Abstract: Objectives: To investigate the effect of temperature elevation on the bonding strength of resin cement to the zirconia ceramic using fractional CO2 laser. Background: Fractional CO2 laser is an effective surface treatment of zirconia ceramic, as it increases the bonding strength of zirconia to resin cement. Methods: Thirty sintered zirconia discs (10 mm diameter, 2 mm thickness) were prepared and divided to three groups (N=10) and five diffident pulse durations were used in each group (0.1, 0.5, 1, 5 and 10 ms). Group A was treated with 10 W power setting, group B with 20 W and group C with 30 W. During laser irradiation, temperature elevation measurement was recorded for each specimen. Luting cement was bonded to the treated zirconia surfaces and cured for 30 seconds. Shear bond strength was evaluated by a testing machine (universal) with bond failure mode determination. Results: The lowest temperature elevation measurement of the irradiated specimen which gave maximum shear bond strength was about 1.6±0.3 Ċ higher than ambient room temperature (27±0.2 ºC). Apparent micromechanical irregularities were seen in the treated samples and cracks formation with increased pulse duration and power setting were also observed. Conclusions: The temperature elevation is a vital factor in the surface roughness of zirconia ceramic with fractional CO2 laser irradiation and the lowest temperature elevation at best shear bond strength of zirconia ceramic to the resin cement is satisfied with the shorter pulse duration of 0.1 millisecond.
Racism changes its meaning, shape, purpose or function according to various factors such as time, place, motives, and backgrounds; among others. It seems, however, to have deep roots back in the history of mankind. Such a concept stems from a perceived difference with the other. It is fed by the feeling of being hierarchically superior in opposition to another party that is depicted as inferior. Since ancient times, racism is disguised in different forms and manifests itself on various levels. It is a truism that this ideology can be best presented via language.
Due to its negative implication, racism lends itself to a critical kind of research. As such, this paper is a critical pragmatic investigation for this phenomenon a
... Show MoreIn the last few years, the Internet of Things (IoT) is gaining remarkable attention in both academic and industrial worlds. The main goal of the IoT is laying on describing everyday objects with different capabilities in an interconnected fashion to the Internet to share resources and to carry out the assigned tasks. Most of the IoT objects are heterogeneous in terms of the amount of energy, processing ability, memory storage, etc. However, one of the most important challenges facing the IoT networks is the energy-efficient task allocation. An efficient task allocation protocol in the IoT network should ensure the fair and efficient distribution of resources for all objects to collaborate dynamically with limited energy. The canonic
... Show MoreAdvertisements containing images of women represent one of the most controversial topics of the advertising industry and has an impact on people and trends. This study aims to determine the typical mental image of women purveyed through visual advertising in the Arab media. It also aims to find out whether these advertisements portray women positively or negatively, in addition to investigating the reasons for the recent negative portrayal of women in commercials. The study adopted a descriptive-analytical approach to achieve these objectives. The results indicate that advertising designs that carry images of women displayed in the Arab media create strong mental images. Repetition reinforces these images, and they emphasize the concept
... Show MoreEducation varies in terms of form and content between verbal and abstract education through the delivery of knowledge and enriching experiences through verbal communication and ephemeral learning and based on sensory experiences that provide visual and audio visualizations that make it imperative to install and retain knowledge and experience. It is obvious that meanings And the concepts grow the more tangible sensory experiences that make the process of communication highly efficient, and the more the learner's acquisition of direct sensory experiences, ie the first source is the life situations and normal circumstances of the process of communication, but if these can not be available It is necessary to a
... Show MoreThe aim of this study is to compare and contrast the science process skills (SPS) included in the 10th-12th grade physics textbooks content utilized in Yemeni schools. The study revealed weaknesses and strengths in the textbooks’ content. For instance, a number of science process skills (SPS), such as measuring, predicting and hypothesizing, have been neglected in the 11th grade textbook. For all three textbooks content, the maximum percentage of basic science process skills (BSPS) was devoted to observation. However, the maximum percentage of integrated science process skills (ISPS) was different for each grade: experimenting had the highest percentage for 10th grade, interpreting data for 11th grade, and operational definitions for 12th
... Show MoreObjective: To investigate and prove that aspirin
protects, or at least attenuates amikacin ototoxicity in
humans.
Method: This study was conducted in 60 patients that
completed all
requirements .The patients were divided into two
groups:
• Control group: receive placebo treatment.
• Drug–treated group: They receive aspirin
coated tablets (1.5gm/ day), 500mg 8 hourly.
Both groups had similar aspects regarding the gender,
age and weight. The duration of therapy was 7 days
and dosage of amikacin was 1gm/day (500mg 12
hourly).
Results: Comparison of Audiometry test in
Ear/Nose/Throat (E.N.T.) Department (Pure Tone
Audiometry) at 1000 Hertz (Hz), 2000 Hz, 4000 Hz,
and 8000 Hz showed sig
This aims tackles the importance of the organizational energy of the hotel organizations that search the success in the business field to penetrate in the whole tourist markets, and to draw the policies and firm rules which must be framed with the administrative strategies that contributed in creativity and achievement the targets besides provide a future vision due to its position among the competitive henceforth achieving the activity. This is what the chapters tackle in the theoretical side. Also many general questions have been arisen to determinate the importance of the research and many other special questions that express the problem of the study. To limit the levels of study alter
... Show MoreMany diseases can produce cardiac overload, of these disease hypertension, valve disease congenital anomaly in addition to many other disease. One of the most common diseases causing left ventricle overload is hypertension. A long term hypertension can cause myocardium hypertrophy leading to changes in the cardiac contractility and reduced efficiency. The investigations were carried out using conventional echocardiography techniques in addition to the tissue Doppler imaging (TDI) from which many noninvasive measurements can be readily obtained. The study has involved the effect of hypertension on the myocardium stiffness index through the measurement of early diastolic filling (E) and the early velocity of lateral mitral annulus (Ea
... Show MoreThis study aims to identfy virtual plastic art exhibitions in light of the challenges of the Corona pandemic. It used a descriptive analytical method through several questions and examining future challenges via the Internet in publishing virtual plastic art exhibitions in many parts of the world in light of the challenges of the Corona pandemic. For that, it used Arab and foreign references.
The study reached many results, the most important of which are: The detection of virtual reality applications and their impact on the plastic arts exhibitions sector. Besides, the insights gained from future art gallery research with VR technology could provide direct and practical value for this sector. By using a technology, similar to the “
Saccharomyces Cerevisiae cells were immobilized in calcium alginate beads and activated charcoal for use in the
production of ethanol from batch fermentation of sugar beet waste. Treatment of the waste with NaOH to increase the
ability of lignocellulose material to hydrolysis by acid (2N H2SO4) to monosaccharide and disaccharide (mainly glucos).
The high reducing sugar concentration obtained was equal to 9.2gm/100ml (10Brix) after treatment. Fermentation
parameters, are (pH, glucose concentration (2.5-25 gm/100ml), immobilized agent concentration (2.5-25 gm/100ml)
were studied to find the optimum physiological condition. And the highest ethanol concentration obtained from the
fermentation in the presence of 20%(wt/v) ca