Generating controllable atom-light entanglement with a Raman atom laser system

We introduce a scheme for creating continuous variable entanglement between an atomic beam and an optical field, by using squeezed light to outcouple atoms from a Bose-Einstein condensate via a Raman transition. We model the full multimode dynamics of the atom laser beam and the squeezed optical field and show that, with appropriate two-photon detuning and two-photon Rabi frequency, the transmitted light is entangled in amplitude and phase with the outcoupled atom laser beam. The degree of entanglement is controllable via changes in the two-photon Rabi frequency of the outcoupling process.     

Hausdorff and packing dimensions of non-normal tuples of numbers: Non-linearity and divergence points

We apply the results in [L. Olsen, Multifractal analysis of divergence points of deformed measure theoretical Birkhoff averages, J. Math. Pures Appl. 82 (2003) 1591-1649; L. Olsen, Multifractal analysis of divergence points of deformed measure theoretical Birkhoff averages. III, Aequationes Math. 71 (2006) 29-53; L. Olsen, Multifractal analysis of divergence points of deformed measure theoretical Birkhoff averages. IV: Divergence points and packing dimension, Bull. Sci. Math. 132 (2008) 650-678; L. Olsen, S. Winter, Multifractal analysis of divergence points of deformed measure theoretical Birkhoff averages. II: Non-linearity, divergence points and Banach space valued spectra, Bull. Sci. Math. 131 (2007) 518-558] to give a systematic and detailed account of the Hausdorff and packing dimensions of sets of d-tuples of numbers defined in terms of the asymptotic behaviour of the frequencies of strings of digits in their N-adic expansion.     

On the Hausdorff and packing measures of typical compact metric spaces

We study the Hausdorff and packing measures of typical compact metric spaces belonging to the Gromov–Hausdorff space (of all compact metric spaces) equipped with the Gromov–Hausdorff metric.     

Yielding Behavior in Injectable Hydrogels from Telechelic Proteins

Injectable hydrogels show substantial promise for use in minimally invasive tissue engineering and drug delivery procedures.1,2 A new injectable hydrogel material, developed from recombinant telechelic proteins expressed in E. coli, demonstrates shear thinning by three orders of magnitude at large strains. Large amplitude oscillatory shear illustrates that shear thinning is due to yielding within the bulk of the gel, and the rheological response and flow profiles are consistent with a shear-banding mechanism for yielding. The sharp yielding transition and large magnitude of the apparent shear thinning allow gels to be injected through narrow gauge needles with only gentle hand pressure. After injection the gels reset to full elastic strength in seconds due to rapid reformation of the physical network junctions, allowing self-supporting structures to be formed. The shear thinning and recovery behavior is largely independent of the midblock length, enabling genetic engineering to be used to control the equilibrium modulus of the gel without loss of the characteristic yielding behavior. The shear-banding mechanism localizes deformation during flow into narrow regions of the gels, allowing more than 95% of seeded cells to survive the injection process.     

Role of the azadithiolate cofactor in models for [FeFe]-hydrogenase: novel structures and catalytic implications

This paper summarizes studies on the redox behavior of synthetic models for the [FeFe]-hydrogenases, consisting of diiron dithiolato carbonyl complexes bearing the amine cofactor and its N-benzyl derivative. Of specific interest are the causes of the low reactivity of oxidized models toward H(2), which contrasts with the high activity of these enzymes for H(2) oxidation. The redox and acid-base properties of the model complexes [Fe(2)[(SCH(2))(2)NR](CO)(3)(dppv)(PMe(3))](+) ([2](+) for R = H and [2'](+) for R = CH(2)C(6)H(5), dppv = cis-1,2-bis(diphenylphosphino)ethylene)) indicate that addition of H(2) followed by deprotonation are (i) endothermic for the mixed valence (Fe(II)Fe(I)) state and (ii) exothermic for the diferrous (Fe(II)Fe(II)) state. The diferrous state is shown to be unstable with respect to coordination of the amine to Fe, a derivative of which was characterized crystallographically. The redox and acid-base properties for the mixed valence models differ strongly for those containing the amine cofactor versus those derived from propanedithiolate. Protonation of [2'](+) induces disproportionation to a 1:1 mixture of the ammonium [H2'](+) (Fe(I)Fe(I)) and the dication [2'](2+) (Fe(II)Fe(II)). This effect is consistent with substantial enhancement of the basicity of the amine in the Fe(I)Fe(I) state vs the Fe(II)Fe(I) state. The Fe(I)Fe(I) ammonium compounds are rapid and efficient H-atom donors toward the nitroxyl compound TEMPO. The atom transfer is proposed to proceed via the hydride. Collectively, the results suggest that proton-coupled electron-transfer pathways should be considered for H(2) activation by the [FeFe]-hydrogenases.     

Unfolding of G-quadruplexes: energetic, and ion and water contributions of G-quartet stacking

It has been shown that DNA oligonucleotides composed, in part, of G repeat sequences can adopt G-quadruplex structures in the presence of specific metal ions. In this work, we use a combination of spectroscopic and calorimetric techniques to determine the spectral and thermodynamic characteristics of two DNA aptamers, d(G2T2G2TGTG2T2G2), G2, and d(G3T2G3TGTG3T2G3), G3; a sequence in the promoter region of the c-MYC oncogene, d(TG4AG3TG4AG3TG4A2G2), NHE-III; and the human telomere sequence d(AG3T2AG3T2AG3T2AG3), 22GG. The circular dichroism spectra of these oligonucleotides in the presence of K+ indicate that all form G-quadruplexes with G-quartets in an antiparallel arrangement (G2), in a parallel arrangement (NHE-III and 22GG), or in a mixed parallel and antiparallel G-quartet arrangement (G3). Melting profiles show transition temperatures, TM, above 45 degrees C that are independent of strand concentration, consistent with the formation of very stable intramolecular G-quadruplexes. We used differential scanning calorimetry to obtain complete thermodynamic profiles for the unfolding of each quadruplex. Subtracting the thermodynamic folding profiles of G2 from those of G3 yielded the following thermodynamic profile for the formation of a G-quartet stack: DeltaG degrees 20 = -2.2 kcal/mol, DeltaHcal = -14.6 kcal/mol, TDeltaScal = -12.4 kcal/mol, DeltanK+ = -0.3 mol of K+/mol, and DeltanW = 13 mol of H2O/mol. Furthermore, we used this profile to estimate the thermodynamic contributions of the loops and/or extra base sequences of each oligonucleotide in the G-quadruplex state. The average free energy contributions of the latter indicate that the incorporation of loops and base overhangs stabilizes quadruplex structures. This stabilization is enthalpy-driven and is due to base-stacking contributions.     

The master two-dimensional gel database of human AMA cell proteins: towards linking protein and genome sequence and mapping information (update 1991).

The master two-dimensional gel database of human AMA cells currently lists 3801 cellular and secreted proteins, of which 371 cellular polypeptides (306 IEF; 65 NEPHGE) were added to the master images during the last 10 months. These include: (i) very basic and acidic proteins that do not focus under normal running conditions and (ii) low-abundant proteins that can only be detected after prolonged gel exposure. Annotation categories updated in this version include "protein name", "antibody against protein", "cellular localization", and "microsequenced proteins". New entries include "human autoantigens" and "cDNAs". For convenience we have included an alphabetical list of all known proteins recorded in this database. In the long run, the main goal of this database is to link protein and DNA sequencing and mapping information (Human Genome Program) and to provide an integrated picture of the expression levels and properties of the thousands of proteins that orchestrate various cellular functions both under physiological and abnormal conditions.