Single-frequency, single-knob tuning of a CW color center laser

We describe a simple way to achieve CW single-frequency laser operation with a grating as the sole tuning element. It is Shown, both experimentally and theoretically, that by proper choice of cavity parameters, the competing hole burning modes can be completely suppressed. Experiments to demonstrate the theoretical calculations were carried out in a CW color center laser using Tl⁰(1) centers. Linewidths of 0.01 cm^-1were obtained and this figure can probably be much improved by proper cavity stabilization. The method can be readily extended to any compact gain medium.     

Compression of Q-switched and mode-locked CW Nd:YAG laser pulses

Using the optical compression technique with a single-mode optical fiber and a grating pair, the 85 ps pulses from aQ-switched, mode-locked CW Nd:YAG laser have been compressed by a factor of 30. On average, an overall enhancement of 7 × in the peak power was achieved.     

Ferroelectric properties of pulsed laser deposited PZT (92/8) thin films

The effect of pulse amplitude on the ferroelectric and switching properties of pulsed laser deposited PZT (92/8) thin films has been studied. The structural analysis revealed that the films had a well crystallized perovskite phase without secondary phases. The atomic force microscopy has been employed to estimate the grain size and surface roughness of the film. A well-saturated P–E hysteresis loop was observed with average values of remnant polarization (P_r) ≈ 16.0 μC/cm², saturation polarization (P_s) ≈ 21.7 μC/cm² and coercive field ≈138 kV/cm. The P–E loops were very stable with frequency, confirming that the contribution of the leakage current and/or mobile free charges to the polarization is minimum. The polarization current exhibits the exponential dependence on the pulse amplitude and the leakage current seems to be governed by the hopping mechanism which is generally associated to structural defects.     

Analytical study of a solution-processed diode based on ZnO nanoparticles using multi-walled carbon nanotubes as Schottky contact

Journal of Materials Science: Materials in Electronics - The search for good electrodes processed by solution has interested several niches to produce printed solar cells, lighting emitting diodes,...     

Evaluation of the addition of wheat residues in the production of Pinus oocarpa agglomerated panels

Clean Technologies and Environmental Policy - The aim of this research was to evaluate the physical and mechanical properties of Pinus oocarpa wood agglomerated panels produced with the addition of...     

The effects of a biocide and a surfactant on the detachment of Pseudomonas fluorescens from glass surfaces

Application of antimicrobial chemicals is a general procedure in the cleaning and disinfection of food-contacting surfaces. Adhesion to glass surfaces and chemically induced detachment of Pseudomonas fluorescens ATCC 13525(T) were studied in situ, under flow conditions, in a well-controlled parallel plate flow chamber (PPFC). Ortho-phthalaldehyde (OPA) and cetyltrimethyl ammonium bromide (CTAB) were applied separately, at several concentrations, to attached bacteria and their subsequent detachment was monitored. Following treatments the remaining adhered bacteria were characterized in terms of viability and cell size. Simultaneously, the planktonic cell surface was characterized in order to correlate PPFC results with thermodynamic approaches for adhesion evaluation, and surface free energy of chemically treated cells with adhesion strength. About 2.8x10(6) cells/cm(2) adhered to the glass surface after 30 min of bacterial flow, although thermodynamic analyses evidenced unfavourable adhesion. The independent application of OPA and CTAB promoted bacterial detachment to a small extent (16% of total cells). The remaining adhering bacteria were totally non-viable for OPA> or =0.75 mM and CTAB> or =0.25 mM, showing a lack of correlation between bacterial viability and detachment. The cellular size decreased as attachment proceeded and with chemical treatment. Both chemicals altered the cell surface properties, increasing the cell-glass adhesion strength, and promoting the emergence of polar characteristics. The overall results emphasize that OPA and CTAB were markedly ineffective in removing glass-attached P. fluorescens, demonstrating that bacteria can be non-viable but remain strongly attached to the adhesion surface.     

Determination of sensory thresholds of Mentha piperita L. essential oil in selected tropical fruit juices and efficacy of sensory accepted concentrations combined with mild heat to inactivate foodborne pathogens

This study determined the compromised acceptance threshold (CAT) and rejection threshold (RT) of Mentha piperita L. essential oil (MPEO) in cajá, guava and mango juices. The MPEO concentrations below the RT values were evaluated alone or combined with mild heat treatment (MHT; 54 °C) to inactivate ≥5-log₁₀ of Escherichia coli O157:H7 and Salmonella Enteritidis PT 4 in the same juices. The CAT of MPEO varied from 0.30 to 0.32 μL mL⁻¹, while the RT was 1.34 or 1.36 μL mL⁻¹ in the tested juices. Only concentrations of MPEO close, or higher than the RT caused ≥5-log₁₀ reductions in the tested pathogens in cajá, guava and mango juices. Combined with MHT, concentrations of MPEO below the RT reduced ≥5-log₁₀ of both pathogens in juices. These findings indicate that MPEO concentrations below the RT in combination with MHT is a feasible preservation technology to ensure the safety of tropical fruit juices.     

Antioxidant and antibacterial activities of a starch film with bioextracts microencapsulated from cactus fruits (Opuntia oligacantha)

Food Science and Biotechnology - The use of unconventional sources is very relevant in the food area. In the present study the development of active films with the addition of bioextract (BE) or...