2,523 research outputs found
AA-stacked bilayer square ice between graphene layers?
Water confined between two layers with separation of a few Angstrom forms
layered two- dimensional ice structure. Using large scale molecular dynamics
simulations with the adoptable ReaxFF interatomic potential we found that flat
monolayer ice with a rhombic-square structure nucleates between graphene layers
which is non-polar and non-ferroelectric. Two layers of water are found to
crystallize into a square lattice close to the experimental found AA-stacking
[G. Algara- Siller et al. Nature 519, 443445 (2015)]. Each layer has a net
dipole moment which are in opposite direction. Bilayer ice is also non-polar
and non-ferroelectric. For three layer ice we found that each layer has a
crystal structure similar to monolayer ice
Strain engineered graphene using a nanostructured substrate: I Deformations
Using atomistic simulations we investigate the morphological properties of
graphene deposited on top of a nanostructured substrate. Sinusoidally
corrugated surfaces, steps, elongated trenches, one dimensional and cubic
barriers, spherical bubbles, Gaussian bump and Gaussian depression are
considered as support structures for graphene. The graphene-substrate
interaction is governed by van der Waals forces and the profile of the graphene
layer is determined by minimizing the energy using molecular dynamics
simulations. Based on the obtained optimum configurations, we found that: (i)
for graphene placed over sinusoidally corrugated substrates with corrugation
wave lengths longer than 2\,nm, the graphene sheet follows the substrate
pattern while for supported graphene it is always suspended across the peaks of
the substrate, (ii) the conformation of graphene to the substrate topography is
enhanced when increasing the energy parameter in the van der Waals model, (iii)
the adhesion of graphene into the trenches depends on the width of the trench
and on graphene's orientation, i.e. in contrast to a small width (3 nm)
nanoribbon with armchair edges, the one with zig-zag edges follows the
substrate profile, (iv) atomic scale graphene follows a Gaussian bump substrate
but not the substrate with a Gaussian depression, and (v) the adhesion energy
due to van der Waals interaction varies in the range [0.1-0.4] J/m^2.Comment: 12 pages and 16 figures, To appear in Phys. Rev.
EFFECT OF DIABETES MELLITUS TYPE II ON ACTIVATED PARTIAL THROMBOPLASTIN TIME AND PROTHROMBIN TIME
Diabetes mellitus contributes for initiation and progression of micro vascular and macro vascular complications. Complication includes coagulation impairment however Shortened activated partial thromboplastin time (aPTT) values may reflect hypercoaguable state, which is associated with increased thrombotic risk and adverse cardiovascular events. Objective: The present study was conducted to study the aPTT and PT levels in patients with diabetes mellitus type II. Material and method: A sample of 50 persons were selected, 30 patients suffering from DM as type II from Al-wahda teaching hospital, Derna-Libya. At the same time a group of 20 randomly selected healthy adults to participate in the study as control group. Result: The mean value of APTT in T2DM individuals was significant lower (28.95 ±7.54) seconds as compare with control, (34.12±2.82) seconds (P = 0.06). Â The mean value of prothrombin time (PT) among T2DM individuals was (14.04 ±2.96) seconds and the mean value of PT among healthy individuals was (13.5 ± 1.54) seconds. There was no significant difference in PT of T2DM individuals P < 0.05. Conclusion: From this study, it may be concluded that shorted APTT confirms that T2DM is a hyper-coagulable state due to which there is increased risk of thrombotic events
EFFECT OF DIABETES MELLITUS TYPE II ON ACTIVATED PARTIAL THROMBOPLASTIN TIME AND PROTHROMBIN TIME
Diabetes mellitus contributes for initiation and progression of micro vascular and macro vascular complications. Complication includes coagulation impairment however Shortened activated partial thromboplastin time (aPTT) values may reflect hypercoaguable state, which is associated with increased thrombotic risk and adverse cardiovascular events. Objective: The present study was conducted to study the aPTT and PT levels in patients with diabetes mellitus type II. Material and method: A sample of 50 persons were selected, 30 patients suffering from DM as type II from Al-wahda teaching hospital, Derna-Libya. At the same time a group of 20 randomly selected healthy adults to participate in the study as control group. Result: The mean value of APTT in T2DM individuals was significant lower (28.95 ±7.54) seconds as compare with control, (34.12±2.82) seconds (P = 0.06). Â The mean value of prothrombin time (PT) among T2DM individuals was (14.04 ±2.96) seconds and the mean value of PT among healthy individuals was (13.5 ± 1.54) seconds. There was no significant difference in PT of T2DM individuals P < 0.05. Conclusion: From this study, it may be concluded that shorted APTT confirms that T2DM is a hyper-coagulable state due to which there is increased risk of thrombotic events
Thermomechanical properties of a single hexagonal boron nitride sheet
Using atomistic simulations we investigate the thermodynamical properties of
a single atomic layer of hexagonal boron nitride (h-BN). The thermal induced
ripples, heat capacity, and thermal lattice expansion of large scale h-BN
sheets are determined and compared to those found for graphene (GE) for
temperatures up to 1000 K. By analyzing the mean square height fluctuations and the height-height correlation function we found that the h-BN
sheet is a less stiff material as compared to graphene. The bending rigidity of
h-BN: i) is about 16% smaller than the one of GE at room temperature (300 K),
and ii) increases with temperature as in GE. The difference in stiffness
between h-BN and GE results in unequal responses to external uniaxial and shear
stress and different buckling transitions. In contrast to a GE sheet, the
buckling transition of a h-BN sheet depends strongly on the direction of the
applied compression. The molar heat capacity, thermal expansion coefficient and
the Gruneisen parameter are estimated to be 25.2 J\,mol\,K,
7.2K and 0.89, respectively
Stakeholder Perception of Service Quality in Qatar Higher Education Institutions: An Application to Qatar University
Managing quality of services offered by institutions of higher education is important in any country due to the inherent aim of producing quality graduates from programs offered in the university. Qatar has made substantial investments in higher education. Qatar University, being the national university of the country, the perception of stakeholders on the service quality in education becomes an important factor for developing a quality education system. Therefore, the main goal of this thesis is studying the perceptual context of quality of services provided by higher education institutions among the students in Qatar University.
A research framework is developed for quality assessment with seven hypotheses that are commonly used in the literature. A survey with 65 instruments was used for gathering the required data for the analysis.
The results presented here are based on survey response of 397 students. Seven dimensions (determinants) of services quality were identified in this study: the original dimensions of the SERVQUAL namely, reliability, responsiveness, assurance, empathy, and tangibles, and; two additional dimensions image and culture/value. The results proved significant positive association between the provided services quality and students' loyalty. Finally, the findings indicated that there are no statistically significant differences in the perception of services quality based on the students' demographic variables (gender, age, nationality, and education level).In terms of perceptions, the analysis showed that the provided services of the university falls short of meeting the students' expectations.
The finding indicates that, in order to provide quality education in Qatar University, expectation of student's needs should be carefully understood and addressed. Management also needs to consider factors such as corporate image and culture/value when measuring service quality.
Although there is a limitation in the responses as the outcome of this study is based on the survey of students, this nevertheless provides an attempt to study services quality in Qatar education sector.
The findings of this thesis is expected to help filling the literature gaps by providing empirical knowledge on quality of services assessment and customer's satisfaction in higher education
Evaluation of the Performance of TN Integrated Food Safety Center of Excellence Online Training Courses
Foodborne disease outbreaks are still a challenge in the United States even with the improvements that are continuously made to the food integrity system. The Center for Agriculture and Food Security and Preparedness (CAFSP), in conjunction with the Tennessee Integrated Food Safety Center of Excellence, has developed two web-based courses to support investigation of foodborne illnesses. These courses are entitled as “Foodborne Outbreak Investigation and Response Team Roles and Responsibilities, Part A and B” respectively. The overall goal of this study was to evaluate each course by assessing the participants\u27 satisfaction, learning, and perception of knowledge gained and impact on job performance.
Participants’ knowledge of foodborne disease outbreak investigation was assessed through a quiz before and after each of the courses. While their satisfaction and perception of knowledge gained and impact on performance were assessed using 5-point Likert-scale questions.
For course A, most participants (89%-99%) were satisfied with the course content, design, and delivery. There was a statistically significant (P \u3c 0.001) difference between pre- (mean=77) and post-test (mean=91) results of participants (n=188). About 85% of participants (18.8%) perceived that course A improved their overall job performance. Similarly, the majority of participants (83%-91%) rated course B positively. The pre- (mean=62) and post-test (mean=82) results of participants (n=87) were statistically significantly (P \u3c 0.001) different. More than 88% of participants (23.5%) indicated that course B improved their knowledge and performance on job.
Overall, both online courses assessed in this study improved participants’ knowledge about foodborne outbreak investigation and their performance on the job. Future efforts should support the improvement of the current online training courses as well the development of new courses to target both consumers and all public health professionals associated with the food supply and delivery. These efforts could reduce the current foodborne illnesses in the United States
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