Internal Energy Transfer Research Articles

A highly sensitive and selective ratiometric fluorescent sensor for Zn2+ ion based on ICT and FRET

A ratiometric sensor (QA) for detecting Zn2+ with high sensitivity and selectivity was reported. The fluorescence changes of sensor upon the addition of Zn2+ were attributed to the conjugation of internal charge transfer and fluorescence resonance energy transfer mechanisms. There is a good linear relationship between the fluorescence ratio I497nm/I420nm and the concentrations of Zn2+ ranging from 0 μM to 40 μM, which makes an effective ratiometric detection of Zn2+ ion. The limit of detection (LOD) was evaluated to be 33.6 nM. The imaging experiments indicated that QA is cell-permeable and can be used to detect Zn2+ within living cells with good selectivity over Cd2+.

An effective theory for meta-mass and meta-material mechanical/electrical devices

A dynamical system comprised of a rigid housing element that encapsulates a large multiplicity of oscillators is said to comprise a “meta-mass,” in that there is no direct interaction of the external environment and the oscillators, the presence of which is inferred in an observed non-Newtonian housing element behavior. For a class of meta-masses, for which the oscillators have more-or-less equal masses with resonances that densely fill a frequency band more-or-less uniformly, the non-Newtonian behavior is most transparently seen in a different “energetics,” i.e., the transfer of energy between the housing element and an external source, this occasioned by an inherently “transitory “internal energy transfer process. Encapsulating a large multiplicity of meta-masses in an ordinary material specimen is said to comprise a meta-material specimen, a somewhat different understanding in not having the direct interaction of each individual oscillator with every other individual oscillator obtain through the behavior of the material matrix. Constructed is a mathematical framework for quantifying limited observable system behavior while not accommodating all underlying physics, i.e., an “effective theory,” this a prerequisite for the design of meta-mass and meta-material mechanical/electrical devices.

Rapid structural change in synaptosomal-associated protein 25 (SNAP25) precedes the fusion of single vesicles with the plasma membrane in live chromaffin cells

The SNARE complex consists of the three proteins synaptobrevin-2, syntaxin, and synaptosomal-associated protein 25 (SNAP25) and is thought to execute a large conformational change as it drives membrane fusion and exocytosis. The relation between changes in the SNARE complex and fusion pore opening is, however, still unknown. We report here a direct measurement relating a change in the SNARE complex to vesicle fusion on the millisecond time scale. In individual chromaffin cells, we tracked conformational changes in SNAP25 by total internal reflection fluorescence resonance energy transfer (FRET) microscopy while exocytotic catecholamine release from single vesicles was simultaneously recorded using a microfabricated electrochemical detector array. A local rapid and transient FRET change occurred precisely where individual vesicles released catecholamine. To overcome the low time resolution of the imaging frames needed to collect sufficient signal intensity, a method named event correlation microscopy was developed, which revealed that the FRET change was abrupt and preceded the opening of an exocytotic fusion pore by ∼90 ms. The FRET change correlated temporally with the opening of the fusion pore and not with its dilation.

Internal energy transfer phenomenon and light-emission properties of γ-LiAlO2 phosphor doped with Mn2+

γ-LiAlO2:Mn2+ phosphor was synthesized using the cellulose-citric acid sol-gel method, and its light emission and energy transfer properties were investigated. Excitation and emission spectrum analysis revealed a decrease in intensity of the spectrum as the amount of Mn2+ doping increased. Blasse’s equation determined the maximum distance for energy transfer between Mn2+ ions as 4.3142 nm. Dexter’s theory verifies that the mechanism of energy transfer between Mn2+ ions conforms to an electric dipole and electric quadrupole interaction.

Control of a model of DNA division via parametric resonance

We study the internal resonance, energy transfer, activation mechanism, and control of a model of DNA division via parametric resonance. While the system is robust to noise, this study shows that it is sensitive to specific fine scale modes and frequencies that could be targeted by low intensity electro-magnetic fields for triggering and controlling the division. The DNA model is a chain of pendula in a Morse potential. While the (possibly parametrically excited) system has a large number of degrees of freedom and a large number of intrinsic time scales, global and slow variables can be identified by (1) first reducing its dynamic to two modes exchanging energy between each other and (2) averaging the dynamic of the reduced system with respect to the phase of the fastest mode. Surprisingly, the global and slow dynamic of the system remains Hamiltonian (despite the parametric excitation) and the study of its associated effective potential shows how parametric excitation can turn the unstable open state into a stable one. Numerical experiments support the accuracy of the time-averaged reduced Hamiltonian in capturing the global and slow dynamic of the full system.

Rovibrational internal energy transfer and dissociation of $\mathbf { \rm N_2(^1\Sigma _g^+)-\rm N(^4S_u)}$N2(1Σg+)−N(4Su) system in hypersonic flows

A rovibrational collisional model is developed to study energy transfer and dissociation of N(2)((1)Σ(g)(+)) molecules interacting with N((4)S(u)) atoms in an ideal isochoric and isothermal chemical reactor. The system examined is a mixture of molecular nitrogen and a small amount of atomic nitrogen. This mixture, initially at room temperature, is heated by several thousands of degrees Kelvin, driving the system toward a strong non-equilibrium condition. The evolution of the population densities of each individual rovibrational level is explicitly determined via the numerical solution of the master equation for temperatures ranging from 5000 to 50,000 K. The reaction rate coefficients are taken from an ab initio database developed at NASA Ames Research Center. The macroscopic relaxation times, energy transfer rates, and dissociation rate coefficients are extracted from the solution of the master equation. The computed rotational-translational (RT) and vibrational-translational (VT) relaxation times are different at low heat bath temperatures (e.g., RT is about two orders of magnitude faster than VT at T = 5000 K), but they converge to a common limiting value at high temperature. This is contrary to the conventional interpretation of thermal relaxation in which translational and rotational relaxation timescales are assumed comparable with vibrational relaxation being considerable slower. Thus, this assumption is questionable under high temperature non-equilibrium conditions. The exchange reaction plays a very significant role in determining the dynamics of the population densities. The macroscopic energy transfer and dissociation rates are found to be slower when exchange processes are neglected. A macroscopic dissociation rate coefficient based on the quasi-stationary distribution, exhibits excellent agreement with experimental data of Appleton et al. [J. Chem. Phys. 48, 599-608 (1968)]. However, at higher temperatures, only about 50% of dissociation is found to take place under quasi-stationary state conditions. This suggest the necessity of explicitly including some rovibrational levels, when solving a global kinetic rate equation.

Internal structure-mediated ultrafast energy transfer in self-assembled polymer-blend dots

Applications of polymeric semiconductors in organic electronics and biosensors depend critically on the nature of energy transfer in these materials. Important questions arise as to how this long-range transport degrades in amorphous condensed solids which are most amenable to low-cost optoelectronic devices and how fast energy transfer could occur. Here, we address these in disordered, densely packed nanoparticles made from green-light-harvesting host polymers (PFBT) and deep-red-emitting dopant polymers (PF-DBT5). By femtosecond selective excitation of donor (BT) units, we study in detail the internal structure-mediated energy transfer to uniformly distributed, seldom acceptor (DBT) units. It has been unambiguously demonstrated that the creation of interchain species is responsible for the limitation of bulk exciton diffusion length in polymer materials. This interchain Förster resonance energy transfer (FRET) becomes a preferred and dominant channel, and near 100% energy transfer efficiency could be achieved at high acceptor concentrations (>10 wt%). Side-chain carboxylic acid groups in functionalized polymer-blend dots slightly slow down the FRET rate, but it could not affect the Förster radius and FRET efficiency. These findings imply that a greater understanding of the role of interchain species could be an efficient approach to improve the cell efficiency.

Direct molecular interaction of caveolin-3 with KCa1.1 channel in living HEK293 cell expression system

Caveolin family is supposed to be essential molecules for the formation of not only caveola structure on cell membrane but also functional molecular complexes in them with direct and/or indirect interaction with other membrane and/or submembrane associated proteins. The direct coupling of caveolin-1 (cav1) with large conductance Ca2+-activated K+ channel, KCa1.1 has been established in several types of cells and in expression system as well. The possible interaction of caveolin-3 (cav3), which shows expression in some differential tissues from cav1, with KCa1.1 remains to be determined. In the present study, the density of KCa1.1 current expressed in HEK293 cells was significantly reduced by the co-expression of cav3, as well as cav1. The co-localization and direct interaction of GFP- or CFP-labeled cav3 (GFP/CFP-cav3) with YFP- or mCherry-labeled KCa1.1 (KCa1.1-YFP/mCherry) were clearly demonstrated by single molecular image analyses using total internal reflection fluorescence (TIRF) microscopy and fluorescence resonance energy transfer (FRET) analyses with acceptor photobleaching method. The deletion of suggested cav1-binding motif in C terminus region of KCa1.1 (KCa1.1ΔCB-YFP) resulted in the marked decrease in cell surface expression, co-localization and FRET efficiency with CFP-cav3 and CFP-cav1. The FLAG-KCa1.1 co-immunoprecipitation with GFP-cav3 or GFP-cav1 also supported their direct molecular interaction. These results strongly suggest that cav3 possesses direct interaction with KCa1.1, presumably at the same domain for cav1 binding. This interaction regulates KCa1.1 expression to cell surface and the formation of functional molecular complex in caveolae in living cells.

Collisional energy transfer with statistical energy exchange: an analytical solution in the statistical limit

Collisional energy transfer between highly vibrationally excited molecules and bath gas is considered with a statistical kernel, describing energy exchange in complex-forming collisions. Knowledge of the bilinear formula for the Laguerre polynomials offers a means for determining eigenvalues and eigenfunctions of the kernel. An exact solution to master equation for the conditional probability is given as an expansion in terms of these eigenfunctions. The bulk averages of internal energy moments and energy transfer moments are calculated analytically.

Investigation of energy transfer in terbium doped Y 2SiO5 phosphor particles

The kinetics of luminescence of sol–gel synthesized terbium doped Y 2SiO5 (YSO) phosphor particles is investigated in detail with reference to Tb concentration in the 0.001%–10% range. By increasing the dopant concentration, the luminescence profile changes from a blue to a green peaked emission spectrum because of the energy transfer among centers. The inter-center energy transfer mechanism is well accounted for by the Inokuti–Hirayama (IH) kinetic model which is based on a statistical average of inter-center distance dependent decay modes of the donor luminescence. The distribution of the decay modes is implemented from the Förster–Dexter resonance theory of energy transfer by assuming a rate constant for the energy transfer by multipolar interactions between donors and acceptors. However, the experimental results recorded in the low concentration limit show the presence of green emission contributions in the luminescence spectrum which cannot be related to the Tb concentration; for this reason an additional internal energy transfer mechanism, occurring among levels of the same center, is proposed to account for the recorded emission properties. Thus, a new and more exhaustive model which includes both the internal and external energy transfer processes is considered; the proposed model allows a better explanation of the spectroscopic features of Tb related centers in YSO crystals and discloses the critical concentration and the quantum yields of the different energy transfer mechanisms.

Enthalpy and exergy transfers of high pressure switching expansion reduction

The energy balance, air internal energy, enthalpy and exergy transfers of high pressure switching expansion reduction (SER) are comparatively analyzed in this paper to give a better understanding about the exergy analysis and its difference between energy conversion analyses for the pneumatics. In SER, the exergy transfer efficiency is much lower than the enthalpy efficiency. The enthalpy efficiency is primarily related to the initial pressure of supply tanks, and the exergy efficiency is primarily related to the pressure reduction ratios. Heat transfers increase the internal energy, enthalpy and exergy of air; the influence on exergy is relatively small. The total enthalpy in SER decreases as the air temperature decreases in the expansion process of the air. And exergy loss is primarily related to the irreversible process of isenthalpic throttling but not energy conversion. Based on the analyses, to improve the exergy efficiency of the pneumatics, the pressure reduction without power output should be avoided.

Phosphoinositide Binding Differentially Regulates NHE1 Na+/H+ Exchanger-dependent Proximal Tubule Cell Survival

Tubular atrophy predicts chronic kidney disease progression, and is caused by proximal tubular epithelial cellcaused by proximal tubular epithelial cell (PTC) apoptosis. The normally quiescent Na(+)/H(+) exchanger-1 (NHE1) defends against PTC apoptosis, and is regulated by PI(4,5)P(2) binding. Because of the vast array of plasma membrane lipids, we hypothesized that NHE1-mediated cell survival is dynamically regulated by multiple anionic inner leaflet phospholipids. In membrane overlay and surface plasmon resonance assays, the NHE1 C terminus bound phospholipids with low affinity and according to valence (PIP(3) > PIP(2) > PIP = PA > PS). NHE1-phosphoinositide binding was enhanced by acidic pH, and abolished by NHE1 Arg/Lys to Ala mutations within two juxtamembrane domains, consistent with electrostatic interactions. PI(4,5)P(2)-incorporated vesicles were distributed to apical and lateral PTC domains, increased NHE1-regulated Na(+)/H(+) exchange, and blunted apoptosis, whereas NHE1 activity was decreased in cells enriched with PI(3,4,5)P(3), which localized to basolateral membranes. Divergent PI(4,5)P(2) and PI(3,4,5)P(3) effects on NHE1-dependent Na(+)/H(+) exchange and apoptosis were confirmed by selective phosphoinositide sequestration with pleckstrin homology domain-containing phospholipase Cδ and Akt peptides, PI 3-kinase, and Akt inhibition in wild-type and NHE1-null PTCs. The results reveal an on-off switch model, whereby NHE1 toggles between weak interactions with PI(4,5)P(2) and PI(3,4,5)P(3). In response to apoptotic stress, NHE1 is stimulated by PI(4,5)P(2), which leads to PI 3-kinase activation, and PI(4,5)P(2) phosphorylation. The resulting PI(3,4,5)P(3) dually stimulates sustained, downstream Akt survival signaling, and dampens NHE1 activity through competitive inhibition and depletion of PI(4,5)P(2).

Amplified spontaneous emission from internal energy transfer process in the copolymer BEHP-co-MEH-PPV

We have studied the Amplified Spontaneous Emission (ASE) characteristics of the conjugated copolymer poly{[2-[2′,5′-bis(2″-ethylhexyloxy)phenyl]-1,4-phenylenevinylene]-co-[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene]} (BEHP-co-MEH-PPV) in a few organic solutions under optical pumping by the third harmonic of Nd:YAG (355 nm). The results show that in BEHP-co-MEH-PPV, the BEHP-PPV component is capable of forcing MEH-PPV to produce ASE at 560 nm, which appears to arise out of the non-excimeric state of MEH-PPV. The ASE of BEHP-co-MEH-PPV was also compared with the conventional laser dyes Rhodamine B (Rh B), Rhodamine 6G (Rh 6G), and also the new laser material MEH-PPV.

Autoparametric vibration absorber effect to reduce the first symmetric mode vibration of a curved beam/panel

This paper presents the implementation of autoparametric phenomena to reduce the symmetrical vibration of a curved beam/panel under external harmonic excitation. The internal energy transfer of a first symmetric mode into first anti-symmetric mode in a curved panel is one example of autoparametric vibration absorber effect. This is similar to the vibration energy transfer from the resonance of a primary structure to the resonance of a secondary spring–mass (tuned mass damper). The nonlinear response of a curved beam is analyzed using an equation with two modes, and a shaker test. The effect of different configurations of the curve beam/panel, including damping ratios and excitation levels, on the energy transfer of the first symmetric mode to the first anti-symmetric mode was studied. The conventional tuned mass damper (TMD) can reduce the resonance response by energy transfer using damping dissipation, whereas an autoparametric vibration absorber (AVA) can reduce the resonance response by energy transfer using parametric interaction. The results indicate that there is a non-absorption region in which vibration is amplified. For the AVA, the non-absorption region can be minimized by tuning the resonance frequency of the first anti-symmetric mode to half of the first symmetric mode resonance frequency using additional mass. No additional damping material is required for achieving sufficient vibration reduction. The AVA can maintain reliable performance in hot and corrosive environments where damping material cannot perform effectively. This paper presents the first successful experimental results of an autoparametric vibration absorption mechanism in a curved beam.

Dynamic Analysis of Steel Tube and Concrete-Filled Steel Tube High-Limit Protection Racks under Impact Loads

The purpose of high-limit protection rack under railway bridge is to protect railway bridge, and avoid passing vehicles under railway bridge colliding bridge. The paper discusses dynamic response and energy transfer of two different structures by analyzing the internal force, deformation, displacement and energy transfer of the steel tube and concrete-filled steel tube protection racks in collision. The result shows that the displacement of concrete-filled steel tube protection rack is smaller, and it can bear larger impact force and have good effect of energy absorption.

AKAP150-Mediated TRPV1 Sensitization is Disrupted by Calcium/Calmodulin

BackgroundThe transient receptor potential vanilloid type1 (TRPV1) is expressed in nociceptive sensory neurons and is sensitive to phosphorylation. A-Kinase Anchoring Protein 79/150 (AKAP150) mediates phosphorylation of TRPV1 by Protein Kinases A and C, modulating channel activity. However, few studies have focused on the regulatory mechanisms that control AKAP150 association with TRPV1. In the present study, we identify a role for calcium/calmodulin in controlling AKAP150 association with, and sensitization of, TRPV1.ResultsIn trigeminal neurons, intracellular accumulation of calcium reduced AKAP150 association with TRPV1 in a manner sensitive to calmodulin antagonism. This was also observed in transfected Chinese hamster ovary (CHO) cells, providing a model for conducting molecular analysis of the association. In CHO cells, the deletion of the C-terminal calmodulin-binding site of TRPV1 resulted in greater association with AKAP150, and increased channel activity. Furthermore, the co-expression of wild-type calmodulin in CHOs significantly reduced TRPV1 association with AKAP150, as evidenced by total internal reflective fluorescence-fluorescence resonance energy transfer (TIRF-FRET) analysis and electrophysiology. Finally, dominant-negative calmodulin co-expression increased TRPV1 association with AKAP150 and increased basal and PKA-sensitized channel activity.Conclusionsthe results from these studies indicate that calcium/calmodulin interferes with the association of AKAP150 with TRPV1, potentially extending resensitization of the channel.

Thrust Augmentation of Solid Rocket Motors Using Beamed Microwave Energy

Abstract : Feasibility of using beamed microwave energy to increase thrust of solid rocket motors during launch is analyzed. Coupling of microwave radiation with internal energies of micron-sized alumina particles and the successive transfer of internal energy of particles to thermal and then kinetic energy of gas is expected to be the main mechanism of thrust increase. A two-phase two-way coupled capability has been developed. For the gas phase, the capability applies an Eulerian approach based on the solution of the Navier-Stokes equations, and uses VAC code modified to include particle source terms. For the particle phase, a Lagrangian approach is used based on a particle tracker that incorporates the impact of the gas and microwave radiation. The developed numerical capability is applied to compute the nozzle flow for a Castor 120 type motor with and without the microwave radiation. High gas density and thus fast collisional relaxation result in highly efficient transfer of microwave energy the kinetic energy of the flow. The total thrust was found to increase by 1.5% for a 100 MW/m2 beam, and 15% for a 1GW/m2 beam.

Contribution of TRPV1-TRPA1 Interaction to the Single Channel Properties of the TRPA1 Channel

Several lines of evidence suggest that TRPA1 and TRPV1 mutually control the transduction of inflammation-induced noxious stimuli in sensory neurons. It was recently shown that certain TRPA1 properties are modulated by TRPV1. However, direct interaction between TRPA1 and TRPV1 as well as regulation of TRPA1 intrinsic characteristics by the TRPV1 channel have not been examined. To address these questions, we have studied a complex formation between TRPA1 and TRPV1 and characterized the influence of TRPV1 on single channel TRPA1-mediated currents. Co-immunoprecipitation analysis revealed direct interactions between TRPA1 and TRPV1 in an expression system as well as in sensory neurons. Data generated with total internal reflection fluorescence-based fluorescence resonance energy transfer indicate that a TRPA1-TRPV1 complex can be formed on the plasma membrane. The fluorescence resonance energy transfer interaction between TRPA1 and TRPV1 channels is as effective as for TRPV1 or TRPA1 homomers. Single channel analysis in a heterologous expression system and in sensory neurons of wild type and TRPV1 knock-out mice demonstrated that co-expression of TRPV1 with TRPA1 results in outward rectification of single channel mustard oil (I(MO)) current-voltage relationships (I-V) and substantial modulation of the open probability at negative holding potentials. TRPV1 also does not influence the characteristics of single channel I(MO) in Ca(2+)-free extracellular solution. However, association of TRPA1 with TRPV1 was not affected in Ca(2+)-free media. To assess a role of intracellular Ca(2+) in TRPV1-dependent modulation of TRPA1 modulation, the TRPA1-mediated single channel WIN55,212-2-gated current (I(WIN)) was recorded in inside-out configuration. Our data indicate that single channel properties of TRPA1 are regulated by TRPV1 independently of intracellular Ca(2+). In summary, our results support the hypothesis that TRPV1 and TRPA1 form a complex and that TRPV1 influences intrinsic characteristics of the TRPA1 channel.

Fourier-domain study of drift turbulence driven sheared flow in a laboratory plasma

Frequency-resolved nonlinear internal and kinetic energy transfer rates have been measured in the Controlled Shear Decorrelation Experiment (CSDX) linear plasma device using a recently developed technique [Xu et al., Phys. Plasmas 16, 042312 (2009)]. The results clearly show a net kinetic energy transfer into the zonal flow frequency region, consistent with previous time-domain observations of turbulence-driven shear flows [Tynan et al., Plasma Phys. Controlled Fusion 48, S51 (2006)]. The experimentally measured dispersion relation has been used to map the frequency-resolved energy transfer rates into the wave number domain, which shows that the shear flow drive comes from midrange (kθρS>0.3) drift fluctuations, and the strongest flow drive comes from kθρS≈1 fluctuations. Linear growth rates have been inferred from a linearized Hasegawa–Wakatani model [Hasegawa et al., Phys. Fluids 22, 2122 (1979)], which indicates that the m=0 mode is linearly stable and the m=1–10 modes (corresponding to kθρS>0.3) are linearly unstable for the n=1 and n=2 radial eigenmodes. This is consistent with our energy transfer measurements.

Internal Dynamics and Energy Transfer in Dansylated POPAM Dendrimers and Their Eosin Complexes

Internal dynamics of dansylated poly(propyleneamine) dendrimers (POPAM, G1-G4) in solution and excitation energy transfer from dansyls to eosin in POPAM-eosin complexes have been studied by time-resolved fluorescence spectroscopy and molecular dynamics (MD) simulations. Combining the results from fluorescence anisotropy and the MD simulation studies suggests three time domains for the internal dynamics of the G3 and G4 generations, about 60 ps for motions of the outer-sphere dansyls, 500-1000 ps for restricted motions of back-folded dansyls, and 1500-2600 ps for the overall rotation. For the smaller generations, the contribution from the restricted motions was not entirely evident. Eosin binding hinders fast rotation of the dansyl fragments in the largest G4 dendrimer, but the motion of back-folded dansyls is more hindered in the pure dendrimer. Both fluorescence anisotropy and MD results for the G4 dendrimer support the "soft" dendrimer picture with almost free mobility and substantial back-folding of the dansyls of the dendrimers in solution. Analysis of time-dependent spectral shifts of fluorescence reveals 20-30 ps excited-state solvation relaxation around a single dansyl of a dendrimer. Dendrimer-independent excitation energy transfer from 4 to 8 ps from dansyls to eosins in POPAM-eosin complexes G2-G4 was observed.