An Experimental Analysis of Embankment on Stone Columns

When embankment is constructed on very soft soil, special construction methods are adopted. One of the techniques is a piled embankment. Piled (stone columns) embankments provide an economic and effective solution to the problem of constructing embankments over soft soils. This method can reduce settlements, construction time and cost. Stone columns provide an effective improvement method for soft soils under light structures such as rail or road embankments. The present work investigates the behavior of the embankment models resting on soft soil reinforced with stone columns. Model tests were performed with different spacing distances between stone columns and two lengths to diameter ratios of the stone columns, in addition to different embankment heights. A total number of 21 model tests were carried out on a soil with undrianed shear strength ≈ 10 kPa. The models consist of stone columns embankment at spacing to diameter ratio equal to 2.5, 3 and 4. Three embankment heights; 200 mm, 250 mm and 300 mm were conducted. Three earth pressure cells were used to measure directly the vertical effective stress on column at the top of the middle stone column under the center line of embankment and on the edge stone column for all models while the third cell was placed at the base of embankment between two columns to measure the vertical effective stress in reinforced soft soil directly. The embankment models constructed on soft clay treated with ordinary stone columns at spacing ratio equal 2.5 revealed maximum bearing improvement ratio equals (1.21, 1.44 and 1.7) for 200 mm, 250 mm and 300 embankment heights, respectively and maximum settlement improvement ratio equals (0.78, 0.67 and 0.56) for 200 mm, 250 mm and 300 embankment heights, respectively

The effect of ZnO addition on the phase transformation, microstructure, and ionic conductivity of 8YSZ ceramics

In this paper the effect of zinc oxide (ZnO) addition on the phase transformation and ionic conductivity of 8 mol % Yttria-stabilised Zirconia (8YSZ) is investigated. Pure 8YSZ and ZnO doped YSZ ceramics are prepared using the solid state reaction method sintered at 1550°C for 2 hours. The X-ray Diffraction (XRD) results reveal the presence of tetragonal, cubic and monoclinic phase of Zirconium dioxide (ZrO2) for all undoped and doped YSZ sintered samples. The phase stability of tetragonal YSZ was found to be increased with the increase in ZnO addition. Minor fraction of monoclinic phase was found in pure YSZ sintered sample and the amount of monoclinic phase decreased with the increasing amount of Zn after sintering at 1550°C for 2 hours. The fraction of cubic phase was also found to decrease with the increase in Zn concentration. The highest ionic conductivity of 1.03×10−3 S cm−1 was obtained at room temperature for samples with 3 mol% ZnO. Pure 8YSZ sintered sample on the other hand, yielded 9.88x10−4 S cm−1

Dementia due to hippocampal sclerosis: Clinical features and comparison to Alzheimer’s disease

OBJECTIVE: To define the clinical and neuropsychological features of dementia due to hippocampal sclerosis (HS) and to compare it to Alzheimer's disease (AD). BACKGROUND: Several autopsy studies have identified HS as an etiology of dementia in the elderly. More recently, dementia due to HS was found to be frequently misdiagnosed as AD. In this study, we attempt to differentiate HS dementia from AD using data collected from subjects enrolled at the Johns Hopkins Alzheimer's Disease Research Center. DESIGN/METHODS: Eight cases of HS and 84 cases of definite AD were included in the study. All 84 AD cases were diagnosed using CERAD criteria and were free of additional pathology. HS was defined by a combination of neuronal loss and gliosis in the hippocampus in the absence of senile plaques, neurofibrillary tangles, or other potential causes of dementia. All subjects were followed longitudinally until death. Data was collected at 6-month intervals. Mean scores on several clinical and cognitive measures from both groups were compared at study entry using the Wilcoxon Rank Sum (nonparametric) test. A group of 23 AD subjects, matched with the HS group on MMSE at study entry, were used for analysis of rate of decline. A weighted regression procedure was used for the latter analysis. RESULTS: The HS group did not differ significantly from the AD group in age at onset, duration of illness prior to study entry, age at death, or education level. At study entry, the HS group had significantly(p<0.05) better test scores on several measures including the Mini-Mental State Exam (MMSE), verbal fluency task, Boston Naming Test, and the orientation subscale of the Psychogeriatric Dependency Rating Scale (PGDRS). There were no significant differences on the physical and behavior subscales of the PGDRS, nor on the Hamilton Depression Scale. Analysis of rate of decline showed significantly slower cognitive decline over 5 years in the HS group, notably on the MMSE (-0.90 points/yr in HS vs. -2.80 points/yr in AD, p<0.01). Surprisingly, the HS group slightly improved on the Boston Naming Test during follow-up (0.26 points/yr in HS vs. -3.2 points/yr in AD, p<0.01). CONCLUSIONS: Dementia due to hippocampal sclerosis appears to be clinically different from Alzheimer's disease. Particularly, patients with HS appear to have slower cognitive decline than AD patients. Larger studies are needed to further characterize HS dementia

Influence of Sintering Temperature on Crystallization Behavior of Cordierite synthesized from Non-Stoichiometric Formulation

Cordierite body with formulation of non-stoichiometric composition (2.5 MgO. 1.8 Al2O3. 5 SiO2) was synthesized using conventional techniques with standard raw materials. The sintering and crystallization behavior of the compositions was observed by Differential Thermal Analysis and Thermogravimetric Analysis (DTA/TG). The sequence of reaction and phase transformation was analyzed using X-ray Diffraction (XRD) technique and Rietveld structural refinement after sintering the samples at different temperature regarding the information from the DTA. The Scanning electron microscopy (SEM) was employed for morphology analysis. The DTA curve shows the crystallization temperature, Tc occur at 1259°C.Rietveld quantitative phase analysis results reveal that α phase Cordierite constitutes up to 96.4 wt% when the samples was sintered for 2 hours at the optimal temperature of 1375°C. The SEM micrograph revealed that the sample was heat treated at 1375°C obtained densified body with well alignment of crystal structure

Influence of Sintering Temperature on Crystallization Behavior of Cordierite synthesized from Non-Stoichiometric Formulation

Cordierite body with formulation of non-stoichiometric composition (2.5 MgO. 1.8 Al2O3. 5 SiO2) was synthesized using conventional techniques with standard raw materials. The sintering and crystallization behavior of the compositions was observed by Differential Thermal Analysis and Thermogravimetric Analysis (DTA/TG). The sequence of reaction and phase transformation was analyzed using X-ray Diffraction (XRD) technique and Rietveld structural refinement after sintering the samples at different temperature regarding the information from the DTA. The Scanning electron microscopy (SEM) was employed for morphology analysis. The DTA curve shows the crystallization temperature, Tc occur at 1259°C.Rietveld quantitative phase analysis results reveal that α phase Cordierite constitutes up to 96.4 wt% when the samples was sintered for 2 hours at the optimal temperature of 1375°C. The SEM micrograph revealed that the sample was heat treated at 1375°C obtained densified body with well alignment of crystal structure

Fabrication and morphological characterization of Biopolymer particles formed by electrostatic complexation of heat treated Lactoferrin and Anionic Polysaccharides

Biopolymer particles fabricated from proteins and/or polysaccharides can be used to encapsulate functional components or to modify various functional properties of materials. In this study, sub-micrometer biopolymer particles were fabricated by electrostatic complexation of heat-denatured protein (lactoferrin, LF) particles with anionic polysaccharides (alginate, carrageenan, or pectin). The aim of the study was to exploit macromolecular electrostatic interactions to form sub-micrometer sized particles and study their stability and morphological characteristics. Initially, protein particles were formed by heat treatment (91 °C, 20 min) of a lactoferrin solution (0.2% LF, pH 7), which led to a suspension of protein particles with mean diameter of 200−400 nm and isoelectric point of pI ≈ 8.5. Biopolymer particles were then formed by mixing the protein particles with anionic polysaccharides at pH 8 and then lowering the pH to promote electrostatic deposition of polysaccharides onto the protein particle surfaces. The influence of pH (2−11) and ionic strength (0−200 mM NaCl) on the properties and stability of the complexes was studied using turbidity, dynamic light scattering, and electrophoresis measurements. Relatively stable particles could be formed from pH 5 to 8, but appreciable aggregation occurred at lower pH which was attributed to charge neutralization and bridging effects. LF−pectin complexes were relatively stable to salt addition, but LF−carrageenan and LF−alginate complexes exhibited aggregation at higher salt concentrations. These results have important implications for the application of lactoferrin−polysaccharide complexes as functional components in commercial products, such as pharmaceuticals, personal care products, and foods