632 research outputs found
Asymptotics of Nonlinear LSE Precoders with Applications to Transmit Antenna Selection
This paper studies the large-system performance of Least Square Error (LSE)
precoders which~minimize~the~input-output distortion over an arbitrary support
subject to a general penalty function. The asymptotics are determined via the
replica method in a general form which encloses the Replica Symmetric (RS) and
Replica Symmetry Breaking (RSB) ans\"atze. As a result, the "marginal
decoupling property" of LSE precoders for -steps of RSB is derived. The
generality of the studied setup enables us to address special cases in which
the number of active transmit antennas are constrained. Our numerical
investigations depict that the computationally efficient forms of LSE precoders
based on "-norm" minimization perform close to the cases with
"zero-norm" penalty function which have a considerable improvements compared to
the random antenna selection. For the case with BPSK signals and restricted
number of active antennas, the results show that RS fails to predict the
performance while the RSB ansatz is consistent with theoretical bounds.Comment: 5 pages; 2 figures; to be presented at ISIT 201
Recommended from our members
Low-Level HIV-I Replication and the Dynamics of the Resting CD4(+) T Cell Reservoir for HIV-I in the Setting of HAART
In the setting of highly active antiretroviral therapy (HAART), plasma levels of human immunodeficiency type-I (HIV-I) rapidly decay to below the limit of detection of standard clinical assays. However, reactivation of remaining latently infected memory CD4(+) T cells is a source of continued virus production, forcing patients to remain on HAART despite clinically undetectable viral loads. Unfortunately, the latent reservoir decays slowly, with a half-life of up to 44 months, making it the major known obstacle to the eradication of HIV-I infection. However, the mechanism underlying the long half-life of the latent reservoir is unknown. The most likely potential mechanisms are low-level viral replication and the intrinsic stability of latently infected cells. Methods: Here we use a mathematical model of T cell dynamics in the setting of HIV-I infection to probe the decay characteristics of the latent reservoir upon initiation of HAART. We compare the behavior of this model to patient derived data in order to gain insight into the role of low-level viral replication in the setting of HAART. Results: By comparing the behavior of our model to patient derived data, we find that the viral dynamics observed in patients on HAART could be consistent with low-level viral replication but that this replication would not significantly affect the decay rate of the latent reservoir. Rather than low-level replication, the intrinsic stability of latently infected cells and the rate at which they are reactivated primarily determine the observed reservoir decay rate according to the predictions of our model. Conclusion: The intrinsic stability of the latent reservoir has important implications for efforts to eradicate HIV-I infection and suggests that intensified HAART would not accelerate the decay of the latent reservoir.NIH AI 065960, AI 143222, AI 51178Doris Duke Charitable FoundationThe Howard Hughes Medical InstituteIntegrative Biolog
Healthcare utilization in patients with esophageal cancer in a high risk area in northeast of Iran
Introduction: Golestan, a province located north of Persian Gulf in northeastern part of Iran is a well known area for high risk of esophageal cancer (EC) in the world. There is no information about healthcare utilization in populations residing in the area. This study was conducted to assess utilization of healthcare and its associated factors among esophageal cancer patients in this region as well as to address ethical implication of this utilization. Methods: All new cases of EC in Golestan province during year of 2007 were recruited. Seven diagnostic and five therapeutic services were used to assess diagnostic utilization index (DUI), and therapeutic utilization index (TUI), respectively. Multivariate regression analysis was used to assess the relationship between variables and DUI or TUI. P-value of less than 0.05 was considered as statistically significant. Results: Tow hundred twenty three, patients were enrolled with mean (Standard Deviation) age of 64.3 (12.5) years with 57.8% male. We observed that occupation (P<0.01), ethnicity (P<0.01) and sex (P=0.03) were strongly associated with DUI. Insurance coverage (P<0.01), place of residency (P<0.01), and occupation (P=0.01) were associated with TUI. Conclusion: We concluded that several factors contribute to disparity in healthcare utilization in the studied population
Kinetics of the viral cycle influence pharmacodynamics of antiretroviral therapy
<p>Abstract</p> <p>Background</p> <p>More and more antiretroviral therapies are being developed for treatment of HIV infection. The <it>in-vivo </it>efficacy of these drugs is commonly predicted based on <it>in-vitro </it>measures of antiviral effect. One primary <it>in-vitro </it>measure is the IC50, the amount of drug required for 50% inhibition of viral replication. We have previously shown that HIV life-cycle kinetics impact clinically observed HIV viral dynamics. Here we present a mathematical model of how they affect the pharmacodynamics of antiretroviral drugs.</p> <p>Results</p> <p>We find that experimentally measured antiretroviral IC50s are determined by three factors: (i) intrinsic drug properties (e.g. drug-target binding), (ii) kinetics of the HIV life cycle, and (iii) kinetics of drug-inhibited infected cells. Our model predicts that the IC50 is a declining function of the duration of the drug-susceptible stage in the host cell. We combine our model with known viral life-cycle kinetics to derive a measure of intrinsic properties, reflecting drug action, for known antiretroviral drugs from previously measured IC50s. We show that this measure of intrinsic drug property correlates very well with <it>in vitro</it>-measured antiviral activity, whereas experimentally measured IC50 does not.</p> <p>Conclusions</p> <p>Our results have implications for understanding pharmacodynamics of and improving activity of antiretroviral drugs. Our findings predict that drug activity can be improved through co-administration of synergistic drugs that delay the viral life cycle but are not inhibitory by themselves. Moreover, our results may easily extend to treatment of other pathogens.</p> <p>This article was reviewed by Dr. Ruy Ribeiro, Dr. Ha Youn Lee, Dr. Alan Perelson and Dr. Christoph Adami.</p
Cancer incidence in Golestan province: Report of an ongoing population-based cancer registry in Iran between 2004 and 2008
Background: Golestan Province, at the western end of the Asian esophageal cancer (EC) belt in northeastern Iran, was reported to have one of the highest worldwide rates of EC in the 1970s. We have previously shown a declining incidence of EC in Golestan during the last decades. This study reports additional new results from the Golestan Population-based Cancer Registry (GPCR). Methods: The GPCR collected data from newly diagnosed (incident) cancer cases from all 68 public and private diagnostic and therapeutic centers in Golestan Province. CanReg-4 software was used for data entry and analysis based on the guidelines of the International Agency for Research on Cancer (IARC). Age-standardized incidence rates (ASR) of cancers were calculated using the 2000 world standard population. Results: From 2004 through 2008, 9007 new cancer cases were reported to the GPCR. The mean (SD) age was 55.5 (18.6) years, and 54 were diagnosed in men. The ASRs of all cancers were 175.3 and 141.1 per 100,000 person-years for males and females, respectively. Cancers of the stomach (ASR:30.7), esophagus (24.3), and lung (15.4) were the most common cancers in males. In females, breast cancer (ASR:26.9) was followed by malignancies of the esophagus (19.1) and stomach (12.4). The diagnosis of cancer was based on histopatho- logical reports in 71 and on death certificate only in 9 ofcases. Conclusions: The EC incidence rate continues to decline in Golestan, while the incidence rates of stomach, colorectal, and breast cancers continue to increase
Recommended from our members
Characterization of aeroallergen sensitivities in children with allergic rhinitis and chronic rhinosinusitis
Allergic rhinitis is a common comorbid condition in pediatric chronic rhinosinusitis (CRS). Testing for aeroallergen sensitization should therefore be considered in the evaluation of children with CRS. At present the aeroallergen sensitivity profile of children with CRS remains uncharacterized. In this study, we retrospectively identify a consecutive series of children with CRS and allergic rhinitis who have undergone joint otolaryngology and allergy evaluation at a single tertiary care center. We describe the aeroallergen sensitivity profiles (based upon formal skin testing) of these children, stratifying them according to co-morbidity status: 1) CRS with cystic fibrosis (CF), 2) CRS with immune deficiency and 3) uncomplicated CRS (without co-morbid CF, immune deficiency or primary ciliary dyskinesia). We identify 208 children (average age 9.3 years, standard deviation 4.8 years) with CRS and allergic rhinitis meeting inclusion criteria, 140 with uncomplicated CRS, 64 with co-morbid immune deficiency and 4 with co-morbid CF. The prevalence of indoor aeroallergen sensitivities (62.9–100.0%) was more common than that of outdoor aeroallergen sensitivities (43.8–50.0%) in all three cohorts of children. In all three cohorts, the most common indoor aeroallergen sensitivity was to dust mites (50.0–75.0%) and the most common outdoor aeroallergen sensitivity was to tree pollens (43.8–50.0%). The aeroallergen sensitivity profile of children with CRS and allergic rhinitis appears to be similar to that of the general pediatric population with allergic rhinitis, and parallels the aeroallergen sensitivities previously described for adults with CRS and allergic rhinitis. Knowledge of the aeroallergen sensitivities in children with CRS and allergic rhinitis will enhance both diagnostic and treatment strategies
- …