Effects of granulation-tissue extracts on collagen synthesis

Bolometer operating at the threshold for circuit quantum electrodynamics

Radiation sensors based on the heating effect of absorbed radiation are typically simple to operate and flexible in terms of input frequency, so they are widely used in gas detection¹, security², terahertz imaging³, astrophysical observations⁴ and medical applications⁵. Several important applications are currently emerging from quantum technology and especially from electrical circuits that behave quantum mechanically, that is, circuit quantum electrodynamics⁶. This field has given rise to single-photon microwave detectors^7-9 and a quantum computer that is superior to classical supercomputers for certain tasks¹⁰. Thermal sensors hold potential for enhancing such devices because they do not add quantum noise and they are smaller, simpler and consume about six orders of magnitude less power than the frequently used travelling-wave parametric amplifiers¹¹. However, despite great progress in the speed¹² and noise levels¹³ of thermal sensors, no bolometer has previously met the threshold for circuit quantum electrodynamics, which lies at a time constant of a few hundred nanoseconds and a simultaneous energy resolution of the order of 10h gigahertz (where h is the Planck constant). Here we experimentally demonstrate a bolometer that operates at this threshold, with a noise-equivalent power of 30 zeptowatts per square-root hertz, comparable to the lowest value reported so far¹³, at a thermal time constant two orders of magnitude shorter, at 500 nanoseconds. Both of these values are measured directly on the same device, giving an accurate estimation of 30h gigahertz for the calorimetric energy resolution. These improvements stem from the use of a graphene monolayer with extremely low specific heat¹⁴ as the active material. The minimum observed time constant of 200 nanoseconds is well below the dephasing times of roughly 100 microseconds reported for superconducting qubits¹⁵ and matches the timescales of currently used readout schemes^16,17, thus enabling circuit quantum electrodynamics applications for bolometers.

The tissue response to epimysial electrodes for diaphragm pacing in dogs

Epimysial electrodes stapled to the abdominal surface of the diaphragm produced a chronic inflammatory response that appeared to be mediated by mechanical stresses placed on the encapsulation tissue by periodic diaphragm contraction. The tissue response surrounding 34 epimysial electrodes implanted in 11 dogs was studied three months post implant. The tissue response was characterized by a capsule having a mean thickness of 1.24 mm between the electrode and the muscle, while having only a very thin capsule on the back, or abdominal side of the electrode. The tissue response between the electrode and the muscle was comprised of two tissue layers: a layer of granulation tissue and a layer of collagen. The granulation tissue layer contained evidence of acute inflammatory processes including the presence of polymorphonuclear leukocytes in 68% of the samples. Granulation layer thickness was inversely correlated with back encapsulation indicating a reduction in granulation tissue for mechanically stabilized electrodes. In addition, encapsulation tissue surrounding the granulation layer was comprised of collagen fibers with an oblique orientation and an extraperitoneal locale suggesting mechanical load transfers between the electrode and the surrounding tissue. As a result, the histological response to epimysial electrodes implanted on the diaphragm suggests that mechanical loading, induced by movement associated with the contraction of adjacent muscle, must be a consideration for devices that employ epimysial electrodes.