On the Hilbert 22-class field tower of some abelian 22-extensions over the field of rational numbers

summary:It is well known by results of Golod and Shafarevich that the Hilbert $2$-class field tower of any real quadratic number field, in which the discriminant is not a sum of two squares and divisible by eight primes, is infinite. The aim of this article is to extend this result to any real abelian $2$-extension over the field of rational numbers. So using genus theory, units of biquadratic number fields and norm residue symbol, we prove that for every real abelian $2$-extension over $\mathbb Q$ in which eight primes ramify and one of theses primes $\equiv -1\pmod 4$, the Hilbert $2$-class field tower is infinite

Case Study of Bacterial Decontamination of an Aromatic and Medicinal Plant: Decontamination of Thymus Satureioides by Gamma Radiation at Low Doses and Impact on Hygienic and Physicochemical Quality

The purpose of our study is to verify the usefulness of gamma irradiation treatment at low doses (0.25, 0.5 and 1 kGy) combined to vacuum packaging on commercial teas of Thymus satureioides deliberately contaminated with Escherichia coli. The efficiency and the influence of the process on contamination level and the shelf life of the product were studied. The phenolic composition and concentration were identified in the unirradiated and irradiated thyme. The total phenolic content (TPC) was assayed by the Folin-Ciocalteu method, the individual phenolic compounds were determined by high liquid chromatography (HPLC) and the essential oil was characterized by gas chromatography coupled to mass spectroscopy (GC-MS). The plant was observed by scanning electrons microscopy and the radioactivity effect was analyzed. The results show a complete decontamination of thyme depending to the dose and the storage time. Privileged hygienic quality was found in the irradiated thyme with the highest concentrations of polyphenols. The process showed the conservation of thyme quality without any alteration of its characteristics or radioactivity effect

Introduction to Protein Folding

While many good textbooks are available on Protein Structure, Molecular Simulations, Thermodynamics and Bioinformatics methods in general, there is no good introductory level book for the field of Structural Bioinformatics. This book aims to give an introduction into Structural Bioinformatics, which is where the previous topics meet to explore three dimensional protein structures through computational analysis. We provide an overview of existing computational techniques, to validate, simulate, predict and analyse protein structures. More importantly, it will aim to provide practical knowledge about how and when to use such techniques. We will consider proteins from three major vantage points: Protein structure quantification, Protein structure prediction, and Protein simulation & dynamics. In this chapter we explore basic physical and chemical concepts required to understand protein folding. We introduce major (de)stabilising factors of folded protein structures such as the hydrophobic effect and backbone entropy. In addition, we consider different states along the folding pathway, as well as natively disordered proteins and aggregated protein states. In this chapter, an intuitive understanding is provided about the protein folding process, to prepare for the next chapter on the thermodynamics of protein folding. In particular, it is emphasized that protein folding is a stochastic process and that proteins unfold and refold in a dynamic equilibrium. The effect of temperature on the stability of the folded and unfolded states is also explained.Comment: editorial responsability: Juami H. M. van Gils, K. Anton Feenstra, Sanne Abeln. This chapter is part of the book "Introduction to Protein Structural Bioinformatics". The Preface arXiv:1801.09442 contains links to all the (published) chapters. The update adds available arxiv hyperlinks for the chapter

Introduction to Protein Folding

While many good textbooks are available on Protein Structure, Molecular Simulations, Thermodynamics and Bioinformatics methods in general, there is no good introductory level book for the field of Structural Bioinformatics. This book aims to give an introduction into Structural Bioinformatics, which is where the previous topics meet to explore three dimensional protein structures through computational analysis. We provide an overview of existing computational techniques, to validate, simulate, predict and analyse protein structures. More importantly, it will aim to provide practical knowledge about how and when to use such techniques. We will consider proteins from three major vantage points: Protein structure quantification, Protein structure prediction, and Protein simulation & dynamics. In this chapter we explore basic physical and chemical concepts required to understand protein folding. We introduce major (de)stabilising factors of folded protein structures such as the hydrophobic effect and backbone entropy. In addition, we consider different states along the folding pathway, as well as natively disordered proteins and aggregated protein states. In this chapter, an intuitive understanding is provided about the protein folding process, to prepare for the next chapter on the thermodynamics of protein folding. In particular, it is emphasized that protein folding is a stochastic process and that proteins unfold and refold in a dynamic equilibrium. The effect of temperature on the stability of the folded and unfolded states is also explained

Molecular Dynamics

While many good textbooks are available on Protein Structure, Molecular Simulations, Thermodynamics and Bioinformatics methods in general, there is no good introductory level book for the field of Structural Bioinformatics. This book aims to give an introduction into Structural Bioinformatics, which is where the previous topics meet to explore three dimensional protein structures through computational analysis. We provide an overview of existing computational techniques, to validate, simulate, predict and analyse protein structures. More importantly, it will aim to provide practical knowledge about how and when to use such techniques. We will consider proteins from three major vantage points: Protein structure quantification, Protein structure prediction, and Protein simulation & dynamics. We know that many proteins have functional motions, and in Chapter "Structure Determination" we already introduced the famous example of the allosteric cooperative binding of oxygen to the haem group in hemoglobin. However, experimentally, such motions are hard to observe. Here, we will introduce MD simulations to investigate the dynamic behaviour of proteins. In a simulation the forces and interactions between particles are used to numerically derive the resulting three-dimensional movement of these particles over a certain time-scale. We will also highlight some applications, and will see how simulation results may be interpreted.Comment: editorial responsability: Halima Mouhib, Sanne Abeln, K. Anton Feenstra. This chapter is part of the book "Introduction to Protein Structural Bioinformatics". The Preface arXiv:1801.09442 contains links to all the (published) chapters. The update adds available arxiv hyperlinks for the chapter

Molecular Dynamics

While many good textbooks are available on Protein Structure, Molecular Simulations, Thermodynamics and Bioinformatics methods in general, there is no good introductory level book for the field of Structural Bioinformatics. This book aims to give an introduction into Structural Bioinformatics, which is where the previous topics meet to explore three dimensional protein structures through computational analysis. We provide an overview of existing computational techniques, to validate, simulate, predict and analyse protein structures. More importantly, it will aim to provide practical knowledge about how and when to use such techniques. We will consider proteins from three major vantage points: Protein structure quantification, Protein structure prediction, and Protein simulation & dynamics. We know that many proteins have functional motions, and in Chapter "Structure Determination" we already introduced the famous example of the allosteric cooperative binding of oxygen to the haem group in hemoglobin. However, experimentally, such motions are hard to observe. Here, we will introduce MD simulations to investigate the dynamic behaviour of proteins. In a simulation the forces and interactions between particles are used to numerically derive the resulting three-dimensional movement of these particles over a certain time-scale. We will also highlight some applications, and will see how simulation results may be interpreted

Existence of biquadratic fields KK for which the Galois group of the second Hilbert 2-class field with respect to KK is semidihedral

summary:Let $K$ be a biquadratic field, $K_2^{(1)}$ be the Hilbert $2$-class field of $K$ and $K_2^{(2)}$ be the Hilbert $2$-class field of $K_2^{(1)}$. Our goal is to prove that there exists a biquadratic field $K$ such that $\operatorname{Gal\,}(K_2^{(1)}/K)\simeq \mathbb Z/2\mathbb Z\times \mathbb Z/2\mathbb Z$ and the group $\operatorname{Gal\,}(K_2^{(2)}/K)$ is semi-dihedral. Résumé. Soient $K$ un corps biquadratique, $K_2^{(1)}$ le $2$-corps de classes de Hilbert de $K$ et $K_2^{(2)}$ le $2$-corps de classes de Hilbert de $K_2^{(1)}$. Notre but est de prouver qu’il existe des corps biquadratiques réels $K$ tels que le groupe $\operatorname{Gal\,}(K_2^{(1)}/K)$ est de type $(2,2)$ et le groupe $\operatorname{Gal\,}(K_2^{(2)}/K)$ est semi-diédral

On the p-class tower OF a Z_p-extension

International audienc

Sur le 2-groupe de classes des corps multiquadratiques réels

International audienc