Chromatic and opto-mechanical dispersion of some characteristic parameters of optical fiber undergoing macrobending

Bending of optical fiber leads to an induced-anisotropy in the index profile that influences many important guiding fiber parameters. An analytical method is described for the measurement of refractive-index-wavelength dispersion in bent optical fibers. Multiple-beam Fizeau fringes technique at transmission is used to analyze the opto-mechanical properties and induced-index anisotropy in a standard single-mode fiber undergoes pure mechanical macrobending. The shift in Fizeau fringes is employed to evaluate the dispersion of the cladding material of the bent fiber. The radial variations in Cauchy’s coefficients and the associated variations of some fiber parameters due to macrobending are carried out. The radial profiles of some material parameters such as oscillation energy, dispersion energy, lattice energy and material dispersion are measured as well. The presented method is capable to achieve quantitative and qualitative measurements, which is not available with other methods. The method has a good index resolution in the order of 10⁻⁴ and spatial resolution of 1.3 μm.     

Mössbauer, X-ray, electrical and magnetic properties of lithium borosilicate glasses containing iron and manganese Part I. Mössbauer measurements

The effect of the replacement of MnO₂ by Fe₂O₃ on the oxidation states of iron in some lithium borosilicate glasses were studied using Mössbauer spectroscopy. DTA and infrared measurements showed the presence of two glassy phases, one of them containing iron and the other manganese. The Mössbauer spectra were measured at room temperature for all the glass samples. The spectra revealed the presence of Fe ions only in ferric state in both tetrahedral and octahedral coordination. Also, it was observed that the ratio between the number of iron ions in both coordination states has not changed with the increase of MnO₂ content.     

Long-term optimal operation of series parallel reservoirs for critical period with specified monthly generation and average monthly storage

We present in this paper an efficient approach for solving the problem of planning the long-term (multiyear) operation of a multireservoir hydroelectric power system for the critical period with a monthly variable load. This load is equal to a certain percentage of the total generation at the end of the year, subject to satisfying a number of constraints on the hydrosystem, using the minimum norm formulation.The proposed method is efficient in computing time and in calculating the total expected benefits from the system during the critical period. Numerical results are reported for a real system in operation consisting of two rivers. Each river has two series reservoirs.This work was supported by the Natural Science and Engineering Research Council of Canada, Grant No. A4146.     

Theoretical analysis of the onset of liquid entrainment for slots of finite width

The onset of liquid entrainment during discharge from large reservoirs containing a stratified mixture of two immiscible fluids through a side slot of a finite width is considered theoretically. A previously reported analysis in which the slot was approximated as a two-dimensional line sink has been extended to account for the finite width of the slot. The model resulting from the present analysis is expressed in terms of two simple algebraic equations suitable for hand calculations. According to the present results, the ratio of the critical height to the slot width is dependent only on the Froude number. Numerical results show that the present model approaches the correct physical limits at low Froude numbers and it converges to the predictions of the previously reported simple model at high Froude numbers.     

New chaos generators

Originating from a sinusoidal oscillator circuit that employs the current feedback op amp (CFOA) as the active building block, a new chaos generator that utilizes a discrete nonlinear device of asymmetrical nonlinearity is proposed. Two different positions of the nonlinearity within the circuit structure are investigated. A slight modification incorporating the addition of a single resistor to the generator is shown to facilitate its tuning and affect the dynamics of its chaotic behavior. Experimental laboratory results agree well with PSpice simulations, and both are included.     

Coaxial Discharge and Transverse Magnetic Field

The study deals with the effect of an applied transverse magnetic field on the dynamics and parameters of the focused and expanded plasma in a coaxial discharge. The experimental results were found with a 3 kJ Plasma focus device of a Mather geometry. The discharge takes place in hydrogen gas with base pressure of 0.5 Torr. The experiments are conducted with a 10 kV bank voltage, which corresponds to 100 kA peak discharge current with rise time 8 μs. Helmholtz magnetic coils are placed outside the expansions chamber to produce a transverse magnetic field with intensity 280 G perpendicular to the plasma expanded from the coaxial electrodes. The investigations have shown that the plasma flow along the expansion chamber axis is restricted when applying the externally transverse magnetic field and the maximum axial velocity of the expanded plasma is decreased by 33%. X-ray probe has been used to measure the focused plasma electron temperature (T_e). The experimental results and the calculations showed that T_e is decreased from 2.2 keV to 800 eV with the application of a transverse magnetic field. The expanded plasma electron temperature and density have been measured by an electric double probe, the results cleared that the expanded plasma electron temperature is decreased by 2.6 times while its density is increased by 9 times, when a transverse magnetic field is applied.     

Isolierung und Nachweis basischer Arzneimittel in der Toxikologie

Zusammenfassung Zu den schwierigsten Aufgaben der toxikologischen Analyse gehört die rasche und sichere Isolierung und Identifizierung organischer Basen aus dem Untersuchungsmaterial. Mit einem entsprechenden Extraktionsverfahren oder durch Fällung mit Tetraphenylborat in einem systematischen Analysengang können sehr günstige Ausbeuten erzielt werden. Die Reinigung der Rohextrakte oder -fällungen erfolgt prinzipiell mittels Dünnschichtchromatographie. Aus den Tetraphenylboratkomplexen werden dabei auf den Kieselgelschichten die reinen Basen in Freiheit gesetzt. An Hand derR _f- Wert-Tabellen ist eine Identifizierung möglich, wobei Substanzen mit gleichemR _f- Wert durch fraktionierte Extraktion bei verschiedenem p_H getrennt werden können. Eine weitere Identifizierung kann mit Hilfe der UV-Spektren erfolgen.

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Summary Among the most difficult problems of toxicological analysis are the rapid and reliable isolation and identification of organic bases from the material under examination. Very satisfactory yields can be obtained by means of a suitable extraction procedure or through precipitation with tetraphenyl borate in a systematic scheme of analysis. The purification of the crude extracts or precipitates is accomplished fundamentally by thin layer chromotography. The pure bases are liberated on the silica layers from the tetraphenyl borate complexes. An identification is possible through reference toR _f- tables; substances with likeR _f value can be separated by fractional extraction at different p_H values. A further identification can be made with the aid of UV spectra.

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Résumé L'isolement rapide et sûr des bases organiques dans une substance à l'étude et leur identification représentent l'un des problèmes les plus difficiles de l'analyse toxicologique. On peut atteindre des rendements très satisfaisants avec un procédé d'extraction analogue ou par précipitation par le tétraphénylborure dans un processus d'analyse systématique. La purification de l'extrait brut ou des produits de précipitation s'effectue principalement au moyen de la chromatographie en couche mince. Les bases pures sont libérées des complexes au tétraphénylborure en opérant sur couches en gel de silice. On peut faire une identification en se servant des valeurs desR _f figurant dans les tables, ce qui permet de séparer les substances de mêmeR _f par extraction fractionnée à des p_H différents. Une identification plus poussée peut avoir lieu à l'aide des spectres UV.

     

Dihydrogen Adduct (Co–H2) Complexes Displaying H-Atom and Hydride Transfer

The prototypical reactivity profiles of transition metal dihydrogen complexes (M-H₂) are well-characterized with respect to oxidative addition (to afford dihydrides, M(H)₂) and as acids, heterolytically delivering H⁺ to a base and H⁻ to the metal. In the course of this study we explored plausible alternative pathways for H₂ activation, namely direct activation through H-atom or hydride transfer from the σ-H₂ adducts. To this end, we describe herein the reactivity of an isostructural pair of a neutral S= and an anionic S=0 Co-H₂ adduct, both supported by a trisphosphine borane ligand (P₃^B). The thermally stable metalloradical, (P₃^B)Co(H₂), serves as a competent precursor for hydrogen atom transfer to ^tBu₃ArO^⋅. What is more, its anionic derivative, the dihydrogen complex [(P₃^B)Co(H₂)]¹⁻, is a competent precursor for hydride transfer to BEt₃, establishing its remarkable hydricity. The latter finding is essentially without precedent among the vast number of M-H₂ complexes known.     

Chemistry of Phosphorus Ylides. Part 22 [1]. Effect of Newly Synthesized Niclosamide Mannich Bases, Phosphopyranones, Phosphoranylidenes, and Oxaphosphinin on Some Metabolic Aspects of Biomphalaria Alexandrina

Niclosamide reacts with secondary amines and formaldehyde under the condition of Mannich reaction, to give new Mannich bases. The reaction of these niclosamide Mannich bases with active phosphacumulene ylides affords the corresponding phenyliminopyranone, pyranone, and pyranthione, respectively. When Wittig reaction was carried out on the pyranone, using p-nitrobenzaldehyde, a new arylidene and triphenylphosphine oxide were obtained. On the other hand, stabilized phosphonium ylides affect the transylidation of niclosamide Mannich bases to the corresponding phosphoranylidenes. When diphenylmethylenetriphenylphosphorane reacts with a niclosamide Mannich base, an oxaphosphinin was obtained. The molluscicidal potency of the newly synthesized derivatives against Biomphalaria alexandrina was studied, too.     

Reductive Elimination of Phenylsulfonyl Groups in the 3‐Position of Benzo[a]heptalene‐2,4‐diols

3‐(Phenylsulfonyl)benzo[a]heptalene‐2,4‐diols 1 can be desulfonylated with an excess of LiAlH₄/MeLi?LiBr in boiling THF in good yields (Scheme 6). When the reaction is run with LiAlH₄/MeLi, mainly the 3,3′‐disulfides 6 of the corresponding 2,4‐dihydroxybenzo[a]heptalene‐3‐thiols are formed after workup (Scheme 7). However, the best yields of desulfonylated products are obtained when the 2,4‐dimethoxy‐substituted benzo[a]heptalenes 2 are reduced with an excess of LiAlH₄/TiCl₄ at ?78→20° in THF (Scheme 10). Attempts to substitute the PhSO₂ group of 2 with freshly prepared MeONa in boiling THF led to a highly selective ether cleavage of the 4‐MeO group, rather than to desulfonylation (Scheme 13).