Mesoscale modeling and computational simulation studies of the self-assembly of heterogeneous colloidal systems.

Over the last two decades researchers have advanced the field of colloidal synthesis by developing new synthesis techniques. Colloidal particles are known to self-assemble into various unique architectures. However, there is still no simple rule relating system condition and particle type to achievable self-assembled structures. The goal of this thesis was to use simulation methods to further develop an understanding of how tailoring interparticle interactions and system parameters (such as temperature and concentration) leads to self-assembled structures. The applicability of one specific colloidal system - nanotetrapods - for use as nanoelectronic circuit elements is investigated. The electrical response for MESFET and JFET nanotetrapods was determined through Technology Aided Design Tools, and it was determined that nanotetrapods have the potential to be utilized as circuit elements. Monte Carlo simulations provide insight into how proper tuning of particle-particle and particle-substrate interactions result in the assembly of ordered arrays of electrically gated nanotetrapods. We used lattice energy calculations and normal mode analysis (NMA) to investigate the thermodynamic and mechanical stability of binary, ionic colloidal crystals with size ratio 1.0 : 0.8. Based on these methods, theoretical predictions were made regarding the stable crystal structure as a function of potential interaction parameters. We found the normal mode results are in agreement with lattice energy results, and were compared to molecular dynamics simulations to determine the capacity for self-assembly. We found that not all predicted structures are kinetically accessible. Additionally, we investigated the self-assembly of colloidal crystals for one specific interaction parameter as a function of density and temperature, and found that, in addition to the theoretically predicted crystal structure, a second entropically stabilized crystal structure formed at higher temperatures. The extension of NMA to finite temperature systems was developed without having to couple to slower simulations. Using the Lennard-Jones model, kinetic energy was introduced into the system by randomly displacing particles in a crystal. Temperature was related to these displacements through the equipartition theorem. Upon comparison with published work on the Lennard-Jones spinodal, we determined that NMA reasonably predicts the limit of mechanical stability at low temperatures, but overestimates it at higher temperatures.Ph.D.Chemical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/78889/1/teichmcg_1.pd

MindMate: a single case experimental design study of a reminder system for people with dementia

Prospective memory difficulties are commonly reported in people with dementia. The evidence supporting the use of prospective memory devices among the dementia population remains limited. MindMate is a recently developed smart device application that aims to support individuals with a diagnosis of dementia, improving self-management skills and quality of life. This study investigated the effectiveness and usability of the reminder tool on the MindMate application as a memory aid. Three participants with a diagnosis of Alzheimer’s disease were recruited to this multiple baseline single-case experimental design study. Partners of the participants recorded their performance on everyday tasks on weekly monitoring forms during a baseline phase (between five and seven weeks) and during the intervention phase (five weeks) whilst using MindMate. Two participants successfully used the app throughout the intervention weeks and gave positive usability ratings. Tau-U analysis showed a significant increase in memory performance between baseline and intervention phase (Tau-U = 1, 0.94, p < .01). A third participant withdrew from the intervention phase following difficulties turning off the reminders and frustrations with the reminder alert sound. For two of the three participants, use of MindMate was feasible and effective in supporting remembering of everyday tasks compared to practice as usual

Breast cancer management pathways during the COVID-19 pandemic: outcomes from the UK ‘Alert Level 4’ phase of the B-MaP-C study

Abstract: Background: The B-MaP-C study aimed to determine alterations to breast cancer (BC) management during the peak transmission period of the UK COVID-19 pandemic and the potential impact of these treatment decisions. Methods: This was a national cohort study of patients with early BC undergoing multidisciplinary team (MDT)-guided treatment recommendations during the pandemic, designated ‘standard’ or ‘COVID-altered’, in the preoperative, operative and post-operative setting. Findings: Of 3776 patients (from 64 UK units) in the study, 2246 (59%) had ‘COVID-altered’ management. ‘Bridging’ endocrine therapy was used (n = 951) where theatre capacity was reduced. There was increasing access to COVID-19 low-risk theatres during the study period (59%). In line with national guidance, immediate breast reconstruction was avoided (n = 299). Where adjuvant chemotherapy was omitted (n = 81), the median benefit was only 3% (IQR 2–9%) using ‘NHS Predict’. There was the rapid adoption of new evidence-based hypofractionated radiotherapy (n = 781, from 46 units). Only 14 patients (1%) tested positive for SARS-CoV-2 during their treatment journey. Conclusions: The majority of ‘COVID-altered’ management decisions were largely in line with pre-COVID evidence-based guidelines, implying that breast cancer survival outcomes are unlikely to be negatively impacted by the pandemic. However, in this study, the potential impact of delays to BC presentation or diagnosis remains unknown

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Swelling Properties of Montmorillonite and Beidellite Clay Minerals from Molecular Simulation: Comparison of Temperature, Interlayer Cation, and Charge Location Effects

The swelling properties of smectite clay minerals are relevant to many engineering applications including environmental remediation, repository design for nuclear waste disposal, borehole stability in drilling operations, and additives for numerous industrial processes and commercial products. We used molecular dynamics and grand canonical Monte Carlo simulations to study the effects of layer charge location, interlayer cation, and temperature on intracrystalline swelling of montmorillonite and beidellite clay minerals. For a beidellite model with layer charge exclusively in the tetrahedral sheet, strong ion–surface interactions shift the onset of the two-layer hydrate to higher water contents. In contrast, for a montmorillonite model with layer charge exclusively in the octahedral sheet, weaker ion–surface interactions result in the formation of fully hydrated ions (two-layer hydrate) at much lower water contents. Clay hydration enthalpies and interlayer atomic density profiles are consistent with the swelling results. Water adsorption isotherms from grand canonical Monte Carlo simulations are used to relate interlayer hydration states to relative humidity, in good agreement with experimental findings

Identification of Metal–Organic Framework Materials for Adsorption Separation of Rare Gases: Applicability of Ideal Adsorbed Solution Theory (IAST) and Effects of Inaccessible Framework Regions

A collection of >3000 MOFs with experimentally confirmed structures were screened for performance in three binary separations: Ar/Kr, Kr/Xe, and Xe/Rn. 70 materials were selected for further analysis, and calculations were performed to account for inaccessible regions. Single component GCMC calculations were performed to parametrize IAST calculations on these 70 materials. An approach that avoids possible imprecision in IAST due to curve-fitting of single component isotherms is introduced. The precision of IAST for these gas pairs was confirmed with extensive binary GCMC calculations. For each binary separation, materials were identified with predicted performance that surpasses the state of the art. A significant number of materials were found to be “reverse selective” in the sense that a smaller gas species is preferably adsorbed over a larger species. The physical origin of this phenomenon is explained. The effect of temperature on separation performance was also examined

Effects of Polarizability on the Adsorption of Noble Gases at Low Pressures in Monohalogenated Isoreticular Metal–Organic Frameworks

A systematic investigation of the effects of linker polarizability on the adsorption properties of weakly interacting gases (N₂, Ar, Kr, and Xe) is reported. Experimental and simulated adsorption properties were measured for a complete isoreticular series of monohalogenated metal–organic frameworks (MOFs). Variations on IRMOF-2, in which one linker hydrogen is replaced with −F, −Cl, −Br, or −I, comprise the series. Both experimental and simulated results indicate that increasing linker polarizability correlates with increased gas uptake. Evidence of increased adsorbate interaction with increased linker polarizability is also observed in the Kr/N₂, Xe/N₂, and Xe/Kr selectivity data and in isosteric heats of adsorption. Unexpectedly, comparison between simulated and experimental isotherms reveals that the agreement between the two improves with the size of the adsorbate, with essentially identical results for Xe. This is apparently due to the creation of regions inaccessible to any of the noble gases as a result of halogen functionalization. Simulated adsorption isotherms are also reported for radon, which is difficult to measure experimentally due to its radioactivity

Postdoctoral program guidelines.

We, the Postdoc Professional Development Program (PD2P) leadership team, wrote these postdoc guidelines to be a starting point for communication between new postdocs, their staff mentors, and their managers. These guidelines detail expectations and responsibilities of the three parties, as well as list relevant contacts. The purpose of the Postdoc Program is to bring in talented, creative people who enrich Sandia's environment by performing innovative R&D, as well as by stimulating intellectual curiosity and learning. Postdocs are temporary employees who come to Sandia for career development and advancement reasons. In general, the postdoc term is 1 year, renewable up to five times for a total of six years. However, center practices may vary; check with your manager. At term, a postdoc may apply for a staff position at Sandia or choose to move to university, industry or another lab. It is our vision that those who leave become long-term collaborators and advocates whose relationships with Sandia have a positive effect upon our national constituency