MIMO capacity for deterministic channel models: sublinear growth

This is the second paper of the authors in a series concerned with the development of a deterministic model for the transfer matrix of a MIMO system. Starting from the Maxwell equations, we have described in \cite{BCFM} the generic structure of such a deterministic transfer matrix. In the current paper we apply the results of \cite{BCFM} in order to study the (Shannon-Foschini) capacity behavior of a MIMO system as a function of the deterministic spread function of the environment, and the number of transmitting and receiving antennas. The antennas are assumed to fill in a given, fixed volume. Under some generic assumptions, we prove that the capacity grows much more slowly than linearly with the number of antennas. These results reinforce previous heuristic results obtained from statistical models of the transfer matrix, which also predict a sublinear behavior.Comment: 12 pages, to appear in Math. Meth. Appl. Sc

Structure and function of fusion pores in exocytosis and ectoplasmic membrane fusion.

Several proteins involved in exocytosis have been identified recently, but it is still completely unclear which molecules perform the fusion event itself. Although in viral fusion the fusion proteins are known, even there the molecular mechanism remains controversial. Investigation of single fusion events by electrophysiological techniques together with fluorimetric measurements have now provided some insight into the properties of the first aqueous connection, the fusion pore. This pore has an initial size similar to an ion channel and allows movement of lipids only after it has substantially expanded, indicating that it is initially not a purely lipidic structure, but incorporates lipids when it expands. Although neurotransmitter release may occur through narrow transient fusion pores, the fusion pore of synaptic vesicles probably expands vey rapidly, making it unlikely that secretion is performed by rapid exo/endocytosis without full fusion under normal conditions. Recent recordings from small membrane patches have made it possible to resolve fusion events from vesicles as small as synaptic vesicles. Future experiments using excised patches may provide an approach to identify the molecular machinery of exocytotic membrane fusion

On the transfer matrix of a MIMO system

We develop a deterministic ab-initio model for the input-output relationship of a multiple-input multiple-output (MIMO) wireless channel, starting from the Maxwell equations combined with Ohm's Law. The main technical tools are scattering and geometric perturbation theories. The derived relationship can lead us to a deep understanding of how the propagation conditions and the coupling effects between the elements of multiple-element arrays affect the properties of a MIMO channel, e.g. its capacity and its number of degrees of freedom.Comment: Accepted for publication in Mathematical Methods in the Applied Science

Addition of biochar to a Swedish sandy soil : effects on nitrous gas emissions, nitrogen retention and water saturation

In a column experiment the effect of three different biochars on nitrous gas emissions, nitrogen retention and water filled pore space (WFPS) were studied in a Swedish sandy soil, classified as a Cryopsamment. Ammonium retention was positively correlated, while KCl-extractable ammonium was negatively correlated, with the specific area of the biochars. The question was raised whether the negative correlation between extractable ammonium and biochar specific area reflects the amount of ammonium present in the soil or its extractability from the biochar, and whether methods for extracting soil mineral nitrogen, like KCl-extractions, have to be modified for application on biochar amended soils. There was a tendency of increased nitrate retention and KCl-extractable nitrate with biochar and KCl-extractable nitrate was positively correlated with the specific area of the biochar. pH was higher for all biochars compared with control, although the differences were not significant, and WFPS was lowered by biochar addition, significantly in one case. Nitrous oxide emissions were generelly lower from biochar amended columns, although emissions from one of the biochars was higher than control in the beginning of the measurements. The effect on nitrous oxide emissions seem, in part, to be mediated by the increase in pH from the biochar addition. Among other factors, nitrous oxide emissions was also negatively correlated with the specific area of the biochar.I ett kolonnförsök studerades effekten av tre sorters biokol på lustgasavgång, kväveretention och andel vattenfyllda porer (WFPS) i en svensk sandjord (klassificerad som Cryopsamment). Ammoniumretentionen var positivt korrelerad med kolets specifika yta, medan KCl-extraherbart ammonium var negativt korrelerad med kolets specifika yta. Det diskuterades huruvida den negativa korrelationen med kolets specifika yta berodde på mängden ammonium i jorden eller dess extraherbarhet och om metoder för att mäta markkväve behöver modifieras för att ge en rättvisande bild på biokolberikade jordar. Det fanns en tendens till ökad nitratretention och mängd KClextraherbart nitrat med biokol och KCl-extraherbart nitrat var positivt korrelerat med den specifika ytan på kolet. pH var högre med alla kolsorter jämfört med kontrollbehandlingen, även om skillnaderna inte var signifikanta, och WFPS minskades av tillsatt biokol, signifikant i ett av fallen. Lustgasavgången var generellt sett lägre från de biokolberikade kolonnerna, men från en av kolsorterna var avgången högre i början av lustgasmätningarna. Effekten på lustgasavgången verkar delvis orsakas av biokolets pH-höjande effekt. Bland andra faktorer korrelerade med lustgasavgången fanns kolets specifika yta som var negativt korrelerad med lustgasavgången

Climate impacts of land use in LCA

INTRODUCTION LCA is a widely used tool for assessing the environmental impacts of products. However, despite the large importance of land use for atmospheric CO2-levels there is still no consensus on how to include the climate impact of land use in LCA and results vary up to several hundred percent depending on method. The purpose of this thesis is to contribute to a formation of consensus about how to handle the climate impact of land use in LCA by suggesting criteria for satisfactory methods to do this. The criteria are meant to limit the number of alternative methods and the variation in results. METHOD The criteria are elaborated through theoretical reasoning that takes its points of departure in the definitions of essential terms and in assumptions of desired properties for LCA such as internal consistency, comprehensiveness (the property of being all-inclusive) and comprehensibility (the property of being easy to understand). RESULTS The analysis resulted in 11 criteria. One effect of the criteria is that when one makes assumptions of land use changes and use GWPs to aggregate emissions, then the impact of the change should be distributed over all the services that are derived during the new use up to the GWP time horizon. Other criteria concern the need to consider e.g. albedo, aerosol formation and impacts on the ability of the used land to provide services. Yet other criteria is about that an LCA should enable readers to understand the potential trade-offs between short and long term climate impacts. DISCUSSION The criteria may be used to evaluate and improve suggested methods, as guidance in design of new methods and to point out research and development needs (e.g. concerning the inclusion of normally ignored climate forcers such as albedo and aerosol formation). Many used and suggested methods are inconsistent and adjustments according to the suggested criteria are likely to decrease the variation in results between methods. There is a need to evaluate the reliability of previous LCA studies and there could be a need to reconsider conclusions based on LCA that do not include climate impacts of land use in a satisfactory way. There is also a need to refine the suggested criteria and/or elaborate more specific standards for specific contexts.INLEDNING Livscykelanalyser (LCA) är analyser för att uppskatta miljöpåverkan av produkter. Trots att markanvändning har en stor påverkan på klimatet finns det fortfarande ingen konsensus kring hur markanvändning ska hanteras i LCA och variationen i resultat kan variera flera hundra procent beroende på metod. Syftet med den här uppsatsen är att bidra till skapandet av konsensus kring hur markanvändning ska hanteras i LCA. Detta genom att föreslå kriterier för tillfredsställande metoder. Kriterierna är menade att begränsa både variationen i resultat beroende på val av metod och antalet alternativa metoder som används. METOD Kriterierna tas fram genom ett teoretiskt resonerande som tar sin utgångspunkt i definitionerna av centrala begrepp och i önskade egenskaper för LCA, som internt konsekventa antaganden, att de tar allt vikitgt i beaktande och att de är lätta att förstå. RESULTAT Analysen resulterade i 11 kriterier. En effekt av kriterierna är att när man gör antaganden om förändrad markanvändning och använder växthusgasernas GWP (vilka bygger på antaganden om permanenta pulsutsläpp) för att sammanväga växthusgasutsläppen i analysen, så måste utsläppen fördelas över alla produkter som erhålls från den nya markanvändningen fram till den tidshorisonten som GWP är definierad över. Andra kriterier berör behovet av att inkludera påverkan på t ex albedo, aerosoler och påverkan på markens bördighet. Ytterligare andra kriterier ställer krav på att en LCA ska möjliggöra för läsaren att föstå eventuella trade-offs mellan klimatpåverkan på kort och lång sikt. DISKUSSION Kriterierna kan användas för att utvärdera och förbättra föreslagna metoder, som guide i design av nya metoder och för att peka ut behov av forskning och utveckling (t ex vad gäller inkluderandet av faktorer som albedo och aerosoler). Många använda och föreslagna metoder är inkonsekventa och justeringar enligt kriterierna skulle sannolikt minska variationen i resultat beroende på metod. Det finns ett behov av att utvärdera tillförlitligheten i tidigare genomförda LCAer och man kan komma att behöva ompröva vissa slutsatser som är baserade på LCA som inte hanterat klimatpåverkan av markanvändning på ett tillfredsställande sätt. Det finns också ett behov av att utveckla kriterierna och/eller utveckla mer specifika standarder för specifika sammanhang som komplement till de här föreslagna generella kriterierna för tillfredsställande metoder för att hantera klimatpåverkan av markanvändning i LCA

The effect of receiver antenna array horizontal orientation on MIMO channel capacity

In multiple-input multiple-output (MIMO) systems the horizontal orientation of a linear array has, in some situations a large influence on the available channel capacity. In this paper, we investigate the effect of horizontal array orientation on channel capacity, eigenvalue distribution and antenna complex correlation coefficient in such systems. We present channel measurements in an office corridor environment for a 6/spl times/6 MIMO system and compare the capacity results to those of a physical and non-physical model based on the measurements. The results show that under LOS conditions the channel capacity can vary significantly depending on the receiver array orientation in the horizontal plane

UWB channel measurements in an industrial environment

In this paper, we present the (to our knowledge) first measurement results for ultra-wideband channels in industrial environments, i.e., a factory hall. The measurements are done with virtual arrays, which allows analysis of the small-scale fading statistics, as well as a directional analysis. We find that there is dense multipath scattering due to the abundance of metallic scatterers in the considered environment. Multiple scatterer clusters can be identified both in the delay and the angular domain. Typical rms delay spreads lie between 30 ns for LOS scenarios and 40 ns for NLOS scenarios. For non-LOS scenarios at large distances, the maximum of the power delay profile is observed some 40 ns after the arrival of the first multipath components. We also draw conclusions about the behavior of typical UWB system designs in the measured channel

Statistical analysis of the UWB channel in an industrial environment

In this paper, we present a statistical model for the ultra-wideband (UWB) channel in an industrial environment. Based on a set of measurements in a factory hall, we find that the abundance of metallic scatterers causes dense multipath scattering. This can be seen to produce mostly a Rayleigh distributed small-scale fading signal, with only a few paths exhibiting Nakagami distributions. For the power delay profile, we suggest a generalization of the Saleh-Valenzuela model where clusters with different excess delays have different ray power decay constants; the decay constants follow a linear dependence on the delay. This model provides an excellent fit to the measured data. We also note that for non-line-of-sight scenarios at larger distances, several hundred multipath components need to be collected to capture 50% of the available energ