Fast and robust anchor calibration in range-based wireless localization

In this paper we investigate the anchor calibration problem where we want to find the anchor positions when the anchors are not able to range between each other. This is a problem of practical interest because in many systems, the anchors are not connected in a network but are just simple responders to range requests. The proposed calibration method is designed to be fast and simple using only a single range-capable device. For the estimation of the inter-anchor distances, we propose a Total Least Squares estimator as well as a L1 norm estimator. Real life experiments using publicly available hardware validate the proposed calibration technique and show the robustness of the algorithm to non-line-of-sight measurements

Bayesian CRLB for hybrid ToA and DoA based wireless localization with anchor uncertainty

In this paper, we derive the Bayesian Cramér-Rao lower bound for three dimensional hybrid localization using time-of-arrival (ToA) and direction-of-arrival (DoA) types of measurements. Unlike previous works, we include the practical constraint that the anchor position is not known exactly but rather up to some error. The resulting bound can be used for error analysis of such a localization system or as an optimality criterion for the selection of suitable anchors

Narrowband AM interference cancellation for broadband multicarrier systems

We consider an overlay system where narrowband AM signals interfere with a broadband multicarrier system. To reduce the effect of the AM narrowband interference on the multicarrier system, we propose a low-complexity algorithm to estimate the AM narrowband interference. Analytical expressions for the performance of this estimator are derived and verified with simulations. The performance of this estimator, however, degrades when the number of interferers increases. To improve the algorithm, we adapt it such that the interferers are estimated in a successive way. The proposed estimators are able to produce accurate estimates of the frequencies, and track the time-varying amplitudes of the AM signals. The estimators can reduce the power of the AM signal to a level that is approximately 20 dB lower than the multicarrier power, independently of the AM signal power

On the structural nature of cooperation in distributed network localization

We demonstrate analytically that the contribution of cooperation in improving the accuracy of distributed network localization has a fundamentally structural nature, rather then statistical as widely believed. To this end we first introduce a new approach to build Fisher Information Matrices (FIMs), in which the individual contribution of each cooperative pair of nodes is captured explicitly by a corresponding information vector. The approach offers new insight onto the structure of FIMs, enabling us to easily account for both anchor and node location uncertainties in assessing lower bounds on localization errors. Using this construction it is surprisingly found that in the presence of node location uncertainty and regardless of ranging error variances or network size, the Fisher information matrix (FIM) terms corresponding to the information added by node-to-node cooperation nearly vanish. In other words, the analysis reveals that the key contribution of cooperation in network localization is not to add statistical node-to-node information (in the Fisher sense), but rather to provide a structure over which information is better exploited

Minimizing technical variation during sample preparation prior to label-free quantitative mass spectrometry

Sample preparation is the crucial starting point to obtain high-quality mass spectrometry data and can be divided into two main steps in a bottom-up proteomics approach: cell/tissue lysis with or without detergents and a(n) (in-solution) digest comprising denaturation, reduction, alkylation, and digesting of the proteins. Here, some important considerations, among others, are that the reagents used for sample preparation can inhibit the digestion enzyme (e.g., 0.1% sodium dodecyl sulfate [SDS] and 0.5 M guanidine HCl), give rise to ion suppression (e.g., polyethylene glycol [PEG]), be incompatible with liquid chromatography tandem mass spectrometry (LC MS/MS) (e.g., SDS), and can induce additional modifications (e.g., urea). Taken together, all of these irreproducible effects are gradually becoming a problem when label-free quantitation of the samples is envisioned such as during the increasingly popular high-definition mass spectrometry (HDMSE) and sequential window acquisition of all theoretical fragment ion spectra (SWATH) data-independent acquisition strategies. Here, we describe the detailed validation of a reproducible method with sufficient protein yield for sample preparation without any known LC MS/MS interfering substances by using 1% sodium deoxycholate (SDC) during both cell lysis and in-solution digest

Characterization of serotonin transporter expression in human T lymphocytes

Serotonin transporter (SERT) expression has been demonstrated in human lymphocytes, including B lymphocytes, NK cells and other immune cells. However, discussion remains on whether human T lymphocytes express SERT. Given the potentially important role of serotonin in lymphocyte activation and proliferation, we investigated SERT expression in purified human T lymphocytes both in resting and activated state. Blood samples were collected from 9 healthy volunteers. PBMCs were isolated using Ficoll density centrifugation and T lymphocytes were further purified with magnetic activated cell sorting. T cells were either processed for mRNA and protein isolation immediately, or activated using anti-CD3/CD28 coated magnetic beads and allowed to proliferate for 72h at 37°C and 5% CO2. SERT mRNA expression was measured using droplet digital PCR to allow for increased sensitivity in comparison with qRT-PCR. SERT protein was detected on western blot. SERT expression was detected both on mRNA and protein level, although expression levels were very low. On mRNA level, SERT was expressed in both resting and activated cells. On the protein level however, only activated cells displayed SERT expression. This observation might point to a ‘translational readiness’ were resting T lymphocytes already produce SERT mRNA, but translation is only induced after activation of the cell