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- Andersson, Per H., et al.
(författare)
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Theoretical study of structural and electronic properties of VHx
- 1998
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 58:9, s. 5230-5235
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Tidskriftsartikel (refereegranskat)abstract
- We have calculated the change in the electronic structure and the distortion of the lattice in vanadium upon hydrogenation from first principles using the full-potential linear muffin-tin-orbital method and the linear augmented plane-wave method in the local-density approximation. The calculated hydrogen induced volume expansions agree with experiment and the change in the c/a ratio is also in good agreement with observations where such are available for single phase VHx. Among several changes in the electronic structure, we note a hybridization of the d band of vanadium with the hydrogen 1s band. We also observe an antiferromagnetically ordered moment at V/Vexp=1.08. The possibility of producing magnetic V by means of hydrogenation in combination with epitaxial growth is suggested.
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| 2. |
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| 3. |
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| 4. |
- Fransson, Jonas, et al.
(författare)
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On the non-orthogonality problem in the description of quantum devices
- 1999
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Ingår i: Physica. B, Condensed matter. - 0921-4526 .- 1873-2135. ; 272:1-4, s. 28-30
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Tidskriftsartikel (refereegranskat)abstract
- An approach which allows to include the corrections from non-orthogonality of electron states in contacts and quantum dots is developed. Comparison of the energy levels and charge distributions of electrons in 1D quantum dot (QD) in equilibrium, obtained within orthogonal (OR) and non-orthogonal representations (NOR), with the exact ones shows that the NOR provides a considerable improvement, for levels below the top of barrier. The approach is extended to non-equilibrium states. A derivation of the tunneling current through a single potential barrier is performed using equations of motion for correlation functions. A formula for transient current derived by means of the diagram technique for Hubbard operators is given for the problem of QD with strongly correlated electrons interacting with electrons in contacts. The non-orthogonality renormalizes the tunneling matrix elements and spectral weights of Green functions.
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| 5. |
- Fundin, Bengt T., et al.
(författare)
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A comprehensive immunofluorescence and lectin binding analysis of intervibrissal fur innervation in the mystacial pad of the rat
- 1997
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Ingår i: Journal of Comparative Neurology. - 0021-9967 .- 1096-9861. ; 385:2, s. 185-206
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Tidskriftsartikel (refereegranskat)abstract
- The innervation of the intervibrissal fur in the mystacial pad of the rat and mouse wasexamined by immunofluorescence with a wide variety of antibodies for neuronal relatedstructural proteins, enzymes, and peptides as well as for lectin binding histofluorescence with Griffonia simplicifolia (GSA). Anti-protein gene product 9.5 (PGP) immunofluorescencelabeled all sets of axons and endings. The innervation in the upper dermis and epidermis wasdistributed through a four tiered dermal plexus. From deep to superficial, the second tier wasthe source of all apparent myelinated mechanorceptors, the third tier of nearly all thepeptidergic and GSA binding innervation, and the fourth tier of nonpeptidergic GSA negativeinnervation (peptide-/GSA-). Three types of mechanoreceptors—Merkel, transverse lanceolate,and longitudinal lanceolate endings—innervated guard hair follicles. All had similarlabeling characteristics for 160 kDa and 200 kDa neurofilament subunits, peripherin,carbonic anhydrase, synaptophysin, and S100. Palisades of longitudinal lanceolate endingswere part of piloneural complexes along circumferentially oriented sets of transverselanceolate endings, peptidergic free nerve endings (FNEs), and peptide-/GSA- FNEs. Thelongitudinal lanceolate endings were the only mechanoreceptors in the mystacial pad that haddetectable calcitonin gene-related peptide. The epidermis contained four types of unmyelinatedendings: simple free nerve endings (FNEs), penicillate endings, cluster endings and bushendings. Only the simple FNEs were clearly peptidergic. Virtually all others were peptide-/GSA-. Each bush ending was actually an intermingled cluster of endings formed by severalunmyelinated axons and occasionally anAd axon. In contrast to the other unmyelinated innervationto the epidermis, bush endings labeled with an antibody against the Schwann cell protein S100. Thenecks and mouths of follicles, as well as superficial vasculature, were innervated by a mixture of unmyelinated peptidergic and/or GSA labeled sensory and sympathetic axons. Small presumptivesweat glands were innervated by three sets of peptidergic axons of which one was immunoreactivefor somatostatin. Potential functions of the various sets of innervation are discussed.
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| 6. |
- Hugosson, Håkan Wilhelm, 1972-, et al.
(författare)
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Theoretical studies of substitutional impurities in molybdenum carbide
- 1999
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 60:22, s. 15123-15130
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Tidskriftsartikel (refereegranskat)abstract
- First-principles full-potential linear muffin-tin orbital calculations have been used to study the effect on the cohesion and electronic structure of cubic δ-MoC when 25% of the carbon is substituted for boron, nitrogen, or oxygen and when 25% of the molybdenum is substituted for niobium, tungsten, or ruthenium. A thorough study of the changes in the electronic structure and the effect of these on the properties of the compounds is made. Special attention is paid to the character (ionic, covalent, or metallic) of the states becoming occupied (or unoccupied) due to the substitution. A study is also made on the properties of the quaternary alloy Mo0.75W0.25C0.75N0.25. This substitution is shown to harden δ-MoC.
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| 7. |
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| 8. |
- Hugosson, Håkan Wilhelm, 1972-, et al.
(författare)
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Theory of phase stabilities and bonding mechanisms in stoichiometric and substoichiometric molybdenum carbide
- 1999
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 86:7, s. 3758-3767
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACTFirst principles, total energy methods have been applied to predict the relative stabilities of the four experimentally verified MoC phases: the cubic δ(NaCl) phase and the three hexagonal γ(WC), η and γ′(TiAs) phases. The effect of vacancies on the relative stability of these four phases was investigated using a model structure with ordered vacancies within the carbon sublattice. For stoichiometric MoC, the γ phase was found to be the most stable followed by γ′, δ, and η, but for substoichiometric MoC0.75,MoC0.75, the order of relative stability was changed and the substoichiometric δ phase was found to have the lowest energy followed by γ′ and γ. A study of the electronic structure revealed vacancy induced peaks in the density of state and the electron density attached to these peaks was analyzed and found to emanate from unscreened Mo–Mo bonds through the carbon vacancy site. Finally, the oxygen stabilization of the γ′ MoC phase was studied.
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| 9. |
- Johansson, Karl H., et al.
(författare)
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Teaching multivariable control using the Quadruple-Tank Process
- 1999
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Ingår i: Proceedings of the 38th IEEE Conference on Decision and Control, 1999. - : IEEE. ; , s. 807-812
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Konferensbidrag (refereegranskat)abstract
- A multivariable laboratory process is presented together with its use in a graduate control course. The process is called the quadruple-tank process and demonstrates a multivariable level control problem. The multivariable zero dynamics of the system can be made both minimum phase and nonminimum phase by simply changing a valve. This makes the quadruple-tank process suitable for illustrating many concepts in linear and nonlinear multivariable control. In the paper some of these are described together with the basic setup of the process. Two computer exercises and one laboratory exercise have been developed as part of a course in multivariable and nonlinear control. These are detailed and some experience from the course is presented.
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| 10. |
- Rice, Frank L, et al.
(författare)
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A comprehensive immunofluorescence and lectin binding analysis of vibrissal follicle sinus complex innervation in the mystacial pad of the rat
- 1997
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Ingår i: Journal of Comparative Neurology. - 0021-9967 .- 1096-9861. ; 385:2, s. 149-184
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Tidskriftsartikel (refereegranskat)abstract
- The innervation of the vibrissal follicle sinus complexes (FSCs) in the mystacial pad of the rat was examined by lectin binding histofluorescence with the B subunit of Griffonia simplicifolia (GSA) and by immunofluorescence with a wide variety of antibodies for neuronal related structural proteins, enzymes, and peptides. Only anti-protein gene product 9.5 labeled all sets of innervation. Several types of mechanoreceptors were distributed to specific different targets by medium to large caliber myelinated axons. All were positive for 200 kDa neurofilament subunit, peripherin, and carbonic anhydrase. Their endings expressed synaptophysin. Labeling for the 160 kDa neurofilament subunit, calbindin, and parvalbumin varied. Anti-Schwann cell protein S100 was completely co-extensive with the axons, terminal arbors, and endings of the mechanoreceptor afferents including Merkel innervation. At least 15 different sets of unmyelinated innervation were evident based upon distribution and labeling characteristics. They consisted of four basic types: 1) peptidergic; 2) GSA binding; 3) peptidergic and GSA binding; and 4) nonpeptidergic and GSA negative (peptide-/GSA-). Previous studies had not revealed that several major sets of unmyelinated innervation were peptide-/GSA-. The unmyelinated innervation had detectable peripherin but not 160 kDa or 200 kDa neurofilament subunits. GSA-positive axons uniquely lacked anti-S100 immunoreactivity. The dense circumferentially oriented unmyelinated innervation of the inner conical body contained major sets of peptide-/GSA- and GSA innervation as well as a smaller peptidergic GSA component. A small contingent of sympathetic and possibly parasympathetic innervation was affiliated with microvasculature in the FSCs. This study confirms and refutes some previous hypotheses about biochemical and morphological relationships between peripheral innervation and sensory ganglion cells.
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