Optical-limiting properties of oleylamine-capped gold nanoparticles for both femtosecond and nanosecond laser pulses.

We report strong broad-band optical-limiting properties of oleylamine-capped gold nanoparticles in solution for both femtosecond and nanosecond laser pulses. The nanosecond optical-limiting effects were characterized by using fluence-dependent transmittance measurements with 7 ns laser pulses at 532 and 1064 nm, and the femtosecond optical-limiting effects were characterized with a z-scan technique using 300 fs laser pulses at 780 nm. The oleylamine-capped gold nanoparticles were found to show strong broad-band optical-limiting effects for nanosecond laser pulses at 532 and 1064 nm and femtosecond laser pulses at 780 nm. These oleylamine-capped gold nanoparticles displayed exceptional optical-limiting effects with thresholds lower than that of carbon nanotube suspension, a benchmark optical limiter. Input-fluence- and angle-dependent scattering measurements suggested that nonlinear scattering played an important role in the observed optical-limiting behavior at 532 and 1064 nm.

Fluorescence enhancement of CdSe Q-Dots with intense femtosecond laser irradiation.

Effects of intense femtosecond (fs) laser irradiation on the optical properties of cadmium selenide (CdSe) nanocrystals are studied. We present the changes in emission and absorption of laser (800 nm, 110 fs, Ti-Sapphire) irradiated CdSe nanocrystals dispersed in dimethylformamide (DMF). It is observed that the absorbance of CdSe nanocrystals capped with trioctylphosphine (TOP) increases with the number of laser pulses. The trap state luminescence intensity of these crystals degrades, whereas the band edge luminescence intensity shows an increase as a function of the fs laser irradiation. We also report strong two photon absorption and reduction in the trap state luminescence intensity after irradiation with the laser pulses.

In situ synthesis of metal nanoparticles in polymer matrix and their optical limiting applications.

We present an overview of the simple and environmentally benign protocol we have developed recently, for the in situ generation of metal nanoparticles inside polymer films by mild thermal annealing, leading to free-standing as well as supported thin films of nanoparticle-embedded polymer. The fabrication chemistry is discussed and spectroscopic/microscopic characterizations of silver and gold nanoparticles in poly(vinyl alcohol) film are presented. Optical limiting characteristics of the silver-polymer system are investigated in detail and preliminary results for the gold-polymer system are reported.

Size dependent multiphoton absorption and refraction of CdSe nanoparticles.

We report a systematic investigation on nonlinear optical properties of CdSe nanoparticles that are smaller as well as larger than the Bohr radius. Multiphoton absorption and nonlinear refraction properties of CdSe nanoparticles observed with 800nm wavelength and 110femtosecond Ti:Sapphire laser are presented. These nonlinear optical studies were undertaken by performing open and closed aperture Z-scan measurements. The four different sizes of CdSe nanoparticles investigated are 5nm, 10nm, 25nm and 400nm. Both the quantum dots 5nm, 10nm sizes (taking the literature value of 10.6nm as the Bohr exciton diameter) show four photon absorption (4PA), while the 25nm and 400nm show the three photon absorption (3PA) properties. All four sizes of CdSe nanoparticles show the positive nonlinear refraction (n2).

Nonlinear optical absorption and switching properties of gold nanoparticle doped SiO2-TiO2 sol-gel films.

The nonlinear optical absorption and switching properties of sol-gel derived of Au nanoparticle doped SiO2-TiO2 sol-gel films having different Au-surface plasmon absorption positions are reported in this paper. The Au nanoparticles are embedded in SiO2 and SiO2-TiO2 mixed glassy film matrices with different refractive index values. To study the nonlinear absorption properties, lasers with three different wavelengths are used. The optical switching behavior is studied by using the pump-probe technique with 532 nm as the excitation wavelength. Ground state conduction band, surface plasmon band, and the free carrier band are taken as three level model to explain theoretically the obtained RSA and SA behaviors.

Anterior dislocation of the ulnar-humeral joint in a so-called 'pulled elbow'.

We describe an unusual case of a missed anterior dislocation of the elbow joint in a 1 year old girl who presented with a pulled elbow. To our knowledge, this is the first report of anterior dislocation as a result of a pulled elbow in the literature. We would like to highlight the rarity of this presentation and the importance of chronological assessment and management in the accident and emergency department.

Nonlinear absorption, scattering and optical limiting studies of CdS nanoparticles.

The nonlinear optical absorption, scattering and optical limiting properties of CdS nanoparticles dispersed in dimethylformamide (DMF) are investigated. The nanoparticles are synthesized using the standard chemical synthesis method with thioglycerol as the capping agent. The investigations are carried out at 532 nm in the ns regime. Strong two-photon absorption and nonlinear scattering are found to be responsible for good optical limiting characteristics in these nanoparticles.

Does neurological recovery in thoracolumbar and lumbar burst fractures depend on the extent of canal compromise?

STUDY DESIGN: Prospective study. OBJECTIVES: Forty-five consecutive cases of thoracolumbar and lumbar burst fractures treated non-operatively were analyzed to correlate the extent of canal compromise at the time of injury with (i) the initial neurologic deficit and (ii) with the extent of neurological recovery at 1 year. The effect of spinal canal remodeling on neurological recovery was also analyzed. SETTING: University teaching hospital in south India. METHODS: The degree of spinal canal compromise and canal remodeling were assessed from computed tomography scans. The neurologic status was assessed by Frankel's grading. RESULTS: The mean canal compromise in patients with neurologic deficit was 46.2% while in patients with no neurological deficit it was 36.3%. The mean spinal canal compromise in patients with neurological recovery was 46.1% and 48.4% in those with no recovery. The amount of canal remodeling in patients who recovered was 51.7% and 46.1% in the patients who did not recover. None of these differences was statistically significant. CONCLUSION: This study shows that there is no correlation between the neurologic deficit and subsequent recovery with the extent of spinal canal compromise in thoracolumbar burst fractures.