Small Core Research Articles

Orogenic eclogites record relative magnitude of deep crustal flow and extent of migmatite-eclogite interaction

In exhumed orogens, refractory mafic rocks have the potential to preserve a record of petrogenesis and high-pressure (H P ) metamorphism that is commonly obliterated in quartzofeldspathic rocks owing to re-equilibration at high-temperature, low-pressure (L P –H T ) conditions. In the Montagne Noire (France) migmatite dome, located in the foreland of the Variscan orogen, eclogite is exposed in both the core and margin of the dome. In this study, we combine in situ U Pb petrochronology and oxygen-isotope analyses of key eclogite phases to demonstrate that eclogites from the two distinct domains had different protoliths and source regions, traveled relatively variable distances in the deep crust, and differentially interacted with surrounding migmatite prior to exhumation. Dome-margin eclogite zircons are small (~40 μm) with well-preserved inherited cores and thin (<15 μm) rims, compared to larger (40–120 μm) neo- and recrystallized dome-core zircons with small relict cores and wide (15–30 μm) recrystallized rims. Protolith and H P metamorphism ages were determined using in situ zircon and rutile petrochronology (LASS-ICP-MS). Both eclogites formed in a continental setting; dome margin protolith zircon cores formed at 442.5 ± 3.4 Ma (steep HREE slope, no Eu-anomaly) whereas zircon cores of the dome-core eclogites yielded scattered dates suggesting protolith crystallization between ~500–400 Ma (steep HREE slope, pronounced Eu-anomaly). Both eclogites experienced H P metamorphism at c. 320–310 Ma in garnet-stable, plagioclase-absent conditions. Most analyzed rutile yielded dates of 307–304 Ma associated with cooling. The record of H P fluid conditions was determined by O-isotope (SIMS) analyses of garnet and zircon. Dome-margin zircon cores and rims have δ 18 O of ~8.2–8.5 ‰, indistinguishable within uncertainty, in isotopic equilibrium with isotopically unzoned garnet (δ 18 O ~ 8.0–8.2 ‰). In contrast, zircons in dome-core eclogites have systematically lower zircon-core δ 18 O values compared to their rims and neocrystallized grains, and zircon cores were in equilibrium with major-cation zoned garnet with respect to oxygen. The two dome-core eclogite samples yielded zircon and garnet δ 18 O values of ~8.6–9.5 ‰ and ~ 9.7–10.5 ‰. Based on these results and existing H P fabric data for these eclogites, we propose that (1) gabbro protoliths for the two eclogites were emplaced at different depths in a Cambro-Ordovician continental crustal package; and (2) dome-core eclogites interacted extensively with surrounding gneiss during burial and foreland-vergent crustal flow, whereas the dome-margin eclogite was sourced proximally to the dome-emplacement location and had minimal chemical interaction with surrounding gneiss. At least parts of the Montagne Noire migmatite dome were deeply sourced, but rocks exhumed in the core had a more extensive and protracted history of deep-crustal flow than deep-crustal rocks exhumed at the margin. • Eclogites in migmatite dome retain memory of deep crust history. • Zircon (re)crystallization extent reveals distinct eclogite source, flow paths. • Petrochronology and O-isotopes record migmatite-eclogite interaction at depth. • Integrated garnet, zircon datasets reveal protolith, peak, exhumation histories. • Domes may exhume crust laterally-sourced >100 s of km from emplacement location.

Effect of Concrete Class, Maximum Aggregate Size and Specimen Size on the Compressive Strength of Cores and Cast Specimens

Abstract Core sampling is the most accurate method of evaluating the compressive strength of concrete structures. However, it is preferable to take only small cores to avoid damaging the structures. It turns out that various elements influence the strength of compressed cores. This study examines the influence of specimen size, aggregate size, concrete class, and curing method on compressive strength. Three aggregates measuring 3/8, 8/15, and 15/25 mm are used to make six sets of concrete compositions with strengths of 25 MPa and 30 MPa. Nine specimens are made, one for each variety of aggregate and concrete. Cores of 100 mm, 75 mm, and 50 mm sizes are made. These cores are extracted from concrete blocks curing in the outside air to simulate the real concrete curing environment. Cast specimens cured in water and air with diameters of 50 mm, 100 mm, and 150 mm are also made. The objective is to compare the average compressive strength of all cast or extracted specimens with that of cylindrical standard specimens of diameter 150/300 mm and the cores and cast specimens. The obtained findings showed that the compressive strength is overestimated when we compare fp100 cores and standard air-cured specimens (fc), with a conversion factor varying from 0.69 to 0.96. However, a decrease is observed in comparison with water-cured specimens. The use of fp75 cores reduced the conversion factors, which are between 0.83 and 0.87 for B25 concrete. The highest fp/fc ratios are obtained for fc50 cores, which can reach 1.24. It turns out that the size of the core and the class of concrete have a much greater influence on the fp/fc ratios.

Characterising the AGB bump and its potential to constrain mixing processes in stellar interiors

Context. In the 1990s, theoretical studies motivated the use of the asymptotic giant branch bump (AGBb) as a standard candle given the weak dependence between its luminosity and stellar metallicity. Because of the small size of observed asymptotic giant branch (AGB) samples, detecting the AGBb is not an easy task. However, this has now been made possible thanks to the wealth of data collected by the CoRoT, Kepler, and TESS space-borne missions. Aims. It is well-known that the AGB bump provides valuable information on the internal structure of low-mass stars, particularly on mixing processes such as core overshooting during the core He-burning phase. Here, we investigate the dependence of the AGBb position on stellar parameters such as the stellar mass and metallicity based on the calibration of stellar models to observations. Methods. In this context, we analysed ∼4000 evolved giants observed by Kepler and TESS, including red giant branch (RGB) stars and AGB stars, for which asteroseismic and spectrometric data are available. By using statistical mixture models, we detected the AGBb both in frequency at maximum oscillation power, νmax, and in effective temperature, Teff. Then, we used the Modules for Experiments in Stellar Astrophysics (MESA) stellar evolution code to model AGB stars and match the AGBb occurrence with observations. Results. From the observations, we were able to derive the AGBb location in 15 bins of mass and metallicity. We noted that the higher the mass, the later the AGBb occurs in the evolutionary track, which agrees with theoretical works. Moreover, we found a slight increase in the luminosity at the AGBb when the metallicity increases. By fitting those observations with stellar models, we noticed that low-mass stars (M ≤ 1.0 M⊙) require a small core overshooting region during the core He-burning phase. This core overshooting extent increases toward high mass; however, above M ≥ 1.5 M⊙, we found that the AGBb location cannot be reproduced with a realistic He-core overshooting alone. Thus, additional mixing processes have to be invoked instead. Conclusions. The observed dependence on metallicity complicates the application of the AGBb as a standard candle. Moreover, different mixing processes may occur according to stellar mass. At low mass (M ≤ 1.5 M⊙), the AGBb location can be used to constrain the He-core overshooting. At high mass (M ≥ 1.5 M⊙), an additional mixing induced, for instance, by rotation is needed to reproduce what is seen in observations.

Incoherent light in tapered graded-index fibre: A study of transmission and modal noise

We investigated the impact of taper length on light transmission through tapered graded-index fibres. We tested commercial fibres from Thorlabs and a custom graded-index fibre using both coherent and incoherent light sources. Our experimental results show optimum performance for taper transition lengths of 25 mm, although our simulations suggest further improvement may be possible for even shorter transition lengths. We also measured the modal noise power fluctuations caused by bending the fibre. Here, we observe that the custom fibre tapers have the highest transmission but suffer from the most modal noise. Accordingly, we find that the commercial graded-index fibre tapers promise practical usage as a beam mode-field converter, as they have lower power fluctuations but retain relatively high transmission if compared to commercial small core step-index fibre.

Dark matter halo cores and the tidal survival of Milky Way satellites

ABSTRACT The cuspy central density profiles of cold dark matter (CDM) haloes make them highly resilient to disruption by tides. Self-interactions between dark matter particles, or the cycling of baryons, may result in the formation of a constant-density core that would make haloes more susceptible to tidal disruption. We use N-body simulations to study the evolution of Navarro–Frenk–White (NFW)-like ‘cored’ subhaloes in the tidal field of a massive host, and identify the criteria and time-scales for full disruption. Our results imply that the survival of Milky Way satellites places constraints on the sizes of dark matter cores. We find that no subhaloes with cores larger than 1 per cent of their initial NFW scale radius can survive for a Hubble time on orbits with pericentres ${\lesssim} 10\, \mathrm{kpc}$. A satellite like Tucana 3, with pericentre ${\sim} 3.5\, \mathrm{kpc}$, must have a core size smaller than ${\sim} 2\, \mathrm{pc}$ to survive just three orbital periods on its current orbit. The core sizes expected in self-interacting dark matter models with a velocity-independent cross-section of $1\, \mathrm{cm^2}\,\mathrm{g}^{-1}$ seem incompatible with ultrafaint satellites with small pericentric radii, such as Tuc 3, Seg 1, Seg 2, Ret 2, Tri 2, and Wil 1, as these should have fully disrupted if accreted on to the Milky Way ${\gtrsim} 10\, \mathrm{Gyr}$ ago. These results suggest that many satellites have vanishingly small core sizes, consistent with CDM cusps. The discovery of further Milky Way satellites on orbits with small pericentric radii would strengthen these conclusions and allow for stricter upper limits on the core sizes.

Non-Conserved Amino Acid Residues Modulate the Thermodynamics of Zn(II) Binding to Classical ββα Zinc Finger Domains

Classical zinc fingers domains (ZFs) bind Zn(II) ion by a pair of cysteine and histidine residues to adopt a characteristic and stable ββα fold containing a small hydrophobic core. As a component of transcription factors, they recognize specific DNA sequences to transcript particular genes. The loss of Zn(II) disrupts the unique structure and function of the whole protein. It has been shown that the saturation of ZFs under cellular conditions is strictly related to their affinity for Zn(II). High affinity warrants their constant saturation, while medium affinity results in their transient structurization depending on cellular zinc availability. Therefore, there must be factors hidden in the sequence and structure of ZFs that impact Zn(II)-to-protein affinities to control their function. Using molecular dynamics simulations and experimental spectroscopic and calorimetric approaches, we showed that particular non-conserved residues derived from ZF sequences impact hydrogen bond formation. Our in silico and in vitro studies show that non-conserved residues can alter metal-coupled folding mechanisms and overall ZF stability. Furthermore, we show that Zn(II) binding to ZFs can also be entropically driven. This preference does not correlate either with Zn(II) binding site or with the extent of the secondary structure but is strictly related to a reservoir of interactions within the second coordination shell, which may loosen or tighten up the structure. Our findings shed new light on how the functionality of ZFs is modulated by non-coordinating residues diversity under cellular conditions. Moreover, they can be helpful for systematic backbone alteration of native ZF ββα scaffold to create artificial foldamers and proteins with improved stability.

Pore distances of particulate organic matter predict [formula omitted] emissions from intact soil at moist conditions

Denitrification in soils is a very complex phenomenon due to the multiple factors it depends on. Therefore, making accurate predictions has been an elusive task. In this study we measured N2O emissions daily during 7 days from a set of 20 undisturbed small soil cores that were subsequently scanned using X-ray micro-tomography. Macropores, particulate organic matter (POM) and the mineral matrix were detected based on a locally-adaptive segmentation method. We proposed an indicator based on the morphology of the soil micro-structure to predict the N2O emissions. The indicator, IdPOM-air, relies on the hypothesis that more N2O will be emitted when POM is occluded in the soil matrix, i.e. is located at large distances from the next air-filled pore, most likely leading to anoxic conditions, favorable to the production of N2O. We computed IdPOM-air as the average value of the geodesic distances from the surface of every POM to the closest air-filled pore. For each of the 7 days of measurements IdPOM-air showed a linear trend (each day with an r2>0.75) with respect to the N2O emissions, indicating that the spatial distributions of the POM and air-filled pores were key factors to determine the N2O emissions in our soil cores.

Surface plasmon resonance tunable gold nanostar synthesis in a symmetric flow-focusing droplet device

Gold nanomaterials are known for their unique optical properties due to their localized surface plasmon resonance (LSPR). Controllable gold nanomaterials synthesis to tune LSPR of specific application demands is of great interest in the scientific community and is technically challenging to achieve in a conventional batch reactor. In this work, we tailored LSPR tunable gold nanostars (Au NS) using a symmetric flow-focusing droplet device after optimizing the flow parameters in 2D simulations. Simulations were used to represent the fluid interface within the device microchannels and helped to study the droplet evolution and their quantification. As nanomaterials synthesis in a droplet device demands the production of homogenous droplets and control over their size and production rate, we optimized the flow parameters from the simulation. By incorporating curved, sinusoidal geometries and semi-spiral microchannels, the mixing of reagents inside the droplet was improved for synthesizing heavily branched Au NS. The best performance was achieved when the flow rate of the shaping reagent was twice that of other reagents. As-synthesized Au NS are non-toxic, uniform and possess a small core diameter, large tip-to-tip length, negative surface zeta potential and red-shifted LSPR. These features are highly favourable for photothermal and photodynamic applications. Thus, our microfluidic platform can produce uniform droplets that provide sufficient mixing of reagents for the application-specific LSPR tunable synthesis of gold nanostars.

Neutronics simulation of China Experimental Fast Reactor start-up tests using FARCOB and ERANOS 2.1 code systems

The neutronics analysis of selected start-up tests conducted from 2010 to 2011 in China Experimental Fast Reactor (CEFR) is carried out using in-house FARCOB and European ERANOS-2.1 code systems as a part of IAEA coordinated research project (CRP) on “Neutronics Benchmark of CEFR Start-Up Tests”. This exercise has the main objective of validation and verification of physical models, neutronics simulation methodology including cross-section libraries that is used for fast reactor core simulations. It is challenging to simulate such a small compact core of enriched uranium with high neutron leakage having stainless steel radial reflector by using 3-D diffusion theory codes. This benchmark analysis used a new simplified approach such as a 3-step method and experimental method for simulating temperature and sodium void reactivity coefficients. Net criticality, control rod worth, temperature and sodium void reactivity coefficients and swap reactivity could be predicted well within their measured error values. This exercise provided an additional validation of the FARCOB system against small sodium-cooled fast reactor (SFR) cores, and it can be confidently used for the design and analysis of small experimental reactor cores.

Plant-frugivore network simplification under habitat fragmentation leaves a small core of interacting generalists

Habitat fragmentation impacts seed dispersal processes that are important in maintaining biodiversity and ecosystem functioning. However, it is still unclear how habitat fragmentation affects frugivorous interactions due to the lack of high-quality data on plant-frugivore networks. Here we recorded 10,117 plant-frugivore interactions from 22 reservoir islands and six nearby mainland sites using the technology of arboreal camera trapping to assess the effects of island area and isolation on the diversity, structure, and stability of plant-frugivore networks. We found that network simplification under habitat fragmentation reduces the number of interactions involving specialized species and large-bodied frugivores. Small islands had more connected, less modular, and more nested networks that consisted mainly of small-bodied birds and abundant plants, as well as showed evidence of interaction release (i.e., dietary expansion of frugivores). Our results reveal the importance of preserving large forest remnants to support plant-frugivore interaction diversity and forest functionality.

Prepared core technology from the Early Pleistocene site of Nyabusosi 18, Uganda

The site of Nyabusosi 18 (NY18), Uganda, is among the westernmost Early Pleistocene archaeological occurrences in the Rift Valley. The site is dated by tephrochronology to c. 1.5 Ma and was initially attributed to the Oldowan techno-complex. The lithic assemblage is mainly composed of small flakes and cores with very few retouched pieces and vein quartz is the dominant raw material. However, it is accepted that NY18 displayed an important quantity of “prepared cores”. After providing the current definition of Prepared Core Technology (PCT), we present a detailed methodology combining qualitative and quantitative analyses. Qualitative technology is based on diacritical sketches and knappers’ gesture analysis whereas quantitative approach relies on the univariate and multivariate analyses of morphometrical patterns of the PCT remains. The results show that several concepts such as bifaciality, surface hierarchy and recurrence characterize the PCT at NY18. However, the intensity of the core blank preparation is highly variable and the “guiding-arrises” from the flaking surfaces are poorly used. This appears to impact on the PCT flakes morphology. The PCT flakes are particularly thin in profile view when compared with other flakes from NY18. However, we argue that their outline and elongation is uncontrolled. We revise the previous affiliation of NY18 to the Oldowan and we discuss PCT in the context of the Early Pleistocene, a threshold period for the evolution of human technologies. We suggest that PCTs are Early Pleistocene technical inventions sub-contemporaneous with other major technical changes in Africa, such as large flake production and bifacial shaping that mark the emergence and development of the Acheulean from 1.7 Ma.

Prevalence and factors associated with sarcopenia in a cohort of patients with chronic pancreatitis

The neutronics analysis of selected start-up tests conducted from 2010 to 2011 in China Experimental Fast Reactor (CEFR) is carried out using in-house FARCOB and European ERANOS-2.1 code systems as a part of IAEA coordinated research project (CRP) on “Neutronics Benchmark of CEFR Start-Up Tests”. This exercise has the main objective of validation and verification of physical models, neutronics simulation methodology including cross-section libraries that is used for fast reactor core simulations. It is challenging to simulate such a small compact core of enriched uranium with high neutron leakage having stainless steel radial reflector by using 3-D diffusion theory codes. This benchmark analysis used a new simplified approach such as a 3-step method and experimental method for simulating temperature and sodium void reactivity coefficients. Net criticality, control rod worth, temperature and sodium void reactivity coefficients and swap reactivity could be predicted well within their measured error values. This exercise provided an additional validation of the FARCOB system against small sodium-cooled fast reactor (SFR) cores, and it can be confidently used for the design and analysis of small experimental reactor cores.

Cell Block or Small Core Biopsy can Provide Sufficient Material for Diagnosis and Assessment of ER, PR, and KI-67 in Patients with Metastatic Breast Cancer in the Era of Precision Medicine

Cell Block or Small Core Biopsy can Provide Sufficient Material for Diagnosis and Assessment of ER, PR, and KI-67 in Patients with Metastatic Breast Cancer in the Era of Precision Medicine

Small Core Needle Biopsies with FNA – A Case for Cytopathologist Management: Practice Data from a Large Academic Institution

Small Core Needle Biopsies with FNA – A Case for Cytopathologist Management: Practice Data from a Large Academic Institution

Deep residual neural-network-based robot joint fault diagnosis method

A data driven method-based robot joint fault diagnosis method using deep residual neural network (DRNN) is proposed, where Resnet-based fault diagnosis method is introduced. The proposed method mainly deals with kinds of fault types, such as gain error, offset error and malfunction for both sensors and actuators, respectively. First, a deep residual network fault diagnosis model is derived by stacking small convolution cores and increasing the core size. meanwhile, the gaussian white noise is injected into the fault data set to verify the noise immunity for the proposed deep residual network. Furthermore, a simulation is conducted, where different fault diagnosis methods including support vector machine (SVM), artificial neural network (ANN), convolutional neural network (CNN), long-term memory network (LTMN) and deep residual neural network (DRNN) are compared, and the simulation results show the accuracy of fault diagnosis for robot system using DRNN is higher, meanwhile, DRNN needs less model training time. Visualization analysis proved the feasibility and effectiveness of the proposed method for robot joint sensor and actuator fault diagnosis using DRNN method.

The development of the combined fission matrix method in small advanced reactor design and optimization

The Monte Carlo neutron transport method is widely used in small advanced reactor core designs and optimizations but with a high computational cost. As an efficient and accurate neutron transport method, the combined fission matrix method is promising in small reactor design and optimization. However, it cannot well predict the strong reflector impact on the fission matrix in small reactors. A predictor–corrector correction ratio method is proposed in this work to solve the problem. The method will be validated in the Holos and Simons transportable small reactors. Compared to the Monte Carlo result, the combined fission matrix method has a 36 pcm keff error with 1.7% 2D RMSE in the Holos core and 9 pcm keff error with 0.3% 2D RMSE in the Simons core. With a similar accuracy, the combined fission matrix method is much faster than the Monte Carlo method.

Evaluation of an Oxygen-Reduced Air Flooding Plugging System and Its Injection Method in the Honghe Oilfield

Oil recovery in a pilot test of gas flooding in the Honghe oilfield was greatly affected by the presence of fractures of various scales and the limited effect of a single plugging system. To elucidate the gas channeling behavior and identify the optimal injection method of oxygen-reduced air flooding in fractured tight oil reservoirs, foam and gel systems were selected to plug small and large fractures, respectively. Various methods of injecting oxygen-reduced air were studied through parallel core flooding tests to compare the gas channeling characteristics and changes in oil recovery during different plugging and displacement processes. Experimental methods including Waring blender, scanning electron microscopy, temperature resistance evaluation, and plugging performance and core flow evaluation were used in this study. The experimental results showed that the optimized FC-2 foam had the best foaming ability and half-life for the gas/liquid ratio of 1:1 and the mass fraction of 0.3%. In addition, the prepared gel had a complex and dense three-dimensional network structure, and the plugging rate was 98.17%. Finally, a displacement experiment showed that the combination of water, gel, FC-2 foam plugging system, and 5% oxygen-reduced air had the best plugging effect and gave the highest oil recovery. Compared with injecting oxygen-reduced air only, oil recovery from the small fracture core, large fracture core, and parallel core were improved by 19.71, 14.66, and 17.53%, respectively.

Development and dual validation on a transient inspired by KRUSTY of the sNDM diffusion method for easy, MC-based, core analysis

Successfully validated on a typical CANDU LOCA and fruitfully applied to safety assessment studies of high conversion water-cooled cores, the Nodal Drift Method (NDM) has recently been generalized. The so-called “super NDM” (sNDM) methodological product offers an even simpler way to core analysis, basically by feeding the diffusion approximation with specific adjustments from Monte Carlo calculations. The test case chosen for validation has been inspired by the KRUSTY experiment of a fast small UMo core driven by its radial BeO reflector, and is defined by a MCNP model of a few cells. The selected heat-up transient consists in a slow reactivity insertion, from nominal steady-state, of 120 pcm in 600 s. Fuel power and average temperature increase from about 2200 W and 1000 K up to 2500 W and 1100 K at the new equilibrium reached one hour later. Using an axisymmetric structured mesh, large nodal volumes and appropriate MCNP tallies, sNDM manages to reproduce the exact same initial equilibrium as its Monte Carlo reference. Lightly completed for reactivity insertion and thermal feedback, sNDM is doubly validated by comparison to both known-valid point kinetics over the whole transient and MCNP neutron balance for two remarkable states. Such a simplifying and promising approach, making full use of MC-based diffusion, is methodologically discussed. Further development effort and small core design applications are finally proposed.

Semiclassical relativistic stars

We present strong evidence that semiclassical gravity can give place to self-consistent ultracompact stars beyond the Buchdahl limit. We integrate the semiclassical equations of (spherically symmetric) stellar equilibrium for a constant-density classical fluid. The semiclassical contribution is modelled by a quantum massless scalar field in the only static vacuum state compatible with asymptotic flatness (Boulware vacuum). The Renormalized Stress-Energy Tensor (RSET) is firstly approximated by the analytic Polyakov approximation. This already reveals a crucial difference with respect to purely classical solutions: stars with compactness close to that of a black hole exhibit bounded pressures and curvatures up to a very small central core compared with the star radius. This suggests that a more refined approximation to the RSET at the core may give rise to strictly regular configurations. Following this suggestion, we prove that a minimal deformation of the Polyakov approximation inside the central core is sufficient to produce regular ultracompact stellar configurations.

Femtosecond tunable solitons up to 4.8 µm using soliton self-frequency shift in an InF3 fiber

A tunable ultrashort soliton pulse source reaching up to 4.8 µm is demonstrated based on a 2.8 µm femtosecond fiber laser coupled to a zirconium fluoride fiber amplifier followed by a small core indium fluoride fiber. This demonstration is extending by 300 nm the long wavelength limit previously reported with soliton self-frequency shift (SSFS) sources based on fluoride fibers. Our experimental and numerical investigation highlighted the spectral dynamics associated with the generation of highly redshifted pulses in the mid-infrared using SSFS enhanced by soliton fission. This study is intended at providing a better understanding of the potential and limitations of SSFS based tunable femtosecond fiber sources in the 3–5 µm spectral range.