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A number of technologies would benefit from developing inorganic compounds and materials with specific electronic and magnetic exchange properties. Unfortunately, designing compounds with these properties is difficult because metal⋅⋅⋅metal coupling schemes are hard to predict and control. Fully characterizing communication between metals in existing compounds that exhibit interesting properties could provide valuable insight and advance those predictive capabilities. One such class of molecules are the series of Lindqvist iron-functionalized and hexavanadium polyoxovanadate-alkoxide clusters, which we characterized here using V K-edge X-ray absorption spectroscopy. Substantial changes in the pre-edge peak intensities were observed that tracked with the V 3d-electron count. The data also suggested substantial delocalization between the vanadium cations. Meanwhile, the FeIII cations were electronically isolated from the polyoxovanadate core.

Alkali atoms trapped in solid hydrogen matrices have demonstrated ultralong electron spin coherence times, and are promising as quantum sensors. Their spin coherence is limited by magnetic noise from naturally-occurring orthohydrogen molecules in the parahydrogen matrix. In the gas phase, the orthohydrogen component of hydrogen can be converted to parahydrogen by flowing it over a catalyst held at cryogenic temperatures, with lower temperatures giving a lower orthohydrogen fraction. In this work, we use a single cryostat to reduce the orthohydrogen fraction of hydrogen gas and grow a solid matrix from the resulting high-purity parahydrogen. We demonstrate operation of the catalyst down to a temperature of 8 K, and we spectroscopically verify that orthohydrogen impurities in the resulting solid are at a level < 1e-6. We also find that, at sufficiently low temperatures, the cryogenic catalyst provides isotopic purification, reducing the HD fraction., 7 pages, 8 figures

It is known from ensemble measurements that rubidium atoms trapped in solid parahydrogen have favorable properties for quantum sensing of magnetic fields. To use a single rubidium atom as a quantum sensor requires a technique capable of efficiently measuring the internal state of a single atom, such as laser-induced fluorescence. In this work we search for laser-induced fluorescence from ensembles of rubidium atoms trapped in solid parahydrogen and, separately, in solid neon. In parahydrogen we find no evidence of fluorescence over the range explored, and we place upper limits on the radiative branching ratio. In neon, we observe laser-induced fluorescence, measure the spectrum of the emitted light, and measure the excited-state lifetime in the matrix. Bleaching of atoms from the excitation light is also reported.

This pre-specified analysis of DAPA-CKD assessed the impact of sodium-glucose cotransporter 2 inhibition on abrupt declines in kidney function in high-risk patients based on having chronic kidney disease (CKD) and substantial albuminuria. DAPA-CKD was a randomized, double-blind, placebo-controlled trial that had a median follow-up of 2.4 years. Adults with CKD (urinary albumin-to-creatinine ratio 200-5000 mg/g and estimated glomerular filtration rate 25-75 mL/min/1.73m2) were randomized to dapagliflozin 10 mg/day matched to placebo (2152 individuals each). An abrupt decline in kidney function was defined as a pre-specified endpoint of doubling of serum creatinine between two subsequent study visits. We also assessed a post-hoc analysis of investigator-reported acute kidney injury-related serious adverse events. Doubling of serum creatinine between two subsequent visits (median time-interval 100 days) occurred in 63 (2.9%) and 91 (4.2%) participants in the dapagliflozin and placebo groups, respectively (hazard ratio 0.68 [95% confidence interval 0.49, 0.94]). Accounting for the competing risk of mortality did not alter our findings. There was no heterogeneity in the effect of dapagliflozin on abrupt declines in kidney function based on baseline subgroups. Acute kidney injury-related serious adverse events were not significantly different and occurred in 52 (2.5%) and 69 (3.2%) participants in the dapagliflozin and placebo groups, respectively (0.77 [0.54, 1.10]). Thus, in patients with CKD and substantial albuminuria, dapagliflozin reduced the risk of abrupt declines in kidney function. HJLH and DC are co-primary authors. The DAPA-CKD Trial Committees and Investigators are listed in the Appendix.

In this work, we measure the properties of ensembles of rubidium atoms trapped in solid neon that are relevant for use as quantum sensors of magnetic fields: the spin coherence of the trapped atoms and the ability to optically control and measure their spin state. We use the rubidium atoms as an AC magnetometer (by employing an appropriate dynamical decoupling sequence) and demonstrate NMR detection of Ne-21 atoms co-trapped in the neon matrix., Comment: 7 pages, 9 figures

We have produced a cryogenic buffer-gas cooled beam of the diatomic molecular radical CH (methylidyne). This molecule is of interest for studying cold chemical reactions and fundamental physics measurements. Its light mass and ground-state structure make it a promising candidate for electrostatic guiding and Stark deceleration, which allows for control over its kinetic energy. This control can facilitate studies of reactions with tuneable collision energies and trapping for precise spectroscopic studies. Here, we have demonstrated electrostatic guiding of CH with fluxes up to $10^9$ molecules per steradian per pulse, 10 pages, 10 figures

Using helium buffer gas cooling, we have prepared dense samples of ground-state molecular calcium monohydride (CaH X 2Σ) at cryogenic temperatures. We have used optical pumping to polarise the spin state of the CaH molecules and we have measured the inelastic collisions of molecular CaH with atomic helium at temperatures from 2 to 7 K. The measured CaH electronic spin depolarisation rate coefficient increases rapidly with increasing temperature, increasing from 2 × 10−13 cm3 s−1 to over 10−11 cm3 s−1. The strong dependence of rate coefficient on temperature is attributed to the CaH population in the first excited rotational state.

We have grown crystals of solid parahydrogen using a single closed-cycle cryostat. We have doped the crystals with rubidium atoms at densities on the order of ${10}^{17}\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}3}$ and used optical pumping to polarize the spin state of the implanted atoms. The optical spectrum of the rubidium atoms shows larger broadening than previous work in which the rubidium was implanted in solid argon or neon. However, the optical pumping behavior is significantly improved, with both a larger optical pumping signal and a longer longitudinal relaxation time. The spin relaxation time shows a strong dependence on orthohydrogen impurity levels in the crystal, as well as the applied magnetic field. Current performance is comparable to state-of-the-art solid state systems at comparable spin densities, with potential for improvement at higher parahydrogen purities.

Graphite nanofibers (GNFs) embedded in paraffin phase change material are found to settle to the bottom of the sample when subjected to repeated thermal cycling. The majority of this settling is found to occur over the first heating/cooling cycle. A method is developed to prevent GNF settling by creating a shape stabilized phase change material using high density polyethylene (HDPE) as a stabilizing polymer. The shape stabilized samples reduced or eliminated GNF settling over repeated thermal cycles with as little as 10% HDPE by weight.

Three types of as prepared and treated graphite nanofibers (GNFs) were used as catalysts in the decomposition of isopropanol to propene and acetone in the presence of oxygen to evaluate the surface chemistry of the fibers. As prepared herringbone fibers were found to produce higher selectivity for propene compared to the as prepared platelet and ribbon fibers at all temperatures explored. Herringbone fibers that had undergone oxidative treatment with nitric acid, phosphoric acid, ruthenium tetroxide or potassium permanganate were also evaluated at a 290 °C. Effects of oxidation treatments on fiber structure were evaluated using a host of analytical techniques including BET, SEM/EDS, TGA, XPS, and fluorescence labeling of surface species. Selectivity for acetone dehydrogenation product or propene dehydration product could be achieved by the appropriate surface treatment. Nitric acid was the mildest treatment and the treated fibers showed minimal changes. (Potassium permanganate was a harsh treatment that almost completely degraded fiber structure, creating amorphous carbon.) Phosphoric acid treated fibers were found to produce very high conversions and almost pure selectivity for propene. Ruthenium tetroxide did not appear to have a large affect on fiber morphology; however, selectivity for acetone was much higher when GNFs were treated with ruthenium tetroxide.

Three types of graphite nanofibers (GNFs), with varying orientations of the graphene sheets (herringbone, platelet, and ribbon), were used as catalysts for the gas-phase oxidative dehydrogenation of ethanol to acetaldehyde and ethyl acetate in the presence of oxygen. The effects of fiber type, temperature, oxygen concentration, and ethanol concentration on conversion and product ratio were explored. When identical processing conditions were employed, herringbone fibers produced higher conversions of ethanol compared to platelet and ribbon fibers, which yielded similar results to one another. Altering equilibrium conditions by increasing oxygen concentration tended to increase conversion as well as increase the percentage of acetaldehyde produced. Adjusting oxygen concentration had a more significant affect on the platelet and ribbon fibers. Temperature also altered the conversion and product ratios as expected. It is believed that the oxygen groups terminating the prismatic edge sites of the graphene planes are responsible for the catalytic activity in oxidative dehydrogenation reactions such as the one explored here.

In this study we explored the use of liquid and supercritical carbon dioxide for the creation of a sustained release drug delivery device. An anti-inflammatory (ketoprofen) was dissolved into carbon dioxide at various temperatures (25−55 °C) and pressures (65−300 bar) and then exposed to biodegradable braided sutures made of poly(lactide-co-glycolide) copolymers. The effect of temperature, pressure (and hence density), and exposure time were explored on the ability of the sutures to absorb ketoprofen. The diffusion of the drug into the suture was modeled, and diffusion coefficients were calculated. The amount of ketoprofen loaded into the suture increased with pressure and density and decreased with temperature; however, increasing temperature tended to speed up the absorption process.

The global kinetics of the oxidation and removal of copper(0) foil were examined in liquid and supercritical CO 2 using tert-butyl peracetate (t-BuPA) as the oxidant and dialkyldithiocarbamate lithium salts (Li + R 2 DTC - , with R = ethyl, propyl, or n-butyl) as the chelating agent. The pressure was kept constant (at 240 bar) for all reactions as density was not found to affect the kinetics at pressures above 150 bar. Temperature was varied between 25 and 60 °C and the concentrations of the oxidant and chelating agents were varied to determine the observed overall reaction orders for each species. Interestingly, under our reaction conditions, the observed global reaction was independent of oxidant concentration but varied due to the R 2 DTC - concentration. The Et 2 DTC - had an observed half order reaction dependence, indicating a complex reaction mechanism while the other two R 2 DTC - had first order dependence suggesting diffusion limitations. Arrhenius expressions were determined by the temperature dependent kinetics of the product, Cu(R 2 DTC) 2 , formation. The apparent activation energy, E a , for the Et 2 DTC - was 66 kJ/mol, confirming a complex reaction mechanism due to its large value. The apparent activation energies for the Pr 2 DTC - and Bu 2 DTC - were 14 and 17 kj/mol, respectively. These low energies are consistent with diffusion limitation.

We report the formation of self-assembled monolayers (SAMs) onto gold substrates by exposure to lithium dialkyldithiocarbamate salts [(Li+(R2DTC-), where R = n-propyl, n-butyl, n-octyl, n-decyl, n-dodecyl, or n-octadecyl] in ethanol or methylene chloride. The crystallinity and composition of the monolayers were assessed by polarized modulation infrared reflection absorption spectroscopy (PM-IRRAS), wettability was characterized by contact angles of water and hexadecane, thickness was measured by spectroscopic ellipsometry, and barrier properties determined by electrochemical impedance spectroscopy. While the shorter R2DTC-s formed monolayers with liquid-like packing, monolayers prepared from the longest R2DTC- (where R = n-octadecyl) exhibit similar thickness, crystallinity, wettability, and capacitance as monolayers prepared from n-octadecanethiol. The hydrocarbon chains within the monolayers prepared from (C18)2DTC- are less canted on average than those prepared from n-octadecanethiol. Nonetheless, the (C18)2DTC- SAM exhibits an order of magnitude lower resistance against the penetration of redox probes, which is attributed to a higher density of pinhole defect sites.

The solubility of two calcium channel blockers, felodipine and nitrendipine, was measured in liquid and supercritical carbon dioxide at (298, 308, and 318) K and at pressures between (80 and 250) bar. The solubilites were measured experimentally through two methods: cloud point measurements and UV absorption. At lower pressures, and hence densities, the UV method was more accurate while at higher pressures and densities the solubilities measured by both methods were basically identical. Both of these compounds showed an increase in solubility with increasing temperature and density. The experimentally determined solubility was accurately modeled using an equation, derived from association laws, which had a strong solvent density and temperature dependence.

Chemical−mechanical planarization (CMP) is a process of oxidizing and chelating the copper overburden present in an interconnect device while mechanically polishing the surface of the wafer. Because the use of condensed CO2 as the solvent for CMP would be environmentally and technically advantageous, several substituted bis(acetylacetonate)ethylenediimine (R4BAE, where R = CH3 or CF3) and lithium or sodium dialkyldithiocarbamate (M+(R2DTC-), where M+ = Li+ or Na+ and R = ethyl, n-propyl, n-butyl, or 1,1,1-trifluoroethyl) ligands were used with t-butylperacetate (t-BuPA, as oxidant) for the oxidative dissolution of copper(0) in supercritical (sc) CO2 at 40 °C and 170−210 bar or in hexanes at 40 °C and atmospheric pressure. The reaction products from the copper etching were determined to be Cu(R4BAE) or Cu(R2DTC)2, respectively. The R2DTC- ligands had higher etch rates than the R4BAE ligands with comparable substituents, and the lithium dialkyldithiocarbamate salts gave higher copper etching rates than thei...

The diffusion and loading of liquid and supercritical carbon dioxide into chitosan spheres with a diameter of 0.5 cm and a mass of 0.055 g was experimentally explored at temperatures of 25, 35, and 45 °C and at fixed carbon dioxide densities of 0.65, 0.75, and 0.85 g/cm3. Loading as high as 1.25 g of carbon dioxide/g of chitosan was achieved. Carbon dioxide loading increased as the carbon dioxide density and temperature each increased. By modeling the loading as unsteady-state radial Fickian diffusion, a diffusion coefficient of carbon dioxide into the chitosan sphere could be obtained at a given exposure temperature and pressure. These diffusion coefficients were on the order of 10-7 m2/s and increased with temperature. Carbon dioxide density did not seem to have a significant effect on the diffusion coefficients, but it did influence the maximum achievable loading.

The solubility of lithium diethyldithiocarbamate, lithium dipropyldithiocarbamate, lithium dibutyldithiocarbamate, and lithium bis(trifluoroethyl)dithiocarbamate was measured in liquid and supercritical carbon dioxide at (298, 308, and 318) K and at pressures between (80 and 250) bar. The solubilites were measured experimentally through traditional cloud point observations using a variable-volume stirred vessel with a sapphire window for visual inspection of the contents. These four short-chain lithium dialkyldithiocarbamates showed an increase in solubility with increasing density (or pressure) at fixed temperature. This increase was fairly independent of the temperature. Solubilites also increased with increasing temperature. The data were accurately modeled using an equation derived from association laws, which had a strong solvent density and temperature dependence.

The use of liquid and supercritical carbon dioxide was explored for the blending of poly(vinyl acetate) and citric acid as a basis for developing a new process for making chewing gum which would allow for flavorings to be released slower during chewing. Mixtures of 75% of polymer and 25% citric acid by mass were blended with carbon dioxide from 5 to 60 min over a temperature range of 25 to 55 °C and a pressure range of 83 to 241 bar in a batch process. Samples were then artificially chewed and citric acid dissolution monitored. Comparisons were made with samples prepared without carbon dioxide. In all cases, carbon dioxide blending produced polymers which retained the critic acid longer and hence produced more desirable products. With carbon dioxide, temperature had the largest effect on citric acid retention while pressure (or density) had only a modest effect. To make the flavoring be retained the longest in the polymer, the highest temperature and pressure (density) should be used with the longest blen...

The phase behavior of five β-adrenergic blocking agents (acebutolol, atenolol, nadolol, pindolol, and propranolol) were explored in liquid and supercritical carbon dioxide at (298, 308, and 318) K and at pressures between (80 and 275) bar. The solubility of the solids in carbon dioxide was experimentally determined by observing the cloud point using a variable-volume stirred vessel with visual access. Although these compounds are very similar structurally, each containing a secondary amine, alcohol, aromatic ring, and ether group, only pindolol was soluble in carbon dioxide under the conditions explored. The other four β blockers were observed to form yellow-brown salt complexes with carbon dioxide and did not show any appreciable solubility. It is believed that pindolol's lower basicity (having a Kb an order of magnitude lower than the other four compounds) prevented it from reacting with carbon dioxide, a Lewis acid, and salting out as the other four β blockers did.

Acylation of a surface-initiated poly(hydroxyethyl methacrylate) (PHEMA) film with a perfluoroalkyl acid chloride (C7F15COCl) results in a highly blocking film with fluorocarbon side groups that orient at the air−film interface to produce an ultralow-energy surface. The kinetics of the acylation step was monitored with reflectance-absorption infrared spectroscopy to reveal that the rate of fluorination depends on the chain length and solution concentration of the perfluorinated acid chloride as well as the solvent used. By control of the time of exposure to C7F15COCl, films with fractional conversion of the hydroxyl groups to fluorinated esters between 0 and 0.8 were produced. Increasing fractional conversion from 0 to ∼0.2 has a dramatic effect on surface wettability and electrochemical barrier properties as a densely packed, oriented fluorocarbon surface region is formed that greatly reduces water and ion transport. Additional fluorination has no effect on wettability but gradually increases film resist...

The solubility of three local anesthetics (benzocaine, lidocaine, and procaine) was measured in liquid and supercritical carbon dioxide at (298, 308, and 318) K and at pressures between (70 and 280) bar. The solubilites were experimentally measured by observing the cloud point using a variable-volume stirred vessel with visual access. Interestingly, although the three anesthetics were structurally very similar, the solubilites of lidocaine and benzocaine were strong functions of only density while that of procaine was a function of both density and temperature. The Peng−Robinson equation of state did not adequately predict the solubilites, while a simple enhancement factor correlation did predict them. The hydrochlorides of lidocaine and procaine did not have any measurable solubility in carbon dioxide over the conditions tested.

The sorption and loading of liquid and supercritical CO2 into chewing gum base spheres with radii of 0.5 cm was experimentally explored over the temperature and pressure ranges of 25−45 °C and 70−276 bar, respectively. Maximum loading amounts were found to be independent of temperature and to increase with increasing CO2 density. The time required to achieve maximum loading decreased with increasing temperature. A loading as high as 0.094 g of CO2 per gram of gum base was achieved. The sorption process was modeled by unsteady-state radial Fickian diffusion assuming a constant diffusion coefficient at a particular temperature and pressure (CO2 density). Volume changes of the polymer blend spheres under the conditions explored were small and ignored in the modeling. Sorption diffusion coefficients were on the order of 10-10 m2/s and increased with increasing temperature and CO2 density.

We report the preparation and characterization of self-assembled monolayers (SAMs) derived from the adsorption of partially fluorinated hexadecanethiols (CF3(CF2)n-1(CH2)mSH; n = 2, 4, 6, and 8; n + m = 16) onto the surface of gold. The quality of the SAMs, as measured by electrochemical impedance spectroscopy, was found to be sensitive to the solvent used as SAMs prepared in dichloromethane exhibited higher resistances and lower capacitances than those prepared in liquid CO2. The extent of fluorination was observed to influence the wettability, structure, and capacitance of the films without significantly affecting their charge-transfer resistance or their stability against exchange by a competing adsorbate. Reflectance-absorption infrared spectra showed that the fluorocarbon chains were oriented more normal to the surface for n = 8 but more parallel to the surface for n = 2. Advancing contact angles of hexadecane increased sharply with fluorination from n = 0 to 4 but slightly with additional fluorinati...

An equilibrium solubility model for the accurate prediction of the end point of semibatch hydroxide precipitation reactions in high ionic strength aqueous solutions is presented. We are interested in end-point and solution-pH predictions to determine the amount of base addition necessary to exactly achieve the base hydroxide solubility limit for the removal of heavy metals without excess base addition. Experimental verification of the model predictions is carried out using a chloride, iron, and magnesium system that is a model of the industrial system of interest. As shown by the experimental results, very good end-point predictions are possible even with the incorporation of a number of simplifying assumptions in the activity coefficient models.

We have performed a type of Autler–Townes spectroscopy to locate a number of rovibrational-hyperfine levels of the a 3Σu+ potential, the lowest triplet potential of the Na2 dimer. The spectroscopy starts with the photoassociation of ultracold atoms in a magneto-optical trap. We have measured the binding energies of over 100 individual states spanning the vibrational levels v=8–15 of this potential (binding energies up to 27 cm−1). We obtain a typical accuracy of 15 MHz and a typical resolution of 20 MHz, improving on the 10 GHz accuracy and 30 GHz resolution previously available for the vibrational states v

Heterogeneous photocatalysis using simulated solar irradiation in the presence of titanium dioxide was studied using dimethyl methylphosphonate (DMMP) as a surrogate for organophosphorus compounds including pesticides and chemical warfare agents. A reduction in solution pH accompanied DMMP degradation with the pH approaching the pKa of DMMP. Addition of peroxide before reaction increased the amount of DMMP degraded. Nearly complete destruction of DMMP was only achieved with the largest addition of peroxide. Photoreaction of DMMP in a pH 10 solution and a pH 10 carbonate buffer degraded a similar percent of the solute, with a more gradual reaction observed for the buffered solution. Variations in reaction conditions were studied to evaluate the effect of potential spill conditions. The presence of fulvic acid in the solution slightly enhanced the oxidation of DMMP and the absence of dissolved oxygen inhibited DMMP oxidation. DMMP solutions prepared in simulated sea water reached similar degradation percentages as pure solutions, however, reacted more slowly.

We report the use of ethanol−supercritical carbon dioxide mixtures as solvents in the formation of n-alkanethiolate self-assembled monolayers (SAMs) on gold. Results from reflectance−absorption infrared spectroscopy and electrochemical impedance spectroscopy reveal that the SAMs formed from these environmentally friendly solvent mixtures are highly crystalline and exhibit large resistances against the diffusion of redox probes. Increasing the percentage of ethanol in the solvent results in SAMs with larger average cant angles and lower charge-transfer resistances, consistent with a greater density of defect sites within the film. The ability to control the defect density within the SAM by simply altering the ethanol−carbon dioxide solvent composition represents a straightforward and environmentally friendly strategy for tuning the properties of these molecular films.

Background: Aminolevulinic acid hydrochloride (ALA, Levulan) applied topically to actinic keratoses (AKs) leads to accumulation of the photosensitizer protoporphyrin IX, which, when activated by exposure to light, eradicates AKs. Objective: We examined the safety and efficacy of photodynamic therapy using topical 20% ALA in a solution formulation and varying blue light doses to treat multiple AKs on the face and scalp. Method: This is a multicenter, investigator-blinded, randomized, vehicle-controlled study. Results: Thirty-six patients with clinically typical AKs were treated with 20% ALA; 14 to 18 hours later, they were irradiated with a nonlaser fluorescent blue light source. With the optimal light dose of 10 J/cm 2 , 88% of the AKs completely cleared 8 weeks after a single photodynamic treatment, compared with 6% after treatment with vehicle and light. Conclusion: Topical ALA PDT using a nonlaser, blue light source is an effective treatment for multiple AKs. (J Am Acad Dermatol 2001;45:96-104.)

We report the formation of self-assembled monolayers (SAMs) on gold substrates by exposure to n-alkanethiols [CH3(CH2)n-1SH; n = 8, 10, 12, 16, and 18] in liquid and supercritical carbon dioxide. The results of this novel study show that an environmentally friendly solvent can be used to form highly crystalline SAMs with few gauche defects and that pressure as well as exposure time can be used to affect the structural and barrier properties of the monolayer film. Reflectance infrared spectroscopy, electrochemical impedance spectroscopy, and wetting measurements were used to characterize the SAMs. The effects of pressure (76−300 bar) and adsorption time (3−90 min) on the formation of the SAMs were explored. The overall chain density of these SAMs was greater than that for SAMs formed in common organic solvents such as ethanol. The properties of the SAMs were slightly affected by the pressure during formation. At 35 °C, as the carbon dioxide pressure increased (from 76 to about 140 bar), the packing density...

Amorphous fumed silica (SiO2) was shown to increase yields and selectivities of several Diels−Alder reactions in gaseous and supercritical CO2. Pressure effects on the Diels−Alder reaction were explored using methyl vinyl ketone and penta-1,3-diene at 80 °C. The selectivity of the reaction was not affected by pressure/density. As pressure was increased, the yield decreased. At the reaction temperature, adsorption isotherms at various pressures were obtained for the reactants and the Diels−Alder adduct. As expected when pressure is increased, the ratio of the amount of reactants adsorbed to the amount of reactants in the fluid phase decreases, thus causing the yield to decrease. The Langmuir adsorption model fit the adsorption data. The Langmuir equilibrium partitioning constants all decreased with increasing pressure. The effect of temperature on adsorption was experimentally determined and traditional heats of adsorption were calculated. However, since supercritical CO2 is a highly compressible fluid, it...

In a recent experiment [Weinstein et al., Nature 395, 148 (1998)] we magnetically trapped 108 ground-state calcium monohydride molecules, CaH(X 2Σ,v″=0, J″=0). The molecules were prepared by laser ablation of a solid sample of CaH2 and loaded via thermalization with a cold (

Although nebulizers can vary widely in performance, there is no uniformly accepted method for bench testing these devices. In the present study, we compared three bench methods of measuring the performance of three commercial jet nebulizers (Whisper Jet [WJ; Marquest Medical, Englewood, CO], Sidestream [SS; Marquest Medical], and Vixone [VO; Westmed, Tucson, AZ] to assess the impact of the method of testing on reported nebulizer performance. Each nebulizer was charged with 3 mL of albuterol mixed with a radiotracer (technetium [99mTc]), and the radioactivity captured on a paper filter was expressed as a percentage of the nebulizer charge (% delivered). The nebulizers were tested with and without duplication of spontaneous respiration by a piston pump (spontaneous respiration and standing cloud methods, respectively). The nebulizers were also tested using a model of mechanical ventilation (mechanical ventilation method). For all three devices, the addition of the standardized breathing pattern significantly reduced the % delivered with all three nebulizers compared with the standing cloud method. For the standing cloud method, the presence of the T-piece/mouth-piece significantly reduced the % delivered with the WJ but not with the other two devices. The mechanical ventilation method had the lowest % delivered for all three devices. The magnitude of the differences between nebulizers varied with duration of treatment. The findings of this study emphasize the importance of bench testing that duplicates intended clinical usage, because significant differences in nebulizer performance may be manifested under certain clinical conditions but not under others.

Many patients with rosacea are unable to tolerate extended treatment periods with topical agents because of the unusually high skin sensitivity that often accompanies rosacea. Kinetin (N(6)-furfuryladenine) is a plant cytokinin that reportedly helps restore skin barrier function and may be useful to ameliorate the signs and symptoms of rosacea. The purpose of this open-label study was to determine the tolerance and efficacy of twice-daily application of kinetin 0.1% lotion for improving the signs and symptoms of mild to moderate facial rosacea. Subjects applied kinetin 0.1% lotion twice daily to the face, with daily use of a sunscreen of sun protection factor 30. Subjects were evaluated at baseline and at 4-week intervals for 12 weeks to assess efficacy and tolerance. Results of this study suggest that kinetin 0.1% lotion is a well-tolerated moisturizing lotion option for subjects with mild to moderate inflammatory rosacea.

We provide new or revised vibrational assignments for three hydrofluorocarbons (HFCs) and one hydrochlorofluorocarbon (HCFC) through the combined use of experimental absolute infrared intensity measurements, experimental Raman measurements and ab initio computations of vibrational frequencies, absolute infrared intensities, and Raman intensities. CHF 2 CH 3 (HFC-152a), CF 3 CH 3 (HFC-143a), CF 3 CHF 2 (HFC-125), and CHCl 2 CF 3 (HCFC-123) are the molecules investigated in this study. We have measured the vapor infrared spectra from 400 to 4000 cm −1 at a resolution (0.08 cm −1 ) sufficient to resolve some overlapping fundamentals and to assign symmetry species for several bands on the basis of their rotational band contours and absolute infrared intensities. Raman spectra were measured for the HFCs at pressures between 3.8 and 11.1 atm and for HCFC-123 in the liquid phase. Second-order Moller–Plessett (MP2) level of theory and the 6-31G** basis set were used to optimize molecular geometry and calculate harmonic vibrational frequencies and infrared intensities; Hartree Fock (HF) level of theory was used to calculate Raman intensities. The higher-resolution infrared spectra and experimental absolute infrared intensities, the Raman spectra and relative Raman intensities, together with the results of the computations, allow a firm assignment of previously ambiguous bands. On the basis of the current assignments, we find that the scaled MP2/6-31G** frequencies are in good agreement with the observed frequencies. Furthermore, the calculated absolute infrared intensities and calculated Raman intensities are generally in good agreement with the experimental measurements.

Spectroscopy of buffer-gas cooled vanadium monoxide (VO) is performed in the presence of a magnetic trapping field and at low field. VO is created via laser ablation. A helium buffer gas, chilled by a dilution refrigerator, cools 1012 VO molecules to 1.8±0.2 K within 10 ms. The measured rotational temperature is 1.5±0.8 K. Spatially resolved Zeeman spectra allow the magnetic broadening terms of several optical transitions to be determined. The density of VO decays with a characteristic time of 60 ms, thus precluding the observation of trapping.

Mg-chelatase catalyzes the ATP-dependent insertion of Mg2+ into protoporphyrin-IX to form Mg-protoporphyrin-IX. This is the first step unique to chlorophyll synthesis, and it lies at the branch point for porphyrin utilization; the other branch leads to heme. Using the stromal fraction of pea (Pisum sativum L. cv Spring) chloroplasts, we have prepared Mg-chelatase in a highly active (1000 pmol 30 min−1 mg−1) and stable form. The reaction had a lag in the time course, which was overcome by preincubation with ATP. The concentration curves for ATP and Mg2+ were sigmoidal, with apparentKm values for Mg2+ and ATP of 14.3 and 0.35 mm, respectively. TheKm for deuteroporphyrin was 8 nm. This Km is 300 times lower than the published porphyrin Km for ferrochelatase. The soluble extract was separated into three fractions by chromatography on blue agarose, followed by size-selective centrifugal ultrafiltration of the column flow-through. All three fractions were required for activity, clearly demonstrating that the plant Mg-chelatase requires at least three protein components. Additionally, only two of the components were required for activation; both were contained in the flow-through from the blue-agarose column.

The advent of buffer-gas loaded magnetic traps for atoms has opened the possibility of trapping paramagnetic molecules. We survey our results on the loading, trapping and spectroscopy of Eu atoms that demonstrated the technique. The principles governing molecular trapping considering in particular the O2 and NO systems are outlined. The trapping of molecules should prove particularly useful in spectroscopy, especially ultra-high resolution spectroscopy that requires cold (slow), trapped (long interaction time) samples. Similar to cold atoms, cold molecules could be interrogated at a level of detail which is likely to provide new insights into their structure and interactions.

Atomic europium has been magnetically trapped using buffer-gas loading. Laser ablated $\mathrm{Eu}(^{8}S_{7/2})$ atoms are thermalized to 800 mK in a ${}^{4}\mathrm{He}$ buffer gas (to 250 mK in a ${}^{3}\mathrm{He}$ buffer gas). Anti-Helmholtz superconducting coils produce a quadrupole magnetic field to trap the ${M}_{J}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}7/2$ state of Eu. Detection is via absorption spectroscopy at 462.7 nm. Up to $1\ifmmode\times\else\texttimes\fi{}{10}^{12}\mathrm{Eu}$ atoms are loaded at a central density of $5\ifmmode\times\else\texttimes\fi{}{10}^{12}\phantom{\rule{0ex}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$. Atoms can be held for longer than 100 s.

We have grown crystals of solid argon doped with rubidium atoms. The spectrum of the implanted atoms depends on the crystal-growth temperature and annealing history. We have used optical pumping to polarize the spin state of the implanted atoms and polarization spectroscopy to detect the spin state and measure the spin-relaxation time. In addition to the desired optical pumping, we also observed modification of the absorption spectrum of the rubidium due to the applied light.

The Diels−Alder reaction of cyclopentadiene and ethyl acrylate was explored in supercritical CO2 from 38 to 88 °C and pressures from 80 to 210 bar. A traditional Arrhenius expression was used to correlate the kinetic data at a constant density of 0.5 g/cm3. Over the temperature range investigated, the activation energy was found to be 40 ± 2 kJ/mol. Traditional transition state theory was used to explore the temperature and density effects on the reaction rate. However, all that is required to accurately predict the global rate constant for this reaction is an empirically-determined activation energy and a pre-exponential term with a linear dependence on the density of solution. An examination of data from other researchers suggests that this is also true for other Diels−Alder reactions in supercritical CO2.

In a plastid-free assay, Mg-chelatase from pea (Pisum sativum L. cv. Spring) and cucumber (Cucumis sativus L. cv. Sumter) chloroplasts is inhibited to equal extents by the mercurial reagents, p-chloromercuribenzoate (PCMB) and p-chloromercuribenzene sulfonate (PCMBS). However, in intact chloroplasts PCMB inhibits Mg-chelatase fourfold more strongly than does PCMBS. Since PCMBS cannot penetrate membranes as readily as PCMB, Mg-chelatase may be localized interior to the inner chloroplast envelope. When Mg-chelatase is assayed with photosynthetically generated ATP, the presence of an external ATP trap does not inhibit activity, suggesting that the enzyme is not located in the interenvelope space. None of the components of Mg-chelatase are integral membrane proteins: Mg-chelatase activity is readily solubilized by washing the total chloroplast membranes in buffers of low MgCl 2 content. This precludes localization by purifying individual thylakoid and envelope membranes which requires low MgCl 2 concentrations.

We use cryogenic helium buffer-gas cooling to form large densities of lithium atoms in a high-density helium gas, from which LiHe molecules form by three-body recombination. These weakly bound van der Waals molecules are detected spectroscopically, and their binding energy is measured from their equilibrium thermodynamic properties.

Using cryogenic helium buffer-gas cooling, we have prepared dense samples of atomic lithium and molecular calcium monohydride at temperatures as low as 1 K. We have measured the $\mathrm{Li}+\mathrm{CaH}\ensuremath{\rightarrow}\mathrm{LiH}+\mathrm{Ca}$ chemical reaction, observed in both the accelerated disappearance of CaH in the presence of high densities of lithium and in the appearance of the LiH molecule.

Mg(2+)-chelatase catalyses the first step unique to chlorophyll synthesis, namely the insertion of Mg2+ into protoporphyrin IX. When pea (Pisum sativum L., cv. Spring) chloroplasts are lysed in a buffer lacking Mg2+ and the thylakoids removed by centrifugation, the remaining mixture of light membranes and soluble proteins (LM/S) has high Mg(2+)-chelatase activity. Several lines of evidence are presented to show that the Mg2+ insertion catalysed by this preparation is a two-step reaction consisting of activation followed by Mg2+ chelation. An activated state of Mg(2+)-chelatase is achieved by preincubating LM/S with ATP. The activated state is observed as the elimination of the approx. 6 min lag in the rate of Mg2+ chelation on addition of the porphyrin substrate. The activity of LM/S assayed at low protein concentrations can be greatly enhanced by preincubating at high protein concentrations (12 mg/ml is optimal). This activation effect requires the presence of both LM and S fractions, as well as ATP. Both steps require ATP, but at different concentrations; the first step is optimal at > 0.5 mM (EC50 = 0.3 mM) and the second step is optimal at 0.3 mM (EC50 < 0.2 mM). ATP in the first step could be replaced by ATP[S]; this analogue could not sustain activity in the second step. This activated state was stable for at least 30 min at room temperature, but chilling of preincubated LM/S on ice for 30 min caused an almost complete loss of the activated state.

In plants, algae, and many bacteria, the heme and chlorophyll precursor, [delta]-aminolevulinic acid (ALA), is synthesized from glutamate in a reaction involving a glutamyl-tRNA intermediate and requiring ATP and NADPH as cofactors. In particulate-free extracts of algae and chloroplasts, ALA synthesis is inhibited by heme. Inclusion of 1.0 mM glutathione (GSH) in an enzyme and tRNA extract, derived from the green alga Chlorella vulgaris, lowered the concentration of heme required for 50% inhibition approximately 10-fold. The effect of GSH could not be duplicated with other reduced sulfhydryl compounds, including mercaptoethanol, dithiothreitol, and cysteine, or with imidazole or bovine serum albumin, which bind to heme and dissociate heme dimers. Absorption spectroscopy indicated that heme was fully reduced in incubation medium containing dithiothreitol, and addition of GSH did not alter the heme reduction state. Oxidized GSH was as effective in enhancing heme inhibition as the reduced form. Co-protoporphyrin IX inhibited ALA synthesis nearly as effectively as heme, and 1.0 mM GSH lowered the concentration required for 50% inhibition approximately 10-fold. Because GSH did not influence the reduction state of heme in the incubation medium, and because GSH could not be replaced by other reduced sulfhydryl compounds or ascorbate, the effect of GSH cannot be explained by action as a sulfhydryl protectant or heme reductant. Preincubation of enzyme extract with GSH, followed by rapid gel filtration, could not substitute for inclusion of GSH with heme during the reaction. The results suggest that GSH must specifically interact with the enzyme extract in the presence of the inhibitor to enhance the inhibition.

A sample of cryogenically cooled atomic ytterbium is used to create a memory for a classical pulse of light. The information of the light pulse is stored in the nuclear spin of ground-state (${}^{1}{S}_{0}$) $^{173}\mathrm{Yb}$ ($I=5/2$). Because nuclear spin states interact very weakly with their environment, the atomic ensemble is resistant to decoherence due to inelastic collisions and inhomogeneous fields, and storage times of hundreds of milliseconds are observed.