154 research outputs found
Photostability of J -aggregates adsorbed on TiO 2 nanoparticles and AFM imaging of J -aggregates on a glass surface
Abstract. Spectral properties and photostability of the 5,5'-6,6'-tetrachloro-1,1'-dioctyl-3,3'-bis-(3-carboxypropyl)-benzimidacarbocyanine (Dye 1) J-aggregate was investigated in solution and upon adsorption on TiO 2 nano-particles. Dye 1 was found to photodegrade on the surface of TiO 2 . Additionally, the self-assembly of Dye 1 was studied on a glass surface by non-contact atomic force microscopy (NCAFM). The dye molecules form a well-defined fiber like structure that extends for tens of micrometers. The internal structure of the fibers was clearly resolved and showed a number of small tubes wrapped around each other to form a helical structure
Study of wavelength-shifting chemicals for use in large-scale water Cherenkov detectors
Cherenkov detectors employ various methods to maximize light collection at
the photomultiplier tubes (PMTs). These generally involve the use of highly
reflective materials lining the interior of the detector, reflective materials
around the PMTs, or wavelength-shifting sheets around the PMTs. Recently, the
use of water-soluble wavelength-shifters has been explored to increase the
measurable light yield of Cherenkov radiation in water. These wave-shifting
chemicals are capable of absorbing light in the ultravoilet and re-emitting the
light in a range detectable by PMTs. Using a 250 L water Cherenkov detector, we
have characterized the increase in light yield from three compounds in water:
4-Methylumbelliferone, Carbostyril-124, and Amino-G Salt. We report the gain in
PMT response at a concentration of 1 ppm as: 1.88 0.02 for
4-Methylumbelliferone, stable to within 0.5% over 50 days, 1.37 0.03 for
Carbostyril-124, and 1.20 0.02 for Amino-G Salt. The response of
4-Methylumbelliferone was modeled, resulting in a simulated gain within 9% of
the experimental gain at 1 ppm concentration. Finally, we report an increase in
neutron detection performance of a large-scale (3.5 kL) gadolinium-doped water
Cherenkov detector at a 4-Methylumbelliferone concentration of 1 ppm.Comment: 7 pages, 9 figures, Submitted to Nuclear Instruments and Methods
Hydrothermal Preparation of Gd+3 -Doped Titanate Nanotubes: Magnetic Properties and Photovoltaic Performance
Pure and Gd+3 -doped titanate nanotubes (TNTs) materials were synthesized by a hydrothermal method. Their morphology, optical properties, thermal stability, and magnetic properties were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), UV-Vis spectroscopy, thermal analysis, and magnetic measurements. It was found that doping renders Gd+3-TNT visible light active and results in smaller crystallite size and larger surface area as well as higher thermal stability compared to pure titanate nanotubes. The estimated magnetic moments point to presence of weak antiferromagnetic interaction. Application of the prepared Gd+3-TNT for modifying conventional photoanodes in polymer solar cells was attempted. Preliminary results show slightly improved photovoltaic energy conversion efficiency in the devices containing the newly designed Gd+3 -doped nanotubes
Factors Affecting the Efficiency of Excited-States Interactions of Complexes between Some Visible Light-Emitting Lanthanide Ions and Cyclophanes Containing Spirobiindanol Phosphonates
The efficiency of excited-states interactions between lanthanide ions Tb3+ and Eu3+ and some new cyclophanes (I, II, and III) has been studied in different media. High luminescence quantum yield values for terbium and europium complexes in DMSO and PMMA were obtained. The photophysical properties of the green and red emissive Tb3+ and Eu3+ complexes have been elucidated, respectively
Enhancing the capabilities of LIGO time-frequency plane searches through clustering
One class of gravitational wave signals LIGO is searching for consists of
short duration bursts of unknown waveforms. Potential sources include core
collapse supernovae, gamma ray burst progenitors, and mergers of binary black
holes or neutron stars. We present a density-based clustering algorithm to
improve the performance of time-frequency searches for such gravitational-wave
bursts when they are extended in time and/or frequency, and not sufficiently
well known to permit matched filtering. We have implemented this algorithm as
an extension to the QPipeline, a gravitational-wave data analysis pipeline for
the detection of bursts, which currently determines the statistical
significance of events based solely on the peak significance observed in
minimum uncertainty regions of the time-frequency plane. Density based
clustering improves the performance of such a search by considering the
aggregate significance of arbitrarily shaped regions in the time-frequency
plane and rejecting the isolated minimum uncertainty features expected from the
background detector noise. In this paper, we present test results for simulated
signals and demonstrate that density based clustering improves the performance
of the QPipeline for signals extended in time and/or frequency.Comment: 17 pages, 6 figures. Submitted to CQG on Dec 12, 2008; accepted on
June 18, 200
Lung inflammation does not affect the clearance kinetics of lipid nanocapsules following pulmonary administration
Lipid nanocapsules (LNCs) are semi-rigid spherical capsules with a triglyceride core that present a promising formulation option for the pulmonary delivery of drugs with poor aqueous solubility. Whilst the biodistribution of LNCs of different size has been studied following intravenous administration, the fate of LNCs following pulmonary delivery has not been reported. We investigated quantitatively whether lung inflammation affects the clearance of 50nm lipid nanocapsules, or is exacerbated by their pulmonary administration. Studies were conducted in mice with lipopolysaccharide-induced lung inflammation compared to healthy controls. Particle deposition and nanocapsule clearance kinetics were measured by single photon emission computed tomography/computed tomography (SPECT/CT) imaging over 48 h. A significantly lower lung dose of (111)In-LNC50 was achieved in the lipopolysaccharide (LPS)-treated animals compared with healthy controls (p<0.001). When normalised to the delivered lung dose, the clearance kinetics of (111)In-LNC50 from the lungs fit a first order model with an elimination half-life of 10.5±0.9h (R(2)=0.995) and 10.6±0.3h (R(2)=1.000) for healthy and inflamed lungs respectively (n=3). In contrast, (111)In-diethylene triamine pentaacetic acid (DTPA), a small hydrophilic molecule, was cleared rapidly from the lungs with the majority of the dose absorbed within 20min of administration. Biodistribution to lungs, stomach-intestine, liver, trachea-throat and blood at the end of the imaging period was unaltered by lung inflammation. This study demonstrated that lung clearance and whole body distribution of lipid nanocapsules were unaffected by the presence of acute lung inflammation
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