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We have observed a strong two-photon absorption in the B 2Σ+←X 2Σ+(3,0) band of CN by means of a resonant enhancement through the A 2Πi, v’=4 level. Many lines are seen in the two-photon spectrum due to multiple single-photon near resonances in the A 2Πi←X 2Σ+(4,0) band. The detuning of the laser from these resonances varies from less than one to hundreds of wave numbers, producing unusually large intensity variations in the two-photon spectrum. This effect is not observed in two-photon transitions far from resonance. Resonant enhancement is observed over a range from N=5 to 20. We know of no other molecular two-photon transition in which a near resonance produces such dramatically varying intensities over a short range of rotational levels. A calculation of the line strengths for these transitions reproduces the major features of the spectrum. [ABSTRACT FROM AUTHOR]

Fluorescence in the A 2A1-X 2B1 system of the NH2 radical has been excited in NH3/N2O/N2, H2/N2O/N2, and CH4/N2O/N2 flames using the 6471 Å line of a krypton ion laser. Rotationally resolved fluorescence spectra indicate that the laser simultaneously pumps two rotational lines in the (0,11,0)–(0,2,0)∑ vibrational hot band of the radical. The placement of the laser line relative to the two molecular transitions has been inferred from intensities in the fluroescence spectrum. Rotational and vibrational energy transfer in the excited state were observed to be very slow in comparison to electronic quenching by the flame molecules. An NH2 density profile in a rich H2/N2O/N2 flame is given. Also, a method for the calculation of Einstein coefficients and oscillator strengths for nonperturbed, main-branch transitions is presented. [ABSTRACT FROM AUTHOR]

Laser induced fluorescence in the (0,0) band of the A 2Σ+–X 2π system of the PO radical (∼2470 Å) has been used to study the radiative properties of the A state. A laser excitation scan of the (0,0) band and a fluorescence scan of the emission are given. Fluorescence from the B 2Σ+ state to the X state was observed (∼3250 Å) when the A state was pumped by the laser. The branching ratio for emission from the A state to the lower B and X states was indirectly determined. The A state was found to have a very short free radiative lifetime, 9.68±0.47 ns. In the absence of quenching, the excited state decay is found to be primarily due to radiative processes. Upper limits were determined for the quenching rates of Ar and He carrier gases. Relative intensities of emission of the v’=0 progression in the A–X system were also measured. These intensities were used to determine the electronic transition moment function in the region of the equilibrium internuclear distance. [ABSTRACT FROM AUTHOR]

Pulsed laser excited fluorescence in the B 2Σ+ ← X 2π system of gas phase PO was used to measure the lifetime for v’=0 of the B state. Rotationally resolved measurements for a few selected J’ levels, at Ar or He carrier gas pressures of ∼2 Torr, reveal no dependence of the lifetime on the rotational level excited. Earlier measurements of relative fluorescence intensities in the v’=0 vibrational progression were reinterpreted to extract the dependence of the electronic transition moment on internuclear distance. Using this transition moment, no lifetime dependence on rotational level is to be expected, even at low pressures. Rate constants for quenching of the B state PO by N2, O2, CO2, and H2O, and upper limits thereof for He and Ar are reported. O2 was found to react with ground state PO. A crude measurement of the rate constant was performed. The result is compared to two other known measurements. The rate constant is in excellent agreement with the previous measurement, but in poor agreement with that of a concurrent study. Further work is required to determine the reason for the discrepancy. A cathode ray–vidicon type waveform digitizer was found to lend itself readily to the lifetime measurements, wherein a low repetition rate laser was used. Unfortunately, it was discovered that small nonlinearities (∼1% of full scale) in the digitizer response have a marked effect on the fits to the exponential lifetime decays and, especially, the quenching rate constants. We believe this problem is not commonly recognized. A simple method for calibration of this type of digitizer and removal of these effects is presented. [ABSTRACT FROM AUTHOR]

The relationship between proton-donor affinity for SmII ions and the reduction of two substrates (anthracene and benzyl chloride) was examined. A combination of spectroscopic, thermochemical, and kinetic studies show that only those proton donors that coordinate or chelate strongly to SmII promote anthracene reduction through a PCET process. These studies demonstrate that the combination of SmII ions and water does not provide a unique reagent system for formal hydrogen atom transfer to substrates. [ABSTRACT FROM AUTHOR]

The relationship between proton-donor affinity for SmII ions and the reduction of two substrates (anthracene and benzyl chloride) was examined. A combination of spectroscopic, thermochemical, and kinetic studies show that only those proton donors that coordinate or chelate strongly to SmII promote anthracene reduction through a PCET process. These studies demonstrate that the combination of SmII ions and water does not provide a unique reagent system for formal hydrogen atom transfer to substrates. [ABSTRACT FROM AUTHOR]

Seven new species of neotropical Malpighiaceae are described: Aspicarpa steinmannii, Bunchosia breedlovei, and Bunchosia cruciana from Mexico; Bunchosia soejartoi, Lophanthera marcelae, and Mascagnia corymbosa from Colombia; and Heteropterys tiinae from Peru. [ABSTRACT FROM AUTHOR]

The approximately 42 lineages of Malpighiaceae currently known in Mexico are identified and briefly described and discussed. All the Mexican lineages have their ultimate roots in South America, although in some cases the connections are inferred only through phylogeny and several Mexican genera probably originated in Mexico. All the lineages have effective adaptations for dispersal except the genus Galphimia, but distributions outside Mexico and a phylogenetic tree suggest that while many Malpighiaceae reached Mexico through "stepping-stone" dispersal, some lineages probably arrived as the result of episodes of long-distance dispersal from South America. [ABSTRACT FROM AUTHOR]

Abstract: The formation of propellant dark zone (DZ) structures in the gaseous flames above many solid propellants has been a subject of recurrent interest to us for about 20years. The DZ structure is controlled by small molecule chemistry. The DZ chemistry is very important in controlling both the flame structure at low pressure (10–100atm) and burning rates at high pressure (above ∼500atm), even though DZs collapse at higher pressures. We developed a detailed, frequently updated mechanism to model it. This report reviews prior work, introduces our most recent modeling results, and documents the first quantitative tests of several key assumptions. All relevant experimental literature is critically assessed to identify datasets for testing our model. Comparison of predictions and experimental results shows reasonable agreement, and thus we advocate use of our mechanism. But the precision of both experiments and predictions is not tight, nor are there many test datasets. Further experimentation is needed, and types of study that would be of greatest benefit are suggested. A detailed discussion of the chemistry that controls DZ structure is presented. [Copyright &y& Elsevier]

• Premise of the study: The Malpighiaceae include ~1300 tropical flowering plant species in which generic definitions and intergeneric relationships have long been problematic. The goals of our study were to resolve relationships among the 11 generic segregates from the New World genus Mascagnia, test the monophyly of the largest remaining Malpighiaceae genera, and clarify the placement of Old World Malpighiaceae. • Methods: We combined DNA sequence data for tour genes (plastid ndhF, matK, and rbcL and nuclear PHYC) from 338 ingroup accessions that represented all 77 currently recognized genera with morphological data from 144 ingroup species to produce a complete generic phylogeny of the family. • Key results and conclusions: The genera are distributed among 14 mostly well-supported clades. The interrelationships of these major subclades have strong support, except for the clade comprising the wing-fruited genera (i.e., the malpighioid+Amorimia, Ectopopterys, hiraeoid, stigmaphylloid, and tetrapteroid clades). These results resolve numerous systematic problems, while others have emerged and constitute opportunities for future study. Malpighiaceae migrated from the New to Old World nine times, with two of those migrants being very recent arrivals from the New World. The seven other Old World clades dispersed much earlier, likely during the Tertiary. Comparison of floral morphology in Old World Malpighiaceae with their closest New World relatives suggests that morphological stasis in the New World likely results from selection by neotropical oil-bee pollinators and that the morphological diversity found in Old World flowers has evolved following their release from selection by those bees. [ABSTRACT FROM AUTHOR]

Callaeum johnsonii (Malpighiaceae), from the state of Puebla, Mexico, is described as new and illustrated. It is similar to C. clavipetalum D. M. Johnson of Oaxaca, differing in characters of the stipules, leaves, bracts, and bracteoles. [ABSTRACT FROM AUTHOR]

Provides information on a study that examined phylogenetic analyses of chloroplast DNA nucleotide sequences to help resolve the phylogeny of Malpighiaceae. Background on Malpighiaceae; Methodology; Results and discussion.

Latex and laticifers are reported for the first time in the genera Galphimia and Verrucularia (Malpighiaceae), with description and illustration of the leaf and stem anatomy of both genera. Those genera and the other two in which latex is known (Lophanthera and Spachea) constitute a single tribe, Galphimieae, that is at or near the base of the family's phylogeny, which suggests that latex in the Malpighiaceae may indicate an ancestor shared with the Euphorbiaceae. [ABSTRACT FROM AUTHOR]

Deals with a study that investigated intergeneric relationships within Malpighiaceae by using phylogenetic analyses of DNA nucleotide sequences from the plastid genes rbcL and matK. Background on Malpighiaceae; Methodology; Results and discussion.

Focuses on the dibenzofuan heterocycles, which relates to organic chemistry. Indepth look at experiments which were conducted.

Two secondary amides (N-methylacetamide and 2-pyrrolidinone) were used as additives with SmI2 in THF to estimate the extent of N-H bond weakening upon coordination. Mechanistic and synthetic studies demonstrate significant bond-weakening, providing a reagent system capable of reducing a range of substrates through formal hydrogen atom transfer. [ABSTRACT FROM AUTHOR]

Abstract: Numerous plant species worldwide including Palicourea marcgravii and Tanaecium bilabiatum in Brazil cause sudden death and are known to contain monofluoroacetate (MFA). Other species in Brazil including some species traditionally assigned to Mascagnia but now properly called Amorimia species and other Palicourea species are reported to cause sudden death in livestock and are suspected to contain MFA due to the similarity of clinical signs. In this study, an HPLC–APCI–MS method to detect and quantify MFA was developed and was used to investigate plant material from field collections and/or herbarium specimens of Mascagnia, Amorimia, and Palicourea species suspected of causing sudden death. MFA was detected in Amorimia amazonica, Amorimia camporum, Amorimia exotropica, Amorimia pubiflora, Amorimia rigida, and Amorimia septentrionalis as well as Palicourea aeneofusca. MFA concentrations differ greatly between Palicourea species and Amorimia species, which may explain the incidence of poisoning and the amount of plant material required to cause sudden death between these taxa. [Copyright &y& Elsevier]

Abstract: The reaction of ground-state NH with H2 has been studied in a high-temperature photochemistry (HTP) reactor. The radicals were generated by the 2-photon 193 nm photolysis of NH3, following the decay of the originally produced radicals. Laser-induced fluorescence on the transition at 336 nm was used to monitor the progress of the reaction. We obtained , with precision limits varying from 12 to 33% and corresponding accuracy levels from 23 to 39%. This result is in excellent agreement with that of Rohrig and Wagner [Proc. Combust. Inst. 25 (1994) 975] and the data sets can be combined to yield . Starting with this agreement, it is argued that their rate coefficients for NH + CO2 could not be significantly in error [Proc. Combust. Inst. 25 (1994) 975]. This, combined with models of several combustion systems, indicates that HNO + CO cannot be the products, contrary to their suggestion [Proc. Combust. Inst. 25 (1994) 975]. Ab initio calculations have been performed which confirm this conclusion by showing the barriers leading to these products to be too high compared to the measured activation energies. The calculations indicate the likelihood of formation of adducts, of low stability. These then may undergo further reactions. The NH + H2O reaction is briefly discussed and it is similarly argued that HNO + H2 cannot be the products, as had been previously suggested. [Copyright &y& Elsevier]

In vivo bioluminescence imaging has been used to monitor Staphylococcus aureus infections in preclinical models by employing bacterial reporter strains possessing a modified lux operon from Photorhabdus luminescens. However, the relatively short emission wavelength of lux (peak 490 nm) has limited tissue penetration. To overcome this limitation, the gene for the click beetle (Pyrophorus plagiophtalamus) red luciferase (luc) (with a longer >600 emission wavelength), was introduced singly and in combination with the lux operon into a methicillin-resistant S. aureus strain. After administration of the substrate D-luciferin, the luc bioluminescent signal was substantially greater than the lux signal in vitro. The luc signal had enhanced tissue penetration and improved anatomical co-registration with infected internal organs compared with the lux signal in a mouse model of S. aureus bacteremia with a sensitivity of approximately 3 × 104 CFU from the kidneys. Finally, in an in vivo mixed bacterial wound infection mouse model, S. aureus luc signals could be spectrally unmixed from Pseudomonas aeruginosa lux signals to noninvasively monitor the bacterial burden of both strains. Therefore, the S. aureus luc reporter may provide a technological advance for monitoring invasive organ dissemination during S. aureus bacteremia and for studying bacterial dynamics during mixed infections. [ABSTRACT FROM AUTHOR]