Advancement of direct drive generator systems for offshore renewable energy production

As machine topologies and technologies mature, the fundamental function of the device is honed. Direct drive machines have the potential to launch the renewable energy sector into a new era of large scale, reliable, offshore power generation. With advancements in new technologies, such as superconductivity, the reduction of generator mass due to incorporation of machine and device structures, the continued advancements in component and system reliability; direct drive generators have the ability to outsize geared wind systems and simplify submerged linear and rotary power generation. The research held within this thesis will focus on improving direct drive power take off systems for offshore renewable energy power generation by splitting the area into four parts. The first part will discuss the various methods of energy extraction within the offshore and marine environment. The future of the sector will be discussed, and a forecast of technological advancement and existing reliability issues will be provided based on current data. The second part will focus on drive trains and direct drive generators, assessing the current topologies and suggesting alternatives that may thrive in a variety of large and small offshore renewable machines. The third part investigates the application of novel linear bearings in direct drive systems for offshore and submerged operation. A brief study of the loads found in wave applications will be presented and the testing of several polymer bearing materials will be outlined. The final part will discuss the potential benefits of flooding the airgap of a direct drive generator with sea water for marine applications. Results will be presented from two linear test rigs and the marinisation of devices will conclude the report

End-Stage Renal Disease Among HIV-Infected Adults in North America

Background. Human immunodeficiency virus (HIV)-infected adults, particularly those of black race, are at high-risk for end-stage renal disease (ESRD), but contributing factors are evolving. We hypothesized that improvements in HIV treatment have led to declines in risk of ESRD, particularly among HIV-infected blacks

One Size Fits (n)One: The Influence of Sex, Age, and Sexual Human Immunodeficiency Virus (HIV) Acquisition Risk on Racial/Ethnic Disparities in the HIV Care Continuum in the United States.

BackgroundThe United States National HIV/AIDS Strategy established goals to reduce disparities in retention in human immunodeficiency virus (HIV) care, antiretroviral therapy (ART) use, and viral suppression. The impact of sex, age, and sexual HIV acquisition risk (ie, heterosexual vs same-sex contact) on the magnitude of HIV-related racial/ethnic disparities is not well understood.MethodsWe estimated age-stratified racial/ethnic differences in the 5-year restricted mean percentage of person-time spent in care, on ART, and virally suppressed among 19 521 women (21.4%), men who have sex with men (MSM; 59.0%), and men who have sex with women (MSW; 19.6%) entering HIV care in the North American AIDS Cohort Collaboration on Research and Design between 2004 and 2014.ResultsAmong women aged 18-29 years, whites spent 12.0% (95% confidence interval [CI], 1.1%-20.2%), 9.2% (95% CI, .4%-20.4%), and 13.5% (95% CI, 2.7%-22.5%) less person-time in care, on ART, and virally suppressed, respectively, than Hispanics. Black MSM aged ≥50 years spent 6.3% (95% CI, 1.3%-11.7%), 11.0% (95% CI, 4.6%-18.1%), and 9.7% (95% CI, 3.6%-16.8%) less person-time in these stages, respectively, than white MSM ≥50 years of age. Among MSM aged 40-49 years, blacks spent 9.8% (95% CI, 2.4%-16.5%) and 11.9% (95% CI, 3.8%-19.3%) less person-time on ART and virally suppressed, respectively, than whites.ConclusionsRacial/ethnic differences in HIV care persist in specific populations defined by sex, age, and sexual HIV acquisition risk. Clinical and public health interventions that jointly target these demographic factors are needed

Current and Past Immunodeficiency Are Associated With Higher Hospitalization Rates Among Persons on Virologically Suppressive Antiretroviral Therapy for up to 11 Years.

BackgroundPersons with HIV (PWH) with persistently low CD4 counts despite efficacious antiretroviral therapy could have higher hospitalization risk.MethodsIn six US and Canadian clinical cohorts, PWH with virologic suppression for ≥1 year in 2005-2015 were followed until virologic failure, loss to follow-up, death, or study end. Stratified by early (Years 2-5) and long-term (Years 6-11) suppression and lowest pre-suppression CD4 count <200 and ≥200 cells/µL, Poisson regression models estimated hospitalization incidence rate ratios (aIRR) comparing patients by time-updated CD4 count category, adjusted for cohort, age, gender, calendar year, suppression duration, and lowest pre-suppression CD4 count.ResultsThe 6997 included patients (19 980 person-years) were 81% cisgender men and 40% White. Among patients with lowest pre-suppression CD4 <200 cells/μL (44%), patients with current CD4 200-350 versus >500 cells/μL had an aIRR of 1.44 during early suppression (95% CI 1.01-2.06), and 1.67 (1.03-2.72) during long-term suppression. Among patients with lowest pre-suppression CD4 ≥200 (56%), patients with current CD4 351-500 versus >500 cells/μL had an aIRR of 1.22 (0.93-1.60) during early suppression and 2.09 (1.18-3.70) during long-term suppression.ConclusionsVirologically suppressed patients with lower CD4 counts experienced higher hospitalization rates, and could potentially benefit from targeted clinical management strategies

Hospitalization Rates and Causes among Persons with HIV in the US and Canada, 2005–2015

BackgroundTo assess the possible impact of antiretroviral therapy improvements, aging, and comorbidities, we examined trends in all-cause and cause-specific hospitalization rates among persons with HIV (PWH) from 2005 to 2015.MethodsIn 6 clinical cohorts, we followed PWH in care (≥1 outpatient CD4 count or HIV load [VL] every 12 months) and categorized ICD codes of primary discharge diagnoses using modified Clinical Classifications Software. Poisson regression estimated hospitalization rate ratios for calendar time trends, adjusted for demographics, HIV risk factor, and annually updated age, CD4, and VL.ResultsAmong 28 057 patients (125 724 person-years), from 2005 to 2015, the median CD4 increased from 389 to 580 cells/µL and virologic suppression from 55% to 85% of patients. Unadjusted all-cause hospitalization rates decreased from 22.3 per 100 person-years in 2005 (95% confidence interval [CI], 20.6-24.1) to 13.0 in 2015 (95% CI, 12.2-14.0). Unadjusted rates decreased for almost all diagnostic categories. Adjusted rates decreased for all-cause, cardiovascular, and AIDS-defining conditions, increased for non-AIDS-defining infection, and were stable for most other categories.ConclusionsAmong PWH with increasing CD4 counts and viral suppression, unadjusted hospitalization rates decreased for all-cause and most cause-specific hospitalizations, despite the potential effects of aging, comorbidities, and cumulative exposure to HIV and antiretrovirals

Association of Immunosuppression and Human Immunodeficiency Virus (HIV) Viremia With Anal Cancer Risk in Persons Living With HIV in the United States and Canada.

BackgroundPeople living with human immunodeficiency virus (HIV; PLWH) have a markedly elevated anal cancer risk, largely due to loss of immunoregulatory control of oncogenic human papillomavirus infection. To better understand anal cancer development and prevention, we determined whether recent, past, cumulative, or nadir/peak CD4+ T-cell count (CD4) and/or HIV-1 RNA level (HIV RNA) best predict anal cancer risk.MethodsWe studied 102 777 PLWH during 1996-2014 from 21 cohorts participating in the North American AIDS Cohort Collaboration on Research and Design. Using demographics-adjusted, cohort-stratified Cox models, we assessed associations between anal cancer risk and various time-updated CD4 and HIV RNA measures, including cumulative and nadir/peak measures during prespecified moving time windows. We compared models using the Akaike information criterion.ResultsCumulative and nadir/peak CD4 or HIV RNA measures from approximately 8.5 to 4.5 years in the past were generally better predictors for anal cancer risk than their corresponding more recent measures. However, the best model included CD4 nadir (ie, the lowest CD4) from approximately 8.5 years to 6 months in the past (hazard ratio [HR] for <50 vs ≥500 cells/µL, 13.4; 95% confidence interval [CI], 3.5-51.0) and proportion of time CD4 <200 cells/µL from approximately 8.5 to 4.5 years in the past (a cumulative measure; HR for 100% vs 0%, 3.1; 95% CI, 1.5-6.6).ConclusionsOur results are consistent with anal cancer promotion by severe, prolonged HIV-induced immunosuppression. Nadir and cumulative CD4 may represent useful markers for identifying PLWH at higher anal cancer risk