The self-assembling properties, stability, and dynamics of hybrid nanocarriers (gold nanoparticles (AuNPs) functionalized with cysteine-based peptides) in solution are studied through a series of classical molecular dynamics simulations based on a recently parametrized reactive force field. The results reveal, at the atomic level, all the details regarding the peptide adsorption mechanisms, nanoparticle stabilization, aggregation, and sintering. The data confirm and explain the experimental findings and disclose aspects that cannot be scrutinized by experiments. The biomolecules are both chemisorbed and physisorbed; self-interactions of the adsorbates and formation of stable networks of interconnected molecules on the AuNP surfaces limit substrate reconstructions, protect the AuNPs from the action of the solvent, and prevent direct interactions of the gold surfaces. The possibility of agglomeration of the functionalized nanoparticles, compared with the sintering of the bare supports in a water solution, is demonstrated through relatively long simulations and fast steered dynamics. The analysis of the trajectories reveals that the AuNPs were well stabilized by the peptides. This prevented particle sintering and kept the particles far apart; however, part of their chains could form interconnections (crosslinks) between neighboring gold vehicles. The excellent agreement of these results with the literature confirm the reliability of the method and its potential application to the modeling of more complex materials relevant to the biomedical sector.
We performed Raman measurements at 18 K and pressures up to 25 GPa in order to construct a tentative phase diagram of the (N2)1–x:(O2)x–system at low temperatures. We varied the composition of the mixed system over the whole concentration range. Here we focused on the systems with high nitrogen concentration and pressures above 2 GPa. It is known that at room temperature oxygen is highly solvable in the –phase of N2. The experimental results show that oxygen suppresses the disorder–order transition –N2. 相似文献
Chinese TLV-bronze mirrors dating to the Han dynasty (206 B.C.-220 A.D.) were popular objects of everyday life as well as highly esteemed works of art. The decorated back of the mirror characterizes the culture of this period as well as the excellent early Chinese casting techniques. 相似文献
We investigate properties ofk-resolution, a restricted version of resolution in which one parent clause must have length at mostk. Starting from a unit-preference strategy, we compare minimal proof lengths of unit-resolution and unrestricted resolution. In particular, we show that the speed-up by using resolution is bound by
if the shortest unit-resolution refutation needst steps. Next we present an algorithm which decides whether the empty clause can be deduced by 2-resolution from a formula and has time complexity O(length()4). Finally we describe effects onk-resolution if a formula is transformed intot-CNF and show that extended 3-resolution is complete and sound. 相似文献
This paper is the first attempt to successfully design efficient approximation algorithms for the single-machine weighted
flow-time minimization problem when jobs have different release dates and weights equal to their processing times under the
assumption that one job is fixed (i.e., the machine is unavailable during a fixed interval corresponding to the fixed job).
Our work is motivated by an interesting algorithmic application to the generation of valid inequalities in a branch-and-cut
method. Our analysis shows that the trivial FIFO sequence can lead to an arbitrary large worst-case performance bound. Hence,
we modify this sequence so that a new 2-approximation solution can be obtained for every instance and we prove the tightness
of this bound. Then, we propose a fully polynomial-time approximation algorithm with efficient running time for the considered
problem. Especially, the complexity of our algorithm is strongly polynomial. 相似文献
Recently, it was shown how the convergence of a class of multigrid methods for computing the stationary distribution of sparse,
irreducible Markov chains can be accelerated by the addition of an outer iteration based on iterant recombination. The acceleration
was performed by selecting a linear combination of previous fine-level iterates with probability constraints to minimize the
two-norm of the residual using a quadratic programming method. In this paper we investigate the alternative of minimizing
the one-norm of the residual. This gives rise to a nonlinear convex program which must be solved at each acceleration step.
To solve this minimization problem we propose to use a deep-cuts ellipsoid method for nonlinear convex programs. The main
purpose of this paper is to investigate whether an iterant recombination approach can be obtained in this way that is competitive
in terms of execution time and robustness. We derive formulas for subgradients of the one-norm objective function and the
constraint functions, and show how an initial ellipsoid can be constructed that is guaranteed to contain the exact solution
and give conditions for its existence. We also investigate using the ellipsoid method to minimize the two-norm. Numerical
tests show that the one-norm and two-norm acceleration procedures yield a similar reduction in the number of multigrid cycles.
The tests also indicate that one-norm ellipsoid acceleration is competitive with two-norm quadratic programming acceleration
in terms of running time with improved robustness. 相似文献
Integral surfaces are ideal tools to illustrate vector fields and fluid flow structures. However, these surfaces can be visually complex and exhibit difficult geometric properties, owing to strong stretching, shearing and folding of the flow from which they are derived. Many techniques for non-photorealistic rendering have been presented previously. It is, however, unclear how these techniques can be applied to integral surfaces. In this paper, we examine how transparency and texturing techniques can be used with integral surfaces to convey both shape and directional information. We present a rendering pipeline that combines these techniques aimed at faithfully and accurately representing integral surfaces while improving visualization insight. The presented pipeline is implemented directly on the GPU, providing real-time interaction for all rendering modes, and does not require expensive preprocessing of integral surfaces after computation. 相似文献
Making changes to software systems can prove costly and it remains a challenge to understand the factors that affect the costs
of software evolution. This study sought to identify such factors by investigating the effort expended by developers to perform
336 change tasks in two different software organizations. We quantitatively analyzed data from version control systems and
change trackers to identify factors that correlated with change effort. In-depth interviews with the developers about a subset
of the change tasks further refined the analysis. Two central quantitative results found that dispersion of changed code and
volatility of the requirements for the change task correlated with change effort. The analysis of the qualitative interviews
pointed to two important, underlying cost drivers: Difficulties in comprehending dispersed code and difficulties in anticipating
side effects of changes. This study demonstrates a novel method for combining qualitative and quantitative analysis to assess
cost drivers of software evolution. Given our findings, we propose improvements to practices and development tools to manage
and reduce the costs. 相似文献
In certain situations the state of a quantum system, after transmission through a quantum channel, can be perfectly restored.
This can be done by “coding” the state space of the system before transmission into a “protected” part of a larger state space,
and by applying a proper “decoding” map afterwards. By a version of the Heisenberg Principle, which we prove, such a protected
space must be “dark” in the sense that no information leaks out during the transmission. We explain the role of the Knill–Laflamme
condition in relation to protection and darkness, and we analyze several degrees of protection, whether related to error correction,
or to state restauration after a measurement. Recent results on higher rank numerical ranges of operators are used to construct
examples. In particular, dark spaces are constructed for any map of rank 2, for a biased permutations channel and for certain
separable maps acting on multipartite systems. Furthermore, error correction subspaces are provided for a class of tri-unitary
noise models. 相似文献