The impact of probe size on measurements of diffusion in active microrheology

Lab on a Chip ◽  
2016 ◽  
Vol 16 (16) ◽  
pp. 3114-3129 ◽  
Author(s):  
Nicholas J. Hoh ◽  
Roseanna N. Zia
Keyword(s):  
Hydrodynamic Size ◽  
Diffusive Behavior ◽  
Approach Distance ◽  
Probe Size ◽  
The Impact

A framework to study the influence of polydispersity on flow-induced diffusion in active microrheology is presented. It is found that diffusive behavior is set entirely and dually by the proximity with which two particles can approach one another, and by the extent to which this minimum approach distance is occupied by the hydrodynamic size of the forced particle.

DART and LICIACUBE: Documenting Kinetic Impact

2021 ◽  
Author(s):  
Andrew Cheng ◽  
Elizabetta Dotto ◽  
Eugene Fahnestock ◽  
Vincenzo Della Corte ◽  
Nancy Chabot ◽  
...  
Keyword(s):  
Time Delay ◽  
Velocity Distribution ◽  
Physical Properties ◽  
Optical Depth ◽  
Depth Profiles ◽  
Full Characterization ◽  
Approach Distance ◽  
Impact Ejecta ◽  
The Impact

<p>The NASA Double Asteroid Redirection Test (DART) mission will demonstrate asteroid deflection by a kinetic impactor. DART will impact Dimorphos, the secondary member of the (65803) Didymos system, in late September to early October, 2022 in order to change the binary orbit period. DART will carry a 6U CubeSat called LICIACube, contributed by the Italian Space Agency, to document the DART impact and to observe the impact ejecta. LICIACube will be released by DART 10 days prior to Didymos encounter, and LICIACube will fly by Dimorphos at closest approach distance of about 51 km and with a closest approach time delay of about 167 s after the DART impact. LICIACube will observe the structure and evolution of the DART impact ejecta plume and will obtain images of the surfaces of both bodies at best ground sampling about 1.4 m per pixel. LICIACube imaging importantly includes the non-impact hemisphere of the target body, the side not imaged by DART.</p> <p> </p> <p>The LICIACube flyby trajectory, notably the closest approach distance and the time delay of closest approach, are designed to optimize the study of ejecta plume evolution without exposing the satellite to impact hazard. LICIACube imaging will determine the direction of the ejecta plume and the ejection angles, and will further help to determine the ejecta momentum transfer efficiency <em>β</em>. The ejecta plume structure, as it evolves over time, is determined by the amount of ejecta that has reached a given altitude at a given time. The LICIACube plume images enable characterization of the ejecta mass versus velocity distribution, which is strongly dependent on target properties like strength and porosity and is therefore a powerful diagnostic of the DART impact, complementary to measurements of the DART impact crater by the ESA Hera mission which will arrive at Didymos in 2026. Hera will measure crater radius and crater volume to determine the total volume of ejecta, which together with a ejecta mass-velocity distribution gives a full characterization of the DART impact.</p> <p> </p> <p>Models of the ejecta plume evolution as imaged by LICIACube show how LICIACube images can discriminate between different target physical properties (mainly strength and porosity), thereby allowing inferences of the magnitude of the ejecta momentum. Measured ejecta plume optical depth profiles can distinguish between gravity-controlled and strength-controlled impact cases and help determine target physical properties. LICIACube ejecta plume images further provide information on the direction of the ejecta momentum as well as the magnitude, requiring full 2-D simulations of the plume images. We will present new simulation model optical depth profiles across the plume at arbitrary positions.</p> <p><br />We thank NASA for support of the DART project at JHU/APL, under Contract # NNN06AA01C, Task Order # NNN15AA05T. The Italian LICIACube team acknowledges financial support from Agenzia Spaziale Italiana (ASI, contract No. 2019-31-HH.0 CUP<br />F84I190012600).</p>

scholarly journals Macromolecular Chromogenic Substrates for Measuring Proteinase Activity

2001 ◽  
Vol 47 (2) ◽  
pp. 215-222 ◽  
Author(s):  
Glen L Hortin ◽  
Ilka Warshawsky ◽  
Maryline Laude-Sharp
Keyword(s):  
Gel Filtration ◽  
Fold Increase ◽  
Coagulation Factors ◽  
Filtration Efficiency ◽  
Hydrodynamic Size ◽  
Chromogenic Substrates ◽  
Functional Assays ◽  
Α2 Macroglobulin ◽  
The Impact ◽  
Physiological Substrates

Abstract Background: Proteinase activities are often measured using chromogenic substrates that are much smaller than physiological substrates. Methods: The hydrodynamic size of macromolecular substrates (macrosubstrates) prepared by linking small chromogenic substrates to polyethylene glycol was determined by gel filtration. Efficiency of macrosubstrate cleavage by proteinases and α2-macroglobulin-proteinase complexes was monitored spectrophotometrically. Results: Macrosubstrates had hydrodynamic radii of ∼20 Å, similar to proteins with a molecular weight of 18 000. Different macrosubstrates served as efficient substrates for chymotrypsin, trypsin, and thrombin. Linking small substrates to a polymer variably affected substrate efficiency, with the impact on activity ranging from a 60-fold decrease to a 30-fold increase. Proteinases complexed with α2-macroglobulin had ∼10-fold lower activity vs macrosubstrates than small substrates. Conclusions: Macrosubstrates are efficient substrates that allow decreased measurement of sterically hindered proteinase molecules such as α2-macroglobulin-proteinase complexes. Thus, macrosubstrates may provide more accurate functional assays of proteinases such as coagulation factors.

scholarly journals Approaching birds with drones: first experiments and ethical guidelines

2015 ◽  
Vol 11 (2) ◽  
pp. 20140754 ◽  
Author(s):  
Elisabeth Vas ◽  
Amélie Lescroël ◽  
Olivier Duriez ◽  
Guillaume Boguszewski ◽  
David Grémillet
Keyword(s):  
Best Practices ◽  
Unmanned Aerial Vehicles ◽  
Ecological Research ◽  
Ethical Guidelines ◽  
Wetland Area ◽  
Physiological Indicators ◽  
Approach Distance ◽  
Aerial Vehicles ◽  
Approach Speed ◽  
The Impact

Unmanned aerial vehicles, commonly called drones, are being increasingly used in ecological research, in particular to approach sensitive wildlife in inaccessible areas. Impact studies leading to recommendations for best practices are urgently needed. We tested the impact of drone colour, speed and flight angle on the behavioural responses of mallards Anas platyrhynchos in a semi-captive situation, and of wild flamingos ( Phoenicopterus roseus ) and common greenshanks ( Tringa nebularia ) in a wetland area. We performed 204 approach flights with a quadricopter drone, and during 80% of those we could approach unaffected birds to within 4 m. Approach speed, drone colour and repeated flights had no measurable impact on bird behaviour, yet they reacted more to drones approaching vertically. We recommend launching drones farther than 100 m from the birds and adjusting approach distance according to species. Our study is a first step towards a sound use of drones for wildlife research. Further studies should assess the impacts of different drones on other taxa, and monitor physiological indicators of stress in animals exposed to drones according to group sizes and reproductive status.

scholarly journals Structural and Energetic Characterization of the Denatured State from the Perspectives of Peptides, the Coil Library, and Intrinsically Disordered Proteins

Molecules ◽  
2021 ◽  
Vol 26 (3) ◽  
pp. 634
Author(s):  
Elisia A. Paiz ◽  
Karen A. Lewis ◽  
Steven T. Whitten
Keyword(s):  
Intrinsically Disordered Proteins ◽  
Cell Function ◽  
Thermodynamic Description ◽  
Disordered Proteins ◽  
Hydrodynamic Size ◽  
Sequence Dependence ◽  
Denatured State ◽  
Intrinsically Disordered ◽  
Heat Effects ◽  
The Impact

The α and polyproline II (PPII) basins are the two most populated regions of the Ramachandran map when constructed from the protein coil library, a widely used denatured state model built from the segments of irregular structure found in the Protein Data Bank. This indicates the α and PPII conformations are dominant components of the ensembles of denatured structures that exist in solution for biological proteins, an observation supported in part by structural studies of short, and thus unfolded, peptides. Although intrinsic conformational propensities have been determined experimentally for the common amino acids in short peptides, and estimated from surveys of the protein coil library, the ability of these intrinsic conformational propensities to quantitatively reproduce structural behavior in intrinsically disordered proteins (IDPs), an increasingly important class of proteins in cell function, has thus far proven elusive to establish. Recently, we demonstrated that the sequence dependence of the mean hydrodynamic size of IDPs in water and the impact of heat on the coil dimensions, provide access to both the sequence dependence and thermodynamic energies that are associated with biases for the α and PPII backbone conformations. Here, we compare results from peptide-based studies of intrinsic conformational propensities and surveys of the protein coil library to those of the sequence-based analysis of heat effects on IDP hydrodynamic size, showing that a common structural and thermodynamic description of the protein denatured state is obtained.

scholarly journals Vitrectomy-Assisted Biopsy: An in vitro Study on the Impact of Cut Rate and Probe Size

2021 ◽  
pp. 1-7
Author(s):  
Erlend Ulltang ◽  
Jens Folke Kiilgaard ◽  
Nazanin Mola ◽  
David Scheie ◽  
Steffen Heegaard ◽  
...  
Keyword(s):  
In Vitro Study ◽  
Probe Type ◽  
Porcine Liver ◽  
Probe Diameter ◽  
Intraocular Tumors ◽  
Probe Size ◽  
23 Gauge ◽  
The Impact ◽  
Conventional Light Microscopy

<b><i>Purpose:</i></b> The aim of this study was to optimize the technique of performing vitrectomy-assisted biopsy of intraocular tumors by comparing the cytohistological findings in specimens obtained with different vitrectomy probes and cut rates. <b><i>Methods:</i></b> Vitrectomy-assisted biopsies were taken from a fresh porcine liver. For each sampling, the vacuum level was 300 mm Hg. The following parameters were compared; cut rate (60, 600 and 6,000 cuts per minute [cpm]), probe type (standard and two-dimensional cutting [TDC]), and probe diameter (23-gauge and 25-gauge). The specimens were assessed by automated whole-slide imaging analysis and conventional light microscopy. <b><i>Results:</i></b> Seventy-two biopsies were analyzed for the number of hepatocytes, total area of tissue fragments, and total stained area of each microscope slide. For all probe types, these parameters were significantly and positively correlated with the cut rate. TDC probes led to significantly higher scores than those of standard probes, independent of the cut rate. There were no significant differences in results when using 23-gauge or 25-gauge standard probes. Light microscopic examination demonstrated well-preserved cells sufficient for cytohistological analyses in all investigated cases. <b><i>Conclusions:</i></b> The higher the cut rate, the larger is the amount of aspirated cellular material. There were no significant differences between 23-gauge and 25-gauge biopsies. Cut rates up to 6,000 cpm did not adversely affect the cytohistological features of the samples.

Formation of Lunar Craters and Bright Rays as a Result of Meteorite Impacts

1962 ◽  
Vol 14 ◽  
pp. 415-418
Author(s):  
K. P. Stanyukovich ◽  
V. A. Bronshten
Keyword(s):  
Explosive Charge ◽  
The Moon ◽  
Meteorite Impacts ◽  
The Earth ◽  
Lunar Craters ◽  
The Impact

The phenomena accompanying the impact of large meteorites on the surface of the Moon or of the Earth can be examined on the basis of the theory of explosive phenomena if we assume that, instead of an exploding meteorite moving inside the rock, we have an explosive charge (equivalent in energy), situated at a certain distance under the surface.

The Geosciences Applied to Lunar Exploration

1962 ◽  
Vol 14 ◽  
pp. 169-257 ◽  
Author(s):  
J. Green
Keyword(s):  
Lunar Surface ◽  
Probable Mechanism ◽  
Point Of View ◽  
Lunar Exploration ◽  
Geological Model ◽  
Apply Geophysics ◽  
Surface Features ◽  
The Impact

The term geo-sciences has been used here to include the disciplines geology, geophysics and geochemistry. However, in order to apply geophysics and geochemistry effectively one must begin with a geological model. Therefore, the science of geology should be used as the basis for lunar exploration. From an astronomical point of view, a lunar terrain heavily impacted with meteors appears the more reasonable; although from a geological standpoint, volcanism seems the more probable mechanism. A surface liberally marked with volcanic features has been advocated by such geologists as Bülow, Dana, Suess, von Wolff, Shaler, Spurr, and Kuno. In this paper, both the impact and volcanic hypotheses are considered in the application of the geo-sciences to manned lunar exploration. However, more emphasis is placed on the volcanic, or more correctly the defluidization, hypothesis to account for lunar surface features.

Asteroid and Comet Impact Speeds upon Mars: Significance for Panspermia and the Supply of Organics

1997 ◽  
Vol 161 ◽  
pp. 197-201 ◽  
Author(s):  
Duncan Steel
Keyword(s):  
Probability Distributions ◽  
Regions Of Interest ◽  
Significant Fraction ◽  
Organic Chemicals ◽  
Impact Speed ◽  
The Mean ◽  
The Impact

AbstractWhilst lithopanspermia depends upon massive impacts occurring at a speed above some limit, the intact delivery of organic chemicals or other volatiles to a planet requires the impact speed to be below some other limit such that a significant fraction of that material escapes destruction. Thus the two opposite ends of the impact speed distributions are the regions of interest in the bioastronomical context, whereas much modelling work on impacts delivers, or makes use of, only the mean speed. Here the probability distributions of impact speeds upon Mars are calculated for (i) the orbital distribution of known asteroids; and (ii) the expected distribution of near-parabolic cometary orbits. It is found that cometary impacts are far more likely to eject rocks from Mars (over 99 percent of the cometary impacts are at speeds above 20 km/sec, but at most 5 percent of the asteroidal impacts); paradoxically, the objects impacting at speeds low enough to make organic/volatile survival possible (the asteroids) are those which are depleted in such species.

Organic Syntheses During the Impact of a Comet with a Gaseous Planet

1997 ◽  
Vol 161 ◽  
pp. 189-195
Author(s):  
Cesare Guaita ◽  
Roberto Crippa ◽  
Federico Manzini
Keyword(s):  
Polymeric Material ◽  
Molecular Form ◽  
Parent Compound ◽  
Blue Filter ◽  
Organic Syntheses ◽  
The Impact

AbstractA large amount of CO has been detected above many SL9/Jupiter impacts. This gas was never detected before the collision. So, in our opinion, CO was released from a parent compound during the collision. We identify this compound as POM (polyoxymethylene), a formaldehyde (HCHO) polymer that, when suddenly heated, reformes monomeric HCHO. At temperatures higher than 1200°K HCHO cannot exist in molecular form and the most probable result of its decomposition is the formation of CO. At lower temperatures, HCHO can react with NH3 and/or HCN to form high UV-absorbing polymeric material. In our opinion, this kind of material has also to be taken in to account to explain the complex evolution of some SL9 impacts that we observed in CCD images taken with a blue filter.

Hydrogen Cyanide Polymers from the Impact of Comet P/Shoemaker-Levy 9 on Jupiter

1997 ◽  
Vol 161 ◽  
pp. 179-187
Author(s):  
Clifford N. Matthews ◽  
Rose A. Pesce-Rodriguez ◽  
Shirley A. Liebman
Keyword(s):  
Amino Acids ◽  
Solar System ◽  
Hydrogen Cyanide ◽  
Nitrogen Heterocycles ◽  
Laboratory Studies ◽  
Heterogeneous Solids ◽  
The Many ◽  
Comet Halley ◽  
The Impact ◽  
By Products

AbstractHydrogen cyanide polymers – heterogeneous solids ranging in color from yellow to orange to brown to black – may be among the organic macromolecules most readily formed within the Solar System. The non-volatile black crust of comet Halley, for example, as well as the extensive orangebrown streaks in the atmosphere of Jupiter, might consist largely of such polymers synthesized from HCN formed by photolysis of methane and ammonia, the color observed depending on the concentration of HCN involved. Laboratory studies of these ubiquitous compounds point to the presence of polyamidine structures synthesized directly from hydrogen cyanide. These would be converted by water to polypeptides which can be further hydrolyzed to α-amino acids. Black polymers and multimers with conjugated ladder structures derived from HCN could also be formed and might well be the source of the many nitrogen heterocycles, adenine included, observed after pyrolysis. The dark brown color arising from the impacts of comet P/Shoemaker-Levy 9 on Jupiter might therefore be mainly caused by the presence of HCN polymers, whether originally present, deposited by the impactor or synthesized directly from HCN. Spectroscopic detection of these predicted macromolecules and their hydrolytic and pyrolytic by-products would strengthen significantly the hypothesis that cyanide polymerization is a preferred pathway for prebiotic and extraterrestrial chemistry.

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