Biomedical subjects

Yuefei Ma

Publications and source records attributed to Yuefei Ma.

5 recordsLinked to original sources

PubMed2006

Atomistic nature of transient and steady-state responses.

We find experimentally that a system comprised of nanosized features no longer shows fixed steady characteristics as in solid-state devices, and instead, because of the chemistry of the nanostructure, the thermal motion of the atoms, and the external fields, the nanosized system shows intermittent behavior, that is, transient behavior. This transient response for nanosized systems might misguide conclusions regarding observed negative differential resistance (NDR) which is due to the collective nuclei rearrangements to more stable conformations under the presence of an applied field yielding, in many cases, resonances between conformations that can sustain during the steady-state period. This NDR yields peculiar behavior that needs to be considered to design molecular and nanoelectronic devices. In addition, the commonly sharp contrast between transient and steady responses blurs at the nanoscale. In nanosize systems, the time constants or transient response times depend on the velocity of the rearrangements of the atoms in the system or molecule.

Journal Article↗

PubMed2006

Transient behavior at the nanoscale.

Transient and steady state responses of a system to an input are well-known features of materials and systems in science and engineering. These responses depend on the intrinsic parameters of the system and on the nature of the input. We find that a system comprised of nanosized features no longer shows the typical stationary characteristics as their microscopic or solid-state counterparts. Interestingly, because of the chemistry of the nanostructure, thermal motion of the atoms, and external fields, the nanosized system shows extended electrical transient behavior, compatible with highly nonlinear features such a negative differential resistance and hysteresis.

Journal Article↗

PubMed2006

Encoding information using molecular vibronics.

Signals carrying information are encoded in molecular vibrational waves (vibronics) rather than in electric currents as widely done in microelectronics. We demonstrate theoretically that signals can be transmitted along a long polypeptide molecule; the signal is modulated in a terahertz carrier corresponding to a frequency of an intrinsic vibrational mode of the backbone of the polypeptide, via amplitude and frequency modulations. The modulated carrier is coupled as a vibrational wave to the polypeptide at one end of the molecule and propagates for more than 168 angstroms towards the other end. Digital signal processing techniques are used to recover the modulated signals.

Computer Simulation↗

PubMed2005

Transmission of vibronic signals in molecular circuits.

It is proposed and demonstrated using molecular dynamics and digital signal processing techniques that molecular vibrations can be used to transport signals in molecular circuits, revealing that signals transmitted along polypeptide molecules by a frequency-modulated carrier in the terahertz domain consume only 0.2 eV to successfully transfer one information bit; this energy is several orders of magnitude smaller than the several thousands of electronvolts needed using electrons in present electronic devices.

Letter↗

PubMed2004

Clustering effects on discontinuous gold film NanoCells.

Reproducible negative differential resistance (NDR)-like switching behavior is observed in NanoCells. This behavior is attributed to the formation of filaments and clusters between the discontinuous gold films. Control experiments are performed by self-assembly of insulating molecules between the gold islands and conducting molecules on these islands. Additional control experiments are performed by removing the filaments and clusters between islands using a piranha bath. The results are consistent with theoretical predictions and extend the domain of molecular electronics based in organic molecules to include nanosized clusters as active units. This facilitates a scenario where synthetically accessible organic molecules, with defined characteristics, can be adjusted by metallic nanoclusters as an in situ fine-tuning element, able to compensate for the lack of addressing in the nanosize regime.

Electric Impedance↗