Measurement of quantum weak values of photon polarization

We experimentally determine weak values for a single photon's polarization, obtained via a weak measurement that employs a two-photon entangling operation, and postselection. The weak values cannot be explained by a semiclassical wave theory, due to the two-photon entanglement. We observe the variation in the size of the weak value with measurement strength, obtaining an average measurement of the S1 Stokes parameter more than an order of magnitude outside of the operator's spectrum for the smallest measurement strengths.     

A novel and highly efficient synthetic route to unsymmetrical organoselenides using cesium bases

A new and convenient one-pot method for the preparation of unsymmetrical selenides has been developed. In the presence of cesium hydroxide, molecular sieves, and DMF, benzeneselenol undergoes direct alkylation with various alkyl halides for the synthesis of alkyl phenyl selenides in moderate to excellent yields. Another method to prepare unsymmetrical organoselenides was also completed by coupling terminal alkynes with benzeneselenyl bromide. As an application, the synthesis of a selenopeptide was also accomplished. Furthermore, this methodology was extended to the synthesis of an organoselenide on solid support.     

A comparative study of myo-inositol quantification using LCmodel at 1.5 T and 3.0 T with 3 D 1H proton spectroscopic imaging of the human brain

Myo-inositol is a strongly coupled system and resonates at four chemical shift positions. At 1.5 T, only the singlet component at 3.57 ppm is detected. However, at 3 T this resonance is resolved into its components at 3.55 ppm and 3.61 ppm. Due to the increased spectral resolution and signal-to-noise ratio, it is anticipated that the quantification of myo-inositol should improve at 3 T. Using data from normal controls and the LCmodel quantification procedure, we found that the quantification precision, reproducibility and detection sensitivity of myo-inositol is significantly better at 3 T relative to 1.5 T.     

The influence of large-scale seafloor slope and average bottom sound speed on low-grazing-angle monostatic acoustic scattering

Variations in large-scale seafloor slope and average seabed sound speed account for a significant portion of the variations in scattering intensity observed in low-grazing-angle monostatic reverberation. Numerical modeling using a finite-difference solution to the elastic wave equation is used to quantify the effect of these large-scale parameters in interpretations of reverberation data. For hard rough seafloor (e.g., basalt), the results of the modeling suggest that the monostatic backscattering strength increases with increasing large-scale seafloor slope up to a slope of about 15 degrees dipping toward the incident direction. Once the grazing angle of the incident wavefield exceeds the critical grazing angle for the flat reference seafloor the backscattering intensity increases only slowly with increasing grazing angle. Similarly, average subseafloor sound speed has a significant effect. Seafloor with low sound speeds characteristic of soft bottoms (e.g., sediment) generate significantly weaker backscatter signals than seafloor with sound speeds characteristic of hard bottoms (e.g., basalt). The difference is that the shear waves can always be passed into soft bottoms because even for a flat seafloor there is no shear wave critical grazing angle.     

Computational studies on the A cluster of acetyl-coenzyme A synthase: geometric and electronic properties of the NiFeC species and mechanistic implications

DFT computational studies on the A cluster of acetyl-coenzyme A synthase are presented and discussed. They aim at evaluating possible A cluster models to settle the ongoing controversy about the nature of the proximal metal site in the catalytically active form of the cluster, recently proposed to be either Ni or Cu. Two possible models for the NiFeC species are considered, [Fe4S4]2+-Ni+CO-Ni2+ and [Fe4S4]2+-Cu+CO-Ni+. While for the former the computed 57Fe, 61Ni, and 13C hyperfine coupling parameters agree reasonably well with corresponding experimental values, for the latter model this agreement is very poor because the actual charge distribution is [Fe4S4]+-Cu+CO-Ni2+. Together, our results provide compelling evidence that the catalytically active A cluster contains Ni rather than Cu at the proximal metal site. Computations on the Ared2 state proposed to be part of the catalytic cycle (Darnault, C.; Volbeda, A.; Kim, E. J.; Legrand, P.; Vernède, X.; Lindahl, P. A.; Fontecilla-Camps, J. C. Nat. Struct. Biol. 2003, 10, 271-279) yield [Fe4S4]+-Ni+-Ni2+, hinting toward a Ni+/Ni3+ redox couple being involved in the methylation reaction.     

Protein prosthesis: a nonnatural residue accelerates folding and increases stability

Nonnatural residues can endow proteins with desirable properties. Here, replacing a proline residue that has a cis peptide bond in native ribonuclease A with 5,5-dimethyl-l-proline is shown to accelerate protein folding by 6-fold and enhance conformational stability by DeltaTm = 2.8 +/- 0.3 degrees C while having no effect on enzymatic activity. The rational use of this and other prosthetic segments could enable chemotherapeutic proteins to survive longer in vivo or retain activity after oral administration.     

NMR analysis of lignins in CAD-deficient plants. Part 1. Incorporation of hydroxycinnamaldehydes and hydroxybenzaldehydes into lignins

Peroxidase/H2O2-mediated radical coupling of 4-hydroxycinnamaldehydes produces 8-O-4-, 8-5-, and 8-8-coupled dehydrodimers as has been documented earlier, as well as the 5-5-coupled dehydrodimer. The 8-5-dehydrodimer is however produced kinetically in its cyclic phenylcoumaran form at neutral pH. Synthetic polymers produced from mixtures of hydroxycinnamaldehydes and normal monolignols provide the next level of complexity. Spectral data from dimers, oligomers, and synthetic polymers have allowed a more substantive assignment of aldehyde components in lignins isolated from a CAD-deficient pine mutant and an antisense-CAD-downregulated transgenic tobacco. CAD-deficient pine lignin shows enhanced levels of the typical benzaldehyde and cinnamaldehyde end-groups, along with evidence for two types of 8-O-4-coupled coniferaldehyde units. The CAD-downregulated tobacco also has higher levels of hydroxycinnamaldehyde and hydroxybenzaldehyde (mainly syringaldehyde) incorporation, but the analogous two types of 8-O-4-coupled products are the dominant features. 8-8-Coupled units are also clearly evident. There is clear evidence for coupling of hydroxycinnamaldehydes to each other and then incorporation into the lignin, as well as for the incorporation of hydroxycinnamaldehyde monomers into the growing lignin polymer. Coniferaldehyde and sinapaldehyde (as well as vanillin and syringaldehyde) co-polymerize with the traditional monolignols into lignins and do so at enhanced levels when CAD-deficiency has an impact on the normal monolignol production. The implication is that, particularly in angiosperms, the aldehydes behave like the traditional monolignols and should probably be regarded as authentic lignin monomers in normal and CAD-deficient plants.     

Function Spaces of Posets with Projections

This paper investigates function spaces of structures consisting of a partially ordered set together with some directed family of projections.More precisely, given a fixed directed index set (I,), we consider triples (D,,(p _i ) _iI ) with (D,) a poset and (p _i ) _iI a monotone net of projections of D. We call them (I,)-pop's (posets with projections). Our main purpose is to study structure preserving maps between (I,)-pop's. Such homomorphisms respect both order and projections.Any (I,)-pop is known to induce a uniformity and thus a topology. The set of all homomorphisms between two (I,)-pop's turns out to form an (I,)-pop itself. We show that its uniformity is the uniformity of uniform convergence. This enables us to prove that properties such as completeness and compactness transfer to function pop's.Concerning categorical properties of (I,)-pop's, we will see that we are in a lucky situation from a computer scientist's point of view: we obtain Cartesian closed categories. Moreover, by a D -construction we get (I,)-pop's that are isomorphic to their own exponent. This yields new models for the untyped -calculus.