DFT and MP2 Study of Intermolecular Interaction of 5‐Aminotetrazole and Hydrazine: Enthalpy of Formation of Hydrazinium 5‐Aminotetrazolate in the Gas Phase

The tautomerism of all possible forms of 5‐aminotetrazole ( AT1 – AT7 ) in the gas phase and continuum solvent was studied theoretically. The calculations were separately performed at the MP2 and CAM‐B3LYP levels of theory, using the 6‐311++G(d,p) basis set. It was found that 5‐aminotetrazole in the 2H form ( AT1) is the most stable isomer in both the gas phase and in solution. In addition, the aggregation of various isomers of 5‐aminotetrazole with hydrazine was investigated in the gas phase and in solution. Finally, the standard enthalpy of formations of the different structures of hydrazinium 5‐aminotetrazolate was determined in the gas phase. Using the calculated standard enthalpy of formation of different structures of hydrazinium 5‐aminotetrazolate in the gas phase and considering their Boltzmann population ratios, a single value has been reported for the standard enthalpy of formation of hydrazinium 5‐aminotetrazolate considering all of the tautomers. The calculated values are in excellent agreement with the experimentally reported heat of formation for the hydrazinium 5‐aminotetrazolate.     

In-situ generated ZnO nanoparticles for enhanced performance of thin film nanocomposite membrane in forward osmosis process

This work developed a novel approach to the in-situ synthesis of ZnO nanoparticles to modify the polysulfone (PSf) porous membrane substrate. The zinc acetate was added to the casting solution, and ZnO nanoparticles were synthesized during phase inversion. The non-solvent pH and zinc acetate concentration controlled the ZnO synthesis and loading. Their effect on the substrates properties in terms of morphology, hydrophilicity and porosity was studied thoroughly. The result shows that the ZnO nanoparticles was not formed in acidic pH, while ZnO nanoparticles with size of 20 nm could be easily formed in basic pH. The successful synthesis of ZnO nanoparticles was investigated using FTIR and EDX analysis. The EDX images verify that in-situ synthesis led to a more uniform dispersion than conventional incorporation method. Then the effect of ZnO loading on the interfacial reaction and polyamide (PA) structure was investigated. SEM images verify the successful synthesis of a uniform and defect-free PA thin film on ZnO modified substrates. FO performance results show an enhancement in water flux and salt rejection as a result of ZnO incorporation in thin film nanocomposite (TFN) membranes, where TFN 1 wt.% in-situ membrane showed 40% higher water flux than the control TFC membrane. The porous and hydrophile substrate in TFN 1 wt.% in-situ membrane is responsible for improved separation performance. These modified membranes displayed uniform dispersion of ZnO nanoparticles within substrates, confirming that this method could effectively restrain the aggregation of the nanoparticles.     

Stability and nonlinear dynamical analysis of functionally graded microplates

Microsystem Technologies - This paper conducts an investigation into the nonlinear dynamical analysis of a functionally graded microplate resting on an elastic foundation. The first part of the...     

Automatic optic disk boundary extraction by the use of curvelet transform and deformable variational level set model

Efficient optic disk (OD) localization and segmentation are important tasks in automated retinal screening. In this paper, we take digital curvelet transform (DCUT) of the enhanced retinal image and modify its coefficients based on the sparsity of curvelet coefficients to get probable location of OD. If there are not yellowish objects in retinal images or their size are negligible, we can then directly detect OD location by performing Canny edge detector to reconstructed image with modified coefficients. Otherwise, if the size of these objects is eminent, we can see circular regions in edge map as candidate regions for OD. In this case, we use some morphological operations to fill these circular regions and erode them to get final locations for candidate regions and remove undesired pixels in edge map. Since usually OD is surrounded by vessels, we choose the candidate region that has maximum summation of pixels in strongest edge map, which obtained by performing an appropriate threshold on the curvelet-based enhanced image, as final location of OD. Finally, the boundary of the OD is extracted by using level set deformable model. This method has been tested on different retinal image datasets and quantitative results are presented.     

Effects of feedback on active fault detection

In recent years there has been increased interest in the use of active approaches for fault detection. In one of these approaches an auxiliary signal is designed such that over a short period it will reveal a fault not otherwise detectable and do so with as little perturbation of system performance as possible. This method is robust in the sense of guaranteeing the detection of the fault for a whole set of bounded uncertainties. Feedback plays an important role in control but its role in active fault detection based on auxiliary signals has not been explored, yet. This paper begins that investigation.     

Lessons from the Ocean: Whale Baleen Fracture Resistance

Whale baleen is a keratin‐based biological material; it provides life‐long (40–100 years) filter‐feeding for baleen whales in place of teeth. This study reveals new aspects of the contribution of the baleen's hierarchical structure to its fracture toughness and connects it to the unique performance requirements, which require anisotropy of fracture resistance. Baleen plates are subjected to competing external effects of hydration and varying loading rates and demonstrate a high fracture toughness in transverse loading, which is the most important direction in the filtering function; in the longitudinal direction, the toughness is much lower since delamination and controlled flexure are expected and desirable. The compressive strength is also established and results support the fracture toughness measurements: it is also highly anisotropic, and exhibits a ductile‐to‐brittle transition with increasing strain rate in the dry condition, which is absent in the hydrated condition, conferring impact resistance to the baleen. Using 3D‐printing prototypes that replicate the three principal structural features of the baleen plate (hollow medulla, mineralized tubules, and sandwich‐tubular structure) are created, and the role of its structure in determining its mechanical behavior is demonstrated. These findings suggest new bioinspired engineering materials.     

Behaviors of capacitive and Pirani vacuum gauges

Knowing the exact pressure of the process has a great impact on the validity of the results, product quality, energy efficiency, and in some processes, on the security of work with the system. Hence, the calibration of the barometers and the accuracy of the readings should be taken seriously. Choosing the appropriate time interval for re-calibration is done according to the extent and conditions of use, uncertainty, and the inaccuracy allowed in measurement, constructive suggestion, and some other things. Failure to pay attention to the importance of periodic calibration in vacuum gauges leads to some irreparable losses in the research project and the vacuum generator system. In this study, using McLeod's barometer, the deviation of capacitive and Pirani vacuum gauges is investigated at different time intervals in the middle vacuum range, and it is determined that the vacuum gauge faces a serious deviation from the actual calibrated amount for upper and lower ranges of middle vacuum in the same working pressure range over time.     

One polymer,one layer,and two opposite functions: Using a pH-switchable polymer to fabricate a hydrophilic–hydrophobic fibrous membrane

Thanks to their permissibility of vapor transmitting and resistance to water penetration, hydrophilic–hydrophobic membranes (HHMs) are a critical factor in so many applications. Current strategies focus on electrospinning hybrid layers from two different hydrophilic–hydrophobic polymers. Here, we report a new generation of HHMs by electrospinning one layer of pH-switchable polymers followed by a simple post-treatment. In doing so, a hydrophobic poly(methyl methacrylate)-co-poly(N,N-diethylaminoethylmethacrylate) (PMMA-co-PDEAEMA) membrane is fabricated using the electrospinning method. Then, hydrochloric acid (HCl) vapor is used to convert one face of the membrane to a hydrophilic state. Field emission-scanning electron microscopy, drop test, water contact angle (WCA), moisture management test (MMT), t ensile strength, water vapor permeability (WVP), air permeability (AP), and cytotoxicity test were used to characterize the obtained membrane. The results show that by HCl vapor exposure, one side of the membrane gets successfully converted into a hydrophilic state, with the other side still remaining hydrophobic. The drop test and the WCA test showed that the optimal exposure time is only 5 min. This trigger has a small effect on the morphology and, subsequently, on water and air permeability as well as on the mechanical behavior of the membrane. This new generation of membranes can have applications in protective clothing and wound dressing.     

Application of reaction equilibrium thermodynamic model for correlation of H2S solubility in ionic liquids [emim][Ace] and [hmim][Ace] using CPA equation of state

Correlation of H₂S solubility in ionic liquids [emim][Ace] and [hmim][Ace] was performed using CPA EoS. For taking into account the effect of possible chemical reactions, the Reaction Equilibrium Thermodynamic Model (RETM) was used. This model assumes that an AB₂ type reaction mechanism between two IL molecules and one H₂S molecule is taken place. Both of H₂S and ILs was considered as association components following 4C and 2B association schemes, respectively. First, pure components parameters achieved using CPA EoS. Consequently, the binary systems were investigated applying RETM. The results show AAD% equal to 4.75 and 12.44 for [emim][Ace] and [hmim][Ace] respectively.