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The effects of foliar application of sodium nitroprusside (SNP), magnesium sulfate (MgSO4) and magnesium oxide nanoparticles (MgO-NPs) on the growth, physiology, and gas exchange parameters of two varieties of spinach (Spinacia oleracea L.) under cadmium (Cd) stress were examined. The experiment was arranged in a completely randomized design with 72 pots. Two varieties of S. oleracea (Desi Palak & Lahori Palak) were used. Two concentrations of Cd (0 µM and 150 µM) in the form of cadmium chloride (CdCl2) were used. Two levels of SNP (0 ppm and 100 ppm) and two levels for each form of Mg i.e. MgSO4 and MgO-NPs (0 and 200 ppm) were foliar sprayed on plants in control and Cd stress. Both varieties behaved similarly under Cd stress and caused reductions in growth, physiology, gas exchange, water content parameters and inorganic ion uptake. However, the biochemical parameters like relative membrane permeability (RMP), malondialdehyde (MDA), and hydrogen peroxide (H2O2) contents were increased. However, all foliar spray treatments increased growth, physiological and gas exchange parameters, water content and inorganic ion uptake. However, this reduced the MDA, RMP, and H2O2 contents. Desi Palak showed the more positive results under foliar application of MgO-NPs. However, Lahori palak showed more positive results under the SNP + MgO-NP treatment. It is concluded that foliar application of SNP, MgSO4 and MgO-NPs could be an innovative approach to alleviated the heavy metals (Cd) toxicity in crop plants. [ABSTRACT FROM AUTHOR]

This study investigates the synthesis and characterization of a novel chitosan–blue-green algae (BGA) composite adsorbent for the efficient removal of Acid Red 73 (AR73) dye from wastewater. The composite was characterized using Fourier transform infrared, zeta potential, an energy-dispersive X-ray analysis, and scanning electron microscopy analyses, revealing the presence of functional groups crucial for dye adsorption and a rough surface morphology indicative of high surface area. Batch adsorption experiments were conducted to evaluate the influence of pH, adsorbent dosage, contact time, and initial dye concentration on AR73 removal. The composite exhibited optimal adsorption at pH 6, with increasing removal efficiency observed with increasing adsorbent dosage and contact time until equilibrium was reached. The adsorption process followed pseudo-second-order kinetics, suggesting chemisorption as the dominant mechanism. In addition, the Freundlich isotherm model best described the adsorption process, suggesting a heterogeneous adsorption mechanism. The composite demonstrated good adsorption capacity (Qm = 142.86 mg/g) in the Langmuir model. The thermodynamic data strongly indicate that the removal process occurs through a physisorption process, and endothermic. Furthermore, the composite demonstrated photocatalytic activity under direct sunlight, effectively degrading AR73 dye and achieving complete removal at higher initial concentrations. The reusability of the composite was also investigated, showing sustained removal efficiency over two cycles, but a significant decrease in the third cycle. Finally, the application of the composite in treating aquaculture wastewater resulted in significant improvements in water quality parameters, including reduced turbidity, nitrate levels, and salinity. This study highlights the potential of the chitosan–BGA composite as a sustainable and efficient adsorbent and photocatalyst for dye removal and wastewater treatment. [ABSTRACT FROM AUTHOR]

Modern large-scale gas turbines are equipped with high-pressure ratio compressors to increase engine work and its overall efficiency. Flow separation and energy losses are also two interrelated phenomenon associated with changes in compressor loading level and performance. This paper examines therefore the control of flow separation using a passive-control technique. An arced divergent-convergent slot grooved from the blade pressure side to its suction side was adopted to control flow separation, reducing the losses through a linear compressor cascade. The spanwise location of the slot was selected based on CFD simulations where the corner separation was predicted. The slot height in the spanwise direction was selected to be 8% of the blade height at the end-wall side. The present work was performed experimentally and numerically at an inlet Reynolds number, R ec = ρ V ∞ C / μ = 2.98 × 10 5 , covering a wide range of incidence angles from + 6 ∘ to - 6 ∘ . The experimental work was carried out using a linear cascade test section consisting of six NACA 65-009 blade profiles integrated into a low-speed wind tunnel. A five-hole pressure probe system was used to obtain main flow parameters. Numerically, four turbulence models, including Spalart–Allmaras (S–A) model, Realizable (R k-ε) model, Shear-Stress Transport (SST k-ω) model, and Reynolds Stress model (RSM) were tested to predict the velocity and pressure fields. Good agreement between the experimental measurements and the numerical results, which were obtained using the RSM turbulence model in terms of velocity profiles and total pressure downstream of blades. It was observed also that the use of the arced-slotted blades for positive incident angles was more effective in reducing the separation than the negative and zero incident angles, approaching a maximum value of 33% for 6° with enhanced blade loading reaching 17.6%. It is to be concluded that, the use of arced slotted blade improves the compressor performance specially for positive incident angles.Article Highlights: Compressor aerodynamic losses were reduced by groove arced diverged-converged slot. Numerical solution based on four turbulence models was proved experimentally. Results using Reynolds Stress turbulence Model were closest to experimental results. Slotted blades reduced losses by 33% for incident + 6° and improved loading by 17.6%. [ABSTRACT FROM AUTHOR]

Structural, electronic, optical, thermoelectric ,and elastic properties of Mo- and W-based group-V compounds, TMX (TM = Mo and W; X = N, P, and As) have been studied by using the full-potential linear augmented plane wave method. Local spin density approximation (LSDA) has been used for exchange–correlation potentials. Pressure-dependent lattice constants and bulk moduli have been obtained using LSDA. Volume optimization, with and without spin-polarization, reveal that the WC-type hexagonal phase (MoN, MoP, and WN) and MoAs and WP in MnP-type orthorhombic phase are energetically stable in a non-magnetic phase. The electronic properties show that all these materials are metallic in nature, while the optical properties showed high reflectivity and low transmission. The thermoelectric properties have also been elaborated, and, as these materials have zero band gap values, they showed high thermal conductivity at high temperatures with low Seebeck and almost constant electrical conductivity. Moreover, the elastic properties of these two phases are surprising with their high bulk and shear moduli. All the materials fall in the category of super-hard materials with ductile and brittle characteristics. [ABSTRACT FROM AUTHOR]

Despite Saudi Arabia being an interesting area from a floristic perspective, its vegetation is still relatively poorly studied. This certainly applies to the Hijaz Mountains and adjacent coastal zones. We aim to describe the flora and vegetation of the foothills of the Hijaz Mountains regarding the environmental conditions. Hijaz Mountains and adjacent coastal zones, Saudi Arabia. We studied the vegetation at the Hijaz Mountains' foothills along two transects of vegetation surveys, one along the coast and one more inland. In addition, soil samples were taken and analyzed for soil texture, pH, electrical conductivity, organic matter, calcium carbonate and the concentration of the elements N, Na, K, Ca, Mg, Fe and Mn were determined. We calculated the data clustering tendency (Hopkins' test analysis) and its optimal number of clusters (Elbow method). We used modified TWINSPAN to cluster the data and validated the resulting communities using the Silhouette algorithm. Seven plant communities resulted, each one dominated by a different plant species, namely: Haloxylon salicornicum, Lycium shawii, Senegalia hamulosa, Vachellia tortilis, Zygophyllum coccineum, Vachellia flavaand Stipagrostis plumosa, and were described based on their floristic composition and could be further grouped into three vegetation clusters. The communities had varying ranges of occurrence in the study area, some dominating certain sections, with latitude and altitude being the biggest distinguishing environmental variables between the communities. We present a description of the vegetation of the Hijaz Mountains foothills. Our study is considered an important basis for decision-making of nature conservation and in-depth surveys of the area. [ABSTRACT FROM AUTHOR]

The global agricultural productivity has been significantly impaired due to the extensive use of heavy metal. Cadmium (Cd) is now recognized as a significant soil and environmental contaminant that is primarily spread by human activity. This study investigates the possible impact of melatonin (ME) in mitigating the toxicity caused by Cd in pepper (Capsicum annuum L.) seedlings. There were three groups of plants used in the experiment: control (CK) plants, Cd-stressed plants and ME-pretreated + Cd-stressed plants. The concentration of ME and Cd was 1 µM and 0.1 mM, respectively, and applied as root application. The results described that Cd treatment remarkably reduced growth parameters, impaired pigment concentration, hindered gas exchange traits. In contrast, ME supplementation significantly recovered these parameters by increase in growth and biomass production of pepper seedlings under Cd toxicity. In addition, ME application considerably increased osmolyte production and protein level in pepper leaves and roots. Furthermore, ME positively upregulated the antioxidant enzymes activity and effectively decreased the oxidative damage in pepper leaves and roots. The enhanced antioxidant enzymes activity performed a significant role in the reduction of H2O2 and MDA concentration in plants under Cd stress. The findings indicated that the application of ME to plants effectively alleviates the stress caused by Cd exposure. Moreover, ME demonstrates significant efficacy in mitigating the adverse impacts of Cd on pepper plants. [ABSTRACT FROM AUTHOR]

Our goal in this paper is to obtain the analytic solutions for stochastic fourth-order (2+1)-dimensional nonlinear Schrödinger equation (NLSE) with higher order odd and even terms. Our Study mainly depends on applying the improved modified extended tanh function method (IMETFM) to get the soliton wave solutions and other exact wave solutions of our model of interest. These solutions such as (bright, dark, singular) solitons, hyperbolic solutions, periodic solutions, singular periodic solutions, rational solutions, Jacobi elliptic functions solutions and Weierstrass elliptic functions solutions. Graphical representations of some of the extracted solutions using different noise intensities are shown to demonstrate the influence of the noise. [ABSTRACT FROM AUTHOR]

Aims: The accretion of Cr in soils is pervasive and toxic to plants. Recently, plant-growth-promoting rhizobacteria and earthworms have attracted attention in relieving metal toxicity in plants. The aim of the current study was to assess the effect of earthworms (Eisenia fetida) and PGPR (Pseudomonas aeruginosa and Burkholderia gladioli) on the morphological and biochemical parameters of Brassica juncea plants under Cr stress. Methods: Plants were grown with or without supplementation of PGPR and earthworms in Cr-treated soils under natural conditions. Different morphological and biochemical parameters were studied during the vegetative and reproductive phases of growth. Results: Cr treatment inhibited root and shoot length, photosynthetic pigments and gaseous exchange attributes, whereas the content of osmoprotectants and phenolic compounds was high in plants raised under Cr stress. Root length was increased by 118.3% and 83.6% in 40- and 70-day-old plants, respectively, with combined treatment of EM1M2. The chlorophyll content was enhanced by 73.8% in 40-day-old plants and 55.6% in 70-day-old plants. The carotenoid content was enhanced by 122.6% and 71.7% in 40-day-old and 70-day-old plants, respectively. The level of total phenols was increased by 40% at 40 days and 26.4% in 70-day-old plants with the EM1M2 treatment. The contents of total carbohydrates, trehalose, total amino acids and proline were also increased as a result of combined treatment of PGPR and earthworms (EM1M2). Conclusions: The outcomes of the current study demonstrated that PGPR and earthworms helped to ameliorate the toxic effects of Cr on plants by enhancing growth, and various metabolites in plants. [ABSTRACT FROM AUTHOR]

This correction notice is for an article titled "Effect of temperature on the biological parameters of pink bollworm, Pectinophora gossypiella Saunders (Lepidoptera: Gelechiidae)" published in Scientific Reports. The correction addresses an incorrect affiliation for one of the authors, Mohamed A. El-Sheikh. The correct affiliation is listed as the Department of Botany and Microbiology, College of Sciences, King Saud University, Riyadh, Saudi Arabia. The original article has been corrected. The authors of the article are Madhu Tadagavadi Nagaraju, Kamanur Murali Mohan, Manikyanahalli Chandrashekara Keerthi, Tenguri Prabhulinga, Shivaji Thube, Vivek Shah, Hosam O. Elansary, Ihab Mohamed Mousa, and Mohamed A. El-Sheikh. [Extracted from the article]

Recently, the use of microalgal bioproducts in aquaculture research has gotten consideration. The current study aims to screen the biochemical components of three microalgae: Nannochloropsis salina, Chlorella salina and Tetraselmis chuii for using in the feeding of Cyclops abyssorum divergens copepods that are suitable prey for the mouth gape of the cultured fish larvae. The effect of different initial densities of these algal cells used for copepods feeding was determined by estimation of proximate composition, polyunsaturated fatty acids (PUFAs), amino acids (AAs) and enzyme activities of copepods. N. salina showed high protein and lipid contents, while C. salina presented high carbohydrate content. C. salina and T. chuii presented high PUFAs, with proportions of 22.35 and 22.67%, respectively, and are considered as the source of n-3 fatty acids. Also, they had higher concentrations of total AAs (21.46 and 24.14 mg. g−1 dry wt., respectively). The experiment study showed that the C. salina diet at an initial concentration of 1 × 106 cells ml−1 resulted in a maximum increase of copepods population density (503.3%) and high protease and trypsin activities (42.65 and 31.80 U. mg−1 protein, respectively) in copepods. T. chuii diet at an initial concentration of 1 × 106 cells ml−1 resulted in a maximum protein, lipid, PUFAs and AAs contents of copepods. Therefore, C. abyssorum divergens copepods after 18 days feeding with an initial concentration of 1 × 106C. salina or T. chuii cells ml−1 are the suitable candidate diets in larviculture because they achieved higher productivity and attained better nutritional composition of the copepods. [ABSTRACT FROM AUTHOR]

Untreated wastewater contains toxic amounts of heavy metals such as chromium (Cr), which poses a serious threat to the growth and physiology of plants when used in irrigation. Though, Cr is among the most widespread toxic trace elements found in agricultural soils due to various anthropogenic activities. To explore the interactive effects of micronutrients with amino acid chelators [iron-lysine (Fe-lys) and zinc-lysine (Zn-lys)], pot experiments were conducted in a controlled environment, using spinach (Spinacia oleracea L.) plant irrigated with tannery wastewater. S. oleracea was treated without Fe and Zn-lys (0 mg/L Zn-lys and 0 mg/L Fe-lys) and also treated with various combinations of (interactive application) Fe and Zn-lys (10 mg/L Zn-lys and 5 mg/L Fe-lys), when cultivated at different levels [0 (control) 33, 66 and 100%) of tannery wastewater in the soil having a toxic level of Cr in it. According to the results, we have found that, high concentration of Cr in the soil significantly (P < 0.05) reduced plant height, fresh biomass of roots and leaves, dry biomass of roots and leaves, root length, number of leaves, leaf area, total chlorophyll contents, carotenoid contents, transpiration rate (E), stomatal conductance (gs), net photosynthesis (PN), and water use efficiency (WUE) and the contents of Zn and Fe in the plant organs without foliar application of Zn and Fe-lys. Moreover, phytotoxicity of Cr increased malondialdehyde (MDA) contents in the plant organs (roots and leaves), which induced oxidative damage in S. oleracea manifested by the contents of hydrogen peroxide (H2O2) and membrane leakage. The negative effects of Cr toxicity could be overturned by Zn and Fe-lys application, which significantly (P < 0.05) increase plant growth, biomass, chlorophyll content, and gaseous exchange attributes by reducing oxidative stress (H2O2, MDA, EL) and increasing the activities of various antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD) catalase (CAT) and ascorbate peroxidase (APX). Furthermore, the supplementation of Zn and Fe-lys increased the contents of essential nutrients (Fe and Zn) and decreased the content of Cr in all plant parts compared to the plants cultivated in tannery wastewater without application of Fe-lys. Taken together, foliar supplementation of Zn and Fe-lys alleviates Cr toxicity in S. oleracea by increased morpho-physiological attributes of the plants, decreased Cr contents and increased micronutrients uptake by the soil, and can be an effective in heavy metal toxicity remedial approach for other crops. [ABSTRACT FROM AUTHOR]

The main objective of this article is to improve and complement some of the oscillation criteria published recently in the literature for third order differential equation of the form (r (t) (z ″ (t)) α) ′ + q (t) f (x (σ (t))) = 0 , t ≥ t 0 > 0 , where z (t) = x (t) + p (t) x (τ (t)) and α is a ratio of odd positive integers in the two cases ∫ t 0 ∞ r − 1 α (s) d s < ∞ and ∫ t 0 ∞ r − 1 α (s) d s = ∞ . Some illustrative examples are presented. [ABSTRACT FROM AUTHOR]

Heavy metal-polluted wetlands could be remediated by harvesting metal accumulating plants, i.e., using phytoextraction. We studied a macrophyte Phragmites australis and assessed its potential to be utilized in the phytoremediation of heavy metal-polluted wetlands, specifically in wadis in the Arabian Peninsula. We sampled six polluted wadi sites and measured Mn, Fe, Ni, Cu, Zn, Cd, and Pb concentrations in the roots, rhizomes, stems, and leaves of P. australis, as well as in sediment and water. We analyzed the correlations between different plant organs, water, and sediment, and calculated the accumulation and translocation of the metals to the plant organs. We found indications for the accumulation of Cd, Zn, and Pb into P. australis and somewhat contradictory indications for the accumulation of Cu. We suggest that P. australis is a good candidate to be utilized in the phytoremediation of heavy metal-polluted wadis in the Arabian Peninsula where the few wadis offer many valuable ecosystem services for urban citizens. [ABSTRACT FROM AUTHOR]

Objective: To compare serum levels of tumor necrosis factor alpha (TNF-α) between type 2 diabetes mellitus patients with and without peripheral neuropathy (PN). Also, to study the relation between peripheral nerves conduction velocity and serum level of TNF-α in those patients. Patients and methods: This study included three groups with 40 patients in each group. Diabetic PN patients (groups I and II) were compared with diabetic patients without PN (group III). Groups I and II differed in the duration of clinical neuropathy with less than 5 years in group I and more than 5 years in group II. All patients were subjected to general and neurological examination, neuropathy symptom score (NSS), neuropathy disability score (NDS), glycosylated hemoglobin (HbA1c), serum level of TNF-α and both sensory and motor nerve conduction study. Results: This study showed raised serum levels of TNF-α in diabetic patients with PN, more with increased duration of neuropathy. TNF-α levels showed statistically significant negative correlation with nerve conduction velocity but positive correlations with each of neuropathy disability score, neuropathy symptom score, and glycosylated hemoglobin. Conclusion: TNF-α might be involved in the pathogenesis of diabetic PN, and its serum level might be used as a biomarker for the severity of diabetic PN. [ABSTRACT FROM AUTHOR]

Kuwait lies at the Northwest corner of the Arabian Gulf, and its eastern coast comprises parallel arcs of nine islands. The present study dealt with vegetation ecology and species diversity analysis of six uninhabited islands, except Failaka, Warba, and Bubiyan islands, with varied sizes of area ranging from 0.5 to 863 km. A total of 70 species of flowering plants (60% annuals and 40% perennials), belonging to 32 families, were collected from the islands and their list is given. The main phytogeographical category was represented by Saharo-Arabian elements followed by the Irano-Turanian and Mediterranean elements. The vegetation type is essentially halophytic with widespread annuals. Six associations were identified with the application of TWINSPAN, DCA, and CCA programs. They were named after the characteristic species as follows: VG I: Polycarpon tetraphyllum, VG II: Zygophyllum qatarense, VG III: Emex spinosa, VG IV: Seidlitzia rosmarinus, VG V: Malva parviflora- Salsola imbricata, and VG VI: Suaeda aegyptiaca. These associations were compared with the plant communities of Kuwait and neighboring countries of Gulf region. The soil characteristic factors alkalinity, moisture, soil texture, and minerals showed the best correlation with the distribution of the associations. Significant differences between island area, species diversity indices, organic matter, and minerals contents of the islands were observed. Flora of these uninhabited islands with un-grazed plants constituted about 37% of the flora of the mainland of Kuwait and their valuable elements warrant prioritized conservation measures. [ABSTRACT FROM AUTHOR]

This study is aimed at collection of all available phytosociological data on vegetation of Sinai Peninsula, a region that is still poorly explored. An overview of the plant communities of Sinai is compiled based on additional field work and inventories. The database for Sinai vegetation will serve as a nucleus for the National Vegetation Databank of Egypt--'VegEgypt'. Aspects like species richness, species turnover, conservation categories, and endemism were given special attention. The database was set up and analysed using the Turboveg and Juice programs. A matrix of 816 relevés and 496 species belonging to 69 families and 281 genera formed the basis for further analysis. Asteraceae, Poaceae and Fabaceae were the most represented families. The lists contain 52 threatened, 16 endemic and 20 sub-endemic species. The percentage of endemic species is highest in insular floras, peninsulas and mountain chains. The vegetation analysis resulted in 21 associations. The plant associations on sand habitats have the lowest species richness and species turnover because of water scarcity. On the other hand, plant communities or associations inhabiting rocky habitats have the highest species richness and species turnover. [ABSTRACT FROM AUTHOR]

Thumamah Nature Park is located at about 100 km north of Arriyadh (Saudi Arabia), having an area of 170 km 2. The Park was established since 30 years ago. The aim of this study is to analyze the vegetation structure in relation to the environmental factors in different habitat types. The phenological activities around the year of the 20 dominant species were monitored. 119 species were identified, of which 51 (43 %) annuals and 68 (57 %) perennials after 30 years of exclusive human impact. The Saharo-Arabian component species were the highest among the monoregional species (64 %) in most life forms, while the Sahelien-Somali Masai attained the highest among the biregionals (46 %). The TWINSPAN, DCA and CCA analyses separated seven vegetation groups. The first two groups were dominated by psammophytic species, which occupy the lower sandy plain as shown in group I with Rhanterium epapposum– Rhazya stricta and group II with Pennisetum divisum– Haloxylon salicornicum. The escarpment habitat was characterized by three groups, viz., group III with Acacia gerrardii– Panicum turgidum, group IV with Panicum turgidum and group V with Acacia ehrenbergiana– Lasiurus scindicus. Vegetation in the upland plateau was represented by the remaining two groups; group VI with Helianthemum lippii and group VII with Helianthemum kahiricum. The environmental variables that affect the species distribution and diversity in the park include the altitude, soil texture, pH, EC, Ca, Mg and Mn. The increased plant species richness, turnover, evenness and cover were mostly due to the increase of the herbaceous species. Plant populations showed interspecific variations in their relative timing of phenological phases with reproductive activity period ranged between 3 and 6 months with unimodal flowering peak. Three flowering-fruiting activities were recorded during late winter–spring, summer and late autumn–early winter. In an attempt to explain the vegetation dynamics after 30 years conservation, the progressive succession varied among the different habitat types, including the lower sandy sites, the escarpment and the upland rocky habitats, which reflect the relationship between altitude, edaphic factors and the type of vegetation units in each habitat type after exclusion of the human impact. [ABSTRACT FROM AUTHOR]

Dowex-50W resins in the form of mono (mea)-, di (dea)-and tri-ethanolamine (tea)-Cu complexes have been used as potentially active catalysts for HO decomposition in an aqueous medium. The rate constant (per g of dry resin) was evaluated with resins containing 2,8 and 12% divinylbenzene (DVB) crosslinkage, over the temperature range 25-40°C. The reaction was first order with respect to [HO] with mea for 8 and 12% DVB (50-100 mesh), second order with mea for 2% DVB (50-100 and 200-400 mesh) and third order with dea and tea for 8% DVB (50-100 mesh). The value of the rate constant (per g of dry resin) of the mea-Cu/Co binary system was compared with that of the mea-Cu/Ni binary system. With a given degree of resin crosslinkage the activation energy increased in the sequence mea < dea < tea, which is the inverse sequence of the basic strength of the free amines. The activation parameters were calculated. Probable mechanisms were proposed for the reaction with the three ethanolamines. [ABSTRACT FROM AUTHOR]

The tetradentate Schiff-base ligand N, N-bis(salicylidene)- o-phenylenediamine (salph) is very strongly sorbed by cation exchange materials with transition metal counter ions, forming stable complexes. The kinetics of catalytic decomposition of HO in the presence of (salph)-Fe sorbed on Dowex-50W resin has been studied in aqueous medium. The reaction is first order with respect to [HO]. The rate constant, k (per g of dry resin) decreased with increasing degree of resin cross-linkage due to a salting out effect. The activation parameters were calculated and a reaction mechanism is proposed. [ABSTRACT FROM AUTHOR]

The slow decomposition of HO in the presence of Dowex-50 W resin in the form of an ethylenediaminecopper(II) complex ion in water is accompanied by an induction period. The reaction is first order with respect to [HO] and the rate constant (perg of dry resin) was deduced. Autocatalytic behaviour was found for the HO decomposition with 2% crosslinked divinylbenzene. The induction period disappeared and the reaction rate increased when the decomposition was carried out with a resin in the form of a peroxo-copper complex, which proves that the formation of an intermediate (active species) retards the reaction rate. The precursor of the active species, formed during the induction period, was not the amine-copper(II) complex ion but a product of the latter with HO. It proved impossible to carry out the decomposition in acid or buffer solutions, in which the resin is regenerated. [ABSTRACT FROM AUTHOR]

Dowex 50 W resin in the form of an ethylamine-Cu complex ion was used as potentially active catalyst for the decomposition of HO in aqueous medium. The stoichiometry of the amine-Cu complex on the resin, determined experimentally, was found to have the total [Cu]: [ethylamine]=1∶4 concentration ratio. The kinetics of the decomposition was studied and the calculated rate constant (per g of dry resin) was found to decrease with increase the degree of resin crosslinking. The active species, formed as an intermediate at the beginning of the reaction, had an inhibiting effect on the reaction rate. The brown peroxo-copper complex formed as a result of HO decomposition, was found to contain the catalytic active species. The order of the reaction increased with decreasing initial HO concentration, a sign of a step-wise mechanism. A quantitative treatment of the decomposition of HO was provided in terms of activation parameters. [ABSTRACT FROM AUTHOR]

The kinetics of the catalytic decomposition of hydrogen peroxide was studied in the presence of Dowex-50W resin in the form of some transition metal-ion ammine complexes in an aqueous medium. The transition metal-ions, Co, Ag, Cd and Zn were chosen in this study and the rate constants (per gram of dry resin) were evaluated at various resin weights in the 25-40°C range. A coloured compound (peroxo-metal complex), which formed at the beginning of the reaction in each case, was found to contain the catalytic active species. Probable mechanisms for the reactions are proposed. The activation energy and the change in the entropy of activation increased in the following sequence: [Ag(NH]]< [Cd(NH)]<[Co(NH)]<[Zn(NH)], which is also the probability sequence for the formation of the activated complex. [ABSTRACT FROM AUTHOR]

Background: The purpose of this in vitro study was to evaluate the effect of different angulations and collar lengths of the implant abutment on screw loosening by measuring removal torque value (RTV) before and after dynamic cyclic loading using digital torque gauge.Methods: A total 90 sets of 4.5 mm diameter × 10 mm length bone level implants with conical hybrid connection were used. They were divided equally according to abutment angulation, into three groups: GI 0° abutment, GII 15° abutment, and GIII 25°. Each group was divided into two subgroups, 15 each, according to collar height: subgroup A (2 mm) and subgroup B (4 mm). Each implant and abutment assembly was positioned vertically in the center of the acrylic resin block using stainless steel cylindrical split mold. Initial analysis was made by abutment screw tightened with 30 Ncm torque twice with 10-min intervals using a digital torque gauge. RTV before and after cyclic loading of the abutment screws were measured in newton centimeter using digital torque gauge. One hundred thousand cycles of eccentric dynamic cyclic loading, at 130 N at a rate of 1 Hz, were applied 5 mm away from the central axis of the implant fixture. Percentage of removal torque loss (%RTL) before and after dynamic cyclic loading were calculated and statistically analyzed using the SPSS version 20.Results: For GI, %initial RTL was 25.0 ± 1.5% and decreased significantly after loading (23.5 ± 2.3%). For GII, %initial RTL was 25.5 ± 1.4% and increased significantly after loading (33.4 ± 3.7%). For GIII, %initial RTL was 25.944 ± 1.2% and increased significantly after loading (40.1 ± 5.1%). There was significant effect on screw loosening for abutment angulations and collar lengths.Conclusion: Within the limitations of this study, results suggested that screw loosening increases with increasing abutment angulations and collar lengths after dynamic cyclic loading. [ABSTRACT FROM AUTHOR]