Cylindrical vector beams for rapid polarization-dependent measurements in atomic systems

We demonstrate the use of cylindrical vector beams - beams with spatially varying polarization - for detecting and preparing the spin of a warm rubidium vapor in a spatially dependent manner. We show that a modified probe vector beam can serve as an atomic spin analyzer for an optically pumped medium, which spatially modulates absorption of the beam. We also demonstrate space-variant atomic spin by optical pumping with the vector beams. The beams are thus beneficial for making singleshot polarization-dependent measurements, as well as for providing a means of preparing samples with position-dependent spin.Comment: 8 pages, 5 figures. Accepted in Optics Expres

Microprobe Analyses of the Potassium-Calcium Distribution Relationship in Predentine

Apex regions of continuously growing incisors of Wistar rats were quickly dissected, shock-frozen in liquid nitrogen-cooled propane, freeze-dried at -80 °C and infiltrated with Spurr\u27s resin . 400nm thick dry sections were cut with a diamond knife on an ultramicrotome . Relatively flat sections were transferred with an eye lash onto collodium coated aluminum grids. They were flattened with a glass stick and by placing another collodi um coated aluminum grid just on top of the first one, exerting a uniform pressure . After carbon coating the sections were observed using the backscattered and secondary electron signals in a scanning microscope. The predentine was analyzed for calcium and potassium with an energy dispersive x-ray analysis system. The xray spectra revealed in the predentine regions with beginning dentine formation, near the apex, an uneven K-distribution with very low as well as more prominent x-ray peaks. The K peaks were always lower than those of calcium. In areas with advanced dentine formation, prominent K-peaks were always observed. They were normally higher than the Ca-peaks up to a distance of 5- 10 µ.m from the dentine border. Closer to the dentine border the K concentration decreased while the Ca-peak increased. This might indicate that (besides Na) K is used to balance the negative charges of the macromolecules till K is replaced by Ca at the onset of apatite crystal formation

Formation of Organic Color Centers in Air-Suspended Carbon Nanotubes Using Vapor-Phase Reaction

Organic color centers in single-walled carbon nanotubes have demonstrated exceptional ability to generate single photons at room temperature in the telecom range. Combining the color centers with pristine air-suspended tubes would be desirable for improved performance, but all current synthetic methods occur in solution which makes them incompatible. Here we demonstrate formation of color centers in air-suspended nanotubes using vapor-phase reaction. Functionalization is directly verified on the same nanotubes by photoluminescence spectroscopy, with unambiguous statistics from more than a few thousand individual nanotubes. The color centers show a strong diameter-dependent emission intensity, which can be explained with a theoretical model for chemical reactivity taking into account strain along the tube curvature. We are also able to estimate the defect density by comparing the experiments with simulations based on a one-dimensional diffusion equation, whereas the analysis of diameter dependent peak energies gives insight to the nature of the dopant states. Time-resolved measurements show a longer lifetime for color center emission compared to E$_{11}$ exciton states. Our results highlight the influence of the tube structure on vapor-phase reactivity and emission properties, providing guidelines for development of high-performance near-infrared quantum light sources.Comment: 8 pages, 6 figure

Room-temperature quantum emission from interface excitons in mixed-dimensional heterostructures

The development of van der Waals heterostructures has introduced unconventional phenomena that emerge at atomically precise interfaces. For example, interlayer excitons in two-dimensional transition metal dichalcogenides show intriguing optical properties at low temperatures. Here we report on room-temperature observation of interface excitons in mixed-dimensional heterostructures consisting of two-dimensional tungsten diselenide and one-dimensional carbon nanotubes. Bright emission peaks originating from the interface are identified, spanning a broad energy range within the telecommunication wavelengths. The effect of band alignment is investigated by systematically varying the nanotube bandgap, and we assign the new peaks to interface excitons as they only appear in type-II heterostructures. Room-temperature localization of low-energy interface excitons is indicated by extended lifetimes as well as small excitation saturation powers, and photon correlation measurements confirm single-photon emission. With mixed-dimensional van der Waals heterostructures where band alignment can be engineered, new opportunities for quantum photonics are envisioned.Comment: 8 pages, 4 figure

Discrete Cylindrical Vector Beam Generation from an Array of Optical Fibers

A novel method is presented for the beam shaping of far field intensity distributions of coherently combined fiber arrays. The fibers are arranged uniformly on the perimeter of a circle, and the linearly polarized beams of equal shape are superimposed such that the far field pattern represents an effective radially polarized vector beam, or discrete cylindrical vector (DCV) beam. The DCV beam is produced by three or more beams that each individually have a varying polarization vector. The beams are appropriately distributed in the near field such that the far field intensity distribution has a central null. This result is in contrast to the situation of parallel linearly polarized beams, where the intensity peaks on axis

Chitinase 3-like 1 expression by human (MG63) osteoblasts in response to lysophosphatidic acid and 1,25-Dihydroxyvitamin D3

Chitinase 3-like 1, otherwise known as YKL-40, is a secreted glycoprotein purported to have a role in extracellular matrix metabolism. The first mammalian cell type found to express YKL-40 was the human osteosarcoma-derived osteoblast, MG63. In that first study the active vitamin D3 metabolite, 1,25-dihydroxycholecalciferol (1,25D), stimulated YKL-40 expression, thereby indicating that a vital factor for skeletal health promoted YKL-40 synthesis by bone forming cells. However, when these MG63 cells were exposed to 1,25D they were also exposed to serum, a rich source of the pleiotropic lipid mediator, lysophosphatidic acid (LPA). Given that 1,25D is now known to co-operate with selected growth factors, including LPA, to influence human osteoblast differentiation we hypothesised that 1,25D and LPA may work together to stimulate osteoblast YKL-40 expression. Herein we report that 1,25D and LPA synergistically promote YKL-40 expression by MG63 cells. Inhibitors targeting AP1, MEK, Sp1 and STAT3 blunted the expression of both alkaline phosphatase and YKL-40 by MG63 cells in response to co-stimulation with 1,25D and LPA. Other ligands of the vitamin D receptor also co-operated with LPA in driving YKL-40 mobilisation. Collectively our findings highlight another important role of 1,25D and LPA in the regulation of human osteoblast function

Enhanced Auditory Brainstem Response and Parental Bonding Style in Children with Gastrointestinal Symptoms

The electrophysiological properties of the brain and influence of parental bonding in childhood irritable bowel syndrome (IBS) are unclear. We hypothesized that children with chronic gastrointestinal (GI) symptoms like IBS may show exaggerated brainstem auditory evoked potential (BAEP) responses and receive more inadequate parental bonding. = 0.024). Multiple regression analysis in females also supported these findings.It is suggested that children with chronic GI symptoms have exaggerated brainstem responses to environmental stimuli and inadequate parental behaviors aggravate these symptoms