MIMO-OFDM communication systems: channel estimation and wireless location

In this new information age, high data rate and strong reliability features our wireless communication systems and is becoming the dominant factor for a successful deployment of commercial networks. MIMO-OFDM (multiple input multiple output-orthogonal frequency division multiplexing), a new wireless broadband technology, has gained great popularity for its capability of high rate transmission and its robustness against multi-path fading and other channel impairments. A major challenge to MIMO-OFDM systems is how to obtain the channel state information accurately and promptly for coherent detection of information symbols and channel synchronization. In the first part, this dissertation formulates the channel estimation problem for MIMO-OFDM systems and proposes a pilot-tone based estimation algorithm. A complex equivalent base-band MIMO-OFDM signal model is presented by matrix representation. By choosing equally-spaced and equally-powered pilot tones from sub-carriers in one OFDM symbol, a down-sampled version of the original signal model is obtained. Furthermore, this signal model is transformed into a linear form solvable for the LS (least-square) estimation algorithm. Based on the resultant model, a simple pilot-tone design is proposed in the form of a unitary matrix, whose rows stand for different pilot-tone sets in the frequency domain and whose columns represent distinct transmit antennas in the spatial domain. From the analysis and synthesis of the pilot-tone design in this dissertation, our estimation algorithm can reduce the computational complexity inherited in MIMO systems by the fact that the pilot-tone matrix is essentially a unitary matrix, and is proven an optimal channel estimator in the sense of achieving the minimum MSE (mean squared error) of channel estimation for a fixed power of pilot tones. In the second part, this dissertation addresses the wireless location problem in WiMax (worldwide interoperability for microwave access) networks, which is mainly based on the MIMO-OFDM technology. From the measurement data of TDOA (time difference of arrival), AOA (angle of arrival) or a combination of those two, a quasi-linear form is formulated for an LS-type solution. It is assumed that the observation data is corrupted by a zero-mean AWGN (additive white Gaussian noise) with a very small variance. Under this assumption, the noise term in the quasi-liner form is proved to hold a normal distribution approximately. Hence the ML (maximum-likelihood) estimation and the LS-type solution are equivalent. But the ML estimation technique is not feasible here due to its computational complexity and the possible nonexistence of the optimal solution. Our proposed method is capable of estimating the MS location very accurately with a much less amount of computations. A final result of the MS (mobile station) location estimation, however, cannot be obtained directly from the LS-type solution without bringing in another independent constraint. To solve this problem, the Lagrange multiplier is explored to find the optimal solution to the constrained LS-type optimization problem

Simulation study and instability of adaptive control

The Minimum-degree Pole Placement algorithm for Self-tuning Regulator design and the Recursive Least-square method and the projection algorithm for plant estimation are studied first in this thesis. Simulation studies for the estimator and controller algorithms are mainly undertaken after describing how to use MATLAB S-function in detail. Not only do Simulation experiments illustrates how and how well the MDPP and RLS algorithms work, but also show how to write and debug MATLAB codes for S-function programs. The robustness of the adaptive control system is intensively discussed subsequently. By using an estimator resistant to the noise contamination, the adaptive control system can not be destablized by the introduced noise at the input of the plant or the estimator. However, the adaptive control system is subject to the unmodeled dynamics that have a magnitude response like an impulse at the crossover frequency of the system. Simulation results also show that a classic feedback controller has a better performance, compared with the adaptive controller

Wear properties of potassium titanate whiskers-reinforced Al-12Si alloy composites

Potassium titanate (K2O·6TiO2) whiskers-reinforced Al-12Si alloy composites were prepared by the squeeze casting technique. Wear properties of the composites were investigated by pin-on-disc tests under dry conditions. The experimental results showed that K2O·6TiO2 whiskers can effectively reinforce the matrix alloy and improve the wear resistance of the composite when the volume fraction of whiskers is low at 10 vol%. However, the composites with a high volume fraction of whiskers showed lower wear resistance than the Al-12Si alloy. The main wear mechanism of the composites is clarified as de-lamination and abrasive wear

Genomic characterization of putative allergen genes in peach/almond and their synteny with apple

<p>Abstract</p> <p>Background</p> <p>Fruits from several species of the Rosaceae family are reported to cause allergic reactions in certain populations. The allergens identified belong to mainly four protein families: pathogenesis related 10 proteins, thaumatin-like proteins, lipid transfer proteins and profilins. These families of putative allergen genes in apple (<it>Mal d 1 </it>to <it>4</it>) have been mapped on linkage maps and subsequent genetic study on allelic diversity and hypoallergenic traits has been carried out recently. In peach (<it>Prunus persica</it>), these allergen gene families are denoted as <it>Pru p 1 </it>to <it>4 </it>and for almond (<it>Prunus dulcis</it>)<it>Pru du 1 </it>to <it>4</it>. Genetic analysis using current molecular tools may be helpful to establish the cause of allergenicity differences observed among different peach cultivars. This study was to characterize putative peach allergen genes for their genomic sequences and linkage map positions, and to compare them with previously characterized homologous genes in apple (<it>Malus domestica</it>).</p> <p>Results</p> <p>Eight <it>Pru p/du 1 </it>genes were identified, four of which were new. All the <it>Pru p/du 1 </it>genes were mapped in a single bin on the top of linkage group 1 (G1). Five <it>Pru p/du 2 </it>genes were mapped on four different linkage groups, two very similar <it>Pru p/du 2.01 </it>genes (<it>A </it>and <it>B</it>) were on G3, <it>Pru p/du 2.02 </it>on G7,<it>Pru p/du 2.03 </it>on G8 and <it>Pru p/du 2.04 </it>on G1. There were differences in the intron and exon structure in these <it>Pru p/du 2 </it>genes and in their amino acid composition. Three <it>Pru p/du 3 </it>genes (3.01–3.03) containing an intron and a mini exon of 10 nt were mapped in a cluster on G6. Two <it>Pru p/du 4 </it>genes (<it>Pru p/du 4.01 </it>and <it>4.02</it>) were located on G1 and G7, respectively. The <it>Pru p/du 1 </it>cluster on G1 aligned to the <it>Mal d 1 </it>clusters on LG16; <it>Pru p/du 2.01A </it>and <it>B </it>on G3 to <it>Mal d 2.01A </it>and <it>B </it>on LG9; the <it>Pru p/du 3 </it>cluster on G6 to <it>Mal d 3.01 </it>on LG12; <it>Pru p/du 4.01 </it>on G1 to <it>Mal d 4.03 </it>on LG2; and <it>Pru p/du 4.02 </it>on G7 to <it>Mal d 4.02 </it>on LG2.</p> <p>Conclusion</p> <p>A total of 18 putative peach/almond allergen genes have been mapped on five linkage groups. Their positions confirm the high macro-synteny between peach/almond and apple. The insight gained will help to identify key genes causing differences in allergenicity among different cultivars of peach and other <it>Prunus </it>species.</p

Increased Sestrin3 Contributes to Post-ischemic Seizures in the Diabetic Condition

Seizures are among the most common neurological sequelae of stroke, and diabetes notably increases the incidence of post-ischemic seizures. Recent studies have indicated that Sestrin3 (SESN3) is a regulator of a proconvulsant gene network in human epileptic hippocampus. But the association of SESN3 and post-ischemic seizures in diabetes remains unclear. The present study aimed to reveal the involvement of SESN3 in seizures following transient cerebral ischemia in diabetes. Diabetes was induced in adult male mice and rats via intraperitoneal injection of streptozotocin (STZ). Forebrain ischemia (15 min) was induced by bilateral common carotid artery occlusion, the 2-vessel occlusion (2VO) in mice and 4-vessel occlusion (4VO) in rats. Our results showed that 59% of the diabetic wild-type mice developed seizures after ischemia while no seizures were observed in non-diabetic mice. Although no apparent cell death was detected in the hippocampus of seizure mice within 24 h after the ischemic insult, the expression of SESN3 was significantly increased in seizure diabetic mice after ischemia. The post-ischemic seizure incidence significantly decreased in SESN3 knockout mice. Furthermore, all diabetic rats suffered from post-ischemic seizures and non-diabetic rats have no seizures. Electrophysiological recording showed an increased excitatory synaptic transmission and intrinsic membrane excitability in dentate granule cells of the rat hippocampus, together with decreased IA currents and Kv4.2 expression levels. The above results suggest that SESN3 up-regulation may contribute to neuronal hyperexcitability and seizure generation in diabetic animals after ischemia. Further studies are needed to explore the molecular mechanism of SESN3 in seizure generation after ischemia in diabetic conditions

Serological analysis of allergic components of house dust mite provides more insight in epidemiological characteristics and clinical symptom development in North China

BackgroundHouse dust mite (HDM) is the most common airborne source causing complex allergy symptoms. There are geographic differences in the allergen molecule sensitization profiles. Serological testing with allergen components may provide more clues for diagnosis and clinical management.ObjectiveThis study aims to investigate the sensitization profile of eight HDM allergen components in a large number of patients enrolled in the clinic and to analyze the relation of gender, age, and clinical symptoms in North China.MethodsThe 548 serum samples of HDM-allergic patients (ImmunoCAP® d1 or d2 IgE ≥0.35) were collected in Beijing City and divided in four different age groups and three allergic symptoms. The specific IgE of HDM allergenic components, Der p 1/Der f 1, Der p 2/Der f 2, Der p 7, Der p 10, Der p 21, and Der p 23, was measured using the micro-arrayed allergen test kit developed by Hangzhou Zheda Dixun Biological Gene Engineering Co., Ltd. The new system was validated by comparing to single-component Der p 1, Der p 2, and Der p 23 tests by ImmunoCAP in 39 sera. The epidemiological study of these IgE profiles and the relation to age and clinical phenotypes were analyzed.ResultsA greater proportion of male patients was in the younger age groups, while more female patients were in the adult groups. Both the sIgE levels and the positive rates (approximately 60%) against Der p 1/Der f 1 and Der p 2/Der f 2 were higher than for the Der p 7, Der p 10, and Der p 21 components (below 25%). The Der f 1 and Der p 2 positive rates were higher in 2–12-year-old children. The Der p 2 and Der f 2 IgE levels and positive rates were higher in the allergic rhinitis group. The positive rates of Der p 10 increased significantly with age. Der p 21 is relevant in allergic dermatitis symptom, while Der p 23 contributes to asthma development.ConclusionHDM groups 1 and 2 were the major sensitizing allergens, with group 2 being the most important component relevant to respiratory symptoms in North China. The Der p 10 sensitization tends to increase with age. Der p 21 and Der p 23 might be associated with the development of allergic skin disease and asthma, respectively. Multiple allergen sensitizations increased the risk of allergic asthma

Prioritized High-Confidence Risk Genes for Intellectual Disability Reveal Molecular Convergence During Brain Development

Dissecting the genetic susceptibility to intellectual disability (ID) based on de novo mutations (DNMs) will aid our understanding of the neurobiological and genetic basis of ID. In this study, we identify 63 high-confidence ID genes with q-values &lt; 0.1 based on four background DNM rates and coding DNM data sets from multiple sequencing cohorts. Bioinformatic annotations revealed a higher burden of these 63 ID genes in FMRP targets and CHD8 targets, and these genes show evolutionary constraint against functional genetic variation. Moreover, these ID risk genes were preferentially expressed in the cortical regions from the early fetal to late mid-fetal stages. In particular, a genome-wide weighted co-expression network analysis suggested that ID genes tightly converge onto two biological modules (M1 and M2) during human brain development. Functional annotations showed specific enrichment of chromatin modification and transcriptional regulation for M1 and synaptic function for M2, implying the divergent etiology of the two modules. In addition, we curated 12 additional strong ID risk genes whose molecular interconnectivity with known ID genes (q-values &lt; 0.3) was greater than random. These findings further highlight the biological convergence of ID risk genes and help improve our understanding of the genetic architecture of ID

BamA β16C strand and periplasmic turns are critical for outer membrane protein insertion and assembly

Outer membrane β-barrel proteins play important roles in importing nutrients, exporting wastes and conducting signals in Gram-negative bacteria, mitochondria and chloroplasts. The outer membrane proteins are inserted and assembled into the outer membrane by OMP85 family proteins. In Escherichia coli , the b-barrel assembly machinery (BAM) contains four lipoproteins BamB, BamC, BamD and BamE, and one outer membrane protein BamA, forming a "top hat"-like structure. Structural and functional studies of the E. coli BAM machinery have revealed that the rotation of periplasmic ring may trigger the barrel b1C-b6C scissor-like movement that promote the unfolded outer membrane protein insertion without using ATP. Here we report the BamA C-terminal barrel structure of Salmonella enterica Typhimurium str. LT2 and functional assays, which reveal that the BamA's C-terminal residue Trp, the b16C strand of the barrel and the periplasmic turns are critical for the functionality of BamA. These findings indicate that the unique b16C and the periplasmic turns of BamA are important for the out membrane insertion and assembly. The periplasmic turns might mediate the rotation of the periplasmic ring to the scissor-like movement of BamA b1C-b6C, triggering the outer membrane protein insertion. These results are important for understanding the outer membrane protein insertion in Gram-negative bacteria, as well as in mitochondria and chloroplasts

Artemisia pollen allergy in China : Component-resolved diagnosis reveals allergic asthma patients have significant multiple allergen sensitization

Background: Artemisia pollen allergy is a major cause of asthma in Northern China. Possible associations between IgE responses to Artemisia allergen components and clinical phenotypes have not yet been evaluated. This study was to establish sensitization patterns of four Artemisia allergens and possible associations with demographic characteristics and clinical phenotypes in three areas of China. Methods: Two hundred and forty patients allergic to Artemisia pollen were examined, 178 from Shanxi and 30 from Shandong Provinces in Northern China, and 32 from Yunnan Province in Southwestern China. Allergic asthma, rhinitis, conjunctivitis, and eczema symptoms were diagnosed. All patients sera were tested by ImmunoCAP with mugwort pollen extract and the natural components nArt v 1, nArt ar 2, nArt v 3, and nArt an 7. Results: The frequency of sensitization and the IgE levels of the four components in Artemisia allergic patients from Southwestern China were significantly lower than in those from the North. Art v 1 and Art an 7 were the most frequently recognized allergens (84% and 87%, respectively), followed by Art v 3 (66%) and Art ar 2 (48%). Patients from Northern China were more likely to have allergic asthma (50%) than patients from Southwestern China (3%), and being sensitized to more than two allergens increased the risk of allergic asthma, in which cosensitization to three major allergens Art v 1, Art v 3, and Art an 7 is prominent. Conclusions: Componentresolved diagnosis of Chinese Artemisia pollenallergic patients helps assess the potential risk of mugwortassociated allergic asthma.(VLID)329956