Relation between bit and symbol error probabilities for frequencyshift keying with limiter-discriminator detection

In M-ary, Gray coded frequency shift keying with limiter discriminator detection the bit error probability is usually approximated by the symbol error probability divided by the number of bits in a symbol. This approximation is known to be excellent for phase shift keying with large energy-to-noise ratios and Gaussian channel. In other cases this may be questionable. The authors compute the exact values of bit error probability as a function of energy-to-noise-ratio per bit for Gaussian, Rayleigh and Rician channels. They also compute the relative error involved in this approximation     

FSK With Limiter-Discriminator Detector in Nakagami Fading Channels With and Without Selection Combining

In this paper, an equation for the error probability of M-ary frequency shift keying with limiter-discriminator detection in Nakagami fading channels for arbitrary m is derived. The authors do the same for selection combining with L diversity channels for integer m and for switch and stay combining with two diversity channels for m=1 (Rayleigh fading). The error probability for various values of m, L, frequency deviation, and filter bandwidth is computed     

Performance of four-dimensional digital communication system infading channels

The authors derive a formula for the bit-error probability (BEP) of a four-dimensional signal and coherent but simple detector in fading channels with Rician or Nakagami probability density function for the received signal envelope. They compute the BEP in both cases and show its dependence on the energy-to-noise ratio per bit, E_b/N_o and channel parameters, K and m, respectively     

On the “dimensionality curse” and the“self-similarity blessing”

Spatial queries in high-dimensional spaces have been studied extensively. Among them, nearest neighbor queries are important in many settings, including spatial databases (Find the k closest cities) and multimedia databases (Find the k most similar images). Previous analyses have concluded that nearest-neighbor search is hopeless in high dimensions due to the notorious “curse of dimensionality”. We show that this may be overpessimistic. We show that what determines the search performance (at least for R-tree-like structures) is the intrinsic dimensionality of the data set and not the dimensionality of the address space (referred to as the embedding dimensionality). The typical (and often implicit) assumption in many previous studies is that the data is uniformly distributed, with independence between attributes. However, real data sets overwhelmingly disobey these assumptions; rather, they typically are skewed and exhibit intrinsic (“fractal”) dimensionalities that are much lower than their embedding dimension, e.g. due to subtle dependencies between attributes. We show how the Hausdorff and Correlation fractal dimensions of a data set can yield extremely accurate formulas that can predict the I/O performance to within one standard deviation on multiple real and synthetic data sets     

Efficient approximation of correlated sums on data streams

In many applications such as IP network management, data arrives in streams and queries over those streams need to be processed online using limited storage. Correlated-sum (CS) aggregates are a natural class of queries formed by composing basic aggregates on (x, y) pairs and are of the form SUM{g(y) : x /spl les/ f(AGG(x))}, where AGG(x) can be any basic aggregate and f(), g() are user-specified functions. CS-aggregates cannot be computed exactly in one pass through a data stream using limited storage; hence, we study the problem of computing approximate CS-aggregates. We guarantee a priori error bounds when AGG(x) can be computed in limited space (e.g., MIN, MAX, AVG), using two variants of Greenwald and Khanna's summary structure for the approximate computation of quantiles. Using real data sets, we experimentally demonstrate that an adaptation of the quantile summary structure uses much less space, and is significantly faster, than a more direct use of the quantile summary structure, for the same a posteriori error bounds. Finally, we prove that, when AGG(x) is a quantile (which cannot be computed over a data stream in limited space), the error of a CS-aggregate can be arbitrarily large.     

A preconcentration system for determination of copper and nickel in water and food samples employing flame atomic absorption spectrometry

A separation/preconcentration procedure using solid phase extraction has been proposed for the flame atomic absorption spectrometric determination of copper and nickel at trace level in food samples. The solid phase is Dowex Optipore SD-2 resin contained on a minicolumn, where analyte ions are sorbed as 5-methyl-4-(2-thiazolylazo) resorcinol chelates. After elution using 1 mol L(-1) nitric acid solution, the analytes are determinate employing flame atomic absorption spectrometry. The optimization step was performed using a full two-level factorial design and the variables studied were: pH, reagent concentration (RC) and amount of resin on the column (AR). Under the experimental conditions established in the optimization step, the procedure allows the determination of copper and nickel with limit of detection of 1.03 and 1.90 microg L(-1), respectively and precision of 7 and 8%, for concentrations of copper and nickel of 200 microg L(-1). The effect of matrix ions was also evaluated. The accuracy was confirmed by analyzing of the followings certified reference materials: NIST SRM 1515 Apple leaves and GBW 07603 Aquatic and Terrestrial Biological Products. The developed method was successfully applied for the determination of copper and nickel in real samples including human hair, chicken meat, black tea and canned fish.     

Coating with artificial matrices from collagen and sulfated hyaluronan influences the osseointegration of dental implants

Dental implants are an established therapy for oral rehabilitation. High success rates are achieved in healthy bone, however, these rates decrease in compromised host bone. Coating of dental implants with components of the extracellular matrix is a promising approach to enhance osseointegration in compromised peri-implant bone. Dental titanium implants were coated with an artificial extracellular matrix (aECM) consisting of collagen type I and either one of two regioselectively low sulfated hyaluronan (sHA) derivatives (coll/sHA1Δ6s and coll/sHA1) and compared to commercial pure titanium implants (control). After extraction of the premolar teeth, 36 implants were inserted into the maxilla of 6 miniature pigs (6 implants per maxilla). The healing periods were 4 and 8 weeks, respectively. After animal sacrifice, the samples were evaluated histomorphologically and histomorphometrically. All surface states led to a sufficient implant osseointegration after 4 and 8 weeks. Inflammatory or foreign body reactions could not be observed. After 4 weeks of healing, implants coated with coll/sHA1Δ6s showed the highest bone implant contact (BIC; coll/sHA1Δ6s: 45.4 %; coll/sHA1: 42.2 %; control: 42.3 %). After 8 weeks, a decrease of BIC could be observed for coll/sHA1Δ6s and controls (coll/sHA1Δ6s: 37.3 %; control: 31.7 %). For implants coated with coll/sHA1, the bone implant contact increased (coll/sHA1: 50.8 %). Statistically significant differences could not be observed. Within the limits of the current study, aECM coatings containing low sHA increase peri-implant bone formation around dental implants in maxillary bone compared to controls in the early healing period.     

The influence of a corrosive wood-cutting environment on the mechanical properties of hardmetal tools

The influence of a corrosive wood-cutting environment on the strength of hardmetals and on their behaviour under static loading conditions has been investigated. Two commercial hardmetals were tested, which differed in hard phase composition. The results show exposure to this environment to have a highly detrimental influence on the strength of both hardmetals investigated, due to localised corrosive attack which results in the formation of stress raisers. The relative loss in strength as a function of corrosion time is the same for both hardmetals. However, the performance of the two grades differ significantly when a static load is applied in this corrosive environment: the strength of the WC-Co grade remains unaffected by the applied load, while the grade containing a mixed carbide phase exhibits stress corrosion cracking which results in a further reduction in strength.     

Characterization of three new apparently related high frequency antigens

1. To study the relative contributions of luminal nutrition, bile and pancreatic secretions and hormonal factors in intestinal adaptation, lactation hyperphagia was chosen as a model for increased luminal nutrition, either alone (intestinal transection control group) or in combination with (i) exclusion of bile and pancreatic secretions from the jejunum (by transposition of the jejunum above the Ampulla of Vater) or (ii) exclusion of bile, pancreatic secretions and exogenous luminal nutrition from the jejunum (proximal Thiry-Vella by-pass group). 2. The results confirm that in lactation there is mucosal hyperplasia with increases in villus height and crypt depth, and in small-bowel wet and defatted dry-tissue weights per unit length of intestine. 3. There are corresponding changes in absorptive function with increased glucose and water absorption per unit length of intestine. 4. These structural and functional adaptive changes are proportionately greater in ileum than in jejunum. 5. The exclusion of exogenous luminal nutrition, bile and pancreatic secretions from the jejunum did not diminish the degree of intestinal mucosal hyperplasia and functional adaptation seen in lactation. 6. Diversion to the ileum of greater than normal amounts of bile, pancreatic secretions and luminal nutrition did not further increase the degree of mucosal hyperplasia and enhanced absorption seen in the lactating intestinal transection control group. 7. Unlike other models of intestinal adaptation, the changes in small-bowel mucosal structure and function seen in lactation are probably due to hormonal factors.