Search results for " secondary"
showing 10 items of 692 documents
An experiment on wind energy
2012
We discuss an experiment on wind energy performed with home-made apparatus. The experiment reproduces a laboratory windmill, which can pump water from a lower level to a higher one. By measuring the gain of the gravitational potential energy of the pumped water, one can determine the power extracted from the wind. The activity was carried out with high-school students, in the framework of the Italian National Plan for Scientific Degrees-Physics. The proposed experiment allows teachers to discuss renewable energy sources with students whose knowledge of physics is limited to mechanics. It gives students the possibility to gain experience with energy and to increase their awareness of this re…
Role of secondary circulation on bank erosion in a large amplitude meandering laboratory channel
2009
This paper reports peculiar results of experimental investigation on the evolution of flow secondary circulation motion along a meander wave. The experiments have been conducted in a large amplitude meandering laboratory channel for two values of the width-to-depth ratio. Attention is focalised on how secondary motion affects the bank shear stress distribution, influencing the bank stability. The analysis essentially highlights that, especially for small width-to-depth ratio, as the channel curvature increases besides the classical central-region secondary circulation cell a counter-rotating circulation cell forms in the outer-bank region. Such counterrotating circulation cell allows to obt…
The ethnobotany, phytochemistry and biological properties of genus Ferulago – A review
2020
Abstract Ethnopharmacological relevance The genus Ferulago, belonging to the Apiaceae family, is found mainly in the Mediterranean area, Southwest and Middle Asia, the Caucasus and North Africa. Since ancient times, species of this genus have been largely employed in traditional medicine for their biological properties such as antimicrobial, anti-inflammatory, antispasmodic, insecticidal, and anti-malaria, cholinesterase inhibition effects, etc. Aims The scope of this paper is to present a comprehensive respect review of this interesting genus including traditional uses, chemical composition of volatile and non-volatile metabolites, and in vitro and in vivo biological properties either util…
Influence of Content Knowledge on Pedagogical Content Knowledge: The case of teaching photosynthesis and plant growth
2009
International audience; Abstract The aim of the research was to investigate the effect of the amount and quality of content knowledge on pedagogical content knowledge (PCK). The biological content photosynthesis and plant growth was used as an example. The research sample consisted of 10 primary and 10 secondary (biology) teacher students. Questionnaires, lesson preparation task and an interview were used to collect data. Primary student teachers' were not aware of students' conceptual difficulties and had problems in choosing the most important content. Neither of the groups had knowledge on suitable experiments and demonstrations, which indicates that PCK should be explicitly taught. The …
Polypept(o)ides: Hybrid Systems Based on Polypeptides and Polypeptoids.
2015
Polypept(o)ides combine the multifunctionality and intrinsic stimuli-responsiveness of synthetic polypeptides with the "stealth"-like properties of the polypeptoid polysarcosine (poly(N-methyl glycine)). This class of block copolymers can be synthesized by sequential ring opening polymerization of α-amino acid N-carboxy-anhydrides (NCAs) and correspondingly of the N-substituted glycine N-carboxyanhydride (NNCA). The resulting block copolymers are characterized by Poisson-like molecular weight distributions, full end group integrity, and dispersities below 1.2. While polysarcosine may be able to tackle the currently arising issues regarding the gold standard PEG, including storage diseases i…
Size-dependent knockdown potential of siRNA-loaded cationic nanohydrogel particles.
2014
To overcome the poor pharmacokinetic conditions of short double-stranded RNA molecules in RNA interference therapies, cationic nanohydrogel particles can be considered as alternative safe and stable carriers for oligonucleotide delivery. For understanding key parameters during this process, two different types of well-defined cationic nanohydrogel particles were synthesized, which provided nearly identical physicochemical properties with regards to their material composition and resulting siRNA loading characteristics. Yet, according to the manufacturing process using amphiphilic reactive ester block copolymers of pentafluorophenyl methacrylate (PFPMA) and tri(ethylene glycol)methyl ether m…
Secondary Structure-Driven Self-Assembly of Thiol-Reactive Polypept(o)ides
2021
Secondary structure formation differentiates polypeptides from most of the other synthetic polymers, and the transitions from random coils to rod-like α-helices or β-sheets represent an additional parameter to direct self-assembly and the morphology of nanostructures. We investigated the influence of distinct secondary structures on the self-assembly of reactive amphiphilic polypept(o)ides. The individual morphologies can be preserved by core cross-linking via chemoselective disulfide bond formation. A series of thiol-responsive copolymers of racemic polysarcosine-block-poly(S-ethylsulfonyl-dl-cysteine) (pSar-b-p(dl)Cys), enantiopure polysarcosine-block-poly(S-ethylsulfonyl-l-cysteine) (pSa…
Secondary Structure-Driven Hydrogelation Using Foldable Telechelic Polymer-Peptide Conjugates.
2018
The synthesis of ABA and ABA' triblock polyethylene glycol-and polysarcosine-peptide conjugates is reported. The A/A' peptides are based on phenylalanine(F)-histidine(H) pentapeptide sequences FHFHF, which promote pH-switchable β-sheet self-assembly into nanorods in water. Only parallel β-sheet-driven folding and intermolecular assembly using ABA triblock polymer-peptide conjugates leads to interstrand cross-linking and hydrogelation, highlighting the impact of supramolecular interactions-directed structure formation at the nano- and mesoscopic level.
Learning from nature: beta-sheet-mimicking copolymers get organized.
2007
The solution structures formed by coil-coil copolymers arise from the selective solvation of one of the two blocks and have been well described. In most cases in such relatively simple synthetic structures there are no specific attractive forces that can aid the aggregation process. Nature, however, provides plenty of inspiring polymeric architectures that are shaped and ordered hierarchically by noncovalent forces. The high level of structural definition displayed by proteins, for example, is unmatched by synthetic polymers. An emerging area of interest in polymer science tries to combine the best of both worlds, the natural and the synthetic, by conjugating synthetic polymers and beta-she…
Infinite orbit depth and length of Melnikov functions
2019
Abstract In this paper we study polynomial Hamiltonian systems d F = 0 in the plane and their small perturbations: d F + ϵ ω = 0 . The first nonzero Melnikov function M μ = M μ ( F , γ , ω ) of the Poincare map along a loop γ of d F = 0 is given by an iterated integral [3] . In [7] , we bounded the length of the iterated integral M μ by a geometric number k = k ( F , γ ) which we call orbit depth. We conjectured that the bound is optimal. Here, we give a simple example of a Hamiltonian system F and its orbit γ having infinite orbit depth. If our conjecture is true, for this example there should exist deformations d F + ϵ ω with arbitrary high length first nonzero Melnikov function M μ along…