Performance Analysis of Dynamic Downlink PPP Cellular Networks over Generalized Fading Channels with MRC Diversity

This paper proposes novel and generalized expressions to characterize the performance of modern cellular networks under realistic user mobility behavior. The η-μ distribution is employed to derive the received power probability density function, the average bit error rate for different modulation schemes, and the coverage probability assuming a Poisson point process spatial distribution of base stations in downlink. The user is assumed to experience fading with Maximum Ratio Combining (MRC) and move according to a random way-point mobility model. To get more insights on the achivable diversity order, accurate asymptotic expressions for the coverage probability and average bit error rate are derived. The derived expressions are applicable to different widely-used fading environments, such as Rayleigh and Nakagami-m as particular cases, by an appropriate selection of the η-μ parameters. Monte Carlo simulation was used to show the validity of the proposed expressions. In addition, the generalized expressions allow the system designer to quantify the effects of user mobility on the cellular network performance, in different propagation environments, and network topologies as a function of the number of base stations and MRC branches

The association of clinical indication for exercise stress testing with all-cause mortality: the FIT Project

INTRODUCTION: We hypothesized that the indication for stress testing provided by the referring physician would be an independent predictor of all-cause mortality. MATERIAL AND METHODS: We studied 48,914 patients from The Henry Ford Exercise Testing Project (The FIT Project) without known congestive heart failure who were referred for a clinical treadmill stress test and followed for 11 ±4.7 years. The reason for stress test referral was abstracted from the clinical test order, and should be considered the primary concerning symptom or indication as stated by the ordering clinician. Hierarchical multivariable Cox proportional hazards regression was performed, after controlling for potential confounders including demographics, risk factors, and medication use as well as additional adjustment for exercise capacity in the final model. RESULTS: A total of 67% of the patients were referred for chest pain, 12% for shortness of breath (SOB), 4% for palpitations, 3% for pre-operative evaluation, 6% for abnormal prior testing, and 7% for risk factors only. There were 6,211 total deaths during follow-up. Compared to chest pain, those referred for palpitations (HR = 0.72, 95% CI: 0.60-0.86) and risk factors only (HR = 0.72, 95% CI: 0.63-0.82) had a lower risk of all-cause mortality, whereas those referred for SOB (HR = 1.15, 95% CI: 1.07-1.23) and pre-operative evaluation (HR = 2.11, 95% CI: 1.94-2.30) had an increased risk. In subgroup analysis, referral for palpitations was protective only in those without coronary artery disease (CAD) (HR = 0.75, 95% CI: 0.62-0.90), while SOB increased mortality risk only in those with established CAD (HR = 1.25, 95% CI: 1.10-1.44). CONCLUSIONS: The indication for stress testing is an independent predictor of mortality, showing an interaction with CAD status. Importantly, SOB may be associated with higher mortality risk than chest pain, particularly in patients with CAD

Higher cardiorespiratory fitness predicts long-term survival in patients with heart failure and preserved ejection fraction: the Henry Ford Exercise Testing (FIT) Project

Introduction: Higher cardiorespiratory fitness (CRF) is associated with improved exercise capacity and quality of life in heart failure with preserved ejection fraction (HFpEF), but there are no large studies evaluating the association of HFpEF, CRF, and long-term survival. We therefore aimed to determine the association between CRF and all-cause mortality, in patients with HFpEF. Material and methods: In the Henry Ford Exercise Testing (FIT) Project, 167 patients had baseline HFpEF, defined as a clinical diagnosis of heart failure with ejection fraction ≥ 50% on echocardiogram. The CRF was estimated from the peak workload (in METs) from a clinician-referred treadmill stress test and categorized as poor (1-4 METs), intermediate (5-6 METs), and moderate-high (≥ 7 METs). Additional analyses assessing the effect of HFpEF and CRF on mortality were also conducted, matching HFpEF patients to non-HFpEF patients using propensity scores. Results: Mean age was 64 ±13 years, with 55% women, and 46% Black. Over a median follow-up of 9.7 (5.2-18.9) years, there were 103 deaths. In fully adjusted models, moderate-high CRF was associated with 63% lower mortality risk (HR = 0.37, 95% CI: 0.18-0.73) compared to the poor-CRF group. In the propensity-matched cohort, HFpEF was associated with a HR of 2.3 (95% CI: 1.7-3.2) for mortality compared to non-HFpEF patients, which was attenuated to 1.8 (95% CI: 1.3-2.5) after adjusting for CRF. Conclusions: Moderate-high CRF in patients with HFpEF is associated with improved survival, and differences in CRF partly explain the intrinsic risk of HFpEF. Randomized trials of interventions aimed at improving CRF in HFpEF are needed

Transition Economies in the Middle East: the Syrian Experience

There have been no in depth studies of post Socialist transition in the Middle East. Syria’s experience is a useful one to explore given its historically important role in the region and its distinctive characteristics. The Syrian economic transition, from the early 1990s to 2011, was in two phases: an incremental liberalisation phase and a transition to Social Market Economy phase. During both phases, Syrian policy makers showed a preference for a gradualist approach to economic transition, rather than a big-bang approach. This was facilitated by oil revenues and subsidies from the Gulf States. The Syrian experience therefore has its own distinct characteristics, as well as elements in common with the transitions in other post Socialist economies

Paleo-Immunology: Evidence Consistent with Insertion of a Primordial Herpes Virus-Like Element in the Origins of Acquired Immunity

BACKGROUND:The RAG encoded proteins, RAG-1 and RAG-2 regulate site-specific recombination events in somatic immune B- and T-lymphocytes to generate the acquired immune repertoire. Catalytic activities of the RAG proteins are related to the recombinase functions of a pre-existing mobile DNA element in the DDE recombinase/RNAse H family, sometimes termed the "RAG transposon". METHODOLOGY/PRINCIPAL FINDINGS:Novel to this work is the suggestion that the DDE recombinase responsible for the origins of acquired immunity was encoded by a primordial herpes virus, rather than a "RAG transposon." A subsequent "arms race" between immunity to herpes infection and the immune system obscured primary amino acid similarities between herpes and immune system proteins but preserved regulatory, structural and functional similarities between the respective recombinase proteins. In support of this hypothesis, evidence is reviewed from previous published data that a modern herpes virus protein family with properties of a viral recombinase is co-regulated with both RAG-1 and RAG-2 by closely linked cis-acting co-regulatory sequences. Structural and functional similarity is also reviewed between the putative herpes recombinase and both DDE site of the RAG-1 protein and another DDE/RNAse H family nuclease, the Argonaute protein component of RISC (RNA induced silencing complex). CONCLUSIONS/SIGNIFICANCE:A "co-regulatory" model of the origins of V(D)J recombination and the acquired immune system can account for the observed linked genomic structure of RAG-1 and RAG-2 in non-vertebrate organisms such as the sea urchin that lack an acquired immune system and V(D)J recombination. Initially the regulated expression of a viral recombinase in immune cells may have been positively selected by its ability to stimulate innate immunity to herpes virus infection rather than V(D)J recombination Unlike the "RAG-transposon" hypothesis, the proposed model can be readily tested by comparative functional analysis of herpes virus replication and V(D)J recombination

Fitness, Fatness, and Mortality: The FIT (Henry Ford Exercise Testing) Project

BACKGROUND: The combined influence of fitness and fatness on mortality risk in diverse populations has not been adequately explored. Our aim was to assess the relative impact of exercise capacity and body mass index (BMI) on all-cause mortality. METHODS: We included 29,257 men and women (mean age 53 years; 27% African American) from The Henry Ford Exercise Testing (FIT) Project without cardiovascular disease and diabetes mellitus at baseline. All patients completed a symptom-limited maximal treadmill stress test between 1991 and 2009. Patients were grouped for analysis by exercise capacity (≥10 metabolic equivalents of task [METs] and \u3c10 \u3eMETs) and obesity status (≥30 kg/m(2) and/m(2)), forming 4 subgroups. Independent and joint associations of BMI and exercise capacity with all-cause mortality were assessed using Cox proportional hazard models. RESULTS: During a mean follow-up of 10.8 years, 1898 patients (6.5%) died. We observed a strong inverse association between exercise capacity (per 1 MET unit) and all-cause mortality (hazard ratio [95% confidence interval], 0.86 [0.85-0.88]). Body mass index (per 1 BMI unit) was inversely related to mortality (hazard ratio [95% confidence interval], 0.98 [0.97-0.99]). In joint analysis, the highest mortality risk was in the//m(2) subgroup. CONCLUSIONS: Reduced exercise capacity was a strong independent risk factor for all-cause mortality in this racially diverse population. Given the comparatively limited impact of BMI, more emphasis should be placed on measuring exercise capacity and developing strategies for its improvement in cardiovascular disease prevention programs

Exercise Capacity and the Obesity Paradox in Heart Failure: The FIT (Henry Ford Exercise Testing) Project

OBJECTIVES: To assess the influence of exercise capacity and body mass index (BMI) on 10-year mortality in patients with heart failure (HF) and to synthesize these results with those of previous studies. PATIENTS AND METHODS: This large biracial sample included 774 men and women (mean age, 60±13 years; 372 [48%] black) with a baseline diagnosis of HF from the Henry Ford Exercise Testing (FIT) Project. All patients completed a symptom-limited maximal treadmill stress test from January 1, 1991, through May 31, 2009. Patients were grouped by World Health Organization BMI categories for Kaplan-Meier survival analyses and stratified by exercise capacity (≥4 metabolic equivalents [METs] of task). Associations of BMI and exercise capacity with all-cause mortality were assessed using multivariable-adjusted Cox proportional hazards models. RESULTS: During a mean follow-up of 10.1±4.6 years, 380 patients (49%) died. Kaplan-Meier survival plots revealed a significant positive association between BMI category and survival for exercise capacity less than 4 METs (log-rank, P=.05), but not greater than or equal to 4 METs (P=.76). In the multivariable-adjusted models, exercise capacity (per 1 MET) was inversely associated, but BMI was not associated, with all-cause mortality (hazard ratio, 0.89; 95% CI, 0.85-0.94; P CONCLUSION: Maximal exercise capacity modified the relationship between BMI and long-term survival in patients with HF, upholding the presence of an exercise capacity-obesity paradox dichotomy as observed over the short-term in previous studies

Association of BMI, Fitness, and Mortality in Patients With Diabetes: Evaluating the Obesity Paradox in the Henry Ford Exercise Testing Project (FIT Project) Cohort

OBJECTIVE: To determine the effect of fitness on the association between BMI and mortality among patients with diabetes. RESEARCH DESIGN AND METHODS: We identified 8,528 patients with diabetes (self-report, medication use, or electronic medical record diagnosis) from the Henry Ford ExercIse Testing Project (FIT Project). Patients with a BMI \u3c18.5 kg/m(2) or cancer were excluded. Fitness was measured as the METs achieved during a physician-referred treadmill stress test and categorized as low (\u3c6), moderate (6-9.9), and high (\u3e/=10). Adjusted hazard ratios for mortality were calculated using standard BMI (kilograms per meter squared) cutoffs of normal (18.5-24.9), overweight (25-29.9), and obese (\u3e/=30). Adjusted splines centered at 22.5 kg/m(2) were used to examine BMI as a continuous variable. RESULTS: Patients had a mean age of 58 +/- 11 years (49% women) with 1,319 deaths over a mean follow-up of 10.0 +/- 4.1 years. Overall, obese patients had a 30% lower mortality hazard (P \u3c 0.001) compared with normal-weight patients. In adjusted spline modeling, higher BMI as a continuous variable was predominantly associated with a lower mortality risk in the lowest fitness group and among patients with moderate fitness and BMI \u3e/=30 kg/m(2). Compared with the lowest fitness group, patients with higher fitness had an approximately 50% (6-9.9 METs) and 70% (\u3e/=10 METs) lower mortality hazard regardless of BMI (P \u3c 0.001). CONCLUSIONS: Among patients with diabetes, the obesity paradox was less pronounced for patients with the highest fitness level, and these patients also had the lowest risk of mortality