In this work, an experimental approach of speckle photography was used for measuring birefringence of thermotropic liquid crystals mixtures at different wavelengths in the visible region. Also the dispersion relations were investigated. The values of the refractive indices were measured for these mixtures of thermotropic liquid crystals in isotropic and liquid crystal phase at different wavelengths. The effect of the end group of these LCs used on the values of birefringence was investigated and discussed.
research objective was to expand the very limited knowledgebase pertaining to the
ecology of fringing coral reefs in the Gulf of Suez, Egypt. Specifically,
determine dominant coral species and investigate why this reef is capable of surviving
at such a high-latitude and extreme harsh environment.
Data collection included annual reef surveys, randomized quadrat sampling, five permanent video transects and in situ seawater temperature. Of the
known Gulf of Suez 35 taxa, only six (Acropora humilis, A. microclados, A.
hemprichii, Litophyton arboretum, Stylophora pistillata, Porites columna, and
P. plantulata), compose 94% of the reef's coral cover. Coral dominance across
species shifted drastically during the study period. However, the six coral
dominance remained unchanged, while some decreased others increased. These six
coral taxa regularly experience daily changes in seawater temperature
and seasonal variations that exceed These extreme temperatures variation
and the fact that only six coral taxa dominance remained unchanged, suggest
that these corals may have developed a mechanism to cope with extreme seawater
temperatures as evidenced by their continued growth and survival over the study
period. We speculate that species dominance shift occurred largely as a result
of a local oil spill rather than exposure to extreme temperatures. Further
scrutiny of these species and the mechanisms by which they are able to thrive
is recommended, as they hold the potential to benefit other coral communities
as a resilient transplant species and model for understanding coral
survivability in extreme environmental conditions.
Manganese nickel ferrite (Mn0.2Ni0.8Fe2O4)
powder was synthesized through oxalate precursor route. The effect of annealing
temperature (400℃ - 1100℃) on the formation, crystalline size, morphology and
magnetic properties was systematically studied. The resultant powders were
investigated by thermal analyzer (TG-DTG-DSC), X-ray diffractometer (XRD), scanning
electron microscopy (SEM) and vibrating sample magnetometer (VSM). Based on thermal
analysis results, the oxalate mixture decomposed thermally in multisteps weight
loss up to about 680℃. XRD indicated that Mn0.2Ni0.8Fe2O4 formed at much lower annealing temperature (≤400℃) but contained α-Fe2O3 impurity. The
hematite phase decreased by increasing the annealing temperature. The lattice parameters
were increased with increasing annealing temperature up to 1000℃.