Bayesian generation of dependent erasures for frequency-hopcommunications and fading channels

The use of block coding and errors-and-erasures decoding can enhance performance in frequency-hop (FH) communication systems, provided that a good scheme is employed to determine which symbols to erase. The problem of making erasure decisions from collections of receiver outputs is investigated in this paper. Methods to determine which received symbols to erase are derived from Bayesian decision theory. Decision rules are developed for a system with M-ary orthogonal signaling, noncoherent demodulation, and frequency-selective fading. One result is a class of Bayesian schemes in which erasure decisions are made independently from symbol to symbol. Within this class is a rule that uses signal amplitude estimates for improved performance. A second result is a Bayesian technique in which erasure decisions are mutually dependent and are made collectively for each codeword. These techniques are analyzed and compared with the performance of receivers that use erasure techniques that require multiple applications of bounded distance decoding. The performance of the Bayesian techniques for dependent erasures are also compared with the performance of receivers that do not permit erasures. It is found that each of the Bayesian techniques offers substantial performance gains over errors-only decoding, and the dependent erasure scheme provides the best performance among the techniques of lower complexity     

Nature-nurture in the classroom: entrance age, school readiness, and learning in children

The impact of entrance age on reading and mathematics achievement in 1st grade was examined. Methodological problems with past research were identified, including small size of achievement differences, failure to take background variables into account, and confusion of achievement levels with degree of learning. Using a pre-post design, growth of reading and mathematics was examined in younger 1st graders, older 1st graders, and older kindergarteners. Comparisons of background information on these groups with children who were either held out prior to or retained an extra year in kindergarten, produced minimal background differences. Results revealed that younger 1st graders made as much progress over the school year as did older 1st graders and made far more progress than older kindergarteners. Overall, findings demonstrated that, in itself, entrance age was not a good predictor of learning or academic risk.     

Heparin effect on hydrolysis of fibrin clots in a bull and a man with varying fibrinolytic systems

Heparin was studied for its effect on the hydrolysis time of clots from desAA fibrin (FB), desAABB fibrin (F0) and fibrinogen (Fg) of a bull and a man by gly-or lys-plasminogen which is activated by the tissue activator. It is shown that heparin in the concentration to 4.6 M does not affect that hydrolysis time of clots from human and bovine Fg and human Fg by gly-plasminogen which is activated by the tissue activator. Heparin increases the hydrolysis time of clots from bovine Fg and F0 by gly-and lys-plasminogen, the tissue activator being present. It firstly increases (in concentrations below 0.5 (microM), and then decreases (in concentrations above 0.5 (microM) the hydrolysis time of clots from human FB, F0 and Fg and bovine FB and F0 by plasmin. In concentration 4.6 microM heparin increases the hydrolysis time of clots from human fibrinogen by fibrinolytic systems. Effect of heparin on fibrinolytic process from the viewpoint of affine interactions between the components of fibrin clots is discussed.     

Real-time NMR investigations of triple-helix folding and collagen folding diseases

Folding of the collagen triple helix provides an opportunity to look at multichain molecular assembly. This triple helix also offers unique advantages for the study of folding because the process is very slow compared to globular proteins, and the kinetics of folding can be obtained in real time by NMR. Studies on triple-helical peptides illustrate the ability to observe kinetic folding intermediates directly and the ability to propose detailed mechanisms of folding through the use of real-time NMR methods. Defective collagen folding has been implicated in various connective tissue diseases and the capacity of NMR to look at the folding of specific sites provides a tool for obtaining information about altered folding mechanisms. Comparison of folding in peptides that model normal and diseased collagens could shed light on the molecular perturbation and the etiology of disease.     

Slow skeletal troponin I gene transfer, expression, and myofilament incorporation enhances adult cardiac myocyte contractile function

The functional significance of the developmental transition from slow skeletal troponin I (ssTnI) to cardiac TnI (cTnI) isoform expression in cardiac myocytes remains unclear. We show here the effects of adenovirus-mediated ssTnI gene transfer on myofilament structure and function in adult cardiac myocytes in primary culture. Gene transfer resulted in the rapid, uniform, and nearly complete replacement of endogenous cTnI with the ssTnI isoform with no detected changes in sarcomeric ultrastructure, or in the isoforms and stoichiometry of other myofilament proteins compared with control myocytes over 7 days in primary culture. In functional studies on permeabilized single cardiac myocytes, the threshold for Ca2+-activated contraction was significantly lowered in adult cardiac myocytes expressing ssTnI relative to control values. The tension-Ca2+ relationship was unchanged from controls in primary cultures of cardiac myocytes treated with adenovirus containing the adult cardiac troponin T (TnT) or cTnI cDNAs. These results indicate that changes in Ca2+ activation of tension in ssTnI-expressing cardiac myocytes were isoform-specific, and not due to nonspecific functional changes resulting from overexpression of a myofilament protein. Further, Ca2+-activated tension development was enhanced in cardiac myocytes expressing ssTnI compared with control values under conditions mimicking the acidosis found during myocardial ischemia. These results show that ssTnI enhances contractile sensitivity to Ca2+ activation under physiological and acidic pH conditions in adult rat cardiac myocytes, and demonstrate the utility of adenovirus vectors for rapid and efficient genetic modification of the cardiac myofilament for structure/function studies in cardiac myocytes.     

Recent developments in the understanding of antinuclear autoantibodies

Cytological identification of soybean mitotic metaphase chromosomes (2n = 40) has been severely limited by their small size and uniform karyomorphology. We have developed fluorescent in situ hybridization (FISH), PCR-primed in situ labelling (PCR-PRINS) procedures, and molecular probes for routine cytological identification and for the physical mapping of soybean somatic chromosomes. Chromosome preparation has been achieved by modifications of previous protocols and through the preparation of root-tip protoplasts prior to chromosome spreading. Initially our probe selection focused on highly repeated DNAs that provide very intense localized hybridization signals. Repetitive gene probes that have proven valuable include the rDNA loci (5S and 45S) which are chromosome specific. We have also developed satellite DNA probes for two different sequence families: the SB92 and the STR120 satellites. Both of these are tandemly arranged at multiple chromosomal loci. By using different cloned examples of each family, we have been able to selectively label unique subsets of soybean chromosomes. Double hybridization with biotin and digoxigenin labeled probes has allowed us to determine the chromosomal overlap between different probes. In addition, we have joined portions of the metaphase chromosome painting patterns with the genetic map by single-copy FISH and PCR-PRINS detection of the RFLP loci G8.15, G17.3, and A199a and A199b. Total genomic DNA in situ hybridization (GISH) patterns were also used to characterize the soybean chromosomes.     

The significance of gastric helicobacteriosis in the genesis hemorrhage from duodenal peptic ulcer

Based on a comprehensive analysis of findings from examination and surgical treatment of 196 patients with bleeding pyloroduodenal ulcers, it was found out that patients with concurrent helicobacteriosis of the stomach are prone to more unfavourable course of their illness, which fact is evidenced by a greater loss of blood and higher risk for bleeding recurrences. A classification is proposed by the authors, taking advantage of the data from endoscopic, microscopic and immunoenzymatic techniques, with the purpose of providing an assessment of degree of severity of helicobacteriosis of the stomach.     

Postural and symptomatic improvement after physiotherapy in patients with dizziness of suspected cervical origin

OBJECTIVE: To assess postural performance in patients with dizziness of suspected cervical origin in whom extracervical causes had been excluded, and to assess the effects of physiotherapy on postural performance and subjective complaints of neck pain and dizziness. DESIGN: Prospective, randomized, controlled trial. SETTING: Primary care centers and a tertiary referral center. PATIENTS AND SUBJECTS: Of 65 referrals, 43 patients were excluded because extracervical etiology was suspected. Of the remaining 22 patients, 17 completed the study (15 women, 2 men, x age 37 yr, range 26-49). The controls were 17 healthy subjects (15 women, 2 men, x age 36 yr, range 25-55). INTERVENTION: Physiotherapy based on analysis of symptoms and findings, and aimed to reduce cervical discomfort. Patients were randomized either to receive immediate physiotherapy (n = 9), or to wait 2 months, undergo repeat measurements, and then receive physiotherapy (n = 8). MAIN OUTCOME MEASURES: Posturography, measuring velocity and variance of vibration-induced body sway and variance of galvanically induced body sway. Subjective intensity of neck pain (Visual Analog Scale ratings, 0-100), intensity and frequency of dizziness (subjective score 0-4). RESULTS: The patients manifested significantly poorer postural performance than did healthy subjects (.05 > p > .0001). Physiotherapy significantly reduced neck pain and intensity and the frequency of dizziness (p < .01), and significantly improved postural performance (.05 > p > .0007). CONCLUSIONS: Patients with dizziness of suspected cervical origin are characterized by impaired postural performance. Physiotherapy reduces neck pain and dizziness and improves postural performance. Neck disorders should be considered when assessing patients complaining of dizziness, but alternative diagnoses are common.     

Pharmacokinetics of newer cephalosporins after subconjunctival and intravitreal injection in rabbits

Pharmacologic considerations suggest that third-generation cephalosporins might penetrate the vitreous humor better after periocular injection and might be eliminated less readily after intravitreous injection than older agents. We studied the sodium salts of ceftizoxime, ceftriaxone, and ceftazidime, and of an investigational cephalosporin, cefepime, in rabbits. After a single subconjunctival injection in animals with normal eyes, vitreous levels ranged from 3 to 13 mg/L. After five subconjunctival injections in rabbits with infected eyes, vitreous concentrations ranged from 12 to 34 mg/L. These concentrations are not appreciably greater than those found with older beta-lactams. The vitreous half-life of the four drugs after intravitreous injection varied from 5.7 to 20 hours in rabbits with uninflamed eyes and from 9.4 to 21.5 hours in rabbits with infected eyes. Except for ceftizoxime, the half-lives were substantially longer than those for older beta-lactams and suggest predominantly anterior route elimination. Vitreous penetration of these new agents after subconjunctival injection does not appear to be sufficient to overcome the need for intravitreous injections in the treatment of endophthalmitis. However, the longer vitreous half-lives of some of the newer agents may be useful if the drugs are to be given intravitreally.