This work is focused on the study of the natural convection boundary-layer flow over a downward-pointing
vertical cone in a porous medium saturated with a non-Newtonian nanofluid in the presence of heat
generation or absorption. The transformed boundary layer governing equations are solved numerically. The
influences of pertinent parameters such as the heat generation or absorption, the solid volume fraction of
nanoparticles and the type of nanofluid on the flow and heat transfer rate in terms of Nusselt number are
discussed. Comparisons with previously published work on special cases of the problem are performed and
found to be in excellent agreement. The generalized governing equations derived in this work can be applied
to different cases of non-Newtonian fluids with different values of the power-law viscosity index. The results
of this parametric study are shown graphically and the physical aspects of the problem are highlighted and
discussed.

The effect of yield stress on the free convective heat transfer of dilute liquid suspensions of nanofluids flowing on a vertical plate saturated
in porous medium under laminar conditions is investigated considering the nanofluid obeys the mathematical model of power-law.
The model used for non-Newtonian nanofluid incorporates the effects of Brownian motion and thermophoresis. The governing boundary-
layer equations are cast into dimensionless system which is solved numerically using a deferred correction technique and Newton
iteration. This solution depends on yield stress parameter Ω, a power-law index n, Lewis number Le, a buoyancy-ratio number Nr, a
Brownian motion number Nb, and a thermophoresis number Nt. Analyses of the results found that the reduced Nusselt and Sherwood
numbers are decreasing functions of the higher yield stress parameter for each dimensionless numbers, n and Le, except the reduced
Sherwood number is an increasing function of higher Nb for different values of yield stress parameter.

Seed and trichome morphology of 13 taxa representing the genus Fagonia in Egypt have been studied using light (LM) and scanning electron microscopy (SEM). Macro- and micro-morphological characters, including seed shape, seed size, seed coat sculpture, trichome density and structure were studied to evaluate their systematic signifi cance. Seed shape and trichome density were found to have only minor taxonomic value, but seed coat sculpturing and trichome structure proved to be valuable characters. Th ese characters off er evidence to combine certain species, e.g. Fagonia kassasii and F. schimperi in F. bruguieri , Fagonia microphylla in F. scabra and Fagonia thebaica in F. arabica . However, F. sinaica , F. tristis, F. boveana and F. isotricha should be maintained as separate species. Generally, the diff erent patterns of seed and trichome morphology are useful in delimitation of species within the genus Fagonia, but they could not be used to characterize groups of related species.

The pollen morphology of 11 species (including two subspecies and two varieties) belonging to two genera (Helianthemum and Fumana) of the family Cistaceae in Egypt was studied using light and scanning electron microscopy. Pollen grains of the studied taxa were found to be radially symmetrical and tricolporate. Pollen size, shape, apertures, and exine ornamentation characteristics were valuable parameters among the studied taxa. The largest pollen size was recorded in H. salicifolium and the smallest one observed in H. kahiricum subsp. schweinfurthii. Pollen shape in the Egyptian taxa varied from (sub-)prolate to prolate spheroidal, but F. arabica is different in having sub-oblate grains. The pollen data confirm that H. lippii and H. sessiliflorum are very closely related species. Pollen sculpture was useful in distinguishing between H. vesicarium var. vesicarium and H. vesicarium var. ciliatum. Three main pollen types of exine ornamentation were recognized: retipilate; reticulate to verrucate; and striate. Based on palynological data, a key for the studied taxa is suggested.

Recent plastid phylogenomic studies have helped clarify the backbone phylogeny of angiosperms. However, the relatively limited taxon sampling in these studies has precluded strongly supported resolution of some regions of angiosperm phylogeny. Other recent work has suggested that the 25,000-bp plastid inverted repeat (IR) region may be a valuable source of characters for resolving these remaining problematic nodes. Consequently, we aligned all available angiosperm IR sequences, resulting in a matrix of 24,702 aligned bases for 246 accessions, including 36 new accessions. Maximum likelihood analyses of the complete data set yielded a generally well-supported topology that is highly congruent with those of recent plastid phylogenomic analyses. However, reducing taxon sampling to match a recent 83-gene plastid analysis resulted in significant changes in bootstrap support at some nodes. Notably, IR analyses resolved Pentapetalae into three well-supported clades: (1) superasterids (comprising Santalales, Caryophyllales, Berberidopsidales, and Asteridae), (2) superrosids (comprising Vitaceae, Saxifragales, and Rosidae), and (3) Dilleniaceae. These results provide important new evidence for a stable, well-supported phylogenetic framework for angiosperms and demonstrate the utility of IR data for resolving the deeper levels of angiosperm phylogeny. They also reiterate the importance of carefully considering taxon sampling in phylogenomic studies.

GaN/Al0.12Ga0.88N and Ga0.99Gd0.01N/Al0.12Ga0.88N multiquantum
well samples with the quantum well thickness of
one nm were grown by a radio-frequency plasma-assisted
molecular-beam epitaxy on GaN (0001) templates. The
epitaxial growth is established in the grown samples. Gd
doped multi-quantum well samples show magnetic behaviour
at room temperature. Photoluminescence measurements
show a strong photoluminescence at the higher
energy side of GaN excitonic peak for the GaN multiquantum
wells. A new luminescence peak at 3.598 eV
was found for Gd doped GaN multi-quantum wells. This
photoluminescence peak is attributed to the formation of
an exciton–polaron in the distorted regions around the Gd
dopants in GaN multi-quantum wells.

Exciton-polaron formation in GaGdN/AlGaN multiquantum wells was inferred from the lower
energy of the photoluminescence peak observed for the GaGdN quantum wells (QWs)
compared with GaN QWs. The rather low value of the excitonic transition energy is attributed
to exciton-polarons bound to the Gd ions. Exciton-polarons are most likely to occur due to the
lattice distortion around the substituted Gd ions in addition to the exchange interaction between
Gd3+ magnetic ions and the strongly confined charge carrier spins in GaGdN QWs. The
mechanism of exciton-polaron formation is discussed. The magnetic behavior is briefly
presented.

The floristic composition and geographical elements of the study area were analyzed resulted in 328 species representing 206 genera in 55 families. This study confirmed the record of 14 species, mostly weeds, which can be considered as new additions to the flora of the study area. Therophytes were the dominant life form, while mono- and bi-regional Saharo-Sindian geoelements were the most represented. Ten species showed dominancy with their Q-values ranged between 0.802 and 0.2, where Zilla spinosa and Zygophyllum coccineum were of common occurrence. Application of cluster analysis and DCA ordination techniques produced 4 major floristic groups (A-D) comprising 7 subgroups. The correlation coefficients (r) between the different subgroups revealed high significant correlations (P=0.01) between floristic group (B) and subgroup (C2) and between subgroups (D1) and (D2). Significant correlations (P=0.05) occurred between subgroup (D1) and both of (A1) and (C2). Comparing the floristic similarities between this investigation and other relevant studies were presented and discussed. On the other hand the low similarity index between the study area and Sinai may be attributed to the geographical position of both deserts where Sinai desert is part of the Irano-Turanian region while the Eastern Desert is a part of the Saharo-Sindian region.

The present work investigated the radioactivity level of the rocks samples collected from different sites
in Egypt. Twenty one rocks samples were analyzed by gamma-ray spectrometry using NaI(Tl) detector
with specially designed shield. The concentration of three natural radionuclides namely 226Ra, 232Th
and 40K has been determined and compared with chemical data obtained by XRF analysis. The results
showed that these radionuclides were present in concentration ranges (3.4–99, 7.5–134 and
93–3382 Bq kg1), (54.9–211.6, 20.71–170.5 and 2068–2344 Bq kg1) and (13–106, 29.25–106.1 and
682–755 Bq kg1) for gneiss, granite and basalt rocks, respectively, while the values were (7.5, 12.5 and
263.9 Bq kg1) and (113, 148.5 and 1672 Bq kg1) for 226Ra, 232Th and 40K in sandstone and siltstone
rocks, respectively. Also radium equivalent activity, total dose rates and external hazard index of the
rocks samples under consideration were calculated. The results showed that granite rocks contain a
high proportion of natural radioactive elements, while sandstone rocks have lesser radioactivity
concentration compared with other types of rocks.

Water from bedrock frequently contains higher concentrations of natural radionuclides than water from other 22
sources. Groundwater from Assalamia-Alhomira and Juban areas (southeast of Sana'a) and hot spring water 23
from Dempt area (south Sana'a) in Yemen were analyzed for 226Ra, 232Th and 40 K activity concentrations. 24
The average activity concentrations for groundwater from Assalamia–Alhomira area were 4.04 Bql−1 and 25
1.81 Bql−1 for 226Ra and 232Th, respectively, while 40 K was not detectable, while that for groundwater sam- 26
ples from Juban area were 2.95 Bql−1, 0.72 Bql−1 and 34.9 Bql−1 for 226Ra, 232Th and 40 K, respectively. On 27
the other hand, the activity concentrations for hot spring water from Dempt area were 3.48 Bql−1, 1.01 28
Bql−1 and 16.05 Bql−1 for 226Ra, 232Th and 40K, respectively. Also annual effective dose equivalent of ingestion 29
of these waters was calculated. The results showed that the annual dose equivalent obtained in the present 30
study was much higher than the recommended value (0.1 mSv year−1) as reported by WHO. The results 31
were compared with those for drinking water.