Imbibition with swelling: Capillary rise in thin deformable porous media

The imbibition of a liquid into a thin deformable porous substrate driven by capillary suction is considered. The substrate is initially dry and has uniform porosity and thickness. Two-phase flow theory is used to describe how the liquid flows through the pore space behind the wetting front when out-of-plane deformation of the solid matrix is considered. Neglecting gravity and evaporation, standard shallow-layer scalings are used to construct a reduced model of the dynamics. The model predicts convergence to a self-similar behavior in all regions except near the wetting front, where a boundary layer arises whose structure narrows with the advance of the front. Over time, the rise height approaches the similarity scaling of t^1/2, as in the classical Washburn or BCLW law. The results are compared with a series of laboratory experiments using cellulose paper sheets, which provide qualitative agreement.Kruger Products, NSER

HiPEP Ion Optics System Evaluation Using Gridlets

Experimental measurements are presented for sub-scale ion optics systems comprised of 7 and 19 aperture pairs with geometrical features that are similar to the HiPEP ion optics system. Effects of hole diameter and grid-to-grid spacing are presented as functions of applied voltage and beamlet current. Recommendations are made for the beamlet current range where the ion optics system can be safely operated without experiencing direct impingement of high energy ions on the accelerator grid surface. Measurements are also presented of the accelerator grid voltage where beam plasma electrons backstream through the ion optics system. Results of numerical simulations obtained with the ffx code are compared to both the impingement limit and backstreaming measurements. An emphasis is placed on identifying differences between measurements and simulation predictions to highlight areas where more research is needed. Relatively large effects are observed in simulations when the discharge chamber plasma properties and ion optics geometry are varied. Parameters investigated using simulations include the applied voltages, grid spacing, hole-to-hole spacing, doubles-to-singles ratio, plasma potential, and electron temperature; and estimates are provided for the sensitivity of impingement limits on these parameters

Atypical plug formation in internal elastoviscoplastic fluid flows over a non-smooth topology

An experimental and computational investigation of the internal flow of elastoviscoplastic fluids over non-smooth topologies is presented in two complimentary studies. In the first study, we visualize the creeping flow of a Carbopol gel over a cavity embedded in a thin slot using Optical Coherence Tomography (OCT) and confocal microscopy. We measure the size and shape of the plug as a function of Bingham and Weissenberg numbers. An asymmetry in the plug shape is observed which is also evident in our second study -- numerical simulations using adaptive finite element method based upon an augmented Lagrangian scheme. We quantify the asymmetry and present the results as a function of the product of the Weissenberg and Bingham numbers which collapse onto a single curve for each of these geometries. These findings underscore the theoretical underpinnings of the synergy between elasticity and plasticity of these complex fluids

Frontal Asymmetry Changes Following Passive Hypo-Hydration

INTRODUCTION: Universal fluid consumption prescriptions among both athletic and non-athletic populations continue to elicit both hypo- and hyper-hydration (hypo-natremia). Thus, the need to find novel, identifiable traits within individuals who may be at higher risk to experience hypo-hydration, as well as hypo-natremia, is warranted. Of interest here, behavior is encapsulated by two motivational systems, referred to as approach/reward (R) or avoidance/non-reward (NR), respectively, in response to a behavioral stimulus. Past literature has revealed individual differences in consumptive traits of various types of foods between these motivational systems. Therefore, the purpose of this study was to evaluate changes in R/NR via frontal asymmetry (FA) in response to water exposure during eu-hydrated and hypo-hydrated conditions. METHODS: Participants included 11 active college-aged males. Electroencephalogram (EEG) assessed motivational orientations to water exposure in both eu-hydrated and hypo-hydrated states. A 5-minute nature video was used to stabilize mood, followed by 2 minutes of resting EEG recordings. Then, FA was assessed with the presentation of a glass of ice water, with instructions to observe, but not consume for 3 minutes. FA was re-assessed in the same manner following a dehydration trial (~90 minutes). Dehydration trials were performed in a controlled hot water bath at a mean of 39°C. Participants remained in the bath until 2% body mass loss, with no fluids consumed during the trials. Urine voids were collected before and after trials to assess specific gravity and color. Body core temperature was monitored throughout the protocol, with \u3e38.7°C set as criteria for removal of the subject. Participants reported perceptual affective measures using Feeling Scale (FS) and Felt Arousal Scale (FAS) throughout the session to account for any unusual affective states. RESULTS: EEG recordings were applied to the Frontal Asymmetry Index (FAI) (log right alpha power minus log left alpha power). Higher scores on the FAI indicate higher relative left frontal lobe activity, corresponding with an affinity to the water (R). Where as a lower score indicates higher relative right frontal activity, thus less reward motivation (NR). Data revealed that FAI decreased by a mean of 0.055 ±0.193 from eu-hydrated to hypo-hydrated states, with eu-hydration and hypo-hydration FAI of 0.06 and 0.004 respectively. In total, 37.4% of participants showed an increased affinity(R) for water from eu-hydrated to hypo-hydrated states. Pre and post FS were 2.91 ±1.51 and .45 ±2.88, respectively. Pre and post FAS were 2.73 ±.91 and 2.73 ±1.49. DISCUSSION: Reward/non-reward motivational orientations (affinity to water) changes were less than anticipated following hypo-hydration trials. However, data revealed that 37.4% of participants exhibited an increased affinity for water according to the FAI scale, supporting the hypothesis. It is possible that 2% body mass loss is insufficient to create distinct motivational orientation changes within the present sample. Due to the small sample size of the current study, little can be concluded thus far. Additional research addressing the aforementioned methods, as well as larger sample sizes is warranted. If motivational orientation state variability can be established during eu-hydrated and hypo-hydrated states, it may be possible to identify the consumptive tendencies of fluids among individuals

Resonant electron transmission through a finite quantum spin chain

Electron transport in a finite one dimensional quantum spin chain (with ferromagnetic exchange) is studied within an $s-d$ exchange Hamiltonian. Spin transfer coefficients strongly depend on the sign of the $s-d$ exchange constant. For a ferromagnetic coupling, they exhibit a novel resonant pattern, reflecting the salient features of the combined electron-spin system. Spin-flip processes are inelastic and feasible at finite voltage or at finite temperature.Comment: 4 pages including 4 .eps figure

Magmatic and tectonic extension at the Chile Ridge: Evidence for mantle controls on ridge segmentation

We use data from an extensive multibeam bathymetry survey of the Chile Ridge to study tectonomagmatic processes at the ridge axis. Specifically, we investigate how abyssal hills evolve from axial faults, how variations in magmatic extension influence morphology and faulting along the spreading axis, and how these variations correlate with ridge segmentation. The bathymetry data are used to estimate the fraction of plate separation accommodated by normal faulting, and the remaining fraction of extension, M, is attributed primarily to magmatic accretion. Results show that M ranges from 0.85 to 0.96, systematically increasing from first-order and second-order ridge segment offsets toward segment centers as the depth of ridge axis shoals relative to the flanking highs of the axial valley. Fault spacing, however, does not correlate with ridge geometry, morphology, or M along the Chile Ridge, which suggests the observed increase in tectonic strain toward segment ends is achieved through increased slip on approximately equally spaced faults. Variations in M along the segments follow variations in petrologic indicators of mantle melt fraction, both showing a preferred length scale of 50620 km that persists even along much longer ridge segments. In comparison, mean M and axial relief fail to show significant correlations with distance offsetting the segments. These two findings suggest a form of magmatic segmentation that is partially decoupled from the geometry of the plate boundary. We hypothesize this magmatic segmentation arises from cells of buoyantly upwelling mantle that influence tectonic segmentation from the mantle, up

Recombination Line vs. Forbidden Line Abundances in Planetary Nebulae

Recombination lines (RLs) of C II, N II, and O II in planetary nebulae (PNs) have been found to give abundances that are much larger in some cases than abundances from collisionally-excited forbidden lines (CELs). The origins of this abundance discrepancy are highly debated. We present new spectroscopic observations of O II and C II recombination lines for six planetary nebulae. With these data we compare the abundances derived from the optical recombination lines with those determined from collisionally-excited lines. Combining our new data with published results on RLs in other PNs, we examine the discrepancy in abundances derived from RLs and CELs. We find that there is a wide range in the measured abundance discrepancy Delta(O+2) = log O+2(RL) - log O+2(CEL), ranging from approximately 0.1 dex up to 1.4 dex. Most RLs yield similar abundances, with the notable exception of O II multiplet V15, known to arise primarily from dielectronic recombination, which gives abundances averaging 0.6 dex higher than other O II RLs. We compare Delta(O+2) against a variety of physical properties of the PNs to look for clues as to the mechanism responsible for the abundance discrepancy. The strongest correlations are found with the nebula diameter and the Balmer surface brightness. An inverse correlation of Delta(O+2) with nebular density is also seen. Similar results are found for carbon in comparing C II RL abundances with ultraviolet measurements of C III].Comment: 48 pages, 14 figures, accepted for publication in the Astrophysical Journal Supplemen

An Adaptive Optics Survey of Stellar Variability at the Galactic Center

We present a $\approx 11.5$ year adaptive optics (AO) study of stellar variability and search for eclipsing binaries in the central $\sim 0.4$ pc ($\sim 10''$) of the Milky Way nuclear star cluster. We measure the photometry of 563 stars using the Keck II NIRC2 imager ($K'$-band, $\lambda_0 = 2.124 \text{ } \mu \text{m}$). We achieve a photometric uncertainty floor of $\Delta m_{K'} \sim 0.03$ ($\approx 3\%$), comparable to the highest precision achieved in other AO studies. Approximately half of our sample ($50 \pm 2 \%$) shows variability. $52 \pm 5\%$ of known early-type young stars and $43 \pm 4 \%$ of known late-type giants are variable. These variability fractions are higher than those of other young, massive star populations or late-type giants in globular clusters, and can be largely explained by two factors. First, our experiment time baseline is sensitive to long-term intrinsic stellar variability. Second, the proper motion of stars behind spatial inhomogeneities in the foreground extinction screen can lead to variability. We recover the two known Galactic center eclipsing binary systems: IRS 16SW and S4-258 (E60). We constrain the Galactic center eclipsing binary fraction of known early-type stars to be at least $2.4 \pm 1.7\%$. We find no evidence of an eclipsing binary among the young S-stars nor among the young stellar disk members. These results are consistent with the local OB eclipsing binary fraction. We identify a new periodic variable, S2-36, with a 39.43 day period. Further observations are necessary to determine the nature of this source.Comment: 69 pages, 28 figures, 12 tables. Accepted for publication in The Astrophysical Journa

One-dimensional compression of a saturated elastoviscoplastic medium

A theoretical and experimental study is presented of the one-dimensional compression of a networked suspension. Particular attention is given to relatively rapid compression where we extend previous works by including an elastoviscoplastic constitutive relation. Solutions of a one-dimensional model are presented, and asymptotic limits explored, for compressions controlling either displacement or load. The results are compared to complementary laboratory experiments using cellulose fiber suspensions, with the material functions appearing in the model calibrated by independent experiments. Measurements of load and local solid velocity as a function of displacement during compression and unloading gauge the importance of elastic effects. The comparison between experiment and theory is satisfying, demonstrating a dramatic improvement over existing inelastic constitutive models in reproducing the observed differential spatial compaction