Service outage based power and rate allocation for parallel fading channels

The service outage based allocation problem explores variable-rate transmission schemes and combines the concepts of ergodic capacity and outage capacity for fading channels. A service outage occurs when the transmission rate is below a given basic rate r/sub o/. The allocation problem is to maximize the expected rate subject to the average power constraint and the constraint that the outage probability is less than /spl epsi/. A general class of probabilistic power allocation schemes is considered for an M-parallel fading channel model. The optimum power allocation scheme is derived and shown to be deterministic except at channel states of a boundary set. The resulting service outage achievable rate ranges from 1-/spl epsi/ of the outage capacity up to the ergodic capacity with increasing average power. Two near-optimum schemes are also derived by exploiting the fact that the outage probability is usually small. The second near-optimum scheme significantly reduces the computational complexity of the optimum solution; moreover, it has a simple structure for the implementation of transmission of mixed real-time and non-real-time services.     

Performance of a randomization test for single-subject (15)O-water PET activation studies

We adapted and implemented a permutation test (Holmes 1994) to single-subject positron emission tomography (PET) activation studies with multiple replications of conditions. That test determines the experimentwise alpha error as well as location and extent of focal activations in each individual. Its performance was assessed in five normal volunteers, using (15)O-H2O-PET data acquired on a high-resolution scanner, with septa retracted (3D mode), during functional activation by repeating words versus resting (four replications each). Calculated alpha errors decreased and the size of activated tissue volumes (voxels with P < or = 0.05) increased with increasing filter kernel size applied to the difference images. At a filter kernel of 12 mm Gaussian full width at half maximum, significant focal activations were seen bilaterally in superior temporal cortex, including Brodmann's areas 41 and 42, in all five subjects. Additional foci were detected in the precentral gyrus, left inferior frontal gyrus, supplementary motor area, and cerebellum of several subjects. The average CBF increase in activated voxels ranged from 17.6% to 28.7%. Activated volumes were smaller than those detected with a standard parametric test procedure. We conclude that the permutation test is a less sensitive procedure, having the advantage of not depending on unproven distributional assumptions, that detects strong activation foci in individual subjects with high reproducibility.     

The coenzyme A-synthesizing protein complex and its proposed role in CoA biosynthesis in bakers'' yeast

An improved procedure is described for the recovery and purification of the coenzyme A-synthesizing protein complex (CoA-SPC) of Saccharomyces cerevisiae (bakers' yeast). The molecular mass of the CoA-SPC, determined prior to and following its purification, is estimated by Sephacryl S-300 size exclusion chromatography to be between 375,000-400,000. Two previously unreported catalytic activities attributed to CoA-SPC have been identified. One of these is CoA-hydrolase activity which catalyzes the hydrolysis of CoA to form 3',5'-ADP and 4'-phosphopantetheine, and the other is dephospho-CoA-pyrophosphorylase activity which catalyzes a reaction between 4'-phosphopantetheine and ATP to form dephospho-CoA. The dephospho-CoA then reacts with ATP, catalyzed by the dephospho-CoA-kinase, to reform CoA. This sequence of reactions, referred to as the CoA/4'-phosphopantetheine cycle, provides a mechanism by which the 4'-phosphopantetheine can be recycled to form CoA. Each turn of the cycle utilizes two mol of ATP and produces one mol of ADP, one mol of PPi, and one mol of 3',5'-ADP. Other than the hydrolysis of CoA by CoA-SPC, the 4'-phosphopantetheine for the cycle apparently could be supplied by alternate sources. One alternate source may be the conventional pathway of CoA biosynthesis. Intact CoA-SPC has been separated into two segments. One segment is designated apo-CoA-SPC and the other segment segment is referred to as the 10,000-15,000 M(r) subunit. The 5'-ADP-4'-pantothenic acid-synthetase, 5'-ADP-4'-pantothenylcysteine-synthetase, 5'-ADP-4'-pantothenylcysteine-decarboxylase, and CoA-hydrolase activities reside in the apo-CoA-SPC segment of CoA-SPC. Whereas the dephospho-CoA-kinase and the dephospho-CoA-pyrophosphorylase activities reside in the 10,000-15,000 M(r) subunit. Thus, the 10,000-15,000 M(r) subunit mimics the bifunctional enzyme complex that catalyzes the final two steps in the conventional pathway of CoA biosynthesis.     

Solution structure of a brodimoprim analogue in its complex with Lactobacillus casei dihydrofolate reductase

Two-dimensional (2D) double-quantum-filtered correlation spectroscopy (DQF-COSY), total correlation spectroscopy (TOCSY), nuclear Overhauser effect spectroscopy (NOESY), and rotating-frame NOESY (ROESY) spectra were used to assign essentially all the protons in a 1:1 complex of Lactobacillus casei dihydrofolate reductase formed with an analogue of the antibacterial drug brodimoprim [2,4-diamino-5-(3',5'-dimethoxy-4'-bromobenzyl)pyrimidine]. The analogue has a 4,6-dicarboxylic acid side chain substituted on the 3'-O position designed to interact with the Arg 57 and His 28 residues in L. casei dihydrofolate reductase; it binds a factor of 10(3) more tightly to the enzyme than does the parent compound. Thirty-eight intermolecular and 11 intramolecular NOEs were measured involving the bound brodimoprim-4,6-dicarboxylic acid analogue. These provided the distance constraints used in conjunction with an energy minimization and simulated annealing protocol (using Discover from Biosym Ltd.) to dock the brodimoprim analogue into dihydrofolate reductase. In calculations where side chains and backbone fragments for binding-site residues were allowed flexibility, 90% of the 40 calculated structures had reasonable covalent geometry and none of them had NOE distance violations of greater than 0.36 A. The conformations of the aromatic rings in the bound ligand were well-defined in all the structures, with torsion angles tau 1 = -153 degrees +/- 4 degrees (C4-C5-C7-C1') and tau 2 = 53 degrees +/- 4 degrees (C5-C7-C1'-C2'): the aromatic rings of the ligand occupied essentially the same space in all the calculated structures (root mean square deviation value 1.83 A). Inclusion of the electrostatic interactions into the energy minimizations indicated that structures in which the 4,6-dicarboxylate group of the ligand interacts with the side chains of Arg 57 and His 28 are of low energy. Significant differences in side-chain and backbone conformations were detected between binding-site residues in the enzyme complexes with the brodimorpim analogue and methotrexate.     

Reproductive sequelae in female rats after in utero and neonatal exposure to the phytoestrogen genistein

OBJECTIVE: To determine reproductive sequelae in female rats after in utero and lactational dietary exposure to genistein. DESIGN: Experimental animal study. SETTING: University laboratory. ANIMAL(S): Sprague Dawley rats. INTERVENTION(S): Pregnant rats were fed control rat chow or rat chow incorporated with genistein (approximately 50 microg/d) beginning on day 17 of gestation and continuing until the end of lactation (postpartum day 21). Genistein-exposed female pups were divided into two groups on day 21. One group continued to receive a genistein-added diet (G70); the other group was changed to a control diet (Ex-G). At necropsy (days 21 and 70), blood and reproductive tissues were collected. MAIN OUTCOME MEASURE(S): Serum levels of gonadotropins and gonadal steroids and histopathologic examination of the ovaries. RESULT(S): The weight of the ovaries and uterus and serum levels of E2 and progesterone in genistein-exposed rats on day 21 (G21) were significantly reduced compared with control rats. On day 70, serum levels of E2, progesterone, LH, and FSH were similar in all groups. Atretic follicles and secondary interstitial glands were more common in G70 and Ex-G rats compared with control rats. Cystic rete ovarii was observed in some G70 and Ex-G rats. CONCLUSION(S): Our data indicate that in utero and lactational exposure to dietary genistein adversely affects reproductive processes in the adult female rat.     

Hypothermic circulatory arrest does not increase the risk of ascending thoracic aortic aneurysm resection

OBJECTIVE: The purpose of this study was to investigate the safety and efficacy of a period of deep hypothermic circulatory arrest (DHCA) during elective replacement of the ascending thoracic aorta. SUMMARY BACKGROUND DATA: DHCA has been implemented in ascending thoracic aortic aneurysm resection whenever the anatomy or pathology of the aorta or arch vessels prevents safe or adequate cross-clamping. Profound hypothermia and retrograde cerebral perfusion have been shown to be neurologically protective during ascending aortic replacement under circulatory arrest. METHODS: The authors conducted a retrospective analysis of 91 consecutive patients who underwent repair of chronic ascending thoracic aortic aneurysms from 1986 to present. The authors hypothesized that patients undergoing DHCA with or without retrograde cerebral perfusion during aneurysm repair were at no greater operative risk than patients who received aneurysm resection while on standard cardiopulmonary bypass. RESULTS: There were no significant differences in hospital mortality, stroke rate, or operative morbidity between patients repaired on DHCA when compared to those repaired on cardiopulmonary bypass. CONCLUSIONS: DHCA with or without retrograde cerebral perfusion does not result in increased morbidity or mortality during the resection of ascending thoracic aortic aneurysms. In fact, this technique may prevent damage to the arch vessels in select cases and avoid the possible complications associated with cross-clamping a friable or atherosclerotic aorta.     

TNK-tissue plasminogen activator compared with front-loaded alteplase in acute myocardial infarction: results of the TIMI 10B trial. Thrombolysis in Myocardial Infarction (TIMI) 10B Investigators

BACKGROUND: Bolus thrombolytic therapy is a simplified means of administering thrombolysis that facilitates rapid time to treatment. TNK-tissue plasminogen activator (TNK-tPA) is a highly fibrin-specific single-bolus thrombolytic agent. METHODS AND RESULTS: In TIMI 10B, 886 patients with acute ST-elevation myocardial infarction presenting within 12 hours were randomized to receive either a single bolus of 30 or 50 mg TNK-tPA or front-loaded tPA and underwent immediate coronary angiography. The 50-mg dose was discontinued early because of increased intracranial hemorrhage and was replaced by a 40-mg dose, and heparin doses were decreased. TNK-tPA 40 mg and tPA produced similar rates of TIMI grade 3 flow at 90 minutes (62.8% versus 62.7%, respectively, P=NS); the rate for the 30-mg dose was significantly lower (54.3%, P=0.035) and was 65. 8% for the 50-mg dose (P=NS). A prespecified analysis of weight-based TNK-tPA dosing using median TIMI frame count demonstrated a dose response (P=0.001). Similar dose responses were observed for serious bleeding and intracranial hemorrhage, but significantly lower rates were observed for both TNK-tPA and tPA after the heparin doses were lowered and titration of the heparin was started at 6 hours. CONCLUSIONS: TNK-tPA, given as a single 40-mg bolus, achieved rates of TIMI grade 3 flow similar to those of the 90-minute bolus and infusion of tPA. Weight-adjusting TNK-tPA appears to be important in achieving optimal reperfusion; reduced heparin dosing appears to improve safety for both agents. Together with the safety results from the parallel Assessment of the Safety of a New Thrombolytic: TNK-tPA (ASSENT I) trial, an appropriate dose of this single-bolus thrombolytic agent has been identified for phase III testing.