Phase Interactions in Monoclinic Zirconia Reinforced Hydroxylapatite Bioceramics

Volume 1 ◽  
2004 ◽  
Author(s):  
Celaletdin Ergun ◽  
Zafer Evis ◽  
Robert H. Doremus
Keyword(s):  
Thermal Analysis ◽  
Tricalcium Phosphate ◽  
Hot Pressing ◽  
Monoclinic Zirconia ◽  
Pure Zirconia ◽  
Different Temperatures ◽  
The Mean ◽  
Zirconia Phase ◽  
Mean Time

Hydroxylapatite composites with pure zirconia were prepared with pressureless air sintering and hot pressing for 1 hour at different temperatures between 900°C and 1300°C. The interaction between the phases was monitored with XRD and thermal analysis. At sintering temperatures higher than 1000°C, an apparent Ca diffusion occurred from hydroxylapatite to pure zirconia phase and changed its structure from monoclinic to tetragonal/cubic. In the mean time, hydroxylapatite decomposed and formed tricalcium phosphate. Also, a reaction was occurred at 1220°C between hydroxylapatite and zirconia phase forming CaZrO3. The existence of air in the processing environment increased the reactivity between hydroxylapatite and zirconia.

Phase Interaction in Hydroxylapatite/LaPO4 Composite

2006 ◽  
Author(s):  
Celaletdin Ergun ◽  
John W. Halloran ◽  
Chang-Jun Bae ◽  
Filiz C¸ınar S¸ahin
Keyword(s):  
Tricalcium Phosphate ◽  
Xrd Analysis ◽  
Phase Interaction ◽  
Lanthanum Phosphate ◽  
Phosphate Phase ◽  
Different Temperatures ◽  
The Mean ◽  
Mean Time

Hydroxylapatite composites with lanthanum phosphate were prepared with pressureless air sintering for 2 hours at different temperatures between 500°C and 1300°C. The interaction between the phases was monitored with XRD analysis. At sintering temperatures higher than 700°C, hydroxylapatite and lanthanum phosphate phase reacted and formed Ca8 La2 (PO4)6O2 as byproduct. In the mean time, hydroxylapatite decomposed and formed tricalcium phosphate.

Oxidation Behaviors of TiB2-TiCX and TiB2-TiCX/15SiC Ceramics

2010 ◽  
Vol 105-106 ◽  
pp. 179-183 ◽  
Author(s):  
De Gui Zhu ◽  
Hong Liang Sun ◽  
Yu Shu Wang ◽  
Liang Hui Wang
Keyword(s):  
Oxidation Resistance ◽  
Effective Temperature ◽  
Hot Isostatic Pressing ◽  
Ceramic Composites ◽  
Optical Micrograph ◽  
Different Temperatures ◽  
The Mean ◽  
Mean Time ◽  
Oxidation Behaviors

Fully dense samples of TiB2-TiCX and TiB2-TiCX/15SiC ceramic composites were fabricated by in-situ synthesis under hot isostatic pressing from TiH2, B4C and SiC powders. Their oxidized behaviors at different temperatures were tested. Optical micrograph studies and thermo-gravimetric analyses show that the highest effective temperature of oxidation resistance is 700°C for TiB2-TiCX, and 1100°C for TiB2-TiCX/15SiC. The weight gain of TiB2-TiCX/15SiC below 1100°C is quite low, and it rises up suddenly when the temperature reaches 1200°C. Thus, the highest effective temperature of oxidation resistance is 1100°C for TiB2-TiCX/15SiC. The oxidation dynamic curves of TiB2-TiCX/15SiC ceramics accord with the parabola’s law. The activation energy of TiB2-TiCx/15SiC (189.87kJ.mol-1) is higher than that of TiB2-TiCx (96.44kJ.mol-1). In the oxidation process of TiB2-TiCx/15SiC, TiB2 reacts with oxygen and generates TiO2 and B2O3 at first. A layer of whole homogeneous oxide film cannot be formed, in the mean time, the oxidation of TiC begins. When temperature goes up to 1000°C, TiC phase is totally oxidized. SiC is oxidized to SiO2 at about 900°C, Meanwhile, TiO2 forms denser film than B2O3, which grows and covers the surface of the material, and gives better property of oxidation resistance.

Thermal Conductivity and Oxygen Tracer Diffusion of Yttria Stabilized Zirconia by Molecular Dynamics

2021 ◽  
Vol 407 ◽  
pp. 51-58
Author(s):  
Leila Momenzadeh ◽  
Irina V. Belova ◽  
Graeme E. Murch
Keyword(s):  
Thermal Conductivity ◽  
Diffusion Coefficient ◽  
Lattice Thermal Conductivity ◽  
Tracer Diffusion ◽  
Yttria Stabilized Zirconia ◽  
Stabilized Zirconia ◽  
Pure Zirconia ◽  
Different Temperatures ◽  
The Mean ◽  
Oxygen Tracer

One of the most technologically beneficial engineering ceramics is yttria stabilized zirconia (YSZ). As a result, research interest about YSZ has been intensive for many years. In this study, the lattice thermal conductivity and oxygen diffusion coefficient of YSZ are investigated at different temperatures (from 700 K to 1300 K) and zero pressure with the Green-Kubo formalism. We find that the lattice thermal conductivity decreases as the temperature increases, particularly at low temperatures and it shows a slightly temperature independence at high temperatures. The results demonstrate that the YSZ has quite a low thermal conductivity compared with pure zirconia. We also show that the oxygen tracer diffusion coefficient, as calculated from the mean square displacements, has an activation energy of 0.85eV.

scholarly journals Morphological characterization and germination of Syagrus schizophylla (Mart.) Glass. (ARECACEAE)

2019 ◽  
Vol 10 (1) ◽  
pp. 54-64
Author(s):  
Rômulo André Beltrame ◽  
Janie Mendes Jasmim ◽  
Henrique Duarte Vieira
Keyword(s):  
Water Absorption ◽  
Average Length ◽  
Seedling Emergence ◽  
Morphological Characterization ◽  
Palm Tree ◽  
Average Width ◽  
Different Temperatures ◽  
Emergence Curve ◽  
The Mean ◽  
Mean Time

The interest in Syagrus schizophylla as an ornamental palm tree and the demand for conservation and preservation of the species led to this research. The objective was to study the physiological characteristics of its germination at different temperatures, as well as the morphological and biometrical characterization of diaspores and seedlings at the initial stages of growth and development. The research was divided into two experiments. In the first one, the aim was to identify the water absorption phases of seeds during germination under five scarification treatments as follows: intact diaspores, scarified diaspores, diaspores with endocarp rupture and intact seeds. In the second experiment, germination was tested at 25, 30 e 25 - 35 ºC; the first germination count, seedling emergence, abnormal seedlings, non-germinated seeds, the emergence curve, the emergence speed index and the mean time of emergence were evaluated. Afterwards, the morphological and biometrical characteristics of diaspores and seedlings were described. The water absorption curve observed under the different scarification treatments showed different water absorption patterns. Emergence percentages were 53, 61 and 47% at 25, 30 and 25 - 35 ºC, respectively. The highest emergence speed index was obtained at 30 ºC. The mean time of emergence was 30 days, approximately, under all the temperatures tested. The diaspores showed a great variability in both shape and size, presenting a globular to ovoid shape with an average length of 2.44 cm and an average width of 1.39 cm. The germination can be classified as hypogeal crypto cotyledonal of the remote-tubular type.

Preparation of Biologically Derived Hydroxyapatite and its Dissolution

2007 ◽  
Vol 342-343 ◽  
pp. 657-660 ◽  
Author(s):  
Dong Seok Seo ◽  
Hwan Kim ◽  
Jong Kook Lee
Keyword(s):  
Tricalcium Phosphate ◽  
The Other ◽  
Distilled Water ◽  
Large Defect ◽  
Human Teeth ◽  
Liquid Environment ◽  
The Matrix ◽  
The Mean ◽  
Lattice Planes ◽  
Mean Time

Hydroxyapatite derived from human teeth was sintered at 1200°C for 2 h. Dissolving behavior of the biologically derived HA (BHA) in distilled water was investigated and compared with an artificial hydroxyapatite (HA) made of synthetic HA powder. All disks were immersed in 40 ml of pH 7.4 distilled water (buffered using 0.05 M Tris.) for 7 and 14 days at 37°C. All detectable peaks in the HA are identical only to HA lattice planes, whereas BHA consisted of a mixture of HA and β-tricalcium phosphate (TCP). In the case of the HA specimen, the surface dissolution was initiated at grain boundaries followed by generated many separated grains and large defect like cavities. On the other hand, biologically derived HA showed that definite grains considered as β-TCP was predominantly dissolved and the grains were separated from the matrix leaving pores. In the mean time, the rest region, mainly consisting of HA, did not show any evidence of dissolution. It seems that BHA is more stable than the artificial HA in liquid environment.

Predicting Daily Maintenance Dose of Fluindione, an Oral Anticoagulant Drug

1996 ◽  
Vol 75 (05) ◽  
pp. 731-733 ◽  
Author(s):  
V Cazaux ◽  
B Gauthier ◽  
A Elias ◽  
D Lefebvre ◽  
J Tredez ◽  
...  
Keyword(s):  
Effective Dose ◽  
Maintenance Dose ◽  
Successive Approximations ◽  
Hemorrhagic Complication ◽  
Simple Method ◽  
Individual Variations ◽  
Anticoagulant Drug ◽  
The Mean ◽  
Mean Time ◽  
Daily Maintenance Dose

SummaryDue to large inter-individual variations, the dose of vitamin K antagonist required to target the desired hypocoagulability is hardly predictible for a given patient, and the time needed to reach therapeutic equilibrium may be excessively long. This work reports on a simple method for predicting the daily maintenance dose of fluindione after the third intake. In a first step, 37 patients were delivered 20 mg of fluindione once a day, at 6 p.m. for 3 consecutive days. On the morning of the 4th day an INR was performed. During the following days the dose was adjusted to target an INR between 2 and 3. There was a good correlation (r = 0.83, p<0.001) between the INR performed on the morning of day 4 and the daily maintenance dose determined later by successive approximations. This allowed us to write a decisional algorithm to predict the effective maintenance dose of fluindione from the INR performed on day 4. The usefulness and the safety of this approach was tested in a second prospective study on 46 patients receiving fluindione according to the same initial scheme. The predicted dose was compared to the effective dose soon after having reached the equilibrium, then 30 and 90 days after. To within 5 mg (one quarter of a tablet), the predicted dose was the effective dose in 98%, 86% and 81% of the patients at the 3 times respectively. The mean time needed to reach the therapeutic equilibrium was reduced from 13 days in the first study to 6 days in the second study. No hemorrhagic complication occurred. Thus the strategy formerly developed to predict the daily maintenance dose of warfarin from the prothrombin time ratio or the thrombotest performed 3 days after starting the treatment may also be applied to fluindione and the INR measurement.

Retrospective analysis of mortality within 30 days of systemic anticancer therapy and comparison with a previous audit at an Australian Regional Cancer Centre

2021 ◽  
pp. 107815522110160
Author(s):  
Bernadatte Zimbwa ◽  
Peter J Gilbar ◽  
Mark R Davis ◽  
Srinivas Kondalsamy-Chennakesavan
Keyword(s):  
Checkpoint Inhibitors ◽  
Anticancer Therapy ◽  
Mortality Rates ◽  
Feedback Process ◽  
Time To Death ◽  
Cancer Centre ◽  
Haematology Patients ◽  
The Mean ◽  
Regional Cancer Centre ◽  
Mean Time

Purpose To retrospectively determine the rate of death occurring within 14 and 30 days of systemic anticancer therapy (SACT), compare this against a previous audit and benchmark results against other cancer centres. Secondly, to determine if the introduction of immune checkpoint inhibitors (ICI), not available at the time of the initial audit, impacted mortality rates. Method All adult solid tumour and haematology patients receiving SACT at an Australian Regional Cancer Centre (RCC) between January 2016 and July 2020 were included. Results Over a 55-month period, 1709 patients received SACT. Patients dying within 14 and 30 days of SACT were 3.3% and 7.0% respectively and is slightly higher than our previous study which was 1.89% and 5.6%. Mean time to death was 15.5 days. Males accounted for 63.9% of patients and the mean age was 66.8 years. 46.2% of the 119 patients dying in the 30 days post SACT started a new line of treatment during that time. Of 98 patients receiving ICI, 22.5% died within 30 days of commencement. Disease progression was the most common cause of death (79%). The most common place of death was the RCC (38.7%). Conclusion The rate of death observed in our re-audit compares favourably with our previous audit and is still at the lower end of that seen in published studies in Australia and internationally. Cases of patients dying within 30 days of SACT should be regularly reviewed to maintain awareness of this benchmark of quality assurance and provide a feedback process for clinicians.

Vitamin D Level Stability in Dystrophinopathy Patients on Vitamin D Supplementation

2021 ◽  
pp. 1-7
Author(s):  
Naomi Vather-Wu ◽  
Matthew D. Krasowski ◽  
Katherine D. Mathews ◽  
Amal Shibli-Rahhal
Keyword(s):  
Vitamin D ◽  
Retrospective Cohort ◽  
Vitamin D Supplementation ◽  
Hydroxyvitamin D ◽  
Frequent Monitoring ◽  
25 Hydroxyvitamin D ◽  
The Mean ◽  
Stable Maintenance ◽  
Mean Time

Background: Expert guidelines recommend annual monitoring of 25-hydroxyvitamin D (25-OHD) and maintaining 25-OHD ≥30 ng/ml in patients with dystrophinopathies. Objective: We hypothesized that 25-OHD remains stable and requires less frequent monitoring in patients taking stable maintenance doses of vitamin D. Methods: We performed a retrospective cohort study, using the electronic health record to identify 26 patients with dystrophinopathies with a baseline 25-OHD ≥30 ng/mL and at least one additional 25-OHD measurement. These patients had received a stable dose of vitamin D for ≥3 months prior to their baseline 25-OHD measurement and throughout follow-up. The main outcome measured was the mean duration time the subjects spent with a 25-OHD ≥30 ng/mL. Results: Only 19% of patients dropped their 25-OHD to <  30 ng/ml, with a mean time to drop of 33 months and a median nadir 25-OHD of 28 ng/mL. Conclusions: These results suggest that measurement of 25-OHD every 2–2.5 years may be sufficient in patients with a baseline 25-OHD ≥30 ng/mL and who are on a stable maintenance dose of vitamin D. Other patients may require more frequent assessments.

scholarly journals Surveillance System in Smart Cities: A Dependability Evaluation Based on Stochastic Models

Electronics ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 876
Author(s):  
Igor Gonçalves ◽  
Laécio Rodrigues ◽  
Francisco Airton Silva ◽  
Tuan Anh Nguyen ◽  
Dugki Min ◽  
...  
Keyword(s):  
Surveillance System ◽  
Smart Cities ◽  
Heterogeneous Data ◽  
Time To Failure ◽  
Video Streams ◽  
Dependability Evaluation ◽  
The Mean ◽  
Mean Time ◽  
The Internet Of Things

Surveillance monitoring systems are highly necessary, aiming to prevent many social problems in smart cities. The internet of things (IoT) nowadays offers a variety of technologies to capture and process massive and heterogeneous data. Due to the fact that (i) advanced analyses of video streams are performed on powerful recording devices; while (ii) surveillance monitoring services require high availability levels in the way that the service must remain connected, for example, to a connection network that offers higher speed than conventional connections; and that (iii) the trust-worthy dependability of a surveillance system depends on various factors, it is not easy to identify which components/devices in a system architecture have the most impact on the dependability for a specific surveillance system in smart cities. In this paper, we developed stochastic Petri net models for a surveillance monitoring system with regard to varying several parameters to obtain the highest dependability. Two main metrics of interest in the dependability of a surveillance system including reliability and availability were analyzed in a comprehensive manner. The analysis results show that the variation in the number of long-term evolution (LTE)-based stations contributes to a number of nines (#9s) increase in availability. The obtained results show that the variation of the mean time to failure (MTTF) of surveillance cameras exposes a high impact on the reliability of the system. The findings of this work have the potential of assisting system architects in planning more optimized systems in this field based on the proposed models.

scholarly journals The impact of COVID-19 infection on hip fracture 30-day mortality

Trauma ◽  
2021 ◽  
pp. 146040862094972
Author(s):  
Ahmed Fadulelmola ◽  
Rob Gregory ◽  
Gavin Gordon ◽  
Fiona Smith ◽  
Andrew Jennings
Keyword(s):  
Hip Fracture ◽  
Hip Fractures ◽  
Hospital Admissions ◽  
The Elderly ◽  
Primary Outcome Measure ◽  
Time To Death ◽  
Significant Difference ◽  
The Mean ◽  
The Impact ◽  
Mean Time

Introduction: A novel virus, SARS-CoV-2, has caused a fatal global pandemic which particularly affects the elderly and those with comorbidities. Hip fractures affect elderly populations, necessitate hospital admissions and place this group at particular risk from COVID-19 infection. This study investigates the effect of COVID-19 infection on 30-day hip fracture mortality. Method: Data related to 75 adult hip fractures admitted to two units during March and April 2020 were reviewed. The mean age was 83.5 years (range 65–98 years), and most (53, 70.7%) were women. The primary outcome measure was 30-day mortality associated with COVID-19 infection. Results: The COVID-19 infection rate was 26.7% (20 patients), with a significant difference in the 30-day mortality rate in the COVID-19-positive group (10/20, 50%) compared to the COVID-19-negative group (4/55, 7.3%), with mean time to death of 19.8 days (95% confidence interval: 17.0–22.5). The mean time from admission to surgery was 43.1 h and 38.3 h, in COVID-19-positive and COVID-19-negative groups, respectively. All COVID-19-positive patients had shown symptoms of fever and cough, and all 10 cases who died were hypoxic. Seven (35%) cases had radiological lung findings consistent of viral pneumonitis which resulted in mortality (70% of mortality). 30% ( n = 6) contracted the COVID-19 infection in the community, and 70% ( n = 14) developed symptoms after hospital admission. Conclusion: Hip fractures associated with COVID-19 infection have a high 30-day mortality. COVID-19 testing and chest X-ray for patients presenting with hip fractures help in early planning of high-risk surgeries and allow counselling of the patients and family using realistic prognosis.

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