The transition zone above a lumbosacral fusion.

PubMed

Hambly, M F; Wiltse, L L; Raghavan, N; Schneiderman, G; Koenig, C

1998-08-15

The clinical and radiographic effect of a lumbar or lumbosacral fusion was studied in 42 patients who had undergone a posterolateral fusion with an average follow-up of 22.6 years. To examine the long-term effects of posterolateral lumbar or lumbosacral fusion on the cephalad two motion segments (transition zone). It is commonly held that accelerated degeneration occurs in the motion segments adjacent to a fusion. Most studies are of short-term, anecdotal, uncontrolled reports that pay particular attention only to the first motion segment immediately cephalad to the fusion. Forty-two patients who had previously undergone a posterolateral lumbar or lumbosacral fusion underwent radiographic and clinical evaluation. Rate of fusion, range of motion, osteophytes, degenerative spondylolisthesis, retrolisthesis, facet arthrosis, disc ossification, dynamic instability, and disc space height were all studied and statistically compared with an age- and gender-matched control group. The patient's self-reported clinical outcome was also recorded. Degenerative changes occurred at the second level above the fused levels with a frequency equal to those occurring in the first level. There was no statistical difference between the study group and the cohort group in the presence of radiographic changes within the transition zone. In those patients undergoing fusion for degenerative processes, 75% reported a good to excellent outcome, whereas 84% of those undergoing fusion for spondylolysis or spondylolisthesis reported a good to excellent outcome. Radiographic changes occur within the transition zone cephalad to a lumbar or lumbosacral fusion. However, these changes are also seen in control subjects who have had no surgery.

Investigation on microstructure and properties of narrow-gap laser welding on reduced activation ferritic/martensitic steel CLF-1 with a thickness of 35 mm

NASA Astrophysics Data System (ADS)

Wu, Shikai; Zhang, Jianchao; Yang, Jiaoxi; Lu, Junxia; Liao, Hongbin; Wang, Xiaoyu

2018-05-01

Reduced activation ferritic martensitic (RAFM) steel is chosen as a structural material for test blanket modules (TBMs) to be constructed in International Thermonuclear Experimental Reactor (ITER) and China Fusion Engineering Test Reactor (CFETR). Chinese specific RAFM steel named with CLF-1 has been developed for CFETR. In this paper, a narrow-gap groove laser multi-pass welding of CLF-1 steel with thickness of 35 mm is conduced by YLS-15000 fiber laser. Further, the microstructures of different regions in the weld joint were characterized, and tensile impact and micro-hardness tests were carried out for evaluating the mecharical properties. The results show that the butt weld joint of CLF-1 steel with a thickness of 35 mm was well-formed using the optimal narrow-gap laser filler wire welding and no obvious defects was found such as incomplete fusion cracks and pores. The microstructures of backing layer is dominated by lath martensites and the Heat-Affected Zone (HAZ) was mainly filled with two-phase hybrid structures of secondary-tempering sorbites and martensites. The filler layer is similar to the backing layer in microstructures. In tensile tests, the tensile samples from different parts of the joint all fractured at base metal (BM). The micro-hardness of weld metal (WM) was found to be higher than that of BM and the Heat-Affected Zone (HAZ) exhibited no obvious softening. After post weld heat treatment (PWHT), it can be observed that the fusion zone of the autogenous welding bead and the upper filling beads mainly consist of lath martensites which caused the lower impact absorbing energy. The HAZ mainly included two-phase hybrid structures of secondary-tempering sorbites and martensites and exhibited favorable impact toughness.

Precipitation behavior of σ phase in fusion zone of dissimilar stainless steel welds during multi-pass GTAW process

NASA Astrophysics Data System (ADS)

Hsieh, Chih-Chun; Chang, Tao-Chih; Lin, Dong-Yih; Chen, Ming-Che; Wu, Weite

2007-10-01

The purpose of this study is to investigate the precipitation characteristics of σ phase in the fusion zone of stainless steel welds at various welding passes during a tungsten are welding (GTAW) process. The morphology, quantity, and chemical composition of the δ-ferrite and σ phase were analyzed using optical microscopy (OM), a ferritscope (FS), a X-ray diffractometer (XRD), scanning electron microscopy (SEM), an electron probe micro-analyzer (EPMA), and a wavelength dispersive spectrometer (WDS), respectively. Massive δ-ferrite was observed in the fusion zone of the first pass welds during welding of dissimilar stainless steels. The σ phase precipitated at the inner δ-ferrite particles and decreased δ-ferrite content during the third pass welding. The σ and δ phases can be stabilized by Si element, which promoted the phase transformation of σ→ϱ+λ2 in the fusion zone of the third pass welds. It was found that the σ phase was a Fe-Cr-Si intermetallic compound found in the fusion zone of the third pass welds during multi-pass welding.

The Strength and Characteristics of VPPA Welded 2219-T87 Aluminum Alloy

NASA Technical Reports Server (NTRS)

Jemian, W. A.

1985-01-01

A study of the variable polarity plasma arc (VPPA) welding process and those factors that control the structure and properties of VPPA welded aluminum alloy 2219-T87 was conducted. The importance of joint preparation, alignment of parts and welding process variables are already established. Internal weld defects have been eliminated. However, a variation of properties was found to be due to the size variation of interdendritic particles in the fusion zone. These particles contribute to the void formation process, which controls the ultimate tensile strength of the welded alloy. A variation of 150 microns in particle size correlated with a 10 ksi variation of ultimate tensile strength. It was found that all fracture surfaces were of the dimple rupture type, with fracture initiating within the fusion zone.

Spontaneous and evoked release are independently regulated at individual active zones.

PubMed

Melom, Jan E; Akbergenova, Yulia; Gavornik, Jeffrey P; Littleton, J Troy

2013-10-30

Neurotransmitter release from synaptic vesicle fusion is the fundamental mechanism for neuronal communication at synapses. Evoked release following an action potential has been well characterized for its function in activating the postsynaptic cell, but the significance of spontaneous release is less clear. Using transgenic tools to image single synaptic vesicle fusion events at individual release sites (active zones) in Drosophila, we characterized the spatial and temporal dynamics of exocytotic events that occur spontaneously or in response to an action potential. We also analyzed the relationship between these two modes of fusion at single release sites. A majority of active zones participate in both modes of fusion, although release probability is not correlated between the two modes of release and is highly variable across the population. A subset of active zones is specifically dedicated to spontaneous release, indicating a population of postsynaptic receptors is uniquely activated by this mode of vesicle fusion. Imaging synaptic transmission at individual release sites also revealed general rules for spontaneous and evoked release, and indicate that active zones with similar release probability can cluster spatially within individual synaptic boutons. These findings suggest neuronal connections contain two information channels that can be spatially segregated and independently regulated to transmit evoked or spontaneous fusion signals.

Influence of gas-powder laser cladding’s technological parameters on structural characteristics of corrosion-resistant steels’ restored surface layer

NASA Astrophysics Data System (ADS)

Krylova, S. E.; Oplesnin, S. P.; Goltyapin, M. I.

2018-03-01

The results of the developed industrial technology for surface restoration of corrosion-resistant steels by laser surfacing are presented in the article. A comparative analysis of the microstructure of the welded wear-resistant layer, the fusion zone with the base material and the diffusion zone for different technological surfacing regimes are given. Dyrometric studies and nondestructive testing of the deposited layer for defects were performed

Deformation behavior of laser welds in high temperature oxidation resistant Fe-Cr-Al alloys for fuel cladding applications

NASA Astrophysics Data System (ADS)

Field, Kevin G.; Gussev, Maxim N.; Yamamoto, Yukinori; Snead, Lance L.

2014-11-01

Ferritic-structured Fe-Cr-Al alloys are being developed and show promise as oxidation resistant accident tolerant light water reactor fuel cladding. This study focuses on investigating the weldability and post-weld mechanical behavior of three model alloys in a range of Fe-(13-17.5)Cr-(3-4.4)Al (wt.%) with a minor addition of yttrium using modern laser-welding techniques. A detailed study on the mechanical performance of bead-on-plate welds using sub-sized, flat dog-bone tensile specimens and digital image correlation (DIC) has been carried out to determine the performance of welds as a function of alloy composition. Results indicated a reduction in the yield strength within the fusion zone compared to the base metal. Yield strength reduction was found to be primarily constrained to the fusion zone due to grain coarsening with a less severe reduction in the heat affected zone. For all proposed alloys, laser welding resulted in a defect free weld devoid of cracking or inclusions.

Effects of heat input on the pitting resistance of Inconel 625 welds by overlay welding

NASA Astrophysics Data System (ADS)

Kim, Jun Seok; Park, Young IL; Lee, Hae Woo

2015-03-01

The objective of this study was to establish the relationship between the dilution ratio of the weld zone and pitting resistance depending on the heat input to welding of the Inconel alloy. Each specimen was produced by electroslag welding using Inconel 625 as the filler metal. In the weld zone of each specimen, dendrite grains were observed near the fusion line and equiaxed grains were observed on the surface. It was also observed that a melted zone with a high Fe content was formed around the fusion line, which became wider as the welding heat input increased. In order to evaluate the pitting resistance, potentiodynamic polarization tests and CPT tests were conducted. The results of these tests confirmed that there is no difference between the pitting resistances of each specimen, as the structures of the surfaces were identical despite the effect of the differences in the welding heat input for each specimen and the minor dilution effect on the surface.

SMAS Fusion Zones Determine the Subfascial and Subcutaneous Anatomy of the Human Face: Fascial Spaces, Fat Compartments, and Models of Facial Aging.

PubMed

Pessa, Joel E

2016-05-01

Fusion zones between superficial fascia and deep fascia have been recognized by surgical anatomists since 1938. Anatomical dissection performed by the author suggested that additional superficial fascia fusion zones exist. A study was performed to evaluate and define fusion zones between the superficial and the deep fascia. Dissection of fresh and minimally preserved cadavers was performed using the accepted technique for defining anatomic spaces: dye injection combined with cross-sectional anatomical dissection. This study identified bilaminar membranes traveling from deep to superficial fascia at consistent locations in all specimens. These membranes exist as fusion zones between superficial and deep fascia, and are referred to as SMAS fusion zones. Nerves, blood vessels and lymphatics transition between the deep and superficial fascia of the face by traveling along and within these membranes, a construct that provides stability and minimizes shear. Bilaminar subfascial membranes continue into the subcutaneous tissues as unilaminar septa on their way to skin. This three-dimensional lattice of interlocking horizontal, vertical, and oblique membranes defines the anatomic boundaries of the fascial spaces as well as the deep and superficial fat compartments of the face. This information facilitates accurate volume augmentation; helps to avoid facial nerve injury; and provides the conceptual basis for understanding jowls as a manifestation of enlargement of the buccal space that occurs with age. © 2016 The American Society for Aesthetic Plastic Surgery, Inc. Reprints and permission: journals.permissions@oup.com.

Fusion welding of a modern borated stainless steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robino, C.V.; Cieslak, M.J.

1997-01-01

Experiments designed to assess the fabrication and service weldability of 304B4A borated stainless steel were conducted. Welding procedures and parameters for manual gas tungsten arc (GTA) welding, autogenous electron beam (EB) welding and filler-added EB welding were developed and found to be similar to those for austenitic stainless steels. Following the procedure development, four test welds were produced and evaluated by microstructural analysis and Charpy impact testing. Further samples were used for determination of the postweld heat treatment (PWHT) response of the welds. The fusion zone structure of welds in this alloy consists of primary austenite dendrites with an interdendriticmore » eutectic-like austenite/boride constituent. Welds also show an appreciable partially molten zone that consists of the austenite/boride eutectic surrounding unmelted austenite islands. The microstructure of the EB welds was substantially finer than that of the GTA welds, and boride coarsening was not observed in the solid state heat-affected zone (HAZ) of either weld type. The impact toughness of as-welded samples was found to be relatively poor, averaging less than 10 J for both GTA and EB welds. For fusion zone notched GTA and EB samples and centerline notched EB samples, fracture generally occurred along the boundary between the partially molten and solid-state regions of the HAZ. The results of the PWHT study were very encouraging, with typical values of the impact energy for HAZ notched samples approaching 40 J, or twice the minimum code-acceptable value.« less

Efficient dispersal and substrate acquisition traits in a marine invasive species via transient chimerism and colony mobility

PubMed Central

Fidler, Andrew E.; Bacq-Labreuil, Aurelie; Rachmilovitz, Elad

2018-01-01

Over the past three decades the colonial ascidian Didemnum vexillum has been expanding its global range, significantly impacting marine habitats and aquaculture facilities. What biological features make D. vexillum so highly invasive? Here, we show that juxtaposed allogeneic D. vexillum colony fragments (‘ramets’) may, initially, form chimeric entities. Subsequently, zooids of the differing genotypes within such chimeras coordinately retreat away from fusion zones. A few days following such post-fusion retreat movements there is further ramet fission and the formation of zooid-depauperate tunic zones. Using polymorphic microsatellite loci to distinguish between genotypes, we found that they were sectorial at the fusion zones and the subsequent ramet movements resulted in further spatial separation of the paired-genotypes indicating that the fusion events observed did not lead to formation of long-term, stable chimeras. Thus, movements of D. vexillum colony ramets from initial fusion zones lead to progressive segregation of genotypes probably minimizing potential somatic/germ-cell competition/parasitism. We speculate that relatively fast (≤10 mm/day) movement of D. vexillum colonies on substrates along with frequent, and perhaps unrestrained, transient allogeneic fusions play significant roles in this species’ striking invasiveness and capacity to colonize new substrates.

ER-associated SNAREs and Sey1p mediate nuclear fusion at two distinct steps during yeast mating.

PubMed

Rogers, Jason V; Arlow, Tim; Inkellis, Elizabeth R; Koo, Timothy S; Rose, Mark D

2013-12-01

During yeast mating, two haploid nuclei fuse membranes to form a single diploid nucleus. However, the known proteins required for nuclear fusion are unlikely to function as direct fusogens (i.e., they are unlikely to directly catalyze lipid bilayer fusion) based on their predicted structure and localization. Therefore we screened known fusogens from vesicle trafficking (soluble N-ethylmaleimide-sensitive factor attachment protein receptors [SNAREs]) and homotypic endoplasmic reticulum (ER) fusion (Sey1p) for additional roles in nuclear fusion. Here we demonstrate that the ER-localized SNAREs Sec20p, Ufe1p, Use1p, and Bos1p are required for efficient nuclear fusion. In contrast, Sey1p is required indirectly for nuclear fusion; sey1Δ zygotes accumulate ER at the zone of cell fusion, causing a block in nuclear congression. However, double mutants of Sey1p and Sec20p, Ufe1p, or Use1p, but not Bos1p, display extreme ER morphology defects, worse than either single mutant, suggesting that retrograde SNAREs fuse ER in the absence of Sey1p. Together these data demonstrate that SNAREs mediate nuclear fusion, ER fusion after cell fusion is necessary to complete nuclear congression, and there exists a SNARE-mediated, Sey1p-independent ER fusion pathway.

The microstructure and microhardness of friction stir welded dissimilar copper/Al-5% Mg alloys

NASA Astrophysics Data System (ADS)

Kalashnikova, T. A.; Shvedov, M. A.; Vasilyev, P. A.

2017-12-01

A friction stir welded joint between copper and aluminum alloy has been investigated and characterized for the microstructure and microhardness number distribution. The microstructural evolution of the joint is studied using optical microscopy and microhardness. The mechanical characteristics in structural zones of FSW joints are determined by Vickers microhardness measurements. Samples were cut across the cross section. It is shown that intermetallic Cu/Al particles are formed at interfaces. The intermetallics microhardness in the dissimilar aluminum/cooper FSW joint differs from that of the joint produced by fusion welding. The grain structures obtained in different dissimilar joint zones are examined.

Visualization and Sequencing of Membrane Remodeling Leading to Influenza Virus Fusion

PubMed Central

Gui, Long; Ebner, Jamie L.; Mileant, Alexander; Williams, James A.

2016-01-01

ABSTRACT Protein-mediated membrane fusion is an essential step in many fundamental biological events, including enveloped virus infection. The nature of protein and membrane intermediates and the sequence of membrane remodeling during these essential processes remain poorly understood. Here we used cryo-electron tomography (cryo-ET) to image the interplay between influenza virus and vesicles with a range of lipid compositions. By following the population kinetics of membrane fusion intermediates imaged by cryo-ET, we found that membrane remodeling commenced with the hemagglutinin fusion protein spikes grappling onto the target membrane, followed by localized target membrane dimpling as local clusters of hemagglutinin started to undergo conformational refolding. The local dimples then transitioned to extended, tightly apposed contact zones where the two proximal membrane leaflets were in most cases indistinguishable from each other, suggesting significant dehydration and possible intermingling of the lipid head groups. Increasing the content of fusion-enhancing cholesterol or bis-monoacylglycerophosphate in the target membrane led to an increase in extended contact zone formation. Interestingly, hemifused intermediates were found to be extremely rare in the influenza virus fusion system studied here, most likely reflecting the instability of this state and its rapid conversion to postfusion complexes, which increased in population over time. By tracking the populations of fusion complexes over time, the architecture and sequence of membrane reorganization leading to efficient enveloped virus fusion were thus resolved. IMPORTANCE Enveloped viruses employ specialized surface proteins to mediate fusion of cellular and viral membranes that results in the formation of pores through which the viral genetic material is delivered to the cell. For influenza virus, the trimeric hemagglutinin (HA) glycoprotein spike mediates host cell attachment and membrane fusion. While structures of a subset of conformations and parts of the fusion machinery have been characterized, the nature and sequence of membrane deformations during fusion have largely eluded characterization. Building upon studies that focused on early stages of HA-mediated membrane remodeling, here cryo-electron tomography (cryo-ET) was used to image the three-dimensional organization of intact influenza virions at different stages of fusion with liposomes, leading all the way to completion of the fusion reaction. By monitoring the evolution of fusion intermediate populations over the course of acid-induced fusion, we identified the progression of membrane reorganization that leads to efficient fusion by an enveloped virus. PMID:27226364

Measurement of spatial refractive index distributions of fusion spliced optical fibers by digital holographic microtomography

NASA Astrophysics Data System (ADS)

Pan, Feng; Deng, Yating; Ma, Xichao; Xiao, Wen

2017-11-01

Digital holographic microtomography is improved and applied to the measurements of three-dimensional refractive index distributions of fusion spliced optical fibers. Tomographic images are reconstructed from full-angle phase projection images obtained with a setup-rotation approach, in which the laser source, the optical system and the image sensor are arranged on an optical breadboard and synchronously rotated around the fixed object. For retrieving high-quality tomographic images, a numerical method is proposed to compensate the unwanted movements of the object in the lateral, axial and vertical directions during rotation. The compensation is implemented on the two-dimensional phase images instead of the sinogram. The experimental results exhibit distinctly the internal structures of fusion splices between a single-mode fiber and other fibers, including a multi-mode fiber, a panda polarization maintaining fiber, a bow-tie polarization maintaining fiber and a photonic crystal fiber. In particular, the internal structure distortion in the fusion areas can be intuitively observed, such as the expansion of the stress zones of polarization maintaining fibers, the collapse of the air holes of photonic crystal fibers, etc.

A comparative evaluation of laser and GTA welds in a high-strength titanium alloy -- Ti-6-22-22S

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baeslack, W.A. III; Hurley, J.; Paskell, T.

1994-12-31

Titanium alloy Ti-6Al-2Sn-2Zr-2Mo-2Cr-025Si (hereafter designated Ti-6-22-22S)is an alpha-beta titanium alloy developed for deep hardenability, high strength, intermediate temperature creep resistance, and moderate toughness. As a potential structural material for next-generation aircraft and aerospace systems, the weldability of Ti-6-22-22S has recently become a subject of increasing importance and concern. In the welding of titanium sheet, achieving satisfactory ductility is the principal limitation to alloy weldability, with poor ductility promoted by a coarse beta grain structure in the weld fusion and near-heat-affected zones. Square-butt welds were produced in 1.6 mm thick Ti-6-22-22S sheet using automatic GTA and CO{sub 2} laser welding systems.more » Microstructure analysis and DPH hardness traverses were performed on mounted. polished and etched specimens. Three-point bend and tensile tests were performed on transverse-weld and longitudinal-weld oriented specimens. Microstructure analysis of the laser welds revealed a fine, columnar fusion zone beta grain macrostructure and a fully-martensitic transformed-beta microstructure. Consistent with the microstructural similarities, fusion zone hardnesses of the laser welds were comparable (385 and 390 DPG, respectively) and greater than that of the base metal (330 DPH). In general, laser welds did not exhibit markedly superior ductilities relative to the GTAW, which was attributed to differences in the nature of the intragranular transformed-beta microstructures, being coarser and softer for the GTAW, the response of these as-welded microstructures to heat treatment, and interactions between the transformed-beta microstructure and the beta grain macrostructure.« less

Weld pool development during GTA and laser beam welding of Type 304 stainless steel; Part II-experimental correlation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zacharia, T.; David, S.A.; Vitek, J.M.

1989-12-01

In part I of the paper, the results of the heat flow and the fluid flow analysis were presented. Here, in Part II of the paper, predictions of the computational model are verified by comparing the numerically predicted and experimentally observed fusion zone size and shape. Stationary gas tungsten arc and laser beam welds were made on Type 304 stainless steel for different times to provide a variety of solidification conditions such as cooling rate and temperature gradient. Calculated temperatures and cooling rates are correlated with the experimentally observed fusion zone structure. In addition, the effect of sulfur on GTAmore » weld penetration was quantitatively evaluated by considering two heats of 304 stainless steel containing 90 and 240 ppm sulfur. Sulfur, as expected, increased the depth/width ratio by altering the surface tension gradient driven flow in the weld pool.« less

Three-dimensional Monte Carlo calculation of some nuclear parameters

NASA Astrophysics Data System (ADS)

Günay, Mehtap; Şeker, Gökmen

2017-09-01

In this study, a fusion-fission hybrid reactor system was designed by using 9Cr2WVTa Ferritic steel structural material and the molten salt-heavy metal mixtures 99-95% Li20Sn80 + 1-5% RG-Pu, 99-95% Li20Sn80 + 1-5% RG-PuF4, and 99-95% Li20Sn80 + 1-5% RG-PuO2, as fluids. The fluids were used in the liquid first wall, blanket and shield zones of a fusion-fission hybrid reactor system. Beryllium (Be) zone with the width of 3 cm was used for the neutron multiplication between the liquid first wall and blanket. This study analyzes the nuclear parameters such as tritium breeding ratio (TBR), energy multiplication factor (M), heat deposition rate, fission reaction rate in liquid first wall, blanket and shield zones and investigates effects of reactor grade Pu content in the designed system on these nuclear parameters. Three-dimensional analyses were performed by using the Monte Carlo code MCNPX-2.7.0 and nuclear data library ENDF/B-VII.0.

Theoretical Model of the Effect of Crack Tip Blunting on the Ultimate Tensile Strength of Welds in 2219-T87 Aluminum

NASA Technical Reports Server (NTRS)

Beil, R. J.

1982-01-01

A theoretical model representing blunting of a crack tip radius through diffusion of vacancies is presented. The model serves as the basis for a computer program which calculates changes, due to successive weld heat passes, in the ultimate tensile strength of 2219-T81 aluminum. In order for the model to yield changes of the same order in the ultimate tensile strength as that observed experimentally, a crack tip radius of the order of .001 microns is required. Such sharp cracks could arise in the fusion zone of a weld from shrinkage cavities or decohered phase boundaries between dendrites and the eutectic phase, or, possibly, from plastic deformation due to thermal stresses encountered during the welding process. Microstructural observations up to X2000 (resolution of about .1 micron) did not, in the fusion zone, show structural details which changed significantly under the influence of a heat pass, with the exception of possible small changes in the configuration of the interdendritic eutectic and in porosity build-up in the remelt zone.

Microstructure and Mechanical Properties of 21-6-9 Stainless Steel Electron Beam Welds

NASA Astrophysics Data System (ADS)

Elmer, John W.; Ellsworth, G. Fred; Florando, Jeffrey N.; Golosker, Ilya V.; Mulay, Rupalee P.

2017-04-01

Welds can either be stronger or weaker than the base metals that they join depending on the microstructures that form in the fusion and heat-affected zones of the weld. In this paper, weld strengthening in the fusion zone of annealed 21-6-9 stainless steel is investigated using cross-weld tensile samples, hardness testing, and microstructural characterization. Due to the stronger nature of the weld, the cross-weld tensile tests failed in the base metal and were not able to generate true fusion zone mechanical properties. Nanoindentation with a spherical indenter was instead used to predict the tensile behavior for the weld metal. Extrapolation of the nanoindentation results to higher strains was performed using the Steinberg-Guinan and Johnson-Cook strength models, and the results can be used for weld strength modeling purposes. The results illustrate how microstructural refinement and residual ferrite formation in the weld fusion zone can be an effective strengthener for 21-6-9 stainless steel.

ER-associated SNAREs and Sey1p mediate nuclear fusion at two distinct steps during yeast mating

PubMed Central

Rogers, Jason V.; Arlow, Tim; Inkellis, Elizabeth R.; Koo, Timothy S.; Rose, Mark D.

2013-01-01

During yeast mating, two haploid nuclei fuse membranes to form a single diploid nucleus. However, the known proteins required for nuclear fusion are unlikely to function as direct fusogens (i.e., they are unlikely to directly catalyze lipid bilayer fusion) based on their predicted structure and localization. Therefore we screened known fusogens from vesicle trafficking (soluble N-ethylmaleimide–sensitive factor attachment protein receptors [SNAREs]) and homotypic endoplasmic reticulum (ER) fusion (Sey1p) for additional roles in nuclear fusion. Here we demonstrate that the ER-localized SNAREs Sec20p, Ufe1p, Use1p, and Bos1p are required for efficient nuclear fusion. In contrast, Sey1p is required indirectly for nuclear fusion; sey1Δ zygotes accumulate ER at the zone of cell fusion, causing a block in nuclear congression. However, double mutants of Sey1p and Sec20p, Ufe1p, or Use1p, but not Bos1p, display extreme ER morphology defects, worse than either single mutant, suggesting that retrograde SNAREs fuse ER in the absence of Sey1p. Together these data demonstrate that SNAREs mediate nuclear fusion, ER fusion after cell fusion is necessary to complete nuclear congression, and there exists a SNARE-mediated, Sey1p-independent ER fusion pathway. PMID:24152736

Structural Pattern Recognition Techniques for Data Retrieval in Massive Fusion Databases

NASA Astrophysics Data System (ADS)

Vega, J.; Murari, A.; Rattá, G. A.; Castro, P.; Pereira, A.; Portas, A.

2008-03-01

Diagnostics of present day reactor class fusion experiments, like the Joint European Torus (JET), generate thousands of signals (time series and video images) in each discharge. There is a direct correspondence between the physical phenomena taking place in the plasma and the set of structural shapes (patterns) that they form in the signals: bumps, unexpected amplitude changes, abrupt peaks, periodic components, high intensity zones or specific edge contours. A major difficulty related to data analysis is the identification, in a rapid and automated way, of a set of discharges with comparable behavior, i.e. discharges with "similar" patterns. Pattern recognition techniques are efficient tools to search for similar structural forms within the database in a fast an intelligent way. To this end, classification systems must be developed to be used as indexation methods to directly fetch the more similar patterns.

Effect of the Parameters of Gas-Powder Laser Surfacing on the Structural Characteristics of Reconditioned Surface Layer of Corrosion-Resistant Steels

NASA Astrophysics Data System (ADS)

Krylova, S. E.; Oplesnin, S. P.; Manakov, N. A.; Yasakov, A. S.; Strizhov, A. O.

2018-01-01

Results of the developed commercial process for reconditioning the surface of corrosion-resistant steels by the method of laser surfacing are presented. A comparative analysis of the microstructures of the deposited wear-resistant layer, of the zone of fusion with the matrix material and of the diffusion zone after different variants of surfacing is performed. The hardness of the deposited layer is measured and a nondestructive inspection of the latter for the presence of flaws is performed.

Double-Sided Single-Pass Submerged Arc Welding for 2205 Duplex Stainless Steel

NASA Astrophysics Data System (ADS)

Luo, Jian; Yuan, Yi; Wang, Xiaoming; Yao, Zongxiang

2013-09-01

The duplex stainless steel (DSS), which combines the characteristics of ferritic steel and austenitic steel, is used widely. The submerged arc welding (SAW) method is usually applied to join thick plates of DSS. However, an effective welding procedure is needed in order to obtain ideal DSS welds with an appropriate proportion of ferrite (δ) and austenite (γ) in the weld zone, particularly in the melted zone and heat-affected zone. This study evaluated the effectiveness of a high efficiency double-sided single-pass (DSSP) SAW joining method for thick DSS plates. The effectiveness of the converse welding procedure, characterizations of weld zone, and mechanical properties of welded joint are analyzed. The results show an increasing appearance and continuous distribution feature of the σ phase in the fusion zone of the leading welded seam. The converse welding procedure promotes the σ phase to precipitate in the fusion zone of leading welded side. The microhardness appears to significantly increase in the center of leading welded side. Ductile fracture mode is observed in the weld zone. A mixture fracture feature appears with a shear lip and tears in the fusion zone near the fusion line. The ductility, plasticity, and microhardness of the joints have a significant relationship with σ phase and heat treatment effect influenced by the converse welding step. An available heat input controlling technology of the DSSP formation method is discussed for SAW of thick DSS plates.

Numerical calculation and experimental research on crack arrest by detour effect and joule heating of high pulsed current in remanufacturing

NASA Astrophysics Data System (ADS)

Yu, Jing; Zhang, Hongchao; Deng, Dewei; Hao, Shengzhi; Iqbal, Asif

2014-07-01

The remanufacturing blanks with cracks were considered as irreparable. With utilization of detour effect and Joule heating of pulsed current, a technique to arrest the crack in martensitic stainless steel FV520B is developed. According to finite element theory, the finite element(FE) model of the cracked rectangular specimen is established firstly. Then, based on electro-thermo-structure coupled theory, the distributions of current density, temperature field, and stress field are calculated for the instant of energizing. Furthermore, the simulation results are verified by some corresponding experiments performed on high pulsed current discharge device of type HCPD-I. Morphology and microstructure around the crack tip before and after electro pulsing treatment are observed by optical microscope(OM) and scanning electron microscope(SEM), and then the diameters of fusion zone and heat affected zone(HAZ) are measured in order to contrast with numerical calculation results. Element distribution, nano-indentation hardness and residual stress in the vicinity of the crack tip are surveyed by energy dispersive spectrometer(EDS), scanning probe microscopy(SPM) and X-ray stress gauge, respectively. The results show that the obvious partition and refined grain around the crack tip can be observed due to the violent temperature change. The contents of carbon and oxygen in fusion zone and HAZ are higher than those in matrix, and however the hardness around the crack tip decreases. Large residual compressive stress is induced in the vicinity of the crack tip and it has the same order of magnitude for measured results and numerical calculation results that is 100 MPa. The relational curves between discharge energies and diameters of the fusion zone and HAZ are obtained by experiments. The difference of diameter of fusion zone between measured and calculated results is less than 18.3%. Numerical calculation is very useful to define the experimental parameters. An effective method to prevent further extension of the crack is presented and can provide a reference for the compressor rotor blade remanufacturing.

Hot cracking of Structural Steel during Laser Welding

NASA Astrophysics Data System (ADS)

Pineda Huitron, Rosa M.; Vuorinen, Esa

2017-10-01

Laser welding is an important technique in many industries due to its high precision in operation, its local and fast processing, narrow welds and its good weld surface quality. However, the process can involve some complications due to the rapid heating and cooling of the material processed, resulting in physical and metallurgical effects as thermal contraction during solidification, giving as a result the presence of residual stresses in the narrow weld. Formation of defects during the process is an important topic to be evaluated in order to achieve better performance of the steels in use. In the present work, defects formed during laser welding of a structural steel have been investigated. The defects formed have been identified and the causes of the defects are discussed. Possible strategies for improvement of the welding procedure and final weld result are proposed. The defects were analysed by optical and scanning electron microscopy and hardness measurement. Cracks were located in the middle of the fusion zone and followed both inter-granular and trans-granular paths. Impurities as manganese sulphides were found along the welding direction, and could act as sites for crack formation. The cracks formed during solidification of the weld are identified as solidification cracks. This kind of cracks is usually caused by solidification shrinkage and thermal contractions during the process, which appear in the fusion zone and sometimes in the heat affected zone.

SNL/SRNL Joint Project on degradation of mechanical properties in structural metals and welds for GTS reservoirs.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ronevich, Joseph Allen; Balch, Dorian K.; San Marchi, Christopher W.

2015-12-01

This project was intended to enable SNL-CA to produce appropriate specimens of relevant stainless steels for testing and perform baseline testing of weld heat-affected zone and weld fusion zone. One of the key deliverables in this project was to establish a procedure for fracture testing stainless steel weld fusion zone and heat affected zones that were pre-charged with hydrogen. Following the establishment of the procedure, a round robin was planned between SNL-CA and SRNL to ensure testing consistency between laboratories. SNL-CA and SRNL would then develop a comprehensive test plan, which would include tritium exposures of several years at SRNLmore » on samples delivered by SNL-CA. Testing would follow the procedures developed at SNL-CA. SRNL will also purchase tritium charging vessels to perform the tritium exposures. Although comprehensive understanding of isotope-induced fracture in GTS reservoir materials is a several year effort, the FY15 work would enabled us to jump-start the tests and initiate long-term tritium exposures to aid comprehensive future investigations. Development of a procedure and laboratory testing consistency between SNL-CA and SNRL ensures reliability in results as future evaluations are performed on aluminum alloys and potentially additively-manufactured components.« less

A Combined Approach of Sensor Data Fusion and Multivariate Geostatistics for Delineation of Homogeneous Zones in an Agricultural Field

PubMed Central

Castrignanò, Annamaria; Quarto, Ruggiero; Vitti, Carolina; Langella, Giuliano; Terribile, Fabio

2017-01-01

To assess spatial variability at the very fine scale required by Precision Agriculture, different proximal and remote sensors have been used. They provide large amounts and different types of data which need to be combined. An integrated approach, using multivariate geostatistical data-fusion techniques and multi-source geophysical sensor data to determine simple summary scale-dependent indices, is described here. These indices can be used to delineate management zones to be submitted to differential management. Such a data fusion approach with geophysical sensors was applied in a soil of an agronomic field cropped with tomato. The synthetic regionalized factors determined, contributed to split the 3D edaphic environment into two main horizontal structures with different hydraulic properties and to disclose two main horizons in the 0–1.0-m depth with a discontinuity probably occurring between 0.40 m and 0.70 m. Comparing this partition with the soil properties measured with a shallow sampling, it was possible to verify the coherence in the topsoil between the dielectric properties and other properties more directly related to agronomic management. These results confirm the advantages of using proximal sensing as a preliminary step in the application of site-specific management. Combining disparate spatial data (data fusion) is not at all a naive problem and novel and powerful methods need to be developed. PMID:29207510

A Combined Approach of Sensor Data Fusion and Multivariate Geostatistics for Delineation of Homogeneous Zones in an Agricultural Field.

PubMed

Castrignanò, Annamaria; Buttafuoco, Gabriele; Quarto, Ruggiero; Vitti, Carolina; Langella, Giuliano; Terribile, Fabio; Venezia, Accursio

2017-12-03

To assess spatial variability at the very fine scale required by Precision Agriculture, different proximal and remote sensors have been used. They provide large amounts and different types of data which need to be combined. An integrated approach, using multivariate geostatistical data-fusion techniques and multi-source geophysical sensor data to determine simple summary scale-dependent indices, is described here. These indices can be used to delineate management zones to be submitted to differential management. Such a data fusion approach with geophysical sensors was applied in a soil of an agronomic field cropped with tomato. The synthetic regionalized factors determined, contributed to split the 3D edaphic environment into two main horizontal structures with different hydraulic properties and to disclose two main horizons in the 0-1.0-m depth with a discontinuity probably occurring between 0.40 m and 0.70 m. Comparing this partition with the soil properties measured with a shallow sampling, it was possible to verify the coherence in the topsoil between the dielectric properties and other properties more directly related to agronomic management. These results confirm the advantages of using proximal sensing as a preliminary step in the application of site-specific management. Combining disparate spatial data (data fusion) is not at all a naive problem and novel and powerful methods need to be developed.

Microstructure and mechanical properties of friction stir welded and laser welded high entropy alloy CrMnFeCoNi

NASA Astrophysics Data System (ADS)

Jo, Min-Gu; Kim, Han-Jin; Kang, Minjung; Madakashira, Phaniraj P.; Park, Eun Soo; Suh, Jin-Yoo; Kim, Dong-Ik; Hong, Sung-Tae; Han, Heung Nam

2018-01-01

The high entropy alloy CrMnFeCoNi has been shown to have promising structural properties. For a new alloy to be used in a structural application it should be weldable. In the present study, friction stir welding (FSW) and laser welding (LW) techniques were used to butt weld thin plates of CrMnFeCoNi. The microstructure, chemical homogeneity and mechanical behavior of the welds were characterized and compared with the base metal. The tensile stress-strain behavior of the welded specimens were reasonable when compared with that of the base metal. FSW refined the grain size in the weld region by a factor of ˜14 when compared with the base metal. High-angle annular dark field transmission electron microscopy in combination with energy dispersive X-ray spectroscopy showed chemical inhomogeneity between dendritic and interdendritic regions in the fusion zone of LW. Large fluctuations in composition (up to 15 at%) did not change the crystal structure in the fusion zone. Hardness measurements were carried out in the weld cross section and discussed in view of the grain size, low angle grain boundaries and twin boundaries in FSW specimens and the dendritic microstructure in LW specimens.

Friction Stir Welding of ODS and RAFM Steels

DOE PAGES

Yu, Zhenzhen; Feng, Zhili; Hoelzer, David; ...

2015-09-14

Advanced structural materials such as oxide dispersion strengthened steels and reduced-activation ferritic/martensitic steels are desired in fusion reactors as primary candidate materials for first wall and blanket structures, due to their excellent radiation and high-temperature creep resistance. However, their poor fusion weldability has been the major technical challenge limiting practical applications. For this reason, solid-state friction stir welding (FSW) has been considered for such applications. In this paper, the effect of FSW parameters on joining similar and dissimilar advanced structural steels was investigated. Scanning electron microscopy and electron backscatter diffraction methods were used to reveal the effects of FSW onmore » grain size, micro-texture distribution, and phase stability. Hardness mapping was performed to evaluate mechanical properties. Finally, post weld heat treatment was also performed to tailor the microstructure in the welds in order to match the weld zone mechanical properties to the base material.« less

Effect of pulsed current GTA welding parameters on the fusion zone microstructure of AA 6061 aluminium alloy

NASA Astrophysics Data System (ADS)

Kumar, T. Senthil; Balasubramanian, V.; Babu, S.; Sanavullah, M. Y.

2007-08-01

AA6061 aluminium alloy (Al-Mg-Si alloy) has gathered wide acceptance in the fabrication of food processing equipment, chemical containers, passenger cars, road tankers, and railway transport systems. The preferred process for welding these aluminium alloys is frequently Gas Tungsten Arc (GTA) welding due to its comparatively easy applicability and lower cost. In the case of single pass GTA welding of thinner sections of this alloy, the pulsed current has been found beneficial due to its advantages over the conventional continuous current processes. The use of pulsed current parameters has been found to improve the mechanical properties of the welds compared to those of continuous current welds of this alloy due to grain refinement occurring in the fusion zone. In this investigation, an attempt has been made to develop a mathematical model to predict the fusion zone grain diameter incorporating pulsed current welding parameters. Statistical tools such as design of experiments, analysis of variance, and regression analysis are used to develop the mathematical model. The developed model can be effectively used to predict the fusion grain diameter at a 95% confidence level for the given pulsed current parameters. The effect of pulsed current GTA welding parameters on the fusion zone grain diameter of AA 6061 aluminium alloy welds is reported in this paper.

ELKS, a Protein Structurally Related to the Active Zone-associated Protein CAST, Is Expressed in Pancreatic β Cells and Functions in Insulin Exocytosis: Interaction of ELKS with Exocytotic Machinery Analyzed by Total Internal Reflection Fluorescence MicroscopyV⃞

PubMed Central

Ohara-Imaizumi, Mica; Ohtsuka, Toshihisa; Matsushima, Satsuki; Akimoto, Yoshihiro; Nishiwaki, Chiyono; Nakamichi, Yoko; Kikuta, Toshiteru; Nagai, Shintaro; Kawakami, Hayato; Watanabe, Takashi; Nagamatsu, Shinya

2005-01-01

The cytomatrix at the active zone (CAZ) has been implicated in defining the site of Ca2+-dependent exocytosis of neurotransmitters. Here, we demonstrate the expression and function of ELKS, a protein structurally related to the CAZ protein CAST, in insulin exocytosis. The results of confocal and immunoelectron microscopic analysis showed that ELKS is present in pancreatic β cells and is localized close to insulin granules docked on the plasma membrane-facing blood vessels. Total internal reflection fluorescence microscopy imaging in insulin-producing clonal cells revealed that the ELKS clusters are less dense and unevenly distributed than syntaxin 1 clusters, which are enriched in the plasma membrane. Most of the ELKS clusters were on the docking sites of insulin granules that were colocalized with syntaxin 1 clusters. Total internal reflection fluorescence images of single-granule motion showed that the fusion events of insulin granules mostly occurred on the ELKS cluster, where repeated fusion was sometimes observed. When the Bassoon-binding region of ELKS was introduced into the cells, the docking and fusion of insulin granules were markedly reduced. Moreover, attenuation of ELKS expression by small interfering RNA reduced the glucose-evoked insulin release. These data suggest that the CAZ-related protein ELKS functions in insulin exocytosis from pancreatic β cells. PMID:15888548

Effect of different filler wires on weld formation for fiber laser welding 6A02 Aluminum alloy

NASA Astrophysics Data System (ADS)

Xu, F.; Chen, L.; Lu, W.; He, E. G.

2017-12-01

6A02 aluminum alloy was welded by fibre laser welding with two different filler wires (ER4043 and ER5356). The weld apperance, microstructure and mechanical properties were analysed. The results show the welding course with ER4043 is more stable than that with ER5356, and the welding spatters of the former are smaller than that of the latter. The microsturtrue of the weld zone, including columnar-grains near the fusion zone and mixed microstructures (columnar grains and equiaxed grains) in the weld center zone, is finer with ER5356 than that with ER4043. So the average microhardness value of the former is higher than the latter. A great number of low melting point eutectic phases disperse in grains boundary. Due to the eutectic phases distributing more in two zones (overheat zone near the fusion zone and the weld center zone) than other zones, the welded joints have these two low hardness and weak strength zones. The ultimate strength and the elongations after fracture of the welded joints with ER4043 are lower than that with ER5356 slihgtly. However, the former are improved obviously and higher than the latter after heat treatment. The tensile properties of all joints can reach to the base material level. And the tensile fractures always occur near the fusion zone.

Evaluation of flow properties in the weldments of vanadium alloys using a novel indentation technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gubbi, A.N.; Rowcliffe, A.F.; Lee, E.H.

1996-10-01

Automated Ball Indentation (ABI) testing, was successfully employed to determine the flow properties of the fusion zone, heat affected zone (HAZ), and base metal of the gas tungsten arc (GTA) and electron beam (EB) welds of the V-4Cr-4Ti (large heat no. 832665) and the V-5Cr-5Ti (heat 832394) alloys. ABI test results showed a clear distinction among the properties of the fusion zone, HAZ, and base metal in both GTA and EB welds of the two alloys. GTA and EB welds of both V-4Cr-4Ti and V-5Cr-5Ti alloys show strengthening of both the fusion zone and the HAZ (compared to base metal)more » with the fusion zone having higher strength than the HAZ. These data correlate well with the Brinell hardness. On the other hand, GTA welds of both alloys, after a post-weld heat treatment of 950{degrees}C for 2 h, show a recovery of the properties to base metal values with V-5Cr-5Ti showing a higher degree of recovery compared to V-4Cr-4Ti. These measurements correlate with the reported recovery of the Charpy impact properties.« less

System and method for making metallic iron with reduced CO.sub.2 emissions

DOEpatents

Kiesel, Richard F; Englund, David J; Schlichting, Mark; Meehan, John; Crouch, Jeremiah; Wilson, Logan

2014-10-14

A method and system for making metallic iron nodules with reduced CO.sub.2 emissions is disclosed. The method includes: assembling a linear hearth furnace having entry and exit portions, at least a conversion zone and a fusion zone, and a moving hearth adapted to move reducible iron bearing material through the furnace on contiguous hearth sections; assembling a shrouded return substantially free of air ingress extending adjacent at least the conversion and fusion zones of the furnace through which hearth sections can move from adjacent the exit portion to adjacent the entry portion of the furnace; transferring the hearth sections from the furnace to the shrouded return adjacent the exit portion; reducing reducible material in the linear hearth furnace to metallic iron nodules; and transporting gases from at least the fusion zone to the shrouded return to heat the hearth sections while in the shrouded return.

Element mixing distribution and structure feature of fusion zone in laser welding between different alloys and pure titanium.

PubMed

Wu, Haishu; Liu, Jihong; Liu, Xuecheng; Li, Changyi; Yu, Zhiwei

2002-07-01

To study micro morphology and element-mixing distribution of different alloys welded in laser and analyze the feasibility of laser welding different alloys. Alloys and titanium were matched into 4 groups: Au-Pt with Ni-Cr; Au-Pt with pure Ti; pure Ti with Ni-Cr; Ni-Cr with Co-Cr. They were welded in laser. Changes in metallography after hybridization of crystalline grain, ranges of heat-affected zone and pores were observed through SEM with ultra-thin windowed X-ray energy atlas. Meanwhile 10 testing points were chosen with area of 300 micro m x 900 micro m along the welding surface from the side A alloy to the side B alloy, than the element mixing distribution and tendency were analyzed with X-ray energy atlas. 1. Hybridization of different alloys: (l) in the group of Au-Pt with Ti, there was titanium element mixing into Au-Pt tissue gradually and evenly on the Au-Pt side of the interface without clear boundary and increasing in size of crystalline grain. However, there was titanium crystalline grain increasing in size, irregular morphology and small sacks on the titanium side with clear boundary. (2) in the group of Ni-Cr with Ti, there was mixing regularly, slow transition and interlocks between crystalline grains on the Ni-Cr side of the in terface. Poor transition, clear boundary and small cracks were observed on titanium side. (3) in the group of Co-Cr with Ni-Cr, there was good transition, obscure boundary on both sides resulting from network, cylinder and branch structure growing. 2. Element-mixing distribution of different alloys. In fusion zone, the metal elements in matched groups mixed well and hybridized into new alloys except titanium blocks. The location of wave peak depended on the composition of alloys. Most of elements were from the alloy far from the fusion zone. The hybridization between pure titanium and any other alloys is not good The effect of laser welding different alloys is ideal except with pure titanium.

Analysis of ablation debris from natural and artificial iron meteorites

NASA Technical Reports Server (NTRS)

Blanchard, M. B.; Davis, A. S.

1977-01-01

Artificial ablation studies were performed on iron and nickel-iron samples using an arc-heated plasma of ionized air. Experiment conditions simulated a meteoroid traveling about 12 km/sec at an altitude of 70 km. The artificially produced fusion crusts and ablation debris show features very similar to natural fusion crusts of the iron meteorites Boguslavka, Norfork, and N'Kandhla and to magnetic spherules recovered from Mn nodules. X-ray diffraction, electron microprobe, optical, and scanning electron microscope analyses reveal that important mineralogical, elemental, and textural changes occur during ablation. Some metal is melted and ablated. The outer margin of the melted rind is oxidized and recrystallizes as a discontinuous crust of magnetite and wustite. Adjacent to the oxidized metallic ablation zone is an unoxidized metallic ablation zone in which structures such as Widmannstatten bands are obliterated as the metal is transformed to unequilibrated alpha 2 nickel-iron. Volatile elements are vaporized and less volatile elements undergo fractionation.

Neurovascular Structures at Risk With Curved Retrograde TTC Fusion Nails.

PubMed

de Cesar Netto, Cesar; Johannesmeyer, David; Cone, Brent; Araoye, Ibukunoluwa; Hudson, Parke William; Sahranavard, Bahman; Johnson, Michael; Shah, Ashish

2017-10-01

The purpose of this study was to assess the risk of iatrogenic injury to plantar neurovascular structures of the foot during insertion of a curved retrograde tibiotalocalcaneal (TTC) fusion nail. Ten below-knee thawed fresh-frozen cadaveric specimens underwent curved retrograde nailing of the ankle. The shortest distance between the nail and the main plantar neurovascular branches and injured structures were recorded during dissection. We also evaluated the relative position of these structures along 2 lines (AB, connecting the calcaneus to the first metatarsal, and BC, connecting the first and fifth metatarsal). The lateral plantar artery was found to be in direct contact with the nail 70% of the time, with a macroscopic laceration 30% of the time. The Baxter nerve was injured 20% of the time, as was the lateral plantar nerve. The medial plantar artery and nerve were never injured. The most proximal structure to cross line AB was the Baxter nerve followed by the lateral plantar artery, the nail, the lateral plantar nerve, and the medial plantar nerve. Our cadaveric anatomic study found that the most common structures at risk for iatrogenic injury by lateral curved retrograde TTC fusion nails were the lateral plantar artery and nerve, and the Baxter nerve. Determination of a true neurovascular safe zone is challenging and therefore warrants careful operative dissection to minimize neurovascular injuries.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Kezhao; Ni, Longchang; Lei, Zhenglong, E-ma

The tensile deformation behavior of laser welded Ti{sub 2}AlNb joints was investigated using in situ analysis methods. The fracture mode of the single-B2-phase fusion zone was quasi-cleavage at room temperature and intergranular at 650 °C, while that of base metal was microvoid coalescence at both room temperature and 650 °C. Tensile deformation at room temperature was observed using in situ SEM tensile testing. In base metal, microcracks nucleated and propagated mainly within the O phase or along O/B2 phase boundaries. While both the cross- and multi-slips were found in the single-B2-phase fusion zone, a confocal laser scanning microscopy was usedmore » to observe the crack initiation and propagation process in situ at 650 °C. Cracks mainly formed along the B2/O phase boundaries in base metal, along the fragile grain boundaries of B2 phase in the fusion zone. The thermal simulation experiment and following TEM analysis indicated that the precipitation of continuous O-phase films along the B2 grain boundaries resulted in the high temperature brittleness of laser welded Ti{sub 2}AlNb joints. - Highlights: •Cracks formed within O phase or along B2/O boundaries in the base metal. •Cross- and multi-slips relieved stress in the fusion zone at room temperature. •Cracks mainly formed along the B2/O boundaries at 650 °C. •In the fusion zone, intergranular cracks were in situ observed at 650 °C. •O-phase films along B2 grain boundaries caused the high temperature brittleness.« less

Characteristics of Laser Beam and Friction Stir Welded AISI 409M Ferritic Stainless Steel Joints

NASA Astrophysics Data System (ADS)

Lakshminarayanan, A. K.; Balasubramanian, V.

2012-04-01

This article presents the comparative evaluation of microstructural features and mechanical properties of friction stir welded (solid-state) and laser beam welded (high energy density fusion welding) AISI 409M grade ferritic stainless steel joints. Optical microscopy, microhardness testing, transverse tensile, and impact tests were performed. The coarse ferrite grains in the base material were changed to fine grains consisting duplex structure of ferrite and martensite due to the rapid cooling rate and high strain induced by severe plastic deformation caused by frictional stirring. On the other hand, columnar dendritic grain structure was observed in fusion zone of laser beam welded joints. Tensile testing indicates overmatching of the weld metal relative to the base metal irrespective of the welding processes used. The LBW joint exhibited superior impact toughness compared to the FSW joint.

Creep Deformation and Rupture Behavior of Single- and Dual-Pass 316LN Stainless-Steel-Activated TIG Weld Joints

NASA Astrophysics Data System (ADS)

Vijayanand, V. D.; Vasudevan, M.; Ganesan, V.; Parameswaran, P.; Laha, K.; Bhaduri, A. K.

2016-06-01

Creep deformation and rupture behavior of single-pass and dual-pass 316LN stainless steel (SS) weld joints fabricated by an autogenous activated tungsten inert gas welding process have been assessed by performing metallography, hardness, and conventional and impression creep tests. The fusion zone of the single-pass joint consisted of columnar zones adjacent to base metals with a central equiaxed zone, which have been modified extensively by the thermal cycle of the second pass in the dual-pass joint. The equiaxed zone in the single-pass joint, as well as in the second pass of the dual-pass joint, displayed the lowest hardness in the joints. In the dual-pass joint, the equiaxed zone of the first pass had hardness comparable to the columnar zone. The hardness variations in the joints influenced the creep deformation. The equiaxed and columnar zone in the first pass of the dual-pass joint was more creep resistant than that of the second pass. Both joints possessed lower creep rupture life than the base metal. However, the creep rupture life of the dual-pass joint was about twofolds more than that of the single-pass joint. Creep failure in the single-pass joint occurred in the central equiaxed fusion zone, whereas creep cavitation that originated in the second pass was blocked at the weld pass interface. The additional interface and strength variation between two passes in the dual-pass joint provides more restraint to creep deformation and crack propagation in the fusion zone, resulting in an increase in the creep rupture life of the dual-pass joint over the single-pass joint. Furthermore, the differences in content, morphology, and distribution of delta ferrite in the fusion zone of the joints favors more creep cavitation resistance in the dual-pass joint over the single-pass joint with the enhancement of creep rupture life.

Fiber Laser Weldability of Austenitic Nickel Alloys

NASA Astrophysics Data System (ADS)

Watson, Jonathan

Recent developments of fiber lasers allow for easier beam delivery facilitating greater applications for laser welding in industry. Welding with high energy density heat sources allows for faster travel speeds, faster cooling rates, and smaller heat affected zones. However, there is a still a lack of knowledge base on how laser welding process parameters affect the weldability of austenitic nickel alloys. In this work, laser welds were made on several austenitic nickel alloys from different alloy families: HAYNESRTM 214RTM alloy, HAYNESRTM 282RTM alloy, HAYNESRTM 230RTM alloy, HAYNESRTM HR-120RTM alloy, HAYNESRTM HR-160 RTM alloy, HAYNESRTM 188 alloy, HAYNESRTM 718 alloy. Welds were made at 25 mm/s at laser powers ranging from 400 to 600 Watts. Solidification cracking was observed in cross-sections of the fusion zone of HR-160RTM alloy and HR-120RTM alloy. Dendritic solidification was found in all alloys, and partitioning within the dendritic structure compared well with Scheil calculations performed using ThermoCalc software. A eutectic liquid rich in carbide forming elements was found at the interdendritic regions in 188, 230RTM, 282 RTM, and 718 alloys and was quantified by processing backscatter electron images of the fusion zone. This interdendritic liquid was found to back fill solidification cracks that formed in the fusion zone during weldability testing. Transverse Varestraint and Sigma-Jig testing were performed to rank the weldability of alloys. During Transvarestraint testing, the ram drop timing was recorded in relation to the laser output, and a type R thermocouple was also placed in the laser path, and the approximate cooling rate of the fusion zone was recorded and used to calculate the solidification cracking temperature range. Rankings of the weldability compared well between Sigma-Jig and Transvarestraint testing, with the exception of 214 alloy and HR-120 alloy, which ranked much better and worse, respectively in Sigma-Jig tests. A possible explanation for this difference is the higher thermal conductivity and lower yields strength of 214 alloy and high temperatures, allowing it to accommodate more stress in the Sigma-Jig test. The final ranking of alloys from more weldable to less weldable by Sigma-Jig testing is 188, 214, 282, 718, 230, HR-120, and HR-160. The final ranking by maximum crack length in Transvarestraint specimens listed from more weldable to less weldable is: 188, 282, HR-120, 718, 230, 214, and HR-160.

Investigation of the Microstructure of Laser-Arc Hybrid Welded Boron Steel

NASA Astrophysics Data System (ADS)

Son, Seungwoo; Lee, Young Ho; Choi, Dong-Won; Cho, Kuk-Rae; Shin, Seung Man; Lee, Youngseog; Kang, Seong-Hoon; Lee, Zonghoon

2018-05-01

The microstructure of boron steel for automotive driving shaft manufacturing after laser-arc hybrid welding was investigated. Laser-arc hybrid welding technology was applied to 3-mm-thick plates of boron steel, ST35MnB. The temperature distribution of the welding pool was analyzed using the finite element method, and the microstructure of the welded boron steel was characterized using optical microscopy and scanning and transmission electron microscopies. The microstructure of the weld joint was classified into the fusion zone, the heat-affected zone (HAZ), and the base material. At the fusion zone, the bainite grains exist in the martensite matrix and show directionality because of heat input from the welding. The HAZ is composed of smaller grains, and the hardness of the HAZ is greater than that of the fusion zone. We discuss that the measured grain size and the hardness of the HAZ originate from undissolved precipitates that retard the grain growth of austenite.

Microstructural characterization of an SA508–309L/308L–316L domestic dissimilar metal welded safe-end joint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ming, Hongliang; Zhang, Zhiming; Wang, Jianqiu, E-mail: wangjianqiu@imr.ac.cn

2014-11-15

The microstructure of an SA508–309L/308L–316L domestic dissimilar metal welded safe-end joint was characterized in this work by optical microscopy, scanning electron microscopy (with electron back scattering diffraction) and micro-hardness testing. Epitaxial growth and competitive growth are evident in the 308L–316L fusion boundary regions. A martensite layer, carbon-depleted zones, and type-II and type-I boundaries are found in the SA508–309L fusion boundary regions, while only martensite and austenite mixed zones are observed in the SA508–308L fusion boundary regions. The microstructure near the fusion boundary and the microstructure transition in the SA508 heat affected zone are quite complex. Both for SA508–309L/308L and 308L–316L,more » the highest residual strain is located on the outside of the weldment. The residual strain and the grain boundary character distribution change with increasing distance from the fusion boundary in the heat affected zone of 316L. Micro-hardness measurements also reveal non-uniform mechanical properties across the weldment. - Highlights: • The microstructure of SA508 HAZ, especially near the FB, is very complex. • The outside of the dissimilar metal welded joint has the highest residual. • The micro-hardness distributions along the DMWJ are non-uniform.« less

Self-recognition in corals facilitates deep-sea habitat engineering

USGS Publications Warehouse

Hennige, Sebastian J; Morrison, Cheryl L.; Form, Armin U.; Buscher, Janina; Kamenos, Nicholas A.; Roberts, J. Murray

2014-01-01

The ability of coral reefs to engineer complex three-dimensional habitats is central to their success and the rich biodiversity they support. In tropical reefs, encrusting coralline algae bind together substrates and dead coral framework to make continuous reef structures, but beyond the photic zone, the cold-water coral Lophelia pertusa also forms large biogenic reefs, facilitated by skeletal fusion. Skeletal fusion in tropical corals can occur in closely related or juvenile individuals as a result of non-aggressive skeletal overgrowth or allogeneic tissue fusion, but contact reactions in many species result in mortality if there is no ‘self-recognition’ on a broad species level. This study reveals areas of ‘flawless’ skeletal fusion in Lophelia pertusa, potentially facilitated by allogeneic tissue fusion, are identified as having small aragonitic crystals or low levels of crystal organisation, and strong molecular bonding. Regardless of the mechanism, the recognition of ‘self’ between adjacent L. pertusa colonies leads to no observable mortality, facilitates ecosystem engineering and reduces aggression-related energetic expenditure in an environment where energy conservation is crucial. The potential for self-recognition at a species level, and subsequent skeletal fusion in framework-forming cold-water corals is an important first step in understanding their significance as ecological engineers in deep-seas worldwide.

Hemifusion and fusion of giant vesicles induced by reduction of inter-membrane distance

NASA Astrophysics Data System (ADS)

Heuvingh, J.; Pincet, F.; Cribier, S.

2004-07-01

Proteins involved in membrane fusion, such as SNARE or influenza virus hemagglutinin, share the common function of pulling together opposing membranes in closer contact. The reduction of inter-membrane distance can be sufficient to induce a lipid transition phase and thus fusion. We have used functionalized lipids bearing DNA bases as head groups incorporated into giant unilamellar vesicles in order to reproduce the reduction of distance between membranes and to trigger fusion in a model system. In our experiments, two vesicles were isolated and brought into adhesion by the mean of micromanipulation; their evolution was monitored by fluorescence microscopy. Actual fusion only occurred in about 5% of the experiments. In most cases, a state of “hemifusion” is observed and quantified. In this state, the outer leaflets of both vesicles' bilayers merged whereas the inner leaflets and the aqueous inner contents remained independent. The kinetics of the lipid probes redistribution is in good agreement with a diffusion model in which lipids freely diffuse at the circumference of the contact zone between the two vesicles. The minimal density of bridging structures, such as stalks, necessary to explain this redistribution kinetics can be estimated.

Microstructure characteristics of Ni/WC composite cladding coatings

NASA Astrophysics Data System (ADS)

Yang, Gui-rong; Huang, Chao-peng; Song, Wen-ming; Li, Jian; Lu, Jin-jun; Ma, Ying; Hao, Yuan

2016-02-01

A multilayer tungsten carbide particle (WCp)-reinforced Ni-based alloy coating was fabricated on a steel substrate using vacuum cladding technology. The morphology, microstructure, and formation mechanism of the coating were studied and discussed in different zones. The microstructure morphology and phase composition were investigated by scanning electron microscopy, optical microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. In the results, the coating presents a dense and homogeneous microstructure with few pores and is free from cracks. The whole coating shows a multilayer structure, including composite, transition, fusion, and diffusion-affected layers. Metallurgical bonding was achieved between the coating and substrate because of the formation of the fusion and diffusion-affected layers. The Ni-based alloy is mainly composed of γ-Ni solid solution with finely dispersed Cr7C3/Cr23C6, CrB, and Ni+Ni3Si. WC particles in the composite layer distribute evenly in areas among initial Ni-based alloying particles, forming a special three-dimensional reticular microstructure. The macrohardness of the coating is HRC 55, which is remarkably improved compared to that of the substrate. The microhardness increases gradually from the substrate to the composite zone, whereas the microhardness remains almost unchanged in the transition and composite zones.

Enhanced fuel production in thorium/lithium hybrid blankets utilizing uranium multipliers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pitulski, R.H.

1979-10-01

A consistent neutronics analysis is performed to determine the effectiveness of uranium bearing neutron multiplier zones on increasing the production of U/sup 233/ in thorium/lithium blankets for use in a tokamak fusion-fission hybrid reactor. The nuclear performance of these blankets is evaluated as a function of zone thicknesses and exposure by using the coupled transport burnup code ANISN-CINDER-HIC. Various parameters such as U/sup 233/, Pu/sup 239/, and H/sup 3/ production rates, the blanket energy multiplication, isotopic composition of the fuels, and neutron leakages into the various zones are evaluated during a 5 year (6 MW.y.m/sup -2/) exposure period. Although themore » results of this study were obtained for a tokomak magnetic fusion device, the qualitative behavior associated with the use of the uranium bearing neutron multiplier should be applicable to all fusion-fission hybrids.« less

Impact deformation behavior of duplex and superaustenitic stainless steels welds by split Hopkinson pressure bar

NASA Astrophysics Data System (ADS)

Wang, Shing-Hoa; Huang, Chih-Sheng; Lee, Woei-Shyan; Chen, Tao-Hsing; Wu, Chia-Chang; Lien, Charles; Tsai, Hung-Yin

2009-12-01

A considerable volume of γ phase increases in the fusion zone (weld metal) for two duplex stainless steels after a high-strain-rate impact. The strain-induced γ phase formation in the fusion zone results in local hardness variation depending on the strain rate. The α phase content in the fusion zone decreases as the impact strain rate increases for SAF 2205 DSS and SAF 2507 DSS. The results of the two-phase content measured by Ferritoscope correspond to that assessed by image analyses. In contrast, superaustenite stainless steel is unaffected by such an impact owing to its fully stable austenization. Impacted welds at a high strain rate of 5 × 103 s-1 reveal feather-like surface creases along the solidified curved columnar grain boundaries. The apparent surface creases are formed due to the presence of diffuse Lüders bands, which are caused by heavy plastic deformation in coarse-grain materials.

Microstructural and Mechanical Properties of Welded High Strength Steel Plate Using SMAW and SAW Method for LPG Storage Tanks

NASA Astrophysics Data System (ADS)

Winarto, Winarto; Riastuti, Rini; Kumeidi, Nur

2018-03-01

Indonesian government policy to convert energy consumption for domestic household from kerosene to liquefied petroleum gas (LPG) may lead to the increasing demand for LPG storage tank. LPG storage tank with a large capacity generally used the HSLA steel material of ASTM A516 Grade 70 joined by SMAW or combination between SMAW and SAW method. The heat input can affect the microstructure and mechanical properties of the weld area. The input heat is proportional to the welding current and the arc voltage, but inversely proportional to its welding speed. The result shows that the combination of SMAW-SAW process yield the lower hardness in the HAZ and the fusion zone compared to the singe SMAW process. PWHT mainly applied to reduce residual stress of welded joint. The result shows that PWHT can reduce the hardness in the HAZ and the fusion zone in comparing with the singe SMAW process. The microstructure of weld joint shows a coarser structure in the combined welding process (SMAW-SAW) comparing with the single welding process (SMAW).

Argon behaviour in an inverted Barrovian sequence, Sikkim Himalaya: The consequences of temperature and timescale on 40Ar/39Ar mica geochronology

NASA Astrophysics Data System (ADS)

Mottram, Catherine M.; Warren, Clare J.; Halton, Alison M.; Kelley, Simon P.; Harris, Nigel B. W.

2015-12-01

40Ar/39Ar dating of metamorphic rocks sometimes yields complicated datasets which are difficult to interpret in terms of timescales of the metamorphic cycle. Single-grain fusion and step-heating data were obtained for rocks sampled through a major thrust-sense shear zone (the Main Central Thrust) and the associated inverted metamorphic zone in the Sikkim region of the eastern Himalaya. This transect provides a natural laboratory to explore factors influencing apparent 40Ar/39Ar ages in similar lithologies at a variety of metamorphic pressure and temperature (P-T) conditions. The 40Ar/39Ar dataset records progressively younger apparent age populations and a decrease in within-sample dispersion with increasing temperature through the sequence. The white mica populations span 2-9 Ma within each sample in the structurally lower levels (garnet grade) but only 0-3 Ma at structurally higher levels (kyanite-sillimanite grade). Mean white mica single-grain fusion population ages vary from 16.2 ± 3.9 Ma (2σ) to 13.2 ± 1.3 Ma (2σ) from lowest to highest levels. White mica step-heating data from the same samples yields plateau ages from 14.27 ± 0.13 Ma to 12.96 ± 0.05 Ma. Biotite yield older apparent age populations with mean single-grain fusion dates varying from 74.7 ± 11.8 Ma (2σ) at the lowest structural levels to 18.6 ± 4.7 Ma (2σ) at the highest structural levels; the step-heating plateaux are commonly disturbed. Temperatures > 600 °C at pressures of 0.4-0.8 GPa sustained over > 5 Ma, appear to be required for white mica and biotite ages to be consistent with diffusive, open-system cooling. At lower temperatures, and/or over shorter metamorphic timescales, more 40Ar is retained than results from simple diffusion models suggest. Diffusion modelling of Ar in white mica from the highest structural levels suggests that the high-temperature rocks cooled at a rate of 50-80 °C Ma- 1, consistent with rapid thrusting, extrusion and exhumation along the Main Central Thrust during the mid-Miocene.

Quantitative Analysis of Microstructural Constituents in Welded Transformation-Induced-Plasticity Steels

NASA Astrophysics Data System (ADS)

Amirthalingam, M.; Hermans, M. J. M.; Zhao, L.; Richardson, I. M.

2010-02-01

A quantitative analysis of retained austenite and nonmetallic inclusions in gas tungsten arc (GTA)-welded aluminum-containing transformation-induced-plasticity (TRIP) steels is presented. The amount of retained austenite in the heat-affected and fusion zones of welded aluminum-containing TRIP steel with different base metal austenite fractions has been measured by magnetic saturation measurements, to study the effect of weld thermal cycles on the stabilization of austenite. It is found that for base metals containing 3 to 14 pct of austenite, 4 to 13 pct of austenite is found in the heat-affected zones and 6 to 10 pct in the fusion zones. The decomposition kinetics of retained austenite in the base metal and welded samples was also studied by thermomagnetic measurements. The decomposition kinetics of the austenite in the fusion zone is found to be slower compared to that in the base metal. Thermomagnetic measurements indicated the formation of ferromagnetic ɛ carbides above 290 °C and paramagnetic η( ɛ') transient iron carbides at approximately 400 °C due to the decomposition of austenite during heating.

Thick SS316 materials TIG welding development activities towards advanced fusion reactor vacuum vessel applications

NASA Astrophysics Data System (ADS)

Kumar, B. Ramesh; Gangradey, R.

2012-11-01

Advanced fusion reactors like ITER and up coming Indian DEMO devices are having challenges in terms of their materials design and fabrication procedures. The operation of these devices is having various loads like structural, thermo-mechanical and neutron irradiation effects on major systems like vacuum vessel, divertor, magnets and blanket modules. The concept of double wall vacuum vessel (VV) is proposed in view of protecting of major reactor subsystems like super conducting magnets, diagnostic systems and other critical components from high energy 14 MeV neutrons generated from fusion plasma produced by D-T reactions. The double walled vacuum vessel is used in combination with pressurized water circulation and some special grade borated steel blocks to shield these high energy neutrons effectively. The fabrication of sub components in VV are mainly used with high thickness SS materials in range of 20 mm- 60 mm of various grades based on the required protocols. The structural components of double wall vacuum vessel uses various parts like shields, ribs, shells and diagnostic vacuum ports. These components are to be developed with various welding techniques like TIG welding, Narrow gap TIG welding, Laser welding, Hybrid TIG laser welding, Electron beam welding based on requirement. In the present paper the samples of 20 mm and 40 mm thick SS 316 materials are developed with TIG welding process and their mechanical properties characterization with Tensile, Bend tests and Impact tests are carried out. In addition Vickers hardness tests and microstructural properties of Base metal, Heat Affected Zone (HAZ) and Weld Zone are done. TIG welding application with high thick SS materials in connection with vacuum vessel requirements and involved criticalities towards welding process are highlighted.

Resistance Element Welding of Magnesium Alloy/austenitic Stainless Steel

NASA Astrophysics Data System (ADS)

Manladan, S. M.; Yusof, F.; Ramesh, S.; Zhang, Y.; Luo, Z.; Ling, Z.

2017-09-01

Multi-material design is increasingly applied in the automotive and aerospace industries to reduce weight, improve crash-worthiness, and reduce environmental pollution. In the present study, a novel variant of resistance spot welding technique, known as resistance element welding was used to join AZ31 Mg alloy to 316 L austenitic stainless steel. The microstructure and mechanical properties of the joints were evaluated. It was found that the nugget consisted of two zones, including a peripheral fusion zone on the stainless steel side and the main fusion zone. The tensile shear properties of the joints are superior to those obtained by traditional resistance spot welding.

46 CFR 54.05-15 - Weldment toughness tests-procedure qualifications.

Code of Federal Regulations, 2012 CFR

2012-10-01

... the weld metal. (2) Three specimens with the notch centered on the fusion line between parent plate and weld. (The fusion line may be identified by etching the specimen with a mild reagent.) (3) Three specimens with the notch centered in the heat affected zone, 1 mm from the fusion line. (4) Same as...

46 CFR 54.05-15 - Weldment toughness tests-procedure qualifications.

Code of Federal Regulations, 2011 CFR

2011-10-01

... the weld metal. (2) Three specimens with the notch centered on the fusion line between parent plate and weld. (The fusion line may be identified by etching the specimen with a mild reagent.) (3) Three specimens with the notch centered in the heat affected zone, 1 mm from the fusion line. (4) Same as...

46 CFR 54.05-15 - Weldment toughness tests-procedure qualifications.

Code of Federal Regulations, 2013 CFR

2013-10-01

... the weld metal. (2) Three specimens with the notch centered on the fusion line between parent plate and weld. (The fusion line may be identified by etching the specimen with a mild reagent.) (3) Three specimens with the notch centered in the heat affected zone, 1 mm from the fusion line. (4) Same as...

46 CFR 54.05-15 - Weldment toughness tests-procedure qualifications.

Code of Federal Regulations, 2014 CFR

2014-10-01

... the weld metal. (2) Three specimens with the notch centered on the fusion line between parent plate and weld. (The fusion line may be identified by etching the specimen with a mild reagent.) (3) Three specimens with the notch centered in the heat affected zone, 1 mm from the fusion line. (4) Same as...

Orientation dependence of microfracture behavior in a dual-phase high-strength low-alloy steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suh, D.; Lee, S.; Kim, N.J.

1997-02-01

In selecting the processing conditions and evaluating the reliability of structural materials, microscopic observations and identification of the fracture mechanisms in local cracking behavior are required. An important instance in the failure of the local brittle zone (LBZ) in the welding zone. The LBZ, which is very brittle, is the coarse-grained heat-affected zone near the fusion line, a zone known to be critical to the fracture toughness of welded parts. Thus, maintaining stable fracture resistance by predicting the microfracture behavior is important when using high-strength low-alloy (HSLA) steels in offshore structural steel welds. Depending on the thermal cycles involved duringmore » welding, the ferrite/martensite structure can have various morphologies of martensite particles, for example, fibrous and blocky martensite. In summary, in situ SEM fracture tests reveal that in the L-oriented IQ DCB specimen, a microcrack tends to propagate relatively uniformly throughout the ferrite and well-distributed fine fibrous martensite, yielding good elongation with high strength level. Also, the IQ structure in the T orientation shows similar microfracture behavior. On the other hand, in the SQ structure, where blocky-type martensite is mixed with ferrite, strain is localized into shear bands mostly in the ferrite region, and a local microcrack propagates along the strain-localized band formed in the ferrite, resulting in the SQ structure in the T orientation, where the ferrite-martensite bands are parallel to the notch direction, the martensite cannot act as an efficient barrier to microcrack advance, and thus the tensile ductility is decreased.« less

Autostereoscopic 3D display system with dynamic fusion of the viewing zone under eye tracking: principles, setup, and evaluation [Invited].

PubMed

Yoon, Ki-Hyuk; Kang, Min-Koo; Lee, Hwasun; Kim, Sung-Kyu

2018-01-01

We study optical technologies for viewer-tracked autostereoscopic 3D display (VTA3D), which provides improved 3D image quality and extended viewing range. In particular, we utilize a technique-the so-called dynamic fusion of viewing zone (DFVZ)-for each 3D optical line to realize image quality equivalent to that achievable at optimal viewing distance, even when a viewer is moving in a depth direction. In addition, we examine quantitative properties of viewing zones provided by the VTA3D system that adopted DFVZ, revealing that the optimal viewing zone can be formed at viewer position. Last, we show that the comfort zone is extended due to DFVZ. This is demonstrated by a viewer's subjective evaluation of the 3D display system that employs both multiview autostereoscopic 3D display and DFVZ.

The effect of potassium on exocytosis of transmitter at the frog neuromuscular junction.

PubMed Central

Ceccarelli, B; Fesce, R; Grohovaz, F; Haimann, C

1988-01-01

1. Electrophysiology and morphology have been combined to investigate the time course of the exocytosis of quanta of neurotransmitter induced by elevated concentrations of K+ at the frog neuromuscular junction. 2. Replicas of freeze-fractured resting nerve terminals fixed in the presence of 20 mM-K+ showed images of fusion of synaptic vesicles with the presynaptic axolemma which were closely associated with the active zones. After 1 min in 20 nM-K+ fusions appeared also outside the active zones, and by 5 min they became uniformly distributed over the presynaptic membrane. 3. The average total density of fusions was not significantly different at the various times examined since it decreased at the active zones while it increased over the rest of the membrane. 4. Resting terminals fixed in 20 mM-K+ released 33,000-45,000 quanta after the addition of fixative; terminals stimulated by 20 mM-K+ for 1-5 min released 50,000-100,000 quanta during fixation. The fixative potentiated K+-induced transmitter release. 5. Fusions were uniformly distributed in terminals pre-incubated for 5 min in 20 mM-K+ without added Ca2+, stimulated by adding Ca2+ for 30 s, and then fixed. Conversely, after 5 min stimulation in hypertonic Ringer solution fusions remained predominantly located near the active zones. A similar distribution was observed after 15 min stimulation by a lower concentration of K+ (15 mM). 6. At all concentrations of K+ tested (10, 15, 20, 25 mM) miniature end-plate potential (MEPP) rate attained a steady-state value within 10-15 min. Values from a single junction were generally lower at higher concentrations of K+, which indicates partial inactivation of the secretion-recycling process. 7. The data indicate that K+ initially activates exocytosis at the active zones. Subsequently, ectopic exocytosis is activated while sites at the active zones appear to undergo partial inactivation. These phenomena are not related to the intensity or to the amount of previous secretion. Images Fig. 1 Fig. 2 Fig. 3 Fig. 8 Fig. 10 PMID:2902217

Multiple-source spatial data fusion and integration research in the region unified planning management information system

NASA Astrophysics Data System (ADS)

Liu, Zhijun; Zhang, Liangpei; Liu, Zhenmin; Jiao, Hongbo; Chen, Liqun

2008-12-01

In order to manage the internal resources of Gulf of Tonkin and integrate multiple-source spatial data, the establishment of region unified plan management system is needed. The data fusion and the integrated research should be carried on because there are some difficulties in the course of the system's establishment. For example, kinds of planning and the project data format are different, and data criterion is not unified. Besides, the time state property is strong, and spatial reference is inconsistent, etc. In this article the ARCGIS ENGINE is introduced as the developing platform, key technologies are researched, such as multiple-source data transformation and fusion, remote sensing data and DEM fusion and integrated, plan and project data integration, and so on. Practice shows that the system improves the working efficiency of Guangxi Gulf of Tonkin Economic Zone Management Committee significantly and promotes planning construction work of the economic zone remarkably.

Laser stereolithography by multilayer sintering of metal powders

NASA Astrophysics Data System (ADS)

Jendrzejewski, Rafal; Serbinski, W.; Sliwinski, Gerard

1997-10-01

Process parameters of the lser stereolithography by means of metal powder sintering are experimentally investigated for the bronze B10, Fe-Cr and Al-Ni alloys, pure Sn, and Cu. The multilaye structures ae prepared trace-on-trace by remelting of the previously deposited mela powder under the cw CO2 laser irradiation in an Ar flow environment. Severl trces of a hiehght of 0.1 - 0.9 mm connected via fusion zones are produced for each samle which results inan efficient formautlion f avolumetric structures of dimensins usfficient for microanalysis ndconsiderationof th emultlayer goemtry. For th beam intensities of about 105 W/cm2 and smaple feeding rates of 0.8 - 1.8 m/min th fusin zone thickness donot 4xceed several percent of th layer height. Rsutls indicate, that th epowderized Fe-Cr anAl-Ni alloys and also bronze B10 are well suited for a fast prorotyping due to th low porosity, homogeneous structure and good mechaniclpropetis acheivable.

Structural and Functional Studies on the Fusion and Attachment Envelope Glycoproteins of Nipah Virus and Hendra Virus

DTIC Science & Technology

2003-01-01

epidemics, caused by Vibrio cholerae have been linked to specific seasons and biogeographical zones. In addition, the population dynamics of V. cholerae in...Climactic warming has directly affected the prevalence of RVFV by prolonging survival rates of the vector involved in disease transmission. 3 Cholera ...climate variability. The study of V. cholerae represents a model system of how climate change affects pathogens (2). Personal human behavior has

Problems of Pore Formation in Welded Joints of Titanium Alloys

NASA Astrophysics Data System (ADS)

Murav'ev, V. I.

2005-07-01

Special features of formation of the connection zone in front of the front of molten pool and changes in the macro- and microstructure of the weld metal are considered for conditions of fusion welding of titanium alloys on an example of pseudo-α-titanium alloy VT20.Ways for forming macrotexture on the surface of joined preforms are determined with the aim of obtaining weld metal with structure and properties close to those of the base metal.

[Element distribution analysis of welded fusion zone by laser-induced breakdown spectroscopy].

PubMed

Yang, Chun; Zhang, Yong; Jia, Yun-Hai; Wang, Hai-Zhou

2014-04-01

Over the past decade there has been intense activity in the study and development of laser-induced breakdown spectroscopy (LIBS). As a new tool for surface microanalysis, it caused widespread in materials science because of the advantage of rapid and high sensitivity. In the present paper, the distribution of Ni, Mn, C and Si near weld fusion line was analyzed on two kinds of weld sample. Line scanning mode analysis was carried out by three different kinds of methods, namely laser-induced breakdown spectroscopy (LIBS), scanning electron microscope/energy dispersive spectrometer (SEM/EDS) and electron probe X-ray microanalyser (EPMA). The concentration variation trend of Ni and Mn acquired by LIBS is coincident with SEM/EDS and EPMA. The result shows that the content of Ni and Mn was significantly different between weld seam and base metal on both the samples. The content of Ni and Mn was much higher in weld seam than in base metal, and a sharp concentration gradient was analyzed in the fusion zone. According to the distribution of Ni and Mn, all the three methods got a similar value of welded fusion zone width. The concentration variation trend of C and Si acquired by LIBS is not coincident with SEM/EDS and EPMA. The concentration difference between weld seam and base metal was analyzed by LIBS, but had not by SEM/EDS and EPMA, because of the low concentration and slight difference. The concentration gradient of C and Si in fusion zone was shows clearly by LIBS. For higher sensitivity performance, LIBS is much more adapted to analyze low content element than SEM/EDS and EPMA.

Phase structures and morphologies of tempered CA6NM stainless steel welded by hybrid laser-arc process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mirakhorli, F., E-mail: Fatemeh.mirakhorli.1@ens.e

The post-weld tempered microstructure of hybrid laser-arc welded CA6NM, a cast low carbon martensitic stainless steel, was investigated. The microstructural evolutions from the fusion zone to the base metal were characterized in detail using optical microscopy, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD) and microhardness techniques. The fusion zone, in its post-weld tempered condition, consisted of tempered lath martensite, residual delta-ferrite with various morphologies, reversed austenite and chromium carbides. The reversed austenite, which can be detected through both EBSD and XRD techniques, was found to be finely dispersed along the martensite lath boundaries, particularly at triplemore » junctions. Based on the EBSD analysis, the orientation relationship between the reversed austenite and the adjacent martensite laths seemed to follow the Kurdjumov-Sachs (K-S) model. The results also revealed the presence of the reversed austenite in the different regions of the heat affected zone after post-weld tempering. The microindentation hardness distribution was measured, and correlated to the evolution of the corresponding microstructure across the welds. - Highlights: •The EBSD analysis was performed on hybrid laser-arc welded CA6NM. •The FZ consisted of tempered lath martensite, reversed austenite, carbides and δ ferrite after tempering. •The reversed γ was formed along the α′ lath boundaries, particularly at triple junctions.« less

The morphometric study of l3-L4 and L4-L5 lumbar spine in Asian population using magnetic resonance imaging: feasibility analysis for transpsoas lumbar interbody fusion.

PubMed

Yusof, Mohd Imran; Nadarajan, Eswaran; Abdullah, Mohd Shafie

2014-06-15

Cross-sectional study on the measurement of relevant magnetic resonance imaging parameters in 100 patients presented for lumbar spine assessment. To determine anatomical position of lumbar plexus and major blood vessels in relation to vertebral body and anterior edge of psoas muscle at L3-L4 and L4-L5 and to define the safe working zone for transpsoas approach for lumbar fusion. Lateral transpsoas lumbar interbody fusion has been shown to be safe and provides alternative for lumbar fusion. However, proximity of neurovascular structures may not allow a safe passage for this procedure in the Asian population. Relevant parameters were measured from axial magnetic resonance images and analyzed, including the psoas muscle and vertebrae endplate diameters, lumbar plexus and psoas muscle distance, lumbar plexus and vertebra body distance, and vena cava to the anterior vertebrae body diameters. The mean anteroposterior diameters of the right and left psoas muscle ranged from 44.0 to 58.6 mm and 44.8 to 54.0 mm, respectively. The mean anteroposterior diameters of vertebra endplate of L3, L4, and L5 were 38.2 mm, 39.3 mm, and 41.4 mm, respectively. The mean distance of posterior border of vena cava from the vertebra body was 4.5 mm at L3-L4 and 14.1 mm at L4-L5. L3-L4 fusion is feasible at both sides in both sexes; however, at L4-L5 level, the procedure is feasible only on the left side. The safe working zone for transpsoas approach to lumbar spine is significantly narrower at L4-L5 in both sexes. Anterior edge of psoas muscle can be used as a reliable guide to locate lumbar plexus within psoas muscle. N/A.

Investigation on Microstructure and Mechanical Properties of Continuous and Pulsed Current Gas Tungsten Arc Welded alloy 600

NASA Astrophysics Data System (ADS)

Srikanth, A.; Manikandan, M.

2018-02-01

The present study investigates the microstructure and mechanical properties of joints fabricated by Continuous and pulsed current gas tungsten arc welded alloy 600. Welding was done by autogenous mode. The macro examination was carried out to evaluate the welding defects in the weld joints. Optical and Scanning Electron Microscope (SEM) were performed to assess the microstructural changes in the fusion zone. Energy Dispersive Spectroscopy (EDS) analysis was carried to evaluate the microsegregation of alloying elements in the fusion zone. The tensile test was conducted to assess the strength of the weld joints. The results show that no welding defects were observed in the fusion zones of Continuous and Pulsed current Gas Tungsten Arc Welding. The refined microstructure was found in the pulsed current compared to continuous current mode. Microsegregation was not noticed in the weld grain boundary of continuous and pulsed current mode. The pulsed current shows improved mechanical properties compared to the continuous current mode.

Influence of Zn Interlayer on Interfacial Microstructure and Mechanical Properties of TIG Lap-Welded Mg/Al Joints

NASA Astrophysics Data System (ADS)

Gao, Qiong; Wang, Kehong

2016-03-01

This study explored 6061 Al alloy and AZ31B Mg alloy joined by TIG lap welding with Zn foils of varying thicknesses, with the additional Zn element being imported into the fusion zone to alloy the weld seam. The microstructures and chemical composition in the fusion zone near the Mg substrate were examined by SEM and EDS, and tensile shear strength tests were conducted to investigate the mechanical properties of the Al/Mg joints, as well as the fracture surfaces, and phase compositions. The results revealed that the introduction of an appropriate amount of Zn transition layer improves the microstructure of Mg/Al joints and effectively reduces the formation of Mg-Al intermetallic compounds (IMCs). The most common IMCs in the fusion zone near the Mg substrate were Mg-Zn and Mg-Al-Zn IMCs. The type and distribution of IMCs generated in the weld zone differed according to Zn additions; Zn interlayer thickness of 0.4 mm improved the sample's mechanical properties considerably compared to thicknesses of less than 0.4 mm; however, any further increase in Zn interlayer thickness of above 0.4 mm caused mechanical properties to deteriorate.

Slab photonic crystals with dimer colloid bases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riley, Erin K.; Liddell Watson, Chekesha M., E-mail: cliddell@ccmr.cornell.edu

2014-06-14

The photonic band gap properties for centered rectangular monolayers of asymmetric dimers are reported. Colloids in suspension have been organized into the phase under confinement. The theoretical model is inspired by the range of asymmetric dimers synthesized via seeded emulsion polymerization and explores, in particular, the band structures as a function of degree of lobe symmetry and degree of lobe fusion. These parameters are varied incrementally from spheres to lobe-tangent dimers over morphologies yielding physically realizable particles. The work addresses the relative scarcity of theoretical studies on photonic crystal slabs with vertical variation that is consistent with colloidal self-assembly. Odd,more » even and polarization independent gaps in the guided modes are determined for direct slab structures. A wide range of lobe symmetry and degree of lobe fusion combinations having Brillouin zones with moderate to high isotropy support gaps between odd mode band indices 3-4 and even mode band indices 1-2 and 2-3.« less

System and method for producing metallic iron

DOEpatents

Englund, David J.; Schlichting, Mark; Meehan, John; Crouch, Jeremiah; Wilson, Logan

2014-07-29

A method of production of metallic iron nodules comprises assembling a hearth furnace having a moveable hearth comprising refractory material and having a conversion zone and a fusion zone, providing a hearth material layer comprising carbonaceous material on the refractory material, providing a layer of reducible material comprising and iron bearing material arranged in discrete portions over at least a portion of the hearth material layer, delivering oxygen gas into the hearth furnace to a ratio of at least 0.8:1 ponds of oxygen to pounds of iron in the reducible material to heat the conversion zone to a temperature sufficient to at least partially reduce the reducible material and to heat the fusion zone to a temperature sufficient to at least partially reduce the reducible material, and heating the reducible material to form one or more metallic iron nodules and slag.

Laser Welding-Brazing of Immiscible AZ31B Mg and Ti-6Al-4V Alloys Using an Electrodeposited Cu Interlayer

NASA Astrophysics Data System (ADS)

Zhang, Zequn; Tan, Caiwang; Wang, Gang; Chen, Bo; Song, Xiaoguo; Zhao, Hongyun; Li, Liqun; Feng, Jicai

2018-03-01

Metallurgical bonding between immiscible system AZ31B magnesium (Mg) and Ti-6Al-4V titanium (Ti) was achieved by adding Cu interlayer using laser welding-brazing process. Effect of the laser power on microstructure evolution and mechanical properties of Mg/Cu-coated Ti joints was studied. Visually acceptable joints were obtained at the range of 1300 to 1500 W. The brazed interface was divided into three parts due to temperature gradient: direct irradiation zone, intermediate zone and seam head zone. Ti3Al phase was produced along the interface at the direct irradiation zone. Ti-Al reaction layer grew slightly with the increase in laser power. A small amount of Ti2(Cu,Al) interfacial compounds formed at the intermediate zone and the ( α-Mg + Mg2Cu) eutectic structure dispersed in the fusion zone instead of gathering when increasing the laser power at this zone. At the seam head zone, Mg-Cu eutectic structure was produced in large quantities under all cases. Joint strength first increased and then decreased with the variation of the laser power. The maximum fracture load of Mg/Cu-coated Ti joint reached 2314 N at the laser power of 1300 W, representing 85.7% joint efficiency when compared with Mg base metal. All specimens fractured at the interface. The feature of fracture surface at the laser power of 1100 W was characterized by overall smooth surface. Obvious tear ridge and Ti3Al particles were observed at the fracture surface with increase in laser power. It suggested atomic diffusion was accelerated with more heat input giving rise to the enhanced interfacial reaction and metallurgical bonding in direct irradiation zone, which determined the mechanical properties of the joint.

Probing heat transfer, fluid flow and microstructural evolution during fusion welding of alloys

NASA Astrophysics Data System (ADS)

Zhang, Wei

The composition, geometry, structure and properties of the welded joints are affected by the various physical processes that take place during fusion welding. Understanding these processes has been an important goal in the contemporary welding research to achieve structurally sound and reliable welds. In the present thesis research, several important physical processes including the heat transfer, fluid flow and microstructural evolution in fusion welding were modeled based on the fundamentals of transport phenomena and phase transformation theory. The heat transfer and fluid flow calculation is focused on the predictions of the liquid metal convection in the weld pool, the temperature distribution in the entire weldment, and the shape and size of the fusion zone (FZ) and heat affected zone (HAZ). The modeling of microstructural evolution is focused on the quantitative understanding of phase transformation kinetics during welding of several important alloys under both low and high heating and cooling conditions. Three numerical models were developed in the present thesis work: (1) a three-dimensional heat transfer and free surface flow model for the gas metal arc (GMA) fillet welding considering the complex weld joint geometry, (2) a phase transformation model based on the Johnson-Mehl-Avrami (JMA) theory, and (3) a one-dimensional numerical diffusion model considering multiple moving interfaces. To check the capabilities of the developed models, several cases were investigated, in which the predictions from the models were compared with the experimental results. The cases studied are the follows. For the modeling of heat transfer and fluid flow, the welding processes studied included gas tungsten arc (GTA) linear welding, GTA transient spot welding, and GMA fillet welding. The calculated weldment geometry and thermal cycles was validated against the experimental data under various welding conditions. For the modeling of microstructural evolution, the welded materials investigated included AISI 1005 low-carbon steel, 1045 medium-carbon steel, 2205 duplex stainless steel (DSS) and Ti-6Al-4V alloy. The calculated phase transformation kinetics were compared with the experimental results obtained using an x-ray diffraction technique by Dr. John W. Elmer of Lawrence Livermore National Laboratory. (Abstract shortened by UMI.)

Characteristics of GTA fusion zones and heat affected zones in superalloy 713C

NASA Astrophysics Data System (ADS)

Lachowicz, M. B.; Dudziński, W.

2012-09-01

In this paper, metallographic examinations, characterising microstructural changes in the 713C superalloy subjected to remelting by GTA method, are presented. In the fusion zone, precipitation of M23C6 or M6C carbides based on chromium and molybdenum was observed. Eutectic mixtures of ( γ- gg')-M x C y type with highly developed morphology were also perceived. It was found that, in the matrix areas with non-homogeneous chemical composition, the eutectic reaction γ-γ' can occur at the temperature close to that of the precipitation of the M x C y carbides. The presence of silicon in the carbide phases can be conducive to lowering their solidification point by creating low-melting compound NbSi. Both in the fusion zone (FZ) and in the heat-affected zone (HAZ), the secondary precipitates of the Ni3(AlTi)- γ' phase, varying in size from 50 to 100 nm, were found. The lattice mismatch factor of the γ and γ' particles was +0.48 % to +0.71 %, which is characteristic of the coherent precipitates of the Ni3Al phase enriched with titanium. No dislocations or stacking faults were observed in the microstructure of the FZ. In the HAZ, some primary undissolved γ' precipitates, with a part of aluminium probably replaced with niobium were observed, which raised their melting point.

Structural Transition and Antibody Binding of EBOV GP and ZIKV E Proteins from Pre-Fusion to Fusion-Initiation State.

PubMed

Lappala, Anna; Nishima, Wataru; Miner, Jacob; Fenimore, Paul; Fischer, Will; Hraber, Peter; Zhang, Ming; McMahon, Benjamin; Tung, Chang-Shung

2018-05-10

Membrane fusion proteins are responsible for viral entry into host cells—a crucial first step in viral infection. These proteins undergo large conformational changes from pre-fusion to fusion-initiation structures, and, despite differences in viral genomes and disease etiology, many fusion proteins are arranged as trimers. Structural information for both pre-fusion and fusion-initiation states is critical for understanding virus neutralization by the host immune system. In the case of Ebola virus glycoprotein (EBOV GP) and Zika virus envelope protein (ZIKV E), pre-fusion state structures have been identified experimentally, but only partial structures of fusion-initiation states have been described. While the fusion-initiation structure is in an energetically unfavorable state that is difficult to solve experimentally, the existing structural information combined with computational approaches enabled the modeling of fusion-initiation state structures of both proteins. These structural models provide an improved understanding of four different neutralizing antibodies in the prevention of viral host entry.

Pulsed Laser Beam Welding of Pd43Cu27Ni10P20 Bulk Metallic Glass.

PubMed

Shao, Ling; Datye, Amit; Huang, Jiankang; Ketkaew, Jittisa; Woo Sohn, Sung; Zhao, Shaofan; Wu, Sujun; Zhang, Yuming; Schwarz, Udo D; Schroers, Jan

2017-08-11

We used pulsed laser beam welding method to join Pd 43 Cu 27 Ni 10 P 20 (at.%) bulk metallic glass and characterized the properties of the joint. Fusion zone and heat-affected zone in the weld joint can be maintained completely amorphous as confirmed by X-ray diffraction and differential scanning calorimetry. No visible defects were observed in the weld joint. Nanoindentation and bend tests were carried out to determine the mechanical properties of the weld joint. Fusion zone and heat-affected zone exhibit very similar elastic moduli and hardness when compared to the base material, and the weld joint shows high ductility in bending which is accomplished through the operation of multiple shear bands. Our results reveal that pulsed laser beam welding under appropriate processing parameters provides a practical viable method to join bulk metallic glasses.

A Novel Synaptic Vesicle Fusion Path in the Rat Cerebral Cortex: The “Saddle” Point Hypothesis

PubMed Central

Zampighi, Guido A.; Serrano, Raul; Vergara, Julio L.

2014-01-01

We improved freeze-fracture electron microscopy to study synapses in the neuropil of the rat cerebral cortex at ∼2 nm resolution and in three-dimensions. In the pre-synaptic axon, we found that “rods” assembled from short filaments protruding from the vesicle and the plasma membrane connects synaptic vesicles to the membrane of the active zone. We equated these “connector rods” to protein complexes involved in “docking” and “priming” vesicles to the active zone. Depending on their orientation, the “rods” define two synaptic vesicle-fusion paths: When parallel to the plasma membrane, the vesicles hemi-fuse anywhere (“randomly”) in the active zone following the conventional path anticipated by the SNARE hypothesis. When perpendicular to the plasma membrane, the vesicles hemi-fuse at the base of sharp crooks, called “indentations,” that are spaced 75–85 nm center-to-center, arranged in files and contained within gutters. They result from primary and secondary membrane curvatures that intersect at stationary inflection (“saddle”) points. Computer simulations indicate that this novel vesicle-fusion path evokes neurotransmitter concentration domains on the post-synaptic spine that are wider, shallower, and that reach higher average concentrations than the more conventional vesicle fusion path. In the post-synaptic spine, large (∼9× ∼15 nm) rectangular particles at densities of 72±10/ µm2 (170–240/spine) match the envelopes of the homotetrameric GluR2 AMPA-sensitive receptor. While these putative receptors join clusters, called the “post-synaptic domains,” the overwhelming majority of the rectangular particles formed bands in the “non-synaptic” plasma membrane of the spine. In conclusion, in the neuropil of the rat cerebral cortex, curvatures of the plasma membrane define a novel vesicle-fusion path that preconditions specific regions of the active zone for neurotransmitter release. We hypothesize that a change in the hybridization of the R-SNARE synaptobrevin from parallel to antiparallel swings the synapse into this novel vesicle-fusion path. PMID:24959848

Ultrastructure of spermiogenesis of Dipylidium caninum (Cestoda, Cyclophyllidea, Dipylidiidae), an intestinal parasite of Canis familiaris.

PubMed

Miquel, J; Bâ, C T; Marchand, B

1998-09-01

We describe for the first time the ultrastructure of spermiogenesis of a representative of the family Dipylidiidae, Dipylidium caninum. Spermiogenesis begins with the formation of a differentiation zone. This conical area presents two centrioles with associated striated roots. One of the centrioles develops a flagellum and posteriorly a proximodistal fusion is produced between the axoneme and a median cytoplasmic process. In a final stage of spermiogenesis a condensation of electron-dense material between cortical microtubules is observed in the anterior part of the differentiation zone. This is the origin of the crest-like body that appears at the end of spermiogenesis. The presence of striated roots associated with centrioles constitutes the first report of these structures in the spermiogenesis of a cyclophyllidean cestode.

Sensing Exocytosis and Triggering Endocytosis at Synapses: Synaptic Vesicle Exocytosis–Endocytosis Coupling

PubMed Central

Lou, Xuelin

2018-01-01

The intact synaptic structure is critical for information processing in neural circuits. During synaptic transmission, rapid vesicle exocytosis increases the size of never terminals and endocytosis counteracts the increase. Accumulating evidence suggests that SV exocytosis and endocytosis are tightly connected in time and space during SV recycling, and this process is essential for synaptic function and structural stability. Research in the past has illustrated the molecular details of synaptic vesicle (SV) exocytosis and endocytosis; however, the mechanisms that timely connect these two fundamental events are poorly understood at central synapses. Here we discuss recent progress in SV recycling and summarize several emerging mechanisms by which synapses can “sense” the occurrence of exocytosis and timely initiate compensatory endocytosis. They include Ca2+ sensing, SV proteins sensing, and local membrane stress sensing. In addition, the spatial organization of endocytic zones adjacent to active zones provides a structural basis for efficient coupling between SV exocytosis and endocytosis. Through linking different endocytosis pathways with SV fusion, these mechanisms ensure necessary plasticity and robustness of nerve terminals to meet diverse physiological needs. PMID:29593500

Analysis of properties laser welded RAK 40/70 steel sheets

NASA Astrophysics Data System (ADS)

Evin, E.; Tomáš, M.; Fujda, M.

2017-11-01

Both, the ecological production and operation of vehicles demand using such materials for deformation zones’ structural parts, which show some specific properties and use innovative technologies to process them. Specific requirements for functionality (strength, stiffness, deformation work, fatigue properties) are closely linked to processability (formability). In the paper are presented results for multiphase TRIP steel RAK40/70 when welded by pulse solid-state fiber laser YLS-5000. Based on microstructure analysis in the fusion zone and heat affected zone the welding parameters were optimised. The influence of laser welding on the strength and deformation properties was verified by characteristics of strength, stiffness and deformation work, as they were calculated from mechanical properties measured by tensile test and three-point bending test. The knowledge gathered in the field of laser welding influence on the strength and deformation properties of multiphase TRIP steel RAK40/70 should help designers when design the lightweight structural parts of the car body.

Tungsten Inert Gas and Friction Stir Welding Characteristics of 4-mm-Thick 2219-T87 Plates at Room Temperature and -196 °C

NASA Astrophysics Data System (ADS)

Lei, Xuefeng; Deng, Ying; Yin, Zhimin; Xu, Guofu

2014-06-01

2219-T87 aluminum alloy is widely used for fabricating liquid rocket propellant storage tank, due to its admirable cryogenic property. Welding is the dominant joining method in the manufacturing process of aerospace components. In this study, the tungsten inert gas welding and friction stir welding (FSW) characteristics of 4-mm-thick 2219-T87 alloy plate at room temperature (25 °C) and deep cryogenic temperature (-196 °C) were investigated by property measurements and microscopy methods. The studied 2219 base alloy exhibits a low strength plane anisotropy and excellent room temperature and cryogenic mechanical properties. The ultimate tensile strength values of TIG and FSW welding joints can reach 265 and 353 MPa at room temperature, and 342 and 438 MPa at -196 °C, respectively. The base metal consists of elongated deformed grains and many nano-scaled θ (Al2Cu) aging precipitates. Fusion zone and heat-affected zone (HAZ) of the TIG joint are characterized by coarsening dendritic grains and equiaxed recrystallized grains, respectively. The FSW-welded joint consists of the weld nugget zone, thermo-mechanically affected zone (TMAZ), and HAZ. In the weld nugget zone, a micro-scaled sub-grain structure is the main microstructure characteristic. The TMAZ and HAZ are both characterized by coarsened aging precipitates and elongated deformed grains. The excellent FSW welding properties are attributed to the preservation of the working structures and homogenous chemical compositions.

Influence of Laser Power on the Microstructure and Mechanical Properties of a Laser Welded-Brazed Mg Alloy/Ni-Coated Steel Dissimilar Joint

NASA Astrophysics Data System (ADS)

Tan, Caiwang; Xiao, Liyuan; Liu, Fuyun; Chen, Bo; Song, Xiaoguo; Li, Liqun; Feng, Jicai

2017-05-01

In this work, we describe a method to improve the bonding of an immiscible Mg/steel system using Ni as an interlayer by coating it on the steel surface. Laser welding-brazing of AZ31B Mg alloy to Ni-coated Q235 steel using Mg-based filler was performed in a lap configuration. The influence of laser power on the weld characteristics, including joint appearance, formation of interfacial reaction layers and mechanical properties was investigated. The results indicated that the presence of the Ni-coating promoted the wetting of the liquid filler metal on the steel surface. A thermal gradient along the interface led to the formation of heterogeneous interfacial reaction layers. When using a low laser power of 1600 W, the reaction products were an FeAl phase in the direct laser irradiation zone, an AlNi phase close to the intermediate zone and mixtures of AlNi phase and an (α-Mg + Mg2Ni) eutectic structure near the interface at the seam head zone. For high powers of more than 2000 W, the FeAl phase grew thicker in the direct laser irradiation zone and a new Fe(Ni) transition layer formed at the interface of the intermediate zone and the seam head zone. However, the AlNi phase and (α-Mg + Mg2Ni) eutectic structure were scattered at the Mg seam. All the joints fractured at the fusion zone, indicating that the improved interface was not the weakest joint region. The maximum tensile-shear strength of the Mg/Ni-coated steel joint reached 190 N/mm, and the joint efficiency was 70% with respect to the Mg alloy base metal.

Laser stereolithography by multilayer cladding of metal powders

NASA Astrophysics Data System (ADS)

Jendrzejewski, Rafal; Rabczuk, Grazyna T.; Zaremba, R.; Sliwinski, Gerard

1998-07-01

3D-structures obtained by means of laser cladding of the metal alloy powders: bronze B10 and stellite 6 and the process parameters are studied experimentally. The structures are made trace-on-trace by remelting of the metal powder injected into the focusing region of the 1.2 kW CO2 laser beam. For the powder and sample feeding rates of 8-22 g/min and 0.4-1.2 m/min, respectively, and the applied beam intensities not exceeding 2 X 105 W cm-2 the process is stable and regular traces connected via fusion zones are produced for each material. The thickness of these zones does not exceed several per cent of the layer height. The process results in the efficient formation of multilayer structures. From their geometry the effect of energy coupling and interaction parameters are deduced. Moreover, the microanalysis by means of SEM- and optical photographs of samples produced under different experimental conditions confirms the expected mechanical properties, low porosity and highly homogenous structure of the multilayers. In addition to the known material stellite 6 the bronze B10 is originally proposed for a rapid prototyping.

Fusion Protein Cytokine Therapy After Rituximab in Treating Patients With B-Cell Non-Hodgkin Lymphoma

ClinicalTrials.gov

2015-06-03

Anaplastic Large Cell Lymphoma; Cutaneous B-cell Non-Hodgkin Lymphoma; Extranodal Marginal Zone B-cell Lymphoma of Mucosa-associated Lymphoid Tissue; Intraocular Lymphoma; Nodal Marginal Zone B-cell Lymphoma; Recurrent Adult Diffuse Small Cleaved Cell Lymphoma; Recurrent Adult Grade III Lymphomatoid Granulomatosis; Recurrent Grade 1 Follicular Lymphoma; Recurrent Grade 2 Follicular Lymphoma; Recurrent Marginal Zone Lymphoma; Small Intestine Lymphoma; Splenic Marginal Zone Lymphoma; Testicular Lymphoma; Waldenstrom Macroglobulinemia

Evaluation between residual stresses obtained by neutron diffraction and simulation for dual phase steel welded by laser process

NASA Astrophysics Data System (ADS)

Kouadri-Henni, Afia; Malard, Benoit

2018-05-01

This study aimed at characterizing the residual stresses (RS) distribution of a Dual Phase Steel (DP600) undergoing a Laser Beam Welding (LBW) with two different laser parameters. The RS in the ferritic phase have been experimentally determined by the use of the neutrons diffraction technique. The results confirmed a gradient of RS among different zones both on the top and below surfaces but also through the thickness of the fusion zone. Low compressive stresses were observed in the Base Metal (BM) close to the Heat Affected Zone (HAZ) whereas high tensile stresses were observed in the Fusion Zone (FZ). Numerical results showed a difference in the RS distribution depending on the model used. In the end, it appears that the high temperature gradient, specific to the laser beam, is the main factor governing the RS. Our results suggest as well that the approach regarding the RS should consider not only the temperature but also process parameters. When comparing simulation results with experimental data, the values converge well in some zones, in particular the FZ and the others less.

Mechanical Characteristics of Submerged Arc Weldment in API Gas Pipeline Steel of Grade X65

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hashemi, S. H.; Mohammadyani, D.

The mechanical properties of submerged arc weldment (SAW) in gas transportation pipeline steel of grade API X65 (65 ksi yield strength) were investigated. This steel is produced by thermo mechanical control rolled (TMC), and is largely used in Iran gas piping systems and networks. The results from laboratory study on three different regions; i.e. base metal (BM), fusion zone (FZ) and heat affected zone (HAZ) were used to compare weldment mechanical characteristics with those specified by API 5L (revision 2004) standard code. Different laboratory experiments were conducted on test specimens taken from 48 inch outside diameter and 14.3 mm wallmore » thickness gas pipeline. The test results showed a gradient of microstructure and Vickers hardness data from the centerline of FZ towards the unaffected MB. Similarly, lower Charpy absorbed energy (compared to BM) was observed in the FZ impact specimens. Despite this, the API specifications were fulfilled in three tested zones, ensuring pipeline structural integrity under working conditions.« less

Weldability of a high entropy CrMnFeCoNi alloy

DOE PAGES

Wu, Zhenggang; David, Stan A.; Feng, Zhili; ...

2016-07-19

We present the high-entropy alloys are unique alloys in which five or more elements are all in high concentrations. In order to determine its potential as a structural alloy, a model face-centered-cubic CrMnFeCoNi alloy was selected to investigate its weldability. Welds produced by electron beam welding show no cracking. The grain structures within the fusion zone (FZ) are controlled by the solidification behavior of the weld pool. The weldment possesses mechanical properties comparable to those of the base metal (BM) at both room and cryogenic temperatures. Finally, compared with the BM, deformation twinning was more pronounced in the FZ ofmore » the tested alloy.« less

Fusion boundary microstructure evolution in aluminum alloys

NASA Astrophysics Data System (ADS)

Kostrivas, Anastasios Dimitrios

2000-10-01

A melting technique was developed to simulate the fusion boundary of aluminum alloys using the GleebleRTM thermal simulator. Using a steel sleeve to contain the aluminum, samples were heated to incremental temperatures above the solidus temperature of a number of alloys. In alloy 2195, a 4wt%Cu-1wt%Li alloy, an equiaxed non-dendritic zone (EQZ) could be formed by heating in the temperature range from approximately 630 to 640°C. At temperatures above 640°C, solidification occurred by the normal epitaxial nucleation and growth mechanism. Fusion boundary behavior was also studied in alloys 5454-H34, 6061-T6, and 2219-T8. Additionally, experimental alloy compositions were produced by making bead on plate welds using an alloy 5454-H32 base metal and 5025 or 5087 filler metals. These filler metals contain zirconium and scandium additions, respectively, and were expected to influence nucleation and growth behavior. Both as-welded and welded/heat treated (540°C and 300°C) substrates were tested by melting simulation, resulting in dendritic and EQZ structures depending on composition and substrate condition. Orientation imaging microscopy (OIM(TM)) was employed to study the crystallographic character of the microstructures produced and to verify the mechanism responsible for EQZ formation. OIM(TM) proved that grains within the EQZ have random orientation. In all other cases, where the simulated microstructures were dendritic in nature, it was shown that epitaxy was the dominant mode of nucleation. The lack of any preferred crystallographic orientation relationship in the EQZ supports a theory proposed by Lippold et al that the EQZ is the result of heterogeneous nucleation within the weld unmixed zone. EDS analysis of the 2195 on STEM revealed particles with ternary composition consisted of Zr, Cu and Al and a tetragonal type crystallographic lattice. Microdiffraction line scans on EQZ grains in the alloy 2195 showed very good agreement between the measured Cu composition within the interior of the non-dendritic grains and the corresponding value the Scheil equation predicts for the first solid to form upon solidification for a binary Al-Cu alloy with identical Cu composition. In the context of the alloys, compositions and substrate conditions examined a mechanistic model for EQZ zone formation is proposed, helpful in adjusting base metal compositions and/or substrate conditions to control fusion boundary microstructure.

Experimental Characterization of Electron Beam Welded SAE 5137H Thick Steel Plate

NASA Astrophysics Data System (ADS)

Kattire, Prakash; Bhawar, Valmik; Thakare, Sandeep; Patil, Sachin; Mane, Santosh; Singh, Rajkumar, Dr.

2017-09-01

Electron beam welding is known for its narrow weld zone with high depth to width ratio, less heat affected zone, less distortion and contamination. Electron beam welding is fusion welding process, where high velocity electrons impinge on material joint to be welded and kinetic energy of this electron is transformed into heat upon impact to fuse the material. In the present work electron beam welding of 60 mm thick SAE 5137H steel is studied. Mechanical and metallurgical properties of electron beam welded joint of SAE 5137H were evaluated. Mechanical properties are analysed by tensile, impact and hardness test. Metallurgical properties are investigated through optical and scanning electron microscope. The hardness traverse across weld zone shows HV 370-380, about 18% increase in the tensile strength and very low toughness of weld joint compared to parent metal. Microstructural observation shows equiaxed dendrite in the fusion zone and partial grain refinement was found in the HAZ.

ELKS active zone proteins as multitasking scaffolds for secretion

PubMed Central

Held, Richard G.

2018-01-01

Synaptic vesicle exocytosis relies on the tethering of release ready vesicles close to voltage-gated Ca2+ channels and specific lipids at the future site of fusion. This enables rapid and efficient neurotransmitter secretion during presynaptic depolarization by an action potential. Extensive research has revealed that this tethering is mediated by an active zone, a protein dense structure that is attached to the presynaptic plasma membrane and opposed to postsynaptic receptors. Although roles of individual active zone proteins in exocytosis are in part understood, the molecular mechanisms that hold the protein scaffold at the active zone together and link it to the presynaptic plasma membrane have remained unknown. This is largely due to redundancy within and across scaffolding protein families at the active zone. Recent studies, however, have uncovered that ELKS proteins, also called ERC, Rab6IP2 or CAST, act as active zone scaffolds redundant with RIMs. This redundancy has led to diverse synaptic phenotypes in studies of ELKS knockout mice, perhaps because different synapses rely to a variable extent on scaffolding redundancy. In this review, we first evaluate the need for presynaptic scaffolding, and we then discuss how the diverse synaptic and non-synaptic functional roles of ELKS support the hypothesis that ELKS provides molecular scaffolding for organizing vesicle traffic at the presynaptic active zone and in other cellular compartments. PMID:29491150

Structure of the Newcastle disease virus F protein in the post-fusion conformation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Swanson, Kurt; Wen, Xiaolin; Leser, George P.

2010-11-17

The paramyxovirus F protein is a class I viral membrane fusion protein which undergoes a significant refolding transition during virus entry. Previous studies of the Newcastle disease virus, human parainfluenza virus 3 and parainfluenza virus 5 F proteins revealed differences in the pre- and post-fusion structures. The NDV Queensland (Q) F structure lacked structural elements observed in the other two structures, which are key to the refolding and fusogenic activity of F. Here we present the NDV Australia-Victoria (AV) F protein post-fusion structure and provide EM evidence for its folding to a pre-fusion form. The NDV AV F structure containsmore » heptad repeat elements missing in the previous NDV Q F structure, forming a post-fusion six-helix bundle (6HB) similar to the post-fusion hPIV3 F structure. Electrostatic and temperature factor analysis of the F structures points to regions of these proteins that may be functionally important in their membrane fusion activity.« less

Heat-Affected Zone Liquation Cracking Resistance of Friction Stir Processed Aluminum-Copper Alloy AA 2219

NASA Astrophysics Data System (ADS)

Karthik, G. M.; Janaki Ram, G. D.; Kottada, Ravi Sankar

2017-04-01

In the current work, the effect of friction stir processing on heat-affected zone (HAZ) liquation cracking resistance of aluminum-copper alloy AA 2219 was evaluated. In Gleeble hot-ductility tests and longitudinal Varestraint tests, the FSPed material, despite its very fine dynamically recrystallized equiaxed grain structure, showed considerably higher susceptibility to HAZ liquation cracking when compared to the base material. Detailed microstructural studies showed that the increased cracking susceptibility of the FSPed material is due to (i) increase in the amount of liquating θ phase (equilibrium Al2Cu) and (ii) increase in the population of grain boundary θ particles. An important learning from the current work is that, in certain materials like alloy 2219, the use of FSP as a pretreatment to fusion welding can be counterproductive.

Hemi-fused structure mediates and controls fusion and fission in live cells

PubMed Central

Zhao, Wei-Dong; Hamid, Edaeni; Shin, Wonchul; Wen, Peter J.; Krystofiak, Evan S.; Villarreal, Seth A.; Chiang, Hsueh-Cheng; Kachar, Bechara; Wu, Ling-Gang

2016-01-01

Membrane fusion and fission are vital to eukaryotes’ life1–5. For three decades, it has been proposed that fusion is mediated by fusion between proximal leaflets of two bilayers (hemi-fusion) that produces a hemi-fused structure, followed by fusion between distal leaflets, whereas fission is via hemi-fission, which also produces a hemi-fused structure, followed by full fission1, 4, 6–10. This hypothesis remained unsupported owing to the lack of observation of hemi-fusion/hemi-fission in live cells. A competing fusion hypothesis involving protein-lined pore formation has also been proposed2, 11–15. Using confocal and super-resolution STED microscopy, we observed the hemi-fused Ω-shaped structure for the first time in live cells, neuroendocrine chromaffin cells and pancreatic β-cells. This structure was generated from fusion pore opening or closure (fission) at the plasma membrane. Unexpectedly, its transition to full fusion or fission was determined by competition between fusion and calcium/dynamin-dependent fission mechanisms, and was surprisingly slow (seconds to tens of seconds) in a significant fraction of the events. These results provide key missing evidence over the past three decades proving the hemi-fusion and hemi-fission hypothesis in live cells, and reveal the hemi-fused intermediate as a key structure controlling fusion/fission, as fusion and fission mechanisms compete to determine its transition to fusion or fission. PMID:27309816

Active contour configuration model for estimating the posterior ablative margin in image fusion of real-time ultrasound and 3D ultrasound or magnetic resonance images for radiofrequency ablation: an experimental study.

PubMed

Lee, Junkyo; Lee, Min Woo; Choi, Dongil; Cha, Dong Ik; Lee, Sunyoung; Kang, Tae Wook; Yang, Jehoon; Jo, Jaemoon; Bang, Won-Chul; Kim, Jongsik; Shin, Dongkuk

2017-12-21

The purpose of this study was to evaluate the accuracy of an active contour model for estimating the posterior ablative margin in images obtained by the fusion of real-time ultrasonography (US) and 3-dimensional (3D) US or magnetic resonance (MR) images of an experimental tumor model for radiofrequency ablation. Chickpeas (n=12) and bovine rump meat (n=12) were used as an experimental tumor model. Grayscale 3D US and T1-weighted MR images were pre-acquired for use as reference datasets. US and MR/3D US fusion was performed for one group (n=4), and US and 3D US fusion only (n=8) was performed for the other group. Half of the models in each group were completely ablated, while the other half were incompletely ablated. Hyperechoic ablation areas were extracted using an active contour model from real-time US images, and the posterior margin of the ablation zone was estimated from the anterior margin. After the experiments, the ablated pieces of bovine rump meat were cut along the electrode path and the cut planes were photographed. The US images with the estimated posterior margin were compared with the photographs and post-ablation MR images. The extracted contours of the ablation zones from 12 US fusion videos and post-ablation MR images were also matched. In the four models fused under real-time US with MR/3D US, compression from the transducer and the insertion of an electrode resulted in misregistration between the real-time US and MR images, making the estimation of the ablation zones less accurate than was achieved through fusion between real-time US and 3D US. Eight of the 12 post-ablation 3D US images were graded as good when compared with the sectioned specimens, and 10 of the 12 were graded as good in a comparison with nicotinamide adenine dinucleotide staining and histopathologic results. Estimating the posterior ablative margin using an active contour model is a feasible way of predicting the ablation area, and US/3D US fusion was more accurate than US/MR fusion.

Materials and fabrication technology of modules intended for irradiation tests of blanket tritium-breeding zones in Russian fusion reactor projects

NASA Astrophysics Data System (ADS)

Kapychev, V.; Davydov, D.; Gorokhov, V.; Ioltukhovskiy, A.; Kazennov, Yu; Tebus, V.; Frolov, V.; Shikov, A.; Shishkov, N.; Kovalenko, V.; Shishkin, N.; Strebkov, Yu

2000-12-01

This paper surveys the modules and materials of blanket tritium-breeding zones developed in the Russian Federation for fusion reactors. Synthesis of lithium orthosilicate, metasilicate and aluminate, fabrication of ceramic pellets and pebbles and experimental reactor units are described. Results of tritium extraction kinetics under irradiation in a water-graphite reactor at a thermal neutron flux of 5×10 13 neutron/(s cm2) are considered. At the present time, development and fabrication of lithium orthosilicate-beryllium modules of the tritium-breeding zone (TBZ), have been carried out within the framework of the ITER and DEMO projects. Two modules containing orthosilicate pellets, porous beryllium and beryllium pebbles are suggested for irradiation tests in the temperature range of 350-700°C. Technical problems associated with manufacturing of the modules are discussed.

Mechanical Properties of Heat Affected Zone of High Strength Steels

NASA Astrophysics Data System (ADS)

Sefcikova, K.; Brtnik, T.; Dolejs, J.; Keltamaki, K.; Topilla, R.

2015-11-01

High Strength Steels became more popular as a construction material during last decade because of their increased availability and affordability. On the other hand, even though general use of Advanced High Strength Steels (AHSS) is expanding, the wide utilization is limited because of insufficient information about their behaviour in structures. The most widely used technique for joining steels is fusion welding. The welding process has an influence not only on the welded connection but on the area near this connection, the so-called heat affected zone, as well. For that reason it is very important to be able to determine the properties in the heat affected zone (HAZ). This area of investigation is being continuously developed in dependence on significant progress in material production, especially regarding new types of steels available. There are currently several types of AHSS on the world market. Two most widely used processes for AHSS production are Thermo-Mechanically Controlled Processing (TMCP) and Quenching in connection with Tempering. In the presented study, TMCP and QC steels grade S960 were investigated. The study is focused on the changes of strength, ductility, hardness and impact strength in heat affected zone based on the used amount of heat input.

Twin-spot laser welding of advanced high-strength multiphase microstructure steel

NASA Astrophysics Data System (ADS)

Grajcar, Adam; Morawiec, Mateusz; Różański, Maciej; Stano, Sebastian

2017-07-01

The study addresses the results concerning the laser welding of TRIP (TRansformation Induced Plasticity) steel using a beam focused at two spots (also referred to as twin-spot laser welding). The analysis involved the effect of variable welding thermal cycles on the properties and microstructure of welded joints. The tests were performed using a linear energy of 0.048 and 0.060 kJ/mm and the laser beam power distribution of 50%:50%, 60%:40% and 70%:30%. The tests also involved welding performed using a linear energy of 0.150 kJ/mm and the laser beam power distribution of 70%:30%. In addition, the research included observations of the microstructure of the fusion zone, heat affected zone and the transition zone using light microscopy and scanning electron microscopy. The fusion zone was composed of blocky-lath martensite whereas the HAZ (heat-affected zone) was characterised by the lath microstructure containing martensite, bainite and retained austenite. The distribution of twin-spot laser beam power significantly affected the microstructure and hardness profiles of welded joints. The highest hardness (480-505 HV), regardless of welding variants used, was observed in the HAZ.

Shallow boomerang-shaped influenza hemagglutinin G13A mutant structure promotes leaky membrane fusion.

PubMed

Lai, Alex L; Tamm, Lukas K

2010-11-26

Our previous studies showed that an angled boomerang-shaped structure of the influenza hemagglutinin (HA) fusion domain is critical for virus entry into host cells by membrane fusion. Because the acute angle of ∼105° of the wild-type fusion domain promotes efficient non-leaky membrane fusion, we asked whether different angles would still support fusion and thus facilitate virus entry. Here, we show that the G13A fusion domain mutant produces a new leaky fusion phenotype. The mutant fusion domain structure was solved by NMR spectroscopy in a lipid environment at fusion pH. The mutant adopted a boomerang structure similar to that of wild type but with a shallower kink angle of ∼150°. G13A perturbed the structure of model membranes to a lesser degree than wild type but to a greater degree than non-fusogenic fusion domain mutants. The strength of G13A binding to lipid bilayers was also intermediate between that of wild type and non-fusogenic mutants. These membrane interactions provide a clear link between structure and function of influenza fusion domains: an acute angle is required to promote clean non-leaky fusion suitable for virus entry presumably by interaction of the fusion domain with the transmembrane domain deep in the lipid bilayer. A shallower angle perturbs the bilayer of the target membrane so that it becomes leaky and unable to form a clean fusion pore. Mutants with no fixed boomerang angle interacted with bilayers weakly and did not promote any fusion or membrane perturbation.

Shallow Boomerang-shaped Influenza Hemagglutinin G13A Mutant Structure Promotes Leaky Membrane Fusion*

PubMed Central

Lai, Alex L.; Tamm, Lukas K.

2010-01-01

Our previous studies showed that an angled boomerang-shaped structure of the influenza hemagglutinin (HA) fusion domain is critical for virus entry into host cells by membrane fusion. Because the acute angle of ∼105° of the wild-type fusion domain promotes efficient non-leaky membrane fusion, we asked whether different angles would still support fusion and thus facilitate virus entry. Here, we show that the G13A fusion domain mutant produces a new leaky fusion phenotype. The mutant fusion domain structure was solved by NMR spectroscopy in a lipid environment at fusion pH. The mutant adopted a boomerang structure similar to that of wild type but with a shallower kink angle of ∼150°. G13A perturbed the structure of model membranes to a lesser degree than wild type but to a greater degree than non-fusogenic fusion domain mutants. The strength of G13A binding to lipid bilayers was also intermediate between that of wild type and non-fusogenic mutants. These membrane interactions provide a clear link between structure and function of influenza fusion domains: an acute angle is required to promote clean non-leaky fusion suitable for virus entry presumably by interaction of the fusion domain with the transmembrane domain deep in the lipid bilayer. A shallower angle perturbs the bilayer of the target membrane so that it becomes leaky and unable to form a clean fusion pore. Mutants with no fixed boomerang angle interacted with bilayers weakly and did not promote any fusion or membrane perturbation. PMID:20826788

46 CFR 54.05-16 - Production toughness testing.

Code of Federal Regulations, 2011 CFR

2011-10-01

... tests, the V-notch is to be centered between the fusion lines. For the heat affected zone tests, the... material shall be taken from one of the heats of material used in the vessel, and both the electrodes and... successive tests between the weld metal and heat affected zone. Thus, approximately half of all weld...

46 CFR 54.05-16 - Production toughness testing.

Code of Federal Regulations, 2013 CFR

2013-10-01

... tests, the V-notch is to be centered between the fusion lines. For the heat affected zone tests, the... material shall be taken from one of the heats of material used in the vessel, and both the electrodes and... successive tests between the weld metal and heat affected zone. Thus, approximately half of all weld...

46 CFR 54.05-16 - Production toughness testing.

Code of Federal Regulations, 2012 CFR

2012-10-01

... tests, the V-notch is to be centered between the fusion lines. For the heat affected zone tests, the... material shall be taken from one of the heats of material used in the vessel, and both the electrodes and... successive tests between the weld metal and heat affected zone. Thus, approximately half of all weld...

46 CFR 54.05-16 - Production toughness testing.

Code of Federal Regulations, 2014 CFR

2014-10-01

... tests, the V-notch is to be centered between the fusion lines. For the heat affected zone tests, the... material shall be taken from one of the heats of material used in the vessel, and both the electrodes and... successive tests between the weld metal and heat affected zone. Thus, approximately half of all weld...

Failure of dissimilar material bonded joints

NASA Astrophysics Data System (ADS)

Konstantakopoulou, M.; Deligianni, A.; Kotsikos, G.

2016-03-01

Joining of materials in structural design has always been a challenge for engineers. Bolting and riveting has been used for many years, until the emergence of fusion welding which revolutionised construction in areas such as shipbuilding, automotive, infrastructure and consumer goods. Extensive research in the past 50 years has resulted in better understanding of the process and minimised the occurrence of failures associated with fusion welding such as, residual stress cracking, stress corrosion and corrosion fatigue cracking, localised reduction in mechanical properties due to microstructural changes (heat affected zone) etc. Bonding has been a technique that has been proposed as an alternative because it eliminates several of the problems associated with fusion welding. But, despite some applications it has not seen wide use. There is however a renewed interest in adhesively bonded joints, as designers look for ever more efficient structures which inevitably leads to the use and consequently joining of combinations of lightweight materials, often with fundamentally different mechanical and physical properties. This chapter provides a review of adhesively bonded joints and reports on improvements to bonded joint strength through the introduction of carbon nanotubes at the bond interface. Results from various workers in the field are reported as well as the findings of the authors in this area of research. It is obvious that there are several challenges that need to be addressed to further enhance the strength of bonded joints and worldwide research is currently underway to address those shortcomings and build confidence in the implementation of these new techniques.

Analysis of the Corrosion Behavior of an A-TIG Welded SS 409 Weld Fusion Zone

NASA Astrophysics Data System (ADS)

Vidyarthy, R. S.; Dwivedi, D. K.

2017-11-01

AISI 409 (SS 409) ferritic stainless steel is generally used as the thick gauge section in freight train wagons, in ocean containers, and in sugar refinery equipment. Activating the flux tungsten inert gas (A-TIG) welding process can reduce the welding cost during fabrication of thick sections. However, corrosion behavior of the A-TIG weld fusion zone is a prime concern for this type of steel. In the present work, the effect of the A-TIG welding process parameters on the corrosion behavior of a weld fusion zone made of 8-mm-thick AISI 409 ferritic stainless-steel plate has been analyzed. Potentiodynamic polarization tests were performed to evaluate the corrosion behavior. The maximum corrosion potential ( E corr) was shown by the weld made using a welding current of 215 A, a welding speed of 95 mm/min, and a flux coating density of 0.81 mg/cm2. The minimum E corr was observed in the weld made using a welding current of 190 A, a welding speed of 120 mm/min, and a flux coating density of 1.40 mg/cm2. The current study also presents the inclusive microstructure-corrosion property relationships using the collective techniques of scanning electron microscopy, energy-dispersive x-ray spectroscopy, and x-ray diffraction.

Fusion peptide of influenza hemagglutinin requires a fixed angle boomerang structure for activity.

PubMed

Lai, Alex L; Park, Heather; White, Judith M; Tamm, Lukas K

2006-03-03

The fusion peptide of influenza hemagglutinin is crucial for cell entry of this virus. Previous studies showed that this peptide adopts a boomerang-shaped structure in lipid model membranes at the pH of membrane fusion. To examine the role of the boomerang in fusion, we changed several residues proposed to stabilize the kink in this structure and measured fusion. Among these, mutants E11A and W14A expressed hemagglutinins with hemifusion and no fusion activities, and F9A and N12A had no effect on fusion, respectively. Binding enthalpies and free energies of mutant peptides to model membranes and their ability to perturb lipid bilayer structures correlated well with the fusion activities of the parent full-length molecules. The structure of W14A determined by NMR and site-directed spin labeling features a flexible kink that points out of the membrane, in sharp contrast to the more ordered boomerang of the wild-type, which points into the membrane. A specific fixed angle boomerang structure is thus required to support membrane fusion.

The effects of Robertsonian fusions on chiasma frequency and distribution in the house mouse (Mus musculus domesticus) from a hybrid zone in northern Scotland.

PubMed

Bidau, C J; Giménez, M D; Palmer, C L; Searle, J B

2001-09-01

Chiasma frequency and distribution were studied in male Mus musculus domesticus from the John O'Groats-standard chromosomal hybrid zone in northern Scotland. Individuals of the John O'Groats race (2n=32; homozygous for the Robertsonian fusions 4.10, 6.13, 9.12 and 11.14) and the standard race (2n=40, all telocentric), and hybrids with various karyotypes, were examined. Chiasma frequency was significantly negatively correlated with the number of Robertsonian configurations in the meiotic cell. The decrease of chiasma frequency can be attributed to intrachromosomal effects that reduce the number of chiasmata in Robertsonian bivalents (formed in homozygotes for Robertsonian fusions) and trivalents (formed in heterozygotes). However, the reduction is more pronounced in Robertsonian bivalents and is related to a shift of chiasmata to the distal ends of the chromosome arms. A different type of repatterning occurs in trivalents where there is a significant increase in proximal and interstitial chiasmata.

Fusion activity of HIV gp41 fusion domain is related to its secondary structure and depth of membrane insertion in a cholesterol-dependent fashion.

PubMed

Lai, Alex L; Moorthy, Anna Eswara; Li, Yinling; Tamm, Lukas K

2012-04-20

The human immunodeficiency virus (HIV) gp41 fusion domain plays a critical role in membrane fusion during viral entry. A thorough understanding of the relationship between the structure and the activity of the fusion domain in different lipid environments helps to formulate mechanistic models on how it might function in mediating membrane fusion. The secondary structure of the fusion domain in small liposomes composed of different lipid mixtures was investigated by circular dichroism spectroscopy.  The fusion domain formed an α-helix in membranes containing less than 30 mol% cholesterol and  formed β-sheet secondary structure in membranes containing ≥30 mol% cholesterol. EPR spectra of spin-labeled fusion domains also indicated different conformations in membranes with and without cholesterol. Power saturation EPR data were further used to determine the orientation and depth of α-helical fusion domains in lipid bilayers. Fusion and membrane perturbation activities of the gp41 fusion domain were measured by lipid mixing and contents leakage. The fusion domain fused membranes in both its helical form and its β-sheet form. High cholesterol, which induced β-sheets, promoted fusion; however, acidic lipids, which promoted relatively deep membrane insertion as an α-helix, also induced fusion. The results indicate that the structure of the HIV gp41 fusion domain is plastic and depends critically on the lipid environment. Provided that their membrane insertion is deep, α-helical and β-sheet conformations contribute to membrane fusion. Copyright © 2012 Elsevier Ltd. All rights reserved.

Multisensor Parallel Largest Ellipsoid Distributed Data Fusion with Unknown Cross-Covariances

PubMed Central

Liu, Baoyu; Zhan, Xingqun; Zhu, Zheng H.

2017-01-01

As the largest ellipsoid (LE) data fusion algorithm can only be applied to two-sensor system, in this contribution, parallel fusion structure is proposed to introduce the LE algorithm into a multisensor system with unknown cross-covariances, and three parallel fusion structures based on different estimate pairing methods are presented and analyzed. In order to assess the influence of fusion structure on fusion performance, two fusion performance assessment parameters are defined as Fusion Distance and Fusion Index. Moreover, the formula for calculating the upper bounds of actual fused error covariances of the presented multisensor LE fusers is also provided. Demonstrated with simulation examples, the Fusion Index indicates fuser’s actual fused accuracy and its sensitivity to the sensor orders, as well as its robustness to the accuracy of newly added sensors. Compared to the LE fuser with sequential structure, the LE fusers with proposed parallel structures not only significantly improve their properties in these aspects, but also embrace better performances in consistency and computation efficiency. The presented multisensor LE fusers generally have better accuracies than covariance intersection (CI) fusion algorithm and are consistent when the local estimates are weakly correlated. PMID:28661442

Low activation steels welding with PWHT and coating for ITER test blanket modules and DEMO

NASA Astrophysics Data System (ADS)

Aubert, P.; Tavassoli, F.; Rieth, M.; Diegele, E.; Poitevin, Y.

2011-02-01

EUROFER weldability is investigated in support of the European material properties database and TBM manufacturing. Electron Beam, Hybrid, laser and narrow gap TIG processes have been carried out on the EUROFER-97 steel (thickness up to 40 mm), a reduced activation ferritic-martensitic steel developed in Europe. These welding processes produce similar welding results with high joint coefficients and are well adapted for minimizing residual distortions. The fusion zones are typically composed of martensite laths, with small grain sizes. In the heat-affected zones, martensite grains contain carbide precipitates. High hardness values are measured in all these zones that if not tempered would degrade toughness and creep resistance. PWHT developments have driven to a one-step PWHT (750 °C/3 h), successfully applied to joints restoring good material performances. It will produce less distortion levels than a full austenitization PWHT process, not really applicable to a complex welded structure such as the TBM. Different tungsten coatings have been successfully processed on EUROFER material. It has shown no really effect on the EUROFER base material microstructure.

TRAVELING WAVE PYROTRON

DOEpatents

Post, R.F.

1963-06-11

The invention relates to a pyrotron, i.e., magnetic mirror device, designed for continuous operation in producing a high-temperature fusion reaction plasma and for directly converting the plasma energy into electrical power. The device utilizes a system in which an axially symmetric magnetic field is produced and transports plasma through a first zone of progressively rising field intensity, a second reaction zone of slowly increasing intensity, and thenceforth through a third zone of progressively decreasing intensity wherein the plasma expands against the magnetic field thereby producing electrical current in magnetic field generating solenoids associated with said third zone. (AEC)

Crystal Structure of the Pre-fusion Nipah Virus Fusion Glycoprotein Reveals a Novel Hexamer-of-Trimers Assembly.

PubMed

Xu, Kai; Chan, Yee-Peng; Bradel-Tretheway, Birgit; Akyol-Ataman, Zeynep; Zhu, Yongqun; Dutta, Somnath; Yan, Lianying; Feng, YanRu; Wang, Lin-Fa; Skiniotis, Georgios; Lee, Benhur; Zhou, Z Hong; Broder, Christopher C; Aguilar, Hector C; Nikolov, Dimitar B

2015-12-01

Nipah virus (NiV) is a paramyxovirus that infects host cells through the coordinated efforts of two envelope glycoproteins. The G glycoprotein attaches to cell receptors, triggering the fusion (F) glycoprotein to execute membrane fusion. Here we report the first crystal structure of the pre-fusion form of the NiV-F glycoprotein ectodomain. Interestingly this structure also revealed a hexamer-of-trimers encircling a central axis. Electron tomography of Nipah virus-like particles supported the hexameric pre-fusion model, and biochemical analyses supported the hexamer-of-trimers F assembly in solution. Importantly, structure-assisted site-directed mutagenesis of the interfaces between F trimers highlighted the functional relevance of the hexameric assembly. Shown here, in both cell-cell fusion and virus-cell fusion systems, our results suggested that this hexamer-of-trimers assembly was important during fusion pore formation. We propose that this assembly would stabilize the pre-fusion F conformation prior to cell attachment and facilitate the coordinated transition to a post-fusion conformation of all six F trimers upon triggering of a single trimer. Together, our data reveal a novel and functional pre-fusion architecture of a paramyxoviral fusion glycoprotein.

Biomechanical analysis of a newly designed bioabsorbable anterior cervical plate. Invited submission from the joint section meeting on disorders of the spine and peripheral nerves, March 2005.

PubMed

Ames, Christopher P; Acosta, Frank L; Chamberlain, Robert H; Larios, Adolfo Espinoza; Crawford, Neil R

2005-12-01

The authors present a biomechanical analysis of a newly designed bioabsorbable anterior cervical plate (ACP) for the treatment of one-level cervical degenerative disc disease. They studied anterior cervical discectomy and fusion (ACDF) in a human cadaveric model, comparing the stability of the cervical spine after placement of the bioabsorbable fusion plate, a bioabsorbable mesh, and a more traditional metallic ACP. Seven human cadaveric specimens underwent a C6-7 fibular graft-assisted ACDF placement. A one-level resorbable ACP was then placed and secured with bioabsorbable screws. Flexibility testing was performed on both intact and instrumented specimens using a servohydraulic system to create flexion-extension, lateral bending, and axial rotation motions. After data analysis, three parameters were calculated: angular range of motion, lax zone, and stiff zone. The results were compared with those obtained in a previous study of a resorbable fusion mesh and with those acquired using metallic fusion ACPs. For all parameters studied, the resorbable plate consistently conferred greater stability than the resorbable mesh. Moreover, it offered comparable stability with that of metallic fusion ACPs. Bioabsorbable plates provide better stability than resorbable mesh. Although the results of this study do not necessarily indicate that a resorbable plate confers equivalent stability to a metal plate, the resorbable ACP certainly yielded better results than the resorbable mesh. Bioabsorbable fusion ACPs should therefore be considered as alternatives to metal plates when a graft containment device is required.

Fission-suppressed fusion breeder on the thorium cycle and nonproliferation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moir, R. W.

2012-06-19

Fusion reactors could be designed to breed fissile material while suppressing fissioning thereby enhancing safety. The produced fuel could be used to startup and makeup fuel for fission reactors. Each fusion reaction can produce typically 0.6 fissile atoms and release about 1.6 times the 14 MeV neutron's energy in the blanket in the fission-suppressed design. This production rate is 2660 kg/1000 MW of fusion power for a year. The revenues would be doubled from such a plant by selling fuel at a price of 60/g and electricity at $0.05/kWh for Q=P{sub fusion}/P{sub input}=4. Fusion reactors could be designed to destroymore » fission wastes by transmutation and fissioning but this is not a natural use of fusion whereas it is a designed use of fission reactors. Fusion could supply makeup fuel to fission reactors that were dedicated to fissioning wastes with some of their neutrons. The design for safety and heat removal and other items is already accomplished with fission reactors. Whereas fusion reactors have geometry that compromises safety with a complex and thin wall separating the fusion zone from the blanket zone where wastes could be destroyed. Nonproliferation can be enhanced by mixing {sup 233}U with {sup 238}U. Also nonproliferation is enhanced in typical fission-suppressed designs by generating up to 0.05 {sup 232}U atoms for each {sup 233}U atom produced from thorium, about twice the IAEA standards of 'reduced protection' or 'self protection.' With 2.4%{sup 232}U, high explosive material is predicted to degrade owing to ionizing radiation after a little over 1/2 year and the heat rate is 77 W just after separation and climbs to over 600 W ten years later. The fissile material can be used to fuel most any fission reactor but is especially appropriate for molten salt reactors (MSR) also called liquid fluoride thorium reactors (LFTR) because of the molten fuel does not need hands on fabrication and handling.« less

Microstructural Evolution of INCONEL® Alloy 740H® Fusion Welds During Creep

NASA Astrophysics Data System (ADS)

Bechetti, Daniel H.; DuPont, John N.; de Barbadillo, John J.; Baker, Brian A.; Watanabe, Masashi

2015-02-01

Electron microscopy techniques have been used to investigate the cause of premature creep failure in the fusion zone of INCONEL® Alloy 740H® (INCONEL and 740H are registered trademarks of Special Metals Corporation) welds. The reduced creep rupture lives of all-weld-metal and cross-weld creep specimens (relative to base metal specimens) have been attributed to the presence of large grain boundary regions that were denuded in fine γ' but contained coarse, elongated particles. Investigation of creep rupture specimens has revealed four factors that influence the formation of these coarsened zones, and the large particles found within them have been identified as γ'. Comparisons of the microstructural characteristics of these zones to the characteristics that are typical of denuded zones formed by a variety of mechanisms identified in the literature have been made. It is concluded that the mechanism of γ'-denuded zone formation in alloy 740H is discontinuous coarsening of the γ' phase. The discontinuous reaction is catalyzed by the grain boundary migration and sliding which occur during creep and likely promoted by the inhomogeneous weld metal microstructure that results from solute segregation during solidification. The increased susceptibility to the formation of the observed γ'-denuded zones in the weld metal as compared to the base metal is discussed in the context of differences in the contributions to the driving force for the discontinuous coarsening reaction.

Characterization of microstructure, local deformation and microchemistry in Alloy 690 heat-affected zone and stress corrosion cracking in high temperature water

NASA Astrophysics Data System (ADS)

Lu, Zhanpeng; Chen, Junjie; Shoji, Tetsuo; Takeda, Yoichi; Yamazaki, Seiya

2015-10-01

With increasing the distance from the weld fusion line in an Alloy 690 heat-affected zone, micro-hardness decreases, kernel average misorientation decreases and the fraction of Σ3 boundaries increases. Chromium depletion at grain boundaries in the Alloy 690 heat-affected zone is less significant than that in an Alloy 600 heat-affected zone. Alloy 690 heat-affected zone exhibits much higher IGSCC resistance than Alloy 600 heat-affected zone in simulated pressurized water reactor primary water. Heavily cold worked Alloy 690 exhibits localized intergranular stress corrosion cracking. The effects of metallurgical and mechanical properties on stress corrosion cracking in Alloy 690 are discussed.

Viral membrane fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harrison, Stephen C., E-mail: harrison@crystal.harvard.edu

2015-05-15

Membrane fusion is an essential step when enveloped viruses enter cells. Lipid bilayer fusion requires catalysis to overcome a high kinetic barrier; viral fusion proteins are the agents that fulfill this catalytic function. Despite a variety of molecular architectures, these proteins facilitate fusion by essentially the same generic mechanism. Stimulated by a signal associated with arrival at the cell to be infected (e.g., receptor or co-receptor binding, proton binding in an endosome), they undergo a series of conformational changes. A hydrophobic segment (a “fusion loop” or “fusion peptide”) engages the target-cell membrane and collapse of the bridging intermediate thus formedmore » draws the two membranes (virus and cell) together. We know of three structural classes for viral fusion proteins. Structures for both pre- and postfusion conformations of illustrate the beginning and end points of a process that can be probed by single-virion measurements of fusion kinetics. - Highlights: • Viral fusion proteins overcome the high energy barrier to lipid bilayer merger. • Different molecular structures but the same catalytic mechanism. • Review describes properties of three known fusion-protein structural classes. • Single-virion fusion experiments elucidate mechanism.« less

Laminated and infused Parafilm® - paper for paper-based analytical devices.

PubMed

Kim, Yong Shin; Yang, Yuanyuan; Henry, Charles S

2018-02-01

Numerous fabrication methods have been reported for microfluidic paper-based analytical devices (μPADs) using barrier materials ranging from photoresist to wax. While these methods have been used with wide success, consistently producing small, high-resolution features using materials and methods that are compatible with solvents and surfactants remains a challenge. Two new methods are presented here for generating μPADs with well-defined, high-resolution structures compatible with solvents and surfactant-containing solutions by partially or fully fusing paper with Parafilm® followed by cutting with a CO 2 laser cutter. Partial fusion leads to laminated paper ( l -paper) while the complete fusion results in infused paper ( i -paper). Patterned structures in l -paper were fabricated by selective removal of the paper but not the underlying Parafilm® using a benchtop CO 2 laser. Under optimized conditions, a gap as small as 137 ± 22 μm could be generated. Using this approach, a miniaturized paper 384-zone plate, consisting of circular detection elements with a diameter of 1.86 mm, was fabricated in 64 × 43 mm 2 area. Furthermore, these ablation-patterned substrates were confirmed to be compatible with surfactant solutions and common organic solvents (methanol, acetonitrile and dimethylformamide), which has been achieved by very few μPAD patterning techniques. Patterns in i -paper were created by completely cutting out zones of the i -paper and then fixing pre-cut paper into these openings similar to the strategy of fitting a jigsaw piece into a puzzle. Upon heating, unmodified paper was readily sealed into these openings due to partial reflow of the paraffin into the paper. This unique and simple bonding method was illustrated by two types of 3D μPADs, a push-on valve and a time-gated flow distributor, without adding adhesive layers. The free-standing jigsaw-patterned sheets showed good structural stability and solution compatibility, which provided a facile alternative method for fabricating complicated μPADs.

STRESS CORROSION CRACK GROWTH RESPONSE FOR ALLOY 152/52 DISSIMILAR METAL WELDS IN PWR PRIMARY WATER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Toloczko, Mychailo B.; Olszta, Matthew J.; Overman, Nicole R.

2015-08-15

As part of ongoing research into primary water stress corrosion cracking (PWSCC) susceptibility of alloy 690 and its welds, SCC tests have been conducted on alloy 152/52 dissimilar metal (DM) welds with cracks positioned with the goal to assess weld dilution and fusion line effects on SCC susceptibility. No increased crack growth rate was found when evaluating a 20% Cr dilution zone in alloy 152M joined to carbon steel (CS) that had not undergone a post-weld heat treatment (PWHT). However, high SCC crack growth rates were observed when the crack reached the fusion line of that material where it propagatedmore » both on the fusion line and in the heat affected zone (HAZ) of the carbon steel. Crack surface and crack profile examinations of the specimen revealed that cracking in the weld region was transgranular (TG) with weld grain boundaries not aligned with the geometric crack growth plane of the specimen. The application of a typical pressure vessel PWHT on a second set of alloy 152/52 – carbon steel DM weld specimens was found to eliminate the high SCC susceptibility in the fusion line and carbon steel HAZ regions. PWSCC tests were also performed on alloy 152-304SS DM weld specimens. Constant K crack growth rates did not exceed 5x10-9 mm/s in this material with post-test examinations revealing cracking primarily on the fusion line and slightly into the 304SS HAZ.« less

Influence of laser power on microstructure and mechanical properties of laser welded-brazed Mg to Ni coated Ti alloys

NASA Astrophysics Data System (ADS)

Tan, Caiwang; Lu, Qingshuang; Chen, Bo; Song, Xiaoguo; Li, Liqun; Feng, Jicai; Wang, Yang

2017-03-01

AZ31B Magnesium (Mg) and Ti-6Al-4V titanium (Ti) alloys with Ni coating were joined by laser welding-brazing process using AZ92 Mg based filler. The influence of laser power on microstructure and mechanical properties were investigated. Ni coating was found to significantly promote good wetting-spreading ability of molten filler on the Ti sheet. Acceptable joints without obvious defects were obtained within a relatively wide processing window. In the process metallurgical bonding was achieved by the formation of Ti3Al phase at direct irradiation zone and Al-Ni phase followed by a layer of Mg-Al-Ni ternary compound adjacent to the fusion zone at the intermediate zone. The thickness of reaction layers increased slowly with the increasing laser power. The tensile-shear test indicated that joints produced at the laser power of 1300 W reached 2387 N fracture load, representing 88.5% joint efficiency with respect to the Mg base metal. The corresponding failure occurred in the fusion zone of the Mg base metal, while joints fractured at the interface at lower/higher laser power due to the crack or excessive intermetallic compound (IMC) formation along the interface.

Influence of laser cladding regimes on structural features and mechanical properties of coatings on titanium substrates

NASA Astrophysics Data System (ADS)

Malyutina, Yulia N.; Lazurenko, Daria V.; Bataev, Ivan A.; Movtchan, Igor A.

2015-10-01

In this paper an influence of the tantalum content on the structure and properties of surface layers of the titanium alloy doped using a laser treatment technology was investigated. It was found that an increase of a quantity of filler powder per one millimeter of a track length contributed to a rise of the content of undissolved particles in coatings. The maximum thickness of a cladded layer was reached at the mass of powder per the length unit equaled to 5.5 g/cm. Coatings were characterized by the formation of a dendrite structure with attributes of segregation. The width of a quenched fusion zone grew with an increase in the rate of powder feed to the treated area. Significant strengthening of the titanium surface layer alloyed with tantalum was not observed; however, the presence of undissolved tantalum particles can decrease the hardness of titanium surface layers.

Grain Refinement of AZ31 Magnesium Alloy Weldments by AC Pulsing Technique

NASA Astrophysics Data System (ADS)

Kishore Babu, N.; Cross, C. E.

2012-11-01

The current study has investigated the influence of alternating current pulsing on the structure and mechanical properties of AZ31 magnesium alloy gas tungsten arc (GTA) weldments. Autogenous full penetration bead-on-plate GTA welds were made under a variety of conditions including variable polarity (VP), variable polarity mixed (VPM), alternating current (AC), and alternating current pulsing (ACPC). AC pulsing resulted in significant refinement of weld metal when compared with the unpulsed conditions. AC pulsing leads to relatively finer and more equiaxed grain structure in GTA welds. In contrast, VP, VPM, and AC welding resulted in predominantly columnar grain structures. The reason for this grain refinement may be attributed to the periodic variations in temperature gradient and solidification rate associated with pulsing as well as weld pool oscillation observed in the ACPC welds. The observed grain refinement was shown to result in an appreciable increase in fusion zone hardness, tensile strength, and ductility.

Centripetal myosin redistribution in thrombin-stimulated platelets. Relationship to platelet Factor 4 secretion.

PubMed

Painter, R G; Ginsberg, M H

1984-11-01

We have examined the F-actin and myosin distribution in resting and thrombin-activated platelets by double label immunofluorescence microscopy. In resting, discoid platelets, F-actin and myosin staining was distributed in a diffuse pattern throughout the interior of the cell with slight accentuation at the cell periphery. In contrast, platelet factor 4 antigen (PF4) was more centrally localized in a fine punctate distribution which is consistent with its localization in alpha-granules. Within 5 sec after thrombin stimulation both F-actin and myosin staining were increased at the periphery of the now spherical platelets. Subsequently, a myosin-containing spherical structure decreased in diameter closely surrounding a phase-dense central zone. In contrast, F-actin staining continued to be accentuated at the cell periphery and was prominent in filopodia and blebs. As previously shown, PF4 staining was localized after 30 sec within large intracellular masses that corresponded to closed vacuolar structures at the ultrastructural level. Morphometric analysis of electron micrographs showed that formation of these vacuolar structures kinetically paralleled alpha-granule disappearance and preceded PF4 release. These PF4-containing structures translocated to the cell periphery after 1-3 min, where they appeared to fuse with the plasma membrane. Ultrastructural analysis of thin sections showed that the myosin-rich spherical structure spatially and temporally correlated with a band of microfilaments that closely surrounded the organelle-rich central zone of the cell. Morphometric analysis of these micrographs showed that the absolute volume of this central zone decreased with time after thrombin addition, showing a significant change after 15 sec and reaching a maximum value after 3-5 min. Changes in the volume of this compartment kinetically preceded PF4 release. On the basis of these data, we propose that an actomyosin contractile force is generated which centripetally redistributes the myosinrich structure and organelle zone. Conceivably this inward force may not only accelerate granule-granule fusion to form intracellular secretory vacuoles, but may also provide aid in their extrusion toward the platelet plasma membrane.

Information fusion for the Gray Zone

NASA Astrophysics Data System (ADS)

Fenstermacher, Laurie

2016-05-01

United States Special Operations Command (SOCOM) recently published a white paper describing the "Gray Zone", security challenges characterized by "ambiguity about the nature of the conflict, opacity of the parties involved…competitive interactions among and within state and non-state actors that fall between the traditional war and peace duality."1 Ambiguity and related uncertainty about actors, situations, relationships, and intent require new approaches to information collection, processing and fusion. General Votel, the current SOCOM commander, during a recent speech on "Operating in the Gray Zone" emphasized that it would be important to get left of the next crises and stated emphatically, "to do that we must understand the Human Domain."2 This understanding of the human domain must come from making meaning based on different perspectives, including the "emic" or first person/participant and "etic" or third person/observer perspectives. Much of the information currently collected and processed is etic. Incorporation and fusion with the emic perspective enables forecasting of behaviors/events and provides context for etic information (e.g., video).3 Gray zone challenges are perspective-dependent; for example, the conflict in Ukraine is interpreted quite differently by Russia, the US and Ukraine. Russia views it as war, necessitating aggressive action, the US views it as a security issue best dealt with by economic sanctions and diplomacy and the Ukraine views it as a threat to its sovereignty.4 General Otto in the Air Force ISR 2023 vision document stated that Air Force ISR is needed to anticipate strategic surprise.5 Anticipatory analysis enabling getting left of a crisis inherently requires a greater focus on information sources that elucidate the human environment as well as new methods that elucidate not only the "who's" and "what's", but the "how's and "why's," extracting features and/or patterns and subtle cues useful for forecasting behaviors and events; for example discourse patterns related to social identity and integrative complexity.6 AFRL has been conducting research to enable analysts to understand the "emic" perspective based on discourse analysis methods and/or text analytics.7 Previous results demonstrated the value of fusion of emic and etic information in terms of improved accuracy (from 39% to 86%) in forecasting violent events.8 This paper will describe new work to extend this to anticipatory analysis in the gray zone.

Multisensor data fusion for integrated maritime surveillance

NASA Astrophysics Data System (ADS)

Premji, A.; Ponsford, A. M.

1995-01-01

A prototype Integrated Coastal Surveillance system has been developed on Canada's East Coast to provide effective surveillance out to and beyond the 200 nautical mile Exclusive Economic Zone. The system has been designed to protect Canada's natural resources, and to monitor and control the coastline for smuggling, drug trafficking, and similar illegal activity. This paper describes the Multiple Sensor - Multiple Target data fusion system that has been developed. The fusion processor has been developed around the celebrated Multiple Hypothesis Tracking algorithm which accommodates multiple targets, new targets, false alarms, and missed detections. This processor performs four major functions: plot-to-track association to form individual radar tracks; fusion of radar tracks with secondary sensor reports; track identification and tagging using secondary reports; and track level fusion to form common tracks. Radar data from coherent and non-coherent radars has been used to evaluate the performance of the processor. This paper presents preliminary results.

Feldspar 40Ar/39Ar dating of ICDP PALEOVAN cores

NASA Astrophysics Data System (ADS)

Engelhardt, Jonathan Franz; Sudo, Masafumi; Stockhecke, Mona; Oberhänsli, Roland

2017-11-01

Volcaniclastic fall deposits in ICDP drilling cores from Lake Van, Turkey, contain sodium-rich sanidine and calcium-rich anorthoclase, which both comprise a variety of textural zoning and inclusions. An age model records the lake's history and is based on climate-stratigraphic correlations, tephrostratigraphy, paleomagnetics, and earlier 40Ar/39Ar analyses (Stockhecke et al., 2014b). Results from total fusion and stepwise heating 40Ar/39Ar analyses presented in this study allow for the comparison of radiometric constraints from texturally diversified feldspar and the multi-proxy lacustrine age model and vice versa. This study has investigated several grain-size fractions of feldspar from 13 volcaniclastic units. The feldspars show textural features that are visible in cathodoluminescence (CL) or back-scattered electron (BSE) images and can be subdivided into three dominant zoning-types: (1) compositional zoning, (2) round pseudo-oscillatory zoning and (3) resorbed and patchy zoning (Ginibre et al., 2004). Round pseudo-oscillatory zoning records a sensitive alternation of Fe and Ca that also reflects resorption processes. This is only visible in CL images. Compositional zoning reflects anticorrelated anorthite and orthoclase contents and is visible in BSE. Eleven inverse isochron ages from total fusion and three from stepwise heating analyses fit the age model. Four experiments resulted in older inverse isochron ages that do not concur with the model within 2σ uncertainties and that deviate from 1 ka to 17 ka minimum. C- and R-type zoning are interpreted as representing growth in magma chamber cupolas, as wall mushes, or in narrow conduits. Persistent compositions of PO-type crystals and abundant surfaces recording dissolution features correspond to formation within a magma chamber. C-type zoning and R-type zoning have revealed an irregular incorporation of melt and fluid inclusions. These two types of zoning in feldspar are interpreted as preferentially contributing either heterogeneously distributed excess 40Ar or inherited 40Ar to the deviating 40Ar/39Ar ages that are discussed in this study.

Visualization of Synchronous or Asynchronous Release of Single Synaptic Vesicle in Active-Zone-Like Membrane Formed on Neuroligin-Coated Glass Surface.

PubMed

Funahashi, Junichiro; Tanaka, Hiromitsu; Hirano, Tomoo

2018-01-01

Fast repetitive synaptic transmission depends on efficient exocytosis and retrieval of synaptic vesicles around a presynaptic active zone. However, the functional organization of an active zone and regulatory mechanisms of exocytosis, endocytosis and reconstruction of release-competent synaptic vesicles have not been fully elucidated. By developing a novel visualization method, we attempted to identify the location of exocytosis of a single synaptic vesicle within an active zone and examined movement of synaptic vesicle protein synaptophysin (Syp) after exocytosis. Using cultured hippocampal neurons, we induced formation of active-zone-like membranes (AZLMs) directly adjacent and parallel to a glass surface coated with neuroligin, and imaged Syp fused to super-ecliptic pHluorin (Syp-SEP) after its translocation to the plasma membrane from a synaptic vesicle using total internal reflection fluorescence microscopy (TIRFM). An AZLM showed characteristic molecular and functional properties of a presynaptic active zone. It contained active zone proteins, cytomatrix at the active zone-associated structural protein (CAST), Bassoon, Piccolo, Munc13 and RIM, and showed an increase in intracellular Ca 2+ concentration upon electrical stimulation. In addition, single-pulse stimulation sometimes induced a transient increase of Syp-SEP signal followed by lateral spread in an AZLM, which was considered to reflect an exocytosis event of a single synaptic vesicle. The diffusion coefficient of Syp-SEP on the presynaptic plasma membrane after the membrane fusion was estimated to be 0.17-0.19 μm 2 /s, suggesting that Syp-SEP diffused without significant obstruction. Synchronous exocytosis just after the electrical stimulation tended to occur at multiple restricted sites within an AZLM, whereas locations of asynchronous release occurring later after the stimulation tended to be more scattered.

Effect of Heat-Affected Zone on Spot Weldability in Automotive Ultra High Strength Steel Sheet

NASA Astrophysics Data System (ADS)

Nagasaka, Akihiko; Naito, Junya; Chinzei, Shota; Hojo, Tomohiko; Horiguchi, Katsumi; Shimizu, Yuki; Furusawa, Takuro; Kitahara, Yu

Effect of heat-affected zone (HAZ) on spot weldability in automotive hot stamping (HS) steel sheet was investigated for automotive applications. Tensile test was performed on a tensile testing machine at a crosshead speed of 3 mm/min, using spot welded test specimen (Parallel length: 60 mm, Width: 20 mm, Thickness: 1.4 mm, Tab: 20×20 mm). The spot welding test was carried out using spot welded test specimen with welding current (I) of 6.3 kA to 9.5 kA. Hardness was measured with the dynamic ultra micro Vickers hardness tester. In HS steel, has very high strength of 1 500 MPa, tensile strength (TS) and total elongation (TEl) of the spot welded test specimen of HS steel were lower than those of base metal test specimen. The spot welded test specimen broke in the weld. The Vickers hardnesses (HVs) of base metal and fusion zone of hot stamping steel were around HV500. In addition, the hardness of HAZ was under HV300. The difference of hardness between fusion zone and HAZ was around HV200. The hardness distribution acted as a notch. On the other hand, in dual phase (DP) steel, has low strength of 590 MPa, the TS of spot welded test specimen of DP steel was the same as the base metal test specimen because of the breaking of base metal. The TEl of the spot welded test specimen of DP steel was smaller than that of base metal test specimen. In the spot welded test specimen of DP steel, the hardness of base metal was around HV200 and the fusion zone was around HV500. The hardness distribution did not act as a notch. The difference in hardness between base metal and HAZ acted on a crack initiation at HAZ softening.

Tritium well depth, tritium well time and sponge mechanism for reducing tritium retention

NASA Astrophysics Data System (ADS)

Deng, B. Q.; Li, Z. X.; Li, C. Y.; Feng, K. M.

2011-07-01

New simulation results are predicted in a fusion reactor operation process. They are somewhat similar to, but quite different from, the xenon poisoning effects resulting from fission-produced iodine during the restart-up process of a fission reactor. We obtained completely new results of tritium well depth and tritium well time in magnetic confinement fusion energy research area. This study is carried out to investigate the following: what will be the least amount of tritium storage required to start up a fusion reactor and how long the fusion reactor needs to be operated for achieving the tritium break-even during the initial start-up phase due to the finite tritium-breeding time, which is dependent on the tritium breeder, specific structure of the breeding zone, layout of the coolant flow pipes, tritium recovery scheme and applied extraction process, the tritium retention of plasma facing component (PFC) and other reactor components, unrecoverable tritium fraction in the breeder, leakage to the inertial gas container and the natural radioactive decay time constant. We describe these new issues and answer these problems by setting up and solving a set of equations, which are described by a dynamic subsystem model of tritium inventory evolution in a fusion experimental breeder (FEB). Reasonable results are obtained using our simulation model. It is found that the tritium well depth is about 0.319 kg and the tritium well time is approximately 235 full power operation days for the reference case of the designed FEB configuration, and it is also found that after one-year operation the tritium storage reaches 0.767 kg, which is more than the least amount of tritium storage required to start up another FEB-like fusion reactor. The results show that the tritium retention in the PFC is equivalent to 11.9% of tritium well depth that is fairly consistent with the result of 10-20% deduced from the integrated particle balance of European tokamaks. Based on our experimental and theoretical studies, some new mechanisms are proposed for reducing the tritium retention in PFC and structure materials of tritium-breeding blanket. In this paper, a qualitative analysis of the 'sponge effect' is carried out. The 'sponge effect' may help us to reduce tritium retention by ~20% in the PFC.

Studies on Fusion Welding of High Nitrogen Stainless Steel: Microstructure, Mechanical and corrosion Behaviour

NASA Astrophysics Data System (ADS)

Mohammed, Raffi; Srinivasa Rao, K.; Madhusudhan Reddy, G.

2018-03-01

An attempt has been made in the present investigation to weld high nitrogen steel of 5mm thick plates using various process i.e., shielded metal arc welding (SMAW), gas tungsten arc welding (GTAW) and autogenous electron beam welding (EBW) process. Present work is aimed at studying the microstructural changes and its effects on mechanical properties and corrosion resistance. Microstructure is characterized by optical, scanning electron microscopy and electron back scattered diffraction technique. Vickers hardness, tensile properties, impact toughness and face bend ductility testing of the welds was carried out. Pitting corrosion resistance of welds was determined using potentio-dynamic polarization testing in 3.5%NaCl solution. Results of the present investigation established that SMA welds made using Cr-Mn-N electrode were observed to have a austenite dendritic grain structure in the weld metal and is having poor mechanical properties but good corrosion resistance. GTA welds made using 18Ni (MDN 250) filler wire were observed to have a reverted austenite in martensite matrix of the weld metal and formation of unmixed zone at the fusion boundary which resulted in better mechanical properties and poor corrosion resistance. Fine grains and uniform distribution of delta ferrite in the austenite matrix and narrow width of weld zone are observed in autogeneous electron beam welds. A good combination of mechanical properties and corrosion resistance was achieved for electron beam welds of high nitrogen steel when compared to SMA and GTA welds.

Assessment of liver ablation using cone beam computed tomography.

PubMed

Abdel-Rehim, Mohamed; Ronot, Maxime; Sibert, Annie; Vilgrain, Valérie

2015-01-14

To investigate the feasibility and accuracy of cone beam computed tomography (CBCT) in assessing the ablation zone after liver tumor ablation. Twenty-three patients (17 men and 6 women, range: 45-85 years old, mean age 65 years) with malignant liver tumors underwent ultrasound-guided percutaneous tumor ablation [radiofrequency (n = 14), microwave (n = 9)] followed by intravenous contrast-enhanced CBCT. Baseline multidetector computed tomography (MDCT) and peri-procedural CBCT images were compared. CBCT image quality was assessed as poor, good, or excellent. Image fusion was performed to assess tumor coverage, and quality of fusion was rated as bad, good, or excellent. Ablation zone volumes on peri-procedural CBCT and post-procedural MDCT were compared using the non-parametric paired Wilcoxon t-test. Rate of primary ablation effectiveness was 100%. There were no complications related to ablation. Local tumor recurrence and new liver tumors were found 3 mo after initial treatment in one patient (4%). The ablation zone was identified in 21/23 (91.3%) patients on CBCT. The fusion of baseline MDCT and peri-procedural CBCT images was feasible in all patients and showed satisfactory tumor coverage (at least 5-mm margin). CBCT image quality was poor, good, and excellent in 2 (9%), 8 (35%), and 13 (56%), patients respectively. Registration quality between peri-procedural CBCT and post-procedural MDCT images was good to excellent in 17/23 (74%) patients. The median ablation volume on peri-procedural CBCT and post-procedural MDCT was 30 cm(3) (range: 4-95 cm(3)) and 30 cm(3) (range: 4-124 cm(3)), respectively (P-value > 0.2). There was a good correlation (r = 0.79) between the volumes of the two techniques. Contrast-enhanced CBCT after tumor ablation of the liver allows early assessment of the ablation zone.

Dynamical Organization of Syntaxin-1A at the Presynaptic Active Zone

PubMed Central

Ullrich, Alexander; Böhme, Mathias A.; Schöneberg, Johannes; Depner, Harald; Sigrist, Stephan J.; Noé, Frank

2015-01-01

Synaptic vesicle fusion is mediated by SNARE proteins forming in between synaptic vesicle (v-SNARE) and plasma membrane (t-SNARE), one of which is Syntaxin-1A. Although exocytosis mainly occurs at active zones, Syntaxin-1A appears to cover the entire neuronal membrane. By using STED super-resolution light microscopy and image analysis of Drosophila neuro-muscular junctions, we show that Syntaxin-1A clusters are more abundant and have an increased size at active zones. A computational particle-based model of syntaxin cluster formation and dynamics is developed. The model is parametrized to reproduce Syntaxin cluster-size distributions found by STED analysis, and successfully reproduces existing FRAP results. The model shows that the neuronal membrane is adjusted in a way to strike a balance between having most syntaxins stored in large clusters, while still keeping a mobile fraction of syntaxins free or in small clusters that can efficiently search the membrane or be traded between clusters. This balance is subtle and can be shifted toward almost no clustering and almost complete clustering by modifying the syntaxin interaction energy on the order of only 1 kBT. This capability appears to be exploited at active zones. The larger active-zone syntaxin clusters are more stable and provide regions of high docking and fusion capability, whereas the smaller clusters outside may serve as flexible reserve pool or sites of spontaneous ectopic release. PMID:26367029

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Wei, E-mail: wang_wei_310@163.com; Lu, Yonghao, E-mail: lu_yonghao@mater.ustb.edu.cn; Ding, Xianfei, E-mail: xfding@ustb.edu.cn

Microstructures and microhardness at fusion boundary of a weld joint were investigated in a 316 stainless steel/Inconel 182 dissimilar weldment. The results showed that there were two alternately distributed typical fusion boundaries, a narrow random boundary (possessed 15% in length) with a clear sharp interface and an epitaxial fusion one with (100){sub BM}//(100){sub WM} at the joint interface. The composition transition, microstructure and hardness across the fusion boundary strongly depended on the type of the fusion boundary. For the random boundary, there was a clear sharp interface and the composition transition with a width of 100 μm took place symmetricallymore » across the grain boundary. For the epitaxial fusion one, however, there were Type-I and Type-II grain boundaries perpendicular and parallel to the epitaxial fusion boundary, respectively. The composition transition took place in the Inconel 182 weld side. Σ3 boundaries in the HAZ of 316SS side and Σ5 grain boundaries in weld metal were usually observed, despite the type of fusion boundary, however the former was much more in epitaxial fusion boundary. Microhardness was continuously decreased across the random fusion boundary from the side of Inconel 182 to 316SS, but a hardening phenomenon appeared in the epitaxial fusion boundary zone because of its fine cellular microstructure. - Highlights: • Two typical fusion boundaries alternately distributed in the fusion interface • The microstructure, composition and hardness across fusion boundary depended on its type. • Different regions in welded joint have different special CSL value boundaries. • Hardening phenomenon only appeared in the epitaxial fusion boundary.« less

Investigation on Microstructure and Mechanical Properties of ATIG welded alloy C-276 with Fe2O3 flux

NASA Astrophysics Data System (ADS)

Surve, Angad; Bhosage, Sharnappa; Mehta, Akshay; Srikanth, A.; Arivarasu, M.; Manikandan, M.; Gokulkumar, K.; Rajan, Deva. N.

2018-02-01

Alloy C-276 susceptible to hot cracking. The microsegregation occurs during solidification is the largely responsible for the hot cracking in the alloy. The present study investigates the microstructure and mechanical properties of alloy C-276 weld joint fabricated by ATIG welding technique. The macro examination was carried out assess the defects in the weld joints. Optical and scanning electron microscope examination was carried out to see the structural changes in the fusion zone. The tensile test was performed to evaluate the strength of the weld joints. The results show the defect free welding was achieved in the established process parameters. The macrograph shows the full depth of penetration was obtained in the single pass by the effect of Marangoni convection. Energy Dispersive X-ray spectroscopy (EDS) analysis illustrates the absence of microsegregation in the interdendritic zone. The tensile test shows the improved mechanical properties compared to the base metal.

Microstructure and Mechanical Properties of Laser Welded Joints of DZ125L and IN718 Nickel Base Superalloys

NASA Astrophysics Data System (ADS)

Liang, Taosha; Wang, Lei; Liu, Yang; Song, Xiu

2018-05-01

The microstructure and mechanical properties of the laser welded joint of DZ125L and IN718 nickel base superalloys were investigated. The results show that the fusion zone (FZ) mainly consists of fine dendrite structure with fine γ', Laves phases and MC carbides inhomogeneously distributed. The high welding temperature induces the partial dissolution of γ' in the heat-affected zone (HAZ) of DZ125L and liquation of grain boundaries in both of the HAZs. After post-weld heat treatment (PWHT), fine γ″ and γ' phases precipitate in the FZ, IN718 HAZ and IN718 base metal (BM), and fine γ' precipitate in the γ channel of the HAZ and BM of DZ125L. With tensile testing, the joints after PWHT show higher strengths than that of the weaker DZ125L alloy. Plastic deformation mainly concentrates in the weaker DZ125L and the joint finally fails in the DZ125L BM.

Structure of the Ebola virus envelope protein MPER/TM domain and its interaction with the fusion loop explains their fusion activity.

PubMed

Lee, Jinwoo; Nyenhuis, David A; Nelson, Elizabeth A; Cafiso, David S; White, Judith M; Tamm, Lukas K

2017-09-19

Ebolavirus (EBOV), an enveloped filamentous RNA virus causing severe hemorrhagic fever, enters cells by macropinocytosis and membrane fusion in a late endosomal compartment. Fusion is mediated by the EBOV envelope glycoprotein GP, which consists of subunits GP1 and GP2. GP1 binds to cellular receptors, including Niemann-Pick C1 (NPC1) protein, and GP2 is responsible for low pH-induced membrane fusion. Proteolytic cleavage and NPC1 binding at endosomal pH lead to conformational rearrangements of GP2 that include exposing the hydrophobic fusion loop (FL) for insertion into the cellular target membrane and forming a six-helix bundle structure. Although major portions of the GP2 structure have been solved in pre- and postfusion states and although current models place the transmembrane (TM) and FL domains of GP2 in close proximity at critical steps of membrane fusion, their structures in membrane environments, and especially interactions between them, have not yet been characterized. Here, we present the structure of the membrane proximal external region (MPER) connected to the TM domain: i.e., the missing parts of the EBOV GP2 structure. The structure, solved by solution NMR and EPR spectroscopy in membrane-mimetic environments, consists of a helix-turn-helix architecture that is independent of pH. Moreover, the MPER region is shown to interact in the membrane interface with the previously determined structure of the EBOV FL through several critical aromatic residues. Mutation of aromatic and neighboring residues in both binding partners decreases fusion and viral entry, highlighting the functional importance of the MPER/TM-FL interaction in EBOV entry and fusion.

Internal structure visualization of flow and flame by process tomography and PLIF data fusion

NASA Astrophysics Data System (ADS)

Liu, J.; Liu, Shi; Sun, S.; Pan, X.; Schlaberg, I. H. I.

2018-02-01

To address the increasing demands on pollution control and energy saving, the study of low-emission and high-efficiency burners has been emphasized worldwide. Swirl-induced environmental burners (EV-burners), have notable features aligned with these requirements. In this study, an EV burner is investigated by both an ECT system and an OH-PLIF system. The aim is to detect the structure of a flame and obtain more information about the combustion process in an EV burner. 3D ECT sensitivity maps are generated for the measurement and OH-PLIF images are acquired in the same combustion zone as for the ECT measurements. The experimental images of a flame by ECT are in good agreement with the OH radical distribution pictures captured by OH-PLIF, which provide a mutual verification of the visualization method.

Pressure-induced coordination changes in alkali-germanate melts - An in situ spectroscopic investigation

NASA Technical Reports Server (NTRS)

Farber, Danial L.; Williams, Quentin

1992-01-01

The structure of liquid Na2Ge2O5-H2O, a silicate melt analog, has been studied with Raman spectroscopy to pressures of 2.2 gigapascals. Upon compression, a peak near more than 240 wavenumbers associated with octahedral GeO6 groups grows relative to a peak near 500 wavenumbers associated with tetrahedral GeO4 groups. This change corresponds to an increase in octahedral germanium in the liquid from near 0 percent at ambient pressures to more than 50 percent at a pressure of 2.2 gigapascals. Silicate liquids pausibly undergo similar coordination changes at depth in the earth. Such structural changes may generate decreases in the fusion slopes of silicates at high pressures as well as neutrally buoyant magmas within the transition zone of the earth's mantle.

Molecular and cellular aspects of rhabdovirus entry.

PubMed

Albertini, Aurélie A V; Baquero, Eduard; Ferlin, Anna; Gaudin, Yves

2012-01-01

Rhabdoviruses enter the cell via the endocytic pathway and subsequently fuse with a cellular membrane within the acidic environment of the endosome. Both receptor recognition and membrane fusion are mediated by a single transmembrane viral glycoprotein (G). Fusion is triggered via a low-pH induced structural rearrangement. G is an atypical fusion protein as there is a pH-dependent equilibrium between its pre- and post-fusion conformations. The elucidation of the atomic structures of these two conformations for the vesicular stomatitis virus (VSV) G has revealed that it is different from the previously characterized class I and class II fusion proteins. In this review, the pre- and post-fusion VSV G structures are presented in detail demonstrating that G combines the features of the class I and class II fusion proteins. In addition to these similarities, these G structures also reveal some particularities that expand our understanding of the working of fusion machineries. Combined with data from recent studies that revealed the cellular aspects of the initial stages of rhabdovirus infection, all these data give an integrated view of the entry pathway of rhabdoviruses into their host cell.

Molecular and Cellular Aspects of Rhabdovirus Entry

PubMed Central

Albertini, Aurélie A. V.; Baquero, Eduard; Ferlin, Anna; Gaudin, Yves

2012-01-01

Rhabdoviruses enter the cell via the endocytic pathway and subsequently fuse with a cellular membrane within the acidic environment of the endosome. Both receptor recognition and membrane fusion are mediated by a single transmembrane viral glycoprotein (G). Fusion is triggered via a low-pH induced structural rearrangement. G is an atypical fusion protein as there is a pH-dependent equilibrium between its pre- and post-fusion conformations. The elucidation of the atomic structures of these two conformations for the vesicular stomatitis virus (VSV) G has revealed that it is different from the previously characterized class I and class II fusion proteins. In this review, the pre- and post-fusion VSV G structures are presented in detail demonstrating that G combines the features of the class I and class II fusion proteins. In addition to these similarities, these G structures also reveal some particularities that expand our understanding of the working of fusion machineries. Combined with data from recent studies that revealed the cellular aspects of the initial stages of rhabdovirus infection, all these data give an integrated view of the entry pathway of rhabdoviruses into their host cell. PMID:22355455

Enabling image fusion for a CT guided needle placement robot

NASA Astrophysics Data System (ADS)

Seifabadi, Reza; Xu, Sheng; Aalamifar, Fereshteh; Velusamy, Gnanasekar; Puhazhendi, Kaliyappan; Wood, Bradford J.

2017-03-01

Purpose: This study presents development and integration of hardware and software that enables ultrasound (US) and computer tomography (CT) fusion for a FDA-approved CT-guided needle placement robot. Having real-time US image registered to a priori-taken intraoperative CT image provides more anatomic information during needle insertion, in order to target hard-to-see lesions or avoid critical structures invisible to CT, track target motion, and to better monitor ablation treatment zone in relation to the tumor location. Method: A passive encoded mechanical arm is developed for the robot in order to hold and track an abdominal US transducer. This 4 degrees of freedom (DOF) arm is designed to attach to the robot end-effector. The arm is locked by default and is released by a press of button. The arm is designed such that the needle is always in plane with US image. The articulated arm is calibrated to improve its accuracy. Custom designed software (OncoNav, NIH) was developed to fuse real-time US image to a priori-taken CT. Results: The accuracy of the end effector before and after passive arm calibration was 7.07mm +/- 4.14mm and 1.74mm +/-1.60mm, respectively. The accuracy of the US image to the arm calibration was 5mm. The feasibility of US-CT fusion using the proposed hardware and software was demonstrated in an abdominal commercial phantom. Conclusions: Calibration significantly improved the accuracy of the arm in US image tracking. Fusion of US to CT using the proposed hardware and software was feasible.

Purification and Crystallization Reveal Two Types of Interactions of the Fusion Protein Homotrimer of Semliki Forest Virus

PubMed Central

Gibbons, Don L.; Reilly, Brigid; Ahn, Anna; Vaney, Marie-Christine; Vigouroux, Armelle; Rey, Felix A.; Kielian, Margaret

2004-01-01

The fusion proteins of the alphaviruses and flaviviruses have a similar native structure and convert to a highly stable homotrimer conformation during the fusion of the viral and target membranes. The properties of the alpha- and flavivirus fusion proteins distinguish them from the class I viral fusion proteins, such as influenza virus hemagglutinin, and establish them as the first members of the class II fusion proteins. Understanding how this new class carries out membrane fusion will require analysis of the structural basis for both the interaction of the protein subunits within the homotrimer and their interaction with the viral and target membranes. To this end we report a purification method for the E1 ectodomain homotrimer from the alphavirus Semliki Forest virus. The purified protein is trimeric, detergent soluble, retains the characteristic stability of the starting homotrimer, and is free of lipid and other contaminants. In contrast to the postfusion structures that have been determined for the class I proteins, the E1 homotrimer contains the fusion peptide region responsible for interaction with target membranes. This E1 trimer preparation is an excellent candidate for structural studies of the class II viral fusion proteins, and we report conditions that generate three-dimensional crystals suitable for analysis by X-ray diffraction. Determination of the structure will provide our first high-resolution views of both the low-pH-induced trimeric conformation and the target membrane-interacting region of the alphavirus fusion protein. PMID:15016874

Development of Stabilimax NZ From Biomechanical Principles.

PubMed

Panjabi, Manohar M; Timm, Jens Peter

2007-01-01

Traditionally, spinal degeneration and injury have been associated with abnormal intervertebral motion; thus, treatment for lowback pain has centered on prevention of motion through spinal fusion. Although the rate of successful spinal fusions is improving, complications such as adjacent-level syndrome emphasize the need to develop alternatives for treating spinal degeneration. In an effort to improve the clinical outcomes associated with such treatment, we hypothesized that spinal stabilization and a consequent reduction in symptoms is achievable without the harsh restrictions to spinal motion imposed by fusion. This idea was based on the principle of the neutral zone and the neutral zone hypothesis of back pain. Performance requirements for a novel device were determined through a series of biomechanical experiments. From these data, the Stabilimax NZ was developed to provide stabilization to a degenerated or surgically destabilized spine while maintaining the maximum possible total range of motion. Applied Spine Technologies Inc has tested 70 bilateral assemblies of the final design of the Stabilimax NZ, and all exceeded the biomechanical, static, fatigue, wear, and histological requirements necessary to initiate clinical investigation. The Stabilimax NZ device has been systematically designed and tested under protocols developed by Applied Spine Technologies in conjunction with Panjabi, Patwardhan, and Goel. The device decreased the neutral zone in destabilized spines while maintaining substantial range of motion. Development testing has been submitted to the US Food and Drug Administration and permission obtained to initiate an investigational device exemption trial to clinically investigate the efficacy of the Stabilimax NZ device.

Laser powder-bed fusion additive manufacturing: Physics of complex melt flow and formation mechanisms of pores, spatter, and denudation zones

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khairallah, Saad A.; Anderson, Andrew T.; Rubenchik, Alexander

Our study demonstrates the significant effect of the recoil pressure and Marangoni convection in laser powder bed fusion (L-PBF) of 316L stainless steel. A three-dimensional high fidelity powder-scale model reveals how the strong dynamical melt flow generates pore defects, material spattering (sparking), and denudation zones. The melt track is divided into three sections: a topological depression, a transition and a tail region, each being the location of specific physical effects. The inclusion of laser ray-tracing energy deposition in the powder-scale model improves over traditional volumetric energy deposition. It enables partial particle melting, which impacts pore defects in the denudation zone.more » Different pore formation mechanisms are observed at the edge of a scan track, at the melt pool bottom (during collapse of the pool depression), and at the end of the melt track (during laser power ramp down). Finally, we discuss remedies to these undesirable pores are discussed. The results are validated against the experiments and the sensitivity to laser absorptivity.« less

Laser powder-bed fusion additive manufacturing: Physics of complex melt flow and formation mechanisms of pores, spatter, and denudation zones

DOE PAGES

Khairallah, Saad A.; Anderson, Andrew T.; Rubenchik, Alexander; ...

2016-02-23

Our study demonstrates the significant effect of the recoil pressure and Marangoni convection in laser powder bed fusion (L-PBF) of 316L stainless steel. A three-dimensional high fidelity powder-scale model reveals how the strong dynamical melt flow generates pore defects, material spattering (sparking), and denudation zones. The melt track is divided into three sections: a topological depression, a transition and a tail region, each being the location of specific physical effects. The inclusion of laser ray-tracing energy deposition in the powder-scale model improves over traditional volumetric energy deposition. It enables partial particle melting, which impacts pore defects in the denudation zone.more » Different pore formation mechanisms are observed at the edge of a scan track, at the melt pool bottom (during collapse of the pool depression), and at the end of the melt track (during laser power ramp down). Finally, we discuss remedies to these undesirable pores are discussed. The results are validated against the experiments and the sensitivity to laser absorptivity.« less

Effect of Heat Input and Post-Weld Heat Treatment on the Mechanical and Metallurgical Characteristics of Laser-Welded Maraging Steel Joints

NASA Astrophysics Data System (ADS)

Karthikeyan, R.; Saravanan, M.; Singaravel, B.; Sathiya, P.

This paper investigates the impact of heat input and post-weld aging behavior at different temperatures on the laser paper welded maraging steel grade 250. Three different levels of heat inputs were chosen and CO2 laser welding was performed. Aging was done at six different temperatures: 360∘C, 400∘C, 440∘C, 480∘C, 520∘C and 560∘C. The macrostructure and microstructure of the fusion zone were obtained using optical microscope. The microhardness test was performed on the weld zone. Tensile tests and impact tests were carried out for the weld samples and different age-treated weld samples. Fracture surfaces were investigated by scanning electron microscopy (SEM). Microhardness values of the fusion zone increased with increasing aging temperature, while the base metal microhardness value decreased. Tensile properties increased with aging temperature up to 480∘C and reduced for 520∘C and 560∘C. This was mainly due to the formation of reverted austenite beyond 500∘C. XRD analysis confirmed the formation of reverted austenite.

A Physical Metallurgical Basis for Heat-Affected Zone and Base-Plate Properties of a Microalloyed HSLA Steel.

DTIC Science & Technology

1986-12-01

system.(a) Schematic diagram.(b) Equipment ...... 64 x * T-3136 FIGURE PAGE 13 Details of subsize charpy specimen and Gleeble HAZ microstructural...simulation specimen ......................................... 71 14 Macrograph profile of subsize charpy specimen illustrating notch location. (a) Specimen...shelf impact energy for subsize charpy specimens as a function of distance from the fusion zone boundary for various nominal heat inputs of both

Effect of Heat Treatment on Microstructure and Hot Impact Toughness of Various Zones of P91 Welded Pipes

NASA Astrophysics Data System (ADS)

Pandey, C.; Mahapatra, M. M.

2016-06-01

The new generation super critical thermal power plants are required to operate at enhanced thermal efficiency of over 50% to reduce the fuel consumption and environmental pollution. Creep strength-enhanced ferritic steels, commonly known as Cr-Mo alloys such as P91 (X10CrMoVNb 9-1) are such material of choice for the next generation power plants. The operating requirement of these next generation power plants is that steam temperature of around 650 °C is maintained. For such high-temperature application, creep strength of material is the primary consideration together with adequate weld heat-affected zone (HAZ) toughness. Present work deals with the effect of high service temperature on impact toughness of P91 (X10CrMoVNb 9-1) base material, weld fusion zone, and HAZ. The impact toughness of HAZ for conventional weld groove design and narrow weld groove design has been evaluated experimentally in as-welded and at different post-weld heat treatment conditions. Fractography of the impact toughness specimens of base metal, weld fusion zone, and HAZ was carried out using scanning electron microscope. The effects of heat treatment schemes on the percentage of element present at the fracture surface were also studied.

Otoferlin acts as a Ca2+ sensor for vesicle fusion and vesicle pool replenishment at auditory hair cell ribbon synapses

PubMed Central

Goutman, Juan D; Auclair, Sarah Marie; Boutet de Monvel, Jacques; Tertrais, Margot; Emptoz, Alice; Parrin, Alexandre; Nouaille, Sylvie; Guillon, Marc; Sachse, Martin; Ciric, Danica; Bahloul, Amel; Hardelin, Jean-Pierre; Sutton, Roger Bryan; Avan, Paul; Krishnakumar, Shyam S; Rothman, James E

2017-01-01

Hearing relies on rapid, temporally precise, and sustained neurotransmitter release at the ribbon synapses of sensory cells, the inner hair cells (IHCs). This process requires otoferlin, a six C2-domain, Ca2+-binding transmembrane protein of synaptic vesicles. To decipher the role of otoferlin in the synaptic vesicle cycle, we produced knock-in mice (Otof Ala515,Ala517/Ala515,Ala517) with lower Ca2+-binding affinity of the C2C domain. The IHC ribbon synapse structure, synaptic Ca2+ currents, and otoferlin distribution were unaffected in these mutant mice, but auditory brainstem response wave-I amplitude was reduced. Lower Ca2+ sensitivity and delay of the fast and sustained components of synaptic exocytosis were revealed by membrane capacitance measurement upon modulations of intracellular Ca2+ concentration, by varying Ca2+ influx through voltage-gated Ca2+-channels or Ca2+ uncaging. Otoferlin thus functions as a Ca2+ sensor, setting the rates of primed vesicle fusion with the presynaptic plasma membrane and synaptic vesicle pool replenishment in the IHC active zone. PMID:29111973

Actin dynamics provides membrane tension to merge fusing vesicles into the plasma membrane

PubMed Central

Wen, Peter J.; Grenklo, Staffan; Arpino, Gianvito; Tan, Xinyu; Liao, Hsien-Shun; Heureaux, Johanna; Peng, Shi-Yong; Chiang, Hsueh-Cheng; Hamid, Edaeni; Zhao, Wei-Dong; Shin, Wonchul; Näreoja, Tuomas; Evergren, Emma; Jin, Yinghui; Karlsson, Roger; Ebert, Steven N.; Jin, Albert; Liu, Allen P.; Shupliakov, Oleg; Wu, Ling-Gang

2016-01-01

Vesicle fusion is executed via formation of an Ω-shaped structure (Ω-profile), followed by closure (kiss-and-run) or merging of the Ω-profile into the plasma membrane (full fusion). Although Ω-profile closure limits release but recycles vesicles economically, Ω-profile merging facilitates release but couples to classical endocytosis for recycling. Despite its crucial role in determining exocytosis/endocytosis modes, how Ω-profile merging is mediated is poorly understood in endocrine cells and neurons containing small ∼30–300 nm vesicles. Here, using confocal and super-resolution STED imaging, force measurements, pharmacology and gene knockout, we show that dynamic assembly of filamentous actin, involving ATP hydrolysis, N-WASP and formin, mediates Ω-profile merging by providing sufficient plasma membrane tension to shrink the Ω-profile in neuroendocrine chromaffin cells containing ∼300 nm vesicles. Actin-directed compounds also induce Ω-profile accumulation at lamprey synaptic active zones, suggesting that actin may mediate Ω-profile merging at synapses. These results uncover molecular and biophysical mechanisms underlying Ω-profile merging. PMID:27576662

Otoferlin acts as a Ca2+ sensor for vesicle fusion and vesicle pool replenishment at auditory hair cell ribbon synapses.

PubMed

Michalski, Nicolas; Goutman, Juan D; Auclair, Sarah Marie; Boutet de Monvel, Jacques; Tertrais, Margot; Emptoz, Alice; Parrin, Alexandre; Nouaille, Sylvie; Guillon, Marc; Sachse, Martin; Ciric, Danica; Bahloul, Amel; Hardelin, Jean-Pierre; Sutton, Roger Bryan; Avan, Paul; Krishnakumar, Shyam S; Rothman, James E; Dulon, Didier; Safieddine, Saaid; Petit, Christine

2017-11-07

Hearing relies on rapid, temporally precise, and sustained neurotransmitter release at the ribbon synapses of sensory cells, the inner hair cells (IHCs). This process requires otoferlin, a six C 2 -domain, Ca 2+ -binding transmembrane protein of synaptic vesicles. To decipher the role of otoferlin in the synaptic vesicle cycle, we produced knock-in mice ( Otof Ala515,Ala517/Ala515,Ala517 ) with lower Ca 2+ -binding affinity of the C 2 C domain. The IHC ribbon synapse structure, synaptic Ca 2+ currents, and otoferlin distribution were unaffected in these mutant mice, but auditory brainstem response wave-I amplitude was reduced. Lower Ca 2+ sensitivity and delay of the fast and sustained components of synaptic exocytosis were revealed by membrane capacitance measurement upon modulations of intracellular Ca 2+ concentration, by varying Ca 2+ influx through voltage-gated Ca 2+ -channels or Ca 2+ uncaging. Otoferlin thus functions as a Ca 2+ sensor, setting the rates of primed vesicle fusion with the presynaptic plasma membrane and synaptic vesicle pool replenishment in the IHC active zone.

Structural basis of viral invasion: lessons from paramyxovirus F

PubMed Central

Lamb, Robert A.; Jardetzky, Theodore S.

2007-01-01

Summary The structures of glycoproteins that mediate enveloped virus entry into cells have revealed dramatic structural changes that accompany membrane fusion and provided mechanistic insights into this process. The group of class I viral fusion proteins includes the influenza hemagglutinin, paramyxovirus F, HIV env and other mechanistically related fusogens, but these proteins are unrelated in sequence and exhibit clearly distinct structural features. Recently determined crystal structures of the paramyxovirus F protein in two conformations, representing prefusion and postfusion states, reveal a novel protein architecture that undergoes large-scale, irreversible refolding during membrane fusion, extending our understanding of this diverse group of membrane fusion machines. PMID:17870467

Ewing's sarcoma precursors are highly enriched in embryonic osteochondrogenic progenitors.

PubMed

Tanaka, Miwa; Yamazaki, Yukari; Kanno, Yohei; Igarashi, Katsuhide; Aisaki, Ken-ichi; Kanno, Jun; Nakamura, Takuro

2014-07-01

Ewing's sarcoma is a highly malignant bone tumor found in children and adolescents, and the origin of this malignancy is not well understood. Here, we introduced a Ewing's sarcoma-associated genetic fusion of the genes encoding the RNA-binding protein EWS and the transcription factor ETS (EWS-ETS) into a fraction of cells enriched for osteochondrogenic progenitors derived from the embryonic superficial zone (eSZ) of long bones collected from late gestational murine embryos. EWS-ETS fusions efficiently induced Ewing's sarcoma-like small round cell sarcoma formation by these cells. Analysis of the eSZ revealed a fraction of a precursor cells that express growth/differentiation factor 5 (Gdf5), the transcription factor Erg, and parathyroid hormone-like hormone (Pthlh), and selection of the Pthlh-positive fraction alone further enhanced EWS-ETS-dependent tumor induction. Genes downstream of the EWS-ETS fusion protein were quite transcriptionally active in eSZ cells, especially in regions in which the chromatin structure of the ETS-responsive locus was open. Inhibition of β-catenin, poly (ADP-ribose) polymerase 1 (PARP1), or enhancer of zeste homolog 2 (EZH2) suppressed cell growth in a murine model of Ewing's sarcoma, suggesting the utility of the current system as a preclinical model. These results indicate that eSZ cells are highly enriched in precursors to Ewing's sarcoma and provide clues to the histogenesis of Ewing's sarcoma in bone.

Hypothesis: spring-loaded boomerang mechanism of influenza hemagglutinin-mediated membrane fusion.

PubMed

Tamm, Lukas K

2003-07-11

Substantial progress has been made in recent years to augment the current understanding of structures and interactions that promote viral membrane fusion. This progress is reviewed with a particular emphasis on recently determined structures of viral fusion domains and their interactions with lipid membranes. The results from the different structural and thermodynamic experimental approaches are synthesized into a new proposed mechanism, termed the "spring-loaded boomerang" mechanism of membrane fusion, which is presented here as a hypothesis.

Electrostatic Architecture of the Infectious Salmon Anemia Virus (ISAV) Core Fusion Protein Illustrates a Carboxyl-Carboxylate pH Sensor.

PubMed

Cook, Jonathan D; Soto-Montoya, Hazel; Korpela, Markus K; Lee, Jeffrey E

2015-07-24

Segment 5, ORF 1 of the infectious salmon anemia virus (ISAV) genome, encodes for the ISAV F protein, which is responsible for viral-host endosomal membrane fusion during a productive ISAV infection. The entry machinery of ISAV is composed of a complex of the ISAV F and ISAV hemagglutinin esterase (HE) proteins in an unknown stoichiometry prior to receptor engagement by ISAV HE. Following binding of the receptor to ISAV HE, dissociation of the ISAV F protein from HE, and subsequent endocytosis, the ISAV F protein resolves into a fusion-competent oligomeric state. Here, we present a 2.1 Å crystal structure of the fusion core of the ISAV F protein determined at low pH. This structure has allowed us to unambiguously demonstrate that the ISAV entry machinery exhibits typical class I viral fusion protein architecture. Furthermore, we have determined stabilizing factors that accommodate the pH-dependent mode of ISAV transmission, and our structure has allowed the identification of a central coil that is conserved across numerous and varied post-fusion viral glycoprotein structures. We then discuss a mechanistic model of ISAV fusion that parallels the paramyxoviral class I fusion strategy wherein attachment and fusion are relegated to separate proteins in a similar fashion to ISAV fusion. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Involvement of vesicle coat material in casein secretion and surface regeneration

PubMed Central

1976-01-01

The ultrastructure of the apical zone of lactating rat mammary epithelial cells was studied with emphasis on vesicle coat structures. Typical 40-60 nm ID "coated vesicles" were abundant, frequently associated with the internal filamentous plasma membrane coat or in direct continuity with secretory vesicles (SV) or plasma membrane proper. Bristle coats partially or totally covered membranes of secretory vesicles identified by their casein micelle content. This coat survived SV isolation. Exocytotic fusion of SV membranes and release of the casein micelles was observed. Frequently, regularly arranged bristle coat structures were identified in those regions of the plasma membrane that were involved in exocytotic processes. Both coated and uncoated surfaces of the casein-containing vesicles, as well as typical "coated vesicles", were frequently associated with microtubules and/or microfilaments. We suggest that coat materials of vesicles are related or identical to components of the internal coat of the surface membrane and that new plasma membrane and associated internal coat is produced concomitantly by fusion and integration of bristle coat moieties. Postexocytotic association of secreted casein micelles with the cell surface, mediated by finely filamentous extensions, provided a marker for the integrated vesicle membrane. An arrangement of SV with the inner surface of the plasma membrane is described which is characterized by regularly spaced, heabily stained membrane to membrane cross-bridges (pre-exocytotic attachment plaques). Such membrane-interconnecting elements may represent a form of coat structure important to recognition and interaction of membrane surfaces. PMID:1254641

Combined NMR and EPR Spectroscopy to Determine Structures of Viral Fusion Domains in Membranes

PubMed Central

Tamm, Lukas K.; Lai, Alex L.; Li, Yinling

2008-01-01

Methods are described to determine the structures of viral membrane fusion domains in detergent micelles by NMR and in lipid bilayers by site-directed spin labeling and EPR spectroscopy. Since in favorable cases, the lower-resolution spin label data obtained in lipid bilayers fully support the higher-resolution structures obtained by solution NMR, it is possible to graft the NMR structural coordinates into membranes using the EPR-derived distance restraints to the lipid bilayer. Electron paramagnetic dynamics and distance measurements in bilayers support conclusions drawn from NMR in detergent micelles. When these methods are applied to a structure determination of the influenza virus fusion domain and four point mutations with different functional phenotypes, it is evident that a fixed-angle boomerang structure with a glycine edge on the outside of the N-terminal arm is both necessary and sufficient to support membrane fusion. The human immunodeficiency virus fusion domain forms a straight helix with a flexible C-terminus. While EPR data for this fusion domain are not yet available, it is tentatively speculated that, because of its higher hydrophobicity, a critically tilted insertion may occur even in the absence of a kinked boomerang structure in this case. PMID:17963720

Adaptive structured dictionary learning for image fusion based on group-sparse-representation

NASA Astrophysics Data System (ADS)

Yang, Jiajie; Sun, Bin; Luo, Chengwei; Wu, Yuzhong; Xu, Limei

2018-04-01

Dictionary learning is the key process of sparse representation which is one of the most widely used image representation theories in image fusion. The existing dictionary learning method does not use the group structure information and the sparse coefficients well. In this paper, we propose a new adaptive structured dictionary learning algorithm and a l1-norm maximum fusion rule that innovatively utilizes grouped sparse coefficients to merge the images. In the dictionary learning algorithm, we do not need prior knowledge about any group structure of the dictionary. By using the characteristics of the dictionary in expressing the signal, our algorithm can automatically find the desired potential structure information that hidden in the dictionary. The fusion rule takes the physical meaning of the group structure dictionary, and makes activity-level judgement on the structure information when the images are being merged. Therefore, the fused image can retain more significant information. Comparisons have been made with several state-of-the-art dictionary learning methods and fusion rules. The experimental results demonstrate that, the dictionary learning algorithm and the fusion rule both outperform others in terms of several objective evaluation metrics.

Creep behavior and in-depth microstructural characterization of dissimilar joints

PubMed Central

Kauffmann, F; Klein, T; Klenk, A; Maile, K

2013-01-01

The 700 °C power plants currently under development will utilize Ni-base alloys such as alloy 617 for components to be operated at temperatures >650 °C. Due to economic reasons for components or parts of components which are subjected to temperatures <650 °C, 2% Cr or 9–12% Cr steels is used, depending on the required mechanical properties. This makes the dissimilar joining of Ni-base alloys and Cr steels a necessity in these plants. Experimental investigations show that these joints have to be identified as weak points with regard to damage development under creep and creep-fatigue loading. The present investigation focuses on welds between the alloy 617 and 2% Cr steel. Under creep load the fracture occurs near the fusion line between the 2% Cr steel base metal and alloy 617 weld metal. To explain the reasons for this fracture location, the microstructure of this fusion line was investigated using TEM and FIB techniques after welding and after creep loading. The TEM investigations have shown a small zone in the weld metal near the fusion line exhibiting chromium depletion and clearly reduced amounts of chromium carbides, leading to a weakening of this zone. PMID:27877551

Flexible Fusion Structure-Based Performance Optimization Learning for Multisensor Target Tracking

PubMed Central

Ge, Quanbo; Wei, Zhongliang; Cheng, Tianfa; Chen, Shaodong; Wang, Xiangfeng

2017-01-01

Compared with the fixed fusion structure, the flexible fusion structure with mixed fusion methods has better adjustment performance for the complex air task network systems, and it can effectively help the system to achieve the goal under the given constraints. Because of the time-varying situation of the task network system induced by moving nodes and non-cooperative target, and limitations such as communication bandwidth and measurement distance, it is necessary to dynamically adjust the system fusion structure including sensors and fusion methods in a given adjustment period. Aiming at this, this paper studies the design of a flexible fusion algorithm by using an optimization learning technology. The purpose is to dynamically determine the sensors’ numbers and the associated sensors to take part in the centralized and distributed fusion processes, respectively, herein termed sensor subsets selection. Firstly, two system performance indexes are introduced. Especially, the survivability index is presented and defined. Secondly, based on the two indexes and considering other conditions such as communication bandwidth and measurement distance, optimization models for both single target tracking and multi-target tracking are established. Correspondingly, solution steps are given for the two optimization models in detail. Simulation examples are demonstrated to validate the proposed algorithms. PMID:28481243

Mechanistic Insight into Bunyavirus-Induced Membrane Fusion from Structure-Function Analyses of the Hantavirus Envelope Glycoprotein Gc

PubMed Central

Stettner, Eva; Jeffers, Scott Allen; Pérez-Vargas, Jimena; Pehau-Arnaudet, Gerard; Tortorici, M. Alejandra; Jestin, Jean-Luc; England, Patrick; Tischler, Nicole D.; Rey, Félix A.

2016-01-01

Hantaviruses are zoonotic viruses transmitted to humans by persistently infected rodents, giving rise to serious outbreaks of hemorrhagic fever with renal syndrome (HFRS) or of hantavirus pulmonary syndrome (HPS), depending on the virus, which are associated with high case fatality rates. There is only limited knowledge about the organization of the viral particles and in particular, about the hantavirus membrane fusion glycoprotein Gc, the function of which is essential for virus entry. We describe here the X-ray structures of Gc from Hantaan virus, the type species hantavirus and responsible for HFRS, both in its neutral pH, monomeric pre-fusion conformation, and in its acidic pH, trimeric post-fusion form. The structures confirm the prediction that Gc is a class II fusion protein, containing the characteristic β-sheet rich domains termed I, II and III as initially identified in the fusion proteins of arboviruses such as alpha- and flaviviruses. The structures also show a number of features of Gc that are distinct from arbovirus class II proteins. In particular, hantavirus Gc inserts residues from three different loops into the target membrane to drive fusion, as confirmed functionally by structure-guided mutagenesis on the HPS-inducing Andes virus, instead of having a single “fusion loop”. We further show that the membrane interacting region of Gc becomes structured only at acidic pH via a set of polar and electrostatic interactions. Furthermore, the structure reveals that hantavirus Gc has an additional N-terminal “tail” that is crucial in stabilizing the post-fusion trimer, accompanying the swapping of domain III in the quaternary arrangement of the trimer as compared to the standard class II fusion proteins. The mechanistic understandings derived from these data are likely to provide a unique handle for devising treatments against these human pathogens. PMID:27783711

Mechanistic Insight into Bunyavirus-Induced Membrane Fusion from Structure-Function Analyses of the Hantavirus Envelope Glycoprotein Gc.

PubMed

Guardado-Calvo, Pablo; Bignon, Eduardo A; Stettner, Eva; Jeffers, Scott Allen; Pérez-Vargas, Jimena; Pehau-Arnaudet, Gerard; Tortorici, M Alejandra; Jestin, Jean-Luc; England, Patrick; Tischler, Nicole D; Rey, Félix A

2016-10-01

Hantaviruses are zoonotic viruses transmitted to humans by persistently infected rodents, giving rise to serious outbreaks of hemorrhagic fever with renal syndrome (HFRS) or of hantavirus pulmonary syndrome (HPS), depending on the virus, which are associated with high case fatality rates. There is only limited knowledge about the organization of the viral particles and in particular, about the hantavirus membrane fusion glycoprotein Gc, the function of which is essential for virus entry. We describe here the X-ray structures of Gc from Hantaan virus, the type species hantavirus and responsible for HFRS, both in its neutral pH, monomeric pre-fusion conformation, and in its acidic pH, trimeric post-fusion form. The structures confirm the prediction that Gc is a class II fusion protein, containing the characteristic β-sheet rich domains termed I, II and III as initially identified in the fusion proteins of arboviruses such as alpha- and flaviviruses. The structures also show a number of features of Gc that are distinct from arbovirus class II proteins. In particular, hantavirus Gc inserts residues from three different loops into the target membrane to drive fusion, as confirmed functionally by structure-guided mutagenesis on the HPS-inducing Andes virus, instead of having a single "fusion loop". We further show that the membrane interacting region of Gc becomes structured only at acidic pH via a set of polar and electrostatic interactions. Furthermore, the structure reveals that hantavirus Gc has an additional N-terminal "tail" that is crucial in stabilizing the post-fusion trimer, accompanying the swapping of domain III in the quaternary arrangement of the trimer as compared to the standard class II fusion proteins. The mechanistic understandings derived from these data are likely to provide a unique handle for devising treatments against these human pathogens.

An Investigation for Ground State Features of Some Structural Fusion Materials

NASA Astrophysics Data System (ADS)

Aytekin, H.; Tel, E.; Baldik, R.; Aydin, A.

2011-02-01

Environmental concerns associated with fossil fuels are creating increased interest in alternative non-fossil energy sources. Nuclear fusion can be one of the most attractive sources of energy from the viewpoint of safety and minimal environmental impact. When considered in all energy systems, the requirements for performance of structural materials in a fusion reactor first wall, blanket or diverter, are arguably more demanding or difficult than for other energy system. The development of fusion materials for the safety of fusion power systems and understanding nuclear properties is important. In this paper, ground state properties for some structural fusion materials as 27Al, 51V, 52Cr, 55Mn, and 56Fe are investigated using Skyrme-Hartree-Fock method. The obtained results have been discussed and compared with the available experimental data.

Membrane events in the acrosomal reaction of Limulus sperm. Membrane fusion, filament-membrane particle attachment, and the source and formation of new membrane surface

PubMed Central

1979-01-01

The membranes of Limulus (horseshoe crab) sperm were examined before and during the acrosomal reaction by using the technique of freeze- fracturing and thin sectioning. We focused on three areas. First, we examined stages in the fusion of the acrosomal vacuole with the cell surface. Fusion takes place in a particle-free zone which is surrounded by a circlet of particles on the P face of the plasma membrane and an underlying circlet of particles on the P face of the acrosomal vauole membrane. These circlets of particles are present before induction. Up to nine focal points of fusion occur within the particle-free zone. Second, we describe a system of fine filaments, each 30 A in diameter, which lies between the acrosomal vacuole and the plasma membrane. These filaments change their orientation as the vacuole opens, a process that takes place in less than 50 ms. Membrane particles seen on the P face of the acrosomal vacuole membrane change their orientation at the same time and in the same way as do the filaments, thus indicating that the membrane particles and filaments are probably connected. Third, we examined the source and the point of fusion of new membrane needed to cover the acrosomal process. This new membrane is almost certainly derived from the outer nuclear envelope and appears to insert into the plasma membrane in a particle-free area adjacent to an area rich in particles. The latter is the region where the particles are probably connected to the cytoplasmic filaments. The relevance of these observations in relation to the process of fertilization of this fantastic sperm is discussed. PMID:582596

Structure of the uncleaved ectodomain of the paramyxovirus (hPIV3) fusion protein

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yin, Hsien-Sheng; Paterson, Reay G.; Wen, Xiaolin

2010-03-08

Class I viral fusion proteins share common mechanistic and structural features but little sequence similarity. Structural insights into the protein conformational changes associated with membrane fusion are based largely on studies of the influenza virus hemagglutinin in pre- and postfusion conformations. Here, we present the crystal structure of the secreted, uncleaved ectodomain of the paramyxovirus, human parainfluenza virus 3 fusion (F) protein, a member of the class I viral fusion protein group. The secreted human parainfluenza virus 3 F forms a trimer with distinct head, neck, and stalk regions. Unexpectedly, the structure reveals a six-helix bundle associated with the postfusionmore » form of F, suggesting that the anchor-minus ectodomain adopts a conformation largely similar to the postfusion state. The transmembrane anchor domains of F may therefore profoundly influence the folding energetics that establish and maintain a metastable, prefusion state.« less

Structure of the parainfluenza virus 5 F protein in its metastable, prefusion conformation.

PubMed

Yin, Hsien-Sheng; Wen, Xiaolin; Paterson, Reay G; Lamb, Robert A; Jardetzky, Theodore S

2006-01-05

Enveloped viruses have evolved complex glycoprotein machinery that drives the fusion of viral and cellular membranes, permitting entry of the viral genome into the cell. For the paramyxoviruses, the fusion (F) protein catalyses this membrane merger and entry step, and it has been postulated that the F protein undergoes complex refolding during this process. Here we report the crystal structure of the parainfluenza virus 5 F protein in its prefusion conformation, stabilized by the addition of a carboxy-terminal trimerization domain. The structure of the F protein shows that there are profound conformational differences between the pre- and postfusion states, involving transformations in secondary and tertiary structure. The positions and structural transitions of key parts of the fusion machinery, including the hydrophobic fusion peptide and two helical heptad repeat regions, clarify the mechanism of membrane fusion mediated by the F protein.

Focal Laser Ablation of Prostate Cancer: Feasibility of Magnetic Resonance Imaging-Ultrasound Fusion for Guidance.

PubMed

Natarajan, Shyam; Jones, Tonye A; Priester, Alan M; Geoghegan, Rory; Lieu, Patricia; Delfin, Merdie; Felker, Ely; Margolis, Daniel J A; Sisk, Anthony; Pantuck, Allan; Grundfest, Warren; Marks, Leonard S

2017-10-01

Focal laser ablation is a potential treatment in some men with prostate cancer. Currently focal laser ablation is performed by radiologists in a magnetic resonance imaging unit (in bore). We evaluated the safety and feasibility of performing focal laser ablation in a urology clinic (out of bore) using magnetic resonance imaging-ultrasound fusion for guidance. A total of 11 men with intermediate risk prostate cancer were enrolled in this prospective, institutional review board approved pilot study. Magnetic resonance imaging-ultrasound fusion was used to guide laser fibers transrectally into regions of interest harboring intermediate risk prostate cancer. Thermal probes were inserted for real-time monitoring of intraprostatic temperatures during laser activation. Multiparametric magnetic resonance imaging (3 Tesla) was done immediately after treatment and at 6 months along with comprehensive fusion biopsy. Ten of 11 patients were successfully treated while under local anesthesia. Mean procedure time was 95 minutes (range 71 to 105). Posttreatment magnetic resonance imaging revealed a confined zone of nonperfusion in all 10 men. Mean zone volume was 4.3 cc (range 2.1 to 6.0). No CTCAE grade 3 or greater adverse events developed and no changes were observed in urinary or sexual function. At 6 months magnetic resonance imaging-ultrasound fusion biopsy of the treatment site showed no cancer in 3 patients, microfocal Gleason 3 + 3 in another 3 and persistent intermediate risk prostate cancer in 4. Focal laser ablation of prostate cancer appears safe and feasible with the patient under local anesthesia in a urology clinic using magnetic resonance imaging-ultrasound fusion for guidance and thermal probes for monitoring. Further development is necessary to refine out of bore focal laser ablation and additional studies are needed to determine appropriate treatment margins and oncologic efficacy. Copyright © 2017 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Diffusional spread and confinement of newly exocytosed synaptic vesicle proteins

PubMed Central

Gimber, Niclas; Tadeus, Georgi; Maritzen, Tanja; Schmoranzer, Jan; Haucke, Volker

2015-01-01

Neurotransmission relies on the calcium-triggered exocytic fusion of non-peptide neurotransmitter-containing small synaptic vesicles (SVs) with the presynaptic membrane at active zones (AZs) followed by compensatory endocytic retrieval of SV membranes. Here, we study the diffusional fate of newly exocytosed SV proteins in hippocampal neurons by high-resolution time-lapse imaging. Newly exocytosed SV proteins rapidly disperse within the first seconds post fusion until confined within the presynaptic bouton. Rapid diffusional spread and confinement is followed by slow reclustering of SV proteins at the periactive endocytic zone. Confinement within the presynaptic bouton is mediated in part by SV protein association with the clathrin-based endocytic machinery to limit diffusional spread of newly exocytosed SV proteins. These data suggest that diffusion, and axonal escape of newly exocytosed vesicle proteins, are counteracted by the clathrin-based endocytic machinery together with a presynaptic diffusion barrier. PMID:26399746

Diffusional spread and confinement of newly exocytosed synaptic vesicle proteins

NASA Astrophysics Data System (ADS)

Gimber, Niclas; Tadeus, Georgi; Maritzen, Tanja; Schmoranzer, Jan; Haucke, Volker

2015-09-01

Neurotransmission relies on the calcium-triggered exocytic fusion of non-peptide neurotransmitter-containing small synaptic vesicles (SVs) with the presynaptic membrane at active zones (AZs) followed by compensatory endocytic retrieval of SV membranes. Here, we study the diffusional fate of newly exocytosed SV proteins in hippocampal neurons by high-resolution time-lapse imaging. Newly exocytosed SV proteins rapidly disperse within the first seconds post fusion until confined within the presynaptic bouton. Rapid diffusional spread and confinement is followed by slow reclustering of SV proteins at the periactive endocytic zone. Confinement within the presynaptic bouton is mediated in part by SV protein association with the clathrin-based endocytic machinery to limit diffusional spread of newly exocytosed SV proteins. These data suggest that diffusion, and axonal escape of newly exocytosed vesicle proteins, are counteracted by the clathrin-based endocytic machinery together with a presynaptic diffusion barrier.

The Effect of Dilution on Microsegregation in AWS ER NiCrMo-14 Alloy Welding Claddings

NASA Astrophysics Data System (ADS)

Miná, Émerson Mendonça; da Silva, Yuri Cruz; Dille, Jean; Silva, Cleiton Carvalho

2016-12-01

Dilution and microsegregation are phenomena inherent to claddings, which, in turn, directly affect their main properties. This study evaluated microsegregation in the fusion zone with different dilution levels. The overlays were welded by the TIG cold wire feed process. Dilution was calculated from the geometric characteristics of the claddings and from the conservation of mass equation using chemical composition measurements. Microsegregation was calculated using energy dispersive X-ray spectroscopy measurements of the dendrites and the chemical composition of the fusion zone. The dilution of the claddings was increased by reducing the wire feed rate. Fe showed potential to be incorporated into the solid phase ( k > 1), and this increased with the increase of dilution. Mo, in turn, was segregated into the liquid phase ( k < 1) and also increased with the increase of dilution. However, Cr and W showed a slight decrease in their partition coefficients ( k) with the increase of dilution.

Effect of Al-Si Coating on Weld Microstructure and Properties of 22MnB5 Steel Joints for Hot Stamping

NASA Astrophysics Data System (ADS)

Lin, Wenhu; Li, Fang; Wu, Dongsheng; Chen, Xiaoguan; Hua, Xueming; Pan, Hua

2018-03-01

22MnB5 hot stamping steels are gradually being used in tailor-welded blank applications. In this experiment, 1-mm-thick Al-Si coated and de-coated 22MnB5 steels were laser-welded and then hot-stamped. The chemical compositions, solidification process, microstructure and mechanical properties were investigated to reveal the effect of Al-Si coating and heat treatment. In the welded condition, the coated joints had an Al content of approximately 2.5 wt.% in the fusion zone and the de-coated joints had 0.5 wt.% Al. The aluminum promoted the δ-ferrite formation as the skeletal structure during solidification. In the high-aluminum weld, the microstructure consisted of martensite and long and band-like δ-ferrite. Meanwhile, the low-aluminum weld was full of lath martensite. After the hot stamping process, the δ-ferrite fraction increased from 10 to 24% in the coated joints and the lath martensite became finer in the de-coated joints. The tensile strengths of the coated joints or de-coated joints were similar to that before hot stamping, but the strength of the coated joints was reduced heavily after hot stamping compared to the de-coated joints and base material. The effect of δ-ferrite on the tensile properties became stronger when the fusion zone was soft and deformed first in the hot-stamped specimens. The coated weld showed a brittle fracture surface with many cleavage planes, and the de-coated weld showed a ductile fracture surface with many dimples in hot-stamped conditions.

Fusion proteins as alternate crystallization paths to difficult structure problems

NASA Technical Reports Server (NTRS)

Carter, Daniel C.; Rueker, Florian; Ho, Joseph X.; Lim, Kap; Keeling, Kim; Gilliland, Gary; Ji, Xinhua

1994-01-01

The three-dimensional structure of a peptide fusion product with glutathione transferase from Schistosoma japonicum (SjGST) has been solved by crystallographic methods to 2.5 A resolution. Peptides or proteins can be fused to SjGST and expressed in a plasmid for rapid synthesis in Escherichia coli. Fusion proteins created by this commercial method can be purified rapidly by chromatography on immobilized glutathione. The potential utility of using SjGST fusion proteins as alternate paths to the crystallization and structure determination of proteins is demonstrated.

Self assembling proteins

DOEpatents

Yeates, Todd O.; Padilla, Jennifer; Colovos, Chris

2004-06-29

Novel fusion proteins capable of self-assembling into regular structures, as well as nucleic acids encoding the same, are provided. The subject fusion proteins comprise at least two oligomerization domains rigidly linked together, e.g. through an alpha helical linking group. Also provided are regular structures comprising a plurality of self-assembled fusion proteins of the subject invention, and methods for producing the same. The subject fusion proteins find use in the preparation of a variety of nanostructures, where such structures include: cages, shells, double-layer rings, two-dimensional layers, three-dimensional crystals, filaments, and tubes.

Influence of laser cladding regimes on structural features and mechanical properties of coatings on titanium substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malyutina, Yulia N., E-mail: iuliiamaliutina@gmail.ru; Lazurenko, Daria V., E-mail: pavlyukova-87@mail.ru; Bataev, Ivan A., E-mail: ivanbataev@ngs.ru

2015-10-27

In this paper an influence of the tantalum content on the structure and properties of surface layers of the titanium alloy doped using a laser treatment technology was investigated. It was found that an increase of a quantity of filler powder per one millimeter of a track length contributed to a rise of the content of undissolved particles in coatings. The maximum thickness of a cladded layer was reached at the mass of powder per the length unit equaled to 5.5 g/cm. Coatings were characterized by the formation of a dendrite structure with attributes of segregation. The width of a quenchedmore » fusion zone grew with an increase in the rate of powder feed to the treated area. Significant strengthening of the titanium surface layer alloyed with tantalum was not observed; however, the presence of undissolved tantalum particles can decrease the hardness of titanium surface layers.« less

Effect of Heat Input on the Tensile Damage Evolution in Pulsed Laser Welded Ti6Al4V Titanium Sheets

NASA Astrophysics Data System (ADS)

Liu, Jing; Gao, Xiaolong; Zhang, Jianxun

2016-11-01

The present paper is focused on studying the effect of heat input on the tensile damage evolution of pulsed Nd:YAG laser welding of Ti6Al4V alloy under monotonic loading. To analyze the reasons that the tensile fracture site of the pulsed-laser-welded Ti6Al4V sheet joints changes with the heat input under monotonic loading, the microstructure of the sample with different nominal strain values was investigated by in situ observation. Experiment results show that the tensile ductility and fatigue life of welded joints with low heat input are higher than that of welded joints with high heat input. Under tensile loads, the critical engineering strain for crack initiation is much lower in the welded joint with high heat input than in the welded joints with low and medium heat input. And the microstructural damage accumulation is much faster in the fusion zone than in the base metal for the welded joints with high input, whereas the microstructural damage accumulation is much faster in the base metal than in the fusion zone for the welded joints with low input. Consequently, the welded joints fractured in the fusion zone for the welds with high heat input, whereas the welded joints ruptured in the base metal for the welds with low heat input. It is proved that the fine grain microstructure produced by low heat input can improve the critical nominal strain for crack initiation and the resistance ability of microstructural damage.

Comparative evaluation of three-dimensional Gd-EOB-DTPA-enhanced MR fusion imaging with CT fusion imaging in the assessment of treatment effect of radiofrequency ablation of hepatocellular carcinoma.

PubMed

Makino, Yuki; Imai, Yasuharu; Igura, Takumi; Hori, Masatoshi; Fukuda, Kazuto; Sawai, Yoshiyuki; Kogita, Sachiyo; Fujita, Norihiko; Takehara, Tetsuo; Murakami, Takamichi

2015-01-01

To assess the feasibility of fusion of pre- and post-ablation gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging (Gd-EOB-DTPA-MRI) to evaluate the effects of radiofrequency ablation (RFA) of hepatocellular carcinoma (HCC), compared with similarly fused CT images This retrospective study included 67 patients with 92 HCCs treated with RFA. Fusion images of pre- and post-RFA dynamic CT, and pre- and post-RFA Gd-EOB-DTPA-MRI were created, using a rigid registration method. The minimal ablative margin measured on fusion imaging was categorized into three groups: (1) tumor protruding outside the ablation zone boundary, (2) ablative margin 0-<5.0 mm beyond the tumor boundary, and (3) ablative margin ≥5.0 mm beyond the tumor boundary. The categorization of minimal ablative margins was compared between CT and MR fusion images. In 57 (62.0%) HCCs, treatment evaluation was possible both on CT and MR fusion images, and the overall agreement between them for the categorization of minimal ablative margin was good (κ coefficient = 0.676, P < 0.01). MR fusion imaging enabled treatment evaluation in a significantly larger number of HCCs than CT fusion imaging (86/92 [93.5%] vs. 62/92 [67.4%], P < 0.05). Fusion of pre- and post-ablation Gd-EOB-DTPA-MRI is feasible for treatment evaluation after RFA. It may enable accurate treatment evaluation in cases where CT fusion imaging is not helpful.

Finite element modeling of residual stresses in electroslag butt welds

DOT National Transportation Integrated Search

2000-03-01

Shop fabricated electroslag (ES) welds used in bridge construction have had a history of low toughness in the fusion and heat affected zones. In addition, conventional inspection of ES weldments under shop fabrication conditions fail to consistently ...

Membrane Assembly during the Infection Cycle of the Giant Mimivirus

PubMed Central

Mutsafi, Yael; Shimoni, Eyal; Shimon, Amir; Minsky, Abraham

2013-01-01

Although extensively studied, the structure, cellular origin and assembly mechanism of internal membranes during viral infection remain unclear. By combining diverse imaging techniques, including the novel Scanning-Transmission Electron Microscopy tomography, we elucidate the structural stages of membrane biogenesis during the assembly of the giant DNA virus Mimivirus. We show that this elaborate multistage process occurs at a well-defined zone localized at the periphery of large viral factories that are generated in the host cytoplasm. Membrane biogenesis is initiated by fusion of multiple vesicles, ∼70 nm in diameter, that apparently derive from the host ER network and enable continuous supply of lipid components to the membrane-assembly zone. The resulting multivesicular bodies subsequently rupture to form large open single-layered membrane sheets from which viral membranes are generated. Membrane generation is accompanied by the assembly of icosahedral viral capsids in a process involving the hypothetical major capsid protein L425 that acts as a scaffolding protein. The assembly model proposed here reveals how multiple Mimivirus progeny can be continuously and efficiently generated and underscores the similarity between the infection cycles of Mimivirus and Vaccinia virus. Moreover, the membrane biogenesis process indicated by our findings provides new insights into the pathways that might mediate assembly of internal viral membranes in general. PMID:23737745

Fusion of Tomography Tests for DNAPL Source Zone Characterization: Technology Development and Validation

DTIC Science & Technology

2011-07-01

alternative to the REV and fracture network concepts, pp. 533-561, Rock Mechanics : Proceedings of the 28th U.S. Symposium, Tucson, Arizona, edited by I.W...spatially integrated measure of residual DNAPL volume in the flow without causing disturbances to the source zone domain [ Jin et al., 1995; Nelson and...step. 6 Hydrological inversion has been a major focus of groundwater hydrology during the last three decades [see Yeh, 1986; Sun , 1994 and

Characterization of microstructure of A508III/309L/308L weld and oxide films formed in deaerated high-temperature water

NASA Astrophysics Data System (ADS)

Xiong, Qi; Li, Hongjuan; Lu, Zhanpeng; Chen, Junjie; Xiao, Qian; Ma, Jiarong; Ru, Xiangkun

2018-01-01

The microstructure of A508III/309L/308L weld clad and the properties of the oxide films formed in simulated pressurized water reactor primary water at 290 °C were characterized. The A508III heat-affected zone (HAZ) consisted primarily of a decarburization zone with ferrite near the fusion line and a following pearlite structure with fine grains. A high hardness region in the HAZ could be the result of C-enrichment. M23C6 and M7C3 precipitates were observed in element transition zone. 308L stainless steel (SS) containing ∼ 12% ferrites exhibited both ferritic-austenitic solidification mode (FA mode, δ→γ) and austenitic-ferritic solidification mode (AF mode, γ→δ), whereas 309L SS containing ∼ 9% ferrites exhibited only FA mode. The A508III surface oxide film was mainly Fe3O4 in deaerated high-temperature water. The coarse grain zone covered with few oxide particles was different from other types of film on the other region of HAZ and the bulk zone. More pitting appears on 309L SS after immersion in deaerated high-temperature water due to the dissolution of inclusions. SS surface oxide films consisted primarily of spinels. The oxide film on SS was divided into two layers. Ni was concentrated mainly at the oxide/substrate interface. The oxide film formed on 309L was thicker than that on the 308L. The ferrite in the stainless steel could improve the oxidation resistance.

Metallurgical and mechanical properties of laser welded high strength low alloy steel

PubMed Central

Oyyaravelu, Ramachandran; Kuppan, Palaniyandi; Arivazhagan, Natarajan

2016-01-01

The study aimed at investigating the microstructure and mechanical properties of Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) laser welded high strength low alloy (HSLA) SA516 grade 70 boiler steel. The weld joint for a 4 mm thick plate was successfully produced using minimum laser power of 2 kW by employing a single pass without any weld preheat treatment. The micrographs revealed the presence of martensite phase in the weld fusion zone which could be due to faster cooling rate of the laser weldment. A good correlation was found between the microstructural features of the weld joints and their mechanical properties. The highest hardness was found to be in the fusion zone of cap region due to formation of martensite and also enrichment of carbon. The hardness results also showed a narrow soft zone at the heat affected zone (HAZ) adjacent to the weld interface, which has no effect on the weld tensile strength. The yield strength and ultimate tensile strength of the welded joints were 338 MPa and 549 MPa, respectively, which were higher than the candidate metal. These tensile results suggested that the laser welding process had improved the weld strength even without any weld preheat treatment and also the fractography of the tensile fractured samples showed the ductile mode of failure. PMID:27222751

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Qianlong; Blissard, Gary W.; Liu, Tong-Xian

The Autographa californica multiple nucleopolyhedrovirus GP64 is a class III viral fusion protein. Although the post-fusion structure of GP64 has been solved, its pre-fusion structure and the detailed mechanism of conformational change are unknown. In GP64, domain V is predicted to interact with two domain I segments that flank fusion loop 2. To evaluate the significance of the amino acids involved in these interactions, we examined 24 amino acid positions that represent interacting and conserved residues within domains I and V. In several cases, substitution of a single amino acid involved in a predicted interaction disrupted membrane fusion activity, butmore » no single amino acid pair appears to be absolutely required. We identified 4 critical residues in domain V (G438, W439, T452, and T456) that are important for membrane fusion, and two residues (G438 and W439) that appear to be important for formation or stability of the pre-fusion conformation of GP64. - Highlights: • The baculovirus envelope glycoprotein GP64 is a class III viral fusion protein. • The detailed mechanism of conformational change of GP64 is unknown. • We analyzed 24 positions that might stabilize the post-fusion structure of GP64. • We identified 4 residues in domain V that were critical for membrane fusion. • Two residues are critical for formation of the pre-fusion conformation of GP64.« less

Fusion competent synaptic vesicles persist upon active zone disruption and loss of vesicle docking

PubMed Central

Wang, Shan Shan H.; Held, Richard G.; Wong, Man Yan; Liu, Changliang; Karakhanyan, Aziz; Kaeser, Pascal S.

2016-01-01

In a nerve terminal, synaptic vesicle docking and release are restricted to an active zone. The active zone is a protein scaffold that is attached to the presynaptic plasma membrane and opposed to postsynaptic receptors. Here, we generated conditional knockout mice removing the active zone proteins RIM and ELKS, which additionally led to loss of Munc13, Bassoon, Piccolo, and RIM-BP, indicating disassembly of the active zone. We observed a near complete lack of synaptic vesicle docking and a strong reduction in vesicular release probability and the speed of exocytosis, but total vesicle numbers, SNARE protein levels, and postsynaptic densities remained unaffected. Despite loss of the priming proteins Munc13 and RIM and of docked vesicles, a pool of releasable vesicles remained. Thus, the active zone is necessary for synaptic vesicle docking and to enhance release probability, but releasable vesicles can be localized distant from the presynaptic plasma membrane. PMID:27537483

The biomechanics of a multilevel lumbar spine hybrid using nucleus replacement in conjunction with fusion.

PubMed

Dahl, Michael C; Ellingson, Arin M; Mehta, Hitesh P; Huelman, Justin H; Nuckley, David J

2013-02-01

Degenerative disc disease is commonly a multilevel pathology with varying deterioration severity. The use of fusion on multiple levels can significantly affect functionality and has been linked to persistent adjacent disc degeneration. A hybrid approach of fusion and nucleus replacement (NR) has been suggested as a solution for mildly degenerated yet painful levels adjacent to fusion. To compare the biomechanical metrics of different hybrid implant constructs, hypothesizing that an NR+fusion hybrid would be similar to a single-level fusion and perform more naturally compared with a two-level fusion. A cadaveric in vitro repeated-measures study was performed to evaluate a multilevel lumbar NR+fusion hybrid. Eight cadaveric spines (L3-S1) were tested in a Spine Kinetic Simulator (Instron, Norwood, MA, USA). Pure moments of 8 Nm were applied in flexion/extension, lateral bending, and axial rotation as well as compression loading. Specimens were tested intact; fused (using transforaminal lumbar interbody fusion instrumentation with posterior rods) at L5-S1; with a nuclectomy at L4-L5 including fusion at L5-S1; with NR at L4-L5 including fusion at L5-S1; and finally with a two-level fusion spanning L4-S1. Repeated-measures analysis of variance and corrected t tests were used to statistically compare outcomes. The NR+fusion hybrid and single-level fusion exhibited no statistical differences for range of motion (ROM), stiffness, neutral zone, and intradiscal pressure in all loading directions. Compared with two-level fusion, the hybrid affords the construct 41.9% more ROM on average. Two-level fusion stiffness was statistically higher than all other constructs and resulted in significantly lower ROM in flexion, extension, and lateral bending. The hybrid construct produced approximately half of the L3-L4 adjacent-level pressures as the two-level fusion case while generating similar pressures to the single-level fusion case. These data portend more natural functional outcomes and fewer adjacent disc complications for a multilevel NR+fusion hybrid compared with the classical two-level fusion. Copyright © 2013 Elsevier Inc. All rights reserved.

Double differential light charged particle emission cross sections for some structural fusion materials

NASA Astrophysics Data System (ADS)

Sarpün, Ismail Hakki; n, Abdullah Aydı; Tel, Eyyup

2017-09-01

In fusion reactors, neutron induced radioactivity strongly depends on the irradiated material. So, a proper selection of structural materials will have been limited the radioactive inventory in a fusion reactor. First-wall and blanket components have high radioactivity concentration due to being the most flux-exposed structures. The main objective of fusion structural material research is the development and selection of materials for reactor components with good thermo-mechanical and physical properties, coupled with low-activation characteristics. Double differential light charged particle emission cross section, which is a fundamental data to determine nuclear heating and material damages in structural fusion material research, for some elements target nuclei have been calculated by the TALYS 1.8 nuclear reaction code at 14-15 MeV neutron incident energy and compared with available experimental data in EXFOR library. Direct, compound and pre-equilibrium reaction contribution have been theoretically calculated and dominant contribution have been determined for each emission of proton, deuteron and alpha particle.

Optimal Sensor Fusion for Structural Health Monitoring of Aircraft Composite Components

DTIC Science & Technology

2011-09-01

sensor networks combine or fuse different types of sensors. Fiber Bragg Grating ( FBG ) sensors can be inserted in layers of composite structures to...consideration. This paper describes an example of optimal sensor fusion, which combines FBG sensors and PZT sensors. Optimal sensor fusion tries to find...Fiber Bragg Grating ( FBG ) sensors can be inserted in layers of composite structures to provide local damage detection, while surface mounted

The exploration and prevention of mine water invasion in Feicheng area based on RS

NASA Astrophysics Data System (ADS)

Zheng, Yong-Guo; Wang, Ping; Ting, He

2004-10-01

Recently, when the ninth and tenth were mined in Feiching city mining area, several mine wells occurred on water invasion. Based on systematic interpretation of TMimages in Fei Cheng mining area, authors find that there are five zones of NS trending lineaments, which nearly distribute in radial in TM images. Image processing can be divided into three types, they are spectrum enhancement, spatial filtering and data fusion, the useful methods in this area are auto-adaptive enhancement, density slicing and K-L transform. With ninth and tenth seam coals mined, three mines of east area have broken out serious accidents of water. Statistical materials and the test of water quality drawing off five limestone indicates water-yielding zone near NS, NNE, and NW trending faults, or near intersection point of its and others. In order to solve the problem, using remote sensing and other techniques, we try to find some influential factors on mine flow. Further analyses, such as, the exploration of geology on earth, and microcosmic from rock slice, the authors find that there are some reasons which lead to water invasion such as geological structure, karsts, index and so on, in which the main reason might be north-south deep fracture which is the pathway of well water's distribution, migration and recharge of mine water. There being more complicate geologic structure in the west of mine area, at last, with RS authors point out important zone of mine water invasion which the prevention-control of hazards from mine water and some measures to avoid water blast in future.

Use of Friction Stir Processing for Improving Heat-Affected Zone Liquation Cracking Resistance of a Cast Magnesium Alloy AZ91D

NASA Astrophysics Data System (ADS)

Karthik, G. M.; Janaki Ram, G. D.; Kottada, Ravi Sankar

2017-12-01

In this work, a cast magnesium alloy AZ91D was friction stir processed. Detailed microstructural studies and Gleeble hot ductility tests were conducted on the as-cast and the FSPed samples to comparatively assess their heat-affected zone liquation cracking behavior. The results show that the use of FSP as a pretreatment to fusion welding can strikingly improve the heat-affected zone liquation cracking resistance of alloy AZ91D by reducing the amount and size of the low-melting eutectic β (Mg17Al12) as well as by refining the matrix grain size.

Modes of Paramyxovirus Fusion: a Henipavirus perspective

PubMed Central

Lee, Benhur; Akyol-Ataman, Zeynep

2011-01-01

Henipavirus is a new genus of paramyxovirus that uses protein-based receptors (EphrinB2 and EphrinB3) for virus entry. Paramyxovirus entry requires the coordinated action of the fusion (F) and attachment viral envelope glycoproteins. Receptor binding to the attachment protein triggers F to undergo a conformational cascade that results in membrane fusion. The accumulation of structural and functional studies on many paramyxoviral fusion and attachment proteins, including recent structures of Nipah and Hendra virus G bound and unbound to cognate ephrinB receptors, indicate that henipavirus entry and fusion differs mechanistically from paramyxoviruses that use glycan-based receptors. PMID:21511478

Ewing’s sarcoma precursors are highly enriched in embryonic osteochondrogenic progenitors

PubMed Central

Tanaka, Miwa; Yamazaki, Yukari; Kanno, Yohei; Igarashi, Katsuhide; Aisaki, Ken-ichi; Kanno, Jun; Nakamura, Takuro

2014-01-01

Ewing’s sarcoma is a highly malignant bone tumor found in children and adolescents, and the origin of this malignancy is not well understood. Here, we introduced a Ewing’s sarcoma–associated genetic fusion of the genes encoding the RNA-binding protein EWS and the transcription factor ETS (EWS-ETS) into a fraction of cells enriched for osteochondrogenic progenitors derived from the embryonic superficial zone (eSZ) of long bones collected from late gestational murine embryos. EWS-ETS fusions efficiently induced Ewing’s sarcoma–like small round cell sarcoma formation by these cells. Analysis of the eSZ revealed a fraction of a precursor cells that express growth/differentiation factor 5 (Gdf5), the transcription factor Erg, and parathyroid hormone-like hormone (Pthlh), and selection of the Pthlh-positive fraction alone further enhanced EWS-ETS–dependent tumor induction. Genes downstream of the EWS-ETS fusion protein were quite transcriptionally active in eSZ cells, especially in regions in which the chromatin structure of the ETS-responsive locus was open. Inhibition of β-catenin, poly (ADP-ribose) polymerase 1 (PARP1), or enhancer of zeste homolog 2 (EZH2) suppressed cell growth in a murine model of Ewing’s sarcoma, suggesting the utility of the current system as a preclinical model. These results indicate that eSZ cells are highly enriched in precursors to Ewing’s sarcoma and provide clues to the histogenesis of Ewing’s sarcoma in bone. PMID:24911143

Stalk model of membrane fusion: solution of energy crisis.

PubMed Central

Kozlovsky, Yonathan; Kozlov, Michael M

2002-01-01

Membrane fusion proceeds via formation of intermediate nonbilayer structures. The stalk model of fusion intermediate is commonly recognized to account for the major phenomenology of the fusion process. However, in its current form, the stalk model poses a challenge. On one hand, it is able to describe qualitatively the modulation of the fusion reaction by the lipid composition of the membranes. On the other, it predicts very large values of the stalk energy, so that the related energy barrier for fusion cannot be overcome by membranes within a biologically reasonable span of time. We suggest a new structure for the fusion stalk, which resolves the energy crisis of the model. Our approach is based on a combined deformation of the stalk membrane including bending of the membrane surface and tilt of the hydrocarbon chains of lipid molecules. We demonstrate that the energy of the fusion stalk is a few times smaller than those predicted previously and the stalks are feasible in real systems. We account quantitatively for the experimental results on dependence of the fusion reaction on the lipid composition of different membrane monolayers. We analyze the dependence of the stalk energy on the distance between the fusing membranes and provide the experimentally testable predictions for the structural features of the stalk intermediates. PMID:11806930

Fusion of Enveloped Viruses in Endosomes

PubMed Central

White, Judith M.; Whittaker, Gary R.

2016-01-01

Ari Helenius launched the field of enveloped virus fusion in endosomes with a seminal paper in the Journal of Cell Biology in 1980. In the intervening years a great deal has been learned about the structures and mechanisms of viral membrane fusion proteins as well as about the endosomes in which different enveloped viruses fuse and the endosomal cues that trigger fusion. We now recognize three classes of viral membrane fusion proteins based on structural criteria and four mechanisms of fusion triggering. After reviewing general features of viral membrane fusion proteins and viral fusion in endosomes, we delve into three characterized mechanisms for viral fusion triggering in endosomes: by low pH, by receptor binding plus low pH, and by receptor binding plus the action of a protease. We end with a discussion of viruses that may employ novel endosomal fusion triggering mechanisms. A key take home message is that enveloped viruses that enter cells by fusing in endosomes traverse the endocytic pathway until they reach an endosome that has all of the environmental conditions (pH, proteases, ions, intracellular receptors, and lipid composition) to (if needed) prime and (in all cases) trigger the fusion protein and to support membrane fusion. PMID:26935856

Inhibition of the Hantavirus Fusion Process by Predicted Domain III and Stem Peptides from Glycoprotein Gc.

PubMed

Barriga, Gonzalo P; Villalón-Letelier, Fernando; Márquez, Chantal L; Bignon, Eduardo A; Acuña, Rodrigo; Ross, Breyan H; Monasterio, Octavio; Mardones, Gonzalo A; Vidal, Simon E; Tischler, Nicole D

2016-07-01

Hantaviruses can cause hantavirus pulmonary syndrome or hemorrhagic fever with renal syndrome in humans. To enter cells, hantaviruses fuse their envelope membrane with host cell membranes. Previously, we have shown that the Gc envelope glycoprotein is the viral fusion protein sharing characteristics with class II fusion proteins. The ectodomain of class II fusion proteins is composed of three domains connected by a stem region to a transmembrane anchor in the viral envelope. These fusion proteins can be inhibited through exogenous fusion protein fragments spanning domain III (DIII) and the stem region. Such fragments are thought to interact with the core of the fusion protein trimer during the transition from its pre-fusion to its post-fusion conformation. Based on our previous homology model structure for Gc from Andes hantavirus (ANDV), here we predicted and generated recombinant DIII and stem peptides to test whether these fragments inhibit hantavirus membrane fusion and cell entry. Recombinant ANDV DIII was soluble, presented disulfide bridges and beta-sheet secondary structure, supporting the in silico model. Using DIII and the C-terminal part of the stem region, the infection of cells by ANDV was blocked up to 60% when fusion of ANDV occurred within the endosomal route, and up to 95% when fusion occurred with the plasma membrane. Furthermore, the fragments impaired ANDV glycoprotein-mediated cell-cell fusion, and cross-inhibited the fusion mediated by the glycoproteins from Puumala virus (PUUV). The Gc fragments interfered in ANDV cell entry by preventing membrane hemifusion and pore formation, retaining Gc in a non-resistant homotrimer stage, as described for DIII and stem peptide inhibitors of class II fusion proteins. Collectively, our results demonstrate that hantavirus Gc shares not only structural, but also mechanistic similarity with class II viral fusion proteins, and will hopefully help in developing novel therapeutic strategies against hantaviruses.

Chimera: a Bioconductor package for secondary analysis of fusion products.

PubMed

Beccuti, Marco; Carrara, Matteo; Cordero, Francesca; Lazzarato, Fulvio; Donatelli, Susanna; Nadalin, Francesca; Policriti, Alberto; Calogero, Raffaele A

2014-12-15

Chimera is a Bioconductor package that organizes, annotates, analyses and validates fusions reported by different fusion detection tools; current implementation can deal with output from bellerophontes, chimeraScan, deFuse, fusionCatcher, FusionFinder, FusionHunter, FusionMap, mapSplice, Rsubread, tophat-fusion and STAR. The core of Chimera is a fusion data structure that can store fusion events detected with any of the aforementioned tools. Fusions are then easily manipulated with standard R functions or through the set of functionalities specifically developed in Chimera with the aim of supporting the user in managing fusions and discriminating false-positive results. © The Author 2014. Published by Oxford University Press.

Crystal Structures of Beta- and Gammaretrovirus Fusion Proteins Reveal a Role for Electrostatic Stapling in Viral Entry

PubMed Central

Aydin, Halil; Cook, Jonathan D.

2014-01-01

Membrane fusion is a key step in the life cycle of all envelope viruses, but this process is energetically unfavorable; the transmembrane fusion subunit (TM) of the virion-attached glycoprotein actively catalyzes the membrane merger process. Retroviral glycoproteins are the prototypical system to study pH-independent viral entry. In this study, we determined crystal structures of extramembrane regions of the TMs from Mason-Pfizer monkey virus (MPMV) and xenotropic murine leukemia virus-related virus (XMRV) at 1.7-Å and 2.2-Å resolution, respectively. The structures are comprised of a trimer of hairpins that is characteristic of class I viral fusion proteins and now completes a structural library of retroviral fusion proteins. Our results allowed us to identify a series of intra- and interchain electrostatic interactions in the heptad repeat and chain reversal regions. Mutagenesis reveals that charge-neutralizing salt bridge mutations significantly destabilize the postfusion six-helix bundle and abrogate retroviral infection, demonstrating that electrostatic stapling of the fusion subunit is essential for viral entry. Our data indicate that salt bridges are a major stabilizing force on the MPMV and XMRV retroviral TMs and likely provide the key energetics for viral and host membrane fusion. PMID:24131724

Fusion Partner Toolchest for the Stabilization and Crystallization of G Protein-Coupled Receptors

PubMed Central

Chun, Eugene; Thompson, Aaron A.; Liu, Wei; Roth, Christopher B.; Griffith, Mark T.; Katritch, Vsevolod; Kunken, Joshua; Xu, Fei; Cherezov, Vadim; Hanson, Michael A.; Stevens, Raymond C.

2012-01-01

SUMMARY Structural studies of human G protein-coupled receptors (GPCRs) have recently been accelerated through the use of the T4 lysozyme fusion partner that was inserted into the third intracellular loop. Using chimeras of the human β2-adrenergic and human A2A adenosine receptors, we present the methodology and data for the selection of five new fusion partners for crystallizing GPCRs. In particular, the use of the thermostabilized apocytochrome b562RIL as a fusion partner displays certain advantages over the previously utilized T4 lysozyme, resulting in a significant improvement in stability and structure in GPCR-fusion constructs. PMID:22681902

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garcia, Natalie K.; Guttman, Miklos; Ebner, Jamie L.

Influenza hemagglutinin (HA) mediates virus attachment to host cells and fusion of the viral and endosomal membranes during entry. While high-resolution structures are available for the pre-fusion HA ectodomain and the post-fusion HA2 subunit, the sequence of conformational changes during HA activation has eluded structural characterization. In this paper, we apply hydrogen-deuterium exchange with mass spectrometry to examine changes in structural dynamics of the HA ectodomain at various stages of activation, and compare the soluble ectodomain with intact HA on virions. At pH conditions approaching activation (pH 6.0–5.5) HA exhibits increased dynamics at the fusion peptide and neighboring regions, whilemore » the interface between receptor binding subunits (HA1) becomes stabilized. In contrast to many activation models, these data suggest that HA responds to endosomal acidification by releasing the fusion peptide prior to HA1 uncaging and the spring-loaded refolding of HA2. Finally, this staged process may facilitate efficient HA-mediated fusion.« less

Paramyxovirus membrane fusion: Lessons from the F and HN atomic structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lamb, Robert A.; Paterson, Reay G.; Jardetzky, Theodore S.

2006-01-05

Paramyxoviruses enter cells by fusion of their lipid envelope with the target cell plasma membrane. Fusion of the viral membrane with the plasma membrane allows entry of the viral genome into the cytoplasm. For paramyxoviruses, membrane fusion occurs at neutral pH, but the trigger mechanism that controls the viral entry machinery such that it occurs at the right time and in the right place remains to be elucidated. Two viral glycoproteins are key to the infection process-an attachment protein that varies among different paramyxoviruses and the fusion (F) protein, which is found in all paramyxoviruses. For many of the paramyxovirusesmore » (parainfluenza viruses 1-5, mumps virus, Newcastle disease virus and others), the attachment protein is the hemagglutinin/neuraminidase (HN) protein. In the last 5 years, atomic structures of paramyxovirus F and HN proteins have been reported. The knowledge gained from these structures towards understanding the mechanism of viral membrane fusion is described.« less

Dynamic changes during acid-induced activation of influenza hemagglutinin

DOE PAGES

Garcia, Natalie K.; Guttman, Miklos; Ebner, Jamie L.; ...

2015-03-12

Influenza hemagglutinin (HA) mediates virus attachment to host cells and fusion of the viral and endosomal membranes during entry. While high-resolution structures are available for the pre-fusion HA ectodomain and the post-fusion HA2 subunit, the sequence of conformational changes during HA activation has eluded structural characterization. In this paper, we apply hydrogen-deuterium exchange with mass spectrometry to examine changes in structural dynamics of the HA ectodomain at various stages of activation, and compare the soluble ectodomain with intact HA on virions. At pH conditions approaching activation (pH 6.0–5.5) HA exhibits increased dynamics at the fusion peptide and neighboring regions, whilemore » the interface between receptor binding subunits (HA1) becomes stabilized. In contrast to many activation models, these data suggest that HA responds to endosomal acidification by releasing the fusion peptide prior to HA1 uncaging and the spring-loaded refolding of HA2. Finally, this staged process may facilitate efficient HA-mediated fusion.« less

[Transformation of antimicrobial peptide fusion gene of cecropin B and rabbit NP-1 to Houttuynia cordata].

PubMed

Dong, Yan; Zhang, Ying; Yi, Lang; Lai, Huili; Zhang, Yaming; Zhou, Lian; Wang, Peixun

2010-07-01

To transform the antimicrobial peptide fusion gene of cecropin B and rabbit NP-1(CN) into Houttuynia cordata to improve its antimicrobic capability. The fusion gene of CN designed and synthesized artificially was recombined with expression vector pBI121. The recombined vector was transformed to Agrobacterium tumefaciens LBA4404, by which CN gene was transformed to the explants of H. cordata. The transgenic regeneration plantlets were selected by kanamycin and rapid screening PCR. The transgenic plants were identified by PCR-Southern of genomic DNA and RT-PCR. The disease resistances were detected by antibacterial zone trail of leaf extracts to E. coli K12 and infection by Rhizoctonia solani. Gene of interesting CN was inserted into genomic DNA and expressed in transformed H, cordata, whose resistance to E. coli K12 and Rh. solani was stronger than that of the non-transformed control. The fusion gene CN can improve antimicrobic capability of transformed H. cordata.

The influence of Sc addition on the welding microstructure of Zr-based bulk metallic glass: The stability of the amorphous phase

NASA Astrophysics Data System (ADS)

Wang, Shing Hoa; Kuo, Pei Hung; Tsang, Hsiao Tsung; Jeng, Rong Ruey; Lin, Yu Lon

2007-10-01

Pulsed direct current autogeneous tungsten inert gas arc welding was conducted on rods of bulk metallic glasses (BMGs) Zr55Cu30Ni5Al10 and (Zr55Cu30Ni5Al10)99.98Sc0.02 under two different cooling conditions. The crystalline precipitates in the fusion zone of BMG Zr55Cu30Ni5Al10 were confirmed by microfocused x-ray diffraction pattern analysis as Zr2Ni and Zr2(Cu,Al) intermetallic compounds. In contrast, BMG with Sc addition (Zr55Cu30Ni5Al10)99.98Sc0.02 shows an excellent stable glass forming ability. The fusion zone of BMG (Zr55Cu30Ni5Al10)99.98Sc0.02 remains in the same amorphous state as that of the amorphous base metal when the weld is cooled with accelerated cooling.

Effect of minor chemistry elements on GTA weld fusion zone characteristics of a commercial grade titanium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marya, S.K.

1996-06-01

Gas Tungsten Arc Welding (GTAW) is the most common technique employed in the fabrication of rolled thin tubes. One of the major manufacturing problems concerns the stability of weld fusion zone on materials from different casts, notwithstanding stringent monitoring of the process parameters -- current, voltage and travel speed. These parameters determine the theoretical weld heat and are expected to control the instantaneous mass of melt. According to the data compiled by Sahoo et al., oxygen is known to reduce the surface tension of most of the metals. However, investigations on the role of minor changes in concentrations of elementsmore » like sulphur, oxygen, selenium, bismuth, aluminium, and titanium in steels have very often attributed the cast to cast variations to different temperature gradients of surface tension over the weldpool. To the author`s knowledge, no reported work so far has revealed changing weld profiles in autogeneous mechanized GTA welds on titanium due to minor composition changes.« less

Effect of the overlapping factor on the microstructure and mechanical properties of pulsed Nd:YAG laser welded Ti6Al4V sheets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Xiao-Long; Liu, Jing; Zhang, Lin-Jie, E-mail: zhanglinjie@mail.xjtu.edu.cn

2014-07-01

The effect of the overlapping factor on the microstructures and mechanical properties of pulsed Nd:YAG laser welded Ti6Al4V alloy sheets was investigated by microstructural observations, microhardness tests, tensile tests and fatigue tests. A microstructural examination shows that by increasing the overlapping factor, the grains in the fusion zone become coarser, and the width of the heat affected zone increases. As overlapping factor increases, the width of region composed completely of martensite α′ and the secondary α phase in the heat affected zone increases, consequently the gradient of microstructure along the direction from the fusion zone to base metal decreases, somore » does the gradient of microhardness. The results of tensile and fatigue tests reveal that the joints made using medium overlapping factor exhibit better mechanical properties than those welded with low and high overlapping factors. Based on the experimental results, it can be stated that a sound weld of Ti6Al4V alloy can be obtained if an appropriate overlapping factor is used. - Highlights: • The weld quality of Ti6Al4V alloy under various overlapping factors was assessed. • Tensile and fatigue tests were conducted with as-welded specimen. • Localized strain across the weld was measured using DIC photogrammetry system. • A sound weld of Ti6Al4V alloy is obtained by using right overlapping factor.« less

Remodeling of the notochord during development of vertebral fusions in Atlantic salmon (Salmo salar).

PubMed

Ytteborg, Elisabeth; Torgersen, Jacob Seilø; Pedersen, Mona E; Baeverfjord, Grete; Hannesson, Kirsten O; Takle, Harald

2010-12-01

Histological characterization of spinal fusions in Atlantic salmon (Salmo salar) has demonstrated shape alterations of vertebral body endplates, a reduced intervertebral space, and replacement of intervertebral cells by ectopic bone. However, the significance of the notochord during the fusion process has not been addressed. We have therefore investigated structural and cellular events in the notochord during the development of vertebral fusions. In order to induce vertebral fusions, Atlantic salmon were exposed to elevated temperatures from fertilization until they attained a size of 15g. Based on results from radiography, intermediate and terminal stages of the fusion process were investigated by immunohistochemistry and real-time quantitative polymerase chain reaction. Examination of structural extracellular matrix proteins such as Perlecan, Aggrecan, Elastin, and Laminin revealed reduced activity and reorganization at early stages in the pathology. Staining for elastic fibers visualized a thinner elastic membrane surrounding the notochord of developing fusions, and immunohistochemistry for Perlecan showed that the notochordal sheath was stretched during fusion. These findings in the outer notochord correlated with the loss of Aggrecan- and Substance-P-positive signals and the further loss of vacuoles from the chordocytes in the central notochord. At more progressed stages of fusion, chordocytes condensed, and the expression of Aggrecan and Substance P reappeared. The hyperdense regions seem to be of importance for the formation of notochordal tissue into bone. Thus, the remodeling of notochord integrity by reduced elasticity, structural alterations, and cellular changes is probably involved in the development of vertebral fusions.

Condorcet and borda count fusion method for ligand-based virtual screening.

PubMed

Ahmed, Ali; Saeed, Faisal; Salim, Naomie; Abdo, Ammar

2014-01-01

It is known that any individual similarity measure will not always give the best recall of active molecule structure for all types of activity classes. Recently, the effectiveness of ligand-based virtual screening approaches can be enhanced by using data fusion. Data fusion can be implemented using two different approaches: group fusion and similarity fusion. Similarity fusion involves searching using multiple similarity measures. The similarity scores, or ranking, for each similarity measure are combined to obtain the final ranking of the compounds in the database. The Condorcet fusion method was examined. This approach combines the outputs of similarity searches from eleven association and distance similarity coefficients, and then the winner measure for each class of molecules, based on Condorcet fusion, was chosen to be the best method of searching. The recall of retrieved active molecules at top 5% and significant test are used to evaluate our proposed method. The MDL drug data report (MDDR), maximum unbiased validation (MUV) and Directory of Useful Decoys (DUD) data sets were used for experiments and were represented by 2D fingerprints. Simulated virtual screening experiments with the standard two data sets show that the use of Condorcet fusion provides a very simple way of improving the ligand-based virtual screening, especially when the active molecules being sought have a lowest degree of structural heterogeneity. However, the effectiveness of the Condorcet fusion was increased slightly when structural sets of high diversity activities were being sought.

Condorcet and borda count fusion method for ligand-based virtual screening

PubMed Central

2014-01-01

Background It is known that any individual similarity measure will not always give the best recall of active molecule structure for all types of activity classes. Recently, the effectiveness of ligand-based virtual screening approaches can be enhanced by using data fusion. Data fusion can be implemented using two different approaches: group fusion and similarity fusion. Similarity fusion involves searching using multiple similarity measures. The similarity scores, or ranking, for each similarity measure are combined to obtain the final ranking of the compounds in the database. Results The Condorcet fusion method was examined. This approach combines the outputs of similarity searches from eleven association and distance similarity coefficients, and then the winner measure for each class of molecules, based on Condorcet fusion, was chosen to be the best method of searching. The recall of retrieved active molecules at top 5% and significant test are used to evaluate our proposed method. The MDL drug data report (MDDR), maximum unbiased validation (MUV) and Directory of Useful Decoys (DUD) data sets were used for experiments and were represented by 2D fingerprints. Conclusions Simulated virtual screening experiments with the standard two data sets show that the use of Condorcet fusion provides a very simple way of improving the ligand-based virtual screening, especially when the active molecules being sought have a lowest degree of structural heterogeneity. However, the effectiveness of the Condorcet fusion was increased slightly when structural sets of high diversity activities were being sought. PMID:24883114

Study on ( n,t) Reactions of Zr, Nb and Ta Nuclei

NASA Astrophysics Data System (ADS)

Tel, E.; Yiğit, M.; Tanır, G.

2012-04-01

The world faces serious energy shortages in the near future. To meet the world energy demand, the nuclear fusion with safety, environmentally acceptability and economic is the best suited. Fusion is attractive as an energy source because of the virtually inexhaustible supply of fuel, the promise of minimal adverse environmental impact, and its inherent safety. Fusion will not produce CO2 or SO2 and thus will not contribute to global warming or acid rain. Furthermore, there are not radioactive nuclear waste problems in the fusion reactors. Although there have been significant research and development studies on the inertial and magnetic fusion reactor technology, there is still a long way to go to penetrate commercial fusion reactors to the energy market. Because, tritium self-sufficiency must be maintained for a commercial power plant. For self-sustaining (D-T) fusion driver tritium breeding ratio should be greater than 1.05. And also, the success of fusion power system is dependent on performance of the first wall, blanket or divertor systems. So, the performance of structural materials for fusion power systems, understanding nuclear properties systematic and working out of ( n,t) reaction cross sections are very important. Zirconium (Zr), Niobium (Nb) and Tantal (Ta) containing alloys are important structural materials for fusion reactors, accelerator-driven systems, and many other fields. In this study, ( n,t) reactions for some structural fusion materials such as 88,90,92,94,96Zr, 93,94,95Nb and 179,181Ta have been investigated. The calculated results are discussed andcompared with the experimental data taken from the literature.

Efficient replication of a paramyxovirus independent of full zippering of the fusion protein six-helix bundle domain

PubMed Central

Brindley, Melinda A.; Plattet, Philippe; Plemper, Richard Karl

2014-01-01

Enveloped viruses such as HIV and members of the paramyxovirus family use metastable, proteinaceous fusion machineries to merge the viral envelope with cellular membranes for infection. A hallmark of the fusogenic glycoproteins of these pathogens is refolding into a thermodynamically highly stable fusion core structure composed of six antiparallel α-helices, and this structure is considered instrumental for pore opening and/or enlargement. Using a paramyxovirus fusion (F) protein, we tested this paradigm by engineering covalently restricted F proteins that are predicted to be unable to close the six-helix bundle core structure fully. Several candidate bonds formed efficiently, resulting in F trimers and higher-order complexes containing covalently linked dimers. The engineered F complexes were incorporated into recombinant virions efficiently and were capable of refolding into a postfusion conformation without temporary or permanent disruption of the disulfide bonds. They efficiently formed fusion pores based on virus replication and quantitative cell-to-cell and virus-to-cell fusion assays. Complementation of these F mutants with a monomeric, fusion-inactive F variant enriched the F oligomers for heterotrimers containing a single disulfide bond, without affecting fusion complementation profiles compared with standard F protein. Our demonstration that complete closure of the fusion core does not drive paramyxovirus entry may aid the design of strategies for inhibiting virus entry. PMID:25157143

Efficient replication of a paramyxovirus independent of full zippering of the fusion protein six-helix bundle domain.

PubMed

Brindley, Melinda A; Plattet, Philippe; Plemper, Richard Karl

2014-09-09

Enveloped viruses such as HIV and members of the paramyxovirus family use metastable, proteinaceous fusion machineries to merge the viral envelope with cellular membranes for infection. A hallmark of the fusogenic glycoproteins of these pathogens is refolding into a thermodynamically highly stable fusion core structure composed of six antiparallel α-helices, and this structure is considered instrumental for pore opening and/or enlargement. Using a paramyxovirus fusion (F) protein, we tested this paradigm by engineering covalently restricted F proteins that are predicted to be unable to close the six-helix bundle core structure fully. Several candidate bonds formed efficiently, resulting in F trimers and higher-order complexes containing covalently linked dimers. The engineered F complexes were incorporated into recombinant virions efficiently and were capable of refolding into a postfusion conformation without temporary or permanent disruption of the disulfide bonds. They efficiently formed fusion pores based on virus replication and quantitative cell-to-cell and virus-to-cell fusion assays. Complementation of these F mutants with a monomeric, fusion-inactive F variant enriched the F oligomers for heterotrimers containing a single disulfide bond, without affecting fusion complementation profiles compared with standard F protein. Our demonstration that complete closure of the fusion core does not drive paramyxovirus entry may aid the design of strategies for inhibiting virus entry.

Detection of EWS/FLI-1 fusion in non-Ewing soft tissue tumors.

PubMed

Trancău, I O; Huică, R; Surcel, M; Munteanu, A; Ursaciuc, C

2015-01-01

EWS/FLI-1 fusion mainly appears in Ewing's sarcoma or the primitive neuroectodermal tumors and represents a genomic marker for these tumors. However, it can appear with lower frequency in other soft tissue tumors. The paper investigates the presence of EWS/FLI-1 fusion in clinically diagnosed sarcoma belonging to different non-Ewing connective tissue tumors in order to search for a possible new biomarker valuable for investigators. 20 patients with soft tissue tumors, who underwent surgery, were tested. Intra-operative samples of normal and tumor tissue were collected for histopathological diagnosis and genetics determinations. The patients' RNA from tumor and normal peritumoral tissue was extracted and EWS/FLI-1 fusion screened by quantitative real-time PCR. The relative expression of the fusion in the tumor sample was compared to the similar expression in normal tissue. The amplification in the threshold zone was shown by 5 samples (25%): 2 clear cell sarcoma, 1 fibrosarcoma, 1 malignant tumor of nerve sheath, 1 metastatic adenocarcinoma. We differentiated between the unspecific amplification and concluded that these are weak positive results. Genomic investigation may establish the tumor malignancy and its possible affiliation earlier than histopathology. It can support the screening of EWS/FLI-1 fusion in a larger variety of clinically diagnosed soft tissue tumors.

Surface preparation effects on GTA weld shape in JBK-75 stainless steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campbell, R.D.; Robertson, A.M.; Heiple, C.R.

1993-02-01

The results of a study are reported here on the effects of surface preparation on the shape of autogenous gas tungsten arc (GTA) welds in JBK-75, an austenitic precipitation hardenable stainless steel similar to A286. Minor changes in surface preparation produced substantial changes in the fusion zone shape and welding behavior of this alloy. Increased and more consistent depth of fusion (higher d/w ratios) along with improved arc stability and less arc wander resulted from wire brushing and other abrasive surface preparations, although chemical and machining methods did not produce any increase in depth of fusion. Abrasive treatments roughen themore » surface, increase the surface area, increase the surface oxide thickness, and entrap oxide. The increased weld d/w ratio is attributed to oxygen added to the weld pool from the surface oxide on the base metal. The added oxygen alters the surface-tension-driven fluid flow pattern in the weld pool. Increased depth of fusion in wire-fed U-groove weld joints also resulted when welding wire with a greater surface oxide thickness was used. Increasing the amount of wire brushing produced even deeper welds. However, a maximum in depth of fusion was observed with further wire brushing, beyond which weld fusion depth decreased.« less

Characterizing the Effect of Laser Power on Laser Metal Deposited Titanium Alloy and Boron Carbide

NASA Astrophysics Data System (ADS)

Akinlabi, E. T.; Erinosho, M. F.

2017-11-01

Titanium alloy has gained acceptance in the aerospace, marine, chemical, and other related industries due to its excellent combination of mechanical and corrosion properties. In order to augment its properties, a hard ceramic, boron carbide has been laser cladded with it at varying laser powers between 0.8 and 2.4 kW. This paper presents the effect of laser power on the laser deposited Ti6Al4V-B4C composites through the evolving microstructures and microhardness. The microstructures of the composites exhibit the formation of α-Ti phase and β-Ti phase and were elongated towards the heat affected zone. These phases were terminated at the fusion zone and globular microstructures were found growing epitaxially just immediately after the fusion zone. Good bondings were formed in all the deposited composites. Sample A1 deposited at a laser power of 0.8 kW and scanning speed of 1 m/min exhibits the highest hardness of HV 432 ± 27, while sample A4 deposited at a laser power of 2.0 kW and scanning speed of 1 m/min displays the lowest hardness of HV 360 ± 18. From the hardness results obtained, ceramic B4C has improved the mechanical properties of the primary alloy.

Interfacial microstructure and properties of copper clad steel produced using friction stir welding versus gas metal arc welding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Z.; Chen, Y.; Haghshenas, M., E-mail: mhaghshe@uwaterloo.ca

A preliminary study compares the feasibility and microstructures of pure copper claddings produced on a pressure vessel A516 Gr. 70 steel plate, using friction stir welding versus gas metal arc welding. A combination of optical and scanning electron microscopy is used to characterize the grain structures in both the copper cladding and heat affected zone in the steel near the fusion line. The friction stir welding technique produces copper cladding with a grain size of around 25 μm, and no evidence of liquid copper penetration into the steel. The gas metal arc welding of copper cladding exhibits grain sizes overmore » 1 mm, and with surface microcracks as well as penetration of liquid copper up to 50 μm into the steel substrate. Transmission electron microscopy reveals that metallurgical bonding is produced in both processes. Increased diffusion of Mn and Si into the copper cladding occurs when using gas metal arc welding, although some nano-pores were detected in the FSW joint interface. - Highlights: • Cladding of steel with pure copper is possible using either FSW or GMAW. • The FSW yielded a finer grain structure in the copper, with no evidence of cracking. • The FSW joint contains some evidence of nano-pores at the interface of the steel/copper. • Copper cladding by GMAW contained surface cracks attributed to high thermal stresses. • The steel adjacent to the fusion line maintained a hardness value below 248 HV.« less

Rational improvement of gp41-targeting HIV-1 fusion inhibitors: an innovatively designed Ile-Asp-Leu tail with alternative conformations.

PubMed

Zhu, Yun; Su, Shan; Qin, Lili; Wang, Qian; Shi, Lei; Ma, Zhenxuan; Tang, Jianchao; Jiang, Shibo; Lu, Lu; Ye, Sheng; Zhang, Rongguang

2016-09-26

Peptides derived from the C-terminal heptad repeat (CHR) of HIV gp41 have been developed as effective fusion inhibitors against HIV-1, but facing the challenges of enhancing potency and stability. Here, we report a rationally designed novel HIV-1 fusion inhibitor derived from CHR-derived peptide (Trp628~Gln653, named CP), but with an innovative Ile-Asp-Leu tail (IDL) that dramatically increased the inhibitory activity by up to 100 folds. We also determined the crystal structures of artificial fusion peptides N36- and N43-L6-CP-IDL. Although the overall structures of both fusion peptides share the canonical six-helix bundle (6-HB) configuration, their IDL tails adopt two different conformations: a one-turn helix with the N36, and a hook-like structure with the longer N43. Structural comparison showed that the hook-like IDL tail possesses a larger interaction interface with NHR than the helical one. Further molecular dynamics simulations of the two 6-HBs and isolated CP-IDL peptides suggested that hook-like form of IDL tail can be stabilized by its binding to NHR trimer. Therefore, CP-IDL has potential for further development as a new HIV fusion inhibitor, and this strategy could be widely used in developing artificial fusion inhibitors against HIV and other enveloped viruses.

Membrane fusion activity of vesicular stomatitis virus glycoprotein G is induced by low pH but not by heat or denaturant.

PubMed

Yao, Yi; Ghosh, Kakoli; Epand, Raquel F; Epand, Richard M; Ghosh, Hara P

2003-06-05

The fusogenic envelope glycoprotein G of the rhabdovirus vesicular stomatitis virus (VSV) induces membrane fusion at acidic pH. At acidic pH the G protein undergoes a major structural reorganization leading to the fusogenic conformation. However, unlike other viral fusion proteins, the low-pH-induced conformational change of VSV G is completely reversible. As well, the presence of an alpha-helical coiled-coil motif required for fusion by a number of viral and cellular fusion proteins was not predicted in VSV G protein by using a number of algorithms. Results of pH dependence of the thermal stability of G protein as determined by intrinsic Trp fluorescence and circular dichroism (CD) spectroscopy show that the G protein is equally stable at neutral or acidic pH. Destabilization of G structure at neutral pH with either heat or urea did not induce membrane fusion or conformational change(s) leading to membrane fusion. Taken together, these data suggest that the mechanism of VSV G-induced fusion is distinct from the fusion mechanism of fusion proteins that involve a coiled-coil motif.

Tetraspanin 7 regulates sealing zone formation and the bone-resorbing activity of osteoclasts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwon, Jun-Oh; Lee, Yong Deok; Kim, Haemin

Tetraspanin family proteins regulate morphology, motility, fusion, and signaling in various cell types. We investigated the role of the tetraspanin 7 (Tspan7) isoform in the differentiation and function of osteoclasts. Tspan7 was up-regulated during osteoclastogenesis. When Tspan7 expression was reduced in primary precursor cells by siRNA-mediated gene knock-down, the generation of multinuclear osteoclasts was not affected. However, a striking cytoskeletal abnormality was observed: the formation of the podosome belt structure was inhibited and the microtubular network were disrupted by Tspan7 knock-down. Decreases in acetylated microtubules and levels of phosphorylated Src and Pyk2 in Tspan7 knock-down cells supported the involvement ofmore » Tspan7 in cytoskeletal rearrangement signaling in osteoclasts. This cytoskeletal defect interfered with sealing zone formation and subsequently the bone-resorbing activity of mature osteoclasts on dentin surfaces. Our results suggest that Tspan7 plays an important role in cytoskeletal organization required for the bone-resorbing function of osteoclasts by regulating signaling to Src, Pyk2, and microtubules. - Highlights: • Tspan7 expression is up-regulated during osteoclastogenesis. • Tspan7 regulates podosome belt organization in osteoclasts. • Tspan7 is crucial for sealing zone formation and bone-resorption by osteoclasts. • Src and Pyk2 phosphorylation and microtubule acetylation mediate Tspan7 function.« less

Effect of laser beam offset on microstructure and mechanical properties of pulsed laser welded BTi-6431S/TA15 dissimilar titanium alloys

NASA Astrophysics Data System (ADS)

Zhang, Hao; Hu, Shengsun; Shen, Junqi; Li, Dalong; Bu, Xianzheng

2015-11-01

Laser beam welding was used to weld dissimilar joints in BTi-6431S/TA15 titanium alloys. The effect of laser beam offset on microstructural characterizations and mechanical properties of the joints were investigated. Microstructural evolution of the joints was characterized by optical microscopy (OM) and X-ray diffraction (XRD). Tensile testing was conducted at room temperature and at 550 °C. The results demonstrated that with the exception of some porosity, a good quality joint could be achieved. Martensite α' and acicular α structures were present in the fusion zone (FZ). The amount of martensite α' present with the -0.2 mm beam offset was less than that with the 0.2 mm beam offset. Acicular α and martensite α' transformations occurred in the high temperature heat-affected zone (HT-HAZ) of both the BTi-6431S and TA15 alloys. In the low-temperature heat-affected zone (LT-HAZ), the BTi-6431S and TA15 alloy microstructures exhibited a mixture of secondary α, primary α, and prior β phases. The microhardness values in the FZ followed the order: -0.2 mm> 0 mm> 0.2 mm. Tensile testing at room temperature and at 550 °C resulted in fracture of the TA15 alloy base metal. The fracture morphology exhibited a ductile dimple feature.

Grounding Lines Detecting Using LANDSAT8 Oli and CRYOSAT-2 Data Fusion

NASA Astrophysics Data System (ADS)

Li, F.; Guo, Y.; Zhang, Y.; Zhang, S.

2018-04-01

The grounding zone is the region where ice transitions from grounded ice sheet to freely floating ice shelf, grounding lines are actually more of a zone, typically over several kilometers. The mass loss from Antarctica is strongly linked to changes in the ice shelves and their grounding lines, since the variation in the grounding line can result in very rapid changes in glacier and ice-shelf behavior. Based on remote sensing observations, five global Antarctic grounding line products have been released internationally, including MOA, ASAID, ICESat, MEaSUREs, and Synthesized grounding lines. However, the five products could not provide the annual grounding line products of the whole Antarctic, even some products have stopped updating, which limits the time series analysis of Antarctic material balance to a certain extent. Besides, the accurate of single remote-sensing data based grounding line products is far from satisficed. Therefore, we use algorithms to extract grounding lines with SAR and Cryosat-2 data respectively, and combine the results of two kinds of grounding lines to obtain new products, we obtain a mature grounding line extraction algorithm process, so that we can realize the extraction of grounding line of the Antarctic each year in the future. The comparison between fusion results and the MOA product results indicate that there is a maximum deviation of 188.67 meters between the MOA product and the fusion result.

Effect of fluorides from various restorative materials on remineralization of adjacent tooth: an in vitro study.

PubMed

Baliga, M S; Bhat, S S

2010-01-01

The aim of the study was to evaluate the extent of surface zone remineralization and the effect of fluoride at the inter-proximal adjacent tooth surface, using restorative materials FusionAlloy, Ketac-Fil and Heliomolar. Ninety extracted molar teeth were used of which 45 were placed in artificial caries for 10 weeks. The remaining 45 teeth were filled with the respective restorative materials, mounted with the artificial carious teeth in proximal contact with plaster and placed in artificial saliva for a period of 28 days. Finally, sectioning of artificially carious teeth was done mesio-distally and observed under the optical microscope and scanning electron microscope. Comparison among the groups was done by one-way analysis of variance [ANOVA] and Fischer's F test. Intercomparison between the groups was done by using Dunnett's t-test. Results obtained from transmitted electron microscopic and scanning electron microscopic observations were almost similar with the Ketac-Fil and Heliomolar showing better results in surface zone remineralization compared to FusionAlloy. Also, Ketac-Fil is a good material in releasing fluoride to remineralize enamel when compared to Heliomolar and FusionAlloy. Thus, it can be used mainly in class II cavity restorations of primary and permanent dentitions due to the potential ability of fluoride containing glass ionomer cements and composite resins to remineralize incipient carious lesions on adjacent teeth.

Metallography studies and hardness measurements on ferritic/martensitic steels irradiated in STIP

NASA Astrophysics Data System (ADS)

Zhang, H.; Long, B.; Dai, Y.

2008-06-01

In this work metallography investigations and microhardness measurements have been performed on 15 ferritic/martensitic (FM) steels and 6 weld metals irradiated in the SINQ Target Irradiation Program (STIP). The results demonstrate that all the steels have quite similar martensite lath structures. However, the sizes of the prior austenite grain (PAG) of these steels are quite different and vary from 10 to 86 μm. The microstructure in the fusion zones (FZ) of electron-beam welds (EBWs) of 5 steels (T91, EM10, MANET-II, F82H and Optifer-IX) is similar in respect to the martensite lath structure and PAG size. The FZ of the inert-gas-tungsten weld (TIGW) of the T91 steel shows a duplex structure of large ferrite gains and martensite laths. The microhardness measurements indicate that the normalized and tempered FM steels have rather close hardness values. The unusual high hardness values of the EBW and TIGW of the T91 steel were detected, which suggests that these materials are without proper tempering or post-welding heat treatment.

Barrier distributions and signatures of transfer channels in the Ca40+Ni58,64 fusion reactions at energies around and below the Coulomb barrier

NASA Astrophysics Data System (ADS)

Bourgin, D.; Courtin, S.; Haas, F.; Stefanini, A. M.; Montagnoli, G.; Goasduff, A.; Montanari, D.; Corradi, L.; Fioretto, E.; Huiming, J.; Scarlassara, F.; Rowley, N.; Szilner, S.; Mijatović, T.

2014-10-01

Background: The nuclear structure of colliding nuclei is known to influence the fusion process. Couplings of the relative motion to nuclear shape deformations and vibrations lead to an enhancement of the sub-barrier fusion cross section in comparison with the predictions of one-dimensional barrier penetration models. This enhancement is explained by coupled-channels calculations including these couplings. The sub-barrier fusion cross section is also affected by nucleon transfer channels between the colliding nuclei. Purpose: The aim of the present experiment is to investigate the influence of the projectile and target nuclear structures on the fusion cross sections in the Ca40+Ni58 and Ca40+Ni64 systems. Methods: The experimental and theoretical fusion excitation functions as well as the barrier distributions were compared for these two systems. Coupled-channels calculations were performed using the ccfull code. Results: Good agreement was found between the measured and calculated fusion cross sections for the Ca40+Ni58 system. The situation is different for the Ca40+Ni64 system where the coupled-channels calculations with no nucleon transfer clearly underestimate the fusion cross sections below the Coulomb barrier. The fusion excitation function was, however, well reproduced at low and high energies by including the coupling to the neutron pair-transfer channel in the calculations. Conclusions: The nuclear structure of the colliding nuclei influences the fusion cross sections below the Coulomb barrier for both Ca40+Ni58,64 systems. Moreover, we highlighted the effect of the neutron pair-transfer channel on the fusion cross sections in Ca40+Ni64.

Full-Length Trimeric Influenza Virus Hemagglutinin II Membrane Fusion Protein and Shorter Constructs Lacking the Fusion Peptide or Transmembrane Domain: Hyperthermostability of the Full-Length Protein and the Soluble Ectodomain and Fusion Peptide Make Significant Contributions to Fusion of Membrane Vesicles†

PubMed Central

Ratnayake, Punsisi U.; Ekanayaka, E. A. Prabodha; Komanduru, Sweta S.; Weliky, David P.

2015-01-01

Influenza virus is a Class I enveloped virus which is initially endocytosed into a host respiratory epithelial cell. Subsequent reduction of the pH to the 5–6 range triggers a structural change of the viral hemagglutinin II (HA2) protein, fusion of the viral and endosomal membranes, and release of the viral nucleocapsid into the cytoplasm. HA2 contains fusion peptide (FP), soluble ectodomain (SE), transmembrane (TM), and intraviral domains with respective lengths of ~25, ~160, ~25, and ~10 residues. The present work provides a straightforward protocol for producing and purifying mg quantities of full-length HA2 from expression in bacteria. Biophysical and structural comparisons are made between full-length HA2 and shorter constructs including SHA2 ≡ SE, FHA2 ≡ FP + SE, and SHA2-TM ≡ SE + TM constructs. The constructs are helical in detergent at pH 7.4 and the dominant trimer species. The proteins are highly thermostable in decylmaltoside detergent with Tm > 90 °C for HA2 with stabilization provided by the SE, FP, and TM domains. The proteins are likely in a trimer-of-hairpins structure, the final protein state during fusion. All constructs induce fusion of negatively-charged vesicles at pH 5.0 with much less fusion at pH 7.4. Attractive protein/vesicle electrostatics play a role in fusion, as the proteins are positively-charged at pH 5.0 and negatively-charged at pH 7.4 and the pH-dependence of fusion is reversed for positively-charged vesicles. Comparison of fusion between constructs supports significant contributions to fusion from the SE and the FP with little effect from the TM. PMID:26297995

Full-length trimeric influenza virus hemagglutinin II membrane fusion protein and shorter constructs lacking the fusion peptide or transmembrane domain: Hyperthermostability of the full-length protein and the soluble ectodomain and fusion peptide make significant contributions to fusion of membrane vesicles.

PubMed

Ratnayake, Punsisi U; Prabodha Ekanayaka, E A; Komanduru, Sweta S; Weliky, David P

2016-01-01

Influenza virus is a class I enveloped virus which is initially endocytosed into a host respiratory epithelial cell. Subsequent reduction of the pH to the 5-6 range triggers a structural change of the viral hemagglutinin II (HA2) protein, fusion of the viral and endosomal membranes, and release of the viral nucleocapsid into the cytoplasm. HA2 contains fusion peptide (FP), soluble ectodomain (SE), transmembrane (TM), and intraviral domains with respective lengths of ∼ 25, ∼ 160, ∼ 25, and ∼ 10 residues. The present work provides a straightforward protocol for producing and purifying mg quantities of full-length HA2 from expression in bacteria. Biophysical and structural comparisons are made between full-length HA2 and shorter constructs including SHA2 ≡ SE, FHA2 ≡ FP+SE, and SHA2-TM ≡ SE+TM constructs. The constructs are helical in detergent at pH 7.4 and the dominant trimer species. The proteins are highly thermostable in decylmaltoside detergent with Tm>90 °C for HA2 with stabilization provided by the SE, FP, and TM domains. The proteins are likely in a trimer-of-hairpins structure, the final protein state during fusion. All constructs induce fusion of negatively-charged vesicles at pH 5.0 with much less fusion at pH 7.4. Attractive protein/vesicle electrostatics play a role in fusion, as the proteins are positively-charged at pH 5.0 and negatively-charged at pH 7.4 and the pH-dependence of fusion is reversed for positively-charged vesicles. Comparison of fusion between constructs supports significant contributions to fusion from the SE and the FP with little effect from the TM. Copyright © 2015 Elsevier Inc. All rights reserved.

Development of the Scale for "Convergence Thinking" in Engineering

ERIC Educational Resources Information Center

Park, Sungmi

2016-01-01

Purpose: The purpose of this paper is to define the concept of "convergence thinking" as a trading zone for knowledge fusion in the engineering field, and develops its measuring scale. Design/ Methodology/Approach: Based on results from literature review, this study clarifies a theoretical ground for "convergence thinking."…

HEAT INPUT AND POST WELD HEAT TREATMENT EFFECTS ON REDUCED-ACTIVATION FERRITIC/MARTENSITIC STEEL FRICTION STIR WELDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Wei; Chen, Gaoqiang; Chen, Jian

Reduced-activation ferritic/martensitic (RAFM) steels are an important class of structural materials for fusion reactor internals developed in recent years because of their improved irradiation resistance. However, they can suffer from welding induced property degradations. In this paper, a solid phase joining technology friction stir welding (FSW) was adopted to join a RAFM steel Eurofer 97 and different FSW parameters/heat input were chosen to produce welds. FSW response parameters, joint microstructures and microhardness were investigated to reveal relationships among welding heat input, weld structure characterization and mechanical properties. In general, FSW heat input results in high hardness inside the stir zonemore » mostly due to a martensitic transformation. It is possible to produce friction stir welds similar to but not with exactly the same base metal hardness when using low power input because of other hardening mechanisms. Further, post weld heat treatment (PWHT) is a very effective way to reduce FSW stir zone hardness values.« less

Solid-state nuclear magnetic resonance measurements of HIV fusion peptide 13CO to lipid 31P proximities support similar partially inserted membrane locations of the α helical and β sheet peptide structures.

PubMed

Gabrys, Charles M; Qiang, Wei; Sun, Yan; Xie, Li; Schmick, Scott D; Weliky, David P

2013-10-03

Fusion of the human immunodeficiency virus (HIV) membrane and the host cell membrane is an initial step of infection of the host cell. Fusion is catalyzed by gp41, which is an integral membrane protein of HIV. The fusion peptide (FP) is the ∼25 N-terminal residues of gp41 and is a domain of gp41 that plays a key role in fusion catalysis likely through interaction with the host cell membrane. Much of our understanding of the FP domain has been accomplished with studies of "HFP", i.e., a ∼25-residue peptide composed of the FP sequence but lacking the rest of gp41. HFP catalyzes fusion between membrane vesicles and serves as a model system to understand fusion catalysis. HFP binds to membranes and the membrane location of HFP is likely a significant determinant of fusion catalysis perhaps because the consequent membrane perturbation reduces the fusion activation energy. In the present study, many HFPs were synthesized and differed in the residue position that was (13)CO backbone labeled. Samples were then prepared that each contained a singly (13)CO labeled HFP incorporated into membranes that lacked cholesterol. HFP had distinct molecular populations with either α helical or oligomeric β sheet structure. Proximity between the HFP (13)CO nuclei and (31)P nuclei in the membrane headgroups was probed by solid-state NMR (SSNMR) rotational-echo double-resonance (REDOR) measurements. For many samples, there were distinct (13)CO shifts for the α helical and β sheet structures so that the proximities to (31)P nuclei could be determined for each structure. Data from several differently labeled HFPs were then incorporated into a membrane location model for the particular structure. In addition to the (13)CO labeled residue position, the HFPs also differed in sequence and/or chemical structure. "HFPmn" was a linear peptide that contained the 23 N-terminal residues of gp41. "HFPmn_V2E" contained the V2E mutation that for HIV leads to greatly reduced extent of fusion and infection. The present study shows that HFPmn_V2E induces much less vesicle fusion than HFPmn. "HFPtr" contained three strands with HFPmn sequence that were chemically cross-linked near their C-termini. HFPtr mimics the trimeric topology of gp41 and induces much more rapid and extensive vesicle fusion than HFPmn. For HFPmn and HFPtr, well-resolved α and β peaks were observed for A6-, L9-, and L12-labeled samples. For each of these samples, there were similar HFP (13)CO to lipid (31)P proximities in the α and β structures, which evidenced comparable membrane locations of the HFP in either structure including insertion into a single membrane leaflet. The data were also consistent with deeper insertion of HFPtr relative to HFPmn in both the α and β structures. The results supported a strong correlation between the membrane insertion depth of the HFP and its fusogenicity. More generally, the results supported membrane location of the HFP as an important determinant of its fusogenicity. The deep insertion of HFPtr in both the α and β structures provides the most relevant membrane location of the FP for HIV gp41-catalyzed membrane fusion because HIV gp41 is natively trimeric. Well-resolved α and β signals were observed in the HFPmn_V2E samples with L9- and L12- but not A6-labeling. The α signals were much more dominant for L9- and L12-labeled HFPmn_V2E than the corresponding HFPmn or HFPtr. The structural model for the less fusogenic HFPmn_V2E includes a shorter helix and less membrane insertion than either HFPmn or HFPtr. This greater helical population and different helical structure and membrane location could result in less membrane perturbation and lower fusogenicity of HFPmn_V2E and suggest that the β sheet fusion peptide is the most functionally relevant structure of HFPmn, HFPtr, and gp41.

Impact of a Structured Reporting Template on Adherence to Prostate Imaging Reporting and Data System Version 2 and on the Diagnostic Performance of Prostate MRI for Clinically Significant Prostate Cancer.

PubMed

Shaish, Hiram; Feltus, Whitney; Steinman, Jonathan; Hecht, Elizabeth; Wenske, Sven; Ahmed, Firas

2018-05-01

The aim of this study was to assess the impact of a structured reporting template on adherence to the Prostate Imaging Reporting and Data System (PI-RADS) version 2 lexicon and on the diagnostic performance of prostate MRI to detect clinically significant prostate cancer (CS-PCa). An imaging database was searched for consecutive patients who underwent prostate MRI followed by MRI-ultrasound fusion biopsy from October 2015 through October 2017. The initial MRI reporting template used included only subheadings. In July 2016, the template was changed to a standardized PI-RADS-compliant structured template incorporating dropdown menus. Lesion, patient characteristics, pathology, and adherence to the PI-RADS lexicon were extracted from MRI reports and patient charts. Diagnostic performance of prostate MRI to detect CS-PCa using combined ultrasound-MRI fusion and systematic biopsy as a reference standard was assessed. Three hundred twenty-four lesions in 202 patients (average age, 67 years; average prostate-specific antigen level, 5.9 ng/mL) were analyzed, including 217 MRI peripheral zone (PZ) lesions, 84 MRI non-PZ lesions, and 23 additional PZ lesions found on systematic biopsy but missed on MRI. Thirty-three percent (106 of 324) were CS-PCa. Adherence to the PI-RADS lexicon improved from 32.9% (50 of 152) to 88.4% (152 of 172) (P < .0001) after introduction of the structured template. The sensitivity of prostate MRI for CS-PCa in the PZ increased from 53% to 70% (P = .011). There was no significant change in specificity (60% versus 55%, P = .458). A structured template with dropdown menus incorporating the PI-RADS lexicon and classification rules improves adherence to PI-RADS and may increase the diagnostic performance of prostate MRI for CS-PCa. Copyright © 2018 American College of Radiology. Published by Elsevier Inc. All rights reserved.

Probing the mechanism of fusion in a two-dimensional computer simulation.

PubMed Central

Chanturiya, Alexandr; Scaria, Puthurapamil; Kuksenok, Oleksandr; Woodle, Martin C

2002-01-01

A two-dimensional (2D) model of lipid bilayers was developed and used to investigate a possible role of membrane lateral tension in membrane fusion. We found that an increase of lateral tension in contacting monolayers of 2D analogs of liposomes and planar membranes could cause not only hemifusion, but also complete fusion when internal pressure is introduced in the model. With a certain set of model parameters it was possible to induce hemifusion-like structural changes by a tension increase in only one of the two contacting bilayers. The effect of lysolipids was modeled as an insertion of a small number of extra molecules into the cis or trans side of the interacting bilayers at different stages of simulation. It was found that cis insertion arrests fusion and trans insertion has no inhibitory effect on fusion. The possibility of protein participation in tension-driven fusion was tested in simulation, with one of two model liposomes containing a number of structures capable of reducing the area occupied by them in the outer monolayer. It was found that condensation of these structures was sufficient to produce membrane reorganization similar to that observed in simulations with "protein-free" bilayers. These data support the hypothesis that changes in membrane lateral tension may be responsible for fusion in both model phospholipid membranes and in biological protein-mediated fusion. PMID:12023230

Imaging the spectral reflectance properties of bipolar radiofrequency-fused bowel tissue

NASA Astrophysics Data System (ADS)

Clancy, Neil T.; Arya, Shobhit; Stoyanov, Danail; Du, Xiaofei; Hanna, George B.; Elson, Daniel S.

2015-07-01

Delivery of radiofrequency (RF) electrical energy is used during surgery to heat and seal tissue, such as vessels, allowing resection without blood loss. Recent work has suggested that this approach may be extended to allow surgical attachment of larger tissue segments for applications such as bowel anastomosis. In a large series of porcine surgical procedures bipolar RF energy was used to resect and re-seal the small bowel in vivo with a commercial tissue fusion device (Ligasure; Covidien PLC, USA). The tissue was then imaged with a multispectral imaging laparoscope to obtain a spectral datacube comprising both fused and healthy tissue. Maps of blood volume, oxygen saturation and scattering power were derived from the measured reflectance spectra using an optimised light-tissue interaction model. A 60% increase in reflectance of visible light (460-700 nm) was observed after fusion, with the tissue taking on a white appearance. Despite this the distinctive shape of the haemoglobin absorption spectrum was still noticeable in the 460-600 nm wavelength range. Scattering power increased in the fused region in comparison to normal serosa, while blood volume and oxygen saturation decreased. Observed fusion-induced changes in the reflectance spectrum are consistent with the biophysical changes induced through tissue denaturation and increased collagen cross-linking. The multispectral imager allows mapping of the spatial extent of these changes and classification of the zone of damaged tissue. Further analysis of the spectral data in parallel with histopathological examination of excised specimens will allow correlation of the optical property changes with microscopic alterations in tissue structure.

Friction stir welding of T joints of dissimilar aluminum alloy: A review

NASA Astrophysics Data System (ADS)

Thakare, Shrikant B.; Kalyankar, Vivek D.

2018-04-01

Aluminum alloys are preferred in the mechanical design due to their advantages like high strength, good corrosion resistance, low density and good weldability. In various industrial applications T joints configuration of aluminum alloys are used. In different fields, T joints having skin (horizontal sheet) strengthen by stringers (vertical sheets) were used to increase the strength of structure without increasing the weight. T joints are usually carried out by fusion welding which has limitations in joining of aluminum alloy due to significant distortion and metallurgical defects. Some aluminum alloys are even non weldable by fusion welding. The friction stir welding (FSW) has an excellent replacement of conventional fusion welding for T joints. In this article, FSW of T joints is reviewed by considering aluminum alloy and various joint geometries for defect analysis. The previous experiments carried out on T joints shows the factors such as tool geometry, fixturing device and joint configurations plays significant role in defect free joints. It is essential to investigate the material flow during FSW to know joining mechanism and the formation of joint. In this study the defect occurred in the FSW are studied for various joint configurations and parameters. Also the effect of the parameters and defects occurs on the tensile strength are studied. It is concluded that the T-joints of different joint configurations can be pretended successfully. Comparing to base metal some loss in tensile strength was observed in the weldments as well as overall reduction of the hardness in the thermos mechanically affected zone also observed.

Stability of concentration-related self-interstitial atoms in fusion material tungsten

NASA Astrophysics Data System (ADS)

Hong, Zhang; Shu-Long, Wen; Min, Pan; Zheng, Huang; Yong, Zhao; Xiang, Liu; Ji-Ming, Chen

2016-05-01

Based on the density functional theory, we calculated the structures of the two main possible self-interstitial atoms (SIAs) as well as the migration energy of tungsten (W) atoms. It was found that the difference of the <110> and <111> formation energies is 0.05-0.3 eV. Further analysis indicated that the stability of SIAs is closely related to the concentration of the defect. When the concentration of the point defect is high, <110> SIAs are more likely to exist, <111> SIAs are the opposite. In addition, the vacancy migration probability and self-recovery zones for these SIAs were researched by making a detailed comparison. The calculation provided a new viewpoint about the stability of point defects for self-interstitial configurations and would benefit the understanding of the control mechanism of defect behavior for this novel fusion material. Project supported by the Fundamental Research Funds for the Central Universities of Ministry of Education of China (Grant Nos. A0920502051411-5 and 2682014ZT30), the Program of International Science and Technology Cooperation, China (Grant No. 2013DFA51050), the National Magnetic Confinement Fusion Science Program, China (Grant Nos. 2011GB112001 and 2013GB110001), the National High Technology Research and Development Program of China (Grant No. 2014AA032701), the National Natural Science Foundation of China (Grant No. 11405138), the Southwestern Institute of Physics Funds, China, the Western Superconducting Technologies Company Limited, China, the Qingmiao Plan of Southwest Jiaotong University, China (Grant No. A0920502051517-6), and the China Postdoctoral Science Foundation (Grant No. 2014M560813).

DOE Office of Scientific and Technical Information (OSTI.GOV)

McLellan, Jason S.; Chen, Man; Chang, Jung-San

Respiratory syncytial virus (RSV) is a major cause of pneumonia and bronchiolitis in infants and elderly people. Currently there is no effective vaccine against RSV, but passive prophylaxis with neutralizing antibodies reduces hospitalizations. To investigate the mechanism of antibody-mediated RSV neutralization, we undertook structure-function studies of monoclonal antibody 101F, which binds a linear epitope in the RSV fusion glycoprotein. Crystal structures of the 101F antigen-binding fragment in complex with peptides from the fusion glycoprotein defined both the extent of the linear epitope and the interactions of residues that are mutated in antibody escape variants. The structure allowed for modeling ofmore » 101F in complex with trimers of the fusion glycoprotein, and the resulting models suggested that 101F may contact additional surfaces located outside the linear epitope. This hypothesis was supported by surface plasmon resonance experiments that demonstrated 101F bound the peptide epitope {approx}16,000-fold more weakly than the fusion glycoprotein. The modeling also showed no substantial clashes between 101F and the fusion glycoprotein in either the pre- or postfusion state, and cell-based assays indicated that 101F neutralization was not associated with blocking virus attachment. Collectively, these results provide a structural basis for RSV neutralization by antibodies that target a major antigenic site on the fusion glycoprotein.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deng,Y.; Liu, J.; Zheng, Q.

Entry of SARS coronavirus into its target cell requires large-scale structural transitions in the viral spike (S) glycoprotein in order to induce fusion of the virus and cell membranes. Here we describe the identification and crystal structures of four distinct a-helical domains derived from the highly conserved heptad-repeat (HR) regions of the S2 fusion subunit. The four domains are an antiparallel four-stranded coiled coil, a parallel trimeric coiled coil, a four-helix bundle, and a six-helix bundle that is likely the final fusogenic form of the protein. When considered together, the structural and thermodynamic features of the four domains suggest amore » possible mechanism whereby the HR regions, initially sequestered in the native S glycoprotein spike, are released and refold sequentially to promote membrane fusion. Our results provide a structural framework for understanding the control of membrane fusion and should guide efforts to intervene in the SARS coronavirus entry process.« less

Mitochondrial network complexity emerges from fission/fusion dynamics.

PubMed

Zamponi, Nahuel; Zamponi, Emiliano; Cannas, Sergio A; Billoni, Orlando V; Helguera, Pablo R; Chialvo, Dante R

2018-01-10

Mitochondrial networks exhibit a variety of complex behaviors, including coordinated cell-wide oscillations of energy states as well as a phase transition (depolarization) in response to oxidative stress. Since functional and structural properties are often interwinded, here we characterized the structure of mitochondrial networks in mouse embryonic fibroblasts using network tools and percolation theory. Subsequently we perturbed the system either by promoting the fusion of mitochondrial segments or by inducing mitochondrial fission. Quantitative analysis of mitochondrial clusters revealed that structural parameters of healthy mitochondria laid in between the extremes of highly fragmented and completely fusioned networks. We confirmed our results by contrasting our empirical findings with the predictions of a recently described computational model of mitochondrial network emergence based on fission-fusion kinetics. Altogether these results offer not only an objective methodology to parametrize the complexity of this organelle but also support the idea that mitochondrial networks behave as critical systems and undergo structural phase transitions.

Structural characterization of Mumps virus fusion protein core

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu Yueyong; Xu Yanhui; Lou Zhiyong

2006-09-29

The fusion proteins of enveloped viruses mediating the fusion between the viral and cellular membranes comprise two discontinuous heptad repeat (HR) domains located at the ectodomain of the enveloped glycoproteins. The crystal structure of the fusion protein core of Mumps virus (MuV) was determined at 2.2 A resolution. The complex is a six-helix bundle in which three HR1 peptides form a central highly hydrophobic coiled-coil and three HR2 peptides pack against the hydrophobic grooves on the surface of central coiled-coil in an oblique antiparallel manner. Fusion core of MuV, like those of simian virus 5 and human respiratory syncytium virus,more » forms typical 3-4-4-4-3 spacing. The similar charecterization in HR1 regions, as well as the existence of O-X-O motif in extended regions of HR2 helix, suggests a basic rule for the formation of the fusion core of viral fusion proteins.« less

[Research progress of multi-model medical image fusion and recognition].

PubMed

Zhou, Tao; Lu, Huiling; Chen, Zhiqiang; Ma, Jingxian

2013-10-01

Medical image fusion and recognition has a wide range of applications, such as focal location, cancer staging and treatment effect assessment. Multi-model medical image fusion and recognition are analyzed and summarized in this paper. Firstly, the question of multi-model medical image fusion and recognition is discussed, and its advantage and key steps are discussed. Secondly, three fusion strategies are reviewed from the point of algorithm, and four fusion recognition structures are discussed. Thirdly, difficulties, challenges and possible future research direction are discussed.

The effect of high energy concentration source irradiation on structure and properties of Fe-based bulk metallic glass

NASA Astrophysics Data System (ADS)

Pilarczyk, Wirginia

2016-06-01

Metallic glasses exhibit metastable structure and maintain this relatively stable amorphous state within certain temperature range. High intensity laser beam was used for the surface irradiation of Fe-Co-B-Si-Nb bulk metallic glasses. The variable parameter was laser beam pulse energy. For the analysis of structure and properties of bulk metallic glasses and their surface after laser remelting the X-ray analysis, microscopic observation and test of mechanical properties were carried out. Examination of the nanostructure of amorphous materials obtained by high pressure copper mold casting method and the irradiated with the use of TITAN 80-300 HRTEM was carried out. Nanohardness and reduced Young's modulus of particular amorphous and amorphous-crystalline material zone of the laser beam were examined with the use of Hysitron TI950 Triboindenter nanoindenter and with the use of Berkovich's indenter. The XRD and microscopic analysis showed that the test material is amorphous in its structure before irradiation. Microstructure observation with electron transmission microscopy gave information about alloy crystallization in the irradiated process. Identification of given crystal phases allows to determine the kind of crystal phases created in the first place and also further changes of phase composition of alloy. The main value of the nanohardness of the surface prepared by laser beam has the order of magnitude similar to bulk metallic glasses formed by casting process irrespective of the laser beam energy used. Research results analysis showed that the area between parent material and fusion zone is characterized by extraordinarily interesting structure which is and will be the subject of further analysis in the scope of bulk metallic glasses amorphous structure and high energy concentration source. The main goal of this work is the results' presentation of structure and chosen properties of the selected bulk metallic glasses after casting process and after irradiation process employing the high energy concentration sources.

Structural basis of influenza virus fusion inhibition by the antiviral drug Arbidol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kadam, Rameshwar U.; Wilson, Ian A.

The broad-spectrum antiviral drug Arbidol shows efficacy against influenza viruses by targeting the hemagglutinin (HA) fusion machinery. However, the structural basis of the mechanism underlying fusion inhibition by Arbidol has remained obscure, thereby hindering its further development as a specific and optimized influenza therapeutic. We determined crystal structures of Arbidol in complex with influenza virus HA from pandemic 1968 H3N2 and recent 2013 H7N9 viruses. Arbidol binds in a hydrophobic cavity in the HA trimer stem at the interface between two protomers. This cavity is distal to the conserved epitope targeted by broadly neutralizing stem antibodies and is ~16 Åmore » from the fusion peptide. Arbidol primarily makes hydrophobic interactions with the binding site but also induces some conformational rearrangements to form a network of inter- and intraprotomer salt bridges. By functioning as molecular glue, Arbidol stabilizes the prefusion conformation of HA that inhibits the large conformational rearrangements associated with membrane fusion in the low pH of the endosome. This unique binding mode compared with the small-molecule inhibitors of other class I fusion proteins enhances our understanding of how small molecules can function as fusion inhibitors and guides the development of broad-spectrum therapeutics against influenza virus.« less

To the non-local theory of cold nuclear fusion.

PubMed

Alexeev, Boris V

2014-10-01

In this paper, we revisit the cold fusion (CF) phenomenon using the generalized Bolzmann kinetics theory which can represent the non-local physics of this CF phenomenon. This approach can identify the conditions when the CF can take place as the soliton creation under the influence of the intensive sound waves. The vast mathematical modelling leads to affirmation that all parts of soliton move with the same velocity and with the small internal change of the pressure. The zone of the high density is shaped on the soliton's front. It means that the regime of the 'acoustic CF' could be realized from the position of the non-local hydrodynamics.

Membranes linked by trans-SNARE complexes require lipids prone to non-bilayer structure for progression to fusion.

PubMed

Zick, Michael; Stroupe, Christopher; Orr, Amy; Douville, Deborah; Wickner, William T

2014-01-01

Like other intracellular fusion events, the homotypic fusion of yeast vacuoles requires a Rab GTPase, a large Rab effector complex, SNARE proteins which can form a 4-helical bundle, and the SNARE disassembly chaperones Sec17p and Sec18p. In addition to these proteins, specific vacuole lipids are required for efficient fusion in vivo and with the purified organelle. Reconstitution of vacuole fusion with all purified components reveals that high SNARE levels can mask the requirement for a complex mixture of vacuole lipids. At lower, more physiological SNARE levels, neutral lipids with small headgroups that tend to form non-bilayer structures (phosphatidylethanolamine, diacylglycerol, and ergosterol) are essential. Membranes without these three lipids can dock and complete trans-SNARE pairing but cannot rearrange their lipids for fusion. DOI: http://dx.doi.org/10.7554/eLife.01879.001.

On the Mechanisms for Martensite Formation in YAG Laser Welded Austenitic NiTi

NASA Astrophysics Data System (ADS)

Oliveira, J. P.; Braz Fernandes, F. M.; Miranda, R. M.; Schell, N.

2016-03-01

Extensive work has been reported on the microstructure of laser-welded NiTi alloys either superelastic or with shape memory effect, motivated by the fact that the microstructure affects the functional properties. However, some effects of laser beam/material interaction with these alloys have not yet been discussed. This paper aims to discuss the mechanisms for the occurrence of martensite in the heat-affected zone and in the fusion zone at room temperature, while the base material is fully austenitic. For this purpose, synchrotron radiation was used together with a simple thermal analytic mathematical model. Two distinct mechanisms are proposed for the presence of martensite in different zones of a weld, which affects the mechanical and functional behavior of a welded component.

Mutagenesis of the La Crosse Virus glycoprotein supports a role for Gc (1066-1087) as the fusion peptide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Plassmeyer, Matthew L.; Graduate Group Molecular and Cell Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6058; Soldan, Samantha S.

The La Crosse Virus (LACV) M segment encodes two glycoproteins (Gn and Gc), and plays a critical role in the neuropathogenesis of LACV infection as the primary determinant of neuroinvasion. A recent study from our group demonstrated that the region comprising the membrane proximal two-thirds of Gc, amino acids 860-1442, is critical in mediating LACV fusion and entry. Furthermore, computational analysis identified structural similarities between a portion of this region, amino acids 970-1350, and the E1 fusion protein of two alphaviruses: Sindbis virus and Semliki Forrest virus (SFV). Within the region 970-1350, a 22-amino-acid hydrophobic segment (1066-1087) is predicted tomore » correlate structurally with the fusion peptides of class II fusion proteins. We performed site-directed mutagenesis of key amino acids in this 22-amino acid segment and determined the functional consequences of these mutations on fusion and entry. Several mutations within this hydrophobic domain affected glycoprotein expression to some extent, but all mutations either shifted the pH threshold of fusion below that of the wild-type protein, reduced fusion efficiency, or abrogated cell-to-cell fusion and pseudotype entry altogether. These results, coupled with the aforementioned computational modeling, suggest that the LACV Gc functions as a class II fusion protein and support a role for the region Gc 1066-1087 as a fusion peptide.« less

NMR structure and localization of a large fragment of the SARS-CoV fusion protein: Implications in viral cell fusion.

PubMed

Mahajan, Mukesh; Chatterjee, Deepak; Bhuvaneswari, Kannaian; Pillay, Shubhadra; Bhattacharjya, Surajit

2018-02-01

The lethal Coronaviruses (CoVs), Severe Acute Respiratory Syndrome-associated Coronavirus (SARS-CoV) and most recently Middle East Respiratory Syndrome Coronavirus, (MERS-CoV) are serious human health hazard. A successful viral infection requires fusion between virus and host cells carried out by the surface spike glycoprotein or S protein of CoV. Current models propose that the S2 subunit of S protein assembled into a hexameric helical bundle exposing hydrophobic fusogenic peptides or fusion peptides (FPs) for membrane insertion. The N-terminus of S2 subunit of SARS-CoV reported to be active in cell fusion whereby FPs have been identified. Atomic-resolution structure of FPs derived either in model membranes or in membrane mimic environment would glean insights toward viral cell fusion mechanism. Here, we have solved 3D structure, dynamics and micelle localization of a 64-residue long fusion peptide or LFP in DPC detergent micelles by NMR methods. Micelle bound structure of LFP is elucidated by the presence of discretely folded helical and intervening loops. The C-terminus region, residues F42-Y62, displays a long hydrophobic helix, whereas the N-terminus is defined by a short amphipathic helix, residues R4-Q12. The intervening residues of LFP assume stretches of loops and helical turns. The N-terminal helix is sustained by close aromatic and aliphatic sidechain packing interactions at the non-polar face. 15 N{ 1 H}NOE studies indicated dynamical motion, at ps-ns timescale, of the helices of LFP in DPC micelles. PRE NMR showed that insertion of several regions of LFP into DPC micelle core. Together, the current study provides insights toward fusion mechanism of SARS-CoV. Copyright © 2017 Elsevier B.V. All rights reserved.

Effects of Welding Parameters on Mechanical Properties in Electron Beam Welded CuCrZr Alloy Plates

NASA Astrophysics Data System (ADS)

Jaypuria, Sanjib; Doshi, Nirav; Pratihar, Dilip Kumar

2018-03-01

CuCrZr alloys are attractive structural materials for plasma-facing components (PFC) and heat sink element in the International Thermonuclear Experimental Reactor (ITER) fusion reactors. This material has gained so much attention because of its high thermal conductivity and fracture toughness, high resistance to radiation damage and stability at elevated temperatures. The objective of this work is to study the effects of electron beam welding parameters on the mechanical strength of the butt welded CuCrZr joint. Taguchi method is used as the design of experiments to optimize the input parameters, such as accelerating voltage, beam current, welding speed, oscillation amplitude and frequency. The joint strength and ductility are the desired responses, which are measured through ultimate tensile strength and percent elongation, respectively. Accelerating voltage and welding speed are found to have significant influence on the strength. A combination of low amplitude and high-frequency oscillation is suggested for the higher joint strength and ductility. There is a close agreement between Taguchi predicted results and experimental ones. Fractographic analysis of joint and weld zone analysis are carried out to study the failure behaviour and microstructural variation in the weld zone, respectively.

Effects of SO42- ions on the corrosion of GH3535 weld joint in FLiNaK molten salt

NASA Astrophysics Data System (ADS)

Zhu, Yasheng; Qiu, Jie; Hou, Juan; Liu, Wenguan; Chen, Huaican; Ai, Hua; Yu, Guojun; Wang, Jianqiang; Zhou, Xingtai

2017-08-01

The present work studied the impact of SO42- ions on the corrosion behaviors of GH3535 weld joint in FLiNaK molten salt. The concentration of SO42- ions in the FLiNaK molten salt was controlled by adjusting the quantity of Na2SO4 added into the salt. Results indicate that the SO42- ions in the FLiNaK salt speed up the corrosion rate remarkably by promoting the dissolution of Cr from the alloy matrix into the salt. With the concentration of SO42- ions in the FLiNaK salt increases from 100 ppm to 1000 ppm, the weight losses and the Cr depletion layer depths of the corroded specimens increase linearly. Even in the case of the heavy corrosion attack caused by the SO42- ions, the corrosion performance is similar between the base zone and fusion zone in the GH3535 weld joint. It is demonstrated that the structural diversity caused by the welding process has little impact on the corrosion performances of GH3535 alloy in FLiNaK molten salt.

Characterization of the fusion core in zebrafish endogenous retroviral envelope protein

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Jian; State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, Hubei 430071; Zhang, Huaidong

2015-05-08

Zebrafish endogenous retrovirus (ZFERV) is the unique endogenous retrovirus in zebrafish, as yet, containing intact open reading frames of its envelope protein gene in zebrafish genome. Similarly, several envelope proteins of endogenous retroviruses in human and other mammalian animal genomes (such as syncytin-1 and 2 in human, syncytin-A and B in mouse) were identified and shown to be functional in induction of cell–cell fusion involved in placental development. ZFERV envelope protein (Env) gene appears to be also functional in vivo because it is expressible. After sequence alignment, we found ZFERV Env shares similar structural profiles with syncytin and other type Imore » viral envelopes, especially in the regions of N- and C-terminal heptad repeats (NHR and CHR) which were crucial for membrane fusion. We expressed the regions of N + C protein in the ZFERV Env (residues 459–567, including predicted NHR and CHR) to characterize the fusion core structure. We found N + C protein could form a stable coiled-coil trimer that consists of three helical NHR regions forming a central trimeric core, and three helical CHR regions packing into the grooves on the surface of the central core. The structural characterization of the fusion core revealed the possible mechanism of fusion mediated by ZFERV Env. These results gave comprehensive explanation of how the ancient virus infects the zebrafish and integrates into the genome million years ago, and showed a rational clue for discovery of physiological significance (e.g., medicate cell–cell fusion). - Highlights: • ZFERV Env shares similar structural profiles with syncytin and other type I viral envelopes. • The fusion core of ZFERV Env forms stable coiled-coil trimer including three NHRs and three CHRs. • The structural mechanism of viral entry mediated by ZFERV Env is disclosed. • The results are helpful for further discovery of physiological function of ZFERV Env in zebrafish.« less

Structure of the Ebola Virus Glycoprotein Bound to An Antibody From a Human Survivor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, J.E.; Fusco, M.L.; Hessell, A.J.

2009-05-20

Ebola virus (EBOV) entry requires the surface glycoprotein (GP) to initiate attachment and fusion of viral and host membranes. Here we report the crystal structure of EBOV GP in its trimeric, pre-fusion conformation (GP1+GP2) bound to a neutralizing antibody, KZ52, derived from a human survivor of the 1995 Kikwit outbreak. Three GP1 viral attachment subunits assemble to form a chalice, cradled by the GP2 fusion subunits, while a novel glycan cap and projected mucin-like domain restrict access to the conserved receptor-binding site sequestered in the chalice bowl. The glycocalyx surrounding GP is likely central to immune evasion and may explainmore » why survivors have insignificant neutralizing antibody titres. KZ52 recognizes a protein epitope at the chalice base where it clamps several regions of the pre-fusion GP2 to the amino terminus of GP1. This structure provides a template for unraveling the mechanism of EBOV GP-mediated fusion and for future immunotherapeutic development.« less

Monte Carlo calculations of the incineration of plutonium and minor actinides of laser fusion inertial confinement fusion fission energy (LIFE) engine

NASA Astrophysics Data System (ADS)

Adem, ACIR; Eşref, BAYSAL

2018-07-01

In this paper, neutronic analysis in a laser fusion inertial confinement fusion fission energy (LIFE) engine fuelled plutonium and minor actinides using a MCNP codes was investigated. LIFE engine fuel zone contained 10 vol% TRISO particles and 90 vol% natural lithium coolant mixture. TRISO fuel compositions have Mod①: reactor grade plutonium (RG-Pu), Mod②: weapon grade plutonium (WG-Pu) and Mod③: minor actinides (MAs). Tritium breeding ratios (TBR) were computed as 1.52, 1.62 and 1.46 for Mod①, Mod② and Mod③, respectively. The operation period was computed as ∼21 years when the reference TBR > 1.05 for a self-sustained reactor for all investigated cases. Blanket energy multiplication values (M) were calculated as 4.18, 4.95 and 3.75 for Mod①, Mod② and Mod③, respectively. The burnup (BU) values were obtained as ∼1230, ∼1550 and ∼1060 GWd tM–1, respectively. As a result, the higher BU were provided with using TRISO particles for all cases in LIFE engine.

Dynamic tubulation of mitochondria drives mitochondrial network formation.

PubMed

Wang, Chong; Du, Wanqing; Su, Qian Peter; Zhu, Mingli; Feng, Peiyuan; Li, Ying; Zhou, Yichen; Mi, Na; Zhu, Yueyao; Jiang, Dong; Zhang, Senyan; Zhang, Zerui; Sun, Yujie; Yu, Li

2015-10-01

Mitochondria form networks. Formation of mitochondrial networks is important for maintaining mitochondrial DNA integrity and interchanging mitochondrial material, whereas disruption of the mitochondrial network affects mitochondrial functions. According to the current view, mitochondrial networks are formed by fusion of individual mitochondria. Here, we report a new mechanism for formation of mitochondrial networks through KIF5B-mediated dynamic tubulation of mitochondria. We found that KIF5B pulls thin, highly dynamic tubules out of mitochondria. Fusion of these dynamic tubules, which is mediated by mitofusins, gives rise to the mitochondrial network. We further demonstrated that dynamic tubulation and fusion is sufficient for mitochondrial network formation, by reconstituting mitochondrial networks in vitro using purified fusion-competent mitochondria, recombinant KIF5B, and polymerized microtubules. Interestingly, KIF5B only controls network formation in the peripheral zone of the cell, indicating that the mitochondrial network is divided into subzones, which may be constructed by different mechanisms. Our data not only uncover an essential mechanism for mitochondrial network formation, but also reveal that different parts of the mitochondrial network are formed by different mechanisms.

Solid-State Nuclear Magnetic Resonance Investigation of the Structural Topology and Lipid Interactions of a Viral Fusion Protein Chimera Containing the Fusion Peptide and Transmembrane Domain.

PubMed

Yao, Hongwei; Lee, Myungwoon; Liao, Shu-Yu; Hong, Mei

2016-12-13

The fusion peptide (FP) and transmembrane domain (TMD) of viral fusion proteins play important roles during virus-cell membrane fusion, by inducing membrane curvature and transient dehydration. The structure of the water-soluble ectodomain of viral fusion proteins has been extensively studied crystallographically, but the structures of the FP and TMD bound to phospholipid membranes are not well understood. We recently investigated the conformations and lipid interactions of the separate FP and TMD peptides of parainfluenza virus 5 (PIV5) fusion protein F using solid-state nuclear magnetic resonance. These studies provide structural information about the two domains when they are spatially well separated in the fusion process. To investigate how these two domains are structured relative to each other in the postfusion state, when the ectodomain forms a six-helix bundle that is thought to force the FP and TMD together in the membrane, we have now expressed and purified a chimera of the FP and TMD, connected by a Gly-Lys linker, and measured the chemical shifts and interdomain contacts of the protein in several lipid membranes. The FP-TMD chimera exhibits α-helical chemical shifts in all the membranes examined and does not cause strong curvature of lamellar membranes or membranes with negative spontaneous curvature. These properties differ qualitatively from those of the separate peptides, indicating that the FP and TMD interact with each other in the lipid membrane. However, no 13 C- 13 C cross peaks are observed in two-dimensional correlation spectra, suggesting that the two helices are not tightly associated. These results suggest that the ectodomain six-helix bundle does not propagate into the membrane to the two hydrophobic termini. However, the loosely associated FP and TMD helices are found to generate significant negative Gaussian curvature to membranes that possess spontaneous positive curvature, consistent with the notion that the FP-TMD assembly may facilitate the transition of the membrane from hemifusion intermediates to the fusion pore.

Single-Pixel Optical Fluctuation Analysis of Calcium Channel Function in Active Zones of Motor Nerve Terminals

PubMed Central

Luo, Fujun; Dittrich, Markus; Stiles, Joel R.; Meriney, Stephen D.

2011-01-01

We used high-resolution fluorescence imaging and single-pixel optical fluctuation analysis to estimate the opening probability of individual voltage-gated calcium (Ca2+) channels during an action potential and the number of such Ca2+ channels within active zones of frog neuromuscular junctions. Analysis revealed ~36 Ca2+ channels within each active zone, similar to the number of docked synaptic vesicles but far less than the total number of transmembrane particles reported based on freeze-fracture analysis (~200–250). The probability that each channel opened during an action potential was only ~0.2. These results suggest why each active zone averages only one quantal release event during every other action potential, despite a substantial number of docked vesicles. With sparse Ca2+ channels and low opening probability, triggering of fusion for each vesicle is primarily controlled by Ca2+ influx through individual Ca2+ channels. In contrast, the entire synapse is highly reliable because it contains hundreds of active zones. PMID:21813687

Microstructure and Hardness Profiles of Bifocal Laser-Welded DP-HSLA Steel Overlap Joints

NASA Astrophysics Data System (ADS)

Grajcar, A.; Matter, P.; Stano, S.; Wilk, Z.; Różański, M.

2017-04-01

The article presents results related to the bifocal laser welding of overlap joints made of HSLA and DP high-strength steels. The joints were made using a disk laser and a head enabling the 50-50% distribution of laser power. The effects of the laser welding rates and the distance between laser spots on morphological features and hardness profiles were analyzed. It was established that the positioning of beams at angles of 0° or 90° determined the hardness of the individual zones of the joints, without causing significant differences in microstructures of the steels. Microstructural features were inspected using scanning electron microscopy. Both steels revealed primarily martensitic-bainitic microstructures in the fusion zone and in the heat-affected zone. Mixed multiphase microstructures were revealed in the inter-critical heat-affected zone of the joint. The research involved the determination of parameters making it possible to reduce the hardness of joints and prevent the formation of the soft zone in the dual-phase steel.

Inverted micellar intermediates and the transitions between lamellar, cubic, and inverted hexagonal lipid phases. II. Implications for membrane-membrane interactions and membrane fusion.

PubMed Central

Siegel, D P

1986-01-01

Results of a kinetic model of thermotropic L alpha----HII phase transitions are used to predict the types and order-of-magnitude rates of interactions between unilamellar vesicles that can occur by intermediates in the L alpha----HII phase transition. These interactions are: outer monolayer lipid exchange between vesicles; vesicle leakage subsequent to aggregation; and (only in systems with ratios of L alpha and HII phase structural dimensions in a certain range or with unusually large bilayer lateral compressibilities) vesicle fusion with retention of contents. It was previously proposed that inverted micellar structures mediate membrane fusion. These inverted micellar structures are thought to form in all systems with such transitions. However, I show that membrane fusion probably occurs via structures that form from these inverted micellar intermediates, and that fusion should occur in only a sub-set of lipid systems that can adopt the HII phase. For single-component phosphatidylethanolamine (PE) systems with thermotropic L alpha----HII transitions, lipid exchange should be observed starting at temperatures several degrees below TH and at all higher temperatures, where TH is the L alpha----HII transition temperature. At temperatures above TH, the HII phase forms between apposed vesicles, and eventually ruptures them (leakage). In most single-component PE systems, fusion via L alpha----HII transition intermediates should not occur. This is the behavior observed by Bentz, Ellens, Lai, Szoka, et al. in PE vesicle systems. Fusion is likely to occur under circumstances in which multilamellar samples of lipid form the so-called "inverted cubic" or "isotropic" phase. This is as observed in the mono-methyl DOPE system (Ellens, H., J. Bentz, and F. C. Szoka. 1986. Fusion of phosphatidylethanolamine containing liposomes and the mechanism of the L alpha-HII phase transition. Biochemistry. In press.) In lipid systems with L alpha----HII transitions driven by cation binding (e.g., Ca2+-cardiolipin), fusion should be more frequent than in thermotropic systems. PMID:3719075

Fusion Imaging for Procedural Guidance.

PubMed

Wiley, Brandon M; Eleid, Mackram F; Thaden, Jeremy J

2018-05-01

The field of percutaneous structural heart interventions has grown tremendously in recent years. This growth has fueled the development of new imaging protocols and technologies in parallel to help facilitate these minimally-invasive procedures. Fusion imaging is an exciting new technology that combines the strength of 2 imaging modalities and has the potential to improve procedural planning and the safety of many commonly performed transcatheter procedures. In this review we discuss the basic concepts of fusion imaging along with the relative strengths and weaknesses of static vs dynamic fusion imaging modalities. This review will focus primarily on echocardiographic-fluoroscopic fusion imaging and its application in commonly performed transcatheter structural heart procedures. Copyright © 2017 Sociedad Española de Cardiología. Published by Elsevier España, S.L.U. All rights reserved.

Characterizing the astrophysical S factor for 12C+12C fusion with wave-packet dynamics

NASA Astrophysics Data System (ADS)

Diaz-Torres, Alexis; Wiescher, Michael

2018-05-01

A quantitative study of the astrophysically important subbarrier fusion of 12C+12C is presented. Low-energy collisions are described in the body-fixed reference frame using wave-packet dynamics within a nuclear molecular picture. A collective Hamiltonian drives the time propagation of the wave packet through the collective potential-energy landscape. The fusion imaginary potential for specific dinuclear configurations is crucial for understanding the appearance of resonances in the fusion cross section. The theoretical subbarrier fusion cross sections explain some observed resonant structures in the astrophysical S factor. These cross sections monotonically decline towards stellar energies. The structures in the data that are not explained are possibly due to cluster effects in the nuclear molecule, which need to be included in the present approach.

Religion in the Public Schools--The Twilight Zones.

ERIC Educational Resources Information Center

Bilger, Jean

This paper analyzes two parts of the First Amendment, the establishment and free exercise clauses, and discusses related court cases. The establishment clause prohibits the fusion of governmental and religious functions or the dependency of one on the other. The free exercise clause guarantees every person the freedom to choose his or her own…

Comparative Sensor Fusion between Hyperspectral and Multispectral Remote Sensing Data for Monitoring Microcystin Distribution in Lake Erie

EPA Science Inventory

Urban growth and agricultural production have caused an influx of nutrients into Lake Erie, leading to eutrophic zones. These conditions result in the formation of algal blooms, some of which are toxic due to the presence of Microcystis (a cyanobacteria), which produces the hepat...

Hot-cracking studies of Inconel 718 weld- heat-affected zones

NASA Technical Reports Server (NTRS)

Thompson, E. G.

1969-01-01

Hot ductility tests, gas-tungsten-arc fillerless fusion tests, and circle patch-weld-restraint tests were conducted on Inconel 718 to better understand and correlate the weldability /resistance to hot cracking/ of the alloy. A correlation of the test results with composition, heat-treat condition, grain size, and microstructure was made.

Chamber free fusion welding root side purging method and apparatus

NASA Technical Reports Server (NTRS)

Mcgee, William F. (Inventor); Rybicki, Daniel J. (Inventor)

1993-01-01

A method and apparati are presented for non-chamber root side purging in fusion welding of oxygen reactive metals which require that the molten weld zone and local solid areas of the weld seam remaining at high temperatures be shielded from normal atmosphere to prevent degradation of the welded area. The apparati provide an inert atmosphere to the root side of a weld joint through a porous medium whereby the jet-like thrust of the plasma arc actually draws the continuously supplied inert atmosphere into the path of the molten or high temperature solid weld zone. The porous medium is configured so it can be placed at the borders of the weld seam and substantially parallel to the seam without restricting the view of the root side of the seam. The inert gas is dispersed evenly through the porous media and across the weld seam, at the point of arc penetration and in front of and behind the arc. The apparati can be constructed so as to limit the amount of inert gas flow and can be mobile and travel synchronously with the welding arc.

Chamber free fusion welding root side purging method and apparatus

NASA Technical Reports Server (NTRS)

Dailey, J. R. (Inventor); Mcgee, William F. (Inventor); Rybicki, Daniel J. (Inventor)

1995-01-01

A method and apparati are presented for non-chamber root side purging in fusion welding of oxygen reactive metals which require that the molten weld zone and local solid areas of the weld seam remaining at high temperatures be shielded from normal atmosphere to prevent degradation of the welded area. The apparati provide an inert atmosphere to the root side of a weld joint through a porous medium whereby the jet-like thrust of the plasma arc actually draws the continuously supplied inert atmosphere into the path of the molten or high temperature solid weld zone. The porous medium is configured so it can be placed at the borders of the weld seam and substantially parallel to the seam without restricting the view of the root side of the seam. The inert gas is dispersed evenly through the porous media and across the weld seam, at the point of arc penetration and in front of and behind the arc. The apparati can be constructed so as to limit the amount of inert gas flow and can be mobile and travel synchronously with the welding arc.

High-temperature calibration of a multi-anvil high pressure apparatus

NASA Astrophysics Data System (ADS)

Sokol, Alexander G.; Borzdov, Yury M.; Palyanov, Yury N.; Khokhryakov, Alexander F.

2015-04-01

Fusion and solidification of Al and Ag samples, as well as Fe93-Al3-C4, Fe56-Co37-Al3-C4, and Fe57.5-Co38-Al1-Pb0.5-C3 alloys (in wt%), have been investigated at 6.3 GPa. Heater power jumps due to heat consumption and release on metal fusion and solidification, respectively, were used to calibrate the thermal electromotive force of the thermocouple against the melting points (mp) for Ag and Al. Thus, obtained corrections are +100°C (for sample periphery) and +65°C (center) within the 1070-1320°C range. For small samples positioned randomly in the low-gradient zone of a high pressure cell, the corrections should be +80°C and +84°C at the temperatures 1070°C and 1320°C, respectively. The temperature contrast recorded in the low-gradient cell zone gives an error about ±17°C. The method has been applied to identify the mp of the systems, which is especially important for temperature-gradient growth of large type IIa synthetic diamonds.

PWSCC Susceptibility in Heat Affected Zones of Alloy 600

NASA Astrophysics Data System (ADS)

Couvant, Thierry; Brossier, Thomas; Cossange, Christian

The recent field experience and several experimental results have shown the possible deleterious effect of a heat affected zone (HAZ) induced by welding on the susceptibility to the stress corrosion cracking (SCC) of Alloy 600 of bottom penetrations exposed to primary water of PWRs. This work tried to quantify the increasing susceptibility to initiation and crack propagation in 600/182 HAZ. The rolled plate did not exhibit any susceptibility to SCC except for a cold work higher than 10% typically. By contrast, the weld metal was well known for its high susceptibility to SCC. Metallurgical and mechanical characterizations of the HAZ indicated a slight gradient of Vickers micro hardness close to the fusion line (up to few mm) and a lack of intergranular precipitates up to 500 µm from the fusion line. SCC tests clearly demonstrated that a non-susceptible plate may exhibit a significant susceptibility to SCC propagation in the HAZ. Results of initiation tests did not allow to observe any SCC in the base metal, due to the high susceptibility to SCC of the weld.

Tensile Fracture Behavior and Failure Mechanism of Additively-Manufactured AISI 4140 Low Alloy Steel by Laser Engineered Net Shaping

PubMed Central

Kim, Hoyeol; Liu, Zhichao; Cong, Weilong; Zhang, Hong-Chao

2017-01-01

AISI 4140 powder was directly deposited on AISI 4140 wrought substrate using laser engineered net shaping (LENS) to investigate the compatibility of a LENS-deposited part with the substrate. Tensile testing at room temperature was performed to evaluate the interface bond performance and fracture behavior of the test specimens. All the samples failed within the as-deposited zone, indicating that the interfacial bond is stronger than the interlayer bond inside the deposit. The fracture surfaces were analyzed using scanning electron microscopy (SEM) and energy disperse X-ray spectrometry (EDS). Results show that the tensile fracture failure of the as-deposited part is primarily affected by lack-of-fusion defects, carbide precipitation, and oxide particles inclusions, which causes premature failure of the deposit by deteriorating the mechanical properties and structural integrity. PMID:29120374

Tensile Fracture Behavior and Failure Mechanism of Additively-Manufactured AISI 4140 Low Alloy Steel by Laser Engineered Net Shaping.

PubMed

Kim, Hoyeol; Liu, Zhichao; Cong, Weilong; Zhang, Hong-Chao

2017-11-09

AISI 4140 powder was directly deposited on AISI 4140 wrought substrate using laser engineered net shaping (LENS) to investigate the compatibility of a LENS-deposited part with the substrate. Tensile testing at room temperature was performed to evaluate the interface bond performance and fracture behavior of the test specimens. All the samples failed within the as-deposited zone, indicating that the interfacial bond is stronger than the interlayer bond inside the deposit. The fracture surfaces were analyzed using scanning electron microscopy (SEM) and energy disperse X-ray spectrometry (EDS). Results show that the tensile fracture failure of the as-deposited part is primarily affected by lack-of-fusion defects, carbide precipitation, and oxide particles inclusions, which causes premature failure of the deposit by deteriorating the mechanical properties and structural integrity.

Structural and kinetic analysis of the unnatural fusion protein 4-coumaroyl-CoA ligase::stilbene synthase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yechun; Yi, Hankuil; Wang, Melissa

2012-10-24

To increase the biochemical efficiency of biosynthetic systems, metabolic engineers have explored different approaches for organizing enzymes, including the generation of unnatural fusion proteins. Previous work aimed at improving the biosynthesis of resveratrol, a stilbene associated a range of health-promoting activities, in yeast used an unnatural engineered fusion protein of Arabidopsis thaliana (thale cress) 4-coumaroyl-CoA ligase (At4CL1) and Vitis vinifera (grape) stilbene synthase (VvSTS) to increase resveratrol levels 15-fold relative to yeast expressing the individual enzymes. Here we present the crystallographic and biochemical analysis of the 4CL::STS fusion protein. Determination of the X-ray crystal structure of 4CL::STS provides the firstmore » molecular view of an artificial didomain adenylation/ketosynthase fusion protein. Comparison of the steady-state kinetic properties of At4CL1, VvSTS, and 4CL::STS demonstrates that the fusion protein improves catalytic efficiency of either reaction less than 3-fold. Structural and kinetic analysis suggests that colocalization of the two enzyme active sites within 70 {angstrom} of each other provides the basis for enhanced in vivo synthesis of resveratrol.« less

Effect of Welding Heat Input on Microstructure and Texture of Inconel 625 Weld Overlay Studied Using the Electron Backscatter Diffraction Method

NASA Astrophysics Data System (ADS)

Kim, Joon-Suk; Lee, Hae-Woo

2016-12-01

The grain size and the texture of three specimens prepared at different heat inputs were determined using optical microscopy and the electron backscatter diffraction method of scanning electron microscopy. Each specimen was equally divided into fusion line zone (FLZ), columnar dendrite zone (CDZ), and surface zone (SZ), according to the location of the weld. Fine dendrites were observed in the FLZ, coarse dendrites in the CDZ, and dendrites grew perpendicular to the FLZ and CDZ. As the heat input increased, the melted zone in the vicinity of the FLZ widened due to the higher Fe content. A lower image quality value was observed for the FLZ compared to the other zones. The results of grain size measurement in each zone showed that the grain size of the SZ became larger as the heat input increased. From the inverse pole figure (IPF) map in the normal direction (ND) and the rolling direction (RD), as the heat input increased, a specific orientation was formed. However, a dominant [001] direction was observed in the RD IPF map.

Local zone-wise elastic-plastic constitutive parameters of Laser-welded aluminium alloy 6061 using digital image correlation

NASA Astrophysics Data System (ADS)

Bai, Ruixiang; Wei, Yuepeng; Lei, Zhenkun; Jiang, Hao; Tao, Wang; Yan, Cheng; Li, Xiaolei

2018-02-01

The mechanical properties of aluminium alloys can be affected by the local high temperature in laser welding. In this paper, an inversion identification method of local zone-wise elastic-plastic constitutive parameters for laser welding of aluminium alloy 6061 was proposed based on full-field optical measurement data using digital image correlation (DIC). Three regions, i.e., the fusion zone, heat-affected zone, and base zone, of the laser-welded joint were distinguished by means of microstructure optical observation and micrometer hardness measurement. The stress data were obtained using a laser-welded specimen via a uniaxial tensile test. Meanwhile, the local strain data of the laser-welded specimen were obtained by the DIC technique. Thus, the stress-strain relationship for different local regions was established. Finally, the constitutive parameters of the Ramberg-Osgood model were identified by least-square fitting to the experimental stress-strain data. Experimental results revealed that the mechanical properties of the local zones of the welded joints clearly weakened, and these results are consistent with the results of the hardness measurement.

An Alternative Time Metric to Modified Tau for Unmanned Aircraft System Detect And Avoid

NASA Technical Reports Server (NTRS)

Wu, Minghong G.; Bageshwar, Vibhor L.; Euteneuer, Eric A.

2017-01-01

A new horizontal time metric, Time to Protected Zone, is proposed for use in the Detect and Avoid (DAA) Systems equipped by unmanned aircraft systems (UAS). This time metric has three advantages over the currently adopted time metric, modified tau: it corresponds to a physical event, it is linear with time, and it can be directly used to prioritize intruding aircraft. The protected zone defines an area around the UAS that can be a function of each intruding aircraft's surveillance measurement errors. Even with its advantages, the Time to Protected Zone depends explicitly on encounter geometry and may be more sensitive to surveillance sensor errors than modified tau. To quantify its sensitivity, simulation of 972 encounters using realistic sensor models and a proprietary fusion tracker is performed. Two sensitivity metrics, the probability of time reversal and the average absolute time error, are computed for both the Time to Protected Zone and modified tau. Results show that the sensitivity of the Time to Protected Zone is comparable to that of modified tau if the dimensions of the protected zone are adequately defined.

Hendra virus fusion protein transmembrane domain contributes to pre-fusion protein stability

PubMed Central

Webb, Stacy; Nagy, Tamas; Moseley, Hunter; Fried, Michael; Dutch, Rebecca

2017-01-01

Enveloped viruses utilize fusion (F) proteins studding the surface of the virus to facilitate membrane fusion with a target cell membrane. Fusion of the viral envelope with a cellular membrane is required for release of viral genomic material, so the virus can ultimately reproduce and spread. To drive fusion, the F protein undergoes an irreversible conformational change, transitioning from a metastable pre-fusion conformation to a more thermodynamically stable post-fusion structure. Understanding the elements that control stability of the pre-fusion state and triggering to the post-fusion conformation is important for understanding F protein function. Mutations in F protein transmembrane (TM) domains implicated the TM domain in the fusion process, but the structural and molecular details in fusion remain unclear. Previously, analytical ultracentrifugation was utilized to demonstrate that isolated TM domains of Hendra virus F protein associate in a monomer-trimer equilibrium (Smith, E. C., Smith, S. E., Carter, J. R., Webb, S. R., Gibson, K. M., Hellman, L. M., Fried, M. G., and Dutch, R. E. (2013) J. Biol. Chem. 288, 35726–35735). To determine factors driving this association, 140 paramyxovirus F protein TM domain sequences were analyzed. A heptad repeat of β-branched residues was found, and analysis of the Hendra virus F TM domain revealed a heptad repeat leucine-isoleucine zipper motif (LIZ). Replacement of the LIZ with alanine resulted in dramatically reduced TM-TM association. Mutation of the LIZ in the whole protein resulted in decreased protein stability, including pre-fusion conformation stability. Together, our data suggest that the heptad repeat LIZ contributed to TM-TM association and is important for F protein function and pre-fusion stability. PMID:28213515

Hendra virus fusion protein transmembrane domain contributes to pre-fusion protein stability.

PubMed

Webb, Stacy; Nagy, Tamas; Moseley, Hunter; Fried, Michael; Dutch, Rebecca

2017-04-07

Enveloped viruses utilize fusion (F) proteins studding the surface of the virus to facilitate membrane fusion with a target cell membrane. Fusion of the viral envelope with a cellular membrane is required for release of viral genomic material, so the virus can ultimately reproduce and spread. To drive fusion, the F protein undergoes an irreversible conformational change, transitioning from a metastable pre-fusion conformation to a more thermodynamically stable post-fusion structure. Understanding the elements that control stability of the pre-fusion state and triggering to the post-fusion conformation is important for understanding F protein function. Mutations in F protein transmembrane (TM) domains implicated the TM domain in the fusion process, but the structural and molecular details in fusion remain unclear. Previously, analytical ultracentrifugation was utilized to demonstrate that isolated TM domains of Hendra virus F protein associate in a monomer-trimer equilibrium (Smith, E. C., Smith, S. E., Carter, J. R., Webb, S. R., Gibson, K. M., Hellman, L. M., Fried, M. G., and Dutch, R. E. (2013) J. Biol. Chem. 288, 35726-35735). To determine factors driving this association, 140 paramyxovirus F protein TM domain sequences were analyzed. A heptad repeat of β-branched residues was found, and analysis of the Hendra virus F TM domain revealed a heptad repeat leucine-isoleucine zipper motif (LIZ). Replacement of the LIZ with alanine resulted in dramatically reduced TM-TM association. Mutation of the LIZ in the whole protein resulted in decreased protein stability, including pre-fusion conformation stability. Together, our data suggest that the heptad repeat LIZ contributed to TM-TM association and is important for F protein function and pre-fusion stability. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Biomechanical Characterization of an Annulus Sparing Spinal Disc Prosthesis

PubMed Central

Buttermann, Glenn R.; Beaubien, Brian P.

2009-01-01

Background Context Current spine arthroplasty devices, require disruption of the annulus fibrosus for implantation. Preliminary studies of a unique annulus sparing intervertebral prosthetic disc (IPD), found that preservation of the annulus resulted in load sharing of the annulus with the prosthesis. Purpose Determine flexibility of the IPD versus fusion constructs in normal and degenerated human spines. Study design/Setting Biomechanical comparison of motion segments in the intact, fusion and mechanical nucleus replacement states for normal and degenerated states. Patient setting Thirty lumbar motion segments. Outcomes Measures Intervertebral height; motion segment range-of-motion (ROM), neutral zone (NZ), stiffness. Methods Motion segments had multi-directional flexibility testing to 7.5 Nm for intact discs, discs reconstructed using the IPD (n=12), or after anterior/posterior fusions (n=18). Interbody height and axial compression stiffness changes were determined for the reconstructed discs by applying axial compression to 1500 N. Analysis included stratifying results to normal mobile vs. rigid degenerated intact motion segments. Results The mean interbody height increase was 1.5 mm for IPD reconstructed discs. vs 3.0 mm for fused segments. Axial compression stiffness was 3.0 ± 0.9 kN/mm for intact compared to 1.2 ± 0.4 kN/mm for IPD reconstructed segments. Reconstructed disc ROM was 9.0° ± 3.7° in flexion-extension, 10.6° ± 3.4° in lateral bending and 2.8° ± 1.4° in axial torsion which was similar to intact values and significantly greater than respective fusion values (p<0.001). Mobile intact segments exhibited significantly greater rotation after fusion vs. their more rigid counterparts (p<0.05), however, intact motion was not related to motion after IPD reconstruction. The NZ and rotational stiffness followed similar trends. Differences in NZ between mobile and rigid intact specimens tended to decrease in the IPD reconstructed state. Conclusion The annulus sparing IPD generally reproduced the intact segment biomechanics in terms of ROM, NZ, and stiffness. Furthermore, the IPD reconstructed discs imparted stability by maintaining a small neutral zone. The IPD reconstructed discs were significantly less rigid than the fusion constructs and may be an attractive alternative for the treatment of DDD. PMID:19540816

Single-crystal micromachining using multiple fusion-bonded layers

NASA Astrophysics Data System (ADS)

Brown, Alan; O'Neill, Garry; Blackstone, Scott C.

2000-08-01

Multi-layer structures have been fabricated using Fusion bonding. The paper shows void free layers of between 2 and 100 microns that have been bonded to form multi-layer structures. Silicon layers have been bonded both with and without interfacial oxide layers.

Advanced fusion welding processes, solid state joining and a successful marriage. [production of aerospace structures

NASA Technical Reports Server (NTRS)

Miller, F. R.

1972-01-01

Joining processes for aerospace systems combine fusion welding and solid state joining during production of metal structures. Detailed characteristics of electron beam welding, plasma arc welding, diffusion welding, inertia welding and weldbond processes are discussed.

High-field neutral beam injection for improving the Q of a gas dynamic trap-based fusion neutron source

NASA Astrophysics Data System (ADS)

Zeng, Qiusun; Chen, Dehong; Wang, Minghuang

2017-12-01

In order to improve the fusion energy gain (Q) of a gas dynamic trap (GDT)-based fusion neutron source, a method in which the neutral beam is obliquely injected at a higher magnetic field position rather than at the mid-plane of the GDT is proposed. This method is beneficial for confining a higher density of fast ions at the turning point in the zone with a higher magnetic field, as well as obtaining a higher mirror ratio by reducing the mid-plane field rather than increasing the mirror field. In this situation, collision scattering loss of fast ions with higher density will occur and change the confinement time, power balance and particle balance. Using an updated calculation model with high-field neutral beam injection for a GDT-based fusion neutron source conceptual design, we got four optimal design schemes for a GDT-based fusion neutron source in which Q was improved to two- to three-fold compared with a conventional design scheme and considering the limitation for avoiding plasma instabilities, especially the fire-hose instability. The distribution of fast ions could be optimized by building a proper magnetic field configuration with enough space for neutron shielding and by multi-beam neutral particle injection at different axial points.

A novel framework of tissue membrane systems for image fusion.

PubMed

Zhang, Zulin; Yi, Xinzhong; Peng, Hong

2014-01-01

This paper proposes a tissue membrane system-based framework to deal with the optimal image fusion problem. A spatial domain fusion algorithm is given, and a tissue membrane system of multiple cells is used as its computing framework. Based on the multicellular structure and inherent communication mechanism of the tissue membrane system, an improved velocity-position model is developed. The performance of the fusion framework is studied with comparison of several traditional fusion methods as well as genetic algorithm (GA)-based and differential evolution (DE)-based spatial domain fusion methods. Experimental results show that the proposed fusion framework is superior or comparable to the other methods and can be efficiently used for image fusion.

Mocr: A novel fusion tag for enhancing solubility that is compatible with structural biology applications

PubMed Central

DelProposto, James; Majmudar, Chinmay Y.; Smith, Janet L.; Brown, William Clay

2010-01-01

A persistent problem in heterologous protein production is insolubility of the target protein when expressed to high level in the host cell. A widely employed strategy for overcoming this problem is the use of fusion tags. The best fusion tags promote solubility, may function as purification handles and either do not interfere with downstream applications or may be removed from the passenger protein preparation. A novel fusion tag is identified that meets these criteria. This fusion tag is a monomeric mutant of the Ocr protein (0.3 gene product) of bacteriophage T7. This fusion tag displays solubilizing activity with a variety of different passenger proteins. We show that it may be used as a purification handle similar to other fusion tags. Its small size and compact structure are compatible with its use in downstream applications of the passenger protein or it may be removed and purified away from the passenger protein. The use of monomeric Ocr (Mocr) as a complement to other fusion tags such as maltose-binding protein will provide greater flexibility in protein production and processing for a wide variety of protein applications. PMID:18824232

Mocr: a novel fusion tag for enhancing solubility that is compatible with structural biology applications.

PubMed

DelProposto, James; Majmudar, Chinmay Y; Smith, Janet L; Brown, William Clay

2009-01-01

A persistent problem in heterologous protein production is insolubility of the target protein when expressed to high level in the host cell. A widely employed strategy for overcoming this problem is the use of fusion tags. The best fusion tags promote solubility, may function as purification handles and either do not interfere with downstream applications or may be removed from the passenger protein preparation. A novel fusion tag is identified that meets these criteria. This fusion tag is a monomeric mutant of the Ocr protein (0.3 gene product) of bacteriophage T7. This fusion tag displays solubilizing activity with a variety of different passenger proteins. We show that it may be used as a purification handle similar to other fusion tags. Its small size and compact structure are compatible with its use in downstream applications of the passenger protein or it may be removed and purified away from the passenger protein. The use of monomeric Ocr (Mocr) as a complement to other fusion tags such as maltose-binding protein will provide greater flexibility in protein production and processing for a wide variety of protein applications.

Phase equilibria constraints on models of subduction zone magmatism

NASA Astrophysics Data System (ADS)

Myers, James D.; Johnston, Dana A.

Petrologic models of subduction zone magmatism can be grouped into three broad classes: (1) predominantly slab-derived, (2) mainly mantle-derived, and (3) multi-source. Slab-derived models assume high-alumina basalt (HAB) approximates primary magma and is derived by partial fusion of the subducting slab. Such melts must, therefore, be saturated with some combination of eclogite phases, e.g. cpx, garnet, qtz, at the pressures, temperatures and water contents of magma generation. In contrast, mantle-dominated models suggest partial melting of the mantle wedge produces primary high-magnesia basalts (HMB) which fractionate to yield derivative HAB magmas. In this context, HMB melts should be saturated with a combination of peridotite phases, i.e. ol, cpx and opx, and have liquid-lines-of-descent that produce high-alumina basalts. HAB generated in this manner must be saturated with a mafic phase assemblage at the intensive conditions of fractionation. Multi-source models combine slab and mantle components in varying proportions to generate the four main lava types (HMB, HAB, high-magnesia andesites (HMA) and evolved lavas) characteristic of subduction zones. The mechanism of mass transfer from slab to wedge as well as the nature and fate of primary magmas vary considerably among these models. Because of their complexity, these models imply a wide range of phase equilibria. Although the experiments conducted on calc-alkaline lavas are limited, they place the following limitations on arc petrologic models: (1) HAB cannot be derived from HMB by crystal fractionation at the intensive conditions thus far investigated, (2) HAB could be produced by anhydrous partial fusion of eclogite at high pressure, (3) HMB liquids can be produced by peridotite partial fusion 50-60 km above the slab-mantle interface, (4) HMA cannot be primary magmas derived by partial melting of the subducted slab, but could have formed by slab melt-peridotite interaction, and (5) many evolved calc-alkaline lavas could have been formed by crystal fractionation at a range of crustal pressures.

The effects of short pulse laser surface cleaning on porosity formation and reduction in laser welding of aluminium alloy for automotive component manufacture

NASA Astrophysics Data System (ADS)

AlShaer, A. W.; Li, L.; Mistry, A.

2014-12-01

Laser welding of aluminium alloys typically results in porosity in the fusion zones, leading to poor mechanical and corrosion performances. Mechanical and chemical cleaning of surfaces has been used previously to remove contaminants for weld joint preparations. However, these methods are slow, ineffective (e.g. due to hydrogen trapping) or lead to environmental hazards. This paper reports the effects of short pulsed laser surface cleaning on porosity formation and reduction in laser welding of AC-170PX (AA6014) aluminium sheets (coated with Ti/Zr and lubricated using a dry lubricant AlO70) with two types of joints: fillet edge and flange couch, using an AA4043 filler wire for automotive component assembly. The effect of laser cleaning on porosity reduction during laser welding using a filler wire has not been reported before. In this work, porosity and weld fusion zone geometry were examined prior to and after laser cleaning. The nanosecond pulsed Nd:YAG laser cleaning was found to reduce porosity significantly in the weld fusion zones. For the fillet edge welds, porosity was reduced to less than 0.5% compared with 10-80% without laser cleaning. For flange couch welds, porosity was reduced to 0.23-0.8% with laser cleaning from 0.7% to 4.3% without laser cleaning. This has been found to be due to the elimination of contaminations and oxide layers that contribute to the porosity formation. The laser cleaning is based on thermal ablation. This research focuses on porosity reduction in laser welding of aluminium alloy. Weld quality was investigated for two joints, fillet edge and flange couch joints. The effect of laser cleaning on porosity reduction after welding was investigated. It was found that laser cleaning reduced porosity less than 1% in both joints. Weld dimensions and strength were evaluated and discussed for both types of joints.

Effects of Mars Atmosphere on Arc Welds: Phase 2

NASA Technical Reports Server (NTRS)

Courtright, Z. S.

2018-01-01

Gas tungsten arc welding (GTAW) is a vital fusion welding process widely used throughout the aerospace industry. Its use may be critical for the repair or manufacture of systems, rockets, or facilities on the Martian surface. Aluminum alloy AA2219-T87 and titanium alloy Ti-6Al-4V butt welds have been investigated for weldability and weld properties in a simulated Martian gas environment. The resulting simulated Martian welds were compared to welds made in a terrestrial atmosphere, all of which used argon shielding gas. It was found that GTAW is a process that may be used in a Martian gas environment, not accounting for pressure and gravitational effects, as long as adequate argon shielding gas is used to protect the weld metal. Simulated Martian welds exhibited higher hardness in all cases and higher tensile strength in the case of AA2219-T87. This has been attributed to the absorption of carbon into the fusion zone, causing carbide precipitates to form. These precipitates may act to pin dislocations upon tensile testing of AA2219-T87. Dissolved carbon may have also led to carburization, which may have caused the increase in hardness within the fusion zone of the welds. Based on the results of this experiment and other similar experiments, GTAW appears to be a promising process for welding in a Martian gas environment. Additional funding and experimentation is necessary to determine the effects of the low pressure and low gravity environment found on Mars on GTAW.

Structure and immune recognition of trimeric pre-fusion HIV-1 Env

DOE PAGES

Pancera, Marie; Zhou, Tongqing; Druz, Aliaksandr; ...

2014-10-08

The human immunodeficiency virus type 1 (HIV-1) envelope (Env) spike, comprising three gp120 and three gp41 subunits, is a conformational machine that facilitates HIV-1 entry by rearranging from a mature unliganded state, through receptor-bound intermediates, to a post-fusion state. As the sole viral antigen on the HIV-1 virion surface, Env is both the target of neutralizing antibodies and a focus of vaccine efforts. Here we report the structure at 3.5 Å resolution for an HIV-1 Env trimer captured in a mature closed state by antibodies PGT122 and 35O22. This structure reveals the pre-fusion conformation of gp41, indicates rearrangements needed formore » fusion activation, and defines parameters of immune evasion and immune recognition. Pre-fusion gp41 encircles amino- and carboxy-terminal strands of gp120 with four helices that form a membrane-proximal collar, fastened by insertion of a fusion peptide-proximal methionine into a gp41-tryptophan clasp. Spike rearrangements required for entry involve opening the clasp and expelling the termini. In conclusion, N-linked glycosylation and sequence-variable regions cover the pre-fusion closed spike; we used chronic cohorts to map the prevalence and location of effective HIV-1-neutralizing responses, which were distinguished by their recognition of N-linked glycan and tolerance for epitope-sequence variation.« less

Structure and immune recognition of trimeric pre-fusion HIV-1 Env

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pancera, Marie; Zhou, Tongqing; Druz, Aliaksandr

The human immunodeficiency virus type 1 (HIV-1) envelope (Env) spike, comprising three gp120 and three gp41 subunits, is a conformational machine that facilitates HIV-1 entry by rearranging from a mature unliganded state, through receptor-bound intermediates, to a post-fusion state. As the sole viral antigen on the HIV-1 virion surface, Env is both the target of neutralizing antibodies and a focus of vaccine efforts. Here we report the structure at 3.5 Å resolution for an HIV-1 Env trimer captured in a mature closed state by antibodies PGT122 and 35O22. This structure reveals the pre-fusion conformation of gp41, indicates rearrangements needed formore » fusion activation, and defines parameters of immune evasion and immune recognition. Pre-fusion gp41 encircles amino- and carboxy-terminal strands of gp120 with four helices that form a membrane-proximal collar, fastened by insertion of a fusion peptide-proximal methionine into a gp41-tryptophan clasp. Spike rearrangements required for entry involve opening the clasp and expelling the termini. In conclusion, N-linked glycosylation and sequence-variable regions cover the pre-fusion closed spike; we used chronic cohorts to map the prevalence and location of effective HIV-1-neutralizing responses, which were distinguished by their recognition of N-linked glycan and tolerance for epitope-sequence variation.« less

Structure-function analysis of myomaker domains required for myoblast fusion.

PubMed

Millay, Douglas P; Gamage, Dilani G; Quinn, Malgorzata E; Min, Yi-Li; Mitani, Yasuyuki; Bassel-Duby, Rhonda; Olson, Eric N

2016-02-23

During skeletal muscle development, myoblasts fuse to form multinucleated myofibers. Myomaker [Transmembrane protein 8c (TMEM8c)] is a muscle-specific protein that is essential for myoblast fusion and sufficient to promote fusion of fibroblasts with muscle cells; however, the structure and biochemical properties of this membrane protein have not been explored. Here, we used CRISPR/Cas9 mutagenesis to disrupt myomaker expression in the C2C12 muscle cell line, which resulted in complete blockade to fusion. To define the functional domains of myomaker required to direct fusion, we established a heterologous cell-cell fusion system, in which fibroblasts expressing mutant versions of myomaker were mixed with WT myoblasts. Our data indicate that the majority of myomaker is embedded in the plasma membrane with seven membrane-spanning regions and a required intracellular C-terminal tail. We show that myomaker function is conserved in other mammalian orthologs; however, related family members (TMEM8a and TMEM8b) do not exhibit fusogenic activity. These findings represent an important step toward deciphering the cellular components and mechanisms that control myoblast fusion and muscle formation.

A comparison of synthesis and integrative approaches for meaning making and information fusion

NASA Astrophysics Data System (ADS)

Eggleston, Robert G.; Fenstermacher, Laurie

2017-05-01

Traditionally, information fusion approaches to meaning making have been integrative or aggregative in nature, creating meaning "containers" in which to put content (e.g., attributes) about object classes. In a large part, this was due to the limits in technology/tools for supporting information fusion (e.g., computers). A different synthesis based approach for meaning making is described which takes advantage of computing advances. The approach is not focused on the events/behaviors being observed/sensed; instead, it is human work centric. The former director of the Defense Intelligence Agency once wrote, "Context is king. Achieving an understanding of what is happening - or will happen - comes from a truly integrated picture of an area, the situation and the various personalities in it…a layered approach over time that builds depth of understanding."1 The synthesis based meaning making framework enables this understanding. It is holistic (both the sum and the parts, the proverbial forest and the trees), multi-perspective and emulative (as opposed to representational). The two approaches are complementary, with the synthesis based meaning making framework as a wrapper. The integrative approach would be dominant at level 0,1 fusion: data fusion, track formation and the synthesis based meaning making becomes dominant at higher fusion levels (levels 2 and 3), although both may be in play. A synthesis based approach to information fusion is thus well suited for "gray zone" challenges in which there is aggression and ambiguity and which are inherently perspective dependent (e.g., recent events in Ukraine).

Ultrasound-ultrasound image overlay fusion improves real-time control of radiofrequency ablation margin in the treatment of hepatocellular carcinoma.

PubMed

Minami, Yasunori; Minami, Tomohiro; Hagiwara, Satoru; Ida, Hiroshi; Ueshima, Kazuomi; Nishida, Naoshi; Murakami, Takamichi; Kudo, Masatoshi

2018-05-01

To assess the clinical feasibility of US-US image overlay fusion with evaluation of the ablative margin in radiofrequency ablation (RFA) for hepatocellular carcinoma (HCC). Fifty-three patients with 68 HCCs measuring 0.9-4.0 cm who underwent RFA guided by US-US overlay image fusion were included in this retrospective study. By an overlay of pre-/postoperative US, the tumor image could be projected onto the ablative hyperechoic zone. Therefore, the ablative margin three-dimensionally could be shown during the RFA procedure. US-US image overlay was compared to dynamic CT a few days after RFA for assessment of early treatment response. Accuracy of graded response was calculated, and the performance of US-US image overlay fusion was compared with that of CT using a Kappa agreement test. Technically effective ablation was achieved in a single session, and 59 HCCs (86.8 %) succeeded in obtaining a 5-mm margin on CT. The response with US-US image overlay correctly predicted early CT evaluation with an accuracy of 92.6 % (63/68) (k = 0.67; 95 % CI: 0.39-0.95). US-US image overlay fusion can be proposed as a feasible guidance in RFA with a safety margin and predicts early response of treatment assessment with high accuracy. • US-US image overlay fusion visualizes the ablative margin during RFA procedure. • Visualizing the margin during the procedure can prompt immediate complementary treatment. • US image fusion correlates with the results of early evaluation CT.

Microstructure and Hydrogen-Induced Failure Mechanisms in Fe and Ni Alloy Weldments

NASA Astrophysics Data System (ADS)

Fenske, J. A.; Robertson, I. M.; Ayer, Raghavan; Hukle, Martin; Lillig, Dan; Newbury, Brian

2012-09-01

The microstructure and fracture morphology of AISI 8630-IN625 and ASTM A182-F22-IN625 dissimilar metal weld interfaces were compared and contrasted as a function of postweld heat treatment (PWHT) duration. For both systems, the microstructure along the weld interface consisted of a coarse grain heat-affected zone in the Fe-base metal followed by discontinuous martensitic partially mixed zones and a continuous partially mixed zone on the Ni side of the fusion line. Within the partially mixed zone on the Ni side, there exists a 200-nm-wide transition zone within a 20- μm-wide planar solidification region followed by a cellular dendritic region with Nb-Mo-rich carbides decorating the dendrite boundaries. Although there were differences in the volume of the partially mixed zones, the major difference in the metal weld interfaces was the presence of M7C3 precipitates in the planar solidification region, which had formed in AISI 8630-IN625 but not in ASTM A182-F22-IN625. These precipitates make the weldment more susceptible to hydrogen embrittlement and provide a low energy fracture path between the discontinuous partially mixed zones.

Capturing a flavivirus pre-fusion intermediate.

PubMed

Kaufmann, Bärbel; Chipman, Paul R; Holdaway, Heather A; Johnson, Syd; Fremont, Daved H; Kuhn, Richard J; Diamond, Michael S; Rossmann, Michael G

2009-11-01

During cell entry of flaviviruses, low endosomal pH triggers the rearrangement of the viral surface glycoproteins to a fusion-active state that allows the release of the infectious RNA into the cytoplasm. In this work, West Nile virus was complexed with Fab fragments of the neutralizing mAb E16 and was subsequently exposed to low pH, trapping the virions in a pre-fusion intermediate state. The structure of the complex was studied by cryo-electron microscopy and provides the first structural glimpse of a flavivirus fusion intermediate near physiological conditions. A radial expansion of the outer protein layer of the virion was observed compared to the structure at pH 8. The resulting approximately 60 A-wide shell of low density between lipid bilayer and outer protein layer is likely traversed by the stem region of the E glycoprotein. By using antibody fragments, we have captured a structural intermediate of a virus that likely occurs during cell entry. The trapping of structural transition states by antibody fragments will be applicable for other processes in the flavivirus life cycle and delineating other cellular events that involve conformational rearrangements.

Modeling the evolution space of breakage fusion bridge cycles with a stochastic folding process.

PubMed

Greenman, C D; Cooke, S L; Marshall, J; Stratton, M R; Campbell, P J

2016-01-01

Breakage-fusion-bridge cycles in cancer arise when a broken segment of DNA is duplicated and an end from each copy joined together. This structure then 'unfolds' into a new piece of palindromic DNA. This is one mechanism responsible for the localised amplicons observed in cancer genome data. Here we study the evolution space of breakage-fusion-bridge structures in detail. We firstly consider discrete representations of this space with 2-d trees to demonstrate that there are [Formula: see text] qualitatively distinct evolutions involving [Formula: see text] breakage-fusion-bridge cycles. Secondly we consider the stochastic nature of the process to show these evolutions are not equally likely, and also describe how amplicons become localized. Finally we highlight these methods by inferring the evolution of breakage-fusion-bridge cycles with data from primary tissue cancer samples.

Sensor fusion IV: Control paradigms and data structures; Proceedings of the Meeting, Boston, MA, Nov. 12-15, 1991

NASA Technical Reports Server (NTRS)

Schenker, Paul S. (Editor)

1992-01-01

Various papers on control paradigms and data structures in sensor fusion are presented. The general topics addressed include: decision models and computational methods, sensor modeling and data representation, active sensing strategies, geometric planning and visualization, task-driven sensing, motion analysis, models motivated biology and psychology, decentralized detection and distributed decision, data fusion architectures, robust estimation of shapes and features, application and implementation. Some of the individual subjects considered are: the Firefly experiment on neural networks for distributed sensor data fusion, manifold traversing as a model for learning control of autonomous robots, choice of coordinate systems for multiple sensor fusion, continuous motion using task-directed stereo vision, interactive and cooperative sensing and control for advanced teleoperation, knowledge-based imaging for terrain analysis, physical and digital simulations for IVA robotics.

Hierarchical Multi-atlas Label Fusion with Multi-scale Feature Representation and Label-specific Patch Partition

PubMed Central

Wu, Guorong; Kim, Minjeong; Sanroma, Gerard; Wang, Qian; Munsell, Brent C.; Shen, Dinggang

2014-01-01

Multi-atlas patch-based label fusion methods have been successfully used to improve segmentation accuracy in many important medical image analysis applications. In general, to achieve label fusion a single target image is first registered to several atlas images, after registration a label is assigned to each target point in the target image by determining the similarity between the underlying target image patch (centered at the target point) and the aligned image patch in each atlas image. To achieve the highest level of accuracy during the label fusion process it’s critical the chosen patch similarity measurement accurately captures the tissue/shape appearance of the anatomical structure. One major limitation of existing state-of-the-art label fusion methods is that they often apply a fixed size image patch throughout the entire label fusion procedure. Doing so may severely affect the fidelity of the patch similarity measurement, which in turn may not adequately capture complex tissue appearance patterns expressed by the anatomical structure. To address this limitation, we advance state-of-the-art by adding three new label fusion contributions: First, each image patch now characterized by a multi-scale feature representation that encodes both local and semi-local image information. Doing so will increase the accuracy of the patch-based similarity measurement. Second, to limit the possibility of the patch-based similarity measurement being wrongly guided by the presence of multiple anatomical structures in the same image patch, each atlas image patch is further partitioned into a set of label-specific partial image patches according to the existing labels. Since image information has now been semantically divided into different patterns, these new label-specific atlas patches make the label fusion process more specific and flexible. Lastly, in order to correct target points that are mislabeled during label fusion, a hierarchically approach is used to improve the label fusion results. In particular, a coarse-to-fine iterative label fusion approach is used that gradually reduces the patch size. To evaluate the accuracy of our label fusion approach, the proposed method was used to segment the hippocampus in the ADNI dataset and 7.0 tesla MR images, sub-cortical regions in LONI LBPA40 dataset, mid-brain regions in SATA dataset from MICCAI 2013 segmentation challenge, and a set of key internal gray matter structures in IXI dataset. In all experiments, the segmentation results of the proposed hierarchical label fusion method with multi-scale feature representations and label-specific atlas patches are more accurate than several well-known state-of-the-art label fusion methods. PMID:25463474

DOE Office of Scientific and Technical Information (OSTI.GOV)

Follis, Kathryn E.; York, Joanne; Nunberg, Jack H.

The fusion subunit of the SARS-CoV S glycoprotein contains two regions of hydrophobic heptad-repeat amino acid sequences that have been shown in biophysical studies to form a six-helix bundle structure typical of the fusion-active core found in Class I viral fusion proteins. Here, we have applied serine-scanning mutagenesis to the C-terminal-most heptad-repeat region in the SARS-CoV S glycoprotein to investigate the functional role of this region in membrane fusion. We show that hydrophobic sidechains at a and d positions only within the short helical segment of the C-terminal heptad-repeat region (I1161, I1165, L1168, A1172, and L1175) are critical for cell-cellmore » fusion. Serine mutations at outlying heptad-repeat residues that form an extended chain in the core structure (V1158, L1179, and L1182) do not affect fusogenicity. Our study provides genetic evidence for the important role of {alpha}-helical packing in promoting S glycoprotein-mediated membrane fusion.« less

Is Self-Interacting Dark Matter Undergoing Dark Fusion?

DOE PAGES

McDermott, Samuel D.

2018-06-01

Here, we suggest that two-to-two dark matter fusion may be the relaxation process that resolves the small-scale structure problems of the cold collisionless dark matter paradigm. In order for the fusion cross section to scale correctly across many decades of astrophysical masses from dwarf galaxies to galaxy clusters, we require the fractional binding energy released to be greater than v n~(10 –(2–3)) n, where n=1, 2 depends on local dark sector chemistry. The size of the dark-sector interaction cross sections must be σ~0.1–1 barn, moderately larger than for standard model deuteron fusion, indicating a dark nuclear scale Λ~O(100 MeV). Darkmore » fusion firmly predicts constant σv below the characteristic velocities of galaxy clusters. Observations of the inner structure of galaxy groups with velocity dispersion of several hundred kilometers per second, of which a handful have been identified, could differentiate dark fusion from a dark photon model.« less

Is Self-Interacting Dark Matter Undergoing Dark Fusion?

DOE Office of Scientific and Technical Information (OSTI.GOV)

McDermott, Samuel D.

2017-11-02

We suggest that two-to-two dark matter fusion may be the relaxation process that resolves the small-scale structure problems of the cold collisionless dark matter paradigm. In order for the fusion cross section to scale correctly across many decades of astrophysical masses from dwarf galaxies to galaxy clusters, we require the fractional binding energy released to be greater than v^n ~ [10^{-(2-3)}]^n, where n=1,2 depends on local dark sector chemistry. The size of the dark-sector interaction cross sections must be sigma ~ 0.1-1 barn, moderately larger than for Standard Model deuteron fusion, indicating a dark nuclear scale Lambda ~ O(100 MeV).more » Dark fusion firmly predicts constant sigma v below the characteristic velocities of galaxy clusters. Observations of the inner structure of galaxy groups with velocity dispersion of several hundred kilometer per second, of which a handful have been identified, could differentiate dark fusion from a dark photon model.« less

Cholesterol suppresses membrane leakage by decreasing water penetrability.

PubMed

Bu, Bing; Crowe, Michael; Diao, Jiajie; Ji, Baohua; Li, Dechang

2018-06-13

Membrane fusion is a fundamental biological process that lies at the heart of enveloped virus infection, synaptic signaling, intracellular vesicle trafficking, gamete fertilization, and cell-cell fusion. Membrane fusion is initiated as two apposed membranes merge to a single bilayer called a hemifusion diaphragm. It is believed that the contents of the two fusing membranes are released through a fusion pore formed at the hemifusion diaphragm, and yet another possible pathway has been proposed in which an undefined pore may form outside the hemifusion diaphragm at the apposed membranes, leading to the so-called leaky fusion. Here, we performed all-atom molecular dynamics simulations to study the evolution of the hemifusion diaphragm structure with various lipid compositions. We found that the lipid cholesterol decreased water penetrability to inhibit leakage pore formation. Biochemical leakage experiments support these simulation results. This study may shed light on the underlying mechanism of the evolution pathways of the hemifusion structure, especially the understanding of content leakage during membrane fusion.

Is Self-Interacting Dark Matter Undergoing Dark Fusion?

NASA Astrophysics Data System (ADS)

McDermott, Samuel D.

2018-06-01

We suggest that two-to-two dark matter fusion may be the relaxation process that resolves the small-scale structure problems of the cold collisionless dark matter paradigm. In order for the fusion cross section to scale correctly across many decades of astrophysical masses from dwarf galaxies to galaxy clusters, we require the fractional binding energy released to be greater than vn˜(10-(2 -3 ))n , where n =1 , 2 depends on local dark sector chemistry. The size of the dark-sector interaction cross sections must be σ˜0.1 - 1 barn, moderately larger than for standard model deuteron fusion, indicating a dark nuclear scale Λ ˜O (100 MeV ) . Dark fusion firmly predicts constant σ v below the characteristic velocities of galaxy clusters. Observations of the inner structure of galaxy groups with velocity dispersion of several hundred kilometers per second, of which a handful have been identified, could differentiate dark fusion from a dark photon model.

Is Self-Interacting Dark Matter Undergoing Dark Fusion?

DOE Office of Scientific and Technical Information (OSTI.GOV)

McDermott, Samuel D.

Here, we suggest that two-to-two dark matter fusion may be the relaxation process that resolves the small-scale structure problems of the cold collisionless dark matter paradigm. In order for the fusion cross section to scale correctly across many decades of astrophysical masses from dwarf galaxies to galaxy clusters, we require the fractional binding energy released to be greater than v n~(10 –(2–3)) n, where n=1, 2 depends on local dark sector chemistry. The size of the dark-sector interaction cross sections must be σ~0.1–1 barn, moderately larger than for standard model deuteron fusion, indicating a dark nuclear scale Λ~O(100 MeV). Darkmore » fusion firmly predicts constant σv below the characteristic velocities of galaxy clusters. Observations of the inner structure of galaxy groups with velocity dispersion of several hundred kilometers per second, of which a handful have been identified, could differentiate dark fusion from a dark photon model.« less

Sensitization of Laser-beam Welded Martensitic Stainless Steels

NASA Astrophysics Data System (ADS)

Dahmen, Martin; Rajendran, Kousika Dhasanur; Lindner, Stefan

Ferritic and martensitic stainless steels are an attractive alternative in vehicle production due to their inherent corrosion resistance. By the opportunity of press hardening, their strength can be increased to up to 2000 MPa, making them competitors for unalloyed ultra-high strength steels. Welding, nevertheless, requires special care, especially when it comes to joining of high strength heat treated materials. With an adopted in-line heat treatment of the welds in as-rolled as well as press hardened condition, materials with sufficient fatigue strength and acceptable structural behavior can be produced. Because of microstructural transformations in the base material such as grain coarsening and forced carbide precipitation, the corrosion resistance of the weld zone may be locally impaired. Typically the material in the heat-affected zone becomes sensitive to intergranular cracking in the form of knife-edge corrosion besides the fusion line. The current study comprises of two text scenarios. By an alternating climate test, general response in a corroding environment is screened. In order to understand the corrosion mechanisms and to localize the sensitive zones, sensitisation tests were undertaken. Furthermore, the applicability of a standard test according to ASTM 763-83 was examined. It was found that the alternative climate test does not reveal any corrosion effects. Testing by the oxalic acid test revealed clearly the effect of welding, weld heat treatment and state of thermal processing. Also application of the standard which originally suited for testing ferritic stainless steels could have been justified.

A Comparison of Coarse-Grained and Continuum Models for Membrane Bending in Lipid Bilayer Fusion Pores

PubMed Central

Yoo, Jejoong; Jackson, Meyer B.; Cui, Qiang

2013-01-01

To establish the validity of continuum mechanics models quantitatively for the analysis of membrane remodeling processes, we compare the shape and energies of the membrane fusion pore predicted by coarse-grained (MARTINI) and continuum mechanics models. The results at these distinct levels of resolution give surprisingly consistent descriptions for the shape of the fusion pore, and the deviation between the continuum and coarse-grained models becomes notable only when the radius of curvature approaches the thickness of a monolayer. Although slow relaxation beyond microseconds is observed in different perturbative simulations, the key structural features (e.g., dimension and shape of the fusion pore near the pore center) are consistent among independent simulations. These observations provide solid support for the use of coarse-grained and continuum models in the analysis of membrane remodeling. The combined coarse-grained and continuum analysis confirms the recent prediction of continuum models that the fusion pore is a metastable structure and that its optimal shape is neither toroidal nor catenoidal. Moreover, our results help reveal a new, to our knowledge, bowing feature in which the bilayers close to the pore axis separate more from one another than those at greater distances from the pore axis; bowing helps reduce the curvature and therefore stabilizes the fusion pore structure. The spread of the bilayer deformations over distances of hundreds of nanometers and the substantial reduction in energy of fusion pore formation provided by this spread indicate that membrane fusion can be enhanced by allowing a larger area of membrane to participate and be deformed. PMID:23442963

Membrane Fusion Proteins as Nanomachines

NASA Astrophysics Data System (ADS)

Tamm, Lukas

2009-03-01

Membrane fusion is key to fertilization, virus infection, and neurotransmission. Specific proteins work like nanomachines to stitch together fluid, yet highly ordered lipid bilayers. The energy gained from large exothermic conformational changes of these proteins is utilized to fuse lipid bilayers that do not fuse spontaneously. Structural studies using x-ray crystallography and NMR spectroscopy have yielded detailed information about architecture and inner workings of these molecular machines. The question now is: how is mechanical energy gained from such protein transformations harnessed to transform membrane topology? To answer this question, we have determined that a boomerang-shaped structure of the influenza fusion peptide is critical to generate a high-energy binding intermediate in the target membrane and to return the ``boomerang'' to its place of release near the viral membrane for completion of the fusion cycle. In presynaptic exocytosis, receptor and acceptor SNAREs are zippered to form a helical bundle that is arrested shortly before the membrane. Ca binding to interlocked synaptotagmin releases the fusion block. Structural NMR and single molecule fluorescence data are combined to arrive at and further refine this picture.

Objective quality assessment for multiexposure multifocus image fusion.

PubMed

Hassen, Rania; Wang, Zhou; Salama, Magdy M A

2015-09-01

There has been a growing interest in image fusion technologies, but how to objectively evaluate the quality of fused images has not been fully understood. Here, we propose a method for objective quality assessment of multiexposure multifocus image fusion based on the evaluation of three key factors of fused image quality: 1) contrast preservation; 2) sharpness; and 3) structure preservation. Subjective experiments are conducted to create an image fusion database, based on which, performance evaluation shows that the proposed fusion quality index correlates well with subjective scores, and gives a significant improvement over the existing fusion quality measures.

Regulation of Herpes Simplex Virus Glycoprotein-Induced Cascade of Events Governing Cell-Cell Fusion

PubMed Central

Saw, Wan Ting; Eisenberg, Roselyn J.; Cohen, Gary H.

2016-01-01

ABSTRACT Receptor-dependent herpes simplex virus (HSV)-induced cell-cell fusion requires glycoproteins gD, gH/gL, and gB. Our current model posits that during fusion, receptor-activated conformational changes in gD activate gH/gL, which subsequently triggers the transformation of the prefusion form of gB into a fusogenic state. To examine the role of each glycoprotein in receptor-dependent cell-cell fusion, we took advantage of our discovery that fusion by wild-type herpes simplex virus 2 (HSV-2) glycoproteins occurs twice as fast as that achieved by HSV-1 glycoproteins. By sequentially swapping each glycoprotein between the two serotypes, we established that fusion speed was governed by gH/gL, with gH being the main contributor. While the mutant forms of gB fuse at distinct rates that are dictated by their molecular structure, these restrictions can be overcome by gH/gL of HSV-2 (gH2/gL2), thereby enhancing their activity. We also found that deregulated forms of gD of HSV-1 (gD1) and gH2/gL2 can alter the fusogenic potential of gB, promoting cell fusion in the absence of a cellular receptor, and that deregulated forms of gB can drive the fusion machinery to even higher levels. Low pH enhanced fusion by affecting the structure of both gB and gH/gL mutants. Together, our data highlight the complexity of the fusion machinery, the impact of the activation state of each glycoprotein on the fusion process, and the critical role of gH/gL in regulating HSV-induced fusion. IMPORTANCE Cell-cell fusion mediated by HSV glycoproteins requires gD, gH/gL, gB, and a gD receptor. Here, we show that fusion by wild-type HSV-2 glycoproteins occurs twice as fast as that achieved by HSV-1 glycoproteins. By sequentially swapping each glycoprotein between the two serotypes, we found that the fusion process was controlled by gH/gL. Restrictions imposed on the gB structure by mutations could be overcome by gH2/gL2, enhancing the activity of the mutants. Under low-pH conditions or when using deregulated forms of gD1 and gH2/gL2, the fusogenic potential of gB could only be increased in the absence of receptor, underlining the exquisite regulation that occurs in the presence of receptor. Our data highlight the complexity of the fusion machinery, the impact of the activation state of each glycoprotein on the fusion process, and the critical role of gH/gL in regulating HSV-induced fusion. PMID:27630245

Recovery of Mechanical Properties of a 6061-T6 Aluminum Weld by Heat Treatment After Welding

NASA Astrophysics Data System (ADS)

Pérez, Javier Serrano; Ambriz, Ricardo Rafael; López, Francisco Fernando Curiel; Vigueras, David Jaramillo

2016-07-01

The dilution effects in welds of a 6061-T6 (Al-Si-Mg) alloy obtained by the modified indirect electric arc (MIEA), using an ER4043 filler metal (Al-Si), and postweld heat treatment (PWHT) were analyzed. The soft zone (55 to 70 HV0.1) formed by the microstructural transformation in the heat-affected zone (HAZ) was eliminated. The hardness measurements were presented on a traditional microhardness profile and mapping representation. A hardening effect of the fusion zone was observed; the hardness values were above 120 HV0.1 and tended to be uniform. This behavior could be attributed to the chemical composition of the filler metal, the Mg migration from the base to the weld metal, and the reversible process of the PWHT, which promotes precipitation hardening. Improvement for yield (260 MPa) and tensile strength (310 MPa) of the MIEA joints was observed; these values were similar to those obtained for the base metal. However, the presence of porosity in the fusion zone limits the ductility of the joints (4.3 pct). Even though the yield and tensile strengths of the base metal and welded joints were similar, the stress concentration due to porosity in the weld metal generated data dispersion in fatigue life. As a consequence, the high-cycle fatigue life decreases with respect to the base metal. In contrast, when the crack propagates under elastic conditions, the crack-tip singularity is affected by the porosity in the weld metal (stress liberator). This aspect, in conjunction with the hardening effect in joints subjected to PWHT, improves the fatigue crack growth rate when compared to the as-welded condition.

Isolation and in vitro binding of mating type plus fertilization tubules from Chlamydomonas.

PubMed

Wilson, Nedra F

2008-01-01

During fertilization in Chlamydomonas, adhesion and fusion of gametes occur at the tip of specialized regions of the plasma membrane, known as mating structures. The mating type minus (mt[-]) structure is a slightly raised dome-shaped region located at the apical end of the cell body. In contrast, the activated mating type plus (mt[+]) structure is an actin-filled, microvillouslike organelle. Interestingly, a similar type of "fusion organelle" is conserved across diverse groups. Chlamydomonas provides an ideal model system for studying the process of gametic cell fusion in that it is amenable to genetic manipulations as well as cell and molecular biological approaches. Moreover, the ease of culturing Chlamydomonas combined with the ability to isolate the mt(+) fertilization tubule and the development of in vitro assays for adhesion makes it an ideal system for biochemical studies focused on dissecting the molecular mechanisms that underlie the complex process of gametic cell fusion.

Advanced low-activation materials. Fibre-reinforced ceramic composites

NASA Astrophysics Data System (ADS)

Fenici, P.; Scholz, H. W.

1994-09-01

A serious safety and environmental concern for thermonuclear fusion reactor development regards the induced radioactivity of the first wall and structural components. The use of low-activation materials (LAM) in a demonstration reactor would reduce considerably its potential risk and facilitate its maintenance. Moreover, decommissioning and waste management including disposal or even recycling of structural materials would be simplified. Ceramic fibre-reinforced SiC materials offer highly appreciable low activation characteristics in combination with good thermomechanical properties. This class of materials is now under experimental investigation for structural application in future fusion reactors. An overview on the recent results is given, covering coolant leak rates, thermophysical properties, compatibility with tritium breeder materials, irradiation effects, and LAM-consistent purity. SiC/SiC materials present characteristics likely to be optimised in order to meet the fusion application challenge. The scope is to put into practice the enormous potential of inherent safety with fusion energy.

Two Horizons of Fusion

ERIC Educational Resources Information Center

Lo, Mun Ling; Chik, Pakey Pui Man

2016-01-01

In this paper, we aim to differentiate the internal and external horizons of "fusion." "Fusion" in the internal horizon relates to the structure and meaning of the object of learning as experienced by the learner. It clarifies the interrelationships among an object's critical features and aspects. It also illuminates the…

Method for creating ideal tissue fusion in soft-tissue structures using radio frequency (RF) energy.

PubMed

Shields, Chelsea A; Schechter, David A; Tetzlaff, Phillip; Baily, Ali L; Dycus, Sean; Cosgriff, Ned

2004-01-01

Bipolar radiofrequency (RF) energy can successfully seal vascular structures up to 7 mm by fusing collagen and elastin in the lumen. Valleylab has created a system to expand this technology beyond vessel sealing with the development of a closed-loop, feedback-control RF generator that closely monitors tissue fusion. This generator, operating with a loop time of approximately 250 micros, continuously adjusts energy output, creating optimized soft-tissue fusion through structural protein amalgamation. In the first study, RF energy was applied to canine lung using the new-generation generator and lung-prototype device. A lobectomy was completed, sealing the lobar bronchus, parenchyma, and pulmonary vasculature. Chronic performance of the seals was evaluated at necropsy on postoperative days 7 and 14. In a second study, RF energy was applied to porcine small intestine using the same closed-loop generator and anastomosis prototype device. Acute tissue fusion was assessed qualitatively for hemostasis and seal quality. Terminal tissue evaluation was completed on postoperative day 7 and analyzed histopathologically. Histopathology confirmed acute and chronic tissue fusion in both the lung and intestine. Normal pathological healing was substantiated by angiogenesis, granulation, and proliferation of fibroblasts. Preliminary studies using canine lung and porcine small intestine demonstrate the potential of this closed-loop generator for soft-tissue amalgamation. Advanced monitoring capabilities make this fusion system applicable in many soft-tissue structures with adequate collagen and elastin. Further investigation of potential surgical applications needs to be completed.

Structure and function of photosystem I–[FeFe] hydrogenase protein fusions: An all-atom molecular dynamics study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harris, Bradley J.; Cheng, Xiaolin; Frymier, Paul

2015-12-15

All-atom molecular dynamics (MD) simulation was used to study the solution dynamics and protein protein interactions of protein fusions of photosystem I (PSI) from Thermosynechococcus elongatus and an [FeFe]-hydrogenase (FeFe H 2ase) from Clostridium pasteurianum, a unique complex capable of photocatalytic hydrogen production. This study involved fusions of these two proteins via dithiol linkers of different length including decanedithiol, octanedithiol, and hexanedithiol, for which experimental data had previously been obtained. Evaluation of root-mean-squared deviations (RMSDs) relative to the respective crystal structures of PSI and the FeFe H 2ase shows that these fusion complexes approach stable equilibrium conformations during the MDmore » simulations. Investigating protein mobility via root-mean-squared fluctuations (RMSFs) reveals that tethering via the shortest hexanedithiol linker results in increased atomic fluctuations of both PSI and the hydrogenase in these fusion complexes. Furthermore, evaluation of the inter- and intraprotein electron transfer distances in these fusion complexes indicates that the structural changes in the FeFe H 2ase arising from ligation to PSI via the shortest hexanedithiol linker may hinder electron transport in the hydrogenase, thus providing a molecular level explanation for the observation that the medium-length octanedithiol linker gives the highest hydrogen production rate.« less

Rubella virus: first calcium-requiring viral fusion protein.

PubMed

Dubé, Mathieu; Rey, Felix A; Kielian, Margaret

2014-12-01

Rubella virus (RuV) infection of pregnant women can cause fetal death, miscarriage, or severe fetal malformations, and remains a significant health problem in much of the underdeveloped world. RuV is a small enveloped RNA virus that infects target cells by receptor-mediated endocytosis and low pH-dependent membrane fusion. The structure of the RuV E1 fusion protein was recently solved in its postfusion conformation. RuV E1 is a member of the class II fusion proteins and is structurally related to the alphavirus and flavivirus fusion proteins. Unlike the other known class II fusion proteins, however, RuV E1 contains two fusion loops, with a metal ion complexed between them by the polar residues N88 and D136. Here we demonstrated that RuV infection specifically requires Ca(2+) during virus entry. Other tested cations did not substitute. Ca(2+) was not required for virus binding to cell surface receptors, endocytic uptake, or formation of the low pH-dependent E1 homotrimer. However, Ca(2+) was required for low pH-triggered E1 liposome insertion, virus fusion and infection. Alanine substitution of N88 or D136 was lethal. While the mutant viruses were efficiently assembled and endocytosed by host cells, E1-membrane insertion and fusion were specifically blocked. Together our data indicate that RuV E1 is the first example of a Ca(2+)-dependent viral fusion protein and has a unique membrane interaction mechanism.

The Formin Diaphanous Regulates Myoblast Fusion through Actin Polymerization and Arp2/3 Regulation

PubMed Central

Deng, Su; Bothe, Ingo; Baylies, Mary K.

2015-01-01

The formation of multinucleated muscle cells through cell-cell fusion is a conserved process from fruit flies to humans. Numerous studies have shown the importance of Arp2/3, its regulators, and branched actin for the formation of an actin structure, the F-actin focus, at the fusion site. This F-actin focus forms the core of an invasive podosome-like structure that is required for myoblast fusion. In this study, we find that the formin Diaphanous (Dia), which nucleates and facilitates the elongation of actin filaments, is essential for Drosophila myoblast fusion. Following cell recognition and adhesion, Dia is enriched at the myoblast fusion site, concomitant with, and having the same dynamics as, the F-actin focus. Through analysis of Dia loss-of-function conditions using mutant alleles but particularly a dominant negative Dia transgene, we demonstrate that reduction in Dia activity in myoblasts leads to a fusion block. Significantly, no actin focus is detected, and neither branched actin regulators, SCAR or WASp, accumulate at the fusion site when Dia levels are reduced. Expression of constitutively active Dia also causes a fusion block that is associated with an increase in highly dynamic filopodia, altered actin turnover rates and F-actin distribution, and mislocalization of SCAR and WASp at the fusion site. Together our data indicate that Dia plays two roles during invasive podosome formation at the fusion site: it dictates the level of linear F-actin polymerization, and it is required for appropriate branched actin polymerization via localization of SCAR and WASp. These studies provide new insight to the mechanisms of cell-cell fusion, the relationship between different regulators of actin polymerization, and invasive podosome formation that occurs in normal development and in disease. PMID:26295716

Identification of novel target sites and an inhibitor of the dengue virus E protein.

PubMed

Yennamalli, Ragothaman; Subbarao, Naidu; Kampmann, Thorsten; McGeary, Ross P; Young, Paul R; Kobe, Bostjan

2009-06-01

Dengue and related flaviviruses represent a significant global health threat. The envelope glycoprotein E mediates virus attachment to a host cell and the subsequent fusion of viral and host cell membranes. The fusion process is driven by conformational changes in the E protein and is an essential step in the virus life cycle. In this study, we analyzed the pre-fusion and post-fusion structures of the dengue virus E protein to identify potential novel sites that could bind small molecules, which could interfere with the conformational transitions that mediate the fusion process. We used an in silico virtual screening approach combining three different docking algorithms (DOCK, GOLD and FlexX) to identify compounds that are likely to bind to these sites. Seven structurally diverse molecules were selected to test experimentally for inhibition of dengue virus propagation. The best compound showed an IC(50) in the micromolar range against dengue virus type 2.

Identification of novel target sites and an inhibitor of the dengue virus E protein

NASA Astrophysics Data System (ADS)

Yennamalli, Ragothaman; Subbarao, Naidu; Kampmann, Thorsten; McGeary, Ross P.; Young, Paul R.; Kobe, Bostjan

2009-06-01

Dengue and related flaviviruses represent a significant global health threat. The envelope glycoprotein E mediates virus attachment to a host cell and the subsequent fusion of viral and host cell membranes. The fusion process is driven by conformational changes in the E protein and is an essential step in the virus life cycle. In this study, we analyzed the pre-fusion and post-fusion structures of the dengue virus E protein to identify potential novel sites that could bind small molecules, which could interfere with the conformational transitions that mediate the fusion process. We used an in silico virtual screening approach combining three different docking algorithms (DOCK, GOLD and FlexX) to identify compounds that are likely to bind to these sites. Seven structurally diverse molecules were selected to test experimentally for inhibition of dengue virus propagation. The best compound showed an IC50 in the micromolar range against dengue virus type 2.

Weber-aware weighted mutual information evaluation for infrared-visible image fusion

NASA Astrophysics Data System (ADS)

Luo, Xiaoyan; Wang, Shining; Yuan, Ding

2016-10-01

A performance metric for infrared and visible image fusion is proposed based on Weber's law. To indicate the stimulus of source images, two Weber components are provided. One is differential excitation to reflect the spectral signal of visible and infrared images, and the other is orientation to capture the scene structure feature. By comparing the corresponding Weber component in infrared and visible images, the source pixels can be marked with different dominant properties in intensity or structure. If the pixels have the same dominant property label, the pixels are grouped to calculate the mutual information (MI) on the corresponding Weber components between dominant source and fused images. Then, the final fusion metric is obtained via weighting the group-wise MI values according to the number of pixels in different groups. Experimental results demonstrate that the proposed metric performs well on popular image fusion cases and outperforms other image fusion metrics.

Fusion of uniluminal vascular spheroids: a model for assembly of blood vessels

PubMed Central

Fleming, Paul A.; Argraves, W. Scott; Gentile, Carmine; Neagu, Adrian; Forgacs, Gabor; Drake, Christopher J.

2010-01-01

Here, we evaluated the self-assembly properties of uniluminal vascular spheroids having outer layers of vascular smooth muscle cells and a contiguous inner layer of endothelial cells lining a central lumen. We showed that while pairs of uniluminal vascular spheroids suspended in culture medium fused to form a larger diameter spheroidal structure, spheroids in collagen hydrogels formed elongated structures. These findings highlight the potential use of uniluminal vascular spheroids as modules to engineer blood vessels. We also demonstrate that uniluminal vascular spheroid fusion conforms to models describing the coalescence of liquid drops. Furthermore, the fusion of uniluminal vascular spheroids in vitro closely resembled the in vivo process by which the descending aorta forms from the fusion of the paired dorsal aortae during embryonic development. Together, the findings indicate that tissue liquidity underlies uniluminal vascular spheroid fusion and that in vivo anastomosis of blood vessels may involve a similar mechanism. PMID:19918756

Microstructural characterization in dissimilar friction stir welding between 304 stainless steel and st37 steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jafarzadegan, M.; State Key Laboratory of Advanced Welding Production Technology, School of Materials Science and Eng., Harbin Institute of Technology, P.O. Box: 150001, Harbin; Feng, A.H.

2012-12-15

In the present study, 3 mm-thick plates of 304 stainless steel and st37 steel were welded together by friction stir welding at a welding speed of 50 mm/min and tool rotational speed of 400 and 800 rpm. X-ray diffraction test was carried out to study the phases which might be formed in the welds. Metallographic examinations, and tensile and microhardness tests were used to analyze the microstructure and mechanical properties of the joint. Four different zones were found in the weld area except the base metals. In the stir zone of the 304 stainless steel, a refined grain structure withmore » some features of dynamic recrystallization was evidenced. A thermomechanically-affected zone was characterized on the 304 steel side with features of dynamic recovery. In the other side of the stir zone, the hot deformation of the st37 steel in the austenite region produced small austenite grains and these grains transformed to fine ferrite and pearlite and some products of displacive transformations such as Widmanstatten ferrite and martensite by cooling the material after friction stir welding. The heat-affected zone in the st37 steel side showed partially and fully refined microstructures like fusion welding processes. The recrystallization in the 304 steel and the transformations in the st37 steel enhanced the hardness of the weld area and therefore, improved the tensile properties of the joint. - Highlights: Black-Right-Pointing-Pointer FSW produced sound welds between st37 low carbon steel and 304 stainless steel. Black-Right-Pointing-Pointer The SZ of the st37 steel contained some products of allotropic transformation. Black-Right-Pointing-Pointer The material in the SZ of the 304 steel showed features of dynamic recrystallization. Black-Right-Pointing-Pointer The finer microstructure in the SZ increased the hardness and tensile strength.« less

Image Fusion for Radiosurgery, Neurosurgery and Hypofractionated Radiotherapy.

PubMed

Inoue, Hiroshi K; Nakajima, Atsushi; Sato, Hiro; Noda, Shin-Ei; Saitoh, Jun-Ichi; Suzuki, Yoshiyuki

2015-03-01

Precise target detection is essential for radiosurgery, neurosurgery and hypofractionated radiotherapy because treatment results and complication rates are related to accuracy of the target definition. In skull base tumors and tumors around the optic pathways, exact anatomical evaluation of cranial nerves are important to avoid adverse effects on these structures close to lesions. Three-dimensional analyses of structures obtained with MR heavy T2-images and image fusion with CT thin-sliced sections are desirable to evaluate fine structures during radiosurgery and microsurgery. In vascular lesions, angiography is most important for evaluations of whole structures from feeder to drainer, shunt, blood flow and risk factors of bleeding. However, exact sites and surrounding structures in the brain are not shown on angiography. True image fusions of angiography, MR images and CT on axial planes are ideal for precise target definition. In malignant tumors, especially recurrent head and neck tumors, biologically active areas of recurrent tumors are main targets of radiosurgery. PET scan is useful for quantitative evaluation of recurrences. However, the examination is not always available at the time of radiosurgery. Image fusion of MR diffusion images with CT is always available during radiosurgery and useful for the detection of recurrent lesions. All images are fused and registered on thin sliced CT sections and exactly demarcated targets are planned for treatment. Follow-up images are also able to register on this CT. Exact target changes, including volume, are possible in this fusion system. The purpose of this review is to describe the usefulness of image fusion for 1) skull base, 2) vascular, 3) recurrent target detection, and 4) follow-up analyses in radiosurgery, neurosurgery and hypofractionated radiotherapy.

Image Fusion for Radiosurgery, Neurosurgery and Hypofractionated Radiotherapy

PubMed Central

Nakajima, Atsushi; Sato, Hiro; Noda, Shin-ei; Saitoh, Jun-ichi; Suzuki, Yoshiyuki

2015-01-01

Precise target detection is essential for radiosurgery, neurosurgery and hypofractionated radiotherapy because treatment results and complication rates are related to accuracy of the target definition. In skull base tumors and tumors around the optic pathways, exact anatomical evaluation of cranial nerves are important to avoid adverse effects on these structures close to lesions. Three-dimensional analyses of structures obtained with MR heavy T2-images and image fusion with CT thin-sliced sections are desirable to evaluate fine structures during radiosurgery and microsurgery. In vascular lesions, angiography is most important for evaluations of whole structures from feeder to drainer, shunt, blood flow and risk factors of bleeding. However, exact sites and surrounding structures in the brain are not shown on angiography. True image fusions of angiography, MR images and CT on axial planes are ideal for precise target definition. In malignant tumors, especially recurrent head and neck tumors, biologically active areas of recurrent tumors are main targets of radiosurgery. PET scan is useful for quantitative evaluation of recurrences. However, the examination is not always available at the time of radiosurgery. Image fusion of MR diffusion images with CT is always available during radiosurgery and useful for the detection of recurrent lesions. All images are fused and registered on thin sliced CT sections and exactly demarcated targets are planned for treatment. Follow-up images are also able to register on this CT. Exact target changes, including volume, are possible in this fusion system. The purpose of this review is to describe the usefulness of image fusion for 1) skull base, 2) vascular, 3) recurrent target detection, and 4) follow-up analyses in radiosurgery, neurosurgery and hypofractionated radiotherapy. PMID:26180676

Timing and conditions of peak metamorphism and cooling across the Zimithang Thrust, Arunachal Pradesh, India

NASA Astrophysics Data System (ADS)

Warren, Clare J.; Singh, Athokpam K.; Roberts, Nick M. W.; Regis, Daniele; Halton, Alison M.; Singh, Rajkumar B.

2014-07-01

The Zimithang Thrust juxtaposes two lithotectonic units of the Greater Himalayan Sequence in Arunachal Pradesh, NE India. Monazite U-Pb, muscovite 40Ar/39Ar and thermobarometric data from rocks in the hanging and footwall constrain the timing and conditions of their juxtaposition across the structure, and their subsequent cooling. Monazite grains in biotite-sillimanite gneiss in the hanging wall yield LA-ICP-MS U-Pb ages of 16 ± 0.2 to 12.7 ± 0.4 Ma. A schistose gneiss within the high strain zone yields overlapping-to-younger monazite ages of 14.9 ± 0.3 to 11.5 ± 0.3 Ma. Garnet-staurolite-mica schists in the immediate footwall yield older monazite ages of 27.3 ± 0.6 to 17.1 ± 0.2 Ma. Temperature estimates from Ti-in-biotite and garnet-biotite thermometry suggest similar peak temperatures were achieved in the hanging and footwalls (~ 525-650 °C). Elevated temperatures of ~ 700 °C appear to have been reached in the high strain zone itself and in the footwall further from the thrust. Single grain fusion 40Ar/39Ar muscovite data from samples either side of the thrust yield ages of ~ 7 Ma, suggesting that movement along the thrust juxtaposed the two units by the time the closure temperature of Ar diffusion in muscovite had been reached. These data confirm previous suggestions that major orogen-parallel out-of-sequence structures disrupt the Greater Himalayan Sequence at different times during Himalayan evolution, and highlight an eastwards-younging trend in 40Ar/39Ar muscovite cooling ages at equivalent structural levels along Himalayan strike.

Hairpin Folding of HIV gp41 Abrogates Lipid Mixing Function at Physiologic pH and Inhibits Lipid Mixing by Exposed gp41 Constructs†

PubMed Central

Sackett, Kelly; Nethercott, Matthew J.; Shai, Yechiel; Weliky, David P.

2009-01-01

Conformational changes in the HIV gp41 protein are directly correlated with fusion between the HIV and target cell plasma membranes which is the initial step of infection. Key gp41 fusion conformations include an early extended conformation termed pre-hairpin which contains exposed regions and a final low energy conformation termed hairpin which has compact six-helix bundle structure. Current fusion models debate the roles of hairpin and pre-hairpin conformations in the process of membrane merger. In the present work, gp41 constructs have been engineered which correspond to fusion relevant parts of both pre-hairpin and hairpin conformations, and have been analyzed for their ability to induce lipid mixing between membrane vesicles. The data correlate membrane fusion function with the pre-hairpin conformation and suggest that one of the roles of the final hairpin conformation is sequestration of membrane perturbing gp41 regions with consequent loss of the membrane disruption induced earlier by the pre-hairpin structure. To our knowledge, this is the first biophysical study to delineate the membrane fusion potential of gp41 constructs modeling key fusion conformations. PMID:19222185

Association of quantitative magnetic resonance imaging parameters with histological findings from MRI/ultrasound fusion prostate biopsy.

PubMed

Dianat, Seyed Saeid; Carter, H Ballentine; Schaeffer, Edward M; Hamper, Ulrik M; Epstein, Jonathan I; Macura, Katarzyna J

2015-10-01

Purpose of this pilot study was to correlate quantitative parameters derived from the multiparametric magnetic resonance imaging (MP-MRI) of the prostate with results from MRI guided transrectal ultrasound (MRI/TRUS) fusion prostate biopsy in men with suspected prostate cancer. Thirty-nine consecutive patients who had 3.0T MP-MRI and subsequent MRI/TRUS fusion prostate biopsy were included and 73 MRI-identified targets were sampled by 177 cores. The pre-biopsy MP-MRI consisted of T2-weighted, diffusion weighted (DWI), and dynamic contrast enhanced (DCE) images. The association of quantitative MRI measurements with biopsy histopathology findings was assessed by Mann-Whitney U- test and Kruskal-Wallis test. Of 73 targets, biopsy showed benign prostate tissue in 46 (63%), cancer in 23 (31.5%), and atypia/high grade prostatic intraepithelial neoplasia in four (5.5%) targets. The median volume of cancer-positive targets was 1.3 cm3. The cancer-positive targets were located in the peripheral zone (56.5%), transition zone (39.1%), and seminal vesicle (4.3%). Nine of 23 (39.1%) cancer-positive targets were higher grade cancer (Gleason grade > 6). Higher grade targets and cancer-positive targets compared to benign lesions exhibited lower mean apparent diffusion coefficient (ADC) value (952.7 < 1167.9 < 1278.9), and lower minimal extracellular volume fraction (ECF) (0.13 < 0.185 < 0.213), respectively. The difference in parameters was more pronounced between higher grade cancer and benign lesions. Our findings from a pilot study indicate that quantitative MRI parameters can predict malignant histology on MRI/TRUS fusion prostate biopsy, which is a valuable technique to ensure adequate sampling of MRI-visible suspicious lesions under TRUS guidance and may impact patient management. The DWI-based quantitative measurement exhibits a stronger association with biopsy findings than the other MRI parameters.

Review of 3d GIS Data Fusion Methods and Progress

NASA Astrophysics Data System (ADS)

Hua, Wei; Hou, Miaole; Hu, Yungang

2018-04-01

3D data fusion is a research hotspot in the field of computer vision and fine mapping, and plays an important role in fine measurement, risk monitoring, data display and other processes. At present, the research of 3D data fusion in the field of Surveying and mapping focuses on the 3D model fusion of terrain and ground objects. This paper summarizes the basic methods of 3D data fusion of terrain and ground objects in recent years, and classified the data structure and the establishment method of 3D model, and some of the most widely used fusion methods are analysed and commented.

The Effect of Oscillating Traverse Welding on Performance of Cr-Fe-C Hardfacing Alloys

NASA Astrophysics Data System (ADS)

Lai, Hsuan-Han; Hsieh, Chih-Chun; Wang, Jia-Siang; Lin, Chi-Ming; Wu, Weite

2015-11-01

In this study, a series of experiments involving Cr-Fe-C hardfacing alloys is conducted to evaluate the effect of oscillating traverse welding on microstructure and performance of clad alloys. The alloys are designed to exhibit hypoeutectic, eutectic, and hypereutectic morphology. The morphology of the heat-affected zone (HAZ) of the unmelted metal, the solidified remelted metal, and the fusion boundary exhibited distinct characteristics. In the hypoeutectic and the eutectic alloys, the same lamellar eutectic structure can be observed as the solidified structure, and they also showed the same evolution in the HAZ. In the hypereutectic alloy, the incomplete weld pool blending results in a eutectic morphology instead of a fully hypereutectic morphology. The hardness result reveals that, for the hypereutectic alloy, the eutectic region, instead of the HAZ, is the weak point. The wear test shows that the hypoeutectic alloy exhibits the same wear behaviors in both the remelted metal and the HAZ, and so is the hypereutectic alloy; the eutectic alloy remelted metal and the HAZ have different wear morphologies.

A Proposed Data Fusion Architecture for Micro-Zone Analysis and Data Mining

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kevin McCarthy; Milos Manic

Data Fusion requires the ability to combine or “fuse” date from multiple data sources. Time Series Analysis is a data mining technique used to predict future values from a data set based upon past values. Unlike other data mining techniques, however, Time Series places special emphasis on periodicity and how seasonal and other time-based factors tend to affect trends over time. One of the difficulties encountered in developing generic time series techniques is the wide variability of the data sets available for analysis. This presents challenges all the way from the data gathering stage to results presentation. This paper presentsmore » an architecture designed and used to facilitate the collection of disparate data sets well suited to Time Series analysis as well as other predictive data mining techniques. Results show this architecture provides a flexible, dynamic framework for the capture and storage of a myriad of dissimilar data sets and can serve as a foundation from which to build a complete data fusion architecture.« less

Factors regulating the abundance and localization of synaptobrevin in the plasma membrane

PubMed Central

Dittman, Jeremy S.; Kaplan, Joshua M.

2006-01-01

After synaptic vesicle fusion, vesicle proteins must be segregated from plasma membrane proteins and recycled to maintain a functional vesicle pool. We monitored the distribution of synaptobrevin, a vesicle protein required for exocytosis, in Caenorhabditis elegans motor neurons by using a pH-sensitive synaptobrevin GFP fusion protein, synaptopHluorin. We estimated that 30% of synaptobrevin was present in the plasma membrane. By using a panel of endocytosis and exocytosis mutants, we found that the majority of surface synaptobrevin derives from fusion of synaptic vesicles and that, in steady state, synaptobrevin equilibrates throughout the axon. The surface synaptobrevin was enriched near active zones, and its spatial extent was regulated by the clathrin adaptin AP180. These results suggest that there is a plasma membrane reservoir of synaptobrevin that is supplied by the synaptic vesicle cycle and available for retrieval throughout the axon. The size of the reservoir is set by the relative rates of exo- and endocytosis. PMID:16844789

Multispecies exclusion process with fusion and fission of rods: A model inspired by intraflagellar transport

NASA Astrophysics Data System (ADS)

Patra, Swayamshree; Chowdhury, Debashish

2018-01-01

We introduce a multispecies exclusion model where length-conserving probabilistic fusion and fission of the hard rods are allowed. Although all rods enter the system with the same initial length ℓ =1 , their length can keep changing, because of fusion and fission, as they move in a step-by-step manner towards the exit. Two neighboring hard rods of lengths ℓ1 and ℓ2 can fuse into a single rod of longer length ℓ =ℓ1+ℓ2 provided ℓ ≤N . Similarly, length-conserving fission of a rod of length ℓ'≤N results in two shorter daughter rods. Based on the extremum current hypothesis, we plot the phase diagram of the model under open boundary conditions utilizing the results derived for the same model under periodic boundary condition using mean-field approximation. The density profile and the flux profile of rods are in excellent agreement with computer simulations. Although the fusion and fission of the rods are motivated by similar phenomena observed in intraflagellar transport (IFT) in eukaryotic flagella, this exclusion model is too simple to account for the quantitative experimental data for any specific organism. Nevertheless, the concepts of "flux profile" and "transition zone" that emerge from the interplay of fusion and fission in this model are likely to have important implications for IFT and for other similar transport phenomena in long cell protrusions.

Individual dose due to radioactivity accidental release from fusion reactor.

PubMed

Nie, Baojie; Ni, Muyi; Wei, Shiping

2017-04-05

As an important index shaping the design of fusion safety system, evaluation of public radiation consequences have risen as a hot topic on the way to develop fusion energy. In this work, the comprehensive public early dose was evaluated due to unit gram tritium (HT/HTO), activated dust, activated corrosion products (ACPs) and activated gases accidental release from ITER like fusion reactor. Meanwhile, considering that we cannot completely eliminate the occurrence likelihood of multi-failure of vacuum vessel and tokamak building, we conservatively evaluated the public radiation consequences and environment restoration after the worst hypothetical accident preliminarily. The comparison results show early dose of different unit radioactivity release under different conditions. After further performing the radiation consequences, we find it possible that the hypothetical accident for ITER like fusion reactor would result in a level 6 accident according to INES, not appear level 7 like Chernobyl or Fukushima accidents. And from the point of environment restoration, we need at least 69 years for case 1 (1kg HTO and 1000kg dust release) and 34-52years for case 2 (1kg HTO and 10kg-100kg dust release) to wait the contaminated zone drop below the general public safety limit (1mSv per year) before it is suitable for human habitation. Copyright © 2016 Elsevier B.V. All rights reserved.

Materials Studies for Magnetic Fusion Energy Applications at Low Temperatures - 6.

DTIC Science & Technology

1983-05-01

structures for the superconducting magnets of magnetic fusion energy power plants and prototypes. The program was conceived and developed jointly by the...staffs of the National Bureau of Standards and the Office of Fusion Energy of the Department of Energy; it is managed by NBS and sponsored by DoE

Sensor fusion III: 3-D perception and recognition; Proceedings of the Meeting, Boston, MA, Nov. 5-8, 1990

NASA Technical Reports Server (NTRS)

Schenker, Paul S. (Editor)

1991-01-01

The volume on data fusion from multiple sources discusses fusing multiple views, temporal analysis and 3D motion interpretation, sensor fusion and eye-to-hand coordination, and integration in human shape perception. Attention is given to surface reconstruction, statistical methods in sensor fusion, fusing sensor data with environmental knowledge, computational models for sensor fusion, and evaluation and selection of sensor fusion techniques. Topics addressed include the structure of a scene from two and three projections, optical flow techniques for moving target detection, tactical sensor-based exploration in a robotic environment, and the fusion of human and machine skills for remote robotic operations. Also discussed are K-nearest-neighbor concepts for sensor fusion, surface reconstruction with discontinuities, a sensor-knowledge-command fusion paradigm for man-machine systems, coordinating sensing and local navigation, and terrain map matching using multisensing techniques for applications to autonomous vehicle navigation.

Sensors and Algorithms for an Unmanned Surf-Zone Robot

DTIC Science & Technology

2015-12-01

71 3. Data Fusion and Filtering................................................ 74 C. VIRTUAL POTENTIAL FIELD (VPF) PATH PLANNING ...iron effects are clearly seen: Soft iron de - calibration (sphere distortion) was caused by proximity of circuit boards. Offset of the center of the...information to perform global tasks such as path- planning , sensors and actuators commands, external communications, etc. Python3 is used as the primary

Microstructure and Mechanical Properties of Hybrid Welded Joints with Laser and CO2-Shielded Arc

NASA Astrophysics Data System (ADS)

Wahba, M.; Mizutani, M.; Katayama, S.

2016-07-01

With the objective of reducing the operating costs, argon-rich shielding gas was replaced by 100% CO2 gas in hybrid laser-arc welding of shipbuilding steel. The welding parameters were optimized to obtain buried-arc transfer in order to mitigate spatter formation. Sound butt joints could be successfully produced for plates of 14 and 17 mm thickness in one welding pass. Subsequently, the welded joints were subjected to different tests to evaluate the influence of CO2 shielding gas on the mechanical properties of the welded joints. All tensile-tested specimens failed in the base material, indicating the higher strength of the welded joints. The impact toughness of the welded joints, measured at -20 °C, reached approximately 76% of that of the base material, which was well above the limit set by the relevant standard. The microstructure of the fusion zone consisted of grain boundary ferrite and acicular ferrite uniformly over the plate thickness except for the joint root where the microstructure was chiefly ferrite with an aligned second phase. This resulted in higher hardness in the root region compared with the top and middle parts of the fusion zone.

Effect of laser welding parameters on the austenite and martensite phase fractions of NiTi

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oliveira, J.P., E-mail: jp.oliveira@campus.fct.unl

Although laser welding is probably the most used joining technique for NiTi shape memory alloys there is still a lack of understanding about the effects of laser welding parameters on the microstructural induced changes: in both the heat affected and fusion zones martensite may be present, while the base material is fully austenitic. Synchrotron X-ray diffraction was used for fine probing laser welded NiTi joints. Through Rietveld refinement the martensite and austenite phase fractions were determined and it was observed that the martensite content increases towards the weld centreline. This is related to a change of the local transformation temperaturesmore » on these regions, which occurs due to compositional variation in those regions. The martensite phase fraction in the thermally affected regions may have significant implications on functional properties on these joints. - Highlights: •Synchrotron X-ray diffraction was used for fine probing of the microstructure in laser welded NiTi joints. •Rietveld refinement allowed to determine the content of martensite along the heat affected and fusion zones. •The martensite content increases from the base material towards the weld centreline.« less

Analysis of laser-induction hybrid cladding processing conditions

NASA Astrophysics Data System (ADS)

Huang, Yongjun; Zeng, Xiaoyan; Hu, Qianwu

2007-12-01

A new cladding approach based on laser-induction hybrid technique on flat sheets is presented in this paper. Coating is produced by means of 5kw cw CO II laser equipped with 100kw high frequent inductor, and the experiments set-up, involving a special machining-head, which can provide laser-induction hybrid heat resources simultaneously. The formation of thick NiCrSiB coating on a steel substrate by off-axial powder feeding is studied from an experimental point of view. A substrate melting energy model is developed to describe the energy relationship between laser-induction hybrid cladding and laser cladding alone quantitatively. By comparing the experimental results with the calculational ones, it is shown that the tendency of fusion zone height of theoretical calculation is in agreement with that of tests in laser-induction hybrid cladding. Via analyses and tests, the conclusions can be lead to that the fusion zone height can be increased easily and the good bond of cladding track can be achieved within wide cladding processing window in laser-induction hybrid processing. It shows that the induction heating has an obvious effect on substrate melting and metallurgical bond.

Microstructural characterization of dissimilar welds between Incoloy 800H and 321 Austenitic Stainless Steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sayiram, G., E-mail: sayiram.g@vit.ac.in; Arivazhagan, N.

2015-04-15

In this work, the microstructural character of dissimilar welds between Incoloy 800H and 321 Stainless Steel has been discussed. The microscopic examination of the base metals, fusion zones and interfaces was characterized using an optical microscope and scanning electron microscopy. The results revealed precipitates of Ti (C, N) in the austenitic matrix along the grain boundaries of the base metals. Migration of grain boundaries in the Inconel 82 weld metal was very extensive when compared to Inconel 617 weldment. Epitaxial growth was observed in the 617 weldment which increases the strength and ductility of the weld metal. Unmixed zone nearmore » the fusion line between 321 Stainless Steel and Inconel 82 weld metal was identified. From the results, it has been concluded that Inconel 617 filler metal is a preferable choice for the joint between Incoloy 800H and 321 Stainless Steel. - Highlights: • Failure mechanisms produced by dissimilar welding of Incoloy 800H to AISI 321SS • Influence of filler wire on microstructure properties • Contemplative comparisons of metallurgical aspects of these weldments • Microstructure and chemical studies including metallography, SEM–EDS • EDS-line scan study at interface.« less

Microstructural studies on failure mechanisms in thermo-mechanical fatigue of repaired DS R80 and IN 738 Superalloys

NASA Astrophysics Data System (ADS)

Abrokwah, Emmanuel Otchere

Directionally solidified Rene 80 (DS R80) and polycrystalline Inconel 738(IN 738) Superalloys were tested in thermo-mechanical fatigue (TMF) over the temperature range of 500-900°C and plastic strain range from 0.1 to 0.8% using a DSI Gleeble thermal simulator. Thermo-mechanical testing was carried out on the parent material (baseline) in the conventional solution treated and aged condition (STA), as well as gas tungsten arc welded (GTAW) with an IN-738 filler, followed by solution treatment and ageing. Comparison of the baseline alloy microstructure with that of the welded and heat treated alloy showed that varying crack initiation mechanisms, notably oxidation by stress assisted grain boundary oxidation, grain boundary MC carbides fatigue crack initiation, fatigue crack initiation from sample surfaces, crack initiation from weld defects and creep deformation were operating, leading to different “weakest link” and failure initiation points. The observations from this study show that the repaired samples had extra crack initiation sites not present in the baseline, which accounted for their occasional poor fatigue life. These defects include lack of fusion between the weld and the base metal, fusion zone cracking, and heat affected zone microfissures.

Mechanical properties and microstructures of a magnesium alloy gas tungsten arc welded with a cadmium chloride flux

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Z.D.; Liu, L.M.; Shen, Y.

2008-01-15

Gas tungsten arc (GTA) welds were prepared on 5-mm thick plates of wrought magnesium AZ31B alloy, using an activated flux. The microstructural characteristics of the weld joint were investigated using optical and scanning microscopy, and the fusion zone microstructure was compared with that of the base metal. The elemental distribution was also investigated by electron probe microanalysis (EPMA). Mechanical properties were determined by standard tensile tests on small-scale specimens. The as-welded fusion zone prepared using a CdCl{sub 2} flux exhibited a larger grain size than that prepared without flux; the microstructure consisted of matrix {alpha}-Mg, eutectic {alpha}-Mg and {beta}-Al{sub 12}Mg{submore » 17}. The HAZ was observed to be slightly wider for the weld prepared with a CdCl{sub 2} flux compared to that prepared without flux; thus the tensile strength was lower for the flux-prepared weld. The fact that neither Cd nor Cl was detected in the weld seam by EPMA indicates that the CdCl{sub 2} flux has a small effect on convection in the weld pool.« less

Weldability Characteristics of Sintered Hot-Forged AISI 4135 Steel Produced through P/M Route by Using Pulsed Current Gas Tungsten Arc Welding

NASA Astrophysics Data System (ADS)

Joseph, Joby; Muthukumaran, S.; Pandey, K. S.

2016-01-01

Present investigation is an attempt to study the weldability characteristics of sintered hot-forged plates of AISI 4135 steel produced through powder metallurgy (P/M) route using matching filler materials of ER80S B2. Compacts of homogeneously blended elemental powders corresponding to the above steel were prepared on a universal testing machine (UTM) by taking pre-weighed powder blend with a suitable die, punch and bottom insert assembly. Indigenously developed ceramic coating was applied on the entire surface of the compacts in order to protect them from oxidation during sintering. Sintered preforms were hot forged to flat, approximately rectangular plates, welded by pulsed current gas tungsten arc welding (PCGTAW) processes with aforementioned filler materials. Microstructural, tensile and hardness evaluations revealed that PCGTAW process with low heat input could produce weldments of good quality with almost nil defects. It was established that PCGTAW joints possess improved tensile properties compared to the base metal and it was mainly attributed to lower heat input, resulting in finer fusion zone grains and higher fusion zone hardness. Thus, the present investigation opens a new and demanding field in research.

Incorporating priors on expert performance parameters for segmentation validation and label fusion: a maximum a posteriori STAPLE

PubMed Central

Commowick, Olivier; Warfield, Simon K

2010-01-01

In order to evaluate the quality of segmentations of an image and assess intra- and inter-expert variability in segmentation performance, an Expectation Maximization (EM) algorithm for Simultaneous Truth And Performance Level Estimation (STAPLE) was recently developed. This algorithm, originally presented for segmentation validation, has since been used for many applications, such as atlas construction and decision fusion. However, the manual delineation of structures of interest is a very time consuming and burdensome task. Further, as the time required and burden of manual delineation increase, the accuracy of the delineation is decreased. Therefore, it may be desirable to ask the experts to delineate only a reduced number of structures or the segmentation of all structures by all experts may simply not be achieved. Fusion from data with some structures not segmented by each expert should be carried out in a manner that accounts for the missing information. In other applications, locally inconsistent segmentations may drive the STAPLE algorithm into an undesirable local optimum, leading to misclassifications or misleading experts performance parameters. We present a new algorithm that allows fusion with partial delineation and which can avoid convergence to undesirable local optima in the presence of strongly inconsistent segmentations. The algorithm extends STAPLE by incorporating prior probabilities for the expert performance parameters. This is achieved through a Maximum A Posteriori formulation, where the prior probabilities for the performance parameters are modeled by a beta distribution. We demonstrate that this new algorithm enables dramatically improved fusion from data with partial delineation by each expert in comparison to fusion with STAPLE. PMID:20879379

Incorporating priors on expert performance parameters for segmentation validation and label fusion: a maximum a posteriori STAPLE.

PubMed

Commowick, Olivier; Warfield, Simon K

2010-01-01

In order to evaluate the quality of segmentations of an image and assess intra- and inter-expert variability in segmentation performance, an Expectation Maximization (EM) algorithm for Simultaneous Truth And Performance Level Estimation (STAPLE) was recently developed. This algorithm, originally presented for segmentation validation, has since been used for many applications, such as atlas construction and decision fusion. However, the manual delineation of structures of interest is a very time consuming and burdensome task. Further, as the time required and burden of manual delineation increase, the accuracy of the delineation is decreased. Therefore, it may be desirable to ask the experts to delineate only a reduced number of structures or the segmentation of all structures by all experts may simply not be achieved. Fusion from data with some structures not segmented by each expert should be carried out in a manner that accounts for the missing information. In other applications, locally inconsistent segmentations may drive the STAPLE algorithm into an undesirable local optimum, leading to misclassifications or misleading experts performance parameters. We present a new algorithm that allows fusion with partial delineation and which can avoid convergence to undesirable local optima in the presence of strongly inconsistent segmentations. The algorithm extends STAPLE by incorporating prior probabilities for the expert performance parameters. This is achieved through a Maximum A Posteriori formulation, where the prior probabilities for the performance parameters are modeled by a beta distribution. We demonstrate that this new algorithm enables dramatically improved fusion from data with partial delineation by each expert in comparison to fusion with STAPLE.

Loss-of-function of the ciliopathy protein Cc2d2a disorganizes the vesicle fusion machinery at the periciliary membrane and indirectly affects Rab8-trafficking in zebrafish photoreceptors

PubMed Central

Gesemann, Matthias; Mateos, José M.; Barmettler, Gery; Forbes, Austin; Ziegler, Urs

2017-01-01

Ciliopathies are human disorders caused by dysfunction of primary cilia, ubiquitous organelles involved in transduction of environmental signals such as light sensation in photoreceptors. Concentration of signal detection proteins such as opsins in the ciliary membrane is achieved by RabGTPase-regulated polarized vesicle trafficking and by a selective barrier at the ciliary base, the transition zone (TZ). Dysfunction of the TZ protein CC2D2A causes Joubert/Meckel syndromes in humans and loss of ciliary protein localization in animal models, including opsins in retinal photoreceptors. The link between the TZ and upstream vesicle trafficking has been little explored to date. Moreover, the role of the small GTPase Rab8 in opsin-carrier vesicle (OCV) trafficking has been recently questioned in a mouse model. Using correlative light and electron microscopy and live imaging in zebrafish photoreceptors, we provide the first live characterization of Rab8-mediated trafficking in photoreceptors in vivo. Our results support a possibly redundant role for both Rab8a/b paralogs in OCV trafficking, based on co-localization of Rab8 and opsins in vesicular structures, and joint movement of Rab8-tagged particles with opsin. We further investigate the role of the TZ protein Cc2d2a in Rab8-mediated trafficking using cc2d2a zebrafish mutants and identify a requirement for Cc2d2a in the latest step of OCV trafficking, namely vesicle fusion. Progressive accumulation of opsin-containing vesicles in the apical portion of photoreceptors lacking Cc2d2a is caused by disorganization of the vesicle fusion machinery at the periciliary membrane with mislocalization and loss of the t-SNAREs SNAP25 and Syntaxin3 and of the exocyst component Exoc4. We further observe secondary defects on upstream Rab8-trafficking with cytoplasmic accumulation of Rab8. Taken together, our results support participation of Rab8 in OCV trafficking and identify a novel role for the TZ protein Cc2d2a in fusion of incoming ciliary-directed vesicles, through organization of the vesicle fusion machinery at the periciliary membrane. PMID:29281629

Loss-of-function of the ciliopathy protein Cc2d2a disorganizes the vesicle fusion machinery at the periciliary membrane and indirectly affects Rab8-trafficking in zebrafish photoreceptors.

PubMed

Ojeda Naharros, Irene; Gesemann, Matthias; Mateos, José M; Barmettler, Gery; Forbes, Austin; Ziegler, Urs; Neuhauss, Stephan C F; Bachmann-Gagescu, Ruxandra

2017-12-01

Ciliopathies are human disorders caused by dysfunction of primary cilia, ubiquitous organelles involved in transduction of environmental signals such as light sensation in photoreceptors. Concentration of signal detection proteins such as opsins in the ciliary membrane is achieved by RabGTPase-regulated polarized vesicle trafficking and by a selective barrier at the ciliary base, the transition zone (TZ). Dysfunction of the TZ protein CC2D2A causes Joubert/Meckel syndromes in humans and loss of ciliary protein localization in animal models, including opsins in retinal photoreceptors. The link between the TZ and upstream vesicle trafficking has been little explored to date. Moreover, the role of the small GTPase Rab8 in opsin-carrier vesicle (OCV) trafficking has been recently questioned in a mouse model. Using correlative light and electron microscopy and live imaging in zebrafish photoreceptors, we provide the first live characterization of Rab8-mediated trafficking in photoreceptors in vivo. Our results support a possibly redundant role for both Rab8a/b paralogs in OCV trafficking, based on co-localization of Rab8 and opsins in vesicular structures, and joint movement of Rab8-tagged particles with opsin. We further investigate the role of the TZ protein Cc2d2a in Rab8-mediated trafficking using cc2d2a zebrafish mutants and identify a requirement for Cc2d2a in the latest step of OCV trafficking, namely vesicle fusion. Progressive accumulation of opsin-containing vesicles in the apical portion of photoreceptors lacking Cc2d2a is caused by disorganization of the vesicle fusion machinery at the periciliary membrane with mislocalization and loss of the t-SNAREs SNAP25 and Syntaxin3 and of the exocyst component Exoc4. We further observe secondary defects on upstream Rab8-trafficking with cytoplasmic accumulation of Rab8. Taken together, our results support participation of Rab8 in OCV trafficking and identify a novel role for the TZ protein Cc2d2a in fusion of incoming ciliary-directed vesicles, through organization of the vesicle fusion machinery at the periciliary membrane.

Microstructure and Corrosion Resistance of Laser-Welded Crossed Nitinol Wires.

PubMed

Dong, Peng; Yao, Runhua; Yan, Zheng; Yan, Zhifeng; Wang, Wenxian; He, Xiuli; Zhou, Jun

2018-05-18

Laser welding has been considered to be one of the most promising joining processes for Nitinol medical device manufacturing. Presently, there is still a limited understanding about how laser welding affects the microstructure and the resultant corrosion behaviors. This work aimed to reveal the microstructural factors that influence the corrosion resistance of laser-welded crossed Nitinol joints. The microstructures within various zones of the joints were characterized by using transmission electron microscopy (TEM), and the corrosion behaviors of the joints in 0.9% NaCl and Hank's solutions were studied. The base metal exhibits a single austenite (B2) phase and the highest corrosion resistance. The phase constituent of the fusion zone is the coexistence of the B2 matrix and some precipitates (T₂Ni, TiNi 3, and Ti₃Ni₄ particles), resulting in a slight decrease in corrosion resistance. The heat affected zone (HAZ) shows the austenite matrix but with the precipitation of R-phase, which considerably reduces the corrosion potential, making it the weakest zone.

Coastal Zone Mapping and Imaging Lidar (CZMIL): first flights and system validation

NASA Astrophysics Data System (ADS)

Feygels, Viktor I.; Park, Joong Yong; Aitken, Jennifer; Kim, Minsu; Payment, Andy; Ramnath, Vinod

2012-09-01

CZMIL is an integrated lidar-imagery sensor system and software suite designed for the highly automated generation of physical and environmental information products for mapping the coastal zone. This paper presents the results of CZMIL system validation in turbid water conditions on the Gulf Coast of Mississippi and in relatively clear water conditions in Florida in late spring 2012. The system performance test shows that CZMIL successfully achieved 7-8m depth in Kd =0.46m-1 (Kd is the diffuse attenuation coefficient) in Mississippi and up to 41m when Kd=0.11m-1 in Florida. With a seven segment array for topographic mode and the shallow water zone, CZMIL generated high resolution products with a maximum pulse rate of 70 kHz, and with 10 kHz in the deep water zone. Diffuse attenuation coefficient, bottom reflectance and other environmental parameters for the whole multi km2 area were estimated based on fusion of lidar and CASI-1500 hyperspectral camera data.

Nuclear Fusion Blast and Electrode Lifetimes in a PJMIF Reactor

NASA Astrophysics Data System (ADS)

Thio, Y. C. Francis; Witherspoon, F. D.; Case, A.; Brockington, S.; Cruz, E.; Luna, M.; Hsu, S. C.

2017-10-01

We present an analysis and numerical simulation of the nuclear blast from the micro-explosion following the completion of the fusion burn for a baseline design of a PJMIF fusion reactor with a fusion gain of 20. The stagnation pressure from the blast against the chamber wall defines the engineering requirement for the structural design of the first wall and the plasma guns. We also present an analysis of the lifetimes of the electrodes of the plasma guns which are exposed to (1) the high current, and (2) the neutron produced by the fusion reactions. We anticipate that the gun electrodes are made of tungsten alloys as plasma facing components reinforced structurally by appropriate steel alloys. Making reasonable assumptions about the electrode erosion rate (100 ng/C transfer), the electrode lifetime limited by the erosion rate is estimated to be between 19 and 24 million pulses before replacement. Based on known neutron radiation effects on structural materials such as steel alloys and plasma facing component materials such as tungsten alloys, the plasma guns are expected to survive some 22 million shots. At 1 Hz, this equal to about 6 months of continuous operation before they need to be replaced. Work supported by Strong Atomics, LLC.

Echocardiographic and Fluoroscopic Fusion Imaging for Procedural Guidance: An Overview and Early Clinical Experience.

PubMed

Thaden, Jeremy J; Sanon, Saurabh; Geske, Jeffrey B; Eleid, Mackram F; Nijhof, Niels; Malouf, Joseph F; Rihal, Charanjit S; Bruce, Charles J

2016-06-01

There has been significant growth in the volume and complexity of percutaneous structural heart procedures in the past decade. Increasing procedural complexity and accompanying reliance on multimodality imaging have fueled the development of fusion imaging to facilitate procedural guidance. The first clinically available system capable of echocardiographic and fluoroscopic fusion for real-time guidance of structural heart procedures was approved by the US Food and Drug Administration in 2012. Echocardiographic-fluoroscopic fusion imaging combines the precise catheter and device visualization of fluoroscopy with the soft tissue anatomy and color flow Doppler information afforded by echocardiography in a single image. This allows the interventionalist to perform precise catheter manipulations under fluoroscopy guidance while visualizing critical tissue anatomy provided by echocardiography. However, there are few data available addressing this technology's strengths and limitations in routine clinical practice. The authors provide a critical review of currently available echocardiographic-fluoroscopic fusion imaging for guidance of structural heart interventions to highlight its strengths, limitations, and potential clinical applications and to guide further research into value of this emerging technology. Copyright © 2016 American Society of Echocardiography. Published by Elsevier Inc. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Jianbin

The microstructure and mechanical properties of resistance-spot-welded A5052 aluminum alloy and DP 600 dual-phase steel joint were studied. The fusion zone (FZ) and heat-affected zone (HAZ) of DP 600 exhibited lath martensite and ferrite-martensite structures, respectively. The microstructure of FZ and HAZ in the A5052 side was composed of cellular crystals and the boundary region of FZ exhibited a columnar crystal morphology. A Fe{sub 2}Al{sub 5} intermetallic compound (IMC) layer with 3.3 μm thickness was found adjacent to the DP 600 side, whereas a needle-shaped Fe{sub 4}Al{sub 13} IMC layer with length of 0.67 μm to 15.8 μm was foundmore » adjacent to the aluminum alloy side. The maximum tensile shear load of the A5052/DP 600 joint was 5.5 KN, with a corresponding molten nugget diameter of 6.3 mm. The fracture morphology of the optimized A5052/DP 600 joint was mainly an elongated dimple fracture accompanied by cleavage fracture. - Highlights: •A5052 and DP 600 with large gaps in properties were investigated by RSW. •The microstructures of RSW joints in DP 600/A5052 were examined detailedly. •The micro/macro-characteristics and strength relations of joints were analyzed.« less

Microstructure formation in partially melted zone during gas tungsten arc welding of AZ91 Mg cast alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu Tianping; Chen, Zhan W.; Gao Wei

2008-11-15

During gas tungsten arc (GTA) welding of AZ91 Mg cast alloy, constitutional liquid forms locally in the original interdendritic regions in the partially melted zone (PMZ). The PMZ re-solidification behaviour has not been well understood. In this study, the gradual change of the re-solidification microstructure within PMZ from base metal side to weld metal side was characterised. High cooling rate experiments using Gleeble thermal simulator were also conducted to understand the morphological change of the {alpha}-Mg/{beta}-Mg{sub 17}Al{sub 12} phase interface formed during re-solidification after partial melting. It was found that the original partially divorced eutectic structure has become a moremore » regular eutectic phase in most of the PMZ, although close to the fusion boundary the re-solidified eutectic is again a divorced one. Proceeding the eutectic re-solidification, if the degree of partial melting is sufficiently high, {alpha}-Mg re-solidified with a cellular growth, resulting in a serrated interface between {alpha}-Mg and {alpha}-Mg/{beta}-Mg{sub 17}Al{sub 12} in the weld sample and between {alpha}-Mg and {beta}-Mg{sub 17}Al{sub 12} (fully divorced eutectic) in Gleeble samples. The morphological changes affected by the peak temperature and cooling rate are also explained.« less

The dissimilar effect of diacylglycerols on Ca(2+)-induced phosphatidylserine vesicle fusion.

PubMed Central

Sánchez-Migallón, M P; Aranda, F J; Gómez-Fernández, J C

1995-01-01

We have studied the effect of physiological concentrations of different diacylglycerols on Ca(2+)-induced fusion between phosphatidylserine vesicles. We monitored vesicle fusion as mixing of membrane lipids under conditions where the limiting factor was the aggregation and also in conditions where this aggregation was not the limiting factor. We found that diacylglycerols have a different modulating effect on the Ca(2+)-induced fusion: i) depending on their interfacial conformation, so that 1,2-isomers of diacylglycerols containing unsaturated or short saturated acyl chains stimulated fusion and their 1,3-isomers did not, and ii) depending on their specific type of bilayer interior perturbation, so that diacylglycerols containing unsaturated or short chain saturated acyl chains stimulated fusion but those containing long-chain saturated acyl chains did not. These requirements resembled those required for the diacylglycerol activation of protein kinase C, suggesting that diacylglycerol acts in both the specific activation of this enzyme and the induction of membrane fusion through the same perturbation of lipid structure. We found that polylysine affected the stimulatory role of 1,2-dioleoylglycerol differently, depending on whether aggregation was the limiting factor of fusion. When we studied the effect of very low concentrations of diacylglycerols on the bulk structural properties of phosphatidylserine, we found that they neither significantly perturbed the thermotropic transitions of phosphatidylserine nor affected the interaction of Ca2+ with the phosphate group of phosphatidylserine. The underlying mechanism of fusion between phosphatidylserine vesicles is discussed. PMID:7696508

Endocytosis regulates membrane localization and function of the fusogen EFF-1.

PubMed

Smurova, Ksenia; Podbilewicz, Benjamin

2017-07-03

Cell fusion is essential for sexual reproduction and formation of muscles, bones, and placenta. Two families of cell fusion proteins (Syncytins and FFs) have been identified in eukaryotes. Syncytins have been shown to form the giant syncytial trophoblasts in the placenta. The FFs are essential to fuse cells in the skin, reproductive, excretory, digestive and nervous systems in nematodes. EFF-1 (Epithelial Fusion Failure 1), a member of the FF family, is a type I membrane glycoprotein that is essential for most cell fusions in C. elegans. The crystal structure of EFF-1 ectodomain reveals striking structural similarity to class II fusion glycoproteins from enveloped viruses (e.g. dengue and rubella) that mediate virus to cell fusion. We found EFF-1 to be present on the plasma membrane and in RAB-5-positive early endosomes, with EFF-1 recycling between these 2 cell compartments. Only when EFF-1 proteins transiently arrive to the surfaces of 2 adjacent cells do they dynamically interact in trans and mediate membrane fusion. EFF-1 is continuously internalized by receptor-mediated endocytosis via the activity of 2 small GTPases: RAB-5 and Dynamin. Here we propose a model that explains how EFF-1 endocytosis together with interactions in trans can control cell-cell fusion. Kontani et al. showed that vacuolar ATPase (vATPase) mutations result in EFF-1-dependent hyperfusion. 1 We propose that vATPase is required for normal degradation of EFF-1. Failure to degrade EFF-1 results in delayed hyperfusion and mislocalization to organelles that appear to be recycling endosomes. EFF-1 is also required to fuse neurons as part of the repair mechanism following injury and to prune dendrites. We speculate that EFF-1 may regulate neuronal tree like structures via endocytosis. Thus, endocytosis of cell-cell fusion proteins functions to prevent merging of cells and to sculpt organs and neurons.

Analysis of decision fusion algorithms in handling uncertainties for integrated health monitoring systems

NASA Astrophysics Data System (ADS)

Zein-Sabatto, Saleh; Mikhail, Maged; Bodruzzaman, Mohammad; DeSimio, Martin; Derriso, Mark; Behbahani, Alireza

2012-06-01

It has been widely accepted that data fusion and information fusion methods can improve the accuracy and robustness of decision-making in structural health monitoring systems. It is arguably true nonetheless, that decision-level is equally beneficial when applied to integrated health monitoring systems. Several decisions at low-levels of abstraction may be produced by different decision-makers; however, decision-level fusion is required at the final stage of the process to provide accurate assessment about the health of the monitored system as a whole. An example of such integrated systems with complex decision-making scenarios is the integrated health monitoring of aircraft. Thorough understanding of the characteristics of the decision-fusion methodologies is a crucial step for successful implementation of such decision-fusion systems. In this paper, we have presented the major information fusion methodologies reported in the literature, i.e., probabilistic, evidential, and artificial intelligent based methods. The theoretical basis and characteristics of these methodologies are explained and their performances are analyzed. Second, candidate methods from the above fusion methodologies, i.e., Bayesian, Dempster-Shafer, and fuzzy logic algorithms are selected and their applications are extended to decisions fusion. Finally, fusion algorithms are developed based on the selected fusion methods and their performance are tested on decisions generated from synthetic data and from experimental data. Also in this paper, a modeling methodology, i.e. cloud model, for generating synthetic decisions is presented and used. Using the cloud model, both types of uncertainties; randomness and fuzziness, involved in real decision-making are modeled. Synthetic decisions are generated with an unbiased process and varying interaction complexities among decisions to provide for fair performance comparison of the selected decision-fusion algorithms. For verification purposes, implementation results of the developed fusion algorithms on structural health monitoring data collected from experimental tests are reported in this paper.

Self-Assembled Materials Made from Functional Recombinant Proteins.

PubMed

Jang, Yeongseon; Champion, Julie A

2016-10-18

Proteins are potent molecules that can be used as therapeutics, sensors, and biocatalysts with many advantages over small-molecule counterparts due to the specificity of their activity based on their amino acid sequence and folded three-dimensional structure. However, they also have significant limitations in their stability, localization, and recovery when used in soluble form. These opportunities and challenges have motivated the creation of materials from such functional proteins in order to protect and present them in a way that enhances their function. We have designed functional recombinant fusion proteins capable of self-assembling into materials with unique structures that maintain or improve the functionality of the protein. Fusion of either a functional protein or an assembly domain to a leucine zipper domain makes the materials design strategy modular, based on the high affinity between leucine zippers. The self-assembly domains, including elastin-like polypeptides (ELPs) and defined-sequence random coil polypeptides, can be fused with a leucine zipper motif in order to promote assembly of the fusion proteins into larger structures upon specific stimuli such as temperature and ionic strength. Fusion of other functional domains with the counterpart leucine zipper motif endows the self-assembled materials with protein-specific functions such as fluorescence or catalytic activity. In this Account, we describe several examples of materials assembled from functional fusion proteins as well as the structural characterization, functionality, and understanding of the assembly mechanism. The first example is zipper fusion proteins containing ELPs that assemble into particles when introduced to a model extracellular matrix and subsequently disassemble over time to release the functional protein for drug delivery applications. Under different conditions, the same fusion proteins can self-assemble into hollow vesicles. The vesicles display a functional protein on the surface and can also carry protein, small-molecule, or nanoparticle cargo in the vesicle lumen. To create a material with a more complex hierarchical structure, we combined calcium phosphate with zipper fusion proteins containing random coil polypeptides to produce hybrid protein-inorganic supraparticles with high surface area and porous structure. The use of a functional enzyme created supraparticles with the ability to degrade inflammatory cytokines. Our characterization of these protein materials revealed that the molecular interactions are complex because of the large size of the protein building blocks, their folded structures, and the number of potential interactions including hydrophobic interactions, electrostatic interactions, van der Waals forces, and specific affinity-based interactions. It is difficult or even impossible to predict the structures a priori. However, once the basic assembly principles are understood, there is opportunity to tune the material properties, such as size, through control of the self-assembly conditions. Our future efforts on the fundamental side will focus on identifying the phase space of self-assembly of these fusion proteins and additional experimental levers with which to control and tune the resulting materials. On the application side, we are investigating an array of different functional proteins to expand the use of these structures in both therapeutic protein delivery and biocatalysis.

Visualization of conserved structures by fusing highly variable datasets.

PubMed

Silverstein, Jonathan C; Chhadia, Ankur; Dech, Fred

2002-01-01

Skill, effort, and time are required to identify and visualize anatomic structures in three-dimensions from radiological data. Fundamentally, automating these processes requires a technique that uses symbolic information not in the dynamic range of the voxel data. We were developing such a technique based on mutual information for automatic multi-modality image fusion (MIAMI Fuse, University of Michigan). This system previously demonstrated facility at fusing one voxel dataset with integrated symbolic structure information to a CT dataset (different scale and resolution) from the same person. The next step of development of our technique was aimed at accommodating the variability of anatomy from patient to patient by using warping to fuse our standard dataset to arbitrary patient CT datasets. A standard symbolic information dataset was created from the full color Visible Human Female by segmenting the liver parenchyma, portal veins, and hepatic veins and overwriting each set of voxels with a fixed color. Two arbitrarily selected patient CT scans of the abdomen were used for reference datasets. We used the warping functions in MIAMI Fuse to align the standard structure data to each patient scan. The key to successful fusion was the focused use of multiple warping control points that place themselves around the structure of interest automatically. The user assigns only a few initial control points to align the scans. Fusion 1 and 2 transformed the atlas with 27 points around the liver to CT1 and CT2 respectively. Fusion 3 transformed the atlas with 45 control points around the liver to CT1 and Fusion 4 transformed the atlas with 5 control points around the portal vein. The CT dataset is augmented with the transformed standard structure dataset, such that the warped structure masks are visualized in combination with the original patient dataset. This combined volume visualization is then rendered interactively in stereo on the ImmersaDesk in an immersive Virtual Reality (VR) environment. The accuracy of the fusions was determined qualitatively by comparing the transformed atlas overlaid on the appropriate CT. It was examined for where the transformed structure atlas was incorrectly overlaid (false positive) and where it was incorrectly not overlaid (false negative). According to this method, fusions 1 and 2 were correct roughly 50-75% of the time, while fusions 3 and 4 were correct roughly 75-100%. The CT dataset augmented with transformed dataset was viewed arbitrarily in user-centered perspective stereo taking advantage of features such as scaling, windowing and volumetric region of interest selection. This process of auto-coloring conserved structures in variable datasets is a step toward the goal of a broader, standardized automatic structure visualization method for radiological data. If successful it would permit identification, visualization or deletion of structures in radiological data by semi-automatically applying canonical structure information to the radiological data (not just processing and visualization of the data's intrinsic dynamic range). More sophisticated selection of control points and patterns of warping may allow for more accurate transforms, and thus advances in visualization, simulation, education, diagnostics, and treatment planning.

Incompletely Mixed Surface Transient Storage Zones at River Restoration Structures: Modeling Implications

NASA Astrophysics Data System (ADS)

Endreny, T. A.; Robinson, J.

2012-12-01

River restoration structures, also known as river steering deflectors, are designed to reduce bank shear stress by generating wake zones between the bank and the constricted conveyance region. There is interest in characterizing the surface transient storage (STS) and associated biogeochemical processing in the STS zones around these structures to quantify the ecosystem benefits of river restoration. This research explored how the hydraulics around river restoration structures prohibits application of transient storage models designed for homogenous, completely mixed STS zones. We used slug and constant rate injections of a conservative tracer in a 3rd order river in Onondaga County, NY over the course of five experiments at varying flow regimes. Recovered breakthrough curves spanned a transect including the main channel and wake zone at a j-hook restoration structure. We noted divergent patterns of peak solute concentration and times within the wake zone regardless of transect location within the structure. Analysis reveals an inhomogeneous STS zone which is frequently still loading tracer after the main channel has peaked. The breakthrough curve loading patterns at the restoration structure violated the assumptions of simplified "random walk" 2 zone transient storage models which seek to identify representative STS zones and zone locations. Use of structure-scale Weiner filter based multi-rate mass transfer models to characterize STS zones residence times are similarly dependent on a representative zone location. Each 2 zone model assumes 1 zone is a completely mixed STS zone and the other a completely mixed main channel. Our research reveals limits to simple application of the recently developed 2 zone models, and raises important questions about the measurement scale necessary to identify critical STS properties at restoration sites. An explanation for the incompletely mixed STS zone may be the distinct hydraulics at restoration sites, including a constrained high velocity conveyance region closely abutting a wake zone that receives periodic disruption from the upstream structure shearing vortices.igure 1. River restoration j-hook with blue dye revealing main channel and edge of wake zone with multiple surface transient storage zones.

Structure of a trimeric variant of the Epstein-Barr virus glycoprotein B

DOE Office of Scientific and Technical Information (OSTI.GOV)

Backovic, Marija; Longnecker, Richard; Jardetzky, Theodore S

Epstein-Barr virus (EBV) is a herpesvirus that is associated with development of malignancies of lymphoid tissue. EBV infections are life-long and occur in >90% of the population. Herpesviruses enter host cells in a process that involves fusion of viral and cellular membranes. The fusion apparatus is comprised of envelope glycoprotein B (gB) and a heterodimeric complex made of glycoproteins H and L. Glycoprotein B is the most conserved envelope glycoprotein in human herpesviruses, and the structure of gB from Herpes simplex virus 1 (HSV-1) is available. Here, we report the crystal structure of the secreted EBV gB ectodomain, which formsmore » 16-nm long spike-like trimers, structurally homologous to the postfusion trimers of the fusion protein G of vesicular stomatitis virus (VSV). Comparative structural analyses of EBV gB and VSV G, which has been solved in its pre and postfusion states, shed light on gB residues that may be involved in conformational changes and membrane fusion. Also, the EBV gB structure reveals that, despite the high sequence conservation of gB in herpesviruses, the relative orientations of individual domains, the surface charge distributions, and the structural details of EBV gB differ from the HSV-1 protein, indicating regions and residues that may have important roles in virus-specific entry.« less

Multifunctional recombinant phycobiliprotein-based fluorescent constructs and phycobilisome display

DOEpatents

Glazer, Alexander N.; Cai, Yuping

2007-01-30

The invention provides multifunctional fusion constructs which are rapidly incorporated into a macromolecular structure such as a phycobilisome such that the fusion proteins are separated from one another and unable to self-associate. The invention provides methods and compositions for displaying a functional polypeptide domain on an oligomeric phycobiliprotein, including fusion proteins comprising a functional displayed domain and a functional phycobiliprotein domain incorporated in a functional oligomeric phycobiliprotein. The fusion proteins provide novel specific labeling reagents.

Multifunctional recombinant phycobiliprotein-based fluorescent constructs and phycobilisome display

DOEpatents

Glazer, Alexander N.; Cai, Yuping

2007-02-13

The invention provides multifunctional fusion constructs which are rapidly incorporated into a macromolecular structure such as a phycobilisome such that the fusion proteins are separated from one another and unable to self-associate. The invention provides methods and compositions for displaying a functional polypeptide domain on an oligomeric phycobiliprotein. including fusion proteins comprising a functional displayed domain and a functional phycobiliprotein domain incorporated in a functional oligomeric phycobiliprotein. The fusion proteins provide novel specific labeling reagents.

Multifunctional recombinant phycobiliprotein-based fluorescent constructs and phycobilisome display

DOEpatents

Glazer, Alexander N.; Cai, Yuping

2003-11-18

The invention provides multifunctional fusion constructs which are rapidly incorporated into a macromolecular structure such as a phycobilisome such that the fusion proteins are separated from one another and unable to self-associate. The invention provides methods and compositions for displaying a functional polypeptide domain on an oligomeric phycobiliprotein, including fusion proteins comprising a functional displayed domain and a functional phycobiliprotein domain incorporated in a functional oligomeric phycobiliprotein. The fusion proteins provide novel specific labeling reagents.

Belief Function Based Decision Fusion for Decentralized Target Classification in Wireless Sensor Networks

PubMed Central

Zhang, Wenyu; Zhang, Zhenjiang

2015-01-01

Decision fusion in sensor networks enables sensors to improve classification accuracy while reducing the energy consumption and bandwidth demand for data transmission. In this paper, we focus on the decentralized multi-class classification fusion problem in wireless sensor networks (WSNs) and a new simple but effective decision fusion rule based on belief function theory is proposed. Unlike existing belief function based decision fusion schemes, the proposed approach is compatible with any type of classifier because the basic belief assignments (BBAs) of each sensor are constructed on the basis of the classifier’s training output confusion matrix and real-time observations. We also derive explicit global BBA in the fusion center under Dempster’s combinational rule, making the decision making operation in the fusion center greatly simplified. Also, sending the whole BBA structure to the fusion center is avoided. Experimental results demonstrate that the proposed fusion rule has better performance in fusion accuracy compared with the naïve Bayes rule and weighted majority voting rule. PMID:26295399

Crystallization and preliminary X-ray diffraction analysis of central structure domains from mumps virus F protein

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yueyong; Xu, Yanhui; Zhu, Jieqing

2005-09-01

Single crystals of the central structure domains from mumps virus F protein have been obtained by the hanging-drop vapour-diffusion method. A diffraction data set has been collected to 2.2 Å resolution. Fusion of members of the Paramyxoviridae family involves two glycoproteins: the attachment protein and the fusion protein. Changes in the fusion-protein conformation were caused by binding of the attachment protein to the cellular receptor. In the membrane-fusion process, two highly conserved heptad-repeat (HR) regions, HR1 and HR2, are believed to form a stable six-helix coiled-coil bundle. However, no crystal structure has yet been determined for this state in themore » mumps virus (MuV, a member of the Paramyxoviridae family). In this study, a single-chain protein consisting of two HR regions connected by a flexible amino-acid linker (named 2-Helix) was expressed, purified and crystallized by the hanging-drop vapour-diffusion method. A complete X-ray data set was obtained in-house to 2.2 Å resolution from a single crystal. The crystal belongs to space group C2, with unit-cell parameters a = 161.2, b = 60.8, c = 40.1 Å, β = 98.4°. The crystal structure will help in understanding the molecular mechanism of Paramyxoviridae family membrane fusion.« less

Structural and Functional Studies on the Marburg Virus GP2 Fusion Loop.

PubMed

Liu, Nina; Tao, Yisong; Brenowitz, Michael D; Girvin, Mark E; Lai, Jonathan R

2015-10-01

Marburg virus (MARV) and the ebolaviruses belong to the family Filoviridae (the members of which are filoviruses) that cause severe hemorrhagic fever. Infection requires fusion of the host and viral membranes, a process that occurs in the host cell endosomal compartment and is facilitated by the envelope glycoprotein fusion subunit, GP2. The N-terminal fusion loop (FL) of GP2 is a hydrophobic disulfide-bonded loop that is postulated to insert and disrupt the host endosomal membrane during fusion. Here, we describe the first structural and functional studies of a protein corresponding to the MARV GP2 FL. We found that this protein undergoes a pH-dependent conformational change, as monitored by circular dichroism and nuclear magnetic resonance. Furthermore, we report that, under low pH conditions, the MARV GP2 FL can induce content leakage from liposomes. The general aspects of this pH-dependent structure and lipid-perturbing behavior are consistent with previous reports on Ebola virus GP2 FL. However, nuclear magnetic resonance studies in lipid bicelles and mutational analysis indicate differences in structure exist between MARV and Ebola virus GP2 FL. These results provide new insight into the mechanism of MARV GP2-mediated cell entry. © The Author 2015. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Structural and functional characterization of EIAV gp45 fusion peptide proximal region and asparagine-rich layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duan, Liangwei; Du, Jiansen; Wang, Xuefeng

Equine infectious anaemia virus (EIAV) and human immunodeficiency virus (HIV) are members of the lentiviral genus. Similar to HIV gp41, EIAV gp45 is a fusogenic protein that mediates fusion between the viral particle and the host cell membrane. The crystal structure of gp45 reported reveals a different conformation in the here that includes the fusion peptide proximal region (FPPR) and neighboring asparagine-rich layer compared with previous HIV-1 gp41 structures. A complicated hydrogen-bond network containing a cluster of solvent molecules appears to be critical for the stability of the gp45 helical bundle. Interestingly, viral replication was relatively unaffected by site-directed mutagenesismore » of EIAV, in striking contrast to that of HIV-1. Based on these observations, we speculate that EIAV is more adaptable to emergent mutations, which might be important for the evolution of EIAV as a quasi-species, and could potentially contribute to the success of the EIAV vaccine. - Highlights: • The crystal structure of EIAV gp45 was determined. • The fusion peptide proximal region adopts a novel conformation different to HIV-1. • The asparagine-rich layer includes an extensive hydrogen-bond network. • These regions of EIAV are highly tolerant to mutations. • The results provide insight into the mechanism of gp41/gp45-mediated membrane fusion.« less

Multilocality and fusion rules on the generalized structure functions in two-dimensional and three-dimensional Navier-Stokes turbulence.

PubMed

Gkioulekas, Eleftherios

2016-09-01

Using the fusion-rules hypothesis for three-dimensional and two-dimensional Navier-Stokes turbulence, we generalize a previous nonperturbative locality proof to multiple applications of the nonlinear interactions operator on generalized structure functions of velocity differences. We call this generalization of nonperturbative locality to multiple applications of the nonlinear interactions operator "multilocality." The resulting cross terms pose a new challenge requiring a new argument and the introduction of a new fusion rule that takes advantage of rotational symmetry. Our main result is that the fusion-rules hypothesis implies both locality and multilocality in both the IR and UV limits for the downscale energy cascade of three-dimensional Navier-Stokes turbulence and the downscale enstrophy cascade and inverse energy cascade of two-dimensional Navier-Stokes turbulence. We stress that these claims relate to nonperturbative locality of generalized structure functions on all orders and not the term-by-term perturbative locality of diagrammatic theories or closure models that involve only two-point correlation and response functions.

Method for vacuum fusion bonding

DOEpatents

Ackler, Harold D.; Swierkowski, Stefan P.; Tarte, Lisa A.; Hicks, Randall K.

2001-01-01

An improved vacuum fusion bonding structure and process for aligned bonding of large area glass plates, patterned with microchannels and access holes and slots, for elevated glass fusion temperatures. Vacuum pumpout of all components is through the bottom platform which yields an untouched, defect free top surface which greatly improves optical access through this smooth surface. Also, a completely non-adherent interlayer, such as graphite, with alignment and location features is located between the main steel platform and the glass plate pair, which makes large improvements in quality, yield, and ease of use, and enables aligned bonding of very large glass structures.

Fusion bonding and alignment fixture

DOEpatents

Ackler, Harold D.; Swierkowski, Stefan P.; Tarte, Lisa A.; Hicks, Randall K.

2000-01-01

An improved vacuum fusion bonding structure and process for aligned bonding of large area glass plates, patterned with microchannels and access holes and slots, for elevated glass fusion temperatures. Vacuum pumpout of all the components is through the bottom platform which yields an untouched, defect free top surface which greatly improves optical access through this smooth surface. Also, a completely non-adherent interlayer, such as graphite, with alignment and location features is located between the main steel platform and the glass plate pair, which makes large improvements in quality, yield, and ease of use, and enables aligned bonding of very large glass structures.

A genetically encoded fluorescent tRNA is active in live-cell protein synthesis

PubMed Central

Masuda, Isao; Igarashi, Takao; Sakaguchi, Reiko; Nitharwal, Ram G.; Takase, Ryuichi; Han, Kyu Young; Leslie, Benjamin J.; Liu, Cuiping; Gamper, Howard; Ha, Taekjip; Sanyal, Suparna

2017-01-01

Abstract Transfer RNAs (tRNAs) perform essential tasks for all living cells. They are major components of the ribosomal machinery for protein synthesis and they also serve in non-ribosomal pathways for regulation and signaling metabolism. We describe the development of a genetically encoded fluorescent tRNA fusion with the potential for imaging in live Escherichia coli cells. This tRNA fusion carries a Spinach aptamer that becomes fluorescent upon binding of a cell-permeable and non-toxic fluorophore. We show that, despite having a structural framework significantly larger than any natural tRNA species, this fusion is a viable probe for monitoring tRNA stability in a cellular quality control mechanism that degrades structurally damaged tRNA. Importantly, this fusion is active in E. coli live-cell protein synthesis allowing peptidyl transfer at a rate sufficient to support cell growth, indicating that it is accommodated by translating ribosomes. Imaging analysis shows that this fusion and ribosomes are both excluded from the nucleoid, indicating that the fusion and ribosomes are in the cytosol together possibly engaged in protein synthesis. This fusion methodology has the potential for developing new tools for live-cell imaging of tRNA with the unique advantage of both stoichiometric labeling and broader application to all cells amenable to genetic engineering. PMID:27956502

Genetic analysis of heptad-repeat regions in the G2 fusion subunit of the Junin arenavirus envelope glycoprotein

DOE Office of Scientific and Technical Information (OSTI.GOV)

York, Joanne; Agnihothram, Sudhakar S.; Romanowski, Victor

2005-12-20

The G2 fusion subunit of the Junin virus envelope glycoprotein GP-C contains two hydrophobic heptad-repeat regions that are postulated to form a six-helix bundle structure required for the membrane fusion activity of Class I viral fusion proteins. We have investigated the role of these heptad-repeat regions and, specifically, the importance of the putative interhelical a and d position sidechains by using alanine-scanning mutagenesis. All the mutant glycoproteins were expressed and transported to the cell surface. Proteolytic maturation at the subtilisin kexin isozyme-1/site-1-protease (SKI-1/S1P) cleavage site was observed in all but two of the mutants. Among the adequately cleaved mutant glycoproteins,more » four positions in the N-terminal region (I333, L336, L347 and L350) and two positions in the C-terminal region (R392 and W395) were shown to be important determinants of cell-cell fusion. Taken together, our results indicate that {alpha}-helical coiled-coil structures are likely critical in promoting arenavirus membrane fusion. These findings support the inclusion of the arenavirus GP-C among the Class I viral fusion proteins and suggest pharmacologic and immunologic strategies for targeting arenavirus infection and hemorrhagic fever.« less

Tandem SUMO fusion vectors for improving soluble protein expression and purification.

PubMed

Guerrero, Fernando; Ciragan, Annika; Iwaï, Hideo

2015-12-01

Availability of highly purified proteins in quantity is crucial for detailed biochemical and structural investigations. Fusion tags are versatile tools to facilitate efficient protein purification and to improve soluble overexpression of proteins. Various purification and fusion tags have been widely used for overexpression in Escherichia coli. However, these tags might interfere with biological functions and/or structural investigations of the protein of interest. Therefore, an additional purification step to remove fusion tags by proteolytic digestion might be required. Here, we describe a set of new vectors in which yeast SUMO (SMT3) was used as the highly specific recognition sequence of ubiquitin-like protease 1, together with other commonly used solubility enhancing proteins, such as glutathione S-transferase, maltose binding protein, thioredoxin and trigger factor for optimizing soluble expression of protein of interest. This tandem SUMO (T-SUMO) fusion system was tested for soluble expression of the C-terminal domain of TonB from different organisms and for the antiviral protein scytovirin. Copyright © 2015 Elsevier Inc. All rights reserved.

Fusion of GFP to the M.EcoKI DNA methyltransferase produces a new probe of Type I DNA restriction and modification enzymes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Kai; Roberts, Gareth A.; Stephanou, Augoustinos S.

2010-07-23

Research highlights: {yields} Successful fusion of GFP to M.EcoKI DNA methyltransferase. {yields} GFP located at C-terminal of sequence specificity subunit does not later enzyme activity. {yields} FRET confirms structural model of M.EcoKI bound to DNA. -- Abstract: We describe the fusion of enhanced green fluorescent protein to the C-terminus of the HsdS DNA sequence-specificity subunit of the Type I DNA modification methyltransferase M.EcoKI. The fusion expresses well in vivo and assembles with the two HsdM modification subunits. The fusion protein functions as a sequence-specific DNA methyltransferase protecting DNA against digestion by the EcoKI restriction endonuclease. The purified enzyme shows Foerstermore » resonance energy transfer to fluorescently-labelled DNA duplexes containing the target sequence and to fluorescently-labelled ocr protein, a DNA mimic that binds to the M.EcoKI enzyme. Distances determined from the energy transfer experiments corroborate the structural model of M.EcoKI.« less

Multiscale Medical Image Fusion in Wavelet Domain

PubMed Central

Khare, Ashish

2013-01-01

Wavelet transforms have emerged as a powerful tool in image fusion. However, the study and analysis of medical image fusion is still a challenging area of research. Therefore, in this paper, we propose a multiscale fusion of multimodal medical images in wavelet domain. Fusion of medical images has been performed at multiple scales varying from minimum to maximum level using maximum selection rule which provides more flexibility and choice to select the relevant fused images. The experimental analysis of the proposed method has been performed with several sets of medical images. Fusion results have been evaluated subjectively and objectively with existing state-of-the-art fusion methods which include several pyramid- and wavelet-transform-based fusion methods and principal component analysis (PCA) fusion method. The comparative analysis of the fusion results has been performed with edge strength (Q), mutual information (MI), entropy (E), standard deviation (SD), blind structural similarity index metric (BSSIM), spatial frequency (SF), and average gradient (AG) metrics. The combined subjective and objective evaluations of the proposed fusion method at multiple scales showed the effectiveness and goodness of the proposed approach. PMID:24453868

In Vitro Reconstitution of Autophagosome-Lysosome Fusion.

PubMed

Diao, J; Li, L; Lai, Y; Zhong, Q

2017-01-01

SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptors) proteins are a highly regulated class of membrane proteins lying in the center of membrane fusion. In conjunction with accessory proteins, SNAREs drive efficient merger of two distinct lipid bilayers into one interconnected structure. This chapter describes our fluorescence resonance energy transfer (FRET)-based proteoliposome fusion assays for the roles of various SNARE proteins, accessory proteins, and effects of different lipid compositions on membrane fusion involved in autophagy. © 2017 Elsevier Inc. All rights reserved.

Relation between hardness and ultrasonic velocity on pipeline steel welded joints

NASA Astrophysics Data System (ADS)

Carreón, H.; Barrera, G.; Natividad, C.; Salazar, M.; Contreras, A.

2016-04-01

In general, the ultrasonic techniques have been used to determine the mechanical properties of materials based on their relationship with metallurgical characteristics. In this research work, the relationship between ultrasonic wave velocity, hardness and the microstructure of steel pipeline welded joints is investigated. Measurements of ultrasonic wave velocity were made as a function of the location across the weld. Hardness measurements were performed in an attempt to correlate with ultrasonic response. In addition, the coarse and dendritic grain structure of the weld material is extreme and unpredictably anisotropic. Thus, due to the acoustic anisotropy of the crystal, weld material of studied joints is anisotropic too. Such structure is no longer direction-independent to the ultrasonic wave propagation; therefore, the ultrasonic beam deflects and redirects and the wave front becomes distorted. Thus, the use of conventional ultrasonic testing techniques using fixed beam angles is very limited and the application of conventional ultrasonic phased array techniques becomes desirable. This technique is proposed to assist pipeline operators in estimating the hardness through ultrasonic measures to evaluate the susceptibility to stress sulphide cracking and hydrogen-induced cracking due to hard spots in steel pipeline welded joints in service. Sound wave velocity and hardness measurements have been carried out on a steel welded joint. For each section of the welding, weld bead, fusion zone, heat affected zone and base metal were found to correspond particular values of the ultrasound velocity. These results were correlated with electron microscopy observations of the microstructure and sectorial scan view of welded joints by ultrasonic phased array.

DARPin-Based Crystallization Chaperones Exploit Molecular Geometry as a Screening Dimension in Protein Crystallography.

PubMed

Batyuk, Alexander; Wu, Yufan; Honegger, Annemarie; Heberling, Matthew M; Plückthun, Andreas

2016-04-24

DARPin libraries, based on a Designed Ankyrin Repeat Protein consensus framework, are a rich source of binding partners for a wide variety of proteins. Their modular structure, stability, ease of in vitro selection and high production yields make DARPins an ideal starting point for further engineering. The X-ray structures of around 30 different DARPin complexes demonstrate their ability to facilitate crystallization of their target proteins by restricting flexibility and preventing undesired interactions of the target molecule. However, their small size (18 kDa), very hydrophilic surface and repetitive structure can limit the DARPins' ability to provide essential crystal contacts and their usefulness as a search model for addressing the crystallographic phase problem in molecular replacement. To optimize DARPins for their application as crystallization chaperones, rigid domain-domain fusions of the DARPins to larger proteins, proven to yield high-resolution crystal structures, were generated. These fusions were designed in such a way that they affect only one of the terminal capping repeats of the DARPin and do not interfere with residues involved in target binding, allowing to exchange at will the binding specificities of the DARPin in the fusion construct. As a proof of principle, we designed rigid fusions of a stabilized version of Escherichia coli TEM-1 β-lactamase to the C-terminal capping repeat of various DARPins in six different relative domain orientations. Five crystal structures representing four different fusion constructs, alone or in complex with the cognate target, show the predicted relative domain orientations and prove the validity of the concept. Copyright © 2016 Elsevier Ltd. All rights reserved.

Structure and Mutagenesis of the Parainfluenza Virus 5 Hemagglutinin-Neuraminidase Stalk Domain Reveals a Four-Helix Bundle and the Role of the Stalk in Fusion Promotion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bose, Sayantan; Welch, Brett D.; Kors, Christopher A.

2014-10-02

Paramyxovirus entry into cells requires the fusion protein (F) and a receptor binding protein (hemagglutinin-neuraminidase [HN], H, or G). The multifunctional HN protein of some paramyxoviruses, besides functioning as the receptor (sialic acid) binding protein (hemagglutinin activity) and the receptor-destroying protein (neuraminidase activity), enhances F activity, presumably by lowering the activation energy required for F to mediate fusion of viral and cellular membranes. Before or upon receptor binding by the HN globular head, F is believed to interact with the HN stalk. Unfortunately, until recently none of the receptor binding protein crystal structures have shown electron density for the stalkmore » domain. Parainfluenza virus 5 (PIV5) HN exists as a noncovalent dimer-of-dimers on the surface of cells, linked by a single disulfide bond in the stalk. Here we present the crystal structure of the PIV5-HN stalk domain at a resolution of 2.65 {angstrom}, revealing a four-helix bundle (4HB) with an upper (N-terminal) straight region and a lower (C-terminal) supercoiled part. The hydrophobic core residues are a mix of an 11-mer repeat and a 3- to 4-heptad repeat. To functionally characterize the role of the HN stalk in F interactions and fusion, we designed mutants along the PIV5-HN stalk that are N-glycosylated to physically disrupt F-HN interactions. By extensive study of receptor binding, neuraminidase activity, oligomerization, and fusion-promoting functions of the mutant proteins, we found a correlation between the position of the N-glycosylation mutants on the stalk structure and their neuraminidase activities as well as their abilities to promote fusion.« less

Structure and Mutagenesis of the Parainfluenza Virus 5 Hemagglutinin-Neuraminidase Stalk Domain Reveals a Four-Helix Bundle and the Role of the Stalk in Fusion Promotion▿

PubMed Central

Bose, Sayantan; Welch, Brett D.; Kors, Christopher A.; Yuan, Ping; Jardetzky, Theodore S.; Lamb, Robert A.

2011-01-01

Paramyxovirus entry into cells requires the fusion protein (F) and a receptor binding protein (hemagglutinin-neuraminidase [HN], H, or G). The multifunctional HN protein of some paramyxoviruses, besides functioning as the receptor (sialic acid) binding protein (hemagglutinin activity) and the receptor-destroying protein (neuraminidase activity), enhances F activity, presumably by lowering the activation energy required for F to mediate fusion of viral and cellular membranes. Before or upon receptor binding by the HN globular head, F is believed to interact with the HN stalk. Unfortunately, until recently none of the receptor binding protein crystal structures have shown electron density for the stalk domain. Parainfluenza virus 5 (PIV5) HN exists as a noncovalent dimer-of-dimers on the surface of cells, linked by a single disulfide bond in the stalk. Here we present the crystal structure of the PIV5-HN stalk domain at a resolution of 2.65 Å, revealing a four-helix bundle (4HB) with an upper (N-terminal) straight region and a lower (C-terminal) supercoiled part. The hydrophobic core residues are a mix of an 11-mer repeat and a 3- to 4-heptad repeat. To functionally characterize the role of the HN stalk in F interactions and fusion, we designed mutants along the PIV5-HN stalk that are N-glycosylated to physically disrupt F-HN interactions. By extensive study of receptor binding, neuraminidase activity, oligomerization, and fusion-promoting functions of the mutant proteins, we found a correlation between the position of the N-glycosylation mutants on the stalk structure and their neuraminidase activities as well as their abilities to promote fusion. PMID:21994464

Fusion zone microstructure and porosity in electron beam welds of an α+β titanium alloy

NASA Astrophysics Data System (ADS)

Mohandas, T.; Banerjee, D.; Kutumba Rao, V. V.

1999-03-01

The effect of electron beam welding parameters on fusion zone (FZ) microstructure and porosity in a Ti -6.8 Al -3.42 Mo -1.9 Zr -0.21 Si alloy (Russian designation VT 9) has been investigated. It has been observed that the FZ grain width increased continuously with increase in heat input when the base metal was in the β heat-treated condition, while in the α+β heat-treated base metal welds, the FZ grain width increased only after a threshold energy input. The difference is attributed to both the weld thermal cycle and the pinning effect of equiaxed primary alpha on grain growth in the heat-affected zone (HAZ) of α+β heat-treated base metal. Postweld heat treatment (PWHT) in the subtransus and supertransus regions did not alter the columnar grain morphology in the FZ, possibly due to the lack of enough driving force for the formation of new grains by the breaking up of the columnar grains and grain boundary movement for grain growth. As the PWHTs were conducted in a furnace, the role of thermal gradients can be ruled out. Intragranular microstructure in the aswelded condition consisted of hexagonal martensite. The scale of the martensite laths depended on welding speed. The highest porosity was observed at intermediate welding speeds. At low speeds, a majority of pores formed at the fusion boundary, while at high speeds, occurrence of porosity was maximum at the weld center. The trends on porosity can be explained on the basis of solubility of hydrogen in titanium as a function of temperature and the influence of weld thermal cycle on nucleation, growth, and escape of hydrogen gas bubbles. The porosity at slow welding speeds is low because sufficient time exists for the nucleation, growth, and escape of hydrogen gas bubbles, while insufficient time exists for the nucleation of gas bubbles at high welding speeds. The effect of pickling of joint surface, vacuum annealing of the base metal, and successive remelting of the weld metal has also been investigated.

Structure of Respiratory Syncytial Virus Fusion Glycoprotein in the Postfusion Conformation Reveals Preservation of Neutralizing Epitopes

DOE Office of Scientific and Technical Information (OSTI.GOV)

McLellan, Jason S.; Yang, Yongping; Graham, Barney S.

2011-09-16

Respiratory syncytial virus (RSV) invades host cells via a type I fusion (F) glycoprotein that undergoes dramatic structural rearrangements during the fusion process. Neutralizing monoclonal antibodies, such as 101F, palivizumab, and motavizumab, target two major antigenic sites on the RSV F glycoprotein. The structures of these sites as peptide complexes with motavizumab and 101F have been previously determined, but a structure for the trimeric RSV F glycoprotein ectodomain has remained elusive. To address this issue, we undertook structural and biophysical studies on stable ectodomain constructs. Here, we present the 2.8-{angstrom} crystal structure of the trimeric RSV F ectodomain in itsmore » postfusion conformation. The structure revealed that the 101F and motavizumab epitopes are present in the postfusion state and that their conformations are similar to those observed in the antibody-bound peptide structures. Both antibodies bound the postfusion F glycoprotein with high affinity in surface plasmon resonance experiments. Modeling of the antibodies bound to the F glycoprotein predicts that the 101F epitope is larger than the linear peptide and restricted to a single protomer in the trimer, whereas motavizumab likely contacts residues on two protomers, indicating a quaternary epitope. Mechanistically, these results suggest that 101F and motavizumab can bind to multiple conformations of the fusion glycoprotein and can neutralize late in the entry process. The structural preservation of neutralizing epitopes in the postfusion state suggests that this conformation can elicit neutralizing antibodies and serve as a useful vaccine antigen.« less

RELATIVE EXPRESSION AND STABILITY OF A CHROMOSOMALLY INTEGRATED AND PLASMID-BORNE MARKER GENE FUSION IN ENVIRONMENTALLY COMPETENT BACTERIA

EPA Science Inventory

A xyIE-iceC transcriptional fusion was created by ligating a DNA fragment harboring the cloned xyIE structural gene from the TOL plasmid of Pseudomonas putida mt-2 into the cloned iceC gene of Pseudomonas syringae Cit7. This fusion construct was integrated into chromosome of Pseu...

Fc-fusion proteins and FcRn: structural insights for longer-lasting and more effective therapeutics

PubMed Central

Rath, Timo; Baker, Kristi; Dumont, Jennifer A.; Peters, Robert T.; Jiang, Haiyan; Qiao, Shuo-Wang; Lencer, Wayne I.; Pierce, Glenn F.; Blumberg, Richard S.

2016-01-01

Nearly 350 IgG-based therapeutics are approved for clinical use or are under development for many diseases lacking adequate treatment options. These include molecularly engineered biologicals comprising the IgG Fc-domain fused to various effector molecules (so-called Fc-fusion proteins) that confer the advantages of IgG, including binding to the neonatal Fc receptor (FcRn) to facilitate in vivo stability, and the therapeutic benefit of the specific effector functions. Advances in IgG structure-function relationships and an understanding of FcRn biology have provided therapeutic opportunities for previously unapproachable diseases. This article discusses approved Fc-fusion therapeutics, novel Fc-fusion proteins and FcRn-dependent delivery approaches in development, and how engineering of the FcRn–Fc interaction can generate longer-lasting and more effective therapeutics. PMID:24156398

A Review on the Potential Use of Austenitic Stainless Steels in Nuclear Fusion Reactors

NASA Astrophysics Data System (ADS)

Şahin, Sümer; Übeyli, Mustafa

2008-12-01

Various engineering materials; austenitic stainless steels, ferritic/martensitic steels, vanadium alloys, refractory metals and composites have been suggested as candidate structural materials for nuclear fusion reactors. Among these structural materials, austenitic steels have an advantage of extensive technological database and lower cost compared to other non-ferrous candidates. Furthermore, they have also advantages of very good mechanical properties and fission operation experience. Moreover, modified austenitic stainless (Ni and Mo free) have relatively low residual radioactivity. Nevertheless, they can't withstand high neutron wall load which is required to get high power density in fusion reactors. On the other hand, a protective flowing liquid wall between plasma and solid first wall in these reactors can eliminate this restriction. This study presents an overview of austenitic stainless steels considered to be used in fusion reactors.

[Magnetic resonance imaging in facial injuries and digital fusion CT/MRI].

PubMed

Kozakiewicz, Marcin; Olszycki, Marek; Arkuszewski, Piotr; Stefańczyk, Ludomir

2006-01-01

Magnetic resonance images [MRI] and their digital fusion with computed tomography [CT] data, observed in patients affected with facial injuries, are presented in this study. The MR imaging of 12 posttraumatic patients was performed in the same plains as their previous CT scans. Evaluation focused on quality of the facial soft tissues depicting, which was unsatisfactory in CT. Using the own "Dental Studio" programme the digital fusion of the both modalities was performed. Pathologic dislocations and injures of facial soft tissues are visualized better in MRI than in CT examination. Especially MRI properly reveals disturbances in intraorbital soft structures. MRI-based assessment is valuable in patients affected with facial soft tissues injuries, especially in case of orbita/sinuses hernia. Fusion CT/MRI scans allows to evaluate simultaneously bone structure and soft tissues of the same region.

In Vivo Efficacy of Measles Virus Fusion Protein-Derived Peptides Is Modulated by the Properties of Self-Assembly and Membrane Residence

PubMed Central

Figueira, T. N.; Palermo, L. M.; Veiga, A. S.; Huey, D.; Alabi, C. A.; Santos, N. C.; Welsch, J. C.; Mathieu, C.; Niewiesk, S.; Moscona, A.

2016-01-01

ABSTRACT Measles virus (MV) infection is undergoing resurgence and remains one of the leading causes of death among young children worldwide despite the availability of an effective measles vaccine. MV infects its target cells by coordinated action of the MV hemagglutinin (H) and fusion (F) envelope glycoproteins; upon receptor engagement by H, the prefusion F undergoes a structural transition, extending and inserting into the target cell membrane and then refolding into a postfusion structure that fuses the viral and cell membranes. By interfering with this structural transition of F, peptides derived from the heptad repeat (HR) regions of F can inhibit MV infection at the entry stage. In previous work, we have generated potent MV fusion inhibitors by dimerizing the F-derived peptides and conjugating them to cholesterol. We have shown that prophylactic intranasal administration of our lead fusion inhibitor efficiently protects from MV infection in vivo. We show here that peptides tagged with lipophilic moieties self-assemble into nanoparticles until they reach the target cells, where they are integrated into cell membranes. The self-assembly feature enhances biodistribution and the half-life of the peptides, while integration into the target cell membrane increases fusion inhibitor potency. These factors together modulate in vivo efficacy. The results suggest a new framework for developing effective fusion inhibitory peptides. IMPORTANCE Measles virus (MV) infection causes an acute illness that may be associated with infection of the central nervous system (CNS) and severe neurological disease. No specific treatment is available. We have shown that fusion-inhibitory peptides delivered intranasally provide effective prophylaxis against MV infection. We show here that specific biophysical properties regulate the in vivo efficacy of MV F-derived peptides. PMID:27733647

In Vivo Efficacy of Measles Virus Fusion Protein-Derived Peptides Is Modulated by the Properties of Self-Assembly and Membrane Residence.

PubMed

Figueira, T N; Palermo, L M; Veiga, A S; Huey, D; Alabi, C A; Santos, N C; Welsch, J C; Mathieu, C; Horvat, B; Niewiesk, S; Moscona, A; Castanho, M A R B; Porotto, M

2017-01-01

Measles virus (MV) infection is undergoing resurgence and remains one of the leading causes of death among young children worldwide despite the availability of an effective measles vaccine. MV infects its target cells by coordinated action of the MV hemagglutinin (H) and fusion (F) envelope glycoproteins; upon receptor engagement by H, the prefusion F undergoes a structural transition, extending and inserting into the target cell membrane and then refolding into a postfusion structure that fuses the viral and cell membranes. By interfering with this structural transition of F, peptides derived from the heptad repeat (HR) regions of F can inhibit MV infection at the entry stage. In previous work, we have generated potent MV fusion inhibitors by dimerizing the F-derived peptides and conjugating them to cholesterol. We have shown that prophylactic intranasal administration of our lead fusion inhibitor efficiently protects from MV infection in vivo We show here that peptides tagged with lipophilic moieties self-assemble into nanoparticles until they reach the target cells, where they are integrated into cell membranes. The self-assembly feature enhances biodistribution and the half-life of the peptides, while integration into the target cell membrane increases fusion inhibitor potency. These factors together modulate in vivo efficacy. The results suggest a new framework for developing effective fusion inhibitory peptides. Measles virus (MV) infection causes an acute illness that may be associated with infection of the central nervous system (CNS) and severe neurological disease. No specific treatment is available. We have shown that fusion-inhibitory peptides delivered intranasally provide effective prophylaxis against MV infection. We show here that specific biophysical properties regulate the in vivo efficacy of MV F-derived peptides. Copyright © 2016 American Society for Microbiology.

Extension of an iterative closest point algorithm for simultaneous localization and mapping in corridor environments

NASA Astrophysics Data System (ADS)

Yue, Haosong; Chen, Weihai; Wu, Xingming; Wang, Jianhua

2016-03-01

Three-dimensional (3-D) simultaneous localization and mapping (SLAM) is a crucial technique for intelligent robots to navigate autonomously and execute complex tasks. It can also be applied to shape measurement, reverse engineering, and many other scientific or engineering fields. A widespread SLAM algorithm, named KinectFusion, performs well in environments with complex shapes. However, it cannot handle translation uncertainties well in highly structured scenes. This paper improves the KinectFusion algorithm and makes it competent in both structured and unstructured environments. 3-D line features are first extracted according to both color and depth data captured by Kinect sensor. Then the lines in the current data frame are matched with the lines extracted from the entire constructed world model. Finally, we fuse the distance errors of these line-pairs into the standard KinectFusion framework and estimate sensor poses using an iterative closest point-based algorithm. Comparative experiments with the KinectFusion algorithm and one state-of-the-art method in a corridor scene have been done. The experimental results demonstrate that after our improvement, the KinectFusion algorithm can also be applied to structured environments and has higher accuracy. Experiments on two open access datasets further validated our improvements.

The Effect of Differentially Designed Fusion Proteins to Elicit Efficient Anti-human Thyroid Stimulating Hormone Immune Responses.

PubMed

Mard-Soltani, Maysam; Rasaee, Mohamad Javad; Khalili, Saeed; Sheikhi, Abdol-Karim; Hedayati, Mehdi; Ghaderi-Zefrehi, Hossein; Alasvand, Milad

2018-04-01

The production of human thyroid stimulating hormone (hTSH) immunoassays requires specific antibodies against hTSH which is a cumbersome process. Therefore, producing specific polyclonal antibodies against engineered recombinant fusion hTSH antigens would be of great significance. The best immunogenic region of the hTSH was selected based on in silico analyses and equipped with two different fusions. Standard methods were used for protein expression, purification, verification, structural evaluation, and immunizations of the white New Zealand rabbits. Ultimately, immunized serums were used for antibody titration, purification and characterization (specificity, sensitivity and cross reactivity). The desired antigens were successfully designed, sub-cloned, expressed, confirmed and used for in vivo immunization. Structural analyses indicated that only the bigger antigen has showed changed 2 dimensional (2D) and 3D structural properties in comparison to the smaller antigen. The raised polyclonal antibodies were capable of specific and sensitive hTSH detection, while the cross reactivity with the other members of the glycoprotein hormone family was minimum and negligible. The fusion which was solely composed of the tetanus toxin epitopes led to better protein folding and was capable of immunizing the host animals resulting into high titer antibody. Therefore, the minimal fusion sequences seem to be more effective in eliciting specific antibody responses.

Light- and transmission-electron-microscopic investigations on distribution of CD44, connexin 43 and actin cytoskeleton during the foreign body reaction to a nanoparticular hydroxyapatite in mini-pigs.

PubMed

Wenisch, Sabine; Cavalcanti-Adam, E Ada; Tryankowski, Eva; Raabe, Oksana; Kilian, Olaf; Heiss, Christian; Alt, Volker; Arnhold, Stefan; Schnettler, Reinhard

2012-07-01

Foreign body giant cells (FBGCs) are formed by fusion of mononucleated macrophages during the foreign body response to a nanoparticulate hydroxyapatite (HA) implanted in defects of mini-pig femura. The molecular mechanisms underlying the formation of FBGCs are still largely obscure. Here we propose connexin 43 (cx43) and CD44 as candidate molecules involved in the fusion process. Immunohistochemistry and ultrastructural immunogold labeling indicated that cx43 is present within the ruffled border of FBGCs and is the main component of gap junctions formed between fusing macrophages. CD44 was strongly expressed during clustering and fusion of mononucleated macrophages. FBGCs adhering apically at the implanted HA showed CD44 reactivity only along the basolateral aspects of the plasma membranes, while podosome formation was observed within the sealing zone and ruffled border. Taken together, these findings demonstrate that cx43 and CD44 are part of the fusion machinery responsible for the formation of FBGCs. Furthermore, the results of microfilament and cx43 labeling suggest a functional role for podosomes and hemi-channels in biomaterial degradation. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Diagnostic pitfall on the histological spectrum of adult-onset renal carcinoma associated with Xp11.2 translocations/TFE3 gene fusions.

PubMed

Kuroda, Naoto; Katto, Kazunobu; Tanaka, Yukichi; Yamaguchi, Tadanori; Inoue, Kaori; Ohara, Masahiko; Mizuno, Keiko; Hes, Ondrej; Michal, Michal; Lee, Gang-Hong

2010-06-01

Renal cell carcinoma (RCC) associated with Xp11.2 translocation/TFE3 gene fusion recently has been found. In this article, we demonstrate an unusual features of such a case. A 73-year-old Japanese woman presented with macroscopic hematuria. The imaging examinations disclosed the renal tumor. Histological examination showed the finding of ASPL-TFE3 RCC, which was characterized by papillary, alveolar, or solid growth of voluminous cell with clear and eosinophilic cells, and stromal psammoma body and hyaline nodules. Additionally, shrunken nuclei, thick cell border, and perinuclear clearing characteristic of chromophobe renal cell carcinoma were observed in the alveolar growth area and the transitional zone between stromal hyalinization, and osseous metaplasia was identified. Immunohistochemically, nuclei of tumorous cell were diffusely positive for TFE3. A RT-PCR study revealed the ASPL-TFE3 chimeric transcript. Finally, pathologists should recognize that the histology of RCC associated with Xp11.2 translocation/TFE3 gene fusion may focally resemble that of chromophobe RCC, but TFE3 immunohistochemistry and molecular genetic study may be helpful in the differential diagnosis. Moreover, osseous metaplasia as well as psammoma bodies should be added to the histological spectrum of the stromal change in RCC associated with Xp11.2 translocations/TFE3 gene fusions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

none,

The Fusion Energy Science Advisory Committee was asked to conduct a review of Fusion Materials Research Program (the Structural Materials portion of the Fusion Program) by Dr. Martha Krebs, Director of Energy Research for the Department of Energy. This request was motivated by the fact that significant changes have been made in the overall direction of the Fusion Program from one primarily focused on the milestones necessary to the construction of successively larger machines to one where the necessary scientific basis for an attractive fusion energy system is. better understood. It was in this context that the review of currentmore » scientific excellence and recommendations for future goals and balance within the Program was requested.« less

Ductility dip cracking susceptibility of Inconel Filler Metal 52 and Inconel Alloy 690

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kikel, J.M.; Parker, D.M.

1998-06-01

Alloy 690 and Filler Metal 52 have become the materials of choice for commercial nuclear steam generator applications in recent years. Filler Metal 52 exhibits improved resistance to weld solidification and weld-metal liquation cracking as compared to other nickel-based filler metals. However, recently published work indicates that Filler Metal 52 is susceptible to ductility dip cracking (DDC) in highly restrained applications. Susceptibility to fusion zone DDC was evaluated using the transverse varestraint test method, while heat affected zone (HAZ) DDC susceptibility was evaluated using a newly developed spot-on-spot varestraint test method. Alloy 690 and Filler Metal 52 cracking susceptibility wasmore » compared to the DDC susceptibility of Alloy 600, Filler Metal 52, and Filler Metal 625. In addition, the effect of grain size and orientation on cracking susceptibility was also included in this study. Alloy 690, Filler Metal 82, Filler Metal 52, and Filler Metal 625 were found more susceptible to fusion zone DDC than Alloy 600. Filler Metal 52 and Alloy 690 were found more susceptible to HAZ DDC when compared to wrought Alloy 600, Filler Metal 82 and Filler Metal 625. Filler Metal 52 exhibited the greatest susceptibility to HAZ DDC of all the weld metals evaluated. The base materials were found much more resistant to HAZ DDC in the wrought condition than when autogenously welded. A smaller grain size was found to offer greater resistance to DDC. For weld metal where grain size is difficult to control, a change in grain orientation was found to improve resistance to DDC.« less

An Atom-Probe Tomographic Study of Arc Welds in a Multi-Component High-Strength Low-Alloy Steel

NASA Astrophysics Data System (ADS)

Hunter, Allen H.; Farren, Jeffrey D.; DuPont, John N.; Seidman, David N.

2013-04-01

An experimental plate steel with the composition Fe-1.39Cu-2.7Ni-0.58Al-0.48Mn-0.48Si-0.065Nb-0.05C (wt pct) or alternatively Fe-1.43Cu-2.61Ni-1.21Al-0.48Mn-0.98Si-0.039Nb-0.23C at. pct has been recently produced at Northwestern University for use in Naval hull and deck applications—it is designated NUCu-140. To understand the microstructural changes occurring in NUCu-140 steel after gas-metal arc welding (GMAW), a detailed study of the heat-affected and fusion zones was performed throughout the weld cross section using microhardness, metallographic, chemical, and atom-probe tomographic analyses. Local-electrode atom-probe (LEAP) tomography was employed to measure the morphology and compositions of Cu-rich precipitates from each region. The mean radius, number density, volume fraction, and compositions of the precipitates, as well as the interfacial concentration profiles, are measured. The Cu precipitates dissolve partially from the heat-affected zone (HAZ) thermal cycle, and freshly formed sub-nanometer radius Cu-rich precipitates nucleate in both the HAZ and fusion zone (FZ) during cooling; however, the precipitation of Cu during cooling in the HAZ and FZ is not sufficient to restore the lost strength. The precipitation in the FZ is reduced compared to the HAZ due to a mismatched Cu composition of the weld. Multi-pass welding is suggested to restore strength in the GMAW sample by promoting Cu precipitate nucleation and growth in the HAZ and FZ.

Denudation of metal powder layers in laser powder bed fusion processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matthews, Manyalibo J.; Guss, Gabe; Khairallah, Saad A.

Understanding laser interaction with metal powder beds is critical in predicting optimum processing regimes in laser powder bed fusion additive manufacturing of metals. In this work, we study the denudation of metal powders that is observed near the laser scan path as a function of laser parameters and ambient gas pressure. We show that the observed depletion of metal powder particles in the zone immediately surrounding the solidified track is due to a competition between outward metal vapor flux directed away from the laser spot and entrainment of powder particles in a shear flow of gas driven by a metalmore » vapor jet at the melt track. Between atmospheric pressure and ~10 Torr of Ar gas, the denuded zone width increases with decreasing ambient gas pressure and is dominated by entrainment from inward gas flow. The denuded zone then decreases from 10 to 2.2 Torr reaching a minimum before increasing again from 2.2 to 0.5 Torr where metal vapor flux and expansion from the melt pool dominates. In addition, the dynamics of the denudation process were captured using high-speed imaging, revealing that the particle movement is a complex interplay among melt pool geometry, metal vapor flow, and ambient gas pressure. The experimental results are rationalized through finite element simulations of the melt track formation and resulting vapor flow patterns. The results presented here represent new insights to denudation and melt track formation that can be important for the prediction and minimization of void defects and surface roughness in additively manufactured metal components.« less

Denudation of metal powder layers in laser powder bed fusion processes

DOE PAGES

Matthews, Manyalibo J.; Guss, Gabe; Khairallah, Saad A.; ...

2016-05-20

Understanding laser interaction with metal powder beds is critical in predicting optimum processing regimes in laser powder bed fusion additive manufacturing of metals. In this work, we study the denudation of metal powders that is observed near the laser scan path as a function of laser parameters and ambient gas pressure. We show that the observed depletion of metal powder particles in the zone immediately surrounding the solidified track is due to a competition between outward metal vapor flux directed away from the laser spot and entrainment of powder particles in a shear flow of gas driven by a metalmore » vapor jet at the melt track. Between atmospheric pressure and ~10 Torr of Ar gas, the denuded zone width increases with decreasing ambient gas pressure and is dominated by entrainment from inward gas flow. The denuded zone then decreases from 10 to 2.2 Torr reaching a minimum before increasing again from 2.2 to 0.5 Torr where metal vapor flux and expansion from the melt pool dominates. In addition, the dynamics of the denudation process were captured using high-speed imaging, revealing that the particle movement is a complex interplay among melt pool geometry, metal vapor flow, and ambient gas pressure. The experimental results are rationalized through finite element simulations of the melt track formation and resulting vapor flow patterns. The results presented here represent new insights to denudation and melt track formation that can be important for the prediction and minimization of void defects and surface roughness in additively manufactured metal components.« less

Comparative Effectiveness of Targeted Prostate Biopsy Using Magnetic Resonance Imaging Ultrasound Fusion Software and Visual Targeting: a Prospective Study.

PubMed

Lee, Daniel J; Recabal, Pedro; Sjoberg, Daniel D; Thong, Alan; Lee, Justin K; Eastham, James A; Scardino, Peter T; Vargas, Hebert Alberto; Coleman, Jonathan; Ehdaie, Behfar

2016-09-01

We compared the diagnostic outcomes of magnetic resonance-ultrasound fusion and visually targeted biopsy for targeting regions of interest on prostate multiparametric magnetic resonance imaging. Patients presenting for prostate biopsy with regions of interest on multiparametric magnetic resonance imaging underwent magnetic resonance imaging targeted biopsy. For each region of interest 2 visually targeted cores were obtained, followed by 2 cores using a magnetic resonance-ultrasound fusion device. Our primary end point was the difference in the detection of high grade (Gleason 7 or greater) and any grade cancer between visually targeted and magnetic resonance-ultrasound fusion, investigated using McNemar's method. Secondary end points were the difference in detection rate by biopsy location using a logistic regression model and the difference in median cancer length using the Wilcoxon signed rank test. We identified 396 regions of interest in 286 men. The difference in the detection of high grade cancer between magnetic resonance-ultrasound fusion biopsy and visually targeted biopsy was -1.4% (95% CI -6.4 to 3.6, p=0.6) and for any grade cancer the difference was 3.5% (95% CI -1.9 to 8.9, p=0.2). Median cancer length detected by magnetic resonance-ultrasound fusion and visually targeted biopsy was 5.5 vs 5.8 mm, respectively (p=0.8). Magnetic resonance-ultrasound fusion biopsy detected 15% more cancers in the transition zone (p=0.046) and visually targeted biopsy detected 11% more high grade cancer at the prostate base (p=0.005). Only 52% of all high grade cancers were detected by both techniques. We found no evidence of a significant difference in the detection of high grade or any grade cancer between visually targeted and magnetic resonance-ultrasound fusion biopsy. However, the performance of each technique varied in specific biopsy locations and the outcomes of both techniques were complementary. Combining visually targeted biopsy and magnetic resonance-ultrasound fusion biopsy may optimize the detection of prostate cancer. Copyright © 2016 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Complexin Mutants Reveal Partial Segregation between Recycling Pathways That Drive Evoked and Spontaneous Neurotransmission

PubMed Central

Sabeva, Nadezhda; Cho, Richard W.; Vasin, Alexander; Gonzalez, Agustin; Littleton, J. Troy

2017-01-01

Synaptic vesicles fuse at morphological specializations in the presynaptic terminal termed active zones (AZs). Vesicle fusion can occur spontaneously or in response to an action potential. Following fusion, vesicles are retrieved and recycled within nerve terminals. It is still unclear whether vesicles that fuse spontaneously or following evoked release share similar recycling mechanisms. Genetic deletion of the SNARE-binding protein complexin dramatically increases spontaneous fusion, with the protein serving as the synaptic vesicle fusion clamp at Drosophila synapses. We examined synaptic vesicle recycling pathways at complexin null neuromuscular junctions, where spontaneous release is dramatically enhanced. We combined loading of the lipophilic dye FM1–43 with photoconversion, electron microscopy, and electrophysiology to monitor evoked and spontaneous recycling vesicle pools. We found that the total number of recycling vesicles was equal to those retrieved through spontaneous and evoked pools, suggesting that retrieval following fusion is partially segregated for spontaneous and evoked release. In addition, the kinetics of FM1–43 destaining and synaptic depression measured in the presence of the vesicle-refilling blocker bafilomycin indicated that spontaneous and evoked recycling pools partially intermix during the release process. Finally, FM1–43 photoconversion combined with electron microscopy analysis indicated that spontaneous recycling preferentially involves synaptic vesicles in the vicinity of AZs, whereas vesicles recycled following evoked release involve a larger intraterminal pool. Together, these results suggest that spontaneous and evoked vesicles use separable recycling pathways and then partially intermix during subsequent rounds of fusion. SIGNIFICANCE STATEMENT Neurotransmitter release involves fusion of synaptic vesicles with the plasma membrane in response to an action potential, or spontaneously in the absence of stimulation. Upon fusion, vesicles are retrieved and recycled, and it is unclear whether recycling pathways for evoked and spontaneous vesicles are segregated after fusion. We addressed this question by taking advantage of preparations lacking the synaptic protein complexin, which have elevated spontaneous release that enables reliable tracking of the spontaneous recycling pool. Our results suggest that spontaneous and evoked recycling pathways are segregated during the retrieval process but can partially intermix during stimulation. PMID:28077717

A Maltose-Binding Protein Fusion Construct Yields a Robust Crystallography Platform for MCL1

PubMed Central

Clifton, Matthew C.; Dranow, David M.; Leed, Alison; Fulroth, Ben; Fairman, James W.; Abendroth, Jan; Atkins, Kateri A.; Wallace, Ellen; Fan, Dazhong; Xu, Guoping; Ni, Z. J.; Daniels, Doug; Van Drie, John; Wei, Guo; Burgin, Alex B.; Golub, Todd R.; Hubbard, Brian K.; Serrano-Wu, Michael H.

2015-01-01

Crystallization of a maltose-binding protein MCL1 fusion has yielded a robust crystallography platform that generated the first apo MCL1 crystal structure, as well as five ligand-bound structures. The ability to obtain fragment-bound structures advances structure-based drug design efforts that, despite considerable effort, had previously been intractable by crystallography. In the ligand-independent crystal form we identify inhibitor binding modes not observed in earlier crystallographic systems. This MBP-MCL1 construct dramatically improves the structural understanding of well-validated MCL1 ligands, and will likely catalyze the structure-based optimization of high affinity MCL1 inhibitors. PMID:25909780

Structure of the cleavage-activated prefusion form of the parainfluenza virus 5 fusion protein.

PubMed

Welch, Brett D; Liu, Yuanyuan; Kors, Christopher A; Leser, George P; Jardetzky, Theodore S; Lamb, Robert A

2012-10-09

The paramyxovirus parainfluenza virus 5 (PIV5) enters cells by fusion of the viral envelope with the plasma membrane through the concerted action of the fusion (F) protein and the receptor binding protein hemagglutinin-neuraminidase. The F protein folds initially to form a trimeric metastable prefusion form that is triggered to undergo large-scale irreversible conformational changes to form the trimeric postfusion conformation. It is thought that F refolding couples the energy released with membrane fusion. The F protein is synthesized as a precursor (F0) that must be cleaved by a host protease to form a biologically active molecule, F1,F2. Cleavage of F protein is a prerequisite for fusion and virus infectivity. Cleavage creates a new N terminus on F1 that contains a hydrophobic region, known as the FP, which intercalates target membranes during F protein refolding. The crystal structure of the soluble ectodomain of the uncleaved form of PIV5 F is known; here we report the crystal structure of the cleavage-activated prefusion form of PIV5 F. The structure shows minimal movement of the residues adjacent to the protease cleavage site. Most of the hydrophobic FP residues are buried in the uncleaved F protein, and only F103 at the newly created N terminus becomes more solvent-accessible after cleavage. The conformational freedom of the charged arginine residues that compose the protease recognition site increases on cleavage of F protein.

Structure of the cleavage-activated prefusion form of the parainfluenza virus 5 fusion protein

PubMed Central

Welch, Brett D.; Liu, Yuanyuan; Kors, Christopher A.; Leser, George P.; Jardetzky, Theodore S.; Lamb, Robert A.

2012-01-01

The paramyxovirus parainfluenza virus 5 (PIV5) enters cells by fusion of the viral envelope with the plasma membrane through the concerted action of the fusion (F) protein and the receptor binding protein hemagglutinin-neuraminidase. The F protein folds initially to form a trimeric metastable prefusion form that is triggered to undergo large-scale irreversible conformational changes to form the trimeric postfusion conformation. It is thought that F refolding couples the energy released with membrane fusion. The F protein is synthesized as a precursor (F0) that must be cleaved by a host protease to form a biologically active molecule, F1,F2. Cleavage of F protein is a prerequisite for fusion and virus infectivity. Cleavage creates a new N terminus on F1 that contains a hydrophobic region, known as the FP, which intercalates target membranes during F protein refolding. The crystal structure of the soluble ectodomain of the uncleaved form of PIV5 F is known; here we report the crystal structure of the cleavage-activated prefusion form of PIV5 F. The structure shows minimal movement of the residues adjacent to the protease cleavage site. Most of the hydrophobic FP residues are buried in the uncleaved F protein, and only F103 at the newly created N terminus becomes more solvent-accessible after cleavage. The conformational freedom of the charged arginine residues that compose the protease recognition site increases on cleavage of F protein. PMID:23012473

Single residues in the surface subunits of oncogenic sheep retrovirus envelopes distinguish receptor-mediated triggering for fusion at low pH and infection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cote, Marceline; Zheng, Yi-Min; Albritton, Lorraine M.

2011-12-20

Jaagsiekte sheep retrovirus (JSRV) and enzootic nasal tumor virus (ENTV) are two closely related oncogenic retroviruses that share the same cellular receptor yet exhibit distinct fusogenicity and infectivity. Here, we find that the low fusogenicity of ENTV envelope protein (Env) is not because of receptor binding, but lies in its intrinsic insensitivity to receptor-mediated triggering for fusion at low pH. Distinct from JSRV, shedding of ENTV surface (SU) subunit into culture medium was not enhanced by a soluble form of receptor, Hyal2 (sHyal2), and sHyal2 was unable to effectively inactivate the ENTV pseudovirions. Remarkably, replacing either of the two aminomore » acid residues, N191 or S195, located in the ENTV SU with the corresponding JSRV residues, H191 or G195, markedly increased the Env-mediated membrane fusion activity and infection. Reciprocal amino acid substitutions also partly switched the sensitivities of ENTV and JSRV pseudovirions to sHyal2-mediated SU shedding and inactivation. While N191 is responsible for an extra N-linked glycosylation of ENTV SU relative to that of JSRV, S195 possibly forms a hydrogen bond with a surrounding amino acid residue. Molecular modeling of the pre-fusion structure of JSRV Env predicts that the segment of SU that contains H191 to G195 contacts the fusion peptide and suggests that the H191N and G195S changes seen in ENTV may stabilize its pre-fusion structure against receptor priming and therefore modulate fusion activation by Hyal2. In summary, our study reveals critical determinants in the SU subunits of JSRV and ENTV Env proteins that likely regulate their local structures and thereby differential receptor-mediated fusion activation at low pH, and these findings explain, at least in part, their distinct viral infectivity.« less

Microstructural and mechanical characterization of CO{sub 2} laser and gas tungsten arc welds of an Al-Li-Cu alloy 2195

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hou, K.H.; Baeslack, W.A. III; Szabo, A.

1994-12-31

Lithium-containing aluminum alloys offer an attractive combination of low density and high strength and stiffness and have been the focus of vigorous research for their promising aerospace applications. To achieve the full potential advantages in using these alloys, the integrity of welded joints, both n the fusion zone and the heat-affected zone, must be ensured. In the present study, Weldalite{sup TM} 049 (designated as alloy 2195) with nominal composition of Al-1.0Li-4.0Cu-0.4Mg0.4Ag-0.14Zr (wt%) was welded autogenously using the gas tungsten-arc (GTA) and CO{sub 2} laser beam (LB) welding processes. The average ultimate tensile strengths for as-welded, 160{degrees}C/16 h-aged, and 190{degrees}C/16 h-agedmore » GTA welds were 296.4 MPa, 304.6 MPa, and 336.8 MPa, and corresponded to joint efficiencies of 61.4%, 48.1% and 56.0%, respectively. Porosity was found occasionally in the laser welds and slightly affected the performance of the aluminum weldments. For laser welds, average ultimate tensile strengths and corresponding joint efficiencies for a-welded, 160{degrees}C/16 h-aged, and 190{degrees}C/16 h-aged weldments were 293.2 MPa (60.8%) 305.9 MPa (48.3%), and 331.0 MPa (55.0%), respectively. Scanning electron fractography revealed that failure of the GTA and LB tensile specimens occurred either within the weld metal or along the fusion boundary. The latter was related to the existence of an equiaxed band along the fusion boundary.« less

Precise age of C33N-C32R magnetic-polarity reversal, San Juan Basin, New Mexico and Colorado

USGS Publications Warehouse

Fassett, James E.; Steiner, Maureen B.

1997-01-01

Polarity-chron boundary C33n-C32r has been identified in the Upper Cretaceous continental Farmington Sandstone Member of the Kirtland Shale in Hunter Wash in the southwest part of the San Juan Basin of New Mexico, and in the marine Lewis Shale at Chimney Rock, Colorado, in the northeast part of the basin. Single- and multiple-crystal laser fusion 40Ar/39Ar ages of sanidine crystals from volcanic ash beds bracketing the C33n-C32r polarity reversal at Hunter Wash establish its age as 73.50 ± 0.18 Ma. The reversal apparently occurs within the Baculites compressus Western Interior ammonite zone and within the Edmontonian land-vertebrate faunal zone. An 8 Ma hiatus separates Cretaceous and Tertiary rocks in the southern San Juan Basin. These findings provide a precise new interpolated Late Cretaceous tie point for geologic time scales, provide the basis for the direct correlation of Western Interior ammonite zones to European open-ocean faunal zones, and establish the first direct tie between continental and marine fossil zones within the Western Interior of North America.

Activation characteristics of candidate structural materials for a near-term Indian fusion reactor and the impact of their impurities on design considerations

NASA Astrophysics Data System (ADS)

H, L. SWAMI; C, DANANI; A, K. SHAW

2018-06-01

Activation analyses play a vital role in nuclear reactor design. Activation analyses, along with nuclear analyses, provide important information for nuclear safety and maintenance strategies. Activation analyses also help in the selection of materials for a nuclear reactor, by providing the radioactivity and dose rate levels after irradiation. This information is important to help define maintenance activity for different parts of the reactor, and to plan decommissioning and radioactive waste disposal strategies. The study of activation analyses of candidate structural materials for near-term fusion reactors or ITER is equally essential, due to the presence of a high-energy neutron environment which makes decisive demands on material selection. This study comprises two parts; in the first part the activation characteristics, in a fusion radiation environment, of several elements which are widely present in structural materials, are studied. It reveals that the presence of a few specific elements in a material can diminish its feasibility for use in the nuclear environment. The second part of the study concentrates on activation analyses of candidate structural materials for near-term fusion reactors and their comparison in fusion radiation conditions. The structural materials selected for this study, i.e. India-specific Reduced Activation Ferritic‑Martensitic steel (IN-RAFMS), P91-grade steel, stainless steel 316LN ITER-grade (SS-316LN-IG), stainless steel 316L and stainless steel 304, are candidates for use in ITER either in vessel components or test blanket systems. Tungsten is also included in this study because of its use for ITER plasma-facing components. The study is carried out using the reference parameters of the ITER fusion reactor. The activation characteristics of the materials are assessed considering the irradiation at an ITER equatorial port. The presence of elements like Nb, Mo, Co and Ta in a structural material enhance the activity level as well as the dose level, which has an impact on design considerations. IN-RAFMS was shown to be a more effective low-activation material than SS-316LN-IG.

Arabidopsis HAP2/GCS1 is a gamete fusion protein homologous to somatic and viral fusogens

PubMed Central

Valansi, Clari; Moi, David; Leikina, Evgenia; Matveev, Elena; Chernomordik, Leonid V.

2017-01-01

Cell–cell fusion is inherent to sexual reproduction. Loss of HAPLESS 2/GENERATIVE CELL SPECIFIC 1 (HAP2/GCS1) proteins results in gamete fusion failure in diverse organisms, but their exact role is unclear. In this study, we show that Arabidopsis thaliana HAP2/GCS1 is sufficient to promote mammalian cell–cell fusion. Hemifusion and complete fusion depend on HAP2/GCS1 presence in both fusing cells. Furthermore, expression of HAP2 on the surface of pseudotyped vesicular stomatitis virus results in homotypic virus–cell fusion. We demonstrate that the Caenorhabditis elegans Epithelial Fusion Failure 1 (EFF-1) somatic cell fusogen can replace HAP2/GCS1 in one of the fusing membranes, indicating that HAP2/GCS1 and EFF-1 share a similar fusion mechanism. Structural modeling of the HAP2/GCS1 protein family predicts that they are homologous to EFF-1 and viral class II fusion proteins (e.g., Zika virus). We name this superfamily Fusexins: fusion proteins essential for sexual reproduction and exoplasmic merger of plasma membranes. We suggest a common origin and evolution of sexual reproduction, enveloped virus entry into cells, and somatic cell fusion. PMID:28137780

Paramyxovirus F1 protein has two fusion peptides: implications for the mechanism of membrane fusion.

PubMed

Peisajovich, S G; Samuel, O; Shai, Y

2000-03-10

Viral fusion proteins contain a highly hydrophobic segment, named the fusion peptide, which is thought to be responsible for the merging of the cellular and viral membranes. Paramyxoviruses are believed to contain a single fusion peptide at the N terminus of the F1 protein. However, here we identified an additional internal segment in the Sendai virus F1 protein (amino acids 214-226) highly homologous to the fusion peptides of HIV-1 and RSV. A synthetic peptide, which includes this region, was found to induce membrane fusion of large unilamellar vesicles, at concentrations where the known N-terminal fusion peptide is not effective. A scrambled peptide as well as several peptides from other regions of the F1 protein, which strongly bind to membranes, are not fusogenic. The functional and structural characterization of this active segment suggest that the F1 protein has an additional internal fusion peptide that could participate in the actual fusion event. The presence of homologous regions in other members of the same family suggests that the concerted action of two fusion peptides, one N-terminal and the other internal, is a general feature of paramyxoviruses. Copyright 2000 Academic Press.

Digital holographic microtomography of fusion spliced optical fibers

NASA Astrophysics Data System (ADS)

Deng, Yating; Xiao, Wen; Ma, Xichao; Pan, Feng

2017-03-01

In this paper, we report three-dimensional(3D) measurement results of structural parameters of fusion spliced optical fibers using digital holographic microtomography. A holographic setup in microscopy configuration with the sample-fixed and setup-rotating scheme is established. A series of holograms is recorded from various incident angles. Then the filtered backprojection algorithm is applied to reconstruct the 3D refractive index (RI) distributions of the fusion spliced optical fibers inserted in the index-matching liquid. Experimental results exhibit the internal and external shapes of three kinds of fusion splices between different fibers, including a single-mode fiber(SMF) and a multimode fiber, an SMF and a panda polarization maintaining fiber (Panda PMF), and an SMF and a bow-tie polarization maintaining fiber (Bow-Tie PMF). With 3D maps of RI, it is intuitive to observe internal structural details of fused fibers and evaluate the splicing quality. This paper describes a powerful method for non-invasive microscopic measurement of fiber splicing. Furthermore, it provides the possibility of detecting fiber splicing loss by 3D structures.

Technique for writing of fiber Bragg gratings over or near preliminary formed macro-structure defects in silica optical fibers

NASA Astrophysics Data System (ADS)

Evtushenko, Alexander S.; Faskhutdinov, Lenar M.; Kafarova, Anastasia M.; Kazakov, Vadim S.; Kuznetzov, Artem A.; Minaeva, Alina Yu.; Sevruk, Nikita L.; Nureev, Ilnur I.; Vasilets, Alexander A.; Andreev, Vladimir A.; Morozov, Oleg G.; Burdin, Vladimir A.; Bourdine, Anton V.

2017-04-01

This work presents method for performing precision macro-structure defects "tapers" and "up-tapers" written in conventional silica telecommunication multimode optical fibers by commercially available field fusion splicer with modified software settings and following writing fiber Bragg gratings over or near them. We developed technique for macrodefect geometry parameters estimation via analysis of photo-image performed after defect writing and displayed on fusion splicer screen. Some research results of defect geometry dependence on fusion current and fusion time values re-set in splicer program are represented that provided ability to choose their "the best" combination. Also experimental statistical researches concerned with "taper" and "up-taper" diameter stability as well as their insertion loss values during their writing under fixed corrected splicer program parameters were performed. We developed technique for FBG writing over or near macro-structure defect. Some results of spectral response measurements produced for short-length samples of multimode optical fiber with fiber Bragg gratings written over and near macro-defects prepared by using proposed technique are presented.

Structures of the prefusion form of measles virus fusion protein in complex with inhibitors.

PubMed

Hashiguchi, Takao; Fukuda, Yoshinari; Matsuoka, Rei; Kuroda, Daisuke; Kubota, Marie; Shirogane, Yuta; Watanabe, Shumpei; Tsumoto, Kouhei; Kohda, Daisuke; Plemper, Richard Karl; Yanagi, Yusuke

2018-03-06

Measles virus (MeV), a major cause of childhood morbidity and mortality, is highly immunotropic and one of the most contagious pathogens. MeV may establish, albeit rarely, persistent infection in the central nervous system, causing fatal and intractable neurodegenerative diseases such as subacute sclerosing panencephalitis and measles inclusion body encephalitis. Recent studies have suggested that particular substitutions in the MeV fusion (F) protein are involved in the pathogenesis by destabilizing the F protein and endowing it with hyperfusogenicity. Here we show the crystal structures of the prefusion MeV-F alone and in complex with the small compound AS-48 or a fusion inhibitor peptide. Notably, these independently developed inhibitors bind the same hydrophobic pocket located at the region connecting the head and stalk of MeV-F, where a number of substitutions in MeV isolates from neurodegenerative diseases are also localized. Since these inhibitors could suppress membrane fusion mediated by most of the hyperfusogenic MeV-F mutants, the development of more effective inhibitors based on the structures may be warranted to treat MeV-induced neurodegenerative diseases.

Optimal fusion offset in splicing photonic crystal fibers

NASA Astrophysics Data System (ADS)

Jin, Wa; Bi, Weihong; Fu, Guangwei

2013-08-01

Heat transfer is very complicate in fusion splicing process of photonic crystal fibers (PCFs) due to different structures and sizes of air hole, which requires different fusion splicing power and offsets of heat source. Based on the heat transfer characteristics, this paper focus on the optimal splicing offset splicing the single mode fiber and PCFs with a CO2 laser irradiation. The theory and experiments both show that the research results can effectively calculate the optimal fusion splicing offset and guide the practical splicing between PCFs and SMFs.

Gallium arsenide-gallium nitride wafer fusion and the n-aluminum gallium arsenide/p-gallium arsenide/n-gallium nitride double heterojunction bipolar transistor

NASA Astrophysics Data System (ADS)

Estrada, Sarah M.

This dissertation describes the n-AlGaAs/p-GaAs/n-GaN heterojunction bipolar transistor (HBT), the first transistor formed via wafer fusion. The fusion process was developed as a way to combine lattice-mismatched materials for high-performance electronic devices, not obtainable via conventional all-epitaxial formation methods. Despite the many challenges of wafer fusion, successful transistors were demonstrated and improved, via the optimization of material structure and fusion process conditions. Thus, this project demonstrated the integration of disparate device materials, chosen for their optimal electronic properties, unrestricted by the conventional (and very limiting) requirement of lattice-matching. By combining an AlGaAs-GaAs emitter-base with a GaN collector, the HBT benefited from the high breakdown voltage of GaN, and from the high emitter injection efficiency and low base transit time of AlGaAs-GaAs. Because the GaAs-GaN lattice mismatch precluded an all-epitaxial formation of the HBT, the GaAs-GaN heterostructure was formed via fusion. This project began with the development of a fusion process that formed mechanically robust and electrically active GaAs-GaN heterojunctions. During the correlation of device electrical performance with a systematic variation of fusion conditions over a wide range (500--750°C, 0.5--2hours), a mid-range fusion temperature was found to induce optimal HBT electrical performance. Transmission electron microscopy (TEM) and secondary ion mass spectrometry (SIMS) were used to assess possible reasons for the variations observed in device electrical performance. Fusion process conditions were correlated with electrical (I-V), structural (TEM), and chemical (SIMS) analyses of the resulting heterojunctions, in order to investigate the trade-off between increased interfacial disorder (TEM) with low fusion temperature and increased diffusion (SIMS) with high fusion temperature. The best do device results (IC ˜ 2.9 kA/cm2 and beta ˜ 3.5, at VCE = 20V and IB = 10mA) were obtained with an HBT formed via fusion at 600°C for 1 hour, with an optimized base-collector design. This was quite an improvement, as compared to an HBT with a simpler base-collector structure, also fused at 600°C for 1 hour (IC ˜ 0.83 kA/cm2 and beta ˜ 0.89, at VCE = 20V and IB = 10mA). Fused AlGaAs-GaAs-GaAs HBTs were compared to fused AlGaAs-GaAs-GaN HBTs, demonstrating that the use of a wider bandgap collector (Eg,GaN > Eg,GaAs) did indeed improve HBT performance at high applied voltages, as desired for high-power applications.

ERS-2 SAR and IRS-1C LISS III data fusion: A PCA approach to improve remote sensing based geological interpretation

NASA Astrophysics Data System (ADS)

Pal, S. K.; Majumdar, T. J.; Bhattacharya, Amit K.

Fusion of optical and synthetic aperture radar data has been attempted in the present study for mapping of various lithologic units over a part of the Singhbhum Shear Zone (SSZ) and its surroundings. ERS-2 SAR data over the study area has been enhanced using Fast Fourier Transformation (FFT) based filtering approach, and also using Frost filtering technique. Both the enhanced SAR imagery have been then separately fused with histogram equalized IRS-1C LISS III image using Principal Component Analysis (PCA) technique. Later, Feature-oriented Principal Components Selection (FPCS) technique has been applied to generate False Color Composite (FCC) images, from which corresponding geological maps have been prepared. Finally, GIS techniques have been successfully used for change detection analysis in the lithological interpretation between the published geological map and the fusion based geological maps. In general, there is good agreement between these maps over a large portion of the study area. Based on the change detection studies, few areas could be identified which need attention for further detailed ground-based geological studies.

AxiaLIF system: minimally invasive device for presacral lumbar interbody spinal fusion

PubMed Central

Rapp, Steven M; Miller, Larry E; Block, Jon E

2011-01-01

Lumbar fusion is commonly performed to alleviate chronic low back and leg pain secondary to disc degeneration, spondylolisthesis with or without concomitant lumbar spinal stenosis, or chronic lumbar instability. However, the risk of iatrogenic injury during traditional anterior, posterior, and transforaminal open fusion surgery is significant. The axial lumbar interbody fusion (AxiaLIF) system is a minimally invasive fusion device that accesses the lumbar (L4–S1) intervertebral disc spaces via a reproducible presacral approach that avoids critical neurovascular and musculoligamentous structures. Since the AxiaLIF system received marketing clearance from the US Food and Drug Administration in 2004, clinical studies of this device have reported high fusion rates without implant subsidence, significant improvements in pain and function, and low complication rates. This paper describes the design and approach of this lumbar fusion system, details the indications for use, and summarizes the clinical experience with the AxiaLIF system to date. PMID:22915939

AxiaLIF system: minimally invasive device for presacral lumbar interbody spinal fusion.

PubMed

Rapp, Steven M; Miller, Larry E; Block, Jon E

2011-01-01

Lumbar fusion is commonly performed to alleviate chronic low back and leg pain secondary to disc degeneration, spondylolisthesis with or without concomitant lumbar spinal stenosis, or chronic lumbar instability. However, the risk of iatrogenic injury during traditional anterior, posterior, and transforaminal open fusion surgery is significant. The axial lumbar interbody fusion (AxiaLIF) system is a minimally invasive fusion device that accesses the lumbar (L4-S1) intervertebral disc spaces via a reproducible presacral approach that avoids critical neurovascular and musculoligamentous structures. Since the AxiaLIF system received marketing clearance from the US Food and Drug Administration in 2004, clinical studies of this device have reported high fusion rates without implant subsidence, significant improvements in pain and function, and low complication rates. This paper describes the design and approach of this lumbar fusion system, details the indications for use, and summarizes the clinical experience with the AxiaLIF system to date.

History of Nuclear Fusion Research in Japan

NASA Astrophysics Data System (ADS)

Iguchi, Harukazu; Matsuoka, Keisuke; Kimura, Kazue; Namba, Chusei; Matsuda, Shinzaburo

In the late 1950s just after the atomic energy research was opened worldwide, there was a lively discussion among scientists on the strategy of nuclear fusion research in Japan. Finally, decision was made that fusion research should be started from the basic, namely, research on plasma physics and from cultivation of human resources at universities under the Ministry of Education, Science and Culture (MOE). However, an endorsement was given that construction of an experimental device for fusion research would be approved sooner or later. Studies on toroidal plasma confinement started at Japan Atomic Energy Research Institute (JAERI) under the Science and Technology Agency (STA) in the mid-1960s. Dualistic fusion research framework in Japan was established. This structure has lasted until now. Fusion research activities over the last 50 years are described by the use of a flowchart, which is convenient to glance the historical development of fusion research in Japan.

Fusion of multi-spectral and panchromatic images based on 2D-PWVD and SSIM

NASA Astrophysics Data System (ADS)

Tan, Dongjie; Liu, Yi; Hou, Ruonan; Xue, Bindang

2016-03-01

A combined method using 2D pseudo Wigner-Ville distribution (2D-PWVD) and structural similarity(SSIM) index is proposed for fusion of low resolution multi-spectral (MS) image and high resolution panchromatic (PAN) image. First, the intensity component of multi-spectral image is extracted with generalized IHS transform. Then, the spectrum diagrams of the intensity components of multi-spectral image and panchromatic image are obtained with 2D-PWVD. Different fusion rules are designed for different frequency information of the spectrum diagrams. SSIM index is used to evaluate the high frequency information of the spectrum diagrams for assigning the weights in the fusion processing adaptively. After the new spectrum diagram is achieved according to the fusion rule, the final fusion image can be obtained by inverse 2D-PWVD and inverse GIHS transform. Experimental results show that, the proposed method can obtain high quality fusion images.

General software design for multisensor data fusion

NASA Astrophysics Data System (ADS)

Zhang, Junliang; Zhao, Yuming

1999-03-01

In this paper a general method of software design for multisensor data fusion is discussed in detail, which adopts object-oriented technology under UNIX operation system. The software for multisensor data fusion is divided into six functional modules: data collection, database management, GIS, target display and alarming data simulation etc. Furthermore, the primary function, the components and some realization methods of each modular is given. The interfaces among these functional modular relations are discussed. The data exchange among each functional modular is performed by interprocess communication IPC, including message queue, semaphore and shared memory. Thus, each functional modular is executed independently, which reduces the dependence among functional modules and helps software programing and testing. This software for multisensor data fusion is designed as hierarchical structure by the inheritance character of classes. Each functional modular is abstracted and encapsulated through class structure, which avoids software redundancy and enhances readability.

Probing the Structure of {sup 74}Ge Nucleus with Coupled-channels Analysis of {sup 74}Ge+{sup 74}Ge Fusion Reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zamrun F, Muhammad; Jurusan Fisika FMIPA, Universitas Haluoleo, Kendari, Sulawesi Tenggara, 93232; Kasim, Hasan Abu

2010-12-23

We study the fusion reaction of the {sup 74}Ge+{sup 74}Ge system in term of the full order coupled-channels formalism. We especially calculated the fusion cross section as well as the fusion barrier distribution of this reaction using transition matrix suggested by recent Coulomb excitation experiment. We compare the results with the one obtained by coupling matrix based on pure vibrational and rotational models. The present coupled-channels calculations for the barrier distributions obtained using experiment coupling matrix is in good agreement with the one obtained with vibrational model, in contrast to the rotational model. This is indicates that {sup 74}Ge nucleusmore » favor a spherical shape than a deformed shape in its ground state. Our results will resolve the debates concerning the structure of this nucleus.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klimenov, V. A., E-mail: klimenov@tpu.ru; National Research Tomsk Polytechnic University, 30 Lenin Av., Tomsk, 634050; Kurgan, K. A., E-mail: kirill-k2.777@mail.ru

The structure of weld joints of the titanium alloy Ti-6Al-4V in the initial ultrafine-grained state, obtained by resistance spot welding, is studied using the optical and scanning electron microscopy method and the X-ray structure analysis. The carried out studies show the relationship of the metal structure in the weld zone with main joint zones. The structure in the core zone and the heat affected zone is represented by finely dispersed grains of needle-shaped martensite, differently oriented in these zones. The change in the microhardness in the longitudinal section of the weld joint clearly correlates with structural changes during welding.

Combat Internist: The Internal Medicine Experience in a Combat Hospital in Afghanistan

DTIC Science & Technology

2015-01-01

massive trans- fusion protocol.6 As such, critical care included frequent monitoring of hemoglobin and coagulation parameters with administration of...ongoing resuscitation. With the rise in nutritional supplement use, it was no sur- prise that they were frequently used in the combat zone. Numerous...recommendations on standard precautions and further care of his vaccine site. Education and Administration There were many opportunities to train and

Microstructural analysis of laser weld fusion zone in Haynes 282 superalloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Osoba, L.O.; Ding, R.G.; Ojo, O.A., E-mail: ojo@cc.umanitoba.ca

Analytical electron microscopy and spectroscopy analyses of the fusion zone (FZ) microstructure in autogenous laser beam welded Haynes 282 (HY 282) superalloy were performed. The micro-segregation patterns observed in the FZ indicate that Co, Cr and Al exhibited a nearly uniform distribution between the dendrite core and interdendritic regions while Ti and Mo were rejected into the interdendritic liquid during the weld solidification. Transmission electron diffraction analysis and energy dispersive X-ray microanalysis revealed the second phase particles formed along the FZ interdendritic region to be Ti-Mo rich MC-type carbide particles. Weld FZ solidification cracking, which is sometimes associated with themore » formation of {gamma}-{gamma}' eutectic in {gamma}' precipitation strengthened nickel-base superalloys, was not observed in the HY 282 superalloy. Modified primary solidification path due to carbon addition in the newly developed superalloy is used to explain preclusion of weld FZ solidification cracking in the material. - Highlights: Black-Right-Pointing-Pointer A newly developed superalloy was welded by CO{sub 2} laser beam joining technique. Black-Right-Pointing-Pointer Electron microscopy characterization of the weld microstructure was performed. Black-Right-Pointing-Pointer Identified interdendritic microconstituents consist of MC-type carbides. Black-Right-Pointing-Pointer Modification of primary solidification path is used to explain cracking resistance.« less

Microstructure and Mechanical Properties of Fiber-Laser-Welded and Diode-Laser-Welded AZ31 Magnesium Alloy

NASA Astrophysics Data System (ADS)

Chowdhury, S. M.; Chen, D. L.; Bhole, S. D.; Powidajko, E.; Weckman, D. C.; Zhou, Y.

2011-07-01

The microstructures, tensile properties, strain hardening, and fatigue strength of fiber-laser-welded (FLW) and diode-laser-welded (DLW) AZ31B-H24 magnesium alloys were studied. Columnar dendrites near the fusion zone (FZ) boundary and equiaxed dendrites at the center of FZ, with divorced eutectic β-Mg17Al12 particles, were observed. The FLW joints had smaller dendrite cell sizes with a narrower FZ than the DLW joints. The heat-affected zone consisted of recrystallized grains. Although the DLW joints fractured at the center of FZ and exhibited lower yield strength (YS), ultimate tensile strength (UTS), and fatigue strength, the FLW joints failed at the fusion boundary and displayed only moderate reduction in the YS, UTS, and fatigue strength with a joint efficiency of ~91 pct. After welding, the strain rate sensitivity basically vanished, and the DLW joints exhibited higher strain-hardening capacity. Stage III hardening occurred after yielding in both base metal (BM) and welded samples. Dimple-like ductile fracture characteristics appeared in the BM, whereas some cleavage-like flat facets together with dimples and river marking were observed in the welded samples. Fatigue crack initiated from the specimen surface or near-surface defects, and crack propagation was characterized by the formation of fatigue striations along with secondary cracks.

The three lives of viral fusion peptides

PubMed Central

Apellániz, Beatriz; Huarte, Nerea; Largo, Eneko; Nieva, José L.

2014-01-01

Fusion peptides comprise conserved hydrophobic domains absolutely required for the fusogenic activity of glycoproteins from divergent virus families. After 30 years of intensive research efforts, the structures and functions underlying their high degree of sequence conservation are not fully elucidated. The long-hydrophobic viral fusion peptide (VFP) sequences are structurally constrained to access three successive states after biogenesis. Firstly, the VFP sequence must fulfill the set of native interactions required for (meta) stable folding within the globular ectodomains of glycoprotein complexes. Secondly, at the onset of the fusion process, they get transferred into the target cell membrane and adopt specific conformations therein. According to commonly accepted mechanistic models, membrane-bound states of the VFP might promote the lipid bilayer remodeling required for virus-cell membrane merger. Finally, at least in some instances, several VFPs co-assemble with transmembrane anchors into membrane integral helical bundles, following a locking movement hypothetically coupled to fusion-pore expansion. Here we review different aspects of the three major states of the VFPs, including the functional assistance by other membrane-transferring glycoprotein regions, and discuss briefly their potential as targets for clinical intervention. PMID:24704587

Calculation of Excitation Function of Some Structural Fusion Material for (n, p) Reactions up to 25 MeV

NASA Astrophysics Data System (ADS)

Reshid, Tarik S.

2013-04-01

Fusion serves an inexhaustible energy for humankind. Although there have been significant research and development studies on the inertial and magnetic fusion reactor technology, Furthermore, there are not radioactive nuclear waste problems in the fusion reactors. In this study, (n, p) reactions for some structural fusion materials such as 27Al, 51V, 52Cr, 55Mn and 56Fe have been investigated. The new calculations on the excitation functions of 27 Al(n, p) 27 Mg, 51 V(n, p) 51 Ti, 52 Cr(n, p) 52 V, 55 Mn(n, p) 55 Cr and 56 Fe(n, p) 56 Mn reactions have been carried out up to 30 MeV incident neutron energy. Statistical model calculations, based on the Hauser-Feshbach formalism, have been carried out using the TALYS-1.0 and were compared with available experimental data in the literature and with ENDF/B-VII, T = 300 K; JENDL-3.3, T = 300 K and JEFF-3.1, T = 300 K evaluated libraries.

Effect of Continuous and Pulsed Current Gas Tungsten Arc Welding on Dissimilar Weldments Between Hastelloy C-276/AISI 321 Austenitic Stainless Steel

NASA Astrophysics Data System (ADS)

Sharma, Sumitra; Taiwade, Ravindra V.; Vashishtha, Himanshu

2017-03-01

In the present investigation, an attempt has been made to join Hastelloy C-276 nickel-based superalloy and AISI 321 austenitic stainless steel using ERNiCrMo-4 filler. The joints were fabricated by continuous and pulsed current gas tungsten arc welding processes. Experimental studies to ascertain the structure-property co-relationship with or without pulsed current mode were carried out using an optical microscope and scanning electron microscope. Further, the energy-dispersive spectroscope was used to evaluate the extent of microsegregation. The microstructure of fusion zone was obtained as finer cellular dendritic structure for pulsed current mode, whereas columnar structure was formed with small amount of cellular structure for continuous current mode. The scanning electron microscope examination witnessed the existence of migrated grain boundaries at the weld interfaces. Moreover, the presence of secondary phases such as P and μ was observed in continuous current weld joints, whereas they were absent in pulsed current weld joints, which needs to be further characterized. Moreover, pulsed current joints resulted in narrower weld bead, refined morphology, reduced elemental segregation and improved strength of the welded joints. The outcomes of the present investigation would help in obtaining good quality dissimilar joints for industrial applications and AISI 321 ASS being cheaper consequently led to cost-effective design also.

Multi-method characterization of a landslide in Champagne vineyards: the case study of the Jacotines landslide (Marne, France)

NASA Astrophysics Data System (ADS)

Nicolas, Bollot; Guillaume, Pierre; Gilles, Grandjean

2014-05-01

Key words : landslide, Champagne vineyards , geomorphology, geophysical data, superficial structure The Champagne region is strongly impacted by landslides. Usually inactive, these landslides suffer from partial reactivations leading to important damages, especially when they occur in the vineyards. In the Marne valley, and particularly in the center of Champagne vineyards area (Reuil), the Jacotines site is representative of such landslides since it presents typical surface characteristics widely observed in the region. However, its size, and especially its internal structure, can't be deduced from the surface analysis only. The aim of this work is to combine surface patterns analysis, geophysical data and borehole data to produce an interpretative model of the landslide. Preliminary geomorphological cartography was used for determining the influence of the landslide. From this information, geophysical investigations were carried out to image the internal structure of the landslide. Geophysical data fusion (combination of seismic and geoelectrical tomograms) was used to estimate the mechanical behavior and the fissuring pattern of the slope. Three transverse and longitudinal tomograms were used to define an heterogeneous area between 20 and 50 meters depth and a weathered zone from 0 to 10-20 meters depth. A 60 meters depth borehole on the main transverse tomogram found the shear plane and clarified the structure of the heterogeneous area as well as the uppermost weathered layer composed by debris flows resulting from partial reactivations processes.

The structural basis for the functional comparability of factor VIII and the long-acting variant recombinant factor VIII Fc fusion protein

DOE PAGES

Leksa, N. C.; Chiu, P. -L.; Bou-Assaf, G. M.; ...

2017-05-03

Fusion of the human IgG 1 Fc domain to the C-terminal C2 domain of B-domain-deleted (BDD) factor VIII (FVIII) results in the recombinant FVIII Fc (rFVIIIFc) fusion protein, which has a 1.5-fold longer half-life in humans. To assess the structural properties of rFVIIIFc by comparing its constituent FVIII and Fc elements with their respective isolated components, and evaluating their structural independence within rFVIIIFc. rFVIIIFc and its isolated FVIII and Fc components were compared by the use of hydrogen–deuterium exchange mass spectrometry (HDX-MS). The structure of rFVIIIFc was also evaluated by the use of X-ray crystallography, small-angle X-ray scattering (SAXS), andmore » electron microscopy (EM). The degree of steric interference by the appended Fc domain was assessed by EM and surface plasmon resonance (SPR). HDX-MS analysis of rFVIIIFc revealed that fusion caused no structural perturbations in FVIII or Fc. The rFVIIIFc crystal structure showed that the FVIII component is indistinguishable from published BDD FVIII structures. The Fc domain was not observed, indicating high mobility. SAXS analysis was consistent with an ensemble of rigid-body models in which the Fc domain exists in a largely extended orientation relative to FVIII. Binding of Fab fragments of anti-C2 domain antibodies to BDD FVIII was visualized by EM, and the affinities of the corresponding intact antibodies for BDD FVIII and rFVIIIFc were comparable by SPR analysis. Thus, the FVIII and Fc components of rFVIIIFc are structurally indistinguishable from their isolated constituents, and show a high degree of structural independence, consistent with the functional comparability of rFVIIIFc and unmodified FVIII.« less

The structural basis for the functional comparability of Factor VIII and the long-acting variant recombinant Factor VIII Fc fusion protein

PubMed Central

Leksa, N.C.; Chiu, P.-L.; Bou-Assaf, G.M.; Quan, C.; Liu, Z.; Goodman, A.B.; Chambers, M.G.; Tsutakawa, S.E.; Hammel, M.; Peters, R.T.; Walz, T.; Kulman, J.D.

2017-01-01

SUMMARY Background Fusion of the human IgG1 Fc domain to the C-terminal C2 domain of B domain-deleted (BDD) factor VIII (FVIII) results in the rFVIIIFc fusion protein that has a 1.5-fold longer half-life in humans. Objective To assess the structural properties of rFVIIIFc by comparing its constituent FVIII and Fc elements with their respective isolated components and evaluating their structural independence within rFVIIIFc. Methods rFVIIIFc and its isolated FVIII and Fc components were compared by hydrogen-deuterium exchange mass spectrometry (HDX-MS). The structure of rFVIIIFc was also evaluated by X-ray crystallography, small-angle X-ray scattering (SAXS), and electron microscopy (EM). The degree of steric interference by the appended Fc domain was assessed by EM and surface plasmon resonance (SPR). Results HDX-MS analysis of rFVIIIFc revealed that fusion caused no structural perturbations in FVIII or Fc. The rFVIIIFc crystal structure showed that the FVIII component is indistinguishable from published BDD FVIII structures. The Fc domain was not observed, indicating high mobility. SAXS analysis was consistent with an ensemble of rigid-body models in which the Fc domain exists in a largely extended orientation relative to FVIII. Binding of Fab fragments of anti-C2 domain antibodies to BDD FVIII was visualized by EM, and the affinities of the corresponding intact antibodies for BDD FVIII and rFVIIIFc were comparable by SPR analysis. Conclusions The FVIII and Fc components of rFVIIIFc are structurally indistinguishable from their isolated constituents and exhibit a high degree of structural independence, consistent with the functional comparability of rFVIIIFc and unmodified FVIII. PMID:28397397

The structural basis for the functional comparability of factor VIII and the long-acting variant recombinant factor VIII Fc fusion protein

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leksa, N. C.; Chiu, P. -L.; Bou-Assaf, G. M.

Fusion of the human IgG 1 Fc domain to the C-terminal C2 domain of B-domain-deleted (BDD) factor VIII (FVIII) results in the recombinant FVIII Fc (rFVIIIFc) fusion protein, which has a 1.5-fold longer half-life in humans. To assess the structural properties of rFVIIIFc by comparing its constituent FVIII and Fc elements with their respective isolated components, and evaluating their structural independence within rFVIIIFc. rFVIIIFc and its isolated FVIII and Fc components were compared by the use of hydrogen–deuterium exchange mass spectrometry (HDX-MS). The structure of rFVIIIFc was also evaluated by the use of X-ray crystallography, small-angle X-ray scattering (SAXS), andmore » electron microscopy (EM). The degree of steric interference by the appended Fc domain was assessed by EM and surface plasmon resonance (SPR). HDX-MS analysis of rFVIIIFc revealed that fusion caused no structural perturbations in FVIII or Fc. The rFVIIIFc crystal structure showed that the FVIII component is indistinguishable from published BDD FVIII structures. The Fc domain was not observed, indicating high mobility. SAXS analysis was consistent with an ensemble of rigid-body models in which the Fc domain exists in a largely extended orientation relative to FVIII. Binding of Fab fragments of anti-C2 domain antibodies to BDD FVIII was visualized by EM, and the affinities of the corresponding intact antibodies for BDD FVIII and rFVIIIFc were comparable by SPR analysis. Thus, the FVIII and Fc components of rFVIIIFc are structurally indistinguishable from their isolated constituents, and show a high degree of structural independence, consistent with the functional comparability of rFVIIIFc and unmodified FVIII.« less

Crystal Structure of Menin Reveals Binding Site for Mixed Lineage Leukemia (MLL) Protein

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murai, Marcelo J.; Chruszcz, Maksymilian; Reddy, Gireesh

2014-10-02

Menin is a tumor suppressor protein that is encoded by the MEN1 (multiple endocrine neoplasia 1) gene and controls cell growth in endocrine tissues. Importantly, menin also serves as a critical oncogenic cofactor of MLL (mixed lineage leukemia) fusion proteins in acute leukemias. Direct association of menin with MLL fusion proteins is required for MLL fusion protein-mediated leukemogenesis in vivo, and this interaction has been validated as a new potential therapeutic target for development of novel anti-leukemia agents. Here, we report the first crystal structure of menin homolog from Nematostella vectensis. Due to a very high sequence similarity, the Nematostellamore » menin is a close homolog of human menin, and these two proteins likely have very similar structures. Menin is predominantly an {alpha}-helical protein with the protein core comprising three tetratricopeptide motifs that are flanked by two {alpha}-helical bundles and covered by a {beta}-sheet motif. A very interesting feature of menin structure is the presence of a large central cavity that is highly conserved between Nematostella and human menin. By employing site-directed mutagenesis, we have demonstrated that this cavity constitutes the binding site for MLL. Our data provide a structural basis for understanding the role of menin as a tumor suppressor protein and as an oncogenic co-factor of MLL fusion proteins. It also provides essential structural information for development of inhibitors targeting the menin-MLL interaction as a novel therapeutic strategy in MLL-related leukemias.« less

A new evaluation method research for fusion quality of infrared and visible images

NASA Astrophysics Data System (ADS)

Ge, Xingguo; Ji, Yiguo; Tao, Zhongxiang; Tian, Chunyan; Ning, Chengda

2017-03-01

In order to objectively evaluate the fusion effect of infrared and visible image, a fusion evaluation method for infrared and visible images based on energy-weighted average structure similarity and edge information retention value is proposed for drawbacks of existing evaluation methods. The evaluation index of this method is given, and the infrared and visible image fusion results under different algorithms and environments are made evaluation experiments on the basis of this index. The experimental results show that the objective evaluation index is consistent with the subjective evaluation results obtained from this method, which shows that the method is a practical and effective fusion image quality evaluation method.

Raman spectroscopic evidence of tissue restructuring in heat-induced tissue fusion.

PubMed

Su, Lei; Cloyd, Kristy L; Arya, Shobhit; Hedegaard, Martin A B; Steele, Joseph A M; Elson, Daniel S; Stevens, Molly M; Hanna, George B

2014-09-01

Heat-induced tissue fusion via radio-frequency (RF) energy has gained wide acceptance clinically and here we present the first optical-Raman-spectroscopy study on tissue fusion samples in vitro. This study provides direct insights into tissue constituent and structural changes on the molecular level, exposing spectroscopic evidence for the loss of distinct collagen fibre rich tissue layers as well as the denaturing and restructuring of collagen crosslinks post RF fusion. These findings open the door for more advanced optical feedback-control methods and characterization during heat-induced tissue fusion, which will lead to new clinical applications of this promising technology. Copyright © 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.

Study of incomplete fusion reaction dynamics in 13C +165 Ho system and its dependence on various entrance channel parameters

NASA Astrophysics Data System (ADS)

Tali, Suhail A.; Kumar, Harish; Ansari, M. Afzal; Ali, Asif; Singh, D.; Ali, Rahbar; Giri, Pankaj K.; Linda, Sneha B.; Parashari, Siddharth; Kumar, R.; Singh, R. P.; Muralithar, S.

2018-02-01

The excitation functions for the evaporation residues populated in the interaction of 13C +165 Ho system have been measured at projectile energies ≈ 4-7 MeV/nucleon. Stacked foil activation technique followed by off-line γ-ray spectroscopy have been employed in the present work. The experimentally measured cross-sections are analyzed in the frame work of statistical model code PACE4, which takes into account only the complete fusion reaction cross-sections. The evaporation residues populated via xn and pxn channels were found to be in good agreement with the PACE4 predictions, while a significant enhancement in the measured cross-sections over PACE4 predictions is observed in case of α-emitting channels, which may be attributed to the incomplete fusion process. For the better understanding of incomplete fusion dynamics, the incomplete fusion fraction has also been deduced and its sensitivity with various entrance channel parameters like: projectile energy, mass-asymmetry, projectile structure in terms of Qα-value and Coulomb effect has been studied in the present work. The incomplete fusion fraction is found to increase with increasing the projectile energy and a strong projectile structure dependent mass-asymmetry systematic is also observed. The incomplete fusion fraction is also found to be small for more negative Qα-value projectile (13C) induced reactions as compared to less negative Qα-value projectiles (12C, 16O and 20Ne) induced reactions with the same target nucleus 165Ho. An interesting trend is obtained on further investigation of incomplete fusion dependence on Coulomb effect (ZPZT).

The Research on Dryland Crop Classification Based on the Fusion of SENTINEL-1A SAR and Optical Images

NASA Astrophysics Data System (ADS)

Liu, F.; Chen, T.; He, J.; Wen, Q.; Yu, F.; Gu, X.; Wang, Z.

2018-04-01

In recent years, the quick upgrading and improvement of SAR sensors provide beneficial complements for the traditional optical remote sensing in the aspects of theory, technology and data. In this paper, Sentinel-1A SAR data and GF-1 optical data were selected for image fusion, and more emphases were put on the dryland crop classification under a complex crop planting structure, regarding corn and cotton as the research objects. Considering the differences among various data fusion methods, the principal component analysis (PCA), Gram-Schmidt (GS), Brovey and wavelet transform (WT) methods were compared with each other, and the GS and Brovey methods were proved to be more applicable in the study area. Then, the classification was conducted based on the object-oriented technique process. And for the GS, Brovey fusion images and GF-1 optical image, the nearest neighbour algorithm was adopted to realize the supervised classification with the same training samples. Based on the sample plots in the study area, the accuracy assessment was conducted subsequently. The values of overall accuracy and kappa coefficient of fusion images were all higher than those of GF-1 optical image, and GS method performed better than Brovey method. In particular, the overall accuracy of GS fusion image was 79.8 %, and the Kappa coefficient was 0.644. Thus, the results showed that GS and Brovey fusion images were superior to optical images for dryland crop classification. This study suggests that the fusion of SAR and optical images is reliable for dryland crop classification under a complex crop planting structure.

Mutations in the Parainfluenza Virus 5 Fusion Protein Reveal Domains Important for Fusion Triggering and Metastability

PubMed Central

Bose, Sayantan; Heath, Carissa M.; Shah, Priya A.; Alayyoubi, Maher; Jardetzky, Theodore S.

2013-01-01

Paramyxovirus membrane glycoproteins F (fusion protein) and HN, H, or G (attachment protein) are critical for virus entry, which occurs through fusion of viral and cellular envelopes. The F protein folds into a homotrimeric, metastable prefusion form that can be triggered by the attachment protein to undergo a series of structural rearrangements, ultimately folding into a stable postfusion form. In paramyxovirus-infected cells, the F protein is activated in the Golgi apparatus by cleavage adjacent to a hydrophobic fusion peptide that inserts into the target membrane, eventually bringing the membranes together by F refolding. However, it is not clear how the attachment protein, known as HN in parainfluenza virus 5 (PIV5), interacts with F and triggers F to initiate fusion. To understand the roles of various F protein domains in fusion triggering and metastability, single point mutations were introduced into the PIV5 F protein. By extensive study of F protein cleavage activation, surface expression, and energetics of fusion triggering, we found a role for an immunoglobulin-like (Ig-like) domain, where multiple hydrophobic residues on the PIV5 F protein may mediate F-HN interactions. Additionally, destabilizing mutations of PIV5 F that resulted in HN trigger-independent mutant F proteins were identified in a region along the border of F trimer subunits. The positions of the potential HN-interacting region and the region important for F stability in the lower part of the PIV5 F prefusion structure provide clues to the receptor-binding initiated, HN-mediated F trigger. PMID:24089572

Field Theoretic Study of Bilayer Membrane Fusion. I. Hemifusion Mechanism

PubMed Central

Katsov, K.; Müller, M.; Schick, M.

2004-01-01

Self-consistent field theory is used to determine structural and energetic properties of metastable intermediates and unstable transition states involved in the standard stalk mechanism of bilayer membrane fusion. A microscopic model of flexible amphiphilic chains dissolved in hydrophilic solvent is employed to describe these self-assembled structures. We find that the barrier to formation of the initial stalk is much smaller than previously estimated by phenomenological theories. Therefore its creation it is not the rate-limiting process. The relevant barrier is associated with the rather limited radial expansion of the stalk into a hemifusion diaphragm. It is strongly affected by the architecture of the amphiphile, decreasing as the effective spontaneous curvature of the amphiphile is made more negative. It is also reduced when the tension is increased. At high tension the fusion pore, created when a hole forms in the hemifusion diaphragm, expands without bound. At very low membrane tension, small fusion pores can be trapped in a flickering metastable state. Successful fusion is severely limited by the architecture of the lipids. If the effective spontaneous curvature is not sufficiently negative, fusion does not occur because metastable stalks, whose existence is a seemingly necessary prerequisite, do not form at all. However if the spontaneous curvature is too negative, stalks are so stable that fusion does not occur because the system is unstable either to a phase of stable radial stalks, or to an inverted-hexagonal phase induced by stable linear stalks. Our results on the architecture and tension needed for successful fusion are summarized in a phase diagram. PMID:15326031

Fusion Centers: Issues and Options for Congress

DTIC Science & Technology

2008-01-18

largely financed and staffed by the states, and there is no one “model” for how a center should be structured. State and local law enforcement and...Information and Receive “Feedback” . . . . . . . . . . . . . . . . . . 69 4e . Establish a Mechanism for Fusion Centers to Have Input into the NIPF...intelligence fusion centers, particularly when networked together nationally, represent a proactive tool to be used to fight a global jihadist adversary which

Porous biodegradable lumbar interbody fusion cage design and fabrication using integrated global-local topology optimization with laser sintering.

PubMed

Kang, Heesuk; Hollister, Scott J; La Marca, Frank; Park, Paul; Lin, Chia-Ying

2013-10-01

Biodegradable cages have received increasing attention for their use in spinal procedures involving interbody fusion to resolve complications associated with the use of nondegradable cages, such as stress shielding and long-term foreign body reaction. However, the relatively weak initial material strength compared to permanent materials and subsequent reduction due to degradation may be problematic. To design a porous biodegradable interbody fusion cage for a preclinical large animal study that can withstand physiological loads while possessing sufficient interconnected porosity for bony bridging and fusion, we developed a multiscale topology optimization technique. Topology optimization at the macroscopic scale provides optimal structural layout that ensures mechanical strength, while optimally designed microstructures, which replace the macroscopic material layout, ensure maximum permeability. Optimally designed cages were fabricated using solid, freeform fabrication of poly(ε-caprolactone) mixed with hydroxyapatite. Compression tests revealed that the yield strength of optimized fusion cages was two times that of typical human lumbar spine loads. Computational analysis further confirmed the mechanical integrity within the human lumbar spine, although the pore structure locally underwent higher stress than yield stress. This optimization technique may be utilized to balance the complex requirements of load-bearing, stress shielding, and interconnected porosity when using biodegradable materials for fusion cages.

An adaptive block-based fusion method with LUE-SSIM for multi-focus images

NASA Astrophysics Data System (ADS)

Zheng, Jianing; Guo, Yongcai; Huang, Yukun

2016-09-01

Because of the lenses' limited depth of field, digital cameras are incapable of acquiring an all-in-focus image of objects at varying distances in a scene. Multi-focus image fusion technique can effectively solve this problem. Aiming at the block-based multi-focus image fusion methods, the problem that blocking-artifacts often occurs. An Adaptive block-based fusion method based on lifting undistorted-edge structural similarity (LUE-SSIM) is put forward. In this method, image quality metrics LUE-SSIM is firstly proposed, which utilizes the characteristics of human visual system (HVS) and structural similarity (SSIM) to make the metrics consistent with the human visual perception. Particle swarm optimization(PSO) algorithm which selects LUE-SSIM as the object function is used for optimizing the block size to construct the fused image. Experimental results on LIVE image database shows that LUE-SSIM outperform SSIM on Gaussian defocus blur images quality assessment. Besides, multi-focus image fusion experiment is carried out to verify our proposed image fusion method in terms of visual and quantitative evaluation. The results show that the proposed method performs better than some other block-based methods, especially in reducing the blocking-artifact of the fused image. And our method can effectively preserve the undistorted-edge details in focus region of the source images.

Relationship between SU Subdomains That Regulate the Receptor-Mediated Transition from the Native (Fusion-Inhibited) to the Fusion-Active Conformation of the Murine Leukemia Virus Glycoprotein

PubMed Central

Lavillette, Dimitri; Ruggieri, Alessia; Boson, Bertrand; Maurice, Marielle; Cosset, François-Loïc

2002-01-01

Envelope glycoproteins (Env) of retroviruses are trimers of SU (surface) and TM (transmembrane) heterodimers and are expressed on virions in fusion-competent forms that are likely to be metastable. Activation of the viral receptor-binding domain (RBD) via its interaction with a cell surface receptor is thought to initiate a cascade of events that lead to refolding of the Env glycoprotein into its stable fusion-active conformation. While the fusion-active conformation of the TM subunit has been described in detail for several retroviruses, little is known about the fusion-competent structure of the retroviral glycoproteins or the molecular events that mediate the transition between the two conformations. By characterizing Env chimeras between the ecotropic and amphotropic murine leukemia virus (MLV) SUs as well as a set of point mutants, we show that alterations of the conformation of the SU glycoprotein strongly elevate Env fusogenicity by disrupting the stability of the Env complex. Compensatory mutations that restored both Env stability and fusion control were also identified, allowing definition of interactions within the Env complex that maintain the stability of the native Env complex. We show that, in the receptor-unbound form, structural interactions between the N terminus of the viral RBD (NTR domain), the proline-rich region (PRR), and the distal part of the C-terminal domain of the SU subunit maintain a conformation of the glycoprotein that is fusion inhibitory. Additionally, we identified mutations that disrupt this fusion-inhibitory conformation and allow fusion activation in the absence of viral receptors, provided that receptor-activated RBD fragments are added in trans during infection. Other mutations were identified that allow fusion activation in the absence of receptors for both the viral glycoprotein and the trans-acting RBD. Finally, we found mutations of the SU that bypass in cis the requirement for the NTR domain in fusion activation. All these different mutations call for a critical role of the PRR in mediating conformational changes of the Env glycoprotein during fusion activation. Our results suggest a model of MLV Env fusion activation in which unlocking of the fusion-inhibitory conformation is initiated by receptor binding of the viral RBD, which, upon disruption of the PRR, allows the NTR domain to promote further events in Env fusion activation. This involves a second type of interaction, in cis or in trans, between the receptor-activated RBD and a median segment of the freed C-terminal domain. PMID:12208946

Modelling structural and plasma facing materials for fusion power plants: Recent advances and outstanding issues in the EURATOM fusion materials programme

NASA Astrophysics Data System (ADS)

Boutard, Jean-Louis; Dudarev, Sergei; Rieth, Michael

2011-10-01

EFDA Fusion Materials Topical Group was established at the end of 2007 to coordinate the EU effort on the development of structural and protection materials able to withstand the very demanding operating conditions of a future DEMO power plant. Focusing on a selection of well identified materials issues, including the behaviour of Reduced Activation Ferritic-Martensitic steels, and W-alloys under the foreseen operation conditions in a future DEMO, this paper describes recent advances in physical modelling and experimental validation, contributing to the definition of chemical composition and microstructure of materials with improved in-service stability at high temperature, high neutron flux and intense ion bombardment.

Thermal Behavior of an HSLA Steel and the Impact in Phase Transformation: Submerged Arc Welding (SAW) Process Approach to Pipelines

NASA Astrophysics Data System (ADS)

Costa, P. S.; Reyes-Valdés, F. A.; Saldaña-Garcés, R.; Delgado, E. R.; Salinas-Rodríguez, A.

Heat input during welding metal fusion generates different transformations, such as grain growth, hydrogen cracking, and the formation of brittle structures, generally associated with the heat-affected zone (HAZ). For this reason, it is very important to know the behavior of this area before welding. This paper presents a study of the thermal behavior and its effect on phase transformations in the HAZ, depending on cooling rates (0.1-200 °C/s) to obtain continuous cooling transformation (CCT) curves for an high-strength low-alloy (HSLA) steel. In order to determine the formed phases, optical microscopy and Vickers microhardness measurement were used. The experimental CCT curve was obtained from an HSLA steel, and the results showed that, with the used cooling conditions, the steel did not provide formation of brittle structures. Therefore, it is unlikely that welds made by submerged arc welding (SAW) may lead to hydrogen embrittlement in the HAZ, which is one of the biggest problems of cracking in gas conduction pipelines. In addition, with these results, it will be possible to control the microstructure to optimize the pipe fabrication with SAW process in industrial plants.

Insights into the Functions of M-T Hook Structure in HIV Fusion Inhibitor Using Molecular Modeling.

PubMed

Tan, Jianjun; Yuan, Hongling; Li, Chunhua; Zhang, Xiaoyi; Wang, Cunxin

2016-04-01

HIV-1 membrane fusion plays an important role in the process that HIV-1 entries host cells. As a treatment strategy targeting HIV-1 entry process, fusion inhibitors have been proposed. Nevertheless, development of a short peptide possessing high anti-HIV potency is considered a daunting challenge. He et al. found that two residues, Met626 and Thr627, located the upstream of the C-terminal heptad repeat of the gp41, formed a unique hook-like structure (M-T hook) that can dramatically improve the binding stability and anti-HIV activity of the inhibitors. In this work, we explored the molecular mechanism why M-T hook structure could improve the anti-HIV activity of inhibitors. Firstly, molecular dynamic simulation was used to obtain information on the time evolution between gp41 and ligands. Secondly, based on the simulations, molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) and molecular mechanics Generalized Born surface area (MM-GBSA) methods were used to calculate the binding free energies. The binding free energy of the ligand with M-T hook was considerably higher than the other without M-T. Further studies showed that the hydrophobic interactions made the dominant contribution to the binding free energy. The numbers of Hydrogen bonds between gp41 and the ligand with M-T hook structure were more than the other. These findings should provide insights into the inhibition mechanism of the short peptide fusion inhibitors and be useful for the rational design of novel fusion inhibitors in the future. Copyright © 2016 Elsevier Ltd. All rights reserved.

New Possibilities in the Fabrication of Hybrid Components with Big Dimensions by Means of Selective Laser Melting (SLM)

NASA Astrophysics Data System (ADS)

Ascari, A.; Fortunato, A.; Liverani, E.; Gamberoni, A.; Tomesani, L.

The application of laser technology to welding of dissimilar AISI316 stainless steel components manufactured with selective laser melting (SLM) and traditional methods has been investigated. The role of laser parameters on weld bead formation has been studied experimentally, with particular attention placed on effects occurring at the interface between the two parts. In order to assess weld bead characteristics, standardised tensile tests were carried out on suitable specimens and the fracture zone was analysed. The results highlighted the possibility of exploiting suitable process parameters to appropriately shape the heat affected and fusion zones in order to maximise the mechanical performance of the component and minimise interactions between the two parent metals in the weld bead.

MAGNETIC END CLOSURES FOR PLASMA CONFINING AND HEATING DEVICES

DOEpatents

Post, R.F.

1963-08-20

More effective magnetic closure field regions for various open-ended containment magnetic fields used in fusion reactor devices are provided by several spaced, coaxially-aligned solenoids utilized to produce a series of nodal field regions of uniform or, preferably, of incrementally increasing intensity separated by lower intensity regions outwardly from the ends of said containment zone. Plasma sources may also be provided to inject plasma into said lower intensity areas to increase plasma density therein. Plasma may then be transported, by plasma diffusion mechanisms provided by the nodal fields, into the containment field. With correlated plasma densities and nodal field spacings approximating the mean free partl cle collision path length in the zones between the nodal fields, optimum closure effectiveness is obtained. (AEC)

Microstructure, Hardness, and Residual Stress Distributions in T-Joint Weld of HSLA S500MC Steel

NASA Astrophysics Data System (ADS)

Frih, Intissar; Montay, Guillaume; Adragna, Pierre-Antoine

2017-03-01

This paper investigates the characterization of the microstructure, hardness, and residual stress distributions of MIG-welded high-strength low-alloy S500MC steel. The T-joint weld for 10-mm-thick plates was joined using a two passes MIG welding technology. The contour method was performed to measure longitudinal welding residual stress. The obtained results highlighted a good correlation between the metallurgical phase constituents and hardness distribution within the weld zones. In fact, the presence of bainite and smaller ferrite grain size in the weld-fusion zone might be the reason for the highest hardness measured in this region. A similar trend of the residual stress and hardness distributions was also obtained.

Automatic Structural Parcellation of Mouse Brain MRI Using Multi-Atlas Label Fusion

PubMed Central

Ma, Da; Cardoso, Manuel J.; Modat, Marc; Powell, Nick; Wells, Jack; Holmes, Holly; Wiseman, Frances; Tybulewicz, Victor; Fisher, Elizabeth; Lythgoe, Mark F.; Ourselin, Sébastien

2014-01-01

Multi-atlas segmentation propagation has evolved quickly in recent years, becoming a state-of-the-art methodology for automatic parcellation of structural images. However, few studies have applied these methods to preclinical research. In this study, we present a fully automatic framework for mouse brain MRI structural parcellation using multi-atlas segmentation propagation. The framework adopts the similarity and truth estimation for propagated segmentations (STEPS) algorithm, which utilises a locally normalised cross correlation similarity metric for atlas selection and an extended simultaneous truth and performance level estimation (STAPLE) framework for multi-label fusion. The segmentation accuracy of the multi-atlas framework was evaluated using publicly available mouse brain atlas databases with pre-segmented manually labelled anatomical structures as the gold standard, and optimised parameters were obtained for the STEPS algorithm in the label fusion to achieve the best segmentation accuracy. We showed that our multi-atlas framework resulted in significantly higher segmentation accuracy compared to single-atlas based segmentation, as well as to the original STAPLE framework. PMID:24475148

Glycoprotein interactions in paramyxovirus fusion

PubMed Central

Iorio, Ronald M; Melanson, Vanessa R; Mahon, Paul J

2009-01-01

The Paramyxoviridae are enveloped, negative-stranded RNA viruses, some of which recognize sialic acid-containing receptors, while others recognize specific proteinaceous receptors. The major cytopathic effect of paramyxovirus infection is membrane fusion-induced syncytium formation. Paramyxoviruses are unusual in that the receptor-binding and fusion-promoting activities reside on two different spike structures, the attachment and fusion glycoproteins, respectively. For most paramyxoviruses, this distribution of functions requires a mechanism by which the two processes can be linked for the promotion of fusion. This is accomplished by a virus-specific interaction between the two proteins. An increasing body of evidence supports the notion that members of this family of viruses utilize this glycoprotein interaction in different ways in order to mediate the regulation of the fusion protein activation, depending on the type of receptor utilized by the virus. PMID:20161127

Stability of different influenza subtypes: How can high hydrostatic pressure be a useful tool for vaccine development?

PubMed

Dumard, Carlos Henrique; Barroso, Shana P C; Santos, Ana Clara V; Alves, Nathalia S; Couceiro, José Nelson S S; Gomes, Andre M O; Santos, Patricia S; Silva, Jerson L; Oliveira, Andréa C

2017-12-01

Avian influenza A viruses can cross naturally into mammals and cause severe diseases, as observed for H5N1. The high lethality of human infections causes major concerns about the real risk of a possible pandemic of severe diseases to which human susceptibility may be high and universal. High hydrostatic pressure (HHP) is a valuable tool for studies regarding the folding of proteins and the assembly of macromolecular structures such as viruses; furthermore, HHP has already been demonstrated to promote viral inactivation. Here, we investigated the structural stability of avian and human influenza viruses using spectroscopic and light-scattering techniques. We found that both particles have similar structural stabilities and that HHP promotes structural changes. HHP induced slight structural changes to both human and avian influenza viruses, and these changes were largely reversible when the pressure returned to its initial level. The spectroscopic data showed that H3N2 was more pressure-sensitive than H3N8. Structural changes did not predict changes in protein function, as H3N2 fusion activity was not affected, while H3N8 fusion activity drastically decreased. The fusion activity of H1N1 was also strongly affected by HHP. In all cases, HHP caused inactivation of the different influenza viruses. HHP may be a useful tool for vaccine development, as it induces minor and reversible structural changes that may be associated with partial preservation of viral biological activities and may potentiate their immunogenic response while abolishing their infectivity. We also confirmed that, although pressure does not promote drastic changes in viral particle structure, it can distinctly affect viral fusion activity. Copyright © 2017 Elsevier B.V. All rights reserved.

Ectopic bone formation and chondrodysplasia in transgenic mice carrying the rat C3(1)/T{sub AG} fusion gene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Green, J.E.; Maroulakou, I.G.; Anver, M.

Transgenic mice expressing the SV40 large T-antigen (T{sup AG}) under the regultory control of the hormone-responsive rat C3(1) prostatein promoter develop unusual bone and cartilage lesions, as well as ectopic bone and cartilage formation. Two lines of transgenic animals have been propagated in which the expression of the transgene in chondrocytes results in a mild to moderate generalized disorganization of cartilage growth which appears to affect multiple tissues, including the trachea, ear pinna and articular cartilage. The epiphyseal plates are also affected with normal architecture of the zones of proliferation and maturation, but marked elongation of the zone of hypertrophy.more » Immunocytochemistry demonstrates that expression of T{sup AG} is limited to the zone of hypertropny in the epiphyseal plates, suggesting that the chondrocytes become hormone-responsive at this particular stage of differentiation. Normal mineralization and trabecular formation in long bone appears to occur. Ectopic bone and cartilage formation occurs in the foot pads of the fore- and hind- feet over the course of several months. This is preceded by proliferation of sweat gland epithelial cells followed by the appearance of nodules of cartilage and bone. The nodules are closely associated with proliferating epithelium but are not contiguous with bony structures normally found in the feet. The roles of BMP`s, growth factors, oncogenes and hormones in the development of these lesions will be presented. These transgenic animals may provide new insights into hormone-responsiveness of chondrocytes, as well as factors involved in the processes of bone and cartilage differentiation and growth. These transgenic animals may serve as a useful model for human heterotopic bone formation.« less

Experimental Investigation of Mechanical Properties of Welded Corten Steel A588 Grade Plate Using ER70S - 6 Filler Material for Construction Application

NASA Astrophysics Data System (ADS)

Deepak, J. R.; Bupesh Raja, V. K.; Janardhan Guptha, Mittapalli; Durga Prasad, Palaparthi Hari; Sriram, V.

2017-05-01

ASTM A588 Grade A steel plate is a high strength, low alloy structural steel with 0.19 % of carbon content. When exposed to the atmosphere, A588 Grade A is suitable for construction in the bare (paint - free) condition. The main problems are lack of fusion, lack of penetration and corrosion on heat affected zone. In this research work Corten ASTM A588 Grade steel of 3mm thickness is electroplated with copper and then both raw and copper electroplated are welded by GMAW welding process with ER70S-6 as a filler material. The welded ASTM A588 is cut according to ASTM size for further testing of mechanical properties. Considering its welding strength after the process of electroplating, this research clearly states the metal can be utilized for better results in any given field. Here both the tensile and hardness are higher in copper electroplated welded when compare to raw welded.

Radiolysis aspects of the aqueous self-cooled blanket concept and the problem of tritium extraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruggeman, A.; Snykers, M.; DeRegge, P.

1988-09-01

In the Aqueous Self-Cooled Blanket (ASCB) concept, an aqueous /sup 6/Li solution in a metallic structure is used as a fusion reactor shielding-breeding blanket. Radiolysis effects could be very important for the design and the use of an ASCB. Although many aspects of the radiation chemistry of water and dilute aqueous solutions are now reasonably well understood, it is not possible to predict the radiochemical behaviour of the concentrated candidate ASCB solutions quantitatively. However, by means of a worst case calculation for a possible ASCB for the Next European Torus (NET) it is shown that even with an important ratemore » of water decomposition the ASCB concept is still workable. Gas bubbles and explosive mixtures can be avoided by increasing the pressure in the neutron irradiated zone and by extracting and/or recombining the radiolytically produced hydrogen and oxygen. This could require an additional inert gas loop, which could also be used as part of the tritium extraction installation.« less

Cracking in dissimilar laser welding of tantalum to molybdenum

NASA Astrophysics Data System (ADS)

Zhou, Xingwen; Huang, Yongde; Hao, Kun; Chen, Yuhua

2018-06-01

Dissimilar joining of tantalum (Ta) to molybdenum (Mo) is of great interest in high temperature structural component applications. However, few reports were found about joining of these two hard-to-weld metals. The objective of this experimental study was to assess the weldability of laser butt joining of 0.2 mm-thick Ta and Mo. In order to study cracking mechanism in Ta/Mo joint, similar Ta/Ta and Mo/Mo joints were compared under the same welding conditions. An optical microscope observation revealed presence of intergranular cracks in the Mo/Mo joint, while both transgranular and intergranular cracks were observed in Ta/Mo joint. The cracking mechanism of the Ta/Mo joint was investigated further by micro-hardness testing, micro X-ray diffraction and scanning electron microscopy. The results showed that solidification cracking tendency of Mo is a main reason for crack initiation in the Ta/Mo joint. Low ductility feature in fusion zone most certainly played a role in the transgranular propagation of cracking.

Structural analysis of the intracellular domain of (pro)renin receptor fused to maltose-binding protein

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yanfeng; Gao, Xiaoli; Michael Garavito, R., E-mail: garavito@msu.edu

2011-04-22

Highlights: {yields} Crystal structure of the intracellular domain of (pro)renin receptor (PRR-IC) as MBP fusion protein at 2.0 A (maltose-free) and 2.15 A (maltose-bound). {yields} MBP fusion protein is a dimer in crystals in the presence and absence of maltose. {yields} PRR-IC domain is responsible for the dimerization of the fusion protein. {yields} Residues in the PRR-IC domain, particularly two tyrosines, dominate the intermolecular interactions, suggesting a role for the PRR-IC domain in PRR dimerization. -- Abstract: The (pro)renin receptor (PRR) is an important component of the renin-angiotensin system (RAS), which regulates blood pressure and cardiovascular function. The integral membranemore » protein PRR contains a large extracellular domain ({approx}310 amino acids), a single transmembrane domain ({approx}20 amino acids) and an intracellular domain ({approx}19 amino acids). Although short, the intracellular (IC) domain of the PRR has functionally important roles in a number of signal transduction pathways activated by (pro)renin binding. Meanwhile, together with the transmembrane domain and a small portion of the extracellular domain ({approx}30 amino acids), the IC domain is also involved in assembly of V{sub 0} portion of the vacuolar proton-translocating ATPase (V-ATPase). To better understand structural and multifunctional roles of the PRR-IC, we report the crystal structure of the PRR-IC domain as maltose-binding protein (MBP) fusion proteins at 2.0 A (maltose-free) and 2.15 A (maltose-bound). In the two separate crystal forms having significantly different unit-cell dimensions and molecular packing, MBP-PRR-IC fusion protein was found to be a dimer, which is different with the natural monomer of native MBP. The PRR-IC domain appears as a relatively flexible loop and is responsible for the dimerization of MBP fusion protein. Residues in the PRR-IC domain, particularly two tyrosines, dominate the intermonomer interactions, suggesting a role for the PRR-IC domain in protein oligomerization.« less

NASA Astrophysics Data System (ADS)

Bechetti, Daniel H.; DuPont, John N.; deBarbadillo, John J.; Baker, Brian A.

2014-06-01

Thermodynamic and kinetic modeling were used to determine appropriate heat treatment schedules for homogenization and second phase dissolution in INCONEL® alloy 740H® (INCONEL and 740H are registered trademarks of Special Metals Corporation) fusion welds. Following these simulations, a two-step heat treatment process was applied to specimens from a single pass gas tungsten arc weld (GTAW). Scanning electron microscopy (SEM) has been used to assess the changes in the distribution of alloying elements as well as changes in the fraction of second phase particles within the fusion zone. Experimental results demonstrate that adequate homogenization of alloy 740H weld metal can be achieved by a 1373 K/4 h (1100 °C/4 h) treatment. Complete dissolution of second phase particles could not be completely achieved, even at exposure to temperatures near the alloy's solidus temperature. These results are in good agreement with thermodynamic and kinetic predictions.

Method and apparatus for making uniform pellets for fusion reactors

DOEpatents

Budrick, Ronald G.; King, Frank T.; Martin, Alfred J.; Nolen, Jr., Robert L.; Solomon, David E.

1977-01-01

A method and apparatus for making uniform pellets for laser driven fusion reactors which comprises selection of a quantity of glass frit which has been accurately classified as to size within a few micrometers and contains an occluded material, such as urea, which gasifies and expands when heated. The sized particles are introduced into an apparatus which includes a heated vertical tube with temperatures ranging from 800.degree. C to 1300.degree. C. The particles are heated during the drop through the tube to molten condition wherein the occluded material gasifies to form hollow microspheres which stabilize in shape and plunge into a collecting liquid at the bottom of the tube. The apparatus includes the vertical heat resistant tube, heaters for the various zones of the tube and means for introducing the frit and collecting the formed microspheres.

Molecular Dynamics Simulations of Folding and Insertion of the Ebola Virus Fusion Peptide into a Membrane Bilayer

DTIC Science & Technology

2008-07-01

Molecular Dynamics Simulations of Folding and Insertion of the Ebola Virus Fusion Peptide into a Membrane Bilayer Mark A. Olson1, In...presents replica-exchange molecular dynamics simulations of the folding and insertion of a 16- residue Ebola virus fusion peptide into a membrane...separate calculated structures into conformational basins. 2.1 Simulation models Molecular dynamics simulations were performed using the all-atom

Spanish version of the Thought-Action Fusion Questionnaire and its application in eating disorders.

PubMed

Jáuregui-Lobera, I; Santed-Germán, Ma; Bolaños-Ríos, P; Garrido-Casals, O

2013-01-01

The aims of the study were to analyze the psychometric properties of the Spanish version of the Thought-Action Fusion Questionnaire (TAF-SP), as well as to determine its validity by evaluating the relationship of the TAF-SP to different instruments. TWO GROUPS WERE STUDIED: one comprising 146 patients with eating disorders; and another a group of 200 students. THREE FACTORS WERE OBTAINED: TAF-Moral; TAF-Likelihood-others; and TAF-Likelihood-oneself. The internal consistency of the TAF-SP was determined by means of Cronbach's α coefficient, with values ranging between 0.84-0.95. The correlations with other instruments refected adequate validity. The three-factor structure was tested by means of a linear structural equation model, and the structure fit satisfactorily. Differences in TAF-SP scores between the diagnostic subgroups were also analyzed. The TAF-SP meets the psychometric requirements for measuring thought-action fusion and shows adequate internal consistency and validity.

The microstructure and fracture behavior of the dissimilar alloy 690-SUS 304L joint with various Nb addition

NASA Astrophysics Data System (ADS)

Lee, H. T.; Jeng, S. L.; Kuo, T. Y.

2003-05-01

This study investigates the microstructure and fracture behavior of dissimilar weldments of alloy 690 and SUS 304L for various additions of niobium (0.1, 1.03, 2.49, and 3.35 wt pct) in the flux. With identical parameters and procedures, weldments were butt welded by the shielding metal arc welding (SMAW) process using three layers, with each layer being deposited in a single pass. The results indicate that the microstructure of the fusion zone was primarily dendritic and that the contents of Ni, Cr, and Fe within this zone remain relatively constant and resemble alloy 690. With Nb addition, it is noted that the microstructure changes from a cellular to columnar dendrite and equiaxed dendrite. Meanwhile, the dendrite arm spacing reduces and the secondary arms grow longer. Moreover, the composition of the interdendritic phase, whose precipitate volume percentage increases from 5 to 25 pct, changes from Al-Ti-O to Nb rich. The spread of the interdendritic phase is less in the root bead than in the cap bead due to the greater influence of base metal dilution in this region. Mechanical tests indicate that Nb addition increases the average hardness of the weldment and reduces its elongation prior to rupture. However, the tensile strength is essentially unchanged by Nb addition. It is found that the average hardness of the root bead is generally lower than the cap bead, and that the tensile specimens all rupture in the fusion zone, with the fracture surfaces exhibiting ductile features. It is noted that the cap bead tends to rupture interdendritically with increasing Nb addition. Finally, fractography shows that the dimples in the root become larger and shallower with Nb addition and are rich with an interdendritic phase.

On the Grothendieck rings of equivariant fusion categories

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burciu, Sebastian, E-mail: sebastian.burciu@imar.ro

2015-07-15

In this paper, we describe a Mackey type decomposition for group actions on abelian categories. This allows us to define new Mackey functors which associates to any subgroup the K-theory of the corresponding equivariantized abelian category. In the case of an action by tensor autoequivalences, the Mackey functor at the level of Grothendieck rings has a Green functor structure. As an application we give a description of the Grothendieck rings of equivariantized fusion categories under group actions by tensor autoequivalences on graded fusion categories. In this settings, a new formula for the tensor product of any two simple objects ofmore » an equivariantized fusion category is given, simplifying the fusion formula from Burciu and Natale [J. Math. Phys. 54, 013511 (2013)].« less

Hypoglossum fujianensis sp. nov. (Delesseriaceae, Rhodophyta) from Fujian Coast, China

NASA Astrophysics Data System (ADS)

Zheng, Yi

1998-12-01

Hypoglossum fujianensis sp. nov. is an epiphytic alga in the intertidal zone. Plants are light red, 0.9 2 cm high. Margin of branches gives rise to uniseriate hair-like rhizoids, formed outward from the fusion of the second-and third-order cells. Blades are single layered (except the midrib) and uncorticated. Tetrasporangial sori are formed on the middle part of blades. The globular tetrasporangia are developed from lateral pericentral cells.

Line-Tension Controlled Mechanism for Influenza Fusion

PubMed Central

Risselada, Herre Jelger; Smirnova, Yuliya G.; Grubmüller, Helmut; Marrink, Siewert Jan; Müller, Marcus

2012-01-01

Our molecular simulations reveal that wild-type influenza fusion peptides are able to stabilize a highly fusogenic pre-fusion structure, i.e. a peptide bundle formed by four or more trans-membrane arranged fusion peptides. We rationalize that the lipid rim around such bundle has a non-vanishing rim energy (line-tension), which is essential to (i) stabilize the initial contact point between the fusing bilayers, i.e. the stalk, and (ii) drive its subsequent evolution. Such line-tension controlled fusion event does not proceed along the hypothesized standard stalk-hemifusion pathway. In modeled influenza fusion, single point mutations in the influenza fusion peptide either completely inhibit fusion (mutants G1V and W14A) or, intriguingly, specifically arrest fusion at a hemifusion state (mutant G1S). Our simulations demonstrate that, within a line-tension controlled fusion mechanism, these known point mutations either completely inhibit fusion by impairing the peptide’s ability to stabilize the required peptide bundle (G1V and W14A) or stabilize a persistent bundle that leads to a kinetically trapped hemifusion state (G1S). In addition, our results further suggest that the recently discovered leaky fusion mutant G13A, which is known to facilitate a pronounced leakage of the target membrane prior to lipid mixing, reduces the membrane integrity by forming a ‘super’ bundle. Our simulations offer a new interpretation for a number of experimentally observed features of the fusion reaction mediated by the prototypical fusion protein, influenza hemagglutinin, and might bring new insights into mechanisms of other viral fusion reactions. PMID:22761674

Structure and Function Study of HIV and Influenza Fusion Proteins

NASA Astrophysics Data System (ADS)

Liang, Shuang

Human immunodeficiency virus (HIV) and influenza virus are membrane-enveloped viruses causing acquired immunodeficiency syndrome (AIDS) and flu. The initial step of HIV and influenza virus infection is fusion between viral and host cell membrane catalyzed by the viral fusion protein gp41 and hemagglutinin (HA) respectively. However, the structure of gp41 and HA as well as the infection mechanism are still not fully understood. This work addresses (1) full length gp41 ectodomain and TM domain structure and function and (2) IFP membrane location and IFP-membrane interaction. My studies of gp41 protein and IFP can provide better understanding of the membrane fusion mechanism and may aid development of anti-viral therapeutics and vaccine. The full length ectodomain and transmembrane domain of gp41 and shorter constructs were expressed, purified and solubilized at physiology conditions. The constructs adopt overall alpha helical structure in SDS and DPC detergents, and showed hyperthermostability with Tm > 90 °C. The oligomeric states of these proteins vary in different detergent buffer: predominant trimer for all constructs and some hexamer fraction for HM and HM_TM protein in SDS at pH 7.4; and mixtures of monomer, trimer, and higher-order oligomer protein in DPC at pH 4.0 and 7.4. Substantial protein-induced vesicle fusion was observed, including fusion of neutral vesicles at neutral pH, which are the conditions similar HIV/cell fusion. Vesicle fusion by a gp41 ectodomain construct has rarely been observed under these conditions, and is aided by inclusion of both the FP and TM, and by protein which is predominantly trimer rather than monomer. Current data was integrated with existing data, and a structural model was proposed. Secondary structure and conformation of IFP is a helix-turn-helix structure in membrane. However, there has been arguments about the IFP membrane location. 13C-2H REDOR solid-state NMR is used to solve this problem. The IFP adopts major alpha helical, minor beta strand secondary structure in PC/PG membrane. The alpha helical IFP's with respectively 13CO labeled Leu-2, Ala-7 and Gly-16 all show close contacts with the lipid acyl chain tail, suggesting IFP has strong interaction with the membrane. By screening the current IFP topology models, it either has a membrane-spanning confirmation, or it promotes lipid trail protrusion. IFP bounded lipid membrane structure was studied by paramagnetic relaxation enhancement (PRE) solid-state NMR to provide more information about the detailed IFP membrane location model. The T2 relaxation time and rate were measured for membrane with or without IFP and with or without Mn2+ . Based on the results, it is concluded that IFP does not promote lipid protrusion at both gel phase and liquid phase, which is evidenced by that the R2 difference with and without Mn2+ is smaller for IFP free membrane than IFP bounded membrane, meaning IFP does not induce a smaller average distance between lipid acyl chain and aqueous layer. By integrating these results, a IFP membrane spanning model was proposed, in which IFP N-terminal helix adopts a 45° angle with respect to membrane normal.

Mutations in the Fusion Protein of Measles Virus That Confer Resistance to the Membrane Fusion Inhibitors Carbobenzoxy-d-Phe-l-Phe-Gly and 4-Nitro-2-Phenylacetyl Amino-Benzamide

PubMed Central

Ha, Michael N.; Delpeut, Sébastien; Noyce, Ryan S.; Sisson, Gary; Black, Karen M.; Lin, Liang-Tzung; Bilimoria, Darius; Plemper, Richard K.; Privé, Gilbert G.

2017-01-01

ABSTRACT The inhibitors carbobenzoxy (Z)-d-Phe-l-Phe-Gly (fusion inhibitor peptide [FIP]) and 4-nitro-2-phenylacetyl amino-benzamide (AS-48) have similar efficacies in blocking membrane fusion and syncytium formation mediated by measles virus (MeV). Other homologues, such as Z-d-Phe, are less effective but may act through the same mechanism. In an attempt to map the site of action of these inhibitors, we generated mutant viruses that were resistant to the inhibitory effects of Z-d-Phe-l-Phe-Gly. These 10 mutations were localized to the heptad repeat B (HRB) region of the fusion protein, and no changes were observed in the viral hemagglutinin, which is the receptor attachment protein. Mutations were validated in a luciferase-based membrane fusion assay, using transfected fusion and hemagglutinin expression plasmids or with syncytium-based assays in Vero, Vero-SLAM, and Vero-Nectin 4 cell lines. The changes I452T, D458N, D458G/V459A, N462K, N462H, G464E, and I483R conferred resistance to both FIP and AS-48 without compromising membrane fusion. The inhibitors did not block hemagglutinin protein-mediated binding to the target cell. Edmonston vaccine/laboratory and IC323 wild-type strains were equally affected by the inhibitors. Escape mutations were mapped upon a three-dimensional (3D) structure modeled from the published crystal structure of parainfluenzavirus 5 fusion protein. The most effective mutations were situated in a region located near the base of the globular head and its junction with the alpha-helical stalk of the prefusion protein. We hypothesize that the fusion inhibitors could interfere with the structural changes that occur between the prefusion and postfusion conformations of the fusion protein. IMPORTANCE Due to lapses in vaccination worldwide that have caused localized outbreaks, measles virus (MeV) has regained importance as a pathogen. Antiviral agents against measles virus are not commercially available but could be useful in conjunction with MeV eradication vaccine programs and as a safeguard in oncolytic viral therapy. Three decades ago, the small hydrophobic peptide Z-d-Phe-l-Phe-Gly (FIP) was shown to block MeV infections and syncytium formation in monkey kidney cell lines. The exact mechanism of its action has yet to be determined, but it does appear to have properties similar to those of another chemical inhibitor, AS-48, which appears to interfere with the conformational change in the viral F protein that is required to elicit membrane fusion. Escape mutations were used to map the site of action for FIP. Knowledge gained from these studies could help in the design of new inhibitors against morbilliviruses and provide additional knowledge concerning the mechanism of virus-mediated membrane fusion. PMID:28904193

Development of advanced high heat flux and plasma-facing materials

NASA Astrophysics Data System (ADS)

Linsmeier, Ch.; Rieth, M.; Aktaa, J.; Chikada, T.; Hoffmann, A.; Hoffmann, J.; Houben, A.; Kurishita, H.; Jin, X.; Li, M.; Litnovsky, A.; Matsuo, S.; von Müller, A.; Nikolic, V.; Palacios, T.; Pippan, R.; Qu, D.; Reiser, J.; Riesch, J.; Shikama, T.; Stieglitz, R.; Weber, T.; Wurster, S.; You, J.-H.; Zhou, Z.

2017-09-01

Plasma-facing materials and components in a fusion reactor are the interface between the plasma and the material part. The operational conditions in this environment are probably the most challenging parameters for any material: high power loads and large particle and neutron fluxes are simultaneously impinging at their surfaces. To realize fusion in a tokamak or stellarator reactor, given the proven geometries and technological solutions, requires an improvement of the thermo-mechanical capabilities of currently available materials. In its first part this article describes the requirements and needs for new, advanced materials for the plasma-facing components. Starting points are capabilities and limitations of tungsten-based alloys and structurally stabilized materials. Furthermore, material requirements from the fusion-specific loading scenarios of a divertor in a water-cooled configuration are described, defining directions for the material development. Finally, safety requirements for a fusion reactor with its specific accident scenarios and their potential environmental impact lead to the definition of inherently passive materials, avoiding release of radioactive material through intrinsic material properties. The second part of this article demonstrates current material development lines answering the fusion-specific requirements for high heat flux materials. New composite materials, in particular fiber-reinforced and laminated structures, as well as mechanically alloyed tungsten materials, allow the extension of the thermo-mechanical operation space towards regions of extreme steady-state and transient loads. Self-passivating tungsten alloys, demonstrating favorable tungsten-like plasma-wall interaction behavior under normal operation conditions, are an intrinsic solution to otherwise catastrophic consequences of loss-of-coolant and air ingress events in a fusion reactor. Permeation barrier layers avoid the escape of tritium into structural and cooling materials, thereby minimizing the release of tritium under normal operation conditions. Finally, solutions for the unique bonding requirements of dissimilar material used in a fusion reactor are demonstrated by describing the current status and prospects of functionally graded materials.

A protein coevolution method uncovers critical features of the Hepatitis C Virus fusion mechanism

PubMed Central

Douam, Florian; Mancip, Jimmy; Mailly, Laurent; Montserret, Roland; Ding, Qiang; Verhoeyen, Els; Baumert, Thomas F.; Ploss, Alexander; Carbone, Alessandra

2018-01-01

Amino-acid coevolution can be referred to mutational compensatory patterns preserving the function of a protein. Viral envelope glycoproteins, which mediate entry of enveloped viruses into their host cells, are shaped by coevolution signals that confer to viruses the plasticity to evade neutralizing antibodies without altering viral entry mechanisms. The functions and structures of the two envelope glycoproteins of the Hepatitis C Virus (HCV), E1 and E2, are poorly described. Especially, how these two proteins mediate the HCV fusion process between the viral and the cell membrane remains elusive. Here, as a proof of concept, we aimed to take advantage of an original coevolution method recently developed to shed light on the HCV fusion mechanism. When first applied to the well-characterized Dengue Virus (DENV) envelope glycoproteins, coevolution analysis was able to predict important structural features and rearrangements of these viral protein complexes. When applied to HCV E1E2, computational coevolution analysis predicted that E1 and E2 refold interdependently during fusion through rearrangements of the E2 Back Layer (BL). Consistently, a soluble BL-derived polypeptide inhibited HCV infection of hepatoma cell lines, primary human hepatocytes and humanized liver mice. We showed that this polypeptide specifically inhibited HCV fusogenic rearrangements, hence supporting the critical role of this domain during HCV fusion. By combining coevolution analysis and in vitro assays, we also uncovered functionally-significant coevolving signals between E1 and E2 BL/Stem regions that govern HCV fusion, demonstrating the accuracy of our coevolution predictions. Altogether, our work shed light on important structural features of the HCV fusion mechanism and contributes to advance our functional understanding of this process. This study also provides an important proof of concept that coevolution can be employed to explore viral protein mediated-processes, and can guide the development of innovative translational strategies against challenging human-tropic viruses. PMID:29505618

Analysis of membrane fusion as a two-state sequential process: evaluation of the stalk model.

PubMed

Weinreb, Gabriel; Lentz, Barry R

2007-06-01

We propose a model that accounts for the time courses of PEG-induced fusion of membrane vesicles of varying lipid compositions and sizes. The model assumes that fusion proceeds from an initial, aggregated vesicle state ((A) membrane contact) through two sequential intermediate states (I(1) and I(2)) and then on to a fusion pore state (FP). Using this model, we interpreted data on the fusion of seven different vesicle systems. We found that the initial aggregated state involved no lipid or content mixing but did produce leakage. The final state (FP) was not leaky. Lipid mixing normally dominated the first intermediate state (I(1)), but content mixing signal was also observed in this state for most systems. The second intermediate state (I(2)) exhibited both lipid and content mixing signals and leakage, and was sometimes the only leaky state. In some systems, the first and second intermediates were indistinguishable and converted directly to the FP state. Having also tested a parallel, two-intermediate model subject to different assumptions about the nature of the intermediates, we conclude that a sequential, two-intermediate model is the simplest model sufficient to describe PEG-mediated fusion in all vesicle systems studied. We conclude as well that a fusion intermediate "state" should not be thought of as a fixed structure (e.g., "stalk" or "transmembrane contact") of uniform properties. Rather, a fusion "state" describes an ensemble of similar structures that can have different mechanical properties. Thus, a "state" can have varying probabilities of having a given functional property such as content mixing, lipid mixing, or leakage. Our data show that the content mixing signal may occur through two processes, one correlated and one not correlated with leakage. Finally, we consider the implications of our results in terms of the "modified stalk" hypothesis for the mechanism of lipid pore formation. We conclude that our results not only support this hypothesis but also provide a means of analyzing fusion time courses so as to test it and gauge the mechanism of action of fusion proteins in the context of the lipidic hypothesis of fusion.

The community-driven BiG CZ software system for integration and analysis of bio- and geoscience data in the critical zone

NASA Astrophysics Data System (ADS)

Aufdenkampe, A. K.; Mayorga, E.; Horsburgh, J. S.; Lehnert, K. A.; Zaslavsky, I.; Valentine, D. W., Jr.; Richard, S. M.; Cheetham, R.; Meyer, F.; Henry, C.; Berg-Cross, G.; Packman, A. I.; Aronson, E. L.

2014-12-01

Here we present the prototypes of a new scientific software system designed around the new Observations Data Model version 2.0 (ODM2, https://github.com/UCHIC/ODM2) to substantially enhance integration of biological and Geological (BiG) data for Critical Zone (CZ) science. The CZ science community takes as its charge the effort to integrate theory, models and data from the multitude of disciplines collectively studying processes on the Earth's surface. The central scientific challenge of the CZ science community is to develop a "grand unifying theory" of the critical zone through a theory-model-data fusion approach, for which the key missing need is a cyberinfrastructure for seamless 4D visual exploration of the integrated knowledge (data, model outputs and interpolations) from all the bio and geoscience disciplines relevant to critical zone structure and function, similar to today's ability to easily explore historical satellite imagery and photographs of the earth's surface using Google Earth. This project takes the first "BiG" steps toward answering that need. The overall goal of this project is to co-develop with the CZ science and broader community, including natural resource managers and stakeholders, a web-based integration and visualization environment for joint analysis of cross-scale bio and geoscience processes in the critical zone (BiG CZ), spanning experimental and observational designs. We will: (1) Engage the CZ and broader community to co-develop and deploy the BiG CZ software stack; (2) Develop the BiG CZ Portal web application for intuitive, high-performance map-based discovery, visualization, access and publication of data by scientists, resource managers, educators and the general public; (3) Develop the BiG CZ Toolbox to enable cyber-savvy CZ scientists to access BiG CZ Application Programming Interfaces (APIs); and (4) Develop the BiG CZ Central software stack to bridge data systems developed for multiple critical zone domains into a single metadata catalog. The entire BiG CZ Software system is being developed on public repositories as a modular suite of open source software projects. It will be built around a new Observations Data Model Version 2.0 (ODM2) that has been developed by members of the BiG CZ project team, with community input, under separate funding.

Progressive multi-atlas label fusion by dictionary evolution.

PubMed

Song, Yantao; Wu, Guorong; Bahrami, Khosro; Sun, Quansen; Shen, Dinggang

2017-02-01

Accurate segmentation of anatomical structures in medical images is important in recent imaging based studies. In the past years, multi-atlas patch-based label fusion methods have achieved a great success in medical image segmentation. In these methods, the appearance of each input image patch is first represented by an atlas patch dictionary (in the image domain), and then the latent label of the input image patch is predicted by applying the estimated representation coefficients to the corresponding anatomical labels of the atlas patches in the atlas label dictionary (in the label domain). However, due to the generally large gap between the patch appearance in the image domain and the patch structure in the label domain, the estimated (patch) representation coefficients from the image domain may not be optimal for the final label fusion, thus reducing the labeling accuracy. To address this issue, we propose a novel label fusion framework to seek for the suitable label fusion weights by progressively constructing a dynamic dictionary in a layer-by-layer manner, where the intermediate dictionaries act as a sequence of guidance to steer the transition of (patch) representation coefficients from the image domain to the label domain. Our proposed multi-layer label fusion framework is flexible enough to be applied to the existing labeling methods for improving their label fusion performance, i.e., by extending their single-layer static dictionary to the multi-layer dynamic dictionary. The experimental results show that our proposed progressive label fusion method achieves more accurate hippocampal segmentation results for the ADNI dataset, compared to the counterpart methods using only the single-layer static dictionary. Copyright © 2016 Elsevier B.V. All rights reserved.

Fusion Simulation Project Workshop Report

NASA Astrophysics Data System (ADS)

Kritz, Arnold; Keyes, David

2009-03-01

The mission of the Fusion Simulation Project is to develop a predictive capability for the integrated modeling of magnetically confined plasmas. This FSP report adds to the previous activities that defined an approach to integrated modeling in magnetic fusion. These previous activities included a Fusion Energy Sciences Advisory Committee panel that was charged to study integrated simulation in 2002. The report of that panel [Journal of Fusion Energy 20, 135 (2001)] recommended the prompt initiation of a Fusion Simulation Project. In 2003, the Office of Fusion Energy Sciences formed a steering committee that developed a project vision, roadmap, and governance concepts [Journal of Fusion Energy 23, 1 (2004)]. The current FSP planning effort involved 46 physicists, applied mathematicians and computer scientists, from 21 institutions, formed into four panels and a coordinating committee. These panels were constituted to consider: Status of Physics Components, Required Computational and Applied Mathematics Tools, Integration and Management of Code Components, and Project Structure and Management. The ideas, reported here, are the products of these panels, working together over several months and culminating in a 3-day workshop in May 2007.

Identity fusion predicts endorsement of pro-group behaviours targeting nationality, religion, or football in Brazilian samples.

PubMed

Bortolini, Tiago; Newson, Martha; Natividade, Jean Carlos; Vázquez, Alexandra; Gómez, Ángel

2018-04-01

A visceral feeling of oneness with a group - identity fusion - has proven to be a stronger predictor of pro-group behaviours than other measures of group bonding, such as group identification. However, the relationship between identity fusion, other group alignment measures and their different roles in predicting pro-group behaviour is still controversial. Here, we test whether identity fusion is related to, but different from, unidimensional and multidimensional measures of group identification. We also show that identity fusion explains further variance of the endorsement of pro-group behaviour than these alternative measures and examine the structural and discriminant properties of identity fusion and group identification measures in three different contexts: nationality, religion, and football fandom. Finally, we extend the fusion literature to a new culture: Brazil. To the best of our knowledge, this is the first research explicitly addressing a comparison between these two forms of group alignment, identity fusion and identification with a group, and their role in predicting pro-group behaviours. © 2018 The British Psychological Society.

Multi-Sensor Optimal Data Fusion Based on the Adaptive Fading Unscented Kalman Filter

PubMed Central

Gao, Bingbing; Hu, Gaoge; Gao, Shesheng; Gu, Chengfan

2018-01-01

This paper presents a new optimal data fusion methodology based on the adaptive fading unscented Kalman filter for multi-sensor nonlinear stochastic systems. This methodology has a two-level fusion structure: at the bottom level, an adaptive fading unscented Kalman filter based on the Mahalanobis distance is developed and serves as local filters to improve the adaptability and robustness of local state estimations against process-modeling error; at the top level, an unscented transformation-based multi-sensor optimal data fusion for the case of N local filters is established according to the principle of linear minimum variance to calculate globally optimal state estimation by fusion of local estimations. The proposed methodology effectively refrains from the influence of process-modeling error on the fusion solution, leading to improved adaptability and robustness of data fusion for multi-sensor nonlinear stochastic systems. It also achieves globally optimal fusion results based on the principle of linear minimum variance. Simulation and experimental results demonstrate the efficacy of the proposed methodology for INS/GNSS/CNS (inertial navigation system/global navigation satellite system/celestial navigation system) integrated navigation. PMID:29415509

Multimerized CHR-derived peptides as HIV-1 fusion inhibitors.

PubMed

Nomura, Wataru; Hashimoto, Chie; Suzuki, Takaharu; Ohashi, Nami; Fujino, Masayuki; Murakami, Tsutomu; Yamamoto, Naoki; Tamamura, Hirokazu

2013-08-01

To date, several HIV-1 fusion inhibitors based on the carboxy-terminal leucine/isoleucine heptad repeat (CHR) region of an HIV-1 envelope protein gp41 have been discovered. We have shown that a synthetic peptide mimetic of a trimer form of the CHR-derived peptide C34 has potent inhibitory activity against the HIV-1 fusion mechanism, compared to a monomer C34 peptide. The present study revealed that a dimeric form of C34 is evidently structurally critical for fusion inhibitors, and that the activity of multimerized CHR-derived peptides in fusion inhibition is affected by the properties of the unit peptides C34, SC34EK, and T20. The fluorescence-based study suggested that the N36-interactive sites of the C34 trimer, including hydrophobic residues, are exposed outside the trimer and that trimerization of C34 caused a remarkable increase in fusion inhibitory activity. The present results could be useful in the design of fusion inhibitors against viral infections which proceed via membrane fusion with host cells. Copyright © 2013 The Authors. Published by Elsevier Ltd.. All rights reserved.

Multi-Sensor Optimal Data Fusion Based on the Adaptive Fading Unscented Kalman Filter.

PubMed

Gao, Bingbing; Hu, Gaoge; Gao, Shesheng; Zhong, Yongmin; Gu, Chengfan

2018-02-06

This paper presents a new optimal data fusion methodology based on the adaptive fading unscented Kalman filter for multi-sensor nonlinear stochastic systems. This methodology has a two-level fusion structure: at the bottom level, an adaptive fading unscented Kalman filter based on the Mahalanobis distance is developed and serves as local filters to improve the adaptability and robustness of local state estimations against process-modeling error; at the top level, an unscented transformation-based multi-sensor optimal data fusion for the case of N local filters is established according to the principle of linear minimum variance to calculate globally optimal state estimation by fusion of local estimations. The proposed methodology effectively refrains from the influence of process-modeling error on the fusion solution, leading to improved adaptability and robustness of data fusion for multi-sensor nonlinear stochastic systems. It also achieves globally optimal fusion results based on the principle of linear minimum variance. Simulation and experimental results demonstrate the efficacy of the proposed methodology for INS/GNSS/CNS (inertial navigation system/global navigation satellite system/celestial navigation system) integrated navigation.

Fusion basis for lattice gauge theory and loop quantum gravity

NASA Astrophysics Data System (ADS)

Delcamp, Clement; Dittrich, Bianca; Riello, Aldo

2017-02-01

We introduce a new basis for the gauge-invariant Hilbert space of lattice gauge theory and loop quantum gravity in (2 + 1) dimensions, the fusion basis. In doing so, we shift the focus from the original lattice (or spin-network) structure directly to that of the magnetic (curvature) and electric (torsion) excitations themselves. These excitations are classified by the irreducible representations of the Drinfel'd double of the gauge group, and can be readily "fused" together by studying the tensor product of such representations. We will also describe in detail the ribbon operators that create and measure these excitations and make the quasi-local structure of the observable algebra explicit. Since the fusion basis allows for both magnetic and electric excitations from the onset, it turns out to be a precious tool for studying the large scale structure and coarse-graining flow of lattice gauge theories and loop quantum gravity. This is in neat contrast with the widely used spin-network basis, in which it is much more complicated to account for electric excitations, i.e. for Gauß constraint violations, emerging at larger scales. Moreover, since the fusion basis comes equipped with a hierarchical structure, it readily provides the language to design states with sophisticated multi-scale structures. Another way to employ this hierarchical structure is to encode a notion of subsystems for lattice gauge theories and (2 + 1) gravity coupled to point particles. In a follow-up work, we have exploited this notion to provide a new definition of entanglement entropy for these theories.

Recombinant human bone morphogenetic protein-2-induced radiculitis in elective minimally invasive transforaminal lumbar interbody fusions: a series review.

PubMed

Mindea, Stefan A; Shih, Patrick; Song, John K

2009-06-15

Retrospective single center analysis. The purpose of our study is to quantify the development of a postoperative radiculitis in our minimally invasive transforaminal lumbar interbody fusion patient population. The application of recombinant human Bone Morphogenetic Protein-2 (BMP) in spinal surgery has allowed for greater success in spinal fusions. This has led to the FDA approving its use in anterior lumbar interbody fusion. However, its well-recognized benefits have generated its "off-label" use in the cervical, thoracic, and lumbar spine. Despite its benefits, the adverse effects of its inflammatory properties are just starting to get recognized. Some clear adverse reactions have been documented in the literature in the cervical spine. However, we feel that these inflammatory properties may be present in the lumbar spine as well. We performed a retrospective chart review of 43 patients who had undergone a minimally invasive transforaminal lumbar interbody fusions. Thirty-five of these patients had BMP and 8 patients did not have BMP. We documented whether there was a preoperative radiculopathy present and whether a radiculopathy was present postoperative. We reviewed radiographic postoperative imaging to establish a structural cause for any radiculopathy. If new or increasing radicular symptoms were present, we attempted to assess the duration of these symptoms. Our analysis, showed that 0 of the 8 patients of the non-BMP group had new radicular symptoms that were not attributed to structural causes. In the BMP group, 4 of the 35 patients (11.4%) had new radicular symptoms without structural etiology. Our analysis suggest that patients undergoing minimally invasive transforaminal lumbar interbody fusions procedures have a higher incidence of developing new radicular symptoms that could be attributed to BMP.

Fusion peptide of HIV-1 as a site of vulnerability to neutralizing antibody

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kong, Rui; Xu, Kai; Zhou, Tongqing

The HIV-1 fusion peptide, comprising 15 to 20 hydrophobic residues at the N terminus of the Env-gp41 subunit, is a critical component of the virus-cell entry machinery. In this paper, we report the identification of a neutralizing antibody, N123-VRC34.01, which targets the fusion peptide and blocks viral entry by inhibiting conformational changes in gp120 and gp41 subunits of Env required for entry. Crystal structures of N123-VRC34.01 liganded to the fusion peptide, and to the full Env trimer, revealed an epitope consisting of the N-terminal eight residues of the gp41 fusion peptide and glycan N88 of gp120, and molecular dynamics showedmore » that the N-terminal portion of the fusion peptide can be solvent-exposed. Finally, these results reveal the fusion peptide to be a neutralizing antibody epitope and thus a target for vaccine design.« less

Fusion peptide of HIV-1 as a site of vulnerability to neutralizing antibody

DOE PAGES

Kong, Rui; Xu, Kai; Zhou, Tongqing; ...

2016-05-13

The HIV-1 fusion peptide, comprising 15 to 20 hydrophobic residues at the N terminus of the Env-gp41 subunit, is a critical component of the virus-cell entry machinery. In this paper, we report the identification of a neutralizing antibody, N123-VRC34.01, which targets the fusion peptide and blocks viral entry by inhibiting conformational changes in gp120 and gp41 subunits of Env required for entry. Crystal structures of N123-VRC34.01 liganded to the fusion peptide, and to the full Env trimer, revealed an epitope consisting of the N-terminal eight residues of the gp41 fusion peptide and glycan N88 of gp120, and molecular dynamics showedmore » that the N-terminal portion of the fusion peptide can be solvent-exposed. Finally, these results reveal the fusion peptide to be a neutralizing antibody epitope and thus a target for vaccine design.« less

Rotary adsorbers for continuous bulk separations

DOEpatents

Baker, Frederick S [Oak Ridge, TN

2011-11-08

A rotary adsorber for continuous bulk separations is disclosed. The rotary adsorber includes an adsorption zone in fluid communication with an influent adsorption fluid stream, and a desorption zone in fluid communication with a desorption fluid stream. The fluid streams may be gas streams or liquid streams. The rotary adsorber includes one or more adsorption blocks including adsorbent structure(s). The adsorbent structure adsorbs the target species that is to be separated from the influent fluid stream. The apparatus includes a rotary wheel for moving each adsorption block through the adsorption zone and the desorption zone. A desorption circuit passes an electrical current through the adsorbent structure in the desorption zone to desorb the species from the adsorbent structure. The adsorbent structure may include porous activated carbon fibers aligned with their longitudinal axis essentially parallel to the flow direction of the desorption fluid stream. The adsorbent structure may be an inherently electrically-conductive honeycomb structure.

Towards a programme of testing and qualification for structural and plasma-facing materials in ‘fusion neutron’ environments

NASA Astrophysics Data System (ADS)

Stork, D.; Heidinger, R.; Muroga, T.; Zinkle, S. J.; Moeslang, A.; Porton, M.; Boutard, J.-L.; Gonzalez, S.; Ibarra, A.

2017-09-01

Materials damage by 14.1MeV neutrons from deuterium-tritium (D-T) fusion reactions can only be characterised definitively by subjecting a relevant configuration of test materials to high-intensity ‘fusion-neutron spectrum sources’, i.e. those simulating closely D-T fusion-neutron spectra. This provides major challenges to programmes to design and construct a demonstration fusion reactor prior to having a large-scale, high-intensity source of such neutrons. In this paper, we discuss the different aspects related to these ‘relevant configuration’ tests, including: • generic issues in materials qualification/validation, comparing safety requirements against those of investment protection; • lessons learned from the fission programme, enabling a reduced fusion materials testing programme; • the use and limitations of presently available possible irradiation sources to optimise a fusion neutron testing program including fission-neutron irradiation of isotopically and chemically tailored steels, ion damage by high-energy helium ions and self-ion beams, or irradiation studies with neutron sources of non-fusion spectra; and • the different potential sources of simulated fusion neutron spectra and the choice using stripping reactions from deuterium-beam ions incident on light-element targets.

Multispectral medical image fusion in Contourlet domain for computer based diagnosis of Alzheimer's disease.

PubMed

Bhateja, Vikrant; Moin, Aisha; Srivastava, Anuja; Bao, Le Nguyen; Lay-Ekuakille, Aimé; Le, Dac-Nhuong

2016-07-01

Computer based diagnosis of Alzheimer's disease can be performed by dint of the analysis of the functional and structural changes in the brain. Multispectral image fusion deliberates upon fusion of the complementary information while discarding the surplus information to achieve a solitary image which encloses both spatial and spectral details. This paper presents a Non-Sub-sampled Contourlet Transform (NSCT) based multispectral image fusion model for computer-aided diagnosis of Alzheimer's disease. The proposed fusion methodology involves color transformation of the input multispectral image. The multispectral image in YIQ color space is decomposed using NSCT followed by dimensionality reduction using modified Principal Component Analysis algorithm on the low frequency coefficients. Further, the high frequency coefficients are enhanced using non-linear enhancement function. Two different fusion rules are then applied to the low-pass and high-pass sub-bands: Phase congruency is applied to low frequency coefficients and a combination of directive contrast and normalized Shannon entropy is applied to high frequency coefficients. The superiority of the fusion response is depicted by the comparisons made with the other state-of-the-art fusion approaches (in terms of various fusion metrics).

Multispectral medical image fusion in Contourlet domain for computer based diagnosis of Alzheimer’s disease

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhateja, Vikrant, E-mail: bhateja.vikrant@gmail.com, E-mail: nhuongld@hus.edu.vn; Moin, Aisha; Srivastava, Anuja

Computer based diagnosis of Alzheimer’s disease can be performed by dint of the analysis of the functional and structural changes in the brain. Multispectral image fusion deliberates upon fusion of the complementary information while discarding the surplus information to achieve a solitary image which encloses both spatial and spectral details. This paper presents a Non-Sub-sampled Contourlet Transform (NSCT) based multispectral image fusion model for computer-aided diagnosis of Alzheimer’s disease. The proposed fusion methodology involves color transformation of the input multispectral image. The multispectral image in YIQ color space is decomposed using NSCT followed by dimensionality reduction using modified Principal Componentmore » Analysis algorithm on the low frequency coefficients. Further, the high frequency coefficients are enhanced using non-linear enhancement function. Two different fusion rules are then applied to the low-pass and high-pass sub-bands: Phase congruency is applied to low frequency coefficients and a combination of directive contrast and normalized Shannon entropy is applied to high frequency coefficients. The superiority of the fusion response is depicted by the comparisons made with the other state-of-the-art fusion approaches (in terms of various fusion metrics).« less

A Cell-Cell Fusion Assay to Assess Arenavirus Envelope Glycoprotein Membrane-Fusion Activity.

PubMed

York, Joanne; Nunberg, Jack H

2018-01-01

For many viruses that enter their target cells through pH-dependent fusion of the viral and endosomal membranes, cell-cell fusion assays can provide an experimental platform for investigating the structure-function relationships that promote envelope glycoprotein membrane-fusion activity. Typically, these assays employ effector cells expressing the recombinant envelope glycoprotein on the cell surface and target cells engineered to quantitatively report fusion with the effector cell. In the protocol described here, Vero cells are transfected with a plasmid encoding the arenavirus envelope glycoprotein complex GPC and infected with the vTF7-3 vaccinia virus expressing the bacteriophage T7 RNA polymerase. These effector cells are mixed with target cells infected with the vCB21R-lacZ vaccinia virus encoding a β-galactosidase reporter under the control of the T7 promoter. Cell-cell fusion is induced upon exposure to low-pH medium (pH 5.0), and the resultant expression of the β-galactosidase reporter is quantitated using a chemiluminescent substrate. We have utilized this robust microplate cell-cell fusion assay extensively to study arenavirus entry and its inhibition by small-molecule fusion inhibitors.

Fusing porphyrins with polycyclic aromatic hydrocarbons and heterocycles for optoelectronic applications

DOEpatents

Thompson, Mark E.; Diev, Viacheslav; Hanson, Kenneth; Forrest, Stephen R.

2015-08-18

A compound that can be used as a donor material in organic photovoltaic devices comprising a non-activated porphyrin fused with one or more non-activated polycyclic aromatic rings or one or more non-activated heterocyclic rings can be obtained by a thermal fusion process. The compounds can include structures of Formula I: ##STR00001## By heating the reaction mixture of non-activated porphyrins with non-activated polycyclic aromatic rings or heterocyclic rings to a fusion temperature and holding for a predetermined time, fusion of one or more polycyclic rings or heterocyclic rings to the non-activated porphyrin core in meso,.beta. fashion is achieved resulting in hybrid structures containing a distorted porphyrin ring with annulated aromatic rings. The porphyrin core can be olygoporphyrins.