MAT-719: INVESTIGATION OF GROUTED PRECAST CONCRETE WALL CONNECTIONS AT SUBFREEZING CONDITIONS

The effect of exposing grouted precast wall connections to subfreezing curing temperatures at early-age was explored in this study. In cold weather construction, heating of the surrounding environment of grouted precast wall connections is usually conducted for short periods of time. Hence, subfreezing conditions can affect the strength of the grout and the bond strength of the connection, which can ultimately compromise the integrity of the structure. In this study, grout specimens typical of that used in precast wall construction were cured at ambient conditions for one day, and then placed in an environmental chamber at subfreezing temperatures (-10°C and -20°C). The compressive strength development of the grout was monitored, and the bond strength of grouted connections cured at cold temperature were quantified and compared to that of specimens cured at ambient temperature. The bond was investigated on 25M deformed steel bars, which is the typical size used in precast concrete wall grouted connections. Test results indicate a reduction in grout strength and the need for a longer embedment length when early-age curing is conducted at subfreezing conditions

Vacancy complexes in nonequilibrium germanium-tin semiconductors

Understanding the nature and behavior of vacancy-like defects in epitaxial GeSn metastable alloys is crucial to elucidate the structural and optoelectronic properties of these emerging semiconductors. The formation of vacancies and their complexes is expected to be promoted by the relatively low substrate temperature required for the epitaxial growth of GeSn layers with Sn contents significantly above the equilibrium solubility of 1 at.%. These defects can impact both the microstructure and charge carrier lifetime. Herein, to identify the vacancy-related complexes and probe their evolution as a function of Sn content, depth-profiled pulsed low-energy positron annihilation lifetime spectroscopy and Doppler broadening spectroscopy were combined to investigate GeSn epitaxial layers with Sn content in the 6.5-13.0 at.% range. The samples were grown by chemical vapor deposition method at temperatures between 300 and 330 {\deg}C. Regardless of the Sn content, all GeSn samples showed the same depth-dependent increase in the positron annihilation line broadening parameters, which confirmed the presence of open volume defects. The measured average positron lifetimes were the highest (380-395 ps) in the region near the surface and monotonically decrease across the analyzed thickness, but remain above 350 ps. All GeSn layers exhibit lifetimes that are 85 to 110 ps higher than the Ge reference layers. Surprisingly, these lifetimes were found to decrease as Sn content increases in GeSn layers. These measurements indicate that divacancies are the dominant defect in the as-grown GeSn layers. However, their corresponding lifetime was found to be shorter than in epitaxial Ge thus suggesting that the presence of Sn may alter the structure of divacancies. Additionally, GeSn layers were found to also contain a small fraction of vacancy clusters, which become less important as Sn content increases

MAT-723: BOND BEHAVIOUR OF GROUTED CONNECTIONS UNDER MONOTONIC TENSILE LOADS

Grouted bar-in-conduit connections are versatile connections widely used in the precast concrete construction. In precast load bearing wall structures, two vertical wall panels are connected by a reinforcing bar, which is projected from one panel and grouted into a sleeve placed in the other. The main function of the ties is to resist tension induced by in-plane and out-of-plane straining actions and to provide ductility to the wall assembly through the yielding of the reinforcement. Limited information is currently available on the behaviour of such connections. This paper presents the findings of an investigation conducted to investigate the behaviour of grouted reinforcing bar connections and their failure mechanisms. The bond strength was evaluated using a pull-out test on a bar extended from a grouted sleeve specimen. The test parameters of the study were the bar surface condition (deformed and smooth) and the embedded length (6, 12 and 36 diameter-of-bar (db)). A total of eight specimens were tested to failure under direct tensile loads and the slip of the bars was recorded. Results indicate that an embedment length of 6db allowed the bar to yield, but bond failure dominated in the strain hardening zone. It was also observed that an embedment length of 12db was sufficient to mobilize the tensile capacity of the bar, after which an increase in the grouted sleeve length resulted in no additional capacity

A New Method for Grain Texture Manipulation in Post-Deposition Niobium Films

Niobium films are frequently grown using forms of energetic condensation, with modest substrate temperatures to control grain structure. As an alternative, energetic deposition onto a cold substrate results in a dense amorphous film, with a much larger energy density than the re-crystallized state. Re-crystallization is then performed using a pulsed UV (HIPPO) laser, with minimal damage to the substrate. In addition, a graded interface between the substrate and Nb film is created during the early stages of energetic deposition. Experimental approach and apparatus are described

Isoeugenol is a selective potentiator of camptothecin cytotoxicity in vertebrate cells lacking TDP1

Camptothecin (CPT), a topoisomerase I (TOP1) inhibitor, exhibits anti-tumor activity against a wide range of tumors. Redundancy of TOP1-mediated repair mechanisms is a major challenge facing the efficiency of TOP1-targetting therapies. This study aims to uncover new TOP1 targeting approaches utilising a selection of natural compounds in the presence or absence of tyrosyl DNA phosphodiesterase I (TDP1); a key TOP1-mediated protein-linked DNA break (PDB) repair enzyme. We identify, isoeugenol, a phenolic ether found in plant essential oils, as a potentiator of CPT cytotoxicity in Tdp1 deficient but not proficient cells. Consistent with our cellular data, isoeugenol did not inhibit Tdp1 enzymatic activity in vitro nor it sensitized cells to the PARP1 inhibitor olaparib. However, biochemical analyses suggest that isoeugenol inhibits TDP2 catalytic activity; a pathway that can compensate for the absence of TDP1. Consistent with this, isoeugenol exacerbated etoposide-induced cytotoxicity, which generates TOP2-mediated PDBs for which TDP2 is required for processing. Together, these findings identify isoeugenol as a potential lead compound for developing TDP2 inhibitors and encourage structure-activity relationship studies to shed more light on its utility in drug discovery programs

Surface Morphology of Laser-Superheated Pb(111) and Pb(100)

The surface step density on the vicinal Pb(111) and the surface vacancy density on Pb(100) after laser superheating and melting are investigated using reflection high-energy electron diffraction. With ∼100-ps laser pulses, Pb(111) surface superheating does not significantly change the density of the steps and step-edge roughness. However, after laser surface melting, the average terrace width and the string length at the step edge become as large as those at room temperature. The average terrace width at 573 K changes from 38±15 to 64±19 Å after laser surface melting, while the average string length at the step edge changes from 90±14 to 250±38 Å. For Pb(100), the surface vacancy density remains unchanged when the surface is superheated without melting. However, when the laser fluence is high enough to cause surface melting, the surface vacancy density increases. This increase in vacancy density is attributed to fast diffusion of atoms in the liquid film formed on Pb(100) during laser melting

Preliminary report on theNeurology workload ina central hospital in Sudan.

Introduction: Identification of the local pattern of neurological diseases is expected to help setting the priorities for good planning of management and public education.Objectives: To identify the pattern of neurological disorders in a second biggest central hospital in Sudan.Methodology: Review of the diagnosis of 170 patients, seen in the out patients neuro-clinic and the neurology ward from March 2010 to February 2011, was done. Patients who were in follow up by other neuro-clinics were excluded.Results: The male to female ratio was 1:1 Patients who were 20-60 years old comprised 54%.About 50% of patients live in Omdurman city. Motor symptoms were the most common presenting symptoms forming 64.1% followed by cranial nerves symptoms 27.6%. Stroke was the commonestencountered diagnosis seen in 20.7%, followed by epilepsy in 16.6%, headache in 9.6%, movement disorders in 7.7%, peripheral neuropathy in 3.6%, demylination in 1.8%, cerebral venous sinus thrombosis (CVST) 1.8% and tumours in 1.2% patients. Stroke was more common in patients from East Sudan and Epilepsy was more common in patients from West Sudan. Vascular and degenerative changes were the commonest abnormalities seen in imaging studies. Demyelination and neoplasms were more common in females.Conclusion: Stroke, epilepsy and headache were the commonest neurological disorders met in Omdurman Teaching Hospital.Key words: general hospital, neurology department, neurological disorders

Evidence for dissociable cognitive and neural pathways from poverty versus maltreatment to deficits in emotion regulation

Poverty and threat exposure (TE) predict deficits in emotion regulation (ER). Effective cognitive ER (i.e., reappraisal) may be supported by: (1) cognitive processes implicated in generating and implementing cognitive reappraisal, supported by activation in brain regions involved in cognitive control (e.g., frontal, insular, and parietal cortices) and (2) emotion processing and reactivity, involving identification, encoding, and maintenance of emotional states and related variation in brain activity of regions involved in emotional reactivity (i.e., amygdala). Poverty is associated with deficits in cognitive control, and TE with alterations in emotion processing and reactivity. Our goal was to identify dissociable emotional and cognitive pathways to ER deficits from poverty and TE. Measures of cognitive ability, emotional processing and reactivity, ER, and neural activity during a sadness ER task, were examined from a prospective longitudinal study of youth at risk for depression (n = 139). Both cognitive ability and left anterior insula extending into the frontal operculum activity during a sadness reappraisal task mediated the relationship between poverty and ER. Emotion processing/reactivity didn\u27t mediate the relationship of TE to ER. Findings support a cognitive pathway from poverty to ER deficits. They also underscore the importance of dissociating mechanisms contributing to ER impairments from adverse early childhood experiences

Lymphocyte subtype dysregulation in a group of children with simple obesity

Background: Obesity as a global public health problem is increasing in prevalence. Reports showed that obese children are more liable to infection than lean ones; it was claimed that obese subjects have altered peripheral blood total lymphocyte counts in addition to reduced lymphocyte proliferative response to mitogen stimulation as well as dysregulated cytokine expression.Objective: This study aimed to evaluate the effect of childhood obesity on cell mediated immunity as indicated by peripheral blood lymphocyte phenotyping.Methods: We enrolled 30 school-aged children (mean age 10±3.27 years). They comprised two groups; 20 obese children with a mean body mass index (BMI) of 39.2± 12.5 and 10 matched control subjects with mean BMI of 18.4± 1.9. They were subjected to detailed anthropometric evaluation including weight, height, and waist hip ratio in addition to calculation of BMI, complete blood counting, and flow cytometric assessment of T-helper (CD4), T-cytotoxic/suppressor (CD8), and natural killer (CD56) cell counts .Results: The absolute lymphocyte (CD3) and natural killer cell (CD56) counts were comparable in both groups. However, the CD4%, CD8%, CD4/CD8 ratio were significantly lower in the obese children (p=0.02, 0.03, 0.015 respectively). A significant negative correlation could be elicited between the CD4 count and bodyweight, BMI, and hip waist ratio (p = 0.00); the same was observed for CD4/CD8 ratio (p = 0.00). On the contrary, CD8 correlated positively to the bodyweight, BMI, and waist hip ratio (p = 0.00 for each) .Conclusion: Obesity has an impact on lymphocytic subset counts and further studies are needed to assess its effect on their function.Keywords: obesity, children immunology; CD markers; lymphocytes; BM