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1

Anion gap, anion gap corrected for albumin, base deficit and unmeasured anions in critically ill patients: implications on the assessment of metabolic acidosis and the diagnosis of hyperlactatemia  

PubMed Central

Background Base deficit (BD), anion gap (AG), and albumin corrected anion gap (ACAG) are used by clinicians to assess the presence or absence of hyperlactatemia (HL). We set out to determine if these tools can diagnose the presence of HL using cotemporaneous samples. Methods We conducted a chart review of ICU patients who had cotemporaneous arterial blood gas, serum chemistry, serum albumin (Alb) and lactate(Lac) levels measured from the same sample. We assessed the capacity of AG, BD, and ACAG to diagnose HL and severe hyperlactatemia (SHL). HL was defined as Lac > 2.5 mmol/L. SHL was defined as a Lac of > 4.0 mmol/L. Results From 143 patients we identified 497 series of lab values that met our study criteria. Mean age was 62.2 ± 15.7 years. Mean Lac was 2.11 ± 2.6 mmol/L, mean AG was 9.0 ± 5.1, mean ACAG was 14.1 ± 3.8, mean BD was 1.50 ± 5.4. The area under the curve for the ROC for BD, AG, and ACAG to diagnose HL were 0.79, 0.70, and 0.72, respectively. Conclusion AG and BD failed to reliably detect the presence of clinically significant hyperlactatemia. Under idealized conditions, ACAG has the capacity to rule out the presence of hyperlactatemia. Lac levels should be obtained routinely in all patients admitted to the ICU in whom the possibility of shock/hypoperfusion is being considered. If an AG assessment is required in the ICU, it must be corrected for albumin for there to be sufficient diagnostic utility.

Chawla, Lakhmir S; Shih, Shirley; Davison, Danielle; Junker, Christopher; Seneff, Michael G

2008-01-01

2

What is the clinical significance of 5-oxoproline (pyroglutamic acid) in high anion gap metabolic acidosis following paracetamol (acetaminophen) exposure?  

PubMed

Abstract Context. Paracetamol (acetaminophen) ingestion is the most frequent pharmaceutical overdose in the developed world. Metabolic acidosis sometimes occurs, but the acidosis is infrequently persistent or severe. A growing number of case reports and case series describe high anion gap metabolic acidosis (HAGMA) following paracetamol exposure with subsequent detection or measurement of 5-oxoproline (also called pyroglutamic acid) in blood, urine, or both. Typically 5-oxoprolinuria or 5-oxoprolinemia occurs in the setting of inborn genetic errors in glutathione metabolism. It is unknown whether 5-oxoprolinemia in the setting of paracetamol exposure reflects an acquired or transient derangement of glutathione metabolism or previously unrecognized genetic defects. Objective. We reviewed the published cases of 5-oxoprolinemia or 5-oxoprolinuria among patients with HAGMA in the setting of paracetamol exposure. Our goal was to identify any consistent features that might increase our understanding of the pathophysiology, diagnosis, and treatment of similar cases. Methods. We searched the medical literature using PUBMED and EMBASE from inception to 28 August 2013 applying search terms ("oxoproline" OR "pyroglutamic acid" AND "paracetamol" OR "acetaminophen"). The intersection of these two searches returned 77 articles, of which 64 involved human subjects and were in English. Two articles, one each in Spanish and Dutch, were reviewed. An additional Google Scholar search was done with the same terms. We manually searched the reference lists of retrieved articles to identify additional four relevant articles. We focused on articles including measured 5-oxoproline concentrations in urine or blood. Results. Twenty-two articles included quantified 5-oxoproline concentrations. Several additional articles mentioned only qualitative detection of 5-oxoproline in urine or blood without concentrations being reported. Our manual reference search yielded four additional articles for a total of 24 articles describing 43 patients with quantified 5-oxoproline concentrations. The cases varied widely in paracetamol dose, duration and circumstances of paracetamol exposure, presence, and degree of elevation in transaminase activities, and when reported observed blood, serum, or urine 5-oxoproline concentrations. Concomitant use of flucloxacillin, another medication associated with oxoprolinemia or oxoprolinuria, confounded several of the cases. No clear dose-response relationship existed between the quantity of paracetamol ingested and the observed concentrations of 5-oxoproline. Clinical outcomes, including mortality, varied with no clear relationship to 5-oxoproline concentrations. Conclusions. In rare cases, HAGMA in the setting of paracetamol exposure is attributable to 5-oxoprolinemia. Clinicians should first exclude commoner and treatable causes of HAGMA, such as lactic acidosis, co-ingested drug administration, and ketoacidosis. It is likely that the propensity for HAGMA following paracetamol exposure may be genetically determined. The effects of acetylcysteine on 5-oxoproline concentrations or clinical outcome are unknown. When HAGMA is diagnosed, the 5-oxoproline concentration and the glutathione synthetase activity should be measured. PMID:24111553

Liss, D B; Paden, M S; Schwarz, E S; Mullins, M E

2013-10-11

3

Urine electrolytes and the urine anion and osmolar gaps  

Microsoft Academic Search

Urine ammonia concentration is crucial to understanding and quantifying the kidney's response to metabolic acidosis. This test is generally not performed by clinical laboratories. The urine anion gap and osmolar gaps have been proposed as surrogate measures of urine ammonia in patients with hyperchloremic acidosis. We measured ammonium and other electrolytes in the urine of patients attending our renal disease

Barry Kirschbaum; Domenic Sica; F. Phillip Anderson

1999-01-01

4

Ion-selective electrode and anion gap range: What should the anion gap be?  

PubMed Central

Background Using flame photometry technique in the 1970s, the normal value of anion gap (AG) was determined to be 12 ± 4 meq/L. However, with introduction of the autoanalyzers using an ion-selective electrode (ISE), the anion gap value has fallen to lower levels. Methods A retrospective study of US veterans from a single medical center was performed to determine the value of the anion gap in subjects with normal renal function and normal serum albumin and in patients with lactic acidosis and end-stage renal disease on dialysis. Results In 409 patients with an estimated glomerular filtration rate ?60 mL/min/1.73 m2 body surface area and serum albumin ?4 g/dL, the mean AG was 7.2 ± 2 (range 3–11) meq/L. In 299 patients with lactic acidosis (lactate level ?4 meq/L) and 68 patients with endstage renal disease on dialysis, the mean AG was 12.5 meq/L and 12.4 meq/L, respectively. A value <2 meq/L should be considered a low anion gap and a possible clue to drug intoxication and paraproteinemic disorders. Conclusion With the advent of ISE for measurement of analytes, the value of the anion gap has fallen. Physicians need to be aware of the normal AG value in their respective institutions, and laboratories need to have an established value for AG based on the type of instrument they are using.

Sadjadi, Seyed-Ali; Manalo, Rendell; Jaipaul, Navin; McMillan, James

2013-01-01

5

Circulating anions usually associated with the Krebs cycle in patients with metabolic acidosis  

Microsoft Academic Search

INTRODUCTION: Acute metabolic acidosis of non-renal origin is usually a result of either lactic or ketoacidosis, both of which are associated with a high anion gap. There is increasing recognition, however, of a group of acidotic patients who have a large anion gap that is not explained by either keto- or lactic acidosis nor, in most cases, is inappropriate fluid

Lui G Forni; William McKinnon; Gwyn A Lord; David F Treacher; Jean-Marie R Peron; Philip J Hilton

2005-01-01

6

Serum Anion Gap and Blood Pressure in the National Health and Nutrition Examination Survey  

Microsoft Academic Search

Increased production of organic acid can result in an elevated serum anion gap and may play a role in the development of hypertension. We studied the cross-sectional associations between anion gap and blood pressure and between serum bicarbonate and blood pressure in the 1999-2000 and 2001-2002 National Health and Nutrition Examination Surveys. We included 5043 adult participants who were not

Eric N. Taylor; John P. Forman; Wildon R. Farwell

2010-01-01

7

Do anionic titanium dioxide nano-clusters reach bulk band gap? A density functional theory study.  

PubMed

The electronic properties of both neutral and anionic (TiO(2))(n) (n = 1-10) clusters are investigated by extensive density functional theory calculations. The predicted electron detachment energies and excitation gaps of anionic clusters agree well with the original experimental anion photoelectron spectra (APES). It is shown that the old way to analyze APES tends to overestimate vertical excitation gaps (VGA) of large anionic clusters, due to the nature of multiple electronic origins for the higher APES bands. Moreover, the VGA of anionic TiO(2) clusters are evidently smaller than those of neutral clusters, which may also be the case for other metal oxide clusters with high electron affinity. PMID:20222057

Qu, Zheng-Wang; Zhu, Hui

2010-07-30

8

Hypoalbuminaemia in critically ill children: incidence, prognosis, and influence on the anion gap  

Microsoft Academic Search

Aims: Hypoalbuminaemia has significance in adult critical illness as an independent predictor of mortality. In addition, the anion gap is predominantly due to the negative charge of albumin, thus hypoalbuminaemia may lead to its underestimation. We examine this phenomenon in critically ill children, documenting the incidence, early evolution, and prognosis of hypoalbuminaemia (<33 g\\/l), and quantify its influence on the

A Durward; A Mayer; S Skellett; D Taylor; S Hanna; S M Tibby; I A Murdoch

2003-01-01

9

The role of chronic anion gap and/or nonanion gap acidosis in the osteodystrophy of chronic renal failure in the predialysis era: a minority report.  

PubMed

Chronic renal failure (CRF) due to (1) glomerulopathies, vascular and tubulointerstitial disorders, and (2) chronic nonazotemic renal tubular disorders creates sustained acidosis in the untreated state. Number 1 represents a mixture of anion and nonanion gap acidosis and number 2 a pure nonanion gap acidosis. There remains significant uncertainty as to the role of the acidosis (CRF) in the associated osteodystrophy. In general, little attention has been given to this subject in recent monographs. It is the purpose of this review ('minority report') to 'reexamine' the information available on this subject in humans and animals. The author has concluded that the chronic metabolic acidosis of CRF may well contribute to the development and maintenance of the osteodystrophy, and that its treatment should be included along with the other modalities of therapy. The subject is not a 'dead issue' but one definitely deserving further investigation. The response of the skeleton to acid loads clearly represents another 'trade-off' in ion metabolism in CRF. PMID:8202057

Kleeman, C R

1994-01-01

10

Metabolic acidosis in toluene sniffing.  

PubMed

ABSTRACTToluene sniffing, frequently described under the generic category of "glue sniffing," is a potential cause of normal anion gap metabolic acidosis due to distal renal tubular acidosis. Urine anion gap is used to diagnose metabolic acidosis of a normal anion gap variety; however, pitfalls exist when using urine anion gap in the setting of toluene sniffing. We present the case of a young woman who had a normal anion gap metabolic acidosis due to toluene sniffing and an unexpectedly low urine anion gap. In such a scenario, the urine anion gap will underestimate the rate of ammonia excretion when the conjugate bases of acids other than HCl are excreted in large quantities. Estimation of the urine osmolal gap will provide a more accurate ammonia excretion rate in these circumstances. The challenges in interpretation of the urine anion gap and ammonia excretion in the setting of distal renal tubular acidosis due to toluene toxicity are discussed. PMID:23778000

Tuchscherer, Jon; Rehman, Habib

2013-07-01

11

Band-gap-confinement and image-state-recapture effects in the survival of anions scattered from metal surfaces  

SciTech Connect

The resonant charge transfer process in the collision of hydrogen anions with metal surfaces is described within a single-active-electron wave-packet propagation method. The ion-survival probability is found to be strongly enhanced at two different surface-specific perpendicular velocities of the ion. It is shown that, while the low-velocity enhancement is induced from a dynamical confinement of the ion level inside the band gap, the high-velocity enhancement is due to electron recapture from transiently populated image states. Results are presented for Li(110), Cu(111), and Pd(111) surfaces.

Schmitz, Andrew; Shaw, John; Chakraborty, Himadri S. [Center for Innovation and Entrepreneurship, Department of Chemistry and Physics, Northwest Missouri State University, Maryville, Missouri 64468 (United States); Thumm, Uwe [Department of Physics and Astronomy, Kansas State University, Manhattan, Kansas 66502 (United States)

2010-04-15

12

Anionic metabolic profiling of urine from antibiotic-treated rats by capillary electrophoresis-mass spectrometry.  

PubMed

A recently developed capillary electrophoresis (CE)-negative-ionisation mass spectrometry (MS) method was used to profile anionic metabolites in a microbial-host co-metabolism study. Urine samples from rats receiving antibiotics (penicillin G and streptomycin sulfate) for 0, 4, or 8 days were analysed. A quality control sample was measured repeatedly to monitor the performance of the applied CE-MS method. After peak alignment, relative standard deviations (RSDs) for migration time of five representative compounds were below 0.4 %, whereas RSDs for peak area were 7.9-13.5 %. Using univariate and principal component analysis of obtained urinary metabolic profiles, groups of rats receiving different antibiotic treatment could be distinguished based on 17 discriminatory compounds, of which 15 were downregulated and 2 were upregulated upon treatment. Eleven compounds remained down- or upregulated after discontinuation of the antibiotics administration, whereas a recovery effect was observed for others. Based on accurate mass, nine compounds were putatively identified; these included the microbial-mammalian co-metabolites hippuric acid and indoxyl sulfate. Some discriminatory compounds were also observed by other analytical techniques, but CE-MS uniquely revealed ten metabolites modulated by antibiotic exposure, including aconitic acid and an oxocholic acid. This clearly demonstrates the added value of CE-MS for nontargeted profiling of small anionic metabolites in biological samples. PMID:23314487

Kok, Miranda G M; Ruijken, Marco M A; Swann, Jonathan R; Wilson, Ian D; Somsen, Govert W; de Jong, Gerhardus J

2013-01-12

13

Regulation of AE1 anion exchanger and H+ATPase in rat cortex by acute metabolic acidosis and alkalosis  

Microsoft Academic Search

Regulation of AE1 anion exchanger and H+-ATPase in rat cortex by acute metabolic acidosis and alkalosis. The cortical collecting duct (CCD) mediates net secretion or reabsorption of protons according to systemic acid\\/base status. Using indirect immunofluorescence, we examined the localization and abundance of the vacuolar H+-ATPase and the AE1 anion exchanger in intercalated cells (IC) of rat kidney connecting segment

Ivan Saboli?; Dennis Brown; Stephen L Gluck; Seth L Alper

1997-01-01

14

Regulation of Mitochondrial Function by Voltage Dependent Anion Channels in Ethanol Metabolism and the Warburg Effect  

PubMed Central

Voltage dependent anion channels (VDAC) are highly conserved proteins that are responsible for permeability of the mitochondrial outer membrane to hydrophilic metabolites like ATP, ADP and respiratory substrates. Although previously assumed to remain open, VDAC closure is emerging as an important mechanism for regulation of global mitochondrial metabolism in apoptotic cells and also in cells that are not dying. During hepatic ethanol oxidation to acetaldehyde, VDAC closure suppresses exchange of mitochondrial metabolites, resulting in inhibition of ureagenesis. In vivo, VDAC closure after ethanol occurs coordinately with mitochondrial uncoupling. Since acetaldehyde passes through membranes independently of channels and transporters, VDAC closure and uncoupling together foster selective and more rapid oxidative metabolism of toxic acetaldehyde to nontoxic acetate by mitochondrial aldehyde dehydrogenase. In single reconstituted VDAC, tubulin decreases VDAC conductance, and in HepG2 hepatoma cells, free tubulin negatively modulates mitochondrial membrane potential, an effect enhanced by protein kinase A. Tubulin-dependent closure of VDAC in cancer cells contributes to suppression of mitochondrial metabolism and may underlie the Warburg phenomenon of aerobic glycolysis.

Lemasters, John J.; Holmuhamedov, Ekhson L.; Czerny, Christoph; Zhong, Zhi; Maldonado, Eduardo N.

2012-01-01

15

The relationship among dietary undetermined anion, acid-base balance, and nutrient metabolism in swine.  

PubMed

Dietary undetermined anion (dUA) reflects, in part, the net acid load contributed by the diet. Although dUA is known to influence performance and nutrient metabolism of swine, a lack of knowledge impairs its application to diet formulation. This study was undertaken to separate the effects of dUA from the individual electrolytes that constitute its calculation. Eighteen 35-kg pigs were fitted with indwelling venous catheters and fed one of three barley and soybean meal-based diets: a control diet (C), an acidogenic diet containing calcium chloride (A), or a compensated acidogenic diet containing alkaline salts of sodium and potassium, as well as calcium chloride (CA). Compared with diet C, diet A lowered (P < .05) blood pH, bicarbonate, and base excess and increased (P < .05) urinary ammonium, titratable acid (TA), and net acid excretion (NAE). Diet CA returned blood acid-base values to normal and reduced urinary ammonium, TA, and NAE relative to diet A. Total nitrogen balance was unaffected by diet. Diet CA increased (P < .05) water intake and urine output. Diet A, but not CA, increased (P < .05) serum ionized Ca and C1. Apparent Ca and S digestibility and retention were reduced by diet A, but not by CA. Sodium retention was enhanced (P < .05) by diets A and CA; potassium retention was impaired (P < .05) by CA. Dietary UA altered systemic and renal acid-base balance in pigs. Mineral, but not nitrogen, metabolism was affected by both dUA and specific ion effects. PMID:9303463

Patience, J F; Chaplin, R K

1997-09-01

16

Manipulation of Dietary Cation-Anion Difference on Nutritionally Related Production Diseases, Productivity, and Metabolic Responses of Dairy Cows1  

Microsoft Academic Search

ABSTRACT Dietary cation-anion difference has been defined as milliequivalents of (Na + K) - (Cl + S) per kilogram,of DM and has a direct impact on blood acid-base metabolism. As this difference decreases, one,or more,of the following,blood parameters change: increased H+, decreased HCO;, and decreased pH. These,changes,are,accompanied,by reduced urinary HCO; excretion and pH as compensatory,mechanisms.,Although other minerals have an impact

Elliot Block

1994-01-01

17

Isolation of a strain of Pseudomonas putida capable of metabolizing anionic detergent sodium dodecyl sulfate (SDS)  

PubMed Central

Background and objectives Sodium Dodecyl Sulfate (SDS) is one of the most widely used anionic detergents. The present study deals with isolation and identification of SDS-degrading bacteria from a detergent contaminated pond situated in Varanasi city, India. Materials and Methods Employing enrichment technique in minimal medium (PBM), SDS-degrading bacteria were isolated from pond water sample. Rate of degradation of SDS was studied in liquid PBM and also degradation of different concentrations of SDS was also studied to find out maximum concentration of SDS degraded by the potent isolates. Alkyl sulfatase activity (key enzyme in SDS degradation) was estimated in crude cell extracts and multiplicity of alkyl sulfatase was studied by Native PAGE Zymography. The potent isolate was identified by 16S rRNA sequence analysis. Results Using enrichment technique in minimal medium containing SDS as a sole carbon source, initially three SDS degrading isolates were recovered. However, only one isolate, SP3, was found to be an efficient degrader of SDS. It was observed that this strain could completely metabolize 0.1% SDS in 16 h, 0.2% SDS in 20 h and 0.3% SDS in 24 h of incubation. Specific activity of alkyl sulfatase was 0.087±0.004 µmol SDS/mg protein/min and Native PAGE Zymography showed presence of alkyl sulfatase of Rf value of 0.21. This isolate was identified as Pseudomonas putida strain SP3. Conclusion This is the report of isolation of SDS-degrading strain of P. putida, which shows high rate of SDS degradation and can degrade up to 0.3% SDS. It appears that this isolate can be exploited for bioremediation of this detergent from water systems.

Chaturvedi, V; Kumar, A

2011-01-01

18

Functional analysis of gapped microbial genomes: Amino acid metabolism of Thiobacillus ferrooxidans  

PubMed Central

A gapped genome sequence of the biomining bacterium Thiobacillus ferrooxidans strain ATCC23270 was assembled from sheared DNA fragments (3.2-times coverage) into 1,912 contigs. A total of 2,712 potential genes (ORFs) were identified in 2.6 Mbp (megabase pairs) of Thiobacillus genomic sequence. Of these genes, 2,159 could be assigned functions by using the WIT-Pro/EMP genome analysis system, most with a high degree of certainty. Nine hundred of the genes have been assigned roles in metabolic pathways, producing an overview of cellular biosynthesis, bioenergetics, and catabolism. Sequence similarities, relative gene positions on the chromosome, and metabolic reconstruction (placement of gene products in metabolic pathways) were all used to aid gene assignments and for development of a functional overview. Amino acid biosynthesis was chosen to demonstrate the analytical capabilities of this approach. Only 10 expected enzymatic activities, of the nearly 150 involved in the biosynthesis of all 20 amino acids, are currently unassigned in the Thiobacillus genome. This result compares favorably with 10 missing genes for amino acid biosynthesis in the complete Escherichia coli genome. Gapped genome analysis can therefore give a decent picture of the central metabolism of a microorganism, equivalent to that of a complete sequence, at significantly lower cost.

Selkov, Evgeni; Overbeek, Ross; Kogan, Yakov; Chu, Lien; Vonstein, Veronika; Holmes, David; Silver, Simon; Haselkorn, Robert; Fonstein, Michael

2000-01-01

19

Unmeasured anions: the unknown unknowns  

Microsoft Academic Search

Evidence is emerging that elevated concentrations of the intermediates of the citric acid cycle may contribute to unmeasured anions in critical illness. Both the anion gap and the strong ion gap are used as scanning tools for recognition of these anions. The mechanisms underlying these elevations and their significance require further clarification.

Bala Venkatesh; Thomas J Morgan

2008-01-01

20

Effects of Organic Acid Anions on the Growth and Metabolism of Syntrophomonas wolfei in Pure Culture and in Defined Consortia  

PubMed Central

The effects of organic acid anions on the growth of Syntrophomonas wolfei was determined by varying the initial concentration of the acid anion in the medium. The addition of 15 mM acetate decreased the growth rate of a butyrate-catabolizing coculture containing Methanospirillum hungatei from 0.0085 to 0.0029 per hour. Higher initial acetate concentrations decreased the butyrate degradation rate and the yield of cells of S. wolfei per butyrate degraded. Inhibition was not due to the counter ion or the effect of acetate on the methanogen. Initial acetate concentrations above 25 mM inhibited crotonate-using pure cultures and cocultures of S. wolfei. Benzoate and lactate inhibited the growth of S. wolfei on crotonate in pure culture and coculture. Lactate was an effective inhibitor of S. wolfei cultures at concentrations greater than 10 mM. High concentrations of acetate and lactate altered the electron flow in crotonate-catabolizing cocultures, resulting in the formation of less methane and more butyrate and caproate. The inclusion of the acetate-using methanogen, Methanosarcina barkeri, in a methanogenic butyrate-catabolizing coculture increased both the yield of S. wolfei cells per butyrate degraded and the efficacy of butyrate degradation. Butyrate degradation by acetate-inhibited cocultures occurred only after the addition of Methanosarcina barkeri. These results showed that the metabolism of S. wolfei was inhibited by high levels of organic acid anions. The activity of acetate-using methanogens is important for the syntrophic degradation of fatty acids when high levels of acetate are present.

Beaty, P. Shawn; McInerney, Michael J.

1989-01-01

21

Severe metabolic alkalosis due to the combination of unmeasured cations and hypochloraemia in a patient with gastroparesia and frequent emesis  

PubMed Central

This report describes a patient with gastroparesia and frequent emesis admitted with severe metabolic alkalaemia, hyperlactataemia and acute renal failure. Metabolic alkalaemia was not only due to hypochloraemia but also due to unmeasured cations. These cations were found to be present by calculating anion gap and strong ion gap (both were negative, which is rare). After massive gastric bleeding the patient had a cardiac arrest; following cardiopulmonary resuscitation and infusion of a large volume of normal saline, new blood tests revealed improvement in chloraemia but also a significant increase in the anion gap, suggesting that unmeasured anions rapidly overcame unmeasured cations. The patient died after sequential episodes of cardiac arrest. Anion gap and strong ion gap were useful in the diagnosis of this “hidden” unusual cause of metabolic alkalosis and also in the diagnosis of metabolic acidosis after cardiac arrest, even with normal/high values of base excess and bicarbonate.

Maciel, Alexandre Toledo

2009-01-01

22

Thyroid hormone transport and metabolism by organic anion transporter 1C1 and consequences of genetic variation.  

PubMed

Organic anion transporting polypeptide (OATP) 1C1 has been characterized as a specific thyroid hormone transporter. Based on its expression in capillaries in different brain regions, OATP1C1 is thought to play a key role in transporting thyroid hormone across the blood-brain barrier. For this reason, we studied the specificity of iodothyronine transport by OATP1C1 in detail by analysis of thyroid hormone uptake in OATP1C1-transfected COS1 cells. Furthermore, we examined whether OATP1C1 is rate limiting in subsequent thyroid hormone metabolism in cells cotransfected with deiodinases. We also studied the effect of genetic variation in the OATP1C1 gene: polymorphisms were determined in 155 blood donors and 1192 Danish twins and related to serum thyroid hormone levels. In vitro effects of the polymorphisms were analyzed in cells transfected with the variants. Cells transfected with OATP1C1 showed increased transport of T4 and T4 sulfate (T4S), little transport of rT3, and no transport of T3 or T3 sulphate, compared with mock transfected cells. Metabolism of T4, T4S, and rT3 by cotransfected deiodinases was greatly augmented in the presence of OATP1C1. The OATP1C1-intron3C>T, Pro143Thr, and C3035T polymorphisms were not consistently associated with thyroid hormone levels, nor did they affect transport function in vitro. In conclusion, OATP1C1 mediates transport of T4, T4S, and rT3 and increases the access of these substrates to the intracellular active sites of the deiodinases. No effect of genetic variation on the function of OATP1C1 was observed. PMID:18566113

van der Deure, Wendy M; Hansen, Pia Skov; Peeters, Robin P; Kyvik, Kirsten Ohm; Friesema, Edith C H; Hegedüs, Laszlo; Visser, Theo J

2008-06-19

23

Effects of anionic salts supplementation on blood pH and mineral status, energy metabolism, reproduction and production in transition dairy cows  

Microsoft Academic Search

The objectives of this study were to determine the effects of a pre-partum diet with lower than recommended (DCAD=?82mEq\\/kg of dietary DM) amounts of anionic salts on metabolism, health, reproductive performance and milk production in dairy cows. Sixty Holstein multiparous cows were enrolled 21days prior to expected calving date. The animals were randomly assigned to receive one of two rations:

Hesam A. Seifi; Mehrdad Mohri; Nima Farzaneh; Hadi Nemati; Shima Vahidi Nejhad

2010-01-01

24

Anion channel sensitivity to cytosolic organic acids implicates a central role for oxaloacetate in integrating ion flux with metabolism in stomatal guard cells  

PubMed Central

Stomatal guard cells play a key role in gas exchange for photosynthesis and in minimizing transpirational water loss from plants by opening and closing the stomatal pore. The bulk of the osmotic content driving stomatal movements depends on ionic fluxes across both the plasma membrane and tonoplast, the metabolism of organic acids, primarily Mal (malate), and its accumulation and loss. Anion channels at the plasma membrane are thought to comprise a major pathway for Mal efflux during stomatal closure, implicating their key role in linking solute flux with metabolism. Nonetheless, little is known of the regulation of anion channel current (ICl) by cytosolic Mal or its immediate metabolite OAA (oxaloacetate). In the present study, we have examined the impact of Mal, OAA and of the monocarboxylic acid anion acetate in guard cells of Vicia faba L. and report that all three organic acids affect ICl, but with markedly different characteristics and sidedness to their activities. Most prominent was a suppression of ICl by OAA within the physiological range of concentrations found in vivo. These findings indicate a capacity for OAA to co-ordinate organic acid metabolism with ICl through the direct effect of organic acid pool size. The findings of the present study also add perspective to in vivo recordings using acetate-based electrolytes.

Wang, Yizhou; Blatt, Michael R.

2011-01-01

25

Hypokalemic metabolic acidosis attributed to cough mixture abuse  

Microsoft Academic Search

This report describes a patient with mixed normal anion gap hyperchloremic metabolic and respiratory acidosis associated with hypokalemia attributed to cough mixture abuse. Metabolic acidosis was likely related to an overdose of ammonium chloride, whereas respiratory acidosis was probably related to the effect of hypokalemia on respiratory muscles, causing hypoventilation. Hypokalemia was caused by a transcellular shift of potassium induced

Kim Ming Wong; Wai Leung Chak; Chi Yuen Cheung; Yiu Han Chan; Koon Shing Choi; Ka Foon Chau; Chun Sang Li

2001-01-01

26

AMPK-associated signaling to bridge the gap between fuel metabolism and hepatocyte viability  

PubMed Central

The adenosine monophosphate-activated protein kinase (AMPK) and p70 ribosomal S6 kinase-1 pathway may serve as a key signaling flow that regulates energy metabolism; thus, this pathway becomes an attractive target for the treatment of liver diseases that result from metabolic derangements. In addition, AMPK emerges as a kinase that controls the redox-state and mitochondrial function, whose activity may be modulated by antioxidants. A close link exists between fuel metabolism and mitochondrial biogenesis. The relationship between fuel metabolism and cell survival strongly implies the existence of a shared signaling network, by which hepatocytes respond to challenges of external stimuli. The AMPK pathway may belong to this network. A series of drugs and therapeutic candidates enable hepatocytes to protect mitochondria from radical stress and increase cell viability, which may be associated with the activation of AMPK, liver kinase B1, and other molecules or components. Consequently, the components downstream of AMPK may contribute to stabilizing mitochondrial membrane potential for hepatocyte survival. In this review, we discuss the role of the AMPK pathway in hepatic energy metabolism and hepatocyte viability. This information may help identify ways to prevent and/or treat hepatic diseases caused by the metabolic syndrome. Moreover, clinical drugs and experimental therapeutic candidates that directly or indirectly modulate the AMPK pathway in distinct manners are discussed here with particular emphasis on their effects on fuel metabolism and mitochondrial function.

Yang, Yoon Mee; Han, Chang Yeob; Kim, Yoon Jun; Kim, Sang Geon

2010-01-01

27

Filling Kinetic Gaps: Dynamic Modeling of Metabolism Where Detailed Kinetic Information Is Lacking  

PubMed Central

Background Integrative analysis between dynamical modeling of metabolic networks and data obtained from high throughput technology represents a worthy effort toward a holistic understanding of the link among phenotype and dynamical response. Even though the theoretical foundation for modeling metabolic network has been extensively treated elsewhere, the lack of kinetic information has limited the analysis in most of the cases. To overcome this constraint, we present and illustrate a new statistical approach that has two purposes: integrate high throughput data and survey the general dynamical mechanisms emerging for a slightly perturbed metabolic network. Methodology/Principal Findings This paper presents a statistic framework capable to study how and how fast the metabolites participating in a perturbed metabolic network reach a steady-state. Instead of requiring accurate kinetic information, this approach uses high throughput metabolome technology to define a feasible kinetic library, which constitutes the base for identifying, statistical and dynamical properties during the relaxation. For the sake of illustration we have applied this approach to the human Red blood cell metabolism (hRBC) and its capacity to predict temporal phenomena was evaluated. Remarkable, the main dynamical properties obtained from a detailed kinetic model in hRBC were recovered by our statistical approach. Furthermore, robust properties in time scale and metabolite organization were identify and one concluded that they are a consequence of the combined performance of redundancies and variability in metabolite participation. Conclusions/Significance In this work we present an approach that integrates high throughput metabolome data to define the dynamic behavior of a slightly perturbed metabolic network where kinetic information is lacking. Having information of metabolite concentrations at steady-state, this method has significant relevance due its potential scope to analyze others genome scale metabolic reconstructions. Thus, I expect this approach will significantly contribute to explore the relationship between dynamic and physiology in other metabolic reconstructions, particularly those whose kinetic information is practically nulls. For instances, I envisage that this approach can be useful in genomic medicine or pharmacogenomics, where the estimation of time scales and the identification of metabolite organization may be crucial to characterize and identify (dis)functional stages.

Resendis-Antonio, Osbaldo

2009-01-01

28

[Study of the kinetics of anion metabolism in the erythrocytes of patients with various forms of hereditary neuromuscular diseases].  

PubMed

The authors have shown an increase in the rate of the anion transport in erythrocytic membranes in patients with hereditary neuromuscular diseases, as well as in probable heterozygotic carriers of Duchenne's progressive muscular dystrophy. It is suggested that the kinetic parameters of chlorine-bicarbonate exchange be used for the early diagnosis and identification of the heterozygotic carriership of Duchenne's myodystrophy gene. PMID:3434056

Sitnikov, V F; Khrennikov, V Iu; Sidorov, E P

1987-01-01

29

Single-Run Separation and Detection of Multiple Metabolic Intermediates by AnionExchange High-Performance Liquid Chromatography and Application to Cell Pool Extracts Prepared from Escherichia coli  

Microsoft Academic Search

A method is described for analysis of the intracellular concentrations of metabolic intermediates of the Embden–Meyerhof–Parnas pathway, the Entner–Doudoroff pathway, the pentose phosphate pathway, and the tricarboxylic acid cycle in cell pool extracts ofEscherichia coli.A single anion-exchange HPLC run of 40 min allowed resolution of 27 anionic metabolite standards. Detection limits of 0.1 nmol per injection were achieved by use

Meenakshi Bhattacharya; Lorra Fuhrman; Andrew Ingram; Kenneth W. Nickerson; Tyrrell Conway

1995-01-01

30

Dysfunction of Organic Anion Transporting Polypeptide 1a1 Alters Intestinal Bacteria and Bile Acid Metabolism in Mice  

Microsoft Academic Search

Organic anion transporting polypeptide 1a1 (Oatp1a1) is predominantly expressed in liver and is able to transport bile acids (BAs) in vitro. Male Oatp1a1-null mice have increased concentrations of taurodeoxycholic acid (TDCA), a secondary BA generated by intestinal bacteria, in both serum and livers. Therefore, in the present study, BA concentrations and intestinal bacteria in wild-type (WT) and Oatp1a1-null mice were

Youcai Zhang; Pallavi B. Limaye; Lois D. Lehman-McKeeman; Curtis D. Klaassen

2012-01-01

31

Uniport of Anionic Citrate and Proton Consumption in Citrate Metabolism Generates a Proton Motive Force in Leuconostoc oenos  

Microsoft Academic Search

The mechanism and energetics of citrate transport in Leuconostoc oenos were investigated. Resting cells of L. oenos generate both a membrane potential (??) and a pH gradient (?pH) upon addition of citrate. After a lag time, the internal alkalinization is followed by a continuous alkalinization of the external medium, demonstrating the involvement of proton-consuming reactions in the metabolic breakdown of

Wil N. Konings; Juke S. Lolkema; Helena Santos; Bert Poolman; Ana Ramos

1994-01-01

32

Single-run separation and detection of multiple metabolic intermediates by anion-exchange high-performance liquid chromatography and application to cell pool extracts prepared from Escherichia coli.  

PubMed

A method is described for analysis of the intracellular concentrations of metabolic intermediates of the Embden-Meyerhof-Parnas pathway, the Entner-Doudoroff pathway, the pentose phosphate pathway, and the tricarboxylic acid cycle in cell pool extracts of Escherichia coli. A single anion-exchange HPLC run of 40 min allowed resolution of 27 anionic metabolite standards. Detection limits of 0.1 nmol per injection were achieved by use of a conductivity detector equipped with an anion self-regenerating suppressor and a uv detector. A boiling water extraction procedure was used to prepare cell pool extracts. Cochromatography of cell pool extracts and metabolite standards was used to confirm the identities of metabolites in the cell pool. As many as 16 metabolites could be detected and quantified in the cell pool extracts by using the described HPLC method. An analysis of metabolite concentrations in E. coli showed the dynamics of glucose metabolism during a 2-min transition from starvation to steady-state metabolism following addition of glucose. The ease and power of this method suggests general utility for in vivo metabolite analysis in a variety of experimental systems. PMID:8600840

Bhattacharya, M; Fuhrman, L; Ingram, A; Nickerson, K W; Conway, T

1995-11-20

33

Analysis of metabolic profiles of bile acids in urine using a lipophilic anion exchanger and computerized gas-liquid chromatorgaphy-mass spectrometry.  

PubMed

A method is described for quantitative analysis of bile acids in urine. Urine is acidified and bile acids are extracted on an Amberlite XAD-2 column. Bile salts are converted to acids on an Amberlyst A-15 column and are separated into groups of unconjugated, glycine, taurine, monosulfated, and polysulfated conjugates using the lipophilic anion exchanger diethylaminohydroxypropyl Sephadex LH-20 (DEAP-LH-20). After solvolysis and hydrolysis, the deconjugated bile acids are purified on DEAP-LH-20, and are converted to methyl ester trimethylsilyl ether derivatives. Identification and quantitation of the individual bile acids is accomplished by computerized gas-liquid chromatography-mass spectrometry. The daily excretion of bile acids in urine from healthy subjects was 6.4-11 micro moles. The mixture of bile acids was quite complex and differed from that in bile. About 30 bile acids were identified or partially characterized. Three of these were monosubstituted: lithocholic, allolithocholic, and 3beta-hydroxy-5-cholenoic acids. Fourteen disubstituted bile acids included epimers of deoxycholic, allodeoxycholic, chenodeoxycholic, allochenodeoxycholic, and hyodeoxycholic acids. 3alpha-Hydroxy-12-keto-5beta-cholanoic acid was the major ketonic bile acid and 3beta,12alpha-dihydroxy-5-cholenoic acid was the major unsaturated bile acid in this group. Nine trihydroxy bile acids included cholic and allocholic acids, epimers of these compounds, hyocholic acid, and a 1-hydroxylated bile acid tentatively characterized as 1,3,12-trihydroxycholanoic acid. Cholestatic subjects excreted tetrahydroxycholanoates carrying hydroxyl groups in positions 1, 3, 6, 7, 12, or 23. All monohydroxy and the predominant part of dihydroxy bile acids were present in the monosulfate fraction. Exceptions were 3alpha,12beta-dihydroxy- and 3alpha-hydroxy-12-keto-5beta-cholanoic acids, which were found mainly in the glycine conjugate fraction. Most of the trihydroxy bile acids were nonsulfated, and cholic and norcholic acids were the major unconjugated bile acids. The tetrahydroxy bile acids and hyocholic acid were present mainly in the taurine conjugate fraction, while 1,3,12-trihydroxycholanoic acid was predominantly found in the glycine conjugate fraction. Sulfation of trihydroxy bile acids was increased in patients with marked cholestasis. All bile acids in the monosulfate fraction were conjugated and carried the sulfate ester group at C-3. Significant amounts of di- and trisulfates were not found. The results indicate selective mechanisms for sulfation, hydroxylation, and renal elimination of bile acid conjugates. Analysis of metabolic profiles of bile acids in urine may be a useful method in studies of the function of organs involved in bile acid metabolism. PMID:864325

Almé, B; Bremmelgaard, A; Sjövall, J; Thomassen, P

1977-05-01

34

Causes of metabolic acidosis in canine hemorrhagic shock: role of unmeasured ions  

PubMed Central

Introduction Metabolic acidosis during hemorrhagic shock is common and conventionally considered to be due to hyperlactatemia. There is increasing awareness, however, that other nonlactate, unmeasured anions contribute to this type of acidosis. Methods Eleven anesthetized dogs were hemorrhaged to a mean arterial pressure of 45 mm Hg and were kept at this level until a metabolic oxygen debt of 120 mLO2/kg body weight had evolved. Blood pH, partial pressure of carbon dioxide, and concentrations of sodium, potassium, magnesium, calcium, chloride, lactate, albumin, and phosphate were measured at baseline, in shock, and during 3 hours post-therapy. Strong ion difference and the amount of weak plasma acid were calculated. To detect the presence of unmeasured anions, anion gap and strong ion gap were determined. Capillary electrophoresis was used to identify potential contributors to unmeasured anions. Results During induction of shock, pH decreased significantly from 7.41 to 7.19. The transient increase in lactate concentration from 1.5 to 5.5 mEq/L during shock was not sufficient to explain the transient increases in anion gap (+11.0 mEq/L) and strong ion gap (+7.1 mEq/L), suggesting that substantial amounts of unmeasured anions must have been generated. Capillary electrophoresis revealed increases in serum concentration of acetate (2.2 mEq/L), citrate (2.2 mEq/L), ?-ketoglutarate (35.3 ?Eq/L), fumarate (6.2 ?Eq/L), sulfate (0.1 mEq/L), and urate (55.9 ?Eq/L) after shock induction. Conclusion Large amounts of unmeasured anions were generated after hemorrhage in this highly standardized model of hemorrhagic shock. Capillary electrophoresis suggested that the hitherto unmeasured anions citrate and acetate, but not sulfate, contributed significantly to the changes in strong ion gap associated with induction of shock.

Bruegger, Dirk; Kemming, Gregor I; Jacob, Matthias; Meisner, Franz G; Wojtczyk, Christoph J; Packert, Kristian B; Keipert, Peter E; Faithfull, N Simon; Habler, Oliver P; Becker, Bernhard F; Rehm, Markus

2007-01-01

35

Metabolism  

MedlinePLUS

Metabolism refers to all the physical and chemical processes in the body that convert or use energy, ... Elsas LJ II. Approach to inborn errors of metabolism. In: Goldman L, Schafer AI, eds. Cecil Medicine . ...

36

Acute kidney injury, hyperosmolality and metabolic acidosis associated with lorazepam  

Microsoft Academic Search

Background A 54-year-old male with a history of multiple admissions for alcohol intoxication was admitted to hospital with right flank pain. He received a high-dose lorazepam infusion for alcohol withdrawal during hospitalization and developed severe hyperosmolality, high anion gap metabolic acidosis, and acute kidney injury on his eighth day of hospitalization.Investigations Serum chemistries, arterial blood gas analysis, and measurement of

Irfan Yusufzai; Anna Sullivan; Charles Graeber; Tausif Zar

2007-01-01

37

Anion Bridging and Anion Electrocatalysis on Mercury.  

National Technical Information Service (NTIS)

The evidence for the existence of anion bridging and anion electrocatalysis on mercury electrodes is reviewed. It is shown to be a rather common mechanism. Its elucidation often requires accurate surface activity data. Some difficulties in obtaining the l...

R. de Levie

1971-01-01

38

Filling Knowledge Gaps in Biological Networks: integrating global approaches to understand H2 metabolism in Chlamydomonas reinhardtii - Final Report  

SciTech Connect

The green alga Chlamydomonas reinhardtii (Chlamydomonas) has numerous genes encoding enzymes that function in fermentative pathways. Among these genes, are the [FeFe]-hydrogenases, pyruvate formate lyase, pyruvate ferredoxin oxidoreductase, acetate kinase, and phosphotransacetylase. We have systematically undertaken a series of targeted mutagenesis approaches to disrupt each of these key genes and �¢����omics�¢���� techniques to characterize alterations in metabolic flux. Funds from DE-FG02-07ER64423 were specifically leveraged to generate mutants with disruptions in the genes encoding the [FeFe]-hydrogenases HYDA1 and HYDA2, pyruvate formate lyase (PFL1), and in bifunctional alcohol/aldehyde alcohol dehydrogenase (ADH1). Additionally funds were used to conduct global transcript profiling experiments of wildtype Chlamydomonas cells, as well as of the hydEF-1 mutant, which is unable to make H2 due to a lesion in the [FeFe]-hydrogenase biosynthetic pathway. In the wildtype cells, formate, acetate and ethanol are the dominant fermentation products with traces of CO2 and H2 also being produced. In the hydEF-1 mutant, succinate production is increased to offset the loss of protons as a terminal electron acceptor. In the pfl-1 mutant, lactate offsets the loss of formate production, and in the adh1-1 mutant glycerol is made instead of ethanol. To further probe the system, we generated a double mutant (pfl1-1 adh1) that is unable to synthesize both formate and ethanol. This strain, like the pfl1 mutants, secreted lactate, but also exhibited a significant increase in the levels of extracellular glycerol, acetate, and intracellular reduced sugars, and a decline in dark, fermentative H2 production. Whereas wild-type Chlamydomonas fermentation primarily produces formate and ethanol, the double mutant performs a complete rerouting of the glycolytic carbon to lactate and glycerol. Lastly, transcriptome data have been analysed for both the wildtype and hydEF-1, that correlate with our observed fermentative metabolites. Intriguingly, over half of the most differentially regulated genes are of unknown function.

Posewitz, Matthew C

2011-06-30

39

Anions in Crystal Engineering  

SciTech Connect

This tutorial review presents a current account of anions in crystal engineering, organized around two main questions: (i) how do anions influence and control crystal structures, and (ii) how do crystal environments recognize and select anions? The first part pertains to deliberate assembly of new crystalline materials using anionic components, by taking advantage of the strong and directional interactions of anions in the solid state. Along this line, the various structural roles of anions in crystals are examined. The second question is related to selective separation of anions by crystallization, by exploiting chemical recognition phenomena in the well-defined and highly structured environment inside crystals.

Custelcean, Radu [ORNL

2010-01-01

40

Pharmacologically-induced metabolic acidosis: a review.  

PubMed

Metabolic acidosis may occasionally develop in the course of treatment with drugs used in everyday clinical practice, as well as with the exposure to certain chemicals. Drug-induced metabolic acidosis, although usually mild, may well be life-threatening, as in cases of lactic acidosis complicating antiretroviral therapy or treatment with biguanides. Therefore, a detailed medical history, with special attention to the recent use of culprit medications, is essential in patients with acid-base derangements. Effective clinical management can be handled through awareness of the adverse effect of certain pharmaceutical compounds on the acid-base status. In this review, we evaluate relevant literature with regard to metabolic acidosis associated with specific drug treatment, and discuss the clinical setting and underlying pathophysiological mechanisms. These mechanisms involve renal inability to excrete the dietary H+ load (including types I and IV renal tubular acidoses), metabolic acidosis owing to increased H+ load (including lactic acidosis, ketoacidosis, ingestion of various substances, administration of hyperalimentation solutions and massive rhabdomyolysis) and metabolic acidosis due to HCO3- loss (including gastrointestinal loss and type II renal tubular acidosis). Determinations of arterial blood gases, the serum anion gap and, in some circumstances, the serum osmolar gap are helpful in delineating the pathogenesis of the acid-base disorder. In all cases of drug-related metabolic acidosis, discontinuation of the culprit medications and avoidance of readministration is advised. PMID:20397738

Liamis, George; Milionis, Haralampos J; Elisaf, Moses

2010-05-01

41

Anion exchange membrane  

DOEpatents

An anion exchange membrane and fuel cell incorporating the anion exchange membrane are detailed in which proazaphosphatrane and azaphosphatrane cations are covalently bonded to a sulfonated fluoropolymer support along with anionic counterions. A positive charge is dispersed in the aforementioned cations which are buried in the support to reduce the cation-anion interactions and increase the mobility of hydroxide ions, for example, across the membrane. The anion exchange membrane has the ability to operate at high temperatures and in highly alkaline environments with high conductivity and low resistance.

Verkade, John G; Wadhwa, Kuldeep; Kong, Xueqian; Schmidt-Rohr, Klaus

2013-05-07

42

Voltammetry of hypoxic cells radiosensitizer etanidazole radical anion in water  

Microsoft Academic Search

Cytotoxic properties of radiosensitizers are due to the fact that, in the metabolic pathway, these compounds undergo one-electron reduction to generate radical anions. In this study we focused our interest on the electrochemical transfer of the first electron on radiosensitizer Etanidazole (ETN) and, consequently, on the ETN radical-anion formation in the buffered aqueous media. ETN was electrochemically treated in the

Miroslav Gál; Magdaléna Hromadová; Lubomír Pospíšil; Ján Híveš; Romana Sokolová; Viliam Kolivoška; Jana Bulí?ková

2010-01-01

43

A new coding system for metabolic disorders demonstrates gaps in the international disease classifications ICD-10 and SNOMED-CT, which can be barriers to genotype-phenotype data sharing.  

PubMed

Data sharing is essential for a better understanding of genetic disorders. Good phenotype coding plays a key role in this process. Unfortunately, the two most widely used coding systems in medicine, ICD-10 and SNOMED-CT, lack information necessary for the detailed classification and annotation of rare and genetic disorders. This prevents the optimal registration of such patients in databases and thus data-sharing efforts. To improve care and to facilitate research for patients with metabolic disorders, we developed a new coding system for metabolic diseases with a dedicated group of clinical specialists. Next, we compared the resulting codes with those in ICD and SNOMED-CT. No matches were found in 76% of cases in ICD-10 and in 54% in SNOMED-CT. We conclude that there are sizable gaps in the SNOMED-CT and ICD coding systems for metabolic disorders. There may be similar gaps for other classes of rare and genetic disorders. We have demonstrated that expert groups can help in addressing such coding issues. Our coding system has been made available to the ICD and SNOMED-CT organizations as well as to the Orphanet and HPO organizations for further public application and updates will be published online (www.ddrmd.nl and www.cineas.org). PMID:23504699

Sollie, Annet; Sijmons, Rolf H; Lindhout, Dick; van der Ploeg, Ans T; Rubio Gozalbo, M Estela; Smit, G Peter A; Verheijen, Frans; Waterham, Hans R; van Weely, Sonja; Wijburg, Frits A; Wijburg, Rudolph; Visser, Gepke

2013-06-03

44

Expression and functions of neuronal gap junctions  

Microsoft Academic Search

Gap junctions are channel-forming structures in contacting plasma membranes that allow direct metabolic and electrical communication between almost all cell types in the mammalian brain. At least 20 connexin genes and 3 pannexin genes probably code for gap junction proteins in mice and humans. Gap junctions between murine neurons (also known as electrical synapses) can be composed of connexin 36,

Goran Söhl; Stephan Maxeiner; Klaus Willecke

2005-01-01

45

Metabolic acidosis of CKD: diagnosis, clinical characteristics, and treatment.  

PubMed

Metabolic acidosis is noted in the majority of patients with chronic kidney disease (CKD) when glomerular filtration rate (GFR) decreases to less than 20% to 25% of normal, although as many as 20% of individuals can have acid-base parameters close to or within the normal range. Acidosis generally is mild to moderate in degree, with plasma bicarbonate concentrations ranging from 12 to 22 mEq/L (mmol/L), and it is rare to see values less than 12 mEq/L (mmol/L) in the absence of an increased acid load. Degree of acidosis approximately correlates with severity of renal failure and usually is more severe at a lower GFR. The metabolic acidosis can be of the high-anion-gap variety, although anion gap can be normal or only moderately increased even with stage 4 to 5 CKD. Several adverse consequences have been associated with metabolic acidosis, including muscle wasting, bone disease, impaired growth, abnormalities in growth hormone and thyroid hormone secretion, impaired insulin sensitivity, progression of renal failure, and exacerbation of beta 2 -microglobulin accumulation. Administration of base aimed at normalization of plasma bicarbonate concentration might be associated with certain complications, such as volume overload, exacerbation of hypertension, and facilitation of vascular calcifications. Whether normalization of plasma bicarbonate concentrations in all patients is desirable therefore requires additional study. In the present review, we describe clinical and laboratory characteristics of metabolic acidosis, discuss potential adverse effects, and address benefits and complications of therapy. PMID:15957126

Kraut, Jeffrey A; Kurtz, Ira

2005-06-01

46

Final Report: Filling Knowledge Gaps in Biological Networks: Integrated Global Approaches to Understand H{sub 2} Metabolism in Chlamydomonas Reinhardtii  

SciTech Connect

The major goal of our part of this project has been to generate mutants in fermentation metabolism and begin to decipher how lesions in the pathways associated with fermentation metabolism impact both H{sub 2} production and the production of other metabolites that accumulate as cells become anoxic. We are also trying to understand how metabolic pathways are regulated as O{sub 2} in the environment becomes depleted.

Grossman, Arthur

2012-05-01

47

The 'gap' in the 'plasma osmolar gap'.  

PubMed

Ethylene glycol poisoning is a medical emergency that presents challenges for clinicians and clinical laboratories. If left untreated, it may cause morbidity and death, but effective therapy is available if diagnosed in time. The diagnosis of ethylene glycol poisoning is not always straightforward and the commonly quoted 'plasma osmolar gap' is not sufficiently sensitive to exclude a small ingestion and has been reported to be normal in a number of serious exposures. The 'plasma osmolar gap' cannot distinguish among ethanol, isopropyl alcohol, methanol or ethylene glycol. Thus, the measurement of serum ethylene glycol and, ideally, glycolic acid, its major toxic metabolite in serum, is definitive. This also holds true for methanol and its metabolite formic acid. Ethylene glycol metabolites target the kidney and lead to reversible oliguric or anuric injury, which in turn slows the elimination of ethylene glycol. The therapeutic options include reversal of metabolic acidosis, inhibition of alcohol dehydrogenase and early haemodialysis. PMID:23929610

Arora, Alok

2013-08-08

48

Living anionic polymerization  

Microsoft Academic Search

For about 40 years living anionic polymerization has been the premier technique for the synthesis of model polymers of controlled architecture and narrow molecular weight distribution (MWD). Nowadays, despite the continuing development of new strategies for the synthesis of well-defined polymers and copolymers (e.g. group transfer polymerization, living radical polymerization, etc.), anionic polymerization continues to be the most reliable and

Kunlun Hong; David Uhrig; Jimmy W Mays

1999-01-01

49

Anion substitution in zinc chalcogenides.  

PubMed

Anion substitution effects on the structure and energy of zinc chalcogenides were studied with the semiempirical molecular orbital method MSINDO. Cyclic clusters of different sizes were chosen as model systems. The convergence of the bulk properties of the perfect clusters with increasing cluster size was tested. Single and multiple substitution of oxygen atoms in zinc oxide by sulfur and of sulfur atoms in zinc sulfide by oxygen served to determine the energetics of substitution for these two cases. It was found that the substitution of oxygen by sulfur in ZnO is easier than the substitution of sulfur by oxygen in ZnS in agreement with experimental results. The interaction between two oxygen atoms vs. two selenium atoms in zinc sulfide was investigated. Oscillations of the cluster energy in dependence of the distance between the two doping atoms were observed. These are explained by the relative sites of the doping atoms in the crystal lattice. The magnitude of the oscillations is smaller in ZnS:Se than in ZnS:O, because the difference between the anion radii of S2- and Se2- is smaller than between S2- and O2-. This is also reflected in the band gap. PMID:16691570

Jug, Karl; Tikhomirov, Viatcheslav A

2006-07-30

50

Anion deposition into ferritin.  

PubMed

When the iron core of equine spleen ferritin is reduced, anions in solution cross the protein shell and enter the ferritin interior as part of a charge balancing reaction. Anion sequestration inside ferritin during iron core reduction was monitored using ion selective electrodes, inductively coupled plasma emission, and energy-dispersive X-ray spectroscopy. The requirement for anion translocation to the ferritin interior occurs because upon iron core reduction, two OH(-) ions per iron are released or neutralized inside ferritin leaving a net positive charge. Halides and oxoanions were tested as anionic substrates for this reaction. A general trend for the halides showed that the smaller halides accumulated inside ferritin in greater abundance than larger halides, presumably because the protein channels restrict the transfer of the larger anionic species. In contrast, oxoanion accumulation inside ferritin did not show selectivity based on size or charge. Vanadate and molybdate accumulated to the highest concentrations and nitrate, phosphate and tungstate showed poor accumulation inside ferritin. Fe(II) remains stably sequestered inside ferritin, as shown by electron microscopy and by column chromatography. Upon oxidation of the iron core, the anions are expelled from ferritin, and OH(-) ions coordinate to the Fe(III) to form the original Fe(O)OH mineral. Anion transport across the ferritin protein shell represents an important mechanism by which ferritin maintains proper charge balance inside the protein cavity. PMID:22265833

Hilton, Robert J; Zhang, Bo; Martineau, L Naomi; Watt, Gerald D; Watt, Richard K

2011-12-27

51

Acyclic Oligopyrrolic Anion Receptors  

NASA Astrophysics Data System (ADS)

Recent progress in the guest-binding and supramolecular chemistry of anion-responsive acyclic oligopyrroles is summarized here in this chapter. The hydrogen-bonding properties of the pyrrole NH sites determine anion binding in acylic oligopyrroles such as guanidinocarbonyl and amidopyrroles, dipyrrins and their analogs, dipyrrolylquinoxalines, and boron complexes of dipyrrolyldiketones. Linear oligopyrroles can be incorporated as subunits in various macromolecules and complexes by means of covalent and noncovalent interactions; in fact, boron complexes of dipyrrolyldiketones form assembled structures and, with the appropriate substituents, soft materials such as anion-responsive supramolecular gels.

Maeda, Hiromitsu

52

R type anion channel  

PubMed Central

Plant genomes code for channels involved in the transport of cations, anions and uncharged molecules through membranes. Although the molecular identity of channels for cations and uncharged molecules has progressed rapidly in the recent years, the molecular identity of anion channels has lagged behind. Electrophysiological studies have identified S-type (slow) and R-type (rapid) anion channels. In this brief review, we summarize the proposed functions of the R-type anion channels which, like the S-type, were first characterized by electrophysiology over 20 years ago, but unlike the S-type, have still yet to be cloned. We show that the R-type channel can play multiple roles.

Diatloff, Eugene; Peyronnet, Remi; Colcombet, Jean; Thomine, Sebastien; Barbier-Brygoo, Helene

2010-01-01

53

Theory of magnetically induced anions  

SciTech Connect

A general quantum theory is presented for unconventional anionic states supported by the presence of an external magnetic field. The theory applies to atomic anions and allows for straightforward extensions to anions formed in magnetic fields by other species, e.g., by clusters or small molecules. A special focus of the theory is on the coupling of the anion's motion across the magnetic field to the motion of the attached electron. Neglecting this coupling, the magnetically induced anionic states are known to constitute an infinite manifold of bound states. In reality, the number of bound anionic states is finite. Typically, the quantized motion of the anion in the field results in sequences of excitations. These might include, depending on properties of the anion and on the magnetic field strengths, a few or a substantial number of states. Explicit results obtained by quantum ab initio calculations are presented and discussed on bound states and radiative transitions for some experimentally relevant atomic anions.

Bezchastnov, Victor G.; Cederbaum, Lorenz S. [Theoretische Chemie, Physikalisch-Chemisches Institut, Universitaet Heidelberg, INF 229, D-69120 Heidelberg (Germany); Schmelcher, Peter [Theoretische Chemie, Physikalisch-Chemisches Institut, Universitaet Heidelberg, INF 229, D-69120 Heidelberg (Germany); Physikalisches Institut, Universitaet Heidelberg, Philosophenweg 12, D-69120 Heidelberg (Germany)

2007-05-15

54

ION CHROMATOGRAPHY OF ANIONS  

EPA Science Inventory

A Dionex Model 10 Ion Chromatograph was evaluated for the measurement of anionic species in water. The theoretical effect of hydrogen ion activity (pH) on the elution time of phosphate and arsenate was tested and empirical selectivity coefficients were determined for the major pr...

55

Hydrated hydride anion clusters.  

PubMed

On the basis of density functional theory (DFT) and high level ab initio theory, we report the structures, binding energies, thermodynamic quantities, IR spectra, and electronic properties of the hydride anion hydrated by up to six water molecules. Ground state DFT molecular dynamics simulations (based on the Born-Oppenheimer potential surface) show that as the temperature increases, the surface-bound hydride anion changes to the internally bound structure. Car-Parrinello molecular dynamics simulations are also carried out for the spectral analysis of the monohydrated hydride. Excited-state ab initio molecular dynamics simulations show that the photoinduced charge-transfer-to-solvent phenomena are accompanied by the formation of the excess electron-water clusters and the detachment of the H radical from the clusters. The dynamics of the detachment process of a hydrogen radical upon the excitation is discussed. PMID:17979342

Lee, Han Myoung; Kim, Dongwook; Singh, N Jiten; Ko?aski, Maciej; Kim, Kwang S

2007-10-28

56

Anion permselective membrane  

NASA Astrophysics Data System (ADS)

Two polymer ion exchange membranes were synthesized to fulfill the needs of both electrical resistivity and anolyte/catholyte separation for utility load leveling utilizing the DOE/NASA mixed electrolyte REDOX battery. Both membranes were shown to meet mixed electrolyte utility load leveling criteria. Several modifications of an anion exchange membrane failed to meet utility load leveling REDOX battery criteria using the unmixed electrolyte REDOX cell.

Hodgdon, R. B.; Waite, W. A.; Alexander, S. S.

1984-07-01

57

Regulation of Gap Junctions by Phosphorylation of Connexins  

Microsoft Academic Search

Gap junctions are a unique type of intercellular junction found in most animal cell types. Gap junctions permit the intercellular passage of small molecules and have been implicated in diverse biological processes, such as development, cellular metabolism, and cellular growth control. In vertebrates, gap junctions are composed of proteins from the “connexin” gene family. The majority of connexins are modified

Paul D. Lampe; Alan F. Lau

2000-01-01

58

Metabolomic profiling of anionic metabolites by capillary electrophoresis mass spectrometry.  

PubMed

We describe a sheath flow capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS) method in the negative mode using a platinum electrospray ionization (ESI) spray needle, which allows the comprehensive analysis of anionic metabolites. The material of the spray needle had significant effect on the measurement of anions. A stainless steel spray needle was oxidized and corroded at the anodic electrode due to electrolysis. The precipitation of iron oxides (rust) plugged the capillary outlet, resulting in shortened capillary lifetime. Many anionic metabolites also formed complexes with the iron oxides or migrating nickel ion, which was also generated by electrolysis and moved toward the cathode (the capillary inlet). The metal-anion complex formation significantly reduced detection sensitivity of the anionic compounds. The use of a platinum ESI needle prevented both oxidation of the metals and needle corrosion. Sensitivity using the platinum needle increased from several- to 63-fold, with the largest improvements for anions exhibiting high metal chelating properties such as carboxylic acids, nucleotides, and coenzyme A compounds. The detection limits for most anions were between 0.03 and 0.87 micromol/L (0.8 and 24 fmol) at a signal-to-noise ratio of 3. This method is quantitative, sensitive, and robust, and its utility was demonstrated by the analysis of the metabolites in the central metabolic pathways extracted from mouse liver. PMID:19522513

Soga, Tomoyoshi; Igarashi, Kaori; Ito, Chiharu; Mizobuchi, Katsuo; Zimmermann, Hans-Peter; Tomita, Masaru

2009-08-01

59

Use of Hydrochloric Acid as a Source of Anions for Prevention of Milk Fever1  

Microsoft Academic Search

Diets that contain high amounts of K induce milk fever by alkalinizing the blood of the cow, reducing the ability of homeostatic mechanisms to maintain normal blood concentrations of Ca. The addition of anions to the diet induces metabolic acidosis, which counteracts the alkalinizing effect of the high cation diets commonly fed to cows. Currently, anions are usually added as

J. P. Goff; R. L. Horst

1998-01-01

60

Unexpectedly severe metabolic acidosis associated with sodium thiosulfate therapy in a patient with calcific uremic arteriolopathy.  

PubMed

Calcific uremic arteriolopathy, formerly known as calciphylaxis is a devastating condition that primarily affects patients with end-stage renal disease. The lesions can progress to massive ulcerations of the subcutaneous tissue that are associated with a high degree of morbidity and mortality, usually related to sepsis. Although the pathophysiology of this condition is poorly understood, it appears to be related to a derangement in calcium-phosphate metabolism. Thus, treatments have focused on the treatment of hyperparathyroidism albeit with poor results. More recently, sodium thiosulfate (STS) has emerged as a promising therapy following multiple case reports of marked disease regression following its use. As STS is a strong acid, metabolic acidosis has been described following its administration, although relatively mild in degree. We report a case of a patient with calciphylaxis who repeatedly developed a severe anion gap metabolic acidosis following each dose of STS requiring a significant reduction in the dose. PMID:21338397

Selk, Natalie; Rodby, Roger A

61

Selective astrocytic gap junctional trafficking of molecules involved in the glycolytic pathway: Impact on cellular brain imaging  

PubMed Central

To assess the specificity of metabolite trafficking among gap junction-coupled astrocytes, we developed novel, real-time, single-cell enzymatic fluorescence assays to assay cell-to-cell transfer of unlabeled glycolytic intermediates and report (i) highly restricted transfer of glucose-6-phosphate(P) and two analogs, deoxyglucose-6-P (DG-6-P), and 2-NBDG-6-P, compared to DG and 2- and 6-NBDG, (ii) extensive junctional diffusion of glyceraldehyde-3-P, NADH, and NADPH plus three anionic fluorescent dyes used as internal standards for transfer assays, and (iii) stimulation of gap junctional communication by increased intracellular Na+ that also evokes metabolic responses in nearby coupled astrocytes. Thus, dye transfer does not predict gap junctional permeability of endogenous metabolites. Intracellular retention of flux-regulating compounds (e.g., glucose-6-P) may be necessary for local metabolic control, whereas ‘syncytial sharing’ may dissipate the work load on peri-synaptic astrocytes. Imaging of brain functional activity depends on local accumulation of exogenous or endogenous signals, and DG-6-P is trapped in the cell where it is phosphorylated, whereas rapid dispersal of cytoplasmic NAD(P)H and labeled glucose metabolites throughout the astrocytic syncytium can interfere with cellular assessment of neuron-astrocyte relationships in autoradiographic, fluorescence microscopic, and magnetic resonance spectroscopic studies.

Gandhi, Gautam K.; Cruz, Nancy F.; Ball, Kelly K.; Theus, Sue A.; Dienel, Gerald A.

2009-01-01

62

Anion-? interactions in supramolecular architectures.  

PubMed

The study of the noncovalent force between ?-acidic aromatic systems and anions, referred to as the anion-? interaction, has recently emerged as a new branch of supramolecular chemistry. The anion-? contact is complementary to the cation-? interaction, a prominent noncovalent force involved in protein structure and enzyme function. Until recently, the scientific community had overlooked the anion-? interaction due to its ostensibly counterintuitive nature. Pioneering theoretical studies in 2002, however, established that anion-? interactions are energetically favorable (~20-70 kJ/mol) and prompted a flurry of reports in support of their existence. The interest in anion-? contacts was further fueled by the importance of anions in key chemical and biological processes and the involvement of ?-rings in anion recognition and transport. Anion-? interactions hold great promise for the design of selective anion receptors, hosts or scaffolds, colorimetric sensors, and catalysts and may also affect biological functions. Currently, the area of anion-? research is highly topical in the scientific community and on a meteoric rise in the chemical literature. This Account highlights our leading findings in this burgeoning area. Our work has focused on comprehensive investigations of several unprecedented supramolecular systems, in which the anions and their close anion-? contacts are the driving elements of the final architectures. We surveyed several heterocyclic ?-acidic aromatic systems amenable to anion-? contacts and explored the subtle interplay between ligand ?-acidity, anion identity, and metal ions in mediating the ensuing self-assembled architectures. The reactions we performed between solvated first-row transition metal ions and the ?-acidic ligands bptz (3,6-bis(2-pyridyl)-1,2,4,5-tetrazine) or bmtz (3,6-bis(2-pyrimidyl)-1,2,4,5-tetrazine) resulted in unprecedented metallacycles. Our investigations revealed that the identity of the encapsulated ion dictates the metallacycle nuclearity and close anion-? contacts are critical for the metallacycle stability. Our X-ray crystallographic, NMR spectroscopic, and mass spectrometric (MS) studies demonstrated that the tetrahedral ([BF4](-), [ClO4](-)) and octahedral ([SbF6](-), [AsF6](-), [PF6](-)) anions template discrete molecular squares and pentagons, respectively. The metal ions occupy the vertices, and bptz or bmtz moieties span the edges of the metallacycles. The encapsulated anions occupy the ?-acidic cavities of the metallacycles and establish multiple close directional F/O···C(tetrazine) contacts with the edges. The observation of notable (19)F solid-state NMR chemical shifts reflects the short contacts of the encapsulated anions, findings that we corroborated by DFT calculations. The solution NMR data support the conclusion that bona fide metallacycle templation and interconversion between the metallacycles in solution occurs only in the presence of the appropriate anions. The NMR, MS, and CV data underscore the remarkable metallapentacycle stability despite the angle strain inherent in pentagons formed by octahedral metal ions. The low anion activation energies of encapsulation (?G(‡) ~ 50 kJ/mol) suggest that anion-? contacts assist the anion templation. We also studied reactions of Ag(I)X (X(-) = [PF6](-), [AsF6](-), [SbF6](-), [BF4](-)) with bptz or bppn (3,6-bis(2-pyridyl)-1,2-pyridazine) to assess the effect of the ligand ?-acidity on the preferred structures. The X-ray data revealed that the higher ?-acidity of the tetrazine ring in bptz leads to propeller-type products [Ag2(bptz)3](2+) exhibiting prominent short anion-? contacts. By contrast, the less ?-acidic bppn preferentially favors grids [Ag4(bppn)4](4+) which exhibit maximized ?-? interactions. Finally, we explored the reactions of the extended ?-acidic heterocycle HAT(CN)6 (1,4,5,8,9,12-hexaazatriphenylene-hexacarbonitrile) with the Cl(-), Br(-), I(-) ions which lead to highly colored solutions/crystals. X-ray crystallographic studies of the HAT(CN)6/halide complexes revealed

Chifotides, Helen T; Dunbar, Kim R

2013-03-11

63

Anion exchange behavior of nobelium  

Microsoft Academic Search

The anion exchange behavior of 255No produced by the 248Cm(12C,5n) reaction has been investigated in 11.5M HCl, 4M HCl and 8M HNO3 to deduce the behavior of 'primordial 257No' produced via 248Cm(18O,5n)261Rf 257No before anion exchange separation in the 261Rf experiment. It was found that 255No is mostly eluted from the anion exchange column with these solutions. The contribution of

A. Toyoshima; K. Tsukada; H. Haba; M. Asai; S. Goto; K. Akiyama; I. Nishinaka; S. Ichikawa; Y. Nagame; A. Shinohara

2003-01-01

64

Direct determination of III-V semiconductor surface band gaps  

Microsoft Academic Search

Applying in situ combination of angle-resolved photoemission and inverse photoemission to cleaved III-V compound semiconductor (110) surfaces, we have determined the surface band gaps between the filled anion-derived dangling-bound state A5 and the empty cation-derived state C3 at the Gamma¯, X¯ ', X¯, and M¯ points of the surface Brillouin zone. The values of the surface band gaps of the

H. Carstensen; R. Claessen; R. Manzke; M. Skibowski

1990-01-01

65

Bound anionic states of adenine  

PubMed Central

Anionic states of nucleic acid bases are involved in DNA damage by low-energy electrons and in charge transfer through DNA. Previous gas phase studies of free, unsolvated nucleic acid base parent anions probed only dipole-bound states, which are not present in condensed phase environments, but did not observe valence anionic states, which for purine bases are thought to be adiabatically unbound. Contrary to this expectation, we have demonstrated that some thus far ignored tautomers of adenine, which result from enamine-imine transformations, support valence anionic states with electron vertical detachment energies as large as 2.2 eV, and at least one of these anionic tautomers is adiabatically bound. Moreover, we predict that the new anionic tautomers should also dominate in solutions and should be characterized by larger values of electron vertical detachment energy than the canonical valence anion. All of the newfound anionic tautomers might be formed in the course of dissociative electron attachment followed by a hydrogen atom attachment to a carbon atom, and they might affect the structure and properties of DNA and RNA exposed to low-energy electrons. The new valence states observed here, unlike the dipole-bound state, could exist in condensed phases and might be relevant to radiobiological damage. The discovery of these valence anionic states of adenine was facilitated by the development of (i) an experimental method for preparing parent anions of nucleic acid bases for photoelectron experiments, and (ii) a combinatorial/quantum chemical approach for identification of the most stable tautomers of organic molecules.

Haranczyk, Maciej; Gutowski, Maciej; Li, Xiang; Bowen, Kit H.

2007-01-01

66

Behind the Pay Gap  

ERIC Educational Resources Information Center

|Women have made remarkable gains in education during the past three decades, yet these achievements have resulted in only modest improvements in pay equity. The gender pay gap has become a fixture of the U.S. workplace and is so ubiquitous that many simply view it as normal. "Behind the Pay Gap" examines the gender pay gap for college graduates.…

Dey, Judy Goldberg; Hill, Catherine

2007-01-01

67

Triggered vacuum gaps  

Microsoft Academic Search

Characteristics of a sealed vacuum gap are described and the difficulties encountered in applying this gap as an overvoltage protection device are discussed. It is shown how these difficulties can be ameliorated by the use of gas-free electrode materials and by triggering the gap when breakdown is required. Several methods of triggering are discussed and some practical triggering devices are

J. M. Lafferty

1966-01-01

68

Anion exchange polymer electrolytes  

DOEpatents

Solid anion exchange polymer electrolytes and compositions comprising chemical compounds comprising a polymeric core, a spacer A, and a guanidine base, wherein said chemical compound is uniformly dispersed in a suitable solvent and has the structure: ##STR00001## wherein: i) A is a spacer having the structure O, S, SO.sub.2, --NH--, --N(CH.sub.2).sub.n, wherein n=1-10, --(CH.sub.2).sub.n--CH.sub.3--, wherein n=1-10, SO.sub.2-Ph, CO-Ph, ##STR00002## wherein R.sub.5, R.sub.6, R.sub.7 and R.sub.8 each are independently --H, --NH.sub.2, F, Cl, Br, CN, or a C.sub.1-C.sub.6 alkyl group, or any combination of thereof; ii) R.sub.9, R.sub.10, R.sub.11, R.sub.12, or R.sub.13 each independently are --H, --CH.sub.3, --NH.sub.2, --NO, --CH.sub.nCH.sub.3 where n=1-6, HC.dbd.O--, NH.sub.2C.dbd.O--, --CH.sub.nCOOH where n=1-6, --(CH.sub.2).sub.n--C(NH.sub.2)--COOH where n=1-6, --CH--(COOH)--CH.sub.2--COOH, --CH.sub.2--CH(O--CH.sub.2CH.sub.3).sub.2, --(C.dbd.S)--NH.sub.2, --(C.dbd.NH)--N--(CH.sub.2).sub.nCH.sub.3, where n=0-6, --NH--(C.dbd.S)--SH, --CH.sub.2--(C.dbd.O)--O--C(CH.sub.3).sub.3, --O--(CH.sub.2).sub.n--CH--(NH.sub.2)--COOH, where n=1-6, --(CH.sub.2).sub.n--CH.dbd.CH wherein n=1-6, --(CH.sub.2).sub.n--CH--CN wherein n=1-6, an aromatic group such as a phenyl, benzyl, phenoxy, methylbenzyl, nitrogen-substituted benzyl or phenyl groups, a halide, or halide-substituted methyl groups; and iii) wherein the composition is suitable for use in a membrane electrode assembly.

Kim, Yu Seung; Kim, Dae Sik; Lee, Kwan-Soo

2013-07-23

69

Deep defects in narrow-gap semiconductors  

NASA Astrophysics Data System (ADS)

We use a Green's-function technique to calculate the position of deep defects in narrow-gap semiconductors. In order to predict chemical trends, we examine the effects of several different chemical elements. Substitutional (including antisite), (ideal) vacancy, and interstitial (self and foreign) deep defects are considered. The compounds considered are mercury cadmium telluride (MCT), mercury zinc telluride (MZT), and mercury zinc selenide (MZS). The effect of relaxation of neighbors is considered for the substitutional and interstitial cases. Relaxation effects can be greater for the interstitial case than for the substitutional one. For all cases we find deep defects in the energy gap only for cation-site s-like orbitals or anion-site p-like orbitals, and for the substitutional case only the latter are appreciably effected by relaxation. For substitutional impurities in MCT, MZT, and MZS, we consider x (the concentration of Cd or Zn) in the range 0.1gap of 0.1 eV. Specific results are given in figures and tables and comparison to experiment and other calculations is made in a limited number of cases. For the substitutional case we find that I, Se, S, Rn, and N are possible defect candidates to form cation-site, s-like levels in MCT, and Zn and Mg are for anion-site, p-like levels. Similarly, in MCT for the interstitial case we find deep defect levels in the band gap for Au, Ag, Hg, Cd, Cu, and Zn for the cation site, and N, Ar, O, and F for the anion site. For the substitutional cases we have some examples where relaxation moves the levels into the band gap, whereas for interstitial cases we have examples where relaxation moves them out of the band gap. We find that the chemical trends of defect levels in MZT are similar to that in MCT. However, the same conclusion does not hold for MZS. We have also used perturbation theory (see the Appendix) to look at the effect of nonparabolicity on shallow donor levels, and find it can increase the binding by 10% or so. Although the absolute accuracy of our results is limited, the precision is good, and hence chemical trends are accurately predicted. Further work involves calculating the effect of charged-state interactions and the effect of relaxation on vacancy levels.

Li, W.; Patterson, J. D.

1994-11-01

70

Effect of Anionic Salts in Prepartum Diets Based on Alfalfa1  

Microsoft Academic Search

This study compared prepartum diets based on grass, alfalfa, or alfalfa and anionic salts to inves- tigate their effect on Ca metabolism, acid-base status, endocrine response, disease incidence, and lactational performance of periparturient dairy cows. Forty-five nonlactating Holstein cows in their last 3 wk of gesta- tion were fed a control diet based on grass hay with a dietary cation-anion

P. W. Joyce; W. K. Sanchez; J. P. Goff

1997-01-01

71

ESR Study of Polyazine Anions  

Microsoft Academic Search

Electron spin resonance measurements have been made on dimethyl sulfoxide solutions of the anion radicals of s-tetrazine, pyridazine, phthalazine, and phenazine, as well as the diprotopyrazine cation radical. The radicals were generated by constant potential electroreduction of the parent compound at a mercury pool cathode within the microwave cavity. Complete assignment of the hyperfine coupling constants to positions of phthalazine

Ellery W. Stone; August H. Maki

1963-01-01

72

Anion separation with metal-organic frameworks  

SciTech Connect

The application of metal-organic frameworks (MOFs) to anion separations with a special emphasis on anion selectivity is reviewed. The coordination frameworks are classified on the basis of the main interactions to the included anion, from weak and non-specific van der Waals forces to more specific interactions such as coordination to Lewis acid metal centers or hydrogen bonding. The importance of anion solvation phenomena to the observed anion selectivities is highlighted, and strategies for reversing the Hofmeister bias that favors large, less hydrophilic anions, and for obtaining peak selectivities based on shape recognition are delineated. Functionalization of the anion-binding sites in MOFs with strong and directional hydrogen-bonding groups that are complementary to the included anion, combined with organizational rigidity of the coordination framework, appears to be the most promising approach for achieving non-Hofmeister selectivity.

Custelcean, Radu [ORNL; Moyer, Bruce A [ORNL

2007-01-01

73

Gap year volunteer tourism  

Microsoft Academic Search

The valorisation of cross-cultural understanding and promotion of an ethic of global citizenship are at the forefront of the recent development and proliferation of international ‘gap year’ travel programs and policies. Governments and industry alike promote gap year travel uncritically as a guaranteed pathway to the development of inclusive ideologies associated with global citizenship. In this paper we examine how

Stephen Wearing; John Neil

74

Confronting the Achievement Gap  

ERIC Educational Resources Information Center

|This article talks about the large achievement gap between children of color and their white peers. The reasons for the achievement gap are varied. First, many urban minorities come from a background of poverty. One of the detrimental effects of growing up in poverty is receiving inadequate nourishment at a time when bodies and brains are rapidly…

Gardner, David

2007-01-01

75

Bridging a Cultural Gap  

ERIC Educational Resources Information Center

|There has been a broad wave of change in tertiary calculus courses in the past decade. However, the much-needed change in tertiary pre-calculus programmes--aimed at bridging the gap between high-school mathematics and tertiary mathematics--is happening at a far slower pace. Following a discussion on the nature of the gap and the objectives of a…

Leviatan, Talma

2008-01-01

76

Knowledge Gaps, Social Locators, and Media Schemata: Gaps, Reverse Gaps, and Gaps of Disaffection  

Microsoft Academic Search

In a study of a public school controversy, a knowledge gap is found that the authors describe as a gap of disaffection. Among women only, higher education leads to greater knowledge, but does so partly through reduced trust of government and lower perceived fairness of the news media. Similar findings occur with other less powerful groups.

Eric S. Fredin; Teresa Haugen Monnett; Gerald M. Kosicki

1994-01-01

77

GAP ACTIVITY TRACKING MATRIX  

EPA Science Inventory

Resource Purpose: The information collected serves the following purposes: (1) provides a summary of funds allocated by tribe for the GAP Program, (2) provides an overview in the types of activities the tribes are engaged in with GAP funds, and (3) allows OW to document the...

78

Biostratigraphic gap analysis  

Microsoft Academic Search

Frequency distributions of biostratigraphic gaps are generated for eight fossil species. The distributions help estimate confidence intervals for biozonation boundaries by providing information on the size of the gap one may reasonably expect between the lowest and highest visible fossil occurrences, seen in cross section, and the actual lowest and highest individuals, unseen within the rock, which occur beyond them.

Michael L. McKinney

1986-01-01

79

Coma, metabolic acidosis, and methemoglobinemia in a patient with acetaminophen toxicity.  

PubMed

We present a case of early coma, metabolic acidosis and methemoglobinemia after substantial acetaminophen toxicity in the absence of hepatic failure. A 77-year-old female presented to the emergency department with a decreased level of consciousness. She was found unresponsive by a family member in her bed, and was reported to be acting normally when she was last seen eight hours earlier. Laboratory results on arrival were: pH 7.19, sodium 139 mmol/L, chloride 106 mmol/L, potassium 3.3 mmol/L, CO2 8 mmol/L, and an anion gap of 25. Both venous lactate (10.2 mmol/L) and methemoglobin (9.4 %) were elevated. The patient's acetaminophen concentration was markedly elevated at 7138 µmol/L (1078 µg/ml). Hepatic enzymes and coagulation tests were normal [alanine transaminase (ALT) 8 U/L, international normalized ratio (INR) 1.0]. Intravenous N-acetylcysteine (NAC) was initiated at a dose of 150 mg/kg over 15 minutes, followed by 50 mg/kg over the next four hours, followed by 100 mg/kg over the next 16 hours. Twenty-four hours after admission, the anion gap metabolic acidosis had resolved, and the methemoglobin was 2.1%. Aminotransferases peaked at 44 U/L and INR peaked at 1.9. A urine 5-oxoproline assay performed five days after admission was negative, suggesting no evidence of a 5-oxoprolinase deficiency. We describe the pathophysiology and discuss the literature on acetaminophen-induced coma and metabolic acidosis in the absence of hepatic injury; and propose mechanisms for associated methemoglobinemia.  PMID:24077426

Kanji, Hussein D; Mithani, Shazma; Boucher, Paul; Dias, Valerian C; Yarema, Mark C

2013-09-06

80

Renal secretion of organic anions and cations  

Microsoft Academic Search

Renal secretion of organic anions and cations. The renal proximal tubule actively transports charged, potentially toxic xenobiotics from blood to lumen. Basolateral uptake of organic anions is indirectly coupled to the sodium gradient through Na-dicarboxylate cotransport and dicar-boxylate-organic anion exchange. Upon entry, a significant fraction of intracellular organic anion is sequestered within vesicles. Disruption of the cellular microtubular network can

John B Pritchard; David S Miller

1996-01-01

81

Both L- and D-lactate contribute to metabolic acidosis in diarrheic calves.  

PubMed

Diarrhea in neonates is often complicated by metabolic acidosis. We used blood gas analysis and HPLC to determine whether bacterial fermentation might contribute to acidosis in diarrheic calves. Diarrheic calves (n = 21) had significantly lower pH, PCO(2), HCO(3)(-) and a higher anion gap than healthy calves (n = 21). Serum concentrations (mean +/- SD, mmol/L) of DL-, L- and D-lactate were also significantly higher in diarrheic (8.9 +/- 5.1, 4.1 +/- 3.4 and 5.2 +/- 5.7) than in healthy calves (1.7 +/- 1.2, 2.0 +/- 1.1 and too low to quantify). D- and L-lactate accounted for 64% anion gap increase in diarrheic calves. Fecal D- and L-lactate concentrations were also significantly higher in diarrheic calves (9.4 +/- 3.0 and 11.9 +/- 2.7 mmol/L) than healthy calves (1.1 +/- 0.1 and 1.6 +/- 0.1 mmol/L). The elevated concentrations of serum and fecal D-lactate suggest gut bacterial fermentation contributes to the development of acidosis in diarrhea. PMID:11481406

Omole, O O; Nappert, G; Naylor, J M; Zello, G A

2001-08-01

82

Polymerization of anionic wormlike micelles.  

PubMed

Polymerizable anionic wormlike micelles are obtained upon mixing the hydrotropic salt p-toluidine hydrochloride (PTHC) with the reactive anionic surfactant sodium 4-(8-methacryloyloxyoctyl)oxybenzene sulfonate (MOBS). Polymerization captures the cross-sectional radius of the micelles (approximately 2 nm), induces micellar growth, and leads to the formation of a stable single-phase dispersion of wormlike micellar polymers. The unpolymerized and polymerized micelles were characterized using static and dynamic laser light scattering, small-angle neutron scattering, 1H NMR, and stopped-flow light scattering. Stopped-flow light scattering was also used to measure the average lifetime of the unpolymerized wormlike micelles. A comparison of the average lifetime of unpolymerized wormlike micelles with the surfactant monomer propagation rate was used to elucidate the mechanism of polymerization. There is a significant correlation between the ratio of the average lifetime to the monomer propagation rate and the average aggregation number of the polymerized wormlike micelles. PMID:16430253

Zhu, Zhiyuan; González, Yamaira I; Xu, Hangxun; Kaler, Eric W; Liu, Shiyong

2006-01-31

83

Aza compounds as anion receptors  

DOEpatents

A family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of Li.sup.+ ion in alkali metal batteries.

Lee, Hung Sui (East Setauket, NY); Yang, Xiao-Qing (Port Jefferson Station, NY); McBreen, James (Bellport, NY)

1998-01-06

84

Aza compounds as anion receptors  

DOEpatents

A family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of Li{sup +} ion in alkali metal batteries. 3 figs.

Lee, H.S.; Yang, X.Q.; McBreen, J.

1998-01-06

85

Multiply Charged Metal Cluster Anions  

SciTech Connect

Formation and stability patterns of silver dianionic and gold trianionic clusters are investigated with Penning-trap experiments and a shell-correction method including shape deformations. The theoretical predictions pertaining to the appearance sizes and electronic shell effects are in remarkable agreement with the experiments. Decay of the multiply anionic clusters occurs predominantly by electron tunneling through a Coulomb barrier rather than via fission, leading to appearance sizes unrelated to those of multiply cationic clusters.

Yannouleas, Constantine; Landman, Uzi; Herlert, Alexander; Schweikhard, Lutz

2001-04-02

86

Plasmalemmal VDAC controversies and maxi-anion channel puzzle.  

PubMed

The maxi-anion channel has been observed in many cell types from the very beginning of the patch-clamp era. The channel is highly conductive for chloride and thus can modulate the resting membrane potential and play a role in fluid secretion/absorption and cell volume regulation. A wide nanoscopic pore of the maxi-anion channel permits passage of excitatory amino acids and nucleotides. The channel-mediated release of these signaling molecules is associated with kidney tubuloglomerular feedback, cardiac ischemia/hypoxia, as well as brain ischemia/hypoxia and excitotoxic neurodegeneration. Despite the ubiquitous expression and physiological/pathophysiological significance, the molecular identity of the maxi-anion channel is still obscure. VDAC is primarily a mitochondrial protein; however several groups detected it on the cellular surface. VDAC in lipid bilayers reproduced the most important biophysical properties of the maxi-anion channel, such as a wide nano-sized pore, closure in response to moderately high voltages, ATP-block and ATP-permeability. However, these similarities turned out to be superficial, and the hypothesis of plasmalemmal VDAC as the maxi-anion channel did not withstand the test by genetic manipulations of VDAC protein expression. VDAC on the cellular surface could also function as a ferricyanide reductase or a receptor for plasminogen kringle 5 and for neuroactive steroids. These ideas, as well as the very presence of VDAC on plasmalemma, remain to be scrutinized by genetic manipulations of the VDAC protein expression. This article is part of a Special Issue entitled: VDAC structure, function, and regulation of mitochondrial metabolism. PMID:21986486

Sabirov, Ravshan Z; Merzlyak, Petr G

2011-10-01

87

Radical anion of isolable dialkylsilylene.  

PubMed

By the reduction of an isolable dialkylsilylene, 2,2,5,5-[tetrakis(trimethylsilyl)]-1-silacyclopentane-1,1-diyl (1), with cesium, rubidium, potassium, sodium, and lithium 4,4'-di(tert-butyl)biphenylide in DME at low temperatures, the corresponding silylene radical anion 2 was generated as the first persistent silylene radical anion in solution and characterized by ESR spectroscopy. Radical anion 2 is rather stable at -70 degrees C in DME but decomposes rapidly at room temperature with a half-life time of ca. 20 min. The g-factor and 29Si hyperfine splitting constants (hfs's) of 2 are almost independent of the countercations, indicating that 2 exists as a free ion or a solvent-separated ion pair in a polar DME solution. A very small hfs due to the 29Si nucleus of the divalent silicon (3.0 mT) as well as a very large g-factor (2.0077) indicates that an unpaired electron is accommodated in the vacant 3ppi orbital of silylene 1. PMID:12630866

Ishida, S; Iwamoto, T; Kira, M

2003-03-19

88

Anion Composition of Aça?? Extracts.  

PubMed

Many products labeled aça?? are presently marketed as natural supplements with various claimed health benefits. Authentic aça?? is expensive; as a result, numerous products labeled as containing aça?? are being sold that actually contain little or no aça??. Authentic aça?? samples from Brazil and Florida as well as several reputed aça?? products were analyzed by suppressed conductometric anion chromatography. Columns with different selectivities were used to obtain a complete separation of all anions. Tandem mass spectrometry was used for confirmation of the less common ions. Quinate, lactate, acetate, formate, galacturonate, chloride, sulfate, malate, oxalate, phosphate, citrate, isocitrate, and myo-inositol hexakisphosphate (phytate) were found. Only the Florida aça?? had detectable levels of hexanoate. No aça?? sample had any detectable levels of tartrate, which is present in abundance in grape juice, the most common adulterant. The highly characteristic anion profile and in particular the absence of tartrate can readily be used to identify authentic aça?? products. Aça?? from Florida had a 6 times greater level of phytate. The present analytical approach for phytate may be superior to extant methods. PMID:23772604

Liao, Hongzhu; Shelor, C Phillip; Chen, Yongjing; Sabaa-Srur, Armando U O; Smith, Robert E; Dasgupta, Purnendu K

2013-06-17

89

Transient Anion States of Biomolecules  

NASA Astrophysics Data System (ADS)

Much of the interest on electron interactions with biomolecules is related to radiation damage [Gohlke and Illenberger, Europhys. News 33, 207 (2002)]. The high energy photons employed in radiology and radiotherapy generate a large number of fast electrons in living cells. These electrons thermalize in a picosecond scale, eventually forming dissociative matestable anions with water and biomolecules. In this work, we employ the parallel version of Schwinger Multichannel Method with Pseudopotentials [Bettega et al., Phys. Rev. A 47, 1111 (1993); Santos et al., J. Phys. Chem. 136, 084307 (2012)] to investigate transient anion states of protein and nucleic acid precursors. We address glycine in both neutral and zwitterionic forms, as well as glycine-water clusters and disulfide bonds. The interest on the two forms of glycine (and other amino acids) relies on the fact that only the neutral form is stable in the gas phase, while the zwitterion is more stable in solution, pointing out limitations of standard gas-phase studies. Electron attachment to disulfide bonds also has potential impact on protein stability. Finally we address transient anion states of substituted uracil molecules in the gas phase. [4pt] In collaboration with M. H. F. Bettega, S. d'A. Sanchez, R. F. da Costa, M. A. P. Lima, J. S. dos Santos, and F. Kossoski.

Varella, Marcio

2012-10-01

90

SPARK GAP SWITCH  

DOEpatents

An improved triggered spark gap switch is described, capable of precisely controllable firing time while switching very large amounts of power. The invention in general comprises three electrodes adjustably spaced and adapted to have a large potential impressed between the outer electrodes. The central electrode includes two separate elements electrically connected togetaer and spaced apart to define a pair of spark gaps between the end electrodes. Means are provided to cause the gas flow in the switch to pass towards the central electrode, through a passage in each separate element, and out an exit disposed between the two separate central electrode elements in order to withdraw ions from the spark gap.

Neal, R.B.

1957-12-17

91

Competition between monovalent and divalent anions for calcined and uncalcined hydrotalcite: anion exchange and adsorption sites  

Microsoft Academic Search

Hydrotalcite compounds are well-known anion exchangers. Their anionic exchange capacity (A.E.C.) increases with thermal treatment together with their specific surface area and porosity. In the presence of mono- and divalent anions such as Cl?, SO42? and CrO42?, calcined hydrotalcite behaves not only as an anion exchanger but also as an oxide adsorbent. In the case of divalent anions, the adsorbed

L. Châtelet; J. Y. Bottero; J. Yvon; A. Bouchelaghem

1996-01-01

92

From anion receptors to transporters.  

PubMed

Cystic fibrosis is the most well-known of a variety of diseases termed channelopathies, in which the regulation of ion transport across cell membranes is so disrupted that the threshold of a pathology is passed. The human toll exacted by these diseases has led a number of research groups, including our own, to create compounds that mediate ion transport across lipid bilayers. In this Account, we discuss three classes of synthetic compounds that were refined to bind and transport anions across lipid bilayer membranes. All of the compounds were originally designed as anion receptors, that is, species that would simply create stable complexes with anions, but were then further developed as transporters. By studying structurally simple systems and varying their properties to change the degree of preorganization, the affinity for anions, or the lipophilicity, we have begun to rationalize why particular anion transport mechanisms (cotransport or antiport processes) occur in particular cases. For example, we have studied the chloride transport properties of receptors based on the closely related structures of isophthalamide and pyridine-2,6-dicarboxamide: the central ring in each case was augmented with pendant methylimidazole groups designed to cotransport H(+) and Cl(-). We observed that the more preorganized pyridine-based receptor was the more efficient transporter, a finding replicated with a series of isophthalamides in which one contained hydroxyl groups designed to preorganize the receptor. This latter class of compound, together with the natural product prodigiosin, can transport bicarbonate (as part of a chloride/bicarbonate antiport process) across lipid bilayer membranes. We have also studied the membrane transport properties of calix[4]pyrroles. Although the parent meso-octamethylcalix[4]pyrrole functions solely as a Cs(+)/Cl(-) cotransporter, other compounds with increased anion affinities can function through an antiport process. One example is octafluoro-meso-octamethylcalix[4]pyrrole; with its electron-withdrawing substituents, it can operate through a chloride/bicarbonate antiport process. Moreover, calix[4]pyrroles with additional hydrogen bond donors can operate through a chloride/nitrate antiport process. Thus, increasing the affinity of the receptor in these cases allows the compound to transport an anion in the absence of a cation. Finally, we have studied the transport properties of simple thioureas and shown that these compounds are highly potent chloride/bicarbonate antiport agents that function at low concentrations. In contrast, the urea analogues are inactive. The higher hydrophobicity (reflected in higher values for the logarithm of the water-octanol partition constant, or log P) and lower polar surface areas of the thiourea compounds compared to their urea analogues may provide a clue to the high potency of these compounds. This observation might serve as a basis for designing future small-molecule transporters. PMID:21207951

Gale, Philip A

2011-01-05

93

Lactate versus non-lactate metabolic acidosis: a retrospective outcome evaluation of critically ill patients  

PubMed Central

Introduction Acid–base abnormalities are common in the intensive care unit (ICU). Differences in outcome exist between respiratory and metabolic acidosis in similar pH ranges. Some forms of metabolic acidosis (for example, lactate) seem to have worse outcomes than others (for example, chloride). The relative incidence of each type of disorder is unknown. We therefore designed this study to determine the nature and clinical significance of metabolic acidosis in critically ill patients. Methods An observational, cohort study of critically ill patients was performed in a tertiary care hospital. Critically ill patients were selected on the clinical suspicion of the presence of lactic acidosis. The inpatient mortality of the entire group was 14%, with a length of stay in hospital of 12 days and a length of stay in the ICU of 5.8 days. Results We reviewed records of 9,799 patients admitted to the ICUs at our institution between 1 January 2001 and 30 June 2002. We selected a cohort in which clinicians caring for patients ordered a measurement of arterial lactate level. We excluded patients in which any necessary variable required to characterize an acid–base disorder was absent. A total of 851 patients (9% of ICU admissions) met our criteria. Of these, 548 patients (64%) had a metabolic acidosis (standard base excess < -2 mEq/l) and these patients had a 45% mortality, compared with 25% for those with no metabolic acidosis (p < 0.001). We then subclassified metabolic acidosis cases on the basis of the predominant anion present (lactate, chloride, or all other anions). The mortality rate was highest for lactic acidosis (56%); for strong ion gap (SIG) acidosis it was 39% and for hyperchloremic acidosis 29% (p < 0.001). A stepwise logistic regression model identified serum lactate, SIG, phosphate, and age as independent predictors of mortality. Conclusion In critically ill patients in which a measurement of lactate level was ordered, lactate and SIG were strong independent predictors of mortality when they were the major source of metabolic acidosis. Overall, patients with metabolic acidosis were nearly twice as likely to die as patients without metabolic acidosis.

Gunnerson, Kyle J; Saul, Melissa; He, Shui; Kellum, John A

2006-01-01

94

There Are GAPS and There Are GAPS  

NSDL National Science Digital Library

Access to the article is free, however registration and sign-in are required. Guanine nucleotide-binding proteins (G proteins) transduce a very large number of cellular regulatory signals. Several recent papers have shown that the larger heterotrimeric G proteins are regulated by a class of molecules known as the RGS proteins (regulators of G protein-signaling family) that are analogous to the GAPs (GTPase activating proteins), which regulate small monomeric G proteins. Iyengar summarizes this evidence and discusses the mechanism of action of the RGS proteins.

Ravi Iyengar (Mount Sinai School of Medicine;Department of Pharmacology)

1997-01-03

95

Mild route to generate gaseous metal anions.  

PubMed

Gaseous metal anions such as Na(-), K(-), Cs(-), and Ag(-) can be generated at ambient temperatures by the collision-induced dissociation of the anions of several dicarboxylic acid salts, including oxalate, maleate, fumarate, succinate, and glutamate salts. The formation of gaseous metal anions in this way is unprecedented because the metal is initially present in its cationic form. The mild process described here could facilitate novel applications of metal anions as selective reagents for gas-phase ion-molecule and ion-ion reactions. Ab initio calculations were used to describe the dissociation process for anions of the oxalate salts. The formation of alkalides occurs via production of a metal-carbon dioxide anion intermediate with a bidentate three-center two-electron bond to the metal. The metal atom acquires a partial negative charge in the intermediate structure. PMID:21337628

Attygalle, Athula B; Axe, Frank U; Weisbecker, Carl S

2011-03-30

96

GAP Analysis. Bulletin Number 11.  

National Technical Information Service (NTIS)

The 2002 issue of the Gap Analysis Bulletin is the eleventh in a series of annual publications produced by the National Gap - -- Analysis Program. Gap Analysis Bulletin No. 11 features 18 articles on various aspects of gap analysis methods and results. Th...

E. S. Brackney R. Brannon K. J. Gergely M. D. Jennings

2002-01-01

97

Tunable photonic band gap fiber  

Microsoft Academic Search

The ability to change the photonic band gap structure continuously and reversibly by modifying the index thermally allows the band gap features to be sensitively tuned, allowing for a thorough investigation of the various band gap guiding properties. Furthermore, it may be possible to use this type of band gap fiber as a tunable filter. Investigations of the dispersion properties

R. T. Bise; R. S. Windeler; K. S. Kranz; C. Kerbage; B. J. Eggleton; D. J. Trevor

2002-01-01

98

Pyrazole complexes as anion receptors.  

PubMed

The behavior of the receptors [Re(CO)3(Hdmpz)3]BAr'4 (Hdmpz = 3,5-dimethylpyrazole) (1) and [Re(CO)3(HtBupz)3]BAr'4 (HtBupz = 3(5)-tert-butylpyrazole) (2; Ar' = 3,5-bis(trifluoromethyl)phenyl) toward the anions fluoride, chloride, bromide, iodide, hydrogensulfate, dihydrogenphosphate, nitrate, and perrhenate was studied in CD3CN solution. In most cases, the receptors were stable. Anion exchange was fast, and binding constants were calculated from the NMR titration profiles. The structure of the adduct [Re(CO)3(HtBupz)3] x NO3 (3) was determined by X-ray diffraction. Two pyrazole moieties are hydrogen-bonded to one nitrate oxygen atom, and the third pyrazole moiety is hydrogen-bonded to an oxygen atom of an adjacent nitrate, leading to infinite chains. The structure of the adduct [Re(CO)3(Hdmpz)3]BAr'4acetone (4), also determined by X-ray diffraction, showed a similar interaction of two pyrazole N-H groups with the acetone oxygen atom. F- and H2PO4(-) deprotonate the receptors, and HSO4(-) decomposed 1. The structure of one of the decomposition products (5), determined by X-ray diffraction, is consistent with pyrazole protonation and substitution by sulfate. PMID:16370004

Nieto, Sonia; Pérez, Julio; Riera, Lucía; Riera, Víctor; Miguel, Daniel

2006-03-01

99

Pyridine and Pyridinium-Based Anion Receptors  

NASA Astrophysics Data System (ADS)

Pyridine and pyridinium heterocycles play an important role in anion receptor chemistry. Hydrogen bond arrays are frequently preorganized by the presence of the pyridine nitrogen lone pair of electrons, whilst the positively charged pyridinium group is capable of interacting with anions via a number of polarized noncovalent interactions. This review describes the development of pyridine and pyridinium-based anion receptors, separated into topologically distinct acyclic, macrocyclic, macrobicyclic and interlocked host systems.

Kilah, Nathan L.; Beer, Paul D.

100

Polyelectrolytes with sterically hindered anionic charges  

SciTech Connect

The central problem in the development of single phase polymer electrolytes with exclusive cation conduction has been inadequate ion mobility due to extensive ion pairing between the mobile cation and the covalently attached anion. We have developed a new class of single ion conducting polymers, or polyelectrolytes, based on highly flexible polysiloxane backbones and attached sterically hindered phenolate anions. The combination of a highly delocalized and sterically enclosed anionic charged separation and consequently enhanced cation mobility. 10 refs., 2 figs.

Yeh, T.F.; Liu, H.; Okamoto, Y.; Lee, H.S.; Skotheim, T.A. (Polytechnic Inst. of Brooklyn, NY (USA); Brookhaven National Lab., Upton, NY (USA))

1989-01-01

101

MULTIPLE SPARK GAP SWITCH  

DOEpatents

A multiple spark gap switch of unique construction is described which will permit controlled, simultaneous discharge of several capacitors into a load. The switch construction includes a disc electrode with a plurality of protuberances of generally convex shape on one surface. A firing electrode is insulatingly supponted In each of the electrode protuberances and extends substantially to the apex thereof. Individual electrodes are disposed on an insulating plate parallel with the disc electrode to form a number of spark gaps with the protuberances. These electrodes are each connected to a separate charged capacitor and when a voltage ls applied simultaneously between the trigger electrodes and the dlsc electrode, each spark gap fires to connect its capacitor to the disc electrode and a subsequent load.

Schofield, A.E.

1958-07-22

102

Bridging a cultural gap  

NASA Astrophysics Data System (ADS)

There has been a broad wave of change in tertiary calculus courses in the past decade. However, the much-needed change in tertiary pre-calculus programmes—aimed at bridging the gap between high-school mathematics and tertiary mathematics—is happening at a far slower pace. Following a discussion on the nature of the gap and the objectives of a potential bridging programme, this paper aims at demonstrating that the gap can be bridged, by presenting an ongoing modular bridging programme especially designed for the diverse types of student populations in teachers training colleges. We also present here some innovative teaching and assessment methods that were judged essential for the success of these programmes—focusing mainly on the "Questionnaire Based Instruction Method". Finally we suggest directions of follow up and research.

Leviatan, Talma

2008-09-01

103

Diffusive anion exchange in polypyrrole films  

SciTech Connect

Anion-exchange experiments performed on electrochemically prepared thin films of polypyrrole/ClO/sub 4//sup -/ demonstrate that the anions are not tightly bound to the polymer matrix. Auger electron spectroscopy reveals that ClO/sub 4//sup -/ can be replaced by a number of different anions. In addition, certain anions will not replace ClO/sub 4//sup -/ while others will induce only partial replacement. The relevance of entropic and steric factors is discussed in relationship to the exchange process.

Curtin, L.S.; Komplin, G.C.; Pietro, W.J.

1988-01-14

104

Adsorption affinity of anions on metal oxyhydroxides  

NASA Astrophysics Data System (ADS)

The dependences of anion (phosphate, carbonate, sulfate, chromate, oxalate, tartrate, and citrate) adsorption affinity anions from geometric characteristics, acid-base properties, and complex forming ability are generalized. It is shown that adsorption depends on the nature of both the anions and the ionic medium and adsorbent. It is established that anions are generally grouped into the following series of adsorption affinity reduction: PO{4/3-}, CO{3/2-} > C2O{4/2-}, C(OH)(CH2)2(COO){3/3-}, (CHOH)2(COO){2/2-} > CrO{4/2-} ? SO{4/2-}.

Pechenyuk, S. I.; Semushina, Yu. P.; Kuz'mich, L. F.

2013-03-01

105

Closing the Health Gap  

NSDL National Science Digital Library

The US Department of Health and Human Services (HHS) and ABC Radio Networks are working together to help African-Americans gain access to the best possible information regarding health issues. HHS reports that life expectancies for African-Americans lag five years behind expectancies for White Americans. The new Website Closing the Health Gap has links to information on health conditions such as diabetes and cancer as well as consumer health resources that relate to African-Americans' particular needs. Each page offers links, publications, and any news related to the subject, all in an effort to close "the health gap."

2001-01-01

106

Spark gap electrode erosion  

NASA Astrophysics Data System (ADS)

The results of a one-year contract on electrode erosion phenomena are summarized. The arc voltage drop in a spark gap was measured for various electrode, gas, and pressure combinations. A previously developed model of self breakdown voltage distribution was extended. A jet model for electrode erosion was proposed and an experimental arrangement for testing the model was constructed. The effects of inhomogeneities and impurities in the electrodes were investigated. Some of the work described here is scheduled for completion in 1985 under a current grant (AFOSR 84-0032). The areas of investigation described here include: (1) Self breakdown voltage distributions; (2) Electrode erosion; (3) Spark gap voltage recovery.

Krompholz, H.; Kristiansen, M.

1984-12-01

107

Photodissociation of nitromethane cluster anions  

SciTech Connect

Three types of anionic fragments are observed in the photodissociation of nitromethane cluster anions, (CH{sub 3}NO{sub 2}){sub n}{sup -}, n=1-6, at 355 nm: NO{sub 2}{sup -}(CH{sub 3}NO{sub 2}){sub k}, (CH{sub 3}NO{sub 2}){sub k}{sup -}, and OH{sup -} (kanion core, CH{sub 3}NO{sub 2}{sup -}, solvated by n-1 neutral nitromethane molecules. The NO{sub 2}{sup -}(CH{sub 3}NO{sub 2}){sub k} and OH{sup -} fragments formed from these clusters are described as core-dissociation products, while the (CH{sub 3}NO{sub 2}){sub k}{sup -} fragments are attributed to energy transfer from excited CH{sub 3}NO{sub 2}{sup -} into the solvent network or a core-dissociation--recombination (caging) mechanism. As with other cluster families, the fraction of caged photofragments shows an overall increase with increasing cluster size. The low-lying A{sup 2}A{sup '} and/or B{sup 2}A{sup '} electronic states of CH{sub 3}NO{sub 2}{sup -} are believed responsible for photoabsorption leading to dissociation to NO{sub 2}{sup -} based fragments, while the C{sup 2}A{sup ''} state is a candidate for the OH{sup -} pathway. Compared to neutral nitromethane, the photodissociation of CH{sub 3}NO{sub 2}{sup -} requires lower energy photons because the photochemically active electron occupies a high energy {pi}{sup *} orbital (which is vacant in the neutral). Although the electronic states in the photodissociation of CH{sub 3}NO{sub 2} and CH{sub 3}NO{sub 2}{sup -} are different, the major fragments, CH{sub 3}+NO{sub 2} and CH{sub 3}+NO{sub 2}{sup -}, respectively, both form via C-N bond cleavage.

Goebbert, Daniel J.; Khuseynov, Dmitry; Sanov, Andrei [Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 84721-0041 (United States)

2010-08-28

108

Differential phosphorylation of the gap junction protein connexin43 in junctional communication-competent and -deficient cell lines  

Microsoft Academic Search

Connexin43 is a member of the highly ho- mologous connexin family of gap junction proteins. We have studied how connexin monomers are assem- bled into functional gap junction plaques by examining the biosynthesis of connexin43 in cell types that differ greatly in their ability to form functional gap junc- tions. Using a combination of metabolic radiolabeling and immunoprecipitation, we have

Linda S. Musil; Bruce A. Cunningham; Gerald M. Edelman; Daniel A. Goodenough

1990-01-01

109

Gaining on the Gap  

ERIC Educational Resources Information Center

|About three-quarters of the 2009 graduates of the highly diverse Arlington, Virginia, Public Schools completed one or more Advanced Placement or International Baccalaureate courses during their high school careers. That figure serves as one indicator of a decade-long initiative to eliminate achievement gaps while raising achievement for all…

Smith, Robert G.

2010-01-01

110

Confronting the Autonomy Gap  

ERIC Educational Resources Information Center

|"The Autonomy Gap," a recent study by the American Institute for Research and the Thomas B. Fordham Institute, found that many public elementary school principals feel constrained by a bureaucracy that impedes their ability to raise student achievement. Unfortunately, those principals are still held accountable for their school's results--even…

Adamowski, Steven; Petrilli, Michael J.

2007-01-01

111

Multiple gap photovoltaic device  

DOEpatents

A multiple gap photovoltaic device having a transparent electrical contact adjacent a first cell which in turn is adjacent a second cell on an opaque electrical contact, includes utilizing an amorphous semiconductor as the first cell and a crystalline semiconductor as the second cell.

Dalal, Vikram L. (Newark, DE)

1981-01-01

112

STEMMING the Gap  

ERIC Educational Resources Information Center

|America has a gap when it comes to youth pursuing science and technology careers. In an effort to improve the knowledge and application of science, technology, engineering, and math (STEM), after-school programs can work in conjunction with formal in-school curriculum to improve science education. One organization that actively addresses this…

Kahler, Jim; Valentine, Nancy

2011-01-01

113

STEMMING the Gap  

ERIC Educational Resources Information Center

America has a gap when it comes to youth pursuing science and technology careers. In an effort to improve the knowledge and application of science, technology, engineering, and math (STEM), after-school programs can work in conjunction with formal in-school curriculum to improve science education. One organization that actively addresses this…

Kahler, Jim; Valentine, Nancy

2011-01-01

114

The Teaching Gap  

ERIC Educational Resources Information Center

One of the most comprehensive studies to highlight the achievement gap between students in the United States and those in many other countries is the Third International Mathematics and Science Study (TIMSS). TIMSS showed that a handful of countries (with Japan near the top) consistently outperformed the others studied (including the United…

Feldman, Sandra

2004-01-01

115

Isovalent Anion Substitution in Gallium-Manganese-pnictide Ferromagnetic Semiconductors  

NASA Astrophysics Data System (ADS)

While remarkable progress has been made towards understanding the properties of Mn-doped GaAs, the fundamental nature of carrier-mediated ferromagnetism in Mn-doped III-V semiconductors remains unclear. The research described in this dissertation focuses on the synthesis of novel ferromagnetic semiconductor alloys using ion implantation and pulsed-laser melting to investigate how changing the host from GaAs to another semiconductor affects ferromagnetism and transport. Using the Ga1-xMnxAs system as a reference, the chemistry of the anion sublattice is manipulated by performing isovalent anion substitution in which either the entire anion sublattice is changed from As to another Group V element (e.g. P) or the As sublattice is dilutely alloyed with isovalent P or N. By choosing isovalent elements of shorter atomic radius the interplay of carrier localization (determined by the Mn acceptor level in the host semiconductor) and exchange strength (determined by the energetic alignment of the Mn 3d and anion p states) can be explored. It will be shown that changing the host semiconductor from GaAs to GaP leads to significant localization of ferromagnetism-mediating holes. Nonetheless, robust carrier-mediated ferromagnetism is observed in Ga1-xMn xP as determined by combined of ion-channeling, SQUID magnetometry, magnetotransport, X-ray magnetic circular dichroism, and magnetic anisotropy experiments. This finding indicates that hole localization does not destroy the carrier-mediated ferromagnetic phase, though TC is generally lower in localized systems. Ternary semiconductor hosts are also explored with particular attention paid to the Ga1-xMn xAs1-yPy system that has attracted considerable theoretical attention as a system in which it is predicted that carrier delocalization and exchange strength are simultaneously maximized. However, this research indicates that TC is not enhanced by dilute P alloying into Ga1-xMnxAs, which is attributed to the scattering of ferromagnetism-mediating holes by the alloy disorder introduced onto the anion sublattice. Finally, the magnetic anisotropy of Ga1-x MnxP is explored in detail and found to be substantially similar to that observed in other III1-xMnxV materials. Collectively this work demonstrates the importance of considering effects of hole localization for predictions of ferromagnetism and transport in III 1-xMnxV materials.

Stone, Peter Robert

116

Organic anion transporter (Slc22a) family members as mediators of toxicity  

SciTech Connect

Exposure of the body to toxic organic anions is unavoidable and occurs from both intentional and unintentional sources. Many hormones, neurotransmitters, and waste products of cellular metabolism, or their metabolites, are organic anions. The same is true for a wide variety of medications, herbicides, pesticides, plant and animal toxins, and industrial chemicals and solvents. Rapid and efficient elimination of these substances is often the body's best defense for limiting both systemic exposure and the duration of their pharmacological or toxicological effects. For organic anions, active transepithelial transport across the renal proximal tubule followed by elimination via the urine is a major pathway in this detoxification process. Accordingly, a large number of organic anion transport proteins belonging to several different gene families have been identified and found to be expressed in the proximal nephron. The function of these transporters, in combination with the high volume of renal blood flow, predisposes the kidney to increased toxic susceptibility. Understanding how the kidney mediates the transport of organic anions is integral to achieving desired therapeutic outcomes in response to drug interactions and chemical exposures, to understanding the progression of some disease states, and to predicting the influence of genetic variation upon these processes. This review will focus on the organic anion transporter (OAT) family and discuss the known members, their mechanisms of action, subcellular localization, and current evidence implicating their function as a determinant of the toxicity of certain endogenous and xenobiotic agents.

Sweet, Douglas H. [Department of Pharmaceutical Sciences, Medical University of South Carolina, 280 Calhoun Street (Room QE218), PO Box 250140, Charleston, SC 29425 (United States)]. E-mail: sweetd@musc.edu

2005-05-01

117

2-(3,5-Dinitrophenyl)-1,3-dithiane carbanion: a benzylic anion with a low energy triplet state.  

PubMed

Calculations at the DFT level predict that benzyl anions with strong ?-electron-withdrawing groups in the meta position(s) have low energy diradical or triplet electronic states. Specifically, the 2-(3,5-dinitrophenyl)-1,3-dithiane carbanion is predicted to have nearly degenerate singlet and triplet states at the (U)B3LYP level as a free anion. Its lithium ion pair is predicted to be a ground-state triplet with a substantial (26 kcal/mol) singlet-triplet energy gap. Experiments on this anion using chemical trapping, NMR, and the Evans method strongly suggest that this anion is either a triplet or a ground-state singlet with a very low energy triplet state. PMID:21870822

Perrotta, Raffaele R; Winter, Arthur H; Coldren, William H; Falvey, Daniel E

2011-09-12

118

Removal of selected nuisance anions by Octolig®  

Microsoft Academic Search

Octolig®, a commercially available immobilized ligand (IMLIG), has been studied for its effectiveness in removing nuisance anions. The material consists of polyethylenediamines covalently linked to high surface-area silica, and has a high affinity for transition metal ions. Previous research indicated that anions could be removed quantitatively from aqueous solutions using the metal derivatives of Octolig® as packing in column chromatography.

Dean F. Martin; Christopher L. Lizardi; Eileen Schulman; Bryan Vo; Darius Wynn

2010-01-01

119

Decontamination of Milk from Radioactive Anionic Ingredients.  

National Technical Information Service (NTIS)

The process is for the anion exchange treatment of milk for the removal of I131. The process involves contacting an anion resin with a charging solution having the same pH value as that of the milk to be treated and having a chloride concentration about f...

G. K. Murthy J. E. Gilcrist J. E. Campbell

1964-01-01

120

Maxi-anion channel and pannexin 1 hemichannel constitute separate pathways for swelling-induced ATP release in murine L929 fibrosarcoma cells.  

PubMed

The maxi-anion channel plays a classically recognized role in controlling the membrane potential through the chloride conductance. It also has novel functions as a regulated pathway for the release of the anionic signaling molecules ATP and excitatory amino acids from cells subjected to osmotic perturbation, ischemia, or hypoxia. Because hemichannels formed by pannexins and connexins have been reported to mediate ATP release from a number of cell types, these hemichannels may represent the molecular correlate of the maxi-anion channel. Here, we found that L929 fibrosarcoma cells express functional maxi-anion channels which mediate a major portion of swelling-induced ATP release, and that ATP released via maxi-anion channels facilitates the regulatory volume decrease after osmotic swelling. Also, it was found that the cells express the mRNA for pannexin 1, pannexin 2, and connexin 43. Hypotonicity-induced ATP release was partially suppressed not only by known blockers of the maxi-anion channel but also by several blockers of pannexins including the pannexin 1-specific blocking peptide (10)Panx1 and small interfering (si)RNA against pannexin 1 but not pannexin 2. The inhibitory effects of maxi-anion channel blockers and pannexin 1 antagonists were additive. In contrast, maxi-anion channel activity was not affected by pannexin 1 antagonists and siRNAs against pannexins 1 and 2. Although a connexin 43-specific blocking peptide, Gap27, slightly suppressed hypotonicity-induced ATP release, maxi-anion channel activity was not affected by Gap27 or connexin 43-specific siRNA. Thus, it is concluded that the maxi-anion channel is a molecular entity distinct from pannexin 1, pannexin 2, and connexin 43, and that the maxi-anion channel and the hemichannels constitute separate pathways for swelling-induced ATP release in L929 cells. PMID:22785119

Islam, Md Rafiqul; Uramoto, Hiromi; Okada, Toshiaki; Sabirov, Ravshan Z; Okada, Yasunobu

2012-07-11

121

Covalent Polymers Containing Discrete Heterocyclic Anion Receptors  

PubMed Central

This chapter covers recent advances in the development of polymeric materials containing discrete heterocyclic anion receptors, and focuses on advances in anion binding and chemosensor chemistry. The development of polymers specific for anionic species is a relatively new and flourishing area of materials chemistry. The incorporation of heterocyclic receptors capable of complexing anions through non-covalent interactions (e.g., hydrogen bonding and electrostatic interactions) provides a route to not only sensitive but also selective polymer materials. Furthermore, these systems have been utilized in the development of polymers capable of extracting anionic species from aqueous environments. These latter materials may lead to advances in water purification and treatment of diseases resulting from surplus ions.

Rambo, Brett M.; Silver, Eric S.; Bielawski, Christopher W.; Sessler, Jonathan L.

2010-01-01

122

Polymers for anion recognition and sensing.  

PubMed

In biological systems, the selective and high-affinity recognition of anionic species is accomplished by macromolecular hosts (anion-binding proteins) that have been "optimized" through evolution. Surprisingly, it is only recently that chemists have systematically attempted to develop anion-responsive synthetic macromolecules for potential applications in medicine, national security, or environmental monitoring. Recent results indicating that unique features of polymeric systems such as signal amplification, multivalency, and cooperative behavior may be exploited productively in the context of anion recognition and sensing are documented. The wide variety of interactions-including Lewis acid/base, ion-pairing, and hydrogen bonding-that have been employed for this purpose is reflected in the structural diversity of anion-responsive macromolecules identified to date. PMID:22038843

Rostami, Ali; Taylor, Mark S

2011-10-31

123

Anion ordering in spinel-type gallium oxonitride  

NASA Astrophysics Data System (ADS)

The specific locations of the anions—nitrogen and oxygen—in the crystallographic sites are not known in the spinel-type gallium oxonitride. We report here on an indirect method for determining the specific location of the light elements N and O in a defect spinel-structured gallium oxonitride, Ga2.79O3.05N0.76. The locations of elements that are adjacent in the periodic table (?Z=±1) are indistinguishable with conventional x-ray diffraction techniques. However, by examining the local electronic structure we show that the anions are spatially ordered such that R3¯m (no. 166) is the most appropriate defect-free space group. Finally, we determined the electronic band gap of Ga2.79O3.05N0.76 experimentally to be 2.95 ± 0.30, agreeing with our calculated value of 2.79 eV (direct) for Ga3O3N using a local density approximation functional including a semilocal potential modified from that of Becke and Johnson (the MBJLDA functional).

Boyko, Teak D.; Zvoriste, Carmen E.; Kinski, Isabel; Riedel, Ralf; Hering, Stefanie; Huppertz, Hubert; Moewes, Alexander

2011-08-01

124

Stabilizers for GAP and GAP-based Propellants Interim Report.  

National Technical Information Service (NTIS)

Stabilizers for Glycidyl Azide Polymer (GAP) and GAP-based propellants were evaluated by Atlantic Research Corporation (ARC) and 3M (subcontract). The objectives of the program were: 1. to determine the stability of GAP; 2. to document the effect of prope...

B. Wheatley E. Nieder

2008-01-01

125

The malaria gap.  

PubMed

Although the correlation between malaria and poverty is apparent, the nature of the linkages in terms of directions and mechanisms of causation is less so, and different methodologic approaches provide widely divergent perspectives concerning the impact of the disease. Certain macroeconomic studies find that in highly endemic countries, malaria may be responsible for reducing economic growth by more than one percentage point a year. Microeconomic studies, which aggregate the cost per case, find a considerably smaller impact, generally less than one percent of annual per capita gross domestic product. The large gap between these estimates suggests economic externalities associated with malaria that make the burden much greater than the sum of the costs of individual cases. Both the magnitude of the burden and the channels through which malaria affects reduces income are important for policymakers. We explore this gap, examining diverse mechanisms through which malaria can affect long-term economic development. PMID:15331830

Malaney, Pia; Spielman, Andrew; Sachs, Jeffrey

2004-08-01

126

Filling the launch gap  

Microsoft Academic Search

Vehicles proposed to fill the gap in the U.S. space program's space transport needs for the next decade resulting from the January Challenger disaster, are discussed. Prior to the accident, the Air Force planned to purchase a Complementary Expendable Launch Vehicle system consisting of 10 single-use Titan-34D7 rockets. Another heavy lift booster now considered is the Phoenix H. Commercial launch

S. Hoeser

1986-01-01

127

Air-gap heterostructures  

SciTech Connect

We demonstrate the fabrication of thin GaAs layers which quasi hover above the underlying GaAs substrate. The hovering layers have a perfect epitaxial relationship to the substrate crystal lattice and are connected to the substrate surface only by lattice matched nanopillars of low density. These air-gap heterostructures are created by combining in situ molecular beam epitaxy compatible self-assembled droplet-etching and ex situ selective wet-chemical etching.

Heyn, Ch.; Schmidt, M.; Schwaiger, S.; Stemmann, A.; Mendach, S.; Hansen, W. [Institut fuer Angewandte Physik und Zentrum fuer Mikrostrukturforschung, Jungiusstrasse 11, D-20355 Hamburg (Germany)

2011-01-17

128

Bridging the gap  

Microsoft Academic Search

Engineers are applying the results of the scientific method to achieving solutions for real world problems. The QFT robust\\u000a design technique was utilized in this paper to illustrate how the bridging of the gap between the scientific and engineering\\u000a methods can be achieved. As an example, an aerospace firm has stated to Professor M. Grimble, University of Strathcldye, the\\u000a following:

C. Houpis

129

[Treatment of glottal gap].  

PubMed

Glottal gaps can be either physiological or pathological. The latter are multifactorial, predominantly organic in origin and occasionally functional. Organic causes include vocal fold paralysis or scarring, as well as a deficiency or excess of tissue. In addition to loss of the mucosal wave, the degree of hoarseness is primarily determined by the circumferential area of the glottal gap. It is thus important to quantify the extent of glottal insufficiency. Although a patient's symptoms form the basis for treatment decisions, these may be subjective and inadequately reflected by the results of auditory-perceptual evaluation, voice analysis and voice performance tests. The therapeutic approach should always combine phonosurgery with conventional voice therapy methods. Voice therapy utilises all the resources made available by the sphincter model of the aerodigestive tract and knowledge on the mechanism of voice production. The aim of phonosurgery is medialization, reconstruction or reinnervation by injection laryngoplasty or larynx framework surgery. These different methods can be combined and often applied directly after vocal fold surgery (primary reconstruction). In conclusion, the techniques described here can be effectively employed to compensate for glottal gaps. PMID:23407775

Voigt-Zimmermann, S; Arens, C

2013-02-01

130

Investigations of Pulsed Vacuum Gap.  

National Technical Information Service (NTIS)

Past research and the current status of understanding of electrical breakdown of vacuum is reviewed. This review includes DC, AC and pulsed vacuum gap breakdown. Measurements have been performed to determine the role of microparticles in pulsed vacuum gap...

J. E. Thompson T. S. Sudarshan J. M. Butner

1981-01-01

131

Nanosecond Spark Gap Switching Measurements.  

National Technical Information Service (NTIS)

The switching time of gas and oil dielectric spark gaps was measured in the nanosecond and subnanosecond time regime. The observed switching characteristics of the two spark gaps were compared with those predicted by empirical formulas. The formulas used ...

J. W. Ginn D. N. Hendricks M. T. Buttram

1986-01-01

132

Dynamics of coupled gap solitons  

SciTech Connect

We show analytically that solitonic states of two modes associated with different gap edges are formed when incident waves are sent in layered dielectric systems with a small band gap. The resulting coupled gap solitons are described through a nonlinear Schr{umlt o}dinger equation and propagate with a speed equal to half the speed of light. We discuss the conditions for the existence of coupled gap solitons. {copyright} {ital 1996 The American Physical Society.}

Konotop, V.V. [Departamento de Fisica, Universidade da Madeira, Praca do Municipio, 9000 Funchal (Portugal); Tsironis, G.P. [Center for Nonlinear Studies, MS 258, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

1996-05-01

133

Gapping, Pseudogapping and Sideward Movement  

Microsoft Academic Search

English Pseudogapping constructions share some surface similarities with both Gapping and Verb Phrase Ellipsis (VPE). Levin (1978, 1979 (main text)) concludes, however, that Pseudogapping is transformationally unrelated to both Gapping and VPE. We argue that this conclusion is only partially correct. Gapping and Pseudogapping are transformationally related in that they both involve the application of verb movement, in particular sideward

Brian Agbayani; Ed Zoerner

2004-01-01

134

Monovalent Cation Permeation through the Connexin40 Gap Junction Channel  

PubMed Central

The unitary conductances and permeability sequences of the rat connexin40 (rCx40) gap junction channels to seven monovalent cations and anions were studied in rCx40-transfected neuroblastoma 2A (N2A) cell pairs using the dual whole cell recording technique. Chloride salt cation substitutions (115 mM principal salt) resulted in the following junctional maximal single channel current-voltage relationship slope conductances (?j in pS): CsCl (153), RbCl (148), KCl (142), NaCl (115), LiCl (86), TMACl (71), TEACl (63). Reversible block of the rCx40 channel was observed with TBA. Potassium anion salt ?j are: Kglutamate (160), Kacetate (160), Kaspartate (158), KNO3 (157), KF (148), KCl (142), and KBr (132). Ion selectivity was verified by measuring reversal potentials for current in rCx40 gap junction channels with asymmetric salt solutions in the two electrodes and using the Goldman-Hodgkin-Katz equation to calculate relative permeabilities. The permeabilities relative to Li+ are: Cs+ (1.38), Rb+ (1.32), K+ (1.31), Na+ (1.16), TMA+ (0.53), TEA+ (0.45), TBA+ (0.03), Cl? (0.19), glutamate? (0.04), and NO3? (0.14), assuming that the monovalent anions permeate the channel by forming ion pairs with permeant monovalent cations within the pore thereby causing proportionate decreases in the channel conductance. This hypothesis can account for why the predicted increasing conductances with increasing ion mobilities in an essentially aqueous channel were not observed for anions in the rCx40 channel. The rCx40 effective channel radius is estimated to be 6.6 ? from a theoretical fit of the relationship of relative permeability and cation radius.

Beblo, Dolores A.; Veenstra, Richard D.

1997-01-01

135

Gapped ferromagnetic graphene nanoribbons.  

PubMed

We theoretically design a graphene-based all-organic ferromagnetic semiconductor by terminating zigzag graphene nanoribbons (ZGNRs) with organic magnets. A large spin-split gap with a 100% spin polarized density of states near the Fermi energy is obtained, which is of potential application in spin transistors. The interactions among electron, spin and lattice degrees of freedom are studied using the first-principles calculations including non-collinear spin orientations. All of the calculations consistently demonstrate that although no d electrons existing, the antiferromagnetic ?-? exchange together with the strong electron-lattice interactions between organic magnets and ZGNRs make the ground state ferromagnetic. PMID:21706114

Hou, Dong; Wei, Jianhua; Xie, Shijie

2011-06-27

136

Mind the gap.  

SciTech Connect

In this summary of the application of Dyson-Schwinger equations to the theory and phenomenology of hadrons, some deductions following from a nonperturbative, symmetry-preserving truncation are highlighted, notable amongst which are results for pseudoscalar mesons. We also describe inferences from the gap equation relating to the radius of convergence of a chiral expansion, applications to heavy-light and heavy-heavy mesons, and quantitative estimates of the contribution of quark orbital angular momentum in pseudoscalar mesons; and recapitulate upon studies of nucleon electromagnetic form factors.

Bhagwat, M. S.; Krassnigg, A.; Maris, P.; Roberts, C. D.; Physics; Univ. Graz; Univ. of Pittsburgh

2007-03-01

137

Electron collisions with diatomic anions  

SciTech Connect

Electron collisions with negative ions (B{sub 2}{minus}, C{sub 2}{minus}, O{sub 2}{minus}, BN{sup {minus}}, and OH) have been performed in a merged- beams experiment at the heavy-ion storage ring ASTRID (Aarhus Storage Ring, Denmark). Absolute cross sections for detachment (e{sup {minus}}+AB{sup {minus}}{r_arrow}AB{sup 0}+2e{sup {minus}}) and detachment plus dissociation (e{sup {minus}}+AB{sup {minus}}{r_arrow}A{sup 0}+B{sup 0}+2e{sup {minus}}) are reported for energies below 40 eV. For the homonuclear ions, X{sub 2}{sup {minus}} (X=B,&hthinsp;C,&hthinsp;O), cross sections are also presented for dissociative reactions leading to an X{sup {minus}} particle in the final state. The detachment process is dominant for all investigated systems. The detachment cross section is characterized by an effective threshold larger than the electron binding energy. The shapes of the detachment cross sections are similar for the studied anions pointing to a common nonresonant mechanism for detachment. Also, the cross section for detachment plus dissociation and pure dissociation show regularities pointing to a general nonresonant mechanism. Structures are observed in the detachment cross section of C{sub 2}{sup {minus}} and BN{sup {minus}} and in the dissociation cross section of B{sub 2}{minus} and C{sub 2}{minus}. The structures are attributed to short-lived dianions (resonances) formed during the collision process. The results are supported by {ital ab initio} calculations, and it is inferred that electronic excitations are important in the resonant reactions. {copyright} {ital 1999} {ital The American Physical Society}

Pedersen, H.B.; Jensen, M.J.; Kella, D.; Safvan, C.P.; Vejby-Christensen, L.; Andersen, L.H. [Institute of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark); Djuric, N. [JILA, University of Colorado and National Institute of Standards and Technology, Boulder, Colorado 80309-0440 (United States); Schmidt, H.T. [Department of Physics, Atomic Physics, Stockholm University, S-10405 Stockholm (Sweden)

1999-10-01

138

Slow anion exchange, conformational equilibria, and fluorescent sensing in venus flytrap aminopyridinium-based anion hosts.  

PubMed

The synthesis, anion binding, and conformational properties of a series of 3-aminopyridinium-based, tripodal, tricationic hosts for anions are described. Slow anion and conformational exchange on the (1)H NMR time scale at low temperature, coupled with NMR titration, results in a high level of understanding of the anion-binding properties of the compounds, particularly with respect to significant conformational change resulting from induced fit complexation. Peak selectivity for halides, particularly Cl(-), is observed. The approach has been extended to dipodal and tripodal podands based on 3-aminopyridinium "arms" containing photoactive anthracenyl moieties. The 1,3,5-tripodal host shows a remarkable selectivity for acetate over other anions, in contrast to the analogous unsubstituted tris(3-aminopyridinium) analogue, despite the fact that low-temperature (1)H NMR experiments reveal a total of four acetate-binding conformations. Photodimerization of anthracene units results in the formation of potential fluorescent anion sensors. PMID:12904036

Wallace, Karl J; Belcher, Warwick J; Turner, David R; Syed, Kauser F; Steed, Jonathan W

2003-08-13

139

Fluorine NMR reporter for phosphate anions.  

PubMed

A fluorine-labelled zinc(II)-dipicolylamine coordination complex reports the presence of phosphate anions in aqueous solution, especially pyrophosphate and ADP, and is used to monitor the enzymatic hydrolysis of ATP. PMID:23619399

Gan, Haiying; Oliver, Allen G; Smith, Bradley D

2013-04-25

140

Method for production of new anion exchangers.  

National Technical Information Service (NTIS)

The invention relates to a method for the production of new anion exchangers that can be used in molecular biology, genetic engineering, biotechnology and phytopathology. According to the invention, halogen-containing polyurethanes are reacted with one or...

G. Behrendt H. D. Hunger

1991-01-01

141

Generation of nitro and superoxide radical anions from 2,4,6-trinitrobenzenesulfonic acid by rat gastrointestinal cells  

Microsoft Academic Search

Reactive oxygen and nitrogen species have been implicated in the inflammation of the gastrointestinal tract. The objective of this study was to investigate mechanisms of free radical formation from the colitis inducer 2,4,6-trinitrobenzene sulfonic acid (TNBS). We showed that TNBS was rapidly metabolized to TNBS nitro radical anion via metabolic reduction by flavinmononucleotide\\/NADPH, xanthine\\/xanthine oxidase as well as the rat

Walee Chamulitrat; John J Spitzer

1997-01-01

142

The superfamily of organic anion transporting polypeptides  

Microsoft Academic Search

Organic anion transporting polypeptides (Oatps\\/OATPs) form a growing gene superfamily and mediate transport of a wide spectrum of amphipathic organic solutes. Different Oatps\\/OATPs have partially overlapping and partially distinct substrate preferences for organic solutes such as bile salts, steroid conjugates, thyroid hormones, anionic oligopeptides, drugs, toxins and other xenobiotics. While some Oatps\\/OATPs are preferentially or even selectively expressed in one

B Hagenbuch; P. J Meier

2003-01-01

143

Benzobisoxazole fluorophore vicariously senses amines, ureas, anions.  

PubMed

A benzobisoxazole-based cruciform fluorophore forms fluorescent complexes with simple boronic acids. Through the changes of their fluorescence emission colours, these complexes can sense and qualitatively distinguish among structurally similar organic nitrogen compounds (amines and ureas) and small organic and inorganic anions. Preliminary results suggest that the intensity of this hybrid sensor's fluorescent response to chloride anions can be quantitatively correlated to chloride concentration. PMID:22983092

Lim, Jaebum; Miljani?, Ognjen Š

2012-10-25

144

Anion reorientation in Na3PO4  

Microsoft Academic Search

The reorientational motion of phosphate anions in the high-temperature phase of Na3PO4 has been investigated with a coherent quasielastic neutron-scattering experiment. Our study aimed at clarifying the relevance of the so-called ``paddle-wheel'' mechanism, i.e., the influence of the anion motion on the translational Na+ ion conduction. In the Q range between 0.3 and 2.3 Å-1, the data could be fitted

D. Wilmer; R. D. Banhatti; J. Fitter; K. Funke; M. Jansen; G. Korus; R. E. Lechner

1998-01-01

145

Anion exchange properties of a mesoporous aluminophosphate  

SciTech Connect

A mesoporous aluminophosphate support, meso-AlPO, was synthesized by phosphate treatment of an AlO{sub 4}Al{sub 12}(OH){sub 24}(H{sub 2}O){sup 7+} cluster/dodecyl sulfate salt, followed by extraction of the surfactant with an acetate/methanol solution. The meso-AlPO product was shown to be an effective anion exchange material. Anion exchange capacities for chromate and several monoanionic and dianionic organic dyes fell in the range from approximately 1.3--1.6 meq/g. Control experiments with the neutral support MCM-41 and a nonionic dye indicated that anion adsorption in meso-AlPO was caused predominantly by electrostatic interactions rather than pure physisorption. Multiple exchanges were possible if the support was regenerated by acid treatment at pH 4.3. While the material exhibited size-selectivity for anionic dyes, the average pore sizes increased during anion exchanges in aqueous solutions. The mesopore structure of meso-AlPO was thermally stable up to 200 C, and anion exchanges at 100 C under aqueous reflux resulted in similar exchange capacities as room-temperature exchanges.

Kron, D.A.; Holland, B.T.; Wipson, R.; Maleke, C.; Stein, A.

1999-11-09

146

The functions of voltage-dependent anion channels in plants.  

PubMed

Voltage-dependent anion channels (VDACs), known as outer mitochondrial membrane proteins, are present in all eukaryotic cells. In mammals, they are now recognized to play crucial roles in the regulation of metabolic and energetic functions of mitochondria as well as in mitochondria-mediated apoptosis, in association with various proteins and non-protein modulators. Although there is much less information available for plant than for animal VDACs, their similar electrophysiological and topological properties suggest that some common functions are conserved among eukaryotic VDACs. Recently, it has been revealed that plant VDACs also have various important physiological functions not only in developmental and reproductive processes, but also in biotic and abiotic stress responses, including programmed cell death. In this review, we summarize recent findings about the sequence motifs, localization, and function of plant VDACs and discuss these results in the light of recent advances in research on animal VDACs. PMID:23568336

Takahashi, Yoshihiro; Tateda, Chika

2013-08-01

147

Localisation and function of voltage-dependent anion channels (VDAC) in bovine spermatozoa  

Microsoft Academic Search

Sperm motility, regulation of cell volume, sperm capacitation, acrosome reaction and tight binding of spermatozoa to the zona\\u000a pellucida are crucial events in the process of fertilisation. Voltage-dependent anion channels (VDAC) are highly conserved\\u000a pore-forming proteins implicated in apoptosis, metabolite transport between mitochondria and cytosol, energy metabolism, and\\u000a cell volume regulation in somatic cells. Several studies have demonstrated the presence

Xenia Triphan; Viviana A. Menzel; Anna M. Petrunkina; M. Carolina Cassará; Wilhelm Wemheuer; Klaus-Dieter Hinsch; Elvira Hinsch

2008-01-01

148

Effect of nickel deficiency on soluble anion, amino acid, and nitrogen levels in barley  

Microsoft Academic Search

Barley (Hordeum vulgare L. cv. ‘Onda’) plants were grown in nutrient solutions supplied either 0 (no Ni added), 0.6, or 1.0 ?M NiSO4. Plants supplied 0 ?M Ni developed Ni deficiency symptoms; Ni deficiency resulted in the disruption of nitrogen metabolism, and affected the concentration\\u000a of malate and various inorganic anions in roots, shoots, and grain of barley.\\u000a \\u000a The concentrations

Patrick H. Brown; Ross M. Welch; James T. Madison

1990-01-01

149

Bileaflet aortic valve prosthesis pivot geometry influences platelet secretion and anionic phospholipid exposure.  

PubMed

The clinical histories of the Medtronic Parallel (MP) and St. Jude Medical (SJM) Standard valves suggest pivot geometry influences the thrombogenic characteristics of bileaflet prostheses. This work studied the effects of various pivot geometries on markers of platelet damage in a controlled, in vitro apparatus. The Medtronic Parallel valve, two St. Jude Medical valves, and two demonstration prostheses were used to study the effects of bileaflet pivot design, gap width, and size on platelet secretion and anionic phospholipid expression during leakage flow. A centrifugal pump was used to drive blood through a circuit containing a bileaflet prosthesis. Samples were taken at set time intervals after the start of the pump. These samples were analyzed by cell counting, flow cytometry, and enzyme-linked immunosorbant assay. No significant differences were observed in platelet secretion or anionic phospholipid expression between experiments with the SJM 27 Standard regular leaker, the SJM 20 regular leaker, and the MP 27 valves. Significant differences in platelet secretion and anionic phospholipid expression were observed between a SJM 27 Standard regular leaker and a SJM 27 high leaker valve. These studies suggest that leakage gap width within bileaflet valve pivots has a significant effect on platelet damage initiated by leakage flow. PMID:11556722

Travis, B R; Marzec, U M; Leo, H L; Momin, T; Sanders, C; Hanson, S R; Yoganathan, A P

2001-08-01

150

Anion selective polymeric membrane electrodes based on metallocenes  

Microsoft Academic Search

Seven types of metallocenes (bis-cyclopentadienyl compounds) were used as anion ionophores for polymeric membrane electrodes and their anion selectivities were examined. The electrodes based on metallocenes exhibited different selectivity behaviour compared with the electrode using a classical anion exchanger such as tetraalkyl ammonium. The selectivity for tetraalkyl ammonium simply obeys the lipophilicity of anions, specifically, hafnocene dichloride exhibited a highly

Hideaki Hisamoto; Dwi Siswanta; Hiroshi Nishihara; Koji Suzuki

1995-01-01

151

Novel pseudo-delocalized anions for lithium battery electrolytes.  

PubMed

A novel anion concept of pseudo-delocalized anions, anions with distinct positive and negative charge regions, has been studied by a computer aided synthesis using DFT calculations. With the aim to find safer and better performing lithium salts for lithium battery electrolytes two factors have been evaluated: the cation-anion interaction strength via the dissociation reaction LiAn ? Li(+) + An(-) and the anion oxidative stability via a vertical ionisation from anion to radical. Based on our computational results some of these anions have shown promise to perform well as lithium salts for modern lithium batteries and should be interesting synthetic targets for future research. PMID:22441354

Jónsson, Erlendur; Armand, Michel; Johansson, Patrik

2012-03-22

152

Filling the launch gap  

NASA Astrophysics Data System (ADS)

Vehicles proposed to fill the gap in the U.S. space program's space transport needs for the next decade resulting from the January Challenger disaster, are discussed. Prior to the accident, the Air Force planned to purchase a Complementary Expendable Launch Vehicle system consisting of 10 single-use Titan-34D7 rockets. Another heavy lift booster now considered is the Phoenix H. Commercial launch vehicle systems projected to be available in the necessary time frame include the 215,000-pound thrust 4000-pound LEO payload capacity NASA Delta, the 11,300-pound LEO payload capacity Atlas Centaur the first ICBM, and the all-solid propellant expendable 2000-pound LEO payload Conestoga rocket. Also considered is the man-rated fully reusable Phoenix vertical take-off and vertical-landing launch vehicle.

Hoeser, S.

1986-05-01

153

The anion gap does not accurately screen for lactic acidosis in emergency department patients  

PubMed Central

Introduction Lactic acidosis portends a poor prognosis in trauma, sepsis, and other shock states and is useful for triaging and resuscitating emergency department (ED) patients. The authors sought to determine whether the AG is a reliable screen for lactic acidosis when applied specifically in the ED setting. Methods The authors performed a retrospective cohort study over a seven month period. Subjects were all ED patients that had a serum lactate obtained. Sensitivity analyses of the AG for detecting presence of lactic acidosis were calculated for the traditional AG normal value (AG <12) and for the lower AG normal value when using newer ion selective electrode assays (AG <6). Results Serum lactate levels were ordered in the ED on 440 occasions. 137 samples were excluded by protocol. Using an AG cutoff of 12, the sensitivity for detecting lactic acidosis was 58.2%, specificity was 81.0%, and the negative predictive value was 89.7%. Using the AG cutoff of 6, the sensitivity was 93.2%, the specificity was 17.3%, and the negative predictive value was 91.8%. Conclusions The traditional definition of AG >12 was insensitive for the presence of lactic acidosis. Using the revised AG of >6 is more sensitive but non?specific for lactic acidosis. The authors conclude that employing the AG as a screen for LA may be inappropriate in ED patients. Instead, they recommend ordering a serum lactate immediately upon suspicion of a shock state. A prospective study to confirm these findings is needed.

Adams, B D; Bonzani, T A; Hunter, C J

2006-01-01

154

Gap and stripline combined monitor  

DOEpatents

A combined gap and stripline monitor device for measuring the intensity and position of a charged particle beam bunch in a beam pipe of a synchrotron radiation facility is disclosed. The monitor has first and second beam pipe portions with an axial gap therebetween. An outer pipe cooperates with the first beam pipe portion to form a gap enclosure, while inner strips cooperate with the first beam pipe portion to form a stripline monitor, with the stripline length being the same as the gap enclosure length. 4 figs.

Yin, Y.

1986-08-19

155

Atrioventricular conduction abnormality and hyperchloremic metabolic acidosis in toluene sniffing.  

PubMed

Toluene is an aromatic hydrocarbon with widespread industrial use as an organic solvent. As a result of the euphoric effect and availability of these substances, inhalation of toluene-based products is popular among young adults and children. Chronic or acute exposure is known to cause acid-base and electrolyte disorders, and to be toxic to the nervous and hematopoietic systems. We report a 38-year-old man who suffered from general muscular weakness of all extremities after toluene sniffing, which was complicated with hypokalemic paralysis, atrioventricular conduction abnormality, and normal anion gap hyperchloremic metabolic acidosis. Renal function, serum potassium and acid-base status normalized within 3 days after aggressive potassium chloride and intravenous fluid replacement. Electrocardiography showed regression of first-degree atrioventricular block. Exposure to toluene can lead to cardiac arrhythmias and sudden sniffing death syndrome. Tachyarrhythmia is the classical manifestation of toluene cardiotoxicity. Atrioventricular conduction abnormalities have been rarely mentioned in the literature. Knowledge of the toxicology and medical complications associated with toluene sniffing is essential for clinical management of these patients. PMID:21982470

Tsao, Jian-Hsiung; Hu, Yu-Hui; How, Chorng-Kuang; Chern, Chii-Hwa; Hung-Tsang Yen, David; Huang, Chun-I

2011-09-09

156

ANNUAL REPORT. SUPRAMOLECULAR CHEMISTRY OF SELECTIVE ANION RECOGNITION FOR ANIONS OF ENVIRONMENTAL RELEVANCE  

EPA Science Inventory

This project involves the design and synthesis of receptors for anions of environmental importance, including emphasis on high level and low activity waste. Polyammonium macrocycles as receptors and nitrate as target anion were the focus of the first phase of this project. A seco...

157

Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance  

SciTech Connect

This project have focuses on the basic chemical aspects of anion receptor design of functional pH independent systems, with the ultimate goal of targeting the selective binding of sulfate, as well as design of separations strategies for selective and efficient removal of targeted anions. Key findings include: (1) the first synthetic sulfate-selective anion-binding agents; (2) simple, structure-based methods for modifying the intrinsic anion selectivity of a given class of anion receptors; and (3) the first system capable of extracting sulfate anion from acidic, nitrate-containing aqueous media. Areas probed during the last funding period include: the design, synthesis, and physical and structural characterization of receptors and investigation of anion and dual ion pair extraction using lipophilic amide receptors for anion binding. A new collaboration has been added to the project in addition to the one with Dr. Bruce Moyer at Oak Ridge National Laboratory, with Professor Jonathan Sessler at the University of Texas at Austin.

Bowman-James, Kristen

2004-12-01

158

Independent 1D nanosized metal-organic tube: anion exchange, separation, and anion-responsive luminescence.  

PubMed

Three independent 1D metal-organic nanotubes AgL(2)X(2) [X = PF(6)(-) (1), ClO(4)(-) (2), and SbF(6)(-) (3)] with anion exchange, separation, and anion-responsive photoluminescence are reported. PMID:22439597

Fang, Chao; Liu, Qi-Kui; Ma, Jian-Ping; Dong, Yu-Bin

2012-03-22

159

Anion-? Interactions of Hexaaryl[3]radialenes.  

PubMed

Coordination polymers and discrete metallo-supramolecular assemblies of hexaaryl[3]radialene compounds exhibit intriguing structures with short anion to ?-centroid distances in the solid-state. Furthermore, these [3]radialene compounds display useful photophysical and electrochemical properties that make them ideal as potential platforms for anion receptors. In this study, hexafluoro[3]radialene was optimized to the MP2/aug-cc-pVTZ level of theory, and its complexes with halide anions were optimized to HF/6-31G++(d,p), MP2/6-31G++(d,p), M06-2X/6-31G++(d,p), and M06-2X/6-311G++(d,p) levels of theory. Hexafluoro[3]radialene was shown to have properties (large positive Q(zz) and areas of positive electrostatic surface potential) comparable to other compounds that show anion-? interactions. The interaction energies of complexes of hexafluoro[3]radialene with halide anions were calculated and found to be favorable and equivalent to those of fluorinated aromatic compounds. A series of synthetically accessible hexaaryl[3]radialenes were optimized to HF/6-31G++(d,p) theory and their complexes with halides optimized to the M06-2X/6-31G++(d,p) level of theory. The calculated properties of the electron-deficient hexaaryl[3]radialenes also show large positive Q(zz) quadrupole moments and two areas of positive potential; at the [3]radialene core and the acidic aryl hydrogen atoms. The interaction energies of the complexes of hexaaryl[3]radialenes and halide anions were found to follow the trend F(-) > Cl(-) ? Br(-) and correlate with the electron-deficient nature of the [3]radialene. Close contacts were observed between the anion and the radialene core and the aryl hydrogen atoms, suggesting a combination of anion-? and hydrogen bonding is important. Mass spectrometry was used to experimentally observe the complexes of a number of hexaaryl[3]radialenes with F(-), Cl(-), and Br(-) predicted computationally. Anion-[3]radialene complexes were successfully detected, and the stability of the complexes in tandem MS/MS experiments was found to support the computational results. PMID:22747096

Evans, Jack D; Hollis, Courtney A; Hack, Sandra; Gentleman, Alexander S; Hoffmann, Peter; Buntine, Mark A; Sumby, Christopher J

2012-07-19

160

Infrared spectroscopy of anionic hydrated fluorobenzenes  

SciTech Connect

We investigate the structural motifs of anionic hydrated fluorobenzenes by infrared photodissociation spectroscopy and density functional theory. Our calculations show that all fluorobenzene anions under investigation are strongly distorted from the neutral planar molecular geometries. In the anions, different F atoms are no longer equivalent, providing structurally different binding sites for water molecules and giving rise to a multitude of low-lying isomers. The absorption bands for hexa- and pentafluorobenzene show that only one isomer for the respective monohydrate complexes is populated in our experiment. For C{sub 6}F{sub 6}{sup -}{center_dot}H{sub 2}O, we can assign these bands to an isomer where water forms a weak double ionic hydrogen bond with two F atoms in the ion, in accord with the results of Bowen et al. [J. Chem. Phys. 127, 014312 (2007), following paper.] The spectroscopic motif of the binary complexes changes slightly with decreasing fluorination of the aromatic anion. For dihydrated hexafluorobenzene anions, several isomers are populated in our experiments, some of which may be due to hydrogen bonding between water molecules.

Schneider, Holger; Vogelhuber, Kristen M.; Weber, J. Mathias [JILA, NIST, and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309 (United States)

2007-09-21

161

Reactive Phosphate Esters as Affinity Labels for Enzymes of Carbohydrate Metabolism.  

National Technical Information Service (NTIS)

Many enzymes of carbohydrate metabolism have an affinity for small organic anions. An attempt was made to exploit the common binding specificities of enzymes, whose substrates are phosphate esters, in the design and use of affinity labels. The basic premi...

F. C. Hartman I. L. Norton C. D. Stringer J. V. Schloss

1978-01-01

162

Effects of Selected Anti-Tumor-Promoting Chemicals on Metabolic Cooperation between Chinese Hamster V79 Cells.  

National Technical Information Service (NTIS)

Many tumor-promoting chemicals inhibit gap junctional communication between cells. The authors investigated the possibility that antipromoting chemicals may act inversely and enhance gap junctional communication. The V79/metabolic cooperation assay is an ...

L. J. Mills S. M. Nelson A. R. Malcolm

1994-01-01

163

Absence of transepithelial anion exchange by rabbit OMCD: Evidence against reversal of cell polarity  

SciTech Connect

In the rabbit cortical collecting duct (CCD), Cl tracer crosses the epithelium predominantly via an anion exchange system that operates in either a Cl-Cl or Cl-HCO{sub 3} exchange mode. In the present study, the authors used the {sup 36}Cl lumen-to-bath rate coefficient (K{sub Cl}, nm/s), a sensitive measurement of CCD transepithelial anion transport, to investigate the nature of Cl transport in the medullary collecting duct dissected from inner stripe, outer medulla (OMCD). The K{sub Cl} in OMCD perfused and bathed in HCO{sub 3}-Ringer solution was low and similar to that value observed in the CCD when anion exchange is inhibited and Cl permeates the epithelium by diffusion. To test the hypothesis that metabolic alkalosis could reverse the polarity of intercalated cells and thus induce an apical Cl-HCO{sub 3} exchanger in H{sup +}-secreting OMCD cells, they measured K{sub Cl} in OMCD from rabbits make alkalotic by deoxycorticosterone and furosemide. Although the base-line K{sub Cl} was slightly higher than in OMCD from control rabbits, the value was still far lower than the K{sub Cl} under comparable conditions in CCD. They conclude (1) Cl transport across the MCD by anion exchange is immeasurably low or nonexistent; (2) unlike the CCD, Cl transport in OMCD is not responsive to cAMP; and (3) metabolic alkalosis does not induce an apical anion exchanger in OMCD, i.e., does not cause epithelial polarity reversal.

Hayashi, Matsuhiko; Schuster, V.L.; Stokes, J.B. (Univ. of Iowa College of Medicine, Iowa City (USA))

1988-08-01

164

CO oxidation by copper cluster anions  

NASA Astrophysics Data System (ADS)

Reactions of CO and O2 on size-selected copper cluster anions, Cu n - ( n = 4-11), have been investigated at the collision energy of 0.2 eV by use of a guided ion beam-tandem mass spectrometer. Oxygen-adsorbed copper anions, Cu n O2 -, in particular Cu5O2 - and Cu9O2 -, show an evidence of the CO oxidation, that is, the formation of the monoxide Cu n O-. The density functional theory calculation reveals that the CO oxidation occurs more exothermically on Cu5O2 - and Cu9O2 - than the other clusters. This can be explained by the relatively small dissociation energy of their Cu-O bonds. In addition, the calculations on Cu5O2 +/- indicate that the CO oxidation proceeds via a low-energy pathway for the anion owing to the structural rearrangement of the copper cluster compared to the cation.

Hirabayashi, Shinichi; Kawazoe, Yoshiyuki; Ichihashi, Masahiko

2013-02-01

165

Patchy proteins, anions and the Hofmeister series  

NASA Astrophysics Data System (ADS)

We investigate specific anion binding to a range of patchy protein models and use our results to probe protein-protein interactions for aqueous lysozyme solutions. Our molecular simulation studies show that the ion-protein interaction mechanism and strength largely depend on the nature of the interfacial amino acid residues. Via direct ion pairing, small anions interact with charged side-chains while larger anions are attracted to non-polar residues due to several solvent assisted mechanisms. Incorporating ion and surface specificity into a mesoscopic model for protein-protein interactions we calculate the free energy of interaction between lysozyme molecules in aqueous solutions of sodium chloride and sodium iodide. In agreement with experiment, our finding is that 'salting out' follows the reverse Hofmeister series for pH below the iso-electric point and the direct series for pH above pI.

Lund, Mikael; Jungwirth, Pavel

2008-12-01

166

Novel Gapped Quantum Wire  

NASA Astrophysics Data System (ADS)

High quality state of the art quantum wires (QWRs) can be fabricated by the novel cleaved edge overgrowth technique, proposed by (Pfeiffer et al., 1990). Transverse quantization in these QWRs leads to a succession of nested energy bands. With the lowest two successive energy levels occupied, gapped phases are possible including, e.g, an intersubband charge density wave (ICDW) and a Cooper phase with strong superconducting fluctuations (Starykh et al., 2000). Due to the possibility of density reorganization, in which it becomes favorable for the two lowest subbands to match their densities, the ICDW is usually the most likely state. Recently, by exploiting the valley degeneracy in AlAs, a single QWR has been fabricated with two degenerate nonoverlapping bands separated in k space by half an Umklapp vector (Moser et al. 2004). For low densities this structure is able to access a multiple subband regime that is not subject to the density reorganizing ICDW, leaving the Cooper phase to flourish. Using Abelian bosonization, we explore the relevant interaction terms for this system, including Umklapp assisted Cooper scattering, and discuss the phase diagram.

Datta, Trinanjan

2005-03-01

167

Novel Gapped Quantum Wire  

NASA Astrophysics Data System (ADS)

High quality state of the art quantum wires (QWRs) can be fabricated by the novel Cleaved Edge Overgrowth (CEO) technique, proposed by (Pfeiffer et al, 1990). Transverse quantization in these QWRs leads to a succession of nested energy bands. With the lowest two successive energy levels occupied, gapped phases are possible including, e.g., an intersubband charge density wave (ICDW) and a Cooper phase with strong superconducting fluctuations (Starykh et al, 2000). Due to the possibility of density reorganization, in which it becomes favorable for the two lowest subbands to match their densities, the ICDW is usually the most likely state. Recently, by exploiting the valley degeneracy in AlAs, a single QWR has been fabricated with two degenerate nonoverlapping bands separated in k space by half an Umklapp vector (Moser et al 2004). For low densities the structure is able to access a multiple subband regime that is not subject to the density reorganizing ICDW, leaving a Cooper phase to flourish. Using Abelian bosonization, we explore the relevant interaction terms for this system, including Umklapp assisted Cooper scattering and discuss the phase diagram.

Datta, Trinanjan

2005-04-01

168

Templating irreversible covalent macrocyclization by using anions.  

PubMed

Inorganic anions were used as templates in the reaction between a diamine and an activated diacid to form macrocyclic amides. The reaction conditions were found to perform the macrocyclization sufficiently slow to observe a template effect. A number of analytical methods were used to clarify the reaction mechanisms and to show that the structure of the intermediate plays a decisive role in determining the product distribution. For the macrocyclization under kinetic control, it was shown that the amount of a template, the conformational rigidity of building blocks, and the anion affinities of reaction components and intermediates are important parameters that one should take into consideration to achieve high yields. PMID:23364908

Kataev, Evgeny A; Kolesnikov, Grigory V; Arnold, Rene; Lavrov, Herman V; Khrustalev, Victor N

2013-01-31

169

Electron transfer dissociation of peptide anions  

Microsoft Academic Search

Ion\\/ion reactions of multiply deprotonated peptide anions with xenon radical cations result in electron abstraction to generate\\u000a charge-reduced peptide anions containing a free-radical site. Peptide backbone cleavage then occurs by hydrogen radical abstraction\\u000a from a backbone amide N to facilitate cleavage of the adjacent C-C bond, thereby producing a- and x-type product ions. Introduction\\u000a of free-radical sites to multiply charged

Joshua J. Coon; Jeffrey Shabanowitz; Donald F. Hunt; John E. P. Syka

2005-01-01

170

Identification and characterization of anion binding sites in RNA  

SciTech Connect

Although RNA molecules are highly negatively charged, anions have been observed bound to RNA in crystal structures. It has been proposed that anion binding sites found within isolated RNAs represent regions of the molecule that could be involved in intermolecular interactions, indicating potential contact points for negatively charged amino acids from proteins or phosphate groups from an RNA. Several types of anion binding sites have been cataloged based on available structures. However, currently there is no method for unambiguously assigning anions to crystallographic electron density, and this has precluded more detailed analysis of RNA-anion interaction motifs and their significance. We therefore soaked selenate into two different types of RNA crystals and used the anomalous signal from these anions to identify binding sites in these RNA molecules unambiguously. Examination of these sites and comparison with other suspected anion binding sites reveals features of anion binding motifs, and shows that selenate may be a useful tool for studying RNA-anion interactions.

Kieft, Jeffrey S.; Chase, Elaine; Costantino, David A.; Golden, Barbara L. (Purdue); (Colorado)

2010-05-24

171

Characterisation of AnBEST1, a functional anion channel in the plasma membrane of the filamentous fungus, Aspergillus nidulans.  

PubMed

Two distant homologues of the bestrophin gene family have been identified in the filamentous fungus, Aspergillus nidulans (anbest1 and anbest2). AnBEST1 was functionally characterised using the patch clamp technique and was shown to be an anion selective channel permeable to citrate. Furthermore, AnBEST1 restored the growth of the pdr12? yeast mutant on inhibitory concentrations of extracellular propionate, benzoate and sorbate, also consistent with carboxylated organic anion permeation of AnBEST1. Similar to its animal counterparts, AnBEST1 currents were activated by elevated cytosolic Ca(2+) with a K(d) of 1.60?M. Single channel currents showed long (>10s) open and closed times with a unitary conductance of 16.3pS. Transformation of A. nidulans with GFP-tagged AnBEST1 revealed that AnBEST1 localised to the plasma membrane. An anbest1 null mutant was generated to investigate the possibility that AnBEST1 mediated organic anion efflux across the plasma membrane. Although organic anion efflux was reduced from anbest1 null mutants, this phenotype was linked to the restoration of uracil/uridine-requiring A. nidulans strains to uracil/uridine prototrophy. In conclusion, this study identifies a new family of organic anion-permeable channels in filamentous fungi. We also reveal that uracil/uridine-requiring Aspergillus strains exhibit altered organic anion metabolism which could have implications for the interpretation of physiological studies using auxotrophic Aspergillus strains. PMID:21596151

Roberts, Stephen K; Milnes, James; Caddick, Mark

2011-05-11

172

Experimental and theoretical studies on the electronic properties of vanadium-benzene sandwich cluster anions, VnBzn+1- (n = 1-5)  

NASA Astrophysics Data System (ADS)

Vanadium-benzene cluster anions, VnBzn+1- (Bz = C6H6) were generated by laser ablation and supersonic jet methods, and studied using photoelectron spectroscopy. The density functional theory was employed to compute their geometric and electronic structures. It is concluded that the VnBzn+1- anions exhibit multiple-decker sandwich structures similar to their corresponding neutrals, and the adiabatic electron affinity increases with the cluster size. Our computation shows that the excess electron of the anion occupies the d orbitals of the vanadium atoms and that it is delocalized one-dimensionally. Furthermore, a very large HOMO-LUMO gap difference between majority and minority spin orbitals is observed for both the neutrals and the anions, and the VnBzn+10/- clusters are found to be completely spin-polarized. These facts confirm the possibility of using VnBzn+1 clusters as spin filters.

Masubuchi, Tsugunosuke; Ohi, Katsuya; Iwasa, Takeshi; Nakajima, Atsushi

2012-12-01

173

Nutrition and metabolism in spaceflight.  

PubMed

The United States Space Station being planned for the 1990s will accommodate six or more crew members on 90-d flights in low earth orbit. Adequate nutrition will be essential for maintaining crew health, effectiveness and morale. Although much is known from prior space experience about in-flight metabolism, nutrition and associated food technology, important gaps in knowledge exist that need additional research, development and analysis to meet Space Station requirements. This paper is a synopsis of a report prepared by the Life Sciences Research Office (LSRO), FASEB, from a study of the nutritional and metabolic aspects of spaceflight. It reviews available data on the metabolic responses to spaceflight including extravehicular activity, physiological responses to microgravity that influence metabolism and energy needs, in-flight nutritional experience, space menus, food packaging, in-flight food service methodology, water supply and disposal of food wastes. The LSRO ad hoc Working Group identified critical gaps in knowledge and suggested corresponding research approaches for acquiring essential new data. The 38 research suggestions detailed in the report address in-flight metabolic needs, nutrient requirements, food systems and nutritional countermeasures. PMID:3572555

Altman, P L; Talbot, J M

1987-03-01

174

Stable Organic Derivatives of Heteropoly Anions, Pentamolybdobisphosphonates.  

National Technical Information Service (NTIS)

Heteropoly molybdates containing covalently bound organic moieties have been prepared and characterized by chemical analysis and spectroscopic measurements. Salts of the anions (RP)2Mo5O21(4-), where R = H, CH3, C2H5, C6H5, C2H4NH3(+) and pCH2C6H4NH3(+), ...

W. Kwak M. T. Pope T. F. Scully

1975-01-01

175

Regulatory Anionic Sites and Brain Acetylcholinesterase.  

National Technical Information Service (NTIS)

The feasibility of using the fluorescent lanthanide terbium as a probe of the peripheral anionic sites on mammalian brain acetylcholinesterase (AChE) was studied. Terbium has been used as a fluorescence probe of Ca2+ binding sites in many enzyme proteins ...

J. K. Marquis

1982-01-01

176

Metal-salophen-based receptors for anions.  

PubMed

In this critical review the use of metal-salophen complexes as anion receptors is discussed with an emphasis on the supramolecular control of selectivity derived by the presence of additional interaction sites on the ligand skeleton. Some examples of application in sensing are also reported (112 references). PMID:20820465

Dalla Cort, Antonella; De Bernardin, Paolo; Forte, Gianpiero; Mihan, Francesco Yafteh

2010-08-31

177

Anionic polymerization of fluorinated vinyl monomers  

Microsoft Academic Search

Several fluorinated vinyl monomers, which were believed to be difficult to homopolymerize under common radical polymerization, were polymerized under anionic conditions. They include hexafluoro-1,3-butadiene, ?,??-trifluorostyrene, ?-trifluoromethylacrylates, and ?-trifluoromethylstyrene which are key monomers whose behavior toward polymerization is unclear and these vinyl monomers have to be investigated individually to complete the overall picture. This knowledge will allow us aalso to yield

T. Narita

1999-01-01

178

Enhanced electrochemical oxidation of anionic surfactants  

Microsoft Academic Search

The surfactant wastewater treatment by electro?chemical oxidation with or without peroxide hydrogen was investigated. The two anionic surfactants studied here were alkylbenzene sulfonate (ABS) and linear alkylbenzene sulfonate (LAS), both of them being widely used in the household and industrial detergents. Experiments were conducted to examine the effects of pH, electrolyte concentration, time of electrochemical oxidation, power input and amount

Homg G. Leu; Sheng H. Lin; Tze M. Lin

1998-01-01

179

Infrared Spectrum of Carbon Dioxide Anion Radical  

Microsoft Academic Search

Pressed alkali halide disks of infrared spectroscopy have been used as matrices to trap and to stabilize the carbon dioxide anion free radical. The radical was generated by exposing disks containing the formate ion in solid solution to gamma rays from a cobalt source. The ESR, the ultraviolet, and the infrared spectra of the radical have been identified. From the

K. O. Hartman; I. C. Hisatsune

1966-01-01

180

Recovery of anionic surfactant by RO process  

Microsoft Academic Search

Crosslinked sodium alginate (SA) membranes which have a protective polyelectrolyte complex layer at a membrane surface were prepared by a simple technique for the reverse osmosis separation of an anionic surfactant that has been used as an emulsifier in PTFE emulsion polymerization. With this technique, when a nascent SA film cast onto a glass plate was dipped in the reaction

C. K Yeom; C. U Kim; B. S Kim; K. J Kim; J. M Lee

1998-01-01

181

Preparation and Reactions of Substituted Ethenesulfenate Anions  

Microsoft Academic Search

Trans-alkyl and gem-silyl substituted ethenesulfenate anions result from the reaction of hexamethyldisilazide bases with anti-alkyl and anti-silyl substituted thiirane-S-oxides, respectively, via a stereoselective deprotonation process. The sulfenates can be captured at sulfur with certain alkyl halides or they can be converted to a series of substituted ethenesulfenic acid amides.

Adrian L. Schwan; Mitchell D. Refvik

1994-01-01

182

Salts of amino acids with hexafluorosilicate anion  

NASA Astrophysics Data System (ADS)

In this work we present our preliminary results on the systematic search for salts of amino acids with hexafluorosilicate (SiF62-) anion. Three types of simple salts have been obtained: 2A+·SiF62- (2Gly+·SiF62-, 2L-Phe+·SiF62-, 2L-Val+·SiF62-, 2L-Glu+·SiF62-, 2L-His+·SiF62-), A2+·SiF62- (L-His2+·SiF62-, L-Lys2+·SiF62-, L-Orn2+·SiF62-) and 2(A···A+)·SiF62- (2(Bet···Bet+)·SiF62-). Furthermore, one example of mixed salts with different anions, including SiF62-, viz. 2L-His2+·2BF4-·SiF62-·2H2O is presented. It was found that the salts of amino acids with SiF62- anion tend to form crystal hydrates and the SiF62- anion is often disordered within the structures.

Ghazaryan, V. V.; Fleck, M.; Petrosyan, A. M.

2013-01-01

183

Anion reorientation in Na3PO4  

NASA Astrophysics Data System (ADS)

The reorientational motion of phosphate anions in the high-temperature phase of Na3PO4 has been investigated with a coherent quasielastic neutron-scattering experiment. Our study aimed at clarifying the relevance of the so-called ``paddle-wheel'' mechanism, i.e., the influence of the anion motion on the translational Na+ ion conduction. In the Q range between 0.3 and 2.3 Å-1, the data could be fitted by the sum of a ? function and a single Lorentzian whose width exhibits an Arrhenius behavior with an activation energy of 0.184 eV. We have calculated Sq(Q,?), the coherent quasielastic structure factor of the oxygen ions, based on several models. A comparison of the model predictions with our experimental data shows that only three oxygen atoms per anion are rotationally mobile. The experiment yields an additional small maximum around 1.5 Å-1, which appears more pronounced at higher temperatures. Its position on the Q scale suggests that sodium ions, further away from the center of rotation, are involved in the reorientational anion motion.

Wilmer, D.; Banhatti, R. D.; Fitter, J.; Funke, K.; Jansen, M.; Korus, G.; Lechner, R. E.

1998-04-01

184

Study of Model Systems in Anionic Exchange.  

National Technical Information Service (NTIS)

Preliminary experiments are reported on the preparation and characterization of anionic sulphate and chloride complexes of UO exp 2+2 and iron(III), benzyl-trimethylammonium cation being used as a model substance for the simulation of positive sites in an...

R. Haegele J. C. A. Boeyens

1977-01-01

185

Transmembrane anion transport by synthetic systems.  

PubMed

This highlight examines recent advances in the development of synthetic membrane transporters for anions, highlighting the underlying principles of transporter design and the promising applications of such transporters to biological systems including potential future treatments for diseases like cystic fibrosis which is caused by dysregulation of chloride transport across epithelial cell membranes. PMID:21594245

Haynes, Cally J E; Gale, Philip A

2011-05-18

186

Anion-conducting polymer, composition, and membrane  

SciTech Connect

Anion-conducing polymers and membranes with enhanced stability to aqueous alkali include a polymer backbone with attached sulfonium, phosphazenium, phosphazene, and guanidinium residues. Compositions also with enhanced stability to aqueous alkali include a support embedded with sulfonium, phosphazenium, and guanidinium salts.

Pivovar, Bryan S. (Los Alamos, NM); Thorn, David L. (Los Alamos, NM)

2011-11-22

187

Spectroscopy and metastability of the HSS anion  

Microsoft Academic Search

Accurate ab initio calculations on the potential energy surfaces (PESs) of the lowest electronic states of the neutral HSS and those of the electronic states of the HSS- negative ion correlating to the bound asymptotes of this molecular system, reveal that the ground state of HSS- (i.e. 1A') and the long range parts of the anionic PESs are stable against

B. Edhay; S. Lahmar; Z. Ben Lakhdar; M. Hochlaf

2007-01-01

188

Photoelectron spectroscopic studies of 5-halouracil anions  

SciTech Connect

The parent negative ions of 5-chlorouracil, UCl{sup -} and 5-fluorouracil, UF{sup -} have been studied using anion photoelectron spectroscopy in order to investigate the electrophilic properties of their corresponding neutral halouracils. The vertical detachment energies (VDE) of these anions and the adiabatic electron affinities (EA) of their neutral molecular counterparts are reported. These results are in good agreement with the results of previously published theoretical calculations. The VDE values for both UCl{sup -} and UF{sup -} and the EA values for their neutral molecular counterparts are much greater than the corresponding values for both anionic and neutral forms of canonical uracil and thymine. These results are consistent with the observation that DNA is more sensitive to radiation damage when thymine is replaced by halouracil. While we also attempted to prepare the parent anion of 5-bromouracil, UBr{sup -}, we did not observe it, the mass spectrum exhibiting only Br{sup -} fragments, i.e., 5-bromouracil apparently underwent dissociative electron attachment. This observation is consistent with a previous assessment, suggesting that 5-bromouracil is the best radio-sensitizer among these three halo-nucleobases.

Radisic, Dunja; Ko, Yeon Jae; Nilles, John M.; Stokes, Sarah T.; Bowen, Kit H. [Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Sevilla, Michael D. [Department of Chemistry, Oakland University, Rochester, Michigan 48309 (United States); Rak, Janusz [Department of Chemistry, University of Gdansk, 80-952 Gdansk (Poland)

2011-01-07

189

Photoelectron spectroscopic studies of 5-halouracil anions  

NASA Astrophysics Data System (ADS)

The parent negative ions of 5-chlorouracil, UCl- and 5-fluorouracil, UF- have been studied using anion photoelectron spectroscopy in order to investigate the electrophilic properties of their corresponding neutral halouracils. The vertical detachment energies (VDE) of these anions and the adiabatic electron affinities (EA) of their neutral molecular counterparts are reported. These results are in good agreement with the results of previously published theoretical calculations. The VDE values for both UCl- and UF- and the EA values for their neutral molecular counterparts are much greater than the corresponding values for both anionic and neutral forms of canonical uracil and thymine. These results are consistent with the observation that DNA is more sensitive to radiation damage when thymine is replaced by halouracil. While we also attempted to prepare the parent anion of 5-bromouracil, UBr-, we did not observe it, the mass spectrum exhibiting only Br- fragments, i.e., 5-bromouracil apparently underwent dissociative electron attachment. This observation is consistent with a previous assessment, suggesting that 5-bromouracil is the best radio-sensitizer among these three halo-nucleobases.

Radisic, Dunja; Ko, Yeon Jae; Nilles, John M.; Stokes, Sarah T.; Sevilla, Michael D.; Rak, Janusz; Bowen, Kit H.

2011-01-01

190

Ion chromatographic determination of anions in rainwater  

SciTech Connect

High acidity rainwater has recently become an issue in environmental pollution because of its great influence on ecological systems with special reference to the human environment. To solve this problem, the chemical behaviors of various pollutants in the air, particularly in the wet atmosphere must be studied. Ion chromatography was used for rapid analysis of trace amounts of anions. As a result, it was found that a combination of 2mM Na/sub 2/CO/sub 3/ and 5mM NaOH as an eluent was suitable for the separation of various anions. The reproducibility of determination of anions in standard solutions was found to be satisfactory with a coefficient of variation (CV) of 2-4% for F/sup -/, Br/sup -/, NO/sup -//sub 3/, SO/sup 2 -//sub 3/, SO/sup 2 -//sub 3/, and PO/sup 3 -//sub 4/, but not for NO/sup -//sub 2/. The determination of NO/sup -//sub 2/ was accomplished by preparing an eluent having almost the same composition and concentration as that of the standard and sample solutions. The precision of the method with rainwater sample was less than 10%, and was considered to be usable for data analysis. In addition, a considerble number of ions in rainwater samples could be determined by using 1-3 ml of the sample without pretreatment. It was found that ion chromatography was one of the best means to obtain information on the chemical behaviors of trace amounts of anions of anions in rainwater.

Oikawa, K.; Saito, H.

1982-01-01

191

Enhancing the anion separations on a polydivinylbenzene-based anion stationary phase  

Microsoft Academic Search

A new anion-exchange stationary phase is described for the separation of inorganic anions by ion chromatography. This stationary phase is made of polydivinylbenzene (P-DVB) based resin with dimetylethanolamine functional groups. The highly cross-linked P-DVB backbone makes this material chemically and mechanically stable under extreme chromatographic conditions. It withstands organic solvents and is stable at a wide range ofpH, temperature and

Lakshmy M. Nair; Brian R. Kildew; Raaidah Saari-Nordhaus

1996-01-01

192

Experimental Detection of the Pentazole Anion, N5(-).  

National Technical Information Service (NTIS)

The pentazole anion has been generated from para- hydroxyphenylpentazole and identified by electrospray ionization mass spectrometry. Whereas at low collision voltages the para-phenoxypentazole anion undergoes stepwise N2 elimination generating the corres...

A. Vij J. G. Pavlovich W. W. Wilson K. O. Christe

2002-01-01

193

Anion-templated assembly of interpenetrated and interlocked structures.  

PubMed

The rational development of a general anion templation strategy for the construction of a variety of interpenetrated and interlocked molecular structures based upon the coupling of anion recognition with ion-pairing is described. The success of this anion templation methodology is demonstrated with the halide anion directed assembly of a series of novel [2]pseudorotaxanes containing pyridinium, pyridinium nicotinamide, imidazolium, benzimidazolium and guanidinium threading components and anion binding macrocyclic ligands. Interlocked [2]rotaxane and [2]catenane molecular structures are also synthesised using this anion templation protocol. These interlocked structures feature unique topologically defined hydrogen bond donating binding domains that exhibit a high degree of selectivity for chloride, the templating anion. A series of rhenium(I) bipyridyl containing [2]pseudorotaxane assemblies and a [2]rotaxane further highlight the potential this strategic anion templation approach has in future chemical sensor design and fabrication. PMID:16703125

Beer, Paul D; Sambrook, Mark R; Curiel, David

2006-03-08

194

Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance  

SciTech Connect

The major thrust of this project, led by the University of Kansas (Prof. Kristin Bowman-James), entails an exploration of the basic determinants of anion recognition and their application to the design, synthesis, and testing of novel sulfate extractants. A key scientific inspiration for the work comes from the need, codified in simple-to-appreciate terms by the Oak Ridge National Laboratory component of the team (viz. Dr. Bruce Moyer), for chemical entities that can help in the extractive removal of species that have low solubilities in borosilicate glass. Among such species, sulfate anion, has been identified as particularly insidious. Its presence interferes with the vitrification process, thus rendering the remediation of tank waste from, e.g., the Hanford site far more difficult and expensive. The availability of effective extractants, that would allow for the separation of separating sulfate from the major competing anions in the waste, especially nitrate, could allow for pre-vitrification removal of sulfate via liquid-liquid extraction. The efforts at The University of Texas, the subject of this report, have thus concentrated on the development of new sulfate receptors. These systems are designed to increase our basic understanding of anion recognition events and set the stage for the development of viable sulfate anion extractants. In conjunction with the Oak Ridge National Laboratory (ORNL) members of the research team, several of these new receptors were studied as putative extractants, with two of the systems being shown to act as promising synergists for anion exchange.

Jonathan L. Sessler

2007-09-21

195

Gaps below strange star crusts  

SciTech Connect

The gap caused by a strong electric field between the quark surface and nuclear crust of a strange star is studied in an improved model including gravity and pressure as well as electrostatic forces. The transition from gap to crust is followed in detail. The properties of the gap are investigated for a wide range of parameters assuming both color-flavor locked and noncolor-flavor locked strange star cores. The maximally allowed crust density is generally lower than that of neutron drip. Finite temperature is shown to increase the gap width, but the effect is significant only at extreme temperatures. Analytical approximations are derived and shown to provide useful fits to the numerical results.

Stejner, Morten; Madsen, Jes [Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark)

2005-12-15

196

Plenary 1 – Gaps in Oncology  

Cancer.gov

The first plenary of the EPEC-O (Education in Palliative and End-of-Life Care for Oncology) Self-Study Original Version provides background for the curriculum and identifies gaps in current and desired comprehensive cancer care.

197

Gap Junctions and Heart Development  

Microsoft Academic Search

\\u000a The function of gap junctions in propagation of the cardiac action potential is one of the best characterized roles for intercellular\\u000a communication. Comprehending the part played by cell-to-cell dialogue in embryological processes, including development of\\u000a the heart, has proven to be a more complex problem. Nonetheless, research at the conjunction of cardiac development and gap\\u000a junctions is a diverse and

Robert G. Gourdie; Wanda H. Litchenberg; Leonard M. Eisenberg

198

The Gender Gap in Ideology  

Microsoft Academic Search

Over the past few decades, a gender gap has emerged in the mass public in ideological self-placement. While most men and women\\u000a moved in the conservative direction, another segment of women retained their liberal self-identifications. A gender gap also\\u000a exists in how men and women define their ideology. Which issues are linked to ideological identities is conditioned by gender\\u000a and

Barbara Norrander; Clyde Wilcox

2008-01-01

199

Eight electrode optical readout gap  

DOEpatents

A protective device for a plurality of electrical circuits includes a plurality of isolated electrodes forming a gap with a common electrode. An output signal, electrically isolated from the circuits being monitored, is obtained by a photosensor viewing the discharge gap through an optical window. Radioactive stabilization of discharge characteristics is provided for slowly changing voltages and carbon tipped dynamic starters provide desirable discharge characteristics for rapidly varying voltages. A hydrogen permeation barrier is provided on external surfaces of the device.

Boettcher, G.E.; Crain, R.W.

1984-01-01

200

Oxidation of silicon surface with atomic oxygen radical anions  

Microsoft Academic Search

The surface oxidation of silicon (Si) wafers by atomic oxygen radical anions (O- anions) and the preparation of metal-oxide-semiconductor (MOS) capacitors on the O- -oxidized Si substrates have been examined for the first time. The O- anions are generated from a recently developed O- storage-emission material of [Ca24Al28O64]4+.4O-(C12A7-O- for short). After it has been irradiated by an O- anion beam

Lian Wang; Chong-Fu Song; Jian-Qiu Sun; Ying Hou; Xiao-Guang Li; Quan-Xin Li

2008-01-01

201

Stable and highly persistent quinoxaline-centered metalloorganic radical anions: preparation, structural, spectroscopic, and computational investigations.  

PubMed

Coordination of diazines such as quinoxaline to transition metals stabilizes radical anions generated by chemical or electrochemical cathodic reduction. However, even though various sorts of radical anionic diazines have been subjected to spectroscopic investigations in the recent past, reports combining structural, solid-state electron paramagnetic resonance (EPR) and computational investigations of kinetically stable species are still missing. In this study, four radical anions derived from tricarbonylmanganese- and tricarbonylrhenium-bound quinoxaline chelates, embedded within a triple-decker architecture, have been prepared from neutral substrates by chemical reduction over alkaline metals (K, Rb); the electronic structure of the latter metalloorganic paramagnetic salts was investigated by the means of structural X-ray diffraction analysis, electrochemistry, solution and crystal EPR spectroscopy, and density functional theory (DFT). Unprecedented structures of three manganese-bound and one rhenium-bound quinoxaline-derived paramagnetic salts were obtained from solutions of the corresponding radical anions crystallized in the presence of cryptand 222. It is inferred from a comparative study of the structures of anionic and neutral quinoxaline complexes that reduction does not have any significant impact over the coordination mode of the metal centers and over the overall geometry of the triple-decker architecture. The most notable changes in the radical-anionic metalloorganic species, as compared to the neutral parent molecules, comprise a slight hapticity shift of the metal-bound benzyl moiety and a weak intraannular distortion of the quinoxalyl core. Single-crystal EPR experiments carried out with the rhenium and manganese compounds produced the respective anisotropic g tensor, which was found in each case to be essentially located at the quinoxalyl fragment. Computations, carried out using DFT methods (B3LYP-LANL2DZ and Becke-Perdew-TZP), corroborated the features suggested by structural analysis. Single-point calculation using the B3LYP functional and various basis sets [LANL2DZ, 6-31G(d), 6-311+G(d), and 6-311+G(2d,p)] provided us with values of anisotropic g tensors and hyperfine coupling constants consistent with those determined experimentally. It is inferred from this study that the two metal centers bound to the nitrogen atoms of the quinoxalyl core contribute in the lowering of the HOMO-LUMO gap in the neutral species. The triple-decker arrangement, which combines chelation of the metal, steric protection, and encapsulation of the central quinoxalyl core, is a stabilizing factor that provides a long-lived character to the radical-anionic species. PMID:19053841

Choua, Sylvie; Djukic, Jean-Pierre; Dalléry, Jérôme; Bieber, André; Welter, Richard; Gisselbrecht, Jean-Paul; Turek, Philippe; Ricard, Louis

2009-01-01

202

Opioid Metabolism  

PubMed Central

Clinicians understand that individual patients differ in their response to specific opioid analgesics and that patients may require trials of several opioids before finding an agent that provides effective analgesia with acceptable tolerability. Reasons for this variability include factors that are not clearly understood, such as allelic variants that dictate the complement of opioid receptors and subtle differences in the receptor-binding profiles of opioids. However, altered opioid metabolism may also influence response in terms of efficacy and tolerability, and several factors contributing to this metabolic variability have been identified. For example, the risk of drug interactions with an opioid is determined largely by which enzyme systems metabolize the opioid. The rate and pathways of opioid metabolism may also be influenced by genetic factors, race, and medical conditions (most notably liver or kidney disease). This review describes the basics of opioid metabolism as well as the factors influencing it and provides recommendations for addressing metabolic issues that may compromise effective pain management. Articles cited in this review were identified via a search of MEDLINE, EMBASE, and PubMed. Articles selected for inclusion discussed general physiologic aspects of opioid metabolism, metabolic characteristics of specific opioids, patient-specific factors influencing drug metabolism, drug interactions, and adverse events.

Smith, Howard S.

2009-01-01

203

Pneumatic gap sensor and method  

SciTech Connect

This patent describes in a casting system which including an apparatus for monitoring the gap between a casting nozzle and a casting surface of a substrate during casting of molten material, wherein the molten material is provided through a channel of the casting nozzle for casting onto the casting surface of the substrate for solidification. It comprises: a pneumatic gap mounted at least partially within a cavity in the casting nozzle adjacent the channel and having a sensor face located within the gap between the nozzle and the casting surface of the substrate, means for supply gas under predetermined pressure to the inlet orifice; and means for measuring the pressure of the gas within the sensor chamber during casting procedures, whereby relative changes in the gap can be determined by corresponding changes in the measured pressure. This patent also describes a method for monitoring the gap between a casting nozzle and a casting surface of a substrate for continuous casting of molten material. It comprises: providing a casting nozzle with a channel for directing the flow of molten material, locating the nozzle and the casting surface is proximity with one another and having a predetermined gap there-between, and dressing the sensor face to correspond in conformation to the casting surface and to adjust the predetermined distance as desired; providing a molten material to the nozzle for casting onto and casting surface; supplying gas at a predetermined pressure to the inlet orifice of the sensor during casting procedures.

Bagdal, K.T.; King, E.L.; Follstaedt, D.W.

1992-03-03

204

Process for solvent extraction of vanadate and molybdate anions  

SciTech Connect

A process for recovery of vanadium and molybdenum from a feed material containing compounds of these metals by reacting at an effective pH an aqueous solution of vanadate and molybdate anions with a quaternary ammonium surfactant dissolved in an organic solvent which is immiscible with water and separating a vanadate anion rich phase from a molybdate anion rich phase.

Nevitt, T.D.

1984-08-28

205

Multiplicity of Hepatic Excretory Mechanisms for Organic Anions  

Microsoft Academic Search

Previous studies based upon competition between different or- ganic anions for biliary excretion in vivo have suggested that all organic anions share a common hepatic secretory mechanism. Corriedale sheep with an in- herited defect in organic anion excretion by the liver were used to study this problem directly without the need for competition studies, the results of which are difficult

SEYMOUR ALPERT; MICHAEL MOSHER; ALAN SHANSKE; IRWIN M. ARIAS

1969-01-01

206

Recent advance in living anionic polymerization of functionalized styrene derivatives  

Microsoft Academic Search

This review covers recent advance of living anionic polymerization of styrene derivatives with functional groups. Although there have so far been reported several successful systems of living anionic polymerization of functionalized styrene derivatives, most useful functional groups are not amenable to the conditions of living anionic polymerization of styrene. Therefore, we herein present two generalized strategies to be able to

Akira Hirao; Surapich Loykulnant; Takashi Ishizone

2002-01-01

207

Anion- interactions in crystal structures: commonplace or extraordinary?  

SciTech Connect

An in-depth analysis of the distribution of anions about planar six-membered rings in the Cambridge Structural Database fails to provide any convincing evidence for anion- interactions with charge-neutral systems, but does provide overwhelming evidence in support of C-H---anion hydrogen bonding.

Hay, Benjamin [ORNL; Custelcean, Radu [ORNL

2009-01-01

208

COMMUNICATIONS Anion photoelectron spectroscopy of iodine-carbon dioxide clusters  

Microsoft Academic Search

Anion photoelectron spectroscopy has proved to be a powerful method for the study of molecular clusters be- cause it combines mass-selectivity and reasonable spectral resolution. Anion photoelectron spectra have been re- ported for elemental and molecular clusters of the type Ai, in which the additional electron is delocalized over the entire anion cluster,'-6 and for mixed clusters of the type

Don W. Arnold; Stephen E. Bradforth; Eun Ha Kim; Daniel M. Neumark

2003-01-01

209

Electronic characterization of defects in narrow gap semiconductors  

NASA Astrophysics Data System (ADS)

We use a Green's function technique to calculate the position of deep defects in narrow gap semiconductors. We consider substitutional (including antisite), vacancy, and interstitial (self and foreign) deep defects. We also use perturbation theory to look at the effect of nonparabolic bands on shallow defect energies and find nonparabolicity can increase the binding by 10 percent or so. We consider mercury cadmium telluride (MCT), mercury zinc telluride (MZT), and mercury zinc selenide (MZS). For substitutional and interstitial defects we look at the situation with and without relaxation. For substitutional impurities in MCT, MZT, and MZS, we consider x (the concentration of Cd or Zn) in the range 0.1 less than x less than 0.3 and also consider appropriate x so E(sub g) = 0.1 eV for each of the three compounds. We consider several cation site s-like deep levels and anion site p-like levels. For E(sub g) = 0.1 eV, we also consider the effects of relaxation. Similar comments apply to the interstitial deep levels whereas no relaxation is considered for the ideal vacancy model. Relaxation effects can be greater for the interstitial than the substitutional cases. Specific results are given in figures and tables and comparison to experiment is made in a limited number of cases. We find, for example, that I, Se, S, Rn, and N are possible cation site, s-like deep levels in MCT and Zn and Mg are for anion site, p-like levels (both levels for substitutional cases). The corresponding cation and anion site levels for interstitial deep defects are (Au, Ag, Hg, Cd, Cu, Zn) and (N, Ar, O, F). For the substitutional cases we have some examples of relaxation moving the levels into the band gap, whereas for the interstitial case we have examples where relaxation moves it out of the band gap. Future work involves calculating the effects of charge state interaction and seeing the effect of relaxation on vacancy levels.

Patterson, James D.

210

Anion photoelectron spectroscopy of radicals and clusters  

SciTech Connect

Anion photoelectron spectroscopy is used to study free radicals and clusters. The low-lying {sup 2}{Sigma} and {sup 2}{Pi} states of C{sub 2n}H (n = 1--4) have been studied. The anion photoelectron spectra yielded electron affinities, term values, and vibrational frequencies for these combustion and astrophysically relevant species. Photoelectron angular distributions allowed the author to correctly assign the electronic symmetry of the ground and first excited states and to assess the degree of vibronic coupling in C{sub 2}H and C{sub 4}H. Other radicals studied include NCN and I{sub 3}. The author was able to observe the low-lying singlet and triplet states of NCN for the first time. Measurement of the electron affinity of I{sub 3} revealed that it has a bound ground state and attachment of an argon atom to this moiety enabled him to resolve the symmetric stretching progression.

Travis, Taylor R.

1999-12-16

211

Modeling peptide binding to anionic membrane pores.  

PubMed

Peptide-induced pore formation in membranes can be dissected into two steps: pore formation and peptide binding to the pore. A computational method is proposed to study the second step in anionic membranes. The electrostatic potential is obtained from numerical solutions to the Poisson-Boltzmann equation and is then used in conjunction with IMM1 (implicit membrane model 1). A double charge layer model is used to incorporate the effects of the membrane dipole potential. Inhomogeneity of the charge density in the pore, characterized by explicit membrane simulations of toroidal pores, is included in the model. This approach was applied to two extensively studied peptides, magainin and melittin. In agreement with previous work, binding to toroidal pores is more favorable than binding to the flat membrane. The dependence of binding energy on anionic content exhibits different patterns for the two peptides, in correlation with the different lipid selectivity that has been observed experimentally. PMID:23580260

He, Yi; Prieto, Lidia; Lazaridis, Themis

2013-04-11

212

Electron transfer dissociation of peptide anions.  

PubMed

Ion/ion reactions of multiply deprotonated peptide anions with xenon radical cations result in electron abstraction to generate charge-reduced peptide anions containing a free-radical site. Peptide backbone cleavage then occurs by hydrogen radical abstraction from a backbone amide N to facilitate cleavage of the adjacent C-C bond, thereby producing a- and x-type product ions. Introduction of free-radical sites to multiply charged peptides allows access to new fragmentation pathways that are otherwise too costly (e.g., lowers activation energies). Further, ion/ion chemistry, namely electron transfer reactions, presents a rapid and efficient means of generating odd-electron multiply charged peptides; these reactions can be used for studying gas-phase chemistries and for peptide sequence analysis. PMID:15907703

Coon, Joshua J; Shabanowitz, Jeffrey; Hunt, Donald F; Syka, John E P

2005-04-14

213

First-principles studies of the electronic properties of native and substitutional anionic defects in bulk iron pyrite  

NASA Astrophysics Data System (ADS)

Systematic spin-polarized density functional theory calculations were performed to investigate the formation energies of native and substitutional anionic point defects in iron pyrite (FeS2) and their impact on bulk electronic structure. A detailed analysis indicates that neutral sulfur and iron vacancies do not act as efficient donors or acceptors. We find that substitutional oxygen does not induce gap states in pyrite and can actually passivate gap states created by sulfur vacancies. Most Group V and VII impurities create mid-gap states and produce spin polarization. In particular, Cl and Br are shallow donors that introduce delocalized spin-polarized electrons for potential use in photovoltaic and spintronics applications.

Hu, Jun; Zhang, Yanning; Law, Matt; Wu, Ruqian

2012-02-01

214

Interaction of haloacetylenephosphonates with anionic nucleophile  

SciTech Connect

This paper studies the reactivity of chloroacetylenephosphonates with respect to anionic nucleophiles. As a result of nucleophilic and radical addition of ethyl mercaptan to ethylthioacetylenephosphonate, the authors obtained regioisomeric 1,2- and 2,2-di (ethylthio) ethenephosphonates. As a result of radical addition of ethyl mercaptan to chloroethylenephonsphonate regioisomeric chloroethylthioethenephonsphonates were obtained The reaction of chloroacetylenephosphonates with monosodium salts of 1,3-diols yielded phosphorylated 1,3-dioxolanes - a new class of organophosphorus compounds.

Garibina, V.A.; Dogadina, A.V.; Ionin, B.I.; Leonov, A.A.; Petrov, A.A.

1986-02-20

215

Stability of polyhedral borane anions and carboranes  

Microsoft Academic Search

Polyhedral borane anions and carboranes that can be constructed formally from the interaction of rings and caps will be stable\\u000a with six interstitial electrons. Interstitial electron count is obtained by summing the number of ? electrons of the ring\\u000a and the electrons of the caps involved in ring cap binding. Thus B7H7\\u000a ?2 (D5h) has 6 interstitial electrons (none from

E. D. Jemmis; P. N. V. Pavankumar

1984-01-01

216

Living polymers and mechanisms of anionic polymerization  

Microsoft Academic Search

Following a short introduction and a brief discussion of thermodynamics of propagation, the kinetics and mechanisms of anionic\\u000a polymerization are reviewed. The systems involving living polymers, a term introduced by this writer, are discussed in greater\\u000a detail because the existence of various ionic species participating in polymerization was clearly revealed by their studies.\\u000a Indeed, a large part of this review

Michael Szwarc

217

Aza crown ether compounds as anion receptors  

DOEpatents

A family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the new family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of LI.sup.+ ion in alkali metal batteries.

Lee, Hung Sui (East Setauket, NY); Yang, Xiao-Oing (Port Jefferson Station, NY); McBreen, James (Bellport, NY)

1998-08-04

218

Nanoheterostructure Cation Exchange: Anionic Framework Conservation  

Microsoft Academic Search

In ionic nanocrystals the cationic sub-lattice can be replaced with a different metal ion via a fast, simple, and reversible place-exchange, allowing post-synthetic modification of the composition of the nanocrystal, while preserving its size and shape. Here, we demonstrate for the first time that during such an exchange, the anionic framework of the crystal is preserved. When applied to nanoheterostructures,

Prashant K. Jain; Lilac Amirav; Shaul Aloni; A. Paul Alivisatos

2010-01-01

219

Controlled Architecture Polymers by Anionic Polymerization  

NASA Astrophysics Data System (ADS)

Anionic polymerization is the most important synthetic tool to produce model polymers and copolymers with complex macromolecular architectures. High vacuum techniques1 have to be used in order to avoid premature living chain termination or linking agent destruction. These techniques are very demanding in glass blowing practice, time consuming and usually lead to the synthesis of a few grams of model polymers. Nevertheless, these Â"limitationsÂ" are a small price to pay given the potential of anionic polymerization to generate true model polymeric materials. By using anionic polymerization and controlled chlorosilane chemistry a variety of macromolecular architectures have been created2. A few examples are the miktoarm stars ( AnB, AnBn), the á,ù-branched polymers ( AnBAn), and the comb-shaped polymers (A-g-B1or2) where A, B are polymeric chains with different molecular weight or chemistry and n, m: 2-8. Recent advances in anionic polymerization methodology led to the synthesis of well-defined cyclic co- and terpolymers3,4, as well as dendritic polymers5, multicomponent multiblock polymers6 and polymeric materials having as building blocks macromonomers7. References 1. N. Hadjichristidis, H. Iatrou, S. Pispas, M. Pitsikalis, J. Polym. Sci., Part A : Polym. Chem. 38, 3211 (2000). 2. N. Hadjichristidis, M. Pitsikalis, S. Pispas, H. Iatrou, Chem. Rev. 101, 3747 (2001). 3. H. Iatrou, N. Hadjichristidis, G. Meier H. Frielinghaus, and M. Monkenbusch, Macromolecules 35 5426 (2002) 4. D. Pantazis, D. Schulz, N. Hadjichristidis, J. Polym. Sci., Part A : Polym.Chem. 40, 1476 (2002) 5. I. Chalari, and N. Hadjichristidis, J. Polym. Sci., Part A: Polym. Chem. 40, 1519 (2002) 6. K. Takahashi, H. Hasegawa, T. Hashimoto, V. Bellas, H. Iatrou, N. Hadjichristidis, Macromolecules 35, 4859 (2002) 7. D. Pantazis, I. Chalari, N. Hadjichristidis, Macromolecules, submitted

Hadjichristidis, Nikos

2003-03-01

220

Aza crown ether compounds as anion receptors  

DOEpatents

A family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the new family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of LI{sup +} ion in alkali metal batteries. 3 figs.

Lee, H.S.; Yang, X.O.; McBreen, J.

1998-08-04

221

Deuterium anions in inertial electrostatic confinement devices  

Microsoft Academic Search

A magnetic deflection-energy analyzer and Faraday trap diagnostic have been used to make measurements of divergent deuterium anion flow in the inertial electrostatic confinement experiment at the University of Wisconsin-Madison (UW-IEC) [J. F. Santarius, G. L. Kulcinski, R. P. Ashley, D. R. Boris, B. B. Cipiti, S. K. Murali, G. R. Piefer, R. F. Radel, I. E. Radel, and A.

D. R. Boris; E. Alderson; G. Becerra; D. C. Donovan; B. Egle; G. A. Emmert; L. Garrison; G. L. Kulcinski; J. F. Santarius; C. Schuff; S. J. Zenobia

2009-01-01

222

Detection of Perchlorate Anion on Functionalized Silver Colloids Using Surface-Enhanced Raman Scattering  

SciTech Connect

Perchlorate anion interferes with the uptake of iodide by the human thyroid gland and consequently disrupts the regulation of metabolism. Chronic exposure to high levels of perchlorate may lead to the formation of thyroid gland tumors. Although the Environmental Protection Agency (EPA) has not set a maximum contaminant level (MCL) for perchlorate, a draft drinking water range of 4-18 ppb based on 2 liter daily consumption of water has been established. The current EPA approved method for detecting perchlorate uses ion chromatography which has a detection limit of ~1ppb and involves lengthy analytical time in the laboratory. A unique combination of the surface-enhanced Raman scattering (SERS) effect and the bifunctional anion exchange resin’s high selectivity may provide an alternative way to detect perchlorate at such low concentrations and with high specificity. SERS, which uses laser excitation of adsorbed perchlorate anions on silver nanoparticles, has been shown to detect perchlorate anions at concentrations as low as 50 ppb. Normal micro-Raman analysis of perchlorate sorbed onto the resin beads has detected an even lower concentration of 10 ppb. In an effort to integrate these two effects, silver nanoparticles were coated with N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride, a functional group similar to that found on the resin bead, and subsequently inserted into different perchlorate concentration environments. This method has resulted in perchlorate detection down to ~10 ppb and a more consistent detection of perchlorate anion at ~50 ppb than that of earlier methods. As suggested by the direct insertion of functionalized silver colloids into perchlorate samples, this technique may potentially allow for the development of a probe using on-site Raman spectrometry to detect significantly low concentrations of perchlorate in situ rather than in the laboratory.

Tio, J.; Wang, W.; Gu, B.

2005-01-01

223

Safe 5-nitrotetrazolate anion transfer reagents.  

PubMed

Silver 5-nitrotetrazolate (1) and copper(ii) 5-nitrotetrazolate 5-nitrotetrazole dihydrate (2) are useful reagents for the synthesis of 5-nitrotetrazole (NT) salts. Both compounds were synthesized and characterized by vibrational spectroscopy (IR and Raman) and differential scanning calorimetry (DSC). In addition, their sensitivity towards friction, shock and electrostatic discharge was tested by standard BAM methods. The extremely high sensitivity of both materials makes the transfer of the NT(-) anion using and hazardous and not suitable for up-scaling. In order to diminish the hazards involved with the transfer of the energetic anion and to render the synthesis of NT salts suitable for an industrial scale the two compounds were stabilized by coordination with a chelating ligand and silver(ethylendiamine) 5-nitrotetrazolate and bis(ethylendiamine)copper(ii) 5-nitrotetrazolate were synthesized in high yields. Both the stabilized NT(-) anion transfer reagents were characterized by analytical and spectroscopic methods. In addition, the crystal structure of the ethylendiamine copper complex was determined: orthorombic, Pbca; a = 7.5200(1), b = 14.0124(2), c = 14.7740(2) A; V = 1556.78(4) A(3). Furthermore, we synthesized triaminocopper(ii) 5-nitrotetrazolate, which has potential as a more environmentally-friendly primary explosive. Lastly, the synthetic potential of the ethylediamine adducts and to form energetic salts of NT was investigated. PMID:19240919

Klapötke, Thomas M; Sabaté, Carles Miró

2009-01-27

224

Photoelectron Spectroscopy of Multiply Charged Anions  

SciTech Connect

Multiply charged anions (MCA’s) are common in the condensed phases, but are challenging to study in the gas phase. An experimental technique coupling photoelectron spectroscopy (PES) with electrospray ionization (ESI) has been developed to investigate properties of free MCA’s in the gas phase. In this article, the principles of this technique, and some initial findings about the intrinsic properties of MCA’s are reviewed. Examples chosen include the observation of the repulsive Coulomb barrier that exists universally in MCA’s and its effects on the dynamic stability and photoelectron spectroscopy of MCA’s. Solvation and solvent stabilization of MCA’s has been studied in the gas phase and will also be discussed. A second generation low-temperature ESI-PES apparatus has been developed, which allows ion temperatures to be controlled between 10 to 350 K. New results from the low-temperature ESI-PES instrument will also be reviewed, including doubly charged fullerene anions, inorganic metal complexes, and temperature-induced conformation changes of complex anions.

Wang, Xue B.; Wang, Lai S.

2009-07-01

225

Binary mixtures of cationic and anionic microgels.  

PubMed

Colloidal behaviors of binary mixtures composed of cationic and anionic microgels are reported. Both microgels were synthesized by aqueous free radical precipitation polymerization using N-isopropylacrylamide and N,N'-methylenebisacrylamide but using different types of water-soluble initiators and comonomer. Effects of temperature and salt concentration on phase behaviors of binary mixtures of cationic and anionic microgels were investigated as well as single-species microgels by UV-vis spectroscopy. We found that the presence of a small amount of NaCl altered the dispersing behavior of the binary mixtures of cationic and anionic microgels when they were in hydrated and swollen states. In particular, scanning electron microscope observation clarified that the binary mixtures containing a small amount of NaCl were not flocculated, and microgels showed non-close-packed structures on a planar substrate in the dry state. Furthermore, flocculations formed when both microgels were in the swollen states could be redispersed by adding a small amount of NaCl and gently stirring. These tunable properties have not been observed in mixtures of hard particles, and are due to the coexistence of electrostatic interactions and steric hindrance of highly hydrated soft particles. PMID:21882877

Suzuki, Daisuke; Horigome, Koji

2011-09-15

226

Donnan membrane technique (DMT) for anion measurement.  

PubMed

Donnan membrane technique (DMT) is developed and tested for determination of free anion concentrations. Time needed to reach the Donnan membrane equilibrium depends on type of ions and the background. The Donnan membrane equilibrium is reached in 1 day for Cl(-), 1-2 days for NO(3)(-), 1-4 days for SO(4)(2-) and SeO(4)(2-), and 1-14 days for H(2)PO(4)(-) in a background of 2-200 mM KCl or K(2)SO(4). The strongest effect of ionic strength on equilibrium time is found for H(2)PO(4)(-), followed by SO(4)(2-) and SeO(4)(2-), and then by Cl(-) and NO(3)(-). The negatively charged organic particles of fulvic and humic acids do not pass the membrane. Two approaches for the measurement of different anion species of the same element, such as SeO(4)(2-) and HSeO(3)(-), using DMT are proposed and tested. These two approaches are based on transport kinetics or response to ionic strength difference. A transport model that was developed previously for cation DMT is applied in this work to analyze the rate-limiting step in the anion DMT. In the absence of mobile/labile complexes, transport tends to be controlled by diffusion in solution at a low ionic strength, whereas at a higher ionic strength, diffusion in the membrane starts to control the transport. PMID:20222663

Vega, Flora Alonso; Weng, Liping; Temminghoff, Erwin J M; Van Riemsdijk, Willem H

2010-04-01

227

Ferrocenylbenzobisimidazoles for recognition of anions and cations.  

PubMed

The preparation of 2,7-disubstituted benzobisimidazoles decorated with substituents displaying different electrooptical properties is described. The presence of redox, chromogenic, and fluorescent groups at the heteroaromatic core, which acts as ditopic binding site, made these receptors potential candidates as multichannel probes for ions. The triad 4 behaves as a selective redox and fluorescent chemosensor for HSO4(-) and Hg(2+) ions, whereas receptor 5 acts as a redox and chromogenic chemosensor molecule for AcO(-) and SO4(2-) anions. The change in the absorption spectra is accompanied by a color change from yellow to orange, while sensing of Zn(2+), Hg(2+), and Pb(2+) cations is carried out only by electrochemical techniques. Receptor 6 exhibits a remarkable cathodic shift of the oxidation wave only in the presence of AcO(-), H2PO4(-), and HP2O7(3-) anions, whereas addition of Pb(2+) induces an anodic shift. A new low energy band in the absorption spectra, which is responsible for the color change from colorless to pale yellow, and an important increase of the monomer emission band is observed only in the presence of H2PO4(-), and HP2O7(3-) anions. The most salient feature of the receptor 6 is its ability to act as a multichannel (redox, chromogenic, and fluorescent) chemodosimeter for Cu(2+), and Hg(2+) metal cations. PMID:24004286

Alfonso, María; Tárraga, Alberto; Molina, Pedro

2013-06-19

228

Modeling Carbon Chain Anions in L1527  

NASA Astrophysics Data System (ADS)

The low-mass protostellar region L1527 is unusual because it contains observable abundances of unsaturated carbon-chain molecules including CnH radicals, H2Cn carbenes, cyanopolyynes, and the negative ions C4H- and C6H-, all of which are more associated with cold cores than with protostellar regions. Sakai et al. suggested that these molecules are formed in L1527 from the chemical precursor methane, which evaporates from the grains during the heat-up of the region. With the gas-phase osu.03.2008 network extended to include negative ions of the families C-n, and CnH-, as well as the newly detected C3N-, we modeled the chemistry that occurs following methane evaporation at T~25-30 K. We are able to reproduce most of the observed molecular abundances in L1527 at a time of ~5×103 yr. At later times, the overall abundance of anions become greater than that of electrons, which has an impact on many organic species and ions. The anion-to-neutral ratio in our calculation is in good agreement with observation for C6H-, but exceeds the observed ratio by more than 3 orders of magnitude for C4H-. In order to explain this difference, further investigation is needed on the rate coefficients for electron attachment and other reactions regarding anions.

Harada, Nanase; Herbst, Eric

2008-09-01

229

Clinico-pathological findings in peripartum dairy cows fed anion salts lowering the dietary cation-anion difference: involvement of serum inorganic phosphorus, chloride and plasma estrogen concentrations in milk fever.  

PubMed

In our previous study, it was demonstrated that the administration of anion salts, which slightly lower the dietary cation-anion difference (DCAD), in the prepartum period is safe and effective for preventing milk fever in multiparous cows. In the present study, several clinico-pathological constituents in serum and urine, which might be related to milk fever, were analyzed using stored samples from the previous study to identify clinico-pathological parameters for easily evaluating the efficacy of lowering DCAD and to further investigate the mechanism by which lowering DCAD prevents milk fever. Among the parameters analyzed in the present study, inorganic phosphorus (iP) was involved in milk fever because the serum concentration and urinary excretion of iP were significantly higher in the group of primiparous cows (heifer group), which did not develop hypocalcemia, than those in other groups of multiparous cows. Serum chloride concentrations in the heifer group and the group of multiparous cows fed anion salts (anion group) tended to remain higher than those in other control groups of multiparous cows suggesting that serum chloride concentration may be utilized for evaluating the status of metabolic acidosis and the efficacy of lowerng DCAD in dairy cows fed anion salts. In addition, plasma estradiol-17beta concentration in the heifer group tended to be lower at parturition compared with that in other multiparous groups suggesting that estrogen known as a potent inhibitor of bone resorption may be involved in developing milk fever. PMID:17596033

Kurosaki, Naotoshi; Yamato, Osamu; Sasamoto, Yoshihiko; Mori, Fuminobu; Imoto, Seiichi; Kojima, Toshiyuki; Yamasaki, Masahiro; Maede, Yoshimitsu

2007-05-01

230

Anionic Polymerization Mechanism of Acrylonitrile Trimer Anions: Key Branching Point between Cyclization and Chain Propagation.  

PubMed

A cluster anion of vinyl compounds in the gaseous phase has served as one of the simplest microscopic models of the initial stages of anionic polymerization. Herein, we describe our investigations into the initial stage mechanisms of anionic polymerization of acrylonitrile (AN; CH(2)?CHCN) trimer anions. While the cyclic oligomer is found in mass and photoelectron spectroscopic studies of (AN)(3)(-), only the chain oligomer is found in the infrared photodissociation (IRPD) spectrum of Ar-tagged (AN)(3)(-). On the basis of the calculated polymerization pathway of (AN)(3)(-), we consider that the chain oligomers are the reaction intermediates in the cyclization of (AN)(3)(-). The rotational isomerization of the (AN)(3)(-) chain oligomer is found to be the bottleneck in the cyclization of (AN)(3)(-). To form the (AN)(4)(-) chain oligomer by chain propagation, the addition of an AN molecule to (AN)(3)(-) should occur prior to the rotational isomerization. We conclude that the rotational isomerization in the (AN)(3)(-) chain oligomer is the key branching point between cyclization (termination) or chain propagation in the anionic polymerization. PMID:22775348

Ohshimo, Keijiro; Inokuchi, Yoshiya; Ebata, Takayuki; Ohno, Koichi

2012-07-23

231

Simultaneous uptake of anionic surfactants and micellar-solubilized contaminants using anion-exchange resins.  

PubMed

This research studied simultaneous uptake of anionic surfactants and micellar-solubilized organic contaminants by anion-exchange resins. Anionic surfactant molecules adsorbed onto the positively charged resin mainly through electrostatic attraction, while the micellar-solubilized contaminants were excluded from aqueous solutions once the remaining micelles could no longer solubilize them. Data suggest that the excess contaminants adsorbed onto the resin skeleton and admicelle layer formed on the resin surface through hydrophobic interactions and eventually partitioned into the resin gel phase matrix. In batch adsorption, the contaminant solubilization capacity did not decrease linearly with respect to surfactant concentration decrease due to the increased solution counterion activity during anion exchange, and caused "delayed" contaminant uptake relative to that of the surfactant. No such effect occurred in continuous column adsorption, where the surfactant and contaminant breakthrough occurred simultaneously. Surfactant head and tail group properties, along with resin structure and particle size significantly affected surfactant and contaminant uptake rates. Relative to recovering the surfactant, the high exchange potential of the anionic surfactant prevented effective surfactant desorption, even at high electrolyte concentration and in the presence of a cosolvent. The resin matrix also had high affinity for the partitioned contaminant, and the contaminant elution from the resin seemed to be controlled by equilibrium partitioning. PMID:12092581

Cheng, Hefa; Sabatini, D A

2002-04-01

232

Valence anions of N-acetylproline in the gas phase: Computational and anion photoelectron spectroscopic studies  

PubMed Central

We report the photoelectron spectrum of anionic N-acetylproline, (N-AcPro)?, measured with 3.49 eV photons. This spectrum, which consists of a band centered at an electron binding energy of 1.4 eV and a higher energy spectral tail, confirms that N-acetylproline forms a valence anion in the gas phase. The neutrals and anions of N-AcPro were also studied computationally at the B3LYP/6-31++G(d,p) level. Based on the calculations, we conclude that the photoelectron spectrum is due to anions which originated from proton transfer induced by electron attachment to the ?* orbital localized at the acetyl group of N-AcPro. We also characterized the energetics of reaction paths leading to pyrrolidine ring opening in the anionic N-AcPro. These data suggest that electron induced decomposition of peptides/proteins comprising proline strongly depends on the presence of proton donors in the close vicinity to the proline residue.

Chomicz, Lidia; Rak, Janusz; Paneth, Piotr; Sevilla, Michael; Ko, Yeon Jae; Wang, Haopeng; Bowen, Kit H.

2011-01-01

233

Valence anions of N-acetylproline in the gas phase: Computational and anion photoelectron spectroscopic studies  

NASA Astrophysics Data System (ADS)

We report the photoelectron spectrum of anionic N-acetylproline, (N-AcPro)-, measured with 3.49 eV photons. This spectrum, which consists of a band centered at an electron binding energy of 1.4 eV and a higher energy spectral tail, confirms that N-acetylproline forms a valence anion in the gas phase. The neutrals and anions of N-AcPro were also studied computationally at the B3LYP/6-31++G(d,p) level. Based on the calculations, we conclude that the photoelectron spectrum is due to anions which originated from proton transfer induced by electron attachment to the ?* orbital localized at the acetyl group of N-AcPro. We also characterized the energetics of reaction paths leading to pyrrolidine ring opening in the anionic N-AcPro. These data suggest that electron induced decomposition of peptides/proteins comprising proline strongly depends on the presence of proton donors in the close vicinity to the proline residue.

Chomicz, Lidia; Rak, Janusz; Paneth, Piotr; Sevilla, Michael; Ko, Yeon Jae; Wang, Haopeng; Bowen, Kit H.

2011-09-01

234

Do coinage metal anions interact with substituted benzene derivatives?  

PubMed

The nature of the anion-? interaction has been investigated by carrying out ab initio calculations of the complexes of coinage metal anions (Au(-), Ag(-), and Cu(-)) with different kinds of ?-systems. The binding energies indicate that gold anion has the highest and copper anion has the lowest affinity for interactions with ?-systems. Different aspects of the anion-? interaction in these systems have been investigated, including charge-transfer effects (using the Merz-Kollman method), "atoms-in-molecules" (AIM) topological parameters, and interaction energies (using energy decomposition analysis, EDA). Our results indicated that, for most M(-)···? interactions, the electrostatic term provides the dominant contribution, whereas polarization, charge transfer, and dispersion effects contribute less than 25 % of the interaction. We believe that the present results should lead to a greater understanding of the basis for anion-? interactions of coinage metal anions. PMID:23989771

Aliakbar Tehrani, Zahra; Jamshidi, Zahra; Farhangian, Hossein

2013-08-30

235

Investigations into alternate spark gap switching techniques  

Microsoft Academic Search

This report documents the design, operation, and experimental results of the evaluation of a new spark gap triggering method. These spark gaps were developed to support ARL's ongoing nuclear electromagnetic pulse (EMP) current injection assessment programs. This trigger method provides operator control, multiple spark gap control with synchronous triggering, and a limited amount of hardware to control the spark gap

Brian G. Smith

1994-01-01

236

ABORT GAP CLEANING IN RHIC.  

SciTech Connect

During the RHIC Au-run in 2001 the 200 MHz storage cavity system was used for the first time. The rebucketing procedure caused significant beam debunching in addition to amplifying debunching due to other mechanisms. At the end of a four hour store, debunched beam could account for approximately 30%-40% of the total beam intensity. Some of it will be in the abort gap. In order to minimize the risk of magnet quenching due to uncontrolled beam losses at the time of a beam dump, a combination of a fast transverse kicker and copper collimators were used to clean the abort gap. This report gives an overview of the gap cleaning procedure and the achieved performance.

DREES,A.; AHRENS,L.; III FLILLER,R.; GASSNER,D.; MCINTYRE,G.T.; MICHNOFF,R.; TRBOJEVIC,D.

2002-06-03

237

Causes of metabolic acidosis in canine hemorrhagic shock: role of unmeasured ions  

Microsoft Academic Search

INTRODUCTION: Metabolic acidosis during hemorrhagic shock is common and conventionally considered to be due to hyperlactatemia. There is increasing awareness, however, that other nonlactate, unmeasured anions contribute to this type of acidosis. METHODS: Eleven anesthetized dogs were hemorrhaged to a mean arterial pressure of 45 mm Hg and were kept at this level until a metabolic oxygen debt of 120

Dirk Bruegger; Gregor I Kemming; Matthias Jacob; Franz G Meisner; Christoph J Wojtczyk; Kristian B Packert; Peter E Keipert; N Simon Faithfull; Oliver P Habler; Bernhard F Becker; Markus Rehm

2007-01-01

238

Connexin-43 hemichannels opened by metabolic inhibition.  

PubMed

The cause of altered ionic homeostasis leading to cell death during ischemia and metabolic inhibition is unclear. Hemichannels, which are precursors to gap junctions, are nonselective ion channels that are permeable to molecules of less than Mr 1000. We show that hemichannels open upon exposure to calcium-free solutions when they are either heterologously overexpressed in HEK293 cells or endogenously expressed in cardiac ventricular myocytes. In the presence of normal extracellular calcium, hemichannels open during metabolic inhibition. During ischemia and other forms of metabolic inhibition, activation of relatively few hemichannels will seriously compromise the cell's ability to maintain ionic homeostasis, which is an essential step promoting cell death. PMID:9867835

John, S A; Kondo, R; Wang, S Y; Goldhaber, J I; Weiss, J N

1999-01-01

239

Anion-aromatic bonding: a case for anion recognition by pi-acidic rings.  

PubMed

The basis for unprecedented noncovalent bonding between anions and the aryl centroid of electron-deficient aromatic rings has been demonstrated by an ab initio study of the interaction between 1,3,5-triazine and the fluoride, chloride, and azide ion at the MP2 level of theory. Minima are also located corresponding to C[bond]H...X(-) hydrogen bonding, reactive complexes for nucleophilic attack on the triazine ring, and pi-stacking interactions (with azide). Trifluoro-1,3,5-triazine also participates in aryl centroid complexation and forms nucleophilic reactive complexes with anions. This novel mode of bonding suggests the development of new cyclophane-type receptors for the recognition of anions. PMID:12033854

Mascal, Mark; Armstrong, Alan; Bartberger, Michael D

2002-06-01

240

Supramolecular chemistry of selective anion recognition for anions of environmental relevance. 1998 annual progress report  

SciTech Connect

'This project has as its focus the design and synthesis of polyammonium macrocyclic receptors for oxoanions of environmental importance. The basic research aspects of this project involve: (1) synthesis (and the search for improved synthetic methods); (2) solid state structure determination and thermodynamics studies (to ascertain structural criteria for and strength of anion binding); and (3) molecular dynamics simulations (to assess solution characteristics of the interactions between anions and their receptors). Applications-oriented goals include the fabrication of more selective anion-selective electrodes and the use of these compounds in liquid-liquid separations. The latter goal comprises the subcontract with Dr. Bruce Moyer at Oak Ridge National Laboratory. This report summarizes work after 1 year and 7 months of a 3-year project. To date, the authors have focussed on the design and synthesis of selective receptors for nitrate and phosphate.'

Bowman-James, K.; Wilson, G.S.; Kuczera, K. [Univ. of Kansas, Lawrence, KS (US); Moyer, B. [Oak Ridge National Lab., TN (US)

1998-06-01

241

Stacked insulator induction accelerator gaps  

SciTech Connect

Stacked insulators, with alternating layers of insulating material and conducting film, have been shown to support high surface electrical field stresses. We have investigated the application of the stacked insulator technology to the design of induction accelerator modules for the Relativistic-Klystron Two-Beam Accelerator program. The rf properties of the accelerating gaps using stacked insulators, particularly the impedance at frequencies above the beam pipe cutoff frequency, are investigated. Low impedance is critical for Relativistic-Klystron Two-Beam Accelerator applications where a high current, bunched beam is trsnsported through many accelerating gaps. An induction accelerator module designs using a stacked insulator is presented.

Houck, T.I.; Westenskow, G.A.; Kim, J.S.; Eylon, S.; Henestroza, E.; Yu, S.S.; Vanecek, D.

1997-05-01

242

Anion recognition: synthetic receptors for anions and their application in sensors.  

PubMed

Important contributions to the field of anion sensing include electrochemical lipophilic uranyl salophene receptors incorporated into membranes that act as fluoride-selective potentiometric microsensors. A promising optical-based sensor, selective for cyclic AMP, involves a preorganized, molecularly imprinted polymer employing an intrinsic fluorophore. Competition methods using ensembles of recognition units and external indicators have been used to sense citrate in highly competitive media and micromolar concentrations of inositol(tris)phosphate in water. In addition, DNA dendrimers immobilized on a quartz-crystal microbalance acted as an elegant biosensor for Cryptosporidium DNA. These designs display the varied methods of anion detection currently being pursued. PMID:10651521

Snowden, T S; Anslyn, E V

1999-12-01

243

Metabolic Disorders  

MedlinePLUS

Metabolism is the process your body uses to get or make energy from the food you eat. Food is made up of proteins, carbohydrates, and fats. Chemicals in your digestive system break the food parts down into sugars and acids, ...

244

Metabolic Myopathies  

MedlinePLUS

... properly. This energy comes from a chemical called ATP. Metabolic myopathies are genetic defects that interfere with ... from a chemical called adenosine triphosphate (sometimes called ATP). ATP is made in cells from sugars or ...

245

The (Non-)Existence of Gapping in Chinese and Its Implications for the Theory of Gapping.  

ERIC Educational Resources Information Center

Shows that there are at least two types of gapping in natural languages: canonical gapping and LPD. Argues that Chinese has some gapping sentences that result from ATB movement from V to "v." Data from Chinese affirm Johnson's (1994) theory of gapping that gapping occurs in those languages only with verb movement. (Author/VWL)

Tang, Sze-Wing

2001-01-01

246

Infared Spectroscopy of Discrete Uranyl Anion Complexes  

SciTech Connect

The Free-Electron Laser for Infrared Experiments (FELIX) w 1 as used to study the wavelength-resolved multiple photon photodissociation of discrete, gas phase uranyl (UO2 2 2+) complexes containing a single anionic ligand (A), with or without ligated solvent molecules (S). The uranyl antisymmetric and symmetric stretching frequencies were measured for complexes with general formula [UO2A(S)n]+, where A was either hydroxide, methoxide, or acetate; S was water, ammonia, acetone, or acetonitrile; and n = 0-3. The values for the antisymmetric stretching frequency for uranyl ligated with only an anion ([UO2A]+) were as low or lower than measurements for [UO2]2+ ligated with as many as five strong neutral donor ligands, and are comparable to solution phase values. This result was surprising because initial DFT calculations predicted values that were 30–40 cm-1 higher, consistent with intuition but not with the data. Modification of the basis sets and use of alternative functionals improved computational accuracy for the methoxide and acetate complexes, but calculated values for the hydroxide were greater than the measurement regardless of the computational method used. Attachment of a neutral donor ligand S to [UO2A]+ produced [UO2AS]+, which produced only very modest changes to the uranyl antisymmetric stretch frequency, and did not universally shift the frequency to lower values. DFT calculations for [UO2AS]+ were in accord with trends in the data, and showed that attachment of the solvent was accommodated by weakening of the U-anion bond as well as the uranyl. When uranyl frequencies were compared for [UO2AS]+ species having different solvent neutrals, values decreased with increasing neutral nucleophilicity.

Groenewold, G. S.; Gianotto, Anita K.; McIIwain, Michael E.; Van Stipdonk, Michael J.; Kullman, Michael; Moore, David T.; Polfer, Nick; Oomens, Jos; Infante, Ivan A.; Visscher, Lucas; Siboulet, Bertrand; De Jong, Wibe A.

2008-01-24

247

Infrared Spectroscopy of Discrete Uranyl Anion Complexes  

SciTech Connect

The Free-Electron Laser for Infrared Experiments, FELIX, was used to study the wavelength-resolved multiphoton dissociation of discrete, gas phase uranyl (UO22+) complexes containing a single anionic ligand (A), with or without ligated solvent molecules (S). The apparent uranyl antisymmetric and symmetric stretching frequencies were measured for complexes with general formula [UO2A(S)n]+, where A was either hydroxide, methoxide or acetate, S was water, ammonia, acetone or acetonitrile, and n = 0-2. The values for the antisymmetric stretching frequency for uranyl ligated with only an anion ([UO2A]+) were as low or lower than measurements for [UO2]2+ ligated with as many as five strong neutral donor ligands, and are comparable to solution phase values. This result was surprising because initial DFT calculations using B3LYP predicted values that were 30 – 40 cm-1 higher, consistent with intuition but not with the data. Modification of the basis set and use of alternative functionals improved computational accuracy for the methoxide and acetate complexes, but calculated values for the hydroxide were greater than the measurement regardless of the computational method used. Attachment of a neutral donor ligand S to [UO2A]+ produced [UO2AS]+, which resulted only very modest changes to the uranyl frequency, and did not universally shift values lower. DFT calculations for [UO2AS]+ were in accord with trends in the data, and showed that attachment of the solvent was accommodated by weakening of the U-anion bond as well as the uranyl. When uranyl frequencies were compared for [UO2AS]+ species having different solvent neutrals, values decreased with increasing neutral nucleophilicity.

Gary S. Groenewold; Anita K. Gianotto; Michael E. McIlwain; Michael J. Van Stipdonk; Michael Kullman; Travis J. Cooper; David T. Moore; Nick Polfer; Jos Oomens; Ivan Infante; Lucas Visscher; Bertrand Siboulet; Wibe A. de Jong

2007-12-01

248

Multiple input electrode gap controller  

DOEpatents

A method and apparatus for controlling vacuum arc remelting (VAR) furnaces by estimation of electrode gap based on a plurality of secondary estimates derived from furnace outputs. The estimation is preferably performed by Kalman filter. Adaptive gain techniques may be employed, as well as detection of process anomalies such as glows. 17 figs.

Hysinger, C.L.; Beaman, J.J.; Melgaard, D.K.; Williamson, R.L.

1999-07-27

249

GAP JUNCTION FUNCTION AND CANCER  

EPA Science Inventory

Gap Junctions (GJs) provide cell-to-cell communication (GJIC) of essential metabolites and ions. Js allow tissues to average responses, clear waste products, and minimize the effects of xenobiotics by dilution and allowing steady-state catabolism. any chemicals can adversely affe...

250

SmartGAP User's Guide.  

National Technical Information Service (NTIS)

This document is the users guide for the Smart Growth Area Planning (SmartGAP) software, which is a tool for evaluating the impact of various smart growth policies. The tool was developed as part of the SHRP 2 C16 project, which provided tools, methods, a...

K. Kockelman R. Cerver

2013-01-01

251

Bridging the Music Semantic Gap  

Microsoft Academic Search

In this paper we present the music information plane and the dieren t levels of information extraction that exist in the musical domain. Based on this approach we propose a way to overcome the existing se- mantic gap in the music eld. Our approximation is twofold: we propose a set of music descriptors that can automatically be extracted from the

Oscar Celma; Perfecto Herrera; Xavier Serra

252

A simple triggered vacuum gap  

Microsoft Academic Search

A simple triggered vacuum gap has previously been described by the authors in this journal (see ibid., vol.5, 415, 1972). Further studies have resulted in improvement of the performance with regard to sensitivity and consistency of the trigger characteristics and immunity from bridging due to metal particles eroded from the arc. The earlier design suffered from rather frequent bridging of

N. Vidyardhi; R. S. N. Rau

1973-01-01

253

Multiple input electrode gap controller  

DOEpatents

A method and apparatus for controlling vacuum arc remelting (VAR) furnaces by estimation of electrode gap based on a plurality of secondary estimates derived from furnace outputs. The estimation is preferably performed by Kalman filter. Adaptive gain techniques may be employed, as well as detection of process anomalies such as glows.

Hysinger, Christopher L. (Austin, TX); Beaman, Joseph J. (Austin, TX); Melgaard, David K. (Albuquerque, NE); Williamson, Rodney L. (Albuquerque, NE)

1999-01-01

254

Brain Responses to Filled Gaps  

ERIC Educational Resources Information Center

An unresolved issue in the study of sentence comprehension is whether the process of gap-filling is mediated by the construction of empty categories (traces), or whether the parser relates fillers directly to the associated verb's argument structure. We conducted an event-related potentials (ERP) study that used the violation paradigm to examine…

Hestvik, Arild; Maxfield, Nathan; Schwartz, Richard G.; Shafer, Valerie

2007-01-01

255

Anionic grafts of monomers onto coal substrates  

SciTech Connect

Anionic grafting of olefinic monomers onto coal substrates is disclosed. The process comprises grafting polymeric side chains onto coal by contacting coal with a covalently bonded alkyl or aryl alkali metal initiator to generate carbon-alkali metal bonds and then reacting these bonds with an olefinically unsaturated monomer for a time sufficient to produce a grafted coal product having polymeric side chains bonded to the coal. The resulting coal grafts evidence enhanced solubility in organic solvents, and liquids derived from the coal grafts evidence reduced sulfur content.

Ebert, L.B.; Matty, L.J.

1981-04-21

256

Electroculture for crop enhancement by air anions  

NASA Astrophysics Data System (ADS)

Electroculture, the practice of applying strong electric fields or other sources of small air ions to growing plants, has potential to markedly increase crop production and to speed crop growth. The considerable evidence for its effectiveness, and the studies of the mechanisms for its actions are discussed. A mild current of air anions (4 pA/cm2) stimulates bean crop growth and also earlier blossoming and increased growth in the annual, Exacum affine (Persian violet), as well as in seedling geraniums. The present results would indicate that the growing period required until the plants reach a saleable stage of maturity can be shortened by about two weeks under greenhouse conditions.

Pohl, H. A.; Todd, G. W.

1981-12-01

257

Design of inorganic compounds with tetrahedral anions  

NASA Astrophysics Data System (ADS)

The review deals with aspects of the modelling of the compositions and properties of inorganic compounds with tetrahedral anions on the basis of crystal-chemical information. One of the possible algorithms employing crystal-chemical data for the modelling of the compositions, structures, and properties of new compounds is proposed on the basis of the structures of six structural types (glaserite, ?-K2SO4, bredigite, palmierite, NASICON, and whitlockite). The likely usefulness of such data for the solution of various problems in materials science is demonstrated. The bibliography includes 208 references.

Lazoryak, B. I.

1996-04-01

258

Anion-exchange displacement centrifugal partition chromatography.  

PubMed

Ion-exchange displacement chromatography has been adapted to centrifugal partition chromatography. The use of an ionic liquid, benzalkonium chloride, as a strong anion-exchanger has proven to be efficient for the preparative separation of phenolic acid regioisomers. Multigram quantities of a mixture of three hydroxycinnamic acid isomers were separated using iodide as a displacer. The displacement process was characterized by a trapezoidal profile of analyte concentration in the eluate with narrow transition zones. By taking advantage of the partition rules involved in support-free liquid-liquid chromatography, a numerical separation model is proposed as a tool for preliminary process validation and further optimization. PMID:15516108

Maciuk, Alexandre; Renault, Jean-Hugues; Margraff, Rodolphe; Trébuchet, Philippe; Zèches-Hanrot, Monique; Nuzillard, Jean-Marc

2004-11-01

259

Air Gap Effects in LX-17  

SciTech Connect

Three experiments done over twenty years on gaps in LX-17 are reported. For the detonation front moving parallel to the gaps, jets of gas products were seen coming from the gaps at velocities greater than the detonation velocity. A case can be made that the jet velocity increased with gap thickness but the data is scattered. For the detonation front moving transverse to the gap, time delays were seen. The delays roughly increase with gap width, going from 0-70 ns at 'zero gap' to around 300 ns at 0.5-1 mm gap. Larger gaps of up to 6 mm width almost certainly stopped the detonation, but this was not proved. Real-time resolution of the parallel jets and determination of the actual re-detonation or failure in the transverse case needs to be done in future experiments.

Souers, P C; Ault, S; Avara, R; Bahl, K L; Boat, R; Cunningham, B; Gidding, D; Janzen, J; Kuklo, D; Lee, R; Lauderbach, L; Weingart, W C; Wu, B; Winer, K

2005-09-26

260

Observational Properties of Protoplanetary Disk Gaps  

NASA Astrophysics Data System (ADS)

We study the effects of an annular gap induced by an embedded protoplanet on disk scattered light images and the infrared spectral energy distribution (SED). We find that the outer edge of a gap is brighter in the scattered light images than a similar location in a gap-free disk. The stellar radiation that would have been scattered by material within the gap is instead scattered by the disk wall at the outer edge of the gap, producing a bright ring surrounding the dark gap in the images. Given sufficient resolution, such gaps can be detected by the presence of this bright ring in scattered light images. A gap in a disk also changes the shape of the SED. Radiation that would have been absorbed by material in the gap is instead reprocessed by the outer gap wall. This leads to a decrease in the SED at wavelengths corresponding to the temperature at the radius of the missing gap material, and to a corresponding flux increase at longer wavelengths corresponding to the temperature of the outer wall. We note, however, that the presence of an annular gap does not change the bolometric IR flux; it simply redistributes the radiation previously produced by material within the gap to longer wavelengths. Although it will be difficult on the basis of the SED alone to distinguish between the presence of a gap and other physical effects, the level of changes can be sufficiently large to be measurable with current instruments (e.g., Spitzer).

Varnière, Peggy; Bjorkman, J. E.; Frank, Adam; Quillen, Alice C.; Carciofi, A. C.; Whitney, Barbara A.; Wood, Kenneth

2006-02-01

261

Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance.  

National Technical Information Service (NTIS)

This project have focuses on the basic chemical aspects of anion receptor design of functional pH independent systems, with the ultimate goal of targeting the selective binding of sulfate, as well as design of separations strategies for selective and effi...

K. Bowman-James

2004-01-01

262

Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance.  

National Technical Information Service (NTIS)

The last three years of this project have focused on the basic chemical aspects of anion receptor design of functional pH independent systems, with the ultimate goal of targeting the selective binding of sulfate, as well as design of separations strategie...

K. Bowman-james B. Moyer G. S. Wilson

2004-01-01

263

PROGRESS REPORT. SUPRAMOLECULAR CHEMISTRY OF SELECTIVE ANION RECOGNITION FOR ANIONS OF ENVIRONMENTAL RELEVANCE  

EPA Science Inventory

This project involves the design and synthesis of receptors for oxoanions of environmental importance and specifically those found in high level waste tanks. Polyammonium macrocycles as receptors and nitrate as anion were the focus of the first phase of this project. A second pha...

264

[Application of high performance anion exchange chromatography for trace analysis of polarizable anions].  

PubMed

Polarizable anions such as Br-, S2O3(2-), I- and SCN- were separated using 45 mmol/L sodium hydroxide solution as the mobile phase on a high hydrophilic IonPac AS16 column. With a pulsed amperometric detector, the detection limits were 0.5, 0.2, 0.05 and 2 microg/L (25.0 microL injected, signal-to-noise ratio of 3) for Br-, S2O3(2-), I- and SCN. The relative standard deviation (RSD) range of trace anions was from 0.8% to 3.7% (n = 9). Under the same chromatographic conditions, these anions were also determined using a suppressed conductivity detector and the detection limits were 1, 1, 2 and 10 microg/L (25 microL injected, signal-to-noise ratio of 3), respectively. The RSD range was from 0.9% to 4.7% (n = 9). Comparing a pulsed amperometric detector with a conductivity detector, the former is 2 to 40 times more sensitive than the latter. For the determination of polarizable anions, a pulsed amperometric detector has higher selectivity, precision and sensitivity. PMID:16499005

Mo, Shumin; Liang, Lina; Cai, Yaqi; Mou, Shifen; Wen, Meijuan

2005-11-01

265

Hepatic organic anion uptake in the rat.  

PubMed Central

The hepatic uptake of bilirubin (BR), indocyanine green (ICG), and sulfobromophthalein (BSP) was studied in 350 anesthetized Sprague-Dawley rats by determining the initial plasma disappearance rate (V) of various doses of unlabeled ICG, or of tracer quantities of [3H]BR or [35S]BSP injected into the jugular vein simultaneously with varying amounts of unlabeled BR or BSP. Similar studies were also performed involving the simultaneous injection of potential inhibitors of hepatic uptake. The results indicate that: (a) hepatic uptake determined by direct tissue measurement could be accurately estimated from the plasma disappearance data; (b) saturation of hepatic uptake with increasing dose was readily demonstrated for each of these three organic anions, and in each instance a plot of V versus dose took the form of a rectangular hyperbola analyzable in terms of Michaelis-Menten kinetics; (c) for BR, the saturable uptake process showed a Vmax more than 100 times the normal net transfer rate from plasma to bile; (d) hepatic uptake of BR, BSP, and ICG showed relatively selective, mutually competitive inhibition; glycoholic acid did not inhibit hepatic uptake of any of these substances; and (e) "counter-transport" could be demonstrated for each of the three test substances. These data are compatible with the existence of a carrier-mediated transport process for hepatic uptake of each of these three organic anions and clarify the relationship of hepatic BR uptake to its overall transport from plasma to bile.

Scharschmidt, B F; Waggoner, J G; Berk, P D

1975-01-01

266

Atoms in the Anionic Domain, Z < N  

NASA Astrophysics Data System (ADS)

We study atoms with N electrons, and nuclear charge Z. It is well known that the cationic regime, Z > N, is qualitatively described by Thomas-Fermi theory. The anionic regime, Z < N, on the other hand, is characterized by an instability threshold at Zc ? N-1, below which the atom spontaneously emits an electron. We compute the slope of the energy curve at Z = N - 1 by means of a simple model that depends on the electron affinity and the covalent radius of the neutral atom with N - 1 electrons. This slope is used in order to estimate Zc, which is compared with previous numerical results. Extrapolation of the linear behavior in the opposite direction, up to Z = N, allows us to estimate the ionization potential of the atom with N electrons. The fact that the obtained ionization potentials are qualitatively correct is an indication that, with regard to certain properties, neutral atoms are closer to the anionic instability threshold than they are to the Thomas-Fermi, large Z, region. A regularized series is written for the ionization potential that fits both, the large Z and Z ? Zc limits.

Gil, Gabriel; Gonzalez, Augusto

2013-09-01

267

Deuterium anions in inertial electrostatic confinement devices  

NASA Astrophysics Data System (ADS)

A magnetic deflection-energy analyzer and Faraday trap diagnostic have been used to make measurements of divergent deuterium anion flow in the inertial electrostatic confinement experiment at the University of Wisconsin-Madison (UW-IEC) [J. F. Santarius, G. L. Kulcinski, R. P. Ashley, D. R. Boris, B. B. Cipiti, S. K. Murali, G. R. Piefer, R. F. Radel, I. E. Radel, and A. L. Wehmeyer, Fusion Sci. Technol. 47, 1238 (2005)], a device to confine high-energy light ions in a spherically symmetric electrostatic potential well. Deuterium anion current densities as high as 8.5?A/cm2 have been measured at the wall of the UW-IEC device, 40 cm from the surface of the device cathode with a detector assembly of admittance area 0.7cm2 . Energy spectra obtained using a magnetic deflection-energy analyzer diagnostic indicate the presence of D2- , and D- ions produced through thermal electron attachment near the device cathode, as well as D- ions produced via charge-transfer processes between the anode and cathode of the device.

Boris, D. R.; Alderson, E.; Becerra, G.; Donovan, D. C.; Egle, B.; Emmert, G. A.; Garrison, L.; Kulcinski, G. L.; Santarius, J. F.; Schuff, C.; Zenobia, S. J.

2009-09-01

268

Deuterium anions in inertial electrostatic confinement devices.  

PubMed

A magnetic deflection-energy analyzer and Faraday trap diagnostic have been used to make measurements of divergent deuterium anion flow in the inertial electrostatic confinement experiment at the University of Wisconsin-Madison (UW-IEC) [J. F. Santarius, G. L. Kulcinski, R. P. Ashley, D. R. Boris, B. B. Cipiti, S. K. Murali, G. R. Piefer, R. F. Radel, I. E. Radel, and A. L. Wehmeyer, Fusion Sci. Technol. 47, 1238 (2005)], a device to confine high-energy light ions in a spherically symmetric electrostatic potential well. Deuterium anion current densities as high as 8.5 microA/cm2 have been measured at the wall of the UW-IEC device, 40 cm from the surface of the device cathode with a detector assembly of admittance area 0.7 cm2. Energy spectra obtained using a magnetic deflection-energy analyzer diagnostic indicate the presence of D2(-), and D- ions produced through thermal electron attachment near the device cathode, as well as D- ions produced via charge-transfer processes between the anode and cathode of the device. PMID:19905231

Boris, D R; Alderson, E; Becerra, G; Donovan, D C; Egle, B; Emmert, G A; Garrison, L; Kulcinski, G L; Santarius, J F; Schuff, C; Zenobia, S J

2009-09-30

269

Porating anion-responsive copolymeric gels.  

PubMed

A polymerizable ionic liquid surfactant, 1-(11-acryloyloxyundecyl)-3-methylimidiazolium bromide (ILBr), was copolymerized with methyl methacrylate (MMA) in aqueous microemulsions at 30% (ILBr w/w) and various water to MMA ratios. The ternary phase diagram of the ILBr/MMA/water system was constructed at 25 and 60 °C. Homopolymers and copolymers of ILBr and MMA were produced by thermally initiated chain radical microemulsion polymerization at various compositions in bicontinuous and reverse microemulsion subdomains. Microemulsion polymerization reaction products varied from being gel-like to solid, and these materials were analyzed by thermal and scanning electron microscopy methods. Microemulsion polymerized materials were insoluble in all solvents tested, consistent with light cross-linking. Ion exchange between Br(-) and PF6(-) in these copolymeric materials resulted in the formation of open-cell porous structures in some of these materials, as was confirmed by scanning electron microscopy (SEM). Several compositions illustrate the capture of prepolymerization nanoscale structure by thermally initiated polymerization, expanding the domain of compositions exhibiting this feat and yet to be demonstrated in any other system. Regular cylindrical pores in interpenetrating ILBr-co-MMA and PMMA networks are produced by anion exchange in the absence of templates. A percolating cluster/bicontinuous transition is "captured" by SEM after using anion exchange to visualize the mixed cluster/pore morphology. Some design principles for achieving this capture and for obtaining stimuli responsive solvogels are articulated, and the importance of producing solvogels in capturing the nanoscale is highlighted. PMID:23968242

England, Dustin; Yan, Feng; Texter, John

2013-09-11

270

Isolation of a carborane-fused triazole radical anion.  

PubMed

Outside the cage: A change in the redox properties of a triazole fused to a carborane anion through methylation to form a zwitterion enabled facile chemical reduction of the compound to an isolable triazole radical anion (see structure: C gray, H white, N blue, B brown, Cl green). The radical anion is stabilized by kinetic protection by the chlorinated carborane and the delocalization of spin density throughout the exo-cluster ??system. PMID:24106045

Asay, Matthew; Kefalidis, Christos E; Estrada, Jess; Weinberger, David S; Wright, James; Moore, Curtis E; Rheingold, Arnold L; Maron, Laurent; Lavallo, Vincent

2013-09-17

271

Organotin anions in solution and in the solid state  

NASA Astrophysics Data System (ADS)

Moessbauer data have been obtained for a series of organotin anions. The spectra of these anions in solution show the presence of two species, a singlet in the tin(IV) region and a doublet in the tin(II) region. The crystal structure of triphenyltin anion with potassium in 18-crown-6 as the cation has been determined. The Moessbauer spectrum of this sample is a doublet in the tin(II) region.

Birchall, T.; Vetrone, J.

1988-02-01

272

The SLC26 gene family of multifunctional anion exchangers  

Microsoft Academic Search

The ten-member SLC26 gene family encodes anion exchangers capable of transporting a wide variety of monovalent and divalent anions. The physiological role(s) of individual paralogs is evidently due to variation in both anion specificity and expression pattern. Three members of the gene family are involved in genetic disease; SLC26A2 in chondrodysplasias, SLC26A3 in chloride-losing diarrhea, and SLC26A4 in Pendred syndrome

David B. Mount; Michael F. Romero

2004-01-01

273

Ultrastructural alteration of glomerular anionic sites in nephrotic patients  

Microsoft Academic Search

The relationship of glomerular anionic sites to proteinuria was examined ultrastructurally in human nephrotic syndrome. The anionic sites were analysed morphometrically in patients with minimal-change nephrotic syndrome (MCNS, 11 patients) and in other glomerulonephritides complicated with nephrotic syndrome (4 patients) by the high-iron diamine-thiocarbohydrazide-silver proteinate method. The anionic sites in MCNS patients in remission (7 patients) were normal. In contrast,

Kazuhiko Washizawa; Shinji Kasai; Tetsuo Mori; Atsushi Komiyama; Hidekazu Shigematsu

1993-01-01

274

Unexpectedly strong anion-? interactions on the graphene flakes.  

PubMed

Interactions of anions with simple aromatic compounds have received growing attention due to their relevancy in various fields. Yet, the anion-? interactions are generally very weak, for example, there is no favorable anion-? interaction for the halide anion F(-) on the simplest benzene surface unless the H-atoms are substituted by the highly negatively charged F. In this article, we report a type of particularly strong anion-? interactions by investigating the adsorptions of three halide anions, that is, F(-), Cl(-), and Br(-), on the hydrogenated-graphene flake using the density functional theory. The anion-? interactions on the graphene flake are shown to be unexpectedly strong compared to those on simple aromatic compounds, for example, the F(-)-adsorption energy is as large as 17.5 kcal/mol on a graphene flake (C(84) H(24)) and 23.5 kcal/mol in the periodic boundary condition model calculations on a graphene flake C(113) (the supercell containing a F(-) ion and 113 carbon atoms). The unexpectedly large adsorption energies of the halide anions on the graphene flake are ascribed to the effective donor-acceptor interactions between the halide anions and the graphene flake. These findings on the presence of very strong anion-? interactions between halide ions and the graphene flake, which are disclosed for the first time, are hoped to strengthen scientific understanding of the chemical and physical characteristics of the graphene in an electrolyte solution. These favorable interactions of anions with electron-deficient graphene flakes may be applicable to the design of a new family of neutral anion receptors and detectors. PMID:22430486

Shi, Guosheng; Ding, Yihong; Fang, Haiping

2012-03-20

275

Potentiometric microtitration of anions with quaternary ammonium halides  

Microsoft Academic Search

Summary Cetyltrimethylammonium bromide has been evaluated for the potentiometric precipitation titration of some water-soluble organic anions. Emf's were monitored with a fluoroborate ion-selective electrode and a double-junction reference electrode. The perchlorate, nitrate, and calcium electrodes also respond to the various anions. Cetyltrimethylammonium chloride and cetylpyridinium chloride are also suitable as titrants for the various anions. They can be used also

Walter Selig

1979-01-01

276

Emplacement Gantry Gap Analysis Study  

SciTech Connect

To date, the project has established important to safety (ITS) performance requirements for structures, systems, and components (SSCs) based on the identification and categorization of event sequences that may result in a radiological release. These performance requirements are defined within the ''Nuclear Safety Design Bases for License Application'' (NSDB) (BSC 2005 [DIRS 171512], Table A-11). Further, SSCs credited with performing safety functions are classified as ITS. In turn, assurance that these SSCs will perform as required is sought through the use of consensus codes and standards. This gap analysis is based on the design completed for license application only. Accordingly, identification of ITS SSCs beyond those defined within the NSDB are based on designs that may be subject to further development during detail design. Furthermore, several design alternatives may still be under consideration to satisfy certain safety functions, and final selection will not be determined until further design development has occurred. Therefore, for completeness, alternative designs currently under consideration will be discussed throughout this study. This gap analysis will evaluate each code and standard identified within the ''Emplacement Gantry ITS Standards Identification Study'' (BSC 2005 [DIRS 173586]) to ensure each ITS performance requirement is fully satisfied. When a performance requirement is not fully satisfied, a gap is highlighted. This study will identify requirements to supplement or augment the code or standard to meet performance requirements. Further, this gap analysis will identify nonstandard areas of the design that will be subject to a design development plan. Nonstandard components and nonstandard design configurations are defined as areas of the design that do not follow standard industry practices or codes and standards. Whereby, assurance that an SSC will perform as required may not be readily sought though the use of consensus standards. This gap analysis is prepared by the Emplacement and Retrieval (E&R) project team and is intended for the sole use of the Engineering department in work regarding the emplacement gantry. Yucca Mountain Project personnel from the E&R project team should be consulted before use of this gap analysis for purposes other than those stated herein or by individuals other than authorized by the Engineering department.

R. Thornley

2005-05-27

277

Identification and characterization of anion binding sites in RNA.  

PubMed

Although RNA molecules are highly negatively charged, anions have been observed bound to RNA in crystal structures. It has been proposed that anion binding sites found within isolated RNAs represent regions of the molecule that could be involved in intermolecular interactions, indicating potential contact points for negatively charged amino acids from proteins or phosphate groups from an RNA. Several types of anion binding sites have been cataloged based on available structures. However, currently there is no method for unambiguously assigning anions to crystallographic electron density, and this has precluded more detailed analysis of RNA-anion interaction motifs and their significance. We therefore soaked selenate into two different types of RNA crystals and used the anomalous signal from these anions to identify binding sites in these RNA molecules unambiguously. Examination of these sites and comparison with other suspected anion binding sites reveals features of anion binding motifs, and shows that selenate may be a useful tool for studying RNA-anion interactions. PMID:20410239

Kieft, Jeffrey S; Chase, Elaine; Costantino, David A; Golden, Barbara L

2010-04-21

278

Three hydroxy aurone compounds as chemosensors for cyanide anions.  

PubMed

Three new 4-hydroxy aurone compounds 1-3 with dimethylamino (1), bromine (2) and cyano (3) as terminal group have been synthesized. Their photophysical properties as well as recognition properties for cyanide anions in acetonitrile and aqueous solution have also been examined. These compounds exhibit remarkable response to cyanide anions with obvious color and fluorescence change owing to hydrogen bonding reaction between cyanide anions and the O-H moiety of the sensors, which allows naked eye detection of cyanide anions. PMID:23973584

Chen, Huihui; Sun, Yunhui; Zhou, Chuanjian; Cao, Duxia; Liu, Zhiqiang; Ma, Lin

2013-08-01

279

Amphibian cathelicidin fills the evolutionary gap of cathelicidin in vertebrate.  

PubMed

Cathelicidins comprise a family of antimicrobial peptides (AMPs) sharing a highly conserved cathelin domain, and play a central role in the innate defense against infection in most of vertebrates. But so far it has not yet been found in amphibians although a large number of other groups of AMPs have been identified. In the current work, the first amphibian cathelicidin (cathelicidin-AL) has been characterized from the frog skin of Amolops loloensis. Cathelicidin-AL (RRSRRGRGGGRRGGSGGRGGRGGGGRSGAGSSIAGVGSRGGGGGRHYA) is a cationic peptide containing 48 amino acid residues (aa) with 12 basic aa and no acidic aa. The chemical synthesized peptide efficiently killed bacteria and some fungal species including clinically isolated drug-resistance microorganisms. The cDNA encoding cathelicidin-AL precursor was cloned from the skin cDNA library of A. loloensis. As other cathelicidins, the precursor of cathelicidin-AL also contains highly conserved anionic cathelin domain of cysteine proteinase inhibitor followed by the AMP fragment at C-terminus. Phylogenetic analysis revealed that as connecting link, the amphibian cathelicidin predates reptilia but postdates fish cathelicidin. The peptide purification combined with gene cloning results confirms the presence of cathelicidin in amphibians and filled the evolutionary gap of cathelicidin in vertebrate, considering amphibians' special niche as the animals bridging the evolutionary land-water gap. PMID:22009138

Hao, Xue; Yang, Hailong; Wei, Ling; Yang, Shilong; Zhu, Wenjuan; Ma, Dongying; Yu, Haining; Lai, Ren

2011-10-19

280

Metabolic Acidosis  

Microsoft Academic Search

\\u000a 1.?Normal acid–base balance is crucial for proper cell function and integrity.\\u000a \\u000a 2.?Metabolic acidosis is due to either the loss of blood buffers, or the gain of non-volatile strong acids.\\u000a \\u000a \\u000a 3.?An organized, step-wise approach (the “ABCDE toolkit”) is crucial in determining both the magnitude and the cause of a\\u000a metabolic acidosis and deciding upon appropriate therapy.\\u000a \\u000a \\u000a \\u000a 4.?Base excess is a measure

Howard E. Corey; Uri S. Alon

281

Finding All Approximate Gapped Palindromes  

Microsoft Academic Search

We study the problem of finding all maximal approximate gapped palindromes in a string. More specifically, given a string S of length n, a parameter q???0 and a threshold k?>?0, the problem is to identify all substrings in S of the form uvw such that (1) the Levenshtein distance between u and w\\u000a \\u000a r\\u000a is at most k, where w

Ping-hui Hsu; Kuan-yu Chen; Kun-mao Chao

2009-01-01

282

Energy Gaps in Graphene Nanoribbons  

Microsoft Academic Search

Based on a first-principles approach, we present scaling rules for the band\\u000agaps of graphene nanoribbons (GNRs) as a function of their widths. The GNRs\\u000aconsidered have either armchair or zigzag shaped edges on both sides with\\u000ahydrogen passivation. Both varieties of ribbons are shown to have band gaps.\\u000aThis differs from the results of simple tight-binding calculations or solutions

Young-Woo Son; Marvin L. Cohen; Steven G. Louie

2006-01-01

283

New functions for gap junctions  

Microsoft Academic Search

The most significant finding of the past year in gap junction research has been the association of connexin defects with human diseases. Connexin32 mutations cause X-linked Charcot-Marie-Tooth disease, a demyelinating peripheral neuropathy. Mutations in connexin43 may underlie cardiac malformations in visceroatrial heterotaxia syndromes. Genetic approaches and gene targeting have provided new insights, but also raise new questions concerning connexin function,

David L Paul

1995-01-01

284

Tracing the Busy Gap Rogues  

Microsoft Academic Search

Busy Gap is one of the earliest attested place names located along the line of the central sector of Hadrian’s Wall in Northumberland,\\u000a yet in Newcastle during the sixteenth and seventeenth centuries it was a term of abuse, applied collectively to those who\\u000a came from upland Tynedale and was synonymous with the Border Reivers. Archaeological and historical sources indicate that

Jim Crow

2007-01-01

285

Probing the Electronic Structure and Band Gap Evolution of Titanium Oxide Clusters (TiO2)n- (n=1-10) Using Photoelectron Spectroscopy  

SciTech Connect

TiO2 is a wide-band gap semiconductor and it is an important material for photocatalysis. Here we report an experimental investigation of the electronic structure of (TiO2)n clusters and how their band gap evolves as a function of size using anion photoelectron spectroscopy (PES). PES spectra of (TiO2)n– clusters for n = 1–10 have been obtained at 193 (6.424 eV) and 157 nm (7.866 eV). The high photon energy at 157 nm allows the band gap of the TiO2 clusters to be clearly revealed up to n = 10. The band gap is observed to be strongly size-dependent for n < 7, but it rapidly approaches the bulk limit at n = 7 and remains constant up to n = 10. All PES features are observed to be very broad, suggesting large geometry changes between the anions and the neutral clusters due to the localized nature of the extra electron in the anions. The measured electron affinities and the energy gaps are compared with available theoretical calculations. The extra electron in the (TiO2)n– clusters for n > 1 appears to be localized in a tricoodinated Ti atom, creating a single Ti3+ site and making these clusters ideal molecular models for mechanistic understanding of TiO2 surface defects and photocatalytic properties.

Zhai, Hua-jin; Wang, Lai S.

2007-03-14

286

Direct band gap wurtzite gallium phosphide nanowires.  

PubMed

The main challenge for light-emitting diodes is to increase the efficiency in the green part of the spectrum. Gallium phosphide (GaP) with the normal cubic crystal structure has an indirect band gap, which severely limits the green emission efficiency. Band structure calculations have predicted a direct band gap for wurtzite GaP. Here, we report the fabrication of GaP nanowires with pure hexagonal crystal structure and demonstrate the direct nature of the band gap. We observe strong photoluminescence at a wavelength of 594 nm with short lifetime, typical for a direct band gap. Furthermore, by incorporation of aluminum or arsenic in the GaP nanowires, the emitted wavelength is tuned across an important range of the visible light spectrum (555-690 nm). This approach of crystal structure engineering enables new pathways to tailor materials properties enhancing the functionality. PMID:23464761

Assali, S; Zardo, I; Plissard, S; Kriegner, D; Verheijen, M A; Bauer, G; Meijerink, A; Belabbes, A; Bechstedt, F; Haverkort, J E M; Bakkers, E P A M

2013-03-18

287

Direct Band Gap Wurtzite Gallium Phosphide Nanowires  

PubMed Central

The main challenge for light-emitting diodes is to increase the efficiency in the green part of the spectrum. Gallium phosphide (GaP) with the normal cubic crystal structure has an indirect band gap, which severely limits the green emission efficiency. Band structure calculations have predicted a direct band gap for wurtzite GaP. Here, we report the fabrication of GaP nanowires with pure hexagonal crystal structure and demonstrate the direct nature of the band gap. We observe strong photoluminescence at a wavelength of 594 nm with short lifetime, typical for a direct band gap. Furthermore, by incorporation of aluminum or arsenic in the GaP nanowires, the emitted wavelength is tuned across an important range of the visible light spectrum (555–690 nm). This approach of crystal structure engineering enables new pathways to tailor materials properties enhancing the functionality.

2013-01-01

288

30 CFR 57.6603 - Air gap.  

Code of Federal Regulations, 2013 CFR

...NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Explosives Extraneous Electricity-Surface and Underground § 57.6603 Air gap. At least a 15-foot air gap shall be provided between the...

2013-07-01

289

Gap detection in the starling ( Sturnus vulgaris )  

Microsoft Academic Search

Gap-detection thresholds of single units were determined from auditory forebrain neurons of the awake starling. Nine different response types were statistically defined from the discharge pattern to a 400 ms broadband noise stimulus. The gap stimuli consisted of two broadband noise bursts which were separated by a gap ranging from 0.4 to 204.8 ms duration. The median minimumdetectable gap for

Elisabeth Buchfellner; Hans-Joachim Leppelsack; Georg M. Klump; Udo Häusler

1989-01-01

290

Once upon anion: a tale of photodetachment.  

PubMed

This contribution is very much a personal history of a journey through the wonderful world of anion chemistry, and a tale of how advances in laser technologies, theoretical methods, and computational capabilities continuously enabled advances in our understanding. It is a story of the excitement and joy that come from the opportunity to add to the fabric of science, and to do so by working as a group of excited explorers with common goals. The participants in this journey include me, my students and postdoctoral associates, my collaborators, and our many generous colleagues. It all happened, in the words of the Beatles, "with a little help from my friends." Actually, it was so much more than a little help! PMID:23216379

Lineberger, W Carl

2012-12-03

291

Once upon Anion: A Tale of Photodetachment  

NASA Astrophysics Data System (ADS)

This contribution is very much a personal history of a journey through the wonderful world of anion chemistry, and a tale of how advances in laser technologies, theoretical methods, and computational capabilities continuously enabled advances in our understanding. It is a story of the excitement and joy that come from the opportunity to add to the fabric of science, and to do so by working as a group of excited explorers with common goals. The participants in this journey include me, my students and postdoctoral associates, my collaborators, and our many generous colleagues. It all happened, in the words of the Beatles, “with a little help from my friends.” Actually, it was so much more than a little help!

Lineberger, W. Carl

2013-04-01

292

Poly(phenylene)-based anion exchange membrane  

DOEpatents

A poly(phenylene) compound of copolymers that can be prepared with either random or multiblock structures where a first polymer has a repeat unit with a structure of four sequentially connected phenyl rings with a total of 2 pendant phenyl groups and 4 pendant tolyl groups and the second polymer has a repeat unit with a structure of four sequentially connected phenyl rings with a total of 6 pendant phenyl groups. The second polymer has chemical groups attached to some of the pendant phenyl groups selected from CH.sub.3, CH.sub.2Br, and CH.sub.2N(CH.sub.3).sub.3Br groups. When at least one group is CH.sub.2N(CH.sub.3).sub.3Br, the material functions as an anion exchange membrane.

Hibbs, Michael (Albuquerque, NM); Cornelius, Christopher J. (Albuquerque, NM); Fujimoto, Cy H. (Albuquerque, NM)

2011-02-15

293

Simulations of zwitterionic and anionic phospholipid monolayers.  

PubMed Central

Results of atomistic molecular dynamics simulations of dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylglycerol monolayers at the air/water interface are presented. Dipalmitoylphosphatidylcholine is zwitterionic and dipalmitoylphosphatidylglycerol is anionic at physiological pH. NaCl and CaCl2 water subphases are simulated. The simulations are carried out at different surface densities, and a simulation cell geometry is chosen that greatly facilitates the investigation of phospholipid monolayer properties. Ensemble average monolayer properties calculated from simulation are in agreement with experimental measurements. The dependence of the properties of the monolayers on the surface density, the type of the headgroup, and the ionic environment are explained in terms of atomistically detailed pair distribution functions and electron density profiles, demonstrating the strength of simulations in investigating complex, multicomponent systems of biological importance.

Kaznessis, Yiannis N; Kim, Sangtae; Larson, Ronald G

2002-01-01

294

Living anionic polymerization using a microfluidic reactor  

SciTech Connect

Living anionic polymerizations were conducted within aluminum-polyimide microfluidic devices. Polymerizations of styrene in cyclohexane were carried out at various conditions, including elevated temperature (60 °C) and high monomer concentration (42%, by volume). The reactions were safely maintained at a controlled temperature at all points in the reactor. Conducting these reactions in a batch reactor results in uncontrolled heat generation with potentially dangerous rises in pressure. Moreover, the microfluidic nature of these devices allows for flexible 2D designing of the flow channel. Four flow designs were examined (straight, periodically pinched, obtuse zigzag, and acute zigzag channels). The ability to use the channel pattern to increase the level of mixing throughout the reactor was evaluated. When moderately high molecular mass polymers with increased viscosity were made, the patterned channels produced polymers with narrower PDI, indicating that passive mixing arising from the channel design is improving the reaction conditions.

Iida, Kazunori; Chastek, Thomas Q.; Beers, Kathryn L.; Cavicchi, Kevin A.; Chun, Jaehun; Fasolka, Michael J.

2009-02-01

295

The Rotational Spectrum of the NCO- Anion  

NASA Astrophysics Data System (ADS)

The rotational spectrum of the negative molecular ion NCO- has been observed both in a supersonic molecular beam and in a low-pressure glow discharge. The identification is ironclad because of the previous infrared detection of NCO-, the presence of well-resolved nitrogen quadrupole hyperfine structure, and the observation of nine harmonically related transitions in the millimeter band. The spectroscopic constants B and D are three orders of magnitude more accurate than those derived from the earlier IR measurements, and the theoretical eQq is in good agreement with that measured. The entire rotational spectrum can now be calculated well into the THz region to 1 km s-1 in equivalent radial velocity or better. NCO- is an excellent candidate for radio astronomical detection because of its high stability, polarity, and favorable partition function. The fairly high concentration of NCO- in our laboratory source implies that other molecular anions containing the NCO group may be detectable in the radio band.

Lattanzi, V.; Gottlieb, C. A.; Thaddeus, P.; Thorwirth, S.; McCarthy, M. C.

2010-09-01

296

Advanced polymer chemistry of organometallic anions  

SciTech Connect

This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of the project was to prepare and characterize new polymers incorporating cobalt dicarbollide. Specific goals were to prepare polymerizable cobalt dicarbollide monomers using the nucleophilic substitution route discovered in laboratories and to establish the reaction conditions required to form polymers from these complexes. This one-year project resulted in two publications (in press), and provided the foundation for further investigations into polymer synthesis and characterization using cobalt dicarbollide and other metallocarboranes. Interest in synthesizing organometallic polymers containing the cobalt bis(dicarbollide) anion is motivated by their possible application as cation exchange materials for the remediation of cesium-137 and strontium-90 from nuclear wastes.

Chamberlin, R.M.; Abney, K.D. [Los Alamos National Lab., NM (United States); Balaich, G.J.; Fino, S.A. [Air Force Academy, CO (United States)

1997-11-01

297

Band gap engineering in BiNbO{sub 4} for visible-light photocatalysis  

SciTech Connect

We have investigated the electronic structure of anionic mono- (S, N, and C) and co-doping (N-N, C-N, S-C, and S-N) on BiNbO{sub 4} for the visible-light photocatalysis. The maximum band gap reduction of pure BiNbO{sub 4} is possible with the (C-S) co-doping and minimum with N mono-doping. The calculated binding energies show that the co-doped systems are more stable than their mono-doped counterparts. Our optical absorption curves indicate that the mono- (C) and co-anionic doped (N-N and C-S) BiNbO{sub 4} systems are promising materials for visible light photocatalysis.

Wang, B. C. [Department of Materials Science and Engineering, Royal Institute of Technology (KTH), S-100 44 Stockholm (Sweden); Nisar, J.; Pathak, B. [Department of Physics and Astronomy, Box 530, Uppsala University, S-751 21 Uppsala (Sweden); Kang, T. W. [QSRC, Department of Physics, Dongguk University, Seoul 100-715 (Korea, Republic of); Ahuja, R. [Department of Materials Science and Engineering, Royal Institute of Technology (KTH), S-100 44 Stockholm (Sweden); Department of Physics and Astronomy, Box 530, Uppsala University, S-751 21 Uppsala (Sweden)

2012-04-30

298

Gender gap index in Spain by regions  

Microsoft Academic Search

Every year, the World Economic Forum publishes the World Gender Gap Report mainly based on the results of the Global Gender Gap Index (GGGI) computed by country. This index is made out of four subindexes to capture the magnitude of the gender gap in 4 areas: educational attainment, economic participation and opportunity, political empowerment, and health and survival; its methodology

Teresa Corbella i Domenech; Misericòrdia Domingo Vernis

2010-01-01

299

The energy band gap of cadmium sulphide  

Microsoft Academic Search

The energy band gap of cadmium sulphide has been determined for the bulk specimen and films prepared by thermal evaporation on glass substrates in vacuum. The energy band gap of the specimens were deduced from their temperature variation of their resistance in the intrinsic range. The results reveal higher energy gaps in the films than in the bulk specimen. The

F. Boakye; D. Nusenu

1997-01-01

300

Narrow band gap amorphous silicon semiconductors  

Microsoft Academic Search

Disclosed is a narrow band gap amorphous silicon semiconductor comprising an alloy of amorphous silicon and a band gap narrowing element selected from the group consisting of Sn, Ge, and Pb, with an electron donor dopant selected from the group consisting of P, As, Sb, Bi and N. The process for producing the narrow band gap amorphous silicon semiconductor comprises

A. Madan; A. H. Mahan

1985-01-01

301

Gender wage gap in Vietnam 1993 - 98  

Microsoft Academic Search

This paper uses the Vietnam Living Standards Surveys 1992–93 and 1997–98 to examine changes in the gender wage gap. The intertemporal decomposition of Juhn et al. (1991) indicates that changes in observed variables, skill prices and wage inequality have tended to narrow the gap, but the gap effect has tended to widen it, with the net effect being one of

Amy Y. C. Liu

2003-01-01

302

Canada's Kyoto GHG emissions gap analysis  

Microsoft Academic Search

The paper describes the Canada's Kyoto GHG emissions gap analysis. It begins by reviewing carbon emission sources inventory, and Kyoto's gap. In the year 2003, Canada's GHG emissions were 24 % above 1990 reference level, and the gap between Canada's Kyoto commitment and total inventoried emissions is becoming more and more alarmingly large. In addition, the increases were exacerbated by

M. Benhaddadi; G. Olivier

2006-01-01

303

Calibration curves for some standard Gap Tests  

SciTech Connect

The relative shock sensitivities of explosive compositions are commonly assessed using a family of experiments that can be described by the generic term ''Gap Test.'' Gap tests include a donor charge, a test sample, and a spacer, or gap, between two explosives charges. The donor charge, gap material, and test dimensions are held constant within each different version of the gap test. The thickness of the gap is then varied to find the value at which 50% of the test samples will detonate. The gap tests measure the ease with a high-order detonation can be established in the test explosive, or the ''detonability,'' of the explosive. Test results are best reported in terms of the gap thickness at the 50% point. It is also useful to define the shock pressure transmitted into the test sample at the detonation threshold. This requires calibrating the gap test in terms of shock pressure in the gap as a function of the gap thickness. It also requires a knowledge of the shock Hugoniot of the sample explosive. We used the 2DE reactive hydrodynamic code with Forest Fire burn rates for the donor explosives to calculate calibration curves for several gap tests. The model calculations give pressure and particle velocity on the centerline of the experimental set-up and provide information about the curvature and pulse width of the shock wave. 10 refs., 1 fig.

Bowman, A.L.; Sommer, S.C.

1989-01-01

304

Drug transport by Organic Anion Transporters (OATs).  

PubMed

Common to all so far functionally characterized Organic Anion Transporters (OATs) is their broad substrate specificity and their ability to exchange extracellular against intracellular organic anions. Many OATs occur in renal proximal tubules, the site of active drug secretion. Exceptions are murine Oat6 (nasal epithelium), human OAT7 (liver), and rat Oat8 (renal collecting ducts). In human kidneys, OAT1, OAT2, and OAT3 are localized in the basolateral membrane, and OAT4, OAT10, and URAT1 in the apical cell membrane of proximal tubule cells, respectively. In rats and mice, Oat1 and Oat3 are located basolaterally, and Oat2, Oat5, Oat9, Oat10, and Urat1 apically. Several classes of drugs interact with human OAT1-3, including ACE inhibitors, angiotensin II receptor antagonists, diuretics, HMG CoA reductase inhibitors, ?-lactam antibiotics, antineoplastic and antiviral drugs, and uricosuric drugs. For most drugs, interaction was demonstrated in vitro by inhibition of OAT-mediated transport of model substrates; for some drugs, transport by OATs was directly proven. Based on IC?? values reported in the literature, OAT1 and OAT3 show comparable affinities for diuretics, cephalosporins, and nonsteroidal anti-inflammatory drugs whereas OAT2 has a lower affinity to most of these compounds. Drug-drug interactions at OAT1 and OAT3 may retard renal drug secretion and cause untoward effects. OAT4, OAT10, and URAT1 in the apical membrane contribute to proximal tubular urate absorption, and OAT10 to nicotinate absorption. OAT4 is in addition able to release drugs, e.g. diuretics, into the tubule lumen. PMID:22841915

Burckhardt, Gerhard

2012-07-25

305

Metabolic profiling.  

PubMed

The concept of chemical individuality was introduced by Garrod in 1908. Inheritance of Mendelian traits including disease states has finally reached a new level of understanding based on the modern principles of gene expression coupled with new insight into the metabolism of RNA species and protein. Over 300 different perturbations in metabolite profiles with their identifying alteration(s) in protein and/or gene structure and/or function have been identified in the past 100 years. With the realization in 1953 that the sentinel disease, phenylketonuria, can be effectively treated by nutritional manipulation tailored to the needs of each individual, we have essentially entered a new phase in metabolic medicine, namely that of nutritional therapeutics. The infant destined for a lifetime of cognitive and motoric handicaps may be rescued by the implementation of a nutritional prescription in early development. Patients with inherited defects that impact on intermediary metabolism need to receive nutritional therapy on an individualized basis. Metabolic profiling, i.e., the array of small molecules or analytes, as well as large macromolecules, measured with precision in body fluids or tissues, can be used to devise a nutritional therapeutic plan, as well as serve as endpoints to evaluate the biochemical efficacy of intervention. PMID:18626193

Berry, Gerard T

2008-01-01

306

Metabolic acidosis  

MedlinePLUS

Arterial blood gas Serum electrolytes Urine pH Arterial blood gas analysis or a serum electrolytes test (such as a basic metabolic panel) will confirm acidosis is present and determine ... test may be needed to determine the cause of the acidosis.

307

Metabolic Analysis  

NASA Astrophysics Data System (ADS)

Analysis of the metabolome with coverage of all of the possibly detectable components in the sample, rather than analysis of each individual metabolite at a given time, can be accomplished by metabolic analysis. Targeted and/or nontargeted approaches are applied as needed for particular experiments. Monitoring hundreds or more metabolites at a given time requires high-throughput and high-end techniques that enable screening for relative changes in, rather than absolute concentrations of, compounds within a wide dynamic range. Most of the analytical techniques useful for these purposes use GC or HPLC/UPLC separation modules coupled to a fast and accurate mass spectrometer. GC separations require chemical modification (derivatization) before analysis, and work efficiently for the small molecules. HPLC separations are better suited for the analysis of labile and nonvolatile polar and nonpolar compounds in their native form. Direct infusion and NMR-based techniques are mostly used for fingerprinting and snap phenotyping, where applicable. Discovery and validation of metabolic biomarkers are exciting and promising opportunities offered by metabolic analysis applied to biological and biomedical experiments. We have demonstrated that GC-TOF-MS, HPLC/UPLC-RP-MS and HILIC-LC-MS techniques used for metabolic analysis offer sufficient metabolome mapping providing researchers with confident data for subsequent multivariate analysis and data mining.

Tolstikov, Vladimir V.

308

Metabolic cardiomyopathies  

PubMed Central

The energy needed by cardiac muscle to maintain proper function is supplied by adenosine Ariphosphate primarily (ATP) production through breakdown of fatty acids. Metabolic cardiomyopathies can be caused by disturbances in metabolism, for example diabetes mellitus, hypertrophy and heart failure or alcoholic cardiomyopathy. Deficiency in enzymes of the mitochondrial ?-oxidation show a varying degree of cardiac manifestation. Aberrations of mitochondrial DNA lead to a wide variety of cardiac disorders, without any obvious correlation between genotype and phenotype. A completely different pathogenetic model comprises cardiac manifestation of systemic metabolic diseases caused by deficiencies of various enzymes in a variety of metabolic pathways. Examples of these disorders are glycogen storage diseases (e.g. glycogenosis type II and III), lysosomal storage diseases (e.g. Niemann-Pick disease, Gaucher disease, I-cell disease, various types of mucopolysaccharidoses, GM1 gangliosidosis, galactosialidosis, carbohydrate–deficient glycoprotein syndromes and Sandhoff's disease). There are some systemic diseases which can also affect the heart, for example triosephosphate isomerase deficiency, hereditary haemochromatosis, CD 36 defect or propionic acidaemia.

Guertl, Barbara; Noehammer, Christa; Hoefler, Gerald

2000-01-01

309

Irsogladine maleate influences the response of gap junctional intercellular communication and IL8 of human gingival epithelial cells following periodontopathogenic bacterial challenge  

Microsoft Academic Search

Gingival epithelial cells first encounter periodontopathogenic bacteria and their metabolic products to produce inflammatory cytokines. Gap junctional intercellular communication (GJIC) is thought to play a critical role in cellular coordination in tissue homeostasis. Gap junctions are structured by connexins (CXs). GJIC response of gingival epithelial cells to the bacteria may be involved in the initiation of periodontal disease. Irsogladine maleate

Yuushi Uchida; Hideki Shiba; Hitoshi Komatsuzawa; Chikara Hirono; Arata Ashikaga; Tsuyoshi Fujita; Hiroyuki Kawaguchi; Motoyuki Sugai; Yoshiki Shiba; Hidemi Kurihara

2005-01-01

310

Intensification of Gold Sorption by Anion Exchange Resins  

Microsoft Academic Search

Gold extraction technology based on anion exchange resins with mixed basicity, commonly used in former soviet countries, includes a complicated and expensive process of resin regeneration and gold stripping by thiocarbamide solution. Satisfactory sorption properties of weak base anion exchange resin at pH 6–8 and low cost of metal stripping by sodium hydroxide solution have aroused considerable interest in these

V. V. AMBAROV; N. O. NIZHEGORODTSEVS

1995-01-01

311

Photodetachment Spectra of Deprotonated Fluorescent Protein Chromophore Anions.  

PubMed

Isolated model anion chromophores of the green and cyan fluorescent proteins were generated in an electrospray ion source, and their photodetachment spectra were recorded using photoelectron imaging. Vertical photodetachment energies of 2.85(10) and 4.08(10) eV have been measured for the model green fluorescent protein chromophore anion, corresponding to photodetachment from the ground electronic state of the anion to the ground and first excited electronic states of the radical, respectively. For the model cyan fluorescent protein chromophore anion, vertical photodetachment energies of 2.88(10) and 3.96(10) eV have been measured, corresponding to detachment from the ground electronic state of the anion to the ground and first excited electronic states of the neutral radical, respectively. We also find evidence suggesting that autoionization of electronically excited states of the chromophore anions competes with direct photodetachment. For comparison and to benchmark our measurements, the vertical photodetachment energies of deprotonated phenol and indole anions have also been recorded and presented. Quantum chemistry calculations support our assignments. We discuss our results in the context of the isolated protein chromophore anions acting as electron donors, one of their potential biological functions. PMID:22738202

Mooney, Ciarán R S; Sanz, M Eugenia; McKay, Adam R; Fitzmaurice, Richard J; Aliev, Abil E; Caddick, Stephen; Fielding, Helen H

2012-07-19

312

Comparison of anion removal capacities of Octolig® and Cuprilig  

Microsoft Academic Search

Mixtures of sodium salts of phosphate, arsenate, and fluoride were used in chromatography and batch experiments to compare the capacity of two immobilized ligands (IMLIGs) to remove these anions: Octolig® and its copper (II)-based metallolig, Cuprilig. The focus of this study was twofold. First, to find out which material, Octolig® or Cuprilig, would remove these anions most effectively; and secondly

Dean F. Martin; Douglas M. Franz

2011-01-01

313

Vertical detachment energies of anionic thymidine: Microhydration effects  

Microsoft Academic Search

Density functional theory has been employed to investigate microhydration effects on the vertical detachment energy (VDE) of the thymidine anion by considering the various structures of its monohydrates. Structures were located using a random searching procedure. Among 14 distinct structures of the anionic thymidine monohydrate, the low-energy structures, in general, have the water molecule bound to the thymine base unit.

Sunghwan Kim; Henry F. Schaefer

2010-01-01

314

Assignment of the optical spectra of metal phthalocyanine anions  

SciTech Connect

Magnetic circular dichroism (MCD) spectroscopy was used to create a general band assignment scheme for main group and transition metal phthalocyanine anion species. The complexity of the overlapping absorption spectra of metal phthalocyanine anion species has been troublesome when creating models of the electronic structure of the phthalocyanine ring. The ZINDO program was used for molecular orbital calculations. 56 refs., 14 figs., 5 tabs.

Mack, J.; Stillman, M.J. [Univ. of Western Ontario, London (Canada)

1997-01-29

315

Process for removing sulfate anions from waste water  

Microsoft Academic Search

A liquid emulsion membrane process for removing sulfate anions from waste water is disclosed. The liquid emulsion membrane process includes the steps of: (a) providing a liquid emulsion formed from an aqueous strip solution and an organic phase that contains an extractant capable of removing sulfate anions from waste water; (b) dispersing the liquid emulsion in globule form into a

David N. Nilsen; Gloria J. Galvan; Gary L. Hundley; John B. Wright

1997-01-01

316

Anion modulation of the slowly activating vacuolar channel.  

PubMed

This study addresses the permeability and modulation by anions of the slowly-activating vacuolar (SV) channel in the tonoplast of Mesembryanthemum crystallinum. Although we conclude that the M. crystallinum SV channel is impermeable to anions, the anion species at the cytosolic side of the membrane clearly affects the channel. We discuss two types of modulation, both consistent with a single binding site for anions at the cytosolic face of the channel. The first effect is related to the conducting properties of SV. When the site is occupied, the bound anion exerts an effect on the Ca2+ and Na+ fluxes through the channel. Because the Stokes-diameter of both ion species is different, both fluxes are not influenced to the same extent. This differential effect on the permeation of both ion species is reflected in a permeability ratio Ca2+ over Na+ (P(Ca)/P(Na)) that depends on the identity of the anion species. The second type of modulation deals with the activation of the channel by anions. Previous studies revealed that a low level of cytosolic Cl- inactivates SV (Pantoja, Dainty & Blumwald, 1992a). We critically evaluated reported effects of anions on the whole-vacuole SV current. Given that cytosolic Ca2+ and Cl- both modulate SV, we conclude that both levels of regulation show some kind of interaction. High cytosolic Ca2+ can overrule the inactivation caused by low cytosolic Cl-. PMID:11562795

Miedema, H; Pantoja, O

2001-09-15

317

Interaction between biphenols and anions: selective receptor for dihydrogenphosphate.  

PubMed

Biphenol was shown to bind dihydrogenphosphate (H2PO4-) selectively over various other anions (MeCO2-, Cl-, Br-, I-, NO3-, HSO4-). The highly selectivity of biphenol toward dihydrogenphosphate is explained in terms of the basicity and shape of the guest anion. PMID:16205002

Ito, Kazuaki; Nishiki, Makoto; Ohba, Yoshihiro

2005-10-01

318

Molecular mapping of human band 3 anion transport regions  

Microsoft Academic Search

Band 3 is a ubiquitous membrane trans- port protein found in Golgi, mitochondrial, nuclear, and cell membranes. It is the most heavily used anion trans- port system in the body because it is responsible for CO, exchange in all tissues and organs and for acid-base balance. The anion transport regions are mapped along the band 3 molecule using synthetic peptides

MARGUERITE M. B. KAY

319

Design and synthesis of selective mesoporous anion traps  

SciTech Connect

Arsenic contamination of groundwater has recently commanded widespread public attention. Under many conditions, arsenic, and certain other environmentally relevant toxic metals such as chromium, exist in nature as oxyanions. Selective binding of anions is one of the most challenging problems in chemistry, biology, and materials and environmental science. In this paper the authors report the synthesis and use of metal-chelated ligands immobilized on mesoporous silica as novel anion binding materials. Nearly complete removal of arsenate and chromate has been achieved in the presence of competing anions for solutions containing more than 100 mg/L (ppm) toxic metal anions under a variety of conditions. Anion loading of more than 120 mg (anion)/g of adsorption materials is observed. A binding mechanism is also proposed on the basis of computer modeling. First, Cu(II) ions are bonded to ethylenediamine (EDA) ligands to form octahedral complexes on the surface of the mesoporous silica. This gives rise to positively charged hosts with 3-fold symmetry that match the geometry of tetrahedral anions. The anion binding involves initial electrosteric coordination, followed by displacement of one ligand and direct binding with the Cu(II) center.

Fryxell, G.E.; Liu, J.; Hauser, T.A.; Nie, Z.; Ferris, K.F.; Mattigod, S.; Gong, M.; Hallen, R.T. [Pacific Northwest National Lab., Richland, WA (United States)

1999-08-01

320

Infrared Predissociation Spectroscopy of H_2TAGGED Dicarboxylic Acid Anions  

Microsoft Academic Search

Singly charged dicarboxylic acid anions, studied in depth by Wang et al. offer insight into the role of ring strain and conformation on the formation of intramolecular hydrogen bonds. These shared proton bonds, common in proteins and polymer systems, can be crucial in secondary and tertiary structure formation. By tracking the infrared spectra of dicarboxylic acid anions as charge and

Arron B. Wolk; Michael Z. Kamrath; Christopher M. Leavitt; Mark A. Johnson

2011-01-01

321

Angiotensin II induces superoxide anion production by mesangial cells  

Microsoft Academic Search

Angiotensin II induces superoxide anion production by mesangial cells.BackgroundThe recognized role of angiotensin II (Ang II) in the pathogenesis of the progression of renal disease cannot be solely attributed to Ang II's hemodynamic effects. Indeed, growth stimulating signals driven by Ang II promote mesangial cell (MC) hypertrophy and extracellular matrix production, prominent features of progressive glomerular injury. Superoxide anion (O2?)

Edgar A Jaimes; Josep Maria Galceran; Leopoldo Raij

1998-01-01

322

Trifluoromethylsulfonyl derivatives of benzofuroxane and their anionic sigma-complexes  

SciTech Connect

Syntheses are reported for 4-nitro-6-trifluoromethylsulfonyl- and 4,6-bis(trifluoromethylsulfonyl)benzofuroxanes and their anionic sigma-complexes with hydroxide and methylate anions. In contrast to its 4,6-dinitro analog, 4,6-bis(trifluoromethylsulfonyl)benzofuroxane forms stable sigma-complexes with sodium acetate and sodium azide and has higher acidity by an order of magnitude.

Yagupol'skii, L.M.; Gogoman, I.V.; Shchupak, G.M.; Boiko, V.N.

1986-09-10

323

The oxidation of exogenously added organic anions by platelets facilitates maintenance of pH during their storage for transfusion at 22 degrees C.  

PubMed

Previous studies of platelet metabolism during the storage of platelet concentrates (PCs) at 22 degrees C for transfusion have shown high rates of both oxygen consumption and aerobic glycolysis with little oxidation of pyruvate produced by glycolysis. During storage in plasma, free fatty acids are major oxidative fuels. Glutamine is also present as a potential fuel but relatively little is metabolized beyond glutamate. In synthetic media, acetate is oxidized and provides a poorly understood buffering function. In the current work, acetate and pyruvate (6 to 25 mmol/L, sometimes with their 14-C-labeled counterparts) were added to PCs stored in plasma. They were both vigorously metabolized, predominantly to CO2 (0.51 +/- 0.08 and 0.31 +/- 0.06 mmol/d/10(12) platelets for acetate and pyruvate, respectively). The metabolism of these exogenous substrates was associated with significantly increased oxygen consumption and decreased glucose consumption, fatty acid oxidation, and bicarbonate utilization for buffering. In a more limited number of studies, similar findings were observed with addition of beta-hydroxy-butyrate. Superior maintenance of pH in the presence of these additives could be attributed to the fact that the metabolism of an organic anion requires that a proton be brought with the anion into the metabolic pathway, thus providing an alkalinizing effect. Pyruvate (but not acetate) also stimulated the metabolism of glutamate. Studies with 14-C-labeled glucose suggested significant activity of the hexose-monophosphate shunt during PC storage and confirmed that little, if any, pyruvate derived from glucose was fully oxidized. Taken together, the results provide a relatively complete picture of the pathways of energy metabolism used by platelets during PC storage and suggest a strategy by which organic anions such as acetate can be used to improve the results of such storage. PMID:7703496

Murphy, S

1995-04-01

324

Adsorptive removal of anionic dye by inorganic–organic hybrid anion-exchange membranes  

Microsoft Academic Search

Anion-exchange membranes with quaternary ammonium groups were prepared by coating a precursor with secondary amino groups (the product of N-[3-(trimethoxysilyl)propyl] ethylene diamine and 3-(triethoxysilyl)propyl isocyanate) on porous glass fiber membranes and further treated with bromoethane. The precursor coating and bromoethane treatment have been proved successful by membrane characterization such as Fourier-transform infrared (FTIR) spectrum, scanning electron microscopy (SEM) photo, contact

Hsin-Chieh Chiu; Chia-Hung Liu; Shiow-Ching Chen; Shing-Yi Suen

2009-01-01

325

Release episodes at the periphery of gaps: a modeling assessment of gap impact extent  

Microsoft Academic Search

Gaps are recognized as important features of temperate forest dynamics and have been extensively studied in the last decades. Their definition has progressively evolved from the simplistic physical projection of the canopy open - ing to a more resource-based and functional approach (extended and species extended gaps). However, to truly define gap extent, the peripheral impact of gaps on the

André Ménard; Patrick Dubé; André Bouchard; Danielle J. Marceau

2002-01-01

326

AT Base Pair Anions vs. (9-methyl-A)(1-methyl-T) Base Pair Anions  

SciTech Connect

The anionic base pairs of adenine and thymine, (AT)-, and 9-methyladenine and 1-methylthymine, (MAMT)-, have been investigated both theoretically and experimentally in a complementary, synergistic study. Calculations on (AT)- found that it had undergone a barrier-free proton transfer (BFPT) similar to that seen in other dimer anion systems and that its structural configuration that was neither Watson-Crick (WC) nor Hoogsteen (HS). The vertical detachment energy (VDE) of (AT)- was determined by anion photoelectron spectroscopy and found to be in agreement with the VDE value predicted by theory for the BFPT mechanism. An AT pair in DNA is structurally immobilized into the WC configuration, in part, by being bonded to the sugars of the double helix. This circumstance was mimicked by methylating the sites on both A and T where these sugars would have been tied, viz., 9-methyladenine and 1-methylthymine. Calculations found no BFPT in (MAMT)- and a resulting (MAMT)- configuration that wa s either HS or WC, with the configurations differing in stability by ca. 2 kcal/mol. The photoelectron spectrum of (MAMT)- occurred at a completely different electron binding energy than had (AT)-. Moreover, the VDE value of (MAMT)- was in agreement with that predicted by theory. The configuration of (MAMT)- and its lack of electron-induced proton transfer are inter-related. While there may be other pathways for electron-induced damage, BFPT in the WC/HS configurations of (AT)- is not feasible.

Radisic, Dunja; Bowen, Kit H.; Dabkowska, Iwona; Storoniak, Piotr; Rak, Janusz; Gutowski, Maciej S.

2005-05-04

327

The Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance  

SciTech Connect

Work at carried out at ORNL since the inception of the project has served to demonstrate that the calix[4]pyrroles from the co-P.I.'s laboratory at the Univ. of Texas strongly enhance the extraction of sulfate by tricaprylmethylammonium nitrate or chloride in the presence of excess nitrate and chloride. Similar results were found in the case of the tetraamide macrocycles synthesized in the Bowman-James laboratory (Univ. of Kansas). Effort at the Univ. of Texas thus focused on generating new pyrrole-amide macrocycles that might combine the most favorable aspects of the calixpyrroles and the tetraamides. This culminated in the synthesis of several new receptors, which provided a ''matched set'' from whence insights into anion recognition could be inferred. As can be inferred from the data summarized in Table 1, small adjustments in the structure allow for a fine-tuning of the anion binding properties in favor of sulfate recognition, or in the case of injudicious modifications, selectivities that favor completely different classes of anionic substrates.

Sessler, Jonathan L.

2005-06-01

328

AT base pair anions versus (9-methyl-A)(1-methyl-T) base pair anions.  

PubMed

The anionic base pairs of adenine and thymine, (AT)(-), and 9-methyladenine and 1-methylthymine, (MAMT)(-), have been investigated both theoretically and experimentally in a complementary, synergistic study. Calculations on (AT)(-) found that it had undergone a barrier-free proton transfer (BFPT) similar to that seen in other dimer anion systems and that its structural configuration was neither Watson-Crick (WC) nor Hoogsteen (HS). The vertical detachment energy (VDE) of (AT)(-) was determined by anion photoelectron spectroscopy and found to be in agreement with the VDE value predicted by theory for the BFPT mechanism. An AT pair in DNA is structurally immobilized into the WC configuration, in part, by being bonded to the sugars of the double helix. This circumstance was mimicked by methylating the sites on both A and T where these sugars would have been tied, viz., 9-methyladenine and 1-methylthymine. Calculations found no BFPT in (MAMT)(-) and a resulting (MAMT)(-) configuration that was either HS or WC, with the configurations differing in stability by ca. 2 kcal/mol. The photoelectron spectrum of (MAMT)(-) occurred at a completely different electron binding energy than had (AT)(-). Moreover, the VDE value of (MAMT)(-) was in agreement with that predicted by theory. The configuration of (MAMT)(-) and its lack of electron-induced proton transfer are inter-related. While there may be other pathways for electron-induced DNA alterations, BFPT in the WC/HS configurations of (AT)(-) is not feasible. PMID:15853352

Radisic, Dunja; Bowen, Kit H; Dabkowska, Iwona; Storoniak, Piotr; Rak, Janusz; Gutowski, Maciej

2005-05-01

329

Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance  

SciTech Connect

The major thrust of this project led by the University of Kansas (Prof. Kristin Bowman-Jones) entails the exploration of the principles of recognition and separation of sulfate by the design, synthesis, and testing of novel sulfate extractants. A key science need for the cleanup of tank wastes at Hanford has been identified in developing methods to separate those bulk waste components that have low solubilities in borosilicate glass. Sulfate has been identified as a particularly difficult and expensive problem in that its concentration in the waste is relatively high, its solubility in glass is especially low, and it interferes with the performance of both vitrification equipment and the glass waste form. The new extractants will be synthesized by the University of Kansas and the University of Texas, Austin. Oak Ridge National Laboratory (ORNL) is subjecting the new extractants to experiments that will determine their properties and effectiveness in separating sulfate from the major competing anions in the waste, especially nitrate. Such experiments will entail primarily liquid-liquid extraction. Current efforts focus on exciting new systems in which the anion receptors act as synergists for anion exchange.

Moyer, Bruce a.; Bostick, Debra A.; Fowler, Christopher J.; Kang, Hyun-Ah; Ruas, Alexandre; Delmau, Laetitia H.; Haverlock, Tamara J.; Llinares, Jose M.; Hossain, Alamgir; Kang, S. O.; Bowman-James, Kristin; Shriver, James A.; Marquez, Manuel; Sessler, Jonathan L.

2005-09-22

330

Rigid oligonaphthalenediimide rods as transmembrane anion-pi slides.  

PubMed

We report the design, synthesis, and evaluation of rigid oligonaphthalenediimide (O-NDI) rods that are expected to act as transmembrane anion-pi slides. Studies in fluorogenic large unilamellar egg yolk phosphatidylcholine vesicles reveal that rigid O-NDI rods mediate anion-selective transport with a rare halide VI selectivity sequence (Cl- > F- > Br- > I-). This and decreasing activity, selectivity, and halide sequence with increasing positive charge of the rod termini support the occurrence of anion-pi interactions. A strong anomalous mole fraction effect in Cl-/I- mixtures is in agreement with the existence of multiple active sites along the anion-pi slide and multi-anion hopping as a mechanism of transport. The strong inverted NDI quadruple moment found by DFT calculations is in excellent agreement with these results. PMID:17105272

Gorteau, Virginie; Bollot, Guillaume; Mareda, Jiri; Perez-Velasco, Alejandro; Matile, Stefan

2006-11-22

331

Superoxide Anion Production by Human Neutrophils Activated by Trichomonas vaginalis  

PubMed Central

Neutrophils are the predominant inflammatory cells found in vaginal discharges of patients infected with Trichomonas vaginalis. In this study, we examined superoxide anion (O2.-) production by neutrophils activated by T. vaginalis. Human neutrophils produced superoxide anions when stimulated with either a lysate of T. vaginalis, its membrane component (MC), or excretory-secretory product (ESP). To assess the role of trichomonad protease in production of superoxide anions by neutrophils, T. vaginalis lysate, ESP, and MC were each pretreated with a protease inhibitor cocktail before incubation with neutrophils. Superoxide anion production was significantly decreased by this treatment. Trichomonad growth was inhibited by preincubation with supernatants of neutrophils incubated for 3 hr with T. vaginalis lysate. Furthermore, myeloperoxidase (MPO) production by neutrophils was stimulated by live trichomonads. These results indicate that the production of superoxide anions and MPO by neutrophils stimulated with T. vaginalis may be a part of defense mechanisms of neutrophils in trichomoniasis.

Song, Hyun-Ouk

2013-01-01

332

Transmembrane anion transport mediated by halogen-bond donors.  

PubMed

In biology and chemistry, the transport of anions across lipid bilayer membranes is usually achieved by sophisticated supramolecular architectures. Significant size reduction of transporters is hampered by the intrinsically hydrophilic nature of typical anion-binding functionalities, hydrogen-bond donors or cations. To maximize the atom efficiency of anion transport, the hydrophobic nature, directionality, and strength of halogen bonds seem promising. Unlike the ubiquitous, structurally similar hydrogen bonds, halogen bonds have not been explored for anion transport. Here we report that transport across lipid bilayers can be achieved with small perfluorinated molecules that are equipped with strong halogen-bond donors. Transport is observed with trifluoroiodomethane (boiling point=-22 °C); that is, it acts as a 'single-carbon' transporter. Contrary to the destructive action of small-molecule detergents, transport with halogen bonds is leakage-free, cooperative, non-ohmic and highly selective, with anion/cation permeability ratios <37. PMID:22713747

Jentzsch, Andreas Vargas; Emery, Daniel; Mareda, Jiri; Nayak, Susanta K; Metrangolo, Pierangelo; Resnati, Giuseppe; Sakai, Naomi; Matile, Stefan

2012-06-19

333

Selectivity Control in Synergistic Liquid-Liquid Anion Exchange of Univalent Anions via Structure-Specific Cooperativity between Quaternary Ammonium Cations and Anion Receptors  

SciTech Connect

Two anion receptors enhance liquid-liquid anion exchange when added to quaternary alkylammonium chloride anion exchangers, but with a striking dependence upon the structure of the alkylammonium cation. Two anion receptors were investigated, meso-octamethylcalix[4]pyrrole (C4P) and the bisthiourea tweezer 1,1'-(propane-1,3-diyl)bis(3-(4-sec-butylphenyl)thiourea (BTU). C4P has the unique ability in its cone anion-binding conformation to accept an appropriately sized electropositive species in the resulting cup formed by its four electron-rich pyrrole groups, while BTU is not expected to be predisposed for a specific host-guest interaction with the quaternary ammonium cations. It was therefore hypothesized that synergism between C4P and methyltri(C8,10)alkylammonium chloride (Aliquat 336) would be uniquely pronounced owing to insertion of the methyl group of the Aliquat cation into the C4P cup, and we present herein data supporting this expectation. While synergism is comparatively weak for both exchangers with the BTU receptor, synergism between C4P and Aliquat 336 is indeed so strong that anion exchange prefers chloride over more extractable nitrate and trifluoroacetate, effectively overcoming the ubiquitous Hofmeister bias. A thermochemical analysis of synergistic anion exchange has been provided for the first time, unraveling the observed selectivity behavior and resulting in the estimation of binding constants for C4P with the ion pairs of A336+ with Cl , Br , OAcF3 , NO3 , and I . The uniquely strong positive cooperativity between A336 and C4P underscores the advantage of a supramolecular approach in the design of synergistic anion exchange systems.

Borman, Christopher J [ORNL; Bonnesen, Peter V [ORNL; Moyer, Bruce A [ORNL

2012-01-01

334

Interval timing with gaps: gap ambiguity as an alternative to temporal decay.  

PubMed

C. V. Buhusi, D. Perera, and W. H. Meck (2005) proposed a hypothesis of timing in rats to account for the results of experiments that have used the peak procedure with gaps. According to this hypothesis, the introduction of a gap causes the animal's memory for the pregap interval to passively decay (subjectively shorten) in direct proportion to the duration and salience of the gap. Thus, animals should pause with short, nonsalient gaps but should reset their clock with longer, salient gaps. The present authors suggest that the ambiguity of the gap (i.e., the similarity between the gap and the intertrial interval in both appearance and relative duration) causes the animal to actively reset the clock and prevents adequate assessments of the fate of timed intervals prior to the gap. Furthermore, when the intertrial interval is discriminable from the gap, the evidence suggests that timed intervals prior to the gap are not lost but are retained in memory. PMID:16248734

Zentall, Thomas R; Kaiser, Daren H

2005-10-01

335

Selectivity control in synergistic liquid-liquid anion exchange of univalent anions via structure-specific cooperativity between quaternary ammonium cations and anion receptors.  

PubMed

Two anion receptors enhance liquid-liquid anion exchange when added to quaternary alkylammonium chloride anion exchangers, but with a striking dependence on the structure of the alkylammonium cation that suggests a supramolecular cooperative effect. Two anion receptors were investigated, meso-octamethylcalix[4]pyrrole (C4P) and the bisthiourea tweezer 1,1'-(propane-1,3-diyl)bis(3-(4-sec-butylphenyl)thiourea (BTU). Whereas synergism is comparatively weak when either methyltri(C(8,10))alkylammonium chloride (Aliquat 336) or tetraheptylammonium chloride is used with the BTU receptor, synergism between C4P and Aliquat 336 is so pronounced that anion exchange prefers chloride over more extractable nitrate and trifluoroacetate, effectively overcoming the ubiquitous Hofmeister bias. A thermochemical analysis of synergistic anion exchange has been provided for the first time, resulting in the estimation of binding constants for C4P with the ion pairs of A336(+) with Cl(-), Br(-), OAc(F3)(-), NO(3)(-), and I(-). PMID:22931168

Borman, Christopher J; Bonnesen, Peter V; Moyer, Bruce A

2012-09-14

336

Electronic properties of doped gapped graphene  

NASA Astrophysics Data System (ADS)

One of the carbon atoms in each Bravais lattice unit cell of pristine graphene plane is substituted by a foreign atom leading to a band gap in the density of states of the system. Then, the gapped graphene is randomly doped by another impurity. The density of states, electronic heat capacity and electrical conductivity of the gapped and doped gapped graphene are investigated within random tight-binding Hamiltonian model and Green's function formalism. The results show that by presence of impurities in the gapped graphene the band gap moves towards lower (higher) values of energy when dopants act as acceptors (donors). The heat capacity decreases (increases) before (after) the Schottky anomaly as well. It is also found that the electrical conductivity of the doped gapped graphene reduces on all ranges of temperature.

Mousavi, Hamze

2013-04-01

337

Compact, low jitter, triggered spark gap  

SciTech Connect

High energy particle accelerators using compact, high gradient cavities will require small, highly reliable, triggered spark gaps. This paper will discuss the design and development of V/N triggered spark gaps operating from 520 kV to 1280 kV. Spark gap jitter of <3 ns has been obtained with trigger voltages of 60 kV. Capacitively balancing the trigger blade electrode, coupled with a trigger voltage rise time of 10 ns, produces three or more arcs across the main electrode gaps. A 2.3 ..cap omega.. injector using 12 parallel spark gaps operating at 1280 kV has been successfully tested. The total number of shots on this injector exceeds 700 without having to refurbish the gaps. A 0.44 ..cap omega.. accelerating cavity with 24 parallel spark gaps and operating at 520 kV charge voltage has also been tested.

Tucker, W.K.; Jones, E.E.; Franklin, T.L.; Bennett, L.F.; Weber, G.

1985-01-01

338

Zintl-phase compounds with SnSb4 tetrahedral anions: electronic structure and thermoelectric properties  

SciTech Connect

We report the investigation of Zintl-phase Na(K){sub 8}SnSb{sub 4} and related compounds that contain SnSb{sub 4} tetrahedral anions using first principles electronic structure, Boltzmann transport, and density functional phonon calculations. We find that these compounds are narrow-gap semiconductors and there is a combination of heavy and light bands at valence band edge, which may lead to a combination of high thermopower and reasonable conductivity. High values of the thermopower are found for p-type doping within the Boltzmann transport theory. Furthermore, these materials are expected to have low thermal conductivity due to their structures that consist of a network of weakly coupled SnSb{sub 4} clusters, which leads to low phonon frequencies. In particular, we find low-frequency optical phonons that should effectively scatter the heat-carrying acoustic phonons. These results are discussed in terms of the structure, which consists of anionic clusters. Based on the results, it is suggested that such compounds may represent a useful paradigm for finding new thermoelectric materials.

Zhang, Lijun [ORNL; Du, Mao-Hua [ORNL; Singh, David J [ORNL

2010-01-01

339

Multiphoton Localization and Propagating Quantum Gap Solitons in a Frequency Gap Medium  

NASA Astrophysics Data System (ADS)

The many-particle spectrum of an isotropic frequency gap medium doped with impurity resonance atoms is studied using the Bethe ansatz technique. The spectrum is shown to contain pairs of quantum correlated ``gap excitations'' and their heavy bound complexes (``gap solitons''), enabling the propagation of quantum information within the classically forbidden gap. In addition, multiparticle localization of the radiation and the medium polarization occurs when such a gap soliton is pinned to the impurity atom.

John, Sajeev; Rupasov, Valery I.

1997-08-01

340

Polluted environment and cold weather induce laying gaps in great tit and pied flycatcher.  

PubMed

We studied the occurrence of laying gaps in free-living populations of the pied flycatcher, Ficedula hypoleuca, and the great tit, Parus major, in a pollution gradient of a copper smelter in south-west Finland. Laying gaps were 2.8 times more common in F. hypoleuca than in P. major. The probability of laying gaps was highest in the heavily polluted zone and lowest in the unpolluted zone for both bird species. Cold weather at the time of laying increased the number of laying gaps in both species, but in P. major this effect was most pronounced in the heavily polluted environment. In the most heavily polluted environment the laying gaps were more likely to occur near the beginning of the laying sequence in both species. The laying gap probability increased with increasing laying date in P. major but not in F. hypoleuca. We suggest that the increased number of laying gaps in the polluted environment results from limited Ca availability and the interference of heavy metals with Ca metabolism in laying females. PMID:19784674

Eeva, Tapio; Lehikoinen, Esa

2009-09-26

341

[Surgical metabolism].  

PubMed

Trauma, operative interventions, infection and other disturbances of homeostasis lead to a uniform reaction of the body, namely release and activation of hormones and cytokines. Profound alterations of substrate flow result, with mobilization of energy stores and degradation of structural and functional proteins of vital organs like the gut mucosa. Due to these reactions the energy demands of the organs are met and energy-consuming synthesis of substrates is indicated. Clinically, hypermetabolism, hyperglycemia, lipolysis and increased urea production with negative nitrogen balance can be observed. The metabolic reactivity is reached by an increased substrate cycling. To avoid negative consequences such as organ dysfunction, a rational situation-adapted substrate supply is warranted as well as reduction of catabolic stimuli and stimulation of anabolic factors. The metabolic care of the surgical patient is still a basic and important task. PMID:9324431

Jauch, K W

1997-06-01

342

Metabolic Myopathies  

Microsoft Academic Search

We consider recent developments in disorders affecting three areas of metabolism: glycogen, fatty acids, and the mitochondrial\\u000a respiratory chain. Among the glycogenoses, new attention has been directed to defects of glycogen synthesis resulting in absence\\u000a rather than excess of muscle glycogen (“aglycogenosis”). These include defects of glycogen synthetase and defects of glycogenin,\\u000a the primer of glycogen synthesis. Considerable progress also

Salvatore DiMauro; Caterina Garone; Ali Naini

2010-01-01

343

Metabolic Syndrome  

Microsoft Academic Search

\\u000a Two separate statements published in the autumn of 2005 expressed diametrically opposed views as to the clinical utility of\\u000a “diagnosing” the metabolic syndrome (MetS). On the one hand (1), the American Heart Association (AHA) and the National Heart, Lung, and Blood Institute (NHLBI) firmly endorsed the need\\u000a to establish such a diagnostic category, and, with some minor modifications, utilized the

Gerald M. Reaven

344

ACTION OF SYNTHETIC DETERGENTS ON THE METABOLISM OF BACTERIA  

PubMed Central

A study of the effects of synthetic detergents and wetting agents on respiration and glycolysis of Gram-positive and Gram-negative microorganisms has led to the following conclusions. 1. All the cationic detergents studied are very effective inhibitors of bacterial metabolism at 1:3000 concentration, and several are equally active at 1:30,000. Few of the anionic detergents inhibit as effectively as the cationic compounds. 2. Gram-positive and Gram-negative microorganisms are equally sensitive to the action of the cationic detergents. On the other hand, all the anionic detergents included in our studies selectively inhibit the metabolism of Gram-positive microorganisms. 3. The inhibitory action of both types of detergents is influenced markedly by hydrogen ion concentration. Cationic detergents exhibit their maximum activity in the alkaline pH range, and the anionic, in the acid range. 4. Studies of homologous series of straight chain alkyl sulfates and sulfoacetates (C8 to C18) demonstrate that maximum inhibition is exerted by the 12, 14, and 16 carbon compounds (lauryl, myristyl, and cetyl). 5. It has been observed that three lauryl esters of amino acids are powerful inhibitors of bacterial metabolism. To our knowledge, the effects on bacterial metabolism of such cationic detergents (without the quaternary ammonium structure) have not been studied previously. Our results demonstrate that other cationic detergents can exhibit an inhibitory activity comparable to quaternary ammonium compounds. 6. Certain detergents stimulate bacterial metabolism at concentrations lower than the inhibiting values. This effect has been found more frequently among the anionic detergents.

Baker, Zelma; Harrison, R. W.; Miller, Benjamin F.

1941-01-01

345

Claudin-17 forms tight junction channels with distinct anion selectivity.  

PubMed

Barrier properties of tight junctions are determined by the claudin protein family. Many claudins seal this barrier, but others form paracellular channels. Among these, no claudins with general and clear-cut anion selectivity have yet been described, while for claudin-10a and claudin-4, only circumstantial or small anion selectivities have been shown. A claudin with unknown function and tissue distribution is claudin-17. We characterized claudin-17 by overexpression and knock-down in two renal cell lines. Overexpression in MDCK C7 cell layers caused a threefold increase in paracellular anion permeability and switched these cells from cation- to anion-selective. Knockdown in LLC-PK(1) cells indorsed the finding of claudin-17-based anion channels. Mutagenesis revealed that claudin-17 anion selectivity critically depends on a positive charge at position 65. Claudin-17 expression was found in two organs: marginal in brain but abundant in kidney, where expression was intense in proximal tubules and gradually decreased towards distal segments. As claudin-17 is predominantly expressed in proximal nephrons, which exhibit substantial, though molecularly not defined, paracellular chloride reabsorption, we suggest that claudin-17 has a unique physiological function in this process. In conclusion, claudin-17 forms channels within tight junctions with distinct anion preference. PMID:22402829

Krug, Susanne M; Günzel, Dorothee; Conrad, Marcel P; Rosenthal, Rita; Fromm, Anja; Amasheh, Salah; Schulzke, Jörg D; Fromm, Michael

2012-03-09

346

Gold-caged metal clusters with large HOMO-LUMO gap and high electron affinity.  

PubMed

We report a series of isoelectronic gold-caged metal clusters, M@Au14 (M = Zr, Hf), and anion clusters, M@Au14- (M = Sc, Y), all having a calculated HOMO-LUMO gap larger than the well-known tetrahedral cluster Au20-the 3D metal cluster with a very large measured HOMO-LUMO gap (1.77 eV). The clusters M@Au14 (M = Sc, Y) also exhibit a calculated electron affinity (EA) and vertical detachment energy (VDE) not only higher than the "superhalogen" icosahedral Al13 cluster but also possibly even higher than a Cl atom which has the highest (measured) elemental EA or VDE (3.61 eV). PMID:16277491

Gao, Yi; Bulusu, Satya; Zeng, Xiao Cheng

2005-11-16

347

Gaps in the GD-1 Star Stream  

NASA Astrophysics Data System (ADS)

GD-1 is a long, thin, Milky Way star stream that has readily visible density variations along its length. We quantify the locations, sizes, and statistical significance of the density structure, i.e., gaps, using a set of scaled filters. The shapes of the filters are based on the gaps that develop in simulations of dark matter sub-halos crossing a star stream. The high Galactic latitude 8.4 kpc long segment of GD-1 that we examine has 8 ± 3 gaps of 99% significance or greater, with the error estimated on the basis of tests of the gap-filtering technique. The cumulative distribution of gaps more than three times the width of the stream is in good agreement with predictions for dark matter sub-halo encounters with cold star streams. The number of gaps narrower than three times the width of the GD-1 stream falls well below the cold stream prediction which is taken into account for the gap creation rate integrated over all sizes. Simple warm stream simulations scaled to GD-1 show that the falloff in gaps is expected for sub-halos below a mass of 106 M ?. The GD-1 gaps requires 100 sub-halos >106 M ? within 30 kpc, the apocenter of GD-1 orbit. These results are consistent with LCDM sub-halo predictions but further improvements in stream signal-to-noise and gap modeling will be welcome.

Carlberg, R. G.; Grillmair, C. J.

2013-05-01

348

Redox cycling of radical anion metabolites of toxic chemicals and drugs and the Marcus Theory of electron transfer  

SciTech Connect

A wide variety of aromatic compounds are enzymatically reduced to form anion free radicals that generally contain one more electron than their parent compounds. In general, the electron donor is any of a wide variety of flavoenzymes. Once formed, these anion free radicals reduce molecular oxygen to superoxide and regenerate the parent compound unchanged. The net reaction is the oxidation of the flavoenzyme's coenzymes and the reduction of molecular oxygen. This catalytic behavior has been described as futile metabolism or redox cycling. Electron transfer theory is being applied to these reactions and, in some cases, has successfully correlated V{sub max} and K{sub m} with the reduction potentials of the aromatic compounds.

Mason, R.P. (National Institute of Environmental Health Sciences, Research Triangle Park, NC (USA))

1990-07-01

349

Superoxide anion radical scavenging property of catecholamines.  

PubMed

The direct effect of the four catecholamines (adrenaline, noradrenaline, dopamine and isoproterenol) on superoxide anion radicals (O2•) was investigated. The reaction between 18-crown-6-ether and potassium superoxide in dimethylsulfoxide was used as a source of O2•. The reactivity of catecholamines with O2• was examined using chemiluminescence, reduction of nitroblue tetrazolium and electron paramagnetic resonance spin-trapping techniques. 5,5-Dimethyl-1-pyrroline-N-oxide was included as the spin trap. The results showed that the four catecholamines were effective and efficient in inhibiting chemiluminescence accompanying the potassium superoxide/18-crown-6-ether system in a dose-dependent manner over the range 0.05-2 mM in the following order: adrenaline > noradrenaline > dopamine > isoproterenol, with, IC50 = 0.15 ± 0.02 mM 0.21 ± 0.03 mM, 0.27 ± 0.03 mM and 0.50 ± 0.04 mM, respectively. The catecholamines examined also exhibited a strong scavenging effect towards O2• when evaluated this property by the inhibition of nitroblue tetrazolium reduction (56-73% at 1 M concentration). A very similar capacity of O2• scavenging was monitored in the 5,5-dimethyl-1-pyrroline-N-oxide spin-trapping assay. The results suggest that catecholamines tested may involve a direct effect on scavenging O2- radicals. PMID:23319391

K?adna, Aleksandra; Berczy?ski, Pawe?; Kruk, Irena; Michalska, Teresa; Aboul-Enein, Hassan Y

2013-01-14

350

Anionic peroxidase production by Arnebia euchroma callus.  

PubMed

Arnebia euchroma callus, obtained from the root cell culture of an Iranian native specimen, has gained a doubling time of 63 H after regular subculturing on Linsmaier-Skoog (LS) medium containing sugar (50 g/L), 2,4-dichlorophenoxyacetic acid (10(-6) M), and kinetin (10(-5) M) under darkness at 25°C. Despite the observed somaclonal variations, peroxidase production by the A. euchroma calli has been stable over 4 years under the aforementioned conditions. Isoelectric focusing experiments revealed that the partially purified A. euchroma peroxidases (AePoxs) are mainly anionic with pI values of about 5.5 and 6.6. AePox reaches its optimal activity at 55°C and pH 7.5. Results of the various kinetic studies suggest that AePox belongs to the type III plant peroxidases with no activity for the oxidation of 3-indoleacetic acid, but seems to play a role in the lignin biosynthesis and H(2) O(2) regulation during the proliferation of the A. euchroma cells on LS medium. Comparing the biochemical properties of AePox with horseradish peroxidase and in view of the ease of solid cell culture, the A. euchroma callus could be considered as a source of plant peroxidase for some biotechnological applications. PMID:22172108

Farhadi, Sahar; Haghbeen, Kamahldin; Marefatjo, Mohammad-Javad; Hoor, Marjan Ghiyami; Zahiri, Hossein Shahbani; Rahimi, Karim

2011-10-31

351

Structures of medium sized tin cluster anions.  

PubMed

The structures of medium sized tin cluster anions Sn(n)(-) (n = 16-29) were determined by a combination of density functional theory, trapped ion electron diffraction and collision induced dissociation (CID). Mostly prolate structures were found with a structural motif based on only three repeatedly appearing subunit clusters, the Sn(7) pentagonal bipyramid, the Sn(9) tricapped trigonal prism and the Sn(10) bicapped tetragonal antiprism. Sn(16)(-) and Sn(17)(-) are composed of two face connected subunits. In Sn(18)(-)-Sn(20)(-) the subunits form cluster dimers. For Sn(21)(-)-Sn(23)(-) additional tin atoms are inserted between the building blocks. Sn(24)(-) and Sn(25)(-) are composed of a Sn(9) or Sn(10) connected to a Sn(15) subunit, which closely resembles the ground state of Sn(15)(-). Finally, in the larger clusters Sn(26)(-)-Sn(29)(-) additional bridging atoms again connect the building blocks. The CID experiments reveal fission as the main fragmentation channel for all investigated cluster sizes. This rather unexpected "pearl-chain" cluster growth mode is rationalized by the extraordinary stability of the building blocks. PMID:22071636

Wiesel, Anne; Drebov, Nedko; Rapps, Thomas; Ahlrichs, Reinhart; Schwarz, Ulrike; Kelting, Rebecca; Weis, Patrick; Kappes, Manfred M; Schooss, Detlef

2011-11-09

352

Neptunium Valence Chemistry in Anion Exchange Processing  

SciTech Connect

The current anion resin in use in HB-Line Phase II, Reillex{trademark} HPQ, was tested in the laboratory under expected plant conditions for Np processing and was found to load between 50 and 70 g Np per liter of resin. Losses varied from 0.2 to 15 percent depending on a number of parameters. Hydrazine in the feed at 0.02 to 0.05 M appeared to keep the Np from oxidizing and increasing the losses within four to seven days after the FS addition. Losses of up to three percent were observed five days after FS addition when hydrazine was not used in the feed, compared with 0.3 percent when the feed was loaded immediately after FS addition. Based on these test results the following processing conditions are recommended: (1) Feed conditions: 8 M HNO{sub 3}, 0.02 M hydrazine, 0.05 M excess FS, less than 5 days storage of solution after FS addition. (2) Wash conditions: 100 liters of 8 M HNO{sub 3}, no FS, no hydrazine. (3) Elution conditions: 0.17 M HNO{sub 3}, 0.05 M hydrazine, no FS. (4) Precipitation feed conditions: 0.03 M excess ascorbic acid, no additional hydrazine, no FS, precipitation within three days.

KYSER, EDWARD

2003-02-01

353

Macrocyclic hexaureas: synthesis, conformation, and anion binding.  

PubMed

Five macrocylic compounds XXXXXX, XXDXXD, XDXDXD, XDDXDD, and DDDDDD with 48-membered rings, in which six xanthene and/or diphenyl ether fragments are linked through six urea (-NH-C(O)-NH-) groups, have been synthesized. In the cyclization step, a linear diamine was allowed to react with the appropriate diisocyanate by using a [5+1] (i.e., "XDXDX+D" for XDXDXD), [4+2] (DDDDDD), or [3+3] (XDDXDD) procedure. Compounds XXXXXX and XXDXXD were prepared from two molecules of the dimeric amine XX and two molecules of the respective monomeric diisocyanate (X or D) in a [2+1+2+1] (or 2x[2+1]) reaction. The (nonoptimized) yields in the cyclization step ranged from 45 to 80%. The linear precursor diamines or diisocyanates were obtained by analogous condensation reactions by using partial protection with a tert-butoxycarbonyl group. All the macrocyclic compounds and synthetic intermediates were characterized by (1)H NMR and mass spectra. Three different crystal structures were obtained for XDDXDD, which show the molecule in a more or less strongly folded conformation determined by intramolecular hydrogen bonding. The interaction of the hexaureas with selected anions was studied by (1)H NMR spectroscopy and UV absorption spectrophotometry. PMID:19296486

Meshcheryakov, Denys; Böhmer, Volker; Bolte, Michael; Hubscher-Bruder, Véronique; Arnaud-Neu, Françoise

2009-01-01

354

Production of bulk chemicals via novel metabolic pathways in microorganisms.  

PubMed

Metabolic engineering has been playing important roles in developing high performance microorganisms capable of producing various chemicals and materials from renewable biomass in a sustainable manner. Synthetic and systems biology are also contributing significantly to the creation of novel pathways and the whole cell-wide optimization of metabolic performance, respectively. In order to expand the spectrum of chemicals that can be produced biotechnologically, it is necessary to broaden the metabolic capacities of microorganisms. Expanding the metabolic pathways for biosynthesizing the target chemicals requires not only the enumeration of a series of known enzymes, but also the identification of biochemical gaps whose corresponding enzymes might not actually exist in nature; this issue is the focus of this paper. First, pathway prediction tools, effectively combining reactions that lead to the production of a target chemical, are analyzed in terms of logics representing chemical information, and designing and ranking the proposed metabolic pathways. Then, several approaches for potentially filling in the gaps of the novel metabolic pathway are suggested along with relevant examples, including the use of promiscuous enzymes that flexibly utilize different substrates, design of novel enzymes for non-natural reactions, and exploration of hypothetical proteins. Finally, strain optimization by systems metabolic engineering in the context of novel metabolic pathways constructed is briefly described. It is hoped that this review paper will provide logical ways of efficiently utilizing 'big' biological data to design and develop novel metabolic pathways for the production of various bulk chemicals that are currently produced from fossil resources. PMID:23280013

Shin, Jae Ho; Kim, Hyun Uk; Kim, Dong In; Lee, Sang Yup

2012-12-29

355

Lithium cluster anions: Photoelectron spectroscopy and ab initio calculations  

NASA Astrophysics Data System (ADS)

Structural and energetic properties of small, deceptively simple anionic clusters of lithium, Lin-, n = 3-7, were determined using a combination of anion photoelectron spectroscopy and ab initio calculations. The most stable isomers of each of these anions, the ones most likely to contribute to the photoelectron spectra, were found using the gradient embedded genetic algorithm program. Subsequently, state-of-the-art ab initio techniques, including time-dependent density functional theory, coupled cluster, and multireference configurational interactions methods, were employed to interpret the experimental spectra.

Alexandrova, Anastassia N.; Boldyrev, Alexander I.; Li, Xiang; Sarkas, Harry W.; Hendricks, Jay H.; Arnold, Susan T.; Bowen, Kit H.

2011-01-01

356

Cooperative anion binding and electrochemical sensing by modular podands  

PubMed Central

A series of podands based on two or three hydrogen bonding “arms” situated in mutually ortho, meta, or para relationships about an aryl core have been prepared, and their affinities for simple inorganic anions were measured. Of the two-arm hosts the meta compound and to a lesser extent the ortho host exhibit a cooperative anion binding effect. The two arms function essentially independently in the para derivative. The mutually meta three-arm host shows dramatically enhanced cooperative binding. Conformational changes within the meta two-arm host result in significantly enhanced electrochemical anion sensing compared with the more conformationally rigid three-arm host.

Abouderbala, Lagili O.; Belcher, Warwick J.; Boutelle, Martyn G.; Cragg, Peter J.; Steed, Jonathan W.; Turner, David R.; Wallace, Karl J.

2002-01-01

357

Anion Photoelectron Angular Distributions: Electron Scattering Resonances in Photodetachment  

NASA Astrophysics Data System (ADS)

To a large degree the photoelectron angular distributions (PAD) of anionic species represent signatures of the bound parent orbital. However, these angular distributions are also influenced by interaction of the outgoing electron with the neutral (atomic, molecular or cluster) residue. The electron kinetic energy evolution (eKE) of the PAD is presented for a number of different species (from molecular to cluster anion), showing the often striking effect of excitation of temporary excited anionic states. These cases highlight the influence of different types of electron-molecule scattering resonances in photodetachment dynamics. Additionally, the possibility of using the eKE evolution of the PAD for structural elucidation is discussed.

Mabbs, Richard

2012-06-01

358

Pyrrole-Based Anion Sensors, Part I: Colorimetric Sensors  

NASA Astrophysics Data System (ADS)

This chapter focuses on chemo-sensing aspects of pyrrole and oligopyrrole-based colorimetric receptors for anions. Since pyrroles can play the role of a receptor as well as a signal transducer very efficiently and because of the focus on anion sensing, they can be organized following the modes of signal transduction such as colorimetry, fluorescence, and electrochemistry rather than structural features of the receptors. This chapter focuses on colorimetric sensors and in particular those based on pyrrole, polypyrrole, and pyrrole benzo-analogs, i.e., indole and carbazole-based sensors for anions.

Anzenbacher, Pavel

359

National GAP Conference 2007-Discussion Groups Report  

USGS Publications Warehouse

We led two discussion groups during the 2007 National GAP Conference. These discussion groups provided information to help develop a survey of National Gap Analysis Program (GAP) data users. One group discussed technical issues, and the second group discussed the use of GAP data for decisionmaking. Themes emerging from the technical issues group included concerns about data quality, need for information on how to use data, and passive data distribution. The decisionmaking discussion included a wide range of topics including the need to understand presentation of information, the need to connect with and understand users of data, the revision of GAP's mission, and the adaptability of products and data. The decisionmaking group also raised concerns regarding technical issues. One conclusion is that a deep commitment to ongoing information transfer and support is a key component of success for the GAP program.

Ratz, Joan M.; Lamb, Berton Lee

2010-01-01

360

Metabolic monitor.  

PubMed

The purpose of this review is to provide information about the technical solutions behind the Datex Deltatrac Metabolic Monitor. Deltatrac measures oxygen consumption (VO2), carbon dioxide production (VCO2) and calculates from those respiratory quotient (RQ = VCO2/VO2) and energy expenditure (EE). Deltatrac can monitor both mechanically ventilated and spontaneously breathing patients. In Deltatrac carbon dioxide is measured with conventional infrared technique but both in oxygen and flow measurement novel innovative methods have been used. A fast differential paramagnetic O2 sensor as well as the gas dilution system to measure flow have been developed specially for this application. PMID:3116131

Meriläinen, P T

1987-01-01

361

Cationic-anionic mediated charge compensation on La2Ti2O7 for visible light photocatalysis.  

PubMed

The cationic-anionic mediated charge compensation effect was studied in the layered perovskite La2Ti2O7 for the visible light photocatalysis. Our screened hybrid density functional study shows that the electronic structure of La2Ti2O7 can be tuned by the cationic (V, Nb, Ta)/anionic (N) mono- and co-doping. Such mono-doping creates impurity states in the band gap which helps the electron-hole recombination. But if the charge compensation is made by the cationic-anionic mediated co-doping then such impurity states can be removed and can be a promising strategy for visible light photocatalysis. The absolute band edge position of the doped La2Ti2O7 has been aligned with respect to the water oxidation/reduction potential. The calculated defect formation energy shows the stability of the co-doping system is improved due to the coulomb interactions and charge compensations effect. PMID:24013462

Liu, Peng; Nisar, Jawad; Pathak, Biswarup; Ahuja, Rajeev

2013-09-25

362

Weather data gap problem resolved  

NASA Astrophysics Data System (ADS)

It looks as though the United States will avoid the crisis situation of a gap in weather data resulting from the aging GOES-7 satellite and technical problems with the next generation of weather satellites (GOESNEXT). Officials at the National Oceanic and Atmospheric Administration, which oversees the National Weather Service, recently announced their decision to borrow at least one and possibly several European satellites until the GOES-NEXT program gets off the ground.The GOES (Geostationary Operational Environmental Satellites) series is currently 3 years behind schedule and $500 million over budget. Problems with its complex design, program management by both NOAA and the National Aeronautics and Space Administration and poor performance by the contractor led Department of Commerce Secretary Robert Mosbacher to slow down the GOES-NEXT series to ensure that it is built right.

Bush, Susan

363

Compact, low jitter, triggered spark gap  

Microsoft Academic Search

High energy particle accelerators using compact, high gradient cavities will require small, highly reliable, triggered spark gaps. This paper will discuss the design and development of V\\/N triggered spark gaps operating from 520 kV to 1280 kV. Spark gap jitter of <3 ns has been obtained with trigger voltages of 60 kV. Capacitively balancing the trigger blade electrode, coupled with

W. K. Tucker; E. E. Jones; T. L. Franklin; L. F. Bennett; G. Weber

1985-01-01

364

Gap between active and passive solar heating  

SciTech Connect

The gap between active and passive solar could hardly be wider. The reasons for this are discussed and advantages to narrowing the gap are analyzed. Ten years of experience in both active and passive systems are reviewed, including costs, frequent problems, performance prediction, performance modeling, monitoring, and cooling concerns. Trends are analyzed, both for solar space heating and for service water heating. A tendency for the active and passive technologies to be converging is observed. Several recommendations for narrowing the gap are presented.

Balcomb, J.D.

1985-01-01

365

Four-wave-mixing gap solitons  

SciTech Connect

We report an experimental demonstration of generating gap soliton trains in a four-wave-mixing (FWM) signal. Such spatial FWM surfacelike gap soliton trains are induced in a periodically modulated self-defocusing atomic medium by the cross-phase modulation, which can be reshaped under different experimental conditions, such as different atomic densities, nonlinear dispersions, and dressing fields. Controlling spatial gap solitons can have important applications in image memory, processing, and communication.

Zhang Yanpeng; Wang Zhiguo; Zheng Huaibin; Yuan Chenzhi; Li Changbiao; Lu Keqing [Key Laboratory for Physical Electronics and Devices of the Ministry of Education and Shaanxi Key Lab of Information Photonic Technique, Xi'an Jiaotong University, Xi'an 710049 (China); Xiao Min [Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701 (United States)

2010-11-15

366

REVIEW ARTICLE: Wide gap semiconductor microwave devices  

Microsoft Academic Search

A review of properties of wide gap semiconductor materials such as diamond, diamond-like carbon films, SiC, GaP, GaN and AlGaN\\/GaN that are relevant to electronic, optoelectronic and microwave applications is presented. We discuss the latest situation and perspectives based on experimental and theoretical results obtained for wide gap semiconductor devices. Parameters are taken from the literature and from some of

V. V. Buniatyan; V. M. Aroutiounian

2007-01-01

367

The optical gap of NiO  

Microsoft Academic Search

The nature of the optical absorption gap in NiO at 4.0 eV is investigated. It is found that this gap is due to a band to band transition, where an electron is taken out of the valence band and placed into the conduction band. The optical gap of 6.0 eV found in Ni:MgO is of a nature, where an electron

S. Hiifner; P. Steiner; I. Sander; F. Reinert; H. Schmitt

1992-01-01

368

Direct band-gap energy of semiconductors  

Microsoft Academic Search

Empirical formulae are obtained relating the direct band-gap energy of semiconductors and the mean atomic number of the constituent atoms. The formulae are used to indicate doubtful values and to obtain the values of bowing parameters of energy band-gaps of ternaries and quaternaries. Derived values of the bowing parameter give band-gap energies of ternaries and quaternaries agreeing with experiments to

B. R. Nag

1995-01-01

369

On the Psychology of Truth-Gaps  

NASA Astrophysics Data System (ADS)

Bonini et al. [2] present psychological data that they take to support an 'epistemic' account of how vague predicates are used in natural language. We argue that their data more strongly supports a 'gap' theory of vagueness, and that their arguments against gap theories are flawed. Additionally, we present more experimental evidence that supports gap theories, and argue for a semantic/pragmatic alternative that unifies super- and subvaluationary approaches to vagueness.

Alxatib, Sam; Pelletier, Jeff

370

Exploiting metabolic differences in glioma therapy.  

PubMed

Brain function depends upon complex metabolic interactions amongst only a few different cell types, with astrocytes providing critical support for neurons. Astrocyte functions include buffering the extracellular space, providing substrates to neurons, interchanging glutamate and glutamine for synaptic transmission with neurons, and facilitating access to blood vessels. Whereas neurons possess highly oxidative metabolism and easily succumb to ischemia, astrocytes rely more on glycolysis and metabolism associated with synthesis of critical intermediates, hence are less susceptible to lack of oxygen. Astrocytoma and higher grade glioma cells demonstrate both basic metabolic mechanisms of astrocytes as well as tumors in general, e.g. they show a high glycolytic rate, lactate extrusion, ability to proliferate even under hypoxia, and opportunistic use of mechanisms to enhance metabolism and blood vessel generation, and suppression of cell death pathways. There may be differences in metabolism between neurons, normal astrocytes and astrocytoma cells, providing therapeutic opportunities against astrocytomas, including a wide range of enzyme and transporter differences, regulation of hypoxia-inducible factor (HIF), glutamate uptake transporters and glutamine utilization, differential sensitivities of monocarboxylate transporters, presence of glycogen, high interlinking with gap junctions, use of NADPH for lipid synthesis, utilizing differential regulation of synthetic enzymes (e.g. isocitrate dehydrogenase, pyruvate carboxylase, pyruvate dehydrogenase, lactate dehydrogenase, malate-aspartate NADH shuttle) and different glucose uptake mechanisms. These unique metabolic susceptibilities may augment conventional therapeutic attacks based on cell division differences and surface receptors alone, and are starting to be implemented in clinical trials. PMID:22339075

Galeffi, Francesca; Turner, Dennis A

2012-12-01

371

Gaps between jets in hadronic collisions  

SciTech Connect

We propose a model to describe diffractive events in hadron-hadron collisions where a rapidity gap is surrounded by two jets. The hard color-singlet object exchanged in the t-channel and responsible for the rapidity gap is described by the perturbative QCD Balitsky-Fadin-Kuraev-Lipatov Pomeron, including corrections due to next-to-leading logarithms. We allow the rapidity gap to be smaller than the interjet rapidity interval, and the corresponding soft radiation is modeled using the HERWIG Monte Carlo. Our model is able to reproduce all Tevatron data, and allows one to estimate the jet-gap-jet cross section at the LHC.

Kepka, O. [IPNP, Faculty of Mathematics and Physics, Charles University, Prague (Czech Republic); Center for Particle Physics, Institute of Physics, Academy of Science, Prague (Czech Republic); Marquet, C. [Physics Department, Theory Unit, CERN, 1211 Geneve 23 (Switzerland); Royon, C. [IRFU/Service de physique des particules, CEA/Saclay, 91191 Gif-sur-Yvette cedex (France)

2011-02-01

372

Anion size modulates salt taste in rats  

PubMed Central

The purpose of this study was to investigate the influence of anion size and the contribution of the epithelial sodium channel (ENaC) and the transient receptor potential vanilloid-1 (TRPV1) channel on sodium-taste responses in rat chorda tympani (CT) neurons. We recorded multiunit responses from the severed CT nerve and single-cell responses from intact, narrowly tuned and broadly tuned, salt-sensitive neurons in the geniculate ganglion simultaneously with stimulus-evoked summated potentials to signal when the stimulus contacted the lingual epithelium. Artificial saliva served as the rinse and solvent for all stimuli (0.3 M NH4Cl, 0.5 M sucrose, 0.03–0.5 M NaCl, 0.01 M citric acid, 0.02 M quinine hydrochloride, 0.1 M KCl, and 0.03–0.5 M Na-gluconate). We used the pharmacological antagonist benzamil to assess NaCl responses mediated by ENaC, and SB-366791 and cetylpyridinium chloride to assess responses mediated by TRPV1. CT nerve responses were greater to NaCl than Na-gluconate at each concentration; this was attributed mostly to broadly tuned, acid-generalist neurons that responded with higher frequency and shorter latency to NaCl than Na-gluconate. In contrast, narrowly tuned NaCl-specialist neurons responded more similarly to the two salts, but with subtle differences in temporal pattern. Benzamil reduced CT nerve and single-cell responses only of narrowly tuned neurons to NaCl. Surprisingly, SB-366791 and cetylpyridinium chloride were without effect on CT nerve or single-cell NaCl responses. Collectively, our data demonstrate the critical role that apical ENaCs in fungiform papillae play in processing information about sodium by peripheral gustatory neurons; the role of TRPV1 channels is an enigma.

Breza, Joseph M.

2012-01-01

373

Anion recognition and sensing with Zn(II)-dipicolylamine complexes.  

PubMed

This critical review covers the developments in anion recognition and sensing using Zn(II)-dipicolylamine functionalized receptors over the past decade with emphasis on recent rapid advances in the last five years. PMID:22688834

Ngo, Huy Tien; Liu, Xuejian; Jolliffe, Katrina A

2012-06-12

374

Carbonate and Bicarbonate Ion Transport in Alkaline Anion Exchange Membranes.  

National Technical Information Service (NTIS)

Anion exchange membranes (AEMs) are being developed for potential use in fuel cell systems which include portable power applications. In a fuel cell, these membranes transport hydroxide ions from the cathode to the anode. If carbon dioxide is present, car...

A. A. Peracchio A. M. Kiss G. J. Nelson K. N. Grew T. D. Myles

2013-01-01

375

Experimental evidence for the functional relevance of anion-? interactions  

NASA Astrophysics Data System (ADS)

Attractive in theory and confirmed to exist, anion-? interactions have never really been seen at work. To catch them in action, we prepared a collection of monomeric, cyclic and rod-shaped naphthalenediimide transporters. Their ability to exert anion-? interactions was demonstrated by electrospray tandem mass spectrometry in combination with theoretical calculations. To relate this structural evidence to transport activity in bilayer membranes, affinity and selectivity sequences were recorded. ?-acidification and active-site decrowding increased binding, transport and chloride > bromide > iodide selectivity, and supramolecular organization inverted acetate > nitrate to nitrate > acetate selectivity. We conclude that anion-? interactions on monomeric surfaces are ideal for chloride recognition, whereas their supramolecular enhancement by ?,?-interactions appears perfect to target nitrate. Chloride transporters are relevant to treat channelopathies, and nitrate sensors to monitor cellular signaling and cardiovascular diseases. A big impact on organocatalysis can be expected from the stabilization of anionic transition states on chiral ?-acidic surfaces.

Dawson, Ryan E.; Hennig, Andreas; Weimann, Dominik P.; Emery, Daniel; Ravikumar, Velayutham; Montenegro, Javier; Takeuchi, Toshihide; Gabutti, Sandro; Mayor, Marcel; Mareda, Jiri; Schalley, Christoph A.; Matile, Stefan

2010-07-01

376

New anion-exchange polymers for improved separations  

SciTech Connect

Objective is to improve the understanding of how the structure of a new class of anion-exchange polymers controls the binding of anionic actinide complexes from solution. This is needed to develop practical separation systems that will reduce the cost of actinide processing operations within the DOE complex. In addition anion exchange is widely used in industry. Several new series of bifunctional anion- exchange polymers have been designed, synthesized, and tested for removing Pu(IV), Am(III), and U(VI) from nitric acid. The polymers contain a pyridinium site derived from the host poly(4-vinylpyridine) and a second cationic site attached through a chain of 2 to 6 methylene groups. The new polymers removed Pu four to ten times more efficiently than the best commercial materials.

Jarvinen, G.D.; Barr, M.E.; Marsh, S.F.

1997-08-01

377

Anionic Photopolymerization of Methyl-2-Cyanoacrylate and Simultaneous Color Formation.  

National Technical Information Service (NTIS)

Anionic polymerization of methyl 2-cyanoacrylate initiated by photoinduced heterolysis of crystal violet leuconitrile (CVCN) and of malachite green leucohydroxide (MGOH) is demonstrated. Polymerization is accompanied by color formation.

V. V. Jarikov D. C. Neckers

2000-01-01

378

Cationic cyclocholamides; toroidal facial amphiphiles with potential for anion transport.  

PubMed

Cholic acid has been transformed into cyclotrimeric and cyclotetrameric toroidal amphiphiles with inward-directed ammonium substituents; the cyclotrimer effects the transport of chloride anions across vesicle bilayer membranes. PMID:18665294

Whitmarsh, Samuel D; Redmond, Adrian P; Sgarlata, Valentina; Davis, Anthony P

2008-06-17

379

The Electronic Spectra of Some Anionic Polymerization Systems.  

National Technical Information Service (NTIS)

The ultraviolet absorption sxectra of living anionic polymerizing systems have been measured with sytrene, butadiene, and isoxrene as the monomers; with lithium, sodium, and potassium as the alkali metals; and with tetrahydrofuran, cyclohexane, and benzen...

S. Bywater A. F. Johnson D. J. Worsfold

1964-01-01

380

Nitrate Anion Exchange in Pu-238 Aqueous Scrap Recovery Operations  

SciTech Connect

Strong base, nitrate anion exchange (IX) is crucial to the purification of {sup 238}Pu solution feedstocks with gross levels of impurities. This paper discusses the work involved in bench scale experiments to optimize the nitrate anion exchange process. In particular, results are presented of experiments conducted to (a) demonstrate that high levels of impurities can be separated from {sup 238}Pu solutions via nitrate anion exchange and, (b) work out chemical pretreatment methodology to adjust and maintain {sup 238}Pu in the IV oxidation state to optimize the Pu(IV)-hexanitrato anionic complex sorption to Reillex-HPQ resin. Additional experiments performed to determine the best chemical treatment methodology to enhance recovery of sorbed Pu from the resin, and VIS-NIR absorption studies to determine the steady state equilibrium of Pu(IV), Pu(III), and Pu(VI) in nitric acid are discussed.

Pansoy-Hjelvik, M.E.; Silver, G.L.; Reimus, M.A.H.; Ramsey, K.B.

1999-01-31

381

The functional layered organosilica materials prepared with anion surfactant templates.  

PubMed

A novel strategy for the synthesis of layered organosilica is demonstrated. The ionic interaction between the anionic group of a surfactant (sodium dodecyl sulfate) and the cationic organic group of an organosilane (3-aminopropyltrimethoxysilane, ATMS) under acidic conditions was utilized to create a layered organosilica at room temperature. The inorganic part of the organosilica layer was an Si-O hexagonal sheet, and organofunctional groups were alternately arranged on both sides of the sheet. The layered structure of the ATMS organosilica was retained after the removal of the surfactant with chloride anion. The properties of the layered ATMS organosilica were investigated. The layered ATMS-Cl organosilica is stable and possesses a definite layer structure in water or ethanol. Various kinds of anions can be intercalated in the interlayer space of the layered ATMS organosilicas and the layer was expanded dependent on the intercalated anions. The structure of the layered ATMS organosilica was well retained during the intercalation processes. PMID:15797421

Yao, Ken; Imai, Yusuke; Shi, LiYi; Dong, AiMei; Adachi, Yoshio; Nishikubo, Keiko; Abe, Eiichi; Tateyama, Hiroshi

2005-05-01

382

The chemistry and complexes of small cyano anions.  

PubMed

The chemistry of the anions dicyanamide and tricyanomethanide (dca and tcm, respectively) has produced a plethora of discoveries over the past few decades, particularly in relation to transition-metal coordination polymers with magnetic coupling. Over recent years there have been an increasing number of reports of heterofunctionalised cyano-containing anions, typically derivatives of dicyanomethanide. Our own group has been particularly concerned with the amide- and nitroso-functionalised anions carbamoyldicyanomethanide (cdm) and dicyanonitrosomethanide (dcnm), respectively. This feature article examines the fascinating diversity of materials and complexes that can be obtained using small cyano anions, ranging from coordination polymers to heterometallic clusters and hydrogen bonding networks. In particular, we focus on results from our own laboratories in the past few years. The magnetic properties of these materials are briefly discussed. PMID:21773626

Turner, David R; Chesman, Anthony S R; Murray, Keith S; Deacon, Glen B; Batten, Stuart R

2011-07-20

383

DETERMINATION OF TRACE ANIONS IN WATER BY MULTIDIMENSIONAL ION CHROMATOGRAPHY  

EPA Science Inventory

Selenate, selenite, and arsenate ions were separated from the major anions chloride, nitrate, and sulfate in drinking water, surface water, and groundwater sources by collecting a selected portion of the ion chromatogram, after suppression, on a concentrator column and reinjectin...

384

Preparation and evaluation of anion exchange open tubular column.  

PubMed

An anion open tubular column (OTC) by coating cationic latex particle onto the silica capillary with surface sulfonate functionalized has been prepared and evaluated. The performance of the OTC was observed to be superior to that of those prepared by the bare silica capillary without sulfonation in term of separation efficiency. To increase the surface area of the capillary, acid and base-based etching method for treating silica capillary wall was carried out and compared. An OTC with multiple layers was prepared by alternatively coating cationic and anionic latex particles aiming to further increase the column capacity. The anion OTC with size of 50 ?m i.d. × 1 m long demonstrated good separation of common inorganic anions with high efficiency (e.g. for NO(2)(-), its theory plate number is 11655 plate/m). PMID:23158296

Diao, Xuefang; Zhang, Feifang; Feng, Feng; Yang, Bingcheng; Liang, Xinmiao; Chu, Xiaogang

2012-09-12

385

On the origin of alternating bond distortions and the emergence of chirality in polyoxometalate anions.  

PubMed

Alternating short and long bond length (ABL) distortions observed within the ring structures of molecular metal oxide anions or polyoxometalates (POMs) are reminiscent of the cooperative linear ABL distortions in perovskite d(0) metal oxides. We show herein that these distortions have a common origin: a pseudo Jahn-Teller (PJT) vibronic instability. Four POM structural types with different M(n)O(n) ring sizes are investigated herein using density functional theoretical methods: Lindqvist [M6O19](q-) (n = 4), Keggin alpha-[XM12O40](q-) (n = 6), Wells-Dawson alpha-[X2M18O62](q-) (n = 8), and Preyssler [(Na)P5W30O110](14-) (n = 10), where M = Mo(VI) and W(VI) and X = Si(IV), Ge(IV), P(V), As(V), S(VI), and Se(VI). Chirality is induced within the latter three structural types by the ABL ring distortions. The calculations confirm the PJT vibronic origin of the ABL distortions with good agreement between calculated geometries and published single-crystal X-ray diffraction data. Both theory and experiment show that the vibronic interaction and distortion magnitude increase for (1) molybdates relative to that of tungstates, (2) larger M(n)O(n) ring sizes, (3) increases in negative charge of the internalized fragments (O(2-) or XO4(q-)), and (4) d(0) versus d(n) metal oxidation states. The PJT vibronic coupling model explains these observations in terms of the energy gap between Kohn-Sham frontier molecular orbitals (MOs) concomitant with the propensity for metal-oxygen pi-bonding within the M(n)O(n) rings. The frontier MOs for the undistorted nuclear configurations are largely nonbonding pi-O(p) (occupied) and pi-M(d) (unoccupied) in character, where smaller HOMO-LUMO (H-L) gap energies lead to greater metal-oxygen pi-orbital mixing under the influence of the nuclear distortion. A reduction in pi-bond order decreases the distortion in mixed-valence POMs. Of the tungstates examined, only the Preyssler anion shows pronounced ABL ring distortions, which derive from its large ring size and concomitant small H-L gap. PMID:18528985

Yan, Likai; López, Xavier; Carbó, Jorge J; Sniatynsky, Richard; Duncan, Dean C; Poblet, Josep M

2008-06-04

386

Gap detection for genome-scale constraint-based models.  

PubMed

Constraint-based metabolic models are currently the most comprehensive system-wide models of cellular metabolism. Several challenges arise when building an in silico constraint-based model of an organism that need to be addressed before flux balance analysis (FBA) can be applied for simulations. An algorithm called FBA-Gap is presented here that aids the construction of a working model based on plausible modifications to a given list of reactions that are known to occur in the organism. When applied to a working model, the algorithm gives a hypothesis concerning a minimal medium for sustaining the cell in culture. The utility of the algorithm is demonstrated in creating a new model organism and is applied to four existing working models for generating hypotheses about culture media. In modifying a partial metabolic reconstruction so that biomass may be produced using FBA, the proposed method is more efficient than a previously proposed method in that fewer new reactions are added to complete the model. The proposed method is also more accurate than other approaches in that only biologically plausible reactions and exchange reactions are used. PMID:22997515

Brooks, J Paul; Burns, William P; Fong, Stephen S; Gowen, Chris M; Roberts, Seth B

2012-09-10

387

Electron Transfer from alpha-Keggin Anions to Dioxygen  

Microsoft Academic Search

Polyoxometalates. Polyoxometalates (POMs), of which alpha-Keggin anions are representative, are a diverse and rapidly growing class of water-soluble cluster-anion structures with applications ranging from molecular catalysis to materials. [1] POMs are inexpensive, minimally or non-toxic, negatively charged clusters comprised of early-transition-metals, usually in their d, electronic configurations (e. g. W(VI), Mo(VI), V(V), Nb(V), Ti(IV)), bridged by oxygens (formally oxide, or

Yurii V. Geletii; Rajai H. Atalla; Craig L. Hill; Ira A. Weinstock

388

Superoxide anion release by peripheral polymorphonuclear leukocytes in welders  

Microsoft Academic Search

Objectives: To investigate peripheral blood neutrophil [polymorphonuclear leukocyte (PMN)] function in a group of 23 welders compared\\u000a with that in an age- and smoking habit-matched non-exposed control group. Methods: Stimulated release of superoxide anions from PMN isolated from peripheral blood of welders and of a matched group was carried\\u000a out. Results: The stimulated release of superoxide anions in PMNs from

Aviva Aloufy; Yehuda Lerman; Ada Tamir; Erica Hoffer

2001-01-01

389

Bi-ionic potentials across liquid anion exchanger membranes  

Microsoft Academic Search

Summary The bi-ionic potentials, B. I. P.'s, arising in cells of the type: A+L-c1| liquid anion exchanger membrane of extreme anionic selectivity| A+M-c1, are surveyed briefly but systematically. The membranes consisted of trioctyl-propyl ammonium salts dissolved ino-dichlorobenzene. As anticipated on the basis of previous theoretical and experimental work on porous membranes, the following regularities were observed. The B.I.P. arising with

Gerald Shean; Karl Sollner

1972-01-01

390

Target-aimed synthesis of anion-deficient perovskites.  

PubMed

The brownmillerite-type A 2B 2O 5 structure is considered as a parent one, giving rise to different derivatives: layered double perovskites, A-site and anion-vacancy-ordered perovskites, and the perovskite-like compounds with crystallographic shear planes. The structural relationships and synthesis pathways for these classes of materials are discussed with particular attention to the ordering at the A or B sublattices, anion vacancy ordering, and their mutual interaction. PMID:18821820

Antipov, Evgeny V; Abakumov, Artem M; Istomin, Sergey Ya

2008-10-01

391

GAS-GRAIN MODELS FOR INTERSTELLAR ANION CHEMISTRY  

SciTech Connect

Long-chain hydrocarbon anions C{sub n}H{sup -} (n = 4, 6, 8) have recently been found to be abundant in a variety of interstellar clouds. In order to explain their large abundances in the denser (prestellar/protostellar) environments, new chemical models are constructed that include gas-grain interactions. Models including accretion of gas-phase species onto dust grains and cosmic-ray-induced desorption of atoms are able to reproduce the observed anion-to-neutral ratios, as well as the absolute abundances of anionic and neutral carbon chains, with a reasonable degree of accuracy. Due to their destructive effects, the depletion of oxygen atoms onto dust results in substantially greater polyyne and anion abundances in high-density gas (with n{sub H{sub 2}}{approx}>10{sup 5} cm{sup -3}). The large abundances of carbon-chain-bearing species observed in the envelopes of protostars such as L1527 can thus be explained without the need for warm carbon-chain chemistry. The C{sub 6}H{sup -} anion-to-neutral ratio is found to be most sensitive to the atomic O and H abundances and the electron density. Therefore, as a core evolves, falling atomic abundances and rising electron densities are found to result in increasing anion-to-neutral ratios. Inclusion of cosmic-ray desorption of atoms in high-density models delays freeze-out, which results in a more temporally stable anion-to-neutral ratio, in better agreement with observations. Our models include reactions between oxygen atoms and carbon-chain anions to produce carbon-chain-oxide species C{sub 6}O, C{sub 7}O, HC{sub 6}O, and HC{sub 7}O, the abundances of which depend on the assumed branching ratios for associative electron detachment.

Cordiner, M. A. [Also at Institute for Astrophysics and Computational Sciences, Catholic University of America, Washington, DC 20064 (United States); Charnley, S. B., E-mail: martin.cordiner@nasa.gov [Astrochemistry Laboratory and Goddard Center for Astrobiology, Mailstop 691, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20770 (United States)

2012-04-20

392

Boron compounds as anion binding agents for nonaqueous battery electrolytes  

DOEpatents

Novel fluorinated boron-based compounds which act as anion receptors in non-aqueous battery electrolytes are provided. When added to non-aqueous battery electrolytes, the fluorinated boron-based compounds of the invention enhance ionic conductivity and cation transference number of non-aqueous electrolytes. The fluorinated boron-based anion receptors include borane and borate compounds bearing different fluorinated alkyl and aryl groups.

Lee, Hung Sui (East Setauket, NY); Yang, Xia-Oing (Port Jefferson Station, NY); McBreen, James (Bellport, NY); Xiang, Caili (Upton, NY)

2000-02-08

393

Anion Separation by Selective Crystallization of Metal-Organic-Frameworks  

Microsoft Academic Search

A novel approach for the separation of anions from aqueous mixtures was demonstrated, which involves their selective crystallization with metal-organic frameworks (MOFs) containing urea functional groups. Self-assembly of Zn{sup 2+} with the N,N-bis(m-pyridyl)urea (BPU) linker results in the formation of one-dimensional MOFs including various anions for charge balance, which interact to different extents with the zinc nodes and the urea

Radu Custelcean; Radu; Bruce A. Moyer

2006-01-01

394

Gas-Grain Models for Interstellar Anion Chemistry  

NASA Astrophysics Data System (ADS)

Long-chain hydrocarbon anions C n H- (n = 4, 6, 8) have recently been found to be abundant in a variety of interstellar clouds. In order to explain their large abundances in the denser (prestellar/protostellar) environments, new chemical models are constructed that include gas-grain interactions. Models including accretion of gas-phase species onto dust grains and cosmic-ray-induced desorption of atoms are able to reproduce the observed anion-to-neutral ratios, as well as the absolute abundances of anionic and neutral carbon chains, with a reasonable degree of accuracy. Due to their destructive effects, the depletion of oxygen atoms onto dust results in substantially greater polyyne and anion abundances in high-density gas (with n_H_2\\gtrsim 10^5 cm-3). The large abundances of carbon-chain-bearing species observed in the envelopes of protostars such as L1527 can thus be explained without the need for warm carbon-chain chemistry. The C6H- anion-to-neutral ratio is found to be most sensitive to the atomic O and H abundances and the electron density. Therefore, as a core evolves, falling atomic abundances and rising electron densities are found to result in increasing anion-to-neutral ratios. Inclusion of cosmic-ray desorption of atoms in high-density models delays freeze-out, which results in a more temporally stable anion-to-neutral ratio, in better agreement with observations. Our models include reactions between oxygen atoms and carbon-chain anions to produce carbon-chain-oxide species C6O, C7O, HC6O, and HC7O, the abundances of which depend on the assumed branching ratios for associative electron detachment.

Cordiner, M. A.; Charnley, S. B.

2012-04-01

395

Low barrier hydrogen bonds within salicylate mono-anions  

Microsoft Academic Search

Progressive incorporation of electron-withdrawing substituents into the aromatic ring of salicylic acid selectively acidifies the ArOH group, until the intrinsic pKa values of the ArOH and ArCO2H groups become matched, as in the case of 3-chloro-5-nitrosalicylic acid. The corresponding salicylate mono-anion at ?50°C in aqueous deuterioacetone solution exhibits a low barrier hydrogen bond intramolecularly linking the adjacent anionic oxygens, according

William L. Mock; Layne A. Morsch

2001-01-01

396

Establishment of a method to rapidly assay bacterial persister metabolism.  

PubMed

Bacterial persisters exhibit an extraordinary tolerance to antibiotics that is dependent on their metabolic state. Although persister metabolism promises to be a rich source of antipersister strategies, there is relatively little known about the metabolism of these rare and transient phenotypic variants. To address this knowledge gap, we explored the use of several techniques, and we found that only one measured persister metabolism. This assay was based on the phenomenon of metabolite-enabled aminoglycoside killing of persisters, and we used it to characterize the metabolic heterogeneity of different persister populations. From these investigations, we determined that glycerol and glucose are the most ubiquitously used carbon sources by various types of Escherichia coli persisters, suggesting that these metabolites might prove beneficial to deliver in conjunction with aminoglycosides for the treatment of chronic and recurrent infections. In addition, we demonstrated that the persister metabolic assay developed here is amenable to high-throughput screening with the use of phenotype arrays. PMID:23817376

Orman, Mehmet A; Brynildsen, Mark P

2013-07-01

397

Anionic dicyanamide frameworks as possible components of multifunctional materials  

NASA Astrophysics Data System (ADS)

The dicyanamide anion, [ N(CN){2}] - (hereafter abbreviated dca), has been shown to be a versatile building block for the assembly of coordination polymers which are components of molecular superconductors, magnets and conducting/magnetic hybrid materials. Significantly different anion topologies have been observed. We report the first study of the use of alkylammonium cations as templates for [ M(dca){3}] - (M = Mn and Ni) anionic networks, including a novel three-dimensional anionic structure in the (Bu{3}NH){4}[ Mn{3}(dca){10}] salt. The molecular superconductors with the highest superconducting transition temperature, kappa -(ET){2}[ Cu(dca)X] [ X = Cl, Br; ET, commonly abbreviated as BEDT-TTF, is bis(ethylenedithio)tetrathiafulvalene] contain chains of diamagnetic Cu(I) ions linked by dca anions. The successful introduction of magnetically active transition metals into the charge-compensating dca layer will also be discussed. Specifically, we have synthesized and characterized the (ET){2}[ Mn(dca){3}] salt that contain a novel triangular, spin frustrated, anion lattice separated by conducting layers of ET radical cations. Key words. BEDT-TTF salt, tetraalkylammonium salts, dicyanamide, x-ray crystal structure.

Schlueter, J. A.; Geiser, U.; Manson, J. L.

2004-04-01

398

Volume-induced increase of anion permeability in human lymphocytes  

PubMed Central

Peripheral blood mononuclear cells (PBM) readjust their volumes after swelling in hypotonic media. This regulatory volume decrease (RVD) is associated with a loss of cellular K+ and is thought to be promoted by an increased permeability to this ion. In contrast, no change in volume was observed when K+ permeability of PBM in isotonic media was increased to comparable or higher levels using valinomycin. Moreover, valinomycin-induced 86Rb+ loss in K+-free medium was considerably slower than in K+-rich medium. These results suggest that anion conductance limits net salt loss in isotonic media. Direct measurements of relative conductance confirmed that in volume-static cells, anion conductance is lower than that of K+. In volume-regulating cells depolarization occurred presumably as a result of increased anion conductance. Accordingly, the efflux of 36Cl from PBM was markedly increased by hypotonic stress. Since both membrane potential and intracellular 36Cl concentration are reduced in hypotonically swollen cells, the increased efflux is probably due to a change in Cl- permeability. Anions and cations seem to move independently through the volume-induced pathways: the initial rate of 86Rb uptake in swollen cells was not affected by replacement of external Cl- by SO=4; conversely, 36Cl fluxes were unaffected by substitution of K+ by Na+. The data indicate that anion conductance is rate-determining in salt and water loss from PBM. An increase in anion conductance is suggested to be the critical step of RVD of human PBM.

1982-01-01

399

Hemibonding of hydroxyl radical and halide anion in aqueous solution.  

PubMed

Molecular geometries and properties of the possible reaction products between the hydroxyl radical and the halide anions in aqueous solution were investigated. The formation of two-center three-electron bonding (hemibonding) between the hydroxyl radical and halide anions (Cl, Br, I) was examined by density functional theory (DFT) calculation with a range-separated hybrid (RSH) exchange-correlation functional. The long-range corrected hybrid functional (LC-?PBE), which have given quantitatively satisfactory results for odd electron systems and excited states, was examined by test calculations for dihalogen radical anions (X(2)(-); X = Cl, Br, I) and hydroxyl radical-water clusters. Equilibrium geometries with hemibonding between the hydroxyl radical and halide anions were located by including four hydrogen-bonded water molecules. Excitation energies and oscillator strengths of ?-?* transitions calculated by the time-dependent DFT method showed good agreement with observed values. Calculated values of the free energy of reaction on the formation of hydroxyl halide radical anion from the hydroxyl radical and halide anion were endothermic for chloride but exothermic for bromide and iodide, which is consistent with experimental values of equilibrium constants. PMID:22136588

Yamaguchi, Makoto

2011-12-05

400

Ligandless, Anionic, Arylpalladium Halide Intermediates in the Heck Reaction  

PubMed Central

We report the isolation and reactivity of a series of “ligandless,” anionic arylpalladium complexes of the general structure [Pd(Ar)Br2]22- by the reaction of (tBu3P)Pd(Ar)(Br) and bromide. These anionic complexes insert olefins at room temperature, and these fast insertions indicate that the anionic complexes are kinetically competent as intermediates in Heck-Mizoroki reactions conducted under “ligandless” conditions (lacking added dative ligand). Kinetic studies showed that the anionic complexes insert olefins much faster than the corresponding neutral, P(t-Bu)3-ligated complexes. Addition of halide to the reaction of the neutral complex (tBu3P)Pd(Ar)(Br) and styrene led to a significant rate acceleration, suggesting that the anionic complex forms rapidly and reversibly in situ from the neutral species prior to migratory insertion. These data, along with studies on the regioselectivity for reaction of aryl halides with butyl vinyl ether in the presence of the different starting catalysts, are consistent with the intermediacy of the same anionic, arylpalladium intermediates in Heck reactions catalyzed by palladium complexes containing bulky trialkylphosphine ligands as in reactions conducted under ligandless conditions.

Carrow, Brad P.

2010-01-01

401

Collision-induced dissociation mass spectra of glucosinolate anions.  

PubMed

Collision-induced dissociation (CID) mass spectra of differently substituted glucosinolates were investigated under negative-ion mode. Data obtained from several glucosinolates and their isotopologues ((34)S and (2)H) revealed that many peaks observed are independent of the nature of the substituent group. For example, all investigated glucosinolate anions fragment to produce a product ion observed at m/z 195 for the thioglucose anion, which further dissociates via an ion/neutral complex to give two peaks at m/z 75 and 119. The other product ions observed at m/z 80, 96 and 97 are characteristic for the sulfate moiety. The peaks at m/z 259 and 275 have been attributed previously to glucose 1-sulfate anion and 1-thioglucose 2-sulfate anion, respectively. However, based on our tandem mass spectrometric experiments, we propose that the peak at m/z 275 represents the glucose 1-thiosulfate anion. In addition to the common peaks, the spectrum of phenyl glucosinolate (beta-D-Glucopyranose, 1-thio-, 1-[N-(sulfooxy)benzenecarboximidate] shows a substituent-group-specific peak at m/z 152 for C(6)H(5)-C(=NOH)S(-), the CID spectrum of which was indistinguishable from that of the anion of synthetic benzothiohydroxamic acid. Similarly, the m/z 201 peak in the spectrum of phenyl glucosinolate was attributed to C(6)H(5)-C(=S)OSO(2)(-). PMID:20033929

Bialecki, Jason B; Ruzicka, Josef; Weisbecker, Carl S; Haribal, Meena; Attygalle, Athula B

2010-03-01

402

Chemical oxidation of nitrated polycyclic aromatic hydrocarbons: Hydroxylation with superoxide anion radical  

SciTech Connect

Nitrated polycyclic aromatic hydrocarbon (nitroPAH) is a potent mutagen which is reductively and/or oxidatively metabolized. Biological oxidation of nitroPAH, such as hydroxylation and epoxidation, is known, but chemical oxidation has been reported in only a few papers. NitroPAH is barely oxidized by various chemical oxidants because of the electron deficient property of the aromatic ring with the nitro substituent. Nucleophilic reactivity of superoxide anion radical is known, and thus the oxidation of nitroPAH with the chemically generated superoxide anion radical was carried out in this study. When 1-nitropyrene was reacted with KO{sub 2}/18-crown-6 in dimethylformamide, 5-,6-,8j-, and 9-hydroxy-1-nitropyrenes and 1-hydroxypyrene were obtained in preparative yields. Three isomeric dinitropyrenes, 3-nitrofluoranthene, 6-nitrobenzo[a]pyrene, and 6j-nitrochrysene, were oxidized to hydrozy derivatives, some of which correspond to the oxidative metabolite of nitroPAH. The oxidation of dinitropyrenes with trifluoroperacetic acid gave K-region oxidized products. 38 refs., 4 tabs.

Fukuhara, K., Miyata, N. [National Institute of Health Sciences, Tokyo (Japan)

1995-01-01

403

Thermal decomposition of GAP and GAP-based double-base propellants  

Microsoft Academic Search

This paper reports the thermal decomposition pattern of GAP and GAP-containing double-base (DB) compositions. Dynamic and isothermal TGA reveal a two-stage decomposition process for GAP. At temperatures below 200°C reactant-product interface diffusion, while at higher temperatures nucleation-based diffusion processes appear to be operative. Inclusion of GAP resulted in a drop in temperature for the onset of freeradical reaction.

S. S. Dhar; S. N. Asthana; H. Singh; G. N. Natu

1993-01-01

404

[Assessment of rate of hydroxyl anions production by Helicobacter pylori in stomach].  

PubMed

Production of hydroxyl anions by tissue samples of pylorus mucous membrane obtained from 45 patients with gastric or duodenal ulcers was investigated. The production was estimated using the recently developed method based on measurement of rate of pH change in urea-containing reaction mixture. The rate of [OH-] generation as a result of H. pylori metabolism accounted on pylorus square varied from 0.4 to 1318.9 mcmol [OH-]/min, and in 90.2% of cases it did not exceed 128.1 mcmol [OH-]/min. This rate is comparable to mean rate of [H+] generation in stomach of healthy man--114.2-238.4 mcmol [H+]/min. Obtained results allow to conclude that this bacterium may participate in regulation of stomach acid-base balance. PMID:19004294

Vartanova, N O; Arzumanian, V G

405

Gap Analysis Program (GAP). User's Manual, Versions 1.0 and 2.0.  

National Technical Information Service (NTIS)

The Gap Analysis Program (GAP) is a Windows 95 computer application created to aid in the analysis and design of overlap gaps in highway noise barriers. The program is intended to be a tool for transportation engineers and planners who are responsible for...

1998-01-01

406

Study of the dielectric properties near the band gap by VEELS: gap measurement in bulk materials  

Microsoft Academic Search

Measuring the band gap of bulk materials by valence electron energy loss spectroscopy (VEELS) is not straightforward. Mathematical procedures used to recover the single scattering distribution from raw data introduce artefacts in the signal, which complicate the gap measurement. In this work, we propose a method to overcome this and measure the direct band gap energy with an accuracy of

S. Schamm; G. Zanchi

2003-01-01

407

Caring Closes the Language-Learning Gap  

ERIC Educational Resources Information Center

The gap in academic achievement between English speakers and English learners continues to concern educators, parents, and legislators. Rising expectations for literacy and the increasing number of students from diverse backgrounds contribute to this achievement gap. In this article, the author discusses a variety of strategies for reaching out to…

Borba, Mary

2009-01-01

408

Spark gap device for precise switching  

Microsoft Academic Search

A spark gap device for precise switching of an energy storage capacitor into an exploding bridge wire load is disclosed. Niobium electrodes having a melting point of 2,415 degrees centigrade are spaced apart by an insulating cylinder to define a spark gap. The electrodes are supported by conductive end caps which, together with the insulating cylinder, form a hermetically sealed

Boettcher

1984-01-01

409

Spark gap device for precise switching  

Microsoft Academic Search

A spark gap device for precise switching of an energy storage capacitor into an exploding bridge wire load is disclosed. Niobium electrodes having a melting point of 2,415 degrees centrigrade are spaced apart by an insulating cylinder to define a spark gap. The electrodes are supported by conductive end caps which, together with the insulating cylinder, form a hermetically sealed

Boettcher; Gordon E

1984-01-01

410

New method for monolithic gap head  

Microsoft Academic Search

A novel monolithic gap (MG) head is proposed and its fabrication process is described for a VCR where the track width and the gap length cannot be determined in a mechanical manner but rather by applying such method as sputtering and photolithography. These methods were applied to a head process with a 50-mm2 wafer, and the practical applicability of the

K. Konishi; N. Arai; K. Kishimoto; H. Ono; H. Akai; N. Gotoh; Y. Noro

1990-01-01

411

A search interpretation of the family gap  

Microsoft Academic Search

This paper proposes a general equilibrium search model to investigate what is known as the family gap: wage differentials between mothers and non-mothers. In the human capital literature a substantial amount of the family gap is left unexplained after controlling for schooling and experience. This paper suggests that differences in labor market behavior between mothers and non-mothers are an important

Yahong Zhang

2012-01-01

412

NSLS prototype small-gap undulator (PSGU).  

National Technical Information Service (NTIS)

The NSLS Prototype Small-Gap Undulator (PSGU) will serve as a tool to study lifetime degradation and the onset of beam instabilities as the beam duct aperture is decreased. The device will consist of variable-gap vacuum vessel had a permanent magnet undul...

P. M. Stefan L. Solomon S. Krinsky G. Rakowsky

1991-01-01

413

Gap Junctions: Basic Structure and Function  

Microsoft Academic Search

Gap junctions allow the exchange of ions, second messengers, and small metabolites between adjacent cells and are formed by two unrelated protein families, the pannexins and connexins. Mutations in connexin genes cause a variety of genetic disorders, implicating a critical role in tissue homeostasis. Association of congenital skin disorders to mutations in different connexins has underscored the importance of gap

Gülistan Me?e; Gabriele Richard; Thomas W White

2007-01-01

414

Gas mixtures for spark gap closing switches  

DOEpatents

Gas mixtures for use in spark gap closing switches comprised of fluorocarbons and low molecular weight, inert buffer gases. To this can be added a third gas having a low ionization potential relative to the buffer gas. The gas mixtures presented possess properties that optimized the efficiency spark gap closing switches. 6 figs.

Christophorou, L.G.; McCorkle, D.L.; Hunter, S.R.

1987-02-20

415

Gas mixtures for spark gap closing switches  

DOEpatents

Gas mixtures for use in spark gap closing switches comprised of fluorocarbons and low molecular weight, inert buffer gases. To this can be added a third gas having a low ionization potential relative to the buffer gas. The gas mixtures presented possess properties that optimized the efficiency spark gap closing switches.

Christophorou, Loucas G. (Oak Ridge, TN); McCorkle, Dennis L. (Knoxville, TN); Hunter, Scott R. (Oak Ridge, TN)

1988-01-01

416

The gender pay gap in the UK  

Microsoft Academic Search

Measuring differences between mens' and womens' earnings, presents estimates from ASHE, the LFS and the NES panel data setThe gender pay gap is a measure of the difference between the earnings of men and women. This article presents estimates of the gender pay gap from the Annual Survey of Hours and Earnings, the Labour Force Survey and the New Earnings

Debra Leaker

2008-01-01

417

Parallel Gap Welding to Thick Film Metallization.  

National Technical Information Service (NTIS)

The parallel gap welding response of a series of gold and platinum-gold thick film conductor materials which were subjected to various peak temperature/belt speed firing profiles was studied. The parallel gap welding was conducted using a variety of weld ...

D. R. Johnson R. E. Knutson

1976-01-01

418

Funding Gaps and Government Shutdowns: CRS Experts  

Microsoft Academic Search

[Excerpt] In the event of a funding gap, the potential impacts of a government shutdown will depend on a program’s or agency’s specific circumstances and how relevant law is interpreted. The following table provides names and contact information for CRS experts on policy concerns relating to funding gaps and the processes and effects that may be associated with a government

Clinton T Brass

2011-01-01

419

Diverse functions of vertebrate gap junctions  

Microsoft Academic Search

Gap junctions are clusters of intercellular channels between adjacent cells. The channels are formed by the direct apposition of oligomeric transmembrane proteins, permitting the direct exchange of ions and small molecules (<1kDa) between cells without involvement of the extracellular space. Vertebrate gap junction channels are composed of oligomers of connexins, an enlarging family of proteins consisting of perhaps >20 members.

Alexander M Simon; Daniel A Goodenough

1998-01-01

420

Complementary Theories of Energy Gaps in HTSC  

Microsoft Academic Search

We examine experiments on energy gaps in high temperature superconductors (HTSC) in terms of experimental probes that utilize momentum, position, or neither. Experiments on very high quality mechanical tunnel junctions show a sharp energy gap with a maximum anisotropy of ~ 10%, while ultrahigh precision ARPES experiments show 100% anisotropy (d-wave pairing). We resolve this conbflict by showing that the

J. C. Phillips; J. Jung; D. Shimada; N. Tsuda

2001-01-01

421

GAP-43 Gene Expression Regulates Information Storage  

ERIC Educational Resources Information Center

Previous reports have shown that overexpression of the growth- and plasticity-associated protein GAP-43 improves memory. However, the relation between the levels of this protein to memory enhancement remains unknown. Here, we studied this issue in transgenic mice (G-Phos) overexpressing native, chick GAP-43. These G-Phos mice could be divided at…

Holahan, Matthew R.; Honegger, Kyle S.; Tabatadze, Nino; Routtenberg, Aryeh

2007-01-01

422

Public Perceptions of the Pay Gap  

ERIC Educational Resources Information Center

|Women have made gains toward closing the gender pay gap during the past two decades. Much of the progress occurred during the 1980s, with smaller gains in the 1990s (Institute for Women's Policy Research 2004). Women's achievements in higher education are partly responsible for narrowing the pay gap in the 1980s and 1990s. As more women earned…

Hill, Catherine; Silva, Elena

2005-01-01

423

Trunnion Collar Removal Machine - Gap Analysis Table  

Microsoft Academic Search

The purpose of this document is to review the existing the trunnion collar removal machine against the ''Nuclear Safety Design Bases for License Application'' (NSDB) [Ref. 10] requirements and to identify codes and standards and supplemental requirements to meet these requirements. If these codes and standards can not fully meet these requirements then a ''gap'' is identified. These gaps will

M. Johnson

2005-01-01

424

Tuning Carbon Nanotube Band Gaps with Strain  

Microsoft Academic Search

We show that the band structure of a carbon nanotube (NT) can be dramatically altered by mechanical strain. We employ an atomic force microscope tip to simultaneously vary the NT strain and to electrostatically gate the tube. We show that strain can open a band gap in a metallic NT and modify the band gap in a semiconducting NT. Theoretical

E. D. Minot; Yuval Yaish; Vera Sazonova; Ji-Yong Park; Markus Brink; Paul L. McEuen

2003-01-01

425

Semiconductor band gap localization via Gaussian function  

Microsoft Academic Search

To determine the band gap of bulk semiconductors with transmission spectroscopy alone is considered as an extremely difficult task because in the higher energy range, approaching and exceeding the band gap energy, the material is opaque yielding no useful data to be recorded. In this paper, by investigating the transmission of industrial GaSb wafers with a thickness of 500 µm,

B Ullrich; G J Brown; H Xi

2012-01-01

426

Temperature dependence of semiconductor band gaps  

Microsoft Academic Search

The application of a simple three-parameter fit to the temperature dependence of semiconductor band gaps is justified on both practical and theoretical grounds. In all trials the fit is numerically better than that obtained using the widely quoted Varshni equation. The formula is shown to be compatible with reasonable assumptions about the influence of phonons on the band-gap energy. Approximate

K. P. O'Donnell; X. Chen

1991-01-01

427

Gender pay gap and its perceptions  

Microsoft Academic Search

Purpose – The purpose of this paper is to broaden the domain of the gender pay gap research by exploring individuals' perceptions of it. Examining the factors that have an impact on the way individuals perceive the gender pay gap helps answering the question of why it persists and how to overcome it. Design\\/methodology\\/approach – The paper provides a conceptual

Violetta Khoreva

2011-01-01

428

The culture gap and its needed closures  

Microsoft Academic Search

The development of an enormous culture gap, in which no individuals of advanced societies possess even a billionth of the non?genetic information possessed by their entire society, has threatened a global collapse of civilisation. Critical parts of that gap must be rapidly bridged so that problems such as climate disruption, toxification of the Earth, loss of biodiversity and ecosystem services,

Paul R. Ehrlich; Anne H. Ehrlich

2010-01-01

429

Caring Closes the Language-Learning Gap  

ERIC Educational Resources Information Center

|The gap in academic achievement between English speakers and English learners continues to concern educators, parents, and legislators. Rising expectations for literacy and the increasing number of students from diverse backgrounds contribute to this achievement gap. In this article, the author discusses a variety of strategies for reaching out…

Borba, Mary

2009-01-01

430

GAP-43 Gene Expression Regulates Information Storage  

ERIC Educational Resources Information Center

|Previous reports have shown that overexpression of the growth- and plasticity-associated protein GAP-43 improves memory. However, the relation between the levels of this protein to memory enhancement remains unknown. Here, we studied this issue in transgenic mice (G-Phos) overexpressing native, chick GAP-43. These G-Phos mice could be divided at…

Holahan, Matthew R.; Honegger, Kyle S.; Tabatadze, Nino; Routtenberg, Aryeh

2007-01-01

431

Closing the Gender Gap: Act Now  

ERIC Educational Resources Information Center

|Gender gaps are pervasive in all walks of economic life and imply large losses in terms of foregone productivity and living standards to the individuals concerned and the economy. This new OECD report focuses on how best to close these gender gaps under four broad headings: (1) Gender equality, social norms and public policies; and gender…

OECD Publishing (NJ3), 2012

2012-01-01

432

Air Anion Density and its Affecting Factors in Greenbelts of Changsha  

Microsoft Academic Search

Air anion has obviously biochemical effect and function, and it is beneficial to human's health. With the improvement of people's living standard, more and more people are careful about environmental quality, especially air anion density. With ALC1000 air anion meter, we measured the air anion density in the greenbelt of Changsha and investigated how it was affected by the vegetation

Yuan Yaoqing; CHEN Xiangji

2008-01-01

433

A channel that allows inwardly directed fluxes of anions in protoplasts derived from wheat roots  

Microsoft Academic Search

An anion channel that only allows outward current flow (anion influx) has been identified in protoplasts derived from wheat (Triticum aestivum L., Triticum turgidum L.) roots. The anion outward rectifier (anion OR) measured by patch-clamp of whole cells activated very quickly, usually reaching a steady-state level in less than 100 ms and was easily distinguished from the cation outward rectifier

M. Skerrett; S. D. Tyerman

1994-01-01

434

Anion transport across the red blood cell membrane mediated by dielectric pores  

Microsoft Academic Search

Summary The anion transport across the red blood cell membrane is assumed to occur by ionic diffusion through dielectric pores which are formed by protein molecules spanning the red blood cell membrane. The access of anions to the dielectric pores is regulated by anion adsorption sites positioned at the entrances of the pores. The adsorption of small inorganic anions to

K. F. Schnell

1977-01-01

435

NEN Division Funding Gap Analysis  

SciTech Connect

The work in NEN Division revolves around proliferation detection. The sponsor funding model seems to have shifted over the last decades. For the past three lustra, sponsors are mainly interested in funding ideas and detection systems that are already at a technical readiness level 6 (TRL 6 -- one step below an industrial prototype) or higher. Once this level is reached, the sponsoring agency is willing to fund the commercialization, implementation, and training for the systems (TRL 8, 9). These sponsors are looking for a fast turnaround (1-2 years) technology development efforts to implement technology. To support the critical national and international needs for nonprolifertion solutions, we have to maintain a fluent stream of subject matter expertise from the fundamental principals of radiation detection through prototype development all the way to the implementation and training of others. NEN Division has large funding gaps in the Valley of Death region. In the current competitive climate for nuclear nonproliferation projects, it is imminent to increase our lead in this field.

Esch, Ernst I. [Los Alamos National Laboratory; Goettee, Jeffrey D. [Los Alamos National Laboratory; Desimone, David J. [Los Alamos National Laboratory; Lakis, Rollin E. [Los Alamos National Laboratory; Miko, David K. [Los Alamos National Laboratory

2012-09-05

436

Genetic Metabolic Disease  

Microsoft Academic Search

The terms inborn errors of metabolism, genetic metabolic disease, disorders of intermediary metabolism, and inherited metabolic disease are used interchangeably. For the sake of clarity, inborn errors of metabolism (IEMs) is used in this chapter. The common\\u000a feature of these disorders is a genetically determined interruption in one (or several related) metabolic pathway. This results\\u000a in clinical symptoms caused by

David R. FitzPatrick

437

Smad ubiquitination regulatory factor-2 controls gap junction intercellular communication by modulating endocytosis and degradation of connexin43.  

PubMed

Gap junctions consist of arrays of intercellular channels that enable adjacent cells to communicate both electrically and metabolically. Gap junction channels are made of a family of integral membrane proteins called connexins, of which the best-studied member is connexin43. Gap junctions are dynamic plasma membrane domains, and connexin43 has a high turnover rate in most tissue types. However, the mechanisms involved in the regulation of connexin43 endocytosis and transport to lysosomes are still poorly understood. Here, we demonstrate by live-cell imaging analysis that treatment of cells with 12-O-tetradecanoylphorbol 13-acetate (TPA) induces endocytosis of subdomains of connexin43 gap junctions. The internalized, connexin43-enriched vesicles were found to fuse with early endosomes, which was followed by transport of connexin43 to the lumen of early endosomes. The HECT E3 ubiquitin ligase smad ubiquitination regulatory factor-2 (Smurf2) was found to be recruited to connexin43 gap junctions in response to TPA treatment. Depletion of Smurf2 by small interfering RNA resulted in enhanced levels of connexin43 gap junctions between adjacent cells and increased gap junction intercellular communication. Smurf2 depletion also counteracted the TPA-induced endocytosis and degradation of connexin43. Collectively, these data identify Smurf2 as a novel regulator of connexin43 gap junctions. PMID:22623726

Fykerud, Tone Aase; Kjenseth, Ane; Schink, Kay Oliver; Sirnes, Solveig; Bruun, Jarle; Omori, Yasufumi; Brech, Andreas; Rivedal, Edgar; Leithe, Edward

2012-05-23

438

Intracellular anion fluorescence assay for sodium/iodide symporter substrates.  

PubMed

The sodium/iodide symporter (NIS) is primarily responsible for iodide accumulation in the thyroid gland for the synthesis of thyroid hormones; however, it can also transport other lyotropic anions in the thyroid gland and nonthyroid tissues. Some NIS substrates have important physiological or clinical roles, and others are environmental contaminants with health-related consequences. The aim of this study was to assess the utility of a yellow fluorescent protein variant, YFP-H148Q/I152L, as a biosensor to monitor the cellular uptake of NIS substrates, including thiocyanate (SCN(-)), nitrate (NO(3)(-)), chlorate (ClO(3)(-)), perchlorate (ClO(4)(-)), and perrhenate (ReO(4)(-)). The fluorescence of purified YFP-H148Q/I152L was suppressed by anions with an order of potency of ReO(4)(-)>ClO(4)(-)=I(-)=SCN(-)=ClO(3)(-)>NO(3)(-)?Cl(-). Anions also suppressed the fluorescence of YFP-H148Q/I152L expressed in FRTL-5, a thyroid cell line with high NIS expression. Quantitation of intracellular concentrations revealed differences among anions in the affinity and maximal velocity of NIS-mediated uptake as well as in the rate constant for passive efflux. These results suggest that YFP-H148Q/I152L can serve as an intracellular biosensor of NIS-transported anions and may be useful to study the physiology of endogenous anions as well as the health-related consequences of environmental anions. PMID:21545783

Di Bernardo, Julie; Iosco, Carmela; Rhoden, Kerry J

2011-04-20

439

Anion Separation by Selective Crystallization of Metal-Organic-Frameworks  

SciTech Connect

A novel approach for the separation of anions from aqueous mixtures was demonstrated, which involves their selective crystallization with metal-organic frameworks (MOFs) containing urea functional groups. Self-assembly of Zn{sup 2+} with the N,N{prime}-bis(m-pyridyl)urea (BPU) linker results in the formation of one-dimensional MOFs including various anions for charge balance, which interact to different extents with the zinc nodes and the urea hydrogen-bonding groups, depending on their coordinating abilities. Thus, Cl{sup -}, Br{sup -}, I{sup -}, and SO{sub 4}{sup 2-}, in the presence of BPU and Zn{sup 2+}, form MOFs from water, in which the anions coordinate the zinc and are hydrogen-bonded to the urea groups, whereas NO{sub 3}{sup -} and ClO{sub 4}{sup -} anions either do not form MOFs or form water-soluble discrete coordination complexes under the same conditions. X-ray diffraction, FTIR, and elemental analysis of the coordination polymers precipitated from aqueous mixtures containing equivalent amounts of these anions indicated total exclusion of the oxoanions and selective crystallization of the halides in the form of solid solutions with the general composition ZnCl{sub x}Br{sub y}I{sub z} {center_dot} BPU (x + y + z = 2), with an anti-Hofmeister selectivity. The concomitant inclusion of the halides in the same structural frameworks facilitates the rationalization of the observed selectivity on the basis of the diminishing interactions with the zinc and urea acidic centers in the MOFs when going from Cl{sup -} to I{sup -}, which correlates with decreasing anionic charge density in the same order. The overall crystal packing efficiency of the coordination frameworks, which ultimately determines their solubility, also plays an important role in the anion crystallization selectivity under thermodynamic equilibration.

Custelcean, Radu [ORNL

2006-01-01

440

Drastic differences in geminate ion kinetics, dependent on anion lifetimes  

NASA Astrophysics Data System (ADS)

We have previously shown that in the case of extremely short-lived halocarbon anions RCl- (like CCl4- or CFCl3-), one observes the decay of the solvent-separated ion pairs (R+||Cl-) instead of the geminate ion recombination between the solvent cation (S+) and the fragment anion (Cl-). If the anions live longer (e.g. CHCl3-) then the expected geminate ion kinetics is seen with a primary geminate pair (S+/CHCl3-) and a secondary geminate pair (S+/Cl-), coupled by the corresponding anion fragmentation rate. Ion pairs like (R+||Cl-) represent a product from ion recombination. The t-0.6 kinetic treatment used so far to analyse such geminate ion mechanism now was modified to allow the product from ion recombination to be an optical absorber with ?p?0. With this theory all the kinetic details of the production of ion pairs (CCl3+||Cl-) and their decay in the CCl4 system can now be explained. In order to understand the mechanistic dependence on fast and slow anion fragmentation, the results are compared with additional halocarbons, covering a wider range of anion lifetimes: hexa-, penta- and tetrachloroethane. For CCl4 the yield of ion pairs is highest and the anion lifetime shortest. The fragment radical CCl3 is available for charge-transfer from the solvent cations for a very long time. For tetrachloroethane or chloroform the release of the fragment radical R is so late, that the ion pair (R+||Cl-) cannot be observed, either due to a rather low efficiency for charge transfer to R, or more likely, because the ion pairs are decaying faster, than they are produced.

Bühler, R. E.

2001-01-01

441

The GapA/B gene duplication marks the origin of Streptophyta (charophytes and land plants).  

PubMed

Independent evidence from morphological, ultrastructural, biochemical, and molecular data have shown that land plants originated from charophycean green algae. However, the branching order within charophytes is still unresolved, and contradictory phylogenies about, for example,the position of the unicellular green alga Mesostigma viride are difficult to reconcile. A comparison of nuclear-encoded Calvin cycle glyceraldehyde-3-phosphate dehydrogenases (GAPDH) indicates that a crucial duplication of the GapA gene occurred early in land plant evolution. The duplicate called GapB acquired a characteristic carboxy-terminal extension (CTE) from the general regulator of the Calvin cycle CP12. This CTE is responsible for thioredoxin-dependent light/dark regulation. In this work, we established GapA, GapB, and CP12 sequences from bryophytes, all orders of charophyte as well as chlorophyte green algae, and the glaucophyte Cyanophora paradoxa. Comprehensive phylogenetic analyses of all available plastid GAPDH sequences suggest that glaucophytes and green plants are sister lineages and support a positioning of Mesostigma basal to all charophycean algae. The exclusive presence of GapB in terrestrial plants, charophytes, and Mesostigma dates the GapA/B gene duplication to the common ancestor of Streptophyta. The conspicuously high degree of GapB sequence conservation suggests an important metabolic role of the newly gained regulatory function. Because the GapB-mediated protein aggregation most likely ensures the complete blockage of the Calvin cycle at night, we propose that this mechanism is also crucial for efficient starch mobilization. This innovation may be one prerequisite for the development of storage tissues in land plants. PMID:16527864

Petersen, Jörn; Teich, René; Becker, Burkhard; Cerff, Rüdiger; Brinkmann, Henner

2006-03-09

442

Lateral segregation of anionic phospholipids in model membranes induced by cytochrome P450 2B1: Bidirectional coupling between CYP2B1 and anionic phospholipid  

Microsoft Academic Search

The lateral segregation of anionic phospholipids phosphatidic acid (PA), phosphatidylinositol (PI), and phosphatidylserine (PS) was detected after addition of cytochrome P450 2B1 (CYP2B1). The tendency of lipid clustering was highly dependent on the type of anionic phospholipids examined. PA was the most highly clustered while PI and PS clustered to a lesser degree. Moreover, liposomes containing anionic phospholipids form anionic

Keon-Hee Kim; Dong-Hyun Kim; Hyun-Hee Jang; Mihee Kim; Dae-Hwan Kim; Joon-Sik Kim; Jeong-Il Kim; Ho Zoon Chae; Taeho Ahn; Chul-Ho Yun

2007-01-01

443

Gap junction and hemichannel functions in osteocytes.  

PubMed

Cell-to-cell and cell-to-matrix communication in bone cells mediated by gap junctions and hemichannels, respectively, maintains bone homeostasis. Gap junctional communication between cells permits the passage of small molecules including calcium and cyclic AMP. This cell-to-cell communication occurs between bone cells including osteoblasts, osteoclasts and osteocytes, and is important in both bone formation and bone resorption. Connexin (Cx) 43 is the predominant gap junction protein in bone cells, and facilitates the communication of cellular signals either through docking of gap junctions between two cells, or through the formation of un-paired hemichannels. Systemic deletion of Cx43 results in perinatal lethality, so conditional deletion models are necessary to study the postnatal role of gap junctions in bone. These models provide the opportunity to determine the role of gap junctions in specific bone cells, notably the osteocyte. In this review, we summarize the key roles that gap junctions and hemichannels in osteocytes play in bone cell response to many stimuli including mechanical loading, intracellular and extracellular stimuli, such as parathyroid hormone, PGE2, plasma calcium levels and pH, as well as in maintaining osteocyte survival. PMID:23069374

Loiselle, Alayna E; Jiang, Jean X; Donahue, Henry J

2012-10-13

444

The treatment gap in mental health care.  

PubMed Central

Mental disorders are highly prevalent and cause considerable suffering and disease burden. To compound this public health problem, many individuals with psychiatric disorders remain untreated although effective treatments exist. We examine the extent of this treatment gap. We reviewed community-based psychiatric epidemiology studies that used standardized diagnostic instruments and included data on the percentage of individuals receiving care for schizophrenia and other non-affective psychotic disorders, major depression, dysthymia, bipolar disorder, generalized anxiety disorder (GAD), panic disorder, obsessive-compulsive disorder (OCD), and alcohol abuse or dependence. The median rates of untreated cases of these disorders were calculated across the studies. Examples of the estimation of the treatment gap for WHO regions are also presented. Thirty-seven studies had information on service utilization. The median treatment gap for schizophrenia, including other non-affective psychosis, was 32.2%. For other disorders the gap was: depression, 56.3%; dysthymia, 56.0%; bipolar disorder, 50.2%; panic disorder, 55.9%; GAD, 57.5%; and OCD, 57.3%. Alcohol abuse and dependence had the widest treatment gap at 78.1%. The treatment gap for mental disorders is universally large, though it varies across regions. It is likely that the gap reported here is an underestimate due to the unavailability of community-based data from developing countries where services are scarcer. To address this major public health challenge, WHO has adopted in 2002 a global action programme that has been endorsed by the Member States.

Kohn, Robert; Saxena, Shekhar; Levav, Itzhak; Saraceno, Benedetto

2004-01-01

445

Anion-induced shuttling of a naphthalimide triazolium rotaxane.  

PubMed

The anion-templated synthesis of a rotaxane structure, incorporating the new naphthalimide triazolium motif, is described and the interlocked host shown to exhibit selective, uni-directional, anion-induced shuttling. Initial pseudorotaxane investigations demonstrate the ability of a naphthalimide triazolium threading component to form interpenetrated assemblies with counter-anion-dependent co-conformations. (1)H NMR studies reveal that the shuttling behaviour of the analogous rotaxane host system is controlled by selective anion binding and by the nature of the solvent conditions. Complete macrocycle translocation only occurs upon the recognition of the smaller halide anions (chloride and bromide). The rotaxane solid-state crystal structure in the presence of chloride is in agreement with the solution-phase co-conformation. The sensitivity of the axle naphthalimide absorbance band to the position of the macrocycle component within the interlocked structure enabled the molecular motion to be observed by UV/Vis spectroscopy, and the chloride-induced shuttling of the rotaxane was reversed upon silver hexafluorophosphate addition. PMID:22550020

Spence, Graeme T; Pitak, Mateusz B; Beer, Paul D

2012-04-30

446

Effects of anions on nanostructuring of cationic amphiphilic peptides.  

PubMed

The effects of addition of a series of stoichiometric salts on the nanostructuring of cationic amphiphilic peptides have been investigated through the combination of atomic force microscopy (AFM), circular dichroism (CD), and turbidity measurements. The results revealed that anions had more pronounced effects than cations in tuning the nanostructures formed from these peptides. Addition of ClO(3)(-), NO(3)(-), and Br(-) could stabilize the primary nanostructures (nanostacks, nanospheres, or short nanorods) formed by A(9)K and I(3)K and effectively inhibit their growth into longer nanostructures (nanorods or nanotubes). In contrast, the anions of Cl(-), SO(4)(2-), HPO(4)(2-), PO(4)(3-), and C(6)H(5)O(7)(3-) (citrate) favored the axial growth of these peptides to form long intersecting nanofibrils and led to an increase in diameter and surface roughness, as well, clearly enhancing their propensity for nanostructuring. The efficiency of different anions in promoting the growth of peptide nanoaggregates into larger ones could be ordered as ClO(3)(-) < NO(3)(-) ? Br(-) < Cl(-) < SO(4)(2-) < HPO(4)(2-) < PO(4)(3-) < C(6)H(5)O(7)(3-), broadly consistent with the Hofmeister anion sequence. These observations were well rationalized by considering different aspects of direct interactions of the anions with the peptide molecules. PMID:21894997

Cao, Meiwen; Wang, Yuming; Ge, Xin; Cao, Changhai; Wang, Jing; Xu, Hai; Xia, Daohong; Zhao, Xiubo; Lu, Jian R

2011-09-28

447

Cation-anion relationships in a nonfacultative halophyte, Galenia pubescens  

SciTech Connect

Galenia pubescens (Eckl. and Zeyh) Druce was grown in solution culture under a variety of conditions to test its cation-anion relationships. It is a plant in which mineral cations exceed mineral anions. It then has from fewer than 100 to 400 or more milliequivalents per 100 grams of organic acid anions to balance cations minus anions. Mineral cations exceeded mineral anions in leaves, stems, and roots whether sodium chloride as added in abundance or whether the nitrogen source was nitrate, ammonia, or urea. When sodium or chlorine was added, both ions tended to accumulate in leaves rather than in roots; sodium was more pronounced in this respect than was chlorine. Galenia pubescens grew as well in a solution or in soil containing 400 meq/liter NaCl as in one without NaCl. The 400 meq/liter Na/sub 2/SO/sub 4/ was excessive. Galenia pubescens is a subtropical nonfacultative halophyte that can grow in nonsaline conditions and also in seawater. It has a very high rate of photosynthesis and capacity to synthesize large quantities of protein. It has possibilities as a biomass crop.

Wallace, A.

1982-07-01

448

Gas-phase chemistry of alkylcarbonate anions and radicals  

NASA Astrophysics Data System (ADS)

Alkylcarbonate anions and radicals ROCOO-/ (R = H, CH3, C2H5, i-C3H7, and t-C4H9) are investigated in the gas phase by means of mass spectrometry and ab initio calculations. Structural parameters and energies are obtained at the MP2/6-311++G(3df,3pd)//MP2/6-311++G(d,p) level of theoryE Standard enthalpies of formation for the anions and radicals are determined via atomization energies and isodesmic reactions using the CBS-Q method. Further, alkylcarbonate anions are probed by metastable ion and collisional activation experiments, and the chemistry of the neutral radicals is investigated by charge-reversal and neutralization-reionization mass spectrometry. Although decarboxylation dominates the unimolecular reactivity of the species for both charge states, some other interesting features are observed, particularly for the anions, such as the formation of the CO3- radical anion or the presence of ionic fragments formed via hydrogen atom transfer.

Soldi-Lose, Héloïse; Schröder, Detlef; Schwarz, Helmut

2008-02-01

449

Slc26A9 - anion exchanger, channel and Na+ transporter  

PubMed Central

The SLC26 gene family encodes anion transporters with diverse functional attributes: (a) anion exchanger, (b) anion sensor and (c) anion conductance (likely channel). We have cloned and studied Slc26a9, a paralog expressed mostly in lung and stomach. Immunohistochemistry shows that Slc26a9 is present at apical and intracellular membranes of lung and stomach epithelia. Using expression in Xenopus laevis oocytes and ion-sensitive microelectrodes, we discovered that Slc26a9 has a novel function not found in any other Slc26 proteins – cation coupling. Intracellular pH and voltage measurements show that Slc26a9 is a nCl--HCO3- exchanger, suggesting roles in gastric HCl secretion or pulmonary HCO3- secretion; Na+ electrodes and uptakes reveal that Slc26a9 has a cation-dependence. Single channel measurements indicate that Slc26a9 displays discrete open and close states. These experiments show that Slc26a9 has three discrete physiological modes: nCl--HCO3- exchanger, Cl- channel, and Na+-anion cotransporter. Thus, the Slc26a9 transporter-channel is uniquely suited for dynamic and tissue-specific physiology or regulation in epithelial tissues.

Chang, Min-Hwang; Plata, Consuelo; Zandi-Nejad, Kambiz; Sin?ic, Aleksandra; Sussman, Caroline R.; Mercado, Adriana; Broumand, Vadjista; Raghuram, Viswanathan; Mount, David B.; Romero, Michael F.

2009-01-01

450

Astronomical identification of CN^-, the smallest observed molecular anion  

NASA Astrophysics Data System (ADS)

We present the first astronomical detection of a diatomic negative ion, the cyanide anion CN^-. CN^- is identified through the observation of the J = 2-1 and J = 3-2 rotational transitions in the C-star envelope IRC +10216 with the IRAM 30-m telescope. The U-shaped line profiles indicate that CN^-, like the large anion C_6H^-, is formed in the outer regions of the envelope. Chemical and excitation model calculations suggest that this species forms from the reaction of large carbon anions with N atoms, rather than from the radiative attachment of an electron to CN, as is the case for large molecular anions. The unexpectedly large abundance derived for CN^-, 0.2 % relative to CN, makes likely its detection in other astronomical sources. A parallel search for the small anion C_2H^- remains so far unconclusive, despite the previous tentative identification of the J = 1-0 rotational transition. The abundance of C_2H^- in IRC +10216 is found to be vanishingly small, < 0.0014 % relative to C_2H.

Agundez, M.; Cernicharo, J.; Guelin, M.; Kahane, C.; Roueff, E.; Klos, J.; Aoiz, F. J.; Lique, F.; Marcelino, N.; Goicoechea, J. R., Gonzalez-Garcia, M.; Gottlieb, C. A.; McCarthy, M. C.; Thaddeus, P.

2011-05-01

451

The oxidative metabolism of circulating phagocytes in ankylosing spondylitis: determination by whole blood chemiluminescence  

Microsoft Academic Search

OBJECTIVESuperoxide anion radicals within the human body are regarded as a major cause of inflammation. However, their role in the pathogenesis of ankylosing spondylitis (AS) has not been well identified. This study aimed at investigating the relation between AS and the oxidative metabolism of phagocytes in whole blood.METHODS24 patients with classic AS were examined to determine their clinical status; complete

Kuo-Jang Ho; Po-Quang Chen; Chiung-Yu Chang; Fung-Jou Lu

2000-01-01

452

Connexin-based gap junction hemichannels: Gating mechanisms  

PubMed Central

Connexins (Cxs) form hemichannels and gap junction channels. Each gap junction channel is composed of two hemichannels, also termed connexons, one from each of the coupled cells. Hemichannels are hexamers assembled in the ER, the Golgi, or a post Golgi compartment. They are transported to the cell surface in vesicles and inserted by vesicle fusion, and then dock with a hemichannel in an apposed membrane to form a cell–cell channel. It was thought that hemichannels should remain closed until docking with another hemichannel because of the leak they would provide if their permeability and conductance were like those of their corresponding cell–cell channels. Now it is clear that hemichannels formed by a number of different connexins can open in at least some cells with a finite if low probability, and that their opening can be modulated under various physiological and pathological conditions. Hemichannels open in different kinds of cells in culture with conductance and permeability properties predictable from those of the corresponding gap junction channels. Cx43 hemichannels are preferentially closed in cultured cells under resting conditions, but their open probability can be increased by the application of positive voltages and by changes in protein phosphorylation and/or redox state. In addition, increased activity can result from the recruitment of hemichannels to the plasma membrane as seen in metabolically inhibited astrocytes. Mutations of connexins that increase hemichannel open probability may explain cellular degeneration in several hereditary diseases. Taken together, the data indicate that hemichannels are gated by multiple mechanisms that independently or cooperatively affect their open probability under physiological as well as pathological conditions.

Saez, Juan C.; Retamal, Mauricio A.; Basilio, Daniel; Bukauskas, Feliksas F.; Bennett, Michael V.L.

2013-01-01

453

Soft superconducting gap in semiconductor Majorana nanowires.  

PubMed

We theoretically consider the ubiquitous soft gap measured in the tunneling conductance of semiconductor-superconductor hybrid structures, in which recently observed signatures of elusive Majorana bound states have created much excitement. We systematically study the effects of magnetic and nonmagnetic disorder, temperature, dissipative Cooper pair breaking, and interface inhomogeneity, which could lead to a soft gap. We find that interface inhomogeneity with moderate dissipation is the only viable mechanism that is consistent with the experimental observations. Our work indicates that improving the quality of the superconductor-semiconductor interface should result in a harder induced gap. PMID:23683232

Takei, So; Fregoso, Benjamin M; Hui, Hoi-Yin; Lobos, Alejandro M; Das Sarma, S

2013-04-30

454

REVIEW ARTICLE: Wide gap semiconductor microwave devices  

NASA Astrophysics Data System (ADS)

A review of properties of wide gap semiconductor materials such as diamond, diamond-like carbon films, SiC, GaP, GaN and AlGaN/GaN that are relevant to electronic, optoelectronic and microwave applications is presented. We discuss the latest situation and perspectives based on experimental and theoretical results obtained for wide gap semiconductor devices. Parameters are taken from the literature and from some of our theoretical works. The correspondence between theoretical results and parameters of devices is critically analysed.

Buniatyan, V. V.; Aroutiounian, V. M.

2007-10-01

455

Closing the Geoscience Talent Gap  

NASA Astrophysics Data System (ADS)

The geosciences, like most technical professions, are facing a critical talent gap into the future, with too few new students entering the profession and too many opportunities for that supply. This situation has evolved as a result of multiple forces, including increased commodity prices, greater strain on water resources, development encroachment on hazardous terrain, and the attrition of Baby Boomers from the workforce. Demand is not the only issue at hand, the legacy of lagging supplies of new students and consequently new professionals has enhanced the problem. The supply issue is a result of the fallout from the 1986 oil bust and the unsubstantiated hopes for an environmental boom in the 1990"s, coupled by the lengthening of academic careers, indefinitely delaying the predicted exodus of faculty. All of these issues are evident in the data collected by AGI, its Member Societies, and the federal government. Two new factors are beginning to play an increased role in the success or failure of geosciences programs: namely student attitudes towards careers and the ability for departments to successfully bridge the demands of the incoming student with the requirements for an individual to succeed in the profession. An issue often lost for geosciences departments is that 95% of geoscientists in the United States work in the private sector or for government agencies, and that those employers drive the profession forward in the long term. Departments that manage to balance the student needs with an end source of gainful employment are witnessing great success and growth. Currently, programs with strong roots in mining, petroleum, and groundwater hydrology are booming, as are graduate programs with strong technology components. The challenge is recognizing the booms, busts, and long-term trends and positioning programs to weather the changes yet retain the core of their program. This level of planning coupled with a profession-wide effort to improve initial recruitment, greater throughput of graduates into the profession, and the development of professionalism for majors will be central to the geosciences future success.

Keane, C. M.

2007-12-01

456

The Hofmeister anion effect and the growth of polyelectrolyte multilayers.  

PubMed

The influence of a variety of counteranions on the properties of polyelectrolyte multilayers deposited by layer-by-layer technique is studied by using ellipsometry and AFM. We found out that in thin dry multilayers (20-90 nm) ofpoly(4-styrenesulfonate) (PSS) and poly(diallyldimethylammonium) (PDADMA), the thickness follows reasonably well the position of the counteranion in the Hofmeister series. The polyelectrolyte-counteranion interaction is studied by means of viscosity measurements of semidilute solutions of PDADMA in the presence of different anions. The dynamic viscosities follow the Hofmeister series of anions and correlate with the thickness of multilayers. Two parameters describing the interaction of ions with water, the Jones-Dole viscosity B coefficient and the hydration entropy, are used to explain the anion effect on the developing multilayer thickness. Reasonably smooth and monotonic functional dependence is observed between the layer thickness and these two parameters. PMID:15875399

Salomäki, Mikko; Tervasmäki, Piia; Areva, Sami; Kankare, Jouko

2004-04-27

457

Cellular Uptake of Ribonuclease A Relies on Anionic Glycans†  

PubMed Central

Bovine pancreatic ribonuclease (RNase A) can enter human cells, even though it lacks a cognate cell-surface receptor protein. Here, we report on the biochemical basis for its cellular uptake. Analyses in vitro and in cellulo revealed that RNase A interacts tightly with abundant cell-surface proteoglycans containing glycosaminoglycans, such as heparan sulfate and chondroitin sulfate, as well as with sialic acid-containing glycoproteins. The uptake of RNase A correlates with cell anionicity, as quantified by measuring electrophoretic mobility. The cellular binding and uptake of RNase A contrast with those of Onconase®, an amphibian homologue that does not interact tightly with anionic cell-surface glycans. As anionic glycans are especially abundant on human tumor cells, our data predicate utility for mammalian ribonucleases as cancer chemotherapeutic agents.

Chao, Tzu-Yuan; Lavis, Luke D.; Raines, Ronald T.

2010-01-01

458

Rational design of a macrocyclic-based chemosensor for anions  

PubMed Central

A macrocyclic-based fluorescence chemosensor has been designed and synthesized from the reaction of dansyl chloride and a hexaaminomacrocycle containing four secondary and two tertiary amines. The new chemosensor has been examined for its binding ability toward phosphate, sulfate, nitrate, iodide, bromide, chloride, and fluoride by fluorescence spectroscopy in DMSO. The results indicate that the compound binds each of the anions with a 1:1 stoichiometry, showing high affinity for the oxoanions, chloride and iodide with the binding constants up to four orders of magnitude. Ab initio calculations based on density functional theory (DFT) suggest that the ligand is deformed in order to encapsulate an anion, and each anion, except fluoride, is bonded to the macrocycle through two NH…X? and four CH…X? interactions.

Dey, Kalpana R.; Wong, Bryan M.; Hossain, Md. Alamgir

2010-01-01

459