We have fabricated and tested submillimeter-wave superconductor–insulator–superconductor ~SIS! mixers using very high-current-density Nb/AlN/Nb tunnel junctions (Jc'30 kA cm ). The junctions have low-resistance-area products (RNA'5.6 V mm ), good subgap-to-normal resistance ratios Rsg /RN'10, and good run-to-run reproducibility. From Fourier transform spectrometer measurements, we infer that vR...

Waveguide SIS mixers are presented in which Nb/Al-AlOx/Nb tunnel junctions are integrated with both NbTiN/SiO2/NbTiN and NbTiN/SiO2/Al tuning circuits. The mixers with a NbTiN/SiO2/NbTiN tuning circuit yield relatively low receiver noise temperatures between 700 and 830 GHz, but their sensitivity drops significantly above ~ 850 GHz. In contrast, low-noise heterodyne mixing near 1 THz is observe...

In this paper we derive two rigorous properties of residence-time distributions for flows in pipes and mixers motivated by computational results of Khakhar et al. [Chem. Eng. Sci. 42, 2909 (1987)], using some concepts from ergodic theory. First, a curious similarity between the isoresidence-time plots and Poincare maps of the flow observed in Khakhar et al. is resolved. It is shown that in long...

To strengthen the anonymity of Bitcoin, several centralized coin-mixing providers (mixers) such as BitcoinFog.com, BitLaundry.com, and Blockchain.info assist users to mix Bitcoins through CoinJoin transactions with multiple inputs and multiple outputs to uncover the relationship between them. However, these mixers know the output address of each user, such that they cannot provide true anonymit...

With the increasing need for molecular reactions with small liquid volume in biomedical and chemical analyses, miniature mixers have captured considerable attention. Due to the nature of laminar flow in a millimeter-size and blow flow channel, mixing, or the molecular mass transfer in miniature mixers is usually dominated by molecular diffusion. The long diffusion time and mixing distance make ...

Balanced receivers are under development at the Caltech Submillimeter Observatory (CSO) for the 230/460 GHz and 345/660 GHz atmospheric windows. The mixers are tunerless, implemented in a balanced configuration, have a 4-8 GHz IF, and can be used in dual frequency observation mode. As shall be seen, the balanced arrangement provides a high level of amplitude noise immunity and allows all of the...

Bitcoin provides only pseudo-anonymous transactions, which can be exploited to link payers and payees – defeating the goal of anonymous payments. To thwart such attacks, several Bitcoin mixers have been proposed, with the objective of providing unlinkability between payers and payees. However, existing Bitcoin mixers are not under widespread use, and can be regarded as either insecure or ineffi...

Polymeric microfluidic systems are well suited for miniaturized devices with complex functionality, and rapid prototyping methods for 3D microfluidic structures are increasingly used. Mixing at the microscale and performing chemical reactions at the microscale are important applications of such systems and we therefore explored feasibility, mixing characteristics and the ability to control a ch...