Hydrocarbon-free resonance transition 795-nm rubidium laser

For what we believe to be the first time, an optical resonance transition rubidium laser (5(2)P(1/2)-->5(2)S(1/2)) has been demonstrated with a hydrocarbon-free buffer gas. Prior demonstrations of alkali resonance transition lasers have used ethane as either the buffer gas or a buffer gas component to promote rapid fine-structure mixing. However, our experience suggests that the alkali vapor reacts with the ethane producing carbon as one of the reaction products. This degrades long term laser reliability. Our recent experimental results with a "clean" helium-only buffer gas system demonstrate all the advantages of the original alkali laser system, but without the reliability issues associated with the use of ethane.     

Oxidative addition of dialkylphosphine oxides and of alkyl alkylphosphonites to iridium(I)

Dimethyl- and diethyl-phosphine oxide, methyl methylphosphonite and ethyl methylphosphonite all oxidatively add to (Me₂PhP)₃IrCl, generated in situ, to give hydrido(dialkylphosphinito)- or alkyl (alkylphosphonito)-iridium(III) complexes.     

Surface acoustic wave devices and applications: 4. Bandpass filters

Surface acoustic wave filters offer a number of advantages over conventional filters in size, simplicity and flexibility. This paper describes the basic design strategy and emphasizes the limitations on available performance. A number of experimental designs are illustrated.     

The synthesis of an unusual dihydropyrene containing one aromatic π-cloud within and perpendicular to a second.

trans-10b-methyl-IOc-phenyl-10,10c-dlhydropyrene is prepared. Its ^?1Hmr spectrum shows the internal aryl protons are the most highly shielded aryl protons yet reported.     

Marrow infarction in sickle cell anemia: correlation with marrow type and distribution by MRI

Ischemic necrosis of bone is believed to occur exclusively in areas of predominantly fatty marrow. Sickle cell disease is unusual in that marrow infarction occurs in areas of active hematopoiesis. MR images of long bone obtained in ten patients with sickle cell anemia (SCA) were analyzed to correlate the distribution and appearance of marrow infarction with the type of marrow. While the hematopoietic marrow predominated in metaphyseal and diaphyseal regions of femurs and tibias, the fatty or mixed marrow was the most common pattern in epiphyses. Infarcts occurred in fatty as well as hematopoietic marrow. Marrow infarcts were isointense or minimally hyperintense on T1 weighted images with the hematopoietic marrow and therefore difficult to detect. On T2 weighted images, the infarcts showed very high signal. T2 weighted images are essential for detection of marrow infarction. Soft tissue changes seen as low signal on T1 and high signal on T2, may be secondary to intramuscular injections of analgesics or muscle ischemia occurring during sickle crisis.     

Kinetics of the reactions of atomic chlorine with methanol and the hydroxymethyl radical with molecular oxygen at 298 K

The rate constants for the reactions Cl + CH₃OD → CH₂OD + HCl (1) and CH₂OH + O₂ → HO₂ + H₂CO (2) have been determined in a discharge flow system near 1 torr pressure with detection of radical and molecular species using collision-free sampling mass spectrometry. The rate constant k₁, determined from the decay of CH₃OD in the presence of excess Cl, is (5.1 ± 1.0) × 10^?11 cm³ s^?1. This is in reasonable agreement with the only previous measurement of k₁. The CH₂OH radical was produced by reaction (1) and its reaction with O₂ was studied by monitoring the decay of the CH₂OH radical in the presence of excess O₂. The result is k₂ = (8.6 ± 2.0) × 10^?12 cm³ s^?1. Previous estimates of k₂ have differed by nearly an order of magnitude, and our value for k₂ supports the more recent high values.