1,595 research outputs found
Recommended from our members
Targeted sequence design within the coarse-grained polymer genome
The chemical design of polymers with target structural and/or functional properties represents a grand challenge in materials science. While data-driven design approaches are promising, success with polymers has been limited, largely due to limitations in data availability. Here, we demonstrate the targeted sequence design of single-chain structure in polymers by combining coarse-grained modeling, machine learning, and model optimization. Nearly 2000 unique coarse-grained polymers are simulated to construct and analyze machine learning models. We find that deep neural networks inexpensively and reliably predict structural properties with limited sequence information as input. By coupling trained ML models with sequential model-based optimization, polymer sequences are proposed to exhibit globular, swollen, or rod-like behaviors, which are verified by explicit simulations. This work highlights the promising integration of coarse-grained modeling with data-driven design and represents a necessary and crucial step toward more complex polymer design efforts
Adaptation to the Edge of Chaos in the Self-Adjusting Logistic Map
Self-adjusting, or adaptive systems have gathered much recent interest. We
present a model for self-adjusting systems which treats the control parameters
of the system as slowly varying, rather than constant. The dynamics of these
parameters is governed by a low-pass filtered feedback from the dynamical
variables of the system. We apply this model to the logistic map and examine
the behavior of the control parameter. We find that the parameter leaves the
chaotic regime. We observe a high probability of finding the parameter at the
boundary between periodicity and chaos. We therefore find that this system
exhibits adaptation to the edge of chaos.Comment: 3 figure
Recommended from our members
New Sequence Perspective on the Devonian Reef Complex and the Frasnian-Famennian Boundary, Canning Basin, Australia
The application of concepts of sequence stratigraphy to seismic and well data has led to a new understanding of the subsurface Devonian reef complex of the Canning Basin. It demonstrates marked reciprocal sedimentation with lowstand terrigenous sediments largely restricted to the basin and transgressive and highstand carbonate sediments on the platform. Preliminary outcrop studies indicate the potential of these concepts to modify significantly the existing lithostratigraphic and biostratigraphic interpretations of this classic exhumed reef complex, including the stratigraphic context of the Frasnian-Famennian boundary in the Canning Basin
Recommended from our members
Multivalent ions induce lateral structural inhomogeneities in polyelectrolyte brushes
Subtle details about a polyelectrolyte's surrounding environment can dictate its structural features and potential applications. Atomic force microscopy (AFM), surface forces apparatus (SFA) measurements, and coarse-grained molecular dynamics simulations are combined to study the structure of planar polyelectrolyte brushes [poly(styrenesulfonate), PSS] in a variety of solvent conditions. More specifically, AFM images provide a first direct visualization of lateral inhomogeneities on the surface of polyelectrolyte brushes collapsed in solutions containing trivalent counterions. These images are interpreted in the context of a coarse-grained molecular model and are corroborated by accompanying interaction force measurements with the SFA. Our findings indicate that lateral inhomogeneities are absent from PSS brush layers collapsed in a poor solvent without multivalent ions. Together, AFM, SFA, and our molecular model present a detailed picture in which solvophobic and multivalent ion-induced effects work in concert to drive strong phase separation, with electrostatic bridging of polyelectrolyte chains playing an essential role in the collapsed structure formation
'Heaven starts at your parents' feet' : adolescent bowing to parents and associated spiritual attitudes
In a quantitative survey of religious attitudes and practices in a multi-religious sample of
369 school pupils aged between 13 and 15 in London, the practice of bowing to parents was
found widespread in 22% of adolescents spanning several religious affiliations and
ethnicities â especially Buddhists, Hindus and those of Indian, African and âOther Asianâ
ethnicity. Whether an adolescent bowed correlated significantly with spiritual attitudes such
as wanting to abstain from alcohol, hearing religious stories, being inspired by religious
festivals and liking the idea of seeing God in everything. Findings suggest bowing to
parents can have religious significance on all three levels of Jacksonâs Interpretive
Approach and therefore cannot be regarded as a âcultural accretionâ of religion. Study of
bowing to parents could form a unifying exercise in shared values for study of religion in
the plural classroom and facilitate community cohesion in certain religious membership
groups
Proglacial groundwater storage dynamics under climate change and glacier retreat
Proglacial aquifers are an important water store in glacierised mountain catchments that supplement meltwaterâfed river flows and support freshwater ecosystems. Climate change and glacier retreat will perturb water storage in these aquifers, yet the climateâglacierâgroundwater response cascade has rarely been studied and remains poorly understood. This study implements an integrated modelling approach that combines distributed glacioâhydrological and groundwater models with climate change projections to evaluate the evolution of groundwater storage dynamics and surfaceâgroundwater exchanges in a temperate, glacierised catchment in Iceland. Focused infiltration along the meltwaterâfed VirkisĂĄ River channel is found to be an important source of groundwater recharge and is projected to provide 14%â20% of total groundwater recharge by the 2080s. The simulations highlight a mechanism by which glacier retreat could inhibit river recharge in the future due to the loss of diurnal melt cycling in the runoff hydrograph. However, the evolution of proglacial groundwater level dynamics show considerable resilience to changes in river recharge and, instead, are driven by changes in the magnitude and seasonal timing of diffuse recharge from yearâround rainfall. The majority of scenarios simulate an overall reduction in groundwater levels with a maximum 30âday average groundwater level reduction of 1âm. The simulations replicate observational studies of baseflow to the river, where up to 15% of the 30âday average river flow comes from groundwater outside of the melt season. This is forecast to reduce to 3%â8% by the 2080s due to increased contributions from rainfall and meltwater runoff. During the melt season, groundwater will continue to contribute 1%â3% of river flow despite significant reductions in meltwater runoff inputs. Therefore it is concluded that, in the proglacial region, groundwater will continue to provide only limited buffering of river flows as the glacier retreats
Apolipoprotein L1 gene variants associate with prevalent kidney but not prevalent cardiovascular disease in the Systolic Blood Pressure Intervention Trial.
Apolipoprotein L1 gene (APOL1) G1 and G2 coding variants are strongly associated with chronic kidney disease (CKD) in African Americans (AAs). Here APOL1 association was tested with baseline estimated glomerular filtration rate (eGFR), urine albumin:creatinine ratio (UACR), and prevalent cardiovascular disease (CVD) in 2571 AAs from the Systolic Blood Pressure Intervention Trial (SPRINT), a trial assessing effects of systolic blood pressure reduction on renal and CVD outcomes. Logistic regression models that adjusted for potentially important confounders tested for association between APOL1 risk variants and baseline clinical CVD (myocardial infarction, coronary, or carotid artery revascularization) and CKD (eGFR under 60âml/min per 1.73âm(2) and/or UACR over 30âmg/g). AA SPRINT participants were 45.3% female with a mean (median) age of 64.3 (63) years, mean arterial pressure 100.7 (100)âmmâHg, eGFR 76.3 (77.1) ml/min per 1.73âm(2), and UACR 49.9 (9.2)âmg/g, and 8.2% had clinical CVD. APOL1 (recessive inheritance) was positively associated with CKD (odds ratio 1.37, 95% confidence interval 1.08-1.73) and log UACR estimated slope (β) 0.33) and negatively associated with eGFR (β -3.58), all significant. APOL1 risk variants were not significantly associated with prevalent CVD (1.02, 0.82-1.27). Thus, SPRINT data show that APOL1 risk variants are associated with mild CKD but not with prevalent CVD in AAs with a UACR under 1000âmg/g
Some observations on meaningful and objective inference in radioecological field studies
1. Anthropogenic releases of radiation are of ongoing importance for environmental protection, but the radiation doses at which natural systems begin to show effects are controversial. More certainty is required in this area to achieve optimal regulation for radioactive substances. We recently carried out a large survey (268 sampled animals and 20 sites) of the association between environmental radiation exposures and small mammal gut-associated microbiomes (fungal and bacterial) in the Chornobyl Exclusion zone (CEZ). Using individual measurements of total absorbed dose rates and a study design and analyses that accounted for spatial non-independence, we found no, or only limited, association.
2. Watts et al. have criticised our study: for not filtering candidate non-resident components prior to our fungal microbiome analyses, for our qualified speculations on the relative merits of faecal and gut samples, and for the design of our study which they felt lacked sufficient replication.
3. The advantage of filtering non-resident-fungal taxa is not clear and it would not have changed the null (spatially adjusted) association we found between radioactive dose and mycobiome composition because the most discriminatory fungal taxa with regard to dose were non-resident taxa.
4. We maintain that it was legitimate for us to make qualified discussion comments on the differences in results between our faecal and gut microbiome analyses and on the relative merits of these sample types.
5. Most importantly, the criticism of our study design by Watts et al. and the designs and analysis of their recent studies in the CEZ show a misunderstanding of the true nature of independent replication in field studies. Recognising the importance of spatial non-independence is essential in the design and analysis of radioecological field surveys
- âŚ