This work addresses the time-dependent response of 3 m×6 m floating edge-cracked rectangular plates of columnar freshwater S2 ice by conducting load control (LC) mode I fracture tests in the Aalto ...Ice Tank of Aalto University. The thickness of the ice plates was about 0.4 m and the temperature at the top surface about −0.3 ∘C. The loading was applied in the direction normal to the columnar grains and consisted of creep/cyclic-recovery sequences followed by a monotonic ramp to fracture. The LC test results were compared with previous monotonically loaded displacement control (DC) experiments of the same ice, and the effect of creep and cyclic sequences on the fracture properties were discussed. To characterize the nonlinear displacement–load relation, Schapery's constitutive model of nonlinear thermodynamics was applied to analyze the experimental data. A numerical optimization procedure using Nelder–Mead's (N-M) method was implemented to evaluate the model functions by matching the displacement record generated by the model and measured by the experiment. The accuracy of the constitutive model is checked and validated against the experimental response at the crack mouth. Under the testing conditions, the creep phases were dominated by a steady phase, and the ice response was overall elastic–viscoplastic; no significant viscoelasticity or major recovery was detected. In addition, there was no clear effect of the creep loading on the fracture properties at crack growth initiation: the failure load and crack opening displacements.
Phosphate (PO
4
3-
, Pi) is the sole phosphorus (P) containing compound utilized for plant growth, leading to the widespread use of Pi containing fertilizers. An alternative form of P, phosphite (PO
...3
3-
, Phi) has increasingly been used in many crop systems, including amenity turfgrass, not only as a nutrient source but also as a pesticide and biostimulant. There are, however, conflicting reports of the efficacy and benefits of Phi as a source of P. This study was conducted to determine the rate of uptake, translocation and fate of Phi when applied as a foliar treatment to amenity turfgrass, and to assess its role as a source of P nutrition, determining the effect Phi treatments have on turfgrass growth, P deficiency responses, tissue and soil P accumulations. Analysis of Phi treated turfgrass using High Performance Ion Chromatography determined that Phi is rapidly taken up and translocated, that sequential Phi treatments lead to cumulative increases in meristematic tissues, an increase in soil P levels and no in planta conversion to Pi. In P sufficient rootzones (> 35 ppm), foliar applied Phi increased biomass in shoot, crowns, and roots, but also led to a reduction in root to shoot ratios. In phosphorus deficient rootzones (< 5 ppm), foliar applied Phi led to growth reductions in leaf, crown and root, and repression of P deficiency responses.
The ascomycete fungus Microdochium nivale is one of the most damaging pathogens of cool season turfgrass. Prevention of and recovery from infection is costly to many sports facilities each year. In ...recent years, use of many chemical plant protectants has been restricted and turfgrass managers have increasingly sought alternative measures for disease control. The use of phosphite has been shown to be effective in reducing M. nivale disease symptoms in Agrostis stolonifera and Poa annua. The aim of this research was to assess initial defence responses in M. nivale‐infected turfgrass, specifically total phenolic content and hydrogen peroxide generation, to determine the effect phosphite treatment has on these responses and on suppression of symptoms. Phenolic compounds and H2O2 are shown to be components of host responses. Phosphite treatment led to enhanced accumulations of total phenolic content, and when applied sequentially or singly to greenhouse plants, it led to significant reductions in M. nivale disease symptoms compared to phosphate‐treated plants or controls. H2O2 extractions indicated that while phosphite treatment increased H2O2 generation compared to controls, the effect was no different to the responses in phosphate‐treated plants.
Phosphite treatment to Poa annua and Agrostis stolonifera enhanced defence‐related phenolic compounds and subsequently significantly reduced Microdochium nivale infection.
Background
Patients with traumatic brain injury, cerebral edema, and severe hyponatremia require rapid augmentation of serum sodium levels. Three percent sodium chloride is commonly used to normalize ...or augment serum sodium level, yet there are limited data available concerning the most appropriate route of administration. Traditionally, 3% sodium chloride is administered through a central venous catheter (CVC) due to the attributed theoretical risk of phlebitis and extravasation injuries when hyperosmolar solution is administered peripherally. CVCs are associated with numerous complications, including arterial puncture, pneumothorax, infection, thrombosis, and air embolus. Peripherally infused 3% sodium chloride may bypass these concerns.
Aims
To explore the evidence for peripherally infused 3% sodium chloride and to implement the findings.
Methods
The Iowa Model of Evidence‐Based Practice (EBP) was used to guide the project. A multidisciplinary team was established, and they developed an evidence‐based protocol for the administration of 3% sodium chloride using peripheral intravenous catheters (PIVs), identified potential barriers to implementation, and developed targeted education to implement this practice change in a large academic medical center.
Results
Of the 103 patients in this project, only three (2.9%) identified adverse events. Two were associated with continuous infusions, and one was associated with a bolus infusion.
Linking Action to Evidence
This is the first study to describe a multidisciplinary protocol development and implementation process for the administration of 3% sodium chloride peripherally. Utilizing a multidisciplinary team is critical to the success of an EBP project. Implementing an evidence‐based PIV protocol with stringent monitoring criteria for the administration of 3% sodium chloride has the potential to reduce adverse events related to CVC injury.
This chapter proposes supplementing traditional assessment strategies with innovative and authentic ways to evaluate students’ performance on intended learning outcomes.
•The method used for the determination of T-stress in the current version of Abaqus is discussed.•Incorrect T-stress results will be obtained in cases when there are tractions applied to the crack ...faces.•The reason for this error and how to fix it is discussed.
In the present note, it is shown that in the current version of Abaqus (6.10 and later), there is an error in the method used for the determination of T-stress. In particular, errors will occur in cases when there are tractions applied to the crack faces. Since T-stress is an important parameter characterizing the crack tip stress field, used widely in fracture mechanics analysis, it is important to point out this to the users of Abaqus. The reason for this error is due to the incorrect interpretation of the asymptotic crack tip stress fields. To obtain correct T-stress results, the users need to remove this error manually.
An isolated cohesive crack in tension Dempsey, John P.; Tan, Li; Wang, Shen
Continuum mechanics and thermodynamics,
09/2010, Letnik:
22, Številka:
6-8
Journal Article
Recenzirano
The shape of the back-calculated stress-separation curves obtained from the in-situ fracture of first-year sea ice in the Arctic and Antarctic is convex, and radically different from those for ...concrete. In these tests, the process zone size changes with crack growth, but the nature of this change differs with the test conditions, load-control or displacement control. These results prompted a closer examination of the cohesive crack model using the simplest cracked configuration, a finite cohesive crack in an infinite elastic medium loaded in tension by a uniform stress at infinity. Different types of strain softening are examined: rectangular softening, linear softening, prescribed cohesive stresses, and prescribed cohesive crack-opening displacements. For each of these cases, crack nucleation is examined; close attention is paid to test control conditions, be they load-control or fixed-grip. The test control conditions alter the fracture, crack nucleation, crack growth, and process zone size behavior significantly. Accurate approximate solutions to linear softening are presented and examined.
IntroductionDespite being a life-preserving medical treatment, the demands of haemodialysis are a significant impost on individuals, posing considerable burdens on their work, vocational activities ...and involvement with family and community. In our region, patients who have had to relocate considerable distances to a regional city for dialysis, and First Nations people, are less likely to attend all scheduled dialysis sessions. Virtual reality (VR) has been shown to improve engagement with care of people on haemodialysis.This manuscript describes the protocol for a cross-over randomised controlled trial (RCT) that will explore the impact of an immersive VR experience for patients attending a northern Queensland, Australia, haemodialysis service. MethodsThe design is a crossover RCT, with 8 clusters according to haemodialysis location and schedule. Clusters (5 participants in each) will be randomized by computer program. Participants in the trial will be patients who undergo haemodialysis three times/week at one of two dialysis units. During the 4-week intervention period (12 haemodialysis sessions), participants will be provided a headset with vision representative of the natural environment, and with audio. The 4-week control period will comprise usual activities, such as watching television, reading and sleeping. Outcomes will be measured by participants': attendance at scheduled dialysis sessions; adherence to lifestyle modifications; wellbeing, anxiety and depression; acceptability and usability of VR; and adverse events such as nausea. The feasibility and acceptability of the intervention from clinicians' perspectives will also be explored. DiscussionIf this VR intervention is feasible, then participants may engage more with haemodialysis regimens and self-care in this very clinical environment. Trial registrationACTRN12621000732886.
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