Ergodic Capacity for the SIMO Nakagami- Channel

This paper presents closed-form expressions for the ergodic channel capacity of SIMO (single-input and multiple output) wireless systems operating in a Nakagami- fading channel. As the performance of SIMO channel is closely related to the diversity combining techniques, we present closed-form expressions for the capacity of maximal ratio combining (MRC), equal gain combining (EGC), selection combining (SC), and switch and stay (SSC) diversity systems operating in Nakagami- fading channels. Also, the ergodic capacity of a SIMO system in a Nakagami- fading channel without any diversity technique is derived. The latter scenario is further investigated for a large amount of receive antennas. Finally, numerical results are presented for illustration

Spinal infection: state of the art and management algorithm

Spinal infection is a rare pathology although a concerning rising incidence has been observed in recent years. This increase might reflect a progressively more susceptible population but also the availability of increased diagnostic accuracy. Yet, even with improved diagnosis tools and procedures, the delay in diagnosis remains an important issue. This review aims to highlight the importance of a methodological attitude towards accurate and prompt diagnosis using an algorithm to aid on spinal infection management. METHODS: Appropriate literature on spinal infection was selected using databases from the US National Library of Medicine and the National Institutes of Health. RESULTS: Literature reveals that histopathological analysis of infected tissues is a paramount for diagnosis and must be performed routinely. Antibiotic therapy is transversal to both conservative and surgical approaches and must be initiated after etiological diagnosis. Indications for surgical treatment include neurological deficits or sepsis, spine instability and/or deformity, presence of epidural abscess and upon failure of conservative treatment. CONCLUSIONS: A methodological assessment could lead to diagnosis effectiveness of spinal infection. Towards this, we present a management algorithm based on literature findings

A small scale fading model with sectored and three dimensional diffuse scattering

In frequency non-selective fading channels the multipath components can arrive at the mobile receiver via a three dimensional (3-D) scattering mechanism. That case occurs especially in urban environments, in which the tall buildings and other obstacles cause an arrival of multipath energy in the elevation plane, besides that arriving in the azimuth one. Another issue, which is a matter of investigation, is that the multipath energy may arrive at the mobile receiver in specific angular sectors. This is caused when a part of energy is blocked by the channel obstacles, or no multipath energy arrives from certain directions, due to lack of scattering objects in those directions, or directional antennas are employed. In this paper we propose a model which takes into account both 3-D multipath scattering and partial arrival of multipath energy. The proposed model assumes that the multipath components arrive at specific angular sectors in the azimuth receiver's plane, whereas in the elevation plane the angles of arrival are of continuous nature. Moreover a specular component with constant amplitude also exists. From the closed form autocorrelation function, the Doppler power spectral density (PSD) of the model is analytically derived Afterwards the probability density function (PDF) of the envelope and phase are analytically calculated. What follows are the second order statistics, level crossing rate (LCR) and average duration of fades (ADF's), in closed form

On the Scatterers' Mobility and Second Order Statistics of Narrowband Fixed Outdoor Wireless Channels

In this paper, we study the temporal behavior of narrowband fixed outdoor wireless channels by modeling the impact of scatterers' mobility on the second order statistics of such channels. We show that the Nakagami-m, gamma, Weibull and lognormal probability density functions (PDFs) can adequately approximate the scatterers' mobility at outdoor environments by comparing the theoretically derived autocorrelation functions (ACFs) with measured ACFs. These theoretical ACFs arise after considering several candidate PDFs for the impact of scatterers mobility. We select that PDF whose ACF provides the best fitting to measurements. The modeling of scatterers' mobility lead us to present analytical expressions for the level crossing rate (LCR) and average fade duration (AFD) together with an exact expression for the power spectral density (PSD)

Simple closed-form channel capacity formulas for the SIMO Nakagami channel

This paper presents simple closed-form expressions for the ergodic channel capacity of SIMO (single-input and multiple output) wireless systems operating in a Nakagami fading channel. As the performance of SIMO channel is closely related to the diversity combining techniques, we present close form expressions for the capacity of maximal ratio combining (MRC), equal gain combining (EGC) and selection combining (SC) diversity systems for Nakagami fading channels. Also for the first time in international literature, the ergodic capacity of a SIMO system in a Nakagami fading channel with none diversity combining technique applied, is derived. Finally numerical results are presented for illustration

Episodes of generalized weakness in two sibs with the C164T mutation of the connexin 32 gene

Two sibs with Charcot-Marie-Tooth disease had repeated episodes of generalized weakness. The patients had distal weakness and atrophy as well as findings of CNS involvement on brain MRI. Both patients bear the C164T mutation of the connexin 32 gene but no mutations of the genes responsible for hyper- or hypokalemic periodic paralysis. It is possible that both patients have one disease with complex phenotype due to abnormal expression of the connexin 32 gene

Three novel mutations in the gap junction beta 1 (GJB1) gene coding region identified in Charcot-Marie-Tooth patients of Greek origin: T55I, R164Q, V120E. Mutation in brief no 236. Online.

Charcot-Marie-Tooth (CMT) disease type CMTX has been linked with mutations in GJB1, a gene on chromosome X coding for a gap junction protein, Connexin 32. We screened the GJB1 gene for mutations by SSCP analysis and sequencing of candidate regions, in five unrelated CMT affected individuals, members of families presenting a mode of transmission and clinical findings compatible with CMTX. Mutations were detected in all five patients. Three not previously reported mutations were identified: C164T, G491A and T359A. Two patients shared the same mutation (C164T) while one had a reported mutation (C43T). Restriction enzyme digestion confirmed the sequencing results, as well as the co-segregation of the mutation with the disease. The same method was used to screen 150 control X chromosomes and the variations were not detected