7 research outputs found
Microwave cavity-enhanced transduction for plug and play nanomechanics at room temperature
Nanomechanical resonators with increasingly high quality factors are enabled
following recent insights into energy storage and loss mechanisms in
nanoelectromechanical systems (NEMS). Consequently, efficient, non-dissipative
transduction schemes are required to avoid the dominating influence of coupling
losses. We present an integrated NEMS transducer based on a microwave cavity
dielectrically coupled to an array of doubly-clamped pre-stressed silicon
nitride beam resonators. This cavity-enhanced detection scheme allows resolving
the resonators' Brownian motion at room temperature while preserving their high
mechanical quality factor of 290,000 at 6.6 MHz. Furthermore, our approach
constitutes an "opto"mechanical system in which backaction effects of the
microwave field are employed to alter the effective damping of the resonators.
In particular, cavity-pumped self-oscillation yields a linewidth of only 5 Hz.
Thereby, an adjustement-free, all-integrated and self-driven
nanoelectromechanical resonator array interfaced by just two microwave
connectors is realised, potentially useful for applications in sensing and
signal processing
Increased hippocampal CA1 cerebral blood volume in schizophrenia
Hippocampal hyperactivity has been proposed as a biomarker in schizophrenia. However, there is a debate whether the CA1 or the CA2/3 subfield is selectively affected. We studied 15 schizophrenia patients and 15 matched healthy control subjects with 3T steady state, gadolinium-enhanced, absolute cerebral blood volume (CBV) maps, perpendicular to the long axis of the hippocampus. The subfields of the hippocampal formation (subiculum, CA1, CA2/3, and hilus/dentate gyrus) were manually segmented to establish CBV values. Comparing anterior CA1 and CA2/3 CBV between patients and controls revealed a significant subfield-by-diagnosis interaction. This interaction was due to the combined effect of a trend of increased CA1 CBV (p = .06) and non-significantly decreased CA2/3 CBV (p = 0.14) in patients relative to healthy controls. These results support the emerging hypothesis of increased hippocampal activity as a biomarker of schizophrenia and highlight the importance of subfield-level investigations