scholarly journals Active, Reactive, and Apparent Power in Dielectrophoresis: Force Corrections from the Capacitive Charging Work on Suspensions Described by Maxwell-Wagner’s Mixing Equation

Micromachines ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 738
Author(s):  
Jan Gimsa
Keyword(s):  
Volume Fraction ◽  
Inhomogeneous Field ◽  
Effective Polarizability ◽  
Polarization Mechanism ◽  
Free Transition ◽  
Lossy Media ◽  
New Perspective ◽  
A Chain ◽  
A Charge ◽  
Induced Changes

A new expression for the dielectrophoresis (DEP) force is derived from the electrical work in a charge-cycle model that allows the field-free transition of a single object between the centers of two adjacent cubic volumes in an inhomogeneous field. The charging work for the capacities of the volumes is calculated in the absence and in the presence of the object using the external permittivity and Maxwell-Wagner’s mixing equation, respectively. The model provides additional terms for the Clausius-Mossotti factor, which vanish for the mathematical boundary transition toward zero volume fraction, but which can be interesting for narrow microfluidic systems. The comparison with the classical solution provides a new perspective on the notorious problem of electrostatic modeling of AC electrokinetic effects in lossy media and gives insight into the relationships between active, reactive, and apparent power in DEP force generation. DEP moves more highly polarizable media to locations with a higher field, making a DEP-related increase in the overall polarizability of suspensions intuitive. Calculations of the passage of single objects through a chain of cubic volumes show increased overall effective polarizability in the system for both positive and negative DEP. Therefore, it is proposed that DEP be considered a conditioned polarization mechanism, even if it is slow with respect to the field oscillation. The DEP-induced changes in permittivity and conductivity describe the increase in the overall energy dissipation in the DEP systems consistent with the law of maximum entropy production. Thermodynamics can help explain DEP accumulation of small objects below the limits of Brownian motion.

scholarly journals Bone health in spacefaring rodents and primates: systematic review and meta-analysis

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Jingyan Fu ◽  
Matthew Goldsmith ◽  
Sequoia D. Crooks ◽  
Sean F. Condon ◽  
Martin Morris ◽  
...  
Keyword(s):  
Bone Formation ◽  
Trabecular Bone ◽  
Bone Health ◽  
Volume Fraction ◽  
Meta Analysis ◽  
Bone Volume ◽  
Trabecular Bone Volume ◽  
Bone Volume Fraction ◽  
Percentage Difference ◽  
Induced Changes

AbstractAnimals in space exploration studies serve both as a model for human physiology and as a means to understand the physiological effects of microgravity. To quantify the microgravity-induced changes to bone health in animals, we systematically searched Medline, Embase, Web of Science, BIOSIS, and NASA Technical reports. We selected 40 papers focusing on the bone health of 95 rats, 61 mice, and 9 rhesus monkeys from 22 space missions. The percentage difference from ground control in rodents was –24.1% [Confidence interval: −43.4, −4.9] for trabecular bone volume fraction and –5.9% [−8.0, −3.8] for the cortical area. In primates, trabecular bone volume fraction was lower by –25.2% [−35.6, −14.7] in spaceflight animals compared to GC. Bone formation indices in rodent trabecular and cortical bone were significantly lower in microgravity. In contrast, osteoclast numbers were not affected in rats and were variably affected in mice. Thus, microgravity induces bone deficits in rodents and primates likely through the suppression of bone formation.

scholarly journals Aggregation kinetics of irreversible patches coupled with reversible isotropic interaction leading to chains, bundles and globules

2018 ◽  
Vol 90 (6) ◽  
pp. 1085-1098 ◽  
Author(s):  
Isha Malhotra ◽  
Sujin B. Babu
Keyword(s):  
Self Assembly ◽  
Patch Size ◽  
Colloidal Particles ◽  
Volume Fraction ◽  
Interaction Strength ◽  
Colloidal System ◽  
Angle Distribution ◽  
Volume Fractions ◽  
Low Volume ◽  
A Chain

Abstract In the present study we are performing simulation of simple model of two patch colloidal particles undergoing irreversible diffusion limited cluster aggregation using patchy Brownian cluster dynamics. In addition to the irreversible aggregation of patches, the spheres are coupled with isotropic reversible aggregation through the Kern–Frenkel potential. Due to the presence of anisotropic and isotropic potential we have also defined three different kinds of clusters formed due to anisotropic potential and isotropic potential only as well as both the potentials together. We have investigated the effect of patch size on self-assembly under different solvent qualities for various volume fractions. We will show that at low volume fractions during aggregation process, we end up in a chain conformation for smaller patch size while in a globular conformation for bigger patch size. We also observed a chain to bundle transformation depending on the attractive interaction strength between the chains or in other words depending on the quality of the solvent. We will also show that bundling process is very similar to nucleation and growth phenomena observed in colloidal system with short range attraction. We have also studied the bond angle distribution for this system, where for small patches only two angles are more probable indicating chain formation, while for bundling at very low volume fraction a tail is developed in the distribution. While for the case of higher patch angle this distribution is broad compared to the case of low patch angles showing we have a more globular conformation. We are also proposing a model for the formation of bundles which are similar to amyloid fibers using two patch colloidal particles.

scholarly journals Molecular-Theory of High Frequency Dielectric Susceptibility of Nematic Nanocomposites

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 970
Author(s):  
Mikhail A. Osipov ◽  
Alexey S. Merekalov ◽  
Alexander A. Ezhov
Keyword(s):  
Plasmon Resonance ◽  
High Frequency ◽  
Volume Fraction ◽  
Simple Expression ◽  
Dielectric Anisotropy ◽  
Dielectric Susceptibility ◽  
Nanoparticle Volume Fraction ◽  
Effective Polarizability ◽  
Dielectric And Optical Properties ◽  
Analytical Expressions

A molecular-statistical theory of the high frequency dielectric susceptibility of the nematic nanocomposites has been developed and approximate analytical expressions for the susceptibility have been obtained in terms of the effective polarizability of a nanoparticle in the nematic host, volume fraction of the nanoparticles and the susceptibility of the pure nematic phase. A simple expression for the split of the plasmon resonance of the nanoparticles in the nematic host has been obtained and it has been shown that in the resonance frequency range the high frequency dielectric anisotropy of the nanocomposite may be significantly larger than that of the pure nematic host. As a result, all dielectric and optical properties of the nanocomposite related to the anisotropy are significantly enhanced which may be important for emerging applications. The components of the dielectric susceptibility have been calculated numerically for particular nematic nanocomposites with gold and silver nanoparicles as functions of the nanoparticle volume fraction and frequency. The splitting of the plasmon resonance has been observed together with the significant dependence on the nanoparticle volume fraction and the parameters of the nematic host phase.

scholarly journals Localization of sites through which C-reactive protein binds and activates complement to residues 14-26 and 76-92 of the human C1q A chain.

1992 ◽  
Vol 175 (5) ◽  
pp. 1373-1379 ◽  
Author(s):  
H Jiang ◽  
F A Robey ◽  
H Gewurz
Keyword(s):  
Amino Acids ◽  
Binding Site ◽  
Immunoglobulin G ◽  
Inhibitory Activity ◽  
Sequence Specificity ◽  
C Reactive Protein ◽  
Reactive Protein ◽  
Binding Regions ◽  
A Chain ◽  
A Charge

Studies were initiated to localize the C-reactive protein (CRP) binding site on the collagen-like region (CLR) of C1q. CRP bound preferentially to the A chain of reduced C1q, in contrast to aggregated immunoglobulin G (Agg-IgG), which reacted preferentially with the C chain. A group of C1q A chain peptides, including peptides identical to residues 81-97, 76-92, and 14-26, respectively, were synthesized from predicted binding regions. Peptide 76-92 contained two proximal lysine groups, and peptide 14-26 contained four proximal arginine groups. CRP-trimers and CRP-ligand complexes did not bind to immobilized peptide 81-97, but bound avidly to immobilized peptides 76-92 and 14-26. Agg-IgG did not bind to any of the peptides. Peptide 76-92 partially, and peptide 14-26 completely, inhibited binding of CRP to intact C1q. Peptide 14-26 also blocked C consumption initiated by CRP, but not by IgG. Replacement of the two prolines with alanines, or scrambling the order of the amino acids, resulted in loss of ability of peptide 14-26 to inhibit C1q binding and C activation by CRP, indicating a sequence specificity, and not a charge specificity alone, as the basis for the inhibitory activity of the peptide. Similar investigations with scrambled peptides showed a sequence specificity for the effects of peptide 76-92 as well. DNA and heparin inhibited binding of CRP trimers to intact C1q, as well as to each peptide 14-26 and 76-92, suggesting involvement of these regions in C1q-CLR binding reactions generally. Collectively, these data identify two cationic regions within residues 14-26 and 76-92 of the C1q A chain CLR as sites through which CRP binds and activates the classical C pathway, and suggest that these residues represent significant regions for C1q CLR binding reactions generally. To our knowledge, this represents the first delineation of sites on C1q through which binding and activation of the classical C pathway can occur.

scholarly journals Compartmentalization of PDGF on extracellular binding sites dependent on exon-6-encoded sequences.

1992 ◽  
Vol 116 (2) ◽  
pp. 533-543 ◽  
Author(s):  
E W Raines ◽  
R Ross
Keyword(s):  
Smooth Muscle ◽  
Biological Activities ◽  
Umbilical Vein ◽  
Fold Increase ◽  
Detectable Effect ◽  
Binding Studies ◽  
Alternatively Spliced ◽  
A Chain ◽  
A Charge ◽  
Umbilical Vein Endothelial Cells

The PDGFs are a family of molecules assembled as disulfide-bonded homo- and heterodimers from two distinct but highly homologous polypeptide chains (PDGF-A and PDGF-B). Two PDGF A-chain transcripts, which arise from alternative usage of the 69-bp exon 6 and exon 7, give rise to two forms of PDGF-A. In spite of the conservation of two PDGF A-chain forms over at least 350 million years, no differences in their biological activities have been identified. We have investigated the activity of the sequence encoded by the alternatively spliced exon 6 of the PDGF A-chain (peptide AL). Addition of peptide AL at 10(-5)-10(-9) M to cultured endothelium and smooth muscle induced a dose-dependent, 3-20-fold increase in PDGF in conditioned media within 30 min. Peptide AL had no detectable effect on A- or B-chain transcript levels, and decrease in culture temperature did not prevent rapid release of PDGF. In human umbilical vein endothelial cells treated with peptide AL, the PDGF release was principally PDGF-BB, while in smooth muscle cells it was primarily PDGF-AA. The capacity to induce release of PDGF is shared by the homologous peptide encoded by exon 6 of the B-chain of PDGF. Binding studies and cross-linking analysis are consistent with a charge-based association of exon 6 sequences with membrane- and matrix-associated heparan-sulfate proteoglycans. We hypothesize that translation of exon 6 of the A- or B-chain of PDGF results in compartmentalization of these forms of PDGF with HS-PG, whereas forms lacking this sequence would be soluble and diffuse.

Directional Tortuosity as a Predictor of Modulus Damage for Vertebral Cancellous Bone

2015 ◽  
Vol 137 (1) ◽  
Author(s):  
David P. Fyhrie ◽  
Roger Zauel
Keyword(s):  
Mechanical Properties ◽  
Cancellous Bone ◽  
Volume Fraction ◽  
Compressive Strain ◽  
Effective Modulus ◽  
Hard Tissue ◽  
Bone Volume Fraction ◽  
Tissue Microstructure ◽  
Induced Changes ◽  
Effective Mechanical Properties

There are many methods used to estimate the undamaged effective (apparent) moduli of cancellous bone as a function of bone volume fraction (BV/TV), mean intercept length (MIL), and other image based average microstructural measures. The MIL and BV/TV are both only functions of the cancellous microstructure and, therefore, cannot directly account for damage induced changes in the intrinsic trabecular hard tissue mechanical properties. Using a nonlinear finite element (FE) approximation for the degradation of effective modulus as a function of applied effective compressive strain, we demonstrate that a measurement of the directional tortuosity of undamaged trabecular hard tissue strongly predicts directional effective modulus (r2 > 0.90) and directional effective modulus degradation (r2 > 0.65). This novel measure of cancellous bone directional tortuosity has the potential for development into an anisotropic approach for calculating effective mechanical properties as a function of trabecular level material damage applicable to understanding how tissue microstructure and intrinsic hard tissue moduli interact to determine cancellous bone quality.

THE EFFECT OF La AND Sn DOPING ON THE STRUCTURAL AND MAGNETIC PROPERTIES OF RuSr2EuCeCu2Oz

2005 ◽  
Vol 19 (01n03) ◽  
pp. 353-359 ◽  
Author(s):  
H. K. LEE ◽  
H. M. Park ◽  
G. V. M. Williams
Keyword(s):  
Magnetic Properties ◽  
Volume Fraction ◽  
Magnetic Ordering ◽  
Structural Data ◽  
Ferromagnetic Phase ◽  
X Ray Diffraction ◽  
Sn Doping ◽  
Ferromagnetic Component ◽  
La Substitution ◽  
Induced Changes

The crystal structure and magnetic properties of ( Ru 1-x Sn x) Sr 2 EuCeCu 2 O z and Ru ( Sr 2-x La x) EuCeCu 2 O z(0≤ x ≤0.1) samples have been investigated to shed light on the doping-induced changes in the magnetic properties of Ru -1222 system. We show that La substitution for Sr leads to an increase in the temperature where the ferromagnetic component is observed and a moderate suppression of the ferromagnetic component whereas Sn substitution for Ru results in a significant decrease of the volume fraction of the ferromagnetic phase as well as a decrease in the magnetic ordering temperature. The experimental results are discussed in connection with the structural data studied by Rietveld refinement of the x-ray diffraction data.

RADIATION-INDUCED CHANGES IN THE UNSATURATION OF POLYISOPRENE

1965 ◽  
Vol 43 (10) ◽  
pp. 2772-2785 ◽  
Author(s):  
Morton. A. Golub ◽  
Jeanne. Danon
Keyword(s):  
Energy Transfer ◽  
Solid State ◽  
Benzene Solution ◽  
Chain Process ◽  
Energy Transfer Mechanism ◽  
Carbonium Ions ◽  
Intermolecular Energy ◽  
Radiation Induced ◽  
A Chain ◽  
Induced Changes

Polyisoprene in the solid state and in benzene solution undergoes radiation-induced cis-trans isomerization and loss of unsaturation. Starting with various cis or trans polymers, the isomerization approaches an equilibrium in which the cis/trans ratio is around 50/50 for polyisoprenes irradiated in solution or in the solid state. The G(isom.) values for either cis → trans or trans → cis isomerization, i.e., the number of cis (or trans) units isomerized initially per 100 eV absorbed by both polymer and solvent, in 1% solution, and by polymer alone, in the solid state, are about 1.0 and 10, respectively. The energy transfer mechanism proposed previously for polybutadiene and squalene isomerization is assumed to hold for polyisoprene as well. The loss of unsaturation in films irradiated with electrons under nitrogen is twice as rapid as in films γ-irradiated in vacuo, the G(-d.b.) (d.b. = double bond) values being 13.4 and 6.7, respectively. Correspondingly, G(-d.b.) for a γ-irradiated solution is 27, calculated in terms of energy absorbed directly by the polymer; intermolecular energy transfer is again indicated, although phenylation may also contribute to the loss of double bonds in solution. The large drop in unsaturation in solution and in the solid state is attributed to a chain process involving cyclization and some cross-linking, with the participation of both free radicals and carbonium ions. Work with polyisoprene-3-d confirmed the importance of isomerization and loss of unsaturation and gave an activation energy of 1.1 kcal/mole for the latter reaction.

Light-induced changes in hydrogen-diluted a-Si : H materials and solar cells: A new perspective on self-consistent analysis

1997 ◽  
Vol 49 (1-4) ◽  
pp. 149-156 ◽  
Author(s):  
Y. Lee ◽  
L. Jiao ◽  
H. Liu ◽  
Z. Lu ◽  
R.W. Collins ◽  
...  
Keyword(s):  
Solar Cells ◽  
Self Consistent ◽  
New Perspective ◽  
Induced Changes

Stripping of Cosmic Spike Spectral Artifacts Using a New Upper-Bound Spectrum Algorithm

2001 ◽  
Vol 55 (11) ◽  
pp. 1523-1531 ◽  
Author(s):  
Dongmao Zhang ◽  
Karim N. Jallad ◽  
Dor Ben-Amotz
Keyword(s):  
Upper Bound ◽  
Band Intensity ◽  
Noise Filtering ◽  
Spectral Distortion ◽  
Charge Coupled Device ◽  
Background Fluorescence ◽  
Ccd Detector ◽  
A Charge ◽  
Induced Changes

A new upper-bound spectrum (UBS) method for removal of cosmic spike artifacts from spectra or images collected using a charge-coupled device (CCD) detector is proposed. This algorithm, which is shown to outperform previous methods, relies on an upper-bound spectrum, derived from scaled copies of consecutively collected spectra, which serves as a threshold for the detection of suspected cosmic spikes. Detected spikes are removed by replacement with the corresponding points in other spectra. Thus, unlike other commonly used methods, the UBS algorithm requires no smoothing or noise filtering and more reliably removes cosmic spikes of all magnitudes while introducing far less (if any) spectral distortion. The UBS method is tested using both synthetic and experimental (gypsum and gypsum/hematite mixture) spectra containing variable background (fluorescence), noise, and cosmic spike interference. The UBS method may in rare instances mistakenly identify spectral noise or photo-induced changes in band intensity (or shape) as cosmic spikes. However, as demonstrated through the use of both synthetic and experimental examples, such misidentifications produce little or no spectral distortion or artifacts in the resulting cosmic-spike-free output spectra.

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