Early detection of diseases in plant tissue using spectroscopy – applications and limitations

Plant diseases can greatly affect the total production of food and agricultural materials, which may lead to high amount of losses in terms of quality, quantity and also in economic sense. To reduce the losses due to plant diseases, early diseases detection either based on a visual inspection or laboratory tests are widely employed. However, these techniques are labor-intensive and time consuming. In a view to overcome the shortcoming of these conventional approaches, several researchers have developed non-invasive techniques. Recently, spectroscopy technique has become one of the most available non-invasive methods utilized in detecting plant diseases. However, most of the studies on the application of this novel technology are still in the experimental stages, and are carried out in isolation with no comprehensive information on the most suitable approach. This problem could affect the advancement and commercialization of spectroscopy technology in early plant disease detection. Here, we review the applications and limitations of spectroscopy techniques (visible/infrared, electrical impedance and fluorescence spectroscopy) in early detection of plant disease. Particular emphasis was given to different spectral level, challenges and future outlook.     

Iron in typical and atypical parkinsonism – Mössbauer spectroscopy and MRI studies

Iron may play important role in neurodegeneration. The results of comparative studies of human brain areas (control and pathological) performed by Mössbauer spectroscopy (MS) and magnetic resonance imaging (MRI) techniques are presented. Mössbauer spectroscopy demonstrated a higher concentration of iron in atypical parkinsonism (progressive supranuclear palsy PSP) in the brain areas Substantia Nigra (SN) and Globus Pallidus (GP) involved in this pathological process, compared to control, while the concentration of iron in pathological tissues in typical parkinsonism (Parkinson’s disease - PD) did not differ from that in control. These results were compared with the changes in 1/T1 and 1/T2 (T1 and T2 being the relaxation times determined by MRI). A good linear correlation curve was found between the concentration of iron as determined by MS in different areas of control human brains and between 1/T1 and 1/T2. Whereas the finding in PSP-GP (the brain area involved in PSP) also fitted to such a correlation, this was not so for the correlation between pathological SN – the brain area involved in both diseases – and 1/T2, indicating a dependence of T2 on other factors than just the concentration of iron.     

A predator–prey model with diseases in both prey and predator

In this paper, we present and analyze a predator–prey model, in which both predator and prey can be infected. Each of the predator and prey is divided into two categories, susceptible and infected. The epidemics cannot be transmitted between prey and predator by predation. The predation ability of susceptible predators is stronger than infected ones. Likewise, it is more difficult to catch a susceptible prey than an infected one. And the diseases cannot be hereditary in both of the predator and prey populations. Based on the assumptions above, we find that there are six equilibrium points in this model. Using the base reproduction number, we discuss the stability of the equilibrium points qualitatively. Then both of the local and global stabilities of the equilibrium points are analyzed quantitatively by mathematical methods. We provide numerical results to discuss some interesting biological cases that our model exhibits. Lastly, we discuss how the infectious rates affect the stability, and how the other parameters work in the five possible cases within this model.     

Case studies on the application of high-resolution electron channelling contrast imaging – investigation of defects and defect arrangements in metallic materials

In 1967, Coates discovered the electron channelling contrast of backscattered electrons (BSEs) in scanning electron microscopy, and by this the possibility to investigate arrangements of lattice defects in deformed microstructures of materials. Since that time, a straightforward development of the scanning electron microscopes as well as of the electron channelling contrast technique took place. Nowadays, the performance of scanning electron microscopes is high enough that the resolution of electron channelling contrast imaging (ECCI) micrographs is comparable with conventional bright field transmission electron microscopy (TEM) micrographs. In the first part of the present paper, a historical review on the development of the ECCI technique starting from its discovery more than 45 years ago up to the combination with other advanced methods of scanning electron microscopy like electron backscatter diffraction or high-resolution selected area channelling patterning in the last few years is given. Major important investigations using this technique for the visualization of individual lattice defects like stacking faults (SFs) and dislocations or dislocation arrangements are chronologically summarized. The second part demonstrates that nowadays, ECCI micrographs taken in high-resolution scanning electron microscopes can be called high-resolution ECCI (HR-ECCI). It is shown that the resolution of individual SFs and dislocations in the HR-ECCI micrographs is comparable to that of conventional TEM (about 15 nm defect image width). Furthermore, the paper is demonstrating that HR-ECCI micrographs can be obtained for various types of materials after different mechanical loadings and different grain sizes ranging from large grain size of 500 μm (cast steel) down to less than 2 μm (γ-TiAl).     

A new perspective on theρ-ω contribution to charge-symmetry violation in the nucleon-nucleon force

The role of- mixing as a mechanism for charge-symmetry violation in the nucleon-nucleon system is apparently well established. However, a common assumption in generating the charge-symmetry-violation potential is that the- mixing amplitude is constant (at the on-mass-shell value) even when the exchanged meson is far off-shell. We construct a simple quark model in which the mixing is generated by theu-d quark mass difference which allows us to test this assumption. It turns out to be surprisingly poor.Dedicated to Profs. Erich Schmid and Ivo laus on the occasion of their 60th birthdays     

Gravitational wave detection by laser interferometry – on earth and in space

The space project LISA is approved by ESA as a cornerstone mission in the field of ‘fundamental physics’, sharing its goal and principle of operation with the ground-based interferometers currently under construction: the detection and measurement of gravitational waves by laser interferometry. Ground and space detection differ in their frequency ranges, and thus the detectable sources. At low frequencies, ground-based detection is limited by seismic noise, and yet more fundamentally by ‘gravity gradient noise’, thus covering the range from a few Hz to a few kHz. On five sites worldwide, detectors of armlengths from 0.3 to 4 km are being built, two of them in Europe (GEO and VIRGO). They will progressively be put in operation between 2001 and 2003. Future improved versions are being planned, with data not until 2008, i.e. near the launch of the space project LISA. It is only in space that detection of signals below, say, 1 Hz is possible, opening a wide window to a different class of interesting sources of gravitational waves. The project LISA consists of three spacecraft in heliocentric orbits, forming a triangle of 5 million km sides.     

A piston-and-cylinder device for compressibility studies on polymers and other “soft” materials

Abstract

We describe an all-steel piston-and-cylinder device for pVT studies on “soft” materials, including liquids, in the range 100–450 K and 0–1.5 GPa. The internal diameter is 15 mm with sample lengths between 10 and 50 mm. Piston displacements are measured to within 0.1 μm using differential transformer transducers. Pressure is calculated from force per unit area and the deformation of pistons and cylinder under pressure are taken into account. The inaccuracy in ΔV/V is less than 0.5%. Experimental data are shown for indium and urea.     

Effect of Nanoparticles on Thermal Properties Enhancement in Different Oils – A Review

The development of stable dispersion of nanoparticles in different oils is gaining momentum for close circuit applications as most of the mineral oils used are not very good thermal conductors. The enhancement of thermal conductivity with optimum enhancement of viscosity of oil with nanoparticles poses a serious challenge for use of such fluids in cooling. Transformer oil, mineral oil, silicon oil, hydrocarbon fuels, biodiesel, and some organic solutions have been used as the base fluids for studying the effect of nanoparticles for improving thermal efficiency. Innovative heat transfer fluids are produced by suspending metallic or nonmetallic nanometer-sized solid particles. Although a large number of sources are available on water-based nanofluids, the number of such reports on oil-based nanofluids is rather limited. The aim of this article is to summarize recent developments on the preparation methods of nanofluids based on oil, its stability, thermal conductivity enhancement, nanoparticle effect on viscosity, heat transfer characteristics, breakdown voltage, dielectric properties, and applications of such nanofluids.     

Surface adsorption studies of benzyl bromide and bromobenzyl cyanide vapours on black phosphorene nanosheets – a first-principles perception

In this research, two-dimensional material, black-phosphorene nanosheets (Black-PNS) have been deployed as a sensing substrate for detecting two tear gas molecules, namely, benzyl bromide and bromobenzyl cyanide. The stability of black phosphorene sheet structure can be ensured by observing its formation energy, which is found to have ?3.895?eV/atom. Besides, the semiconducting nature of Black-PNS reinforces that it can be a potential base material to get deployed as a chemical sensor. The deviations in the density of states are noticed upon adsorption of benzyl bromide and bromobenzyl cyanide molecules on black phosphorene nanosheets. The energy of adsorption, energy gap variation and Bader charge transfer analysis are intended to investigate the assimilation properties of benzyl bromide and bromobenzyl cyanide on Black-PNS. The final results exhibit the possibility of using Black-PNS as a nanosensor substrate for lachrymator agents such as benzyl bromide and bromobenzyl cyanide.     

Microstructural studies on degradation of interface between LSM–YSZ cathode and YSZ electrolyte in SOFCs

The changes in the cathode/electrolyte interface microstructure have been studied on anode-supported technological solid oxide fuel cells (SOFCs) that were subjected to long-term (1500 h) testing at 750 °C under high electrical loading (a current density of 0.75 A/cm²). These cells exhibit different cathode degradation rates depending on, among others, the composition of the cathode gas, being significantly smaller in oxygen than in air. FE-SEM and high resolution analytical TEM were applied for characterization of the interface on a submicron- and nano-scale. The interface degradation has been identified as the loss of LSM coverage and the loss of three-phase-boundary (TPB) length. Firstly, the degradation is caused by the size reduction of the individual LSM/YSZ electrolyte contact points (areas) that are initially of 100–200 nm in diameter. Quantitative microstructure evaluation shows that in the cell tested in air this mechanism contributes to an estimated overall reduction in the LSM coverage and the TPB length by 50 and 30%, respectively. For the cell tested in oxygen the corresponding values are 10 and 4%. Secondly, in the cell tested in air the LSM coverage and the TPB length appear to decrease further due to the more pronounced formation of insulating zirconate phases that are present locally and preferably in LSM/YSZ electrolyte contact areas. The effects of the cathode gas on the interface degradation are discussed considering the change of oxygen activity at the interface, possible changes in the Mn diffusion pattern as well as the LSM/YSZ reactivity. Finally, based on thermodynamic calculations a T–p(O₂) diagram predicting the safe and risky operation conditions in terms of the zirconate formation is presented and compared with the experimental observations.     

A Study on the Correlation Between Poles and Cuts in ππ Scattering

In this paper we propose a dispersive method to describe two-body scattering with unitarity imposed. This approach is applied to elastic ππ scattering. The amplitudes keep single-channel unitarity and describe the experimental data well, and the low-energy amplitudes are consistent with that of chiral perturbation theory. The pole locations of the σ, f0(980), ρ(770) and f2(1270) and their couplings to ππ are obtained. A virtual state appearing in the isospin-two S-wave is confirmed. The correlations between the left(and right) hand cut and the poles are discussed. Our results show that the poles are more sensitive to the right hand cut rather than the left hand cut. The proposed method could be used to study other two-body scattering processes.     

Impact of process parameters in the generation of novel aspirin nanoemulsions – Comparative studies between ultrasound cavitation and microfluidizer

In the present investigation, the operating efficiency of a bench-top air-driven microfluidizer has been compared to that of a bench-top high power ultrasound horn in the production of pharmaceutical grade nanoemulsions using aspirin as a model drug. The influence of important process variables as well as the pre-homogenization and drug loading on the resultant mean droplet diameter and size distribution of emulsion droplets was studied in an oil-in-water nanoemulsion incorporated with a model drug aspirin. Results obtained show that both the emulsification methods were capable of producing very fine nanoemulsions containing aspirin with the minimum droplet size ranging from 150 to 170 nm. In case of using the microfluidizer, it has been observed that the size of the emulsion droplets obtained was almost independent of the applied microfluidization pressure (200–600 bar) and the number of passes (up to 10 passes) while the pre-homogenization and drug loading had a marginal effect in increasing the droplet size. Whereas, in the case of ultrasound emulsification, the droplet size was generally decreased with an increase in sonication amplitude (50–70%) and period of sonication but the resultant emulsion was found to be dependent on the pre-homogenization and drug loading. The STEM microscopic observations illustrated that the optimized formulations obtained using ultrasound cavitation technique are comparable to microfluidized emulsions. These comparative results demonstrated that ultrasound cavitation is a relatively energy-efficient yet promising method of pharmaceutical nanoemulsions as compared to microfluidizer although the means used to generate the nanoemulsions are different.     

A study on the role of nickel chloride in bisthiourea magnesium chloride – Linear semiorganic crystal

Single crystals of bisthiourea magnesium chloride (BTMGC) mixed with nickel chloride were grown by slow evaporation solution growth technique using water as solvent in a constant temperature bath designed by the authors. The lattice parameters of the grown crystals are measured from X-ray diffraction studies. Infrared spectra were recorded to determine the symmetries of the molecular structure. The observed infrared bands were also assigned and discussed. The optical transmission spectral study was carried out to test the transmitting ability of these crystals in the visible range. The second harmonic generation test of BTMGC revealed that the linear nature of the pure BTMGC crystal gets transformed into non-linear nature when mixed with nickel chloride. The TGA/DTA curves recorded for the investigated crystals depict small changes upon mixing.     

Spatiotemporal self-organization in the oscillatory HCOOH oxidation on a Pt ribbon electrode – Theory and experiments

Since the current density near the edges of ribbon and disk electrodes is enhanced, the resulting stationary and non-stationary double layer potential is generally inhomogeneous in all electrochemical reactions. We investigate the impact of this edge effect induced spatial inhomogeneity on the pattern formation of the oscillatory formic acid oxidation on thin Pt ribbon electrodes. In order to be able to theoretically describe the spatiotemporal behavior of the double layer potential distribution, we derive and discuss the properties of the electrochemical ribbon coupling function for various distances of the reference electrode. The resulting reaction–migration equation is analyzed in connection with a chemical model accounting for the specific reaction mechanism of the formic acid oxidation. The interaction of structural inhomogeneity, chemically induced temporal instability and nonlocal spatial coupling due to ion migration gives rise to novel types of spatiotemporal behavior. The results compare favorably with experiments conducted so far, which are presented as well and can be explained within the framework of reaction–migration equations.     

Optical spectroscopy studies on FeTelxSex and AxFe2uSe2 （A = K, Rb, Cs）： A brief overview

In this short overview, we summarize the optical spectroscopy FeTezxSex and AxFe2-ySe2. We elaborate that optical spectroscopy band structure evolution across the AFM phase transition temperature, studies on iron selenide superconducting systems measurements yield fruitful information about the the electronic correlation effect, the superconduct- ing pairing energy gap, the condensed carrier density or penetration depth, the inhomogeneity and the nanoscale phase separation between superconductivity and antiferromagnetism in those systems.     

Photophysical and light scattering studies on the aggregation behaviour of Triton X-100 in formamide—water mixed solvents

Micelle formation and structure of the non-ionic surfactant p-tert-octyl-phenoxy (9.5) polyethylene ether (Triton X-100) in mixed solvents consisting of water and formamide have been investigated. Changes in the critical micelle concentration of the surfactant upon the addition of formamide were examined by using the pyrene 1:3 ratio method. The observed increase in the critical micelle concentration was attributed to a rise in the solubility of the surfactant as the formamide content increased in the solvent system. Micelle structure parameters were obtained as a function of the co-solvent concentration by using combined static and dynamic light scattering measurements. It was found that the decrease in the micelle size, produced by the addition of formamide, is mainly due to a reduction in the mean aggregation number rather than to changes in the magnitude of the whole solvation of micelles. This fact was also supported by the observed trend in the partial specific volume of the TX-100 micelles, obtained by complementary density measurements. However, the postulated changes in the composition of the solvation layer of micelles were supported by the rise in both the surface area per head group and the cloud point of the surfactant. From the photophysical response of different fluorescent probes incorporated in the micellar phase, we obtained information on the changes in the microstructure of Triton X-100 micelles upon the addition of formamide. The pyrene 1:3 ratio index revealed an increasing micropolarity as the formamide content increases in the solvent system. On the other hand, studies based on both fluorescence polarization of coumarin 6 and intermolecular pyrene excimer formation have shown that the microviscosity of Triton X-100 decreases with the presence of co-solvent. These results were interpreted on the basis of considerable contact of the co-solvent with the inner region of the micelles.     

A review on iron chelators as potential therapeutic agents for the treatment of Alzheimer’s and Parkinson’s diseases

Iron plays a vital role in several cellular functions due to its unique physiochemical properties. Iron concentration increases in the brain with age due to multiple factors. Excessive amount of iron can lead to formation of reactive oxygen species. Neurodegenerative disorders are characterized by iron supplemented increase in oxidative stress and cellular damage. There is an urgent need of novel therapies which should not only provide symptomatic relief but also be able to modulate iron accumulation in the brain. Therefore, the development of novel iron chelators as neuroprotective agents for the treatment of neurodegeneration is an emerging trend. Several iron chelators including 8-hydroxyquinoline derivatives, dopaminergic agonists and natural products are under preclinical and clinical investigations for the treatment of neurodegenerative disorders.

     

Optical switching in a Ξ system: A comparative study on DROP and EIT

Liquid Lennard-Jones clusters with magic number of atoms N = 55, 147, 309, 561 and 923 were cooled down in Monte Carlo simulations until freezing. Structural properties of the clusters, including the radial dependence of atomic concentration/density and the local regular structure in arrangement of atoms, just before freezing were analysed. Existence of spherical layers in atomic density around the centre of mass of liquid LJ clusters was confirmed. Formation of layers is explained by central net forces acting on every cluster atom and leading to positioning an atom close to the cluster centre of mass. The strong layering in small clusters of N = 55 and 147 affects atomic diffusion in radial and tangential directions inside the cluster, leading to easier movement of atoms on the layer surface. Analysis of radial profiles of four types of structural units detected in liquid clusters reveals that icosahedral units are the most numerous and are located mainly near cluster surface of all clusters and also in the centre of small clusters.