Time- and Frequency-Varying KK-Factor of Non-Stationary Vehicular Channels for Safety Relevant Scenarios

Vehicular communication channels are characterized by a non-stationary time- and frequency-selective fading process due to fast changes in the environment. We characterize the distribution of the envelope of the first delay bin in vehicle-to-vehicle channels by means of its Rician $K$-factor. We analyze the time-frequency variability of this channel parameter using vehicular channel measurements at 5.6 GHz with a bandwidth of 240 MHz for safety-relevant scenarios in intelligent transportation systems (ITS). This data enables a frequency-variability analysis from an IEEE 802.11p system point of view, which uses 10 MHz channels. We show that the small-scale fading of the envelope of the first delay bin is Ricean distributed with a varying $K$-factor. The later delay bins are Rayleigh distributed. We demonstrate that the $K$-factor cannot be assumed to be constant in time and frequency. The causes of these variations are the frequency-varying antenna radiation patterns as well as the time-varying number of active scatterers, and the effects of vegetation. We also present a simple but accurate bi-modal Gaussian mixture model, that allows to capture the $K$-factor variability in time for safety-relevant ITS scenarios.Comment: 26 pages, 12 figures, submitted to IEEE Transactions on Intelligent Transportation Systems for possible publicatio

Overview of vehicle-to-vehicle radio channel measurements for collision avoidance applications

In this paper we present an overview of a vehicle-to-vehicle radio channel measurement campaign at 5.6GHz. The selected measurement scenarios are based on important safety-related applications. We explain why these scenarios are interesting from the aspect of radio propagation. Further we describe the power-delay profile and the Doppler spectral density of two situations especially suitable for collision avoidance applications: A traffic congestion situation where one car is overtaking another one, and a general line-of-sight obstruction between the transmitter and the receiver car. The evaluations show that in these situations the radio channel is highly influenced by the rich scattering environment. Most important scatterers are traffic signs, trucks, and bridges, whereas other cars do not significantly contribute to the multipath propagation

An Integrative Structural Biology Analysis of Von Willebrand Factor Binding and Processing by ADAMTS-13 in Solution

Von Willebrand Factor (vWF), a 300-kDa plasma protein key to homeostasis, is cleaved at a single site by multi-domain metallopeptidase ADAMTS-13. vWF is the only known substrate of this peptidase, which circulates in a latent form and becomes allosterically activated by substrate binding. Herein, we characterised the complex formed by a competent peptidase construct (AD13-MDTCS) comprising metallopeptidase (M), disintegrin-like (D), thrombospondin (T), cysteine-rich (C), and spacer (S) domains, with a 73-residue functionally relevant vWF-peptide, using nine complementary techniques. Pull-down assays, gel electrophoresis, and surface plasmon resonance revealed tight binding with sub-micromolar affinity. Cross-linking mass spectrometry with four reagents showed that, within the peptidase, domain D approaches M, C, and S. S is positioned close to M and C, and the peptide contacts all domains. Hydrogen/deuterium exchange mass spectrometry revealed strong and weak protection for C/D and M/S, respectively. Structural analysis by multi-angle laser light scattering and small-angle X-ray scattering in solution revealed that the enzyme adopted highly flexible unbound, latent structures and peptide-bound, active structures that differed from the AD13-MDTCS crystal structure. Moreover, the peptide behaved like a self-avoiding random chain. We integrated the results with computational approaches, derived an ensemble of structures that collectively satisfied all experimental restraints, and discussed the functional implications. The interaction conforms to a ‘fuzzy complex’ that follows a ‘dynamic zipper’ mechanism involving numerous reversible, weak but additive interactions that result in strong binding and cleavage. Our findings contribute to illuminating the biochemistry of the vWF:ADAMTS-13 axis.This study was supported in part by grants from Spanish, French, Danish and Catalan public and private bodies (grant/fellowship references PID2019-107725RG-I00, BES-2015-074583, ANR-10-LABX-12-01, 6108-00031B, 8022-00385B, LF18039, NNF18OC0032724, Novo Nordisk Foundation “Bio-MS”, 2017SGR3 and Fundació “La Marató de TV3” 201815). This work was also supported by EPICS-XS, project 823839, funded by the Horizon 2020 programme of the European Union. The CBS is a member of France-BioImaging (FBI) and the French Infrastructure for Integrated Structural Biology (FRISBI), which are national infrastructures supported by the French National Research Agency (grants ANR-10-INBS-04-01 and ANR-10-INBS-05, respectively). Finally, we acknowledge the Structural Mass Spectrometry Unit of CIISB, an Instruct-CZ Centre, which was supported by MEYS CR (LM2018127)

An integrative structural biology analysis of von Willebrand factor binding and processing by ADAMTS-13 in solution

Peer reviewe

Gasdermin B over-expression modulates HER2-targeted therapy resistance by inducing protective autophagy through Rab7 activation

Gasdermin B (GSDMB) over-expression promotes poor prognosis and aggressive behavior in HER2 breast cancer by increasing resistance to therapy. Decoding the molecular mechanism of GSDMB-mediated drug resistance is crucial to identify novel effective targeted treatments for HER2/GSDMB aggressive tumors. Different in vitro approaches (immunoblot, qRT-PCR, flow cytometry, proteomic analysis, immunoprecipitation, and confocal/electron microscopy) were performed in HER2 breast and gastroesophageal carcinoma cell models. Results were then validated using in vivo preclinical animal models and analyzing human breast and gastric cancer samples. GSDMB up-regulation renders HER2 cancer cells more resistant to anti-HER2 agents by promoting protective autophagy. Accordingly, the combination of lapatinib with the autophagy inhibitor chloroquine increases the therapeutic response of GSDMB-positive cancers in vitro and in zebrafish and mice tumor xenograft in vivo models. Mechanistically, GSDMB N-terminal domain interacts with the key components of the autophagy machinery LC3B and Rab7, facilitating the Rab7 activation during pro-survival autophagy in response to anti-HER2 therapies. Finally, we validated these results in clinical samples where GSDMB/Rab7/LC3B co-expression associates significantly with relapse in HER2 breast and gastric cancers. Our findings uncover for the first time a functional link between GSDMB over-expression and protective autophagy in response to HER2-targeted therapies. GSDMB behaves like an autophagy adaptor and plays a pivotal role in modulating autophagosome maturation through Rab7 activation. Finally, our results provide a new and accessible therapeutic approach for HER2/GSDMB + cancers with adverse clinical outcome. The online version contains supplementary material available at 10.1186/s13046-022-02497-w

Physical Layer Simulation Results for IEEE 802.11p using Vehicular non-Stationary Channel Model

Abstract—Traffic safety can be improved by using a vehicular dedicated communication protocol. The standard IEEE 802.11p is being developed for this purpose. The physical layer properties of this draft are based on the already widely used IEEE 802.11a standard. Nevertheless, the propagation conditions in vehicular communications are different to the ones considered for 802.11a, which is focusing on nomadic indoor usage, and well studied until now. In this paper we present the simulation results obtained from an implemented physical layer model for this standard. The used channel model describes the very peculiar characteristics of the vehicular radio channel, specially the nonstationarity. Several channel estimators are tested based on the pilot structure defined in the standard focusing on low complexity implementations. The results show that diffuse components, present in vehicular channels on highways, have a very significant impact on the system performance. Furthermore, in situations of poor line-of-sight contribution, an acceptable frame error rate is not achievable even at high signal-to-noise ratio values. Therefore, more complex channel estimation and equalization techniques based on the current standard pilot pattern have to be developed that are able to cope with the properties of the vehicular radio channel. I

Complexity Reduction for Vehicular Channel Estimation Using the Filter Divergence Measure

Abstract—A key component in vehicular communications systems is the channel estimation filter that suppresses the additive noise in the channel estimates from pilot symbols. A filter which offers the best performance in terms of mean square error (MSE) is the well known Wiener filter. A drawback of using filters based on second order statistics is that they have to be recalculated when the statistical properties of the channel have changed. In vehicular communications the observed channels do not follow the wide-sense stationary (WSS) uncorrelatedscattering (US) properties, and therefore their power spectral density varies over time. A non-stationary process can be divided in time into consecutive stationarity regions where the WSS and US properties are assumed to hold, allowing to calculate the coefficients of a Wiener filter. In this paper we analyze the increase of the MSE observed when using a mismatched Wiener filter. The mismatch results from using the filter coefficients calculated for a past stationarity region. We relate this concept of performance degradation to spectral distance metrics. We use the spectral divergence between scattering functions at different time instances. Furthermore, we introduce a new metric, the filter divergence, which takes noise into account. We show that, by accepting an increase of MSE, the same filter coefficients can be used for several time regions, which allows computational complexity reduction in a real system. I