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Notes: Spatially resolved arc temperatures and sodium density measurements are presented for two high-pressure sodium arcs. Absolute intensities of the optically thick 818/819-nm lines were used to determine the arc temperature while the radial profile of the optically thin 514-nm line was Abel inverted to determine the Na atomic density. Agreement with an independent measurement of the Na density obtained by controlling pressure of sodium in the lamp with a tin bath consistently required a value for the Na 514-nm transition probability 2–3 times smaller than the literature value (A=0.011×108 s−1 ) of Wiese, Smith, and Miles [Atomic Transition Probabilities, NSRDS-NBS 4 (NBS, Washington, DC, 1971), Vol. II], obtained from quantum mechanical calculations. The results of three separate experiments indicate that the value should be modified to A=0.0040×108 s−1 with a standard deviation of ±21%. A more detailed error analysis including systematic error would indicate an accuracy to within ±33%.

Notes: At Deobhog, migmatitic gneisses and granulites of the Eastern Ghats Belt are juxtaposed against a cratonic ensemble of banded augen gneiss, amphibolite and calcsilicate gneiss, intruded by late hornblende granite and dolerite. In the migmatitic gneiss unit, early isoclinal folds (syn-D1M and D2M) are reoriented along N–S-trending and E-dipping shear planes (S3M), with (S1M–S3M) intersection lineations having steep to moderate plunges. The near-peak P–T  condition was syn-D3M (≥900 °C, 9.5 kbar), as inferred from syn-D3M Grt+Opx-bearing leucosomes in mafic granulites, and from thermobarometry on Grt (corona)–Opx/Cpx–Pl–Qtz assemblages. The P–T  values are consistent with the occurrence of Opx–Spr–Crd assemblages in spatially associated high-Mg–Al pelites. A subsequent period of cooling followed by isothermal decompression (800–850 °C, c. 7 kbar) is documented by the formation of coronal garnet and its decomposition to Opx+Pl symplectites in mafic granulites. Hydrous fluid infiltration accompanying the retrograde changes is manifested in biotite replacing Opx in some lithologies.The cratonic banded gneiss–granite unit also documents two phases of isoclinal folding (D1B & D2B), with the L2B lineation girdle different from the lineation spread in the migmatitic gneiss unit. Calcsilicate gneiss (Hbl–Pl–Cpx–Scap–Cal) and amphibolite (Hbl–Pl±Grt±Cpx) within banded gneisses record syn-D2B peak metamorphic conditions (c. 700 °C, 6.5 kbar), followed by cooling (to c. 500 °C) manifested in the stabilization of coronal clinozoisite–epidote. The D3B shear deformation post-dates granite and dolerite intrusions and is characterized by top-to-the-west movement along N–S-trending, E-dipping shear planes. Deformation mechanisms of quartz and feldspar in granites and banded gneisses and amphibole–plagioclase thermometry within shear bands in dolerites document an inverted syn-D3B thermal gradient with temperature increasing from 350 to 550 °C in the west to ≥700 °C near the contact with the migmatitic gneiss unit. The thermal gradient is reflected in the stabilization of chlorite after hornblende in S3B shears to the west, and post-D2B neosome segregation along D3B folds and shears to the east.The contrasting lithologies, early structures and peak metamorphic conditions in the two units indicate unconnected pre-D3P–T –deformation histories. The shared D3 deformation in the two units, the syn-D3 inverted thermal gradient preserved in the footwall cratonic rocks and the complementary cooling and hydration of the hanging wall granulites across the contact are attributed to westward thrusting of ‘hot’ Eastern Ghats granulites on ‘cool’ cratonic crust. It is suggested that the Eastern Ghats migmatitic gneiss unit is not a reworked part of the craton, but a para-autochthonous/allochthonous unit emplaced on and amalgamated to the craton.

Notes: Manganese-rich and manganese-poor iron formations which occur as thin layers in the Halaguru-Satnuru area, south of Kabbaldurga, Karnataka, India are chemically intermediate between the ‘Algoma’and ‘Lake Superior’types, but higher in their MnO and TiO2 contents. The rocks are of four petrographic varieties: (a) quartz-magnetite-orthopyroxene-clinopyroxene, (b) quartz-magnetite-orthopyroxene-clinopyroxene-garnet, (c) quartz-magnetite-clinopyroxene-garnet, and (d) quartz-magnetite-clinopyroxene-garnet-plagioclase.In the orthopyroxene-clinopyroxene pairs, Mn-Mg and Mn-Fe exchange is ideal irrespective of the MnSiO3 contents of orthopyroxenes (0.6–1.8 mol. % in Mn-poor and 15–25 mol. % in Mn-rich compositions). Mg-Fe exchange in the same pair is however non-ideal. Mn-Fe exchange in orthopyroxene-garnet pairs is ideal. The distribution patterns in the other binaries are inconclusive regarding ideality of exchange. Orthopyroxene-garnet and clinopyroxene-garnet geothermometers, modified for high spessartine contents, give temperatures of 800 ± 30° C. A modified version of the Harley (1984) geothermometer registers 740 ± 60° C, in agreement with the consensus temperature value.The equilibrium log ffo2 values in the iron formations, as calculated from the reaction 6FeSiO3+ O2= 2Fe3O4+ 6SiO2 are in the range of −14.2 to −15.5. Algebraic analysis of variations of fo2 with composition of phases indicates buffering of O2 in the rocks. The absence of grunerite in these assemblages is compatible with XH2O being less than 0.3 in the ambient fluid. Computations from volatile equilibria in the C-O-H system, however, predict high XH2O values (〉0.7) at ac= 1.0, implying that the activity of graphite must have been greatly reduced—this is in accordance with the absence of graphite in these rocks.

Notes: Entamoeba histolytica, the protozoan parasite, is the causative agent of amoebiasis. The degree of virulence, as inferred from invasiveness, of potentially pathogenic strains may be regulated by both host and parasite factors that determine the gut environment. One such factor that plays an important role is the bacterial flora in the gut. Previous studies have clearly shown that bacterial flora is an important determinant of virulence in E. histolytica. However, the exact nature of changes induced in E. histolytica in response to bacteria and their role in virulence is not clear. In this study the levels of a number of molecules potentially important in virulence mechanisms were determined in E. histolytica cells grown with and without normal human bacterial flora, using enzyme-linked immunosorbent assay. Significant changes were observed only after the E. histolytica cells had been adapted to grow with bacterial flora for a number of generations, and not in short term culture.

Notes: A laser-induced fluorescence method for measuring the loss rate of barium from Ba-Sr-Ca oxide coated electrodes of low-pressure discharge lamps is presented. The oxide coating from the electrode surface is depleted during lamp operation. Using this technique, the Ba loss rate from an electrode, when it is acting both as a cathode and an anode during ac operation, was measured. A significantly larger amount of neutral barium is detected in the vicinity of the electrode when it acts as an anode over when it acts as a cathode. The consumption rate of Ba and hence the life of an oxide coating depends upon the phase of the lamp current, the shape, and the magnitude of the current supplied by the lamp ballast. The consumption rate for the coating increases linearly with the discharge current. A simplified theoretical analysis of the technique for a three-level atomic system irradiated by a pulse laser beam is discussed.

Notes: A laser-induced fluorescence technique for the detection and measurement of ionized barium atoms near the vicinity of an oxide-coated electrode in a low-pressure discharge lamp is presented. Ionized Ba atoms are produced by the ionization of neutral Ba atoms in the electrode fall region of the discharge. Radiation at 455.4 nm obtained from a pulsed dye laser was used to excite Ba ii from the ground state, 62S1/2, to the resonance level, 62P3/2, and the fluorescence radiation at 614.2 nm for the 62P3/2→52D5/2 transition was measured. The number density of Ba ii atoms as determined from the measured intensity of the fluorescence signal (614.2 nm) is dependent on the discharge current, and the polarity of the neighboring electrode. It is found to be larger when it is acting as an anode than when it is a cathode.

Notes: 3 W cw output power has been obtained from aluminum-free, strained-layer double-quantum well (DQW) InGaAs/InGaAsP/InGaP uncoated, 100-μm-wide stripe diode lasers (λ=0.945 μm) grown by low-pressure MOCVD on exact (100) GaAs substrates. The combination of high-band-gap (1.62 eV) InGaAsP confinement layers and the DQW structure provides relatively weak temperature dependence for both the threshold current Ith as well as the external differential quantum efficiency ηd. Furthermore, the series electrical resistance for 100 μm×600 μm stripe-contact devices is as low as 0.12 Ω. As a result, the power conversion efficiency reaches a maximum of 40% at 8×Ith, and decreases to only 33% at the maximum power (i.e., 3 W) at 28×Ith. Low-temperature (12 K) photoluminescence measurements of InGaAs/InGaAsP quantum-well structures exhibit narrow linewidths (〈10 meV) for material grown on exact (100) GaAs substrates, while growths on misoriented substrates exhibit linewidth broadening, as a result of "step bunching.'' Laser structures grown on misoriented substrates exhibit increased temperature sensitivity of both Ith and ηd, compared with structures grown on exact (100) substrates. © 1995 American Institute of Physics.

Notes: Al-free 980 nm InGaAs/InGaAsP/InGaP laser structures grown by low-pressure metalorganic chemical vapor deposition (LP-MOCVD) have been optimized for high cw output power by incorporating a broad waveguide design. Increasing the optical-confinement layer total thickness from 0.2 to 1.0 μm decreases the internal loss fivefold to 1.0–1.5 cm−1, and doubles the transverse spot size to 0.6 μm (full width half-maximum). Consequently, 4-mm long, 100-μm-aperture devices emit up to 8.1 W front-facet cw power. cw power conversion efficiencies as high as 59% are obtained from 0.5-mm long devices. Catastrophic-optical-mirror-damage (COMD) power-density levels reach 15.0–15.5 MW/cm2, and are found similar to those for InGaAs/AlGaAs facet-coated diode lasers. © 1996 American Institute of Physics.