Reconfigurable Antireflection Coatings Enabled by PDMS Oligomer Infusion in Templated Nanoporous Polymer Films.

The diffusion of uncured polydimethylsiloxane (PDMS) oligomers out of bulk PDMS elastomers is usually detrimental to many biomedical and microfluidic applications due to the inevitable contamination of the contacting fluids and substrates. Here, we transform this detrimental process into an enabling technology for achieving novel reconfigurable antireflection (AR) coatings, which are of great technological importance in the development of new nano-optical and optoelectronic applications. Self-assembled monolayer silica colloidal crystals are first used as sacrificial templates in fabricating nanoporous polymer AR coatings. When air in the templated nanopores is replaced with infused PDMS oligomers simply by pressing a PDMS stamp on a nanoporous AR film, the original antireflection conditions are lost, and the coating transforms from a low-reflection configuration to a high-reflection state. The original antireflection performance can be fully recovered by dissolving the infused oligomers in the appropriate solvents (e.g., hexane). This novel tuning mechanism for achieving reconfigurable AR properties has been confirmed by systematic investigations using various microscopes, optical spectroscopy, nanoindentation, thermomechanical tests, and X-ray photoelectron spectroscopy. Complex micropatterns with micrometer-scale spatial resolution and drastically different AR performances can be easily printed on nanoporous AR films by using a soft lithography-based microcontact printing process. Numerical finite-difference time-domain simulations match well with experimental antireflection measurements and reveal a linear relationship between the optical transmission and the amount of infused PDMS oligomers in nanopores.

Clinical and biochemical responses to treatment of uncomplicated severe acute malnutrition: a multicenter observational cohort from the OptiDiag study.

BACKGROUND: Severe acute malnutrition (SAM) can be diagnosed using weight-for-height Z-score (WHZ) and/or mid-upper arm circumference (MUAC). Although some favor using MUAC alone, valuing its presumed ability to identify children at greatest need for nutritional care, the functional severity and physiological responses to treatment in children with varying deficits in WHZ and MUAC remain inadequately characterized. OBJECTIVE: We aimed to compare clinical and biochemical responses to treatment in children with 1) both low MUAC and low WHZ, 2) low MUAC-only, and 3) low WHZ-only. METHODS: A multicenter, observational cohort study was conducted in children aged 6-59 mo with nonedematous, uncomplicated SAM in Bangladesh, Burkina Faso, and Liberia. Anthropometric measurements and critical indicators were collected 3 times during treatment; metrics included clinical status, nutritional status, viability, and serum leptin, a biomarker of mortality risk in SAM. RESULTS: Children with combined MUAC and WHZ deficits had greater increases in leptin levels during treatment than those with low MUAC alone, showing a 34.4% greater increase on the second visit (95% confidence interval [CI]: 7.6%, 43.6%; P = 0.02) and a 34.3% greater increase on the third visit (95% CI: 13.2%, 50.3%; P = 0.01). Similarly, weight gain velocity was higher by 1.56 g/kg/d in the combined deficit group (95% CI: 0.38, 2.75; P = 0.03) compared with children with low MUAC-only. Children with combined deficits had higher rates of iron deficiency and wasting while those with low WHZ alone and combined deficits had higher rates of tachypnea and pneumonia during treatment. CONCLUSIONS: Given the comparable treatment responses of children with low WHZ alone and those with low MUAC alone, and the greater vulnerability at admission and during treatment in those with combined deficits, our findings support retaining WHZ as an independent diagnostic and admission criterion of SAM, alongside MUAC. This trial was registered at www. CLINICALTRIALS: gov/study/NCT03400930 as NCT03400930.

Protocol for a seamless phase 2A-phase 2B randomized double-blind placebo-controlled trial to evaluate the safety and efficacy of benfotiamine in patients with early Alzheimer's disease (BenfoTeam).

BACKGROUND: Benfotiamine provides an important novel therapeutic direction in Alzheimer's disease (AD) with possible additive or synergistic effects to amyloid targeting therapeutic approaches. OBJECTIVE: To conduct a seamless phase 2A-2B proof of concept trial investigating tolerability, safety, and efficacy of benfotiamine, a prodrug of thiamine, as a first-in-class small molecule oral treatment for early AD. METHODS: This is the protocol for a randomized, double-blind, placebo-controlled 72-week clinical trial of benfotiamine in 406 participants with early AD. Phase 2A determines the highest safe and well-tolerated dose of benfotiamine to be carried forward to phase 2B. During phase 2A, real-time monitoring of pre-defined safety stopping criteria in the first approximately 150 enrollees will help determine which dose (600 mg or 1200 mg) will be carried forward into phase 2B. The phase 2A primary analysis will test whether the rate of tolerability events (TEs) is unacceptably high in the high-dose arm compared to placebo. The primary safety endpoint in phase 2A is the rate of TEs compared between active and placebo arms, at each dose. The completion of phase 2A will seamlessly transition to phase 2B without pausing or stopping the trial. Phase 2B will assess efficacy and longer-term safety of benfotiamine in a larger group of participants through 72 weeks of treatment, at the selected dose. The co-primary efficacy endpoints in phase 2B are CDR-Sum of Boxes and ADAS-Cog13. Secondary endpoints include safety and tolerability measures; pharmacokinetic measures of thiamine and its esters, erythrocyte transketolase activity as blood markers of efficacy of drug delivery; ADCS-ADL-MCI; and MoCA. CONCLUSION: The BenfoTeam trial utilizes an innovative seamless phase 2A-2B design to achieve proof of concept. It includes an adaptive dose decision rule, thus optimizing exposure to the highest and best-tolerated dose. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT06223360, registered on January 25, 2024. https://classic.clinicaltrials.gov/ct2/show/NCT06223360.

Collagen Networks under Indentation and Compression Behave Like Cellular Solids.

Simple synthetic and natural hydrogels can be formulated to have elastic moduli that match biological tissues, leading to their widespread application as model systems for tissue engineering, medical device development, and drug delivery vehicles. However, two different hydrogels having the same elastic modulus but differing in microstructure or nanostructure can exhibit drastically different mechanical responses, including their poroelasticity, lubricity, and load bearing capabilities. Here, we investigate the mechanical response of collagen-1 networks to local and bulk compressive loads. We compare these results to the behavior of polyacrylamide, a fundamentally different class of hydrogel network consisting of flexible polymer chains. We find that the high bending rigidity of collagen fibers, which suppresses entropic bending fluctuations and osmotic pressure, facilitates the bulk compression of collagen networks under infinitesimal applied stress. These results are fundamentally different from the behavior of flexible polymer networks in which the entropic thermal fluctuations of the polymer chains result in an osmotic pressure that must first be overcome before bulk compression can occur. Furthermore, we observe minimal transverse strain during the axial loading of collagen networks, a behavior reminiscent of open-celled cellular solids. Inspired by these results, we applied mechanical models of cellular solids to predict the elastic moduli of the collagen networks and found agreement with the moduli values measured through contact indentation. Collectively, these results suggest that unlike flexible polymer networks that are often considered incompressible, collagen hydrogels behave like rigid porous solids that volumetrically compress and expel water rather than spreading laterally under applied normal loads.

Clinical and Biochemical Markers of Risk in Uncomplicated Severe Acute Malnutrition.

BACKGROUND AND OBJECTIVES: Use of mid-upper arm circumference (MUAC) as a single screening tool for severe acute malnutrition (SAM) assumes that children with a low weight-for-height z score (WHZ) and normal MUAC have lower risks of morbidity and mortality. However, the pathophysiology and functional severity associated with different anthropometric phenotypes of SAM have never been well characterized. We compared clinical characteristics, biochemical features, and health and nutrition histories of nonedematous children with SAM who had (1) low WHZ only, (2) both low WHZ and low MUAC, or (3) low MUAC only. METHODS: In Bangladesh, Burkina Faso, and Liberia, we conducted a multicentric cohort study in uncomplicated, nonedematous children with SAM and low MUAC only (n = 161), low WHZ only (n = 138), or a combination of low MUAC and low WHZ (n = 152). Alongside routine anthropometric measurements, we collected a wide range of critical indicators of clinical and nutritional status and viability; these included serum leptin, an adipocytokine negatively associated with mortality risk in SAM. RESULTS: Median leptin levels at diagnosis were lower in children with low WHZ only (215.8 pg/mL; P < .001) and in those with combined WHZ and MUAC deficits (180.1 pg/mL; P < .001) than in children with low MUAC only (331.50 pg/mL). The same pattern emerged on a wide range of clinical indicators, including signs of severe wasting, dehydration, serum ferritin levels, and caretaker-reported health deterioration, and was replicated across study sites. CONCLUSIONS: Illustrative of the likely heterogeneous functional severity of the different anthropometric phenotypes of SAM, our results confirm the need to retain low WHZ as an independent diagnostic criterion.

Evaporation-Induced Hierarchical Assembly of Rigid Silicon Nanopillars Fabricated by a Scalable Two-Level Colloidal Lithography Approach.

Periodic arrays of silicon nanowires/nanopillars are of great technological importance in developing novel electrical, optical, biosensing, and electromechanical devices. Here, we report a novel two-level colloidal lithography technology for making periodic arrays of single-crystalline silicon nanopillars (or nanocolumns) over large areas. Spin-coated monolayer silica colloidal crystals with unusual nonclose-packed structures are utilized as first-level etching masks in generating ordered polymer posts whose sizes can be much smaller than the templating silica microspheres. These polymer posts can then be used as second-level structural templates in fabricating highly ordered silicon nanopillars with broadly tunable geometries by employing metal-assisted chemical etching. As the silicon nanopillars are produced by direct wet etching on the surface of a single-crystalline silicon wafer, they are relatively free of volume defects and thus their bending strength approaches the predicted theoretical maximum. Most importantly, the unique nonclose-packed structure of the original colloidal template and the close-to-ideal mechanical property enables the formation of unusual open-structured hierarchical assemblies of rigid silicon nanopillars during water evaporation. Both experiments and numerical finite-difference time-domain modeling confirm the importance of high aspect ratios of the templated silicon nanopillars in achieving superior broadband antireflection properties. The large fraction of entrapped air in the hierarchically assembled silicon nanopillars further facilitates to accomplish superhydrophobic surface states, promising for developing self-cleaning antireflection coatings for many important optoelectronic applications.

Memantine and Acetylcholinesterase Inhibitor Use in Alzheimer's Disease Clinical Trials: Potential for Confounding by Indication.

BACKGROUND: Acetylcholinesterase inhibitors (AChEIs) and memantine are commonly prescribed medications for Alzheimer's disease (AD). Their concurrent use in AD randomized clinical trials (RCTs) is generally allowed but their effect in outcome measures is unsettled. OBJECTIVE: To evaluate whether use of AChEIs and/or memantine across AD RCTs are associated with different rates of cognitive/functional decline. METHODS: We pooled data from 5 RCTs of mild to moderate AD conducted by the Alzheimer's Disease Cooperative Study (ADCS) between 2002-2013. 1,423 participants with MMSE of 14-26 and completion of 12-18 months follow-up visits were analyzed. Trials did not randomize with respect to AChEIs or memantine. We defined 4 groups: AChEI (27%), memantine (16%), AChEIs+memantine (46%), and non-users (11%). Outcome measures were change in ADAS-cog-11, ADCS-ADL, and MMSE from baseline to 18 months. Fisher's exact test, Wilcoxon signed rank, and Spearman's tests were used to identify confounding variables. Mixed model repeated measures were used for adjustments and pairwise tests for comparing change in scores. RESULTS: Age, apolipoprotein E, and initial MMSE were identified as covariates. Memantine and/or AChEIs users had greater impairment at entry than non-users. There was a significant decline on the ADAS-cog-11 in the memantine (estimate -4.2 p < 0.0001) and AChEIs+memantine groups (estimate -3.5 p < 0.0001) than non-users, while there was significantly more decline in MMSE (estimate 2.5 p < 0.0001) and ADCS-ADL in the AChEIs+memantine group (estimate 4.3 p < 0.0001)Conclusion: Memantine monotherapy or combined with AChEIs are associated with more rapid cognitive and functional decline than non-users. We postulated a potential selection bias by indication.

Hierarchical Characterization and Nanomechanical Assessment of Biomimetic Scaffolds Mimicking Lamellar Bone via Atomic Force Microscopy Cantilever-Based Nanoindentation.

The hierarchical structure of bone and intrinsic material properties of its two primary constituents, carbonated apatite and fibrillar collagen, when being synergistically organized into an interpenetrating hard-soft composite, contribute to its excellent mechanical properties. Lamellar bone is the predominant structural motif in mammalian hard tissues; therefore, we believe the fabrication of a collagen/apatite composite with a hierarchical structure that emulates bone, consisting of a dense lamellar microstructure and a mineralized collagen fibril nanostructure, is an important first step toward the goal of regenerative bone tissue engineering. In this work, we exploit the liquid crystalline properties of collagen to fabricate dense matrices that assemble with cholesteric organization. The matrices were crosslinked via carbodiimide chemistry to improve mechanical properties, and are subsequently mineralized via the polymer-induced liquid-precursor (PILP) process to promote intrafibrillar mineralization. Neither the crosslinking procedure nor the mineralization affected the cholesteric collagen microstructures; notably, there was a positive trend toward higher stiffness with increasing crosslink density when measured by cantilever-based atomic force microscopy (AFM) nanoindentation. In the dry state, the average moduli of moderately (X51; 4.8 ± 4.3 GPa) and highly (X76; 7.8 ± 6.7 GPa) crosslinked PILP-mineralized liquid crystalline collagen (LCC) scaffolds were higher than the average modulus of bovine bone (5.5 ± 5.6 GPa).

Chromogenic Photonic Crystal Sensors Enabled by Multistimuli-Responsive Shape Memory Polymers.

Here novel chromogenic photonic crystal sensors based on smart shape memory polymers (SMPs) comprising polyester/polyether-based urethane acrylates blended with tripropylene glycol diacrylate are reported, which exhibit nontraditional all-room-temperature shape memory (SM) effects. Stepwise recovery of the collapsed macropores with 350 nm diameter created by a "cold" programming process leads to easily perceived color changes that can be correlated with the concentrations of swelling analytes in complex, multicomponent nonswelling mixtures. High sensitivity (as low as 10 ppm) and unprecedented measurement range (from 10 ppm to 30 vol%) for analyzing ethanol in octane and gasoline have been demonstrated by leveraging colorimetric sensing in both liquid and gas phases. Proof-of-concept tests for specifically detecting ethanol in consumer medical and healthcare products have also been demonstrated. These sensors are inexpensive, reusable, durable, and readily deployable with mobile platforms for quantitative analysis. Additionally, theoretical modeling of solvent diffusion in macroporous SMPs provides fundamental insights into the mechanisms of nanoscopic SM recovery, which is a topic that has received little examination. These novel sensors are of great technological importance in a wide spectrum of applications ranging from environmental monitoring and workplace hazard identification to threat detection and process/product control in chemical, petroleum, and pharmaceutical industries.

Preliminary Impacts of an HIV-Prevention Program Targeting Out-of-School Youth in Postconflict Liberia.

Adolescents in Sub-Saharan Africa account for greater HIV/STI (human immuno defiency virus/sexually transmitted infection) burdens and difficult-to-reach populations. This study implemented a community-based HIV/STI program to reach at-risk youth aged 15 to 17 years in postconflict Liberia. Using a randomized controlled trial, community youths were assigned to an adapted version of an effective HIV/STI program, Making Proud Choices, or attention-matched comparison curriculum, General Health Program. Both programs were of similar doses, reach and coverage, and administered in classroom settings by trained health educators. The findings suggest that the adapted HIV/STI program had positive effects on knowledge, sexual refusal and condom use self-efficacy, condom negotiation self-efficacy, positive condom attitudes, parental communication about sex, and negative condom attitudes over time. Culturally adapted community-based, behavioral-driven programs can positively affect mediators of sexual behaviors in at-risk adolescents in postconflict settings. This is the first published report of an evidence-based HIV/STI program on sexual risk-taking behaviors of community youths in Liberia.

Reconfigurable Photonic Crystals Enabled by Multistimuli-Responsive Shape Memory Polymers Possessing Room Temperature Shape Processability.

Traditional shape memory polymers (SMPs) are mostly thermoresponsive, and their applications in nano-optics are hindered by heat-demanding programming and recovery processes. By integrating a polyurethane-based shape memory copolymer with templating nanofabrication, reconfigurable/rewritable macroporous photonic crystals have been demonstrated. This SMP coupled with the unique macroporous structure enables unusual all-room-temperature shape memory cycles. "Cold" programming involving microscopic order-disorder transitions of the templated macropores is achieved by mechanically deforming the macroporous SMP membranes. The rapid recovery of the permanent, highly ordered photonic crystal structure from the temporary, disordered configuration can be triggered by multiple stimuli including a large variety of vapors and solvents, heat, and microwave radiation. Importantly, the striking chromogenic effects associated with these athermal and thermal processes render a sensitive and noninvasive optical methodology for quantitatively characterizing the intriguing nanoscopic shape memory effects. Some critical parameters/mechanisms that could significantly affect the final performance of SMP-based reconfigurable photonic crystals including strain recovery ratio, dynamics and reversibility of shape recovery, as well as capillary condensation of vapors in macropores, which play a crucial role in vapor-triggered recovery, can be evaluated using this new optical technology.

Stability of High Speed 3D Printing in Liquid-Like Solids.

Fluid instabilities limit the ability of features to hold their shape in many types of 3D printing as liquid inks solidify into written structures. By 3D printing directly into a continuum of jammed granular microgels, these instabilities are circumvented by eliminating surface tension and body forces. However, this type of 3D printing process is potentially limited by inertial instabilities if performed at high speeds where turbulence may destroy features as they are written. Here, we design and test a high-speed 3D printing experimental system to identify the instabilities that arise when an injection nozzle translates at 1 m/s. We find that the viscosity of the injected material can control the Reynold's instability, and we discover an additional, unanticipated instability near the top surface of the granular microgel medium.

Direct Writing of Three-Dimensional Macroporous Photonic Crystals on Pressure-Responsive Shape Memory Polymers.

Here we report a single-step direct writing technology for making three-dimensional (3D) macroporous photonic crystal patterns on a new type of pressure-responsive shape memory polymer (SMP). This approach integrates two disparate fields that do not typically intersect: the well-established templating nanofabrication and shape memory materials. Periodic arrays of polymer macropores templated from self-assembled colloidal crystals are squeezed into disordered arrays in an unusual shape memory "cold" programming process. The recovery of the original macroporous photonic crystal lattices can be triggered by direct writing at ambient conditions using both macroscopic and nanoscopic tools, like a pencil or a nanoindenter. Interestingly, this shape memory disorder-order transition is reversible and the photonic crystal patterns can be erased and regenerated hundreds of times, promising the making of reconfigurable/rewritable nanooptical devices. Quantitative insights into the shape memory recovery of collapsed macropores induced by the lateral shear stresses in direct writing are gained through fundamental investigations on important process parameters, including the tip material, the critical pressure and writing speed for triggering the recovery of the deformed macropores, and the minimal feature size that can be directly written on the SMP membranes. Besides straightforward applications in photonic crystal devices, these smart mechanochromic SMPs that are sensitive to various mechanical stresses could render important technological applications ranging from chromogenic stress and impact sensors to rewritable high-density optical data storage media.

Reconfigurable photonic crystals enabled by pressure-responsive shape-memory polymers.

Smart shape-memory polymers can memorize and recover their permanent shape in response to an external stimulus (for example, heat). They have been extensively exploited for a wide spectrum of applications ranging from biomedical devices to aerospace morphing structures. However, most of the existing shape-memory polymers are thermoresponsive and their performance is hindered by heat-demanding programming and recovery steps. Although pressure is an easily adjustable process variable such as temperature, pressure-responsive shape-memory polymers are largely unexplored. Here we report a series of shape-memory polymers that enable unusual 'cold' programming and instantaneous shape recovery triggered by applying a contact pressure at ambient conditions. Moreover, the interdisciplinary integration of scientific principles drawn from two disparate fields--the fast-growing photonic crystal and shape-memory polymer technologies--enables fabrication of reconfigurable photonic crystals and simultaneously provides a simple and sensitive optical technique for investigating the intriguing shape-memory effects at nanoscale.

Chromogenic Photonic Crystals Enabled by Novel Vapor-Responsive Shape-Memory Polymers.

A new type of shape-memory polymer (SMP) is developed by integrating scientific principles drawn from two disparate fields: the fast-growing photonic crystal and SMP technologies. This new SMP enables room-temperature operation for the entire shape-memory cycle and instantaneous shape recovery triggered by exposure to a variety of organic vapors.

Structural remodeling of coronary resistance arteries: effects of age and exercise training.

Age is known to induce remodeling and stiffening of large-conduit arteries; however, little is known of the effects of age on remodeling and mechanical properties of coronary resistance arteries. We employed a rat model of aging to investigate whether 1) age increases wall thickness and stiffness of coronary resistance arteries, and 2) exercise training reverses putative age-induced increases in wall thickness and stiffness of coronary resistance arteries. Young (4 mo) and old (21 mo) Fischer 344 rats remained sedentary or underwent 10 wk of treadmill exercise training. Coronary resistance arteries were isolated for determination of wall-to-lumen ratio, effective elastic modulus, and active and passive responses to changes in intraluminal pressure. Elastin and collagen content of the vascular wall were assessed histologically. Wall-to-lumen ratio increased with age, but this increase was reversed by exercise training. In contrast, age reduced stiffness, and exercise training increased stiffness in coronary resistance arteries from old rats. Myogenic responsiveness was reduced with age and restored by exercise training. Collagen-to-elastin ratio (C/E) of the wall did not change with age and was reduced with exercise training in arteries from old rats. Thus age induces hypertrophic remodeling of the vessel wall and reduces the stiffness and myogenic function of coronary resistance arteries. Exercise training reduces wall-to-lumen ratio, increases wall stiffness, and restores myogenic function in aged coronary resistance arteries. The restorative effect of exercise training on myogenic function of coronary resistance arteries may be due to both changes in vascular smooth muscle phenotype and expression of extracellular matrix proteins.

Neuropsychiatric symptoms and regional neocortical atrophy in mild cognitive impairment and Alzheimer's disease.

BACKGROUND: To assess the relationship between regional neocortical atrophy and psychotic symptoms in adults with mild cognitive impairment (MCI) and Alzheimer's disease (AD). METHODS: Rates of change in regional neocortical atrophy as measured by longitudinal magnetic resonance imaging scans and the occurrence of psychotic symptoms and/or the long-term use of antipsychotic medications in 389 outpatients with MCI or AD in Alzheimer's Disease Neuroimaging Initiative. RESULTS: Atrophy rate of 3 specific neocortical regions, lateral frontal, lateral parietal, and anterior cingulate gyrus, was significantly associated with the onset of psychosis including delusions, agitation, wandering, and hallucinations and/or the need for chronic antipsychotic medications. Atrophy rate of the lateral frontal lobe correlated most significantly with onset of psychotic symptoms or need for chronic antipsychotic medications. CONCLUSIONS: Psychosis was associated with volume loss in specific regions of the lateral frontal and parietal lobes as well as anterior cingulate gyrus.

A highly compliant serpentine shaped polyimide interconnect for front-end strain relief in chronic neural implants.

While the signal quality of recording neural electrodes is observed to degrade over time, the degradation mechanisms are complex and less easily observable. Recording microelectrodes failures are attributed to different biological factors such as tissue encapsulation, immune response, and disruption of blood-brain barrier (BBB) and non-biological factors such as strain due to micromotion, insulation delamination, corrosion, and surface roughness on the recording site (1-4). Strain due to brain micromotion is considered to be one of the important abiotic factors contributing to the failure of the neural implants. To reduce the forces exerted by the electrode on the brain, a high compliance 2D serpentine shaped electrode cable was designed, simulated, and measured using polyimide as the substrate material. Serpentine electrode cables were fabricated using MEMS microfabrication techniques, and the prototypes were subjected to load tests to experimentally measure the compliance. The compliance of the serpentine cable was numerically modeled and quantitatively measured to be up to 10 times higher than the compliance of a straight cable of same dimensions and material.

Spaceflight-induced alterations in cerebral artery vasoconstrictor, mechanical, and structural properties: implications for elevated cerebral perfusion and intracranial pressure.

Evidence indicates that cerebral blood flow is both increased and diminished in astronauts on return to Earth. Data from ground-based animal models simulating the effects of microgravity have shown that decrements in cerebral perfusion are associated with enhanced vasoconstriction and structural remodeling of cerebral arteries. Based on these results, the purpose of this study was to test the hypothesis that 13 d of spaceflight [Space Transportation System (STS)-135 shuttle mission] enhances myogenic vasoconstriction, increases medial wall thickness, and elicits no change in the mechanical properties of mouse cerebral arteries. Basilar and posterior communicating arteries (PCAs) were isolated from 9-wk-old female C57BL/6 mice for in vitro vascular and mechanical testing. Contrary to that hypothesized, myogenic vasoconstrictor responses were lower and vascular distensibility greater in arteries from spaceflight group (SF) mice (n=7) relative to ground-based control group (GC) mice (n=12). Basilar artery maximal diameter was greater in SF mice (SF: 236±9 µm and GC: 215±5 µm) with no difference in medial wall thickness (SF: 12.4±1.6 µm; GC: 12.2±1.2 µm). Stiffness of the PCA, as characterized via nanoindentation, was lower in SF mice (SF: 3.4±0.3 N/m; GC: 5.4±0.8 N/m). Collectively, spaceflight-induced reductions in myogenic vasoconstriction and stiffness and increases in maximal diameter of cerebral arteries signify that elevations in brain blood flow may occur during spaceflight. Such changes in cerebral vascular control of perfusion could contribute to increases in intracranial pressure and an associated impairment of visual acuity in astronauts during spaceflight.

Reducing sexual risk taking behaviors among adolescents who engage in transactional sex in post-conflict Liberia.

Transactional sex (TS) has been correlated with HIV/STD infection, pregnancy, early marriage, and sexual violence in sub-Saharan Africa (SSA). Few Western-based HIV prevention programs adapted for SSA have examined intervention impacts for this group. This article examines whether an HIV prevention intervention, delivered to sixth-grade students in Liberia (age range 14-17) and found to increase condom use and other mediators for the larger sample, significantly impacted sexual behaviors and mediators for those who engaged in TS. Using an attention-matched, group-randomized controlled design, four matched pairs of elementary schools in Monrovia, Liberia, were randomly assigned to an adapted eight-module HIV prevention or a general health curriculum. Nine-month impacts of the intervention on sexual risk behaviors and mediators for those who engaged in TS, when compared with other study participants, are presented. Twelve percent of our sample of sixth graders (n = 714) ever engaged in TS. The majority of females reported being promised something in exchange for sex (52%), whereas the majority of males (52%) reported being both the giver and recipient of gifts in exchange for sex. Compared with other students, those who engaged in TS reported greater increases in the number of sex partners, reported greater frequency of sexual intercourse, were more likely to try to get pregnant or someone else pregnant, and reported greater reductions in protective sexual attitudes and HIV risk perception at the nine month follow-up, in both the intervention and the control groups. Our intervention, although successful for the general in-school adolescent sample, did not impact risk behaviors or mediators for adolescents who engaged in TS. Future research should explore the complex sexual economy in which TS is embedded and consider adapting HIV prevention interventions to the needs of this high-risk group.