Operating Small Sat Swarms as a Single Entity: Introducing SODA

NASA’s decadal survey determined that simultaneous measurements from a 3D volume of space are advantageous for a variety of studies in space physics and Earth science. Therefore, swarm concepts with multiple spacecraft in close proximity are a growing topic of interest in the small satellite community. Among the capabilities needed for swarm missions is a means to maintain operator-specified geometry, alignment, or separation. Swarm stationkeeping poses a planning challenge due to the limited scalability of ground resources. To address scalable control of orbital dynamics, we introduce SODA – Swarm Orbital Dynamics Advisor – a tool that accepts high-level configuration commands and provides the orbital maneuvers needed to achieve the desired type of swarm relative motion. Rather than conventional path planning, SODA’s innovation is the use of artificial potential functions to define boundaries and keepout regions. The software architecture includes high fidelity propagation, accommodates manual or automated inputs, displays motion animations, and returns maneuver commands and analytical results. Currently, two swarm types are enabled: in-train distribution and an ellipsoid volume container. Additional swarm types, simulation applications, and orbital destinations are in planning stages

The role of Myostatin polymorphisms in the Finnhorse and Shetland pony breeds

Myostatin, encoded by the MSTN gene, is a member of the transforming growth factor β that normally acts to limit skeletal muscle mass by regulating both the number and growth of muscle fibers. Natural mutations that decrease the amounts of myostatin and/or inhibit its function have been identified in several cattle, sheep and dog breeds, where loss-of-function mutations cause increased skeletal muscle mass and produce a phenotype known as “double-muscling”. This gene has also been associated with racing performance in Thoroughbreds, where studies have found two Myostatin polymorphisms (PR3737 and PR8604) to be strongly associated with genetic potential and athletic phenotype, affecting both speed and muscularity, although no such associations have been found in harness-racing breeds such as the Swedish-Norwegian Coldblooded trotter. Single nucleotide polymorphisms have also been shown to have an effect on conformation, where these SNPs have been found to have different genotype distributions between horse breeds with different origin, morphology and uses. Such is the case with Icelandic horses, where significantly different genotype distributions for another SNP, PR5826, were observed between horses used for different purposes. This study investigated the association of these MSTN polymorphisms with harness racing performance in the Finnhorse and body conformation in the Shetland pony. Finnhorses used for different disciplines were genotyped for three SNPs (PR5826, PR3737 and PR8604) and were divided into three categories based on their use: harness racing horses (n=223), representing those horses with at least one start in harness racing; riding horses (n=79) used for recreational riding of which owner questionnaire information was available and horses with no performance data (n=112). An association analysis was performed on the raced group, where the genotypes were evaluated for association with life-time racing performance results for: number of starts, victories, placings (1-3) and unplaced, along with proportions for each of these traits, as well as earnings, earnings per start and race times for volt- and autostart. Additionally, the genotypes were evaluated for association with these performance results obtained between 3 and 6 years of age (n=207) and 7 to 10 years of age (n=183). Significant associations were found in the 3 to 6 years of age group as well as the 7 to 10 group. In both cases, TT horses for PR3737 earned more money, were faster for both racing methods and presented a lower number of disqualifications than the CT horses. Concerning PR8604, a similar effect was observed, where the TT horses also earned more money, were faster in auto start racing method and presented a lower number of disqualifications. This study concluded that MSTN sequence polymorphisms seem to have an effect on harness racing performance in the Finnhorse. Concerning body conformation on the Shetland pony, a breed which presents a “Heavy” body type and a “Light” body type, no significant associations were found between conformation and MSTN genotype. However, further investigation is needed before drawing the conclusion that MSTN has no effect on Shetland pony conformation. This is due to the small sample size and classification method, which could be expanded to include morphological measurements

The role of polymorphisms of the MSTN, GRIN2B and DOCK8 genes in the performance of pace-racing Icelandic horses

This study investigated the association of single-nucleotide polymorphisms (SNPs) of three different genes with pace racing performance in the Icelandic horse. The SNPs chosen were PR3737, PR8604 and PR9482 of the Myostatin gene; SNPs g.41206762 C>T and g.41218272 T>C of the GRIN2B gene and SNP g.22496787 T>C of the DOCK8 gene. Icelandic horses that compete frequently in any of the three pace race disciplines (P1 over 250m, P2 over 100m and P3 over 150m) were genotyped for all SNPs mentioned above. The horses in the sample (n=131) were divided into “Speed groups” based on consistency of racing times and training schemes. Three groups were created: Fast (n=37), Average (n=75) and Slow (n=19). Differences in genotype distribution among the different Speed groups were evaluated using Fisher’s Exact Test. Significant differences were found for all SNPs except PR9482 when comparing only Fast versus Slow horses. Significant differences were also found between all three groups when comparing allele frequencies. Moreover, a drastic difference in allele frequency of the mutant allele for the DOCK8 SNP was found between horses of the Fast group (frequency of the mutant allele was of 0.70) and 280 Icelandic horses genotyped for other studies (mutant allele frequency ranging between 0.33 (n=95) and 0.43 (n=192)). This implies an important role of this SNP and its mutant allele in pace-racing performance. Additionally, horses were evaluated by owners in terms of three temperament traits: Nervousness, Focus and Motivation. Significant differences were found in the distribution of scores for these temperament traits between horses with the different genotypes of the GRIN2B SNPs, suggesting a beneficial effect of the mutant alleles on the horse’s temperament. An association analysis was also performed, where the genotypes were evaluated for association with life-time racing performance results for race times (P1, P2 and/or P3), Breeding Field Test (BFT) assessment scores for pace and estimated breeding values (EBV) for pace at BFTs. Additionally, the genotypes were evaluated for association with performance results obtained when the horses competed at the age of 13 years or under (n=117) and over 13 years of age (n=64). Significant associations were found for PR9482, where the C allele (stamina-related in other breeds) was beneficial to performance in the longer P1 races and the T allele (speed-related in other breeds) was beneficial to performance in P3 for horses of ages 13 and under. Associations were also found for the GRIN2B SNP, with the C (mutant) allele having a beneficial effect in the shorter P3 races for both lifetime career and performance in the age group of 13 years and under. As for DOCK8, associations were also found in relation to P2, with the mutant (T) allele having a positive effect on the performance. No associations were found with any of the studied polymorphisms with BFT assessment scores for pace or with estimated breeding values. This study concludes that a SNP at the DOCK8 gene may well be beneficial to performance in pace-racing Icelandic horses due to the associations found with racing times and, more interestingly, the difference found in mutant allele frequencies between an elite group of racers and the rest of the population. Additionally, the study showcases the importance of temperament traits as factors that affect performance in pace-racing, as evidenced by the associations found between the mutant allele of the GRIN2B polymorphism and temperament scores, along with racing times. Furthermore, the study concludes that Myostatin SNPs have little effect in pace-racing performance, seeing as only one polymorphism affected performance and only in one of the age groups. Moreover, comparing mutant allele frequencies between the elite racers and a large number of Icelandic horses that were not selected for pace racing showed no variation at all. This further indicates these mutations may not play a major role in performance as they do in other breeds, such as the Thoroughbreds

Propulsion Trade Studies for Spacecraft Swarm Mission Design

Spacecraft swarms constitute a challenge from an orbital mechanics standpoint. Traditional mission design involves the application of methodical processes where predefined maneuvers for an individual spacecraft are planned in advance. This approach does not scale to spacecraft swarms consisting of many satellites orbiting in close proximity; non-deterministic maneuvers cannot be preplanned due to the large number of units and the uncertainties associated with their differential deployment and orbital motion. For autonomous small sat swarms in LEO, we investigate two approaches for controlling the relative motion of a swarm. The first method involves modified miniature phasing maneuvers, where maneuvers are prescribed that cancel the differential delta V of each CubeSat's deployment vector. The second method relies on artificial potential functions (APFs) to contain the spacecraft within a volumetric boundary and avoid collisions. Performance results and required delta V budgets are summarized, indicating that each method has advantages and drawbacks for particular applications. The mini phasing maneuvers are more predictable and sustainable. The APF approach provides a more responsive and distributed performance, but at considerable propellant cost. After considering current state of the art CubeSat propulsion systems, we conclude that the first approach is feasible, but the modified APF method of requires too much control authority to be enabled by current propulsion systems

Most Common Single-Nucleotide Polymorphisms Associated With Rheumatoid Arthritis in Persons of European Ancestry Confer Risk of Rheumatoid Arthritis in African Americans

Objective. Large-scale genetic association studies have identified \u3e20 rheumatoid arthritis (RA) risk alleles among individuals of European ancestry. The influence of these risk alleles has not been comprehensively studied in African Americans. We therefore sought to examine whether these validated RA risk alleles are associated with RA risk in an African American population. Methods. Twenty-seven candidate single-nucleotide polymorphisms (SNPs) were genotyped in 556 autoantibody-positive African Americans with RA and 791 healthy African American control subjects. Odds ratios (ORs) and 95% confidence intervals (95% CIs) for each SNP were compared with previously published ORs for RA patients of European ancestry. We then calculated a composite genetic risk score (GRS) for each individual based on the sum of all risk alleles. Results. Overlap of the ORs and 95% CIs between the European and African American populations was observed for 24 of the 27 candidate SNPs. Conversely, 3 of the 27 SNPs (CCR6 rs3093023, TAGAP rs394581, and TNFAIP3 rs6920220) demonstrated ORs in the opposite direction from those reported for RA patients of European ancestry. The GRS analysis indicated a small but highly significant probability that African American patients relative to control subjects were enriched for the risk alleles validated in European RA patients (P = 0.00005). Conclusion. The majority of RA risk alleles previously validated for RA patients of European ancestry showed similar ORs in our population of African Americans with RA. Furthermore, the aggregate GRS supports the hypothesis that these SNPs are risk alleles for RA in the African American population. Future large-scale genetic studies are needed to validate these risk alleles and identify novel RA risk alleles in African Americans

Surveillance for Unexplained Deaths and Critical Illnesses

Population-based surveillance for unexplained death and critical illness possibly due to infectious causes (UNEX) was conducted in four U.S. Emerging Infections Program sites (population 7.7 million) from May 1, 1995, to December 31, 1998, to define the incidence, epidemiologic features, and etiology of this syndrome. A case was defined as death or critical illness in a hospitalized, previously healthy person, 1 to 49 years of age, with infection hallmarks but no cause identified after routine testing. A total of 137 cases were identified (incidence rate 0.5 per 100,000 per year). Patients’ median age was 20 years, 72 (53%) were female, 112 (82%) were white, and 41 (30%) died. The most common clinical presentations were neurologic (29%), respiratory (27%), and cardiac (21%). Infectious causes were identified for 34 cases (28% of the 122 cases with clinical specimens); 23 (68%) were diagnosed by reference serologic tests, and 11 (32%) by polymerase chain reaction-based methods. The UNEX network model would improve U.S. diagnostic capacities and preparedness for emerging infections

The genetic consequences of dog breed formation-Accumulation of deleterious genetic variation and fixation of mutations associated with myxomatous mitral valve disease in cavalier King Charles spaniels

Selective breeding for desirable traits in strictly controlled populations has generated an extraordinary diversity in canine morphology and behaviour, but has also led to loss of genetic variation and random entrapment of disease alleles. As a consequence, specific diseases are now prevalent in certain breeds, but whether the recent breeding practice led to an overall increase in genetic load remains unclear. Here we generate whole genome sequencing (WGS) data from 20 dogs per breed from eight breeds and document a similar to 10% rise in the number of derived alleles per genome at evolutionarily conserved sites in the heavily bottlenecked cavalier King Charles spaniel breed (cKCs) relative to in most breeds studied here. Our finding represents the first clear indication of a relative increase in levels of deleterious genetic variation in a specific breed, arguing that recent breeding practices probably were associated with an accumulation of genetic load in dogs. We then use the WGS data to identify candidate risk alleles for the most common cause for veterinary care in cKCs-the heart disease myxomatous mitral valve disease (MMVD). We verify a potential link to MMVD for candidate variants near the heart specific NEBL gene in a dachshund population and show that two of the NEBL candidate variants have regulatory potential in heartderived cell lines and are associated with reduced NEBL isoform nebulette expression in papillary muscle (but not in mitral valve, nor in left ventricular wall). Alleles linked to reduced nebulette expression may hence predispose cKCs and other breeds to MMVD via loss of papillary muscle integrity