Fast algorithms for single frequency estimation

In this paper, some new estimators of the frequency of a single complex sinusoid are presented. The rotate-add-decimate (RAD) method of Crozier is first refined to more closely approach the Cramer-Rao Bound (CRB). An additional modification yields an unbiased estimator (ERAD) that essentially achieves the CRB above a signal-to-noise ratio (SNR) threshold comparable to that of RAD. In addition, this estimator is proven to achieve the CRB for high SNR. The ERAD method requires approximately 2N complex multiply-adds and log/sub 2/N arctangents. A modified ERAD (MERAD) is proposed that matches the SNR threshold and computational complexity of the RAD method (approximately 3N complex multiply-adds and log/sub 2/N arctangents) but achieves the CRB for high SNR.     

An exploration of expertise of knowledge workers: towards a definition of the universe of discourse for knowledge acquisition

Abstract. Knowledge systems development and use have been significantly encumbered by the difficulties of eliciting and formalizing the expertise upon which knowledge workers rely. This paper approaches the problem from an examination of the knowledge competencies of knowledge workers in order to define a universe of discourse for knowledge elicitation. It outlines two categories and several types of knowledge that could serve as the foundations for the development of a theory of expertise.     

MODELING LIGNIN LIQUEFACTION 1. CATALYTIC HYDROPROCESSING OF LIGNIN-RELATED METHOXYPHENOLS AND INTERAROMATIC UNIT LINKAGES

The reactions of two sets of lignin model compounds over a sulfided CoOMoO3/γ-Al2O3 catalyst were studied. The first set mimicked lignin methoxyphenol residues and comprised 4-methyl-guaiacol, 4-methyl catechol, eugenol and vanillin. Deoxygenation and hydrogenation were facile and led to ultimate molar yields of single-ring products as high as 0.70. The selectivity to single-ring products increased with increases in temperature, o-hydroxydiphenylmethane, phenyl ether and o,o'-biphenol constituted the second set that mimicked thermally stable lignin bonds.Fragmentation of o-hydroxydiphenylmethane and phenyl ether occurred readily; o,o'-biphenol reacted to dibenzofuran.

These results suggest that the single-ring products obtained from catalytic liquefaction of lignins should be more desirable than those obtained from pyrolysis because of both higher yields and reduced complexity.     

Intracellular study of interaction of paired-pulse facilitation and late phase of hippocampal long-term potentiation]

Presynaptic paired-pulse facilitation (PPF) rate decreased in most CA1 pyramidal neurones following the long-term potantiation (LTP) induction. The decrease correlated with the LTP magnitude as well as with the initial (pretetanic) PPF rate. The data obtained suggests an involvement of presynaptic mechanisms in maintaining the early and the delayed LTPs.     

Detection of skeletal metastases in Nigerian breast cancer patients: evaluation of radioisotope bone scan and radiography

Cerebellar granule cells isolated from postnatal day 7 mice, and cultured in minimal medium containing only insulin-like growth factor-I (IGF-I), both survive and differentiate. This differentiation is marked by neurite growth and expression of genes associated with terminal differentiation, the myocyte-specific enhancer factor 2A (MEF2A) and the alpha 6 subunit of the gamma-aminobutyric acidA receptor (GABAA alpha 6). Percoll gradient purified granule cells maintained without IGF-I, in minimal medium alone or in medium containing the antioxidant N-acetylcysteine (NAC), also express MEF2A and GABAA alpha 6. Thus, cultured granule neurons can differentiate to some extent cell-autonomously and IGF-I may not be a critical factor for this process.     

Acadesine extends the window of protection afforded by ischaemic preconditioning in conscious rabbits

OBJECTIVE: Ischaemic preconditioning protects myocardium from infarction if the reperfusion interval between the brief and prolonged ischaemic intervals is less than 1 h. In anaesthetised rabbits acadesine (5-amino-4-imidazolecarboxamide riboside, AICAR), an adenosine enhancer which increases tissue adenosine during ischaemia, prolongs the window of protection to 2 h. The aim of this study was to try to determine the maximum extension of this window of protection, using chronically instrumented, unsedated rabbits. METHODS: Rabbits were instrumented with a balloon occluder around a major branch of the left coronary artery for reversible coronary occlusion. Five to seven days after surgery all animals underwent a 30 min coronary occlusion. Animals were randomised to one of seven groups: (1) No additional treatment (control); (2) Ischaemic preconditioning with 5 min regional ischaemia followed by 10 min reperfusion before the 30 min coronary occlusion; (3) and (4) Ischaemic preconditioning followed by 2 or 4 h of reperfusion before the 30 min occlusion, respectively; (5) Treatment with acadesine (2.5 mg.kg-1.min-1 intravenously for 5 min and then 0.5 mg.kg-1.min-1 beginning 45 min before and continuing until 30 min after release of the 30 min occlusion) without ischaemic preconditioning; (6) and (7) Treatment with the higher dose of acadesine for 5 min beginning 35 min before the 5 min ischaemic period, and then the lower dose continuing until 30 min after release of the 30 min coronary occlusion in rabbits with 4 or 6 h reperfusion intervals, respectively. RESULTS: Rabbits with ischaemic preconditioning with 10 min reperfusion preceding the 30 min coronary occlusion (group 2) had only 5.6(SEM 1.1)% infarction of the ischaemic zone. Ischaemic preconditioning followed by 2 h reperfusion (group 3) offered continued protection [18.2(2.2)% infarction] as compared to control animals [37.7(2.6)% infarction]. However, protection waned if ischaemic preconditioning was followed by 4 h reperfusion (group 4) [36.7(3.0)% infarction]. Additionally, treatment with acadesine alone did not modify infarct size (group 7) [39.5(4.0)%], but acadesine largely restored the protection of ischaemic preconditioning despite a 4 h reperfusion interval (group 5) [20.4(3.0)% infarction, P < 0.01 v control]. However, when reperfusion was extended to 6 h (group 6) acadesine could no longer restore protection [36.2(0.9)% infarction]. CONCLUSIONS: The protection afforded by a 5 min ischaemic preconditioning period lasts from 2 to 4 h in the awake, unsedated rabbit, and acadesine can extend the duration of this window of protection to at least 4 h but not to 6 h.     

IL-1 beta and TNF alpha modulate delta 9-tetrahydrocannabinol-induced catalepsy in mice

The role of the proinflammatory cytokines interleukin-1 alpha (IL-1 alpha), interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF alpha) in THC-induced catalepsy in mice was examined. Recombinant IL-1 beta (400 ng/mouse, IV) and TNF alpha (500 ng/mouse, IV) were effective in potentiating the cataleptic effect of low-dose THC (10 micrograms/mouse, IV). Recombinant IL-1 alpha and IL-6 did not potentiate catalepsy at any dose tested. Anti-IL-1 beta and anti-TNF alpha antibodies were effective in attenuating high-dose (75 micrograms/mouse) THC-induced catalepsy. Antibodies to IL-1 alpha and IL-6 had no effect on catalepsy. Early onset catalepsy (10 min postinjection) was potentiated by exogenous recombinant IL-1 beta and TNF alpha but only later catalepsy (2 h postinjection) was attenuated by antibodies to endogenous IL-1 beta or TNF alpha. This divergence of the cytokine effect suggests that these substances regulate, by different mechanisms, the early and late THC-induced cataleptic response.     

Effects of intrathecal administration of adrenergic agonists on the frequency of copulatory pelvic thrusting of the male rat

The effects of the intrathecal perispinal administration of adrenergic agonists on the characteristics of frequency, duration, and vigor of pelvic thrusting displayed by male rats during copulation was assessed by an accelerometric technique. A different dose of one drug (noradrenaline, clonidine or isoproterenol) and saline as control was administered at the lumbosacral level of the spinal cord to sexually active male rats in tests of sexual behavior performed at weekly intervals. The intrathecal administration of noradrenaline (alpha-adrenoceptor agonist) increased the frequency of pelvic thrusting in mount and intromission responses, whereas both the alpha 2-adrenoceptor agonist clonidine (25 micrograms) and the beta-adrenoceptor agonist isoproterenol (40 micrograms) reduced the frequency of pelvic thrusting in these responses as compared to values obtained under the intrathecal administration of saline. On the other hand, the duration of the thrusting trains and the potency or vigor of pelvic thrusting in mounts and intromissions did not differ from values obtained under saline treatment. These findings indicate a possible participation of noradrenaline in the modulation of the spinal mechanisms involved in the generation of rhythmic pelvic thrusting performed by the male rat during copulation.