An experimental and numerical study on an innovative metastructure for 3D printed thermoplastic polyurethane with auxetic performance

Metamaterials are specifically designed materials that possess unique properties that cannot be found in naturally occurring substances. These remarkable materials have the capability to bring about a significant transformation across a wide range of industries. Auxetic structures are a recent area of research possess a distinctive characteristic known as a negative Poisson's ratio. Unlike conventional materials that contract when stretched, auxetic structures actually expand in two dimensions. In this study, a new auxetic structure was introduced, and thermoplastic polyurethane samples were 3D printed using a fused filament fabrication method. The samples are then subjected to strains ranging from 5% to 50% and Poisson's ratios are measured both experimentally and numerically using finite element method in Ansys software. By comparing the results of the experimental research and simulation, it is evident that applying strains within this range causes the Poisson's ratio of the samples to change from −0.81 to −0.14 and it showed that the newly introduced structure is auxetic. According to the analysis of root mean square error, the hexagonal mesh with a size of 0.7 mm consistently produced the most accurate results, aligning closely with the experimental sample. Given that this is an entirely novel auxetic structure within the category of arrow-head auxetic structures, there is potential for future research to be conducted in order to further develop and enhance this model.     

KCC-1 aminopropyl-functionalized supported on iron oxide magnetic nanoparticles as a novel magnetic nanocatalyst for the green and efficient synthesis of sulfonamide derivatives

A new magnetic nanocatalyst (Fe₃O₄@KCC-1-npr-NH₂) was synthesized directly through the reaction of Fe₃O₄@KCC-1 with (3-aminopropyl) triethoxysilane (APTES) using a hydrothermal protocol. Prepared nanocomposite was used as a magnetically reusable nanocatalyst for an efficient synthesis of a broad range of sulfonamide derivatives in water as a green solvent at room temperature and the products are collected by filtration with excellent yields (85–97%). The nanocatalyst could be remarkably recovered and reused after ten times without any significant decrease in activity. This mild and simple synthesis method offers some advantages including short reaction time, high yield and simple work-up procedure.     

Iron oxide magnetic nanoparticles supported on amino propyl-functionalized KCC-1 as robust recyclable catalyst for one pot and green synthesis of tetrahydrodipyrazolopyridines and cytotoxicity evaluation

In this study, paramagnetic dendritic fibrous nano-silica functionalized by aminopropyltriethoxysilan (Fe₃O₄@KCC-1-nPr-NH₂) was synthesized using a novel hydrothermal protocol and used as a highly efficient, recyclable and heterogeneous nanocatalyst for the synthesis of a wide range of tetrahydrodipyrazolopyridines derivatives ( 5a-5 m ). The influence of different reaction parameters, such as the effects of solvent, temperature, time and concentration of catalyst for the synthesis of tetrahydrodipyrazolopyridine (2a) were studied. This catalyst could be reused for ten consecutive recycles without any considerable loss in its catalytic activity. This novel synthesis method offers some advantages including short reaction time, high yield and simple work-up procedure. Finally, the newly synthesized tetrahydrodipyrazolopyridines derivatives ( 5a-5f ) were characterized by ¹H and ¹³C NMR, IR and CHN.     

Convenient synthesis of novel pyrimido[4,5-b][1,5]benzothiazepines

Reaction of 4,6-dichloropyrimidine-5-carbaldehyde with amines in chloroform gave 4-(substitutedamino)-6-chloro-pyrimidine-5-carbaldehydes derivatives at low temperature. Treatment of the latter products with 2-aminobenzenethiol in alkaline benzene and then in boiling acetonitrile gave a novel group of 11H-pyrimido[4,5-b][1,5]benzodiazepine derivatives. Structures of the products confirmed by ¹HNMR, IR, and mass spectra.     

Oxygen Reduction Reaction on a Rotating Ag/GC Disk Electrode in Acidic Solution

Finding an appropriate mechanism of oxygen reduction reaction, without having kinetic parameters and intermediate species at hand, is an impossible task. In view of the fact that this reaction is one of the important reactions, it was tried to overcome this problem through computing the kinetic parameters by means of Ag/GC rotating disc electrode in an acidic solution. Using this electrode, two values were obtained for electron transfer coefficient and reaction order was calculated through relative equations. Based on this information, an ECE (electrochemical chemical electrochemical) mechanism has been proposed.     

Polystyrene-graphene oxide modified glassy carbon electrode as a new class of polymeric nanosensors for electrochemical determination of histamine

A simple and rapid protocol for the synthesis of polystyrene-graphene oxide nanocomposite(PS/GONC)was achieved for first time using an in situ polymerization method.PS/GONC modified glassy carbon electrode(PS/GONC/GCE) has been employed as an efficient nanosensor for the electrooxidation of histamine.The PS/GONC/GCE is used as an electrochemical nanosensors for monitoring histamine using differential pulse voltammetry techniques(detection limit 0.03 μmol/L).In addition,the prepared nanosensor was successfully applied to determine histamine in fish samples,yielding satisfactory results.The spiked recoveries were in the range of 98.2%-103.1%.     

An MRI denoising method using image data redundancy and local SNR estimation

This paper presents an LMMSE-based method for the three-dimensional (3D) denoising of MR images assuming a Rician noise model. Conventionally, the LMMSE method estimates the noise-less signal values using the observed MR data samples within local neighborhoods. This is not an efficient procedure to deal with this issue while the 3D MR data intrinsically includes many similar samples that can be used to improve the estimation results. To overcome this problem, we model MR data as random fields and establish a principled way which is capable of choosing the samples not only from a local neighborhood but also from a large portion of the given data. To follow the similar samples within the MR data, an effective similarity measure based on the local statistical moments of images is presented. The parameters of the proposed filter are automatically chosen from the estimated local signal-to-noise ratio. To further enhance the denoising performance, a recursive version of the introduced approach is also addressed. The proposed filter is compared with related state-of-the-art filters using both synthetic and real MR datasets. The experimental results demonstrate the superior performance of our proposal in removing the noise and preserving the anatomical structures of MR images.     

Chalcopyrite and pyrite floatabilities in the presence of sodium sulfide and sodium metabisulfite in a high pyritic copper complex ore

One of the principal problems in flotation of copper complex ores is the presence of pyrite and copper-activated pyrite in moderately alkaline pHs. Misreported pyrite into copper concentrates dramatically declines copper grade and its recovery. In this study, the effect of sodium sulfide, sodium metabisulfite (SMBS), and their dosages (100, 200, 300, and 400 g/t) were investigated on chalcopyrite and pyrite floatabilities in a high pyritic copper sulfide ore. Furthermore, the role of particle size distribution (PSD) in three different levels (i.e., d₇₀, d₇₅, and d₈₀ of passing 75 µm) was evaluated by a series of batch flotation experiments. It was revealed that using 200 g/t SMBS provides not only the highest and the lowest chalcopyrite and pyrite recoveries, but also the maximum and minimum copper and iron grades. Pyrite recovery was sharply increased by the addition of sodium sulfide in light of sodium sulfide-induced collectorless flotation; however, it showed a very weak effect on chalcopyrite floatability. In addition, the highest and lowest chalcopyrite and pyrite recoveries were, respectively, identified when d₇₅ equaled to 70% 75 µm. In other words, for the high pyritic copper ore type, it is feasible to achieve the highest chalcopyrite recovery consuming the lowest grinding energy.     

A vertical heat pipe: an experimental and statistical study of the thermal performance in the presence of low-frequency vibrations

New experimental results present the effects of low-frequency vibrations in a vertical heat pipe. The thermal resistance was investigated under different heat transfer rates, filling ratios and frequencies, increase of which improved the thermal performance. The vibrations were effective 33.83 % on the performance, and the best performance was estimated using the L16 array of Taguchi method, and it was achieved with the thermal resistance 0.064 K/W in the frequency 30 Hz.     

Thermodynamic Study of the Binding of Mercury Ion to Human Growth Hormone at Different Temperatures

The interaction of human growth hormone (hGH) with the divalent mercury ion was studied by isothermal titration calorimetry at two temperatures of 27 °C and 37 °C in aqueous solutions. We found that there is a set of two identical and non-interacting binding sites for Hg²⁺ ions. The intrinsic dissociation equilibrium constant and the molar enthalpy of binding are 4.2 mmol⋅L⁻¹ and −14.8 kJ⋅mol⁻¹ at 27 °C and 5.1 mmol⋅L⁻¹ and −14.2 kJ⋅mol⁻¹ at 37 °C, respectively. The results obtained indicate that the stability of the protein increases due to the binding of mercury ions using the extended solvation theory.