Double Absorption Peak Research Articles

The use of population pharmacokinetics to extrapolate food effects from human adults and beagle dogs to the pediatric population illustrated with ibuprofen as a case

Oral drug administration is the most convenient route of administration in the pediatric population. However, children are often not fasted when drugs are orally administered, hence potential food-drug interactions might occur. Most of these interactions are extrapolated from studies performed in human adults where a recommended high-fat, high-calorie meal is administered prior to drug dosing. As the recommended protocols are based on studies in support of adult drug development, these studies do not mimic the meal composition administered to the pediatric population, especially the very young ones, which renders food-drug interactions in this population understudied. Therefore, it was evaluated to what extent population pharmacokinetics could reliably extrapolate food effects from human adults and beagle dogs to mimic the real-life situation in the pediatric population. Eight human adults and six beagle dogs received ibuprofen under different dosing conditions (fasted, reference meal fed condition, infant formula fed condition). Population pharmacokinetic analysis was performed to derive the pharmacokinetic parameters to be scaled to pediatric ages. For both species, a one-compartment model best described the data, where in human adults a dual-input function to capture the double absorption peak significantly improved the model fit. Simulations for a virtual pediatric population demonstrated that the predictive ability of human adults and beagle dogs to inform absorption effects under different dosing conditions using population pharmacokinetic modeling appeared to be reasonable. However, to be able to fully validate the predictability of both species for ibuprofen, additional studies in the pediatric population are required to generate more informative data.

A quinoline-salt-based fluorescent probe for precise monitoring of pH changes on mitochondria and water

A novel fluorescent probe (cys-pH) based on intramolecular charge transfer (ICT) mechanism for pH detection targeting mitochondria was developed. cys-pH has excellent mitochondrial targeting, a suitable pKa (8.53), a good linear range in the pH range of 6.50–10.00, and a sensitive response to fluctuations in mitochondrial pH. cys-pH has been succeeded in applying to monitor the pH of mitochondria in living cells and the pH detection of water samples in environmental systems. In addition, pH test papers and standard colorimetric cards of cys-pH are prepared. We reasonably explained the double absorption peak of cys-pH UV–vis spectrum in the long wavelength region.

A photochromic salicylaldehyde hydrazone derivative based on C[dbnd]N isomerization and ESIPT mechanisms and its detection of Al3+ in aqueous solution

A simple photochromic Schiff base was successfully prepared by the condensation of salicylaldehyde and benzoyl hydrazine. This compound has reversible photochromic properties based on isomerization and ESIPT mechanisms. In organic solvents, after irradiation with 365 nm UV light for 2 min, the absorption peak at 367 nm of the compound showed a significant decrease, while a double absorption peak appeared at 418 nm and 438 nm, accompanied by a significant change of the solution color from colorless to yellow. The compound can also complex with Al3+ at the molar ratio of 2:1 in the water solution (acetonitrile/water, v/v, 1:99), resulting in significantly enhanced fluorescence of the compound, so as to achieve fluorescence detection of Al3+ in living cells and water samples.

Desmopressin oral lyophilisate in young children: new insights in pharmacokinetics and pharmacodynamics

ObjectiveTo study the pharmacokinetic (PK)/pharmacodynamic (PD) characteristics of desmopressin (dDAVP) oral lyophilisate in children below the age of 8 years with special emphasis on age-related and size-related differences in bioavailability.DesignOpen...

Preparation and properties of composite phase-change nanofiber membrane by improved bubble electrospinning

Bubble electrospinning technology can be used for mass production of nanofibers, it has been widely used in polymer electrospinning such as PVA, PVP and PAN, but there are no reports on the preparation of composite phase-change nanofibers by this method. In this paper, the transparent solution 1(PEG was put into formic acid according to the mass fraction of 60%) was mixed with the transparent solution 2 (PA66 was put into formic acid according to the mass fraction of 15%) according to the mass ratio of 15:85 , 25:75 , 35:65 and 45:55 to prepare four kinds of spinning solutions. And the pure PA66 nanofiber membrane(PNM) and PA66/PEG composite nanofiber membrane(PGCNM) were fabricated by the improved bubble electrospinning device on the basis of bubble electrospinning device invented by He Jihuan etc Also we analyzed their surface microstructure and tested their mechanical properties, thermal properties and molecular structure. The lower the content of PA66, the smaller the adhesion granular matter on the nanofiber surface and the thicker the diameter of the nanofiber, but the surface of the nanofiber is more smooth. The PGNCM appeared double absorption peak at 1515.5 cm−1 and 1642 cm−1 and existed weak absorption peak at 3298 cm−1 ∼ 3302 cm−1. The tensile strength and the elongation at break of the PGNCM was less than that of the PNM. The hot decomposition process of the PGNCM was composed the melting exothermic process of PEG and PA66. When the mixed ratio between PA66 and PEG was 15:85, the decomposition rate of residues between 210 ∼ 310 °C was the fastest.

Pediatric Pharmacology of Desmopressin in Children with Enuresis: A Comprehensive Review.

Desmopressin is a synthetic analogue of the natural antidiuretic hormone arginine vasopressin. Over the years, it has been clinically used to manage nocturnal polyuria in children with enuresis. Various pharmaceutical formulations of desmopressin have been commercialized for this indication-nasal spray, nasal drops, oral tablet and oral lyophilizate. Despite the fact that desmopressin is a frequently prescribed drug in children, its use and posology is based on limited pediatric data. This review provides an overview of the current pediatric pharmacological data related to the different desmopressin formulations, including their pharmacokinetics, pharmacodynamics and adverse events. Regarding the pharmacokinetics, a profound food effect on the oral bioavailability was demonstrated as well as different plasma concentration-time profiles (double absorption peak) of the desmopressin lyophilizate between adults and children. Literature about maturational differences in distribution, metabolism and excretion of desmopressin is rather limited. Regarding the pharmacodynamics, formulation/dose/food effect and predictors of response were evaluated. The lyophilizate is the preferred formulation, but the claimed bioequivalence in adults (200µg tablet and 120µg lyophilizate), could not be readily extrapolated to children. Prescribing the standard flat-dose regimen to the entire pediatric population might be insufficient to attain response to desmopressin treatment, whereby dosing schemes based on age and weight were proposed. Moreover, response to desmopressin is variable, whereby complete-, partial- and non-responders are reported. Different reasons were enumerated that might explain the difference in response rate to desmopressin observed: different pathophysiological mechanisms, bladder capacity and other predictive factors (i.e. breast feeding, familial history, compliance, sex, etc.). Also, the relapse rate of desmopressin treatment was high, rendering it necessary to use a pragmatic approach for the treatment of enuresis, whereby careful consideration of the position of desmopressin within this treatment is required. Regarding the safety of the different desmopressin formulations, the use of desmopressin was generally considered safe, but additional measures should be taken to prevent severe hyponatremia. To conclude the review, to date, major knowledge gaps in pediatric pharmacological aspects of the different desmopressin formulations still remain. Additional information should be collected about the clinical relevance of the double absorption peak, the food effect, the bioequivalence/therapeutic equivalence, the pediatric adapted dosing regimens, the study endpoints and the difference between performing studies at daytime or at nighttime. To fill in these gaps, additional well designed pharmacokinetic and pharmacodynamic studies in children should be performed.

Energy transfer dynamics in B-phycoerythrin from the red alga Porphyridium purpureum

The B-phycoerythrin hexamer (αβ)6γ of Porphyridium purpureum was isolated and purified. The absorption, circular dichroism, fluorescence and ultrafast time-resolved spectra were obtained. The results showed a double absorption peak at 545 nm and 565 nm and a shoulder peak at 498 nm, and fluorescence emission maxima at 580 nm and 620 nm were observed. The circular dichroism spectra in the near-ultraviolet region were obtained and resolved for the first time, which showed that the two peaks at 260 nm and 305 nm were considered to be correlated to phenylalanine (Phe) and tryptophan (Trp) in a conservative hydrophobic microenvironment, respectively. The circular dichroism spectra in the visible region showed that PEB139α/PEB158β and PEB82α/PEB82β existed as two exciton-coupled bilin pairs. Energy transfer within the exciton-coupled pairs was by exciton splitting, while between the exciton-coupled pairs was by Förster resonance. From the studies of the energy transfer dynamics by ultrafast time-resolved fluorescence spectroscopy, it was confirmed that the energy transfer of the B-PE hexamer had three time components of 8 ps, 60 ps, and 1200 ps. In addition, the internal energy transfer pathways of B-phycoerythrin hexamer were identified by deconvoluting the fluorescence decay curve at different detection wavelengths.

Enhanced microwave absorption properties of Zr4+-doped Fe3O4 for coordinated impedance matching and attenuation performances

In this work, a series of the single-phased Zr4+-doped Fe3O4 (Fe3-xZrxO4, x = 0–0.5) powders with spherical morphology were synthesized by one-step hydrothermal method. The results show that the lattice parameter ‘a’ decreases initially from 0.8410 nm (x = 0) to 0.8299 nm (x = 0.3) and then increases to 0.8338 nm (x = 0.5) whilst Fe2+ concentration improves and crystallinity reduces gradually from x = 0 to x = 0.5 in Fe3-xZrxO4. The ε′ reduces largely from 9.36 to 8.34 without doping to 6.8–5.05 with x = 0.5, and the ε′′ increases from ∼0.70 to ∼1.14 over 2–12 GHz while the relaxation phenomenon occurring above 12 GHz of the undoped-sample disappears with the addition of Zr4+ ions. Meanwhile, the permeability decreases only a little with the increment of x, which leads to the impedance matching of Fe3-xZrxO4 progressively increase while attenuation ability continuously decrease. Finally, contributed by coordinated impedance matching and attenuation performances, Fe3-xZrxO4 with x = 0.1 exhibits strong reflection loss of −41.56 dB and broad bandwidth of 5.57 GHz with double absorption peak at the thickness of 5.75 mm. This study provides a valid avenue to develop high-efficiency absorbing materials by coordinating impedance matching and attenuation performances.

Formation mechanism and electromagnetic-microwave-absorbing properties of carbon-encapsulated permalloy nanoparticles prepared by detonation

In this study, we used detonation to synthesise carbon-encapsulated Fe–Ni alloy nanoparticles using safety-composite explosive precursors doped with Fe (NO3)3·9H2O and Ni(NO3)2·6H2O. We characterised the morphology, components and structure of the synthesised carbon-encapsulated alloy nanoparticles by X-ray diffraction, Raman spectroscopy and a transmission electron microscope equipped with an energy dispersive X-ray spectroscope (EDS). The results revealed the carbon-encapsulated Fe–Ni nanoparticles to have a core-shell structure. The grains ranged in size from 40 nm to 60 nm and were uniformly distributed. We determined the encapsulated metal core to be mainly composed of different proportions of Fe and Ni and the outer shell to be composed of graphite and amorphous carbon. In addition, we observed onion carbon formed by the graphitisation of diamond clusters in the vicinity of the nanoparticles. We determined the electromagnetic characteristics of the Fe–Ni alloy nanoparticle composites using an Agilent microwave network analyser in a band range of 2–18 GHz. The experimental results for a coating thickness of 2 mm are as follows: In nanoparticles in which the atomic ratio of iron and nickel is 1: 4, the reflection loss R(dB) of the absorption layer has a double absorption peak, with peak values of −14.6 dB (9.7 GHz) and −7.7 dB (14.3 GHz) and the absorption band of −10 dB ranges from 8.5 GHz to 11.8 GHz. In nanoparticles in which the atomic ratio of iron and nickel is 1: 1, the reflection loss R(dB) reaches 30 dB at 12.88 GHz and the absorption band of −10 dB ranges from 9.7 to 14.4 GHz, which indicates a wide absorption band and an excellent absorbing property.

Microwave absorption enhancement of rectangular activated carbon fibers screen composites

The radar absorbing materials composited of activated carbon fibers (ACF) as wave-absorber and glass fibers (GF) as impedance modifier were successfully prepared. The structure parameters of rectangular ACF felt screen, the influences of GF-piece and the reflection properties were investigated. It was observed that the effective bandwidth (the reflection loss below −10 dB) increased with the aspect ratio (a/b) increasing, but decreased with aperture spacing (δ) increasing. A double absorption peak (16.1 dB and 14.2 dB) for the optimized configuration (a/b = 3, δ = 5 mm, a = 30 mm) appeared at 5.8 GHz and 16.9 GHz, and a wide absorption bandwidth (4–17.6 GHz) could be achieved. When a 30 mm × 15 mm rectangular aperture was filled by GF-piece of 20 mm × 10 mm, the effective bandwidth was improved to 12.1 GHz. The composites with a wide absorption bandwidth could be achieved via designing the proper element parameters and adjusting the composition of ACF and GF.

CO2 Detection Using Microstructured Chalcogenide Fibers

In this work, detection in the mid-infrared (mid-IR) of carbon dioxide, so called greenhouse gas, using Fiber Evanescent Wave Spectroscopy (FEWS) technique is investigated. Since each pollutant gas shows a characteristic optical absorption spectrum in the mid-infrared, it is possible to detect selectively and quantitatively the presence of gases in a given environment by analysing mid-IR spectra. The main infrared signature of carbon dioxide gas consist in a double absorption peak located at 4.26 μm. Chalcogenide optical fibres, transmitting light in the 1-6 μm range, are well-adapted for CO2 analysis. Thus, tapered and microstructured chalcogenide fibers have especially been designed for CO2 detection. They present low optical losses in the spectral region of the CO2 absorption band. The fabrication of tapered and microstructured fibers is reported. Then, using a tapered fiber the detection limit of CO2 is around 20 vol.%. On the other hand, for the first time to our knowledge, the detection of gas in the mid-infrared is demonstrated with a chalcogenide microstructured fiber.

Infrared monitoring of underground CO 2 storage using chalcogenide glass fibers

An optical-fiber-based system suitable for monitoring the presence of carbon dioxide, so-called “greenhouse gas”, is investigated. Since each pollutant gas shows a characteristic optical absorption spectrum in the mid-infrared (mid-IR), it is possible to detect selectively and quantitatively the presence of gases in a given environment by analysing mid-IR spectra. The main infrared signature of carbon dioxide gas is a double absorption peak located at 4.2 μm. Chalcogenide optical fibers, which can transmit light in the 1–6 μm range, are well-adapted for CO 2 analysis. In this wavelength range, they show attenuation losses that compare favourably with other types of fiber such as silver halide fibers. In this paper, the detection limit of CO 2 is established as a function of optical path length. The dynamic parameters of the sensors, such as reversibility, response time and recovery time, are also studied. It is concluded that optical fibers based on chalcogenide glasses could be used to transport infrared light from a black body source to a remote CO 2 geological storage zone in order to monitor, in real time, CO 2 gas leakage.

The molecular aspect of the double absorption peak in the dielectric spectrum of the antiferroelectric liquid crystal phase

Abstract The dielectric spectrum of the antiferroelectric smectic C∗ phase exhibits a low and a high frequency absorption peak (Pl, Ph) which have been studied as a function of temperature and bias electric field. Measurements from 10 Hz to 10 MHz were carried out with smectic layers parallel and quasi-perpendicular to the cell plates for the multicomponent mixture CS-4000 (Chisso). In addition to the orthogonal smectic A∗ phase, this material has four tilted phases, three narrow phases with a dielectric behaviour permitting us to classify two of them as C∗α (82·80° to 81·91°C) and C∗γ (80·10° to 79.17°C), and one broad antiferroelectric phase (79.17° to −10°C). On applying an increasing bias field, Δ∊ for both processes first increases by about a factor of two, then exhibits a maximum at a threshold field E c corresponding to the antiferroelectric-ferroelectric transition at which it decreases by almost one order of magnitude. In fact, at E c the PH peak vanishes and the PL peak shows up at a frequency s...

The determination of mercury by atomic-absorption spectrophotometry with the “delves sampling cup” technique

Summary The use of the absorption tube and crucible method of atomization has been evaluated for the atomic-absorption determination of mercury in small sample volumes. The optimal flame type and absorption tube temperature are considered in relation to the sensitivity obtained and the degree of interference from selected extraneous ions. A double absorption peak was obtained for mercury and the limit of detection with a 5-μl sample volume and a triple-row capillary hydrogen diffusion flame was 0.17 ng of mercury. The interferences observed in this method of atomization are not necessarily the same as those common to conventional nebulizer techniques.

Optical absorption coefficients of vanadium pentoxide single crystals

The optical absorption coefficients of orthorhombic V 2O 5 single crystals were evaluated using incident polarized light over the wavelength range 0.47–1·8μ, and in unpolarized light from 1·5 to 7·5μ. The intrinsic absorption edges were found to have an exponential dependence on photon energy. Fundamental absorption was observed at incident photon energies of 2·15, 2·22 and 2·17 eV for E∥ a, E∥ b and E∥ c, respectively. Some evidence for a direct forbidden transition mechanism with band gaps of 2·36 and 2·34 eV was observed for E∥ a and E∥ c, respectively. A double absorption peak was observed for the polarization E∥ a; the major peak occurs at 1·00 μ and the minor peak at 0·83 μ. Since this peak is completely missing in the absorption spectra when E∥ b and E∥ c, the mechanism associated with the absorption peak for E∥ a must itself be optically anisotropic. This double peak is associated with nonstoichiometric defects which act as donors. For wavelengths greater than 1·0μ there is an absence of absorption maxima until lattice or impurity absorption sets in at 4·4μ. A critical comparison of the results of this investigation with earlier studies of the optical properties of V 2O 5 is presented.