Polynomial matrix decomposition techniques for frequency selective MIMO channels

For a narrowband, instantaneous mixing multi-input, multi-output (MIMO) communications system, the channel is represented as a scalar matrix. In this scenario, singular value decomposition (SVD) provides a number of independent spatial subchannels which can be used to enhance data rates or to increase diversity. Alternatively, a QR decomposition can be used to reduce the MIMO channel equalization problem to a set of single channel equalization problems. In the case of a frequency selective MIMO system, the multipath channel is represented as a polynomial matrix. Thus conventional matrix decomposition techniques can no longer be applied. The traditional solution to this broadband problem is to reduce it to narrowband form by using a discrete Fourier transform (DFT) to split the broadband channel into N narrow uniformly spaced frequency bands and applying scalar decomposition techniques within each band. This describes an orthogonal frequency division multiplexing (OFDM) based system. However, a novel algorithm has been developed for calculating the eigenvalue decomposition of a para-Hermitian polynomial matrix, known as the sequential best rotation (SBR2) algorithm. SBR2 and its QR based derivatives allow a true polynomial singular value and QR decomposition to be formulated. The application of these algorithms within frequency selective MIMO systems results in a fundamentally new approach to exploiting spatial diversity. Polynomial matrix decomposition and OFDM based solutions are compared for a wide variety of broadband MIMO communication systems. SVD is used to create a robust, high gain communications channel for ultra low signal-to-noise ratio (SNR) environments. Due to the frequency selective nature of the channels produced by polynomial matrix decomposition, additional processing is required at the receiver resulting in two distinct equalization techniques based around turbo and Viterbi equalization. The proposed approach is found to provide identical performance to that of an existing OFDM scheme while supporting a wider range of access schemes. This work is then extended to QR decomposition based communications systems, where the proposed polynomial approach is found to not only provide superior bit-error-rate (BER) performance but significantly reduce the complexity of transmitter design. Finally both techniques are combined to create a nulti-user MIMO system that provides superior BER performance over an OFDM based scheme. Throughout the work the robustness of the proposed scheme to channel state information (CSI) error is considered, resulting in a rigorous demonstration of the capabilities of the polynomial approach

Remagnetization and magnetization dynamics in complex magnetic textures, from antidots lattice to nanodots

Wydział FizykiLokalne zaburzenie uporządkowania magnetycznego, które może rozprzestrzeniać się w postaci fali w materiale magnetycznym, zostało przewidziane przez Blocha w 1929 roku i nazwane falą spinową. Periodycznie strukturyzowane układy magnoniczne są sztucznymi ośrodkami o okresowo modulowanych właściwościach magnetycznych, zwane kryształami magnonicznymi. W takich strukturach można znaleźć skomplikowane tekstury magnetyczne takie jak domeny magnetyczne, worteksy czy skyrmiony. Skyrmion jest kwazicząsteczką, charakteryzującą się tzw. ładunkiem topologicznym, będącą możliwie najmniejszym i jednocześnie stabilnym zakłóceniem jednorodnego namagnesowania. W ramach pracy doktorskiej autor zaprezentował pięć publikacji naukowych zawierających wyniki badań: procesów przemagnesowania, rezonansu ferromagnetycznego, propagacji fal spinowych w strukturalizowanych materiałach ferromagnetycznych; stabilizacji skyrmionów w nanokropkach magnetycznych w których możliwe jest istnienie dwóch stanów skyrmionowych (skyrmionu o małej i dużej średnicy) o zbliżonych poziomach energetycznych; badania możliwości formowania skyrmionów w sieci kwadratowej dziur w trakcie procesu przemagnesowania; badania sieci dziur w wielowarstwach ferromagnetycznych z prostopadłą anizotropią, w których zaobserwowano skomplikowaną teksturę magnetyczną. W ostatnim rozdziale doktoratu autor zaprezentował podsumowanie, plany badawcze oraz krótkie zestawienie innych osiągnięć naukowych.Bloch predicted a disturbance in the local magnetic order which can propagate in a magnetic material in a form of wave in 1929. It named as a spin wave since it is related to a collective excitation of the spins in ferromagnetic media. Magnonic crystals are artificial magnetic media with periodically modulated magnetic properties in space, well known as a structure where spin waves band structure consists of intervals of allowed bands of spin-wave frequencies and forbidden band gaps, making them structures with interesting properties. Magnetic skyrmions are solitonic magnetisation textures, whose stability is protected by their topology. In this thesis, the author presents the results of studying the static and dynamic properties of the complex ferromagnetic structures and unique skyrmion properties. The author studied magnetisation textures in patterned thin films during the remagnetisation process. In the next step, he studied the ferromagnetic resonance and characteristic of propagating spin-waves in the same structures. Then, he started investigations of skyrmion stabilisation in nanodisc and skyrmion nucleation process in antidot lattice during the remagnetisation process. Finally, he analysed the complex magnetic textures in patterned multilayers with perpendicular magnetic anisotropy and Dzyaloshinskii-Moriya interaction.Various parts of the presented thesis were supported by the Polish National Science Centre (NCN), Ministry of Science and Higher Education (MNiSW), and European Union Horizon 2020 and other: 1. NCN PRELUDIUM 14, Grant No. 2018/31/N/ST7/03918 (PI), 2. NCN SONATA BIS 2 (2013-2018), Grant No. 2012/07/ST3/00538. 3. EU Horizon 2020 project MagIC Grant No. 644348, 4. Scholarship founded by Adam Mickiewicz University Foundation, 5. Scholarship founded by dr Jan Kulczyk Foundation, 6. OPUS11 (2017-2019), Grant No. 2016/21/B/ST3/00452, 7. OPUS9 (2016-2019), Grant No. 2015/17/B/ST3/00118, 8. "Premia na Horyzoncie" - MNiSW Grant No. 328712/PnH/2016, 9. National Scholarship Program of the Slovak Republic funded by the Ministry of Education, Science, Research, and Sport of the Slovak Republic (two scholarships in 2016/2017 and 2017/2018), 10. The simulations were partially performed at the Poznan Supercomputing and Networking Center (Grant No. 398)

Current Topics in Gastritis

Gastritis, as a medical term, exists for the last 150 years, however, terminology and etiology (including the prognosis ) has changed. Gastritis related medical problems are in the focus of different sub-disciplines: internists , gastroenterologists, pathologists, immunologists, bacteriologists, genetics, biologists etc. After the publications by Marshall and Warren most of the clinicians accepted only the etiopathological role of Helicobacter pylori in the development of gastric and duodenal ulcer , as well as in the gastric cancer. This book presents chapters abou the history of gastritis terminology, animal models, epidemiology, new gastric mucosal endogenous defensive neural mechanism (capsaicin-sinsitive afferentation), different research and clinical methods applied to the background studies and the molecular pathology, biochemistry and genetics involved in the pathways from Helicobacter pylori infection to development of gastric cancer. Intended audience of this book are internists, gastroenterologists, pathologists, bacteriologists, pharmacologists, genetics, biologists , immunologists and other interested researchers

Targeting tumor microenvironment crosstalk through GPCR receptors and PI3K pathway

[eng] The tumor microenvironment (TME) is gaining momentum due to its contribution to cancer progression and therapy resistance. This TME has a direct crosstalk with tumor cells that involves the activation of different pathways. Follicular lymphoma (FL) is the most common indolent non-Hodgkin lymphoma. Although FL is generally characterized by slow progression and high response rates to therapy, it is still considered incurable, because almost virtually all the patients relapse. FL is probably the NHL with the highest dependence on microenvironment. PI3K is a common denominator transducing the signaling from FL crosstalk with the TME and plays an important role in multiple cellular functions, and also contributes to cancer promoting aspects of the TME, such as angiogenesis and inflammatory cell recruitment. Idelalisib is a first-in-class δ isoform- specific PI3K inhibitor that receive regulatory approval for relapsed CLL, SLL and FL in 2014. Idelalisib blocks PI3K δ which is restricted to leukocytes. BCL2 deregulation is paramount in the pathogenesis of FL, as a consequence of the t(14;18), and therefore it is an attractive target for novel therapeutic approaches. Venetoclax (ABT-199, AbbVie) is a small BCL-2 inhibitors. Even though 85% of FL patients harbor the t(14;18), the results of the first clinical trial with venetoclax were not satisfactory (overall response 38%). From this first study we conclude that Idelalisib modulates key pathways in the germinal center and shapes the FL immune microenvironment by decreasing the recruitment of TFH and Treg to the tumor site leading to less immunesuppresive phenotype. Furthermore Idelalisib induces a moderate cytotoxic effect on FL cells in co-cultures. This co-culture decrease FL dependence on BCL-2 and consequently, venetoclax cytotoxicity, but Idelalisib sensitizes FL co-cultures to venetoclax. In summary, Idelalisib interferes with the crosstalk of FL and its immune microenvironment and potentiates the activity of venetoclax targeting the tumor cells, thus representing a promising combination therapy that may improve FL outcome. Colorectal cancer (CRC) is the third most common cancer in males and the second in females, and the fourth most common cause of cancer-related death worldwide. Patients with advanced and distal metastatic disease (stage IV), the survival rate drops to 10%, which accounts for approximately 18% of cases. The TME in CRC, is a complex structure composed by different type of cells, which are interacting each other’s and secreting a variety of growth factors and other molecules, such as cytokines and chemokines. Tumor development is based on the crosstalk between tumor cells and their surrounding microenvironment, and this crosstalk is mediated by the receptors and its ligand expression in both types of cells. G protein-coupled receptors (GPCRs) are an important family of membrane signaling receptors, which have an important role in cancer growth and development. Originally, GPCRs were considered as monomeric functional entities, nevertheless, in recent years has become evident that GPCRs form dimers and this dimers formation may modify the cellular response. In cancer, CXCR4 (has been studied extensively) plays an important role at different stages of cancer development, and is involved in the metastasis process of tumor cells. The up- regulation of CXCR4 in CRC correlates with a poor prognosis. Another GPCR, CB2 receptor modulates the downstream signaling and it is able to activate a wide range of signaling pathways, including extracellular signal-regulated kinases 1/2 (ERK1/2). In CRC, it has been described an up-regulation of CB2 receptor expression. GPCRs show differential expression in cancer cells and tissues, and they are highly druggable sites. From this second study we concluded that CXCR4 and CB2 expression is increased in primary colon tumor cells and in metastasis cells compared to normal epithelial cells from colon mucosa, and they formed heterodimers in colon tumoral cells and are associated with more aggressive phenotypes. Moreover, a bidirectional cross-antagonism crosstalk is established between these receptors. These heterodimers regulate in vitro CXCL12-induced migration, and in vivo, the simultaneous inhibition of both receptors shows superior anti-tumoral and anti-metastatic activities than the single agent inhibition. In summary, targeting the heterodimerization of CXCR4 and CB2 that are biologically relevant in cancer can be an effective way to reduce proliferation and dissemination in CRC.[spa] El estudio del microambiente tumoral está ganando importancia en las últimas décadas debido a su contribución en la formación y desarrollo del cáncer, además de contribuir en la resistencia de las células tumorales a diferentes terapias. Este microambiente interactúa con las células tumorales y activa diferentes vías. El linfoma folicular (FL), es el linfoma no Hodgkin indolente más común y con mayor dependencia del microambiente tumoral, además es considerado incurable. PI3K desempeña un papel importante en la comunicación con el microambiente, y es importante en múltiples funciones celulares, además de contribuir en la angiogénesis, reclutamiento de células inflamatorias y promover el crecimiento tumoral. Idelalisib es un inhibidor de PI3K (específicamente de la isoforma δ), que se aprobó en 2014 por la FDA. Paralelamente la desregulación de BCL2 es primordial en la patogénesis de FL, como consecuencia de la t (14; 18), presente en un 85% de los pacientes, y por lo tanto es un objetivo atractivo para novedosos enfoques terapéuticos. Venetoclax (ABT-199, AbbVie) es un pequeño inhibidor de BCL2, que mostró unos resultados del primer ensayo clínico no satisfactorios (respuesta global del 38%). De este primer estudio concluimos que Idelalisib interfiere en la comunicación de FL y su microambiente inmune, además potencia la actividad de venetoclax atacando a las células tumorales, lo que representa una terapia de combinación prometedora que puede mejorar el resultado del tratamiento de FL