BER Performance of IM/DD FSO System with OOK using APD Receiver

In this paper, the performance of intensity-modulated with direct detection (IM/DD) free space optical (FSO) system using the on-off keying (OOK) and avalanche photodiode (APD) receiver is observed. The gamma-gamma model is used to describe the effect of atmospheric turbulence since it provides good agreement in the wide range of atmospheric conditions. In addition, the same FSO system with equal gain combining applied at the reception is analyzed. After theoretical derivation of the expression for the bit error rate (BER), the numerical integration with previously specified relative calculation error is performed. Numerical results are presented and confirmed by Monte Carlo simulations. The effects of the FSO link and receiver parameters on the BER performance are discussed. The results illustrate that the optimal APD gain in the minimum BER sense depends considerably on the link distance, atmospheric turbulence strength and receiver temperature. In addition, the value of this optimal gain is slightly different in the case of spatial diversity application compared with single channel reception

Craniovertebral anomalies associated with pituitary gland duplication

Background: An extremely rare occurrence of the pituitary gland duplication inspired us to examine in detail the accompanying craniovertebral congenital anomalies in a patient involved. Materials and methods: T1-wighted magnetic resonance imaging (MRI) was performed, as well as the multislice computerised tomography (MSCT) and MSCT angiography in our patient, as well as in a control group of 10 healthy subjects. Results: In a 20-year-old male a double pituitary gland was identified, as well as hypothalamic enlargement, tuberomamillary fusion and hamartoma. In addition, the patient also showed a duplicated hypophyseal fossa and posterior clinoid processes, notch of the upper sphenoid, prominent inner relief of the skull, inverse shape of the foramen magnum, third occipital condyle, partial aplasia of the anterior and posterior arches of the atlas with a left arcuate foramen, duplication of the odontoid process and the C2 body, and fusion of the C2–C4 and T12–L1 vertebrae. The MSCT angiography presented a segmental dilatation of both vertebral arteries and the A2 segment of the anterior cerebral artery, as well as a duplication of the basilar artery. Conclusions: This patient is unique due to complex craniovertebral congenital anomalies associated with a duplication of the pituitary gland

Morphometric multislice computed tomography examination of the craniovertebral junction in neck flexion and extension

Background: Detailed study of the craniovertebral junction (CVJ) is necessary to completely understand the mechanism of its flexion and extension. Materials and methods: One cadaver head was sectioned in the sagittal plane. Also, in 22 volunteers, examined using the multislice computed tomography (MSCT), 14 parameters and 2 angles were measured in the neutral position, flexion and extension. Results: The obtained measurements showed the anterior part of the occiput to move inferiorly in flexion, and the anterior atlas arch and the tip of the dens to get closer to the basion. At the same time, the opisthion moves superiorly, but the cervical spine bends anteriorly. Consequently, the dens-opisthion diameter and the opisthion-posterior atlas arch distance slightly decrease in length, whilst the arches of the atlas (C1), axis (C2) and C3 vertebra become more distant. Following extension, the posterior part of the occiput moves inferiorly, so that the basion-dens tip, the basion-axis arch, and the basion-posterior atlas arch distances increase in length. In contrast, the distances of the C1–C3 arches decrease in length. The angle between the foramen magnum and the dens tip decreases 1.620 on average in flexion, but increases 3.230 on average in extension. The angle between the axis body and the opisthion also decreases in flexion (mean, 3.360) and increases in extension (mean, 6.570). Among the congenital anomalies, a partial agenesis of the posterior atlas arch was revealed (4.5%), as well as an anterior dehiscence of the C1 foramen transversarium (13.6%). Conclusions: The mentioned measurements improved our understanding of the CVJ biomechanics. The obtained data can be useful in the evaluation of the CVJ instability caused by trauma, congenital anomalies and certain spine diseases

Brain and art: illustrations of the cerebral convolutions. A review

Background: Aesthetics and functional significance of the cerebral cortical relief gave us the idea to find out how often the convolutions are presented in fine art, and in which techniques, conceptual meaning and pathophysiological aspect.Materials and methods: We examined 27,614 art works created by 2,856 authors and presented in art literature, and in Google images search.Results: The cerebral gyri were shown in 0.85% of the art works created by 2.35% of the authors. The concept of the brain was first mentioned in ancient Egypt some 3,700 years ago. The first artistic drawing of the convolutions was made by Leonardo da Vinci, and the first colour picture by an unknown Italian author. Rembrandt van Rijn was the first to paint the gyri. Dozens of modern authors, who are professional artists, medical experts or designers, presented the cerebralc onvolutions in drawings, paintings, digital works or sculptures, with various aesthetic, symbolic and metaphorical connotation. Some artistic compositions and natural forms show a gyral pattern. The convolutions, whose cortical layers enable the cognitive functions, can be affected by various disorders. Some artists suffered from those disorders, and some others presented them in their artworks.Conclusions: The cerebral convolutions or gyri, thanks to their extensive cortical mantle, are the specific morphological basis for the human mind, but also the structures with their own aesthetics. Contemporary authors relatively often depictor model the cerebral convolutions, either from the aesthetic or conceptual aspect. In this way, they make a connection between the neuroscience and fineart

Structure and immunohistochemistry of the human lenticulostriate arteries

Background: Data about the structure and immunohistochemistry of the lenticulostriatearteries (LSAs), although very important for medical research and clinicalpractice, have been rarely reported in literature.Materials and methods: Fourty serially sectioned LSAs were stained with hematoxilinand eosin, and prepared for immunohistochemistry.Results: Our examination revealed a typical endothelial lining and a narrow subendothelialspace with subintimal smooth muscle cells occasionally. The internalelastic lamina was fragmented or absent in the smallest LSAs branches. The mediacoat, with a mean diameter of 148.5 μm, contained typical smooth muscle cellswhich formed 14.2 layers on average and showed a positive immune reactions foralfa-actin, desmine, laminin and collagen IV. The thin adventitial coat containedfibroblasts, collagen fibers, and nerve bundles, with the strongest immunopositivityto thyrosin hydroxilase. The immune reactions against CD31 and CD34 proteins,endothelial nitric oxide synthase, S 100 protein, neurofilament protein and synaptophysin,seem to be performed in the LSAs wall for the first time. Similarly,the thickness of the LSAs wall and its coats have never been reported, nor thenumber of the smooth muscle cell layers.Conclusions: Our results related to the structure and immunohistochemistry ofthe LSAs could be important in cerebrovascular pathology, neurology and neurosurgery

A 3 tesla magnetic resonance imaging volumetric analysis of the hippocampal formation: dependence on handedness and age

Background: The hippocampal formation (HF) is one of the most important parts of the brain in the magnetic resonance imaging (MRI) volumetric analysis in various domains, but not completely from all aspects, including the handedness. The aim of our study was to evaluate the possible differences in the volume of the right and left HF among the healthy right-handed and left-handed subjects, and to determine whether the volume differences are age related. Materials and methods: The MRI of this prospective study was performed using T1 fast field echo (FFE) sequence. The 124 subsequent coronal slices (thickness 1.5 mm) were performed in each participant. The obtained HF volumes were normalised and statistically compared. Volunteers comprised 30 persons aged 22.0 years, 12 of whom were the left-handed, and 30 persons aged 75.2 years on average, 9 of whom were the left-handed. Results: The right and left HF volumes averaged 2.986 cm3 and 2.858 cm3 in the right-handed, and 2.879 cm3 and 3.020 cm3 in the left-handed young volunteers, as well as 2.728 cm3 and 2.650 cm3 in the right-handed, and 2.617 cm3 and 2.780 cm3 in the left-handed elderly persons. The HF volume ratios in the young left-handed participants showed a significant left-greater-than-right asymmetry. A significant difference was also noticed within the right-to-left volume ratios of the right- and left-handed young and elderly participants. The latter reduction in the HF volume within the aged group can be interpreted as a slight atrophy of the HF. Conclusions: There is a significant difference in the volumes of the left and right HF of the left-handed young participants. The age related HF volume differences were proven between the groups of the young and elderly volunteers. The obtained data should be included into the future MRI studies of the HF volumes in various clinical domains.

Kinematic magnetic resonance imaging study of the brain stem and cervical cord by dynamic neck motion

Background: The aim was to examine the position of the brain stem and cervical cord following the neck flexion and extension. Materials and methods: The serial sagittal T2-weighted magnetic resonance imaging (MRI) sections of the cervical cord and brain stem were made in 6 volunteers. The images were mainly used to measure certain distances and angles of the brain stem and cervical cord in the neutral position, and then following the head and neck flexion and extension. Results: The measurements showed that the pons is slightly closer to the clivus following the neck flexion; the medulla oblongata is somewhat distant to the basion but closer to the odontoid process. At the same time, the spino-medullary angle diminishes in size. On the other hand, the upper cervical cord slightly approaches the posterior wall of the spinal canal, the lower cervical cord is closer to the anterior wall, while the angle between them is significantly larger in size. After the cervical cord extension, the rostral pons is somewhat distant to the clivus, whereas the caudal pons and the medulla are slightly closer to the clivus and the basion. At the same time, the spino-medullary angle diminishes in size. The cervical cord is mainly closer to the posterior wall of the spinal canal, whilst its angle is significantly smaller. Conclusions: The obtained results regarding the brain stem and cervical cord motion can be useful in the kinetic MRI examination of certain congenital disorders, degenerative diseases, and traumatic injuries of the craniovertebral junction and the cervical spine

AVERAGE BER PERFORMANCE OF SIM-DPSK FSO SYSTEM WITH APD RECEIVER

In this paper, average bit error rate (BER) analysis of the free-space optical (FSO) system employing subcarrier intensity modulation (SIM) with differential phase-shift keying (DPSK) and avalanche photodiode (APD) receiver is presented. The atmospheric turbulence is described by the Gamma-Gamma statistical model taking the pointing errors into account. Numerical results are presented and confirmed by Monte Carlo simulations. The effects of atmospheric turbulence, pointing errors and receiver parameters on the average BER performance are observed and discussed. Based on the presented results, it is concluded that the minimum of the average BER exists for an optimal value of APD gain, which is heavily dependent on receiver noise temperature, bit rate and atmospheric conditions

Ispitivanje bioremedijacionog potencijala bakterijskih konzorcijuma sedimenata čukaričkog kanala (Beograd)

Poster presented at: Prvi naučnog skupa:“Zaštita životne sredine“, (26. maj 2011., Sremska Kamenica)Abstract: [https://cherry.chem.bg.ac.rs/handle/123456789/5421

Ispitivanje bioremedijacionog potencijala bakterijskih konzorcijuma sedimenata čukaričkog kanala (Beograd)

Poster presented at: Prvi naučnog skupa:“Zaštita životne sredine“, (26. maj 2011., Sremska Kamenica)Abstract: [https://cer.ihtm.bg.ac.rs/handle/123456789/5063