Single Exponential Curve Research Articles

Ballistic impact wave and bulge profile propagation characteristics and blunt injury assessment of UHMWPE laminate composite

Amid escalating localized conflicts worldwide, the elucidation of the mechanisms and quantification blunt trauma the emergency services and military personnel confronted becomes imperatively. However, the understanding of bullet-induced bulge formation on the laminate's back face, impact wave propagation, and consequent trauma assessment methods remains incomplete. This study applies 3-dimension digital image correlation (3D-DIC) method to reveals these phenomena by utilizing a lead-core bullet traveling at 334.93 m/s to impact an ultra-high molecular weight polyethylene (UHMWPE) laminate. The results show that the initial transverse propagation velocity of bulge profile is 24.79% smaller than the theoretical calculation, which indicates the reduction caused by cohesive matrix. The transverse wave demonstrates a double exponential attenuation pattern, which could be decomposed into two single exponential attenuation curves. The bulge profile shows hyperbolic pattern, which reveals the stability of the bulge shape and the temporal evolution pattern. Increasing the laminate-body gap leads to a decline in Blunt Criterion (BC) and the Abbreviated Injury Scale (AIS) values reduce from 2 to 0 correspondingly. The numerical model confirms the compression wave velocity as 1447.77 ± 123.10 m/s in the thickness direction and 9542.86 ± 3087.75 m/s in the fiber direction. These findings reveals and quantified the propagation patterns of back bulge and compressive wave, and thus could provide data-driven insights to improve body armor performance and blunt trauma assessment for individual soldiers.

Multi-objective optimization of membrane cavity curve of diaphragm compressor and its verification

According to the trend of compressor upgrades in hydrogen refueling stations, this article optimizes the single exponential curve of membrane chamber volume and diaphragm stress that performs poorly. First, set the optimization goals as the membrane cavity volume and the arc length of the curve, use the MOPSO algorithm to optimize the curve, and fit the optimization results to obtain a new curve mathematical model. Then, select three curves for comparison. Theoretical calculations and finite element simulations were performed on the membrane cavity volume and diaphragm stress, and the theoretical calculation methods and results were verified with the help of existing experiments. Finally, it was found that the new curve can increase the membrane cavity volume and reduce the diaphragm stress requirement by changing its own parameters, and the new curve has a small amount of cavity volume near the transition point, which has little impact on the membrane cavity volume. Under the same maximum radial stress, the membrane cavity volume of the new curve can be increased by 5.56% compared to the single exponential curve, while under the same membrane cavity volume, the new curve can reduce the maximum stress on the gas side by 8.9% compared with the single exponential curve, and the maximum stress on the oil sides is reduced by 9.8%.

Sandwich Immunosensor Based on Particle Motion: How Do Reactant Concentrations and Reaction Pathways Determine the Time-Dependent Response of the Sensor?

To control and optimize the speed of a molecular biosensor, it is crucial to quantify and understand the mechanisms that underlie the time-dependent response of the sensor. Here, we study how the kinetic properties of a particle-based sandwich immunosensor depend on underlying parameters, such as reactant concentrations and the size of the reaction chamber. The data of the measured sensor responses could be fitted with single-exponential curves, with characteristic response times that depend on the analyte concentration and the binder concentrations on the particle and substrate. By comparing characteristic response times at different incubation configurations, the data clarifies how two distinct reaction pathways play a role in the sandwich immunosensor, namely, analyte binding first to particles and thereafter to the substrate, and analyte binding first to the substrate and thereafter to a particle. For a concrete biosensor design, we found that the biosensor is dominated by the reaction pathway where analyte molecules bind first to the substrate and thereafter to a particle. Within this pathway, the binding of a particle to the substrate-bound analyte dominates the sensor response time. Thus, the probability of a particle interacting with the substrate was identified as the main direction to improve the speed of the biosensor while maintaining good sensitivity. We expect that the developed immunosensor and research methodology can be generally applied to understand the reaction mechanisms and optimize the kinetic properties of sandwich immunosensors with particle labels.

Length reduction kinetics of multiwalled carbon nanotubes correlated to planetary ball mill impact energy

Four commercial multiwalled carbon nanotubes with distinct lengths and diameters were subject to planetary ball milling to induce length reduction. The Burgio-Rojac energy model was employed to calculate the single impact energy and cumulative energy dissipated to the carbon nanotubes during milling. The ratio of sample mass to bead mass and the nanotube bulk density did not affect length reduction during grinding. The minimum impact energy barrier for carbon nanotube length reduction appeared directly proportional to nanotube diameter for parallel wall morphologies, although a nanotube sample with a cup-stacked wall morphology showed a much lower energy barrier. A normalized exponential equation relating carbon nanotube length and cumulative impact energy collapsed all data to a single exponential master curve described by the same scaling parameters, namely a pre-exponential term that includes the initial nanotube length and a scaling energy in the exponent.

Photocarrier dynamics in Cd<sub>0.96</sub>Zn<sub>0.04</sub>Te measured by optical-pump terahertz-probe spectroscopy

Photogenerated carrier relaxation process and terahertz conductivity of Cd<sub>0.96</sub>Zn<sub>0.04</sub>Te are investigated by optical pump-terahertz probe spectroscopy at room temperature. With photoexcitation at 800 nm, the photogenerated carrier recovery process can be fitted with a single exponential curve, and its recovery time lasts several nanoseconds, which decreases with the increase of photogenerated carrier densities in a certain range of photogenerated carrier densities, relating to the radiative recombination of electron-hole pairs. The transient transmittance change of terahertz pulse remains the same with the photogenerated carrier densities increasing from 4.51×10<sup>16</sup> cm<sup>–3</sup> to 1.81×10<sup>17</sup> cm<sup>–3</sup>, which is because the number of loss carriers by defect trapping is approximate to the augment of carriers by photoexcitation. As the photogenerated carrier density increases from 1.81×10<sup>17</sup> cm<sup>–3</sup> to 1.44×10<sup>18</sup> cm<sup>–3</sup>, the magnitude of photoinduced absorption increases linearly with the increase of photogenerated carrier density due to the fact that most of the defects are occupied. When the photogenerated carrier densities are higher than 1.44×10<sup>18</sup> cm<sup>–3</sup>, the magnitude of photoinduced absorption remains almost the same, because the absorption of 800 nm pump pulse reaches a saturation level. The evolution of complex conductivity with photogenerated carrier density in a delay time of about 50 ps can be well fitted with Drude-Smith model. Our analysis provides an important data support and theoretical basis for designing and fabricating of Cd<sub>1–<i>x</i></sub>Zn<sub><i>x</i></sub>Te detection.

The growth and properties of Y admixed LuAG:Ce scintillating single crystal fiber fabricated by laser heated pedestal growth method

Aluminum garnet crystal has great potential in detecting the high-energy photons and particles for its good scintillation properties and preparing the high time and spatial resolution fiber-array detector for its' easy preparation as single crystal fiber. 0.2 at% Ce: Lu1-xYxAG (x = 0, 0.25, 0.5, 0.75, 1) scintillating single crystal fibers were successfully prepared by laser heated pedestal growth method. The 5d1 energy level of Ce3+ luminescence center is shifting to lower energy and 5d2 energy level of Ce3+ luminescence center is shifting to higher energy with the Y admixture increasing. The photoluminescence decay was fitted by single-exponential decay curve and the scintillation decay were fitted by double-exponential decay curve instead for the different luminescence mechanism. The highest scintillation light yield of 32,457 Ph/MeV and 10,617 Ph/MeV was obtained from the horizontal-direction and longitudinal-direction sides of 0.2 at% Ce: Lu0.25Y0.75AG scintillating single crystal fiber respectively, demonstrating its perspective for application in High Energy Physics.

Determination of Hardness of a Pharmaceutical Oral Jelly by Using T2 Relaxation Behavior Measured by Time-Domain NMR.

Hardness is a critical quality characteristic of pharmaceutical oral jelly. In this study, the hardness was determined by using the T2 relaxation curves measured by time-domain NMR. For sample preparation, kappa- and iota-carrageenans, and locust bean gum, were used as gel-forming agents. Ten test jellies with different gel-forming agent composition were prepared, and their hardness and T2 relaxation curves were measured by a texture analyzer and time-domain NMR (TD-NMR). A negative correlation between T2 relaxation time (T2) and hardness was observed; however, it was difficult to determine the hardness directly from the T2 value. That is probably because the T2 relaxation curve contains information about molecular states, not only of water but also of the solute, and T2 values calculated by single-exponential curve fitting only express one property of the test jelly. By considering this issue, partial least squares (PLS) regression analysis was performed on the T2 relaxation curves for hardness determination of the test jellies. According to the analysis, an accurate and reliable PLS model was created that enabled accurate assessment of the hardness of the test jellies. TD-NMR enables the measurement of samples nondestructively and rapidly with low cost, and so could be a promising method for evaluation of the hardness of pharmaceutical oral jellies.

Quantitative Hydrogen/Deuterium Exchange Mass Spectrometry.

This Account describes considerations for the data generation, data analysis, and data interpretation of a hydrogen/deuterium exchange-mass spectrometry (HDX-MS) experiment to have a quantitative argument. Although HDX-MS has gained its popularity as a biophysical tool, the argument from its data often remains qualitative. To generate HDX-MS data that are more suitable for a quantitative argument, the sequence coverage and sequence resolution should be optimized during the feasibility stage, and the time window coverage and time window resolution should be improved during the HDX stage. To extract biophysically meaningful values for a certain perturbation from medium-resolution HDX-MS data, there are two major ways: (i) estimating the area between the two deuterium buildup curves using centroid values with and without the perturbation when plotted against log time scale and (ii) dissecting into multiple single-exponential curves using the isotope envelopes. To have more accurate arguments for an HDX-MS perturbation study, (i) false negatives due to sequence coverage, (ii) false negatives due to time window coverage, (iii) false positives due to sequence resolution, and (iv) false positives due to allosteric effects should be carefully examined.

Luminescence studies on varied concentration of Eu3+ doped SrO-ZnO-PbO-P2O5 glasses for photonic applications

Optical and structural properties of concentration variation of Eu3+ doped SrO-ZnO-PbO-P2O5 glasses have been reported. The structural properties are analysed from XRD and FTIR spectra. The oscillator strength and Judd-Ofelt intensity parameters are determined from the absorption. The strongest emission peak is obtained at 612 nm (red) for 5D0→7F2 transition. The luminescence emission waning is observed for more than 2 mol% Eu3+ concentration due to loss of excitation energy by cross-relaxation and migration process. Different radiative parameters are calculated using the Judd-Ofelt parameters. Effect of concentration quenching on the radiative parameters has been highlighted. The decay profiles are fitted with single-exponential curves. The CIE chromaticity coordinates are located in the reddish-orange region. The present EuSrZnLP glasses could be potentially used for LED and photonic devices.

Dynamism of Metabolic Carbon Flow of Starch and Lipids in Chlamydomonas debaryana.

Microalgae have the potential to recycle CO2 as starch and triacylglycerol (TAG), which provide alternative source of biofuel and high added-value chemicals. Starch accumulates in the chloroplast, whereas TAG accumulates in the cytoplasmic lipid droplets (LD). Preferential accumulation of starch or TAG may be achieved by switching intracellular metabolic carbon flow, but our knowledge on this control remains limited. Are these two products mutually exclusive? Or, does starch act as a precursor to TAG synthesis, or vice versa? To answer these questions, we analyzed carbon flow in starch and lipids using a stable isotope 13C in Chlamydomonas debaryana NIES-2212, which accumulates, without nutrient limitation, starch in the exponential growth phase and TAG in the stationary phase. Pulse labeling experiments as well as pulse labeling and chase experiments were conducted, and then, gas chromatography-mass spectrometry (GC-MS) analysis was performed on starch-derived glucose and lipid-bound fatty acids. We exploited the previously developed method of isotopomer analysis to estimate the proportion of various pools with different isotopic abundance. Starch turned over rapidly to provide carbon for the synthesis of fatty acids in the exponential phase cells. Most fatty acids showed rapid and slow components of metabolism, whereas oleic acid decayed according to a single exponential curve. Highly labeled population of fatty acids that accumulated during the initial labeling decreased rapidly, and replaced by low abundance population during the chase time, indicating that highly labeled fatty acids were degraded and the resulting carbons were re-used in the re-synthesis with about 9-fold unlabeled, newly fixed carbons. Elongation of C16–C18 acids in vivo was indicated by partially labeled C18 acids. The accumulation of TAG in the stationary growth phase was accounted for by both de novo synthesis and remodeling of membrane lipids. These results suggest that de novo synthesis of starch and TAG was rapid and transient, and also almost independent to each other, but there is a pool of starch quickly turning over for the synthesis of fatty acids. Fatty acids were also subject to re-synthesis. Evidence was also provided for remodeling of lipids, namely, re-use of acyl groups in polar lipids for TAG synthesis.

Magnetic resonance imaging of the zone of calcified cartilage in the knee joint using 3-dimensional ultrashort echo time cones sequences.

Background:The zone of calcified cartilage (ZCC) plays an important role in the pathogenesis of osteoarthritis (OA) but has never been imaged in vivo with magnetic resonance (MR) imaging techniques. We investigated the feasibility of direct imaging of the ZCC in both cadaveric whole knee specimens and in vivo healthy knees using a 3-dimensional ultrashort echo time cones (3D UTE-Cones) sequence on a clinical 3T scanner.Methods:In all, 12 cadaveric knee joints and 10 in vivo healthy were collected. At a 3T MR scanner with an 8-channel knee coil, a fat-saturated 3D dual-echo UTE-Cones sequence was used to image the ZCC, following with a short rectangular pulse excitation and 3D spiral sampling with conical view ordering. The regions of interests (ROIs) were delineated by a blinded observer. Single-component T2∗ and T2 values were calculated from fat-saturated 3D dual-echo UTE-Cones and a Carr-Purcell-Meiboom-Gill (T2 CPMG) data using a semi-automated MATLAB code.Results:The single-exponential fitting curve of ZCC was accurately obtained with R2 of 0.989. For keen joint samples, the ZCC has a short T2∗ ranging from 0.62 to 2.55 ms, with the mean ± standard deviation (SD) of 1.49 ± 0.66 ms, and with 95% confidence intervals (CI) of 1.20–1.78 ms. For volunteers, the short T2∗ ranges from 0.93 to 3.52 ms, with the mean ± SD of 2.09 ± 0.56 ms, and the 95% CI is 1.43 to 2.74 ms in ZCC.Conclusions:The high-resolution 3D UTE-Cones sequence might be used to directly image ZCC in the human knee joint on a clinical 3T scanner with a scan time of more than 10 min. Using this non-invasive technique, the T2∗ relaxation time of the ZCC can be further detected.

Pump fluence dependence of ultrafast carrier dynamics in InSb measured by optical pump-terahertz probe spectroscopy.

Ultrafast carrier dynamics in intrinsic and n-doped InSb crystals were studied by time-resolved terahertz spectroscopy using an optical pump-terahertz probe setup with pump fluence from 32 μJ/cm2 to 1910 μJ/cm2. With photoexcitation at 800nm, the ultrafast photoinduced absorption and carrier recovery process of intrinsic and n-doped InSb showed strong pump fluence dependence. It was found that the magnitude of photoinduced absorption first increased and then decreased with pump fluence. The carrier recovery process could be well fitted with a single exponential curve at low pump fluence, but could be well fitted with a biexponential curve at high pump fluence when a fast photocarrier relaxation appeared. The magnitude of photoinduced absorption increased gradually at low pump fluence due to the increase of the carrier at the bottom of the conduction band by impact ionization. The magnitude of photoinduced absorption decreased gradually at high pump fluence, possibly due to the efficiency of transient Auger recombination greater than the rate of carriers generated in the impact ionization process. The fast decay process appearing at high pump fluence was thought to be dominated by transient Auger recombination.

Optical properties of Nd3+ doped barium lithium fluoroborate glasses for near-infrared (NIR) emission

The neodymium doped barium lithium fluoroborate (Nd3+: BLFB) glasses with the chemical composition (70-x) H3BO3 - 10 Li2CO3 - 10 BaCO3- 5 CaF2-5 ZnO - x Nd2O3 (where x = 0.05, 0.1, 0.25, 0.5, 1, 2 in wt %) have been prepared by the conventional melt quenching technique and characterised through optical absorption, near infrared emission and decay-time measurements. The x-ray diffraction studies confirm the amorphous nature of the prepared glasses. The optical absorption spectra and emission spectra were recorded in the wavelength ranges of 190–1100 nm. The optical band gap (Eg) and Urbach energy (ΔE) values were calculated from the absorption spectra. The Judd-Ofelt intensity parameters were determined from the systematic analysis of the absorption spectrum of neodymium ions in the prepared glasses. The emission spectra exhibited three prominent peaks at 874, 1057, 1331 nm corresponding to the 4F3/2 → 4I9/2, 11/2, 13/2 transitions levels respectively in the near infrared region. The emission intensity of the 4F3/2 → 4I11/2 transition increases with the increase in neodymium concentration up to 0.5 wt% and the concentration quenching mechanism was observed for 1 wt% and 2 wt% concentrations. The lifetime of the 4F3/2 level was found to decrease with increasing Nd3+ ion concentration. The nature of energy transfer process was a single exponential curve which was studied for all the glasses and analysed.

Microindentation Hardness of Protein Crystals under Controlled Relative Humidity

Vickers microindentation hardness of protein crystals was investigated on the (110) habit plane of tetragonal hen egg-white lysozyme crystals containing intracrystalline water at controlled relative humidity. The time evolution of the hardness of the crystals exposed to air with different humidities exhibits three stages such as the incubation, transition, and saturation stages. The hardness in the incubation stage keeps a constant value of 16 MPa, which is independent of the humidity. The incubation hardness can correspond to the intrinsic one in the wet condition. The increase of the hardness in the transition and saturation stages is well fitted with the single exponential curve, and is correlated with the reduction of water content in the crystal by the evaporation. The saturated maximum hardness also strongly depends on the water content equilibrated with the humidity. The slip traces corresponding to the (11 ̅0)[110] slip system around the indentation marks are observed in not only incubation but also saturation stages. It is suggested that the plastic deformation in protein crystals by the indentation can be attributed to dislocation multiplication and motion inducing the slip. The indentation hardness in protein crystals is discussed in light of dislocation mechanism with Peierls stress and intracrystalline water.

Detonation velocity behavior and scaling analysis for ethylene-nitrous oxide mixture

In this study, a detailed experimental investigation of the detonation propagation velocity behavior of stoichiometric ethylene-nitrous oxide in narrow channels is conducted. The experimental results in 4mm (inner diameter) round tube indicate the detonation experiences three propagation modes with the decreasing of initial pressure (p0), i.e., steady mode (p0>40kPa), unstable mode (40–27kPa) and decay mode (p0<27kPa), it is confirmed that below pc=27kPa the failure of detonation occurs. The maximum of the velocity deficit at the critical pressure is 35% VCJ. However, only steady and decay detonation modes are observed in 14mm round tube, and the critical pressure for the detonation limits is 15kPa, at which the maximum velocity deficit is 15% VCJ. In 36mm round tube, there are steady and decay modes can be found, the critical pressure for detonation limits is 5.2kPa, its corresponding maximum velocity deficit is 12% VCJ. The results indicate that with the decreasing initial pressure and tube diameter, boundary layer displacement thickness increases and causes more losses through the flow divergence and hence the increasing of velocity deficits. A linear relationship is obtained between the normalized detonation average velocity and (p0·d)−1 by scaling analysis. It suggests the normalized velocity and dimensionless parameter of length scale, i.e., ratio of tube diameter and ZND induction zone length (d/ΔI) collapse to a single exponential curve.

Uncertainty quantification and sensitivity analysis of an arterial wall mechanics model for evaluation of vascular drug therapies

Quantification of the uncertainty in constitutive model predictions describing arterial wall mechanics is vital towards non-invasive assessment of vascular drug therapies. Therefore, we perform uncertainty quantification to determine uncertainty in mechanical characteristics describing the vessel wall response upon loading. Furthermore, a global variance-based sensitivity analysis is performed to pinpoint measurements that are most rewarding to be measured more precisely. We used previously published carotid diameter–pressure and intima–media thickness (IMT) data (measured in triplicate), and Holzapfel–Gasser–Ogden models. A virtual data set containing 5000 diastolic and systolic diameter–pressure points, and IMT values was generated by adding measurement error to the average of the measured data. The model was fitted to single-exponential curves calculated from the data, obtaining distributions of constitutive parameters and constituent load bearing parameters. Additionally, we (1) simulated vascular drug treatment to assess the relevance of model uncertainty and (2) evaluated how increasing the number of measurement repetitions influences model uncertainty. We found substantial uncertainty in constitutive parameters. Simulating vascular drug treatment predicted a 6% point reduction in collagen load bearing (L_mathrm {coll}), approximately 50% of its uncertainty. Sensitivity analysis indicated that the uncertainty in L_{mathrm {coll}} was primarily caused by noise in distension and IMT measurements. Spread in L_{mathrm {coll}} could be decreased by 50% when increasing the number of measurement repetitions from 3 to 10. Model uncertainty, notably that in L_{mathrm {coll}}, could conceal effects of vascular drug therapy. However, this uncertainty could be reduced by increasing the number of measurement repetitions of distension and wall thickness measurements used for model parameterisation.

The AMPK V199i Mutation in Berkshire Pigs Decreases the Rate of Postmortem pH Decline in Skeletal Muscle

ObjectivesAMP-activated protein kinase (AMPK) is a heterotrimeric enzyme that participates in the regulation of cellular energy homeostasis and is comprised of an ɑ, β, and γ subunit. In pigs, two known genetic mutations in the skeletal muscle specific γ3 regulatory subunit alter fresh pork quality. The first mutation, AMPKγ3R200Q (Rendement Napole mutation), arises from an arginine to glutamine substitution and makes AMPK constitutively active. Animals with this mutation produce meat with an abnormally low ultimate pH known as acid meat. The second mutation, AMPKγ3V199I, arises from a valine to isoleucine substitution making AMPK unresponsive to AMP. While the AMPKγ3V199I mutation has been associated with improved pork quality, little information is available elucidating the biochemical mechanism responsible. Therefore, our objective was to investigate the role of the AMPKγ3V199I mutation in determining fresh meat quality during the conversion of muscle to meat.Materials and MethodsWe investigated this mutation using Berkshire pigs, a breed known to carry the AMPKg3V199I mutation with a high frequency (80 to 90% homozygous mutants). Homozygous mutant (n = 12) and heterozygous Berkshire pigs (n = 9) were harvested at The Ohio State University’s Meat Laboratory. Muscle samples were collected from the longissimus lumborum et thoracis at 0, 30, 60, 120, 240, and 1440 min postmortem and frozen in liquid nitrogen to measure pH decline. To determine the rate of pH decline, a single exponential decay curve was fit to the data to derive a rate constant for each pig. After 1440 min, carcass data were measured for dressing percentage, backfat thickness, loin eye area, and Minolta color (L*, a*, and b*). Data were analyzed with a mixed model in JMP. The LSMeans were compared using a Student’s t test and considered significant at P ≤ 0.05.ResultsNo differences were detected in any carcass measurements. The homozygous mutant pigs exhibited a decreased rate of postmortem pH decline (P = 0.0325). This difference primarily arose from the elevated muscle pH of homozygous mutant muscle at 30 min (P = 0.0036) and 60 min (P = 0.0391) postmortem compared to the heterozygous pigs. The slower postmortem pH decline may explain the superior meat quality associated with Berkshire pigs and may be due to a decreased glycolytic capacity in the homozygous pigs.ConclusionThe AMPKγ3V199I mutation results in a slower pH decline in homozygous mutants compared to heterozygotes. The data also suggest that the AMPKγ3V199I mutation may be a recessive mutation compared to the dominant AMPKγ3R200Q mutation.

Manifestations of Varying Grading Level in CdSe/ZnSe Core–Shell Nanocrystals

Graded interface core–shell nanocrystals (NCs) are being investigated to attain highly luminescent systems and are also anticipated to be “blinking-free” at the single-particle level. In the present work, CdSe/ZnSe-graded core–shell NCs with varying confinement potential profile are studied at the single-particle level. The internal structure of NCs is determined with the aid of optical, structural, and chemical probes. Notably, the radiative lifetime for different nanostructures decays monoexponentially. The variation in the radiative lifetime due to differing internal structure is understood on the basis of recently reported first-principles study on different interfaces of core–shell NCs, in particular attributed to varying overlap of electron–hole wave functions. The single NC measurements reveal that the percentage of nonblinking NCs is higher for slowly varying confinement potential. Statistically suppressed blinking (∼80%) and a single exponential PL decay curve, accompanied by a very narrow (∼30 m...

Control of wavelength and decay time of photoluminescence for InAs quantum dots grown on InP(311)B using the digital embedding method

A lattice-matched InGaAs and InAlAs superlattice (SL) was used to embed InAs quantum dots (QDs) on an InP(311)B substrate; this is called the digital embedding method (DEM). We controlled the emission wavelength of the InAs QDs by changing the period of the SL or the ratio of the thickness of InGaAs to that of InAlAs. In addition, we investigated the time-resolved photoluminescence (PL) of the InAs QDs using the DEM. The decay time of the PL from the QDs was estimated by fitting a single exponential curve and was 380 ps in the DEM sample and 700 ps in the reference sample with a conventional InGaAlAs barrier. The decay time was clearly altered by changing the embedding structure. Therefore, carrier dynamics could be controlled using the DEM.

Regulation of metabolism: the work-to-rest transition in skeletal muscle.

The behavior of oxidative phosphorylation predicted by a model for the mechanism and kinetics of cytochrome c oxidase is compared with the experimentally observed behavior during the work-to-rest transition in skeletal muscle. For both experiment and model, when work stops, the increase in creatine phosphate and decrease in creatine and inorganic phosphate concentrations ([CrP], [Cr], and [Pi]) begin immediately. The rate of change for each is maximal and then progressively slows as the increasing energy state ([ATP]/[ADP][Pi]) suppresses the rate of oxidative phosphorylation. The time courses can be reasonably fitted to single exponential curves with similar time constants. The energy state in the working and resting steady states at constant Po2 are dependent on the intramitochondrial [NAD+]/[NADH], mitochondrial content, and size of the creatine pool ([CrP] + [Cr]). The rate of change in [CrP] is linearly correlated with [CrP] and with [Pi] and [Cr]. The time constant for [CrP] increase in the resting and working steady states, and the rate of decrease in oxygen consumption are similarly dependent on the Po2 in the inspired gas (experimental) or tissue Po2 (model). Myoglobin strongly buffers intracellular Po2 below ∼15 torr, truncating the low end of the oxygen distribution in the tissue and suppressing intra- and intermyocyte oxygen gradients. The predictions of the model are consistent with the experimental data throughout the work/rest transition, providing valuable insights into the regulation of cellular and tissue metabolism.