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UC Merced Previously Published Works

Cover page of Maintaining Transient Diversity Is a General Principle for Improving Collective Problem Solving.

Maintaining Transient Diversity Is a General Principle for Improving Collective Problem Solving.

(2024)

Humans regularly solve complex problems in cooperative teams. A wide range of mechanisms have been identified that improve the quality of solutions achieved by those teams on reaching consensus. We argue that many of these mechanisms work via increasing the transient diversity of solutions while the group attempts to reach a consensus. These mechanisms can operate at the level of individual psychology (e.g., behavioral inertia), interpersonal communication (e.g., transmission noise), or group structure (e.g., sparse social networks). Transient diversity can be increased by widening the search space of possible solutions or by slowing the diffusion of information and delaying consensus. All of these mechanisms increase the quality of the solution at the cost of increased time to reach it. We review specific mechanisms that facilitate transient diversity and synthesize evidence from both empirical studies and diverse formal models-including multiarmed bandits, NK landscapes, cumulative-innovation models, and evolutionary-transmission models. Apparent exceptions to this principle occur primarily when problems are sufficiently simple that they can be solved by mere trial and error or when the incentives of team members are insufficiently aligned. This work has implications for our understanding of collective intelligence, problem solving, innovation, and cumulative cultural evolution.

Cover page of Atypical RhoUV GTPases in development and disease

Atypical RhoUV GTPases in development and disease

(2024)

RhoU and RhoV are members of the Rho family of small GTPases that comprise their own subfamily. RhoUV GTPases are classified as atypical due to the kinetics of their GTP/GDP binding cycles. They also possess unique N- and C-termini that regulate their subcellular localization and activity. RhoU and RhoV have been linked to cytoskeletal regulation, cell adhesion, and cell migration. They each exhibit distinct expression patterns during embryonic development and diseases such as cancer metastasis, suggesting they have specialized functions. In this review, we will discuss the known functions of RhoU and RhoV, with a focus on their roles in early development, organogenesis, and disease.

Cover page of Seroprevalence of the Hepatitis E Virus in Indigenous and Non-Indigenous Communities from the Brazilian Amazon Basin.

Seroprevalence of the Hepatitis E Virus in Indigenous and Non-Indigenous Communities from the Brazilian Amazon Basin.

(2024)

Hepatitis E virus (HEV) infection is a common cause of acute viral hepatitis in tropical regions. In Brazil, HEV G3 is the only genotype detected to date. Reports on HEV prevalence are heterogeneous. We aimed to compare the prevalence of anti-HEV among three populations living in the Brazilian Amazon basin. Two cross-sectional studies were conducted in urban, rural, and Yanomami indigenous areas. Plasma samples from 428 indigenous and 383 non-indigenous subjects were tested for anti-HEV IgG using enzyme-linked immunosorbent assays. The overall prevalence of anti-HEV was 6.8% (95%CI: 5.25-8.72), with 2.8% (12/428) found in the Yanomami areas, 3% (3/101) in an urban area, and 14.2% (40/282) in a rural area. Multivariate logistic analysis indicated that patients aged 31-45 years or ≥46 years are more likely to present anti-HEV positivity, with a respective aOR of 2.76 (95%CI: 1.09-7.5) and 4.27 (95%CI: 1.58-12.35). Furthermore, residence in a rural area (aOR: 7.67; 95%CI: 2.50-33.67) represents a relevant risk factor for HEV infection. Additional studies detecting HEV RNA in fecal samples from both humans and potential animal reservoirs are necessary to comprehensively identify risk factors associated with HEV exposure.

Cover page of Tandem manganese catalysis for the chemo-, regio-, and stereoselective hydroboration of terminal alkynes: in situ precatalyst activation as a key to enhanced chemoselectivity.

Tandem manganese catalysis for the chemo-, regio-, and stereoselective hydroboration of terminal alkynes: in situ precatalyst activation as a key to enhanced chemoselectivity.

(2024)

The manganese(ii) complex [Mn(iPrPNP)Cl2] (iPrPNP = 2,6-bis(diisopropylphosphinomethyl)pyridine) was found to catalyze the stereo- and regioselective hydroboration of terminal alkynes employing HBPin (pinacolborane). In the absence of in situ activators, mixtures of alkynylboronate and E-alkenylboronate esters were formed, whereas when NaHBEt3 was employed as the in situ activator, E-alkenylboronate esters were exclusively accessed. Mechanistic studies revealed a tandem C-H borylation/semihydrogenation pathway accounting for the formation of the products. Stoichiometric reactions hint toward reaction of a Mn-H active species with the terminal alkyne as the catalyst entry pathway to the cycle, whereas reaction with HBPin led to catalyst deactivation.

Cover page of Separating Geometric and Diffusive Contributions to the Surface Nucleation of Dislocations in Nanoparticles

Separating Geometric and Diffusive Contributions to the Surface Nucleation of Dislocations in Nanoparticles

(2024)

While metal nanoparticles are widely used, their small size makes them mechanically unstable. Extensive prior research has demonstrated that nanoparticles with sizes in the range of 10-50 nm fail by the surface nucleation of dislocations, which is a thermally activated process. Two different contributions have been suggested to cause the weakening of smaller particles: first, geometric effects such as increased surface curvature reduce the barrier for dislocation nucleation; second, surface diffusion happens faster on smaller particles, thus accelerating the formation of surface kinks which nucleate dislocations. These two factors are difficult to disentangle. Here we use in situ compression testing inside a transmission electron microscope to measure the strength and deformation behavior of platinum particles in three groups: 12 nm bare particles, 16 nm bare particles, and 12 nm silica-coated particles. Thermodynamics calculations show that, if surface diffusion were the dominant factor, the last two groups would show equal strengthening. Our experimental results refute this, instead demonstrating a 100% increase in mean yield strength with increased particle size and no statistically significant increase in strength due to the addition of a coating. A separate analysis of stable plastic flow corroborates the findings, showing an order-of-magnitude increase in the rate of dislocation nucleation with a change in particle size and no change with coating. Taken together, these results demonstrate that surface diffusion plays a far smaller role in the failure of nanoparticles by dislocations as compared to geometric factors that reduce the energy barrier for dislocation nucleation.

Cover page of Shear-activation of mechanochemical reactions through molecular deformation.

Shear-activation of mechanochemical reactions through molecular deformation.

(2024)

Mechanical stress can directly activate chemical reactions by reducing the reaction energy barrier. A possible mechanism of such mechanochemical activation is structural deformation of the reactant species. However, the effect of deformation on the reaction energetics is unclear, especially, for shear stress-driven reactions. Here, we investigated shear stress-driven oligomerization reactions of cyclohexene on silica using a combination of reactive molecular dynamics simulations and ball-on-flat tribometer experiments. Both simulations and experiments captured an exponential increase in reaction yield with shear stress. Elemental analysis of ball-on-flat reaction products revealed the presence of oxygen in the polymers, a trend corroborated by the simulations, highlighting the critical role of surface oxygen atoms in oligomerization reactions. Structural analysis of the reacting molecules in simulations indicated the reactants were deformed just before a reaction occurred. Quantitative evidence of shear-induced deformation was established by comparing bond lengths in cyclohexene molecules in equilibrium and prior to reactions. Nudged elastic band calculations showed that the deformation had a small effect on the transition state energy but notably increased the reactant state energy, ultimately leading to a reduction in the energy barrier. Finally, a quantitative relationship was developed between molecular deformation and energy barrier reduction by mechanical stress.

Cover page of The Effect of 5-HTTLPR Polymorphism on Callous-Unemotional Traits in Adolescent Psychopaths

The Effect of 5-HTTLPR Polymorphism on Callous-Unemotional Traits in Adolescent Psychopaths

(2024)

This paper reviews the outcome of serotonin production in callous-unemotional (CU) traits, varied by the SLC6A4 gene’s 5-HTTLPR repeat polymorphisms, which includes the short-allele by 44bp deletion and long-allele by 44bp insertion. Specifically, this research looked into the long-allele possibly causing decreased serotonin production, resulting in CU-traits. Previous studies found psychopathic key characteristics to be environmentally and genetically influenced in unique ways, with CU-traits being genetically affected by 5-HTTLPR polymorphisms. This research was conducted by searching for articles with keywords on the Google Scholar search engine, such as “psychopathic risk factors” and “psychopathy in adolescents.” A focus of 5-HTTLPR polymorphisms was established by its observed repetitive mentions, followed by filtering out unrelated sources already collected, then synthesizing the remaining information deemed relevant to the respectively formed research question. The data search surrounded adolescents between 12-19 year-olds, but was supported by data of other age groups, also due to severely limited research on CU-adolescents. Results within these studies were typically derived from neuroimaging, PCR, twin studies, and checklists. Treatments for psychopathic adolescents are based on positive encouragement, a preventative technique stemming from the biological foundations of CU-specific psychopathy. It was concluded that serotonin production is not depleted, but has fast reuptake from the synaptic cleft by increased 5-HT transporter mRNA. This lowers serotonin usage availability, which has been tightly associated with CU traits from previous research. Further studies should focus more on trying to understand the mechanisms of the long-allele directly impacting increased 5-HT transporter mRNA concentrations.

Cover page of Associations of Broader Parental Factors with Childrens Happiness and Weight Status through Child Food Intake, Physical Activity, and Screen Time: A Longitudinal Modeling Analysis of South Korean Families.

Associations of Broader Parental Factors with Childrens Happiness and Weight Status through Child Food Intake, Physical Activity, and Screen Time: A Longitudinal Modeling Analysis of South Korean Families.

(2024)

This study investigated how broader parental factors including parental happiness, parental play engagement, and parenting stress are related to Korean childrens happiness and weight status across three years via indirect pathways through the childrens energy-related behaviors of healthy and unhealthy food intake, physical activity, and screen time. Data from 1551 Korean parent pairs and 7-year-old children in the Panel Study on Korean Children were analyzed. A path analysis and gender-based multi-group analysis were conducted. Maternal happiness was negatively related to child screen time. Maternal play engagement showed positive concurrent associations with child healthy food intake and physical activity and negative associations with screen time. Maternal parenting stress was negatively related to child healthy eating. There was one significant finding related to fathers role on childrens energy-related behaviors, happiness, and weight status: the positive association between parental happiness and boys unhealthy food intake. Child screen time was positively related to child weight status and negatively to child happiness at each age. Broader maternal parenting factors can serve as a protective factor for childhood happiness and weight status in 7-to-9-year-olds through being associated with a reduction in child screen time.

Cover page of Can the Cans: Determinants of Container Deposit Behavior before and after Introduction of a Container Refund Scheme.

Can the Cans: Determinants of Container Deposit Behavior before and after Introduction of a Container Refund Scheme.

(2024)

OBJECTIVE: Container deposit schemes are often hailed as a useful avenue to increase consumer recycling rates. Yet, there is little research investigating within-person changes in peoples beliefs and behavior following the implementation of these schemes, or tests of the mechanisms by which such change has occurred. METHODS: The current study fills this knowledge gap and assessed container recycling behavior and habits as well as the social cognition factors of attitudes, subjective norms, perceived behavioral control, and intentions in a sample of 90 Queenslanders before the implementation of the container deposit scheme and one and three months post-implementation. RESULTS: Analysis of variance indicated more frequent recycling behavior following the implementation of the scheme, as well as stronger habits, intentions, and perceived behavioral control. CONCLUSIONS: Such a concomitant change in behavior, beliefs, and habits provides support for behavior change theory, while also flagging potential targets for strategies that can be paired with container deposit schemes to enhance their efficacy and uptake.

Cover page of Satellite Remote Sensing: A Tool to Support Harmful Algal Bloom Monitoring and Recreational Health Advisories in a California Reservoir.

Satellite Remote Sensing: A Tool to Support Harmful Algal Bloom Monitoring and Recreational Health Advisories in a California Reservoir.

(2024)

Cyanobacterial harmful algal blooms (cyanoHABs) can harm people, animals, and affect consumptive and recreational use of inland waters. Monitoring cyanoHABs is often limited. However, chlorophyll-a (chl-a) is a common water quality metric and has been shown to have a relationship with cyanobacteria. The World Health Organization (WHO) recently updated their previous 1999 cyanoHAB guidance values (GVs) to be more practical by basing the GVs on chl-a concentration rather than cyanobacterial counts. This creates an opportunity for widespread cyanoHAB monitoring based on chl-a proxies, with satellite remote sensing (SRS) being a potentially powerful tool. We used Sentinel-2 (S2) and Sentinel-3 (S3) to map chl-a and cyanobacteria, respectively, classified chl-a values according to WHO GVs, and then compared them to cyanotoxin advisories issued by the California Department of Water Resources (DWR) at San Luis Reservoir, key infrastructure in Californias water system. We found reasonably high rates of total agreement between advisories by DWR and SRS, however rates of agreement varied for S2 based on algorithm. Total agreement was 83% for S3, and 52%-79% for S2. False positive and false negative rates for S3 were 12% and 23%, respectively. S2 had 12%-80% false positive rate and 0%-38% false negative rate, depending on algorithm. Using SRS-based chl-a GVs as an early indicator for possible exposure advisories and as a trigger for in situ sampling may be effective to improve public health warnings. Implementing SRS for cyanoHAB monitoring could fill temporal data gaps and provide greater spatial information not available from in situ measurements alone.