Orbital Targeting Using Reduced Eccentric Anomaly Low-Thrust Coefficients

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90625/1/AIAA-51336-469.pd

Equivalent Average Trajectory Dynamics Using the Reduced Low-Thrust Coefficients

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83639/1/AIAA-2010-7829-955.pd

Reduction of Low-Thrust Continuous Controls for Trajectory Dynamics and Orbital Targeting.

A novel method to evaluate the trajectory dynamics of low-thrust spacecraft is developed. Using a two-body Newtonian model, the spacecraft thrust vector components are represented by Fourier series in terms of eccentric anomaly, and Gauss's variational equations are averaged over one orbit to obtain a set of secular equations. These secular equations are a function of 14 of the thrust Fourier coefficients, regardless of the order of the original Fourier series, and are sufficient to determine a low-thrust spiral trajectory with signi cantly reduced computational requirements as compared with integration of the full Newtonian problem. This method is applied to orbital targeting problems. The targeting problems are de fined as two-point boundary value problems with fixed endpoint constraints. Average low-thrust controls that solve these problems are found using the averaged variational equations and a cost function represented also as a Fourier series. The resulting fuel costs and dynamic fidelity of the targeting solutions are evaluated. Low-thrust controls with equivalent average trajectory dynamics but diff erent thrust pro files are also studied. Higher-order control coefficients that do not affect the average dynamics are used to reduce fuel costs and transform time-varying controls into controls with constant thrust arcs, which can be implemented more easily by low-thrust propulsion systems. These methods have applications to low-thrust mission design and space situational awareness. Example problems based on past missions and potential future scenarios demonstrate the effectiveness of these methods.Ph.D.Aerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/78860/1/jshudson_1.pd

Ultralow phase noise microwave generation with an Er:fiber-based optical frequency divider

We present an optical frequency divider based on a 200 MHz repetition rate Er:fiber mode-locked laser that, when locked to a stable optical frequency reference, generates microwave signals with absolute phase noise that is equal to or better than cryogenic microwave oscillators. At 1 Hz offset from a 10 GHz carrier, the phase noise is below -100 dBc/Hz, limited by the optical reference. For offset frequencies > 10 kHz, the phase noise is shot noise limited at -145 dBc/Hz. An analysis of the contribution of the residual noise from the Er:fiber optical frequency divider is also presented.Comment: 4 pages, 3 figure

The maize brown midrib6 (bm6) mutation encodes a functional GTP Cyclohydrolase1

Brown midrib mutations in maize (Zea mays L.) and sorghum (Sorghum bicolor L.) alter lignin composition and enhance cell wall digestibility. These mutations are prime candidates for silage breeding. Six brown midrib mutants are currently known, brown midrib1 (bm1) to brown midrib6 (bm6). The bm1 and bm3 mutations are being used commercially for silage. The underlying genes responsible for five of the six bm mutations in maize (bm1, bm2, bm3, bm4, and bm5) are known. Chen and co-workers (2012) characterized the bm6 mutation, demonstratingthat bm6 increases cell wall digestibility and physically mapped bm6 within a 180 kilobase region on chromosome 2. The present investigation utilized map-based cloning to identify the candidate gene responsible for the bm6 phenotype as GTP Cyclohydrolase1 (GCH1) and validated the candidate gene through reverse genetics. Orthologs of bm6 include at least one paralogous gene in maize on chromosome 10 and various homologs in other grasses and dicots. The discovery that GCH1 is  responsible for the maize bm6 phenotype suggests that GCH1 plays a role in the tetrahydrofolate biosynthetic process

'The difference in determinants of Chlamydia trachomatis and Mycoplasma genitalium in a sample of young Australian women.'

BACKGROUND Differences in the determinants of Chlamydia trachomatis ('chlamydia') and Mycoplasma genitalium (MG) genital infection in women are not well understood. METHODS A cohort study of 16 to 25 year old Australian women recruited from primary health care clinics, aimed to determine chlamydia and MG prevalence and incidence. Vaginal swabs collected at recruitment were used to measure chlamydia and MG prevalence, organism-load and chlamydia-serovar a cross-sectional analysis undertaken on the baseline results is presented here. RESULTS Of 1116 participants, chlamydia prevalence was 4.9% (95% CI: 2.9, 7.0) (n = 55) and MG prevalence was 2.4% (95% CI: 1.5, 3.3) (n = 27). Differences in the determinants were found - chlamydia not MG, was associated with younger age [AOR:0.9 (95% CI: 0.8, 1.0)] and recent antibiotic use [AOR:0.4 (95% CI: 0.2, 1.0)], and MG not chlamydia was associated with symptoms [AOR:2.1 (95% CI: 1.1, 4.0)]. Having two or more partners in last 12 months was more strongly associated with chlamydia [AOR:6.4 (95% CI: 3.6, 11.3)] than MG [AOR:2.2 (95% CI: 1.0, 4.6)] but unprotected sex with three or more partners was less strongly associated with chlamydia [AOR:3.1 (95%CI: 1.0, 9.5)] than MG [AOR:16.6 (95%CI: 2.0, 138.0)]. Median organism load for MG was 100 times lower (5.7 × 104/swab) than chlamydia (5.6 × 10⁶/swab) (p < 0.01) and not associated with age or symptoms for chlamydia or MG. CONCLUSIONS These results demonstrate significant chlamydia and MG prevalence in Australian women, and suggest that the differences in strengths of association between numbers of sexual partners and unprotected sex and chlamydia and MG might be due to differences in the transmission dynamics between these infections.This project was funded by the Commonwealth of Australia, as part of a National Chlamydia Pilot program that is currently running to test the effectiveness of a number of models for chlamydia testing in Australia. This project will assist in developing possible recommendations for a National Chlamydia Program. The analysis of MG was funded by the National Health and Research Council (research grant number 509144)

Reduction of Low-Thrust Continuous Controls for Trajectory Dynamics

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76670/1/AIAA-40619-128.pd

Prevalent and incident bacterial vaginosis are associated with sexual and contraceptive behaviours in young Australian women

BACKGROUND To determine prevalence and incidence of bacterial vaginosis (BV) and risk factors in young sexually-active Australian women. METHODS 1093 women aged 16-25 years were recruited from primary-care clinics. Participants completed 3-monthly questionnaires and self-collected vaginal smears 6-monthly for 12-months. The primary endpoint was a Nugent Score = 7-10 (BV) and the secondary endpoint was a NS = 4-10 (abnormal flora [AF]). BV and AF prevalence estimates and 95% confidence intervals (95%CI) were derived, and adjusted odds ratios (AOR) calculated to explore epidemiological associations with prevalent BV and AF. Proportional-hazards regression models were used to examine factors associated with incident BV and AF. RESULTS At baseline 129 women had BV [11.8% (95%CI: 9.4-14.2)] and 188 AF (17.2%; 15.1-19.5). Prevalent BV was associated with having a recent female partner [AOR = 2.1; 1.0-4.4] and lack of tertiary-education [AOR = 1.9; 1.2-3.0]; use of an oestrogen-containing contraceptive (OCC) was associated with reduced risk [AOR = 0.6; 0.4-0.9]. Prevalent AF was associated with the same factors, and additionally with >5 male partners (MSP) in 12-months [AOR = 1.8; 1.2-2.5)], and detection of C.trachomatis or M.genitalium [AOR = 2.1; 1.0-4.5]. There were 82 cases of incident BV (9.4%;7.7-11.7/100 person-years) and 129 with incident AF (14.8%; 12.5-17.6/100 person-years). Incident BV and AF were associated with a new MSP [adjusted rate ratio (ARR) = 1.5; 1.1-2.2 and ARR = 1.5; 1.1-2.0], respectively. OCC-use was associated with reduced risk of incident AF [ARR = 0.7; 0.5-1.0]. CONCLUSION This paper presents BV and AF prevalence and incidence estimates from a large prospective cohort of young Australian women predominantly recruited from primary-care clinics. These data support the concept that sexual activity is strongly associated with the development of BV and AF and that use of an OCC is associated with reduced risk.This work was supported by the Commonwealth of Australia, as part of a National Chlamydia Pilot Program and the Australian National Health and Research Council (research grant number 509144). CSB, and JSH were supported by research fellowships issued by the Australian National Health and Medical Research Council (fellowship numbers 456164 and 566576 respectively). MP was supported by a Primary Health Care Research Evaluation and Development MidCareer Fellowship, Department of Health and Aging

Efficacy of D-cycloserine augmented brief intensive cognitive-behavioural therapy for paediatric obsessive-compulsive disorder: A randomised clinical trial

Objective: To examine the efficacy of weight-adjusted D-cycloserine (DCS) (35 or 70 mg) relative to placebo augmentation of intensive exposure therapy for youth with obsessive-compulsive disorder (OCD) in a double-blind, randomised controlled trial, and examine whether antidepressant medication or patient age moderated outcomes. Methods: Youth (n = 100, 7–17 years) with OCD were randomised in a 1:1 ratio to either DCS + exposure (n = 49) or placebo + exposure (n = 51). Assessments occurred posttreatment, 1 month later, and at 3 and 6 months. Pills were ingested immediately before sessions. Results: Significant improvements on all outcomes were observed at posttreatment, and to 6-month follow-up. Treatment arms did not differ across time, with no significant time-by-medication interactions on symptom severity (T1 to T2 estimate: 9.3, 95% confidence interval [CI]: −11.2 to −7.4, and estimate −10.7, 95% CI: −12.6 to −8.7), diagnostic severity (T1 to T2 estimate: −2.0, 95% CI: −2.4 to −1.5 and estimate −2.5, 95% CI: −3.0 to −2.0) or global functioning (T1 to T2 estimate: 13.8, 95% CI: 10.6 to 17.0, and estimate 16.6, 95% CI: 13.2 to 19.9). Neither antidepressants at baseline nor age moderated primary outcomes. There were significantly fewer responders/remitters at 1- and 6-month follow-up among youth in the DCS condition stabilised on SSRIs, relative to youth not taking SSRIs. Conclusions: DCS augmented intensive exposure therapy did not result in overall additional benefits relative to placebo. Intensive exposure proved effective in reducing symptoms for the overall sample