5,865 research outputs found
Wettability-independent droplet transport by \emph{Bendotaxis}
We demonstrate \textit{bendotaxis}, a novel mechanism for droplet
self-transport at small scales. A combination of bending and capillarity in a
thin channel causes a pressure gradient that, in turn, results in the
spontaneous movement of a liquid droplet. Surprisingly, the direction of this
motion is always the same, regardless of the wettability of the channel. We use
a combination of experiments at a macroscopic scale and a simple mathematical
model to study this motion, focussing in particular on the time scale
associated with the motion. We suggest that \emph{bendotaxis} may be a useful
means of transporting droplets in technological applications, for example in
developing self-cleaning surfaces, and discuss the implications of our results
for such applications.Comment: 5 pages, 4 figures. Supplementary Information available on reques
Influence of Dielectric Environment upon Isotope Effects onGlycoside Heterolysis: Computational Evaluation and AtomicHessian Analysis
Isotope effects depend upon the polarity of the bulk medium in which a chemical process occurs. Implicit solvent calculations with molecule-shaped cavities show that the equilibrium isotope effect (EIE) for heterolysis of the glycosidic bonds in 5′-methylthioadenosine and in 2-(p-nitrophenoxy)tetrahydropyran, both in water, are very sensitive in the range 2 ≤ ε ≤ 10 to the relative permittivity of the continuum surrounding the oxacarbenium ion. However, different implementations of nominally the same PCM method can lead to opposite trends being predicted for the same molecule. Computational modeling of the influence of the inhomogeneous effective dielectric surrounding a substrate within the protein environment of an enzymic reaction requires an explicit treatment. The EIE (KH/KD) for transfer of cyclopentyl, cyclohexyl, tetrahydrofuranyl and tetrahydropyranyl cations from water to cyclohexane is predicted by B3LYP/6-31+G(d) calculations with implicit solvation and confirmed by B3LYP/6-31+G(d)/OPLS-AA calculations with averaging over many explicit solvation configurations. Atomic Hessian analysis, whereby the full Hessian is reduced to the elements belonging to a single atom at the site of isotopic substitution, reveals a remarkable result for both implicit and explicit solvation: the influence of the solvent environment on these EIEs is essentially captured completely by only a 3 × 3 block of the Hessian, although these values must correctly reflect the influence of the whole environment. QM/MM simulation with ensemble averaging has an important role to play in assisting the meaningful interpretation of observed isotope effects for chemical reactions both in solution and catalyzed by enzymes
Element-centric clustering comparison unifies overlaps and hierarchy
Clustering is one of the most universal approaches for understanding complex
data. A pivotal aspect of clustering analysis is quantitatively comparing
clusterings; clustering comparison is the basis for many tasks such as
clustering evaluation, consensus clustering, and tracking the temporal
evolution of clusters. In particular, the extrinsic evaluation of clustering
methods requires comparing the uncovered clusterings to planted clusterings or
known metadata. Yet, as we demonstrate, existing clustering comparison measures
have critical biases which undermine their usefulness, and no measure
accommodates both overlapping and hierarchical clusterings. Here we unify the
comparison of disjoint, overlapping, and hierarchically structured clusterings
by proposing a new element-centric framework: elements are compared based on
the relationships induced by the cluster structure, as opposed to the
traditional cluster-centric philosophy. We demonstrate that, in contrast to
standard clustering similarity measures, our framework does not suffer from
critical biases and naturally provides unique insights into how the clusterings
differ. We illustrate the strengths of our framework by revealing new insights
into the organization of clusters in two applications: the improved
classification of schizophrenia based on the overlapping and hierarchical
community structure of fMRI brain networks, and the disentanglement of various
social homophily factors in Facebook social networks. The universality of
clustering suggests far-reaching impact of our framework throughout all areas
of science
Imaginary-time matrix product state impurity solver for dynamical mean-field theory
We present a new impurity solver for dynamical mean-field theory based on
imaginary-time evolution of matrix product states. This converges the
self-consistency loop on the imaginary-frequency axis and obtains
real-frequency information in a final real-time evolution. Relative to
computations on the real-frequency axis, required bath sizes are much smaller
and less entanglement is generated, so much larger systems can be studied. The
power of the method is demonstrated by solutions of a three band model in the
single and two-site dynamical mean-field approximation. Technical issues are
discussed, including details of the method, efficiency as compared to other
matrix product state based impurity solvers, bath construction and its relation
to real-frequency computations and the analytic continuation problem of quantum
Monte Carlo, the choice of basis in dynamical cluster approximation, and
perspectives for off-diagonal hybridization functions.Comment: 8 pages + 4 pages appendix, 9 figure
Lunar basalt chronology, mantle differentiation and implications for determining the age of the Moon
Despite more than 40 years of studying Apollo samples, the age and early evolution of the Moon remain contentious. Following the formation of the Moon in the aftermath of a giant impact, the resulting Lunar Magma Ocean (LMO) is predicted to have generated major geochemically distinct silicate reservoirs, including the sources of lunar basalts. Samples of these basalts, therefore, provide a unique opportunity to characterize these reservoirs. However, the precise timing and extent of geochemical fractionation is poorly constrained, not least due to the difficulty in determining accurate ages and initial Pb isotopic compositions of lunar basalts. Application of an in situ ion microprobe approach to Pb isotope analysis has allowed us to obtain precise crystallization ages from six lunar basalts, typically with an uncertainty of about
±10Ma, as well as constrain their initial Pb-isotopic compositions. This has enabled construction of a two-stage model for the Pb-isotopic evolution of lunar silicate reservoirs, which necessitates the prolonged existence of high-μ reservoirs in order to explain the very radiogenic compositions of the samples. Further, once firm constraints on U and Pb partitioning behaviour are established, this model has the potential to help distinguish between conflicting estimates for the age of the Moon. Nonetheless, we are able to constrain the timing of a lunar mantle reservoir differentiation event at 4376±18Ma, which is consistent with that derived from the Sm–Nd and Lu–Hf isotopic systems, and is interpreted as an average estimate of the time at which the high-μ urKREEP reservoir was established and the Ferroan Anorthosite (FAN) suite was formed
Comment on "mt-Keima detects PINK1-PRKN mitophagy in vivo with greater sensitivity than mito-QC"
Peer reviewe
Data Logging System for a Synthetic Aperture Radar Unit
A small, existing radar unit lacked the ability to automatically store the data it was receiving, which made its use clunky and cumbersome. A system was constructed to allow an on-board microprocessor to track distance traveled, and automatically store the data output from the radar unit to a portable memory unit for later data processing. Distance traveled is determined using a specially designed mobile cart, which electronically converts the rotation of a wheel into an electrical signal while also providing stability for taking accurate radar measurements. The output data from the radar unit is stored as a properly-formatted sound file to allow for immediate data analysis
Nonequilibrium capture of impurities that completely block kinks during crystal growth
Some impurities cannot integrate into isolated kinks because they completely block the growth of the kinks to which they adsorb. For this class of impurity, we derive an equation for the amount that incorporates into a crystal during growth of the elementary step by assuming that such an impurity incorporates if and only if it gets captured between a kink and an antikink. We show that the impurity concentration in the crystal increases monotonically with the impurity concentration in the mother phase, but that it can vary non-monotonically with both the supersaturation of the mother phase and the kink density of the step. In contrast to other capture mechanisms, we find that weakly adsorbed impurities incorporate to an extent that is independent of the supersaturation when the supersaturation is high. Irrespective of the growth conditions, the amount of impurity that can incorporate into a crystal is limited by an upper bound determined by the kink density
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