Satellite Imaging Service Analysis using Queueing Theory

Earth observation using small satellites is leaving demonstration status and being proposed for more and more commercial applications. By analysing such a service from both end-user and satellite operator point-of-view, it is hoped to provide the information such as service performance, on-board resource status and key parameters for system optimisation before the spacecraft is designed, launched and put into service. In this paper, queueing theory, traditionally used to perform tra_c and e_ciency analysis in tele-communication and other queueing system, is applied in this new area - a commercial imaging service using small satellites. The introduction of queueing theory in our application will eliminate the main di_culty of using the traditional solution - operation simulation which is huge computational complexity that arises when the operation spans a long period. In this paper, only the imaging download process, which is usually the system bottleneck for Low Earth Observation spacecraft, will be analyzed. Unlike traditional queueing systems where the service is continuous, our application su_ers regular idle periods when the satellite is not visible from the ground-station for image download. The distribution and duration of such idle periods are the subject of orbital-dynamics. Therefore available queueing theory is not applicable directly and needs some extension to handle this speci_c problem of satellite imaging services. In this paper, three queueing models are discussed: M/G/1, M/Gx/1 and GI/G/1 together with the analysis of their suitability to our application. An extension to using M/Gx/1 is outlined which can provide a better approximation of the service than traditional queueing models. Some basic service parameters, such as queue length distribution, mean service occupation and mean service waiting time, can thereby be calculated. All results presented are compared with that from operation simulation. Limitation and constraints of using queueing theory in this application are also discussed. As a conclusion of this research work, it is shown that queueing theory will be appropriate for the early stage performance analysis in a quick but gross manner which can provide some basic performance parameters, while operation simulation can be treated as a re_nement and a method capable of providing more complete solutions that will certainly take much longer time

Equilibrium Properties of A Monomer-Monomer Catalytic Reaction on A One-Dimensional Chain

We study the equilibrium properties of a lattice-gas model of an $A + B \to 0$ catalytic reaction on a one-dimensional chain in contact with a reservoir for the particles. The particles of species $A$ and $B$ are in thermal contact with their vapor phases acting as reservoirs, i.e., they may adsorb onto empty lattice sites and may desorb from the lattice. If adsorbed $A$ and $B$ particles appear at neighboring lattice sites they instantaneously react and both desorb. For this model of a catalytic reaction in the adsorption-controlled limit, we derive analytically the expression of the pressure and present exact results for the mean densities of particles and for the compressibilities of the adsorbate as function of the chemical potentials of the two species.Comment: 19 pages, 5 figures, submitted to Phys. Rev.

Identification of independent association signals and putative functional variants for breast cancer risk through fine-scale mapping of the 12p11 locus.

BACKGROUND: Multiple recent genome-wide association studies (GWAS) have identified a single nucleotide polymorphism (SNP), rs10771399, at 12p11 that is associated with breast cancer risk. METHOD: We performed a fine-scale mapping study of a 700 kb region including 441 genotyped and more than 1300 imputed genetic variants in 48,155 cases and 43,612 controls of European descent, 6269 cases and 6624 controls of East Asian descent and 1116 cases and 932 controls of African descent in the Breast Cancer Association Consortium (BCAC; http://bcac.ccge.medschl.cam.ac.uk/ ), and in 15,252 BRCA1 mutation carriers in the Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA). Stepwise regression analyses were performed to identify independent association signals. Data from the Encyclopedia of DNA Elements project (ENCODE) and the Cancer Genome Atlas (TCGA) were used for functional annotation. RESULTS: Analysis of data from European descendants found evidence for four independent association signals at 12p11, represented by rs7297051 (odds ratio (OR) = 1.09, 95 % confidence interval (CI) = 1.06-1.12; P = 3 × 10(-9)), rs805510 (OR = 1.08, 95 % CI = 1.04-1.12, P = 2 × 10(-5)), and rs1871152 (OR = 1.04, 95 % CI = 1.02-1.06; P = 2 × 10(-4)) identified in the general populations, and rs113824616 (P = 7 × 10(-5)) identified in the meta-analysis of BCAC ER-negative cases and BRCA1 mutation carriers. SNPs rs7297051, rs805510 and rs113824616 were also associated with breast cancer risk at P < 0.05 in East Asians, but none of the associations were statistically significant in African descendants. Multiple candidate functional variants are located in putative enhancer sequences. Chromatin interaction data suggested that PTHLH was the likely target gene of these enhancers. Of the six variants with the strongest evidence of potential functionality, rs11049453 was statistically significantly associated with the expression of PTHLH and its nearby gene CCDC91 at P < 0.05. CONCLUSION: This study identified four independent association signals at 12p11 and revealed potentially functional variants, providing additional insights into the underlying biological mechanism(s) for the association observed between variants at 12p11 and breast cancer risk.UK funding includes Cancer Research UK and NIH.This is the final version of the article. It first appeared from BioMed Central via http://dx.doi.org/10.1186/s13058-016-0718-

Associations of common breast cancer susceptibility alleles with risk of breast cancer subtypes in BRCA1 and BRCA2 mutation carriers

Introduction: More than 70 common alleles are known to be involved in breast cancer (BC) susceptibility, and several exhibit significant heterogeneity in their associations with different BC subtypes. Although there are differences in the association patterns between BRCA1 and BRCA2 mutation carriers and the general population for several loci, no study has comprehensively evaluated the associations of all known BC susceptibility alleles with risk of BC subtypes in BRCA1 and BRCA2 carriers. Methods: We used data from 15,252 BRCA1 and 8,211 BRCA2 carriers to analyze the associations between approximately 200,000 genetic variants on the iCOGS array and risk of BC subtypes defined by estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2) and triple-negative- (TN) status; morphologic subtypes; histological grade; and nodal involvement. Results: The estimated BC hazard ratios (HRs) for the 74 known BC alleles in BRCA1 carriers exhibited moderate correlations with the corresponding odds ratios from the general population. However, their associations with ER-positive BC in BRCA1 carriers were more consistent with the ER-positive as

Assessing associations between the AURKAHMMR-TPX2-TUBG1 functional module and breast cancer risk in BRCA1/2 mutation carriers

While interplay between BRCA1 and AURKA-RHAMM-TPX2-TUBG1 regulates mammary epithelial polarization, common genetic variation in HMMR (gene product RHAMM) may be associated with risk of breast cancer in BRCA1 mutation carriers. Following on these observations, we further assessed the link between the AURKA-HMMR-TPX2-TUBG1 functional module and risk of breast cancer in BRCA1 or BRCA2 mutation carriers. Forty-one single nucleotide polymorphisms (SNPs) were genotyped in 15,252 BRCA1 and 8,211 BRCA2 mutation carriers and subsequently analyzed using a retrospective likelihood appr

Genome-Wide Association Study in BRCA1 Mutation Carriers Identifies Novel Loci Associated with Breast and Ovarian Cancer Risk

BRCA1-associated breast and ovarian cancer risks can be modified by common genetic variants. To identify further cancer risk-modifying loci, we performed a multi-stage GWAS of 11,705 BRCA1 carriers (of whom 5,920 were diagnosed with breast and 1,839 were diagnosed with ovarian cancer), with a further replication in an additional sample of 2,646 BRCA1 carriers. We identified a novel breast cancer risk modifier locus at 1q32 for BRCA1 carriers (rs2290854, P = 2.7×10-8, HR = 1.14, 95% CI: 1.09-1.20). In addition, we identified two novel ovarian cancer risk modifier loci: 17q21.31 (rs17631303, P = 1.4×10-8, HR = 1.27, 95% CI: 1.17-1.38) and 4q32.3 (rs4691139, P = 3.4×10-8, HR = 1.20, 95% CI: 1.17-1.38). The 4q32.3 locus was not associated with ovarian cancer risk in the general population or BRCA2 carriers, suggesting a BRCA1-specific associat

A Fast Prediction Algorithm of Satellite Passes

Low cost, fast access and multi-functional small satellites are being increasingly used to provide and exchange information for a wide variety of professions. They are particularly useful, for example, as a resource in very remote areas where they can provide useful information such as to rescue teams for changing conditions in a disaster zone and monitoring the sea state to warn approaching shipping. Unlike terrestrial communication systems, the receiver/transmitter in these di_erent application areas needs to be powered on and contact to specialised satellites to exchange data at speci_c time rather than consuming valuable power at all the time. This, therefore, requires accurate knowledge of when these satellites will pass over the horizon of the given location over a timescale of months in some cases. On the other hand, long term orbit estimation with high accuracy is also a key part for mission analysis and Earth observation operation planning. The same algorithm is also needed onboard satellites for autonomous on-board data management. The principal di_culty of predicting satellite passes over such long timescales is to take account of the e_ects of atmospheric drag. In this paper, we present a fast algorithm for the prediction of passes of a LEO satellite over any given location which provides high accuracy over a long period. The method exploits sophisticated analytic models of the orbit and provides direct computation of rise-set times and nadir tracking without the need of orbit propagation for hill climbing. This provides for a very small fast algorithm so more suitable for low-end computers and hand-held sets. Since the atmospheric drag is the key factor that a_ects the accuracy for long-term estimation for satellite in LEO, this model not only includes secular perturbation and periodic perturbations, on the other hand a drag model based on the well acknowledged NASA atmosphere statistics is incorporated. Di_erent from those in other orbit prediction methods, for example, the most widely used SGP4, the drag model here has a variable parameter which is subject to modify as time being on according to periodical atmosphere properties changing. Simulation result shows it can provide quite accurate estimation for long look-ahead period

Prevalence of Family History of Breast, Colorectal, Prostate, and Lung Cancer in a Population-Based Study

BACKGROUND: A positive family history is a known risk factor for several cancers; thus, obtaining a thorough family cancer history is essential in cancer risk evaluation and prevention management. METHODS: The Family Health Study, a telephone survey in Connecticut, was conducted in 2001. A total of 1,019 participants with demographic information and family cancer history were included in this study. Prevalence of a positive family history of breast, colorectal, prostate, and lung cancer for first- and second-degree relatives was estimated. Logistic regression was used to compare prevalence by demographic factors. RESULTS: A positive family history among first-degree relatives was reported by 10.9% (95% Confidence Interval, CI = 8.8–13.3) of respondents for breast cancer, 5.1% (95% CI = 3.9–6.7) for colorectal cancer, 7.0% (95% CI = 5.2–9.4) for prostate cancer, and 6.4% (95% CI = 4.9–8.3) for lung cancer. The reported prevalence of family history of specific cancers varied by sex, age and race/ethnicity of the respondents. CONCLUSION: Family history prevalence for 4 of the most common adult solid tumors is substantial and the reported prevalence varied by respondent characteristics. Additional studies are needed to evaluate tools to promote accurate reporting of family history of cancer