A review of antennas and propagation for MIMO wireless communications

Multiple-input-multiple-output (MIMO) wireless systems use multiple antenna elements at transmit and receive to offer improved capacity over single antenna topologies in multipath channels. In such systems, the antenna properties as well as the multipath channel characteristics play a key role in determining communication performance. This paper reviews recent research findings concerning antennas and propagation in MIMO systems. Issues considered include channel capacity computation, channel measurement and modeling approaches, and the impact of antenna element properties and array configuration on system performance. Throughout the discussion, outstanding research questions in these areas are highlighted.     

On the intersubject generalization ability in extracting kinematic information from afferent nervous signals

In the recent past, many efforts have been carried out in order to evaluate the feasibility of implementing closed-loop controlled neuroprostheses based on the processing of sensory electroneurographic (ENG) signals. The success of these techniques mostly relies on the development of processing algorithms capable of extracting the necessary kinematic information from these signals. Soft-computing algorithms can be very useful when dealing with the complexity of the neuromuscular system because of their generalization ability and model-free structure. In this paper, these techniques were used to extract angular position information from the ENG signals recorded from muscle afferents in animal model using cuff electrodes. Specifically, a genetic algorithm-based dynamic nonsingleton fuzzy logic system (named GA-DNSFLS) was developed and tested on different types of angular trajectories (characterized by small or large angular excursions). In particular, two different Takagi-Sugeno-Kang (TSK)-like structures were used in the consequent part of the neuro-fuzzy model in order to verify which one could improve the generalization abilities (intrasubject and intersubject). The results showed that the GA-DNSFLS was able to reconstruct the trajectories giving interesting results in terms of correlation between the actual and the predicted trajectories for small excursion movements during intrasubject and intersubject tests. Particularly, one of the TSK models showed better results in terms of intersubject generalization. The simulations conducted with the large excursion movements led in some cases to interesting results but further experiments are necessary in order to analyze this point more in deep.     

A Content Analysis of Print News Coverage of Media Violence and Aggression Research

We conducted a content analysis of news articles (N = 540) to examine whether news coverage of media violence accurately reflects scientific knowledge about exposure to media violence and its effects on viewer aggression. The analysis revealed that over the past 30 years, news articles generally suggested that a link between media violence and aggression exists. However, the tone shifted sharply back toward a neutral conclusion since 2000. This shift may be attributable to the type of medium discussed (e.g., television vs. video games), the number of unaffiliated sources that are cited in the news article, and the sex of the journalist. Implications for how this news coverage may influence news readers are discussed.     

Nitrate leaching from loamy soils as affected by crop rotation and nitrogen fertilizer application

Nitrate leaching as affected by cropping system/crop rotation, history of farmyard manure application or fertilizer nitrogen application (0 N, 0.5 N and 1 N) was studied at nine sites on loamy soils during 1986/87, 1987/88 and 1988/89. Soil solution from 80 to 90 cm soil depth was sampled every second week in the period November to May by the use of porous ceramic cups and analysed for NO₃-N and Cl. Climatical conditions were obtained from standard meteorological observations in the region. Drainage from soil profiles was calculated from measured and simulated values of precipitation and actual evapotranspiration, respectively.The results show that type of crop is of the utmost importance for the leaching magnitude of nitrate as 40% of the total variance in nitrate concentrations in the soil solution could be explained by the type of crop.The second factor of importance was the history of farmyard manure (FYM) application, which was able to explain 28% of the total variation in nitrate concentration in the soil solution. Nitrate concentration/leaching from arable land without FYM ever being applied was considerably lower than from arable land which received periodical FYM applications until the early 70's or from arable land which besides periodical FYM applications in the past presently still receives regular applications of FYM. Only about 1% of the total variation in nitrate concentration in the soil solution was explainable by the level of fertilizer nitrogen application.Differences between years explained 14% of the total variation in nitrate concentration in the soil solution due to differences between the years in soil temperatures and water run-off. The run-off during the autumn and winter of 1986/87, 1987/88 and 1988/89 was 95, 275 and 55 mm, respectively. As expected nitrate leaching increased with increasing run off. However, nitrate leaching at the 275 mm run off was considerably lower than expected, which seems explainable by a substantial denitrification. The soil at the sites in question seems thus partly to purify the soil solution for nitrate before it leaves the root zone at the observed high run off conditions.     

Unsuccessful retrieval attempts enhance subsequent learning.

Taking tests enhances learning. But what happens when one cannot answer a test question—does an unsuccessful retrieval attempt impede future learning or enhance it? The authors examined this question using materials that ensured that retrieval attempts would be unsuccessful. In Experiments 1 and 2, participants were asked fictional general-knowledge questions (e.g., “What peace treaty ended the Calumet War?”). In Experiments 3–6, participants were shown a cue word (e.g., whale) and were asked to guess a weak associate (e.g., mammal); the rare trials on which participants guessed the correct response were excluded from the analyses. In the test condition, participants attempted to answer the question before being shown the answer; in the read-only condition, the question and answer were presented together. Unsuccessful retrieval attempts enhanced learning with both types of materials. These results demonstrate that retrieval attempts enhance future learning; they also suggest that taking challenging tests—instead of avoiding errors—may be one key to effective learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Indentation deformation and cracking behavior of hydrated aluminoborate glasses

Aluminoborate glasses have recently been found to feature high resistance to crack initiation during indentation due to a highly flexible network structure. In cesium aluminoborate glasses, it has been found that the use of a simple post-treatment, namely aging in a humid atmosphere, can further improve this resistance. To better understand the mechanical properties of this glass family upon humid aging, we here study the effect of aging conditions on the structure and mechanical properties of Li,K,Cs-aluminoborate glasses. As expected, we find that higher humidity and longer aging time cause more pronounced permeation of atmospheric water into the glasses. Due to their denser structure and stronger modifier-oxygen bonds, the humid aging has a relatively smaller effect on the mechanical properties of Li- and K-containing glasses relative to Cs-containing glasses, with the latter achieving an ultrahigh crack resistance. We find that the humid aging leads to the formation of a hydration layer in the Cs-aluminoborate glass surface, with a thickness of around 26 μm upon aging at 23 °C with 40% relative humidity for 7 days. Moreover, a remarkable indentation behavior, that is, the observation of μm-sized shear bands inside the imprint of the Cs-glass upon aging at 60% relative humidity is reported. Taken as a whole, the work provides guidelines for how to control the humid aging rate as a function of relative humidity and temperature to form a hydration layer and thus achieve improved crack resistance in such glasses.     

Real-time in situ monitoring of the thermal cure of a bisphenol cyanate: A view toward intelligent processing

A dispersive fiber-optic Raman spectrometer was used to remotely monitor, in real-time, the local temperature and the extent of reaction of a commercial cyanate ester polymer (AroCy L-10). The local temperature was determined by solving the Boltzmann relation governing the intensity ratio of the Raman Stokes and anti-Stokes scattering of a reference mode which does not vary with the reaction chemistry. The extent of the reaction can be monitored using either individual peaks assciated with the reactant or product or by using the entire spectrum and principal component multivariate calibration. The use of principal component analysis has distinct advantages over the single-peak method. © 1996 John Wiley & Sons, Inc.     

Fractality of tics as a quantitative assessment tool for Tourette syndrome

Tics manifest as brief, purposeless and unintentional movements or noises that, for many individuals, can be suppressed temporarily with effort. Previous work has hypothesized that the chaotic temporal nature of tics could possess an inherent fractality, that is, have neighbour-to-neighbour correlation at all levels of timescale. However, demonstrating this phenomenon has eluded researchers for more than two decades, primarily because of the challenges associated with estimating the scale-invariant, power law exponent—called the fractal dimension D_f—from fractional Brownian noise. Here, we confirm this hypothesis and establish the fractality of tics by examining two tic time series datasets collected 6–12 months apart in children with tics, using random walk models and directional statistics. We find that D_f is correlated with tic severity as measured by the YGTTS total tic score, and that D_f is a sensitive parameter in examining the effect of several tic suppression conditions on the tic time series. Our findings pave the way for using the fractal nature of tics as a robust quantitative tool for estimating tic severity and treatment effectiveness, as well as a possible marker for differentiating typical from functional tics.     

3- Instead of 4-helix formation in a de novo designed protein in solution revealed by small-angle X-ray scattering

De novo design and chemical synthesis of proteins and their mimics are central approaches for understanding protein folding and accessing proteins with novel functions. We have previously described carbohydrates as templates for the assembly of artificial proteins, so-called carboproteins. Here, we describe the preparation and structural studies of three alpha-helical bundle carboproteins, which were assembled from three different carbohydrate templates and one amphiphilic hexadecapeptide sequence. This heptad repeat peptide sequence has been reported to lead to 4-alpha-helix formation. The low resolution solution structures of the three carboproteins were analyzed by means of small-angle X-ray scattering (SAXS) and synchrotron radiation circular dichroism (SRCD). The ab initio SAXS data analysis revealed that all three carboproteins adopted an unexpected 3+1-helix folding topology in solution, while the free peptide formed a 3-helix bundle. This finding is consistent with the calculated alpha-helicities based on the SRCD data, which are 72 and 68 % for two of the carboproteins. The choice of template did not affect the overall folding topology (that is for the 3+1 helix bundle) the template did have a noticeable impact on the solution structure. This was particularly evident when comparing 4-helix carboprotein monomers with the 2x2-helix carboprotein dimer as the latter adopted a more compact conformation. Furthermore, the clear conformational differences observed between the two 4-helix (3+1) carboproteins based on D-altropyranoside and D-galactopyranoside support the notion that folding is affected by the template, and subtle variations in template distance-geometry design may be exploited to control the solution fold. In addition, the SRCD data show that template assembly significantly increases thermostability.     

A computer program for randomizing patients with near-even distribution of important parameters.

In clinical trials, the methods for achieving an event or near-even distribution of important patient parameters have been tedious and often disappointing. In this paper, a computer program for minimizing differences between experimental groups with respect to such important parameters, based on a method described by Traves (Clin. Pharmacol. Ther. London 15, 443, 1974) is presented. The program is available from the author.