Erasure Multiple Descriptions

We consider a binary erasure version of the n-channel multiple descriptions problem with symmetric descriptions, i.e., the rates of the n descriptions are the same and the distortion constraint depends only on the number of messages received. We consider the case where there is no excess rate for every k out of n descriptions. Our goal is to characterize the achievable distortions D_1, D_2,...,D_n. We measure the fidelity of reconstruction using two distortion criteria: an average-case distortion criterion, under which distortion is measured by taking the average of the per-letter distortion over all source sequences, and a worst-case distortion criterion, under which distortion is measured by taking the maximum of the per-letter distortion over all source sequences. We present achievability schemes, based on random binning for average-case distortion and systematic MDS (maximum distance separable) codes for worst-case distortion, and prove optimality results for the corresponding achievable distortion regions. We then use the binary erasure multiple descriptions setup to propose a layered coding framework for multiple descriptions, which we then apply to vector Gaussian multiple descriptions and prove its optimality for symmetric scalar Gaussian multiple descriptions with two levels of receivers and no excess rate for the central receiver. We also prove a new outer bound for the general multi-terminal source coding problem and use it to prove an optimality result for the robust binary erasure CEO problem. For the latter, we provide a tight lower bound on the distortion for \ell messages for any coding scheme that achieves the minimum achievable distortion for k messages where k is less than or equal to \ell.Comment: 48 pages, 2 figures, submitted to IEEE Trans. Inf. Theor

The Role and Impact of English as a Language and a Medium of Instruction in Saudi Higher Education Institutions: Students-Instructors Perspective

English as a medium of Instruction in higher education institutions across the Kingdom of Saudi Arabia is a debatable subject. The Ministry of Higher Education mandates English as the Medium Instruction (EMI) in all the higher education institutions across the kingdom. Since Arabic is the mother tongue of the natives and the only spoken language in the entire region, it is the only medium of instruction in all the schools up to the secondary level. English is formally introduced as the language of instruction in undergraduate level. This sudden shift in language produces a barrier which creates chaos and repulsive issues with the medium of instruction. All the universities have their separate English Language Centre (ELC) as well as Preparatory Year Program (PYP) where they intensively train and prepare students for the English language. Emphasis is laid upon improving students reading, writing, speaking, and listening skills. However, many studies conducted to examine the issue of medium of instruction have revealed an existence of a huge gap between teaching and learning, knowledge acquisition, and overall understanding of the subjects using English medium of instruction. Arabization is also a major contributing factor in making the situation difficult. Students and instructors encounter high levels of challenges and obstacles during the course of classroom instruction. This paper identifies the gap between English medium instruction (EMI) and Arab medium instruction (AMI) and investigates the root cause of the issues taking into account the reports of other case studies. The paper concludes with recommendations to address these issues

From the Indian Ocean to the Persian: Pakistan\u27s Historical Links with the Middle East in the 1970s

“From the Indian Ocean to the Persian Gulf” assesses Pakistan’s connections to two of the Persian Gulf’s principal actors, Iran and Saudi Arabia from 1971 to 1977. In the aftermath of the 1971 Indo-Pak War, Islamabad began orienting its foreign policy toward the Gulf politically, economically, militarily, and religiously. These relationships in the 1970s established the foundation for Pakistan’s relations with the Gulf in the 1980s and subsequent decades. Utilizing Pakistani news media, Zulfikar Ali Bhutto’s speeches and statements, memoirs from Pakistani diplomats, and American archival material, I argue that understanding the ways in which Pakistan, Iran, and Saudi Arabia interacted with each other in this period helps to explain the cooperation seen during the Soviet war in Afghanistan and the Iran-Iraq War of the 1980s. Furthermore, this project sheds light on the importance of regional constructions to foreign policy interests. Islamabad, Tehran, and Riyadh all consciously placed themselves in one interconnected region, aligning the interests of the Persian Gulf with that of the Indian Ocean. The United States was also heavily involved in promoting this regional construction to suit its own foreign policy interests. While the U.S. angle is examined in some detail, this project is largely concerned with the ways in which states in the global south interacted with each other and the implications of these relations

Survival analysis of chronic dialysis patients

Background: The number of dialysis patients is steadily rising in Canada because of demographic changes as well as an increased prevalence of associated risk factors such as hypertension, diabetes, and aging (Clark & Khan, 2010). Therefore, survival analysis of dialysis patients and the investigation of factors associated with survival outcome is crucial. This study aimed to estimate the survival rate of dialysis patients in Grand River Hospital (GRH), compare the survival outcome of Peritoneal Dialysis (PD) and Hemodialysis (HD) patients and assess the factors affecting survival outcome. Methods: This retrospective study was based on the data on incident chronic dialysis patients (>30 days of dialysis) who initiated dialysis from January 2012 to September 2017. Acute dialysis patients and those who initiated dialysis before the start of the study were excluded. Kaplan-Meier (KM) survival curves were generated to estimate the overall survival of the cohort as well as by different age categories, gender and, type of modality. The Cox Proportional Hazard (PH) model was used to identify variables significantly associated with survival outcome. Results: A total of 723 incident chronic dialysis with the average age of 64.86 years contributed to this analysis. The median survival time in this population was 39.8 months. Estimated 1-, 3- and 5- year survival rates were, 0.8, 0.54 and 0.34, respectively. Using the log-rank test, there was no statistical differences in survival outcome between patients undergoing HD and PD in this study (p=0.464). Backward elimination procedure with the two cut-offs (p>0.1 and p>0.2) resulted in two models in which hypertension was found to be significant in both (model A: adjusted HR = 0.62, p=0.013; model B: adjusted HR = 0.65, p=0.023). Conclusion: This research showed comparable survival rates for incident chronic dialysis patients receiving care in GRH, similar survival experience of HD and PD patients and protective impact of hypertension on survival outcome. Long-term survival outcome results were similar between both groups; however, PD patients had an improved survival outcome during the first 18 months of the study

Pressure dependence of the Verwey transition in magnetite: an infrared spectroscopic point of view

We investigated the electronic and vibrational properties of magnetite at temperatures from 300 K down to 10 K and for pressures up to 10 GPa by far-infrared reflectivity measurements. The Verwey transition is manifested by a drastic decrease of the overall reflectance and the splitting of the phonon modes as well as the activation of additional phonon modes. In the whole studied pressure range the down-shift of the overall reflectance spectrum saturates and the maximum number of phonon modes is reached at a critical temperature, which sets a lower bound for the Verwey transition temperature T$_{\mathrm{v}}$. Based on these optical results a pressure-temperature phase diagram for magnetite is proposed.Comment: 5 pages, 4 figures; accepted for publication in J. Appl. Phy

Optical signature of the pressure-induced dimerization in the honeycomb iridate α\alpha-Li2_2IrO3_3

We studied the effect of external pressure on the electrodynamic properties of $\alpha$-Li$_2$IrO$_3$ single crystals in the frequency range of the phonon modes and the Ir $d$-$d$ transitions. The abrupt hardening of several phonon modes under pressure supports the onset of the dimerized phase at the critical pressure $P_c$=3.8 GPa. With increasing pressure an overall decrease in spectral weight of the Ir $d$-$d$ transitions is found up to $P_c$. Above $P_c$, the local (on-site) $d$-$d$ excitations gain spectral weight with increasing pressure, which hints at a pressure-induced increase in the octahedral distortions. The non-local (intersite) Ir $d$-$d$ transitions show a monotonic blue-shift and decrease in spectral weight. The changes observed for the non-local excitations are most prominent well above $P_c$, namely for pressures $\geq$12 GPa, and only small changes occur for pressures close to $P_c$. The profile of the optical conductivity at high pressures ($\sim$20 GPa) appears to be indicative for the dimerized state in iridates.Comment: 10 pages, 6 figures; accepted for publication in Phys. Rev.

Minimum-cost multicast over coded packet networks

We consider the problem of establishing minimum-cost multicast connections over coded packet networks, i.e., packet networks where the contents of outgoing packets are arbitrary, causal functions of the contents of received packets. We consider both wireline and wireless packet networks as well as both static multicast (where membership of the multicast group remains constant for the duration of the connection) and dynamic multicast (where membership of the multicast group changes in time, with nodes joining and leaving the group). For static multicast, we reduce the problem to a polynomial-time solvable optimization problem, and we present decentralized algorithms for solving it. These algorithms, when coupled with existing decentralized schemes for constructing network codes, yield a fully decentralized approach for achieving minimum-cost multicast. By contrast, establishing minimum-cost static multicast connections over routed packet networks is a very difficult problem even using centralized computation, except in the special cases of unicast and broadcast connections. For dynamic multicast, we reduce the problem to a dynamic programming problem and apply the theory of dynamic programming to suggest how it may be solved