| 1. |
- CHAKAROV, DV, et al.
(author)
-
PHOTOSTIMULATED DESORPTION OF METAL ADATOMS - POTASSIUM ON GRAPHITE
- 1994
-
In: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 311:3, s. L724-L730
-
Journal article (peer-reviewed)abstract
- Photodesorption is observed of single K atoms from a graphite surface covered with less than 1 monolayer of potassium. The desorption cross section has a threshold at homegaBAR almost-equal-to 3 eV and a maximum at homega(max)BAR almost-equal-to 4.9 eV. Polarization measurements indicate a substrate-mediated mechanism. The coverage dependence suggests that only the ionic 2D, K-phase is photoactive. The proposed mechanism includes attachment of hot electrons, photoexcited in the bulk, to the K4s adsorbate resonance of energy E(res). The band structure of graphite causes a narrow energy distribution of hot electrons, which yields homega(max)BAR almost-equal-to 2E(res).
|
|
| 2. |
- Chakarov, D V, et al.
(author)
-
Photos induced desorption and intercalation of potassium atoms deposited on graphite(0001)
- 1996
-
In: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 106, s. 186-192
-
Journal article (peer-reviewed)abstract
- In addition to the photodesorption phenomenon previously observed for single K atoms from a graphite surface covered with a monolayer of potassium we present new results related to the photon stimulated interaction of potassium with graphite, which concerns alternative routes for energy relaxation of the photo excited K adatoms: photoinduced intercalation. The desorption yield has a threshold at h omega approximate to 3 eV and a maximum at h omega(max) approximate to 4.9 eV, Polarization measurements indicate a substrate-mediated mechanism. The coverage dependence suggests that only the ionic 2D, K-phase is photo active. The proposed mechanism includes attachment of photo-generated hot electrons to the K 4s adsorbate resonance of energy E(res). Assuming an analogous excitation process we discuss different mechanisms for the K photo intercalation and possible applications of the photon stimulated doping of carboneous materials at low temperature.
|
|
| 3. |
- Hellsing, B, et al.
(author)
-
Photoinduced desorption of potassium atoms from a two dimensional overlayer on graphite
- 1997
-
In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 106:3, s. 982-1002
-
Journal article (peer-reviewed)abstract
- We present an experimental and theoretical investigation of K atom desorption from the basal plane of graphite at 83 K induced by low energy photons (3-6 eV). The 2D potassium overlayer is characterized by low energy electron diffraction (LEED), high-resolution electron energy loss spectroscopy (HREELS), thermal desorption spectroscopy (TDS), and work function measurements. At monolayer coverage (5.2 x 10(14) atoms cm(-2)), the dependence of the cross section on photon energy has a threshold at (h) over bar omega approximate to 3.0 eV and rises up to a maximum of 1.8 +/- 0.4 x 10(-20) cm(2) at 4.8 eV. The coverage dependence of the photoyield reflects the existence of two phases of adsorbed K, dilute ionized photo-active and close-packed photo-neutral, respectively. The observed photodesorption is a single-photon, nonthermal event, consistent with a substrate-mediated mechanism. The desorption results from attachment of optically excited hot electrons to the empty 4s state of ionized potassium. The theory predicts in this case a Gaussian line shape of the photoyield vs photon energy. Fitting the model parameters to the experimental data, we determine (i) the energy and slope of the excited state potential energy curve, and (ii) the position and width of the potassium-induced 4s resonance. The present findings combined with other available data for potassium on graphite are used to construct 1D potential energy curves along the surface normal for K+ and K-0. The calculated cross sections for s- and p-polarized Light are in qualitative agreement with the measurements. (C) 1997 American Institute of Physics.
|
|
| 4. |
- Hellsing, B, et al.
(author)
-
Photoinduced desorption of potassium atoms from graphite
- 1996
-
In: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 363:1-3, s. 247-251
-
Journal article (peer-reviewed)abstract
- We present an experimental and theoretical investigation of desorption of potassium atoms from the basal plane of graphite induced by photons with energies from 2 to 6 eV. The intensity of the photon flux employed in the measurements is low, and the observed photodesorption is a single-photon, non-thermal event. At monolayer coverage the photon-energy dependence of the cross section has a maximum at 4.8 eV. The experimental observations are interpreted in terms of a hot carrier mechanism, which involves attachment of optically excited substrate hot electrons to the empty 4s state of ionized potassium, and then desorption. The theory predicts a Gaussian line shape of the photoyield versus photon energy. Fitting the model parameters to the experimental data, we determine: (i) the potential energy for Gr + K+ and Gr + K-0; and (ii) the position (2.4 eV above the Fermi level) and width (0.15 eV) of the potassium 4s resonance, which is in good agreement with independent experimental observations.
|
|
| 5. |
- Graf, W, et al.
(author)
-
The influence of early postoperative intraperitoneal chemotherapy on human wound healing.
- 1994
-
In: Journal of Surgical Research. - : Elsevier BV. - 0022-4804 .- 1095-8673. ; 57:3, s. 394-400
-
Journal article (peer-reviewed)abstract
- Cell ingrowth, hydroxyproline accumulation, and mRNA expression of collagen I were measured in two polytetrafluoroethylene grafts implanted subcutaneously at the time of colorectal cancer surgery to evaluate the influence of early postoperative chemotherapy on human wound healing. Eleven patients treated with intraperitoneal 5-fluorouracil and intravenous folinic acid Days 1-6 after operation were compared with 15 patients who underwent surgery alone. At 1 week, chemotherapy-treated patients had accumulated less hydroxyproline (mean 0.35 +/- 0.33 micrograms/cm) compared with untreated patients (mean 0.73 +/- 0.37 micrograms/cm, P < 0.05). By 2 weeks, the hydroxyproline content had increased sixfold in the chemotherapy group (P < 0.01) and threefold in the nonchemotherapy group (P < 0.01) and there was no difference between the groups. Cell and connective tissue ingrowth and total RNA content did not differ between the groups at any point in time, but at 1 week the mRNA expression of collagen I was higher in the chemotherapy group (P < 0.05). These results indicate that collagen accumulation in human subjects is reduced during a short course of postoperative chemotherapy and normalizes after the end of treatment.
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
- Hellsing, Maja S., et al.
(author)
-
Structure of flocs of latex particles formed by addition of protein from Moringa seeds
- 2014
-
In: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 460, s. 460-467
-
Journal article (peer-reviewed)abstract
- Proteins extracted from the seeds of Moringa trees are effective flocculents for particles dispersed in water and are attractive as a natural and sustainable product for use in water purification. Studies with a model system consisting of polystyrene latex particles have shown that the protein adsorbs to the surface and causes flocculation as unusually dense aggregates. Small-angle neutron scattering that exploits contrast matching of deuterated latex particles dispersed in D2O to highlight bound protein has shown that the adsorbed amount reaches about 3 mg m(-2). The particles form very compact flocs that are characterized by fractal dimensions that approach the theoretical maximum of 3. Ultra small-angle neutron scattering allows these flocs to be characterized for a range of particle and protein concentrations. Proteins from two species of Moringa trees were investigated. The protein from Moringa stenopetala seeds gave rise to slightly lower fractal dimensions compared to Moringa oleifera, but still much larger than values observed for conventional ionic or polymeric flocculents that are in the range 1.75-2.3. Compact flocs are desirable for efficient separation of impurities and dewatering of sludge as well as other applications. A trend of increasing fractal dimension with particle concentration was observed when M. stenopetala seed protein was used and this resembles the behaviour predicted in Brownian dynamics simulation of flocculation. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.
|
|
| 9. |
|
|
| 10. |
- Lou, L, et al.
(author)
-
Electronic structure and kinetics of K on graphite
- 2000
-
In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 112:10, s. 4788-4796
-
Journal article (peer-reviewed)abstract
- The K/graphite adsorption system is studied in a cluster model using ab initio density-functional methods. From the investigation of the potential energy surface a lower bound for the potassium atom binding energy 1.5 eV is obtained, and a surface diffusion barrier of 0.2 eV. To simulate experimentally reported thermal desorption spectra, a two-phase kinetic model is investigated and a desorption energy of 1 eV is found. The thermally activated surface diffusion of K atoms leads to intercalation at defects or steps, which is followed by desorption when further heating the sample. A normal mode analysis yields a K-graphite in-phase and out-of-phase vibrational mode with an energy split of 8 meV, which indicates a relatively strong dynamical coupling between the adsorbed K atom and the graphite substrate. The calculated electron density distribution is verified by an accurate reproduction of the measured dipole moment. From a projected density of state analysis we find a K 4s and an antibonding K 4p resonance located slightly above and 2.6 eV above the Fermi level, respectively. The location of the K 4s resonance, with a lower occupied tail, is consistent with an incomplete charge transfer, and the location of the K 4p resonance is consistent with a proposed hot-electron model to explain recent photodesorption data. The new assignment of the K-induced states near the Fermi level resolves previous apparent discrepancies of the charge state of the dispersed K atom. (C) 2000 American Institute of Physics. [S0021-9606(00)70310-2].
|
|
| 11. |
- Xu, Yu, 1996, et al.
(author)
-
Improved efficiency with adaptive front and rear axle independently driven powertrain and disconnect functionality
- 2023
-
In: Transportation Engineering. - 2666-691X. ; 13
-
Journal article (peer-reviewed)abstract
- Front and rear axle independently driven (FRID) powertrains are becoming a popular solution for electric vehicles (EVs) due to torque distribution capability which can enhance powertrain energy efficiency. Typically, permanent magnet synchronous machines (PMSMs) are used for FRID powertrains due to their high torque, and power density. However, the drive-cycle efficiency of FRID powertrains with PMSMs is typically reduced in comparison to single motor drives. This is due to the unwanted no-load losses of PMSMs in the field weakening region. To overcome this drawback of PMSM FRIDs, this paper proposes an adaptive front- and rear-axle independently driven (AFRID) powertrain, utilizing two dog clutches, so that the powertrain can be operated in different modes (rear, front, and all-wheel drive) by adaptively connecting and disconnecting the front and/or rear electric drive unit (EDU). A rule-based mode selection strategy is developed to utilize the flexibility of different powertrain operating modes of the powertrain for maximizing the energy efficiency of the EDU. The simulation results show that the suggested AFRID powertrain, in comparison to a common FRID powertrain, can improve the WLTC drive-cycle consumption from 22.17 kWhh to 20.50 kWhh per 100 km. Based on the route and road-load information, the energy-saving potential of the AFRID powertrain can be further improved to 20.37 kWhh per 100 km by a suggested predictive mode selection strategy, achieving an optimal mode selection.
|
|
