Nanometer-sized gelatin particles prepared by means of gamma-ray irradiation

Nanometer-sized gelatin particles have been prepared by means of gamma-ray irradiation and characterized by static and dynamic light scattering combined with circular dichroism (CD) measurements. The molecular weight of the nanoparticles was much larger than that of the original gelatin molecules, whereas the hydrodynamic radius was much smaller. Radius of gyration evaluated from the angular dependence of the static light scattering intensity decreased with increasing irradiation dose. CD spectra of the gelatin nanoparticles were independent of temperature, and it is suggested that the nanoparticles consist of highly and randomly packed gelatin and their conformation is stable against the temperature change.     

Rapid liquid chromatographic determination of oxytetracycline in milk.

A simple method for the determination of residual oxytetracycline (OTC) in milk by high-performance liquid chromatography (HPLC) was developed. The sample preparation could be made without complex extraction and clean-up procedures. A LiChrospher 100 RP-8 end-capped column and a mobile phase of acetonitrile-acetic acid-water (28:4:68, v/v/v) with a photo-diode array detector was used. The average recoveries from spiked OTC (0.1, 0.5 and 1.0 microgram/ml) were in excess of 89.8% with coefficients of variation between 0.6 and 4.1%. The limit of detection was 0.05 microgram/ml. The total time required for the analysis of one sample was below 10 min.     

Application of shielded column liquid chromatography for determination of sulfamonomethoxine, sulfadimethoxine, and their N4-acetyl metabolites in milk

A hazardous-chemical free method for simultaneous determination of sulfamonomethoxine (SMM), sulfadimethoxine (SDM), and their N4-acetyl metabolites in raw milk using shielded column liquid chromatography is developed. The target analytes are extracted by mixing with ethanol-acetic acid (97:3, v/v) followed by centrifugation. The procedure uses a Hisep shielded hydrophobic phase (SHP) column, isocratic elution with 0.1% acetic acid solution (pH 3.1, in water)-ethanol (75:25, v/v), and a photo-diode array detector. Average recoveries from samples spiked at 25-500 ng/ml for each drug were >81% with relative standard deviations within 5%. The limits of quantitation were <25 ng/ml.     

Nonlinear femtosecond pulse compression at high average power levels by use of a large-mode-area holey fiber

We demonstrate that nonlinear fiber compression is possible at unprecedented average power levels by use of a large-mode-area holey (microstructured) fiber and a passively mode-locked thin disk Yb:YAG laser operating at 1030 nm. We broaden the optical spectrum of the 810-fs pump pulses by nonlinear propagation in the fiber and remove the resultant chirp with a dispersive prism pair to achieve 18 W of average power in 33-fs pulses with a peak power of 12 MW and a repetition rate of 34 MHz. The output beam is nearly diffraction limited and is linearly polarized.     

Optical parametric oscillator with a pulse repetition rate of 39 GHz and 2.1-W signal average output power in the spectral region near 1.5 microm

We present a singly resonant, synchronously pumped optical parametric oscillator with a record-high repetition rate of 39 GHz. The transform-limited 2.2-ps pulses at 1570 nm have as much as 2.1-W average output power. The all-solid-state pump source is based on a diode-pumped passively mode-locked 39-GHz Nd:YVO4 laser and an efficient ytterbium-doped fiber amplifier.     

Nanoscale hydrophobic interaction and nanobubble nucleation

We report large-scale atomistic simulation of midrange nanoscale hydrophobic interaction, manifested by the nucleation of nanobubble between nanometer-sized hydrophobes at constrained equilibrium. When the length scale of the hydrophobes is greater than 2 nm, the nanobubble formation shows hysteresis behavior resembling the first-order transition. Calculation of the potential of mean force versus interhydrophobe distance provides a quantitative measure of the strength of the nanoscale hydrophobic interaction.     

Comparative study of large-mode holey and conventional fibers

Little information exists regarding how large-mode holey fibers compare, in practical terms, with their conventional counterparts. We present what is to our knowledge the first experimental study of mode area and bend loss for a range of large-mode holey and conventional fibers. It is demonstrated here that large-mode holey fibers exhibit mode areas and bending losses that are comparable to those of conventional fibers at 1.55mu . However, the novel wavelength dependence of the numerical aperture in a holey fiber offers a significant advantage for broadband and short-wavelength applications in which single-mode operation is required.     

Simplified liquid-chromatographic determination of residues of tetracycline antibiotics in eggs

Summary A high-performance liquid chromatographic (HPLC) procedure is described for the identification and quantification of residues of tetracycline antibiotics (TCA) (oxytetracycline, tetracycline, chlortetracycline, and doxycycline), in eggs. Spiked and blank samples were prepared by homogenization with 1∶1 (v/v) acetonitrile-mixed Mcllvaine buffer and EDTA solution (pH 4.0) then centrifugal ultrafiltration. HPLC was performed on a reversed-phase column with acetonitrile-5% (v/v) aqueous acetic acid, 35∶65 (v/v), as mobile phase and photo-diode array detection. Average recoveries (each drug spiked at 0.1, 0.2, 0.3, 0.5 and 1.0 μg g⁻¹) were >-77% with standard deviations (SD) between 1.5 and 3.5%. The inter-assay variabilities and theirSD were <3.4% and <0.7%, respectively, and intra-assay variability was between 2.0 and 3.9%. The limits of quantitation (LOQ) were 0.064 0.087, 0.121, and 0.131 μg g⁻¹ for OTC, TC, CTC, and DC, respectively. The total time required for the analysis of one sample was less than 30 min.