SDTrimSP Simulations of Solar Wind Sputtering on Mercury: A Sensitivity Study to Establish a Best-Practice

Understanding the role solar wind (SW) ions play on surface sputtering of Mercury is critical to any exosphere model. The most common models use binary collision approximation (BCA) tools such as SDTrimSP. However, this state-of-the-art tool has many user-specific inputs and that are not immediately clear for more complex substrates such as minerals on celestial surfaces. These include surface binding energies, SW compositions, static vs. dynamic, and impact energy. Previous research has not kept these parameters consistent, making it unclear how sensitive sputtering behavior is to these parameters. As such, we have conducted a detailed sensitivity study into SDTrimSP parameters for simulating SW impacts. We have considered how several important simulation choices affect sputtering yields, composition, energy distribution, and damage. Results show that sputtering behavior is highly dependent on these parameters and can be used to establish a best practice methodology for SDTrimSP

The Prevalence and Social Determinants of HIV-Associated Neurocognitive Disorders among American Indians and Alaskan Natives

American Indian and Alaskan Native people living with HIV (AI/AN PLWH) have the poorest HIV survival rates of any U.S racial/ethnic group (CDC, 2015 & 2016), suggesting limited access and utilization of health care. However, no studies to date have examined HIV-associated Neurocognitive Disorder (HAND) or the potential social determinants of HAND in this population. This cross-sectional study aimed to identify the prevalence and social determinants (i.e., HIV clinical characteristics, comorbid conditions, quality of education) of HAND among AI/AN PLWH. An English-speaking sample of 109 AI/AN and 105 non-Latinx white (NLW) PLWH (86.4% Male; Mage = 41.5 ± 9.9 years; Meducation = 12.9 ± 3.1 years) completed comprehensive neurocognitive, functional, neuromedical, and psychiatric/substance use evaluations (Heaton et al., 2010). The Wide Range Achievement Test- Edition 3 (WRAT-3) Reading Subtest served as a proxy for quality of education. A series of multinomial and binomial stepwise logistic regression analyses were conducted to examine the effects of ethnoracial status and social determinants of health upon HAND and neurocognitive impairment. AI/AN PLWH demonstrated worse social determinants of health as defined by nadir CD4, CD4 cell count per mL \u3c 200, and WRAT-3 (all ps ≤ .05). The prevalence of HAND was greater among the AI/AN group compared to the NLW group (64.0% vs. 40.0%; χ2(1) = 14.6, p \u3c .01). AI/AN PWH were 7.1 times at greater risk for neurocognitive impairment (B(SE) =.39(.15), χ2 = 6.9, p \u3c .01). The WRAT-3 was the only social determinant significantly associated with ethnoracial disparity in neurocognitive impairment (all ps ≤ .01). Reducing the increased risk for HAND is a priority among AI/AN PWH. This study provides insight into the modifiable risk factors for HAND, particularly emphasizing social determinants of neurocognitive health. Future work should examine possible disparity in neurocognitive decline among AI/AN PLWH

Barriers and Facilitators to PrEP Initiation and Adherence Among Transgender and Gender Non-Binary Individuals in Southern California.

While transgender and gender non-binary (trans/nb) individuals are disproportionately affected by HIV, pre-exposure prophylaxis (PrEP) uptake remains low in this underserved population. We conducted four focus groups with 37 trans/nb individuals in San Diego and Los Angeles to assess barriers and facilitators of PrEP usage. Transcripts were coded for qualitative themes. Although overall PrEP awareness was high, participants reported limited knowledge and misinformation about PrEP. Barriers to PrEP use included: structural access (e.g., discrimination from health care providers, lack of trans-inclusive services, financial barriers), mental health struggles limiting ability to access PrEP, and concerns about potential side effects, drug-drug interactions with hormone therapy, and lack of other STI protection. Facilitators of PrEP usage included: increased PrEP availability, prior experience taking daily medications, and motivation to have active and healthy lives without fear of contracting HIV. Addressing both structural and psychosocial/behavioral factors in trans-affirming health care environments is crucial to designing inclusive, effective PrEP interventions

Latinx brain health disparities in cognitive aging: The role of acculturation on brain integrity and cognition among older HIV+ adults

BackgroundThe US Latinx population is the largest ethnoracial minority group and the fastest growing sector of the aging population (Escarce et al., 2006; US Census Bureau, 2008). Compared to non- Latinx whites (NLW), the Latinx population bears a disproportionate dementia burden secondary to multiple etiologies (e.g., Alzheimer- s, HIV- infection; Babulal et al., 2018; Rivera Mindt et al., 2014). Yet, little is understood regarding the sociocultural factors underlying these significant brain health disparities. This aim of cross- sectional study was to investigate indices of brain integrity, cognition, and acculturation in older HIV+ Latinx and NLW adults.MethodParticipants included 75 older HIV+ adults (Age: M=60 yrs [SD=6.9]; Education: M=13.6 yrs [SD=3.1]; 47% Latinx [primarily Caribbean heritage] & 53% NLW; and 71% male) who completed multimodal neuroimaging (structural MRI and resting state fMRI [rs- fMRI]), cognitive (seven domains; e.g., leaning, memory, executive function), neuromedical (HIV clinical indices [HIV viral load]), and sociocultural (e.g., acculturation [Abbreviated Multidimensional Acculturation Scale, AMAS]) evaluations. Global and domain- specific Average T- scores were computed on individual tests based on demographically- adjusted norms.ResultCompared to the NLW group, the Latinx group had greater white matter lesion volumes ([mL], FLAIR; Cohen- s d=1.13, p<.01) and lower hippocampal and posterior cingulate intrinsic activity (rs- fMRI fALFF values; d- s =.61 - .67), and worse global cognition, learning, memory, and processing speed (ds=.53 - .83, ps< .05), with the largest effects in learning and memory. Lower acculturation to US majority culture (i.e., AMAS US Total Score) was related to reduced intrinsic activity of the right hippocampus and posterior cingulate cortex at the trend level (rs- fMRI fALFF values; rs=.61 - .63, ps<.10) and worse global cognition, learning, memory, and processing speed (rs = .39 - .51, ps<.05).ConclusionThese findings highlight marked disparities in brain integrity and cognition in older HIV+ Latinx adults. Acculturation may be an important factor for understanding these disparities. Future longitudinal research is needed with HIV- controls, larger sample sizes, and the inclusion of other Latinx subpopulations (i.e., Mexican- American, South American) to extend the current findings and inform culturally- targeted interventions to promote Latinx brain health. Acknowledgements: The authors thank the Alzheimer- s Association for their support of this study (AARGD- 16- 446038).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/163840/1/alz046503.pd