Specific Absorption Research Articles

A novel “off–on” ratiometric aptasensor based on dual-emissive persistent luminescent nanoparticles for the detection of dopamine

Dopamine, a neurotransmitter with multiple functions in the brain. The abnormal of dopamine levels are generally considered to be associated with various nervous system diseases. Herein, a novel ‘‘off–on” single-excited dual-emissive ratio luminescent aptasensor for highly sensitive and accurate monitoring of DA levels has been prepared via electrostatic interaction connecting persistent luminescent nanoparticles (PLNPs) ZnGaO:Sm and ZnGeO:Mn with different emission wavelengths. ZnGaO:Sm@Cy5.5-ZnGeO:Mn (ZGS@Cy5.5-ZGM), this ratiometric aptasensor exhibits two-emission peaks at 533 and 700 nm under a single-excitation wavelength of 254 nm. The afterglow luminescence of ZnGaO:Sm-apt@Cy5.5 at 700 nm is effective quenched by complementary chains of Cy5.5-modified DA aptamers with 710 nm specific absorption and only efficiently recovered by DA; meanwhile, the afterglow luminescence of ZnGeO:Mn as reference at 533 nm remains unchanged. The as-designed autofluorescence-free and exogenous-free interference ratiometric sensing system ZGS@Cy5.5-ZGM showed high selectivity for DA in complex biological samples. Under optimal detection conditions, the luminescence intensity ratio Δ(I700/I533) showed a good linear relationship with the concentration of DA in the range of 0.02–80 μM and the detection limit as low as 4 nM. The recoveries of DA in serum, urine and sweat were 97.4 % to 105.3 %, 96.4 % to103.4 %, and 95.1 % to 104.4 %, respectively. Current strategies based on PLNPs ratiometric sensors provide an effective method with high selectivity and accuracy for the detection of DA in clinical samples.

Formulation and Evaluation of Gastro-retentive Drug Delivery Systems of Cinnarizine

Background and Aim Cinnarizine is an antihistamine and calcium channel blocker used for the treatment of vertigo and vomiting. It has poor bioavailability and a half-life of 3.4 hours. Cinnarizine has low solubility and low dissolution rate in the gastrointestinal tract which causes the main problem for systemic circulation after oral administration. Hence this study aimed to achieve 24-hour drug release and floating cinnarizine effervescent floating tablets formulated using synthetic and natural polymers.Methods Gastro retentive floating sustained-release tablets of Cinnarizine an H-1 anti-histaminic drug were prepared by direct compression. The tablets were prepared to enhance bioavailability and observe the effects of synthetic polymers such as sodium CMC HPMC K5M polyox and natural polymers such as guar gum and xanthan gum. Pre- and post-formulation parameters were also evaluated.Results A better release profile was observed for drugs in the gastro-retentive drug delivery system because of its specific absorption. The prepared tablets started floating within three minutes and continued to float for gt 24 h. All the results were within the limits.Conclusion The present study aids in overcoming the dosing frequency by providing sustained release.

Edremit yağlık zeytini yağında bazı kalite-kontrol parametrelerinin incelenmesi

Throughout history, people have searched for the secret of long life and these researchers continue at full speed in parallel with the developments in science and technology in recent years. It is inevitable that the secret of a long and healthy life depends on nutrition and that nutrition should be with natural and high-quality nutrients. The Mediterranean diet, which is based on olive oil, has emerged as a popular diet in recent years. Due to the positive effects of olive oil on health, it is also economically valuable. For olive oil users to reach pure and high-quality olive oil, olive oils should be evaluated within the scope of some quality control parameters with the help of various analyzes. In this study, the quality parameters of free fatty acidity, peroxide value, and specific absorption(K₂₃₂, K₂₇₀, and ∆K) values in ultraviolet light were determined in olive oils obtained from Edremit Yağlık olives. The compliance of the values found with the Turkish Food Codex Communiqué on Olive Oil and Edible Pomace Oil (Communiqué No: 2017/26) has been evaluated. As a result of the analyzes made, the amount of free fatty acid was determined as 0.11% in %oleic acid, the average peroxide number was 0.50 meq O2/kg oil, the meanK₂₃₂ values were 0.4501, the K₂₇₀values were on average 0.0446, and the mean ∆K values were -0.0248. It has been determined that all studied samples comply with the criteria for extra virgin olive oil specified in the Turkish Food Codex 2017/26 Communiqué.

Remediation of charged organic pollutants—binding motifs for highly efficient water cleaning with nanoparticles

AbstractMany charged organic molecules behave as persistent and hazardous pollutants with harmful effects on human health and ecosystems. They are widely distributed related to their charged molecular structure that provides water solubility. In order to track the fate and behavior of such pollutants, charged dyes with specific absorption in the visible spectra serve as convenient model compounds. We provide a platform of smart adsorbers that efficiently remediate positively and negatively charged dyes (crystal violet and Amaranth) from water. Metal oxide nanoparticles serve as a core with an intrinsically large surface area. The surface potential was tuned towards positive or negative by decorating the cores with self‐assembled monolayers of dedicated long‐chained phosphonic acid derivatives. Selective remediation of the dyes was obtained with corresponding oppositely charged core‐shell nanoparticles. Mixed dye solution can be cleaned by a cascade approach or by applying both particle systems simultaneously. The removal efficiency was determined as a function of particle concentration via UV‐spectroscopy. The results of remediation experiments at different pH values and using superparamagnetic iron oxide nanoparticle cores lead to a simple process with recycling capability.

Extractive Spectrophotometric Detection of Sn(II) Using 6-bromo-3-hydroxy-2-(5-methylfuran-2-yl)-4H-chromen-4-one.

For the determination of tin(II) traces, an extractive spectrophotometric approach is devised. The applied method serves a powerful tool for determination of tin(II), involves the formation of yellow colored complex after thebinding of 6-bromo-3-hydroxy-2-(5-methylfuran-2-yl)-4H-chromen-4-one (BHMF) and tin(II) in 1:2 stiochiometry in a slightly acidic medium (HCl). The complex shows absorbance at 434nm with respect of the blank reagent. The outcomes of spectral investigation for complexation showed a Beer's range of 0-1.3μg Sn mL-1, molar absorptivity, specific absorptivity and Sandell's complex sensitivity are 9.291 × 104 L mol-1cm-1, 0.490mLg-1cm-1 and 0.002040μgcm-2 at 434nm that was stable for two days. The interferences studyresults showed that this method is free from interferences, when tested with metal ions including Ag,Be, Bi, Ca,Cd, Ce, Co,Hg, Mo,Re,Pt, Se,Ti,U,V, W and other common cations, anions, and complexing agents. Theapplied method is quite simple, highly selective, and sensitive with good re-producibility. This method has been satisfactorily by utilizing the proposed procedure, and its applicability has been tested by analyzing synthetic samples and an alloy sample of gunmetal. The procedure assumes this because of the scarcity of better methods for determining tin(II). The results are in good agreement with the certified value.

Interactions Between Direct Oral Anticoagulants (DOACs) and Antiseizure Medications: Potential Implications on DOAC Treatment.

The use of direct oral anticoagulants (DOACs) is increasing because of their superior efficacy and safety compared with vitamin K antagonists. Pharmacokinetic drug interactions, particularly those involving cytochrome P450- mediated metabolism andP-glycoprotein transport, significantly affect the efficacy and safety of DOACs. In this article, we assess the effects of cytochrome P450- and P-glycoprotein-inducing antiseizure medications on DOAC pharmacokinetics in comparison to rifampicin. Rifampicin decreases to a varying extent the plasma exposure (area under the concentration-time curve) and peak concentration of each DOAC, consistent with its specific absorption and elimination pathways. For apixaban and rivaroxaban, rifampicin had a greater effect on the area under the concentration-time curve than on peak concentration. Therefore, using peak concentration to monitor DOAC concentrations may underestimate the effect of rifampicin on DOAC exposure. Antiseizure medications that are cytochrome P450 and P-glycoprotein inducers are commonly used with DOACs. Several studies have observed a correlation between the concomitant use of DOACs and enzyme-inducing antiseizure medications and DOAC treatment failure, for example, ischemic and thrombotic events. The European Society of Cardiology recommends avoiding this combination, as well as the combination of DOACs with levetiracetam and valproic acid, owing to a risk of low DOAC concentrations. However, levetiracetam and valproic acid are not cytochrome P450 or P-glycoprotein inducers, and the implications of their use with DOACs remain to be elucidated. Our comparative analysis suggests DOAC plasma concentration monitoring as a possible strategy to guide dosing owing to the predictable correlation between DOACs' plasma concentration and effect. Patients taking concomitant enzyme-inducing antiseizure medications are at risk for low DOAC concentrations and subsequently, treatment failure and thus can benefit from DOAC concentration monitoring to prophylactically identify this risk.

Computational Insights in the Spectrophotometrically Analyzed Niobium (V)- 3-Hydroxy-2-(4-methylphenyl)-4H-chromen-4-one Complex using DFT Method

Using 3-hydroxy-2-(4-methylphenyl)-4H-chromen-4-one (HMC) as a complexing agent in an acidic medium, a simple, quick, highly sensitive, and selective approach for the extractive spectrophotometric measurement of micro quantities of niobium (V) is developed. The yellowish 1:3 complex can be extracted 100 % in dichloromethane (DCM), attaining maximum absorbance in the wavelength range 388-407 nm. At 400 nm, the selected wavelength, the approach follows a linear calibration curve up to 2.2 g Nb (V) ml-1 and 0.395-1.78 ppm Nb (V) as identified from the Ringbom Plot with molar absorptivity, specific absorptivity, and Sandell's sensitivity of 4.926 × 104 l mol-1 cm-1, 0.5302 ml g-1 cm-1 and 0.0019 µg Nb cm-2, respectively. With a correlation coefficient of 0.9994, the linear regression equation is Y = 0.514 X + 0.016. The method's detection limit is 0.0698 µg ml-1. The presented determination of pentavalent niobium is unaffected by 33 cations and 22 anions/complexing agents. The approach has good reproducibility and can be used to determine niobium in a satisfactory manner. The analytical study has been correlated well with the theoretical approach of Density Functional Theory (DFT) for quantum chemical calculations. DFT effectively helped determine and interpret the chemical behavior of the obtained Nb(V)-HMC complex, explaining its stability and reactivity pattern.

Energy Absorption Characteristics and Elastoplastic Damage Response of Hybrid Epoxy/Coir Fibre-Reinforced Aluminum 6063 Tubes in Axial Deformation

Occupant safety is one of the critical performance criteria established in the aerospace industry. Several composite materials have been developed but the energy absorption properties are not yet satisfactory. This study investigates the energy absorption characteristics of aluminum tubes reinforced with coir-fiber/epoxy system at varying proportions (10-90%) according to the specifications of hybrid tube thickness compositions (10T, 15T, 20T) towards evolving a criterion for optimal performance. Finite element analysis was conducted in ABAQUS to determine the load–displacement response and the crashworthiness properties of the tubes while a representative volume element (RVE) model was formulated to obtain the elastic properties of the reinforcement phase. The results indicated that the incidence of high peak forces Pmax is related to tube thickness variations where the 20T tubes were found to give the best performance, while the 15T tubes showed a superior performance under progressive crushing and presented the best responses for specific energy absorption (SEA). A multi-objective optimization plan was implemented and through the Pareto fronts, tube configurations (C20T60F), (C15T70F) and (C20T40F) were found to be most consistent with the design criteria. Results from experimental validation were found to be in close agreement with numerical predictions and satisfied the overall objective of achieving a good balance in lightweight design for crashworthiness applications.

The Mechanical Properties of Wood-Based Grid Sandwich Structures

In order to reduce the weight of the panels used in buildings and minimize the use of wood, it is of great practical significance to study the mechanical properties of wood-based sandwich structures for adaptation to modern wood-structured buildings. In this paper, a wood-based pyramid structure specimen with large interconnection space was designed and prepared first. Based on the results of the flat compression, in order to strengthen the core layer of the sandwich structure, an interlocking grid structure can be used. The mechanical properties of two kinds of structure specimens, including bearing capacity, compressive strength, specific strength, load–mass ratio, safety factor distribution, and specific energy absorption, were studied by means of experimental test, theoretical analysis, and finite element analysis. It was concluded that the apparent density of the two structures was lower than that of the materials of which they were composed. However, the overall flat compressive strength of the two structures was higher than that of their constituent materials, which were high-strength materials in the field of natural materials. The mechanical properties of the interlocking grid structures were better than those of the pyramid structures. Based on the criterion of cell structure stability, it can be concluded that the wood-based pyramid structure was a flexural-dominant structure, and the interlocking grid structure was a tensile-dominant structure. The results show that the core layer design plays an important role in the mechanical properties and failure modes of wood-based sandwich structures.

Quasi-static crushing response of additive manufactured 3D reentrant circular auxetics with different polymer matrices

In the past decades, auxetic metamaterials have attracted extensive interest due to their excellent mechanical properties. In this study, we proposed a novel three-dimensional (3D) reentrant circular (REC) auxetic metamaterial, and investigated its quasi-static crushing responses through experimental tests and numerical simulations. The 3D REC metamaterials were fabricated by the additive manufactured (AM) technique based on different polymer matrix materials, including polyamide-carbon fiber (PA-CF), polyamide (PA) and polypropylene (PP). The morphological characterizations of strut surfaces were revealed, and the effect of matrix material on the crushing behaviors of the REC specimens was examined. The numerical plateau stress and SEA agree well with the experimental results with a maximum relative error of 14.5%. The results show that the PA-CF- and PA-based specimens exhibit different fracture failures, while the PP-based specimen does not fracture during the crushing process. The initial force peak, plateau stress and specific energy absorption (SEA) of the REC specimens decrease in the order of PA-CF > PA > PP, and the larger relative density leads to larger values. In addition, the PP-based specimen shows the smallest Poisson’s ratio under quasi-static crushing, i.e. the most obvious NPR effect, while the PA-CF-based specimen shows the largest Poisson’s ratio.

A novel post-processing method for progressive failure analysis of brittle composite compression

Finite element analysis of brittle materials in axial compression typically uses element deletion to allow continued global deformation post-element-failure. However, element deletion produces cyclic load-displacement curves that underestimate energy absorption and are not representative of a continuum system. Two key observations support the conclusion that results from an appropriately discretized model can be an adequate representation of a continuum system. Specifically, the frequency of the oscillations in the load-displacement curve is directly dependent upon element length in the loading direction, and the peak amplitudes of oscillations are mesh size independent. A method of post-processing the analysis results, by connecting the peak amplitudes of oscillations, is proposed and applied to a series of continuous carbon fiber composite crush tubes. The load-displacement curve, stable crushing load, and specific energy absorption of the post-processed results compare well to an experimental study of crush tubes with similar layups.

Crashworthiness reinforcements of multi-cell thin-walled tubes through topology optimized lattice structures under axial and lateral loadings

Thin-walled tubes have been predominantly utilized in passive vehicle safety systems as crash energy absorbers. With the increasing popularity of additive manufacturing technique, it is feasible to fabricate novel internal reinforcement structures to further reinforce the crashworthy performances of thin-walled tubes. In the present work, a novel nonuniform Lattice-reinforced multi-cell tube based on topology optimization was put forward to explore the crashworthy performances under axial loading and lateral bending. Numeric models validated against the experiments were established to reveal the crashworthy performances of lattice material infilled multi-cell tubes (MCTs). It is observed that the optimized nonuniform lattice structure absorbs more energy than the uniform counterpart. In addition, the hybrid multi-cell filled tubes exhibit remarkable improvements in terms of energy absorption and crushing force efficiency in contrast to the corresponding empty tubes. Furthermore, the specific energy absorption of the three-layer hybrid multi-cell tube is improved by 38.2% and 20.0% under two loading conditions respectively relative to the sum of individual components on account of interplay effect. Collectively, the hybrid nonuniform lattice reinforcement tube provides a promising method for the crashworthy design of MCTs, which can be recommended as an underlying candidate for passive safety protection applications.

Crashworthiness performance of novel pre-deformation method applied square aluminum tubes

In this study, the energy absorption capability and crashworthiness performance of Al6063-T4/T6 aluminum alloy square tubes subjected to axial crushing were investigated experimentally. To enhance the energy absorbed value, PVC foam and polyurethane springs were used as reinforcement materials. In addition, a novel pre-deformation process was applied to the tube inner surfaces by a specifically manufactured apparatus. All the tube walls were identically crushed by 15% of the wall thickness to achieve locally increased wall strength. Thus, the folding length was restricted by the local strength-increased regions. The experiment revealed that the foam filling enhanced the energy absorbed, in both T4 and T6 temper, more than the wall-crushing process. However, the wall-crushed tubes offered higher specific energy absorption compared to the foam-filled sample in the T6 temper. In T6 temper, the absorbed energy was increased 85% compared to the base tube while the increase in specific energy absorption value was 26%. According to the crashworthiness performance of the samples which contains foam filling and wall crushing together, it is concluded that using polyurethane spring contributed by far compared to that of the other samples.

Numerical study on energy absorption characteristics of bio-mimetic multi-cell thin-walled structures with different hierarchy

Horsetail plant is the most primitive terrestrial plant bred by spores. After hundreds of millions of years of evolution, the internal structure of horsetail plant stem is composed of multiple cavity which brings excellent impact resistance. The investigation of the internal thin-walled structure of horsetail plant can be used to improve the energy absorption property of the existing thin-walled structure, and has important significance and application potential for the design of anti-collision structure. In this study, four kinds of bio-mimetic thin-walled models with different shapes of cross-sections were proposed and established based on the horsetail plants, and the energy absorption values of the structures were calculated and analyzed by numerical method. The squ-3rd structure with the highest specific energy absorption value of 49.121 kJ/kg was obtained. Then the specific energy absorption value and crushing force efficiency of the structure under different parameters, including wall thickness, side length height ratio, and impact angle were calculated and discussed. Based on the numerical simulation results, we found that for the third-order form of structure with square cross-section, the structure with the wall thickness between 1 and 1.25 mm showed better crushing resistance. And, the energy absorption characteristics of the structure were found to have better performance when the side length height ratio is 1:1.

An investigation of the crashworthiness performance and optimization of tetra-chiral and reentrant crash boxes

In this study, the crash performances of square and cylindrical crash boxes with tetra-chiral and reentrant unit cell structures were explored and optimized. First, tensile tests were conducted to determine the mechanical properties of the Al 6061-T6. These mechanical properties were then incorporated in the finite element (FE) models generated using LS-DYNA. To validate the FE models, tetra-chiral and reentrant crash plates were produced, and the FE analysis results were compared with the test results. Subsequent to this validation, for each crash box design type (i.e., tetra-chiral cylindrical, tetra-chiral square, reentrant cylindrical, and reentrant square), Kriging surrogate models were constructed using MATLAB for two crash metrics: specific energy absorption (SEA) and crash load efficiency (CLE). Finally, a multi-objective optimization problem was formulated for each crash box design type, the generated Kriging models are integrated into genetic algorithm available in MATLAB, and the Pareto optimal crash box designs were obtained. It was found that the SEA and CLE of reentrant crash boxes were better than those of the tetra-chiral crash boxes. In addition, the reentrant cylindrical crash box displayed better performance than the reentrant square, as well as the tetra-chiral cylindrical and square crash boxes.

Assessment of Geotechnical Properties of Laki Limestone for Coarse Aggregate, Nooriabad, Jamshoro Sindh, Pakistan

Present study is aimed at assessment of geotechnical properties of Laki limestone as coarse aggregate which is being quarried in Nooriabad area, Sindh, Pakistan. Coarse aggregate samples (n=20) of limestone were collected for the evaluation of physico-mechanical properties of the aggregate. Petrographic analysis revealed that the aggregate comprises of hard, compact, massive, crystalline and fossiliferous limestone. It is devoid of any reactive silica (chert, chalcedony) and other harmful constituents like clays or organic matter. Average values of specific gravity, absorption,bulk density, void content and combined index (EI + FI) of collected samples are 2.5, 2.1%, 1.54 g/cc, 38.55% and 13.04% respectively. The values of specific gravity (2.3-2.9), absorption (0-8%), bulk density (1.28 g/cc-1.92 g/cc) and void content (30%-45%) are varying within the range of normal weight aggregate as per American concrete institute (ACI)specifications. On the other hand, absorption values of aggregate samples are slightly higher (2.1%) than the reference range (2%) but meet other requirements. Mechanical properties including aggregate impact value (8.58%), aggregate crushing value (26.66%), Loss Angeles abrasion value (24.77%), sodium sulfate soundness (4.72%), water soluble sulfate (0.006%) and water soluble chloride (0.005%) are found to be within corresponding guidelines set by ASTM. On the other hand, average carbonate content is found to be 89.64% indicating that Laki limestone is of slightly low purity. Except absorption, all physical and mechanical properties lie within specified ranges. It is concluded that Laki limestone is suitable for use as road aggregate and concrete mix design.

Pre-Tensioned CFRP Tubes for Improved Energy Absorption

The use of materials like CFRP has shot into prominence to achieve lightweight designs without compromising on structural integrity. Circular thin tubes are often employed in passenger cars as energy absorbers to absorb the impact energy during an accident. When such tubes are made of materials like CFRP it contributes to weight reduction besides leading to reduced fuel consumption. Also due to their lower weight, such tubes shall be capable of absorbing more energy per unit mass compared to metallic designs, which is defined as specific energy absorption capacity (SEA). Pre-stressing techniques are widely used by civil engineers across the globe to impart more stress/energy bearing capacity for the structures. Based on pre-stressing principles, the introduction of pre-tension during the fabrication stage for thin CFRP tubular structures has been experimentally studied to validate the applicability of pre-stress concepts for more SEA. The study investigates experimentally the additional advantage prestressing can bring for a CFRP tube in terms of SEA improvement.

Nonlinear static and dynamic modeling of energy absorption lattice structures behavior

Belonging to cellular solids subclasses, lattice structures have recently obtained much interest in the lightweight engineering sector thanks to the potential of their specific structural properties. This investigation explores the mechanical properties of lattice cells selected for their energy absorption capacity while considering strut orientation angle, vertical reinforcement, combination of cells and aspect ratio as geometrical and topological parameters. Truss lattices are examined given their excellent results from the point of view of energy absorption behavior. While non-linear static analyses are used to determine both volumetric and specific energy absorption, dynamic calculations are employed to identify the densification point and assess on the crashing load efficiency of the considered cells. This contribution aims at providing a deeper understanding of the mechanical behavior of lattice structures in order to provide construction guidelines that can be employed in rapid prototyping and design of lightweight structures.

Reconnaissance Study of Gypsum from the Fatha Formation as Raw Material for Production of Gypsum Powder in Shaqlawa Area, Erbil, Kurdistan Region, Iraq

The quality of gypsum rock as raw material from the Fatha Formation in Talajar Village in the Shaqlawa area for ground gypsum production was assessed. A total of three samples of gypsum were collected from different locations of the same horizon in the outcrop for comparing the chemical and physical properties according to the Iraqi Standard Specification 26-1988 and American Standard for Testing and Materials C471-16. The analyses of major oxides for the bulk gypsum samples especially the main components for gypsum (SO3, CaO, and combined water) showed good results and good purity. The apparent specific gravity and absorption of water were performed according to Iraqi Standard Specification 27-1988 at room temperature. These obtained data from chemical analyses and physical tests results revealed that the gypsum quality is in conformance with Iraqi Standard Specification requirements. The quality assessments from the study area show that the gypsum in the selected area is suitable as raw material for ground gypsum production.

Sintesis Senyawa-Senyawa Epoksi dari Asam Lemak Minyak Nyamplung (Calophyllum inophyllum L.)

Epoxidation is a reaction of a carbon double bond with active oxygen, which results in the addition of an oxygen atom, converting the original double bond into a three-membered epoxide (oxirane) ring. Generally, the raw material for making epoxy comes from petroleum. Nyamplung kernel oil is a non-edible oil that can be used as an alternative raw material for making epoxy derivatives. The purpose of this study was to determine the optimum conditions and characterization of epoxy materials. The fatty acids of Nyamplung kernel oil were reacted formic acid and hydrogen peroxide with sulfuric acid as a catalyst. The optimum condition of the following parameters on the study of this process was investigated: the epoxidation time, temperature, and the mole ratio of formic acid and hydrogen peroxide. The results showed that the optimum reaction conditions with the temperature was 65 oC, the mole ratio of formic acid and hydrogen peroxide was 1:6, and the reaction time was 75 minutes. The results of the characterization under optimum conditions showed the oxirane value of 1.69, the iodine number of 9.63 mg iod/100 g, and the epoxy conversion of 67.6 %. The results of FTIR characterization showed absorption at a wavenumber of 820.03 cm-1 which is a specific absorption from the oxirane ring of the epoxy compound.