A study of the mechanical, thermal and morphological properties of microcrystalline cellulose particles prepared from cotton slivers using different acid concentrations

Microcrystalline cellulose (MCC) particles are mostly prepared by acid hydrolysis of various agro sources. Acid hydrolysis is usually carried out with high concentration (64 wt%) of sulfuric acid. Here, an attempt has been made to optimize lower acid concentrations which can effectively produce MCC particles. In this work, different concentrations of sulfuric acid (20, 30, 35, 40, 47 and 64 wt%) have been used to prepare MCC particles, which have been characterized by XRD, particle size analysis, scanning electron microscopy, transmission electron microscopy, nanoindentation and thermogravimetric analysis. MCC prepared with 35 and 47% sulfuric acid (MCC 35 and MCC 47) had finest particle size and fibrils were produced in the range of 15–25 nm. MCC 20 showed wide particle size distribution, indicating low breakdown of the cellulose chains. The energy absorption behavior and mechanical properties of the MCC pellets were determined by nanoindentation test for the first time. MCC 35 pellets exhibited lowest modulus and hardness.     

Performance analysis of a double-pass solar air heater system with asymmetric channel flow passages

Journal of Thermal Analysis and Calorimetry - The present work seeks to address the forced convection heat transfer behaviour of a double-pass solar air heater system (DPSAHS) provided with...     

Probing interfacial interactions of nafion ionomer: Thermal expansion of nafion thin films on substrates of different hydrophilicity/hydrophobicity

Interfacial interactions of Nafion ionomer with superhydrophilic (Pt, Au), hydrophilic (SiO₂), and hydrophobic (graphene, octyltrichlorosilane [OTS]‐modified SiO₂) is investigated, using in situ thermal ellipsometry, by quantification of substrate‐ and thickness‐dependent thermal properties of the ultrathin Nafion films of nominal thickness ranging 25–135 nm. For sub‐50 nm thin Nafion films, the thermal expansion coefficient of films decreased in the order of most hydrophobic to most hydrophilic substrate: OTS > graphene > SiO₂ > Au > Pt, implying weaker interpolymer and polymer–substrate interactions for films on hydrophobic substrates. Expansion coefficient of films on SiO₂, graphene, and OTS‐modified SiO₂ decreased with thickness whereas that of films on Au and Pt substrates increased with thickness. Above ~100 nm of thickness, films on all substrates converged toward a common value representative of bulk Nafion. Thermal transition temperature was found to be higher for films on hydrophilic SiO₂ than that for films on hydrophobic graphene and OTS‐modified SiO₂ but was not discernible for films on Au and Pt substrates. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 343–352     

Enhancement of mechanical and barrier properties of LLDPE composite film via PET fiber incorporation for agricultural application

A study was conducted to determine the potential of linear low‐density polyethylene (LLDPE)‐PET fiber composite films to be used as an agricultural mulching film. Incorporation of 1 wt% PET fiber into the LLDPE matrix improved the tensile strength and percent elongation. The water vapor transmission rate was significantly lowered because of the presence of PET fibers. Also, the effect of continuous exposure of films to pesticide and UV light has been reported in terms of deterioration of mechanical and optical properties of the films. Differential scanning calorimetry shows that there is no effect of the presence of PET fibers on processing temperature of LLDPE at optimized loading; however, it was found that it lowers the latent heat of fusion and crystallization.     

QSAR analyses of 3-(4-benzylpiperidin-1-yl)-N-phenylpropylamine derivatives as potent CCR5 antagonists

CCR5 receptor binding affinity of a series of 3-(4-benzylpiperidin-1-yl)propylamine congeners was subjected to QSAR study using the linear free energy related (LFER) model of Hansch. Appropriate indicator variables encoding different group contributions and different physicochemical variables such as hydrophobicity (pi), electronic (Hammett sigma), and steric (molar refractivity, STERIMOL values) parameters of phenyl ring substituents of the compounds were used as predictor variables. The Hansch analysis explores the importance of the lipophilicity and electron-donating substituents for the binding affinity. However, this method could not give more insight into the structure-activity relationships because of the diverse molecular features in the data set. 3D-QSAR analyses of the same data set using Molecular Shape Analysis (MSA), Receptor Surface Analysis (RSA), and Molecular Field Analysis (MFA) techniques were also performed. The best model with acceptable statistical quality was derived from the MSA, which showed the importance of the relative negative charge (RNCG): substituents with a high RNCG value have more binding affinity than the unsubstituted piperidine and phenyl (R1 position) congeners. The relative negative charge surface area (RNCS) is detrimental (e.g. R2 = 3,4-Cl2) for the activity. An increase in the length of the molecule in the Z dimension (Lz) is conducive (e.g. R3 = sulfonylmorpholino), while an increase in the area of the molecular shadow in the XZ plane (Sxz) is detrimental (e.g. R1 = N-c-hexylmethyl-5-oxopyrrolidin-3-yl) for the binding affinity. The presence of a chiral center makes the molecule less active (e.g. R1 = N-methyl-5-oxopyrrolidin-3-yl). An increase in the van der Waals area, the molecular volume, and the difference between the volume of the individual molecule and the shape reference compound are conducive (e.g. R3 = (CH3)2NSO2-) for the binding affinity. Substituents with higher JursFPSA_2 values (fractional charged partial surface area) like the N-methylsulfonylpiperidin-4-yl (R1 position) group have better binding affinity than the substituents such as 4-chlorophenylamino (R1 position). Unsubstituted piperidines (R1 position) with less JursFNSA_1 values have lower binding affinity than the 4-chlorophenyl substituted compounds. The MFA derived equation shows interaction energies at different grid points, while the RSA model shows the importance of hydrophobicity and charge at different regions of the molecules. The models were validated through the leave-one-out, leave-15%-out, and leave-25%-out cross-validation techniques. The developed models were also subjected to a randomization test (99% confidence level). Although the MSA derived models had excellent statistical qualities both for the training as well as test sets, RSA and MFA results for the test sets are not comparable statistically with the MSA derived models.     

Low-Frequency Sub-Terahertz Absorption in HgII−XCN−FeII (X=S,Se) Coordination Polymers

Self-assembly Fe^II complexes of phenazine (Phen), quinoxaline (Qxn), and 4,4′-trimethylenedipyridine (Tmp) with tetrahedral building blocks of [Hg^II(XCN)₄]²⁻ (X=S or Se) formed six new high-dimensional frameworks with the general formula of [Fe(L)_m][Hg(XCN)₄]⋅solvents (L=Phen, m/X=2/S, 1 ; L=Qxn, m/X=2/S, 2 ; L=Qxn, m/X=1/S, 3 ; L=Qxn, m/X=1/Se, 3-Se ; L=Tmp, m/X=1/S, 4 ; and L=Tmp, m/X=1/Se, 4-Se ). 1 , 3 , and 3-Se show an intense sub-terahertz (sub-THz) absorbance of around 0.60 THz due to vibrations of the solvent molecules coordinated to the Fe^II ions and crystallization organic molecules. In addition, crystals of 1 , 4 , and 4-Se display low-frequency Raman scattering with exceptionally low values of 0.44, 0.51, and 0.53 THz, respectively. These results indicate that heavy metal Fe^II−Hg^II systems are promising platforms to construct sub-THz absorbers.     

Novel True Random Number Generator Based Hardware Cryptographic Architecture Using Quantum-Dot Cellular Automata

International Journal of Theoretical Physics - Information processing and conventional computing are usually resource constrained; evermore they need to operate in a physically suspicious...