Analytical and Experimental Investigation of Squeeze-Film Dampers Executing Circular Orbits

We have referred here the first results obtained in the course of an experimental research intended to examine oil film pressure of a squeeze film damper (with inertialess lubricant) executing circular orbits. An analytical expression for pressure arising into the gap was obtained before, for the short bearing SFD, in the general case of offset circular orbits. The expression obtained has permitted, in a simple way, the examination of the influence of the offset on pressure. Two approximated expressions for pressure (the one for pressure as a function of time at a fixed measuring section, the other for pressure along the circumference of the bearing at a given time), corresponding to centered orbits, were compared with the exact ones. We observed that the limits within which the nondimensional offset can be considered negligible, change according to comparisons between circumferential pressure diagrams or between pressure diagrams as functions of time. In the second case they are much wider. The experimental results concerned offset orbits with nominal radius r=0.5C and offset <0.1. Good accordance between theoretical and experimental pressure trends has been found, as concerns the positive part of dynamic pressure. As concerns the negative part of dynamic pressure, tests have shown that cavitation takes place for a more or less wide length, depending on feeding groove pressure, other conditions being equal. Complete effective pressure diagram coinciding with the theoretical one has been found for particular feeding conditions. Oil film tensile stresses have been frequently detected with both complete and incomplete diagrams owing to cavitation. Maximum measured tensile stress was about 220kN/m². It was finally found that theoretical and experimental trends are coincident only if the SFD is not starved. Analytical expression for pressure in the long bearing SFD executing offset circular orbits is referred in the appendix.     

Application of neutron activation analysis to metallobiochemistry

Some typical applications of long-term/low-level exposure (LLE) is presented including in vivo LLE study on rats and in vitro experiments on some metal binding components as well as on cadimium binding protein.     

Radiochemical separations by retention on ionic precipitate adsorption tests on 11 materials

The retention of different radio-ions on columns of eleven ionic precipitates from different acid media was studied, in view of possible applications for radiochemical separations. The results of about 2,000 adsorption experiments, carried out in a standardized way, are presented schematically in periodic tables.     

Analysis of thiols by HPLC after fluorescent prelabelling with 4-(6-methylnaphthalen-2-yl)-4-oxobuten-2-oic acid

Summary The use of 4-(6-methylnaphthalen-2-yl)-4-oxobuten-2-oic acid as a fluorogenic reagent in pre-column derivatization for the high-performance liquid chromatography (HPLC) of biologically important thiols (L-cysteine, glutathione, N-acetylcysteine, homocysteine and mercaptopropionylglycine) was investigated. The aroylacrylic acid reacts selectively and rapidly (15 min. at room temperature) with the thiol compounds to give stable fluorescent adducts which can be separated by reversedphase HPLC and detected fluorometrically (_ex 300nm); _em 445nm). The experimental conditions for the thiol derivatization and chromatographic separation are discussed. Applications to the determination of N-acetylcysteine, mercaptopropionylglycine and cysteine are described.Presented in part at Bononiachem, XVI Congresso Nazionale di Chimica, Bologna, October 9–14, 1988.     

Laser photochemistry: The intramolecular cyclization of carvone to carvonecamphor

Kr-ion laser irradiation of carvone ($\text{1}$) at 350.7 and 356.4 nm gave carvonecamphor ($\text{2}$) in a much higher yield (88%) than in conventional photochemistry, while ($\text{3}$) was a primary photo-by-product.     

A saturation phenomenon for a nonlinear nonlocal eigenvalue problem

Given \(1\le q \le 2\) and \(\alpha \in \mathbb {R}\), we study the properties of the solutions of the minimum problem

$$\begin{aligned} \lambda (\alpha ,q)=\min \left\{ \dfrac{\displaystyle \int _{-1}^{1}|u'|^{2}dx+\alpha \left| \int _{-1}^{1}|u|^{q-1}u\, dx\right| ^{\frac{2}{q}}}{\displaystyle \int _{-1}^{1}|u|^{2}dx}, u\in H_{0}^{1}(-1,1),\,u\not \equiv 0\right\} . \end{aligned}$$

In particular, depending on \(\alpha \) and q, we show that the minimizers have constant sign up to a critical value of \(\alpha =\alpha _{q}\), and when \(\alpha >\alpha _{q}\) the minimizers are odd.

     

Simultaneous separation of 14 antiarrhythmic drugs and determination of mexiletine and flecainide by capillary zone electrophoresis

A method using capillary zone electrophoresis was developed for the simultaneous separation of 14 antiarrhythmic drugs belonging to various classes. The drugs are separated on a fused-silica capillary, 90 cm x 75 microm (72 cm effective length), with phosphate and acetate buffers as background electrolytes and UV detection at 217 nm. The effects of buffer pH, temperature, and applied voltage on the migration of the drugs were studied. The pH was found to be the most significant factor determining effective separation. The antiarrhythmic compounds are completely separated within a relatively short time (< 7 min) by using 70 mM phosphate buffer at pH 7.91, an applied voltage of 28 kV, and a temperature of 32 degrees C. Mexiletine (MEX) and flecainide (FLE) were quantified under conditions of the optimum separation. The calibration graphs were constructed over the concentration range of 4.0-14.0 microg/mL for both drugs with good correlation (r > or = 0.9999). Detection and quantitation limits were found to be 0.5 and 1.5 microg/mL for FLE and 0.7 and 2.1 microg/mL for MEX, respectively. The proposed method was used for the determination of both drugs in their commercial forms with satisfactory precision (relative standard deviations of 0.36-1.21% for FLE and 0.78-1.66% for MEX) and accuracy (relative standard errors of 0.13-1.17% for FLE and 0.35-1.18% for MEX).     

Configuration,Conformation, and Reactivity of Highly Functionalized Eunicellane Diterpenes Isolated from the Gorgonians Eunicella cavolinii and Eunicella singularis from Marseille

Eunicellane diterpenes with a C(7)=C(16) (Δ^7,16; see 17 – 19 ), (Z)‐C(7)=C(8) ((7Z)Δ^7,8; see 20 – 23 ), and (Z)‐C(6)=C(7) ((6Z)Δ^6,7; see 10 ) bond, an uncommon feature in the case of extensive functionalization at the cyclohexane ring and the latter exhibiting uncommon configurations, were isolated from the gorgonian Eunicella cavolinii from Marseille (Figs. 5 and 2). The gorgonian Eunicella singularis (=Eunicella stricta) from the same area gave (7Z)Δ^7,8, Δ^7,16, and (6E)Δ^6,7 analogs 24 , 25 , and 13 , respectively (Fig. 5 and Scheme). The (6E)Δ^6,7 moiety of 13 – characterized by a slow 180° conformational flipping (Fig. 3) that results in broadening of NMR signals – makes the macrocycle highly strained. This may explain the spontaneous conversion of 13 to the 6‐methoxy‐7‐hydroxy derivative 14 in the presence of MeOH at −20° in the dark (Scheme). The isomeric, deacylated analogue 10 showed only little broadening of NMR signals and proved stable, in accordance with the less strained nature of this compound (Fig. 4).     

A Novel Type of a Second Epoxy Bridge in Eunicellane Diterpenes: Isolation and Characterization of Massileunicellins A – C from the Gorgonian Eunicella cavolinii

Massileunicellins A ( 7 ), B ( 9 ), and C ( 11 ) – which show a novel type of a second epoxy bridge in eunicellane diterpenes – were isolated from the gorgonian Eunicella cavoliniii collected near Marseille. Structural assignments are based on NMR and MS data of these compounds and of their ketal derivatives 8 , 10 , and 12 . Negligible activity of the massileunicellins on L1210 and KB tumor cell lines, and similar results for related known compounds, cast doubt on high cytotoxicity reported for the latter by other authors.