Microscopic treatment of a barrel drop on fibers and nanofibers.

PubMed

Berim, Gersh O; Ruckenstein, Eli

2005-06-15

The microscopic approach of Berim and Ruckenstein (J. Phys. Chem. B 108 (2004) 19330, 19339) regarding the shape and stability of a liquid drop on a planar bare solid surface is extended to a liquid barrel drop on the bare surface of a solid cylinder (fiber) of arbitrary radius. Assuming the interaction potentials of the liquid molecules between themselves and with the molecules of the solid of the London-van der Waals form, the potential energy of a liquid molecule with an infinitely long fiber was calculated analytically. A differential equation for the drop profile was derived by the variational minimization of the total potential energy of the drop by taking into account the structuring of the liquid near the fiber. This equation was solved in quadrature and the shape and stability of the barrel drop were analyzed as functions of the radius of the fiber and the microscopic contact angle theta(0) which the drop profile makes with the surface of the fiber. The latter angle is dependent on the fiber radius and on the microscopic parameters of the model (strength of the intermolecular interactions, densities of the liquid and solid phases, hard core radii, etc.). Expressions for the evaluation of the microcontact angle from experimentally measurable characteristics of the drop profile (height, length, volume, location of inflection point) are obtained. All drop characteristics, such as stability, shape, are functions of theta(0) and a certain parameter a which depends on the model parameters. In particular, the range of drop stability consists of three domains in the plane theta(0)-a, separated by two critical curves a=a(c)(theta(0)) and a=a(c1)(theta(0)) [a(c)(theta(0))h(m1) cannot exist, whereas in the third domain (between those curves) the drop can have values of h(m) either smaller than h(m1) or larger than h(m2), where h(m2)>h(m1) is a second critical height. For sufficiently large fiber radii, R(f)1 >/= microm, the critical curves almost coincide and only two domains, the first and the second, remain. The smaller the radius, the larger is the difference between the critical curves and the larger is the second domain of drop stability. The shape of the drop depends on whether the point (theta(0),a) on the theta(0)-a plane is far from the critical curve or near it. In the first case the drop profile has generally a large circular part, while in the second case the shape is either almost planar or contains a long manchon that is similar to a film on the fiber.

Oxidation-Reduction Potential of Saturated Forest Soils

Treesearch

F. T. Bonner; C. W. Ralston

1968-01-01

Large decreases in redox potentials of saturated soil over a 25-day incubation period were favored by high temperature and the addition of sucrose, loblolly pine needles (Pinus taeda L. ), or yellow-poplar leaves (Liriodendron tulipifera L.). The addition of a complete nutrient solution had no effect in soils incubated with sucrose, but it reduced the drop in potential...

Ground-states for the liquid drop and TFDW models with long-range attraction

NASA Astrophysics Data System (ADS)

Alama, Stan; Bronsard, Lia; Choksi, Rustum; Topaloglu, Ihsan

2017-10-01

We prove that both the liquid drop model in R 3 with an attractive background nucleus and the Thomas-Fermi-Dirac-von Weizsäcker (TFDW) model attain their ground-states for all masses as long as the external potential V(x) in these models is of long range, that is, it decays slower than Newtonian (e.g., V ( x ) ≫ | x | - 1 for large |x|.) For the TFDW model, we adapt classical concentration-compactness arguments by Lions, whereas for the liquid drop model with background attraction, we utilize a recent compactness result for sets of finite perimeter by Frank and Lieb.

Comparison of actual and seismologically inferred stress drops in dynamic models of microseismicity

NASA Astrophysics Data System (ADS)

Lin, Y. Y.; Lapusta, N.

2017-12-01

Estimating source parameters for small earthquakes is commonly based on either Brune or Madariaga source models. These models assume circular rupture that starts from the center of a fault and spreads axisymmetrically with a constant rupture speed. The resulting stress drops are moment-independent, with large scatter. However, more complex source behaviors are commonly discovered by finite-fault inversions for both large and small earthquakes, including directivity, heterogeneous slip, and non-circular shapes. Recent studies (Noda, Lapusta, and Kanamori, GJI, 2013; Kaneko and Shearer, GJI, 2014; JGR, 2015) have shown that slip heterogeneity and directivity can result in large discrepancies between the actual and estimated stress drops. We explore the relation between the actual and seismologically estimated stress drops for several types of numerically produced microearthquakes. For example, an asperity-type circular fault patch with increasing normal stress towards the middle of the patch, surrounded by a creeping region, is a potentially common microseismicity source. In such models, a number of events rupture the portion of the patch near its circumference, producing ring-like ruptures, before a patch-spanning event occurs. We calculate the far-field synthetic waveforms for our simulated sources and estimate their spectral properties. The distribution of corner frequencies over the focal sphere is markedly different for the ring-like sources compared to the Madariaga model. Furthermore, most waveforms for the ring-like sources are better fitted by a high-frequency fall-off rate different from the commonly assumed value of 2 (from the so-called omega-squared model), with the average value over the focal sphere being 1.5. The application of Brune- or Madariaga-type analysis to these sources results in the stress drops estimates different from the actual stress drops by a factor of up to 125 in the models we considered. We will report on our current studies of other types of seismic sources, such as repeating earthquakes and foreshock-like events, and whether the potentially realistic and common sources different from the standard Brune and Madariaga models can be identified from their focal spectral signatures and studied using a more tailored seismological analysis.

A parallel interaction potential approach coupled with the immersed boundary method for fully resolved simulations of deformable interfaces and membranes

NASA Astrophysics Data System (ADS)

Spandan, Vamsi; Meschini, Valentina; Ostilla-Mónico, Rodolfo; Lohse, Detlef; Querzoli, Giorgio; de Tullio, Marco D.; Verzicco, Roberto

2017-11-01

In this paper we show and discuss how the deformation dynamics of closed liquid-liquid interfaces (for example drops and bubbles) can be replicated with use of a phenomenological interaction potential model. This new approach to simulate liquid-liquid interfaces is based on the fundamental principle of minimum potential energy where the total potential energy depends on the extent of deformation of a spring network distributed on the surface of the immersed drop or bubble. Simulating liquid-liquid interfaces using this model require computing ad-hoc elastic constants which is done through a reverse-engineered approach. The results from our simulations agree very well with previous studies on the deformation of drops in standard flow configurations such as a deforming drop in a shear flow or cross flow. The interaction potential model is highly versatile, computationally efficient and can be easily incorporated into generic single phase fluid solvers to also simulate complex fluid-structure interaction problems. This is shown by simulating flow in the left ventricle of the heart with mechanical and natural mitral valves where the imposed flow, motion of ventricle and valves dynamically govern the behaviour of each other. Results from these simulations are compared with ad-hoc in-house experimental measurements. Finally, we present a simple and easy to implement parallelisation scheme, as high performance computing is unavoidable when studying large scale problems involving several thousands of simultaneously deforming bodies in highly turbulent flows.

Plasma dynamics on current-carrying magnetic flux tubes

NASA Technical Reports Server (NTRS)

Swift, Daniel W.

1992-01-01

A 1D numerical simulation is used to investigate the evolution of a plasma in a current-carrying magnetic flux tube of variable cross section. A large potential difference, parallel to the magnetic field, is applied across the domain. The result is that density minimum tends to deepen, primarily in the cathode end, and the entire potential drop becomes concentrated across the region of density minimum. The evolution of the simulation shows some sensitivity to particle boundary conditions, but the simulations inevitably evolve into a final state with a nearly stationary double layer near the cathode end. The simulation results are at sufficient variance with observations that it appears unlikely that auroral electrons can be explained by a simple process of acceleration through a field-aligned potential drop.

Determination of Interfacial Rheological Properties through Microgravity Oscillations of Bubbles and Drops

NASA Technical Reports Server (NTRS)

Nadim, Ali; Rush, Brian M.

2000-01-01

This report summarizes our derivations of analytical expressions for the frequencies and damping constants for small-amplitude axisymmetric shape oscillations of a liquid drop suspended in an immiscible fluid host in microgravity. In particular, this work addresses large Reynolds number shape oscillations and focuses on the surface rheological effects that arise from the presence of insoluble surfactants at the interface. Parameters characterizing viscous effects from the bulk phases, surface viscous effects, Marangoni effects from the surface advection and diffusion of surfactants, and the Gibbs elasticity are all considered and analyzed to determine the relative importance of each contribution. Supplementing the analytical treatment for small-amplitude oscillations, a numerical boundary integral equation formulation is developed for the study of large-amplittide axisymmetric oscillations of a drop in vacuum. The boundary integral formulation is an extension of classical potential flow theory and approximately accounts for viscous effects in the bulk fluid as well as the surface viscous and Marangoni effects resulting from an insoluble surfactant contaminating the interface. Theoretical and numerical results are presented for four distinct cases. These, range from the case when the effects of the surfactants are 'negligible' to 'large' when compared to the viscous effects in the bulk phases. The feasibility of the non-contact measurement of the surface parameters, using experimental observations for the oscillation frequencies and damping constants of drops and bubbles, is discussed.

Large charged drop levitation against gravity

NASA Technical Reports Server (NTRS)

Rhim, Won-Kyu; Chung, Sang Kun; Hyson, Michael T.; Trinh, Eugene H.; Elleman, Daniel D.

1987-01-01

A hybrid electrostatic-acoustic levitator that can levitate and manipulate a large liquid drop in one gravity is presented. To the authors' knowledge, this is the first time such large drops (up to 4 mm in diameter in the case of water) have been levitated against 1-gravity. This makes possible, for the first time, many new experiments both in space and in ground-based laboratories, such as 1)supercooling and superheating, 2) containerless crystal growth from various salt solutions or melts, 3) drop dynamics of oscillating or rotating liquid drops, 4) drop evaporation and Rayleigh bursting, and 5) containerless material processing in space. The digital control system, liquid drop launch process, principles of electrode design, and design of a multipurpose room temperature levitation chamber are described. Preliminary results that demonstrate drop oscillation and rotation, and crystal growth from supersaturated salt solutions are presented.

Small-Scale Drop-Size Variability: Empirical Models for Drop-Size-Dependent Clustering in Clouds

NASA Technical Reports Server (NTRS)

Marshak, Alexander; Knyazikhin, Yuri; Larsen, Michael L.; Wiscombe, Warren J.

2005-01-01

By analyzing aircraft measurements of individual drop sizes in clouds, it has been shown in a companion paper that the probability of finding a drop of radius r at a linear scale l decreases as l(sup D(r)), where 0 less than or equals D(r) less than or equals 1. This paper shows striking examples of the spatial distribution of large cloud drops using models that simulate the observed power laws. In contrast to currently used models that assume homogeneity and a Poisson distribution of cloud drops, these models illustrate strong drop clustering, especially with larger drops. The degree of clustering is determined by the observed exponents D(r). The strong clustering of large drops arises naturally from the observed power-law statistics. This clustering has vital consequences for rain physics, including how fast rain can form. For radiative transfer theory, clustering of large drops enhances their impact on the cloud optical path. The clustering phenomenon also helps explain why remotely sensed cloud drop size is generally larger than that measured in situ.

Spatial Distribution of Large Cloud Drops

NASA Technical Reports Server (NTRS)

Marshak, A.; Knyazikhin, Y.; Larsen, M.; Wiscombe, W.

2004-01-01

By analyzing aircraft measurements of individual drop sizes in clouds, we have shown in a companion paper (Knyazikhin et al., 2004) that the probability of finding a drop of radius r at a linear scale l decreases as l(sup D(r)) where 0 less than or equal to D(r) less than or equal to 1. This paper shows striking examples of the spatial distribution of large cloud drops using models that simulate the observed power laws. In contrast to currently used models that assume homogeneity and therefore a Poisson distribution of cloud drops, these models show strong drop clustering, the more so the larger the drops. The degree of clustering is determined by the observed exponents D(r). The strong clustering of large drops arises naturally from the observed power-law statistics. This clustering has vital consequences for rain physics explaining how rain can form so fast. It also helps explain why remotely sensed cloud drop size is generally biased and why clouds absorb more sunlight than conventional radiative transfer models predict.

Hydrophobic properties of a wavy rough substrate.

PubMed

Carbone, G; Mangialardi, L

2005-01-01

The wetting/non-wetting properties of a liquid drop in contact with a chemically hydrophobic rough surface (thermodynamic contact angle theta(e)>pi/2) are studied for the case of an extremely idealized rough profile: the liquid drop is considered to lie on a simple sinusoidal profile. Depending on surface geometry and pressure values, it is found that the Cassie and Wenzel states can coexist. But if the amplitude h of the substrate is sufficiently large the only possible stable state is the Cassie one, whereas if h is below a certain critical value hcr a transition to the Wenzel state occurs. Since in many potential applications of such super-hydrophobic surfaces, liquid drops often collide with the substrate (e.g. vehicle windscreens), in the paper the critical drop pressure pW is calculated at which the Cassie state is no longer stable and the liquid jumps into full contact with the substrate (Wenzel state). By analyzing the asymptotic behavior of the systems in the limiting case of a large substrate corrugation, a simple criterion is also proposed to calculate the minimum height asperity h necessary to prevent the Wenzel state from being formed, to preserve the super-hydrophobic properties of the substrate, and, hence, to design a robust super-hydrophobic surface.

Comparison of the safety and protective efficacy of vaccination with glycoprotein-G-deficient infectious laryngotracheitis virus delivered via eye-drop, drinking water or aerosol.

PubMed

Devlin, J M; Browning, G F; Gilkerson, J R; Fenton, S P; Hartley, C A

2008-02-01

Infectious laryngotracheitis virus (ILTV), an alphaherpesvirus, causes respiratory disease in chickens and is commonly controlled by vaccination with conventionally attenuated virus strains. These vaccines have limitations due to residual pathogenicity and reversion to virulence. To avoid these problems and to better control disease, attention has recently turned towards developing a novel vaccine strain that lacks virulence gene(s). Glycoprotein G (gG) is a virulence factor in ILTV. A gG-deficient strain of ILTV has been shown to be less pathogenic than currently available vaccine strains following intratracheal inoculation of specific pathogen free chickens. Intratracheal inoculation of gG-deficient ILTV has also been shown to induce protection against disease following challenge with virulent virus. Intratracheal inoculation, however, is not suitable for large-scale vaccination of commercial poultry flocks. In this study, inoculation of gG-deficient ILTV via eye-drop, drinking water and aerosol were investigated. Aerosol inoculation resulted in undesirably low levels of safety and protective efficacy. Inoculation via eye-drop and drinking water was safe, and the levels of protective efficacy were comparable with intratracheal inoculation. Thus, gG-deficient ILTV appears to have potential for use in large-scale poultry vaccination programmes when administered via eye-drop or in drinking water.

Ion distribution effects of turbulence on a kinetic auroral arc model

NASA Technical Reports Server (NTRS)

Cornwall, J. M.; Chiu, Y. T.

1982-01-01

An inverted-V auroral arc structure plasma-kinetic model is extended to phenomenologically include the effects of electrostatic turbulence, with k-parallel/k-perpendicular being much less than unity. It is shown that, unless plasma sheet ions are very much more energetic than the electrons, anomalous resistivity is not a large contributor to parallel electrostatic potential drops, since the support of the observed potential drop requires a greater dissipation of energy than can be provided by the plasma sheet. Wave turbulence can, however, be present, with the ion cyclotron turbulence levels suggested by the ion resonance broadening saturation mechanism of Dum and Dupree (1970) being comparable to those observed on auroral field lines. The diffusion coefficient and net growth rate are much smaller than estimates based solely on local plasma properties.

Thermocapillary Migration and Interactions of Bubbles and Drops

NASA Technical Reports Server (NTRS)

Subramaniam, R. Shankar; Balasubramaniam, R.; Wozniak, G.; Hadland, P. H.

1999-01-01

Experiments were performed aboard the LMS mission of the Space Shuttle in summer 1996 in the BDPU on isolated air bubbles and Fluorinert FC-75 drops as well as on interacting bubbles/drops migrating in a temperature gradient in a Dow-Corning DC-200 series silicone oil of nominal viscosity 10 centistokes. The data, recorded in the form of videotape images as well as cine images in selected runs, have been analyzed. The behavior of the isolated objects is consistent with earlier observations made aboard the IML-2 mission while the range of Reynolds and Marangoni numbers has been extended substantially over that in the IML-2 experiments. Large bubbles were found to be slightly deformed to an oblate shape while no deformation could be detected in the case of similarly large drops. Results on interacting drops and bubbles display interesting and unanticipated features. In some experiments, drops are found to follow a three-dimensional trajectory. In others, trailing drops and bubbles are found to move off the axis of the cell when migrating behind a leading drop or bubble which moves along the axis. In this type of run, if the trailing drop is sufficiently large, it is found to pass the leading drop. Finally, behavior similar to that observed in IML-2, namely that a small leading drop slows the movement of a larger trailing drop moving along the cell axis, was observed as well.

Rain Drop Charge Sensor

NASA Astrophysics Data System (ADS)

S, Sreekanth T.

begin{center} Large Large Rain Drop Charge Sensor Sreekanth T S*, Suby Symon*, G. Mohan Kumar (1) , S. Murali Das (2) *Atmospheric Sciences Division, Centre for Earth Science Studies, Thiruvananthapuram 695011 (1) D-330, Swathi Nagar, West Fort, Thiruvananthapuram 695023 (2) Kavyam, Manacaud, Thiruvananthapuram 695009 begin{center} ABSTRACT To study the inter-relations with precipitation electricity and precipitation microphysical parameters a rain drop charge sensor was designed and developed at CESS Electronics & Instrumentation Laboratory. Simultaneous measurement of electric charge and fall speed of rain drops could be done using this charge sensor. A cylindrical metal tube (sensor tube) of 30 cm length is placed inside another thick metal cover opened at top and bottom for electromagnetic shielding. Mouth of the sensor tube is exposed and bottom part is covered with metal net in the shielding cover. The instrument is designed in such a way that rain drops can pass only through unhindered inside the sensor tube. When electrically charged rain drops pass through the sensor tube, it is charged to the same magnitude of drop charge but with opposite polarity. The sensor tube is electrically connected the inverted input of a current to voltage converter operational amplifier using op-amp AD549. Since the sensor is electrically connected to the virtual ground of the op-amp, the charge flows to the ground and the generated current is converted to amplified voltage. This output voltage is recorded using a high frequency (1kHz) voltage recorder. From the recorded pulse, charge magnitude, polarity and fall speed of rain drop are calculated. From the fall speed drop diameter also can be calculated. The prototype is now under test running at CESS campus. As the magnitude of charge in rain drops is an indication of accumulated charge in clouds in lightning, this instrument has potential application in the field of risk and disaster management. By knowing the charge magnitude of initial drops from a precipitation event, gross cloud charge can be estimated and necessary precautions can be taken during convective cloud events. Being a site of high lightning incidence in tropics, Kerala state is affected in India and calls for much attention in lightning hazards mitigation. Installing this charge sensor and atmospheric electric field mill, an attempt to a better warning system can be attempted.

Levitation of a drop over a film flow

NASA Astrophysics Data System (ADS)

Sreenivas, K. R.; de, P. K.; Arakeri, Jaywant H.

1999-02-01

A vertical jet of water impinging on a horizontal surface produces a radial film flow followed by a circular hydraulic jump. We report a phenomenon where fairly large (1 ml) drops of liquid levitate just upstream of the jump on a thin air layer between the drop and the film flow. We explain the phenomenon using lubrication theory. Bearing action both in the air film and the water film seems to be necessary to support large drops. Horizontal support is given to the drop by the hydraulic jump. A variety of drop shapes is observed depending on the volume of the drop and liquid properties. We show that interaction of the forces due to gravity, surface tension, viscosity and inertia produces these various shapes.

Stick-slip behavior of Indian gabbro as studied using a NIED large-scale biaxial friction apparatus

NASA Astrophysics Data System (ADS)

Togo, Tetsuhiro; Shimamoto, Toshihiko; Yamashita, Futoshi; Fukuyama, Eiichi; Mizoguchi, Kazuo; Urata, Yumi

2015-04-01

This paper reports stick-slip behaviors of Indian gabbro as studied using a new large-scale biaxial friction apparatus, built in the National Research Institute for Earth Science and Disaster Prevention (NIED), Tsukuba, Japan. The apparatus consists of the existing shaking table as the shear-loading device up to 3,600 kN, the main frame for holding two large rectangular prismatic specimens with a sliding area of 0.75 m2 and for applying normal stresses σ n up to 1.33 MPa, and a reaction force unit holding the stationary specimen to the ground. The shaking table can produce loading rates v up to 1.0 m/s, accelerations up to 9.4 m/s2, and displacements d up to 0.44 m, using four servocontrolled actuators. We report results from eight preliminary experiments conducted with room humidity on the same gabbro specimens at v = 0.1-100 mm/s and σ n = 0.66-1.33 MPa, and with d of about 0.39 m. The peak and steady-state friction coefficients were about 0.8 and 0.6, respectively, consistent with the Byerlee friction. The axial force drop or shear stress drop during an abrupt slip is linearly proportional to the amount of displacement, and the slope of this relationship determines the stiffness of the apparatus as 1.15 × 108 N/m or 153 MPa/m for the specimens we used. This low stiffness makes fault motion very unstable and the overshooting of shear stress to a negative value was recognized in some violent stick-slip events. An abrupt slip occurred in a constant rise time of 16-18 ms despite wide variation of the stress drop, and an average velocity during an abrupt slip is linearly proportional to the stress drop. The use of a large-scale shaking table has a great potential in increasing the slip rate and total displacement in biaxial friction experiments with large specimens.

Are the Stress Drops of Small Earthquakes Good Predictors of the Stress Drops of Larger Earthquakes?

NASA Astrophysics Data System (ADS)

Hardebeck, J.

2017-12-01

Uncertainty in PSHA could be reduced through better estimates of stress drop for possible future large earthquakes. Studies of small earthquakes find spatial variability in stress drop; if large earthquakes have similar spatial patterns, their stress drops may be better predicted using the stress drops of small local events. This regionalization implies the variance with respect to the local mean stress drop may be smaller than the variance with respect to the global mean. I test this idea using the Shearer et al. (2006) stress drop catalog for M1.5-3.1 events in southern California. I apply quality control (Hauksson, 2015) and remove near-field aftershocks (Wooddell & Abrahamson, 2014). The standard deviation of the distribution of the log10 stress drop is reduced from 0.45 (factor of 3) to 0.31 (factor of 2) by normalizing each event's stress drop by the local mean. I explore whether a similar variance reduction is possible when using the Shearer catalog to predict stress drops of larger southern California events. For catalogs of moderate-sized events (e.g. Kanamori, 1993; Mayeda & Walter, 1996; Boyd, 2017), normalizing by the Shearer catalog's local mean stress drop does not reduce the standard deviation compared to the unmodified stress drops. I compile stress drops of larger events from the literature, and identify 15 M5.5-7.5 earthquakes with at least three estimates. Because of the wide range of stress drop estimates for each event, and the different techniques and assumptions, it is difficult to assign a single stress drop value to each event. Instead, I compare the distributions of stress drop estimates for pairs of events, and test whether the means of the distributions are statistically significantly different. The events divide into 3 categories: low, medium, and high stress drop, with significant differences in mean stress drop between events in the low and the high stress drop categories. I test whether the spatial patterns of the Shearer catalog stress drops can predict the categories of the 15 events. I find that they cannot, rather the large event stress drops are uncorrelated with the local mean stress drop from the Shearer catalog. These results imply that the regionalization of stress drops of small events does not extend to the larger events, at least with current standard techniques of stress drop estimation.

Self-Diffusion of Drops in a Dilute Sheared Emulsion

NASA Technical Reports Server (NTRS)

Loewenberg, Michael; Hinch, E. J.

1996-01-01

Self-diffusion coefficients that describe cross-flow migration of non-Brownian drops in a dilute sheared emulsion were obtained by trajectory calculations. A boundary integral formulation was used to describe pairwise interactions between deformable drops; interactions between undeformed drops were described with mobility functions for spherical drops. The results indicate that drops have large anisotropic self-diffusivities which depend strongly on the drop viscosity and modestly on the shear-rate. Pairwise interactions between drops in shear-flow do not appreciably promote drop breakup.

Motion of deformable drops through granular media and other confined geometries.

PubMed

Davis, Robert H; Zinchenko, Alexander Z

2009-06-15

This article features recent simulation studies of the flow of emulsions containing deformable drops through pores, constrictions, and granular media. The flow is assumed to be at low Reynolds number, so that viscous forces dominate, and boundary-integral methods are used to determine interfacial velocities and, hence, track the drop motion and shapes. A single drop in a flat channel migrates to the channel centerplane due to deformation-induced drift, which increases its steady-state velocity along the channel. A drop moving towards a smaller interparticle constriction squeezes through the constriction if the capillary number (ratio of viscous deforming forces and interfacial tension forces) is large enough, but it becomes trapped when the capillary number is below a critical value. These concepts then influence the flow of an emulsion through a granular medium, for which the drop phase moves faster than the suspending liquid at large capillary numbers but slower than the suspending liquid at smaller capillary numbers. The permeabilities of the granular medium to both phases increase with increasing capillary number, due to the reduced resistance to squeezing of easily deformed drops, though drop breakup must also be considered at large capillary numbers.

Electric breakdowns of the "plasma capacitors" occurs on insulation coating of the ISS surface

NASA Astrophysics Data System (ADS)

Homin, Taras; Korsun, Anatolii

High electric fields and currents are occurred in the spacecrafts plasma environment by onboard electric generators. Thus the high voltage solar array (SA) of the American segment of International Space Station (ISS) generates potential 160 V. Its negative pole is shorted to the frames of all the ISS segments. There is electric current between the SA and the frame through the plasma environment, i.e. electric discharge occurs. As a result a potential drop exists between the frames of all the ISS segments and the environmental plasma [1], which is cathode drop potential varphi _{c} defined. When ISS orbiting, the φc varies greatly in the range 0-100 V. A large area of the ISS frames and SA surface is coated with a thin dielectric film. Because of cathode drop potential the frame surfaces accumulate ion charges and the SA surfaces accumulate electron charges. These surfaces become plasma capacitors, which accumulate much charge and energy. Micrometeorite impacts or buildup of potential drop in excess of breakdown threshold varphi_{b} (varphi _{c} > varphi _{b} = 60 V) may cause breakdowns of these capacitors. Following a breakdown, the charge collected at the surfaces disperses and transforms into a layer of dense plasma [2]. This plasma environment of the spacecraft produces great pulsed electric fields E at the frame surfaces as well as heavy currents between construction elements which in turn induce great magnetic fields H. Therefore the conductive frame and the environmental plasma is plasma inductors. We have calculated that the densities of these pulsing and high-frequency fields E and H generated in the plasma environment of the spacecraft may exceed values hazardous to human. Besides, these fields must induce large electromagnetic impulses in the space-suit and in the power supply and control circuits of onboard systems. During astronaut’s space-suit activity, these fields will penetrate the space-suit and the human body with possible hazardous effects. These effects need to be studied, and appropriate remedies are to be developed. References 1. Mikatarian, R., et al., «Electrical Charging of the International Space Station», AIAA Paper No. 2003-1079, 41th. Aerospace Sciences Meeting and Exhibit, January 2003. 2. A.G. Korsun, «Electric discharge processes intensification mechanisms on International Space Station surface». Astronautics and rocket production, 1, 2011 (in Russian).

Comparison of polar cap potential drops estimated from solar wind and ground magnetometer data - CDAW 6

NASA Technical Reports Server (NTRS)

Reiff, P. H.; Spiro, R. W.; Wolf, R. A.; Kamide, Y.; King, J. H.

1985-01-01

It is pointed out that the maximum electrostatic potential difference across the polar cap, Phi, is a fundamental measure of the coupling between the solar wind and the earth's magnetosphere/ionosphere sytem. During the Coordinated Data Analysis Workshop (CDAW) 6 intervals, no suitably instrumented spacecraft was in an appropriate orbit to determine the polar-cap potential drop directly. However, two recently developed independent techniques make it possible to estimate the polar-cap potential drop for times when direct spacecraft data are not available. The present investigation is concerned with a comparison of cross-polar-cap potential drop estimates calculated for the two CDAW 6 intervals on the basis of these two techniques. In the case of one interval, the agreement between the potential drops and Joule heating rates is relatively good. In the second interval, however, the agreement is not very good. Explanations for this discrepancy are discussed.

Vestibular evoked myogenic potential (VEMP) in patients with Ménière's disease with drop attacks.

PubMed

Timmer, Ferdinand C A; Zhou, Guangwei; Guinan, John J; Kujawa, Sharon G; Herrmann, Barbara S; Rauch, Steven D

2006-05-01

In this retrospective study, we tested the hypothesis that vestibular evoked myogenic potential (VEMP) thresholds are more often elevated or absent in patients with Ménière's disease experiencing Tumarkin drop attacks than in other patients with Ménière's disease. Subjects included normal subjects (n = 14) and patients with unilateral Ménière's disease by AAO-HNS (1995) diagnostic criteria with (n = 12) and without (n = 82) Tumarkin drop attacks at a large specialty hospital otology service. VEMP threshold testing was conducted using 250, 500, and 1,000 Hz tone burst stimuli. VEMP responses were present in at all frequencies in both ears of all normal subjects. In unaffected ears of patients with unilateral Ménière's disease, VEMPs were undetectable in 13% of measurements attempted. This number rose to 18% in affected ears of patients with unilateral Ménière's disease and to 41% in Meniere ears with Tumarkin drop attacks. Frequency tuning of the VEMP response in normal subjects showed lowest thresholds at 500 Hz. In Meniere ears, the tuning was altered such that the 500-Hz thresholds were higher than the 1,000-Hz thresholds. There was a gradient of threshold elevation and altered tuning that corresponded to the gradient of worsening disease. Our findings support the hypothesis that Tumarkin drop attacks arise from advanced disease involving the saccule and that VEMP may be a clinically valuable metric of disease severity or progression in patients with Ménière's disease.

Large-Scale Integration of Solid-State Microfluidic Valves With No Moving Parts

DTIC Science & Technology

2005-01-01

compact and diffuse layer is called outer Helmholtz plane ( OHP ). Potential drop across the diffusion layer is called the zeta potential, ζ. As the...Gouy-Chapman model. This is shown in Fig. 3. The plane at x2 is called the outer Helmholtz plane ( OHP ). Then the total double layer capacitance Cd...Enhanced Electro-Osmotic Pumping With Liquid Bridge and Field Effect Flow Rectification, ” Presented in IEEE MEMS 2004 Conference, Maastricht, The

Motivational Factors Influencing the Persistence of Developmental Education Students at a Technical College

ERIC Educational Resources Information Center

Etienne, John

2012-01-01

A department of computer information systems at a community college in the southeastern United States was struggling to retain students, a large number of whom often dropped out within the first and second semester of enrollment. Identifying potential solutions to the retention problem is important to department leaders, faculty, and students…

49 CFR 178.965 - Drop test.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 3 2013-10-01 2013-10-01 false Drop test. 178.965 Section 178.965 Transportation... Packagings § 178.965 Drop test. (a) General. The drop test must be conducted for the qualification of all...) Special preparation for the drop test. Large Packagings must be filled in accordance with § 178.960. (c...

The influence of drop size-dependent fog chemistry on aerosol processing by San Joaquin Valley fogs

NASA Astrophysics Data System (ADS)

Hoag, Katherine J.; Collett, Jeffrey L., Jr.; Pandis, Spyros N.

Drop size-resolved measurements of fog chemistry in California's San Joaquin Valley during the 1995 Integrated Monitoring Study reveal that fog composition varies with drop size. Small fog drops were less alkaline and typically contained higher major ion (nitrate, sulfate, ammonium) concentrations than large drops. Small drops often contained higher concentrations of Fe and Mn than large drops while H 2O 2 concentrations exhibited no strong drop size dependence. Simulation of an extended fog episode in Fresno, California revealed the capability of a drop size-resolved fog chemistry model to reproduce the measured (based on two drop size categories) drop size dependence of several key species. The model was also able to satisfactorily reproduce measured species-dependent deposition rates (ammonium>sulfate>nitrate) resulting from fog drop sedimentation. Both the model simulation and direct analysis of size-resolved fog composition observations and measured gas-phase oxidant concentrations indicate the importance of ozone as an aqueous-phase S(IV) oxidant in these high pH fogs. Due to the nonlinear dependence of the rate law for the ozone pathway on the hydrogen ion concentration, use of the average fog drop composition can lead to significant underprediction of aqueous phase sulfate production rates in these chemically heterogeneous fogs.

Auroral particle acceleration: An example of a universal plasma process

NASA Astrophysics Data System (ADS)

Haerendel, G.

1980-06-01

The occurrence of discrete and narrow auroral arcs is attributed to a sudden release of magnetic tensions set up in a magnetospheric-ionospheric current circuit of high strength. At altitudes of several 1000 km the condition of frozen in magnetic fields can be broken temporarily in thin regions corresponding to the observed width of auroral arcs. This implies magnetic field-aligned potential drops of several kilovolts supported by certain anomalous transport processes which can only be maintained in a quasi-stationary fashion if the current density exceeds a critical limit. The region of field aligned potential drops is structured by two pairs of standing waves which are generalized Alfven waves of large amplitude across which the parallel electric field has a finite jump. The waves are emitted from the leading edge of the acceleration region which propagates slowly into the stressed magnetic field.

Load drop evaluation for TWRS FSAR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Julyk, L.J.; Ralston, G.L.

1996-09-30

Operational or remediation activities associated with existing underground high-level waste storage tank structures at the Hanford Site often require the installation/removal of various equipment items. To gain tank access for installation or removal of this equipment, large concrete cover blocks must be removed and reinstalled in existing concrete pits above the tanks. An accidental drop of the equipment or cover blocks while being moved over the tanks that results in the release of contaminants to the air poses a potential risk to onsite workers or to the offsite public. To minimize this potential risk, the use of critical lift hoistingmore » and rigging procedures and restrictions on lift height are being considered during development of the new tank farm Basis for Interim Operation and Final Safety Analysis Report. The analysis contained herein provides information for selecting the appropriate lift height restrictions for these activities.« less

Puddle Jumping

NASA Astrophysics Data System (ADS)

Wollman, Andrew; Snyder, Trevor; Weislogel, Mark

2014-11-01

Rebounding droplets from superhydrophobic surfaces have attracted significant public and scientific attention because they are both enjoyable as well as industrially relevant. Demonstrations of bouncing droplets with volumes between 0.003 and 0.03 ml are common in the literature and limited primarily by gravity. In this presentation we demonstrate large droplet ``rebounds'' made possible by low-gravity testing in a drop tower. The up to 300 ml drops are best described as puddles that launch in a nearly identical manner to rebounding drops 4 orders of magnitude smaller in volume. A variety of jumping liquid and gas puddles are shown including puddles of highly specified and unusual initial geometry. The large length sales of the capillary fluidic surfaces ~ O (10 cm) enable 3D printing of all superhydrophobic surface topologies demonstrated. In addition, we demonstrate such puddle jumping as a passive drop-on-demand technique for large low-gravity drop dynamics investigations; such as collisions, rebounds, heat and mass transfer, and containerless possessing.

[Optimize dropping process of Ginkgo biloba dropping pills by using design space approach].

PubMed

Shen, Ji-Chen; Wang, Qing-Qing; Chen, An; Pan, Fang-Lai; Gong, Xing-Chu; Qu, Hai-Bin

2017-07-01

In this paper, a design space approach was applied to optimize the dropping process of Ginkgo biloba dropping pills. Firstly, potential critical process parameters and potential process critical quality attributes were determined through literature research and pre-experiments. Secondly, experiments were carried out according to Box-Behnken design. Then the critical process parameters and critical quality attributes were determined based on the experimental results. Thirdly, second-order polynomial models were used to describe the quantitative relationships between critical process parameters and critical quality attributes. Finally, a probability-based design space was calculated and verified. The verification results showed that efficient production of Ginkgo biloba dropping pills can be guaranteed by operating within the design space parameters. The recommended operation ranges for the critical dropping process parameters of Ginkgo biloba dropping pills were as follows: dropping distance of 5.5-6.7 cm, and dropping speed of 59-60 drops per minute, providing a reference for industrial production of Ginkgo biloba dropping pills. Copyright© by the Chinese Pharmaceutical Association.

Emulsion stabilizing capacity of intact starch granules modified by heat treatment or octenyl succinic anhydride.

PubMed

Timgren, Anna; Rayner, Marilyn; Dejmek, Petr; Marku, Diana; Sjöö, Malin

2013-03-01

Starch granules are an interesting stabilizer candidate for food-grade Pickering emulsions. The stabilizing capacity of seven different intact starch granules for making oil-in-water emulsions has been the topic of this screening study. The starches were from quinoa; rice; maize; waxy varieties of rice, maize, and barley; and high-amylose maize. The starches were studied in their native state, heat treated, and modified by octenyl succinic anhydride (OSA). The effect of varying the continuous phase, both with and without salt in a phosphate buffer, was also studied. Quinoa, which had the smallest granule size, had the best capacity to stabilize oil drops, especially when the granules had been hydrophobically modified by heat treatment or by OSA. The average drop diameter (d 32) in these emulsions varied from 270 to 50 μm, where decreasing drop size and less aggregation was promoted by high starch concentration and absence of salt in the system. Of all the starch varieties studied, quinoa had the best overall emulsifying capacity, and OSA modified quinoa starch in particular. Although the size of the drops was relatively large, the drops themselves were in many instances extremely stable. In the cases where the system could stabilize droplets, even when they were so large that they were visible to the naked eye, they remained stable and the measured droplet sizes after 2 years of storage were essentially unchanged from the initial droplet size. This somewhat surprising result has been attributed to the thickness of the adsorbed starch layer providing steric stabilization. The starch particle-stabilized Pickering emulsion systems studied in this work has potential practical application such as being suitable for encapsulation of ingredients in food and pharmaceutical products.

Plasma theory and simulation

NASA Astrophysics Data System (ADS)

Birdsall, Charles K.

1986-12-01

The Pierce diode linear behavior with external R, C, or L was verified very accurately by particle simulation. The Pierce diode non-linear equilibria with R, C, or L are described theoretically and explored via computer simulation. A simple model of the sheath outside the separatrix of an FRC was modeled electrostatically in 2d and large potentials due to the magnetic well and peak which were found. These may explain the anomalously high ion confinement in the FRC edge layer. A planar plasma source with cold ions and warm electrons produces a source sheath with sufficient potential drop to accelerate ions to sound velocity, which obviates the need for a Bohm pre-collector-sheath electric field. Final reports were prepared for collector sheath, presheath, and source sheath in a collisionless, finite ion temperature plasma; potential drop and transport in a bounded plasma with ion reflection at the collector; potential drop and transport in a bounded plasma with secondary electron emission at the collector. A movie has been made displaying the long-lived vortices resulting from the Kelvin-Helmholtz instability in a magnetized sheath. A relativistic Monte Carlo binary (Coulomb) collision model has been developed and tested for inclusion into the electrostatic particle simulation code TESS. Two direct implicit time integration schemes are tested for self-heating and self-cooling and regions of neither are found as a function of delta t and delta x for the model of a freely expanding plasma slab.

CSU-CHILL Polarimetric Radar Measurements from a Severe Hail Storm in Eastern Colorado.

NASA Astrophysics Data System (ADS)

Hubbert, J.; Bringi, V. N.; Carey, L. D.; Bolen, S.

1998-08-01

Polarimetric radar measurements made by the recently upgraded CSU-CHILL radar system in a severe hailstorm are analyzed permitting for the first time the combined use of Zh, ZDR, linear depolarization ratio (LDR), KDP, and h to infer hydrometeor types. A chase van equipped for manual collection of hail, and instrumented with a rain gauge, intercepted the storm core for 50 min. The period of golfball-sized hail is easily distinguished by high LDR (greater than or equal to 18 dB), negative ZDR (less than or equal to 0.5 dB), and low h (less than or equal to 0.93) values near the surface. Rainfall accumulation over the entire event (about 40 mm) estimated using KDP is in excellent agreement with the rain gauge measurement. Limited dual-Doppler synthesis using the CSU-CHILL and Denver WSR-88D radars permit estimates of the horizontal convergence at altitudes less than 3 km above ground level (AGL) at 1747 and 1812 mountain daylight time (MDT). Locations of peak horizontal convergence at these times are centered on well-defined positive ZDR columns. Vertical sections of multiparameter radar data at 1812 MDT are interpreted in terms of hydrometeor type. In particular, an enhanced LDR `cap' area on top of the the positive ZDR column is interpreted as a region of mixed phase with large drops mixed with partially frozen and frozen hydrometeors. A positive KDP column on the the western fringe of the main updraft is inferred to be the result of drops (1-2 mm) shed by wet hailstones. Swaths of large hail at the surface (inferred from LDR signatures) and positive ZDR at 3.5 km AGL suggest that potential frozen drop embryos are favorably located for growth into large hailstones. Thin section analysis of a sample of the large hailstones shows that 30%-40% have frozen drop embryos.

Using hyperspectral imagery to predict post-wildfire soil water repellency

Treesearch

Sarah A. Lewis; Peter R. Robichaud; Bruce E. Frazier; Joan Q. Wu; Denise Y. M. Laes

2008-01-01

A principal task of evaluating large wildfires is to assess fire's effect on the soil in order to predict the potential watershed response. Two types of soil water repellency tests, the water drop penetration time (WDPT) test and the mini-disk infiltrometer (MDI) test, were performed after the Hayman Fire in Colorado, in the summer of 2002 to assess the...

Electrochemical Oscillations of Nickel Electrodissolution in an Epoxy-Based Microchip Flow Cell

PubMed Central

Cioffi, Alexander G.; Martin, R. Scott; Kiss, István Z.

2011-01-01

We investigate the nonlinear dynamics of transpassive electrodissolution of nickel in sulfuric acid in an epoxy-based microchip flow cell. We observed bistability, smooth, relaxation, and period-2 waveform current oscillations with external resistance attached to the electrode in the microfabricated electrochemical cell with 0.05 mm diameter Ni wire under potentiostatic control. Experiments with 1mm × 0.1 mm Ni electrode show spontaneous oscillations without attached external resistance; similar surface area electrode in macrocell does not exhibit spontaneous oscillations. Combined experimental and numerical studies show that spontaneous oscillation with the on-chip fabricated electrochemical cell occurs because of the unusually large ohmic potential drop due to the constrained current in the narrow flow channel. This large IR potential drop is expected to have an important role in destabilizing negative differential resistance electrochemical (e.g., metal dissolution and electrocatalytic) systems in on-chip integrated microfludic flow cells. The proposed experimental setup can be extendend to multi-electrode configurations; the epoxy-based substrate procedure thus holds promise in electroanalytical applications that require collector-generator multi-electrodes wires with various electrode sizes, compositions, and spacings as well as controlled flow conditions. PMID:21822407

Electrochemical Oscillations of Nickel Electrodissolution in an Epoxy-Based Microchip Flow Cell.

PubMed

Cioffi, Alexander G; Martin, R Scott; Kiss, István Z

2011-08-01

We investigate the nonlinear dynamics of transpassive electrodissolution of nickel in sulfuric acid in an epoxy-based microchip flow cell. We observed bistability, smooth, relaxation, and period-2 waveform current oscillations with external resistance attached to the electrode in the microfabricated electrochemical cell with 0.05 mm diameter Ni wire under potentiostatic control. Experiments with 1mm × 0.1 mm Ni electrode show spontaneous oscillations without attached external resistance; similar surface area electrode in macrocell does not exhibit spontaneous oscillations. Combined experimental and numerical studies show that spontaneous oscillation with the on-chip fabricated electrochemical cell occurs because of the unusually large ohmic potential drop due to the constrained current in the narrow flow channel. This large IR potential drop is expected to have an important role in destabilizing negative differential resistance electrochemical (e.g., metal dissolution and electrocatalytic) systems in on-chip integrated microfludic flow cells. The proposed experimental setup can be extendend to multi-electrode configurations; the epoxy-based substrate procedure thus holds promise in electroanalytical applications that require collector-generator multi-electrodes wires with various electrode sizes, compositions, and spacings as well as controlled flow conditions.

Bacillus subtilis based-formulation for the control of postbloom fruit drop of citrus.

PubMed

Klein, Mariana Nadjara; da Silva, Aline Caroline; Kupper, Katia Cristina

2016-12-01

Postbloom fruit drop (PFD) caused by Colletotrichum acutatum affects flowers and causes early fruit drop in all commercial varieties of citrus. Biological control with the isolate ACB-69 of Bacillus subtilis has been considered as a potential method for controlling this disease. This study aimed to develop and optimize a B. subtilis based-formulation with a potential for large-scale applications and evaluate its effect on C. acutatum in vitro and in vivo. Bacillus subtilis based-formulations were developed using different carrier materials, and their ability to control PFD was evaluated. The results of the assays led to the selection of the B. subtilis based-formulation with talc + urea (0.02 %) and talc + ammonium molybdate (1 mM), which inhibited mycelial growth and germination of C. acutatum. Studies with detached citrus flowers showed that the formulations were effective in controlling the pathogen. In field conditions, talc + urea (0.02 %) provided 73 % asymptomatic citrus flowers and 56 % of the average number of effective fruit (ANEF), equating with fungicide treatment. On the contrary, non-treated trees had 8.8 % of asymptomatic citrus flowers and 0.83 % ANEF. The results suggest that B. subtilis based-formulations with talc as the carrier supplemented with a nitrogen source had a high potential for PFD control.

Space Shuttle Solid Rocket Booster decelerator subsystem - Air drop test vehicle/B-52 design

NASA Technical Reports Server (NTRS)

Runkle, R. E.; Drobnik, R. F.

1979-01-01

The air drop development test program for the Space Shuttle Solid Rocket Booster Recovery System required the design of a large drop test vehicle that would meet all the stringent requirements placed on it by structural loads, safety considerations, flight recovery system interfaces, and sequence. The drop test vehicle had to have the capability to test the drogue and the three main parachutes both separately and in the total flight deployment sequence and still be low-cost to fit in a low-budget development program. The design to test large ribbon parachutes to loads of 300,000 pounds required the detailed investigation and integration of several parameters such as carrier aircraft mechanical interface, drop test vehicle ground transportability, impact point ground penetration, salvageability, drop test vehicle intelligence, flight design hardware interfaces, and packaging fidelity.

Very Large Rain Drops from 2D Video Disdrometers and Concomitant Polarimetric Radar Observations

NASA Technical Reports Server (NTRS)

Thurai, Merhala; Gatlin, Patrick; Bringi, V. N.; Carey, Lawrence

2014-01-01

Drop size distribution (DSD) measurements using ground-based disdrometers (point measurements) have often been used to derive equations to relate radar observations to the integral rainfall parameters (Atlas et al. 1999, Bringi et al., 2003, Kozu et al., 2006, Tokay and Short, 1996, Ajayi and Owolabi, 1987, Battan, 1973). Disdrometers such as JWD, MRR and several others have a major limitation in measuring drops with equi-volume diameters (D(sub eq)) larger than 5 mm because they often rely on the velocity-diameter relationship which plateaus beyond this diameter range (Atlas et al., 1973, Gunn & Kinzer, 1949). Other disdrometers such as Parsivel also lack accuracy beyond this diameter range. The 2D video disdrometer (2DVD: Schönhuber et al., 2008) on the other hand gives drop-shape contours and velocities for each individual drop/hydrometeor falling through its sensor area; this provides a unique opportunity to study the role of very-large drops on radar measurements in particular those with polarimetric radar capability where DSDs with a significant component of very large drops may require special consideration given that the differential reflectivity and other polarimetric radar parameters including attenuation-correction methods will be sensitive to the concentrations of these large drops. A recent study on the occurrence of large drops by Gatlin et al. (2014) has compiled a large and diverse set of measurements made with the 2D video disdrometers from many locations around the globe. Some of the largest drops found in this study were 9 mm D(sub eq) and larger, and in this paper, we report on three such events, with maximum D(sub eq's) of 9.0, 9.1 and 9.7 mm, which occurred in Colorado, Northern Alabama, and Oklahoma, respectively. Detailed examination of the 2DVD data - in terms of shapes and fall velocities - has confirmed that these are fully-melted hydrometeors, although for the last case in Oklahoma, a bigger and non-fully-melted hydrometeor was also observed. All three events were also captured by polarimetric radars, namely the S-band CHILL radar operated by Colorado State University (Brunkow et al., 2000), the C-band ARMOR radar (Petersen et al., 2007) operated by University of Alabama in Huntsville, and NEXRADKVNX, operated by the US National Weather Service, respectively. For the last event, several other radar observations were also made, including two X-band radars operated by the US Dept. of Energy. Analyses of 2DVD data in conjunction with the corresponding radar observations are presented, along with some discussion on sampling issues related to the measurements of such large rain drops. The latter is addressed using maximum diameter D(sub max) measurements from 1-minute DSDs using two collocated 2DVDs for 37 events in Huntsville.

The effect of mining data k-means clustering toward students profile model drop out potential

NASA Astrophysics Data System (ADS)

Purba, Windania; Tamba, Saut; Saragih, Jepronel

2018-04-01

The high of student success and the low of student failure can reflect the quality of a college. One of the factors of fail students was drop out. To solve the problem, so mining data with K-means Clustering was applied. K-Means Clustering method would be implemented to clustering the drop out students potentially. Firstly the the result data would be clustering to get the information of all students condition. Based on the model taken was found that students who potentially drop out because of the unexciting students in learning, unsupported parents, diffident students and less of students behavior time. The result of process of K-Means Clustering could known that students who more potentially drop out were in Cluster 1 caused Credit Total System, Quality Total, and the lowest Grade Point Average (GPA) compared between cluster 2 and 3.

Enhanced intelligent water drops algorithm for multi-depot vehicle routing problem

PubMed Central

Akutsah, Francis; Olusanya, Micheal O.; Adewumi, Aderemi O.

2018-01-01

The intelligent water drop algorithm is a swarm-based metaheuristic algorithm, inspired by the characteristics of water drops in the river and the environmental changes resulting from the action of the flowing river. Since its appearance as an alternative stochastic optimization method, the algorithm has found applications in solving a wide range of combinatorial and functional optimization problems. This paper presents an improved intelligent water drop algorithm for solving multi-depot vehicle routing problems. A simulated annealing algorithm was introduced into the proposed algorithm as a local search metaheuristic to prevent the intelligent water drop algorithm from getting trapped into local minima and also improve its solution quality. In addition, some of the potential problematic issues associated with using simulated annealing that include high computational runtime and exponential calculation of the probability of acceptance criteria, are investigated. The exponential calculation of the probability of acceptance criteria for the simulated annealing based techniques is computationally expensive. Therefore, in order to maximize the performance of the intelligent water drop algorithm using simulated annealing, a better way of calculating the probability of acceptance criteria is considered. The performance of the proposed hybrid algorithm is evaluated by using 33 standard test problems, with the results obtained compared with the solutions offered by four well-known techniques from the subject literature. Experimental results and statistical tests show that the new method possesses outstanding performance in terms of solution quality and runtime consumed. In addition, the proposed algorithm is suitable for solving large-scale problems. PMID:29554662

Enhanced intelligent water drops algorithm for multi-depot vehicle routing problem.

PubMed

Ezugwu, Absalom E; Akutsah, Francis; Olusanya, Micheal O; Adewumi, Aderemi O

2018-01-01

The intelligent water drop algorithm is a swarm-based metaheuristic algorithm, inspired by the characteristics of water drops in the river and the environmental changes resulting from the action of the flowing river. Since its appearance as an alternative stochastic optimization method, the algorithm has found applications in solving a wide range of combinatorial and functional optimization problems. This paper presents an improved intelligent water drop algorithm for solving multi-depot vehicle routing problems. A simulated annealing algorithm was introduced into the proposed algorithm as a local search metaheuristic to prevent the intelligent water drop algorithm from getting trapped into local minima and also improve its solution quality. In addition, some of the potential problematic issues associated with using simulated annealing that include high computational runtime and exponential calculation of the probability of acceptance criteria, are investigated. The exponential calculation of the probability of acceptance criteria for the simulated annealing based techniques is computationally expensive. Therefore, in order to maximize the performance of the intelligent water drop algorithm using simulated annealing, a better way of calculating the probability of acceptance criteria is considered. The performance of the proposed hybrid algorithm is evaluated by using 33 standard test problems, with the results obtained compared with the solutions offered by four well-known techniques from the subject literature. Experimental results and statistical tests show that the new method possesses outstanding performance in terms of solution quality and runtime consumed. In addition, the proposed algorithm is suitable for solving large-scale problems.

Liquid drop stability for protein crystal growth in microgravity

NASA Technical Reports Server (NTRS)

Owen, Robert B.; Broom, Beth H.; Snyder, Robert S.; Daniel, Ron

1987-01-01

It is possible to grow protein crystals for biomedical research in microgravity by deploying a protein-rich solution from a syringe, forming a drop in which crystallization can occur with the proper degree of supersaturation. Drop stability is critical to the success of this research, due to the large drop sizes which can be achieved in space. In order to determine the type of syringe tips most suitable to support these large drops, tests were performed during brief periods of weightlessness onboard the NASA KC-135 low-gravity simulation aircraft. The drops were analyzed using three simple models in which the samples were approximated by modified pendulum and spring systems. It was concluded that the higher frequency systems were the most stable, indicating that of the syringes utilized, a disk-shaped configuration provided the most stable environment of low-gravity protein crystal growth.

A hybrid chip based on aerodynamics and electrostatics for the size-dependent classification of ultrafine and nano particles.

PubMed

Kim, Yong-Ho; Park, Dongho; Hwang, Jungho; Kim, Yong-Jun

2009-09-21

Conventional virtual impactors experience a large pressure drop when they classify particles according to size, in particular ultrafine particles smaller than 100 nm in diameter. Therefore, most virtual impactors have been used to classify particles larger than 100 nm. Their cut-off diameters are also fixed by the geometry of their flow channels. In the proposed virtual impactor, particles smaller than 100 nm are accelerated by applying DC potentials to an integrated electrode pair. By the electrical acceleration, the large pressure drop could be significantly decreased and new cut-off diameters smaller than 100 nm could be successfully added. The geometric cut-off diameter (GCD) of the proposed virtual impactor was designed to be 1.0 microm. Performances including the GCD and wall loss were examined by classifying dioctyl sebacate of 100 to 600 nm in size and carbon particles of 0.6 to 10 microm in size. The GCD was measured to be 0.95 microm, and the wall loss was highest at 1.1 microm. To add new cut-off diameters, monodisperse NaCl particles ranging from 15 to 70 nm were classified using the proposed virtual impactor with applying a DC potential of 0.25 to 3.0 kV. In this range of the potential, the new cut-off diameters ranging from 15 to 35 nm was added.

A theory of electrophoresis of emulsion drops in aqueous two-phase polymer systems

NASA Technical Reports Server (NTRS)

Levine, S.

1982-01-01

An electrophoresis study has been carried out in an emulsion formed from an electrically neutral aqueous mixture of dextran and polyethylene glycol equilibrated at sufficient concentrations in the presence of electrolytes. Electrophoresis of a drop of one phase suspended in the other is observed, and the direction of the drop's motion is reversed when the disperse phase and the continuous phase are interchanged. In the presence of sulfate, phosphate, or citrate ions, an electrostatic potential difference of the order of a few mV exists between the two phases. The potential implied by the direction of the electrophoretic motion is opposite to the Donnan potential observed between the two phases. The mobility of an emulsion drop increases with the drop radius and depends on ion concentration. These results are explained in terms of a model postulating an electric dipole layer associated with a mixture of oriented polymer molecules at the surface of a drop, with a potential difference between the interiors of the two phases resulting from the unequal ion distribution.

Effects of drop acceleration and deceleration on particle capture in a cross-flow gravity tower at intermediate drop Reynolds numbers.

PubMed

Kumar, Anoop; Gupta, S K; Kale, S R

2007-04-01

Cross-flow gravity towers are particle scrubbing devices in which water is sprayed from the top into particle-laden flow moving horizontally. Models for predicting particle capture assume drops traveling at terminal velocity and potential flow (ReD > 1000) around it, however, Reynolds numbers in the intermediate range of 1 to 1000 are common in gravity towers. Drops are usually injected at velocities greater than their terminal velocities (as in nozzles) or from near rest (perforated tray) and they accelerate/decelerate to their terminal velocity in the tower. Also, the effects of intermediate drop Reynolds number on capture efficiency have been simulated for (a) drops at their terminal velocity and (b) drops accelerating/decelerating to their terminal velocity. Tower efficiency based on potential flow about the drop is 40%-50% greater than for 200 mm drops traveling at their terminal velocity. The corresponding values for 500 mm drops are about 10%-20%. The drop injection velocity is important operating parameter. Increase in tower efficiency by about 40% for particles smaller than 5 mm is observed for increase in injection velocity from 0 to 20 m/s for 200 and 500mm drops.

Multilingual Literacy Skill Development in Kenya: Results from Medium Scale Randomized Controlled Trials

ERIC Educational Resources Information Center

Piper, Benjamin

2016-01-01

If children do not learn how to read in the first few years of primary school, they at greater risk of dropping out. It is therefore crucial to identify and test interventions that have the potential of making a large impact, can be implemented quickly, and are affordable to be taken to scale by the Kenyan government. This paper presents the…

Use of Dual-Polarization Radar Variables to Assess Low-Level Wind Shear in Severe Thunderstorm Near-storm Environments in the Tennessee Valley

NASA Technical Reports Server (NTRS)

Crowe, Christina C.; Schultz, Christopher J.; Kumjian, Matthew; Carey, Lawerence D.; Petersen, Walter A.

2011-01-01

The upgrade of the National Weather Service (NWS) network of S ]band dual-polarization radars is currently underway, and the incorporation of polarimetric information into the real ]time forecasting process will enhance the forecaster fs ability to assess thunderstorms and their near ]storm environments. Recent research has suggested that the combination of polarimetric variables differential reflectivity (ZDR) and specific differential phase (KDP) can be useful in the assessment of low level wind shear within a thunderstorm. In an environment with strong low ]level veering of the wind, ZDR values will be largest along the right inflow edge of the thunderstorm near a large gradient in horizontal reflectivity (indicative of large raindrops falling with a relative lack of smaller drops), and take the shape of an arc. Meanwhile, KDP values, which are proportional to liquid water content and indicative of a large number of smaller drops, are maximized deeper into the forward flank precipitation shield than the ZDR arc as the smaller drops are being advected further from the updraft core by the low level winds than the larger raindrops. Using findings from previous work, three severe weather events that occurred in North Alabama were examined in order to assess the utility of these signatures in determining the potential for tornadic activity. The first case is from October 26, 2010, where a large number of storms indicated tornadic potential from a standard reflectivity and velocity analysis but very few storms actually produced tornadoes. The second event is from February 28, 2011, where tornadic storms were present early on in the event, but as the day progressed, the tornado threat transitioned to a high wind threat. The third case is from April 27, 2011, where multiple rounds of tornadic storms ransacked the Tennessee Valley. This event provides a dataset including multiple modes of tornadic development, including QLCS and supercell structures. The overarching goal of examining these three events is to compare dual ]polarization features from this larger dataset to previous work and to determine if these signatures can be a useful indication of the potential for tornadic activity associated with the amount of low ]level wind shear in the near ]storm environment.

Stress Drop and Its Relationship to Radiated Energy, Ground Motion and Uncertainty

NASA Astrophysics Data System (ADS)

Baltay, A.

2014-12-01

Despite the seemingly diverse circumstances under which crustal earthquakes occur, scale-invariant stress drop and apparent stress, the ratio of radiated seismic energy to moment, is observed. The magnitude-independence of these parameters is central to our understanding of both earthquake physics and strong ground motion genesis. Estimates of stress drop and radiated energy, however, display large amounts of scatter potentially masking any secondary trends in the data. We investigate sources of this uncertainty within the framework of constant stress drop and apparent stress. We first re-visit estimates of energy and stress drop from a variety of earthquake observations and methods, for events ranging from magnitude ~2 to ~9. Using an empirical Green's function (eGf) deconvolution method, which removes the path and site effects, radiated energy and Brune stress drop are estimated for both regional events in the western US and Eastern Honshu, Japan from the HiNet network, as well as teleseismically recorded global great earthquakes [Baltay et al., 2010, 2011, 2014]. In addition to eGf methods, ground-motion based metrics for stress drop are considered, using both KikNet data from Japan [Baltay et al., 2013] and the NGA-West2 data, a very well curated ground-motion database. Both the eGf-based stress drop estimates and those from the NGA-West2 database show a marked decrease in scatter, allowing us to identify deterministic secondary trends in stress drop. We find both an increasing stress drop with depth, as well as a larger stress drop of about 30% on average for mainshock events as compared to on-fault aftershocks. While both of these effects are already included in some ground-motion prediction equations (GMPE), many previous seismological studies have been unable to conclusively uncover these trends because of their considerable scatter. Elucidating these effects in the context of reduced and quantified epistemic uncertainty can help both seismologists and engineers to understand the true aleatory variability of the earthquake source, which may be due to the complex and diverse circumstances under which these earthquake occur and which we are yet unable to model.

A deformable surface model for real-time water drop animation.

PubMed

Zhang, Yizhong; Wang, Huamin; Wang, Shuai; Tong, Yiying; Zhou, Kun

2012-08-01

A water drop behaves differently from a large water body because of its strong viscosity and surface tension under the small scale. Surface tension causes the motion of a water drop to be largely determined by its boundary surface. Meanwhile, viscosity makes the interior of a water drop less relevant to its motion, as the smooth velocity field can be well approximated by an interpolation of the velocity on the boundary. Consequently, we propose a fast deformable surface model to realistically animate water drops and their flowing behaviors on solid surfaces. Our system efficiently simulates water drop motions in a Lagrangian fashion, by reducing 3D fluid dynamics over the whole liquid volume to a deformable surface model. In each time step, the model uses an implicit mean curvature flow operator to produce surface tension effects, a contact angle operator to change droplet shapes on solid surfaces, and a set of mesh connectivity updates to handle topological changes and improve mesh quality over time. Our numerical experiments demonstrate a variety of physically plausible water drop phenomena at a real-time rate, including capillary waves when water drops collide, pinch-off of water jets, and droplets flowing over solid materials. The whole system performs orders-of-magnitude faster than existing simulation approaches that generate comparable water drop effects.

Measurement of the potential drop across the earth's collisionless bow shock

NASA Technical Reports Server (NTRS)

Formisano, V.

1982-01-01

The normal component of the dc electric field measured on ISEE-1 ordinarily exhibits an enhancement of a few mV/m over both upstream and downstream values at the earth's bow shock. Using the measured relative velocity between the shock and the spacecraft (from the ISEE-1/2 time delay in the magnetometer data), it is possible to transform the observed E enhancement to a potential drop (delta phi). For a subcritical shock the potential drop is found to be very close to the measured change of particle kinetic energy (delta phi, approximately 280 V on day 330, 1977), whereas for a supercritical shock the potential drop is only a fraction of the measured change of kinetic energy (delta phi, approximately 140 V on day 324, 1977).

Automatic Control of Arc Process for Making Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Scott, Carl D.; Pulumbarit, Robert B.; Victor, Joe

2004-01-01

An automatic-control system has been devised for a process in which carbon nanotubes are produced in an arc between a catalyst-filled carbon anode and a graphite cathode. The control system includes a motor-driven screw that adjusts the distance between the electrodes. The system also includes a bridge circuit that puts out a voltage proportional to the difference between (1) the actual value of potential drop across the arc and (2) a reference value between 38 and 40 V (corresponding to a current of about 100 A) at which the yield of carbon nanotubes is maximized. Utilizing the fact that the potential drop across the arc increases with the interelectrode gap, the output of the bridge circuit is fed to a motor-control circuit that causes the motor to move the anode toward or away from the cathode if the actual potential drop is more or less, respectively, than the reference potential. Thus, the system regulates the interelectrode gap to maintain the optimum potential drop. The system also includes circuitry that records the potential drop across the arc and the relative position of the anode holder as function of time.

Design of a Helmet Liner for Improved Low Velocity Impact Protection

DTIC Science & Technology

2013-05-01

FIGURE 14. MONORAIL DROP TEST WITH DOT-SIZE C HEADFORM AND HEMISPHERICAL ANVIL ........................... 14  FIGURE 15. ACH PAD CONFIGURATION. LEFT...materials. In this project, the monorail drop test device, used for the helmeted headform drop test, was modified for material testing as shown in Figure...a guided free fall drop test using a monorail drop test apparatus as shown in Figure 14. All helmets tested in this study were ACH-Size Large and

Microwave Dielectric Heating of Drops in Microfluidic Devices†

PubMed Central

Issadore, David; Humphry, Katherine J.; Brown, Keith A.; Sandberg, Lori; Weitz, David; Westervelt, Robert M.

2010-01-01

We present a technique to locally and rapidly heat water drops in microfluidic devices with microwave dielectric heating. Water absorbs microwave power more efficiently than polymers, glass, and oils due to its permanent molecular dipole moment that has a large dielectric loss at GHz frequencies. The relevant heat capacity of the system is a single thermally isolated picoliter drop of water and this enables very fast thermal cycling. We demonstrate microwave dielectric heating in a microfluidic device that integrates a flow-focusing drop maker, drop splitters, and metal electrodes to locally deliver microwave power from an inexpensive, commercially available 3.0 GHz source and amplifier. The temperature of the drops is measured by observing the temperature dependent fluorescence intensity of cadmium selenide nanocrystals suspended in the water drops. We demonstrate characteristic heating times as short as 15 ms to steady-state temperatures as large as 30°C above the base temperature of the microfluidic device. Many common biological and chemical applications require rapid and local control of temperature, such as PCR amplification of DNA, and can benefit from this new technique. PMID:19495453

Potential of Svalbard reindeer winter droppings for emission/absorption of methane and nitrous oxide during summer

NASA Astrophysics Data System (ADS)

Hayashi, Kentaro; Cooper, Elisabeth J.; Loonen, Maarten J. J. E.; Kishimoto-Mo, Ayaka W.; Motohka, Takeshi; Uchida, Masaki; Nakatsubo, Takayuki

2014-06-01

Droppings of Svalbard reindeer (Rangifer tarandus platyrhynchus) could affect the carbon and nitrogen cycles in tundra ecosystems. The aim of this study was to evaluate the potential of reindeer droppings originating from the winter diet for emission and/or absorption of methane (CH4) and nitrous oxide (N2O) in summer. An incubation experiment was conducted over 14 days using reindeer droppings and mineral subsoil collected from a mound near Ny-Ålesund, Svalbard, to determine the potential exchanges of CH4 and N2O for combinations of two factors, reindeer droppings (presence or absence) and soil moisture (dry, moderate, or wet). A line transect survey was conducted to determine the distribution density of winter droppings at the study site. The incubation experiment showed a weak absorption of CH4 and a weak emission of N2O. Reindeer droppings originating from the winter diet had a negligible effect on the exchange fluxes of both CH4 and N2O. Although the presence of droppings resulted in a short-lasting increase in N2O emissions on day 1 (24 h from the start) for moderate and wet conditions, the emission rates were still very small, up to 3 μg N2O m-2 h-1.

Microscopic description of a drop on a solid surface.

PubMed

Ruckenstein, Eli; Berim, Gersh O

2010-06-14

Two approaches recently suggested for the treatment of macro- or nanodrops on smooth or rough, planar or curved, solid surfaces, based on fluid-fluid and fluid-solid interaction potentials are reviewed. The first one employs the minimization of the total potential energy of a drop by assuming that the drop has a well defined profile and a constant liquid density in its entire volume with the exception of the monolayer nearest to the surface where the density has a different value. As a result, a differential equation for the drop profile as well as the necessary boundary conditions are derived which involve the parameters of the interaction potentials and do not contain such macroscopic characteristics as the surface tensions. As a consequence, the macroscopic and microscopic contact angles which the drop profile makes with the surface can be calculated. The macroscopic angle is obtained via the extrapolation of the circular part of the drop profile valid at some distance from the surface up to the solid surface. The microscopic angle is formed at the intersection of the real profile (which is not circular near the surface) with the surface. The theory provides a relation between these two angles. The ranges of the microscopic parameters of the interaction potentials for which (i) the drop can have any height (volume), (ii) the drop can have a restricted height but unrestricted volume, and (iii) a drop cannot be formed on the surface were identified. The theory was also extended to the description of a drop on a rough surface. The second approach is based on a nonlocal density functional theory (DFT), which accounts for the inhomogeneity of the liquid density and temperature effects, features which are missing in the first approach. Although the computational difficulties restrict its application to drops of only several nanometers, the theory can be applied indirectly to macrodrops by calculating the surface tensions and using the Young equation to determine the contact angle. Employing the canonical ensemble version of the DFT, nanodrops on smooth and rough solid surfaces could be investigated and their characteristics, such as the drop profile, contact angle, as well as the fluid density distribution inside the drop can be determined as functions of the parameters of the interaction potentials and temperature. It was found that the contact angle of the drop has a simple (quasi)universal dependence on the energy parameter epsilon(fs) of the fluid-solid interaction potential and temperature. The main feature of this dependence is the existence of a fixed value theta(0) of the contact angle theta which separates the solid substrates (characterized by the energy parameter epsilon(fs) of the fluid-solid interaction potential) into two classes with respect to their temperature dependence. For theta>theta(0) the contact angle monotonously increases and for theta

Reading Skill Transfer across Languages: Outcomes from Longitudinal Bilingual Randomized Control Trials in Kenya and Haiti

ERIC Educational Resources Information Center

Piper, Benjamin; Bulat, Jennae; Johnston, Andrew

2015-01-01

If children do not learn how to read in the first few years of primary school, they will struggle to complete the cycle, and are at greater risk of dropping out. It is therefore crucial to identify and test interventions that have the potential of making a large impact, can be implemented quickly, and are affordable to be taken to scale. This is…

Effects of Auroral Potential Drops on Field-Aligned Currents and Nightside Reconnection Dynamos

NASA Astrophysics Data System (ADS)

Lotko, W.; Xi, S.; Zhang, B.; Wiltberger, M. J.; Lyon, J.

2016-12-01

The reaction of the magnetosphere-ionosphere system to dynamic auroral potential drops is investigated using the Lyon-Fedder-Mobarry global model and, for the first time in a global simulation, including the dissipative load of field-aligned potential drops in the low-altitude boundary condition. This extra load reduces the demand for field-aligned current (j||) from nightside reconnection dynamos. The system adapts by forcing the nightside x-line closer to Earth to reduce current lensing (j||/B = constant) at the ionosphere, with the plasma sheet undergoing additional contraction during substorm recovery and steady magnetospheric convection. For steady and moderate solar wind driving and with constant ionospheric conductance, the cross-polar cap potential and hemispheric field-aligned current are lower by approximately the ratio of the peak field-aligned potential drop to the cross polar cap potential (10-15%) when potential drops are included. Hemispheric ionospheric Joule dissipation is less by 8%, while the area-integrated, average work done on the fluid by the reconnecting magnetotail field increases by 50% within |y| < 8 RE. Effects on the nightside plasma sheet include: (1) an average x-line 4 RE closer to Earth; (2) a 12% higher mean reconnection rate; and (3) dawn-dusk asymmetry in reconnection with a 17% higher rate in the premidnight sector.

Effects of auroral potential drops on plasma sheet dynamics

NASA Astrophysics Data System (ADS)

Xi, Sheng; Lotko, William; Zhang, Binzheng; Wiltberger, Michael; Lyon, John

2016-11-01

The reaction of the magnetosphere-ionosphere system to dynamic auroral potential drops is investigated using the Lyon-Fedder-Mobarry global model including, for the first time in a global simulation, the dissipative load of field-aligned potential drops in the low-altitude boundary condition. This extra load reduces the field-aligned current (j||) supplied by nightside reconnection dynamos. The system adapts by forcing the nightside X line closer to Earth, with a corresponding reduction in current lensing (j||/B = constant) at the ionosphere and additional contraction of the plasma sheet during substorm recovery and steady magnetospheric convection. For steady and moderate solar wind driving and with constant ionospheric conductance, the cross polar cap potential and hemispheric field-aligned current are lower by approximately the ratio of the peak field-aligned potential drop to the cross polar cap potential (10-15%) when potential drops are included. Hemispheric ionospheric Joule dissipation is less by 8%, while the area-integrated, average work done on the fluid by the reconnecting magnetotail field increases by 50% within |y| < 8 RE. Effects on the nightside plasma sheet include (1) an average X line 4 RE closer to Earth; (2) a 12% higher mean reconnection rate; and (3) dawn-dusk asymmetry in reconnection with a 17% higher rate in the premidnight sector.

Physical phenomena in containerless glass processing

NASA Technical Reports Server (NTRS)

Subramanian, R. Shankar; Cole, Robert

1988-01-01

Flight experiments are planned on drops containing bubbles. The experiments involve stimulating the drop via non-uniform heating and rotation. The resulting trajectories of the bubbles as well as the shapes of the drops and bubble will be videotaped and analyzed later frame-by-frame on the ground. Supporting ground based experiments are planned in the area of surface tension driven motion of bubbles, the behavior of compound drops settling in an immiscible liquid and the shapes and trajectories of large bubbles and drops in a rotating liquid. Theoretical efforts will be directed at thermocapillary migration of drops and bubbles, surfactant effects on such migration, and the behavior of compound drops.

Log-normal spray drop distribution...analyzed by two new computer programs

Treesearch

Gerald S. Walton

1968-01-01

Results of U.S. Forest Service research on chemical insecticides suggest that large drops are not as effective as small drops in carrying insecticides to target insects. Two new computer programs have been written to analyze size distribution properties of drops from spray nozzles. Coded in Fortran IV, the programs have been tested on both the CDC 6400 and the IBM 7094...

Nondestructive hall coefficient measurements using ACPD techniques

NASA Astrophysics Data System (ADS)

Velicheti, Dheeraj; Nagy, Peter B.; Hassan, Waled

2018-04-01

Hall coefficient measurements offer great opportunities as well as major challenges for nondestructive materials characterization. The Hall effect is produced by the magnetic Lorentz force acting on moving charge carriers in the presence of an applied magnetic field. The magnetic perturbation gives rise to a Hall current that is normal to the conduction current but does not directly perturb the electric potential distribution. Therefore, Hall coefficient measurements usually exploit the so-called transverse galvanomagnetic potential drop effect that arises when the Hall current is intercepted by the boundaries of the specimen and thereby produce a measurable potential drop. In contrast, no Hall potential is produced in a large plate in the presence of a uniform normal field at quasi-static low frequencies. In other words, conventional Hall coefficient measurements are inherently destructive since they require cutting the material under tests. This study investigated the feasibility of using alternating current potential drop (ACPD) techniques for nondestructive Hall coefficient measurements in plates. Specifically, the directional four-point square-electrode configuration is investigated with superimposed external magnetic field. Two methods are suggested to make Hall coefficient measurements in large plates without destructive machining. At low frequencies, constraining the bias magnetic field can replace constraining the dimensions of the specimen, which is inherently destructive. For example, when a cylindrical permanent magnet is used to provide the bias magnetic field, the peak Hall voltage is produced when the diameter of the magnet is equal to the diagonal of the square ACPD probe. Although this method is less effective than cutting the specimen to a finite size, the loss of sensitivity is less than one order of magnitude even at very low frequencies. In contrast, at sufficiently high inspection frequencies the magnetic field of the Hall current induces a strong enough Hall electric field that produces measurable potential differences between points lying on the path followed by the Hall current even when it is not intercepted by either the edge of the specimen or the edge of the magnetic field. The induced Hall voltage increases proportionally to the square root of frequency as the current is squeezed into a shallow electromagnetic skin of decreasing depth. This approach could be exploited to measure the Hall coefficient near the surface at high frequencies without cutting the specimen.

Drop Tower Workshop

NASA Technical Reports Server (NTRS)

Urban, David

2013-01-01

Ground based microgravity facilities are an important proving ground for space experiments, ground-based research and space hardware risk mitigation. An overview of existing platforms will be discussed with an emphasis on drop tower capabilities. The potential for extension to partial gravity conditions will be discussed. Input will be solicited from attendees for their potential to use drop towers in the future and the need for enhanced capabilities (e.g. partial gravity)

Dropwise condensation

PubMed Central

Leach, R. N.; Stevens, F.; Langford, S. C.; Dickinson, J. T.

2008-01-01

Dropwise condensation of water vapor from a naturally cooling, hot water reservoir onto a hydrophobic polymer film and a silanized glass slide was studied by direct observation and simulations. The observed drop growth kinetics suggest that smallest drops grow principally by the diffusion of water adsorbed on the substrate to the drop perimeter, while drops larger than 50 μm in diameter grow principally by direct deposition from the vapor onto the drop surface. Drop coalescence plays a critical role in determining the drop size distribution, and stimulates the nucleation of new, small drops on the substrates. Simulations of drop growth incorporating these growth mechanisms provide a good description of the observed drop size distribution. Because of the large role played by coalescence, details of individual drop growth make little difference to the final drop size distribution. The rate of condensation per unit substrate area is especially high for the smallest drops, and may help account for the high heat transfer rates associated with dropwise condensation relative to filmwise condensation in heat exchange applications. PMID:17014129

Commensurability-driven structural defects in double emulsions produced with two-step microfluidic techniques.

PubMed

Schmit, Alexandre; Salkin, Louis; Courbin, Laurent; Panizza, Pascal

2014-07-14

The combination of two drop makers such as flow focusing geometries or ┬ junctions is commonly used in microfluidics to fabricate monodisperse double emulsions and novel fluid-based materials. Here we investigate the physics of the encapsulation of small droplets inside large drops that is at the core of such processes. The number of droplets per drop studied over time for large sequences of consecutive drops reveals that the dynamics of these systems are complex: we find a succession of well-defined elementary patterns and defects. We present a simple model based on a discrete approach that predicts the nature of these patterns and their non-trivial scheme of arrangement in a sequence as a function of the ratio of the two timescales of the problem, the production times of droplets and drops. Experiments validate our model as they concur very well with predictions.

Large Eddy Simulation of jets laden with evaporating drops

NASA Technical Reports Server (NTRS)

Leboissetier, A.; Okong'o, N.; Bellan, J.

2004-01-01

LES of a circular jet laden with evaporating liquid drops are conducted to assess computational-drop modeling and three different SGS-flux models: the Scale Similarity model (SSC), using a constant coefficient calibrated on a temporal mixing layer DNS database, and dynamic-coefficient Gradient and Smagorinsky models.

A Computational Study of the Modification of Raindrop Size Distributions in Subcloud Downdrafts.

DTIC Science & Technology

1981-08-01

Schumann (1939) and Findeisen (1939). It is characterized by a raindrop distribution consisting of many small droplets and a few large drops; all large...rain by means of sequential rain drop size distributions. Quart. J. Roy. Meteor. Soc., 88, 301-314. Findeisen , W., 1939: Zur Frage der

Self-consistent quasi-static parallel electric field associated with substorm growth phase

NASA Astrophysics Data System (ADS)

Le Contel, O.; Pellat, R.; Roux, A.

2000-06-01

A new approach is proposed to calculate the self-consistent parallel electric field associated with the response of a plasma to quasi-static electromagnetic perturbations (ωωd<ω and ωd>ω (ωd being the bounce averaged magnetic drift frequency equal to kyvd, where ky is the wave number in the y direction and vd the bounce averaged magnetic drift velocity). The first regime (ωd<ω) corresponds to small particle energy and/or small ky, while the second regime (ωd>ω) is adapted to large energies and/or large ky. In particular, in the limit ωd<ω and |vd|<|uy|, where uy is the diamagnetic velocity proportional to the pressure gradient, we find a parallel electric field proportional to the pressure gradient and directed toward the ionosphere in the dusk sector and toward the equator in the dawn sector. This parallel electric field corresponds to a potential drop of a few hundred volts that can accelerate electrons and produce a differential drift between electrons and ions.

Shaping liquid drops by vibration

NASA Astrophysics Data System (ADS)

Pototsky, Andrey; Bestehorn, Michael

2018-02-01

We present and analyze a minimal hydrodynamic model of a vertically vibrated liquid drop that undergoes dynamic shape transformations. In agreement with experiments, a circular lens-shaped drop is unstable above a critical vibration amplitude, spontaneously elongating in the horizontal direction. Smaller drops elongate into localized states that oscillate with half of the vibration frequency. Larger drops evolve by transforming into a snake-like structure with gradually increasing length. The worm state is long-lasting with a potential to fragment into smaller drops.

The Flow Induced by the Coalescence of Two Initially Stationary Drops

NASA Technical Reports Server (NTRS)

Nobari, M. R.; Tryggvason, G.

1994-01-01

The coalescence of two initially stationary drops of different size is investigated by solving the unsteady, axisymmetric Navier-Stokes equations numerically, using a Front-Tracking/Finite Difference method. Initially, the drops are put next to each other and the film between them ruptured. Due to surface tension forces, the drops coalesce rapidly and the fluid from the small drop is injected into the larger one. For low nondimensional viscosity, or Ohnesorge number, little mixing takes place and the small drop fluid forms a blob near the point where the drops touched initially. For low Ohnesorge number, on the other hand, the small drop forms a jet that penetrates far into the large drop. The penetration depth also depends on the size of the drops and shows that for a given fluid of sufficiently low viscosity, there is a maximum penetration depth for intermediate size ratios.

Redistribution of ice nuclei between cloud and rain droplets: Parameterization and application to deep convective clouds

NASA Astrophysics Data System (ADS)

Paukert, M.; Hoose, C.; Simmel, M.

2017-03-01

In model studies of aerosol-dependent immersion freezing in clouds, a common assumption is that each ice nucleating aerosol particle corresponds to exactly one cloud droplet. In contrast, the immersion freezing of larger drops—"rain"—is usually represented by a liquid volume-dependent approach, making the parameterizations of rain freezing independent of specific aerosol types and concentrations. This may lead to inconsistencies when aerosol effects on clouds and precipitation shall be investigated, since raindrops consist of the cloud droplets—and corresponding aerosol particles—that have been involved in drop-drop-collisions. Here we introduce an extension to a two-moment microphysical scheme in order to account explicitly for particle accumulation in raindrops by tracking the rates of selfcollection, autoconversion, and accretion. This provides a direct link between ice nuclei and the primary formation of large precipitating ice particles. A new parameterization scheme of drop freezing is presented to consider multiple ice nuclei within one drop and effective drop cooling rates. In our test cases of deep convective clouds, we find that at altitudes which are most relevant for immersion freezing, the majority of potential ice nuclei have been converted from cloud droplets into raindrops. Compared to the standard treatment of freezing in our model, the less efficient mineral dust-based freezing results in higher rainwater contents in the convective core, affecting both rain and hail precipitation. The aerosol-dependent treatment of rain freezing can reverse the signs of simulated precipitation sensitivities to ice nuclei perturbations.

A third-order silicon racetrack add-drop filter with a moderate feature size

NASA Astrophysics Data System (ADS)

Wang, Ying; Zhou, Xin; Chen, Qian; Shao, Yue; Chen, Xiangning; Huang, Qingzhong; Jiang, Wei

2018-01-01

In this work, we design and fabricate a highly compact third-order racetrack add-drop filter consisting of silicon waveguides with modified widths on a silicon-on-insulator (SOI) wafer. Compared to the previous approach that requires an exceedingly narrow coupling gap less than 100nm, we propose a new approach that enlarges the minimum feature size of the whole device to be 300 nm to reduce the process requirement. The three-dimensional finite-difference time-domain (3D-FDTD) method is used for simulation. Experiment results show good agreement with simulation results in property. In the experiment, the filter shows a nearly box-like channel dropping response, which has a large flat 3-dB bandwidth ({3 nm), relatively large FSR ({13.3 nm) and out-of-band rejection larger than 14 dB at the drop port with a footprint of 0.0006 mm2 . The device is small and simple enough to have a wide range of applications in large scale on-chip photonic integration circuits.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barleon, L.; Buehler, L.; Molokov, S.

Magnetohydrodynamic (MHD) flow through a 90{degrees} bend, in which the flow is turned from the direction perpendicular to magnetic field lines into a direction aligned with the field, is characterized by strong three-dimensional effects leading to additional pressure drop and large deformations in the velocity distribution. Since such bends are basic elements of a fusion reactor blanket, the question whether the additional pressure drop exceeds unacceptable limits or whether the change in flow distribution may lead to unfavorable heat transfer conditions as to be answered. To investigate MHD flows in a right angle bend, several experiments have been performed inmore » a wide range of the relevant parameters. In the lower range of the interaction parameter N (N {much_lt} 10{sup 4}) the total pressure drop over the whole bend shows a pronounced N-dependence but only a weak dependence on the Hartmann number M. Both effects can be combined to a pressure drop correlation. At higher values of N and M the experimental results for pressure drop and potential distribution agree rather well with theoretical ones obtained on the basis of an asymptotic approach for high N and M. It can be shown theoretically and confirmed by the experiment that, even at high N and M the additional pressure drop in a right angle bend is not excessively high. For the investigated bend with conducting channel walls the predicted flow distribution does not show any stagnant zone at the high heat flux walls in the perfectly aligned part of the duct. This result, however, could not be checked experimentally because there is still no reliable velocity measurement technique available for field-aligned flows.« less

Relationship between large slip area and static stress drop of aftershocks of inland earthquake :Example of the 2007 Noto Hanto earthquake

NASA Astrophysics Data System (ADS)

Urano, S.; Hiramatsu, Y.; Yamada, T.

2013-12-01

The 2007 Noto Hanto earthquake (MJMA 6.9; hereafter referred to the main shock) occurred at 0:41(UTC) on March 25, 2007 at a depth of 11km beneath the west coast of Noto Peninsula, central Japan. The dominant slip of the main shock was on a reverse fault with a right-lateral slip and the large slip area was distributed from hypocenter to the shallow part on the fault plane (Horikawa, 2008). The aftershocks are distributed not only in the small slip area but also in the large slip area (Hiramatsu et al., 2011). In this study, we estimate static stress drops of aftershocks on the fault plane of the main shock. We discuss the relationship between the static stress drops of the aftershocks and the large slip area of the main shock by investigating spatial pattern of the values of the static stress drops. We use the waveform data obtained by the group for the joint aftershock observations of the 2007 Noto Hanto Earthquake (Sakai et al., 2007). The sampling frequency of the waveform data is 100 Hz or 200 Hz. Focusing on similar aftershocks reported by Hiramatsu et al. (2011), we analyze static stress drops by using the method of empirical Green's function (EGF) (Hough, 1997) as follows. The smallest earthquake (MJMA≥2.0) of each group of similar earthquakes is set to the EGF earthquake, and the largest earthquake (MJMA≥2.5) is set to the target earthquake. We then deconvolve the waveform of an interested earthquake with that of the EGF earthquake at each station and obtain the spectral ratio of the sources that cancels the propagation effects (path and site effects). Following the procedure of Yamada et al. (2010), we finally estimate static stress drops for P- and S-waves from corner frequencies of the spectral ratio by using a model of Madariaga (1976). The estimated average value of static stress drop is 8.2×1.3 MPa (8.6×2.2 MPa for P-wave and 7.8×1.3 MPa for S-wave). These values are coincident approximately with the static stress drop of aftershocks of other inland earthquakes in Japan (Ito et al., 2005; Iio et al., 2006) and independent of the seismic moment. We then compare the values with the coseismic slip distribution of the main shock reported by Horikawa (2008). If we define large slip areas as areas with a slip exceeding 1 m, the average value of static stress drop is 12×2.3 (MPa) in the area. On the other hand, the average value is 5.7×0.9 (MPa) outside the large slip area. These results suggest that aftershocks in the large slip area likely have larger values of static stress drop, which would reflect the spatial heterogeneity of shear strength and dynamic stress level. Our results are coincident with the result of Yamada et al. (2010).

Static shape of an acoustically levitated drop with wave-drop interaction

NASA Astrophysics Data System (ADS)

Lee, C. P.; Anilkumar, A. V.; Wang, T. G.

1994-11-01

The static shape of a drop levitated and flattened by an acoustic standing wave field in air is calculated, requiring self-consistency between the drop shape and the wave. The wave is calculated for a given shape using the boundary integral method. From the resulting radiation stress on the drop surface, the shape is determined by solving the Young-Laplace equation, completing an iteration cycle. The iteration is continued until both the shape and the wave converge. Of particular interest are the shapes of large drops that sustain equilibrium, beyond a certain degree of flattening, by becoming more flattened at a decreasing sound pressure level. The predictions for flattening versus acoustic radiation stress, for drops of different sizes, compare favorably with experimental data.

Stress drop inferred from dynamic rupture simulations consistent with Moment-Rupture area empirical scaling models: Effects of week shallow zone

NASA Astrophysics Data System (ADS)

Dalguer, L. A.; Miyake, H.; Irikura, K.; Wu, H., Sr.

2016-12-01

Empirical scaling models of seismic moment and rupture area provide constraints to parameterize source parameters, such as stress drop, for numerical simulations of ground motion. There are several scaling models published in the literature. The effect of the finite width seismogenic zone and the free-surface have been attributed to cause the breaking of the well know self-similar scaling (e.g. Dalguer et al, 2008) given origin to the so called L and W models for large faults. These models imply the existence of three-stage scaling relationship between seismic moment and rupture area (e.g. Irikura and Miyake, 2011). In this paper we extend the work done by Dalguer et al 2008, in which these authors calibrated fault models that match the observations showing that the average stress drop is independent of earthquake size for buried earthquakes, but scale dependent for surface-rupturing earthquakes. Here we have developed additional sets of dynamic rupture models for vertical strike slip faults to evaluate the effect of the weak shallow layer (WSL) zone for the calibration of stress drop. Rupture in the WSL zone is expected to operate with enhanced energy absorption mechanism. The set of dynamic models consists of fault models with width 20km and fault length L=20km, 40km, 60km, 80km, 100km, 120km, 200km, 300km and 400km and average stress drop values of 2.0MPa, 2.5MPa, 3.0MPa, 3.5MPa, 5.0MPa and 7.5MPa. For models that break the free-surface, the WSL zone is modeled assuming a 2km width with stress drop 0.0MPa or -2.0 MPa. Our results show that depending on the characterization of the WSL zone, the average stress drop at the seismogenic zone that fit the empirical models changes. If WSL zone is not considered, that is, stress drop at SL zone is the same as the seismogenic zone, average stress drop is about 20% smaller than models with WSL zone. By introducing more energy absorption at the SL zone, that could be the case of large mature faults, the average stress drop in the seismogenic zone increases. Suggesting that large earthquakes need higher stress drop to break the fault than buried and moderate earthquakes. Therefore, the value of the average stress drop for large events that break the free-source depend on the definition of the WSL. Suggesting that the WSL plays an important role on the prediction of final slip and fault displacement.

Plasma layers near the electrodes of a cesium diode - Anode layer

NASA Astrophysics Data System (ADS)

Oganezov, Z. A.; Timoshenko, L. S.; Tskhakaya, V. K.

1982-08-01

A planar electron beam probe is used to study the plasma layer in contact with a nonemitting electrode. It is found that the field distribution in the space-charge region of the layer adjacent to a nonemitting electrode is linear and obeys a specific empirical relation over a large range of variation in the plasma parameters, while the potential distribution has a corresponding parabolic form. In order for these values to be consistent, it is necessary to assume that the potential at the boundary between the quasi-neutral plasma and the space-charge is equal to a value which is substantially larger than the theoretically permitted potential drop in a quasi-neutral plasma.

Stress Drops of Earthquakes on the Subducting Pacific Plate in the South-East off Hokkaido, Japan

NASA Astrophysics Data System (ADS)

Saito, Y.; Yamada, T.

2013-12-01

Large earthquakes have been occurring repeatedly in the South-East of Hokkaido, Japan, where the Pacific Plate subducts beneath the Okhotsk Plate in the north-west direction. For example, the 2003 Tokachi-oki earthquake (Mw8.3 determined by USGS) took place in the region on September 26, 2003. Yamanaka and Kikuchi (2003) analyzed the slip distribution of the earthquake and concluded that the 2003 earthquake had ruptured the deeper half of the fault plane of the 1952 Tokachi-oki earthquake. Miyazaki et al. (2004) reported that a notable afterslip was observed at adjacent areas to the coseismic rupture zone of the 2003 earthquake, which suggests that there would be significant heterogeneities of strength, stress and frictional properties on the surface of the Pacific Plate in the region. In addition, some previous studies suggest that the region with a large slip in large earthquakes permanently have large difference of strength and the dynamic frictional stress level and that it would be able to predict the spatial pattern of slip in the next large earthquake by analyzing the stress drop of small earthquakes (e.g. Allmann and Shearer, 2007 and Yamada et al., 2010). We estimated stress drops of 150 earthquakes (4.2 ≤ M ≤ 5.0), using S-coda waves, or the waveforms from 4.00 to 9.11 seconds after the S wave arrivals, of Hi-net data. The 150 earthquakes were the ones that occurred from June, 2002 to December, 2010 in south-east of Hokkaido, Japan, from 40.5N to 43.5N and from 141.0E to 146.5E. First we selected waveforms of the closest earthquakes with magnitudes between 3.0 and 3.2 to individual 150 earthquakes as empirical Green's functions. We then calculated source spectral ratios of the 150 pairs of interested earthquakes and EGFs by deconvolving the individual S-coda waves. We finally estimated corner frequencies of earthquakes from the spectral ratios by assuming the omega-squared model of Boatwright (1978) and calculated stress drops of the earthquakes by using the model of Madariaga (1976). The estimated values of stress drop range from 1 to 10 MPa with a little number of outliers(Fig.(a)). Fig.(b) shows the spatial distribution of stress drops in south-east off Hokkaido, Japan. We found that earthquakes occurred around 42N 145E had larger stress drops. We are going to analyze smaller earthquakes and investigate the spatial pattern of the stress drop in the future. Fig. (a) Estimated values of stress drop with respect to seismic moments of earthquakes. (b) Spatial distribution of stress drops.

[Use of an aerosol generator (Guard) to control injurious insects in forestry, agriculture, and medical disinsection].

PubMed

Abdraziakov, O N; Ermishev, Iu V; Levkov, P A

2012-01-01

The Guard aerosol generator is a universal multioperational device without a field-of-use restriction in the application of permitted chemical and biological substances, by combining the function of a controlled dispersion aerosol generator and a remote small- and large-drop sprayer in one mechanism and can use aerosol pesticides. The drop fractionation range is as follows: 3-50, 50-100, 100-300, and 200-400 microm for aerosol, dead water, small-drop, and large-drop spraying, respectively, with smooth and step control of working liquid drops. Treatment using the Guard generator has been shown to be highly effective against agricultural and forestry pests. This paper describes the advantages of the Guard sprayer over those of the conventional air and ground ones. The long-term use of the Guard generator to control mosquitoes and ticks in the Tyumen region could substantially improve the epidemiological situation of tick-borne infections and protect children's recreation centers from attacks of bloodsuckers.

Simple, robust storage of drops and fluids in a microfluidic device.

PubMed

Boukellal, Hakim; Selimović, Seila; Jia, Yanwei; Cristobal, Galder; Fraden, Seth

2009-01-21

We describe a single microfluidic device and two methods for the passive storage of aqueous drops in a continuous stream of oil without any external control but hydrodynamic flow. Advantages of this device are that it is simple to manufacture, robust under operation, and drops never come into contact with each other, making it unnecessary to stabilize drops against coalescence. In one method the device can be used to store drops that are created upstream from the storage zone. In the second method the same device can be used to simultaneously create and store drops from a single large continuous fluid stream without resorting to the usual flow focusing or T-junction drop generation processes. Additionally, this device stores all the fluid introduced, including the first amount, with zero waste. Transport of drops in this device depends, however, on whether or not the aqueous drops wet the device walls. Analysis of drop transport in these two cases is presented. Finally, a method for extraction of the drops from the device is also presented, which works best when drops do not wet the walls of the chip.

Effect of drop size on the impact thermodynamics for supercooled large droplet in aircraft icing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Chen; Liu, Hong, E-mail: hongliu@sjtu.edu.cn

Supercooled large droplet (SLD), which can cause abnormal icing, is a well-known issue in aerospace engineering. Although efforts have been exerted to understand large droplet impact dynamics and the supercooled feature in the film/substrate interface, respectively, the thermodynamic effect during the SLD impact process has not received sufficient attention. This work conducts experimental studies to determine the effects of drop size on the thermodynamics for supercooled large droplet impingement. Through phenomenological reproduction, the rapid-freezing characteristics are observed in diameters of 400, 800, and 1300 μm. The experimental analysis provides information on the maximum spreading rate and the shrinkage rate ofmore » the drop, the supercooled diffusive rate, and the freezing time. A physical explanation of this unsteady heat transfer process is proposed theoretically, which indicates that the drop size is a critical factor influencing the supercooled heat exchange and effective heat transfer duration between the film/substrate interface. On the basis of the present experimental data and theoretical analysis, an impinging heating model is developed and applied to typical SLD cases. The model behaves as anticipated, which underlines the wide applicability to SLD icing problems in related fields.« less

Backscatter and extinction measurements in cloud and drizzle at CO2 laser wavelengths

NASA Technical Reports Server (NTRS)

Jennings, S. G.

1986-01-01

The backscatter and extinction of laboratory generated cloud and drizzle sized water drops were measured at carbon dioxide laser wavelengths (predominately at lambda = 10.591 micrometers). Two distinctly different drop size regimes were studied: one which covers the range normally encompassed by natural cloud droplets and the other representative of mist or drizzle sized drops. The derivation and verification of the relation between extinction and backscatter at carbon dioxide laser wavelengths should allow the determination of large cloud drop and drizzle extinction coefficient solely from a lidar return signal without requiring knowledge of the drop size distribution. This result will also apply to precipitation sized drops so long as they are spherical.

Possible relationship between Seismic Electric Signals (SES) lead time and earthquake stress drop

PubMed Central

DOLOGLOU, Elizabeth

2008-01-01

Stress drop values for fourteen large earthquakes with MW ≥ 5.4 which occurred in Greece during the period 1983–2007 are available. All these earthquakes were preceded by Seismic Electric Signals (SES). An attempt has been made to investigate possible correlation between their stress drop values and the corresponding SES lead times. For the stress drop, we considered the Brune stress drop, ΔσB, estimated from far field body wave displacement source spectra and ΔσSB derived from the strong motion acceleration response spectra. The results show a relation may exist between Brune stress drop, ΔσB, and lead time which implies that earthquakes with higher stress drop values are preceded by SES with shorter lead time. PMID:18941291

Star-shaped oscillations of Leidenfrost drops

NASA Astrophysics Data System (ADS)

Ma, Xiaolei; Liétor-Santos, Juan-José; Burton, Justin C.

2017-03-01

We experimentally investigate the self-sustained, star-shaped oscillations of Leidenfrost drops. The drops levitate on a cushion of evaporated vapor over a heated, curved surface. We observe modes with n =2 -13 lobes around the drop periphery. We find that the wavelength of the oscillations depends only on the capillary length of the liquid and is independent of the drop radius and substrate temperature. However, the number of observed modes depends sensitively on the liquid viscosity. The dominant frequency of pressure variations in the vapor layer is approximately twice the drop oscillation frequency, consistent with a parametric forcing mechanism. Our results show that the star-shaped oscillations are driven by capillary waves of a characteristic wavelength beneath the drop and that the waves are generated by a large shear stress at the liquid-vapor interface.

Development of Ultrasonically Levitated Drops as Microreactors for Study of Enzyme Kinetics and Potential as a Universal Portable Analysis System

DTIC Science & Technology

2008-12-01

1 DEVELOPMENT OF ULTRASONICALLY LEVITATED DROPS AS MICROREAC- TORS FOR STUDY OF ENZYME KINETICS AND POTENTIAL AS A UNIVERSAL PORTABLE ANALYSIS...microfluidic systems are incompatible with the chemistry one wishes to study. We have devel- oped an alternative approach. We use ultrasonically levitated ...since at least the 1940’s, we are the second group to carry out enzyme reactions in levitated drops, (Weis; Nardozzi 2005) and have fab- ricated the

Development of Alternating Current Potential Drop (ACPD) Procedures for Crack Detection in Aluminum Aircraft Panels.

DOT National Transportation Integrated Search

1993-12-01

The Alternating Current Potential Drop (ACPD) method is investigated as a means of making measurements in laboratory experiments on the initiation and growth of multiple site damage (MSD) cracks in a common aluminum alloy used for aircraft constructi...

Convergent-Filament Nonmechanical Pump

NASA Technical Reports Server (NTRS)

Collins, Earl R., Jr.

1989-01-01

Simple device induces small flow of liquid without help of moving parts, in presence or absence of gravity. Drops of liquid move on filaments from wide end of cone to narrow end. Gradually blend with drops on adjacent filaments to form large drops with menisci. Important use expected to be returning liquid condensate in heat pipes, and collection of samples from clouds or fog.

Bubble and Drop Nonlinear Dynamics (BDND)

NASA Technical Reports Server (NTRS)

Trinh, E. H.; Leal, L. Gary; Thomas, D. A.; Crouch, R. K.

1998-01-01

Free drops and bubbles are weakly nonlinear mechanical systems that are relatively simple to characterize experimentally in 1-G as well as in microgravity. The understanding of the details of their motion contributes to the fundamental study of nonlinear phenomena and to the measurement of the thermophysical properties of freely levitated melts. The goal of this Glovebox-based experimental investigation is the low-gravity assessment of the capabilities of a modular apparatus based on ultrasonic resonators and on the pseudo- extinction optical method. The required experimental task is the accurate measurements of the large-amplitude dynamics of free drops and bubbles in the absence of large biasing influences such as gravity and levitation fields. A single-axis levitator used for the positioning of drops in air, and an ultrasonic water-filled resonator for the trapping of air bubbles have been evaluated in low-gravity and in 1-G. The basic feasibility of drop positioning and shape oscillations measurements has been verified by using a laptop-interfaced automated data acquisition and the optical extinction technique. The major purpose of the investigation was to identify the salient technical issues associated with the development of a full-scale Microgravity experiment on single drop and bubble dynamics.

Auxiliary soft beam for the amplification of the elasto-capillary coiling: Towards stretchable electronics.

PubMed

Grandgeorge, Paul; Antkowiak, Arnaud; Neukirch, Sébastien

2017-09-18

A flexible fiber carrying a liquid drop may coil inside the drop thereby creating a drop-on-fiber system with an ultra-extensible behavior. During compression, the excess fiber is spooled inside the droplet and capillary forces keep the system taut. During subsequent elongation, the fiber is gradually released and if a large number of spools is uncoiled a high stretchability is achieved. This mechanical behaviour is of interest for stretchable connectors but information, may it be electronic or photonic, usually travels through stiff functional materials. These high Young's moduli, leading to large bending rigidity, prevent in-drop coiling. Here we overcome this limitation by attaching a beam of soft elastomer to the functional fiber, thereby creating a composite system which exhibits in-drop coiling and carries information while being ultra-extensible. We present a simple model to explain the underlying mechanics of the addition of the soft beam and we show how it favors in-drop coiling. We illustrate the method with a two-centimeter long micronic PEDOT:PSS conductive fiber joined to a PVS soft beam, showing that the system conveys electricity throughout a 1900% elongation. Copyright © 2017 Elsevier B.V. All rights reserved.

Redistribution of ice nuclei between cloud and rain droplets: Parameterization and application to deep convective clouds: ICE NUCLEI IN RAIN DROPLETS

DOE PAGES

Paukert, M.; Hoose, C.; Simmel, M.

2017-02-21

In model studies of aerosol-dependent immersion freezing in clouds, a common assumption is that each ice nucleating aerosol particle corresponds to exactly one cloud droplet. Conversely, the immersion freezing of larger drops—“rain”—is usually represented by a liquid volume-dependent approach, making the parameterizations of rain freezing independent of specific aerosol types and concentrations. This may lead to inconsistencies when aerosol effects on clouds and precipitation shall be investigated, since raindrops consist of the cloud droplets—and corresponding aerosol particles—that have been involved in drop-drop-collisions. We introduce an extension to a two-moment microphysical scheme in order to account explicitly for particle accumulation inmore » raindrops by tracking the rates of selfcollection, autoconversion, and accretion. This also provides a direct link between ice nuclei and the primary formation of large precipitating ice particles. A new parameterization scheme of drop freezing is presented to consider multiple ice nuclei within one drop and effective drop cooling rates. In our test cases of deep convective clouds, we find that at altitudes which are most relevant for immersion freezing, the majority of potential ice nuclei have been converted from cloud droplets into raindrops. Compared to the standard treatment of freezing in our model, the less efficient mineral dust-based freezing results in higher rainwater contents in the convective core, affecting both rain and hail precipitation. The aerosol-dependent treatment of rain freezing can reverse the signs of simulated precipitation sensitivities to ice nuclei perturbations.« less

Redistribution of ice nuclei between cloud and rain droplets: Parameterization and application to deep convective clouds: ICE NUCLEI IN RAIN DROPLETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paukert, M.; Hoose, C.; Simmel, M.

In model studies of aerosol-dependent immersion freezing in clouds, a common assumption is that each ice nucleating aerosol particle corresponds to exactly one cloud droplet. Conversely, the immersion freezing of larger drops—“rain”—is usually represented by a liquid volume-dependent approach, making the parameterizations of rain freezing independent of specific aerosol types and concentrations. This may lead to inconsistencies when aerosol effects on clouds and precipitation shall be investigated, since raindrops consist of the cloud droplets—and corresponding aerosol particles—that have been involved in drop-drop-collisions. We introduce an extension to a two-moment microphysical scheme in order to account explicitly for particle accumulation inmore » raindrops by tracking the rates of selfcollection, autoconversion, and accretion. This also provides a direct link between ice nuclei and the primary formation of large precipitating ice particles. A new parameterization scheme of drop freezing is presented to consider multiple ice nuclei within one drop and effective drop cooling rates. In our test cases of deep convective clouds, we find that at altitudes which are most relevant for immersion freezing, the majority of potential ice nuclei have been converted from cloud droplets into raindrops. Compared to the standard treatment of freezing in our model, the less efficient mineral dust-based freezing results in higher rainwater contents in the convective core, affecting both rain and hail precipitation. The aerosol-dependent treatment of rain freezing can reverse the signs of simulated precipitation sensitivities to ice nuclei perturbations.« less

Increased sensitivity of anodic stripping voltammetry at the hanging mercury drop electrode by ultracathodic deposition.

PubMed

Rodrigues, José A; Rodrigues, Carlos M; Almeida, Paulo J; Valente, Inês M; Gonçalves, Luís M; Compton, Richard G; Barros, Aquiles A

2011-09-09

An improved approach to the anodic stripping voltammetric (ASV) determination of heavy metals, using the hanging mercury drop electrode (HMDE), is reported. It was discovered that using very cathodic accumulation potentials, at which the solvent reduction occurs (overpotential deposition), the voltammetric signals of zinc(II), cadmium(II), lead(II) and copper(II) increase. When compared with the classical methodology a 5 to 10-fold signal increase is obtained. This effect is likely due to both mercury drop oscillation at such cathodic potentials and added local convection at the mercury drop surface caused by the evolution of hydrogen bubbles. Copyright © 2011 Elsevier B.V. All rights reserved.

An Alternate Path: The Experience of High-Potential Individuals Who Left School

ERIC Educational Resources Information Center

Ritchotte, Jennifer A.; Graefe, Amy K.

2017-01-01

Dropping out of school represents the culmination of a process that begins long before a student enters high school. It is estimated that a quarter of students with high potential leave school without a high school diploma; however, research on how high-potential students uniquely experience dropping out of school is in its beginning stages. This…

Is There a Maximum Size of Water Drops in Nature?

ERIC Educational Resources Information Center

Vollmer, Michael; Mollmann, Klaus-Peter

2013-01-01

In nature, water drops can have a large variety of sizes and shapes. Small droplets with diameters of the order of 5 to 10 µm are present in fog and clouds. This is not sufficiently large for gravity to dominate their behavior. In contrast, raindrops typically have sizes of the order of 1 mm, with observed maximum sizes in nature of around 5 mm in…

Parallel Electric Field on Auroral Magnetic Field Lines.

NASA Astrophysics Data System (ADS)

Yeh, Huey-Ching Betty

1982-03-01

The interaction of Birkeland (magnetic-field-aligned) current carriers and the Earth's magnetic field results in electrostatic potential drops along magnetic field lines. The statistical distributions of the field-aligned potential difference (phi)(,(PARLL)) were determined from the energy spectra of electron inverted "V" events observed at ionospheric altitude for different conditions of geomagnetic activity as indicated by the AE index. Data of 1270 electron inverted "V"'s were obtained from Low-Energy Electron measurements of the Atmosphere Explorer-C and -D Satellite (despun mode) in the interval January 1974-April 1976. In general, (phi)(,(PARLL)) is largest in the dusk to pre-midnight sector, smaller in the post-midnight to dawn sector, and smallest in the near noon sector during quiet and disturbed geomagnetic conditions; there is a steady dusk-dawn-noon asymmetry of the global (phi)(,(PARLL)) distribution. As the geomagnetic activity level increases, the (phi)(,(PARLL)) pattern expands to lower invariant latitudes, and the magnitude of (phi)(,(PARLL)) in the 13-24 magnetic local time sector increases significantly. The spatial structure and intensity variation of the global (phi)(,(PARLL)) distribution are statistically more variable, and the magnitudes of (phi)(,(PARLL)) have smaller correlation with the AE-index, in the post-midnight to dawn sector. A strong correlation is found to exist between upward Birkeland current systems and global parallel potential drops, and between auroral electron precipitation patterns and parallel potential drops, regarding their mophology, their intensity and their dependence of geomagnetic activity. An analysis of the fine-scale simultaneous current-voltage relationship for upward Birkeland currents in Region 1 shows that typical field-aligned potential drops are consistent with model predictions based on linear acceleration of the charge carriers through an electrostatic potential drop along convergent magnetic field lines to maintain current continuity. In a steady state, this model of simple electrostatic acceleration without anomalous resistivity also predicts observable relations between global parallel currents and parallel potential drops and between global energy deposition and parallel potential drops. The temperature, density, and species of the unaccelerated charge carriers are the relevant parameters of the model. The dusk-dawn -noon asymmetry of the global (phi)(,(PARLL)) distribution can be explained by the above steady-state (phi)(,(PARLL)) process if we associate the source regions of upward Birkeland current carriers in Region 1, Region 2, and the cusp region with the plasma sheet boundary layer, the near-Earth plasma sheet, and the magnetosheath, respectively. The results of this study provide observational information on the global distribution of parallel potential drops and the prevailing process of generating and maintaining potential gradients (parallel electric fields) along auroral magnetic field lines.

Characteristics of large three-dimensional heaps of particles produced by ballistic deposition from extended sources

NASA Astrophysics Data System (ADS)

Topic, Nikola; Gallas, Jason A. C.; Pöschel, Thorsten

2013-11-01

This paper reports a detailed numerical investigation of the geometrical and structural properties of three-dimensional heaps of particles. Our goal is the characterization of very large heaps produced by ballistic deposition from extended circular dropping areas. First, we provide an in-depth study of the formation of monodisperse heaps of particles. We find very large heaps to contain three new geometrical characteristics: they may display two external angles of repose, one internal angle of repose, and four distinct packing fraction (density) regions. Such features are found to be directly connected with the size of the dropping zone. We derive a differential equation describing the boundary of an unexpected triangular packing fraction zone formed under the dropping area. We investigate the impact that noise during the deposition has on the final heap structure. In addition, we perform two complementary experiments designed to test the robustness of the novel features found. The first experiment considers changes due to polydispersity. The second checks what happens when letting the extended dropping zone to become a point-like source of particles, the more common type of source.

Motion of a Drop on a Solid Surface Due to a Wettability Gradient

NASA Technical Reports Server (NTRS)

Subramanian, R.; Moumen, Nadjoua; McLaughlin, John B.

2005-01-01

The hydrodynamic force experienced by a spherical-cap drop moving on a solid surface is obtained from two approximate analytical solutions and used to predict the quasi-steady speed of the drop in a wettability gradient. One solution is based on approximation of the shape of the drop as a collection of wedges, and the other is based on lubrication theory. Also, asymptotic results from both approximations for small contact angles, as well as an asymptotic result from lubrication theory that is good when the length scale of the drop is large compared with the slip length, are given. The results for the hydrodynamic force also can be used to predict the quasi-steady speed of a drop sliding down an incline.

Groups of meteorite-producing meteoroids containing carbonaceous chondrite meteorites

NASA Astrophysics Data System (ADS)

Konovalova, N. A.; A.. Ibrohimov, A.; Kalashnikova, T. M.

2017-09-01

Proposed probable links of meteorite and meteorite-producing fireballs were been considered. Group associations between meteorite-producing meteoroids and meteorites were been determined for four carbonaceous chondrites Murchison, Maribo, Shutters Mill and Tagish Lake and potentially meteorite-producing bolides on the basis of links of their orbits. In result the several meteorite-producing sporadic slowly fireballs were found as the possible members of groups of four studied carbonaceous chondrite meteorites. One can presume that at present the identified groups may still contain large meteorite-dropping bodies.

The effect of roof strength on reducing occupant injury in rollovers.

PubMed

Herbst, Brian; Forrest, Steve; Orton, Tia; Meyer, Steven E; Sances, Anthony; Kumaresan, Srirangam

2005-01-01

Roof crush occurs and potentially contributes to serious or fatal occupant injury in 26% of rollovers. It is likely that glazing retention is related to the degree of roof crush experienced in rollover accidents. Occupant ejection (including partial ejection) is the leading cause of death and injury in rollover accidents. In fatal passenger car accidents involving ejection, 34% were ejected through the side windows. Side window glass retention during a rollover is likely to significantly reduce occupant ejections. The inverted drop test methodology is a test procedure to evaluate the structural integrity of roofs under loadings similar to those seen in real world rollovers. Recent testing on many different vehicle types indicates that damage consistent with field rollover accidents can be achieved through inverted drop testing at very small drop heights. Drop test comparisons were performed on 16 pairs of vehicles representing a large spectrum of vehicle types. Each vehicle pair includes a production vehicle and a vehicle with a reinforced roof structure dropped under the same test conditions. This paper offers several examples of post-production reinforcements to roof structures that significantly increase the crush resistance of the roof as measured by inverted drop tests. These modifications were implemented with minimal impact on vehicle styling, interior space and visual clearances. The results of these modifications indicate that roof crush can be mitigated by nearly an order of magnitude, as roof crush was reduced by 44-91% with only a 1-2.3% increase in vehicle weight. Additionally, this paper analyzes the glazing breakage patterns in the moveable tempered side windows on the side adjacent to the vehicle impact point in the inverted drop tests. A comparison is made between the production vehicles and the reinforced vehicles in order to determine if the amount roof crush is related to glazing integrity in the side windows. Lastly, two drop test pairs, performed with Hybrid III test dummies, indicates that the reduction of roof crush resulted in a direct reduction in neck loading and therefore an increase in occupant protection.

A hollow sphere soft lithography approach for long-term hanging drop methods.

PubMed

Lee, Won Gu; Ortmann, Daniel; Hancock, Matthew J; Bae, Hojae; Khademhosseini, Ali

2010-04-01

In conventional hanging drop (HD) methods, embryonic stem cell aggregates or embryoid bodies (EBs) are often maintained in small inverted droplets. Gravity limits the volumes of these droplets to less than 50 microL, and hence such cell cultures can only be sustained for a few days without frequent media changes. Here we present a new approach to performing long-term HD methods (10-15 days) that can provide larger media reservoirs in a HD format to maintain more consistent culture media conditions. To implement this approach, we fabricated hollow sphere (HS) structures by injecting liquid drops into noncured poly(dimethylsiloxane) mixtures. These structures served as cell culture chambers with large media volumes (500 microL in each sphere) where EBs could grow without media depletion. The results showed that the sizes of the EBs cultured in the HS structures in a long-term HD format were approximately twice those of conventional HD methods after 10 days in culture. Further, HS cultures showed multilineage differentiation, similar to EBs cultured in the HD method. Due to its ease of fabrication and enhanced features, this approach may be of potential benefit as a stem cell culture method for regenerative medicine.

A Hollow Sphere Soft Lithography Approach for Long-Term Hanging Drop Methods

PubMed Central

Lee, Won Gu; Ortmann, Daniel; Hancock, Matthew J.; Bae, Hojae

2010-01-01

In conventional hanging drop (HD) methods, embryonic stem cell aggregates or embryoid bodies (EBs) are often maintained in small inverted droplets. Gravity limits the volumes of these droplets to less than 50 μL, and hence such cell cultures can only be sustained for a few days without frequent media changes. Here we present a new approach to performing long-term HD methods (10–15 days) that can provide larger media reservoirs in a HD format to maintain more consistent culture media conditions. To implement this approach, we fabricated hollow sphere (HS) structures by injecting liquid drops into noncured poly(dimethylsiloxane) mixtures. These structures served as cell culture chambers with large media volumes (500 μL in each sphere) where EBs could grow without media depletion. The results showed that the sizes of the EBs cultured in the HS structures in a long-term HD format were approximately twice those of conventional HD methods after 10 days in culture. Further, HS cultures showed multilineage differentiation, similar to EBs cultured in the HD method. Due to its ease of fabrication and enhanced features, this approach may be of potential benefit as a stem cell culture method for regenerative medicine. PMID:19505251

Three-Dimensional Simulation of Liquid Drop Dynamics Within Unsaturated Vertical Hele-Shaw Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hai Huang; Paul Meakin

A three-dimensional, multiphase fluid flow model with volume of fluid-interface tracking was developed and applied to study the multiphase dynamics of moving liquid drops of different sizes within vertical Hele-Shaw cells. The simulated moving velocities are significantly different from those obtained from a first-order analytical approximation, based on simple force-balance concepts. The simulation results also indicate that the moving drops can exhibit a variety of shapes and that the transition among these different shapes is largely determined by the moving velocities. More important, there is a transition from a linear moving regime at small capillary numbers, in which the capillarymore » number scales linearly with the Bond number, to a nonlinear moving regime at large capillary numbers, in which the moving drop releases a train of droplets from its trailing edge. The train of droplets forms a variety of patterns at different moving velocities.« less

Nonlinear oscillations of inviscid free drops

NASA Technical Reports Server (NTRS)

Patzek, T. W.; Benner, R. E., Jr.; Basaran, O. A.; Scriven, L. E.

1991-01-01

The present analysis of free liquid drops' inviscid oscillations proceeds through solution of Bernoulli's equation to obtain the free surface shape and of Laplace's equation for the velocity potential field. Results thus obtained encompass drop-shape sequences, pressure distributions, particle paths, and the temporal evolution of kinetic and surface energies; accuracy is verified by the near-constant drop volume and total energy, as well as the diminutiveness of mass and momentum fluxes across drop surfaces. Further insight into the nature of oscillations is provided by Fourier power spectrum analyses of mode interactions and frequency shifts.

Consistent Large-Eddy Simulation of a Temporal Mixing Layer Laden with Evaporating Drops. Part 2; A Posteriori Modelling

NASA Technical Reports Server (NTRS)

Leboissertier, Anthony; Okong'O, Nora; Bellan, Josette

2005-01-01

Large-eddy simulation (LES) is conducted of a three-dimensional temporal mixing layer whose lower stream is initially laden with liquid drops which may evaporate during the simulation. The gas-phase equations are written in an Eulerian frame for two perfect gas species (carrier gas and vapour emanating from the drops), while the liquid-phase equations are written in a Lagrangian frame. The effect of drop evaporation on the gas phase is considered through mass, species, momentum and energy source terms. The drop evolution is modelled using physical drops, or using computational drops to represent the physical drops. Simulations are performed using various LES models previously assessed on a database obtained from direct numerical simulations (DNS). These LES models are for: (i) the subgrid-scale (SGS) fluxes and (ii) the filtered source terms (FSTs) based on computational drops. The LES, which are compared to filtered-and-coarsened (FC) DNS results at the coarser LES grid, are conducted with 64 times fewer grid points than the DNS, and up to 64 times fewer computational than physical drops. It is found that both constant-coefficient and dynamic Smagorinsky SGS-flux models, though numerically stable, are overly dissipative and damp generated small-resolved-scale (SRS) turbulent structures. Although the global growth and mixing predictions of LES using Smagorinsky models are in good agreement with the FC-DNS, the spatial distributions of the drops differ significantly. In contrast, the constant-coefficient scale-similarity model and the dynamic gradient model perform well in predicting most flow features, with the latter model having the advantage of not requiring a priori calibration of the model coefficient. The ability of the dynamic models to determine the model coefficient during LES is found to be essential since the constant-coefficient gradient model, although more accurate than the Smagorinsky model, is not consistently numerically stable despite using DNS-calibrated coefficients. With accurate SGS-flux models, namely scale-similarity and dynamic gradient, the FST model allows up to a 32-fold reduction in computational drops compared to the number of physical drops, without degradation of accuracy; a 64-fold reduction leads to a slight decrease in accuracy.

Review on drop towers and long drop tubes

NASA Technical Reports Server (NTRS)

Bayuzick, R. J.; Hofmeister, W. H.; Robinson, M. B.

1987-01-01

A drop tube is an enclosure in which a molten sample can be solidified while falling; three such large tubes are currently in existence, all at NASA research facilities, and are engaged in combustion and fluid physics-related experiments rather than in materials research. JPL possesses smaller tubes, one of which can be cryogenically cooled to produce glass and metal microshells. A new small drop tube will soon begin operating at NASA Lewis that is equipped with four high-speed two-color pyrometers spaced equidistantly along the column.

Controlling Vapor Pressure In Hanging-Drop Crystallization

NASA Technical Reports Server (NTRS)

Carter, Daniel C.; Smith, Robbie

1988-01-01

Rate of evaporation adjusted to produce larger crystals. Device helps to control vapor pressure of water and other solvents in vicinity of hanging drop of solution containing dissolved enzyme protein. Well of porous frit (sintered glass) holds solution in proximity to drop of solution containing protein or enzyme. Vapor from solution in frit controls evaporation of solvent from drop to control precipitation of protein or enzyme. With device, rate of nucleation limited to decrease number and increase size (and perhaps quality) of crystals - large crystals of higher quality needed for x-ray diffraction studies of macromolecules.

Low-Energy Electron Effects on the Polar Wind Observed by the POLAR Spacecraft

NASA Technical Reports Server (NTRS)

Horwitz, J. L.; Su, Y.-J.; Dors, E. E.; Moore, Thomas E.; Giles, Barbara L.; Chandler, Michael O.; Craven, Paul D.; Chang, S.-W.; Scudder, J.

1998-01-01

Large ion outflow velocity variation at POLAR apogee have been observed. The observed H+ flow velocities were in the range of 23-110 km/s and 0+ flow velocities were in the range of 5-25 km/s. These velocity ranges lie between those predicted by simulations of the photoelectron-driven polar wind and "baseline" polar wind. The electric current contributions of the photoelectrons and polar rain are expected to control the size and altitude of an electric potential drop which accelerates the polar wind at relatively high altitudes. In this presentation, we compare polar wind characteristics observed near 5000 km and 8 RE altitudes by the Thermal Ion Dynamics Experiment (TIDE) with measurements of low-energy electrons sampled by HYDRA, both from the POLAR spacecraft, to examine possible effects of the polar rain and photoelectrons on the polar wind. Both correlations and anti-correlations are found between the polar wind velocities and the polar rain fluxes at POLAR apogee during different polar cap crossings. Also, the low-altitude upward/downward photoelectron spectra are used to estimates the potential drops above the spacecraft. We interpret these observations in terms of the effects that both photoelectrons and polar rain may have on the electric potential and polar wind acceleration along polar cap magnetic field lines.

Breakup of a thin drop under a stagnation point flow

NASA Astrophysics Data System (ADS)

Hooshanginejad, Alireza; Lee, Sungyon; Shelley, Michael

2017-11-01

Recent studies by Hooshanginejad and Lee (2017) have demonstrated complex depinning behaviors of a partially wetting droplet under wind. Motivated by this study, we examine the coupled evolution of a 2D thin drop and external wind, when it is initially held against a fast stagnation point flow. Our drop lubrication model employs the potential flow and Prandtl boundary layer theory for outer flow to compute the internal drop flow corresponding to drop deformations. Furthermore, both the analytical and numerical steady state solutions provide a partial prediction for the drop's final shape and help identify the range of droplet sizes that undergo a breakup for the given flow condition.

Fast H-DROP: A thirty times accelerated version of H-DROP for interactive SVM-based prediction of helical domain linkers

NASA Astrophysics Data System (ADS)

Richa, Tambi; Ide, Soichiro; Suzuki, Ryosuke; Ebina, Teppei; Kuroda, Yutaka

2017-02-01

Efficient and rapid prediction of domain regions from amino acid sequence information alone is often required for swift structural and functional characterization of large multi-domain proteins. Here we introduce Fast H-DROP, a thirty times accelerated version of our previously reported H-DROP (Helical Domain linker pRediction using OPtimal features), which is unique in specifically predicting helical domain linkers (boundaries). Fast H-DROP, analogously to H-DROP, uses optimum features selected from a set of 3000 ones by combining a random forest and a stepwise feature selection protocol. We reduced the computational time from 8.5 min per sequence in H-DROP to 14 s per sequence in Fast H-DROP on an 8 Xeon processor Linux server by using SWISS-PROT instead of Genbank non-redundant (nr) database for generating the PSSMs. The sensitivity and precision of Fast H-DROP assessed by cross-validation were 33.7 and 36.2%, which were merely 2% lower than that of H-DROP. The reduced computational time of Fast H-DROP, without affecting prediction performances, makes it more interactive and user-friendly. Fast H-DROP and H-DROP are freely available from http://domserv.lab.tuat.ac.jp/.

Energetic Electron Injections Deep Into the Inner Magnetosphere: A Result of the Subauroral Polarization Stream (SAPS) Potential Drop

NASA Astrophysics Data System (ADS)

Lejosne, Solène; Kunduri, B. S. R.; Mozer, F. S.; Turner, D. L.

2018-05-01

It has been reported that the dynamics of energetic (tens to hundreds of keV) electrons and ions is inconsistent with the theoretical picture in which the large-scale electric field is a superposition of corotation and convection electric fields. Combining one year of measurements by the Super Dual Auroral Radar Network, DMSP F-18, and the Van Allen Probes, we show that subauroral polarization streams (SAPSs) are observed when energetic electrons have penetrated below L = 4. Outside the plasmasphere in the premidnight region, potential energy is subtracted from the total energy of ions and added to the total energy of electrons during SAPS onset. This potential energy is converted into radial motion as the energetic particles drift around Earth and leave the SAPS azimuthal sector. As a result, energetic electrons are injected deeper than energetic ions when SAPSs are included in the large-scale electric field picture, in line with observations.

An effective medium approach to predict the apparent contact angle of drops on super-hydrophobic randomly rough surfaces.

PubMed

Bottiglione, F; Carbone, G

2015-01-14

The apparent contact angle of large 2D drops with randomly rough self-affine profiles is numerically investigated. The numerical approach is based upon the assumption of large separation of length scales, i.e. it is assumed that the roughness length scales are much smaller than the drop size, thus making it possible to treat the problem through a mean-field like approach relying on the large-separation of scales. The apparent contact angle at equilibrium is calculated in all wetting regimes from full wetting (Wenzel state) to partial wetting (Cassie state). It was found that for very large values of the roughness Wenzel parameter (r(W) > -1/ cos θ(Y), where θ(Y) is the Young's contact angle), the interface approaches the perfect non-wetting condition and the apparent contact angle is almost equal to 180°. The results are compared with the case of roughness on one single scale (sinusoidal surface) and it is found that, given the same value of the Wenzel roughness parameter rW, the apparent contact angle is much larger for the case of a randomly rough surface, proving that the multi-scale character of randomly rough surfaces is a key factor to enhance superhydrophobicity. Moreover, it is shown that for millimetre-sized drops, the actual drop pressure at static equilibrium weakly affects the wetting regime, which instead seems to be dominated by the roughness parameter. For this reason a methodology to estimate the apparent contact angle is proposed, which relies only upon the micro-scale properties of the rough surface.

Detailed characteristics of drop-laden mixing layers: LES predictions compared to DNS

NASA Technical Reports Server (NTRS)

Okong'o, N.; Leboissetier, A.; Bellan, J.

2004-01-01

Results have been compared from Direct Numerical Simulation (DNS) and Large Eddy Simulation (LES) of a temporal mixing layer laden with evaporating drops, to assess the ability of LES to reproduce detailed characteristics of DNS.

Thermal imaging of levitated fresh and salt water drops during laser irradiation

NASA Astrophysics Data System (ADS)

Brownell, Cody; Biggs, Harrison

2017-11-01

Simulation of high energy laser propagation and scattering in the maritime environment is problematic, due to the high likelihood of turbulence, fog, and rain or sea spray within the beam path. Considering large water drops (diameters of approximately 1-mm), such as those found in a light rain, an incident high energy laser will lead to rapid evaporation of the water drop as it traverses the beam path. In this work we present surface temperature measurements of a water drop obtained using a FLIR IR camera. The drop is acoustically levitated, and subject to a continuous wave laser with a wavelength of 1070-nm and a mean irradiance of approximately 800 W/cm2. These measurements show that the steady-state surface temperature of the drop is well below the saturation temperature, and for pure substances the equilibrium temperature decreases with decreasing drop volume similar to observations with smaller aqueous aerosols. Temperature non-uniformity within the drop is also assessed from statistics of the surface temperature fluctuations. Preliminary results from irradiated salt water drops show notably different behavior from fresh water drops, including temperature spikes as the drop volume decreases and occasional nucleate boiling. Acknowledge support from ONR #N00014-17-WX-00031.

Looking Under a Leidenfrost Drop

NASA Astrophysics Data System (ADS)

Burton, Justin; Sharpe, Aaron; van der Veen, Roeland; Franco, Andres; Nagel, Sidney

2011-11-01

The Leidenfrost effect can be observed when small water drops move around effortlessly without sticking on a hot pan. The transition to a levitated state, where the drops rest on an insulating layer of vapor, occurs at the Leidenfrost temperature. Experiment and theory have examined the lifetime and maximum size of Leidenfrost drops. However, the liquid-vapor interface beneath the drop has not been fully charcterized. We report experiments using laser-light interference to measure the geometry of the liquid-vapor interface. By imaging the interference fringes produced between the bottom surface of the liquid and the hot substrate, we can measure the curvature of the vapor pocket beneath the drop as well as the azimuthal undulations along the neck that sits closest to the surface. From these measurements, we can extrapolate the shape of the bottom of the drop, which fluctuates in time with a period of a few milliseconds for millimeter-sized water drops. Our measurements of the azimuthal neck radius agree with predictions: the difference between the drop and neck radii, (Rd -Rn) ~0.53 λ in the limit of large drops where λ is the capillary length of the fluid. For small drops we recover the result found in that Rn ~Rd2 / λ .

Analysis of the convective evaporation of nondilute clusters of drops

NASA Technical Reports Server (NTRS)

Bellan, J.; Harstad, K.

1987-01-01

The penetration distance of an outer flow into a drop cluster volume is the critical, evaporation mode-controlling parameter in the present model for nondilute drop clusters' convective evaporation. The model is found to perform well for such low penetration distances as those obtained for dense clusters in hot environments and low relative velocities between the outer gases and the cluster. For large penetration distances, however, the predictive power of the model deteriorates; in addition, the evaporation time is found to be a weak function of the initial relative velocity and a strong function of the initial drop temperature. The results generally show that the interior drop temperature was transient throughout the drop lifetime, although temperature nonuniformities persisted up to the first third of the total evaporation time at most.

Acoustically levitated dancing drops: Self-excited oscillation to chaotic shedding.

PubMed

Lin, Po-Cheng; I, Lin

2016-02-01

We experimentally demonstrate self-excited oscillation and shedding of millimeter-sized water drops, acoustically levitated in a single-node standing waves cavity, by decreasing the steady acoustic wave intensity below a threshold. The perturbation of the acoustic field by drop motion is a possible source for providing an effective negative damping for sustaining the growing amplitude of the self-excited motion. Its further interplay with surface tension, drop inertia, gravity and acoustic intensities, select various self-excited modes for different size of drops and acoustic intensity. The large drop exhibits quasiperiodic motion from a vertical mode and a zonal mode with growing coupling, as oscillation amplitudes grow, until falling on the floor. For small drops, chaotic oscillations constituted by several broadened sectorial modes and corresponding zonal modes are self-excited. The growing oscillation amplitude leads to droplet shedding from the edges of highly stretched lobes, where surface tension no longer holds the rapid expanding flow.

Acoustically levitated dancing drops: Self-excited oscillation to chaotic shedding

NASA Astrophysics Data System (ADS)

Lin, Po-Cheng; I, Lin

2016-02-01

We experimentally demonstrate self-excited oscillation and shedding of millimeter-sized water drops, acoustically levitated in a single-node standing waves cavity, by decreasing the steady acoustic wave intensity below a threshold. The perturbation of the acoustic field by drop motion is a possible source for providing an effective negative damping for sustaining the growing amplitude of the self-excited motion. Its further interplay with surface tension, drop inertia, gravity and acoustic intensities, select various self-excited modes for different size of drops and acoustic intensity. The large drop exhibits quasiperiodic motion from a vertical mode and a zonal mode with growing coupling, as oscillation amplitudes grow, until falling on the floor. For small drops, chaotic oscillations constituted by several broadened sectorial modes and corresponding zonal modes are self-excited. The growing oscillation amplitude leads to droplet shedding from the edges of highly stretched lobes, where surface tension no longer holds the rapid expanding flow.

Creation of nano eye-drops and effective drug delivery to the interior of the eye

NASA Astrophysics Data System (ADS)

Ikuta, Yoshikazu; Aoyagi, Shigenobu; Tanaka, Yuji; Sato, Kota; Inada, Satoshi; Koseki, Yoshitaka; Onodera, Tsunenobu; Oikawa, Hidetoshi; Kasai, Hitoshi

2017-03-01

Nano eye-drops are a new type of ophthalmic treatment with increased potency and reduced side effects. Compounds in conventional eye-drops barely penetrate into the eye because the cornea, located at the surface of eye, has a strong barrier function for preventing invasion of hydrophilic or large-sized materials from the outside. In this work, we describe the utility of nano eye-drops utilising brinzolamide, a commercially available glaucoma treatment drug, as a target compound. Fabrication of the nanoparticles of brinzolamide prodrug increases the eye penetration rate and results in high drug efficacy, compared with that of commercially available brinzolamide eye-drops formulated as micro-sized structures. In addition, the resulting nano eye-drops were not toxic to the corneal epithelium after repeated administration for 1 week. The nano eye-drops may have applications as a next-generation ophthalmic treatment.

Large daily stock variation is associated with cardiovascular mortality in two cities of Guangdong, China.

PubMed

Lin, Hualiang; Zhang, Yonghui; Xu, Yanjun; Liu, Tao; Xiao, Jianpeng; Luo, Yuan; Xu, Xiaojun; He, Yanhui; Ma, Wenjun

2013-01-01

The current study aimed to examine the effects of daily change of the Shenzhen Stock Exchange Index on cardiovascular mortality in Guangzhou and Taishan, China. Daily mortality and stock performance data during 2006-2010 were collected to construct the time series for the two cities. A distributed lag non-linear model was utilized to examine the effect of daily stock index changes on cardiovascular mortality after controlling for potential confounding factors. We observed a delayed non-linear effect of the stock index change on cardiovascular mortality: both rising and declining of the stock index were associated with increased cardiovascular deaths. In Guangzhou, the 15-25 lag days cumulative relative risk of an 800 index drop was 2.08 (95% CI: 1.38-3.14), and 2.38 (95% CI: 1.31-4.31) for an 800 stock index increase on the cardiovascular mortality, respectively. In Taishan, the cumulative relative risk over 15-25 days lag was 1.65 (95% CI: 1.13-2.42) for an 800 index drop and 2.08 (95% CI: 1.26-3.42) for an 800 index rising, respectively. Large ups and downs in daily stock index might be important predictor of cardiovascular mortality.

A threshold effect for spacecraft charging

NASA Technical Reports Server (NTRS)

Olsen, R. C.

1983-01-01

The borderline case between no charging and large (kV) negative potentials for eclipse charging events on geosynchronous satellites is investigated, and the dependence of this transition on a threshold energy in the ambient plasma is examined. Data from the Applied Technology Satellite 6 and P78-2 (SCATHA) show that plasma sheet fluxes must extend above 10 keV for these satellites to charge in eclipse. The threshold effect is a result of the shape of the normal secondary yield curve, in particular the high energy crossover, where the secondary yield drops below 1. It is found that a large portion of the ambient electron flux must exceed this energy for a negative current to exist.

Motion of Deformable Drops Through Porous Media

NASA Astrophysics Data System (ADS)

Zinchenko, Alexander Z.; Davis, Robert H.

2017-01-01

This review describes recent progress in the fundamental understanding of deformable drop motion through porous media with well-defined microstructures, through rigorous first-principles hydrodynamical simulations and experiments. Tight squeezing conditions, when the drops are much larger than the pore throats, are particularly challenging numerically, as the drops nearly coat the porous material skeleton with small surface clearance, requiring very high surface resolution in the algorithms. Small-scale prototype problems for flow-induced drop motion through round capillaries and three-dimensional (3D) constrictions between solid particles, and for gravity-induced squeezing through round orifices and 3D constrictions, show how forcing above critical conditions is needed to overcome trapping. Scaling laws for the squeezing time are suggested. Large-scale multidrop/multiparticle simulations for emulsion flow through a random granular material with multiple drop breakup show that the drop phase generally moves faster than the carrier fluid; both phase velocities equilibrate much faster to the statistical steady state than does the drop-size distribution.

Clustering of particles and pathogens within evaporating drops

NASA Astrophysics Data System (ADS)

Park, Jaebum; Kim, Ho-Young

2017-11-01

The evaporation of sessile suspension drops leads to accumulation of the particles around the pinned contact line, which is widely termed the coffee ring effect. However, the evaporation behavior of a liquid drop containing a small number of particles with the size comparable to the host drop is unclear yet. Thus, here we investigate the motion and spatial distribution of large particles within a sessile drop. The spherical particles cluster only when their initial distance is below a critical value, which is a function of the diameter and wettability of particle as well as the surface tension and size of the host drop. We rationalize such a critical distance for self-assembly based on the balance of the capillary force and the frictional resistance to sliding and rolling of the particles on a solid substrate. We further discuss the physical significance of this drop-mediated ``Cheerios effect'' in connection with the fate of pathogens residing in drops as a result of sneezing and coughing.

Achieving Zero Current for Polar Wind Outflow on Open Flux Tubes Subjected to Large Photoelectron Fluxes

NASA Technical Reports Server (NTRS)

Wilson, G. R.; Khazanov, G.; Horwitz, J. L.

1997-01-01

In this study we investigate how the condition of zero current on open flux tubes with polar wind outflow, subjected to large photoelectron fluxes, can be achieved. We employ a steady state collisionless semikinetic model to determine the density profiles of O(+), H(+), thermal electrons and photoelectrons coming from the ionosphere along with H(+), ions and electrons coming from the magnetosphere. The model solution attains a potential distribution which both satisfies the condition of charge neutrality and zero current. For the range of parameters considered in this study we find that a 45-60 volt discontinuous potential drop may develop to reflect most of the photoelectrons back toward the ionosphere. This develops because the downward flux of electrons from the magnetosphere to the ionosphere on typical open flux tubes (e.g. the polar rain) appears to be insufficient to balance the photoelectron flux from the ionosphere.

Carbon dioxide recycling: emerging large-scale technologies with industrial potential.

PubMed

Quadrelli, Elsje Alessandra; Centi, Gabriele; Duplan, Jean-Luc; Perathoner, Siglinda

2011-09-19

This Review introduces this special issue of ChemSusChem dedicated to CO(2) recycling. Its aim is to offer an up-to-date overview of CO(2) chemical utilization (inorganic mineralization, organic carboxylation, reduction reactions, and biochemical conversion), as a continuation and extension of earlier books and reviews on this topic, but with a specific focus on large-volume routes and projects/pilot plants that are currently emerging at (pre-)industrial level. The Review also highlights how some of these routes will offer a valuable opportunity to introduce renewable energy into the existing energy and chemical infrastructure (i.e., "drop-in" renewable energy) by synthesis of chemicals from CO(2) that are easy to transport and store. CO(2) conversion therefore has the potential to become a key pillar of the sustainable and resource-efficient production of chemicals and energy from renewables. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Drop "impact" on an airfoil surface.

PubMed

Wu, Zhenlong

2018-06-01

Drop impact on an airfoil surface takes place in drop-laden two-phase flow conditions such as rain and icing, which are encountered by wind turbines or airplanes. This phenomenon is characterized by complex nonlinear interactions that manifest rich flow physics and pose unique modeling challenges. In this article, the state of the art of the research about drop impact on airfoil surface in the natural drop-laden two-phase flow environment is presented. The potential flow physics, hazards, characteristic parameters, droplet trajectory calculation, drop impact dynamics and effects are discussed. The most key points in establishing the governing equations for a drop-laden flow lie in the modeling of raindrop splash and water film. The various factors affecting the drop impact dynamics and the effects of drop impact on airfoil aerodynamic performance are summarized. Finally, the principle challenges and future research directions in the field as well as some promising measures to deal with the adverse effects of drop-laden flows on airfoil performance are proposed. Copyright © 2018 Elsevier B.V. All rights reserved.

Electrohydrodynamics of drops in strong uniform dc electric fields

NASA Astrophysics Data System (ADS)

Salipante, Paul F.; Vlahovska, Petia M.

2010-11-01

Drop deformation in an uniform dc electric field is a classic problem. The pioneering work of Taylor demonstrated that for weakly conducting media, the drop fluid undergoes a toroidal flow and the drop adopts a prolate or oblate spheroidal shape, the flow and shape being axisymmetrically aligned with the applied field. However, recent studies have revealed a nonaxisymmetric rotational flow in strong fields, similar to the rotation of solid dielectric particles observed by Quincke in the 19th century. We present a systematic experimental study of this phenomenon, which highlights the importance of charge convection along the drop surface. The critical electric field, drop inclination angle, and rate of rotation are measured. We find that for small, high viscosity drops, the threshold field strength is well approximated by the Quincke rotation criterion. Reducing the viscosity ratio shifts the onset for rotation to stronger fields. The drop inclination angle increases with field strength. The rotation rate is approximately given by the inverse Maxwell-Wagner polarization time. Novel features are also observed such as a hysteresis in the tilt angle for large low-viscosity drops.

Coplanar electrowetting-induced stirring as a tool to manipulate biological samples in lubricated digital microfluidics. Impact of ambient phase on drop internal flow patterna)

PubMed Central

Davoust, Laurent; Fouillet, Yves; Malk, Rachid; Theisen, Johannes

2013-01-01

Oscillating electrowetting on dielectrics (EWOD) with coplanar electrodes is investigated in this paper as a way to provide efficient stirring within a drop with biological content. A supporting model inspired from Ko et al. [Appl. Phys. Lett. 94, 194102 (2009)] is proposed allowing to interpret oscillating EWOD-induced drop internal flow as the result of a current streaming along the drop surface deformed by capillary waves. Current streaming behaves essentially as a surface flow generator and the momentum it sustains within the (viscous) drop is even more significant as the surface to volume ratio is small. With the circular electrode pair considered in this paper, oscillating EWOD sustains toroidal vortical flows when the experiments are conducted with aqueous drops in air as ambient phase. But when oil is used as ambient phase, it is demonstrated that the presence of an electrode gap is responsible for a change in drop shape: a pinch-off at the electrode gap yields a peanut-shaped drop and a symmetry break-up of the EWOD-induced flow pattern. Viscosity of oil is also responsible for promoting an efficient damping of the capillary waves which populate the surface of the actuated drop. As a result, the capillary network switches from one standing wave to two superimposed traveling waves of different mechanical energy, provided that actuation frequency is large enough, for instance, as large as the one commonly used in electrowetting applications (f ∼ 500 Hz and beyond). Special emphasis is put on stirring of biological samples. As a typical application, it is demonstrated how beads or cell clusters can be focused under flow either at mid-height of the drop or near the wetting plane, depending on how the nature of the capillary waves is (standing or traveling), and therefore, depending on the actuation frequency (150 Hz–1 KHz). PMID:24404038

Characterization of new eye drops with choline salicylate and assessment of their irritancy by in vitro short time exposure tests.

PubMed

Wroblewska, Katarzyna; Kucinska, Małgorzata; Murias, Marek; Lulek, Janina

2015-09-01

The aim of our study was to examine the irritation potential of new eye drops containing 2% choline salicylate (CS) as an active pharmaceutical ingredient (API) and various polymers increasing eye drop viscosity (hydroxyethylcellulose, hydroxypropyl methylcellulose, methylcellulose, polyvinyl alcohol, polyvinylpyrrolidone). The standard method for assessing the potential of irritating substances has been the Draize rabbit eye test. However the European Centre for Validation of Alternative Methods and the Coordinating Committee for Validation of Alternative Methods recommend, short time exposure (STE) in vitro tests as an alternative method for assessing eye irritation. The eye irritation potential was determined using cytotoxicity test methods for rabbit corneal cell line (SIRC) after 5 min exposure. The viability of cells was determined using two cytotoxicity assays: MTT and Neutral Red Uptake. According to the irritation rankings for the short time exposure test, all tested eye drops are classified as non-irritating (cell viability >70%).

Characterization of new eye drops with choline salicylate and assessment of their irritancy by in vitro short time exposure tests

PubMed Central

Wroblewska, Katarzyna; Kucinska, Małgorzata; Murias, Marek; Lulek, Janina

2014-01-01

The aim of our study was to examine the irritation potential of new eye drops containing 2% choline salicylate (CS) as an active pharmaceutical ingredient (API) and various polymers increasing eye drop viscosity (hydroxyethylcellulose, hydroxypropyl methylcellulose, methylcellulose, polyvinyl alcohol, polyvinylpyrrolidone). The standard method for assessing the potential of irritating substances has been the Draize rabbit eye test. However the European Centre for Validation of Alternative Methods and the Coordinating Committee for Validation of Alternative Methods recommend, short time exposure (STE) in vitro tests as an alternative method for assessing eye irritation. The eye irritation potential was determined using cytotoxicity test methods for rabbit corneal cell line (SIRC) after 5 min exposure. The viability of cells was determined using two cytotoxicity assays: MTT and Neutral Red Uptake. According to the irritation rankings for the short time exposure test, all tested eye drops are classified as non-irritating (cell viability >70%). PMID:27134543

Gyroscopic instability of a drop trapped inside an inclined circular hydraulic jump.

PubMed

Pirat, Christophe; Lebon, Luc; Fruleux, Antoine; Roche, Jean-Sébastien; Limat, Laurent

2010-08-20

A drop of moderate size deposited inside a circular hydraulic jump remains trapped at the shock front and does not coalesce with the liquid flowing across the jump. For a small inclination of the plate on which the liquid is impacting, the drop does not always stay at the lowest position and oscillates around it with a sometimes large amplitude, and a frequency that slightly decreases with flow rate. We suggest that this striking behavior is linked to a gyroscopic instability in which the drop tries to keep constant its angular momentum while sliding along the jump.

Improved Control of Charging Voltage for Li-Ion Battery

NASA Technical Reports Server (NTRS)

Timmerman, Paul; Bugga, Ratnakumar

2006-01-01

The protocol for charging a lithium-ion battery would be modified, according to a proposal, to compensate for the internal voltage drop (charging current internal resistance of the battery). The essence of the modification is to provide for measurement of the internal voltage drop and to increase the terminal-voltage setting by the amount of the internal voltage drop. Ordinarily, a lithium-ion battery is charged at constant current until its terminal voltage attains a set value equal to the nominal full-charge potential. The set value is chosen carefully so as not to exceed the lithium-plating potential, because plated lithium in metallic form constitutes a hazard. When the battery is charged at low temperature, the internal voltage drop is considerable because the electrical conductivity of the battery electrolyte is low at low temperature. Charging the battery at high current at any temperature also gives rise to a high internal voltage drop. In some cases, the internal voltage drop can be as high as 1 volt per cell. Because the voltage available for charging is less than the terminal voltage by the amount of the internal voltage drop, the battery is not fully charged (see figure), even when the terminal voltage reaches the set value. In the modified protocol, the charging current would be periodically interrupted so that the zero-current battery-terminal voltage indicative of the state of charge could be measured. The terminal voltage would also be measured at full charging current. The difference between the full-current and zero-current voltages would equal the internal voltage drop. The set value of terminal voltage would then be increased beyond the nominal full-charge potential by the amount of the internal voltage drop. This adjustment would be performed repeatedly, in real time, so that the voltage setting would track variations in the internal voltage drop to afford full charge without risk of lithium plating. If the charging current and voltage settings were controlled by a computer, then this method of charge control could readily be implemented in software.

Calorimetric determination of thermal parameters for the Li/BrCl in SOCl2 (BCX) chemistry

NASA Technical Reports Server (NTRS)

Darcy, Eric C.; Kalu, Eric E.; White, Ralph E.

1990-01-01

The heat capacity of a Li-BCX DD-cell was found to be dependent on its state of charge by drop calorimetry measurements. The method of drop calorimetry involves measuring the energy (joules) gained or lost from a sample that is transferred from a bath at temperature A to one at temperature B. The thermoneutral potential is defined as the cell potential where the cell electrochemical reactions are neither exothermic nor endothermic. A Hart scientific calorimeter system, Model No. S77XX, designed for heat conduction calorimetry and drop calorimetry was used. Calorimetric analysis yielded a thermoneutral potential of 4.14 volts and a cell heat capacity dependent on the state of charge.

Effects of turbulence on a kinetic auroral arc model

NASA Technical Reports Server (NTRS)

Cornwall, J. M.; Chiu, Y. T.

1981-01-01

A plasma kinetic model of an inverted-V auroral arc structure which includes the effects of electrostatic turbulence is proposed. In the absence of turbulence, a parallel potential drop is supported by magnetic mirror forces and charge quasi neutrality, with energetic auroral ions penetrating to low altitudes; relative to the electrons, the ions' pitch angle distribution is skewed toward smaller pitch angles. The electrons energized by the potential drop form a current which excites electrostatic turbulence. In equilibrium the plasma is marginally stable. The conventional anomalous resistivity contribution to the potential drop is very small. Anomalous resistivity processes are far too dissipative to be powered by auroral particles. It is concluded that under certain circumstances equilibrium may be impossible and relaxation oscillations set in.

Accurate potential drop sheet resistance measurements of laser-doped areas in semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heinrich, Martin, E-mail: mh.seris@gmail.com; NUS Graduate School for Integrative Science and Engineering, National University of Singapore, Singapore 117456; Kluska, Sven

2014-10-07

It is investigated how potential drop sheet resistance measurements of areas formed by laser-assisted doping in crystalline Si wafers are affected by typically occurring experimental factors like sample size, inhomogeneities, surface roughness, or coatings. Measurements are obtained with a collinear four point probe setup and a modified transfer length measurement setup to measure sheet resistances of laser-doped lines. Inhomogeneities in doping depth are observed from scanning electron microscope images and electron beam induced current measurements. It is observed that influences from sample size, inhomogeneities, surface roughness, and coatings can be neglected if certain preconditions are met. Guidelines are given onmore » how to obtain accurate potential drop sheet resistance measurements on laser-doped regions.« less

The possible equilibrium shapes of static pendant drops

NASA Astrophysics Data System (ADS)

Sumesh, P. T.; Govindarajan, Rama

2010-10-01

Analytical and numerical studies are carried out on the shapes of two-dimensional and axisymmetric pendant drops hanging under gravity from a solid surface. Drop shapes with both pinned and equilibrium contact angles are obtained naturally from a single boundary condition in the analytical energy optimization procedure. The numerical procedure also yields optimum energy shapes, satisfying Young's equation without the explicit imposition of a boundary condition at the plate. It is shown analytically that a static pendant two-dimensional drop can never be longer than 3.42 times the capillary length. A related finding is that a range of existing solutions for long two-dimensional drops correspond to unphysical drop shapes. Therefore, two-dimensional drops of small volume display only one static solution. In contrast, it is known that axisymmetric drops can display multiple solutions for a given volume. We demonstrate numerically that there is no limit to the height of multiple-lobed Kelvin drops, but the total volume is finite, with the volume of successive lobes forming a convergent series. The stability of such drops is in question, though. Drops of small volume can attain large heights. A bifurcation is found within the one-parameter space of Laplacian shapes, with a range of longer drops displaying a minimum in energy in the investigated space. Axisymmetric Kelvin drops exhibit an infinite number of bifurcations.

Countercurrent distribution of biological cells

NASA Technical Reports Server (NTRS)

Brooks, D. E.

1982-01-01

Detailed physiochemical studies of dextran/poly(ethylene glycol) (PEG) two phase systems were carried out to characterize and provide understanding of the properties of the systems which determine cell partition and the electrophoretic behavior of phase drops responsible for electric field driven phase separation. A detailed study of the electrostatic and electrokinetic potentials developed in these systems was carried out. The salt partition was examined both in phase systems and with pure polymer solutions via equilibrium dialysis and mechanism of sulfate, chloride and phosphate partition shown to be exclusion by PEG rather than binding by dextran. Salt partition was shown to have a strong effect on the polymer compositions of the phases as well, an effect which produces large changes in the interfacial tension between them. These effects were characterized and the interfacial tension shown to obey a power law with respect to its dependence on the length of the tie line describing the system composition on a phase diagram. The electrostatic potential differences measured via salt bridges were shown to obey thermodynamic predictions. The electrophoretic mobilities measured were utilized to provide a partial test of Levine's incomplete theory of phase drop electrophoresis. The data were consistent with Levine's expression over a limited range of the variables tested.

Properties of nuclear matter from macroscopic-microscopic mass formulas

NASA Astrophysics Data System (ADS)

Wang, Ning; Liu, Min; Ou, Li; Zhang, Yingxun

2015-12-01

Based on the standard Skyrme energy density functionals together with the extended Thomas-Fermi approach, the properties of symmetric and asymmetric nuclear matter represented in two macroscopic-microscopic mass formulas: Lublin-Strasbourg nuclear drop energy (LSD) formula and Weizsäcker-Skyrme (WS*) formula, are extracted through matching the energy per particle of finite nuclei. For LSD and WS*, the obtained incompressibility coefficients of symmetric nuclear matter are K∞ = 230 ± 11 MeV and 235 ± 11 MeV, respectively. The slope parameter of symmetry energy at saturation density is L = 41.6 ± 7.6 MeV for LSD and 51.5 ± 9.6 MeV for WS*, respectively, which is compatible with the liquid-drop analysis of Lattimer and Lim [4]. The density dependence of the mean-field isoscalar and isovector effective mass, and the neutron-proton effective masses splitting for neutron matter are simultaneously investigated. The results are generally consistent with those from the Skyrme Hartree-Fock-Bogoliubov calculations and nucleon optical potentials, and the standard deviations are large and increase rapidly with density. A better constraint for the effective mass is helpful to reduce uncertainties of the depth of the mean-field potential.

The Japanese containerless experiments

NASA Technical Reports Server (NTRS)

Azuma, Hisao

1990-01-01

There are three sets of Japanese containerless experiments. The first is Drop dynamics research. It consists of acoustic levitation and large amplitude drop oscillation. The second is Optical materials processing in an acoustic levitation furnace. And the third is Electrostatic levitator development by two different Japanese companies.

[Dropped head syndrome as first manifestation of primary hyperparathyroid myopathy].

PubMed

Ota, Kiyobumi; Koseki, Sayo; Ikegami, Kenji; Onishi, Iichiroh; Tomimitsu, Hiyoryuki; Shintani, Shuzo

2018-03-28

75 years old woman presented with 6-month history of progressive dropped head syndrome. Neurological examination revealed moderate weakness of flexor and extensor of neck and mild weakness of proximal appendicular muscles with normal deep tendon reflexes. The needle electromyography showed short duration and low amplitude motor unit potential. No fibrillation potentials or positive sharp waves were seen. Biopsy of deltoid muscle was normal. Laboratory studies showed elevated levels of serum calcium (11.8 mg/dl, upper limit of normal 10.1) and intact parathyroid hormone (104 pg/ml, upper limit of normal 65), and decreased level of serum phosphorus (2.3 mg/dl, lower limit of normal 2.7). Ultrasonography and enhanced computed tomography revealed a parathyroid tumor. The tumor was removed surgically. Pathological examination proved tumor to be parathyroid adenoma. Dropped head and weakness of muscles were dramatically improved within a week after the operation. Although hyperparathyroidism is a rare cause of dropped head syndrome, neurologists must recognize hyperparathyroidism as a treatable cause of dropped head syndrome.

Differential photoelectric charging of nonconducting surfaces in space. [on sunlit strip

NASA Technical Reports Server (NTRS)

Pelizzari, M. A.; Criswell, D. R.

1978-01-01

The photoelectric charging caused by an infinitely long strip of sunlight across a nonconducting plane is studied by use of a model which contains an electrical cutoff radius, and the results of numerical calculations are presented. The model simulates charging of a sunlit area with dimensions equal to the strip's width, exposed to a plasma with a comparatively large Debye length. Uniform potential is quickly established on a uniformly sunlit strip as a result of charge redistribution by low-energy photoelectrons. The results are in accord with a theoretical surface conductivity derived for photoelectron sheaths above highly charged sunlit areas. The surface potential, which drops sharply across the sunlight-shadow boundary, is discussed.

The study of the effects of sea-spray drops on the marine atmospheric boundary layer by direct numerical simulation

NASA Astrophysics Data System (ADS)

Druzhinin, O.; Troitskaya, Yu; Zilitinkevich, S.

2018-01-01

The detailed knowledge of turbulent exchange processes occurring in the atmospheric marine boundary layer are of primary importance for their correct parameterization in large-scale prognostic models. These processes are complicated, especially at sufficiently strong wind forcing conditions, by the presence of sea-spray drops which are torn off the crests of sufficiently steep surface waves by the wind gusts. Natural observations indicate that mass fraction of sea-spray drops increases with wind speed and their impact on the dynamics of the air in the vicinity of the sea surface can become quite significant. Field experiments, however, are limited by insufficient accuracy of the acquired data and are in general costly and difficult. Laboratory modeling presents another route to investigate the spray-mediated exchange processes in much more detail as compared to the natural experiments. However, laboratory measurements, contact as well as Particle Image Velocimetry (PIV) methods, also suffer from inability to resolve the dynamics of the near-surface air-flow, especially in the surface wave troughs. In this report, we present a first attempt to use Direct Numerical Simulation (DNS) as tool for investigation of the drops-mediated momentum, heat and moisture transfer in a turbulent, droplet-laden air flow over a wavy water surface. DNS is capable of resolving the details of the transfer processes and do not involve any closure assumptions typical of Large-Eddy and Reynolds Averaged Navier-Stokes (LES and RANS) simulations. Thus DNS provides a basis for improving parameterizations in LES and RANS closure models and further development of large-scale prognostic models. In particular, we discuss numerical results showing the details of the modification of the air flow velocity, temperature and relative humidity fields by multidisperse, evaporating drops. We use Eulerian-Lagrangian approach where the equations for the air-flow fields are solved in a Eulerian frame whereas the drops dymanics equations are solved in a Largangain frame. The effects of air flow and drops on the water surface wave are neglected. A point-force approximation is employed to model the feed-back contributions by the drops to the air momentum, heat and moisture transfer.

Analysis of Skylab IV fluid mechanic science demonstration

NASA Technical Reports Server (NTRS)

Klett, M. G.; Bourgeois, S. V.

1975-01-01

Several science demonstrations performed on Skylab III and IV were concerned with the behavior of fluid drops free floating in microgravity. These demonstrations, with large liquid drops, included the oscillation, rotation, impact and coalescence, and air injection into the drops. Rayleigh's analysis of the oscillation of spherical drops of a liquid predicts accurately the effect of size and surface tension on the frequency of vibrated water globules in the Skylab demonstration. However, damping occurred much faster than predicted by Lamb's or Scriven's analyses of the damping time for spherical drops. The impact demonstrations indicated that a minimum velocity is necessary to overcome surface forces and effect a coalescence, but a precise criterion for the coalescence of liquids in low g could not be determined.

Stress Drop and Directivity Patterns Observed in Small-Magnitude (

NASA Astrophysics Data System (ADS)

Ruhl, C. J.; Hatch, R. L.; Abercrombie, R. E.; Smith, K.

2017-12-01

Recent improvements in seismic instrumentation and network coverage in the Reno, NV area have provided high-quality records of abundant microseismicity, including several swarms and clusters. Here, we discuss stress drop and directivity patterns of small-magnitude seismicity in the 2008 Mw4.9 Mogul earthquake swarm in Reno, NV and in the nearby region of an ML3.2 sequence near Virginia City, NV. In both sequences, double-difference relocated earthquakes cluster on multiple distinct structures consistent with focal mechanism and moment tensor fault plane solutions. Both sequences also show migration potentially related to fluid flow. We estimate corner frequency and stress drop using EGF-derived spectral ratios, convolving earthquake pairs (target*EGF) such that we preserve phase and recover source-time functions (STF) on a station-by-station basis. We then stack individual STFs per station for all EGF-target pairs per target earthquake, increasing the signal-to-noise of our results. By applying an azimuthal- and incidence-angle-dependent stretching factor to STFs in the time domain, we are able to invert for rupture directivity and velocity assuming both unilateral and bilateral rupture. Earthquakes in both sequences, some as low as ML2.1, show strong unilateral directivity consistent with independent fault plane solutions. We investigate and compare the relationship between rupture and migration directions on subfaults within each sequence. Average stress drops for both sequences are 4 MPa, but there is large variation in individual estimates for both sequences. Although this variation is not explained simply by any one parameter (e.g., depth), spatiotemporal variation in the Mogul swarm is distinct: coherent clusters of high and low stress drop earthquakes along the mainshock fault plane are seen, and high-stress-drop foreshocks correlate with an area of reduced aftershock productivity. These observations are best explained by a difference in rheology along the fault plane. The unprecedented detail achieved for these small magnitude earthquakes confirms that stress drop, when measured precisely, is a valuable observation of physically-meaningful fault zone properties and earthquake behavior.

Formation of superheavy elements in the capture of very heavy ions at high excitation energies

NASA Astrophysics Data System (ADS)

Royer, G.

2013-05-01

The potential barriers governing the reactions 58Fe+244Pu, 238U+64Ni, and 238U+72Ge have been determined from a liquid-drop model taking into account the proximity energy, shell energies, rotational energy, and deformation of the incoming nuclei in the quasimolecular shape valley. Double-humped potential barriers appear in these entrance channels. The external saddle-point corresponds to two touching ellipsoidal nuclei when the shell and pairing effects are taken into account, while the inner barrier is due to the shell effects at the vicinity of the spherical shape of the composite system. Between them, a large potential pocket exists and persists at very high angular momenta allowing the capture of very heavy ions at high excitation energies.

Serration Behavior of a Zr-Based Metallic Glass Under Different Constrained Loading Conditions

NASA Astrophysics Data System (ADS)

Yang, G. N.; Gu, J. L.; Chen, S. Q.; Shao, Y.; Wang, H.; Yao, K. F.

2016-11-01

To understand the plastic behavior and shear band dynamics of metallic glasses (MGs) being tuned by the external constraint, uniaxial compression tests were performed on Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 MG samples with aspect ratios of 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, and 3:1. Better plasticity was observed for the samples with smaller aspect ratio (under higher constraint degree). In the beginning of yielding, increasing serration (jerky stress drop) size on the loading curves was noticed for all samples. Statistical analysis of the serration patterns indicated that the small stress-drop serrations and large stress-drop serrations follow self-organized critical and chaotic dynamics, respectively. Under constrained loading, the large stress-drop serrations are depressed, while the small stress-drop serrations are less affected. When changing the external constraint level by varying the sample aspect ratio, the serration pattern, shear band dynamics, and plastic behavior will change accordingly. This study provides a perspective from tuning shear band dynamics to understand the plastic behavior of MGs under different external constraint.

Vapor condensation onto a non-volatile liquid drop

DOE Office of Scientific and Technical Information (OSTI.GOV)

Inci, Levent; Bowles, Richard K., E-mail: richard.bowles@usask.ca

2013-12-07

Molecular dynamics simulations of miscible and partially miscible binary Lennard–Jones mixtures are used to study the dynamics and thermodynamics of vapor condensation onto a non-volatile liquid drop in the canonical ensemble. When the system volume is large, the driving force for condensation is low and only a submonolayer of the solvent is adsorbed onto the liquid drop. A small degree of mixing of the solvent phase into the core of the particles occurs for the miscible system. At smaller volumes, complete film formation is observed and the dynamics of film growth are dominated by cluster-cluster coalescence. Mixing into the coremore » of the droplet is also observed for partially miscible systems below an onset volume suggesting the presence of a solubility transition. We also develop a non-volatile liquid drop model, based on the capillarity approximations, that exhibits a solubility transition between small and large drops for partially miscible mixtures and has a hysteresis loop similar to the one observed in the deliquescence of small soluble salt particles. The properties of the model are compared to our simulation results and the model is used to study the formulation of classical nucleation theory for systems with low free energy barriers.« less

Fragment size distribution in viscous bag breakup of a drop

NASA Astrophysics Data System (ADS)

Kulkarni, Varun; Bulusu, Kartik V.; Plesniak, Michael W.; Sojka, Paul E.

2015-11-01

In this study we examine the drop size distribution resulting from the fragmentation of a single drop in the presence of a continuous air jet. Specifically, we study the effect of Weber number, We, and Ohnesorge number, Oh on the disintegration process. The regime of breakup considered is observed between 12 <= We <= 16 for Oh <= 0.1. Experiments are conducted using phase Doppler anemometry. Both the number and volume fragment size probability distributions are plotted. The volume probability distribution revealed a bi-modal behavior with two distinct peaks: one corresponding to the rim fragments and the other to the bag fragments. This behavior was suppressed in the number probability distribution. Additionally, we employ an in-house particle detection code to isolate the rim fragment size distribution from the total probability distributions. Our experiments showed that the bag fragments are smaller in diameter and larger in number, while the rim fragments are larger in diameter and smaller in number. Furthermore, with increasing We for a given Ohwe observe a large number of small-diameter drops and small number of large-diameter drops. On the other hand, with increasing Oh for a fixed We the opposite is seen.

Imaging transport phenomena during lysozyme protein crystal growth by the hanging drop technique

NASA Astrophysics Data System (ADS)

Sethia Gupta, Anamika; Gupta, Rajive; Panigrahi, P. K.; Muralidhar, K.

2013-06-01

The present study reports the transport process that occurs during the growth of lysozyme protein crystals by the hanging drop technique. A rainbow schlieren technique has been employed for imaging changes in salt concentration. A one dimensional color filter is used to record the deflection of the light beam. An optical microscope and an X-ray crystallography unit are used to characterize the size, tetragonal shape and Bravais lattice constants of the grown crystals. A parametric study on the effect of drop composition, drop size, reservoir height and number of drops on the crystal size and quality is reported. Changes in refractive index are not large enough to create a meaningful schlieren image in the air gap between the drop and the reservoir. However, condensation of fresh water over the reservoir solution creates large changes in the concentration of NaCl, giving rise to clear color patterns in the schlieren images. These have been analyzed to obtain salt concentration profiles near the free surface of the reservoir solution as a function of time. The diffusion of fresh water into the reservoir solution at the early stages of crystal growth followed by the mass flux of salt from the bulk solution towards the free surface has been recorded. The overall crystal growth process can be classified into two regimes, as demarcated by the changes in slope of salt concentration within the reservoir. The salt concentration in the reservoir equilibrates at long times when the crystallization process is complete. Thus, transport processes in the reservoir emerge as the route to monitor protein crystal growth in the hanging drop configuration. Results show that crystal growth rate is faster for a higher lysozyme concentration, smaller drops, and larger reservoir heights.

Buckling vs. particle desorption in a particle-covered drop subject to compressive surface stresses: a simulation study.

PubMed

Gu, Chuan; Botto, Lorenzo

2018-01-31

Predicting the behaviour of particle-covered fluid interfaces under compression has implications in several fields. The surface-tension driven adhesion of particles to drops and bubbles is exploited for example to enhance the stability of foams and emulsion and develop new generation materials. When a particle-covered fluid interface is compressed, one can observe either smooth buckling or particle desorption from the interface. The microscopic mechanisms leading to the buckling-to-desorption transition are not fully understood. In this paper we simulate a spherical drop covered by a monolayer of spherical particles. The particle-covered interface is subject to time-dependent compressive surface stresses that mimic the slow deflation of the drop. The buckling-to-desorption transition depends in a non-trivial way on three non-dimensional parameters: the ratio Π s /γ of particle-induced surface pressure and bare surface tension, the ratio a/R of particle and drop radii, and the parameter f characterising the strength of adhesion of each particle to the interface. Based on the insights from the simulations, we propose a configuration diagram describing the effect of these controlling parameters. We find that particle desorption is highly correlated with a mechanical instability that produces small-scale undulations of the monolayer of the order of the particle size that grow when the surface pressure is sufficiently large. We argue that the large local curvature associated with these small undulations can produce large normal forces, enhancing the probability of desorption.

High-precision drop shape analysis on inclining flat surfaces: introduction and comparison of this special method with commercial contact angle analysis.

PubMed

Schmitt, Michael; Heib, Florian

2013-10-07

Drop shape analysis is one of the most important and frequently used methods to characterise surfaces in the scientific and industrial communities. An especially large number of studies, which use contact angle measurements to analyse surfaces, are characterised by incorrect or misdirected conclusions such as the determination of surface energies from poorly performed contact angle determinations. In particular, the characterisation of surfaces, which leads to correlations between the contact angle and other effects, must be critically validated for some publications. A large number of works exist concerning the theoretical and thermodynamic aspects of two- and tri-phase boundaries. The linkage between theory and experiment is generally performed by an axisymmetric drop shape analysis, that is, simulations of the theoretical drop profiles by numerical integration onto a number of points of the drop meniscus (approximately 20). These methods work very well for axisymmetric profiles such as those obtained by pendant drop measurements, but in the case of a sessile drop onto real surfaces, additional unknown and misunderstood effects on the dependence of the surface must be considered. We present a special experimental and practical investigation as another way to transition from experiment to theory. This procedure was developed to be especially sensitive to small variations in the dependence of the dynamic contact angle on the surface; as a result, this procedure will allow the properties of the surface to be monitored with a higher precession and sensitivity. In this context, water drops onto a 111 silicon wafer are dynamically measured by video recording and by inclining the surface, which results in a sequence of non-axisymmetric drops. The drop profiles are analysed by commercial software and by the developed and presented high-precision drop shape analysis. In addition to the enhanced sensitivity for contact angle determination, this analysis technique, in combination with innovative fit algorithms and data presentations, can result in enhanced reproducibility and comparability of the contact angle measurements in terms of the material characterisation in a comprehensible way.

High-precision drop shape analysis on inclining flat surfaces: Introduction and comparison of this special method with commercial contact angle analysis

NASA Astrophysics Data System (ADS)

Schmitt, Michael; Heib, Florian

2013-10-01

Drop shape analysis is one of the most important and frequently used methods to characterise surfaces in the scientific and industrial communities. An especially large number of studies, which use contact angle measurements to analyse surfaces, are characterised by incorrect or misdirected conclusions such as the determination of surface energies from poorly performed contact angle determinations. In particular, the characterisation of surfaces, which leads to correlations between the contact angle and other effects, must be critically validated for some publications. A large number of works exist concerning the theoretical and thermodynamic aspects of two- and tri-phase boundaries. The linkage between theory and experiment is generally performed by an axisymmetric drop shape analysis, that is, simulations of the theoretical drop profiles by numerical integration onto a number of points of the drop meniscus (approximately 20). These methods work very well for axisymmetric profiles such as those obtained by pendant drop measurements, but in the case of a sessile drop onto real surfaces, additional unknown and misunderstood effects on the dependence of the surface must be considered. We present a special experimental and practical investigation as another way to transition from experiment to theory. This procedure was developed to be especially sensitive to small variations in the dependence of the dynamic contact angle on the surface; as a result, this procedure will allow the properties of the surface to be monitored with a higher precession and sensitivity. In this context, water drops onto a 111 silicon wafer are dynamically measured by video recording and by inclining the surface, which results in a sequence of non-axisymmetric drops. The drop profiles are analysed by commercial software and by the developed and presented high-precision drop shape analysis. In addition to the enhanced sensitivity for contact angle determination, this analysis technique, in combination with innovative fit algorithms and data presentations, can result in enhanced reproducibility and comparability of the contact angle measurements in terms of the material characterisation in a comprehensible way.

Dynamics and Morphology of Superfluid Helium Drops in a Microgravity Environment

NASA Technical Reports Server (NTRS)

Seidel, George M.; Maris, Humphrey J.

2001-01-01

We developed an apparatus that makes it possible to observe and study magnetically levitated drops of superfluid helium. The force on a diamagnetic substance in a magnetic field is proportional to the gradient of the square of the magnetic field B. For the magnetic force on helium to be equal to the gravitational force on Earth, it is necessary for the product of B with the field gradient dB/d z to be 21.5 T(exp 2)/cm. In addition, in order for the magnetic field to provide a stable trap, the value of B(exp 2) must increase in all directions in the horizontal plane that passes through the point where the field/field gradient product in the vertical direction has the critical value of 21.5 T(exp 2)/cm. A specially designed superconducting magnet that meets these specifications has been installed in a large helium dewar with optical access. Helium drops levitated by the magnet can be viewed along the axis of the solenoid. The sample chamber within the bore of the magnet is thermally isolated from the magnet and helium reservoir. Its temperature can be varied between 4 and 0.5 K, the lower part of the range being reached using a He-3 refrigerator. Liquid helium can be injected into the magnetic trap using a small capillary. Once a drop is contained in the trap it can be held there indefinitely. With this apparatus we have conducted a number of different types of experiments on helium drops so as to gain information necessary for performing experiments in space. With magnetically levitated drops we are limited to working with drops of 1 cm. or less in diameter. The shape of the drops larger than a few mm diameter can be distorted by the profile of the magnetic field. The study of phenomena such as the initial motion of the surfaces of two drops as they just make contact, requires the use large drops to resolve the behavior of interest. We have performed a detailed investigation of the shape oscillations of superfluid drops.

New and modified techniques for studying nitrogen-fixing bacteria in small mammal droppings.

Treesearch

C.Y. Li; Chris Maser

1986-01-01

Nitrogen-fixing bacteria in small mammal droppings are potentially important to forest productivity. As we study this phenomenon, however, we continually find unknowns, such as bacteria that we cannot isolate and purify because we do not know which techniques to use. For example, we have recently observed acetylene reduction in the droppings of the tundra vole (

How Well Does the Theory of Planned Behavior Predict Graduation among College and University Students with Disabilities?

ERIC Educational Resources Information Center

Fichten, Catherine S.; Nguyen, Mai Nhu; Amsel, Rhonda; Jorgensen, Shirley; Budd, Jillian; Jorgensen, Mary; Asuncion, Jennison; Barile, Maria

2014-01-01

The goal of this research was to develop a model to predict which students with disabilities will drop out before graduation and to investigate the drop out pattern of students with disabilities. To accomplish this we evaluated potential predictors of persistence and drop-out among 611 college and university students with various disabilities and…

Electrohydrodynamic generation of millimetric drops and control of electrification

NASA Astrophysics Data System (ADS)

Yun, Sungchan

2017-07-01

We report a simple method for millimetric drop generation by electrohydrodynamic (EHD) detachment using a conventional nozzle-ring device. The EHD detachment method provides distinct features of uniform-size and controlled electrification of millimetric drops. The drop dynamics of detachment and shape oscillation are recorded using a high-speed camera and analyzed for several dc voltages applied to the electrode. Experimental studies show that an oscillation frequency can be closely related to the amount of electric charge, which can be explained based on both effective interfacial tension and inviscid Rayleigh and Lamb frequency. Furthermore, we present a concept to generate a neutral drop by adjusting the duration time of a pulse signal and discuss a drop oscillation induced by the detachment. This study can provide potential implications for drop manipulation, such as transporting, merging, and mixing, in microfluidic platforms.

Chlamydia psittaci and C. avium in feral pigeon (Columba livia domestica) droppings in two cities in the Netherlands.

PubMed

Burt, Sara A; Röring, Romy E; Heijne, Marloes

2018-06-05

Feral pigeons (Columba livia domestica) live and breed in many city centres and contact with their droppings can be a hazard for human health if the birds carry Chlamydia psittaci. The aim of this study was to establish whether pigeon droppings in two Dutch cities (Utrecht and Haarlem) contain C. psittaci and/or C. avium, which could be a potential hazard for transmission to humans. In May 2017 seven feral pigeon 'hot spots' with between 5 and 40+ pigeons present were identified in two cities by visual observations over two days. During the following ten days fresh droppings were collected at these hot spots and the samples were pooled per three droppings to achieve 40-41 samples per city. Samples were analysed for Chlamydia DNA with a broad range 23S Chlamydiaceae Real-Time PCR and positive samples were tested with a specific C. psittaci and C. avium Real-Time PCR. Positive C. psittaci samples were genotyped. C. psittaci and C. avium were detected in both cities. For C. psittaci the prevalences in Utrecht and Haarlem were 2.4% and 7.5%, respectively; for C. avium 36.6% and 20.0%, respectively. One sample contained both species. All C. psittaci samples belonged to genotype B. C. psittaci and C. avium are present in feral pigeon droppings in Utrecht and Haarlem. Human contact with droppings from infected pigeons or inhalation of dust from dried droppings represent a potential hazard to public health.

[Predicting drop-out during the systems training for emotional predictability and problem solving (STEPPS)].

PubMed

van Diepen, J B; de Groot, I W

2016-01-01

Drop-out is a complex problem in mental health care and in STEPPS. Research has revealed a variety of predicting factors and has produced contradictory results. To investigate whether the information available at the start of STEPPS can pinpoint predictors of drop-out. The ROM data for 150 patients were used to test the link between the following factors: age, gender, education, employment, substance abuse, anxiety, hostility, interpersonal relations, responsibility and social concordance with drop-out. The method used for testing was logistic regression analysis. Factors that contributed significantly to the prediction of drop-out were gender and employment status. These factors made up 16% of the explained variation (R2 Nagelkerkes) in drop-out. Gender was the strongest predictive factor. Concerning the other factors, no differences were found between groups (drop-out and non-dropouts). In its present form STEPPS does not suit a large number of the male participants. Drop-out during STEPPS is hard to predict on the basis of ROM-questionnaires. Future research should focus on preconditions and marginal conditions that influence patients to complete their training.

Evidence for Coseismic Rupture Beyond the Base of the Seismogenic Layer

NASA Astrophysics Data System (ADS)

Zielke, O.; Wesnousky, S.

2010-12-01

For scientific reasons and hazard assessment it is important to better understand the physics and rupture characteristics of large, destructive earthquakes. However, those events occur infrequently, severely obstructing their analysis. Smaller but more frequent earthquakes are usually studied and their characteristics are extrapolated to assess large earthquake behavior, assuming that small and large events are associated with the same physical processes and parameters. For small and moderate size earthquakes it was observed and independently derived from elastic models that coseismic stress drop is independent of earthquake size and that slip is proportional to the smallest rupture dimension. It is therefore assumed that large earthquake stress drops are essentially equal to the stress drop of their smaller size siblings. It is further assumed that the slip amount of large events does not further increase once it ruptures the full seismogenic layer--the base of the seismogenic layer is commonly thought to limit the earthquake down-dip rupture extend and thus defines the smallest rupture dimension. However, slip observations for many large strike-slip events show how offset gradually increases with rupture length. Two explanations have been formulated: If the rupture width of those events were indeed limited by the base of the seismogenic layer, the observations would imply larger stress drops and possibly other processes involved in large earthquake rupture, questioning the validity of the aforementioned extrapolation from small to large earthquakes. On the other hand, if rupture width of large earthquakes were not limited by the base of the seismogenic layer but were allowed to extend further down (as suggested by recent studies), the increased slip amount may be explained without an increase in stress drop or additional rupture mechanisms for large earthquakes. For the study we present here, we analyzed seismic data constraining the depth extent of large earthquakes relative to the depth of the seismogenic base. We utilized time series data of aftershock depths for a number of large strike-slip earthquakes, generating aftershock time vs. depth histograms to investigate the temporal variation in depth distribution. Based on hypocenter depth of small earthquakes along the Landers fault (causing the 1992 M7.3 Landers earthquake), we identified the base of the seismogenic layer at ~10km. Aftershocks that occurred only days after the Landers earthquake had maximum depths of ~18km, suggesting that rupture of the main shock extended this far down and therefore went well below the base of the seismogenic layer. Maximum aftershock depth then decayed roughly logarithmically, reaching the previous value of ~10km after about 5.5years. We argue that these observations are a logical consequence of the visco-elastic rheology of crustal rocks: Coseismically highly increased strains elevate the crustal stiffness, temporarily lowering the base of the seismogenic layer and permitting initiation of slip instabilities at depths that are otherwise characterized by viscous behavior. Extrapolation from small to large earthquakes is therefore permitted. No additional stress drop or rupture mechanism is required to explain the data.

Effects of moisture and grain size on the mechanisms of rainsplash transport

NASA Astrophysics Data System (ADS)

Taube, S. R.; Furbish, D. J.

2010-12-01

Desert shrubs accumulate soil mounds beneath their canopies through rainsplash transport. Previous studies of this process have suggested that there is a preferential concentration of smaller grain sizes closer to the base of the shrub, based on the idea that smaller material is more readily splashed inward beneath the shrub. However, our studies have shown that there are two mechanisms of ejection of the grains with moist soil conditions, each preferentially moving either large or small grain sizes. Larger grains tend to be launched from grain-to-grain collisions following drop impact and travel as individual grains. Smaller grains appear to clump together and move as a single large "grain". The medium-sized grains generally had a greater travel distance than the very large or very small grains, potentially because they involve both modes of transport with a greater effective transfer of energy from the raindrop to the grains. The average travel distance is greatest near 100 microns, which is reflected by the data of Leguedois, et al. (2005). Experiments using high-speed imaging reveals that there is a marked difference between the mechanism of transport when the sediment grains are dry versus when they are moist. The dry grains are rapidly deposited about the impact site with a small proportion moving far from the site. However, moist grains tend to clump together to form “blobs” of water and sediment. Immediately after impact, the drop creates a water corona with entrained sediment, which then contracts into water-sediment blobs that are rocketed outwards from the impact, leaving little to no grain mass near the impact site. Varying degrees of moisture content appeared to have little influence on grain dispersal, leading us to believe that once the soil material is moist (but not saturated), its splash behavior is mostly related to details of the drop corona.

Thermocapillary-Induced Phase Separation with Coalescence

NASA Technical Reports Server (NTRS)

Davis, Robert H.

2003-01-01

Research has been undertaken on interactions of two or more deformable drops (or bubbles) in a viscous fluid and subject to a temperature, gravitational, or flow field. An asymptotic theory for nearly spherical drops shows that small deformations reduce the coalescence and phase separation rates. Boundary-integral simulations for large deformations show that bubbles experience alignment and enhanced coalescence, whereas more viscous drops may break as a result of hydrodynamic interactions. Experiments for buoyancy motion confirm these observations. Simulations of the sedimentation of many drops show clustering phenomena due to deformations, which lead to enhanced phase separation rates, and simulations of sheared emulsions show that deformations cause a reduction in the effective viscosity.

The role of drop velocity in statistical spray description

NASA Technical Reports Server (NTRS)

Groeneweg, J. F.; El-Wakil, M. M.; Myers, P. S.; Uyehara, O. A.

1978-01-01

The justification for describing a spray by treating drop velocity as a random variable on an equal statistical basis with drop size was studied experimentally. A double exposure technique using fluorescent drop photography was used to make size and velocity measurements at selected locations in a steady ethanol spray formed by a swirl atomizer. The size velocity data were categorized to construct bivariate spray density functions to describe the spray immediately after formation and during downstream propagation. Bimodal density functions were formed by environmental interaction during downstream propagation. Large differences were also found between spatial mass density and mass flux size distribution at the same location.

Ground Motion Prediction Equations Empowered by Stress Drop Measurement

NASA Astrophysics Data System (ADS)

Miyake, H.; Oth, A.

2015-12-01

Significant variation of stress drop is a crucial issue for ground motion prediction equations and probabilistic seismic hazard assessment, since only a few ground motion prediction equations take into account stress drop. In addition to average and sigma studies of stress drop and ground motion prediction equations (e.g., Cotton et al., 2013; Baltay and Hanks, 2014), we explore 1-to-1 relationship for each earthquake between stress drop and between-event residual of a ground motion prediction equation. We used the stress drop dataset of Oth (2013) for Japanese crustal earthquakes ranging 0.1 to 100 MPa and K-NET/KiK-net ground motion dataset against for several ground motion prediction equations with volcanic front treatment. Between-event residuals for ground accelerations and velocities are generally coincident with stress drop, as investigated by seismic intensity measures of Oth et al. (2015). Moreover, we found faster attenuation of ground acceleration and velocities for large stress drop events for the similar fault distance range and focal depth. It may suggest an alternative parameterization of stress drop to control attenuation distance rate for ground motion prediction equations. We also investigate 1-to-1 relationship and sigma for regional/national-scale stress drop variation and current national-scale ground motion equations.

Piling-to-buckling transition in the drying process of polymer solution drop on substrate having a large contact angle.

PubMed

Kajiya, Tadashi; Nishitani, Eisuke; Yamaue, Tatsuya; Doi, Masao

2006-01-01

We studied the drying process of polymer solution drops placed on a substrate having a large contact angle with the drop. The drying process takes place in three stages. First, the droplet evaporates keeping the contact line fixed. Second, the droplet shrinks uniformly with receding contact line. Finally the contact line is pinned again, and the droplet starts to be deformed. The shape of the final polymer deposit changes from concave dot, to flat dot, and then to concave dot again with the increase of the initial polymer concentration. This shape change is caused by the gradual transition from the solute piling mechanism proposed by Deegan to the crust buckling mechanism proposed by de Gennes and Pauchard.

Trapping of drops by wetting defects

PubMed Central

't Mannetje, Dieter; Ghosh, Somnath; Lagraauw, Rudy; Otten, Simon; Pit, Arjen; Berendsen, Christian; Zeegers, Jos; van den Ende, Dirk; Mugele, Frieder

2014-01-01

Controlling the motion of drops on solid surfaces is crucial in many natural phenomena and technological processes including the collection and removal of rain drops, cleaning technology and heat exchangers. Topographic and chemical heterogeneities on solid surfaces give rise to pinning forces that can capture and steer drops in desired directions. Here we determine general physical conditions required for capturing sliding drops on an inclined plane that is equipped with electrically tunable wetting defects. By mapping the drop dynamics on the one-dimensional motion of a point mass, we demonstrate that the trapping process is controlled by two dimensionless parameters, the trapping strength measured in units of the driving force and the ratio between a viscous and an inertial time scale. Complementary experiments involving superhydrophobic surfaces with wetting defects demonstrate the general applicability of the concept. Moreover, we show that electrically tunable defects can be used to guide sliding drops along actively switchable tracks—with potential applications in microfluidics. PMID:24721935

Physical Watermarking for Securing Cyber-Physical Systems via Packet Drop Injections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ozel, Omur; Weekrakkody, Sean; Sinopoli, Bruno

Physical watermarking is a well known solution for detecting integrity attacks on Cyber-Physical Systems (CPSs) such as the smart grid. Here, a random control input is injected into the system in order to authenticate physical dynamics and sensors which may have been corrupted by adversaries. Packet drops may naturally occur in a CPS due to network imperfections. To our knowledge, previous work has not considered the role of packet drops in detecting integrity attacks. In this paper, we investigate the merit of injecting Bernoulli packet drops into the control inputs sent to actuators as a new physical watermarking scheme. Withmore » the classical linear quadratic objective function and an independent and identically distributed packet drop injection sequence, we study the effect of packet drops on meeting security and control objectives. Our results indicate that the packet drops could act as a potential physical watermark for attack detection in CPSs.« less

Drizzle formation in stratocumulus clouds: Effects of turbulent mixing

DOE PAGES

Magaritz-Ronen, L.; Pinsky, M.; Khain, A.

2016-02-17

The mechanism of drizzle formation in shallow stratocumulus clouds and the effect of turbulent mixing on this process are investigated. A Lagrangian–Eularian model of the cloud-topped boundary layer is used to simulate the cloud measured during flight RF07 of the DYCOMS-II field experiment. The model contains ~ 2000 air parcels that are advected in a turbulence-like velocity field. In the model all microphysical processes are described for each Lagrangian air volume, and turbulent mixing between the parcels is also taken into account. It was found that the first large drops form in air volumes that are closest to adiabatic andmore » characterized by high humidity, extended residence near cloud top, and maximum values of liquid water content, allowing the formation of drops as a result of efficient collisions. The first large drops form near cloud top and initiate drizzle formation in the cloud. Drizzle is developed only when turbulent mixing of parcels is included in the model. Without mixing, the cloud structure is extremely inhomogeneous and the few large drops that do form in the cloud evaporate during their sedimentation. Lastly, it was found that turbulent mixing can delay the process of drizzle initiation but is essential for the further development of drizzle in the cloud.« less

Drizzle formation in stratocumulus clouds: Effects of turbulent mixing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Magaritz-Ronen, L.; Pinsky, M.; Khain, A.

The mechanism of drizzle formation in shallow stratocumulus clouds and the effect of turbulent mixing on this process are investigated. A Lagrangian–Eularian model of the cloud-topped boundary layer is used to simulate the cloud measured during flight RF07 of the DYCOMS-II field experiment. The model contains ~ 2000 air parcels that are advected in a turbulence-like velocity field. In the model all microphysical processes are described for each Lagrangian air volume, and turbulent mixing between the parcels is also taken into account. It was found that the first large drops form in air volumes that are closest to adiabatic andmore » characterized by high humidity, extended residence near cloud top, and maximum values of liquid water content, allowing the formation of drops as a result of efficient collisions. The first large drops form near cloud top and initiate drizzle formation in the cloud. Drizzle is developed only when turbulent mixing of parcels is included in the model. Without mixing, the cloud structure is extremely inhomogeneous and the few large drops that do form in the cloud evaporate during their sedimentation. Lastly, it was found that turbulent mixing can delay the process of drizzle initiation but is essential for the further development of drizzle in the cloud.« less

Leidenfrost drops on a heated liquid pool

NASA Astrophysics Data System (ADS)

Maquet, L.; Sobac, B.; Darbois-Texier, B.; Duchesne, A.; Brandenbourger, M.; Rednikov, A.; Colinet, P.; Dorbolo, S.

2016-09-01

We show that a volatile liquid drop placed at the surface of a nonvolatile liquid pool warmer than the boiling point of the drop can be held in a Leidenfrost state even for vanishingly small superheats. Such an observation points to the importance of the substrate roughness, negligible in the case considered here, in determining the threshold Leidenfrost temperature. A theoretical model based on the one proposed by Sobac et al. [Phys. Rev. E 90, 053011 (2014), 10.1103/PhysRevE.90.053011] is developed in order to rationalize the experimental data. The shapes of the drop and of the liquid substrate are analyzed. The model notably provides scalings for the vapor film thickness profile. For small drops, these scalings appear to be identical to the case of a Leidenfrost drop on a solid substrate. For large drops, in contrast, they are different, and no evidence of chimney formation has been observed either experimentally or theoretically in the range of drop sizes considered in this study. Concerning the evaporation dynamics, the radius is shown to decrease linearly with time whatever the drop size, which differs from the case of a Leidenfrost drop on a solid substrate. For high superheats, the characteristic lifetime of the drops versus the superheat follows a scaling law that is derived from the model, but, at low superheats, it deviates from this scaling by rather saturating.

Inkjet printing of TiO2/AlOOH heterostructures for the formation of interference color images with high optical visibility

PubMed Central

Yakovlev, Aleksandr V.; Milichko, Valentin A.; Pidko, Evgeny A.; Vinogradov, Vladimir V.; Vinogradov, Alexandr V.

2016-01-01

This paper describes a practical approach for the fabrication of highly visible interference color images using sol-gel ink technique and a common desktop inkjet printer. We show the potential of titania-boehmite inks for the production of optical heterostructures on various surfaces, which after drying on air produce optical solid layers with low and high refractive index. The optical properties of the surface heterostructures were adjusted following the principles of antireflection coating resulting in the enhancement of the interference color optical visibility of the prints by as much as 32%. Finally, the presented technique was optimized following the insights into the mechanisms of the drop-surface interactions and the drop-on-surface coalescence to make it suitable for the production of even thickness coatings suitable for printing at a large scale. We propose that the technology described herein is a promising new green and sustainable approach for color printing. PMID:27848979

The Experiment CPLM (Comportamiento De Puentes Líquidos En Microgravedad) On Board MINISAT 01

NASA Astrophysics Data System (ADS)

Sanz-Andrés, Angel; Rodríguez-De-Francisco, Pablo; Santiago-Prowald, Julián

2001-03-01

The Universidad Politécnica de Madrid participates in the MINISAT 01 program as the experiment CPLM responsible. This experiment aims at the study of the fluid behaviour in reduced gravity conditions. The interest of this study is and has been widely recognised by the scientific community and has potential applications in the pharmaceutical and microelectronic technologies (crystal growth), among others. The scientific team which has developed the CPLM experiment has a wide experience in this field and had participate in the performance of a large number of experiments on the fluid behaviour in reduced gravity conditions in flight (Spacelab missions, TEXUS sounding rockets, KC-135 and Caravelle aeroplanes, drop towers, as well as on earth labs (neutral buoyancy and small scale simulations). The experimental equipment used in CPLMis a version of the payload developed for experimentation on drop towers and on board microsatellites as the UPM-Sat 1, adapted to fly on board MINISAT 01.

Reliable WDM multicast in optical burst-switched networks

NASA Astrophysics Data System (ADS)

Jeong, Myoungki; Qiao, Chunming; Xiong, Yijun

2000-09-01

IN this paper,l we present a reliable WDM (Wavelength-Division Multiplexing) multicast protocol in optical burst-switched (OBS) networks. Since the burst dropping (loss) probability may be potentially high in a heavily loaded OBS backbone network, reliable multicast protocols that have developed for IP networks at the transport (or application) layer may incur heavy overheads such as a large number of duplicate retransmissions. In addition, it may take a longer time for an end host to detect and then recover from burst dropping (loss) occurred at the WDM layer. For efficiency reasons, we propose burst loss recovery within the OBS backbone (i.e., at the WDM link layer). The proposed protocol requires two additional functions to be performed by the WDM switch controller: subcasting and maintaining burst states, when the WDM switch has more than one downstream on the WDM multicast tree. We show that these additional functions are simple to implement and the overhead associated with them is manageable.

Pressure at the ground in a large tornado

NASA Astrophysics Data System (ADS)

Winn, W. P.; Hunyady, S. J.; Aulich, G. D.

1999-09-01

A number of instruments were placed on the ground across the path of a large tornado that passed west of the town of Allison, Texas, on June 8, 1995. The center of the tornado came within 660 m of the closest instrument, which recorded a pressure drop of 55 mbar and a subsequent pressure rise of 60 mbar. During the lowest recorded pressures (near r = 660 m), there were large and rapid pressure fluctuations; the largest fluctuation was a 10-mbar spike lasting 2 s. A second instrument on the opposite side of the tornado recorded a pressure drop of 26 mbar. From the pressure variations with time P(t) at the two instruments, the variation of pressure with distance p(r) from the center of the tornado has been deduced for r>660 m. As r decreases, the measured pressure function p(r) drops more abruptly than would be expected from conservation of angular momentum of air spiraling inward near the ground level.

Electric generation and ratcheted transport of contact-charged drops

NASA Astrophysics Data System (ADS)

Cartier, Charles A.; Graybill, Jason R.; Bishop, Kyle J. M.

2017-10-01

We describe a simple microfluidic system that enables the steady generation and efficient transport of aqueous drops using only a constant voltage input. Drop generation is achieved through an electrohydrodynamic dripping mechanism by which conductive drops grow and detach from a grounded nozzle in response to an electric field. The now-charged drops are transported down a ratcheted channel by contact charge electrophoresis powered by the same voltage input used for drop generation. We investigate how the drop size, generation frequency, and transport velocity depend on system parameters such as the liquid viscosity, interfacial tension, applied voltage, and channel dimensions. The observed trends are well explained by a series of scaling analyses that provide insight into the dominant physical mechanisms underlying drop generation and ratcheted transport. We identify the conditions necessary for achieving reliable operation and discuss the various modes of failure that can arise when these conditions are violated. Our results demonstrate that simple electric inputs can power increasingly complex droplet operations with potential opportunities for inexpensive and portable microfluidic systems.

Electric generation and ratcheted transport of contact-charged drops.

PubMed

Cartier, Charles A; Graybill, Jason R; Bishop, Kyle J M

2017-10-01

We describe a simple microfluidic system that enables the steady generation and efficient transport of aqueous drops using only a constant voltage input. Drop generation is achieved through an electrohydrodynamic dripping mechanism by which conductive drops grow and detach from a grounded nozzle in response to an electric field. The now-charged drops are transported down a ratcheted channel by contact charge electrophoresis powered by the same voltage input used for drop generation. We investigate how the drop size, generation frequency, and transport velocity depend on system parameters such as the liquid viscosity, interfacial tension, applied voltage, and channel dimensions. The observed trends are well explained by a series of scaling analyses that provide insight into the dominant physical mechanisms underlying drop generation and ratcheted transport. We identify the conditions necessary for achieving reliable operation and discuss the various modes of failure that can arise when these conditions are violated. Our results demonstrate that simple electric inputs can power increasingly complex droplet operations with potential opportunities for inexpensive and portable microfluidic systems.

Numerical simulations of gas mixing effect in electron cyclotron resonance ion sources

NASA Astrophysics Data System (ADS)

Mironov, V.; Bogomolov, S.; Bondarchenko, A.; Efremov, A.; Loginov, V.

2017-01-01

The particle-in-cell Monte Carlo collisions code nam-ecris is used to simulate the electron cyclotron resonance ion source (ECRIS) plasma sustained in a mixture of Kr with O2 , N2 , Ar, Ne, and He. The model assumes that ions are electrostatically confined in the ECR zone by a dip in the plasma potential. A gain in the extracted krypton ion currents is seen for the highest charge states; the gain is maximized when oxygen is used as a mixing gas. The special feature of oxygen is that most of the singly charged oxygen ions are produced after the dissociative ionization of oxygen molecules with a large kinetic energy release of around 5 eV per ion. The increased loss rate of energetic lowly charged ions of the mixing element requires a building up of the retarding potential barrier close to the ECR surface to equilibrate electron and ion losses out of the plasma. In the mixed plasmas, the barrier value is large (˜1 V ) compared to pure Kr plasma (˜0.01 V ), with longer confinement times of krypton ions and with much higher ion temperatures. The temperature of the krypton ions is increased because of extra heating by the energetic oxygen ions and a longer time of ion confinement. In calculations, a drop of the highly charged ion currents of lighter elements is observed when adding small fluxes of krypton into the source. This drop is caused by the accumulation of the krypton ions inside plasma, which decreases the electron and ion confinement times.

In vitro differentiation of mouse embryonic stem (mES) cells using the hanging drop method.

PubMed

Wang, Xiang; Yang, Phillip

2008-07-23

Stem cells have the remarkable potential to develop into many different cell types. When a stem cell divides, each new cell has the potential to either remain a stem cell or become another type of cell with a more specialized function, This promising of science is leading scientists to investigate the possibility of cell-based therapies to treat disease. When culture in suspension without antidifferentiation factors, embryonic stem cells spontaneously differentiate and form three-dimensional multicellular aggregates. These cell aggregates are called embryoid bodies(EB). Hanging drop culture is a widely used EB formation induction method. The rounded bottom of hanging drop allows the aggregation of ES cells which can provide mES cells a good environment for forming EBs. The number of ES cells aggregatied in a hanging drop can be controlled by varying the number of cells in the initial cell suspension to be hung as a drop from the lid of Petri dish. Using this method we can reproducibly form homogeneous EBs from a predetermined number of ES cells.

Using Large-Eddy Simulation to Explore Microphysical Precursor Conditions for Precipitation Initiation in Marine Stratocumulus

NASA Astrophysics Data System (ADS)

Chandler, H.; Mechem, D. B.; Fridlind, A. M.; Ackerman, A. S.

2016-12-01

Although the classical model of how a population of cloud droplets grows to precipitation-sized drops through the condensation and coalescence processes is well accepted, it does not fully address the history of how nascent precipitation drops come about in warm clouds. Precipitation initiation is influenced by the properties of the cloud drop distribution and in bulk large-eddy simulation (LES) models is parameterized by autoconversion. Double-moment formulations of autoconversion rate generally weight cloud water content qc more than cloud drop concentration Nc (e.g., qc2.47Nc-1.79, Khairoutdinov and Kogan 2000) and precipitation rate scalings derived from field campaigns suggest a dominance of thermodynamic over aerosol factors. However, the mechanisms that drive precipitation initiation in any given cloud are still uncertain. From the perspective of autoconversion, do the regions where precipitation onset occurs experience large liquid water content values (large qc), or are they anomalously clean (small Nc)? Recent laboratory measurements suggest that fluctuations in the supersaturation field may also play a role in precipitation initiation. This study explores the nature of precursor conditions to precipitation onset within marine stratocumulus clouds. We apply an LES model with size-resolving microphysics to a case of marine stratocumulus over the eastern north Atlantic. Backward trajectories originating from regions of precipitation initiation are calculated from the time-evolving LES flow fields to examine the history of fluid parcels that ultimately contain embryonic precipitation.

Large Daily Stock Variation Is Associated with Cardiovascular Mortality in Two Cities of Guangdong, China

PubMed Central

Lin, Hualiang; Zhang, Yonghui; Xu, Yanjun; Liu, Tao; Xiao, Jianpeng; Luo, Yuan; Xu, Xiaojun; He, Yanhui; Ma, Wenjun

2013-01-01

Objective The current study aimed to examine the effects of daily change of the Shenzhen Stock Exchange Index on cardiovascular mortality in Guangzhou and Taishan, China. Methods Daily mortality and stock performance data during 2006–2010 were collected to construct the time series for the two cities. A distributed lag non-linear model was utilized to examine the effect of daily stock index changes on cardiovascular mortality after controlling for potential confounding factors. Results We observed a delayed non-linear effect of the stock index change on cardiovascular mortality: both rising and declining of the stock index were associated with increased cardiovascular deaths. In Guangzhou, the 15–25 lag days cumulative relative risk of an 800 index drop was 2.08 (95% CI: 1.38–3.14), and 2.38 (95% CI: 1.31–4.31) for an 800 stock index increase on the cardiovascular mortality, respectively. In Taishan, the cumulative relative risk over 15–25 days lag was 1.65 (95% CI: 1.13–2.42) for an 800 index drop and 2.08 (95% CI: 1.26–3.42) for an 800 index rising, respectively. Conclusions Large ups and downs in daily stock index might be important predictor of cardiovascular mortality. PMID:23874619

Pharmacological activities of an eye drop containing Matricaria chamomilla and Euphrasia officinalis extracts in UVB-induced oxidative stress and inflammation of human corneal cells.

PubMed

Bigagli, Elisabetta; Cinci, Lorenzo; D'Ambrosio, Mario; Luceri, Cristina

2017-08-01

Ultraviolet B (UVB) exposure is a risk factor for corneal damage resulting in oxidative stress, inflammation and cell death. The aim of this study was to investigate the potential protective effects of a commercial eye drop (Dacriovis™) containing Matricaria chamomilla and Euphrasia officinalis extracts on human corneal epithelial cells (HCEC-12) against UVB radiation-induced oxidative stress and inflammation as well as the underlying mechanisms. The antioxidant potential of the eye drops was evaluated by measuring the ferric reducing antioxidant power and the total phenolic content by Folin-Ciocalteu reagent. HCEC-12 cells were exposed to UVB radiation and treated with the eye drops at various concentrations. Cell viability, wound healing assay, reactive oxygen species (ROS) levels, protein and lipid oxidative damage and COX-2, IL-1β, iNOS, SOD-2, HO-1 and GSS gene expression, were assessed. Eye drops were able to protect corneal epithelial cells from UVB-induced cell death and ameliorated the wound healing; the eye drops exhibited a strong antioxidant activity, decreasing ROS levels and protein and lipid oxidative damage. Eye drops also exerted anti-inflammatory activities by decreasing COX-2, IL-1β, iNOS expression, counteracted UVB-induced GSS and SOD-2 expression and restored HO-1 expression to control levels. These findings suggest that an eye drop containing Matricaria chamomilla and Euphrasia officinalis extracts exerts positive effects against UVB induced oxidative stress and inflammation and may be useful in protecting corneal epithelial cells from UVB exposure. Copyright © 2017 Elsevier B.V. All rights reserved.

Employee responses to health insurance premium increases.

PubMed

Goldman, Dana P; Leibowitz, Arleen A; Robalino, David A

2004-01-01

To determine the sensitivity of employees' health insurance decisions--including the decision to not choose health maintenance organization or fee-for-service coverage--during periods of rapidly escalating healthcare costs. A retrospective cohort study of employee plan choices at a single large firm with a "cafeteria-style" benefits plan wherein employees paid all the additional cost of purchasing more generous insurance. We modeled the probability that an employee would drop coverage or switch plans in response to employee premium increases using data from a single large US company with employees across 47 states during the 3-year period of 1989 through 1991, a time of large premium increases within and across plans. Premium increases induced substantial plan switching. Single employees were more likely to respond to premium increases by dropping coverage, whereas families tended to switch to another plan. Premium increases of 10% induced 7% of single employees to drop or severely cut back on coverage; 13% to switch to another plan; and 80% to remain in their existing plan. Similar figures for those with family coverage were 11%, 12%, and 77%, respectively. Simulation results that control for known covariates show similar increases. When faced with a dramatic increase in premiums--on the order of 20%--nearly one fifth of the single employees dropped coverage compared with 10% of those with family coverage. Employee coverage decisions are sensitive to rapidly increasing premiums, and single employees may be likely to drop coverage. This finding suggests that sustained premium increases could induce substantial increases in the number of uninsured individuals.

Water drop impact onto oil covered solid surfaces

NASA Astrophysics Data System (ADS)

Chen, Ningli; Chen, Huanchen; Amirfazli, Alidad

2016-11-01

Droplet impact onto an oily surface can be encountered routinely in industrial applications; e.g., in spray cooling. It is not clear from literature what impact an oil film may have on the impact process. In this work, water drop impact onto both hydrophobic (glass) and hydrophilic (OTS) substrates which were covered by oil films (silicone) of different thickness (5um-50um) and viscosity (5cst-100cst) were performed. The effects of drop impact velocity, film thickness, and viscosity of the oil film and wettability of the substrate were studied. Our results show that when the film viscosity and impact velocity is low, the water drop deformed into the usual disk shape after impact, and rebounded from the surface. Such rebound phenomena disappears, when the viscosity of oil becomes very large. With the increase of the impact velocity, crown and splashing appears in the spreading phase. The crown and splashing behavior appears more easily with the increase of film thickness and decrease of its viscosity. It was also found that the substrate wettability can only affect the impact process in cases which drop has a large Webber number (We = 594), and the film's viscosity and thickness are small. This work was support by National Natural Science Foundation of China and the Project Number is 51506084.

The variability of the rainfall rate as a function of area

NASA Astrophysics Data System (ADS)

Jameson, A. R.; Larsen, M. L.

2016-01-01

Distributions of drop sizes can be expressed as DSD = Nt × PSD, where Nt is the total number of drops in a sample and PSD is the frequency distribution of drop diameters (D). Their discovery permitted remote sensing techniques for rainfall estimation using radars and satellites measuring over large domains of several kilometers. Because these techniques depend heavily on higher moments of the PSD, there has been a bias toward attributing the variability of the intrinsic rainfall rates R over areas (σR) to the variability of the PSDs. While this variability does increase up to a point with increasing domain dimension L, the variability of the rainfall rate R also depends upon the variability in the total number of drops Nt. We show that while the importance of PSDs looms large for small domains used in past studies, it is the variability of Nt that dominates the variability of R as L increases to 1 km and beyond. The PSDs contribute to the variability of R through the relative dispersion of χ = D3Vt, where Vt is the terminal fall speed of drops of diameter D. However, the variability of χ is inherently limited because drop sizes and fall speeds are physically limited. In contrast, it is shown that the variance of Nt continuously increases as the domain expands for physical reasons explained below. Over domains larger than around 1 km, it is shown that Nt dominates the variance of the rainfall rate with increasing L regardless of the PSD.

Streaming potential of superhydrophobic microchannels.

PubMed

Park, Hung Mok; Kim, Damoa; Kim, Se Young

2017-03-01

For the purpose of gaining larger streaming potential, it has been suggested to employ superhydrophobic microchannels with a large velocity slip. There are two kinds of superhydrophobic surfaces, one having a smooth wall with a large Navier slip coefficient caused by the hydrophobicity of the wall material, and the other having a periodic array of no- shear slots of air pockets embedded in a nonslip wall. The electrokinetic flows over these two superhydrophobic surfaces are modelled using the Navier-Stokes equation and convection-diffusion equations of the ionic species. The Navier slip coefficient of the first kind surfaces and the no-shear slot ratio of the second kind surfaces are similar in the sense that the volumetric flow rate increases as these parameter values increase. However, although the streaming potential increases monotonically with respect to the Navier slip coefficient, it reaches a maximum and afterward decreases as the no-shear ratio increases. The results of the present investigation imply that the characterization of superhydrophobic surfaces employing only the measurement of volumetric flow rate against pressure drop is not appropriate and the fine structure of the superhydrophobic surfaces must be verified before predicting the streaming potential and electrokinetic flows accurately. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Relationship between field-aligned currents and inverted-V parallel potential drops observed at midaltitudes

NASA Astrophysics Data System (ADS)

Sakanoi, T.; Fukunishi, H.; Mukai, T.

1995-10-01

The inverted-V field-aligned acceleration region existing in the altitude range of several thousand kilometers plays an essential role for the magnetosphere-ionosphere coupling system. The adiabatic plasma theory predicts a linear relationship between field-aligned current density (J∥) and parallel potential drop (Φ∥), that is, J∥=KΦ∥, where K is the field-aligned conductance. We examined this relationship using the charged particle and magnetic field data obtained from the Akebono (Exos D) satellite. The potential drop above the satellite was derived from the peak energy of downward electrons, while the potential drop below the satellite was derived from two different methods: the peak energy of upward ions and the energy-dependent widening of electron loss cone. On the other hand, field-aligned current densities in the inverted-V region were estimated from the Akebono magnetometer data. Using these potential drops and field-aligned current densities, we estimated the linear field-aligned conductance KJΦ. Further, we obtained the corrected field-aligned conductance KCJΦ by applying the full Knight's formula to the current-voltage relationship. We also independently estimated the field-aligned conductance KTN from the number density and the thermal temperature of magnetospheric source electrons which were obtained by fitting accelerated Maxwellian functions for precipitating electrons. The results are summarized as follows: (1) The latitudinal dependence of parallel potential drops is characterized by a narrow V-shaped structure with a width of 0.4°-1.0°. (2) Although the inverted-V potential region exactly corresponds to the upward field aligned current region, the latitudinal dependence of upward current intensity is an inverted-U shape rather than an inverted-V shape. Thus it is suggested that the field-aligned conductance KCJΦ changes with a V-shaped latitudinal dependence. In many cases, KCJΦ values at the edge of the inverted-V region are about 5-10 times larger than those at the center. (3) By comparing KCJΦ with KTN, KCJΦ is found to be about 2-20 times larger than KTN. These results suggest that low-energy electrons such as trapped electrons, secondary and back-scattered electrons, and ionospheric electrons significantly contribute to upward field-aligned currents in the inverted-V region. It is therefore inferred that non adiabatic pitch angle scattering processes play an important role in the inverted-V region. .

WE-A-17A-09: Exploiting Electromagnetic Technologies for Real-Time Seed Drop Position Validation in Permanent Implant Brachytherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Racine, E; Hautvast, G; Binnekamp, D

Purpose: To report on preliminary results validating the performance of a specially designed LDR brachytherapy needle prototype possessing both electromagnetic (EM) tracking and seed drop detection abilities. Methods: An EM hollow needle prototype has been designed and constructed in collaboration with research partner Philips Healthcare. The needle possesses conventional 3D tracking capabilities, along with a novel seed drop detection mechanism exploiting local changes of electromagnetic properties generated by the passage of seeds in the needle's embedded sensor coils. These two capabilities are exploited by proprietary engineering and signal processing techniques to generate seed drop position estimates in real-time treatment delivery.more » The electromagnetic tracking system (EMTS) used for the experiment is the NDI Aurora Planar Field Generator. The experiment consisted of dropping a total of 35 seeds in a prismatic agarose phantom, and comparing the 3D seed drop positions of the EMTS to those obtained by an image analysis of subsequent micro-CT scans. Drop position error computations and statistical analysis were performed after a 3D registration of the two seed distributions. Results: Of the 35 seeds dropped in the phantom, 32 were properly detected by the needle prototype. Absolute drop position errors among the detected seeds ranged from 0.5 to 4.8 mm with mean and standard deviation values of 1.6 and 0.9 mm, respectively. Error measurements also include undesirable and uncontrollable effects such as seed motion upon deposition. The true accuracy performance of the needle prototype is therefore underestimated. Conclusion: This preliminary study demonstrates the potential benefits of EM technologies in detecting the passage of seeds in a hollow needle as a means of generating drop position estimates in real-time treatment delivery. Such tools could therefore represent a potentially interesting addition to existing brachytherapy protocols for rapid dosimetry validation. Equipments and fundings for this project were provided by Philips Medical.« less

Correlation Of Giant Nuclei With Cloud Droplet Concentration

NASA Astrophysics Data System (ADS)

Jha, V.; Hudson, J. G.; Noble, S.

2011-12-01

The effect of giant nuclei (GN; larger than 1 micrometer particles produced by wind on the ocean surface) on warm rain has been debated for decades. During RICO (Rain in Cumulus over the Ocean) Hudson et al. (2011) found a negative correlation (R) between CCN concentrations at 1% supersaturation (S) and large cloud droplet concentrations (Fig. 1A). This reversal from positive R for CCN with total (or small) cloud droplet concentrations (left side of Fig. 1A) was explained by the greater competition for condensate, which thus limits droplet sizes when CCN concentrations are higher. The negative R increased in magnitude with altitude, and the droplet size where the maximum negative R occurred increased with altitude (Fig. 1A). However, at all altitudes this negative R decreased in magnitude for even larger cloud and drizzle drops (right side of Fig. 1A except highest altitude). The decrease in magnitude of the negative R was greater for increasing drop sizes at higher altitudes. Thus, at the higher altitudes, R for CCN with large drizzle drops was of low negative magnitude and even positive at the highest RICO altitudes. The disparity between CCN and drizzle drop concentrations precluded a causal relationship. But the high R between GN and drizzle drop concentrations at the highest altitudes (Fig. 1B) and the comparable concentrations indicated that GN were engendering drizzle. This is supported by the increasing R with altitude of the GN-drizzle drop R (right side of Fig. 1B). The conclusion of a GN-drizzle connection is also supported by the fact that CCN concentrations should inhibit drizzle. This analysis of Hudson et al. (2011) is here expanded to include correlations of CCN concentrations at lower S with cloud and drizzle drop concentrations to investigate intermediate relationships; i.e., between large nuclei (i.e., 0.1-1 micrometer; critical S 0.1-0.01%) and drizzle drop concentrations. A shortcoming of Hudson et al. (2011) was the small number of high altitude flights, which limited the significance of the R values. The very recent (July 2011) ICE-T project was a similar study in the same region (Caribbean). The greater number of high altitude cloud measurements during the summer season should provide better statistics to test the GN warm rain hypothesis.

Coalescence of Drops of a Power-law Fluid

NASA Astrophysics Data System (ADS)

Kamat, Pritish; Thete, Sumeet; Basaran, Osman

2014-11-01

Drop coalescence is crucial in a host of industrial, household, and natural processes that involve dispersions. Coalescence is a rate-controlling process in breaking emulsions and strongly influences drop-size-distributions in sprays. In a continuum approach, coalescence begins by the formation of a microscopic, non-slender bridge connecting the two drops. Indefinitely large axial curvature at the neck results in local lowering of pressure that drives fluid from the bulk of the drops toward the neck, thereby causing the bridge radius r (t) and height z (t) to increase in time t. The coalescence of Newtonian drops in air has heretofore been thoroughly studied. Here, we extend these earlier studies by analyzing the coalescence of drops of power-law fluids because many fluids encountered in real applications, including cosmetic creams, shampoos, grease, and paint, exhibit power-law (deformation-rate thinning) rheology. On account of the non-slender geometry of the liquid bridge connecting the two drops (z << r) , we analyze the resulting free surface flow problem by numerical simulation. Among other results, we present and discuss the nature of flows and scaling behaviors for r and z as functions of the initial viscosity and power-law index (0 < n <= 1) .

U. S. plastics demand drops sharply

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

According to the Society of the Plastics Industry, plastics demand dropped sharply in the U.S. during second-quarter 1980. U.S. exports of themoplastics are down slightly from year-ago levels, and PVC and low-density polyethylene (LDPE) exports are increasing strongly, but strong exports can not offset a weak domestic market. The weakness in domestic PVC sales is due mostly to large drops in contruction pipe (-49%) and automotive uses, its leading markets, in the last year. LDPE sales have dropped 3% over the year, and 8% in film, LPDE's largest market. Polypropylene's two largest U.S. markets, molding and fibers, have also droppedmore » sharply. Epoxy resin showed a May 1979 to May 1980 gain of 28% in exports, but three other thermosets, polyesters, urea-melamine, and phenolics, have dropped sharply since May 1979.« less

Drop-port study of microresonator frequency combs: power transfer, spectra and time-domain characterization.

PubMed

Wang, Pei-Hsun; Xuan, Yi; Fan, Li; Varghese, Leo Tom; Wang, Jian; Liu, Yang; Xue, Xiaoxiao; Leaird, Daniel E; Qi, Minghao; Weiner, Andrew M

2013-09-23

We use a drop-port geometry to characterize frequency combs generated from silicon nitride on-chip microresonators in the normal group velocity regime. In sharp contrast with the traditional transmission geometry, we observe smooth output spectra with comparable powers in the pump and adjacent comb lines. The power transfer into the comb may be explained to a large extent by the coupling parameters characterizing the linear operation of the resonances studied. Furthermore, comparison of thru- and drop-port spectra shows that much of the ASE noise is filtered out by transmission to the drop-port. Autocorrelation measurements are performed on the drop-port output, without the need to filter out or suppress the strong pump line as is necessary in thru-port experiments. Passively mode-locked pulses with low background are observed in a normal dispersion microcavity.

Influence of solidification on the impact of supercooled water drops onto cold surfaces

NASA Astrophysics Data System (ADS)

Li, Hai; Roisman, Ilia V.; Tropea, Cameron

2015-06-01

This study presents an experimental investigation of the impact of a supercooled drop onto hydrophilic and superhydrophobic substrates. The aim is to better understand the process of airframe icing caused by supercooled large droplets, which has been recently identified as a severe hazard in aviation. The Weber number and Reynolds number of the impinging drop ranged from 200 to 300 and from 2600 to 5800, respectively. Drop impact, spreading, and rebound were observed using a high-speed video system. The maximum spreading diameter of an impacting drop on hydrophilic surfaces was measured. The temperature effect on this parameter was only minor for a wide range of the drop and substrate temperatures. However, ice/water mixtures emerged when both the drop and substrate temperatures were below 0 °C. Similarly, drop rebound on superhydrophobic substrates was significantly hindered by solidification when supercooled drop impacted onto substrates below the freezing point. The minimum receding diameter and the speed of ice accretion on the substrate were measured for various wall temperatures. Both parameters increased almost linearly with decreasing wall temperature, but eventually leveled off beyond a certain substrate temperature. The rate of ice formation on the substrate was significantly higher than the growth rate of free ice dendrites, implying that multiple nucleation sites were present.

Drop size distributions and related properties of fog for five locations measured from aircraft

NASA Technical Reports Server (NTRS)

Zak, J. Allen

1994-01-01

Fog drop size distributions were collected from aircraft as part of the Synthetic Vision Technology Demonstration Program. Three west coast marine advection fogs, one frontal fog, and a radiation fog were sampled from the top of the cloud to the bottom as the aircraft descended on a 3-degree glideslope. Drop size versus altitude versus concentration are shown in three dimensional plots for each 10-meter altitude interval from 1-minute samples. Also shown are median volume radius and liquid water content. Advection fogs contained the largest drops with median volume radius of 5-8 micrometers, although the drop sizes in the radiation fog were also large just above the runway surface. Liquid water content increased with height, and the total number of drops generally increased with time. Multimodal variations in number density and particle size were noted in most samples where there was a peak concentration of small drops (2-5 micrometers) at low altitudes, midaltitude peak of drops 5-11 micrometers, and high-altitude peak of the larger drops (11-15 micrometers and above). These observations are compared with others and corroborate previous results in fog gross properties, although there is considerable variation with time and altitude even in the same type of fog.

Surface temperature measurements of a levitated water drop during laser irradiation

NASA Astrophysics Data System (ADS)

Brownell, Cody; Tracey, Timothy

2016-11-01

Simulation of high energy laser propagation and scattering in the maritime environment is problematic, due to the high liklihood of turbulence, fog, and rain or sea spray within the beam path. Laser interactions with large water drops (diameters of approximately 1-mm), such as those found in a light rain, have received relatively less attention. In this regime a high energy laser will rapidly heat and vaporize a water drop as it traverses the beam path, but the exact heating / vaporization rate, its dependence on impurities, and ancillary effects on the drop or surroundings are unclear. In this work we present surface temperature measurements of a water drop obtained using a FLIR IR camera. The drop is acoustically levitated, and subject to a continuous wave laser with a wavelength of 1070-nm and a mean irradiance of approximately 500 W/cm2. These measurements show that the steady-state surface temperature of the drop is well below the saturation temperature, yet based on the time history of the drop volume vaporization begins almost immediately upon laser strike. Inferences on the turbulence characteristics within the drop are also made from measurements of the fluctuations in the surface temperature. Supported by ONR, HEL-JTO, and USNA Trident Scholar Program.

Drop Ejection From an Oscillating Rod

NASA Technical Reports Server (NTRS)

Wilkes, E. D.; Basaran, O. A.

1999-01-01

The dynamics of a drop of a Newtonian liquid that is pendant from or sessile on a solid rod that is forced to undergo time-periodic oscillations along its axis is studied theoretically. The free boundary problem governing the time evolution of the shape of the drop and the flow field inside it is solved by a method of lines using a finite element algorithm incorporating an adaptive mesh. When the forcing amplitude is small, the drop approaches a limit cycle at large times and undergoes steady oscillations thereafter. However, drop breakup is the consequence if the forcing amplitude exceeds a critical value. Over a wide range of amplitudes above this critical value, drop ejection from the rod occurs during the second oscillation period from the commencement of rod motion. Remarkably, the shape of the interface at breakup and the volume of the primary drop formed are insensitive to changes in forcing amplitude. The interface shape at times close to and at breakup is a multi-valued function of distance measured along the rod axis and hence cannot be described by recently popularized one-dimensional approximations. The computations show that drop ejection occurs without the formation of a long neck. Therefore, this method of drop formation holds promise of preventing formation of undesirable satellite droplets.

Drop impact onto a thin film: Miscibility effect

NASA Astrophysics Data System (ADS)

Chen, Ningli; Chen, H.; Amirfazli, A.

2017-09-01

In this work a systematic experimental study was performed to understand the process of liquid drop impact onto a thin film made of a different liquid from drop. The drop and film liquids can be miscible or immiscible. Three general outcomes of deposition, crown formation without splashing, and splashing, were observed in the advancing phase of the drop impact onto a solid surface covered by either a miscible or an immiscible thin film. However, for a miscible film, a larger Weber number and film thickness are needed for the formation of a crown and splashing comparing with immiscible cases. The advancing phase of drop impact onto a thin immiscible film with a large viscosity is similar to that of drop impact onto a dry surface; for a miscible film viscous film, the behavior is far from that of a dry surface. The behavior of liquid lamella in the receding phase of drop impact onto a thin miscible film is reported for the first time. The results show that immiscibility is not a necessary condition for the existence of a receding phase. The existence of a receding phase is highly dependent on the interfacial tension between the drop and the film. The miscibility can significantly affect the receding morphology as it will cause mixing of the two liquids.

DNS of moderate-temperature gaseous mixing layers laden with multicomponent-fuel drops

NASA Technical Reports Server (NTRS)

Clercq, P. C. Le; Bellan, J.

2004-01-01

A formulation representing multicomponent-fuel (MC-fuel) composition as a Probability Distribution Function (PDF) depending on the molar weight is used to construct a model of a large number of MC-fuel drops evaporating in a gas flow, so as to assess the extent of fuel specificity on the vapor composition.

Prediction of dynamic and mixing characteristics of drop-laden mixing layers using DNS and LES

NASA Technical Reports Server (NTRS)

Okong'o, N.; Leboissetier, A.; Bellan, J.

2004-01-01

Direct Numerical Simulation (DNS) and Large Eddy Simulation (LES) have been conducted of a temporal mixing layer laden with evaporating drops, in order to assess the ability of LES to reproduce dynamic and mixing aspects of the DNS which affect combustion, independently of combustion models.

Water Penetration through a Superhydrophobic Mesh During a Drop Impact.

PubMed

Ryu, Seunggeol; Sen, Prosenjit; Nam, Youngsuk; Lee, Choongyeop

2017-01-06

When a water drop impacts a mesh having submillimeter pores, a part of the drop penetrates through the mesh if the impact velocity is sufficiently large. Here we show that different surface wettability, i.e., hydrophobicity and superhydrophobicity, leads to different water penetration dynamics on a mesh during drop impact. We show, despite the water repellence of a superhydrophobic surface, that water can penetrate a superhydrophobic mesh more easily (i.e., at a lower impact velocity) over a hydrophobic mesh via a penetration mechanism unique to a superhydrophobic mesh. On a superhydrophobic mesh, the water penetration can occur during the drop recoil stage, which appears at a lower impact velocity than the critical impact velocity for water penetration right upon impact. We propose that this unique water penetration on a superhydrophobic mesh can be attributed to the combination of the hydrodynamic focusing and the momentum transfer from the water drop when it is about to bounce off the surface, at which point the water drop retrieves most of its kinetic energy due to the negligible friction on superhydrophobic surfaces.

Water Penetration through a Superhydrophobic Mesh During a Drop Impact

NASA Astrophysics Data System (ADS)

Ryu, Seunggeol; Sen, Prosenjit; Nam, Youngsuk; Lee, Choongyeop

2017-01-01

When a water drop impacts a mesh having submillimeter pores, a part of the drop penetrates through the mesh if the impact velocity is sufficiently large. Here we show that different surface wettability, i.e., hydrophobicity and superhydrophobicity, leads to different water penetration dynamics on a mesh during drop impact. We show, despite the water repellence of a superhydrophobic surface, that water can penetrate a superhydrophobic mesh more easily (i.e., at a lower impact velocity) over a hydrophobic mesh via a penetration mechanism unique to a superhydrophobic mesh. On a superhydrophobic mesh, the water penetration can occur during the drop recoil stage, which appears at a lower impact velocity than the critical impact velocity for water penetration right upon impact. We propose that this unique water penetration on a superhydrophobic mesh can be attributed to the combination of the hydrodynamic focusing and the momentum transfer from the water drop when it is about to bounce off the surface, at which point the water drop retrieves most of its kinetic energy due to the negligible friction on superhydrophobic surfaces.

Constant Stress Drop Fits Earthquake Surface Slip-Length Data

NASA Astrophysics Data System (ADS)

Shaw, B. E.

2011-12-01

Slip at the surface of the Earth provides a direct window into the earthquake source. A longstanding controversy surrounds the scaling of average surface slip with rupture length, which shows the puzzling feature of continuing to increase with rupture length for lengths many times the seismogenic width. Here we show that a more careful treatment of how ruptures transition from small circular ruptures to large rectangular ruptures combined with an assumption of constant stress drop provides a new scaling law for slip versus length which (1) does an excellent job fitting the data, (2) gives an explanation for the large crossover lengthscale at which slip begins to saturate, and (3) supports constant stress drop scaling which matches that seen for small earthquakes. We additionally discuss how the new scaling can be usefully applied to seismic hazard estimates.

49 CFR 178.965 - Drop test.

Code of Federal Regulations, 2010 CFR

2010-10-01

...) Conditioning. Rigid plastic Large Packagings and Large Packagings with plastic inner receptacles must be... having essentially the same physical characteristics. (3) The specific gravity and viscosity of a...

Initial basalt target site selection evaluation for the Mars penetrator drop test

NASA Technical Reports Server (NTRS)

Bunch, T. E.; Quaide, W. L.; Polkowski, G.

1976-01-01

Potential basalt target sites for an air drop penetrator test were described and the criteria involved in site selection were discussed. A summary of the background field geology and recommendations for optimum sites are also presented.

False capacity for lane drops : final report.

DOT National Transportation Integrated Search

2005-02-01

Lane drops downstream of signalized intersections are found on many urban and suburban streets and highways. Since : drivers tend to avoid using the short lane due to the potential for stressful merges downstream of the signal, the short lane is : ty...

Crystal nucleation and glass formation in metallic alloy melts

NASA Technical Reports Server (NTRS)

Spaepen, F.

1984-01-01

Homogeneous nucleation, containerless solidification, and bulk formation of metallic glasses are discussed. Homogeneous nucleation is not a limiting factor for metallic glass formation at slow cooling rates if the reduced glass transition temperature is high enough. Such glasses can be made in bulk if heterogeneous nucleants are removed. Containerless processing eleminates potential sources of nucleants, but as drop tube experiments on the Pd-Si alloys show, the free surface may still be a very effective heterogeneous nucleant. Combination of etching and heating in vacuum or fluxing can be effective for cleaning fairly large ingots of nucleants. Reduced gravity processing has a potentially useful role in the fluxing technique, for example to keep large metallic ingots surrounded by a low density, low fluidity flux if this proved difficult under ground conditions. For systems where heterogeneous nucleants in the bulk of the ingot need gravity to segregate to the flux-metal interface, reduced gravity processing may not be appropriate for bulk glass formation.

Self-Heating Effects In Polysilicon Source Gated Transistors

PubMed Central

Sporea, R. A.; Burridge, T.; Silva, S. R. P.

2015-01-01

Source-gated transistors (SGTs) are thin-film devices which rely on a potential barrier at the source to achieve high gain, tolerance to fabrication variability, and low series voltage drop, relevant to a multitude of energy-efficient, large-area, cost effective applications. The current through the reverse-biased source barrier has a potentially high positive temperature coefficient, which may lead to undesirable thermal runaway effects and even device failure through self-heating. Using numerical simulations we show that, even in highly thermally-confined scenarios and at high current levels, self-heating is insufficient to compromise device integrity. Performance is minimally affected through a modest increase in output conductance, which may limit the maximum attainable gain. Measurements on polysilicon devices confirm the simulated results, with even smaller penalties in performance, largely due to improved heat dissipation through metal contacts. We conclude that SGTs can be reliably used for high gain, power efficient analog and digital circuits without significant performance impact due to self-heating. This further demonstrates the robustness of SGTs. PMID:26351099

Computational analysis of drop formation before and after the first singularity: the fate of free and satellite drops during simple dripping and DOD drop formation

NASA Astrophysics Data System (ADS)

Chen, Alvin U.; Basaran, Osman A.

2000-11-01

Drop formation from a capillary --- dripping mode --- or an ink jet nozzle --- drop-on-demand (DOD) mode --- falls into a class of scientifically challenging yet practically useful free surface flows that exhibit a finite time singularity, i.e. the breakup of an initially single liquid mass into two or more fragments. While computational tools to model such problems have been developed recently, they lack the accuracy needed to quantitatively predict all the dynamics observed in experiments. Here we present a new finite element method (FEM) based on a robust algorithm for elliptic mesh generation and remeshing to handle extremely large interface deformations. The new algorithm allows continuation of computations beyond the first singularity to track fates of both primary and any satellite drops. The accuracy of the computations is demonstrated by comparison of simulations with experimental measurements made possible with an ultra high-speed digital imager capable of recording 100 million frames per second.

Temporal sequencing of throughfall drop generation as revealed by use of a large-scale rainfall simulator

NASA Astrophysics Data System (ADS)

Nanko, K.; Levia, D. F., Jr.; Iida, S.; SUN, X.; Shinohara, Y.; Sakai, N.

2017-12-01

Scientists have been interested in throughfall drop size and its distribution because of its importance to soil erosion and the forest water balance. An indoor experiment was employed to deepen our understanding of throughfall drop generation processes to promote better management of forested ecosystems. The indoor experiment provides a unique opportunity to examine an array of constant rainfall intensities that are ideal conditions to pick up the effect of changing intensities and not found in the fields. Throughfall drop generation was examined for three species- Cryptomeria japonica D. Don (Japanese cedar), Chamaecyparis obtusa (Siebold & Zucc.) Endl. (Japanese cypress), and Zelkova serrata Thunb. (Japanese zelkova)- under both leafed and leafless conditions in the large-scale rainfall simulator in the National Research Institute for Earth Science and Disaster Resilience (Tsukuba, Japan) at varying rainfall intensities ranging from15 to 100 mm h-1. Drop size distributions of the applied rainfall and throughfall were measured simultaneously by 20 laser disdrometers. Utilizing the drop size dataset, throughfall was separated into three components: free throughfall, canopy drip, and splash throughfall. The temporal sequencing of the throughfall components were analyzed on a 1-min interval during each experimental run. The throughfall component percentage and drop size of canopy drip differed among tree species and rainfall intensities and by elapsed time from the beginning of the rainfall event. Preliminary analysis revealed that the time differences to produce branch drip as compared to leaf (or needle) drip was partly due to differential canopy wet-up processes and the disappearance of branch drips due to canopy saturation, leading to dissimilar throughfall drop size distributions beneath the various tree species examined. This research was supported by JSPS Invitation Fellowship for Research in Japan (Grant No.: S16088) and JSPS KAKENHI (Grant No.: JP15H05626).

Estimation and applicability of attenuation characteristics for source parameters and scaling relations in the Garhwal Kumaun Himalaya region, India

NASA Astrophysics Data System (ADS)

Singh, Rakesh; Paul, Ajay; Kumar, Arjun; Kumar, Parveen; Sundriyal, Y. P.

2018-06-01

Source parameters of the small to moderate earthquakes are significant for understanding the dynamic rupture process, the scaling relations of the earthquakes and for assessment of seismic hazard potential of a region. In this study, the source parameters were determined for 58 small to moderate size earthquakes (3.0 ≤ Mw ≤ 5.0) occurred during 2007-2015 in the Garhwal-Kumaun region. The estimated shear wave quality factor (Qβ(f)) values for each station at different frequencies have been applied to eliminate any bias in the determination of source parameters. The Qβ(f) values have been estimated by using coda wave normalization method in the frequency range 1.5-16 Hz. A frequency-dependent S wave quality factor relation is obtained as Qβ(f) = (152.9 ± 7) f(0.82±0.005) by fitting a power-law frequency dependence model for the estimated values over the whole study region. The spectral (low-frequency spectral level and corner frequency) and source (static stress drop, seismic moment, apparent stress and radiated energy) parameters are obtained assuming ω-2 source model. The displacement spectra are corrected for estimated frequency-dependent attenuation, site effect using spectral decay parameter "Kappa". The frequency resolution limit was resolved by quantifying the bias in corner frequencies, stress drop and radiated energy estimates due to finite-bandwidth effect. The data of the region shows shallow focused earthquakes with low stress drop. The estimation of Zúñiga parameter (ε) suggests the partial stress drop mechanism in the region. The observed low stress drop and apparent stress can be explained by partial stress drop and low effective stress model. Presence of subsurface fluid at seismogenic depth certainly manipulates the dynamics of the region. However, the limited event selection may strongly bias the scaling relation even after taking as much as possible precaution in considering effects of finite bandwidth, attenuation and site corrections. Although, the scaling can be improved further with the integration of large dataset of microearthquakes and use of a stable and robust approach.

Wetting-induced formation of controllable monodisperse multiple emulsions in microfluidics.

PubMed

Deng, Nan-Nan; Wang, Wei; Ju, Xiao-Jie; Xie, Rui; Weitz, David A; Chu, Liang-Yin

2013-10-21

Multiple emulsions, which are widely applied in a myriad of fields because of their unique ability to encapsulate and protect active ingredients, are typically produced by sequential drop-formations and drop-encapsulations using shear-induced emulsification. Here we report a qualitatively novel method of creating highly controlled multiple emulsions from lower-order emulsions. By carefully controlling the interfacial energies, we adjust the spreading coefficients between different phases to cause drops of one fluid to completely engulf other drops of immiscible fluids; as a result multiple emulsions are directly formed by simply putting preformed lower-order emulsion drops together. Our approach has highly controllable flexibility. We demonstrate this in preparation of both double and triple emulsions with a controlled number of inner drops and precisely adjusted shell thicknesses including ultra-thin shells. Moreover, this controllable drop-engulfing-drop approach has a high potential in further investigations and applications of microfluidics. Importantly, this innovative approach opens a window to exploit new phenomena occurring in fluids at the microscale level, which is of great significance for developing novel microfluidics.

On Electron Hole Evolution in Inhomogeneous Plasmas

NASA Astrophysics Data System (ADS)

Kuzichev, I.; Vasko, I.; Agapitov, O. V.; Mozer, F.; Artemyev, A.

2017-12-01

Electron holes (EHs) are the stationary localized non-linear structures in phase space existing due to an electron population trapped within EH electrostatic potential. EHs were found to be a common phenomenon in the Earth's magnetosphere. Such structures were observed in reconnecting current sheets, injection fronts in the outer radiation belt, and in many other situations. EHs usually propagate along magnetic field lines with velocities about electron thermal velocity, are localized on the scale of about 4-10 Debye lengths, and have the field amplitude up to hundreds of mV/m. Generation of these structures, evolution, and their role in relaxation of instabilities and energy dissipation, particle energization, supporting large-scale potential drops is under active investigation. In this report, we present the results of 1.5D gyrokinetic Vlasov-Maxwell simulations of the EH evolution in plasmas with inhomogeneous magnetic field and inhomogeneous density. Our calculations show that the inhomogeneity has a critical effect on the EH dynamics. EHs propagating into stronger (weaker) magnetic field are decelerated (accelerated) with deceleration (acceleration) rate dependent on the magnetic field gradient. During the deceleration of EH, the potential drop (weak double layer) along EH is generated. Such a potential drop might be experimentally observable even for single EH in the reconnecting current sheets. The same holds for the propagation in the plasma with inhomogeneous density. For some parameters of the system, the deceleration results in the turning of the hole. The interesting feature of this process is that the turning point depends only on the EH parameters, being independent of the average inhomogeneity scale. Our calculations also demonstrate the significant difference between "quasi-particle" concept and real evolution of the hole. Indeed, the EH is accelerated (decelerated) faster than it follows from a quasi-particle energy conservation law. It indicates that the efficient energy exchange between the EH and resonant untrapped electrons takes place. We expect that the revealed features will be helpful for interpreting spacecraft observations and results of advanced particle simulations. I.K. was supported by RFBR 16-32-00721. I.V., O.A., and F. M. by JHU/APL contract 922613 (RBSPEFW).

Drop Migration and Demixing of Biphasic Aqueous Systems in an Applied Electric Field

NASA Astrophysics Data System (ADS)

Todd, Paul; Raghavarao, Karumanchi S. M. S.

1999-11-01

Applying an electric field to a demixing emulsion of poly(ethylene glycol)(PEG) and dextran (or maltodextrin) in phosphate-buffered aqueous solution shortens the demixing time up to 6 fold. Phosphate ions partition into the dextran-rich phase imparting a small electrical potential between the phases. PEG-rich drops migrate cathodally, and their electrophoretic mobility is directly proportional to their radius and increases with increased ionization of phosphate. An electric field, either parallel or antiparallel to the gravity vector, can enhance demixing. A theory consistent with these observations states that drops move due to external and internal electroosmotic flow (tractor treading). Enhanced demixing in an electric field whose polarity opposes buoyancy is thought to be caused by initial increased drop growth during retardation by the electric field so that the drop becomes more buoyant. However, at infinite internal drop viscosity the theory does not extrapolate to the result for solid colloid particles.

Self-wrapping of an ouzo drop induced by evaporation on a superamphiphobic surface.

PubMed

Tan, Huanshu; Diddens, Christian; Versluis, Michel; Butt, Hans-Jürgen; Lohse, Detlef; Zhang, Xuehua

2017-04-12

Evaporation of multi-component drops is crucial to various technologies and has numerous potential applications because of its ubiquity in nature. Superamphiphobic surfaces, which are both superhydrophobic and superoleophobic, can give a low wettability not only for water drops but also for oil drops. In this paper, we experimentally, numerically and theoretically investigate the evaporation process of millimetric sessile ouzo drops (a transparent mixture of water, ethanol, and trans-anethole) with low wettability on a superamphiphobic surface. The evaporation-triggered ouzo effect, i.e. the spontaneous emulsification of oil microdroplets below a specific ethanol concentration, preferentially occurs at the apex of the drop due to the evaporation flux distribution and volatility difference between water and ethanol. This observation is also reproduced by numerical simulations. The volume decrease of the ouzo drop is characterized by two distinct slopes. The initial steep slope is dominantly caused by the evaporation of ethanol, followed by the slower evaporation of water. At later stages, thanks to Marangoni forces the oil wraps around the drop and an oil shell forms. We propose an approximate diffusion model for the drying characteristics, which predicts the evaporation of the drops in agreement with experiment and numerical simulation results. This work provides an advanced understanding of the evaporation process of ouzo (multi-component) drops.

Quadricep and hamstring activation during drop jumps with changes in drop height.

PubMed

Peng, Hsien-Te; Kernozek, Thomas W; Song, Chen-Yi

2011-08-01

Compare the muscle activation patterns of the quadricep-hamstring during drop jumps with increasing demands of drop heights. Observational. University biomechanics laboratory. Fifteen male and eight female college physical education students. Electromyographic activity of the rectus femoris (RF) and biceps femoris (BF) during the landing and takeoff phase of drop jumps from 20 to 60-cm heights. The ground contact time, vertical ground reaction force (vGRF), knee flexion angle during ground contact, and jump height after takeoff were also analyzed. The activation of RF was higher in the drop jump from 60-cm than that from 20- and 30-cm (comparing 107.0 ± 45.9 to 82.3 ± 30.8 and 88.9 ± 38.9 %MVIC, P<.05) during the landing phase. Activation of BF remained similar across all drop heights. Drop jump from 60-cm resulted in greater contact time during takeoff phase and peak vGRF, and resulted in greater maximum knee flexion but straighter knee at ground contact than from lower drop heights. At drop height of 60-cm, the altered knee muscular activation and movement patterns may diminish the effectiveness of plyometric training and increase the potential injury risk of knee. Copyright © 2010 Elsevier Ltd. All rights reserved.

School Climate and Dropping Out of School in the Era of Accountability

ERIC Educational Resources Information Center

Kotok, Stephen; Ikoma, Sakiko; Bodovski, Katerina

2016-01-01

Using data from the High School Longitudinal Study of 2009 (HSLS:09)--a large nationally representative sample of US high school students--we employed multilevel structural equation modeling (SEM) to examine the relationship between school characteristics and the likelihood that a student will drop out of high school. We used a multifaceted…

The unique case of foot drop secondary to a large ovarian cyst.

PubMed

Ahmad, Maleeha; Kumar, Aditaya; Thomson, Simon

2014-08-01

We describe the unique case of a 58-year-old woman who presented with right leg radiculopathy caused by an ovarian cyst mimicking lumbar pathology. A review of the literature shows that this is a rare case where a histologically confirmed benign ovarian cystadenoma (of indeterminate type) is shown to cause foot drop and radiculopathy.

Observed source parameters for dynamic rupture with non-uniform initial stressand relatively high fracture energy

USGS Publications Warehouse

Beeler, Nicholas M.; Kilgore, Brian D.; McGarr, Arthur F.; Fletcher, Jon Peter B.; Evans, John R.; Steven R. Baker,

2012-01-01

We have conducted dynamic rupture propagation experiments to establish the relations between in-source stress drop, fracture energy and the resulting particle velocity during slip of an unconfined 2 m long laboratory fault at normal stresses between 4 and 8 MPa. To produce high fracture energy in the source we use a rough fault that has a large slip weakening distance. An artifact of the high fracture energy is that the nucleation zone is large such that precursory slip reduces fault strength over a large fraction of the total fault length prior to dynamic rupture, making the initial stress non-uniform. Shear stress, particle velocity, fault slip and acceleration were recorded coseismically at multiple locations along strike and at small fault-normal distances. Stress drop increases weakly with normal stress. Average slip rate depends linearly on the fault strength loss and on static stress drop, both with a nonzero intercept. A minimum fracture energy of 1.8 J/m2 and a linear slip weakening distance of 33 μm are inferred from the intercept. The large slip weakening distance also affects the average slip rate which is reduced by in-source energy dissipation from on-fault fracture energy.Because of the low normal stress and small per event slip (∼86 μm), no thermal weakening such as melting or pore fluid pressurization occurs in these experiments. Despite the relatively high fracture energy, and the very low heat production, energy partitioning during these laboratory earthquakes is very similar to typical earthquake source properties. The product of fracture energy and fault area is larger than the radiated energy. Seismic efficiency is low at ∼2%. The ratio of apparent stress to static stress drop is ∼27%, consistent with measured overshoot. The fracture efficiency is ∼33%. The static and dynamic stress drops when extrapolated to crustal stresses are 2–7.3 MPa and in the range of typical earthquake stress drops. As the relatively high fracture energy reduces the slip velocities in these experiments, the extrapolated average particle velocities for crustal stresses are 0.18–0.6 m/s. That these experiments are consistent with typical earthquake source properties suggests, albeit indirectly, that thermal weakening mechanisms such as thermal pressurization and melting which lead to near complete stress drops, dominate earthquake source properties only for exceptional events unless crustal stresses are low.

Deformation and Breakup of Two Fluid Jets

NASA Astrophysics Data System (ADS)

Doshi, Pankaj; Ramkrishna, Doraiswamy; Basaran, Osman

2001-11-01

Two fluid jets consists of an inner liquid core surrounded by an annulus of outer immiscible liquid. The perturbation in the inner and outer interphase could cause capillary instability resulting in large deformation and breakup of the jet into drops. The jet breakup and drop size distribution is largely influenced by the properties of inner and outer fluid phases. Out of the various jet breakup phenomena one with most technological importance is the one in which inner interphase ruptures followed by the outer interphase resulting in the formation of compound drops. The compound drop formation is very useful for the microencapsulation technology, which find use in diverse pharmaceutical and chemical industry applications. In this paper we present a computational analysis of non-linear deformation and breakup of two fluid jets of Newtonian fluids. The analysis involves study of capillary instability driven deformation of a free jet with periodic boundary conditions. Although small amplitude deformation of two fluid jets have previously been studied, large amplitude deformation exhibiting interesting nonlinear dynamics and eventual breakup of the two fluid jets have been beyond the reach of previously used analytical and computational techniques. The computational difficulties result from the facts that (1) the inner and outer interphase can overturn during the motion and (2) pressure and normal stress are discontinuous at the inner interphase. We overcome both of these difficulties by using a new Galerkin/finite element algorithm that relies on a powerful elliptic mesh generation technique. The results to be presented includes jet deformation and breakup time as a function of inner and outer fluid phase properties. The highlight of the results will be prediction of drop size distribution which is of critical importance for microencapsulation technology.

Method for reducing pressure drop through filters, and filter exhibiting reduced pressure drop

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sappok, Alexander; Wong, Victor

Methods for generating and applying coatings to filters with porous material in order to reduce large pressure drop increases as material accumulates in a filter, as well as the filter exhibiting reduced and/or more uniform pressure drop. The filter can be a diesel particulate trap for removing particulate matter such as soot from the exhaust of a diesel engine. Porous material such as ash is loaded on the surface of the substrate or filter walls, such as by coating, depositing, distributing or layering the porous material along the channel walls of the filter in an amount effective for minimizing ormore » preventing depth filtration during use of the filter. Efficient filtration at acceptable flow rates is achieved.« less

Response of an Impact Test Apparatus for Fall Protective Headgear Testing Using a Hybrid-III Head/Neck Assembly

PubMed Central

Caccese, V.; Ferguson, J.; Lloyd, J.; Edgecomb, M.; Seidi, M.; Hajiaghamemar, M.

2017-01-01

A test method based upon a Hybrid-III head and neck assembly that includes measurement of both linear and angular acceleration is investigated for potential use in impact testing of protective headgear. The test apparatus is based upon a twin wire drop test system modified with the head/neck assembly and associated flyarm components. This study represents a preliminary assessment of the test apparatus for use in the development of protective headgear designed to prevent injury due to falls. By including angular acceleration in the test protocol it becomes possible to assess and intentionally reduce this component of acceleration. Comparisons of standard and reduced durometer necks, various anvils, front, rear, and side drop orientations, and response data on performance of the apparatus are provided. Injury measures summarized for an unprotected drop include maximum linear and angular acceleration, head injury criteria (HIC), rotational injury criteria (RIC), and power rotational head injury criteria (PRHIC). Coefficient of variation for multiple drops ranged from 0.4 to 6.7% for linear acceleration. Angular acceleration recorded in a side drop orientation resulted in highest coefficient of variation of 16.3%. The drop test apparatus results in a reasonably repeatable test method that has potential to be used in studies of headgear designed to reduce head impact injury. PMID:28216804

Attempting to bridge the gap between laboratory and seismic estimates of fracture energy

USGS Publications Warehouse

McGarr, A.; Fletcher, Joe B.; Beeler, N.M.

2004-01-01

To investigate the behavior of the fracture energy associated with expanding the rupture zone of an earthquake, we have used the results of a large-scale, biaxial stick-slip friction experiment to set the parameters of an equivalent dynamic rupture model. This model is determined by matching the fault slip, the static stress drop and the apparent stress. After confirming that the fracture energy associated with this model earthquake is in reasonable agreement with corresponding laboratory values, we can use it to determine fracture energies for earthquakes as functions of stress drop, rupture velocity and fault slip. If we take account of the state of stress at seismogenic depths, the model extrapolation to larger fault slips yields fracture energies that agree with independent estimates by others based on dynamic rupture models for large earthquakes. For fixed stress drop and rupture speed, the fracture energy scales linearly with fault slip.

A mix-and-read drop-based in vitro two-hybrid method for screening high-affinity peptide binders

PubMed Central

Cui, Naiwen; Zhang, Huidan; Schneider, Nils; Tao, Ye; Asahara, Haruichi; Sun, Zhiyi; Cai, Yamei; Koehler, Stephan A.; de Greef, Tom F. A.; Abbaspourrad, Alireza; Weitz, David A.; Chong, Shaorong

2016-01-01

Drop-based microfluidics have recently become a novel tool by providing a stable linkage between phenotype and genotype for high throughput screening. However, use of drop-based microfluidics for screening high-affinity peptide binders has not been demonstrated due to the lack of a sensitive functional assay that can detect single DNA molecules in drops. To address this sensitivity issue, we introduced in vitro two-hybrid system (IVT2H) into microfluidic drops and developed a streamlined mix-and-read drop-IVT2H method to screen a random DNA library. Drop-IVT2H was based on the correlation between the binding affinity of two interacting protein domains and transcriptional activation of a fluorescent reporter. A DNA library encoding potential peptide binders was encapsulated with IVT2H such that single DNA molecules were distributed in individual drops. We validated drop-IVT2H by screening a three-random-residue library derived from a high-affinity MDM2 inhibitor PMI. The current drop-IVT2H platform is ideally suited for affinity screening of small-to-medium-sized libraries (103–106). It can obtain hits within a single day while consuming minimal amounts of reagents. Drop-IVT2H simplifies and accelerates the drop-based microfluidics workflow for screening random DNA libraries, and represents a novel alternative method for protein engineering and in vitro directed protein evolution. PMID:26940078

Internal seed dispersal by parrots: an overview of a neglected mutualism

PubMed Central

Bravo, Carolina; Pacifico, Erica C.; Chamorro, Daniel; Speziale, Karina L.; Lambertucci, Sergio A.; Hiraldo, Fernando; Tella, José L.

2016-01-01

Despite the fact that parrots (Psitacifformes) are generalist apex frugivores, they have largely been considered plant antagonists and thus neglected as seed dispersers of their food plants. Internal dispersal was investigated by searching for seeds in faeces opportunistically collected at communal roosts, foraging sites and nests of eleven parrot species in different habitats and biomes in the Neotropics. Multiple intact seeds of seven plant species of five families were found in a variable proportion of faeces from four parrot species. The mean number of seeds of each plant species per dropping ranged between one and about sixty, with a maximum of almost five hundred seeds from the cacti Pilosocereus pachycladus in a single dropping of Lear’s Macaw (Anodorhynchus leari). All seeds retrieved were small (<3 mm) and corresponded to herbs and relatively large, multiple-seeded fleshy berries and infrutescences from shrubs, trees and columnar cacti, often also dispersed by stomatochory. An overview of the potential constraints driving seed dispersal suggest that, despite the obvious size difference between seeds dispersed by endozoochory and stomatochory, there is no clear difference in fruit size depending on the dispersal mode. Regardless of the enhanced or limited germination capability after gut transit, a relatively large proportion of cacti seeds frequently found in the faeces of two parrot species were viable according to the tetrazolium test and germination experiments. The conservative results of our exploratory sampling and a literature review clearly indicate that the importance of parrots as endozoochorous dispersers has been largely under-appreciated due to the lack of research systematically searching for seeds in their faeces. We encourage the evaluation of seed dispersal and other mutualistic interactions mediated by parrots before their generalized population declines contribute to the collapse of key ecosystem processes. PMID:26925322

Comparison of Raindrop Size Distribution Measurements by Collocated Disdrometers

NASA Technical Reports Server (NTRS)

Tokay, Ali; Petersen, Walter A.; Gatlin, Patrick; Wingo, Matthew

2013-01-01

An impact-type Joss-Waldvogel disdrometer (JWD), a two-dimensional video disdrometer (2DVD), and a laser optical OTT Particle Size and Velocity (PARSIVEL) disdrometer (PD) were used to measure the raindrop size distribution (DSD) over a 6-month period in Huntsville, Alabama. Comparisons indicate event rain totals for all three disdrometers that were in reasonable agreement with a reference rain gauge. In a relative sense, hourly composite DSDs revealed that the JWD was more sensitive to small drops (,1 mm), while the PD appeared to severely underestimate small drops less than 0.76mm in diameter. The JWD and 2DVD measured comparable number concentrations of midsize drops (1-3mm) and large drops (3-5 mm), while the PD tended to measure relatively higher drop concentrations at sizes larger than 2.44mm in diameter. This concentration disparity tended to occur when hourly rain rates and drop counts exceeded 2.5mm/h and 400/min, respectively. Based on interactions with the PD manufacturer, the partially inhomogeneous laser beam is considered the cause of the PD drop count overestimation. PD drop fall speeds followed the expected terminal fall speed relationship quite well, while the 2DVD occasionally measured slower drops for diameters larger than 2.4mm, coinciding with events where wind speeds were greater than 4m/s. The underestimation of small drops by the PD had a pronounced effect on the intercept and shape of parameters of gamma-fitted DSDs, while the overestimation of midsize and larger drops resulted in higher mean values for PD integral rain parameters

Combining spray nozzle simulators with meshes: characterization of rainfall intensity and drop properties

NASA Astrophysics Data System (ADS)

Carvalho, Sílvia C. P.; de Lima, João L. M. P.; de Lima, M. Isabel P.

2013-04-01

Rainfall simulators can be a powerful tool to increase our understanding of hydrological and geomorphological processes. Nevertheless, rainfall simulators' design and operation might be rather demanding, for achieving specific rainfall intensity distributions and drop characteristics. The pressurized simulators have some advantages over the non-pressurized simulators: drops do not rely on gravity to reach terminal velocity, but are sprayed out under pressure; pressurized simulators also yield a broad range of drop sizes in comparison with drop-formers simulators. The main purpose of this study was to explore in the laboratory the potential of combining spray nozzle simulators with meshes in order to change rainfall characteristics (rainfall intensity and diameters and fall speed of drops). Different types of spray nozzles were tested, such as single full-cone and multiple full-cone nozzles. The impact of the meshes on the simulated rain was studied by testing different materials (i.e. plastic and steel meshes), square apertures and wire thicknesses, and different vertical distances between the nozzle and the meshes underneath. The diameter and fall speed of the rain drops were measured using a Laser Precipitation Monitor (Thies Clima). The rainfall intensity range and coefficients of uniformity of the sprays and the drop size distribution, fall speed and kinetic energy were analysed. Results show that when meshes intercept drop trajectories the spatial distribution of rainfall intensity and the drop size distribution are affected. As the spray nozzles generate typically small drop sizes and narrow drop size distributions, meshes can be used to promote the formation of bigger drops and random their landing positions.

Development of Low Global Warming Potential Refrigerant Solutions for Commercial Refrigeration Systems using a Life Cycle Climate Performance Design Tool

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdelaziz, Omar; Fricke, Brian A; Vineyard, Edward Allan

Commercial refrigeration systems are known to be prone to high leak rates and to consume large amounts of electricity. As such, direct emissions related to refrigerant leakage and indirect emissions resulting from primary energy consumption contribute greatly to their Life Cycle Climate Performance (LCCP). In this paper, an LCCP design tool is used to evaluate the performance of a typical commercial refrigeration system with alternative refrigerants and minor system modifications to provide lower Global Warming Potential (GWP) refrigerant solutions with improved LCCP compared to baseline systems. The LCCP design tool accounts for system performance, ambient temperature, and system load; systemmore » performance is evaluated using a validated vapor compression system simulation tool while ambient temperature and system load are devised from a widely used building energy modeling tool (EnergyPlus). The LCCP design tool also accounts for the change in hourly electricity emission rate to yield an accurate prediction of indirect emissions. The analysis shows that conventional commercial refrigeration system life cycle emissions are largely due to direct emissions associated with refrigerant leaks and that system efficiency plays a smaller role in the LCCP. However, as a transition occurs to low GWP refrigerants, the indirect emissions become more relevant. Low GWP refrigerants may not be suitable for drop-in replacements in conventional commercial refrigeration systems; however some mixtures may be introduced as transitional drop-in replacements. These transitional refrigerants have a significantly lower GWP than baseline refrigerants and as such, improved LCCP. The paper concludes with a brief discussion on the tradeoffs between refrigerant GWP, efficiency and capacity.« less

Reducing cyclone pressure drop with evasés

USDA-ARS?s Scientific Manuscript database

Cyclones are widely used to separate particles from gas flows and as air emissions control devices. Their cost of operation is proportional to the fan energy required to overcome their pressure drop. Evasés or exit diffusers potentially could reduce exit pressure losses without affecting collection...

Sensitive photo-thermal response of graphene oxide for mid-infrared detection

NASA Astrophysics Data System (ADS)

Bae, Jung Jun; Yoon, Jung Hyun; Jeong, Sooyeon; Moon, Byoung Hee; Han, Joong Tark; Jeong, Hee Jin; Lee, Geon-Woong; Hwang, Ha Ryong; Lee, Young Hee; Jeong, Seung Yol; Lim, Seong Chu

2015-09-01

This study characterizes the effects of incident infrared (IR) radiation on the electrical conductivity of graphene oxide (GO) and examines its potential for mid-IR detection. Analysis of the mildly reduced GO (m-GO) transport mechanism near room temperature reveals variable range hopping (VRH) for the conduction of electrons. This VRH behavior causes the m-GO resistance to exhibit a strong temperature dependence, with a large negative temperature coefficient of resistance of approximately -2 to -4% K-1. In addition to this hopping transport, the presence of various oxygen-related functional groups within GO enhances the absorption of IR radiation significantly. These two GO material properties are synergically coupled and provoke a remarkable photothermal effect within this material; specifically, a large resistance drop is exhibited by m-GO in response to the increase in temperature caused by the IR absorption. The m-GO bolometer effect identified in this study is different from that exhibited in vanadium oxides, which require added gold-black films that function as IR absorbers owing to their limited IR absorption capability.This study characterizes the effects of incident infrared (IR) radiation on the electrical conductivity of graphene oxide (GO) and examines its potential for mid-IR detection. Analysis of the mildly reduced GO (m-GO) transport mechanism near room temperature reveals variable range hopping (VRH) for the conduction of electrons. This VRH behavior causes the m-GO resistance to exhibit a strong temperature dependence, with a large negative temperature coefficient of resistance of approximately -2 to -4% K-1. In addition to this hopping transport, the presence of various oxygen-related functional groups within GO enhances the absorption of IR radiation significantly. These two GO material properties are synergically coupled and provoke a remarkable photothermal effect within this material; specifically, a large resistance drop is exhibited by m-GO in response to the increase in temperature caused by the IR absorption. The m-GO bolometer effect identified in this study is different from that exhibited in vanadium oxides, which require added gold-black films that function as IR absorbers owing to their limited IR absorption capability. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr04039f

Boston College Sees a Sharp Drop in Applications after Adding an Essay

ERIC Educational Resources Information Center

Hoover, Eric

2013-01-01

Boston College saw a 26-percent decrease in applications this year, a drop officials largely attribute to a new essay requirement. Last year the private Jesuit institution received a record 34,051 applications for 2,250 spots in its freshman class. This year approximately 25,000 students applied, and all of them had to do one thing their…

DIME Participant Builds a Potential Drop Tower Candidate

NASA Technical Reports Server (NTRS)

2002-01-01

A student assembles a Lego (TM) Challenge device designed to operate in the portable drop tower demonstrator as part of the second Dropping in a Microgravity Environment (DIME) competition held April 23-25, 2002, at NASA's Glenn Research Center. Competitors included two teams from Sycamore High School, Cincinnati, OH, and one each from Bay High School, Bay Village, OH, and COSI Academy, Columbus, OH. DIME is part of NASA's education and outreach activities. Details are on line at http://microgravity.grc.nasa.gov/DIME_2002.html.

Enhanced Oral Bioavailability of Pueraria Flavones by a Novel Solid Self-microemulsifying Drug Delivery System (SMEDDS) Dropping Pills.

PubMed

Guan, Qingxiang; Zhang, Guangyuan; Sun, Shilin; Fan, Hongbo; Sun, Cheng; Zhang, Shaoyuan

2016-05-01

To improve bioavailability of pueraria flavones (PF), a self-microemulsifying drug delivery system (SMEDDS) dropping pills composed of PF, Crodamol GTCC, Maisine 35-1, Cremophor RH 40, 1,2-propylene glycol and polyethylene glycol 6000 (PEG6000) was developed. Particle size, zeta potential, morphology and in vitro drug release were investigated, respectively. Pharmacokinetics, bioavailability of PF-SMEDDS dropping pills and commercial Yufengningxin dropping pills were also evaluated and compared in rats. Puerarin treated as the representative component of PF was analyzed. Dynamic light scattering showed the ability of PF-SMEDDS dropping pills to form a nanoemulsion droplet size in aqueous media. The type of media showed no significant effects on the release rate of PF. PF-SMEDDS dropping pills were able to improve the in vitro release rate of PF, and the in vitro release of these dropping pills was significantly faster than that of Yufengningxin dropping pills. There was a dramatic difference between the mean value of t1/2, peak concentration (Cmax), the area of concentration-time curve from 0 to 6 h (AUC0-6 h) of PF-SMEDDS dropping pills and that of commercial Yufengningxin dropping pills. A pharmacokinetic study showed that the bioavailability of PF was greatly enhanced by PF-SMEDDS dropping pills. The value of Cmax and relative bioavailability of PF-SMEDDS dropping pills were dramatically improved by an average of 1.69- and 2.36-fold compared with that of Yufengningxin dropping pills after gavage administration, respectively. It was concluded that bioavailability of PF was greatly improved and that PF-SMEDDS dropping pills might be an encouraging strategy to enhance the oral bioavailability of PF.

NASA Glenn Icing Research Tunnel: 2014 and 2015 Cloud Calibration Procedures and Results

NASA Technical Reports Server (NTRS)

Steen, Laura E.; Ide, Robert F.; Van Zante, Judith F.; Acosta, Waldo J.

2015-01-01

This report summarizes the current status of the NASA Glenn Research Center (GRC) Icing Research Tunnel cloud calibration: specifically, the cloud uniformity, liquid water content, and drop-size calibration results from both the January-February 2014 full cloud calibration and the January 2015 interim cloud calibration. Some aspects of the cloud have remained the same as what was reported for the 2014 full calibration, including the cloud uniformity from the Standard nozzles, the drop-size equations for Standard and Mod1 nozzles, and the liquid water content for large-drop conditions. Overall, the tests performed in January 2015 showed good repeatability to 2014, but there is new information to report as well. There have been minor updates to the Mod1 cloud uniformity on the north side of the test section. Also, successful testing with the OAP-230Y has allowed the IRT to re-expand its operating envelopes for large-drop conditions to a maximum median volumetric diameter of 270 microns. Lastly, improvements to the collection-efficiency correction for the SEA multi-wire have resulted in new calibration equations for Standard- and Mod1-nozzle liquid water content.

Rate/state Coulomb stress transfer model for the CSEP Japan seismicity forecast

NASA Astrophysics Data System (ADS)

Toda, Shinji; Enescu, Bogdan

2011-03-01

Numerous studies retrospectively found that seismicity rate jumps (drops) by coseismic Coulomb stress increase (decrease). The Collaboratory for the Study of Earthquake Prediction (CSEP) instead provides us an opportunity for prospective testing of the Coulomb hypothesis. Here we adapt our stress transfer model incorporating rate and state dependent friction law to the CSEP Japan seismicity forecast. We demonstrate how to compute the forecast rates of large shocks in 2009 using the large earthquakes during the past 120 years. The time dependent impact of the coseismic stress perturbations explains qualitatively well the occurrence of the recent moderate size shocks. Such ability is partly similar to that of statistical earthquake clustering models. However, our model differs from them as follows: the off-fault aftershock zones can be simulated using finite fault sources; the regional areal patterns of triggered seismicity are modified by the dominant mechanisms of the potential sources; the imparted stresses due to large earthquakes produce stress shadows that lead to a reduction of the forecasted number of earthquakes. Although the model relies on several unknown parameters, it is the first physics based model submitted to the CSEP Japan test center and has the potential to be tuned for short-term earthquake forecasts.

Hyperbolic umbilic caustics from oblate water drops with tilted illumination: Observations

NASA Astrophysics Data System (ADS)

Jobe, Oli; Thiessen, David B.; Marston, Philip L.

2017-11-01

Various groups have reported observations of hyperbolic umbilic diffraction catastrophe patterns in the far-field scattering by oblate acoustically levitated drops with symmetric illumination. In observations of that type the drop's symmetry axis is vertical and the illuminating light beam (typically an expanded laser beam) travels horizontally. In the research summarized here, scattering patterns in the primary rainbow region and drop measurements were recorded with vertically tilted laser beam illumination having a grazing angle as large as 4 degrees. The findings from these observations may be summarized as follows: (a) It remains possible to adjust the drop aspect ratio (diameter/height) = D/H so as to produce a V-shaped hyperbolic umbilic focal section (HUFS) in the far-field scattering. (b) The shift in the required D/H was typically an increase of less than 1% and was quadratic in the tilt. (c) The apex of the V-shaped HUFS was shifted vertically by an amount proportional to the tilt with a coefficient close to unity. The levitated drops had negligible up-down asymmetry. Our method of investigation should be useful for other generalized rainbows with tilted illumination.

Non-contact temperature measurement of a falling drop

NASA Technical Reports Server (NTRS)

Hofmeister, William; Bayuzick, R. J.; Robinson, M. B.

1989-01-01

The 105 meter drop tube at NASA-Marshall has been used in a number of experiments to determine the effects of containerless, microgravity processing on the undercooling and solidification behavior of metals and alloys. These experiments have been limited, however, because direct temperature measurement of the falling drops has not been available. Undercooling and nucleation temperatures are calculated from thermophysical properties based on droplet cooling models. In most cases these properties are not well known, particularly in the undercooled state. This results in a large amount of uncertainty in the determination of nucleation temperatures. If temperature measurement can be accomplished then the thermal history of the drops could be well documented. This would lead to a better understanding of the thermophysical and thermal radiative properties of undercooled melts. An effort to measure the temperature of a falling drop is under way. The technique uses two color pyrometry and high speed data acquisition. The approach is presented along with some preliminary data from drop tube experiments. The results from droplet cooling models is compared with noncontact temperature measurements.

Dynamics of Oscillating and Rotating Liquid Drop using Electrostatic Levitator

NASA Astrophysics Data System (ADS)

Matsumoto, Satoshi; Awazu, Shigeru; Abe, Yutaka; Watanabe, Tadashi; Nishinari, Katsuhiro; Yoda, Shinichi

2006-11-01

In order to understand the nonlinear behavior of liquid drop with oscillatory and/or rotational motions, an experimental study was performed. The electrostatic levitator was employed to achieve liquid drop formation on ground. A liquid drop with about 3 mm in diameter was levitated. The oscillation of mode n=2 along the vertical axis was induced by an external electrostatic force. The oscillatory motions were observed to clarify the nonlinearities of oscillatory behavior. A relationship between amplitude and frequency shift was made clear and the effect of frequency shift on amplitude agreed well with the theory. The frequency shift became larger with increasing the amplitude of oscillation. To confirm the nonlinear effects, we modeled the oscillation by employing the mass-spring-damper system included the nonlinear term. The result indicates that the large-amplitude oscillation includes the effect of nonlinear oscillation. The sound pressure was imposed to rotate the liquid drop along a vertical axis by using a pair of acoustic transducers. The drop transited to the two lobed shape due to centrifugal force when nondimensional angular velocity exceeded to 0.58.

Dropping fire retardants by helicopter: tests of three new helitanks

Treesearch

James B. Davis

1963-01-01

Late model helicopters equipped with new helitanks and adequately supplied can accurately deliver as much fire retardant as most fixed-wing air tankers at a potentially lower cost. Viscous water dropped from helicopters clung to fuel surfaces and was concentrated in a narrower pattern than plain water.

Transition from single to multiple axial potential structure in expanding helicon plasma

NASA Astrophysics Data System (ADS)

Ghosh, Soumen; Chattopadhyay, P. K.; Ghosh, J.; Pal, R.; Bora, D.

2017-02-01

Transition from single to multiple axial potential structure (MAPS) formation is reported in expanding helicon plasma. This transition is created by forming a cusp magnetic field at the downstream after the expansion throat. Two distinct potential drops are separated by a uniform axial potential zone. Non-uniform axial density distribution exists in expanding helicon systems. A cusp-like field nourishes both the axial density gradients sufficient enough for the formation of these two distinct potential drops. It is also shown that both single and multiple axial potential structures are observed only when both geometric and magnetic expansions closely coincide with each other. Coexistence of these two expansions at the same location enhances plasma expansion which facilitates deviation from Boltzmann distribution and violates quasi-neutrality locally.

Nonlinear dynamics of drops and bubbles and chaotic phenomena

NASA Technical Reports Server (NTRS)

Trinh, Eugene H.; Leal, L. G.; Feng, Z. C.; Holt, R. G.

1994-01-01

Nonlinear phenomena associated with the dynamics of free drops and bubbles are investigated analytically, numerically and experimentally. Although newly developed levitation and measurement techniques have been implemented, the full experimental validation of theoretical predictions has been hindered by interfering artifacts associated with levitation in the Earth gravitational field. The low gravity environment of orbital space flight has been shown to provide a more quiescent environment which can be utilized to better match the idealized theoretical conditions. The research effort described in this paper is a closely coupled collaboration between predictive and guiding theoretical activities and a unique experimental program involving the ultrasonic and electrostatic levitation of single droplets and bubbles. The goal is to develop and to validate methods based on nonlinear dynamics for the understanding of the large amplitude oscillatory response of single drops and bubbles to both isotropic and asymmetric pressure stimuli. The first specific area on interest has been the resonant coupling between volume and shape oscillatory modes isolated gas or vapor bubbles in a liquid host. The result of multiple time-scale asymptotic treatment, combined with domain perturbation and bifurcation methods, has been the prediction of resonant and near-resonant coupling between volume and shape modes leading to stable as well as chaotic oscillations. Experimental investigations of the large amplitude shape oscillation modes of centimeter-size single bubbles trapped in water at 1 G and under reduced hydrostatic pressure, have suggested the possibility of a low gravity experiment to study the direct coupling between these low frequency shape modes and the volume pulsation, sound-radiating mode. The second subject of interest has involved numerical modeling, using the boundary integral method, of the large amplitude shape oscillations of charged and uncharged drops in the presence of a static or time-varying electric field. Theoretically predicted non linearity in the resonant frequency of the fundamental quadrupole mode has been verified by the accompanying experimental studies. Additional phenomena such as hysteresis in the frequency response of ultrasoncially levitated droplets in the presence of a time varying electric field, and mode coupling in the oscillations of ultrasonically modulated droplets, have also been uncovered. One of the results of this ground-based research has been the identification and characterization of phenomena strictly associated with the influence of the gravitational field. This has also allowed us to identify the specific requirements for potential microgravity investigations yielding new information not obtainable on Earth.

Nonlinear dynamics of drops and bubbles and chaotic phenomena

NASA Astrophysics Data System (ADS)

Trinh, Eugene H.; Leal, L. G.; Feng, Z. C.; Holt, R. G.

1994-08-01

Nonlinear phenomena associated with the dynamics of free drops and bubbles are investigated analytically, numerically and experimentally. Although newly developed levitation and measurement techniques have been implemented, the full experimental validation of theoretical predictions has been hindered by interfering artifacts associated with levitation in the Earth gravitational field. The low gravity environment of orbital space flight has been shown to provide a more quiescent environment which can be utilized to better match the idealized theoretical conditions. The research effort described in this paper is a closely coupled collaboration between predictive and guiding theoretical activities and a unique experimental program involving the ultrasonic and electrostatic levitation of single droplets and bubbles. The goal is to develop and to validate methods based on nonlinear dynamics for the understanding of the large amplitude oscillatory response of single drops and bubbles to both isotropic and asymmetric pressure stimuli. The first specific area on interest has been the resonant coupling between volume and shape oscillatory modes isolated gas or vapor bubbles in a liquid host. The result of multiple time-scale asymptotic treatment, combined with domain perturbation and bifurcation methods, has been the prediction of resonant and near-resonant coupling between volume and shape modes leading to stable as well as chaotic oscillations. Experimental investigations of the large amplitude shape oscillation modes of centimeter-size single bubbles trapped in water at 1 G and under reduced hydrostatic pressure, have suggested the possibility of a low gravity experiment to study the direct coupling between these low frequency shape modes and the volume pulsation, sound-radiating mode. The second subject of interest has involved numerical modeling, using the boundary integral method, of the large amplitude shape oscillations of charged and uncharged drops in the presence of a static or time-varying electric field. Theoretically predicted non linearity in the resonant frequency of the fundamental quadrupole mode has been verified by the accompanying experimental studies. Additional phenomena such as hysteresis in the frequency response of ultrasoncially levitated droplets in the presence of a time varying electric field, and mode coupling in the oscillations of ultrasonically modulated droplets, have also been uncovered. One of the results of this ground-based research has been the identification and characterization of phenomena strictly associated with the influence of the gravitational field. This has also allowed us to identify the specific requirements for potential microgravity investigations yielding new information not obtainable on Earth.

Preparation of anti-inflammatory mesenchymal stem/precursor cells (MSCs) through sphere formation using hanging-drop culture technique.

PubMed

Bartosh, Thomas J; Ylostalo, Joni H

2014-02-06

Herein, we describe a protocol for preparation of pre-activated anti-inflammatory human mesenchymal stem/precursor cells (MSCs) in 3-D culture without addition of exogenous chemicals or gene-transfer approaches. MSCs are an easily procurable source of multipotent adult stem cells with therapeutic potential largely attributed to their paracrine regulation of inflammation and immunity. However, the culture conditions to prepare the ideal MSCs for cell therapy remain elusive. Furthermore, the reported lag time for activation in experimental models has prompted investigations on pre-activating the cells prior to their administration. In this protocol, standard 2-D culture-expanded MSCs are activated by aggregation into 3-D spheres using hanging-drop cultures. MSC activation is evaluated by real-time PCR and/or ELISA for anti-inflammatory factors (TSG-6, STC-1, PGE2), and by a functional assay using lipopolysaccharide-stimulated macrophage cultures. Further, we elucidate methods to prepare MSC-sphere conditioned medium, intact spheres, and suspension of single cells from spheres for experimental and clinical applications. Copyright © 2014 John Wiley & Sons, Inc.

Preparation of anti-inflammatory mesenchymal stem/precursor cells (MSCs) through sphere formation using hanging drop culture technique

PubMed Central

Bartosh, Thomas J.

2014-01-01

Herein, we describe a protocol for preparation of pre-activated anti-inflammatory human mesenchymal stem/precursor cells (MSCs) in 3D culture without addition of exogenous chemicals or gene transfer approaches. MSCs are an easily procurable source of multipotent adult stem cells with therapeutic potential largely attributed to their paracrine regulation of inflammation and immunity. However, the culture conditions to prepare the ideal MSCs for cell therapy remain elusive. Furthermore, reported lag time for activation in experimental models have prompted investigations to pre-activate the cells prior to their administration. In this protocol, standard 2D culture expanded MSCs are activated by aggregation into 3D spheres using hanging drop cultures. MSC activation is evaluated by real-time PCR and/or ELISA for anti-inflammatory factors (TSG-6, STC-1, PGE2), and by a functional assay using lipopolysaccharide-stimulated macrophage cultures. Furthermore, we elucidate methods to prepare MSC sphere conditioned medium, intact spheres, and suspension of single cells from spheres for experimental and clinical applications. PMID:24510769

Distinguishing between microscale gaseous bubbles and liquid drops

NASA Astrophysics Data System (ADS)

Tan, Beng Hau; An, Hongjie; Chan, Chon U.; Ohl, Claus-Dieter

2015-11-01

In recent years, there has been strong research interest in decorating surfaces with tiny bubbles and drops due to their potential applications in reducing slippage in micro and nanofluidic devices. Both nanobubbles and nanodrops are typically nucleated by exchanging fluids over a suitable substrate. However, the nucleation experiments present many challenges, such as reproducibility and the possibility of contamination. The use of one-use plastic syringes and needle cannulas in nucleation experiments can introduce polymeric contamination. A contaminated experiment may nucleate bubbles, drops or both. Moreover, it is surprisingly difficult to distinguish between bubbles and drops under the usual atomic force microscopy or optical techniques. Here we present an experimental study comparing bubbles and oil (PDMS) drops on an atomically smooth surface (HOPG). Instead of nucleating the objects via solvent exchange, we directly introduced bubbles via electrolysis, and oil drops by injecting a dilute solution. Contrary to previous reports, we find that under careful AFM characterisation, liquid drops and gaseous bubbles respond differently to a change in imaging force, and moreover present different characteristic force curves.

Electrochemistry in an acoustically levitated drop.

PubMed

Chainani, Edward T; Ngo, Khanh T; Scheeline, Alexander

2013-02-19

Levitated drops show potential as microreactors, especially when radicals are present as reactants or products. Solid/liquid interfaces are absent or minimized, avoiding adsorption and interfacial reaction of conventional microfluidics. We report amperometric detection in an acoustically levitated drop with simultaneous ballistic addition of reactant. A gold microelectrode sensor was fabricated with a lithographic process; active electrode area was defined by a photosensitive polyimide mask. The microdisk gold working electrode of radius 19 μm was characterized using ferrocenemethanol in aqueous buffer. Using cyclic voltammetry, the electrochemically active surface area was estimated by combining a recessed microdisk electrode model with the Randles-Sevcik equation. Computer-controlled ballistic introduction of reactant droplets into the levitated drop was developed. Chronoamperometric measurements of ferrocyanide added ballistically demonstrate electrochemical monitoring using the microfabricated electrode in a levitated drop. Although concentration increases with time due to drop evaporation, the extent of concentration is predictable with a linear evaporation model. Comparison of diffusion-limited currents in pendant and levitated drops show that convection arising from acoustic levitation causes an enhancement of diffusion-limited current on the order of 16%.

Bacterial and fungal flora of seagull droppings in Jersey

PubMed Central

Cragg, John; Clayton, Yvonne M.

1971-01-01

In Jersey 166 fresh and 122 dried seagull droppings were obtained and studied locally and in London for the presence of bacteria and fungi of potentially pathogenic nature. There were no salmonella or shigella bacteria isolated from the two groups but there was a high proportion of Candida albicans obtained from the fresh material (21·7%) and only 1·6% from the dry faeces. Cryptococcus neoformans and Histoplasma capsulatum were not found in either the dry or fresh droppings. The normal bacterial and fungal flora of the seagull was established and it is considered that the C. albicans in fresh gull droppings would not materially increase albicans infections in man. PMID:5104846

Profiles of electrified drops and bubbles

NASA Technical Reports Server (NTRS)

Basaran, O. A.; Scriven, L. E.

1982-01-01

Axisymmetric equilibrium shapes of conducting drops and bubbles, (1) pendant or sessile on one face of a circular parallel-plate capacitor or (2) free and surface-charged, are found by solving simultaneously the free boundary problem consisting of the augmented Young-Laplace equation for surface shape and the Laplace equation for electrostatic field, given the surface potential. The problem is nonlinear and the method is a finite element algorithm employing Newton iteration, a modified frontal solver, and triangular as well as quadrilateral tessellations of the domain exterior to the drop in order to facilitate refined analysis of sharply curved drop tips seen in experiments. The stability limit predicted by this computer-aided theoretical analysis agrees well with experiments.

Drop-on-demand drop formation of polyethylene oxide solutions

NASA Astrophysics Data System (ADS)

Yan, Xuejia; Carr, Wallace W.; Dong, Hongming

2011-10-01

The dynamics of drop-on-demand (DOD) drop formation for solutions containing polyethylene oxide (PEO) have been studied experimentally. Using a piezoelectrical actuated inkjet printhead with the nozzle orifice diameter of 53 μm, experiments were conducted for a series of PEO aqueous solutions with molecular weights ranging from 14 to 1000 kg/mol, polydispersity from 1.02 to 2.5, and concentrations from 0.005 to 10 wt. %. The addition of a small amount of PEO can have a significant effect on the DOD drop formation process, increasing breakup time, decreasing primary drop speed, and decreasing the number of satellite drops in some cases. The effects depend on both molecular weight and concentration. At lower molecular weights (14 and 35 kg/mol), the effect of PEO over the dilute solution regime is insignificant even at concentrations large enough that the solution does not fall in the dilute regime. As PEO molecular weight increased, the effects became significant. For monodispersed PEO solutions, breakup time and primary drop speed closely correlated with effective relaxation time but not for polydispersed PEO. Effective relaxation time depended greatly on molecular weight distribution. Viscosity-average molecular weight, used in calculating effective relaxation time for polydispersed PEO solutions, did not adequately account for high molecular fractions in the molecular weight distribution of the polydispersed PEOs. A mixture rule was developed to calculate the effective relaxation times for aqueous solutions containing mixtures of monodispersed PEO, and breakup times and primary drop speeds correlated well with effective relaxation times. For our experiments, DOD drop formation was limited to Deborah number ≲ 23.

Probing the nanoscale with high-speed interferometry of an impacting drop

NASA Astrophysics Data System (ADS)

Thoroddsen, S. T.; Li, E. Q.; Vakarelski, I. U.; Langley, K.

2017-02-01

The simple phenomenon of a water drop falling onto a glass plate may seem like a trivial fluid mechanics problem. However, detailed imaging has shown that this process is highly complex and a small air-bubble is always entrapped under the drop when it makes contact with the solid. This bubble can interfere with the uniformity of spray coatings and degrade inkjet fabrication of displays etc. We will describe how we use high-speed interferometry at 5 million frames per second to understand the details of this process. As the impacting drop approaches the solid, the dynamics are characterized by a balance between the lubrication pressure in the thin air layer and the inertia of the bot-tom of the drop. This deforms the drop, forming a dimple at its bottom and making the drop touch the surface along a ring, thereby entrapping the air-layer, which is typically 1-3 μm thick. This air-layer can be highly compressed and the deceleration of the bottom of the drop can be as large as 300,000 g. We describe how the thickness evolution of the lubricating air-layer is extracted from following the interference fringes between frames. Two-color interferometry is also used to extract absolute layer thicknesses. Finally, we identify the effects of nanometric surface roughness on the first contact of the drop with the substrate. Here we need to resolve the 100 nm thickness changes occurring during 200 ns intervals, requiring these state of the art high-speed cameras. Surprisingly, we see a ring of micro-bubbles marking the first contact of the drop with the glass, only for microscope slides, which have a typical roughness of 20 nm, while such rings are absent for drop impacts onto molecularly smooth mica surfaces.

Large Devaluations and the Real Exchange Rate

ERIC Educational Resources Information Center

Burstein, Ariel; Eichenbaum, Martin; Rebelo, Sergio

2005-01-01

In this paper we argue that the primary force behind the large drop in real exchange rates that occurs after large devaluations is the slow adjustment in the prices of nontradable goods and services. Our empirical analysis uses data from five large devaluation episodes: Argentina (2002), Brazil (1999), Korea (1997), Mexico (1994), and Thailand…

Li + Defects in a Solid-State Li Ion Battery: Theoretical Insights with a Li 3 OCl Electrolyte

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stegmaier, Saskia; Voss, Johannes; Reuter, Karsten

In a solid-state Li ion battery, the solid-state electrolyte exits principally in regions of high externally applied potentials, and this varies rapidly at the interfaces with electrodes due to the formation of electrochemical double layers. Here, we investigate the implications of these for a model solid-state Li ion battery Li|Li 3OCl|C, where C is simply a metallic intercalation cathode. We use DFT to calculate the potential dependence of the formation energies of the Li + charge carriers in superionic Li 3OCl. We find that Li+ vacancies are the dominant species at the cathode while Li+ interstitials dominate at the anode.more » With typical Mg aliovalent doping of Li 3OCl, Li + vacancies dominate the bulk of the electrolyte as well, with freely mobile vacancies only ~ 10 -4 of the Mg doping density at room temperature. We study the repulsive interaction between Li+ vacancies and find that this is extremely short range, typically only one lattice constant due to local structural relaxation around the vacancy and this is significantly shorter than pure electrostatic screening. We model a Li 3OCl- cathode interface by treating the cathode as a nearly ideal metal using a polarizable continuum model with an ε r = 1000. There is a large interface segregation free energy of ~ - 1 eV per Li + vacancy. Combined with the short range for repulsive interactions of the vacancies, this means that very large vacancy concentrations will build up in a single layer of Li 3OCl at the cathode interface to form a compact double layer. The calculated potential drop across the interface is ~ 3 V for a nearly full concentration of vacancies at the surface. This suggests that nearly all the cathode potential drop in Li 3OCl occurs at the Helmholtz plane rather than in a diffuse space-charge region. We suggest that the conclusions found here will be general to other superionic conductors as well.« less

Li + Defects in a Solid-State Li Ion Battery: Theoretical Insights with a Li 3 OCl Electrolyte

DOE PAGES

Stegmaier, Saskia; Voss, Johannes; Reuter, Karsten; ...

2017-04-26

In a solid-state Li ion battery, the solid-state electrolyte exits principally in regions of high externally applied potentials, and this varies rapidly at the interfaces with electrodes due to the formation of electrochemical double layers. Here, we investigate the implications of these for a model solid-state Li ion battery Li|Li 3OCl|C, where C is simply a metallic intercalation cathode. We use DFT to calculate the potential dependence of the formation energies of the Li + charge carriers in superionic Li 3OCl. We find that Li+ vacancies are the dominant species at the cathode while Li+ interstitials dominate at the anode.more » With typical Mg aliovalent doping of Li 3OCl, Li + vacancies dominate the bulk of the electrolyte as well, with freely mobile vacancies only ~ 10 -4 of the Mg doping density at room temperature. We study the repulsive interaction between Li+ vacancies and find that this is extremely short range, typically only one lattice constant due to local structural relaxation around the vacancy and this is significantly shorter than pure electrostatic screening. We model a Li 3OCl- cathode interface by treating the cathode as a nearly ideal metal using a polarizable continuum model with an ε r = 1000. There is a large interface segregation free energy of ~ - 1 eV per Li + vacancy. Combined with the short range for repulsive interactions of the vacancies, this means that very large vacancy concentrations will build up in a single layer of Li 3OCl at the cathode interface to form a compact double layer. The calculated potential drop across the interface is ~ 3 V for a nearly full concentration of vacancies at the surface. This suggests that nearly all the cathode potential drop in Li 3OCl occurs at the Helmholtz plane rather than in a diffuse space-charge region. We suggest that the conclusions found here will be general to other superionic conductors as well.« less

Studying the field induced breakup of acoustically levitated drops

NASA Astrophysics Data System (ADS)

Warschat, C.; Riedel, J.

2017-10-01

Coulomb fission of charged droplets (The terms drop and droplet are often used synonymous. Throughout this manuscript, to avoid confusion, the terms drop and droplet will be used for liquid spheres with radii in the millimeter range and the micrometer range, respectively. In our experiments, the first correspond to the parent drop while the latter describes the ejected progeny droplets.) is a well-studied natural phenomenon. Controlled droplet fission is already successfully employed in several technological applications. Still, since the occurring surface rupture relies on the exact understanding and description of the liquid gas boundary, some details are still under debate. Most empirical systematic studies observe falling micrometer droplets passing through the electric field inside a plate capacitor. This approach, although easily applicable and reliable, limits the experimental degrees of freedom regarding the observable time and the maximum size of the drops and can only be performed in consecutive individual observations of different subsequent drops. Here we present a novel setup to study the field induced breakup of acoustically levitated drops. The design does not bear any restrictions towards the temporal window of observation, and allows handling of drops of a tunable radius ranging from 10 μm to several millimeters and a real-time monitoring of one single drop. Our comprehensive study includes a time resolved visual inspection, laser shadowgraphy, laser induced fluorescence imaging, and ambient mass spectrometric interrogation of the nascent Taylor cone. The results shown for a millimeter sized drop, previously inaccessible for Coulomb fission experiments, are mostly comparable with previous results for smaller drops. The major difference is the time scale and the threshold potential of the drop rupture. Both values, however, resemble theoretically extrapolations to the larger radius. The technique allows for a systematic study of breakup behavior of drops of different charge, material, and size.

Inverted drop testing and neck injury potential.

PubMed

Forrest, Stephen; Herbst, Brian; Meyer, Steve; Sances, Anthony; Kumaresan, Srirangam

2003-01-01

Inverted drop testing of vehicles is a methodology that has long been used by the automotive industry and researchers to test roof integrity and is currently being considered by the National Highway Traffic Safety Administration as a roof strength test. In 1990 a study was reported which involved 8 dolly rollover tests and 5 inverted drop tests. These studies were conducted with restrained Hybrid III instrumented Anthropometric Test Devices (ATD) in production and rollcaged vehicles to investigate the relationship between roof strength and occupant injury potential. The 5 inverted drop tests included in the study provided a methodology producing "repeatable roof impacts" exposing the ATDs to the similar impact environment as those seen in the dolly rollover tests. Authors have conducted two inverted drop test sets as part of an investigation of two real world rollover accidents. Hybrid-III ATD's were used in each test with instrumented head and necks. Both test sets confirm that reduction of roof intrusion and increased headroom can significantly enhance occupant protection. In both test pairs, the neck force of the dummy in the vehicle with less crush and more survival space was significantly lower. Reduced roof crush and dynamic preservation of the occupant survival space resulted in only minor occupant contact and minimal occupant loading, establishing a clear causal relationship between roof crush and neck injuries.

Human Finger-Prick Induced Pluripotent Stem Cells Facilitate the Development of Stem Cell Banking

PubMed Central

Tan, Hong-Kee; Toh, Cheng-Xu Delon; Ma, Dongrui; Yang, Binxia; Liu, Tong Ming; Lu, Jun; Wong, Chee-Wai; Tan, Tze-Kai; Li, Hu; Syn, Christopher; Tan, Eng-Lee; Lim, Bing; Lim, Yoon-Pin; Cook, Stuart A.

2014-01-01

Induced pluripotent stem cells (iPSCs) derived from somatic cells of patients can be a good model for studying human diseases and for future therapeutic regenerative medicine. Current initiatives to establish human iPSC (hiPSC) banking face challenges in recruiting large numbers of donors with diverse diseased, genetic, and phenotypic representations. In this study, we describe the efficient derivation of transgene-free hiPSCs from human finger-prick blood. Finger-prick sample collection can be performed on a “do-it-yourself” basis by donors and sent to the hiPSC facility for reprogramming. We show that single-drop volumes of finger-prick samples are sufficient for performing cellular reprogramming, DNA sequencing, and blood serotyping in parallel. Our novel strategy has the potential to facilitate the development of large-scale hiPSC banking worldwide. PMID:24646489

A Validated All-Pressure Fluid Drop Model and Lewis Number Effects for a Binary Mixture

NASA Technical Reports Server (NTRS)

Harstad, K.; Bellan, J.

1999-01-01

The differences between subcritical liquid drop and supercritical fluid drop behavior are discussed. Under subcritical, evaporative high emission rate conditions, a film layer is present in the inner part of the drop surface which contributes to the unique determination of the boundary conditions; it is this film layer which contributes to the solution's convective-diffusive character. In contrast, under supercritical condition as the boundary conditions contain a degree of arbitrariness due to the absence of a surface, and the solution has then a purely diffusive character. Results from simulations of a free fluid drop under no-gravity conditions are compared to microgravity experimental data from suspended, large drop experiments at high, low and intermediary temperatures and in a range of pressures encompassing the sub-and supercritical regime. Despite the difference between the conditions of the simulations and experiments (suspension vs. free floating), the time rate of variation of the drop diameter square is remarkably well predicted in the linear curve regime. The drop diameter is determined in the simulations from the location of the maximum density gradient, and agrees well with the data. It is also shown that the classical calculation of the Lewis number gives qualitatively erroneous results at supercritical conditions, but that an effective Lewis number previously defined gives qualitatively correct estimates of the length scales for heat and mass transfer at all pressures.

40 CFR Table 2 to Subpart Zzzzz of... - Procedures for Establishing Operating Limits for New Affected Sources Classified as Large Foundries

Code of Federal Regulations, 2012 CFR

2012-07-01

... using the procedures in the following table: For . . . You must . . . 1. Each wet scrubber subject to the operating limits in § 63.10895(d)(1) for pressure drop and scrubber water flow rate. Using the CPMS required in § 63.10897(b), measure and record the pressure drop and scrubber water flow rate in...

40 CFR Table 2 to Subpart Zzzzz of... - Procedures for Establishing Operating Limits for New Affected Sources Classified as Large Foundries

Code of Federal Regulations, 2010 CFR

2010-07-01

... using the procedures in the following table: For . . . You must . . . 1. Each wet scrubber subject to the operating limits in § 63.10895(d)(1) for pressure drop and scrubber water flow rate. Using the CPMS required in § 63.10897(b), measure and record the pressure drop and scrubber water flow rate in...

40 CFR Table 2 to Subpart Zzzzz of... - Procedures for Establishing Operating Limits for New Affected Sources Classified as Large Foundries

Code of Federal Regulations, 2011 CFR

2011-07-01

... using the procedures in the following table: For . . . You must . . . 1. Each wet scrubber subject to the operating limits in § 63.10895(d)(1) for pressure drop and scrubber water flow rate. Using the CPMS required in § 63.10897(b), measure and record the pressure drop and scrubber water flow rate in...

Evaluation of Off-season Potential Breeding Sources for Spotted Wing Drosophila (Drosophila suzukii Matsumura) in Michigan.

PubMed

Bal, Harit K; Adams, Christopher; Grieshop, Matthew

2017-12-05

It has been suggested that fruit wastes including dropped and unharvested fruits, and fruit byproducts (i.e., pomace) found in fruit plantings and cideries or wine-making facilities could serve as potential off-season breeding sites for spotted wing Drosophila (Drosophila suzukii Matsumura (Diptera: Drosophilidae)). This idea, however, has yet to be widely tested. The goal of our study was to determine the potential of dropped fruit and fruit wastes as Fall spotted wing Drosophila breeding resources in Michigan, USA. Fruit waste samples were collected from 15 farms across the lower peninsula of Michigan and were evaluated for spotted wing Drosophila and other drosophilid emergence and used in host suitability bioassays. All of the dropped apples, pears, grapes, and raspberries and 40% of apple and 100% of grape fruit pomace evaluated were found to contain spotted wing Drosophila with the highest numbers collected from dropped grapes and pears. Greater spotted wing Drosophila recovery was found in fruit wastes at sites attached with cideries and wine-making facilities and with multiple cultivated fruit crops than sites with no cideries and only one crop. Females oviposited in raspberry, pear, apple, grape, apple pomace and grape pomace samples with the highest rates of reproduction in raspberries. Our results demonstrate that fruit wastes including dropped berry, pomme and stone fruits, as well as fruit compost may be important late season reproductive resources for spotted wing Drosophila. © The Author(s) 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

The long-term performance of electrically charged filters in a ventilation system.

PubMed

Raynor, Peter C; Chae, Soo Jae

2004-07-01

The efficiency and pressure drop of filters made from polyolefin fibers carrying electrical charges were compared with efficiency and pressure drop for filters made from uncharged glass fibers to determine if the efficiency of the charged filters changed with use. Thirty glass fiber filters and 30 polyolefin fiber filters were placed in different, but nearly identical, air-handling units that supplied outside air to a large building. Using two kinds of real-time aerosol counting and sizing instruments, the efficiency of both sets of filters was measured repeatedly for more than 19 weeks while the air-handling units operated almost continuously. Pressure drop was recorded by the ventilation system's computer control. Measurements showed that the efficiency of the glass fiber filters remained almost constant with time. However, the charged polyolefin fiber filters exhibited large efficiency reductions with time before the efficiency began to increase again toward the end of the test. For particles 0.6 microm in diameter, the efficiency of the polyolefin fiber filters declined from 85% to 45% after 11 weeks before recovering to 65% at the end of the test. The pressure drops of the glass fiber filters increased by about 0.40 in. H2O, whereas the pressure drop of the polyolefin fiber filters increased by only 0.28 in. H2O. The results indicate that dust loading reduces the effectiveness of electrical charges on filter fibers. Copyright 2004 JOEH, LLC

MEASUREMENT OF THE HIGH-FIELD Q-DROP IN A LARGE-GRAIN NIOBIUM CAVITY FOR DIFFERENT OXIDATION PROCESSES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gianluigi Ciovati; Peter Kneisel; Alex Gurevich

In this contribution, we present the results from a series of RF tests at 1.7 K and 2.0 K on a single-cell cavity made of high-purity large (with area of the order of few cm2) grain niobium which underwent various oxidation processes. After initial buffered chemical polishing, anodization, baking in pure oxygen atmosphere and baking in air up to 180 °C was applied with the objective of clearly identifying the role of oxygen and the oxide layer on the Q-drop. During each rf test a temperature mapping system was used allowing to measure the local temperature rise of the cavitymore » outer surface due to RF losses, which gives information about the losses location, their field dependence and space distribution on the RF surface. The results confirmed that the depth affected by baking is about 20 – 30 nm from the surface and showed that the Q-drop did not re-appear in a previously baked cavity by further baking at 120 °C in pure oxygen atmosphere or in air up to 180 °C. A statistic of the position of the “hot-spots” on the cavity surface showed that grain-boundaries are not the preferred location. An interesting correlation was found between the Q-drop onset, the quench field and the low-field energy gap, which supports the hypothesis of thermo-magnetic instability governing the Q-drop and the baking effect.« less

MEASUREMENT OF THE HIGH-FIELD Q-DROP IN A LARGE-GRAIN NIOBIUM CAVITY FOR DIFFERENT OXIDATION PROCESSES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ciovati, Gianluigi; Kneisel, Peter; Gurevich, Alex

In this contribution, we present the results from a series of RF tests at 1.7 K and 2.0 K on a single-cell cavity made of high-purity large (with area of the order of few cm2) grain niobium which underwent various oxidation processes. After initial buffered chemical polishing, anodization, baking in pure oxygen atmosphere and baking in air up to 180 °C was applied with the objective of clearly identifying the role of oxygen and the oxide layer on the Q-drop. During each rf test a temperature mapping system was used allowing to measure the local temperature rise of the cavitymore » outer surface due to RF losses, which gives information about the losses location, their field dependence and space distribution on the RF surface. The results confirmed that the depth affected by baking is about 20 – 30 nm from the surface and showed that the Q-drop did not re-appear in a previously baked cavity by further baking at 120 °C in pure oxygen atmosphere or in air up to 180 °C. A statistic of the position of the "hot-spots" on the cavity surface showed that grain-boundaries are not the preferred location. An interesting correlation was found between the Q-drop onset, the quench field and the low-field energy gap, which supports the hypothesis of thermomagnetic instability governing the Q-drop and the baking effect.« less

How (not) to interpret a non-causal association in sports injury science.

PubMed

Hjerrild, Mette; Videbaek, Solvej; Theisen, Daniel; Malisoux, Laurent; Oestergaard Nielsen, Rasmus

2018-07-01

To discuss the interpretability of non-causal associations to sports injury development exemplified via the relationship between navicular drop (ND) and running-related injury (RRI) in novice runners using neutral shoes. 1-year prospective cohort study. Denmark. 926 novice runners, representing 1852 feet, were included. The outcome was "a musculoskeletal complaint of the lower extremity or back caused by running, which restricted the amount of running for at least a week". Fewer feet with small ND than those feet with a reference ND sustained injuries at 50 (risk difference (RD) = -4.1% [95%CI = -7.9%;-0.4%]) and 100 km (RD = -5.3% [95%CI = -9.9%;-0.7%]). Similarly, fewer feet with a large ND sustained injuries than the feet with a reference drop at 250 (RD = -7.6% [95%CI = -14.9%;-0.3%]) and 500 km (RD = -9.8% [95%CI = -19.1%;-0.4%]). Non-causal associations can help to identify sub-groups of athletes at an increased or decreased risk of sports injury. Based on the current results, those with a small or large navicular drop sustain fewer injuries than those with a reference drop. Importantly, navicular drop does not cause RRIs, but influences the relationship between training load and RRI. This illustrates that non-causal associations are unsuitable to respond to the question: Why do sports injury develop? Copyright © 2018 Elsevier Ltd. All rights reserved.

Freja Studies of the Current-Voltage Relation in Substorm-Related Events

NASA Technical Reports Server (NTRS)

Olsson, A.; Andersson, Laila; Eriksson, A. I.; Clemmons, J.; Erlandsson, R. E.; Reeves, G.; Hughes, T.; Murphee, J. S.

2000-01-01

Field-aligned currents and electrostatic potentials play important roles in the coupling between the magnetosphere and the ionosphere. If one assumes that the ionosphere-magnetosphere potential difference is mainly due to the mirror force, one can use the single particle adiabatic kinetic theory to describe the system. From this theory, a linear relationship j(sub II) = KV between field-aligned current density j(sub II) and potential drop V along the same field line can be derived, provided that the potential drop is not too large and not too small. With rare exceptions, observational tests of this relation have mainly concentrated on quiet magnetospheric situations, with acceleration voltages V approx. less than 5 kV. Here we use observations from the Freja satellite of precipitating auroral electrons at 1.700 km altitude to study substorm related events, with acceleration voltages up to 20 keV. The observations are found to be consistent with a linear current-voltage relation even i n these conditions, although with values of the field aligned K lower than previously reported (1-5 x 10(exp 11 S/sq m). This can be explained by lower densities and higher characteristic electron energies in the magnetospheric source region of the precipitating electrons. We analyze the data by three different methods, which are all found to be in general agreement. The results are in agreement with a previous study, where the spectra of precipitating electrons --were indirectly inferred by inversion of data from the EISCAT incoherent scatter radar, thereby validating the use of radar data for studies of auroral electrons. Comparisons with previous studies are made, emphasizing the dependence of the results on the type of auroral structure and magnetospheric conditions.

Freja studies of the current-voltage relation in substorm-related events

NASA Astrophysics Data System (ADS)

Olsson, A.; Andersson, L.; Eriksson, A. I.; Clemmons, J.; Erlandsson, R. E.; Reeves, G.; Huges, T.; Murphee, J. S.

1998-03-01

Field-aligned currents and electrostatic potentials play important roles in the coupling between the magnetosphere and the ionosphere. If one assumes that the ionosphere-magnetosphere potential difference is mainly due to the mirror force, one can use the single particle adiabatic kinetic theory to describe the system. From this theory, a linear relationship j∥=KV between field-aligned current density j∥ and potential drop V along the same field line can be derived, provided that the potential drop is not too large and not too small. With rare exceptions, observational tests of this relation have mainly concentrated on quiet magnetospheric situations, with acceleration voltages V<~5kV. Here we use observations from the Freja satellite of precipitating auroral electrons at 1.700 km altitude to study substorm related events, with acceleration voltages up to 20 keV. The observations are found to be consistent with a linear current-voltage relation even in these conditions, although with values of the field aligned K lower than previously reported (1-5×10-11S/m2). This can be explained by lower densities and higher characteristic electron energies in the magnetospheric source region of the precipitating electrons. We analyze the data by three different methods, which are all found to be in general agreement. The results are in agreement with a previous study [Olsson et al., 1996 b], where the spectra of precipitating electrons were indirectly infered by inversion of data from the EISCAT incoherent scatter radar, thereby validating the use of radar data for studies of auroral electrons. Comparisons with previous studies are made, emphasizing the dependence of the results on the type of auroral structure and magnetospheric conditions.

Big Hydrophobic Capillary Fluidics; Basically Water Ping Pong in Space

NASA Astrophysics Data System (ADS)

Weislogel, Mark; Attari, Babak; Wollman, Andrew; Cardin, Karl; Geile, John; Lindner, Thomas

2016-11-01

Capillary surfaces can be enormous in environments where the effects of gravity are small. In this presentation we review a number of interesting examples from demonstrative experiments performed in drop towers and aboard the International Space Station. The topic then focuses on large length scale hydrophobic phenomena including puddle jumping, spontaneous particle ejections, and large drop rebounds akin to water ping pong in space. Unseen footage of NASA Astronaut Scott Kelly playing water ping pong in space will be shown. Quantitative and qualitative results are offered to assist in the design of experiments for ongoing research. NASA NNX12A047A.

Direct numerical simulations of two-phase laminar jet flows with different cross-section injection geometries

NASA Astrophysics Data System (ADS)

Abdel-Hameed, H.; Bellan, J.

2002-10-01

Direct numerical simulations are performed of spatial, three-dimensional, laminar jets of different inlet geometric configurations for the purpose of quantifying the characteristics of the flows; both single-phase (SP) and two-phase (TP) free jets are considered. The TP jets consist of gas laden with liquid drops randomly injected at the inlet. Drop evaporation ensues both due to the gaseous flow being initially unvitiated by the vapor species corresponding to the liquid drops, and to drop heating as the initial drop temperature is lower than that of the carrier gas. The conservation equations for the TP flow include complete couplings of mass, momentum, and energy based on thermodynamically self-consistent specification of the vapor enthalpy, internal energy, and latent heat of vaporization. Inlet geometries investigated are circular, elliptic, rectangular, square, and triangular. The results focus both on the different spreading achieved according to the inlet geometry, as well as on the considerable change in the flow field due to the presence of the drops. The most important consequence of the drop interaction with the flow is the production of streamwise vorticity that alters entrainment and species mixing according to the inlet geometry. Similar to their SP equivalent, TP jets are shown to reach steady-state entrainment; examination of the flows at this time station shows that the potential cores of TP jets are shorter by an order of magnitude than their SP counterpart. Moreover, whereas the TP circular jet exhibits a symmetric entrainment pattern well past the streamwise location of the potential core, noncircular jets display at the same location strong departures from symmetry. Furthermore, the SP-jet phenomenon of axis switching is no longer present in TP jets. The distributions of drop-number density, liquid mass, and evaporated species are compared for different inlet cross sections and recommendations are made regarding the optimal choice for different applications.

The effect of hardhats on head and neck response to vertical impacts from large construction objects.

PubMed

Suderman, Bethany L; Hoover, Ryan W; Ching, Randal P; Scher, Irving S

2014-12-01

We evaluated the effectiveness of hardhats in attenuating head acceleration and neck force in vertical impacts from large construction objects. Two weight-matched objects (lead shot bag and concrete block) weighing 9.1 kg were dropped from three heights (0.91 m, 1.83 m and 2.74 m) onto the head of a 50th percentile male Hybrid III anthropomorphic test device (ATD). Two headgear conditions were tested: no head protection and an ANSI Type-I, Class-E hardhat. A third headgear condition (snow sport helmet) was tested at 1.83 m for comparison with the hardhat. Hardhats significantly reduced the resultant linear acceleration for the concrete block impacts by 70-95% when compared to the unprotected head condition. Upper neck compression was also significantly reduced by 26-60% with the use of a hardhat when compared to the unprotected head condition for the 0.91 and 1.83 m drop heights for both lead shot and concrete block drop objects. In this study we found that hardhats can be effective in reducing both head accelerations and compressive neck forces for large construction objects in vertical impacts. Copyright © 2014 Elsevier Ltd. All rights reserved.

Acoustic Levitation With One Transducer

NASA Technical Reports Server (NTRS)

Barmatz, Martin B.

1987-01-01

Higher resonator modes enables simplification of equipment. Experimental acoustic levitator for high-temperature containerless processing has round cylindrical levitation chamber and only one acoustic transducer. Stable levitation of solid particle or liquid drop achieved by exciting sound in chamber to higher-order resonant mode that makes potential well for levitated particle or drop at some point within chamber.

Method to produce large, uniform hollow spherical shells

DOEpatents

Hendricks, C.D.

1983-09-26

The invention is a method to produce large uniform hollow spherical shells by (1) forming uniform size drops of heat decomposable or vaporizable material, (2) evaporating the drops to form dried particles, (3) coating the dried particles with a layer of shell forming material and (4) heating the composite particles to melt the outer layer and to decompose or vaporize the inner particle to form an expanding inner gas bubble. The expanding gas bubble forms the molten outer layer into a shell of relatively large diameter. By cycling the temperature and pressure on the molten shell, nonuniformities in wall thickness can be reduced. The method of the invention is utilized to produce large uniform spherical shells, in the millimeter to centimeter diameter size range, from a variety of materials and of high quality, including sphericity, concentricity and surface smoothness, for use as laser fusion or other inertial confinement fusion targets as well as other applications.

Effects of drop freezing on microphysics of an ascending cloud parcel under biomass burning conditions

NASA Astrophysics Data System (ADS)

Diehl, K.; Simmel, M.; Wurzler, S.

There is some evidence that the initiation of warm rain is suppressed in clouds over regions with vegetation fires. Thus, the ice phase becomes important as another possibility to initiate precipitation. Numerical simulations were performed to investigate heterogeneous drop freezing for a biomass-burning situation. An air parcel model with a sectional two-dimensional description of the cloud microphysics was employed with parameterizations for immersion and contact freezing which consider the different ice nucleating efficiencies of various ice nuclei. Three scenarios were simulated resulting to mixed-phase or completely glaciated clouds. According to the high insoluble fraction of the biomass-burning particles drop freezing via immersion and contact modes was very efficient. The preferential freezing of large drops followed by riming (i.e. the deposition of liquid drops on ice particles) and the evaporation of the liquid drops (Bergeron-Findeisen process) caused a further decrease of the liquid drops' effective radius in higher altitudes. In turn ice particle sizes increased so that they could serve as germs for graupel or hailstone formation. The effects of ice initiation on the vertical cloud dynamics were fairly significant leading to a development of the cloud to much higher altitudes than in a warm cloud without ice formation.

Priority Queue Based Reactive Buffer Management Policy for Delay Tolerant Network under City Based Environments.

PubMed

Ayub, Qaisar; Ngadi, Asri; Rashid, Sulma; Habib, Hafiz Adnan

2018-01-01

Delay Tolerant Network (DTN) multi-copy routing protocols are privileged to create and transmit multiple copies of each message that causes congestion and some messages are dropped. This process is known as reactive drop because messages were dropped re-actively to overcome buffer overflows. The existing reactive buffer management policies apply a single metric to drop source, relay and destine messages. Hereby, selection to drop a message is dubious because each message as source, relay or destine may have consumed dissimilar magnitude of network resources. Similarly, DTN has included time to live (ttl) parameter which defines lifetime of message. Hence, when ttl expires then message is automatically destroyed from relay nodes. However, time-to-live (ttl) is not applicable on messages reached at their destinations. Moreover, nodes keep replicating messages till ttl expires even-though large number of messages has already been dispersed. In this paper, we have proposed Priority Queue Based Reactive Buffer Management Policy (PQB-R) for DTN under City Based Environments. The PQB-R classifies buffered messages into source, relay and destine queues. Moreover, separate drop metric has been applied on individual queue. The experiment results prove that proposed PQB-R has reduced number of messages transmissions, message drop and increases delivery ratio.

Priority Queue Based Reactive Buffer Management Policy for Delay Tolerant Network under City Based Environments

PubMed Central

Ngadi, Asri; Rashid, Sulma; Habib, Hafiz Adnan

2018-01-01

Delay Tolerant Network (DTN) multi-copy routing protocols are privileged to create and transmit multiple copies of each message that causes congestion and some messages are dropped. This process is known as reactive drop because messages were dropped re-actively to overcome buffer overflows. The existing reactive buffer management policies apply a single metric to drop source, relay and destine messages. Hereby, selection to drop a message is dubious because each message as source, relay or destine may have consumed dissimilar magnitude of network resources. Similarly, DTN has included time to live (ttl) parameter which defines lifetime of message. Hence, when ttl expires then message is automatically destroyed from relay nodes. However, time-to-live (ttl) is not applicable on messages reached at their destinations. Moreover, nodes keep replicating messages till ttl expires even-though large number of messages has already been dispersed. In this paper, we have proposed Priority Queue Based Reactive Buffer Management Policy (PQB-R) for DTN under City Based Environments. The PQB-R classifies buffered messages into source, relay and destine queues. Moreover, separate drop metric has been applied on individual queue. The experiment results prove that proposed PQB-R has reduced number of messages transmissions, message drop and increases delivery ratio. PMID:29438438

NASA Glenn Icing Research Tunnel: 2014 Cloud Calibration Procedure and Results

NASA Technical Reports Server (NTRS)

Van Zante, Judith F.; Ide, Robert F.; Steen, Laura E.; Acosta, Waldo J.

2014-01-01

The results of the December 2013 to February 2014 Icing Research Tunnel full icing cloud calibration are presented. The calibration steps included establishing a uniform cloud and conducting drop size and liquid water content calibrations. The goal of the calibration was to develop a uniform cloud, and to generate a transfer function from the inputs of air speed, spray bar atomizing air pressure and water pressure to the outputs of median volumetric drop diameter and liquid water content. This was done for both 14 CFR Parts 25 and 29, Appendix C ('typical' icing) and soon-to-be released Appendix O (supercooled large drop) conditions.

Solidification of Undercooled Melts of Al-Based Alloys on Earth and in Space

NASA Astrophysics Data System (ADS)

Herlach, Dieter M.; Burggraf, Stefan; Galenko, Peter; Gandin, Charles-André; Garcia-Escorial, Asuncion; Henein, Hani; Karrasch, Christian; Mullis, Andrew; Rettenmayr, Markus; Valloton, Jonas

2017-08-01

Containerless processing of droplets and drops by atomization and electromagnetic levitation are applied to undercool metallic melts and alloys prior to solidification. Heterogeneous nucleation on crucible walls is completely avoided giving access to large undercoolings. Experiments are performed both under terrestrial (1 g) conditions and in reduced gravity ( µg) as well. Microgravity conditions are realized by the free fall of small droplets during atomization of a spray of droplets, individual drops in a drop tube and by electromagnetic levitation of drops during parabolic flights, sounding rocket missions, and using the electro-magnetic levitator multi-user facility on board the International Space Station. The comparison of both sets of experiments in 1 g and µg leads to an estimation of the influence of forced convection on dendrite growth kinetics and microstructure evolution.

Performance evaluation of Space Shuttle SRB parachutes from air drop and scaled model wind tunnel tests. [Solid Rocket Booster recovery system

NASA Technical Reports Server (NTRS)

Moog, R. D.; Bacchus, D. L.; Utreja, L. R.

1979-01-01

The aerodynamic performance characteristics have been determined for the Space Shuttle Solid Rocket Booster drogue, main, and pilot parachutes. The performance evaluation on the 20-degree conical ribbon parachutes is based primarily on air drop tests of full scale prototype parachutes. In addition, parametric wind tunnel tests were performed and used in parachute configuration development and preliminary performance assessments. The wind tunnel test data are compared to the drop test results and both sets of data are used to determine the predicted performance of the Solid Rocket Booster flight parachutes. Data from other drop tests of large ribbon parachutes are also compared with the Solid Rocket Booster parachute performance characteristics. Parameters assessed include full open terminal drag coefficients, reefed drag area, opening characteristics, clustering effects, and forebody interference.

Analysis of Drop Shapes during Electrowetting on a Dielectric

NASA Astrophysics Data System (ADS)

Daneshbod, Yousef

2005-03-01

Electrowetting refers to the electrostatic control of the interfacial energy of a liquid on a solid, primarily used for the transport of micro-liter volumes of drops on surfaces with embedded electrode arrays. In the present work, the drop is modeled as a two-dimensional lens-like conductor immersed in an infinite dielectric medium slightly above a planar conductor. A matched asymptotic expansion is used to approximate the electrostatic field surrounding the drop. The outer problem models the drop as a conducting circular segment resting on the conducting plane, each maintained at a separate constant potential. The inner problem corrects the region near the edge of the drop by modeling it as an infinite planar conducting wedge lying slightly above the conducting plane. By matching the inner and outer solutions, the charge density along the entire surface of the drop can be approximated, enabling the calculation of the total capacitance of the system. An energy minimization method similar to that of Shapiro et al. [J. Appl. Phys., 93, 5794 (2003)] is applied to the total energy consisting of the liquid/gas, liquid/solid and solid/gas surface energies, together with the electrostatic contribution, subject to the constraint that the drop volume remains constant. A modified form of the Young-Lippmann equation is thus derived that includes the contribution from the extra capacitance of the drop obtained via matched asymptotics.

Queues with Dropping Functions and General Arrival Processes

PubMed Central

Chydzinski, Andrzej; Mrozowski, Pawel

2016-01-01

In a queueing system with the dropping function the arriving customer can be denied service (dropped) with the probability that is a function of the queue length at the time of arrival of this customer. The potential applicability of such mechanism is very wide due to the fact that by choosing the shape of this function one can easily manipulate several performance characteristics of the queueing system. In this paper we carry out analysis of the queueing system with the dropping function and a very general model of arrival process—the model which includes batch arrivals and the interarrival time autocorrelation, and allows for fitting the actual shape of the interarrival time distribution and its moments. For such a system we obtain formulas for the distribution of the queue length and the overall customer loss ratio. The analytical results are accompanied with numerical examples computed for several dropping functions. PMID:26943171

Liquid drops attract or repel by the inverted Cheerios effect.

PubMed

Karpitschka, Stefan; Pandey, Anupam; Lubbers, Luuk A; Weijs, Joost H; Botto, Lorenzo; Das, Siddhartha; Andreotti, Bruno; Snoeijer, Jacco H

2016-07-05

Solid particles floating at a liquid interface exhibit a long-ranged attraction mediated by surface tension. In the absence of bulk elasticity, this is the dominant lateral interaction of mechanical origin. Here, we show that an analogous long-range interaction occurs between adjacent droplets on solid substrates, which crucially relies on a combination of capillarity and bulk elasticity. We experimentally observe the interaction between droplets on soft gels and provide a theoretical framework that quantitatively predicts the interaction force between the droplets. Remarkably, we find that, although on thick substrates the interaction is purely attractive and leads to drop-drop coalescence, for relatively thin substrates a short-range repulsion occurs, which prevents the two drops from coming into direct contact. This versatile interaction is the liquid-on-solid analog of the "Cheerios effect." The effect will strongly influence the condensation and coarsening of drops on soft polymer films, and has potential implications for colloidal assembly and mechanobiology.

Development of an automated large-scale protein-crystallization and monitoring system for high-throughput protein-structure analyses.

PubMed

Hiraki, Masahiko; Kato, Ryuichi; Nagai, Minoru; Satoh, Tadashi; Hirano, Satoshi; Ihara, Kentaro; Kudo, Norio; Nagae, Masamichi; Kobayashi, Masanori; Inoue, Michio; Uejima, Tamami; Oda, Shunichiro; Chavas, Leonard M G; Akutsu, Masato; Yamada, Yusuke; Kawasaki, Masato; Matsugaki, Naohiro; Igarashi, Noriyuki; Suzuki, Mamoru; Wakatsuki, Soichi

2006-09-01

Protein crystallization remains one of the bottlenecks in crystallographic analysis of macromolecules. An automated large-scale protein-crystallization system named PXS has been developed consisting of the following subsystems, which proceed in parallel under unified control software: dispensing precipitants and protein solutions, sealing crystallization plates, carrying robot, incubators, observation system and image-storage server. A sitting-drop crystallization plate specialized for PXS has also been designed and developed. PXS can set up 7680 drops for vapour diffusion per hour, which includes time for replenishing supplies such as disposable tips and crystallization plates. Images of the crystallization drops are automatically recorded according to a preprogrammed schedule and can be viewed by users remotely using web-based browser software. A number of protein crystals were successfully produced and several protein structures could be determined directly from crystals grown by PXS. In other cases, X-ray quality crystals were obtained by further optimization by manual screening based on the conditions found by PXS.

Characteristics of a Sensitive Well Showing Pre-Earthquake Water-Level Changes

NASA Astrophysics Data System (ADS)

King, Chi-Yu

2018-04-01

Water-level data recorded at a sensitive well next to a fault in central Japan between 1989 and 1998 showed many coseismic water-level drops and a large (60 cm) and long (6-month) pre-earthquake drop before a rare local earthquake of magnitude 5.8 on 17 March 1997, as well as 5 smaller pre-earthquake drops during a 7-year period prior to this earthquake. The pre-earthquake changes were previously attributed to leakage through the fault-gouge zone caused by small but broad-scaled crustal-stress increments. These increments now seem to be induced by some large slow-slip events. The coseismic changes are attributed to seismic shaking-induced fissures in the adjacent aquitards, in addition to leakage through the fault. The well's high-sensitivity is attributed to its tapping a highly permeable aquifer, which is connected to the fractured side of the fault, and its near-critical condition for leakage, especially during the 7 years before the magnitude 5.8 earthquake.

Experimental evidence of a double layer in a large volume helicon reactor.

PubMed

Sutherland, O; Charles, C; Plihon, N; Boswell, R W

2005-11-11

The self-consistently generated current-free electric double layer (DL) is shown to scale up with the source tube diameter and appears not to be affected by rf driving frequency and changes in reactor geometry. This Letter presents the first simultaneous measurements of local plasma potential and beam energy as a function of axial position. The DL is shown to be no more than 5 mm thick (20 D lengths) and positioned just downstream of the maximum in the magnetic field gradient. Furthermore, its position relative to the magnetic field is observed to be invariant as the magnetic field is translated axially. Measurements of the potential drop across the DL are presented for pressures down to 0.09 mTorr and the DL strength (phiDL/T(e)) is determined to be between 5 and 7.

Electrical potential difference during laser welding

NASA Astrophysics Data System (ADS)

Zohm, H.; Ambrosy, G.; Lackner, K.

2015-01-01

We present a new model for the generation of thermoelectric currents during laser welding, taking into account sheath effects at both contact points as well as the potential drop within the quasi-neutral plasma generated by the laser. We show that the model is in good agreement with experimentally measured electric potential difference between the hot and the cold parts of the welded workpiece. In particular, all three elements of the model are needed to correctly reproduce the sign of the measured voltage difference. The mechanism proposed relies on the temperature dependence of the electron flux from the plasma to the workpiece and hence does not need thermoemission from the workpiece surface to explain the experimentally observed sign and magnitude of the potential drop.

Two-dimensional quasineutral description of particles and fields above discrete auroral arcs

NASA Technical Reports Server (NTRS)

Newman, A. L.; Chiu, Y. T.; Cornwall, J. M.

1985-01-01

Stationary hot and cool particle distributions in the auroral magnetosphere are modelled using adiabatic assumptions of particle motion in the presence of broad-scale electrostatic potential structure. The study has identified geometrical restrictions on the type of broadscale potential structure which can be supported by a multispecies plasma having specified sources and energies. Without energization of cool thermal ionospheric electrons, a substantial parallel potential drop cannot be supported down to altitudes of 2000 km or less. Observed upward-directed field-aligned currents must be closed by return currents along field lines which support little net potential drop. In such regions the plasma density appears significantly enhanced. Model details agree well with recent broad-scale implications of satellite observations.

An Analysis of the Role of Social Safety Net Scholarships in Reducing School Drop-Out during the Indonesian Economic Crisis. Innocenti Working Papers.

ERIC Educational Resources Information Center

Cameron, Lisa A.

This paper uses regression and matching techniques to evaluate Indonesia's Social Safety Net Scholarships Programme. The scholarships program was developed to try to prevent large numbers of children from dropping out of school as a result of the Asian financial crisis. The expectation was that many families would find it difficult to keep their…

The scaling of relativistic double-year widths - Poisson-Vlasov solutions and particle-in-cell simulations

NASA Technical Reports Server (NTRS)

Sulkanen, Martin E.; Borovsky, Joseph E.

1992-01-01

The study of relativistic plasma double layers is described through the solution of the one-dimensional, unmagnetized, steady-state Poisson-Vlasov equations and by means of one-dimensional, unmagnetized, particle-in-cell simulations. The thickness vs potential-drop scaling law is extended to relativistic potential drops and relativistic plasma temperatures. The transition in the scaling law for 'strong' double layers suggested by analytical two-beam models by Carlqvist (1982) is confirmed, and causality problems of standard double-layer simulation techniques applied to relativistic plasma systems are discussed.

Low Velocity Airdrop Tests of an X-38 Backup Parachute Design

NASA Technical Reports Server (NTRS)

Stein, Jenny M.; Machin, Ricardo A.; Wolf, Dean F.; Hillebrandt, F. David

2007-01-01

The NASA Johnson Space Center's X-38 program designed a new backup parachute system to recover the 25,000 lb X-38 prototype for the Crew Return Vehicle spacecraft. Due to weight and cost constraints, the main backup parachute design incorporated rapid and low cost fabrication techniques using off-the-shelf materials. Near the vent, the canopy was constructed of continuous ribbons, to provide more damage tolerance. The remainder of the canopy was a constructed with a continuous ringslot design. After cancellation of the X-38 program, the parachute design was resized, built, and drop tested for Natick Soldiers Center's Low Velocity Air Drop (LVAD) program to deliver cargo loads up to 22,000 lbs from altitudes as low as 500 feet above the ground. Drop tests results showed that the 500-foot LVAD parachute deployment conditions cause severe skirt inversion and inflation problems for large parachutes. The bag strip occurred at a high angle of attack, causing skirt inversion before the parachute could inflate. The addition of a short reefing line prevented the skirt inversion. Using a lower porosity in the vent area, than is normally used in large parachutes, improved inflation. The drop testing demonstrated that the parachute design could be refined to meet the requirements for the 500-foot LVAD mission.

From drop impact physics to spray cooling models: a critical review

NASA Astrophysics Data System (ADS)

Breitenbach, Jan; Roisman, Ilia V.; Tropea, Cameron

2018-03-01

Spray-wall interaction is an important process encountered in a large number of existing and emerging technologies and is the underlying phenomenon associated with spray cooling. Spray cooling is a very efficient technology, surpassing all other conventional cooling methods, especially those not involving phase change and not exploiting the latent heat of vaporization. However, the effectiveness of spray cooling is dependent on a large number of parameters, including spray characteristics like drop size, velocity and number density, the surface morphology, but also on the temperature range and thermal properties of the materials involved. Indeed, the temperature of the substrate can have significant influence on the hydrodynamics of drop and spray impact, an aspect which is seldom considered in model formulation. This process is extremely complex, thus most design rules to date are highly empirical in nature. On the other hand, significant theoretical progress has been made in recent years about the interaction of single drops with heated walls and improvements to the fundamentals of spray cooling can now be anticipated. The present review has the objective of summarizing some of these recent advances and to establish a framework for future development of more reliable and universal physics-based correlations to describe quantities involved in spray cooling.

Drop Breakup in Fixed Bed Flows as Model Stochastic Flow Fields

NASA Technical Reports Server (NTRS)

Shaqfeh, Eric S. G.; Mosler, Alisa B.; Patel, Prateek

1999-01-01

We examine drop breakup in a class of stochastic flow fields as a model for the flow through fixed fiber beds and to elucidate the general mechanisms whereby drops breakup in disordered, Lagrangian unsteady flows. Our study consists of two parallel streams of investigation. First, large scale numerical simulations of drop breakup in a class of anisotropic Gaussian fields will be presented. These fields are generated spectrally and have been shown in a previous publication to be exact representations of the flow in a dilute disordered bed of fibers if close interactions between the fibers and the drops are dynamically unimportant. In these simulations the drop shape is represented by second and third order small deformation theories which have been shown to be excellent for the prediction of drop breakup in steady strong flows. We show via these simulations that the mechanisms of drop breakup in these flows are quite different than in steady flows. The predominant mechanism of breakup appears to be very short lived twist breakups. Moreover, the occurrence of breakup events is poorly predicted by either the strength of the local flow in which the drop finds itself at breakup, or the degree of deformation that the drop achieves prior to breakup. It is suggested that a correlation function of both is necessary to be predictive of breakup events. In the second part of our research experiments are presented where the drop deformation and breakup in PDMS/polyisobutylene emulsions is considered. We consider very dilute emulsions such that coalescence is unimportant. The flows considered are simple shear and the flow through fixed fiber beds. Turbidity, small angle light scattering, dichroism and microscopy are used to interrogate the drop deformation process in both flows. It is demonstrated that breakup at very low capillary numbers occurs in both flows but larger drop deformation occurs in the fixed bed flow. Moreover, it is witnessed that breakup in the bed occurs continuously during flow and apparently with uniform probability through the bed length. The drop deformations witnessed in our experiments are larger than those predicted by the numerical simulations, and future plans to investigate these differences are discussed.

Crystalline desiccation patterns and film break up from evaporating drops on hydrophobic oxide surfaces

NASA Astrophysics Data System (ADS)

McBride, Samantha; Dash, Susmita; Khan, Sami; Varanasi, Kripa

2017-11-01

Solute-laden sessile drops evaporating on a substrate will often force crystallization of the solute at the triple phase contact line between the drop, substrate, and air in an effect similar to the ``coffee-ring'' deposition of particles from a particle-laden drop. We report new observations of ring-shaped desiccation patterns of gypsum crystals on hydrophobic oxide substrates; ceria, erbia, and silica. These surfaces have similar contact angles ( 105 degrees), and evaporation of sessile drops proceeds at the same rate and without contact angle hysteresis on all three substrates. However, despite the apparent similarity, the patterns of crystal deposits exhibit large differences across the substrates. The supersaturation and elapsed time at the onset of crystallization also varied across substrates, despite overall evaporation rates being identical. The differences in patterns can be explained in light of the position and morphology of the crystals just prior to completion of evaporation when the sessile drop has transitioned to a thin film spread over the deposit area. Break-up of this film occurs very differently on the different surfaces, and is simultaneously influenced by existing crystals while also influencing final crystalline patterns. This work was supported by the NSF GRFP.

Shear shedding of drops and the use of superhydrophobic surfaces in microgravity: PFC and ground based results

NASA Astrophysics Data System (ADS)

Milne, Andrew; Amirfazli, Alidad

In free fall, the absence of gravity poses many challenges for fluid handling systems. One such example of this is condensers. On earth, the condensed liquid is removed from the tilted condenser plate by gravity forced shedding. In microgravity, proposed solutions include the use of surfaces with gradients in wettability [1], the use of electrowetting [2], and shearing airflow [3]. In this talk, shear shedding results for a variety of surface (hydrophilic to superhydrophobic (extremely water repelling)) will be presented. Surface science and aerodynamics are used to reveal fundamental parameters controlling incipient motion for drops exposed to shearing airflow. It is found that wetting parameters such as contact angle and surface tension are very influential in determining the minimum required air velocity for drop shedding. Based on experimental results for drops of water and hexadecane (0.5-100 l) on PMMA, Teflon, and a superhydrophobic aluminum surface, an exponential function is proposed that relates the critical air velocity for shedding to the ratio of drop base length to projected area. The results for the water systems can be collapsed to a self similar curve by normalization, which also explains results from other researchers. Since shedding from superhydrophobic surfaces (SHS) is seen to be easier compared to other surfaces, the behaviour of SHS is also probed in this talk. SHS have space-based applications to shedding, self cleaning, anti-icing (spacecraft launch/re-entry), anti-fouling, fluid actuation, and decreased fluid friction. The mechanism for SHS is understood to be the existence of an air layer between large portions of the drop and solid. The first concrete visual evidence of this was gained performing a parabolic flight experiment with the ESA. Results of this experi-ment will be discussed, showing the extreme water repelling potential of SHS in microgravity, and demonstrating how the wetting behaviours seen (partial penetration, transition of wetting states, unpredicted contact angle behaviour) affect models of superhydrophobicity and the use of SHS to both space and Earth based applications. 1) Darhuber, A. A.; Troian, S. M. Annual Review of Fluid Mechanics 2005, 425-455. 2) Berthier, J.; Dubois, P.; Clementz, P.; Claustre, P.; Peponnet, C.; Fouillet, Y. Sensors and Actuators A: Physical 2007, 134, 471-479. 3) Milne, A. J. B.; Amirfazli, A. Langmuir 2009, 25, 14155-14164.

Stress Drop and Depth Controls on Ground Motion From Induced Earthquakes

NASA Astrophysics Data System (ADS)

Baltay, A.; Rubinstein, J. L.; Terra, F. M.; Hanks, T. C.; Herrmann, R. B.

2015-12-01

Induced earthquakes in the central United States pose a risk to local populations, but there is not yet agreement on how to portray their hazard. A large source of uncertainty in the hazard arises from ground motion prediction, which depends on the magnitude and distance of the causative earthquake. However, ground motion models for induced earthquakes may be very different than models previously developed for either the eastern or western United States. A key question is whether ground motions from induced earthquakes are similar to those from natural earthquakes, yet there is little history of natural events in the same region with which to compare the induced ground motions. To address these problems, we explore how earthquake source properties, such as stress drop or depth, affect the recorded ground motion of induced earthquakes. Typically, due to stress drop increasing with depth, ground motion prediction equations model shallower events to have smaller ground motions, when considering the same absolute hypocentral distance to the station. Induced earthquakes tend to occur at shallower depths, with respect to natural eastern US earthquakes, and may also exhibit lower stress drops, which begs the question of how these two parameters interact to control ground motion. Can the ground motions of induced earthquakes simply be understood by scaling our known source-ground motion relations to account for the shallow depth or potentially smaller stress drops of these induced earthquakes, or is there an inherently different mechanism in play for these induced earthquakes? We study peak ground-motion velocity (PGV) and acceleration (PGA) from induced earthquakes in Oklahoma and Kansas, recorded by USGS networks at source-station distances of less than 20 km, in order to model the source effects. We compare these records to those in both the NGA-West2 database (primarily from California) as well as NGA-East, which covers the central and eastern United States and Canada. Preliminary analysis indicates that the induced ground motions appear similar to those from the NGA-West2 database. However, upon consideration of their shallower depths, ground motion behavior from induced events seems to fall in between the West data and that of NGA-East, so we explore the control of stress drop and depth on ground motion in more detail.

"Open mesh" or "strictly selected population" recruitment? The experience of the randomized controlled MeMeMe trial.

PubMed

Cortellini, Mauro; Berrino, Franco; Pasanisi, Patrizia

2017-01-01

Among randomized controlled trials (RCTs), trials for primary prevention require large samples and long follow-up to obtain a high-quality outcome; therefore the recruitment process and the drop-out rates largely dictate the adequacy of the results. We are conducting a Phase III trial on persons with metabolic syndrome to test the hypothesis that comprehensive lifestyle changes and/or metformin treatment prevents age-related chronic diseases (the MeMeMe trial, EudraCT number: 2012-005427-32, also registered on ClinicalTrials.gov [NCT02960711]). Here, we briefly analyze and discuss the reasons which may lead to participants dropping out from trials. In our experience, participants may back out of a trial for different reasons. Drug-induced side effects are certainly the most compelling reason. But what are the other reasons, relating to the participants' perception of the progress of the trial which led them to withdraw after randomization? What about the time-dependent drop-out rate in primary prevention trials? The primary outcome of this analysis is the point of drop-out from trial, defined as the time from the randomization date to the withdrawal date. Survival functions were non-parametrically estimated using the product-limit estimator. The curves were statistically compared using the log-rank test ( P =0.64, not significant). Researchers involved in primary prevention RCTs seem to have to deal with the paradox of the proverbial "short blanket syndrome". Recruiting only highly motivated candidates might be useful for the smooth progress of the trial but it may lead to a very low enrollment rate. On the other hand, what about enrolling all the eligible subjects without considering their motivation? This might boost the enrollment rate, but it can lead to biased results on account of large proportions of drop-outs. Our experience suggests that participants do not change their mind depending on the allocation group (intervention or control). There is no single answer to sort out the short blanket syndrome.

Preliminary investigation into the analytical potential of a multiwavelength fiber drop analyzer with special reference to applications in medical diagnostics

NASA Astrophysics Data System (ADS)

McMillan, Norman D.; O'Mongain, Eon; Walsh, James E.; Breen, Liam; McMillan, Duncan G.; Power, Michael J.; O'Dea, John P.; Kinsella, Seamus M.; Kelly, Mairead P.; Hammil, Conor; Orr, Dermot

1994-12-01

A preliminary investigation into the use of multiwavelength fiber drop analyzer (FDA) for the measurement of viscosity, spectral absorbance and refractive index is made with a view to obtaining conservative estimates of the instrumental capability of the FDA for these measurands. Some important new insights into drop vibrations are made from studies on the fiber drop traces (FDTs) of mechanically excited damped vibrations in drops with a set volume. A brief description of the feasibility measurements on the first application of the FDA in the diagnosis of disease in synovial fluid is given. Strong experimental evidence is reported for the existence of the surface-guided wave peak of the fiber drop trace and some new insights into the nature of the FDT are suggested based on a comparative study of the FDTs from a multiple-wavelength and a single-wavelength FDA. The earlier reported drop period dependence on applied electric field is critically reexamined, a new interpretation of this effect, is suggested, and an experimental study of clarification is given. Finally, a brief review of the projected capabilities of the FDA based on the work reported here is provided.

Sensitivity of C-Band Polarimetric Radar-Based Drop Size Distribution Measurements to Maximum Diameter Assumptions

NASA Technical Reports Server (NTRS)

Carey, Lawrence D.; Petersen, Walter A.

2011-01-01

The estimation of rain drop size distribution (DSD) parameters from polarimetric radar observations is accomplished by first establishing a relationship between differential reflectivity (Z(sub dr)) and the central tendency of the rain DSD such as the median volume diameter (D0). Since Z(sub dr) does not provide a direct measurement of DSD central tendency, the relationship is typically derived empirically from rain drop and radar scattering models (e.g., D0 = F[Z (sub dr)] ). Past studies have explored the general sensitivity of these models to temperature, radar wavelength, the drop shape vs. size relation, and DSD variability. Much progress has been made in recent years in measuring the drop shape and DSD variability using surface-based disdrometers, such as the 2D Video disdrometer (2DVD), and documenting their impact on polarimetric radar techniques. In addition to measuring drop shape, another advantage of the 2DVD over earlier impact type disdrometers is its ability to resolve drop diameters in excess of 5 mm. Despite this improvement, the sampling limitations of a disdrometer, including the 2DVD, make it very difficult to adequately measure the maximum drop diameter (D(sub max)) present in a typical radar resolution volume. As a result, D(sub max) must still be assumed in the drop and radar models from which D0 = F[Z(sub dr)] is derived. Since scattering resonance at C-band wavelengths begins to occur in drop diameters larger than about 5 mm, modeled C-band radar parameters, particularly Z(sub dr), can be sensitive to D(sub max) assumptions. In past C-band radar studies, a variety of D(sub max) assumptions have been made, including the actual disdrometer estimate of D(sub max) during a typical sampling period (e.g., 1-3 minutes), D(sub max) = C (where C is constant at values from 5 to 8 mm), and D(sub max) = M*D0 (where the constant multiple, M, is fixed at values ranging from 2.5 to 3.5). The overall objective of this NASA Global Precipitation Measurement Mission (GPM/PMM Science Team)-funded study is to document the sensitivity of DSD measurements, including estimates of D0, from C-band Z(sub dr) and reflectivity to this range of D(sub max) assumptions. For this study, GPM Ground Validation 2DVD's were operated under the scanning domain of the UAHuntsville ARMOR C-band dual-polarimetric radar. Approximately 7500 minutes of DSD data were collected and processed to create gamma size distribution parameters using a truncated method of moments approach. After creating the gamma parameter datasets the DSD's were then used as input to a T-matrix model for computation of polarimetric radar moments at C-band. All necessary model parameterizations, such as temperature, drop shape, and drop fall mode, were fixed at typically accepted values while the D(sub max) assumption was allowed to vary in sensitivity tests. By hypothesizing a DSD model with D(sub max) (fit) from which the empirical fit to D0 = F[Z(sub dr)] was derived via non-linear least squares regression and a separate reference DSD model with D(sub max) (truth), bias and standard error in D0 retrievals were estimated in the presence of Z(sub dr) measurement error and hypothesized mismatch in D(sub max) assumptions. Although the normalized standard error for D0 = F[Z(sub dr)r] can increase slightly (as much as from 11% to 16% for all 7500 DSDs) when the D(sub max) (fit) does not match D(sub max) (truth), the primary impact of uncertainty in D(sub max) is a potential increase in normalized bias error in D0 (from 0% to as much as 10% over all 7500 DSDs, depending on the extent of the mismatch between D(sub max) (fit) and D(sub max) (truth)). For DSDs characterized by large Z(sub dr) (Z(sub dr) > 1.5 to 2.0 dB), the normalized bias error for D0 estimation at C-band is sometimes unacceptably large (> 10%), again depending on the extent of the hypothesized D(sub max) mismatch. Modeled errors in D0 retrievals from Z(sub dr) at C-band are demonstrated in detail and comparedo similar modeled retrieval errors at S-band and X-band where the sensitivity to D(sub max) is expected to be less. The impact of D(sub max) assumptions to the retrieval of other DSD parameters such as Nw, the liquid water content normalized intercept parameter, are also explored. Likely implications for DSD retrievals using C-band polarimetric radar for GPM are assessed by considering current community knowledge regarding D(sub max) and quantifying the statistical distribution of Z(sub dr) from ARMOR over a large variety of meteorological conditions. Based on these results and the prevalence of C-band polarimetric radars worldwide, a call for more emphasis on constraining our observational estimate of D(sub max) within a typical radar resolution volume is made

Effects of heat-treatment on plasma rich in growth factors-derived autologous eye drop.

PubMed

Anitua, E; Muruzabal, F; De la Fuente, M; Merayo-Lloves, J; Orive, G

2014-02-01

We have developed and characterized a new type of plasma rich in growth factors (PRGF) derived eye-drop therapy for patients suffering from autoimmune diseases. To determine the concentration of several growth factors, proteins, immunoglobulins and complement activity of the heat-inactivated eye-drop and to study its biological effects on cell proliferation and migration of different ocular surface cells, blood from healthy donors was collected, centrifuged and PRGF was prepared avoiding the buffy coat. The half volume of the obtained plasma supernatant from each donor was heat-inactivated at 56 °C for 1 h (heat-inactivated PRGF). The concentration of several proteins involved on corneal wound healing, immunoglubolins G, M and E and functional integrity of the complement system assayed by CH50 test were determined. The proliferative and migratory potential of inactivated and non-inactivated PRGF eye drops were assayed on corneal epithelial cells (HCE), keratocytes (HK) and conjunctival fibroblasts (HConF). Heat-inactivated PRGF preserves the content of most of the proteins and morphogens involved in its wound healing effects while reduces drastically the content of IgE and complement activity. Heat-inactivated PRGF eye drops increased proliferation and migration potential of ocular surface cells with regard to PRGF showing significant differences on proliferation and migration rate of HCE and HConF respectively. In summary, heat-inactivation of PRGF eye drops completely reduced complement activity and deceased significantly the presence of IgE, maintaining the biological activity of PRGF on ocular surface cells. Copyright © 2013 Elsevier Ltd. All rights reserved.

Educational Exclusion: Drop Out, Push Out, and School-to-Prison Pipeline among LGBTQ Youth

ERIC Educational Resources Information Center

Gay, Lesbian and Straight Education Network (GLSEN), 2016

2016-01-01

"Educational Exclusion: Drop Out, Push Out, and the School-to-Prison Pipeline among LGBTQ Youth" provides an in-depth look at the conditions that effectively push LGBTQ youth out of school and potentially into the criminal justice system. The report provides specific, real world guidance to address the hostile school climates and…

Experimental verification of hopping mechanism using permanent magnets for an asteroid rover at drop tower

NASA Astrophysics Data System (ADS)

Kurisu, Masamitsu; Yano, Hajime; Yoshimitsu, Tetsuo; Kubota, Takashi; Adachi, Tadashi; Kuroda, Yoji

Verification of the hopping mechanism using permanent magnets by microgravity experiments at ZARM drop tower will be presented in this report. The mechanism, which is called HMPM (Hopping Mechanism with Permanent Magnets) was developed for a small asteroid exploration rover to replace with conventional locomotion mechanism such as wheels and crawlers. The main part of HMPM consists of three permanent magnets which are two stationary magnets and one movable magnet aligned between them. HMPM itself hops by utilizing the impact force generated when the movable magnet sticks to one of the stationary magnets. The features of HMPM are that the large impact force can be generated in spite of low-power consumption, and that it can be easily miniaturized and modularized. On the other hand, the weak point of HMPM is that the performance of the mechanism cannot be controlled directly, since the performance is decided by its design. Therefore, it is significant to evaluate the performance of HMPM before it is mounted on a flight model of rover. On the microgravity experiments at the drop tower, an imitation rover with 0.8kg weight is tested to hop with the operation of a prototype HMPM mounted on the rover. The prototype module weighs only 0.03kg with dimension 0.033 m in width, 0.046 m in height, and 0.012 m in depth, except the drive circuit and power source. Experimental results show the availability of HMPM. Also, the hopping performance of HMPM which is evaluated from the motion of rover recorded by cameras equipped inside the dropping capsule is compared with the estimated performance derived from the theoretical model. From the investigation, validity of the evaluation method based on the theoretical model is discussed. In order that the potential ability of HMPM is fully derived, optimal design of HMPM will require the evaluation method. The experiments at ZARM drop tower were accomplished based on the agreement on the Hayabusa-2 project by DLR-JAXA. And we received technical and operation supports from ZARM. We express our gratitude to ZARM, DLR and JAXA.

Roughness-Dominated Hydraulic Fracture Propagation

NASA Astrophysics Data System (ADS)

Garagash, D.

2015-12-01

Current understanding suggests that the energy to propagate a hydraulic fracture is defined by the viscous fluid pressure drop along the fracture channel, while the energy dissipation in the immediate vicinity of the fracture front (i.e. fracture toughness) is negligible. This status quo relies on the assumption of Poiseuille flow in the fracture, which transmissivity varies as cube of the aperture. We re-evaluate this assumption in the vicinity of the fracture tip, where the aperture roughness and/or branching of the fracture path may lead to very significant deviations from the cubic law. Existing relationships suggest rough fracture transmissivity power laws ~ wr with 4.5 ≤ r ≤ 6, when aperture w is smaller than the roughness. Solving for the tip region of a steadily propagating hydraulic fracture with the "rough fracture" transmissivity, we are able to show (a) larger energy dissipation than predicted by the Poiseuille flow model; (b) localization of the fluid pressure drop into the low-transmissivity, rough tip region; and (c) emergence of potentially preeminent "toughness-dominated" fracture propagation regime where most of the energy is dissipated at the tip and can be described in the context of classical fracture mechanics by invoking the effective fracture toughness dependent upon the details of the pressure drop in the rough tip. We establish that the ratio of the roughness scale wc to the viscous aperture scale wμ = μVE / σ02, controls the pressure drop localization. (Here V - propagation speed, μ - fluid viscosity, E - rock modulus, and σ0 - in-situ stress). For a range of industrial fracturing fluids (from slick-water to linear gels) and treatment conditions, wc/wμ is large, suggesting a fully-localized pressure drop and energy dissipation. The latter is adequately described by the effective toughness - a function of the propagation velocity, confining stress and material parameters, which estimated values are much larger than the "dry" rock fracture toughness measured in the lab. Using the effective, velocity-dependent fracture toughness to predict the evolution of a penny-shape fracture, we are able to show how/when the classical viscosity-dominated and toughness-dominated solutions based upon the Poiseuille law and the "dry", laboratory fracture toughness values, respectively, may become inadequate.

Laboratory constraints on models of earthquake recurrence

NASA Astrophysics Data System (ADS)

Beeler, N. M.; Tullis, Terry; Junger, Jenni; Kilgore, Brian; Goldsby, David

2014-12-01

In this study, rock friction "stick-slip" experiments are used to develop constraints on models of earthquake recurrence. Constant rate loading of bare rock surfaces in high-quality experiments produces stick-slip recurrence that is periodic at least to second order. When the loading rate is varied, recurrence is approximately inversely proportional to loading rate. These laboratory events initiate due to a slip-rate-dependent process that also determines the size of the stress drop and, as a consequence, stress drop varies weakly but systematically with loading rate. This is especially evident in experiments where the loading rate is changed by orders of magnitude, as is thought to be the loading condition of naturally occurring, small repeating earthquakes driven by afterslip, or low-frequency earthquakes loaded by episodic slip. The experimentally observed stress drops are well described by a logarithmic dependence on recurrence interval that can be cast as a nonlinear slip predictable model. The fault's rate dependence of strength is the key physical parameter. Additionally, even at constant loading rate the most reproducible laboratory recurrence is not exactly periodic, unlike existing friction recurrence models. We present example laboratory catalogs that document the variance and show that in large catalogs, even at constant loading rate, stress drop and recurrence covary systematically. The origin of this covariance is largely consistent with variability of the dependence of fault strength on slip rate. Laboratory catalogs show aspects of both slip and time predictability, and successive stress drops are strongly correlated indicating a "memory" of prior slip history that extends over at least one recurrence cycle.

Spatially resolved measurements of ion heating during impulsive reconnection in the Madison Symmetric Torus.

PubMed

Gangadhara, S; Craig, D; Ennis, D A; Hartog, D J Den; Fiksel, G; Prager, S C

2007-02-16

The impurity ion temperature evolution has been measured during three types of impulsive reconnection events in the Madison Symmetric Torus reversed field pinch. During an edge reconnection event, the drop in stored magnetic energy is small and ion heating is observed to be limited to the outer half of the plasma. Conversely, during a global reconnection event the drop in stored magnetic energy is large, and significant heating is observed at all radii. For both kinds of events, the drop in magnetic energy is sufficient to explain the increase in ion thermal energy. However, not all types of reconnection lead to ion heating. During a core reconnection event, both the stored magnetic energy and impurity ion temperature remain constant. The results suggest that a drop in magnetic energy is required for ions to be heated during reconnection, and that when this occurs heating is localized near the reconnection layer.

Swing-leg trajectory of running guinea fowl suggests task-level priority of force regulation rather than disturbance rejection.

PubMed

Blum, Yvonne; Vejdani, Hamid R; Birn-Jeffery, Aleksandra V; Hubicki, Christian M; Hurst, Jonathan W; Daley, Monica A

2014-01-01

To achieve robust and stable legged locomotion in uneven terrain, animals must effectively coordinate limb swing and stance phases, which involve distinct yet coupled dynamics. Recent theoretical studies have highlighted the critical influence of swing-leg trajectory on stability, disturbance rejection, leg loading and economy of walking and running. Yet, simulations suggest that not all these factors can be simultaneously optimized. A potential trade-off arises between the optimal swing-leg trajectory for disturbance rejection (to maintain steady gait) versus regulation of leg loading (for injury avoidance and economy). Here we investigate how running guinea fowl manage this potential trade-off by comparing experimental data to predictions of hypothesis-based simulations of running over a terrain drop perturbation. We use a simple model to predict swing-leg trajectory and running dynamics. In simulations, we generate optimized swing-leg trajectories based upon specific hypotheses for task-level control priorities. We optimized swing trajectories to achieve i) constant peak force, ii) constant axial impulse, or iii) perfect disturbance rejection (steady gait) in the stance following a terrain drop. We compare simulation predictions to experimental data on guinea fowl running over a visible step down. Swing and stance dynamics of running guinea fowl closely match simulations optimized to regulate leg loading (priorities i and ii), and do not match the simulations optimized for disturbance rejection (priority iii). The simulations reinforce previous findings that swing-leg trajectory targeting disturbance rejection demands large increases in stance leg force following a terrain drop. Guinea fowl negotiate a downward step using unsteady dynamics with forward acceleration, and recover to steady gait in subsequent steps. Our results suggest that guinea fowl use swing-leg trajectory consistent with priority for load regulation, and not for steadiness of gait. Swing-leg trajectory optimized for load regulation may facilitate economy and injury avoidance in uneven terrain.

Swing-Leg Trajectory of Running Guinea Fowl Suggests Task-Level Priority of Force Regulation Rather than Disturbance Rejection

PubMed Central

Blum, Yvonne; Vejdani, Hamid R.; Birn-Jeffery, Aleksandra V.; Hubicki, Christian M.; Hurst, Jonathan W.; Daley, Monica A.

2014-01-01

To achieve robust and stable legged locomotion in uneven terrain, animals must effectively coordinate limb swing and stance phases, which involve distinct yet coupled dynamics. Recent theoretical studies have highlighted the critical influence of swing-leg trajectory on stability, disturbance rejection, leg loading and economy of walking and running. Yet, simulations suggest that not all these factors can be simultaneously optimized. A potential trade-off arises between the optimal swing-leg trajectory for disturbance rejection (to maintain steady gait) versus regulation of leg loading (for injury avoidance and economy). Here we investigate how running guinea fowl manage this potential trade-off by comparing experimental data to predictions of hypothesis-based simulations of running over a terrain drop perturbation. We use a simple model to predict swing-leg trajectory and running dynamics. In simulations, we generate optimized swing-leg trajectories based upon specific hypotheses for task-level control priorities. We optimized swing trajectories to achieve i) constant peak force, ii) constant axial impulse, or iii) perfect disturbance rejection (steady gait) in the stance following a terrain drop. We compare simulation predictions to experimental data on guinea fowl running over a visible step down. Swing and stance dynamics of running guinea fowl closely match simulations optimized to regulate leg loading (priorities i and ii), and do not match the simulations optimized for disturbance rejection (priority iii). The simulations reinforce previous findings that swing-leg trajectory targeting disturbance rejection demands large increases in stance leg force following a terrain drop. Guinea fowl negotiate a downward step using unsteady dynamics with forward acceleration, and recover to steady gait in subsequent steps. Our results suggest that guinea fowl use swing-leg trajectory consistent with priority for load regulation, and not for steadiness of gait. Swing-leg trajectory optimized for load regulation may facilitate economy and injury avoidance in uneven terrain. PMID:24979750

Stochastic growth of cloud droplets by collisions during settling

NASA Astrophysics Data System (ADS)

Madival, Deepak G.

2018-04-01

In the last stage of droplet growth in clouds which leads to drizzle formation, larger droplets begin to settle under gravity and collide and coalesce with smaller droplets in their path. In this article, we shall deal with the simplified problem of a large drop settling amidst a population of identical smaller droplets. We present an expression for the probability that a given large drop suffers a given number of collisions, for a general statistically homogeneous distribution of droplets. We hope that our approach will serve as a valuable tool in dealing with droplet distribution in real clouds, which has been found to deviate from the idealized Poisson distribution due to mechanisms such as inertial clustering.

O the Electrohydrodynamics of Drop Extraction from a Conductive Liquid Meniscus

NASA Astrophysics Data System (ADS)

Wright, Graham Scott

This thesis is concerned with the use of an electric field in the extraction of liquid drops from a capillary orifice or nozzle. The motivating application is ink jet printing. Current drop-on-demand ink jets use pressure pulses to eject drops. Literature on electrostatic spraying suggests that by using an electric field, drops could be produced with a wider range of sizes and speeds than is possible with pressure ejection. Previous efforts to apply electric spraying to printing or similar selective coating tasks have taken an experimental approach based on steady or periodic spraying phenomena, without attempting cycle -by-cycle drop control. The centerpiece of this thesis is a simulation tool developed to explore such possibilities. A simplified analytic model is developed as a preliminary step, yielding formulas for force and time scales that provide an appropriate basis for nondimensionalization of the governing differential equations; important dimensionless parameters are identified. The complete self-consistent model permits simulation of meniscus behavior under time -varying applied voltage or pressure, with the electric field solution continually updated as the surface changes shape. The model uses a quasi-one-dimensional hydrodynamic formulation and a two-dimensional axisymmetric boundary element solution for the electric field. The simulation is checked against experimental results for meniscus stability, resonant modes, and drop emission under electric field. The simulation faithfully captures important qualitative aspects of meniscus behavior and gives reasonable quantitative agreement within the limitations of the model. Insights gained in simulation point the way to a successful laboratory demonstration of drop extraction using a shaped voltage pulse. Drop size control is pursued in simulation using pressure and voltage pulses both alone and in combination, for both light and viscous liquids. Combining pressure and field pulses is shown to be synergistic; drop volumes over a range of 175 to 1 were obtained, while maintaining good drop velocity. The differing strategies for obtaining large and small drops are described. Drop extraction using only the electric field is more difficult, but promising approaches remain open.

Optical Add-Drop Filters Based on Photonic Crystal Ring Resonators

DTIC Science & Technology

2007-02-19

34 Appl. Phys. Lett. 81,2499-2501 (2002). 17. V. Dinesh Kumar , T. Srinivas, A. Selvarajan, "Investigation of ring resonators in photonic crystal...No.4 / opncs EXPRESS 1824 Kumar et al. [17], where a large single quasi-rectangular ring was introduced as the frequency selective dropping elements...were introduced by Kumar et al. as well, in order to suppress the counter propagating modes which can cause spurious dips in the transmission spectrum

Why Tenth Graders Fail to Finish High School: A Dropout Typology Latent Class Analysis

ERIC Educational Resources Information Center

Bowers, Alex J.; Sprott, Ryan

2012-01-01

A large percentage of the students who drop out of K-12 schools in the United States do so at the end of high school, at some point after grade 10. Yet little is known about the differences between types of students who drop out near the end of high school. The purpose of this study is to examine a typology of high school dropouts from a large…

High School Graduation Rates through Two Decades of District Change: The Influence of Policies, Data Records, and Demographic Shifts. Research Report

ERIC Educational Resources Information Center

Allensworth, Elaine M.; Healey, Kaleen; Gwynne, Julia A.; Crespin, René

2016-01-01

High school graduation rates in the Chicago Public Schools (CPS) have shown remarkable improvements over the past 16 years. Students used to be about as likely to drop out as they were to graduate; now they are three times as likely to graduate as to drop out. Moreover, recent large improvements in the percentage of students on-track to graduate…

Distribution of Cryptococcus neoformans in a natural site.

PubMed Central

Ruiz, A; Fromtling, R A; Bulmer, G S

1981-01-01

Pigeon droppings in a vacant tower were assayed for the number and size of viable cells of Cryptococcus neoformans. The dry, thinly scattered floor debris contained 2.6 x 10(6) viable cells per g--300 times more cells than were cultured from a large, compact pile of pigeon droppings (7.4 x 10(3) cells per g). Aerosols generated from floor debris containing pigeon droppings had an average of 360 viable cells in 31 liters of air; 27 of these cells (7.5%) were 1.1 to 3.3 micrometers in diameter and, therefore, capable of human lung deposition. Environmental factors which may influence the distribution, survival, and proliferation of C. neoformans in nature are discussed. PMID:7012011

Workers on the margin: who drops health coverage when prices rise?

PubMed

Okeke, Edward N; Hirth, Richard A; Grazier, Kyle

2010-01-01

We revisit the question of price elasticity of employer-sponsored insurance (ESI) take-up by directly examining changes in the take-up of ESI at a large firm in response to exogenous changes in employee premium contributions. We find that, on average, a 10% increase in the employee's out-of-pocket premium increases the probability of dropping coverage by approximately 1%. More importantly, we find heterogeneous impacts: married workers are much more price-sensitive than single employees, and lower-paid workers are disproportionately more likely to drop coverage than higher-paid workers. Elasticity estimates for employees below the 25th percentile of salary distribution in our sample are nearly twice the average.

Device For Controlling Crystallization Of Protein

NASA Technical Reports Server (NTRS)

Noever, David A.

1993-01-01

Variable sandwich spacer enables optimization of evaporative driving force that governs crystallization of protein from solution. Mechanically more rigid than hanging-drop and sitting-drop devices. Large oscillations and dislodgment of drop of solution in response to vibrations suppressed by glass plates. Other advantages include: suitable for automated delivery, stable handling, and programmable evaporation of protein solution; controlled configuration enables simple and accurate determination of volume of solution without disrupting crystallization; pH and concentration of precipitant controlled dynamically because pH and concentration coupled to rate of evaporation, controllable via adjustment of gap between plates; and enables variation of ratio between surface area and volume of protein solution. Alternative version, plates oriented vertically instead of horizontally.

Natural product discovery: past, present, and future.

PubMed

Katz, Leonard; Baltz, Richard H

2016-03-01

Microorganisms have provided abundant sources of natural products which have been developed as commercial products for human medicine, animal health, and plant crop protection. In the early years of natural product discovery from microorganisms (The Golden Age), new antibiotics were found with relative ease from low-throughput fermentation and whole cell screening methods. Later, molecular genetic and medicinal chemistry approaches were applied to modify and improve the activities of important chemical scaffolds, and more sophisticated screening methods were directed at target disease states. In the 1990s, the pharmaceutical industry moved to high-throughput screening of synthetic chemical libraries against many potential therapeutic targets, including new targets identified from the human genome sequencing project, largely to the exclusion of natural products, and discovery rates dropped dramatically. Nonetheless, natural products continued to provide key scaffolds for drug development. In the current millennium, it was discovered from genome sequencing that microbes with large genomes have the capacity to produce about ten times as many secondary metabolites as was previously recognized. Indeed, the most gifted actinomycetes have the capacity to produce around 30-50 secondary metabolites. With the precipitous drop in cost for genome sequencing, it is now feasible to sequence thousands of actinomycete genomes to identify the "biosynthetic dark matter" as sources for the discovery of new and novel secondary metabolites. Advances in bioinformatics, mass spectrometry, proteomics, transcriptomics, metabolomics and gene expression are driving the new field of microbial genome mining for applications in natural product discovery and development.

Excitation of high-frequency electromagnetic waves by energetic electrons with a loss cone distribution in a field-aligned potential drop

NASA Technical Reports Server (NTRS)

Fung, Shing F.; Vinas, Adolfo F.

1994-01-01

The electron cyclotron maser instability (CMI) driven by momentum space anisotropy (df/dp (sub perpendicular) greater than 0) has been invoked to explain many aspects, such as the modes of propagation, harmonic emissions, and the source characteristics of the auroral kilometric radiation (AKR). Recent satellite observations of AKR sources indicate that the source regions are often imbedded within the auroral acceleration region characterized by the presence of a field-aligned potential drop. In this paper we investigate the excitation of the fundamental extraordinary mode radiation due to the accelerated electrons. The momentum space distribution of these energetic electrons is modeled by a realistic upward loss cone as modified by the presence of a parallel potential drop below the observation point. On the basis of linear growth rate calculations we present the emission characteristics, such as the frequency spectrum and the emission angular distribution as functions of the plasma parameters. We will discuss the implication of our results on the generation of the AKR from the edges of the auroral density cavities.

Effects of melting layer on Ku-band signal depolarization

NASA Astrophysics Data System (ADS)

Sarkar, Thumree; Das, Saurabh; Maitra, Animesh

2014-09-01

Propagation effects on Ku-band over an earth-space path is carried out at Kolkata, India, a tropical location, by receiving a Ku-band signal with horizontal plane polarization transmitted from the geostationary satellite NSS-6 (at 95°E). The amplitude of co-polar attenuation has been monitored along with the measurements of rain rate, rain drop size distribution and height profile of rain rate. The cross-polar enhancement of the signal is also monitored by receiving the same signal in orthogonal direction with another identical receiver. The experimental observations are used to study the effect of melting layer on both co-polar attenuation and cross-polar enhancement for the rain events observed during 2012-2013. Melting layer is indicated by the bright band signature in vertical profile of rain rate. The ground based drop size measurements indicate that the stratiform rain has more number of small drops whereas convective rain composed of large rain drops. The results indicate that the depolarization due to melting layer is more dominant compared to that due to the drop deformation mechanism at low rain rates.

Numerical Investigation of Temperature Distribution in an Eroded Bend Pipe and Prediction of Erosion Reduced Thickness

PubMed Central

Zhu, Hongjun; Feng, Guang; Wang, Qijun

2014-01-01

Accurate prediction of erosion thickness is essential for pipe engineering. The objective of the present paper is to study the temperature distribution in an eroded bend pipe and find a new method to predict the erosion reduced thickness. Computational fluid dynamic (CFD) simulations with FLUENT software are carried out to investigate the temperature field. And effects of oil inlet rate, oil inlet temperature, and erosion reduced thickness are examined. The presence of erosion pit brings about the obvious fluctuation of temperature drop along the extrados of bend. And the minimum temperature drop presents at the most severe erosion point. Small inlet temperature or large inlet velocity can lead to small temperature drop, while shallow erosion pit causes great temperature drop. The dimensionless minimum temperature drop is analyzed and the fitting formula is obtained. Using the formula we can calculate the erosion reduced thickness, which is only needed to monitor the outer surface temperature of bend pipe. This new method can provide useful guidance for pipeline monitoring and replacement. PMID:24719576

Preparation and Characterization of Silymarin Synchronized and Sustained Release Dropping Pill.

PubMed

Liu, Zhi-Hong; Li, Xue-Jing; Huang, Ai-Wen; Zhang, Jing; Song, Hong-Tao

2017-01-01

This study aimed to develop a synchronized and sustained-release silymarin dropping pill, and to evaluate its pharmacokinetic characteristics. Polyoxyethylene stearate, glyceryl monostearate, and stearic acid were used to prepare the dropping pills. X-ray powder diffraction, differential scanning calorimetry, and release were used to evaluate its physicochemical properties. The plasma concentration of silybin in beagle dogs after oral administration of silymarin dropping pills and silymarin capsule was determined by RP-HPLC. Synchronized release was achieved with high similarity factor f2 values between every set of two of the five components. Mean plasma concentration-time curves of silymarin after oral administration of dropping pills in beagle dogs were in accordance with first-order absorption and open twocompartment model. The Tmax, Cmax, and AUC0-∞ of dropping pills in beagle dogs were 0.8750±0.13 h, 0.8183±0.07 μg·ml-1, and 2.274±0.90 μg·h·ml-1, respectively. Silymarin dropping pills prolonged in vivo exposure and reduced maximum in vivo concentration, achieving a stable level in the serum. The combination of solid dispersion technique and dropping pill formulation allowed synchronized release of multiple components in herbal medicine, and has potential application in the development of sustained release in herbal medicine. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Family Involvement in the Education of Potential Drop-Out Children: A Comparative Study between Spain and Cyprus

ERIC Educational Resources Information Center

Martinez-Gonzalez, Raquel-Amaya; Symeou, Loizos; Alvarez-Blanco, Lucia; Roussounidou, Eleni; Iglesias-Muniz, Jesus; Cao-Fernandez, Maria-Auxiliadora

2008-01-01

This paper focuses on family involvement in the education of teenagers at risk of dropping out from compulsory secondary school. A questionnaire was completed by 131 Spanish and Cypriot families with children at six schools--three in each country. The questionnaire investigated: (1) parental perceptions of their children's activities in their free…

Change in failure stress on the southern San Andreas fault system caused by the 1992 magnitude = 7.4 Landers earthquake

USGS Publications Warehouse

Stein, R.S.; King, G.C.P.; Lin, J.

1992-01-01

The 28 June Landers earthquake brought the San Andreas fault significantly closer to failure near San Bernardino, a site that has not sustained a large shock since 1812. Stress also increased on the San Jacinto fault near San Bernardino and on the San Andreas fault southeast of Palm Springs. Unless creep or moderate earthquakes relieve these stress changes, the next great earthquake on the southern San Andreas fault is likely to be advanced by one to two decades. In contrast, stress on the San Andreas north of Los Angeles dropped, potentially delaying the next great earthquake there by 2 to 10 years.

Nectar and pollination drops: how different are they?

PubMed

Nepi, Massimo; von Aderkas, Patrick; Wagner, Rebecca; Mugnaini, Serena; Coulter, Andrea; Pacini, Ettore

2009-08-01

Pollination drops and nectars (floral nectars) are secretions related to plant reproduction. The pollination drop is the landing site for the majority of gymnosperm pollen, whereas nectar of angiosperm flowers represents a common nutritional resource for a large variety of pollinators. Extrafloral nectars also are known from all vascular plants, although among the gymnosperms they are restricted to the Gnetales. Extrafloral nectars are not generally involved in reproduction but serve as 'reward' for ants defending plants against herbivores (indirect defence). Although very different in their task, nectars and pollination drops share some features, e.g. basic chemical composition and eventual consumption by animals. This has led some authors to call these secretions collectively nectar. Modern techniques that permit chemical analysis and protein characterization have very recently added important information about these sugary secretions that appear to be much more than a 'reward' for pollinating (floral nectar) and defending animals (extrafloral nectar) or a landing site for pollen (pollination drop). Nectar and pollination drops contain sugars as the main components, but the total concentration and the relative proportions are different. They also contain amino acids, of which proline is frequently the most abundant. Proteomic studies have revealed the presence of common functional classes of proteins such as invertases and defence-related proteins in nectar (floral and extrafloral) and pollination drops. Invertases allow for dynamic rearrangement of sugar composition following secretion. Defence-related proteins provide protection from invasion by fungi and bacteria. Currently, only few species have been studied in any depth. The chemical composition of the pollination drop must be investigated in a larger number of species if eventual phylogenetic relationships are to be revealed. Much more information can be provided from further proteomic studies of both nectar and pollination drop that will contribute to the study of plant reproduction and evolution.

Assessing Stream Restoration Potential of Recreational Enhancements on an Urban Stream, Springfield, OH

NASA Astrophysics Data System (ADS)

Ritter, J. B.; Evelsizor, A.; Minter, K.; Rigsby, C.; Shaw, K.; Shearer, K.

2010-12-01

Restoration potential of urban streams is inherently constrained by urban infrastructure. Roads and built structures may necessitate a static stream planform while water, sewage, and electrical utilities buried in the stream channel require a stable grade. A privately-led initiative to improve the recreational potential of a 9-km reach of Buck Creek and its tributary Beaver Creek in Springfield, Ohio, includes the modification of four lowhead dams with hydraulic heights up to 3 m. Modifications to the dams include replacing their hydraulic height with a series of drop structures engineered to create hydraulics conducive to kayak play. Two of the lowhead dams have been modified to date. The purpose of this study is to assess the potential benefits of modifications designed for their recreational value for stream restoration. The drop structure is a constructed channel constriction comprised of a hard step in the long stream profile immediately upstream of a scour pool, forming a morphologic sequence of constriction, step, and pool. Up to 4 drop structures are used along a given stream reach, constructed in the area of the former dam, its scour pool and a portion of the impounded area. Though not designed for stream restoration purposes, these structures potentially act as series a riffle-pool sequences. Changes in the stream habitat, water chemistry, and macroinvertebrates in response to dam modification highlight the potential for incorporating stream restoration into the engineering design. Following modification of two of the dams, the in-stream habitat quality, as measured by physical and biological indices, increased at one site and decreased at the other site, depending on whether the uppermost drop structure at the site reduced or expanded the impounded area. In the best case, channel sands and gravels, free of fine sand, silt, and organics, have deposited in a crescentic-shaped bar paralleling and grading to the constriction and step. Greater abundance and diversity of pollution-intolerant macroinvertebrates, supported by higher dissolved oxygen in the substrate, characterizes riffles at these sites.

Plasma propulsion for space applications

NASA Astrophysics Data System (ADS)

Fruchtman, Amnon

2000-04-01

The various mechanisms for plasma acceleration employed in electric propulsion of space vehicles will be described. Special attention will be given to the Hall thruster. Electric propulsion utilizes electric and magnetic fields to accelerate a propellant to a much higher velocity than chemical propulsion does, and, as a result, the required propellant mass is reduced. Because of limitations on electric power density, electric thrusters will be low thrust engines compared with chemical rockets. The large jet velocity and small thrust of electric thrusters make them most suitable for space applications such as station keeping of GEO communication satellites, low orbit drag compensation, orbit raising and interplanetary missions. The acceleration in the thruster is either thermal, electrostatic or electromagnetic. The arcjet is an electrothermal device in which the propellant is heated by an electric arc and accelerated while passing through a supersonic nozzle to a relatively low velocity. In the Pulsed Plasma Thruster a solid propellant is accelerated by a magnetic field pressure in a way that is similar in principle to pulsed acceleration of plasmas in other, very different devices, such as the railgun or the plasma opening switch. Magnetoplasmadynamic thrusters also employ magnetic field pressure for the acceleration but with a reasonable efficiency at high power only. In an ion thruster ions are extracted from a plasma through a double grid structure. Ion thrusters provide a high jet velocity but the thrust density is low due to space-charge limitations. The Hall thruster, which in recent years has enjoyed impressive progress, employs a quasi-neutral plasma, and therefore is not subject to a space-charge limit on the current. An applied radial magnetic field impedes the mobility of the electrons so that the applied potential drops across a large region inside the plasma. Methods for separately controlling the profiles of the electric and the magnetic fields will be described. The role of the sonic transition in plasma accelerators will be discussed. It will be shown that large potential drops can be localized to regions of an abrupt sonic transition in a Hall plasma. A configuration with segmented side electrodes can be used to further control the electric field profile and to increase the efficiency.

Modeling of Carbon Nanotube Schottky Barrier Reduction for Holes in Air

NASA Technical Reports Server (NTRS)

Yamada, Toshishige

2003-01-01

A model is proposed for the previously reported lower Schottky barrier for holes Phi(sub Bh) in air than in vacuum at a metallic electrode - semiconducting carbon nanotube (CNT) junction. We consider that there is a transition region between the electrode and the CNT, and an appreciable potential can drop there. The role of the oxidation is to increase this potential drop with negatively charged oxygen molecules on the CNT, leading to lower Phi(sub Bh) after oxidation. The mechanism prevails in both p- and n-CNTs, and the model consistently explains the key experimental findings.

Evidence for Field-parallel Electron Acceleration in Solar Flares

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haerendel, G.

It is proposed that the coincidence of higher brightness and upward electric current observed by Janvier et al. during a flare indicates electron acceleration by field-parallel potential drops sustained by extremely strong field-aligned currents of the order of 10{sup 4} A m{sup −2}. A consequence of this is the concentration of the currents in sheets with widths of the order of 1 m. The high current density suggests that the field-parallel potential drops are maintained by current-driven anomalous resistivity. The origin of these currents remains a strong challenge for theorists.

THE RABIT: A RAPID AUTOMATED BIODOSIMETRY TOOL FOR RADIOLOGICAL TRIAGE

PubMed Central

Garty, Guy; Chen, Youhua; Salerno, Alessio; Turner, Helen; Zhang, Jian; Lyulko, Oleksandra; Bertucci, Antonella; Xu, Yanping; Wang, Hongliang; Simaan, Nabil; Randers-Pehrson, Gerhard; Yao, Y. Lawrence; Amundson, Sally A.; Brenner, David J.

2010-01-01

In response to the recognized need for high throughput biodosimetry methods for use after large scale radiological events, a logical approach is complete automation of standard biodosimetric assays that are currently performed manually. We describe progress to date on the RABIT (Rapid Automated BIodosimetry Tool), designed to score micronuclei or γ-H2AX fluorescence in lymphocytes derived from a single drop of blood from a fingerstick. The RABIT system is designed to be completely automated, from the input of the capillary blood sample into the machine, to the output of a dose estimate. Improvements in throughput are achieved through use of a single drop of blood, optimization of the biological protocols for in-situ analysis in multi-well plates, implementation of robotic plate and liquid handling, and new developments in high-speed imaging. Automating well-established bioassays represents a promising approach to high-throughput radiation biodosimetry, both because high throughputs can be achieved, but also because the time to deployment is potentially much shorter than for a new biological assay. Here we describe the development of each of the individual modules of the RABIT system, and show preliminary data from key modules. Ongoing is system integration, followed by calibration and validation. PMID:20065685

Derivation and characterization of gut-like structures from embryonic stem cells.

PubMed

Yamada, Takatsugu; Nakajima, Yoshiyuki

2006-01-01

Embryonic stem (ES) cells have a pluripotent ability to differentiate into a variety of cell lineages of all three embryonic germ layers in vitro. The hanging drop culture of ES cell suspension in the absence of leukemia inhibitory factor induces aggregation and differentiation of the cells into simple or cystic embryoid bodies (EBs). After 6 d of hanging drop culture, the resulting EBs are plated onto plastic dishes for the outgrowth culture. At d 21 after outgrowth culture, cell populations of EBs can give rise to three-dimensional gut-like structures that exhibit spontaneous contraction and highly coordinated peristalsis. The gut-like structures have large lumens surrounded by three layers: epithelium, lamina propria, and muscularis. Ganglia are scattered along the periphery, and interstitial cells of Cajal are distributed among the smooth muscle cells. The fundamental process of formation of the in vitro organized gut-like structures is similar to embryonic gastrointestinal development in vivo. The EBs at the 6-d egg-cylinder stage may have the potential to regulate developmental programs associated with cell lineage commitment and provide an appropriate microenvironment to differentiate ES cells into enteric derivatives of all three embryonic germ layers and reproduce the gut organization process in vitro.

CFD Lagrangian Modeling of Water Droplet Transport for ISS Hygiene Activity Application

NASA Technical Reports Server (NTRS)

Son, Chang H.

2013-01-01

The goal of this study was to assess the impacts of free water propagation in the Waste and Hygiene Compartment (WHC) installed in Node 3. Free water can be generated inside the WHC in small quantities due to crew hygiene activity. To mitigate potential impact of free water in Node 3 cabin the WHC doorway is enclosed by a waterproof bump-out, Kabin, with openings at the top and bottom. At the overhead side of the rack, there is a screen that prevents large drops of water from exiting. However, as the avionics fan in the WHC causes airflow toward the deck side of the rack, small quantities of free water may exit at the bottom of the Kabin. A Computational Fluid Dynamics (CFD) analysis of Node 3 cabin airflow enable identifying the paths of water transport. To simulate the droplet transport the Lagrangian discrete phase approach was used. Various initial droplet distributions were considered in the study. The droplet diameter was varied in the range of 5-20 mm. The results of the computations showed that most of the drops fall to the rack surface not far from the WHC curtain.

Channel add-drop filter based on dual photonic crystal cavities in push-pull mode.

PubMed

Poulton, Christopher V; Zeng, Xiaoge; Wade, Mark T; Popović, Miloš A

2015-09-15

We demonstrate an add-drop filter based on a dual photonic crystal nanobeam cavity system that emulates the operation of a traveling wave resonator, and, thus, provides separation of the through and drop port transmission from the input port. The device is on a 3×3  mm chip fabricated in an advanced microelectronics silicon-on-insulator complementary metal-oxide semiconductor (SOI CMOS) process (IBM 45 nm SOI) without any foundry process modifications. The filter shows 1 dB of insertion loss in the drop port with a 3 dB bandwidth of 64 GHz, and 16 dB extinction in the through port. To the best of our knowledge, this is the first implementation of a port-separating, add-drop filter based on standing wave cavities coupled to conventional waveguides, and demonstrates a performance that suggests potential for photonic crystal devices within optical immersion lithography-based advanced CMOS electronics-photonics integration.

Theory of the interface between a classical plasma and a hard wall

NASA Astrophysics Data System (ADS)

Ballone, P.; Pastore, G.; Tosi, M. P.

1983-09-01

The interfacial density profile of a classical one-component plasma confined by a hard wall is studied in planar and spherical geometries. The approach adapts to interfacial problems a modified hypernetted-chain approximation developed by Lado and by Rosenfeld and Ashcroft for the bulk structure of simple liquids. The specific new aim is to embody selfconsistently into the theory a contact theorem, fixing the plasma density at the wall through an equilibrium condition which involves the electrical potential drop across the interface and the bulk pressure. The theory is brought into fully quantitative contact with computer simulation data for a plasma confined in a spherical cavity of large but finite radius. The interfacial potential at the point of zero charge is accurately reproduced by suitably combining the contact theorem with relevant bulk properties in a simple, approximate representation of the interfacial charge density profile.

Theory of the interface between a classical plasma and a hard wall

NASA Astrophysics Data System (ADS)

Ballone, P.; Pastore, G.; Tosi, M. P.

1984-12-01

The interfacial density profile of a classical one-component plasma confined by a hard wall is studied in planar and spherical geometries. The approach adapts to interfacial problems a modified hypernetted-chain approximation developed by Lado and by Rosenfeld and Ashcroft for the bulk structure of simple liquids. The specific new aim is to embody self-consistently into the theory a “contact theorem”, fixing the plasma density at the wall through an equilibrium condition which involves the electrical potential drop across the interface and the bulk pressure. The theory is brought into fully quantitative contact with computer simulation data for a plasma confined in a spherical cavity of large but finite radius. It is also shown that the interfacial potential at the point of zero charge is accurately reproduced by suitably combining the contact theorem with relevant bulk properties in a simple, approximate representation of the interfacial charge density profile.

Rough Gold Electrodes for Decreasing Impedance at the Electrolyte/Electrode Interface

PubMed Central

Koklu, Anil; Sabuncu, Ahmet C.; Beskok, Ali

2016-01-01

Electrode polarization at the electrolyte/electrode interface is often undesirable for bio-sensing applications, where charge accumulated over an electrode at constant potential causes large potential drop at the interface and low measurement sensitivity. In this study, novel rough electrodes were developed for decreasing electrical impedance at the interface. The electrodes were fabricated using electrochemical deposition of gold and sintering of gold nanoparticles. The performances of the gold electrodes were compared with platinum black electrodes. A constant phase element model was used to describe the interfacial impedance. Hundred folds of decrease in interfacial impedance were observed for fractal gold electrodes and platinum black. Biotoxicity, contact angle, and surface morphology of the electrodes were investigated. Relatively low toxicity and hydrophilic nature of the fractal and granulated gold electrodes make them suitable for bioimpedance and cell electromanipulation studies compared to platinum black electrodes which are both hydrophobic and toxic. PMID:27695132

DEVICE AND METHOD FOR PRODUCING A HIGH INTENSITY ARC DISCHARGE

DOEpatents

Luce, J.S.

1960-01-01

A device is described for producing an energetic d-c carbon arc discharge between widely spaced electrodes with arc currents in excess of 100 amperes in a magnetic field of about 3000 gauss and witnin an evacuated enclo sure at a pressure of about 10/sup -5/ mm Hg. No defining electrodes are used in the device, thus essentially eliminating the problems of shorting which heretofore limited the amount of current that could be produced in an arc discharge. The energetic carbon arc discharge is sustained by the potential across the electrodes and by carbon ions and electrons released from the electrodes during arc operation. A large part of the potential drop of the arc occurs along the arc and many energetic electrons reach the anode because the arc pressure is relatively low, and few collisions occur. The carbon discharge is also an efficient ion pump.

Rapid determination of caffeine in one drop of beverages and foods using drop-to-drop solvent microextraction with gas chromatography/mass spectrometry.

PubMed

Shrivas, Kamlesh; Wu, Hui-Fen

2007-11-02

A simple and rapid sample cleanup and preconcentration method for the quantitative determination of caffeine in one drop of beverages and foods by gas chromatography/mass spectrometry (GC/MS) has been proposed using drop-to-drop solvent microextraction (DDSME). The best optimum experimental conditions for DDSME were: chloroform as the extraction solvent, 5 min extraction time, 0.5 microL exposure volume of the extraction phase and no salt addition at room temperature. The optimized methodology exhibited good linearity between 0.05 and 5.0 microg/mL with correlation coefficient of 0.980. The relative standard deviation (RSD) and limits of detection (LOD) of the DDSME/GC/MS method were 4.4% and 4.0 ng/mL, respectively. Relative recovery of caffeine in beverages and foods were found to be 96.6-101%, which showing good reliability of this method. This DDSME excludes the major disadvantages of conventional method of caffeine extraction, like large amount of organic solvent and sample consumption and long sample pre-treatment process. So, this approach proves that the DDSME/GC/MS technique can be applied as a simple, fast and feasible diagnosis tool for environmental, food and biological application for extremely small amount of real sample analysis.

Estimation of methacrylate monolith binding capacity from pressure drop data.

PubMed

Podgornik, Aleš; Smrekar, Vida; Krajnc, Peter; Strancar, Aleš

2013-01-11

Convective chromatographic media comprising of membranes and monoliths represent an important group of chromatographic supports due to their flow-unaffected chromatographic properties and consequently fast separation and purification even of large biological macromolecules. Consisting of a single piece of material, common characterization procedures based on analysis of a small sample assuming to be representative for the entire batch, cannot be applied. Because of that, non-invasive characterization methods are preferred. In this work pressure drop was investigated for an estimation of dynamic binding capacity (DBC) of proteins and plasmid DNA for monoliths with different pore sizes. It was demonstrated that methacrylate monolith surface area is reciprocally proportional to pore diameter and that pressure drop on monolith is reciprocally proportional to square pore size demonstrating that methacrylate monolith microstructure is preserved by changing pore size. Based on these facts mathematical formalism has been derived predicting that DBC is in linear correlation with the square root of pressure drop. This was experimentally confirmed for ion-exchange and hydrophobic interactions for proteins and plasmid DNA. Furthermore, pressure drop was also applied for an estimation of DBC in grafted layers of different thicknesses as estimated from the pressure drop data. It was demonstrated that the capacity is proportional to the estimated grafted layer thickness. Copyright © 2012 Elsevier B.V. All rights reserved.

Collective flows of pions in Au+Au collisions at energies 1.0 and 1.5 GeV/nucleon

NASA Astrophysics Data System (ADS)

Liu, Yangyang; Wang, Yongjia; Li, Qingfeng; Liu, Ling

2018-03-01

Based on the newly updated version of the ultrarelativistic quantum molecular dynamics (UrQMD) model, the pion potentials obtained from the in-medium dispersion relation of the Δ -hole model and from the modified phenomenological approach are further introduced. Both the rapidity y0 and transverse-velocity ut 0 dependence of directed v1 and elliptic v2 flows of π+ and π- charged mesons produced from Au+Au collisions at two beam energies of 1.0 and 1.5 GeV/nucleon and within a large centrality region of 0

Confinement of plasma along shaped open magnetic fields from the centrifugal force of supersonic plasma rotation.

PubMed

Teodorescu, C; Young, W C; Swan, G W S; Ellis, R F; Hassam, A B; Romero-Talamas, C A

2010-08-20

Interferometric density measurements in plasmas rotating in shaped, open magnetic fields demonstrate strong confinement of plasma parallel to the magnetic field, with density drops of more than a factor of 10. Taken together with spectroscopic measurements of supersonic E × B rotation of sonic Mach 2, these measurements are in agreement with ideal MHD theory which predicts large parallel pressure drops balanced by centrifugal forces in supersonically rotating plasmas.

Deployment and Drop Test of Inflatable Aeroshell for Atmospheric Entry Capsule with using Large Scientific Balloon

NASA Astrophysics Data System (ADS)

Yamada, Kazuhiko; Suzuki, Kojiro; Honma, Naohiko; Abe, Daisuke; Makino, Hitoshi; Nagata, Yasunori; Kimura, Yusuke; Koyama, Masashi; Akita, Daisuke; Hayashi, Koichi; Abe, Takashi

A deployable and flexible aeroshell for atmospheric entry vehicles has attracted attention as an innovative space transportation system in the near future, because the large-area, low-mass aeroshell dramatically reduces aerodynamic heating and achieves a soft landing without a conventional parachute system thanks to its low ballistic coefficient. Various concepts of flexible aeroshell have been proposed in the past. Our group are researching and developing a flare-type membrane aeroshell sustained by inflatable torus. As a part of the development, a deployment and drop test of a capsule-type experimental vehicle with a 1.264-m-diameter flare-type membrane aeroshell sustained by inflatable torus was carried out using a large scientific balloon in August, 2009. The objectives of this experiment are 1) to demonstrate the remote inflation system of inflatable aeroshell, 2) to acquire aerodynamic performance of a low ballistic coefficient vehicle including an inflatable structure in subsonic region, and 3) to observe behavior and deformation of the flexible aeroshell during free flight. In this test, the inflatable aeroshell was deployed at an altitude 24.6km by radio command from ground station. After deployment, the experimental vehicle was dropped from the balloon and underwent free flight. The flight data and images of the aeroshell collected using onboard sensors were transmitted successfully during the flight by the telemetry system. The data showed that the vehicle was almost stable in free flight condition and the inflatable aeroshell was collapsed at expected altitude. This deployment and drop test was very successful and useful data for design of actual atmospheric-entry vehicles with inflatable structure was acquired as planned.

Three-dimensional assessment of squats and drop jumps using the Microsoft Xbox One Kinect: Reliability and validity.

PubMed

Mentiplay, Benjamin F; Hasanki, Ksaniel; Perraton, Luke G; Pua, Yong-Hao; Charlton, Paula C; Clark, Ross A

2018-03-01

The Microsoft Xbox One Kinect™ (Kinect V2) contains a depth camera that can be used to manually identify anatomical landmark positions in three-dimensions independent of the standard skeletal tracking, and therefore has potential for low-cost, time-efficient three-dimensional movement analysis (3DMA). This study examined inter-session reliability and concurrent validity of the Kinect V2 for the assessment of coronal and sagittal plane kinematics for the trunk, hip and knee during single leg squats (SLS) and drop vertical jumps (DVJ). Thirty young, healthy participants (age = 23 ± 5yrs, male/female = 15/15) performed a SLS and DVJ protocol that was recorded concurrently by the Kinect V2 and 3DMA during two sessions, one week apart. The Kinect V2 demonstrated good to excellent reliability for all SLS and DVJ variables (ICC ≥ 0.73). Concurrent validity ranged from poor to excellent (ICC = 0.02 to 0.98) during the SLS task, although trunk, hip and knee flexion and two-dimensional measures of knee abduction and frontal plane projection angle all demonstrated good to excellent validity (ICC ≥ 0.80). Concurrent validity for the DVJ task was typically worse, with only two variables exceeding ICC = 0.75 (trunk and hip flexion). These findings indicate that the Kinect V2 may have potential for large-scale screening for ACL injury risk, however future prospective research is required.

The spatial distribution of earthquake stress rotations following large subduction zone earthquakes

USGS Publications Warehouse

Hardebeck, Jeanne L.

2017-01-01

Rotations of the principal stress axes due to great subduction zone earthquakes have been used to infer low differential stress and near-complete stress drop. The spatial distribution of coseismic and postseismic stress rotation as a function of depth and along-strike distance is explored for three recent M ≥ 8.8 subduction megathrust earthquakes. In the down-dip direction, the largest coseismic stress rotations are found just above the Moho depth of the overriding plate. This zone has been identified as hosting large patches of large slip in great earthquakes, based on the lack of high-frequency radiated energy. The large continuous slip patches may facilitate near-complete stress drop. There is seismological evidence for high fluid pressures in the subducted slab around the Moho depth of the overriding plate, suggesting low differential stress levels in this zone due to high fluid pressure, also facilitating stress rotations. The coseismic stress rotations have similar along-strike extent as the mainshock rupture. Postseismic stress rotations tend to occur in the same locations as the coseismic stress rotations, probably due to the very low remaining differential stress following the near-complete coseismic stress drop. The spatial complexity of the observed stress changes suggests that an analytical solution for finding the differential stress from the coseismic stress rotation may be overly simplistic, and that modeling of the full spatial distribution of the mainshock static stress changes is necessary.

Drop interaction with solid boundaries in liquid/liquid systems

NASA Astrophysics Data System (ADS)

Bordoloi, Ankur Deep

The present experimental work was motivated primarily by the CO 2 sequestration process. In a possible scenario during this process, gravity driven CO2 bubbles coalesce at an interface near the rock surface. In another scenario, trapped CO2 fluid may escape from a porous matrix overcoming interfacial force inside a pore. Based on these potential scenarios, the current research was divided into two broad experimental studies. In the first part, coalescence at a quiescent interface of two analogous fluids (silicone oil and water/glycerin mixture) was investigated for water/glycerin drops with Bond number (Bo) ~7 and Ohnesorge number ~ 0.01 using high-speed imaging and time-resolved tomographic PIV. Two perturbation cases with a solid particle wetted in oil and water/glycerin placed adjacent to the coalescing drop were considered. The results were compared with coalescence of a single drop and that of a drop neighBored by a second drop of equivalent size. Each perturbing object caused an initial tilting of the drop, influencing its rupture location, subsequent film retraction and eventual collapse behavior. Once tilted, drops typically ruptured near their lowest vertical position which was located either toward or away from the perturbing object depending on the case. The trends in local retraction speed of the ruptured film and the overall dynamics of the collapsing drops were discussed in detail. In the second part, the motion of gravity driven drops (B o~0.8-11) through a confining orifice d/D<1) was studied using high speed imaging and planar PIV. Drops of water/glycerin, surrounded by silicone oil, fall toward and encounter the orifice plate after reaching terminal speed. The effects of surface wettability were investigated for Both round-edged and sharp-edged orifices. For the round-edged case, a thin film of surrounding oil prevented the drop fluid from contacting the orifice surface, such that the flow outcomes of the drops were independent of surface wettability. For d/D<0.8, the Boundary between drop capture and release depended on a modified Bond number relating drop gravitational time scale to orifice surface tension time scale. For the sharp-edged case, contact was initiated at the orifice edge immediately upon impact, such that surface wettability influenced the drop outcome.

Predicting who will drop out of nursing courses: a machine learning exercise.

PubMed

Moseley, Laurence G; Mead, Donna M

2008-05-01

The concepts of causation and prediction are different, and have different implications for practice. This distinction is applied here to studies of the problem of student attrition (although it is more widely applicable). Studies of attrition from nursing courses have tended to concentrate on causation, trying, largely unsuccessfully, to elicit what causes drop out. However, the problem may more fruitfully be cast in terms of predicting who is likely to drop out. One powerful method for attempting to make predictions is rule induction. This paper reports the use of the Answer Tree package from SPSS for that purpose. The main data set consisted of 3978 records on 528 nursing students, split into a training set and a test set. The source was standard university student records. The method obtained 84% sensitivity, 70% specificity, and 94% accuracy on previously unseen cases. The method requires large amounts of high quality data. When such data are available, rule induction offers a way to reduce attrition. It would be desirable to compare its results with those of predictions made by tutors using more informal conventional methods.

Early Teen Marriage and Future Poverty

PubMed Central

DAHL, GORDON B.

2010-01-01

Both early teen marriage and dropping out of high school have historically been associated with a variety of negative outcomes, including higher poverty rates throughout life. Are these negative outcomes due to preexisting differences, or do they represent the causal effect of marriage and schooling choices? To better understand the true personal and societal consequences, in this article, I use an instrumental variables (IV) approach that takes advantage of variation in state laws regulating the age at which individuals are allowed to marry, drop out of school, and begin work. The baseline IV estimate indicates that a woman who marries young is 31 percentage points more likely to live in poverty when she is older. Similarly, a woman who drops out of school is 11 percentage points more likely to be poor. The results are robust to a variety of alternative specifications and estimation methods, including limited information maximum likelihood (LIML) estimation and a control function approach. While grouped ordinary least squares (OLS) estimates for the early teen marriage variable are also large, OLS estimates based on individual-level data are small, consistent with a large amount of measurement error. PMID:20879684

Early teen marriage and future poverty.

PubMed

Dahl, Gordon B

2010-08-01

Both early teen marriage and dropping out of high school have historically been associated with a variety of negative outcomes, including higher poverty rates throughout life. Are these negative outcomes due to preexisting differences, or do they represent the causal effect of marriage and schooling choices? To better understand the true personal and societal consequences, in this article, I use an instrumental variables (IV) approach that takes advantage of variation in state laws regulating the age at which individuals are allowed to marry, drop out of school, and begin work. The baseline IV estimate indicates that a woman who marries young is 31 percentage points more likely to live in poverty when she is older. Similarly, a woman who drops out of school is 11 percentage points more likely to be poor. The results are robust to a variety of alternative specifications and estimation methods, including limited information maximum likelihood (LIML) estimation and a control function approach. While grouped ordinary least squares (OLS) estimates for the early teen marriage variable are also large, OLS estimates based on individual-level data are small, consistent with a large amount of measurement error

Influence of Computational Drop Representation in LES of a Droplet-Laden Mixing Layer

NASA Technical Reports Server (NTRS)

Bellan, Josette; Radhakrishnan, Senthilkumaran

2013-01-01

Multiphase turbulent flows are encountered in many practical applications including turbine engines or natural phenomena involving particle dispersion. Numerical computations of multiphase turbulent flows are important because they provide a cheaper alternative to performing experiments during an engine design process or because they can provide predictions of pollutant dispersion, etc. Two-phase flows contain millions and sometimes billions of particles. For flows with volumetrically dilute particle loading, the most accurate method of numerically simulating the flow is based on direct numerical simulation (DNS) of the governing equations in which all scales of the flow including the small scales that are responsible for the overwhelming amount of dissipation are resolved. DNS, however, requires high computational cost and cannot be used in engineering design applications where iterations among several design conditions are necessary. Because of high computational cost, numerical simulations of such flows cannot track all these drops. The objective of this work is to quantify the influence of the number of computational drops and grid spacing on the accuracy of predicted flow statistics, and to possibly identify the minimum number, or, if not possible, the optimal number of computational drops that provide minimal error in flow prediction. For this purpose, several Large Eddy Simulation (LES) of a mixing layer with evaporating drops have been performed by using coarse, medium, and fine grid spacings and computational drops, rather than physical drops. To define computational drops, an integer NR is introduced that represents the ratio of the number of existing physical drops to the desired number of computational drops; for example, if NR=8, this means that a computational drop represents 8 physical drops in the flow field. The desired number of computational drops is determined by the available computational resources; the larger NR is, the less computationally intensive is the simulation. A set of first order and second order flow statistics, and of drop statistics are extracted from LES predictions and are compared to results obtained by filtering a DNS database. First order statistics such as Favre averaged stream-wise velocity, Favre averaged vapor mass fraction, and the drop stream-wise velocity, are predicted accurately independent of the number of computational drops and grid spacing. Second order flow statistics depend both on the number of computational drops and on grid spacing. The scalar variance and turbulent vapor flux are predicted accurately by the fine mesh LES only when NR is less than 32, and by the coarse mesh LES reasonably accurately for all NR values. This is attributed to the fact that when the grid spacing is coarsened, the number of drops in a computational cell must not be significantly lower than that in the DNS.

Ultrafast cavitation induced by an X-ray laser in water drops

NASA Astrophysics Data System (ADS)

Stan, Claudiu; Willmott, Philip; Stone, Howard; Koglin, Jason; Liang, Mengning; Aquila, Andrew; Robinson, Joseph; Gumerlock, Karl; Blaj, Gabriel; Sierra, Raymond; Boutet, Sebastien; Guillet, Serge; Curtis, Robin; Vetter, Sharon; Loos, Henrik; Turner, James; Decker, Franz-Josef

2016-11-01

Cavitation in pure water is determined by an intrinsic heterogeneous cavitation mechanism, which prevents in general the experimental generation of large tensions (negative pressures) in bulk liquid water. We developed an ultrafast decompression technique, based on the reflection of shock waves generated by an X-ray laser inside liquid drops, to stretch liquids to large negative pressures in a few nanoseconds. Using this method, we observed cavitation in liquid water at pressures below -100 MPa. These large tensions exceed significantly those achieved previously, mainly due to the ultrafast decompression. The decompression induced by shock waves generated by an X-ray laser is rapid enough to continue to stretch the liquid phase after the heterogeneous cavitation occurs in water, despite the rapid growth of cavitation nanobubbles. We developed a nucleation-and-growth hydrodynamic cavitation model that explains our results and estimates the concentration of heterogeneous cavitation nuclei in water.

Investigation of Critical Burning of Fuel Droplets. [of liquid rocket propellant

NASA Technical Reports Server (NTRS)

Chanin, S. P.; Shearer, A. J.; Faeth, G. M.

1976-01-01

An earlier analysis for the combustion response of a liquid monopropellant strand (hydrazine) was extended to consider individual droplets and sprays. While small drops gave low or negative response, large droplets provided response near unity at low frequencies, with the response declining at frequencies greater than the characteristic liquid phase frequency. Temperature gradients in the liquid phase resulted in response peaks greater than unity. A second response peak was found for large drops which corresponded to gas phase transient effects. Spray response was generally reduced from the response of the largest injected droplet, however, even a small percentage of large droplets can yield appreciable response. An apparatus was designed and fabricated to allow observation of bipropellant fuel spray combustion at elevated pressures. A locally homogeneous model was developed to describe this combustion process which allows for high pressure phenomena associated with the thermodynamic critical point.

Direct Numerical Simulation of Transitional Multicomponent-Species Gaseous and Multicomponent-Liquid Drop-Laden Mixing

NASA Technical Reports Server (NTRS)

Selle, Laurent C.; Bellan, Josette

2006-01-01

A model of multicomponent-liquid (MC-liquid) drop evaporation in a three-dimensional mixing layer is here exercised at larger Reynolds numbers than in a previous study, and transitional states are obtained. The gas phase is followed in an Eulerian frame and the multitude of drops is described in a Lagrangian frame. Complete coupling between phases is included with source terms in the gas conservation equations accounting for the drop/flow interaction in terms of drop drag, drop heating and species evaporation. The liquid composition, initially specified as a single-Gamma (SG) probability distribution function (PDF) depending on the molar mass is allowed to evolve into a linear combination of two SGPDFs, called the double-Gamma PDF (DGPDF). The compositions of liquid and vapor emanating from the drops are calculated through four moments of the DGPDFs, which are drop-specific and location-specific, respectively. The mixing layer is initially excited to promote the double pairing of its four initial spanwise vortices into an ultimate vortex in which small scales proliferate. Simulations are performed for four liquids of different compositions and the effect of the initial mass loading and initial free-stream gas temperature are explored. For reference, Simulations are also performed for gaseous multicomponent mixing layers for which the effect of Reynolds number is investigated. The results encompass examination of the global layer characteristics, flow visualizations and homogeneous-plane statistics at transition. Comparisons are performed with previous pre-transitional MC-liquid simulations and with transitional single-component (SC) liquid studies. It is found that MCC flows at transition, the classical energy cascade is of similar strength, but that the smallest scales contain orders of magnitude less energy than SC flows, which is confirmed by the larger viscous dissipation in the former case. Contrasting to pre-transitional MC flows, the vorticity and drop organization depend on the initial gas temperature, this being due to the drop/turbulence coupling. The vapor-composition mean molar mass and standard deviation distributions strongly correlate with the initial liquid-composition PDF; such a correlation only exists for the magnitude of the mean but not for that of the standard deviation. Unlike in pre-transitional situations, regions of large composition standard deviation no longer necessarily coincide with regions of large mean molar mass. The kinetic energy, rotational and composition characteristics, and dissipation are liquid specific and the variation among liquids is amplified with increasing free-stream gas temperature. Eulerian and Lagrangian statistics of gas-phase quantities show that the different. Observation framework may affect the perception of the flow characteristics. The gas composition, of which the first four moments are calculated, is shown to be close to, but distinct from a SGPDF. The PDF of the scalar dissipation rate is calculated for drop-laden layers and is shown to depart more significantly from the typically assumed Gaussian in gaseous flows than experimentally measured gaseous scalar dissipation rates, this being attributed to the increased heterogeneity due to drop/flow interactions.

"Who Am I Supposed to Let Down?": The Caring Work and Emotional Practices of Vocational Educational Training Teachers Working with Potential Drop-Out Students

ERIC Educational Resources Information Center

Lippke, Lena

2012-01-01

Purpose: Because of high drop-out rates among the students entering vocational education in Denmark retention of students has become pivotal to Danish educational policy. Thus vocational educational training (VET) colleges have been asked to work on implementing different kinds of retention initiatives and as a result, most colleges have…

Acceptability and Potential Effectiveness of a Foot Drop Stimulator in Children and Adolescents with Cerebral Palsy

ERIC Educational Resources Information Center

Prosser, Laura A.; Curatalo, Lindsey A.; Alter, Katharine E.; Damiano, Diane L.

2012-01-01

Aim: Ankle-foot orthoses are the standard of care for foot drop in cerebral palsy (CP), but may overly constrain ankle movement and limit function in those with mild CP. Functional electrical stimulation (FES) may be a less restrictive and more effective alternative, but has rarely been used in CP. The primary objective of this study was to…

Cationic Thiolated Poly(aspartamide) Polymer as a Potential Excipient for Artificial Tear Formulations.

PubMed

Budai-Szűcs, Mária; Horvát, Gabriella; Szilágyi, Barnabás Áron; Gyarmati, Benjámin; Szilágyi, András; Berkó, Szilvia; Szabó-Révész, Piroska; Sandri, Giuseppina; Bonferoni, Maria Cristina; Caramella, Carla; Soós, Judit; Facskó, Andrea; Csányi, Erzsébet

2016-01-01

Dry eye disease is a relatively common ocular problem, which causes eye discomfort and visual disorders leading to a decrease in the quality of life. The aim of this study was to find a possible excipient for eye drop formulations, which is able to stabilize the tear film. A cationic thiolated polyaspartamide polymer, poly[(N-mercaptoethylaspartamide)-co-(N-(N',N'-dimethylaminoethyl)aspartamide)] (ThioPASP-DME), was used as a potential vehicle. Besides satisfying the basic requirements, the chemical structure of ThioPASP-DME is similar to those of ocular mucins as it is a protein-like polymer bearing a considerable number of thiol groups. The solution of the polymer is therefore able to mimic the physiological properties of the mucins and it can interact with the mucus layer via disulphide bond formation. The resultant mucoadhesion provides a prolonged residence time and ensures protective effect for the corneal/conjunctival epithelium. ThioPASP-DME also has an antioxidant effect due to the presence of the thiol groups. The applicability of ThioPASP-DME as a potential excipient in eye drops was determined by means of ocular compatibility tests and through examinations of the interactions with the mucosal surface. The results indicate that ThioPASP-DME can serve as a potential eye drop excipient for the therapy of dry eye disease.

Relating emulsion stability to interfacial properties for pharmaceutical emulsions stabilized by Pluronic F68 surfactant.

PubMed

Powell, Kristin Conrad; Damitz, Robert; Chauhan, Anuj

2017-04-15

We explore mechanisms of emulsion stability for several systems using Pluronic F68 and a range of oils commonly used in pharmaceutics and cosmetics. We report measurements of dynamic emulsion drop size, zeta potential, and creaming time, as well as dynamic interfacial tension and interfacial viscoelasticity. Experiments show that with 1wt% Pluronic F68, soybean oil emulsions were the most stable with no creaming over six months, followed by isopropyl myristate, octanoic acid, and then ethyl butyrate. The eventual destabilization occurred due to the rising of large drops which formed through Ostwald ripening and coalescence. While Ostwald ripening is important, it is not the dominant destabilization mechanism for the time scale of interest in pharmaceutical emulsions. The more significant destabilization mechanism, coalescence, is reduced through surfactant adsorption, which decreases surface tension, increases surface elasticity, and adds a stearic hindrance to collisions. Though the measured values of elasticity obtained using a standard oscillatory pendant drop method did not correlate to emulsion stability, this is because the frequencies for the measurements were orders of magnitude below those relevant to coalescence in emulsions. However, we show that the high frequency elasticity obtained by fitting the surface tension data to a Langmuir isotherm has very good correlation with the emulsion stability, indicating that the elasticity of the interface plays a key role in stabilizing these pharmaceutical formulations. Further, this study highlights how these important high frequency elasticity values can be easily estimated from surface isotherms. Copyright © 2017 Elsevier B.V. All rights reserved.

Calcium-Phosphate-Osteopontin Particles Reduce Biofilm Formation and pH Drops in in situ Grown Dental Biofilms.

PubMed

Schlafer, Sebastian; Ibsen, Casper J S; Birkedal, Henrik; Nyvad, Bente

2017-01-01

This 2-period crossover study investigated the effect of calcium-phosphate-osteopontin particles on biofilm formation and pH in 48-h biofilms grown in situ. Bovine milk osteopontin is a highly phosphorylated glycoprotein that has been shown to interfere with bacterial adhesion to salivary-coated surfaces. Calcium-phosphate-osteopontin particles have been shown to reduce biofilm formation and pH drops in a 5-species laboratory model of dental biofilm without affecting bacterial viability. Here, smooth surface biofilms from 10 individuals were treated ex vivo 6 times/day for 30 min with either calcium-phosphate-osteopontin particles or sterile saline. After growth, the amount of biofilm formed was determined by confocal microscopy, and pH drops upon exposure to glucose were monitored using confocal-microscopy-based pH ratiometry. A total of 160 biofilms were analysed. No adverse effects of repeated ex vivo treatment with calcium-phosphate-osteopontin particles were observed. Particle treatment resulted in a 32% lower amount of biofilm formed (p < 0.05), but large inter-individual differences could be observed. Biofilm pH was significantly higher upon particle treatment, both shortly after the addition of glucose and after 30 min of incubation with glucose (p < 0.05). Calcium-phosphate-osteopontin particles may represent a new therapeutic approach to caries control and aim at directly targeting virulence factors involved in the caries process. Further studies are required to determine the effect of particle treatment on more acidogenic/aciduric biofilms as well as the remineralizing potential of the particles. © 2016 S. Karger AG, Basel.

An algorithm for selecting the most accurate protocol for contact angle measurement by drop shape analysis.

PubMed

Xu, Z N

2014-12-01

In this study, an error analysis is performed to study real water drop images and the corresponding numerically generated water drop profiles for three widely used static contact angle algorithms: the circle- and ellipse-fitting algorithms and the axisymmetric drop shape analysis-profile (ADSA-P) algorithm. The results demonstrate the accuracy of the numerically generated drop profiles based on the Laplace equation. A significant number of water drop profiles with different volumes, contact angles, and noise levels are generated, and the influences of the three factors on the accuracies of the three algorithms are systematically investigated. The results reveal that the above-mentioned three algorithms are complementary. In fact, the circle- and ellipse-fitting algorithms show low errors and are highly resistant to noise for water drops with small/medium volumes and contact angles, while for water drop with large volumes and contact angles just the ADSA-P algorithm can meet accuracy requirement. However, this algorithm introduces significant errors in the case of small volumes and contact angles because of its high sensitivity to noise. The critical water drop volumes of the circle- and ellipse-fitting algorithms corresponding to a certain contact angle error are obtained through a significant amount of computation. To improve the precision of the static contact angle measurement, a more accurate algorithm based on a combination of the three algorithms is proposed. Following a systematic investigation, the algorithm selection rule is described in detail, while maintaining the advantages of the three algorithms and overcoming their deficiencies. In general, static contact angles over the entire hydrophobicity range can be accurately evaluated using the proposed algorithm. The ease of erroneous judgment in static contact angle measurements is avoided. The proposed algorithm is validated by a static contact angle evaluation of real and numerically generated water drop images with different hydrophobicity values and volumes.

Atomistic modeling of dropwise condensation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sikarwar, B. S., E-mail: bssikarwar@amity.edu; Singh, P. L.; Muralidhar, K.

The basic aim of the atomistic modeling of condensation of water is to determine the size of the stable cluster and connect phenomena occurring at atomic scale to the macroscale. In this paper, a population balance model is described in terms of the rate equations to obtain the number density distribution of the resulting clusters. The residence time is taken to be large enough so that sufficient time is available for all the adatoms existing in vapor-phase to loose their latent heat and get condensed. The simulation assumes clusters of a given size to be formed from clusters of smallermore » sizes, but not by the disintegration of the larger clusters. The largest stable cluster size in the number density distribution is taken to be representative of the minimum drop radius formed in a dropwise condensation process. A numerical confirmation of this result against predictions based on a thermodynamic model has been obtained. Results show that the number density distribution is sensitive to the surface diffusion coefficient and the rate of vapor flux impinging on the substrate. The minimum drop radius increases with the diffusion coefficient and the impinging vapor flux; however, the dependence is weak. The minimum drop radius predicted from thermodynamic considerations matches the prediction of the cluster model, though the former does not take into account the effect of the surface properties on the nucleation phenomena. For a chemically passive surface, the diffusion coefficient and the residence time are dependent on the surface texture via the coefficient of friction. Thus, physical texturing provides a means of changing, within limits, the minimum drop radius. The study reveals that surface texturing at the scale of the minimum drop radius does not provide controllability of the macro-scale dropwise condensation at large timescales when a dynamic steady-state is reached.« less

Laboratory constraints on models of earthquake recurrence

USGS Publications Warehouse

Beeler, Nicholas M.; Tullis, Terry; Junger, Jenni; Kilgore, Brian D.; Goldsby, David L.

2014-01-01

In this study, rock friction ‘stick-slip’ experiments are used to develop constraints on models of earthquake recurrence. Constant-rate loading of bare rock surfaces in high quality experiments produces stick-slip recurrence that is periodic at least to second order. When the loading rate is varied, recurrence is approximately inversely proportional to loading rate. These laboratory events initiate due to a slip rate-dependent process that also determines the size of the stress drop [Dieterich, 1979; Ruina, 1983] and as a consequence, stress drop varies weakly but systematically with loading rate [e.g., Gu and Wong, 1991; Karner and Marone, 2000; McLaskey et al., 2012]. This is especially evident in experiments where the loading rate is changed by orders of magnitude, as is thought to be the loading condition of naturally occurring, small repeating earthquakes driven by afterslip, or low-frequency earthquakes loaded by episodic slip. As follows from the previous studies referred to above, experimentally observed stress drops are well described by a logarithmic dependence on recurrence interval that can be cast as a non-linear slip-predictable model. The fault’s rate dependence of strength is the key physical parameter. Additionally, even at constant loading rate the most reproducible laboratory recurrence is not exactly periodic, unlike existing friction recurrence models. We present example laboratory catalogs that document the variance and show that in large catalogs, even at constant loading rate, stress drop and recurrence co-vary systematically. The origin of this covariance is largely consistent with variability of the dependence of fault strength on slip rate. Laboratory catalogs show aspects of both slip and time predictability and successive stress drops are strongly correlated indicating a ‘memory’ of prior slip history that extends over at least one recurrence cycle.

Rolling viscous drops on a non-wettable surface containing both micro- and macro-scale roughness

NASA Astrophysics Data System (ADS)

Abolghasemibizaki, Mehran; Robertson, Connor J.; Fergusson, Christian P.; McMasters, Robert L.; Mohammadi, Reza

2018-02-01

It has previously been shown that when a liquid drop of high viscosity is placed on a non-wettable inclined surface, it rolls down at a constant descent velocity determined by the balance between viscous dissipation and the reduction rate of its gravitational potential energy. Since increasing the roughness of the surface boosts its non-wetting property, the drop should move faster on a surface structured with macrotextures (ribbed surface). Such a surface was obtained from a superhydrophobic soot coating on a solid specimen printed with an extruder-type 3D printer. The sample became superoleophobic after a functionalization process. The descent velocity of glycerol drops of different radii was then measured on the prepared surface for varied tilting angles. Our data show that the drops roll down on the ribbed surface approximately 27% faster (along the ridges) than on the macroscopically smooth counterpart. This faster velocity demonstrates that ribbed surfaces can be promising candidates for drag-reduction and self-cleaning applications. Moreover, we came up with a modified scaling model to predict the descent velocity of viscous rolling drops more accurately than what has previously been reported in the literature.

Liquid toroidal drop under uniform electric field

NASA Astrophysics Data System (ADS)

Zabarankin, Michael

2017-06-01

The problem of a stationary liquid toroidal drop freely suspended in another fluid and subjected to an electric field uniform at infinity is addressed analytically. Taylor's discriminating function implies that, when the phases have equal viscosities and are assumed to be slightly conducting (leaky dielectrics), a spherical drop is stationary when Q=(2R2+3R+2)/(7R2), where R and Q are ratios of the phases' electric conductivities and dielectric constants, respectively. This condition holds for any electric capillary number, CaE, that defines the ratio of electric stress to surface tension. Pairam and Fernández-Nieves showed experimentally that, in the absence of external forces (CaE=0), a toroidal drop shrinks towards its centre, and, consequently, the drop can be stationary only for some CaE>0. This work finds Q and CaE such that, under the presence of an electric field and with equal viscosities of the phases, a toroidal drop having major radius ρ and volume 4π/3 is qualitatively stationary-the normal velocity of the drop's interface is minute and the interface coincides visually with a streamline. The found Q and CaE depend on R and ρ, and for large ρ, e.g. ρ≥3, they have simple approximations: Q˜(R2+R+1)/(3R2) and CaE∼3 √{3 π ρ / 2 } (6 ln ⁡ρ +2 ln ⁡[96 π ]-9 )/ (12 ln ⁡ρ +4 ln ⁡[96 π ]-17 ) (R+1 ) 2/ (R-1 ) 2.

The role of jet and film drops in controlling the mixing state of submicron sea spray aerosol particles

NASA Astrophysics Data System (ADS)

Wang, Xiaofei; Deane, Grant B.; Moore, Kathryn A.; Ryder, Olivia S.; Stokes, M. Dale; Beall, Charlotte M.; Collins, Douglas B.; Santander, Mitchell V.; Burrows, Susannah M.; Sultana, Camille M.; Prather, Kimberly A.

2017-07-01

The oceans represent a significant global source of atmospheric aerosols. Sea spray aerosol (SSA) particles comprise sea salts and organic species in varying proportions. In addition to size, the overall composition of SSA particles determines how effectively they can form cloud droplets and ice crystals. Thus, understanding the factors controlling SSA composition is critical to predicting aerosol impacts on clouds and climate. It is often assumed that submicrometer SSAs are mainly formed by film drops produced from bursting bubble-cap films, which become enriched with hydrophobic organic species contained within the sea surface microlayer. In contrast, jet drops formed from the base of bursting bubbles are postulated to mainly produce larger supermicrometer particles from bulk seawater, which comprises largely salts and water-soluble organic species. However, here we demonstrate that jet drops produce up to 43% of total submicrometer SSA number concentrations, and that the fraction of SSA produced by jet drops can be modulated by marine biological activity. We show that the chemical composition, organic volume fraction, and ice nucleating ability of submicrometer particles from jet drops differ from those formed from film drops. Thus, the chemical composition of a substantial fraction of submicrometer particles will not be controlled by the composition of the sea surface microlayer, a major assumption in previous studies. This finding has significant ramifications for understanding the factors controlling the mixing state of submicrometer SSA particles and must be taken into consideration when predicting SSA impacts on clouds and climate.

Relationship of Topside Ionospheric Ion Outflows to Auroral Forms and Precipitations, Plasma Waves, and Convection Observed by POLAR

NASA Technical Reports Server (NTRS)

Hirahara, M.; Horwitz, J. L.; Moore, T. E.; Germany, G. A.; Spann, J. F.; Peterson, W. K.; Shelley, E. G.; Chandler, M. O.; Giles, B. L.; Craven, P. D.;

Relationship of Topside Ionospheric Ion Outflows to Auroral Forms and Precipitation, Plasma Waves, and Convection Observed by Polar

NASA Technical Reports Server (NTRS)

Hirahara, M.; Horwitz, J. L.; Moore, T. E.; Germany, G. A.; Spann, J. F.; Peterson, W. K.; Shelley, E. G.; Chandler, M. O.; Giles, B. L.; Craven, P. D.;

Vlasov simulations of electron hole dynamics in inhomogeneous magnetic field

NASA Astrophysics Data System (ADS)

Kuzichev, Ilya; Vasko, Ivan; Agapitov, Oleksiy; Mozer, Forrest; Artemyev, Anton

2017-04-01

Electron holes (EHs) or phase space vortices are solitary electrostatic waves existing due to electrons trapped within EH electrostatic potential. Since the first direct observation [1], EHs have been widely observed in the Earth's magnetosphere: in reconnecting current sheets [2], injection fronts [3], auroral region [4], and many other space plasma systems. EHs have typical spatial scales up to tens of Debye lengths, electric field amplitudes up to hundreds of mV/m and propagate along magnetic field lines with velocities of about electron thermal velocity [5]. The role of EHs in energy dissipation and supporting of large-scale potential drops is under active investigation. The accurate interpretation of spacecraft observations requires understanding of EH evolution in inhomogeneous plasma. The critical role of plasma density gradients in EH evolution was demonstrated in [6] using PIC simulations. Interestingly, up to date no studies have addressed a role of magnetic field gradients in EH evolution. In this report, we use 1.5D gyrokinetic Vlasov code to demonstrate the critical role of magnetic field gradients in EH dynamics. We show that EHs propagating into stronger (weaker) magnetic field are decelerated (accelerated) with deceleration (acceleration) rate dependent on the magnetic field gradient. Remarkably, the reflection points of decelerating EHs are independent of the average magnetic field gradient in the system and depend only on the EH parameters. EHs are decelerated (accelerated) faster than would follow from the "quasi-particle" concept assuming that EH is decelerated (accelerated) entirely due to the mirror force acting on electrons trapped within EH. We demonstrate that EH propagation in inhomogeneous magnetic fields results in development of a net potential drop along an EH, which depends on the magnetic field gradient. The revealed features will be helpful for interpreting spacecraft observations and results of advanced particle simulations. In particular, our simulations suggest that slow EHs (which generation is usually attributed to the Buneman instability) can arise due to slowing down of fast EH generated by electron-beam instability. The estimate of the potential drop along EHs allow to estimate the parallel potential drop provided by EHs in a particular plasma system. 1. Matsumoto, H., H. Kojima, T. Miyatake, Y. Omura, M. Okada, I. Nagano, and M. Tsutsui, Electrotastic Solitary Waves (ESW) in the magnetotail: BEN wave forms observed by GEOTAIL, Geophys. Res. Lett., 21, 2915-2918, doi:10.1029/94GL01284, 1994. 2. Norgren, C., M. Andŕe, A. Vaivads, and Y. V. Khotyaintsev, Slow electron phase space holes: Magnetotail observations, Geophys. Res. Lett., 42, 1654-1661, doi:10.1002/2015GL063218, 2015. 3. Malaspina, D. M., J. R. Wygant, R. E. Ergun, G. D. Reeves, R. M. Skoug, and B. A. Larsen, Electric field structures and waves at plasma boundaries in the inner magnetosphere, Journal of Geophysical Research (Space Physics), 120, 4246-4263, doi:10.1002/2015JA021137, 2015. 4. Franz, J. R., P. M. Kintner, J. S. Pickett, and L.-J. Chen, Properties of small-amplitude electron phase-space holes observed by Polar, Journal of Geophysical Research (Space Physics), 110, A09212, doi:10.1029/2005JA011095, 2005. 5. Cattell, C., C. Neiman, J. Dombeck, J. Crumley, J. Wygant, C. A. Kletzing, W. K. Peterson, F. S. Mozer, and M. André (2003), Large amplitude solitary waves in and near the Earth's magnetosphere, magnetopause and bow shock: Polar and Cluster observations, Nonlinear Processes Geophys., 10, 13-26. 6. Mandrake, L., P. L. Pritchett, and F. V. Coroniti, Electron beam generated solitary structures in a nonuniform plasma system, Geophys. Res. Lett., 27, 2869-2872, doi:10.1029/2000GL003785, 2000. The work of I.K. was supported by Russian Foundation for Basic Research 16-32-00721 mol_a. The work of I.V., O.A. and F.M. was supported by JHU/APL contract 922613 (RBSPEFW).

X-ray diffraction analysis of Nb-3Ge and NbGe alloys

NASA Technical Reports Server (NTRS)

Davis, J. H.; House, K. W.

1983-01-01

Of all the A-15 samples of NbGe alloy examined, DT 094 is unique in that it was at least 99% pure A-15 phase. Also its diffraction peaks were noisy as if there were about a one percent compositional variation on this phase. DT 094, however, was only a large fragment of the drop tube drop, and thus its small sample size may have reduced the intensity, thus enhancing fluctuations enough to explain some of the loss of peak resolution.

Comparison of hemagglutination inhibition test and ELISA in quantification of antibodies to egg drop syndrome virus.

PubMed

Raj, G Dhinakar; Ratnapraba, S; Matheswaran, K; Nachimuthu, K

2004-01-01

A single-serum dilution ELISA for egg drop syndrome (EDS) virus-specific antibodies was developed. In testing 425 chicken sera it was found to have a 93.6% sensitivity and 98.7% specificity relative to a hemagglutination inhibition (HI) test. The correlation coefficient for ELISA and HI titers was 0.793. The ELISA was efficacious in quantification of both vaccinal and infection antibodies and could routinely be used for screening large numbers of field sera.

Film boiling of mercury droplets

NASA Technical Reports Server (NTRS)

Baumeister, K. J.; Schoessow, G. J.; Chmielewski, C. E.

1975-01-01

Vaporization times of mercury droplets in Leidenfrost film boiling on a flat horizontal plate are measured in an air atmosphere. Extreme care was used to prevent large amplitude droplet vibrations and surface wetting; therefore, these data can be compared to film boiling theory. Diffusion from the upper surface of the drop appears as a dominant mode of mass transfer from the drop. A closed-form analytical film boiling theory is developed to account for the diffusive evaporation. Reasonable agreement between data and theory is seen.

75 FR 49865 - Extension of Comment Period; Airplane and Engine Certification Requirements in Supercooled Large...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-16

... Ice Crystal Icing Conditions AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of... airplanes most affected by these icing conditions, mixed phase and ice crystal conditions for all transport category airplanes, and supercooled large drop, mixed phase, and ice crystal icing conditions for all...

Axial p-n-junctions in nanowires.

PubMed

Fernandes, C; Shik, A; Byrne, K; Lynall, D; Blumin, M; Saveliev, I; Ruda, H E

2015-02-27

The charge distribution and potential profile of p-n-junctions in thin semiconductor nanowires (NWs) were analyzed. The characteristics of screening in one-dimensional systems result in a specific profile with large electric field at the boundary between the n- and p- regions, and long tails with a logarithmic drop in the potential and charge density. As a result of these tails, the junction properties depend sensitively on the geometry of external contacts and its capacity has an anomalously large value and frequency dispersion. In the presence of an external voltage, electrons and holes in the NWs can not be described by constant quasi-Fermi levels, due to small values of the average electric field, mobility, and lifetime of carriers. Thus, instead of the classical Sah-Noice-Shockley theory, the junction current-voltage characteristic was described by an alternative theory suitable for fast generation-recombination and slow diffusion-drift processes. For the non-uniform electric field in the junction, this theory predicts the forward branch of the characteristic to have a non-ideality factor η several times larger than the values 1 < η < 2 from classical theory. Such values of η have been experimentally observed by a number of researchers, as well as in the present work.

Study of ion-ion plasma formation in negative ion sources by a three-dimensional in real space and three-dimensional in velocity space particle in cell model

NASA Astrophysics Data System (ADS)

Nishioka, S.; Goto, I.; Miyamoto, K.; Hatayama, A.; Fukano, A.

2016-01-01

Recently, in large-scale hydrogen negative ion sources, the experimental results have shown that ion-ion plasma is formed in the vicinity of the extraction hole under the surface negative ion production case. The purpose of this paper is to clarify the mechanism of the ion-ion plasma formation by our three dimensional particle-in-cell simulation. In the present model, the electron loss along the magnetic filter field is taken into account by the " √{τ///τ⊥ } model." The simulation results show that the ion-ion plasma formation is due to the electron loss along the magnetic filter field. Moreover, the potential profile for the ion-ion plasma case has been looked into carefully in order to discuss the ion-ion plasma formation. Our present results show that the potential drop of the virtual cathode in front of the plasma grid is large when the ion-ion plasma is formed. This tendency has been explained by a relationship between the virtual cathode depth and the net particle flux density at the virtual cathode.

Interactions Forces and the Flow-Induced Coalescence of Drops and Bubbles

NASA Technical Reports Server (NTRS)

Leal, L. Gary; Israelachvili, J.

2004-01-01

In order to accomplish the proposed macroscale experimental goals, we designed and built a pair of miniaturized computer-controlled four-roll mills, similar but much smaller than the 4-roll mill that had been develop earlier in Prof. Leal's group for studies of drop deformation and breakup. This unique experimental facility allows for controlled experiments on the breakup and coalescence of very small drops in the size range of 20-200 micrometers in diameter for a wide variety of flows and under a wide range of flow conditions including time-dependent flows, etc. The small size of this device is necessary for coalescence studies, since coalescence occurs in viscous fluids at capillary numbers that are large enough to be experimentally accessible only for drops that are smaller than approximately 100_m in diameter. Using these miniaturized 4-roll mills, we have obtained the first quantitative data (so far as we are aware) on the flow-induced coalescence process.

Time-Dependent Liquid Transport on a Biomimetic Topological Surface.

PubMed

Yu, Cunlong; Li, Chuxin; Gao, Can; Dong, Zhichao; Wu, Lei; Jiang, Lei

2018-05-02

Liquid drops impacting on a solid surface is a familiar phenomenon. On rainy days, it is quite important for leaves to drain off impacting raindrops. Water can bounce off or flow down a water-repellent leaf easily, but with difficulty on a hydrophilic leaf. Here, we show an interesting phenomenon in which impacting drops on the hydrophilic pitcher rim of Nepenthes alata can spread outward to prohibit water filling the pitcher tank. We mimic the peristome surface through a designed 3D printing and replicating way and report a time-dependently switchable liquid transport based on biomimetic topological structures, where surface curvature can work synergistically with the surface microtextures to manipulate the switchable spreading performance. Motived by this strange behavior, we construct a large-scaled peristome-mimetic surface in a 3D profile, demonstrating the ability to reduce the need to mop or to squeegee drops that form during the drop impacting process on pipes or other curved surfaces in food processing, moisture transfer, heat management, etc.

Modeling of Schottky Barrier Modulation due to Oxidation at Metallic Electrode and Semiconducting Carbon Nanotube Junction

NASA Technical Reports Server (NTRS)

Yamada, Toshishige; Biegel, Bryan (Technical Monitor)

2003-01-01

A model is proposed for the previously reported lower Schottky barrier for holes PHI (sub bH) in air than in vacuum at a metallic electrode - semiconducting carbon nanotube (CNT) junction. We assume that there is a transition region between the electrode and the CNT, and an appreciable potential can drop there. The role of the oxidation is to increase this potential drop with negatively charged oxygen molecules on the CNT, leading to lower PHI(sub Bh) after oxidation. The mechanism prevails in both p- and n-CNTs, and the model consistently explains the key experimental findings.

Effective Ion Heating in Guide Field Reconnection

NASA Astrophysics Data System (ADS)

Guo, Xuehan; Horiuchi, Ritoku; Usami, Shunsuke; Ono, Yasushi

2017-10-01

The energy conversion mechanism for ion perpendicular thermal energy is investigated by means of two-dimensional, full particle simulations in an open system. It is shown that ions gain kinetic energy due to the plasma potential drop, which is caused by the charge separation in the one pair of separatrix arms. Based on the force balance in the inflow direction, the strength of the normalized charge density can be expressed by electron Alfvén velocity, which is measurable value in the laboratory experiment and/or satellite observation. Meanwhile, we found that the accelerated ions form a ring shape like distribution in f(v1 ,v2) , as a result, the ion perpendicular temperature Ti , perp increases from inflow region. Here, both v1 and v2 are perpendicular to the magnetic field and v2 is parallel to the in-plane. The mixing of particle populations is verified by means of tracing ions and it is shown three typical particle orbits and each orbit has different entry angle to the potential drop. This ring shape like distribution consists three different population due to the difference of the entry angles to the potential drop. This mixing process will thermalize ions and produce entropy without collisions.

Nonlinear Dynamics of Formation of Drops of Non-Newtonian Liquids from Capillaries: Satellite Formation and Flow Transitions

NASA Astrophysics Data System (ADS)

Yildirim, Ozgur E.; Basaran, Osman A.

1999-11-01

Drop formation from capillaries, and the often undesired phenomenon of satellite generation, play a central role in diverse applications including ink-jet printing, biochip processors, and spray coating, where the working fluid is usually non-Newtonian. Although some work has been done in related areas, the phenomenon of formation of drops of non--Newtonian fluids from capillaries has remained largely unexplored. Here a theoretical approach is adopted to study the dripping of axisymmetric drops of non--Newtonian liquids from capillaries. The constitutive equation used accounts for both shear thinning and strain hardening. First, regular perturbation theory is utilized to reduce the spatial dimension of the governing equations to one. The computations rely on Galerkin/finite element analysis with adaptive finite differencing for time integration. The dynamics are followed beyond the first breakup to investigate conditions for occurrence of satellites. Effect of increasing flow rate is also studied to uncover transitions that occur as one moves from a regime of periodic drop formation to one of jetting.

Is drop impact the same for both moving and inclined surfaces?

NASA Astrophysics Data System (ADS)

Buksh, Salman; Marengo, Marco; Amirfazli, Alidad; -Team

2017-11-01

Drop impact is an important phenomenon in a wide variety of applications. Researchers have largely examined drop impact onto a moving surface, and an inclined surface separately. Given that in both systems the impact phenomenon is influenced by tangential and normal velocity components, the question remains, if these two systems are essentially equivalent or gravity and boundary layer effects are such that the outcomes will be different. Experiments have been performed by varying liquid surface tension, viscosity and both normal and tangential velocities (0.3 to 2.9 m/s). The desired velocity components were achieved by changing the height where drop is released, the surface inclination angle for inclined system, and the horizontal velocity for the moving surface. To compare the systems, spreading was analyzed by measuring the width and length of the lamella at various time intervals; for splashing, top view images were compared to see the extent of splashing at initial stage. The data suggests that, for the given velocity, neither the boundary layer differences between the two systems nor the gravity play a role on spreading and splashing of the drop, as such one system can replace the other for future studies.

A new approach to stability and oscillations of constrained drops and capillary bridges

NASA Astrophysics Data System (ADS)

Fabre, David; Chireux, Veronique; Risso, Frederic; Tordjeman, Philippe

2014-11-01

Static equilibria of liquid inclusions under the effect of gravity and capillarity is a large class of situations which encompasses drops hanging from a ceiling or from a capillary, sessile drops, liquid bridges, etc... In such equilibria the surface shape is governed by the Yong-Laplace equation, which is usually solved in a local way using a ``shooting'' method. We introduce a new method which solves the Laplace-Young in a global way, using an iterative deformation of the shape towards the equilibrium shape. The method is easy to implement and versatile, and allows to prescribe constraints such as the volume of liquid, the angle of attachment, etc... We subsequently consider the issue of stability and oscillations of such configurations. Using finite elements and considering small-amplitude displacements of the surface with respect to the static configuration previously computed, we introduce a global stability approach which allows to predict the stability limits, the oscillation frequencies and the eigenmode shapes for quite general geometries. The approach will be illustrated and compared with experiments in two situations, namely a drop attached to a capilary and a liquid bridge resulting from the coalescence of two facing millimetric drops.

Water collection behavior and hanging ability of bioinspired fiber.

PubMed

Hou, Yongping; Chen, Yuan; Xue, Yan; Zheng, Yongmei; Jiang, Lei

2012-03-13

Since the water-collecting ability of the wetted cribellate spider capture silk is the result of a unique fiber structure, bioinspired fibers have been researched significantly so as to expose a new water-acquiring route in fogging-collection projects. However, the design of the geometry of bioinspired fiber is related to the ability of hanging drops, which has not been investigated in depth so far. Here, we fabricate bioinspired fibers to investigate the water collection behavior and the influence of geometry (i.e., periodicity of spindle knot) on the hanging-drop ability. We especially discuss water collection related to the periodicity of geometry on the bioinspired fiber. We reveal the length of the three phase contact line (TCL) at threshold conditions in conjunction with the maximal volume of a hanging drop at different modes. The study demonstrates that the geometrical structure of bioinspired fiber induces much stronger water hanging ability than that of uniform fiber, attributed to such special geometry that offers effectively an increasing TCL length or limits the contact length to be shorted. In addition, the geometry also improves the fog-collection efficiency by controlling tiny water drops to be collected in the large water drops at a given location.

The initial regime of drop coalescence

NASA Astrophysics Data System (ADS)

Anthony, Christopher; Harris, Michael; Basaran, Osman

2017-11-01

Drop coalescence plays a key role in both industry and nature. Consequently, study of the phenomenon has been the focus of numerous experimental, computational and theoretical works to date. In coalescence, two drops come into contact and a liquid bridge forms between them. As time advances, this bridge grows from microscopic to macroscopic scales. Despite the large volume of work dedicated to this problem, currently experiment, theory, and computation are not in perfect agreement with respect to the earliest times following the initial contact of the drops. Experiments report an initial regime where the radius of the connecting bridge grows linearly in time before a transition to either a Stokes regime or an inertial regime where either viscous or inertial forces balance capillary force. In the initial linear regime, referred to as the inertially-limited viscous regime, all three forces are thought to be important. This is in contrast to theory which predicts that all coalescence events begin in the Stokes regime. We use high accuracy numerical simulation to show that the existing discrepancy in the literature can be resolved by paying careful attention to the initial conditions that set the shape and size of the bridge connecting the two drops.

Drop Shapes Versus Fall Velocities in Rain: 2 Contrasting Examples

NASA Technical Reports Server (NTRS)

Thurai, M.; Bringi, V. N.; Petersen, W. A.; Carey, L. D.; Gatlin, P. N.; Tokay, A.

2011-01-01

Rainfall retrievals from polarimetric radar measurements require the knowledge of four fundamental rain microstructure parameters, namely, drop size distribution, drop shape distribution, canting angles and drop fall velocities. Some recent measurements of all four parameters in natural rain are summarized in [1]. In this paper, we perform an in-depth analysis of two events, using two co-located 2D video disdrometers (2DVD; see [2]) both with high calibration accuracy, and a C-band polarimetric radar [3], located 15 km away. The two events, which occurred 7 days apart (on the 18th and the 25th of Dec 2009), had moderate-to-intense rainfall rates, but the second event had an embedded convection line within the storm. The line had passed over the 2DVD site, thus enabling the shapes and fall velocities to be determined as the line crossed the site. The first event was also captured in a similar manner by both the 2DVDs as well as the C-band radar. Drop fall velocity measurements for, say, the 3 mm drops show noticeable differences between the two events. Whereas for the first event, the velocity distribution showed a narrow and symmetric distribution, with a mode at the expected value (7.95 m/s, as given by the formula in [4]), the second event produced a wider distribution with a significant skewness towards lower velocities (although its mode too was close to the expected value). Moreover, the slower 3 mm drops in the second event occurred when the convection line was directly over the 2DVD site (03:35-03:45 utc), and not before nor after. A similar trend was observed in terms of the horizontal dimensions of the 3 mm drops, i.e. large fluctuations during the same time period, but not outside the period. Vertical dimensions of the drops also fluctuated but not to the same extent. Interestingly, the horizontal dimensions tended towards larger values during the 10-minute period, implying an increase in drop oblateness, which in turn indicates the possibility of the horizontal mode oscillation, one of the three fundamental modes of drop oscillations [5], albeit the most difficult one to excite.

Observational constraints on earthquake source scaling: Understanding the limits in resolution

USGS Publications Warehouse

Hough, S.E.

1996-01-01

I examine the resolution of the type of stress drop estimates that have been used to place observational constraints on the scaling of earthquake source processes. I first show that apparent stress and Brune stress drop are equivalent to within a constant given any source spectral decay between ??1.5 and ??3 (i.e., any plausible value) and so consistent scaling is expected for the two estimates. I then discuss the resolution and scaling of Brune stress drop estimates, in the context of empirical Green's function results from recent earthquake sequences, including the 1992 Joshua Tree, California, mainshock and its aftershocks. I show that no definitive scaling of stress drop with moment is revealed over the moment range 1019-1025; within this sequence, however, there is a tendency for moderate-sized (M 4-5) events to be characterized by high stress drops. However, well-resolved results for recent M > 6 events are inconsistent with any extrapolated stress increase with moment for the aftershocks. Focusing on comer frequency estimates for smaller (M < 3.5) events, I show that resolution is extremely limited even after empirical Green's function deconvolutions. A fundamental limitation to resolution is the paucity of good signal-to-noise at frequencies above 60 Hz, a limitation that will affect nearly all surficial recordings of ground motion in California and many other regions. Thus, while the best available observational results support a constant stress drop for moderate-to large-sized events, very little robust observational evidence exists to constrain the quantities that bear most critically on our understanding of source processes: stress drop values and stress drop scaling for small events.

Usage of drip drops as stimuli in an auditory P300 BCI paradigm.

PubMed

Huang, Minqiang; Jin, Jing; Zhang, Yu; Hu, Dewen; Wang, Xingyu

2018-02-01

Recently, many auditory BCIs are using beeps as auditory stimuli, while beeps sound unnatural and unpleasant for some people. It is proved that natural sounds make people feel comfortable, decrease fatigue, and improve the performance of auditory BCI systems. Drip drop is a kind of natural sounds that makes humans feel relaxed and comfortable. In this work, three kinds of drip drops were used as stimuli in an auditory-based BCI system to improve the user-friendness of the system. This study explored whether drip drops could be used as stimuli in the auditory BCI system. The auditory BCI paradigm with drip-drop stimuli, which was called the drip-drop paradigm (DP), was compared with the auditory paradigm with beep stimuli, also known as the beep paradigm (BP), in items of event-related potential amplitudes, online accuracies and scores on the likability and difficulty to demonstrate the advantages of DP. DP obtained significantly higher online accuracy and information transfer rate than the BP ( p  < 0.05, Wilcoxon signed test; p  < 0.05, Wilcoxon signed test). Besides, DP obtained higher scores on the likability with no significant difference on the difficulty ( p  < 0.05, Wilcoxon signed test). The results showed that the drip drops were reliable acoustic materials as stimuli in an auditory BCI system.

Droplets move over viscoelastic substrates by surfing a ridge

PubMed Central

Karpitschka, S.; Das, S.; van Gorcum, M.; Perrin, H.; Andreotti, B.; Snoeijer, J. H.

2015-01-01

Liquid drops on soft solids generate strong deformations below the contact line, resulting from a balance of capillary and elastic forces. The movement of these drops may cause strong, potentially singular dissipation in the soft solid. Here we show that a drop on a soft substrate moves by surfing a ridge: the initially flat solid surface is deformed into a sharp ridge whose orientation angle depends on the contact line velocity. We measure this angle for water on a silicone gel and develop a theory based on the substrate rheology. We quantitatively recover the dynamic contact angle and provide a mechanism for stick–slip motion when a drop is forced strongly: the contact line depins and slides down the wetting ridge, forming a new one after a transient. We anticipate that our theory will have implications in problems such as self-organization of cell tissues or the design of capillarity-based microrheometers. PMID:26238436

Green chemistry and nanofabrication in a levitated Leidenfrost drop

NASA Astrophysics Data System (ADS)

Abdelaziz, Ramzy; Disci-Zayed, Duygu; Hedayati, Mehdi Keshavarz; Pöhls, Jan-Hendrik; Zillohu, Ahnaf Usman; Erkartal, Burak; Chakravadhanula, Venkata Sai Kiran; Duppel, Viola; Kienle, Lorenz; Elbahri, Mady

2013-10-01

Green nanotechnology focuses on the development of new and sustainable methods of creating nanoparticles, their localized assembly and integration into useful systems and devices in a cost-effective, simple and eco-friendly manner. Here we present our experimental findings on the use of the Leidenfrost drop as an overheated and charged green chemical reactor. Employing a droplet of aqueous solution on hot substrates, this method is capable of fabricating nanoparticles, creating nanoscale coatings on complex objects and designing porous metal in suspension and foam form, all in a levitated Leidenfrost drop. As examples of the potential applications of the Leidenfrost drop, fabrication of nanoporous black gold as a plasmonic wideband superabsorber, and synthesis of superhydrophilic and thermal resistive metal-polymer hybrid foams are demonstrated. We believe that the presented nanofabrication method may be a promising strategy towards the sustainable production of functional nanomaterials.

Green chemistry and nanofabrication in a levitated Leidenfrost drop

PubMed Central

Abdelaziz, Ramzy; Disci-Zayed, Duygu; Hedayati, Mehdi Keshavarz; Pöhls, Jan-Hendrik; Zillohu, Ahnaf Usman; Erkartal, Burak; Chakravadhanula, Venkata Sai Kiran; Duppel, Viola; Kienle, Lorenz; Elbahri, Mady

2013-01-01

Green nanotechnology focuses on the development of new and sustainable methods of creating nanoparticles, their localized assembly and integration into useful systems and devices in a cost-effective, simple and eco-friendly manner. Here we present our experimental findings on the use of the Leidenfrost drop as an overheated and charged green chemical reactor. Employing a droplet of aqueous solution on hot substrates, this method is capable of fabricating nanoparticles, creating nanoscale coatings on complex objects and designing porous metal in suspension and foam form, all in a levitated Leidenfrost drop. As examples of the potential applications of the Leidenfrost drop, fabrication of nanoporous black gold as a plasmonic wideband superabsorber, and synthesis of superhydrophilic and thermal resistive metal–polymer hybrid foams are demonstrated. We believe that the presented nanofabrication method may be a promising strategy towards the sustainable production of functional nanomaterials. PMID:24169567

Droppings From Captive Coturnix coturnix (Galliformes: Phasianidae) as a Fly Breeding Resource

PubMed Central

Horenstein, M. Battán; Lynch-Ianniello, I.; de Dio, B.; Gleiser, R. M.

2014-01-01

Abstract The aim of this study was to describe the fauna of flies associated with captive Coturnix coturnix (L.) (Galliformes: Phasianidae) droppings. Samples of 150 g of quail droppings were exposed in the quail house for 48 h in plastic containers to promote eventual access of flies, and then placed in emergence traps. The number of adults and species emerging was recorded daily. This procedure was carried out in spring 2008 and spring and autumn 2009. In total, 2,138 adults belonging to Muscidae, Calliphoridae, Piophilidae, Phoridae, Fanniidae, and Milichiidae families were collected. The most numerous family was Muscidae (representing >82% of the total specimens), with Musca domestica L. being the most abundant species followed by Ophyra aenescens (Wiedemann) (both Diptera: Muscidae). Quail breeding should include adequate droppings management policies to avoid potential sanitary issues related to fly production. PMID:25347840

Spume Drops: Their Potential Role in Air-Sea Gas Exchange

NASA Astrophysics Data System (ADS)

Monahan, Edward C.; Staniec, Allison; Vlahos, Penny

2017-12-01

After summarizing the time scales defining the change of the physical properties of spume and other droplets cast up from the sea surface, the time scales governing drop-atmosphere gas exchange are compared. Following a broad review of the spume drop production functions described in the literature, a subset of these functions is selected via objective criteria, to represent typical, upper bound, and lower bound production functions. Three complementary mechanisms driving spume-atmosphere gas exchange are described, and one is then used to estimate the relative importance, over a broad range of wind speeds, of this spume drop mechanism compared to the conventional, diffusional, sea surface mechanism in air-sea gas exchange. While remaining uncertainties in the wind dependence of the spume drop production flux, and in the immediate sea surface gas flux, preclude a definitive conclusion, the findings of this study strongly suggest that, at high wind speeds (>20 m s-1 for dimethyl sulfide and >30 m s-1 for gases such a carbon dioxide), spume drops do make a significant contribution to air-sea gas exchange.