Relationship of Mineralogical Composition to Thermal Expansion,Spectral Reflectance,and Physico-Mechanical Aspects of Commercial Ornamental Granitic Rocks

The aim of the present study is to link the thermal expansion, spectral reflectance, and physico-mechanical aspects of different types of commercial granitic rocks with their mineralogical and chemical composition. The granitic rock types were characterized using several analyses, including petrography, chemical, mineralogical, and thermo-gravimetrical analysis using XRF, XRD, and TG/DTG/DSC techniques. The rock types were subjected to several performance tests, such as tests of their thermal expansion, spectral reflectance, and physico-mechanical properties. The results revealed that quartz, albite, and potash feldspar with minor amounts of mica (biotite/muscovite/annite) are the main mineralogical constitutes, in addition to some alteration minerals, such as kaolinite, saussorite, and prehnite. The studied granitic rocks were classified as monzogranite/syenogranite of high K-calc-alkaline and peraluminous characters and are related to late- to post-collisional settings. The thermogravimetrical analysis revealed that the overall mass loss over the whole temperature range up to 978 °C did not exceed 3% of the initial weight for all studied rocks. The results of thermal expansion revealed that the maximum change in linear thermal expansion for all rock types did not exceed 0.015% of their initial lengths at an unusual air temperature of 50 °C. The spectral analysis revealed that iron and hydroxyl ions are the main spectral absorption features that appeared in the VIS-NIR and SWIR regions, in addition to the appearance of the common and distinctive absorption peaks of the main mineral composition. Furthermore, the spectral reflectance demonstrated that the granitic rock types of low iron oxide content achieved a high reflectivity percent in the VIS-NIR and SWIR spectral regions compared with those of high iron content. As a general trend, the granitic rock types of high iron content and/or lower quartz content exhibited a high performance regarding their physical and mechanical properties, such as water absorption, apparent porosity, bulk density, compressive strength, and abrasion resistance. The results of water absorption, density, strength, and abrasion resistance of the studied granitic rocks are in the range of 0.14–0.31%, 2582–2644 kg/m³, 77.85–222.75 MPa, and 26.27–55.91 Ha, respectively, conforming to the requirements of ornamental stones according to the ASTM standard.     

Retinopathy of prematurity: Mutations in the Norrie disease gene and the risk of progression to advanced stages

BACKGROUND: Retinopathy of prematurity (ROP) is a retinal vascular disease that occurs in infants with short gestational age and low birth weight and may lead to retinal detachment and blindness. Missense mutations in the Norrie disease (ND) gene have been associated with the risk of progression to advanced stages in cases of ROP from the US and also in clinically similar ND and familial exudative vitreoretinopathy. METHODS: We have screened two ND gene mutations, namely A105T and Val60Glu, by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and allele-specific PCR methods, respectively, in 210 Kuwaiti premature newborns to replicate these findings in a different ethnic group. RESULTS: In the Kuwaiti premature newborn cohort, 115 of 210 babies had no eye problems and served as controls, while 95 were cases of ROP. In 71 of 95 ROP cases, the disease regressed spontaneously on or before stage 3, while in 24 of 95 ROP cases the disease progressed to advanced stages 4 and 5. In case of missense mutation (A105T), the AA genotype was detected in 96% of controls compared with 87% of ROP cases (NS); similarly no significant difference was found between spontaneously regressed ROP cases and those who progressed to advanced stages. For the Val60Glu mutation, no significant association was detected between the genotype and progression of ROP to advanced stages. CONCLUSIONS: Unlike data from the US, our findings from a Kuwaiti cohort of ROP cases and controls suggest a lack of association between the two ND gene mutations (A105T and Val60Glu) and ROP and the risk of progression of the disease to advanced stages.     

Agenesis of the corpus cállosum in Turner syndrome with ring X

An 8-year-old girl with Turner syndrome and 45,X/48,X,r (X) mosaicism was found to have agenesis of the corpus callosum and various other characteristics including 'kabuki makeup' facial features and mild learning disability. Only two other cases of Turner syndrome associated with agenesis of the corpus callosum have been reported, both in patients with a 45,X karyotype. In both of those patients the constellation of signs differed from those of the present patient in a number of ways. It remains to be confirmed whether there is a higher incidence of CNS malformation in girls who have Turner syndrome with a ring X than has been reported for girls with Turner syndrome in general.     

Quantifying learning in medical students during a critical care medicine elective: a comparison of three evaluation instruments

OBJECTIVE: To compare three different evaluative instruments and determine which is able to measure different aspects of medical student learning. DESIGN: Student learning was evaluated by using written examinations, objective structured clinical examination, and patient simulator that used two clinical scenarios before and after a structured critical care elective, by using a crossover design. PARTICIPATION: Twenty-four 4th-yr students enrolled in the critical care medicine elective. INTERVENTIONS: All students took a multiple-choice written examination; evaluated a live simulated critically ill patient, requested data from a nurse, and intervened as appropriate at different stations (objective structured clinical examination); and evaluated the computer-controlled patient simulator and intervened as appropriate. MEASUREMENTS AND MAIN RESULTS: Students' knowledge was assessed by using a multiple-choice examination containing the same data incorporated into the other examinations. Student performance on the objective structured clinical examination was evaluated at five stations. Both objective structured clinical examination and simulator tests were videotaped for subsequent scores of responses, quality of responses, and response time. The videotapes were reviewed for specific behaviors by faculty masked to time of examination. Students were expected to perform the following: a) assess airway, breathing, and circulation; b) prepare a mannequin for intubation; c) provide appropriate ventilator settings; d) manage hypotension; and e) request, interpret, and provide appropriate intervention for pulmonary artery catheter data. Students were expected to perform identical behaviors during the simulator examination; however, the entire examination was performed on the whole-body computer-controlled mannequin. The primary outcome measure was the difference in examination scores before and after the rotation. The mean preelective scores were 77 +/- 16%, 47 +/- 15%, and 41 +/- 14% for the written examination, objective structured clinical examination, and simulator, respectively, compared with 89 +/- 11%, 76 +/- 12%, and 62 +/- 15% after the elective (p <.0001). Prerotation scores for the written examination were significantly higher than the objective structured clinical examination or the simulator; postrotation scores were highest for the written examination and lowest for the simulator. CONCLUSION: Written examinations measure acquisition of knowledge but fail to predict if students can apply knowledge to problem solving, whereas both the objective structured clinical examination and the computer-controlled patient simulator can be used as effective performance evaluation tools.     

Efficient Use of Graphene Oxide and Silica Fume in Cement-Based Composites

Incorporation of graphene oxide (GO) and silica fume (SF) to cement composites enhances their mechanical properties if suitable proportional amounts of GO and SF are used. This study presents a simplified approach to determine experimentally the optimum GO and SF contents that should be added to the cementitious mixture to obtain a proper and stable dispersion of GO sheets within the cement matrix. Composite mortar specimens with different GO and SF contents were designed and tested under flexural and compression loading. The phase formation and the microstructure of selected samples were also investigated to give an in-depth interpretation of the test results. The main criterion to determine the GO and SF contents was the ultimate strength required of the GO–cement composite. It was found that there was a composite interaction between the SF and GO contents in the cementitious mixture, which an envelope surface could describe if all other mix design parameters are kept constant.