Publications

Cooperation in the Low Power Regime for the MAC Using Multiplexed Rateless Codes

Cooperation in the Low Power Regime for the MAC Using Multiplexed Rateless Codes

In this paper, we consider cooperation in the low power (low SNR) regime for the multiple access channel with the assumption that the transmitters have no channel state information. A relevant performance measure to consider is therefore the outage capacity.
Time evolution of the Lamb shift

Time evolution of the Lamb shift

The time evolution of the Lamb shift that accompanies the real photon emission is studied for the first time (to our knowledge). The investigation of the explicit time dependence of the Lamb shift becomes possible because the self-energy of the free electron, which is divergent, is subtracted from the Hamiltonian after a unitary transformation. The Lamb shift can then be separated into two parts: one is the time-independent shift due to the virtual photon exchange, and the other is the time-dependent shift due to the real photon emission. The time evolution depends on the nature of the coupling spectrum of the reservoir. (C) 2010 Optical Society of America
Quantum teleportation of four-dimensional qudits

Quantum teleportation of four-dimensional qudits

A protocol for the teleportation of arbitrary quantum states of four-dimensional qudits is presented. The qudit to be teleported is encoded in the combined state of two ensembles of atoms placed in a cavity at the sender's side. The receiver uses a similar setup, with his atoms prepared in a particular initial state. The teleportation protocol then consists of adiabatic mapping of the ensemble states onto photonic degrees of freedom, which are then directed onto a specific beam splitter and detection setup. For part of the measurement outcome, the qudit state is fully transferred to the receiver. Other detection events lead to partial teleportation or failed teleportation attempts. The interpretation of the different detection outcomes and possible ways of improving the full teleportation probability are discussed.
Evidence of intense ongoing endemic transmission of hepatitis C virus in Egypt

Evidence of intense ongoing endemic transmission of hepatitis C virus in Egypt

Egypt has the highest prevalence of antibodies to hepatitis C virus (HCV) in the world, estimated nationally at 14.7%. An estimated 9.8% are chronically infected. Numerous HCV prevalence studies in Egypt have published various estimates from different Egyptian communities, suggesting that Egypt, relative to the other nations of the world, might be experiencing intense ongoing HCV transmission. More importantly, a new national study provided an opportunity to apply established epidemiologic models to estimate incidence. Validated mathematical models for estimating incidence from age-specific prevalence were used. All previous prevalence studies of HCV in Egypt were reviewed and used to estimate incidence provided that there was sufficient age-specific data required by the models. All reports of anti-HCV antibody prevalence were much higher than any single other national estimate. Age was the strongest and most consistently associated factor to HCV prevalence and HCV RNA positivity. It was not possible to establish a prior reference point for HCV prevalence or incidence to compare with the 2009 incidence estimates. The modeled incidence from the national study and collectively from the modeled incidence from the previous community studies was 6.9/1,000 [95% confidence interval (CI), 5.5-7.4] per person per year and 6.6/1,000 (95% CI, 5.1-7.0) per person per year, respectively. Projected to the age structure of the Egyptian population, more than 500,000 new HCV infections per year were estimated. Iatrogenic transmission is the most likely, underlining exposure to the ongoing transmission. The study demonstrates the urgency to reduce HCV transmission in Egypt.
Ligand substitution from the (eta(5)-DMP)Mn(CO)(2)(Solv) [DMP=2,5-dimethylpyrrole, Solv = solvent] complexes: To ring slip or not to ring slip?

Ligand substitution from the (eta(5)-DMP)Mn(CO)(2)(Solv) [DMP=2,5-dimethylpyrrole, Solv = solvent] complexes: To ring slip or not to ring slip?

The mechanism and energetics of the displacement of solvent from photolytically generated (eta(5)-DMP)Mn(CO)(2)(Solv) complexes has been studied [DMP = 2,5-dimethylpyrrole, Solv = solvent]. Rate enhancement relative to the eta(5)-cyclopentadienyl (Cp) system is not observed in the displacement of weakly bound solvents. The bond dissociation enthalpies obtained from the kinetic analysis are in good agreement with the values obtained by detailed density functional theory (DFT) calculations. The results indicate that for both the Cp and the DMP based systems the displacement of weakly bound solvents proceeds by a dissociative or I-d mechanism. This is in sharp contrast to CO displacement from (eta(5)-DMP)Mn(CO)(3), which is known to proceed by an associative mechanism by way of an eta(3) ring slip intermediate. The associative substitution pathway only becomes competitive with the dissociative channel when the Mn-Solv bond dissociation enthalpy is more than 33 kcal/mol.
Cognitive-Radio Systems for Spectrum, Location, and Environmental Awareness

Cognitive-Radio Systems for Spectrum, Location, and Environmental Awareness

In order to perform reliable communications, a system needs to have sufficient information about its operational environment, such as spectral resources and propagation characteristics. Cognitive-radio technology has capabilities for acquiring accurate spectrum, location, and environmental information, due to its unique features such as spectrum, location, and environmental awareness. The goal of this paper is to give a comprehensive review of the implementation of these concepts. In addition, the dynamic nature of cognitive-radio systems - including dynamic spectrum utilization, transmission, the propagation channel, and reception - is discussed, along with performance limits, challenges, mitigation techniques, and open issues. The capabilities of cognitive-radio systems for accurate characterization of operational environments are emphasized. These are crucial for efficient communications, localization, and radar systems.
Does consanguinity lead to decreased incidence of breast cancer?

Does consanguinity lead to decreased incidence of breast cancer?

Background In the Middle East region, consanguinity remains to be a central feature where it has shown an increasing trend Breast cancer is an extremely complex disease, characterized by a progressive multistep process caused by interactions of both environmental and genetic factors AIM The aim of this study was to examine the possible effect of consanguinity on the risk of breast cancer in a population with a high rate of consanguinity and find the associated risk-modifying factors Subjects and methods The study included 167 Qatari and other Arab expatriates women with breast cancer and 341 age and ethnicity matched control women A questionnaire that included the socio-demographic information, type of consanguinity, medical history, life style habits, dietary intake and tumor grade was designed to collect, the information of cases and controls A total number of 214 breast cancer patients were approached and 167 cases completed the questionnaires with a response rate of 78% Of the 417 healthy women who agreed to participate in this study. 341 responded to the questionnaire (81 8%) 
GENDER AND AGE-RELATED DIFFERENCES IN PATIENTS WITH THE METABOLIC SYNDROME IN A HIGHLY ENDOGAMOUS POPUL

GENDER AND AGE-RELATED DIFFERENCES IN PATIENTS WITH THE METABOLIC SYNDROME IN A HIGHLY ENDOGAMOUS POPUL

The objective of the study was to examine the differences in gender and age prevalences of metabolic syndrome (MetS) among adult Qatari population according to the revised criteria of NCEP ATP III and IDF, assess which component contributed to the higher prevalence of the MetS and identify the characteristics of the subjects with MetS. The study was designed as a cross-sectional study. The survey was carried out in urban and semi-urban primary health care centers. The survey was conducted in the period from January 2007 to July 2008 among Qatari nationals above 20 years of age. Of the 1536 subjects who were approached to participate in the study, 1222 (79.6%) gave their consent.
Sampling theorems associated with biorthogonal q-Bessel functions

Sampling theorems associated with biorthogonal q-Bessel functions

This paper deals with the derivation of sampling theorems associated with q-biorthogonal systems. We derive interpolation expansions for q-Hankel transforms whose kernels are the second-type q-Bessel functions J(nu)((2))(z; q), nu > 0, 0 < q < 1.
Population Genetic Structure of the People of Qatar

Population Genetic Structure of the People of Qatar

People of the Qatar peninsula represent a relatively recent founding by a small number of families from three tribes of the Arabian Peninsula, Persia, and Oman, with indications of African admixture.
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DeSIGN: Guided Practice for Sign Language

DeSIGN: Guided Practice for Sign Language

Children learn and practice their vocabulary through interaction with parents and friends as well as through formal instruction at school. However, for deaf children, sign language is the main method of communication. Despite the importance of strong vocabulary skills for understanding text, effective verbal communication and integration into society, the average deaf student graduates from American high schools with a fourth grade reading level. This can be partially attributed to the fact that 90% of deaf children are born to hearing parents who are rarely fluent in sign language.

Calcium channels determine how life begins, and ends
Calcium channels determine how life begins, and ends

Calcium channels determine how life begins, and ends

Ongoing work at Weill Cornell Medical College in Qatar (WCMC-Q) is investigating how intracellular calcium (Ca2+) signaling pathways are involved in the very beginning of life as they prepare the egg for fertilization and the initiation of embryogenesis. The National Priorities Research Program-funded work also has wider implications. Since all cells use Ca2+ signals, these studies could impact the treatment of various pathological conditions including infertility, hypertension, and cancer.
Cells in the human body need to be able to sense their environment in order to respond to cues to perform some function. Intercellular signaling, using hormones sent from one part of the body to another, allow, for example, the brain to tell your hand to pick up a pen as neurons in the brain fire action potentials to trigger the relevant muscle actions. For other cells, the message may be to divide or to die if infected by a virus.

Taking gas-to-liquid technology to the next level
Taking gas-to-liquid technology to the next level

Taking gas-to-liquid technology to the next level

In the 1920s, two German scientists—Franz Fischer and Hans Tropsch—developed revolutionary chemical reactions that could transform gas into liquid. These reactions proved particularly valuable to natural gas-based fuel processing. Since the Fischer-Tropsch days, engineers around the world have been working on ways to tweak these gas-to-liquid (GTL) reactions to produce more products, more efficiently and with less environmental impact. An international research team headquartered at Texas A&M University at Qatar (TAMUQ) is making remarkable progress along these lines.

Researchers discover a remarkably easy way to make filters at the nano scale
Researchers discover a remarkably easy way to make filters at the nano scale

Researchers discover a remarkably easy way to make filters at the nano scale

From your average spaghetti strainer to the screen on your windows, filters are a part of our every-day life. In their simplest form, they keep debris out of air and water. Yet as filter technology advances, so does the level of precision around what we can keep out.
Today, it’s possible to create membranes that filter a range of substances on a nano (microscopic) scale, and a QNRF, NPRP grant-funded project has made significant progress in doing just that. A member of the team and advanced research fellow in experimental physics in the Biological and Soft Sciences Department at the University of Cambridge, Dr. Easan Sivaniah, explained:

Researchers build the case for wind and wave studies in Qatar
Researchers build the case for wind and wave studies in Qatar

Researchers build the case for wind and wave studies in Qatar

For the first time, fine detail about the wind and wave conditions around the coast of Qatar has been recorded. By arranging the most sophisticated equipment available on the edge of a 500-meter pier extending into the Gulf, a research team at Texas A&M University at Qatar (TAMUQ) has collected detailed readings of air and wave currents around the peninsula. Their findings highlight a dearth of information on coastal conditions that have the potential to offer vital insights into many sectors.
“The actual research started in trying to understand the relationship between the wind and waves,” said Dr. Reza Sadr, Assistant Professor in the Mechanical Engineering Department at TAMUQ. “Why do we need this? Because there are very poor models to track wind current and predict ocean waves, and this information affects, among other things, marine life, the offshore oil and gas industry and renewable energy initiatives.”
Around the world, the methods for measuring the patterns of wind and waves, also known as the atmospheric surface layer (ASL), are so far based on weather and wind models combined with analysis of the ocean dynamics. Dr. Sadr said that these models, however, need to be fortified with more sophisticated data and analysis for each region in the globe.

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