23,955 research outputs found
Recommended from our members
Ensuring Access to Safe and Nutritious Food for All Through the Transformation of Food Systems
Emergence simulation of cell-like morphologies with evolutionary potential by virtual molecular interactions
This study explores the emergence of life through a simulation model
approach. The model "Multi-set chemical lattice model" is a model that allows
virtual molecules of multiple types to be placed in each lattice cell on a
two-dimensional space. This model is capable of describing a wide variety of
states and interactions in a limited number of lattice cell spaces, such as
diffusion, chemical reaction, and polymerization of virtual molecules. This
model is also capable of describing a wide variety of states and interactions
even in the limited lattice cell space of 100 x 100 cells. Furthermore it was
considered energy metabolism and energy resources environment. It was able to
reproduce the "evolution" in which a certain cell-like shapes adapted to the
environment survives under conditions of decreasing amounts of energy resources
in the environment. This enabled the emergence of cell-like shapes with the
four minimum cellular requirements: boundary, metabolism, replication, and
evolution, based solely on the interaction of virtual molecules.Comment: arXiv admin note: text overlap with arXiv:2204.0968
A hybrid quantum algorithm to detect conical intersections
Conical intersections are topologically protected crossings between the
potential energy surfaces of a molecular Hamiltonian, known to play an
important role in chemical processes such as photoisomerization and
non-radiative relaxation. They are characterized by a non-zero Berry phase,
which is a topological invariant defined on a closed path in atomic coordinate
space, taking the value when the path encircles the intersection
manifold. In this work, we show that for real molecular Hamiltonians, the Berry
phase can be obtained by tracing a local optimum of a variational ansatz along
the chosen path and estimating the overlap between the initial and final state
with a control-free Hadamard test. Moreover, by discretizing the path into
points, we can use single Newton-Raphson steps to update our state
non-variationally. Finally, since the Berry phase can only take two discrete
values (0 or ), our procedure succeeds even for a cumulative error bounded
by a constant; this allows us to bound the total sampling cost and to readily
verify the success of the procedure. We demonstrate numerically the application
of our algorithm on small toy models of the formaldimine molecule
(\ce{H2C=NH}).Comment: 15 + 10 pages, 4 figure
Thread-safe lattice Boltzmann for high-performance computing on GPUs
We present thread-safe, highly-optimized lattice Boltzmann implementations,
specifically aimed at exploiting the high memory bandwidth of GPU-based
architectures. At variance with standard approaches to LB coding, the proposed
strategy, based on the reconstruction of the post-collision distribution via
Hermite projection, enforces data locality and avoids the onset of memory
dependencies, which may arise during the propagation step, with no need to
resort to more complex streaming strategies. The thread-safe lattice Boltzmann
achieves peak performances, both in two and three dimensions and it allows to
sensibly reduce the allocated memory ( tens of GigaBytes for order billions
lattice nodes simulations) by retaining the algorithmic simplicity of standard
LB computing. Our findings open attractive prospects for high-performance
simulations of complex flows on GPU-based architectures
Recommended from our members
Seeing Below The Surface Of Mars: Volatile sublimation in the martian regolith
The discovery of buried carbon dioxide (CO2) ice between water (H2O) ice layers within the martian south polar layered deposits has renewed interest in subsurface CO2 ice. In this thesis, subsurface CO2 ice stability is explored using a 1-D thermal and vapour diffusion numerical model that simulates three phases of H2O, two phases of CO2, and adsorption of both for the first time.
Numerical experiments were run to examine how these two ices influence one another, under a variety of ice-layer configurations that are expected to be valid for Mars. The results demonstrate that an overlying near-surface H2O ice-filled regolith layer increases subsurface CO2 ice stability by an order of magnitude. This stability increases further with the addition of an underlying H2O ice-filled regolith layer. The initial porosity and geological materials used to represent the subsurface also have a large influence on CO2 ice stability. The porosity limits the vapour diffusion rate, while the geological materials influence thermal conductivity and, therefore, subsurface temperatures.
Simulations at different orbital obliquities demonstrate that CO2 ice stability in the polar regions is greatest at low obliquities and smallest at high obliquities. The reverse is true for the equatorial regions. At higher obliquities (>45◦) and atmospheric pressures, the results suggest subsurface CO2 ice deposition could occur in the equatorial region.
The model results suggest that a 0.7–27 km CO2 ice layer could sublimate away while 1 m of low-porosity H2O ice forms (in 14–550 kyr depending on method) in the south polar layered deposits. The results also suggest CO2 ice sublimation is dependent on obliquity: ∼0.15 km sublimates at low obliquity and ∼1.9 km sublimates at high
obliquity over 100 kyr.
The subsurface model is a useful tool for future investigations into the historical behaviour of ices on Mars, particularly during the Noachian period when the CO2 frost-point temperature was higher
Structure and adsorption properties of gas-ionic liquid interfaces
Supported ionic liquids are a diverse class of materials that have been considered
as a promising approach to design new surface properties within solids for gas
adsorption and separation applications. In these materials, the surface morphology and
composition of a porous solid are modified by depositing ionic liquid. The resulting
materials exhibit a unique combination of structural and gas adsorption properties
arising from both components, the support, and the liquid. Naturally, theoretical and
experimental studies devoted to understanding the underlying principles of exhibited
interfacial properties have been an intense area of research. However, a complete
understanding of the interplay between interfacial gas-liquid and liquid-solid
interactions as well as molecular details of these processes remains elusive.
The proposed problem is challenging and in this thesis, it is approached from
two different perspectives applying computational and experimental techniques. In
particular, molecular dynamics simulations are used to model gas adsorption in films
of ionic liquids on a molecular level. A detailed description of the modeled systems is
possible if the interfacial and bulk properties of ionic liquid films are separated. In this
study, we use a unique method that recognizes the interfacial and bulk structures of
ionic liquids and distinguishes gas adsorption from gas solubility. By combining
classical nitrogen sorption experiments with a mean-field theory, we study how liquid-solid interactions influence the adsorption of ionic liquids on the surface of the porous
support.
The developed approach was applied to a range of ionic liquids that feature
different interaction behavior with gas and porous support. Using molecular
simulations with interfacial analysis, it was discovered that gas adsorption capacity
can be directly related to gas solubility data, allowing the development of a predictive
model for the gas adsorption performance of ionic liquid films. Furthermore, it was
found that this CO2 adsorption on the surface of ionic liquid films is determined by the
specific arrangement of cations and anions on the surface. A particularly important
result is that, for the first time, a quantitative relation between these structural and
adsorption properties of different ionic liquid films has been established. This link
between two types of properties determines design principles for supported ionic
liquids.
However, the proposed predictive model and design principles rely on the
assumption that the ionic liquid is uniformly distributed on the surface of the porous
support. To test how ionic liquids behave under confinement, nitrogen physisorption
experiments were conducted for micro‐ and mesopore analysis of supported ionic
liquid materials. In conjunction with mean-field density functional theory applied to
the lattice gas and pore models, we revealed different scenarios for the pore-filling
mechanism depending on the strength of the liquid-solid interactions.
In this thesis, a combination of computational and experimental studies provides
a framework for the characterization of complex interfacial gas-liquid and liquid-solid
processes. It is shown that interfacial analysis is a powerful tool for studying
molecular-level interactions between different phases. Finally, nitrogen sorption
experiments were effectively used to obtain information on the structure of supported
ionic liquids
Ionic Liquids on Oxide Surfaces
Ionic liquids supported on oxide surfaces are being investigated for numerous applications including catalysis, batteries, capacitors, transistors, lubricants, solar cells, corrosion inhibitors, nanoparticle synthesis and biomedical applications. The study of ionic liquids with oxide surfaces presents challenges both experimentally and computationally. The interaction between ionic liquids and oxide surfaces can be rather complex, with defects in the oxide surface playing a key role in the adsorption behaviour and resulting electronic properties. The choice of the cation/anion pair is also important and can influence molecular ordering and electronic properties at the interface. These controllable interfacial behaviours make ionic liquid/oxide systems desirable for a number of different technological applications as well as being utilised for nanoparticle synthesis. This topical review aims to bring together recent experimental and theoretical work on the interaction of ionic liquids with oxide surfaces, including TiO2, ZnO, Al2O3, SnO2 and transition metal oxides. It focusses on the behaviour of ionic liquids at model single crystal surfaces, the interaction between ionic liquids and nanoparticulate oxides, and their performance in prototype devices
Recommended from our members
Atomic Ordering at the Interfaces between Liquid Aluminum and Polar AlN{0 0 0 1} Substrates
Engineering & Physical Sciences Research Council UK grant number EP/N007638/1 (Light-weighting in the transport sector: tailored design of Mg alloys and processes (PLATFORM)
Genome-wide identification of the genetic basis of amyotrophic lateral sclerosis
Amyotrophic lateral sclerosis (ALS) is a complex disease that leads to motor neuron death. Despite heritability estimates of 52%, genome-wide association studies (GWASs) have discovered relatively few loci. We developed a machine learning approach called RefMap, which integrates functional genomics with GWAS summary statistics for gene discovery. With transcriptomic and epigenetic profiling of motor neurons derived from induced pluripotent stem cells (iPSCs), RefMap identified 690 ALS-associated genes that represent a 5-fold increase in recovered heritability. Extensive conservation, transcriptome, network, and rare variant analyses demonstrated the functional significance of candidate genes in healthy and diseased motor neurons and brain tissues. Genetic convergence between common and rare variation highlighted KANK1 as a new ALS gene. Reproducing KANK1 patient mutations in human neurons led to neurotoxicity and demonstrated that TDP-43 mislocalization, a hallmark pathology of ALS, is downstream of axonal dysfunction. RefMap can be readily applied to other complex diseases
Gendered spaces in contemporary Irish poetry
The thrust of this thesis is summarized by the following questions: How does contemporary Irish poetry migrate from traditional conceptions of identity drawn on by the cultural nationalism of the Irish Literary Revival, and what effects does this have on understanding gendered and national identity formation? Chapters are on the following: Seamus Heaney, Tom Paulin, Paul Muldoon, MedbhMcGuckian, Eavan Boland and Sara Berkeley. These poets are chosen for discussion since their work most effectively engages with the relationship between woman and nation, the representation of gendered national identity, and the importance of feminist and post-colonial theorization. Focusing on poetry worth and South of the border from the last fifteen years, the thesis asks how a younger generation of poets provide a response to nationality which is significantly different from their predecessors. The thesis is composed of three parts: the first understand how the male poets depart from conventional conceptions of the nation with reference to post-colonial theorization; the second explores how feminist theorization informs readings of how the female poets respond to the nation; the final part investigates migration in the poetry and problematizes this in terms of post-nationalism. Discussing the issue of deterritorialization in Irish poetry, the thesis notice how as the poets attempt to take flight from the mythologies of nationhood, they undermine the monoliths of gendered and national identity inscribed within Irish political discourse, which is typified at a representative level by the figure of Mother Ireland or Cathleen Ni Houlihan. Investigating the ways in which gender and nation, and the body and space are reinscribed by the poets, the thesis argues that their poetry challenges authentic conceptions of Irish identity and the nation-state, so as to loosen the legacy of a colonial and nationalist inheritance
- …