Search results for "force"
showing 10 items of 3423 documents
Temperature and pressure dependence of quercetin-3-O-palmitate interaction with a model phospholipid membrane: film balance and scanning probe micros…
2004
The molecular interaction of quercetin-3-O-palmitate (QP) with dimyristoylphosphatidylcholine (DMPC) has been studied. Film balance measurements of the average molecular area vs QP molar fraction in DMPC/QP mixed monolayers showed that relevant positive deviations from ideality, i.e., a less dense monolayer packing, occurred for a temperature of 10 degrees C, below the critical melting transition temperature of DMPC monolayers T c m approximately equal 20 degrees C), while ideal behavior was observed at 37 degrees C, above this phase transition temperature. The positive deviation observed at low temperatures in the average molecular area increased with the surface pressure. Scanning probe m…
ChemInform Abstract: Scanning Force Microscopy of Artificial Membranes
2010
Visualization of biological membranes by scanning force microscopy (SFM) has tremendously improved the current understanding of protein ‐ lipid interactions under physiological conditions. SFM is the only tool to directly image processes on surfaces in aqueous solution at molecular resolution. Besides being a supportive means to confirm results on lipid phases and domains obtained from fluorescence spectroscopy, calorimetry, and X-ray crystallography, SFM has contributed distinct aspects on the formation of 2D crystals of various membrane-confined proteins and morphological changes of membranes due to the interaction of peptides and proteins. This review will focus on recent results in SFM …
The Dreaming Variational Autoencoder for Reinforcement Learning Environments
2018
Reinforcement learning has shown great potential in generalizing over raw sensory data using only a single neural network for value optimization. There are several challenges in the current state-of-the-art reinforcement learning algorithms that prevent them from converging towards the global optima. It is likely that the solution to these problems lies in short- and long-term planning, exploration and memory management for reinforcement learning algorithms. Games are often used to benchmark reinforcement learning algorithms as they provide a flexible, reproducible, and easy to control environment. Regardless, few games feature a state-space where results in exploration, memory, and plannin…
Model of scanning force microscopy on ionic surfaces.
1995
We present a theoretical model of the scanning force microscope using an atomistic simulation technique for the interaction between a crystalline sample and a tip nanoasperity combined with a semi- empirical treatment of the mesoscopic van der Waals attraction between tip and surface, and the macroscopic parameter of cantilever deflection. For the nanoasperity at the end of the tip, we used a neutral and a protonated (MgO${)}_{32}$ cube, which model a hard tip made of oxide material. Static calculations based on total-energy minimization were used to determine the surface and tip geometries and total energy as a function of tip position. Scan lines of the perfect (001) surfaces of NaCl and …
Micro- and mesoscopic process interactions in protein coagulation
2000
It has recently been recognized that pathological protein coagulation is responsible for lethal pathologies as diverse as amyloidosis, Alzheimer and TSE. Understanding the coagulation mechanisms is therefore stirring great interest. In previous studies we have shown that on profoundly different systems coagulation is the result of a strong interaction between two processes on different length scales (mesoscopic and microscopic). Here we report experiments on bovine serum albumin (BSA) showing that the overall mechanism is the result of at least 3 distinct and strongly intertwined processes, on both length scales: molecular conformational changes, solution demixing and intermolecular crossli…
Magneto-structural correlations in Ni(ii) [2 × 2] metallogrids featuring a variable number of μ-aquo or μ-hydroxo extra bridges
2019
Four new [2 × 2] grid-type metallosupramolecular species have been obtained by using the ditopic 3,6-bis(2′-pyridyl)pyridazine ligand (dppn) and nickel(II) salts containing poorly coordinating anions. Three of them have the formula [Ni4(μ-dppn)4(μ-OH)2(μ-H2O)2]X6·nH2O [with X = ClO4− (1), NO3− (2) and CF3SO3− (3), and n = 6.5 (1), 14 (2) and 4 (3)]. Their crystal structure shows the same tetranuclear core, constituted by four six-coordinate metal ions and four dppn molecules. Two hydroxo groups and two water molecules efficiently interact forming two hydrated hydroxide (H3O2−) supramolecular bridging anions, further stabilizing the grid. The other compound, [Ni4(μ-dppn)4(μ-OH)3(μ-H2O)](ClO4…
Ten Facets, One Force Field: The GAL19 Force Field for Water - Noble Metal Interfaces
2020
<div>Understanding the structure of the water/metal interfaces plays an important role in many are as ranging from surface chemistry to environmental processes. Due to their intrinsic complexity, the water/metal interfaces cannot yet be adequately described by quantum mechanical approaches and accurate force-fields are therefore needed. We develop and parametrize GAL19, a novel force-field to describe the interaction of water with two facets (111 and 100) of five metals (Pt, Pd, Au, Ag, Cu). To increase transferability compared to its predecessor GAL17, the water-metal interaction is described as a sum of pair-wise terms. The interaction energy has three contributions: (i) physisorption …
First Diastereoselective Synthesis of (−)-Methyl Thyrsiflorin A, (−)-Methyl Thyrsiflorin B Acetate, and (−)-Thyrsiflorin C
2000
An efficient procedure for the synthesis of scopadulan diterpenes, using (+)-podocarp-8(14)-en-13-one 13 as starting material, is reported. This procedure has been used for the diastereoselective synthesis of (-)-methyl thyrsiflorin A (8), (-)-methyl thyrsiflorin B acetate (9), and (-)-thyrsiflorin C (7). Key steps in our strategy are the intramolecular cyclopropanation of diazoketone 19 and the regioselective cleavage of the cyclopropane ring.
Investigation of a tunnel pasteurizer for “Nocellara del Belice” table olives processed according to the “Castelvetrano method”
2014
The influence of pasteurization temperature and time of treatment on the flesh firmness and the evolution of microbial communities was studied for table olives Cv. Nocellara del Belice, packed in glass jars and processed with a tunnel pasteurizer. The experiment was first carried out on the laboratory level in order to select the optimal combination of pasteurization time/temperature so as to obtain the proper balance between the consistency of the pulp and the microbiological quality of the final product. Pasteurization at industrial scale was then carried out in a tunnel pasteurizer applying the treatment at 75 °C for 8 min in the thermal center of the jars. Besides flesh firmness and mic…
El uso de la fuerza contra el Estado Islámico en Irak y Siria: problemas de fundamentación jurídica
2017
Current military campaign against the Islamic State in Iraq and Syria raises the question of the admissibility of the right to use force in self-defence against attacks by non-State actors in other States. International law in this area remains controversial and State practice ambiguous and inconsistent. This article analyses the legal basis invoked by States to justify their military operations against ISIL. Consent provided by the Iraqi government is lacking in the case of Syria, leaving only self-defence as feasible legal basis. The broad support for the use of force against Islamic State sides with conflicting views regarding the need of territorial State consent to the use of force on …