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

“Inverted and non inverted” <i>ex ovo</i> culture of chicken embryos.

<p>(A) The content of the egg was deposited into a petri dish, the thick albumen was removed and and the blastoderm was positioned upwards. (B) A piece of filter paper, with a central hole, was placed on the yolk, positioning the blastoderm in the central hole and the border of the filter paper with the embryo attached cut with scissors. (C) Before (B), a 500 μl drop of PBS was placed in a petri dish with a glass bottom. (D) The embryo attached to the filter paper was placed on the drop of PBS in an “inverted” or “non inverted” position. The lid of the petri dish was coated with (PBS) humidified paper before closing the petri dish. (E) The petri dish containing the embryo was sealed with parafilm. Scale bars: 1 cm in A,B,E and 1 cm in C,D.</p

Passive displacement of somatopleure and splanchnopleure due to the sinking of the head in proamnion.

<p>(A) Whole mount HH12 chicken embryo with the anterior amnion fold forming (yellow arrow) and an axial strip visible from the proamnion until the area opaca (red arrow). (B) Whole amount HH13 chicken embryo showing the head sinking in the proamnion, which already covers the tip of the head (white dotted line and black arrow in the magnified view in the top left corner), and that the anterior amnion fold has developed posteriorly (yellow dotted line and yellow arrows in the magnified view in the top left corner). (C) Transversal section of a HH13 chicken embryo showing the head completely surrounded by proamnion and the avascular region of splanchnopleure/yolk sac (in between asterisks) attached to the somatopleure by a double layer of mesoderm (red arrow). (D) In embryos cultured <i>ex ovo</i> “in suspension”, from HH5 to HH17 (for 48 hours), the head did not sink in proamnion and therefore the formation of the amnion was impaired. White arrows point to the somatopleure. Abbreviations: ys, yolk sac. Scale bars: 500 μm (A, B), 200 μm (C) and 1 mm (E).</p

The anterior amnion fold did not develop in embryos growing “inverted”.

<p>(A) Scheme of the “inverted” culture system where HH11 chicken embryos were cultured for 7∶30 hours and compared with embryos growing <i>in ovo</i>. (B) Number of somite pairs at the start (0 hours) and after 7∶30 hours of incubation in each group. (C) Distance between the tip of the anterior intestinal portal and the border between the proamnion and the yolk sac in each group. *, <i>P</i><0.05. (D-E) HH12 embryos growing <i>in ovo</i> (D) and in the “inverted” culture system (E) transversally sectioned (F) at the indicated levels (a–c and a’–c’). In the control embryo note the avascular region of splanchnopleure/yolk sac (in between asterisks in a) attached to the somatopleure by a double layer of mesoderm (red arrow in a and b). Abbreviations: ys, yolk sac. Scale bars: 500 μm (D,E) and 200 μm (F).</p

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

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

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

Immature Schwann cells along the peripheral processes express NGFR.

<p>(A–D) Confocal images of the lower basal turn of a cochlea at W9 showing DAPI (A), TUBB3 (B) and NGFR (C) and the merged image (D). The spiral ganglion is delineated by the dotted line. The asterisk marks two NGFR+ cells in the center of the spiral ganglion. (E–I) Confocal images of the lower basal turn of a cochlea at W10.4 showing DAPI (E), TUBB3 (F), SOX10 (G) and NGFR (H) and the merged image (I). The spiral ganglion is delineated by the dotted line. The inset shows a deconvoluted, high-magnification view of TUBB3 and NGFR at the distal tips of the peripheral processes. Abbreviations: SG, spiral ganglion. Scale bar = 50 µm or 5 µm (inset in I).</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

Capturing PGCs in the human cochlea.

<p>(A) Schematic model of PGC development in the human fetal cochlea. Neural crest cells differentiate via a Schwann cell precursor stage into S100+ immature Schwann cells. The immature Schwann cells subsequently maturate into myelinating and non-myelinating Schwann cells, and (presumably) satellite glial cells. (B) Schematic illustration of a mid-modiolar cut of the adult human cochlea, showing the lower basal turn (B1), upper basal turn (B2), lower middle turn (M1), upper middle turn (M2) and the apex (A). (C) Schematic illustration of the PGCs in the adult human cochlea. Satellite glial cells (green) envelop all SGN cell bodies. Non-myelinating Schwann cells (light blue) ensheath both the central and peripheral processes of the type II SGNs (yellow) that innervate the outer hair cells (OHC). Myelinating Schwann cells (dark blue) ensheath and myelinate both processes of the type I SGNs (red) that innervate the inner hair cells (IHC). Beyond the habenula perforata, in the organ of Corti, neither Schwann cell types ensheath the most distal part of the peripheral processes of type I and type II SGNs.</p