Vibrational frequencies associated with the inter-stitial carbon atoms in the large metal cluster complexes (NMe4)2[Os10C(CO)24] and H2Os10C(CO)24

Determination of the vibrational frequencies of the interstitial carbon atoms in the metal clusters [Os₁₀C(CO)₂₄]^2? and H₂Os₁₀C(CO)₂₄, confirmed in the latter by ¹³C enrichment, shows that the protonated cluster species exhibits considerable deviation from pseudo-cubic symmetry in the crystal, in contrast to the dianion.     

A Nanocage for Nanomedicine: Polyhedral Oligomeric Silsesquioxane (POSS)

Ground‐breaking advances in nanomedicine (defined as the application of nanotechnology in medicine) have proposed novel therapeutics and diagnostics, which can potentially revolutionize current medical practice. Polyhedral oligomeric silsesquioxane (POSS) with a distinctive nanocage structure consisting of an inner inorganic framework of silicon and oxygen atoms, and an outer shell of organic functional groups is one of the most promising nanomaterials for medical applications. Enhanced biocompatibility and physicochemical (material bulk and surface) properties have resulted in the development of a wide range of nanocomposite POSS copolymers for biomedical applications, such as the development of biomedical devices, tissue engineering scaffolds, drug delivery systems, dental applications, and biological sensors. The application of POSS nanocomposites in combination with other nanostructures has also been investigated including silver nanoparticles and quantum dot nanocrystals. Chemical functionalization confers antimicrobial efficacy to POSS, and the use of polymer nanocomposites provides a biocompatible surface coating for quantum dot nanocrystals to enhance the efficacy of the materials for different biomedical and biotechnological applications. Interestingly, a family of POSS‐containing nanocomposite materials can be engineered either as completely non‐biodegradable materials or as biodegradable materials with tuneable degradation rates required for tissue engineering applications. These highly versatile POSS derivatives have created new horizons for the field of biomaterials research and beyond. Currently, the application of POSS‐containing polymers in various fields of nanomedicine is under intensive investigation with expectedly encouraging outcomes.

     

Optical Properties of Micro-patterned Silver Nanoparticle Substrates

In this paper, we describe a novel technique for depositing metal nanoparticles (NPs) on a planar substrate whereby the NPs are micro-patterned on the surface by a simple stamp-printing procedure. The method exploits the attractive force between negatively charged colloidal metal NPs and positively-charged polyelectrolyte layers which have been selectively deposited on the surface. Using this technique, large uniform areas of patterned metal NPs, with different plasmonic properties, were achieved by optimisation of the stamping process. We report the observation of unusual fluorescence emission from these structures. The emission was measured using epifluorescence microscopy. Fluorescence lifetime behaviour was also measured. Furthermore, the μ-patterned NPs exhibited blinking behaviour under 469 nm excitation and the fluorescence spectrum was multi-peaked. It has been established that the fluorescence is independent of the plasmon resonance properties of the NPs. As well as optimising the novel NP μ-patterning technique, this work discusses the origin and characteristics of the anomalous fluorescence behaviour in order to characterise and minimise this unwanted background contribution in the use of metal NPs for plasmonic enhancement of fluorescence for optical biochip applications.     

Advances in biological NMR circa WWMR 2010 in Florence

We summarize the advances and breakthroughs of 'biological' NMR that were presented at the Joint EUROMAR 2010 - 17th ISMAR Conference - aka 'World Wide Magnetic Resonance 2010' in Florence, Italy.     

Negative-muon capture in <Superscript>150</Superscript>Sm

The energy and time spectra of γ rays emitted during negative-muon capture in ¹⁵⁰Sm were studied. The total muon lifetime in ¹⁵⁰Sm was measured. The yields of several radioactive isotopes in this reaction were determined. The partial γ-ray yield upon muon capture by a ¹⁵⁰Sm nucleus were measured.     

Size-fractionated characterization and quantification of nanoparticle release rates from a consumer spray product containing engineered nanoparticles

This study describes methods developed for reliable quantification of size- and element-specific release of engineered nanoparticles (ENP) from consumer spray products. A modified glove box setup was designed to allow controlled spray experiments in a particle-minimized environment. Time dependence of the particle size distribution in a size range of 10–500 nm and ENP release rates were studied using a scanning mobility particle sizer (SMPS). In parallel, the aerosol was transferred to a size-calibrated electrostatic TEM sampler. The deposited particles were investigated using electron microscopy techniques in combination with image processing software. This approach enables the chemical and morphological characterization as well as quantification of released nanoparticles from a spray product. The differentiation of solid ENP from the released nano-sized droplets was achieved by applying a thermo-desorbing unit. After optimization, the setup was applied to investigate different spray situations using both pump and gas propellant spray dispensers for a commercially available water-based nano-silver spray. The pump spray situation showed no measurable nanoparticle release, whereas in the case of the gas spray, a significant release was observed. From the results it can be assumed that the homogeneously distributed ENP from the original dispersion grow in size and change morphology during and after the spray process but still exist as nanometer particles of size <100 nm. Furthermore, it seems that the release of ENP correlates with the generated aerosol droplet size distribution produced by the spray vessel type used. This is the first study presenting results concerning the release of ENP from spray products.     

Embedded minimal disks with prescribed curvature blowup

We construct a sequence of compact embedded minimal disks in a ball in , whose boundaries lie in the boundary of the ball, such that the curvature blows up only at a prescribed discrete (and hence, finite) set of points on the -axis. This extends a result of Colding and Minicozzi, who constructed a sequence for which the curvature blows up only at the center of the ball, and is a partial affirmative answer to the larger question of the existence of a sequence for which the curvature blows up precisely on a prescribed closed set on the -axis.

     

Frequency discrimination of complex tones; assessing the role of component resolvability and temporal fine structure

Thresholds for discriminating the fundamental frequency (FO) of a complex tone, FODLs, are small when low harmonics are present, but increase when the number of the lowest harmonic, N, is above eight. To assess whether the relatively small FODLs for N in the range 8-10 are based on (partly) resolved harmonics or on temporal fine structure information, FODLs were measured as a function of N for tones with three successive harmonics which were added either in cosine or alternating phase. The center frequency was 2000 Hz, and N was varied by changing the mean FO. A background noise was used to mask combination tones. The value of FO was roved across trials to force subjects to make within-trial comparisons. N was roved by +/- 1 for every stimulus, to prevent subjects from using excitation pattern cues. FODLs were not influenced by component phase for N= 6 or 7, but were smaller for cosine than for alternating phase once N exceeded 7, suggesting that temporal fine structure plays a role in this range. When the center frequency was increased to 5000 Hz, performance was much worse for low N, suggesting that phase locking is important for obtaining low FODLs with resolved harmonics.     

Effects of level and frequency on the audibility of partials in inharmonic complex tones

The effect of level and frequency on the audibility of partials was measured for complex tones with partials uniformly spaced on an equivalent rectangular bandwidth (ERB(N)) number scale. On each trial, subjects heard a sinusoidal "probe" followed by a complex tone. The probe was mistuned downwards or upwards (at random) by 4.5% from the frequency of one randomly selected partial in the complex. The subject indicated whether the probe was higher or lower in frequency than the nearest partial in the complex. The frequencies were roved from trial to trial, keeping frequency ratios fixed. In experiment 1, the level per partial, L, was 40 or 70 dB SPL and the mean frequency of the central partial, f(c), was 1201 Hz. Scores for the highest and lowest partials in the complexes were generally high for all spacings. Scores for the inner partials were close to chance at 0.75-ERB(N) spacing, and improved as the spacing was increased up to 2 ERB(N). For intermediate spacings, performance was better for the lower level used. In experiment 2, L was 70 dB SPL and f(c) was 3544 Hz. Performance worsened markedly for partial frequencies above 3544 Hz, consistent with a role of phase locking.     

Isolating the energetic component of speech-on-speech masking with ideal time-frequency segregation

When a target speech signal is obscured by an interfering speech wave form, comprehension of the target message depends both on the successful detection of the energy from the target speech wave form and on the successful extraction and recognition of the spectro-temporal energy pattern of the target out of a background of acoustically similar masker sounds. This study attempted to isolate the effects that energetic masking, defined as the loss of detectable target information due to the spectral overlap of the target and masking signals, has on multitalker speech perception. This was achieved through the use of ideal time-frequency binary masks that retained those spectro-temporal regions of the acoustic mixture that were dominated by the target speech but eliminated those regions that were dominated by the interfering speech. The results suggest that energetic masking plays a relatively small role in the overall masking that occurs when speech is masked by interfering speech but a much more significant role when speech is masked by interfering noise.