Simple Bond Research Articles

Shear behavior model for steel fiber-reinforced concrete members without transverse reinforcements

Due to the complex shear mechanism of steel fiber-reinforced concrete (SFRC) members, there is lack of comprehensive shear behavior models for SFRC members. The shear behavior model, based on a smeared crack model, requires the tensile stress–strain constitutive equation of SFRC membrane subjected to biaxial stresses. After SFRC panel tests under biaxial stresses were recently conducted, it has been possible to create a more complete smeared crack model for estimating the shear behavior of SFRC members. It is, however, very difficult to conduct such experiments for different types of steel fibers, various amount of steel fibers, different ranges of concrete strengths, etc. Thus, in this study, steel fibers are modeled as average direct tensile contribution elements in a modified smeared crack truss model, considering directionality and distribution of fibers. In this way, only simple bond tests are required to reflect the effects of different characteristics of SFRC. In addition, the shear contribution of steel fibers can be obtained considering the bond failure of steel fibers. The proposed model was compared to the test results of 8 SFRC panels and 80 SFRC beams, and the shear behavior of the SFRC members was well estimated.

“Leading from the Middle,” and Other Contrarian Essays on Library Leadership (review)

Reviewed by: “Leading from the Middle,” and Other Contrarian Essays on Library Leadership Dennis T. Clark “Leading from the Middle,” and Other Contrarian Essays on Library Leadership, John Lubans, Jr. Santa Barbara: Libraries Unlimited, 2010. 298p. $50 (ISBN 978-1- 59884-577-8). Seasoned library administrator, experienced library school professor, and eminently readable commentator on the library profession, John Lubans, Jr., possesses a [End Page 1008] perspective on leadership in the library profession unique among authors of administration and management manuals. “Leading from the Middle” embodies his unique perspective in three specific ways. First, Lubans differentiates throughout the book between administration and leadership. Leadership (and “followership,” he would add) is or should be a significant factor for change at any level in an organization. Second, his focus on contrarian leadership, using change as a leadership goal, differs vastly from the rash of recently published library administration texts that typically focus on the process of management. The third significant difference is his reach outside of libraries and higher education to other industries (airlines, classical music, sports) to find wisdom that pertains to libraries. The book primarily comprises revised columns from Library Administration and Management during the period 2000 to 2009. Lubans shapes the thirty-six columns around four themes that library leaders know well: Leadership, Leaders, Coaching, and Techniques. The columns on leadership encourage librarians to lead in different ways—in self-directed teams, for example—not typically associated with academic libraries or higher education in general. The chapters on leaders are often case studies—more like thoughtful portraits— of leaders like Herbert Kelleher of Southwest Airlines; Simone Young, the orchestra conductor; and Saul Zabar, the food impresario, that focus on their soft leadership skills. Kelleher is hailed as an ethical CEO, Young as a collaborative, though demanding, musician, and Zabar as the “head of a family.” (p. 106) The theme of coaching and collaboration highlights the opportunity for library organizations to become increasingly self-managed in order to meet an evolving information landscape. Leaning on lessons learned from travels, conferences, and adventure courses, Lubans uses these chapters to challenge the reader to look in unexpected and unusual places for leadership and management lessons. In one chapter, Lubans uses concepts such as the Aboriginal model of ownership and Adam Smith’s writings on morality to question library fines (p. 159). The final section, on Techniques, requires less reach and advises more direct action. Chapters dealing with customer service, evaluations, and “mess finding” give readers a practical set of articles to immediately digest and apply, with Lubans’ easy-reading style encouraging quick engagement. A simple bond holds these chapters together. Lubans has constantly searched for leaders in institutions and non-traditional cultural settings, mostly outside the library rather than within, who create and support positive and affirming change in their respective communities. He brings these narratives to life in a witty, self-effacing way. Lubans has crafted an excellent primer on embracing organizational change in libraries. Librarians of all stripes are encouraged to read these essays. Dennis T. Clark Virginia Commonwealth University dtclark@vcu.edu Copyright © 2011 The Johns Hopkins University Press

Fragmentation of valine and proline in resonant free electron capture reactions

The processes of resonant electron capture by molecules of valine and proline were studied. The main dissociative decay channels of molecular ions and the structures of fragment ions were established. The reactions of simple bond cleavage and H-shift rearrangement processes were revealed. The dissociative electron attachment cross-sections for [M - H]− ions were measured in the region of 1.25 eV. The metastable decay of [M - H]− ions were found in the energy region of 4.5–8 eV. The structures of decomposing parent ions were determined using the statistical model of metastable fragmentation.

A study of morphological patterns of lip prints in relation to gender of North Indian population

Establishing a person's identity is a very important process in civil and criminal cases. Dental, fingerprint and DNA comparisons are probably the most common techniques allowing fast and secure identification processes. However, in certain circumstances related to the scene of the crime or due to lack of experienced personnel, these techniques might be unavailable; so there is still an increasing need for reliable alternative methods of establishing identity. The objective of the study was to check for any peculiar lip patterns in relation to the sex of the individual and determine the most common lip patterns in the given population. This study was conducted on 150 subjects, which included 75 males and 75 females, in the age group of 18-30 years. After applying lipstick evenly, the lip print of each subject was obtained on a simple bond paper by a researcher, and later the lip print was then analyzed and interpreted. The intersected type was most commonly seen in females and branched in males. Reticular pattern was the least common type in both males and females. This study shows that the lip prints are unique to an individual and behold the potential for recognition of the sex of an individual.

Aromaticity in heterocycles: new HOMA index parametrization

A new parametrization for the Harmonic Oscillator Model of Aromaticity (HOMA) index to deter- mine aromaticity of heterocycles is introduced. The new HOMA for Heterocycle Electron Delocalization (HOM- HED) is based on the experimental data from electron diffraction X-ray for the reference molecules used to esti- mate the simple, double, and optimal bond lengths. Bond length of ''pure'' single and double bonds of non-conju- gated systems or systems without p-electrons and/or n-electron delocalization were considered. The HOMHED index was determined for a series of five and six hetero- cycles with C-C, C-N, C-O, C-S, N-N, N-O, and N-S bonds. The p-electron delocalization of these heterocycles was determined by Krygowski-reformulated HOMA and HOMHED and it was proved that HOMHED worked in line with HOMA for all heterocycles, except those con- taining oxygen, which were found to be weak aromatic from Krygowski rHOMA calculations.

Synthesis and evaluation of cytotoxic effects of hanultarin and its derivatives

One of the known cytotoxic lignans is (-)-1-O-feruloyl-secoisolariciresinol designated as hanultarin, which was isolated from the seeds of Trichosanthes kirilowii. In this Letter, we described the first synthesis of 1-O-feruloyl-secoisolariciresinol, 1,4-O-diferuloyl-secoisolariceresinol and their analogues. The cytotoxicities of these compounds were evaluated against several cancer cell lines. Interestingly, we found that the feruloyl diester derivative of secoisolariciresinol was the most active cytotoxic compound against all the cancer cells tested in this experiment. The IC(50) values of the1,4-O-diferuloyl-secoisolariceresinol were in the range of 7.1-9.8μM except one cell line. In considering that both ferulic acid and secoisolariciresinol are commonly found in many plants and have no cytotoxicity, this finding is remarkable in that simple covalent bonds between the ferulic acid and secoisolariciresinol cause a cytotoxic effect.

Overlapping Length and Lifetime Influence on Load of Simple Over-lapped Adhesive Bond

Výrobni proces je V jednotlivých průmyslových odvětvich různorodý, ma vsak obvykle jeden spolecný prvek a tim je spojovani materialu. Na zakladě analýz výrobni sfery je moţno konstatovat, ţe nejrozsiřenějsi aplikaci technologie lepeni jsou jednoduse přeplatovane lepene spoje, kterým se věnuje I výzkum zveřejněni V tomto clanku. Hodnocen byl vliv delky přeplatovani a ţivotnosti lepe-neho spoje po dobu 1000 dni. Výsledky stanovuji optimalni kriterium konstrukcniho tvaru spoje tj. vliv delky přeplatovani a jednotkove naklady vztaţena na pořizeni lepidla.

Enhanced bonding between YSZ surfaces using a gas‐phase fluorination pretreatment

The present investigation focuses on the surface modification, via gas-phase fluorination process, of yttria- stabilized zirconia (YSZ) to increase its wettability and chemical bonding directly to acrylate-based resin cements. YSZ plates and cylinders, as-received and roughened, were pretreated in a fluorine containing plasma and bonded with a commercially available resin cement for simple shear bond adhesion testing. No organo-silane coupling agent was used to enhance bonding between the two substrates. Shear bond tests revealed that bond strength increased with fluorination time. Furthermore, the pretreated, as received (nonroughened) specimen group displayed relatively high bond strengths suggesting surface reactivity and direct chemical bonding with the resin cement. X-ray photoelectron spectroscopy analysis revealed the surface conversion layer to be a mixture of phases; zirconium oxyfluoride, zirconium fluoride, and yttrium fluoride. It is hypothesized that these fluoride and oxyfluoride phases have the potential to increase surface hydroxylation, enabling direct covalent bonding between YSZ and resin cement. It is believed that this surface treatment has broad reaching impact when using high-strength ceramics in a multitude of bioapplications.

A Brief Synthesis of (−)-Englerin A

Englerins A and B are guaiane sesquiterpenes that were isolated from the bark of Phyllanthus engleri, a plant indigenous to east Africa. The englerins consist of a 5-6-5 fused tricyclic structure with an ether bridge and two ester-bearing stereogenic centers, including a highly unusual glycolate residue. Englerin A is a potent and selective inhibitor of the growth of six human renal cancer cell lines. We report herein an efficient, eight-step synthesis of englerin A that leverages simple carbonyl-enabled carbon-carbon bond formations. Our route is amenable to the production of a diverse series of analogues for structure-function studies and determination of the mode of action of these natural products.

Modeling DNA response to terahertz radiation

Collective response of DNA to terahertz electric fields is studied in a simple pair bond model. We confirm, with some caveats, a previous observation of destabilizing DNA breather modes and explore the parameter dependence of these modes. It is shown that breather modes are eliminated under reasonable physical conditions and that thermal effects are significant.

Thermal Decomposition of 2-Butanol as a Potential Nonfossil Fuel: A Computational Study

The thermochemistry and kinetics of the pyrolysis of 2-butanol have been conducted using ab initio methods (CBS-QB3 and CCSD(T)) and density functional theory (DFT). The enthalpies of formation and bond dissociation energies of some alcohols including 2-butanol and its derived radicals have been calculated. A variety of simple and complex dissociations have been examined. The results indicated that dehydration to 1- and 2-butene through four-center transition states is the most dominant channel at low to moderate temperatures (T ≤ 700 K), where formation of butenes is kinetically and thermodynamically more favorable than other complex and simple bond scission reactions. Although the C-C bond fission channels require more energy than needed for some complex decomposition reactions, the former pathways predominate at higher temperatures (T ≥ 800 K) due to the higher values of the pre-exponential factors. The progress of the complex decomposition reactions has been followed through intrinsic reaction coordinate (IRC) calculations to understand the mechanism of transformation of 2-butanol to different products.

Scaling relationships for adsorption energies of C 2 hydrocarbons on transition metal surfaces

Using density functional theory calculations we show that the adsorption energies for C 2H x -type adsorbates on transition metal surfaces scale with each other according to a simple bond order conservation model. This observation generalizes some recently recognized adsorption energy scaling laws for AH x -type adsorbates to unsaturated hydrocarbons and establishes a coherent simplified description of saturated as well as unsaturated hydrocarbons adsorbed on transition metal surfaces. A number of potential applications are discussed. We apply the model to the dehydrogenation of ethane over pure transition metal catalysts. Comparison with the corresponding full density functional theory calculations shows excellent agreement.

Push-Pull Fluorophores Based on Imidazole-4,5-dicarbonitrile: A Comparison of Spectral Properties in Solution and Polymer Matrices

Spectral properties of novel type of fluorophores consist of a π-conjugated system end-capped with an electron-donating N,N-dimethylaminophenyl group and an electron-withdrawing imidazole-4,5-dicarbonitrile moiety were examined. An additional π-linker separating these two structural units comprises simple bond (B1P), phenyl (B2B), styryl (B3S) and ethynylphenyl (B4A) moieties. The absorption and fluorescence spectra were taken in cyclohexane, chloroform, acetonitrile, methanol and in polymer matrices such as polystyrene, poly(methyl methacrylate) and poly(vinylchloride). The longest-wavelength absorption band was observed in the range of 300 to 400 nm. Intense fluorescence with quantum yields of 0.2 to 1.0 was observed in cyclohexane, chloroform and in polymer matrices within the range of 380 to 500 nm. The fluorescence was strongly quenched in neat acetonitrile and methanol. The fluorescence lifetimes are in the range of 1-4 ns for all measured fluorophores. The large Stokes shift (4,000 to 8,000 cm(-1)) indicates a large difference in the spatial arrangement of the chromophore in the absorbing and the emitting states. The observed fluorescence of all fluorophores in chloroform was quenched by 1-oxo-2,2,6,6-tetramethyl-4-hydroxy piperidine by the diffusion-controlled bimolecular rate (cca 2 × 10(10) L mol(-1) s(-1)). Polar solvents such as acetonitrile and methanol quenched the fluorescence as well but probably via a different mechanism.

Roaming Radical Reactions

An unusual decomposition mechanism of highly vibrationally excited molecules, dubbed the “roaming mechanism”, has recently been discovered and is now an active area of investigation. In these reactions, a molecule undergoes partial dissociation to radical fragments by simple bond fission. When the fragments separate to 3−4 Å, roaming reorientation becomes feasible as the kinetic energy is low and the angular forces may be comparable to the radial forces. If this leads the system to access a distinct reactive domain, intramolecular abstraction may take place, giving molecular products with large vibrational excitation. This pathway may deviate substantially from the nominal minimum-energy path and in some cases appears to avoid the normal transition-state geometry entirely. Many of the details have come to light through high-resolution ion imaging studies of formaldehyde, in concert with quasi-classical trajectory calculations from Bowman and co-workers. Many other examples of roaming dynamics have recently been reported, both in experiment and theory. In this Perspective, we highlight key aspects of roaming reactions and point to some interesting future directions for study.

Development of a Crack Sealant Adhesion Test (CSADT) Specification for Hot-Poured Bituminous Sealants

Abstract Current crack sealant specifications utilize a simple empirical bond test [ASTM D5329, “Standard Test Methods for Sealants and Fillers, Hot-Applied, for Joints and Cracks in Asphaltic and Portland Cement Concrete Pavements”] to measure a sealant’s ability to adhere to concrete briquettes. However, no correlation exists between the results of this standard test and a sealant’s field performance. To bridge the gap between sealants’ fundamental properties and field performance, performance-based guidelines for the selection of hot-poured crack sealants have been developed. This paper proposes a new test procedure to help assess the capability of sealants to adhere to the sides of cracks in pavement. The proposed crack sealant adhesion direct tensile (CSADT) test procedure calls for the use of a direct tensile tester with modifications to the end pieces and the specimen holder. Sealant is confined between two aluminum pieces, which will move apart at 0.05 mm/s until failure occurs. Failure load and the displacement at failure are recorded and then used to assess the sealant’s adhesion capability. A crack created on one side of the assembly during specimen preparation determines the initial failure location and ensures that the failure occurs at the interface and not within the sealant. The specimen preparation is designed to simulate sealant installation, and experimental conditions have been developed to represent crack openings during pavement contraction in cold weather. The repeatability of the suggested procedure was acceptable with an average coefficient of variation of 10.9 %. No significant difference existed between two operators or between two test setups.

Development of a novel surface modification for improved bonding to zirconia

Objective This report presents a novel pretreatment technique, whereby the zirconia surface is converted to a more reactive zirconium oxyfluoride, enabling improved chemical bonding to other dental substrates via conventional silanation approaches. Methods The study leverages a novel gas-phase fluorination process that creates a thin oxyfluoride conversion layer on the surface of zirconia, making it more reactive for conventional adhesive bonding techniques. Zirconia specimens, polished and roughened, were pretreated and composite cylinders bonded using conventional adhesive techniques. All specimens were subjected to a force at a crosshead speed of 0.5 mm/min in an electro-mechanical testing device. Single-factor analysis of variance (ANOVA) at a 5% confidence level was performed for the bonding strength data. Optical microscopy and scanning electron microscopy (SEM) were used to evaluate and quantify failure surfaces. Results Shear bond strengths were analyzed using single-factor ANOVA ( p < 0.05). Mechanical testing results revealed that fluorinated zirconia specimens (both rough and polished) displayed the highest shear bond strengths as compared to other commercially available treatments. X-ray photoelectron spectroscopy analysis helped determine that this novel pretreatment created a more reactive, 2–4 nm thick oxyfluoride conversion layer with approximate stoichiometry, ZrO 3F 4. Conclusion Simple shear bond mechanical tests demonstrated that a fluorination pre-treatment is a viable method to chemically modify zirconia to produce a reactive surface for adhesive bonding.

Dissociative electron attachment to carbonyl fluoride, F 2CO

Low energy electron attachment to gas phase carbonyl fluoride, F 2CO, has been performed by means of a crossed electron-molecular beam experiment in an electron energy range from 0 to 30 eV with an energy resolution of ∼0.5 eV. The most intense signal is observed at 19 amu due to F − and two other anionic species with lower intensities at 38 and 47 amu assigned to F 2 − and COF −, respectively. Anion efficiency curves of the three anions have been measured. Product anions (F − and COF −) are observed mainly in the low energy region arising from simple bond breaking, while F 2 − is being produced from two bond cleavages with further structural and electronic rearrangement. Quantum chemical calculations on the electronic properties of F 2CO have been performed in order to complement the experimental results.

ChemInform Abstract: Magnesium‐Induced Regiospecific C‐Silylation of Suitably Substituted Enoates and Dienoates.

AbstractThe C‐silylation selectivity is very high over the reductive dimerization or simple double bond reduction.

A novel detection technique of hydrazine hydrate: modality change of hydrogen bonding-induced rapid and ultrasensitive colorimetric assay

Ultrasensitive visual detection of hydrazine hydrate using a Au nanoparticles-based colorimetric sensing system (ANCSS) is reported for the first time, which is based on the hydrogen bonding recognition and the modality change of hydrogen bonding from "linear" (simple hydrogen bond interactions) to "nonlinear" (a complicated hydrogen bond network) between as-modified Au nanoparticles (Au NPs).

Correlation between thermal conductivity and bond length alternation in carbon nanotubes: A combined reverse nonequilibrium molecular dynamics-Crystal orbital analysis

The thermal conductivity (λ) of carbon nanotubes (CNTs) with chirality indices (5,0), (10,0), (5,5), and (10,10) has been studied by reverse nonequilibrium molecular dynamics (RNEMD) simulations as a function of different bond length alternation patterns (Δr(i) ). The Δr(i) dependence of the bond force constant (k(rx) ) in the molecular dynamics force field has been modeled with the help of an electronic band structure approach. These calculations show that the Δr(i) dependence of k(rx) in tubes with not too small a diameter can be mapped by a simple linear bond length-bond order correlation. A bond length alternation with an overall reduction in the length of the nanotube causes an enhancement of λ, whereas an alternation scheme leading to an elongation of the tube is coupled to a decrease of the thermal conductivity. This effect is more pronounced in carbon nanotubes with larger diameters. The formation of a polyene-like structure in the direction of the longitudinal axis has a negligible influence on λ. A comparative analysis of the RNEMD and crystal orbital results indicates that Δr(i) -dependent modifications of λ and the electrical conductivity are uncorrelated. This behavior is in-line with a heat transfer that is not carried by electrons. Modifications of λ as a function of the bond alternation in the (10,10) nanotube are explained with the help of power spectra, which provide access to the density of vibrational states. We have suggested longitudinal low-energy modes in the spectra that might be responsible for the Δr(i) dependence of λ.