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Background: Mycobacterium abscessus (MABS) group are environmental organisms that can cause infection in people with cystic fibrosis (CF) and other suppurative lung diseases. There is potential for person-to-person airborne transmission of MABS among people with CF attending the same care centre. Ultraviolet light (band C, UV-C) is used for Mycobacterium tuberculosis control indoors; however, no studies have assessed UV-C for airborne MABS.Aim: To determine whether a range of UV-C doses increased the inactivation of airborne MABS, compared with no-UVC conditions.Methods: MABS was generated by a vibrating mesh nebulizer located within a 400 L rotating drum sampler, and then exposed to an array of 265 nm UV-C light-emitting diodes (LED). A six-stage Andersen Cascade Impactor was used to collect aerosols. Standard microbiological protocols were used for enumerating MABS, and these quantified the effectiveness of UV-C doses (in triplicate). UV-C effectiveness was estimated using the difference between inactivation with and without UV-C.Findings: Sixteen tests were performed, with UV-C doses ranging from 276 to 1104 μW s/cm2. Mean (±SD) UV-C effectiveness ranged from 47.1% (±13.4) to 83.6% (±3.3). UV-C led to significantly greater inactivation of MABS (all P-values ≤0.045) than natural decay at all doses assessed. Using an indoor model of the hospital environment, it was estimated that UV-C doses in the range studied here could be safely delivered in clinical settings where patients and staff are present.Conclusion: This study provides empirical in-vitro evidence that nebulized MABS are susceptible to UV-C inactivation. [ABSTRACT FROM AUTHOR]

We present a non-contact method of determining temperature change in a lithium niobate crystal. The technique has the advantage of being simple to implement and offers a precision at least as good as conventional temperature measurement methods over large ranges (∼ 200 K). A novel application of this technique involves measuring temperature in different regions of the crystal simultaneously, which could be useful for determining stresses and heat diffusion parameters. The technique could be successfully applied to monitor crystal temperature for thermal fixing of holograms or related applications.

Pseudomonas aeruginosa ( Pa ) is the predominant bacterial pathogen in people with cystic fibrosis (CF) and can be transmitted by airborne droplet nuclei. Little is known about the ability of ultraviolet band C (UV-C) irradiation to inactivate Pa at doses and conditions relevant to implementation in indoor clinical settings. We assessed the effectiveness of UV-C (265 nm) at up to seven doses on the decay of nebulized Pa aerosols (clonal Pa strain) under a range of experimental conditions. Experiments were done in a 400 L rotating sampling drum. A six-stage Andersen cascade impactor was used to collect aerosols inside the drum and the particle size distribution was characterized by an optical particle counter. UV-C effectiveness was characterized relative to control tests (no UV-C) of the natural decay of Pa . We performed 112 tests in total across all experimental conditions. The addition of UV-C significantly increased the inactivation of Pa compared with natural decay alone at all but one of the UV-C doses assessed. UV-C doses from 246-1968 µW s/cm 2 had an estimated effectiveness of approximately 50-90% for airborne Pa . The effectiveness of doses ≥984 µW s/cm 2 were not significantly different from each other ( p -values: 0.365 to ~1), consistent with a flattening of effectiveness at higher doses. Modelling showed that delivering the highest dose associated with significant improvement in effectiveness (984 µW s/cm 2 ) to the upper air of three clinical rooms would lead to lower room doses from 37-49% of the 8 h occupational limit. Our results suggest that UV-C can expedite the inactivation of nebulized airborne Pa under controlled conditions, at levels that can be delivered safely in occupied settings. These findings need corroboration, but UV-C may have potential applications in locations where people with CF congregate, coupled with other indoor and administrative infection control measures.

Objectives: Stability of bone splitting sternotomy is essential for normal healing after open cardiac surgery. Mechanical vibration transmittance may offer a means for early detection of separation of bone (diastasis) in the sternotomy and prevent further complications. This article describes the technical implementation and validation of vibration analysis-based prototype device built for measuring sternal bone connectivity after sternotomy., Methods: An in-house built measurement system, sternal vibration device, consisting of actuator, sensor, and main controller and signal acquisition unit was designed and manufactured. The system was validated, and three different test settings were studied in mockups (polylactide rods in ballistic gel) and in two human sternums: intact, stable wire fixation, and unstable wire fixation with a gap mimicking bone diastasis. The transmittance of vibration stimulus across the median sternotomy was measured., Results: The validation showed that the force produced by the actuator was stable, and the sensor could be calibrated to precisely measure the acceleration values. The vibration transmittance response to material cut and sternotomy was evident and detectable in the 20 Hz to 2 kHz band. The transmittance decreased when the connectivity between the sternal halves became unstable. The trend was visible in all the settings., Conclusion: Technical solutions and description of validation process were given. The device was calibrated, and the vibration transmittance analysis differentiated intact and cut polylactide rod. In the sternum, intact bone, wire fixation with exact apposition, and with a gap were identified separately. Although further studies are needed to assess the accuracy of the method to detect different levels of diastases, the method appears to be feasible.

By investigating the action spectra (the relationship between the irradiation wavelength and apparent quantum efficiency of reactions under constant irradiance) of a number of reactions catalyzed by nanoparticles including plasmonic metals, nonplasmonic metals, and their alloys at near-ambient temperatures, we found that a photon energy threshold exists in each photocatalytic reaction; only photons with sufficient energy (e.g., higher than the energy level of the lowest unoccupied molecular orbitals) can initiate the reactions. This energy alignment (and the photon energy threshold) is determined by various factors, including the wavelength and intensity of irradiation, molecule structure, reaction temperature, and so forth. Hence, distinct action spectra were observed in the same type of reaction catalyzed by the same catalyst due to a different substituent group, a slightly changed reaction temperature. These results indicate that photon-electron excitations, instead of the photothermal effect, play a dominant role in direct photocatalysis of metal nanoparticles for many reactions.

With the rapid development of display-related markets, transparent conductive films (TCFs) with wide viewing angles, high transmittance and low sheet resistance are in high demand. However, as a promising TCF material, metallic membranes with a submicrometer-sized periodicity pattern fabricated by currently available techniques always reveal the angle-dependent structure color which can be a major issue in the development of wide-angle viewing display-related applications. In this work, we demonstrate an Au nanomesh with disordered dual-size apertures as a novel TCF with wide viewing angles which is made via a modified nanosphere lithography technique. The as-prepared Au nanomesh film shows good optoelectronic properties (Rs = 160 Ω sq(-1), T = 80%; Rs = 8 Ω sq(-1), T = 57%) that are similar to the Au nanomesh with single size apertures, while the former exhibits excellent wide-angle viewing performance. There is no obvious change in the film when the viewing angle, the light incidence angle or the orientation of substrate vary in the range of 0-90°. In contrast, a rainbow color is observed with the film with ordered single-size apertures. Electrochromic devices based on the novel metallic film show more uniform color distribution than the devices based on metallic film with ordered single-size apertures under indoor natural light irradiation. These findings demonstrate the applicability of the Au nanomesh film with dual-size apertures in enhancing display quality of high-performance optoelectronic devices.

In this paper we report the design and experimental realisation of a novel refractive index sensor based on coupling between three nanoscale stripe waveguides. The sensor is highly compact and designed to operate at a single wavelength. We demonstrate that the sensor exhibits linear response with a resolution of 6 × 10(-4) RIU (refractive index unit) for a change in relative output intensity of 1%. Authors expect that the outcome of this paper will prove beneficial in highly compact, label-free and highly sensitive refractive index analysis.

Recent advances in direct-use plasmonic-metal nanoparticles (NPs) as photocatalysts to drive organic synthesis reactions under visible-light irradiation have attracted great interest. Plasmonic-metal NPs are characterized by their strong interaction with visible light through excitation of the localized surface plasmon resonance (LSPR). Herein, we review recent developments in direct photocatalysis using plasmonic-metal NPs and their applications. We focus on the role played by the LSPR of the metal NPs in catalyzing organic transformations and, more broadly, the role that light irradiation plays in catalyzing the reactions. Through this, the reaction mechanisms that these light-excited energetic electrons promote will be highlighted. This review will be of particular interest to researchers who are designing and fabricating new plasmonic-metal NP photocatalysts by identifying important reaction mechanisms that occur through light irradiation., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A miniaturized flow-through system consisting of a gold coated silicon substrate based on enhanced Raman spectroscopy has been used to study the detection of vapour from model explosive compounds. The measurements show that the detectability of the vapour molecules at room temperature depends sensitively on the interaction between the molecule and the substrate. The results highlight the capability of a flow system combined with Raman spectroscopy for detecting low vapour pressure compounds with a limit of detection of 0.2 ppb as demonstrated by the detection of bis(2-ethylhexyl)phthalate, a common polymer additive emitted from a commercial polyvinyl chloride (PVC) tubing at room temperature.

Supported nanoparticles (NPs) of nonplasmonic transition metals (Pd, Pt, Rh, and Ir) are widely used as thermally activated catalysts for the synthesis of important organic compounds, but little is known about their photocatalytic capabilities. We discovered that irradiation with light can significantly enhance the intrinsic catalytic performance of these metal NPs at ambient temperatures for several types of reactions. These metal NPs strongly absorb the light mainly through interband electronic transitions. The excited electrons interact with the reactant molecules on the particles to accelerate these reactions. The rate of the catalyzed reaction depends on the concentration and energy of the excited electrons, which can be increased by increasing the light intensity or by reducing the irradiation wavelength. The metal NPs can also effectively couple thermal and light energy sources to more efficiently drive chemical transformations., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We present a method for optical encryption of information, based on the time-dependent dynamics of writing and erasure of refractive index changes in a bulk lithium niobate medium. Information is written into the photorefractive crystal with a spatially amplitude-modulated laser beam which when overexposed significantly degrades the stored data making it unrecognizable. We show that the degradation can be reversed and that a one-to-one relationship exists between the degradation and recovery rates. It is shown that this simple relationship can be used to determine the erasure time required for decrypting the scrambled index patterns. In addition, this method could be used as a straightforward general technique for determining characteristic writing and erasure rates in photorefractive media.

Current concerns regarding terrorism and international crime highlight the need for new techniques for detecting unknown and hazardous substances. A novel Raman spectroscopy-based technique, spatially offset Raman spectroscopy (SORS), was recently devised for noninvasively probing the contents of diffusely scattering and opaque containers. Here, we demonstrate a modified portable SORS sensor for detecting concealed substances in-field under different background lighting conditions. Samples including explosive precursors, drugs, and an organophosphate insecticide (chemical warfare agent surrogate) were concealed inside diffusely scattering packaging including plastic, paper, and cloth. Measurements were carried out under incandescent and fluorescent light as well as under daylight to assess the suitability of the probe for different real-life conditions. In each case, it was possible to identify the substances against their reference Raman spectra in less than 1 min. The developed sensor has potential for rapid detection of concealed hazardous substances in airports, mail distribution centers, and customs checkpoints., (© 2013 American Academy of Forensic Sciences.)

Residual amplitude modulation (RAM) is an unwanted noise source in electro-optic phase modulators. The analysis presented shows that while the magnitude of the RAM produced by a MgO:LiNbO(3) modulator increases with intensity, its associated phase becomes less well defined. This combination results in temporal fluctuations in RAM that increase with intensity. This behavior is explained by the presented phenomenological model based on gradually evolving photorefractive scattering centers randomly distributed throughout the optically thick medium. This understanding is exploited to show that RAM can be reduced to below the 10(-5) level by introducing an intense optical beam to erase the photorefractive scatter.

The intrinsic catalytic activity of palladium (Pd) is significantly enhanced in gold (Au)-Pd alloy nanoparticles (NPs) under visible light irradiation at ambient temperatures. The alloy NPs strongly absorb light and efficiently enhance the conversion of several reactions, including Suzuki-Miyaura cross coupling, oxidative addition of benzylamine, selective oxidation of aromatic alcohols to corresponding aldehydes and ketones, and phenol oxidation. The Au/Pd molar ratio of the alloy NPs has an important impact on performance of the catalysts since it determines both the electronic heterogeneity and the distribution of Pd sites at the NP surface, with these two factors playing key roles in the catalytic activity. Irradiating with light produces an even more profound enhancement in the catalytic performance of the NPs. For example, the best conversion rate achieved thermally at 30 °C for Suzuki-Miyaura cross coupling was 37% at a Au/Pd ratio of 1:1.86, while under light illumination the yield increased to 96% under the same conditions. The catalytic activity of the alloy NPs depends on the intensity and wavelength of incident light. Light absorption due to the Localized Surface Plasmon Resonance of gold nanocrystals plays an important role in enhancing catalyst performance. We believe that the conduction electrons of the NPs gain the light absorbed energy producing energetic electrons at the surface Pd sites, which enhances the sites' intrinsic catalytic ability. These findings provide useful guidelines for designing efficient catalysts composed of alloys of a plasmonic metal and a catalytically active transition metal for various organic syntheses driven by sunlight.

Noninvasive standoff deep Raman spectroscopy has been utilised for the detection of explosives precursors in highly fluorescing packaging from 15m. To our knowledge this is the first time standoff deep Raman spectroscopy of concealed substances in highly fluorescing coloured packaging is demonstrated. Time-resolved Raman spectroscopy, spatially offset Raman spectroscopy and time-resolved spatially offset Raman spectroscopy have been compared to identify their selectivity towards the deep layers of a sample. The selectivity of time-resolved Raman spectroscopy towards the concealed chemical substances was found to be comparable to that of spatially offset Raman spectroscopy. However, time-resolved Raman spectroscopy did not require precise translation of the laser excitation beam onto the surface of the interrogated packaging as in the case of spatially offset Raman spectroscopy. Our results confirm that standoff time-resolved spatially offset Raman spectroscopy has significantly higher selectivity towards the deep layers of a sample when compared to the other deep Raman spectroscopy modes. The developed spectrometer was capable of detecting the concealed substances within 5s of data acquisition. By using time-resolved spatially Raman spectroscopy, a Raman spectrum that is representative of the content alone was acquired without the use of sophisticated algorithms to eliminate the spectral contributions of the packaging material within the acquired spectrum as in the case of time-resolved Raman spectroscopy and spatially offset Raman spectroscopy., (Copyright © 2012 Elsevier B.V. All rights reserved.)

A novel gold coated femtosecond laser nanostructured sapphire surface - an "optical nose" - based on surface-enhanced Raman spectroscopy (SERS) for detecting vapours of explosive substances was investigated. Four different nitroaromatic vapours at room temperature were tested. Sensor responses were unambiguous and showed response in the range of 0.05-15 μM at 25 °C. The laser fabricated substrate nanostructures produced up to an eight-fold increase in Raman signal over that observed on the unstructured portions of the substrate. This work demonstrates a simple sensing system that is compatible with commercial manufacturing practices to detect taggants in explosives which can undertake as part of an integrated security or investigative mission.

Residual amplitude modulation (RAM) mechanisms in electro-optic phase modulators are detrimental in applications that require high purity phase modulation of the incident laser beam. While the origins of RAM are not fully understood, measurements have revealed that it depends on the beam properties of the laser as well as the properties of the medium. Here we present experimental and theoretical results that demonstrate, for the first time, the dependence of RAM production in electro-optic phase modulators on beam intensity. The results show an order of magnitude increase in the level of RAM, around 10 dB, with a fifteenfold enhancement in the input intensity from 12 to 190  mW/mm2. We show that this intensity dependent RAM is photorefractive in origin.

Deep Raman spectroscopy has been utilized for the standoff detection of concealed chemical threat agents from a distance of 15 m under real life background illumination conditions. By using combined time and space resolved measurements, various explosive precursors hidden in opaque plastic containers were identified non-invasively. Our results confirm that combined time and space resolved Raman spectroscopy leads to higher selectivity towards the sub-layer over the surface layer as well as enhanced rejection of fluorescence from the container surface when compared to standoff spatially offset Raman spectroscopy. Raman spectra that have minimal interference from the packaging material and good signal-to-noise ratio were acquired within 5 s of measurement time. A new combined time and space resolved Raman spectrometer has been designed with nanosecond laser excitation and gated detection, making it of lower cost and complexity than picosecond-based laboratory systems., (Copyright © 2012 Elsevier B.V. All rights reserved.)

A time-resolved inverse spatially offset Raman spectrometer was constructed for depth profiling of Raman-active substances under both the lab and the field environments. The system operating principles and performance are discussed along with its advantages relative to traditional continuous wave spatially offset Raman spectrometer. The developed spectrometer uses a combination of space- and time-resolved detection in order to obtain high-quality Raman spectra from substances hidden behind coloured opaque surface layers, such as plastic and garments, with a single measurement. The time-gated spatially offset Raman spectrometer was successfully used to detect concealed explosives and drug precursors under incandescent and fluorescent background light as well as under daylight. The average screening time was 50 s per measurement. The excitation energy requirements were relatively low (20 mW) which makes the probe safe for screening hazardous substances. The unit has been designed with nanosecond laser excitation and gated detection, making it of lower cost and complexity than previous picosecond-based systems, to provide a functional platform for in-line or in-field sensing of chemical substances.

Spatially offset Raman spectroscopy (SORS) is a powerful new technique for the non-invasive detection and identification of concealed substances and drugs. Here, we demonstrate the SORS technique in several scenarios that are relevant to customs screening, postal screening, drug detection and forensics applications. The examples include analysis of a multi-layered postal package to identify a concealed substance; identification of an antibiotic capsule inside its plastic blister pack; analysis of an envelope containing a powder; and identification of a drug dissolved in a clear solvent, contained in a non-transparent plastic bottle. As well as providing practical examples of SORS, the results highlight several considerations regarding the use of SORS in the field, including the advantages of different analysis geometries and the ability to tailor instrument parameters and optics to suit different types of packages and samples. We also discuss the features and benefits of SORS in relation to existing Raman techniques, including confocal microscopy, wide area illumination and the conventional backscattered Raman spectroscopy. The results will contribute to the recognition of SORS as a promising method for the rapid, chemically specific analysis and detection of drugs and pharmaceuticals., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

Numerous materials are polycrystalline or consist with crystals of different phases. However, materials consisting of crystals on the nanometer scale (nanocrystals) are not simply aggregates of randomly oriented crystals as is generally regarded. We found, that in four different materials that consist of nanocrystals of two different phases and were obtained by different approaches, the nanocrystals of different phases are combined coherently forming interfaces with a close crystallographic registry between adjacent crystals (coherent interfaces). The four materials were fabricated by (i) depositing Ag(2)O nanoparticles on titanate nanofibers, (ii) phase transition from TiO(2)(B) nanofibers to the nanofibers of mixed TiO(2)(B) and anatase phases, (iii) dehydration of the single crystal fibril titanate core coated with anatase nanocrystals, and (iv) attaching zeolite Y nanocrystals on the surface of titanate nanofibers. The finding suggests that preferred orientations and coherent interfaces generally exist in nanocrystal systems, and according to our results, they are largely unaffected by the fabrication process that was used. This is because the preferred orientations require that the engaged crystal planes from two connected crystals have the same basal spacing and that the crystals can interlock tightly at the atomic level to form thermodynamically stable interfaces. Hence it is rational that the preferred orientations and coherent interfaces dominant the nanostructures formed between the different nanocrystals and play a key role in assembling the composite nanostructures. The orientation and interfaces between crystals of different phases in mixed-phase materials are extremely difficult to determine. Nonetheless, the thermodynamic stability of the coherent interfaces allows us to apply phase-transformation invariant line strain theory to predict the preferred orientation (and thus the structure of the coherent interfaces). The theoretical predications agree remarkably with the transmission electron microscopy (TEM) analysis. This implies that we may acquire knowledge of the orientation and the interface structures in the mixed-phase materials without TEM measurement, and the knowledge is essential for comprehensively understanding properties of the many materials and processes that depend on the interfaces.

Gold nanoparticles strongly absorb both visible light and ultraviolet light to drive an oxidation reaction for a synthetic dye, as well as phenol degradation and selective oxidation of benzyl alcohol under UV light.

We report on the reversal of degradation of information masks stored in self-defocusing lithium niobate. After a long writing time, the image degradation appears as the splitting of refractive-index patterns stored in the medium. The reversal is achieved simply by illuminating the crystal with incoherent light from a halogen lamp. The reversal occurs because the refractive-index changes responsible for the splitting are of a smaller magnitude and are therefore erased first during incoherent illumination. Additionally, we gain insight into the storage, degradation, and erasure dynamics using a time-dependent numerical model of the photorefractive effect in this medium. Since the data can be recovered from a degraded state in which the original data are unrecognizable, this technique could be utilized in such applications as image scrambling or encryption.