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1

Robust superamphiphobic coatings based on silica particles bearing bifunctional random copolymers.  

PubMed

Reported herein is the growth of bifunctional random copolymer chains from silica particles through a "grafting from" approach and the use of these copolymer-bearing particles to fabricate superamphiphobic coatings. The silica particles had a diameter of 90 ± 7 nm and were prepared through a modified Stöber process before atom transfer radical polymerization (ATRP) initiators were introduced onto their surfaces. Bifunctional copolymer chains bearing low-surface-free-energy fluorinated units and sol-gel-forming units were then grafted from these silica particles by surface-initiated ATRP. Perfluorooctyl ethyl acrylate (FOEA) and 3-(triisopropyloxy)silylpropyl methacrylate (IPSMA) were respectively used as fluorinated and sol-gel-forming monomers in this reaction. Hydrolyzing the IPSMA units in the presence of an acid catalyst yielded silica particles that were adorned with silanol-bearing copolymer chains. Coatings were prepared by spraying these hydrolyzed silica particles onto glass and cotton substrates. A series of four different copolymer-functionalized silica particles samples bearing copolymers with similar FOEA molar fractions (fF) of ~80% but with different copolymer grafting mass ratios (gm) that ranged between 12.3 wt% and 58.8 wt%, relative to silica, were prepared by varying the polymerization protocols. These copolymer-bearing silica particles with a gm exceeding 34.1 wt% were used to coat glass and cotton substrates, yielding superamphiphobic surfaces. More importantly, these particulate-based coatings were robust and resistant to solvent extraction and NaOH etching thanks to the self-cross-linking of the copolymer chains and their covalent attachment to the substrates. PMID:24256180

Zhang, Ganwei; Lin, Shudong; Wyman, Ian; Zou, Hailiang; Hu, Jiwen; Liu, Guojun; Wang, Jiandong; Li, Fei; Liu, Feng; Hu, Meilong

2013-12-26

2

Asymmetrical Bifunctional Organic Peroxides as Initiators for the High-Pressure Polymerization of Ethylene  

Microsoft Academic Search

As a follow-up to earlier investigations into the high-pressure polymerization of ethylene with symmetrically substituted bifunctional peroxides, the suitability of 2,5-dimethylhexane-2-t-butylperoxy-5-perpivalate, a peroxide with different substituents on both O—O groups, has been tested. The polymerization tests were carried out in continuous operation in a stirred autoclave at 1700 bar, 240–285°C, a residence time of 60 s, and an initiator concentration

Gerhard Luft; Max Dorn

1988-01-01

3

Bifunctional nanoparticles with fluorescence and magnetism via surface-initiated AGET ATRP mediated by an iron catalyst.  

PubMed

Fluorescent/magnetic nanoparticles are of interest in many applications in biotechnology and nanomedicine for its living detection. In this study, a novel method of surface modification of nanoparticles was first used to modify a fluorescent monomer on the surfaces of magnetic nanoparticles directly. This was achieved via iron(III)-mediated atom-transfer radical polymerization with activators generated by electron transfer (AGET ATRP). Fluorescent monomer 9-(4-vinylbenzyl)-9H-carbazole (VBK) was synthesized and was grafted from magnetic nanoparticles (ferroferric oxide) via AGET ATRP using FeCl(3)·6H(2)O as the catalyst, tris(3,6-dioxaheptyl)amine (TDA-1) as the ligand, and ascorbic acid (AsAc) as the reducing agent. The initiator for ATRP was modified on magnetic nanoparticles with the reported method: ligand exchange with 3-aminopropyltriethoxysilane (APTES) and then esterification with 2-bromoisobutyryl bromide. After polymerization, a well-defined nanocomposite (Fe(3)O(4)@PVBK) was yielded with a magnetic core and a fluorescent shell (PVBK). Subsequently, well-dispersed bifunctional nanoparticles (Fe(3)O(4)@PVBK-b-P(PEGMA)) in water were obtained via consecutive AGET ATRP of hydrophilic monomer poly(ethylene glycol) methyl ether methacrylate (PEGMA). The chemical composition of the magnetic nanoparticles' surface at different surface modification stages was investigated with Fourier transform infrared (FT-IR) spectra. The magnetic and fluorescent properties were validated with a vibrating sample magnetometer (VSM) and a fluorophotometer. The Fe(3)O(4)@PVBK-b-P(PEGMA) nanoparticles showed an effective imaging ability in enhancing the negative contrast in magnetic resonance imaging (MRI). PMID:21882878

Liu, Jiliang; He, Weiwei; Zhang, Lifen; Zhang, Zhengbiao; Zhu, Jian; Yuan, Lin; Chen, Hong; Cheng, Zhenping; Zhu, Xiulin

2011-10-18

4

Synthesis of bifunctional imido alkylidene bispyrrolide complexes of molybdenum and their conversion into bifunctional imido alkylidene diolate complexes that can be employed as ROMP initiators.  

PubMed

Addition of four equivalents of lithium 2,5-dimethylpyrrolide to a solution of [Mo(NAr)(OR(F6))(2)(CHC(5)H(4))](2)Fe (OR(F6)=OCMe(CF(3))(2)) in dichloromethane led to [Mo(NAr)(Me(2)Pyr)(2)(CHC(5)H(4))](2)Fe (2; Me(2)Pyr=2,5-dimethylpyrrolide) and lithium hexafluoro-tert-butoxide, which crystallizes out upon cooling the reaction mixture to -35 degrees C. Attempts to prepare parent pyrrolide complexes analogous to 2 resulted in the formation of a mixture of two products. The one that could be isolated contains one equivalent of lithium pyrrolide per molybdenum, that is [Mo(NAr)(Pyr)(3)(CHC(5)H(4))](2)FeLi(2) (3). The X-ray structure obtained shows it to be a dimer of dimers in which each lithium atom is bound to three pyrrolides. Addition of four equivalents of lithium 2,5-dimethylpyrrolide to [Mo(NAr)(OR(F6))(2)](2)(DME)(2)(CH-1,4-C(6)H(4)CH) (1 b) in cold DME produced [Mo(NAr)(Me(2)Pyr)(2)](2)(CH-1,4-C(6)H(4)CH) (4) in good yield, in which the bridging alkylidene is derived from 1,4-divinylbenzene. Three equivalents of (S)-H(2)[Biphen] are required for a clean reaction with 3 to form [Mo(NAr)(Biphen)(CHC(5)H(4))](2)Fe (5) (H(2)[Biphen]=3,3'-di-tert-butyl-5,5',6,6'-tetramethyl-1,1'-biphenyl-2,2'-diol), Li(2)[Biphen], and two equivalents of pyrrole. Reactions involving 4 with the chiral diols are the best behaved. Brown [Mo(NAr)(Benz(2)Bitet)](2)(CH-1,4-C(6)H(4)CH) (6) can be isolated upon addition of (R)-H(2)[Benz(2)Bitet] (H(2)[Benz(2)Bitet]=(3,3'-dibenzhydryl-5,5',6,6',7,7',8,8'-octahydro-1,1'-binaphthyl-2,2'-diol) to 4, while addition of (R)-H(2)[Mes(2)Bitet] (H(2)[Mes(2)Bitet]=3,3'-dimesityl-5,5',6,6',7,7',8,8'-octahydro-1,1'-binaphthyl-2,2'-diol) to 4 yields [Mo(NAr)(Mes(2)Bitet)](2)(CH-1,4-C(6)H(4)CH) (7). Compounds 5, 6, and 7 were employed as initiators for the polymerization of 2,3-dicarbomethoxynorbornadiene (DCMNBD) and 2,3-bis(trifluoromethyl)norbornadiene (NBDF6). PMID:18604823

Gabert, Andrea J; Schrock, Richard R; Müller, Peter

2008-09-01

5

77 FR 47624 - Tall Bear Group, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request...  

Federal Register 2010, 2011, 2012, 2013

...Regulatory Commission [Docket No. ER12-2374-000] Tall Bear Group, LLC; Supplemental Notice That Initial Market- Based...supplemental notice in the above-referenced proceeding, of Tall Bear Group, LLC's application for market-based rate...

2012-08-09

6

78 FR 2984 - Silver Bear Power, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes...  

Federal Register 2010, 2011, 2012, 2013

...Energy Regulatory Commission [Docket No. ER13-733-000] Silver Bear Power, LLC; Supplemental Notice That Initial Market...supplemental notice in the above-referenced proceeding, of Silver Bear Power, LLC's application for market-based rate...

2013-01-15

7

Initial non-weight-bearing therapy is important for preventing vertebral body collapse in elderly patients with clinical vertebral fractures  

PubMed Central

Purpose The aim of the present conventional observational study was to compare the clinical outcomes of initial non-weight-bearing therapy and conventional relative rest therapy among elderly patients with clinical vertebral fractures. Methods In total, 196 consecutive patients with clinical vertebral fractures (mean age: 78 years) who were hospitalized for treatment between January 1999 and March 2007 were analyzed. Initial non-weight-bearing therapy consisted of complete bed rest allowing rolling on the bed without any weight-bearing to the spine for 2 weeks, followed by rehabilitation wearing a soft brace. The indications for initial non-weight-bearing therapy were vertebral fracture involving the posterior portion of the vertebral body at the thoraco-lumbar spine, mild neurological deficit, instability of the fracture site, severe pain, multiple vertebral fractures arising from trauma, malalignment at the fracture site, and mild spinal canal stenosis caused by the fracture. Patients who met the indication criteria were treated with initial non-weight-bearing therapy (n = 103), while the other patients were treated with conventional relative rest (n = 93). All the patients were uniformly treated with intramuscular elcatonin to relieve pain. The primary endpoint was progression of the vertebral fracture. The secondary endpoints included bony union and subjective back pain. The follow-up period was 12 weeks. Results Compared with the conventional relative rest group, the collapse rate of the anterior and posterior portions of the vertebral body was significantly smaller in the initial non-weight-bearing group. The bony union rate was 100% in the initial non-weight-bearing group and 97% in the conventional relative rest group. The number of patients who experienced back pain was significantly lower in the initial non-weight-bearing group than in the conventional relative rest group. Conclusion These results suggest that initial non-weight-bearing therapy is important for preventing vertebral body collapse and for relieving pain among elderly patients with clinical vertebral fractures.

Kishikawa, Yoichi

2012-01-01

8

MTBE OXIDATION BY BIFUNCTIONAL ALUMINUN  

EPA Science Inventory

Bifunctional aluminum, prepared by sulfating zero-valent aluminum with sulfuric acid, is an innovative extension of zero-valent metal (ZVM) technology for ground water remediation. Bifunctional aluminum has a dual functionality of simultaneously decomposing both reductively- an...

9

MTBE OXIDATION BY BIFUNCTIONAL ALUMINUM  

EPA Science Inventory

Bifunctional aluminum, prepared by sulfating zero-valent aluminum with sulfuric acid, has a dual functionality of simultaneously decomposing both reductively- and oxidatively-degradable contaminants. In this work, the use of bifunctional aluminum for the degradation of methyl te...

10

Mechanism of dent initiated flaking and bearing life enhancement technology under contaminated lubrication condition. Part II: Effect of rolling element surface roughness on flaking resulting from dents, and life enhancement technology of rolling bearings under contaminated lubrication condition  

Microsoft Academic Search

The dent initiated flaking life of a bearing is sometimes shorter than the calculated life. Therefore, it is important to develop an enhanced-life bearing for contaminated lubrication conditions. In this paper, the authors indicated that the dent initiated flaking life of a raceway is significantly reduced in bearings where the general surface roughness of the rolling elements is increased by

T. Ueda; N. Mitamura

2009-01-01

11

Initial in vivo evaluation of the newly developed axial flow turbo pump with hydrodynamic bearings.  

PubMed

An implantable, compact rotary blood pump has been newly developed using an axial flow turbo pump with hydrodynamic bearings. The rotating impeller, which is hydrodynamically levitated with the assistance of repulsive magnetic force, has no contact with the inner surface of the pump. To evaluate the hemodynamic performance and biocompatibility, the pump was installed into four calves for up to 90 days. The pump was installed in the left heart bypass fashion, and placed paracorporeally in the first two calves and in the thoracic cavity in the other two calves. All calves received anticoagulation and antiaggregation therapy during the study. Aortic pressure, heart rate and pump-operating parameters were continuously measured. Hematologic and biochemical tests to evaluate anemia, hepato-renal function and the extent of hemolysis were performed on schedule. Each calf was killed at the termination of the experiments, and pathological analysis for the biocompatibility of the pump system was performed, including the thrombi in the device, emboli in the systemic organs and signs of infection. The pump stably produced a flow of 5 l/min. Each calf was supported for 78, 50, 90 and 90 days, respectively, with no incidence of hemorrhage, organ failure or significant hemolysis. No thrombus formation or mechanical wearing was observed inside the pump. There was no evidence of heat injury around the pump. Device-related infections were observed, but the severity of infection was mild in the implant case compared to the paracorporeal case. The pump demonstrated acceptable hemodynamic performance and biocompatibility in the initial in vivo testing. PMID:21207088

Tanaka, Hideyuki; Tsukiya, Tomonori; Tatsumi, Eisuke; Mizuno, Toshihide; Hidaka, Tatsuya; Okubo, Takeshi; Osada, Toshiyuki; Miyamoto, Shinji; Taenaka, Yoshiyuki

2011-03-01

12

Bifunctional oxygen electrodes  

NASA Astrophysics Data System (ADS)

The objective of the research on bifunctional oxygen electrodes for alkaline electrolytes was to improve significantly both the cathodic and anodic polarization as well as the cycle life of such electrodes. The research has focused on finding high-efficiency, long-life electrocatalysts for O2 reduction and generation and achieving an understanding of the mechanisms of the catalysis. Catalyst systems which have been examined in alkaline electrolytes have included the following:various types of carbons and graphites; chemically-modified carbons and graphites using adsorptive attachment (e.g., various quinones, macrocycles and chemical linkages); silver and various intermetallics; various oxide systems including perovskites, spinels, pyrochlores and other mixed transition metal oxides; transition metal macrocycles including porphyrins, phthalocyanines, naphthalocyanines and tetraazaannulenes; and thermally-treated macrocycles. Mechanistic studies have particularly focused on the reduction of O2 on various carbon/graphite surfaces and the role of the O2(-) radical ion.

Tryk, D.; Aldred, W.; Chen, Z.; Fierro, C.; Hashiguchi, J.; Hossain, M.; Zhang, Z.; Zhao, F.

1985-01-01

13

rRNA-protein neighbourhood in Escherichia coli 70 S ribosomes and 70 S initiation complex. Probing by bifunctional Pt(II)-containing reagent.  

PubMed

The cleavable homobifunctional reagent dichloro[N,N,N',N'-tetrakis(2-aminoethyl)-1,6-hexamethylenediamminedi platinum (II)] dichloride was used for studying rRNA-protein cross-links in free 35S-labelled 70 S ribosomes and within initiation complex ribosome.AUGU6.fMet-tRNA(fMet). It was shown that the sets of proteins cross-linked to 16 S and 23 S rRNA in free 70 S ribosomes and in 70 S initiation complex do not differ significantly. The authors are the first to demonstrate most of the 23 S rRNA-protein cross-links and some 16 S rRNA-protein cross-links, in particular those with L7/L12 protein. PMID:3042466

Chistyakov, P G; Abdukayumov, M N; Veniaminova, A G; Vladimirov, S N; Graifer, D M; Kazakov, S A; Karpova, G G

1988-08-15

14

Differences in 23 S rRNA-protein neighbourhood in Escherichia coli 70 S ribosomes and 70 S initiation complex. Probing by bifunctional Pt(II)-containing reagent.  

PubMed

rRNA-protein cross-links in free E. coli 35S-labeled 70 S ribosomes and in the initiation complex 35S-labeled 70 S ribosome.AUGU6.fMet-tRNA(fMet) were studied with the aid of a new type of binuclear Pt(II) compound - dichlorotetra-ammine(1,6-hexamethylenediaminediplatinum++ +) dichloride. The use of this reagent allowed us to reveal differences in the rRNA-protein neighbourhood in free 70 S ribosomes and in the initiation complex. Proteins L3, L6, L23 and L25 were shown to cross-link to 23 S rRNA only in the initiation complex, whereas proteins L1, L13, L14, L16, L17, L18, L22, L28 and S1 did so in both free ribosomes and the complex. 16 S rRNA was found to be cross-linked preferentially to a single protein, S1, in both states of the ribosomes. PMID:2495985

Chistyakov, P G; Venjaminova, A G; Vladimirov, S N; Graifer, D M; Kazakov, S A; Karpova, G G

1989-03-27

15

Initial in vivo evaluation of the newly developed axial flow turbo pump with hydrodynamic bearings  

Microsoft Academic Search

An implantable, compact rotary blood pump has been newly developed using an axial flow turbo pump with hydrodynamic bearings.\\u000a The rotating impeller, which is hydrodynamically levitated with the assistance of repulsive magnetic force, has no contact\\u000a with the inner surface of the pump. To evaluate the hemodynamic performance and biocompatibility, the pump was installed into\\u000a four calves for up to

Tomonori Tsukiya; Eisuke Tatsumi; Toshihide Mizuno; Tatsuya Hidaka; Takeshi Okubo; Toshiyuki Osada; Shinji Miyamoto; Yoshiyuki Taenaka

2011-01-01

16

Bifunctional Inhibitors of Pepsin  

PubMed Central

Two bifunctional reagents designed to probe the active site of pepsin and other acid proteinases are described. One of these, the bisdiazoketone 1,1-bis(diazoacetyl)-2-phenylethane inactivates pepsin at pH 5.0 much more rapidly than the corresponding monodiazoketon 1-diazoacetyl-2-phenylethane, whereas the other, the bromodiazoketone dl-1-diazoacetyl-1-bromo-2-phenylethane is less effective in this regard. The inactivation is greatly accelerated by the presence of Cu(II), and the pH dependence of the process is consistent with the interaction of the enzyme with the metal complex of the carbene derived from the reagent. The bisdiazoketone appears to react stoichiometrically with pepsin in a 1:1 ratio to form a product whose apparent molecular size is the same as that of untreated pepsin. The inactivation of pepsin by the bromodiazoketone is accompanied by the release of stoichiometric amounts of bromide ions and the formation of a major product whose apparent size is similar to that of pepsin, and a minor component larger than the untreated enzyme.

Husain, S. S.; Ferguson, John B.; Fruton, Joseph S.

1971-01-01

17

Leucine-rich diet alters the eukaryotic translation initiation factors expression in skeletal muscle of tumour-bearing rats  

PubMed Central

Background Cancer-cachexia induces a variety of metabolic disorders on protein turnorver, decreasing protein synthesis and increasing protein degradation. Controversly, insulin, other hormones, and branched-chain amino acids, especially leucine, stimulate protein synthesis and modulate the activity of translation initiation factors involved in protein synthesis. Since the tumour effects are more pronounced when associated with pregnancy, ehancing muscle-wasting proteolysis, in this study, the influence of a leucine-rich diet on the protein synthesis caused by cancer were investigated. Methods Pregnant rats with or without Walker 256 tumour were distributed into six groups. During 20 days of experiment, three groups were fed with a control diet: C – pregnant control, W – tumour-bearing, and P – pair-fed, which received the same amount of food as ingested by the W group; three other groups of pregnant rats were fed a leucine-rich diet: L – pregnant leucine, WL – tumour-bearing, and PL – pair-fed, which received the same amount of food as ingested by the WL group. Results The gastrocnemius muscle of WL rats showed increased incorporation of leucine in protein compared to W rats; the leucine-rich diet also prevented the decrease in plasma insulin normally seen in W. The expression of translation initiation factors increased when tumour-bearing rats fed leucine-rich diet, with increase of ~35% for eIF2? and eIF5, ~17% for eIF4E and 20% for eIF4G; the expression of protein kinase S6K1 and protein kinase C was also highly enhanced. Conclusion The results suggest that a leucine-rich diet increased the protein synthesis in skeletal muscle in tumour-bearing rats possibly through the activation of eIF factors and/or the S6kinase pathway.

Ventrucci, Gislaine; Mello, Maria Alice R; Gomes-Marcondes, Maria Cristina C

2007-01-01

18

Initial studies on sperm cryopreservation of a live-bearing fish, the green swordtail Xiphophorus helleri.  

PubMed

Swordtails and platyfish of the genus Xiphophorus are valuable models for biomedical research and are also commercially raised as ornamental fish valued by aquarists. While research use and commercial interest increases yearly in these fish, cryopreservation of sperm is unexplored in this genus. Xiphophorus are live-bearing fishes characterized by small body sizes, limited sperm volumes, and internal fertilization, an atypical reproductive mode for fish. These attributes make research involving cryopreservation of Xiphophorus germplasm challenging. To explore methods for sperm cryopreservation, this study evaluated the effect of different loading volumes of sperm suspension in 0.25-ml French straws, different dilution ratios of sperm to extender, an osmolality range of extender without cryoprotectant and with dimethyl sulfoxide (DMSO) as cryoprotectant, and short-term storage at room temperature and 4 degrees C after thawing. No significant difference in sperm motility due to straw loading volume was observed after thawing. Sperm motility was observed to decrease with increasing dilution. The osmolality of Hanks' balanced salt solution (HBSS) without cryoprotectant in which the highest sperm motility (67%) was observed was 320 +/- 3 mOsm/kg, which was also the osmolality of X. helleri blood plasma. When cryopreserved with 10% DMSO, however, the highest motilities within 10 min after thawing were observed with HBSS in the range of 240-300 mOsm/kg. Sperm suspended in HBSS at 320 mOsm/kg with a dilution factor of 100 maintained motility for 24h at room temperature, but persisted for 10 days when stored at 4 degrees C. These results provided the first evidence that cryopreservation may be applied to conservation of genetic resources in live-bearing fishes. PMID:15159112

Huang, Changjiang; Dong, Qiaoxiang; Walter, Ronald B; Tiersch, Terrence R

2004-07-01

19

Bifunctional DTPA-type ligand  

SciTech Connect

The subject matter of the invention relates to bifunctional cyclohexyl DTPA ligands and methods of using these compounds. Specifically, such ligands are useful for radiolabeling proteins with radioactive metals, and can consequently be utilized with respect to radioimmunoimaging and/or radioimmunotherapy.

Gansow, O.A.; Brechbiel, M.W.

1990-03-26

20

Bifunctional oxygen/air electrodes  

NASA Astrophysics Data System (ADS)

A selective review on the materials and construction principles used for bifunctional oxygen/air electrodes is given. The discussion emphasizes the catalytically active materials used for the construction of these electrodes, which are a key component in electrically rechargeable air breathing electrochemical systems. Whereas, in acid electrolytes normally noble metal catalysts must be used, there is a possibility to use less expensive transition metal oxides in alkaline electrolytes. Typical transition metal oxides have the perovskite, pyrochlore and spinel structure.

Jörissen, Ludwig

21

Redirecting splicing with bifunctional oligonucleotides  

PubMed Central

Ectopic modulators of alternative splicing are important tools to study the function of splice variants and for correcting mis-splicing events that cause human diseases. Such modulators can be bifunctional oligonucleotides made of an antisense portion that determines target specificity, and a non-hybridizing tail that recruits proteins or RNA/protein complexes that affect splice site selection (TOSS and TOES, respectively, for targeted oligonucleotide silencer of splicing and targeted oligonucleotide enhancer of splicing). The use of TOSS and TOES has been restricted to a handful of targets. To generalize the applicability and demonstrate the robustness of TOSS, we have tested this approach on more than 50 alternative splicing events. Moreover, we have developed an algorithm that can design active TOSS with a success rate of 80%. To produce bifunctional oligonucleotides capable of stimulating splicing, we built on the observation that binding sites for TDP-43 can stimulate splicing and improve U1 snRNP binding when inserted downstream from 5? splice sites. A TOES designed to recruit TDP-43 improved exon 7 inclusion in SMN2. Overall, our study shows that bifunctional oligonucleotides can redirect splicing on a variety of genes, justifying their inclusion in the molecular arsenal that aims to alter the production of splice variants.

Brosseau, Jean-Philippe; Lucier, Jean-Francois; Lamarche, Andree-Anne; Shkreta, Lulzim; Gendron, Daniel; Lapointe, Elvy; Thibault, Philippe; Paquet, Eric; Perreault, Jean-Pierre; Abou Elela, Sherif; Chabot, Benoit

2014-01-01

22

Poly(ether-ether-ketone) orthopedic bearing surface modified by self-initiated surface grafting of poly(2-methacryloyloxyethyl phosphorylcholine).  

PubMed

We investigated the production of free radicals on a poly(ether-ether-ketone) (PEEK) substrate under ultraviolet (UV) irradiation. The amount of the ketyl radicals produced from the benzophenone (BP) units in the PEEK molecular structure initially increased rapidly and then became almost constant. Our observations revealed that the BP units in PEEK acted as photoinitiators, and that it was possible to use them to control the graft polymerization of poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC). This "self-initiated surface graft polymerization" method is very convenient in the absence of external photoinitiator. We also investigated the effects of the monomer concentration and UV irradiation time on the extent of the grafted PMPC layer. Furthermore, as an application to improving the durability of artificial hips, we demonstrated the nanometer-scale photoinduced grafting of PMPC onto PEEK and carbon fiber-reinforced PEEK (CFR-PEEK) orthopedic bearing surfaces and interfaces. A variety of test revealed significant improvements in the water wettability, frictional properties, and wear resistance of the surfaces and interfaces. PMID:23891520

Kyomoto, Masayuki; Moro, Toru; Yamane, Shihori; Hashimoto, Masami; Takatori, Yoshio; Ishihara, Kazuhiko

2013-10-01

23

Bifunctional transfer-messenger RNA  

PubMed Central

Transfer-messenger RNA (tmRNA) is a bifunctional RNA that has properties of a tRNA and an mRNA. tmRNA uses these two functions to release ribosomes stalled during translation and target the nascent polypeptides for degradation. This concerted reaction, known as trans-translation, contributes to translational quality control and regulation of gene expression in bacteria. tmRNA is conserved throughout bacteria, and is one of the most abundant RNAs in the cell, suggesting that trans-translation is of fundamental importance for bacterial fitness. Mutants lacking tmRNA activity typically have severe phenotypes, including defects in viability, virulence, and responses to environmental stresses.

Ramadoss, Nitya S.

2011-01-01

24

Bifunctional transfer-messenger RNA.  

PubMed

Transfer-messenger RNA (tmRNA) is a bifunctional RNA that has properties of a tRNA and an mRNA. tmRNA uses these two functions to release ribosomes stalled during translation and target the nascent polypeptides for degradation. This concerted reaction, known as trans-translation, contributes to translational quality control and regulation of gene expression in bacteria. tmRNA is conserved throughout bacteria, and is one of the most abundant RNAs in the cell, suggesting that trans-translation is of fundamental importance for bacterial fitness. Mutants lacking tmRNA activity typically have severe phenotypes, including defects in viability, virulence, and responses to environmental stresses. PMID:21664408

Keiler, Kenneth C; Ramadoss, Nitya S

2011-11-01

25

Tailored bifunctional polymer for plutonium monitoring.  

PubMed

Monitoring of actinides with sophisticated conventional methods is affected by matrix interferences, spectral interferences, isobaric interferences, polyatomic interferences, and abundance sensitivity problems. To circumvent these limitations, a self-supported disk and membrane-supported bifunctional polymer were tailored in the present work for acidity-dependent selectivity toward Pu(IV). The bifunctional polymer was found to be better than the polymer containing either a phosphate group or a sulfonic acid group in terms of (i) higher Pu(IV) sorption efficiency at 3-4 mol L(-1) HNO3, (ii) selective preconcentration of Pu(IV) in the presence of a trivalent actinide such as Am(III), and (iii) preferential sorption of Pu(IV) in the presence of a large excess of U(VI). The bifunctional polymer was formed as a self-supported matrix by bulk polymerization and also as a 1-2 ?m thin layer anchored on a microporous poly(ether sulfone) by surface grafting. The proportions of sulfonic acid and phosphate groups in both the self-supported disk and membrane-supported bifunctional polymer were found to be the same as expected from the mole proportions of monomers in polymerizing solutions used for syntheses. ? radiography by a solid-state nuclear track detector indicated fairly homogeneous anchoring of the bifunctional polymer on the surface of the membrane. Pu(IV) preconcentrated on a single bifunctional bead was used for determination of the Pu isotopic composition by thermal ionization mass spectrometry. The membrane-supported bifunctional polymer was used for preconcentration and subsequent quantification of Pu(IV) by ? spectrometry using the absolute efficiency at a fixed counting geometry. The analytical performance of the membrane-supported-bifunctional-polymer-based ? spectrometry method was found to be highly reproducible for assay of Pu(IV) in a variety of complex samples. PMID:24901969

Paul, Sumana; Pandey, Ashok K; Kumar, Pranaw; Kaity, Santu; Aggarwal, Suresh K

2014-07-01

26

Report to Participants in the Workshops to Initiate a Collaborative Planning Process for the Wyoming State Grizzly Bear Management Plan.  

National Technical Information Service (NTIS)

The Wyoming Game and Fish Department (WGFD) is faced with a knotty problem: how to manage grizzly bears in many parts of the state after they are taken off the endangered list. There are many facets to this problem. However, the question of how to conduct...

B. L. Lamb J. G. Taylor N. Burkardt P. D. Ponds L. Caughlan N. Sexton

2000-01-01

27

Polar Bears  

NSDL National Science Digital Library

Use the following websites to answer questions about the rapid disappearance of polar bears in the Arctic region. Polar Bear picture Polar Bear Tracker 1: What region in the world has the fewest polar bears? 2: Using the internet as a resource, provide some reasons as to why this region is suffering from the most polar bear differences? Polar Bears Change Diet 1: Why are polar bears having to change their diets? 2: List some other factors (besides diet) in the ...

Thomas, Mr.

2010-09-27

28

Synthesis and evaluation of bifunctional chelating agents derived from bis(2-aminophenylthio)alkane for radioimaging with 99mTc.  

PubMed

Novel bifunctional chelating agents bearing an aromatic rigid backbone have been synthesized and characterized on the basis of spectroscopic techniques. These macrocyclic multidentate chelating agents were conjugated with monoclonal antibody which forms stable complexes with 99mTc with high radiochemical purity. PMID:16052734

Chhikara, Bhupender S; Kumar, Nitin; Tandon, Vibha; Mishra, Anil K

2005-08-01

29

Bear Spray Safety Program  

USGS Publications Warehouse

A bear spray safety program for the U.S. Geological Survey (USGS) was officially initiated by the Firearms Safety Committee to address accident prevention and to promote personnel training in bear spray and its transportation, storage, and use for defense against wild animals. Used as part of a system including firearms, or used alone for those who choose not to carry a firearm, bear spray is recognized as an effective tool that can prevent injury in a wild animal attack.

Blome, C. D.; Kuzniar, R. L.

2009-01-01

30

Synthesis and evaluation of a new bifunctional chelating agent for the preparation of radioimmunoconjugates.  

PubMed

The conjugation of radiometals to monoclonal antibodies results in agents for radioimmunoimaging and other medical applications. Due to remarkable ability to form stable metal complexes with a great number of metal ions in different oxidation states, polyaminocarboxylate chelates are useful tools for this purpose. Bifunctional chelators that can hold radiometals with high stability under physiological conditions are essential to avoid radiation damage to non-target organs. We have synthesized a new bifunctional chelate 2-(p-aminobenzyl)-1,3-propylenediamine-N,N,N',N'-tetraacetic acid by a simple method and studied the rate of loss of radioactivity from the radiolabeled (111In, 90Y) chelates to serum proteins in human serum at 37 degrees C. The relative stability constant of this new bifunctional chelate was found to be very similar to the underivated form. This chelate was conjugated to murine monoclonal antibody (B43) and immunoreactivity of the conjugated was determined by competitive binding analysis, which showed no significant change in its immunological activity. Biodistribution of the 111In radioconjugate was examined in conventional Balb/c and tumor-bearing (-OVCAR-3) athymic Balb/c mice. PMID:8624793

Somayaji, V V; Guay, V; Peng, Z; Sykes, T R; Noujaim, A A

1995-12-01

31

Bifunctional hydrogen bonds in monohydrated cycloether complexes.  

PubMed

In this work, the cooperative effects implicated in bifunctional hydrogen bonds (H-bonds) were studied (in monohydrated six-membered cycloether) within the framework of the atoms in molecules (AIM) theory and of the natural bond orbitals (NBO) analysis. The study was carried out in complexes formed by six-membered cycloether compounds (tetrahydropyrane, 1,4-dioxane, and 1,3-dioxane) and a water molecule. These compounds were used as model systems instead of more complicated molecules of biological importance. All the results were obtained at the second-order Møller-Plesset (MP2) level theory using a 6-311++G(d,p) basis set. Attention was focused on the indicators of the cooperative effects that arise when a water molecule interacts simultaneously with a polar and a nonpolar portion of a six-membered cycloether (via bifunctional hydrogen bonds) and compared with conventional H-bonds where the water molecule only interacts with the polar portion of the cycloether. Different indicators of H-bonds strength, such as structural and spectroscopic data, electron charge density, population analysis, hyperconjugation energy and charge transference, consistently showed significant cooperative effects in bifunctional H-bonds. From the AIM, as well as from the NBO analysis, the obtained results allowed us to state that in the monohydrated six-membered cycloether, where the water molecule plays a dual role, as proton acceptor and proton donor, a mutual reinforcement of the two interactions occurs. Because of this feature, the complexes engaged by bifunctional hydrogen bonds are more stabilized than the complexes linked by conventional hydrogen bonds. PMID:20136161

Vallejos, Margarita M; Angelina, Emilio L; Peruchena, Nélida M

2010-03-01

32

Bifunctional nanoparticles with magnetism and NIR fluorescence: controlled synthesis from combination of AGET ATRP and ‘click’ reaction  

NASA Astrophysics Data System (ADS)

In this work, bifunctional nanoparticles (NPs) capable of emitting near infrared (NIR) fluorescence and generating superparamagnetism under an external magnetic field were prepared by combination of ‘click’ reaction and surface-initiated activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP) of water-soluble poly(ethylene glycol) monomethyl ether methacrylate (PEGMA) and glycidyl methacrylate (GMA) using biocompatible iron as the catalyst on the surface of silica-coated iron oxide (Fe3O4@SiO2) NPs. The nanosized Fe3O4@SiO2@PPEGMA-co-PGMA@N3 was prepared through AGET ATRP and alkynyl bearing NIR dye was also prepared; afterwards they were integrated together by ‘click’ reaction. The different stages of surface modification were approved by employing different characterization techniques such as TEM, XRD, XPS, VSM and FT-IR, and the properties of the final NPs were thoroughly studied. Their suitability as dual model imaging agents for magnetic resonance (MR) and fluorescence imaging was investigated, indicating them to be a competitive candidate for imaging contrast agents.

He, Weiwei; Cheng, Liang; Zhang, Lifen; Jiang, Xiaowu; Liu, Zhuang; Cheng, Zhenping; Zhu, Xiulin

2014-01-01

33

Development of Benzophenone-Alkyne Bifunctional Sigma Receptor Ligands  

PubMed Central

Sigma (?) receptors represent unique non-opioid binding sites that are associated with a broad range of disease states. Sigma-2 receptors provide a promising target for diagnostic imaging and pharmacological interventions to curb tumor progression. Most recently, the progesterone receptor (PGRMC1, 25 kDa) has been identified to contain ?2 receptor-like binding properties, highlighting the need to understand the biological function of an 18-kDa protein that exhibits ?2-like photoaffinity labeling (herein denoted as ?2-18k) but the amino acid sequence of which is not known. In order to provide novel tools for the study of the ?2-18k protein, we have developed bifunctional sigma receptor ligands that bear a benzophenone photo-crosslinking moiety and an alkyne group, to which an azide-containing biotin affinity tag can be covalently attached via click chemistry following photo-crosslink. While several compounds showed favorable ?2 binding properties, compound 22 exhibited the highest affinity (2 nM) and the greatest potency in blocking photolabeling of the ?2-18k by a radioactive photoaffinity ligand. Thus, these benzophenone-alkyne sigma receptor ligands may be amenable for studying the ?2-18k protein via chemical biology approaches. To our knowledge, these compounds represent the first reported benzophenone-containing clickable sigma receptor ligands, which may potentially serve broad applications by “plugging” in various tags.

Guo, Lian-Wang; Hajipour, Abdol R.; Karaoglu, Kerim; Mavlyutov, Timur A.; Ruoho, Arnold E.

2012-01-01

34

Diversity-oriented synthesis leads to an effective class of bifunctional linchpins uniting anion relay chemistry (ARC) with benzyne reactivity  

PubMed Central

In conjunction with the construction of a diversity-oriented synthesis library of 10-membered ring “natural product-like” macrolides, the design, synthesis, and validation of a unique class of bifunctional linchpins, uniting benzyne reactivity initiated by type II anion relay chemistry (ARC) has been achieved, permitting access to diverse [2+2], [3+2], and [4+2] cycloadducts.

Smith, Amos B.; Kim, Won-Suk

2011-01-01

35

Polar Bear  

NSDL National Science Digital Library

This site from the World Wildlife Fund (WWF) International provides general information about polar bears as well as data on the movements of two radio-collared bears, along with the ice status, through a series of online maps.

2007-01-01

36

Bifunctional bacterial magnetic nanoparticles for tumor targeting  

NASA Astrophysics Data System (ADS)

Bifunctional bacterial magnetic nanoparticles (BBMPs), which present both magnetic drug targeting and tumor bio-targeting properties, have been developed by chemically coupling both doxorubicin and a galactosyl ligand on to the membrane surface of the bacterial magnetic nanoparticles (BMPs). The BBMP product has a high drug load ratio and magnetic respondence, and exhibits a narrow size distribution and is sensitive to pH to enable drug release. In comparison to doxorubicin-coupled BMPs, without modification with a galactosyl ligand, BBMPs present a higher uptake by the target asialoglycoprotein receptor (ASGP-R) expressed by HepG2 cells and display stronger cytotoxicity.

Guo, Lin; Huang, Ji; Zheng, Li-Min

2012-01-01

37

Gear bearings  

NASA Technical Reports Server (NTRS)

A gear bearing having a first gear and a second gear, each having a plurality of teeth. Each gear operates on two non-parallel surfaces of the opposing gear teeth to perform both gear and bearing functions simultaneously. The gears are moving at substantially the same speed at their contact points. The gears may be roller gear bearings or phase-shifted gear bearings, and may be arranged in a planet/sun system or used as a transmission.

Vranish, John M. (Inventor)

2003-01-01

38

A new look at Pennsylvanian coal-bearing strata of the East Midlands, UK: initial data from the Smalley open pit mine  

NASA Astrophysics Data System (ADS)

Outcrops of Pennsylvanian (Duckmantian) age coal-bearing strata in the East Midlands of England are rare and have become rarer as more of the surface environment has been developed. Much of the stratigraphic correlation and paleoenvironmental interpretation of these strata have thus been based on subsurface data from deep mine workings and coal exploration boreholes. However, in 2009, coal mining commenced at an open pit mine near Smalley, east Derbyshire in the UK East Midlands. The mine provides a unique opportunity to carry out examination of a large-scale outcrop of Pennsylvanian coal-bearing strata in order to undertake detailed palaeoenvironmental reconstructions. The coals that will be exposed during working belong to the Waterloo group of seams of Duckmantian age. Initial examination of the workings has been concentrated on two successive intervals: from the basal Third Waterloo Seam to the Bottom Second Waterloo seam, and the from above the Bottom Second Waterloo seam to the Top Second Waterloo seam. The two inter-seam intervals are approximately 10-12 meters thick. Examination of the coal seams and inter-seam intervals will continue as new faces are exposed, supplemented by exploration drilling data. Initial field observations on the first sections exposed suggest that the two inter-seam intervals represent the infill of lakes formed on a fluvio-lacustrine plain, with negligible marine influence. The strata immediately above the Third Waterloo Seam consist of dark grey fissile shaly mudrocks overlain by an upward coarsening sequence of pale grey siltstones with sandy laminae and current ripples indicating unidirectional tractional flows. These pass upwards into rippled fine sandstones, cut by shallow channels towards the top. The overall inter-seam sequence is interpreted as the deposits of a lacustrine delta system that infilled a shallow lake that was initially anoxic. Once the lake had been infilled, a peat mire was able to form, now represented by the Bottom Second Waterloo Seam. The interval between the Bottom and Top Waterloo Seams contains an upward-coarsening sequence of laminated siltstones, overlain by a series of sharp-based rippled sandstones, each up to about 60 cm thick. The sharp based sandstones are interpreted as being crevasse splay deposits, which would have been fed by a nearby fluvial channel, which has not yet been located. As additional exposures are created during the lifetime of the mine, the temporal, spatial and environmental relationships of the coals and inter-seam strata will be investigated further by recording stratigraphic sections and directional data and producing photo panels. This should enable detailed paleoenvironmental reconstructions for each of the intervals investigated, which will be considered in the light of recent research on analogous ancient and recent environments. Data from adjacent former mines and coal exploration boreholes containing lateral continuations of the intervals examined will then allow the Smalley mine geology to be placed within the regional context of the East Midlands Coalfield, and enable us to consider broad scale paleoenvironmental variation across the area. It is anticipated that by enhancing our understanding of inter-seam deposits, prediction of geological conditions ahead of mining will be improved.

Sian Davies-Vollum, K.; Guion, Paul; Satterfield, Dorothy; Suthren, Roger

2010-05-01

39

Analysis of Bearing Incidents in Aircraft Gas Turbine Mainshaft Bearings  

Microsoft Academic Search

An examination of approximately 200 bearing incidents in current aircraft engines has shown that damage in the bearing is initiated at the surface. Twenty-one cases were studied in detail, and five typical incidents are presented here. The initial damage was produced by abrasive particles, dents, grinding scores, skidding, large carbides and corrosion pits. The first phase of the failure mechanism

B. L. Averbach; E. N. Bamberger

1991-01-01

40

Bone Marrow Lesions and Joint Effusion are Strongly and Independently Associated with Weight-Bearing Pain in Knee Osteoarthritis: Data from the Osteoarthritis Initiative  

PubMed Central

Objective It is widely believed that there are multiple sources of pain at a tissue level in osteoarthritis (OA). MRIs provide a wealth of anatomic information and may allow identification of specific features associated with pain. We hypothesized that in knees with OA, bone marrow lesions (BMLs), synovitis, and effusion would be associated with weight-bearing and (less so with) non-weight-bearing pain independently. Methods In a cross-sectional study of persons with symptomatic knee OA using univariate and multivariate logistic regressions with maximal BML, effusion, and synovitis defined by Boston Leeds Osteoarthritis Knee Score as predictors, and knee pain using weight-bearing and non-weight-bearing Western Ontario and McMaster University OA Index pain questions as the outcome, we tested the association between MRI findings and knee symptoms Results 160 participants, mean age 61 (±9.9), mean BMI 30.3 (±4.7) and 50% female, stronger associations were seen with weight-bearing compared with non-weight-bearing knee pain with adjusted risk ratios (RRs) of weight-bearing knee pain, for increasing maximal BML scores of 1.0 (referent) (maximal BML = 0), 1.2, 1.9, and 2.0 (p for trend = 0.006). For effusion scores, adjusted ORs of knee pain were 1.0, 1.7, 2.0, and 2.6 (p for trend = 0.0004); and for synovitis scores, adjusted ORs were 1.0, 1.4, 1.5, and 1.9 (p for trend = 0.22). Conclusion Cross-sectionally, maximal BML and effusion scores are independently associated with weight-bearing and less so with non-weight-bearing knee pain, supporting the idea that pain in OA is multifactorial. These MRI features should be considered as possible new treatment targets in knee OA.

Lo, GH; McAlindon, TE; Niu, J; Zhang, Y; Beals, C; Dabrowski, C; Hellio Le Graverand, MP; Hunter, DJ

2009-01-01

41

Bearing fatigue investigation 3  

NASA Technical Reports Server (NTRS)

The operating characteristics of large diameter rolling-element bearings in the ultra high speed regimes expected in advanced turbine engines for high performance aircraft were investigated. A high temperature lubricant, DuPont Krytox 143 AC, was evaluated at bearing speeds to 3 million DN. Compared to the results of earlier, similar tests using a MIL-L-23699 (Type II) lubricant, bearings lubricated with the high density Krytox fluid showed significantly higher power requirements. Additionally, short bearing lives were observed when this fluid was used with AISI M50 bearings in an air atmosphere. The primary mode of failure was corrosion initiated surface distress (fatigue) on the raceways. The potential of a case-carburized bearing to sustain a combination of high-tangential and hertzian stresses without experiencing race fracture was also investigated. Limited full scale bearing tests of a 120 mm bore ball bearing at a speed of 25,000 rpm (3 million DN) indicated that a carburized material could sustain spalling fatigue without subsequent propagation to fracture. Planned life tests of the carburized material had to be aborted, however, because of apparent processing-induced material defects.

Nahm, A. H.; Bamberger, E. N.; Signer, H. R.

1982-01-01

42

Thrust bearing  

NASA Technical Reports Server (NTRS)

A gas lubricated thrust bearing is described which employs relatively rigid inwardly cantilevered spokes carrying a relatively resilient annular member or annulus. This annulus acts as a beam on which are mounted bearing pads. The resilience of the beam mount causes the pads to accept the load and, with proper design, responds to a rotating thrust-transmitting collar by creating a gas film between the pads and the thrust collar. The bearing may be arranged for load equalization thereby avoiding the necessity of gimbal mounts or the like for the bearing. It may also be arranged to respond to rotation in one or both directions.

Anderson, W. J. (inventor)

1976-01-01

43

Hybrid Bearing Prognostic Test Rig  

NASA Technical Reports Server (NTRS)

The NASA Glenn Research Center has developed a new Hybrid Bearing Prognostic Test Rig to evaluate the performance of sensors and algorithms in predicting failures of rolling element bearings for aeronautics and space applications. The failure progression of both conventional and hybrid (ceramic rolling elements, metal races) bearings can be tested from fault initiation to total failure. The effects of different lubricants on bearing life can also be evaluated. Test conditions monitored and recorded during the test include load, oil temperature, vibration, and oil debris. New diagnostic research instrumentation will also be evaluated for hybrid bearing damage detection. This paper summarizes the capabilities of this new test rig.

Dempsey, Paula J.; Certo, Joseph M.; Handschuh, Robert F.; Dimofte, Florin

2005-01-01

44

Bifunctional ligands allow deliberate extrinsic reprogramming of the glucocorticoid receptor.  

PubMed

Therapies based on conventional nuclear receptor ligands are extremely powerful, yet their broad and long-term use is often hindered by undesired side effects that are often part of the receptor's biological function. Selective control of nuclear receptors such as the glucocorticoid receptor (GR) using conventional ligands has proven particularly challenging. Because they act solely in an allosteric manner, conventional ligands are constrained to act via cofactors that can intrinsically partner with the receptor. Furthermore, effective means to rationally encode a bias for specific coregulators are generally lacking. Using the (GR) as a framework, we demonstrate here a versatile approach, based on bifunctional ligands, that extends the regulatory repertoire of GR in a deliberate and controlled manner. By linking the macrolide FK506 to a conventional agonist (dexamethasone) or antagonist (RU-486), we demonstrate that it is possible to bridge the intact receptor to either positively or negatively acting coregulatory proteins bearing an FK506 binding protein domain. Using this strategy, we show that extrinsic recruitment of a strong activation function can enhance the efficacy of the full agonist dexamethasone and reverse the antagonist character of RU-486 at an endogenous locus. Notably, the extrinsic recruitment of histone deacetylase-1 reduces the ability of GR to activate transcription from a canonical GR response element while preserving ligand-mediated repression of nuclear factor-?B. By providing novel ways for the receptor to engage specific coregulators, this unique ligand design approach has the potential to yield both novel tools for GR study and more selective therapeutics. PMID:24422633

Højfeldt, Jonas W; Cruz-Rodríguez, Osvaldo; Imaeda, Yasuhiro; Van Dyke, Aaron R; Carolan, James P; Mapp, Anna K; Iñiguez-Lluhí, Jorge A

2014-02-01

45

A bifunctional protein regulates mitochondrial protein synthesis  

PubMed Central

Mitochondrial gene expression is predominantly regulated at the post-transcriptional level and mitochondrial ribonucleic acid (RNA)-binding proteins play a key role in RNA metabolism and protein synthesis. The AU-binding homolog of enoyl-coenzyme A (CoA) hydratase (AUH) is a bifunctional protein with RNA-binding activity and a role in leucine catabolism. AUH has a mitochondrial targeting sequence, however, its role in mitochondrial function has not been investigated. Here, we found that AUH localizes to the inner mitochondrial membrane and matrix where it associates with mitochondrial ribosomes and regulates protein synthesis. Decrease or overexpression of the AUH protein in cells causes defects in mitochondrial translation that lead to changes in mitochondrial morphology, decreased mitochondrial RNA stability, biogenesis and respiratory function. Because of its role in leucine metabolism, we investigated the importance of the catalytic activity of AUH and found that it affects the regulation of mitochondrial translation and biogenesis in response to leucine.

Richman, Tara R.; Davies, Stefan M.K.; Shearwood, Anne-Marie J.; Ermer, Judith A.; Scott, Louis H.; Hibbs, Moira E.; Rackham, Oliver; Filipovska, Aleksandra

2014-01-01

46

Good bearings reduce downtime  

SciTech Connect

Points out that a poorly maintained $100 bearing can hold up the operation of a $1-million conveyor. Of all the moving parts in a coal conveyor system, few cost less or last longer than anti-friction bearings. Most modern conveyor systems are equipped with 2 types of bearings: troughing idlers, spaced at regular intervals to support the conveyor belt as it travels throughout the system, and the adaptermounted spherical roller bearing pillow blocks that are used in the head, tail, bend and takeup pulleys that drive, alter the direction of, or regulate tension in the belt to allow for repairs or splicing. Explains how pillow blocks should handle radial or axial loads, how to mount bearings correctly, and how rings prevent infiltration. Concludes that by making certain that the proper bearing types are built into the system initially, or used as replacements in case of failures, paying close attention to installation procedures and devoting adequate time to maintenance, conveyor system bearings can provide decades of problem-free service.

Kinney, J.; Foster, J.

1982-12-01

47

Dry Friction Bearings.  

National Technical Information Service (NTIS)

Contents: Porous metal ceramic bearings; Mineral ceramic bearings; Self-lubricating pressed wood bearings; Metal materials for special bearings; Operation of rolling surface bearings under dry friction conditions; Rolling surface bearings with solid lubri...

B. D. Voronkov

1970-01-01

48

Synthesis and Preclinical Evaluation of Bifunctional Ligands for Improved Chelation Chemistry of 90Y and 177Lu for Targeted Radioimmunotherapy  

PubMed Central

We report a practical and high yield synthesis of a bimodal bifunctional ligand 3p-C-NETA-NCS containing the isothiocyanate group for conjugation to a tumor targeting antibody. 3p-C-NETA-NCS was conjugated to a tumor-targeting antibody, trastuzumab, and the corresponding 3p-C-NETA-trastuzumab conjugate was evaluated and compared to trastuzumab conjugates of the known bifunctional ligands C-DOTA, C-DTPA, C-NOTA, and 3p-C-DEPA for radiolabeling kinetics with 90Y and 177Lu. 3p-C-NETA-trastuzumab conjugate exhibited extremely rapid complexation kinetics with 90Y and 177Lu. 90Y-3p-C-NETA-trastuzumab and 177Lu-3p-C-NETA-trastuzumab conjugates were stable in human serum for 2 weeks. A pilot biodistribution study was conducted to evaluate in vivo stability and tumor targeting of 177Lu-radiolabeled trastuzumab conjugate using nude mice bearing ZR-75-1 human breast cancer. 177Lu-3p-C-NETA-trastuzumab conjugate displayed low radioactivity level at blood (1.6%), low organ uptake (<2.2%), and high tumor-to-blood ratio (6.4) at 120 h. 3p-C-NETA possesses favorable in vitro and in vivo profiles and is an excellent bifunctional chelator that can be used for targeted RIT applications using 90Y and 177Lu and has potential to replace DOTA and DTPA analogues in current clinical use.

Kang, Chi Soo; Sun, Xiang; Jia, Fang; Song, Hyun A; Chen, Yunwei; Lewis, Michael; Chong, Hyun-Soon

2012-01-01

49

Magnetic Bearing  

NASA Technical Reports Server (NTRS)

AVCON, Inc. produces advanced magnetic bearing systems for industrial use, offering a unique technological approach based on contract work done at Marshall Space Flight Center and Lewis Research Center. Designed for the turbopump of the Space Shuttle main engine, they are now used in applications such as electric power generation, petroleum refining, machine tool operation and natural gas pipelines. Magnetic bearings support moving machinery without physical contact; AVCON's homopolar approach is a hybrid of permanent and electromagnets which are one-third the weight, smaller and more power- efficient than previous magnetic bearings.

1996-01-01

50

Preparation of bifunctional mesoporous silica nanoparticles by orthogonal click reactions and their application in cooperative catalysis.  

PubMed

The synthesis of bifunctional mesoporous silica nanoparticles is described. Two chemically orthogonal functionalities are incorporated into mesoporous silica by co-condensation of tetraethoxysilane with two orthogonally functionalized triethoxyalkylsilanes. Post-functionalization is achieved by orthogonal surface chemistry. A thiol-ene reaction, Cu-catalyzed 1,3-dipolar alkyne/azide cycloaddition, and a radical nitroxide exchange reaction are used as orthogonal processes to install two functionalities at the surface that differ in reactivity. Preparation of mesoporous silica nanoparticles bearing acidic and basic sites by this approach is discussed. Particles are analyzed by solid state NMR spectroscopy, elemental analysis, infrared-spectroscopy, and scanning electron microscopy. As a first application, these particles are successfully used as cooperative catalysts in the Henry reaction. PMID:23132649

Dickschat, Arne T; Behrends, Frederik; Bühner, Martin; Ren, Jinjun; Weiss, Mark; Eckert, Hellmut; Studer, Armido

2012-12-21

51

Bobbie Bear  

NSDL National Science Digital Library

Using a virtual manipulative, children construct combinations of different colored shirts and pants to help Bobbie Bear, who is planning a vacation and wants to know how many different outfits he will be able to make from these combinations.

Mathematics, Illuminations N.

2009-03-06

52

Sorption and detoxification of toxic compounds by a bifunctional organoclay.  

PubMed

Organoclays are excellent sorbents for nonionic contaminants and therefore may have many environmental applications. A major limitation on the use of organoclays is that the contaminant merely changes its location from one environmental compartment to another while still remaining intact. In this study, a new type of organoclay, termed a bifunctional organoclay, has been prepared. It is able not only to sorb organophosphate pesticides, but also to catalyze their hydrolysis, and thereby detoxify them. The bifunctional organoclay prepared in this study is based on sodium montmorillonite, in which the inorganic counter ions are replaced by N-decyl-N,N-dimethyl-N-(2-aminoethyl) ammonium (DDMAEA). The detoxifying capacity of this organoclay for two organophosphate pesticides, methyl parathion [O,O-dimethyl O-(p-nitrophenyl) thionophosphate] and tetrachlorvinphos [2-chloro-1-(2,4,5-trichlorophenyl)ethenyl dimethyl phosphate], was demonstrated. It was shown that although the sorption of these pesticides on the bifunctional organoclay is very similar to that on N-decyl-N,N,N-trimethyl ammonium (DTMA) organoclay (the corresponding nonbifunctional organoclay), the hydrolysis of these pesticides is substantially enhanced only by the bifunctional organoclay. The half-life for the hydrolysis of the investigated pesticides in the presence of the bifunctional organoclay is about 12 times less than for their spontaneous hydrolysis, and the enhancement is even more pronounced relative to the hydrolysis of these pesticides in the presence of the DTMA organoclay (which actually inhibits their hydrolysis). Based on kinetic measurements, the pK(a) of the ethylamino group of the bifunctional organoclay was estimated to be around 9.0. It is postulated that the catalytic effect of the bifunctional organoclay can be attributed to a nucleophilic attack of the unprotonated ethylamino group of the organoclay on the organophosphate ester. PMID:15356256

Groisman, Ludmila; Rav-Acha, Chaim; Gerstl, Zev; Mingelgrin, Uri

2004-01-01

53

Pharmacokinetics of Recombinant Bifunctional Fusion Proteins  

PubMed Central

Introduction The development of biotechnology has enabled the creation of various recombinant fusion proteins as a new class of biotherapeutics. The uniqueness of fusion proteins lies in their ability to fuse two or more protein domains, providing vast opportunities to generate novel combinations of functions. Pharmacokinetic (PK) studies, which are critical components in preclinical and clinical drug development, have not been fully explored for fusion proteins. The lack of general PK models and study guidelines has become a bottleneck for translation of fusion proteins from basic research to the clinic. Areas covered This article reviews the current status of PK studies for fusion proteins, covering the processes that affect PK. According to their PK properties, a classification of fusion proteins is suggested along with examples from the clinic or under development. Current limitations and future perspectives for PK of fusion proteins are also discussed. Expert opinion A PK model for bifunctional fusion proteins is presented to highlight the importance of mechanistic studies for a thorough understanding of the PK properties of fusion proteins. The model suggests investigating the receptor binding and subsequent intracellular disposition of individual domains, which can have dramatic impact on the PK of fusion proteins.

Chen, Xiaoying; Zaro, Jennica L.; Shen, Wei-Chiang

2013-01-01

54

Synthesis of covalently bonded cellulose derivative chiral stationary phases with a bifunctional reagent of 3-(triethoxysilyl)propyl isocyanate  

Microsoft Academic Search

A bifunctional reagent of 3-(triethoxysilyl)propyl isocyanate (TEPI) was initially adopted as a spacer reagent to prepare the bonded types of chiral stationary phases (CSPs) with cellulose derivatives. The silica-based CSPs were chemically prepared with non-regioselective and regioselective approaches and their chiral resolving capabilities were evaluated in terms of HPLC resolution of test enantiomers. It was observed that the chiral recognition

Xiaoming Chen; Yueqi Liu; Feng Qin; Liang Kong; Hanfa Zou

2003-01-01

55

Bifunctional chelates optimized for molecular MRI.  

PubMed

Important requirements for exogenous dyes or contrast agents in magnetic resonance imaging (MRI) include an effective concentration of paramagnetic or superparamagnetic ions at the target to be imaged. We report the concise synthesis and characterization of several new enantiopure bifunctional derivatives of (?(1)R,?(4)R,?(7)R,?(10)R)-?(1),?(4),?(7),?(10)-tetramethyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTMA) (and their 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) analogues as controls) that can be covalently attached to a contrast agent delivery system using either click or peptide coupling chemistry. Gd complexes of these derivatives can be attached to delivery systems while maintaining optimal water residence time for increased molecular imaging sensitivity. Long chain biotin (LC-biotin) derivatives of the Eu(III) and Gd(III) chelates associated with avidin are used to demonstrate higher efficiencies. Variable-temperature relaxometry, (17)O NMR, and nuclear magnetic resonance dispersion (NMRD) spectroscopy used on the complexes and biotin-avidin adducts measure the influence of water residence time and rotational correlation time on constrained and unconstrained systems. The Gd(III)-DOTMA derivative has a shorter water residence time than the Gd(III)-DOTA derivative. Compared to the constrained Gd(III)-DOTA derivatives, the rotationally constrained Gd(III)-DOTMA derivative has ?40% higher relaxivity at 37 °C, which could increase its sensitivity as an MRI agent as well as reduce the dose of the targeting agent. PMID:24933389

Wiener, Erik C; Abadjian, Marie-Caline; Sengar, Raghvendra; Vander Elst, Luce; Van Niekerk, Christoffel; Grotjahn, Douglas B; Leung, Po Yee; Schulte, Christie; Moore, Curtis E; Rheingold, Arnold L

2014-07-01

56

Availability of ground water for large-scale use in the Malad Valley-Bear River areas of southeastern Idaho: an initial assessment  

USGS Publications Warehouse

Five areas within the Bear River drainage of southeastern Idaho offer potential for further development of ground water--the valley north of Bear Lake, north of Soda Springs, Gem Valley, Cache Valley in Idaho, and Malad Valley in Idaho. Saturated deposits north of Bear Lake are too fine-textured to yield large quantities to wells; the areas north of Soda Springs and in Gem Valley would provide large yields, but at the expense of current beneficial discharge. Northern Cache Valley has small areas of high yield in the northwestern part, but total annual yield would be only about 20,000 acre-feet and seasonal water-level fluctuation would be large. Malad Valley contains a large aquifer system within valley fill underlying about 75 square miles. The aquifer system is several hundred feet thick, and contains about 1.8 million acre-feet of water in storage in the top 300 feet of saturated thickness. Average annual recharge to the valley-fill aquifer is about 64,000 acre-feet. Lowering of the water level 100 feet uniformly over the valley area would theoretically yield about 300,000 acre-feet from storage and salvage a present-day large nonbeneficial discharge. Sufficient water to irrigate all lands in a planned project near Samaria could be pumped with a maximum 200-foot pumping lift and then delivered by gravity flow. Such pumping would cause water-level lowering of a few feet to a few tens of feet in present artesian areas, and would cause many present-day artesian wells to cease flowing at land surface. Chemical-quality problems in Malad Valley seem not to be sufficient to prohibit development and use of the ground-water resource.

Burnham, W. L.; Harder, A. H.; Dion, N. P.

1969-01-01

57

Bear Bones  

NSDL National Science Digital Library

An estimated ten million Americans have osteoporosis, an age-related disease in which the bones gradually become brittle and weak. Now, scientists are looking to animals for clues on how to combat this condition. This resource describes the study of sustaining bone strength of hibernating bears.

Science Update;

2004-03-08

58

Bifunctional mesoporous silicas with clearly distinguished localization of grafted groups  

NASA Astrophysics Data System (ADS)

Bifunctional mesoporous silicas with clearly distinguished localization of grafted groups on the surface of particles and inside their pores were obtained by means of sol-gel synthesis with postsynthetic vapor-phase treatment in vacuum. It was found that the synthesized materials have the hexagonally ordered porous structure typical of MCM-41 type silica.

Roik, N. V.; Belyakova, L. A.

2013-12-01

59

Supramolecular hydrogen-bonding assembly of silanediols with bifunctional heterocycles.  

PubMed

X-ray crystallography showcases the distinct self-association and hydrogen-bonding patterns of organic silanediols, R2Si(OH)2, with bifunctional heterocycles for supramolecular assembly. Diffusion-ordered spectroscopy (DOSY) studies identify the dominant hydrogen-bonding patterns and structures in solution, which correlate with solid-state patterns at high concentrations. PMID:24577634

Tran, Ngon T; Wilson, Sean O; Franz, Annaliese K

2014-04-11

60

Designed synthesis of ferrocenylanthraquinones and their bifunctional electrochromic properties.  

PubMed

New bifunctional electrochromic systems were developed by combination of reductive anthraquinone with oxidative ferrocene redox systems. The resultant ferrocenylanthraquinones demonstrated enhanced stability in electrochromic performance through the concomitant reductive electrochromism and oxidative counting action. The displayed colors were dependent on the position of the ferrocenyl group. PMID:20565113

Sharmoukh, W; Ko, Kyoung Chul; Ko, Ju Hong; Jung, Ii Gu; Noh, Changho; Lee, Jin Young; Son, Seung Uk

2010-07-16

61

Synthesis of acrylic and allylic bifunctional cross-linking monomers derived from PET waste  

NASA Astrophysics Data System (ADS)

An acrylic and two novel allylic monomers synthesized from bis (hydroxyethyl) terephthalate, BHET, are reported. This was obtained by glycolysis of post-consumer PET with boiling ethylene glycol. The bifunctional monomer bis(2-(acryloyloxy)ethyl) terephthalate was obtained from acryloyl chloride, while the allylic monomers 2-(((allyloxi)carbonyl)oxy) ethyl (2-hydroxyethyl) terephthalate and bis(2-(((allyloxi)carbonyl)oxy)ethyl) terephthalate, from allyl chloroformate. Cross-linking was studied in bulk polymerization using two different thermal initiators. Monomers were analyzed by means of 1H NMR and the cross-linked polymers by infrared spectroscopy. Gel content higher than 90% was obtained for the acrylic monomer. In the case of the mixture of the allylic monomers, the cross-linked polymer was 80 % using BPO initiator, being this mixture 24 times less reactive than the acrylic monomer.

Cruz-Aguilar, A.; Herrera-González, A. M.; Vázquez-García, R. A.; Navarro-Rodríguez, D.; Coreño, J.

2013-06-01

62

Performance analysis of high-speed spindle aerostatic bearings  

Microsoft Academic Search

The methods adopted to derive the pressure distribution and precision of bearing rotation are fundamental issues in the arena of gas bearing design. The current study presents a detailed theoretical analysis of bearing performance, in which the gas flow within the bearing is initially expressed in the form of simplified dimensionless Navier Stokes equations. Adopting the assumption of mass flow

Cheng-Ying Lo; Cheng-Chi Wang; Yu-Han Lee

2005-01-01

63

Automated Assistance for Designing Active Magnetic Bearings  

NASA Technical Reports Server (NTRS)

MagBear12 is a computer code that assists in the design of radial, heteropolar active magnetic bearings (AMBs). MagBear12 was developed to help in designing the system described in "Advanced Active-Magnetic-Bearing Thrust-Measurement System". Beyond this initial application, MagBear12 is expected to be useful for designing AMBs for a variety of rotating machinery. This program incorporates design rules and governing equations that are also implemented in other, proprietary design software used by AMB manufacturers. In addition, this program incorporates an advanced unpublished fringing-magnetic-field model that increases accuracy beyond that offered by the other AMB-design software.

Imlach, Joseph

2008-01-01

64

Cryogenic turbopump bearing materials  

NASA Technical Reports Server (NTRS)

Materials used for modern cryogenic turbopump bearings must withstand extreme conditions of loads and speeds under marginal lubrication. Naturally, these extreme conditions tend to limit the bearing life. It is possible to significantly improve the life of these bearings, however, by improving the fatigue and wear resistance of bearing alloys, and improving the strength, liquid oxygen compatibility and lubricating ability of the bearing cage materials. Improved cooling will also help to keep the bearing temperatures low and hence prolong the bearing life.

Bhat, Biliyar N.

1989-01-01

65

Preparation of a Versatile Bifunctional Zeolite for Targeted Imaging Applications  

PubMed Central

Bifunctional zeolite Y was prepared for use in targeted in vivo molecular imaging applications. The strategy involved functionalization of the external surface of zeolite Y with chloropropyltriethoxysilane followed by reaction with sodium azide to form azide-functionalized NaY, which is amenable to copper(1) catalyzed click chemistry. In this study, a model alkyne (4-pentyn-1-ol) was attached to the azide-terminated surface via click chemistry to demonstrate feasibility for attachment of molecular targeting vectors (e.g., peptides, aptamers) to the zeolite surface. The modified particle efficiently incorporates the imaging radioisotope gallium-68 (68Ga) into the pores of the azide-functionalized NaY zeolite to form a stable bifunctional molecular targeting vector. The result is a versatile “clickable” zeolite platform that can be tailored for future in vivo molecular targeting and imaging modalities.

Ndiege, Nicholas; Raidoo, Renugan; Schultz, Michael K.; Larsen, Sarah

2011-01-01

66

Engineering isoflavone metabolism with an artificial bifunctional enzyme  

Microsoft Academic Search

Plant secondary metabolism has been a focus of research in recent years due to its significant roles in plant defense and\\u000a in human medicine and nutrition. A protein engineering strategy was designed to more effectively manipulate plant secondary\\u000a metabolite (isoflavonoid) biosynthesis. A bifunctional isoflavone synthase\\/chalcone isomerase (IFS\\/CHI) enzyme was constructed\\u000a by in-frame gene fusion, and expressed in yeast and tobacco.

L. Tian; R. A. Dixon

2006-01-01

67

Room Temperature Hydrosilylation of Silicon Nanocrystals with Bifunctional Terminal Alkenes  

PubMed Central

H-terminated Si nanocrystals undergo room temperature hydrosilylation with bifunctional alkenes with distal polar moieties—ethyl-, methyl-ester or carboxylic acids—without the aid of light or added catalyst. The passivated Si nanocrystals exhibit bright photoluminescence (PL) and disperse in polar solvents, including water. We propose a reaction mechanism in which ester or carboxylic acid groups facilitate direct nucleophilic attack of the highly curved Si surface of the nanocrystals by the alkene.

Yu, Yixuan; Hessel, Colin M.; Bogart, Timothy; Panthani, Matthew G.; Rasch, Michael R.; Korgel, Brian A.

2013-01-01

68

Bifunctional air electrodes containing elemental iron powder charging additive  

DOEpatents

A bifunctional air electrode for use in electrochemical energy cells is made, comprising a hydrophilic layer and a hydrophobic layer, where the hydrophilic layer essentially comprises a hydrophilic composite which includes: (i) carbon; (ii) elemental iron particles having a particle size of between about 25 microns and about 700 microns diameter; (iii) an oxygen evolution material; (iv) a nonwetting agent; and (v) a catalyst, where at least one current collector is formed into said composite.

Liu, Chia-tsun (Monroeville, PA); Demczyk, Brian G. (Rostrover Township, Westmoreland County, PA); Gongaware, Paul R. (Penn Township, Westmoreland County, PA)

1982-01-01

69

(Bifunctional chelates of Rh-105, Au-199, and other metallic radionuclides as potential radiotherapeutic agents)  

SciTech Connect

Progress during this period is reported under the following headings: Diethylenetriamine based and related bifunctional chelating agents and their complexation with Rh-105, Au-198, Pd-109, cu-67, In-111, and Co-57; studies of Pd-109, Rh-105 and Tc-99m with bifunctional chelates based on phenylenediamine; establishment of an appropriate protein assay method for conjugated proteins; studies of new bifunctional Bi, Tri and tetradentate amine oxime ligands with Rh-105; IgG and antibody B72.3 conjugation studies by HPLC Techniques with bifunctional metal chelates; and progress on ligand systems for Au(III).

Not Available

1991-01-01

70

[Bifunctional chelates of Rh-105, Au-199, and other metallic radionuclides as potential radiotherapeutic agents  

SciTech Connect

Progress during this period is reported under the following headings: Diethylenetriamine based and related bifunctional chelating agents and their complexation with Rh-105, Au-198, Pd-109, cu-67, In-111, and Co-57; studies of Pd-109, Rh-105 and Tc-99m with bifunctional chelates based on phenylenediamine; establishment of an appropriate protein assay method for conjugated proteins; studies of new bifunctional Bi, Tri and tetradentate amine oxime ligands with Rh-105; IgG and antibody B72.3 conjugation studies by HPLC Techniques with bifunctional metal chelates; and progress on ligand systems for Au(III).

Not Available

1991-12-31

71

Potent antitumor bifunctional DNA alkylating agents, synthesis and biological activities of 3a-aza-cyclopenta[a]indenes.  

PubMed

A series of bifunctional DNA interstrand cross-linking agents, bis(hydroxymethyl)- and bis(carbamates)-8H-3a-azacyclopenta[a]indene-1-yl derivatives were synthesized for antitumor evaluation. The preliminary antitumor studies revealed that these agents exhibited potent cytotoxicity in vitro and antitumor therapeutic efficacy against human tumor xenografts in vivo. Furthermore, these derivatives have little or no cross-resistance to either Taxol or Vinblastine. Remarkably, complete tumor remission in nude mice bearing human breast carcinoma MX-1 xenograft by 13a,b and 14g,h and significant suppression against prostate adenocarcinoma PC3 xenograft by 13b were achieved at the maximum tolerable dose with relatively low toxicity. In addition, these agents induce DNA interstrand cross-linking and substantial G2/M phase arrest in human non-small lung carcinoma H1299 cells. The current studies suggested that these agents are promising candidates for preclinical studies. PMID:19576785

Kakadiya, Rajesh; Dong, Huajin; Lee, Pei-Chih; Kapuriya, Naval; Zhang, Xiuguo; Chou, Ting-Chao; Lee, Te-Chang; Kapuriya, Kalpana; Shah, Anamik; Su, Tsann-Long

2009-08-01

72

Bearings for Extreme Environments.  

National Technical Information Service (NTIS)

Dry lubricated bearings for applications under extreme environmental conditions were developed. Results with ball bearings assembled from bearing rings coated with hard carbide layers, steel balls, and cages of various materials with self-lubricating prop...

H. Gass H. E. Hintermann G. Stehle H. M. Briscoe

1975-01-01

73

Initial comparison of Cu-67-and Cu-64-labeled anti-colorectal carcinoma Mab 1A3 as agents for radioimmunotherapy in tumor-bearing hamsters  

SciTech Connect

For imaging or radiotherapy, {sup 64}Cu (T{sub 1/2}=12.8 h) has advantages over {sup 67}Cu (T{sub 1/2}=62h) that include wider availibility, lower cost, and a higher specific activity. {sup 67}Cu- and {sup 64}Cu- labeled monoclonal antibody (MAb) 1A3 showed similar lethal efficiencies in vitro to LS174T human colon cancer cells. To compare the lethal effiencies of these agents in vivo, 200 or 400 {mu}Ci of {sup 67}Cu-labeled Mab 1A3 and 500, 1000 or 2000 {mu}Ci of {sup 64}Cu-labeled 1A3 were administered into hamsters carrying 2 day old GW-39 human colon tumors in their thigh musculature. In another group of hamsters, {sup 67}Cu- and {sup 64}Cu-labeled non-specific Mab MOPC were also administered in corresponding amounts. A control group was injected with saline solution. At all doses, hamsters that were given either {sup 64}Cu- or {sup 67}Cu-labeled 1A3 showed inhibition of tumor growth over hamsters injected with either saline or {sup 64}Cu- or {sup 67}Cu-labeled MOPC. Tumor weights in hamsters administered with 2000 {mu}Ci of {sup 64}Cu-1A3 showed an 11-fold decrease over tumors in hamsters given saline (0.184 {plus_minus} 0.106 (n=3) vs 2.056 {plus_minus} 0.369 (n=10)), and a 5-fold decrease over those where {sup 64}Cu-MOPC was administered (0.184 {plus_minus} 0.106 (n=3) vs 0.961 {plus_minus} 0.228 (n=4)). In hamsters injected with 400 {mu}Ci {sup 67}Cu-1A3, a 13-fold decrease in tumor weight was observed over control hamsters given saline (0.345 {plus_minus} 0.129 (n=5)vs 4.457 {plus_minus}0.405 (n=10)), and a 7-fold decrease was observed when {sup 67}Cu-MOPC was injected (0.345 {plus_minus} 0.129 (n=5) vs 2.507 {plus_minus} 1.064 (n=5)). Given the 5-fold difference in half-life between {sup 67}Cu and {sup 64}Cu, at corresponding doses the inhibition of tumor growth was similar. These initial experiments indicate that {sup 64}Cu has a radiotherapeutic potential comparable to {sup 67}Cu when labeled to Mab 1A3.

Anderson, C.J.; Connett, J.M.; Guo, L.W. [Washington Univ. School of Medicine, St. Louis, MO (United States)] [and others

1994-05-01

74

Chromium(VI) removal via reduction-sorption on bi-functional silica adsorbents.  

PubMed

Organically-modified silica gels bearing mercaptopropyl and ethylenediaminetriacetate groups (SiO2-SH/ED3A) have been used for reduction and subsequent sequestration of Cr(VI) species. The uptake mechanism involves Cr(VI) reduction by thiol groups (SH) and further immobilization of the so-generated Cr(III) species via complexation to the ethylenediaminetriacetate moieties (ED3A). The most appropriate pH range (1-3) for complete Cr(VI) reduction-sorption by SiO2-SH/ED3A originates from the balance between full reduction of Cr(VI) by SH, requiring low pH values, and quantitative complexation of Cr(III) by ED3A, which is favored in less acidic media. Such bi-functional adsorbents are considerably more effective at removal of Cr(VI) than those simply modified with thiol groups alone. The whole reduction-sorption process was characterized by fast kinetics, thus permitting efficient use of the SiO2-SH/ED3A adsorbent in dynamic conditions (column experiments). Monitoring the amount of immobilized chromium species on the solid was achieved using X-ray fluorescence spectroscopy and UV-vis spectroscopy. Studying the influence of ionic strength and presence of heavy metals revealed few interference on Cr(VI) removal. PMID:23500426

Zaitseva, Nataliya; Zaitsev, Vladimir; Walcarius, Alain

2013-04-15

75

Changes in leucocyte populations following murine bifunctional antibody infusion in colon cancer patients.  

PubMed Central

This study was undertaken to determine whether infusion of a unique ZCE/CHA bifunctional antibody (BFA, 5-40 mg) could alter the composition and functions of peripheral blood leucocytes in 18 patients with colon cancer. The BFA is made by combining chemically the Fab' fragments of two murine monoclonal antibodies. One fragment (ZCE 025) binds to the carcino-embryonic antigen (CEA) and the other (CHA 225) to an epitope, present on an 111In-benzyl EDTA analog of bleomycin (BLEDTA IV) and on 111In-hydroxy-ethyl-thiourea benzyl EDTA (EOTUBE). The radiolabelled epitope (111In-BLEDTA IV or 111In-EOTUBE) was given 4 days after prelocalization with BFA. Peripheral blood samples were tested before BFA infusion, at the end of infusion (1 h later), and at 4 and 7 days post-infusion. A 50% or greater suppression in lymphocyte responsiveness to phytohaemagglutinin (PHA) and concanavalin A (Con A) was seen in 13 out of 18 and 12 out of 18 subjects, respectively, at some time after BFA infusion; this was especially evident in those patients with pre-infusion stimulation indices of greater than 50 (PHA) and/or greater than 10 (Con A). In contrast, natural killer (NK) cell cytotoxicity and oxygen radical production increased in five out of 15 and in seven out of 18 subjects, respectively. Little or no change was observed in CD3, CD4, CD8, CD16, and CD19 markers on lymphocyte subpopulations as determined by flow cytometry. These data suggest that significant changes in mitogen-induced lymphoproliferation. NK cell cytotoxicity, and oxygen radical production can occur in a substantial proportion of cancer patients after infusion of the ZCE/CHA bifunctional antibody system. The immunomodulation was unrelated to initial BFA dose, dose of BFA as a carrier, or to subsequent infusion of either form of the 111In epitope. The clinical significance of these phenomena, if any, remains to be determined.

Gridley, D S; Stickney, D R

1991-01-01

76

Defective DNA cross-link removal in Chinese hamster cell mutants hypersensitive to bifunctional alkylating agents  

SciTech Connect

DNA repair-deficient mutants from five genetic complementation groups isolated previously from Chinese hamster cells were assayed for survival after exposure to the bifunctional alkylating agents mitomycin C or diepoxybutane. Groups 1, 3, and 5 exhibited 1.6- to 3-fold hypersensitivity compared to the wild-type cells, whereas Groups 2 and 4 exhibited extraordinary hypersensitivity. Mutants from Groups 1 and 2 were exposed to 22 other bifunctional alkylating agents in a rapid assay that compared cytotoxicity of the mutants to the wild-type parental strain, AA8. With all but two of the compounds, the Group 2 mutant (UV4) was 15- to 60-fold more sensitive than AA8 or the Group 1 mutant (UV5). UV4 showed only 6-fold hypersensitivity to quinacrine mustard. Alkaline elution measurements showed that this compound produced few DNA interstrand cross-links but numerous strand breaks. Therefore, the extreme hypersensitivity of mutants from Groups 2 and 4 appeared specific for compounds the main cytotoxic lesions of which were DNA cross-links. Mutant UV5 was only 1- to 4-fold hypersensitive to all the compounds. Although the initial number of cross-links was similar for the three cell lines, the efficiency of removal of cross-links was lowest in UV4 and intermediate in UV5. These results suggest that the different levels of sensitivity are specifically related to different efficiencies of DNA cross-link removal. The phenotype of hypersensitivity to both UV radiation and cross-link damage exhibited by the mutants in Groups 2 and 4 appears to differ from those of the known human DNA repair syndromes.

Hoy, C.A.; Thompson, L.H.; Mooney, C.L.; Salazar, E.P.

1985-04-01

77

REDUCTIVE ACTIVATION OF DIOXYGEN FOR DEGRADATION OF METHYL TERT-BUTYL ETHER BY BIFUNCTION  

EPA Science Inventory

Bifunctional aluminum is prepared by sulfating aluminum metal with sulfuric acid. The use of bifunctional aluminum to degrade methyl tert-butyl ether (MTBE) in the presence of dioxygen has been examined using batch systems. Primary degradation products were tert-butyl alcohol, ...

78

Magnetic perturbation inspection of inner bearing races  

NASA Technical Reports Server (NTRS)

Approximately 100 inner race bearings were inspected nondestructively prior to endurance testing. Two of the bearings which failed during testing spalled at the sites of subsurface inclusions previously detected by using magnetic field perturbation. At other sites initially judged to be suspect, subsurface inclusion-nucleated cracking was observed. Inspection records and metallurgical sectioning results are presented and discussed.

Barton, J. R.; Lankford, J.

1972-01-01

79

Encapsulated ball bearings for rotary micro machines  

Microsoft Academic Search

We report on the first encapsulated rotary ball bearing mechanism using silicon microfabrication and stainless steel balls. The method of capturing stainless steel balls within a silicon race to support a silicon rotor both axially and radially is developed for rotary micro machines and MEMS ball bearing tribology studies. Initial demonstrations show speeds up to 6.8 krpm without lubrication, while

C. Mike Waits; Bruce Geil; Reza Ghodssi

2007-01-01

80

Interference Fit Life Factors for Roller Bearings  

NASA Technical Reports Server (NTRS)

The effect of hoop stresses in reducing cylindrical roller bearing fatigue life was determined for various classes of inner ring interference fit. Calculations were performed for up to seven interference fit classes for each of ten bearing sizes. Each fit was taken at tightest, average and loosest values within the fit class for RBEC-5 tolerance, thus requiring 486 separate analyses. The hoop stresses were superimposed on the Hertzian principal stresses created by the applied radial load to calculate roller bearing fatigue life. The method was developed through a series of equations to calculate the life reduction for cylindrical roller bearings based on interference fit. All calculated lives are for zero initial bearing internal clearance. Any reduction in bearing clearance due to interference fit was compensated by increasing the initial (unmounted) clearance. Results are presented as tables and charts of life factors for bearings with light, moderate and heavy loads and interference fits ranging from extremely light to extremely heavy and for bearing accuracy class RBEC 5 (ISO class 5). Interference fits on the inner bearing ring of a cylindrical roller bearing can significantly reduce bearing fatigue life. In general, life factors are smaller (lower life) for bearings running under light load where the unfactored life is highest. The various bearing series within a particular bore size had almost identical interference fit life factors for a particular fit. The tightest fit at the high end of the RBEC-5 tolerance band defined in ANSI/ABMA shaft fit tables produces a life factor of approximately 0.40 for an inner-race maximum Hertz stress of 1200 MPa (175 ksi) and a life factor of 0.60 for an inner-race maximum Hertz stress of 2200 MPa (320 ksi). Interference fits also impact the maximum Hertz stress-life relation.

Oswald, Fred B.; Zaretsky, Erwin V.; Poplawski, Joseph V.

2008-01-01

81

A bifunctional perovskite catalyst for oxygen reduction and evolution.  

PubMed

La0.3(Ba0.5Sr0.5)0.7Co0.8Fe0.2O3d is a promising bifunctional perovskite catalyst for the oxygen reduction reaction and the oxygen evolution reaction. This catalyst has circa 10 nm-scale rhombohedral LaCoO3 cobaltite particles distributed on the surface. The dynamic microstructure phenomena are attributed to the charge imbalance from the replacement of A-site cations with La3+ and local stress on Cosite sub-lattice with the cubic perovskite structure. PMID:24757039

Jung, Jae-Il; Jeong, Hu Young; Lee, Jang-Soo; Kim, Min Gyu; Cho, Jaephil

2014-04-25

82

Enantioselective Iodolactonization of Disubstituted Olefinic Acids Using a Bifunctional Catalyst  

PubMed Central

The enantioselective iodolactonizations of a series of diversely-substituted olefinic carboxylic acids are promoted by a BINOL-derived, bifunctional catalyst. Reactions involving 5-alkyl- and 5-aryl-4(Z)-pentenoic acids and 6-alkyl- and 6-aryl-5(Z)-hexenoic acids provide the corresponding ?- and ?-lactones having stereogenic C–I bonds in excellent yields and >97:3 er. Significantly, this represents the first organocatalyst that promotes both bromo- and iodolactonization with high enantioselectivities. The potential of this catalyst to induce kinetic resolutions of racemic unsaturated acids is also demonstrated.

Fang, Chao; Paull, Daniel H.; Hethcox, J. Caleb; Shugrue, Christopher R.; Martin, Stephen F.

2012-01-01

83

Thrust bearing for turbocharger  

Microsoft Academic Search

A thrust bearing is described for sustaining the thrust load of the rotor shaft of a turbocharger, the thrust bearing having a first and second opposed side surface, comprising: A first groove formed in the first side surface of the thrust bearing for holding lubricating oil supplied to the bearing; at least one first oil passage extending from the groove

T. Tamura; N. Shibata; T. Kawakami

1987-01-01

84

Passive magnetic bearing configurations  

DOEpatents

A journal bearing provides vertical and radial stability to a rotor of a passive magnetic bearing system when the rotor is not rotating and when it is rotating. In the passive magnetic bearing system, the rotor has a vertical axis of rotation. Without the journal bearing, the rotor is vertically and radially unstable when stationary, and is vertically stable and radially unstable when rotating.

Post, Richard F. (Walnut Creek, CA) [Walnut Creek, CA

2011-01-25

85

Getting Your Bearings  

NSDL National Science Digital Library

In this activity, learners explore the concept of friction and how ball bearings reduce friction. Learners investigate different uses for ball bearings, how the design has changed over time to incorporate roller bearings, test friction using marbles, and identify the use of ball bearings in everyday items.

Ieee

2013-08-30

86

Rolling-Element Bearings  

NASA Technical Reports Server (NTRS)

Rolling element bearings are a precision, yet simple, machine element of great utility. A brief history of rolling element bearings is reviewed and the type of rolling element bearings, their geometry and kinematics, as well as the materials they are made from and the manufacturing processes they involve are described. Unloaded and unlubricated rolling element bearings, loaded but unlubricated rolling element bearings and loaded and lubricated rolling element bearings are considered. The recognition and understanding of elastohydrodynamic lubrication covered, represents one of the major development in rolling element bearings.

Hamrock, B. J.; Anderson, W. J.

1983-01-01

87

Introduction to ball bearings  

NASA Technical Reports Server (NTRS)

The purpose of a ball bearing is to provide a relative positioning and rotational freedom while transmitting a load between two structures, usually a shaft and a housing. For high rotational speeds (e.g., in gyroscope ball bearings) the purpose can be expanded to include rotational freedom with practically no wear in the bearing. This condition can be achieved by separating the bearing parts with a coherent film of fluid known as an elastohydrodynamic film. This film can be maintained not only when the bearing carries the load on a shaft, but also when the bearing is preloaded to position the shaft to within micro- or nano-inch accuracy and stability. Background information on ball bearings is provided, different types of ball bearings and their geometry and kinematics are defined, bearing materials, manufacturing processes, and separators are discussed. It is assumed, for the purposes of analysis, that the bearing carries no load.

Hamrock, B. J.; Dowson, D.

1981-01-01

88

High efficiency magnetic bearings  

NASA Technical Reports Server (NTRS)

Research activities concerning high efficiency permanent magnet plus electromagnet (PM/EM) pancake magnetic bearings at the University of Maryland are reported. A description of the construction and working of the magnetic bearing is provided. Next, parameters needed to describe the bearing are explained. Then, methods developed for the design and testing of magnetic bearings are summarized. Finally, a new magnetic bearing which allows active torque control in the off axes directions is discussed.

Studer, Philip A.; Jayaraman, Chaitanya P.; Anand, Davinder K.; Kirk, James A.

1993-01-01

89

A versatile bifunctional dendritic cell targeting vaccine vector.  

PubMed

We have developed an efficient versatile in vivo dendritic cell (DC) targeting vector for delivering different classes of antigens such as proteins, peptide, glycolipids and naked DNA for vaccine applications. A single chain antibody (scFv) that recognizes DEC-205 receptor of DC was fused with a core-streptavidin domain and expressed in Escherichia coli using the T7 expression system. The bifunctional fusion protein (bfFp) was expressed as a periplasmic soluble protein and affinity-purified in its monomeric form. The bifunctional activity against DEC-205 and biotin was characterized by ELISA and Western blot. In vivo DC targeting of a diverse group of biotinylated antigens such as viral and bacterial proteins, a cancer peptide, gangliosides and DNA of certain infectious diseases was conducted in mice. Results show that in the presence of bfFp and costimulatory anti-CD40 mAb, both humoral and cell-mediated responses were augmented in either the single antigen or multiple antigen targeting strategy. Lastly, bfFp based DC targeting of antigens in low doses may be a useful strategy for the design of monovalent or polyvalent vaccines for the masses. PMID:19053535

Wang, Welson W; Das, Dipankar; Suresh, Mavanur R

2009-01-01

90

Urinary bile acids and peroxisomal bifunctional enzyme deficiency.  

PubMed

The biosynthesis of normal bile acids involves beta-oxidation of the 8-carbon side-chain of cholesterol, in addition to numerous modifications of the sterol nucleus. Because beta-oxidation of the sterol side-chain has been localized to the peroxisome, bile acid analysis has been suggested to be useful in the diagnostic evaluation of individuals suspected of having peroxisomal disorders. Although data from subjects with generalized peroxisomal disorders support this, few data exist regarding the bile acids in individuals having single peroxisomal beta-oxidation enzyme disorders. In this study, we analyzed the urinary bile acids from 12 patients with peroxisomal bifunctional protein deficiency using continuous flow fast atom bombardment mass spectrometry. All 12 patients had abnormal spectra, although their ion profiles and rank order of intensity of ions varied considerably. Ten of 12 individuals had abnormal spectra with presence of taurine-conjugated tetrahydroxycholestenoates, allowing a definite diagnosis of a peroxisomal beta-oxidation defect and a presumptive diagnosis of bifunctional protein deficiency; the other two cases were nondiagnostically abnormal. The strengths and limitations of urinary bile acid analysis for the diagnosis of peroxisomal beta-oxidation disorders are discussed. PMID:8725785

Natowicz, M R; Evans, J E; Kelley, R I; Moser, A B; Watkins, P A; Moser, H W

1996-05-17

91

Bi-functional CD22 ligands use multimeric immunoglobulins as protein scaffolds in assembly of immune complexes on B cells  

PubMed Central

CD22 is a B cell specific sialic-acid-binding immunoglobulin-like lectin (Siglec) whose function as a regulator of B cell signaling is modulated by its interaction with glycan ligands bearing the sequence NeuAc?2-6Gal. To date, only highly multivalent polymeric ligands (n=450) have achieved sufficient avidity to bind to CD22 on native B cells. Here we demonstrate that a synthetic bi-functional molecule comprising a ligand of CD22 linked to an antigen (nitrophenol; NP) can use a monoclonal anti-NP-IgM as a decavalent protein scaffold to efficiently drive assembly of IgM-CD22 complexes on the surface of native B cells. Surprisingly, anti-NP antibodies of lower valency, IgA (n =4) and IgG (n =2), were also found to drive complex formation, though with lower avidity. Ligands bearing alternate linkers of variable length and structure were constructed to establish the importance of a minimal length requirement, and versatility in the structural requirement. We show that the ligand drives assembly of IgM complexes exclusively on the surface of B cells and not other classes of white blood cells that do not express CD22, which lends itself to the possibility of targeting B cells in certain hematopoietic malignancies.

O'Reilly, Mary K.; Collins, Brian E.; Han, Shoufa; Liao, Liang; Rillahan, Cory; Kitov, Pavel I.; Bundle, David R.; Paulson, James C.

2008-01-01

92

Effects of targeting moiety, linker, bifunctional chelator, and molecular charge on biological properties of 64Cu-labeled triphenylphosphonium cations.  

PubMed

In this report, we present the synthesis and evaluation of six new 64Cu-labeled triphenylphosphonium (TPP) cations. Biodistribution studies were performed using the athymic nude mice bearing U87MG human glioma xenografts to explore the impact of TPP moieties, linkers, bifunctional chelators (BFCs), and molecular charge on biological properties of 64Cu radiotracers. On the basis of the results from this study, it is concluded that (1) mTPP (tris(4-methoxyphenyl)phosphonium) is a better mitochondrion-targeting molecule than TPP and 3mTPP (tris(2,4,6-trimethoxyphenyl)phosphonium); (2) DO3A (1,4,7,10-tetraazacyclododecane-4,7,10-triacetic acid) and DO2A (1,4,7,10-tetraazacyclododecane-4,7-diacetic acid) are suitable BFCs for the 64Cu-labeling of TPP cations; (3) NOTA-Bn ( S-2-(4-thioureidobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid) has a significant adverse effect on the radiotracer tumor uptake and tumor-to-background ratios; and (4) monoanionic BFCs should be avoided to ensure that 64Cu chelate has a neutral or negative charge. Considering the tumor uptake and tumor/liver ratios, 64Cu(DO2A-xy-TPP)+ is the best candidate for more extensive evaluations in different tumor-bearing animal models. PMID:18419113

Kim, Young-Seung; Yang, Chang-Tong; Wang, Jianjun; Wang, Lijun; Li, Zi-Bo; Chen, Xiaoyuan; Liu, Shuang

2008-05-22

93

Zinc/air battery R and D research and development of bifunctional oxygen electrode: Tasks 1 and 2  

NASA Astrophysics Data System (ADS)

The bifunctional oxygen electrode is examined. The development of a rechargeable metal-oxygen (air) cell is hampered to a great extent by the lack of a stable and cost effective oxygen electrode capable of use during both charge and discharge. The first type of bifunctional electrode consists of two distinct catalytic layers. The oxygen reduction catalyst layer containing a supported gold catalyst is in contact with a hydrophilic nickel layer in which evolution of oxygen takes place. Loadings of gold from 0.5 to 1.0 mg/sq cm were investigated; carbon, graphite, metal, and spinel oxides were evaluated as substrates. The second part of the research effort was centered on developing a reversible oxygen electrode containing only one catalytic layer for both reduction and evolution of oxygen. The work was directed specifically to the study of perovskite type of oxides with the composition AA sup 1 BO sub 3, where A is an element of the lanthanide series, A sup 1 is an alkaline earth metal and B, a first row transition element. Initial polarization data obtained in unscrubbed air gave a value of approximately 200 millivolts vs Hg/HgO reference electrode at a current density of 50 ma/cm. Electrodes were made both by roll-bonding and by pelletizing techniques and tested for polarization and cycle life.

Klein, M.; Viswanathan, S.

1986-12-01

94

Active Magnetic Bearings.  

National Technical Information Service (NTIS)

The paper deals with a nonconventional type of bearing that is active magnetic bearing (AMB). Rotor suspension in AMB is achieved by attractive forces of electromagnetic poles. To stabilize the rotor position, the automatic control system is introduced. T...

Y. N. Zhuravlyov

1992-01-01

95

High Efficiency Magnetic Bearings.  

National Technical Information Service (NTIS)

Research activities concerning high efficiency permanent magnet plus electromagnet (PM/EM) pancake magnetic bearings at the University of Maryland are reported. A description of the construction and working of the magnetic bearing is provided. Next, param...

P. A. Studer C. P. Jayaraman D. K. Anand J. A. Kirk

1993-01-01

96

Shielded Bearing Lubrication.  

National Technical Information Service (NTIS)

Precise quantities of lubricant under automatic control are injected through chambers of housings into shielded rolling element bearings. Separate feed line conduits directly deliver the lubricant to the shielded critical surfaces of such bearings and ins...

J. A. Wong T. L. Daugherty G. D. Huntzberry

1996-01-01

97

Mechanical spin bearings  

NASA Technical Reports Server (NTRS)

A spin bearing assembly including, a pair of mutually opposing complementary bearing support members having mutually spaced apart bearing support surfaces which may be, for example, bearing races and a set of spin bearings located therebetween. Each spin bearing includes a pair of end faces, a central rotational axis passing through the end faces, a waist region substantially mid-way between the end faces and having a first thickness dimension, and discrete side surface regions located between the waist region and the end faces and having a second thickness dimension different from the first thickness dimension of the waist region and wherein the side surface regions further have respective curvilinear contact surfaces adapted to provide a plurality of bearing contact points on the bearing support members.

Vranish, John M. (Inventor)

1998-01-01

98

HARVEST CHARACTERISTICS OF BROWN BEARS IN NORTHERN HOKKAIDO, JAPAN  

Microsoft Academic Search

A population study of the Ezo brown bear (Ursus arctos yesoensis) was initiated in 1975 in northern Hokkaido. One hundred fifty-two brown bear skulls collected from 1980 to 1985 were used to determine age. Most of these bears were killed in nuisance control hunts conducted during the early spring. The youngest age classes of bears (0-5 years old) constituted 67.7%

TOSHIKI AOI

99

Axial Halbach Magnetic Bearings  

NASA Technical Reports Server (NTRS)

Axial Halbach magnetic bearings have been investigated as part of an effort to develop increasingly reliable noncontact bearings for future high-speed rotary machines that may be used in such applications as aircraft, industrial, and land-vehicle power systems and in some medical and scientific instrumentation systems. Axial Halbach magnetic bearings are passive in the sense that unlike most other magnetic bearings that have been developed in recent years, they effect stable magnetic levitation without need for complex active control.

Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

2008-01-01

100

Polar Bears Change Diet  

NSDL National Science Digital Library

This radio broadcast from 2001 explains how polar bears have adjusted their diet due to the climate warming around Hudson Bay, Canada. The ringed seals that polar bears normally eat have been harder for polar bears to get to, due to disappearing ice. This has forced polar bears to begin eating harbor seals and bearded seals. The clip is 4 minutes and 15 seconds in length.

Schneider, Doug

2007-12-12

101

The Bi-Functional Organization of Human Basement Membranes  

PubMed Central

The current basement membrane (BM) model proposes a single-layered extracellular matrix (ECM) sheet that is predominantly composed of laminins, collagen IVs and proteoglycans. The present data show that BM proteins and their domains are asymmetrically organized providing human BMs with side-specific properties: A) isolated human BMs roll up in a side-specific pattern, with the epithelial side facing outward and the stromal side inward. The rolling is independent of the curvature of the tissue from which the BMs were isolated. B) The epithelial side of BMs is twice as stiff as the stromal side, and C) epithelial cells adhere to the epithelial side of BMs only. Side-selective cell adhesion was also confirmed for BMs from mice and from chick embryos. We propose that the bi-functional organization of BMs is an inherent property of BMs and helps build the basic tissue architecture of metazoans with alternating epithelial and connective tissue layers.

Halfter, Willi; Monnier, Christophe; Muller, David; Oertle, Philipp; Uechi, Guy; Balasubramani, Manimalha; Safi, Farhad; Lim, Roderick; Loparic, Marko; Henrich, Paul Bernhard

2013-01-01

102

Tracking Polar Bears  

USGS Multimedia Gallery

Movements of 9 satellite-collared adult female polar bears were tracked in February, 2010 by satellite telemetry. Bears were collared in 2007, 2008, and 2009 on the spring-time sea ice of the southern Beaufort Sea or on the autumn pack ice in 2009. Polar bear satellite telemetry data are shown with ...

2010-04-13

103

Efficient bifunctional gallium-68 chelators for positron emission tomography: tris(hydroxypyridinone) ligands  

PubMed Central

A new tripodal tris(hydroxypyridinone) bifunctional chelator for gallium allows easy production of 68Ga-labelled proteins rapidly under mild conditions in high yields at exceptionally high specific activity and low concentration.

Berry, David J.; Ma, Yongmin; Ballinger, James R.; Tavare, Richard; Koers, Alexander; Sunassee, Kavitha; Zhou, Tao; Nawaz, Saima; Mullen, Gregory E. D.; Hider, Robert C.; Blower, Philip J.

2014-01-01

104

Cryogenic Hybrid Magnetic Bearing  

NASA Technical Reports Server (NTRS)

Cryogenic hybrid magnetic bearing is example of class of magnetic bearings in which permanent magnets and electromagnets used to suspend shafts. Electromagnets provide active control of position of shaft. Bearing operates at temperatures from -320 degrees F (-196 degrees C) to 650 degrees F (343 degrees C); designed for possible use in rocket-engine turbopumps, where effects of cryogenic environment and fluid severely limit lubrication of conventional ball bearings. This and similar bearings also suitable for terrestrial rotating machinery; for example, gas-turbine engines, high-vacuum pumps, canned pumps, precise gimbals that suspend sensors, and pumps that handle corrosive or gritty fluids.

Meeks, Crawford R.; Dirusso, Eliseo; Brown, Gerald V.

1994-01-01

105

Performance of a hybrid cylindrical roller bearing  

NASA Astrophysics Data System (ADS)

A 206-size hybrid (ceramic/steel) cylindrical roller bearing was tested in MIL-L-23699 C oil at several speeds and loads. Heat-generation data was collected and subsequently correlated with bearing-analysis software. Bearing-cage slip data was also collected at various oil-flow rates, oil temperatures, and with both MIL-L-7808 J and MIL-L-23699 C oils. The hybrid bearing was tested in MIL-L-23699 C oil for for 25 hours at 2220 N radial load and 1.08 MDN shaft speed. The hybrid bearing technology demonstrated in the report is applicable to the Integrated High Performance Turbine Engine Technology Initiative.

Schrader, Stephen M.

1992-08-01

106

Performance of a hybrid cylindrical roller bearing  

SciTech Connect

A 206-size hybrid (ceramic/steel) cylindrical roller bearing was tested in MIL-L-23699 C oil at several speeds and loads. Heat-generation data was collected and subsequently correlated with bearing-analysis software. Bearing-cage slip data was also collected at various oil-flow rates, oil temperatures, and with both MIL-L-7808 J and MIL-L-23699 C oils. The hybrid bearing was tested in MIL-L-23699 C oil for for 25 hours at 2220 N radial load and 1.08 MDN shaft speed. The hybrid bearing technology demonstrated in the report is applicable to the Integrated High Performance Turbine Engine Technology Initiative. 15 refs.

Schrader, S.M. (General Motors Corp., Allison Gas Turbine Div., Indianapolis, IN (United States))

1992-08-01

107

Status of understanding for bearing materials  

SciTech Connect

The structural materials and potential failure modes for high technology aircraft gas turbine bearings are reviewed. Among the failure modes discussed for iron-base through-hardened bearing materials are fatigue, surface distress, and corrosion. It is shown that the sub-surface initiated rolling-contact fatigue failure mode is reasonably well understood and in most cases can be controlled by proper material selection and design. Current bearing materials provide long life and high reliability in existing applications. A new generation of materials are being developed which will provide improved fracture toughness, better corrosion resistance, and a further extension of bearing fatigue life. Bearing problems due to surface distress, caused by a variety of surface and near surface anomalies, are less well understood. This area will require the implementation of an interdisciplinary effort to improve the level of understanding of metallic surface-lubricant reactions and interactions.

Bamberger, E.N.

1984-04-01

108

Novel 16-substituted bifunctional derivatives of huperzine B: multifunctional cholinesterase inhibitors  

Microsoft Academic Search

Aim:To design novel bifunctional derivatives of huperzine B (HupB) based on the concept of dual binding site of acetylcholinesterase (AChE) and evaluate their pharmacological activities for seeking new drug candidates against Alzheimer's disease (AD).Methods:Novel 16-substituted bifunctional derivatives of HupB were synthesized through chemical reactions. The inhibitory activities of the derivatives toward AChE and butyrylcholinesterase (BuChE) were determined in vitro by

Yu-fang Shi; Hai-yan Zhang; Wei Wang; Yan Fu; Yu Xia; Xi-can Tang; Dong-lu Bai; Xu-chang He

2009-01-01

109

Induction of endothelial cell apoptosis by lipid hydroperoxide-derived bifunctional electrophiles  

Microsoft Academic Search

Endothelial dysfunction is considered to be the earliest event in atherogenesis. Oxidative stress, inflammation, and apoptosis play critical roles in its progression and onset. Lipid peroxidation, which occurs during oxidative stress, results in the formation of lipid hydroperoxide-derived bifunctional electrophiles such as 4-hydroxy-2(E)-nonenal that induce apoptosis. In this study, recently identified lipid hydroperoxide-derived bifunctional electrophiles 4-oxo-2(E)-nonenal (ONE; 5–30 ?M) and

Wenying Jian; Jasbir S. Arora; Tomoyuki Oe; Vladimir V. Shuvaev; Ian A. Blair

2005-01-01

110

Preparation of bi-functional silica particles for antibacterial and self cleaning surfaces  

Microsoft Academic Search

Synthesis of bi-functional silica particles by a simple wet chemical method is described where the mixture of ultra fine nanoparticles (1–3nm) of titania and silver were attached on the silica particle surface in a controlled way to form a core–shell structure. The silica surface showed efficient bi-functional activity of photo-catalytically self cleaning and antibacterial activity due to nanotitania and nanosilver

Neha Y. Hebalkar; Snigdhatanu Acharya; Tata N. Rao

2011-01-01

111

Detection and isolation of nucleic acid sequences using a bifunctional hybridization probe  

DOEpatents

A method for detecting and isolating a target sequence in a sample of nucleic acids is provided using a bifunctional hybridization probe capable of hybridizing to the target sequence that includes a detectable marker and a first complexing agent capable of forming a binding pair with a second complexing agent. A kit is also provided for detecting a target sequence in a sample of nucleic acids using a bifunctional hybridization probe according to this method.

Lucas, Joe N. (San Ramon, CA); Straume, Tore (Tracy, CA); Bogen, Kenneth T. (Walnut Creek, CA)

2000-01-01

112

6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase: head-to-head with a bifunctional enzyme that controls glycolysis  

PubMed Central

Fru-2,6-P2 (fructose 2,6-bisphosphate) is a signal molecule that controls glycolysis. Since its discovery more than 20 years ago, inroads have been made towards the understanding of the structure–function relationships in PFK-2 (6-phosphofructo-2-kinase)/FBPase-2 (fructose-2,6-bisphosphatase), the homodimeric bifunctional enzyme that catalyses the synthesis and degradation of Fru-2,6-P2. The FBPase-2 domain of the enzyme subunit bears sequence, mechanistic and structural similarity to the histidine phosphatase family of enzymes. The PFK-2 domain was originally thought to resemble bacterial PFK-1 (6-phosphofructo-1-kinase), but this proved not to be correct. Molecular modelling of the PFK-2 domain revealed that, instead, it has the same fold as adenylate kinase. This was confirmed by X-ray crystallography. A PFK-2/FBPase-2 sequence in the genome of one prokaryote, the proteobacterium Desulfovibrio desulfuricans, could be the result of horizontal gene transfer from a eukaryote distantly related to all other organisms, possibly a protist. This, together with the presence of PFK-2/FBPase-2 genes in trypanosomatids (albeit with possibly only one of the domains active), indicates that fusion of genes initially coding for separate PFK-2 and FBPase-2 domains might have occurred early in evolution. In the enzyme homodimer, the PFK-2 domains come together in a head-to-head like fashion, whereas the FBPase-2 domains can function as monomers. There are four PFK-2/FBPase-2 isoenzymes in mammals, each coded by a different gene that expresses several isoforms of each isoenzyme. In these genes, regulatory sequences have been identified which account for their long-term control by hormones and tissue-specific transcription factors. One of these, HNF-6 (hepatocyte nuclear factor-6), was discovered in this way. As to short-term control, the liver isoenzyme is phosphorylated at the N-terminus, adjacent to the PFK-2 domain, by PKA (cAMP-dependent protein kinase), leading to PFK-2 inactivation and FBPase-2 activation. In contrast, the heart isoenzyme is phosphorylated at the C-terminus by several protein kinases in different signalling pathways, resulting in PFK-2 activation.

2004-01-01

113

Bearings: Technology and needs  

NASA Technical Reports Server (NTRS)

A brief status report on bearing technology and present and near-term future problems that warrant research support is presented. For rolling element bearings a material with improved fracture toughness, life data in the low Lambda region, a comprehensive failure theory verified by life data and incorporated into dynamic analyses, and an improved corrosion resistant alloy are perceived as important needs. For hydrodynamic bearings better definition of cavitation boundaries and pressure distributions for squeeze film dampers, and geometry optimization for minimum power loss in turbulent film bearings are needed. For gas film bearings, foil bearing geometries that form more nearly optimum film shapes for maximum load capacity, and more effective surface protective coatings for high temperature operation are needed.

Anderson, W. J.

1982-01-01

114

On The Dynamic and Thermal Performance of a Zero Clearance Auxiliary Bearing(zcab) for a Magnetic Bearing System  

Microsoft Academic Search

Structural and thermal analysis of a zero clearance auxiliary bearing (ZCAB) for magnetic bearing systems is presented. The ZCAB consists a series of rollers whose centers are initially placed on a circle. At the open condition all rollers have an initial clearance about the rotating shaft. As the shaft drops on the ZCAB rollers, either due to failure of the

Mohsen Salehi; Hooshang Heshmat

2000-01-01

115

The Incredible Water Bear  

NSDL National Science Digital Library

This image-rich Micscape Magazine article explores how water bears can be found almost everywhere yet are still unknown to almost everybody, why there are relatively few light microscope photographs of water bears in the literature and on the Web, and how light microscopy can outperform scanning electron microscopy when viewing these animals. It includes a list of historical references, early sketches, and colorful images of water bears, also known as tardigrades.

Mach, Martin; Magazine, Micscape

116

Bearing restoration by grinding  

NASA Technical Reports Server (NTRS)

A joint program was undertaken by the NASA Lewis Research Center and the Army Aviation Systems Command to restore by grinding those rolling-element bearings which are currently being discarded at aircraft engine and transmission overhaul. Three bearing types were selected from the UH-1 helicopter engine (T-53) and transmission for the pilot program. No bearing failures occurred related to the restoration by grinding process. The risk and cost of a bearing restoration by grinding programs was analyzed. A microeconomic impact analysis was performed.

Hanau, H.; Parker, R. J.; Zaretsky, E. V.; Chen, S. M.; Bull, H. L.

1976-01-01

117

Design principles for bifunctional targeted oligonucleotide enhancers of splicing.  

PubMed

Controlling the patterns of splicing of specific genes is an important goal in the development of new therapies. We have shown that the splicing of a refractory exon, SMN2 exon 7, could be increased in fibroblasts derived from patients with spinal muscular atrophy by using bifunctional targeted oligonucleotide enhancers of splicing (TOES) oligonucleotides that anneal to the exon and contain a 'tail' of enhancer sequences that recruit activating proteins. We show here that there are striking agreements between the effects of oligonucleotides on splicing in vitro and on both splicing and SMN2 protein expression in patient-derived fibroblasts, indicating that the effects on splicing are the major determinant of success. Increased exon inclusion depends on the number, sequence and chemistry of the motifs that bind the activator protein SRSF1, but it is not improved by increasing the strength of annealing to the target site. The optimal oligonucleotide increases protein levels in transfected fibroblasts by a mean value of 2.6-fold (maximum 4.6-fold), and after two rounds of transfection the effect lasted for a month. Oligonucleotides targeted to the upstream exon (exon 6 in SMN) are also effective. We conclude that TOES oligonucleotides are highly effective reagents for restoring the splicing of refractory exons and can act across long introns. PMID:21602265

Owen, Nicholas; Zhou, Haiyan; Malygin, Alexey A; Sangha, Jason; Smith, Lindsay D; Muntoni, Francesco; Eperon, Ian C

2011-09-01

118

Bifunctional Avidin with Covalently Modifiable Ligand Binding Site  

PubMed Central

The extensive use of avidin and streptavidin in life sciences originates from the extraordinary tight biotin-binding affinity of these tetrameric proteins. Numerous studies have been performed to modify the biotin-binding affinity of (strept)avidin to improve the existing applications. Even so, (strept)avidin greatly favours its natural ligand, biotin. Here we engineered the biotin-binding pocket of avidin with a single point mutation S16C and thus introduced a chemically active thiol group, which could be covalently coupled with thiol-reactive molecules. This approach was applied to the previously reported bivalent dual chain avidin by modifying one binding site while preserving the other one intact. Maleimide was then coupled to the modified binding site resulting in a decrease in biotin affinity. Furthermore, we showed that this thiol could be covalently coupled to other maleimide derivatives, for instance fluorescent labels, allowing intratetrameric FRET. The bifunctional avidins described here provide improved and novel tools for applications such as the biofunctionalization of surfaces.

Leppiniemi, Jenni; Maatta, Juha A. E.; Hammaren, Henrik; Soikkeli, Mikko; Laitaoja, Mikko; Janis, Janne; Kulomaa, Markku S.; Hytonen, Vesa P.

2011-01-01

119

Bifunctional Polymeric Inhibitors of Human Influenza A Viruses  

PubMed Central

Purpose New antiviral agents were prepared by attaching derivatives of sialic acid (1) and of the drug zanamivir (2) to poly(isobutylene-alt-maleic anhydride) (poly-(1+2)) or by mixing poly-1 and poly-2, followed by assaying them against wild-type and drug-resistant influenza A Wuhan viruses. Methods Individually or together, 1 and 2 were covalently bonded to the polymer. The antiviral potencies of the resultant poly-1, poly-2, poly-(1+2), and poly-1 + poly-2, as well as 1 and 2, were assessed using plaque reduction assay. Results Attaching 1 to the polymer improved at best millimolar IC50 values over three orders of magnitude. While 2 exhibited micromolar IC50 values, poly-2 was >100-fold even more potent. The IC50 of poly-(1+2) against the wild-type strain was >300-fold and ~17-fold better than of poly-1 and poly-2, respectively. In contrast, the potency of poly-(1+2) vs. poly-2 against the mutant strain merely doubled. The mixture of poly-1 + poly-2 inhibited both viral strains similarly to poly-2. Conclusions The bifunctional poly-(1+2) acts synergistically against the wild-type influenza virus, but not against its drug-resistant mutant, as compared to a physical mixture of the monofunctional poly-1 and poly-2.

Haldar, Jayanta; Alvarez de Cienfuegos, Luis; Tumpey, Terrence M.; Gubareva, Larisa V.; Chen, Jianzhu; Klibanov, Alexander M.

2010-01-01

120

Discovery of a bifunctional cardiolipin/phosphatidylethanolamine synthase in bacteria.  

PubMed

Phosphatidylethanolamine (PE) and cardiolipin (CL) are major components of bacterial and eukaryotic membranes. In bacteria, synthesis of PE usually occurs via decarboxylation of phosphatidylserine (PS) by PS decarboxylases (Psd). CL is produced by various CL synthases (Cls). Membranes of the plant pathogen Xanthomonas campestris predominantly contain PE, phosphatidylglycerol (PG) and CL. The X. campestris genome encodes one Psd and six putative CLs. Deletion of psd resulted in loss of PE and accumulation of PS. The mutant was severely affected in growth and cell size. PE synthesis, growth and cell division were partially restored when cells were supplied with ethanolamine (EA) suggesting a previously unknown PE synthase activity. Via mutagenesis, we identified a Cls enzyme (Xc_0186) responsible for EA-dependent PE biosynthesis. Xanthomonas lacking xc_0186 not only lost its ability to utilize EA for PE synthesis but also produced less CL suggesting a bifunctional enzyme. Recombinant Xc_0186 in E. coli and in cell-free extracts uses cytidine diphosphate diacylglycerol (CDP-DAG) and PG for CL synthesis. It is also able to use CDP-DAG and EA for PE synthesis. Owing to its dual function in CL and PE production, we consider Xc_0186 the founding member of a new class of enzymes called CL/PE synthase (CL/PEs). PMID:24707916

Moser, Roman; Aktas, Meriyem; Fritz, Christiane; Narberhaus, Franz

2014-06-01

121

Monodisperse Magneto-Fluorescent Bifunctional Nanoprobes for Bioapplications  

NASA Astrophysics Data System (ADS)

We present the work on the synthesis of dye-doped monodisperse Fe/SiO2 core/shell nanoparticles as bifunctional probes for bioapplications. Magnetic nanoparticles (NP) have been widely studied as nano-probes for bio-imaging, sensing as well as for cancer therapy. Among all the NPs, Fe NPs have been the focus because they have very high magnetization. However, Fe NPs are usually not stable in ambient due to the fast surface oxidation of the NPs. On the other hand, dye molecules have long been used as probes for bio-imaging. But they are sensitive to environmental conditions. It requires passivation for both so that they can be stable for applications. In this work, monodisperse Fe NPs with sizes ranging from 13-20 nm have been synthesized through the chemical thermal-decomposition in a solution. Silica shells were then coated on the Fe NPs by a two-phase oil-in-water method. Dye molecules were first bonded to a silica precursor and then encapsulated into the silica shell during the coating process. The silica shells protect both the Fe NPs and dye molecules, which makes them as robust probes. The dye doped Fe/SiO2 core/shell NPs remain both highly magnetic and highly fluorescent. The stable dye doped Fe/SiO2NPs have been used as a dual functional probe for both magnetic heating and local nanoscale temperature sending, and their performance will be reported.

Zhang, Hongwang; Huang, Heng; Pralle, Arnd; Zeng, Hao

2013-03-01

122

The Effect of Bearing Deformation in Slider-bearing Lubrication  

Microsoft Academic Search

The slider-bearing with the bearing elastic is analyzed for its load carrying characteristics. The deflection of the bearing under load acts to reduce the load capacity by an amount which can be significant as is illustrated by a numerical example. Contributed by the ASLE Technical Committee on Bearings and Bearing Lubrication and presented at the Annual Meeting of the American

F. Osterle; Edward Saibel

1958-01-01

123

Grizzly bears and forestry  

Microsoft Academic Search

Timber harvesting and oil and gas extraction create ecological change beyond just the footprint of the resource extraction. These activities also create a permanent network of roads that can have lasting effects on forest ecology. Grizzly bears (Ursus arctos) suffer higher mortality when in close proximity to roads, yet bears in the foothills of west-central Alberta, continue to use these

C. L. Roever; M. S. Boyce; G. B. Stenhouse

2008-01-01

124

Bearing Lubrication Apparatus.  

National Technical Information Service (NTIS)

The patent described apparatus for lubrication of anti-friction bearings which uses the oil bleeding characteristics of grease. The apparatus consists of a housing for attachment to a bearing and a grease reservoir wherein the grease is retained in a slop...

K. H. Warren

1970-01-01

125

Homogeneous and Label-Free Detection of MicroRNAs Using Bifunctional Strand Displacement Amplification-Mediated Hyperbranched Rolling Circle Amplification.  

PubMed

MicroRNAs (miRNAs) are an emerging class of biomarkers and therapeutic targets for various diseases including cancers. Here, we develop a homogeneous and label-free method for sensitive detection of let-7a miRNA based on bifunctional strand displacement amplification (SDA)-mediated hyperbranched rolling circle amplification (HRCA). The binding of target miRNA with the linear template initiates the bifunctional SDA reaction, generating two different kinds of triggers which can hybridize with the linear template to initiate new rounds of SDA reaction for the production of more and more triggers. In the meantime, the released two different kinds of triggers can function as the first and the second primers, respectively, to initiate the HRCA reaction whose products can be simply monitored by a standard fluorometer with SYBR Green I as the fluorescent indicator. The proposed method exhibits high sensitivity with a detection limit of as low as 1.8 × 10(-13) M and a large dynamic range of 5 orders of magnitude from 0.1 pM to 10 nM, and it can even discriminate the single-base difference among the miRNA family members. Moreover, this method can be used to analyze the total RNA samples from the human lung tissues and might be further applied for sensitive detection of various proteins, small molecules, and metal ions in combination with specific aptamers. PMID:24903889

Zhang, Li-Rong; Zhu, Guichi; Zhang, Chun-Yang

2014-07-01

126

Past Performance analysis of HPOTP bearings  

NASA Technical Reports Server (NTRS)

The past performance analysis conducted on three High Pressure Oxygen Turbopump (HPOTP) bearings from the Space Shuttle Main Engine is presented. Metallurgical analysis of failed bearing balls and races, and wear track and crack configuration analyses were carried out. In addition, one bearing was tested in laboratory at very high axial loads. The results showed that the cracks were surface initiated and propagated into subsurface locations at relatively small angles. Subsurface cracks were much more extensive than was appeared on the surface. The location of major cracks in the races corresponded to high radial loads rather than high axial loads. There was evidence to suggest that the inner races were heated to elevated temperatures. A failure scenario was developed based on the above findings. According to this scenario the HPOTP bearings are heated by a combination of high loads and high coefficient of friction (poor lubrication). Different methods of extending the HPOTP bearing life are also discussed. These include reduction of axial loads, improvements in bearing design, lubrication and cooling, and use of improved bearing materials.

Bhat, B. N.; Dolan, F. J.

1982-01-01

127

Antident Bearing-Ball Retainer  

NASA Technical Reports Server (NTRS)

Jig prevents indentation of bearing balls by hard contact with edges of inner bearing rings during assembly. Jig is retaining ring which includes fingers that separates balls and pushes them against outer bearing and out of contact with inner bearing rings. Eliminates need for ball-retaining tabs on bearing cage.

Thomas, Larry L., Jr.

1995-01-01

128

Adenosine-5?-phosphosulfate - a multifaceted modulator of bifunctional 3?-phospho-adenosine-5?-phosphosulfate synthases and related enzymes  

PubMed Central

All sulfation reactions rely on active sulfate in the form of 3?-phospho-adenosine-5?-phosphosulfate (PAPS). In fungi, bacteria, and plants, the enzymes responsible for PAPS synthesis, ATP sulfurylase and adenosine-5?-phosphosulfate (APS) kinase, reside on separate polypeptide chains. In metazoans, however, bifunctional PAPS synthases catalyze the consecutive steps of sulfate activation by converting sulfate to PAPS via the intermediate APS. This intricate molecule and the related nucleotides PAPS and 3?-phospho-adenosine-5?-phosphate modulate the function of various enzymes from sulfation pathways, and these effects are summarized in this review. On the ATP sulfurylase domain that initially produces APS from sulfate and ATP, APS acts as a potent product inhibitor, being competitive with both ATP and sulfate. For the APS kinase domain that phosphorylates APS to PAPS, APS is an uncompetitive substrate inhibitor that can bind both at the ATP/ADP-binding site and the PAPS/APS-binding site. For human PAPS synthase 1, the steady-state concentration of APS has been modelled to be 1.6 ?m, but this may increase up to 60 ?m under conditions of sulfate excess. It is noteworthy that the APS concentration for maximal APS kinase activity is 15 ?m. Finally, we recognized APS as a highly specific stabilizer of bifunctional PAPS synthases. APS most likely stabilizes the APS kinase part of these proteins by forming a dead-end enzyme–ADP–APS complex at APS concentrations between 0.5 and 5 ?m; at higher concentrations, APS may bind to the catalytic centers of ATP sulfurylase. Based on the assumption that cellular concentrations of APS fluctuate within this range, APS can therefore be regarded as a key modulator of PAPS synthase functions.

Mueller, Jonathan W; Shafqat, Naeem

2013-01-01

129

Zinc\\/air battery R and D research and development of bifunctional oxygen electrode: Tasks I and II, Final report  

Microsoft Academic Search

Studies were conducted of the bifunctional oxygen electrode. The development of a rechargeable metal-oxygen (air) cell has been hampered to a great extent by the lack of a stable and cost effective oxygen electrode capable of use during both charge and discharge. The first type of bifunctional electrode consists of two distinct catalytifc layers. The oxygen reduction catalyst layer containing

M. Klein; S. Viswanathan

1986-01-01

130

Zinc\\/air battery R and D research and development of bifunctional oxygen electrode: Tasks 1 and 2  

Microsoft Academic Search

The bifunctional oxygen electrode is examined. The development of a rechargeable metal-oxygen (air) cell is hampered to a great extent by the lack of a stable and cost effective oxygen electrode capable of use during both charge and discharge. The first type of bifunctional electrode consists of two distinct catalytic layers. The oxygen reduction catalyst layer containing a supported gold

M. Klein; S. Viswanathan

1986-01-01

131

Enantiopure bifunctional chelators for copper radiopharmaceuticals - Does chirality matter in radiotracer design?  

PubMed

It is well recognized that carbon chirality plays a critical role in the design of drug molecules. However, very little information is available regarding the effect of stereoisomerism of macrocyclic bifunctional chelators (BFC) on biological behaviors of the corresponding radiopharmaceuticals. To evaluate such effects, three enantiopure stereoisomers of a copper radiopharmaceutical BFC bearing two chiral carbon atoms were synthesized in forms of R,R-, S,S-, and R,S-. Their corresponding peptide conjugates were prepared by coupling with a model peptide sequence, c(RGDyK), which targets the ?v?3 integrin for in vitro and in vivo evaluation of their biological behaviors as compared to the racemic conjugate. Despite the chirality differences, all the conjugates showed a similar in vitro binding affinity profile to the ?v?3 integrin (106, 108, 85 and 100 nM for rac-H2-1, RR-H2-1, SS-H2-1, and RS-H2-1 respectively with all p values > 0.05) and a similar level of in vivo tumor uptake (2.72 ± 0.45, 2.60 ± 0.52, 2.45 ± 0.48 and 2.88 ± 0.59 for rac-(64)Cu-1, RR-(64)Cu-1, SS-(64)Cu-1, and RS-(64)Cu-1 at 1 h p.i. respectively). Furthermore, they demonstrated a nearly identical biodistribution pattern in major organs (e.g. 2.07 ± 0.21, 2.13 ± 0.58, 1.70 ± 0.20 and 1.90 ± 0.46 %ID/g at 24 h p.i. in liver for rac-(64)Cu-1, RR-(64)Cu-1, SS-(64)Cu-1, and RS-(64)Cu-1 respectively; 1.80 ± 0.46, 2.30 ± 1.49, 1.73 ± 0.31 and 2.23 ± 0.71 at 24 h p.i. in kidneys for rac-(64)Cu-1, RR-(64)Cu-1, SS-(64)Cu-1, and RS-(64)Cu-1 respectively). Therefore we conclude that the chirality of BFC plays a negligible role in ?v?3-targeted copper radiopharmaceuticals. However, we believe it is still worthwhile to consider the chirality effects of BFCs on other targeted imaging or therapeutic agents. PMID:24793881

Singh, Ajay N; Dakanali, Marianna; Hao, Guiyang; Ramezani, Saleh; Kumar, Amit; Sun, Xiankai

2014-06-10

132

Polymer-Supported Reagents: The Role of Bifunctionality in the Design of Ion-Selective Complexants  

SciTech Connect

The importance of multi-functionality in the preparation of ion-selective polymers is evident from the structure of enzymes where specific metal ions are bound through cooperative interactions among different amino acids. In synthetic polymers, ionic selectivity is enhanced when a chemical reaction is superimposed on an ion-exchange process. The concept of reactive ion exchange has been extended through the synthesis of crosslinked polymers whose metal ion selectivity is a function of reduction, coordination or precipitation reactions as determined by various covalently bound ligands. Development of three classes of dual mechanism bifunctional polymers, a new series of bifunctional diphosphonate polymers, and novel bifunctional ion-selective polymers with enhanced ionic accessibility has been accomplished.

Alexandratos, S. D.

2001-06-01

133

HTS magnetic bearings  

NASA Astrophysics Data System (ADS)

Radial HTS magnetic bearings (SMB) up to 200 mm size are developed and tested in prototype fast rotating machines to demonstrate the potential to replace conventional bearings. The individual rotational bearing components HTS and PM, their physical interaction and technology is reviewed. Characterisation experiments are conducted to understand the rotor dynamic behaviour. In terms of unbalance and critical speeds the suspended wheels and rotors compare favourably with conventional bearing devices. The rationale of our present bearing technology lies in the assembling of both low-speed magnetic bearings for centrifugal and wafer processing units up to 20,000 rpm as well as a high-speed optical mirror accelerated to rim speed of more than 500 m/s (174,000 rpm) confirming stable low-drag and low energy operation. Two new-type U shaped semicircle HTS bearings coupled each with a 6 W/80 K cryocooler of the Stirling type allow the contact-free operation of a Si wafer carrier in semiconductor wet processes.

Werfel, Frank N.; Flögel-Delor, Uta; Rothfeld, Rolf; Wippich, Dieter; Riedel, Thomas

2002-08-01

134

Measuring Bearing-Cage Rotation  

NASA Technical Reports Server (NTRS)

Bearing slip measured optically. Concept for measuring rotational speed of bearing cage promises to be simple and accurate. Based on fiber optics, requires no contact between measuring device and bearing, and would not introduce wear.

Roschak, E. J.

1987-01-01

135

Magnetically-controlled bearing lubrication  

NASA Technical Reports Server (NTRS)

Proposed magnetic-lubricant ball-bearing assembly has permanently-magnetized bearing retainer fabricated of porous material. Pores of retainer are filled with ferrolubricant. Surface tension causes retainer to deliver sufficient lubricant to nonmagnetic ball bearings.

Whitaker, A. F.

1977-01-01

136

Ball and Roller Bearings. A Teaching Reference.  

ERIC Educational Resources Information Center

The manual provides a subject reference for ball and roller bearings. The following topics are included: (1) bearing nomenclature, (2) bearing uses, (3) bearing capacities, (4) shop area working conditions, (5) bearing removal, (6) bearing cleaning and inspection, (7) bearing replacement, (8) bearing lubrication, (9) bearing installation, (10)…

American Association for Vocational Instructional Materials, Athens, GA.

137

Effects of Receptor Binding on Plasma Half-life of Bifunctional Transferrin Fusion Proteins  

PubMed Central

In contrast to the wide applications of recombinant bifunctional fusion proteins in clinical usage, the systematic study for the pharmacokinetics (PK) of bifunctional fusion proteins is left blank. In this report, recombinant fusion proteins consisting of transferrin (Tf) and growth hormone (GH) or granulocyte colony-stimulating factor (G-CSF) have been constructed as a model for studying the PK of bifunctional fusion proteins. The results showed that the insertion of different linkers between the two protein domains altered the binding affinities of the fusion proteins to both domain receptors, and that the fusion proteins’ plasma half-lives were greatly affected. A strong correlation between GH receptor binding affinity and plasma half-life of GH-Tf fusion proteins was observed. In addition, we demonstrated that the intracellular processing after receptor binding plays an important role in determining the half-life of fusion proteins. While the binding of the GH domain to the GH receptor will lead to endocytosis and lysosomal degradation in target cells, binding of the Tf domain to the Tf receptor may recycle the fusion protein and prolong its plasma half-life. To further confirm the effects of receptor binding on plasma half-life, G-CSF-Tf bifunctional fusion proteins with the same three linkers as GH-Tf were evaluated. While the 3 fusion proteins showed a similar G-CSF receptor binding affinity, the G-CSF-Tf fusion protein with the higher Tf receptor binding affinity exhibited longer plasma half-life. The linker insertion further demonstrated the involvement of Tf in recycling and prolonging plasma half-life. Based on our results, a model was developed to summarize the factors in determining the PK of the bifunctional fusion proteins. Our findings are useful for predicting the plasma half-lives, as well as for improving the pharmacokinetic profiles of therapeutic bifunctional fusion proteins by applying linker technology.

Chen, Xiaoying; Lee, Hsin-Fang; Zaro, Jennica L.; Shen, Wei-Chiang

2012-01-01

138

Ball Bearing Mechanics  

NASA Technical Reports Server (NTRS)

Load-deflection relationships for different types of elliptical contacts such as those found in a ball bearing are developed. Simplified expressions that allow quick calculations of deformation to be made simply from a knowledge of the applied load, the material properties, and the geometry of the contacting elements are presented. Ball bearings subjected to radial, thrust and combined ball loads are analyzed. A design criterion for fatigue life of ball bearings is developed. The section of a satisfactory lubricant, as well as describing systems that provide a constant flow of lubricant to the contact, is considered.

Hamrock, B. J.; Dowson, D.

1981-01-01

139

Intrinsic kinetics study of LPDME process from syngas over bi-functional catalyst  

Microsoft Academic Search

The intrinsic kinetics of the three-phase dimethyl ether (DME) synthesis from syngas over a bi-functional catalyst has been investigated in a agitated slurry reactor at 20–50bar, 200–240°C and H2\\/CO feed ratio from 1 to 2. The bi-functional catalyst was prepared by physical mixing of CuO\\/ZnO\\/Al2O3 as methanol synthesis catalyst and H-ZSM-5 as methanol dehydration catalyst. The three reactions including methanol

G. R. Moradi; J. Ahmadpour; F. Yaripour

2008-01-01

140

Characterization of the bisintercalative DNA binding mode of a bifunctional platinum-acridine agent.  

PubMed

The DNA interactions of PT-BIS(ACRAMTU) ([Pt(en)(ACRAMTU)2](NO3)4; ACRAMTU = 1-[2-(acridin-9-ylamino)ethyl]-1,3-dimethylthiourea, en = ethylenediamine), a bifunctional platinum-acridine conjugate, have been studied in native and synthetic double-stranded DNAs and model duplexes using various biophysical techniques. These include ethidium-DNA fluorescence quenching and thermal melting experiments, circular dichroism (CD) spectroscopy and plasmid unwinding assays. In addition, the binding mode was studied in a short octamer by NMR spectroscopy in conjunction with molecular modeling. In alternating copolymers, PT-BIS(ACRAMTU) shows a distinct preference for poly(dA-dT)2, which is approximately 3-fold higher than that of ACRAMTU. In the ligand-oligomer complex, d(GCTATAGC)2.PT-BIS(ACRAMTU) (complex I*), PT-BIS(ACRAMTU) increases the thermal stability of the B-form host duplex by DeltaT(m) > 30 K (CD and UV melting experiments). The agent unwinds pSP73 plasmid DNA by 44(+/-2) degrees per bound molecule, indicating bisintercalative binding. A 2-D NMR study unequivocally demonstrates that PT-BIS(ACRAMTU)'s chromophores deeply bisintercalate into the 5'-TA/TA base pair steps in I*, while the platinum linker lies in the minor groove. An AMBER model reflecting the NMR results shows that bracketing of the central AT base pairs in a classical nearest neighbor excluded fashion is feasible. PT-BIS(ACRAMTU) inhibits DNA hydrolysis by BstZ17 I at the enzyme's restriction site, GTA downward arrowTAC. Possible consequences for other relevant DNA-protein interactions, such as those involved in TATA-box-mediated transcription initiation and the utility of the platinum-intercalator technology for the design of sequence-specific agents are discussed. PMID:16192574

Choudhury, Jayati Roy; Bierbach, Ulrich

2005-01-01

141

PCs and Polar Bears  

NSDL National Science Digital Library

This article looks at the growing energy consumption from consumer electronics and the increases it may cause in greenhouse gases and global warming. The article appears in the free, online magazine Beyond Penguins and Polar Bears.

Fries-Gaither, Jessica

2011-01-01

142

Optimal Synchronizability of Bearings  

NASA Astrophysics Data System (ADS)

Bearings are mechanical dissipative systems that, when perturbed, relax toward a synchronized (bearing) state. Here we find that bearings can be perceived as physical realizations of complex networks of oscillators with asymmetrically weighted couplings. Accordingly, these networks can exhibit optimal synchronization properties through fine-tuning of the local interaction strength as a function of node degree [Motter, Zhou, and Kurths, Phys. Rev. E 71, 016116 (2005)PLEEE81539-3755]. We show that, in analogy, the synchronizability of bearings can be maximized by counterbalancing the number of contacts and the inertia of their constituting rotor disks through the mass-radius relation, m˜r?, with an optimal exponent ?=?× which converges to unity for a large number of rotors. Under this condition, and regardless of the presence of a long-tailed distribution of disk radii composing the mechanical system, the average participation per disk is maximized and the energy dissipation rate is homogeneously distributed among elementary rotors.

Araújo, N. A. M.; Seybold, H.; Baram, R. M.; Herrmann, H. J.; Andrade, J. S., Jr.

2013-02-01

143

Magnetic Bearing System.  

National Technical Information Service (NTIS)

A magnetic bearing system is described which includes a high magnetic permeability interior disc member that is symmetrical about a longitudinal z axis. An annular member of high magnetic permeability is coaxial with and surrounds the disc, but is mechani...

P. A. Studer

1975-01-01

144

Asymmetric synthesis of ?-alkyl ?-selenocarbonyl compounds catalyzed by bifunctional organocatalysts.  

PubMed

A new organocatalytic approach for the synthesis of a variety of ?-alkyl, ?-phenylselenyl ketones as well as their corresponding esters and amides, by the addition of ?-selenocarbonyl derivatives to nitroalkenes catalyzed by thiourea or squaramide cinchona catalysts, is presented. This catalytic system allows the preparation in high yields of enantiomerically enriched selenocarbonyl derivatives bearing two chiral centers with excellent ee's and dr's by using catalytic loadings of 3 mol%. PMID:21591622

Marcos, Vanesa; Alemán, Jose; Ruano, Jose L Garcia; Marini, Francesca; Tiecco, Marcello

2011-06-17

145

Chromatography-free Wittig reactions using a bifunctional polymeric reagent.  

PubMed

The first example of a polystyrene bearing two distinct reagent groups has been prepared. This phosphine and amine functionalized material was used in one-pot Wittig reactions with an aldehyde and either an ?-halo-ester, -ketone, or -amide. Due to the heterogeneous nature of the polymer, the desired alkene product of these reactions could be isolated in excellent yield in essentially pure form after only filtration and solvent removal. PMID:20936814

Leung, Peter Shu-Wai; Teng, Yan; Toy, Patrick H

2010-11-01

146

Gear bearing drive  

NASA Technical Reports Server (NTRS)

A gear bearing drive provides a compact mechanism that operates as an actuator providing torque and as a joint providing support. The drive includes a gear arrangement integrating an external rotor DC motor within a sun gear. Locking surfaces maintain the components of the drive in alignment and provide support for axial loads and moments. The gear bearing drive has a variety of applications, including as a joint in robotic arms and prosthetic limbs.

Weinberg, Brian (Inventor); Mavroidis, Constantinos (Inventor); Vranish, John M. (Inventor)

2011-01-01

147

Investigation of Pressurized Wave Bearings  

NASA Technical Reports Server (NTRS)

The wave bearing has been pioneered and developed by Dr. Dimofte over the past several years. This bearing will be the main focus of this research. It is believed that the wave bearing offers a number of advantages over the foil bearing, which is the bearing that NASA is currently pursuing for turbomachinery applications. The wave bearing is basically a journal bearing whose film thickness varies around the circumference approximately sinusoidally, with usually 3 or 4 waves. Being a rigid geometry bearing, it provides precise control of shaft centerlines. The wave profile also provides good load capacity and makes the bearing very stable. Manufacturing techniques have been devised that should allow the production of wave bearings almost as cheaply as conventional full-circular bearings.

Keith, Theo G., Jr.; Dimofte, Florin

2003-01-01

148

Load responsive hydrodynamic bearing  

DOEpatents

A load responsive hydrodynamic bearing is provided in the form of a thrust bearing or journal bearing for supporting, guiding and lubricating a relatively rotatable member to minimize wear thereof responsive to relative rotation under severe load. In the space between spaced relatively rotatable members and in the presence of a liquid or grease lubricant, one or more continuous ring shaped integral generally circular bearing bodies each define at least one dynamic surface and a plurality of support regions. Each of the support regions defines a static surface which is oriented in generally opposed relation with the dynamic surface for contact with one of the relatively rotatable members. A plurality of flexing regions are defined by the generally circular body of the bearing and are integral with and located between adjacent support regions. Each of the flexing regions has a first beam-like element being connected by an integral flexible hinge with one of the support regions and a second beam-like element having an integral flexible hinge connection with an adjacent support region. A least one local weakening geometry of the flexing region is located intermediate the first and second beam-like elements. In response to application of load from one of the relatively rotatable elements to the bearing, the beam-like elements and the local weakening geometry become flexed, causing the dynamic surface to deform and establish a hydrodynamic geometry for wedging lubricant into the dynamic interface.

Kalsi, Manmohan S. (Houston, TX); Somogyi, Dezso (Sugar Land, TX); Dietle, Lannie L. (Stafford, TX)

2002-01-01

149

Bifunctional Antibody: A Binary Radiopharmaceutical Delivery System for Imaging Colorectal Carcinoma  

Microsoft Academic Search

In clinical studies we have evaluated a unique monoclonal antibody- based drug delivery system, a bifunctional antibody designed to deliver imaging or therapeutic agents, such as radioisotopes, drugs, or biologies, to tumor cells, while minimizing the dose to normal tissue. The bifunc tional antibody, with one specificity to a tumor-associated antigen (car- cinoembryonic antigen) and another specificity to a hapten,

Dwight R. Stickney; Leslie D. Anderson; James B. Slater; Clarence N. Ahlem; Gerald A. Kirk; Sally A. Schweighardt; James M. Frincke

150

Bifunctional N-Heterocyclic Carbene-Catalyzed Highly Enantioselective Synthesis of Spirocyclic Oxindolo-?-lactams.  

PubMed

The N-heterocyclic carbene-catalyzed Staudinger reaction of ketenes with isatin-derived ketimines was investigated. The bifunctional NHCs with a free hydroxyl group were demonstrated as efficient catalysts for the reaction, giving the corresponding spirocyclic oxindolo-?-lactams in high yields with excellent diastereo- and enantioselectivities. PMID:24856000

Zhang, Han-Ming; Gao, Zhong-Hua; Ye, Song

2014-06-01

151

Improved Bone Morphogenetic Protein-2 Retention in an Injectable Collagen Matrix Using Bifunctional Peptides  

PubMed Central

To promote healing of many orthopedic injuries, tissue engineering approaches are being developed that combine growth factors such as Bone Morphogenetic Proteins (BMP) with biomaterial carriers. Although these technologies have shown great promise, they still face limitations. We describe a generalized approach to create target-specific modular peptides that bind growth factors to implantable biomaterials. These bifunctional peptide coatings provide a novel way to modulate biology on the surface of an implant. Using phage display techniques, we have identified peptides that bind with high affinity to BMP-2. The peptides that bind to BMP-2 fall into two different sequence clusters. The first cluster of peptide sequences contains the motif W-X-X-F-X-X-L (where X can be any amino acid) and the second cluster contains the motif F-P-L-K-G. We have synthesized bifunctional peptide linkers that contain BMP-2 and collagen-binding domains. Using a rat ectopic bone formation model, we have injected rhBMP-2 into a collagen matrix with or without a bifunctional BMP-2: collagen peptide (BC-1). The presence of BC-1 significantly increased osteogenic cellular activity, the area of bone formed, and bone maturity at the site of injection. Our results suggest that bifunctional peptides that can simultaneously bind to a growth factor and an implantable biomaterial can be used to control the delivery and release of growth factors at the site of implantation.

Hamilton, Paul T.; Jansen, Michelle S.; Ganesan, Sathya; Benson, R. Edward; Hyde-DeRuyscher, Robin; Beyer, Wayne F.; Gile, Joseph C.; Nair, Shrikumar A.; Hodges, Jonathan A.; Gr?n, Hanne

2013-01-01

152

Formation of ceramophilic chitin and biohybrid materials enabled by a genetically engineered bifunctional protein.  

PubMed

A bifunctional protein composed of a highly negatively charged oyster shell protein and a chitin-binding domain enabled the formation of biohybrid materials through non-covalent surface modification of chitin nanofibres. The results demonstrate that specific biomolecular interactions offer a route for the formation of biosynthetic materials. PMID:24871427

Malho, Jani-Markus; Heinonen, Hanna; Kontro, Inkeri; Mushi, Ngesa E; Serimaa, Ritva; Hentze, Hans-Peter; Linder, Markus B; Szilvay, Géza R

2014-06-12

153

Organocatalytic asymmetric decarboxylative cyanomethylation of isatins using l-proline derived bifunctional thiourea.  

PubMed

First asymmetric decarboxylative cyanomethylation of isatins is reported herewith using bifunctional thiourea derived from l-proline in good yields and enantioselectivities. This strategy enables the construction of various 3-cyanomethylene substituted 3-hydroxyoxindoles in enantioselective manner. Enantioselective synthesis of CPC-1 alkaloid has been accomplished in fewer steps. PMID:24824863

Pratap Reddy Gajulapalli, V; Vinayagam, Poopathy; Kesavan, Venkitasamy

2014-05-28

154

Kinetic resolution of chiral alcohols in bifunctional membrane exhibiting enzyme activity and enantioselective permeation  

Microsoft Academic Search

The paper deals with the kinetic resolution of chiral alcohols in a transesterification process performed in the reactor containing a bifunctional polymer membrane. The membrane was prepared using an asymmetric polyamide film. It exhibits enantioselective permeabilities caused by an embedded imprinted polymer as well as catalytic properties induced by the immobilised lipase. The transesterification of vinyl acetate with (±)-trans-2-phenyl-1-cyclohexanol, performed

Izabela Koter; Józef Ceynowa

2003-01-01

155

Fault tolerant magnetic bearings  

SciTech Connect

A fault tolerant magnetic bearing system was developed and demonstrated on a large flexible-rotor test rig. The bearing system comprises a high speed, fault tolerant digital controller, three high capacity radial magnetic bearings, one thrust bearing, conventional variable reluctance position sensors, and an array of commercial switching amplifiers. Controller fault tolerance is achieved through a very high speed voting mechanism which implements triple modular redundancy with a powered spare CPU, thereby permitting failure of up to three CPU modules without system failure. Amplifier/cabling/coil fault tolerance is achieved by using a separate power amplifier for each bearing coil and permitting amplifier reconfiguration by the controller upon detection of faults. This allows hot replacement of failed amplifiers without any system degradation and without providing any excess amplifier kVA capacity over the nominal system requirement. Implemented on a large (2440 mm in length) flexible rotor, the system shows excellent rejection of faults including the failure of three CPUs as well as failure of two adjacent amplifiers (or cabling) controlling an entire stator quadrant.

Maslen, E.H.; Sortore, C.K.; Gillies, G.T.; Williams, R.D.; Fedigan, S.J. [Univ. of Virginia, Charlottesville, VA (United States); Aimone, R.J. [Mobile Technology Co., Paulsboro, NJ (United States)

1999-07-01

156

Encapsulated ball bearings for rotary micro machines  

NASA Astrophysics Data System (ADS)

We report on the first encapsulated rotary ball bearing mechanism using silicon microfabrication and stainless steel balls. The method of capturing stainless steel balls within a silicon race to support a silicon rotor both axially and radially is developed for rotary micro machines and MEMS ball bearing tribology studies. Initial demonstrations show speeds up to 6.8 krpm without lubrication, while speeds up to 15.6 krpm with lubrication are possible. Qualitative analysis is used to explain start-up behavior and investigate the wear of the stainless steel ball and silicon race.

Waits, C. Mike; Geil, Bruce; Ghodssi, Reza

2007-09-01

157

Partial tooth gear bearings  

NASA Technical Reports Server (NTRS)

A partial gear bearing including an upper half, comprising peak partial teeth, and a lower, or bottom, half, comprising valley partial teeth. The upper half also has an integrated roller section between each of the peak partial teeth with a radius equal to the gear pitch radius of the radially outwardly extending peak partial teeth. Conversely, the lower half has an integrated roller section between each of the valley half teeth with a radius also equal to the gear pitch radius of the peak partial teeth. The valley partial teeth extend radially inwardly from its roller section. The peak and valley partial teeth are exactly out of phase with each other, as are the roller sections of the upper and lower halves. Essentially, the end roller bearing of the typical gear bearing has been integrated into the normal gear tooth pattern.

Vranish, John M. (Inventor)

2010-01-01

158

Radial Halbach Magnetic Bearings  

NASA Technical Reports Server (NTRS)

Radial Halbach magnetic bearings have been investigated as part of an effort to develop increasingly reliable noncontact bearings for future high-speed rotary machines that may be used in such applications as aircraft, industrial, and land-vehicle power systems and in some medical and scientific instrumentation systems. Radial Halbach magnetic bearings are based on the same principle as that of axial Halbach magnetic bearings, differing in geometry as the names of these two types of bearings suggest. Both radial and axial Halbach magnetic bearings are passive in the sense that unlike most other magnetic bearings that have been developed in recent years, they effect stable magnetic levitation without need for complex active control. Axial Halbach magnetic bearings were described in Axial Halbach Magnetic Bearings (LEW-18066-1), NASA Tech Briefs, Vol. 32, No. 7 (July 2008), page 85. In the remainder of this article, the description of the principle of operation from the cited prior article is recapitulated and updated to incorporate the present radial geometry. In simplest terms, the basic principle of levitation in an axial or radial Halbach magnetic bearing is that of the repulsive electromagnetic force between (1) a moving permanent magnet and (2) an electric current induced in a stationary electrical conductor by the motion of the magnetic field. An axial or radial Halbach bearing includes multiple permanent magnets arranged in a Halbach array ("Halbach array" is defined below) in a rotor and multiple conductors in the form of wire coils in a stator, all arranged so the rotary motion produces an axial or radial repulsion that is sufficient to levitate the rotor. A basic Halbach array (see Figure 1) consists of a row of permanent magnets, each oriented so that its magnetic field is at a right angle to that of the adjacent magnet, and the right-angle turns are sequenced so as to maximize the magnitude of the magnetic flux density on one side of the row while minimizing it on the opposite side. The advantage of this configuration is that it makes it possible to approach the theoretical maximum force per unit area that could be exerted by a given amount of permanent-magnet material. The configuration is named after physicist Klaus Halbach, who conceived it for use in particle accelerators. Halbach arrays have also been studied for use in magnetic-levitation ("maglev") railroad trains. In a radial Halbach magnetic bearing, the basic Halbach arrangement is modified into a symmetrical arrangement of sector-shaped permanent magnets mounted on the outer cylindrical surface of a drum rotor (see Figure 2). The magnets are oriented to concentrate the magnetic field on their radially outermost surface. The stator coils are mounted in a stator shell surrounding the rotor.

Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

2009-01-01

159

Blood Pump Bearing System  

NASA Technical Reports Server (NTRS)

An apparatus is provided for a blood pump bearing system within a pump housing to support long-term highspeed rotation of a rotor with an impeller blade having a plurality of individual magnets disposed thereon to provide a small radial air gap between the magnets and a stator of less than 0.025 inches. The bearing system may be mounted within a flow straightener, diffuser, or other pump element to support the shaft of a pump rotor. The bearing system includes a zirconia shaft having a radiused end. The radiused end has a first radius selected to be about three times greater than the radius of the zirconia shaft. The radiused end of the zirconia shaft engages a flat sapphire endstone. Due to the relative hardness of these materials a flat is quickly produced during break-in on the zirconia radiused end of precisely the size necessary to support thrust loads whereupon wear substantially ceases. Due to the selection of the first radius, the change in shaft end-play during pump break-in is limited to a total desired end-play of less than about 0.010 inches. Radial loads are supported by an olive hole ring jewel that makes near line contact around the circumference of the Ir shaft to support big speed rotation with little friction. The width of olive hole ring jewel is small to allow heat to conduct through to thereby prevent heat build-up in the bearing. A void defined by the bearing elements may fill with blood that then coagulates within the void. The coagulated blood is then conformed to the shape of the bearing surfaces.

Aber, Gregory S. (Inventor)

2000-01-01

160

Blood Pump Bearing System  

NASA Technical Reports Server (NTRS)

Methods and apparatus are provided for a blood pump bearing system within a pump housing to support long-term high-speed rotation of a rotor with an impeller blade having a plurality of individual magnets disposed thereon to provide a small radial air gap between the magnets and a stator of less than 0.025 inches. The bearing system may be mounted within a flow straightener, diffuser, or other pump element to support the shaft of a pump rotor. The bearing system includes a zirconia shaft having a radiused end. The radiused end has a first radius selected to be about three times greater than the radius of the zirconia shaft. The radiused end of the zirconia shaft engages a flat sapphire endstone. Due to the relative hardness of these materials a flat is quickly produced during break-in on the zirconia radiused end of precisely the size necessary to support thrust loads whereupon wear substantially ceases. Due to the selection of the first radius, the change in shaft end-play during pump break-in is limited to a total desired end-play of less than about 0.010 inches. Radial loads are supported by an olive hole ring jewel that makes near line contact around the circumference of the shaft to support high speed rotation with little friction. The width of olive hole ring jewel is small to allow heat to conduct through to thereby prevent heat build-up in the bearing. A void defined by the bearing elements may fill with blood that then coagulates within the void. The coagulated blood is then conformed to the shape of the bearing surfaces.

Aber, Gregory S. (Inventor)

1999-01-01

161

Modular gear bearings  

NASA Technical Reports Server (NTRS)

A gearing system using modular gear bearing components. Each component is composed of a core, one or more modules attached to the core and two or more fastening modules rigidly attaching the modules to the core. The modules, which are attached to the core, may consist of gears, rollers or gear bearing components. The core orientation affects the orientation of the modules attached to the core. This is achieved via the keying arrangement of the core and the component modules that attach to the core. Such an arrangement will also facilitate the phase tuning of gear modules with respect to the core and other gear modules attached to the core.

Vranish, John M. (Inventor)

2009-01-01

162

Amos Bear Gets Hurt.  

ERIC Educational Resources Information Center

A three-day experiment set up by an early childhood teacher explored Piaget's view that children younger than age eight lack ability to take another's point of view. The experiment focused on a bear, the class mascot, and observations of children's empathetic behavior toward its "injury." Age-related differences in the children's responses were…

Read, Laurie

1995-01-01

163

The Teddy Bears' Disc.  

ERIC Educational Resources Information Center

Reports an evaluation of the Teddy Bear disc, an interactive videodisc developed at the Open University for a second-level course in metallurgy and materials technology. Findings from observation of students utilizing the videodisc are reviewed; successful design features and design problems are considered; and development costs are outlined. (MBR)

Laurillard, Diana

1985-01-01

164

History of ball bearings  

NASA Technical Reports Server (NTRS)

The familiar precision rolling-element bearings of the twentieth century are products of exacting technology and sophisticated science. Their very effectiveness and basic simplicity of form may discourage further interest in their history and development. Yet the full story covers a large portion of recorded history and surprising evidence of an early recognition of the advantages of rolling motion over sliding action and progress toward the development of rolling-element bearings. The development of rolling-element bearings is followed from the earliest civilizations to the end of the eighteenth century. The influence of general technological developments, particularly those concerned with the movement of large building blocks, road transportation, instruments, water-raising equipment, and windmills are discussed, together with the emergence of studies of the nature of rolling friction and the impact of economic factors. By 1800 the essential features of ball and rolling-element bearings had emerged and it only remained for precision manufacture and mass production to confirm the value of these fascinating machine elements.

Dowson, D.; Hamrock, B. J.

1981-01-01

165

Tardigrada (Water Bears)  

NSDL National Science Digital Library

This reference page offers a brief description of Tardigrades, also known as water bears. It includes information about their physical appearance, an explanation of their name, likely habitats, internal organs and other distinguishing features, and a few images. A diagram of a common tardigrade, Macrobiotus macronyx, is also provided via an internal link.

Micrographia

166

Magnetic Bearings For Turbopumps  

NASA Technical Reports Server (NTRS)

Report presents study of feasibility of magnetic bearings in turbopumps. Liquid-oxygen turbopump in space shuttle main engine selected for study. Other potential applications include manned and unmanned spacecraft, gas turbines for commercial and military aircraft, turbomachinery for petro-chemical and gas operations, suspension systems for precise machinery, and precise pointing and tracking systems.

Meeks, Crawford R.; Mendez, Antonio J.

1995-01-01

167

Beam Experiments Aboard a Rocket (BEAR) Project  

SciTech Connect

The US Department of Defense's Strategic Defense Initiative Organization is sponsoring the development of neutral particle beam (NPB) technology for strategic defense applications. The first step in demonstrating the functioning of an NPB in space was the development and launch of the Beam Experiments Aboard a Rocket (BEAR) in New Mexico in July 1989. A government, laboratory, and industrial team, under the technical coordination of Los Alamos National Laboratory, designed, developed, and tested the BEAR payload. The primary objective of BEAR was the operation of an NPB accelerator in space. The payload was also designed to study (1) the effects on the space vehicle of emitting an NPB and associated charged beams into the space environment; (2) the propagation and attenuation characteristics of an NPB in space; (3) the dynamics of the charged particle components of the beam in the geomagnetic field; (4) the effects of neutral effluents from the vehicle; and (5) any anomalous or unanticipated phenomena associated with operating an NPB in the space environment. The BEAR experiment successfully demonstrated operation of an NPB accelerator and propagation of the neutral beam as predicted in space, obtained first-of-a-kind NPB physics data, and demonstrated the ability of the BEAR accelerator to survive recovery and to continue operating normally. No unanticipated phenomena were encountered that would significantly delay further development of NPB technology for defensive, space-based weapon systems.

Nunz, G.J.

1990-01-01

168

Synthesis of hetero-polymer functionalized nanocarriers by combining surface-initiated ATRP and RAFT polymerization.  

PubMed

Smart nanocarriers are created based on a bi-functional hetero-initiator for RAFT and ATRP technique, bi-functionalizing mesoporous silica nanoparticles with two polymer types. The pH-dependent behavior of PDEAEMA as the gatekeeper polymer is verified by electrokinetic measurements and a controlled release behavior is demonstrated using doxorubicin as the drug. PMID:22911545

Huang, Xin; Hauptmann, Nicole; Appelhans, Dietmar; Formanek, Petr; Frank, Simon; Kaskel, Stefan; Temme, Achim; Voit, Brigitte

2012-12-01

169

Flexure Bearing Reduces Startup Friction  

NASA Technical Reports Server (NTRS)

Design concept for ball bearing incorporates small pieces of shim stock, wire spokes like those in bicycle wheels, or other flexing elements to reduce both stiction and friction slope. In flexure bearing, flexing elements placed between outer race of ball bearing and outer ring. Elements flex when ball bearings encounter small frictional-torque "bumps" or even larger ones when bearing balls encounter buildups of grease on inner or outer race. Flexure of elements reduce high friction slopes of "bumps", helping to keep torque between outer ring and inner race low and more nearly constant. Concept intended for bearings in gimbals on laser and/or antenna mirrors.

Clingman, W. Dean

1991-01-01

170

Lubricant effects on bearing life  

NASA Technical Reports Server (NTRS)

Lubricant considerations for rolling-element bearings have within the last two decades taken on added importance in the design and operation of mechanical systems. The phenomenon which limits the useful life of bearings is rolling-element or surface pitting fatigue. The elastohydrodynamic (EHD) film thickness which separates the ball or roller surface from those of the raceways of the bearing directly affects bearing life. Chemical additives added to the lubricant can also significantly affect bearings life and reliability. The interaction of these physical and chemical effects is important to the design engineer and user of these systems. Design methods and lubricant selection for rolling-element bearings are presented and discussed.

Zaretsky, Erwin V.

1986-01-01

171

49 CFR 40.385 - Who bears the burden of proof in a PIE proceeding?  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Who bears the burden of proof in a PIE proceeding...Interest Exclusions § 40.385 Who bears the burden of proof in a PIE proceeding...issuing a PIE, the initiating official bears the burden of proof. (b) This...

2010-10-01

172

49 CFR 40.385 - Who bears the burden of proof in a PIE proceeding?  

Code of Federal Regulations, 2010 CFR

...2009-10-01 2009-10-01 false Who bears the burden of proof in a PIE proceeding...Interest Exclusions § 40.385 Who bears the burden of proof in a PIE proceeding...issuing a PIE, the initiating official bears the burden of proof. (b) This...

2009-10-01

173

On the mechanism of bifunctional squaramide-catalyzed organocatalytic Michael addition: a protonated catalyst as an oxyanion hole.  

PubMed

A joint experimental-theoretical study of a bifunctional squaramide-amine-catalyzed Michael addition reaction between 1,3-dioxo nucleophiles and nitrostyrene has been undertaken to gain insight into the nature of bifunctional organocatalytic activation. For this highly stereoselective reaction, three previously proposed mechanistic scenarios for the critical C?C bond-formation step were examined. Accordingly, the formation of the major stereoisomeric products is most plausible by one of the bifunctional pathways that involve electrophile activation by the protonated amine group of the catalyst. However, some of the minor product isomers are also accessible through alternative reaction routes. Structural analysis of transition states points to the structural invariance of certain fragments of the transition state, such as the protonated catalyst and the anionic fragment of approaching reactants. Our topological analysis provides deeper insight and a more general understanding of bifunctional noncovalent organocatalysis. PMID:24677388

Kótai, Bianka; Kardos, György; Hamza, Andrea; Farkas, Viktor; Pápai, Imre; Soós, Tibor

2014-05-01

174

Bifunctional fluorescent carbon nanodots: green synthesis via soy milk and application as metal-free electrocatalysts for oxygen reduction.  

PubMed

We demonstrated a facile and green approach to synthesize bifunctional fluorescent carbon nanodots via soy milk, which not only showed favorable photoluminescent properties, but also exhibited good electrocatalytic activity towards oxygen reduction reaction. PMID:22911246

Zhu, Chengzhou; Zhai, Junfeng; Dong, Shaojun

2012-09-28

175

Bearing Line Tracking and Bearing-Only Target Motion Analysis  

Microsoft Academic Search

The framework of this paper is a passive sonar system, more precisely at the core of bearing estimation and bearings-only target motion analysis (BO-TMA). A cosine of relative bearing estimation and bearings v.s. time image is first obtained by a conventional frequency-domain beam-former [D.H Johnson et al, 1993]. Computing the first two moments of each line of this image, we

Fabien BONNETON; Claude JAUFFRET

2007-01-01

176

Development of novel bifunctional anion-exchange resins with improved selectivity for pertechnetate sorption from contaminated groundwater  

Microsoft Academic Search

The present study evaluated a new class of bifunctional anion-exchange resins with improved selectivity and sorption kinetics for removing pertechnetate (TcOâ⁻) from contaminated groundwater. Both laboratory-column and field flow-through experiments were performed, and results indicated that superior performance of the bifunctional resins has been achieved through the use of two quaternary ammonium groups, one having long chains (trihexylamine) for higher

Baohua Gu; Gilbert M. Brown; Peter V. Bonnesen; Liyuan Liang; Bruce A. Moyer; Robert Ober; Spiro D. Alexandratos

2000-01-01

177

Impact of bifunctional chelators on biological properties of 111In-labeled cyclic peptide RGD dimers.  

PubMed

The present study describes the synthesis and biological evaluation of (111)In(DOTA-3P-RGD(2)) (DOTA = 1,4,7,10-tetraazacyclo-dodecane-1,4,7,10-tetraacetic acid; 3P-RGD(2) = PEG(4)-E[PEG(4)-c(RGDfK)](2); PEG(4) = 15-amino-4,7,10,13-tetraoxapentadecanoic acid), (111)In(DTPA-3P-RGD(2)) (DTPA = diethylenetriaminepentaacetic acid) and (111)In(DTPA-Bn-3P-RGD(2)) (DTPA-Bn = 2-(p-thioureidobenzyl)-diethylenetriaminepentaacetic acid) as potential radiotracers for imaging tumor integrin ?(v)?(3) expression in athymic nude mice bearing U87MG glioma xenografts. The aim of the study is to assess the impact of the bifunctional chelator (BFC) (DOTA vs. DTPA or DTPA-Bn) on the biodistribution characteristics of the (111)In-labeled 3P-RGD(2). IC(50) values of DOTA-3P-RGD(2), DTPA-3P-RGD(2) and DTPA-Bn-3P-RGD(2) were determined to be 1.3 ± 0.2, 1.4 ± 0.3, 1.3 ± 0.3 nM, respectively, against (125)I-c(RGDyK) bound to U87MG human glioma cells. Radiotracers were prepared by reacting (111)InCl(3) with the RGD peptide conjugates in NH(4)OAc buffer (100 mM, pH 5.5). For DOTA-3P-RGD(2), successful radiolabeling could be completed by heating the reaction mixture at 100°C for 15-20 min. For DTPA-3P-RGD(2) and DTPA-Bn-3P-RGD(2), the radiolabeling was almost instantaneous at room temperature. The specific activity was ~50 mCi/mg (or ~100 mCi/?mol) for (111)In(DOTA-3P-RGD(2)) and ~200 mCi/mg (or ~400 mCi/?mol) for (111)In(DTPA-3P-RGD(2)). The results from biodistribution studies showed that all the three radiotracers have high tumor uptake and excellent tumor-to-background (T/B) ratios up to 4-h postinjection. After that time point, both (111)In(DTPA-3P-RGD(2)) and (111)In(DTPA-Bn-3P-RGD(2)) showed a much faster tumor washout and poorer T/B ratios than (111)In(DOTA-3P-RGD(2)). The tumor uptake of (111)In(DOTA-3P-RGD(2)) is integrin ?(v)?(3)- and RGD-specific. (111)In(DOTA-3P-RGD(2)) is metabolically stable while only ~25% of (111)In(DTPA-Bn-3P-RGD(2)) remains intact in the feces during 2-h period. On the basis of results from this study, it was concluded that (111)In(DTPA-3P-RGD(2)) can be an effective integrin ?(v)?(3)-targeted radiotracer if the high-specific activity is required. However, DOTA remains to be the BFC of choice for the development of therapeutic lanthanide radiotracers. PMID:20052508

Shi, Jiyun; Kim, Young-Seung; Chakraborty, Sudipta; Zhou, Yang; Wang, Fan; Liu, Shuang

2011-11-01

178

Interference-Fit Life Factors for Roller Bearings  

NASA Technical Reports Server (NTRS)

The effect of hoop stresses in reducing cylindrical roller bearing fatigue life was determined for various classes of inner-ring interference fit. Calculations were performed for up to 7 fit classes for each of 10 bearing sizes. The hoop stresses were superimposed on the Hertzian principal stresses created by the applied radial load to calculate roller bearing fatigue life. A method was developed through a series of equations to calculate the life reduction for cylindrical roller bearings. All calculated lives are for zero initial internal clearance. Any reduction in bearing clearance due to interference fit would be compensated by increasing the initial (unmounted) clearance. Results are presented as tables and charts of life factors for bearings with light, moderate, and heavy loads and interference fits ranging from extremely light to extremely heavy for bearing accuracy class RBEC-5 (ISO class 5). Interference fits on the inner ring of a cylindrical roller bearing can significantly reduce bearing fatigue life. In general, life factors are smaller (lower life) for bearings running under light load where the unfactored life is highest. The various bearing series within a particular bore size had almost identical interference-fit life factors for a particular fit. The tightest fit at the high end of the tolerance band produces a life factor of approximately 0.40 for an inner-race maximum Hertz stress of 1200 MPa (175 ksi) and a life factor of 0.60 for an inner-race maximum Hertz stress of 2200 MPa (320 ksi). Interference fits also impact the maximum Hertz stress-life relation.

Oswald, Fred B.; Zaretsky, Erwin V.; Poplawski, Joseph V.

2009-01-01

179

Vygotsky and the Three Bears  

ERIC Educational Resources Information Center

Peggy Kulczewski, a kindergarten classroom teacher, remembers the day when students enjoyed a story she told them from the book "The Three Bears". The students' discussion about comparison of the bears was very helpful to the whole group.

Kulczewski, Peggy

2004-01-01

180

Nonlinear Control of Magnetic Bearings.  

National Technical Information Service (NTIS)

In this paper we present a variety of nonlinear controllers for the magnetic bearing that ensure both stability and robustness. We utilize techniques of discontinuous control to design novel control laws for the magnetic bearing. We present in particular ...

A. K. Pradeep R. Gurumoorthy

1994-01-01

181

Self-Lubricating Bearing Materials.  

National Technical Information Service (NTIS)

A survey is given of progress in the development of self-lubricating materials for load-carrying components (bearings and gears) or for transfer lubrication (rolling element bearing retainers). Various methods for producing composites of inorganic solid l...

J. K. Lancaster

1965-01-01

182

Aerospace Applications of Magnetic Bearings.  

National Technical Information Service (NTIS)

Magnetic bearings have traditionally been considered for use in aerospace applications only where performance advantages have been the primary, if not only, consideration. Conventional wisdom has been that magnetic bearings have certain performance advant...

J. Downer J. Goldie V. Gondhalekar R. Hockney

1994-01-01

183

Magnetic bearings grow more attractive  

SciTech Connect

Advances in materials and electronics have enabled designers to devise simpler, smaller magnetic bearings. As a result, costs have dropped, widening the applications for these very-low-friction devices. Avcon (Advanced Controls Technology) has patented a permanent-magnet bias actively controlled bearing. Here high-energy rare earth permanent-magnet materials supply the basic bearing load levitation, while servo-driven electromagnets generate stabilization and centering forces for motion contol. Previous heavy-duty magnetic bearings used electromagnets entirely for suspension and control, which led to large bearings and control systems with higher power requirements. Avcon has developed several types of permanent-magnet bias bearings. The simplest is the radial repulsion bearing. Avcon's homopolar permanent-magnet bias active bearing is the most versatile of the company's designs.

Not Available

1993-10-01

184

Leakage-free journal bearings  

NASA Technical Reports Server (NTRS)

A new concept of a journal bearing is developed which prevents side leakage of the lubricant, thus eliminating the need for sealing and collecting this leakage. The cooling of the bearing is accomplished by the prevailing circumferential flow. An analysis is performed and solutions are given for the bearing geometries and inlet pressures required to achieve the above purpose.

Pinkus, O.; Etsion, I.

1976-01-01

185

Magnetic bearings for cryogenic turbomachines  

Microsoft Academic Search

Magnetic bearings offer a number of advantages over gas bearings for the support of rotors in cryogenic turboexpanders and compressors. Their performance is relatively independent of the temperature or pressure of the process gas for a large range of conditions. Active magnetic bearing systems that use capacitive sensors have been developed for high speed compressors for use in cryogenic refrigerators.

Victor Iannello; Herbert Sixsmith

1991-01-01

186

Radiometals (non-Tc, non-Re) and Bifunctional Labeling Chemistry  

NASA Astrophysics Data System (ADS)

Radiometals are of increased current interest because of the growing use of targeted radiotherapy for tumors and the development of generators that produce positron-emitting radiometals. In addition, biomedical cyclotrons allow the cheap production of some relevant radiometals. The design of the corresponding radiopharmaceuticals includes the synthesis of bifunctional chelators, which carry a functional unit for the immobilization of the radiometal and a functional group for the covalent attachment to a vector molecule. Radiometals of interest for therapeutic applications are some lanthanides, 67Cu, and 90Y. For diagnostic applications 61Cu, 62Cu, 64Cu, 89Zr, and 68Ga are currently used and corresponding radiopharmaceuticals are being designed. In this chapter, some properties and the synthesis of bifunctional chelators including metal ion selectivity and special aspects of coupling chemistry are being described.

Fani, M.; Good, S.; Maecke, H. R.

187

Sorption of Pu(IV) from nitric acid by bifunctional anion-exchange resins  

SciTech Connect

Anion exchange is attractive for separating plutonium because the Pu(IV) nitrate complex is very strongly sorbed and few other metal ions form competing anionic nitrate complexes. The major disadvantage of this process has been the unusually slow rate at which the Pu(IV) nitrate complex is sorbed by the resin. The paper summarizes the concept of bifunctional anion-exchange resins, proposed mechanism for Pu(IV) sorption, synthesis of the alkylating agent, calculation of K{sub d} values from Pu(IV) sorption results, and conclusions from the study of Pu(IV) sorption from 7M nitric acid by macroporous anion-exchange resins including level of crosslinking, level of alkylation, length of spacer, and bifunctional vs. monofunctional anion-exchange resins.

Bartsch, R.A.; Zhang, Z.Y.; Elshani, S.; Zhao, W. [Texas Tech Univ., Lubbock, TX (United States). Dept. of Chemistry and Biochemistry; Jarvinen, G.D.; Barr, M.E.; Marsh, S.F.; Chamberlin, R.M. [Los Alamos National Lab., NM (United States). Nuclear Materials Technology Div.

1999-06-01

188

Sinorhizobium meliloti flavin secretion and bacteria-host interaction: role of the bifunctional RibBA protein.  

PubMed

Sinorhizobium meliloti, the nitrogen-fixing bacterial symbiont of Medicago spp. and other legumes, secretes a considerable amount of riboflavin. This precursor of the cofactors flavin mononucleotide and flavin adenine dinucleotide is a bioactive molecule that has a beneficial effect on plant growth. The ribBA gene of S. meliloti codes for a putative bifunctional enzyme with dihydroxybutanone phosphate synthase and guanosine triphosphate (GTP) cyclohydrolase II activities, catalyzing the initial steps of the riboflavin biosynthesis pathway. We show here that an in-frame deletion of ribBA does not cause riboflavin auxotrophy or affect the ability of S. meliloti to establish an effective symbiosis with the host plant but does affect the ability of the bacteria to secrete flavins, colonize host-plant roots, and compete for nodulation. A strain missing the RibBA protein retains considerable GTP cyclohydrolase II activity. Based on these results, we hypothesize that S. meliloti has two partly interchangeable modules for biosynthesis of riboflavin, one fulfilling the internal need for flavins in bacterial metabolism and the other producing riboflavin for secretion. Our data also indicate that bacteria-derived flavins play a role in communication between rhizobia and the legume host and that the RibBA protein is important in this communication process even though it is not essential for riboflavin biosynthesis and symbiosis. PMID:24405035

Yurgel, Svetlana N; Rice, Jennifer; Domreis, Elizabeth; Lynch, Joseph; Sa, Na; Qamar, Zeeshan; Rajamani, Sathish; Gao, Mengsheng; Roje, Sanja; Bauer, Wolfgang D

2014-05-01

189

Night of the Bear  

NSDL National Science Digital Library

The NOAA Ocean Exploration program strives to engage broad audiences to enhance America's environmental literacy through the excitement of ocean discovery. Increasing this literacy requires high-quality, effective collaborations between ocean explorers and America's teachers. NOAA is forming such collaborations to reach out in new ways to the public to improve the literacy of learners with respect to ocean issues. This site is a daily log of exploration in the Arctic and research on the Polar Bear.

Debenham, Casey; Timmermans, Mary-Louise

2002-08-25

190

Big Bear Solar Observatory  

NASA Astrophysics Data System (ADS)

Big Bear Solar Observatory (BBSO) is located at the end of a causeway in a mountain lake more than 2 km above sea level. The site has more than 300 sunny days a year and a natural inversion caused by the lake which makes for very clean images. BBSO is the only university observatory in the US making high-resolution observations of the Sun. Its daily images are posted at http://www.bbso.njit.e...

Murdin, P.

2000-11-01

191

Bitumen-bearing rocks  

Microsoft Academic Search

Bitumen-bearing rocks occur in many areas of the U.S., but few of the deposits have been evaluated for their energy potential or exploited. Those deposits which have been evaluated are a relatively small part of North American resources of tar sands and probably will not contribute to U.S. energy needs before 1985. Studies of known but unappraised deposits, especially extensive

Cashion

1973-01-01

192

Turbogear bearing analysis  

Microsoft Academic Search

To optimize process energy efficiency, many plants are considering variable-speed electric motor drives with speed-increasing gears for centrifugal compressors. Variable-speed systems are much more complex than fixed-speed systems, especially when power and speed change independently across the compressor performance map, for example, from start-of-run to end-of-run. There are more mechanical design issues that impact reliable operation. Bearing analysis of turbogears

Cassolato

1997-01-01

193

Experimental Chemotherapy of Human Medulloblastoma Cell Lines and Transplantable Xenografts with Bifunctional Alkylating Agents1  

Microsoft Academic Search

A seríes of bifunctional al kviators were tested against the genotypically and phenotypically heterogeneous continuous human medulloblastoma cell lines, TE-671, Daoy, and D283 Med in vitro and against TE-671 and Daoy growing as s.c. and intracranial xenografts in athymic mice. Drugs tested included melphalan, cyclophosphamide, iphosphamide, phenylketocyclophosphamide, thiotepa, l,3-bis(2-chloroethyl)-l-nitro- sourea (in vivo),and busulfan (in vivo).Melphalan and phenylketocyclo phosphamide were the

Henry S. Friedman; O. Michael Colvin; Susan M. Ludeman; Gertrude B. Elion; S. CliffordSchold; Phillip F. Jacobsen; Darell D. Bigner

194

Bifunctional air electrodes for metal-air batteries. Final report, September 15, 1993December 14, 1994  

Microsoft Academic Search

The program was directed to the need for development of bifunctional air electrodes for Zn-Air batteries for the consumer market. The Zn-Air system, widely used as a primary cell for hearing-aid batteries and as a remote-site power source in industrial applications, has the advantage of high energy density, since it consumes oxygen from the ambient air utilizing a thin, efficient

L. L. Swette; M. Manoukian; A. B. LaConti

1995-01-01

195

Purification, characterization, and identification of a novel bifunctional catalase-phenol oxidase from Scytalidium thermophilum  

Microsoft Academic Search

A novel bifunctional catalase with an additional phenol oxidase activity was isolated from a thermophilic fungus, Scytalidium thermophilum. This extracellular enzyme was purified ca. 10-fold with 46% yield and was biochemically characterized. The enzyme contains\\u000a heme and has a molecular weight of 320 kDa with four 80 kDa subunits and an isoelectric point of 5.0. Catalase and phenol\\u000a oxidase activities were most

Didem Sutay Kocabas; Ufuk Bakir; Simon E. V. Phillips; Michael J. McPherson; Zumrut B. Ogel

2008-01-01

196

Enantioselective, organocatalytic reduction of ketones using bifunctional thiourea-amine catalysts.  

PubMed

Prochiral ketones are reduced to enantioenriched, secondary alcohols using catecholborane and a family of air-stable, bifunctional thiourea-amine organocatalysts. Asymmetric induction is proposed to arise from the in situ complexation between the borane and chiral thiourea-amine organocatalyst resulting in a stereochemically biased boronate-amine complex. The hydride in the complex is endowed with enhanced nucleophilicity while the thiourea concomitantly embraces and activates the carbonyl. PMID:20334398

Li, De Run; He, Anyu; Falck, J R

2010-04-16

197

Characterization of the bisintercalative DNA binding mode of a bifunctional platinum-acridine agent  

Microsoft Academic Search

The DNA interactions of PT-BIS(ACRAMTU) ((Pt(en)- (ACRAMTU)2)(NO3)4; ACRAMTU = 1-(2-(acridin-9- ylamino)ethyl)-1,3-dimethylthiourea, en = ethylene- diamine), a bifunctional platinum-acridine conjugate, have been studied in native and synthetic double- stranded DNAs and model duplexes using various biophysical techniques. These include ethidium- DNA fluorescence quenching and thermal melting experiments, circular dichroism (CD) spectroscopy and plasmid unwinding assays. In addition, the bind- ing mode

Jayati Roy Choudhury; Ulrich Bierbach

2005-01-01

198

Molecular characterization of a bifunctional glyoxylate cycle enzyme, malate synthase\\/isocitrate lyase, in Euglena gracilis  

Microsoft Academic Search

Euglena gracilis induced glyoxylate cycle enzymes when ethanol was fed as a sole carbon source. We purified, cloned and characterized a bifunctional glyoxylate cycle enzyme from E. gracilis (EgGCE). This enzyme consists of an N-terminal malate synthase (MS) domain fused to a C-terminal isocitrate lyase (ICL) domain in a single polypeptide chain. This domain order is inverted compared to the

Masami Nakazawa; Tomomi Minami; Koji Teramura; Shohei Kumamoto; Sayaka Hanato; Shigeo Takenaka; Mitsuhiro Ueda; Hiroshi Inui; Yoshihisa Nakano; Kazutaka Miyatake

2005-01-01

199

Bifunctional Metalloporphyrins-Catalyzed Coupling Reaction of Epoxides and CO 2 to Cyclic Carbonates  

Microsoft Academic Search

New catalysts of water soluble bifunctional metalloporphyrins M(TTMAPP)I4(X) (M = Co, Fe, Mn, and Cr; X = OAc, CF3COO, CCl3COO, OTs, Cl, Br, and I) were synthesized and used to catalyze the synthesis of cyclic carbonate through the coupling reaction of terminal epoxides and CO2. The effects of reaction temperature, various metals as the Lewis acidic center, counterions, and recycling

Dongsheng BAI; Xiaoxuan WANG; Yingying SONG; Bo LI; Lilong ZHANG; Peng YAN; Huanwang JING

2010-01-01

200

Grafting of bifunctional phosphonic and carboxylic acids on Phynox: Impact of induction heating  

NASA Astrophysics Data System (ADS)

Phynox, a cobalt-chromium alloy, exhibits interesting mechanical properties making it a valuable material for a number of applications. However, its applications (especially biomedical ones) often require specific surface properties that can be imparted via suitable surface functionalizations. Based on Faraday's law of induction, induction heating is a widely used method to heat metallic substrates directly and contactless. The aim of this work is to compare the influence of induction heating and a conventional heating method on the functionalization of Phynox surfaces with bifunctional (6-phosphonohexanoic and 11-phosphoundecanoic acids) monolayers in order to create a platform for a large variety of post-grafting chemical reactions, e.g. with alcohols and amines, to modify and control the surface properties. In a first part, we assess the influence of the heating method on the interaction between the two terminal moieties of the 6-phosphonohexanoic and 11-phosphoundecanoic acids and the Phynox surface by studying the grafting of n-dodecylphosphonic acid and n-dodecanoic acid separately. The suitability of such bifunctional molecules for post-grafting chemical reactions has then been assessed by studying the post-grafting of a fluorinated alcohol by the Steglich esterification reaction between the carboxylic end of the grafted bifunctional molecules and the alcohol function of the post-grafted molecule. It has been shown that induction heating can lead to a much more selective adsorption of bifunctional molecules on the surface of Phynox, leaving a higher amount of free carboxylic acid functions to react during the second modification step.

Devillers, S.; Lanners, L.; Delhalle, J.; Mekhalif, Z.

2011-05-01

201

The improved performance of dye sensitized solar cells by bifunctional aminosilane modified dye sensitized photoanode  

Microsoft Academic Search

The dye sensitized photoanode is modified by the bifunctional 3-aminopropyltriethoxysilane (APTS). The attenuated total reflection–Fourier transform infrared spectroscopy, the UV-IR spectroscopy, the dye adsorption amount, and the electrochemical impedance spectroscopy were carried out to examine the modification effect. The experiments indicated that the APTS with amino endgroup and triethoxysilane group deprotonated the surface of the dye sensitized photoanode and formed

Jing Zhang; Guangtao Yang; Qiang Sun; Jun Zheng; Peiqing Wang; Yuejin Zhu; Xingzhong Zhao

2010-01-01

202

Bifunctional anthracene derivatives as non-doped blue emitters and hole-transporters for electroluminescent devices.  

PubMed

New highly fluorescent bifunctional anthracenes showed high thermal and electrochemical stability, and great potential as both blue emitters and hole-transporters for OLEDs. Deep-blue and Alq3-based green devices with maximum efficiencies and CIE coordinates of 1.65 and 6.25 cd A(-1), and (0.15, 0.16) and (0.26, 0.49) were achieved, respectively. PMID:21614369

Thangthong, A-monrat; Meunmart, Duangratchaneekorn; Prachumrak, Narid; Jungsuttiwong, Siriporn; Keawin, Tinnagon; Sudyoadsuk, Taweesak; Promarak, Vinich

2011-07-01

203

Rare earth modified silica-aluminas as supports for bifunctional catalysis  

Microsoft Academic Search

We have explored rare earth oxide-modified amorphous silica-aluminas as “permanent” intermediate strength acids used as supports for bifunctional catalysts. The addition of well dispersed weakly basic rare earth oxides “titrates” the stronger acid sites of amorphous silica-alumina and lowers the acid strength to the level shown by halided aluminas. Physical and chemical probes, as well as model olefin and paraffin

Stuart L. Soled; Gary McVicker; Sal Miseo; William Gates; Joe Baumgartner; Exxon

1996-01-01

204

Synthesis of bifunctional polymeric adsorbent and its application in purification of stevia glycosides  

Microsoft Academic Search

Polymeric adsorbents with both functions of adsorption and decolorization were synthesized by introducing quaternary ammonium groups (e.g. –N+(CH3)3 groups) into conventional resinic adsorbent used to adsorb stevia glycosides in production. The relation between the adsorption capacity of the bifunctional adsorbents for stevia glycosides and the structure of adsorbents, and that between the decolorization efficiency and the structure were investigated. The

Rongfu Shi; Mancai Xu; Zuoqing Shi; Yunge Fan; Xianzhi Guo; Yongning Liu; Chunhong Wang; Binglin He

2002-01-01

205

(S)-5-(p-Nitrobenzyl)-PCTA, a Promising Bifunctional Ligand with Advantageous Metal Ion Complexation Kinetics  

PubMed Central

A bifunctional version of PCTA (3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3,6,9,-triacetic acid) that exhibits fast complexation kinetics with the trivalent lanthanide(III) ions was synthesized in reasonable yields starting from N, N?, N?-tristosyl-(S)-2-(p-nitrobenzyl)-diethylenetriamine. pH-potentiometric studies showed that the basicities of p-nitrobenzyl-PCTA and the parent ligand PCTA were similar. The stability of M(NO2-Bn-PCTA) (M = Mg2+, Ca2+, Cu2+, Zn2+) complexes was similar to that of the corresponding PCTA complexes while the stability of Ln3+ complexes of the bifunctional ligand is somewhat lower than that of PCTA chelates. The rate of complex formation of Ln(NO2-Bn-PCTA) complexes was found to be quite similar to that of PCTA, a ligand known to exhibit the fastest formation rates among all lanthanide macrocyclic ligand complexes studied to date. The acid catalyzed decomplexation kinetic studies of the selected Ln(NO2-Bn-PCTA) complexes showed that the kinetic inertness of the complexes was comparable to that of Ln(DOTA) chelates making the bifunctional ligand NO2-Bn-PCTA suitable for labeling biological vectors with radioisotopes for nuclear medicine applications.

Tircso, Gyula; Benyo, Eniko Tircsone; Suh, Eul Hyun; Jurek, Paul; Kiefer, Garry E.; Sherry, A. Dean; Kovacs, Zoltan

2009-01-01

206

Bearing, gearing, and lubrication technology  

NASA Technical Reports Server (NTRS)

Results of selected NASA research programs on rolling-element and fluid-film bearings, gears, and elastohydrodynamic lubrication are reported. Advances in rolling-element bearing material technology, which have resulted in a significant improvement in fatigue life, and which make possible new applications for rolling bearings, are discussed. Research on whirl-resistant, fluid-film bearings, suitable for very high-speed applications, is discussed. An improved method for predicting gear pitting life is reported. An improved formula for calculating the thickness of elastohydrodynamic films (the existence of which help to define the operating regime of concentrated contact mechanisms such as bearings, gears, and cams) is described.

Anderson, W. J.

1978-01-01

207

Anti-backlash gear bearings  

NASA Technical Reports Server (NTRS)

A gear bearing having a first gear and a second gear, each having a plurality of teeth. Each gear operates on two non-parallel surfaces of the opposing gear teeth to perform both gear and bearing functions simultaneously. The gears are moving at substantially the same speed at their contact points. The gears may be roller gear bearings or phase-shifted gear bearings, and may be arranged in a planet/sun system or used as a transmission. One preferred embodiment discloses and describes an anti-backlash feature to counter ''dead zones'' in the gear bearing movement.

Vranish, John M. (Inventor)

2009-01-01

208

Bearing for liquid metal pump  

DOEpatents

A liquid metal pump bearing support comprises a series of tangentially oriented spokes that connect the bearing cylinder to the pump internals structure. The spokes may be arranged in a plurality of planes extending from the bearing cylinder to the pump internals with the spokes in one plane being arranged alternately with those in the next plane. The bearing support structure provides the pump with sufficient lateral support for the bearing structure together with the capability of accommodating differential thermal expansion without adversely affecting pump performance.

Dickinson, Robert J. (Shaler Township, Allegheny County, PA); Wasko, John (Plum Borough, PA); Pennell, William E. (Unity Township, Allegheny County, PA)

1984-01-01

209

Stability of finite journal bearings from bearings--linear and nonlinear bearing forces  

Microsoft Academic Search

The paper investigates the relationship between the stability contour determined from the nonlinear simulation and that from the linear theory. The nonlinear bearing forces are directly obtained from the bearing pressure distribution which is solved from the Reynolds equation at each journal position. It is found that the critical speeds in the case of nonlinear bearing forces are the same

A. K. Tieu; Z. L. Qiu

1995-01-01

210

Bearing construction for refrigeration compresssor  

DOEpatents

A hermetic refrigeration compressor has a cylinder block and a crankshaft rotatable about a vertical axis to reciprocate a piston in a cylinder on the cylinder block. A separate bearing housing is secured to the central portion of the cylinder block and extends vertically along the crankshaft, where it carries a pair of roller bearings to journal the crankshaft. The crankshaft has a radially extending flange which is journaled by a thrust-type roller bearing above the bearing housing to absorb the vertical forces on the crankshaft so that all three of the roller bearings are between the crankshaft and the bearing housing to maintain and control the close tolerances required by such bearings.

Middleton, Marc G. (Wyoming, MI) [Wyoming, MI; Nelson, Richard T. (Worthington, OH) [Worthington, OH

1988-01-01

211

Wave Journal Bearing with Compressible Lubricant—Part II: A Comparison of the Wave Bearing with a Wave-Groove Bearing and a Lobe Bearing  

Microsoft Academic Search

To identify the potential advantages of the wave journal bearing, a three-wave journal bearing was compared to both a three-wave-groove bearing (a wave bearing with axial grooves that isolate each wave) and a three-lobe bearing. The lobe bearing's profile was selected to approximate the wave journal bearing's profile. The lubricant was assumed to be compressible (gas). The bearing number, A,

Florin Dimofte

1995-01-01

212

Gold-bearing skarns  

USGS Publications Warehouse

In recent years, a significant proportion of the mining industry's interest has been centered on discovery of gold deposits; this includes discovery of additional deposits where gold occurs in skarn, such as at Fortitude, Nevada, and at Red Dome, Australia. Under the classification of Au-bearing skarns, we have modeled these and similar gold-rich deposits that have a gold grade of at least 1 g/t and exhibit distinctive skarn mineralogy. Two subtypes, Au-skarns and byproduct Au-skarns, can be recognized on the basis of gold, silver, and base-metal grades, although many other geological factors apparently are still undistinguishable largely because of a lack of detailed studies of the Au-skarns. Median grades and tonnage for 40 Au-skarn deposits are 8.6 g/t Au, 5.0 g/t Ag, and 213,000 t. Median grades and tonnage for 50 byproduct and Au-skarn deposits are 3.7 g/t Au, 37 g/t Ag, and 330,000 t. Gold-bearing skarns are generally calcic exoskarns associated with intense retrograde hydrosilicate alteration. These skarns may contain economic amounts of numerous other commodities (Cu, Fe, Pb, Zn, As, Bi, W, Sb, Co, Cd, and S) as well as gold and silver. Most Au-bearing skarns are found in Paleozoic and Cenozoic orogenic-belt and island-arc settings and are associated with felsic to intermediate intrusive rocks of Paleozoic to Tertiary age. Native gold, electru, pyrite, pyrrhotite, chalcopyrite, arsenopyrite, sphalerite, galena, bismuth minerals, and magnetite or hematite are the most common opaque minerals. Gangue minerals typically include garnet (andradite-grossular), pyroxene (diopside-hedenbergite), wollastonite, chlorite, epidote, quartz, actinolite-tremolite, and (or) calcite.

Theodore, Ted G.; Orris, Greta J.; Hammerstrom, Jane M.; Bliss, James D.

1991-01-01

213

Linear magnetic bearings  

NASA Technical Reports Server (NTRS)

A self regulating, nonfrictional, active magnetic bearing is disclosed which has an elongated cylindrical housing for containing a shaft type armature with quadrature positioned shaft position sensors and equidistantly positioned electromagnets located at one end of the housing. Each set of sensors is responsive to orthogonal displacement of the armature and is used to generate control signals to energize the electromagnets to center the armature. A bumper magnet assembly is located at one end of the housing for dampening any undesired axial movement of the armature or to axially move the armature either continuously or fixedly.

Goldowskiy, M. P.

1984-01-01

214

Dialogue for Kids Wild About Bears Sleepy Bear Lesson Plan  

NSDL National Science Digital Library

Each winter, bears hunker down, slow their metabolisms, and pretty much wait out the winter in the safety of some sort of den. This lesson plan, from Idaho Public Television, is a fun way to illustrate to children (probably elementary grades primarily) the process of hibernation. At this site, educators are given the complete lesson plan instructions as well as several links to all sorts of great resources, including links to information on: Bear Diet, Home Range, Reproduction, Bear Research, People and Bears, more Classroom Activities, and more. And, the great addition to the site is a link to a 30-minute video about bears. While the site is somewhat focused on Idaho-specific bear information, teachers should be able to easily integrate the lesson no matter where you are.

215

Aerospace applications of magnetic bearings  

NASA Technical Reports Server (NTRS)

Magnetic bearings have traditionally been considered for use in aerospace applications only where performance advantages have been the primary, if not only, consideration. Conventional wisdom has been that magnetic bearings have certain performance advantages which must be traded off against increased weight, volume, electric power consumption, and system complexity. These perceptions have hampered the use of magnetic bearings in many aerospace applications because weight, volume, and power are almost always primary considerations. This paper will review progress on several active aerospace magnetic bearings programs at SatCon Technology Corporation. The magnetic bearing programs at SatCon cover a broad spectrum of applications including: a magnetically-suspended spacecraft integrated power and attitude control system (IPACS), a magnetically-suspended momentum wheel, magnetic bearings for the gas generator rotor of a turboshaft engine, a vibration-attenuating magnetic bearing system for an airborne telescope, and magnetic bearings for the compressor of a space-rated heat pump system. The emphasis of these programs is to develop magnetic bearing technologies to the point where magnetic bearings can be truly useful, reliable, and well tested components for the aerospace community.

Downer, James; Goldie, James; Gondhalekar, Vijay; Hockney, Richard

1994-01-01

216

Dislocation of Large Diameter Metal-On-Metal Bearings  

Microsoft Academic Search

We report 3 patients who underwent total hip arthroplasty (THA) using large diameter metal-on-metal bearing. These patients initially presented with pain but went on to develop dislocation of the THA while awaiting investigations. Any pain following metal-on-metal bearing THA should be taken seriously and should trigger investigations to identify a metal reaction. If left untreated, these reactions can cause progressive

Bipin Theruvil; Nijil Vasukutty; Nick Hancock; David Higgs; Douglas G. Dunlop; Jeremy M. Latham

2011-01-01

217

Kalman Filter Behavior in Bearings-Only Tracking Applications  

Microsoft Academic Search

The extended Kalman filter applied to bearings-only target tracking is theoretically analyzed. Closed-form expressions for the state vector and its associated covariance matrix are introduced, and subsequently used to demonstrate how bearing and range estimation errors can interact to cause filter instability (i.e., premature covariance collapse and divergence). Further investigation reveals that conventional initialization techniques often precipitate such anomalous behavior.

Vincent Aidala

1979-01-01

218

Bearing Dynamic Coefficients of Flexible-Pad Journal Bearings  

Microsoft Academic Search

The application of flexible-pad journal bearings for high-speed rotating machinery has recently gained attention from equipment manufacturers for its simplicity of one-piece design which can eliminate the manufacturing tolerance stack-up and possible lower functional power loss. This paper presents a general method for the calculation of bearing dynamic coefficients of flexible-pad journal bearings. These coefficients are critical to the rotor

Wen Jeng Chen

1995-01-01

219

Reduction in bearing size due to superconductors in magnetic bearings  

NASA Technical Reports Server (NTRS)

A design concept that reduces the size of magnetic bearings is assessed. The small size will enable magnetic bearings to fit into limited available bearing volume of cryogenic machinery. The design concept, called SUPERC, uses (high Tc) superconductors or high-purity aluminum conductors in windings instead of copper. The relatively high-current density of these conductors reduces the slot radial thickness for windings, which reduces the size of the bearings. MTI developed a sizing program called SUPERC that translates the high-current density of these conductors into smaller sized bearings. This program was used to size a superconducting bearing to carry a 500 lb. load. The sizes of magnetic bearings needed by various design concepts are as follows: SUPERC design concept = 3.75 in.; magnet-bias design concept = 5.25 in.; and all electromagnet design concept = 7.0 in. These results indicate that the SUPERC design concept can significantly reduce the size of the bearing. This reduction, in turn, reduces the weight and yields a lighter bearing. Since the superconductors have inherently near-zero resistance, they are also expected to save power needed for operation considerably.

Rao, Dantam K.; Lewis, Paul; Dill, James F.

1991-01-01

220

Effect of Bearing Cleaning on Long Term Bearing Life  

NASA Technical Reports Server (NTRS)

For many years chlorofluorocarbon (CFC ) based solvents, such as Freon and 1,1,1, Trichloroethane (TCA), were used as bearing cleaning solvents for space mechanisms. The 1995 ban on the production of ozone depleting chemicals (ODC) such as CFCs caused a change to new ODC-free cleaners for the precision bearing cleaning. With this change the question arises what effect if any do these new cleaners have on long term bearing life. The purpose of this study was to evaluate this effect. A one year test using 60 small electrical motors (two bearings per motor) was conducted in a high vacuum environment (2.0* 10(exp -6) torr) at a temperature of 90C. Prior to testing the bearings were cleaned with one of four cleaners. These cleaners included two aqueous based cleaners, a CFC based cleaner and supercritical carbon dioxide. Three space compatible greases were tested. After testing the mass of each lubricated bearing was measured both pre and post test. Along with mass loss measurements a profilometer trace of each bearing was taken to measure post test wear of the bearings. In addition the bearings were visually examined and analyzed using an optical microscope.

Jett, Timothy Raymond; Thom, Robert L.

1998-01-01

221

Crystallization, dehydration and experimental phasing of WbdD, a bifunctional kinase and methyltransferase from Escherichia coli O9a  

PubMed Central

WbdD is a bifunctional kinase/methyltransferase that is responsible for regulation of lipopolysaccharide O antigen polysaccharide chain length in Escherichia coli serotype O9a. Solving the crystal structure of this protein proved to be a challenge because the available crystals belonging to space group I23 only diffracted to low resolution (>95% of the crystals diffracted to resolution lower than 4?Å and most only to 8?Å) and were non-isomorphous, with changes in unit-cell dimensions of greater than 10%. Data from a serendipitously found single native crystal that diffracted to 3.0?Å resolution were non-isomorphous with a lower (3.5?Å) resolution selenomethionine data set. Here, a strategy for improving poor (3.5?Å resolution) initial phases by density modification and cross-crystal averaging with an additional 4.2?Å resolution data set to build a crude model of WbdD is desribed. Using this crude model as a mask to cut out the 3.5?Å resolution electron density yielded a successful molecular-replacement solution of the 3.0?Å resolution data set. The resulting map was used to build a complete model of WbdD. The hydration status of individual crystals appears to underpin the variable diffraction quality of WbdD crystals. After the initial structure had been solved, methods to control the hydration status of WbdD were developed and it was thus possible to routinely obtain high-resolution diffraction (to better than 2.5?Å resolution). This novel and facile crystal-dehydration protocol may be useful for similar challenging situations.

Hagelueken, Gregor; Huang, Hexian; Harlos, Karl; Clarke, Bradley R.; Whitfield, Chris; Naismith, James H.

2012-01-01

222

Fretting fatigue mechanism of bearing cap bolted joints.  

PubMed

Fretting fatigue is a common type of failure of the bearing cap bolted joints. This paper proposes a methodology to analyze the fretting fatigue mechanism of the bearing cap bolted joint. A biaxially loading system was designed to simulate fretting fatigue failure under typical engine working condition. Meanwhile, a submodel was developed in the finite element calculation to analyze the contact status and stress distribution of the structural models. The test result shows that long inclined cracks (about 650 ?m long, orientation at 17°-34°) initiate at the middle region of the contact interface. As the increase of the bolt pretension load (from 6000 N to 10?000 N), the crack initial location is getting away from the bolt screw, and the fretting fatigue lives is increasing (from 7.8 × 10(5) to 6.0 × 10(6)). With the fatigue phenomenon and the stress field analysis result, it concludes that the crack initiation is governed by the maximum shear stress; the bolt pretension load and the additional rotate torque caused by the bearing load are the two main factors which affect the fretting fatigue mechanism of the bearing cap bolted joints. It is beneficial to fretting fatigue lives of the bearing cap joints by increasing the bolt pretension load and restraining the oscillation of the bearing cap. PMID:24880414

Li, Xin; Zuo, Zhengxing; Qin, Wenjie

2014-05-01

223

Fretting fatigue mechanism of bearing cap bolted joints  

NASA Astrophysics Data System (ADS)

Fretting fatigue is a common type of failure of the bearing cap bolted joints. This paper proposes a methodology to analyze the fretting fatigue mechanism of the bearing cap bolted joint. A biaxially loading system was designed to simulate fretting fatigue failure under typical engine working condition. Meanwhile, a submodel was developed in the finite element calculation to analyze the contact status and stress distribution of the structural models. The test result shows that long inclined cracks (about 650 ?m long, orientation at 17°-34°) initiate at the middle region of the contact interface. As the increase of the bolt pretension load (from 6000 N to 10 000 N), the crack initial location is getting away from the bolt screw, and the fretting fatigue lives is increasing (from 7.8 × 105 to 6.0 × 106). With the fatigue phenomenon and the stress field analysis result, it concludes that the crack initiation is governed by the maximum shear stress; the bolt pretension load and the additional rotate torque caused by the bearing load are the two main factors which affect the fretting fatigue mechanism of the bearing cap bolted joints. It is beneficial to fretting fatigue lives of the bearing cap joints by increasing the bolt pretension load and restraining the oscillation of the bearing cap.

Li, Xin; Zuo, Zhengxing; Qin, Wenjie

2014-05-01

224

Bear maul craniocerebral trauma in Kashmir Valley.  

PubMed

Craniocerebral injuries constitute the bulk of the trauma patients in all the tertiary-care hospitals. Bear attacks as a cause of trauma to the brain and its protective covering are rare. This was a hospital-based retrospective (January 1990 to July 2005) and prospective study (August 2005 to December 2010). Craniocerebral trauma was seen in 49 patients of bear maul injuries. Loss of scalp tissue was seen in 17 patients, 13 of whom had exposed pericranium and needed split-thickness skin grafting, while 4 patients with exposed skull bones required scalp transposition flaps as an initial procedure. Skull bone fractures without associated brain injury were observed in 24 cases. Frontal bone was the site of fracture in the majority of cases (95%). Surgical intervention was needed in 18 patients for significantly depressed fractures. Three of these patients had depressed frontal bone fractures with underlying contusions and needed brain debridement and duraplasty. Injury to the brain was observed in 8 patients. Trauma to the brain and its protective coverings as a result of bear attacks is rarely known. Brain injury occurs less commonly as compared to soft tissue and bony injury. Craniocerebral trauma as a result of bear assaults has been a hitherto neglected area of trauma as the past reported incidence has been very low. Of late, the incidence and severity of such attacks has assumed grave proportions in areas adjacent to known bear habitats. An innocuous-looking surface wound might be the only presentation of an underlying severe brain trauma. Public awareness has to be generated to protect the people living in hilly areas. PMID:23348323

Bashir, Sheikh Adil; Rasool, Altaf; Zaroo, Mohamad Inam; Wani, Adil Hafeez; Zargar, Haroon Rashid; Darzi, Mohammad Ashraf; Khursheed, Nayil

2013-01-01

225

Ball bearing heat analysis program (BABHAP)  

NASA Technical Reports Server (NTRS)

The Ball Bearing Heat Analysis Program (BABHAP) is an attempt to assemble a series of equations, some of which are non-linear algebraic systems, in a logical order, which when solved, provide a complex analysis of load distribution among the balls, ball velocities, heat generation resulting from friction, applied load, and ball spinning, minimum lubricant film thickness, and many additional characteristics of ball bearing systems. Although initial design requirements for BABHAP were dictated by the core limitations of the PDP 11/45 computer, (approximately 8K of real words with limited number of instructions) the program dimensions can easily be expanded for large core computers such as the UNIVAC 1108. The PDP version of BABHAP is also operational on the UNIVAC system with the exception that the PDP uses 029 punch and the UNIVAC uses 026. A conversion program was written to allow transfer between machines.

1978-01-01

226

The crystal structure reveals the molecular mechanism of bifunctional 3,4-dihydroxy-2-butanone 4-phosphate synthase/GTP cyclohydrolase II (Rv1415) from Mycobacterium tuberculosis.  

PubMed

The enzymes 3,4-dihydroxy-2-butanone 4-phosphate synthase (DHBPS) and GTP cyclohydrolase II (GCHII) catalyze the initial steps of both branches of the bacterial riboflavin-biosynthesis pathway. The structures and molecular mechanisms of DHBPS and GCHII as separate polypeptides are known; however, their organization and molecular mechanism as a bifunctional enzyme are unknown to date. Here, the crystal structure of an essential bifunctional DHBPS/GCHII enzyme from Mycobacterium tuberculosis (Mtb-ribA2) is reported at 3.0?Å resolution. The crystal structure revealed two conformationally different molecules of Mtb-ribA2 in the asymmetric unit that form a dimer via their GCHII domains. Interestingly, analysis of the crystal packing revealed a long `helical-like oligomer' formed by DHBPS and GCHII functional homodimers, thus generating an `open-ended' unit-cell lattice. However, size-exclusion chromatography studies suggest that Mtb-ribA2 exists as a dimer in solution. To understand the discrepancy between the oligomerization observed in solution and in the crystal structure, the DHBPS (Mtb-DHBPS) and GCHII (Mtb-GCHII) domains of Mtb-ribA2 have been cloned, expressed and purified as His-tagged proteins. Size-exclusion chromatography studies indicated that Mtb-GCHII is a dimer while Mtb-DHBPS exists as a monomer in solution. Moreover, kinetic studies revealed that the GCHII activities of Mtb-ribA2 and Mtb-GCHII are similar, while the DHBPS activity of Mtb-ribA2 is much higher than that of Mtb-DHBPS alone. Taken together, the results strongly suggest that Mtb-ribA2 exists as a dimer formed through its GCHII domains and requires full-length Mtb-ribA2 for optimal DHBPS activity. PMID:23999287

Singh, Mirage; Kumar, Pankaj; Yadav, Savita; Gautam, Ruchi; Sharma, Nidhi; Karthikeyan, Subramanian

2013-09-01

227

Mechanistic and Structural Analysis of Aminoglycoside N-Acetyltransferase AAC(6?)-Ib and Its Bifunctional, Fluoroquinolone-Active AAC(6?)-Ib-cr Variant†,‡  

PubMed Central

Enzymatic modification of aminoglycoside antibiotics mediated by regioselective aminoglycoside N-acetyltransferases is the predominant cause of bacterial resistance to aminoglycosides. A recently discovered bifunctional aminoglycoside acetyltransferase (AAC(6?)-Ib variant, AAC(6?)-Ib-cr) has been shown to catalyze the acetylation of fluoroquinolones as well as aminoglycosides. We have expressed and purified AAC(6?)-Ib-wt and its bifunctional variant AAC(6?)-Ib-cr in Escherichia coli and characterized their kinetic and chemical mechanism. Initial velocity and dead-end inhibition studies support an ordered sequential mechanism for the enzyme(s). The three-dimensional structure of AAC(6?)-Ib-wt was determined in various complexes with donor and acceptor ligands to resolutions greater than 2.2 Å. Observation of the direct, and optimally positioned, interaction between the 6?-NH2 and Asp115 suggests that Asp115 acts as a general base to accept a proton in the reaction. The structure of AAC(6?)-Ib-wt permits the construction of a molecular model of the interactions of fluoroquinolones with the AAC(6?)-Ib-cr variant. The model suggests that a major contribution to the fluoroquinolone acetylation activity comes from the Asp179Tyr mutation, where Tyr179 makes ?-stacking interactions with the quinolone ring facilitating quinolone binding. The model also suggests that fluoroquinolones and aminoglycosides have different binding modes. On the basis of kinetic properties, the pH dependence of the kinetic parameters, and structural information, we propose an acid/base-assisted reaction catalyzed by AAC(6?)-Ib-wt and the AAC(6?)-Ib-cr variant involving a ternary complex.

Vetting, Matthew W.; Park, Chi Hye; Hegde, Subray S.; Jacoby, George A.; Hooper, David C.; Blanchard, John S.

2010-01-01

228

In vivo evaluation of a radiogallium-labeled bifunctional radiopharmaceutical, Ga-DOTA-MN2, for hypoxic tumor imaging.  

PubMed

On the basis of the findings obtained by X-ray crystallography of Ga-DOTA chelates and the drug design concept of bifunctional radiopharmaceuticals, we previously designed and synthesized a radiogallium-labeled DOTA chelate containing two metronidazole moieties, (67)Ga-DOTA-MN2, for hypoxic tumor imaging. As expected, (67)Ga-DOTA-MN2 exhibited high in vivo stability, although two carboxyl groups in the DOTA skeleton were conjugated with metronidazole moieties. In this study, we evaluated (67/68)Ga-DOTA-MN2 as a nuclear imaging agent for hypoxic tumors. (67)Ga-labeling of DOTA-MN2 with (67)GaCl(3) was achieved with high radiochemical yield (>85%) by 1-min of microwave irradiation (50 W). The pharmacokinetics of (67)Ga-DOTA-MN2 were examined in FM3A tumor-bearing mice, and compared with those of (67)Ga-DOTA-MN1 containing one metronidazole unit and (67)Ga-DOTA. Upon administration, (67)Ga-DOTA-MN2 exhibited higher accumulation in the implanted tumors than (67)Ga-DOTA. Tumor-to-blood ratios of (67)Ga-DOTA-MN2 were about two-fold higher than those of (67)Ga-DOTA-MN1. Autoradiographic analysis showed the heterogeneous localization of (67)Ga-DOTA-MN2 in the tumors, which corresponds to hypoxic regions suggested by well-established hypoxia marker drug, pimonidazole. Furthermore, in positron emission tomography (PET) study, the tumors of mice administered (68)Ga-labeled DOTA-MN2 were clearly imaged by small-animal PET at 1 h after administration. This study demonstrates the potential usefulness of (67/68)Ga-DOTA-MN2 as a nuclear imaging agent for hypoxic tumors and suggests that two functional moieties, such as metronidazole, can be conjugated to radiogallium-DOTA chelate without reducing the complex stability. The present findings provide useful information about the chemical design of radiogallium-labeled radiopharmaceuticals for PET and single photon emission computed tomography (SPECT) studies. PMID:23546294

Sano, Kohei; Okada, Mayumi; Hisada, Hayato; Shimokawa, Kenta; Saji, Hideo; Maeda, Minoru; Mukai, Takahiro

2013-01-01

229

Rubber supported hydrostatic thrust bearings with rigid bearing surfaces  

Microsoft Academic Search

The film pressure of tilted hydrostatic thrust bearings results in a tilt opposing moment. This self-aligning action of the tilt opposing moment can be used effectively to reduce the deflection of the film contour. For this reduction some adjustment (elasticity) of the bearing system is necessary. Such elasticity is realized by means of a rubber support.

A. van Beek; A. Segal

1997-01-01

230

Superconducting levitating bearing  

NASA Technical Reports Server (NTRS)

A superconducting bearing assembly includes a coil field source that may be superconducting and a superconducting structure. The coil field source assembly and superconducting structure are positioned so as to enable relative rotary movement therebetween. The structure and coil field source are brought to a supercooled temperature before a power supply induces a current in the coil field source. A Meissner-like effect is thereby obtained and little or no penetration of the field lines is seen in the superconducting structure. Also, the field that can be obtained from the superconducting coil is 2-8 times higher than that of permanent magnets. Since the magnetic pressure is proportioned to the square of the field, magnetic pressures from 4 to 64 times higher are achieved.

Moon, Francis C. (Inventor)

1996-01-01

231

Measurements of changes in the atmospheric partitioning of bifunctional carbonyls near a road in a suburban area  

NASA Astrophysics Data System (ADS)

Bifunctional carbonyls are ubiquitous in the atmosphere and are important contributors to atmospheric aerosols through heterogenous reactions. However, the actual contributions of bifunctional carbonyls to atmospheric aerosols have been little measured because of their capacity to coexist in both the gaseous phase and the particulate phase, making it difficult to sample them in both phases simultaneously. Using a short time resolution (2 h), we measured the atmospheric partitioning of semivolatile species to understand their contributions to atmospheric aerosols. Our results indicate that equilibrium between the gaseous phase and the particulate phase was due not only to thermodynamic partitioning but also to an aging process. Fresh emissions from motor vehicles affected the partitioning, and partitioning coefficients stabilized when the aerosols aged. The contribution of bifunctional carbonyl compounds to atmospheric aerosols was 3-8 orders of magnitude higher than that estimated by thermodynamic predictions, corroborating previous findings.

Ortiz, R.; Shimada, S.; Sekiguchi, K.; Wang, Q.; Sakamoto, K.

2013-12-01

232

Characterization of a bifunctional cytidine 5'-monophosphate N-acetylneuraminic acid synthetase cloned from Streptococcus agalactiae.  

PubMed

Recombinant CMP-sialic acid synthetase, cloned from Streptococcus agalactiae serotype V strain 2603 V/R, is bifunctional having both CMP-sialic acid synthetase and acetylhydrolase (acylesterase) activities. The enzyme is active over a wide pH range with an optimal CMP-sialic acid synthetase activity at pH 9.0 and an optimal acetylhydrolase activity at pH 8.0. A metal cofactor (either Mg(2+) or Mn(2+)) is required for the CMP-sialic acid synthetase activity but is not for acetylhydrolase activity. Both catalytic functions, however, are impaired by high concentrations of Mn(2+). PMID:16369694

Yu, Hui; Ryan, Wesley; Yu, Hai; Chen, Xi

2006-01-01

233

Asymmetric organocatalytic formal [2 + 2]-cycloadditions via bifunctional H-bond directing dienamine catalysis.  

PubMed

A new concept in organocatalysis allowing for the construction of cyclobutanes with four contiguous stereocenters with complete diastereo- and enantiomeric control by a formal [2 + 2]-cycloaddition is presented. The concept is based on simultaneous dual activation of ?,?-unsaturated aldehydes and nitroolefins by amino- and hydrogen-bonding catalysis, respectively. A new bifunctional squaramide-based aminocatalyst has been designed and synthesized in order to enable such an activation strategy. The potential and scope of the reaction are demonstrated, and computational studies which account for the stereochemical outcome are presented. PMID:22280440

Albrecht, ?ukasz; Dickmeiss, Gustav; Cruz Acosta, Fabio; Rodríguez-Escrich, Carles; Davis, Rebecca L; Jørgensen, Karl Anker

2012-02-01

234

Preparation and protein conjugation of a divinyl sulphone derivatized bifunctional chelating agent.  

PubMed

A new bifunctional chelating agent with a novel linking arm, 2-[p-¿N-benzyl-N-(2-vinylsulfoethyl)¿- (aminobenzyl)¿-1,3-propane-diamine-N,N,N',N'-tetraacetic acid (VS-PDTA) was synthesized and was conjugated to protein for the purpose of attaching radiometals to monoclonal antibodies (MAbs). The effect of various parameters such as ligand concentration, protein concentration, pH, temperature and reaction period on the conjugation have been examined using chromatographic (SE and TLC) analysis after labeling with 111In. The parameters and chemical variables studied have significant effects on the efficiency and rate of protein conjugation. PMID:10851501

Somayaji, V V; Naicker, S S; Sykes, T R; Guay, V; Noujaim, A A

1996-12-01

235

Peptide-imprinted polymer microspheres prepared by precipitation polymerization using a single bi-functional monomer.  

PubMed

A single bi-functional monomer, N,O-bismethacryloyl ethanolamine (NOBE), was used in precipitation polymerization system to synthesize molecularly imprinted polymer (MIP) microspheres. Highly specific binding sites were obtained for N-terminal protected neuropeptides, Boc-Leu-enkephalin and Pyr-Leu-enkephalin. The use of NOBE allowed binding sites to be formed in polymer microspheres that are able to recognize target peptides through the consensus C-terminal sequence. The interesting molecular binding results suggest a new approach for peptide analysis combining in situ chemical modification with MIP recognition under non-aqueous conditions. PMID:19305921

Yoshimatsu, Keiichi; LeJeune, Jason; Spivak, David A; Ye, Lei

2009-04-01

236

Isolation of a bifunctional domain from the pentafunctional arom enzyme complex of Neurospora crassa.  

PubMed

Limited proteolysis of the arom enzyme complex of Neurospora crassa by trypsin or subtilisin yielded a stable fragment of Mr 68000. This fragment, which was purified by two-dimensional polyacrylamide-gel electrophoresis, was shown by activity staining to contain the shikimate dehydrogenase active site, and by substrate labelling with 3-dehydroquinate and NaB3H4 to contain the 3-dehydroquinase active site. The fragment thus constitutes a bifunctional domain containing the two enzymic activities that are known, from genetic evidence, to be located adjacently at the C-terminal end of the pentafunctional arom polypeptide. PMID:6225423

Smith, D D; Coggins, J R

1983-08-01

237

Bifunctional Iminophosphorane Organocatalysts for Enantioselective Synthesis: Application to the Ketimine Nitro-Mannich Reaction  

PubMed Central

The design, synthesis, and development of a new class of modular, strongly basic, and tunable bifunctional Brønsted base/H-bond-donor organocatalysts are reported. These catalysts incorporate a triaryliminophosphorane as the Brønsted basic moiety and are readily synthesized via a last step Staudinger reaction of a chiral organoazide and a triarylphosphine. Their application to the first general enantioselective organocatalytic nitro-Mannich reaction of nitromethane to unactivated ketone-derived imines allows the enantioselective construction of ?-nitroamines possessing a fully substituted carbon atom. The reaction is amenable to multigram scale-up, and the products are useful for the synthesis of enantiopure 1,2-diamine and ?-amino acid derivatives.

2013-01-01

238

Bifunctional iminophosphorane organocatalysts for enantioselective synthesis: application to the ketimine nitro-Mannich reaction.  

PubMed

The design, synthesis, and development of a new class of modular, strongly basic, and tunable bifunctional Brønsted base/H-bond-donor organocatalysts are reported. These catalysts incorporate a triaryliminophosphorane as the Brønsted basic moiety and are readily synthesized via a last step Staudinger reaction of a chiral organoazide and a triarylphosphine. Their application to the first general enantioselective organocatalytic nitro-Mannich reaction of nitromethane to unactivated ketone-derived imines allows the enantioselective construction of ?-nitroamines possessing a fully substituted carbon atom. The reaction is amenable to multigram scale-up, and the products are useful for the synthesis of enantiopure 1,2-diamine and ?-amino acid derivatives. PMID:24107070

Núñez, Marta G; Farley, Alistair J M; Dixon, Darren J

2013-11-01

239

A novel bifunctional maleimido CHX-A'' chelator for conjugation to thiol-containing biomolecules.  

PubMed

A novel bifunctional maleimido CHX-A'' DTPA chelator 5 was developed and conjugated to the monoclonal antibody trastuzumab (Herceptin) and subsequently radiolabeled with (111)In. The resulting (111)In labeled immunoconjugate 2 was demonstrated to bind to SKOV-3 ovarian cancer cells comparably to an isothiocyanato CHX-A'' DTPA modified native trastuzumab, 1. Through efficient thiol-maleimide chemistry, antibodies, peptides or other targeting vectors can now be modified with an established radioactive metal chelating agent CHX-A'' DTPA for imaging and/or therapies of cancer. PMID:18359632

Xu, Heng; Baidoo, Kwamena E; Wong, Karen J; Brechbiel, Martin W

2008-04-15

240

Radial Clearance of Antifriction Bearings.  

National Technical Information Service (NTIS)

The article concerns in detail the radial clearance of different antifriction bearings which belong to important parameters which influence the longevity of the bearing to a certain extent. The effect of the influence of assembly and the wear on the radia...

V. Patocka

1968-01-01

241

Lubrication of rolling element bearings  

NASA Technical Reports Server (NTRS)

This paper is a broad survey of the lubrication of rolling-element bearings. Emphasis is on the critical design aspects related to speed, temperature, and ambient pressure environment. Types of lubrication including grease, jets, mist, wick, and through-the-race are discussed. The paper covers the historical development, present state of technology, and the future problems of rolling-element bearing lubrication.

Parker, R. J.

1980-01-01

242

Permanent-Magnet Meissner Bearing  

NASA Technical Reports Server (NTRS)

Permanent-magnet meissner bearing features inherently stable, self-centering conical configuration. Bearing made stiffer or less stiff by selection of magnets, springs, and spring adjustments. Cylindrical permanent magnets with axial magnetization stacked coaxially on rotor with alternating polarity. Typically, rare-earth magnets used. Magnets machined and fitted together to form conical outer surface.

Robertson, Glen A.

1994-01-01

243

Ion Implantation of Ceramic Bearings.  

National Technical Information Service (NTIS)

This report explores the use of ion implantation techniques to form solid lubricating surfaces on all ceramic (silicon nitride) and hybrid ball bearings. Techniques were developed to implant and/or cost silicon nitride and 52100 bearing steel with MoS2, B...

A. J. Armini S. N. Bunker

1989-01-01

244

Intrinsic kinetics of one-step dimethyl ether synthesis from hydrogen-rich synthesis gas over bi-functional catalyst  

Microsoft Academic Search

The reaction kinetics of the dimethyl ether synthesis from hydrogen-rich synthesis gas over bi-functional catalyst was investigated\\u000a using an isothermal integral reactor at 220–260°C temperature, 3–7 MPa pressure, and 1,000–2,500 mL\\/g·h space velocity. The\\u000a H2\\/CO ratio of the synthetic gas was chosen between 3 : 1 and 6 : 1. The bi-functional catalyst was prepared by physically mixing\\u000a commercial CuO\\/ZnO\\/Al2O3

Chengyuan Cheng; Haitao Zhang; Weiyong Ying; Dingye Fang

2011-01-01

245

Nonlinear control of magnetic bearings  

NASA Technical Reports Server (NTRS)

In this paper we present a variety of nonlinear controllers for the magnetic bearing that ensure both stability and robustness. We utilize techniques of discontinuous control to design novel control laws for the magnetic bearing. We present in particular sliding mode controllers, time optimal controllers, winding algorithm based controllers, nested switching controllers, fractional controllers, and synchronous switching controllers for the magnetic bearing. We show existence of solutions to systems governed by discontinuous control laws, and prove stability and robustness of the chosen control laws in a rigorous setting. We design sliding mode observers for the magnetic bearing and prove the convergence of the state estimates to their true values. We present simulation results of the performance of the magnetic bearing subject to the aforementioned control laws, and conclude with comments on design.

Pradeep, A. K.; Gurumoorthy, R.

1994-01-01

246

Geophagy by yellowstone grizzly bears  

USGS Publications Warehouse

We documented 12 sites in the Yellowstone ecosystem where grizzly bears (Ursus arctos horribilis) had purposefully consumed soil (an activity known as geophagy). We also documented soil in numerous grizzly bear feces. Geophagy primarily occurred at sites barren of vegetation where surficial geology had been modified by geothermal activity. There was no evidence of ungulate use at most sites. Purposeful consumption of soil by bears peaked first from March to May and again from August to October, synchronous with peaks in consumption of ungulate meat and mushrooms. Geophageous soils were distinguished from ungulate mineral licks and soils in general by exceptionally high concentrations of potassium (K) and high concentrations of magnesium (Mg) and sulphur (S). Our results do not support the hypotheses that bears were consuming soil to detoxify secondary compounds in grazed foliage, as postulated for primates, or to supplement dietary sodium, as known for ungulates. Our results suggest that grizzly bears could have been consuming soil as an anti-diarrheal.

Mattson, D. J.; Green, G. I.; Swalley, R.

1999-01-01

247

Acquired arteriovenous fistula in a grizzly bear (Ursus arctos horribilis).  

PubMed

A captive adult male grizzly bear (Ursus arctos horribilis) was evaluated due to multifocal wounds of the skin and subcutaneous tissues sustained as a result of trauma from another grizzly bear. On presentation, one lesion that was located in the perineal region seemed to be a deep puncture with purple tissue protruding from it. This perineal wound did not heal in the same manner or rate as did the other wounds. Twenty-five days after initial detection, substantial active hemorrhage from the lesion occurred and necessitated anesthesia for examination of the bear. The entire lesion was surgically excised, which later proved curative. An acquired arteriovenous fistula was diagnosed via histopathology. Arteriovenous fistulas can develop after traumatic injury and should be considered as a potential complication in bears with nonhealing wounds. PMID:19368261

Tuttle, Allison D; MacLean, Robert A; Linder, Keith; Cullen, John M; Wolfe, Barbara A; Loomis, Michael

2009-03-01

248

Ambient air measurements of six bifunctional carbonyls in a suburban area  

NASA Astrophysics Data System (ADS)

Low-molecular-weight carbonyl compounds, generated by photochemical reactions in the atmosphere and found in the exhaust of motor vehicles, have recently come to the attention of researchers because some of them are suspected carcinogens or mutagens. Six bifunctional carbonyl compounds were detected and measured in a suburban site 30 km northwest of the Tokyo metropolitan area. Samples were taken on five sunny days between 2 August and 11 August 2003 with a low-volume denuder and three-filter tandem system using O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) as a sorbent. Bifunctional carbonyls were measured by gas chromatography-mass spectrometry after two derivatization processes with PFBHA and N, O-bis(trimethylsilyl)-trifluoroacetamide (BSTFA). The average total (gas plus particle) concentrations were 162.8 ng m - 3 for pyruvic acid, 113.7 ng m - 3 for methylglyoxal, 36.0 ng m - 3 for glycolaldehyde and 58.6 ng m - 3 for glyoxal.

Ortiz, Ricardo; Hagino, Hiroyuki; Sekiguchi, Kazuhiko; Wang, Qingyue; Sakamoto, Kazuhiko

2006-12-01

249

Bifunctional compounds eliciting both anti-inflammatory and cholinergic activity as potential drugs for neuroinflammatory impairments.  

PubMed

We tested two novel bifunctional compounds: ibuprofen-N-octyl-pyridostigmine bromide (IBU-PO) and ibuprofen-N-decyl-pyridostigmine bromide (IBU-PD). They both contain a non-steroidal anti-inflammatory drug (NSAID), ibuprofen (IBU) and pyridostigmine (PO), a cholinesterase inhibitor that acts as a cholinergic up-regulator (CURE). The two moieties are conjugated by a hydrocarbon spacer consisting of 8 (octyl) and 10 (decyl) carbons, respectively. The compounds were tested for their efficiency in reducing the neurological symptoms observed in experimental autoimmune encephalomyelitis induced in mice by myelin oligodendrocyte glycoprotein (MOG). IBU-PO and IBU-PD significantly ameliorated the clinical score (a 40-50% reduction in disease severity) over a period of 30 days, following daily administration of 1 and 0.1mg/kg, i.p., respectively. Clinical improvement was accompanied by reduced responsiveness of MOG-specific T-cells. In addition, IBU-PO and IBU-PD down-regulated the production of nitric oxide (NO) and prostaglandin E2 (PGE2) in cultured astrocytes. To determine which moiety was responsible for these effects, we tested each of the two components, IBU and PO. Our findings indicate that combining NSAID with cholinergic intervention contributes an added therapeutic value for each distinct entity and that these bifunctional compounds act both on the peripheral immunological system and on the central nervous system (CNS) inflammatory pathways. PMID:15694272

Nizri, Eran; Adani, Rellie; Meshulam, Haim; Amitai, Gabi; Brenner, Talma

2005-03-01

250

Pushing the Theoretical Limit of Li-CFx Batteries: A Tale of Bi-functional Electrolyte  

SciTech Connect

In a typical battery, electrodes deliver capacities less or equal the theoretical maxima of the electrode materials.1 The inert electrolyte functions solely as the ionic conductor without contribution to the cell capacity because of its distinct mono-function in the concept of conventional batteries. Here we demonstrate that the most energy-dense Li-CFx battery2 delivers a capacity exceeding the theoretical maximum of CFx with a solid electrolyte of Li3PS4 (LPS) that has dual functions: as the inert electrolyte at the anode and the active component at the cathode. Such a bi-functional electrolyte reconciles both inert and active characteristics through a synergistic discharge mechanism of CFx and LPS. Li3PS4 is known as an inactive solid electrolyte with a broad electrochemical window over 5 V.3 The synergy at the cathode is through LiF, the discharge product of CFx, which activates the electrochemical discharge of LPS at a close electrochemical potential of CFx. Therefore, the solid-state Li-CFx batteries output 126.6% energy beyond their theoretic limits without compromising the stability of the cell voltage. The extra energy comes from the electrochemical discharge of LPS, the inert electrolyte. This bi-functional electrolyte revolutionizes the concept of conventional batteries and opens a new avenue for the design of batteries with an unprecedentedly high energy density.

Rangasamy, Ezhiylmurugan [ORNL] [ORNL; Li, Juchuan [ORNL] [ORNL; Sahu, Gayatri [ORNL] [ORNL; Dudney, Nancy J [ORNL] [ORNL; Liang, Chengdu [ORNL] [ORNL

2014-01-01

251

Characteristics of bifunctional acidic endoglucanase (Cel5B) from Gloeophyllum trabeum.  

PubMed

The endoglucanase (Cel5B) from the filamentous fungus Gloeophyllum trabeum was cloned and expressed without a signal peptide, and alanine residue 22 converted to glutamine in Pichia pastoris GS115. The DNA sequence of Cel5B had an open reading frame of 1,077 bp, encoding a protein of 359 amino acid residues with a molecular weight of 47 kDa. On the basis of sequence similarity, Cel5B displayed active site residues at Glu-175 and Glu-287. Both residues lost full hydrolytic activity when replaced with alanine through point mutation. The purified recombinant Cel5B showed very high specific activity, about 80- to 1,000-fold and 13- to 70-fold in comparison with other endoglucanases and cellobiohydrolase, on carboxymethylcellulose and filter paper, respectively, at pH 3.5 and 55°C. Cel5B displayed bifunctional characteristics under acidic conditions. The kinetic properties of the enzyme determined using a Lineweaver-Burk plot indicated that Cel5B is a catalytically efficient cellulolytic enzyme. These results suggest that Cel5B has high bifunctional endo- and exoglucanase activity under acidic conditions and is a good candidate for bioconversion of lignocellulose. PMID:22395898

Kim, Ho Myeong; Lee, Yoon Gyo; Patel, Darshan H; Lee, Kwang Ho; Lee, Dae-Seok; Bae, Hyeun-Jong

2012-07-01

252

Bifunctional graphene/?-Fe?O? hybrid aerogels with double nanocrystalline networks for enzyme immobilization.  

PubMed

Highly porous hosting materials with conducting (favorable to electron transfer) and magnetic (favorable to product separation) bicontinuous networks should possess great potentials for immobilization of various enzymes in the field of biocatalytic engineering, but the synthesis of such materials is still a great challenge. Herein, bifunctional graphene/?-Fe2 O3 hybrid aerogels with quite low density (30-65 mg cm(-3) ), large specific surface area (270-414 m(2) g(-1) ), high electrical conductivity (0.5-5 × 10(-2) S m(-1) ), and superior saturation magnetization (23-54 emu g(-1) ) are fabricated. Single networks of either graphene aerogels or ?-Fe2 O3 aerogels are obtained by etching of the hybrid aerogels with acid solution or calcining of the hybrid aerogels in air, indicative of the double networks of the as-synthesized graphene/?-Fe2 O3 hybrid aerogels for the first time. The resulting bifunctional aerogels are used to immobilize ?-glucuronidase for biocatalytic transformation of glycyrrhizin into glycyrrhetinic acid monoglucuronide or glycyrrhetinic acid, with high biocatalytic activity and definite repeatability. PMID:23423944

Chen, Liang; Wei, Bin; Zhang, Xuetong; Li, Chun

2013-07-01

253

The Bifunctional Pyruvate Decarboxylase/Pyruvate Ferredoxin Oxidoreductase from Thermococcus guaymasensis  

PubMed Central

The hyperthermophilic archaeon Thermococcus guaymasensis produces ethanol as a metabolic end product, and an alcohol dehydrogenase (ADH) catalyzing the reduction of acetaldehyde to ethanol has been purified and characterized. However, the enzyme catalyzing the formation of acetaldehyde has not been identified. In this study an enzyme catalyzing the production of acetaldehyde from pyruvate was purified and characterized from T. guaymasensis under strictly anaerobic conditions. The enzyme had both pyruvate decarboxylase (PDC) and pyruvate ferredoxin oxidoreductase (POR) activities. It was oxygen sensitive, and the optimal temperatures were 85°C and >95°C for the PDC and POR activities, respectively. The purified enzyme had activities of 3.8 ± 0.22?U?mg?1 and 20.2 ± 1.8?U?mg?1, with optimal pH-values of 9.5 and 8.4 for each activity, respectively. Coenzyme A was essential for both activities, although it did not serve as a substrate for the former. Enzyme kinetic parameters were determined separately for each activity. The purified enzyme was a heterotetramer. The sequences of the genes encoding the subunits of the bifunctional PDC/POR were determined. It is predicted that all hyperthermophilic ?-keto acids ferredoxin oxidoreductases are bifunctional, catalyzing the activities of nonoxidative and oxidative decarboxylation of the corresponding ?-keto acids.

2014-01-01

254

Rational Design and Generation of a Bimodal Bifunctional Ligand for Antibody-Targeted Radiation Cancer Therapy  

PubMed Central

An antibody-targeted radiation therapy (radioimmunotherapy, RIT) employs a bifunctional ligand that can effectively hold a cytotoxic metal with clinically acceptable complexation kinetics and stability while being attached to a tumor-specific antibody. Clinical exploration of the therapeutic potential of RIT has been challenged by the absence of adequate ligand, a critical component for enhancing the efficacy of the cancer therapy. To address this deficiency, the bifunctional ligand C-NETA in a unique structural class possessing both a macrocyclic cavity and a flexible acyclic moiety was designed. The practical, reproducible, and readily scalable synthetic route to C-NETA was developed, and its potential as the chelator of 212Bi, 213Bi, and 177Lu for RIT was evaluated in vitro and in vivo. C-NETA rapidly binds both Lu(III) and Bi(III), and the respective metal complexes remain extremely stable in serum for 14 days. 177Lu—C-NETA and 205/6Bi—C-NETA possess an excellent or acceptable in vivo biodistribution profile.

Chong, Hyun-Soon; Ma, Xiang; Le, Thien; Kwamena, Baidoo; Milenic, Diane E.; Brady, Erik D.; Song, Hyun A.; Brechbiel, Martin W.

2008-01-01

255

Modeling Chemotaxis Reveals the Role of Reversed Phosphotransfer and a Bi-Functional Kinase-Phosphatase  

PubMed Central

Understanding how multiple signals are integrated in living cells to produce a balanced response is a major challenge in biology. Two-component signal transduction pathways, such as bacterial chemotaxis, comprise histidine protein kinases (HPKs) and response regulators (RRs). These are used to sense and respond to changes in the environment. Rhodobacter sphaeroides has a complex chemosensory network with two signaling clusters, each containing a HPK, CheA. Here we demonstrate, using a mathematical model, how the outputs of the two signaling clusters may be integrated. We use our mathematical model supported by experimental data to predict that: (1) the main RR controlling flagellar rotation, CheY6, aided by its specific phosphatase, the bifunctional kinase CheA3, acts as a phosphate sink for the other RRs; and (2) a phosphorelay pathway involving CheB2 connects the cytoplasmic cluster kinase CheA3 with the polar localised kinase CheA2, and allows CheA3-P to phosphorylate non-cognate chemotaxis RRs. These two mechanisms enable the bifunctional kinase/phosphatase activity of CheA3 to integrate and tune the sensory output of each signaling cluster to produce a balanced response. The signal integration mechanisms identified here may be widely used by other bacteria, since like R. sphaeroides, over 50% of chemotactic bacteria have multiple cheA homologues and need to integrate signals from different sources.

Maini, Philip K.; Armitage, Judith P.

2010-01-01

256

MULT1E/mIL-12: a novel bifunctional protein for natural killer cell activation.  

PubMed

Natural killer (NK) cells have the potential to be effective killers of tumor cells. They are governed by inhibitory and activating receptors like NKG2D, whose ligands are normally upregulated in cells that are stressed, like cancer cells. Advanced cancer cells, however, have ways to reduce these ligands' expression, leaving them less detectable by NK cells. Along with these receptors, NK cells also require activating cytokines, like interleukin 12 (IL-12). The goal of this study is to develop a novel bi-functional fusion protein for enhanced NK cell activation. The proposed protein combines the extracellular domain of the NKG2D ligand Mouse UL-16-binding protein-like transcript 1 (MULT1E) and mouse IL-12 (mIL-12). It is hypothesized that when expressed by tumor cells, the protein will activate NK and other killer cells using the NKG2D receptor, and deliver mIL-12 to the NK cells where it can interact with the IL-12R and enhance cytotoxicity. The fusion protein, when expressed by engineered tumor cells, indeed activated NK cells in vitro as assayed by increased production of interferon-? and cytotoxicity and significantly reduced tumor growth in vivo. Although the study is preliminary, the data suggest that the MULT1E/mIL-12 bi-functional fusion protein is an effective activator of NK cells for cancer treatment. PMID:24572784

Tietje, A; Li, J; Yu, X; Wei, Y

2014-05-01

257

Pushing the Theoretical Limit of Li-CFx Batteries: A Tale of Bifunctional Electrolyte.  

PubMed

In a typical battery, the inert electrolyte functions solely as the ionic conductor without contribution to the cell capacity. Here we demonstrate that the most energy-dense Li-CFx battery delivers a capacity exceeding the theoretical maximum of CFx with a solid electrolyte of Li3PS4 (LPS) that has dual functions: as the inert electrolyte at the anode and the active component at the cathode. Such a bifunctional electrolyte reconciles both inert and active characteristics through a synergistic discharge mechanism of CFx and LPS. The synergy at the cathode is through LiF, the discharge product of CFx, which activates the electrochemical discharge of LPS at a close electrochemical potential of CFx. Therefore, the solid-state Li-CFx batteries output 126.6% energy beyond their theoretic limits without compromising the stability of the cell voltage. The additional energy comes from the electrochemical discharge of LPS, the inert electrolyte. This bifunctional electrolyte revolutionizes the concept of conventional batteries and opens a new avenue for the design of batteries with unprecedented energy density. PMID:24730570

Rangasamy, Ezhiylmurugan; Li, Juchuan; Sahu, Gayatri; Dudney, Nancy; Liang, Chengdu

2014-05-14

258

A Bifunctional Enzyme That Has Both Monoacylglycerol Acyltransferase and Acyl Hydrolase Activities1[W][OA  

PubMed Central

Monoacylglycerol acyltransferase (MGAT) catalyzes the synthesis of diacylglycerol, the precursor of triacylglycerol biosynthesis and an important signaling molecule. Here, we describe the isolation and characterization of the peanut (Arachis hypogaea) MGAT gene. The soluble enzyme utilizes invariant histidine-62 and aspartate-67 residues of the acyltransferase motif for its MGAT activity. A sequence analysis revealed the presence of a hydrolase (GXSXG) motif, and enzyme assays revealed the presence of monoacylglycerol (MAG) and lysophosphatidylcholine (LPC) hydrolytic activities, indicating the bifunctional nature of the enzyme. The overexpression of the MGAT gene in yeast (Saccharomyces cerevisiae) caused an increase in triacylglycerol accumulation. Similar to the peanut MGAT, the Arabidopsis (Arabidopsis thaliana) homolog (At1g52760) also exhibited both acyltransferase and hydrolase activities. Interestingly, the yeast homolog lacks the conserved HX4D motif, and it is deficient in the acyltransferase function but exhibits MAG and LPC hydrolase activities. This study demonstrates the presence of a soluble MGAT/hydrolase in plants. The predicted three-dimensional homology modeling and substrate docking suggested the presence of two separate substrate (MAG and LPC)-binding sites in a single polypeptide. Our study describes a soluble bifunctional enzyme that has both MGAT and hydrolase functions.

Vijayaraj, Panneerselvam; Jashal, Charnitkaur B.; Vijayakumar, Anitha; Rani, Sapa Hima; Venkata Rao, D.K.; Rajasekharan, Ram

2012-01-01

259

Construction of a bifunctional enzyme fusion for the combined determination of biogenic amines in foods.  

PubMed

Biogenic amines (BAs) are a group of low-molecular-mass organic bases derived from free amino acids. Due to the undesirable effects of BAs on human health, amine oxidase-based detection methods for BAs in foods have been developed. Here, we developed a bifunctional enzyme fusion (MAPO) using a Cu(2+)-containing monoamine oxidase (AMAO2) and a flavin adenine dinucleotide-containing putrescine oxidase (APUO) from Arthrobacter aurescens. It was necessary to activate MAPO with supplementary Cu(2+) ions, leading to a 6- to 12-fold improvement in catalytic efficiency (kcat/KM) for monoamines. The optimal temperatures of Cu(2+)-activated MAPO (cMAPO) for both tyramine and putrescine were 50 °C, and the optimal pH values for tyramine and putrescine were pH 7.0 and pH 8.0, respectively, consistent with those of AMAO2 and APUO, respectively. The cMAPO showed relative specific activities of 100, 99, 32, and 32 for 2-phenylethylamine, tyramine, histamine, and putrescine, respectively. The tyramine-equivalent BA contents of fermented soybean pastes by cMAPO were more than 90% of the total BA determined by HPLC. In conclusion, cMAPO is fully bifunctional toward biogenic monoamines and putrescine, allowing the combined determination of multiple BAs in foods. This colorimetric determination method could be useful for point-of-care testing to screen safety-guaranteed products prior to instrumental analyses. PMID:24001036

Lee, Jae-Ick; Jang, Jun-Hyuck; Yu, Mi-Ji; Kim, Young-Wan

2013-09-25

260

Characterization of a bifunctional enzyme with (p)ppGpp-hydrolase/synthase activity in Leptospira interrogans.  

PubMed

Alarmone Guanosine 5'-diphosphate (or 5'-triphosphate) 3'-diphosphate [(p)ppGpp] is the key component that globally regulates stringent control in bacteria. There are two homologous enzymes, RelA and SpoT in Escherichia coli, which are responsible for fluctuations in (p)ppGpp concentration inside the cell, whereas there exists only a single RelA/SpoT enzyme in Gram-positive bacteria. We have identified a bifunctional enzyme with (p)ppGpp-hydrolase/synthase activity in Leptospira interrogans. We show that the relLin gene (LA_3085) encodes a protein that fully complements the relA/spoT double mutants in E. coli. The protein functions as a (p)ppGpp degradase as well as a (p)ppGpp synthase when the cells encounter amino acid stress and deprivation of carbon sources. N-terminus HD and RSD domains of relLin (relLinN ) were observed to restore growth of double mutants of E. coli. Finally, We demonstrate that purified RelLin and RelLinN show high (p)ppGpp synthesis activity in vitro. Taken together, our results suggest that L. interrogans contain a single Rel-like bifunctional protein, RelLin , which plays an important role in maintaining the basal level of (p)ppGpp in the cell potentially contributing to the regulation of bacterial stress response. PMID:24111633

He, Ping; Deng, Cong; Liu, Boyu; Zeng, LingBing; Zhao, Wei; Zhang, Yan; Jiang, XuCheng; Guo, XiaoKui; Qin, JinHong

2013-11-01

261

Isolation of the bifunctional enzyme lysine 2-oxoglutarate reductase-saccharopine dehydrogenase from Phaseolus vulgaris.  

PubMed

Lysine is catabolyzed by the bifunctional enzyme lysine 2-oxoglutarate reductase-saccharopine dehydrogenase (LOR-SDH) in both animals and plants. LOR condenses lysine and 2-oxoglutarate into saccharopine, using NADPH as cofactor and SDH converts saccharopine into alpha-aminoadipate delta-semialdehyde and glutamic acid, using NAD as cofactor. The distribution pattern of LOR and SDH among different tissues of Phaseolus vulgaris was determined. The hypocotyl contained the highest specific activity, whereas in seeds the activities of LOR and SDH were below the limit of detection. Precipitation of hypocotyl proteins with increasing concentrations of PEG 8000 revealed one broad peak of SDH activity, indicating that two isoforms may be present, a bifunctional LOR-SDH and possibly a monofunctional SDH. During the purification of the hypocotyl enzyme, the LOR activity proved to be very unstable, following ion-exchange chromatography. Depending on the purification procedure, the protein eluted as a monomer of 91-94 kDa containing only SDH activity, or as a dimer of 190 kDa with both, LOR and SDH activities, eluting together. PMID:12624751

Cunha Lima, S T; Azevedo, R A; Santoro, L G; Gaziola, S A; Lea, P J

2003-01-01

262

Evaluation of K(HYNIC)2 as A Bifunctional Chelator for 99mTc-Labeling of Small Biomolecules  

PubMed Central

This study sought to evaluate K(HYNIC)2 (K = lysine and HYNIC = 6-hydrazinonicotinyl) as a bifunctional chelator for 99mTc-labeling of biomolecule. In this study, four K(HYNIC)2–conjugated cyclic RGD peptides, K(HYNIC)2-RGD2 (RGD2 = E[c(RGDfK)]2), K(HYNIC)2-3G-RGD2 (3G-RGD2 = Gly-Gly-Gly-E[Gly-Gly-Gly-c(RGDfK)]2), K(HYNIC)2-2P-RGD2 (2P-RGD2 = E[PEG4-c(RGDfK)]2, and PEG4 = 15-amino-4,7,10,13-tetraoxapentadecanoic acid), and K(HYNIC)2-3P-RGD2 (3P-RGD2 = PEG4-E[PEG4-c(RGDfK)]2) were prepared, and evaluated for their integrin ?v?3 binding affinity. IC50 values were determined to be 47 ± 2, 35 ± 2, 37 ± 2, 85 ± 2 and 422 ± 15 nM for K(HYNIC)2-2P-RGD2, K(HYNIC)2-3P-RGD2, K(HYNIC)2-3G-RGD2, K(HYNIC)2-RGD2 and c(RGDyK), respectively, against 125I-echistatin bound to U87MG cells. Macrocyclic complexes [99mTc(K(HYNIC)2-RGD2)(tricine)] (1), [99mTc(K(HYNIC)2-3G-RGD2)(tricine)] (2), [99mTc(K(HYNIC)2-2P-RGD2)(tricine)] (3), and [99mTc(K(HYNIC)2-3P-RGD2)(tricine)] (4) were prepared, and evaluated in athymic nude mice bearing U87MG glioma xenografts for their tumor targeting capability and biodistribution. It was found that 1 – 4 all had high solution stability and more than two isomers, as evidenced by the presence of multiple radiometric peaks in their radio-HPLC chromatograms. The tumor uptake of 1 – 4 was 3.78 ± 0.81, 7.46 ± 1.68, 9.74 ± 1.65 and 8.59 ± 1.52 %ID/g, respectively, which was completely consistent with trend of integrin ?v?3 binding affinity for cyclic RGD peptides. Replacing [99mTc(HYNIC)(tricine)(TPPTS)] (TPPTS = trisodium triphenylphosphine-3,3?,3?-trisulfonate) with [99mTc(K(HYNIC)2)(tricine)] had little impact on radiotracer tumor uptake; but it had significant effect on the uptake of radiotracer in kidneys, lungs and spleen. The tumor was clearly visualized by SPECT/CT with excellent contrast in a glioma-bearing mouse administered with 4. K(HYNIC)2 would be particularly useful for 99mTc-labeling of small biomolecules with one or more disulfide linkages.

Ji, Shundong; Zhou, Yang; Shao, Guoqiang; Liu, Shuang

2013-01-01

263

Evaluation of K(HYNIC)(2) as a bifunctional chelator for (99m)Tc-labeling of small biomolecules.  

PubMed

This study sought to evaluate K(HYNIC)(2) (K = lysine and HYNIC = 6-hydrazinonicotinyl) as a bifunctional chelator for (99m)Tc-labeling of biomolecule. In this study, four K(HYNIC)(2)-conjugated cyclic RGD peptides, K(HYNIC)(2)-RGD(2) (RGD(2) = E[c(RGDfK)](2)), K(HYNIC)(2)-3G-RGD(2) (3G-RGD(2) = Gly-Gly-Gly-E[Gly-Gly-Gly-c(RGDfK)](2)), K(HYNIC)(2)-2P-RGD(2) (2P-RGD(2) = E[PEG4-c(RGDfK)](2), and PEG(4) = 15-amino-4,7,10,13-tetraoxapentadecanoic acid), and K(HYNIC)(2)-3P-RGD(2) (3P-RGD(2) = PEG4-E[PEG4-c(RGDfK)]2) were prepared, and evaluated for their integrin ?v?3 binding affinity. IC(50) values were determined to be 47 ± 2, 35 ± 2, 37 ± 2, 85 ± 2, and 422 ± 15 nM for K(HYNIC)(2)-2P-RGD(2), K(HYNIC)(2)-3P-RGD(2), K(HYNIC)(2)-3G-RGD(2), K(HYNIC)(2)-RGD(2), and c(RGDyK), respectively, against (125)I-echistatin bound to U87MG cells. Macrocyclic complexes [(99m)Tc(K(HYNIC)(2)-RGD(2))(tricine)] (1), [(99m)Tc(K(HYNIC)(2)-3G-RGD(2))(tricine)] (2), [(99m)Tc(K(HYNIC)(2)-2P-RGD(2))(tricine)] (3), and [(99m)Tc(K(HYNIC)(2)-3P-RGD(2))(tricine)] (4) were prepared, and evaluated in athymic nude mice bearing U87MG glioma xenografts for their tumor targeting capability and biodistribution. It was found that 1-4 all had high solution stability and more than two isomers, as evidenced by the presence of multiple radiometric peaks in their radio-HPLC chromatograms. The tumor uptake of 1-4 was 3.78 ± 0.81, 7.46 ± 1.68, 9.74 ± 1.65, and 8.59 ± 1.52%ID/g, respectively, which was completely consistent with trend of integrin ?(v)?(3) binding affinity for cyclic RGD peptides. Replacing [(99m)Tc(HYNIC)(tricine)(TPPTS)] (TPPTS = trisodium triphenylphosphine-3,3',3"-trisulfonate) with [(99m)Tc(K(HYNIC)(2))(tricine)] had little impact on radiotracer tumor uptake; but it had significant effect on the uptake of radiotracer in kidneys, lungs, and spleen. The tumor was clearly visualized by SPECT/CT with excellent contrast in a glioma-bearing mouse administered with 4. K(HYNIC)(2) would be particularly useful for (99m)Tc-labeling of small biomolecules with one or more disulfide linkages. PMID:23521129

Ji, Shundong; Zhou, Yang; Shao, Guoqiang; Liu, Shuang

2013-04-17

264

SSME turbopump bearing analytical study  

NASA Technical Reports Server (NTRS)

Three shuttle pump bearings operating under severe overspeed and shut-down conditions are evaluated. The specific parameters investigated include outer race stresses, cage stresses, cage-race drag, bearing heating, and crush loading. A quasi-dynamic version of the BASDAP computer code was utilized which involved the calculation of ball-race forces (inner and outer), contact pressures, contact dimensions, and contact angles as a function of (1) axial load, (2) radial load, and (3) centrifugal load on the bearing. Generally, radial loads on the order of 13,300 N (3000 pounds) per bearing or 26,700 N (6000 pounds) per bearing pair, could be expected to cause severe problems to any of the bearings with a 17,800 N (4000 pounds) axial load. Further, when possible temperature excursions are considered, even a load of 8900 N (2000 pounds) may be excessive. However, high momentary radial loads with a 3800 N (850 pounds) axial load would not be anticipated to cause catastrophic failure of the fuel pump bearing.

Kannel, J. W.; Merriman, T.

1980-01-01

265

Magnetic Bearings at Draper Laboratory  

NASA Technical Reports Server (NTRS)

Magnetic bearings, unlike traditional mechanical bearings, consist of a series of components mated together to form a stabilized system. The correct design of the actuator and sensor will provide a cost effective device with low power requirements. The proper choice of a control system utilizes the variables necessary to control the system in an efficient manner. The specific application will determine the optimum design of the magnetic bearing system including the touch down bearing. Draper for the past 30 years has been a leader in all these fields. This paper summarizes the results carried out at Draper in the field of magnetic bearing development. A 3-D radial magnetic bearing is detailed in this paper. Data obtained from recently completed projects using this design are included. One project was a high radial load (1000 pound) application. The second was a high speed (35,000 rpm), low loss flywheel application. The development of a low loss axial magnetic bearing is also included in this paper.

Kondoleon, Anthony S.; Kelleher, William P.; Possel, Peter D.

1996-01-01

266

Adaptive Spindle Balancing Using Magnetically Levitated Bearings.  

National Technical Information Service (NTIS)

A technological break through for supporting rotating shafts is the active magnetic bearing (AMB). Active magnetic bearings off some important advantages over conventional ball, roller, or journal bearings such as reduced frictional drag, no physical cont...

Barney Lauffer Petteys Redmond Sullivan

1999-01-01

267

Bearing Error and the Central Limit Theorem.  

National Technical Information Service (NTIS)

Bearings are frequently computed as the average of the number of readings. Most of fixing theory assumes that the bearing error is normal is distributed. Averages are usually much closer to bearing normally distributed than individual readings. The amount...

1987-01-01

268

Influence of Foreign Particles on Bearing Metals.  

National Technical Information Service (NTIS)

Incidents of damage to automobile engine bearings caused by foreign particles are discussed. Granular materials can cause cracks and intrusions into soft bearing surfaces, leaving scratches in the bearing metals.

S. Mori

1988-01-01

269

Surficial Deposits in the Bear Lake Basin.  

National Technical Information Service (NTIS)

Mapping and dating of surficial deposits in the Bear Lake drainage basin were undertaken to provide a geologic context for interpretation of cores taken from deposits beneath Bear Lake, which sometimes receives water and sediment from the glaciated Bear R...

M. C. Reheis B. J. C. Laabs R. M. Forester J. P. McGeehin D. S. Kaufman J. Bright

2005-01-01

270

Military and Commercial Aircraft Bearing Field Experience.  

National Technical Information Service (NTIS)

This report contains the results of a study performed on the field experience of aircraft bearings. The study pertains primarily to airframe bearings with emphasis on teflon and fabroid types. Source of field experience for evaluating these bearings was A...

W. C. Barnes

1969-01-01

271

Passive Magnetic Bearing with Ferrofluid Stabilization.  

National Technical Information Service (NTIS)

A new class of magnetic bearings is shown to exist analytically and is demonstrated experimentally. The class of magnetic bearings utilize a ferrofluid/solid magnet interaction to stabilize the axial degree of freedom of a permanent magnet radial bearing....

R. Jansen E. Dirusso

1996-01-01

272

Thermal Interactions in Rolling Bearing Dynamics.  

National Technical Information Service (NTIS)

Numerical enhancements to the established bearing dynamics computer code, Advanced Dynamics of Rolling Elements (ADORE), have been accomplished for improved computation of bearing heat generation and geometrical variation in bearing element dimensions. Th...

P. K. Gupta

2002-01-01

273

Random Bearings and Their Stability  

NASA Astrophysics Data System (ADS)

Self-similar space-filling bearings have been proposed some time ago as models for the motion of tectonic plates and appearance of seismic gaps. These models have two features which, however, seem unrealistic, namely, high symmetry in the arrangement of the particles, and lack of a lower cutoff in the size of the particles. In this work, an algorithm for generating random bearings in both two and three dimensions is presented. Introducing a lower cutoff for the sizes of the particles, the instabilities of the bearing under an external force such as gravity, are studied.

Baram, Reza Mahmoodi; Herrmann, Hans J.

2005-11-01

274

Random bearings and their stability.  

PubMed

Self-similar space-filling bearings have been proposed some time ago as models for the motion of tectonic plates and appearance of seismic gaps. These models have two features which, however, seem unrealistic, namely, high symmetry in the arrangement of the particles, and lack of a lower cutoff in the size of the particles. In this work, an algorithm for generating random bearings in both two and three dimensions is presented. Introducing a lower cutoff for the sizes of the particles, the instabilities of the bearing under an external force such as gravity, are studied. PMID:16384225

Mahmoodi Baram, Reza; Herrmann, Hans J

2005-11-25

275

Analytical investigation of access holes in load-bearing diaphragms of steel box girders  

Microsoft Academic Search

This paper presents a series of parametric studies on the effect of access holes on the strength of the load-bearing diaphragms in steel box girder bridges. These parameters include the number of bearings, initial imperfections, the size and location of access holes, and the size of stiffeners around the openings. The load-bearing diaphragms were modeled using three-dimensional finite element analyses

Dong Y. Yoon; Sung C. Lee; Chai H. Yoo

2005-01-01

276

Zinc/Air Battery R and D Research and Development of Bifunctional Oxygen Electrode: Tasks I and II, Final Report.  

National Technical Information Service (NTIS)

Studies were conducted of the bifunctional oxygen electrode. The development of a rechargeable metal-oxygen (air) cell has been hampered to a great extent by the lack of a stable and cost effective oxygen electrode capable of use during both charge and di...

M. Klein S. Viswanathan

1986-01-01

277

Aminocyanation by the addition of N-CN bonds to arynes: chemoselective synthesis of 1,2-bifunctional aminobenzonitriles.  

PubMed

An efficient aminocyanation by the direct addition of aryl cyanamides to arynes is described, enabling incorporation of highly useful amino and cyano groups synchronously via cleavage of inert N-CN bonds, affording synthetically useful 1,2-bifunctional aminobenzonitriles. The postsynthetic functionalization of the aminocyanation products allows diverse formation of synthetically important derivatives such as drug molecule Ponstan and fused heterocycles. PMID:24325782

Rao, Bin; Zeng, Xiaoming

2014-01-01

278

Facile synthesis of 4-vinyl- and 4-fluorovinyl-1,2,3-triazoles via bifunctional "click-olefination" reagents  

PubMed Central

Modular synthesis of vinyl and fluorovinyl triazoles can be achieved from bifunctional propargyl and fluoropropargyl sulfones by Cu-catalyzed azide-alkyne ligation and Julia-Kocienski olefination. Competitive click reactions of the protio and fluoropropargyl sulfones show higher reactivity of the latter, and a preliminary DFT analysis was performed.

Kumar, Rakesh; Pradhan, Padmanava; Zajc, Barbara

2011-01-01

279

Field trial of novel bifunctional resins for removing pertechnetate (TcO(sub 4)(sup (minus))) from contaminated groundwater.  

National Technical Information Service (NTIS)

A field trial using a custom-designed bifunctional synthetic resin prepared at the University of Tennessee and designed to selectively remove pertechnetate (TcO(sub 4)(sup (minus))) from groundwater was conducted in summer 1997 at the Northwest Plume Pump...

B. Gu L. Liang G. M. Brown P. V. Bonnesen B. A. Moyer

1998-01-01

280

Bi-functional air electrodes for metal-air batteries. Final report, September 15, 1993--December 14, 1994.  

National Technical Information Service (NTIS)

The program was directed to the need for development of bifunctional air electrodes for Zn-Air batteries for the consumer market. The Zn-Air system, widely used as a primary cell for hearing-aid batteries and as a remote-site power source in industrial ap...

L. L. Swette M. Manoukian A. B. LaConti

1995-01-01

281

Bifunctional chelates of Rh-105 and Au-199 as potential radiotherapeutic agents. (Progress report, June 1, 1989-May 31, 1990).  

National Technical Information Service (NTIS)

Since last year we have: continued the synthesis of pentadentate bifunctional chelating agents based on diethylene triamine; studied the chelation Rh-105, Au-198 (as model for Au-199) and Tc-99m with these agents as well as chelation of Pd-109, Cu-67, In-...

D. E. Troutner E. O. Schlemper

1990-01-01

282

PREPARATION AND CHROMATOGRAPHIC BEHAVIOR OF A BIFUNCTIONAL CONTINUOUS ROD FOR WEAK CATION EXCHANGE AND IMMOBILIZED METAL AFFINITY CHROMATOGRAPHY  

Microsoft Academic Search

A procedure for the preparation of a bifunctional continuous rod for weak ion exchange chromatography (WCX) and immobilized metal affinity chromatography (IMAC) is presented. Without chelated metal, from the retention behavior of proteins, the rod, which carries iminoacetic acid and iminodiacetic acid (IDA) groups was found to be a relatively strong cation exchanger and exhibits an excellent separation of proteins

Yinmao Wei; Xiaodong Huang; Qiang Chen; Xindu Geng

2001-01-01

283

Gas bearing operates in vacuum  

NASA Technical Reports Server (NTRS)

Bearing has restrictions to reduce air leaks and is connected to external pumpout facility which removes exhausted air. Token amount of air which is lost to vacuum is easily removed by conventional vacuum pump.

Perkins, G. S.

1975-01-01

284

Mixed-mu superconducting bearings  

DOEpatents

A mixed-mu superconducting bearing including a ferrite structure disposed for rotation adjacent a stationary superconductor material structure and a stationary permanent magnet structure. The ferrite structure is levitated by said stationary permanent magnet structure.

Hull, John R. (Hinsdale, IL); Mulcahy, Thomas M. (Western Springs, IL)

1998-01-01

285

A Passive Magnetic Bearing Flywheel  

NASA Technical Reports Server (NTRS)

A 100 percent passive magnetic bearing flywheel rig employing no active control components was designed, constructed, and tested. The suspension clothe rotor was provided by two sets of radial permanent magnetic bearings operating in the repulsive mode. The axial support was provided by jewel bearings on both ends of the rotor. The rig was successfully operated to speeds of 5500 rpm, which is 65 percent above the first critical speed of 3336 rpm. Operation was not continued beyond this point because of the excessive noise generated by the air impeller and because of inadequate containment in case of failure. Radial and axial stiffnesses of the permanent magnetic bearings were experimentally measured and then compared to finite element results. The natural damping of the rotor was measured and a damping coefficient was calculated.

Siebert, Mark; Ebihara, Ben; Jansen, Ralph; Fusaro, Robert L.; Morales, Wilfredo; Kascak, Albert; Kenny, Andrew

2002-01-01

286

Myrmecophagy by Yellowstone grizzly bears  

USGS Publications Warehouse

I used data collected during a study of radio-marked grizzly bears (Ursus arctos horribilis) in the Yellowstone region from 1977 to 1992 to investigate myrmecophagy by this population. Although generally not an important source of energy for the bears (averaging 8 mm long) nested in logs over small ants (6 mm long) nested under stones. Optimal conditions for consumption of ants occurred on the warmest sites with ample substrate suitable for ant nests. For ants in mounds, this occurred at low elevations at non-forested sites. For ants in logs, this occurred at low elevations or on southerly aspects where there was abundant, large-diameter, well-decomposed woody debris under an open forest canopy. Grizzly bears selected moderately decomposed logs 4a??5 dm in diameter at midpoint. Ants will likely become a more important food for Yellowstone's grizzly bears as currently important foods decline, owing to disease and warming of the regional climate.

Mattson, D. J.

2001-01-01

287

ATM CMG bearing failure analysis  

NASA Technical Reports Server (NTRS)

The cause or causes for the failure of ATM CMG S/N 5 (Skylab 1) and the anomalies associated with ATM CMG S/N 6 (Skylab 2) were investigated. Skylab telemetry data were reviewed and presented in the form of parameter distributions. The theory that the problems were caused by marginal bearing lubrication was studied along with the effects of orbital conditions on lubricants. Bearing tests were performed to investigate the effect of lubricant or lack of lubricant in the ATM CMG bearings and the dispersion and migration of the lubricant. The vacuum and weightless conditions of space were simulated in the bearing tests. Analysis of the results of the tests conducted points to inadequate lubrication as the predominant factor causing the failure of ATM CMG S/N 5 (Skylab 1) and the anomalies associated with ATM CMG S/N 6 (Skylab 2).

1975-01-01

288

Bearing capacity of desiccated tailings  

SciTech Connect

The development of matric suctions in soils contributes to their shear strength, resulting in an enhanced factor of safety against bearing-capacity failure. In this paper, matric suction profiles of desiccated mine tailings are predicted from a steady-state solution for evaporative conditions, and from an isothermal mathematical model that simulates liquid and vapor water flow through soils. The shear-strength envelope with respect to matric suction is established by testing reconstituted tailings samples in a modified triaxial cell, in which matric suction can be controlled. The contribution of matric suction to the shear strength is interpreted as an additional apparent cohesion for use in bearing-capacity calculations. Because of the nonlinearity of the shear-strength profile, a numerical method of analysis is adopted to predict the ultimate bearing capacity of the desiccated tailings. A subsequent decrease in bearing capacity following 2D water infiltration into a partially capped tailings deposit and accompanying suction loss is investigated.

Rassam, D.W.; Williams, D.J. [Univ. of Queensland, Brisbane, Queensland (Australia). Dept. of Civil Engineering] [Univ. of Queensland, Brisbane, Queensland (Australia). Dept. of Civil Engineering

1999-07-01

289

Mixed-mu superconducting bearings  

DOEpatents

A mixed-mu superconducting bearing is disclosed including a ferrite structure disposed for rotation adjacent a stationary superconductor material structure and a stationary permanent magnet structure. The ferrite structure is levitated by said stationary permanent magnet structure. 9 figs.

Hull, J.R.; Mulcahy, T.M.

1998-03-03

290

CCPI bears first fruit  

SciTech Connect

In 2002, the Bush administration launched the Clean Coal Power Initiative (CCCPI) in the hope that it would develop the missing technology piece of the cleaner energy puzzle. Four years and two rounds later, the US electric power industry is seeing the first usable clean coal technologies emerge before its eyes. This article describe progress on one of the eight selected projects in the initial phase of the CCPI - led by NeuCo Inc. and carried out at Dynegy's Baldwin Energy Complex in Illinois - to increase efficiency and reduce emissions of the station's three coal-fired units with plant optimization software. In year one, a combustion/post-combustion (SCR) optimization system called CombustOpt was installed on cyclone boilers of units 1 and 2. They were also retrofitted with NeuCo's PerformanceOpt system. The fuel technology piece is MainenanceOpt to determine root causes of problems affecting unit efficiency and capacity. 5 figs.

Wicker, K.

2006-01-15

291

Lateral dampers for thrust bearings  

NASA Technical Reports Server (NTRS)

The development of lateral damping schemes for thrust bearings was examined, ranking their applicability to various engine classes, selecting the best concept for each engine class and performing an in-depth evaluation. Five major engine classes were considered: large transport, military, small general aviation, turboshaft, and non-manrated. Damper concepts developed for evaluation were: curved beam, constrained and unconstrained elastomer, hybrid boost bearing, hydraulic thrust piston, conical squeeze film, and rolling element thrust face.

Hibner, D. H.; Szafir, D. R.

1985-01-01

292

Teddy Bear Line-Up  

NSDL National Science Digital Library

This problem requires children to develop logical reasoning and promotes using visualization to plan ahead. Students are presented with a line of four blue, then four red followed by four yellow and finally four green bears and are asked to rearrange them using the least number of moves so that no two bears of the same color are next to each other. The Teachers' Notes page offers rationale, suggestions for implementation, discussion questions, and an idea for support and extension.

2009-04-01

293

Analysis of foil bearings for high speed operation in cryogenic applications  

NASA Technical Reports Server (NTRS)

The general objective of this project is to develop analysis tools which are required for the design of foil bearings to be used in cryogenic applications. During the second year of this project, a general analysis approach and code for journal bearings operating under steady state conditions will be completed. This will be followed by the initiation of an investigation into transient behavior of foil bearings to determine their performance in rotor systems. Foil bearings have been proposed as an alternative to rolling element bearings for use in cryogenic turbopumps in liquid propellant rocket engines. This type of bearing offers several advantages over rolling element bearings since they would use the cryogenic pump fluid for a lubricant and have structural flexibility. These bearings have the potential of high reliability and long life. The bearing surface is constructed of a 'foil' which resists deflection by a combination of bending, membrane, and elastic foundation effects. The relative motion between the rotating shaft and the foil causes pressure in the fluid film to develop. This pressure deflects the the foil surface away from the shaft. Once a full fluid film is established between the foil and the rotor shaft, contact no longer takes place and there is no subsequent wear of the surfaces. The flexible foil structure of the bearing allows it to compensate for minor tolerance and manufacturing defects. This same flexibility also has a significant effect on the dynamic performance of the rotor-bearing system.

Carpino, Marc

1991-01-01

294

Development of novel bifunctional anion-exchange resins with improved selectivity for pertechnetate sorption from contaminated groundwater  

SciTech Connect

The present study evaluated a new class of bifunctional anion-exchange resins with improved selectivity and sorption kinetics for removing pertechnetate (TcO{sub 4}{sup {minus}}) from contaminated groundwater. Both laboratory-column and field flow-through experiments were performed, and results indicated that superior performance of the bifunctional resins has been achieved through the use of two quaternary ammonium groups, one having long chains (trihexylamine) for higher selectivity for poorly hydrated large anions and one having shorter chains (triethylamine) for enhanced kinetics and exchange capacity. Field results indicated that the bifunctional resin performed {approximately}5 times better than one of the best commercial monofunctional anion-exchange resins with respect to the removal of TcO{sub 4}{sup {minus}} from contaminated groundwater. Less than 3% of TcO{sub 4}{sup {minus}} breakthrough was observed after {approximately}700,000 bed volumes (BV) of contaminated groundwater had been treated by the bifunctional resin column at the US Department of Energy's Paducah Gaseous Diffusion Plant site. The results also demonstrate that the new resin is particularly effective in removing low levels of TcO{sub 4}{sup {minus}}, and a cost saving may be realized by using the bifunctional resins for the treatment of large quantities of contaminated groundwater because of its increased selectivity, treatment efficiently, and longevity. The new resin may also be applied for the efficient treatment of other poorly hydrated large anions such as perchlorate (ClO{sub 4}{sup {minus}}) from contaminated groundwater or surface water.

Gu, B.; Brown, G.M.; Bonnesen, P.V.; Liang, L.; Moyer, B.A.; Ober, R.; Alexandratos, S.D.

2000-03-15

295

Reciprocal regulation as a source of ultrasensitivity in two-component systems with a bifunctional sensor kinase.  

PubMed

Two-component signal transduction systems, where the phosphorylation state of a regulator protein is modulated by a sensor kinase, are common in bacteria and other microbes. In many of these systems, the sensor kinase is bifunctional catalyzing both, the phosphorylation and the dephosphorylation of the regulator protein in response to input signals. Previous studies have shown that systems with a bifunctional enzyme can adjust the phosphorylation level of the regulator protein independently of the total protein concentrations - a property known as concentration robustness. Here, I argue that two-component systems with a bifunctional enzyme may also exhibit ultrasensitivity if the input signal reciprocally affects multiple activities of the sensor kinase. To this end, I consider the case where an allosteric effector inhibits autophosphorylation and, concomitantly, activates the enzyme's phosphatase activity, as observed experimentally in the PhoQ/PhoP and NRII/NRI systems. A theoretical analysis reveals two operating regimes under steady state conditions depending on the effector affinity: If the affinity is low the system produces a graded response with respect to input signals and exhibits stimulus-dependent concentration robustness - consistent with previous experiments. In contrast, a high-affinity effector may generate ultrasensitivity by a similar mechanism as phosphorylation-dephosphorylation cycles with distinct converter enzymes. The occurrence of ultrasensitivity requires saturation of the sensor kinase's phosphatase activity, but is restricted to low effector concentrations, which suggests that this mode of operation might be employed for the detection and amplification of low abundant input signals. Interestingly, the same mechanism also applies to covalent modification cycles with a bifunctional converter enzyme, which suggests that reciprocal regulation, as a mechanism to generate ultrasensitivity, is not restricted to two-component systems, but may apply more generally to bifunctional enzyme systems. PMID:24809699

Straube, Ronny

2014-05-01

296

Reciprocal Regulation as a Source of Ultrasensitivity in Two-Component Systems with a Bifunctional Sensor Kinase  

PubMed Central

Two-component signal transduction systems, where the phosphorylation state of a regulator protein is modulated by a sensor kinase, are common in bacteria and other microbes. In many of these systems, the sensor kinase is bifunctional catalyzing both, the phosphorylation and the dephosphorylation of the regulator protein in response to input signals. Previous studies have shown that systems with a bifunctional enzyme can adjust the phosphorylation level of the regulator protein independently of the total protein concentrations – a property known as concentration robustness. Here, I argue that two-component systems with a bifunctional enzyme may also exhibit ultrasensitivity if the input signal reciprocally affects multiple activities of the sensor kinase. To this end, I consider the case where an allosteric effector inhibits autophosphorylation and, concomitantly, activates the enzyme's phosphatase activity, as observed experimentally in the PhoQ/PhoP and NRII/NRI systems. A theoretical analysis reveals two operating regimes under steady state conditions depending on the effector affinity: If the affinity is low the system produces a graded response with respect to input signals and exhibits stimulus-dependent concentration robustness – consistent with previous experiments. In contrast, a high-affinity effector may generate ultrasensitivity by a similar mechanism as phosphorylation-dephosphorylation cycles with distinct converter enzymes. The occurrence of ultrasensitivity requires saturation of the sensor kinase's phosphatase activity, but is restricted to low effector concentrations, which suggests that this mode of operation might be employed for the detection and amplification of low abundant input signals. Interestingly, the same mechanism also applies to covalent modification cycles with a bifunctional converter enzyme, which suggests that reciprocal regulation, as a mechanism to generate ultrasensitivity, is not restricted to two-component systems, but may apply more generally to bifunctional enzyme systems.

Straube, Ronny

2014-01-01

297

Grease Inhibits Stress-Corrosion Cracking In Bearing Race  

NASA Technical Reports Server (NTRS)

Coating with suitable grease found to inhibit stress-corrosion cracking in bore of inner race of ball-bearing assembly operating in liquid oxygen. Protects bore and its corner radii from corrosion-initiating and -accelerating substances like moisture and contaminants, which enter during assembly. Operating life extended at low cost, and involves very little extra assembly time.

Beatty, Robert F.; Mcvey, Scott E.

1991-01-01

298

END CLOSURE FOR PLUTONIUM BEARING ZIRCALOY2CLAD FUEL ELEMENTS  

Microsoft Academic Search

An investigation was initiated to evaluate the fillet head weld (Figure ; 1) on both plutonium aluminum alloy and plutonium oxide bearing, Zircaloy-2-clad ; fuel elements, using the tungsten inert gas process. The integrity of this weld ; has been subjected to a series of destructive tests including fatigue, torsion, ; tensile and autoclave, without weld failure. Results show no

1959-01-01

299

ON GEARED ROTORDYNAMIC SYSTEMS WITH OIL JOURNAL BEARINGS  

Microsoft Academic Search

This study investigates response and stability characteristics of rotordynamic systems interconnected with gear pairs and supported on oil journal bearings. The systems examined are driven by a motor providing a known torque, which is transferred to a load element through shafts and a gear box. Initially, the emphasis is placed on the gear-pair action, by assuming that the interconnecting shafts

S. Theodossiades; S. Natsiavas

2001-01-01

300

Chaotic motions of a rigid rotor in short journal bearings  

Microsoft Academic Search

In the present paper the conditions that give rise to chaotic motions in a rigid rotor on short journal bearings are investigated and determined. A suitable symmetry was given to the rotor, to the supporting system, to the acting system of forces and to the system of initial conditions, in order to restrict the motions of the rotor to translatory

G. Adiletta; A. R. Guido; C. Rossi

1996-01-01

301

The Role of Radial Clearance on the Performance of Foil Air Bearings  

Microsoft Academic Search

Load capacity tests were conducted to determine how radial clearance variations affect the load capacity coefficient of foil air bearings. Two Generation III foil air bearings with the same design but possessing different initial radial clearances were tested at room temperature against an as-ground PS304 coated journal operating at 30000 rpm. Increases in radial clearance were accomplished by reducing the

Kevin Radil; Samuel Howard; Brian Dykas

2002-01-01

302

A comparative study of the pin-bearing responses of two glass-based fibre metal laminates  

Microsoft Academic Search

The pin-bearing behaviour of two commercially available glass-based fibre metal laminates (FMLs), GLARE® 2 and GLARE® 3, is presented. Results shown include bearing stress, strain, stiffness and strength, surface strains in the vicinity of the hole, and damage progression using microscopy. The initial stiffness, the bearing strain at which non-linearity first occurs and the initial rate of stiffness loss were

R. M. Frizzell; C. T. McCarthy; M. A. McCarthy

2008-01-01

303

Structures of a bifunctional cell wall hydrolase CwlT containing a novel bacterial lysozyme and an NlpC/P60 DL-endopeptidase.  

PubMed

Tn916-like conjugative transposons carrying antibiotic resistance genes are found in a diverse range of bacteria. Orf14 within the conjugation module encodes a bifunctional cell wall hydrolase CwlT that consists of an N-terminal bacterial lysozyme domain (N-acetylmuramidase, bLysG) and a C-terminal NlpC/P60 domain (?-d-glutamyl-l-diamino acid endopeptidase) and is expected to play an important role in the spread of the transposons. We determined the crystal structures of CwlT from two pathogens, Staphylococcus aureus Mu50 (SaCwlT) and Clostridium difficile 630 (CdCwlT). These structures reveal that NlpC/P60 and LysG domains are compact and conserved modules, connected by a short flexible linker. The LysG domain represents a novel family of widely distributed bacterial lysozymes. The overall structure and the active site of bLysG bear significant similarity to other members of the glycoside hydrolase family 23 (GH23), such as the g-type lysozyme (LysG) and Escherichia coli lytic transglycosylase MltE. The active site of bLysG contains a unique structural and sequence signature (DxxQSSES+S) that is important for coordinating a catalytic water. Molecular modeling suggests that the bLysG domain may recognize glycan in a similar manner to MltE. The C-terminal NlpC/P60 domain contains a conserved active site (Cys-His-His-Tyr) that appears to be specific to murein tetrapeptide. Access to the active site is likely regulated by isomerism of a side chain atop the catalytic cysteine, allowing substrate entry or product release (open state), or catalysis (closed state). PMID:24051416

Xu, Qingping; Chiu, Hsiu-Ju; Farr, Carol L; Jaroszewski, Lukasz; Knuth, Mark W; Miller, Mitchell D; Lesley, Scott A; Godzik, Adam; Elsliger, Marc-André; Deacon, Ashley M; Wilson, Ian A

2014-01-01

304

Development of tartaric esters as bifunctional additives of methanol-gasoline  

PubMed Central

Background Methanol has become an alternative fuel for gasoline, which is facing a rapidly rising world demand with a limited oil supply. Methanol-gasoline has been used in China, but phase stability and vapor lock still need to be resolved in methanol-gasoline applications. In this paper, a series of tartaric esters were synthesized and used as phase stabilizers and saturation vapor pressure depressors for methanol-gasoline. Results The results showed that the phase stabilities of tartaric esters for methanol-gasoline depend on the length of the alkoxy group. Several tartaric esters were found to be effective in various gasoline-methanol blends, and the tartaric esters display high capacity to depress the saturation vapor pressure of methanol-gasoline. Conclusion According to the results, it can be concluded that the tartaric esters have great potential to be bifunctional gasoline-methanol additives.

2014-01-01

305

The fabrication of a bifunctional oxygen electrode without carbon components for alkaline secondary batteries  

NASA Astrophysics Data System (ADS)

The fabrication of a gas diffusion electrode (GDE) without carbon components is described. It is therefore suitable for use as a bifunctional oxygen electrode in alkaline secondary batteries. The electrode is fabricated in two stages (a) the formation of a PTFE-bonded nickel powder layer on a nickel foam substrate and (b) the deposition of a NiCo2O4 spinel electrocatalyst layer by dip coating in a nitrate solution and thermal decomposition. The influence of modifications to the procedure on the performance of the GDEs in 8 M NaOH at 333 K is described. The GDEs can support current densities up to 100 mA cm-2 with state-of-the-art overpotentials for both oxygen evolution and oxygen reduction. Stable performance during >50 successive, 1 h oxygen reduction/evolution cycles at a current density of 50 mA cm-2 has been achieved.

Price, Stephen W. T.; Thompson, Stephen J.; Li, Xiaohong; Gorman, Scott F.; Pletcher, Derek; Russell, Andrea E.; Walsh, Frank C.; Wills, Richard G. A.

306

Design and synthesis of new bifunctional sigma-1 selective ligands with antioxidant activity.  

PubMed

Herein we report the synthesis of new bifunctional sigma-1 (?1)-selective ligands with antioxidant activity. To achieve this goal, we combined the structure of lipoic acid, a universal antioxidant, with an appropriate sigma aminic moiety. Ligands 14 and 26 displayed high affinity and selectivity for ?1 receptors (Ki?1 = 1.8 and 5.5 nM; Ki?2/?1 = 354 and 414, respectively). Compound 26 exhibited in vivo antiopioid effects on kappa opioid (KOP) receptor-mediated analgesia. In rat liver and brain mitochondria (RLM, RBM), this compound significantly reduced the swelling and the oxidation of thiol groups induced by calcium ions. Our results demonstrate that the tested compound has protective effects against oxidative stress. PMID:23470245

Prezzavento, O; Arena, E; Parenti, C; Pasquinucci, L; Aricò, G; Scoto, G M; Grancara, S; Toninello, A; Ronsisvalle, S

2013-03-28

307

Quantification of noise in bifunctionality-induced post-translational modification.  

PubMed

We present a generic analytical scheme for the quantification of fluctuations due to bifunctionality-induced signal transduction within the members of a bacterial two-component system. The proposed model takes into account post-translational modifications in terms of elementary phosphotransfer kinetics. Sources of fluctuations due to autophosphorylation, kinase, and phosphatase activity of the sensor kinase have been considered in the model via Langevin equations, which are then solved within the framework of linear noise approximation. The resultant analytical expression of phosphorylated response regulators are then used to quantify the noise profile of biologically motivated single and branched pathways. Enhancement and reduction of noise in terms of extra phosphate outflux and influx, respectively, have been analyzed for the branched system. Furthermore, the role of fluctuations of the network output in the regulation of a promoter with random activation-deactivation dynamics has been analyzed. PMID:24125303

Maity, Alok Kumar; Bandyopadhyay, Arnab; Chattopadhyay, Sudip; Chaudhuri, Jyotipratim Ray; Metzler, Ralf; Chaudhury, Pinaki; Banik, Suman K

2013-09-01

308

Synthesis and luminescence properties of lanthanide complexes with a new aryl amide bifunctional bridging ligand  

NASA Astrophysics Data System (ADS)

A new aryl amide type bifunctional bridging ligand 4,4'-bis{[(2?-benzylaminoformyl)phenoxyl]methyl}-1,1'-biphenyl ( L) and its complexes with lanthanide ions (Ln = Pr, Eu, Gd, Tb, Ho, Er) were synthesized and characterized by elemental analysis, infrared spectra, conductivity measurements and thermal analysis. At the same time, the luminescence properties of the Eu and Tb complexes in acetone solutions were investigated. Under the excitation of UV light, these two complexes exhibited characteristic emission of europium and terbium ions. And the lowest triplet state energy level T 1 of this ligand matches better to the lowest resonance energy level of Tb(III) than to Eu(III) ion.

Song, Yu-Lan; Tang, Yu; Liu, Wei-Sheng; Tan, Min-Yu

2006-06-01

309

"Click" chemistry mildly stabilizes bifunctional gold nanoparticles for sensing and catalysis.  

PubMed

A large family of bifunctional 1,2,3-triazole derivatives that contain both a polyethylene glycol (PEG) chain and another functional fragment (e.g., a polymer, dendron, alcohol, carboxylic acid, allyl, fluorescence dye, redox-robust metal complex, or a ?-cyclodextrin unit) has been synthesized by facile "click" chemistry and mildly coordinated to nanogold particles, thus providing stable water-soluble gold nanoparticles (AuNPs) in the size range 3.0-11.2?nm with various properties and applications. In particular, the sensing properties of these AuNPs are illustrated through the detection of an analogue of a warfare agent (i.e., sulfur mustard) by means of a fluorescence "turn-on" assay, and the catalytic activity of the smallest triazole-AuNPs (core of 3.0?nm) is excellent for the reduction of 4-nitrophenol in water. PMID:24891131

Li, Na; Zhao, Pengxiang; Liu, Na; Echeverria, María; Moya, Sergio; Salmon, Lionel; Ruiz, Jaime; Astruc, Didier

2014-07-01

310

The combined hydrolysis and hydrogenation of inulin catalyzed by bifunctional Ru/C.  

PubMed

A one-pot process for hydrolysis and hydrogenation of inulin to D-mannitol and D-glucitol over a bifunctional Ru/C catalyst was developed. The hydrolysis is catalyzed by the carbon support, onto which acidity was introduced by pre-oxidation. The effect of different carbon treatments on the hydrolysis of inulin was studied. Oxidation with ammonium peroxydisulfate resulted in a carbon with the highest hydrolysis activity. On this carbon, long chain inulin is hydrolyzed faster than inulin rich in short chains. The application of high pressure (up to 100 bar) increased the hydrolysis rate substantially. The combined process was successfully conducted with a Ru-catalyst supported on this oxidized carbon. PMID:11270817

Heinen, A W; Peters, J A; van Bekkum, H

2001-02-15

311

A Surprising Mechanistic "Switch" in Lewis Acid Activation: A Bifunctional, Asymmetric Approach to ?-Hydroxy Acid Derivatives  

PubMed Central

We report a detailed synthetic and mechanistic study of an unusual bifunctional, sequential hetero-Diels–Alder/ring-opening reaction in which chiral, metal complexed ketene enolates react with o-quinones to afford highly enantioenriched, ?-hydroxylated carbonyl derivatives in excellent yield. A number of Lewis acids were screened in tandem with cinchona alkaloid derivatives; surprisingly, trans-(Ph3P)2PdCl2 was found to afford the most dramatic increase in yield and rate of reaction. A series of Lewis acid binding motifs were explored through molecular modeling, as well as IR, UV and NMR spectroscopy. Our observations document a fundamental mechanistic “switch” – namely the formation of a tandem Lewis base/Lewis acid activated metal enolate in preference to a metal-coordinated quinone species (as observed in other reactions of o-quinone derivatives). This new method was applied to the syntheses of several pharmaceutical targets, each of which was obtained in high yield and enantioselectivity.

Abraham, Ciby J.; Paull, Daniel H.; Bekele, Tefsit; Scerba, Michael T.; Dudding, Travis; Lectka, Thomas

2009-01-01

312

Growth and optical characterization of colloidal CdTe nanoparticles capped by a bifunctional molecule  

NASA Astrophysics Data System (ADS)

Thiol-capped CdTe nanoparticles were synthesized in aqueous solution by wet chemical route. CdTe nanoparticles with bifunctional molecule mercaptoacetic acid as a stabilizer were synthesized at pH?11.2 and using potassium tellurite as tellurium source. The effect of refluxing time on the preparation of these samples was measured using UV-vis absorption and photoluminescence analysis. By increasing the refluxing time the UV-vis absorption and photoluminescence results show that the band edge emission is redshifted. The synthesized thiol-capped CdTe were characterized with FT-IR, TEM and TG-DTA. The particle size was calculated by the effective mass approximation (EMA). The role of precursors, their composition, pH and reaction procedure on the development of nanoparticles are analyzed.

Abd El-sadek, M. S.; Moorthy Babu, S.

2010-08-01

313

Use of Raman spectroscopy to evaluate the selectivity of bifunctional anion exchange resins for perchlorate.  

PubMed

Raman spectroscopy is used to evaluate the selectivity of two bifunctional anion exchange resins, Purolite A-530 and Amberlite PWA-2. It was found that the adsorption of anions on the resins is described by a Frumkin isotherm, which is determined by the ion pair constant, K, and the Frumkin parameter, g. The ion pair constant, K, is a measure of the strength of interaction between the resin and the anion and the Frumkin parameter, g, takes into account interactions between adsorbed anions. Although both resins have a polystyrene backbone and trihexylammonium and triethylammonium functional groups, the Purolite A-530 resin exhibits greater selectivity for perchlorate. The only discernable differences between the two resins is that the Amberlite PWA-2 has a higher trihexylamine content and the Purolite A-530 resin exhibits greater cross-linking. How the trihexylamine/triethylamine content and the degree of cross-linking affects the performance of these resins is discussed. PMID:18284790

Mosier-Boss, P A

2008-02-01

314

Pure blue-light emissive poly(oligofluorenes) with bifunctional poss in the main chain.  

PubMed

Emission of conjugated polymers is known to undergo bathochromic shift from solution to film formation due to ?-? stacking in the solid state. In this report, a series of pearl-necklace-like hybrid polymers is designed via the hydrosilylation condensation between bifunctional polyhedral oligomeric silsesquioxanes (B-POSS) and oligofluorene segments. Optoelectronic analyses unequivocally show that the presence of these interconnecting B-POSS can effectively reduce red-shift in photoluminescence and electroluminescence during film formation. These hybrid poly(oligofluorenes) display stable blue emission with high color purity. Thermal analyses also indicate that they are vitrified polymers with high glass transition temperature (up to 125 °C). We believe that this strategy can be extended to other conjugated systems to control color purity in electroactive materials and holds promise as new emissive materials for various applications. PMID:24677615

Chi, Hong; Lim, Siew Lay; Wang, Fuke; Wang, Xizu; He, Chaobin; Chin, Wee Shong

2014-04-01

315

Convenient Synthesis and Evaluation of Heptadentate Bifunctional Ligand for Radioimmunotherapy Applications  

PubMed Central

An efficient synthetic route to a bifunctional chelating agent C-NE3TA-NCS for antibody-targeted radioimmunotherapy (RIT) applications was developed. Various synthetic methods centered on the key reaction steps including bimolecular cyclization, ring opening reactions of aziridine and aziridinium cations, and reductive aminiation were explored to optimize the preparation of a tetraaza-based chelate TANPA and C-NE3TA analogues. Heptadentate C-NE3TA-NCS was conjugated to a tumor targeting antibody and compared to hexadentate C-NOTA-NCS for radiolabeling reaction kinetics with lanthanides for RIT. C-NE3TA-antibody conjugate displayed significantly enhanced complexation kinetics with 90Y as compared to C-NOTA-antibody conjugate. The synthetic methods for TANPA and C-NE3TA-NCS reported herein have broad applications for preparation of bifunctioanl macrocyclic chelating agents.

Chong, Hyun-Soon; Sun, Xiang; Dong, Pengfei; Kang, Chi Soo

2013-01-01

316

Photorefractive properties of bifunctional N-arylated carbazole derivatives in a carbazole polymer host matrix  

NASA Astrophysics Data System (ADS)

We report on the synthesis and the molecular properties of new N-arylated carbazole derivatives that are used as bifunctional chromophores in photorefractive (PR) polymer composites. The C-N bond of the N-aryl carbazole chromophore was formed directly by a nucleophilic aromatic substitution and Ullmann type coupling of carbazole with aryl halides. We performed calculations on the molecular conformation, the magnitude of the dipole moment and the linear polarizability tensor and their relative orientation. The PR performance of the chromophores, doped in an inert polymer host matrix and in a carbazole matrix, with C 60 as sensitizer, was evaluated using four-wave mixing experiments and photoconductivity measurements at 680 nm. The impact of the relative orientation of dipole moment and polarizability tensor on the Figure-Of-Merit (FOM) of photorefractive experiments was clearly demonstrated.

Schaerlaekens, M.; Hendrickx, E.; Hameurlaine, A.; Dehaen, W.; Persoons, A.

2002-03-01

317

Synthesis and characterization of bifunctional oligo-?-aminopyridines and their copper(II) complexes  

Microsoft Academic Search

The synthesis of two new bifunctional oligo-?-aminopyridine ligands, N-(6-{6-[3-(6-amino-pyridin-2-ylamino)-phenylamino]-pyridin-2-ylamino}-pyridin-2-yl)-4-methylbenzenesulfonamide (apppm) and N-(6-{6-[3-(6-bromo-pyridin-2-ylamino)-phenylamino-pyridin-2-yl-amino]-pyridin-2-yl)-4-methylbenzenesulfonamide (bpppm), by double aminated couplings and Pd-catalization is presented in this paper. NaNH2 was used as a critical base in the first step of the aminated coupling for synthesizing the key building block N-(6-bromo-pyridin-2-yl)-pyridine-2,6-diamine (bppd) in 96% yield. Pyridine was then used in the second step of the

Hasanov Hasan; Uan-Kang Tan; Yu-Sheng Lin; Chung-Chou Lee; Gene-Hsiang Lee; Tzu-Wei Lin; Shie-Ming Peng

2003-01-01

318

A novel copper(II) coordination polymer with carboxylate and isoindol backbones of a bifunctional ligand  

NASA Astrophysics Data System (ADS)

The reaction of a bifunctional ligand, 3-(1-oxo-1,3-dihydro-isoindol-2-yl)-propionic acid (Hpda) with Cu(NO3)2?3H2O in methanol-water in the presence of NaOH at room temperature produces a novel dinuclear copper(II) coordination polymer [Cu2(pda)4]n. The complex is fully characterized in the solid state as well as in solution using various analytical techniques including single crystal X-ray diffraction study. The single crystal X-ray structure analysis reveals that the monomeric unit of complex consists of Cu2(O2CR)4 paddlewheel building unit, where the two copper centers acquire a distorted square pyramidal geometry with amide oxygen of the isoindol ring of an adjacent Hpda ligand sitting on the axial positions.

Patra, Ayan; Sen, Tamal K.; Musie, Ghezai T.; Mandal, Swadhin K.; Bera, Manindranath

2013-09-01

319

Bifunctional nanoparticles for SERS monitoring and magnetic intervention of assembly and enzyme cutting of DNAs  

SciTech Connect

The ability to detect and intervene in DNA assembly, disassembly, and enzyme cutting processes in a solution phase requires effective signal transduction and stimulus response. This report demonstrates a novel bifunctional strategy for the creation of this ability using gold- and silver-coated MnZn ferrite nanoparticles (MZF@Au or MZF@Ag) that impart magnetic and surfaceenhanced Raman scattering (SERS) functionalities to these processes. The double-stranded DNA linkage of labeled gold nanoparticles with MZF@Au (or MZF@Ag) produces interparticle "hot-spots" for real-time SERS monitoring of the DNA assembly, disassembly, or enzyme cutting processes, during which the magnetic component provides an effective means for intervention in the solution. The unique combination of the nanoprobes functionalities serves a new paradigm for the design of functional nanoprobes in biomolecular recognition and intervention.

Lin, Liqin; Crew, Elizabeth; Yan, Hong; Shan, Shiyao; Skeete, Zakiya; Mott, Derrick; Krentsel, Tatiana; Yin, Jun; Chernova, Natasha A.; Luo, Jin; Engelhard, Mark H.; Wang, Chong M.; Li, Qingbiao; Zhong, Chuan-Jian

2013-07-27

320

Quantification of noise in bifunctionality-induced post-translational modification  

NASA Astrophysics Data System (ADS)

We present a generic analytical scheme for the quantification of fluctuations due to bifunctionality-induced signal transduction within the members of a bacterial two-component system. The proposed model takes into account post-translational modifications in terms of elementary phosphotransfer kinetics. Sources of fluctuations due to autophosphorylation, kinase, and phosphatase activity of the sensor kinase have been considered in the model via Langevin equations, which are then solved within the framework of linear noise approximation. The resultant analytical expression of phosphorylated response regulators are then used to quantify the noise profile of biologically motivated single and branched pathways. Enhancement and reduction of noise in terms of extra phosphate outflux and influx, respectively, have been analyzed for the branched system. Furthermore, the role of fluctuations of the network output in the regulation of a promoter with random activation-deactivation dynamics has been analyzed.

Maity, Alok Kumar; Bandyopadhyay, Arnab; Chattopadhyay, Sudip; Chaudhuri, Jyotipratim Ray; Metzler, Ralf; Chaudhury, Pinaki; Banik, Suman K.

2013-09-01

321

Hydrostatic liquid-bearing for precision gyro  

NASA Technical Reports Server (NTRS)

Unit with 2W power increase and slightly larger overall dimensions performs as well as or better than its gas-bearing counterpart. Liquid-bearings are built by reworking serviceable gas-bearing components /sleeves, endplates, and cylinders/. Hydrostatic bearing is self-centered, requiring no magnetic suspension or centering jewel.

Sgambati, R. J.

1971-01-01

322

Wear Resistance of Polyformaldehyde in Sleeve Bearings.  

National Technical Information Service (NTIS)

Tests showed, that sleeve bearings made of PFA are 3-4 times more wear resistant than caprone bearings, and 1.5 to 2 times than ceramet bushings and bearings. PFA bearings retain stability of dimensions and assure reliable operation of friction units.

V. N. Kestelman D. I. Feldman N. Y. Kestelman

1965-01-01

323

Liquid oxygen cooled bearing ignition potential assessment  

NASA Technical Reports Server (NTRS)

Space Shuttle Main Engine High Pressure Oxygen Turbopump bearings have shown evidence of heavy oxidation on the surfaces of the balls and races. Extensive analyses were performed to assess the ignition potential in the bearing system during normal and off-nominal operation. Test programs and analyses were used to determine the bearing thermal condition and bearing material ignition characteristics.

Page, Arthur T.; Goode, Brian K.; Owen, James W.

1990-01-01

324

Laser measurements in the motor bearing diagnostics  

Microsoft Academic Search

A b s t r a c t - Statistics say that bearings are this part of indu ction motors which is most susceptible to damage. That is why the issues connected with diagn ostics of bearings are so important. The equipment employed for bearing diagnostics usually makes use of vibrations as the criterion for technical condition of the bearings.

Ariel Dzwonkowski; Leon Sw

325

Dimerization and bifunctionality confer robustness to the isocitrate dehydrogenase regulatory system in Escherichia coli.  

PubMed

An important goal of systems biology is to develop quantitative models that explain how specific molecular features give rise to systems-level properties. Metabolic and regulatory pathways that contain multifunctional proteins are especially interesting to study from this perspective because they have frequently been observed to exhibit robustness: the ability for a system to perform its proper function even as levels of its components change. In this study, we use extensive biochemical data and algebraic modeling to develop and analyze a model that shows how robust behavior arises in the isocitrate dehydrogenase (IDH) regulatory system of Escherichia coli, which was shown in 1985 to experimentally exhibit robustness. E. coli IDH is regulated by reversible phosphorylation catalyzed by the bifunctional isocitrate dehydrogenase kinase/phosphatase (IDHKP), and the level of IDH activity determines whether carbon flux is directed through the glyoxylate bypass (for growth on two-carbon substrates) or the full tricarboxylic acid cycle. Our model, which incorporates recent structural data on IDHKP, identifies several specific biochemical features of the system (including homodimerization of IDH and bifunctionality of IDHKP) that provide a potential explanation for robustness. Using algebraic techniques, we derive an invariant that summarizes the steady-state relationship between the phospho-forms of IDH. We use the invariant in combination with kinetic data on IDHKP to calculate IDH activity at a range of total IDH levels and find that our model predicts robustness. Our work unifies much of the known biochemistry of the IDH regulatory system into a single quantitative framework and highlights the importance of constructing biochemically realistic models in systems biology. PMID:23192354

Dexter, Joseph P; Gunawardena, Jeremy

2013-02-22

326

Cyclic RGD peptidomimetics containing bifunctional diketopiperazine scaffolds as new potent integrin ligands.  

PubMed

The synthesis of eight bifunctional diketopiperazine (DKP) scaffolds is described; these were formally derived from 2,3-diaminopropionic acid and aspartic acid (DKP-1-DKP-7) or glutamic acid (DKP-8) and feature an amine and a carboxylic acid functional group. The scaffolds differ in the configuration at the two stereocenters and the substitution at the diketopiperazinic nitrogen atoms. The bifunctional diketopiperazines were introduced into eight cyclic peptidomimetics containing the Arg-Gly-Asp (RGD) sequence. The resulting RGD peptidomimetics were screened for their ability to inhibit biotinylated vitronectin binding to the purified integrins ?(v)?(3) and ?(v)?(5), which are involved in tumor angiogenesis. Nanomolar IC(50) values were obtained for the RGD peptidomimetics derived from trans DKP scaffolds (DKP-2-DKP-8). Conformational studies of the cyclic RGD peptidomimetics by (1)H?NMR spectroscopy experiments (VT-NMR and NOESY spectroscopy) in aqueous solution and Monte Carlo/Stochastic Dynamics (MC/SD) simulations revealed that the highest affinity ligands display well-defined preferred conformations featuring intramolecular hydrogen-bonded turn motifs and an extended arrangement of the RGD sequence [C?(Arg)-C?(Asp) average distance ?8.8?Å]. Docking studies were performed, starting from the representative conformations obtained from the MC/SD simulations and taking as a reference model the crystal structure of the extracellular segment of integrin ?(v)?(3) complexed with the cyclic pentapeptide, Cilengitide. The highest affinity ligands produced top-ranked poses conserving all the important interactions of the X-ray complex. PMID:22517378

Marchini, Mattia; Mingozzi, Michele; Colombo, Raffaele; Guzzetti, Ileana; Belvisi, Laura; Vasile, Francesca; Potenza, Donatella; Piarulli, Umberto; Arosio, Daniela; Gennari, Cesare

2012-05-14

327

Proteasome inhibitors act as bifunctional antagonists of human immunodeficiency virus type 1 latency and replication  

PubMed Central

Background Existing highly active antiretroviral therapy (HAART) effectively controls viral replication in human immunodeficiency virus type 1 (HIV-1) infected individuals but cannot completely eradicate the infection, at least in part due to the persistence of latently infected cells. One strategy that is being actively pursued to eliminate the latent aspect of HIV-1 infection involves therapies combining latency antagonists with HAART. However, discordant pharmacokinetics between these types of drugs can potentially create sites of active viral replication within certain tissues that might be impervious to HAART. Results A preliminary reverse genetic screen indicated that the proteasome might be involved in the maintenance of the latent state. This prompted testing to determine the effects of proteasome inhibitors (PIs) on latently infected cells. Experiments demonstrated that PIs effectively activated latent HIV-1 in several model systems, including primary T cell models, thereby defining PIs as a new class of HIV-1 latency antagonists. Expanding upon experiments from previous reports, it was also confirmed that PIs inhibit viral replication. Moreover, it was possible to show that PIs act as bifunctional antagonists of HIV-1. The data indicate that PIs activate latent provirus and subsequently decrease viral titers and promote the production of defective virions from activated cells. Conclusions These results represent a proof-of-concept that bifunctional antagonists of HIV-1 can be developed and have the capacity to ensure precise tissue overlap of anti-latency and anti-replication functions, which is of significant importance in the consideration of future drug therapies aimed at viral clearance.

2013-01-01

328

Carbon dioxide fixation: bifunctional complexes containing acidic and basic sites working as reversible carriers  

SciTech Connect

Carbon dioxide fixation in its intact form is achieved from ''bifunctional'' complexes containing in their structure a nucleophilic cobalt(I) and an alkali cation: Co(R-salen)M (R-salen = substituted salen ligand; salen = N,N'-ethylenebis(salicylideneaminato); M = Li, Na, K, Cs). The fixation of CO/sub 2/ by such systems displays different degrees of reversibility depending on the reaction solvent and the nature of the alkali cation. The X-ray analysis carried out on (Co(n-Pr-salen)K-(CO)/sub 2/(THF)) shows carbon dioxide anchored to the cobalt through a Co-C sigma bond, while the oxygens interact with the alkali cation, in a polymeric structure. IR spectra are diagnostic for the presence of CO/sub 2/ bonded as a bent molecule in a reduced form displaying three strong bands in the following ranges: 1700-1650, 1300-1250, and 1250-1200 cm/sup -1/. The binding of CO/sub 2/ is partially prevented in the presence of a crown ether, which can complex the alkali cation. The reaction of (Co(salen)Na(CO/sub 2/)) and (Co(salen)Na(THF)) with dicyclohexano-18 crown-6(DCHC) gave a complex, (Co(salen)Na)/sub 2/(DCHC), whose structure shows the presence of the intact bifunctional unit where, however, all the coordination sites around the alkali cation are filled by the oxygens from salen and DCHC and are not further available for binding the oxygen atoms of the CO/sub 2/ molecule. Crystallographic details and the final R factor for specific observed reflections are given for (Co(n-Pr-salen)K(CO/sub 2/)(THF))/sub n/, (CO(n-Pr-salen)K(CO/sub 2/)(THF))/sub n/, (Co(salen)Na)/sub 2/(DCHC).

Gambarotta, S. (Universita' di Pisa, Italy); Arena, F., Zanazzi, P.

1982-09-22

329

Space Shuttle Body Flap Actuator Bearing Testing For NASA Return to Flight  

NASA Technical Reports Server (NTRS)

The Space Shuttle body flap is located beneath the main engine nozzles and is required for proper aerodynamic control during orbital descent. Routine inspection of one of four body flap actuatols found one of the actuator bearings had degraded and blackened balls. A test program was initiated to demonstrate that it is acceptable to operate bearings which are degraded from operation over several flights. This test exposed the bearing to predicted flight axial loads, speeds and temperatures. Testing has been completed, and results indicate the previously flown bearings are acceptable for up to 12 additional missions.

Jett, Timothy R.; Thom, Robert L.; Moore, Lewis E.; Gibson, Howard G.; Hall, Phillip B.; Predmore, Roamer E.

2005-01-01

330

Hydrostatic bearings for a turbine fluid flow metering device  

Microsoft Academic Search

A rotor assembly fluid metering device has been improved by development of a hydrostatic bearing fluid system which provides bearing fluid at a common pressure to rotor assembly bearing surfaces. The bearing fluid distribution system produces a uniform film of fluid between bearing surfaces and allows rapid replacement of bearing fluid between bearing surfaces, thereby minimizing bearing wear and corrosion.

Fincke

1982-01-01

331

Hydrostatic bearings for a turbine fluid flow metering device  

DOEpatents

A rotor assembly fluid metering device has been improved by development of a hydrostatic bearing fluid system which provides bearing fluid at a common pressure to rotor assembly bearing surfaces. The bearing fluid distribution system produces a uniform film of fluid between bearing surfaces and allows rapid replacement of bearing fluid between bearing surfaces, thereby minimizing bearing wear and corrosion. 3 figs.

Fincke, J.R.

1982-05-04

332

Ball Bearings Equipped for In Situ Lubrication on Demand  

NASA Technical Reports Server (NTRS)

In situ systems that provide fresh lubricants to ball/race contacts on demand have been developed to prolong the operational lives of ball bearings. These systems were originally intended to be incorporated into ball bearings in mechanisms that are required to operate in outer space for years, in conditions in which lubricants tend to deteriorate and/or evaporate. These systems may also be useful for similarly prolonging bearing lifetimes on Earth. Reservoirs have been among the means used previously to resupply lubricants. Lubricant- resupply reservoirs are bulky and add complexity to bearing assemblies. In addition, such a reservoir cannot be turned on or off as needed: it supplies lubricant continuously, often leading to an excess of lubricant in the bearing. A lubricator of the present type includes a porous ring cartridge attached to the inner or the outer ring of a ball bearing (see Figure 1). Oil is stored in the porous cartridge and is released by heating the cartridge: Because the thermal expansion of the oil exceeds that of the cartridge, heating causes the ejection of some oil. A metal film can be deposited on a face of the cartridge to serve as an electrical-resistance heater. The heater can be activated in response to a measured increase in torque that signals depletion of oil from the bearing/race contacts. Because the oil has low surface tension and readily wets the bearing-ring material, it spreads over the bearing ring and eventually reaches the ball/race contacts. The Marangoni effect (a surface-tension gradient associated with a temperature gradient) is utilized to enhance the desired transfer of lubricant to the ball/race contacts during heating. For a test, a ball bearing designed for use at low speed was assembled without lubricant and equipped with a porous-ring lubricator, the resistance heater of which consumed a power of less than 1 W when triggered on by a torque-measuring device. In the test, a load of 20 lb (.89 N) was applied and the bearing was turned at a rate of 200 RPM. The lubricator control was turned on at the beginning of the test, turned off for about 800 seconds, then turned on again. As shown in Figure 2, the controlled lubricator stabilized the torque in a low range, starting immediately after initial turn-on and immediately after resumption of the lubricator control.

Marchetti, Mario; Jones, William R., Jr.; Pepper, Stephen V.; Jansen, Mark; Predmore, Roamer

2005-01-01

333

Cryogenic Magnetic Bearing Test Facility (CMBTF)  

NASA Technical Reports Server (NTRS)

The Cryogenic Magnetic Bearing Test Facility (CMBTF) was designed and built to evaluate compact, lightweight magnetic bearings for use in the SSME's (space shuttle main engine) liquid oxygen and liquid hydrogen turbopumps. State of the art and tradeoff studies were conducted which indicated that a hybrid permanent magnet bias homopolar magnetic bearing design would be smaller, lighter, and much more efficient than conventional industrial bearings. A test bearing of this type was designed for the test rig for use at both room temperature and cryogenic temperature (-320 F). The bearing was fabricated from state-of-the-art materials and incorporated into the CMBTF. Testing at room temperature was accomplished at Avcon's facility. These preliminary tests indicated that this magnetic bearing is a feasible alternative to older bearing technologies. Analyses showed that the hybrid magnetic bearing is one-third the weight, considerably smaller, and uses less power than previous generations of magnetic bearings.

1992-01-01

334

Wave journal bearing with compressible lubricant--Part 1: The wave bearing concept and a comparison to the plain circular bearing  

Microsoft Academic Search

To improve hydrodynamic journal bearing steady-state and dynamic performance, a new bearing concept, the wave journal bearing, was developed at the author's lab. This concept features a waved inner bearing diameter. Compared to other alternative bearing geometries used to improve bearing performance such as spiral or herring-bone grooves, steps, etc., the wave bearing's design is relatively simple and allows the

Florin Dimofte

1995-01-01

335

A Fatigue Life Comparison of Two-Row Tapered Roller Bearings and Spherical Roller Bearings  

Microsoft Academic Search

Tests were run to compare the fatigue life of two-row tapered roller bearings to that of spherical roller bearings. Both bearing types had an outer diameter of 110 mm with the spherical roller bearing having a 22 percent larger dynamic radial load rating than the tapered roller bearings. All tests were run at 165 percent of the respective two-row dynamic

Harry Zantopulos; Joel Z. Russell

1999-01-01

336

Magnetic bearings with zero bias  

NASA Technical Reports Server (NTRS)

A magnetic bearing operating without a bias field has supported a shaft rotating at speeds up to 12,000 rpm with the usual four power supplies and with only two. A magnetic bearing is commonly operated with a bias current equal to half of the maximum current allowable in its coils. This linearizes the relation between net force and control current and improves the force slewing rate and hence the band width. The steady bias current dissipates power, even when no force is required from the bearing. The power wasted is equal to two-thirds of the power at maximum force output. Examined here is the zero bias idea. The advantages and disadvantages are noted.

Brown, Gerald V.; Grodsinsky, Carlos M.

1991-01-01

337

Detection of amyloid plaques targeted by bifunctional USPIO in Alzheimer's disease transgenic mice using magnetic resonance microimaging.  

PubMed

Amyloid plaques are a key pathological hallmark of Alzheimer's disease (AD). The detection of amyloid plaques in the brain is important for the diagnosis of AD, as well as for following potential amyloid targeting therapeutic interventions. Our group has developed several contrast agents to detect amyloid plaques in vivo using magnetic resonance microimaging (µMRI) in AD transgenic mice, where we used mannitol to enhance blood brain barrier (BBB) permeability. In the present study, we used bifunctional ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles, chemically coupled with A?1-42 peptide to image amyloid plaque deposition in the mouse brain. We coupled the nanoparticles to polyethylene glycol (PEG) in order to improve BBB permeability. These USPIO-PEG-A?1-42 nanoparticles were injected intravenously in AD model transgenic mice followed by initial in vivo and subsequent ex vivo ?MRI. A 3D gradient multi-echo sequence was used for imaging with a 100 µm isotropic resolution. The amyloid plaques detected by T2*-weighted ?MRI were confirmed with matched histological sections. The region of interest-based quantitative measurement of T2* values obtained from the in vivo ?MRI showed contrast injected AD Tg mice had significantly reduced T2* values compared to wild-type mice. In addition, the ex vivo scans were examined with voxel-based analysis (VBA) using statistical parametric mapping (SPM) for comparison of USPIO-PEG-A?1-42 injected AD transgenic and USPIO alone injected AD transgenic mice. The regional differences seen by VBA in the USPIO-PEG-A?1-42 injected AD transgenic correlated with the amyloid plaque distribution histologically. Our results indicate that USPIO-PEG-A?1-42 can be used for amyloid plaque detection in vivo by intravenous injection without the need to co-inject an agent which increases permeability of the BBB. This technique could aid the development of novel amyloid targeting drugs by allowing therapeutic effects to be followed longitudinally in model AD mice. PMID:23468919

Wadghiri, Youssef Zaim; Li, Jialin; Wang, Jinhuan; Hoang, Dung Minh; Sun, Yanjie; Xu, Hong; Tsui, Wai; Li, Yongsheng; Boutajangout, Allal; Wang, Andrew; de Leon, Mony; Wisniewski, Thomas

2013-01-01

338

Space Shuttle Body Flap Actuator Bearing Testing for NASA Return to Flight  

NASA Technical Reports Server (NTRS)

The Space Shuttle body flap is located beneath the main engine nozzles and is required for proper aerodynamic control during orbital descent. Routine inspection of one of four body flap actuators found one of the actuator bearings had degraded and blackened balls. A test program was initiated to demonstrate that it is acceptable to operate bearings which are degraded from operation over several flights. This test exposed the bearing to predicted flight axial loads, speeds and temperatures. Testing at 140 F has been completed, and results indicate the previously flown bearings are acceptable for up to 12 additional missions. Additional testing is underway to determine the lubricant life at various temperatures and stresses and to further understand the mechanism that caused the blacken balls. Initial results of this testing indicates that bearing life is shorten at room temperature possibly due fact that higher temperature (140 F) accelerates the flow of grease and oil into the wear surface

Jett, Timothy R.; Predmore, Roamer E.; Dube, Michael J.; Jones, William R., Jr.

2006-01-01

339

The Optimum Design of Hydrodynamic Lubrication Bearing for Minimization of the Total Life Cost  

NASA Astrophysics Data System (ADS)

This paper proposes an optimum design method of journal bearing for minimizing the total life cost which includes not only the initial cost but also the running cost. Journal bearing is one of the typical friction part and physically severe part in machine elements. Therefore, maintenance is required to prevent failure and to keep performance. For this object, the running cost by the maintenance is user's burden. Thus, the optimum design method of the bearing for minimization of the total life cost is required. In this research, the evaluation functions of the total life cost which contains the initial cost and the running cost of the bearing are discussed and the optimum design is proposed under the physical constrain, that is Thermo Hydrodynamic Lubrication theory (THL theory), and inequality constraints. Then design valuables of the optimum journal bearing are obtained.

Iwatsubo, Takuzo; Yamabayashi, Jun

340

Wave journal bearing. Part 1: Analysis  

NASA Technical Reports Server (NTRS)

A wave journal bearing concept features a waved inner bearing diameter of the non-rotating bearing side and it is an alternative to the plain journal bearing. The wave journal bearing has a significantly increased load capacity in comparison to the plain journal bearing operating at the same eccentricity. It also offers greater stability than the plain circular bearing under all operating conditions. The wave bearing's design is relatively simple and allows the shaft to rotate in either direction. Three wave bearings are sensitive to the direction of an applied stationary side load. Increasing the number of waves reduces the wave bearing's sensitivity to the direction of the applied load relative to the wave. However, the range in which the bearing performance can be varied decreases as the number of waves increases. Therefore, both the number and the amplitude of the waves must be properly selected to optimize the wave bearing design for a specific application. It is concluded that the stiffness of an air journal bearing, due to hydrodynamic effect, could be doubled and made to run stably by using a six or eight wave geometry with a wave amplitude approximately half of the bearing radial clearance.

Dimofte, Florin

1995-01-01

341

Nonlinear dynamics of attractive magnetic bearings  

NASA Technical Reports Server (NTRS)

The nonlinear dynamics of a ferromagnetic shaft suspended by the force of attraction of 1, 2, or 4 independent electromagnets is presented. Each model includes a state variable feedback controller which has been designed using the pole placement method. The constitutive relationships for the magnets are derived analytically from magnetic circuit theory, and the effects of induced eddy currents due to the rotation of the journal are included using Maxwell's field relations. A rotor suspended by four electro-magnets with closed loop feedback is shown to have nine equilibrium points within the bearing clearance space. As the rotor spin speed increases, the system is shown to pass through a Hopf bifurcation (a flutter instability). Using center manifold theory, this bifurcation can be shown to be of the subcritical type, indicating an unstable limit cycle below the critical speed. The bearing is very sensitive to initial conditions, and the equilibrium position is easily upset by transient excitation. The results are confirmed by numerical simulation.

Hebbale, K. V.; Taylor, D. L.

1987-01-01

342

Spinel mn-co oxide in N-doped carbon nanotubes as a bifunctional electrocatalyst synthesized by oxidative cutting.  

PubMed

The notorious instability of non-precious-metal catalysts for oxygen reduction and evolution is by far the single unresolved impediment for their practical applications. We have designed highly stable and active bifunctional catalysts for reversible oxygen electrodes by oxidative thermal scission, where we concurrently rupture nitrogen-doped carbon nanotubes and oxidize Co and Mn nanoparticles buried inside them to form spinel Mn-Co oxide nanoparticles partially embedded in the nanotubes. Impressively high dual activity for oxygen reduction and evolution is achieved using these catalysts, surpassing those of Pt/C, RuO2, and IrO2 and thus raising the prospect of functional low-cost, non-precious-metal bifunctional catalysts in metal-air batteries and reversible fuel cells, among others, for a sustainable and green energy future. PMID:24815686

Zhao, Anqi; Masa, Justus; Xia, Wei; Maljusch, Artjom; Willinger, Marc-Georg; Clavel, Guylhaine; Xie, Kunpeng; Schlögl, Robert; Schuhmann, Wolfgang; Muhler, Martin

2014-05-28

343

Crystal structure of CelM2, a bifunctional glucanase-xylanase protein from a metagenome library.  

PubMed

Degradation of polysaccharides by cellulases and xylanases plays an important role in the carbon cycle, but only occurs in plant cell walls, a few bacteria and some animals. This process is also critical in processes such as biomass degradation and fuel production in the conversion cycles of cellulosic biomass. The enzyme CelM2 is bifunctional, because it is able to effectively hydrolyze barley glucan and xylan. Here, we show the crystal structure of the bifunctional enzyme CelM2, isolated from a metagenome library, and describe the sequence information and structure of its two domains. We believe that CelM2 is attractive as an industrial enzyme and that the structural results presented herein provide insights that are relevant to the genetic engineering of multifunctional enzymes. PMID:19345197

Nam, Ki Hyun; Kim, Soo-Jin; Hwang, Kwang Yeon

2009-05-29

344

Metal-on-metal bearings: the problem is edge-loading wear.  

PubMed

Metal-on-metal bearings are promoted as a low wear bearing alternative to traditional hip replacement bearings. While most in vitro studies support this, recent clinical reviews have found a significant number of early revisions in some designs of metal-on-metal bearings related to wear. Metal-on-metal bearings exhibit a bi-phasic wear pattern with high initial wear that generally settles down to low steady state wear. Previous publications from the authors have found that steady state wear occurs due to the formation of a critical conforming contact area. This contact area was found to be surprisingly constant regardless of bearing size, clearance, or even contact mode. The authors hypothesized that steady state wear may never be reached if formation of this critical conforming contact area is disrupted. Several hip simulator tests were performed to assess the wear performance of generic metal-on-metal samples at various angles of inclination. Three-dimensional modeling was performed on the generic bearing design as well as typical resurfacing and hemispherical bearing designs including various sizes and clearance ranges. Simulator results support the hypotheses, and wear rates were linear or accelerating when the critical contact area size could not be achieved due to its proximity to the rim of the bearing. Modeling studies show a correlation between bearing size and design and the maximum inclination angle allowed to reach steady state conditions. Smaller bearing size and shallower cup designs were found to reduce the maximum safe inclination angle and this corresponds to clinical observation of increased failure rates in these bearings. This simple method for assessing runaway wear risk can be utilized in the design of more robust and forgiving metal-on-metal bearings. PMID:21082578

Lee, Reginald K; Longaray, Jason; Essner, Aaron; Wang, Aiguo

2010-10-01

345

The HtrA/DegP family protease MamE is a bifunctional protein with roles in magnetosome protein localization and magnetite biomineralization  

PubMed Central

Summary Magnetotactic bacteria contain nanometer-sized, membrane-bound organelles, called magnetosomes, which are tasked with the biomineralization of small crystals of the iron oxide magnetite allowing the organism to use geomagnetic field lines for navigation. A key player in this process is the HtrA/DegP family protease MamE. In its absence, Magnetospirillum magneticum str AMB-1 is able to form magnetosome membranes but not magnetite crystals, a defect previously linked to the mislocalization of magnetosome proteins. In this work we use a directed genetic approach to find that MamE, and another predicted magnetosome-associated protease, MamO, likely function as proteases in vivo. However, as opposed to the complete loss of mamE where no biomineralization is observed, the protease-deficient variant of this protein still supports the initiation and formation of small, 20 nm-sized crystals of magnetite, too small to hold a permanent magnetic dipole moment. This analysis also reveals that MamE is a bifunctional protein with a protease-independent role in magnetosome protein localization and a protease-dependent role in maturation of small magnetite crystals. Together these results imply the existence of a previously unrecognized “checkpoint” in biomineralization where MamE moderates the completion of magnetite formation and thus committal to magneto-aerotaxis as the organism’s dominant mode of navigating the environment.

Quinlan, Anna; Murat, Dorothee; Vali, Hojatollah; Komeili, Arash

2011-01-01

346

The cbiS Gene of the Archaeon Methanopyrus kandleri AV19 Encodes a Bifunctional Enzyme with Adenosylcobinamide Amidohydrolase and ?-Ribazole-Phosphate Phosphatase Activities  

PubMed Central

Here we report the initial biochemical characterization of the bifunctional ?-ribazole-P (?-RP) phosphatase, adenosylcobinamide (AdoCbi) amidohydrolase CbiS enzyme from the hyperthermophilic methanogenic archaeon Methanopyrus kandleri AV19. The cbiS gene encodes a 39-kDa protein with two distinct segments, one of which is homologous to the AdoCbi amidohydrolase (CbiZ, EC 3.5.1.90) enzyme and the other of which is homologous to the recently discovered archaeal ?-RP phosphatase (CobZ, EC 3.1.3.73) enzyme. CbiS function restored AdoCbi salvaging and ?-RP phosphatase activity in strains of the bacterium Salmonella enterica where either step was blocked. The two halves of the cbiS genes retained their function in vivo when they were cloned separately. The CbiS enzyme was overproduced in Escherichia coli and was isolated to >95% homogeneity. High-performance liquid chromatography, UV-visible spectroscopy, and mass spectroscopy established ?-ribazole and cobyric acid as the products of the phosphatase and amidohydrolase reactions, respectively. Reasons why the CbiZ and CobZ enzymes are fused in some archaea are discussed.

Woodson, Jesse D.; Escalante-Semerena, Jorge C.

2006-01-01

347

A novel bifunctional histone protein in Streptomyces: a candidate for structural coupling between DNA conformation and transcription during development and stress?  

PubMed

Antibiotic-producing Streptomyces are complex bacteria that remodel global transcription patterns and their nucleoids during development. Here, we describe a novel developmentally regulated nucleoid-associated protein, DdbA, of the genus that consists of an N-terminal DNA-binding histone H1-like domain and a C-terminal DksA-like domain that can potentially modulate RNA polymerase activity in conjunction with ppGpp. Owing to its N-terminal domain, the protein can efficiently bind and condense DNA in vitro. Loss of function of this DNA-binding protein results in changes in both DNA condensation during development and the ability to adjust DNA supercoiling in response to osmotic stress. Initial analysis of the DksA-like activity of DdbA indicates that overexpression of the protein suppresses a conditional deficiency in antibiotic production of relA mutants that are unable to synthesise ppGpp, just as DksA overexpression in Escherichia coli can suppress ppGpp(0) phenotypes. The null mutant is also sensitive to oxidative stress owing to impaired upregulation of transcription of sigR, encoding an alternative sigma factor. Consequently, we propose this bifunctional histone-like protein as a candidate that could structurally couple changes in DNA conformation and transcription during the streptomycete life-cycle and in response to stress. PMID:23525459

Aldridge, Matthew; Facey, Paul; Francis, Lewis; Bayliss, Sion; Del Sol, Ricardo; Dyson, Paul

2013-05-01

348

Gas bearings for gas lasers  

Microsoft Academic Search

This patent describes a long-life transverse electric discharge laser assembly. It comprises: a housing for containing an excimer laser gas; means for electrically exciting the laser gas within the housing; means for circulating the laser gas within the housing; and gas bearings including means for supporting the circulating means on a cushion of laser gas to reduce friction and to

G. A. Murray; R. A. Golobic; S. G. Derrickson

1990-01-01

349

Intelligent Engine Systems: Bearing System  

NASA Technical Reports Server (NTRS)

The overall requirements necessary for sensing bearing distress and the related criteria to select a particular rotating sensor were established during the phase I. The current phase II efforts performed studies to evaluate the Robustness and Durability Enhancement of the rotating sensors, and to design, and develop the Built-in Telemetry System concepts for an aircraft engine differential sump. A generic test vehicle that can test the proposed bearing diagnostic system was designed, developed, and built. The Timken Company, who also assisted with testing the GE concept of using rotating sensors for the differential bearing diagnostics during previous phase, was selected as a subcontractor to assist General Electric (GE) for the design, and procurement of the test vehicle. A purchase order was prepared to define the different sub-tasks, and deliverables for this task. The University of Akron was selected to provide the necessary support for installing, and integrating the test vehicle with their newly designed test facility capable of simulating the operating environment for the planned testing. The planned testing with good and damaged bearings will be on hold pending further continuation of this effort during next phase.

Singh, Arnant P.

2008-01-01

350

Plain Facts About Plain Bearings.  

National Technical Information Service (NTIS)

This citation summarizes a one-page announcement of technology available for utilization. A special report has been prepared as a concise, practical, easy-to-read guide for anyone with an interest in or need for plain bearings. It begins with a brief hist...

1982-01-01

351

Bradycardia of the Polar Bear.  

National Technical Information Service (NTIS)

For several years two male polar bears have been studied by long-life implanted physiological radio capsules at the Naval Arctic Research Laboratory, at Point Barrow. A regular measurement has been the resting heart rate; for this we used the lowest heart...

G. E. Folk J. J. Berberich D. K. Sanders

1973-01-01

352

Tardigrades: Bears of the Moss  

NSDL National Science Digital Library

This online PowerPoint presentation is dedicated to the phylum Tardigrada. It discusses distinguishing characteristics of Tardigrades (also known as water bears), their relationship to arthropods and nematodes, internal structures, life stages, cryptobiosis, research opportunities, classification, identification, habitat, distribution, ease of study in the lab, and more. Each slide contains illustrations and descriptions of the microscopic animal.

Miller, William; College, Southwestern

353

Fuzzy control of magnetic bearings  

NASA Technical Reports Server (NTRS)

The use of an adaptive fuzzy control algorithm implemented on a VLSI chip for the control of a magnetic bearing was considered. The architecture of the adaptive fuzzy controller is similar to that of a neural network. The performance of the fuzzy controller is compared to that of a conventional controller by computer simulation.

Feeley, J. J.; Niederauer, G. M.; Ahlstrom, D. J.

1991-01-01

354

High performance rolling element bearing  

NASA Technical Reports Server (NTRS)

A high performance rolling element bearing (5) which is particularly suitable for use in a cryogenically cooled environment, comprises a composite cage (45) formed from glass fibers disposed in a solid lubricant matrix of a fluorocarbon polymer. The cage includes inserts (50) formed from a mixture of a soft metal and a solid lubricant such as a fluorocarbon polymer.

Bursey, Jr., Roger W. (Inventor); Olinger, Jr., John B. (Inventor); Owen, Samuel S. (Inventor); Poole, William E. (Inventor); Haluck, David A. (Inventor)

1993-01-01

355

Hyperthermia Enhances Localization ofInIn-labeled Hapten to Bifunctional Antibody in Human Colon Tumor Xenografts1  

Microsoft Academic Search

A unique bifunctional antibody (BKA) delivery system was examined for radiolocalization and distribution following hyperthermia (41.5°C, 45 min) of T380h human colon tumor xcnografts. The UFA is an F(ab')2 fragment made by combining two murine monoclonal antibodies with different specificities, one directed against carcinoembryonic antigen (monoclonal antibody MM 231) and the other (monoclonal antibody CHA 255) against a hapten found

Daila S. Gridlcy; Karen L. Ewart; Jeffrey D. Cao; Dwight R. Stickney

356

Enhanced uptake of porous silica microparticles by bifunctional surface modification with a targeting antibody and a biocompatible polymer.  

PubMed

Strategies were developed by which mesoporous microparticles were modified on their external surfaces with tetraethylene glycol (TEG), a protein, or both, leaving the pore surfaces available for modification with a separate moiety, such as a dye. Only particles bifunctionally modified with both TEG and a cell-specific antibody were taken up specifically by a targeted cancer cell line. In contrast to similarly functionalized nanoparticles, endocytosed microparticles were not contained within a lysosome. PMID:20707315

Cheng, Kai; Blumen, Steven R; MacPherson, Maximilian B; Steinbacher, Jeremy L; Mossman, Brooke T; Landry, Christopher C

2010-09-01

357

Synthesis and characterization of a bifunctional amido-thiophene monomer and its copolymer with thiophene and electrochemical properties  

Microsoft Academic Search

A bifunctional amido-thiophene namely hexamethylene (bis-3-thiophene acetamide) (HMTA) was synthesized by the reaction of 3-thiophene acetic acid with hexamethylene diamine. Copolymerization in the presence of thiophene was achieved electrochemically in tetrabutylammonium tetrafluoroborate\\/acetonitrile (TBAFB\\/AN). Spectroelectrochemical analysis of the resulting copolymer [P(HMTA-co-Th)] reflected electronic transitions at 505nm, 740nm and ?1000nm, revealing ? to ?* transition, polaron and bipolaron band formation respectively. Switching

Metin Ak; Ali Cirpan; Faruk Y?lmaz; Levent Toppare

2005-01-01

358

Deferoxamine, a promising bifunctional chelating agent for labeling proteins with gallium: Ga67 DF-HSA: concise communication  

Microsoft Academic Search

A new efficient method has been developed for the labeling of various biologically important proteins with radiogallium, using deferoxamine (DF) as a bifunctional chelating agent. Human serum albumin (HSA) was chosen for studying the DF coupling reaction by a glutaraldehyde two-step method. The DF-HSA conjugate obtained was then easily labeled with Ga-67 with high efficiency and reproducibility. High stability of

A. Yokoyama; Y. Ohmomo; K. Horiuchi; H. Saji; H. Tanaka; K. Yamamoto; Y. Ishii; K. Torizuka

1982-01-01

359

Melt complex viscosity and molecular weights for homo-polypropylene modified by grafting bifunctional monomers under electron beam irradiation  

Microsoft Academic Search

High melt viscosity polypropylene was manufactured by grafting bifunctional monomers, HDDA (1,6-hexanediol diacrylate) and TPGDA (tripropyleneglycol diacrylate), onto homo-polypropylene under an electron beam irradiation. Melt complex viscosity (??) of modified polypropylene was sensitive to irradiation dose and monomer content. The melt viscosity of the polypropylene modified with TPGDA increased to 132,290Pas (at 190°C and 0.1rad\\/s of frequency) from 5039Pas for

Do-Hung Han; Jae-Hyuk Jang; Byung-Gi Cho; Byung-Nam Kim; Gil-Soo Seo

2006-01-01

360

Alkali-exchanged sepiolites containing palladium as bifunctional (basic sites and noble metal) catalysts for the Heck and Suzuki reactions  

Microsoft Academic Search

Alkali-exchanged sepiolites-containing PdCl2 act as bifunctional heterogeneous catalysts for the Heck and Suzuki cross-coupling in the absence of extrinsic base. The catalyst becomes deactivated upon reuse and partial reactivation can be achieved by mild steaming at 150°C. Sodium sepiolites were found the most suitable support of the series. Surprisingly, natural sepiolite exhibiting very weak basicity being not able to catalyse

Avelino Corma; Hermenegildo Garc??a; Antonio Leyva; Ana Primo

2004-01-01

361

Highly active and durable core-corona structured bifunctional catalyst for rechargeable metal-air battery application.  

PubMed

A new class of core-corona structured bifunctional catalyst (CCBC) consisting of lanthanum nickelate centers supporting nitrogen-doped carbon nanotubes (NCNT) has been developed for rechargeable metal-air battery application. The nanostructured design of the catalyst allows the core and corona to catalyze the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), respectively. These materials displayed exemplary OER and ORR activity through half-cell testing, comparable to state of the art commercial lanthanum nickelate (LaNiO(3)) and carbon-supported platinum (Pt/C), with added bifunctional capabilities allowing metal-air battery rechargeability. LaNiO(3) and Pt/C are currently the most accepted benchmark electrocatalyst materials for the OER and ORR, respectively; thus with comparable activity toward both of these reactions, CCBC are presented as a novel, inexpensive catalyst component for the cathode of rechargeable metal-air batteries. Moreover, after full-range degradation testing (FDT) CCBC retained excellent activity, retaining 3 and 13 times greater ORR and OER current upon comparison to state of the art Pt/C. Zinc-air battery performances of CCBC is in good agreement with the half-cell experiments with this bifunctional electrocatalyst displaying high activity and stability during battery discharge, charge, and cycling processes. Owing to its outstanding performance toward both the OER and ORR, comparable with the highest performing commercial catalysts to date for each of the respective reaction, coupled with high stability and rechargeability, CCBC is presented as a novel class of bifunctional catalyst material that is very applicable to future generation rechargeable metal-air batteries. PMID:22372510

Chen, Zhu; Yu, Aiping; Higgins, Drew; Li, Hui; Wang, Haijiang; Chen, Zhongwei

2012-04-11

362

Synthesis, docking and in vitro antimalarial evaluation of bifunctional hybrids derived from ?-lactams and 7-chloroquinoline using click chemistry.  

PubMed

1,2,3-Triazole tethered ?-lactam and 7-chloroquinoline bifunctional hybrids were synthesized and evaluated as potential antimalarial agents. Activity against cultured Plasmodium falciparum was dependent on the N-substituent of the ?-lactam ring as well as the presence of bis-triazole at the C-3 position. The observed activity profiles were further substantiated by docking studies via inhibition of P. falciparum dihydrofolate reductase (PfDHFR), a potential target for the development of new anti-malarials. PMID:22172698

Singh, Pardeep; Singh, Parvesh; Kumar, Malkeet; Gut, Jiri; Rosenthal, Philip J; Kumar, Kewal; Kumar, Vipan; Mahajan, Mohinder P; Bisetty, Krishna

2012-01-01

363

Functional analysis of the essential bifunctional tobacco enzyme 3-dehydroquinate dehydratase\\/shikimate dehydrogenase in transgenic tobacco plants  

Microsoft Academic Search

In plants, the shikimate pathway occurs in the plastid and leads to the biosynthesis of aromatic amino acids. The bifunctional 3-dehydroquinate dehydratase\\/shiki- mate dehydrogenase (DHD\\/SHD) catalyses the conver- sion of dehydroquinate into shikimate. Expression of NtDHD\\/SHD was suppressed by RNAi in transgenic tobacco plants. Transgenic lines with <40% of wild- type activity displayed severe growth retardation and reduced content of

Li Ding; Daniel Hofius; Mohammad-Reza Hajirezaei; Alisdair R. Fernie; Frederik Bornke; Uwe Sonnewald

2007-01-01

364

Pros and cons of bifunctional platinum(iv) antitumor prodrugs: two are (not always) better than one.  

PubMed

This article evaluates the efficacy and applicability of bifunctional prodrugs consisting of a six-coordinate Pt(iv) octahedral core and one or more bioactive molecules. The platinum(iv) complexes release upon reduction the corresponding cytotoxic Pt(ii) agents and the bioactive molecules, able to inhibit some biochemical mechanisms of cancer growth and/or prevent the deactivation of the Pt(ii) metabolites. PMID:24874896

Gabano, Elisabetta; Ravera, Mauro; Osella, Domenico

2014-07-14

365

Recovery of plutonium from nitric acid containing oxalate and fluoride by a macroporous bifunctional phosphinic acid resin (MPBPA)  

Microsoft Academic Search

Summary  The sorption of Pu from nitric acid solutions containing oxalate\\/fluoride was studied using an indigenously available macroporous\\u000a bifunctional phosphinic acid (MPBPA) resin. Batch experiments were carried out to obtain the distribution data of Pu(IV) with\\u000a a view to optimize conditions for its recovery from nitric acid waste solutions containing oxalate or fluoride ions. The measurements\\u000a showed high distribution ratio (D)

K. Venugopal Chetty; A. G. Godbole; R. Swarup; V. N. Vaidya; V. Venugopal; P. R. Vasudeva Rao

2005-01-01

366

A Bifunctional Targeted Peptide that Blocks HER2 Tyrosine Kinase and Disables Mitochondrial Function in HER2Positive Carcinoma Cells  

Microsoft Academic Search

The HER-2 oncoprotein is commonly overexpressed in a variety of human malignancies and has become an attractive antitumor target. A number of strategies to inhibit the HER-2 receptor tyrosine kinase are currently the focus of intensive preclinical and clinical research. In the present study, we have engineered a bifunctional peptide, BHAP, which consists of two modular domains: a HER-2-targeting\\/neutralizing do-

Valeria R. Fantin; Marcelo J. Berardi; Holger Babbe; Montserrat V. Michelman; Charlene M. Manning; Philip Leder

2005-01-01

367

Enhanced Uptake of Porous Silica Microparticles by Bifunctional Surface Modification with a Targeting Antibody and a Biocompatible Polymer  

PubMed Central

Strategies were developed by which mesoporous microparticles were modified on their external surfaces with tetraethylene glycol (TEG), a protein, or both, leaving the pore surfaces available for modification with a separate moiety, such as a dye. Only particles bifunctionally modified with both TEG and a cell-specific antibody were taken up specifically by a targeted cancer cell line. In contrast to similarly functionalized nanoparticles, endocytosed microparticles were not contained within a lysosome.

Cheng, Kai; Blumen, Steven R.; MacPherson, Maximilian B.; Steinbacher, Jeremy L.; Mossman, Brooke T.; Landry, Christopher C.

2010-01-01

368

Application of computational fluid dynamics on cavitation in journal bearings  

NASA Astrophysics Data System (ADS)

Journal bearings are applied in internal combustion engines due to their favourable wearing quality and operating characteristics. Under certain operating conditions damage of the journal bearing can occur caused by cavitation. The cavitation reduces the load capacity and leads to material erosion. Experimental investigations of cavitating flows in dimension of real journal bearing are difficult to realize or almost impossible caused by the small gap and transient flow conditions. Therefore numerical simulation is a very helpful engineering tool to research the cavitation behaviour. The CFD-Code OpenFOAM is used to analyse the flow field inside the bearing. The numerical cavitation model based on a bubble dynamic approach and requires necessary initial parameter for the calculation, such as nuclei bubble diameter, the number of nuclei and two empirical constants. The first part of this paper shows the influence of these parameters on the solution. For the adjustment of the parameters an experiment of Jakobsson et.al. [1] was used to validate the numerical flow model. The parameters have been varied according to the method Design of Experiments (DoE). With a defined model equation the parameters determined, to identify the parameter for CFD-calculations in comparison to the experimental values. The second part of the paper presents investigations on different geometrical changes in the bearing geometry. The effect of these geometrical changes on cavitation was compared with experimental results from Wollfarth [2] and Garner et.al. [3].

Riedel, Marco; Schmidt, Marcus; Reinke, Peter; Nobis, Matthias; Redlich, Marcel

2014-03-01

369

QM/MM studies of the mechanism of unusual bifunctional fructose-1,6-bisphosphate aldolase/phosphatase.  

PubMed

Archaeal fructose-1,6-bisphosphate aldolase/phosphatase (FBPA/P) is a newly identified unusual bifunctional enzyme (Nature, 2010, 464, 1077), which contains one single catalytic domain but catalyzes two chemically distinct reactions of gluconeogenesis. It is different from the ordinary enzymes whose active sites are responsible for a specific reaction. To explore the catalytic characteristic of FBPA/P, the aldol condensation mechanism of bifunctional FBPA/P has been investigated using quantum mechanics/molecular mechanics (QM/MM) method. The whole reaction process can be divided into two half-reactions involving seven elementary steps. A Schiff base intermediate is theoretically confirmed, agreeing well with the recently resolved crystal structures (Nature, 2011, 478, 538). The free energy barrier of the rate-limiting step is calculated to be 22.2 kcal mol(-1), which is a concerted process of a nucleophilic attack by the enolic carbon to the ketonic carbon and a proton transfer from Tyr229 to the ketonic oxygen. Lys232 plays an important role in forming a Schiff base intermediate with the substrate (DHAP). Tyr229 functions as a proton shuttle during the catalysis. This is the first theoretical study on the aldol condensation mechanism of FBPA/P, which may provide useful information for understanding bifunctional enzymes. PMID:24798757

Hou, Qianqian; Sheng, Xiang; Liu, Yongjun

2014-06-21

370

A fundamental trade-off in covalent switching and its circumvention by enzyme bifunctionality in glucose homeostasis.  

PubMed

Covalent modification provides a mechanism for modulating molecular state and regulating physiology. A cycle of competing enzymes that add and remove a single modification can act as a molecular switch between "on" and "off" and has been widely studied as a core motif in systems biology. Here, we exploit the recently developed "linear framework" for time scale separation to determine the general principles of such switches. These methods are not limited to Michaelis-Menten assumptions, and our conclusions hold for enzymes whose mechanisms may be arbitrarily complicated. We show that switching efficiency improves with increasing irreversibility of the enzymes and that the on/off transition occurs when the ratio of enzyme levels reaches a value that depends only on the rate constants. Fluctuations in enzyme levels, which habitually occur due to cellular heterogeneity, can cause flipping back and forth between on and off, leading to incoherent mosaic behavior in tissues, that worsens as switching becomes sharper. This trade-off can be circumvented if enzyme levels are correlated. In particular, if the competing catalytic domains are on the same protein but do not influence each other, the resulting bifunctional enzyme can switch sharply while remaining coherent. In the mammalian liver, the switch between glycolysis and gluconeogenesis is regulated by the bifunctional 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2/FBPase-2). We suggest that bifunctionality of PFK-2/FBPase-2 complements the metabolic zonation of the liver by ensuring coherent switching in response to insulin and glucagon. PMID:24634222

Dasgupta, Tathagata; Croll, David H; Owen, Jeremy A; Vander Heiden, Matthew G; Locasale, Jason W; Alon, Uri; Cantley, Lewis C; Gunawardena, Jeremy

2014-05-01

371

Hybrid bearings for turbopumps and the like  

NASA Technical Reports Server (NTRS)

In rocket engines power is usually obtained by burning fuel and oxidizer which are mixed, pressurized, and directed to a combustion chamber by means of turbopumps. Roller bearings are generally used in these turbopumps, but because of bearing demands hydrostatic bearings were proposed. The use of such bearings is quite feasible because during flight hydrostatic lubrication can reduce roller bearing wear. A disadvantage of such proposals is that during startup, acceleration, and shutdown high pressure fluids are not available for hydrostatic bearings. The fluid lubrication film is not always present in bearings of turbopumps. During these periods a second bearing is required to carry the load. This requirement suggests the use of hybrid bearings in rocket engine turbopumps. Such duplex bearings were provided, but when their inner races are keyed to the shaft or journal two of them are required. And such duplex bearings do not wear evenly. A hybrid hydrostatic-rolling element bearing was provided wherein the rolling element bearing is locked on the stationary housing rather than on the rotating journal.

Justak, John F. (inventor); Owens, Gregg R. (inventor)

1994-01-01

372

Journal and Wave Bearing Impedance Calculation Software  

NASA Technical Reports Server (NTRS)

The wave bearing software suite is a MALTA application that computes bearing properties for user-specified wave bearing conditions, as well as plain journal bearings. Wave bearings are fluid film journal bearings with multi-lobed wave patterns around the circumference of the bearing surface. In this software suite, the dynamic coefficients are outputted in a way for easy implementation in a finite element model used in rotor dynamics analysis. The software has a graphical user interface (GUI) for inputting bearing geometry parameters, and uses MATLAB s structure interface for ease of interpreting data. This innovation was developed to provide the stiffness and damping components of wave bearing impedances. The computational method for computing bearing coefficients was originally designed for plain journal bearings and tilting pad bearings. Modifications to include a wave bearing profile consisted of changing the film thickness profile given by an equation, and writing an algorithm to locate the integration limits for each fluid region. Careful consideration was needed to implement the correct integration limits while computing the dynamic coefficients, depending on the form of the input/output variables specified in the algorithm.

Hanford, Amanda; Campbell, Robert

2012-01-01

373

The Mycobacterium tuberculosis Rv2540c DNA sequence encodes a bifunctional chorismate synthase  

PubMed Central

Background The emergence of multi- and extensively-drug resistant Mycobacterium tuberculosis strains has created an urgent need for new agents to treat tuberculosis (TB). The enzymes of shikimate pathway are attractive targets to the development of antitubercular agents because it is essential for M. tuberculosis and is absent from humans. Chorismate synthase (CS) is the seventh enzyme of this route and catalyzes the NADH- and FMN-dependent synthesis of chorismate, a precursor of aromatic amino acids, naphthoquinones, menaquinones, and mycobactins. Although the M. tuberculosis Rv2540c (aroF) sequence has been annotated to encode a chorismate synthase, there has been no report on its correct assignment and functional characterization of its protein product. Results In the present work, we describe DNA amplification of aroF-encoded CS from M. tuberculosis (MtCS), molecular cloning, protein expression, and purification to homogeneity. N-terminal amino acid sequencing, mass spectrometry and gel filtration chromatography were employed to determine identity, subunit molecular weight and oligomeric state in solution of homogeneous recombinant MtCS. The bifunctionality of MtCS was determined by measurements of both chorismate synthase and NADH:FMN oxidoreductase activities. The flavin reductase activity was characterized, showing the existence of a complex between FMNox and MtCS. FMNox and NADH equilibrium binding was measured. Primary deuterium, solvent and multiple kinetic isotope effects are described and suggest distinct steps for hydride and proton transfers, with the former being more rate-limiting. Conclusion This is the first report showing that a bacterial CS is bifunctional. Primary deuterium kinetic isotope effects show that C4-proS hydrogen is being transferred during the reduction of FMNox by NADH and that hydride transfer contributes significantly to the rate-limiting step of FMN reduction reaction. Solvent kinetic isotope effects and proton inventory results indicate that proton transfer from solvent partially limits the rate of FMN reduction and that a single proton transfer gives rise to the observed solvent isotope effect. Multiple isotope effects suggest a stepwise mechanism for the reduction of FMNox. The results on enzyme kinetics described here provide evidence for the mode of action of MtCS and should thus pave the way for the rational design of antitubercular agents.

Ely, Fernanda; Nunes, Jose ES; Schroeder, Evelyn K; Frazzon, Jeverson; Palma, Mario S; Santos, Diogenes S; Basso, Luiz A

2008-01-01

374

Cloning and characterization of bifunctional enzyme farnesyl diphosphate/geranylgeranyl diphosphate synthase from Plasmodium falciparum.  

PubMed

BACKGROUND: Isoprenoids are the most diverse and abundant group of natural products. In Plasmodium falciparum, isoprenoid synthesis proceeds through the methyl erythritol diphosphate pathway and the products are further metabolized by farnesyl diphosphate synthase (FPPS), turning this enzyme into a key branch point of the isoprenoid synthesis. Changes in FPPS activity could alter the flux of isoprenoid compounds downstream of FPPS and, hence, play a central role in the regulation of a number of essential functions in Plasmodium parasites. METHODS: The isolation and cloning of gene PF3D7_18400 was done by amplification from cDNA from mixed stage parasites of P. falciparum. After sequencing, the fragment was subcloned in pGEX2T for recombinant protein expression. To verify if the PF3D7_1128400 gene encodes a functional rPfFPPS protein, its catalytic activity was assessed using the substrate [4-14C] isopentenyl diphosphate and three different allylic substrates: dimethylallyl diphosphate, geranyl diphosphate or farnesyl diphosphate. The reaction products were identified by thin layer chromatography and reverse phase high-performance liquid chromatography. To confirm the product spectrum formed of rPfFPPS, isoprenic compounds were also identified by mass spectrometry. Apparent kinetic constants KM and Vmax for each substrate were determined by Michaelis--Menten; also, inhibition assays were performed using risedronate. RESULTS: The expressed protein of P. falciparum FPPS (rPfFPPS) catalyzes the synthesis of farnesyl diphosphate, as well as geranylgeranyl diphosphate, being therefore a bifunctional FPPS/geranylgeranyl diphosphate synthase (GGPPS) enzyme. The apparent KM values for the substrates dimethylallyl diphosphate, geranyl diphosphate and farnesyl diphosphate were, respectively, 68 +/- 5 muM, 7.8 +/- 1.3 muM and 2.06 +/- 0.4 muM. The protein is expressed constitutively in all intra-erythrocytic stages of P. falciparum, demonstrated by using transgenic parasites with a haemagglutinin-tagged version of FPPS. Also, the present data demonstrate that the recombinant protein is inhibited by risedronate. CONCLUSIONS: The rPfFPPS is a bifunctional FPPS/GGPPS enzyme and the structure of products FOH and GGOH were confirmed mass spectrometry. Plasmodial FPPS represents a potential target for the rational design of chemotherapeutic agents to treat malaria. PMID:23734739

Jordão, Fabiana M; Gabriel, Heloisa B; Alves, João Mp; Angeli, Claudia B; Bifano, Thaís D; Breda, Ardala; de Azevedo, Mauro F; Basso, Luiz A; Wunderlich, Gerhard; Kimura, Emilia A; Katzin, Alejandro M

2013-06-01

375

Cloning and characterization of bifunctional enzyme farnesyl diphosphate/geranylgeranyl diphosphate synthase from Plasmodium falciparum  

PubMed Central

Background Isoprenoids are the most diverse and abundant group of natural products. In Plasmodium falciparum, isoprenoid synthesis proceeds through the methyl erythritol diphosphate pathway and the products are further metabolized by farnesyl diphosphate synthase (FPPS), turning this enzyme into a key branch point of the isoprenoid synthesis. Changes in FPPS activity could alter the flux of isoprenoid compounds downstream of FPPS and, hence, play a central role in the regulation of a number of essential functions in Plasmodium parasites. Methods The isolation and cloning of gene PF3D7_18400 was done by amplification from cDNA from mixed stage parasites of P. falciparum. After sequencing, the fragment was subcloned in pGEX2T for recombinant protein expression. To verify if the PF3D7_1128400 gene encodes a functional rPfFPPS protein, its catalytic activity was assessed using the substrate [4-14C] isopentenyl diphosphate and three different allylic substrates: dimethylallyl diphosphate, geranyl diphosphate or farnesyl diphosphate. The reaction products were identified by thin layer chromatography and reverse phase high-performance liquid chromatography. To confirm the product spectrum formed of rPfFPPS, isoprenic compounds were also identified by mass spectrometry. Apparent kinetic constants KM and Vmax for each substrate were determined by Michaelis–Menten; also, inhibition assays were performed using risedronate. Results The expressed protein of P. falciparum FPPS (rPfFPPS) catalyzes the synthesis of farnesyl diphosphate, as well as geranylgeranyl diphosphate, being therefore a bifunctional FPPS/geranylgeranyl diphosphate synthase (GGPPS) enzyme. The apparent KM values for the substrates dimethylallyl diphosphate, geranyl diphosphate and farnesyl diphosphate were, respectively, 68?±?5 ?M, 7.8?±?1.3 ?M and 2.06?±?0.4 ?M. The protein is expressed constitutively in all intra-erythrocytic stages of P. falciparum, demonstrated by using transgenic parasites with a haemagglutinin-tagged version of FPPS. Also, the present data demonstrate that the recombinant protein is inhibited by risedronate. Conclusions The rPfFPPS is a bifunctional FPPS/GGPPS enzyme and the structure of products FOH and GGOH were confirmed mass spectrometry. Plasmodial FPPS represents a potential target for the rational design of chemotherapeutic agents to treat malaria.

2013-01-01

376

Short-bearing approximation for full journal bearings  

NASA Technical Reports Server (NTRS)

A short-bearing approximation of pressure distribution in the oil film is presented which is an extension of the pressure-distribution function of Michell and Cardullo and includes end-leakage effects. Equations giving applied load, attitude angle, location and magnitude of peak film pressure, friction, and required oil flow rate as functions of the eccentricity ratio are also given. The capacity number, a basic non dimensional quantity resulting from this analysis is the product of the Sommerfeld number and the square of the length-diameter ratio. Curves determined by this analysis are compared with previously published experimental data and theoretical curves of Sommerfeld and Cameron and Wood. Conclusions reached indicate that this approximation is of practical value for analysis of short bearings.

Ocvirk, F W

1952-01-01

377

Effects of bearing deadbands on bearing loads and rotor stability  

NASA Technical Reports Server (NTRS)

A generic model of a turbopump, simplified to bring out these effects is examined. This model demonstrates that bearing deadbands which are of the same order of magnitude or larger than the center-of-mass offset of a rotor due to mass imbalances cause significantly different dynamic behavior than would be expected of a linear, dynamical system. This fundamentally nonlinear behavior yields altered stability characteristics and altered bearing loading tendencies. It is shown that side forces can enhance system stability in the small, i.e., as long as the mass imbalance does not exceed some thresholds value or as long as no large, impulsive disturbances cause the motion to depart significantly from the region of stability. Limit cycles are investigated in this report and techniques for determining these limit cycles are developed. These limit cycles are the major source of bearing loading and appear in both synchronous and nonsynchronous forms. The synchronous limit cycles are driven by rotor imbalances. The nonsynchronous limit cycles (also called subsynchronous whirls) are self-excited and are the sources of instability.

1984-01-01

378

Use of Interstate Passageways by Black Bears.  

National Technical Information Service (NTIS)

Vehicle collisions account for up to forty black bear (Ursus americanus) deaths per year in Tennessee. Historically, a relatively high number of bear deaths have occurred on Interstate Highway 40 between mile marker 440 and the North Carolina state line. ...

F. T. Manen A. B. Coley M. R. Pelton

1995-01-01

379

Elastic orifice automatically regulates gas bearings  

NASA Technical Reports Server (NTRS)

Elastic, pressure-sensitive orifice is used to automatically regulate the rate of gas flow into bearings under varying loads. Formed of a molded elastomer, theses orifices increase the stability of gas bearings.

Batsch, F.; Laub, J. L.

1964-01-01

380

Bear-inflicted human injury and fatality.  

PubMed

This review attempts to summarize credible scientific information, and to dispel myths, regarding bear attacks. Publications in the scientific literature were sought through a Medline search and by reviewing the bibliographies of related books and scientific articles. Personal experience and interviews with authorities were also used in preparation of this review, although only published articles or books are cited. This is a summary of case series reported or observed elsewhere. Bear-inflicted human injury and death is rare. Brown bear attacks tend to be severe and to occur suddenly, without provocation. Black bear attacks usually result in minor injuries and tend to be predacious. Polar bear attacks are exceedingly rare, and the ferocity of polar bears has probably been overemphasized. Bear-inflicted wounds should be treated as major trauma in accordance with advanced trauma life support guidelines. This information may be useful in counseling patients with regard to prevention of injury or death from bear attack. PMID:10442155

Floyd, T

1999-01-01

381

Complex Demodulation for Bearing Fault Detection.  

National Technical Information Service (NTIS)

Vibration analysis using the high frequency resonance technique has been used successfully to detect incipient failure in rolling element bearings. This memo outlines a new method of obtaining the demodulated narrow band envelope of a bearing vibration si...

I. M. Howard

1989-01-01

382

Magnetic Perturbation Inspection of Inner Bearing Races.  

National Technical Information Service (NTIS)

Approximately 100 inner race bearings were inspected nondestructively prior to endurance testing. Two of the bearings which failed during testing spalled at the sites of subsurface inclusions previously detected by using magnetic field perturbation. At ot...

J. Lankford J. R. Barton

1972-01-01

383

Ultralow Friction in a Superconducting Magnetic Bearing.  

National Technical Information Service (NTIS)

Passive levitation by superconducting magnetic bearings can be utilized in flywheels for energy storage. Basic design criteria of such a bearing are high levitation force, sufficient vertical and horizontal stability and low friction. A test facility was ...

H. J. Bornemann M. Siegel O. Zaitsev M. Bareiss H. Laschuetza

1996-01-01

384

A Preliminary Foil Gas Bearing Performance Map  

NASA Technical Reports Server (NTRS)

Recent breakthrough improvements in foil gas bearing load capacity, high temperature tribological coatings and computer based modeling have enabled the development of increasingly larger and more advanced Oil-Free Turbomachinery systems. Successful integration of foil gas bearings into turbomachinery requires a step wise approach that includes conceptual design and feasibility studies, bearing testing, and rotor testing prior to full scale system level demonstrations. Unfortunately, the current level of understanding of foil gas bearings and especially their tribological behavior is often insufficient to avoid developmental problems thereby hampering commercialization of new applications. In this paper, a new approach loosely based upon accepted hydrodynamic theory, is developed which results in a "Foil Gas Bearing Performance Map" to guide the integration process. This performance map, which resembles a Stribeck curve for bearing friction, is useful in describing bearing operating regimes, performance safety margins, the effects of load on performance and limiting factors for foil gas bearings.

DellaCorte, Christopher; Radil, Kevin C.; Bruckner, Robert J.; Howard, S. Adam

2006-01-01

385

Hunting for 'bears' in the backyard  

NSDL National Science Digital Library

This Micscape Magazine article offers practical hints about how to collect and study tardigrades, or water bears, from mosses in your backyard. It features a general introduction of water bears, a video, and a section of references for further reading.

Walker, Dave; Magazine, Micscape

386

Cryogenic Fluid Film Bearing Tester Development Study.  

National Technical Information Service (NTIS)

Conceptual designs were developed for the determination of rotordynamic coefficients of cryogenic fluid film bearings. The designs encompassed the use of magnetic and conventional excitation sources as well as the use of magnetic bearings as support beari...

J. K. Scharrer B. T. Murphy L. A. Hawkins

1993-01-01

387

Happy Birthday Smokey Bear from Joe Acaba  

NASA Video Gallery

Expedition 32 Flight Engineer Joe Acaba wishes Smokey Bear a Happy Birthday. For 68 years Smokey Bear has been promoting fire safety and prevention through the message, â??Only You Can Prevent Wild...

388

Stable isotopes to detect food-conditioned bears and to evaluate human-bear management  

USGS Publications Warehouse

We used genetic and stable isotope analysis of hair from free-ranging black bears (Ursus americanus) in Yosemite National Park, California, USA to: 1) identify bears that consume human food, 2) estimate the diets of these bears, and 3) evaluate the Yosemite human–bear management program. Specifically, we analyzed the isotopic composition of hair from bears known a priori to be food-conditioned or non-food-conditioned and used these data to predict whether bears with an unknown management status were food-conditioned (FC) or non-food-conditioned (NFC). We used a stable isotope mixing model to estimate the proportional contribution of natural foods (plants and animals) versus human food in the diets of FC bears. We then used results from both analyses to evaluate proactive (population-level) and reactive (individual-level) human–bear management, and discussed new metrics to evaluate the overall human–bear management program in Yosemite. Our results indicated that 19 out of 145 (13%) unknown bears sampled from 2005 to 2007 were food-conditioned. The proportion of human food in the diets of known FC bears likely declined from 2001–2003 to 2005–2007, suggesting proactive management was successful in reducing the amount of human food available to bears. In contrast, reactive management was not successful in changing the management status of known FC bears to NFC bears, or in reducing the contribution of human food to the diets of FC bears. Nine known FC bears were recaptured on 14 occasions from 2001 to 2007; all bears were classified as FC during subsequent recaptures, and human–bear management did not reduce the amount of human food in the diets of FC bears. Based on our results, we suggest Yosemite continue implementing proactive human–bear management, reevaluate reactive management, and consider removing problem bears (those involved in repeated bear incidents) from the population.

Hopkins, John B., III; Koch, Paul L.; Schwartz, Charles C.; Ferguson, Jake M.; Greenleaf, Schuyler S.; Kalinowski, Steven T.

2012-01-01

389

Performance of a hybrid cylindrical roller bearing  

Microsoft Academic Search

A 206-size hybrid (ceramic\\/steel) cylindrical roller bearing was tested in MIL-L-23699 C oil at several speeds and loads. Heat-generation data was collected and subsequently correlated with bearing-analysis software. Bearing-cage slip data was also collected at various oil-flow rates, oil temperatures, and with both MIL-L-7808 J and MIL-L-23699 C oils. The hybrid bearing was tested in MIL-L-23699 C oil for for

Stephen M. Schrader

1992-01-01

390

Cartridge Bearing System for Space Applications  

NASA Technical Reports Server (NTRS)

Conventional spin axis ball bearings have been unreliable in spacecraft, often failing by two heretofore uncontrolled processes: ball retainer instability and lubricant breakdown. The Space Cartridge Bearing System (SCBS) addresses each of these mechanisms directly, leading to a bearing system with absolute freedom from retainer instability and negligible lubricant degradation rate. The result is a reliable plug-in bearing cartridge with a definite design life.

Kingsbury, Edward P.; Hanson, Robert A.; Jones, William R.; Mohr, Terry W.

1999-01-01

391

Research In Diagnosing Bearing Defects From Vibrations  

NASA Technical Reports Server (NTRS)

Report describes research in bearing-defect signature analysis - use of vibration-signal analysis to diagnose defects in roller and ball bearings. Experiments performed on bearings in good condition and other bearings in which various parts scratched to provide known defects correlated with vibration signals. Experiments performed on highly instrumented motor-driven rotor assembly at speeds up to 10,050 r/min, using accelerometers, velocity probes, and proximity sensors mounted at various locations on assembly to measure vibrations.

Zoladz, T.; Earhart, E.; Fiorucci, T.

1995-01-01

392

Hydrology of the Bear Lake Basin, Utah  

Microsoft Academic Search

Bear Lake’s natural watershed is made up of relatively low mountains covered with sagebrush at lower elevations and southern exposures and fir-aspen forests at higher elevations and northern exposures. The basin is traversed by the Bear River that begins high in the Unita Mountains and flows through Utah, Idaho, and Wyoming before feeding the Great Salt Lake. The Bear River

Patsy Palacios; Chris Luecke; Justin Robinson

2007-01-01

393

36 CFR 13.1236 - Bear orientation.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Bear orientation. 13.1236 Section 13...Brooks Camp Developed Area § 13.1236 Bear orientation. All persons visiting the BCDA must receive an NPS-approved Bear Orientation. Failure to receive an...

2010-07-01

394

36 CFR 13.1236 - Bear orientation.  

Code of Federal Regulations, 2010 CFR

...2009-07-01 2009-07-01 false Bear orientation. 13.1236 Section 13...Brooks Camp Developed Area § 13.1236 Bear orientation. All persons visiting the BCDA must receive an NPS-approved Bear Orientation. Failure to receive an...

2009-07-01

395

Teaching American History with Teddy's Bear.  

ERIC Educational Resources Information Center

Discusses the origins of "Teddy's bear," tracing back to a cartoon published in 1902. States that Teddy's bear can shed light on U.S. culture and society. Focuses on the role of Teddy's bear as a symbol of conservationism, an embodiment of male dominance and female nurturance, and a manifestation of white racial supremacy. (CMK)

Forman-Brunell, Miriam

2001-01-01

396

Minimizing electric bearing currents in ASD systems  

Microsoft Academic Search

During recent years, an increase in bearing failures has been seen in ASD-fed electric motors, as well as in gearboxes, and other connected machinery, caused by electric current flow through such bearings. The theories presented in this paper focus on bearing currents in ASDs of the voltage source pulse width modulated (PWM) type, for use with AC induction motors, although

P. J. Link

1999-01-01

397

Bearing-Mounting Concept Accommodates Thermal Expansion  

NASA Technical Reports Server (NTRS)

Pins or splines allow radial expansion without slippage. Design concept for mounting rotary bearing accommodates differential thermal expansion between bearing and any structure(s) to which bearing connected. Prevents buildup of thermal stresses by allowing thermal expansion to occur freely but accommodating expansion in such way not to introduce looseness. Pin-in-slot configuration also maintains concentricity.

Nespodzany, Robert; Davis, Toren S.

1995-01-01

398

Fixed-Wheel Gate Bearing Studies.  

National Technical Information Service (NTIS)

Tests to determine friction coefficients and bearing behavior in 3 types of bearings--2 self-lubricating and 1 plain bronze--show that increased allowable bearing pressures of 6,000 psi and a design coefficient of friction of 0.10 can be used for one of t...

G. I. Brooks, M. Lopez, D. B. Mountjoy

1964-01-01

399

Foil bearing lubrication theory including compressibility effects  

NASA Technical Reports Server (NTRS)

An analysis is presented to determine the film thickness in a foil bearing. Using the Reynolds equation and including the compressibility effects of the gas, an equation was developed applicable to the film thickness in a foil bearing. The bearing was divided into three regions, namely, the entrance region, middle region and exit region. Solutions are obtained for the film thickness in each region.

Gorla, Rama Subba Reddy; Catalano, Daniel A.

1987-01-01

400

Sliding bearings lubricated with magnetic fluids  

Microsoft Academic Search

Purpose – This paper seeks to present some new designs of sliding bearings lubricated with magnetic fluids (ferrofluids) and the possibility of using them in modern bearing technology, in new computer and audiovisual equipment among others. Design\\/methodology\\/approach – The paper presents new designs of journal, thrust and journal-thrust sliding bearings lubricated and sealed with magnetic fluids such as: magnetic fluid

W. Ocho?ski

2007-01-01

401

49 CFR 229.64 - Plain bearings.  

Code of Federal Regulations, 2013 CFR

...Transportation 4 2013-10-01 2013-10-01 false Plain bearings. 229.64 Section 229.64 Transportation...Safety Requirements Suspension System § 229.64 Plain bearings. A plain bearing box shall contain visible free oil and may...

2013-10-01

402

Optimum energy loss in electro magnetic bearing  

Microsoft Academic Search

This paper includes weight optimization method of rotor and analysis of total power loss in radial magnetic bearing consisting of four, eight and twelve poles. Weight optimization reduces copper loss in bearing since the electromagnetic force is reduced due to optimized rotor. Further numbers of poles in magnetic bearing are varied for same electromagnetic force 350 N and stator is

Santosh Shelke; R. V. Chalam

2011-01-01

403

Bifunctional Lipocalin Ameliorates Murine Immune Complex-induced Acute Lung Injury  

PubMed Central

Molecules that simultaneously inhibit independent or co-dependent proinflammatory pathways may have advantages over conventional monotherapeutics. OmCI is a bifunctional protein derived from blood-feeding ticks that specifically prevents complement (C)-mediated C5 activation and also sequesters leukotriene B4 (LTB4) within an internal binding pocket. Here, we examined the effect of LTB4 binding on OmCI structure and function and investigated the relative importance of C-mediated C5 activation and LTB4 in a mouse model of immune complex-induced acute lung injury (IC-ALI). We describe two crystal structures of bacterially expressed OmCI: one binding a C16 fatty acid and the other binding LTB4 (C20). We show that the C5 and LTB4 binding activities of the molecule are independent of each other and that OmCI is a potent inhibitor of experimental IC-ALI, equally dependent on both C5 inhibition and LTB4 binding for full activity. The data highlight the importance of LTB4 in IC-ALI and activation of C5 by the complement pathway C5 convertase rather than by non-C proteases. The findings suggest that dual inhibition of C5 and LTB4 may be useful for treatment of human immune complex-dependent diseases.

Roversi, Pietro; Ryffel, Bernhard; Togbe, Dieudonnee; Maillet, Isabelle; Teixeira, Mauro; Ahmat, Nurfilza; Paesen, Guido C.; Lissina, Olga; Boland, Wilhelm; Ploss, Kerstin; Caesar, Joseph J. E.; Leonhartsberger, Susanne; Lea, Susan M.; Nunn, Miles A.

2013-01-01

404

DEER EPR measurements for membrane protein structures via bifunctional spin labels and lipodisq nanoparticles.  

PubMed

Pulsed EPR DEER structural studies of membrane proteins in a lipid bilayer have often been hindered by difficulties in extracting accurate distances when compared to those of globular proteins. In this study, we employed a combination of three recently developed methodologies, (1) bifunctional spin labels (BSL), (2) SMA-Lipodisq nanoparticles, and (3) Q band pulsed EPR measurements, to obtain improved signal sensitivity, increased transverse relaxation time, and more accurate and precise distances in DEER measurements on the integral membrane protein KCNE1. The KCNE1 EPR data indicated an ?2-fold increase in the transverse relaxation time for the SMA-Lipodisq nanoparticles when compared to those of proteoliposomes and narrower distance distributions for the BSL when compared to those of the standard MTSL. The certainty of information content in DEER data obtained for KCNE1 in SMA-Lipodisq nanoparticles is comparable to that in micelles. The combination of techniques will enable researchers to potentially obtain more precise distances in cases where the traditional spin labels and membrane systems yield imprecise distance distributions. PMID:23984855

Sahu, Indra D; McCarrick, Robert M; Troxel, Kaylee R; Zhang, Rongfu; Smith, Hubbell J; Dunagan, Megan M; Swartz, Max S; Rajan, Prashant V; Kroncke, Brett M; Sanders, Charles R; Lorigan, Gary A

2013-09-24

405

Production of a bifunctional hybrid molecule B72.3/metallothionein-1 by protein engineering.  

PubMed Central

A hybrid anti-tumour B72.3 antibody/metallothionein protein B72.3MT-1 was produced by the construction of the expression vector mpSV2neo-EP1-B72.3MT-1. This vector contained the neo gene as a selection marker, the murine immunoglobulin promoter and enhancer, and the hybrid B72.3 heavy chain gene fragment with mouse metallothionein-1 cDNA gene ligated into its CH2 domain. The expression vector was transfected to the heavy chain loss mutant B72.3Mut(K) cell line. The hybrid protein B72.3MT-1 was purified from transfectant supernates using a Protein G column. We showed that the hybrid protein retained the binding reactivity for the TAG72 antigen as the original B72.3 antibody, and the metal-binding capacity of the native metallothionein molecule. Therefore, the bifunctional hybrid protein B72.3MT-1 may be very useful in cancer imaging when labelled with radionuclides such as 99mTc. Images Figure 3 Figure 6 Figure 7

Xiang, J; Koropatnick, J; Qi, Y; Luo, X; Moyana, T; Li, K; Chen, Y

1993-01-01

406

Energy- and electron-transfer shuttling by a soluble, bifunctional redox polymer  

SciTech Connect

A soluble, bifunctional polymer ((PS-An{sub 28.5}PTZ{sub 1.5})) based on derivatized polystyrene was prepared in which there are both energy-transfer acceptors (modified anthracene, An) and electron-transfer donors (derivatized phenothiazene, PTZ). The polymer was successfully incorporated into a photochemical electron-transfer sequence based on (Ru(BPY){sub 3}){sup 2+} (bpy is 2,2{prime}-bipyridine) in which separate oxidative and reductive equivalents were generated in solution. In the sequence, sensitized formation of the triplet excited state of the polymer-bound anthryl sites ((PS-{sup 3}An*An{sub 27.5}PTZ{sub 1.5})) occurred by diffusion and energy transfer from (Ru(bpy){sub 3}){sup 2+}* following visible excitation of (Ru(bpy){sub 3}){sup 2+}. In the presence of the oxidative quencher paraquat (PQ{sup 2+}), a series of electron-transfer steps led, ultimately, to the appearance of (PS-An{sub 28.5}PTZ{sup +}PTZ{sub 0.5}) and monomeric PQ{sup +} in solution. The recombination rate constant between PQ{sup +} and (PS-An{sub 28.5}PTZ{sup +}PTZ{sub 0.5}) was reduced by a factor of {approximately} 7 relative to back electron transfer between the unbound, 10-methylphenothiazene cation (10-MePTZ{sup +}) and PQ{sup +}.

Younathan, J.N.; Jones, W.E. Jr.; Meyer, T.J. (Univ. of North Carolina, Chapel Hill (USA))

1991-01-10

407

Charge migration in the bifunctional PENNA cation induced and probed by ultrafast ionization: a dynamical study  

NASA Astrophysics Data System (ADS)

A full dynamical simulation shows that the charge transfer between the amine and the phenyl moieties of the cation of the bifunctional molecule 2-phenylethyl-N,N-dimethylamine can be induced and subsequently probed by two ultrashort photoionizations. The first ionization of the pump–probe scheme is by a 1.5 fs UV or 6 fs IR pulse that ionizes the neutral. The pump pulse can be tailored to produce a coherent superposition of the electronic states of the cation that differ in their energy and spatial localization of their electron density. The time-dependent amplitudes of the states of the superposition means that the state of the cation is not stationary and we show that it is beating between the two ends of the molecule. This beating is next probed by a second attosecond XUV pulse. The ultrafast photoionization of the cation to the dication probes the spatial charge reorganization in the cation. We use the computed time-dependent molecular frame photoelectron angular distributions as a quantitative measure of the charge migration. The computation of the dynamics are carried out by a coupled equation scheme that includes an electronic manifold for the three charge states: neutral, cation and dication, the coupling to the ionization continua of the cation and the dication and the dynamics induced by the pump and the probe pulses.

Mignolet, B.; Levine, R. D.; Remacle, F.

2014-06-01

408

Identification of novel bifunctional calmodulin-binding and microtubule-stabilizing motifs in STOP proteins.  

PubMed

Although microtubules are intrinsically labile tubulin assemblies, many cell types contain stable polymers, resisting depolymerizing conditions such as exposure to the cold or the drug nocodazole. This microtubule stabilization is largely due to polymer association with STOP proteins. There are several STOP variants, some with capacity to induce microtubule resistance to both the cold and nocodazole, others with microtubule cold stabilizing activity only. These microtubule-stabilizing effects of STOP proteins are inhibited by calmodulin and we now demonstrate that they are determined by two distinct kinds of repeated modular sequences (Mn and Mc), both containing a calmodulin-binding peptide, but displaying different microtubule stabilizing activities. Mn modules induce microtubule resistance to both the cold and nocodazole when expressed in cells. Mc modules, which correspond to the STOP central repeats, have microtubule cold stabilizing activity only. Mouse neuronal STOPs, which induce both cold and drug resistance in cellular microtubules, contain three Mn modules and four Mc modules. Compared with neuronal STOPs, the non-neuronal F-STOP lacks multiple Mn modules and this corresponds with an inability to induce nocodazole resistance. STOP modules represent novel bifunctional calmodulin-binding and microtubule-stabilizing sequences that may be essential for the generation of the different patterns of microtubule stabilization observed in cells. PMID:11413126

Bosc, C; Frank, R; Denarier, E; Ronjat, M; Schweitzer, A; Wehland, J; Job, D

2001-08-17

409

Bifunctional Compounds for Controlling Metal-Mediated Aggregation of the A?42 Peptide  

PubMed Central

Abnormal interactions of Cu and Zn ions with the amyloid ? (A?) peptide are proposed to play an important role in the pathogenesis of Alzheimer’s disease (AD). Disruption of these metal–peptide interactions using chemical agents holds considerable promise as a therapeutic strategy to combat this incurable disease. Reported herein are two bifunctional compounds (BFCs) L1 and L2 that contain both amyloid-binding and metal-chelating molecular motifs. Both L1 and L2 exhibit high stability constants for Cu2+ and Zn2+ and thus are good chelators for these metal ions. In addition, L1 and L2 show strong affinity toward A? species. Both compounds are efficient inhibitors of the metal–mediated aggregation of the A?42 peptide and promote disaggregation of amyloid fibrils, as observed by ThT fluorescence, native gel electrophoresis/Western blotting, and transmission electron microscopy (TEM). Interestingly, the formation of soluble A?42 oligomers in presence of metal ions and BFCs leads to an increased cellular toxicity. These results suggest that for the A?42 peptide – in contrast to the A?40 peptide, the previously employed strategy of inhibiting A? aggregation and promoting amyloid fibril dissagregation may not be optimal for the development of potential AD therapeutics, due to formation of neurotoxic soluble A?42 oligomers.

Sharma, Anuj K.; Pavlova, Stephanie T.; Kim, Jaekwang; Finkelstein, Darren; Hawco, Nicholas J.; Rath, Nigam P.; Kim, Jungsu; Mirica, Liviu M.

2012-01-01

410

Employing bifunctional enzymes for enhanced extraction of bioactives from plants: flavonoids as an example.  

PubMed

A cost-effective and environmentally friendly approach was developed to improve the extraction of active ingredients from plants, in which a bifunctional enzyme was employed for not only facilitating cell wall degradation but also increasing the bioactivity of target compounds in the extract. In the aqueous extraction of flavonoids from Glycyrrhizae radix, Trichoderma viride cellulase, a commercial cell-wall-degrading enzyme, was found to efficiently deglycosylate liquiritin and isoliquiritin, which are of high content but low bioactivity, into their aglycones that have much higher physiological activities for dietary and medicinal uses. Under optimized conditions, the extraction yield of liquiritigenin and isoliquiritigenin aglycones reached 4.23 and 0.39 mg/g of dry weight (dw) with 6.51- and 3.55-fold increases, respectively. The same approach was expanded to the extraction of flavonoids from Scutellariae radix using Penicillium decumbens naringinase, where enhanced production of more bioactive bacalein and wogonin was achieved via enzymatic deglycosylation of bacalin and wogonoside. PMID:23869387

Xu, Ming-Shu; Chen, Shuo; Wang, Wen-Quan; Liu, Si-Qin

2013-08-21

411

Bifunctional NMN adenylyltransferase/ADP ribose pyrophosphatase: structure and function in bacterial NAD metabolism  

PubMed Central

Summary Bacterial NadM-Nudix is a bifunctional enzyme containing a nicotinamide mononucleotide (NMN) adenylyltransferase and an ADP-ribose pyrophosphatase domain. While most members of this enzyme family, such as that from a model cyanobacterium Synechocystis sp., are involved primarily in NAD savage/recycling pathways, its close homolog in a category A biodefense pathogen Francisella tularensis likely plays a central role in a recently discovered novel pathway of NAD de novo synthesis. The crystal structures of NadM-Nudix from both species, including their complexes with various ligands and catalytic metal ions, revealed detailed configurations of the substrate binding and catalytic sites in both domains. The structure of the N-terminal NadM domain may be exploited for designing new anti-tularemia therapeutics. The ADP-ribose binding site in the C-terminal Nudix domain is substantially different from that of E. coli ADP-ribose pyrophosphatase, and is more similar to human NUDT9. The latter observation provided new insights into the ligand binding mode of ADPR-gated Ca2+ channel TRPM2.

Huang, Nian; Sorci, Leonardo; Zhang, Xuejun; Brautigan, Chad; Li, Xiaoqing; Raffaelli, Nadia; Magni, Giulio; Grishin, Nick V.; Osterman, Andrei; Zhang, Hong

2008-01-01

412

The determination of the rate of conjugation immunoglobuline with bifunctional chelator  

NASA Astrophysics Data System (ADS)

The work was performed under the GACR project: "Technology of preparation of radionuclides and their labelled compounds for nuclear medicine and pharmacy with the use of the reactor LVR-15" reg. no. 104/03/0499. Imaging of cell’s antigens with the use of labelled immunoglobulines allows imaging of specific receptors on cell membrane and specific tumours. It is necessary to carry out the labelling of the immunoglobulines with radionuclides of suitable physical properties, which form cations (e.g., 111In, 90Y, 177Lu) that form very strong chelates of sufficiently high stability constant preventing the dissociation of complexes or the radionuclide under “in-vivo” conditions. The immunoglobuline must be conjugated with the bifunctional chelator (BCH), which contains both chelating unit and reactive group for binding to the immunoglobuline. In our laboratory we have conjugated human IgG and monoclonal antibody CD20 with diethylenetriamine pentaacetic acid dianhydride (cDTPAA). Radionuclides 90Y and 177Lu prepared on the LVR-15 reactor in NRI Rez were used for labelling. After conjugation and labelling the yields in relation to the amount of isotopic carrier have been determined.

Málek, Z.; Miler, V.; Budský, F.

2006-01-01

413

Drosophila SPF45: A Bifunctional Protein with Roles in Both Splicing and DNA Repair  

PubMed Central

The sequence of the SPF45 protein is significantly conserved, yet functional studies have identified it as a splicing factor in animal cells and as a DNA-repair protein in plants. Using a combined genetic and biochemical approach to investigate this apparent functional discrepancy, we unify and validate both of these studies by demonstrating that the Drosophila melanogaster protein is bifunctional, with independent functions in DNA repair and splicing. We find that SPF45 associates with the U2 snRNP and that mutations that remove the C-terminal end of the protein disrupt this interaction. Although animals carrying this mutation are viable, they are nevertheless compromised in their ability to regulate Sex-lethal splicing, demonstrating that Sex-lethal is an important physiological target of SPF45. Furthermore, these mutant animals exhibit phenotypes diagnostic of difficulties in recovering from exogenously induced DNA damage. The conclusion that SPF45 functions in the DNA-repair pathway is strengthened by finding both genetic and physical interactions between SPF45 and RAD201, a previously uncharacterized member of the RecA/Rad51 protein family. Together with our finding that the fly SPF45 protein increases the survival rate of mutagen-treated bacteria lacking the RecG helicase, these studies provide the tantalizing suggestion that SPF45 has an ancient and evolutionarily conserved role in DNA repair.

Chaouki, Ahmad Sami; Salz, Helen K

2006-01-01

414

Isolation and molecular characterization of the bifunctional hydroxymethyldihydropterin pyrophosphokinase-dihydropteroate synthase gene from Toxoplasma gondii.  

PubMed

Toxoplasma gondii is an important cause of AIDS-related opportunistic infection, manifest as toxoplasmic encephalitis. The clinical treatment of choice is the synergistic combination of antifolate agents, pyrimethamine and sulphadiazine, of which the latter targets the parasite's dihydropteroate synthase (DHPS) activity. Here, we describe the isolation of the gene encoding this activity in T. gondii. The nucleotide sequence contains an open reading frame interrupted by five introns, which encodes a protein of 664 amino acids with an M(r) of 72991. Sequence analysis revealed that, in addition to DHPS, the predicted protein contains a second enzyme function, hydroxymethyldihydropterin pyrophosphokinase (PPPK). This enzyme immediately precedes DHPS in the folate biosynthetic pathway. The bifunctional arrangement of the T. gondii pppk-dhps gene is the same as that observed in the related protozoan parasite, Plasmodium falciparum, and confirms previous biochemical data that these activities were inseparable. Recently, specific mutations within conserved motifs of the DHPS gene of P. falciparum have been identified which give rise to sulphonamide drug resistance. Analysis of seven clinical isolates of T. gondii did not reveal any similar mutations in this limited sample of organisms that had been subjected to drug pressure. PMID:9178266

Pashley, T V; Volpe, F; Pudney, M; Hyde, J E; Sims, P F; Delves, C J

1997-05-01

415

Myocardin is a bifunctional switch for smooth versus skeletal muscle differentiation  

PubMed Central

Skeletal and smooth muscle can mutually transdifferentiate, but little molecular insight exists as to how each muscle program may be subverted to the other. The myogenic basic helix–loop–helix transcription factors MyoD and myogenin (Myog) direct the development of skeletal muscle and are thought to be dominant over the program of smooth muscle cell (SMC) differentiation. Myocardin (Myocd) is a serum response factor (SRF) coactivator that promotes SMC differentiation through transcriptional stimulation of SRF-dependent smooth muscle genes. Here we show by lineage-tracing studies that Myocd is expressed transiently in skeletal muscle progenitor cells of the somite, and a majority of skeletal muscle is derived from Myocd-expressing cell lineages. However, rather than activating skeletal muscle-specific gene expression, Myocd functions as a transcriptional repressor of Myog, inhibiting skeletal muscle differentiation while activating SMC-specific genes. This repressor function of Myocd is complex, involving histone deacetylase 5 silencing of the Myog promoter and Myocd's physical contact with MyoD, which undermines MyoD DNA binding and transcriptional synergy with MEF2. These results reveal a previously unrecognized role for Myocd in repressing the skeletal muscle differentiation program and suggest that this transcriptional coregulator acts as a bifunctional molecular switch for the smooth versus skeletal muscle phenotypes.

Long, Xiaochun; Creemers, Esther E.; Wang, Da-Zhi; Olson, Eric N.; Miano, Joseph M.

2007-01-01

416

Developmental Roles of D-bifunctional Protein-A Zebrafish Model of Peroxisome Dysfunction  

PubMed Central

The peroxisome is an intracellular organelle that responds dynamically to environmental changes. Various model organisms have been used to study the roles of peroxisomal proteins in maintaining cellular homeostasis. By taking advantage of the zebrafish model whose early stage of embryogenesis is dependent on yolk components, we examined the developmental roles of the D-bifunctional protein (Dbp), an essential enzyme in the peroxisomal ?-oxidation. The knockdown of dbp in zebrafish phenocopied clinical manifestations of its deficiency in human, including defective craniofacial morphogenesis, growth retardation, and abnormal neuronal development. Overexpression of murine Dbp rescued the morphological phenotypes induced by dbp knockdown, indicative of conserved roles of Dbp during zebrafish and mammalian development. Knockdown of dbp impaired normal development of blood, blood vessels, and most strikingly, endoderm-derived organs including the liver and pancreas - a phenotype not reported elsewhere in connection with peroxisome dysfunction. Taken together, our results demonstrate for the first time that zebrafish might be a useful model animal to study the role of peroxisomes during vertebrate development.

Kim, Yong-Il; Bhandari, Sushil; Lee, Joon No; Yoo, Kyeong-Won; Kim, Se-Jin; Oh, Gi-Su; Kim, Hyung-Jin; Cho, Meyoung; Kwak, Jong-Young; So, Hong-Seob; Park, Raekil; Choe, Seong-Kyu

2014-01-01

417

NSs Encoded by Groundnut Bud Necrosis Virus Is a Bifunctional Enzyme  

PubMed Central

Groundnut bud necrosis virus (GBNV), a member of genus Tospovirus in the family Bunyaviridae, infects a large number of leguminosae and solanaceae plants in India. With a view to elucidate the function of nonstructural protein, NSs encoded by the small RNA genome (S RNA), the NSs protein of GBNV- tomato (Karnataka) [1] was over-expressed in E. coli and purified by Ni-NTA chromatography. The purified rNSs protein exhibited an RNA stimulated NTPase activity. Further, this activity was metal ion dependent and was inhibited by adenosine 5? (?, ? imido) triphosphate, an ATP analog. The rNSs could also hydrolyze dATP. Interestingly, in addition to the NTPase and dATPase activities, the rNSs exhibited ATP independent 5? RNA/DNA phosphatase activity that was completely inhibited by AMP. The 5? ? phosphate could be removed from ssDNA, ssRNA, dsDNA and dsRNA thus confirming that rNSs has a novel 5? ? phosphatase activity. K189A mutation in the Walker motif A (GxxxxGKT) resulted in complete loss of ATPase activity, but the 5? phosphatase activity was unaffected. On the other hand, D159A mutation in the Walker motif B (DExx) resulted in partial loss of both the activities. These results demonstrate for the first time that NSs is a bifunctional enzyme, which could participate in viral movement, replication or in suppression of the host defense mechanism.

Lokesh, Bhushan; Rashmi, Panigrahi R.; Amruta, Bhat S.; Srisathiyanarayanan, Dharmaiah; Murthy, Mathur R. N.; Savithri, Handanahal S.

2010-01-01

418

Bifunctional Coupling Agents for Radiolabeling of Biomolecules and Target-Specific Delivery of Metallic Radionuclides  

PubMed Central

Receptor-based radiopharmaceuticals are of great current interest in early molecular imaging and radiotherapy of cancers, and provide a unique tool for target-specific delivery of radionuclides to the diseased tissues. In general, a target-specific radiopharmaceutical can be divided into four parts: targeting biomolecule (BM), pharmacokinetic modifying (PKM) linker, bifunctional coupling or chelating agent (BFC), and radionuclide. The targeting biomolecule serves as a “carrier” for specific delivery of the radionuclide. PKM linkers are used to modify radiotracer excretion kinetics. BFC is needed for radiolabeling of biomolecules with a metallic radionuclide. Different radiometals have significant difference in their coordination chemistry, and require BFCs with different donor atoms and chelator frameworks. Since the radiometal chelate can have a significant impact on physical and biological properties of the target-specific radiopharmaceutical, its excretion kinetics can be altered by modifying the coordination environment with various chelators or coligand, if needed. This review will focus on the design of BFCs and their coordination chemistry with technetium, copper, gallium, indium, yttrium and lanthanide radiometals.

Liu, Shuang

2008-01-01

419

The structure of the conserved neurotrophic factors MANF and CDNF explains why they are bifunctional.  

PubMed

We have solved the structures of mammalian mesencephalic astrocyte-derived neurotrophic factor (MANF) and conserved dopamine neurotrophic factor (CDNF). CDNF protects and repairs midbrain dopaminergic neurons in vivo; MANF supports their survival in culture and is also cytoprotective against endoplasmic reticulum (ER) stress. Neither protein structure resembles any known growth factor but the N-terminal domain is a saposin-like lipid-binding domain. MANF and CDNF may thus bind lipids or membranes. Consistent with this, there are two patches of conserved lysines and arginines. The natively unfolded MANF C-terminus contains a CKGC disulphide bridge, such as reductases and disulphide isomerases, consistent with a role in ER stress response. The structure thus explains why MANF and CDNF are bifunctional; neurotrophic activity may reside in the N-terminal domain and ER stress response in the C-terminal domain. Finally, we identified three changes, (MANF)I10-->K(CDNF), (MANF)E79-->M(CDNF) and (MANF)K88-->L(CDNF), that may account for the biological differences between the proteins. PMID:19258449

Parkash, Vimal; Lindholm, Päivi; Peränen, Johan; Kalkkinen, Nisse; Oksanen, Esko; Saarma, Mart; Leppänen, Veli-Matti; Goldman, Adrian

2009-04-01

420

Genetic engineering of a bifunctional IgG fusion protein with iduronate-2-sulfatase.  

PubMed

Iduronate-2-sulfatase (IDS) is a lysosomal sulfatase that prevents the accumulation within the brain of glycosoaminoglycans. However, IDS does not cross the blood-brain barrier (BBB). To enable BBB transport, human IDS, minus its signal peptide, was fused to the carboxyl terminus of the heavy chain of a chimeric monoclonal antibody (mAb) to the human insulin receptor (HIR). The HIRMAb crosses the BBB on the endogenous insulin receptor and acts as a molecular Trojan horse to ferry the IDS into brain. The HIRMAb-IDS fusion protein was expressed in COS cells and purified with protein A affinity chromatography. The size of the fusion heavy chain, as measured with Western blotting and antibodies to either human IDS or human IgG, was increased about 80 kDa, relative to the size of the heavy chain of the parent HIRMAb. The HIRMAb-IDS fusion protein retained high-affinity binding for the HIR. The IDS enzyme specific activity of the fusion protein was 51 +/- 7 nmol/h per microgram of protein, which is comparable to the enzyme activity of recombinant IDS. The fusion protein was taken up by human fibroblasts, and the accumulation of glycosoaminoglycans in fibroblasts null for the sulfatase was decreased 84% by treatment with the fusion protein. The HIRMAb-IDS fusion protein is a bifunctional IgG-sulfatase fusion protein, which has been specifically engineered for targeted drug delivery across the human BBB. PMID:20000684

Lu, Jeff Zhiqiang; Hui, Eric Ka-Wai; Boado, Ruben J; Pardridge, William M

2010-01-01

421

BIFUNCTIONAL CATALYSTS FOR THE SELECTIVE CATALYTIC REDUCTION OF NO BY HYDROCARBONS  

SciTech Connect

Novel bifunctional catalysts combining two active phases, typically Cu-ZSM-5 and a modifier, were prepared and tested for the selective catalytic reduction of nitrogen oxides using propylene in order to overcome the hindering effects of water typically seen for single-phase catalysts such as Cu-ZSM-5. The catalysts were made by typical preparation techniques, but parameters could be varied to influence the catalyst. The physical characterization of the materials showed that the modification phase was added strictly to the external surface of the zeolite without hindering any internal surface area. Chemical characterization by temperature programmed reactions, DRIFTS and x-ray absorption spectroscopy indicated strong interaction between the two phases, primarily producing materials that exhibited lower reduction temperatures. Two improvements in NOx reduction activity (1000 ppm NO, 1000 ppm C3H6, 2% O2, 30,000 hr-1 GHSV) were seen for these catalysts compared with Cu- ZSM-5: a lower temperature of maximum NOx conversion activity (as low at 250 C), and an enhancement of activity when water was present in the system. The use of a second phase provides a way to further tune the properties of the catalyst in order to achieve mechanistic conditions necessary to maximize NOx remediation.

Neylon, M; Castagnola, M; Kropf, A.; Marshall, C

2003-08-24

422

A new bifunctional chelator enables facile biocoupling and radiolabeling as the basis for a bioconjugation kit.  

PubMed

A new tridentate bifunctional chelator, N-(-2-picolyl)(-4-hydroxy)(-3-amino)benzoic acid (PHAB), was designed to efficiently coordinate the [(99m)Tc(CO)3](+) core and facilitate coupling reactions to biomolecules. The chelator can be procured in the form of the corresponding benzotriazole ester (PHAB-OBT), which can be stored and used as a bioconjugation kit. PHAB-OBT reacts with modified carbohydrates with high selectivity and efficiency in a single step in both aqueous and organic media. As is desirable for a kit, no complicated chemical bench work is required. Glycoconjugate postlabeling resulted in neutral radiolabeled glycans with high radiochemical yields. Prelabeling approaches were assessed by successive reaction of PHAB-OBT with the [(99m)Tc(CO)3](+) core and a modified galactose model. The radiolabeled galactose was obtained in 84% yield as defined by HPLC analysis. Biodistribution of the radioactive (99m)Tc-labeled chelator, as well as the glycoconjugates, were examined in mice. Noticeably different biodistribution patterns were observed that reflect trends in the uptake of carbohydrate analogues by various organs. PMID:24723504

Barandov, Ali; Grünstein, Dan; Apostolova, Ivalaya; Buchert, Ralph; Roger, Michel; Brenner, Winfried; Abram, Ulrich; Seeberger, Peter H

2014-05-01

423

Transient Ru-methyl formate intermediates generated with bifunctional transfer hydrogenation catalysts  

PubMed Central

Desorption electrospray ionization (DESI) coupled to high-resolution Orbitrap mass spectrometry (MS) was used to study the reactivity of a (?-amino alcohol)(arene)RuCl transfer hydrogenation catalytic precursor in methanol (CH3OH). By placing [(p-cymene)RuCl2]2 on a surface and spraying a solution of ?-amino alcohol in methanol, two unique transient intermediates having lifetimes in the submillisecond to millisecond range were detected. These intermediates were identified as Ru (II) and Ru (IV) complexes incorporating methyl formate (HCOOCH3). The Ru (IV) intermediate is not observed when the DESI spray solution is sparged with Ar gas, indicating that O2 dissolved in the solvent is necessary for oxidizing Ru (II) to Ru (IV). These proposed intermediates are supported by high-resolution and high mass accuracy measurements and by comparing experimental to calculated isotope profiles. Additionally, analyzing the bulk reaction mixture using gas chromatography-MS and nuclear magnetic resonance spectroscopy confirms the formation of HCOOCH3. These results represent an example that species generated from the (?-amino alcohol)(arene)RuCl (II) catalytic precursor can selectively oxidize CH3OH to HCOOCH3. This observation leads us to propose a pathway that can compete with the hydrogen transfer catalytic cycle. Although bifunctional hydrogen transfer with Ru catalysts has been well-studied, the ability of DESI to intercept intermediates formed in the first few milliseconds of a chemical reaction allowed identification of previously unrecognized intermediates and reaction pathways in this catalytic system.

Perry, Richard H.; Brownell, Kristen R.; Chingin, Konstantin; Cahill, Thomas J.; Waymouth, Robert M.; Zare, Richard N.

2012-01-01

424

Platinum-gold nanoparticles: a highly active bifunctional electrocatalyst for rechargeable lithium-air batteries.  

PubMed

PtAu nanoparticles (NPs) were shown to strongly enhance the kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in rechargeable Li-O(2) cells. Li-O(2) cells with PtAu/C were found to exhibit the highest round-trip efficiency reported to date. During ORR via xLi(+) + O(2) + xe(-) --> Li(x)O(2), the discharge voltage with PtAu/C was considerably higher than that of pure carbon and comparable to that of Au/C. During OER via Li(x)O(2) --> xLi(+) + O(2) + xe(-), the charge voltages with PtAu/C fell in the range from 3.4 to 3.8 V(Li), which is slightly lower than obtained with Pt. It is hypothesized that PtAu NPs exhibit bifunctional catalytic activity, having surface Au and Pt atoms primarily responsible for ORR and OER kinetics in Li-O(2) cells, respectively. PMID:20527774

Lu, Yi-Chun; Xu, Zhichuan; Gasteiger, Hubert A; Chen, Shuo; Hamad-Schifferli, Kimberly; Shao-Horn, Yang

2010-09-01

425

Characterisation of two bifunctional cellulase-xylanase enzymes isolated from a bovine rumen metagenome library.  

PubMed

Ruminant digestive tract microbes hydrolyse plant biomass, and the application of metagenomic techniques can provide good coverage of their glycosyl hydrolase enzymes. A metagenomic library of circa 70,000 fosmids was constructed from bacterial DNA isolated from bovine rumen and subsequently screened for cellulose hydrolysing activities on a CMC agar medium. Two clones were selected based on large clearance zones on the CMC agar plates. Following nucleotide sequencing, translational analysis and homology searches, two cellulase encoding genes (cel5A and cel5B) belonging to the glycosyl hydrolyse family 5 were identified. Both genes encoded pre-proteins of about 62 kDa, containing signal leader peptides which could be cleaved to form mature proteins of about 60 kDa. Biochemical characterisation revealed that both enzymes showed alkaline pH optima of 9.0 and the temperature optima of 65 °C. Substrate specificity profiling of the two enzymes using 1,4-?-D-cello- and xylo-oligosaccharides revealed preference for longer oligosaccharides (n ? 3) for both enzymes, suggesting that they are endo-cellulases/xylanases. The bifunctional properties of the two identified enzymes render them potentially useful in degrading the ?-1,4 bonds of both the cellulose and hemicellulose polymers. PMID:23086538

Rashamuse, K J; Visser, D F; Hennessy, F; Kemp, J; Roux-van der Merwe, M P; Badenhorst, J; Ronneburg, T; Francis-Pope, R; Brady, D

2013-02-01

426

Bifunctional silica nanoparticles for the exploration of biofilms of Pseudomonas aeruginosa.  

PubMed

Luminescent silica nanoparticles are frequently employed for biotechnology applications mainly because of their easy functionalization, photo-stability, and biocompatibility. Bifunctional silica nanoparticles (BSNPs) are described here as new efficient tools for investigating complex biological systems such as biofilms. Photoluminescence is brought about by the incorporation of a silylated ruthenium(II) complex. The surface properties of the silica particles were designed by reaction with amino-organosilanes, quaternary ammonium-organosilanes, carboxylate-organosilanes and hexamethyldisilazane. BSNPs were characterized extensively by DRIFT, (13)C and (29)Si solid state NMR, XPS, and photoluminescence. Zeta potential and contact angle measurements exhibited various surface properties (hydrophilic/hydrophobic balance and electric charge) according to the functional groups. Confocal laser scanning microscopy (CLSM) measurements showed that the spatial distribution of these nanoparticles inside a biofilm of Pseudomonas aeruginosa PAO1 depends more on their hydrophilic/hydrophobic characteristics than on their size. CLSM observations using two nanosized particles (25 and 68 nm) suggest that narrow diffusion paths exist through the extracellular polymeric substances matrix. PMID:23805884

Mauline, L; Gressier, M; Roques, C; Hammer, P; Ribeiro, S J L; Caiut, J M A; Menu, M-J

2013-01-01

427

First report of a bifunctional chitinase/lysozyme produced by Bacillus pumilus SG2.  

PubMed

Bacillus pumilus SG2 isolated from high salinity ecosystem in Iran produces two chitinases (ChiS and ChiL) and secretes them into the medium. In this study, chiS and chiL genes were cloned in pQE-30 expression vector and were expressed in the cytoplasm of Escherichia coli strain M15. The recombinant proteins were purified using Ni-NTA column. The optimum pH and optimum temperature for enzyme activity of ChiS were pH 6, 50°C; those of ChiL were pH 6.5, 40°C. The purified chitinases showed antifungal activity against Fusarium graminearum, Rhizoctonia solani, Magnaporthe grisea, Sclerotinia sclerotiorum, Trichoderma reesei, Botrytis cinerea and Bipolaris sp. Moreover, purified ChiS was identified as chitinase/lysozyme, which are capable of degrading the chitin component of fungal cell walls and the peptidoglycan component of cell walls with many kinds of bacteria (Xanthomonas translucens pv. hordei, Xanthomonas axonopodis pv. citri, Bacillus licheniformis, E. coli C600, E. coli TOP10, Pseudomonas aeruginosa and Pseudomonas putida). Strong homology was found between the three-dimensional structures of ChiS and a chitinase/lysozyme from Bacillus circulans WL-12. This is the first report of a bifunctional chitinase/lysozyme from B. pumilus. PMID:22112904

Ghasemi, Seyedhadi; Ahmadian, Gholamreza; Sadeghi, Mehdi; Zeigler, Daniel R; Rahimian, Heshmatollah; Ghandili, Soheila; Naghibzadeh, Neda; Dehestani, Ali

2011-03-01

428

Amphipathic Homopolymers for siRNA Delivery: Probing Impact of Bifunctional Polymer Composition on Transfection.  

PubMed

In this study, we systematically explore the influence of the lipophilic group on the siRNA transfection properties of the polycationic-based delivery vectors. For this, a novel and modular synthetic strategy was developed for the preparation of polymers carrying a cationic site and a lipophilic group at each polymer repeat unit. These bifunctional polymers could form a complex with siRNA and deliver it to human colon carcinoma cells (HT-29-luc). In general, transfection capability increased with an increase in the chain length of the lipophilic moiety. The best transfection agent, a polymer containing ammonium groups and pentyl side chains, exhibited lower toxicity and higher transfection efficiency than branched and linear polyethylenimines (PEI). Moreover, as opposed to PEI, the transfection efficiency of polymer/siRNA complexes remained unchanged in the presence of bafilomycin A1, a proton pump inhibitor, suggesting that the present system did not rely on the "proton sponge" effect for siRNA delivery. PMID:24754338

Buerkli, Christian; Lee, Soo Hyeon; Moroz, Elena; Stuparu, Mihaiela C; Leroux, Jean-Christophe; Khan, Anzar

2014-05-12

429

Thin film superconductor magnetic bearings  

DOEpatents

A superconductor magnetic bearing includes a shaft (10) that is subject to a load (L) and rotatable around an axis of rotation, a magnet (12) mounted to the shaft, and a stator (14) in proximity to the shaft. The stator (14) has a superconductor thin film assembly (16) positioned to interact with the magnet (12) to produce a levitation force on the shaft (10) that supports the load (L). The thin film assembly (16) includes at least two superconductor thin films (18) and at least one substrate (20). Each thin film (18) is positioned on a substrate (20) and all the thin films are positioned such that an applied magnetic field from the magnet (12) passes through all the thin films. A similar bearing in which the thin film assembly (16) is mounted on the shaft (10) and the magnet (12) is part of the stator (14) also can be constructed.

Weinberger, Bernard R. (Avon, CT)

1995-12-26

430

The BEAR Beamline at Elettra  

SciTech Connect

The BEAR (Bending Magnet for Emission Absorption and Reflectivity) beamline is installed at the right exit of the 8.1 bending magnet at ELETTRA. The beamline - in operation since January 2003 - delivers linear and circularly polarized radiation in the 5 - 1600 eV energy range. The experimental station is composed of a UHV chamber for reflectivity, absorption, fluorescence and angle resolved photoemission measurements and a UHV chamber for in-situ sample preparation.

Nannarone, S.; Pasquali, L.; Selvaggi, G. [UdR-INFM Modena, Universita di Modena and Reggio Emilia, Via Vignolese 905, 41100 Modena (Italy); Borgatti, F.; DeLuisa, A.; Doyle, B.P.; Gazzadi, G.C.; Giglia, A.; Finetti, P.; Pedio, M. [TASC-INFM, MM building in Area Science Park, s.s.14 km 163.5, 34012 Basovizza, Trieste (Italy); Mahne, N. [TASC-INFM, Universita di Trieste, Trieste (Italy); Naletto, G.; Pelizzo, M.G.; Tondello, G. [LUXOR-INFM, Universita di Padova, Padua (Italy)

2004-05-12

431

Bearing capacity of desiccated tailings  

Microsoft Academic Search

The development of matric suctions in soils contributes to their shear strength, resulting in an enhanced factor of safety against bearing-capacity failure. In this paper, matric suction profiles of desiccated mine tailings are predicted from a steady-state solution for evaporative conditions, and from an isothermal mathematical model that simulates liquid and vapor water flow through soils. The shear-strength envelope with

Daud W. Rassam; David J. Williams

1999-01-01

432

Rolling element bearings in space  

NASA Technical Reports Server (NTRS)

Some of the advances in tribology that have been associated with aerospace mechanisms are discussed. The needs of aerospace have been the dominant forces leading to improvements in understanding and applying tribology technology. In the past two decades improvements in understanding bearing torque, elastohydrodynamic lubrication, lubricant distribution, cage stability, and transfer film lubricants have been made. It is anticipated that further developments will be made in response to future aerospace requirements.

Kannel, J. W.; Dufrane, K. F.

1986-01-01

433

Fault Tolerant Homopolar Magnetic Bearings  

NASA Technical Reports Server (NTRS)

Magnetic suspensions (MS) satisfy the long life and low loss conditions demanded by satellite and ISS based flywheels used for Energy Storage and Attitude Control (ACESE) service. This paper summarizes the development of a novel MS that improves reliability via fault tolerant operation. Specifically, flux coupling between poles of a homopolar magnetic bearing is shown to deliver desired forces even after termination of coil currents to a subset of failed poles . Linear, coordinate decoupled force-voltage relations are also maintained before and after failure by bias linearization. Current distribution matrices (CDM) which adjust the currents and fluxes following a pole set failure are determined for many faulted pole combinations. The CDM s and the system responses are obtained utilizing 1D magnetic circuit models with fringe and leakage factors derived from detailed, 3D, finite element field models. Reliability results are presented vs. detection/correction delay time and individual power amplifier reliability for 4, 6, and 7 pole configurations. Reliability is shown for two success criteria, i.e. (a) no catcher bearing contact following pole failures and (b) re-levitation off of the catcher bearings following pole failures. An advantage of the method presented over other redundant operation approaches is a significantly reduced requirement for backup hardware such as additional actuators or power amplifiers.

Li, Ming-Hsiu; Palazzolo, Alan; Kenny, Andrew; Provenza, Andrew; Beach, Raymond; Kascak, Albert

2003-01-01

434

The Design of Externally Pressurized Gas Lubricated Bearings by the Method of Bearing Equivalence  

Microsoft Academic Search

This paper presents the theoretical development and experimental verification of a simplified technique for the design of externally pressurized gas lubricated bearings. The general procedure is to establish an equivalent rectangular bearing which is the performance replica of an arbitrary gas bearing configuration. The resulting equivalent bearing has the same load support, clearance, area, source pressure, entrance losses, and mass

Richard C. Turnblade

1962-01-01

435

The effects of bearing distortion on the performance of hydrodynamic thrust bearings  

Microsoft Academic Search

Purpose – In this work, the performance characteristics of thrust bearings are studied by taking into account bearing distortions. Design\\/methodology\\/approach – The pressure distribution in the bearing is found using Reynolds' equation. Reynolds' equation is solved under isothermal conditions by assuming oil viscosity constant. The amount of deformation in the bearing is determined using constitute equations applied to linear elastic

Emin Güllü

2005-01-01

436

Oil Exchange Between Ball Bearings and Cotton-Phenolic Bail-Bearing Retainers  

Microsoft Academic Search

Experiments have been performed that determine for the first time the transfer of oil between cotton-phenolic ball-bearing retainers and operating ball bearings. A full retainer exchanges oil with the metal park of the bearing, probably by diffusional mixing. There is no net delivery of oil from the retrainer to the metal parts of the bearing. A partially filled retainer (such

P. A. Bertrand; D. J. Carré; Reinhold Bauer

1995-01-01

437

Valve assembly having remotely replaceable bearings  

DOEpatents

A valve assembly having remotely replaceable bearings is disclosed wherein a valve disc is supported within a flow duct for rotation about a pair of axially aligned bearings, one of which is carried by a spindle received within a diametral bore in the valve disc, and the other of which is carried by a bearing support block releasably mounted on the duct circumferentially of an annular collar on the valve disc coaxial with its diametrical bore. The spindle and bearing support block are adapted for remote removal to facilitate servicing or replacement of the valve disc support bearings.

Johnson, Evan R. (San Diego, CA) [San Diego, CA; Tanner, David E. (Poway, CA) [Poway, CA

1980-01-01

438

Servo Reduces Friction In Flexure Bearing  

NASA Technical Reports Server (NTRS)

Proposed servocontrol device reduces such resistive torques as stiction, friction, ripple, and cogging in flexure bearing described in LAR-14348, "Flexure Bearing Reduces Startup Friction". Reduces frictional "bump" torque encountered when bearing ball runs into buildup of grease on bearing race. Also used as cable follower to reduce torque caused by cable and hoses when they bend because of motion of bearing. New device includes torquer across ball race. Torquer controlled by servo striving to keep flexure at null, removing torque to outer ring. In effect, device is inner control loop reducing friction, but does not control platforms or any outer-control-loop functions.

Clingman, W. Dean

1991-01-01

439

Equations For Elastohydrodynamic Lubrication Of Bearings  

NASA Technical Reports Server (NTRS)

Equation for thickness of elastohydrodynamic (EHD) lubricant film in rolling-element bearing reduced to simplified form involving only inside and outside diameters of bearing, speed of rotation, parameter related to type of lubricant, and viscosity of lubricant at temperature of bearing. In addition, experimentally derived graph of EHD-film-thickness-reduction factor as function of contact-lubricant-flow number. Accounts for lubricant starvation within Hertzian contact. Graph relating ratio of minimum film thickness to composite roughness of bearing surfaces and to lubrication-life correction factor also provided. Life-correction factor used to determine resultant life of bearing.

Zaretsky, Erwin V.

1993-01-01

440

Polar Bears International: Wrangel Island, Russia  

NSDL National Science Digital Library

This site describes the ongoing research of the polar bears in the Russian High Arctic. Wrangel Island with neighboring small island, Herald Island, are the key reproductive areas for the Chukchi-Alaskan polar bear population. Marine areas and Wrangel and Herald islands provide optimum foraging habitats for polar bears, and polar bear densities in these marine habitats are high all year round. Approximately 350-500 pregnant female polar bears construct their maternity dens on Wrangel and Herald islands every fall, emerging with their cubs in spring. The research is described in terms of goals and objectives, structure, methods, equipment, staff, and implementations.

441

High-Load Multi-Rotational Bridge Bearings.  

National Technical Information Service (NTIS)

This report contains the results of a study on high-load multi-rotational bridge bearings. Information on various bearing types, including pot bearings, disk bearings, and polytetrafluorethylene (PTFE) sliding surfaces is included. Design and selection gu...

J. F. Stanton

1999-01-01

442

Design review of fluid film bearing testers  

NASA Technical Reports Server (NTRS)

The designs of three existing testers (Hybrid Bearing Tester, OTV Bearing Tester, and Long Life Bearing Tester) owned by NASA were reviewed for their capability to serve as a multi-purpose cryogenic fluid film bearing tester. The primary tester function is the validation of analytical predictions for fluid film bearing steady state and dynamic performance. Evaluation criteria were established for test bearing configurations, test fluids, instrumentation, and test objectives. Each tester was evaluated with respect to these criteria. A determination was made of design improvements which would allow the testers to meet the stated criteria. The cost and time required to make the design changes were estimated. A recommendation based on the results of this study was made to proceed with the Hybrid Bearing Tester.

Scharrer, Joseph K.

1993-01-01

443

Lubrication for high load duplex bearings  

SciTech Connect

Three ES and H-compatible lubricants (Environment, Safety and Health) for high load duplex bearing applications were evaluated and compared against trichlorotrifluoroethane (Freon) deposition of low molecular weight polytetrafluoroethylene (PTFE) bearing lubricant extracted from Vydax{trademark}. Vydax is a product manufactured by DuPont consisting of various molecular weights of PTFE suspended in trichlorotrifluoroethane (Freon) which is an ozone-depleting solvent. Bearings with Supercritical CO{sub 2} deposition of PTFE extracted from Vydax AR/IPA, bearings with titanium carbide coated balls, and bearings with diamond-like carbon races and retainers were evaluated. Bearings with Supercritical CO{sub 2} deposition of PTFE from Vydax AR/IPA performed as well as bearings with Freon deposition of PTFE from Freon-based Vydax.

Steinhoff, R.G.

1997-08-01

444

Pratt and Whitney cryogenic turbopump bearing experience  

NASA Technical Reports Server (NTRS)

Successful, reusable bearings require lubrication, traditionally, a transfer film from sacrificial cage wear. Early testing included materials screening programs to identify suitable cryogenic cage materials. A specially developed element tester that simulated the function of a ball bearing cage was used. Suitable materials must provide lubrication with an acceptably low wear rate, without abrading contacting surfaces. The most promising materials were tested in full scale bearings at speeds up to 4 MDN. Teflon, filled with 40 percent bronze powder, was the best performing material. A variety of bearings were designed and successfully tested in LH2 and LOX. Bearings with bronze filled Teflon cages were successfully tested for 150 hrs. In overload tests, the same design was tested for 5 hrs at maximum Hertz stresses above 450 ksi and an additional 5 hrs with a maximum Hertz stress exceeding 500 ksi. Four bearings were tested in LOX for 25 hrs, with a maximum time per bearing of 10 hrs.

Poole, W. E.; Bursey, R. W., Jr.

1988-01-01

445

Wave Journal Bearings Under Dynamic Loads  

NASA Technical Reports Server (NTRS)

The dynamic behavior of the wave journal bearing was determined by running a three-wave bearing with an eccentrically mounted shaft. A transient analysis was developed and used to predict numerical data for the experimental cases. The three-wave journal bearing ran stably under dynamic loads with orbits well inside the bearing clearance. The orbits were almost circular and nearly free of the influence of, but dynamically dependent on, bearing wave shape. Experimental observations for both the absolute bearing-housing-center orbits and the relative bearing-housing-center-to-shaft-center orbits agreed well with the predictions. Moreover, the subsynchronous whirl motion generated by the fluid film was found experimentally and predicted theoretically for certain speeds.

Hendricks, Robert C.; Dimofte, Florin

2002-01-01

446

Calf stretching in non-weight bearing versus weight bearing.  

PubMed

Limited ankle dorsiflexion passive range of motion (DF PROM) has been associated with lower extremity overuse injuries. Therefore, clinicians often prescribe stretching exercises to increase ankle DF PROM. However, there is limited evidence to indicate if any particular gastrocnemius stretching exercise results in greater improvement in DF PROM. The aim of this study was to determine if gastrocnemius stretching in non-weight bearing (NWB) or weight bearing (WB) results in a greater increase of ankle DF PROM. 28 healthy volunteers, aged 18-55 years, who exhibited less than 10 degrees of ankle DF PROM completed the study. Participants were randomized into 2 stretching groups: NWB and WB. Both groups completed a 3-week home gastrocnemius stretching program, consisting of 5 repetitions held for 30 s each, 2 times daily. Participants' ankle DF PROM was measured with a blinded standard goniometer in NWB and WB positions before and after participation in a 3-week home gastrocnemius stretching program. Two 3-way mixed model ANOVAs demonstrated no significant difference in ankle DF PROM between the NWB and WB groups for either the NWB measurement condition (p=0.49) or WB measurement condition (p=0.86). Gastrocnemius stretching exercises performed in NWB or WB were equally effective in increasing ankle DF PROM. PMID:21181639

Dinh, N V; Freeman, H; Granger, J; Wong, S; Johanson, M

2011-03-01

447

Identifying Bearing Rotordynamic Coefficients using an Extended Kalman Filter  

NASA Technical Reports Server (NTRS)

An Extended Kalman Filter is developed to estimate the linearized direct and indirect stiffness and damping force coefficients for bearings in rotor-dynamic applications from noisy measurements of the shaft displacement in response to imbalance and impact excitation. The bearing properties are modeled as stochastic random variables using a Gauss-Markov model. Noise terms are introduced into the system model to account for all of the estimation error, including modeling errors and uncertainties and the propagation of measurement errors into the parameter estimates. The system model contains two user-defined parameters that can be tuned to improve the filter s performance; these parameters correspond to the covariance of the system and measurement noise variables. The filter is also strongly influenced by the initial values of the states and the error covariance matrix. The filter is demonstrated using numerically simulated data for a rotor-bearing system with two identical bearings, which reduces the number of unknown linear dynamic coefficients to eight. The filter estimates for the direct damping coefficients and all four stiffness coefficients correlated well with actual values, whereas the estimates for the cross-coupled damping coefficients were the least accurate.

Miller, Bard A.; Howard, Samuel A.

2008-01-01

448

Identifying Bearing Rotodynamic Coefficients Using an Extended Kalman Filter  

NASA Technical Reports Server (NTRS)

An Extended Kalman Filter is developed to estimate the linearized direct and indirect stiffness and damping force coefficients for bearings in rotor dynamic applications from noisy measurements of the shaft displacement in response to imbalance and impact excitation. The bearing properties are modeled as stochastic random variables using a Gauss-Markov model. Noise terms are introduced into the system model to account for all of the estimation error, including modeling errors and uncertainties and the propagation of measurement errors into the parameter estimates. The system model contains two user-defined parameters that can be tuned to improve the filter's performance; these parameters correspond to the covariance of the system and measurement noise variables. The filter is also strongly influenced by the initial values of the states and the error covariance matrix. The filter is demonstrated using numerically simulated data for a rotor bearing system with two identical bearings, which reduces the number of unknown linear dynamic coefficients to eight. The filter estimates for the direct damping coefficients and all four stiffness coefficients correlated well with actual values, whereas the estimates for the cross-coupled damping coefficients were the least accurate.

Miller, Brad A.; Howard, Samuel A.

2008-01-01

449

Hydrostatic bearings for a turbine fluid flow metering device  

Microsoft Academic Search

A rotor assembly fluid metering device has been improved by development of a hydrostatic bearing fluid system which provides bearing fluid at a common pressure to rotor assembly bearing surfaces. The bearing fluid distribution system produces a uniform film of fluid distribution system produces a uniform film of fluid between bearing surfaces and allows rapid replacement of bearing fluid between

Fincke

1980-01-01

450

Aging Initiative  

MedlinePLUS

... for the "Aging Initiative" Listserver! News & Publications Blog: Sustainable, Visitable and Universal by Design AARP recognizes Self-Management Assessment and Resource Tool (SMART) Aging News Releases Growing Smarter, Living Healthier: ...

451

Life of Pennzane and 815Z-Lubricated Instrument Bearings Cleaned with Non-CFC Solvents  

NASA Technical Reports Server (NTRS)

This report takes the form of two papers: (1) "Life of Pennzane and 815Z-Lubricated Instrument Bearings cleaned with Non-CFC Solvents" and (2) a published paper, entitled "Instrument bearing life with NON-CFC cleaners". Abstract for paper # 1 : Bearings used in spacecraft mechanisms have historically been cleaned with chlorofluorocarbon CFC-1 13 (Freon) solvents and lubricated with a perfluorinated polyalkylether (PFPE) oils like 815-Z. Little full-scale bearing life test data exists to evaluate the effects of the newer class environmental-friendly bearing cleaners or improved synthetic hydrocarbon space oils like Pennzane. To address the lack of data, a cooperative, bearing life test program was initiated between NASA, Lockheed Martin and MPB. The objective was to obtain comparative long-term, life test data for flight-quality bearings, cleaned with non-CFC solvents versus CFC-1 13 under flight-like conditions with two space oils. A goal was to gain a better understanding of the lubricant surface chemistry effects with such solvents. A second objective was to obtain well-controlled, full-scale bearing life test data with a relatively new synthetic oil (Pennzane), touted as an improvement to Bray 815Z, an oil with considerable space flight history. The second paper, which serves as an attachment, is abstracted below: Bearings used in spacecraft mechanisms have historically been cleaned with chlorofluorocarbon CFC-113 (Freon) solvents and lubricated with a perfluorinated polyalkylether (PFPE) oils like 815-Z. Little full-scale bearing life test data exists to evaluate the effects of the newer class environmental-friendly bearing cleaners or improved synthetic hydrocarbon space oils like Pennzane. To address the lack of data, a cooperative, bearing life test program was initiated between NASA, Lockheed Martin and MPB. The objective was to obtain comparative long-term, life test data for flight-quality bearings, cleaned with non-CFC solvents versus CFC-1 13 under flight-like conditions with two space oils. A goal was to gain a better understanding of the lubricant surface chemistry effects with such solvents. A second objective was to obtain well-controlled, full-scale bearing life test data with a relatively new synthetic oil (Pennzane), touted as an improvement to Bray 815Z, an oil with considerable space flight history.

Loewenthal, Stuart; Jones, William; Predmore, Roamer

1999-01-01

452

Transfer Lubrication For Cryogenic Bearings  

NASA Technical Reports Server (NTRS)

Report presents evaluation of bronze-filled polytetrafluoroethylene (PTFE), known as Salox M, as cage material for ball bearings in high-pressure turbopumps for liquid oxygen. Material evaluated as potentially longer-lived replacement for glass-filled PTFE, known as Armalon. Cage transfers PTFE to balls to form solid lubricant film. However, glass fibers in glass-filled material tend to interfere with transfer. Two cage-design concepts developed; one involves metal-reinforced cage of bronze-filled PTFE; other calls for bronze-filled PTFE inserts in metal structure.

Barber, S. A.; Kannel, J. W.; Dufrane, K. F.

1988-01-01

453

Precision magnetic suspension linear bearing  

NASA Technical Reports Server (NTRS)

We have shown the design and analyzed the electromechanics of a linear motor suitable for independently controlling two suspension degrees of freedom. This motor, at least on paper, meets the requirements for driving an X-Y stage of 10 Kg mass with about 4 m/sq sec acceleration, with travel of several hundred millimeters in X and Y, and with reasonable power dissipation. A conceptual design for such a stage is presented. The theoretical feasibility of linear and planar bearings using single or multiple magnetic suspension linear motors is demonstrated.

Trumper, David L.; Queen, Michael A.

1992-01-01

454