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PubMed2006

Event-related potentials of single-digit addition, subtraction, and multiplication.

This study compared the event-related potentials elicited by single-digit addition, subtraction, and multiplication problems. With a delayed verification paradigm, 18 Chinese undergraduates were first asked to solve the arithmetic problems that were presented visually for 200 ms and, after 1.5 s, to judge whether a presented solution was correct or not. Results showed that, compared to addition and subtraction, multiplication elicited a greater N300 at the left frontal electrodes peaking around 320 ms (in the interval between 275 and 334 ms after the onset of the arithmetic problem). To control for the confounding effects of task difficulty and solution size, comparisons were further made between "large" addition problems (with sums between 11 and 17) and "small" multiplication problems (with products between 6 and 24). Similar results were obtained (i.e., a significant difference between addition and multiplication in the N300 component between 296 and 444 ms). Source analyses demonstrated that a single dipole in the left anterior brain areas could have contributed to the topographies of the difference waveforms ("multiplication-addition", "multiplication-subtraction", and "'small' multiplication-'large' addition"). These results are interpreted in terms of the greater reliance on phonological processing for the retrieval of multiplication facts than for the retrieval of addition and subtraction facts.

Adolescent↗
PubMed2005

Enhanced granulation by natural ionic polymer additives in UASB reactor treating low-strength wastewater.

Effect of natural ionic polymer additives on granulation in lab-scale UASB reactors treating low-strength synthetic wastewater (COD 750-850 mg/L) was examined. The organic loading rate was 1.477+/-0.118 kgCOD/m3/day. Under identical conditions four similar reactors were operated in parallel with the following additives: control with no additive, anionic part of Reetha (Sapindus trifoliata) extract, cationic part of Reetha extract, and Chitosan. By the end of the study period, Chitosan as an additive produced largest granules with mean size of 0.15 mm closely followed by the cationic fraction of the Reetha extract with mean size of 0.144 mm, and anionic fractions of the Reetha extract with 0.139 mm. Control reactor with no additives had the smallest size granules with mean size of 0.128 mm. The fraction of granules in the sludge bed of size >0.1 mm showed similar trend. The largest granule size observed in the reactors with additives was 4-5mm as compared to 2 mm in the control reactor. Cationic polymers were more effective additives for enhancing sludge granulation. Exo-cellular protein, lipid, sugar and total polymer increased with granulation in the reactors. A COD removal efficiency of 95-98% was achieved in all the reactors.

Biocompatible Materials↗
PubMed2006

Size of metastasis in the sentinel node predicts additional nodal involvement in penile carcinoma.

PURPOSE: The majority of patients with penile cancer with a tumor positive sentinel node do not benefit from complementary lymph node dissection because of absent additional involved nodes. We analyzed factors that may determine the involvement of additional nodes. MATERIALS AND METHODS: A total of 158 patients with clinically node negative penile carcinoma underwent sentinel node biopsy. Complementary inguinal lymph node dissection was performed when the sentinel node was tumor positive. The size of the sentinel node metastasis was measured and classified as micrometastasis--2 mm or less, or macrometastasis--more than 2 mm. Sentinel and dissection specimen nodes were step-sectioned. Factors were analyzed for their association with additional nodal involvement, including stage, diameter, grade, absence or presence of vascular invasion of the primary tumor, and sentinel node metastasis size. RESULTS: Tumor positive sentinel nodes were found in 46 groins and complementary lymph node dissection was performed. Nine of these 46 groins (20%) contained additional involved lymph nodes. On univariate and multivariate analyses the size of the sentinel node metastasis proved to be the only significant prognostic variable for additional lymph node involvement (each p = 0.02). None of the 15 groins with only micrometastasis in the sentinel node contained additional involved nodes. CONCLUSIONS: In penile carcinoma additional nodal involvement was related to the size of the metastasis in the sentinel node. Sentinel node micrometastasis was not associated with other involved lymph nodes. This finding suggests that these patients can be spared complementary lymph node dissection.

Carcinoma, Squamous Cell↗
PubMed2000

Addition of polar organic solvents can improve the product selectivity of cyclodextrin glycosyltransferase. Solvent effects on cgtase.

Cyclodextrin glycosyltransferase (EC 2.4.1.19, CGTase) is an enzyme that produces cyclodextrins from starch via an intramolecular transglycosylation reaction. Addition of small amounts (10% v/v) of polar organic solvents can affect both the overall production yield and the type of cyclodextrin produced from a maltodextrin substrate under simulated industrial process conditions. Using CGTase from Thermoanaerobacter sp. all solvents produced an increase in cyclodextrin yield when compared with a control, the greatest increase being obtained with addition of ethanol (26%). In addition product selectivity was affected by the nature of the organic solvent used: beta-cyclodextrin was favoured in the absence of any solvent and on the addition of dimethylsulphoxide, t-butanol and dimethylformanide while alpha-cyclodextrin was favoured by addition of acetonitrile, ethanol and tetrahydrofuran. With CGTase from Bacillus circulans strain 251 relatively smaller increases in overall cyclodextrin production were achieved (between 5-10%). Addition of t-butanol to a B. circulans catalysed reaction however did produce the largest selectivity for beta-cyclodextrin of any solvent-enzyme combination (82%). The effect of solvent addition was shown not to be related to the product inhibition of CGTase, but may be related to reduced competition from the intermolecular transglycosylation reaction that causes degradation of cyclodextrin products. This rate of this reaction was shown to be dependent on the nature of the organic solvent used.

Journal Article↗
PubMed2003

Logistic or additive EuroSCORE for high-risk patients?

OBJECTIVES: To assess whether the use of the full logistic European System for Cardiac Operative Risk Evaluation (EuroSCORE) is superior to the standard additive EuroSCORE in predicting mortality in high-risk cardiac surgical patients. METHODS: Both the simple additive EuroSCORE and the full logistic EuroSCORE were applied to 14,799 cardiac surgical patients from across Europe, of whom there were 4293 high-risk patients (additive EuroSCORE of 6 or more). The systems were compared for absolute prediction and discrimination (area under the receiver operating characteristic (ROC) curve). RESULTS: Actual mortality was 4.72%. The logistic model was closer to this than the additive model (4.84% (4.72-4.94) versus 4.21 (4.21-4.26)). Most of this difference was due to high-risk patients where actual mortality was 11.18% and predicted was 7.83% (additive) and 11.23% (logistic). Discrimination was similar in both systems as measured by the area under the ROC curve (additive 0.783, logistic 0.785). CONCLUSIONS: The additive EuroSCORE model remains a simple "gold standard" for risk assessment in European cardiac surgery, usable at the bedside without complex calculations or information technology. The logistic model is a better risk predictor especially in high-risk patients and may be of interest to institutions engaged in the study and development of risk stratification.

Aged↗
PubMed2002

Nontemplated nucleotide addition by HIV-1 reverse transcriptase.

We studied the kinetics of nontemplated nucleotide addition by the reverse transcriptase (RT) of human immunodeficiency virus type 1 (HIV-1) using model substrates derived from the 3' end of HIV-1 minus-strand strong-stop DNA. The addition of a nontemplated nucleotide was highly dependent on the nature of the base (fastest addition with dATP), type of nucleoside, and pH of the reaction buffer. The salt concentration, presence or absence of nucleocapsid protein, and nature of the blunt-ended duplex (DNA/DNA versus RNA/DNA) had only limited effects. The efficiency and base specificity were strongly affected by the sequence at the 3' end of the blunt-ended duplex. In every case, nontemplated nucleotide addition was much slower than templated polymerization. The K(d) for the incoming dNTP with an RT bound to a blunt-ended duplex was at least 1000-fold higher than with a duplex with a template overhang. At concentrations normally found in vivo, ATP can compete with dNTPs for binding to the polymerase active site and reduce the efficiency of nontemplated nucleotide addition. Although a stable ternary complex RT/DNA/dNTP could be readily detected by gel retardation assays if the DNA had a template overhang, stable ternary complexes were not observed with a blunt-ended duplex substrate. At in vivo concentrations of dNTPs (5-10 microM), nontemplated nucleotide addition occurred, but it was very inefficient and the rate of nontemplated polymerization is at least 10000-fold slower than the rate of templated polymerization. We could conclude that, in vivo, the unfavorable binding of the incoming dNTP, low concentration of dNTPs, the presence of a large concentration of ATP, and the inability to form a stable ternary complex prior to the polymerization step collaborate to reduce the efficiency of nontemplated nucleotide addition.

Adenosine Triphosphate↗
PubMed1998

A Density Functional Study of [2+3] versus [2+2] Addition of Ethylene to Chromium-Oxygen Bonds in Chromyl Chloride.

Density functional theory (DFT) calculations have been carried out on the [2+2] and [2+3] addition of ethylene to Cr=O bonds in CrO(2)Cl(2). The [2+3] addition was found to be more favorable with an electronic reaction enthalpy of -9.6 kcal/mol and an activation barrier of 15.8 kcal/mol. The corresponding values for the [2+2] addition were 15.4 and 27.9 kcal/mol, respectively. It was concluded that epoxides formed in the reaction between CrO(2)Cl(2) and olefins are unlikely to originate from a [2+2] addition path to a Cr=O bond as previously suggested. The two addition reactions were analyzed by the intrinsic reaction coordinate method, and comparisons were made to a previous study of [2+2] and [2+3] addition by ethylene to OsO(4). Qualitative considerations were used to rationalize why the addition of ethylene to metal-oxygen bonds in tetrahedral d(0) oxo complexes seems more prone to proceed by a [2+3] mechanism.

Journal Article↗
PubMed2001

The regioselectivity of addition of organolithium reagents to enones and enals: the role of HMPA.

The role of polar solvents (particularly HMPA) in controlling the ratio of 1,2 to 1,4 addition of sulfur-substituted organolithium reagents to cyclohexenones and hexenal was studied. Low-temperature, multinuclear NMR studies provided quantitative information about the ratio of contact (CIP) and solvent-separated (SIP) ion pairs in solutions of dithianyllithiums and phenylthiobenzyllithiums in THF-HMPA solutions. The ratio of contact and separated ion pairs was manipulated by changes in the strength of solvation (generally through the addition of HMPA). Although the results are consistent with the CIP/SIP distribution being an important factor in determining the regioselectivity of these additions (Curtin-Hammett limitations prevent a direct correlation), it cannot be the only one. Changes in diastereomeric product ratios upon addition of HMPA suggest that complexation of HMPA to lithium has two effects. First, it causes ion pair separation, which enhances 1,4 addition. Second, it lowers the Lewis acidity and catalytic effectiveness of the lithium cation, which also favors 1,4 addition. For most sulfur-stabilized lithium reagents, 2 equiv of HMPA suffice to achieve >95% 1,4 addition, whereas 4 equiv of DMPU are required to achieve identical regiochemical and stereochemical results.

Journal Article↗
PubMed2005

Identity hydride-ion transfer from C-H donors to C acceptor sites. Enthalpies of hydride addition and enthalpies of activation. Comparison with C...H...C proton transfer. An ab initio study.

Enthalpies of addition of hydride ion to eleven carbonyl acceptors (X-CHO), two conjugate addition sites (X-CH=CH2; X = CHO, NO2), eight carbenium ion acceptors, fulvene, borane, and SiH3(+) were calculated at the MP2/6-311+G level. Correlation between calculated and experimental enthalpies of addition of hydride ion is excellent. Transition states (ts) for the identity hydride transfers between the acceptors and their corresponding hydride adducts (hydride donors) were also calculated. The carbonyl and fulvene reactions have transition states with one imaginary frequency: the hydrogen transfer coordinate. The carbenium ions, borane, and SiH3(+) gave not transition states but stable compounds upon addition of the hydride donor. Computational differences between these hydride transfers and previously reported proton transfers include shorter partial C...H bonds and a tendency toward bent C...H...C angles for the hydride transfer ts and addition compound structures, particularly when a bent geometry improves interactions elsewhere in the structure. These and other differences are explained by modeling the hydride transfer ts and addition compounds as two-electron, three-center systems involving the transfer termini and the shared hydrogen but the proton transfer ts structures as four-electron, three-center systems. Charge and geometry measures suggest transition states in which these features change synchronously, again in contrast to many proton transfer reactions. For the X-CHO set, polar effects dominate enthalpies of hydride addition, with resonance effects also important for resonance donors; these preferentially stabilize the acceptor, reducing its hydride ion affinity. Activation enthalpies are dominated by resonance stabilization of the acceptors, greatly attenuated in the transition states.

Journal Article↗
PubMed2004

Mechanism and ligand-transfer selectivity of 1,2-addition of organozincate complexes to aldehyde.

Density functional theory (DFT) calculations have been performed to investigate the origin of the reactivity and ligand-transfer selectivity of organozincates in the 1,2-addition to carbonyl compounds. Examination of the addition of Me(3)ZnLi to formaldehyde as compared with that of Me(2)Zn showed that the addition reaction is facilitated by the push-pull synergy of the Lewis acidic Li atom and the negatively charged Me(3)Zn moiety. This analysis then provided an answer to the mechanistic question about the experimentally established ligand-transfer selectivity in the 1,2-addition of heteroleptic organozincate Me(2)Zn(X)Li (X = H-, R(2)N-, and R(3)Si-). The addition of these heteroleptic zincate compounds results in selective transfer of H, R(2)N, and R(3)Si groups owing to the favorable orbital interaction between these groups and the carbonyl pi-system. The addition reaction of the zincate compounds conforms to the mechanistic framework of the conventional nucleophilic reaction, such as the addition reaction of MeLi dimer, and is different from the reaction of organocuprates, where oxidation/reduction of the copper atom is involved.

Journal Article↗
PubMed2006

Chiral phosphoramide-catalyzed aldol additions of ketone trichlorosilyl enolates. Mechanistic aspects.

The mechanism of the catalytic, enantioselective addition of trichlorosilyl enolates to aldehydes has been investigated. Kinetic studies using ReactIR and rapid injection NMR (RINMR) spectroscopy have confirmed the simultaneous operation of dual mechanistic pathways involving either one or two phosphoramides bound to a siliconium ion organizational center. This mechanistic dichotomy was initially postulated on the basis of catalyst loading studies and nonlinear effects studies. This duality explains the difference in reactivity and stereoselectivity of various classes of phosphoramides. Determination of Arrhenius activation parameters revealed that aldol addition occurs through the reversible albeit unfavorable formation of an activated complex, and natural-abundance 13C NMR kinetic isotope effect (KIE) studies have determined that the turnover limiting step is the aldol addition. A thorough examination of a range of phosphoramides has established empirical structure-activity selectivity relationships. In addition, the effects of catalyst loading, rate of addition, solvents, and additives have been studied and together allow the formulation of a unified mechanistic picture for the aldol addition.

Journal Article↗
PubMed2007

Kinetic and thermodynamic stability of acenes: Theoretical study of nucleophilic and electrophilic addition.

To understand the reactivity of acenes, particularly pentacene, the addition of HCl and water to acenes was studied for the benzene-nonacene series at the B3LYP/6-31G(d) level of theory. Surprisingly, the reactivity of the acenes increases along the series up to hexacene and remains constant from hexacene and above due to the biradical character of the ground state of higher acenes. While the exothermicity of HCl and water additions are very similar, the activation barriers for HCl and water additions differ by a constant factor of ca. 27 kcal/mol. The barrier for the addition of HCl varies from 44 kcal/mol for benzene to 16-18 kcal/mol for pentacene-nonacene, whereas the barrier for the addition of water varies from 71 kcal/mol for benzene to 43-46 kcal/mol for pentacene-nonacene. The transition states (TSs) for the addition of water to acenes are relatively "late" on the reaction coordinate, compared to the "earlier" TSs for the addition of HCl. There is a substantial substituent effect on the energy barriers for these reactions. HCl behaves as an electrophile, with rhoHCl (vs rho p) = -4.48 and -3.39 for anthracenes and pentacenes, respectively, while water behaves as a nucleophile, with rhoHCl (vs rho p) = 2.35 and 1.39 for anthracenes and pentacenes, respectively.

Journal Article↗
PubMed2001

The preparation of additional smears from a cervical scrape: impact on the rate of detection of cervical neoplasia.

The preparation of additional smears from a cervical scrape: impact on the rate of detection of cervical neoplasia It has been known for some time that only a proportion of the cells on the smear-taking device is transferred to the slide. This can give rise to errors in reporting although the smear may have been taken correctly. This study was undertaken to identify a quick and simple method of improving the accuracy of the Papanicolaou test. A conventional smear and five additional smears were obtained from 62 women attending a Genito-Urinary Medicine clinic. The cell content of the conventional smears and the additional smears was compared. Dyskaryotic cells were detected both in the conventional smear and in the first and second additional smears from 22 women. Dyskaryotic cells were detected in the first and second additional smears only in five women. Thus, the conventional smear failed to detect biopsy-confirmed cervical abnormality in these women. A cell count of the first additional smear in the five cases where the conventional smear was negative showed that they contained, on average, 310 dyskaryotic cells. The preparation of one additional cervical smear per cervical scrape could significantly increase the accuracy of the cervical smear test by 11% (P=0.025, McNemar's test).

Adult↗
PubMed2001

Simulation of cardiac work transitions, in vitro: effects of simultaneous Ca2+ and ATPase additions on isolated porcine heart mitochondria.

During increases in cardiac work there are net increases in cytosolic [Ca(2+)] and ATP hydrolysis by myofiliments and ion transport ATPases. However, it is still unclear what role Ca(2+)or the ATP hydrolysis products, ADP and Pi, have on the regulation of mitochondrial ATP production. In this study, work jumps were simulated by simultaneous additions of Ca(2+) and ATPase to porcine heart mitochondria. The net effects on the mitochondrial ATP production were monitored by simultaneously monitoring respiration (mVo2), [NADH], [ADP] and membrane potential (deltapsi) at 37 degrees C. Addition of exogenous ATPase (300 mlU.ml(-1))]ATP (3.4 mM) was used to generate a 'resting' background production of ADP. This resting metabolic rate was 200% higher than the quiescent rate while [NADH] and deltapsi were reduced. Subsequent ATPase additions (1.3IU.ml(-)) were made with varying amounts of Ca(2+)(0 to 535 nM) to simulate step increases in cardiac work. Ca(2+) additions increased mVo2 and depolarized deltapsi, and were consistent with an activation of Fo/F1)ATPase. In contrast, Ca(2+) reduced the [NADH] response to the ATPase addition, consistent with Ca(2+)-sensitive dehydrogenase activity (CaDH). The calculated free ADP response to ATPase decreased \2-fold in the presence of Ca(2+). The addition of 172nM free Ca(2+)] ATPase increased mVo2 by 300% (P<0.05, n=8) while deltapsi decreased by 14.9+/-0.1 mV without changes in [NADH] (P > or =0.05, n=8), consistent with working heart preparations. The addition of Ca(2+) and ATPase combined increased the mitochondrial ATP production rate with changes in deltapsi, NADH and [ADP], consistent with an activation of CaDH and F o /F(1)ATPase activity. These balancing effects of ATPase activity and [Ca(2+)] may explain several aspects of metabolic regulation in the heart during work transitions in vivo.

Adenosine Diphosphate↗
PubMed2001

Early events in glycosylphosphatidylinositol anchor addition. substrate proteins associate with the transamidase subunit gpi8p.

The addition of glycosylphosphatidylinositol (GPI) anchors to proteins occurs by a transamidase-catalyzed reaction mechanism soon after completion of polypeptide synthesis and translocation. We show that placental alkaline phosphatase becomes efficiently GPI-anchored when translated in the presence of semipermeabilized K562 cells but is not GPI-anchored in cell lines defective in the transamidase subunit hGpi8p. By studying the synthesis of placental alkaline phosphatase, we demonstrate that folding of the protein is not influenced by the addition of a GPI anchor and conversely that GPI anchor addition does not require protein folding. These results demonstrate that folding of the ectodomain and GPI addition are two distinct processes and can be mutually exclusive. When GPI addition is prevented, either by synthesis of the protein in the presence of cell lines defective in GPI addition or by mutation of the GPI carboxyl-terminal signal sequence cleavage site, the substrate forms a prolonged association with the transamidase subunit hGpi8p. The ability of the transamidase to recognize and associate with GPI anchor signal sequences provides an explanation for the retention of GPI-anchored protein within the ER in the absence of GPI anchor addition.

Acyltransferases↗
PubMed1976

On estimating non-additive genetic parameters in chickens.

Several economically important traits in two Leghorn populations (over 9000 birds) were examined for additive and non-additive components of genetic variance and sex-linked effects. Data were analysed by two different statistical models based on least-squares procedures. 2. Six different covariances were first calculated between relatives; i.e., full-sibs 3/4-sisters, half-sisters, dam-daughters, grandam-granddaughters and aunt-nieces. 3. From the covariances, weighted least-squares equations were used to obtain estimates of variance components for additive genetic, dominance, maternal and sex-linkage effects. 4. The estimates of non-additive components were highly variable but generally small compared with the additive genetic estimates. 5. In general this study suggests that for most traits, with the possible exception of rate of egg production, there is relatively little non-additive genetic variation. 6. The consequences of possible negative correlations between additive effects and maternal effects are considered as they might apply to egg production in poultry.

Animals↗
PubMedDate not supplied

Correlation of specific migration (Cf) of plastics additives with their initial concentration in the polymer (Cp).

The first list of plastics additives which may be assigned restrictions in a future amendment to Directive 90/128/ EEC is likely to contain over 200 substances. If food consumption factors are taken into account many compounds on this list could have restrictions removed but there would, without doubt, still be many additives with restrictions. Extensive migration testing of food contact plastics containing restricted additives to ensure compliance would be required. These limits would be difficult to enforce, add significant cost burdens on the packaging industry and, for these reasons, may not provide improved consumer safeguards. An alternative means of control has been proposed based upon polymer composition. However, in order to support such a scheme a reliable correlation between migration of additives to their composition in the polymer must be demonstrated. There has been strong interest in establishing this relationship and a feasibility project to investigate the specific migration of four commonly used additives has been successfully completed. The study was initially funded for 1 year, by the Ministry of Agriculture, Fisheries and Food (MAFF) and industry. Analytical methods to determine the additives in food simulants have been developed and linear correlations have been demonstrated between the concentration of all four additives and their specific migration levels for each polymer studied. Experimental migration data have been compared with those generated by mathematical models.

Diffusion↗
PubMed2002

Effects of different additives on the performance of spray dryer system during incineration process.

The spray dryer system was conventionally employed to remove the SOx, NOx, and HCl in the flue gas. However, the removal efficiency of acid gas in the practical incineration flue gas, which contains dust, heavy metals, and acid gas itself, was seldom mentioned in the literature. The alkaline sorbents possess large specific surface that was a main factor on the adsorption of heavy metals and acid gas. Therefore, the primary objective of this study was focused on the effect of different additives on the removal efficiency of acid gas and heavy metals (Cr, Cd and Pb). The mass and element size distribution of heavy metals in fly ash under different additives were also investigated. The results indicated that the removal efficiency of HCl in the spray dryer system was higher than 97.8%. The effects of additives on the removal efficiency of HCl, however, were undistinguished. In the desulfurization process, the highest removal efficiency was 71.3% when the additive of amorphous SiO2 was added in the spray dryer system. The removal efficiency was 66.0% with the additive of CaCl2 and 63.1% without any additives, respectively. It was also found that the spray dryer system could decrease the concentration of metal in fly ash but increase the amount of fly ash. In addition, amorphous SiO2 in the alkaline sorbent tended to increase the adsorption of heavy metal on reactant, because it could enhance the dispersion of alkaline sorbent.

Adsorption↗