3,497 research outputs found

    Distal Interphalangeal Joint Arthrodesis Complicated by Postoperative Infection: A Rare Presentation of Disseminated Herpes Simplex Virus.

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    Postoperative infection after elective arthrodesis of the interphalangeal joint is an uncommon complication often necessitating urgent debridement. We present the rare case of a female patient with a history of oral herpetic lesions, who underwent elective arthrodesis of the middle and index fingers for treatment of erosive osteoarthritis and subsequently developed a postoperative herpetic infection at the surgical site

    Long-Range Proton Conduction Across Free-Standing Serum Albumin

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    Free‐standing serum‐albumin mats can transport protons over millimetre length‐scales. The results of photoinduced proton transfer and voltage‐driven proton‐conductivity measurements, together with temperature‐dependent and isotope‐effect studies, suggest that oxo‐amino‐acids of the protein serum albumin play a major role in the translocation of protons via an “over‐the‐barrier” hopping mechanism. The use of proton‐conducting protein mats opens new possibilities for bioelectronic interfaces

    Fluid‐driven tensile fracture and fracture toughness in Nash Point shale at elevated pressure

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    A number of key processes, both natural and anthropogenic, involve the fracture of rocks subjected to tensile stress, including vein growth and mineralization, and the extraction of hydrocarbons through hydraulic fracturing. In each case, the fundamental material property of mode‐I fracture toughness must be overcome in order for a tensile fracture to propagate. While measuring this parameter is relatively straightforward at ambient pressure, estimating fracture toughness of rocks at depth, where they experience confining pressure, is technically challenging. Here we report a new analysis that combines results from thick‐walled cylinder burst tests with quantitative acoustic emission to estimate the mode‐I fracture toughness (K_{Ic}) of Nash Point Shale at confining pressure simulating in situ conditions to approximately 1‐km depth. In the most favorable orientation, the pressure required to fracture the rock shell (injection pressure, P_{inj}) increases from 6.1 MPa at 2.2‐MPa confining pressure (P_{c}), to 34 MPa at 20‐MPa confining pressure. When fractures are forced to cross the shale bedding, the required injection pressures are 30.3 MPa (at P_{c} = 4.5MPa) and 58 MPa (P_{c} = 20 MPa), respectively. Applying the model of Abou‐Sayed et al. (1978, https://doi.org/10.1029/JB083iB06p02851) to estimate the initial flaw size, we calculate that this pressure increase equates to an increase in K_{Ic} from 0.36 to 4.05 MPa·m^{1/2} as differential fluid pressure (P_{inj} - P_{c}) increases from 3.2 to 22.0 MPa. We conclude that the increasing pressure due to depth in the Earth will have a significant influence on fracture toughness, which is also a function of the inherent anisotropy

    Basal Cover of Perennial Native Grasses Increases Due to Seasonal Conditions

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    Australian native pastures in the high rainfall zone (\u3e 600 mm AAR) in northern Victoria and southern NSW are usually dominated by annual species, and occupy a considerable proportion of the landscape (Pearson et al., 1997; Hill et al., 1999). Productivity of native pastures can potentially be increased by using fertiliser (Lodge 1979; Garden and Bolger, 2001) but this nearly always comes at the expense of the native perennial grasses (Garden et al., 2000; Garden and Bolger, 2001). However, using a combination of fertiliser inputs and rotational grazing can provide increased productivity while maintaining the native perennial pasture base (Garden et al., 2003). Maintaining and improving the current native perennial pasture base in this hilly landscape is essential for maintaining ground cover and meeting natural resource management targets (Virgona et al., 2003). This experiment was conducted as part of the Ever Graze project (Avery et al., 2009), which had the aim of demonstrating that substantial increases in profitability can be achieved while improving environmental management by putting the Ever Graze Principle of ‘Right Plant, Right Place, Right Purpose, Right Management’ into action. The hypothesis for this research was that it is possible to maintain the persistence of native perennial grasses by appropriately combining fertiliser (superphosphate) application with appropriate grazing management

    Effect of plasma density on diffusion rates due to wave particle interactions with chorus and plasmaspheric hiss: extreme event analysis

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    Wave particle interactions play an important role in controlling the dynamics of the radiation belts. The purpose of this study is to estimate how variations in the plasma density can affect diffusion rates resulting from interactions between chorus waves and plasmaspheric hiss with energetic particles and the resulting evolution of the energetic electron population. We perform a statistical analysis of the electron density derived from the plasma wave experiment on the CRRES satellite for two magnetic local time sectors corresponding to near midnight and near noon. We present the cumulative probability distribution of the electron plasma density for three levels of magnetic activity as measured by Kp. The largest densities are seen near L* = 2.5 while the smallest occur near L* = 6. The broadest distribution, corresponding to the greatest variability, occurs near L* = 4. We calculate diffusion coefficients for plasmaspheric hiss and whistler mode chorus for extreme values of the electron density and estimate the effects on the radiation belts using the SalammbĂŽ model. At L* = 4 and L* = 6, in the low density case, using the density from the 5th percentile of the cumulative distribution function, electron energy diffusion by chorus waves is strongest at 2 MeV and increases the flux by up to 3 orders of magnitude over a period of 24 h. In contrast, in the high density case, using the density from the 95th percentile, there is little acceleration at energies above 800 keV at L* = 6, and virtually no acceleration at L* = 4. In this case the strongest energy diffusion occurs at lower energies around 400 keV where the flux at L* = 6 increases 3 orders of magnitude

    Extraction of photogenerated charge carriers by linearly increasing voltage in the case of Langevin recombination

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    Charge extraction by linearly increasing voltage (CELIV) is a powerful and widely used technique for studying charge transport physics, particularly in disordered systems such as organic semiconductors. In this article, we show that CELIV photocurrent transients are strongly dependent on experimental conditions, such as the light intensity and absorption proïŹle. With this in mind, we introduce a universal correction factor that qualitatively extends previously derived CELIV equations, allowing carrier mobility to be estimated at various photogenerated carrier concentrations and, most importantly, photogeneration proïŹles. In addition, we demonstrate how the CELIV technique can be conveniently used to determine precisely the presence of Langevin bimolecular carrier recombination

    Shift from Carbon Flow through the Microbial Loop to the Viral Shunt in Coastal Antarctic Waters during Austral Summer

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    The relative flow of carbon through the viral shunt and the microbial loop is a pivotal factor controlling the contribution of secondary production to the food web and to rates of nutrient remineralization and respiration. The current study examines the significance of these processes in the coastal waters of the Antarctic during the productive austral summer months. Throughout the study a general trend towards lower bacterioplankton and heterotrophic nanoflagellate (HNF) abundances was observed, whereas virioplankton concentration increased. A corresponding decline of HNF grazing rates and shift towards viral production, indicative of viral infection, was measured. Carbon flow mediated by HNF grazing decreased by more than half from 5.7 ”g C L−1 day−1 on average in December and January to 2.4 ”g C L−1 day−1 in February. Conversely, carbon flow through the viral shunt increased substantially over the study from on average 0.9 ”g C L−1 day−1 in December to 7.6 ”g C L−1 day−1 in February. This study shows that functioning of the coastal Antarctic microbial community varied considerably over the productive summer months. In early summer, the system favors transfer of matter and energy to higher trophic levels via the microbial loop, however towards the end of summer carbon flow is redirected towards the viral shunt, causing a switch towards more recycling and therefore increased respiration and regeneration

    Recent Developments in the Radiation Belt Environment Model

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    The fluxes of energetic particles in the radiation belts are found to be strongly controlled by the solar wind conditions. In order to understand and predict the radiation particle intensities, we have developed a physics-based Radiation Belt Environment (RBE) model that considers the influences from the solar wind, ring current and plasmasphere. Recently, an improved calculation of wave-particle interactions has been incorporated. In particular, the model now includes cross diffusion in energy and pitch-angle. We find that the exclusion of cross diffusion could cause significant overestimation of electron flux enhancement during storm recovery. The RBE model is also connected to MHD fields so that the response of the radiation belts to fast variations in the global magnetosphere can be studied.Weare able to reproduce the rapid flux increase during a substorm dipolarization on 4 September 2008. The timing is much shorter than the time scale of wave associated acceleration
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