Theoretical analysis of multimodal four-wave mixing in optical microwires

Optical fiber microwires (OFMs) are nonlinear optical waveguides that support several spatial modes. The multimodal generalized nonlinear Schrodinger equation (MM-GNLSE) is deduced taking into account the linear and nonlinear modal coupling. A detailed theoretical description of four-wave mixing (FWM) considering the modal coupling is developed. Both, the intramode and the intermode phase-matching conditions is calculated for an optical microwire in a strong guiding regime. Finally, the FWM dynamics is studied and the amplitude evolution of the pump beams, the signal and the idler are analyzed

Towards real-time simulation of deformable structures by means of co-rotational finite element formulation

Whereas typical Finite Element (FE) computations are performed off-line, many virtual-reality (VR) applications put a demand for interactive simulations involving deformable objects. Interactive simulation implies real-time or nearly real-time computation and graphical representation of modeled deformable objects. The growing computational power of modern conventional hardware calls for FEM developments in this direction. Depending on specific VR applications, the developments need to account for different aspects of physical behavior, with geometrically nonlinear deformations emerging as one of most important and frequent. This paper proposes a simplified co-rotational FE formulation that considers the overall finite element motion as a superposition of rigid-body rotation and deformation described by a linear model with respect to the co-rotated reference frame. By neglecting the stress stiffening effect and the dependence of the element stiffness matrix on the deformational displacements, the formulation aims at meeting the objectives of highly efficient simulation, under certain conditions even real-time simulation, and with acceptable deviation in accuracy compared to the rigorous nonlinear FE formulation. Computations with both solid and shell elements are addressed. A set of examples is provided to illustrate and discuss the aspects of accuracy and achievable simulation speed

ABAQUS IMPLEMENTATION OF A COROTATIONAL PIEZOELECTRIC 3-NODE SHELL ELEMENT WITH DRILLING DEGREE OF FREEDOM

Integration of classical, passive structures and active elements based on multi-functional materials resulted in a novel structural concept denoted as active structures. The new structural systems are characterized by self-sensing and actuation. Coupling the two distinctive features by means of a controller enables a number of exquisite functionalities such as vibration suppression, noise attenuation, shape control, structural health monitoring, etc. Reliable, accurate and highly efficient modeling tools are an important ingredient of the active structure design. This paper addresses the Abaqus implementation of a recently developed piezoelectric 3-node shell element. The element uses co-rotational formulation to cover geometric nonlinearities. Special techniques are used to address the issues originating from low-order interpolation functions. The discrete shear gap is used to resolve the shear locking, while the assumed natural deviatoric strain technique improves the membrane behavior. Examples are computed in Abaqus upon implementation of the developed element

Efficient three-node finite shell element for linear and geometrically nonlinear analyses of piezoelectric laminated structures

Fiber-reinforced composite laminates involving piezoelectric layers represent a very attractive material system. It combines the advantages of using rather lightweight and stiff material with the possibility of sensing structural changes and actively influencing its state by means of sensors and actuators. A three-node shell element is proposed as an efficient tool for modeling structures made of such a material system. Thoroughly tested solutions are implemented to resolve locking problems intrinsic for shell elements. The embedded piezoelectric layers are considered to be polarized in the thickness direction. Furthermore, the extension of the formulation to geometrically nonlinear finite element analysis is based on a co-rotational formulation. Numerical examples are given to demonstrate the applicability of developed element in linear and geometrically nonlinear finite element analyses covering both actuator and sensor cases

High performance 3-node shell element for linear and geometrically nonlinear analysis of composite laminates

Thin-walled structures hold primacy among modern engineering structures. All the advantages offered by the curved geometry and thinness of the walls come even more to the fore when combined with exquisite properties of fiber-reinforced composite laminates. Directionally dependant material properties open vast possibilities for tailoring global structural properties and, therewith, optimization. Successful design of such structures calls for high performance shell type finite elements. This paper presents a linear triangular shell element based on the equivalent single-layer approach and the first-order shear deformation theory. The shear locking effect is resolved by the descrete shear gap (DSG) approach combined with the cell smoothing technique. To improve the element performance with respect to the membrane behavior, the assumed natural deviatoric strains (ANDES) formulation is applied, with necessary modifications to meet the requirements of curved structures with anisotropic material properties. Geometric nonlinearities are addressed by the co-rotational formulation. Examples demonstrate the element applicability and performance

Newborn Urinary Metabolic Signatures of Prematurity and Other Disorders: A Case Control Study

This work assesses the urinary metabolite signature of prematurity in newborns by nuclear magnetic resonance (NMR) spectroscopy, while establishing the role of possible confounders and signature specificity, through comparison to other disorders. Gender and delivery mode are shown to impact importantly on newborn urine composition, their analysis pointing out at specific metabolite variations requiring consideration in unmatched subject groups. Premature newborns are, however, characterized by a stronger signature of varying metabolites, suggestive of disturbances in nucleotide metabolism, lung surfactants biosynthesis and renal function, along with enhancement of tricarboxylic acid (TCA) cycle activity, fatty acids oxidation, and oxidative stress. Comparison with other abnormal conditions (respiratory depression episode, large for gestational age, malformations, jaundice and premature rupture of membranes) reveals that such signature seems to be largely specific of preterm newborns, showing that NMR metabolomics can retrieve particular disorder effects, as well as general stress effects. These results provide valuable novel information on the metabolic impact of prematurity, contributing to the better understanding of its effects on the newborn's state of health.info:eu-repo/semantics/publishedVersio

Newborn Urinary Metabolic Signatures of Prematurity and Other Disorders: A Case Control Study

This work assesses the urinary metabolite signature of prematurity in newborns by nuclear magnetic resonance (NMR) spectroscopy, while establishing the role of possible confounders and signature specificity, through comparison to other disorders. Gender and delivery mode are shown to impact importantly on newborn urine composition, their analysis pointing out at specific metabolite variations requiring consideration in unmatched subject groups. Premature newborns are, however, characterized by a stronger signature of varying metabolites, suggestive of disturbances in nucleotide metabolism, lung surfactants biosynthesis and renal function, along with enhancement of tricarboxylic acid (TCA) cycle activity, fatty acids oxidation, and oxidative stress. Comparison with other abnormal conditions (respiratory depression episode, large for gestational age, malformations, jaundice and premature rupture of membranes) reveals that such signature seems to be largely specific of preterm newborns, showing that NMR metabolomics can retrieve particular disorder effects, as well as general stress effects. These results provide valuable novel information on the metabolic impact of prematurity, contributing to the better understanding of its effects on the newborn's state of health.info:eu-repo/semantics/publishedVersio

HIV- 1 lentivirus tethering to the genome is associated with transcription factor binding sites found in genes that favour virus survival

Lentiviral vectors (LV) are attractive for permanent and effective gene therapy. However, integration into the host genome can cause insertional mutagenesis highlighting the importance of understanding of LV integration. Insertion site (IS) tethering is believed to involve cellular proteins such as PSIP1/LEDGF/p75, which binds to the virus pre-integration complexes (PICs) helping to target the virus genome. Transcription factors (TF) that bind both the vector LTR and host genome are also suspected influential to this. To determine the role of TF in the tethering process, we mapped predicted transcription factor binding sites (pTFBS) near to IS chosen by HIV-1 LV using a narrow 20 bp window in infected human induced pluripotent stem cells (iPSCs) and their hepatocyte-like cell (HLC) derivatives. We then aligned the pTFBS with these sequences found in the LTRs of native and self-inactivated LTRs. We found significant enrichment of these sequences for pTFBS essential to HIV-1 life cycle and virus survival. These same sites also appear in HIV-1 patient IS and in mice infected with HIV-1 based LV. This in silco data analysis suggests pTFBS present in the virus LTR and IS sites selected by HIV-1 LV are important to virus survival and propagation