Concurrent ratcheting and stress relaxation at the notch root of steel samples undergoing asymmetric tensile loading cycles

The current study intends to develop a framework model to assess ratcheting and stress relaxation at the notch root of 1045 steel samples over asymmetric loading cycles. The framework involves the Ahmadzadeh‐Varvani (A‐V) kinematic hardening rule to control ratcheting progress and Neuber rule to accommodate for local stress and strain components at the vicinity of notch root. Plastic strain at notch root was first coupled with its counterpart in the A‐V model to establish a relation between local stress and backstress components. Calculated local stress and strain values at turning points enabled the A‐V model to assess ratcheting strain over each loading cycle. The stepwise drop in stresses at peak‐valley tips of hysteresis loops at the notch root was associated to coupled framework of the A‐V model and Neuber rule through constancy in local strain while ratcheting progressed over each cycle. This relaxed out the local stresses at tips of hysteresis loops to position on Neuber hyperbolic curve. Predicted ratcheting values at notch root of various diameters closely agreed with those of measured in steel samples over stress cycles.     

Interactive two-channel message authentication based on Interactive-Collision Resistant hash functions

We propose an Interactive Message Authentication Protocol (IMAP) using two channels; an insecure broadband channel and an authenticated narrow-band channel. We consider the problem in the context of ad hoc networks, where it is assumed that there is neither a secret key shared among the two parties, nor a public-key infrastructure in place. The security of our IMAP is based on the existence of Interactive-Collision Resistant (ICR) hash functions, a new notion of hash function security. Our IMAP is based on the computational assumption that ICR hash functions exist. It performs better than message authentication protocols that are based on computational assumptions. That is, while achieving the same level of security, the amount of information sent over the authenticated channel in our IMAP is smaller than the most secure IMAP and Non-interactive Message Authentication Protocol (NIMAP) in the literature. In other words, if we send the same amount of information over the authenticated channel, we can allow much stronger adversaries compared to the existing protocols in the literature. Moreover, our IMAP benefits from a simple structure and works under fewer security assumptions compared to other IMAPs in the literature. The efficient and easy-to-use structure of our IMAP makes it very practical in real world ad hoc network scenarios.     

β-Polymorph enhancement in poly(vinylidene fluoride) by blending with polyamide 6 and barium titanate nanoparticles

Polyamide 6 (PA6) as a cost-effective polar polymer and barium titanate (BT) as piezoelectric ceramic nanofiller were melt compounded with poly(vinylidene fluoride) (PVDF) matrix to enhance the β electroactive phase. A series of samples with two blending ratios of PVDF/PA6 (90/10 and 70/30 [wt%/wt%]) each containing 1, 3, and 5 wt% of BT were prepared. The SEM results revealed that the addition of BT to the neat blends refined the biphasic morphology which is mainly due to selective localization of BTs in PA6 dispersed phase as confirmed by TEM observation and wetting parameter predictions. The EDX analysis demonstrated a uniform distribution of BT nanoparticles in the filled systems. FTIR and XRD results showed that β content increased as a result of blending while the α phase was suppressed. The BT nanoparticles inclusion to the blends showed a synergistic effect on the β-polymorph content. These results in combination with the data derived from DSC (indicating reduction of the total crystallinity) complement the idea of β enhancement by the addition of BT nanoparticles and PA6 into PVDF.     

Pronounced Catalytic Effect of Micellar Solution of Sodium Dodecyl Sulfate (SDS) for Regioselective Iodination of Aromatic Compounds with a Sodium Iodide/Cerium(IV) Trihydroxide Hydroperoxide System

Micellar solutions of sodium dodecyl sulfate (SDS) catalyze the regioselective iodination of a wide range of aromatic compounds with sodium iodide in the presence of the easily prepared, water‐resistant and recyclable cerium(IV) trihydroxide hydroperoxide, Ce(OH)₃O₂H, at room temperature. By this protocol, structurally diverse aromatic compounds including benzene and naphthalene were iodinated in good to excellent yields.     

Scale-up studies for stable,long-term indoor and outdoor production of hydrogen by immobilized Rhodobacter capsulatus

Photofermentative hydrogen production by immobilized Rhodobacter capsulatus YO3 was carried out in a novel photobioreactor in sequential batch mode under indoor and outdoor conditions. Long-term H₂ production was realized in a 1.4 L photobioreactor for 64 days using Rhodobacter capsulatus YO3 immobilized with 4% (w/v) agar on 5 mM sucrose and 4 mM glutamate. The highest hydrogen yield (19 mol H₂/mol sucrose) and hydrogen productivity (0.73 mmol H₂ L^?1 h^?1) were achieved indoors on 5 mM sucrose. The effect of initial sucrose concentration (5 mM, 10 mM, and 20 mM) on hydrogen production was also investigated. Sustained hydrogen production was carried out under natural, outdoor conditions as well. For the outdoor experiments, the highest hydrogen productivity and yield were obtained as 0.87 ± 0.06 mmol H₂ L^?1 h^?1 and 6.1 ± 0.2 mol H₂/mol sucrose, respectively on 10 mM sucrose. Furthermore, this system prevented sudden pH drops and fluctuations caused by the utilization of sucrose throughout the process. These results demonstrate that a proper immobilization setup can lead to long-term efficient and robust hydrogen production even under naturally varying conditions.     

Micromorphology and Optical Bandgap Characterization of Copper Oxide Nanowires

Due to the industrial applications of nasno materials, the growth of Copper oxide (CuO) nanowires (NWs) at the same and opposite directions of the electric and gravitational fields was investigated to study the effects of fields on the NWs properties. The experiments were designed to grow NWs using thermal oxidation method at 450 ^°C for 50 h. NWs growth was evaluated to study two distinct cases; first, substrates exposed to the gravitational field and second those treated with electric field (EF) in-lined with gravitation field (GF). It was observed that the electric field developed a diameter homogeneity while compressing the NWs and decreasing the diameters. Furthermore, the GF influenced only the length of the NWs, while the EF had an impact on both length and diameter of the NWs. The direction of fields played an important role in NWs morphology and intensity of XRD pattern and optical properties. It was also observed that field direction greatly influenced the NWs length and diameter.     

Preparation and characterization of silk fibroin hydrogel as injectable implants for sustained release of Risperidone

The principal objective of the present study is to achieve a depot formulation of Risperidone by gelation of silk fibroin (SF). For this purpose, hydrochloric acid (HCl)/acetone-based and methanol-based hydrogels were prepared with different drug/polymer ratios (1:3, 1:6, and 1:15). For all the drug-loaded methanol-based hydrogels, gel transition of SF solutions occurred immediately and the gelation time was 1?min, while the gelation time of HCL/acetone-based hydrogels was around 360?min. According to the results obtined from Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) spectra, solvent systems and Risperidone could induce β-sheet structure, but HCL/acetone system had the lowest effect on induction of β-sheets. The crystallinity was increased by increasing the amount of Risperidone, and drug to polymer ratio of 1:3 possessed the highest crystallinity. Thermogravimetric analysis (TGA) indicated that increasing the amount of drug in formulation increased the stability of hydrogels, and methanol-based hydrogel with a ratio of 1:3 had the most stable structure. The release rate of Risperidone from methanol-based hydrogel at ratio of 1:3 was lower than that for HCl/acetone-based one, and it decreased by increasing the amount of Risperidone. The release of Risperidone from methanol hydrogel at ratios 1:3 and 1:6 continued up to 25?d which is acceptable for depot form of Risperidone and shows that the extended release of Risperidone was achieved successfully. In conclusion, SF hydrogel with the ability to respond to the environmental stimuli is an excellent candidate for injectable implants for extended release of Risperidone.     

Neck,shoulder and low back pain in secondary schoolchildren in relation to schoolbag carriage: Should the recommended weight limits be gender-specific?

The occurrence of neck, shoulder and low back complaints in relation to schoolbag carriage and other potential risk factors were investigated in a cross-sectional study of 586 Iranian schoolchildren aged 12–14 years. The average load carried by schoolchildren was 2.8 kg. Neck, shoulder and low back complaints during the preceding month were reported by 35.3%, 26.1% and 33% of the students, respectively. Gender was an independent factor predicting musculoskeletal symptoms in schoolchildren. Girls were more likely than boys to suffer from neck, shoulder and low back complaints, although there was no significant difference between genders in terms of schoolbag carriage variables. The findings suggest that the recommended weight limit for schoolbag carriage may need to differ between boys and girls. The associations between schoolbag variables and reported symptoms are also discussed. The results provide evidence that the current weight limit should consider a broader combination of factors that influence the use of schoolbags.     

Ammonia borane confined by poly(methyl methacrylate)/multiwall carbon nanotube nanofiber composite,as a polymeric hydrogen storage material

In this work, poly(methyl methacrylate)/ammonia borane/multiwall carbon nanotube (PMMA/AB/MWCNT) nanofiber composites have been fabricated and the synergetic nanoconfinement effect of nanofiber and CNT components on dehydrogenation temperature and liberating unwanted byproducts of AB (NH₃BH₃) have been studied. The results of dehydrogenation of PMMA/AB and PMMA/AB/MWCNT samples show 112 and 85 °C exothermic reaction temperatures, which are dramatically lower than pure AB (120 °C). Furthermore, by capture and interaction of AB molecules in the MWCNT and PMMA nanofiber structures, the enthalpy of exothermic decomposition decreases from ?21.00 to ?1.83 kJ mol^?1 H₂, suggesting that this type of AB nanofiber composite can provide a convenient reversible hydrogen storage material. The utilization of MWCNT as carbon catalyst and confining of AB result in a decrease of ammonia borane weight loss from 60.00 to 2.88 wt% which in turn can vigorously decline the emission of byproduct impurities. The synthesis process of PMMA/AB/MWCNT nanofiber composites causes the crystal structure of AB particles changed to the amorphous structure which has been clearly confirmed by X-ray diffraction analyses. The strategy of combining nanofiber structure and MWCNT as carbon catalyst with AB particles can be presented as a practicable solution to reach lower operational temperature and to decline undesirable volatile products.