Improved Spatial Modulation for High Spectral Efficiency

Spatial Modulation (SM) is a technique that can enhance the capacity of MIMO schemes by exploiting the index of transmit antenna to convey information bits. In this paper, we describe this technique, and present a new MIMO transmission scheme that combines SM and spatial multiplexing. In the basic form of SM, only one out of MT available antennas is selected for transmission in any given symbol interval. We propose to use more than one antenna to transmit several symbols simultaneously. This would increase the spectral efficiency. At the receiver, an optimal detector is employed to jointly estimate the transmitted symbols as well as the index of the active transmit antennas. In this paper we evaluate the performance of this scheme in an uncorrelated Rayleigh fading channel. The simulations results show that the proposed scheme outperforms the optimal SM and V-BLAST (Vertical Bell Laboratories Layered space-time at high signal-to-noise ratio (SNR). For example, if we seek a spectral efficiency of 8 bits/s/Hz at bit error rate (BER) of 10^-5, the proposed scheme provides 5dB and 7dB improvements over SM and V-BLAST, respectively.Comment: 7 pages, 4 figures, 1 table, International Journal of Distributed and Parallel Systems (IJDPS) Vol.3, No.2, March 201

Mitigation and control of electric fields on spacers' surfaces in gas insulated systems

Research in the area of gas insulated systems' (GIS) reliability is still attracting a considerable attention from the electric utilities and the scientific community in many countries. Solid insulating spacers in GIS represent the weakest points in these systems, and several troubles and systems' outages have been reported allover the world due to their failure. So it is essential to determine the electric field distribution along their surfaces and hence evaluate the degree of their reliability. Several researchers evaluated the electric field distribution on the spacers' surfaces in gas insulated systems and studied the effects of their dimensions and its relative permittivity on the electric field stress distribution. The outcome of these investigations is that the electric field stresses intensify around the triple junction and they are the main reason to initiate breakdown in gas insulated systems. Due to the previously mentioned spacers' troubles, they should be precisely designed to realize more or less uniform field distribution along their surfaces. The spacer's profile is considered the main variable, which controls the field distribution and hence field uniformity can be achieved by adopting the appropriate profile. This paper uses the artificial neural network technique "ANN" to optimize the electric field on the spacer's surface, and introduces a novel method based on replacing the spacer's material with a constant permittivity by another one having a functionally graded permittivity to optimize and control the electric field along its surface. The use of the ANN enabled the authors to design a spacer with a pre-selected almost uniform field along its surface. The error between the target field and the evaluated one is ± 5%. Also the use of FGM reduced the electric field near the triple junction at the enclosure to les than 50% in some cases

Sudden cardiac arrest and coexisting mitral valve prolapse: a case report and literature review

The aetiology of sudden cardiac arrest can often be identified to underlying cardiac pathology. Mitral valve prolapse is a relatively common valvular pathology with symptoms manifesting with increasing severity of mitral regurgitation (MR). It is unusual for severe MR to be present without symptoms, and there is growing evidence that this subset of patients may be at increased risk of sudden cardiac arrest or death. The difficulty lies in identifying those patients at risk and applying measures that are appropriate to halting progression to cardiac arrest. This article examines the association of mitral valve prolapse with cardiac arrests, the underlying pathophysiological process and the strategies for identifying those at risk

Role of ankle-brachial pressure index as a predictor of coronary artery disease severity in diabetic and non-diabetic patients

PurposeThe aim of the study was to estimate the role of ankle-brachial pressure index (ABI) in predicting severity of coronary artery disease (CAD) in patients with or without diabetes mellitus.MethodsThis study included 120 patients with CAD proved by coronary angiography and ABI was measured for all of them. They were divided into 4 groups; Group (A): Non-diabetic patients without peripheral arterial disease (PAD) (ABI < or =0.9) , Group (B):diabetic patients without PAD (ABI < or =0.9), Group (C):Non-diabetic patients with PAD (ABI>0.9) and Group (D):diabetic patients with PAD (ABI>0.9).ResultsHypertension was more prevalent in group (D) (p value>0.05). Group (C) had the highest mean age and the highest percentage of smokers, after normalization of the effects of the risk factors mean Gensini score, mean number of affected coronary vessels, mean number of coronary artery lesions and the percentage of coronary artery chronic total occlusions (CTO) were significantly higher in groups (C & D) (p>0.001) (Table 1).ConclusionABI had a significant relationship with the degree of CAD severity. Therefore ABI seems to be a reliable independent prognostic marker of CAD severity in patients with or without diabetes mellitus

Rotating Scheimpflug Imaging Indices in Different Grades of Keratoconus

Purpose. To evaluate accuracy of various Keratoconus (KC) screening indices, in relation to Topographic Keratoconus (TKC) grading. Setting. Al Watany Eye Hospital, Cairo, Egypt. Methods. Data of 103 normal (group 1) and 73 KC eyes (group 2), imaged by Pentacam (branded as Allegro Oculyzer), were analysed. Group 2 was divided into 2a: 14 eyes (TKC = 1, early KC), 2b: 25 eyes (TKC = 1 to 2 or 2, moderate KC), and 2c: 34 eyes (TKC = 2 to 3 up to 4, severe KC). Participants were followed up for six years to confirm diagnosis. Area under the receiver operating characteristic curve (AUROC) was calculated for evaluated curvature, elevation, and pachymetry indices with various reference shapes at different diameters. Results. When comparing normal to KC eyes, ten indices had significantly higher AUROC. Only five of them had significantly higher AUROC in early KC compared to normal corneas: Pachymetry Progression Index- (PPI-) Maximum (Max), Ambrósio’s Relational Thickness- (ART-) Max, PPI-Max minus PPI-Minimum (Min), central corneal thickness (CCT), and diagonal decentration of thinnest point from the apex (AUROC = 0.690, 0.690, 0.687, 0.683, and 0.674, resp.). Conclusion. Generally, ten pachymetry and elevation-based indices had significantly higher AUROC. Five indices had statistically significant high AUROC when comparing early KC to normal corneas

The Effect of Different Irrigant Activation Methods on Postoperative Pain After Endodontic Retreatment

Objective: This study was designed to evaluate the effect of different irrigant activation methods on post operative pain after endodontic retreatment. Materials and Methods : Seventy eight patients need non surgical retreatment in mandibular first molar were involved in the study. The retreatment was performed in two visits ,at first visit cases were randomly divided into three groups according to methods of irrigant activation after root canal retreatment with protaper next rotary Ni-TI system. Group A (n=26) Root canals were irrigated using 2.6% sodium hypochlorite (NaOCl) with manual dynamic agitation using master cone Group B (n=26) Root canals were irrigated using 2.6% sodium hypochlorite (NaOCl) using ultrasonic machine (ultra-x) for 60 seconds. Group C (n=26) Root canals were irrigated using 2.6% sodium hypochlorite (NaOCl) with NaviTip (29-gauge 27 mm) with double side tip. At second visit after one week, obturation was performed using modified single cone technique ans access cavity was filled with coronal restoration. After two visits root canal treatment and a specific method of agitation, depending on each group, the patients were given a questionnaire on which the patient would mark the degree of pain in a scale from 0 to 10 at 6, 12, 24, 48 72 hrs and one week post-obturation. Data were statistically analyzed with a significance level of P ≤0.05. Results: At 6,12,24 hrs, there was significant difference between the groups in pain intensity where control group C (Navitip with side vented needle) showed more pain scores than in the intervention groups (Ultra X and manual dynamic agitation). On the other hand, at 48, 72 hours and 7 days post- operative ,there was no statistically significant difference in pain among tested groups. Conclusion: Agitation of the irrigation is reliable safe to clinican and effective as final step irrigation protocol with successful management of postoperative pain in retreatment cases. The intensity of postoperative pain decreased with time regardless of final irrigation protocol used

Predictors of contractile recovery after successful primary percutaneous coronary intervention

Background: Accurate diagnosis, characterization, and quantification of myocardial infarction (MI) are essential to assess the impact of therapy and to aid in predicting prognosis of patients with ischaemic heart disease.Objective: This study aimed to define different parameters regarding prediction of myocardial functional recovery following successful reperfusion of acute ST segment elevation myocardial infarction (STEMI).Patients and methods: This prospective study was carried out in Zagazig University and National Heart Institute (NHI) of Egypt during the period from June 2020 to June 2021. The study included 48 patients admitted with first acute STEMI. All patients were subjected to demographic data taking, electrocardiography and echocardiography examination (two examinations were done, the first was immediately after reperfusion and the second was 3 months from primary percutaneous coronary intervention (PCI).Results: There was no statistically significant difference between demographic data and risk factors except smoking habit. Regarding laboratory findings there were significant lower troponin value, peak CKMB value compared to patients had remolding (p=0.0001, p=0.027 respectively). Regarding ECG parameters, there was no statistical significant difference between the study groups regarding sum ST elevation and MI territory (p value &gt; 0.05), but there was highly statistically significant difference between the study groups regarding 90 min ST resolution among contractile recovery (group I) p=0.0001.Conclusions: In this study patients affected by AMI with ST segment elevation and treated by primary PCI showed contractile recovery in 60.4% of the patients, while the remodeling of the LV has been observed in 39.6%