Noncoherent Space-Time Coding: An Algebraic Perspective

Cataloged from PDF version of article.The design of space–time signals for noncoherent block-fading channels where the channel state information is not known a priori at the transmitter and the receiver is considered. In particular, a new algebraic formulation for the diversity advantage design criterion is developed. The new criterion encompasses, as a special case, the well-known diversity advantage for unitary space–time signals and, more importantly, applies to arbitrary signaling schemes and arbitrary channel distributions. This criterion is used to establish the optimal diversity-versus-rate tradeoff for training based schemes in block-fading channels. Our results are then specialized to the class of affine space–time signals which allows for a low complexity decoder. Within this class, space–time constellations based on the threaded algebraic space–time (TAST) architecture are considered. These constellations achieve the optimal diversity-versus-rate tradeoff over noncoherent block-fading channels and outperform previously proposed codes in the considered scenarios as demonstrated by the numerical results. Using the analytical and numerical results developed in this paper, nonunitary space–time codes are argued to offer certain advantages in block-fading channels where the appropriate use of coherent space–time codes is shown to offer a very efficient solution to the noncoherent space–time communication paradigm

Recovering the state sequence of hidden Markov models using mean-field approximations

Inferring the sequence of states from observations is one of the most fundamental problems in Hidden Markov Models. In statistical physics language, this problem is equivalent to computing the marginals of a one-dimensional model with a random external field. While this task can be accomplished through transfer matrix methods, it becomes quickly intractable when the underlying state space is large. This paper develops several low-complexity approximate algorithms to address this inference problem when the state space becomes large. The new algorithms are based on various mean-field approximations of the transfer matrix. Their performances are studied in detail on a simple realistic model for DNA pyrosequencing.Comment: 43 pages, 41 figure

Computer-Based Clinical Examination (CCE) in Surgery: Would It Complement or Replace the OSCE in the Post-COVID-19 Era?

Objectives: Surgical clinical assessment of medical students is confronted by many challenges particularly the increasing numbers of students with limited resources, and pandemics. The search for new tools of assessment continues. Our objectives were: (1) To develop a computer-based clinical exam (CCE) and identify its characteristics (2) To assess its acceptability of the students. Method: The study was conducted at the Surgical Department, Alzaiem Alazhari University (AAU) between February and August, 2017. We used the modular objectoriented dynamic learning environment (MOODLE) program as a platform to upload and deliver the exam. The exam consisted of 45 questions (stations). Each consisted of a clinical scenario accompanied by a photograph (of a patient or investigation) or short video followed by multiple choice questions (MCQs). A questionnaire was designed to get the students’ feedback. We analyzed the questionnaire and scores obtained by the students and compared them to their performance in other tools of the surgical exam, using SPSS statistical program. Results: The study included 188 final year medical students. There was a highly significant correlation of the CCE scores of each student with their final result (r= 0.67), and with other tools of the surgery exam particularly the objective structured clinical examination (OSCE). Students’ acceptability was high. Conclusion: The CCE is valid and practicable. It saves time and is popular with the students and tutors. It complements the OSCE in the assessment of clinical competency and allows wide coverage of the curriculum. It is expected to gain importance and popularity in the post-COVID-19 era

Joint source-channel coding for a quantum multiple access channel

Suppose that two senders each obtain one share of the output of a classical, bivariate, correlated information source. They would like to transmit the correlated source to a receiver using a quantum multiple access channel. In prior work, Cover, El Gamal, and Salehi provided a combined source-channel coding strategy for a classical multiple access channel which outperforms the simpler "separation" strategy where separate codebooks are used for the source coding and the channel coding tasks. In the present paper, we prove that a coding strategy similar to the Cover-El Gamal-Salehi strategy and a corresponding quantum simultaneous decoder allow for the reliable transmission of a source over a quantum multiple access channel, as long as a set of information inequalities involving the Holevo quantity hold.Comment: 21 pages, v2: minor changes, accepted into Journal of Physics

Root extracts of Saussurea costus as prospective detoxifying food additive against sodium nitrite toxicity in male rats

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGThe goal of this study was to investigate the effects of three different extracts of Saussurea costus roots (ethanol, methanol, and water) as a food additive in alleviating the harmful effect of sodium nitrite in rat meals. Thirty-five adult male rats were divided into five groups as follows: control, sodium nitrite (NaNO2; 75 mg/kg BW, single oral dose), S. costus 70% ethanol, 70% methanol, and aqueous extracts (300 mg/kg BW), respectively for four weeks followed by a single dose of NaNO2 24h before decapitation. Results showed that the 70% ethanol extract of S. costus has a higher concentration of total phenolic content, total flavonoids, and antioxidant effect than the 70% methanol and water extracts. Rats pretreated with S. costus extracts reduced the harmful effects induced by NaNO2 and improved the hematological parameters, liver, and kidney function biomarkers as well as lipid profile as compared to the NaNO2 group. Furthermore, S. costus improved the histopathological alterations in the liver and kidney induced by NaNO2 and improved meat sensory evaluation. Conclusively, the 70% ethanol extract of S. costus roots is the most effective extract as an antioxidant against the toxicity of sodium nitrite in male rats and might be used safely as a natural additive in the food industry

Characterization of Inertial Electrostatic Confinement Fusion Plasma Device

Inetial electrostatic confinment fusion (IECF) device constructed at the Egyptian Atomic Energy Authority (EAEA-IEC), is introduced the characterization of the IEC plasma device. The x-ray and visible light emissions in IEC plasma device were investigated by employing time -resolved detector and measure of the total amount of visible light using lux meter

Neutrophil functions in late preterm neonates with respiratory distress syndrome

Background: Studies that have addressed the effects of respiratory distress syndrome (RDS) on neutrophil function suggested that neutrophil functions other than the generation of the respiratory burst are not impaired. Yet, results have been confusing and in some cases contradictory.Objectives: The aim of this cross-sectional controlled study is to assess neutrophil number and function in late preterm neonates with RDS.Methods: Thirty patients underwent clinical and laboratory evaluation including complete blood counts and tests of neutrophil functions (CD11b, CD62L and Dihydrorhodamine 123 by flowcytometry) in comparison to 15 healthy term controls. RDS was assessed clinically and radiologically (chest x-ray).Results: Fifty percent of patients (12 females and 18 males) had grade II respiratory distress followed by grade III then grade I. DHR, CD 11b and CD62L results were lower among the patients group (mean ± SD: 62.1± 12.23, 63.22 ± 11.41, 15.03 ± 8.7 respectively). There were no significant correlations between neutrophils count, DHR, CD11b and CD62L. Only CD11b was significantly lower with higher grades of RDS.Conclusion: Neonates with RDS show variable affection of neutrophil functions. Further studies are recommended to elucidate the exact mechanisms by which RDS can affect neutrophil functions and whether these effects are associated with increased incidence of infections.Keywords: Neutrophils, function, respiratory distress syndrome, late preterm, innate immunity, infections, adhesion molecule

Development and optimization of fluoxetine orally disintegrating tablets using Box-Behnken design

Purpose: To develop and optimise some variables that influence fluoxetine orally disintegrating tablets (ODTs) formulation.Methods: Fluoxetine ODTs tablets were prepared using direct compression method. Three-factor, 3- level Box-Behnken design was used to optimize and develop fluoxetine ODT formulation. The design suggested 15 formulations of different lubricant concentration (X1), lubricant mixing time (X2), and compression force (X3) and then their effect was monitored on tablet weight (Y1), thickness (Y2), hardness (Y3), % friability (Y4), and disintegration time (Y5).Results: All powder blends showed acceptable flow properties, ranging from good to excellent. The disintegration time (Y5) was affected directly by lubricant concentration (X1). Lubricant mixing time (X2) had a direct effect on tablet thickness (Y2) and hardness (Y3), while compression force (X3) had a direct impact on tablet hardness (Y3), % friability (Y4) and disintegration time (Y5). Accordingly, Box-Behnken design suggested an optimized formula of 0.86 mg (X1), 15.3 min (X2), and 10.6 KN (X3). Finally, the prediction error percentage responses of Y1, Y2, Y3, Y4, and Y5 were 0.31, 0.52, 2.13, 3.92 and 3.75 %, respectively. Formula 4 and 8 achieved 90 % of drug release within the first 5 min of dissolution test.Conclusion: Fluoxetine ODT formulation has been developed and optimized successfully using Box- Behnken design and has also been manufactured efficiently using direct compression technique.Keywords: Box-Behnken experimental design, Orally disintegrating tablets, Direct compression, Antidepressant, Magnesium stearate, Mixing tim