Iron-catalyzed regio- and stereoselective ring opening of [2.2.1]- and [3.2.1]oxabicyclic alkenes with a Grignard reagent

[reaction: see text] Arylative and alkenylative ring-opening reactions of a [2.2.1]- or [3.2.1]oxabicyclic alkene with a Grignard reagent take place in the presence of a catalytic amount of iron(III) chloride and a stoichiometric amount of TMEDA to produce a highly substituted 3-cyclohexen-1-ol or 3-cyclohepten-1-ol in good yield with high regio- and stereoselectivity.     

Cosmic microwave background radiation anisotropies in brane worlds

We propose a new formulation to calculate the cosmic microwave background (CMB) spectrum in the Randall-Sundrum two-brane model based on recent progress in solving the bulk geometry using a low energy approximation. The evolution of the anisotropic stress imprinted on the brane by the 5D Weyl tensor is calculated. An impact of the dark radiation perturbation on the CMB spectrum is investigated in a simple model assuming an initially scale-invariant adiabatic perturbation. The dark radiation perturbation induces isocurvature perturbations, but the resultant spectrum can be quite different from the prediction of simple mixtures of adiabatic and isocurvature perturbations due to Weyl anisotropic stress.     

Three-dimensional micro-channels in polymers: one-step fabrication

We report on the femtosecond laser fabrication of micro-channels of sub-micrometer cross section recorded in polymethylmethacrylate (PMMA) films in a single processing step. Both axial lengths of an elliptical cross section smaller than 0.4 m were achieved for a fabrication irradiance close to the dielectric breakdown of PMMA. Femtosecond pulsed irradiation was scanned along the three-dimensional (3D) patterns inside the film. Channels have a self-formed densified cladding and can be 3D stacked into any pre-designed pattern and can extend over a mm length. These features are prospective for micro-total analysis system (-TAS) chip fabrication, micro- or nano-fluidic studies, and photonic applications such as photonic crystals . PACS 42.70.-a; 42.70.Jk; 81.16.-c; 81.40.-z; 82.35.Lr     

Solute accumulation in heat seedlings during cold acclimation: contribution to increased freezing tolerance

Accumulation of sugars, amino acids and glycinebetaine in leaf tissues during cold acclimation was simultaneously monitored and compared in three wheat cultivars that have different freezing tolerance. Freezing tolerance was the decreasing order of cv. Norstar (NO) > cv. Chihokukomugi (CH) > or = cv. Haruyutaka (HA). During cold acclimation, there was a significant increase in osmotic concentration in the three cultivars. The increase was largely due to the increase in soluble sugars and the extent of the increase was the greatest in NO and the least in HA. While there was a considerable increase in glucose, fructose and sucrose during the first week of cold acclimation, the increase in raffinose occurred only after the second week. The total sugar content was the order of NO > CH > HA after 4 weeks of cold acclimation. Proline increased in all cultivars after 1 week of cold acclimation but a prolonged cold acclimation resulted in different profiles: no further increase occurred in HA while an additional increase occurred in other two cultivars. In all three cultivars, a noticeable increase of glycinebetaine occurred only after the second week of cold acclimation with the amount being the order of NO > CH > HA. It is concluded that a substantial part of the increase in osmotic concentration during cold acclimation was due to the increase in sugars, but the extent of the contribution of each compatible solute is cultivar-specific and can be associated with the degree of the maximum freezing tolerance attainable.     

Formation of embedded patterns in glasses using femtosecond irradiation

Channel formation in glasses is demonstrated and discussed. Photosensitive glass (Foturan) was microstructured using femtosecond irradiation at 800 nm and 400 nm wavelengths, with subsequent thermal annealing, and HF etching of a lithium-silicate phase formed by exposure-annealing. It was found that there is a significant difference in the volume of lithium-silicate when the exposure was made with and without optical breakdown. Channels with a minimum cross section of approximately 10 m were achieved.In silicate glasses, the optically induced dielectric breakdown was used for the recording of channel patterns. The highest wet etching rate in a HF based solution was observed when the irradiance corresponded to the 2.5–3.0 thresholds of dielectric breakdown and the adjacent pulses were overlapping by more than 50% of the diameter of the focussed beam. Under these conditions, the formation of a void inside the glass was confirmed by optical observation of single shot damage under a microscope. The mechanism of selective wet etching in silicate glasses is discussed in terms of the stress corrosion effect, which explains crack propagation in glasses via the reaction of stretched Si–O–Si bonds at the tip of a crack with water, resulting in SiOH formation. It is shown that intra-connection of voxels was the key factor to achieve etching of high aspect ratio patterns in silica glass. PACS 42.70.Ce; 81.05.Kf; 82.50.Pt; 87.80.Mj     

On-chip graphene oxide aptasensor for multiple protein detection

The versatility of an on-chip graphene oxide (GO) aptasensor was successfully confirmed by the detection of three different proteins, namely, thrombin (TB), prostate specific antigen (PSA), and hemagglutinin (HA), simply by changing the aptamers but with the sensor composition remaining the same. The results indicate that both DNA and RNA aptamers immobilized on the GO surface are sufficiently active to realize an on-chip aptasensor. Molecular selectivity and concentration dependence were investigated in relation to TB and PSA detection by using a dual, triple, and quintuple microchannel configuration. The multiple target detection of TB and PSA on a single chip was also demonstrated by using a 2 × 3 linear-array GO aptasensor. This work enables us to apply this sensor to the development of a multicomponent analysis system for a wide variety of targets by choosing appropriate aptamers.