Solubility of gases in a hydroformylation solvent

The solubility of reactants used in homogeneously catalyzed hydroformylation of alkene was studied in a pressurized, semi-batch autoclave. The solubilities of alkene, carbon monoxide and hydrogen in the 2,2,4-trimethyl-1,3-pentanediol mono(2-methylpropanoate) solvent (NX 795) were determined by precise pressure and weight measurements. The measured solubilities were tested against empirical and theoretical models. Logarithmic empirical models gave a very good fit to experimental solubility data. To obtain nonempirical equations for the gas solubility, thermodynamic models based on activity coefficients and equations of state were used. The activity coefficient models based on regular solution theory (RST) predicted the solubilities well, but the selection of the model is the critical issue. For 1-butene, the best prediction was provided by the Yen and McKetta modification of the RST, whereas for carbon monoxide and hydrogen it was necessary to include a mixing entropy term in the RST. The Soave-Redlich-Kwong equation of state gave a fairly good prediction of the solubilities, but not as good as the RST-based models.     

Numerical optimization of conduction cooled current leads for low current applications

The basic design principles of current leads for superconducting magnets are well established but HTS materials and conduction cooled systems call for new numerical methods. In this paper the design of current leads was formulated as an optimization problem. Both time integration and finite differencing were examined as possible ways to compute the temperature distribution inside the leads. Three examples about optimization of conduction cooled as well as gas cooled systems are presented. First, the design of tubular normal conducting gas cooled current leads was studied. Second, normal conducting leads cooled with a two-stage cryocooler were examined. Third, the optimization was applied to current leads consisting of HTS tapes at the low temperature end of a normal conducting bar. The study took into account the magnetic field and temperature dependent voltage-current characteristics of the anisotropic Bi-2223 material. The results are compared with traditional analytical ones and the numerical optimization is shown to be an efficient design tool for both normal conducting and HTS current leads.     

Impacts of automatic control systems of loop restoration scheme on the distribution system reliability

Loop restoration scheme (LRS) is a special feeder automation (FA) scheme, which is used by utilities to improve distribution system reliability. The LRS is controlled and managed by its automatic control system (ACS). The impacts on distribution system reliability indices of implementing LRS mainly depend on the type of its ACS. Two common types of ACS of LRS are presented and used in this study. Successful operation of ACS is dependent on the protection and automatic control functions of switching devices of LRS. Different failure modes of these switching devices can therefore affect the procedure of ACS in fault detecting, isolating and service restoration. The impacts of failure of protection and automatic control functions of switching devices and fuse of lateral distributors on reliability indices are illustrated. The worth of implementing LRS and its ACS type is represented by the reduction in expected customer interruption cost. A distribution test system is utilised to examine the impacts of two common types of ACS of LRS on the distribution system reliability. Selecting the type of ACS of LRS by utilities relies on the desired level of load-point and system reliability improvement. This study aims to quantitatively assess the impacts of two common types of ACS of LRS on the distribution system reliability.     

Integrated pharmacokinetics and pharmacodynamics of the novel calcium sensitizer levosimendan as assessed by systolic time intervals

BACKGROUND: Levosimendan is a new calcium sensitizer, acting calcium-dependently on cardiac troponin C. In the present study pharmacokinetic-pharmacodynamic interrelations of levosimendan were assessed. SUBJECTS AND METHODS: Ten healthy subjects (22-27 years) were given single doses of 2 mg of levosimendan in 4 different formulations: intravenous (i.v.), conventional tablet (CT), conventional capsule (CC), and slow-release tablet (SR) on different days. Systolic time intervals and impedance cardiography were recorded up to 4 hours post drug. Plasma concentrations of levosimendan and its metabolite OR-1855 were analyzed using HPLC. Hysteresis loops were constructed by connecting the effect-concentration points in time order. In addition, pharmacokinetic-pharmacodynamic modelling was performed with the i.v. data. RESULTS: The i.v. administration, giving a maximal levosimendan concentration of 180 ng x ml(-1), increased heart rate by 8 beats min(-1) and cardiac output by 18%. It shortened heart rate corrected electromechanical systole QS2i by 23 ms, indicating a fairly strong positive inotropic effect. The conventional oral formulations (giving maximal drug concentrations of about 70-80 ng x ml(-1)) increased heart rate by 4-5 beats min(-1) and cardiac output by 5-8%, while QS2i shortened by 9-13 ms. The SR formulation resulted in low drug concentrations and generally weaker effects than the other formulations. The bioavailability of CT and CC was 83 and 87%, while that of SR was only 31%. QS2i showed counter-clockwise hysteresis after all formulations (p < 0.01). The mean equilibration half-time (ln(2)/k(e0)) after i.v. administration was 9.6 min. Only after SR, OR-1855 was detected in appreciable amounts in plasma, the highest value being 2.2 ng x ml(-1) which occurred 24 hours after drug intake. CONCLUSION: In conclusion, the pharmacokinetic-dynamic behavior of the inotropy index QS2i indicates an equilibration delay of levosimendan, which most probably reflects the time the drug requires to distribute from plasma to its cardiac site of action. The deviant kinetic-dynamic profile of the oral slow-release formulation suggests a different absorption pattern of levosimendan from this formulation.     

SPUDT filters for the 2.45 GHz ISM band

Filters based on using single-phase, unidirectional transducers (SPUDT) consisting of lambda/4 and wider electrodes are presented. The design variants exploit the significant difference between the reflectivity of short-circuited lambda/4 electrodes and that of floating wide electrodes on 128 degree lithium niobate (LiNbO3). The surface acoustic wave (SAW) devices operating at 2.45 GHz have critical dimensions of about 0.3-0.4 microm, accessible to standard optical lithography. When matched, the fabricated SPUDT filters exhibit minimum insertion losses of 5.5-7.9 dB together with 3 dB passbands of 89-102 MHz. The majority of the insertion loss can be attributed to the attenuation on free surface and inside the grating, and to the resistivity of the electrodes.     

Distinguishing organic wines from normal wines on the basis of concentrations of phenolic compounds and spectral data

This study was undertaken to determine whether it is possible to distinguish organic wines from normal wines on the basis of chemical composition and spectral data. A total of 58 wine samples including organic and normal red and white wines from France and Germany were analysed. The concentrations of several phenolic compounds, including trans-resveratrol, were determined using reversed-phase high-performance liquid chromatography with both diode array and coulometric electrode array detection. In addition, total phenols, total acids, pH and SO₂ were determined. The ultraviolet-visible (UV-vis) spectra of wines were measured, and the absorbances at four different wavelengths were determined. The data were processed statistically using principal component analysis (PCA). Despite several different combinations of variables, separation of white wines was only achieved according to geographical origin. PCA differentiated well between organic Burgundy red wines and normal Burgundy wines. The separation was based on the concentrations of caffeic and gallic acids, total phenol content and the absorbance ratios A₂₅₄/A₂₇₆, A₂₇₆/A₃₂₀ and A₃₂₀/A₅₂₀. PCA was unable to differentiate organic white wines from corresponding normal wines. The mean trans-resveratrol concentrations of 16 organic red wines and 16 normal red wines were 5.6 mg/l and 2.9 mg/l, respectively. The highest concentration, 14,5 mg/l, was found in an organic red wine from the Loire district in France.     

Permanent open shunt as a reason for impotence or reduced potency after surgical treatment of priapism in 26 patients

A permanent open shunt as a cause of impotence or impaired potency after a shunt operation for priapism is an unusual situation. In this series we studied the persistence of an open shunt in 26 patients who had developed impotence or impaired potency after operative treatment for priapism. All patients had been examined by cavernosography on the suspicion of an open shunt, giving a positive finding in five of 26 cases, in all of which impotence was cured by closure of the shunt. In five patients without a permanent open shunt potency returned to normal only after 6-12 months.