Finite constants: characterizations of a new decidable set of constants

Constant propagation, the replacement of program terms which represent a unique value at run time by their values, is a classical program optimization method. In spite of being treated for years, constant propagation still has been in the unsatisfactory phase of heuristics. We enhance the known constant propagation techniques to obtain an algorithm which is optimal for programs without loops. Fundamental is the introduction of a new decidable set of constants, the finite constants. This set has two different characterizations: a denotational one, which directly specifies our iterative algorithm and an operational one, which delivers the completeness or optimality of this algorithm for programs without loops. The algorithm is implemented in a commercial compiler project.     

Modellqualität als Indikator für Softwarequalität: eine Taxonomie

Zusammenfassung  Komplexit?t, Anforderungsmanagement und Variantenvielfalt sind zentrale Herausforderungen bei der Entwicklung und Evolution heutiger softwaregesteuerter Systeme. Diesen wird zunehmend durch den Einsatz modellbasierter Entwicklungsmethoden begegnet. Dadurch wird das Modell zum zentralen Artefakt und die Erstellung und Nutzung von Modellen zu einer zentralen T?tigkeit in der Softwareentwicklung. Mit der Bedeutung der Modelle steigen auch die Ansprüche an ihre Qualit?t. Dieser Beitrag untersucht die Implikationen, die daraus entstehen, insbesondere werden sinnvolle Qualit?tsmerkmale für softwarebeschreibende Modelle identifiziert und diskutiert.     

Unfavorable mechanical effects of heat and moisture exchangers in ventilated patients

OBJECTIVE: To investigate the mechanical effects of artificial noses. SETTING: A general intensive care unit of a university hospital. PATIENTS: 10 patients in pressure support ventilation for acute respiratory failure. INTERVENTIONS: The following three conditions were randomly tested on each patient: the use of a heated humidifier (control condition), the use of a heat and moisture exchanger without filtering function (HME), and the use of a combined heat and moisture exchanger and mechanical filter (HMEF). The pressure support level was automatically adapted by means of a closed-loop control in order to obtain constancy, throughout the study, of patient inspiratory effort as evaluated from airway occlusion pressure at 0.1 s (P0.1). Patient's ventilatory pattern, P0.1, work of breathing, and blood gases were recorded. MEASUREMENTS AND MAIN RESULTS: The artificial noses increased different components of the inspiratory load: inspiratory resistance, ventilation requirements (due to increased dead space ventilation), and dynamic intrinsic positive end-expiratory pressure (PEEP). The additional load imposed by the artificial noses was entirely undertaken by the ventilator, being the closed-loop control of P0.1 effective to maintain constancy of patient inspiratory work by means of adequate increases in pressure support level. CONCLUSIONS: The artificial noses cause unfavorable mechanical effects by increasing inspiratory resistance, ventilation requirements, and dynamic intrinsic PEEP. Clinicians should consider these effects when setting mechanical ventilation and when assessing patients' ability to breathe spontaneously.     

Evidence for disturbed S-adenosylmethionine : S-adenosylhomocysteine ratio in patients with end-stage renal failure: a cause for disturbed methylation reactions?

BACKGROUND: Elevated homocysteine concentrations have been associated with premature arteriosclerosis and with impairment of key methylation reactions through accumulation of the homocysteine metabolite S-adenosylhomocysteine. In end-stage renal failure high homocysteine concentrations are commonly found but thus far the concentrations of related adenosylated metabolites in plasma have not been assessed. METHODS: In this prospective study we determined plasma homocysteine and related metabolites in 25 patients on regular haemodialysis, and in 40 healthy volunteers. Blood samples from patients were drawn immediately before and in 10 patients additionally after the dialysis session. RESULTS: Folic acid and vitamin B12 in plasma were similar in patients (mean +/- SEM 25+/-2 nmol/l and 400+/-41 pmol/l respectively) and controls (24+/-3 and 324+/-23 respectively). In patients plasma homocysteine, S-adenosylmethionine and S-adenosylhomocysteine were markedly elevated (36.6+/-3.6 micromol/l, 381+/-32nmol/l and 1074+/-55 nmol/l respectively) compared to the control values (6.8+/-0.4 micromol/l, 60+/-3 nmol/l and 24.4+/-1.1 nmol/l respectively) whereas the molar ratio of plasma S-adenosylmethionine and S-adenosylhomocysteine was significantly decreased (0.36+/-0.02 and 2.7+/-0.2 in patients and controls respectively). Haemodialysis failed to normalize the abnormal levels of these metabolites. CONCLUSION: Since the ratio of S-adenosylmethionine : S-adenosylhomocysteine is closely linked to the activity of numerous enzymatic methylation reactions, these results suggest that methylation may be impaired in these patients.     

The protease-protected 30 kDa domain of SecA is largely inaccessible to the membrane lipid phase

SecA binds to the inner membrane of Escherichia coli through low affinity lipid interactions or with high affinity at SecYEG, the integral domain of preprotein translocase. Upon addition of preprotein and nucleotide, a 30 kDa domain of SecYEG-bound SecA is protected from proteolysis via membrane insertion. Such protection could result from some combination of insertion into the lipid phase, into a proteinaceous environment or across the membrane. To assess the exposure of SecYEG-bound SecA to membrane lipids, a radiolabeled, photoactivatable and lipid-partitioning crosslinker, 3-trifluoromethyl-3-(m[125I]iodophenyl) diazirine benzoic acid ester, was incorporated into inner membrane vesicles. The 30 kDa domain of SecYEG-bound SecA, inserted into the membrane in response to translocation ligands, is 18-fold less labeled than SecY, which is labeled effectively. In contrast, incorporation of the purified 30 kDa SecA fragment into crosslinker-containing detergent micelles or addition of detergent to crosslinker-containing membranes bearing the protease-protected SecA domain readily allows for labeling of this domain. We propose that the protease-inaccessible 30 kDa SecA domain is shielded from the fatty acyl membrane phase by membrane-spanning SecYEG helices and/or is largely exposed to the periplasm.     

Generation of chromosome fragment specific bovine DNA sequences by microdissection and DOP-PCR

Trends in causative organisms and sources of infection were studied in a series of 288 episodes of bacteremia in neutropenic cancer patients observed in a single institution from 1986 to 1993. The incidence of bacteremia increased significantly from 20 episodes per 1000 admissions in 1986 to 50 episodes per 1000 admissions in 1993 (p = 0.00001). Over the study period, a continuous increment in gram-positive bacteremia, which reached 81% of episodes in 1993 (p = 0.000001), was observed. Conversely, the incidence of gram-negative bacteremia remained stable. Coagulase-negative staphylococci and viridans group streptococci were the most commonly isolated pathogens. Bacteremia caused by coagulase-negative staphylococci increased from 3 episodes per 1000 admissions to 19 episodes per 1000 admissions (p = 0.0001), and viridans group streptococci bacteremia increased from 0 episodes per 1000 admissions to 19 episodes per 1000 admissions (p = 0.000001). The upward trend in gram-positive bacteremia appeared to be related to a significant increase in both intravascular catheters (p = 0.003) and oral mucositis (p = 0.003) as sources of infection. Specific strategies to prevent chemotherapy-induced mucositis and catheter-related bacteremia merit further investigations.     

Symbolic control of visual attention: The role of working memory and attentional control settings.

This study examined how 1 symbol is selected to control the allocation of attention when several symbols appear in the visual field. In Experiments 1-3, the critical target feature was color, and it was found that uninformative central arrows that matched the color of the target were selected and produced unintentional shifts of attention (i.e., involuntary, initiated slowly, producing long-lasting facilitatory effects). Experiment 4 tested whether such selection is the result of an attentional filter or of a competition bias due to a match of incoming information against integrated object representations stored in working memory. Here, the critical feature was shape and color was irrelevant, but matching color arrows were still selected. Thus, features of objects in working memory will bias the selection of symbols in the visual field, and such selected symbols are capable of producing unintentional shifts of attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hydroformylierung einfach und mehrfach ungesättigter Fettstoffe mit heterogenisierten Cobaltcarbonyl- und R

Hydroformylation of mono and multiple unsaturated fatty substances with heterogenized cobaltcarbonyl and rhodiumcarbonyl catalysts. Heterogenized cobalt and rhodiumcarbonyl catalyst systems can be used for the hydroformylation of mono and polyunsatured fatty substances in a technically simple and satisfying manner to useful chemical intermediates. The used solid tert. phosphane complex ligands have a silicate matrix and therefore they are also suitable for the cobalt catalyzed hydroformylation which is best performed at temperatures of 160–180^oC. The cobalt catalyzed reaction gives with polyunsaturated fatty substances almost only products with monofunctionalized fatty acid chains. Whereas, the rhodium catalyzed reaction gives with linolic acid compounds inhomogeneous mixtures of mono- and diformyl derivatives of these fatty substances. The heterogenized rhodium carbonyl catalyst systems therefore seem to be more suitable for the hydroformylation of monounsaturated compounds. This is also true for rhodiumcarbonylsupported aqueous phase-catalysts which give likewise mixtures of mono and diformyl derivatives in the hydroformylation of polyunsaturated fatty substances. In batch process after the complete conversion of the olefin and reduction of the CO/H₂-pressure the loss of catalyst metal from the support is negligible and in most cases below the detection limit (<1 ppm).     

Choice between fixed and variable delays with different reward amounts.

Choice between a variable and a fixed food source was studied in pigeons. The variable source yielded different durations of access to food (changed across experimental conditions) uniquely associated with equiprobable delays of either 20 sec or 60 sec, timed from the choice point. A comparison, elapsing alternative (time-left procedure [J. Gibbon and R. M. Church; see PA, Vol 67:2812]), was associated with fixed access to feeder after a 60-sec delay, timed from the beginning of the trial. Preference was best characterized as reflecting an average of the 2 local rates of reinforcement in the variable alternative (the average of the ratio of each standard amount and its associated delay). The averaging rule characterized initial choice link data well, but terminal link responding showed that Ss also remembered the 2 delay–amount combinations separately. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of forest and bioenergy strategies in the global carbon cycle

Forest and bioenergy strategies offer the prospect of reduced CO₂ emissions to the atmosphere. Such strategies can affect the net flux of carbon to the atmosphere through 4 mechanisms: storage of C in the biosphere; storage of C in forest products; use of biofuels to displace fossil-fuel use; use of wood products which often displaces other products that require more fossil fuel for their production. We use the mathematical model GORCAM (Graz/Oak Ridge Carbon Accounting Model) to examine these mechanisms for 16 land-use scenarios. Over long time intervals the amount of C stored in the biosphere and in forest products reaches a steady state and continuing mitigation of C emissions depends on the extent to which fossil fuel use is displaced by the use of bioenergy and wood products. The relative effectiveness of alternative forest and bioenergy strategies and their impact on net C emissions strongly depend, for example, on the productivity of the site, its current usage, and the efficiency with which the harvest is used. When growth rates are high and harvest is used efficiently, the dominant opportunity for net reduction in C emissions is seen to be fossil-fuel displacement. At the growth rates and efficiencies of harvest utilization adopted in many of our base scenarios, the net C balance at the end of 100 years is very similar whether trees are harvested and used for energy and traditional forest products, or reforestation and forest protection strategies are implemented. The C balance on a plantation system that provides a constant output of biomass products can look different than the balance of a single parcel of land.