Spin-mediated dissipation and frequency shifts of a cantilever at milliKelvin temperatures

We measure the dissipation and frequency shift of a magnetically coupled cantilever in the vicinity of a silicon chip, down to $25$ mK. The dissipation and frequency shift originates from the interaction with the unpaired electrons, associated with the dangling bonds in the native oxide layer of the silicon, which form a two dimensional system of electron spins. We approach the sample with a $3.43$ $\mu$m-diameter magnetic particle attached to an ultrasoft cantilever, and measure the frequency shift and quality factor as a function of temperature and the distance. Using a recent theoretical analysis [J. M. de Voogd et al., arXiv:1508.07972 (2015)] of the dynamics of a system consisting of a spin and a magnetic resonator, we are able to fit the data and extract the relaxation time $T_1=0.39\pm0.08$ ms and spin density $\sigma=0.14\pm0.01$ spins per nm$^2$. Our analysis shows that at temperatures $\leq500$ mK magnetic dissipation is an important source of non-contact friction.Comment: 5 pages, 3 figure

Device for obtaining respiratory information of a subject

A device and method for reliably and accurately obtaining respiratory information of a subject despite motion of the subject are disclosed. The proposed device comprises a motion signal computing unit for computing a number M of motion signals for a plurality of pixels and/or groups of pixels of at least a region of interest for a number N of image frames of a subject, a transformation unit for computing, for some or all M motion signals, a number of source signals representing independent motions within said images by applying a transformation to the respective motion signals to obtain source signals representing independent motions within said N image frames, and a selection unit for selecting a source signal from among said computed source signals representing respiration of said subject by examining one or more properties of said source signals for some or all of said computed source signals

Uncovering regulatory pathways that affect hematopoietic stem cell function using 'genetical genomics'

We combined large-scale mRNA expression analysis and gene mapping to identify genes and loci that control hematopoietic stem cell (HSC) function. We measured mRNA expression levels in purified HSCs isolated from a panel of densely genotyped recombinant inbred mouse strains. We mapped quantitative trait loci (QTLs) associated with variation in expression of thousands of transcripts. By comparing the physical transcript position with the location of the controlling QTL, we identified polymorphic cis-acting stem cell genes. We also identified multiple trans-acting control loci that modify expression of large numbers of genes. These groups of coregulated transcripts identify pathways that specify variation in stem cells. We illustrate this concept with the identification of candidate genes involved with HSC turnover. We compared expression QTLs in HSCs and brain from the same mice and identified both shared and tissue-specific QTLs. Our data are accessible through WebQTL, a web-based interface that allows custom genetic linkage analysis and identification of coregulated transcripts.

Correlations of record events as a test for heavy-tailed distributions

A record is an entry in a time series that is larger or smaller than all previous entries. If the time series consists of independent, identically distributed random variables with a superimposed linear trend, record events are positively (negatively) correlated when the tail of the distribution is heavier (lighter) than exponential. Here we use these correlations to detect heavy-tailed behavior in small sets of independent random variables. The method consists of converting random subsets of the data into time series with a tunable linear drift and computing the resulting record correlations.Comment: Revised version, to appear in Physical Review Letter

Wearable devices with two stage of use

A two-statewearable device may include a wearable band (e.g., a watch band) and a displaymodule (e.g. ̧ a watch face).In a "detached" state, the wearable band and display module act as separate devices, and the display module can be charging its battery while the wearable band gathers sensor data (e.g., sleep tracking data) and provides a vibrating/audio alarm clock function. In an "attached" state, the wearable band and display module act together as a single device, meaning that the data collected by the wearable band during the "detached" state is sent to and stored at the display module, and that sleep settings input at a user interface of the display module impact the wearable band's alarm function. The display module may also use its newly-recharged battery to recharge the wearable band's battery so that it can be used the next night.</p