Shell-side distribution and the influence of inlet conditions in a model of a disc-and-doughnut heat exchanger

Measurements of wall pressure and of three orthogonal velocity components with their corresponding fluctuations are reported for two systems of alternating and equi-spaced doughnut and disc baffles axisymmetrically located in a water turbulent pipe flow, simulating the isothermal shell-side flow in shell and tube heat exchangers. The influence of inlet Reynolds number and of asymmetric inlet flow conditions was studied for two geometries. The velocity field was dominated by the pressure gradient and the flow around each individual baffle was influenced by the relative position of its neighbouring baffles.List of symbols C _p wall static-pressure coefficient - D internal diameter of upstream and downstream pipes (mm) - D _s internal diameter of test section (mm) - d _d disc diameter (mm) - d _c doughnut-hole diameter (mm) - l baffle-pitch (mm) - l _i entrance length in the model before first baffle (mm) - l ₀ exit length in the model after last baffle (mm) - mass flow rate (kg/s) - p local wall-static pressure (mm H₂O) - p density of water (1.006 kg/dm³ at 17°C) - Re _b Reynolds number based on bulk velocity - U _b bulk velocity - U _max maximum centre-line axial velocity (ms^–1) - x, y, z Cartesian coordinates - mean and turbulent velocity components along x, y, z respectively     

Velocity and concentration measurements in a model diesel engine

Laser Doppler anemometry and Rayleigh scattering have been used to quantify the velocity and concentration fields after the start of injection in a model diesel engine motored at 200 rpm in the absence of compression. Fuel injection was simulated by a transient jet of vapour Freon-12 initiated at 40 degrees before top-dead-centre through a nozzle incorporated into the centre of a permanently open intake valve. Swirl was induced by means of 60 degree vanes located in the inlet, port. The piston configurations comprised a flat and a re-entrant piston-bowl.The results indicate that for the two nozzle geometries investigated the mass flux decays faster than momentum with nearly constant decay rates along the centreline. The nozzle with the larger exit diameter and wider jet angle gave rise to slower decay of both mass and momentum with associated lower velocity and concentration fluctuations.List of symbols D ₀ nozzle diameter - r radial coordinate - mean axial velocity - mean axial velocity at the centreline - ₀ mean axial velocity at the nozzle exit - rms of axial velocity fluctuations - mean concentration (mole fraction) - mean concentration at the nozzle exit - rms of concentration fluctuations - x axial coordinate A version of this paper was presented at the ASME Winter Annual Meeting of 1984 and printed in AMD, Vol. 66     

A New Validated Potentiometric Method for Batch and Continuous Quality Control Monitoring of Oseltamivir Phosphate (Taminil) in Drug Formulations and Biological Fluids

A new validated potentiometric method is described for batch and continuous quality control monitoring of the drug oseltamivir phosphate (Taminil) (OST). The method involves the development of a potentiometric sensor responsive to the drug based on the use of the ion‐association complex of (OST⁺) cation with phosphomolybdate anion (PMA^?) as an electroactive material in a poly(vinyl chloride) matrix membrane plasticized with o‐nitrophenyloctyl ether (o‐NPOE). Optimization of the performance characteristics of the sensor is described. A membrane incorporating the OST‐PMA‐NPOE complex in a tubular flow through detector is used in a two channel flow injection set up for continuous monitoring of the drug at a frequency of ～30 samples h^?1. The sensor shows fast near‐Nernstian response for OST over the concentration range 5.2×10^?5–0.8×10^?2 M (21.34 µg mL^?1–3.23 mg mL^?1) with a detection limit of 9.1×10^?6 M (3.73 µg mL^?1) over the pH range 4.6–6.1. The sensor displays good selectivity for OST drug over some basic drugs, inorganic cations, excipients and diluents commonly used in the drug formulations. Validation of the assay method is tested by measuring the lower detection limit, range, linearity, bias, trueness, accuracy, precision, and between‐day‐variability, within day reproducibility, selectivity and ruggedness (robustness). The results reveal good potentiometric performance of the proposed sensor for determination of OST in pharmaceutical capsules and in biological fluid matrices as well as for testing the dissolution profile of the drug and drug homogeneity.     

Optimization Studies of Porous Carbon Preparation from Oil Shale Using Response Surface Methodology and Its Application for Phenol Adsorption

This paper discusses the elaboration of adsorbents from oil shale. The experimental designs a response surface methodology(RSM), which has been applied to optimize the significant preparation factors, such as temperature, time, and the activating agent percentage. The results obtained from central composite design(CCD) revealed that the interaction between the factors was significant for the maximum quantity of adsorption(response). Planned results have shown that a maximum quantity of adsorption for methylene blue is 65 mg/g, which could be achieved with a temperature of 275℃ over 2 h and a percentage of the activating agent of 45%. The predicted values agreed with the experimental finding, with a determination coefficient(R²) of 0.96. The model has been validated by experiments after conditions optimization. The new material(RHO) was characterized by cation exchange capacity, zero charge pH, surface functions, X-ray fluorescence, specific surface area, and electron microscopy analysis. Phenol adsorption was determined using Langmuir, Freundlich and Temkin, which were used to describe the adsorption isotherms. The adsorption capacity of the material was about 263 mg/g, and the kinetic studies showed rapid adsorption.     

Diaryl Sulfoxides from Aryl Benzyl Sulfoxides: A Single Palladium‐Catalyzed Triple Relay Process

A novel approach to produce diaryl sulfoxides from aryl benzyl sulfoxides is reported. Optimization of the reaction conditions was performed using high‐throughput experimentation techniques. The [Pd(dba)₂]/NiXantPhos catalyst system successfully promotes a triple relay process involving sulfoxide α‐arylation, C? S bond cleavage, and C? S bond formation. The byproduct benzophenone is formed by an additional palladium‐catalyzed process. It is noteworthy that palladium‐catalyzed benzylative C? S bond cleavage of sulfoxides is unprecedented. A wide range of aryl benzyl sulfoxides, as well as alkyl benzyl sulfoxides with various (hetero)aryl bromides were employed in the triple relay process in good to excellent yields (85–99 %). Moreover, aryl methyl sulfoxides, dibenzyl sulfoxides, and dimethylsulfoxide could be utilized to generate diaryl sulfoxides involving multiple catalytic cycles by a single catalyst.     

The integrated number of vibrational states in acetylene (12C2H2, 13C2H2, 12C2D2)

A calculated exhaustive set of vibrational state energies in ¹²C₂H₂, ¹³C₂H₂ and ¹²C₂D₂ has been used to analyse the evolution of the integrated number of states with increasing vibrational energy N(E) up to 15000 cm^?1, 12000cm^?1 and 10000 cm^?1 in each isotopomer, respectively. The regular contribution to N(E) was modelled analytically and numerical parameters were fitted. The other expected contribution to N(E), which is of oscillatory nature, was quantified and is discussed using energyand time-dependent theories. Related periods of oscillation and temporal recurrences are interpreted consistently in terms of the constant of the motion N_r = 5v₂ + 3v₂ + 5v₃ + v₄ + v₅ and of an average vibrational quantum. More pragmatically, the vibrational dynamics appear to be dominated by the bending vibrations, i.e., by the slowest oscillators.     

Optical characterization of InGaN/AlGaN/GaN diode grown on silicon carbide

Electroluminescence (EL) properties of In_xGa_1−xN/Al_yGa_1−yN/GaN/SiC diode were studied. The spectral range for which EL spectra were recorded is 1–3.5 eV. Room temperature EL was obtained for forward bias (3.18 V, 220 μA) at 446.067 nm (blue luminescence band), 606.98 nm (yellow luminescence band) and 893.84 nm (Infrared luminescence band). The EL temperature dependence shows that, BL band is mostly given by e–h recombination corresponding to indium composition equal to 0.17 ± 0.01 and 0.14 ± 0.02 obtained theoretically and experimentally, respectively. The yellow band is generally weak and absent at low temperature. The IRL band is more consistent with the DAP recombination and could be explained by the thermal activation of Mg states. The luminescence bands shift to lower energies is due probably to the larger potential fluctuations effect.     

Self‐Assembled Gels Formed in Deep Eutectic Solvents: Supramolecular Eutectogels with High Ionic Conductivity

1,3:2,4‐Dibenzylidene‐d ‐sorbitol (DBS), a simple, commercially relevant compound, was found to self‐assemble as a result of intermolecular noncovalent interactions into supramolecular gels in deep eutectic solvents (DESs) based on choline chloride combined with alcohols/ureas. DBS formed gels at a loading of 5 % w/v. Rheology confirmed the gel‐like nature of the materials, electron microscopy and X‐ray diffraction indicated underpinning nanofibrillar DBS networks, and differential scanning calorimetry showed the DES nature of the liquid‐like phase was retained. The ionic conductivities of the gels were similar to those of the unmodified DESs, thus proving the deep eutectic nature of the ionic liquid‐like phase. Gelation was tolerant of ionic additives Li⁺, Mg²⁺, and Ca²⁺; the resulting gels had similar conductivities to electrolyte dissolved in the native DES. The low‐molecular‐weight gelator DBS is thus a low‐cost additive that forms gels in DESs from readily available constituents, with conductivity levels suitable for practical applications.     

Sub region-specific modulation of synchronous neuronal burst firing after a kainic acid insult in organotypic hippocampal cultures

Background  

Excitotoxicity occurs in a number of pathogenic states including stroke and epilepsy. The adaptations of neuronal circuits in response to such insults may be expected to play an underlying role in pathogenesis. Synchronous neuronal firing can be induced in isolated hippocampal slices and involves all regions of this structure, thereby providing a measure of circuit activity. The effect of an excitotoxic insult (kainic acid, KA) on Mg²⁺-free-induced synchronized neuronal firing was tested in organotypic hippocampal culture by measuring extracellular field activity in CA1 and CA3.