126 research outputs found

    Prevalence, Risk Factors, and Clinical Relevance of Fluoroquinolone-Resistant Organisms in Rectal Cultures: Should We Target Antibiotic Prophylaxis Prior to Prostate Biopsy?

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    The rise of infectious complications after prostate biopsy has been linked to the growing resistance of enterobacteria to fluoroquinolone (FQ) antibiotics. In this review, we investigated the potential benefit of targeted antibiotic prophylaxis based on rectal cultures prior to prostate biopsy. An electronic search for all related literature published in English was performed from April until June 2015 using the MEDLINE and EMBASE databases. Data were obtained regarding the true prevalence of FQ-resistant bacteria in the rectum of patients, the identification of those patients at risk of harbouring FQ-resistant bacteria, the risk of infectious complications after transrectal prostate biopsy in patients with FQ-resistant bacteria, and the effect of targeted prophylaxis. Although there is limited evidence that a targeted approach might be beneficial, we conclude that current studies on the use of rectal cultures in the prebiopsy setting have too many limitations and confounding variables to definitely accept this approach in clinical practice. Whether this methodology is useful in a certain region will greatly depend on local fluoroquinolone-resistance rates

    Prevalence, Risk Factors, and Clinical Relevance of Fluoroquinolone-Resistant Organisms in Rectal Cultures: Should We Target Antibiotic Prophylaxis Prior to Prostate Biopsy?

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    The rise of infectious complications after prostate biopsy has been linked to the growing resistance of enterobacteria to fluoroquinolone (FQ) antibiotics. In this review, we investigated the potential benefit of targeted antibiotic prophylaxis based on rectal cultures prior to prostate biopsy. An electronic search for all related literature published in English was performed from April until June 2015 using the MEDLINE and EMBASE databases. Data were obtained regarding the true prevalence of FQresistant bacteria in the rectum of patients, the identification of those patients at risk of harbouring FQ-resistant bacteria, the risk of infectious complications after transrectal prostate biopsy in patients with FQ-resistant bacteria, and the effect of targeted prophylaxis. Although there is limited evidence that a targeted approach might be beneficial, we conclude that current studies on the use of rectal cultures in the prebiopsy setting have too many limitations and confounding variables to definitely accept this approach in clinical practice. Whether this methodology is useful in a certain region will greatly depend on local fluoroquinolone-resistance rates

    Strain-induced kinetics of intergrain defects as the mechanism of slow dynamics in the nonlinear resonant response of humid sandstone bars

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    A closed-form description is proposed to explain nonlinear and slow dynamics effects exhibited by sandstone bars in longitudinal resonance experiments. Along with the fast subsystem of longitudinal nonlinear displacements we examine the strain-dependent slow subsystem of broken intergrain and interlamina cohesive bonds. We show that even the simplest but phenomenologically correct modelling of their mutual feedback elucidates the main experimental findings typical for forced longitudinal oscillations of sandstone bars, namely, (i) hysteretic behavior of a resonance curve on both its up- and down-slopes, (ii) linear softening of resonant frequency with increase of driving level, and (iii) gradual recovery (increase) of resonant frequency at low dynamical strains after the sample was conditioned by high strains. In order to reproduce the highly nonlinear elastic features of sandstone grained structure a realistic non-perturbative form of strain potential energy was adopted. In our theory slow dynamics associated with the experimentally observed memory of peak strain history is attributed to strain-induced kinetic changes in concentration of ruptured inter-grain and inter-lamina cohesive bonds causing a net hysteretic effect on the elastic Young's modulus. Finally, we explain how enhancement of hysteretic phenomena originates from an increase in equilibrium concentration of ruptured cohesive bonds that are due to water saturation.Comment: 5 pages, 3 figure

    Damage signature of fatigued fabric reinforced plastics in the pulsed ultrasonic polar scan

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    This study investigates the use of both the amplitude and time-of-flight based pulsed ultrasonic polar scan (P-UPS) for the nondestructive detection and evaluation of fatigue damage in fiber reinforced composites. Several thermoplastic carbon fabric reinforced PPS specimens (CETEX), loaded under various fatigue conditions, have been scanned at multiple material spots according to the P-UPS technique in order to extract material degradation in a quantitative way. The P-UPS results indicate that shear dominated fatigued carbon/PPS goes with a reduction of shear properties combined with large fiber distortions. The P-UPS results of the tension-tension fatigued carbon/PPS samples on the other hand reveal a directional degradation of the stiffness properties, reaching a maximum reduction of -12.8% along the loading direction. The P-UPS extracted damage characteristics are fully supported by simulations, conventional destructive tests as well as visual inspection. The results demonstrate the excellent capability of the P-UPS method for nondestructively assessing and quantifying both shear-dominated and tension-tension fatigue damage in fabric reinforced plastics

    Directed graph mapping shows rotors maintain non-terminating and focal sources maintain self-terminating Torsade de Pointes in canine model

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    Torsade de Pointes is a polymorphic ventricular tachycardia which is as yet incompletely understood. While the onset of a TdP episode is generally accepted to be caused by triggered activity, the mechanisms for the perpetuation is still under debate. In this study, we analysed data from 54 TdP episodes divided over 5 dogs (4 female, 1 male) with chronic atrioventricular block. Previous research on this dataset showed both reentry and triggered activity to perpetuate the arrhythmia. 13 of those TdP episodes showed reentry as part of the driving mechanism of perpetuating the episode. The remaining 41 episodes were purely ectopic. Reentry was the main mechanism in long-lasting episodes (>14 beats), while focal sources were responsible for maintaining shorter episodes. Building on these results, we re-analysed the data using directed graph mapping This program uses principles from network theory and a combination of positional data and local activation times to identify reentry loops and focal sources within the data. The results of this study are twofold. First, concerning reentry loops, we found that on average non-terminating (NT) episodes (≥10 s) show significantly more simultaneous reentry loops than self-terminating (ST) TdP (<10 s). Non-terminating episodes have on average 2.72 ± 1.48 simultaneous loops, compared to an average of 1.33 ± 0.66 for self-terminating episodes. In addition, each NT episode showed a presence of (bi-)ventricular loops between 10.10% and 69.62% of their total reentry duration. Compared to the ST episodes, only 1 in 4 episodes (25%) showed (bi-)ventricular reentry, lasting only 7.12% of its total reentry duration. This suggests that while focal beats trigger TdP, macro-reentry and multiple simultaneous localized reentries are the major drivers of long-lasting episodes. Second, using heatmaps, we found focal sources to occur in preferred locations, instead of being distributed randomly. This may have implications on treatment if such focal origins can be disabled reliably

    The effect of crack orientation on the nonlinear interaction of a P wave with an S wave

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    Cracks, joints, fluids, and other pore-scale structures have long been hypothesized to be the cause of the large elastic nonlinearity observed in rocks. It is difficult to definitively say which pore-scale features are most important, however, because of the difficulty in isolating the source of the nonlinear interaction. In this work, we focus on the influence of cracks on the recorded nonlinear signal and in particular on how the orientation of microcracks changes the strength of the nonlinear interaction. We do this by studying the effect of orientation on the measurements in a rock with anisotropy correlated with the presence and alignment of microcracks. We measure the nonlinear response via the traveltime delay induced in a low-amplitude P wave probe by a high-amplitude S wave pump. We find evidence that crack orientation has a significant effect on the nonlinear signal

    Generator coordinate method calculations of one-nucleon removal reactions on 40^{40}Ca

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    An approach to the Generator Coordinate Method (GCM) using Skyrme-type effective forces and Woods-Saxon construction potential is applied to calculate the single-particle proton and neutron overlap functions in 40^{40}Ca. The relationship between the bound-state overlap functions and the one-body density matrix has been used. These overlap functions are applied to calculate the cross sections of one-nucleon removal reactions such as (e,epe,e'p), (γ,p\gamma,p) and (p,dp,d) on 40^{40}Ca on the same theoretical footing. A consistent description of data for the different reactions is achieved. The shapes of the experimental cross sections for transitions to the 3/2+3/2^{+} ground state and the first 1/2+1/2^{+} excited state of the residual nuclei are well reproduced by the overlap functions obtained within the GCM. An additional spectroscopic factor accounting for correlations not included in the overlap function must be applied to the calculated results to reproduce the size of the experimental cross sections.Comment: 16 pages, 6 figures, to be published in Phys. Rev.

    Directed graph mapping shows rotors maintain non-terminating and focal sources maintain self-terminating Torsade de Pointes in canine model

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    Torsade de Pointes is a polymorphic ventricular tachycardia which is as yet incompletely understood. While the onset of a TdP episode is generally accepted to be caused by triggered activity, the mechanisms for the perpetuation is still under debate. In this study, we analysed data from 54 TdP episodes divided over 5 dogs (4 female, 1 male) with chronic atrioventricular block. Previous research on this dataset showed both reentry and triggered activity to perpetuate the arrhythmia. 13 of those TdP episodes showed reentry as part of the driving mechanism of perpetuating the episode. The remaining 41 episodes were purely ectopic. Reentry was the main mechanism in long-lasting episodes (&gt;14 beats), while focal sources were responsible for maintaining shorter episodes. Building on these results, we re-analysed the data using directed graph mapping This program uses principles from network theory and a combination of positional data and local activation times to identify reentry loops and focal sources within the data. The results of this study are twofold. First, concerning reentry loops, we found that on average non-terminating (NT) episodes (≥10 s) show significantly more simultaneous reentry loops than self-terminating (ST) TdP (&lt;10 s). Non-terminating episodes have on average 2.72 ± 1.48 simultaneous loops, compared to an average of 1.33 ± 0.66 for self-terminating episodes. In addition, each NT episode showed a presence of (bi-)ventricular loops between 10.10% and 69.62% of their total reentry duration. Compared to the ST episodes, only 1 in 4 episodes (25%) showed (bi-)ventricular reentry, lasting only 7.12% of its total reentry duration. This suggests that while focal beats trigger TdP, macro-reentry and multiple simultaneous localized reentries are the major drivers of long-lasting episodes. Second, using heatmaps, we found focal sources to occur in preferred locations, instead of being distributed randomly. This may have implications on treatment if such focal origins can be disabled reliably

    Drivers and impact of antifungal therapy in critically ill patients with Aspergillus-positive respiratory tract cultures

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    Invasive pulmonary aspergillosis (IPA) is an increasingly recognised problem in critically ill patients. Little is known about how intensivists react to an Aspergillus-positive respiratory sample or the efficacy of antifungal therapy (AFT). This study aimed to identify drivers of AFT prescription and diagnostic workup in patients with Aspergillus isolation in respiratory specimens as well as the impact of AFT in these patients. ICU patients with an Aspergillus-positive respiratory sample from the database of a previous observational, multicentre study were analysed. Cases were classified as proven/putative IPA or Aspergillus colonisation. Demographic, microbiological, diagnostic and therapeutic data were collected. Outcome was recorded 12 weeks after Aspergillus isolation. Patients with putative/proven IPA were more likely to receive AFT than colonised patients (78.7% vs. 25.5%; P 7) (68.4% vs. 36.9%) (both P < 0.001). Once adjusted for disease severity, initiation of AFT did not alter the odds of survival (HR = 1.40, 95% CI 0.89–2.21). Likewise, treatment within 48 h following diagnosis did not change the clinical outcome (75.7% vs. 61.4%; P = 0.63). Treatment decisions appear to be based on diagnostic criteria and underlying disease severity at the time of Aspergillus isolation. IPA in this population has a dire prognosis and AFT is not associated with reduced mortality. This may be explained by delayed diagnosis and an often inevitable death due to advanced multiorgan failure

    Nondestructive monitoring of ageing of Alkali resistant Glass fiber reinforced cement (GRC)

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    Glass fiber reinforced cement (GRC) is a composite material made of portland cement mortar and alkali resistant (AR) fibers. AR fibers are added to portland cement to give the material additional flexural strength and toughness. However, ageing deteriorates the fibers and as a result the improvement in the mechanical properties resulted from the fiber addition disappears as the structure becomes old. The aim of this paper is monitoring GRC ageing by nondestructive evaluation (NDE) techniques. Two different NDE techniques (1) nonlinear impact resonant acoustic spectroscopy analysis and (2) propagating ultrasonic guided waves are used for this purpose. Both techniques revealed a reduction of the nonlinear behavior in the GRC material with ageing. Specimens are then loaded to failure to obtain their strength and stiffness. Compared to the un-aged specimens, the aged specimens are found to exhibit more linear behavior, have more stiffness but less toughness. Finally, undisturbed fragments on the fracture surface from mechanical tests are inspected under the electron microscope, to understand the fundamental mechanisms that cause the change in the GRC behavior with ageing.The authors want to acknowledge the financial support of the Ministerio de Ciencia e Innovacion MICINN, Spain, and FEDER funding (Ondacem Project: BIA 2010-19933) and BES-2011-044624. Also thanks to PAID-02-11 Program from Universitat Politecnica de Valencia.Eiras Fernández, JN.; Kundu, T.; Bonilla Salvador, MM.; Paya Bernabeu, JJ. (2013). Nondestructive monitoring of ageing of Alkali resistant Glass fiber reinforced cement (GRC). Journal of Nondestructive Evaluation - NDT and E International. 32:300-314. https://doi.org/10.1007/s10921-013-0183-yS30031432Bentur, A., Fibre, M.S.: Reinforced Cementitious Composites, 2nd edn. Taylor and Francis, New York (2007)Purnell, P., Short, N.R., Page, C.L.: A static fatigue model for the durability of glass fibre reinforced cement. J. Mater. Sci. 36(22), 5385–5390 (2001)Ferreira, J.G., Branco, F.A.: Structural application of GRC in telecommunication towers. Constr. Build. Mater. 21(1), 19–28 (2007)Bentur, A., Ben-Bassat, M., Schneider, D.: Durability of glass-fiber-reinforced cements with different alkali-resistant glass fibers. J. Am. Ceram. Soc. 68(4), 203–208 (1985)Cheng, J., Liang, W., Hu, Y., Chen, Q., Frischat, G.H.: Development of a new alkali resistant coating. J. Sol-Gel Sci. Technol. 27(3), 309–313 (2003)Liang, W., Cheng, J., Hu, Y., Luo, H.: Improved properties of GRC composites using commercial E-glass fibers with new coatings. Mater. Res. Bull. 37(4), 641–646 (2002)Payá, J., Bonilla, M., Borrachero, M.V., Monzó, J., Peris-Mora, E., Lalinde, L.F.: Reusing fly ash in glass fibre reinforced cement: a new generation of high-quality GRC composites. Waste Manag. 27(10), 1416–1421 (2007)Zhang, Y., Sun, W., Shang, L., Pan, G.: The effect of high content of fly ash on the properties of glass fiber reinforced cementitious composites. Cem. Concr. Res. 27(12), 1885–1891 (1997)Purnell, P., Short, N., Page, C.: Super-critical carbonation of glass-fibre reinforced cement. Part 1: mechanical testing and chemical analysis. Composites, Part A, Appl. Sci. Manuf. 32(12), 1777–1787 (2001)EN 1170-8:2008. Test method for glass-fibre reinforced cement. Cyclic weathering type testPurnell, P.: Interpretation of climatic temperature variations for accelerated ageing models. J. Mater. Sci. 39(1), 113–118 (2004)Enfedaque, A., Sánchez Paradela, L., Sánchez-Gálvez, V.: An alternative methodology to predict aging effects on the mechanical properties of glass fiber reinforced cements (GRC). Constr. Build. Mater. 27(1), 425–431 (2012)Litherland, K.L., Maguire, P., Proctor, B.A.: A test method for the strength of glass fibres in cement. Int. J. Cem. Compos. Lightweight Concr. 6(1), 39–45 (1984)Itterbeeck, P., Cuypers, H., Orlowsky, J., Wastiels, J.: Evaluation of the strand in cement (SIC) test for GRCs with improved durability. Mater. Struct. 41(6), 1109–1116 (2007)Guyer, R.A., Johnson, P.A.: Nonlinear mesoscopic elasticity: evidence for a new class of materials. Phys. Today 52, 30 (1999)Johnson, P.A.: Nonequilibrium nonlinear dynamics in solids: state of the art. In: Delsanto, P.P. (ed.) Universality of Nonclassical Nonlinearity, pp. 49–69. Springer, New York (2006)Guyer, R.A., McCall, K.R., Boitnott, G.N.: Hysteresis, discrete memory, and nonlinear wave propagation in rock: a new paradigm. Phys. Rev. Lett. 74(17), 3491–3494 (1995)Mayergoyz, I.D.: Mathematical Models of Hysteresis and Their Applications. Academic Press, New York (2003)Van Den Abeele, K.E.A., Carmeliet, J., Ten Cate, J.A., Johnson, P.A.: Nonlinear elastic wave spectroscopy (NEWS) techniques to discern material damage, part II: single-mode nonlinear resonance acoustic spectroscopy. Res. Nondestruct. Eval. 12(1), 31–42 (2000)Chen, J., Jayapalan, A.R., Kim, J.Y., Kurtis, K.E., Jacobs, L.J.: Rapid evaluation of alkali–silica reactivity of aggregates using a nonlinear resonance spectroscopy technique. Cem. Concr. Res. 40(6), 914–923 (2010)Leśnicki, K.J., Kim, J.Y., Kurtis, K.E., Jacobs, L.J.: Characterization of ASR damage in concrete using nonlinear impact resonance acoustic spectroscopy technique. Nondestruct. Test. Eval. Int. 44(8), 721–727 (2011)Bouchaala, F., Payan, C., Garnier, V., Balayssac, J.P.: Carbonation assessment in concrete by nonlinear ultrasound. Cem. Concr. Res. 41(5), 557–559 (2011)Eiras, J.N., Popovics, J.S., Borrachero, M.V., Monzó, J., Payá, J.: Nonlinear impact resonant acoustic spectroscopy to discern mechanical damage in cement based materials. In: 15th International Conference on Experimental Mechanics, Porto, Portugal (2012)Kundu, T.: Ultrasonic Nondestructive Evaluation: Engineering and Biological Material Characterization. CRC Press, Boca Raton (2004)Kundu, T.: Ultrasonic and Electromagnetic NDE for Structure and Material Characterization—Engineering and Biomedical Applications. CRC Press, Boca Raton (2012)Dutta, D., Sohn, H., Harries, K.A., Rizzo, P.: A nonlinear acoustic technique for crack detection in metallic structures. Struct. Health Monit. 8(3), 251–262 (2009)Aymerich, F., Staszewski, W.J.: Impact damage detection in composite laminates using nonlinear acoustics. Composites, Part A, Appl. Sci. Manuf. 41(9), 1084–1092 (2010)EN 1170-1:1998. Precast concrete products. Test method for glass-fibre reinforced cement. Measuring the consistency of the matrix, “Slump test” methodMontgomery, P.L.: A block Lanczos algorithm for finding dependencies over GF(2). In: EUROCRYPT ’95. Lecture Notes in Computer Science, vol. 921, pp. 106–120. Springer, Berlin (1995)EN 1170-5:1998. Precast concrete products. Test method for glass-fibre reinforced cement. Measuring bending strength, “complete bending test” methodRomero, R., Zúnica, L.R.: Métodos Estadísticos en Ingeniería. Universitat Politècnica València, Valencia (2005)Kundu, T.: Fundamentals of Fracture Mechanics. CRC Press, Boca Raton (2008)ASTM C 215:08. Standard Test Method for Fundamental Transverse, Longitudinal, and Torsional Frequencies of Concrete Specimens (2008)Hewlett, P.C.: Lea’s Chemistry of Cement and Concrete, 4th edn. Butterworth-Heinemann, Oxford (2003)Zhu, W., Bartos, P.J.M.: Assessment of interfacial microstructure and bond properties in aged GRC using a novel microindentation method. Cem. Concr. Res. 27(11), 1701–1711 (1997)Purnell, P., Buchanan, A.J., Short, N.R., Page, C.L., Majumdar, A.J.: Determination of bond strength in glass fibre reinforced cement using petrography and image analysis. J. Mater. Sci. 35(18), 4653–4659 (2000)Visalvanich, K., Naaman, A.E.: Fracture model for fiber reinforced concrete. J. ACI Proc. 80(2), 128–138 (1983)Kundu, T., Jang, H.S., Cha, Y.H., Desai, C.S.: A simple model to predict the effect of volume fraction, diameter, and length of fibers on strength variation of fiber reinforced brittle matrix composites. Int. J. Numer. Anal. Methods Geomech. 24, 655–673 (2000)Li, V.C., Maalej, M.: Toughening in cement based composites. Part II: fiber reinforced composites. Cem. Concr. Compos. 18, 239–249 (1996)Van Den Abeele, K.E.A., Johnson, P.A., Sutin, A.: Nonlinear elastic wave spectroscopy (NEWS) techniques to discern material damage, part I: nonlinear wave modulation spectroscopy (NWMS). Res. Nondestruct. Eval. 12(1), 17–30 (2000
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