Densities,Viscosities, Speeds of Sound,and Refractive Indices of Binary Mixtures of 2-Octanol with Chlorobenzenes

Densities, ρ, viscosities, η, speeds of sound, u, and refractive indices, n _D, of binary liquid mixtures of 2-octanol with 1,2-dichlorobenzene, 1,3-dichlorobenzene, and 1,2,4-trichlorobenzene have been measured over the entire range of composition at 298.15 K, 303.15 K, and 308.15 K and at atmospheric pressure. From the experimental data of the density, speed of sound, viscosity, and refractive index, the values of the excess molar volume, V ^E, deviations in isentropic compressibility, Δκ _S , and deviations in molar refraction, ΔR have been calculated. The calculated excess and deviation functions have been analyzed in terms of molecular interactions and structural effects.     

Densities,Viscosities, Speeds of Sound,and Refractive Indices of Binary Mixtures of 1-Decanol with Isomeric Chlorotoluenes

Densities, ρ, viscosities, η, speeds of sound, u, and refractive indices, n _D, of binary liquid mixtures of 1-decanol with o-chlorotoluene, m-chlorotoluene, and p-chlorotoluene have been measured over the entire range of composition at 298.15 K, 303.15 K, and 308.15 K and at atmospheric pressure. From the experimental data of density, speed of sound, viscosity and refractive index, the values of the excess molar volume, V ^E, deviations in isentropic compressibility, Δκ _S , and deviations in molar refraction, ΔR, have been calculated. The calculated excess and deviation functions have been analyzed in terms of molecular interactions and structural effects.     

Analysis of antibiotic residues in raw and commercial milk in Punjab,India vis‐à‐vis human health risk assessment

The present study quantitatively analyzed the occurrence of antibiotic residues in 524 milk samples (492 raw milk samples from dairy farms and 32 commercial milk samples) from Punjab, India using high‐performance liquid chromatography (HPLC). Tetracyclines, sulphonamides, fluoroquinolones (commonly used in veterinary practice in Punjab), and chloramphenicol (banned in food animals in India) were targeted and analyzed using multiresidue HPLC method. Out of 492 dairy farms milk samples, 78 (16%) were found to be positive for antibiotic residues with 20 (4%) exceeded the maximum residue limits (MRLs). Among 32 commercial milk samples, 4 (12.5%) were positive for antibiotic residues with one (3.1%) sample violated the MRL. Assessment of human health risks revealed that the current levels of antibiotic residues in milk pose no significant toxicological effects on the health of consumers. However, the results highlighted an immediate need of effective strategies for prevention of nonprudent use of antibiotics in veterinary practice for safeguarding consumer's health.     

Drop impact reliability of edge-bonded lead-free chip scale packages

This paper presents the drop test reliability results for edge-bonded 0.5 mm pitch lead-free chip scale packages (CSPs) on a standard JEDEC drop reliability test board. The test boards were subjected to drop tests at several impact pulses, including a peak acceleration of 900 Gs with a pulse duration of 0.7 ms, a peak acceleration of 1500 Gs with a pulse duration of 0.5 ms, and a peak acceleration of 2900 Gs with a pulse duration of 0.3 ms. A high-speed dynamic resistance measurement system was used to monitor the failure of the solder joints. Two edge-bond materials used in this study were a UV-cured acrylic and a thermal-cured epoxy material. Tests were conducted on CSPs with edge-bond materials and CSPs without edge bonding. Statistics of the number of drops-to-failure for the 15 component locations on each test board are reported. The test results show that the drop test performance of edge-bonded CSPs is five to eight times better than the CSPs without edge bonding. Failure analysis was performed using dye-penetrant and scanning electron microscopy (SEM) methods. The most common failure mode observed is pad lift causing trace breakage. Solder crack and pad lift failure locations are characterized with the dye-penetrant method and optical microscopy.     

Backward walking simulation of humans using optimization

The objective of this study is to formulate, simulate and study the backward walking motion of a full-body skeletal digital human model using an optimization approach. Predictive dynamics is used to simulate the task in which joint angle profiles are treated as primary unknowns in the formulation. The joint torques are treated as dependent variables that are evaluated directly from the equations of motion. For the performance measure, the normalized dynamic effort represented by the integral of the squares of all the normalized joint torques is minimized subject to the associated physical constraints. Backward walking at different speeds is simulated and analyzed. The backward walking is validated with motion capture data and the available data in the literature. The results of the backward walking motion are compared to those of the forward walking motion in order to study the differences between the two walking patterns. It is seen that the joint torque profiles for hip and knee of backward walk are quite similar to those of forward walk with reverse sequence, but with different time duration of flexion and extension activations. These findings can impact many fields, such as improvement of human performance, rehabilitation from injuries, and others.     

A sensitivity interpretation of adjoint variables in optimal design

The adjoint method of computing derivatives of cost and constraint functions with respect to design variables requires the calculation of certain adjoint variables. Until now, the adjoint variables have been looked upon only as some intermediate vectors needed to calculate design derivatives. In this paper, they are shown to have an important significance. They represent the sensitivity of the cost and constraint functions with respect to the loading or forcing function in the design problem. A sensitivity theorem for the adjoint variables is presented for structural, mechanical dynamic, and distributed parameter systems. These results offer some immediate practical advantages, such as a method for computing influence coefficients for structural systems, and a method for verifying (debugging) the analytical calculation of adjoint variables in development of a computer code.     

Mixed Micellization Behavior of<Emphasis Type="Italic"> m</Emphasis>-2-<Emphasis Type="Italic">m</Emphasis> Gemini Surfactants with Some Conventional Surfactants at Different Temperatures

Mixed micellization behavior of dimeric cationic surfactants ethanediyl-1,2-bis(dimethyl alkyl ammonium bromide) (m-2-m where m = 10, 12) with conventional single chain cationic surfactants like cetyltrimethyl ammonium bromide (CTAB), cetylpyridinium chloride (CPC), tetradecyl dimethyl benzyl ammonium chloride (C14BCl) and cetyl dimethyl benzyl ammonium chloride (C16BCl) were studied in aqueous and aqueous polyethylene glycol (PEG) solutions at 298.15, 308.15 and 318.15 K respectively using conductometric and viscometric methods. In aqueous solutions, all the combinations (except 12-2-12 + CTAB) were found to behave nonideally with mutual synergism which decreases with increase in temperature. Various thermodynamic parameters of micellization like \UpdeltaG_\textm^\texto {{\Updelta}}G_{\text{m}}^{\text{o}} , \UpdeltaH_\textm^\texto {{\Updelta}}H_{\text{m}}^{\text{o}} and \UpdeltaS_\textm^\texto {{\Updelta}}S_{\text{m}}^{\text{o}} were evaluated and discussed. Similarly in presence of PEG, the thermodynamic properties like \UpdeltaG_\textt^\texto {{\Updelta}}G_{\text{t}}^{\text{o}} , \UpdeltaH_\textt^\texto {{\Updelta}}H_{\text{t}}^{\text{o}} and \UpdeltaS_\textt^\texto {{\Updelta}}S_{\text{t}}^{\text{o}} associated with the transfer of surfactant monomers from the medium consisting of polymer-free mixed micelles to polymer-bound mixed micelles at various temperatures were also calculated. The negative values of \UpdeltaH_\textt^\texto {{\Updelta}}H_{\text{t}}^{\text{o}} show that aggregation process is more exothermic than micellization whereas the negative values of \UpdeltaS_\textt^\texto {{\Updelta}}S_{\text{t}}^{\text{o}} indicate that the presence of polymer bound mixed micelles decreases the degree of randomness of the system. Viscosity studies show that in aqueous solutions all the combinations of 10-2-10/12-2-12 display negative departure in the relative viscosity (η_r) from additivity rule which decreases with increase in temperature. Similarly in the presence of 5% PEG solutions the magnitude of the negative departure decreases for all the combinations and becomes positive in the case of C14BCl and CPC combinations with the studied gemini surfactants at higher temperatures.     

A simple method for the synthesis of ceramides and radiolabeled analogues

A simple method has been developed for the coupling of amines to carboxylic acids.N-Fatty-acyl-sphingosine, cerebroside, and GM₃, as well as their respective [¹⁴C] analogues, were synthesized using diethylphosphoryl cyanide as a potent coupling agent in the presence of triethylamine. The reaction procedure is rapid, racemization-free, and utilizes acids without derivatization. The desired ceramide products were obtained in 85–90% yield within one hour. The facile method presented here can also be used to synthesize [³H]-N-acyl-labeled, as well as [¹⁴C] [³H] double-labeled, ceramides.     

A review of optimization of structures subjected to transient loads

Various aspects of structural optimization techniques under transient loads are extensively reviewed. The main themes of the paper are treatment of time-dependent constraints, calculation of design sensitivity, and approximation. Each subject is reviewed with corresponding papers that have been published since the 1970s. The treatment of time-dependent constraints in both the direct method and the transformation method is discussed. Two ways of calculating design sensitivity of a structure under transient loads are discussed—direct differentiation method and adjoint variable method. The approximation concept mainly focuses on the response surface method in crashworthiness and local approximation with the intermediate variables. Especially, a method using the equivalent static load is discussed as an approximation method. It takes advantage of the well-established static response optimization. The structural optimization in flexible multibody dynamic systems is reviewed in the viewpoint of the above three themes.