Fabrication and characterization of large numerical aperture, high-resolution optical fiber bundles based on high-contrast pairs of soft glasses for fluorescence imaging.

Fabrication and characterization of flexible optical fiber bundles (FBs) with in-house synthesized high-index and low-index thermally matched glasses are presented. The FBs composed of around 15000 single-core fibers with pixel sizes between 1.1 and 10 µm are fabricated using the stack-and-draw technique from sets of thermally matched zirconium-silicate ZR3, borosilicate SK222, sodium-silicate K209, and F2 glasses. With high refractive index contrast pair of glasses ZR3/SK222 and K209/F2, FBs with numerical apertures (NAs) of 0.53 and 0.59 are obtained, respectively. Among the studied glass materials, ZR3, SK222, and K209 are in-house synthesized, while F2 is commercially acquired. Seven different FBs with varying pixel sizes and bundle diameters are characterized. Brightfield imaging of a micro-ruler and a Convallaria majalis sample and fluorescence imaging of a dye-stained paper tissue and a cirrhotic mice liver tissue are demonstrated using these FBs, demonstrating their good potential for microendoscopic imaging. Brightfield and fluorescence imaging performance of the studied FBs are compared. For both sets of glass compositions, good imaging performance is observed for FBs, with core diameter and core-to-core distance values larger than 1.6 µm and 2.3 µm, respectively. FBs fabricated with K209/F2 glass pairs revealed better performance in fluorescence imaging due to their higher NA of 0.59.

The Effects of Freezing and Supplementation of Molasses and Inoculants on Chemical and Nutritional Composition of Sunflower Silage.

This study was conducted to determine the effects of freezing and supplementation of molasses (M), lactic acid bacteria (LAB) and LAB+enzyme mixture on chemical and nutritional composition of sunflower silage (SF). Sunflower crops were harvested (at about 29.2%±1.2% dry matter) and half of fresh sunflower was ensiled alone and half was frozen (F) at -20°C for 7 days. Silage additives were admixed into frozen SF material. All samples were ensiled in glass jars with six replicates for 90 days. The treatments were as follows: i) positive control (non-frozen and no additives, NF), ii) negative control (frozen, no additives, F), iii) F+5% molasses (FM), iv) F+LAB (1.5 g/tons, Lactobacillus plantarum and Enterococcus faecium, FLAB); v) F+LAB+enzyme (2 g/tons Lactobacillus plantarum and Enterococcus faecium and cellulase and amylase enzymes, FLEN). Freezing silage increased dry matter, crude ash, neutral detergent fiber, and acid detergent lignin. The organic matter, total digestible nutrient, non-fiber carbohydrate, metabolizable energy and in vitro dry matter digestibility were negatively influenced by freezing treatments (p<0.05). In conclusion, freezing sunflower plants prior to ensiling may negatively affect silage quality, while molasses supplementation improved some quality traits of frozen silage. Lactic acid bacteria and LAB+enzyme inoculations did not effectively compensate the negative impacts of freezing on sunflower silage.

Investigation of the effects of oleuropein rich diet on rat enteric bacterial flora.

OBJECTIVES AND BACKGROUND: Oleuropein is a phenolic compound of olive leaves. Enteric bacterial flora is very important for human health and diet is a directly affecting factor of enteric bacterial flora composition. In this study, it was hypothesized that oleuropein could reduce total aerobic bacterial count in rat caecal flora. METHODS: Twenty adult, male, Wistar albino rats were randomly divided into two groups. Group C (n=10) was fed with standard rat chow and water for 30 days. Group O (n=10) received olive leaf extract 20 mg/kg/day by intragastric gavage in addition to standard rat chow and water for 30 days. One gram of caecal content was collected from each rat and then consecutive 10-fold serial dilutions were prepared with a final concentration of 10-8. Then 0.1 ml of each dilution were spread onto the surfaces of Plate Count Agar and Violet Red Bile Glucose Agar to enumerate the aerobic enteric bacteria. RESULTS: Total aerobic bacterial counts of Group O were significantly lower than of Group C in all agar plates inoculated with ceacal samples for every dilution (p<0.05). CONCLUSION: Adding oleuropein to enteral feeding solutions of critically ill patients may be adventageous in the presence of clinical conditions predisposing to bacterial translocation by reducing enteric bacterial counts (Tab. 1, Ref. 32).

Dye lasing in optically manipulated liquid aerosols.

We report lasing in airborne, rhodamine B-doped glycerol-water droplets with diameters ranging between 7.7 and 11.0 µm, which were localized using optical tweezers. While being trapped near the focal point of an infrared laser, the droplets were pumped with a Q-switched green laser. Our experiments revealed nonlinear dependence of the intensity of the droplet whispering gallery modes (WGMs) on the pump laser fluence, indicating dye lasing. The average wavelength of the lasing WGMs could be tuned between 600 and 630 nm by changing the droplet size. These results may lead to new ways of probing airborne particles, exploiting the high sensitivity of stimulated emission to small perturbations in the droplet laser cavity and the gain medium.

A new finding in a patient with Mowat Wilson syndrome: peripupillary atrophy and gingival hypertrophy.

Mowat-Wilson syndrome is a genetic disease characterized by typical facial features, Hirschsprung disease and multiple congenital abnormalities. MWS is a single gene disorder. One of the most specific clinical signs in MWS is the distinctive face. We report a two-year-old boy with multiple congenital anomalies. He had peripupillary atrophy and gingival hypertrophy different from the literature. The patient was also diagnosed with his clinical findings. These features may be important in Mowat-Wilson syndrome and clinicians should keep these findings in mind.

Prolonged Raman lasing in size-stabilized salt-water microdroplets on a superhydrophobic surface.

We demonstrate prolonged Raman lasing from individual salt-water microdroplets with 10-20 microm diameters located on a superhydrophobic surface. The mechanism is based on the absorption heating of a 1064 nm cw IR laser and the resonant heating of a 532 nm pulsed, pump laser. A clear hysteresis is observed in the lasing intensity as the droplet size is photothermally tuned by the IR laser, indicating a self-stabilization mechanism due to the resonant absorption of the pump laser. Using this mechanism, Raman lasing near 650 nm is sustained for up to 25 min, approximately 1000 times longer than lasing durations reported in previous studies.

Photothermal self-stability and optical bistability of single NaCl-water microdroplets on a superhydrophobic surface.

A self-stabilization mechanism locking the size of single inorganic salt (NaCl)-water microdroplets that are standing on a superhydrophobic surface and kept in a humidity-controlled chamber is demonstrated. The effect is based on the hysteretic behavior of a photothermal tuning cycle caused by the whispering gallery mode (WGM) absorption resonances that are observed when scanning the power of an infrared laser focused at the rim of a microdroplet. When locked, the microdroplet size and WGM spectrum are resilient to environmental perturbations and can be maintained for hours as the mechanism does not rely on a photobleachable dye. The bistable nature of the system is also demonstrated, enabling reversible switching between two sizes. A rate equation-based thermodynamical model of the hysteretic behavior is provided, giving good agreement with the experimental results. Our results may be used to establish stable experimental conditions for ultrahigh resolution spectroscopy of microdroplets. Other optical and biological applications that require exactly size-matched microdroplets can also benefit from the demonstrated self-stabilization mechanism.

Reversible photothermal tuning of a salty water microdroplet.

A fully reversible photothermal tuning of an inorganic salt (NaCl)-water microdroplet standing on a superhydrophobic surface is demonstrated. The size change of the microdroplet is caused by a focused infrared laser beam in a humidity-controlled chamber and a fully reversible large spectral tuning up to approximately 40 nm is achieved. The evaporation and growth of the microdroplet are modeled using a lumped system formulation of mass and energy conservations and a good agreement is observed between the experimental and theoretical results.

Large spectral tuning of a water-glycerol microdroplet by a focused laser: characterization and modeling.

Large spectral tuning of a water-glycerol microdroplet standing on a superhydrophobic surface by local heating with a focused infrared laser is studied both experimentally by optical spectroscopy and computationally using a lumped system formulation of the mass and heat transfer between the microdroplet and the chamber. The effects of optical scattering force, chamber humidity, size of microdroplet and laser power on the tuning mechanism are examined. The reversibility of the tuning mechanism is also studied. In spite of its negligibly small volatility compared to that of water, irreversibility is found to be mainly caused by evaporation of glycerol. It is also found that reversibility increases dramatically with the relative water and glycerol humidities, and spectral tuning can be made almost fully reversible when the chamber is saturated with glycerol vapor and the relative water humidity approaches unity. Some hysteresis effects are observed, especially in large microdroplets, and this behavior is attributed to the whispering-gallery mode resonances in laser absorption. The time response of the tuning mechanism is also analyzed both experimentally and computationally. The technique presented can find applications in optical communication systems, and can be used in fundamental studies in cavity quantum electrodynamics and in characterizing liquid aerosols on a surface.

Raman lasing near 630 nm from stationary glycerol-water microdroplets on a superhydrophobic surface.

We demonstrate, for the first time to our knowledge, Raman lasing from stationary microdroplets on a superhydrophobic surface. In the experiments, glycerol-water microdroplets with radii in the 11-15 microm range were pumped at 532 nm with a pulsed, frequency-doubled Nd:YAG laser. Two distinct operation regimes of the microdroplets were observed: cavity-enhanced Raman scattering and Raman lasing. In the latter case, the Raman lasing signal was higher than the background by more than 30 dB. Investigation of the Raman spectra of various glycerol-water mixtures indicates that lasing occurs within the glycerol Raman band. Raman lasing was not sustained; rather, oscillation would occur in temporally separated bursts. Increasing the rate of convective cooling by nitrogen purging improved the lasing performance and reduced the average interburst separation from 2.3 to 0.4 s.

Indistinguishable photons from a single molecule.

We report the results of coincidence counting experiments at the output, of a Michelson interferometer using the zero-phonon-line emission of a single molecule at 1.4 K. Under continuous wave excitation, we observe the absence of coincidence counts as an indication of two-photon interference. This corresponds to the observation of Hong-Ou-Mandel correlations and proves the suitability of the zero-phonon-line emission of single molecules for applications in linear optics quantum computation.

A quantum dot single-photon turnstile device.

Quantum communication relies on the availability of light pulses with strong quantum correlations among photons. An example of such an optical source is a single-photon pulse with a vanishing probability for detecting two or more photons. Using pulsed laser excitation of a single quantum dot, a single-photon turnstile device that generates a train of single-photon pulses was demonstrated. For a spectrally isolated quantum dot, nearly 100% of the excitation pulses lead to emission of a single photon, yielding an ideal single-photon source.