Current Channel Models Research Articles

Wireless power distributions in multi-cavity systems at high frequencies.

The next generations of wireless networks will work in frequency bands ranging from sub-6 GHz up to 100 GHz. Radio signal propagation differs here in several critical aspects from the behaviour in the microwave frequencies currently used. With wavelengths in the millimetre range (mmWave), both penetration loss and free-space path loss increase, while specular reflection will dominate over diffraction as an important propagation channel. Thus, current channel model protocols used for the generation of mobile networks and based on statistical parameter distributions obtained from measurements become insufficient due to the lack of deterministic information about the surroundings of the base station and the receiver-devices. These challenges call for new modelling tools for channel modelling which work in the short-wavelength/high-frequency limit and incorporate site-specific details—both indoors and outdoors. Typical high-frequency tools used in this context—besides purely statistical approaches—are based on ray-tracing techniques. Ray-tracing can become challenging when multiple reflections dominate. In this context, mesh-based energy flow methods have become popular in recent years. In this study, we compare the two approaches both in terms of accuracy and efficiency and benchmark them against traditional power balance methods.

Oversized ubiquinones as molecular probes for structural dynamics of the ubiquinone reaction site in mitochondrial respiratory complex I

NADH-quinone oxidoreductase (complex I) couples electron transfer from NADH to quinone with proton translocation across the membrane. Quinone reduction is a key step for energy transmission from the site of quinone reduction to the remotely located proton-pumping machinery of the enzyme. Although structural biology studies have proposed the existence of a long and narrow quinone-access channel, the physiological relevance of this channel remains debatable. We investigated here whether complex I in bovine heart submitochondrial particles (SMPs) can catalytically reduce a series of oversized ubiquinones (OS-UQs), which are highly unlikely to transit the narrow channel because their side chain includes a bulky "block" that is ∼13 Å across. We found that some OS-UQs function as efficient electron acceptors from complex I, accepting electrons with an efficiency comparable with ubiquinone-2. The catalytic reduction and proton translocation coupled with this reduction were completely inhibited by different quinone-site inhibitors, indicating that the reduction of OS-UQs takes place at the physiological reaction site for ubiquinone. Notably, the proton-translocating efficiencies of OS-UQs significantly varied depending on their side-chain structures, suggesting that the reaction characteristics of OS-UQs affect the predicted structural changes of the quinone reaction site required for triggering proton translocation. These results are difficult to reconcile with the current channel model; rather, the access path for ubiquinone may be open to allow OS-UQs to access the reaction site. Nevertheless, contrary to the observations in SMPs, OS-UQs were not catalytically reduced by isolated complex I reconstituted into liposomes. We discuss possible reasons for these contradictory results.

Exploring the quinone/inhibitor-binding pocket in mitochondrial respiratory complex I by chemical biology approaches

NADH-quinone oxidoreductase (respiratory complex I) couples NADH-to-quinone electron transfer to the translocation of protons across the membrane. Even though the architecture of the quinone-access channel in the enzyme has been modeled by X-ray crystallography and cryo-EM, conflicting findings raise the question whether the models fully reflect physiologically relevant states present throughout the catalytic cycle. To gain further insights into the structural features of the binding pocket for quinone/inhibitor, we performed chemical biology experiments using bovine heart sub-mitochondrial particles. We synthesized ubiquinones that are oversized (SF-UQs) or lipid-like (PC-UQs) and are highly unlikely to enter and transit the predicted narrow channel. We found that SF-UQs and PC-UQs can be catalytically reduced by complex I, albeit only at moderate or low rates. Moreover, quinone-site inhibitors completely blocked the catalytic reduction and the membrane potential formation coupled to this reduction. Photoaffinity-labeling experiments revealed that amiloride-type inhibitors bind to the interfacial domain of multiple core subunits (49 kDa, ND1, and PSST) and the 39-kDa supernumerary subunit, although the latter does not make up the channel cavity in the current models. The binding of amilorides to the multiple target subunits was remarkably suppressed by other quinone-site inhibitors and SF-UQs. Taken together, the present results are difficult to reconcile with the current channel models. On the basis of comprehensive interpretations of the present results and of previous findings, we discuss the physiological relevance of these models.

Photoaffinity Labeling of Respiratory Complex I in Bovine Heart Submitochondrial Particles by Photoreactive [125I] amilorides.

The architecture of quinone/inhibitor-access channel in proton-translocating NADH-quinone oxidoreductase (respiratory complex I) was modeled by X-ray crystallography and cryo-EM, however, it remains debatable whether the channel model reflects the physiologically relevant state present throughout the catalytic cycle. Using photoreactive [125I]amilorides, we demonstrated that amiloride-type inhibitors bind to the interfacial region of multiple subunits (49-kDa, ND1, PSST, and 39-kDa subunits), which is difficult to reconcile with the current channel model. This report describes the procedures for photoaffinity labeling of bovine submitochondrial particles by photoreactive [125I]amilorides. The protocol could be widely applicable for the characterization of various biologically active compounds, whose target protein remains to be identified or characterized.

The Federal Communications Commission

Previous articleNext article No AccessThe Federal Communications CommissionR. H. CoaseR. H. CoaseUniversity of Virginia Search for more articles by this author University of VirginiaPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Journal of Law and Economics Volume 56, Number 4November 2013 Sponsored by The University of Chicago Booth School of Business and The University of Chicago Law School Article DOIhttps://doi.org/10.1086/674871 Views: 695Total views on this site Citations: 13Citations are reported from Crossref © 1959 by The University of Chicago. All rights reservedPDF download Crossref reports the following articles citing this article:Shunfu Jin, Wuyi Yue Spectrum Reservation Strategy with Retrial Feedback and Perfect-Sensing Results, (Mar 2021): 187–208.https://doi.org/10.1007/978-981-15-7756-7_10Colin Harris, Meina Cai, Ilia Murtazashvili, Jennifer Murtazashvili The Origins and Consequences of Property Rights, 6 (Nov 2020).https://doi.org/10.1017/9781108979122Glenn Furton, Adam Martin Beyond market failure and government failure, Public Choice 178, no.1-21-2 (Oct 2018): 197–216.https://doi.org/10.1007/s11127-018-0623-4Patrick Gourley Farmer Brown v. Rancher Wyatt: Teaching the Coase Theorem, The Journal of Economic Education 49, no.22 (Mar 2018): 194–199.https://doi.org/10.1080/00220485.2018.1438864Glenn Furton, Adam G. Martin Beyond Market Failure and Government Failure, SSRN Electronic Journal (Jan 2018).https://doi.org/10.2139/ssrn.3201195G. Martino, J. Tóth, A. Frascarelli 14. Concepts in European policy intervention and food exchange: a Delphi approach, (Dec 2017): 263–281.https://doi.org/10.3920/978-90-8686-844-5_14Mahfuza Khatun, Hani Mehrpouyan, David Matolak, Ismail Guvenc Millimeter wave systems for airports and short-range aviation communications: A survey of the current channel models at mmWave frequencies, (Sep 2017): 1–8.https://doi.org/10.1109/DASC.2017.8102042Vidya Muthukumar, Anant Sahai Fundamental Limits on Ex-Post Enforcement and Implications for Spectrum Rights, IEEE Transactions on Cognitive Communications and Networking 3, no.33 (Sep 2017): 491–504.https://doi.org/10.1109/TCCN.2017.2747579Liya Palagashvili, Ennio Piano, David Skarbek The Decline and Rise of Institutions, 27 (Aug 2017).https://doi.org/10.1017/9781108186179Vidya Muthukumar, Anant Sahai Fundamental limits on ex-post enforcement and implications for spectrum rights, (Mar 2017): 1–10.https://doi.org/10.1109/DySPAN.2017.7920755Winston J. Maxwell References, (Jan 2017).https://doi.org/10.4000/books.pressesmines.3708Nahid Aslanbeigui, Guy Oakes On Coaseana: Critique of a Political Economy, OEconomia , no.5-35-3 (Sep 2015): 271–293.https://doi.org/10.4000/oeconomia.2085Clotilde Champeyrache The Assumption of Law Neutrality: Property Rights Theory Versus Legal-Economic Nexus, OEconomia , no.3-33-3 (Sep 2013): 391–419.https://doi.org/10.4000/oeconomia.171

Outdoor to indoor channel characteristics on two different floors

AbstractRecently the fusion of positioning and wireless communication has gained many interests due to the merits of location information for future communication systems. Both positioning and wireless communication are highly dependent on the air channel. Current channel models are well suited for communication applications but less for positioning. Therefore, we investigate and compare the channel characteristics of different floors in favour of positioning based on an outdoor to indoor broadband channel sounder measurement campaign. Power delay profiles on both floors show similar structure caused by outdoor wave propagation, and angle of arrivals mostly arrive from the same direction. Differences can be seen in the RMS delay spread, power, NLoS error and coherence characteristics. Copyright © 2010 John Wiley & Sons, Ltd.