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.

A sliding technique to load thin endothelial donor lamella onto Busin glide for Descemet-stripping automated endothelial keratoplasty

PubMed Central

Kobayashi, Akira; Yokogawa, Hideaki; Sugiyama, Kazuhisa

2012-01-01

We describe a modified technique for loading donor corneal endothelial lamella onto a Busin glide® without causing wrinkles, as part of the procedure of Descemet-stripping automated endothelial keratoplasty. Briefly, after punching out a composite of the donor-endothelial lamella and a microkeratome-dissected cap, several drops of dispersive ophthalmic viscosurgical device are placed onto the endothelial surface. The Busin glide surface is then wetted with several drops of balanced salt solution. After the composite is transferred onto the Busin glide, hydrodissection of the potential space between the donor-endothelial lamella and the microkeratome-dissected cap is carefully performed to enable smooth detachment of these two lamellae. Whereas simply dragging the donor-endothelial lamella directly onto the glide can cause wrinkling or folding of the donor lamella, this technique enables smooth detachment of the composite without wrinkle or fold formation, and results in less endothelial cell damage. PMID:22927732

Electro-hydrodynamic printing of drugs onto edible substrates

NASA Astrophysics Data System (ADS)

Shen, Yueyang; Elele, Ezinwa; Palle, Prashanth; Khusid, Boris; Basaran, Osman; McGough, Patrick T.; Collins, Robert T.

2009-11-01

While most existing drugs are manufactured as tablets using powder processing techniques, there is growing interest in printing drops containing pharmaceutical actives on edible substrates. We have developed a drop-on-demand (DOD) printing method appropriate for either replacing existing manufacturing platforms or enabling personalized medicine that overcomes the various critical challenges facing current DOD technologies. To eliminate adverse effects of electro-chemical reactions at the fluid-electrode interface, the fluid is infused into an electrically insulating nozzle to form a pendant drop that serves as a floating electrode capacitively coupled to external electrodes. A liquid bridge is formed and broken as the voltage applied at the electrode is varied in time. This gentle method for drop deposition has been demonstrated to operate with fluids spanning over three orders of magnitude in viscosity and conductivity. The proposed method has the potential for the evolving field of pharmaceutical and biomedical applications requiring the deposition of fluids at the exact locations with high volume accuracy.

Unravelling the electrochemical double layer by direct probing of the solid/liquid interface

DOE PAGES

Favaro, Marco; Jeong, Beomgyun; Ross, Philip N.; ...

2016-08-31

The electrochemical double layer plays a critical role in electrochemical processes. Whilst there have been many theoretical models predicting structural and electrical organization of the electrochemical double layer, the experimental verification of these models has been challenging due to the limitations of available experimental techniques. The induced potential drop in the electrolyte has never been directly observed and verified experimentally, to the best of our knowledge. In this study, we report the direct probing of the potential drop as well as the potential of zero charge by means of ambient pressure X-ray photoelectron spectroscopy performed under polarization conditions. By analyzingmore » the spectra of the solvent (water) and a spectator neutral molecule with numerical simulations of the electric field, we discern the shape of the electrochemical double layer profile. In addition, we determine how the electrochemical double layer changes as a function of both the electrolyte concentration and applied potential.« less

Artificial tektites: an experimental technique for capturing the shapes of spinning drops

NASA Astrophysics Data System (ADS)

Baldwin, K. A.

2014-12-01

Tektites are small stones formed from rapidly cooling drops of molten rock ejected from high velocity asteroid impacts with the Earth, that freeze into a myriad of shapes during flight. Many splash-form tektites have an elongated or dumb-bell shape owing to their rotation prior to solidification[1]. Here we present a novel method for creating 'artificial tektites' from spinning drops of molten wax, using diamagnetic levitation to suspend the drops[2]. We find that the solid wax models produced this way are the stable equilibrium shapes of a spinning liquid droplet held together by surface tension. In addition to the geophysical interest in tektite formation, the stable equilibrium shapes of liquid drops have implications for many physical phenomena, covering a wide range of length scales, from nuclear physics (e.g. in studies of rapidly rotating atomic nuclei), to astrophysics (e.g. in studies of the shapes of astronomical bodies such as asteroids, rapidly rotating stars and event horizons of rotating black holes). For liquid drops bound by surface tension, analytical and numerical methods predict a series of stable equilibrium shapes with increasing angular momentum. Slowly spinning drops have an oblate-like shape. With increasing angular momentum these shapes become secularly unstable to a series of triaxial pseudo-ellipsoids that then evolve into a family of two-lobed 'dumb-bell' shapes as the angular momentum is increased still further. Our experimental method allows accurate measurements of the drops to be taken, which are useful to validate numerical models. This method has provided a means for observing tektite formation, and has additionally confirmed experimentally the stable equilibrium shapes of liquid drops, distinct from the equivalent shapes of rotating astronomical bodies. Potentially, this technique could be applied to observe the non-equilibrium dynamic processes that are also important in real tektite formation, involving, e.g. viscoelastic effects, non-uniform solidification, surface wrinkling (Schlieren), and rapid separation/fission of dumb-bells via the Rayleigh-Plateau instability. [1] M. R. Stauffer and S. L. Butler, Earth Moon Planets, 107, 169 (2009). [2] R. J. A. Hill and L. Eaves, Phys. Rev. Lett. 101, 234501 (2008).

The effects of flexion-distraction and drop techniques on disorders and Ferguson’s angle in female patients with lumbar intervertebral disc herniation

PubMed Central

Oh, Hyunju; Lee, Sangyong; Lee, Kwansub; Jeong, Mugeun

2018-01-01

[Purpose] This study examines the effects of the flexion-distraction technique and the drop technique on disorders and on Ferguson’s angle in female patients with lumbar intervertebral disc herniation. [Subjects and Methods] Thirty female patients with lumbar intervertebral disc herniation were divided into an experimental group (n=15) treated with flexion-distraction and drop techniques and a control group (n=15) treated with spinal decompression therapy. Both groups were treated three times a week over an eight-week period. [Results] In the comparison of changes within each group after treatment, both groups showed statistically significant decreases in disorders and in Ferguson’s angle. [Conclusion] Flexion-distraction and drop techniques may be an effective intervention to improve disorders and Ferguson’s angle in female patients with lumbar intervertebral disc herniation. PMID:29706701

Measurement of Aqueous Foam Rheology by Acoustic Levitation

NASA Technical Reports Server (NTRS)

McDaniel, J. Gregory; Holt, R. Glynn; Rogers, Rich (Technical Monitor)

2000-01-01

An experimental technique is demonstrated for acoustically levitating aqueous foam drops and exciting their spheroidal modes. This allows fundamental studies of foam-drop dynamics that provide an alternative means of estimating the viscoelastic properties of the foam. One unique advantage of the technique is the lack of interactions between the foam and container surfaces, which must be accounted for in other techniques. Results are presented in which a foam drop with gas volume fraction phi = 0.77 is levitated at 30 kHz and excited into its first quadrupole resonance at 63 +/- 3 Hz. By modeling the drop as an elastic sphere, the shear modulus of the foam was estimated at 75 +/- 3 Pa.

Acoustic levitation of liquid drops: Dynamics, manipulation and phase transitions.

PubMed

Zang, Duyang; Yu, Yinkai; Chen, Zhen; Li, Xiaoguang; Wu, Hongjing; Geng, Xingguo

2017-05-01

The technique of acoustic levitation normally produces a standing wave and the potential well of the sound field can be used to trap small objects. Since no solid surface is involved it has been widely applied for the study of fluid physics, nucleation, bio/chemical processes, and various forms of soft matter. In this article, we survey the works on drop dynamics in acoustic levitation, focus on how the dynamic behavior is related to the rheological properties and discuss the possibility to develop a novel rheometer based on this technique. We review the methods and applications of acoustic levitation for the manipulation of both liquid and solid samples and emphasize the important progress made in the study of phase transitions and bio-chemical analysis. We also highlight the possible open areas for future research. Copyright © 2017 Elsevier B.V. All rights reserved.

Ultrasonic Substrate Vibration-Assisted Drop Casting (SVADC) for the Fabrication of Photovoltaic Solar Cell Arrays and Thin-Film Devices.

PubMed

Eslamian, Morteza; Zabihi, Fatemeh

2015-12-01

A simple, low-cost, versatile, and potentially scalable casting method is proposed for the fabrication of micro- and nano-thin films, herein termed as ultrasonic "substrate vibration-assisted drop casting" (SVADC). The impingement of a solution drop onto a substrate in a simple process called drop casting, usually results in spreading of the liquid solution and the formation of a non-uniform thin solid film after solvent evaporation. Our previous and current supporting results, as well as few similar reports by others, confirm that imposing ultrasonic vibration on the substrate can simply convert the uncontrollable drop casting method into a controllable coating technique. Therefore, the SVADC may be used to fabricate an array of emerging thin-film solar cells, such as polymer, perovskite, and quantum-dot solar cells, as well as other small thin-film devices, in a roll-to-roll and automated fabrication process. The preliminary results demonstrate a ten-fold increase in electrical conductivity of PSS made by SVADC compared with the film made by conventional drop casting. Also, simple planar perovskite solar cells made here using SVADC show promising performance with an efficiency of over 3 % for a simple structure without performing process optimization or using expensive materials and treatments.

Drop-off detection with the long cane: effect of cane shaft weight and rigidity on performance

PubMed Central

Kim, Dae Shik; Emerson, Robert Wall; Naghshineh, Koorosh; Auer, Alexander

2016-01-01

Most travellers who are blind rely on a long cane to detect drop-offs on their walking paths. We examined how different cane shaft materials affect drop-off detection performance through providing different vibrotactile and proprioceptive feedbacks to the cane user. Results of the study showed a significant interaction between cane shaft weight and how the cane is used. A heavier cane was advantageous for detecting drop-offs when the individual used the ‘constant contact technique’ – cane tip stays in contact with the walking surface at all times – but not when he used the ‘two-point touch technique’ – cane tip is rhythmically tapped on the surface. In addition, a more flexible cane was advantageous for detecting drop-offs when the two-point touch technique was used but not when the constant contact technique was used. It is recommended that, when blind individuals select a cane shaft material, they consider which long cane technique they use more often. Practitioner Summary: Long cane shaft material affects how well a blind individual can detect drop-offs. A heavier shaft was advantageous when using the constant contact technique (cane tip stays in continuous contact with the surface), while a more flexible shaft was better when using the two-point touch technique (cane tip rhythmically taps the surface). PMID:27065052

Characterization and reproducibility of HepG2 hanging drop spheroids toxicology in vitro.

PubMed

Hurrell, Tracey; Ellero, Andrea Antonio; Masso, Zelie Flavienne; Cromarty, Allan Duncan

2018-02-21

Hepatotoxicity remains a major challenge in drug development despite preclinical toxicity screening using hepatocytes of human origin. To overcome some limitations of reproducing the hepatic phenotype, more structurally and functionally authentic cultures in vitro can be introduced by growing cells in 3D spheroid cultures. Characterisation and reproducibility of HepG2 spheroid cultures using a high-throughput hanging drop technique was performed and features contributing to potential phenotypic variation highlighted. Cultured HepG2 cells were seeded into Perfecta 3D® 96-well hanging drop plates and assessed over time for morphology, viability, cell cycle distribution, protein content and protein-mass profiles. Divergent aspects which were assessed included cell stocks, seeding density, volume of culture medium and use of extracellular matrix additives. Hanging drops are advantageous due to no complex culture matrix being present, enabling background free extractions for downstream experimentation. Varying characteristics were observed across cell stocks and batches, seeding density, culture medium volume and extracellular matrix when using immortalized HepG2 cells. These factors contribute to wide-ranging cellular responses and highlights concerns with respect to generating a reproducible phenotype in HepG2 hanging drop spheroids. Copyright © 2018 Elsevier Ltd. All rights reserved.

Proceedings of the Second International Colloquium on Drops and Bubbles

NASA Technical Reports Server (NTRS)

Lecroissette, D. H. (Editor)

1982-01-01

Applications of bubble and drop technologies are discussed and include: low gravity manufacturing, containerless melts, microballoon fabrication, ink printers, laser fusion targets, generation of organic glass and metal shells, and space processing. The fluid dynamics of bubbles and drops were examined. Thermomigration, capillary flow, and interfacial tension are discussed. Techniques for drop control are presented and include drop size control and drop shape control.

A Cost-effective and Reliable Method to Predict Mechanical Stress in Single-use and Standard Pumps

PubMed Central

Dittler, Ina; Dornfeld, Wolfgang; Schöb, Reto; Cocke, Jared; Rojahn, Jürgen; Kraume, Matthias; Eibl, Dieter

2015-01-01

Pumps are mainly used when transferring sterile culture broths in biopharmaceutical and biotechnological production processes. However, during the pumping process shear forces occur which can lead to qualitative and/or quantitative product loss. To calculate the mechanical stress with limited experimental expense, an oil-water emulsion system was used, whose suitability was demonstrated for drop size detections in bioreactors1. As drop breakup of the oil-water emulsion system is a function of mechanical stress, drop sizes need to be counted over the experimental time of shear stress investigations. In previous studies, the inline endoscopy has been shown to be an accurate and reliable measurement technique for drop size detections in liquid/liquid dispersions. The aim of this protocol is to show the suitability of the inline endoscopy technique for drop size measurements in pumping processes. In order to express the drop size, the Sauter mean diameter d32 was used as the representative diameter of drops in the oil-water emulsion. The results showed low variation in the Sauter mean diameters, which were quantified by standard deviations of below 15%, indicating the reliability of the measurement technique. PMID:26274765

Analysis of user characteristics related to drop-off detection with long cane

PubMed Central

Kim, Dae Shik; Emerson, Robert Wall; Curtis, Amy

2010-01-01

This study examined how user characteristics affect drop-off detection with the long cane. A mixed-measures design with block randomization was used for the study, in which 32 visually impaired adults attempted to detect the drop-offs using different cane techniques. Younger cane users detected drop-offs significantly more reliably (mean +/− standard deviation = 74.2% +/− 11.2% of the time) than older cane users (60.9% +/− 10.8%), p = 0.009. The drop-off detection threshold of the younger participants (5.2 +/− 2.1 cm) was also statistically significantly smaller than that of the older participants (7.9 +/− 2.2 cm), p = 0.007. Those with early-onset visual impairment (78.0% +/− 9.0%) also detected drop-offs significantly more reliably than those with later-onset visual impairment (67.3% +/− 12.4%), p = 0.01. No interaction occurred between examined user characteristics (age and age at onset of visual impairment) and the type of cane technique used in drop-off detection. The findings of the study may help orientation and mobility specialists select appropriate cane techniques in accordance with the cane user’s age and onset of visual impairment. PMID:20665349

Surface Tension Guided Hanging-Drop: Producing Controllable 3D Spheroid of High-Passaged Human Dermal Papilla Cells and Forming Inductive Microtissues for Hair-Follicle Regeneration.

PubMed

Lin, Bojie; Miao, Yong; Wang, Jin; Fan, Zhexiang; Du, Lijuan; Su, Yongsheng; Liu, Bingcheng; Hu, Zhiqi; Xing, Malcolm

2016-03-09

Human dermal papilla (DP) cells have been studied extensively when grown in the conventional monolayer. However, because of great deviation from the real in vivo three-dimensional (3D) environment, these two-dimensional (2D) grown cells tend to lose the hair-inducible capability during passaging. Hence, these 2D caused concerns have motivated the development of novel 3D culture techniques to produce cellular microtissues with suitable mimics. The hanging-drop approach is based on surface tension-based technique and the interaction between surface tension and gravity field that makes a convergence of liquid drops. This study used this technique in a converged drop to form cellular spheroids of dermal papilla cells. It leads to a controllable 3Dspheroid model for scalable fabrication of inductive DP microtissues. The optimal conditions for culturing high-passaged (P8) DP spheroids were determined first. Then, the morphological, histological and functional studies were performed. In addition, expressions of hair-inductive markers including alkaline phosphatase, α-smooth muscle actin and neural cell adhesion molecule were also analyzed by quantitative RT-PCR, immunostaining and immunoblotting. Finally, P8-DP microtissues were coimplanted with newborn mouse epidermal cells (EPCs) into nude mice. Our results indicated that the formation of 3D microtissues not only endowed P8-DP microtissues many similarities to primary DP, but also confer these microtissues an enhanced ability to induce hair-follicle (HF) neogenesis in vivo. This model provides a potential to elucidate the native biology of human DP, and also shows the promising for the controllable and scalable production of inductive DP cells applied in future follicle regeneration.

Culturing muscle fibres in hanging drop: a novel approach to solve an old problem.

PubMed

Archacka, Karolina; Pozzobon, Michela; Repele, Andrea; Rossi, Carlo Alberto; Campanella, Michelangelo; De Coppi, Paolo

2014-02-01

The satellite cells (SCs) associated with muscle fibres play a key role in postnatal growth and regeneration of skeletal muscle. Commonly used methods of isolation and in vitro culture of SCs lead to the mixture of their subpopulations that exist within muscle. To solve this problem, we used the well established technique, the hanging drop system, to culture SCs in a three-dimensional environment and thus, to monitor them in their original niche. Using hanging drop technique, we were able to culture SCs associated with the fibre at least for 9 days with one transfer of fibres to the fresh drops. In comparison, in the classical method of myofibres culture, that is, on the dishes coated with Matrigel, SCs leave the fibres within 3 days after the isolation. Cells cultured in both systems differed in expression of Pax7 and MyoD. While almost all cells cultured in adhesion system expressed MyoD before the fifth day of the culture, the majority of SCs cultured in hanging drop still maintained expression of Pax7 and were not characterised by the presence of MyoD. Among the cells cultured with single myofibre for up to 9 days, we identified two different subclones of SCs: low proliferative clone and high proliferative clone, which differed in proliferation rate and membrane potential. The hanging drop enables the myofibres to be kept in suspension for at least 9 days, and thus, allows SCs and their niche to interact each other for prolonged time. In a consequence, SCs cultured in hanging drop maintain expression of Pax7 while those cultured in a traditional adhesion culture, that is, devoid of signals from the original niche, activate and preferentially undergo differentiation as manifested by expression of MyoD. Thus, the innovative method of SCs culturing in the hanging drop system may serve as a useful tool to study the fate of different subpopulations of these cells in their anatomical location and to determine reciprocal interactions between them and their niche. © 2013 Société Française des Microscopies and Société de Biologie Cellulaire de France. Published by John Wiley & Sons Ltd.

Coherent Pound-Drever-Hall technique for high resolution fiber optic strain sensor at very low light power

NASA Astrophysics Data System (ADS)

Wu, Mengxin; Liu, Qingwen; Chen, Jiageng; He, Zuyuan

2017-04-01

Pound-Drever-Hall (PDH) technique has been widely adopted for ultrahigh resolution fiber-optic sensors, but its performance degenerates seriously as the light power drops. To solve this problem, we developed a coherent PDH technique for weak optical signal detection, with which the signal-to-noise ratio (SNR) of demodulated PDH signal is dramatically improved. In the demonstrational experiments, a high resolution fiber-optic sensor using the proposed technique is realized, and n"-order strain resolution at a low light power down to -43 dBm is achieved, which is about 15 dB lower compared with classical PDH technique. The proposed coherent PDH technique has great potentials in longer distance and larger scale sensor networks.

In situ electrostatic characterisation of ion beams in the region of ion acceleration

NASA Astrophysics Data System (ADS)

Bennet, Alexander; Charles, Christine; Boswell, Rod

2018-02-01

In situ and ex situ techniques have been used to measure directional ion beams created by a sharp axial potential drop in low pressure expanding plasmas. Although Retarding Field Energy Analysers (RFEAs) are the most convenient technique to measure the ion velocities and plasma potentials along with the plasma density, they are bulky and are contained in a grounded shield that may perturb the electric potential profile of the expanding plasma. In principle, ex situ techniques produce a more reliable measurement and Laser Induced Fluorescence spectroscopy (LIF) has previously been used to characterise the spatial velocity profile of ion beams in the same region of acceleration for a range of pressures. Here, satisfactory agreement between the ion velocity profiles measured by LIF and RFEA techniques has allowed the RFEA method to be confidently used to probe the ion beam characteristics in the regions of high gradients in plasma density and DC electric fields which have previously proven difficult.

Optical sensors based on the NiPc-CoPc composite films deposited by drop casting and under the action of centrifugal force

NASA Astrophysics Data System (ADS)

Fatima, Noshin; Ahmed, Muhammad M.; Karimov, Khasan S.; Ahmad, Zubair; Fariq Muhammad, Fahmi

2017-06-01

In this study, solution processed composite films of nickel phthalocyanine (NiPc) and cobalt phthalocyanine (CoPc) are deposited by drop casting and under centrifugal force. The films are deposited on surface-type inter-digitated silver electrodes on ceramic alumina substrates. The effects of illumination on the impedance and capacitance of the NiPc-CoPc composite samples are investigated. The samples deposited under centrifugal force show better conductivity than the samples deposited by drop casting technique. In terms of impedance and capacitance sensitivities the samples fabricated under centrifugal force are more sensitive than the drop casting samples. The values of impedance sensitivity ({S}z) are equal to (-1.83) {{M}}{{Ω }}\\cdot {{cm}}2/{mW} and (-5.365){{M}}{{Ω }}\\cdot {{cm}}2/{mW} for the samples fabricated using drop casting and under centrifugal force, respectively. Similarly, the values of capacitance sensitivity ({S}{{c}}) are equal to 0.083 {pF}\\cdot {{cm}}2/{mW} and 0.185 {pF}\\cdot {{cm}}2/{mW} for the samples fabricated by drop casting and under centrifugal force. The films deposited using the different procedures could potentially be viable for different operational modes (i.e., conductive or capacitive) of the optical sensors. Both experimental and simulated results are discussed. Project supported by the Center for Advanced Materials (CAM), Qatar University, Qatar.

An optimized protocol for handling and processing fragile acini cultured with the hanging drop technique.

PubMed

Snyman, Celia; Elliott, Edith

2011-12-15

The hanging drop three-dimensional culture technique allows cultivation of functional three-dimensional mammary constructs without exogenous extracellular matrix. The fragile acini are, however, difficult to preserve during processing steps for advanced microscopic investigation. We describe adaptations to the protocol for handling of hanging drop cultures to include investigation using confocal, scanning, and electron microscopy, with minimal loss of cell culture components. Copyright © 2011 Elsevier Inc. All rights reserved.

Pendant-Drop Surface-Tension Measurement On Molten Metal

NASA Technical Reports Server (NTRS)

Man, Kin Fung; Thiessen, David

1996-01-01

Method of measuring surface tension of molten metal based on pendant-drop method implemented in quasi-containerless manner and augmented with digital processing of image data. Electrons bombard lower end of sample rod in vacuum, generating hanging drop of molten metal. Surface tension of drop computed from its shape. Technique minimizes effects of contamination.

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

Kamiya, Shoji; Sato, Hisashi; Nishida, Masahiro

Reliability of electronic devices has been an issue of serious importance. One of the potential factors to spoil the reliability is possible local drops of strength on the interface of multilayered structure. A new technique for the evaluation of local interface adhesion energy was applied to the interface between Cu and cap layer in a Cu damascene interconnect structure, in order to elucidate variation in adhesion strength as a function of measurement location.

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

Transfer molding processes for nanoscale patterning of poly-L-lactic acid (PLLA) films

NASA Astrophysics Data System (ADS)

Dhakal, Rabin; Peer, Akshit; Biswas, Rana; Kim, Jaeyoun

2016-03-01

Nanoscale patterned structures composed of biomaterials exhibit great potential for the fabrication of functional biostructures. In this paper, we report cost-effective, rapid, and highly reproducible soft lithographic transfer-molding techniques for creating periodic micro- and nano-scale textures on poly (L-lactic acid) (PLLA) surface. These artificial textures can increase the overall surface area and change the release dynamics of the therapeutic agents coated on it. Specifically, we use the double replication technique in which the master pattern is first transferred to the PDMS mold and the pattern on PDMS is then transferred to the PLLA films through drop-casting as well as nano-imprinting. The ensuing comparison studies reveal that the drop-cast PLLA allows pattern transfer at higher levels of fidelity, enabling the realization of nano-hole and nano-cone arrays with pitch down to ~700 nm. The nano-patterned PLLA film was then coated with rapamycin to make it drug-eluting.

How glaucoma patient characteristics, self-efficacy, and patient-provider communication are associated with eye drop technique

PubMed Central

Sayner, Robyn; Carpenter, Delesha M; Robin, Alan L; Blalock, Susan J; Muir, Kelly W; Vitko, Michelle; Hartnett, Mary Elizabeth; Lawrence, Scott D; Giangiacomo, Annette L; Tudor, Gail; Goldsmith, Jason A; Sleath, Betsy

2017-01-01

Objectives The objective of this study was to examine the extent to which patient characteristics, eye drop technique self-efficacy, and ophthalmologist–patient communication about eye drop administration are associated with glaucoma patients’ ability to instil a single drop, have the drop land in the eye, and avoid touching the applicator tip of the medication bottle to the eye or face while self-administering eye drops. Methods Glaucoma patients (n = 279) were recruited from six ophthalmology clinics. Medical visits were videotape-recorded. Afterwards, patients were interviewed and demonstrated administering an eye drop on a videotaped-recording. Generalized estimating equations were used to analyse the data. Key findings Ophthalmologists provided eye drop administration instruction to 40 patients. Patients with more years of education were significantly more likely to both instil a single drop (P = 0.017) and have the drop land in their eye (P = 0.017). Women were significantly more likely to touch the applicator tip to their eyes or face (P = 0.014). Patients with severe glaucoma (P = 0.016), women (P = 0.026), and patients who asked at least one eye drop administration question (P = 0.001) were significantly less likely to instil a single drop. Patients with arthritis were significantly less likely to have the drop land in their eye (P = 0.008). African American patients were significantly less likely to touch the applicator tip to their eyes or face (P = 0.008). Conclusions Some glaucoma patients have a difficult time self-administering eye drops. As so few patients received eye drop administration instruction from their providers, there is an opportunity for pharmacists to complement care. PMID:26303667

How glaucoma patient characteristics, self-efficacy and patient-provider communication are associated with eye drop technique.

PubMed

Sayner, Robyn; Carpenter, Delesha M; Robin, Alan L; Blalock, Susan J; Muir, Kelly W; Vitko, Michelle; Hartnett, Mary Elizabeth; Lawrence, Scott D; Giangiacomo, Annette L; Tudor, Gail; Goldsmith, Jason A; Sleath, Betsy

2016-04-01

The objective of this study was to examine the extent to which patient characteristics, eye drop technique self-efficacy, and ophthalmologist-patient communication about eye drop administration are associated with glaucoma patients' ability to instil a single drop, have the drop land in the eye, and avoid touching the applicator tip of the medication bottle to the eye or face while self-administering eye drops. Glaucoma patients (n = 279) were recruited from six ophthalmology clinics. Medical visits were videotape-recorded. Afterwards, patients were interviewed and demonstrated administering an eye drop on a videotaped-recording. Generalized estimating equations were used to analyse the data. Ophthalmologists provided eye drop administration instruction to 40 patients. Patients with more years of education were significantly more likely to both instil a single drop (P = 0.017) and have the drop land in their eye (P = 0.017). Women were significantly more likely to touch the applicator tip to their eyes or face (P = 0.014). Patients with severe glaucoma (P = 0.016), women (P = 0.026), and patients who asked at least one eye drop administration question (P = 0.001) were significantly less likely to instil a single drop. Patients with arthritis were significantly less likely to have the drop land in their eye (P = 0.008). African American patients were significantly less likely to touch the applicator tip to their eyes or face (P = 0.008). Some glaucoma patients have a difficult time self-administering eye drops. As so few patients received eye drop administration instruction from their providers, there is an opportunity for pharmacists to complement care. © 2015 Royal Pharmaceutical Society.

Laser capillary spectrophotometric acquisition of bivariate drop size and concentration data for liquid-liquid dispersion

DOEpatents

Tavlarides, Lawrence L.; Bae, Jae-Heum

1991-01-01

A laser capillary spectrophotometric technique measures real time or near real time bivariate drop size and concentration distribution for a reactive liquid-liquid dispersion system. The dispersion is drawn into a precision-bore glass capillary and an appropriate light source is used to distinguish the aqueous phase from slugs of the organic phase at two points along the capillary whose separation is precisely known. The suction velocity is measured, as is the length of each slug from which the drop free diameter is calculated. For each drop, the absorptivity at a given wavelength is related to the molar concentration of a solute of interest, and the concentration of given drops of the organic phase is derived from pulse heights of the detected light. This technique permits on-line monitoring and control of liquid-liquid dispersion processes.

CYCLAM - Recycling by a Laser-driven Drop Jet from Waste that Feeds AM

NASA Astrophysics Data System (ADS)

Kaplan, Alexander F. H.; Samarjy, Ramiz S. M.

Additive manufacturing of metal parts is supplied by powder or wire. Manufacturing of this raw material causes additional costs and environmental impact. A new technique is proposed where the feeding directly originates from a metal sheet, which can even be waste. When cutting is done by laser-induced boiling, melt is continuously ejected downwards underneath the sheet. The ejected melt is deposited as a track on a substrate, enabling additive manufacturing by substrate movement along a desired path. The melt first flows downwards as a column and after a few millimeters separates into drops, here about 500 micrometer in diameter, as observed by high speed imaging. The drops incorporate sequentially and calmly into a long melt pool on the substrate. While steel drops formed regular tracks on steel and aluminium substrates, on copper substrate periodic drops solidified instead. For this new technique, called CYCLAM, the laser beam acts indirectly while the drop jet becomes the main tool. From imaging, properties like the width or fluctuations of the drop jet can be statistically evaluated. Despite oscillation of the liquid column, the divergence of the drop jet remained small, improving the precision and robustness. The melt leaves the cut sheet as a liquid column, 1 to 4 mm in length, which periodically separates drops that are transferred as a liquid jet to the substrate. For very short distance of 2 to 3 mm between the two sheets this liquid column can transfer the melt continuously as a liquid bridge. This phenomenon was observed, as a variant of the technique, but the duration of the bridge was limited by fluid mechanic instabilities.

Instrumentation and telemetry systems for free-flight drop model testing

NASA Technical Reports Server (NTRS)

Hyde, Charles R.; Massie, Jeffrey J.

1993-01-01

This paper presents instrumentation and telemetry system techniques used in free-flight research drop model testing at the NASA Langley Research Center. The free-flight drop model test technique is used to conduct flight dynamics research of high performance aircraft using dynamically scaled models. The free-flight drop model flight testing supplements research using computer analysis and wind tunnel testing. The drop models are scaled to approximately 20 percent of the size of the actual aircraft. This paper presents an introduction to the Free-Flight Drop Model Program which is followed by a description of the current instrumentation and telemetry systems used at the NASA Langley Research Center, Plum Tree Test Site. The paper describes three telemetry downlinks used to acquire the data, video, and radar tracking information from the model. Also described are two telemetry uplinks, one used to fly the model employing a ground-based flight control computer and a second to activate commands for visual tracking and parachute recovery of the model. The paper concludes with a discussion of free-flight drop model instrumentation and telemetry system development currently in progress for future drop model projects at the NASA Langley Research Center.

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

Head-on collision of drops: A numerical investigation

NASA Technical Reports Server (NTRS)

Nobari, M. R.; Jan, Y.-J.; Tryggvason, G.

1993-01-01

The head-on collision of equal sized drops is studied by full numerical simulations. The Navier-Stokes equations are solved for fluid motion both inside and outside the drops using a front tracking/finite difference technique. The drops are accelerated toward each other by a body force that is turned off before the drops collide. When the drops collide, the fluid between them is pushed outward leaving a thin later bounded by the drop surface. This layer gets progressively thinner as the drops continue to deform and in several of the calculations this double layer is artificially removed once it is thin enough, thus modeling rupture. If no rupture takes place, the drops always rebound, but if the film is ruptured the drops may coalesce permanently or coalesce temporarily and then split again.

Laser capillary spectrophotometric acquisition of bivariate drop size and concentration data for liquid-liquid dispersion

DOEpatents

Tavlarides, L.L.; Bae, J.H.

1991-12-24

A laser capillary spectrophotometric technique measures real time or near real time bivariate drop size and concentration distribution for a reactive liquid-liquid dispersion system. The dispersion is drawn into a precision-bore glass capillary and an appropriate light source is used to distinguish the aqueous phase from slugs of the organic phase at two points along the capillary whose separation is precisely known. The suction velocity is measured, as is the length of each slug from which the drop free diameter is calculated. For each drop, the absorptivity at a given wavelength is related to the molar concentration of a solute of interest, and the concentration of given drops of the organic phase is derived from pulse heights of the detected light. This technique permits on-line monitoring and control of liquid-liquid dispersion processes. 17 figures.

Undercooling measurement in a low-gravity containerless environment

NASA Technical Reports Server (NTRS)

Robinson, M. B.

1981-01-01

A technique is described for measuring the amount of undercooling for samples processed in a low-gravity containerless environment. The time of undercooling is determined by measuring the time of cooling before nucleation and recalescence by two infrared detectors. Once the cooling curve for each drop is calculated, the amount of undercooling can then be found. The technique is demonstrated by measuring the amount of undercooling for drops of pure niobium and select compositions of the niobium-germanium alloy system while free falling in a 32 n evacuated drop tube. The total hemispherical emissivities and specific heats for these materials were measured using a high-temperature containerless calorimeter. An overview of the effect of undercooling on drops of niobium and niobium-germanium is given.

Computations of Drop Collision and Coalescence

NASA Technical Reports Server (NTRS)

Tryggvason, Gretar; Juric, Damir; Nas, Selman; Mortazavi, Saeed

1996-01-01

Computations of drops collisions, coalescence, and other problems involving drops are presented. The computations are made possible by a finite difference/front tracking technique that allows direct solutions of the Navier-Stokes equations for a multi-fluid system with complex, unsteady internal boundaries. This method has been used to examine the various collision modes for binary collisions of drops of equal size, mixing of two drops of unequal size, behavior of a suspension of drops in linear and parabolic shear flows, and the thermal migration of several drops. The key results from these simulations are reviewed. Extensions of the method to phase change problems and preliminary results for boiling are also shown.

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.

Using Single Drop Microextraction for Headspace Analysis with Gas Chromatography

ERIC Educational Resources Information Center

Riccio, Daniel; Wood, Derrick C.; Miller, James M.

2008-01-01

Headspace (HS) gas chromatography (GC) is commonly used to analyze samples that contain non-volatiles. In 1996, a new sampling technique called single drop microextraction, SDME, was introduced, and in 2001 it was applied to HS analysis. It is a simple technique that uses equipment normally found in the undergraduate laboratory, making it ideal…

[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.

Isoflurane waste anesthetic gas concentrations associated with the open-drop method.

PubMed

Taylor, Douglas K; Mook, Deborah M

2009-01-01

The open-drop technique is used frequently for anesthetic delivery to small rodents. Operator exposure to waste anesthetic gas (WAG) is a potential occupational hazard if this method is used without WAG scavenging. This study was conducted to determine whether administration of isoflurane by the open-drop technique without exposure controls generates significant WAG concentrations. We placed 0.1, 0.2, or 0.3 ml of liquid isoflurane into screw-top 500 or 1000 ml glass jars. WAG concentration was measured at the opening of the container and 20 and 40 cm from the opening, a distance at which users likely would operate, at 1, 2, or 3 min WAG was measured by using a portable infrared gas analyzer. Mean WAG concentrations at the vessel opening were as high as 662 +/- 168 ppm with a 500 ml jar and 122 +/- 87 ppm with a 1000 ml jar. At operator levels, WAG concentrations were always at or near 0 ppm. For measurements made at the vessel opening, time was the only factor that significantly affected WAG concentration when using the 500 ml jar. Neither time nor liquid volume were significant factors when using 1000 ml jar. At all liquid volumes and time points, the WAG concentration associated with using the 500 ml container was marginally to significantly greater than that for the 1000 ml jar.

Airborne chemistry: acoustic levitation in chemical analysis.

PubMed

Santesson, Sabina; Nilsson, Staffan

2004-04-01

This review with 60 references describes a unique path to miniaturisation, that is, the use of acoustic levitation in analytical and bioanalytical chemistry applications. Levitation of small volumes of sample by means of a levitation technique can be used as a way to avoid solid walls around the sample, thus circumventing the main problem of miniaturisation, the unfavourable surface-to-volume ratio. Different techniques for sample levitation have been developed and improved. Of the levitation techniques described, acoustic or ultrasonic levitation fulfils all requirements for analytical chemistry applications. This technique has previously been used to study properties of molten materials and the equilibrium shape()and stability of liquid drops. Temperature and mass transfer in levitated drops have also been described, as have crystallisation and microgravity applications. The airborne analytical system described here is equipped with different and exchangeable remote detection systems. The levitated drops are normally in the 100 nL-2 microL volume range and additions to the levitated drop can be made in the pL-volume range. The use of levitated drops in analytical and bioanalytical chemistry offers several benefits. Several remote detection systems are compatible with acoustic levitation, including fluorescence imaging detection, right angle light scattering, Raman spectroscopy, and X-ray diffraction. Applications include liquid/liquid extractions, solvent exchange, analyte enrichment, single-cell analysis, cell-cell communication studies, precipitation screening of proteins to establish nucleation conditions, and crystallisation of proteins and pharmaceuticals.

Ground Based Studies of Thermocapillary Flows in Levitated Drops

NASA Technical Reports Server (NTRS)

Sadhal, Satwindar Singh; Trinh, Eugene H.

1996-01-01

Ground-based experiments together with analytical studies are presently being conducted for levitated drops. Both acoustic and electrostatic techniques are being employed to achieve levitation of drops in a gaseous environment. The scientific effort is principally on the thermal and the fluid phenomena associated with the local heating of levitated drops, both at 1-g and at low-g. In particular, the thermocapillary flow associated with local spot heating is being studied. Fairly stable acoustic levitation of drops has been achieved with some exceptions when random rotational motion of the drop persists. The flow visualization has been carried out by light scattering from smoke particles for the exterior flow and fluorescent tracer particles in the drop. The results indicate a lack of axial symmetry in the internal flow even though the apparatus and the heating are symmetric. The theoretical studies for the past year have included fundamental analyses of acoustically levitated spherical drops. The flow associated with a particle near the velocity antinode is being investigated by the singular perturbation technique. As a first step towards understanding the effect of the particle displacement from the antinode, the flow field about the node has been calculated for the first time. The effect of the acoustic field on the interior of a liquid drop has also been investigated. The results predict that the internal flow field is very weak.

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.

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.

Characterization of polymorphic states in energetic samples of 1,3,5-trinitro-1,3,5-triazine (RDX) fabricated using drop-on-demand inkjet technology.

PubMed

Emmons, Erik D; Farrell, Mikella E; Holthoff, Ellen L; Tripathi, Ashish; Green, Norman; Moon, Raphael P; Guicheteau, Jason A; Christesen, Steven D; Pellegrino, Paul M; Fountain, Augustus W

2012-06-01

The United States Army and the first responder community are evaluating optical detection systems for the trace detection of hazardous energetic materials. Fielded detection systems must be evaluated with the appropriate material concentrations to accurately identify the residue in theater. Trace levels of energetic materials have been observed in mutable polymorphic phases and, therefore, the systems being evaluated must be able to detect and accurately identify variant sample phases observed in spectral data. In this work, we report on the novel application of drop-on-demand technology for the fabrication of standardized trace 1,3,5-trinitro-1,3,5-triazine (RDX) samples. The drop-on-demand sample fabrication technique is compared both visually and spectrally to the more commonly used drop-and-dry technique. As the drop-on-demand technique allows for the fabrication of trace level hazard materials, concerted efforts focused on characterization of the polymorphic phase changes observed with low concentrations of RDX commonly used in drop-on-demand processing. This information is important when evaluating optical detection technologies using samples prepared with a drop-on-demand inkjet system, as the technology may be "trained" to detect the common bulk α phase of the explosive based on its spectral features but fall short in positively detecting a trace quantity of RDX (β-phase). We report the polymorphic shifts observed between α- and β-phases of this energetic material and discuss the conditions leading to the favoring of one phase over the other.

No Bridge Too High: Infants Decide Whether to Cross Based on the Probability of Falling not the Severity of the Potential Fall

ERIC Educational Resources Information Center

Kretch, Kari S.; Adolph, Karen E.

2013-01-01

Do infants, like adults, consider both the probability of falling and the severity of a potential fall when deciding whether to cross a bridge? Crawling and walking infants were encouraged to cross bridges varying in width over a small drop-off, a large drop-off, or no drop-off. Bridge width affects the probability of falling, whereas drop-off…

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.

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.

An empirically derived basis for calculating the area, rate, and distribution of water-drop impingement on airfoils

NASA Technical Reports Server (NTRS)

Bergrun, Norman R

1952-01-01

An empirically derived basis for predicting the area, rate, and distribution of water-drop impingement on airfoils of arbitrary section is presented. The concepts involved represent an initial step toward the development of a calculation technique which is generally applicable to the design of thermal ice-prevention equipment for airplane wing and tail surfaces. It is shown that sufficiently accurate estimates, for the purpose of heated-wing design, can be obtained by a few numerical computations once the velocity distribution over the airfoil has been determined. The calculation technique presented is based on results of extensive water-drop trajectory computations for five airfoil cases which consisted of 15-percent-thick airfoils encompassing a moderate lift-coefficient range. The differential equations pertaining to the paths of the drops were solved by a differential analyzer.

Fabrication of polymer micro-lens array with pneumatically diaphragm-driven drop-on-demand inkjet technology.

PubMed

Xie, Dan; Zhang, Honghai; Shu, Xiayun; Xiao, Junfeng

2012-07-02

The paper reports an effective method to fabricate micro-lens arrays with the ultraviolet-curable polymer, using an original pneumatically diaphragm-driven drop-on-demand inkjet system. An array of plano convex micro-lenses can be formed on the glass substrate due to surface tension and hydrophobic effect. The micro-lens arrays have uniform focusing function, smooth and real planar surface. The fabrication process showed good repeatability as well, fifty micro-lenses randomly selected form 9 × 9 miro-lens array with an average diameter of 333.28μm showed 1.1% variations. Also, the focal length, the surface roughness and optical property of the fabricated micro-lenses are measured, analyzed and proved satisfactory. The technique shows great potential for fabricating polymer micro-lens arrays with high flexibility, simple technological process and low production cost.

Flow visualization and characterization of evaporating liquid drops

NASA Technical Reports Server (NTRS)

Chao, David F. (Inventor); Zhang, Nengli (Inventor)

2004-01-01

An optical system, consisting of drop-reflection image, reflection-refracted shadowgraphy and top-view photography, is used to measure the spreading and instant dynamic contact angle of a volatile-liquid drop on a non-transparent substrate. The drop-reflection image and the shadowgraphy is shown by projecting the images of a collimated laser beam partially reflected by the drop and partially passing through the drop onto a screen while the top view photograph is separately viewed by use of a camera video recorder and monitor. For a transparent liquid on a reflective solid surface, thermocapillary convection in the drop, induced by evaporation, can be viewed nonintrusively, and the drop real-time profile data are synchronously recorded by video recording systems. Experimental results obtained from this technique clearly reveal that evaporation and thermocapillary convection greatly affect the spreading process and the characteristics of dynamic contact angle of the drop.

Drop Testing Representative Multi-Canister Overpacks

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

Snow, Spencer D.; Morton, Dana K.

The objective of the work reported herein was to determine the ability of the Multi- Canister Overpack (MCO) canister design to maintain its containment boundary after an accidental drop event. Two test MCO canisters were assembled at Hanford, prepared for testing at the Idaho National Engineering and Environmental Laboratory (INEEL), drop tested at Sandia National Laboratories, and evaluated back at the INEEL. In addition to the actual testing efforts, finite element plastic analysis techniques were used to make both pre-test and post-test predictions of the test MCOs structural deformations. The completed effort has demonstrated that the canister design is capablemore » of maintaining a 50 psig pressure boundary after drop testing. Based on helium leak testing methods, one test MCO was determined to have a leakage rate not greater than 1x10 -5 std cc/sec (prior internal helium presence prevented a more rigorous test) and the remaining test MCO had a measured leakage rate less than 1x10 -7 std cc/sec (i.e., a leaktight containment) after the drop test. The effort has also demonstrated the capability of finite element methods using plastic analysis techniques to accurately predict the structural deformations of canisters subjected to an accidental drop event.« less

Surface active properties of lipid nanocapsules

PubMed Central

Mouzouvi, Celia R. A.; Bigot, André K.; Saulnier, Patrick

2017-01-01

Lipid nanocapsules (LNCs) are biomimetic nanocarriers used for the encapsulation of a broad variety of active ingredients. Similar to surface active compounds, LNCs contain both hydrophilic and hydrophobic parts in their structure. Moreover, the components of LNCs, macrogol 15 hydroxystearate (MHS) and lecithin, are known for their surface active properties. Therefore, the aim of this paper was to investigate the capability of the LNCs to decrease surface tension using two techniques: drop tensiometry and the Wilhelmy plate method. LNCs with diameters ranging from 30 to 100 nm were successfully obtained using a phase inversion technique. The LNCs’ properties, such as size and zeta potential, depend on the composition. LNCs exhibit a lower limiting surface tension compared to MHS (34.8–35.0 mN/m and 37.7–38.8 mN/m, respectively), as confirmed by both drop tensiometry and the Wilhelmy plate method. LNCs have exhibited a saturated interfacial concentration (SIC) that was 10-fold higher than the critical micellar concentration (CMC) of MHS or the SIC of binary and ternary mixtures of LNC ingredients. The SIC of the LNC formulations depended on the mass mixing ratio of the MHS/triglycerides but not on the presence of lecithin. The CMC/SIC values measured by the Wilhelmy plate method were higher than those obtained using drop tensiometry because of the longer duration of the tensiometry measurement. In conclusion, the surfactant-like properties of the LNCs offer new possibilities for medical and pharmaceutical applications. PMID:28796777

Surface active properties of lipid nanocapsules.

PubMed

Mouzouvi, Celia R A; Umerska, Anita; Bigot, André K; Saulnier, Patrick

2017-01-01

Lipid nanocapsules (LNCs) are biomimetic nanocarriers used for the encapsulation of a broad variety of active ingredients. Similar to surface active compounds, LNCs contain both hydrophilic and hydrophobic parts in their structure. Moreover, the components of LNCs, macrogol 15 hydroxystearate (MHS) and lecithin, are known for their surface active properties. Therefore, the aim of this paper was to investigate the capability of the LNCs to decrease surface tension using two techniques: drop tensiometry and the Wilhelmy plate method. LNCs with diameters ranging from 30 to 100 nm were successfully obtained using a phase inversion technique. The LNCs' properties, such as size and zeta potential, depend on the composition. LNCs exhibit a lower limiting surface tension compared to MHS (34.8-35.0 mN/m and 37.7-38.8 mN/m, respectively), as confirmed by both drop tensiometry and the Wilhelmy plate method. LNCs have exhibited a saturated interfacial concentration (SIC) that was 10-fold higher than the critical micellar concentration (CMC) of MHS or the SIC of binary and ternary mixtures of LNC ingredients. The SIC of the LNC formulations depended on the mass mixing ratio of the MHS/triglycerides but not on the presence of lecithin. The CMC/SIC values measured by the Wilhelmy plate method were higher than those obtained using drop tensiometry because of the longer duration of the tensiometry measurement. In conclusion, the surfactant-like properties of the LNCs offer new possibilities for medical and pharmaceutical applications.

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

Reduction of the field-aligned potential drop in the polar cap during large geomagnetic storms

NASA Astrophysics Data System (ADS)

Kitamura, N.; Seki, K.; Nishimura, Y.; Hori, T.; Terada, N.; Ono, T.; Strangeway, R. J.

2013-12-01

We have studied photoelectron flows and the inferred field-aligned potential drop in the polar cap during 5 large geomagnetic storms that occurred in the periods when the photoelectron observations in the polar cap were available near the apogee of the FAST satellite (~4000 km) at solar maximum, and the footprint of the satellite paths in the polar cap was under sunlit conditions most of the time. In contrast to the ~20 V potential drop during geomagnetically quiet periods at solar maximum identified by Kitamura et al. [JGR, 2012], the field-aligned potential drop frequently became smaller than ~5 V during the main and early recovery phases of the large geomagnetic storms. Because the potential acts to inhibit photoelectron escape, this result indicates that the corresponding acceleration of ions by the field-aligned potential drop in the polar cap and the lobe region is smaller during the main and early recovery phases of large geomagnetic storms compared to during geomagnetically quiet periods. Under small field-aligned current conditions, the number flux of outflowing ions should be nearly equal to the net escaping electron number flux. Since ions with large flux originating from the cusp/cleft ionosphere convect into the polar cap during geomagnetic storms [e.g., Kitamura et al., JGR, 2010], the net escaping electron number flux should increase to balance the enhanced ion outflows. The magnitude of the field-aligned potential drop would be reduced to let a larger fraction of photoelectrons escape.

Flow Visualization in Evaporating Liquid Drops and Measurement of Dynamic Contact Angles and Spreading Rate

NASA Technical Reports Server (NTRS)

Zhang, Neng-Li; Chao, David F.

2001-01-01

A new hybrid optical system, consisting of reflection-refracted shadowgraphy and top-view photography, is used to visualize flow phenomena and simultaneously measure the spreading and instant dynamic contact angle in a volatile-liquid drop on a nontransparent substrate. Thermocapillary convection in the drop, induced by evaporation, and the drop real-time profile data are synchronously recorded by video recording systems. Experimental results obtained from this unique technique clearly reveal that thermocapillary convection strongly affects the spreading process and the characteristics of dynamic contact angle of the drop. Comprehensive information of a sessile drop, including the local contact angle along the periphery, the instability of the three-phase contact line, and the deformation of the drop shape is obtained and analyzed.

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.

Generalized Kinetic Description of Steady-State Collisionless Plasmas

NASA Technical Reports Server (NTRS)

Khazanov, G. V.; Liemohn, M. W.; Krivorutsky, E. N.

1997-01-01

We present a general solution to the collisionless Boltzmann (Vlasov) equation for a free-flowing plasma along a magnetic field line using Liouville's theorem, allowing for an arbitrary potential structure including non-monotonicities. The constraints of the existing collisionless kinetic transport models are explored, and the need for a more general approach to the problem of self- consistent potential energy calculations is described. Then a technique that handles an arbitrary potential energy distribution along the field line is presented and discussed. For precipitation of magnetospherically trapped hot plasma, this model yields moment calculations that vary by up to a factor of two for various potential energy structures with the same total potential drop. The differences are much greater for the high-latitude outflow scenario, giving order of magnitude variations depending on the shape of the potential energy distribution.

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

Shape oscillations of microparticles on an optical microscope stage.

PubMed

Zhu, Z M; Apfel, R E

1985-11-01

A modulated acoustic radiation pressure technique to produce quadrupole shape oscillations of drops ranging in diameter from 50-220 micron has been used by us. These drops have been suspended by acoustic levitation in a small chamber mounted on a stage of an optical microscope, which allowed easy viewing. The fission of drops and the deformation of sea urchin eggs were also observed.

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.

The stopped-drop method: a novel setup for containment-free and time-resolved measurements

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

Schiener, Andreas; Seifert, Soenke; Magerl, Andreas

2016-03-01

A novel setup for containment-free time-resolved experiments at a free-hanging drop is reported. Within a dead-time of 100 ms a drop of mixed reactant solutions is formed and the time evolution of a reaction can be followed from thereon by various techniques. As an example, a small-angle X-ray scattering study on the formation mechanism of EDTA-stabilized CdS both at a synchrotron and a laboratory X-ray source is presented here. While the evolution can be followed with one drop only at a synchrotron source, a stroboscopic mode with many drops is preferable for the laboratory source.

Thermally driven oscillations and wave motion of a liquid drop

NASA Technical Reports Server (NTRS)

Baumeister, K. J.; Hendricks, R. C.; Schoessow, G. J.

1977-01-01

In the state of Leidenfrost boiling, liquid drops are observed to vibrate in a variety of modal patterns. Theories are presented which predict the frequency of oscillation and show that the observed modal patterns of drops correspond to the minimum energy oscillatory excitation state. High-speed photographic techniques were used to record these motions and substantiate the theories. An incipient temperature was also found for water drops in film boiling below which free oscillations do not exist. In addition to these oscillations, photographic sequences are presented which show that wave motion can exist along the circumference of the drop. Following the study of free oscillations, the system was mounted on a shaker table and the drop subjected to a range of forced frequencies and accelerations.

Thermally Driven Oscillations and Wave Motion of a Liquid Drop

NASA Technical Reports Server (NTRS)

Baumeister, K. J.; Hendricks, R. C.; Schoessow, G. J.

1977-01-01

In the state of Leidenfrost boiling, liquid drops are observed to vibrate in a variety of modal patterns. Theories are presented which predict the frequency of oscillation and show that the observed model patterns of drops correspond to the minimum energy oscillatory excitation state. High-speed photographic techniques were used to record these motions and substantiate the theories. An incipient temperature was also found for water drops in film boiling below which free oscillations do not exist. In addition to these oscillations, photographic sequences are presented which show that wave motion can exist along the circumference of the drop. Following the study of free oscillations, the system was mounted on a shaker table and the drop subjected to a range of forced frequencies and accelerations.

Determination of auroral electrostatic potentials using high- and low-altitude particle distributions

NASA Technical Reports Server (NTRS)

Reiff, P. H.; Collin, H. L.; Craven, J. D.; Burch, J. L.; Winningham, J. D.

1988-01-01

The auroral electrostatic potential differences were determined from the particle distribution functions obtained nearly simultaneously above and below the auroral acceleration region by DE-1 at altitudes 9000-15,000 km and DE-2 at 400-800 km. Three independent techniques were used: (1) the peak energies of precipitating electrons observed by DE-2, (2) the widening of loss cones for upward traveling electrons observed by DE-1, and (3) the energies of upgoing ions observed by DE-1. The assumed parallel electrostatic potential difference calculated by the three methods was nearly the same. The results confirmed the hypothesis that parallel electrostatic fields of 1-10 kV potential drop at 1-2 earth radii altitude are an important source for auroral particle acceleration.

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)

Droplet morphometry and velocimetry (DMV): a video processing software for time-resolved, label-free tracking of droplet parameters.

PubMed

Basu, Amar S

2013-05-21

Emerging assays in droplet microfluidics require the measurement of parameters such as drop size, velocity, trajectory, shape deformation, fluorescence intensity, and others. While micro particle image velocimetry (μPIV) and related techniques are suitable for measuring flow using tracer particles, no tool exists for tracking droplets at the granularity of a single entity. This paper presents droplet morphometry and velocimetry (DMV), a digital video processing software for time-resolved droplet analysis. Droplets are identified through a series of image processing steps which operate on transparent, translucent, fluorescent, or opaque droplets. The steps include background image generation, background subtraction, edge detection, small object removal, morphological close and fill, and shape discrimination. A frame correlation step then links droplets spanning multiple frames via a nearest neighbor search with user-defined matching criteria. Each step can be individually tuned for maximum compatibility. For each droplet found, DMV provides a time-history of 20 different parameters, including trajectory, velocity, area, dimensions, shape deformation, orientation, nearest neighbour spacing, and pixel statistics. The data can be reported via scatter plots, histograms, and tables at the granularity of individual droplets or by statistics accrued over the population. We present several case studies from industry and academic labs, including the measurement of 1) size distributions and flow perturbations in a drop generator, 2) size distributions and mixing rates in drop splitting/merging devices, 3) efficiency of single cell encapsulation devices, 4) position tracking in electrowetting operations, 5) chemical concentrations in a serial drop dilutor, 6) drop sorting efficiency of a tensiophoresis device, 7) plug length and orientation of nonspherical plugs in a serpentine channel, and 8) high throughput tracking of >250 drops in a reinjection system. Performance metrics show that highest accuracy and precision is obtained when the video resolution is >300 pixels per drop. Analysis time increases proportionally with video resolution. The current version of the software provides throughputs of 2-30 fps, suggesting the potential for real time analysis.

Heat loss and drag of spherical drop tube samples

NASA Technical Reports Server (NTRS)

Wallace, D. B.

1982-01-01

Analysis techniques for three aspects of the performance of the NASA/MSFC 32 meter drop tube are considered. Heat loss through the support wire in a pendant drop sample, temperature history of a drop falling through the drop tube when the tube is filled with helium gas at various pressures, and drag and resulting g-levels experienced by a drop falling through the tube when the tube is filled with helium gas at various pressures are addressed. The developed methods apply to systems with sufficiently small Knudsen numbers for which continuum theory may be applied. Sample results are presented, using niobium drops, to indicate the magnitudes of the effects. Helium gas at one atmosphere pressure can approximately double the amount of possible undercooling but it results in an apparent gravity levels of up to 0.1 g.

Drop coating deposition Raman spectroscopy of blood plasma for the detection of colorectal cancer

NASA Astrophysics Data System (ADS)

Li, Pengpeng; Chen, Changshui; Deng, Xiaoyuan; Mao, Hua; Jin, Shaoqin

2015-03-01

We have recently applied the technique of drop coating deposition Raman (DCDR) spectroscopy for colorectal cancer (CRC) detection using blood plasma. The aim of this study was to develop a more convenient and stable method based on blood plasma for noninvasive CRC detection. Significant differences are observed in DCDR spectra between healthy (n=105) and cancer (n=75) plasma from 15 CRC patients and 21 volunteers, particularly in the spectra that are related to proteins, nucleic acids, and β-carotene. The multivariate analysis principal components analysis and the linear discriminate analysis, together with leave-one-out, cross validation were used on DCDR spectra and yielded a sensitivity of 100% (75/75) and specificity of 98.1% (103/105) for detection of CRC. This study demonstrates that DCDR spectroscopy of blood plasma associated with multivariate statistical algorithms has the potential for the noninvasive detection of CRC.

All-organic superhydrophobic coatings with mechanochemical robustness and liquid impalement resistance

NASA Astrophysics Data System (ADS)

Peng, Chaoyi; Chen, Zhuyang; Tiwari, Manish K.

2018-03-01

Superhydrophobicity is a remarkable evolutionary adaption manifested by several natural surfaces. Artificial superhydrophobic coatings with good mechanical robustness, substrate adhesion and chemical robustness have been achieved separately. However, a simultaneous demonstration of these features along with resistance to liquid impalement via high-speed drop/jet impact is challenging. Here, we describe all-organic, flexible superhydrophobic nanocomposite coatings that demonstrate strong mechanical robustness under cyclic tape peels and Taber abrasion, sustain exposure to highly corrosive media, namely aqua regia and sodium hydroxide solutions, and can be applied to surfaces through scalable techniques such as spraying and brushing. In addition, the mechanical flexibility of our coatings enables impalement resistance to high-speed drops and turbulent jets at least up to 35 m s-1 and a Weber number of 43,000. With multifaceted robustness and scalability, these coatings should find potential usage in harsh chemical engineering as well as infrastructure, transport vehicles and communication equipment.

A burnout prediction model based around char morphology

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

Tao Wu; Edward Lester; Michael Cloke

Several combustion models have been developed that can make predictions about coal burnout and burnout potential. Most of these kinetic models require standard parameters such as volatile content and particle size to make a burnout prediction. This article presents a new model called the char burnout (ChB) model, which also uses detailed information about char morphology in its prediction. The input data to the model is based on information derived from two different image analysis techniques. One technique generates characterization data from real char samples, and the other predicts char types based on characterization data from image analysis of coalmore » particles. The pyrolyzed chars in this study were created in a drop tube furnace operating at 1300{sup o}C, 200 ms, and 1% oxygen. Modeling results were compared with a different carbon burnout kinetic model as well as the actual burnout data from refiring the same chars in a drop tube furnace operating at 1300{sup o}C, 5% oxygen, and residence times of 200, 400, and 600 ms. A good agreement between ChB model and experimental data indicates that the inclusion of char morphology in combustion models could well improve model predictions. 38 refs., 5 figs., 6 tabs.« less

A computerized test system for thermal-mechanical fatigue crack growth

NASA Technical Reports Server (NTRS)

Marchand, N.; Pelloux, R. M.

1986-01-01

A computerized testing system to measure fatigue crack growth under thermal-mechanical fatigue conditions is described. Built around a servohydraulic machine, the system is capable of a push-pull test under stress-controlled or strain-controlled conditions in the temperature range of 25 to 1050 C. Temperature and mechanical strain are independently controlled by the closed-loop system to simulate the complex inservice strain-temperature relationship. A d-c electrical potential method is used to measure crack growth rates. The correction procedure of the potential signal to take into account powerline and RF-induced noises and thermal changes is described. It is shown that the potential drop technique can be used for physical mechanism studies and for modelling crack tip processes.

Development, validation and comparison of NIR and Raman methods for the identification and assay of poor-quality oral quinine drops.

PubMed

Mbinze, J K; Sacré, P-Y; Yemoa, A; Mavar Tayey Mbay, J; Habyalimana, V; Kalenda, N; Hubert, Ph; Marini, R D; Ziemons, E

2015-01-01

Poor quality antimalarial drugs are one of the public's major health problems in Africa. The depth of this problem may be explained in part by the lack of effective enforcement and the lack of efficient local drug analysis laboratories. To tackle part of this issue, two spectroscopic methods with the ability to detect and to quantify quinine dihydrochloride in children's oral drops formulations were developed and validated. Raman and near infrared (NIR) spectroscopy were selected for the drug analysis due to their low cost, non-destructive and rapid characteristics. Both of the methods developed were successfully validated using the total error approach in the range of 50-150% of the target concentration (20%W/V) within the 10% acceptance limits. Samples collected on the Congolese pharmaceutical market were analyzed by both techniques to detect potentially substandard drugs. After a comparison of the analytical performance of both methods, it has been decided to implement the method based on NIR spectroscopy to perform the routine analysis of quinine oral drop samples in the Quality Control Laboratory of Drugs at the University of Kinshasa (DRC). Copyright © 2015 Elsevier B.V. All rights reserved.

Viscosity measurements of metallic melts using the oscillating drop technique

NASA Astrophysics Data System (ADS)

Heintzmann, P.; Yang, F.; Schneider, S.; Lohöfer, G.; Meyer, A.

2016-06-01

By means of benchmarking reduced gravity experiments, we have verified the measured viscosity of binary Zr-Ni glass forming liquids utilizing the oscillating drop technique combined with ground-based electrostatic levitation (ESL). Reliable viscosity data can be obtained as long as internal viscous damping of a single oscillation mode of a levitated drop dominates external perturbations. This can be verified by the absence of a sample mass dependence of the results. Hence, ESL is an excellent tool for studying the viscosity of metallic glass forming melts in the range of about 10-250 mPa s, with sample masses below 100 mg. To this end, we show that, for binary Zr-Ni melts, the viscosity is qualitatively controlled by the packing density.

Experimental studies in fluid mechanics and materials science using acoustic levitation

NASA Technical Reports Server (NTRS)

Trinh, E. H.; Robey, J.; Arce, A.; Gaspar, M.

1987-01-01

Ground-based and short-duration low gravity experiments have been carried out with the use of ultrasonic levitators to study the dynamics of freely suspended liquid drops under the influence of predominantly capillary and acoustic radiation forces. Some of the effects of the levitating field on the shape as well as the fluid flow fields within the drop have been determined. The development and refinement of measurement techniques using levitated drops with size on the order of 2 mm in diameter have yielded methods having direct application to experiments in microgravity. In addition, containerless melting, undercooling, and freezing of organic materials as well as low melting metals have provided experimental data and observations on the application of acoustic positioning techniques to materials studies.

The role of mass transport in protein crystallization.

PubMed

García-Ruiz, Juan Manuel; Otálora, Fermín; García-Caballero, Alfonso

2016-02-01

Mass transport takes place within the mesoscopic to macroscopic scale range and plays a key role in crystal growth that may affect the result of the crystallization experiment. The influence of mass transport is different depending on the crystallization technique employed, essentially because each technique reaches supersaturation in its own unique way. In the case of batch experiments, there are some complex phenomena that take place at the interface between solutions upon mixing. These transport instabilities may drastically affect the reproducibility of crystallization experiments, and different outcomes may be obtained depending on whether or not the drop is homogenized. In diffusion experiments with aqueous solutions, evaporation leads to fascinating transport phenomena. When a drop starts to evaporate, there is an increase in concentration near the interface between the drop and the air until a nucleation event eventually takes place. Upon growth, the weight of the floating crystal overcomes the surface tension and the crystal falls to the bottom of the drop. The very growth of the crystal then triggers convective flow and inhomogeneities in supersaturation values in the drop owing to buoyancy of the lighter concentration-depleted solution surrounding the crystal. Finally, the counter-diffusion technique works if, and only if, diffusive mass transport is assured. The technique relies on the propagation of a supersaturation wave that moves across the elongated protein chamber and is the result of the coupling of reaction (crystallization) and diffusion. The goal of this review is to convince protein crystal growers that in spite of the small volume of the typical protein crystallization setup, transport plays a key role in the crystal quality, size and phase in both screening and optimization experiments.

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.

Ballistic Jumping Drops on Superhydrophobic Surfaces via Electrostatic Manipulation.

PubMed

Li, Ning; Wu, Lei; Yu, Cunlong; Dai, Haoyu; Wang, Ting; Dong, Zhichao; Jiang, Lei

2018-02-01

The ballistic ejection of liquid drops by electrostatic manipulating has both fundamental and practical implications, from raindrops in thunderclouds to self-cleaning, anti-icing, condensation, and heat transfer enhancements. In this paper, the ballistic jumping behavior of liquid drops from a superhydrophobic surface is investigated. Powered by the repulsion of the same kind of charges, water drops can jump from the surface. The electrostatic acting time for the jumping of a microliter supercooled drop only takes several milliseconds, even shorter than the time for icing. In addition, one can control the ballistic jumping direction precisely by the relative position above the electrostatic field. The approach offers a facile method that can be used to manipulate the ballistic drop jumping via an electrostatic field, opening the possibility of energy efficient drop detaching techniques in various applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Application of a Novel DCPD Adjustment Method for the J-R Curve Characterization: A study based on ORNL and ASTM Interlaboratory Results

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

Chen, Xiang; Sokolov, Mikhail A; Nanstad, Randy K

Material fracture toughness in the fully ductile region can be described by a J-integral vs. crack growth resistance curve (J-R curve). As a conventional J-R curve measurement method, the elastic unloading compliance (EUC) method becomes impractical for elevated temperature testing due to relaxation of the material and friction induced back-up shape of the J-R curve. One alternative solution of J-R curve testing applies the Direct Current Potential Drop (DCPD) technique for measuring crack extension. However, besides crack growth, potential drop can also be influenced by plastic deformation, crack tip blunting, etc., and uncertainties exist in the current DCPD methodology especiallymore » in differentiating potential drop due to stable crack growth and due to material deformation. Thus, using DCPD for J-R curve determination remains a challenging task. In this study, a new adjustment procedure for applying DCPD to derive the J-R curve has been developed for conventional fracture toughness specimens, including compact tension, three-point bend, and disk-shaped compact specimens. Data analysis has been performed on Oak Ridge National Laboratory (ORNL) and American Society for Testing and Materials (ASTM) interlaboratory results covering different specimen thicknesses, test temperatures, and materials, to evaluate the applicability of the new DCPD adjustment procedure for J-R curve characterization. After applying the newly-developed procedure, direct comparison between the DCPD method and the normalization method on the same specimens indicated close agreement for the overall J-R curves, as well as the provisional values of fracture toughness near the onset of ductile crack extension, Jq, and of tearing modulus.« less

Experimental studies of contact angle hysteresis phenomena on polymer surfaces – Toward the understanding and control of wettability for different applications.

PubMed

Grundke, K; Pöschel, K; Synytska, A; Frenzel, R; Drechsler, A; Nitschke, M; Cordeiro, A L; Uhlmann, P; Welzel, P B

2015-08-01

Contact angle hysteresis phenomena on polymer surfaces have been studied by contact angle measurements using sessile liquid droplets and captive air bubbles in conjunction with a drop shape method known as Axisymmetric Drop Shape Analysis - Profile (ADSA-P). In addition, commercially available sessile drop goniometer techniques were used. The polymer surfaces were characterized with respect to their surface structure (morphology, roughness, swelling) and surface chemistry (elemental surface composition, acid-base characteristics) by scanning electron microscopy (SEM), scanning force microscopy (SFM), ellipsometry, X-ray photoelectron spectroscopy (XPS) and streaming potential measurements. Heterogeneous polymer surfaces with controlled roughness and chemical composition were prepared by different routes using plasma etching and subsequent dip coating or grafting of polymer brushes, anodic oxidation of aluminium substrates coated with thin polymer films, deposition techniques to create regular patterned and rough fractal surfaces from core-shell particles, and block copolymers. To reveal the effects of swelling and reorientation at the solid/liquid interface contact angle hysteresis phenomena on polyimide surfaces, cellulose membranes, and thermo-responsive hydrogels have been studied. The effect of different solutes in the liquid (electrolytes, surfactants) and their impact on contact angle hysteresis were characterized for solid polymers without and with ionizable functional surface groups in aqueous electrolyte solutions of different ion concentrations and pH and for photoresist surfaces in cationic aqueous surfactant solutions. The work is an attempt toward the understanding of contact angle hysteresis phenomena on polymer surfaces aimed at the control of wettability for different applications. Copyright © 2014 Elsevier B.V. All rights reserved.

Effect of drop jump technique on the reactive strength index.

PubMed

Struzik, Artur; Juras, Grzegorz; Pietraszewski, Bogdan; Rokita, Andrzej

2016-09-01

The basic drill of plyometric training aimed at improving lower limb power and jump height is a drop jump. This exercise can be performed using different techniques, which substantially affects jump variables. Therefore, the aim of this study was to compare the values of the reactive strength index (RSI) for countermovement drop jumps (CDJs) and bounce drop jumps (BDJs). The study was carried out in a group of 8 male youth basketball players. The tests were conducted using the AMTI BP600900 force plate to measure ground reaction forces and the Noraxon MyoMotion system to record kinematic data. Each player performed two CDJs and two BDJs from the height of 15, 30, 45 and 60 cm. The RSI was calculated as a ratio of jump height and contact time. Moreover, the RSI was determined for the amortization and take-off phases separately. Significant differences (p < 0.05) between RSI values for CDJs and BDJs were recorded for jumps from 30, 45 and 60 cm. Differences in RSI values for jumps from 15 cm were not significant. Furthermore, CDJ height values were significantly higher (p < 0.05) than the values recorded for BDJs. Times of contact, amortization and take-off during BDJs were significantly shorter (p < 0.05) than the respective values obtained for CDJs. Therefore, the use of the RSI to monitor plyometric training should be based on the drop jump technique that is commonly performed by basketball players.

Effect of drop jump technique on the reactive strength index

PubMed Central

Juras, Grzegorz; Pietraszewski, Bogdan; Rokita, Andrzej

2016-01-01

Abstract The basic drill of plyometric training aimed at improving lower limb power and jump height is a drop jump. This exercise can be performed using different techniques, which substantially affects jump variables. Therefore, the aim of this study was to compare the values of the reactive strength index (RSI) for countermovement drop jumps (CDJs) and bounce drop jumps (BDJs). The study was carried out in a group of 8 male youth basketball players. The tests were conducted using the AMTI BP600900 force plate to measure ground reaction forces and the Noraxon MyoMotion system to record kinematic data. Each player performed two CDJs and two BDJs from the height of 15, 30, 45 and 60 cm. The RSI was calculated as a ratio of jump height and contact time. Moreover, the RSI was determined for the amortization and take-off phases separately. Significant differences (p < 0.05) between RSI values for CDJs and BDJs were recorded for jumps from 30, 45 and 60 cm. Differences in RSI values for jumps from 15 cm were not significant. Furthermore, CDJ height values were significantly higher (p < 0.05) than the values recorded for BDJs. Times of contact, amortization and take-off during BDJs were significantly shorter (p < 0.05) than the respective values obtained for CDJs. Therefore, the use of the RSI to monitor plyometric training should be based on the drop jump technique that is commonly performed by basketball players. PMID:28149403

Rapid detection of atrazine and metolachlor in farm soils: gas chromatography-mass spectrometry-based analysis using the bubble-in-drop single drop microextraction enrichment method.

PubMed

Williams, D Bradley G; George, Mosotho J; Marjanovic, Ljiljana

2014-08-06

Tracking of metolachlor and atrazine herbicides in agricultural soils, from spraying through to harvest, was conducted using our recently reported "bubble-in-drop single-drop microextraction" method. The method showed good linearity (R(2) = 0.999 and 0.999) in the concentration range of 0.01-1.0 ng/mL with LOD values of 0.01 and 0.02 ng/mL for atrazine and metolachlor, respectively. Sonication methods were poor at releasing these herbicides from the soil matrixes, while hot water extraction readily liberated them, providing an efficient accessible alternative to sonication techniques. Good recoveries of 97% and 105% were shown for atrazine and metolachlor, respectively, from the soil. The spiking protocol was also investigated, resulting in a traceless spiking method. We demonstrate a very sensitive technique by which to assess, for example, the length of residence of pesticides in given soils and thus risk of exposure.

Liquid Alumina: Detailed Atomic Coordination Determined from Neutron Diffraction Data Using Empirical Potential Structure Refinement

NASA Astrophysics Data System (ADS)

Landron, C.; Hennet, L.; Jenkins, T. E.; Greaves, G. N.; Coutures, J. P.; Soper, A. K.

2001-05-01

The neutron scattering structure factor SN\\(Q\\) for a 40 mg drop of molten alumina ( Al2O3) held at 2500 K, using a laser-heated aerodynamic levitation furnace, is measured for the first time. A 1700 atom model of liquid alumina is generated from these data using the technique of empirical potential structural refinement. About 62% of the aluminum sites are 4-fold coordinated, matching the mostly triply coordinated oxygen sites, but some 24% of the aluminum sites are 5-fold coordinated. The octahedral aluminum sites found in crystalline α-Al2O3 occur only at the 2% level in liquid alumina.

Drop shape visualization and contact angle measurement on curved surfaces.

PubMed

Guilizzoni, Manfredo

2011-12-01

The shape and contact angles of drops on curved surfaces is experimentally investigated. Image processing, spline fitting and numerical integration are used to extract the drop contour in a number of cross-sections. The three-dimensional surfaces which describe the surface-air and drop-air interfaces can be visualized and a simple procedure to determine the equilibrium contact angle starting from measurements on curved surfaces is proposed. Contact angles on flat surfaces serve as a reference term and a procedure to measure them is proposed. Such procedure is not as accurate as the axisymmetric drop shape analysis algorithms, but it has the advantage of requiring only a side view of the drop-surface couple and no further information. It can therefore be used also for fluids with unknown surface tension and there is no need to measure the drop volume. Examples of application of the proposed techniques for distilled water drops on gemstones confirm that they can be useful for drop shape analysis and contact angle measurement on three-dimensional sculptured surfaces. Copyright © 2011 Elsevier Inc. All rights reserved.

Automation of static and dynamic non-dispersive liquid phase microextraction. Part 1: Approaches based on extractant drop-, plug-, film- and microflow-formation.

PubMed

Alexovič, Michal; Horstkotte, Burkhard; Solich, Petr; Sabo, Ján

2016-02-04

Simplicity, effectiveness, swiftness, and environmental friendliness - these are the typical requirements for the state of the art development of green analytical techniques. Liquid phase microextraction (LPME) stands for a family of elegant sample pretreatment and analyte preconcentration techniques preserving these principles in numerous applications. By using only fractions of solvent and sample compared to classical liquid-liquid extraction, the extraction kinetics, the preconcentration factor, and the cost efficiency can be increased. Moreover, significant improvements can be made by automation, which is still a hot topic in analytical chemistry. This review surveys comprehensively and in two parts the developments of automation of non-dispersive LPME methodologies performed in static and dynamic modes. Their advantages and limitations and the reported analytical performances are discussed and put into perspective with the corresponding manual procedures. The automation strategies, techniques, and their operation advantages as well as their potentials are further described and discussed. In this first part, an introduction to LPME and their static and dynamic operation modes as well as their automation methodologies is given. The LPME techniques are classified according to the different approaches of protection of the extraction solvent using either a tip-like (needle/tube/rod) support (drop-based approaches), a wall support (film-based approaches), or microfluidic devices. In the second part, the LPME techniques based on porous supports for the extraction solvent such as membranes and porous media are overviewed. An outlook on future demands and perspectives in this promising area of analytical chemistry is finally given. Copyright © 2015 Elsevier B.V. All rights reserved.

Drop jumping. II. The influence of dropping height on the biomechanics of drop jumping.

PubMed

Bobbert, M F; Huijing, P A; van Ingen Schenau, G J

1987-08-01

In the literature, athletes preparing for explosive activities are recommended to include drop jumping in their training programs. For the execution of drop jumps, different techniques and different dropping heights can be used. This study was designed to investigate for the performance of bounce drop jumps the influence of dropping height on the biomechanics of the jumps. Six subjects executed bounce drop jumps from heights of 20 cm (designated here as DJ20), 40 cm (designated here as DJ40), and 60 cm (designated here as DJ60). During jumping, they were filmed, and ground reaction forces were recorded. The results of a biomechanical analysis show no difference between DJ20 and DJ40 in mechanical output about the joints during the push-off phase. Peak values of moment and power output about the ankles during the push-off phase were found to be smaller in DJ60 than in DJ40 (DJ20 = DJ60). The amplitude of joint reaction forces increased with dropping height. During DJ60, the net joint reaction forces showed a sharp peak on the instant that the heels came down on the ground. Based on the results, researchers are advised to limit dropping height to 20 or 40 cm when investigating training effects of the execution of bounce drop jumps.

DROP: Detecting Return-Oriented Programming Malicious Code

NASA Astrophysics Data System (ADS)

Chen, Ping; Xiao, Hai; Shen, Xiaobin; Yin, Xinchun; Mao, Bing; Xie, Li

Return-Oriented Programming (ROP) is a new technique that helps the attacker construct malicious code mounted on x86/SPARC executables without any function call at all. Such technique makes the ROP malicious code contain no instruction, which is different from existing attacks. Moreover, it hides the malicious code in benign code. Thus, it circumvents the approaches that prevent control flow diversion outside legitimate regions (such as W ⊕ X ) and most malicious code scanning techniques (such as anti-virus scanners). However, ROP has its own intrinsic feature which is different from normal program design: (1) uses short instruction sequence ending in "ret", which is called gadget, and (2) executes the gadgets contiguously in specific memory space, such as standard GNU libc. Based on the features of the ROP malicious code, in this paper, we present a tool DROP, which is focused on dynamically detecting ROP malicious code. Preliminary experimental results show that DROP can efficiently detect ROP malicious code, and have no false positives and negatives.

Photoelectron Effects on the Self-Consistent Potential in the Collisionless Polar Wind

NASA Technical Reports Server (NTRS)

Khazanov, G. V.; Liemohn, M. W.; Moore, T. E.

1997-01-01

The presence of unthermalized photoelectrons in the sunlit polar cap leads to an enhanced ambipolar potential drop and enhanced upward ion acceleration. Observations in the topside ionosphere have led to the conclusion that large-scale electrostatic potential drops exist above the spacecraft along polar magnetic field lines connected to regions of photoelectron production. A kinetic approach is used for the O(+), H(+), and photoelectron (p) distributions, while a fluid approach is used to describe the thermal electrons (e) and self-consistent electric field (E(sub II)) electrons are allowed to carry a flux that compensates for photoelectron escape, a critical assumption. Collisional processes are excluded, leading to easier escape of polar wind particles and therefore to the formation of the largest potential drop consistent with this general approach. We compute the steady state electric field enhancement and net potential drop expected in the polar wind due to the presence of photoelectrons as a function of the fractional photoelectron content and the thermal plasma characteristics. For a set of low-altitude boundary conditions typical of the polar wind ionosphere, including 0.1% photoelectron content, we found a potential drop from 500 km to 5 R(sub E) of 6.5 V and a maximum thermal electron temperature of 8800 K. The reasonable agreement of our results with the observed polar wind suggests that the assumptions of this approach are valid.

Frequency-Dependence of Relative Permeability in Steel

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

Bowler, N.

2006-03-06

A study to characterize metal plates by means of a model-based, broadband, four-point potential drop measurement technique has shown that the relative permeability of alloy 1018 low-carbon steel is complex and a function of frequency. A magnetic relaxation is observed at approximately 5 kHz. The relaxation can be described in terms of a parametric (Cole-Cole) model. Factors which influence the frequency, amplitude and breadth of the relaxation, such as applied current amplitude, sample geometry and disorder (e.g. percent carbon content and surface condition), are considered.

Particle-size dependence of immersion freezing: Investigation of INUIT test aerosol particles with freely suspended water drops.

NASA Astrophysics Data System (ADS)

Diehl, Karoline; Debertshäuser, Michael; Eppers, Oliver; Jantsch, Evelyn; Mitra, Subir K.

2014-05-01

One goal of the research group INUIT (Ice Nuclei research UnIT) is to investigate the efficiencies of several test ice nuclei under comparable conditions but with different experimental techniques. In the present studies, two methods are used: the Mainz vertical wind tunnel and an acoustic levitator placed inside a cold chamber. In both cases drops are freely levitated, either at their terminal velocity in the wind tunnel updraft or around the nodes of a standing ultrasonic wave in the acoustic levitator. Thus, heat transfer conditions are well approximated, and wall contact effects on freezing as well as electrical charges of the drops are avoided. Drop radii are 370 μm and 1 mm, respectively. In the wind tunnel, drops are investigated at constant temperatures within a certain time period and the onset of freezing is observed directly. In the acoustic levitator, the drop temperature decreases during the experiments and is measured by an in-situ calibrated Infrared thermometer. The onset of freezing is indicated by a rapid rise of the drop surface temperature because of the release of latent heat. Investigated test ice nuclei are Snomax® as a proxy of biological particles and illite NX as well as K-feldspar as represents of mineral dust. The particle concentrations are 1 × 10-12 to 3 × 10-6 g Snomax® per drop and 5 × 10-9 to 5 × 10-5 g mineral dust per drop. Freezing temperatures are between -2 and -18° C in case of Snomax® and between -14 and -26° C in case of mineral dust. The lower the particle masses per drop the lower are the freezing temperatures. For similar particle concentrations in the drops, the median freezing temperatures determined by the two techniques agree well within the measurement errors. With the knowledge of the specific particle surface area of the mineral dusts, the results are interpreted also in terms of particle surface area per drop. Results from the wind tunnel experiments which are performed at constant temperatures indicate that the freezing times are shorter the lower the temperatures are. For evaluation and comparisons of the data, two models of heterogeneous freezing are applied, the stochastic and the time-independent singular description. The nucleation rate coefficients J(T) as well as the surface densities of active sites ns(T) or the numbers of active sites nm(T) are determined from the experimental data. It is shown that both models are suited to describe the present heterogeneous freezing results for the range of investigated particle masses or surface areas per drop. The comparison of the results from the two experimental techniques evaluated with the time-independent singular model indicates an excellent agreement within the measurement errors.

Stress Corrosion Cracking Study of Aluminum Alloys Using Electrochemical Noise Analysis

NASA Astrophysics Data System (ADS)

Rathod, R. C.; Sapate, S. G.; Raman, R.; Rathod, W. S.

2013-12-01

Stress corrosion cracking studies of aluminum alloys AA2219, AA8090, and AA5456 in heat-treated and non heat-treated condition were carried out using electrochemical noise technique with various applied stresses. Electrochemical noise time series data (corrosion potential vs. time) was obtained for the stressed tensile specimens in 3.5% NaCl aqueous solution at room temperature (27 °C). The values of drop in corrosion potential, total corrosion potential, mean corrosion potential, and hydrogen overpotential were evaluated from corrosion potential versus time series data. The electrochemical noise time series data was further analyzed with rescaled range ( R/ S) analysis proposed by Hurst to obtain the Hurst exponent. According to the results, higher values of the Hurst exponents with increased applied stresses showed more susceptibility to stress corrosion cracking as confirmed in case of alloy AA 2219 and AA8090.

HIV Patients Drop Out in Indonesia: Associated Factors and Potential Productivity Loss.

PubMed

Siregar, Adiatma Ym; Pitriyan, Pipit; Wisaksana, Rudi

2016-07-01

this study reported various factors associated with a higher probability of HIV patients drop out, and potential productivity loss due to HIV patients drop out. we analyzed data of 658 HIV patients from a database in a main referral hospital in Bandung city, West Java, Indonesia from 2007 to 2013. First, we utilized probit regression analysis and included, among others, the following variables: patients' status (active or drop out), CD4 cell count, TB and opportunistic infection (OI), work status, sex, history of injecting drugs, and support from family and peers. Second, we used the drop out data from our database and CD 4 cell count decline rate from another study to estimate the productivity loss due to HIV patients drop out. lower CD4 cell count was associated with a higher probability of drop out. Support from family/peers, living with family, and diagnosed with TB were associated with lower probability of drop out. The productivity loss at national level due to treatment drop out (consequently, due to CD4 cell count decline) can reach US$365 million (using average wage). first, as lower CD 4 cell count was associated with higher probability of drop out, we recommend (to optimize) early ARV initiation at a higher CD 4 cell count, involving scaling up HIV service at the community level. Second, family/peer support should be further emphasized to further ensure treatment success. Third, dropping out from ART will result in a relatively large productivity loss.

Optimal formation of genetically modified and functional pancreatic islet spheroids by using hanging-drop strategy.

PubMed

Kim, H J; Alam, Z; Hwang, J W; Hwang, Y H; Kim, M J; Yoon, S; Byun, Y; Lee, D Y

2013-03-01

Rejection and hypoxia are important factors causing islet loss at an early stage after pancreatic islet transplantation. Recently, islets have been dissociated into single cells for reaggregation into so-called islet spheroids. Herein, we used a hanging-drop strategy to form islet spheroids to achieve functional equivalence to intact islets. To obtain single islet cells, we dissociated islets with trypsin-EDTA digestion for 10 minutes. To obtain spheroids, we dropped various numbers of single cells (125, 250, or 500 cells/30 μL drop) onto a Petri dish, that was inverted for incubation in humidified air containing 5% CO(2) at 37 °C for 7 days. The aggregated spheroids in the droplets were harvested for further culture. The size of the aggregated islet spheroids depended on the number of single cells (125-500 cells/30 μL droplet). Their morphology was similar to that of intact islets without any cellular damage. When treated with various concentrations of glucose to evaluate responsiveness, their glucose-mediated stimulation index value was similar to that of intact islets, an observation that was attributed to strong cell-to-cell interactions in islet spheroids. However, islet spheroids aggregated in general culture dishes showed abnormal glucose responsiveness owing to weak cell-to-cell interactions. Cell-to-cell interactions in islet spheroids were confirmed with an anti-connexin-36 monoclonal antibody. Finally, nonviral poly(ethylene imine)-mediated interleukin-10 cytokine gene delivered beforehand into dissociated single cells before formation of islet spheroids increased the gene transfection efficacy and interleukin-10 secretion from islet spheroids >4-fold compared with intact islets. These results demonstrated the potential application of genetically modified, functional islet spheroids with of controlled size and morphology using an hanging-drop technique. Copyright © 2013 Elsevier Inc. All rights reserved.

Effect of interface deformability on thermocapillary motion of a drop in a tube

NASA Astrophysics Data System (ADS)

Mahesri, S.; Haj-Hariri, H.; Borhan, A.

2014-03-01

The effect of an externally imposed axial temperature gradient on the mobility and deformation of a drop in an otherwise stagnant liquid within an insulated cylindrical tube is investigated. In the absence of bulk transport of momentum and energy, the boundary integral technique is used to obtain the flow and temperature fields inside and outside the deformable drop. The steady drop shapes and the corresponding migration velocities are examined over a wide range of the dimensionless parameters. The steady drop shape is nearly spherical for dimensionless drop sizes <0.5, but becomes slightly elongated in the axial direction for drop sizes comparable to tube diameter. The adverse effect of drop deformation on the effective temperature gradient driving the motion is slightly more pronounced than its favorable effect of reducing drag, thereby leading to a slight reduction in drop mobility with increasing drop deformation. Increasing the viscosity ratio reduces drop deformation and leads to a slight enhancement in the relative mobility (with respect to free thermocapillary motion) of confined drops. When the drop fluid has a lower thermal conductivity than the exterior phase, the presence of the thermally-insulating wall increases the thermal driving force for drop motion (compared to that for the same drop in unbounded domain) by causing more pronounced bending of the isotherms toward the drop. However, the favorable thermal effect of the confining wall is overwhelmed by its retarding hydrodynamic effect, causing the confined drop to always move slower than its unbounded counterpart regardless of the value of the thermal conductivity ratio.

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

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.

Resistive method for measuring the disintegration speed of Prince Rupert's drops

NASA Astrophysics Data System (ADS)

Bochkov, Mark; Gusenkova, Daria; Glushkov, Evgenii; Zotova, Julia; Zhabin, S. N.

2016-09-01

We have successfully applied the resistance grid technique to measure the disintegration speed in a special type of glass objects, widely known as Prince Rupert's drops. We use a fast digital oscilloscope and a simple electrical circuit, glued to the surface of the drops, to detect the voltage changes, corresponding to the breaks in the specific parts of the drops. The results obtained using this method are in good qualitative and quantitative agreement with theoretical predictions and previously published data. Moreover, the proposed experimental setup does not include any expensive equipment (such as a high-speed camera) and can therefore be widely used in high schools and universities.

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...

Comparison of spring-loaded, loss of resistance and hanging drop techniques in lumbar epidural blocks.

PubMed

Gülen, Güven; Akkaya, Taylan; Ozkan, Derya; Kaydul, Mehmet; Gözaydin, Orhan; Gümüş, Haluk

2012-01-01

The spring-loaded syringe is a loss of resistance syringe that provide a more objective sign that the epidural space has been entered compared with the traditional techniques. The aim of this study was to compare the time required to locate the epidural space and the backache incidence with the spring-loaded (SL), loss of resistance (LOR) and the hanging drop (HD) techniques for epidural blocks in patients undergoing transurethral resection procedure. Sixty patients undergoing transurethral resections were enrolled in the study. The patients were randomly assigned to one of three groups. Epidural block was performed in the first group with a spring-loaded syringe (n=20), in the second group with loss-of-resistance syringe (n=20), and in the third group with the hanging drop technique (n=20). The required time to locate the epidural space, the number of attempts, the incidence of dural puncture and the backache incidence were assessed during the procedure and for four weeks after the procedure in all patients. The required time to locate the epidural space was 29.1 ± 9.16 seconds in Group 1; 45.25 ± 19.58 seconds in Group 2, and 47.35 ± 11.42 seconds in Group 3 (p<0.001). In Group 1 this was significantly shorter than the other two groups. There was no significant difference in the number of attempts, the incidence of dural puncture and backache incidence between the three groups (p>0.05). The use of SL syringe was found to have a shorter time period to locate the epidural space when compared with the LOR syringe and hanging drop technique.

Droplet Breakup Mechanisms in Air-blast Atomizers

NASA Astrophysics Data System (ADS)

Aliabadi, Amir Abbas; Taghavi, Seyed Mohammad; Lim, Kelly

2011-11-01

Atomization processes are encountered in many natural and man-made phenomena. Examples are pollen release by plants, human cough or sneeze, engine fuel injectors, spray paint and many more. The physics governing the atomization of liquids is important in understanding and utilizing atomization processes in both natural and industrial processes. We have observed the governing physics of droplet breakup in an air-blast water atomizer using a high magnification, high speed, and high resolution LASER imaging technique. The droplet breakup mechanisms are investigated in three major categories. First, the liquid drops are flattened to form an oblate ellipsoid (lenticular deformation). Subsequent deformation depends on the magnitude of the internal forces relative to external forces. The ellipsoid is converted into a torus that becomes stretched and disintegrates into smaller drops. Second, the drops become elongated to form a long cylindrical thread or ligament that break up into smaller drops (Cigar-shaped deformation). Third, local deformation on the drop surface creates bulges and protuberances that eventually detach themselves from the parent drop to form smaller drops.

Actuation of digital micro drops by electrowetting on open microfluidic chips fabricated in photolithography.

PubMed

Ko, Hyojin; Lee, Jeong Soo; Jung, Chan-Hee; Choi, Jae-Hak; Kwon, Oh-Sun; Shin, Kwanwoo

2014-08-01

Basic manipulations of discrete liquid drops on opened microfluidic chips based on electrowetting on dielectrics were described. While most developed microfluidic chips are closed systems equipped with a top plate to cover mechanically and to contact electrically to drop samples, our chips are opened systems with a single plate without any electric contact to drops directly. The chips consist of a linear array of patterned electrodes at 1.8 mm pitch was fabricated on a glass plate coated with thin hydrophobic and dielectric layers by using various methods including photolithography, spin coating and ion sputtering. Several actuations such as lateral oscillation, colliding mergence and translational motion for 3-10 μL water drops have been demonstrated satisfactory. All these kinetic performances of opened chips were similar to those of closed chip systems, indicating superiority of a none-contact method for the transport of drops on opened microfluidic chips actuated by using electrowetting technique.

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.

A method for determining the actual rate of orientation switching of DNA self-assembled monolayers using optical and electrochemical frequency response analysis.

PubMed

Casanova-Moreno, J; Bizzotto, D

2015-02-17

Electrostatic control of the orientation of fluorophore-labeled DNA strands immobilized on an electrode surface has been shown to be an effective bioanalytical tool. Modulation techniques and later time-resolved measurements were used to evaluate the kinetics of the switching between lying and standing DNA conformations. These measurements, however, are the result of a convolution between the DNA "switching" response time and the other frequency limited responses in the measurement. In this work, a method for analyzing the response of a potential driven DNA sensor is presented by calculating the potential effectively dropped across the electrode interface (using electrochemical impedance spectroscopy) as opposed to the potential applied to the electrochemical cell. This effectively deconvolutes the effect of the charging time on the observed frequency response. The corrected response shows that DNA is able to switch conformation faster than previously reported using modulation techniques. This approach will ensure accurate measurements independent of the electrochemical system, removing the uncertainty in the analysis of the switching response, enabling comparison between samples and measurement systems.

Comparative study of electromechanical impedance and Lamb wave techniques for fatigue crack detection and monitoring in metallic structures

NASA Astrophysics Data System (ADS)

Lim, Say Ian; Liu, Yu; Soh, Chee Kiong

2012-04-01

Fatigue cracks often initiate at the weld toes of welded steel connections. Usually, these cracks cannot be identified by the naked eyes. Existing identification methods like dye-penetration test and alternating current potential drop (ACPD) may be useful for detecting fatigue cracks at the weld toes. To apply these non-destructive evaluation (NDE) techniques, the potential sites have to be accessible during inspection. Therefore, there is a need to explore other detection and monitoring techniques for fatigue cracks especially when their locations are inaccessible or cost of access is uneconomical. Electro-mechanical Impedance (EMI) and Lamb wave techniques are two fast growing techniques in the Structural Health Monitoring (SHM) community. These techniques use piezoelectric ceramics (PZT) for actuation and sensing. Since the monitoring site is only needed to be accessed once for the instrumentation of the transducers, remote monitoring is made possible. The permanent locations of these transducers also translate to having consistent measurement for monitoring. The main focus of this study is to conduct a comparative investigation on the effectiveness and efficiency of the EMI technique and the Lamb wave technique for successful fatigue crack identification and monitoring of welded steel connections using piezoelectric transducers. A laboratory-sized non-load carrying fillet weld specimen is used in this study. The specimen is subjected to cyclic tensile load and data for both techniques are acquired at stipulated intervals. It can be concluded that the EMI technique is sensitive to the crack initiation phase while the Lamb wave technique correlates well with the crack propagation phase.

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…

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.

A split-root technique for measuring root water potential.

PubMed

Adeoye, K B; Rawlins, S L

1981-07-01

Water encounters various resistances in moving along a path of decreasing potential energy from the soil through the plant to the atmosphere. The reported relative magnitudes of these pathway resistances vary widely and often these results are conflicting. One reason for such inconsistency is the difficulty in measuring the potential drop across various segments of the soil-plant-atmosphere continuum. The measurement of water potentials at the soil-root interface and in the root xylem of a transpiring plant remains a challenging problem.In the divided root experiment reported here, the measured water potential of an enclosed, nonabsorbing branch of the root system of young corn (Bonanza) plants to infer the water potential of the remaining roots growing in soil was used. The selected root branch of the seedling was grown in a specially constructed Teflon test tube into which a screen-enclosed thermocouple psychrometer was inserted and sealed to monitor the root's water potential. The root and its surrounding atmosphere were assumed to be in vapor equilibrium.

A Split-Root Technique for Measuring Root Water Potential

PubMed Central

Adeoye, Kingsley B.; Rawlins, Stephen L.

1981-01-01

Water encounters various resistances in moving along a path of decreasing potential energy from the soil through the plant to the atmosphere. The reported relative magnitudes of these pathway resistances vary widely and often these results are conflicting. One reason for such inconsistency is the difficulty in measuring the potential drop across various segments of the soil-plant-atmosphere continuum. The measurement of water potentials at the soil-root interface and in the root xylem of a transpiring plant remains a challenging problem. In the divided root experiment reported here, the measured water potential of an enclosed, nonabsorbing branch of the root system of young corn (Bonanza) plants to infer the water potential of the remaining roots growing in soil was used. The selected root branch of the seedling was grown in a specially constructed Teflon test tube into which a screen-enclosed thermocouple psychrometer was inserted and sealed to monitor the root's water potential. The root and its surrounding atmosphere were assumed to be in vapor equilibrium. Images PMID:16661886

Exploration of Ultralight Nanofiber Aerogels as Particle Filters: Capacity and Efficiency.

PubMed

Deuber, Fabian; Mousavi, Sara; Federer, Lukas; Hofer, Marco; Adlhart, Christian

2018-03-14

Ultralight nanofiber aerogels (NFAs) or nanofiber sponges are a truly three-dimensional derivative of the intrinsically flat electrospun nanofiber mats or membranes (NFMs). Here we investigated the potential of such materials for particle or aerosol filtration because particle filtration is a major application of NFMs. Ultralight NFAs were synthesized from electrospun nanofibers using a solid-templating technique. These materials had a tunable hierarchical cellular open-pore structure. We observed high filtration efficiencies of up to 99.999% at the most penetrating particle size. By tailoring the porosity of the NFAs through the processing parameters, we were able to adjust the number of permeated particles by a factor of 1000 and the pressure drop by a factor of 9. These NFAs acted as a deep-bed filter, and they were capable of handling high dust loadings without any indication of performance loss or an increase in the pressure drop. When the face velocity was increased from 0.75 to 6 cm s -1 , the filtration efficiency remained high within a factor of 1.1-10. Both characteristics were in contrast to the behavior of two commercial NFM particle filters, which showed significant increases in the pressure drop with the filtration time as well as a susceptibility against high face velocities by a factor of 105.

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.

Detailed statistical contact angle analyses; "slow moving" drops on inclining silicon-oxide surfaces.

PubMed

Schmitt, M; Groß, K; Grub, J; Heib, F

2015-06-01

Contact angle determination by sessile drop technique is essential to characterise surface properties in science and in industry. Different specific angles can be observed on every solid which are correlated with the advancing or the receding of the triple line. Different procedures and definitions for the determination of specific angles exist which are often not comprehensible or reproducible. Therefore one of the most important things in this area is to build standard, reproducible and valid methods for determining advancing/receding contact angles. This contribution introduces novel techniques to analyse dynamic contact angle measurements (sessile drop) in detail which are applicable for axisymmetric and non-axisymmetric drops. Not only the recently presented fit solution by sigmoid function and the independent analysis of the different parameters (inclination, contact angle, velocity of the triple point) but also the dependent analysis will be firstly explained in detail. These approaches lead to contact angle data and different access on specific contact angles which are independent from "user-skills" and subjectivity of the operator. As example the motion behaviour of droplets on flat silicon-oxide surfaces after different surface treatments is dynamically measured by sessile drop technique when inclining the sample plate. The triple points, the inclination angles, the downhill (advancing motion) and the uphill angles (receding motion) obtained by high-precision drop shape analysis are independently and dependently statistically analysed. Due to the small covered distance for the dependent analysis (<0.4mm) and the dominance of counted events with small velocity the measurements are less influenced by motion dynamics and the procedure can be called "slow moving" analysis. The presented procedures as performed are especially sensitive to the range which reaches from the static to the "slow moving" dynamic contact angle determination. They are characterised by small deviations of the computed values. Additional to the detailed introduction of this novel analytical approaches plus fit solution special motion relations for the drop on inclined surfaces and detailed relations about the reactivity of the freshly cleaned silicon wafer surface resulting in acceleration behaviour (reactive de-wetting) are presented. Copyright © 2014 Elsevier Inc. All rights reserved.

Secondary electron emission from a dielectric film subjected to an electric field. M.S. Thesis

NASA Technical Reports Server (NTRS)

Quoc-Nguyen, N.

1977-01-01

An electric field in the range of 0.3,3.3 kV/mm is created normal to a thin film FEP teflon sample which accumulates potential of up to 8.8, 13.7 or 18.3 kV when exposed to an electron beam having energy of 10.0, 15.0 or 20.0 kV, respectively. It is found that the secondary electron emission from the charged sample varies with field. The threshold voltage, at which the secondary electron emission coefficient sigma is unity, drops down from a low field value of 13.73 kV to a high field value of 13.11 kV for a 15.0 kV beam. A computational technique was developed that generates equipotential lines or contours and field vectors above a plane where potential is known. The utilization of conformal transformations allows the extension of the technique to configurations which map into a plane.

Apparatus to collect, classify, concentrate, and characterize gas-borne particles

DOEpatents

Rader, Daniel J.; Torczynski, John R.; Wally, Karl; Brockmann, John E.

2002-01-01

An aerosol lab-on-a-chip (ALOC) integrates one or more of a variety of aerosol collection, classification, concentration (enrichment), and characterization processes onto a single substrate or layered stack of such substrates. By taking advantage of modern micro-machining capabilities, an entire suite of discrete laboratory aerosol handling and characterization techniques can be combined in a single portable device that can provide a wealth of data on the aerosol being sampled. The ALOC offers parallel characterization techniques and close proximity of the various characterization modules helps ensure that the same aerosol is available to all devices (dramatically reducing sampling and transport errors). Micro-machine fabrication of the ALOC significantly reduces unit costs relative to existing technology, and enables the fabrication of small, portable ALOC devices, as well as the potential for rugged design to allow operation in harsh environments. Miniaturization also offers the potential of working with smaller particle sizes and lower pressure drops (leading to reduction of power consumption).

Lifetime of oil drops pressed by buoyancy against a planar interface: Large drops

NASA Astrophysics Data System (ADS)

Rojas, Clara; García-Sucre, Máximo; Urbina-Villalba, Germán

2010-11-01

In a previous report [C. Rojas, G. Urbina-Villalba, and M. García-Sucre, Phys. Rev. E 81, 016302 (2010)10.1103/PhysRevE.81.016302] it was shown that emulsion stability simulations are able to reproduce the lifetime of micrometer-size drops of hexadecane pressed by buoyancy against a planar water-hexadecane interface. It was confirmed that small drops (ri<10μm) stabilized with β -casein behave as nondeformable particles, moving with a combination of Stokes and Taylor tensors as they approach the interface. Here, a similar methodology is used to parametrize the potential of interaction of drops of soybean oil stabilized with bovine serum albumin. The potential obtained is then employed to study the lifetime of deformable drops in the range 10≤ri≤1000μm . It is established that the average lifetime of these drops can be adequately replicated using the model of truncated spheres. However, the results depend sensibly on the expressions of the initial distance of deformation and the maximum film radius used in the calculations. The set of equations adequate for large drops is not satisfactory for medium-size drops (10≤ri≤100μm) , and vice versa. In the case of large particles, the increase in the interfacial area as a consequence of the deformation of the drops generates a very large repulsive barrier which opposes coalescence. Nevertheless, the buoyancy force prevails. As a consequence, it is the hydrodynamic tensor of the drops which determine the characteristic behavior of the lifetime as a function of the particle size. While the average values of the coalescence time of the drops can be justified by the mechanism of film thinning, the scattering of the experimental data of large drops cannot be rationalized using the methodology previously described. A possible explanation of this phenomenon required elaborate simulations which combine deformable drops, capillary waves, repulsive interaction forces, and a time-dependent surfactant adsorption.

Calculation of Water Drop Trajectories to and About Arbitrary Three-Dimensional Bodies in Potential Airflow

NASA Technical Reports Server (NTRS)

Norment, H. G.

1980-01-01

Calculations can be performed for any atmospheric conditions and for all water drop sizes, from the smallest cloud droplet to large raindrops. Any subsonic, external, non-lifting flow can be accommodated; flow into, but not through, inlets also can be simulated. Experimental water drop drag relations are used in the water drop equations of motion and effects of gravity settling are included. Seven codes are described: (1) a code used to debug and plot body surface description data; (2) a code that processes the body surface data to yield the potential flow field; (3) a code that computes flow velocities at arrays of points in space; (4) a code that computes water drop trajectories from an array of points in space; (5) a code that computes water drop trajectories and fluxes to arbitrary target points; (6) a code that computes water drop trajectories tangent to the body; and (7) a code that produces stereo pair plots which include both the body and trajectories. Code descriptions include operating instructions, card inputs and printouts for example problems, and listing of the FORTRAN codes. Accuracy of the calculations is discussed, and trajectory calculation results are compared with prior calculations and with experimental data.

Application of a free-energy-landscape approach to study tension-dependent bilayer tubulation mediated by curvature-inducing proteins.

PubMed

Tourdot, Richard W; Ramakrishnan, N; Baumgart, Tobias; Radhakrishnan, Ravi

2015-10-01

We investigate the phenomenon of protein-induced tubulation of lipid bilayer membranes within a continuum framework using Monte Carlo simulations coupled with the Widom insertion technique to compute excess chemical potentials. Tubular morphologies are spontaneously formed when the density and the curvature-field strength of the membrane-bound proteins exceed their respective thresholds and this transition is marked by a sharp drop in the excess chemical potential. We find that the planar to tubular transition can be described by a micellar model and that the corresponding free-energy barrier increases with an increase in the curvature-field strength (i.e., of protein-membrane interactions) and also with an increase in membrane tension.

Application of Hanging Drop Technique for Kidney Tissue Culture.

PubMed

Wang, Shaohui; Wang, Ximing; Boone, Jasmine; Wie, Jin; Yip, Kay-Pong; Zhang, Jie; Wang, Lei; Liu, Ruisheng

2017-01-01

The hanging drop technique is a well-established method used in culture of animal tissues. However, this method has not been used in adult kidney tissue culture yet. This study was to explore the feasibility of using this technique for culturing adult kidney cortex to study the time course of RNA viability in the tubules and vasculature, as well as the tissue structural integrity. In each Petri dish with the plate covered with sterile buffer, a section of mouse renal cortex was cultured within a drop of DMEM culture medium on the inner surface of the lip facing downward. The tissue were then harvested at each specific time points for Real-time PCR analysis and histological studies. The results showed that the mRNA level of most Na+ related transporters and cotransporters were stably maintained within 6 hours in culture, and that the mRNA level of most receptors found in the vasculature and glomeruli were stably maintained for up to 9 days in culture. Paraffin sections of the cultured renal cortex indicated that the tubules began to lose tubular integrity after 6 hours, but the glomeruli and vasculatures were still recognizable up to 9 days in culture. We concluded that adult kidney tissue culture by hanging drop method can be used to study gene expressions in vasculature and glomeruli. © 2017 The Author(s). Published by S. Karger AG, Basel.

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.

Wettability Switching Techniques on Superhydrophobic Surfaces

PubMed Central

2007-01-01

The wetting properties of superhydrophobic surfaces have generated worldwide research interest. A water drop on these surfaces forms a nearly perfect spherical pearl. Superhydrophobic materials hold considerable promise for potential applications ranging from self cleaning surfaces, completely water impermeable textiles to low cost energy displacement of liquids in lab-on-chip devices. However, the dynamic modification of the liquid droplets behavior and in particular of their wetting properties on these surfaces is still a challenging issue. In this review, after a brief overview on superhydrophobic states definition, the techniques leading to the modification of wettability behavior on superhydrophobic surfaces under specific conditions: optical, magnetic, mechanical, chemical, thermal are discussed. Finally, a focus on electrowetting is made from historical phenomenon pointed out some decades ago on classical planar hydrophobic surfaces to recent breakthrough obtained on superhydrophobic surfaces.

Picoliter Drop-On-Demand Dispensing for Multiplex Liquid Cell Transmission Electron Microscopy

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

Patterson, Joseph P.; Parent, Lucas R.; Cantlon, Joshua

2016-05-03

Abstract Liquid cell transmission electron microscopy (LCTEM) provides a unique insight into the dynamics of nanomaterials in solution. Controlling the addition of multiple solutions to the liquid cell remains a key hurdle in our ability to increase throughput and to study processes dependent on solution mixing including chemical reactions. Here, we report that a piezo dispensing technique allows for mixing of multiple solutions directly within the viewing area. This technique permits deposition of 50 pL droplets of various aqueous solutions onto the liquid cell window, before assembly of the cell in a fully controlled manner. This proof-of-concept study highlights themore » great potential of picoliter dispensing in combination with LCTEM for observing nanoparticle mixing in the solution phase and the creation of chemical gradients.« less

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.

Max Launch Abort System (MLAS) Landing Parachute Demonstrator (LPD) Drop Test

NASA Technical Reports Server (NTRS)

Shreves, Christopher M.

2011-01-01

The Landing Parachute Demonstrator (LPD) was conceived as a low-cost, rapidly-developed means of providing soft landing for the Max Launch Abort System (MLAS) crew module (CM). Its experimental main parachute cluster deployment technique and off-the-shelf hardware necessitated a full-scale drop test prior to the MLAS mission in order to reduce overall mission risk. This test was successfully conducted at Wallops Flight Facility on March 6, 2009, with all vehicle and parachute systems functioning as planned. The results of the drop test successfully qualified the LPD system for the MLAS flight test. This document captures the design, concept of operations and results of the drop test.

Rotating Molten Metallic Drops and Related Phenomena: A New Approach to the Surface Tension Measurement

NASA Technical Reports Server (NTRS)

Rhim, Won-Kyu; Ishikawa, Takehiko

2000-01-01

Molten aluminum and tin drops were levitated in a high vacuum by controlled electric fields, and they were systematically rotated by applying by a rotating magnetic field. When the evolution of the drop shape was measured as a function of rotation frequency, it agreed quantitatively well with the Brown and Scriven's theoretical prediction. The normalized rotation frequencies at the bifurcation point agreed with the predicted value 0.559, within 2%. An anomalous phenomenon which totally deviated from the prediction was observed in rotating molten tin drops when they were kept in a high rotation rate for several hours. No anomaly was observed in aluminum drops when they underwent similar condition. It was speculated that under the strong centrifugal force in the drop the tin isotopes must be separating. Since Al-27 is essentially the only naturally abundant isotope in the aluminum drops, the same anomaly is not expected. Based on the shape deformation of a rotating drop, an alternate approach to the surface tension measurement was verified. This new surface tension measurement technique was applied to a glassforming alloy, Zr(41.2)Ti(13.8)Cu(12.5)Ni(10.0)Be(22.5) in its highly viscous states. Also demonstrated in the paper was a use of a molten aluminum drop to verify the Busse's prediction of the influence of the drop rotation on the drop oscillation frequency.

Comparison of Personal, Social and Academic Variables Related to University Drop-out and Persistence.

PubMed

Bernardo, Ana; Esteban, María; Fernández, Estrella; Cervero, Antonio; Tuero, Ellián; Solano, Paula

2016-01-01

Dropping out of university has serious consequences not only for the student who drops out but also for the institution and society as a whole. Although this phenomenon has been widely studied, there is a need for broader knowledge of the context in which it occurs. Yet research on the subject often focuses on variables that, although they affect drop-out rates, lie beyond a university's control. This makes it hard to come up with effective preventive measures. That is why a northern Spanish university has undertaken a ex post facto holistic research study on 1,311 freshmen (2008/9, 2009/10, and 2010/11 cohorts). The study falls within the framework of the ALFA-GUIA European Project and focuses on those drop-out factors where there is scope for taking remedial measures. This research explored the possible relationship of degree drop-out and different categories of variables: variables related to the educational stage prior to university entry (path to entry university and main reason for degree choice), variables related to integration and coexistence at university (social integration, academic integration, relationships with teachers/peers and value of the living environment) financial status and performance during university studies (in terms of compliance with the program, time devoted to study, use of study techniques and class attendance). Descriptive, correlational and variance analyses were conducted to discover which of these variables really distinguish those students who drop-out from their peers who complete their studies. Results highlight the influence of vocation as main reason for degree choice, path to university entry, financial independency, social and academic adaptation, time devoted to study, use of study techniques and program compliance in the studied phenomenon.

Comparison of Personal, Social and Academic Variables Related to University Drop-out and Persistence

PubMed Central

Bernardo, Ana; Esteban, María; Fernández, Estrella; Cervero, Antonio; Tuero, Ellián; Solano, Paula

2016-01-01

Dropping out of university has serious consequences not only for the student who drops out but also for the institution and society as a whole. Although this phenomenon has been widely studied, there is a need for broader knowledge of the context in which it occurs. Yet research on the subject often focuses on variables that, although they affect drop-out rates, lie beyond a university’s control. This makes it hard to come up with effective preventive measures. That is why a northern Spanish university has undertaken a ex post facto holistic research study on 1,311 freshmen (2008/9, 2009/10, and 2010/11 cohorts). The study falls within the framework of the ALFA-GUIA European Project and focuses on those drop-out factors where there is scope for taking remedial measures. This research explored the possible relationship of degree drop-out and different categories of variables: variables related to the educational stage prior to university entry (path to entry university and main reason for degree choice), variables related to integration and coexistence at university (social integration, academic integration, relationships with teachers/peers and value of the living environment) financial status and performance during university studies (in terms of compliance with the program, time devoted to study, use of study techniques and class attendance). Descriptive, correlational and variance analyses were conducted to discover which of these variables really distinguish those students who drop-out from their peers who complete their studies. Results highlight the influence of vocation as main reason for degree choice, path to university entry, financial independency, social and academic adaptation, time devoted to study, use of study techniques and program compliance in the studied phenomenon. PMID:27803684

Remote Sensing of In-Flight Icing Conditions: Operational, Meteorological, and Technological Considerations

NASA Technical Reports Server (NTRS)

Ryerson, Charles C.

2000-01-01

Remote-sensing systems that map aircraft icing conditions in the flight path from airports or aircraft would allow icing to be avoided and exited. Icing remote-sensing system development requires consideration of the operational environment, the meteorological environment, and the technology available. Operationally, pilots need unambiguous cockpit icing displays for risk management decision-making. Human factors, aircraft integration, integration of remotely sensed icing information into the weather system infrastructures, and avoid-and-exit issues need resolution. Cost, maintenance, power, weight, and space concern manufacturers, operators, and regulators. An icing remote-sensing system detects cloud and precipitation liquid water, drop size, and temperature. An algorithm is needed to convert these conditions into icing potential estimates for cockpit display. Specification development requires that magnitudes of cloud microphysical conditions and their spatial and temporal variability be understood at multiple scales. The core of an icing remote-sensing system is the technology that senses icing microphysical conditions. Radar and microwave radiometers penetrate clouds and can estimate liquid water and drop size. Retrieval development is needed; differential attenuation and neural network assessment of multiple-band radar returns are most promising to date. Airport-based radar or radiometers are the most viable near-term technologies. A radiometer that profiles cloud liquid water, and experimental techniques to use radiometers horizontally, are promising. The most critical operational research needs are to assess cockpit and aircraft system integration, develop avoid-and-exit protocols, assess human factors, and integrate remote-sensing information into weather and air traffic control infrastructures. Improved spatial characterization of cloud and precipitation liquid-water content, drop-size spectra, and temperature are needed, as well as an algorithm to convert sensed conditions into a measure of icing potential. Technology development also requires refinement of inversion techniques. These goals can be accomplished with collaboration among federal agencies including NASA, the FAA, the National Center for Atmospheric Research, NOAA, and the Department of Defense. This report reviews operational, meteorological, and technological considerations in developing the capability to remotely map in-flight icing conditions from the ground and from the air.

Simulating New Drop Test Vehicles and Test Techniques for the Orion CEV Parachute Assembly System

NASA Technical Reports Server (NTRS)

Morris, Aaron L.; Fraire, Usbaldo, Jr.; Bledsoe, Kristin J.; Ray, Eric; Moore, Jim W.; Olson, Leah M.

2011-01-01

The Crew Exploration Vehicle Parachute Assembly System (CPAS) project is engaged in a multi-year design and test campaign to qualify a parachute recovery system for human use on the Orion Spacecraft. Test and simulation techniques have evolved concurrently to keep up with the demands of a challenging and complex system. The primary simulations used for preflight predictions and post-test data reconstructions are Decelerator System Simulation (DSS), Decelerator System Simulation Application (DSSA), and Drop Test Vehicle Simulation (DTV-SIM). The goal of this paper is to provide a roadmap to future programs on the test technique challenges and obstacles involved in executing a large-scale, multi-year parachute test program. A focus on flight simulation modeling and correlation to test techniques executed to obtain parachute performance parameters are presented.

Measurement of surface tension by sessile drop tensiometer with superoleophobic surface

NASA Astrophysics Data System (ADS)

Kwak, Wonshik; Park, Jun Kwon; Yoon, Jinsung; Lee, Sanghyun; Hwang, Woonbong

2018-03-01

A sessile drop tensiometer provides a simple and efficient method of determining the surface tension of various liquids. The technique involves obtaining the shape of an axisymmetric liquid droplet and iterative fitting of the Young-Laplace equation, which balances the gravitational deformation of the drop. Since the advent of high quality digital cameras and desktop computers, this process has been automated with precision. However, despite its appealing simplicity, there are complications and limitations in a sessile drop tensiometer, i.e., it must dispense spherical droplets with low surface tension. We propose a method of measuring surface tension using a sessile drop tensiometer with a superoleophobic surface fabricated by acidic etching and anodization for liquids with low surface tension and investigate the accuracy of the measurement by changing the wettability of the measuring plate surface.

Techniques for Teachers Section

ERIC Educational Resources Information Center

Tait, A., Ed.

1973-01-01

Includes a simple technique to demonstrate Millikan's oil drop experiment, an environmental studies experiment to measure dissolved oxygen in water samples, and a technique to demonstrate action-reaction. Science materials described are the Pol-A-Star Tomiscope, Nuffield chemistry film loops, air pucks and pH meters. (JR)

Printability of calcium phosphate: calcium sulfate powders for the application of tissue engineered bone scaffolds using the 3D printing technique.

PubMed

Zhou, Zuoxin; Buchanan, Fraser; Mitchell, Christina; Dunne, Nicholas

2014-05-01

In this study, calcium phosphate (CaP) powders were blended with a three-dimensional printing (3DP) calcium sulfate (CaSO4)-based powder and the resulting composite powders were printed with a water-based binder using the 3DP technology. Application of a water-based binder ensured the manufacture of CaP:CaSO4 constructs on a reliable and repeatable basis, without long term damage of the printhead. Printability of CaP:CaSO4 powders was quantitatively assessed by investigating the key 3DP process parameters, i.e. in-process powder bed packing, drop penetration behavior and the quality of printed solid constructs. Effects of particle size, CaP:CaSO4 ratio and CaP powder type on the 3DP process were considered. The drop penetration technique was used to reliably identify powder formulations that could be potentially used for the application of tissue engineered bone scaffolds using the 3DP technique. Significant improvements (p<0.05) in the 3DP process parameters were found for CaP (30-110 μm):CaSO4 powders compared to CaP (<20 μm):CaSO4 powders. Higher compressive strength was obtained for the powders with the higher CaP:CaSO4 ratio. Hydroxyapatite (HA):CaSO4 powders showed better results than beta-tricalcium phosphate (β-TCP):CaSO4 powders. Solid and porous constructs were manufactured using the 3DP technique from the optimized CaP:CaSO4 powder formulations. High-quality printed constructs were manufactured, which exhibited appropriate green compressive strength and a high level of printing accuracy. Copyright © 2014 Elsevier B.V. All rights reserved.

Systematic Improvement of Protein Crystals by Determining the Supersolubility Curves of Phase Diagrams

PubMed Central

Saridakis, Emmanuel; Chayen, Naomi E.

2003-01-01

A systematic approach for improving protein crystals by growing them in the metastable zone using the vapor diffusion technique is described. This is a simple technique for optimization of crystallization conditions. Screening around known conditions is performed to establish a working phase diagram for the crystallization of the protein. Dilutions of the crystallization drops across the supersolubility curve into the metastable zone are then carried out as follows: the coverslips holding the hanging drops are transferred, after being incubated for some time at conditions normally giving many small crystals, over reservoirs at concentrations which normally yield clear drops. Fewer, much larger crystals are obtained when the incubation times are optimized, compared with conventional crystallization at similar conditions. This systematic approach has led to the structure determination of the light-harvesting protein C-phycocyanin to the highest-ever resolution of 1.45 Å. PMID:12547801

Utilization of Low Gravity Environment for Measuring Liquid Viscosity

NASA Technical Reports Server (NTRS)

Antar, Basil N.; Ethridge, Edwin

1998-01-01

The method of drop coalescence is used for determining the viscosity of highly viscous undercooled liquids. Low gravity environment is necessary in order to allow for examining large volumes affording much higher accuracy for the viscosity calculations than possible for smaller volumes available under 1 - g conditions. The drop coalescence method is preferred over the drop oscillation technique since the latter method can only be applied for liquids with vanishingly small viscosities. The technique developed relies on both the highly accurate solution of the Navier-Stokes equations as well as on data from experiments conducted in near zero gravity environment. Results are presented for method validation experiments recently performed on board the NASA/KC-135 aircraft. While the numerical solution was produced using the Boundary Element Method. In these tests the viscosity of a highly viscous liquid, glycerine at room temperature, was determined using the liquid coalescence method. The results from these experiments will be discussed.

Spray nozzle designs for agricultural aviation applications. [relation of drop size to spray characteristics and nozzle efficiency

NASA Technical Reports Server (NTRS)

Lee, K. W.; Putnam, A. A.; Gieseke, J. A.; Golovin, M. N.; Hale, J. A.

1979-01-01

Techniques of generating monodisperse sprays and information concerning chemical liquids used in agricultural aviation are surveyed. The periodic dispersion of liquid jet, the spinning disk method, and ultrasonic atomization are the techniques discussed. Conceptually designed spray nozzles for generating monodisperse sprays are assessed. These are based on the classification of the drops using centrifugal force, on using two opposing liquid laden air jets, and on operating a spinning disk at an overloaded flow. Performance requirements for the designs are described and estimates of the operational characteristics are presented.

Search for free fractional electric charge elementary particles using an automated millikan oil drop technique

PubMed

Halyo; Kim; Lee; Lee; Loomba; Perl

2000-03-20

We have carried out a direct search in bulk matter for free fractional electric charge elementary particles using the largest mass single sample ever studied-about 17.4 mg of silicone oil. The search used an improved and highly automated Millikan oil drop technique. No evidence for fractional charge particles was found. The concentration of particles with fractional charge more than 0. 16e ( e being the magnitude of the electron charge) from the nearest integer charge is less than 4.71x10(-22) particles per nucleon with 95% confidence.

Final Technical Report: Electrohydrodynamic Tip Streaming

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

Basaran, Osman

2016-01-06

When subjected to strong electric fields, liquid drops and films form conical tips and emit thin jets from their tips. Such electrodydrodynamic (EDH) tip streaming or cone-jetting phenomena, which are sometimes referred to as electrospraying, occur widely in nature, e.g., in ejection of streams of small charged drops from pointed tips of raindrops in thunderclouds, and technology, e.g., in electrospray mass spectrometry or electric field-driven solvent extraction. More recently, EHD cone-jetting has emerged as a powerful technique for direct printing of solar cells, micro- and nano- particle production, and microencapsulation for controlled release. In many of the aforementioned situations, ofmore » equal importance to the processes by which one drop disintegrates to form several drops are those by which (a) two drops come together and coalesce and (b) two drops are coupled to form a double droplet system (DDS) or a capillary switch (CS). the main objective of this research program is to advance through simulation, theory, and experiment the breakup, coalescence, and oscillatory dynamics of single and pairs of charged as well as uncharged drops.« less

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.

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

Acoustically induced oscillation and rotation of a large drop in space

NASA Astrophysics Data System (ADS)

Jacobi, N.; Croonquist, A. P.; Elleman, D. D.; Wang, T. G.

1982-03-01

A 2.5 cm diameter water drop was successfully deployed and manipulated in a triaxial acoustic resonance chamber during a 240 sec low-gravity SPAR rocket flight. Oscillation and rotation were induced by modulating and phase shifting the signals to the speakers. Portions of the film record were digitized and analyzed. Spectral analysis brought out the n = 2, 3, 4 free oscillation modes of the drop, its very low-frequency center-of-mass motion in the acoustic potential well, and the forced oscillation frequency. The drop boundaries were least-square fitted to general ellipses, providing eccentricities of the distorted drop. The normalized equatorial area of the rotating drop was plotted vs a rotational parameter, and was in excellent agreement with values derived from the theory of equilibrium shapes of rotating liquid drops.

Synchronous Half-Wave Rectifier

NASA Technical Reports Server (NTRS)

Rippel, Wally E.

1989-01-01

Synchronous rectifying circuit behaves like diode having unusually low voltage drop during forward-voltage half cycles. Circuit particularly useful in power supplies with potentials of 5 Vdc or less, where normal forward-voltage drops in ordinary diodes unacceptably large. Fabricated as monolithic assembly or as hybrid. Synchronous half-wave rectifier includes active circuits to attain low forward voltage drop and high rectification efficiency.

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.

CFD simulation of liquid-liquid dispersions in a stirred tank bioreactor

NASA Astrophysics Data System (ADS)

Gelves, R.

2013-10-01

In this paper simulations were developed in order to allow the examinations of drop sizes in liquid-liquid dispersions (oil-water) in a stirred tank bioreactor using CFD simulations (Computational Fluid Dynamics). The effects of turbulence, rotating flow, drop breakage were simulated by using the k-e, MRF (Multiple Reference Frame) and PBM (Population Balance Model), respectively. The numerical results from different operational conditions are compared with experimental data obtained from an endoscope technique and good agreement is achieved. Motivated by these simulated and experimental results CFD simulations are qualified as a very promising tool for predicting hydrodynamics and drop sizes especially useful for liquid-liquid applications which are characterized by the challenging problem of emulsion stability due to undesired drop sizes.

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

Calculation of water drop trajectories to and about arbitrary three-dimensional lifting and nonlifting bodies in potential airflow

NASA Technical Reports Server (NTRS)

Norment, H. G.

1985-01-01

Subsonic, external flow about nonlifting bodies, lifting bodies or combinations of lifting and nonlifting bodies is calculated by a modified version of the Hess lifting code. Trajectory calculations can be performed for any atmospheric conditions and for all water drop sizes, from the smallest cloud droplet to large raindrops. Experimental water drop drag relations are used in the water drop equations of motion and effects of gravity settling are included. Inlet flow can be accommodated, and high Mach number compressibility effects are corrected for approximately. Seven codes are described: (1) a code used to debug and plot body surface description data; (2) a code that processes the body surface data to yield the potential flow field; (3) a code that computes flow velocities at arrays of points in space; (4) a code that computes water drop trajectories from an array of points in space; (5) a code that computes water drop trajectories and fluxes to arbitrary target points; (6) a code that computes water drop trajectories tangent to the body; and (7) a code that produces stereo pair plots which include both the body and trajectories. Accuracy of the calculations is discussed, and trajectory calculation results are compared with prior calculations and with experimental data.

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.

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.

Analysis of preparation of Chinese traditional medicine based on the fiber fingerprint drop trace

NASA Astrophysics Data System (ADS)

Zhang, Zhilin; Wang, Jialu; Sun, Weimin; Yan, Qi

2010-11-01

The purpose of the fiber micro-drop analyzing technique is to measure the characteristics of liquids using optical methods. The fiber fingerprint drop trace (FFDT) is a curve of light intensity vs. time. This curve indicates the forming, growing and dripping processes of the liquid drops. A pair of fibers was used to monitor the dripping process. The FFDTs are acquired and analyzed by a computer. Different liquid samples of many kinds of preparation of Chinese traditional medicines were tested by using the fiber micro-drop sensor in the experiments. The FFDTs of preparation of Chinese traditional medicines with different concentrations were analyzed in different ways. Considering the characters of the FFDTs, a novel method is proposed to measure the different preparation of Chinese traditional medicines and its concentration based on the corresponding relationship of FFDTs and the physical and chemical parameters of the liquids.

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

NASA Technical Reports Server (NTRS)

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

1986-01-01

Models are presented for particle distributions, electric fields and currents in an adiabatic treatment of auroral electrostatic potential distributions in order to describe the quiet-time evening auroral arcs featuring both upward and return currents. The models are consistent with current continuity and charge balance requirements for particle populations controlled by adiabatic invariants and quasi-neutrality in the magnetosphere. The effective energy of the cool electron population is demonstrated to have a significant effect on the latitudinal breadth of the auroral electrostatic potential structure and the extent of the penetration of the accelerating potential into the ionosphere. Another finding is that the energy of any parallel potential drop in the lowest few thousand kilometers of the field line is of the same order of magnitude as the thermal energy of the cool electrons. Additional predictions include density cavities along field lines that support large potential drops, and density enhancements along field lines at the edge of an inverted V with a small potential drop.

[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.

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

Tao, Keyu; Shenzhen Key Laboratory of Micro-Nano Photonic Information Technology, Shenzhen 518067; College of Electronic Science and Technology, Shenzhen University, Shenzhen 518067

We present a versatile add-drop integrated photonic filter (ADF) consisting of nonreciprocal waveguides in which the propagation of light is restricted in one predetermined direction. With the bus and add/drop waveguides symmetrically coupled through a cavity, the four-port device allows each individual port to add and/or drop a signal of the same frequency. The scheme is general and we demonstrate the nonreciprocal ADF with magneto-optical photonic crystals. The filter is immune to waveguide defects, allowing straightforward implementation of multi-channel ADFs by cascading the four-port designs. The results should find applications in wavelength-division multiplexing and related integrated photonic techniques.

Structure and Dynamics of Interfaces: Drops and Films

NASA Technical Reports Server (NTRS)

Mann, J. Adin, Jr.; Mann, Elizabeth K.; Meyer, William V.; Neumann, A. Wilhelm; Tavana, Hossein

2015-01-01

We aim to acquire measurements of the structure and dynamics of certain liquid-fluid interfaces using an ensemble of techniques in collaboration: (1) Total internal reflection (TIR) Surface light scattering spectroscopy (SLSS), (2) Brewster angle microscopy (BAM), and (3) Drop-shape analysis. SLSS and BAM can be done on a shared interfacial footprint. Results using a 50-50 mixture of pentane-isohexane, which extends the range of NASA's Confined Vapor Bubble (CVB) experiment, yield surface tension results that differ from the expected Langmuir Fit. These results were confirmed using both the SLSS and drop-shape analysis approaches.

Sensing Technologies for Detection of Acetone in Human Breath for Diabetes Diagnosis and Monitoring

PubMed Central

Saasa, Valentine; Malwela, Thomas; Beukes, Mervyn; Mokgotho, Matlou; Liu, Chaun-Pu; Mwakikunga, Bonex

2018-01-01

The review describes the technologies used in the field of breath analysis to diagnose and monitor diabetes mellitus. Currently the diagnosis and monitoring of blood glucose and ketone bodies that are used in clinical studies involve the use of blood tests. This method entails pricking fingers for a drop of blood and placing a drop on a sensitive area of a strip which is pre-inserted into an electronic reading instrument. Furthermore, it is painful, invasive and expensive, and can be unsafe if proper handling is not undertaken. Human breath analysis offers a non-invasive and rapid method for detecting various volatile organic compounds thatare indicators for different diseases. In patients with diabetes mellitus, the body produces excess amounts of ketones such as acetoacetate, beta-hydroxybutyrate and acetone. Acetone is exhaled during respiration. The production of acetone is a result of the body metabolising fats instead of glucose to produce energy. There are various techniques that are used to analyse exhaled breath including Gas Chromatography Mass Spectrometry (GC–MS), Proton Transfer Reaction Mass Spectrometry (PTR–MS), Selected Ion Flow Tube-Mass Spectrometry (SIFT–MS), laser photoacoustic spectrometry and so on. All these techniques are not portable, therefore this review places emphasis on how nanotechnology, through semiconductor sensing nanomaterials, has the potential to help individuals living with diabetes mellitus monitor their disease with cheap and portable devices. PMID:29385067

The effect of surface conditions on the work function of insulators and semiconductors

NASA Technical Reports Server (NTRS)

George, A.

1973-01-01

Ionization energies of organic semiconductors were determined using single crystals of the material. The theory of the method is essentially that of Millikan's oil drop experiment. The technique employed in the experiment is based on the electrostatic method of balancing a charged particle in an electric field against the force of gravity for different excitation energies above the threshold value, and from an estimate of the balancing voltages, read off the ionization energy from the intercept of the energy axis in a plot wavelength corresponding to the balancing potential for the incident radiation of wavelength. In the modified technique which is adopted in the present experimental investigation, a small single crystal is suspended by a fine quartz fiber between two vertical capacitor plates to which a suitable high voltage is applied.

A Novel Approach to Realize of All Optical Frequency Encoded Dibit Based XOR and XNOR Logic Gates Using Optical Switches with Simulated Verification

NASA Astrophysics Data System (ADS)

Ghosh, B.; Hazra, S.; Haldar, N.; Roy, D.; Patra, S. N.; Swarnakar, J.; Sarkar, P. P.; Mukhopadhyay, S.

2018-03-01

Since last few decades optics has already proved its strong potentiality for conducting parallel logic, arithmetic and algebraic operations due to its super-fast speed in communication and computation. So many different logical and sequential operations using all optical frequency encoding technique have been proposed by several authors. Here, we have keened out all optical dibit representation technique, which has the advantages of high speed operation as well as reducing the bit error problem. Exploiting this phenomenon, we have proposed all optical frequency encoded dibit based XOR and XNOR logic gates using the optical switches like add/drop multiplexer (ADM) and reflected semiconductor optical amplifier (RSOA). Also the operations of these gates have been verified through proper simulation using MATLAB (R2008a).

Just the Right Mix: Identifying Potential Dropouts in Montgomery County Public Schools Using an Early Warning Indicators Approach

ERIC Educational Resources Information Center

West, Thomas C.

2013-01-01

Each school year, roughly a thousand students drop out of Montgomery County (Maryland) Public Schools (MCPS). However, unlike other large, urban school districts where students who drop out skip school and are suspended often (Balfanz & Byrnes, 2010), students who drop out of MCPS are present in school; they just are not doing well…

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.

Novel Sessile Drop Software for Quantitative Estimation of Slag Foaming in Carbon/Slag Interactions

NASA Astrophysics Data System (ADS)

Khanna, Rita; Rahman, Mahfuzur; Leow, Richard; Sahajwalla, Veena

2007-08-01

Novel video-processing software has been developed for the sessile drop technique for a rapid and quantitative estimation of slag foaming. The data processing was carried out in two stages: the first stage involved the initial transformation of digital video/audio signals into a format compatible with computing software, and the second stage involved the computation of slag droplet volume and area of contact in a chosen video frame. Experimental results are presented on slag foaming from synthetic graphite/slag system at 1550 °C. This technique can be used for determining the extent and stability of foam as a function of time.

Using Single Drop Microextraction for Headspace Analysis with Gas Chromatography

NASA Astrophysics Data System (ADS)

Riccio, Daniel; Wood, Derrick C.; Miller, James M.

2008-07-01

Headspace (HS) gas chromatography (GC) is commonly used to analyze samples that contain non-volatiles. In 1996, a new sampling technique called single drop microextraction, SDME, was introduced, and in 2001 it was applied to HS analysis. It is a simple technique that uses equipment normally found in the undergraduate laboratory, making it ideal for instructional use, especially to illustrate HS analysis or as an alternative to solid-phase microextraction (SPME) to which it is very similar. The basic principles and practice of HS-GC using SDME are described, including a complete review of the literature. Some possible experiments are suggested using water and N -methylpyrrolidone (NMP) as solvents.

Micro-structural characterization of precipitation-synthesized fluorapatite nano-material by transmission electron microscopy using different sample preparation techniques.

PubMed

Chinthaka Silva, G W; Ma, Longzhou; Hemmers, Oliver; Lindle, Dennis

2008-01-01

Fluorapatite is a naturally occurring mineral of the apatite group and it is well known for its high physical and chemical stability. There is a recent interest in this ceramic to be used as a radioactive waste form material due to its intriguing chemical and physical properties. In this study, the nano-sized fluorapatite particles were synthesized using a precipitation method and the material was characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Two well-known methods, called solution-drop and the microtome cutting, were used to prepare the sample for TEM analysis. It was found that the microtome cutting technique is advantageous for examining the particle shape and cross-sectional morphology as well as for obtaining ultra-thin samples. However, this method introduces artifacts and strong background contrast for high-resolution transmission electron microscopy (HRTEM) observation. On the other hand, phase image simulations showed that the solution-drop method is reliable and stable for HRTEM analysis. Therefore, in order to comprehensively analyze the microstructure and morphology of the nano-material, it is necessary to combine both solution-drop and microtome cutting techniques for TEM sample preparation.

Growth factors mediated differentiation of mesenchymal stem cells to cardiac polymicrotissue using hanging drop and bioreactor.

PubMed

Konstantinou, Dimitrios; Lei, Ming; Xia, Zhidao; Kanamarlapudi, Venkateswarlu

2015-04-01

Heart disease is the major leading cause of death worldwide and the use of stem cells promises new ways for its treatment. The relatively easy and quick acquisition of human umbilical cord matrix mesenchymal stem cells (HUMSCs) and their properties make them useful for the treatment of cardiac diseases. Therefore, the main aim of this investigation was to create cardiac polymicrotissue from HUMSCs using a combination of growth factors [sphingosine-1-phosphate (S1P) and suramin] and techniques (hanging drop and bioreactor). Using designated culture conditions of the growth factors (100 nM S1P and 500 µM suramin), cardiomyocyte differentiation medium (CDM), hanging drop, bioreactor and differentiation for 7 days, a potential specific cardiac polymicrotissue was derived from HUMSCs. The effectiveness of growth factors alone or in combination in differentiation of HUMSCs to cardiac polymicrotissue was analysed by assessing the presence of cardiac markers by immunocytochemistry. This analysis demonstrated the importance of those growth factors for the differentiation. This study for the first time demonstrated the formation of a cardiac polymicrotissue under specific culture conditions. The polymicrotissue thus obtained may be used in future as a 'patch' to cover the injured cardiac region and would thereby be useful for the treatment of heart diseases. © 2014 International Federation for Cell Biology.

Biomimetic coatings enhance tribocorrosion behavior and cell responses of commercially pure titanium surfaces

PubMed Central

Marques, Isabella da Silva Vieira; Alfaro, Maria Fernanda; Saito, Miki Taketomi; da Cruz, Nilson Cristino; Takoudis, Christos; Landers, Richard; Mesquita, Marcelo Ferraz; Nociti Junior, Francisco Humberto; Mathew, Mathew T.; Sukotjo, Cortino; Barão, Valentim Adelino Ricardo

2016-01-01

Biofunctionalized surfaces for implants are currently receiving much attention in the health care sector. Our aims were (1) to create bioactive Ti-coatings doped with Ca, P, Si, and Ag produced by microarc oxidation (MAO) to improve the surface properties of biomedical implants, (2) to investigate the TiO2 layer stability under wear and corrosion, and (3) to evaluate human mesenchymal stem cells (hMSCs) responses cultured on the modified surfaces. Tribocorrosion and cell experiments were performed following the MAO treatment. Samples were divided as a function of different Ca/P concentrations and treatment duration. Higher Ca concentration produced larger porous and harder coatings compared to the untreated group (p < 0.001), due to the presence of rutile structure. Free potentials experiments showed lower drops (−0.6 V) and higher coating lifetime during sliding for higher Ca concentration, whereas lower concentrations presented similar drops (−0.8 V) compared to an untreated group wherein the drop occurred immediately after the sliding started. MAO-treated surfaces improved the matrix formation and osteogenic gene expression levels of hMSCs. Higher Ca/P ratios and the addition of Ag nanoparticles into the oxide layer presented better surface properties, tribocorrosive behavior, and cell responses. MAO is a promising technique to enhance the biological, chemical, and mechanical properties of dental implant surfaces. PMID:27514370

Biomimetic coatings enhance tribocorrosion behavior and cell responses of commercially pure titanium surfaces.

PubMed

Marques, Isabella da Silva Vieira; Alfaro, Maria Fernanda; Saito, Miki Taketomi; da Cruz, Nilson Cristino; Takoudis, Christos; Landers, Richard; Mesquita, Marcelo Ferraz; Nociti Junior, Francisco Humberto; Mathew, Mathew T; Sukotjo, Cortino; Barão, Valentim Adelino Ricardo

2016-09-11

Biofunctionalized surfaces for implants are currently receiving much attention in the health care sector. Our aims were (1) to create bioactive Ti-coatings doped with Ca, P, Si, and Ag produced by microarc oxidation (MAO) to improve the surface properties of biomedical implants, (2) to investigate the TiO2 layer stability under wear and corrosion, and (3) to evaluate human mesenchymal stem cells (hMSCs) responses cultured on the modified surfaces. Tribocorrosion and cell experiments were performed following the MAO treatment. Samples were divided as a function of different Ca/P concentrations and treatment duration. Higher Ca concentration produced larger porous and harder coatings compared to the untreated group (p < 0.001), due to the presence of rutile structure. Free potentials experiments showed lower drops (-0.6 V) and higher coating lifetime during sliding for higher Ca concentration, whereas lower concentrations presented similar drops (-0.8 V) compared to an untreated group wherein the drop occurred immediately after the sliding started. MAO-treated surfaces improved the matrix formation and osteogenic gene expression levels of hMSCs. Higher Ca/P ratios and the addition of Ag nanoparticles into the oxide layer presented better surface properties, tribocorrosive behavior, and cell responses. MAO is a promising technique to enhance the biological, chemical, and mechanical properties of dental implant surfaces.

Sequential depolarization of root cortical and stelar cells induced by an acute salt shock - implications for Na(+) and K(+) transport into xylem vessels.

PubMed

Wegner, Lars H; Stefano, Giovanni; Shabala, Lana; Rossi, Marika; Mancuso, Stefano; Shabala, Sergey

2011-05-01

Early events in NaCl-induced root ion and water transport were investigated in maize (Zea mays L) roots using a range of microelectrode and imaging techniques. Addition of 100 mm NaCl to the bath resulted in an exponential drop in root xylem pressure, rapid depolarization of trans-root potential and a transient drop in xylem K(+) activity (A(K+) ) within ∼1 min after stress onset. At this time, no detectable amounts of Na(+) were released into the xylem vessels. The observed drop in A(K+) was unexpected, given the fact that application of the physiologically relevant concentrations of Na(+) to isolated stele has caused rapid plasma membrane depolarization and a subsequent K(+) efflux from the stelar tissues. This controversy was explained by the difference in kinetics of NaCl-induced depolarization between cortical and stelar cells. As root cortical cells are first to be depolarized and lose K(+) to the environment, this is associated with some K(+) shift from the stelar symplast to the cortex, resulting in K(+) being transiently removed from the xylem. Once Na(+) is loaded into the xylem (between 1 and 5 min of root exposure to NaCl), stelar cells become more depolarized, and a gradual recovery in A(K+) occurs. © 2011 Blackwell Publishing Ltd.

Inertial Gait Phase Detection for control of a drop foot stimulator Inertial sensing for gait phase detection.

PubMed

Kotiadis, D; Hermens, H J; Veltink, P H

2010-05-01

An Inertial Gait Phase Detection system was developed to replace heel switches and footswitches currently being used for the triggering of drop foot stimulators. A series of four algorithms utilising accelerometers and gyroscopes individually and in combination were tested and initial results are shown. Sensors were positioned on the outside of the upper shank. Tests were performed on data gathered from a subject, sufferer of stroke, implanted with a drop foot stimulator and triggered with the current trigger, the heel switch. Data tested includes a variety of activities representing everyday life. Flat surface walking, rough terrain and carpet walking show 100% detection and the ability of the algorithms to ignore non-gait events such as weight shifts. Timing analysis is performed against the current triggering method, the heel switch. After evaluating the heel switch timing against a reference system, namely the Vicon 370 marker and force plates system. Initial results show a close correlation between the current trigger detection and the inertial sensor based triggering algorithms. Algorithms were tested for stairs up and stairs down. Best results are observed for algorithms using gyroscope data. Algorithms were designed using threshold techniques for lowest possible computational load and with least possible sensor components to minimize power requirements and to allow for potential future implantation of sensor system.

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.

Conditions for Destabilizing Pickering emulsions using external electric fields

NASA Astrophysics Data System (ADS)

Hwang, Kyuho; Singh, Pushpendra; Aubry, Nadine

2009-11-01

Fine particles are readily adsorbed at fluid-fluid interfaces, and can be used as stabilizers in emulsion technology by preventing adjacent drops from coalescing with each other. We investigate a new technique to destabilize such emulsions, or Pickering emulsions, by applying an external electric field. Experiments show that the latter has two effects: (i) the drops elongate in the direction of the electric field, (ii) the local particle density varies on the drop surface due to the dielectrophoretic (DEP) force acting on the particles. It is shown that the latter is the dominant factor in the destabilization process. Particularly, the success of the method depends on the values of certain dimensionless parameters; specifically, the ratio of the work done by the dielectrophoretic force must be larger than the work done by the buoyant force. Moreover, drops do not coalesce through the regions where the particles locally cluster, whether those are gathered at the poles or at the equator of the drops. As particles move, particle-free openings form on the drop's surface, which allow for adjacent drops to merge. This process takes place even if the particles are fully packed on the drops' surfaces as particles get ejected from the clustering areas due to a buckling phenomenon.

A novel generation of 3D SAR-based passive micromixer: efficient mixing and low pressure drop at a low Reynolds number

NASA Astrophysics Data System (ADS)

Viktorov, Vladimir; Nimafar, Mohammad

2013-05-01

This study introduces a novel generation of 3D splitting and recombination (SAR) passive micromixer with microstructures placed on the top and bottom floors of microchannels called a ‘chain mixer’. Both experimental verification and numerical analysis of the flow structure of this type of passive micromixer have been performed to evaluate the mixing performance and pressure drop of the microchannel, respectively. We propose here two types of chain mixer—chain 1 and chain 2—and compare their mixing performance and pressure drop with other micromixers, T-, o- and tear-drop micromixers. Experimental tests carried out in the laminar flow regime with a low Reynolds number range, 0.083 ≤ Re ≤ 4.166, and image-based techniques are used to evaluate the mixing efficiency. Also, the computational fluid dynamics code, ANSYS FLUENT-13.0 has been used to analyze the flow and pressure drop in the microchannel. Experimental results show that the chain and tear-drop mixer's efficiency is very high because of the SAR process: specifically, an efficiency of up to 98% can be achieved at the tested Reynolds number. The results also show that chain mixers have a lower required pressure drop in comparison with a tear-drop micromixer.

Hy-wire measurements of atmospheric potential

NASA Astrophysics Data System (ADS)

Holzworth, Robert H.

1984-02-01

A method of directly measuring the electric potential drop across the lowest portion of the atmosphere by using an apparatus called Hy-wire is described. This tethered balloon-borne system has been operated extensively at altitudes near 0.62 km at which voltages over 150 k V were measured with a high impedance device. Also described are measurements of system parameters such as system capacitance (5.6 pf/m), impedance (1010Ω), and response time (tens of seconds). Hy-wire measurements from an around the-clock experiment at Wallops Island, Va., having a characteristic repetitive diurnal pattern of variability exceeding 40% of the mean, are presented. This diurnal pattern is discussed in terms of both local and global current sources. A demonstration using Hy-wire as a lightning channel model is also presented. These experiments have so far been conducted at mid-latitudes but can also be flown from other locations in an effort to determine whether the lowest atmospheric electric circuit is affected by high altitude and possibly global current systems, and if so how much. The data presented in this paper are not definitive about the source of potential variations. The data are, however, representative of the new Hy-wire technique and demonstrative of the potential usefulness of this technique.

Comparison of the hanging-drop technique and running-drip method for identifying the epidural space in dogs.

PubMed

Martinez-Taboada, Fernando; Redondo, José I

2017-03-01

To compare the running-drip and hanging-drop techniques for locating the epidural space in dogs. Prospective, randomized, clinical trial. Forty-five healthy dogs requiring epidural anaesthesia. Dogs were randomized into four groups and administered epidural anaesthesia in sternal (S) or lateral (L) recumbency. All blocks were performed by the same person using Tuohy needles with either a fluid-prefilled hub (HDo) or connected to a drip set attached to a fluid bag elevated 60 cm (RDi). The number of attempts, 'pop' sensation, clear drop aspiration or fluid dripping, time to locate the epidural space (TTLES) and presence of cerebrospinal fluid (CSF) were recorded. A morphine-bupivacaine combination was injected after positive identification. The success of the block was assessed by experienced observers based on perioperative usage of rescue analgesia. Data were checked for normality. Binomial variables were analysed with the chi-squared or Fisher's exact test as appropriate. Non-parametric data were analysed using Kruskal-Wallis and Mann-Whitney tests. Normal data were studied with an anova followed by a Tukey's means comparison for groups of the same size. A p-value of < 0.05 was considered to indicate statistical significance. Lateral recumbency HDo required more attempts (six of 11 dogs required more than one attempt) than SRDi (none of 11 dogs) (p = 0.0062). Drop aspiration was observed more often in SHDo (nine of 11 dogs) than in LHDo (two of 11 dogs) (p = 0.045). Mean (range) TTLES was longer in LHDo [47 (18-82) seconds] than in SHDo [20 (14-79) seconds] (p = 0.006) and SRDi [(34 (17-53) seconds] (p = 0.038). There were no differences in 'pop' sensation, presence of CSF, rescue analgesia or pain scores between the groups. The running-drip method is a useful and fast alternative technique for identifying the epidural space in dogs. The hanging-drop technique in lateral recumbency was more difficult to perform than the other methods, requiring more time and attempts. Copyright © 2017 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.

Investigating a Drop-on-Demand Microdispenser for Standardized Sample Preparation

DTIC Science & Technology

2011-09-01

including the printing of photodiodes , polymer and protein arrays , and in electronics manufacturing (4–7). These applications benefit from the wide...photograph of an array of microdroplets demonstrates a more even sample dispersion when sample is dispensed with a DOD microdispenser... threats encountered. A variety of techniques that offer temporary alternatives have been employed, including drop-and-dry (dropcasting) and spray

Ground Truth Events with Source Geometry in Eurasia and the Middle East

DTIC Science & Technology

2016-06-02

source properties, including seismic moment, corner frequency, radiated energy , and stress drop have been obtained using spectra for S waves following...PARAMETERS Other source parameters, including radiated energy , corner frequency, seismic moment, and static stress drop were calculated using a spectral...technique (Richardson & Jordan, 2002; Andrews, 1986). The process entails separating event and station spectra and median- stacking each event’s

Prediction of pressure drop in fluid tuned mounts using analytical and computational techniques

NASA Technical Reports Server (NTRS)

Lasher, William C.; Khalilollahi, Amir; Mischler, John; Uhric, Tom

1993-01-01

A simplified model for predicting pressure drop in fluid tuned isolator mounts was developed. The model is based on an exact solution to the Navier-Stokes equations and was made more general through the use of empirical coefficients. The values of these coefficients were determined by numerical simulation of the flow using the commercial computational fluid dynamics (CFD) package FIDAP.

Mobility based key management technique for multicast security in mobile ad hoc networks.

PubMed

Madhusudhanan, B; Chitra, S; Rajan, C

2015-01-01

In MANET multicasting, forward and backward secrecy result in increased packet drop rate owing to mobility. Frequent rekeying causes large message overhead which increases energy consumption and end-to-end delay. Particularly, the prevailing group key management techniques cause frequent mobility and disconnections. So there is a need to design a multicast key management technique to overcome these problems. In this paper, we propose the mobility based key management technique for multicast security in MANET. Initially, the nodes are categorized according to their stability index which is estimated based on the link availability and mobility. A multicast tree is constructed such that for every weak node, there is a strong parent node. A session key-based encryption technique is utilized to transmit a multicast data. The rekeying process is performed periodically by the initiator node. The rekeying interval is fixed depending on the node category so that this technique greatly minimizes the rekeying overhead. By simulation results, we show that our proposed approach reduces the packet drop rate and improves the data confidentiality.

D.R.O.P. The Durable Reconnaissance and Observation Platform

NASA Technical Reports Server (NTRS)

McKenzie, Clifford; Parness, Aaron

2012-01-01

The Durable Reconnaissance and Observation Platform (DROP) is a prototype robotic platform with the ability to climb concrete surfaces up to 85deg at a rate of 25cm/s, make rapid horizontal to vertical transitions, carry an audio/visual reconnaissance payload, and survive impacts from 3 meters. DROP is manufactured using a combination of selective laser sintering (SLS) and shape deposition manufacturing (SDM) techniques. The platform uses a two-wheel, two-motor design that delivers high mobility with low complexity. DROP extends microspine climbing technology from linear to rotary applications, providing improved transition ability, increased speeds, and simpler body mechanics while maintaining microspines ability to opportunistically grip rough surfaces. Various aspects of prototype design and performance are discussed, including the climbing mechanism, body design, and impact survival.

Chronology of DIC technique based on the fundamental mathematical modeling and dehydration impact.

PubMed

Alias, Norma; Saipol, Hafizah Farhah Saipan; Ghani, Asnida Che Abd

2014-12-01

A chronology of mathematical models for heat and mass transfer equation is proposed for the prediction of moisture and temperature behavior during drying using DIC (Détente Instantanée Contrôlée) or instant controlled pressure drop technique. DIC technique has the potential as most commonly used dehydration method for high impact food value including the nutrition maintenance and the best possible quality for food storage. The model is governed by the regression model, followed by 2D Fick's and Fourier's parabolic equation and 2D elliptic-parabolic equation in a rectangular slice. The models neglect the effect of shrinkage and radiation effects. The simulations of heat and mass transfer equations with parabolic and elliptic-parabolic types through some numerical methods based on finite difference method (FDM) have been illustrated. Intel®Core™2Duo processors with Linux operating system and C programming language have been considered as a computational platform for the simulation. Qualitative and quantitative differences between DIC technique and the conventional drying methods have been shown as a comparative.

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.

Effect of rasanjana madhu ashchyotana in netra abhishyanda (mucopurulent conjunctivitis).

PubMed

Bhardwaj, Atul; Tanwar, Manoj

2011-07-01

To evaluate the comparative efficacy of Ayurvedic formulation a Rasanjana Madhu (RM) eye drops and Honey Rose (HR) water eye drops in Netra Abhishyanda in mucopurulent conjunctivitis, the current study is planned. Total of 35 patients attending the outpatient department of Shalakya Tantra at R. G. G. Postgraduate Ayurvedic College, Paprola, Distt. Kangra, Himachal Pradesh with characteristic features of Netra Abhishyanda were selected for the present study. Twenty patients were given trial drug, i.e., RM eye drops, while 15 patients were given HR eye drops. Random sampling technique was adopted for the present study. The duration of the treatment was 7 days with 1 week follow-up. Patients receiving the trial group demonstrated reduction of redness, burning sensation, lacrimation, photophobia, foreign body sensation, discharge, and congestion, which were statistically significant with 93% patients cured or markedly improved category. Signs and symptoms stated above were also statistically reduced with HR eye drops, probably because of well-documented hygroscopic and bacteriocidal properties of honey. Based on the study, it can be concluded that, RM eye drops are very effective in the management of Netra Abhishyanda viz. Infective conjunctivitis.

Effect of Rasanjana Madhu Ashchyotana in Netra Abhishyanda (Mucopurulent Conjunctivitis)

PubMed Central

Bhardwaj, Atul; Tanwar, Manoj

2011-01-01

To evaluate the comparative efficacy of Ayurvedic formulation a Rasanjana Madhu (RM) eye drops and Honey Rose (HR) water eye drops in Netra Abhishyanda in mucopurulent conjunctivitis, the current study is planned. Total of 35 patients attending the outpatient department of Shalakya Tantra at R. G. G. Postgraduate Ayurvedic College, Paprola, Distt. Kangra, Himachal Pradesh with characteristic features of Netra Abhishyanda were selected for the present study. Twenty patients were given trial drug, i.e., RM eye drops, while 15 patients were given HR eye drops. Random sampling technique was adopted for the present study. The duration of the treatment was 7 days with 1 week follow-up. Patients receiving the trial group demonstrated reduction of redness, burning sensation, lacrimation, photophobia, foreign body sensation, discharge, and congestion, which were statistically significant with 93% patients cured or markedly improved category. Signs and symptoms stated above were also statistically reduced with HR eye drops, probably because of well-documented hygroscopic and bacteriocidal properties of honey. Based on the study, it can be concluded that, RM eye drops are very effective in the management of Netra Abhishyanda viz. Infective conjunctivitis. PMID:22529652

Ceramic microparticles and capsules via microfluidic processing of a preceramic polymer

PubMed Central

Ye, Congwang; Chen, Anthony; Colombo, Paolo; Martinez, Carlos

2010-01-01

We have developed a robust technique to fabricate monodispersed solid and porous ceramic particles and capsules from single and double emulsion drops composed of silsesquioxane preceramic polymer. A microcapillary microfluidic device was used to generate the monodispersed drops. In this device, two round capillaries are aligned facing each other inside a square capillary. Three fluids are needed to generate the double emulsions. The inner fluid, which flows through the input capillary, and the middle fluid, which flows through the void space between the square and inner fluid capillaries, form a coaxial co-flow in a direction that is opposite to the flow of the outer fluid. As the three fluids are forced through the exit capillary, the inner and middle fluids break into monodispersed double emulsion drops in a single-step process, at rates of up to 2000 drops s−1. Once the drops are generated, the silsesquioxane is cross-linked in solution and the cross-linked particles are dried and pyrolysed in an inert atmosphere to form oxycarbide glass particles. Particles with diameters ranging from 30 to 180 µm, shell thicknesses ranging from 10 to 50 µm and shell pore diameters ranging from 1 to 10 µm were easily prepared by changing fluid flow rates, device dimensions and fluid composition. The produced particles and capsules can be used in their polymeric state or pyrolysed to ceramic. This technique can be extended to other preceramic polymers and can be used to generate unique core–shell multimaterial particles. PMID:20484226

Ceramic microparticles and capsules via microfluidic processing of a preceramic polymer.

PubMed

Ye, Congwang; Chen, Anthony; Colombo, Paolo; Martinez, Carlos

2010-08-06

We have developed a robust technique to fabricate monodispersed solid and porous ceramic particles and capsules from single and double emulsion drops composed of silsesquioxane preceramic polymer. A microcapillary microfluidic device was used to generate the monodispersed drops. In this device, two round capillaries are aligned facing each other inside a square capillary. Three fluids are needed to generate the double emulsions. The inner fluid, which flows through the input capillary, and the middle fluid, which flows through the void space between the square and inner fluid capillaries, form a coaxial co-flow in a direction that is opposite to the flow of the outer fluid. As the three fluids are forced through the exit capillary, the inner and middle fluids break into monodispersed double emulsion drops in a single-step process, at rates of up to 2000 drops s(-1). Once the drops are generated, the silsesquioxane is cross-linked in solution and the cross-linked particles are dried and pyrolysed in an inert atmosphere to form oxycarbide glass particles. Particles with diameters ranging from 30 to 180 microm, shell thicknesses ranging from 10 to 50 microm and shell pore diameters ranging from 1 to 10 microm were easily prepared by changing fluid flow rates, device dimensions and fluid composition. The produced particles and capsules can be used in their polymeric state or pyrolysed to ceramic. This technique can be extended to other preceramic polymers and can be used to generate unique core-shell multimaterial particles.

Enhanced Condensation Heat Transfer On Patterned Surfaces

NASA Astrophysics Data System (ADS)

Alizadeh-Birjandi, Elaheh; Kavehpour, H. Pirouz

2017-11-01

Transition from film to drop wise condensation can improve the efficiency of thermal management applications and result in considerable savings in investments and operating costs by millions of dollars every year. The current methods available are either hydrophobic coating or nanostructured surfaces. The former has little adhesion to the structure which tends to detach easily under working conditions, the fabrication techniques of the latter are neither cost-effective nor scalable, and both are made with low thermal conductivity materials that would negate the heat transfer enhancement by drop wise condensation. Therefore, the existing technologies have limitations in enhancing vapor-to-liquid condensation. This work focuses on development of surfaces with wettability contrast to boost drop wise condensation, which its overall heat transfer efficiency is 2-3 times film wise condensation, while maintaining high conduction rate through the surface at low manufacturing costs. The variation in interfacial energy is achieved through crafting hydrophobic patterns to the surface of the metal via scalable fabrication techniques. The results of experimental and surface optimization studies are also presented.

The formation of intestinal organoids in a hanging drop culture.

PubMed

Panek, Malgorzata; Grabacka, Maja; Pierzchalska, Malgorzata

2018-01-25

Recently organoids have become widely used in vitro models of many tissue and organs. These type of structures, originated from embryonic or adult mammalian intestines, are called "mini guts". They organize spontaneously when intestinal crypts or stem cells are embedded in the extracellular matrix proteins preparation scaffold (Matrigel). This approach has some disadvantages, as Matrigel is undefined (the concentrations of growth factors and other biologically active components in it may vary from batch to batch), difficult to handle and expensive. Here we show that the organoids derived from chicken embryo intestine are formed in a hanging drop without embedding, providing an attractive alternative for currently used protocols. Using this technique we obtained compact structures composed of contiguous organoids, which were generally similar to chicken organoids cultured in Matrigel in terms of morphology and expression of intestinal epithelial markers. Due to the simplicity, high reproducibility and throughput capacity of hanging drop technique our model may be applied in various studies concerning the gut biology.

Application of hanging drop technique to optimize human IgG formulations.

PubMed

Li, Guohua; Kasha, Purna C; Late, Sameer; Banga, Ajay K

2010-01-01

The purpose of this work is to assess the hanging drop technique in screening excipients to develop optimal formulations for human immunoglobulin G (IgG). A microdrop of human IgG and test solution hanging from a cover slide and undergoing vapour diffusion was monitored by a stereomicroscope. Aqueous solutions of IgG in the presence of different pH, salt concentrations and excipients were prepared and characterized. Low concentration of either sodium/potassium phosphate or McIlvaine buffer favoured the solubility of IgG. Addition of sucrose favoured the stability of this antibody while addition of NaCl caused more aggregation. Antimicrobial preservatives were also screened and a complex effect at different buffer conditions was observed. Dynamic light scattering, differential scanning calorimetry and size exclusion chromatography studies were performed to further validate the results. In conclusion, hanging drop is a very easy and effective approach to screen protein formulations in the early stage of formulation development.

Evaluation of surface deformability of lipid nanocapsules by drop tensiometer technique, and its experimental assessment by dialysis and tangential flow filtration.

PubMed

Hirsjärvi, Samuli; Bastiat, Guillaume; Saulnier, Patrick; Benoît, Jean-Pierre

2012-09-15

Deformability of nanoparticles might affect their behaviour at biological interfaces. Lipid nanocapsules (LNCs) are semi-solid particles resembling a hybrid of polymer nanoparticles and liposomes. Deformability of LNCs of different sizes was modelled by drop tensiometer technique. Two purification methods, dialysis and tangential flow filtration (TFF), were applied to study experimental behaviour and deformability of LNCs in order to evaluate if these properties contributed to membrane passing. Rheological parameters obtained from the drop tensiometer analysis suggested decreasing surface deformability of LNCs with increase in diameter. Dialysis results showed that up to 10% of LNCs can be lost during the process (e.g. membrane accumulation) but no clear evidence of the membrane passing was observed. Instead, LNCs with initial size and size distribution could be found in the TFF filtrate although molecular weight cut-off (MWCO) of the membrane used was smaller than the LNC diameter. Copyright © 2012 Elsevier B.V. All rights reserved.

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

Deposition dynamics of multi-solvent bioinks

NASA Astrophysics Data System (ADS)

Kaneelil, Paul; Pack, Min; Cui, Chunxiao; Han, Li-Hsin; Sun, Ying

2017-11-01

Inkjet printing cellular scaffolds using bioinks is gaining popularity due to the advancement of printing technology as well as the growing demands of regenerative medicine. Numerous studies have been conducted on printing scaffolds of biomimetic structures that support the cell production of human tissues. However, the underlying physics of the deposition dynamics of bioinks remains elusive. Of particular interest is the unclear deposition dynamics of multi-solvent bioinks, which is often used to tune the micro-architecture formation. Here we systematically studied the effects of jetting frequency, solvent properties, substrate wettability, and temperature on the three-dimensional deposition patterns of bioinks made of Methacrylated Gelatin and Carboxylated Gelatin. The microflows inside the inkjet-printed picolitre drops were visualized using fluorescence tracer particles to decipher the complex processes of multi-solvent evaporation and solute self-assembly. The evolution of droplet shape was observed using interferometry. With the integrated techniques, the interplay of solvent evaporation, biopolymer deposition, and multi-drop interactions were directly observed for various ink and substrate properties, and printing conditions. Such knowledge enables the design and fabrication of a variety of tissue engineering scaffolds for potential use in regenerative medicine.

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

An in vitro and in vivo evaluation of the virulence of egg drop syndrome virus for the chicken reproductive tract.

PubMed

Raj, G D; Sivakumar, S; Manohar, B M; Nachimuthu, K; Nainar, A M

2001-02-01

The virulence of strains of egg drop syndrome (EDS) 1976 virus for the female reproductive tract of chickens was assessed in vitro using oviduct organ cultures (OOC) prepared from precociously induced oviducts in young chicks by oestrogen treatment. Ciliostasis, haemagglutination and virus titres in infected OOC supernatants, histology and immunoperoxidase test results indicated the pathogenic ability of the four viruses for the precocious oviducts. One of the isolates, EDS TN4, produced higher virus titres in the supernatants of infected OOC and more severe glandular atrophy and necrosis, but caused slightly delayed ciliostasis. When this isolate was used in vivo, virus could not be detected by haemagglutination, but was detected in a few birds using a polymerase chain reaction on the allantoic fluids of infected duck embryos. Ciliostasis of OOC and histological lesions were confined to early stages of infection. This technique could be a pointer to possible variations in virulence of EDS virus isolates, and warrants further investigation. The potential value of OOC from young chickens for EDS diagnosis is emphasized.

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.

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.

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.

Redifferentiation of in vitro expanded adult articular chondrocytes by combining the hanging-drop cultivation method with hypoxic environment.

PubMed

Martinez, Inigo; Elvenes, Jan; Olsen, Randi; Bertheussen, Kjell; Johansen, Oddmund

2008-01-01

The main purpose of this work has been to establish a new culturing technique to improve the chondrogenic commitment of isolated adult human chondrocytes, with the aim of being used during cell-based therapies or tissue engineering strategies. By using a rather novel technique to generate scaffold-free three-dimensional (3D) structures from in vitro expanded chondrocytes, we have explored the effects of different culture environments on cartilage formation. Three-dimensional chondrospheroids were developed by applying the hanging-drop technique. Cartilage tissue formation was attempted after combining critical factors such as serum-containing or serum-free media and atmospheric (20%) or low (2.5%) oxygen tensions. The quality of the formed microtissues was analyzed by histology, immunohistochemistry, electron microscopy, and real-time PCR, and directly compared with native adult cartilage. Our results revealed highly organized, 3D tissue-like structures developed by the hanging-drop method. All culture conditions allowed formation of 3D spheroids; however, cartilage generated under low oxygen tension had a bigger size, enhanced matrix deposition, and higher quality of cartilage formation. Real-time PCR demonstrated enhanced expression of cartilage-specific genes such us collagen type II and aggrecan in 3D cultures when compared to monolayers. Cartilage-specific matrix proteins and genes expressed in hanging-drop-developed spheroids were comparable to the expression obtained by applying the pellet culture system. In summary, our results indicate that a combination of 3D cultures of chondrocytes in hanging drops and a low oxygen environment represent an easy and convenient way to generate cartilage-like microstructures. We also show that a new specially tailored serum-free medium is suitable for in vitro cartilage tissue formation. This new methodology opens up the possibility of using autogenously produced solid 3D structures with redifferentiated chondrocytes as an attractive alternative to the currently used autologous chondrocyte transplantation for cartilage repair.

Computational Study of Surface Tension and Wall Adhesion Effects on an Oil Film Flow Underneath an Air Boundary Layer

NASA Technical Reports Server (NTRS)

Celic, Alan; Zilliac, Gregory G.

1998-01-01

The fringe-imaging skin friction (FISF) technique, which was originally developed by D. J. Monson and G. G. Mateer at Ames Research Center and recently extended to 3-D flows, is the most accurate skin friction measurement technique currently available. The principle of this technique is that the skin friction at a point on an aerodynamic surface can be determined by measuring the time-rate-of-change of the thickness of an oil drop placed on the surface under the influence of the external air boundary layer. Lubrication theory is used to relate the oil-patch thickness variation to shear stress. The uncertainty of FISF measurements is estimated to be as low as 4 percent, yet little is known about the effects of surface tension and wall adhesion forces on the measured results. A modified version of the free-surface Navier-Stokes solver RIPPLE, developed at Los Alamos National Laboratories, was used to compute the time development of an oil drop on a surface under a simulated air boundary layer. RIPPLE uses the volume of fluid method to track the surface and the continuum surface force approach to model surface tension and wall adhesion effects. The development of an oil drop, over a time period of approximately 4 seconds, was studied. Under the influence of shear imposed by an air boundary layer, the computed profile of the drop rapidly changes from its initial circular-arc shape to a wedge-like shape. Comparison of the time-varying oil-thickness distributions computed using RIPPLE and also computed using a greatly simplified numerical model of an oil drop equation which does not include surface tension and wall adhesion effects) was used to evaluate the effects of surface tension on FISF measurement results. The effects of surface tension were found to be small but not necessarily negligible in some cases.

Heat Transfer Enhancement for Finned-Tube Heat Exchangers with Vortex Generators: Experimental and Numerical Results

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

O'Brien, James Edward; Sohal, Manohar Singh; Huff, George Albert

2002-08-01

A combined experimental and numerical investigation is under way to investigate heat transfer enhancement techniques that may be applicable to large-scale air-cooled condensers such as those used in geothermal power applications. The research is focused on whether air-side heat transfer can be improved through the use of finsurface vortex generators (winglets,) while maintaining low heat exchanger pressure drop. A transient heat transfer visualization and measurement technique has been employed in order to obtain detailed distributions of local heat transfer coefficients on model fin surfaces. Pressure drop measurements have also been acquired in a separate multiple-tube row apparatus. In addition, numericalmore » modeling techniques have been developed to allow prediction of local and average heat transfer for these low-Reynolds-number flows with and without winglets. Representative experimental and numerical results presented in this paper reveal quantitative details of local fin-surface heat transfer in the vicinity of a circular tube with a single delta winglet pair downstream of the cylinder. The winglets were triangular (delta) with a 1:2 height/length aspect ratio and a height equal to 90% of the channel height. Overall mean fin-surface Nusselt-number results indicate a significant level of heat transfer enhancement (average enhancement ratio 35%) associated with the deployment of the winglets with oval tubes. Pressure drop measurements have also been obtained for a variety of tube and winglet configurations using a single-channel flow apparatus that includes four tube rows in a staggered array. Comparisons of heat transfer and pressure drop results for the elliptical tube versus a circular tube with and without winglets are provided. Heat transfer and pressure-drop results have been obtained for flow Reynolds numbers based on channel height and mean flow velocity ranging from 700 to 6500.« less

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.

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…

Characterization of highly hydrophobic textiles by means of X-ray microtomography, wettability analysis and drop impact

NASA Astrophysics Data System (ADS)

Santini, M.; Guilizzoni, M.; Fest-Santini, S.; Lorenzi, M.

2017-11-01

Highly hydrophobic surfaces have been intensively investigated in the last years because their properties may lead to very promising technological spillovers encompassing both everyday use and high-tech fields. Focusing on textiles, hydrophobic fabrics are of major interest for applications ranging from clothes to architecture to environment protection and energy conversion. Gas diffusion media - made by a gas diffusion layer (GDL) and a microporous layer (MPL) - for fuel cells are a good benchmark to develop techniques aimed at characterizing the wetting performances of engineered textiles. An experimental investigation was carried out about carbon-based, PTFE-treated GDLs with and without MPLs. Two samples (woven and woven-non-woven) were analysed before and after coating with a MPL. Their three-dimensional structure was reconstructed and analysed by computer-aided X-ray microtomography (µCT). Static and dynamic wettability analyses were then carried out using a modified axisymmetric drop shape analysis technique. All the surfaces exhibited very high hydrophobicity, three of them near to a super-hydrophobic behavior. Water drop impacts were performed, evidencing different bouncing, sticking and fragmentation outcomes for which critical values of the Weber number were identified. Finally, a µCT scan of a drop on a GDL was performed, confirming the Cassie-Baxter wetting state on such surface.

Development of techniques for processing metal-metal oxide systems

NASA Technical Reports Server (NTRS)

Johnson, P. C.

1976-01-01

Techniques for producing model metal-metal oxide systems for the purpose of evaluating the results of processing such systems in the low-gravity environment afforded by a drop tower facility are described. Because of the lack of success in producing suitable materials samples and techniques for processing in the 3.5 seconds available, the program was discontinued.

Magnetic field line reconnection experiments. V - Current disruptions and double layers

NASA Technical Reports Server (NTRS)

Stenzel, R. L.; Gekelman, W.; Wild, N.

1983-01-01

An investigation is conducted of the stability of a large laboratory plasma current sheet, which has been generated in the process of magnetic field line reconnection, with respect to local current increases. Magnetic flux variations in regions remote from the current sheet generate an inductive voltage in the current loop that drops off inside the plasma in the form of a potential double layer, leading to particle acceleration with velocities much larger than those expected from the steady state electric fields in the plasma. A model for the mechanism of the current disruptions is formulated in which the potential structure leads to ion expulsion, creating a localized density drop. The associated current drop in an inductive circuit drives the potential structure, providing feedback for the disruptive instability. Similarities to, and differences from, magnetospheric substorm phenomena are noted.

Investigation of powder injection moulded oblique fin heat sinks

NASA Astrophysics Data System (ADS)

Sai, Vadri Siva

The present work attempts to study the fluid flow and heat transfer characteristics of PIM oblique finned microchannel heat sink both numerically and experimentally. Experimental results such as thermal resistance and pressure drop have been well validated with ANSYS FLUENT simulations. Hot spots are observed at the most downstream location of the channel is due to the effect of flow migration. Finally, a novel technique has been proposed to reduce the pressure drop on creating additional channels by removing some material at the middle portion of oblique fins. It is found that the creation of oblique cuts incurred a reduction in both pressure drop and Nuavg up to 31.36 % and 16.66 % respectively at a flow rate of 500 ml/min. Nevertheless, for all the flowrates considered in this analysis. % reduction in pressure drop is almost double as compared with % reduction in Nuavg. Therefore, this analysis is beneflcial in reducing the additional cost incurs due to pressure drop penalty.

Estimating the irreversible pressure drop across a stenosis by quantifying turbulence production using 4D Flow MRI

PubMed Central

Ha, Hojin; Lantz, Jonas; Ziegler, Magnus; Casas, Belen; Karlsson, Matts; Dyverfeldt, Petter; Ebbers, Tino

2017-01-01

The pressure drop across a stenotic vessel is an important parameter in medicine, providing a commonly used and intuitive metric for evaluating the severity of the stenosis. However, non-invasive estimation of the pressure drop under pathological conditions has remained difficult. This study demonstrates a novel method to quantify the irreversible pressure drop across a stenosis using 4D Flow MRI by calculating the total turbulence production of the flow. Simulation MRI acquisitions showed that the energy lost to turbulence production can be accurately quantified with 4D Flow MRI within a range of practical spatial resolutions (1–3 mm; regression slope = 0.91, R2 = 0.96). The quantification of the turbulence production was not substantially influenced by the signal-to-noise ratio (SNR), resulting in less than 2% mean bias at SNR > 10. Pressure drop estimation based on turbulence production robustly predicted the irreversible pressure drop, regardless of the stenosis severity and post-stenosis dilatation (regression slope = 0.956, R2 = 0.96). In vitro validation of the technique in a 75% stenosis channel confirmed that pressure drop prediction based on the turbulence production agreed with the measured pressure drop (regression slope = 1.15, R2 = 0.999, Bland-Altman agreement = 0.75 ± 3.93 mmHg). PMID:28425452

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. .

A Boilerplate Capsule Test Technique for the Orion Parachute Test Program

NASA Technical Reports Server (NTRS)

Moore, James W.; Fraire, Usbaldo, Jr.

2013-01-01

The test program developing parachutes for the Orion/MPCV includes drop tests of a Parachute Test Vehicle designed to emulate the wake of the Orion capsule. Delivery of this test vehicle to the initial velocity, altitude, and orientation required for the test is a difficult problem involving multiple engineering disciplines. The available delivery of aircraft options imposed constraints on the test vehicle development and concept of operations. This paper describes the development of this test technique. The engineering challenges include the extraction from an aircraft and separation of two aerodynamically unstable vehicles, one of which will be delivered to a specific orientation with reasonably small rates. The desired attitude is achieved by precisely targeting the separation point using on-board monitoring of the motion. The design of the test vehicle is described. The trajectory simulations and other analyses used to develop this technique and predict the behavior of the test article are reviewed in detail. The application of the technique on several successful drop tests is summarized.

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...

Self-Injurious Behavior: An Animal Model of an Autism Endophenotype

DTIC Science & Technology

2012-01-01

time there was a visible release of the pasta (not a drop) or a reformation of the digits holding the pasta via motor patterns of flexion/extension...review of 18 pasta -trials, nine trials randomly selected from each experimental group. Behaviors included on the code sheet were number of drops...failure to contact reaches, angling with head tilt, abnormal posture, use of a unilateral paw technique, and twirling of the pasta . Specific descriptions

Droplet size distributions in waveplate demisters using optical techniques

NASA Astrophysics Data System (ADS)

Layton, J. S.; Zaidi, Sohail H.; Altunbas, Ayse; Walters, J. K.; Azzopardi, B. J.

1997-11-01

Droplet separators or demisters are extensively used in the chemical industry. The effectiveness of many demisters is decisively affected by droplet sizes. As the misty gas passes through the demister, the liquid droplets impinge on the walls and form a liquid film. A part of this film can be re-entrained by the gas flow in the form of larger droplets. These droplets can escape the demister, affecting its efficiency. The measurement of drop size distributions inside the zigzag passages of the demister can provide useful information about the complex flow phenomena occurring within the demister. In the present work, a wave plate demister of the industrial dimensional specifications has been chosen to investigate the drop size distributions at various flow conditions. The laser diffraction technique has been employed for this purpose. This paper describes the suitability of the technique and presents some laser results to describe the effect of changing flow conditions inside and outside the demister.

Railway crossing risk area detection using linear regression and terrain drop compensation techniques.

PubMed

Chen, Wen-Yuan; Wang, Mei; Fu, Zhou-Xing

2014-06-16

Most railway accidents happen at railway crossings. Therefore, how to detect humans or objects present in the risk area of a railway crossing and thus prevent accidents are important tasks. In this paper, three strategies are used to detect the risk area of a railway crossing: (1) we use a terrain drop compensation (TDC) technique to solve the problem of the concavity of railway crossings; (2) we use a linear regression technique to predict the position and length of an object from image processing; (3) we have developed a novel strategy called calculating local maximum Y-coordinate object points (CLMYOP) to obtain the ground points of the object. In addition, image preprocessing is also applied to filter out the noise and successfully improve the object detection. From the experimental results, it is demonstrated that our scheme is an effective and corrective method for the detection of railway crossing risk areas.

Railway Crossing Risk Area Detection Using Linear Regression and Terrain Drop Compensation Techniques

PubMed Central

Chen, Wen-Yuan; Wang, Mei; Fu, Zhou-Xing

2014-01-01

Most railway accidents happen at railway crossings. Therefore, how to detect humans or objects present in the risk area of a railway crossing and thus prevent accidents are important tasks. In this paper, three strategies are used to detect the risk area of a railway crossing: (1) we use a terrain drop compensation (TDC) technique to solve the problem of the concavity of railway crossings; (2) we use a linear regression technique to predict the position and length of an object from image processing; (3) we have developed a novel strategy called calculating local maximum Y-coordinate object points (CLMYOP) to obtain the ground points of the object. In addition, image preprocessing is also applied to filter out the noise and successfully improve the object detection. From the experimental results, it is demonstrated that our scheme is an effective and corrective method for the detection of railway crossing risk areas. PMID:24936948

Water Impact Test and Simulation of a Composite Energy Absorbing Fuselage Section

NASA Technical Reports Server (NTRS)

Fasanella, Edwin L.; Jackson, Karen E.; Sparks, Chad; Sareen, Ashish

2003-01-01

In March 2002, a 25-ft/s vertical drop test of a composite fuselage section was conducted onto water. The purpose of the test was to obtain experimental data characterizing the structural response of the fuselage section during water impact for comparison with two previous drop tests that were performed onto a rigid surface and soft soil. For the drop test, the fuselage section was configured with ten 100-lb. lead masses, five per side, that were attached to seat rails mounted to the floor. The fuselage section was raised to a height of 10-ft. and dropped vertically into a 15-ft. diameter pool filled to a depth of 3.5-ft. with water. Approximately 70 channels of data were collected during the drop test at a 10-kHz sampling rate. The test data were used to validate crash simulations of the water impact that were developed using the nonlinear, explicit transient dynamic codes, MSC.Dytran and LS-DYNA. The fuselage structure was modeled using shell and solid elements with a Lagrangian mesh, and the water was modeled with both Eulerian and Lagrangian techniques. The fluid-structure interactions were executed using the fast general coupling in MSC.Dytran and the Arbitrary Lagrange-Euler (ALE) coupling in LS-DYNA. Additionally, the smooth particle hydrodynamics (SPH) meshless Lagrangian technique was used in LS-DYNA to represent the fluid. The simulation results were correlated with the test data to validate the modeling approach. Additional simulation studies were performed to determine how changes in mesh density, mesh uniformity, fluid viscosity, and failure strain influence the test-analysis correlation.

Acoustic containerless experiment system: A non-contact surface tension measurement

NASA Technical Reports Server (NTRS)

Elleman, D. D.; Wang, T. G.; Barmatz, M.

1988-01-01

The Acoustic Containerless Experiment System (ACES) was flown on STS 41-B in February 1984 and was scheduled to be reflown in 1986. The primary experiment that was to be conducted with the ACES module was the containerless melting and processing of a fluoride glass sample. A second experiment that was to be conducted was the verification of a non-contact surface tension measurement technique using the molten glass sample. The ACES module consisted of a three-axis acoustic positioning module that was inside an electric furnace capable of heating the system above the melting temperature of the sample. The acoustic module is able to hold the sample with acoustic forces in the center of the chamber and, in addition, has the capability of applying a modulating force on the sample along one axis of the chamber so that the molten sample or liquid drop could be driven into one of its normal oscillation modes. The acoustic module could also be adjusted so that it could place a torque on the molten drop and cause the drop to rotate. In the ACES, a modulating frequency was applied to the drop and swept through a range of frequencies that would include the n = 2 mode. A maximum amplitude of the drop oscillation would indicate when resonance was reached and from that data the surface tension could be calculated. For large viscosity samples, a second technique for measuring surface tension was developed. The results of the ACES experiment and some of the problems encountered during the actual flight of the experiment will be discussed.

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.

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.

Reduction technique of drop voltage and power losses to improve power quality using ETAP Power Station simulation model

NASA Astrophysics Data System (ADS)

Satrio, Reza Indra; Subiyanto

2018-03-01

The effect of electric loads growth emerged direct impact in power systems distribution. Drop voltage and power losses one of the important things in power systems distribution. This paper presents modelling approach used to restructrure electrical network configuration, reduce drop voltage, reduce power losses and add new distribution transformer to enhance reliability of power systems distribution. Restructrure electrical network was aimed to analyse and investigate electric loads of a distribution transformer. Measurement of real voltage and real current were finished two times for each consumer, that were morning period and night period or when peak load. Design and simulation were conduct by using ETAP Power Station Software. Based on result of simulation and real measurement precentage of drop voltage and total power losses were mismatch with SPLN (Standard PLN) 72:1987. After added a new distribution transformer and restructrured electricity network configuration, the result of simulation could reduce drop voltage from 1.3 % - 31.3 % to 8.1 % - 9.6 % and power losses from 646.7 watt to 233.29 watt. Result showed, restructrure electricity network configuration and added new distribution transformer can be applied as an effective method to reduce drop voltage and reduce power losses.

Deformation and breakup of liquid-liquid threads, jets, and drops

NASA Astrophysics Data System (ADS)

Doshi, Pankaj

The formation and breakup of two-fluid jets and drops find application in various industrially important processes like microencapsulation, inkjet printing, dispersion and emulsion formation, micro fluidics. Two important aspects of these problems are studied in this thesis. The first regards the study of the dynamics of a two-fluid jet issuing out of a concentric nozzle and breaking into multiple liquid drops. The second aspect concerns the study of the dynamics of liquid-liquid interface rupture. Highly robust and accurate numerical algorithms based on the Galerkin finite element method (G/FEM) and elliptic mesh generation technique are developed. The most important results of this research are the prediction of compound drop formation and volume partitioning between primary drop and satellite drops, which are of critical importance for microencapsulation technology. Another equally important result is computational and experimental demonstration of a self-similar behavior for the rupture of liquid-liquid interface. The final focus is the study of the pinch-off dynamics of generalized-Newtonian fluids with deformation-rate-dependent rheology using asymptotic analysis and numerical computation. A significant result is the first ever prediction of self-similar pinch-off of liquid threads of generalized Newtonian fluids.

Cavity optomechanics in a levitated helium drop

NASA Astrophysics Data System (ADS)

Childress, L.; Schmidt, M. P.; Kashkanova, A. D.; Brown, C. D.; Harris, G. I.; Aiello, A.; Marquardt, F.; Harris, J. G. E.

2017-12-01

We describe a proposal for a type of optomechanical system based on a drop of liquid helium that is magnetically levitated in vacuum. In the proposed device, the drop would serve three roles: its optical whispering-gallery modes would provide the optical cavity, its surface vibrations would constitute the mechanical element, and evaporation of He atoms from its surface would provide continuous refrigeration. We analyze the feasibility of such a system in light of previous experimental demonstrations of its essential components: magnetic levitation of mm-scale and cm-scale drops of liquid He , evaporative cooling of He droplets in vacuum, and coupling to high-quality optical whispering-gallery modes in a wide range of liquids. We find that the combination of these features could result in a device that approaches the single-photon strong-coupling regime, due to the high optical quality factors attainable at low temperatures. Moreover, the system offers a unique opportunity to use optical techniques to study the motion of a superfluid that is freely levitating in vacuum (in the case of 4He). Alternatively, for a normal fluid drop of 3He, we propose to exploit the coupling between the drop's rotations and vibrations to perform quantum nondemolition measurements of angular momentum.

Compensation of voltage drops in solid-state switches used with thermoelectric generators

NASA Technical Reports Server (NTRS)

Shimada, K.

1972-01-01

Seebeck effect solid state switch was developed eliminating thermoelectric generator switch voltage drops. Semiconductor switches were fabricated from materials with large Seebeck coefficients, arranged such that Seebeck potential is generated with such polarity that current flow is aided.

Spacelab

NASA Image and Video Library

1992-06-01

The first United States Microgravity Laboratory (USML-1) was one of NASA's science and technology programs that provided scientists an opportunity to research various scientific investigations in a weightlessness environment inside the Spacelab module. It also provided demonstrations of new equipment to help prepare for advanced microgravity research and processing aboard the Space Station. The USML-1 flew in orbit for extended periods, providing greater opportunities for research in materials science, fluid dynamics, biotechnology (crystal growth), and combustion science. This is a close-up view of the Drop Physics Module (DPM) in the USML science laboratory. The DPM was dedicated to the detailed study of the dynamics of fluid drops in microgravity: their equilibrium shapes, the dynamics of their flows, and their stable and chaotic behaviors. It also demonstrated a technique known as containerless processing. The DPM and microgravity combine to remove the effects of the container, such as chemical contamination and shape, on the sample being studied. Sound waves, generating acoustic forces, were used to suspend a sample in microgravity and to hold a sample of free drops away from the walls of the experiment chamber, which isolated the sample from potentially harmful external influences. The DPM gave scientists the opportunity to test theories of classical fluid physics, which have not been confirmed by experiments conducted on Earth. This image is a close-up view of the DPM. The USML-1 flew aboard the STS-50 mission on June 1992, and was managed by the Marshall Space Flight Center.

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.

Load and dynamic assessment of B-52B-008 carrier aircraft for finned configuration 1 space shuttle solid rocket booster decelerator subsystem drop test vehicle. Volume 2: Airplane flutter and load analysis results

NASA Technical Reports Server (NTRS)

Quade, D. A.

1978-01-01

The airplane flutter and maneuver-gust load analysis results obtained during B-52B drop test vehicle configuration (with fins) evaluation are presented. These data are presented as supplementary data to that given in Volume 1 of this document. A brief mathematical description of airspeed notation and gust load factor criteria are provided as a help to the user. References are defined which provide mathematical description of the airplane flutter and load analysis techniques. Air-speed-load factor diagrams are provided for the airplane weight configurations reanalyzed for finned drop test vehicle configuration.

Primary acoustic signal structure during free falling drop collision with a water surface

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

Chashechkin, Yu. D., E-mail: chakin@ipmnet.ru; Prokhorov, V. E., E-mail: prohorov@ipmnet.ru

2016-04-15

Consistent optical and acoustic techniques have been used to study the structure of hydrodynamic disturbances and acoustic signals generated as a free falling drop penetrates water. The relationship between the structures of hydrodynamic and acoustic perturbations arising as a result of a falling drop contacting with the water surface and subsequent immersion into water is traced. The primary acoustic signal is characterized, in addition to stably reproduced features (steep leading edge followed by long decay with local pressure maxima), by irregular high-frequency packets, which are studied for the first time. Reproducible experimental data are used to recognize constant and variablemore » components of the primary acoustic signal.« less

A Broadband Microwave Radiometer Technique at X-band for Rain and Drop Size Distribution Estimation

NASA Technical Reports Server (NTRS)

Meneghini, R.

2005-01-01

Radiometric brightess temperatures below about 12 GHz provide accurate estimates of path attenuation through precipitation and cloud water. Multiple brightness temperature measurements at X-band frequencies can be used to estimate rainfall rate and parameters of the drop size distribution once correction for cloud water attenuation is made. Employing a stratiform storm model, calculations of the brightness temperatures at 9.5, 10 and 12 GHz are used to simulate estimates of path-averaged median mass diameter, number concentration and rainfall rate. The results indicate that reasonably accurate estimates of rainfall rate and information on the drop size distribution can be derived over ocean under low to moderate wind speed conditions.

Biomechanical symmetry in elite rugby union players during dynamic tasks: an investigation using discrete and continuous data analysis techniques.

PubMed

Marshall, Brendan; Franklyn-Miller, Andrew; Moran, Kieran; King, Enda; Richter, Chris; Gore, Shane; Strike, Siobhán; Falvey, Éanna

2015-01-01

While measures of asymmetry may provide a means of identifying individuals predisposed to injury, normative asymmetry values for challenging sport specific movements in elite athletes are currently lacking in the literature. In addition, previous studies have typically investigated symmetry using discrete point analyses alone. This study examined biomechanical symmetry in elite rugby union players using both discrete point and continuous data analysis techniques. Twenty elite injury free international rugby union players (mean ± SD: age 20.4 ± 1.0 years; height 1.86 ± 0.08 m; mass 98.4 ± 9.9 kg) underwent biomechanical assessment. A single leg drop landing, a single leg hurdle hop, and a running cut were analysed. Peak joint angles and moments were examined in the discrete point analysis while analysis of characterising phases (ACP) techniques were used to examine the continuous data. Dominant side was compared to non-dominant side using dependent t-tests for normally distributed data or Wilcoxon signed-rank test for non-normally distributed data. The significance level was set at α = 0.05. The majority of variables were found to be symmetrical with a total of 57/60 variables displaying symmetry in the discrete point analysis and 55/60 in the ACP. The five variables that were found to be asymmetrical were hip abductor moment in the drop landing (p = 0.02), pelvis lift/drop in the drop landing (p = 0.04) and hurdle hop (p = 0.02), ankle internal rotation moment in the cut (p = 0.04) and ankle dorsiflexion angle also in the cut (p = 0.01). The ACP identified two additional asymmetries not identified in the discrete point analysis. Elite injury free rugby union players tended to exhibit bi-lateral symmetry across a range of biomechanical variables in a drop landing, hurdle hop and cut. This study provides useful normative values for inter-limb symmetry in these movement tests. When examining symmetry it is recommended to incorporate continuous data analysis techniques rather than a discrete point analysis alone; a discrete point analysis was unable to detect two of the five asymmetries identified.

Viscosity Measurement via Drop Coalescence: A Space Station Experiment

NASA Technical Reports Server (NTRS)

Antar, Basil; Ethridge, Edwin C.

2010-01-01

The concept of using low gravity experimental data together with CFD simulations for measuring the viscosity of highly viscous liquids was recently validated on onboard the International Space Station (ISS). A series of microgravity tests were conducted for this purpose on the ISS in July, 2004 and in May of 2005. In these experiments two liquid drops were brought manually together until they touched and were allowed to coalesce under the action of the capillary force alone. The coalescence process was recorded photographically from which the contact radius speed of the merging drops was measured. The liquid viscosity was determined by fitting the measured data with accurate numerical simulation of the coalescence process. Several liquids were tested and for each liquid several drop diameters were employed. Experimental and numerical results will be presented in which the viscosity of several highly viscous liquids were determined using this technique.

Violence, schools, and dropping out: racial and ethnic disparities in the educational consequence of student victimization.

PubMed

Peguero, Anthony A

2011-12-01

Without a doubt, exposure to violence and victimization can be profoundly detrimental to the overall well-being and development of all youth. Moreover, violence and victimization that occurs within a school context is particularly alarming because a successful educational process is essential toward establishing socioeconomic success later in life. The educational consequence of exposure to violence and victimization at school is uncertain for racial and ethnic minority students. This study utilizes data from the Education Longitudinal Study of 2002 and incorporates multilevel modeling techniques to examine the impact of violence and victimization at school on dropping out. The results indicate Black/African Americans and Latino American students who are victimized at school are at higher risk of dropping out. The implications of the evident racial and ethnic disparities in the relationship between victimization and dropping out within the U.S. school system are discussed.

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.

Techniques for Examining Drop Size Spectra in Water Sprays and Clouds

DTIC Science & Technology

1979-04-01

surface perpendicular to the air stream was essential to avoid elliptical or comet -like impressions. 5.1.2 Oil Wetted Slides While, with this technique...55 Commonwealth Aircraft Corporation, Library 56 Hawker de Havilland Pty Ltd, Librarian, Bankstown 57 Hawker de Havilland Pty Ltd, Manager, Lidcombe 58

Micro-explosion of compound drops

NASA Astrophysics Data System (ADS)

Chen, Chun-Kuei; Lin, Ta-Hui

2014-08-01

Introducing water into spray combustion systems, by either water-in-oil emulsification or supplementary water injection, is one of the major techniques for combustion improvement and NOx reduction. Plentiful researches are available on combustion of water-in-oil emulsion fuel drops. The emulsified liquid is a heterogeneous mixture of immiscible liquids. One component forms the continuous phase and the other component forms the discrete phase. The discrete phase consists of globules of the one fluid that are suspended in the continuous phase fluid. Water-in-oil emulsions are commonly considered for combustion applications because emulsions can result in micro-explosion, thereby reducing the average drop diameter to enhance liquid vaporization, and suppressing the formation of soot and NOx. However, the water addition generally does not exceed about 20% for smooth engine operations[!, 21. The combustion characteristics and micro-explosion of emulsion drop were studied by many researchers. The micro-explosion of water in fuel emulsion drops was caused by very fast growth of superheated water vapor bubbles, its superheat limits must be lower than the boiling point temperature of the fuel. These bubbles were primarily governed by the pressure difference between the superheated vapor and the liquid, and by the inertia imparted to the liquid by the motion of the bubble surface[3 6 In this study, we used a coaxial nozzle to generation the multi-component drop. The different type of water-in-oil fuel drops called the compound drops. Unlike an emulsion drop, a compound drop consists of a water core and a fuel shell, which can originate from the phase separation of emulsion[7, 81 or a water drop colliding with a fuel drop[9, 101 Burning and micro-explosion of compound drops have been found to be distinct from those of emulsion drops[9-111 Wang et al.[9 , 101 studied the combustion characteristics of collision merged alkane-water drops. The merged drops appeared in adhesive and inserted manners. The drop ignition delay time increased with increasing water content. The average burning rate of alkane-water drops decreased with increasing water content. In the burning process, hexadecane-water drops exhibited flash vaporization or flame extinction. Heterogeneous explosion was occasionally observed in drops with trapped air bubbles. The air bubbles were assumed to be the nucleation points of the heterogeneous explosions. Chen and Lin[11 studied the characteristics of water-in-dodecane compound drop with different water content, diameter of drop and environmental oxygen concentration. The vaporization rate increased with increasing environmental oxygen concentration. The compound drops micro-exploded during the burning process in a random way. The number of micro-explosions was majorly influenced by drop diameter, followed by environmental oxygen concentration. Water content had a weaker effect on micro-explosion. As available literature and research results of compound drop burning are scarce, their combustion and micro-explosion behaviors are still poorly understood. In this regard, we changed the drop nature as compound drops to study their combustion characteristics and micro-explosion phenomena.

Irreversible Entropy Production in Two-Phase Mixing Layers

NASA Technical Reports Server (NTRS)

Okongo, Nora

2003-01-01

This report presents a study of dissipation (irreversible production of entropy) in three-dimensional, temporal mixing layers laden with evaporating liquid drops. The purpose of the study is to examine the effects of evaporating drops on the development of turbulent features in flows. Direct numerical simulations were performed to analyze transitional states of three mixing layers: one without drops, and two that included drops at different initial mass loadings. Without drops, the dissipation is essentially due to viscous effects. It was found that in the presence of drops, the largest contribution to dissipation was made by heating and evaporation of the drops, and that at large length scales, this contribution is positive (signifying that the drops reduce turbulence), while at small scales, this contribution is negative (the drops increase turbulence). The second largest contribution to dissipation was found to be associated with the chemical potential, which leads to an increase in turbulence at large scales and a decrease in turbulence at small scales. The next smaller contribution was found to be that of viscosity. The fact that viscosity effects are only third in order of magnitude in the dissipation is in sharp contrast to the situation for the mixing layer without the drops. The next smaller contribution - that of the drag and momentum of the vapor from the drops - was found to be negative at lower mass loading but to become positive at higher mass loading.

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

Investigation of new radar-data-reduction techniques used to determine drag characteristics of a free-flight vehicle

NASA Technical Reports Server (NTRS)

Woodbury, G. E.; Wallace, J. W.

1974-01-01

An investigation was conducted of new techniques used to determine the complete transonic drag characteristics of a series of free-flight drop-test models using principally radar tracking data. The full capabilities of the radar tracking and meteorological measurement systems were utilized. In addition, preflight trajectory design, exact kinematic equations, and visual-analytical filtering procedures were employed. The results of this study were compared with the results obtained from analysis of the onboard, accelerometer and pressure sensor data of the only drop-test model that was instrumented. The accelerometer-pressure drag curve was approximated by the radar-data drag curve. However, a small amplitude oscillation on the latter curve precluded a precise definition of its drag rise.

Development and characterization of nano-fiber patch for the treatment of glaucoma.

PubMed

Gagandeep; Garg, Tarun; Malik, Basant; Rath, Goutam; Goyal, Amit K

2014-03-12

In the present work polymeric nano-fiber patches was developed for the effective treatment of glaucoma using timolol maleate and dorzolamide hydrochloride as model drugs. The nano-fibers were prepared by electrospinning technique and were characterized on the basis of fiber diameter, morphology, entrapment efficiency, mucoadhesive strength, and drug release behavior, etc. Final formulations were inserted in the cul-de-sac of glaucoma induced rabbits and the efficacy of the formulation was evaluated. The results clearly indicated the potential of the developed formulation for occur drug delivery. There was a significant fall in the intraocular pressure compared to commercial eye drops. Copyright © 2013 Elsevier B.V. All rights reserved.

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

Resonant Rectifier ICs for Piezoelectric Energy Harvesting Using Low-Voltage Drop Diode Equivalents

PubMed Central

Din, Amad Ud; Chandrathna, Seneke Chamith; Lee, Jong-Wook

2017-01-01

Herein, we present the design technique of a resonant rectifier for piezoelectric (PE) energy harvesting. We propose two diode equivalents to reduce the voltage drop in the rectifier operation, a minuscule-drop-diode equivalent (MDDE) and a low-drop-diode equivalent (LDDE). The diode equivalents are embedded in resonant rectifier integrated circuits (ICs), which use symmetric bias-flip to reduce the power used for charging and discharging the internal capacitance of a PE transducer. The self-startup function is supported by synchronously generating control pulses for the bias-flip from the PE transducer. Two resonant rectifier ICs, using both MDDE and LDDE, are fabricated in a 0.18 μm CMOS process and their performances are characterized under external and self-power conditions. Under the external-power condition, the rectifier using LDDE delivers an output power POUT of 564 μW and a rectifier output voltage VRECT of 3.36 V with a power transfer efficiency of 68.1%. Under self-power conditions, the rectifier using MDDE delivers a POUT of 288 μW and a VRECT of 2.4 V with a corresponding efficiency of 78.4%. Using the proposed bias-flip technique, the power extraction capability of the proposed rectifier is 5.9 and 3.0 times higher than that of a conventional full-bridge rectifier. PMID:28422085

Resonant Rectifier ICs for Piezoelectric Energy Harvesting Using Low-Voltage Drop Diode Equivalents.

PubMed

Din, Amad Ud; Chandrathna, Seneke Chamith; Lee, Jong-Wook

2017-04-19

Herein, we present the design technique of a resonant rectifier for piezoelectric (PE) energy harvesting. We propose two diode equivalents to reduce the voltage drop in the rectifier operation, a minuscule-drop-diode equivalent (MDDE) and a low-drop-diode equivalent (LDDE). The diode equivalents are embedded in resonant rectifier integrated circuits (ICs), which use symmetric bias-flip to reduce the power used for charging and discharging the internal capacitance of a PE transducer. The self-startup function is supported by synchronously generating control pulses for the bias-flip from the PE transducer. Two resonant rectifier ICs, using both MDDE and LDDE, are fabricated in a 0.18 μm CMOS process and their performances are characterized under external and self-power conditions. Under the external-power condition, the rectifier using LDDE delivers an output power P OUT of 564 μW and a rectifier output voltage V RECT of 3.36 V with a power transfer efficiency of 68.1%. Under self-power conditions, the rectifier using MDDE delivers a P OUT of 288 μW and a V RECT of 2.4 V with a corresponding efficiency of 78.4%. Using the proposed bias-flip technique, the power extraction capability of the proposed rectifier is 5.9 and 3.0 times higher than that of a conventional full-bridge rectifier.

Micro-valve pump light valve display

DOEpatents

Yeechun Lee.

1993-01-19

A flat panel display incorporates a plurality of micro-pump light valves (MLV's) to form pixels for recreating an image. Each MLV consists of a dielectric drop sandwiched between substrates, at least one of which is transparent, a holding electrode for maintaining the drop outside a viewing area, and a switching electrode from accelerating the drop from a location within the holding electrode to a location within the viewing area. The sustrates may further define non-wetting surface areas to create potential energy barriers to assist in controlling movement of the drop. The forces acting on the drop are quadratic in nature to provide a nonlinear response for increased image contrast. A crossed electrode structure can be used to activate the pixels whereby a large flat panel display is formed without active driver components at each pixel.

Micro-valve pump light valve display

DOEpatents

Lee, Yee-Chun

1993-01-01

A flat panel display incorporates a plurality of micro-pump light valves (MLV's) to form pixels for recreating an image. Each MLV consists of a dielectric drop sandwiched between substrates, at least one of which is transparent, a holding electrode for maintaining the drop outside a viewing area, and a switching electrode from accelerating the drop from a location within the holding electrode to a location within the viewing area. The sustrates may further define non-wetting surface areas to create potential energy barriers to assist in controlling movement of the drop. The forces acting on the drop are quadratic in nature to provide a nonlinear response for increased image contrast. A crossed electrode structure can be used to activate the pixels whereby a large flat panel display is formed without active driver components at each pixel.

Singularities in Free Surface Flows

NASA Astrophysics Data System (ADS)

Thete, Sumeet Suresh

Free surface flows where the shape of the interface separating two or more phases or liquids are unknown apriori, are commonplace in industrial applications and nature. Distribution of drop sizes, coalescence rate of drops, and the behavior of thin liquid films are crucial to understanding and enhancing industrial practices such as ink-jet printing, spraying, separations of chemicals, and coating flows. When a contiguous mass of liquid such as a drop, filament or a film undergoes breakup to give rise to multiple masses, the topological transition is accompanied with a finite-time singularity . Such singularity also arises when two or more masses of liquid merge into each other or coalesce. Thus the dynamics close to singularity determines the fate of about-to-form drops or films and applications they are involved in, and therefore needs to be analyzed precisely. The primary goal of this thesis is to resolve and analyze the dynamics close to singularity when free surface flows experience a topological transition, using a combination of theory, experiments, and numerical simulations. The first problem under consideration focuses on the dynamics following flow shut-off in bottle filling applications that are relevant to pharmaceutical and consumer products industry, using numerical techniques based on Galerkin Finite Element Methods (GFEM). The second problem addresses the dual flow behavior of aqueous foams that are observed in oil and gas fields and estimates the relevant parameters that describe such flows through a series of experiments. The third problem aims at understanding the drop formation of Newtonian and Carreau fluids, computationally using GFEM. The drops are formed as a result of imposed flow rates or expanding bubbles similar to those of piezo actuated and thermal ink-jet nozzles. The focus of fourth problem is on the evolution of thinning threads of Newtonian fluids and suspensions towards singularity, using computations based on GFEM and experimental techniques. The aim of fifth problem is to analyze the coalescence dynamics of drops through a combination of GFEM and scaling theory. Lastly, the sixth problem concerns the thinning and rupture dynamics of thin films of Newtonian and power-law fluids using scaling theory based on asymptotic analysis and the predictions of this theory are corroborated using computations based on GFEM.

Drop Axis Ratio Distributions in Stratiform and Convective Rain

NASA Technical Reports Server (NTRS)

Thurai, M.; Bringi, V. N.; Petersen, W. A.; Schultz, C.

2010-01-01

A fully calibrated low profile 2D video disdrometer (2DVD) has been recording many different rainfall events in Northern Alabama (USA) since June 2007. An earlier publication reported drop shapes and axis ratio distributions determined for some of the events. For one of the cases examined, a noticeable shift in the 3.5 - 3.75 mm drop axis ratio distribution was noted. In this paper, we extend the earlier work by separating the 2DVD measurements into stratiform and convective rain. The separation is made possible by using the minute-by-minute drop size distribution (DSD) measured by the 2DVD. The 1-minute DSDs are fitted to a gamma distribution, and using a simple indexing technique which involves two of the fitted parameters, periods of convective and stratiform rain are separated for a given event. The output of the DSD indexing technique is qualitatively confirmed by comparing with simultaneous time series observations from a co-located UHF profiler which continuously records height profiles of reflectivity, Doppler mean and spectral width, all of which enable the identification of bright-band periods and, furthermore, periods of moderate and deep convection. Excellent consistency is found between the output of the DSD-based separation method and the profiler observations. Next, we utilize the output of DSD index-based separation method to flag the periods of severe convection for a given event. Drop axis ratios during the flagged periods are derived and compared with those during stratiform rain periods. Five cases have been considered. Axis ratio distributions do not show appreciable differences between stratiform and convective periods for four of the cases. The fifth case (the same case as reported earlier) shows a shift in the 3.5 - 3.75 mm drop axis ratios during a prolonged period of convection. The contoured shapes for these drops determined from the 2DVD camera data indicate the possibility of non-axisymmetric oscillations, compared with the contoured images for other events which fit well to our reference drop shapes. For all of above cases, observations from a C-band polarimetric radar - situated 15 km away are examined. The variations between the co-polar radar reflectivity and the differential reflectivity as well as the specific differential phase are compared with the 2DVD data based scattering calculations for the 5 events. The implications will be discussed.

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.

Identification of potential local isolated for biosurfactant production

NASA Astrophysics Data System (ADS)

Shafiei, Zahra; Yusoff, Wan Mohtar Wan; Hamid, Aidil Abdul; Moazami, Nasrin; Hamzah, Ainon; Fooladi, Taybeh

2013-11-01

Biosurfactant are amphiphilic molecule that have received increasing attention in recent years because of their role in the growth of microorganisms on water-insoluble hydrophobic materials such as hydrocarbons as well as their commercial potential in the cosmetics, food, oil recovery and agricultural industries. In this study a potential biosurfactant producing strain was isolated from several soil samples of Terengganu oil refinery, Malaysia and selected during preliminary screening using hemolytic activity, oil spreading and drop collapsed technique. Isolates with at least more than one positive response to these three methods were subjected to complementary screening by measuring surface tension reduction as well as emulsification capacity. The biosurfactant produced by isolated 5M was able to reduced surface tension of culture medium from 60 mN/m to30mN/m. The biochemical and morphological characterization, 16SrRNA gene sequencing showed that the isolated 5M belongs to bacillus groups. The maximum production of biosurfactant by Bacillus 5M was observed after 48 h of incubation.

Containerless processing of undercooled melts

NASA Technical Reports Server (NTRS)

Shong, D. S.; Graves, J. A.; Ujiie, Y.; Perepezko, J. H.

1987-01-01

Containerless drop tube processing allows for significant levels of liquid undercooling through control of parameters such as sample size, surface coating and cooling rate. A laboratory scale (3 m) drop tube has been developed which allows the undercooling and solidification behavior of powder samples to be evaluated under low gravity free-fall conditions. The level of undercooling obtained in an InSb-Sb eutectic alloy has been evaluated by comparing the eutectic spacing in drop tube samples with a spacing/undercooling relationship established using thermal analysis techniques. Undercoolings of 0.17 and 0.23 T(e) were produced by processing under vacuum and He gas conditions respectively. Alternatively, the formation of an amorphous phase in a Ni-Nb eutectic alloy indicates that undercooling levels of approximately 500 C were obtained by drop tube processing. The influence of droplet size and gas environment on undercooling behavior in the Ni-Nb eutectic was evaluated through their effect on the amorphous/crystalline phase ratio. To supplement the structural analysis, heat flow modeling has been developed to describe the undercooling history during drop tube processing, and the model has been tested experimentally.

Wavelength division multiplexed and double-port pumped time-bin entangled photon pair generation using Si ring resonator.

PubMed

Fujiwara, Mikio; Wakabayashi, Ryota; Sasaki, Masahide; Takeoka, Masahiro

2017-02-20

We report a wavelength division multiplexed time-bin entangled photon pair source in telecom wavelength using a 10 μm radius Si ring resonator. This compact resonator has two add ports and two drop ports. By pumping one add port by a continuous laser, we demonstrate an efficient generation of two-wavelength division multiplexed time-bin entangled photon pairs in the telecom C-band, which come out of one drop port, and are then split into the signal and idler photons via a wavelength filter. The resonator structure enhances four-wave mixing for pair generation. Moreover, we demonstrate the double-port pumping where two counter propagating pump lights are injected to generate entanglement from the two drop ports simultaneously. We successfully observe the highly entangled outputs from both two drop ports. Surprisingly, the count rate at each drop port is even increased by twice that of the single-port pumping. Possible mechanisms of this observation are discussed. Our technique allows for the efficient use of the Si ring resonator and widens its functionality for variety of applications.

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...

A new encoding scheme for visible light communications with applications to mobile connections

NASA Astrophysics Data System (ADS)

Benton, David M.; St. John Brittan, Paul

2017-10-01

A new, novel and unconventional encoding scheme called concurrent coding, has recently been demonstrated and shown to offer interesting features and benefits in comparison to conventional techniques, such as robustness against burst errors and improved efficiency of transmitted power. Free space optical communications can suffer particularly from issues of alignment which requires stable, fixed links to be established and beam wander which can interrupt communications. Concurrent coding has the potential to help ease these difficulties and enable mobile, flexible optical communications to be implemented through the use of a source encoding technique. This concept has been applied for the first time to optical communications where standard light emitting diodes (LEDs) have been used to transmit information encoded with concurrent coding. The technique successfully transmits and decodes data despite unpredictable interruptions to the transmission causing significant drop-outs to the detected signal. The technique also shows how it is possible to send a single block of data in isolation with no pre-synchronisation required between transmitter and receiver, and no specific synchronisation sequence appended to the transmission. Such systems are robust against interference - intentional or otherwise - as well as intermittent beam blockage.

Free-to-Roll Investigation of the Pre-Production F/A-18E Powered Approach Wing Drop

NASA Technical Reports Server (NTRS)

Owens, D. Bruce; Bryant, Elaine M.; Barlow, Jewel B.

2005-01-01

A free-to-roll study of the low-speed lateral characteristics of the pre-production F/A-18E was conducted in the NASA Langley 12-Foot Low-Speed Tunnel. In developmental flight tests the F/A-18E unexpectedly experienced uncommanded lateral motions in the power approach configuration. The objective of this study was to determine the feasibility of using the free-to-roll technique for the detection of uncommanded lateral motions for the pre-production F/A-18E in the power approach configuration. The data revealed that this technique in conjunction with static data revealed insight into the cause of the lateral motions. The free-to-roll technique identified uncommanded lateral motions at the same angle-of-attack range as experienced in flight tests. The cause of the uncommanded lateral motions was unsteady asymmetric wing stall. The paper also shows that free-to-roll data or static force and moment data alone are not enough to accurately capture the potential for an aircraft to experience uncommanded lateral motion.

Corrosion pitting and environmentally assisted small crack growth

PubMed Central

Turnbull, Alan

2014-01-01

In many applications, corrosion pits act as precursors to cracking, but qualitative and quantitative prediction of damage evolution has been hampered by lack of insights into the process by which a crack develops from a pit. An overview is given of recent breakthroughs in characterization and understanding of the pit-to-crack transition using advanced three-dimensional imaging techniques such as X-ray computed tomography and focused ion beam machining with scanning electron microscopy. These techniques provided novel insights with respect to the location of crack development from a pit, supported by finite-element analysis. This inspired a new concept for the role of pitting in stress corrosion cracking based on the growing pit inducing local dynamic plastic strain, a critical factor in the development of stress corrosion cracks. Challenges in quantifying the subsequent growth rate of the emerging small cracks are then outlined with the potential drop technique being the most viable. A comparison is made with the growth rate for short cracks (through-thickness crack in fracture mechanics specimen) and long cracks and an electrochemical crack size effect invoked to rationalize the data. PMID:25197249

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.

The rate of the reaction between CN and C2H2 at interstellar temperatures.

PubMed

Woon, D E; Herbst, E

1997-03-01

The rate coefficient for the important interstellar reaction between CN and C2H2 has been calculated as a function of temperature between 10 and 300 K. The potential surface for this reaction has been determined through ab initio quantum chemical techniques; the potential exhibits no barrier in the entrance channel but does show a small exit channel barrier, which lies below the energy of reactants. Phase-space calculations for the reaction dynamics, which take the exit channel barrier into account, show the same unusual temperature dependence as determined by experiment, in which the rate coefficient at first increases as the temperature is reduced below room temperature and then starts to decrease as the temperature drops below 50-100 K. The agreement between theory and experiment provides strong confirmation that the reaction occurs appreciably at cool interstellar temperatures.

Inertial Confinement fusion targets

NASA Technical Reports Server (NTRS)

Hendricks, C. D.

1982-01-01

Inertial confinement fusion (ICF) targets are made as simple flat discs, as hollow shells or as complicated multilayer structures. Many techniques were devised for producing the targets. Glass and metal shells are made by using drop and bubble techniques. Solid hydrogen shells are also produced by adapting old methods to the solution of modern problems. Some of these techniques, problems, and solutions are discussed. In addition, the applications of many of the techniques to fabrication of ICF targets is presented.

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.

Viscosity Measurement of Highly Viscous Liquids Using Drop Coalescence in Low Gravity

NASA Technical Reports Server (NTRS)

Antar, Basil N.; Ethridge, Edwin; Maxwell, Daniel

1999-01-01

The method of drop coalescence is being investigated for use as a method for determining the viscosity of highly viscous undercooled liquids. Low gravity environment is necessary in this case to minimize the undesirable effects of body forces and liquid motion in levitated drops. Also, the low gravity environment will allow for investigating large liquid volumes which can lead to much higher accuracy for the viscosity calculations than possible under 1 - g conditions. The drop coalescence method is preferred over the drop oscillation technique since the latter method can only be applied for liquids with vanishingly small viscosities. The technique developed relies on both the highly accurate solution of the Navier-Stokes equations as well as on data from experiments conducted in near zero gravity environment. In the analytical aspect of the method two liquid volumes are brought into contact which will coalesce under the action of surface tension alone. The free surface geometry development as well as its velocity during coalescence which are obtained from numerical computations are compared with an analogous experimental model. The viscosity in the numerical computations is then adjusted to bring into agreement of the experimental results with the calculations. The true liquid viscosity is the one which brings the experiment closest to the calculations. Results are presented for method validation experiments performed recently on board the NASA/KC-135 aircraft. The numerical solution for this validation case was produced using the Boundary Element Method. In these tests the viscosity of a highly viscous liquid, in this case glycerine at room temperature, was determined to high degree of accuracy using the liquid coalescence method. These experiments gave very encouraging results which will be discussed together with plans for implementing the method in a shuttle flight experiment.

Detection and characterization of elongated bubbles and drops in two-phase flow using magnetic fields

NASA Astrophysics Data System (ADS)

Wiederhold, A.; Boeck, T.; Resagk, C.

2017-08-01

We report a method to detect and to measure the size and velocity of elongated bubbles or drops in a dispersed two-phase flow. The difference of the magnetic susceptibilities between two phases causes a force on the interface between both phases when it is exposed to an external magnetic field. The force is measured with a state-of-the-art electromagnetic compensation balance. While the front and the back of the bubble pass the magnetic field, two peaks in the force signal appear, which can be used to calculate the velocity and geometry parameters of the bubble. We achieve a substantial advantage over other bubble detection techniques because this technique is contactless, non-invasive, independent of the electrical conductivity and can be applied to opaque or aggressive fluids. The measurements are performed in an inclined channel with air bubbles and paraffin oil drops in water. The bubble length is in the range of 0.1-0.25 m and the bubble velocity lies between 0.02-0.22 m s-1. Furthermore we show that it is possible to apply this measurement principle for nondestructive testing (NDT) of diamagnetic and paramagnetic materials like metal, plastics or glass, provided that defects are in the range of 10‒2 m. This technique opens up new possibilities in industrial applications to measure two-phase flow parameters and in material testing.

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.

Electric Mars: A Large Trans-Terminator Electric Potential Drop on Closed Magnetic Field Lines Above Utopia Planitia

NASA Technical Reports Server (NTRS)

Collinson, Glyn; Mitchell, David; Xu, Shaosui; Glocer, Alex; Grebowsky, Joseph; Hara, Takuya; Lillis, Robert; Espley, Jared; Mazelle, Christian; Sauvaud, Jean-Andre

2017-01-01

Abstract Parallel electric fields and their associated electric potential structures play a crucial role inionospheric-magnetospheric interactions at any planet. Although there is abundant evidence that parallel electric fields play key roles in Martian ionospheric outflow and auroral electron acceleration, the fields themselves are challenging to directly measure due to their relatively weak nature. Using measurements by the Solar Wind Electron Analyzer instrument aboard the NASA Mars Atmosphere and Volatile EvolutioN(MAVEN) Mars Scout, we present the discovery and measurement of a substantial (Phi) Mars 7.7 +/-0.6 V) parallel electric potential drop on closed magnetic field lines spanning the terminator from day to night above the great impact basin of Utopia Planitia, a region largely free of crustal magnetic fields. A survey of the previous 26 orbits passing over a range of longitudes revealed similar signatures on seven orbits, with a mean potential drop (Phi) Mars of 10.9 +/- 0.8 V, suggestive that although trans-terminator electric fields of comparable strength are not ubiquitous, they may be common, at least at these northerly latitudes.

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.

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%.

Measuring Rock-Fluid Adhesion Directly

NASA Astrophysics Data System (ADS)

Tadmor, R.

2017-12-01

We show how to measure directly solid-liquid adhesion. We consider the normal adhesion, the work adhesion, and the lateral adhesion. The technique at the center of the method is Centrifugal Adhesion Balance (CAB) which allows coordinated manipulation of normal and lateral forces. For example: 1. It allows to induce an increase in the normal force which pulls on a liquid drop while keeping zero lateral force. This method mimics a drop that is subjected to a gravitational force that is gradually increasing. 2. It allows to increase the lateral force at zero normal force, mimicking zero gravity. From this one can obtain additional solid-liquid interaction parameters. When performing work of adhesion measurements, the values obtained are independent of drop size and are in agreement with theoretical predictions.

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.

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.

Optical measurements in evolving dispersed pipe flows

NASA Astrophysics Data System (ADS)

Voulgaropoulos, Victor; Angeli, Panagiota

2017-12-01

Optical laser-based techniques and an extensive data analysis methodology have been developed to acquire flow and separation characteristics of concentrated liquid-liquid dispersions. A helical static mixer was used at the inlet of an acrylic 4 m long horizontal pipe to actuate the dispersed flows at low mixture velocities. The organic (913 kg m^{-3}, 0.0046 Pa s) and aqueous phases (1146 kg m^{-3}, 0.0084 Pa s) were chosen to have matched refractive indices. Measurements were conducted at 15 and 135 equivalent pipe diameters downstream the inlet. Planar laser induced fluorescence (PLIF) measurements illustrated the flow structures and provided the local in-situ holdup profiles. It was found that along the pipe the drops segregate and in some cases coalesce either with other drops or with the corresponding continuous phase. A multi-level threshold algorithm was developed to measure the drop sizes from the PLIF images. The velocity profiles in the aqueous phase were measured with particle image velocimetry (PIV), while the settling velocities of the organic dispersed drops were acquired with particle tracking velocimetry (PTV). It was also possible to capture coalescence events of a drop with an interface over time and to acquire the instantaneous velocity and vorticity fields in the coalescing drop.

Measurement of sheath potential by three emissive-probe methods in DC filament plasmas near a biased grid

NASA Astrophysics Data System (ADS)

Kang, In-Je; Park, In-Sun; Wackerbarth, Eugene; Bae, Min-Keun; Hershkowitz, Noah; Severn, Greg; Chung, Kyu-Sun

2017-10-01

Plasma potential structures are measured with an emissive probe near a negatively biased grid ( - 100 V , 80mm diam., 40 lines/cm) immersed in a hot filament DC discharge in Kr. Three different methods of analysis are compared: inflection point (IP), floating potential (FP) and separation point (SE) methods. The plasma device at the University of San Diego (length = 64 cm, diameter = 32 cm, source = filament DC discharge) was operated with 5 ×108

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.

Etiology and use of the "hanging drop" technique: a review.

PubMed

Todorov, Ludmil; VadeBoncouer, Timothy

2014-01-01

Background. The hanging drop (HD) technique presumably relies on the presence of subatmospheric epidural pressure. It is not clear whether this negative pressure is intrinsic or an artifact and how it is affected by body position. There are few data to indicate how often HD is currently being used. Methods. We identified studies that measured subatmospheric pressures and looked at the effect of the sitting position. We also looked at the technique used for cervical and thoracic epidural anesthesia in the last 10 years. Results. Intrinsic subatmospheric pressures were measured in the thoracic and cervical spine. Three trials studied the effect of body position, indicating a higher incidence of subatmospheric pressures when sitting. The results show lower epidural pressure (-10.7 mmHg) with the sitting position. 28.8% of trials of cervical and thoracic epidural anesthesia that documented the technique used, utilized the HD technique. When adjusting for possible bias, the rate of HD use can be as low as 11.7%. Conclusions. Intrinsic negative pressure might be present in the cervical and thoracic epidural space. This effect is more pronounced when sitting. This position might be preferable when using HD. Future studies are needed to compare it with the loss of resistance technique.

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.

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.

Final Report of the HyPER Harvester Project

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

Prasad, Nadipuram R; Ranade, Satishkuma J

The HyPER Harvester Project resulted in the first full­scale design, fabrication and testing of two vertical­axis harvester prototypes at the Elephant Butte Irrigation District Drop 8 Station in Southern New Mexico. The design, followed by fabrication, and deployment clearly demonstrated the feasibility to manufacture and deploy harvester prototypes at low cost. While several issues common to irrigation canal systems have to be overcome, the electromechanical performance of the integrated turbine­generator system demonstrated proof­of­concept. Proof­of­concept includes 1) feasibility for using additive manufacturing techniques to fabricate Carbon­composite turbine­generator components at low cost, 2) ease of transportation and deployment, and 3) the harvestermore » performance. The benefits of modularity were demonstrated in terms of rapid deployment at the Drop 8 Station. Scalability and adaptability were proven in terms of the custom­fitting characteristics that enabled rapid deployment. While keeping the same shape and form, the harvester can be easily adapted to any drop environment. Self­supporting ability makes the harvester design minimally intrusive on existing structures. There are two technical challenges ahead that have to be addressed. Irregular flow patterns in canal flow induce vertical oscillations due to pressure change across the impeller. Despite the nosecone in conventional Kaplan turbine design that ordinarily dampens oscillations, an effective coupling design is required to eliminate the hydrodynamic effect on the generating system. In arid areas where tumbleweed is present, a robust design to prevent trash entering the drop is required. The compact shape and form have an aesthetic appearance and appear to illustrate an environmentally friendly attribute. The systems­engineered design enables rapid manufacturing and assembly of desired size units that can be deployed at sites along U.S. waterways as small hydropower plants. There is worldwide potential for this technology to provide sustainable hydropower to communities isolated from grid­ supply.« less

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.

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.

Proposition of stair climb of a drop using chemical wettability gradient

NASA Astrophysics Data System (ADS)

Seerha, Prabh P. S.; Kumar, Parmod; Das, Arup K.; Mitra, Sushanta K.

2017-07-01

We propose a passive technique for a drop to climb along the staircase textured surface using chemical wettability gradients. The stair structure, droplet configuration, and contact angle gradient are modeled using Lagrangian smoothed particle hydrodynamics. The stair climb efficiency of the droplet is found to be a function of wettability gradient strength. Using analytical balance of actuation and resistive forces across droplets, physical reasons behind stair climbing are established and influencing parameters are identified. Evolution of the droplet shape along with the advancing and the receding contact angles is presented from where instantaneous actuation and hysteresis forces are calculated. Using history of Lagrangian particles, circulation at the foot of stairs and progressing development of the advancing drop front are monitored. Higher efficiency in stair climbing in the case of a bigger sized drop than smaller one is obtained from simulation results and realized from force balance. Difficulty in climbing steeper stairs is also demonstrated to delineate the effect of gravitational pull against the actuation force due to the wettability gradient.

LOX/Hydrogen Coaxial Injector Atomization Test Program

NASA Technical Reports Server (NTRS)

Zaller, M.

1990-01-01

Quantitative information about the atomization of injector sprays is needed to improve the accuracy of computational models that predict the performance and stability margin of liquid propellant rocket engines. To obtain this data, a facility for the study of spray atomization is being established at NASA-Lewis to determine the drop size and velocity distributions occurring in vaporizing liquid sprays at supercritical pressures. Hardware configuration and test conditions are selected to make the cold flow simulant testing correspond as closely as possible to conditions in liquid oxygen (LOX)/gaseous H2 rocket engines. Drop size correlations from the literature, developed for liquid/gas coaxial injector geometries, are used to make drop size predictions for LOX/H2 coaxial injectors. The mean drop size predictions for a single element coaxial injector range from 0.1 to 2000 microns, emphasizing the need for additional studies of the atomization process in LOX/H2 engines. Selection of cold flow simulants, measured techniques, and hardware for LOX/H2 atomization simulations are discussed.

Generation and characterization of surface layers on acoustically levitated drops.

PubMed

Tuckermann, Rudolf; Bauerecker, Sigurd; Cammenga, Heiko K

2007-06-15

Surface layers of natural and technical amphiphiles, e.g., octadecanol, stearic acid and related compounds as well as perfluorinated fatty alcohols (PFA), have been investigated on the surface of acoustically levitated drops. In contrast to Langmuir troughs, traditionally used in the research of surface layers at the air-water interface, acoustic levitation offers the advantages of a minimized and contact-less technique. Although the film pressure cannot be directly adjusted on acoustically levitated drops, it runs through a wide pressure range due to the shrinking surface of an evaporating drop. During this process, different states of the generated surface layer have been identified, in particular the phase transition from the gaseous or liquid-expanded to the liquid-condensed state of surface layers of octadecanol and other related amphiphiles. Characteristic parameters, such as the relative permeation resistance and the area per molecule in a condensed surface layer, have been quantified and were found comparable to results obtained from surface layers generated on Langmuir troughs.

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.

Accurate high-speed liquid handling of very small biological samples.

PubMed

Schober, A; Günther, R; Schwienhorst, A; Döring, M; Lindemann, B F

1993-08-01

Molecular biology techniques require the accurate pipetting of buffers and solutions with volumes in the microliter range. Traditionally, hand-held pipetting devices are used to fulfill these requirements, but many laboratories have also introduced robotic workstations for the handling of liquids. Piston-operated pumps are commonly used in manually as well as automatically operated pipettors. These devices cannot meet the demands for extremely accurate pipetting of very small volumes at the high speed that would be necessary for certain applications (e.g., in sequencing projects with high throughput). In this paper we describe a technique for the accurate microdispensation of biochemically relevant solutions and suspensions with the aid of a piezoelectric transducer. It is suitable for liquids of a viscosity between 0.5 and 500 milliPascals. The obtainable drop sizes range from 5 picoliters to a few nanoliters with up to 10,000 drops per second. Liquids can be dispensed in single or accumulated drops to handle a wide volume range. The system proved to be excellently suitable for the handling of biological samples. It did not show any detectable negative impact on the biological function of dissolved or suspended molecules or particles.

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.

Techniques and instrumentation for the measurement of transient sound energy flux

NASA Astrophysics Data System (ADS)

Watkinson, P. S.; Fahy, F. J.

1983-12-01

The evaluation of sound intensity distributions, and sound powers, of essentially continuous sources such as automotive engines, electric motors, production line machinery, furnaces, earth moving machinery and various types of process plants were studied. Although such systems are important sources of community disturbance and, to a lesser extent, of industrial health hazard, the most serious sources of hearing hazard in industry are machines operating on an impact principle, such as drop forges, hammers and punches. Controlled experiments to identify major noise source regions and mechanisms are difficult because it is normally impossible to install them in quiet, anechoic environments. The potential for sound intensity measurement to provide a means of overcoming these difficulties has given promising results, indicating the possibility of separation of directly radiated and reverberant sound fields. However, because of the complexity of transient sound fields, a fundamental investigation is necessary to establish the practicability of intensity field decomposition, which is basic to source characterization techniques.

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

Kimura, Tomoharu; Yamada, Hirofumi, E-mail: h-yamada@kuee.kyoto-u.ac.jp; Kobayashi, Kei

The device performances of organic thin film transistors are often limited by the metal–organic interface because of the disordered molecular layers at the interface and the energy barriers against the carrier injection. It is important to study the local impedance at the interface without being affected by the interface morphology. We combined frequency modulation atomic force microscopy with scanning impedance microscopy (SIM) to sensitively measure the ac responses of the interface to an ac voltage applied across the interface and the dc potential drop at the interface. By using the frequency-modulation SIM (FM-SIM) technique, we characterized the interface impedance ofmore » a Pt electrode and a single pentacene grain as a parallel circuit of a contact resistance and a capacitance. We found that the reduction of the contact resistance was caused by the reduction of the energy level mismatch at the interface by the FM-SIM measurements, demonstrating the usefulness of the FM-SIM technique for investigation of the local interface impedance without being affected by its morphology.« less

Interaction Between Graphene-Coated SiC Single Crystal and Liquid Copper

NASA Astrophysics Data System (ADS)

Homa, M.; Sobczak, N.; Sobczak, J. J.; Kudyba, A.; Bruzda, G.; Nowak, R.; Pietrzak, K.; Chmielewski, M.; Strupiński, W.

2018-04-01

The wettability of graphene-coated SiC single crystal (CGn/SiCsc) by liquid Cu (99.99%) was investigated by a sessile drop method in vacuum conditions at temperature of 1100 °C. The graphene layer was produced via a chemical vapor deposition routine using 4H-SiC single crystal cut out from 6″ wafer. A dispensed drop technique combined with a non-contact heating of a couple of materials was applied. The Cu drop was squeezed from a graphite capillary and deposited on the substrate directly in a vacuum chamber. The first Cu drop did not wet the CGn/SiCsc substrate and showed a lack of adhesion to the substrate: the falling Cu drop only touched the substrate forming a contact angle of θ 0 = 121° and then immediately rolled like a ball along the substrate surface. After settling near the edge of the substrate in about 0.15 s, the Cu drop formed an asymmetric shape with the right and left contact angles of different values (θ R = 86° and θ L = 70°, respectively), while in the next 30 min, θ R and θ L achieved the same final value of 52°. The second Cu drop was put down on the displacement path of the first drop, and immediately after the deposition, it also did not wet the substrate (θ = 123°). This drop kept symmetry and the primary position, but its wetting behavior was unusual: both θ R and θ L decreased in 17 min to the value of 23° and next, they increased to a final value of 65°. Visual observations revealed a presence of 2.5-mm-thick interfacial phase layer reactively formed under the second drop. Scanning electron microscopy (SEM) investigations revealed the presence of carbon-enriched precipitates on the top surface of the first Cu drop. These precipitates were identified by the Raman spectroscopy as double-layer graphene. The Raman spectrum taken from the substrate far from the drop revealed the presence of graphene, while that obtained from the first drop displacement path exhibited a decreased intensity of 2D peak. The results of SEM investigations and Raman spectroscopy studies suggest that the presence of graphene layer on the SiC substrate suppresses but does not completely prevent chemical interaction between liquid Cu drop and SiC. Both chemical degradation (etching) and mechanical degradation of the graphene layer during drop rolling due to high adhesion of the Cu drop to the SiC substrate are responsible for mass transfer through the 2nd drop/substrate interface that in turn results in significant changes of structure and chemistry of the drop and the interface.

Interaction Between Graphene-Coated SiC Single Crystal and Liquid Copper

NASA Astrophysics Data System (ADS)

Homa, M.; Sobczak, N.; Sobczak, J. J.; Kudyba, A.; Bruzda, G.; Nowak, R.; Pietrzak, K.; Chmielewski, M.; Strupiński, W.

2018-05-01

The wettability of graphene-coated SiC single crystal (CGn/SiCsc) by liquid Cu (99.99%) was investigated by a sessile drop method in vacuum conditions at temperature of 1100 °C. The graphene layer was produced via a chemical vapor deposition routine using 4H-SiC single crystal cut out from 6″ wafer. A dispensed drop technique combined with a non-contact heating of a couple of materials was applied. The Cu drop was squeezed from a graphite capillary and deposited on the substrate directly in a vacuum chamber. The first Cu drop did not wet the CGn/SiCsc substrate and showed a lack of adhesion to the substrate: the falling Cu drop only touched the substrate forming a contact angle of θ 0 = 121° and then immediately rolled like a ball along the substrate surface. After settling near the edge of the substrate in about 0.15 s, the Cu drop formed an asymmetric shape with the right and left contact angles of different values ( θ R = 86° and θ L = 70°, respectively), while in the next 30 min, θ R and θ L achieved the same final value of 52°. The second Cu drop was put down on the displacement path of the first drop, and immediately after the deposition, it also did not wet the substrate ( θ = 123°). This drop kept symmetry and the primary position, but its wetting behavior was unusual: both θ R and θ L decreased in 17 min to the value of 23° and next, they increased to a final value of 65°. Visual observations revealed a presence of 2.5-mm-thick interfacial phase layer reactively formed under the second drop. Scanning electron microscopy (SEM) investigations revealed the presence of carbon-enriched precipitates on the top surface of the first Cu drop. These precipitates were identified by the Raman spectroscopy as double-layer graphene. The Raman spectrum taken from the substrate far from the drop revealed the presence of graphene, while that obtained from the first drop displacement path exhibited a decreased intensity of 2D peak. The results of SEM investigations and Raman spectroscopy studies suggest that the presence of graphene layer on the SiC substrate suppresses but does not completely prevent chemical interaction between liquid Cu drop and SiC. Both chemical degradation (etching) and mechanical degradation of the graphene layer during drop rolling due to high adhesion of the Cu drop to the SiC substrate are responsible for mass transfer through the 2nd drop/substrate interface that in turn results in significant changes of structure and chemistry of the drop and the interface.

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.

The Measurement of Wettability

ERIC Educational Resources Information Center

Pirie, Brian J. S.; Gregory, David W.

1973-01-01

Discusses the use of a simple apparatus to measure contact angles between a liquid drop and a solid surface which are determining factors of wettability. Included are examples of applying this technique to various experimental situations. (CC)

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.

A multi-material coating containing chemically-modified apatites for combined enhanced bioactivity and reduced infection via a drop-on-demand micro-dispensing technique.

PubMed

Lim, Poon Nian; Wang, Zuyong; Chang, Lei; Konishi, Toshiisa; Choong, Cleo; Ho, Bow; Thian, Eng San

2017-01-01

Prevention of infection and enhanced osseointegration are closely related, and required for a successful orthopaedic implant, which necessitate implant designs to consider both criteria in tandem. A multi-material coating containing 1:1 ratio of silicon-substituted hydroxyapatite and silver-substituted hydroxyapatite as the top functional layer, and hydroxyapatite as the base layer, was produced via the drop-on-demand micro-dispensing technique, as a strategic approach in the fight against infection along with the promotion of bone tissue regeneration. The homogeneous distribution of silicon-substituted hydroxyapatite and silver-substituted hydroxyapatite micro-droplets at alternate position in silicon-substituted hydroxyapatite-silver-substituted hydroxyapatite/hydroxyapatite coating delayed the exponential growth of Staphylococcus aureus for up to 24 h, and gave rise to up-regulated expression of alkaline phosphatase activity, type I collagen and osteocalcin as compared to hydroxyapatite and silver-substituted hydroxyapatite coatings. Despite containing reduced amounts of silicon-substituted hydroxyapatite and silver-substituted hydroxyapatite micro-droplets over the coated area than silicon-substituted hydroxyapatite and silver-substituted hydroxyapatite coatings, silicon-substituted hydroxyapatite-silver-substituted hydroxyapatite/hydroxyapatite coating exhibited effective antibacterial property with enhanced bioactivity. By exhibiting good controllability of distributing silicon-substituted hydroxyapatite, silver-substituted hydroxyapatite and hydroxyapatite micro-droplets, it was demonstrated that drop-on-demand micro-dispensing technique was capable in harnessing the advantages of silver-substituted hydroxyapatite, silicon-substituted hydroxyapatite and hydroxyapatite to produce a multi-material coating along with enhanced bioactivity and reduced infection.

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…

Effects of wind on the dynamics of the central jet during drop impact onto a deep-water surface

NASA Astrophysics Data System (ADS)

Liu, Xinan; Wang, An; Wang, Shuang; Dai, Dejun

2018-05-01

The cavity and central jet generated by the impact of a single water drop on a deep-water surface in a wind field are experimentally studied. Different experiments are performed by varying the impacting drop diameter and wind speed. The contour profile histories of the cavity (also called crater) and central jet (also called stalk) are measured in detail with a backlit cinematic shadowgraph technique. The results show that shortly after the drop hits the water surface an asymmetrical cavity appears along the wind direction, with a train of capillary waves on the cavity wall. This is followed by the formation of an inclined central jet at the location of the drop impact. It is found that the wind has little effect on the penetration depth of the cavity at the early stage of the cavity expansion, but markedly changes the capillary waves during the retraction of the cavity. The capillary waves in turn shift the position of the central jet formation leeward. The dynamics of the central jet are dominated by two mechanisms: (i) the oblique drop impact produced by the wind and (ii) the wind drag force directly acting on the jet. The maximum height of the central jet, called the stalk height, is drastically affected by the wind, and the nondimensional stalk height H /D decreases with increasing θ Re-1 , where D is the drop diameter, θ is the impingement angle of drop impact, and Re=ρaUwD /μa is the Reynolds number with air density ρa, wind speed Uw, and air viscosity μa.

Development of a constant surface pressure penetration langmuir balance based on axisymmetric drop shape analysis.

PubMed

Wege, H A; Holgado-Terriza, J A; Cabrerizo-Vílchez, M A

2002-05-15

A new constant pressure pendant-drop penetration surface balance has been developed combining a pendant-drop surface balance, a rapid-subphase-exchange technique, and a fuzzy logic control algorithm. Beside the determination of insoluble monolayer compression-expansion isotherms, it allows performance of noninvasive kinetic studies of the adsorption of surfactants added to the new subphase onto the free surface and of the adsorption/penetration/reaction of the former onto/into/with surface layers, respectively. The interfacial pressure pi is a fundamental parameter in these studies: by working at constant pi one controls the height of the energy barrier to adsorption/penetration and can select different regimes and steps of the adsorption/penetration process. In our device a solution drop is formed at the tip of a coaxial double capillary, connected to a double microinjector. Drop profiles are extracted from digital drop micrographs and fitted to the equation of capillarity, yielding pi, the drop volume V, and the interfacial area A. pi is varied changing V (and hence A) with the microinjector. Control is based on a case-adaptable modulated fuzzy-logic PID algorithm able to maintain constant pi (or A) under a wide range of experimental conditions. The drop subphase liquid can be exchanged quantitatively by the coaxial capillaries. The adsorption/penetration/reaction kinetics at constant pi are then studied monitoring A(t), i.e., determining the relative area change necessary at each instant to compensate the pressure variation due to the interaction of the surfactant in the subsurface with the surface layer. A fully Windows-integrated program manages the whole setup. Examples of experimental protein adsorption and monolayer penetration kinetics are presented.

Can orthoses and navicular drop affect foot motion patterns during running?

PubMed

Eslami, Mansour; Ferber, Reed

2013-07-01

The purpose of this study was to examine the influence of semi-rigid foot orthoses on forefoot-rearfoot joint coupling patterns in individuals with different navicular drop measures during heel-toe running. Ten trials were collected from twenty-three male subjects who ran slowly shod at 170 steps per minute (2.23m/s) with a semi-rigid orthoses and without. Forefoot-rearfoot coupling motions were assessed using a vector coding technique during four intervals across the first 50% of stance. Subjects were divided into two groups based on navicular drop measures. A three way ANOVA was performed to examine the interaction and main effects of stance interval, orthoses condition and navicular drop (p<0.05). There were no interaction effects among stance interval, orthoses condition, or navicular drop (p=0.14) whereas an interaction effect of orthoses condition and stance interval was observed (p=0.01; effect size=0.74). Forefoot-rearfoot coupling motion in the no-orthoses condition increased from heel-strike to foot-flat phase at a rate faster than the orthoses condition (p=0.02). Foot orthoses significantly decrease the forefoot-rearfoot joint coupling angle by reducing forefoot frontal plane motion relative to the rearfoot. Navicular drop measures did not influence joint coupling relationships between the forefoot and rearfoot during the first 50% of stance regardless of orthotic condition. Copyright © 2012 Sports Medicine Australia. All rights reserved.

3D Hanging Drop Culture to Establish Prostate Cancer Organoids.

PubMed

Eder, Theresa; Eder, Iris E

2017-01-01

Three-dimensional (3D) cell culture enables the growth of cells in a multidimensional and multicellular manner compared to conventional cell culture techniques. Especially in prostate cancer research there is a big need for more tissue-recapitulating models to get a better understanding of the mechanisms driving prostate cancer as well as to screen for more efficient drugs that can be used for treatment. In this chapter we describe a 3D hanging drop system that can be used to culture prostate cancer organoids as tumor epithelial monocultures and as epithelial-stromal cocultures.

Chemical analysis of acoustically levitated drops by Raman spectroscopy.

PubMed

Tuckermann, Rudolf; Puskar, Ljiljana; Zavabeti, Mahta; Sekine, Ryo; McNaughton, Don

2009-07-01

An experimental apparatus combining Raman spectroscopy with acoustic levitation, Raman acoustic levitation spectroscopy (RALS), is investigated in the field of physical and chemical analytics. Whereas acoustic levitation enables the contactless handling of microsized samples, Raman spectroscopy offers the advantage of a noninvasive method without complex sample preparation. After carrying out some systematic tests to probe the sensitivity of the technique to drop size, shape, and position, RALS has been successfully applied in monitoring sample dilution and preconcentration, evaporation, crystallization, an acid-base reaction, and analytes in a surface-enhanced Raman spectroscopy colloidal suspension.

Quasi-Uniform High Speed Foam Crush Testing Using a Guided Drop Mass Impact

NASA Technical Reports Server (NTRS)

Jones, Lisa E. (Technical Monitor); Kellas, Sotiris

2004-01-01

A relatively simple method for measuring the dynamic crush response of foam materials at various loading rates is described. The method utilizes a drop mass impact configuration with mass and impact velocity selected such that the crush speed remains approximately uniform during the entire sample crushing event. Instrumentation, data acquisition, and data processing techniques are presented, and limitations of the test method are discussed. The objective of the test method is to produce input data for dynamic finite element modeling involving crash and energy absorption characteristics of foam materials.

Development of Drop/Shock Test in Microelectronics and Impact Dynamic Analysis for Uniform Board Response

NASA Astrophysics Data System (ADS)

Kallolimath, Sharan Chandrashekar

For the past several years, many researchers are constantly developing and improving board level drop test procedures and specifications to quantify the solder joint reliability performance of consumer electronics products. Predictive finite element analysis (FEA) by utilizing simulation software has become widely acceptable verification method which can reduce time and cost of the real-time test process. However, due to testing and metrological limitations it is difficult not only to simulate exact drop condition and capture critical measurement data but also tedious to calibrate the system to improve test methods. Moreover, some of the important ever changing factors such as board flexural rigidity, damping, drop height, and drop orientation results in non-uniform stress/strain distribution throughout the test board. In addition, one of the most challenging tasks is to quantify uniform stress and strain distribution throughout the test board and identify critical failure factors. The major contributions of this work are in the four aspects of the drop test in electronics as following. First of all, an analytical FEA model was developed to study the board natural frequencies and responses of the system with the consideration of dynamic stiffness, damping behavior of the material and effect of impact loading condition. An approach to find the key parameters that affect stress and strain distributions under predominate mode responses was proposed and verified with theoretical solutions. Input-G method was adopted to study board response behavior and cut boundary interpolation methods was used to analyze local model solder joint stresses with the development of global/local FEA model in ANSYS software. Second, no ring phenomenon during the drop test was identified theoretically when the test board was modeled as both discrete system and continuous system. Numerical analysis was then conducted by FEA method for detailed geometry of attached chips with solder-joints. No ring test conditions was proposed and verified for the current widely used JEDEC standard. The significance of impact loading parameters such as pulse magnitude, pulse duration, pulse shapes and board dynamic parameter such as linear hysteretic damping and dynamic stiffness were discussed. Third, Kirchhoff's plate theory by principle of minimum potential energy was adopted to develop the FEA formulation to consider the effect of material hysteretic damping for the currently used JEDEC board test and proposed no-ring response test condition. Fourth, a hexagonal symmetrical board model was proposed to address the uniform stress and strain distribution throughout the test board and identify the critical failure factors. Dynamic stress and strain of the hexagonal board model were then compared with standard JEDEC board for both standard and proposed no-ring test conditions. In general, this line of research demonstrates that advanced techniques of FEA analysis can provide useful insights concerning the optimal design of drop test in microelectronics.

Measurement of interfacial tension by use of pendant drop video techniques

NASA Astrophysics Data System (ADS)

Herd, Melvin D.; Thomas, Charles P.; Bala, Gregory A.; Lassahn, Gordon D.

1993-09-01

This report describes an instrument to measure the interfacial tension (IFT) of aqueous surfactant solutions and crude oil. The method involves injection of a drop of fluid (such as crude oil) into a second immiscible phase to determine the IFT between the two phases. The instrument is composed of an AT-class computer, optical cell, illumination, video camera and lens, video frame digitizer board, monitor, and software. The camera displays an image of the pendant drop on the monitor, which is then processed by the frame digitizer board and non-proprietary software to determine the IFT. Several binary and ternary phase systems were taken from the literature and used to measure the precision and accuracy of the instrument in determining IFT's. A copy of the software program is included in the report. A copy of the program on diskette can be obtained from the Energy Science and Technology Software Center, P.O. Box 1020, Oak Ridge, TN 37831-1020. The accuracy and precision of the technique and apparatus presented is very good for measurement of IFT's in the range from 72 to 10(exp -2) mN/m, which is adequate for many EOR applications. With modifications to the equipment and the numerical techniques, measurements of ultralow IFT's (less than 10(exp -3) mN/m) should be possible as well as measurements at reservoir temperature and pressure conditions. The instrument has been used at the Idaho National Engineering Laboratory to support the research program on microbial enhanced oil recovery. Measurements of IFT's for several bacterial supernatants and unfractionated acid precipitates of microbial cultures containing biosurfactants against medium to heavy crude oils are reported. These experiments demonstrate that the use of automated video imaging of pendant drops is a simple and fast method to reliably determine interfacial tension between two immiscible liquid phases, or between a gas and a liquid phase.

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.

Contact angle and surface tension measurements of a five-ring polyphenyl ether

NASA Technical Reports Server (NTRS)

Jones, W. R., Jr.

1986-01-01

Contact angle measurements were performed for a five-ring polyphenyl ether isomeric mixture on M-50 steel in a dry nitrogen atmosphere. Two different techniques were used: (1) a tilting plate apparatus, and (2) a sessile drop apparatus. Measurements were made for the temperature range 25 to 190 C. Surface tension was measured by a differential maximum bubble pressure technique over the range 23 to 220 C in room air. The critical surface energy of spreading (gamma /sub c/) was determined for the polyphenyl ether by plotting the cosine of the contact angle (theta) versus the surface tension (gamma /sub LV/). The straight line intercept at cosine theta = 1 is defined as gamma (sub c). Gamma (sub c) was found to be 30.1 dyn/cm for the tilting plate technique and 31.3 dyn/cm for the sessile drop technique. These results indicate that the polyphenyl ether is inherently autophobic (i.e., it will not spread on its own surface film until its surface tension is less than gamma /sub c/). This phenomenon is discussed in light of the wettability and wear problems encountered with this fluid.

Contact angle and surface tension measurements of a five-ring polyphenyl ether

NASA Technical Reports Server (NTRS)

Jones, W. R., Jr.

1985-01-01

Contact angle measurements were performed for a five-ring polyphenyl ether isomeric mixture on M-50 steel in a dry nitrogen atmosphere. Two different techniques were used: (1) a tilting plate apparatus, and (2) a sessile drop apparatus. Measurements were made for the temperature range 25 to 190 C. Surface tension was measured by a differential maximum bubble pressure technique over the range 23 to 220C in room air. The critical surface energy of spreading (gamma (sub c)) was determined for the polyphenyl ether by plotting the cosine of the contact angle (theta) versus the surface tension (gamma (sub LV)). The straight line intercept at cosine theta = 1 is defined as gamma (sub c). Gamma (sub c) was found to be 30.1 dyn/cm for the tilting plate technique and 31.3 dyn/cm for the sessile drop technique. These results indicate that the polyphenyl ether is inherently autophobic (i.e., it will not spread on its own surface film until its surface tension is less than gamma (sub c). This phenomenon is discussed in light of the wettability and wear problems encountered with this fluid.

On the relation of earthquake stress drop and ground motion variability

NASA Astrophysics Data System (ADS)

Oth, Adrien; Miyake, Hiroe; Bindi, Dino

2017-07-01

One of the key parameters for earthquake source physics is stress drop since it can be directly linked to the spectral level of ground motion. Stress drop estimates from moment corner frequency analysis have been shown to be extremely variable, and this to a much larger degree than expected from the between-event ground motion variability. This discrepancy raises the question whether classically determined stress drop variability is too large, which would have significant consequences for seismic hazard analysis. We use a large high-quality data set from Japan with well-studied stress drop data to address this issue. Nonparametric and parametric reference ground motion models are derived, and the relation of between-event residuals for Japan Meteorological Agency equivalent seismic intensity and peak ground acceleration with stress drop is analyzed for crustal earthquakes. We find a clear correlation of the between-event residuals with stress drops estimates; however, while the island of Kyushu is characterized by substantially larger stress drops than Honshu, the between-event residuals do not reflect this observation, leading to the appearance of two event families with different stress drop levels yet similar range of between-event residuals. Both the within-family and between-family stress drop variations are larger than expected from the ground motion between-event variability. A systematic common analysis of these parameters holds the potential to provide important constraints on the relative robustness of different groups of data in the different parameter spaces and to improve our understanding on how much of the observed source parameter variability is likely to be true source physics variability.

Membrane Bioprobe Electrodes

ERIC Educational Resources Information Center

Rechnitz, Garry A.

1975-01-01

Describes the design of ion selective electrodes coupled with immobilized enzymes which operate either continuously or on drop-sized samples. Cites techniques for urea, L-phenylalanine and amygdalin. Micro size electrodes for use in single cells are discussed. (GH)

Experimental Techniques for Thermodynamic Measurements of Ceramics

NASA Technical Reports Server (NTRS)

Jacobson, Nathan S.; Putnam, Robert L.; Navrotsky, Alexandra

1999-01-01

Experimental techniques for thermodynamic measurements on ceramic materials are reviewed. For total molar quantities, calorimetry is used. Total enthalpies are determined with combustion calorimetry or solution calorimetry. Heat capacities and entropies are determined with drop calorimetry, differential thermal methods, and adiabatic calorimetry . Three major techniques for determining partial molar quantities are discussed. These are gas equilibration techniques, Knudsen cell methods, and electrochemical techniques. Throughout this report, issues unique to ceramics are emphasized. Ceramic materials encompass a wide range of stabilities and this must be considered. In general data at high temperatures is required and the need for inert container materials presents a particular challenge.

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.

Nectar and pollination drops: how different are they?

PubMed Central

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

2009-01-01

Background 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). Scope 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). Conclusions 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. PMID:19477895

Direct detection of cancer biomarkers in blood using a "place n play" modular polydimethylsiloxane pump.

PubMed

Zhang, Honglian; Li, Gang; Liao, Lingying; Mao, Hongju; Jin, Qinghui; Zhao, Jianlong

2013-01-01

Cancer biomarkers have significant potential as reliable tools for the early detection of the disease and for monitoring its recurrence. However, most current methods for biomarker detection have technical difficulties (such as sample preparation and specific detector requirements) which limit their application in point of care diagnostics. We developed an extremely simple, power-free microfluidic system for direct detection of cancer biomarkers in microliter volumes of whole blood. CEA and CYFRA21-1 were chosen as model cancer biomarkers. The system automatically extracted blood plasma from less than 3 μl of whole blood and performed a multiplex sample-to-answer assay (nano-ELISA (enzyme-linked immunosorbent assay) technique) without the use of external power or extra components. By taking advantage of the nano-ELISA technique, this microfluidic system detected CEA at a concentration of 50 pg/ml and CYFRA21-1 at a concentration of 60 pg/ml within 60 min. The combination of PnP polydimethylsiloxane (PDMS) pump and nano-ELISA technique in a single microchip system shows great promise for the detection of cancer biomarkers in a drop of blood.

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…

The effect of body position on the 'hanging drop' method for identifying the extradural space in anaesthetized dogs.

PubMed

Naganobu, Kiyokazu; Hagio, Mitsuyoshi

2007-01-01

To assess the accuracy of the 'hanging drop method' for identifying the extradural space in anaesthetized dogs positioned in sternal or lateral recumbency. Prospective randomized-experimental study. Seventeen clinically healthy adult dogs, 10 females and seven males weighing 8.4-26.2 kg. Dogs were positioned in either sternal (n = 8) or lateral (n = 9) recumbency under general anaesthesia. A 20 SWG spinal needle pre-filled with 0.9% saline was advanced through the skin into the lumbosacral extradural space and the response of the saline drop recorded, i.e. whether it: 1) was aspirated from the hub into the needle; 2) remained within the hub, or 3) moved synchronously with i) spontaneous respiration, ii) heart beat or iii) manual lung inflation. The position of the needle tip was ultimately determined by positive contrast radiography. One dog positioned in lateral recumbency was excluded from the study because bleeding occurred from the needle hub. Saline was aspirated into the needle in seven of eight dogs held in sternal recumbency but in none of the dogs positioned in lateral recumbency. Accurate needle tip placement in the extradural space was confirmed by positive contrast radiography in all dogs. The 'hanging drop' method, when performed with a spinal needle, appears to be a useful technique for identifying the location of the extradural space in anaesthetized medium-sized dogs positioned in sternal, but not in lateral recumbency. The technique may yield 'false negative' results when performed in dogs positioned in sternal recumbency.

Virtual prototyping of drop test using explicit analysis

NASA Astrophysics Data System (ADS)

Todorov, Georgi; Kamberov, Konstantin

2017-12-01

Increased requirements for reliability and safety, included in contemporary standards and norms, has high impact over new product development. New numerical techniques based on virtual prototyping technology, facilitates imrpoving product development cycle, resutling in reduced time/money spent for this stage as well as increased knowledge about certain failure mechanism. So called "drop test" became nearly a "must" step in development of any human operated product. This study aims to demonstrate dynamic behaviour assessment of a structure under impact loads, based on virtual prototyping using a typical nonlinear analysis - explicit dynamics. An example is presneted, based on a plastic container that is used as cartridge for a dispenser machine exposed to various work conditions. Different drop orientations were analyzed and critical load cases and design weaknesses have been found. Several design modifications have been proposed, based on detailed analyses results review.

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.

A Review of Recruitment, Adherence and Drop-Out Rates in Omega-3 Polyunsaturated Fatty Acid Supplementation Trials in Children and Adolescents.

PubMed

van der Wurff, Inge S M; Meyer, Barbara J; de Groot, Renate H M

2017-05-10

The influence of n -3 long-chain polyunsaturated fatty acids ( n -3 LCPUFA) supplementation on health outcomes has been studied extensively with randomized controlled trials (RCT). In many research fields, difficulties with recruitment, adherence and high drop-out rates have been reported. However, what is unknown is how common these problems are in n -3 LCPUFA supplementation studies in children and adolescents. Therefore, this paper will review n -3 LCPUFA supplementation studies in children and adolescents with regard to recruitment, adherence and drop-out rates. The Web of Science, PubMed and Ovid databases were searched for papers reporting on RCT supplementing children and adolescents (2-18 years) with a form of n -3 LCPUFA (or placebo) for at least four weeks. As a proxy for abiding to CONSORT guidelines, we noted whether manuscripts provided a flow-chart and provided dates defining the period of recruitment and follow-up. Ninety manuscripts (reporting on 75 studies) met the inclusion criteria. The majority of the studies did not abide by the CONSORT guidelines: 55% did not provide a flow-chart, while 70% did not provide dates. The majority of studies provided minimal details about the recruitment process. Only 25 of the 75 studies reported an adherence rate which was on average 85%. Sixty-five of the 75 studies included drop-out rates which were on average 17%. Less than half of the included studies abided by the CONSORT guidelines (45% included a flow chart, while 30% reported dates). Problems with recruitment and drop-out seem to be common in n -3 LCPUFA supplementation trials in children and adolescents. However, reporting about recruitment, adherence and dropout rates was very heterogeneous and minimal in the included studies. Some techniques to improve recruitment, adherence and dropout rates were identified from the literature, however these techniques may need to be tailored to n -3 LCPUFA supplementation studies in children and adolescents.

Ordered alternating binary polymer nanodroplet array by sequential spin dewetting.

PubMed

Bhandaru, Nandini; Das, Anuja; Salunke, Namrata; Mukherjee, Rabibrata

2014-12-10

We report a facile technique for fabricating an ordered array of nearly equal-sized mesoscale polymer droplets of two constituent polymers (polystyrene, PS and poly(methyl methacrylate), PMMA) arranged in an alternating manner on a topographically patterned substrate. The self-organized array of binary polymers is realized by sequential spin dewetting. First, a dilute solution of PMMA is spin-dewetted on a patterned substrate, resulting in an array of isolated PMMA droplets arranged along the substrate grooves due to self-organization during spin coating itself. The sample is then silanized with octadecyltrichlorosilane (OTS), and subsequently, a dilute solution of PS is spin-coated on to it, which also undergoes spin dewetting. The spin-dewetted PS drops having a size nearly equal to the pre-existing PMMA droplets position themselves between two adjacent PMMA drops under appropriate conditions, forming an alternating binary polymer droplet array. The alternating array formation takes place for a narrow range of solution concentration for both the polymers and depends on the geometry of the substrate. The size of the droplets depends on the extent of confinement, and droplets as small as 100 nm can be obtained by this method, on a suitable template. The findings open up the possibility of creating novel surfaces having ordered multimaterial domains with a potential multifunctional capability.

Visualization of hydraulic conditions inside the feed channel of Reverse Osmosis: A practical comparison of velocity between empty and spacer-filled channel.

PubMed

Haidari, A H; Heijman, S G J; van der Meer, W G J

2016-12-01

It is widely accepted that our understanding about the membrane process increases by investigation of the hydraulic conditions of membranes. While numerical studies have been broadly used for this purpose, the experimental studies of a comparable resolution are scarce. In this study, we compared the pressure drop, the temporal and the spatial velocity maps of a spacer-filled channel and an empty channel of the same size to determine the effect of presence of the feeds spacer on hydraulic conditions. The velocity maps are obtained experimentally by using of the Particle Image Velocimetry (PIV) technique. Application of the feed spacer caused 2-8.5 higher pressure drop increase in the experimental conditions in this research. The flow had a spatial distribution in the form of a unimodal symmetric curve of normal distribution in the empty channel and a bimodal asymmetric curve in the spacer-filled channel. The bimodal curve indicates the presence of high- and low-velocity zones. Additionally, the low-velocity zones showed also a lower variation of velocity in time, which indicates the high fouling potential of these locations. The results from this study may be uses for validation of numerical studies. Copyright © 2016 Elsevier Ltd. All rights reserved.

Characterization and detection of acceleration-induced cavitation in soft materials using a drop-tower-based integrated system

NASA Astrophysics Data System (ADS)

Kang, Wonmo; Chen, YungChia; Bagchi, Amit; O'Shaughnessy, Thomas J.

2017-12-01

The material response of biologically relevant soft materials, e.g., extracellular matrix or cell cytoplasm, at high rate loading conditions is becoming increasingly important for emerging medical implications including the potential of cavitation-induced brain injury or cavitation created by medical devices, whether intentional or not. However, accurately probing soft samples remains challenging due to their delicate nature, which often excludes the use of conventional techniques requiring direct contact with a sample-loading frame. We present a drop-tower-based method, integrated with a unique sample holder and a series of effective springs and dampers, for testing soft samples with an emphasis on high-rate loading conditions. Our theoretical studies on the transient dynamics of the system show that well-controlled impacts between a movable mass and sample holder can be used as a means to rapidly load soft samples. For demonstrating the integrated system, we experimentally quantify the critical acceleration that corresponds to the onset of cavitation nucleation for pure water and 7.5% gelatin samples. This study reveals that 7.5% gelatin has a significantly higher, approximately double, critical acceleration as compared to pure water. Finally, we have also demonstrated a non-optical method of detecting cavitation in soft materials by correlating cavitation collapse with structural resonance of the sample container.

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.

Preparation and In Vitro/Ex Vivo Evaluation of Moxifloxacin-Loaded PLGA Nanosuspensions for Ophthalmic Application.

PubMed

Mudgil, Meetali; Pawar, Pravin K

2013-01-01

The aim of the present investigation was to prepare a colloidal ophthalmic formulation to improve the residence time of moxifloxacin. Moxifloxacin-loaded poly(dl-lactide-co-glycolide) (PLGA) nanosuspensions were prepared by using the solvent evaporation technique. The nanosuspensions were characterised physically by using different techniques like particle size, zeta potential, FTIR, DSC, and XRD analysis. In vitro and ex vivo studies of nanosuspensions were carried out using a modified USP dissolution apparatus and all-glass Franz diffusion cells, respectively. The antibacterial activities of the nanosuspension and marketed formulations were performed against S. aureus and P. aeroginosa. The moxifloxacin-loaded PLGA nanosuspensions showed uniform particle size, ranging between 164-490 nm with negative zeta potential for all batches. The percentage entrapment efficiency of the drug-loaded nano-suspension was found to be between 84.09 to 92.05%. In vitro drug release studies suggest that all of the formulations showed extended drug release profiles and follow Korsemeyer-Peppas release kinetics. In vitro corneal permeability was found to be comparable with that of the marketed formulation across isolated goat cornea, indicating the suitability of the nanosuspension formulation in the ophthalmic delivery of moxifloxacin. The optimised nano-suspension was found to be more active against S. aureus and P. aeruginosa compared to the marketed eye drops.

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.

Crystallization and preliminary crystallographic studies of the Pasteurella multocida toxin catalytic domain

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

Miyazawa, Masayuki; Kitadokoro, Kengo; Kamitani, Shigeki

2006-09-01

The C-terminal catalytic domain of P. multocida toxin, which is the virulence factor of the organism in P. multocida, has been expressed, purified and subsequently crystallized using the sitting-drop vapour-diffusion technique. The C-terminal catalytic domain of Pasteurella multocida toxin, which is the virulence factor of the organism in P. multocida, has been expressed, purified and subsequently crystallized using the sitting-drop vapour-diffusion technique. Native diffraction data to 1.9 Å resolution were obtained at the BL44XU beamline of SPring-8 from a flash-frozen crystal at 100 K. The crystals belong to space group C2, with unit-cell parameters a = 111.0, b = 150.4,more » c = 77.1 Å, β = 105.5°, and are likely to contain one C-PMT (726 residues) per asymmetric unit.« less

OpenDrop: An Integrated Do-It-Yourself Platform for Personal Use of Biochips

PubMed Central

Alistar, Mirela; Gaudenz, Urs

2017-01-01

Biochips, or digital labs-on-chip, are developed with the purpose of being used by laboratory technicians or biologists in laboratories or clinics. In this article, we expand this vision with the goal of enabling everyone, regardless of their expertise, to use biochips for their own personal purposes. We developed OpenDrop, an integrated electromicrofluidic platform that allows users to develop and program their own bio-applications. We address the main challenges that users may encounter: accessibility, bio-protocol design and interaction with microfluidics. OpenDrop consists of a do-it-yourself biochip, an automated software tool with visual interface and a detailed technique for at-home operations of microfluidics. We report on two years of use of OpenDrop, released as an open-source platform. Our platform attracted a highly diverse user base with participants originating from maker communities, academia and industry. Our findings show that 47% of attempts to replicate OpenDrop were successful, the main challenge remaining the assembly of the device. In terms of usability, the users managed to operate their platforms at home and are working on designing their own bio-applications. Our work provides a step towards a future in which everyone will be able to create microfluidic devices for their personal applications, thereby democratizing parts of health care. PMID:28952524

Splash evaluation of SRB designs

NASA Technical Reports Server (NTRS)

Counter, D. N.

1974-01-01

A technique is developed to optimize the shuttle solid rocket booster (SRB) design for water impact loads. The SRB is dropped by parachute and recovered at sea for reuse. Loads experienced at water impact are design critical. The probability of each water impact load is determined using a Monte Carlo technique and an aerodynamic analysis of the SRB parachute system. Meteorological effects are included and four configurations are evaluated.

Experimental and Computational Study of the Hydrodynamics of Trickle Bed Flow Reactor Operating Under Different Pressure Conditions

NASA Astrophysics Data System (ADS)

Rabbani, S.; Ben Salem, I.; Nadeem, H.; Kurnia, J. C.; Shamim, T.; Sassi, M.

2014-12-01

Pressure drop estimation and prediction of liquid holdup play a crucial role in design and operation of trickle bed reactors. Experiments are performed for Light Gas Oil (LGO)-nitrogen system in ambient temperature conditions in an industrial pilot plant with reactor height 0.79 m and diameter of 0.0183 m and pressure ranging from atmospheric to 10 bars. It was found that pressure drop increased with increase in system pressure, superficial gas velocity and superficial liquid velocity. It was demonstrated in the experiments that liquid holdup of the system increases with the increase in superficial liquid velocity and tends to decrease with increase in superficial gas velocity which is in good agreement with existing literature. Similar conditions were also simulated using CFD-software FLUENT. The Volume of Fluid (VoF) technique was employed in combination with "discrete particle approach" and results were compared with that of experiments. The overall pressure drop results were compared with the different available models and a new comprehensive model was proposed to predict the pressure drop in Trickle Bed Flow Reactor.

Comparative analysis of tumor spheroid generation techniques for differential in vitro drug toxicity

PubMed Central

Raghavan, Shreya; Rowley, Katelyn R.; Mehta, Geeta

2016-01-01

Multicellular tumor spheroids are powerful in vitro models to perform preclinical chemosensitivity assays. We compare different methodologies to generate tumor spheroids in terms of resultant spheroid morphology, cellular arrangement and chemosensitivity. We used two cancer cell lines (MCF7 and OVCAR8) to generate spheroids using i) hanging drop array plates; ii) liquid overlay on ultra-low attachment plates; iii) liquid overlay on ultra-low attachment plates with rotating mixing (nutator plates). Analysis of spheroid morphometry indicated that cellular compaction was increased in spheroids generated on nutator and hanging drop array plates. Collagen staining also indicated higher compaction and remodeling in tumor spheroids on nutator and hanging drop arrays compared to conventional liquid overlay. Consequently, spheroids generated on nutator or hanging drop plates had increased chemoresistance to cisplatin treatment (20-60% viability) compared to spheroids on ultra low attachment plates (10-20% viability). Lastly, we used a mathematical model to demonstrate minimal changes in oxygen and cisplatin diffusion within experimentally generated spheroids. Our results demonstrate that in vitro methods of tumor spheroid generation result in varied cellular arrangement and chemosensitivity. PMID:26918944

The field experiments on the HTO washout from the atmosphere

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

Golubev, A.V.; Mavrin, S.V.; Golubeva, V.N.

2015-03-15

HTO (tritiated water) wash-out from the atmosphere is one of the key processes governing the HTO transport from the atmosphere into soil and plants. Experimental studies of the HTO interaction with water drops were carried out both in laboratories and in the field. In the course of experiments, the following rain characteristics were recorded: rain intensity, size distribution of drops, and falling velocities and their dependence on drop diameter. A laser optical device was designed and used to measure the distribution of the drop radius and velocities during the period of experiment. The tritium source was placed at a heightmore » of 30 m. Rainwater samples were collected in plastic bottles and their HTO activity was determined by liquid scintillation techniques. The data obtained for the experimental values of the scavenging rate are within the range from 4.12*10{sup -5} to 1.57*10{sup -4} s{sup -1} and correspond to the precipitation intensity from 0.3 to 1.26 mm/hour. These results are in sufficiently good agreement with the results of earlier papers.« less

Optimizing the use of a skin prick test device on children.

PubMed

Buyuktiryaki, Betul; Sahiner, Umit Murat; Karabulut, Erdem; Cavkaytar, Ozlem; Tuncer, Ayfer; Sekerel, Bulent Enis

2013-01-01

Studies comparing skin prick test (SPT) devices have revealed varying results in performance and there is little known about their use on children. We performed 2 complementary studies to test the sensitivity, reproducibility and acceptability of commercially available SPT devices (Stallerpoint, Antony, France) using different application techniques. In the first part, histamine/saline was put on as a drop by use of a vial (V), and in the second part it was transferred from a well with the aid of the test device (W). The techniques were as follows: apply vertical pressure (Stallerpoint-VP or Stallerpoint-WP), apply vertical pressure with 90° clockwise rotation (Stallerpoint-VC or Stallerpoint-WC) and apply vertical pressure with 90° clockwise and counter-clockwise rotations (Stallerpoint-VCC or Stallerpoint-WCC). For comparison, ALK Lancet was used with a technique of 'drop and apply vertical pressure'. In the first part, sensitivities of the Stallerpoint-VC (96.6%), Stallerpoint-VCC (95.5%) and ALK Lancet (93.2%) techniques were superior (p < 0.001) to the other Stallerpoint-VP and Stallerpoint-WP techniques (76.1 and 46.6%). Intrapatient coefficient of variation (CV) values were 15.0, 18.9, 15.4, 22.4 and 48.5%, respectively. Interpatient CV ranged between 22.8 and 55.1%. In the second part, the Stallerpoint-WC (98.8%), WCC (97.5%) and ALK Lancet (98.8%) techniques yielded high sensitivities, whereas the sensitivity of Stallerpoint-WP (28.7%) was very low. There were false-positive reactions in the Stallerpoint-VCC and WCC techniques. In children, the SPT technique was found to be as important as the testing device. Stallerpoint-VC and WC techniques are reliable, tolerable and comparable with the ALK Lancet technique. Copyright © 2013 S. Karger AG, Basel.

Optical Characterization of a Multipoint Lean Direct Injector for Gas Turbine Combustors: Velocity and Fuel Drop Size Measurements

NASA Technical Reports Server (NTRS)

Heath, Christopher M.; Anderson, Robert C.; Locke, Randy J.; Hicks, Yolanda R.

2010-01-01

Performance of a multipoint, lean direct injection (MP-LDI) strategy for low emission aero-propulsion systems has been tested in a Jet-A fueled, lean flame tube combustion rig. Operating conditions for the series of tests included inlet air temperatures between 672 and 828 K, pressures between 1034 and 1379 kPa and total equivalence ratios between 0.41 and 0.45, resulting in equilibrium flame temperatures approaching 1800 K. Ranges of operation were selected to represent the spectrum of subsonic and supersonic flight conditions projected for the next-generation of commercial aircraft. This document reports laser-based measurements of in situ fuel velocities and fuel drop sizes for the NASA 9-point LDI hardware arranged in a 3 3 square grid configuration. Data obtained represent a region of the flame tube combustor with optical access that extends 38.1-mm downstream of the fuel injection site. All data were obtained within reacting flows, without particle seeding. Two diagnostic methods were employed to evaluate the resulting flow path. Three-component velocity fields have been captured using phase Doppler interferometry (PDI), and two-component velocity distributions using planar particle image velocimetry (PIV). Data from these techniques have also offered insight into fuel drop size and distribution, fuel injector spray angle and pattern, turbulence intensity, degree of vaporization and extent of reaction. This research serves to characterize operation of the baseline NASA 9- point LDI strategy for potential use in future gas-turbine combustor applications. An additional motive is the compilation of a comprehensive database to facilitate understanding of combustor fuel injector aerodynamics and fuel vaporization processes, which in turn may be used to validate computational fluid dynamics codes, such as the National Combustor Code (NCC), among others.

Comparison of immunodiffusion and enzyme linked immunosorbent assay in the detection of abnormal antibodies in pigeon breeder's disease.

PubMed Central

Simpson, C.; Shirodaria, P. V.; Evans, J. P.; Simpson, D. I.; Stanford, C. F.

1992-01-01

AIMS: To compare the sensitivity of two methods for the detection of serum antibodies to pigeon faecal antigens in patients with pigeon breeder's disease. METHODS: Serum samples stored at -20 degrees C from 50 patients with pigeon breeder's disease, 50 control samples from patients with other respiratory diseases, and 50 healthy blood donors were examined for the precipitating antibodies and IgG antibodies to antigens present in extract of pigeon droppings by immunodiffusion and enzyme linked immunosorbent assay (ELISA), respectively. RESULTS: Both antigen preparations of pigeon dropping extract were equally effective. A positive immunodiffusion reaction gave one or more precipitin lines and these antibodies were detected only in undiluted sera from 80% of the patients with pigeon breeder's disease. In the ELISA the sera were tested at a starting dilution of 1 in 100 because positive reactions were observed with sera from healthy blood donors at lower dilutions. All sera which gave optical density readings above 3 SD of the control value were considered to have IgG antibodies. These antibodies were detected in sera from all the patients with pigeon breeder's disease. The antibody titres were much higher in those patients who had precipitating antibodies (range 800-51,200) than those without (range 100-800). The antibodies were not detected in the sera of patients with respiratory diseases or healthy blood donors by either method. CONCLUSIONS: Antibodies to pigeon dropping antigens were detected by immunodiffusion and ELISA in sera from patients with pigeon breeder's disease but not in control sera. ELISA was a more sensitive method for detecting antibodies and therefore seems to have considerable potential as a routine technique in the serological diagnosis of pigeon breeder's disease. PMID:1624596

Using high frequency consumption data to identify demand response potential for solar energy integration

NASA Astrophysics Data System (ADS)

Jin, L.; Borgeson, S.; Fredman, D.; Hans, L.; Spurlock, A.; Todd, A.

2015-12-01

California's renewable portfolio standard (2012) requires the state to get 33% of its electricity from renewable sources by 2020. Increased share of variable renewable sources such as solar and wind in the California electricity system may require more grid flexibility to insure reliable power services. Such grid flexibility can be potentially provided by changes in end use electricity consumptions in response to grid conditions (demand-response). In the solar case, residential consumption in the late afternoon can be used as reserve capacity to balance the drop in solar generation. This study presents our initial attempt to identify, from a behavior perspective, residential demand response potentials in relation to solar ramp events using a data-driven approach. Based on hourly residential energy consumption data, we derive representative daily load shapes focusing on discretionary consumption with an innovative clustering analysis technique. We aggregate the representative load shapes into behavior groups in terms of the timing and rhythm of energy use in the context of solar ramp events. Households of different behavior groups that are active during hours with high solar ramp rates are identified for capturing demand response potential. Insights into the nature and predictability of response to demand-response programs are provided.

Stable Rotation of Microparticles using a Combination of Dielectrophoresis and Electroosmosis

NASA Astrophysics Data System (ADS)

Dutta, Prashanta; Rezanoor, Walid

2016-11-01

Electric field induced microparticle rotation has become a powerful technique to evaluate cell membrane dielectric properties and cell morphology. In this study, stable rotations of microparticles are demonstrated in a stationary AC electric field created from a set of coplanar interdigitated microelectrodes. The medium, particle size, and material are carefully chosen so that particle can be controlled by dielectrophoretic force, while a sufficiently high AC electroosmotic flow is produced for continuous particle rotation. Stable rotation up to 218 rpm is observed at 30 Vp-p applied sinusoidal potential in the frequency range of 80 - 1000 Hz. The particle spin rate observed from the experimental study is then validated with a numerical model. The model is formulated around complex charge conservation equation to determine the electric potential distribution in the domain. Stokes equation is employed to solve for AC electroosmotic fluid flow in the domain. Complexity arising from nonlinear potential drop across the electric double layer due to the application of a very large electric potential is also addressed by introducing modified capacitance equation which considers steric effect. This work was supported in part by the U.S. National Science Foundation under Grant No. DMS 1317671.

Microfluidic techniques for the study of self-assembly of soft materials

NASA Astrophysics Data System (ADS)

Aguade Cabanas, Rafael

This research is an approach to the study of soft condensed matter where the use of new microfluidic technology plays a central role. Often, in the study of soft matter, the sample volumes are very small, of the order of nanoliters. Therefore to quantitatively measure the equilibrium or non-equilibrium phase behavior requires microfluidics. Presented here are (1) a new way of producing aqueous drops of order 1 nl volume, in oil, (2) a new fabrication protocol to make microfluidic devices out of epoxy glue, and (3) a new microfluidic flow cell to study colloidal self-assembly. Also presented here is a new kind of colloidal particle, consisting of single strands of DNA linked to the surface of fd virus. This new particle may serve as a liquid crystalline colloid with a temperature dependent tunable potential. The fabrication process is the first step in the study of the self-assembly of rod-like particles with a temperature dependent potential.

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.

Atomic Gravitational Wave Interferometric Sensors (AGIS) in Space

NASA Astrophysics Data System (ADS)

Sugarbaker, Alex; Hogan, Jason; Johnson, David; Dickerson, Susannah; Kovachy, Tim; Chiow, Sheng-Wey; Kasevich, Mark

2012-06-01

Atom interferometers have the potential to make sensitive gravitational wave detectors, which would reinforce our fundamental understanding of gravity and provide a new means of observing the universe. We focus here on the AGIS-LEO proposal [1]. Gravitational waves can be observed by comparing a pair of atom interferometers separated over an extended baseline. The mission would offer a strain sensitivity that would provide access to a rich scientific region with substantial discovery potential. This band is not currently addressed with the LIGO or LISA instruments. We analyze systematic backgrounds that are relevant to the mission and discuss how they can be mitigated at the required levels. Some of these effects do not appear to have been considered previously in the context of atom interferometry, and we therefore expect that our analysis will be broadly relevant to atom interferometric precision measurements. Many of the techniques relevant to an AGIS mission can be investigated in the Stanford 10-m drop tower.[4pt] [1] J.M. Hogan, et al., Gen. Rel. Grav. 43, 1953-2009 (2011).

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.

Swimming using surface acoustic waves.

PubMed

Bourquin, Yannyk; Cooper, Jonathan M

2013-01-01

Microactuation of free standing objects in fluids is currently dominated by the rotary propeller, giving rise to a range of potential applications in the military, aeronautic and biomedical fields. Previously, surface acoustic waves (SAWs) have been shown to be of increasing interest in the field of microfluidics, where the refraction of a SAW into a drop of fluid creates a convective flow, a phenomenon generally known as SAW streaming. We now show how SAWs, generated at microelectronic devices, can be used as an efficient method of propulsion actuated by localised fluid streaming. The direction of the force arising from such streaming is optimal when the devices are maintained at the Rayleigh angle. The technique provides propulsion without any moving parts, and, due to the inherent design of the SAW transducer, enables simple control of the direction of travel.

The current role of on-line extraction approaches in clinical and forensic toxicology.

PubMed

Mueller, Daniel M

2014-08-01

In today's clinical and forensic toxicological laboratories, automation is of interest because of its ability to optimize processes, to reduce manual workload and handling errors and to minimize exposition to potentially infectious samples. Extraction is usually the most time-consuming step; therefore, automation of this step is reasonable. Currently, from the field of clinical and forensic toxicology, methods using the following on-line extraction techniques have been published: on-line solid-phase extraction, turbulent flow chromatography, solid-phase microextraction, microextraction by packed sorbent, single-drop microextraction and on-line desorption of dried blood spots. Most of these published methods are either single-analyte or multicomponent procedures; methods intended for systematic toxicological analysis are relatively scarce. However, the use of on-line extraction will certainly increase in the near future.

Automated Droplet Manipulation Using Closed-Loop Axisymmetric Drop Shape Analysis.

PubMed

Yu, Kyle; Yang, Jinlong; Zuo, Yi Y

2016-05-17

Droplet manipulation plays an important role in a wide range of scientific and industrial applications, such as synthesis of thin-film materials, control of interfacial reactions, and operation of digital microfluidics. Compared to micron-sized droplets, which are commonly considered as spherical beads, millimeter-sized droplets are generally deformable by gravity, thus introducing nonlinearity into control of droplet properties. Such a nonlinear drop shape effect is especially crucial for droplet manipulation, even for small droplets, at the presence of surfactants. In this paper, we have developed a novel closed-loop axisymmetric drop shape analysis (ADSA), integrated into a constrained drop surfactometer (CDS), for manipulating millimeter-sized droplets. The closed-loop ADSA generalizes applications of the traditional drop shape analysis from a surface tension measurement methodology to a sophisticated tool for manipulating droplets in real time. We have demonstrated the feasibility and advantages of the closed-loop ADSA in three applications, including control of drop volume by automatically compensating natural evaporation, precise control of surface area variations for high-fidelity biophysical simulations of natural pulmonary surfactant, and steady control of surface pressure for in situ Langmuir-Blodgett transfer from droplets. All these applications have demonstrated the accuracy, versatility, applicability, and automation of this new ADSA-based droplet manipulation technique. Combining with CDS, the closed-loop ADSA holds great promise for advancing droplet manipulation in a variety of material and surface science applications, such as thin-film fabrication, self-assembly, and biophysical study of pulmonary surfactant.

Spreading dynamics of superposed liquid drops on a spinning disk

NASA Astrophysics Data System (ADS)

Sahoo, Subhadarshinee; Orpe, Ashish V.; Doshi, Pankaj

2018-01-01

We have experimentally studied simultaneous spreading of superposed drops of two Newtonian liquids on top of a horizontal spinning disk using the flow visualization technique. An inner drop of high surface tension liquid is placed centrally on the disk followed by a drop of outer liquid (lower surface tension) placed exactly above that. The disk is then rotated at a desired speed for a range of volume ratios of two liquids. Such an arrangement of two superposed liquid drops does not affect the spreading behavior of the outer liquid but influences that of the inner liquid significantly. The drop spreads to a larger extent and breaks into more fingers (Nf) as compared to the case where the same liquid is spreading in the absence of outer liquid. The experimentally observed number of fingers is compared with the prediction using available theory for single liquid. It is found that the theory over-predicts the value of Nf for the inner liquid while it is covered by an outer liquid. We provide a theoretical justification for this observation using linear stability analysis. Our analysis demonstrates that for small but finite surface tension ratio of the two liquids, the presence of the outer interface reduces the value of the most unstable wave number which is equivalent to the decrease in the number of fingers observed experimentally. Finally, sustained rotation of the disk leads to the formation of droplets at the tip of the fingers traveling outwards.

A Novel Virus Causes Scale Drop Disease in Lates calcarifer

PubMed Central

de Groof, Ad; Guelen, Lars; Deijs, Martin; van der Wal, Yorick; Miyata, Masato; Ng, Kah Sing; van Grinsven, Lotte; Simmelink, Bartjan; Biermann, Yvonne; Grisez, Luc; van Lent, Jan; de Ronde, Anthony; Chang, Siow Foong; Schrier, Carla; van der Hoek, Lia

2015-01-01

From 1992 onwards, outbreaks of a previously unknown illness have been reported in Asian seabass (Lates calcarifer) kept in maricultures in Southeast Asia. The most striking symptom of this emerging disease is the loss of scales. It was referred to as scale drop syndrome, but the etiology remained enigmatic. By using a next-generation virus discovery technique, VIDISCA-454, sequences of an unknown virus were detected in serum of diseased fish. The near complete genome sequence of the virus was determined, which shows a unique genome organization, and low levels of identity to known members of the Iridoviridae. Based on homology of a series of putatively encoded proteins, the virus is a novel member of the Megalocytivirus genus of the Iridoviridae family. The virus was isolated and propagated in cell culture, where it caused a cytopathogenic effect in infected Asian seabass kidney and brain cells. Electron microscopy revealed icosahedral virions of about 140 nm, characteristic for the Iridoviridae. In vitro cultured virus induced scale drop syndrome in Asian seabass in vivo and the virus could be reisolated from these infected fish. These findings show that the virus is the causative agent for the scale drop syndrome, as each of Koch’s postulates is fulfilled. We have named the virus Scale Drop Disease Virus. Vaccines prepared from BEI- and formalin inactivated virus, as well as from E. coli produced major capsid protein provide efficacious protection against scale drop disease. PMID:26252390

Pulsed arc plasma jet synchronized with drop-on-demand dispenser

NASA Astrophysics Data System (ADS)

Mavier, F.; Lemesre, L.; Rat, V.; Bienia, M.; Lejeune, M.; Coudert, J.-F.

2017-04-01

This work concerns with the liquid injection in arc plasma spraying for the development of finely structured ceramics coatings. Nanostructured coatings can be now achieved with nanopowders dispersed in a liquid (SPS: Suspension Plasma Spraying) or with a salt dissolved into a liquid (SPPS: Solution Precursor Plasma Spraying) injected into the plasma jet. Controlling electric arc instabilities confined in non-transferred arc plasma torch is therefore a key issue to get reproducible coating properties. Adjustment of parameters with a mono-cathode arc plasma allows a new resonance mode called “Mosquito”. A pulsed arc plasma producing a periodic regular voltage signal with modulation of enthalpy is obtained. The basic idea is to synchronize the injection system with the arc to introduce the liquid material in each plasma oscillation in the same conditions, in order to control the plasma treatment of the material in-fly. A custom-developed pulsed arc plasma torch is used with a drop-on-demand dispenser triggered by the arc voltage. A delay is added to adjust the droplets emission time and their penetration into the plasma gusts. Indeed, the treatment of droplets is also shown to be dependent on this injection delay. A TiO2 suspension and an aqueous solution of aluminium nitrate were optimized to get ejectable inks forming individual droplets. The feasibility of the process was demonstrated for SPS and SPPS techniques. Coatings from the suspension and the solution were achieved. First synchronized sprayings show a good penetration of the droplets into the plasma. Coatings show a fine structure of cauliflowers shapes. The synchronization of the ejection allows a control of morphology and a better deposition efficiency. Further investigations will find the optimal operating parameters to show the full potential of this original liquid injection technique.

Metallic nanoparticle deposition techniques for enhanced organic photovoltaic cells

NASA Astrophysics Data System (ADS)

Cacha, Brian Joseph Gonda

Energy generation via organic photovoltaic (OPV) cells provide many advantages over alternative processes including flexibility and price. However, more efficient OPVs are required in order to be competitive for applications. One way to enhance efficiency is through manipulation of exciton mechanisms within the OPV, for example by inserting a thin film of bathocuproine (BCP) and gold nanoparticles between the C60/Al and ZnPc/ITO interfaces, respectively. We find that BCP increases efficiencies by 330% due to gains of open circuit voltage (Voc) by 160% and short circuit current (Jsc) by 130%. However, these gains are complicated by the anomalous photovoltaic effect and an internal chemical potential. Exploration in the tuning of metallic nanoparticle deposition on ITO was done through four techniques. Drop casting Ag nanoparticle solution showed arduous control on deposited morphology. Spin-coating deposited very low densities of nanoparticles. Drop casting and spin-coating methods showed arduous control on Ag nanoparticle morphology due to clustering and low deposition density, respectively. Sputtered gold on glass was initially created to aid the adherence of Ag nanoparticles but instead showed a quick way to deposit aggregated gold nanoparticles. Electrodeposition of gold nanoparticles (AuNP) proved a quick method to tune nanoparticle morphology on ITO substrates. Control of deposition parameters affected AuNP size and distribution. AFM images of electrodeposited AuNPs showed sizes ranging from 39 to 58 nm. UV-Vis spectroscopy showed the presence of localized plasmon resonance through absorption peaks ranging from 503 to 614 nm. A linear correlation between electrodeposited AuNP size and peak absorbance was seen with a slope of 3.26 wavelength(nm)/diameter(nm).

Capabilities and limitations of dispersive liquid-liquid microextraction with solidification of floating organic drop for the extraction of organic pollutants from water samples.

PubMed

Vera-Avila, Luz E; Rojo-Portillo, Tania; Covarrubias-Herrera, Rosario; Peña-Alvarez, Araceli

2013-12-17

Dispersive liquid-liquid microextraction with solidification of floating organic drop (DLLME-SFO) is one of the most interesting sample preparation techniques developed in recent years. Although several applications have been reported, the potentiality and limitations of this simple and rapid extraction technique have not been made sufficiently explicit. In this work, the extraction efficiency of DLLME-SFO for pollutants from different chemical families was determined. Studied compounds include: 10 polycyclic aromatic hydrocarbons, 5 pesticides (chlorophenoxy herbicides and DDT), 8 phenols and 6 sulfonamides, thus, covering a large range of polarity and hydrophobicity (LogKow 0-7, overall). After optimization of extraction conditions using 1-dodecanol as extractant, the procedure was applied for extraction of each family from 10-mL spiked water samples, only adjusting sample pH as required. Absolute recoveries for pollutants with LogKow 3-7 were >70% and recovery values within this group (18 compounds) were independent of structure or hydrophobicity; the precision of recovery was very acceptable (RSD<12%) and linear behavior was observed in the studied concentration range (r(2)>0.995). Extraction recoveries for pollutants with LogKow 1.46-2.8 were in the range 13-62%, directly depending on individual LogKow values; however, good linearity (r(2)>0.993) and precision (RSD<6.5%) were also demonstrated for these polar solutes, despite recovery level. DLLME-SFO with 1-dodecanol completely failed for extraction of compounds with LogKow≤1 (sulfa drugs), other more polar extraction solvents (ionic liquids) should be explored for highly hydrophilic pollutants. Copyright © 2013 Elsevier B.V. All rights reserved.

Nucleation of Quantized Vortices from Rotating Superfluid Drops

NASA Technical Reports Server (NTRS)

Donnelly, Russell J.

2001-01-01

The long-term goal of this project is to study the nucleation of quantized vortices in helium II by investigating the behavior of rotating droplets of helium II in a reduced gravity environment. The objective of this ground-based research grant was to develop new experimental techniques to aid in accomplishing that goal. The development of an electrostatic levitator for superfluid helium, described below, and the successful suspension of charged superfluid drops in modest electric fields was the primary focus of this work. Other key technologies of general low temperature use were developed and are also discussed.

Square wave voltammetry at the dropping mercury electrode: Experimental

USGS Publications Warehouse

Turner, J.A.; Christie, J.H.; Vukovic, M.; Osteryoung, R.A.

1977-01-01

Experimental verification of earlier theoretical work for square wave voltammetry at the dropping mercury electrode is given. Experiments using ferric oxalate and cadmium(II) in HCl confirm excellent agreement with theory. Experimental peak heights and peak widths are found to be within 2% of calculated results. An example of trace analysis using square wave voltammetry at the DME is presented. The technique is shown to have the same order of sensitivity as differential pulse polarography but is much faster to perform. A detection limit for cadmium in 0.1 M HCl for the system used here was 7 ?? 10-8 M.

The use of containerless processing in researching reactive materials

NASA Technical Reports Server (NTRS)

Weber, J. K. R.; Krishnan, Shankar; Nordine, Paul C.

1991-01-01

It has recently become possible to perform containerless, high-temperature liquid-phase processing of many nonvolatile materials without resort to orbital microgravity, thereby facilitating the conduct of materials research in conjunction with noncontact diagnostic instruments. The melt-levitation techniques are electromagnetic, aerodynamic, acoustic, aeroacoustic, and electrostatic; nonorbital microgravity conditions are obtainable aboard NASA's KC-135 aircraft on parabolic flight paths, as well as in drop tubes and towers. Applications encompass the purification of metals and the creation of nonequilibrium and metastable structures. Process control and property measurements include optical pyrometry and emissivity, laser polarimetry, and drop calorimetry.

Genomic characterization of Indian isolates of egg drop syndrome 1976 virus.

PubMed

Raj, G D; Sivakumar, S; Sudharsan, S; Mohan, A C; Nachimuthu, K

2001-02-01

Five Indian isolates of egg drop syndrome (EDS) 1976 virus and the reference strain 127 were compared by restriction enzyme analysis of viral DNA, and the hexon gene amplified by polymerase chain reaction. Using these techniques, no differences were seen among these viruses. However, partial sequencing of the hexon gene revealed major differences (4.6%) in one of the isolates sequenced, EDS Kerala. Phylogenetic analysis also placed this isolate in a different lineage compared with the other isolates. The need for constant monitoring of the genetic nature of the field isolates of EDS viruses is emphasized.

"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.

Enhancing the cyber-security of smart grids with applications to synchrophasor data

NASA Astrophysics Data System (ADS)

Pal, Seemita

In the power grids, Supervisory Control and Data Acquisition (SCADA) systems are used as part of the Energy Management System (EMS) for enabling grid monitoring, control and protection. In recent times, with the ongoing installation of thousands of Phasor Measurement Units (PMUs), system operators are becoming increasingly reliant on PMU-generated synchrophasor measurements for executing wide-area monitoring and real-time control. The availability of PMU data facilitates dynamic state estimation of the system, thus improving the efficiency and resiliency of the grid. Since the SCADA and PMU data are used to make critical control decisions including actuation of physical systems, the timely availability and integrity of this networked data is of paramount importance. Absence or wrong control actions can potentially lead to disruption of operations, monetary loss, damage to equipments or surroundings or even blackout. This has posed new challenges to information security especially in this age of ever-increasing cyber-attacks. In this thesis, potential cyber-attacks on smart grids are presented and effective and implementable schemes are proposed for detecting them. The focus is mainly on three kinds of cyber-attacks and their detection: (i) gray-hole attacks on synchrophasor systems, (ii) PMU data manipulation attacks and (iii) data integrity attacks on SCADA systems. In the case of gray-hole attacks, also known as packet-drop attacks, the adversary may arbitrarily drop PMU data packets as they traverse the network, resulting in unavailability of time-sensitive data for the various critical power system applications. The fundamental challenge is to distinguish packets dropped by the adversary from those that occur naturally due to network congestion.The proposed gray-hole attack detection technique is based on exploiting the inherent timing information in the GPS time-stamped PMU data packets and using the temporal trends of the latencies to classify the cause of packet-drops and finally detect attacks, if any. In the case of PMU data manipulation attacks, the attacker may modify the data in the PMU packets in order to bias the system states and influence the control center into taking wrong decisions. The proposed detection technique is based on evaluating the equivalent impedances of the transmission lines and classifying the observed anomalies to determine the presence of attack and its location. The scheme for detecting data integrity attacks on SCADA systems is based on utilizing synchrophasor measurements from available PMUs in the grid. The proposed method uses a difference measure, developed in this thesis, to determine the relative divergence and mis-correlation between the datasets. Based on the estimated difference measure, tampered and genuine data can be distinguished. The proposed detection mechanisms have demonstrated high accuracy in real-time detection of attacks of various magnitudes, simulated on real PMU data obtained from the NY grid. By performing alarm clustering, the occurrence of false alarms has been reduced to almost zero. The solutions are computationally inexpensive, low on cost, do not add any overhead, and do not require any feedback from the network.

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.

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.

Falling drops skating on a film of air

NASA Astrophysics Data System (ADS)

Rubinstein, Shmuel

2012-02-01

When a raindrop hits a window, the surface immediately becomes wet as the water spreads. Indeed, this common observation of a drop impacting a surface is ubiquitous in our everyday experience. I will show that the impact of a drop on a surface is a much richer, more complex phenomenon than our simple experience may suggests: To completely wet the surface the drop must first expel all the air beneath it; however, this does not happened instantaneously. Instead, a very thin film of air, only a few tens of nanometers thick, remains trapped between the falling drop and the surface as the fluid spreads. The thin film of air serves to lubricate the drop enabling the fluid to skate laterally outward at strikingly high velocities. Simultaneously, the wetting fluid spreads inward at a much slower velocity, trapping a bubble of air within the drop. However, these events occur at diminutive length scales and fleeting time scales; therefore, to visualize them we develop new imaging modalities that are sensitive to the behavior right at the surface and that have time resolution superior to even the very fastest cameras. These imaging techniques reveal that the ultimate wetting of the surface occurs through a completely new mechanism, the breakup of the thin film of air through a spinodal like dewetting process that breaks the cylindrical symmetry of the impact and drives an anomalously rapid spreading of a wetting front. These results are in accord with recent theoretical predictions and challenge the prevailing paradigm in which contact between the liquid and solid occurs immediately, and spreading is dominated by the dynamics of a single contact line.

Impulsively Induced Jets from Viscoelastic Films for High-Resolution Printing

NASA Astrophysics Data System (ADS)

Turkoz, Emre; Perazzo, Antonio; Kim, Hyoungsoo; Stone, Howard A.; Arnold, Craig B.

2018-02-01

Understanding jet formation from non-Newtonian fluids is important for improving the quality of various printing and dispensing techniques. Here, we use a laser-based nozzleless method to investigate impulsively formed jets of non-Newtonian fluids. Experiments with a time-resolved imaging setup demonstrate multiple regimes during jet formation that can result in zero, single, or multiple drops per laser pulse. These regimes depend on the ink thickness, ink rheology, and laser energy. For optimized printing, it is desirable to select parameters that result in a single-drop breakup; however, the strain-rate dependent rheology of these inks makes it challenging to determine these conditions a priori. Rather, we present a methodology for characterizing these regimes using dimensionless parameters evaluated from the process parameters and measured ink rheology that are obtained prior to printing and, so, offer a criterion for a single-drop breakup.

Finite amplitude effects on drop levitation for material properties measurement

NASA Astrophysics Data System (ADS)

Ansari Hosseinzadeh, Vahideh; Holt, R. Glynn

2017-05-01

The method of exciting shape oscillation of drops to extract material properties has a long history, which is most often coupled with the technique of acoustic levitation to achieve non-contact manipulation of the drop sample. We revisit this method with application to the inference of bulk shear viscosity and surface tension. The literature is replete with references to a "10% oscillation amplitude" as a sufficient condition for the application of Lamb's analytical expressions for the shape oscillations of viscous liquids. Our results show that even a 10% oscillation amplitude leads to dynamic effects which render Lamb's results inapplicable. By comparison with samples of known viscosity and surface tension, we illustrate the complicating finite-amplitude effects (mode-splitting and excess dissipation associated with vorticity) that can occur and then show that sufficiently small oscillations allow us to recover the correct material properties using Lamb's formula.

Photogrammetric Measurements of CEV Airbag Landing Attenuation Systems

NASA Technical Reports Server (NTRS)

Barrows, Danny A.; Burner, Alpheus W.; Berry, Felecia C.; Dismond, Harriett R.; Cate, Kenneth H.

2008-01-01

High-speed photogrammetric measurements are being used to assess the impact dynamics of the Orion Crew Exploration Vehicle (CEV) for ground landing contingency upon return to earth. Test articles representative of the Orion capsule are dropped at the NASA Langley Landing and Impact Research (LandIR) Facility onto a sand/clay mixture representative of a dry lakebed from elevations as high as 62 feet (18.9 meters). Two different types of test articles have been evaluated: (1) half-scale metal shell models utilized to establish baseline impact dynamics and soil characterization, and (2) geometric full-scale drop models with shock-absorbing airbags which are being evaluated for their ability to cushion the impact of the Orion CEV with the earth s surface. This paper describes the application of the photogrammetric measurement technique and provides drop model trajectory and impact data that indicate the performance of the photogrammetric measurement system.

Rhizosphere biophysics and root water uptake

NASA Astrophysics Data System (ADS)

Carminati, Andrea; Zarebanadkouki, Mohsen; Ahmed, Mutez A.; Passioura, John

2016-04-01

The flow of water into the roots and the (putative) presence of a large resistance at the root-soil interface have attracted the attention of plant and soil scientists for decades. Such resistance has been attributed to a partial contact between roots and soil, large gradients in soil matric potential around the roots, or accumulation of solutes at the root surface creating a negative osmotic potential. Our hypothesis is that roots are capable of altering the biophysical properties of the soil around the roots, the rhizosphere, facilitating root water uptake in dry soils. In particular, we expect that root hairs and mucilage optimally connect the roots to the soil maintaining the hydraulic continuity across the rhizosphere. Using a pressure chamber apparatus we measured the relation between transpiration rate and the water potential difference between soil and leaf xylem during drying cycles in barley mutants with and without root hairs. The samples were grown in well structured soils. At low soil moistures and high transpiration rates, large drops in water potential developed around the roots. These drops in water potential recovered very slowly, even after transpiration was severely decreased. The drops in water potential were much bigger in barley mutants without root hairs. These mutants failed to sustain high transpiration rates in dry conditions. To explain the nature of such drops in water potential across the rhizosphere we performed high resolution neutron tomography of the rhizosphere of the barleys with and without root hairs growing in the same soil described above. The tomograms suggested that the hydraulic contact between the soil structures was the highest resistance for the water flow in dry conditions. The tomograms also indicate that root hairs and mucilage improved the hydraulic contact between roots and soil structures. At high transpiration rates and low water contents, roots extracted water from the rhizosphere, while the bulk soil, due its low unsaturated conductivity, failed to compensate root water uptake. We conclude that root hairs are functional to increase the contact area between the roots and the soil structures and mucilage maintains wet the soil region between root hairs. These observations demonstrate the importance of the biophysical processes in the rhizosphere in modulating root water uptake.

High resolution seismic reflection profiling at Aberdeen Proving Grounds, Maryland

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

Miller, R.D.; Xia, Jianghai; Swartzel, S.

1996-11-01

The effectiveness of shallow high resolution seismic reflection (i.e., resolution potential) to image geologic interfaces between about 70 and 750 ft at the Aberdeen Proving Grounds, Maryland (APG), appears to vary locally with the geometric complexity of the unconsolidated sediments that overlay crystalline bedrock. The bedrock surface (which represents the primary geologic target of this study) was imaged at each of three test areas on walkaway noise tests and CDP (common depth point) stacked data. Proven high resolution techniques were used to design and acquire data on this survey. Feasibility of the technique and minimum acquisition requirements were determined throughmore » evaluation and correlation of walkaway noise tests, CDP survey lines, and a downhole velocity check shot survey. Data processing and analysis revealed several critical attributes of shallow seismic data from APG that need careful consideration and compensation on reflection data sets. This survey determined: (1) the feasibility of the technique, (2) the resolution potential (both horizontal and vertical) of the technique, (3) the optimum source for this site, (4) the optimum acquisition geometries, (5) general processing flow, and (6) a basic idea of the acoustic variability across this site. Source testing involved an accelerated weight drop, land air gun, downhole black powder charge, sledge hammer/plate, and high frequency vibrator. Shallow seismic reflection profiles provided for a more detailed picture of the geometric complexity and variability of the distinct clay sequences (aquatards), previously inferred from drilling to be present, based on sparse drill holes and basewide conceptual models. The seismic data also reveal a clear explanation for the difficulties previously noted in correlating individual, borehole-identified sand or clay units over even short distances.« less

Monitoring sperm mitochondrial respiration response in a laser trap using ratiometric fluorescence

NASA Astrophysics Data System (ADS)

Mei, Adrian; Botvinick, Elliot; Berns, Michael

2005-08-01

Sperm motility is an important area in understanding male infertility. Various techniques, such as the Computer Assisted Sperm Analysis (CASA), have been used to understand sperm motility. Sperm motility is related to the energy (ATP) production of sperm. ATP is produced by the depolarization of the membrane potential of the inner membrane of the mitochondria. In this study, a mitochondrial dye, JC-1, has been used to monitor the energetics of the mitochondria. This fluorescent dye can emit at two different wavelengths, depending on the membrane potential of the mitochondria. It can fluoresce green at low membrane potential and red at high membrane potential. The ratio of the two colors (red/green) allows for an accurate measurement of the change of membrane potential. Various experiments were conducted to quantify the behavior of the dye within the sperm and the reaction of the sperm to trap. Sperm were trapped using laser tweezers. Results have shown that the ratio drops dramatically when sperm are trapped, indicating a depolarization of the membrane. The physiological response to this depolarization is yet to be determined, but the studies indicate that the sperm could have been slightly damaged by the laser. However, knowing that sperm depolarizes their membrane when trapped can help understand how sperm react to their environment and consequently help treat male infertility.

A robust calibration technique for acoustic emission systems based on momentum transfer from a ball drop

USGS Publications Warehouse

McLaskey, Gregory C.; Lockner, David A.; Kilgore, Brian D.; Beeler, Nicholas M.

2015-01-01

We describe a technique to estimate the seismic moment of acoustic emissions and other extremely small seismic events. Unlike previous calibration techniques, it does not require modeling of the wave propagation, sensor response, or signal conditioning. Rather, this technique calibrates the recording system as a whole and uses a ball impact as a reference source or empirical Green’s function. To correctly apply this technique, we develop mathematical expressions that link the seismic moment $M_{0}$ of internal seismic sources (i.e., earthquakes and acoustic emissions) to the impulse, or change in momentum $\\Delta p $, of externally applied seismic sources (i.e., meteor impacts or, in this case, ball impact). We find that, at low frequencies, moment and impulse are linked by a constant, which we call the force‐moment‐rate scale factor $C_{F\\dot{M}} = M_{0}/\\Delta p$. This constant is equal to twice the speed of sound in the material from which the seismic sources were generated. Next, we demonstrate the calibration technique on two different experimental rock mechanics facilities. The first example is a saw‐cut cylindrical granite sample that is loaded in a triaxial apparatus at 40 MPa confining pressure. The second example is a 2 m long fault cut in a granite sample and deformed in a large biaxial apparatus at lower stress levels. Using the empirical calibration technique, we are able to determine absolute source parameters including the seismic moment, corner frequency, stress drop, and radiated energy of these magnitude −2.5 to −7 seismic events.

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.

Energy absorbing system for mechanical impacts

NASA Technical Reports Server (NTRS)

Collins, E. R., Jr.

1972-01-01

System is described based on use of arrangement of crushable hollow spheres bonded together in layers of progressively different diameter, with largest diameter spheres positioned to receive impact forces initially. System is particularly useful for delivery of payloads by air-drop techniques.

Graphene induces spontaneous cardiac differentiation in embryoid bodies

NASA Astrophysics Data System (ADS)

Ahadian, Samad; Zhou, Yuanshu; Yamada, Shukuyo; Estili, Mehdi; Liang, Xiaobin; Nakajima, Ken; Shiku, Hitoshi; Matsue, Tomokazu

2016-03-01

Graphene was embedded into the structure of mouse embryoid bodies (EBs) using the hanging drop technique. The inclusion of 0.2 mg per mL graphene in the EBs did not affect the viability of the stem cells. However, the graphene decreased the stem cell proliferation, probably by accelerating cell differentiation. The graphene also enhanced the mechanical properties and electrical conductivity of the EBs. Interestingly, the cardiac differentiation of the EB-graphene was significantly greater than that of the EBs at day 5 of culture, as confirmed by high-throughput gene analysis. Electrical stimulation (voltage, 4 V; frequency, 1 Hz; and duration, 10 ms for 2 continuous days) further enhanced the cardiac differentiation of the EBs, as demonstrated by analyses of the cardiac protein and gene expression and the beating activity of the EBs. Taken together, the results demonstrated that graphene played a major role in directing the cardiac differentiation of EBs, which has potential cell therapy and tissue regeneration applications.Graphene was embedded into the structure of mouse embryoid bodies (EBs) using the hanging drop technique. The inclusion of 0.2 mg per mL graphene in the EBs did not affect the viability of the stem cells. However, the graphene decreased the stem cell proliferation, probably by accelerating cell differentiation. The graphene also enhanced the mechanical properties and electrical conductivity of the EBs. Interestingly, the cardiac differentiation of the EB-graphene was significantly greater than that of the EBs at day 5 of culture, as confirmed by high-throughput gene analysis. Electrical stimulation (voltage, 4 V; frequency, 1 Hz; and duration, 10 ms for 2 continuous days) further enhanced the cardiac differentiation of the EBs, as demonstrated by analyses of the cardiac protein and gene expression and the beating activity of the EBs. Taken together, the results demonstrated that graphene played a major role in directing the cardiac differentiation of EBs, which has potential cell therapy and tissue regeneration applications. Electronic supplementary information (ESI) available: Fig. S1-S3, Tables S1-S4, and Movies S1-S4. See DOI: 10.1039/c5nr07059g

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.

Visualizing the Zero-Potential Line of Bipolar Electrodes with Arbitrary Geometry.

PubMed

Li, Meng; Liu, Shasha; Jiang, Yingyan; Wang, Wei

2018-06-05

In a typical bipolar electrochemistry (BPE) configuration, voltage applied between the two driving electrodes induced a potential drop through solution filled in the microchannel, resulting in an interfacial potential difference between solution and BPE varied along the BPE. In the present work, we employed a recently developed plasmonic imaging technique to map the distribution of surface potential of bipolar electrodes with various geometries including round, triangle, hexagon, star, and rhombus shapes under the nonfaradaic charging process, from which the line of zero potential (LZP) was visualized and determined. We further investigated the dependence of LZP on electrode geometry and the distribution of external electric field and explained the experimental results with a charge balance mechanism. The triangular and star-shaped BPEs show quite different LZP features from the other ones with symmetrical geometry. These experimentally obtained potential distributions are all in good agreement with electromagnetic simulations. Finally, the line of zero overpotential (LZO) of the triangular-shaped BPE under faradaic reactions were investigated. The results confirm the shift of LZO when faradaic reactions occurred at the corresponding ends of BPE. The present work demonstrates the first experimental capability to map the potential distribution of BPE with arbitrary geometry under an arbitrary driving field. It is anticipated to help the design and optimization on the geometry of electrodes and microchannels with implications for boosting their applications in chemical sensing and materials synthesis.

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.