Thin Spots Research Articles

Three-dimensional wall-thickness distributions of unruptured intracranial aneurysms characterized by micro-computed tomography

Aneurysmal rupture is associated with wall thinning, but the mechanism is poorly understood. This study aimed to characterize the three-dimensional wall-thickness distributions of unruptured intracranial aneurysms. Five aneurysmal tissues were investigated using micro-computed tomography. First, the wall thickness was related to the aneurysmal wall appearances during surgery. The median wall thicknesses of the translucent and non-translucent walls were 50.56 and 155.93 µm, respectively (p < 0.05) with significant variation in the non-translucent wall thicknesses (p < 0.05). The three-dimensional observations characterized the spatial variation of wall thicknesses. Thin walls showed a uniform thickness profile ranging from 10 to 40 µm, whereas thick walls presented a peaked thickness profile ranging from 300 to 500 µm. In transition walls, the profile undulated due to the formation of focal thin/thick spots. Overall, the aneurysmal wall thicknesses were strongly site-dependent and spatially varied by 10 to 40 times within individual cases. Aneurysmal walls are exposed to wall stress driven by blood pressure. In theory, the magnitude of wall stress is inversely proportional to wall thickness. Thus, the observed spatial variation of wall thickness may increase the spatial variation of wall stress to a similar extent. The irregular wall thickness may yield stress concentration. The observed thin walls and focal thin spots may be caused by excessive wall stresses at the range of mechanical failure inducing wall injuries, such as microscopic tears, during aneurysmal enlargement. The present results suggested that blood pressure (wall stress) may have a potential of acting as a trigger of aneurysmal wall injury.

Yarn quality analysis in non-cellulosic and metal contents of cotton fibre of various locations

The fibre physical properties can be influenced by non-cellulosic and metal contents present in it which ultimately may impact the quality and spinning performance of resultant yarn. The concentration of these materials largely depends upon cotton variety, growing area and atmospheric conditions. In this back drop the present research study was planned to investigate the impact of various varieties and locations on non-cellulosic and metal contents of raw cotton and their eventual effects on subsequent yarn quality. So four varieties of single-season upland cottons from four different cotton-growing locations in Pakistan were selected for the study. The collected cotton samples were subjected to chemical and physical testing to know the concentrations of non-cellulosic and metal contents present in them along with other physical parameters. Then they were subjected to yarn manufacturing by conventional ring spinning method. At the end the yarn quality testing was carried in respect of its tensile and imperfections characteristics. The results disclosed significant impacts of selected variables on yarn quality. The reduction in non-cellulosic contents and metal contents put negative impact on Count Lea Strength Product (CLSP), yarn lea strength, single yarn strength, breaking length, evenness, thin spots, and neps count of resultant yarn.

Impact of areal-density asymmetries on the loss of confinement and ignition threshold in inertial confinement fusion capsules

In inertial confinement fusion implosion experiments, variations in the shell areal density reduce the shell's inertia to confine the core pressure. Distorted capsules with large areal-density modulations decompress faster than uniform capsules in the disassembly phase. A simple 3D analytic hot-spot model is derived to include the effects of low-mode areal-density modulations in the ignition criterion. The generalized 3D ignition criterion for low modes is shown to depend on both the harmonic mean and the arithmetic mean of the areal density. The “thin spots” in the shell are shown to dominate the loss of confinement as reflected by the harmonic mean definition of areal densities.

ЕКОНОМІЧНИЙ НІГІЛІЗМ ЛІДЕРІВ УКРАЇНСЬКОЇ РЕВОЛЮЦІЇ 1917–1921 рр. ЯК ДЕТЕРМІНАНТ ПОРАЗКИ ЗА УКРАЇНСЬКУ ДЕРЖАВНІСТЬ НА ПОЧАТКУ XX ст.

The economic factor, as an important determinant of defeat of the Ukrainian Revolution of 1917-1921 is still insufficiently studied. At the same time, the very nature of human development since the transition to capitalism has led the economic sphere to a key position in the life of every person. This trend has intensified since the early 20th century. This was evidenced by two world wars and other military-political conflicts, constantly increasing acceleration in the nature of economic development and the formation of a society of mass consumption, which in itself increased the dependence on the economic sphere of each individual. So, this is an axiom. Given the importance of the economy for the life of modern society, it is advisable to find out how the leaders of Ukrainian statehood reacted to it on the beginning of the 20th century. Moreover, there are still not enough studies of this kind. As a result of the study, a complex of actual data is obtained, which shows – economic factor was important in the defeat of the Ukrainian Revolution of 1917-1921, because Ukrainian statesmen at that time did not understand the importance of the economic sphere of life. The data that proves it can be conditionally divided into two groups. The first one – are the initial negative factors, which were not caused by the activities of Ukrainian political leaders, but were laid down by a long period of previous colonial development of Ukraine. However, these leaders did not take any steps to overcome that negative influence. These included: the absence of a significant number of truly wealthy people among the leaders of Ukrainian statehood, and therefore antagonism about the wealthy people between those leaders, which eventually deprived the Ukrainian statehood of internal material resources; disbelief in the possibility of independent development of Ukraine and stubborn clinging to autonomous ties with Russia; anarchism of the masses (especially the peasantry), generated by the years of war and especially by the brutal policies of the previous imperial government, which was reinforced by the activities of the Bolsheviks; shortage of patriotic specialists; the revived Ukrainian statehood lived in war conditions throughout the period of its existence, which made normal economic development impossible; the main region where the Ukrainian government lasted longer was the agrarian Right-Bank, while the industrial east was always quickly captured by enemy and the Ukrainian government had almost no influence on cities, where industry was concentrated and without its potential the existence of state is simply impossible. The second group of factors that affected negatively on the cause of the Ukrainian statehood in the beginning of the 20th century – are the practical actions of the then Ukrainian political leaders in the economic sphere. These included: the indefiniteness of the higher authorities competence and the uncertainty of their legal status; slow establishment of Ukrainian organs of power, who were responsible for economic issues; there was no clear vertical of accountable local authorities, and consequently the lack of understanding of the situation outside Kyiv; legislative framework, created in the economic sphere, was limited mainly to declarations and was not completed; Ukrainian political leaders did not have a single vision of solving a key issue for Ukraine’s economy – agriculture; inefficiency in addressing other economic issues (adjustment of industry, transport, trade, food supplies, taxation and money circulation). Separately should be highlighted the excessive idealism and, at the same time, a widespread fascination with socialistic doctrine, which at its core contradicted the normal construction of the economy. Establishment of these “thin spots” in the economic policy of the Ukrainian government in the beginning of the 20th century is important for today, because a number of mistakes of that time are presented in the policy of the modern Ukrainian government. Accordingly, the bitter experience of the past (loss of statehood due to neglect / procrastination of important economic issues) should play the role of the most powerful argument in the need for rapid change of the situation in economic construction right now.

Impact of Electrode Thick Spot Irregularities on Polymer Electrolyte Membrane Fuel Cell Performance

Polymer electrolyte membrane fuel cells (PEMFC) have great potential for power generation in many applications, but to implement them on a larger scale, understanding of quality requirements, tolerances, and controls during manufacturing must improve. As part of this broad challenge, irregularities resulting from the membrane electrode assembly (MEA) production process must be studied to determine if they impact the performance of the cell.1,2 One potential irregularity is a locally increased thickness of the coated or deposited electrode. In order to understand and provide insight into the impact of such irregularities, we intentionally created thick spots in the center of cathode electrodes, either by liquid casting or ultrasonic spraying of the additional catalyst ink. The thick spots fabricated by these two different approaches exhibited different sizes, morphologies, and Pt loading distributions, which were carefully characterized by optical microscopy, X-ray fluorescence spectroscopy (XRF), and scanning electron microscopy (SEM). Edge-protected MEAs were fabricated using both pristine electrodes and electrodes with thick spot irregularities. The effect of these irregularities on MEA structure were investigated by cross-sectional SEM. Electrochemical performance, including electrochemically active surface area (ECSA), H2/O2 polarization curves, mass activity and H2/air polarization curves, was measured to study the impact of the electrode irregularities on catalyst utilization and PEMFC initial performance. NREL’s segmented cell was utilized to investigate the resulting spatial performance of a representative thick spot MEA.The results indicate that thick spot irregularities that are present in the center of the cathode electrode impact initial cell performance although the impact of the thick spots on ECSA and mass activity was minimal. The latter suggests that the number of active Pt sites and the kinetics were not significantly altered. However, the H2/air polarization curves indicated that liquid-cast thick spots and large sprayed thick spots decrease cell performance dramatically at current densities above 0.8 A/cm2. Based on cross-sectional SEM analysis, the likely causes of this performance drop may originate from (i) delamination between the GDL and CL, (ii) the presence of thin spots in the membrane due to deformation associated with the thick spot, (iii) additional compression of the GDL and/or (iv) thick catalyst layer sections inhibiting local mass transport. Spatial performance diagnostics confirmed that the performance loss of MEAs containing liquid-cast thick spots is more pronounced at high current density than at low current density. Moreover, the performance of the area surrounding the liquid-cast thick spot is impacted as well, likely due to the various morphological changes resulting from the irregularity. We expect that the morphological changes resulting from these irregularities could serve as seed points for premature cell failure in long-term PEMFC operation. Future work will focus on the impact of electrode thick spot irregularities on PEMFC performance-over-time and lifetime, for both reinforced and non-reinforced membranes.

Effective Electrode Edge Protection for Proton Exchange Membrane Fuel Cell Drive Cycle Operation

Roll-to-Roll (R2R) manufacturing techniques have been demonstrated to be a cost-effective approach to continuously fabricate polymer electrolyte membrane fuel cell (PEMFC) materials at a large scale.1 In practical R2R manufacturing, non-uniformities including electrode coating irregularities do appear during the fabrication of the PEMFC membrane electrode assembly (MEA). In-line diagnostic tools to monitor quality have been developed at the National Renewable Energy Laboratory (NREL) and have been used to successfully detect a variety of electrode coating irregularities in a R2R manufacturing setting.2-3 However, limited understanding exists regarding if and to what extent electrode irregularities impact PEMFC performance and lifetime. Previously, we have investigated how cathode irregularities (bare and thin spots) impact MEA lifetime using a quasi in-situ infrared thermography technique in combination with accelerated stress tests (AST).4 In this work, driving cycle (DC) tests based on the New European driving cycle (NEDC)5 were employed to study the impact of cathode irregularities on degradation of MEA performance over time. Previous degradation studies indicated that the edge of the electrode area was the dominant failure location of the MEAs used. This observation was attributed to the excessive mechanical stress that was created by the relative humidity (RH) cycling procedure of the utilized AST.6 Edge protection techniques have been developed by the community to lengthen MEA lifetime and to prevent the immediate failure in ASTs.4, 6-7 Driving cycle tests employ rapid load cycling which will result in rapidly changing local operating conditions and consequently high non-uniform mechanical stress at the electrode perimeter. In order to better investigate the impact of electrode irregularities on the long-term behavior of the cell, it is necessary to exclude the edge effects of the MEAs as a failure mode. Therefore, an effective electrode edge protection technique using thin protective gaskets and a hot-pressing procedure was developed which dramatically prolonged DC lifetime from 288 hours to 1296 hours and additionally resulted in MEA performance improvements. Open circuit voltage (OCV), electrochemically active surface area (ECSA), air polarization and hydrogen crossover limiting current (iH2) data were monitored during the driving cycle tests. With edge protection, the OCV decay and the iH2 growth of the MEA was slowed. For post-DC ex situ analysis, an in-house developed pinhole detection apparatus (PDA) was employed to analyze quantity, size, and location of the failure locations of MEAs with and without edge protection. Non-protected MEAs typically developed tears at the electrode perimeter, while the longer-lasting protected MEAs exhibited seemingly random pinhole development. To better understand the degradation behavior of protected MEAs during the DC tests, scanning electron microscopy with energy dispersive X-Ray spectroscopy (SEM/EDS), transmission electron microscopy (TEM), and X-ray diffraction (XRD) were employed to study the morphology and structure of the MEAs at the beginning of life (BOL) and the end of life (EOL). Results will be discussed in the presentation.

Degradation Mechanisms and Accelerated Stress-Test Protocols for Polymer Electrolyte Water Electrolyzers

If polymer electrolyte water electrolysis (PEWE) is to be deployed to serve as an energy storage technology in the grid, the potential challenges related to the component durability need to be understood and addressed. The US Department of Energy (DOE) targets a cost of 2 $/kg H2 for the year 2020. Maintaining stack efficiency is key to a competitive end-cost of H2, as the main contribution is projected to come from the cost of electricity (1). The development of tailored PEWE components therefore needs to go hand-in-hand with the development of accelerated stress-tests that trigger specific degradation mechanisms. In this study, different degradation mechanisms were induced by subjecting commercial catalyst-coated membranes (CCMs) to specific operating conditions. PEWE cells were operated for 300 h to estimate the effects of the imposed stressors, and the cell performance was compared to the 300 h non-stressed benchmarks. The cell response was analyzed using electrochemical impedance spectroscopy (EIS). Individual catalyst layer (CL) characteristics were probed in the H2/N2 regime, and the cyclic voltamograms were recorded. Finally, samples were post-test investigated using scanning electron microscopy (SEM). The effect of the cell compression on the CL performance was stessed using cell assemblies with Ti-sintered porous transport layers (PTLs) of different morphological surface properties. Rigid PTL-surface features have induced local variation in CL porosity, and increased CL proton transport resistance (RCLa H+). In the case of PTLs with large voids, CCM creep led to the formation of thin spots and an increase in measured H2 in the O2 outlet. We have found that the increased gas crossover with mechanically stressed and locally thinned CCM results in a higher fluoride release rate over 300 h. The effects of start-stop operation on the CL stability were quantified over 300 h by periodically analyzing the anodic water using ICP-mass spectroscopy for traces of precious metals. Additionally, elemental mapping was done on the post-test CCM cross-sections to deterime if potentially dissolved species had deposited in the PEM (2). As water impurities are an important factor determining the electrolyzer lifetime (3), we have designed Ir2+ doping experiments to simulate the accelerated reverisble contamination of the CCM. A detalied overpotential analysis was done to determine the effect on the ohmic, activation and mass-transport overpotential. A specially designed cell was used to conduct operando neutron imaging of the contaminated CCM, and track the distribution of metal cations in the CCM cross-section under various operating conditions. EIS was done in paralell to correlate the impact of contaminants on the cell performance with their cross-sectional position. We established an comprehensive degradation matrix based on the PEWE degradation-inducing experiments, highlighting the stressors, degradation mechanisms and the affected aspects of PEWE performance.

Fundamental Issues Related to Flow Boiling and Two-Phase Flow Patterns in Microchannels – Experimental Challenges and Opportunities

ABSTRACTFlow boiling heat transfer in microchannels is used today in many diverse applications. The previous studies addressing the effect of channel size, heat flux, vapor quality, and mass flux on heat transfer during flow boiling are reviewed in the present paper. The relationship between flow characteristics and flow boiling heat transfer was studied experimentally for refrigerant R-C318 at moderate reduced pressures where the contribution of nucleate boiling is decisive. Flow boiling mechanisms were identified using an annular microchannel with transparent outer wall for successive visualization of boiling. The considerable suppression of nucleate boiling heat transfer was observed at transition to annular flow and explained by formation of a liquid flow with thin film and dry spots. A general equation for prediction of two-phase flow boiling heat transfer inside the circular, annular, and rectangular microchannels is proposed and verified using the experimental data. This equation accounts for the nucleate boiling suppression, forced convection, and thin film evaporative heat transfer in the form that allows to distinguish more clearly the contribution of each mechanism of heat transfer under the conditions, when it is predominant. A new approach for prediction of transition to the annular flow is proposed and verified, using the experimental data.

Studi Antibodi Poliklonal Anti-TBC dan Potensinya sebagai Rapid Test Kit pendeteksi TBC

Tuberculosis (TB) is one of the long-known diseases and is still the leading cause of death in the world. A variety of detection methods have been and are being implemented in order to suppress TB prevalence. The aim of this study was to isolate protein from serum pulmonary tuberculosis patients with sputum BTA (+), isolate protein from serum pulmonary tuberculosis patients with sputum BTA (-), and to know the level of antibody specificity in serum pulmonary tuberculosis patients with sputum BTA (+) and serum pulmonary tuberculosis patients with sputum BTA (-). The type of research used was laboratory experimental in Wistar rat experimental animals with Control Group Post Test Design research design. The research design was used with 3 different treatment groups, ie Control Group (without treatment), Group I (treated with isolate protein from serum of Pulmonary TB patients with sputum BTA (+)), and Group II (treated with protein isolate from serum of Pulmonary TB patient with sputum BTA (-) From collected data After dot blot is complete, tabulation of diagnostic test result (dot blot.) To obtain a standard in assessing the results of dot in each of these studies used CorelPhotopaint X4 program to obtain accurate data about the thickness of thin black spots (nilaimean) on the nitrocellulose membrane quantitatively.The data collected is processed using software (software) statistics SPSS version 11.5 From the electrophoresis test results of an exciting protein sample m of Pulmonary TB patients with BTA (+) and protein from serum of Pulmonary TB patients with AFB (-), obtained specific protein with molecular weight of 39 kDa. From the serum 1 serum easternbloting test result from pulmonary TB patients with BTA (+) and serum 2 protein derived from serum of Pulmonary TB patients with BTA (-), positive reaction occurred between antibodipoliklonal (anti 39 kDa) and serum protein of Pulmonary TB with BTA (+), or proteins from serum patients with pulmonary TB with AFB (-). The anti-tuberculosis polyclonal antibody in the study appears to be quite sensitive as Rapid tuberculosis detection test, but no specificity as evidenced by statistical calculation has significance&gt; 0.05, so the anti-tuberculosis polyclonal antibody in this study is quite sensitive, but not specifically used as an MTb detection device Keywords: tuberculosis, specific protein, polyclonal antibody, specificity test Tuberculosis (TB) is one of the long-known diseases and is still the leading cause of death in the world. A variety of detection methods have been and are being implemented in order to suppress TB prevalence. The aim of this study was to isolate protein from serum pulmonary tuberculosis patients with sputum BTA (+), isolate protein from serum pulmonary tuberculosis patients with sputum BTA (-), and to know the level of antibody specificity in serum pulmonary tuberculosis patients with sputum BTA (+) and serum pulmonary tuberculosis patients with sputum BTA (-). The type of research used was laboratory experimental in Wistar rat experimental animals with Control Group Post Test Design research design. The research design was used with 3 different treatment groups, ie Control Group (without treatment), Group I (treated with isolate protein from serum of Pulmonary TB patients with sputum BTA (+)), and Group II (treated with protein isolate from serum of Pulmonary TB patient with sputum BTA (-) From collected data After dot blot is complete, tabulation of diagnostic test result (dot blot.) To obtain a standard in assessing the results of dot in each of these studies used CorelPhotopaint X4 program to obtain accurate data about the thickness of thin black spots (nilaimean) on the nitrocellulose membrane quantitatively.The data collected is processed using software (software) statistics SPSS version 11.5 From the electrophoresis test results of an exciting protein sample m of Pulmonary TB patients with BTA (+) and protein from serum of Pulmonary TB patients with AFB (-), obtained specific protein with molecular weight of 39 kDa. From the serum 1 serum easternbloting test result from pulmonary TB patients with BTA (+) and serum 2 protein derived from serum of Pulmonary TB patients with BTA (-), positive reaction occurred between antibodipoliklonal (anti 39 kDa) and serum protein of Pulmonary TB with BTA (+), or proteins from serum patients with pulmonary TB with AFB (-). The anti-tuberculosis polyclonal antibody in the study appears to be quite sensitive as Rapid tuberculosis detection test, but no specificity as evidenced by statistical calculation has significance&gt; 0.05, so the anti-tuberculosis polyclonal antibody in this study is quite sensitive, but not specifically used as an MTb detection device

Optimization of Temperature Sensing with Polymer-Embedded Luminescent Ru(II) Complexes.

Temperature is a key parameter in many fields and luminescence-based temperature sensing is a solution for those applications in which traditional (mechanical, electrical, or IR-based) thermometers struggle. Amongst the indicator dyes for luminescence thermometry, Ru(II) polyazaheteroaromatic complexes are an appealing option to profit from the widespread commercial technologies for oxygen optosensing based on them. Six ruthenium dyes have been studied, engineering their structure for both photostability and highest temperature sensitivity of their luminescence. The most apt Ru(II) complex turned out to be bis(1,10-phenanthroline)(4-chloro-1,10-phenanthroline)ruthenium(II), due to the combination of two strong-field chelating ligands (phen) and a substituent with electron withdrawing effect on a conjugated position of the third ligand (4-Clphen). In order to produce functional sensors, the dye has been best embedded into poly(ethyl cyanoacrylate), due to its low permeability to O2, high temperature sensitivity of the indicator dye incorporated into this polymer, ease of fabrication, and excellent optical quality. Thermosensitive elements have been fabricated thereof as optical fiber tips for macroscopic applications (water courses monitoring) and thin spots for microscopic uses (temperature measurements in cell culture-on-a-chip). With such dye/polymer combination, temperature sensing based on luminescence lifetime measurements allows 0.05 °C resolution with linear response in the range of interest (0–40 °C).

Factors affecting the stability of water-oil-water emulsion films

Water-oil-water (oily) liquid films appear between the droplets in water-in-oil emulsions. Here we report results from systematic experiments, aimed to clarify how several important factors affect the stability and drainage of such oily films, in the presence of the nonionic oil-soluble surfactant Span 80. These results reveal that: (1) At Span 80 concentrations around the CMC, the film lifetime coincides with the duration of film drainage. When the oily films reach a critical thickness of around 40nm, unstable thinner black spots of thickness <10nm are formed due to attractive van der Waals forces, and the films rupture within seconds; (2) At intermediate concentrations of 3–30 times the CMC, the films are again unstable, but their lifetime increases significantly with Span 80 concentration, due to a longer drainage time and higher stability of the formed thin black spots. The increased drainage time is explained with a faster surfactant adsorption which leads to lower interfacial tension and, hence, to lower capillary pressure driving the film thinning. (3) At even higher Span 80 concentrations (around and above 100 CMC) the drainage time approaches a constant value, ≈600s. The films live much longer which is due mostly to the increased stability of the thin black films, formed after the black spot expansion. The film drainage time at intermediate and high Span concentrations agrees very well with the theoretical predictions. Surprisingly, the addition of 500mM NaCl into the aqueous phase leads to formation of non-equilibrium thick oil films, with drainage time >1h. This effect is explained with a mass transfer of molecules between the aqueous and the oil phases which keeps the oil films out of equilibrium for a long period. These results can be used to explain and control the formation and stability of water-in-oil emulsions, in the presence of nonionic oil-soluble surfactants.

Flow-induced buckling of flexible shells with non-zero Gaussian curvatures and thin spots.

We study the influence of one or multiple thin spots on the flow-induced instabilities of flexible shells of revolution with non-zero Gaussian curvatures. The shell's equation of motion is described by a thin doubly-curved shell theory and is coupled with perturbed flow pressure, calculated based on an inviscid flow model. We show that for shells with positive Gaussian curvatures conveying fluid, the existence of a thin spot results in a localized flow-induced buckling response of the shell in the neighborhood of the thin spot, and significantly reduces the critical flow velocity for buckling instability. For shells with negative Gaussian curvatures, the buckling response is extended along the shell's characteristic lines and the critical flow velocity is only slightly reduced. We also show that the length scale of the localized deformation generated by a thin spot is proportional to the shell's global thickness when the stiffness of the thin spot is negligible compared with the stiffness of the rest of the shell. When two thin spots exist at a distance, their influences are independent from each other for shells with positive Gaussian curvatures, but large-scale deformations can be created due to multiple thin spots on shells with negative curvatures, depending on the thin spots' relative position.

Bulk crustal properties of the Borborema Province, NE Brazil, from P-wave receiver functions: Implications for models of intraplate Cenozoic uplift

We investigate variations in crustal thickness and bulk VP/VS ratio across the Borborema Province of NE Brazil by analyzing teleseismic P-to-S conversions recorded at 52 seismic stations in the Province. The Borborema Province represents the western portion of a larger Neoproterozoic mobile belt that resulted from the assembly of Gondwanaland, and that split from the African continent during Mesozoic times. The evolution of the Province after continental breakup was marked by episodes of diffuse intraplate magmatism, perhaps leading to uplift of the Borborema Plateau in the Cenozoic. A number of geodynamic models have been proposed to explain coeval Cenozoic magmatism and uplift in the Province, which invoke either thermal anomalies under the Plateau and related mantle upwellings, channeling along lithospheric thin spots from a distant mantle plume, and small-scale convection at the continental edge. Alternatively, plateau uplift might have resulted from thickening of the crust after depth-dependent stretching of the continental lithosphere in the Mesozoic. Most of the models imply mafic underplating of the Plateau's crust in order to fully explain its elevated topography, but the volume of such mafic underplate varies among them. Our results show that: (i) the crust is 32–40km thick under the Borborema Plateau, (ii) the crust is generally thinner – about 30–33km – under the lower topographies surrounding the Plateau, and (iii) VP/VS ratios are in the 1.68–1.80 range for both regions of higher and lower topography. No apparent correlation is observed between VP/VS ratio and crustal thickness. Our results suggest that compositional differences between thick and thin crust across the Borborema Province are minimal, and that models of plateau uplift involving a small volume of mafic underplate provide a more plausible explanation for the observed topography of the Borborema Plateau.

A laser microwelding method for assembly of polymer based microfluidic devices

This paper presents the development of a laser microwelding method for assembly and packaging of polymer based microfluidic devices. In this approach a diode laser was used to weld two poly(methyl methacrylate) (PMMA) substrates together at the interface using a thin film metal spot based intermediate layer design as a localized absorber. A broad laser beam with a top-hat profile was used to carry out the laser microwelding work. The effects of laser power and processing time on the resultant heated affected zone (HAZ) and the melted zone were investigated. For large area welding, a 2×2 array of thin film metal spots were used to investigate the effect of separation between the spots on the resultant interfacial bond between the two polymer substrates. For comparison, a large area titanium film with a comparable size to that of the 2×2 array was also studied. The results show that the discrete film pattern based design is better than a single large area film in order to reduce the effect of substrate distortion resulting from the higher temperature rise associated with the latter. The tensile strength of the laser welded joints was determined to be about 6MPa for a sample produced using the 2×2 array of circular titanium spot pattern design. The laser microwelding method has been demonstrated successfully in leak-free encapsulation of a microfluidic channel.

Michael B. Miller. Europe and the Maritime World: A Twentieth-Century History.

Rewards in the history profession flow as much to reworking fashionable topics as to original enquiry. The consequences are occasional thin spots in the literature. One candidate for attention is the twentieth century conceived as a whole rather than as halves sundered by World War II. Another is the rise of East Asia, which historians have left largely to the social scientists. Michael B. Miller's commanding book on the maritime world helps to thicken both these narratives. He finds the nearest thing to a twentieth-century break during the 1960s with the expansion of cruise shipping and container traffic. He also discusses East Asia, while nevertheless concentrating on Europe's dominance of the sea lanes for most of the century. Maritime history is a saga of which European endeavor uncontestably forms the starting point. Several highly significant themes in world history recur in this complex and ambitious book, including the role and retreat of empire and the nature of globalization, which is carefully weighed. The topic that appears most often is networking among the managerial staffs of shipping companies. Miller never formalizes this aspect nor assimilates it to “network theory,” which he would scorn as business-school speak, but rather documents it in enormously rich detail. He is entranced by the creation of cadres of specialist shippers who made it possible to weave torrents of multifarious goods from place to place across the oceans. These specialists were welded into teams by the frankly snobbish hiring practices of London firms, whose principals sought to reproduce their own likenesses in the public-school and Oxbridge men they chose as agents.

In-Process Detection of Faying Surface Sealant Application Flaws in Friction Stir Welding

In this study, a process for detecting faying surface sealant application flaws in friction stir welded (FSW) lap joints is developed. The process uses a technique shown previously to enable the detection of machined gaps in the same joint type. This technique involves computing the frequency spectra of the process forces and reducing the dimensions of the data using well-known methods for discrimination purposes. Aluminum alloys 2024-T3 and 7075-T6 in 0.063-in.- (1.6-mm-) thick sheets were welded with a variety of PR-1432-GP sealant configurations, including in both the cured and uncured state, and applied in the tool path and adjacent to the tool path. It is shown that sealant flaws such as gaps or thin spots can indeed be discriminated from control welds with proper sealant application, and the success of this technique depends directly on the input force signal, the sealant configuration, and the dimensional reduction method. Factors affecting the real-time implementation of this technology in aerospace manufacturing are also examined.

X-ray photoelectron spectroscopy analysis for undegraded and degraded Gd2O2S:Tb3+ phosphor thin films

This paper presents the X-ray Photoelectron Spectroscopy (XPS) analysis for the undegraded and degraded Gd2O2S:Tb3+ thin film phosphor. The thin films were grown with the pulsed laser deposition (PLD) technique. XPS measurements were done on Gd2O2S:Tb3+ phosphor thin films before and after electron degradation. The XPS technique has proven the presence of Gd2O3 on the degraded and undegraded thin film spots. The presence of the SO2 bonding was also detected after degradation. This clearly indicates that surface reactions did occur during prolonged electron bombardment in an oxygen atmosphere.

Rapid Microarray Detection of DNA and Proteins in Microliter Volumes with Surface Plasmon Resonance Imaging Measurements

A four-chamber microfluidic biochip is fabricated for the rapid detection of multiple proteins and nucleic acids from microliter volume samples with the technique of surface plasmon resonance imaging (SPRI). The 18 mm × 18 mm biochip consists of four 3 μL microfluidic chambers attached to an SF10 glass substrate, each of which contains three individually addressable SPRI gold thin film microarray elements. The 12-element (4 × 3) SPRI microarray consists of gold thin film spots (1 mm(2) area; 45 nm thickness), each in individually addressable 0.5 μL volume microchannels. Microarrays of single-stranded DNA and RNA (ssDNA and ssRNA, respectively) are fabricated by either chemical and/or enzymatic attachment reactions in these microchannels; the SPRI microarrays are then used to detect femtomole amounts (nanomolar concentrations) of DNA and proteins (ssDNA binding protein and thrombin via aptamer-protein bioaffinity interactions). Microarrays of ssRNA microarray elements are also used for the ultrasensitive detection of zeptomole amounts (femtomolar concentrations) of DNA via the technique of RNase H-amplified SPRI. Enzymatic removal of ssRNA from the surface due to the hybridization adsorption of target ssDNA is detected as a reflectivity decrease in the SPR imaging measurements. The observed reflectivity loss is proportional to the log of the target ssDNA concentration with a detection limit of 10 fM or 30 zeptomoles (18 000 molecules). This enzymatic amplified ssDNA detection method is not limited by diffusion of ssDNA to the interface, and thus is extremely fast, requiring only 200 s in the microliter volume format.

Plio-Pleistocene intra-plate magmatism from the southern Sulu Arc, Semporna peninsula, Sabah, Borneo: Implications for high-Nb basalt in subduction zones

New analyses of major and trace element concentrations and Sr, Nd and Pb isotopic ratios are presented for Plio-Pleistocene basalts and basaltic andesites from the Semporna peninsula in Sabah, Borneo, at the southern end of the Sulu Arc. Depletion of high field strength elements (HFSE), which is characteristic of many subduction-related magmatic suites, is present in more evolved Semporna rocks but is associated with radiogenic Sr and Pb, and less radiogenic Nd isotopic ratios and results from contamination of mafic melt by, possibly ancient, crustal basement. The most mafic lavas from Semporna, and elsewhere in the Sulu Arc, display no HFSE depletion relative to other elements with similar compatibility. High-Nb basalt from Semporna formed when mantle resembling the source of Ocean Island Basalt (OIB) upwelled into lithospheric thin spots created during earlier subduction. This mantle did not experience enrichment by fluids or melt derived from subducted crust. The presence of similar lavas throughout the Sulu Arc and around the South China Sea suggests that the OIB-like component resides in the convecting upper mantle. Depletion of light rare earth elements, with respect to other incompatible elements, throughout the Sulu Arc could result from melt–mantle interaction during magma transport through the lithosphere. Such depletion is absent in suites from the South China Sea, where magma probably migrated along large, lithosphere-penetrating structures. Semporna high-Nb basalts are not associated with adakitic magmatism which is a frequent, but not ubiquitous, association in some active subduction zones. Both geochemical signatures are developed early in the history of a melt pulse, either in the source (high-Nb basalt) or during deep differentiation (adakite). Preservation of these distinctive geochemical signatures is favoured in settings that minimise (1) interaction with other, more copious melt types, and/or (2) subsequent differentiation in the shallow crust. Where found, the high-Nb basalt–adakite association is a result of transport through favourable lithospheric conditions and not due to any link between their mantle sources.

High resolution three-dimensional reconstruction of the collagenous matrix of the human optic nerve head

Glaucoma is the second most common cause of blindness worldwide, leading to irreversible loss of vision. Prior studies indicate that ocular pressure-induced displacement of the lamina cribrosa (LC) may be responsible for retinal ganglion cell axon damage inside the neural canal. We present a novel approach to imaging the entire lamina cribrosa and the scleral canal at high lateral and axial resolution by using a combination of array tomography and nonlinear optical imaging of serial ultrathin orthogonal sections to detect second harmonic generated (SHG) signals from collagen. The resulting images can be analyzed individually or combined to form a three-dimensional reconstruction of the lamina. Due to the specificity of SHG generated from collagen the density and distribution of collagen inside the scleral canal can be objectively quantified with a high degree of accuracy. The reconstruction shows a non-uniform distribution of collagen along both the longitudinal and orthogonal axes. Mapping the collagen density by geographic region reveals significant differences in collagen content that result in “thin spots” with low collagen density as well as areas of very high collagen content. This suggests a non-uniform mechanical stiffness across the lamina that may account for increased axon damage observed in glaucoma patients. The inferior temporal region of the ONH in particular is marked by low collagen density, which corresponds with clinical observations identifying this region as being more susceptible to damage during the onset of glaucoma. Further application of this technique will help characterize the relationship of age, race and gender on the morphology of the LC.