Thinning Profile Research Articles

Effect of silica nanoparticles on crude oil emulsions stabilized by a natural surfactant from Fenugreek Seeds and polyacrylamide for subsurface oil mobilization applications

Emulsions represent a sustainable method for subsurface resource recovery due to their superior performance in pore plugging, mobility control and interfacial tension reduction. However, the stability of emulsion plays a vital role in determining the success of field implementation. In this work, a novel formulation is reported for emulsions wherein they have been stabilized by natural surfactant extracted from fenugreek seed. In this work, two emulsion systems are reported, that is surfactant polymer and nanoparticle-surfactant-polymer emulsion. Surfactant-polymer emulsions are stabilized by natural surfactant whereas nanoparticle-surfactant-polymer emulsion are stabilized in presence of nanoparticle and natural surfactant. Both the emulsions exhibit shear thinning profile as observed from rheological studies. Nanoparticle-surfactant-polymer emulsions were found to be thermally stable than that of Surfactant-polymer emulsions as evident from microscopic and rheological studies. An increase in temperature has the unfavorable impact on surfactant-polymer emulsion as huge drop in viscosity profile was observed. The viscosity profiles of nanoparticle-surfactant-polymer emulsions were found to be best fitted by the Krieger-Dougherty model with the value of coefficient correlation R2 = 0.99. The contact angle studies showed that NSP solution can reduce the contact angle to much lower value, which is 111˚ to 30˚ whereas surfactant-polymer solution was able to reduce from 116˚ to 57˚ only. Adsorption of silica nanoparticle was also observed in presence of sandstone and decrease in 27.32 % of peak absorbance was observed in span of 20 days. Therefore, finding of the study indicates that nanoparticle-surfactant-polymer emulsions has potential to perform better than surfactant-polymer emulsions, even at elevated temperature, and can be a better and cost-effective alternative to the conventional emulsions used in oilfield applications.

Inland thinning of Byrd Glacier, Antarctica, during Ross Ice Shelf formation

AbstractGeomorphological records of past ice sheet change offer the opportunity to examine their centennial‐scale response to changing boundary conditions, which are not adequately captured in the satellite record. Here, we present the first reconstruction of ice surface lowering at Byrd Glacier, the largest outlet glacier of the Transantarctic Mountains. Using surface exposure ages from glacial erratic cobbles collected in two vertical transects along the Lonewolf Nunataks, we find the initial emergence of this set of nunataks occurred at ~15 ka, with a rapid pulse of thinning at ~8 ka. We compare our glacier thinning profiles with modelled ice sheet thickness and grounding line histories from two model ensembles to identify key processes responsible for ice sheet change. All model runs from the two ensembles predict grounding line retreat and inland thinning to occur in one rapid step from Last Glacial Maximum to present, in line with marine geology records, our exposure age data and derived glacier thinning rates. Experiments best matching the glacial thickness constraints, reconstructed from the surface exposure data, have faster basal sliding (i.e., promote greater sliding rates resulting in thinner ice). However, experiments best matching the timing and rapid rate of ice thinning derived from the same surface exposure data have higher basal friction. This apparent change in the modelled basal sliding regime, from when the ice surface is at maximum thickness, to the rapid thinning at ~8 ka, occurs as the grounding line retreats towards the Byrd Glacier and Ross Ice Shelf forms during the Holocene. This past context has implications for the stability of the modern grounding line of Byrd Glacier, which is characterised by high basal melt rates at the terminus—a process that has the potential to propagate glacier thinning far inland, impacting the overall (in)stability of the Byrd Glacier and Ross Ice Shelf.

Effect of loading paths on hydroforming ability of stepped hollow shaft components from double layer pipes

The step hollow shaft components are composed of two layers of different materials, they are formed using tube hydroforming process due to its high strength and rigidity, low weight and flexible profiles, compared to traditional casting, welding, and forming methods. These products are effectively used in industries such as the automotive, shipbuilding, aerospace and defense, and oil and gas sectors. The success of various double layer pipe hydroforming process depends on several factors, with the most important being the internal pressure path and axial loading path. This paper presents research on the effect of input loading paths on the hydroforming ability of a different two-layer metal structure - an outer layer of SUS304 stainless steel and an inner layer of CDA110 copper - using 3D numerical simulations on Abaqus/CAE software. Output criteria were used to evaluate the forming ability of the formed components, including Von Mises stress, Plastic strain component (PEmax), wall thinning, and pipe profile, based on which the input loading paths were combined during the forming process. These output criteria allow for more accurate predictions of material behavior during the hydroforming process, as well as deformation and stress distribution. This can support the design process, improve product quality, reduce errors, and increase production efficiency. The research results can be applied as a basis for optimizing load paths for the next experimental step in the near future, for undergraduate and graduate training, as well as allowing designers and engineers to optimize the process of hydroforming of different 2-layer tubes, reducing costs, improving accuracy, flexible design, minimizing risks, and increasing efficiency

Advanced Prediction Model for Pipe Wall Thinning Tendency by Flow Accelerated Corrosion at Junction Piping

Flow Accelerated Corrosion (FAC) is a pipe wall thinning phenomenon to be monitored and managed in the power plants with high priority. Its management has been conducted with conservative evaluation of thinning rate, and residual lifetime of piping based on wall thickness measurements. However, noticeable case of the wall thinning occurred in branch and junction piping (tee tube). There is a problem to manage the wall thickness beneath reinforcing plate of the tee tube, because measurement of this area is difficult to be conducted with ordinary ultrasonic testing devices due to the presence of the reinforcing plate. In this study, numerical analysis for the tee tube was conducted, and the wall thinning profile due to the FAC was evaluated by calculating the mass transfer coefficient. It was found that a localized wall thinning distribution occurs in the area where the reinforcing plate of the tee tube exists. And this tendency is affected by Reynolds number. In previous studies, a model was introduced to predict this trend, but in this study, the model was improved to take into account the effect of the Reynolds number.

Critical Shear Rate of Polymer-Enhanced Hydraulic Fluids

Many application-relevant fluids exhibit shear thinning, where viscosity decreases with shear rate above some critical shear rate. For hydraulic fluids formulated with polymeric additives, the critical shear rate is a function of the molecular weight and concentration of the polymers. Here we present a model for predicting the critical shear rate and Newtonian viscosity of fluids, with the goal of identifying a fluid that shear thins in a specific range relevant to hydraulic pumps. The model is applied to predict the properties of fluids comprising polyisobutene polymer and polyalphaolefin base oil. The theoretical predictions are validated by comparison to viscosities obtained from experimental measurements and molecular dynamics simulations across many decades of shear rates. Results demonstrate that the molecular weight of the polymer plays a key role in determining the critical shear rate, whereas the concentration of polymer primarily affects the Newtonian viscosity. The simulations are further used to show the molecular origins of shear thinning and critical shear rate. The atomistic simulations and simple model developed in this work can ultimately be used to formulate polymer-enhanced fluids with ideal shear thinning profiles that maximize the efficiency of hydraulic systems.

On the eruptive origins of lunar localized pyroclastic deposits

Localized pyroclastic deposits (LPDs) are low-albedo accumulates of pyroclastic material with distinct positive topographic signatures that are found dominantly along highland-mare boundaries. Previous workers hypothesized that LPDs represent products of a lunar equivalent of Vulcanian-style eruptions, based in part on the observation that some of the deposits in Alphonsus Crater have large vent volumes in comparison with their deposit volumes, indicating a low proportion of juvenile material in the deposits. The objective of this study is to better understand eruption mechanisms by determining how the proportion of juvenile material, as calculated using deposit and vent volumes, varies among LPDs in Alphonsus Crater and elsewhere on the Moon using contemporary data and methods. Deposit and vent volumes for 23 LPDs from eleven sites were calculated by differencing current and modeled pre-eruption surfaces using digital terrain models (DTMs) derived from Lunar Reconnaissance Orbiter Camera Narrow Angle Camera (LROC NAC). Results show that LPDs have a wide range of juvenile proportions, many of which are more juvenile-rich than previously thought. Additionally, there is a positive relationship between juvenile material proportion and deposit volume and thickness, and a positive relationship between juvenile volume and dispersal area. LPDs also bear a broad range of thinning profiles which span a range of multiple eruption types on Earth. These findings, along with previous studies employing spectroscopic analysis of these deposits, indicate there is greater diversity among LPDs in composition and morphometry than previously understood, and that previously published simplified Vulcanian models may apply only to the deposits containing the least amount of juvenile material, with all others perhaps requiring a combination of multiple eruptive mechanisms. Furthermore, dynamic model results suggest that the most widespread lunar deposits in this study were formed by magma containing 2000–5000 ppm of dissolved volatiles, consistent with recent estimates via melt inclusion analysis, but contrary to long-held ideas that the Moon was largely degassed during its formation.

Formability and fracture in deep drawing sheet metals: Extended studies for pre-strained anisotropic thin sheets

In this study, experimental and numerical investigations were conducted to predict the formability and fracture behavior of as-received and pre-strained sheet materials during deep drawing process. In this context, various laboratory scale experimental setups were developed to impart different types and amounts of pre-strain such as 5% and 10% equi-biaxial pre-strains (5% EBP and 10% EBP), 10% plane strain pre-strain (10% PSP), and 10% uni-axial pre-strain (10% UP) on the extra deep drawing (EDD) steel and aluminum alloy (AA5052) sheets of 1.2 mm thickness. Further, all the pre-strained sheet samples were deformed using a cylindrical deep drawing setup. The forming limit diagrams (FLDs) of as-received sheets were predicted by the Marciniak–Kuczyński (MK) model incorporating different anisotropic yield functions such as Hill48 models identified based on r-values (Hill48-r), and yield stresses (Hill48-σ), and the non-quadratic plane stress Yld2000-2d model. Also, the Bao–Wierzbicki (BW) fracture curve was calibrated using different anisotropic yield functions. Subsequently, the formability in terms of limiting drawing ratio (LDR) was predicted using the MK-FLD. The BW fracture curve was incorporated into the generalized incremental stress state dependent damage model (GISSMO) platform in LS-Dyna software and the fracture behavior was predicted in terms of failure location and cup height at the onset of fracture. It was also found that the incorporation of Barlat Yld2000-2d yield function into the FE simulation efficiently predicted the necking and fracture behavior of as-received sheets. Furthermore, the concept of path independent polar effective plastic strain (PEPS) based failure model was used to predict LDR, thinning profile and fracture cup height of all the different pre-strained sheets. Finally, the strain paths and experimental fracture strains were plotted in 3D fracture locus to get insight into the deformation behavior during the deep drawing experiments.

Variable structure and function relationship of compressive optic neuropathy at the time of diagnosis.

PurposeTo illustrate the structure–function relationship of compressive optic neuropathy (CON) at the time of diagnosis.Patients and methodsThirty-two eyes of newly diagnosed suprasellar CON and 60 healthy eyes were included in the study. The peripapillary retinal nerve fiber layer (RNFL) thickness and macular ganglion cell-inner plexiform layer (GCIPL) thickness were obtained using Cirrus spectral domain optical coherence tomography (SD-OCT). CON eyes were stratified based on the similar degree and pattern of both RNFL and GCIPL.ResultsFrom 32 eyes of newly diagnosed suprasellar CON eyes, 27 eyes had a predominantly nasal hemiretina thinning of macular GCIPL, 4 eyes showed a generalized macular thinning, and 1 eye showed a predominantly superior macular thinning. The corresponding temporal peripapillary RNFL thinning with nasal hemiretina GCIPL thinning were inconsistently manifested. Structure–function analysis of stratified CON eyes with similar thinning profiles showed that a range rather than a fixed value of visual field loss based on mean deviation (MD) index was associated to each thinning profile. The maximal limit of visual field loss range was ubiquitously nonrestricted to any structural thinning profile. While the minimal limit of the associated MD range was gradually reduced from 0 to about −16.0 dB, the nasal hemiretina macular GCIPL thinning was the only manifestation and decreased from 75 to 45 µm. However, the different degrees of temporal hemiretina macular GCIPL and superior–inferior peripapillary RNFL thinning were only seen in 10 of 32 eyes of which their nasal hemiretina GCIPL and temporal RNFL thinning had reached significant thinning. Interestingly when present, the minimal limit of associated MD range continued to decrease from −16.0 to −32.0 dB.ConclusionCON eyes can present with variable structure and function relationship at the time of diagnosis. Using structural parameters at the time of diagnosis to predict the prognosis should be used with caution.

Integrating softwood biorefinery lignin into polyhydroxybutyrate composites and application in 3D printing

The massive volumes of residual lignin that will be generated as a biorefinery industry by-product provide an opportunity for bio-composite manufacture. In this context, biorefinery lignin produced from the saccharification of Pinus radiata wood pulp without any further derivatization or coupling or chemical modifications was blended and melt extruded with polyhydroxybutyrate (PHB) to form composite filaments. The filaments were cut into pellets and compression moulded into films. The pellets/films were characterised by FTIR, SEM, 13C NMR, water contact angle, TGA and DSC. The FTIR and SEM analyses suggested a particulate polymer composite in which filaments have a PHB-rich surface and discrete lignin particles contained within the filament core. The 13C NMR spectroscopy showed the proportion of phenolic carbon signal associated with aromatic moieties in lignin increased with the proportion of the biorefinery lignin added into the composite. The decomposition, melting and crystallization temperature of PHB polymer did not appreciably change after the inclusion of biorefinery lignin into the composite. The PHB composite containing biorefinery lignin had a shear thinning profile which enhanced layer adhesion during 3D printing. The water contact angle of the moulded films was increased with the addition of the biorefinery lignin indicating lignin exerted a hydrophobic effect on the PHB films. The rheology results indicate that lignin when added as a filler at 20% w/w changes melt viscosity and is conducive for 3D printing. Hence, as an example of the additive manufacturing, the extruded composite filament with 20% biorefinery lignin was 3D printed and showed between 34 to 78% less warpage compared to the 100% PHB printed object. Incorporating biorefinery lignin into 3D printed PHB filaments represents a potential application for valorising softwood biorefinery lignin.

Wall Thinning Profile by Flow Accelerated Corrosion in Heat Recovery Steam Generator of Thermal Power Station

Wall Thinning Profile by Flow Accelerated Corrosion in Heat Recovery Steam Generator of Thermal Power Station

Numerical and experimental investigations for hot metal gas forming of stainless steel X2CrTiNb18

Abstract The article deals with the numerical modeling of hot metal gas forming (HMGF) of ferritic stainless steel X2CrTiNb18 with conductive heating using a demonstration part. In this context, in particular, the locally existing strains are considered under varying local temperature and strain rate conditions. The evaluation of the simulation results is finally carried out on the basis of measured thinning profiles of experimental parts. The basic curve character is correctly reflected in the simulation results. However, there are component areas with very good agreement as well as with larger deviations of the remaining wall thickness. Finally, possible causes of deviations are highlighted. A more extensive provision of information from the experiments is considered to be essential for an improvement of the simulation accuracy (e.g. temperature distribution of the tube at forming start, measurement of the radial tube forming during pressure build-up).

Association of Prenatal Exposure to Population-Wide Folic Acid Fortification With Altered Cerebral Cortex Maturation in Youths

ImportancePresently, 81 countries mandate the fortification of grain products with folic acid to lessen the risk of neural tube defects in the developing fetus. Epidemiologic data on severe mental illness suggest potentially broader effects of prenatal folate exposure on postnatal brain development, but this link remains unsubstantiated by biological evidence.ObjectiveTo evaluate associations among fetal folic acid exposure, cortical maturation, and psychiatric risk in youths.Design, Setting, and ParticipantsA retrospective, observational clinical cohort study was conducted at Massachusetts General Hospital (MGH) among 292 youths 8 to 18 years of age born between January 1993 and December 2001 (inclusive of folic acid fortification rollout ±3.5 years) with normative results of clinical magnetic resonance imaging, divided into 3 age-matched groups based on birthdate and related level of prenatal folic acid fortification exposure (none, partial, or full). Magnetic resonance imaging was performed between January 2005 and March 2015. Two independent, observational, community-based cohorts (Philadelphia Neurodevelopmental Cohort [PNC] and National Institutes of Health Magnetic Resonance Imaging Study of Normal Brain Development [NIH]) comprising 1078 youths 8 to 18 years of age born throughout (PNC, 1992-2003) or before (NIH, 1983-1995) the rollout of folic acid fortification were studied for replication, clinical extension, and specificity. Statistical analysis was conducted from 2015 to 2018.ExposuresUnited States–mandated grain product fortification with folic acid, introduced in late 1996 and fully in effect by mid-1997.Main Outcomes and MeasuresDifferences in cortical thickness among nonexposed, partially exposed, and fully exposed youths (MGH) and underlying associations between age and cortical thickness (all cohorts). Analysis of the PNC cohort also examined the association of age–cortical thickness slopes with the odds of psychotic symptoms.ResultsThe MGH cohort (139 girls and 153 boys; mean [SD] age, 13.3 [2.3] years) demonstrated exposure-associated cortical thickness increases in bilateral frontal and temporal regions (9.9% to 11.6%; corrected P < .001 to P = .03) and emergence of quadratic (delayed) age-associated thinning in temporal and parietal regions (β = –11.1 to –13.9; corrected P = .002). The contemporaneous PNC cohort (417 girls and 444 boys; mean [SD] age, 13.5 [2.7] years) also exhibited exposure-associated delays of cortical thinning (β = –1.59 to –1.73; corrected P < .001 to P = .02), located in similar regions and with similar durations of delay as in the MGH cohort. Flatter thinning profiles in frontal, temporal, and parietal regions were associated with lower odds of psychosis spectrum symptoms in the PNC cohort (odds ratio, 0.37-0.59; corrected P < .05). All identified regions displayed earlier thinning in the nonexposed NIH cohort (118 girls and 99 boys; mean [SD] age, 13.3 [2.6] years).Conclusions and RelevanceThe results of this study suggest an association between gestational exposure to fortification of grain products with folic acid and altered cortical development and, in turn, with reduction in the risk of psychosis in youths.

Structural Evolution of the Rifted Margin off Northern Labrador: The Role of Hyperextension and Magmatism

AbstractHigh‐quality seismic reflection data from the offshore northern Labrador rifted margin allow imaging of the extended and rifted crust both along and across the continental margin and are described in conjunction with available seismic velocity and gravity data. The margin formed within cold, thick cratonic lithosphere. Both Archean continental basement and a discrete, undulating, high‐amplitude, deep reflection about 10 km below basement are observed. The deeper reflection can be correlated with the crust‐mantle boundary as measured on previous wide‐angle seismic data in the region. This reflection, termed here the L‐reflection, appears to be the equivalent to other top‐mantle detachments found elsewhere on magma‐poor rifted margins. However, normal mantle velocities have been observed to lie just below the reflection, suggesting that it may not be related to the formation of weak serpentinized mantle. A high‐velocity and density zone occupies the outer shelf seaward of the L‐reflection where basement is transparent, which may represent highly mafic crust or serpentinized mantle. A crustal reconstruction of this margin and its conjugate shows marked asymmetry, with a wider zone of crustal thinning on the Greenland margin. These crustal thinning profiles are comparable to those on other conjugate margins within cratonic lithosphere. While some of the attributes of this margin are those of a magma‐poor system, at the ocean‐continent transition, thick igneous crust created a magma‐rich zone in Paleocene time when a hot spot was active in the Davis Strait to the north. Thus, this margin exhibits characteristics of both magma‐rich and magma‐poor systems.

Numerical and experimental study on the steady cone-jet mode of electro-centrifugal spinning

This study focuses on a numerical investigation of an initial stable jet through the air-sealed electro-centrifugal spinning process, which is known as a viable method for the mass production of nanofibers. A liquid jet undergoing electric and centrifugal forces, as well as other forces, first travels in a stable trajectory and then goes through an unstable curled path to the collector. In numerical modeling, hydrodynamic equations have been solved using the perturbation method—and the boundary integral method has been implemented to efficiently solve the electric potential equation. Hydrodynamic equations have been coupled with the electric field using stress boundary conditions at the fluid-fluid interface. Perturbation equations were discretized by a second order finite difference method, and the Newton method was implemented to solve the discretized non-linear system. Also, the boundary element method was utilized to solve electrostatic equations. In the theoretical study, the fluid was described as a leaky dielectric with charges only on the surface of the jet traveling in dielectric air. The effect of the electric field induced around the nozzle tip on the jet instability and trajectory deviation was also experimentally studied through plate-plate geometry as well as point-plate geometry. It was numerically found that the centrifugal force prevails on electric force by increasing the rotational speed. Therefore, the alteration of the applied voltage does not significantly affect the jet thinning profile or the jet trajectory.

Corneal remodeling after implantation of a shape-changing inlay concurrent with myopic or hyperopic laser in situ keratomileusis

To compare the induced addition (add)-power profile and epithelial remodeling between patients receiving hyperopic and myopic laser insitu keratomileusis (LASIK) concurrently with implantation of a corneal shape-changing inlay. Specialty clinics in Monterrey and Tijuana, Mexico. Retrospective case series. Preoperative hyperopic patients (mean spherical equivalent [SE] treatment +1.71 diopters [D]±0.51 [SD]) and myopic patients (mean SE treatment -2.48±1.33 D) had implantation of a Raindrop Near Vision Inlay in the nondominant eye immediately after the excimer laser ablation in both eyes under a corneal flap. Monocular and binocular visual acuities were recorded at 6m. Wavefront measurement analysis yielded the mean inlay add-power profile, and optical coherence tomography images yielded the mean epithelial remodeling profile. In the inlay eye in the hyperopic group (n=34) and myopic group (n=29), the mean uncorrected near visual acuity exceeded 20/25 (85% 20/25 or better), the mean uncorrected distance visual acuity (UDVA) was 20/32 (62% 20/32 or better), and the mean binocular UDVA was 20/18 (100% 20/25 or better). The add-power profiles for the hyperopic and myopic groups were similar. The epithelial thinning profiles were also the same, thinning centrally by approximately 19μm, and were uncorrelated with the treated refractive error. After concurrent LASIK and inlay implantation, the visual acuity, induced add-power profile, and epithelial remodeling were the same, regardless of hyperopic or myopic treatment.

Crossover behavior study of a thinning liquid bridge using the dissipative particle dynamics method

In this work, the dissipative particle dynamics method is used to explore the thinning process of a liquid bridge transforming from macroscopic factor domination to thermal fluctuation domination. Both the inertial–force–dominated thinning profile and the thermal–fluctuation–dominated thinning profile are of self–similarity characteristics. Our simulations show that the scaling factors are in accordance with theoretical results. To explore crossover behavior, concentration is on the transitional regime, where both macroscopic factor domination and microscopic factor domination can be observed. The crossover time depends mainly on the stochastic coefficient. With the conservative forces not being considered, the decrease of the stochastic coefficient results in a wider thermal-fluctuation-dominated regime, but the crossover radius remains nearly unchanged. It is found that the increase in viscosity aids in the dominance of the thermal fluctuations and the emergence of the double–cone breakup profile. Surface stress fluctuations and bulk density fluctuations are examined to investigate the origin of the crossover. The results of these simulations suggest that the key factor of the crossover is the fluctuation correlation length, rather than the strength of the interfacial stress fluctuations. The simulation results also support the conclusion of previous researchers who have determined that it is the balance between the driving capillary pressure and the thermal energy density in the neck that causes crossover.

連続配管要素体系における流れ加速型腐食による減肉傾向

連続配管要素体系における流れ加速型腐食による減肉傾向

Thinning factor distributions viewed through numerical models of continental extension

A longstanding question surrounding rifted margins concerns how the observed fault-restored extension in the upper crust is usually less than that calculated from subsidence models or from crustal thickness estimates, the so-called “extension discrepancy”. Here, we revisit this issue drawing on recently completed numerical results. We extract thinning profiles from four end-member geodynamic model rifts with varying width and asymmetry, and propose tectonic models that best explain those results. We then relate the spatial and temporal evolution of upper to lower crustal thinning, or crustal depth-dependent thinning (DDT), and crustal thinning to mantle thinning, or lithospheric DDT, which are difficult to achieve in natural systems due to the lack of observations that constrain thinning at different stages between pre-rift extension and lithospheric breakup. Our results support the hypothesis that crustal DDT cannot be the main cause of the extension discrepancy, which may be overestimated because of the difficulty in recognizing distributed deformation, and polyphase and detachment faulting in seismic data. More importantly, the results support that lithospheric DDT is likely to dominate at specific stages of rift evolution because crustal and mantle thinning distributions are not always spatially coincident, and at times are not even balanced by an equal magnitude of thinning in two-dimensions. Moreover, either pure or simple shear models can apply at various points of time and space depending on the type of rift. Both DDT and pure-/simple-shear variations across space and time can result in observed complex fault geometries, uplift/subsidence, and thermal histories.

The observation and evaluation of extensional filament deformation and breakup profiles for Non Newtonian fluids using a high strain rate double piston apparatus

Summary This paper reports a new design of experimental double piston filament stretching apparatus that can stretch fluids to very high extensional strain rates. Using high speed photography, filament deformation and breakup profiles of a strategically selected range of fluids including low and higher viscosity Newtonian liquids together with a viscoelastic polymer solution, biological and yield stress fluids were tested for the first time at extensional strain rates in excess of 1000 s−1. The stretching rate was sufficiently high that observation of low viscosity Newtonian fluid stretching, end pinching and break was observed during the stretching period of the deformation, whereas for a higher Newtonian viscosity, filament thinning and breakup occurred after the cessation of piston movement. Different fluid rheologies resulted in very different thinning and breakup profiles and the kinetics, in particular of yield stress fluids showed a striking contrast to Newtonians or viscoelastic fluids. Surprisingly all the tested fluids had an initial sub millisecond “wine glass” profile of deformation which could be approximately captured using a simple parabolic mass balance equation. Subsequent deformation profiles were however very sensitive to the rheology of the test fluid and where the final breakup occurred before or after piston cessation. In certain cases the thinning and break up was successfully matched with a 1D numerical simulation demonstrating the way numerical modelling can be used with the fluids correct rheological characterization to gain physical insight into how rheologically complex fluids deform and breakup at very high extensional deformation rates.

Heterogeneous glacier thinning patterns over the last 40 years in Langtang Himal, Nepal

Abstract. This study presents volume and mass changes of seven (five partially debris-covered, two debris-free) glaciers in the upper Langtang catchment in Nepal. We use a digital elevation model (DEM) from 1974 stereo Hexagon satellite data and seven DEMs derived from 2006–2015 stereo or tri-stereo satellite imagery (e.g., SPOT6/7). The availability of multiple independent DEM differences allows the identification of a robust signal and narrowing down of the uncertainty about recent volume changes. The volume changes calculated over several multiyear periods between 2006 and 2015 consistently indicate that glacier thinning has accelerated with respect to the period 1974–2006. We calculate an ensemble-mean elevation change rate of –0.45 ± 0.18 m a−1 for 2006–2015, while for the period 1974–2006 we compute a rate of −0.24 ± 0.08 m a−1. However, the behavior of glaciers in the study area is heterogeneous, and the presence or absence of debris does not seem to be a good predictor for mass balance trends. Debris-covered tongues have nonlinear thinning profiles, and we show that recent accelerations in thinning correlate with the presence of supraglacial cliffs and lakes. At stagnating glacier areas near the glacier front, however, thinning rates decreased with time or remained constant. The April 2015 Nepal earthquake triggered large avalanches in the study catchment. Analysis of two post-earthquake DEMs revealed that the avalanche deposit volumes remaining 6 months after the earthquake are negligible in comparison to 2006–2015 elevation changes. However, the deposits compensate about 40 % the mass loss of debris-covered tongues of 1 average year.