New Atom/Group Volume Additivity Method to Compensate for the Impact of Strong Hydrogen Bonding on Densities of Energetic Materials

2008 ◽  
Vol 53 (2) ◽  
pp. 520-524 ◽  
Author(s):  
Chengfeng Ye ◽  
Jean’ne M. Shreeve
Keyword(s):  
Hydrogen Bonding ◽  
Energetic Materials ◽  
Atom Group ◽  
The Impact

scholarly journals Small Changes: Using Assessment to Direct Instructional Practices in Large-Enrollment Biochemistry Courses

2017 ◽  
Vol 16 (1) ◽  
pp. ar7 ◽  
Author(s):  
Xiaoying Xu ◽  
Jennifer E. Lewis ◽  
Jennifer Loertscher ◽  
Vicky Minderhout ◽  
Heather L. Tienson
Keyword(s):  
Hydrogen Bonding ◽  
Student Performance ◽  
Bond Energy ◽  
Multiple Choice ◽  
Instructional Interventions ◽  
Student Responses ◽  
Large Classes ◽  
Instructional Effect ◽  
Large Enrollment ◽  
The Impact

Multiple-choice assessments provide a straightforward way for instructors of large classes to collect data related to student understanding of key concepts at the beginning and end of a course. By tracking student performance over time, instructors receive formative feedback about their teaching and can assess the impact of instructional changes. The evidence of instructional effectiveness can in turn inform future instruction, and vice versa. In this study, we analyzed student responses on an optimized pretest and posttest administered during four different quarters in a large-enrollment biochemistry course. Student performance and the effect of instructional interventions related to three fundamental concepts—hydrogen bonding, bond energy, and pKa—were analyzed. After instructional interventions, a larger proportion of students demonstrated knowledge of these concepts compared with data collected before instructional interventions. Student responses trended from inconsistent to consistent and from incorrect to correct. The instructional effect was particularly remarkable for the later three quarters related to hydrogen bonding and bond energy. This study supports the use of multiple-choice instruments to assess the effectiveness of instructional interventions, especially in large classes, by providing instructors with quick and reliable feedback on student knowledge of each specific fundamental concept.

Evaluation of thermal and physical properties of PMMA/PMVEMA-ES blends as organic coating

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Shameer Hisham ◽  
Hairul Anuar Tajuddin ◽  
Norazilawati Muhamad Sarih ◽  
Nur Zarith Diana Diana Zakaria ◽  
Zul Hazrin Zainal Abidin ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Physical Properties ◽  
Organic Coating ◽  
Adhesion Property ◽  
Intermolecular Hydrogen Bonding ◽  
Scanning Calorimetry ◽  
Adhesion Promoter ◽  
Adhesion Properties ◽  
Content Type ◽  
The Impact

Purpose In this work, the blends of poly(methyl methacrylate), PMMA and poly(methyl vinyl ether-alt-maleic acid monoethyl ester), PMVEMA-ES are studied as organic coatings to evaluate the impact of intermolecular hydrogen bonding on the physical and thermal characteristics of the prepared coatings. Design/methodology/approach PMMA (Mw = 120,000 g mol-1) was chosen as our binder material. Due to the low adhesion property of PMMA on polar substrates, it was blended with PMVEMA-ES, which contains polar –COOH groups, to improve the adhesion and thermal properties of the coatings by forming intermolecular hydrogen bonds. A cross-hatch adhesion test was carried out to evaluate the adhesion strength of different ratios of PMMA/PMVEMA-ES blends as coatings. In addition, changes in the glass-transition temperature, Tg as the composition varies were studied using Differential Scanning Calorimetry, DSC. Then, glossiness and hiding power tests were also conducted to evaluate the physical properties of the prepared coatings. Findings Upon a closer look at the DSC results, it was found that blends consisting of 12.5, 25.0 and 87.5 wt. % PMMA were completely compatible due to the presence of only a single Tg in their thermograms. Other blend compositions showed two distinct Tgs, indicating partial compatibility. Furthermore, the addition of PMVEMA-ES caused the Tg of PMMA to shift to lower temperatures, a strong indication of intermolecular hydrogen bonding interactions between the two components. From the cross-hatch adhesion results, the addition of PMVEMA-ES improved the adhesion properties of PMMA coating, except for blends consisting of 62.5 and 75.0 wt. % PMMA possibly due to the partial incompatibility between the two components. These findings were further corroborated with the results of glossiness and hiding power measurements. The superior result was seen for the blend consisting of 12.5 wt. % PMMA with strong adhesion property, high glossiness, compatibility and high translucency. Practical implications PMVEMA-ES can potentially be used as an adhesion promoter in PMMA-based coating formulations. Originality/value This is the first report on the properties of PMMA/PMVEMA-ES blends as coatings.

scholarly journals Selectivity of tungsten mediated dinitrogen splitting vs. proton reduction

2019 ◽  
Vol 10 (44) ◽  
pp. 10275-10282 ◽  
Author(s):  
Bastian Schluschaß ◽  
Josh Abbenseth ◽  
Serhiy Demeshko ◽  
Markus Finger ◽  
Alicja Franke ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Hydrogen Evolution ◽  
Computational Results ◽  
Reaction Conditions ◽  
Proton Reduction ◽  
Reaction Selectivity ◽  
The Impact

An N2-bridged ditungsten complex is presented that undergoes N2-splitting or hydrogen evolution upon protonation depending on the acid and reaction conditions. Spectroscopic, kinetic and computational results emphasize the impact of hydrogen bonding on the reaction selectivity.

The impact on the ring related vibrational frequencies of pyridine of hydrogen bonds with haloforms – a topology perspective

2019 ◽  
Vol 21 (4) ◽  
pp. 1724-1736 ◽  
Author(s):  
Enrico Benassi ◽  
Kamila Akhmetova ◽  
Haiyan Fan
Keyword(s):  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Ring Structure ◽  
Vibrational Frequencies ◽  
Bonding System ◽  
Hydrogen Bonding System ◽  
The Impact

An intermolecular ring structure is identified for the hydrogen bonding system of pyridine and haloforms.

scholarly journals Experimental Study on the Energy-Release Characteristics of Fine-Grained Fe/Al Energetic Jets under Impact Loading

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3317
Author(s):  
Li ◽  
Du
Keyword(s):  
Experimental Data ◽  
Energy Release ◽  
Impact Energy ◽  
Impact Loading ◽  
Energetic Materials ◽  
Chemical Properties ◽  
Microscopic Analysis ◽  
Specific Content ◽  
Fine Grained ◽  
The Impact

The energy released by the active metal phase in fine-grained Fe/Al energetic materials enables the replacement of conventional materials in new types of weapons. This paper describes an experiment designed to study the energy-release characteristics of fine-grained Fe/Al energetic jets under impact loading. By means of dynamic mechanical properties analysis, the physical and chemical properties of Fe/Al energetic materials with specific content are studied, and the preparation process is determined. The energy-release properties of fine-grained Fe/Al jets subject to different impact conditions are studied based on experimental data, and energy-release differences are discussed. The results show that for fine-grained Fe/Al energetic materials to remain active and exhibit high strength, the highest sintering temperature is 550 °C. With increasing impact energy, the energy release of fine-grained Fe/Al energetic jets increases. At an impact-energy threshold of 121.1 J/mm2, the chemical reaction of the fine-grained Fe/Al energetic jets is saturated. The experimental data and microscopic analysis show that when the impact energy reaches the threshold, the energy efficiency ratio of Fe/Al energetic jets can reach 95.3%.

Polyamino-Substituted Guanyl-Triazole Dinitramide Salts with Extensive Hydrogen Bonding: Synthesis and Properties as New Energetic Materials

2008 ◽  
Vol 20 (19) ◽  
pp. 6176-6182 ◽  
Author(s):  
Zhuo Zeng ◽  
Ruihu Wang ◽  
Brendan Twamley ◽  
Damon A. Parrish ◽  
Jean’ne M. Shreeve
Keyword(s):  
Hydrogen Bonding ◽  
Energetic Materials ◽  
Dinitramide Salts

Design of task-specific fluorinated ionic liquids: nanosegregation versus hydrogen-bonding ability in aqueous solutions

2018 ◽  
Vol 54 (28) ◽  
pp. 3524-3527 ◽  
Author(s):  
Joana C. Bastos ◽  
Sara F. Carvalho ◽  
Tom Welton ◽  
José N. Canongia Lopes ◽  
Luís Paulo N. Rebelo ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Ionic Liquids ◽  
Aqueous Solutions ◽  
The Impact

Fluorinated ionic liquids rich-nanosegregated behaviour reduces the impact of the addition of water upon the ionic liquids's H-bond acceptance ability.

scholarly journals The Impacts of Various Media on the Electronic Spectrum of Aniline Violet

2021 ◽  
Vol 2 (24) ◽  
pp. 28-55
Author(s):  
Sokaina Hemdan ◽  
◽  
Asma Al Jebaly ◽  
Fatma Ali
Keyword(s):  
Hydrogen Bonding ◽  
Absorption Band ◽  
Dissociation Constant ◽  
Relative Permittivity ◽  
Spectral Characteristics ◽  
Solvent Polarity ◽  
Isosbestic Point ◽  
Solvent Interactions ◽  
Solvent Parameters ◽  
The Impact

The solvent impact can be decided by Solvent polarity scales, a solvatochromic parameter that has a distinctive position of UV-Visible absorption band within the extend between 250 and 700 nm. The spectral characteristics of Aniline Violet in several solvents at room temperature were analyzed which is that the point of considering the impact of solvents on the absorption spectra of this cationic dye in organic solvent of distinctive characters. The solvent impacts on the wavenumber of the absorption band maxima (max) were talked about utilizing the taking after solvent parameters, refractive index, n, relative permittivity, ε and therefore the empirical solvent polarity ET (30), (*,  and ) and (SA, SB, SP and SPd). The solute–solvent interactions were decided on the premise of multilinear solvation energy relationships concept. The fitting coefficients gotten from this analysis allowed us to estimate the contribution of each type of interactions to the total spectral shifts in solution. The set up dependences between max and the solvent parameters emphasize that the visible band of the examined molecule is influenced by both non-specific and specific solute–solvent interactions. The results appeared the solvent polarizability has major impact on the spectral shift instead of hydrogen bonding accepting ability. Catalan strategy show higher acceptable correlation than Kamlet-Taft methodology and Katritzky methodology. The dissociation constant pKa and the isosbestic point of the explored compound were shown the presence of the individual predominate ionic species was assigned by constructing distribution charts at diverse pH ranges. The results showed that the relative permittivity constant, ε, is important factor affecting on the magnitude of the dissociation constant beside the hydrogen bonding of the solvent.

scholarly journals The Role of Surfactant Force Field on the Properties of Liquid/Liquid Interfaces

2019 ◽  
Author(s):  
Michael Servis ◽  
Alex McCue ◽  
Amanda Casella ◽  
Aurora Clark
Keyword(s):  
Hydrogen Bonding ◽  
Thermodynamic Properties ◽  
Force Field ◽  
Driving Forces ◽  
Dynamic Properties ◽  
Dynamics Simulation ◽  
Liquid Interfaces ◽  
Force Field Parameters ◽  
Organizational Patterns ◽  
The Impact

Surfactant-laden liquid/liquid interfaces mediate numerous chemical processes, from commercial applications of microemulsions to chemical separations. Classical molecular dynamics simulation is a prevalent method for studying microscopic and thermodynamic properties of such interfaces. However, the extent to which these features can be reliably predicted, and the variations in predicted behavior, depend upon the force field parameters employed. At present, the impact of force fields upon simulated properties is relatively understudied. Yet recent advances to sampling and analysis algorithms are increasing the interpretation of simulation data and therefore understanding force field dependence is increasingly relevant. In this study, the impact of the force field of the surfactant tri-n-butyl phosphate (TBP), as well as that of water, is investigated at a water/(n-hexane + surfactant) interface. Empirical charge scaling was employed to modulate the hydrophilicity of the surfactant. As anticipated, the relative hydrophilicity of TBP influences a number of properties, including the adsorbed concentrations of TBP at the interface, and macroscopic properties that result from hydrogen bonding interactions, such as interfacial tension and width. The dynamic properties of solvents at the interface are strongly modulated by the variation in hydrogen bond strength caused by different charge scaling of the TBP model. This includes the residence times of water at the interface, where stronger water-TBP hydrogen bonding causes long-lived residences. Interestingly, there are a number of features that are relatively insensitive to the TBP hydrophilicity. In one important case, the concentration of water-bridged TBP dimers was only impacted for the least hydrophilic model. As these dimeric species are the building block of surface protrusions that lead to water transport across the interface, this implies that collective organizational patterns and surface structures that derive from multiple driving forces (e.g. TBP hydrophilicity and organic solvent free energies of solvation) are less sensitive to individual force field parameters. Further, we note that competitive interactions can "cancel" the effects of changing TBP charge on interfacial properties. One example is the orientation and hydrogen bonding structure of interfacial water, where the direct TBP-water hydrogen bonding competes against the indirect TBP-induced interfacial roughness. In combination, these observations may assist future simulation studies in calibrating surfactant models to, or interpreting results of, a broad range of dynamic, structural and thermodynamic properties.

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