We present an interferometric sensor for investigating macroscopic quantum mechanics on a table-top scale. The sensor consists of a pair of suspended optical cavities with finesse over 350,000 ...comprising 10 g fused silica mirrors. The interferometer is suspended by a four-stage, light, in-vacuum suspension with three common stages, which allows for us to suppress common-mode motion at low frequency. The seismic noise is further suppressed by an active isolation scheme, which reduces the input motion to the suspension point by up to an order of magnitude starting from 0.7 Hz. In the current room-temperature operation, we achieve a peak sensitivity of 0.5 fm/Hz in the acoustic frequency band, limited by a combination of readout noise and suspension thermal noise. Additional improvements of the readout electronics and suspension parameters will enable us to reach the quantum radiation pressure noise. Such a sensor can eventually be utilized for demonstrating macroscopic entanglement and for testing semi-classical and quantum gravity models.
Compact Michelson interferometers are well positioned to replace existing displacement sensors in the readout of seismometers and suspension systems, such as those used in contemporary ...gravitational-wave detectors. Here, we continue our previous investigation of a customised compact displacement sensor built by SmarAct that operates on the principle of deep frequency modulation. The focus of this paper is the linearity of this device and its subsequent impact on sensitivity. We show the three primary sources of nonlinearity that arise in the sensor: residual ellipticity, intrinsic distortion of the Lissajous figure, and distortion caused by exceeding the velocity limit imposed by the demodulation algorithm. We verify the theoretical models through an experimental demonstration, where we show the detrimental impact that these nonlinear effects have on device sensitivity. Finally, we simulate the effect that these nonlinearities are likely to have if implemented in the readout of the Advanced LIGO suspensions and show that the noise from nonlinearities should not dominate across the key sub-10 Hz frequency band.
Abstract Axions and axion-like particles (ALPs) are leading candidates for dark matter. They are well motivated in many extensions of the standard model and supported by astronomical observations. We ...propose an iterative transformation of the existing facilities of the gravitational-wave detector and technology testbed GEO600, located near Ruthe in Germany, into a kilometre-scale upgrade of the laser-interferometric axion detector LIDA. The final DarkGEO detector could search for coincident signatures of axions and ALPs and significantly surpass the current constraints of both direct searches and astrophysical observations in the measurement band from 10 −16 to 10 −8 eV. We discuss design parameters and sensitivities for the configurations of the different iteration steps as well as technical challenges known from the first LIDA results. The proposed DarkGEO detector will be well suited to probe the mass-coupling parameter space associated with predictions from theoretical models, like grand-unified theories, as well as from astrophysical evidence, like the cosmic infrared background.
Precision measurements using a traditional heterodyne readout suffer a 3 dB quantum noise penalty compared with a homodyne readout. The extra noise is caused by the quantum fluctuations in the image ...vacuum. We propose a two-carrier gravitational-wave detector design that evades the 3 dB quantum penalty of the heterodyne readout. We further propose a new way of realizing frequency-dependent squeezing utilizing two-mode squeezing in our scheme. It naturally achieves more precise audio frequency signal measurements with radio frequency squeezing. In addition, the detector is compatible with other quantum nondemolition techniques.
Video emergency calls (VCs) represent a feasible future trend in medical dispatching. Acceptance among callers and dispatchers seems to be good. Indications, potential problems, limitations, and ...directions of research of adding a live video from smartphones to an emergency call have not been reviewed outside the context of out-of-hospital cardiac arrest (OHCA).
The main objective of this study is to examine the scope and nature of research publications on the topic of VC. The secondary goal is to identify research gaps and discuss the potential directions of research efforts of VC.
Following PRISMA-ScR guidelines, online bibliographic databases PubMed, Web of Science, SCOPUS, Google Scholar, ClinicalTrials.gov, and gray literature were searched from the period of January 1, 2012 through March 1, 2022 in English. Only studies focusing on video transfer via mobile phone to emergency medical dispatch centers (EMDCs) were included.
Twelve articles were included in the qualitative synthesis and six main themes were identified: (1) cardiopulmonary resuscitation (CPR) guided by VC; (2) indications of VCs; (3) dispatchers' feedback and perception; (4) technical aspects of VCs; (5) callers' acceptance; and (6) confidentiality and legal issues.
Video emergency calls are feasible and seem to be a well-accepted auxiliary method among dispatchers and callers. Some promising clinical results exist, especially for video-assisted CPR. On the other hand, there are still enormous knowledge gaps in the vast majority of implementation aspects of VC into practice.
► Comparison of one stage (co-current) and two stage gasification of wood pellets. ► Original arrangement with grate-less reactor and upward moving bed of the pellets. ► Two stage gasification leads ...to drastic reduction of tar content in gas. ► One stage gasification produces gas with higher LHV at lower overall ER. ► Content of ammonia in gas is lower in two stage moving bed gasification.
A pilot scale gasification unit with novel co-current, updraft arrangement in the first stage and counter-current downdraft in the second stage was developed and exploited for studying effects of two stage gasification in comparison with one stage gasification of biomass (wood pellets) on fuel gas composition and attainable gas purity. Significant producer gas parameters (gas composition, heating value, content of tar compounds, content of inorganic gas impurities) were compared for the two stage and the one stage method of the gasification arrangement with only the upward moving bed (co-current updraft). The main novel features of the gasifier conception include grate-less reactor, upward moving bed of biomass particles (e.g. pellets) by means of a screw elevator with changeable rotational speed and gradual expanding diameter of the cylindrical reactor in the part above the upper end of the screw. The gasifier concept and arrangement are considered convenient for thermal power range 100–350kWth. The second stage of the gasifier served mainly for tar compounds destruction/reforming by increased temperature (around 950°C) and for gasification reaction of the fuel gas with char. The second stage used additional combustion of the fuel gas by preheated secondary air for attaining higher temperature and faster gasification of the remaining char from the first stage. The measurements of gas composition and tar compound contents confirmed superiority of the two stage gasification system, drastic decrease of aromatic compounds with two and higher number of benzene rings by 1–2 orders. On the other hand the two stage gasification (with overall ER=0.71) led to substantial reduction of gas heating value (LHV=3.15MJ/Nm3), elevation of gas volume and increase of nitrogen content in fuel gas. The increased temperature (>950°C) at the entrance to the char bed caused also substantial decrease of ammonia content in fuel gas. The char with higher content of ash leaving the second stage presented only few mass% of the inlet biomass stream.
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