Cognitive radio network in vehicular ad hoc network (VANET): a survey

Cognitive radio network and vehicular ad hoc network (VANET) are recent emerging concepts in wireless networking. Cognitive radio network obtains knowledge of its operational geographical environment to manage sharing of spectrum between primary and secondary users, while VANET shares emergency safety messages among vehicles to ensure safety of users on the road. Cognitive radio network is employed in VANET to ensure the efficient use of spectrum, as well as to support VANET’s deployment. Random increase and decrease of spectrum users, unpredictable nature of VANET, high mobility, varying interference, security, packet scheduling, and priority assignment are the challenges encountered in a typical cognitive VANET environment. This paper provides survey and critical analysis on different challenges of cognitive radio VANET, with discussion on the open issues, challenges, and performance metrics for different cognitive radio VANET applications

PGCs expressed SOX10, SOX9 and S100B in the W10.4 human fetal cochlea.

<p>(A–B) Confocal images of the lower basal turn of a W10.4 cochlea immunostained for SOX10 and SOX10 merged with DAPI. (C–D) Confocal images of an adjacent section immunostained for SOX9 and SOX9 merged with DAPI. (E–G) Confocal images of the lower basal turn of a W10.4 cochlea immunostained for S100B (E) and TUBB3 (F) and the merged image with DAPI (G). (H–J) High-magnification view of the center of the spiral ganglion. (K–M) Detail of the peripheral processes at their distal end. Abbreviations: cd, cochlear duct; SG, spiral ganglion. Scale bar = 50 µm (A–G) or 20 µm (H–M).</p

Distinct fascicular pattern visible within 5 days.

<p>One day after seeding, fluorescent HFBSCs migrated under the quarter-turn explant and began migrating into the explant within the next day (2 days). Over time, more EF1α-copGFP HFBSCs settled in the explant (3 days) forming a distinct fascicular pattern after 5 days. Within the next two days the pattern enhanced as the number of HFBSCs within the explant increased.</p

EF1α-copGFP HFBSCs and DCX-copGFP HFBSCs form a similar distinct fascicular pattern.

<p>(A) Set of stitched fluorescence images showing the distinct fascicular pattern that is formed by the copGFP-expressing cells (green). The stitched phase-contrast images depict the morphology of the quarter-turn explant (gray) and the merged set of images reveals the position of the green fluorescent cells within the explant. (B) DCX-copGFP cells formed a similar fascicular pattern of fluorescent cells within the explant (green). The merged image of phase-contrast (gray) and fluorescence images depicts the location of DCX-copGFP-expressing cells within the explant.</p

Primary antibodies used for immunohistochemistry (in alphabetical order).

<p>Primary antibodies used for immunohistochemistry (in alphabetical order).</p

Immunoprofile of the HFBSCs in the pattern as compared to non-co-cultured HFBSCs.

<p>Immunoprofile of the HFBSCs in the pattern as compared to non-co-cultured HFBSCs.</p

Terminal differentiation of Schwann cells in the cochlear nerve.

<p>(A–C) Deconvoluted confocal images of the cochlear nerve at W9 showing TUBB3 (A, red), S100B (B, green), and the merged image with DAPI (C). (D–G) Deconvoluted confocal images of an axial transection of the cochlear nerve at W22 showing DAPI (D), TUBB3 (E), S100B (F) and the merged image (G). The upper inset in G shows a high-magnification of TUBB3+ cochlear nerve fibers each enveloped by S100B+ Schwann cells, the lower inset shows a Remak bundle. (H–K) Deconvoluted confocal images of a sagittal transection of the cochlear nerve at W22 showing DAPI (H), TUBB3 (I), MBP (J) and the merged image (K). The inset shows a high-magnification view of a myelinated nerve fiber. Scale bar = 10 µm or 1 µm (insets in G and K).</p

Myelination of spiral ganglion neurons at W22.

<p>(A–E) Confocal images of a spiral ganglion in the middle turn of a cochlea at W22 showing DAPI (A), TUBB3 (B), PRPH (C), MBP (D) and the merged image (E). The spiral ganglion is delineated by the dotted line. (F–J) Confocal images of an axial transection of the cochlear nerve at W22 showing DAPI (F), TUBB3 (G), PRPH (H), MBP (I) and the merged image (J). (K–O) Deconvoluted confocal images of an axial transection of the cochlear nerve at W22 showing DAPI (K), TUBB3 (L), PRPH (M), MBP (N) and the merged image (O). Insets show TUBB3 (left), PRPH (middle) and the merge with MBP and DAPI (right) in high-magnifications examples of PRPH−/TUBB3+/MBP+ cochlear nerve fibers (upper inset) and PRPH+/TUBB3+/MBP+ cochlear nerve fibers (lower inset). Scale bar = 20 µm or 1 µm (insets in O).</p

Migration of copGFP-expressing cells.

<p>(A) Green fluorescent HFBSCs before co-culture expressed copGFP. (B) Schematic set-up of the migration experiment. At the border of the well (bottom diameter 21 mm), cells were seeded (green) and a modiolus was placed in the middle. (B’) Light-microscope image illustrating the situation directly after seeding and addition of medium (0 h). Fluorescent cells are located at the border of the well, while the modiolus is located in the center as indicated by faint background fluorescence. (C) Groups of cells approached the modiolus (circles) after 68 hours, as is demonstrated at high magnification. (C’) Overview of area depicted in C (boxed area) reveals that brightly fluorescent HFBSCs radially migrated up to 6.8 mm and 6.2mm, respectively, from their point of origin (i.e., the border of the well) towards the modiolus. (D) After 96 hours, HFBSCs reached the modiolus. The arrow indicates the position of the cells located underneath the modiolus. (D’) Overview of area depicted in D (boxed area) illustrating how the first cells reached the modiolus after migrating another 1.2 mm and 0.4 mm, respectively (arrow), after 92 hours. Cells migrated over a cell-free zone (gray) towards the modiolus. In control experiments, i.e. wells without a modiolus in the center, cells proliferated at the border of the well, but did not migrate towards the center of the well (data not shown).</p

NGFR expression in the cochlear duct epithelium.

<p>(A–C) Confocal images of the cochlear duct epithelium in the upper middle turn of a cochlea at W12 showing TUBB3 (A, red), S100B (B, green) and the merged image with DAPI (C). The arrow points to penetrating TUBB3+ peripheral processes. (D–F) Confocal images of the cochlear duct epithelium in the lower basal turn showing TUBB3 (D, red), S100B (E, green) and the merged image with DAPI (F). The arrowhead points to the first developing (inner) hair cell. (G–H) Confocal images of the cochlear duct epithelium of the lower basal turn of a cochlea at W12 showing NGFR (G, green) and the merged image with DAPI (H) and MYO7A (red). The bold arrows point to the NGFR+ Schwann cells. The thin arrows outline the epithelial cells that weakly express NGFR. (I–J) Upper middle turn of a cochlea at W14 showing NGFR (I, green) and the merged image (J) with DAPI (blue) and MYO7A (red). The bold arrows point to the NGFR+ Schwann cells. (K–L) Lower middle turn of a W14 cochlea immunostained for NGFR (K, green) and the merged image with DAPI (blue) and MYO7A (red). The bold arrow points to the NGFR+ Schwann cells. The thin arrow points to a bright band of NGFR. (M–N) Lower basal turn of a W14 cochlea immunostained for NGFR (M, green) and the merged image (N) with DAPI (blue) and MYO7A (red). The bold arrows point to the NGFR+ Schwann cells. The thin arrow points to a band brightly immunostained for NGFR. (O–Q) Confocal images of the spiral ganglion in the lower basal turn of a cochlea at W18 showing TUBB3 (O), NGFR (P, green) and the merged image with DAPI (Q). (R–S) Confocal images of the organ of Corti of a cochlea at W18 showing NGFR (R, green) and the merged image with DAPI (S). Abbreviations: cd, cochlear duct; m, mesenchyme; B1, lower basal turn; M1, lower middle turn; M2, upper middle turn; SG, spiral ganglion; PPs, peripheral processes. * = autofluorescence of erythrocytes. Scale bar = 20 µm (A–N, R–S) or 50 µm (O–Q).</p