JETSPIN: a specific-purpose open-source software for simulations of nanofiber electrospinning

We present the open-source computer program JETSPIN, specifically designed to simulate the electrospinning process of nanofibers. Its capabilities are shown with proper reference to the underlying model, as well as a description of the relevant input variables and associated test-case simulations. The various interactions included in the electrospinning model implemented in JETSPIN are discussed in detail. The code is designed to exploit different computational architectures, from single to parallel processor workstations. This paper provides an overview of JETSPIN, focusing primarily on its structure, parallel implementations, functionality, performance, and availability.Comment: 22 pages, 11 figures. arXiv admin note: substantial text overlap with arXiv:1507.0701

Theoretical studies of elastic effects in segregation of small molecules in complex polymer mixtures-Impact on consumer goods industry

When a polymer mixture of two types of polymers having different molecular weights are left to equilibrate, the polymer having the lower molecular weight migrates to the free interface. This phenomenon is known as surface migration. We present a theoretical framework to explain this phenomenon and to quantitatively predict the amount of material that migrates to the interface. In what follows, we provide a review of the background literature, emphasizing the phenomenology behind such a segregation process, the different theoretical developments including variational methods and self consistent field theory as well as the experimental techniques that have been used to measure the amount of material leeches as a function of parameters e.g. temperature, surface tension and the mixing parameter (that determines whether the bulk polymeric phase is mixed or phase separated). The main hypothesis presented in this thesis is that the elasticity of the polymer matrix through which the low molecular weight species migrates to the free interface is an important parameter that has not been taken into account so far. This raises the interesting possibility of controlling surface migration by tuning matrix rigidity by changing polymer elasticity with broad industrial applications

Center for Space Microelectronics Technology

The 1990 technical report of the Jet Propulsion Laboratory Center for Space Microelectronics Technology summarizes the technical accomplishments, publications, presentations, and patents of the center during 1990. The report lists 130 publications, 226 presentations, and 87 new technology reports and patents

Poly (PEGDMA-MAA) copolymeric micro and nanoparticles for oral insulin delivery : A molecular mechanistic revisit

Poly(ethylene glycol) dimethacrylate (PEGDMA) and methacrylic acid (MAA) based micro and nanoparticles were prepared for oral insulin delivery. The reactional profiles of MAA, PEGDMA and PEGDMA-MAA were elucidated using molecular mechanics energy relationships (MMER) in vacuum and in a solvated system by exploring the spatial disposition of different concentrations of polymers with respect to each other. Furthermore, the incorporation of insulin within the polymeric matrix was modeled using connolly molecular surfaces. The computational results corroborated with the experimental and analytical data. The ability to effectively control blood glucose level coupled with the non toxic behavior of the nanoparticles renders them a potential candidate for insulin deliver

When you can't count, sample! Computable entropies beyond equilibrium from basin volumes

In statistical mechanics, measuring the number of available states and their probabilities, and thus the system's entropy, enables the prediction of the macroscopic properties of a physical system at equilibrium. This predictive capacity hinges on the knowledge of the a priori probabilities of observing the states of the system, given by the Boltzmann distribution. Unfortunately, the successes of equilibrium statistical mechanics are hard to replicate out of equilibrium, where the a priori probabilities of observing states are in general not known, precluding the na\"ive application of usual tools. In the last decade, exciting developments have occurred that enable the direct numerical estimation of the entropy and density of states of athermal and non-equilibrium systems, thanks to significant methodological advances in the computation of the volume of high-dimensional basins of attraction. Here, we provide a detailed account of these methods, underscoring the challenges that lie in such estimations, recent progress on the matter, and promising directions for future work.Comment: 18 pages, 11 figure

Exploring high thermal conductivity polymers via interpretable machine learning with physical descriptors

The efficient and economical exploitation of polymers with high thermal conductivity is essential to solve the issue of heat dissipation in organic devices. Currently, the experimental preparation of functional thermal conductivity polymers remains a trial and error process due to the multi-degrees of freedom during the synthesis and characterization process. In this work, we have proposed a high-throughput screening framework for polymer chains with high thermal conductivity via interpretable machine learning and physical-feature engineering. The polymer thermal conductivity datasets for training were first collected by molecular dynamics simulation. Inspired by the drug-like small molecule representation and molecular force field, 320 polymer monomer descriptors were calculated and the 20 optimized descriptors with physical meaning were extracted by hierarchical down-selection. All the machine learning models achieve a prediction accuracy R2 greater than 0.80, which is superior to that of represented by traditional graph descriptors. Further, the cross-sectional area and dihedral stiffness descriptors were identified for positive/negative contribution to thermal conductivity, and 107 promising polymer structures with thermal conductivity greater than 20.00 W/mK were obtained. Mathematical formulas for predicting the polymer thermal conductivity were also constructed by using symbolic regression. The high thermal conductivity polymer structures are mostly {\pi}-conjugated, whose overlapping p-orbitals enable easily to maintain strong chain stiffness and large group velocities. The proposed data-driven framework should facilitate the theoretical and experimental design of polymers with desirable properties

The Schwinger Model with Perfect Staggered Fermions

We construct and test a quasi-perfect lattice action for staggered fermions. The construction starts from free fermions, where we suggest a new blocking scheme, which leads to excellent locality of the perfect action. An adequate truncation preserves a high quality of the free action. An Abelian gauge field is inserted in d=2 by effectively tuning the couplings to a few short-ranged lattice paths, based on the behavior of topological zero modes. We simulate the Schwinger model with this action, applying a new variant of Hybrid Monte Carlo, which damps the computational overhead due to the non-standard couplings. We obtain a tiny ``pion'' mass down to very small \beta, while the ``\eta'' mass follows very closely the prediction of asymptotic scaling. The observation that even short-ranged quasi-perfect actions can yield strong improvement is most relevant in view of QCD.Comment: 30 pages, 16 figures. Following the referee's suggestions, we have incorporated the material of hep-lat/9803018 in this comprehensive pape