ABSTRACT
Diatoms Thalassiosira pseudonana and Chaetoceros muelleri (Bacillariophyceae) were cultured at three different salinities (26, 36 and 46 practical salinity units (PSU)) and their silica content examined using natural abundance 29Si magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The samples were investigated using both single pulse (SP) and cross-polarisation (CP) MAS experiments. In addition, samples of T. pseudonana were examined using variable contact time CP MAS experiments allowing the dynamics (TSiH and T1rρH) of CP to be determined. Comparison of SP and CP results revealed a change to a less condensed silica state when diatoms were cultured at salinities away from optimal (36 PSU). Further, an increased amount of organic material (but not its composition) was determined to be present for such samples affecting CP experiments. The location of the organic material, on the diatom surface or within the frustule, was unable to be determined.
ABSTRACT
BACKGROUND: The Fahn's pull (or retropulsion) test is an item in the motor section of the Unified Parkinson's Disease Rating Scale, which is used almost exclusively to classify postural instability in Parkinson's disease (PD). However, the test is hard to standardize and is often performed incorrectly, making it hard to interpret. Moreover, it may not be safe to administer in patients who experience pain in the shoulders, neck, trunk and/or lower extremities. Identifying and grading postural instability in PD without requiring a physical challenge would not only be useful for the clinician but would assist patients and caregivers in its recognition. We propose the use of the rapid assessment of postural instability in Parkinson's disease (RAPID) questionnaire as a non-physical assessment tool. METHODS: We determined the associations between the pull test and items on a risk-assessment questionnaire that consisted of three parts: activities of daily living, fear of falling, and frequency of falling. RESULTS: Significant correlations were found between the pull test and the predictor variables, which ranged between 0.51 and 0.56 whilst the correlations amongst the predictor variables ranged between 0.58 and 0.70. The three parts of the questionnaire, when used in combination, produced a 96% sensitivity in the classification of postural instability. CONCLUSIONS: The RAPID questionnaire can be used as an adjunct to the pull test or solely if the pull test is contraindicated. It may also be possible to administer the questionnaire via the telephone or Internet. It is hoped that the rapid identification of postural instability would lead to fewer falls.
Subject(s)
Parkinson Disease/complications , Postural Balance , Sensation Disorders/diagnosis , Surveys and Questionnaires , Area Under Curve , Humans , Pilot Projects , ROC Curve , Sensation Disorders/etiology , Sensitivity and Specificity , Time FactorsABSTRACT
Moderate acid treatment of double-walled carbon nanotubes (DWCNTs) has given rise to two new experimentally observed second-order double resonant Raman scattering frequencies centered at 1901 cm(-1) and 1942 cm(-1), in the highly dispersive LOLA region. These LOLA overtones and combination modes have been predicted by double resonance theory for two phonons associated with the K- and Gamma-points, respectively.
Subject(s)
Acids/chemistry , Nanotubes, Carbon/chemistry , Microscopy, Electron, Transmission , Nanotubes, Carbon/ultrastructure , Spectrum Analysis, RamanABSTRACT
We compare the fundamental transport mechanism in multi-walled carbon nanotubes (MWNTs) by means of electron spin resonance (ESR) and Raman spectroscopy as a function of acid treatment. The ESR and Raman results show that the acid treatment reduces the density of states at the Fermi level. Defects introduced through the acid treatment move the Fermi level closer to the K points in the valence band, and consequently conduction is reduced. These defects are identified as Stone-Wales type from the Raman results.
Subject(s)
Carbon/chemistry , Electron Spin Resonance Spectroscopy/methods , Nanostructures/chemistry , Nitric Acid/chemistry , Spectrum Analysis, Raman/methods , Sulfuric Acids/chemistry , Kinetics , Oxidation-ReductionABSTRACT
Spectroscopic analysis and atomic force microscopy (AFM) phase imaging studies show self-assembly of phenosafranin (PSF) to multiwalled carbon nanotubes (MWNTs). The shift in absorption spectra is associated with charge transfer of valence electrons from PSF to electron accepting sites on the MWNTs. The Raman-active disorder modes are used to fingerprint PSF attachment to MWNTs via defect states. AFM phase imaging was used to obtain a molecular topographic visual confirmation of PSF attached to the MWNT.
ABSTRACT
We demonstrate a new, room-temperature approach to assemble two-dimensional and three-dimensional networks of gold nanowires by agitating nanoparticles in a toluene-aqueous mixture, without the use of templates. The nanowires have a uniform diameter of about 5 nm and consist of coalesced face-centered cubic nanocrystals. Toluene molecules passivate the gold surfaces during nanoparticle coalescence, rendering the nanowires hydrophobic and enabling their transfer into the toluene layer. Such templateless low-temperature assembly of mesostructures from nanoscale building blocks open up new possibilities for creating porous self-supporting nanocatalysts, nanowires for device interconnection, and low-density high-strength nanofillers for composites.
