Nonlinear modal testing performed by pulsed-air jet excitation system

This paper presents a novel approach for testing structural component to nonlinear vibrations. Nowadays, nonlinear testing is mainly carried out by using electromagnetic shakers. These are efficient and powerful excitation systems which transmit the force by a rigid stinger and can be driven by different excitation signals. The rigid connection contributes to create mechanical impedance mismatch between the shaker and the test structure thus reducing the efficiency of the driving force. An alternative solution to shakers is represented by use of a pulsed air jet excitation method, which drives the force by a pulsed air-jets and therefore contactless. This condition eliminates the mechanical impedance mismatch with the test structure and the excitation can be more efficient than the one created by shakers. The pulsed air-jet excitation system is used to study nonlinear vibrations of composites components. These were designed to be mock-ups of fan blades the layup of which was varied for the three types of components used in this work. Tests were carried out by performing forced response and free decay measurements. The free decay type of test revealed interesting results and the novelty of using such an exciter for nonlinear testing. The major novelty consists of interrupting the air flow from a steady state condition and let happen the free decay, all these without experiencing undesired dynamics as experienced by contact excitatio

Human Pluripotent Stem Cell Differentiation into Authentic Striatal Projection Neurons

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Genome-wide definition of promoter and enhancer usage during neural induction of human embryonic stem cells

Genome-wide mapping of transcriptional regulatory elements is an essential tool for understanding the molecular events orchestrating self-renewal, commitment and differentiation of stem cells. We combined high-throughput identification of transcription start sites with genome-wide profiling of histones modifications to map active promoters and enhancers in embryonic stem cells (ESCs) induced to neuroepithelial-like stem cells (NESCs). Our analysis showed that most promoters are active in both cell types while approximately half of the enhancers are cell-specific and account for most of the epigenetic changes occurring during neural induction, and most likely for the modulation of the promoters to generate cell-specific gene expression programs. Interestingly, the majority of the promoters activated or up-regulated during neural induction have a "bivalent" histone modification signature in ESCs, suggesting that developmentally-regulated promoters are already poised for transcription in ESCs, which are apparently pre-committed to neuroectodermal differentiation. Overall, our study provides a collection of differentially used enhancers, promoters, transcription starts sites, protein-coding and non-coding RNAs in human ESCs and ESC-derived NESCs, and a broad, genome-wide description of promoter and enhancer usage and of gene expression programs characterizing the transition from a pluripotent to a neural-restricted cell fate

Robust induction of DARPP32-expressing GABAergic striatal neurons from human pluripotent stem cells

Efficient generation of disease relevant neuronal subtypes from human pluripotent stem cells (PSCs) is fundamental for realizing their promise in disease modeling, pharmaceutical drug screening and cell therapy. Here we describe a step-by-step protocol for directing the differentiation of human embryonic and induced PSCs (hESCs and hiPSCs, respectively) toward medium spiny neurons, the type of cells that are preferentially lost in Huntington’s disease patients. This method is based on a novel concept of Activin A-dependent induction of the lateral ganglionic/striatal fate using a simple monolayer culture paradigm under chemically defined conditions. Transplantable medium spiny neuron progenitors amenable for cryopreservation are produced in less than 20 days, which differentiate and mature into a high yield of dopamine- and cAMP-regulated phosphoprotein, Mr 32 kDa (DARPP32) expressing gamma-aminobutyric acid (GABA)-ergic neurons in vitro and in the adult rat brain after transplantation. This method has been validated in multiple hESC and hiPSC lines, and is independent of the regime for PSC maintenance

a case study on the selection of promising functional starter strains from grape yeasts a report by student of food science and technology degree university of foggia southern italy

The main aim of this research, performed by some students in Food Science and Technology of Foggia University, is to show how perform the selection of a functional starter through a step-by-step procedure. Fifteen yeast strains were studied in order to assess their biotechnological traits, e.g. catalase, urease, B-glucosidase, pectolytic and xylanolytic activities, production of H2S, resistance to copper, SO2 and acetic acid, growth at different temperatures, alkaline pH, in presence of different amounts of ethanol and glucose, and some probiotic properties. After studying these abilities, yeasts were identified through the miniaturized system API 20 C AUX and two kinds of multivariate analyses (Cluster Analysis and Principal Component Analysis) were performed to highlight the best strains.</p

Model updating strategy for structures with localised nonlinearities using frequency response measurements

This paper proposes a model updating strategy for localised nonlinear structures. It utilises an initial finite-element (FE) model of the structure and primary harmonic response data taken from low and high amplitude excitations. The underlying linear part of the FE model is first updated using low-amplitude test data with established techniques. Then, using this linear FE model, the nonlinear elements are localised, characterised, and quantified with primary harmonic response data measured under stepped-sine or swept-sine excitations. Finally, the resulting model is validated by comparing the analytical predictions with both the measured responses used in the updating and with additional test data. The proposed strategy is applied to a clamped beam with a nonlinear mechanism and good agreements between the analytical predictions and measured responses are achieved. Discussions on issues of damping estimation and dealing with data from amplitude-varying force input in the updating process are also provided

RD-Connect, NeurOmics and EURenOmics: collaborative European initiative for rare diseases

Functional Genomics of Muscle, Nerve and Brain Disorder