Kinetic Components Research Articles

Large intracranial meningioma masquerading as Parkinson's disease

A previously healthy 58-year-old right-handed woman presented with a 2-month history of progressive asymmetrical extrapyramidal symptoms and signs suggestive of idiopathic Parkinson's disease. On examination, she had moderate hypomimic facies...

Influences of weaving architectures on the impact resistance of multi-layer fabrics

Fabrics constructed from different weaving architectures such as plain, basket, twill and satin provide varying flexibility and durability when applied on surfaces of complex structures for protective applications. They also affect the manufacturing processes and mechanical properties of both fabrics and composite structures in various applications such as soft armours, helmets, aircraft engine cowlings or automobile monocoques. In this work, the influences of weaving architectures on the ballistic resistance and energy absorption of both single and multi-layer Twaron® fabrics are investigated. A mesoscale yarn model is constructed, validated experimentally, and analytical. Finite element fabric models of different fabric structures are then developed and their firmness is quantified using interlacing factors. Numerical models for plain weave are validated against experimental results from single-ply ballistic tests. The evolutions of kinetic, strain, and friction energy components, normalised with areal mass, are presented to demonstrate the better ballistic protection of the plain weave compared with other weaving architectures. Further investigations on multi-ply systems illustrate the energy absorption capacities for different types of woven fabrics and the associated ballistic resistances. The research results indicate that weaving architectures and fabric firmness are less influential on the overall ballistic protection of multi-ply systems compared to the single-ply cases.

Dewar Lesion Formation in Single- and Double-Stranded DNA is Quenched by Neighboring Bases

UV-induced Dewar lesion formation is investigated in single- and double-stranded oligonucleotides with ultrafast vibrational spectroscopy. The quantum yield for the conversion of the (6-4) lesion to the Dewar isomer in DNA strands is reduced by a factor of 4 in comparison to model dinucleotides. Time resolved spectroscopy reveals a fast process in the excited state with spectral characteristics of bases which are adjacent to the excited (6-4) lesion. These kinetic components have large amplitudes and indicate that an additional quenching channel acts in the stranded DNA systems and reduces the Dewar formation yield. Presumably relaxation evolves via a charge transfer to the neighboring guanine and the paired cytosine participates in a double-stranded oligomer. Changes in the decay of the relaxed excited electronic state of the (6-4) chromophore point to modifications in the excited state energy landscape which may lead to an additional reduction of the Dewar formation yield.

Dynamics of Energy and Electron Transfer in the FMO-Reaction Center Core Complex from the Phototrophic Green Sulfur Bacterium Chlorobaculum tepidum

The reaction center core (RCC) complex and the RCC with associated Fenna-Matthews-Olson protein (FMO-RCC) complex from the green sulfur bacterium Chlorobaculum tepidum were studied comparatively by steady-state and time-resolved fluorescence (TRF) and femtosecond time-resolved transient absorption (TA) spectroscopies. The energy transfer efficiency from the FMO to the RCC complex was calculated to be ∼40% based on the steady-state fluorescence. TRF showed that most of the FMO complexes (66%), regardless of the fact that they were physically attached to the RCC, were not able to transfer excitation energy to the reaction center. The TA spectra of the RCC complex showed a 30-38 ps lifetime component regardless of the excitation wavelengths, which is attributed to charge separation. Excitonic equilibration was shown in TA spectra of the RCC complex when excited into the BChl a Qx band at 590 nm and the Chl a Qy band at 670 nm, while excitation at 840 nm directly populated the low-energy excited state and equilibration within the excitonic BChl a manifold was not observed. The TA spectra for the FMO-RCC complex excited into the BChl a Qx band could be interpreted by a combination of the excited FMO protein and RCC complex. The FMO-RCC complex showed an additional fast kinetic component compared with the FMO protein and the RCC complex, which may be due to FMO-to-RCC energy transfer.

Rp-cAMPS Prodrugs Reveal the cAMP Dependence of First-Phase Glucose-Stimulated Insulin Secretion.

cAMP-elevating agents such as the incretin hormone glucagon-like peptide-1 potentiate glucose-stimulated insulin secretion (GSIS) from pancreatic β-cells. However, a debate has existed since the 1970s concerning whether or not cAMP signaling is essential for glucose alone to stimulate insulin secretion. Here, we report that the first-phase kinetic component of GSIS is cAMP-dependent, as revealed through the use of a novel highly membrane permeable para-acetoxybenzyl (pAB) ester prodrug that is a bioactivatable derivative of the cAMP antagonist adenosine-3',5'-cyclic monophosphorothioate, Rp-isomer (Rp-cAMPS). In dynamic perifusion assays of human or rat islets, a step-wise increase of glucose concentration leads to biphasic insulin secretion, and under these conditions, 8-bromoadenosine-3',5'-cyclic monophosphorothioate, Rp-isomer, 4-acetoxybenzyl ester (Rp-8-Br-cAMPS-pAB) inhibits first-phase GSIS by up to 80%. Surprisingly, second-phase GSIS is inhibited to a much smaller extent (≤20%). Using luciferase, fluorescence resonance energy transfer, and bioluminescence resonance energy transfer assays performed in living cells, we validate that Rp-8-Br-cAMPS-pAB does in fact block cAMP-dependent protein kinase activation. Novel effects of Rp-8-Br-cAMPS-pAB to block the activation of cAMP-regulated guanine nucleotide exchange factors (Epac1, Epac2) are also validated using genetically encoded Epac biosensors, and are independently confirmed in an in vitro Rap1 activation assay using Rp-cAMPS and Rp-8-Br-cAMPS. Thus, in addition to revealing the cAMP dependence of first-phase GSIS from human and rat islets, these findings establish a pAB-based chemistry for the synthesis of highly membrane permeable prodrug derivatives of Rp-cAMPS that act with micromolar or even nanomolar potency to inhibit cAMP signaling in living cells.

Brown Adipose Tissue Response Dynamics: In Vivo Insights with the Voltage Sensor 18F-Fluorobenzyl Triphenyl Phosphonium.

Brown adipose tissue (BAT) thermogenesis is an emerging target for prevention and treatment of obesity. Mitochondria are the heat generators of BAT. Yet, there is no noninvasive means to image the temporal dynamics of the mitochondrial activity in BAT in vivo. Here, we report a technology for quantitative monitoring of principal kinetic components of BAT adaptive thermogenesis in the living animal, using the PET imaging voltage sensor 18F-fluorobenzyltriphenylphosphonium (18F-FBnTP). 18F-FBnTP targets the mitochondrial membrane potential (ΔΨm)—the voltage analog of heat produced by mitochondria. Dynamic 18F-FBnTP PET imaging of rat’s BAT was acquired just before and during localized skin cooling or systemic pharmacologic stimulation, with and without administration of propranolol. At ambient temperature, 18F-FBnTP demonstrated rapid uptake and prolonged steady-state retention in BAT. Conversely, cold-induced mitochondrial uncoupling resulted in an immediate washout of 18F-FBnTP from BAT, which was blocked by propranolol. Specific variables of BAT evoked activity were identified and quantified, including response latency, magnitude and kinetics. Cold stimulation resulted in partial washout of 18F-FBnTP (39.1%±14.4% of basal activity). The bulk of 18F-FBnTP washout response occurred within the first minutes of the cold stimulation, while colonic temperature remained nearly intact. Drop of colonic temperature to shivering zone did not have an additive effect. The ß3-adrenergic agonist CL-316,243 elicited 18F-FBnTP washout from BAT of kinetics similar to those caused by cold stimulation. Thus, monitoring ΔΨm in vivo using 18F-FBnTP PET provides insights into the kinetic physiology of BAT. 18F-FBnTP PET depicts BAT as a highly sensitive and rapidly responsive organ, emitting heat in short burst during the first minutes of stimulation, and preceding change in core temperature. 18F-FBnTP PET provides a novel set of quantitative metrics highly important for identifying novel therapeutic targets at the mitochondrial level, for developing means to maximize BAT mass and activity, and assessing intervention efficacy.

Biocatalytic Pathway Selection in Transient Tripeptide Nanostructures

AbstractStructural adaption in living systems is achieved by competing catalytic pathways that drive assembly and disassembly of molecular components under the influence of chemical fuels. We report on a simple mimic of such a system that displays transient, sequence‐dependent formation of supramolecular nanostructures based on biocatalytic formation and hydrolysis of self‐assembling tripeptides. The systems are catalyzed by α‐chymotrypsin and driven by hydrolysis of dipeptide aspartyl‐phenylalanine‐methyl ester (the sweetener aspartame, DF‐OMe). We observed switch‐like pathway selection, with the kinetics and consequent lifetime of transient nanostructures controlled by the peptide sequence. In direct competition, kinetic (rather than thermodynamic) component selection is observed.

Biocatalytic Pathway Selection in Transient Tripeptide Nanostructures.

Structural adaption in living systems is achieved by competing catalytic pathways that drive assembly and disassembly of molecular components under the influence of chemical fuels. We report on a simple mimic of such a system that displays transient, sequence-dependent formation of supramolecular nanostructures based on biocatalytic formation and hydrolysis of self-assembling tripeptides. The systems are catalyzed by α-chymotrypsin and driven by hydrolysis of dipeptide aspartyl-phenylalanine-methyl ester (the sweetener aspartame, DF-OMe). We observed switch-like pathway selection, with the kinetics and consequent lifetime of transient nanostructures controlled by the peptide sequence. In direct competition, kinetic (rather than thermodynamic) component selection is observed.

Different AMPA receptor subtypes mediate the distinct kinetic components of a biphasic EPSC in hippocampal interneurons.

CA1 hippocampal interneurons at the border between stratum radiatum (SR) and stratum lacunosum-moleculare (SLM) have AMPA receptor (AMPAR)-mediated excitatory postsynaptic currents (EPSCs) that consist of two distinct phases: a typical fast component (FC), and a highly unusual slow component (SC) that persists for hundreds of milliseconds. To determine whether these kinetically distinct components of the EPSC are mediated by distinct AMPAR subpopulations, we examined the relative contributions of GluA2-containing and—lacking AMPARs to the SC. GluA2-containing AMPARs mediated the majority of the FC whereas GluA2-lacking AMPARs preferentially generated the SC. When glutamate uptake through the glial glutamate transporter excitatory amino acid transporter (EAAT1) was inhibited, spill over-mediated AMPAR activation recruited an even slower third kinetic component that persisted for several seconds; however, this spillover-mediated current was mediated predominantly by GluA2-containing AMPARs and therefore was clearly distinct from the SC when uptake is intact. Thus, different AMPAR subpopulations that vary in GluA2 content mediate the distinct components of the AMPAR EPSC. The SC is developmentally downregulated in mice, declining after the second postnatal week. This downregulation affects both GluA2-containing and GluA2-lacking AMPARs mediating the SC, and is not accompanied by developmental changes in the GluA2 content of AMPARs underlying the FC. Thus, the downregulation of the SC appears to be independent of synaptic GluA2 expression, suggesting the involvement of another AMPAR subunit or an auxiliary protein. Our results therefore identify GluA2-dependent and GluA2-independent determinants of the SC: GluA2-lacking AMPARs preferentially contribute to the SC, while the developmental downregulation of the SC is independent of GluA2 content.

Kinetic effects on double hysteresis in spin crossover molecular magnets analyzed with first order reversal curve diagram technique

In this paper, we analyze two types of hysteresis in spin crossover molecular magnets compounds in the framework of the First Order Reversal Curve (FORC) method. The switching between the two stable states in these compounds is accompanied by hysteresis phenomena if the intermolecular interactions are higher than a threshold. We have measured the static thermal hysteresis (TH) and the kinetic light induced thermal hysteresis (LITH) major loops and FORCs for the polycrystalline Fe(II) spin crossover compound [Fe1−xZnx(bbtr)3](ClO4)2 (bbtr = 1,4-di(1,2,3-triazol-1-yl)butane), either in a pure state (x = 0) or doped with Zn ions (x = 0.33) considering different sweeping rates. Here, we use this method not only to infer the domains distribution but also to disentangle between kinetic and static components of the LITH and to estimate the changes in the intermolecular interactions introduced by dopants. We also determined the qualitative relationship between FORC distributions measured for TH and LITH.

Quantitative analysis of vesicle recycling at the calyx of Held synapse

Vesicle recycling is pivotal for maintaining reliable synaptic signaling, but its basic properties remain poorly understood. Here, we developed an approach to quantitatively analyze the kinetics of vesicle recycling with exquisite signal and temporal resolution at the calyx of Held synapse. The combination of this electrophysiological approach with electron microscopy revealed that ∼80% of vesicles (∼270,000 out of ∼330,000) in the nerve terminal are involved in recycling. Under sustained stimulation, recycled vesicles start to be reused in tens of seconds when ∼47% of the preserved vesicles in the recycling pool (RP) are depleted. The heterogeneity of vesicle recycling as well as two kinetic components of RP depletion revealed the existence of a replenishable pool of vesicles before the priming stage and led to a realistic kinetic model that assesses the size of the subpools of the RP. Thus, our study quantified the kinetics of vesicle recycling and kinetically dissected the whole vesicle pool in the calyceal terminal into the readily releasable pool (∼0.6%), the readily priming pool (∼46%), the premature pool (∼33%), and the resting pool (∼20%).

A phase field model for segregation and precipitation induced by irradiation in alloys

A phase field model is introduced to model the evolution of multicomponent alloys under irradiation, including radiation-induced segregation and precipitation. The thermodynamic and kinetic components of this model are derived using a mean-field model. The mobility coefficient and the contribution of chemical heterogeneity to free energy are rescaled by the cell size used in the phase field model, yielding microstructural evolutions that are independent of the cell size. A new treatment is proposed for point defect clusters, using a mixed discrete-continuous approach to capture the stochastic character of defect cluster production in displacement cascades, while retaining the efficient modeling of the fate of these clusters using diffusion equations. The model is tested on unary and binary alloy systems using two-dimensional simulations. In a unary system, the evolution of point defects under irradiation is studied in the presence of defect clusters, either pre-existing ones or those created by irradiation, and compared with rate theory calculations. Binary alloys with zero and positive heats of mixing are then studied to investigate the effect of point defect clustering on radiation-induced segregation and precipitation in undersaturated solid solutions. Lastly, irradiation conditions and alloy parameters leading to irradiation-induced homogeneous precipitation are investigated. The results are discussed in the context of experimental results reported for Ni–Si and Al–Zn undersaturated solid solutions subjected to irradiation.

A nonlocal finite element method for torsional statics and dynamics of circular nanostructures

The torsional static and dynamic nonlocal effects for circular nanostructures subjected to concentrated and distributed torques are investigated based on the nonlocal elasticity stress theory. The total strain energy and kinetic energy components are derived and the variational energy principle is applied to derive the governing equation of motion and the corresponding boundary conditions. A new nonlocal finite element method (NL-FEM) is developed to solve the integral nonlocal equation. New numerical solutions for statics and dynamics of nonlocal nanoshafts, nanorods and nanotubes with various loads and boundary conditions are presented. The NL-FE numerical solutions are compared with analytical solutions obtained by solving the differential nonlocal equation. It is observed that the deformation angle as well as the ratio of nonlocal to classical deformation angle increases with increasing nonlocal nanoscale while the natural frequency for free torsional vibration decreases with increasing nanoscale. This paper concludes that the analytical nonlocal model and solutions, which apply the differential nonlocal constitutive relation, fails to capture the nonlocal boundary effects. The NL-FEM, which solves directly the original integral nonlocal stress relation, demonstrates nonlocal boundary effects for all cases of study. The differences of the differential and integral nonlocal stress relations are reported using representative numerical examples.

Deciphering the stepwise binding mode of HRG1β to HER3 by surface plasmon resonance and interaction map.

For the development of efficient anti-cancer therapeutics against the HER receptor family it is indispensable to understand the mechanistic model of the HER receptor activation upon ligand binding. Due to its high complexity the binding mode of Heregulin 1 beta (HRG1β) with its receptor HER3 is so far not understood. Analysis of the interaction of HRG1β with surface immobilized HER3 extracellular domain by time-resolved Surface Plasmon Resonance (SPR) was so far not interpretable using any regular analysis method as the interaction was highly complex. Here, we show that Interaction Map (IM) made it possible to shed light on this interaction. IM allowed deciphering the rate limiting kinetic contributions from complex SPR sensorgrams and thereby enabling the extraction of discrete kinetic rate components from the apparently heterogeneous interactions. We could resolve details from the complex avidity-driven binding mode of HRG1β with HER3 by using a combination of SPR and IM data. Our findings contribute to the general understanding that a major conformational change of HER3 during its activation is induced by a complex sequential HRG1β docking mode.

Music, dance and memory: Towards deliberation of field research of dance

Although ethnochoreology and ethnomusicology as related academic disciplines have decades-long histories, reviewing and redefining their basic epistemological and methodological principles remained one of the main focuses of disciplinary discussion. Most ethnochoreologists and ethnomusicologist agrees that ?field? work (in all its traditional and contemporary forms) remains an essential and constitutive quality of their research and disciplinary fields. The inherent interdisciplinary networking of ethnochoreology and ethnomusicology starts from the theoretical premise that the relationship between the kinetic and musical components of dance is not only unbreakable, but also interactive, and that complex and dynamic manifestations of dance performances represents an expressive medium through which a particular community constructs and represents itself. Since the importance of the individual experience of researchers has been ephasized during the last few decades, a comprehensive method of participant observation remains a central and unifying aspect of fieldwork, both in ethnochoreology and ethnomusicology. Based on field research of musical and dance practices of the village of Svinica (Svini?a) in Romania, this paper reviews the application and combination of various methods of field research (observation, participation in the performance process, filming, interviews and writing field notes) as the primary tools for the acquisition and shaping of scientific knowledge about dance and music. Issues that will be discussed include the following questions: What are the advantages of personal kinetic/auditory experience during simultaneous perception of dance movement and dance music? How can different methods of field research be combined in order to improve cognitive processes? Are there border areas between ethnochoreological and ethnomusicological fieldwork? Does the variety of methods of field research represents a weakness of the interdisciplinary approach or its advantage? On which information recorded during the fieldwork does a researcher usually build his post-field ethnochoreological/ethnomusical narratives? Through discussion of all these issues, particular emphasis will therefore be placed on the consideration of processes of memorization (visual, auditory and kinetic) when applying the method of participation in the dance performance.

Effects of Training Program wearing Balance Shoes to Reduce Knee and Lower Extremity Injuries in Junior Athletes: A Randomized Controlled Trial

Objective: The purpose of this randomized controlled trial was to compare the effectiveness of an original 15-minute exercise program wearing the ReaLine Balanceshoes (RBS) and a conventional injury prevention program in reducing lower extremity injuries. Methods: We recruited athletic club teams from local junior high schools. Inclusion criteria were adolescents who were a member of their interscholastic athletic club team. Players with an injury within 6 weeks that prevented full participation in sports, a history of systemic disease or neurologic disorder at the start of the intervention, and those already using an injury prevention program were excluded. Participants were individually randomized within a team into one of the study groups (RBS or control). The RBS group used the RBS, a shoe-type training device designed for correcting dynamic knee valgus. A 6-staged progressive exercise program was developed, including slow closed kinetic chain strengthening, joint realignment, balancing, feedforward, feedback, and plyometric components. The control group performed an injury prevention program previously used to reduce injury risk. One 15-minute session was performed 3 days/week for 12 months. The primary outcome was incidence of anterior cruciate ligament (ACL) injury and acute knee injuries. Results: One hundred twenty three players completed the study (RBS, n=65; control, n=58). No ACL injury or acute knee injury occurred among RBS athletes versus 1 ACL injury [RR 0.298, 95% CI (0.012, 7.175)] and 3 acute knee injuries [RR 0.127, 95%CI (0.007, 2.421)] among control athletes. Conclusion: The RBS program was not significantly more effective than a conventional injury prevention program in reducing the incidence of ACL injury and other acute lower extremity injuries in junior athletes.

Flow and Turbulence over an Oyster Reef

ABSTRACT Styles, R., 2015. Flow and turbulence over an oyster reef. Simultaneous measurements of near-bed flow and turbulence were collected on opposite banks of an intertidal channel in the North Inlet/Winyah Bay National Estuary Research Reserve. One bank supported an extensive cover of oysters and the other a mixture of sand and mud. The measurements allow comparisons of flow and turbulence characteristics in a similar flow regime but widely varying roughness conditions. Near-bed velocities are higher over the sandbank and occur during the maximum flood portion of the tidal cycle. In contrast, turbulence parameters are higher over the oyster reef, resulting from the presence of the larger roughness elements. Turbulent kinetic energy and Reynolds stress components increase as a function of flow speed, consistent with equilibrium boundary layer shear flows. For some bursts, the energy spectrum exhibits a −5/3 slope, indicating a defined inertial subrange. Dissipation over the oyster bank is on the order ...

Collective Calculation of Actual Values of Non-Photochemical Quenching from Their Apparent Values after Chloroplast Movement and Photoinhibition

Chlorophyll fluorescence parameters such as Fv/Fm, NPQ and ΦII (YII) are widely used to estimate the fitness and photosynthetic activity of plant leaves and non-photochemical dissipation of excessive excitation energy in photosystem II. The effect of chloroplast movement on these fluorescence parameters reduces the accuracy of estimations of the size of de-excitation processes, but there is no method to calculate correct parameters from altered (fluctuated) parameters. Chloroplast movement was recently identified as the “middle” kinetic component of NPQ. In this paper, we devised a complex but reasonable mathematical method to remove the effect of chloroplast movement on fluorescence parameters, based on our previously reported fluorescence theory. The fraction of “S fluctuation” (designated as σ) was estimated from fluorescence observations and used to calculate the non-fluctuated Fs and F′m. fluorescence yields. From the σ values, the fractional change of light absorbance by a leaf caused by chloroplast movement was estimated at 70% - 100%, which varied according to the experimental conditions and plant species. The effect of photoinhibition on fluorescence parameters was also examined in this paper. The photochemical and non-photochemical de-excitation sizes during photoinhibition (measured by the parameters qPI and qSlow) changed on a single regression line. Using this correlation, qPI and qSlow can be predicted from Fv/Fm, and the non-fluctuated Fm and Fo values can be estimated from the fluctuated F″m and F″o values.

Determining the impact behavior of concrete beams through experimental testing and meso-scale simulation: II. Particle element simulation and comparison

A complete model of the hammer–transducer–concrete beam system using meso-scale particle elements is proposed. Drop-weight tests are performed with a constant weight and varying drop heights. The numerical results are compared with those from the impact tests in Part I. The results of impact loads, deflections, and strains exhibit satisfactory agreement. The validated model is then used to predict dynamic behavior under higher loading rates. Different fracture modes are observed in the simulation. The strain-fracture energy concept is introduced to particle element modeling and the energy conversion between kinetic and strain-fracture energy components are discussed for different strain rates.

Electron-emission processes in highly charged Ar and Xe ions impinging on highly ordered pyrolytic graphite at energies just above the kinetic threshold

At keV energies, many electronic processes contribute to the emission of secondary electrons in the interaction of highly charged ions on surfaces. To unravel contributions resulting from isolated hollow atoms in front of the surface or embedded in the electron gas of the target, heavy highly charged Ar and Xe ions are collided on highly ordered pyrolytic graphite (HOPG). A light target material as HOPG assures straight-line trajectories in the subsurface range. By a systematic change of incidence angle and energy of low-charged Ar and Xe ions, the kinetic electron emission component is determined. Separating out the kinetic energy contribution for the highly charged ions yields pure potential-energy-driven secondary-electron yields. From these yields it is concluded that in contrast to metallic targets, only a small fraction of the secondary electrons stem from above the surface. The lack of above-surface emission is likely due to the semimetallic electronic structure of HOPG. The subsurface emission is found to scale with the increase in binding energy of the inner-shell hole when incrementing the charge state of the projectile Ar or Xe ions.