Quire Interaction of Certain Nitramine Type Explosives with Proton——A DFT Study

The composites of certain nitramine type explosives, TETRYL, RDX and EDNA, with proton in vacuum have been considered within the constraints of density functional theory at the level of B3LYP/6-31++G(d,p) (restricted and unrestricted).The results indicate that unexpectedly hydrogen molecule production occurs by the interaction of proton and a hydrogen of CH3 (TETRYL) and CH2 (RDX and EDNA) groups.As a result, a carbocation is generated on the explosive molecules.Thereafter, TETRYL which potentially has many protonation sites were investigated in more detail in vacuum and aqueous conditions.The data reveals that the composite system (TETRYL+proton) is less stable than TETRYL protonated on nitramine NH or oxygen of the nitro groups.     

Evaluation of the Interaction and Adsorption of γ-Glycidoxy propyl trimethoxy silane with Grit-Blasted Aluminium: A ToF-SIMS and XPS Study

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) have been employed to study the adsorption and interaction of γ-glycidoxy propyl trimethoxy silane (GPS) with grit-blasted aluminium.

GPS displaces adventitious hydrocarbon either by covalent bond formation between GPS and aluminium, or adsorption, when GPS is deposited on the aluminium. ToF-SIMS fragments present at a nominal mass m/z = 71 were peak-fitted to seven peaks by using CasaXPS Software. AlOSi⁺ and Si⁺ were used to establish a relationship between covalent bond formation and the adsorption process. It is found that the adsorption isotherms of Si⁺ relating to the adsorption of GPS were of the Langmuir type. The interfacial bonding between GPS and aluminium is mainly covalent at low solution concentrations. At higher concentrations (greater than 4.5 × 10^?4 M) all the sites for the covalent bond formation appear to be occupied while these for the acid-base interaction are still available and then become fully occupied at solution concentrations of 4.5 × 10^?2 M and above.     

Interaction of Cetrimide with Nonionic Surfactants—Triton X-100 and Brij-35: A Conductometric and Tensiometric Study

Conductometric and surface tension techniques were employed to study the different mole fractions of nonionic surfactants (TX-100 and Brij-35) with cetrimide. The standard Gibbs energies of micellization (\(\Delta G_{\text{m}}^{0}\)) and the Gibbs energies of transfer (\(\Delta G_{\text{trans}}^{0}\)) in the mixture of surfactants were also calculated; the micellization becomes more spontaneous on increasing the amount of nonionic surfactants in the mixture. It was observed that the values of excess surface concentration (Γ_max) in surfactant mixtures decrease in comparison to the pure surfactants but the values of minimum area per surfactant molecule (A _min) increase in surfactant mixtures than in the pure ones. It was also observed that the values of the interaction parameter (β) are negative at all mole fractions. A gradual decrease in β with temperature is observed indicating the synergism between the two components and is attributed to the decrease in the electrostatic repulsion between the charged heads of the cationic surfactant as the nonionic surfactant is being intercalated into the micelle. The activity coefficients were found out to be less than unity confirming nonideality of the system and the negative values of excess free energy of mixing confirm that the mixed micelles formed were stable.     

Repletion of n-3 Fatty Acid Deficient Dams with α-Linolenic Acid: Effects on Fetal Brain and Liver Fatty Acid Composition

Docosahexaenoic acid (DHA) supply to the fetal brain depends upon the dam’s dietary intake of n-3 fats. In this study, we measured the incorporation of DHA into the fetal brain and liver in n-3 fatty acid deficient (0.1% alpha-linolenate) mice upon switching to an n-3 fatty acid adequate (2.1% alpha-linolenate) diet. Second generation mice raised and maintained on an n-3 deficient diet during mating were switched to an n-3 adequate diet on embryonic day 1 (ED 1) or ED 13. Fatty acid analysis was performed on fetal brains and livers and on maternal serum on ED 13, 15, 17, and 19. Although fetal brain and liver DHA began at a very low level (both exhibited an 85% decline), recovery was nearly complete by ED 15 in the group switched near conception but thereafter diverged. The maternal serum and fetal liver were very similar in their DHA and docosapentaenoic acid time courses. However, when repletion began on ED 13, brain DHA recovery was only about 44%. These results suggest that a nutritional intervention with alpha-linolenic acid can nearly but incompletely rescue the mouse fetal DHA deficiency if began at the time of conception but that the third trimester is too late, thus leaving a large DHA gap.     

Polymer Nanocomposites Containing N-Trimellitylimido-L-phenylalanine Dicarboxylic Acid Moieties Reinforced with α-Al2O3 Nanoparticles Modified with Citric Acid: Synthesis and Characterization

In field of nanotechnology, polymer based nanocomposites (NCs) with inorganic nanoparticles (NPs) have become a noticeable area of recent researches. In this work, citric acid (CA) was used as a biocompatible “modifier” for the alumina (α-Al₂O₃) NPs to prevent their agglomeration and create effective interaction with polymer matrix. In addition, chiral poly(amide-imide) (PAI) was synthesized by a direct polycondensation of N-trimellitylimido-L-phenylalanine dicarboxylic acid and 1,5-naphthalenediamine in ionic liquid as green solvent. Then modified (α-Al₂O₃-CA) NPs were incorporated into the obtained PAI through ultrasonic process for the preparation of PAI/α-Al₂O₃-CA NCs. Finally, the PAI/α-Al₂O₃-CA NCs were characterized by different methods.     

Effect of Stapling Architecture on Physiochemical Properties and Cell Permeability of Stapled α-Helical Peptides: A Comparative Study

Stapled peptides have emerged as a new class of targeting molecules with high binding affinity and specificity for intracellular undruggable targets. Their ability to penetrate cell membranes is exceptionally intriguing but remains elusively and controversially discussed. To understand the effect of stapling architectures on their physiochemical properties and to aid in promoting their cell permeability, we report herein a comparative study on the physiochemical properties and cell permeability of stapled α-helical peptides with different types of crosslinks. We highlight the decisive impact of the intrinsic properties of the crosslinks on cell permeability rather than the helical contents of the peptides in model amphipathic sequences targeting estrogen receptor–coactivator interaction. We envision this finding to shed further light on the chemical optimization of stapled α-helical peptides or macrocyclic cell-penetrating peptides for enhanced cell penetration.     

Autoxidation of Conjugated Linoleic Acid Methyl Ester in the Presence of α-Tocopherol: The Hydroperoxide Pathway

Autoxidation of conjugated linoleic acid (CLA) methyl ester follows at least partly Farmer's hydroperoxide theory. A mechanism for this hydroperoxide pathway has been proposed based on autoxidation of 9-cis,11-trans-CLA methyl ester. This investigation aims at confirming and further clarifying the mechanism by analyzing the hydroperoxides produced from 10-trans,12-cis-CLA methyl ester and by theoretical calculations. Five methyl hydroxyoctadecadienoates were isolated by HPLC and characterized by UV, GC-MS, and 1D- and 2D-NMR techniques. In addition, an HPLC method for the separation of the intact hydroperoxides was developed. The autoxidation of 10-trans,12-cis-CLA methyl ester in the presence of high amount of alpha-tocopherol (20%) was diastereoselective in favor of one geometric isomer, namely Me 9-OOH-10t,12c, and produced new positional isomers 10- and 14-hydroperoxides (Me 10-OOH-11t,13t; Me 14-OOH-10t,12c; and Me 14-OOH-10t,12t). Importantly, one of these new isomers, which was characterized as an intact hydroperoxide, had an unusual cis,trans geometry where the cis double bond is adjacent to the hydroperoxyl-bearing methine carbon. Further insight to the mechanism was provided by calculating the relative energies for different conformations of the precursor lipid, the allylic carbon-hydrogen bond dissociation enthalpies, and the spin distributions on the intermediate pentadienyl radicals. As a result, a better understanding of the isomeric distribution of the product hydroperoxides was achieved and a modified mechanism that accounts for these calculations is presented.     

Cationic Micelles Modulated in the Presence of α,ω-Alkanediols: A SANS,NMR and Conductometric Study

The solution behavior of a typical cationic surfactant, tetradecyltrimethylammonium bromide, in mixed solvent systems composed of water and varying concentrations of α,ω-alkanediols; 1,2-ethanediol (ED), 1,4-butanediol (BD), 1,6-hexanediol (HD) and 1,8-octanediol (OD) was examined via electrical conductance measurements, ¹³C-NMR spectroscopy and small angle neutron scattering (SANS) measurements. The critical micelle concentration (CMC) values and degree of counterion dissociation (α) indicate that both ED and BD oppose micellization, whereas HD and OD enhance micelle formation. Changes in the ¹³C-NMR chemical shifts (∆δ values) reveal that the short chain diols reside almost exclusively in the bulk phase and hence, affect the formation of micelles by altering the solvent properties in the bulk of the solution, whereas HD and OD partition between the pseudomicellar phase and the bulk phase. SANS studies indicated that both the micellar size and aggregation number (N _agg) decrease in the presence of all diols. ED and BD behave like cosolvents and increase the α and CMC values and decrease N _agg. We note that the effect of HD and OD on the properties of the micelles is concentration dependent; at low concentrations, these diols interact with the micelles and behave as cosurfactants (as evidenced by the trends in the micellar properties), while at higher concentrations, they enhance the surfactant solubility and behave as a cosolvent.     

Synthesis,Characterization, and Micellization Behavior of Cationic Surfactants: n-Alkyl-3-Methylpyridinium Bromides and Their Drug Interaction Study by UV–Visible Spectroscopy and Conductometry

The synthesis of new cationic surfactants i.e., n-hexyl-3-methylpyridium bromide ( a ) and n-octyl-3-methylpyridium bromide ( b ), and their characterization using multinuclear nuclear magnetic resonance spectroscopy (NMR) (¹H, ¹³C) and Fourier-transform infrared spectroscopy (FT-IR) spectroscopic techniques were reported. The micellization behavior of the synthesized surfactants was studied using conductometry and ultraviolet–Visible spectroscopy. The critical micelle concentration (CMC) of compounds a and b was found to be 0.41 and 0.35 m mol L⁻¹, respectively. The effect of temperature on the CMC of these compounds was examined in the range of 298–318 K and thermodynamic parameters (ΔG, ΔH, and ΔS) of the micellization process were calculated. The antibacterial study of the synthesized surfactants revealed their strong activity against different bacterial strains. Moreover, the interaction of drugs i.e., flurbiprofen and ketoprofen, with the synthesized surfactants was investigated for gaining insights into the role of micelles as drug-delivery devices. Drug–surfactant interactions were also confirmed via a conductometric method.     

Large-scale precipitation synthesis of α-alumina with poly aluminum chloride: Optimization of synthesis parameters

α-Alumina production has been industrialized since many years ago. Nevertheless, there are still challenges in the efficient synthesis of α-alumina with subtle specifications for high-tech applications, specifically on large scales. So, here, we investigated the large-scale synthesis of α-alumina by the precipitation method and with industrial grade poly aluminum chloride (PAC) as the aluminum precursor, for the first time. The synthesis procedure was optimized in terms of synthesis yield and facilitation of α-alumina formation by adjusting the concentration of the precursor (PAC) and precipitant (NaOH) solutions. The samples were characterized by conducting several analyses, including X-ray diffraction, X-ray fluorescence, field emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, dynamic light scattering, and gas adsorption. The results indicated the significant effects of PAC and NaOH concentrations on the synthesis yield and facilitation of the α-alumina formation. According to the results and process considerations, working at higher levels of PAC (.75 g/ml) and NaOH (1.0 M) concentrations was found to be the optimum synthesis conditions. Moreover, the potential of the optimized sample as the abrasive material and the catalyst support was evaluated. The results confirmed the high potential of the optimized sample in these applications. This study therefore introduces a promising and cost-effective method for the large-scale synthesis of versatile α-alumina.     

Competitive Binding of Off-Flavor Compounds with Soy Protein and β-Cyclodextrin in a Ternary System: A Model Study

Removal of soy protein (SP)-bound 2-nonanone by β-cyclodextrin (βCD) was studied using an equilibrium dialysis technique. It was observed that in the presence of βCD, a significant (p < 0.05) amount of SP-bound 2-nonanone could be removed in a concentration-dependent manner. Up to 94% of SP-bound 2-nonanone was stripped from SP when 6 mM βCD was present in the system. However, in thermodynamic terms, the net standard free energy change for transfer of 2-nonanone from SP to βCD, i.e., \( \Updelta \Updelta G^\circ_{{{\text{SP}} \to \beta {\text{CD}}}} \), was essentially zero, implying that the apparent equilibrium binding constant for the formation of βCD–2-nonanone complex was essentially same as that for the SP–2-nonanone complex formation in the ternary system. This indicated that stripping-off of 2-nonanone from SP by βCD was driven by the mass action ratio. Based on these results, it is shown that βCD can be used effectively for removing SP-bound off-flavor carbonyl compounds.     

Sintering behavior of ZrB2–SiC composites doped with Si3N4: A fractographical approach

ZrB₂–SiC composite ceramics were doped with 0, 1, 3 and 5 wt% Si₃N₄ plus 1.6 wt% carbon (pyrolized phenolic resin) as sintering aids and fabricated by hot pressing process under a relatively low pressure of 10 MPa at 1900 °C for 2 h. For a comparative study, similar ceramic compositions were also prepared by pressureless sintering route in the same processing conditions, with no applied external pressure. The effect of silicon nitride dopant on the microstructural evolution and sintering process of such ceramic composites was investigated by a fractographical approach as well as a thermodynamical analysis. The relative density increased by the addition of Si₃N₄ in hot pressed samples as a fully dense composite was achieved by adding 5 wt% silicon nitride. A reverse trend was observed in pressureless sintered composites and the relative density values decreased by further addition of Si₃N₄, due to the formation of gaseous products which resulted in the entrapment of more porosities in the final structure. The formation of ZrC phases in pressureless sintered samples and layered BN structures in hot pressed ceramics was detected by HRXRD method and discussed by fractographical SEM-EDS as well as thermodynamical analyses.     

A Study of the Acid–Base Properties of Melts in the Na2O–B2O3–SiO2System: I. Composition Joins with a Na2O Content of Less Than 20 mol %

Three composition joins in the Na₂O–B₂O₃–SiO₂system at constant Na₂O contents of 5, 10, and 15 mol % are studied by the high-temperature method of determining oxygen ion exponents pO for oxide melts. It is found that the basicity of melts increases in going from the binary sodium borate system to the sodium silicate system. The acid–base properties of ternary melts are simulated under the assumption that their basicity is determined by the interaction in pseudobinary systems. It is shown that the basicity of the studied melts is governed, to a large extent, by the formation of the Na₂O · B₂O₃· 2SiO₂ternary compound.     

Extraction and Separation of α-lactalbumin and β-Lactoglobulin from Skim Milk by Microfiltration and Ultrafiltration at High Shear Rates: A Feasibility Study

Abstract

This paper presents a two-stage membrane filtration process for extracting and separating α-Lactalbumin (α-La) and β-Lactoglobulin (β-Lg), from UHT skim milk, using dynamic filtration. The 1st stage separates casein micelles in retentate from whey proteins in the permeate with rotating 0.2 µm pores ceramic membrane disks. Casein micelles rejection was excellent, while α-La and β-Lg transmissions remained between 80 and 90%. The permeate flux at 40°C ranged from 105 to 40 Lh^?1m^?2 at a volume reduction ratio of VRR = 4. The 2nd stage consisted of ultrafiltration of the previous permeate with a metal disk rotating at 2000 rpm near a fixed 50 kDa PES membrane, in order to concentrate β-Lg in retentate, while collecting α-La in the permeate. The flux dropped from 270 Lh^?1m^?2 at VRR = 1, and remained nearly constant at 200 Lh^?1m^?2 until a VRR of 3.3. α-La transmission increased with VRR to reach 23% at VRR = 3.3, while β-Lg transmission decayed at increasing VRR to 3%, to give a maximum selectivity of 8.     

Life Cycle Analysis: Assessment of Technologies for Droplet Separation – A Case Study

For the assessment of separation technologies from an ecological and economic perspective, a case study was performed to investigate the influence of entrainment on energy and resource demand of a single apparatus and on a single production process. Taking the example of the Rectisol process, the influence of droplet entrainment on individual separation equipment as well as on the process as a whole was identified via flowsheet simulation. Based on the calculated mass and energy balances, an LCA and LCC approach was used for the quantification of the entrainment influence.