44 research outputs found
Carbon nanotube sensor for vibrating molecules
The transport properties of a CNT capacitively coupled to a molecule
vibrating along one of its librational modes are studied and its transport
properties analyzed in the presence of an STM tip. We evaluate the linear
charge and thermal conductances of the system and its thermopower. They are
dominated by position-dependent Franck-Condon factors, governed by a
position-dependent effective coupling constant peaked at the molecule position.
Both conductance and thermopower allow to extract some information on the
position of the molecule along the CNT. Crucially, however, thermopower sheds
also light on the vibrational levelspacing, allowing to obtain a more complete
characterization of the molecule even in the linear regime
Quantum dissipative effects in graphene-like mirrors
We study quantum dissipative effects due to the accelerated motion of a
single, imperfect, zero-width mirror. It is assumed that the microscopic
degrees of freedom on the mirror are confined to it, like in plasma or graphene
sheets. Therefore, the mirror is described by a vacuum polarization tensor
concentrated on a time-dependent surface. Under certain
assumptions about the microscopic model for the mirror, we obtain a rather
general expression for the Euclidean effective action, a functional of the
time-dependent mirror's position, in terms of two invariants that characterize
the tensor . The final result can be written in terms of the
TE and TM reflection coefficients of the mirror, with qualitatively different
contributions coming from them. We apply that general expression to derive the
imaginary part of the `in-out' effective action, which measures dissipative
effects induced by the mirror's motion, in different models, in particular for
an accelerated graphene sheet.Comment: 8 pages, 2 figures. Minor changes, version to be published in Phys.
Rev.
Towards Micromechanical Sensors with (La,Sr)MnO3 Epitaxial Filmsâ
Abstract The rich spectrum of functionalities exhibited by oxide thin films is an appealing feature for the development of micro and nanomechanical devices [1,2] . MEMS made of heterostructures of crystalline oxide materials having targeted physical properties may be applied as sensors having different integrated functionalities. In this work, we explore the feasibility of manganite thin film based epitaxial MEMS for magnetic micromechanical sensing. We investigate the electromechanical properties of LSMO freestanding structures for future applications in the field of micromechanical magnetic sensors
Object-based reverberation for spatial audio
Object-based audio is gaining momentum as a means for future audio content to be more immersive, interactive, and accessible. Recent standardization developments make recommendations for object formats; however, the capture, production, and reproduction of reverberation is an open issue. In this paper parametric approaches for capturing, representing, editing, and rendering reverberation over a 3D spatial audio system are reviewed. A framework is proposed for a Reverberant Spatial Audio Object (RSAO), which synthesizes reverberation inside an audio object renderer. An implementation example of an object scheme utilizing the RSAO framework is provided, and supported with listening test results, showing that: the approach correctly retains the sense of room size compared to a convolved reference; editing RSAO parameters can alter the perceived room size and source distance; and, format-agnostic rendering can be exploited to alter listener envelopment
The adaptation of lipid profile of human fibroblasts to alginate 2D films and 3D printed scaffolds
Background: The investigation of the interactions between cells and active materials is pivotal in the emerging 3D printing-biomaterial application fields. Here, lipidomics has been used to explore the early impact of alginate (ALG) hydrogel architecture (2D films or 3D printed scaffolds) and the type of gelling agent (CaCl2 or FeCl3) on the lipid profile of human fibroblasts. Methods: 2D and 3D ALG scaffolds were prepared and characterized in terms of water content, swelling, mechanical resistance and morphology before human fibroblast seeding (8 days). Using a liquid chromatography-triple quadrupole-tandem mass spectrometry approach, selected ceramides (CER), lysophosphatidylcholines (LPC), lysophosphatidic acids (LPA) and free fatty acids (FFA) were analyzed. Results: The results showed a clear alteration in the CER expression profile depending of both the geometry and the gelling agent used to prepare the hydrogels. As for LPCs, the main parameter affecting their distribution is the scaffold architecture with a significant decrease in the relative expression levels of the species with higher chain length (C20 to C22) for 3D scaffolds compared to 2D films. In the case of FFAs and LPAs only slight differences were observed as a function of scaffold geometry or gelling agent. Conclusions: Variations in the cell membrane lipid profile were observed for 3D cell cultures compared to 2D and these data are consistent with activation processes occurring through the mutual interactions between fibroblasts and ALG support. These unknown physiologically relevant changes add insights into the discussion about the relationship between biomaterial and the variations of cell biological functions
A digital waveguide-based approach for Clavinet modeling and synthesis
The Clavinet is an electromechanical musical instrument produced in the mid-twentieth century. As is the case for other vintage instruments, it is subject to aging and requires great effort to be maintained or restored. This paper reports analyses conducted on a Hohner Clavinet D6 and proposes a computational model to faithfully reproduce the Clavinet sound in real time, from tone generation to the emulation of the electronic components. The string excitation signal model is physically inspired and represents a cheap solution in terms of both computational resources and especially memory requirements (compared, e.g., to sample playback systems). Pickups and amplifier models have been implemented which enhance the natural character of the sound with respect to previous work. A model has been implemented on a real-time software platform, Pure Data, capable of a 10-voice polyphony with low latency on an embedded device. Finally, subjective listening tests conducted using the current model are compared to previous tests showing slightly improved results
Alginate SelfâCrosslinking Ink for 3D ExtrusionâBased Cryoprinting and Application for EpirubicinâHCl Delivery on MCFâ7 Cells
3Dâprinted hydrogels are particularly advantageous as drugâdelivery platforms but their loading with waterâsoluble active compounds remains a challenge requiring the development of innovative inks. Here, we propose a new 3D extrusionâbased approach that, by exploiting the internal gelation of the alginate, avoids the postâprinting crosslinking process and allows the loading of epirubicinâHCl (EPI). The critical combinations of alginate, calcium carbonate and dâ gluconoâÎŽâlactone (GDL) combined with the scaffold production parameters (extrusion time, temperature, and curing time) were evaluated and discussed. The internal gelation in tandem with 3D extrusion allowed the preparation of alginate hydrogels with a complex shape and good handling properties. The dispersion of epirubicinâHCl in the hydrogel matrix confirmed the potential of this selfâcrosslinking alginateâbased ink for the preparation of 3Dâprinted drugâdelivery platforms. Drug release from 3Dâprinted hydrogels was monitored, and the cytotoxic activity was tested against MCFâ7 cells. Finally, the change in the expression pattern of antiâapoptotic, pro-apoptotic, and autophagy protein markers was monitored by liquidâchromatography tandem-massâspectrometry after exposure of MCFâ7 to the EPIâloaded hydrogels
Visualization of compact microphone array room impulse responses
For many audio applications, availability of recorded multi-channel room impulse responses (MC-RIRs) is fundamental. They enable development and testing of acoustic systems for reflective rooms. We present multiple MC-RIR datasets recorded in diverse rooms, using up to 60 loudspeaker positions and various uniform compact microphone arrays. These datasets complement existing RIR libraries and have dense spatial sampling of a listening position. To reveal the encapsulated spatial information, several state of the art room visualization methods are presented. Results confirm the measurement fidelity and graphically depict the geometry of the recorded rooms. Further investigation of these recordings and visualization methods will facilitate object-based RIR encoding, integration of audio with other forms of spatial information, and meaningful extrapolation and manipulation of recorded compact microphone array RIRs