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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
131

The effect of real time and accelerated aging on the physical and mechanical properties of YTTRIA partially stabilized zirconia

Alalawi, Haidar Ali 22 May 2020 (has links)
OBJECTIVES: To evaluate accelerated and real time aging effect on microstructure and mechanical properties of different types of zirconia’s with various surface treatments. METHODS: In this in-vitro study 830 discs were prepared from four Y-TZP based materials. These materials were TZ-3YSB-E, ZPex®, ZPex® Smile (Tosoh Corporation, Japan), and Cercon®xt extra translucent zirconia (Dentsply-Sirona). Final dimensions of each specimen disc were about 15 mm in diameter and 1.5 mm thick. An accelerated aging process for 5, 24, and 168 hours of steam aging at 134°C under a pressure of 0.2 MPa was applied to the specimens. Real time aging was performed for one year in normal saline solution at 37°C in an incubator. Sandblasting was performed using a PrepStar® system with Al2O3 50μm particle size at pressure of 60 psi, rate 4.2 gram/minute. Grinding with a Buehler AutoMet 250 was performed using a 240 μm diamond disc with a 0.0034 kg/mm2 load and speed of 120 rpm for two minutes. Bruker D8 advance diffractometer was used for the acquisition of X-ray diffraction (XRD) spectrum. Biaxial flexural strength was determined using a ball-on-three-balls configuration in a universal testing machine. Scanning Electron Microscopy (SEM) was used to examine the sample's surface topography. RESULTS: The results of this study show that the zirconia materials with smaller grain size have higher flexural strength. Sandblasting and grinding treatment increases the tensile flexural strength of TZ-3YSB-E and ZPex® compared to the controlled group of the same material. XRD analysis shows that TZ-3YSB-E at room temperature does not have any monoclinic phase before surface treatment and it increased after aging, sandblasting and grinding. Cercon®xt has the highest amount of cubic phase and it increases with surface treatment. CONCLUSION: Sandblasting surface treatment should not be applied to all types of zirconia and it has to be material specific. Within the scope of this study, accelerated aging process did not affect the grain size of all materials control groups. The smaller grain size of zirconia is correlated to higher flexural strength of the material. The smaller amount of cubic phase present is correlated to higher biaxial flexural strength.
132

Clinical Commentary: Benefits from Treatment Do Not Outweigh Risks Unless Maternal BP Moderately High

Holt, Jim 01 June 2004 (has links)
Excerpt: I have always felt uneasy with treatment of mild to moderate hypertension in pregnancy, as chronic hypertension must be differentiated from preeclampsia; and the treatments seem counterintuitive.
133

Influence of Various Surface Treatments on Power Losses of Spur Gear Pairs

Jaiswal, Preetish 21 September 2017 (has links)
No description available.
134

Pretest CS Cueing Facilitates the Recovery of Avoidance Behavior Following Visual Cortex Lesions in the Rat

Fritts, Mary E., Asbury, E. Trey, Isaac, Walter L. 15 February 1998 (has links)
Rats were trained on a four-way shuttle box with a compound light-tone conditioned stimulus (CS) until they emitted 7 avoidance responses in 10 trials (7/10) prior to bilateral ablation of the visual cortex or sham surgery. On Day 5 after surgery, rats were cued with either the compound light-tone CS, the light or tone portion of the CS only, or had no exposure to the CS. On Day 10 after surgery, all animals were tested for avoidance retention under the same conditions as preoperative training. The findings indicate that following a lesion, cueing with the light-tone compound CS facilitates performance as does light alone. Cueing to the tone alone has no effect. In sham animals, only cueing with the light-tone CS was effective in enhancing avoidance retention. Results are interpreted as early and modality-specific sensory cueing may facilitate the recovery process.
135

Comparative Efficacy of LEAP, TEACCH and Non-Model-Specific Special Education Programs for Preschoolers With Autism Spectrum Disorders

Boyd, Brian A., Hume, Kara, McBee, Matthew T., Alessandri, Michael, Gutierrez, Anibal, Johnson, Le Anne, Sperry, Laurie, Odom, Samuel L. 01 January 2014 (has links)
LEAP and TEACCH represent two comprehensive treatment models (CTMs) that have been widely used across several decades to educate young children with autism spectrum disorders. The purpose of this quasi-experimental study was to compare high fidelity LEAP (n = 22) and TEACCH (n = 25) classrooms to each other and a control condition (n = 28), in which teachers in high quality special education programs used non-model-specific practices. A total of 198 children were included in data analysis. Across conditions, children's performances improved over time. This study raises issues of the replication of effects for CTMs, and whether having access to a high quality special education program is as beneficial as access to a specific CTM.
136

The effect of saliva contamination and different surface treatments on the shear bond strength of two resin cements to zirconia

Radain, Sora 02 July 2018 (has links)
OBJECTIVES: The purpose of this study was to investigate the influence of saliva contamination and subsequent surface treatments on the shear bond strength of two different resin cements to zirconia. MATERIALS AND METHODS: One hundred sintered zirconia specimens were divided into two groups (n=50), one for each resin cement to be tested. Each group was divided into five sub-groups (n=10) based on the surface treatment the zirconia plates were going to receive; namely control (CL), saliva contaminated (SC), water washed (WW), Ivoclean (IC) and air abrasion (AA). In the control group, no contamination or surface treatment was performed. Specimen surfaces of the rest of the experimental groups were contaminated with saliva, and then submitted to drying with air only (SC); washed with water (WW); treated with Ivoclean cleaning paste (IC); or sandblasted with aluminum oxide particles (Al2O3) (AA). Multilink Automix (MA) and RelyX Ultimate (RU) resin cement cylinders were made and bonded to conditioned zirconia specimens using the Ultradent jig method. All bonded specimens were placed inside glass containers filled with deionized water inside an incubator at 37 °C for 24 h. After 24 h, the shear bond strength of the bonded specimens was tested using an Instron Universal Testing Machine with a crosshead speed of 0.5 mm/minutes. Statistical analysis was performed by ANOVA and data were analyzed with Tukey-Kramer HSD multiple comparison tests at the 0.05 level of significance. RESULTS: Within the limitations of this in vitro study, it was determined that saliva contamination significantly reduced resin bond strengths to zirconia ceramic. Airborne-particle abrasion was the most effective cleaning and surface treatment. It significantly increased the shear bond strength of (MA) (13.73 ± 1.39 MPa) and (RU) (6.34± 0.8 MPa). The IC was effective in removing saliva contamination and enhancing the resin bond strength of (MA) (10.9 ± 1.28 MPa) and (RU) (3.1± 0.16MPa). Water did not remove saliva contamination and did not improve (RU) bond strength to zirconia (1.73 ± 0.25 MPa). There was no significant difference (p>0.05) between the shear bond strengths of (MA), water washing (4.7± 0.64 MPa), and control groups (4.9± 0.27 MPa). CONCLUSIONS: If contamination occurs, a surface treatment is required to guarantee an adequate interaction between the resin cement and the zirconia surface. Airborne-particle abrasion and Ivoclean surface treatments are effective in removing saliva contamination and enhancing the resin bond strength. Washing with water alone did not improve resin bond strength.
137

The Effects of Chemical and Cultural Treatments on Gibberlin Levels in Strawberry Leaves and on the Induction of Secondary Flowering

Arteca, Richard N. 01 May 1976 (has links)
Gibberellins 3, 4 and 7 were isolated from "Shasta" Strawberry (Fragaria X ananassa Duch.) leaves and identified by gas and thin layer chromatography. In young expanding leaves GA3 occurred at 5 times the concentration of either GA4 or GA7. CCC (2-chloroethyl-trimethylammonium chloride), SADH (Succinamic acid-2,2-dimethyl hydrazide), ethephon (2-chloroethylphosphonic acid), and UBI-P293 (2,3-dihydro-5-6-diphenyl-1,4-oxathiin) were applied to established plantings of three June-bearing strawberry (Fragaria X ananassa Ouch.) cultivars: 11 Shasta, 11 "Fresno" and "Tioga." Treatments were applied on alternate days for three weeks following anthesis of the king blossom. Levels of GA3 and GA4 were reduced by all treatments, but GA7 occurred at such low concentrations that treatment effects could not be measured statistically. Three weeks' exposure to short-daylengths (8 hours of light and 16 hours of darkness) resulted in no change in GA3 or GA7, but GA4 concentrations were significantly reduced . Leaf tissue was analyzed t o e valuate treatment effects on chlorophyll content; no significant changes were observed. No secondary flowering as a result of photoperiod , post-harvest defoliation or growth retardant treatments was observed.
138

Physicochemical Modifications of Milk Fat Globule Membrane Proteins During Temperature Processing of Milk

Yu, Feiran January 2018 (has links)
No description available.
139

Postemergence Control of Palmer Amaranth with Mesotrione-Based Herbicide Mixtures and the Impact of Lactofen and Planting Date on the Growth, Development, and Yield of Indeterminate Soybean

Mangialardi, Joseph Paul 14 August 2015 (has links)
Research was conducted in 2013 and 2014 to evaluate the postemergence control of Palmer amaranth [Amaranthus palmeri (S.) Wats.] with mesotrione alone and in mixtures with fomesafen and/or glyphosate and to evaluate the impact of lactofen and planting date on growth, development, and yield of indeterminate soybean [Glycine max (L.) Merr.]. Studies included a greenhouse evaluation of different rates of mesotrione on the control of 5- and 10-cm Palmer amaranth and field studies evaluating the control of 5- to 10-cm Palmer amaranth with three rates of mesotrione applied alone and in mixtures with fomesafen and/or glyphosate. Lactofen studies include a planting date study evaluating one rate of lactofen applied at V2 soybean stage with planting dates of April 15, May 1, May 15, and June 1 and a lactofen timing study where one rate of lactofen was applied at soybean growth stages ranging from V1 to R5.
140

Management Practices for Corn Producers Implementing Early Planting as a Production Strategy

Hock, Matthew W 08 December 2017 (has links)
Producers choosing to implement an early corn planting management strategy often experience several yield limiting biotic and abiotic factors. Field variability, flooding, sub-optimal soil temperatures which leads to poor nutrient uptake, delayed emergence and reduced root growth can limit grain production. Three separate experiments were conducted to address some of the negative effects associated with early corn planting. Experiment 1 evaluated flooding effects on several morpho-physiological traits including root system architecture during early crop development. Hybrids (DKC 6208, Pioneer 1197) were flooded at planting (V0) and growth stages V1, V2, V3 for 0, 6, 12, 24, 48, 96 hours. Plants flooded at V0 11% suffered the steepest decline in collar height. Plants flooded at V2 10% were more susceptible than plants flooded V1 4%. Overall, there was a linear decline in nutrient concentration if flooding occurred at planting. Tissue Na levels were the most affected by flood duration and K was the least affected. Experiment 2 evaluated biologic compounds developed to increase immobile nutrients P and K to improve fertilizer use efficiency and provide slow developing roots essential nutrients. The effectiveness of microbial products (B-300, QR, Mammoth, EM-1) with/without starter fertilizer influenced yield, emergence, plant growth, and nutrient uptake. Biologic seed treatments compared to the control, resulted in a positive yield advantage for all treatments. Yields ranged from 37 to 48% higher if biologic compounds were applied. On average, yields increased from 26 to 38% after starter fertilizer was added to the biologic compounds. Phosphorus levels at VT were significantly higher for QR and K content was higher for B300, SF-B300, QR, Mamm, and SF-Mamm compared to the control. Experiment 3 addressed soil physical/chemical properties affecting plant development and there yield plant density relationship. On average, yields significantly increased 40% as plant population increased from 49,400 to 103,740 plants ha−1. Based on the quadratic model agronomically yields would be highest at 61,360 plants ha−1. Correlation analysis among yield and soil physical and chemical properties revealed positive correlations for grain yield, sand% (r2 = 0.42), soil K (r2 = 0.17) soil Na (r2 = 0.46), and soil P (r2 = 0.49).

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