Analysis of the nonlinear reverberation of titanium alloys fatigued at high amplitude ultrasonic vibration

6 pages.-- PACS nr.: 81.40.-Z.-- Communication presented at: Forum Acusticum Sevilla 2002 (Sevilla, Spain, 16-20 Sep 2002), comprising: 3rd European Congress on Acoustics; XXXIII Spanish Congress on Acoustics (TecniAcústica 2002); European and Japanese Symposium on Acoustics; 3rd Iberian Congress on Acoustics.-- Special issue of the journal Revista de Acústica, Vol. XXXIII, year 2002.The strong amplitude dependence of material parameters of microinhomogeneous materials can be used to link observations of nonlinearity to micro-scale damage. We have measured the amplitude dependence of the resonance frequency and damping characteristics in the reverberation field of the fundamental eigenmode of titanium alloy samples at regular instances during dynamic fatigue loading at high strains. The analysis of the reverberation is performed in the frequency domain using classical time-windowed FFT, as well as in the time domain using analytical functions with iteratively optimised parameters over each time window. The results show a significant increase of the nonlinearity in the frequency and damping characteristics of the signals observed during the fatiguing process.The authors would like to thank the ESF organisation for support of this research in the frame of the PESC-program NATEMIS (www.polito.it/research/natemis/).Peer reviewe

Diagnostic approach for detection and identification of emerging enteric pathogens revisited : the (Ali)arcobacter lanthieri case

An immunocompetent patient without a history of recent travel or animal exposure developed persistent abdominal bloating and cramps without diarrhoea or fever. Negative additional investigations excluded gastritis, infectious colitis, inflammatory bowel disease and neoplasia, but routine stool culture detected a Campylobacter-like organism. The isolate was obtained with use of a polycarbonate filter technique, emphasizing the importance of culture to support and validate the occurrence of emerging and new bacterial enteric pathogens. The ensuing extensive laboratory examinations proved challenging in identifying this potential pathogen. Phylogenetic marker analysis based on the 16S ribosomal RNA and rpoB gene sequences revealed that the isolate was most closely related to Arcobacter lanthieri and Arcobacter faecis. Subsequent analysis of a draft whole genome sequence assigned the isolate to A. lanthieri. We report the presence of five virulence genes, cadF, ciaB, mviN, hecA and iroE, indicating a possible pathogenic nature of this organism. This case demonstrated the importance of the use of agnostic methods for the detection of emerging pathogens in cases of enteric disease with a wide array of gastrointestinal symptoms

Spinal cord stimulation for predominant low back pain in failed back surgery syndrome: study protocol for an international multicenter randomized controlled trial (PROMISE study)

Background: Although results of case series support the use of spinal cord stimulation in failed back surgery syndrome patients with predominant low back pain, no confirmatory randomized controlled trial has been undertaken in this patient group to date. PROMISE is a multicenter, prospective, randomized, open-label, parallel-group study designed to compare the clinical effectiveness of spinal cord stimulation plus optimal medical management with optimal medical management alone in patients with failed back surgery syndrome and predominant low back pain. Method/Design: Patients will be recruited in approximately 30 centers across Canada, Europe, and the United States. Eligible patients with low back pain exceeding leg pain and an average Numeric Pain Rating Scale score >= 5 for low back pain will be randomized 1:1 to spinal cord stimulation plus optimal medical management or to optimal medical management alone. The investigators will tailor individual optimal medical management treatment plans to their patients. Excluded from study treatments are intrathecal drug delivery, peripheral nerve stimulation, back surgery related to the original back pain complaint, and experimental therapies. Patients randomized to the spinal cord stimulation group will undergo trial stimulation, and if they achieve adequate low back pain relief a neurostimulation system using the Specify (R) 5-6-5 multi-column lead (Medtronic Inc., Minneapolis, MN, USA) will be implanted to capture low back pain preferentially in these patients. Outcome assessment will occur at baseline (pre-randomization) and at 1, 3, 6, 9, 12, 18, and 24 months post randomization. After the 6-month visit, patients can change treatment to that received by the other randomized group. The primary outcome is the proportion of patients with >= 50% reduction in low back pain at the 6-month visit. Additional outcomes include changes in low back and leg pain, functional disability, health-related quality of life, return to work, healthcare utilization including medication usage, and patient satisfaction. Data on adverse events will be collected. The primary analysis will follow the intention-to-treat principle. Healthcare use data will be used to assess costs and long-term cost-effectiveness. Discussion: Recruitment began in January 2013 and will continue until 2016

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

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

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

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

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

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 $^{40}$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 ($e,e'p$), ($\gamma,p$) and ($p,d$) on $^{40}$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 $3/2^{+}$ ground state and the first $1/2^{+}$ 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.

Ambient-aware continuous care through semantic context dissemination

Background: The ultimate ambient-intelligent care room contains numerous sensors and devices to monitor the patient, sense and adjust the environment and support the staff. This sensor-based approach results in a large amount of data, which can be processed by current and future applications, e. g., task management and alerting systems. Today, nurses are responsible for coordinating all these applications and supplied information, which reduces the added value and slows down the adoption rate. The aim of the presented research is the design of a pervasive and scalable framework that is able to optimize continuous care processes by intelligently reasoning on the large amount of heterogeneous care data. Methods: The developed Ontology-based Care Platform (OCarePlatform) consists of modular components that perform a specific reasoning task. Consequently, they can easily be replicated and distributed. Complex reasoning is achieved by combining the results of different components. To ensure that the components only receive information, which is of interest to them at that time, they are able to dynamically generate and register filter rules with a Semantic Communication Bus (SCB). This SCB semantically filters all the heterogeneous care data according to the registered rules by using a continuous care ontology. The SCB can be distributed and a cache can be employed to ensure scalability. Results: A prototype implementation is presented consisting of a new-generation nurse call system supported by a localization and a home automation component. The amount of data that is filtered and the performance of the SCB are evaluated by testing the prototype in a living lab. The delay introduced by processing the filter rules is negligible when 10 or fewer rules are registered. Conclusions: The OCarePlatform allows disseminating relevant care data for the different applications and additionally supports composing complex applications from a set of smaller independent components. This way, the platform significantly reduces the amount of information that needs to be processed by the nurses. The delay resulting from processing the filter rules is linear in the amount of rules. Distributed deployment of the SCB and using a cache allows further improvement of these performance results