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Background In temperate regions many small mammals including bats hibernate during winter. During hibernation these small mammals occasionally wake up (arouse) to restore electrolyte and water balance. However, field data on water stress and concentration of bodily fluids during hibernation is scarce. Urinary creatinine concentration has long been used to calibrate urinary hormone concentration due to its close correlation with urine concentration. Therefore, by investigating urinary creatinine concentration, we can estimate bodily fluid concentration. In this study, we investigated changes in urinary creatinine from greater horseshoe bats (Rhinolophus ferrumequinum) hibernating in abandoned mineshafts in two regions in South Korea. Results We collected 74 urine samples from hibernating greater horseshoe bats from 2018 to 2019. We found that urinary creatinine concentration was higher in February and March and then declined in April. There were also indications of a sex difference in the pattern of change in creatinine concentration over the three months. Bats in the warmer and less humid mineshaft had higher urinary creatinine concentrations than bats in the colder and more humid mineshaft. Conclusions These results indicate that hibernating bats face water stress as urinary concentration increases during winter and that water stress may vary depending on the microenvironment. Sex differences in behaviour during hibernation may influence arousal frequency and result in sex differences in changes in urinary creatinine concentration as hibernation progresses. Although further behavioural and endocrinal investigations are needed, our study suggests that urinary creatinine concentration can be used as a proxy to estimate the hydration status of bats and the effect of sex and environmental factors on arousal patterns during hibernation.

Jade, a popular gemstone symbolizing beauty, grace, and longevity, is known to improve blood circulation, however, scientific research evidence is still lacking. The effect of black jade extract on the expression levels of apoptotic and osteogenic genes was validated using qPCR and flow cytometry. In combination with the use of a fluorescence microscope, osteogenic differentiation and the stained osteocytes count were analyzed. Under the pressure of benzo(a)pyrene, dermal cell apoptosis was accelerated and the osteogenic differentiation of adipose-derived stem cells (ASCs) was suppressed, but black jade extract counteracted the effects. Through an anti-apoptotic mechanism, the extract suppressed the expression of apoptotic proteins Bax and cytochrome C to 9 and 4.8 times, respectively, compared to that in dermal cells exposed to benzo(a)pyrene. During osteogenic differentiation of ASCs, the extract enhanced their differentiation despite being exposed to benzo(a)pyrene, and the relative levels of the osteoblast differentiation markers osteoponin, osteocalcin, and sclerostin were 1.87, 2.54, and 3.9 times higher, respectively, than those in the conditioned medium by benzo(a)pyrene. These effects of the extract indicate that black jade extract is very useful when applied as a functional biomaterial.

The objective of this study is to determine the transfer function between the heat release rate and the velocity oscillations in perforated-plate stabilized flames under different power and equivalence ratios. Previous planar flame models have been successfully extended to account for the conical flame surfaces formed downstream of the burner plate holes. The coupled effects of the heat loss to the burner plate and the flame kinematics have been modeled. The resonant peaks are determined by the burning velocity oscillations of the flame which arise as a result of the heat loss mechanism. Flame area oscillations become significant above the resonant frequency, introducing heat release rate oscillations and reducing the lag between the net heat release rate and the inlet velocity. The model results were compared to the experimental measurements, and good agreement is obtained. When the equivalence ratio is raised, the heat loss increases, the flame temperature drops, and the flame moves closer to the burner increasing the burner plate surface temperature and the resonant frequency. When the inlet velocity is raised, the area of the flame increases, causing substantial heat release rate oscillations at frequencies significantly higher than the resonant frequency.

We conducted a 7-d co-existence experiment to verify the inhibitory activity of an aquatic vascular plant,Myriophyllum spicatum, on the cyanobacteriumMicrocystis aeruginosa, and to screen for allelopathic compounds. Plants were placed on a modified solid M4 medium whileM. aeruginosa was cultured in an L16 liquid medium. Our treatments included rearingMyriophyllum spicatum alone (Plant-Only; PO) or withMicrocystis aeruginosa (Plant-Cyanobacteria; PCB), as well as an untreated control, or plates with the cyanobacterium alone. In the PCB treatment,M. aeruginosa became transparent in three replicates on the 6th day and in four replicates on Day 7. To make the distinction inMyriophyllum spicatum metabolites between the PO and PCB treatments, we obtained 13 m/z profiles using a 15 T Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Principle component analyses were performed on those profiles, from which we obtained accurate mass values for selected peaks that had most negative loadings on the first principal component and most positive loadings on the second principal component: 282.06983 and 283.06836. We identified those peaks as C7H17N5O3S2 and C10H12N4O6, respectively. The Dictionary of Natural Products database suggests that the latter is either oxanosine or xanthosine.

Highly luminescent graphene oxide (GO)-phosphor hybrid thin films with a maximum quantum yield of 9.6% were synthesized via a simple chemical method. An intense luminescence emission peak at 537 nm and a broad emission peak at 400 nm were observed from the GO-phosphor hybrid films. The maximum quantum yield of the emissions from the hybrid films was found to be 9.6%, which is 48 times higher than that of pristine GO films. The GO-phosphor hybrids were prepared via spin-coating and subsequent postannealing of the films, resulting in scrolling of the GO sheets. The resulting GO nanoscrolls exhibited a length of ∼2 μm with nanoscale interior cavities. Transmission electron microscopy and selected-area electron diffraction analyses revealed that the lattice structure of the tubular scrolls is similar to that of carbon nanotubes. While pristine GO films are p-type, in the GO-phosphor hybrids, the Fermi level shifted upward and fell between the HOMO-LUMO gap due to phosphor attachment via C-N bonding. The highly luminescent GO-phosphor hybrids will find important applications in graphene-based optoelectronic devices.

Combustion dynamics leading to thermoacoustic instability in a rearward-facing step stabilized premixed flame is experimentally examined with the objective of investigating the fluid dynamic mechanism that drives heat release rate fluctuations, and how it couples with the acoustic field. The field is probed visually, using linear photodiode arrays that capture the spatiotemporal distribution of CH* and OH*; an equivalence ratio monitor; and a number of pressure sensors. Results show resonance between the acoustic quarter wave mode of the combustion tunnel and a fluid dynamic mode of the wake. Under unstable conditions, the flame is convoluted around a large vortex that extends several step heights downstream. During a typical cycle, while the velocity is decreasing, the vortex grows, and the flame extends downstream around its outer edge. As the velocity reaches its minimum, becoming mostly negative, the vortex reaches its maximum size, and the flame collides with the upper wall; its leading edge folds, trapping reactants pockets, and its trailing edge propagates far upstream of the step. In the next phase, while the velocity is increasing, the heat release grows rapidly as trapped reactant’ pockets are consumed by flames converging towards their centers, and the upstream flame is dislodged back downstream. The heat release rate reaches its maximum halfway into the velocity rise period, leading the maximum velocity by about 90°. In this quarter-wave mode, the pressure leads the velocity by 90° as well, that is, it is in phase with the heat release rate. Numerical modeling results support this mechanism. Equivalence ratio contribution to the instability mechanism is shown to be minor, i.e., heat release dynamics are governed by the cyclical formation of the wake vortex and its interaction with the flame.

We experimentally study lean premixed combustion stabilized behind a backward-facing step. For a propane–air mixture, the lean blowout limit is associated with strong pressure fluctuation arising simultaneously with strong flame–vortex interactions, which have been shown to constitute the mechanism of heat release dynamics in this flow. A high-speed air jet, issuing from a small slot and injected perpendicular to the main flow near the step, is used to disrupt this mechanism. For momentum ratio of jet to main flow below unity, the jet dilutes the mixture, further destabilizing the flame or leading to complete blowout. Above unity, the flame becomes more stable, and the pressure oscillations are suppressed. Flow visualization and OH*/CH* chemiluminescence measurements show that a strong jet produces a more compact flame that is less driven by the wake vortex, anchored closer to the step, and deflected upwards away from the lower wall of the channel. This renders the flame less vulnerable to heat loss and strong strains, which improves its stability and extends the flammability limit. Adding hydrogen to the main fuel improves the flame stability over the entire range of the air jet mass flow, with better results for momentum ratio larger than 1; H 2 pulls the flame further upstream, away from the shear zone and the unsteady vortex. NO x emission benefits from the air jet, while, with H 2 addition, NO x concentration is higher in the products as the overall burning temperature rises. However, hydrogen addition enables extending the flammability limit further by increasing air supply in the primary stream, hence achieving lower NO x . The study suggests a simpler, almost passive, multi-objective combustion control technique and indicates that hydrogen addition can be a successful in situ approach for NO x reduction.

In this study, we compare the performance of solid oxide fuel cells (SOFC) having composite Cu-based anodes but made with the following low-temperature electrolytes: samaria-doped ceria (SDC), Sr- and Mg-doped lanthanum gallate (LSGM), and scandia-stabilized zirconia (ScSZ). Performance (V-I) curves and impedance spectra were measured using H2 and n-butane fuels at 973 K. The results suggest that the use of electrolyte materials with higher ionic conductivity can lead to improved anodes for direct-utilization SOFC, although the performance of each of the cells in n-butane appears to be at least partially limited by the electrochemical oxidation reaction.

We present a heat release dynamics model which utilizes a well-stirred reactor (WSR) and one-step kinetics to describe the unsteady combustion process. The analysis incorporates the linearized mass and energy equations to describe the response of the reactor to external perturbations and is cast in the form of a first order filter. We are able to predict the phase between the mass flow rate oscillations and the resulting heat release fluctuations, as function of the operating conditions, for example, the mean equivalence ratio and mass flow rate. The model predicts a 180° sudden shift in phase between imposed flow oscillations and resulting heat release between the maximum reaction rate and the blow-out limit. We show that this phase change may trigger combustion instability as the equivalence ratio is lowered or the average mass flow rate is increased. A number of experimental investigations, in which the inlet nozzles were choked to minimize equivalence ratio oscillations, are used to corroborate this conclusion. Next, the heat release-mass flow relationship is coupled with the acoustic field and is applied to predict instability conditions in high swirl combustion. The predictions agree qualitatively with the corresponding experimental observations.

Combustion instability arises mostly due to the coupling between heat-release dynamics and system acoustics. In these cases, the acoustic field acts as the resonator, while the heat-release dynamics, induced due to the impact of pressure or flow velocity perturbations on the equivalence ratio, flame length, residence time, shear layer, etc., supplies energy to support pressure oscillations. In this paper, we discuss another mechanism in which the resonator may not be the acoustic field: instead, it is an absolutely unstable shear layer mode acting as the source of sustained oscillations; which morph as large-scale eddies at a frequency different from acoustic modes. These perturb the flame motion and provide energy to the acoustic field, acting here as an amplifier to support pressure oscillations. We present evidence for the existence of this mechanism from several experiments, in which a pressure spectral peak can not be explained using acoustic analysis of the system, but instead matches the predicted absolute instability mode of the separated shear layer, and from numerical simulations. We also examine the impact of the mean velocity and temperature distribution on the frequency and growth rate to determine the dynamics leading to an absolute instability, and show that absolutely unstable modes are likely to arise at low-equivalence ratios. In some cases, they can also be present at near-stoichiometric conditions, that is, only low- and near-unity stoichiometry can support an absolutely unstable mode. We use numerical simulation to distinguish between different unstable modes in the separating shear layer, the layer mode and the wake mode, and derive a reduced-order model for the shear-driven instability using proper orthogonal decomposition analysis. Estimates of pressure amplitudes of fluid dynamic modes, when applied as forcing functions to the acoustic field, using this analysis compare favorably with experimental data.

We report a tunable magnetoresistance (MR) behavior in suspended graphitic multilayers through point defect engineering by ion implantation. We find that ion implantation drastically changes the MR behavior: the linear positive MR in pure graphitic multilayers transforms into a negative MR after introducing significant short-range disorders (implanted boron or carbon atoms), consistent with recent non-Markovian transport theory. Our experiments suggest the important role of the non-Markovian process in the intriguing MR behavior for graphitic systems, and open a new window for understanding transport phenomena beyond the Drude-Boltzmann approach and tailoring the electronic properties of graphitic layers., Comment: 21 pages, 8 figures (including supplementary materials); http://link.aps.org/doi/10.1103/PhysRevB.83.235410

For nanoscale electrical characterization and device fabrication it is often desirable to fabricate planar metal electrodes separated by large aspect ratio gaps with interelectrode distances well below 100 nm. We demonstrate a self-aligned process to accomplish this goal using a thin Cr film as a sacrificial etch layer. The resulting gaps can be as small as 10 nm and have aspect ratios exceeding 1000, with excellent interelectrode isolation. Such Ti/Au electrodes are demonstrated on Si substrates and are used to examine a voltage-driven transition in magnetite nanostructures. This shows the utility of this fabrication approach even with relatively reactive substrates., 4 pages, 4 figures

Magnetite (Fe$_{3}$O$_{4}$), an archetypal transition metal oxide, has been used for thousands of years, from lodestones in primitive compasses[1] to a candidate material for magnetoelectronic devices.[2] In 1939 Verwey[3] found that bulk magnetite undergoes a transition at T$_{V}$ $\approx$ 120 K from a high temperature "bad metal" conducting phase to a low-temperature insulating phase. He suggested[4] that high temperature conduction is via the fluctuating and correlated valences of the octahedral iron atoms, and that the transition is the onset of charge ordering upon cooling. The Verwey transition mechanism and the question of charge ordering remain highly controversial.[5-11] Here we show that magnetite nanocrystals and single-crystal thin films exhibit an electrically driven phase transition below the Verwey temperature. The signature of this transition is the onset of sharp conductance switching in high electric fields, hysteretic in voltage. We demonstrate that this transition is not due to local heating, but instead is due to the breakdown of the correlated insulating state when driven out of equilibrium by electrical bias. We anticipate that further studies of this newly observed transition and its low-temperature conducting phase will shed light on how charge ordering and vibrational degrees of freedom determine the ground state of this important compound., Comment: 17 pages, 4 figures

Quantum transport phenomena allow experimental determinations of the phase coherence information in metals. We report quantitative comparisons of inferred coherence lengths from independent measurements of the weak localization magnetoresistance and time‐dependent universal conductance fluctuations’ magnetic field dependence. Strong agreement is observed in both quasi‐2D and quasi‐1D AuPd samples. However, quantitative agreement is not seen in quasi‐1D Ag wires below 10 K and quasi‐1D Au wires below 14 K. A possible explanation for this disagreement will be discussed. Attempts to produce changes in the coherence length in Au by annealing have also been made and results will be reported.

�� � † ‡ We study experimentally the impact of static and modulated transverse jet injected near the flame anchoring zone on the stability and emissions in a premixed backward facing step combustor. The combustor shows strong pressure oscillations at 38 Hz. Parametric studies using multiple sensors indicate that flame -vortex interactions are responsible for the heat release dynamics under unstable conditions. We demonstrate that with sufficient momentum, a static air jet injected perpendicular to the incoming flow near the step favorably modifies the flame -vortex interactions and reduces the pressure oscillations by up to 14 dB (OASPL), and the NOx emission by an order of magnitude. Adding small amount of hydrogen to the primary fuel further reduces the pressu re oscillations. We also investigate the impact of the transverse jet modulation. Result shows that one can reduce the amount of air necessary for stabilization by 50% from the static case by using closed -loop control and jet modulation.