Observation of Zeeman degeneracy effects in collisional intense field resonance fluorescence

We report observation of the scattered spectrum from a Zeeman degenerate atom at high laser intensities. For a J = 0 to J = 1 transition in the presence of collisions we observe an asymmetric triplet in the polarization parallel to the incident laser and an asymmetric doublet in the polarization perpendicular to the incident laser.     

Gadolinium oxide: a protoype agent for contrast enhanced imaging of the liver and spleen with magnetic resonance

Gd2O3 particles (less than 2 microns) in suspension were evaluated as a potential contrast agent for liver-spleen imaging with magnetic resonance. The agent was administered IV to rabbits in doses ranging from 10 to 120 mumol/kg and the tissues removed after sacrifice for in vitro T1 and T2 analysis. The temporal response was determined in liver and spleen samples of rabbits given a fixed dose (60 mumol/kg) and sacrificed at intervals from 15 min to 60 hr later. Documentation of the subanatomic location of Gd2O3 particles in tissue was accomplished by electron microscopy and x-ray dispersion microanalysis. T1 weighted images were obtained at 0.12T on a prototype resistive scanner. The liver, spleen, and lung relaxation times are very responsive to Gd2O3 IV and the effect is dose related. A peak effect is observed between 3-7 hr after injection and relaxation times may normalize by 60 hr. By electron microscopic and x-ray analysis, Gd2O3 is most prominently found in the hepatic and splenic sinusoids. The images show marked enhancement of liver and splenic tissues, aiding in the clear delineation of these tissues from neighboring structures.     

CO2 laser induced compton effect in underdense hydrogen plasma

Recent experimental observation of induced scattering of CO₂ laser radiation by an underdense hydrogen plasma can be explained theoretically by non-linear and Compton scattering from ions in the highly cooperative plasma conditions prevailing (kλ_D? 1).     

Preliminary experiments on the rheology of bovine blood-clot

Summary The bahaviour of clotted cow's blood, subjected at 32° C to stresses in a U-tube gelometer designed to follow the coagulation of milk, may be closely represented by a simple (Maxwell) model consisting of a dashpot and spring in series. The dashpot contains aNewtonian fluid and the spring is very nearlyHookean. The elasticity shows no appreciable after-effect or static fatigue. This simple form of behaviour is confirmed in creep and in all but the latest stages of constant strain relaxation, the relaxation time being about 70 sec. In all these respects, the clotted cow's blood proves to be a much simpler rheological system than is the milk gel.

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Zusammenfassung Das Verhalten von geronnenem Rinderblut bei 32° C in einem U-R?hren-Gelometer, das gebaut wurde, um die Koagulation der Milch zu verfolgen, mechanischer Beanspruchung unterworfen, kann ziemlich genau durch ein einfaches (Maxwell-) Modell dargestellt werden, das aus einem D?mpfungskolben und einer Feder in Reihe besteht. Der Kolben verh?lt sich newtonisch und die Feder entspricht nahezu der einer demHooke- schen Gesetz folgenden. Die Elastizit?t zeigt keinen wesentlichen Nacheffekt, keine statische Ermüdung. Diese einfache Art des Verhaltens best?tigt sich auch aus dem Kriechverhalten und für alle au?er den Endstadien, aus der Spannungsrelaxation, wobei die Relaxationszeit ungef?hr 70 sec betr?gt. In allen Hinsichten erweist sich das geronnene Rinderblut als ein viel einfacheres rheologisches System als koagulierte Milch.

     

[(2,3-O-Isopropylidene-5-O-(triphenylmethyl)-α-D-ribofuranosyl]-triphenylstannane

The synthesis, IR, MS, solution and solid state NMR spectra and X-ray structure of (2,3-O-isopropylidene-5-O-(triphenylmethyl)--D-ribofuranosyl]triphenylstannane 1 (R₃Sn) are reported. Compound, 1 (R₃Sn) crystallizes in the orthorhombic space group C222₁ (Z = 8), with a = 8.935(4), b = 17.058(7), c = 47.94(5)Å. There are two short tin–oxygen separations, at 3.030(7) [involving O4, on an alpha carbon] and 3.094(7) Å [involving O2, on a beta carbon]. Only the O4 atom is considered to form a weak and additional bond to tin; this results in a deviation of the geometry at tin toward trigonal bypramid from tetrahedral, with O4 and C34 in the axial sites [C34– Sn–O4=152.3(3)°]. The conformation of the ribofuranosyl ring in the solid state is E _o [P, the phase angle of pseudorotation, = 268.4(9)° and _max , the puckering amplitude, = 38.0(6)°], while the isopropylidene ring conformation is between the envelope form, E _C6, and the twist form, ^O3 T _C6 [P = 46.5(10)° and _max = 36.9(6)°]. In solution, the ribofuranosyl ring adopts a conformation between E _o and ¹ T _o.     

O-[(Triorganostannyl)methyl] derivatives of 1,2-O-isopropylidene-α-D-xylofuranose

The synthesis, mass, IR and NMR spectra of 3-O-benzyl-1,2-O-isopropylidene-5-O-[(triphenylstannyl)methyl]--D-xylofuranose (9) and 1,2-O-isopropylidene-3-O-(R₃SnCH₂)-5-O-triphenylmethyl--D-xylofuranose (10, R=Bu or Ph) are reported, as is the X-ray structure of10 (R=Ph). Compound10 (R=Ph), crystallizes in the orthorhombic space groupP2₁2₁2₁ (Z=4), witha=11.006(4) Å,b=17.096(6) Å,c=21.164(7) Å. The conformation of the furanose ring in solid10 (R=Ph) is a 8218 mixture of the envelope (E₄) and twist (³T₄) forms: the isopropylidene ring conformation is similarly a mixture of envelope and twist forms, with the former dominant. On dissolution, the furanose ring of10 (R=Ph) undergoes a conformation change, with the³T₂ conformation becoming the major form. The tin center in10 is four-coordinate and has a tetrahedral geometry.     

Determination of arsenic in organic compounds rapid micro and semimicro methods

Rapid micro and semimicro methods for determination of arsenic in organic compounds have been developed using 28% chloric acid as the digesting agent for the organic arsenical. This wet acid digestion procedure does not lead to loss of arsenic even in the presence of 4 M chloride.The semimicro method completes the assay by reduction of the pentavalent arsenic with iodide, destruction of the iodine liberated with thiosulfate and re-oxidation to pentavalent arsenic with iodine in a buffered solution. The micro method completes the assay by development of a heteropoly molybdenum blue using a single solution reagent at room temperature. The color is reproducible so that only a single calibration curve for the instrument used is necessary.     

Relating the microscopic rules in coalescence-fragmentation models to the cluster-size distribution

Coalescence-fragmentation problems are now of great interest across the physical, biological, and social sciences. They are typically studied from the perspective of rate equations, at the heart of which are the rules used for coalescence and fragmentation. Here we discuss how changes in these microscopic rules affect the macroscopic cluster-size distribution which emerges from the solution to the rate equation. Our analysis elucidates the crucial role that the fragmentation rule can play in such dynamical grouping models. We focus our discussion on two well-known models whose fragmentation rules lie at opposite extremes. In particular, we provide a range of generalizations and new analytic results for the well-known model of social group formation developed by Eguíluz and Zimmermann, [Phys. Rev. Lett. 85, 5659 (2000)]. We develop analytic perturbation treatments of this original model, and extend the analytic analysis to the treatment of growing and declining populations.