Coherent bisection of 141 THz using sum frequency generation of 1064 and 709 nm radiation

The frequency interval (141 THz) that exists between 1064 nm radiation and the unusual semiconductor wavelength of 709 nm has been coherently divided by using an optical phase-locked loop to control a slave laser lying at the mean frequency of these two wavelengths. The 709 nm radiation has been generated by a combination of wavelength tuning in an extended cavity and temperature tuning of a ridge-waveguide semiconductor laser with a nominal wavelength of 728 nm. Two nonlinear processes have been used to produce the coherent division: the sum frequency mixing of 1064 and 709 nm radiation to produce 425 nm radiation and the second harmonic generation of 851 nm light to produce the same wavelength radiation.     

High-spin states in the N = 84 nucleus 152Er

High-spin states in ¹⁵²Er have been populated through the ¹⁴⁴Sm(¹²C, 4n)¹⁵²Er reaction. Excitation functions, angular distributions, prompt and delayed coincidences against the beam burst were measured. Three isomeric states at 2183 keV (τ = 1.8 ns), 4519 keV (τ = 1.2 ns) and 4915 keV (τ = 6.6 ns) have been observed. The decay scheme is developed up to 7 MeV and is discussed and compared with that of ¹⁵⁰Dy.     

Use of silica gels and mesoporous molecular sieves as supports for the solid-phase Claisen rearrangement

A series of silica gels and mesoporous molecular sieves differing in both the range of particle size and mean pore size were derivatized with the p-[(R,S)-α-[1-(9H-fluoren-9-yl)-methoxyformamido]-2,4-dimethoxybenzyl]-p henoxyacetic acid linker and their loading capacities were measured. Loading capacities ranging between 0.4–0.6 mmol Fmoc/g were achieved. Several of these silica based materials were derivatized with the hydroxymethyl benzoic acid linker and used as supports for the solid phase Claisen rearrangement of a support bound phenyl allyl ether. Both the silica gel and mesoporous supports were heated at 225 °C for 3 h to effect the Claisen rearrangement. The results showed that, compared to the same reaction run homogeneously, the silica gel support achieved similar total product yields and ratios for two Claisen products. The mesoporous supports were found to selectively produce one of the Claisen products over the other. Analysis shows that the molecules bound to the mesoporous support are physically further separated from each other as compared to those bound to the silica gel support. A mechanism is presented which accounts for the selectivity of the mesoporous support in forming one Claisen product over the other. The Claisen product was further derivatized to the resulting phenyl ethyl ether through a solid phase Mitsunobu reaction on the mesoporous support. This revised version was published online in August 2006 with corrections to the Cover Date.     

An abstract Radon-Nikodym theorem

In this paper we obtain a Radon-Nikodym theorem for positive linear functionals on a B¹-algebra M. Some corollaries analogous to those obtained in the classical case are also obtained here. It is known that if X is a Banach space, then the space $\text{L}{}_1\text{(Ω, X)}$ of Bochner integrable functions on a probability space Ω with values in X is the completion (in a suitable topology) of the tensor product $\text{L}{}_1\text{(Ω) ? X}$. Using our theorem, it is possible to extend this result for certain linear mappings from M ? X to X.     

Shrinkage effects in photopolymerizable resins containing filling agents: Application to stereophotolithography

The influence of porous additives with various structures on the shrinkage of resins used for stereolithographic applications was studied by measuring the dependence of the specific gravity of the charged polymer material as a function of the charge fraction. The investigations were conducted on difunctional monomers photopolymerized either by a radical (acrylate) or a cationic (epoxy) mechanism. The improvement resulting from the incorporation of charges in the formulation is accounted for in a semi-quantitative way by an adsorption-desorption equilibrium of monomer molecules between the pores and the bulk phase. Thus, the pores of the charges which are initially filled with monomer molecules play the role of buffers which discharge their content as the photopolymerization develops in the liquid phase. It is also worth mentioning that the viscosities of the photosensitive charged resins used in these experiments are quite suitable for use in stereophotolithography. © 1992 John Wiley & Sons, Inc.     

Kinetics of partly diffusion controlled reactions. III. Competition between physical and chemical kinetics. Experimental results

In a previous paper (II in this series), we showed that the kinetic parameters of a partly diffusion controlled reaction could be calculated when the p Three examples of fluorescence quenching of electronically excited states were studied: pyrene by biacetyl; sulforhodamine G by I^?; and POPOP by fluorescence and fluorescence polarization measurements. They illustrate the kinetic models derived in papers I and II of this series.     

6-aza-5,8,10-trideaza analogues of tetrahydrofolic acid and tetrahydroaminopterin: Synthesis and biological studies

6-Aza-5,8,10-trideaza-5,6,7,8-tetrahydrofolic acid ( 3 ) and 6-aza-5,8,10-trideaza-5,6,7,8-tetrahydroamino-pterin ( 4 ) were synthesized from 6-aza-5,8,10-trideaza-5,6,7,8-tetrahydropteroic acid ( 5 ) and 4-amino-6-aza-5,8,10-trideaza-4-deoxy-5,6,7,8-tetrahydropteroic acid ( 6 ), respectively, by mixed carboxylic-carbonic anhydride condensation with dimethyl L-glutamate followed by ester hydrolysis. The pteroic acid analogues 5 and 6 were prepared in several steps from 1-benzyl-3-carbethoxypiperidin-4-one via 2-amino-6-benzyl-5,6,7,8-te-trahydropyrido[4,3-d]pyrimidin-4(3H)-one ( 7 ). Compound 3 did not inhibit the growth of L1210 mouse leukemia cells in culture, and was not an inhibitor of dihydrofolate reductase (DHFR) or thymidylate synthase (TS). It was a very poor substrate for mouse liver folylpolyglutamate synthetase (FPGS). The 2,4-diamino analogue 4 was only a marginal substrate for FPGS, yet showed activity comparable to methotrexate as a DHFR inhibitor and as an inhibitor of tumor cell growth. The cytotoxicity of 4 is noteworthy because this compound is, to our knowledge, the first example of a classical antifolate which forms polyglutamates poorly even though it contains an intact p-aminobenzoyl-L-glutamic acid side-chain. The inability of 3 and 4 to form polyglutamates indicates that a basic nitrogen at position 6 is highly unfavorable for binding to FPGS.     

All free of complex expansion null orbits type-D electrovac solutions with λ

The free of complex expansion type-D solutions of Einstein-Maxwell equations with cosmological constant possessing a noninvertible group of local isometries with null orbits for the alignment of the general electromagnetic field along the doubleD-P directions are presented. These solutions are endowed with five continuous parameters, and are found to be a special case of the Carter non-null orbits metricB(–).     

Increased apparent sensitivity by means of constant-energy synchronous spectrofluorimetry

Synchronous fluorescence scanning at constant wavenumber (i.e., energy) difference between excitation and emission brings several improvements when compared to the classical spectrofluorimetry or to the method of synchrnous wavelength scanning. When quantitative results are required, the constant energy-difference technique should be used whenever the difference between the excitation and emission wavelengths exceeds the difference between the wavelengths of the Rayleigh and Raman peaks. Otherwise, the technique brings only minor advantages in comparison with synchronous wavelength scanning.