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We show that the near-infrared-absorbing polymethine cyanine dyes exhibit nonlinear absorption (NLA) in the visible region, where they have negligible or very low linear absorption. In chloroform solvent, the studied cyanines were...
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We show that the near-infrared-absorbing polymethine cyanine dyes exhibit nonlinear absorption (NLA) in the visible region, where they have negligible or very low linear absorption. In chloroform solvent, the studied cyanines were found to be photo-unstable and exhibited photo-degradation under prolonged exposures as compared to methanol and dimethyl sulphoxide solvents, where they were stable. Excitation with femtosecond (fs) pulses in the visible region (400-750 nm) exhibits excited state absorption (ESA) as characterized by positive differential absorption (Delta OD) in transient absorption signal. Non-resonant excitations in the visible region are governed by reverse saturable absorption (RSA) mechanism leading to ESA. Excitation with nanosecond pulses also shows NLA owing to ESA from triplet states as compared to that from singlet states under fs excitations. Single beam Z-scan studies were performed with nanosecond (ns) pulses to evaluate ground (sigma(gr)) and excited state (sigma(ex)) absorption cross-sections, which confirms the mechanism of RSA as sigma(ex) were found to be greater than sigma(gr). The population relaxation from higher excited singlet states shows ultrafast behavior with multi-exponential decay components. The fast time component decay varies from a few hundreds of fs (tau(1)) to some hundreds of picoseconds (tau(2)), and the long-time decay is in the ns domain (tau(3)).
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This work characterizes, both numerically and analytically, the heat and mass transfer in a fan-shaped liquid sheet of LiBr-H_2O solution that absorbs the surrounding water vapor inside an adiabatic absorber for absorption chiller...
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This work characterizes, both numerically and analytically, the heat and mass transfer in a fan-shaped liquid sheet of LiBr-H_2O solution that absorbs the surrounding water vapor inside an adiabatic absorber for absorption chillers. A model for the simultaneous heat and mass transfer into the fan-shaped liquid sheet is presented together with the assumptions and simplifications that yield to an affordable problem. The increasing mass flow rate in the sheet due to the absorption of vapor is included in the model, thus resulting in a nonlinear system of equations. The coupled temperature and water mass fraction flow fields in the sheet are numerically solved. Additionally, an approximate analytical solution of the problem is obtained in the form of a series solution. Profiles of normalized temperature and mass fraction in main flow and transverse directions are presented. The radial distribution of local and mean Sherwood number is also evaluated. The results show the existence of temperature and mass fraction regions in the fan sheet which are analogous to the regions present in nonexpanding sheets. Good agreement between the fully nonlinear equations and the analytical approximation is found downstream of the boundary-layer region. Comparison of results for different sheet aperture angles is performed, confirming a significant reduction of the saturation length with the increase of the aperture angle.
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The oral bioavailability of hydrophilic drugs and macromolecular drugs is generally poor because tey are impermeable through the intestinal mucosa.For systemic delivery of these drugs,parenteral administration is currently require...
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The oral bioavailability of hydrophilic drugs and macromolecular drugs is generally poor because tey are impermeable through the intestinal mucosa.For systemic delivery of these drugs,parenteral administration is currently required to achieve their therapeutic activities.However,this administration is poorly accepted by patients and may cause allergic reactions and serious side effects.Therefore,varous approaches have been examined to overcome the delivery problems of these drugs when they administered to the gastrointestinal tract and otehr mucosal sites.These approaches include (1)to use additives such as absorption enhancers,(2)to develop an administration method for drugs that can serve as an lternative to oral and injection administration,(3)to modify the molecular structure of drugs to produce prodrugs and analogues,and (4)to sue the dosage forms to these drugs.In this study,we demonstrated that intestinal absorption of poorly absorbable drugs including peptide drugs could be improved by using these approaches.Therefore,these approaches may give us basic information to improve the intestinal absorption of poory absorbable drugs.
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The weight gain due to fluid absorption was measured in γ-sterilized, ethylene oxide (ETO) gas-sterilized, and unsterilized ultra-high molecular weight (UHMW) polyethylene acetabular cups. After about 2 months the total average f...
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The weight gain due to fluid absorption was measured in γ-sterilized, ethylene oxide (ETO) gas-sterilized, and unsterilized ultra-high molecular weight (UHMW) polyethylene acetabular cups. After about 2 months the total average fluid absorption gain of the polyethylene cups was: 1.76 ± 0.45 mg (average ± standard deviation) for the unsterilized polyethylene cups, 2.81 ± 0.95 mg for the γ-sterilized polyethylene cups and 1.51 ± 0.34 for the ETO gas-sterilized polyethylene cups. There was little difference in fluid absorption between the sterilized and unsterilized specimens. In particular, the γ-sterilized acetabular cups absorbed more than the ETO gas-sterilized and the unsterilized cups. However, the weight gain was higher in serum compared with that in water.
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Wave function-based embedded cluster ab initio calculations have been carried out in order to study the 4f~2 and 4f5d energy levels of the cubic substitutional defect of Pr-doped CaF2. The 4f~2 → 4f5d absorption spectrum and 4f5d...
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Wave function-based embedded cluster ab initio calculations have been carried out in order to study the 4f~2 and 4f5d energy levels of the cubic substitutional defect of Pr-doped CaF2. The 4f~2 → 4f5d absorption spectrum and 4f5d → 4f~2 emission spectrum have been calculated. The 4f~2 1S0 level is found to be immersed in the 4f5d(e_g) manifold, so that no quantum cutting from 1S0 can occur and only strong 4f5d(e_g) → 4f~2 emission is predicted, which supports previous assumptions made in order to explain results in CaF_2:Pr~(3+). The details of the 4f~2 → 4f5d(e_g) and 4f~2 → 4f5d(t2g) bands of the absorption spectrum are interpreted and assignments are made. The lowest level of the 4f5d(e_g) configuration is found to have 80% of singlet character, in opposition to Hund’s Rules, and the issue is discussed in detail. The comparison between the experimental 4f5d(e_g) → 4f~2 high resolution emission spectrum of the cubic site of CaF_2:Pr~(3+) and the calculated emission spectra from the two lowest 4f5d(e_g) states 1T_(2u)(~1T_(2u)) and 1Eu(1~3T_(2u)) suggests the possibility that the experimental emission of the cubic Pr defect of CaF_2:Pr~(3+) is in fact a multiple emission.
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Absolute peak absorption cross sections and pressure broadening coefficients have been recorded with sub-Doppler limited instrumental resolution for selected rotational lines in the 2_0~24_0~1 vibronic band of the formaldehyde _~1...
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Absolute peak absorption cross sections and pressure broadening coefficients have been recorded with sub-Doppler limited instrumental resolution for selected rotational lines in the 2_0~24_0~1 vibronic band of the formaldehyde _~1A_2_X~1A_1 electronic transition. The measured absorption cross sections range between (0.18 ± 0.01) and (10.1 ± 0.08) × 10~(-19) cm~2 molecule~(-1) and are considerably larger than values from the literature recorded using apparatus where instrumental broadening was significant. However, comparisons with spectral simulations with equivalent resolution from Smith et al. (J. Phys. Chem. A 2006, 110, 11645-11653) are in excellent agreement. Pressure broadening was studied for the collision partners CH_2O, CO_2, N_2, O_2, Ne, Kr, Ar, and He, and the resulting broadening coefficients were found to be reduced in comparison to equivalent values measured in infrared regions, consistent with the reduced dipole moment of the upper state probed in this work. Cavity-enhanced absorption spectroscopy (CEAS) measurements were undertaken using calibrated low concentration (2.9-4.6 ppmv) samples from a permeation source and demonstrate a noise equivalent absorption of 1.2 × 10~(-6) cm~(-1) Hz~(-1/2). This implies a minimum detectable formaldehyde concentration with the current system in atmospheric air of 172 ppbv Hz~(-1/2).
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A series of eight 4-substituted 1-(adamantane- 1 -carbonyloxy)pyridine-2(1H)-thiones (1, X = H,0071115, Me, CF3, SC3H7, CN, COOMe, and CD was prepared and characterized by UV-visspectroscopy in MeCN and cyclohexane. The observed l...
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A series of eight 4-substituted 1-(adamantane- 1 -carbonyloxy)pyridine-2(1H)-thiones (1, X = H,0071115, Me, CF3, SC3H7, CN, COOMe, and CD was prepared and characterized by UV-visspectroscopy in MeCN and cyclohexane. The observed lowest energy transition, designated as Jrcs -ering, exhibits a substantial substituent effect and Amax ranges from 333 (X = 0071115) to 415 nm(X = CN). Experimental .1.??? values for all esters except for lb (X = 007H15) correlate with the crj,-parameter (p = 0.41 ± 0.03, r2 = 0.95). In contrast, the energy of the absorption band at about295 nm, designated as gcs ecs, is practically substituent independent. Both absorption bandsexhibit a modest negative solvatochromic effect. The experimental absorption energies correlatebetter with excitation energies calculated for N-acetyloxy analogues 2 with the ZINDO//DFT thanwith the TD-DFT//DFT method. Calculations for a series of 12 N-acetates 2 predict the most blue-shifted π→π~*transition for the alkoxy substituent and most red-shifted for theNO2group relative tothe parent 2a (X = H).
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The problem of non-isothermal absorption of vapour into freely expanding liquid sheets is addressed in this study. This is done in the context of four models that characterise the coupled heat and mass transfer in the liquid phase...
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The problem of non-isothermal absorption of vapour into freely expanding liquid sheets is addressed in this study. This is done in the context of four models that characterise the coupled heat and mass transfer in the liquid phase: a nonlinear model retaining the effect of sheet growth, an approximate model for slowly increasing mass flow rate in the sheet, a large Lewis number model and finally, a boundary layer model. These models have been numerically or analytically solved and applied to the comparative analysis of two different working pairs, LiBr-H_2O and LiNO_3-NH_3, under conditions representative of adia-batic absorption in refrigeration systems. The limits of applicability of each model have been assessed and the sensitivity of the results to the sheet aperture angle, heat of absorption and initial subcooling has also been tested. For equal initial mass fraction and subcooling, the models indicate that Sherwood number and the rate of absorption in laminar expanding sheets for the LiNO_3-NH_3 solution are always superior to those for the LiBr-H_2O solution.
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An analytical model for laser-plasma interaction during the oblique incidence by an ultrashort ultraintense p-polarized laser on a solid-density plasma is proposed. Both the resonant absorption and not-so-resonant absorption are s...
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An analytical model for laser-plasma interaction during the oblique incidence by an ultrashort ultraintense p-polarized laser on a solid-density plasma is proposed. Both the resonant absorption and not-so-resonant absorption are self-consistently included. Different from the previous theoretical works, the physics of resonant absorption is found to be valid in more general conditions as the steepening of the electron density profile is considered. Even for a relativistic intensity laser, resonant absorption can still exist under certain plasma scale length. For shorter plasma scale length or higher laser intensity, the not-so-resonant absorption tends to be dominant, since the electron density is steepened to a critical level by the ponderomotive force. The laser energy absorption rates for both mechanisms are discussed in detail, and the difference and transition between these two mechanisms are presented.
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