51 research outputs found
Acoustic analysis of passive metamaterial panels using the finite element method and homogenized properties
No full textHomogenization and free-vibration analysis of elastic metamaterial plates by Carrera Unified Formulation finite elements
No full textThis work focuses on the assessment of a novel so-called “homogenization method” allowing to transform a heterogeneous material with inclusions or holes into an equivalent homogeneous material with equal mechanical behavior. The aim is to avoid meshing holes of the real material in finite-element codes, thus improving computation time for further analysis of the material. Typical periodic structure of passive acoustic metamaterial plates is considered here, with inclusions/holes that should improve the acoustic performances in the low-frequency range. The three-dimensional homogenization method, based on Carrera unified formulation (CUF) [E. Carrera, M. Cinefra, M. Petrolo, and E. Zappino. Finite Element Analysis of Structures through Unified Formulation. John Wiley & Sons, 2014] and Mechanics of Structure Genome, is assessed for a perforated plate made of a linear elastic material with periodic arrangement of holes. Different configurations of the metamaterial plate are considered, changing the number of the holes. The results obtained from the free-vibration analysis of the homogenized plates, performed by higher-order two-dimensional models contained in CUF, are compared with ABAQUS results and both numerical and experimental results provided in literature
Souvenir de vacances
No full textWe describe a case of a 67-year old woman who develops
three painful subcutaneous nodules with surrounding
erythema and a central hemorrhagic crust
localized on the left wrist and the upper back after having
spent her holidays in Mexico. Soon after the first
visit at our clinic she was able to extract a larva, allowing
to diagnose a cutaneous myiasis from furuncular
subtype.
There is a worldwide distribution of myiasis, but with
more species and abundance in lower socioeconomic
regions of tropical and subtropical regions. With
a higher number of returning travelers from these regions
we are more often confronted with tropical infections
or parasites implicating knowledge about
differential diagnosis, diagnostic and therapeutic
approaches
Hypereosinophilic Syndromes
No full textIn den vergangenen Jahren wurden zahlreiche neue Erkenntnisse zur Biologie eosinophiler Granulozyten, ihrer Rolle für die Gesundheit und bei Krankheiten gewonnen. Differenzierte Kenntnisse zur Pathogenese, neue diagnostische Methoden und Therapeutika haben das Verständnis zur Hypereosinophilie und damit assoziierten Erkrankungen und Syndromen fundamental geändert. In dieser Übersichtsarbeit diskutieren wir die gegenwärtige Klassifikation der Hypereosinophiliesyndrome und neue Therapieansätze.In recent years, the knowledge on eosinophil biology as well as their role in health and disease has dramatically increased. Differential insights in the pathogenesis, new diagnostic techniques and therapeutic substances have modified our understanding of hypereosinophilia and associated diseases and syndromes. In this review, we discuss the current classification of hypereosinophilic syndromes as well as therapeutic strategies
Additive Manufacturing of Liquid Crystal Polymers: Interlayer features: formation and impact on interlaminar shear strength
No full textRecent findings have highlighted the potential of a 3D-printable high-strength Liquid Crystal Polymer, whose anisotropy can be fostered for topology optimization intents. The mesostructure of a 3D-printed liquid crystal polymer is studied: the observation of interlayer features under the form of regular notches or spiraling patterns swirls is reported on optical microscopy of cross-sections. A formation mechanism is proposed: interlayer features may be formed as a result of an offset in placement of material. Another question is raised by the observation of these crenelated shapes: by providing mechanical interlocking between layers, they are expected to enhance interlaminar shear strength of a part. Short-beam shear tests indicate that when interlayer features are tall with respect to the layer height, and oriented perpendicular to the shear loading direction, the interlaminar shear strength of the 3D-printed part is enhanced by up to 112%. Microscopic evidence further indicates the crack-arrest ability of these features.Aerospace Engineerin
Interlaminar toughening approaches for additively manufactured liquid crystal polymers
No full textLiquid crystalline polymers have recently attracted attention for their great tensile properties. However, their interlaminar fracture toughness is low. To solve this, toughening approaches inspired by Nature are applied, exploiting the shaping freedom of fused deposition modelling. Three approaches are studied: the matchstick approach, z-pinning and sawtooth layers. Their effectiveness in increasing the Mode I interlaminar toughness of the material is evaluated through compact tension tests.These tests reveal that z-pinning fails to increase toughness, while the matchstick approach and especially the sawtooth layers have a beneficial effect. The matchstick approach increases the interlaminar toughness of Vectra A950 by strengthening fiber bridging, a toughening phenomenon natural to the material. The sawtooth layers stall crack growth through geometry, but also trigger fiber bridging more reliably and postpone fibre tearing. This synergy quadruples the toughness. These two methods prove that bio-inspired structures are an excellent way to provide toughness in additive manufacturing.Aerospace Engineerin
Interlaboratory comparison of untargeted mass spectrometry data uncovers underlying causes for variability
No full textDespite the value of mass spectrometry in modern natural products discovery workflows, it remains very difficult to compare data sets between laboratories. In this study we compared mass spectrometry data for the same sample set from two different laboratories (quadrupole time-of-flight and quadrupole-Orbitrap) and evaluated the similarity between these two data sets in terms of both mass spectrometry features and their ability to describe the chemical composition of the sample set. Somewhat surprisingly, the two data sets, collected with appropriate controls and replication, had very low feature overlap (25.7% of Laboratory A features overlapping 21.8% of Laboratory B features). Our data clearly demonstrate that differences in fragmentation, charge state, and adduct formation in the ionization source are a major underlying cause for these differences. Consistent with other recent literature, these findings challenge the conventional wisdom that electrospray ionization mass spectrometry (ESI-MS) yields a simple one-to-one correspondence between analytes in solution and features in the data set. Importantly, despite low overlap in feature lists, principal component analysis (PCA) generated qualitatively similar PCA plots. Overall, our findings demonstrate that comparing untargeted metabolomics data between laboratories is challenging, but that data sets with low feature overlap can yield the same qualitative description of a sample set using PCA
Emission of toxic sulfur gases from polymers coming in contact with food products and with infants
No full textThe analysis of the volatiles evolved from a number of polymer samples commonly used in domestic applications show that carbon disulfide, CS, and carbonyl sulfide, COS, are emitted in the
lower range of temperatures, from room temperature up to 150 °C. Emission of COS in the ppm range was also monitored from materials used in the fabrication of the teats for baby's feeding
bottles and from similar devices. Given the lack of legal tolerance limits on the toxicity of COS, it is urgent that such norms be set for this compound
Arithmetic Bounds-Lenstra's Constant and Torsion of K-Groups
No full textThis thesis is concerned with computations of bounds for two different arithmetic invariants. In both cases it is done with the intention of proving some algebraic or arithmetic properties for number fields. The first part is devoted to computations of lower bounds for the Lenstra's constant. For a number field K the Lenstra's constant is denoted Λ(K) and defined as the length of the largest exceptional sequence in K. An exceptional sequence is a set of units in K such that for any two among them their difference is a unit as well. H.W. Lenstra showed that if Λ(K) is large enough – bigger than a constant depending on the degree and the discriminant of K – then the ring of integers of K is Euclidean with respect to the norm. Using computer software PARI/GP and some algorithms from graph theory we construct exceptional sequences in number fields having a small discriminant. These exceptional sequences yield lower bounds for Lenstra's constant which are large enough to prove the existence of 42 new Euclidean number fields of degree 8 to 12. The aim of the second part of this thesis is proving upper bounds for the torsion part of the K-groups of a number field ring of integers. A method due to C. Soulé yields bounds for the torsion of these K-groups depending on an invariant of hermitian lattices over number fields. Firstly we describe some properties of rank one hermitian lattices, especially of ideal lattices. Secondly we apply these properties to arbitrary rank hermitian lattices and this implies a significant improvement of the upper bounds for their invariants and accordingly for the torsion of K-groups. The progress mainly achieves much lower contributions of the number field attributes, particularly the degree and the absolute discriminant.CSA
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