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31.
J Farrar S Portolano N Willcox A Vincent L Jacobson J Newsom-Davis B Rapoport SM McLachlan 《Canadian Metallurgical Quarterly》1997,9(9):1311-1318
The muscle weakness in myasthenia gravis (MG) is caused by heterogeneous high-affinity IgG autoantibodies to the nicotinic acetylcholine receptor (AChR), a complex ion channel glycoprotein. These antibodies are clearly responsible for reducing AChR numbers at the neuromuscular junction in myasthenia; however, the origins, diversity, specificity and pathogenicity of individual antibodies have not yet been established. We have cloned and characterized four different AChR-specific Fab from an MG patient's thymus by screening an IgG1/kappa gene combinatorial lambda phage library with soluble human AChR labeled with [125I] alpha-bungarotoxin. Unlike most previously cloned human antibodies, all four Fab immunoprecipitated soluble human muscle AChR. Two Fab strongly inhibited binding of mAb to the main immunogenic region on the alpha subunits and one Fab bound to an epitope on the fetal-specific gamma subunit. In sensitivity and fine specificity, these Fab resembled the anti-AChR antibodies found in many MG patients, including the donor. The closest germline counterparts for their heavy chains were in VH families 1, 3 and 4; however, there were many differences consistent with an antigen-driven response of diverse B cell clones. The combinatorial approach holds promise for further analysis of human autoantibodies. 相似文献
32.
Christopher L Brown Gillian Bushell Michael W Whitehouse DS Agrawal SG Tupe KM Paknikar Edward RT Tiekink 《Gold bulletin》2007,40(3):245-250
Nanosized gold particles (27 +/− 3 nm) have been proven to be effective in ameliorating the symptoms of mycobacterial-, collagen-
and pristane-induced arthritis in rat models. This contrasts with the drug sodium aurothiomalate that was only effective against
mycobacterial-induced arthritis but not to the same extent as Au0. Gold in the traditional Indian Ayurvedic medicine,Swarna bhasma (gold ash), has been characterized as globular particles of gold with an average size of 56–57 nm. 相似文献
33.
Lynnette S. Walsh Hentges Donald C. Beitz Norman L. Jacobson A. Dare McGilliard Jeffrey J. Veenhuizen 《Lipids》1985,20(11):735-742
In a 2×2 factorial arrangement, miniature pigs were fed four diets containing vegetable protein/fat (soybean) and animal protein
(egg white)/fat (beef tallow) to demonstrate the effects of protein and fat source on total plasma cholesterol, lipoprotein
distribution, low density lipoprotein (LDL) composition, and plasma clearance of LDL-cholesterol and protein. Beef tallow
consumption resulted in greater plasma cholesterol concentration, decreased LDL-cholesterol concentration, and a lower LDL-cholesterol
to LDL-protein ratio than did consumption of soybean oil. High density lipoprotein (HDL)-cholesterol concentration was increased
by beef tallow consumption. Cholesterol percentage by weight in LDL was significantly greater in pigs consuming soybean oil
than those consuming beef tallow. Percentages by weight of protein, triglyceride and phospholipid in LDL were not significantly
different in any group. Dietary protein source had no significant effect on total plasma cholesterol concentration, lipoprotein
concentration or LDL composition. Egg white consumption decreased fractional catabolic rate and irreversible loss of LDL-cholesterol
and LDL-protein when compared with consumption of soy protein. Dietary fat source had no consistent effect on LDL clearance
from plasma. Dietary fat and protein seemed to influence lipoprotein metabolism by different mechanisms. Fat source altered
lipoprotein concentration and LDL composition, whereas protein source affected the removal rate of LDL from plasma.
Data taken from a dissertation submitted to Iowa State University by L. S. Walsh Hentges as partial fulfillment of the requirements
for the Ph.D. degree. A preliminary paper, was presented at the meeting of the American Oil Chemists' Society in Dallas, Texas,
May, 1984. 相似文献
34.
Carbon and boron nitride are used as fiber coatings in silicon-based composites. In order to assess the long-term stability of these materials, reactions of carbon/Si3 N4 and BN/SiC were studied at high temperatures with Knudsen effusion, coupon tests, and by microstructural examination. In the carbon/Si3 N4 system, carbon reacted with Si3 N4 to form gaseous N2 and SiC. The formation of SiC limited further reaction by physically separating the carbon and Si3 N4 . Consequently, the development of high p (N2 ) at the interface, predicted from thermochemical calculations, did not occur, thus limiting the potential deleterious effects of the reaction on the composite. Strong indications of a reaction between BN and SiC were shown by TEM and SIMS analysis of the BN/SiC interface. In long-term exposures, this reaction can lead to a depletion of a BN coating and/or an unfavorable change of the interfacial properties, limiting the beneficial effects of the coating. 相似文献
35.
Adam Jacobson Fan Zeng David Smith Nigel Boswell Thierry Peynot Michael Milford 《野外机器人技术杂志》2021,38(1):5-27
Robustly and accurately localizing vehicles in underground mines is particularly challenging due to the unavailability of GPS, variable and often poor lighting conditions, visual aliasing in long tunnels, and airborne dust and water. In this paper, we present a novel, infrastructure‐less, multisensor localization method for robust autonomous operation within underground mines. The proposed method integrates with existing mine site commissioning and operation procedures and includes both an offline map‐building process and an online localization algorithm. The approach combines the strengths of visual‐based place recognition, LIDAR‐based localization, and odometry in a particle filter fusion process. We provide an extensive experimental validation using new large data sets acquired in two operational Australian underground hard‐rock mines (including a 600m‐deep multilevel mine with approximately 33 km of mapping data and 7 km of vehicle localization) by actual mining vehicles during production operations. We demonstrate a significant increase in localization accuracy over prior state‐of‐the‐art SLAM research systems and real‐time operation, with processing times in the order of 10 Hz. We present results showing a mean error of 0.68 m from the Queensland Mine data set and 1.32 m from the New South Wales Mine data set and at least 86% reduction in error compared with prior state of the art. We also analyze the impact of the particle filter parameters with respect to localization accuracy. Together this study represents a new approach to positioning systems for currently deployed autonomous vehicles within underground mine environments. 相似文献
36.
A. Luo D. L. Jacobson R. Ponnappan 《Journal of Materials Engineering and Performance》1992,1(6):755-761
Thermal energy storage capsules made of Inconel 617 alloy were filled with high- purity LiF- MgF2- KF salts and thermally
cycled at 983 ± 100 K in vacuum for up to 5 years. The containment life performance characteristics with fluoride salts and
in vacuum were examined. Metallographic study indicated that the inside surfaces of the post- test containers had a corrosion
damage of 100 um in depth after 5 years of thermal cycling. The outer surface showed a vaporization damage of 120 μm after
the same period. After 5 years of thermal cycling, the aluminum concentration at the capsule interior surface was reduced
to 0.424 wt% from a nominal concentration of 1.34 wt% and chromium was reduced to 18.7 wt% from a nominal concentration of
21.8 wt%. A more significant depletion of aluminum and chromium was observed at the outer surfaces. Atomic absorption spectroscopy
(AAS) and differential thermal analysis (DTA) were used to reveal the alloying element dissolution and the changes in melting
temperature and heat of fusion of fluoride salts during thermal cycling. A modified diffusion equation for a one-dimensional
semi-infinite bar was applied to the depletion of aluminum on the interior surfaces of the containers. Good agreement was
obtained between the analysis and the measured concentration profiles.
Inconel 617 is a registered trademark of the Inco Alloys International, Inc. 相似文献
37.
Sodium sulfate: Deposition and dissolution of silica 总被引:1,自引:0,他引:1
Nathan S. Jacobson 《Oxidation of Metals》1989,31(1-2):91-103
The hot-corrosion process for SiO2-protected materials involves deposition of Na2SO4 and dissolution of the protective SiO2
scale. Dew points for Na
2SO4 deposition are calculated as a function of pressure, sodium content, and sulfur content. Expected dissolution regimes for SiO2 are calculated as a function of Na2SO4 basicity, hence
generated by fuels with 0.5% and 0.05% S. Controlled-condition burner-rig tests on quartz verify some of these predicted dissolution regimes. However, the basicity of Na2SO4 is not always a simple function of
(Na2O) show that carbon creates basic conditions in Na2SO4, which explains the extensive corrosion of SiO2-protected materials containing carbon, such as SiC. 相似文献
38.
The formation of SiO(g) from SiC by either active oxidation or an oxidation-reduction process is discussed. The Wagner criterion for the transition from active to passive oxidation is generalized for any oxidant. Kinetic modeling of both active oxidation and oxidation-reduction is described.Symbols
-
-
MW
SiC/MW
Si
- CO
CO(g) boundary layer thickness
- ox
gaseous-oxidant, boundary layer thickness
-
stoichiometric factor from Eqs. (2)–(4), # of CO produced/# of oxidant (on oxygen atom basis)
-
gas viscosity
-
concentration of diffusing gas species in boundary layer
-
concentration of major gas species in boundary layer
- oxide
density of SiO2
-
D
diffusion coefficient of diffusing species in gas-boundary layer
-
D
CO
diffusion coefficient of CO(g)
-
D
ox
gas diffusion coefficient of oxidant
-
J
flux, rate of weight loss limited by diffusion in gas-boundary layer
-
J
CO
flux of CO(g)
-
J
ox
flux of gaseous oxidant
-
K
g
linear oxide growth constant, weight/(length2 time)
-
k
g
linear oxide growth constant, length/time
-
k
l
linear volatilization constant for SiO2,k
lo+k
ls, weight/(length2 time)
-
k
lo
linear volatilization constant for oxygen from SiO2, weight/(length2 time)
-
k
ls
linear volatilization constant for silicon from SiO2, weight/(length2 time)
-
k
l
linear volatilization constant for SiO2, length/time
-
k
p
parabolic oxide growth constant, weight2/(length4 time)
-
k
p
parabolic oxide growth constant, length2/time
-
L
sample length parallel to gas flow direction
- (M/A)1
specific weight change due to oxygen gain and associated carbon loss in paralinear oxidation
- (M/A)1L
limiting value of weight change due to oxygen gain and associated carbon loss in paralinear oxidation
- (M/A)2
specific weight change due to silicon loss and associated carbon loss in paralinear oxidation
-
MW
C
molecular weight of carbon
-
molecular weight of O2
-
MW
Si
molecular weight of silicon
-
MW
SiC
molecular weight of silicon carbide
-
molecular weight of silica
-
n
number of oxygen atoms per oxidant molecule
-
P
CO
eq
eqiilibrium CO(g) pressure
-
P
CO
g
CO(g) pressure outside of boundary layer
-
P
CO
i
CO(g) pressure at SiC-gas interface
-
P
ox
g
oxidant gas pressure outside of boundary layer
-
P
ox
i
oxidant gas pressure at SiC-gas interface
-
R
gas constant
-
t
time
-
T
absolute temperature
-
v
linear gas velocity
-
x
oxide thickness
-
x
L
limiting oxide thickness achieved in paralinear oxidation
-
x
t
oxide thickness at which transition from linear to parabolic growth occurs 相似文献
39.
The purpose of the present study was to evaluate the effect of barrier membrane exposure on the success of guided tissue regeneration in Class II furcation defects. Twenty-six subjects with mandibular Class II furcation defects received initial periodontal therapy followed by guided tissue regeneration surgery. The membrane was placed and the flaps were repositioned so that the membrane was totally submerged. Membranes were removed 4 to 6 weeks later, at which time the extent of their exposure was recorded. An overall improvement in all clinical parameters was observed for all subjects 1 year after surgery. Half of the patients had experienced no membrane exposure, while the other 13 subjects had experienced mild to pronounced exposure; both groups showed similar improvement in all clinical and surgical parameters. In light of the comparable results obtained in exposed sites, and the anatomic difficulties sometimes encountered in covering a membrane completely, in some of these cases the membrane may be left only partially submerged. This approach will allow for tighter occlusal "seal" of the tooth-membrane interface and preservation of the keratinized gingiva. 相似文献
40.
The effects of the selective adenosine (ADO) A3 receptor agonist IB-MECA (N6-(3-iodobenzyl)adenosine-5'-N-methylcarboxamide) on cultured newborn rat cardiomyocytes were examined in comparison with ADO, the ADO A1 receptor-selective agonist R-PIA (N6-R-phenylisopropyladenosine), or the ADO A3 selective antagonist MRS 1191 (3-ethyl-5-benzyl-2-methyl-6-phenyl-4-phenylethynyl-1, 4-(+/-)-dihydropyridine-3,5 dicarboxylate), using digital image analysis of Feulgen-stained nuclei. At high concentration, IB-MECA (>/=10 microM ) and ADO (200 microM) induced apoptosis; however, R-PIA or MRS 1191 did not have any detectable effects on cardiac cells. In addition, DNA breaks in cardiomyocytes undergoing apoptosis following treatment by IB-MECA were identified in situ using the nick end labeling of DNA ("TUNEL"-like) assay. In the presence of >/=10 microM IB-MECA, disorder in the contraction waves appeared, and a decrease in the frequency of beats was observed. Analysis with light microscopy revealed that the number of contracting cells decreased in a concentration-dependent manner. The A3 receptor agonist IB-MECA caused an increase in intracellular free calcium concentration ([Ca2+]i). The drug produced a rapid rise followed by a sustained increase in [Ca2+]i, which lasted for 40-60 s. Finally, cessation of beating and Ca2+ transients were observed. Full recovery of contractile activity and rhythmical Ca2+ transients were observed 15-20 min after IB-MECA treatment. The induction of apoptosis in the cardiocytes by IB-MECA led to the appearance of features of apoptotic nuclei: the onset of condensation, compacting, and margination of nuclear chromatin. These effects were accompanied by the disintegration of the structural framework of the nucleus and nuclear breakdown. The results suggest that activation of the A3 adenosine receptor may participate in the process of apoptosis in cardiomyocytes. 相似文献