Acoustic emission multiplets as early warnings of fatigue failure in metallic materials

Fatigue, i.e. the failure of mechanical structures under cycling loading, remains a considerable technological challenge as it occurs unexpectedly when the structure is operating apparently in a safe and steady state regime, without external signs of mechanical deterioration. Here we report for the first time, in different metallic materials, the detection of acoustic emissions specific of fatigue crack growth. These so-called acoustic multiplets are characterized by nearly identical waveforms, signature of a unique source, are repeatedly triggered over many successive loading cycles at the same stress level, and originate from a single location. They mark the slow, incremental propagation of a fatigue crack at each cycle, or the rubbing along its faces. Being specific to fatigue cracking, they can be used as early warnings of crack propagation, which will ultimately lead to structural failure. Their detection and characterization thus open the way towards a new, reliable monitoring of the onset of fatigue cracking during mechanical tests or within structures in service.

A small spacecraft for multipoint measurement of ionospheric plasma

Measurement of ionospheric plasma is often performed by a single in situ device or remotely using cameras and radar. This article describes a small, low-resource, deployed spacecraft used as part of a local, multipoint measurement network. A B-field aligned sounding rocket ejects four of these spin-stabilized spacecraft in a cross pattern. In this application, each spacecraft carries two retarding potential analyzers which are used to determine plasma density, flow, and ion temperature. An inertial measurement unit and a light-emitting diode array are used to determine the position and orientation of the devices after deployment. The design of this spacecraft is first described, and then results from a recent test flight are discussed. This flight demonstrated the successful operation of the deployment mechanism and telemetry systems, provided some preliminary plasma measurements in a simple mid-latitude environment, and revealed several design issues.

Leaching of Conductive Species: Implications to Measurements of Electrical Resistivity

Electrical tests have been used to characterize the microstructure of porous materials, the measured electrical response being determined by the contribution of the microstructure (porosity and tortuosity) and the electrical properties of the solution (conductivity of the pore solution) inside the pores of the material. This study has shown how differences in concentration between the pore solution (i.e., the solution in the pores) and the storage solution surrounding the test specimen leads to significant transport (leaching) of the conductive ionic species between the pore solution and the storage solution. Leaching influences the resistivity of the pore solution, thereby influencing electrical measurements on the bulk material from either a surface or uniaxial bulk resistance test. This paper has three main conclusions: 1.) Leaching of conductive species does occur with concentration gradients and that a diffusion based approach can be used to estimate the time scale associated with this change. 2.) Leaching of ions in the pore solution can influence resistivity measurements, and the ratio of surface to uniaxial resistivity can be used as a method to assess the presence of leaching and 3.) An estimation of the magnitude of leaching for standardized tests of cementitious materials.

Benefits and Harms of Intensive Blood Pressure Treatment in Adults Aged 60 Years or Older: A Systematic Review and Meta-analysis

BACKGROUND

Recent guidelines recommend a systolic blood pressure (SBP) goal of less than 150 mm Hg for adults aged 60 years or older, but the balance of benefits and harms is unclear in light of newer evidence.

PURPOSE

To systematically review the effects of more versus less intensive BP control in older adults.

DATA SOURCES

Multiple databases through January 2015 and MEDLINE to September 2016.

STUDY SELECTION

21 randomized, controlled trials comparing BP targets or treatment intensity, and 3 observational studies that assessed harms.

DATA EXTRACTION

Two investigators extracted data, assessed study quality, and graded the evidence using published criteria.

DATA SYNTHESIS

Nine trials provided high-strength evidence that BP control to less than 150/90 mm Hg reduces mortality (relative risk [RR], 0.90 [95% CI, 0.83 to 0.98]), cardiac events (RR, 0.77 [CI, 0.68 to 0.89]), and stroke (RR, 0.74 [CI, 0.65 to 0.84]). Six trials yielded low- to moderate-strength evidence that lower targets (≤140/85 mm Hg) are associated with marginally significant decreases in cardiac events (RR, 0.82 [CI, 0.64 to 1.00]) and stroke (RR, 0.79 [CI, 0.59 to 0.99]) and nonsignificantly fewer deaths (RR, 0.86 [CI, 0.69 to 1.06]). Low- to moderate-strength evidence showed that lower BP targets do not increase falls or cognitive impairment.

LIMITATION

Data relevant to frail elderly adults and the effect of multimorbidity are limited.

CONCLUSION

Treatment to at least current guideline standards for BP (<150/90 mm Hg) substantially improves health outcomes in older adults. There is less consistent evidence, largely from 1 trial targeting SBP less than 120 mm Hg, that lower BP targets are beneficial for high-risk patients. Lower BP targets did not increase falls or cognitive decline but are associated with hypotension, syncope, and greater medication burden.

PRIMARY FUNDING SOURCE

U.S. Department of Veterans Affairs, Veterans Health Administration, Office of Research and Development, Quality Enhancement Research Initiative. (PROSPERO 2015: CRD42015017677).

Antimicrobial efficacy of sequentially applied eugenol against food spoilage micro-organisms

AIMS

Compare the survival behaviour of food spoilage micro-organisms treated with sequential doses or all at once treatments of eugenol.

METHODS AND RESULTS

Staphylococcus carnosus, Listeria innocua, Escherichia coli and Pseudomonas fluorescens were exposed to a minimal lethal concentration (MLC) initially, or to half doses over time, with first half dose applied immediately and a second half dose applied after 3, 4, 6 and 8 h, of eugenol. Direct plate counts were determined at regular time intervals. Population dynamics were analysed using a combined growth and mortality model. Effect of sequential dosing varied significantly between tested organisms. High antimicrobial efficacy on E. coli K12 was observed regardless of timing of the two doses. Reduced effectiveness was observed against Staph. carnosus and L. innocua the later the second half dose was applied. Complete cell reduction occurred after immediate exposure to full MLC dose, while sequential half doses were bacteriostatic regardless of application times.

CONCLUSION

Time in between antimicrobial dose application had substantial impact on effectiveness, attributed to organisms becoming more tolerant.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study contributes to the evaluation of encapsulated antimicrobial systems, where antimicrobials are released over time and antimicrobial concentrations may only reach MLC levels after some time.

Fundamentalism, Multiculturalism and Problems of Conducting Research with Populations in Developing Nations

A growing number of nurse researchers travel globally to conduct research in poor and underserved populations in developing nations. These researchers, while well versed in research ethics, often find it difficult to apply traditional ethical standards to populations in developing countries. The problem of applying ethical standards across cultures is explained by a long-standing debate about the nature of ethical principles. Fundamentalism is the philosophical stance that ethical principles are universal, while the anthropologically-based ‘multicultural’ model claims the philosophical position that principles are culturally bound. The authors explicate the two philosophical stances and advocate a morally sensitive but moderate position of ‘ethical multiculturalism’ rather than favouring either of the above philosophical positions. The final section suggests ways to promote ethical multiculturalism while planning and conducting nursing research.

Pertinent parameters in photo-generation of electrons: Comparative study of anatase-based nano-TiO2 suspensions

In the field of solar fuel cells, the development of efficient photo-converting semiconductors remains a major challenge. A rational analysis of experimental photocatalytic results obtained with material in colloïdal suspensions is needed to access fundamental knowledge required to improve the design and properties of new materials. In this study, a simple system electron donor/nano-TiO2 is considered and examined via spin scavenging electron paramagnetic resonance as well as a panel of analytical techniques (composition, optical spectroscopy and dynamic light scattering) for selected type of nano-TiO2. Independent variables (pH, electron donor concentration and TiO2 amount) have been varied and interdependent variables (aggregate size, aggregate surface vs. volume and acid/base groups distribution) are discussed. This work shows that reliable understanding involves thoughtful combination of interdependent parameters, whereas the specific surface area seems not a pertinent parameter. The conclusion emphasizes the difficulty to identify the key features of the mechanisms governing photocatalytic properties in nano-TiO2.

VALIDATION OF THE LYMPHEDEMA LIFE IMPACT SCALE (LLIS): A CONDITION-SPECIFIC MEASUREMENT TOOL FOR PERSONS WITH LYMPHEDEMA

Evidence-based practice supports the use of validated outcome measures to assess the impact of lymphedema; however, condition-specific lymphedema assessment measures are needed. The Lymphedema Life Impact Scale (LLIS) was developed as a comprehensive, lymphedema-specific instrument to assess the effects of lymphedema in any extremity. The LLIS is an 18-item measure of physical, psychosocial, and functional impairments caused by lymphedema. The purpose of this multicenter, cross sectional study was to investigate the reliability and validity of the LLIS. Test-retest reliability was assessed in a subgroup of 17 participants. Internal consistency and validity was assessed in 71 participants with upper (nUE = 37) or lower limb (nLE = 34) lymphedema, and a control group of 31 participants without lymphedema. Intraclass correlation coefficients for test-retest reliability ranged from .965 to .990. Cronbach's alpha coefficients for internal consistency ranged between .841 and .926. Construct validity of the LLIS was upheld with symptoms, but not with edema severity. The LLIS correlated highly with other comparison measures used in this study. Minimal clinically important difference of the LLIS was 7.31; MDC95 = 11.53. Our results showed the LLIS to be a valid and reliable tool for the assessment of severity of impairment among patients with lymphedema.

[First data concerning the medical supply of patients with non-alcoholic fatty liver disease in Germany - a survey in university hospital centers of hepatology]

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) currently is one oft the most common reasons for chronic liver injury in the western world. In the European and American population the prevalence is up to 30 %. The medical supply of German patients with NAFLD is variable and has not been analyzed to date.

METHODS

We sent questionnaires to all university liver centers in Germany (11 questions) concerning the medical supply of patients with NAFLD. Questions included the rate of patients with fatty liver disease in the outpatient clinics, metabolic comorbidities and the kind of assignment. Besides that, individual clinical standards were documented. We compared longitudinal changes between 2008 and 2013.

RESULTS

The return rate of questionnaires was 65 % (n = 20). Analysis showed that the portion of NAFLD patients in the university outpatient clinics had increased between 2008 and 2013 with the predominant part of patients being assigned from external practitioners and not from internal departments of the hospital. Only few patients were assigned by diabetologists or endocrinologists, but on the other hand most liver outpatient clinics investigated their NAFLD patients for metabolic disorders. Cooperation between liver outpatient clinics and other medical services was moderate and was rated average, joint conferences were held rarely. Follow-up visits of patients with NAFLD take place regularly in all centers, however based on different criterions. A consistent algorithm concerning risk assessment and invasive workup does not exist.

CONCLUSION

The awareness concerning patients with NAFLD seems to have grown in recent years. Nevertheless, the medical supply of these patients is quite heterogenous and consistent standards do not exist. Therefore, a common guidline is urgently required.

From mild to wild fluctuations in crystal plasticity

Macroscopic crystal plasticity is classically viewed as an outcome of uncorrelated dislocation motions producing Gaussian fluctuations. An apparently conflicting picture emerged in recent years emphasizing highly correlated dislocation dynamics characterized by power-law distributed fluctuations. We use acoustic emission measurements in crystals with different symmetries to show that intermittent and continuous visions of plastic flow are not incompatible. We demonstrate the existence of crossover regimes where strongly intermittent events coexist with a Gaussian quasiequilibrium background and propose a simple theoretical framework compatible with these observations.