Images of a Bose-Einstein condensate in position and momentum space

In the Bogoliubov theory, a condensate initially prepared in its ground state described by a stationary Bogoliubov vacuum and later perturbed by a time-dependent potential or interaction strength evolves into a time-dependent excited state which is a dynamical Bogoliubov vacuum. The dynamical vacuum has a simple diagonal form in a time-dependent orthonormal basis of single-particle modes. This diagonal representation leads to a Gaussian probability distribution for possible density-measurement outcomes in position and momentum space.     

Insensitivity of leptogenesis with flavor effects to low energy leptonic CP violation

If the baryon asymmetry of the Universe is produced by leptogenesis, CP violation is required in the lepton sector. In the seesaw extension of the standard model with three hierarchical right-handed neutrinos, we show that the baryon asymmetry is insensitive to the Pontecorvo-Maki-Nagakawa-Sakata phases: thermal leptogenesis can work for any value of the observable phases. This result was well known when there were no flavor effects in leptogenesis; we show that it remains true when flavor effects are included.     

Oak-Associated Negativicute Equipped with Ancestral Aromatic Polyketide Synthase Produces Antimycobacterial Dendrubins

Anaerobic bacteria have only recently been recognized as a source of antibiotics; yet, the metabolic potential of Negativicutes (Gram-negative staining Firmicutes) such as the oak-associated Dendrosporobacter quercicolus has remained unknown. Genome mining of D. quercicolus and phylogenetic analyses revealed a gene cluster for a type II polyketide synthase (PKS) complex that belongs to the most ancestral enzyme systems of this type. Metabolic profiling, NMR analyses, and stable-isotope labeling led to the discovery of a new family of anthraquinone-type polyphenols, the dendrubins, which are diversified by acylation, methylation, and dimerization. Dendrubin A and B were identified as strong antibiotics against a range of clinically relevant, human-pathogenic mycobacteria.     

Far-infrared spectroscopy of small polycyclic aromatic hydrocarbons

Both experimental and theoretical spectroscopic studies on small gas phase polycyclic aromatic hydrocarbons in the far-infrared spectral region are reported. The experimental set-up based on thermal emission and Fourier transform far infrared analysis led to the detection of relatively broad vibrational bands, unresolved in rotation, representative of each molecule. Detailed theoretical investigations were performed, including both ab initio calculations and spectral simulations. For the majority of the samples, this study provides the first detection of the vibrational modes associated with the skeleton motions.     

UV-induced bursting of cell-sized multicomponent lipid vesicles in a photosensitive surfactant solution

We study the behavior of multicomponent giant unilamellar vesicles (GUVs) in the presence of AzoTAB, a photosensitive surfactant. GUVs are made of an equimolar ratio of dioleoylphosphatidylcholine (DOPC) and dipalmitoylphosphatidylcholine (DPPC) and various amounts of cholesterol (Chol), where the lipid membrane shows a phase separation into a DPPC-rich liquid-ordered (L(o)) phase and a DOPC-rich liquid-disordered (L(d)) phase. We find that UV illumination at 365 nm for 1 s induces the bursting of a significant fraction of the GUV population. The percentage of UV-induced disrupted vesicles, called bursting rate (Y(burst)), increases with an increase in [AzoTAB] and depends on [Chol] in a non-monotonous manner. Y(burst) decreases when [Chol] increases from 0 to 10 mol % and then increases with a further increase in [Chol], which can be correlated with the phase composition of the membrane. We show that Y(burst) increases with the appearance of solid domains ([Chol] = 0) or with an increase in area fraction of L(o) phase (with increasing [Chol] ≥ 10 mol %). Under our conditions (UV illumination at 365 nm for 1 s), maximal bursting efficiency (Y(burst) = 53%) is obtained for [AzoTAB] = 1 mM and [Chol] = 40 mol %. Finally, by restricting the illumination area, we demonstrate the first selective UV-induced bursting of individual target GUVs. These results show a new method to probe biomembrane mechanical properties using light as well as pave the way for novel strategies of light-induced drug delivery.     

Identification and assay of underivatized urinary acylcarnitines by paper spray tandem mass spectrometry

A new analytical approach, using paper spray tandem mass spectrometry, has been developed for assay of carnitine and acylcarnitines in urine. Paper spray (PS) is a very promising technique, especially in clinical investigations, because of its simplicity, low cost, and rapid sample preparation. A home-made paper spray device was used for assay of urinary acylcarnitines (C2–C18). The performance of solvents with different elution efficiency and paper substrates with different porosity grade and structure were tested by use of spiked synthetic urine. Tandem mass spectrometry in multiple reaction monitoring (MRM) mode was optimized to obtain better specificity and sensitivity. Analyte signals were evaluated for stability and reproducibility. Calibration with [²H₃]propionylcarnitine (C3-d3), [²H₃]octanoylcarnitine (C8-d3), and [²H₃] palmitoylcarnitine (C16-d3) as internal standards was used for quantification. Very good linearity was obtained, with correlation coefficients >0.99 for C0–C12 and C16 acylcarnitines and >0.96 for C14 and C18 acylcarnitines. Accuracy and precision (RSD, %) of the proposed procedure were tested at concentrations of 0.8, 8, and 20 mg L^?1 with very satisfactory results: overall mean accuracy was 98.9 % and overall mean relative standard deviation 1 %. Limits of detection (LOD) between 6 and 208 μg L^?1 for propionylcarnitine and tetradecanoylcarnitine, respectively, can be regarded as very satisfactory. Application of the method to real urine proved that paper spray tandem mass spectrometry is a simple, rapid, and direct tool (no derivatization is required) for assay of carnitine and C2–C12 acylcarnitines in urine.     

Vibrations and thermodynamics of clusters of polycyclic aromatic hydrocarbon molecules: the role of internal modes

The vibrational spectra of clusters of coronene molecules are theoretically calculated using a mixed quantum/classical scheme, each molecule being described by a tight-binding Hamiltonian, the intermolecular forces being provided by explicit Lennard-Jones and point charge sites. The normal modes of vibrations are shown to exhibit significant variations upon clustering. In particular, for large clusters intra- and intermolecular modes tend to mix and fill the mid-infrared range. We also calculate the heat capacity of the (C24H12)8 cluster as a function of temperature, emphasizing the isomerizations that take place during melting. Quantum delocalization effects, as obtained from the Pitzer-Gwinn semiclassical approximation, are important enough to wash out all signatures of the structural transitions on the caloric curve. On the basis of a simple two-state model we estimate that clusters containing about 300 molecules are required for melting to be detected on the caloric curve.