Process zone and acoustic-emission measurements in concrete

It is necessary to study the microlevel failure mechanisms of a material in order to improve its quality and to develop a rational constitutive model to describe the material. Nonlinearity and strain-softening behavior of concrete has to be incorporated into any model which can be implemented into efficient design. Acoustic-emission (AE) techniques are useful for obtaining information pertaining to internal cracking and investigating the applicability of a particular material model.The process of localization of cracks and movement of the fracture process zone was studied using acoustic-emission techniques. The rate of acoustic-emission events and sources of acoustic-emission activity were studied for plain-mortar and model-concrete specimens loaded in direct tension.The study shows that acoustic-emission events localize to a region near the notch before peak load is attained. The region of activity progresses through the specimen during further loading and subsequent strain softening. Acoustic-emission events were used to locate the fracture-process zone (FPZ), and to check this location against the location of the effective crack tip as evaluated by a modified linear-elastic fracturemechanics model for concrete as well as by microscopical observations.Paper was presented at the 1986 SEM Spring Conference on Experimental Mechanics held in New Orleans, LA on June 8–13.     

Solution of fractional-order integro-differential equations using optimal homotopy asymptotic method

Journal of Thermal Analysis and Calorimetry - In this article, a semi-analytical technique called optimal homotopy asymptotic method (OHAM) is presented for numerical solutions of fractional-order...     

Mathematical assessment of a fractional-order vector–host disease model with the Caputo–Fabrizio derivative

Vector–host diseases outbreak is a major public health concern, and it has greatly affected human health and economy in various regions around the globe. Different approaches have been adopted to investigate the dynamical behavior and possible control of these diseases. In this study, we present a compartmental transmission model in order to explore the dynamics of vector–host infectious diseases. The saturated incidence rate instead of bilinear (or standard) and saturated treatment function is considered in model formulation which enhance the biological suitability of the proposed model. We first formulate the model based on nonlinear classical integer-order differential equations. Then, the proposed integer-order model is reformulated using the fractional-order operator in Caputo–Fabrizio sense with nonsingular kernel. We investigate the model equilibria and evaluate the expression for the most important threshold parameter known as the basic reproduction number. Furthermore, the existence and uniqueness are presented via the fixed point approach. Additionally, using an efficient numerical scheme, the iterative solution of the model is obtained. Finally, we present the model simulations to illustrate the impact of arbitrary fractional order and some of other important parameters involved in the model on the disease dynamics and minimization.     

Formation of benzofuran and chlorobenzofuran from 1,3‐dichloropropene: A quantum chemical investigation

We present a quantum chemical investigation of benzofuran and cholorobenzofuran formation mechanisms during the combustion of 1,3‐dichloropropene. Density functional theory and Gaussian‐n thermochemical methods are used to propose detailed mechanistic reaction pathways. These calculations indicate that oxidation of phenylvinyl radical intermediates and subsequent ring closure are key mechanistic pathways in the formation of benzofuran and chlorobenzofuran. Thermochemical and kinetic parameters presented herein will assist in further elucidation of dioxin formation mechanisms from thermolyses of hydrocarbon moieties. © 2015 Wiley Periodicals, Inc.     

Structural diversities and preliminary antimicrobial studies of 1-((<Emphasis Type="Italic">E</Emphasis>)-(pentylimino)methyl)naphthalen-2-ol and its metal complexes

Schiff bases and their metal complexes have a number of biological activities such as antidepressant, analgesic, antimicrobial, antiviral, and antitumor. In the present studies, the 1-((E)-(pentylimino)methyl)naphthalen-2-ol ligand is prepared by the reaction of 2-hydroxynaphthaldehyde with n-amyl amine. The ligand results in CoL₃, NiL₂ and CuL₂ complexes when reacted with the cobalt acetate, nickel acetate, and copper acetate salts respectively. The complexes along with their ligand are fully characterized by X-ray diffraction studies and biologically screened. The ligand structure reveals that it is a zwitterion species where the iminic nitrogen atom is protonated and the C–O bond shows a high double bond character. The cobalt complex has an octahedral geometry around the metal center and each nitrogen atom is in the trans position to the oxygen donor site. On the other hand, the copper complex shows a centrosymmetric square planar coordination, and in this case, the nitrogen sites are trans to each other. The complexes and the ligand are found to be more potent than the standard drugs used against some microbes in their preliminary biological studies.     

Distinct Role of Sesn2 in Response to UVB‐Induced DNA Damage and UVA‐Induced Oxidative Stress in Melanocytes

Ultraviolet (UV) radiation, including both UVB and UVA irradiation, is the major risk factor for causing skin cancer including melanoma. Recently, we have shown that Sesn2, a member of the evolutionarily conserved stress‐inducible protein family Sestrins (Sesn), is upregulated in human melanomas as compared to melanocytes in normal human skin, suggesting an oncogenic role of Sesn2. However, the role of Sesn2 in UVB and UVA response is unknown. Here, we demonstrated that both UVB and UVA induce Sesn2 upregulation in melanocytes and melanoma cells. UVB induces Sesn2 expression through the p53 and AKT3 pathways. Sesn2 negatively regulates UVB‐induced DNA damage repair. In comparison, UVA induces Sesn2 upregulation through mitochondria but not Nrf2. Sesn2 ablation increased UVA‐induced Nrf2 induction and inhibits UVA‐induced ROS production, indicating that Sesn2 acts as an upstream regulator of Nrf2. These findings suggest previously unrecognized mechanisms in melanocyte response to UVB and UVA irradiation and potentially in melanoma formation.     

Water fragmentation and energy loss by carbon ions at the distal region of the Bragg peak

Time-of-flight mass spectrometry was used to investigate fragmentation and energy transfer processes in water by C ions at the distal part of the Bragg peak. Measurements of the positive ion fragments from ionization, electron capture, electron loss, transfer-loss and loss-ionization channels have allowed us for the first time (a) to obtain a quantitative determination of the energy lost by C ions in water and (b) to show that total water fragment ion production has a much flatter profile with projectile energy than would be expected if the water radical formation was assumed to follow the energy-loss profile obtained from available stopping power models.     

Synthesis of highly soluble and oxidatively stable tetraceno[2,3-b]thiophenes and pentacenes

A comparative study of suitably functionalized, highly soluble tetraceno[2,3-b]thiophenes (1-3) and pentacenes (4-6) that show higher photoxidative stability than that of unfunctionalized corresponding acenes is reported. The absorption and emission of 1-3 (Amax = 624-656 nm, lambda max = 634-672 nm, PhiF approximately 10%) and 4-6 (Amax = 672-704 nm, lambda max = 682-718 nm, PhiF approximately 10%) were found to be systematically red-shifted by the substitution in the order of the tert-butylethynyl < triisopropylsilylethynyl < phenylethynyl groups. The oxidation potentials of these compounds were similar (E1/2 approximately 0.70 V), except for 4, which showed lower oxidation potential (E1/2 approximately 0.63 V).     

Proton-detected solid-state NMR spectroscopy of fully protonated proteins at 40 kHz magic-angle spinning

Remarkable progress in solid-state NMR has enabled complete structure determination of uniformly labeled proteins in the size range of 5-10 kDa. Expanding these applications to larger or mass-limited systems requires further improvements in spectral sensitivity, for which inverse detection of 13C and 15N signals with 1H is one promising approach. Proton detection has previously been demonstrated to offer sensitivity benefits in the limit of sparse protonation or with approximately 30 kHz magic-angle spinning (MAS). Here we focus on experimental schemes for proteins with approximately 100% protonation. Full protonation simplifies sample preparation and permits more complete chemical shift information to be obtained from a single sample. We demonstrate experimental schemes using the fully protonated, uniformly 13C,15N-labeled protein GB1 at 40 kHz MAS rate with 1.6-mm rotors. At 500 MHz proton frequency, 1-ppm proton line widths were observed (500 +/- 150 Hz), and the sensitivity was enhanced by 3 and 4 times, respectively, versus direct 13C and 15N detection. The enhanced sensitivity enabled a family of 3D experiments for spectral assignment to be performed in a time-efficient manner with less than a micromole of protein. CANH, CONH, and NCAH 3D spectra provided sufficient resolution and sensitivity to make full backbone and partial side-chain proton assignments. At 750 MHz proton frequency and 40 kHz MAS rate, proton line widths improve further in an absolute sense (360 +/- 115 Hz). Sensitivity and resolution increase in a better than linear manner with increasing magnetic field, resulting in 14 times greater sensitivity for 1H detection relative to that of 15N detection.     

Water-driven chemoselective reaction of squarate derivatives with amino acids and peptides

Here, we report a new class of highly chemoselective reactions between squarate derivatives and the amino acid cysteine or unprotected peptides with a N-terminus cysteine that proceed most efficiently in entirely aqueous solution at neutral pH. Kinetic and structural studies reveal that the presence of hydrogen bonding in water is primarily responsible for both the high yield and fast rate of the reaction.