Equilibria of dynamic games with many players: Existence, approximation, and market structure

In this paper we study stochastic dynamic games with many players; these are a fundamental model for a wide range of economic applications. The standard solution concept for such games is Markov perfect equilibrium (MPE), but it is well known that MPE computation becomes intractable as the number of players increases. We instead consider the notion of stationary equilibrium (SE), where players optimize assuming the empirical distribution of others' states remains constant at its long run average. We make two main contributions. First, we provide a rigorous justification for using SE. In particular, we provide a parsimonious collection of exogenous conditions over model primitives that guarantee existence of SE, and ensure that an appropriate approximation property to MPE holds, in a general model with possibly unbounded state spaces. Second, we draw a significant connection between the validity of SE, and market structure: under the same conditions that imply SE exist and approximates MPE well, the market becomes fragmented in the limit of many firms. To illustrate this connection, we study in detail a series of dynamic oligopoly examples. These examples show that our conditions enforce a form of “decreasing returns to larger states;” this yields fragmented industries in the SE limit. By contrast, violation of these conditions suggests “increasing returns to larger states” and potential market concentration. In that sense, our work uses a fully dynamic framework to also contribute to a longstanding issue in industrial organization: understanding the determinants of market structure in different industries

Price Experimentation and Interference in Online Platforms

In this paper, we examine the biases arising in A/B tests where a firm modifies a continuous parameter, such as price, to estimate the global treatment effect associated to a given performance metric. Such biases emerge from canonical designs and estimators due to interference among market participants. We employ structural modeling and differential calculus to derive intuitive structural characterizations of this bias. We then specialize our general model to a standard revenue management pricing problem. This setting highlights a key potential pitfall in the use of pricing experiments to guide profit maximization: notably, the canonical estimator for the change in profits can have the {\em wrong sign}. In other words, following the guidance of the canonical estimator may lead the firm to move prices in the wrong direction, and thereby decrease profits relative to the status quo. We apply these results to a two-sided market model and show how this ``change of sign" regime depends on model parameters, and discuss structural and practical implications for platform operators

Thyroid profile and LDH Isoenzymes as prognostic biomarkers for diabetic and/or obese subjects

Background: This study aimed to evaluate the levels of thyroid hormones and lactate dehydrogenase (LDH) isoenzymes in obese and/or diabetic patients. Subjects and methods: Forty male subjects categorized into four equal groups; group 1: Non obese control subjects, group 2: Subjects suffering from type 2 diabetes mellitus (T2DM), group 3: Obese subjects (BMI ≥ 30 kg/m2) and group 4: Subjects thatwere obese and had type 2 diabetes mellitus (T2DM). Liver, kidney, lipid, thyroid hormones, total LDH and LDH isoenzymes levels were determined. Results: There was a significant increase of TSH level (p<0.001) in diabetic group as compared with control group and a highly significant increase of TSH was obtained in obese and obese diabetic groups versus control and diabetic patients. LDH 2 was also highly significantly decreased in obese and obese diabetic groups versus diabetic patients. Percentage of LDH 4 was significantly decreased in both diabetic and obese groups and not significantly changed in obese diabetic patients as compared with the control group. LDH 5 percentage showed very highly significant decrease in diabetic, obese and highly significant decrease in obese diabetic groups when compared with control subjects while it was not significantly changed in obese and obese diabetic groups as compared with diabetic patients. Conclusion: LDH isozymes can be used as valuable diagnostic markers for metabolic syndrome. This may help to explore the metabolic changes associated with obesity and diabetes complication and following up the complication of these abnormalities.Keywords: Thyroid profile, lactate dehydrogenase, obesity, diabetes

Intelligent Dynamic Traffic Light Sequence Using RFID

The proposed RFID traffic control avoids problems that usually arise with standard traffic control systems, especially those related to image processing and beam interruption techniques. This RFID technique deals with a multi-vehicle, multilane, multi road junction area. It provides an efficient time management scheme, in which a dynamic time schedule is worked out in real time for the passage of each traffic column. The real time operation of the system emulates the judgment of a traffic policeman on duty. The number of vehicles in each column and the routing are proprieties, upon which the calculations and the judgments are based

Ubiquitous RFID network for highway monitoring and management

A simplified approach for the implementation of ubiquitous RFID networks in a Highway Management System is presented. The technique aims at deploying tagging identification in transport statistical analysis. The RFID network architecture has been designed as part of an existing system to make it more cost effective with a higher reliability. The usefulness and the merits of this easy access and user friendly approach are identified and discussed

Effects of stent design on LDL accumulation at the carotid artery bifurcation

Restenosis typically occurs in regions of low and oscillating wall shear stress which also favours the accumulation of atherogenic macromolecules such as low-density lipoprotein (LDL). This study aims to determine how stent strut design may affect in-stent restenosis at the carotid artery bifurcation following carotid artery stenting (CAS) by means of computational simulation. LDL concentrations were compared for post-stent carotid and the contralateral models reconstructed from patient-specific images. Our results show that closed-cell stent designs are more likely to create atheroprone and procoagulant flow conditions than open-cell designs due to larger area exposed to high LDL concentration

Using Community-Owned Resource Persons to Provide Early Diagnosis and Treatment and Estimate Malaria Burden at Community Level in North-Eastern Tanzania.

Although early diagnosis and prompt treatment is an important strategy for control of malaria, using fever to initiate presumptive treatment with expensive artemisinin combination therapy is a major challenge; particularly in areas with declining burden of malaria. This study was conducted using community-owned resource persons (CORPs) to provide early diagnosis and treatment of malaria, and collect data for estimation of malaria burden in four villages of Korogwe district, north-eastern Tanzania.In 2006, individuals with history of fever within 24 hours or fever (axillary temperature ≥37.5°C) at presentation were presumptively treated using sulphadoxine/pyrimethamine. Between 2007 and 2010, individuals aged five years and above, with positive rapid diagnostic tests (RDTs) were treated with artemether/lumefantrine (AL) while under-fives were treated irrespective of RDT results. Reduction in anti-malarial consumption was determined by comparing the number of cases that would have been presumptively treated and those that were actually treated based on RDTs results. Trends of malaria incidence and slide positivity rates were compared between lowlands and highlands. Of 15,729 cases attended, slide positivity rate was 20.4% and declined by >72.0% from 2008, reaching <10.0% from 2009 onwards; and the slide positivity rates were similar in lowlands and highlands from 2009 onwards. Cases with fever at presentation declined slightly, but remained at >40.0% in under-fives and >20.0% among individuals aged five years and above. With use of RDTs, cases treated with AL decreased from <58.0% in 2007 to <11.0% in 2010 and the numbers of adult courses saved were 3,284 and 1,591 in lowlands and highlands respectively. Malaria incidence declined consistently from 2008 onwards; and the highest incidence of malaria shifted from children aged <10 years to individuals aged 10-19 years from 2009. With basic training, supervision and RDTs, CORPs successfully provided early diagnosis and treatment and reduced consumption of anti-malarials. Progressively declining malaria incidence and slide positivity rates suggest that all fever cases should be tested with RDTs before treatment. Data collected by CORPs was used to plan phase 1b MSP3 malaria vaccine trial and will be used for monitoring and evaluation of different health interventions. The current situation indicates that there is a remarkable changing pattern of malaria and these areas might be moving from control to pre-elimination levels

CHO genome mining for synthetic promoter design

Synthetic promoters are an attractive alternative for use in mammalian hosts such as CHO cells as they can be designed de novo with user-defined functionalities. In this study, we describe and validate a method for bioprocess-directed design of synthetic promoters utilizing CHO genomic sequence information. We designed promoters with two objective features, (i) constitutive high-level recombinant gene transcription, and (ii) upregulated transcription under mild hypothermia or late-stage culture. CHO genes varying in transcriptional activity were selected based on a comparative analysis of RNA-Seq transcript levels in normal and biphasic cultures in combination with estimates of mRNA half-life from published genome scale datasets. Discrete transcription factor regulatory elements (TFREs) upstream of these genes were informatically identified and functionally screened in vitro to identify a subset of TFREs with the potential to support high activity recombinant gene transcription during biphasic cell culture processes. Two libraries of heterotypic synthetic promoters with varying TFRE combinations were then designed in silico that exhibited a maximal 2.5-fold increase in transcriptional strength over the CMV-IE promoter after transient transfection into host CHO-K1 cells. A subset of synthetic promoters was then used to create stable transfectant pools using CHO-K1 cells under glutamine synthetase selection. Whilst not achieving the maximal 2.5-fold increase in productivity over stable pools harboring the CMV promoter, all stably transfected cells utilizing synthetic promoters exhibited increased reporter production - up to 1.6-fold that of cells employing CMV, both in the presence or absence of intron A immediately downstream of the promoter. The increased productivity of stably transfected cells harboring synthetic promoters was maintained during fed-batch culture, with or without a transition to mild hypothermia at the onset of stationary phase. Our data exemplify that it is important to consider both host cell and intended bioprocess contexts as design criteria in the de novo construction of synthetic genetic parts for mammalian cell engineering