier and that the new method is also computationally more convenient     

Bounding the average length of optimal source codes via majorization theory

We consider the problem of bounding the average length of an optimal (Huffman) source code when only limited knowledge of the source symbol probability distribution is available. For instance, we provide tight upper and lower bounds on the average length of optimal source codes when only the largest or the smallest source symbol probability is known. Our results rely on basic results of majorization theory and on the Schur concavity of the minimum average length of variable-length source codes for discrete memoryless sources. In the way to prove our main result we also give closed formula expressions for the average length of Huffman codes for several classes of probability distributions.     

Unconventional method used in synthesis of polyphosphoesters

Polyphosphonates, polyphosphates, polyarylazophosphonates and polyarylazophosphates were synthesized by a new alternative to the classical phase transfer catalysis, respectively, the modified inverse phase transfer catalysis (IPTC) polycondensation of various phenylphosphonic (phosphoric) dichlorides (phenylphosphonic dichloride, phenylphosphoric dichloride, p-chlorophenylphosphoric dichloride) with bisphenols: bisphenol A, tetrabromobisphenol A, bis-(4-hydroxyphenyl)methane (bisphenol F), 4,4′-dihydroxyazobenzene. The polymers were characterized by infrared spectroscopy and magnetic resonance (¹H-NMR, ³¹P-NMR, ¹³C-NMR) spectroscopy. Yields in the range of 63.5–85% and molecular weights (M _w) of ~2,000–8,200 g mol^?1 were obtained. Polyphosphonates were stable up 210–270 °C and polyphosphates up 190–220 °C in air atmosphere. For a correct estimation of the thermal behavior of similar compounds, a kinetic analysis using a modified version of Non Parametric Kinetic method for representative polyphosphonate and polyphosphate was realized. The studies made on the hydrolytic degradation of the synthesized polyphosphates show that the most stable polymer under alkali-catalyzed degradation is the polyphosphate obtained by IPTC of phenylphosphoric dichloride and bisphenol A.     

MicroRNA Cross-Involvement in Acne Vulgaris and Hidradenitis Suppurativa: A Literature Review

Acne Vulgaris (AV) and Hidradenitis suppurativa (HS) are common chronic inflammatory skin conditions that affect the follicular units that often coexist or are involved in differential diagnoses. Inflammation in both these diseases may result from shared pathways, which may partially explain their frequent coexistence. MicroRNAs (miRNAs) are a class of endogenous, short, non-protein coding, gene-silencing or promoting RNAs that may promote various inflammatory diseases. This narrative review investigates the current knowledge regarding miRNAs and their link to AV and HS. The aim is to examine the role of these molecules in the pathogenesis of AV and HS and to identify possible common miRNAs that could explain the similar characteristics of these two diseases. Five miRNA (miR-155 miR-223-, miR-21, and miRNA-146a) levels were found to be altered in both HS and AV. These miRNAs are related to pathogenetic aspects common to both pathologies, such as the regulation of the innate immune response, regulation of the Th1/Th17 axis, and fibrosis processes that induce scar formation. This review provides a starting point for further studies aimed at investigating the role of miRNAs in AV and HS for their possible use as diagnostic-therapeutic targets.     

Adjusting Some Properties of Poly(methacrylic acid) (Nano)Composite Hydrogels by Means of Silicon-Containing Inorganic Fillers

The present work aims to show how the main properties of poly(methacrylic acid) (PMAA) hydrogels can be engineered by means of several silicon-based fillers (Laponite XLS/XLG, montmorillonite (Mt), pyrogenic silica (PS)) employed at 10 wt% concentration based on MAA. Various techniques (FT-IR, XRD, TGA, SEM, TEM, DLS, rheological measurements, UV-VIS) were used to comparatively study the effect of these fillers, in correlation with their characteristics, upon the structure and swelling, viscoelastic, and water decontamination properties of (nano)composite hydrogels. The experiments demonstrated that the nanocomposite hydrogel morphology was dictated by the way the filler particles dispersed in water. The equilibrium swelling degree (SDe) depended on both the pH of the environment and the filler nature. At pH 1.2, a slight crosslinking effect of the fillers was evidenced, increasing in the order Mt < Laponite < PS. At pH > pKa_MAA (pH 5.4; 7.4; 9.5), the Laponite/Mt-containing hydrogels displayed a higher SDe as compared to the neat one, while at pH 7.4/9.5 the PS-filled hydrogels surprisingly displayed the highest SDe. Rheological measurements on as-prepared hydrogels showed that the filler addition improved the mechanical properties. After equilibrium swelling at pH 5.4, G’ and G” depended on the filler, the Laponite-reinforced hydrogels proving to be the strongest. The (nano)composite hydrogels synthesized displayed filler-dependent absorption properties of two cationic dyes used as model water pollutants, Laponite XLS-reinforced hydrogel demonstrating both the highest absorption rate and absorption capacity. Besides wastewater purification, the (nano)composite hydrogels described here may also find applications in the pharmaceutical field as devices for the controlled release of drugs.