Achieving peak brightness in an atom laser

In this Letter we present experimental results and a simple analytic theory on the first continuous (long pulse) Raman atom laser. We analyze the flux and brightness of a generic two state atom laser with an analytic model that shows excellent agreement with our experiments. We show that, for the same source size, the brightness achievable with a Raman atom laser is at least 3 orders of magnitude greater than achievable in any other demonstrated continuously outcoupled atom laser.     

Gevrey vectors in involutive tube structures and Gevrey regularity for the solutions of certain classes of semilinear systems

In this work, we introduce the notion of s-Gevrey vectors in locally integrable structures of tube type. Under the hypothesis of analytic hypoellipticity, we study the Gevrey regularity of such vectors and also show how this notion can be applied to the study of the Gevrey regularity of solutions of certain classes of semilinear equations.     

Influence of solution constituents, solution conditioning and seeding on the crystalline phase of aluminium hydroxide using in situ X-ray diffraction

Filtering, drying and aging of crystalline solids can affect crystalline phase(s) and therefore ex situ X-ray diffraction is not necessarily indicative of the in situ crystalline components. This paper examines some of the factors affecting the crystallised phase of aluminium hydroxides in highly caustic solutions. Caustic aluminate solutions were prepared using several different methodologies. Where solutions were prepared from aluminium metal, gibbsite and bayerite were observed to be the crystallisation products. Where gibbsite was used as the aluminium source in the liquors, the crystallised phase was found to be a function of solution conditioning. Solutions prepared at 100°C and at atmospheric pressure crystallised to form only gibbsite. These same solutions subsequently heated to 160°C for 16 h crystallised as gibbsite and bayerite. It has been concluded from these results that the caustic aluminate solutions made using gibbsite were not dissolved on the molecular scale (although optically clear) if the solutions were heated to only 100°C. Further heating at elevated temperatures completed the dissolution process so that the species in solution were similar to those found in solutions made from aluminium metal. Solutions seeded with either bayerite or gibbsite crystallised to form only gibbsite. Only crystallisation in the bulk solution and not on the seed surfaces was recorded. In some cases seeding altered the expected crystallisation products, i.e. from gibbsite and bayerite to only gibbsite.     

Structural and NMR Studies of the Hexameric Copper(I) Complex with N‐n‐butyl‐N′‐ethoxycarbonyl‐thioureate

The copper sulfide mineral flotation collector, N‐n‐butyl‐N′‐ethoxycarbonyl‐thiourea (H₂bectu), and the 1:1 hexameric copper(I) thioureate complex, [Cu(Hbectu)]₆, have been characterized by single crystal X‐ray diffraction. H₂bectu crystallizes in the triclinic space group with a = 5.2754(4), b = 9.0042(7), c = 12.6030(9) Å, α = 80.528(6), β = 90.173(6), γ = 76.472(7)°. An intramolecular N‐H···O hydrogen bond between the thioamide proton and carbonyl oxygen forms a planar six‐membered ring in the central core of the molecule with C=O, C=S and C‐N bond lengths in accord with those reported for other N‐alkyl/aryl‐N′‐acyl‐thiourea compounds. [Cu(Hbectu)]₆ crystallizes in the monoclinic space group C2/c with a = 23.269(5), b = 13.243(4), c = 23.037(7) Å, β = 91.81(2)° as discrete hexameric clusters disposed about a crystallographic centre of symmetry with a Cu₆S₆ core consisting of two Cu₃S₃ chair‐shaped rings linked by coordination of the deprotonated amide nitrogen atom to a copper atom in the adjacent ring. The six ligands assemble as a paddlewheel structure with the ethoxy and n‐butyl substituents packing in an alternating head to tail arrangement. Temperature dependent solution ¹H NMR spectroscopic studies show that the hexameric structure of the complex is maintained in solution.     

A principal component analysis based method to discover chemical differences in comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GCxGC-TOFMS) separations of metabolites in plant samples

Comprehensive two-dimensional gas chromatography combined with time-of-flight mass spectrometry (GC × GC-TOFMS) provides high resolution separations of complex samples with a mass spectrum at every point in the separation space. The large volumes of multidimensional data obtained by GC × GC-TOFMS analysis are analyzed using a principal component analysis (PCA) method described herein to quickly and objectively discover differences between complex samples. In this work, we submitted 54 chromatograms to PCA to automatically compare the metabolite profiles of three different species of plants, namely basil (Ocimum basilicum), peppermint (Mentha piperita), and sweet herb stevia (Stevia rebaudiana), where there were 18 chromatograms for each type of plant. The 54 scores of the m/z 73 data set clustered in three groups according to the three types of plants. Principal component 1 (PC 1) separated the stevia cluster from the basil and peppermint clusters, capturing 61.84% of the total variance. Principal component 2 (PC 2) separated the basil cluster from the peppermint cluster, capturing 16.78% of the total variance. The PCA method revealed that relative abundances of amino acids, carboxylic acids, and carbohydrates were responsible for differentiating the three plants. A brief list of the 16 most significant metabolites is reported. After PCA, the 54 scores of the m/z 217 data set clustered in three groups according to the three types of plants, as well, yielding highly loaded variables corresponding with chemical differences between plants that were complementary to the m/z 73 information. The PCA data mining method is applicable to all of the monitored selective mass channels, utilizing all of the collected data, to discover unknown differences in complex sample profiles.     

Transannular Anti-Michael Addition: Formation of 4H-Pyrazolo[5,1-c]thiazines

The reaction of 2-(diphenylmethylene)thietan-3-one (2) with 1,2,4,5-tetrazines (3a-c) in KOH/MeOH/THF gives 4H-pyrazolo[5,1-c]thiazines (7a-c). This novel condensation reaction proceeds via the intermediacy of an 8-(diphenylmethylene)-2H-1,4,5-thiadiazocin-7(8H)-one (5), which undergoes a multi-step rearrangement including a rare anti-Michael addition.     

Synthesis of 2-alkenyl-3-(alkoxycarbonyl)furans based on Feist-Benary cyclocondensation of (2,4-dioxobutylidene)phosphoranes with alpha-haloketones and alpha-chloracetaldehyde

3-Acyl-2-alkenylfurans were prepared by "Feist-Benary cyclocondensation" of (2,4-dioxobutylidene)phosphoranes with chloracetaldehyde and alpha-haloketones and subsequent Wittig reactions.     

Tension trapping of carbonyl ylides facilitated by a change in polymer backbone

Epoxidized polybutadiene and epoxidized polynorbornene were subjected to pulsed ultrasound in the presence of small molecules capable of being trapped by carbonyl ylides. When epoxidized polybutadiene was sonicated, there was no observable small molecule addition to the polymer. Concurrently, no appreciable isomerization (cis to trans epoxide) was observed, indicating that the epoxide rings along the backbone are not mechanically active under the experimental conditions employed. In contrast, when epoxidized polynorbornene was subjected to the same conditions, both addition of ylide trapping reagents and net isomerization of cis to trans epoxide were observed. The results demonstrate the mechanical activity of epoxides, show that mechanophore activity is determined not only by the functional group but also the polymer backbone in which it is embedded, and facilitate a characterization of the reactivity of the ring-opened dialkyl epoxide.     

Quantitation of glucosamine sulfate in plasma by HPLC-MS/MS after administration of powder for oral solution formulation

A rapid method for the quantification of glucosamine in human plasma using high‐performance liquid chromatography coupled to tandem mass spectrometry was developed and validated. The sample preparation includes a simple deproteinization step, using d ‐[1‐¹³C] glucosamine hydrochloride as an internal standard. Chromatographic separation was performed on an ACE Ciano column using isocratic elution with acetonitrile and aqueous 2 mm ammonium acetate containing 0.025% formic acid (80:20). Selected reaction monitoring was performed using the transitions m/z 180.1 → m/z 72.1 and m/z 181.0 → m/z 74.6 to quantify glucosamine and internal standard, respectively. The method was validated and proved to be linear, accurate and precise over the range 50–5000 ng/mL of glucosamine. Recovery rates higher than 90% were obtained for both glucosamine and internal standard. No matrix effect was detected in the samples. The validated method was successfully applied to a pharmacokinetic study after oral administration of a powder for oral solution formulation containing glucosamine sulfate. Copyright © 2011 John Wiley & Sons, Ltd.