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PubMed2006

The influence of additional surgical margins on the total specimen volume excised and the reoperative rate after breast-conserving surgery.

BACKGROUND: It is unclear whether the additional removal of breast tissue during breast-conserving therapy (BCT) for breast cancer beyond the standard lumpectomy reduces the incidence of inadequate microscopic margins found at pathological examination and subsequent reoperation. This study compares the reoperative rates after initial BCT in 3 groups of patients who underwent lumpectomy with complete resection of 4 to 6 additional margins, lumpectomy with selective resection of 1 to 3 additional margins, or standard lumpectomy. METHODS: Retrospective data were reviewed from 171 selected cases of BCT, from May 2000 to February 2006. Forty-five cases involved lumpectomy with complete resection of 4 to 6 additional margins; 77 involved lumpectomy with selective resection of 1 to 3 additional margins, whereas 49 involved standard lumpectomy. All samples underwent pathologic analysis of inked resection margins by permanent section. The 3 groups were compared for patient demographics, tumor size and histologic subtype, tumor stage, margin status, excised specimen volume, and eventual subsequent reoperation. Adequate surgical margin was defined as any negative margin greater than 2 mm. RESULTS: The group with complete resection of 4 to 6 additional margins had a subsequent reoperation rate of 17.7%, whereas the group with selective resection of 1 to 3 additional margins and the standard lumpectomy group had a subsequent reoperation rate of 32.5% and 38.7%, respectively, because of inadequate margins. The mean total excised specimen volume in the 3 groups was 129.19, 46.04, and 37.44 cm3, respectively. CONCLUSIONS: The complete resection of 4 to 6 additional margins during the initial BCT resulted in the lowest subsequent reoperation rate, and the largest total volume specimen excised among the 3 techniques studied.

Adult↗
PubMed2006

A randomised trial of the effects of an additional communication strategy on recruitment into a large-scale, multi-centre trial.

Timely participant recruitment remains a significant challenge for most clinical trials. We evaluated the effects on participant recruitment of communication between the central trial coordinators and the clinical sites in the setting of a large international multi-centre clinical trial. The effects of communication were determined in a single-blind randomised controlled trial involving 167 clinical sites in 19 countries. Clinical sites were randomised to either additional or usual communication strategies - the additional communication group received a communication package based on additional, individually-tailored feedback about recruitment, in addition to the usual correspondence from the central trial coordinators that was provided to the control group. The two study outcomes were the median time to half randomisation target and the median total number of participants randomised per clinical site. Eighty-five clinical centres were randomised to receive additional communication and 82 to receive usual communication. At the conclusion of recruitment, there was no significant difference in the median number of participants randomised per centre between the additional and usual groups (37.5 vs. 37.0, p=0.68). The median time to half randomisation target was lower in the additional communication group compared to the usual group, however this difference did not achieve conventional levels of statistical significance (4.4 months vs. 5.8 months, p=0.08). The findings suggest that the additional communication strategy may be of some incremental benefit in helping sites achieve recruitment targets sooner.

Communication↗
PubMed2005

Effect of anionic additive type on ion pair formation constants of basic pharmaceuticals.

Due to their beneficial effect on selectivity, peak shape, and sample loading, the use of mobile phase anionic additives, such as formate (HCOO-), chloride (Cl-), and trifluoroacetate (CF3COO-), is increasing in both reversed-phase chromatography (RPLC) and liquid chromatography-mass spectrometry (LC/MS). Similarly, perchlorate is a common "ion pair" agent in reversed-phase separation of peptides. Although many studies have suggested that anions effect in chromatography is due to the formation of ion pairs in the mobile phase between the anions and cationic analytes, there has been no independent verification that ion pairs are, in fact, responsible for these observations. In order to understand the mechanisms by which anionic additives influence retention in chromatography and ionization efficiency in electrospray mass spectrometry, we studied the formation of ion pairs between a number of prototypical basic drugs and various additives by measuring the effect of anionic additives on the electrophoretic mobility of the probe drugs under solvent conditions commonly used in chromatography. For the first time, ion pair formation between basic drugs and anionic additives under conditions commonly used in reversed-phase liquid chromatography has been confirmed independently with all anions (i.e. hexafluorophosphate, perchlorate, trifluoroacetate, and chloride) used in this study. We measured ion pair formation constants (Kip) for different anionic additives using capillary electrophoresis (CE) and obtained quantitative estimates for the extent of ion pairing in buffered acetonitrile-water. The data clearly indicate that different anionic additives ion pair with cationic drugs to quite different extents. The ion pair formation constants show a clear trend with the order being: PF6- > ClO4- > CF3COO- > Cl-. However, the extent of ion pairing is not large. At a typical RPLC mobile phase additive concentration of 20mM, the percentages of the analytes that are present as ion pairs are about 15%, 6%, and 3% for hexafluorophosphate, perchlorate, and trifluoroacetate, respectively. The fraction of the analytes present as a chloride pair is even smaller.

Amitriptyline↗
PubMed2006

The logistic EuroSCORE predicts the hospital mortality of the thoracic aortic surgery in consecutive 327 Japanese patients better than the additive EuroSCORE.

OBJECTIVE: Risk stratification in thoracic aortic surgery is a topic of major interest. Recent studies have shown the European System for Cardiac Operative Risk Evaluation (EuroSCORE) to be an extremely useful and reliable risk stratification score and also a good indicator of quality of care in cardiac surgery. The purpose of this study was to evaluate the significance of the additive and logistic EuroSCOREs in patients undergoing surgery on the thoracic aorta in Japan. METHODS: We calculated the predicted mortality according to the additive and logistic EuroSCORE algorithms in 327 consecutive patients who underwent surgery of the thoracic aorta during a 30-year period (between 1976 and 2005). We compared the score validity between the two algorithms and also evaluated the score validity for the patients who underwent thoracic aortic surgery. The score validity was assessed by calculating the area under the receiver operating characteristic (ROC) curve. RESULTS: The overall in-hospital mortality was 13%. The area under the ROC curve was satisfactorily high for the additive (0.68, 0.73, 0.73) as well as the logistic EuroSCORE (0.69, 0.74, 0.75) in the patients who underwent thoracic aortic surgery during 30-, 20-, and 10-year periods, respectively. The actual mortality was 7% (Group 1; an additive EuroSCORE of 3-6), 16% (Group 2; 7-11), and 37% (Group 3; >12). The mortality expected by the additive and logistic EuroSCORE in the three different risk groups were (5%, 9%, 19%) and (5%, 14%, 43%), respectively. Namely, the mortality expected by the logistic EuroSCORE perfectly matched with the actual mortality in any of the three risk groups. In contrast, the mortality expected by the additive EuroSCORE tended to dissociate when the number of risks increased. Significant difference was observed between the observed mortality and the mortality expected by the additive EuroSCORE algorithm in the high-risk group (p=0.0473). CONCLUSIONS: Although both the additive and the logistic EuroSCORE reliably predicted the overall operative mortality for thoracic aortic surgery in 327 Japanese patients, the logistic EuroSCORE better matched with the actual mortality in the operative risk especially in the high-risk group.

Aged↗
PubMed2004

Effect of vermiculite addition on compost produced from Korean food wastes.

To evaluate the effect of vermiculite addition on composting food wastes from Korean households, food wastes were composted in three small bins to which different additives were added. The following three bins were employed: in Case I, only recycled compost was composted; in Case II, food wastes with recycled compost; and in Case III, food wastes with recycled compost and vermiculite. In the experiment performed for 30 days, it was confirmed that the supplementary addition of vermiculite to the composting mixture did not significantly improve the weight loss rate and the decomposition rate of food wastes. Due to dilution through the use of inorganic vermiculite, the vermiculite addition reduced the organic matter concentration of the composting mixtures. Vermiculite addition did not raise the pH value. Weight losses of roughly 70% were observed based on calculating moisture loss as well as dry food waste loss and not considering additives, while dry food waste loss was 29.4% and 35.8% with and without the addition of vermiculite, respectively. For these experiments, the major portion of the weight loss was the loss of water. The results indicate a need to differentiate between weight loss percentages and decomposition percentages, and a need to indicate if either of these percentages includes or excludes the mass of additives.

Aluminum Silicates↗
PubMed2003

Additional stenting promotes intimal proliferation and compromises the results of intravascular radiation therapy: an intravascular ultrasound study.

BACKGROUND: Vascular brachytherapy (VBT) reduces in-stent restenosis (ISR). However, additional stenting at the time of radiation may be associated with a worse outcome. METHODS AND RESULTS: Intravascular ultrasound (IVUS) was performed after VBT and at 6 months follow-up in 79 native artery ISR patients treated with gamma-radiation who participated in the Washington Radiation for In-Stent restenosis Trial (WRIST), Gamma-1, and Angiorad Radiation Technology for In-Stent restenosis Trial in Coronaries (ARTISTIC) trials. Patients were treated with (192)Ir at 14 or 15 Gy at 2 mm from the source. Additional stents were used to treat the ISR lesions in 45 patients; these patients were then compared with the 34 patients treated without restenting. Paired measurements included stent, lumen, and intimal hyperplasia volumes. After the VBT procedure, intimal hyperplasia volume was smaller in the group treated with additional stents (54 +/- 33 mm(3) vs 34 +/- 33 mm(3), P =.012), but minimal lumen area was similar between the 2 groups (4.3 +/- 1.5 mm(2) vs 4.7 +/- 1.4 mm(2) respectively, P = NS). Between the time of the VBT procedure and follow-up, intimal hyperplasia volume increased by 27 +/- 19 mm(3) in the restented group and by 9 +/- 21 mm(3) in the group treated without additional stents (P =.014). At 6 months, intimal volume was similar in the 2 groups, but minimal lumen area was slightly smaller in the group treated with additional stents (3.4 +/- 1.8 mm(2) vs 4.2 +/- 1.7 mm(2), P =.053). Patients treated with additional stents had more target lesion revascularizations than the group treated without additional stents (38% vs 15%, P =.02). CONCLUSIONS: Additional stenting reduces intimal hyperplasia within the stents acutely. However, it compromises the benefit of VBT by promoting higher intimal regrowth within months after radiation.

Brachytherapy↗
PubMed2003

Addition of right-sided and posterior precordial leads during stress testing.

BACKGROUND: Exercise treadmill testing has limited sensitivity for the detection of coronary artery disease, frequently requiring the addition of imaging modalities to enhance the predictive value of the test. Recently, there has been interest in using nonstandard electrocardiographic (ECG) leads during exercise testing. METHODS: We consecutively enrolled all patients undergoing exercise myocardial imaging with four additional leads recorded (V4R, V7, V8, and V9). The test characteristics of the 12-lead, the 15-lead (12-lead, V7, V8, V9), and the 16-lead (12-lead, V4R, V7, V8, V9) ECGs were compared with stress imaging in all patients. In the subset of patients who underwent angiography within 60 days of stress testing, these lead arrays were compared with the catheterization findings. RESULTS: There were 727 subjects who met entry criteria. The mean age was 58.5 +/- 12.3 years, and 366 (50.3%) were women. Pretest probability for disease was high in 241 (33.1%), intermediate in 347 (47.7%), and low in 139 (19.1%). A total of 166 subjects had an abnormal 12-lead ECG during exercise. The addition of 3 posterior leads to the standard 12-lead ECG resulted in 7 additional subjects having an abnormal electrocardiographic response to exercise. The addition of V4R resulted in only 1 additional patient having an abnormal ECG during exercise. The sensitivity of the ECG for detecting ischemia as determined by stress imaging was 36.6%, 39.2%, and 40.0% (P = NS) for the 12-lead, 15-lead, and 16-lead ECGs, respectively. In those with catheterization data (n = 123), the sensitivity for determining obstructive coronary artery disease was 43.5%, 45.2%, and 45.2% (P = NS) for the 12-lead, 15-lead, and 16-lead ECGs, respectively. The sensitivity of imaging modalities was 77.4% when compared with catheterization. CONCLUSIONS: In patients undergoing stress imaging studies, the addition of right-sided and posterior leads did not significantly increase the sensitivity of the ECG for the detection of myocardial ischemia. Additional leads should not be used to replace imaging modalities for the detection of coronary artery disease.

Aged↗
PubMed2000

Comparison of separation selectivity in capillary electrokinetic chromatography using a cationic linear polymeric pseudo-stationary phase or monomeric additives of similar structure.

The retention properties in electrically driven systems with monomeric additives were compared to an electrokinetic chromatographic system with a linear, charged polymer of similar chemical structure (all additives are quaternary tetraalkyl ammonium ions). The monomeric additives were tetramethylammonium (TMA), tetraethylammonium (TEA) and dimethylpyrrolidinium (DMP), respectively, the polymeric additive was poly(diallyldimethyl)ammonium (PDADMA). The additive concentration in the background electrolyte was 2 and 4% (w/w). The retention characteristics were based on the apparent mobilities of 10 non-charged analytes with different chemical functionality, which were transported by the anodic electroosmotic flow in the dynamically coated capillary, and retained by the counter-flowing cationic additives. From these data capacity factors were derived, which ranged up to 0.8. Association constants were calculated, and were found between 10 and 170. Roughly, the association constants increased for a given analyte in the sequence TMA<TEA<DMP< PDADMA. However, changes in the retention order were observed for some cases, reflecting the different selectivity of the particular systems for certain pairs of analytes. A general advantage of polymeric pseudo-stationary phases compared to monomeric additives is given by the negligible reduction of the mobility of the analyte-polymer associate in relation to the free additive ion, resulting in a broader retention window under most practical conditions.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed2002

Effect of alcohol addition on the movement of petroleum hydrocarbon fuels in soil.

Groundwater contamination by fuel spills from aboveground and underground storage tanks has been of growing concern in recent years. This problem has been magnified by the addition of oxygenates, such as ethanol and methyl-tertiary-butyl ether (MTBE) to fuels to reduce vehicular emissions to the atmosphere. These additives, although beneficial in reducing atmospheric pollution, may, however, increase groundwater contamination due to the co-solvency of petroleum hydrocarbons and by the provision of a preferential substrate for microbial utilisation. With the introduction of ethanol to diesel fuel imminent and the move away from MTBE use in many states of the USA, the environmental implications associated with ethanol additive fuels must be thoroughly investigated. Diesel fuel movement was followed in a 1-m soil column and the effect of ethanol addition to diesel fuel on this movement determined. The addition of 5% ethanol to diesel fuel was found to enhance the downward migration of the diesel fuel components, thus increasing the risk of groundwater contamination. A novel method using soil packed HPLC columns allowed the influence of ethanol on individual aromatic hydrocarbon movement to be studied. The levels of ethanol addition investigated were at the current additive level (approx. 25%) for ethanol additive fuels in Brazil and values above (50%) and below (10%) this level. An aqueous ethanol concentration above 10% was required for any movement to occur. At 25% aqueous ethanol, the majority of hydrocarbons were mobilised and the retention behaviour of the soil column lessened. At 50% aqueous ethanol, all the hydrocarbons were found to move unimpeded through the columns. The retention behaviour of the soil was found to change significantly when both organic matter content and silt/clay content was reduced. Unexpectedly, sandy soil with low organic matter and low silt/clay was found to have a retentive behaviour similar to sandy subsoil with moderate silt/clay, but little organic matter. It was concluded that sand grains might have a more important role in the adsorption of petroleum hydrocarbons than first realised. This method has shown that soil packed HPLC columns can be used to provide a quick estimate of petroleum hydrocarbon, and possibly other organic contaminant, movement in a variety of different soil types.

Adsorption↗
PubMed1999

Effect of additives on the physicochemical properties of liquid suppository bases.

To investigate the effects of additives on the physicochemical properties of in situ gelling and mucoadhesive liquid suppository base, gelation temperature, gel strength and bioadhesive force of liquid suppository base, poloxamer 407 (P 407) and poloxamer 188 (P 188) (15/15%) were evaluated in the presence of following additives: solvent (ethanol, propylene glycol, glycerin), ionic strength-controlling agent (sodium chloride) and pH-controlling agent (hydrochloric acid, sodium monohydrogen phosphate, sodium dihydrogen phosphate). Among the additives studied, sodium chloride, sodium monohydrogen phosphate and sodium dihydrogen phosphate increased to a great extent the gel strength and the bioadhesive force of P 407/P 188 (15/15%) with a decrease in gelation temperature. Glycerin slightly decreased the gelation temperature and slightly increased the gel strength and bioadhesive force. However, the addition of 1% of sodium chloride, sodium monohydrogen phosphate or sodium dihydrogen phosphate caused a greater than 60-fold increase in gel strength and over a tenfold increase in bioadhesive force with 2-4 degrees C decrease of gelation temperature within optimal range, compared with P 407/P 188 (15/15%) alone. On the other hand, ethanol, propylene glycol and hydrochloric acid increased the gelation temperature and slightly decreased the gel strength and the bioadhesive force. Taken together, these findings indicate that the effect of additives on the physicochemical properties of liquid suppository bases depends on their bonding capacities, in that additives such as sodium chloride, sodium monohydrogen phosphate and sodium dihydrogen phosphate having strong cross-linking bonds with the components of liquid suppository base increase the strength and bioadhesive force of a gel compared to liquid suppository base alone, while additives such as ethanol, propylene glycol and hydrochloric acid having weaker hydrogen bonding result in a weaker response. Thus, sodium chloride and sodium phosphates appear to be promising additives for in situ gelling and mucoadhesive liquid suppository base, if used in adequate amounts.

Adhesiveness↗
PubMed2002

Combined computational and experimental study of substituent effects on the thermodynamics of H(2), CO, arene, and alkane addition to iridium.

The thermodynamics of small-molecule (H(2), arene, alkane, and CO) addition to pincer-ligated iridium complexes of several different configurations (three-coordinate d(8), four-coordinate d(8), and five-coordinate d(6)) have been investigated by computational and experimental means. The substituent para to the iridium (Y) has been varied in complexes containing the (Y-PCP)Ir unit (Y-PCP = eta(3)-1,3,5-C(6)H(2)[CH(2)PR(2)](2)Y; R = methyl for computations; R = tert-butyl for experiments); substituent effects have been studied for the addition of H(2), C-H, and CO to the complexes (Y-PCP)Ir, (Y-PCP)Ir(CO), and (Y-PCP)Ir(H)(2). Para substituents on arenes undergoing C-H bond addition to (PCP)Ir or to (PCP)Ir(CO) have also been varied computationally and experimentally. In general, increasing electron donation by the substituent Y in the 16-electron complexes, (Y-PCP)Ir(CO) or (Y-PCP)Ir(H)(2), disfavors addition of H-H or C-H bonds, in contradiction to the idea of such additions being oxidative. Addition of CO to the same 16-electron complexes is also disfavored by increased electron donation from Y. By contrast, addition of H-H and C-H bonds or CO to the three-coordinate parent species (Y-PCP)Ir is favored by increased electron donation. In general, the effects of varying Y are markedly similar for H(2), C-H, and CO addition. The trends can be fully rationalized in terms of simple molecular orbital interactions but not in terms of concepts related to oxidation, such as charge-transfer or electronegativity differences.

Journal Article↗
PubMed2005

Distinct mechanisms for the oxidative addition of chloro-, bromo-, and iodoarenes to a bisphosphine palladium(0) complex with hindered ligands.

We report an example of a bisphosphine palladium(0) complex with hindered ligands that undergoes oxidative addition of chloro-, bromo-, and iodoarenes in high yield. Addition of PhX (X = I, Br, Cl) to [Pd(Q-phos-tol)2] produced [Pd(Q-phos-tol)(Ph)(I)], [Pd(Q-phos-tol)(Ph)(Br)], and [Pd(Q-phos-tol)(Ph)(Cl)]2. To study the mechanisms of the oxidative addition of the three haloarenes to [Pd(Q-phos-tol)2], we determined the order of the reaction on the concentration of ligand and haloarene. The different haloarenes reacted through different mechanistic pathways. Addition of iodobenzene occurred by irreversible associative displacement of a phosphine. Addition of bromobenzene occurred by rate-limiting dissociation of phosphine. Addition of chlorobenzene occurred by reversible dissociation of phosphine, followed by rate-limiting oxidative addition. The mechanism of exchange of ligands from the Pd(0)L2 was also studied. The rate constant value for dissociation of ligand calculated from ligand exchange experiments is in agreement with the value calculated through experiments on oxidative addition.

Benzene Derivatives↗
PubMed2005

Theoretical study of the addition patterns of C60 fluorination: C60Fn (n = 1-60).

A systematic study is presented of addition patterns occurring upon fluorination of C60. We use the program SACHA, which increments the number of fluorine addends, tests all available addition sites within a given cutoff radius, and selects the most energetically stable structure for further addition on the basis of full AM1 optimizations for every isomer. The lowest energy structures are optimized at HF/3-21G level of theory. A number of distinct addition routes are predicted, based on octahedral, 'S', and 'T' addition patterns, leading both to experimentally observed C60F(n) isomers and to isomers not previously described in the literature. Furthermore the main addition routes were analyzed for C60F2n isomers, using ab initio global and local aromaticity calculations. For this, magnetizability and NICS calculations have been carried out at HF/3-21G level of theory. We show the possibility of using NICS to predict the next preferential addition site, matching the above-described addition routes.

Journal Article↗
PubMed2005

Open versus closed 1,3-dipolar additions of C60: a theoretical investigation on their mechanism and regioselectivity.

[reactions: see text] 1,3-Dipolar additions of C60 with dipoles, diazomethane, nitrile oxide, and nitrone have been modeled at the B3LYP/6-31G(d,p)//AM1 level, and their mechanism, regiochemistry, and nature of addition are investigated. All of these reactions lead to the formation of fullerene fused heterocycles; theoretically, these reactions can take up four types of additions, viz., closed [6,6], open [5,6], closed [5,6], and open [6,6] additions, and all of them have been examined. Energetics and thermodynamic analysis of these reactions show that closed [5,6] and open [6,6] additions are not probable and that closed [6,6] additions are the most favored ones and follow a concerted mechanism. Experimental evidence that C60-diazomethane reactions yielded closed [6,6] fullerenopyrazoline provides good support to the theoretical predictions. The observed order of reactivity has been explained based on the double bond character, forcing double bonds in the pentagons of C60, and strain. During the addition, dipoles distort more than C60 and concerted closed [6,6] TSs are found to be more reactant-like or early TS. Inclusion of toluene as solvent through the PCM model increases the reaction rate and exothermicity. NICS values computed at the centers of the reacting benzenoid ring of fullerene clearly reveal, in both open and closed additions, the loss in them of aromaticity during the reaction.

Journal Article↗
PubMed2005

Radical addition approach to asymmetric amine synthesis: design, implementation, and comparison of chiral N-acylhydrazones.

Intermolecular radical addition to C=N bonds with acyclic stereocontrol offers excellent potential as a mild, nonbasic carbon-carbon bond construction approach to chiral amines. Here, complete details of the first radical additions to chiral N-acylhydrazones as an approach to asymmetric amine synthesis are disclosed. Novel N-acylhydrazones were designed as chiral C=N radical acceptors with Lewis acid activation, restriction of conformational mobility, and commercial availability of precursors. Amination of 4-alkyl-2-oxazolidinones with O-(mesitylenesulfonyl)hydroxylamine or O-(p-nitrobenzoyl)hydroxylamine afforded N-aminooxazolidinones which were condensed with aldehydes to afford N-acylhydrazones 3-8. Three synthetic methods were developed, implementing these N-acylhydrazones in Lewis acid-promoted intermolecular radical additions to C=N bonds. First, additions of various secondary and tertiary alkyl iodides to propionaldehyde and benzaldehyde hydrazones (3 and 7) under tin hydride radical chain conditions in the presence of ZnCl2 gave N-acylhydrazine adducts with diastereomeric ratios ranging from 93:7 to 99:1. Radical additions to a series of N-acylhydrazones with different substituents on the oxazolidinone revealed that benzyl and diphenylmethyl were more effective stereocontrol elements than those with the aromatic ring directly attached to the oxazolidinone. Second, a tin-free method, exploiting dual functions of triethylborane for both initiation and chain propagation, enabled improved yields in addition of secondary alkyl iodides. Third, under photolytic conditions with hexamethylditin, primary radical addition could be achieved with ethyl iodide in the presence of diethyl ether as cosolvent; the 1-ethoxyethyl adduct was observed as a minor product. Chloromethyl addition was achieved under both the tin-free and photolytic conditions; in this case, the adduct bears alkyl chloride functionality with potential for further elaboration.

Journal Article↗
PubMed2006

Postirradiation electron transfer vs differential radical decay in X-irradiated DNA and its mixtures with additives. Electron spin resonance spectroscopy in LiBr glass at low temperatures.

Free radical formation in DNA and in colyophilized mixtures of DNA with the additives mitoxantrone and riboflavin was monitored after X-ray irradiation in frozen aqueous glasses (7 M LiBr/D2O) at 77 K by electron spin resonance (ESR) spectroscopy. Specifically, the postirradiation time course at 77 K of the respective free radical intensity residing on DNA or on the additive was probed in order to test the hypothesis of electron transfer from DNA, e.g., to mitoxantrone after irradiation under these conditions (e.g., Messer, A.; Carpenter, K.; Forzley, K.; Buchanan, J.; Yang, S.; Razskazovskii, Y.; Cai, Z.; Sevilla, M. D. J. Phys. Chem. B 2000, 104, 1128). For both additives, different additive loadings and irradiation doses were employed. The observed relative change in contributions of DNA and of additive radical components to the experimental spectra with time could be ascribed, for both additives, unequivocally to independent, differential fading of component radicals. Transfer from DNA to the additive, e.g., by electron tunneling as proposed before could be ruled out to occur by a detailed, quantitative analysis of the experimental spectra using reconstruction techniques. Additional studies were performed with the nucleotides TMP and dCMP and its mixtures with mitoxantrone in order to describe the time course in systems which are expected to behave independently; the results supported the conclusions arrived at from the analysis of the DNA/additive system. A model was proposed to describe the postirradiation radical fading mechanisms which involve liberation of radiation-induced matrix-trapped defects with time. It was assumed that these defects are ESR-mute and react with radicals by net radical destruction. Some experimental observations are presented concerning influence of temperature and of the matrix on the fading processes. These seem to argue in favor of such a model although a detailed, quantitative description is still not possible.

Bromides↗
PubMed2006

Dynamic light scattering studies of additive effects on the microstructure of aqueous gemini micelles.

Dynamic light scattering (DLS) measurements have been performed at 30 degrees C to see the effects of additives on the microstructure of gemini alkanediyl-alpha,omega-bis(dimethylcetylammonium bromide) surfactants, (Br-, n-C16H33N+Me2-(CH2)s-Me2- N+n-C16H33, Br-, 16-s-16, where s = 4, 5, 6). In pure aqueous solutions, the hydrodynamic diameter, Dh, was found to increase rapidly with geminis in comparison to their monomeric counterpart cetyltrimethylammonium bromide (n-C16H33N+Me3, Br-, CTAB) on increasing surfactant concentration. The additives considered in the present study are n-alcohols (C4-C6OH) and n-hexylamine (C6NH2) on the micellar growth of 0.03 M 16-4-16 in the presence and absence of 0.001 M KBr. The presence of 0.001 M KBr or organic additives at lower concentrations singly or jointly has little effect on the micellar size. As the chain length of the additive increases, the size increases with the increase of additive concentration, the magnitude being substantial in the presence of 0.001 M KBr. However, for equal chain length additives (C6OH, C6NH2), the effect was greater for C6OH. In case of C6NH2, the value of Dh reaches to almost constancy when the concentration of the additive was increased. Increased effectiveness of additives in the presence of added salt (KBr) is discussed in light of electrostatic and hydrophobic forces operating in the solution, which are always responsible for growth processes.

Journal Article↗
PubMed1993

Growth and morphology of L-alanine crystals: influence of additive adsorption.

The effect of L-amino acids, as additives, on the crystal growth and morphology of L-alanine crystals has been studied. The crystal growth of L-alanine is described by the spiral growth mechanism. From examining the growth rate dependence on supersaturation at constant additive concentration, it is concluded that there is no change in the growth mechanism due to the presence of the different additives. L-Alanine crystals were grown both in the absence and in the presence of additives. The crystal morphology was characterized by optical goniometry assigning the different Miller indices to the well-developed crystal faces. The addition of L-amino acids selectively inhibits the development of certain L-alanine crystal faces. L-Alanine crystals grown in the presence of nonpolar amino acids, such as L-leucine, L-phenylalanine, and L-valine, at concentrations as low as 0.20 m (0.3%, w/w) develop the [120] faces, whereas the [010], [110], and [210] faces are not developed. The effect of these additives on the morphology of L-alanine is explained at the molecular level based on crystallographic considerations. The molecular structure of a face will determine the availability of sites that favor the adsorption of the additives. The availability of sites and their energy, on a particular crystal face, will determine the extent of adsorption. The growth rate of a crystal face is decreased by the adsorption of the additive.(ABSTRACT TRUNCATED AT 250 WORDS)

Adsorption↗