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Gravitational waves from coalescing neutron stars encode information about nuclear matter at extreme densities, inaccessible by laboratory experiments. The late inspiral is influenced by the presence of tides, which depend on the neutron star equation of state. Neutron star mergers are expected to often produce rapidly rotating remnant neutron stars that emit gravitational waves. These will provide clues to the extremely hot post-merger environment. This signature of nuclear matter in gravitational waves contains most information in the 2–4 kHz frequency band, which is outside of the most sensitive band of current detectors. We present the design concept and science case for a Neutron Star Extreme Matter Observatory (NEMO): a gravitational-wave interferometer optimised to study nuclear physics with merging neutron stars. The concept uses high-circulating laser power, quantum squeezing, and a detector topology specifically designed to achieve the high-frequency sensitivity necessary to probe nuclear matter using gravitational waves. Above 1 kHz, the proposed strain sensitivity is comparable to full third-generation detectors at a fraction of the cost. Such sensitivity changes expected event rates for detection of post-merger remnants from approximately one per few decades with two A+ detectors to a few per year and potentially allow for the first gravitational-wave observations of supernovae, isolated neutron stars, and other exotica.
Tonsillectomy is one of the most common otolaryngological procedures. Nonetheless, there is still no universally approved ‘gold standard’ technique.
To compare the safety and efficacy of argon plasma coagulation and coblation techniques in tonsillectomy.
A multi-institutional, retrospective cohort study was conducted, comprising 283 patients who underwent bilateral tonsillectomies performed by a single surgeon between 2014 and 2017. The outcome measures included: operative time, intra-operative blood loss, post-operative pain and post-operative haemorrhage.
In the argon plasma coagulation group, mean operative time and post-operative haemorrhage rate were significantly reduced, p = 0.0006 and p = 0.003 respectively. There was no statistically significant difference between the two groups in terms of post-operative pain and intra-operative blood loss.
The argon plasma coagulation technique is easy, safe and efficacious. Argon plasma coagulation tonsillectomy seems cost-effective compared to coblation tonsillectomy: the single-use disposable electrode tip and wand used in this study cost AUD$76.50 and AUD$380 respectively. Argon plasma coagulation appears to be a favourable alternative to current modalities such as coblation.
Acute mastoiditis remains the commonest intratemporal complication of otitis media in the paediatric population. There has been a lack of consensus regarding the diagnosis and management of acute mastoiditis, resulting in considerable disparity in conservative and surgical management.
To review the current literature, proposing recommendations for the management of paediatric acute mastoiditis and appraising the treatment outcomes.
A systematic review was conducted using PubMed, Web of Science and Cochrane Library databases.
Twenty-one studies were included, with a total of 564 patients. Cure rates of medical treatment, conservative surgery and mastoidectomy were 95.9 per cent, 96.3 per cent and 89.1 per cent, respectively.
Mastoidectomy may be the most definitive treatment available; however, reviewed data suggest that conservative treatment alone has high efficacy as first-line treatment in uncomplicated cases of acute mastoiditis, and conservative therapy may be an appropriate first-line management when treating acute mastoiditis.
An association between metabolic syndrome (MetS) and disturbances in neurocognitive function has been identified in Caucasians but the nature and extent of impaired cognition in Asian MetS patients, who may be at greater risk of degenerative cognitive decline, remains unspecified.
A cross-sectional study was conducted at the National University Hospital of Singapore. Participants were recruited from a diabetes clinic at the National University Hospital. Fifty-three patients who met MetS criteria and 44 clinical controls were recruited. All participants were 55 years and above and community ambulant. Neurocognitive function was assessed using the Cambridge Neuropsychological Test Automated Battery (CANTAB). CANTAB performances between MetS and control groups were examined with analysis of variance (ANOVA) and the relative contributions of vascular risk, and intrademographic factors on CANTAB scores were dilineated with stepwise regression analyses.
Participants with MetS consistently performed significantly worse than controls across all CANTAB subtests. Education and Chinese race were found to be potential protective factors.
Executive and memory impairment is present in Asian patients with midlife MetS who may be particularly vulnerable to the detrimental impact of MetS in midlife.
CVD polycrystalline diamond surfaces were etched using reactive ion etching system with either a conventional stainless steel electrode or MgO sintered ceramic containing electrode. The micro-needle array of high aspect on diamond substrate surfaces obtained with MgO electrode was fabricated by using back-sputtering from MgO electrode. The RMS roughness of diamond substrate surfaces obtained with MgO electrode is higher than those obtained with stainless steel electrode.
The present paper reports the utilization of a boron-doped nanocrystalline diamond film (BDD) in electrochemical oxidization (ECO) process of organic phenol compound in 0.1 M H2SO4 water solution. The nano BDD films were synthesized by microwave plasma chemical vapor deposition (MWPCVD), and then characterized by Raman spectroscopy and SEM before and after the electrochemical oxidation treatment. For the ECO treatment performed to the test sample solution, an observation of the first and the last voltammetric plots exhibited a qualitatively differences between the two plots where the first one represent the initial concentration and the last one the signal produced by the organic solution after treatment. UV-Vis analysis through the application of a standard calibration curve, quantitatively confirmed the composition of phenol remaining in the sample solution subdued to the ECO treatment.
We report the deposition and field emission properties of nanostructured composites consisting of carbon nanowalls (CNWs) and nanocrystalline diamond films by introducing two kinds of substrate scratching pretreatment, i.e., undulation and ultrasonic vibration. With increasing duration of scratching pretreatment, the morphology of the deposits changes from simple CNWs to a film/CNW composite and lastly to CNWs on a film, and then the space between the walls is increased. The emission turn-on field is reduced from 2.1 V/μm for simple CNWs to around 1.2 V/μm for the composite films, accompanied by an increase in field enhancement factor. The results indicate that electric field screening between the walls is successfully suppressed by widening of the wall spacing.
Weekly (August 2003–December 2008) numbers of five common paediatric diseases and the incidence of respiratory viruses were obtained from a children's hospital in Singapore and correlated with climate data using multivariate time-series techniques. Upper respiratory tract infections were positively correlated with the incidences of influenza A, B, respiratory syncytial virus (RSV) and parainfluenza viruses (types 1–3 combined). Lower respiratory tract infections were positively correlated with only the incidence of RSV. Both upper and lower respiratory tract infections were negatively correlated with relative humidity. Asthma admissions were negatively correlated with maximum temperature and positively correlated with the incidence of influenza B and increasing hours of sunshine. Although sporadic cases of adenovirus infection were identified, not enough cases were available for a more detailed analysis. Gastroenteritis and urinary tract infections, included as control diseases, were not correlated significantly with any climate parameters. These correlations are compatible with current understanding of respiratory virus survival under certain climate conditions and may assist the prediction of disease burdens and hospital resource planning in such tropical environments.
We report electrochemical characteristics of hydrogen terminated charge-transfer doped intrinsic microcrystalline diamond films. Microcrystalline diamond was synthesized by Direct- Current Plasma Enhanced Chemical Vapor Deposition (DC-PECVD) in methane diluted by hydrogen. The diamond films were subjected to further treatment by microwave plasma in pure hydrogen to increase the hydrogen termination of the diamond surfaces and their negative electron affinity. When the diamond is exposed to the ambient moisture, valance electrons tend to tunnel from the first few atomic layers of the diamond surface to the adsorbed water adlayer. This charge transfer process results in the surface of hydrogen-terminated diamond behaving like a p-type semiconductor.
Electrochemical characteristics of hydrogen-terminated diamond films were exposed to an air plasma for depleting the surface hydrogen atoms and then re-hydrogenated the same diamond films with atomic hydrogen. Cyclic voltammetry in 0.1M H2S04 aqueous solution and 0.01M Fe(CN)6-4/-3+0.1M KCl aqueous solution was applied to reveal high current density and wide potential window for hydrogen-terminated diamond grown on silicon substrates. The faceted surface morphology has been observed by SEM. The crystalline characteristics and carbon phases in the diamond film were examined by Raman spectroscopy.
We describe a facile and direct method for the functionalization of single-walled carbon nanotubes with 4’-substituted phenyls and biphenyls. By means of Raman spectroscopy and thermogravimetric analysis we demonstrate that a simple protocol of a direct chemical grafting in acetonitrile solution of the corresponding diazonium salts at room temperature results in a formation of stable aryl monolayers on carbon nanotubes.
We report first principles modeling of partially hydrogenated graphene, with a variety of hydrogen induced superstructures. The dependence of the optical gap on hydrogen content and coverage is examined, to assess the best configurations suitable for optoelectronic applications. Electron and optical DFT LDA gaps in the range between 0.2 and 1.5 eV were obtained for low hydrogen coverage. For such systems, hydrogen clustering (by saturating neighbouring C dangling bonds at the opposite sides of the graphene sheet) is energetically most favourable and generally produces larger gap. More homogeneous H distribution one-side bonded to C-host atoms is, in contrast, less energetically favourable or even structurally unstable and generally produces smaller gap. In addition, ordering of hydrogen was observed at 50% of H, that offers a possibility of transforming 2D graphene to an array of 1D nanowires Calculated linear optical anisotropy and nonlinear second harmonic generation (this will be discussed in a forthcoming paper) indicate these are not only gap sensitive, but can provide an access to microscopic details of the 2D nano-sheets such as symmetry, hydrogen induced structure, degree of hydrogenation, chemical bonding and many others, all promising for device application. The approach developed can be used for graphene/ graphane single layer or bilayer, formed on top of various substrates, where experimental geometries may not provide conditions for complete hydrogenation of the 2D nano-sheet(s).
We investigated the effects of tensile direction and periodic boundary condition (PBC) on the mechanical properties of single crystal diamond (SCD) under tensile loading, using MD simulations with the second-generation reactive empirical bond order (REBO) potential. We found that when the Poisson’s ratio is assumed to be constant under the canonical (NVT) ensemble and the PBC is applied to all directions of X, Y, and Z, each qualitative relation between a mechanical property such as tensile strength or Young’s modulus and the tensile direction is in agreement with both the results calculated by the first principle and by the cleavage energy method. In addition, we found that when the PBC is applied only to the Y direction under the NVT ensemble, each qualitative relation between a mechanical property and the tensile directions is in agreement with the MD results using the Tersoff potential.
Our results indicate that the second-generation REBO potential is also useful for MD simulations on the tension of diamond.
Using molecular dynamics (MD) simulation, we investigated the mechanical properties of graphene and graphite, which contain cluster-type vacancies. We found that as the vacancy size increases, the tensile strength drastically decreases to at least 56% of that of pristine graphene, whereas Young’s modulus hardly changes. In vacancy-containing graphene, we also found that slip deformation followed by fracture occurs under zigzag tension. In general, tensile strength decreases as the size of cluster-type vacancies increases. However, the tensile strength of graphene with a clustered sextuple vacancy increases as the vacancy disappears because slip deformation proceeds. Furthermore, we found that slip deformation by vacancies in graphite occurs less easily than in graphene.
Our results suggest that the shape of vacancies affects the strengths of graphene and graphite.
It is essential to control the electronic properties of a graphene field effect transistor (GFET). And the ability to accurately control the intrinsic electrical transport properties and to locally change the carrier density will be significant for graphene devices. We succeeded in achieving and controlling the Dirac point (neutrality point) simply by doping block co-polymer (BCP) covered GFET with CF4 plasma. By exposing polymer covered GFET to CF4 plasma for a short time the electronic transport was altered significantly. The hexagonal structure of BCP produces patterns with nanoscale spacing for heterogeneous patterns which provides a new approach to tune the electron and the hole conductivity simultaneously. Exploitation of fluorine doping provides a general route to control electronic property of any polymer coated GFET. The BCP protected GFET could detect 1mM NaF solution in “dry” condition in 60s. The sensing property demonstrates that BCP protected GFET could be a good candidate for stable and sensitive chemical or biological sensor. Furthermore, the distinct property of two functional groups within BCP facilitates the selective sensing property. These findings pave the way for developing more stable and sensitive sensors under ambient conditions.
In this work, a determination of the surface energy for hydrogen terminated nanocrystalline diamond grown with microwave plasma enhanced chemical vapor deposition is presented. Five identical hydrogen terminated nanocrystalline diamond layers of ~150 nm thick are deposited on silicon substrates and examined with X-ray photoelectron spectroscopy to determine the surface groups and possible surface contaminations. In order to evaluate the surface energy, contact angle measurements are performed using the sessile drop method in combination with data analysis based on the ‘Owens, Wendt, Rabel and Kaelble’ method. Four different experimental approaches to evaluate the surface energy of hydrogen terminated nanocrystalline diamond are discussed.
Single Walled Carbon Nanotubes (SWNTs) dispersions are obtained after ultrasonication in Cellulose Nanocrystals (CNs) colloidal suspensions and they are found to be stable during several months. Similarly to CNs suspensions, SWNTs/CNs dispersions are used to elaborate multilayered thin films by the layer by layer method. Characterizations of the growth pattern, Raman and optical properties of the films are investigated. The presence of isolated SWNTs in each bi-layer is attested by characteristic Raman and luminescence signals. These films may be interesting for sensing applications.
Oxidized single-walled carbon nanotubes (SWNTs) have been prepared following a widely reported two-step purification/oxidation procedure in the presence or absence of a treatment with base (NaOH). The oxidized nanotube samples washed with solvents or base appear close to identical with respect to both appearance and properties. Efficient removal of both metal and carbonaceous impurities and introduction of –COOH groups on the nanotube surface have been demonstrated by AFM, Raman and FTIR spectroscopy. Furthermore, persistence of optical properties was confirmed using UV-vis/NIR absorption and NIR photoluminescence spectroscopies.
In this poster we will present the photo-electrical effect of pristine and nitric acid treated graphene field effect transistors made by chemical vapor deposition (CVD). The results of the decreased electrical conductance and shift of Dirac point arise from the molecular photodesorption from graphene. When post treated with nitric acid the photodesorption efficiency was decrease from 52% to 21%, which was proposed to be caused by the passivation of oxygen-bearing functionalities to CVD graphene structural defects. This result provides a new strategy of stabilizing the electrical performance of CVD graphene which is promising candidate as highly conductively photoelectrical material.