| 1. |
- Edelson, R. A., et al.
(author)
-
Multiwavelength observations of short-timescale variability in NGC 4151. IV. Analysis of multiwavelength continuum variability
- 1996
-
In: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 470:1, s. 364-377377
-
Journal article (peer-reviewed)abstract
- For pt.III see ibid., vol.470, no.1, p.349-63 (1996). Combines data from the three preceding papers in order to analyze the multi wave-band variability and spectral energy distribution of the Seyfert 1 galaxy NGC 4151 during the 1993 December monitoring campaign. The source, which was near its peak historical brightness, showed strong, correlated variability at X-ray, ultraviolet, and optical wavelengths. The strongest variations were seen in medium-energy (~1.5 keV) X-rays, with a normalized variability amplitude (NVA) of 24%. Weaker (NVA=6%) variations (uncorrelated with those at lower energies) were seen at soft gamma-ray energies of ~100 keV. No significant variability was seen in softer (0.1-1 keV) X-ray bands. In the ultraviolet/optical regime, the NVA decreased from 9% to 1% as the wavelength increased from 1275 to 6900 Aring. These data do not probe extreme ultraviolet (1200 Aring to 0.1 keV) or hard X-ray (250 keV) variability. The phase differences between variations in different bands were consistent with zero lag, with upper limits of lsim0.15 day between 1275 Aring and the other ultraviolet bands, lsim0.3 day between 1275 Aring and 1.5 keV, and lsim1 day between 1275 and 5125 Aring. These tight limits represent more than an order of magnitude improvement over those determined in previous multi-wave-band AGN monitoring campaigns. The ultraviolet fluctuation power spectra showed no evidence for periodicity, but were instead well fitted with a very steep, red power law (ales-2.5)
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| 2. |
- Crenshaw, D. M., et al.
(author)
-
Multiwavelength observations of short-timescale variability in NGC 4151. I. Ultraviolet observations
- 1996
-
In: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 470:1, s. 322-335335
-
Journal article (peer-reviewed)abstract
- Presents the results of an intensive ultraviolet monitoring campaign on the Seyfert 1 galaxy NGC 4151, as part of an effort to study its short-timescale variability over a broad range in wavelength. The nucleus of NGC 4151 was observed continuously with the International Ultraviolet Explorer for 9.3 days, yielding a pair of LWP and SWP spectra every ~70 minutes, and during 4 hr periods for 4 days prior to and 5 days after the continuous-monitoring period. The sampling frequency of the observations is an order of magnitude higher than that of any previous UV monitoring campaign on a Seyfert galaxy. The continuum fluxes in bands from 1275 to 2688 Aring went through four significant and well-defined ldquoeventsrdquo of duration 2-3 days during the continuous-monitoring period. The authors find that the amplitudes of the continuum variations decrease with increasing wavelength, which extends a general trend for this and other Seyfert galaxies to smaller timescales (i.e., a few days). The continuum variations in all the UV bands are simultaneous to within an accuracy of ~0.15 days, providing a strict constraint on continuum models. The emission-line light curves show only one major event during the continuous monitoring (a slow rise followed by a shallow dip) and do not correlate well with continuum light curves over the short duration of the campaign, because the timescale for continuum variations is apparently smaller than the response times of the emission lines
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| 3. |
- Akselsson, Roland, et al.
(author)
-
Multidisciplinary Research on Integration of Human Factors and Production Concepts such as TQM - A Participatory Discussion Session
- 1999
-
In: Proceedings of the Conference on TQM and Human Factors. - 9172195207 ; 2, s. 439-448
-
Conference paper (peer-reviewed)abstract
- A discussion session where the conference participants are invited to participate is planned. One topic for the session is to discuss experiences of multidisciplinary research on integration of human factors and different production concepts applied in change processes within Swedish companies. An important question that the discussion will focus on is: How to get high quality in multidisciplinary research? Another topic is to discuss how people from different disciplines in the companies interact with each other and with the researchers. Researchers from the centre Change@Work at Lund University in Sweden will present some of their experiences from several years of multidisciplinary research in companies. As a background the research questions within Change@Work are presented below. Discussions during the workshop will be performed according to methods used by the researchers in their research in the companies. All discussion will be documented and later sent to all workshop participants.
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| 4. |
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| 5. |
- Birznieks, Ingvars, et al.
(author)
-
Mechanisms for force adjustments to unpredictable frictional changes at individual digits during two-fingered manipulation.
- 1998
-
In: Journal of Neurophysiology. - 0022-3077 .- 1522-1598. ; 80:4, s. 1989-2002
-
Journal article (peer-reviewed)abstract
- Previous studies on adaptation of fingertip forces to local friction at individual digit-object interfaces largely focused on static phases of manipulative tasks in which humans could rely on anticipatory control based on the friction in previous trials. Here we instead analyze mechanisms underlying this adaptation after unpredictable changes in local friction between consecutive trials. With the tips of the right index and middle fingers or the right and left index fingers, subjects restrained a manipulandum whose horizontal contact surfaces were located side by side. At unpredictable moments a tangential force was applied to the contact surfaces in the distal direction at 16 N/s to a plateau at 4 N. The subjects were free to use any combination of normal and tangential forces at the two fingers, but the sum of the tangential forces had to counterbalance the imposed load. The contact surface of the right index finger was fine-grained sandpaper, whereas that of the cooperating finger was changed between sandpaper and the more slippery rayon. The load increase automatically triggered normal force responses at both fingers. When a finger contacted rayon, subjects allowed slips to occur at this finger during the load force increase instead of elevating the normal force. These slips accounted for a partitioning of the load force between the digits that resulted in an adequate adjustment of the normal:tangential force ratios to the local friction at each digit. This mechanism required a fine control of the normal forces. Although the normal force at the more slippery surface had to be comparatively low to allow slippage, the normal forces applied by the nonslipping digit at the same time had to be high enough to prevent loss of the manipulandum. The frictional changes influenced the normal forces applied before the load ramp as well as the size of the triggered normal force responses similarly at both fingers, that is, with rayon at one contact surface the normal forces increased at both fingers. Thus to independently adapt fingertip forces to the local friction the normal forces were controlled at an interdigital level by using sensory information from both engaged digits. Furthermore, subjects used both short- and long-term anticipatory mechanisms in a manner consistent with the notion that the central nervous system (CNS) entertains internal models of relevant object and task properties during manipulation.
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| 6. |
- Burstedt, Magnus K, et al.
(author)
-
Control of forces applied by individual fingers engaged in restraint of an active object.
- 1997
-
In: Journal of Neurophysiology. - 0022-3077 .- 1522-1598. ; 78:1, s. 117-128
-
Journal article (peer-reviewed)abstract
- We investigated the coordination of fingertip forces in subjects who used the tips of two fingers to restrain an instrumented manipulandum with horizontally oriented grip surfaces. The grip surfaces were subjected to tangential pulling forces in the distal direction in relation to the fingers. The subjects used either the right index and middle fingers (unimanual grasp) or both index fingers (bimanual grasp) to restrain the manipulandum. To change the frictional condition at the digit-object interfaces, either both grip surfaces were covered with sandpaper or one was covered with sandpaper and the other with rayon. The forces applied normally and tangentially to the grip surfaces were measured separately at each plate along with the position of the plates. Subjects could have performed the present task successfully with many different force distributions between the digits. However, they partitioned the load in a manner that reflected the frictional condition at the local digit-object interfaces. When both digits contacted sandpaper, they typically partitioned the load symmetrically, but when one digit made contact with rayon and the other with sandpaper, the digit contacting the less slippery material (sandpaper) took up a larger part of the load. The normal forces were also influenced by the frictional condition, but they reflected the average friction at the two contact sites rather than the local friction. That is, when friction was low at one of the digit-object interfaces, only the applied normal forces increased at both digits. Thus sensory information related to the local frictional condition at the respective digit-object interfaces controlled the normal force at both digits. The normal:tangential force ratio at each digit appeared to be a controlled variable. It was adjusted independently at each digit to the minimum ratio required to prevent frictional slippage, keeping an adequate safety margin against slippage. This was accomplished by the scaling of the normal forces to the average friction and by partitioning of the load according to frictional differences between the digit-object interfaces. In conclusion, by adjusting the normal:tangential force ratios to the local frictional condition, subjects avoided excessive normal forces at the individual digit-object interfaces, and by partitioning the load according the frictional difference, subjects avoided high normal forces. Thus the local frictional condition at the separate digit-object interfaces is one factor that can strongly influence the distribution of forces across digits engaged in a manipulative act.
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| 7. |
- Burstedt, Magnus K, et al.
(author)
-
Coordination of fingertip forces during human manipulation can emerge from independent neural networks controlling each engaged digit.
- 1997
-
In: Experimental Brain Research. - : Springer Science and Business Media LLC. - 0014-4819 .- 1432-1106. ; 117:1, s. 67-79
-
Journal article (peer-reviewed)abstract
- We investigated the coordination of fingertip forces in subjects who lifted an object (i) using the index finger and thumb of their right hand, (ii) using their left and right index fingers, and (iii) cooperatively with another subject using the right index finger. The forces applied normal and tangential to the two parallel grip surfaces of the test object and the vertical movement of the object were recorded. The friction between the object and the digits was varied independently at each surface between blocks of trials by changing the materials covering the grip surfaces. The object's weight and surface materials were held constant across consecutive trials. The performance was remarkably similar whether the task was shared by two subjects or carried out unimanually or bimanually by a single subject. The local friction was the main factor determining the normal:tangential force ratio employed at each digit-object interface. Irrespective of grasp configuration, the subjects adapted the force ratios to the local frictional conditions such that they maintained adequate safety margins against slips at each of the engaged digits during the various phases of the lifting task. Importantly, the observed force adjustments were not obligatory mechanical consequences of the task. In all three grasp configurations an incidental slip at one of the digits elicited a normal force increase at both engaged digits such that the normal:tangential force ratio was restored at the non-slipping digit and increased at the slipping digit. The initial development of the fingertip forces prior to object lift-off revealed that the subjects employed digit-specific anticipatory mechanisms using weight and frictional experiences in the previous trial. Because grasp stability was accomplished in a similar manner whether the task was carried out by one subject or cooperatively by two subjects, it was concluded that anticipatory adjustments of the fingertip forces can emerge from the action of anatomically independent neural networks controlling each engaged digit. In contrast, important aspects of the temporal coordination of the digits was organized by a "higher level" sensory-based control that influenced both digits. In lifts by single subjects this control was mast probably based on tactile and visual input and on communication between neural control mechanisms associated with each digit. In the two-subject grasp configuration this synchronization information was based on auditory and visual cues.
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| 8. |
- Edin, Benoni B, et al.
(author)
-
Independent control of human finger-tip forces at individual digits during precision lifting.
- 1992
-
In: Journal of Physiology. - 0022-3751 .- 1469-7793. ; 450, s. 547-64
-
Journal article (peer-reviewed)abstract
- 1. Subjects lifted an object with two parallel vertical grip surfaces and a low centre of gravity using the precision grip between the tips of the thumb and index finger. The friction between the object and the digits was varied independently at each digit by changing the contact surfaces between lifts. 2. With equal frictional conditions at the two grip surfaces, the finger-tip forces were about equal at the two digits, i.e. similar vertical lifting forces and grip forces were used. With different frictions, the digit touching the most slippery surface exerted less vertical lifting force than the digit in contact with the rougher surface. Thus, the safety margins against slips were similar at the two digits whether they made contact with surfaces of similar or different friction. 3. During digital nerve block, large and variable safety margins were employed, i.e. the finger-tip forces did not reflect the surface conditions. Slips occurred more frequently than under normal conditions (14% of all trials with nerve block, <5% during normal conditions), and they only occasionally elicited compensatory adjustments of the finger-tip forces and then at prolonged latencies. 4. The partitioning of the vertical lifting force between the digits was thus dependent on digital afferent inputs and resulted from active automatic regulation and not just from the mechanics of the task. 5. The safety margin employed at a particular digit was mainly determined by the frictional conditions encountered by the digit, and to a lesser degree by the surface condition at the same digit in the previous lift (anticipatory control), but was barely influenced by the surface condition at the other digit. 6. It was concluded that the finger-tip forces were independently controlled for each digit according to a 'non-slip strategy'. The findings suggest that the force distribution among the digits represents a digit-specific lower-level neural control establishing a stable grasp. This control relies on digit-specific afferent inputs and somatosensory memory information. It is apparently subordinated to a higher-level control that is related to the total vertical lifting and normal forces required by the lifting task and the relevant physical properties of the manipulated object.
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| 9. |
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| 10. |
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| 11. |
- Hansson, Lars, et al.
(author)
-
Annie, a Tool for Integrating Ergonomics in the Design of Car Interiors
- 1999
-
Conference paper (other academic/artistic)abstract
- An example of a result from a long-term cooperation with Lund University (together with professor Roland Axelsson at the Department for Work Environment) there some of the authors. (Engström) gained extensive grants (Wallenberg Stifelsen regarding equipment as well as other founding from e.g. the Swedish Work Environment Found).
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| 12. |
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| 13. |
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| 14. |
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| 15. |
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| 16. |
- Lindh, Roland, 1958-, et al.
(author)
-
Ab Initio Study of the Bergman Reaction : The Autoaromatization of Hex-3-ene-1,5-diyne
- 1994
-
In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 116:11, s. 4963-4969
-
Journal article (peer-reviewed)abstract
- The Bergman reaction of the hex-3-ene-1,5-diyne molecule (enediyne) to form the singlet biradical p-benzyne structure under ring closure has been studied by ab initio methods. The complete active space (CAS) SCF method was used for geometry optimizations at five points along the reaction path of the Bergman reaction. Subsequent calculations using the multireference second-order perturbation theory based on a CASSCF reference (CASPT2) established the energetics along the reaction path, especially for the reactant, transition state, and product. The energetics were further corrected for zero point vibrational energy at the CASSCF level of theory. The study incorporated four different basis sets: a double-zeta plus polarization (DZP), a triple-zeta plus double polarization (TZ2P), and two different average atomic natural orbital (ANO) basis sets. The study predicts the energy barrier to ring closure to be 25.0 +/- 3.1 kcal/mol and the enthalpy of reaction to be 4.9 +/- 3.2 kcal/mol. The latter value deviates significantly from the value estimated on the basis of group additivity and the Born-Haber cycle. The enediyne moiety is the main functional group of a new class of anticancer agents. The activation of the Bergman reaction in these drugs has been argued to be due to a small structural change in the terminal-terminal carbon distance of about -0.5 Angstrom originating from an epoxide conversion in the rest of the drug. The present study indicates that such a structural change is not sufficient for the Bergman autoaromatization to proceed at an appreciable rate. A new reaction path involving no biradical formation, resulting in the same products, is suggested.
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| 17. |
- Lindh, Roland, 1958-, et al.
(author)
-
Accurate abinitio calculations of the quadrupole-moment of acetylene : a combined study of basis set, correlation, and vibrational effects
- 1991
-
In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 94:6, s. 4356-4368
-
Journal article (peer-reviewed)abstract
- The quadrupole moment of acetylene has been studied at the multiconfiguration self-consistent field (MCSCF) and multireference single and double configuration interaction (MRSDCI) level of theory. At the MCSCF level the pi-CI complete active space SCF (CASSCF) and the valence-CI CASSCF were employed. The subsequent MRSDCI calculations were continued until the reference space included all configuration state functions (CSFs) of the MCSCF wave function with a coefficient larger than 0.01 [MRSDCI(0.01)]. The higher level basis sets in this study were all based on van Duijneveldt’s C(13s 8p) and H(6s) and extensions of that basis set. The study shows in a consistent way that both the one- and n-particle spaces are saturated at the highest level of theory. The study has revealed that in addition to the well known increase of the quadrupole moment due to the inclusion of polarizing functions in the basis (typically 0.20 a.u.), the inclusion of electronic correlation in the model wave function as well as vibrational corrections will decrease the quadrupole moment significantly more, -0.66, -0.49, and -0.36 a.u., for the correlation correction and zero-point correction for HCCH and DCCD, respectively. The most accurate computations predict the quadrupole moment of HCCH, including zero-point correction, to be 4.29 +/- 0.12 a.u., which discriminates the experimental estimates of 4.03 +/- 0.30, 4.28 +/- 0.30, and 4.57 +/- 0.30 a.u. (the first being the favored value). The quadrupole moment of DCCD is computed to 4.42 +/- 0.10 a.u. In the study it was observed that in contradiction to previous experiences the use of the model equilibrium geometries rather than the experimental geometry gives a smoother convergence as the level of theory is increased. The effects of basis set quality and electron correlation on the quadrupole moment are studied in detail. These effects are analyzed with reference to the redistribution of the electronic charge.
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| 18. |
- Lindh, Roland, 1958-, et al.
(author)
-
Research Article Extended ab Initio and Theoretical Thermodynamics Studies of the Bergman Reaction and the Energy Splitting of the Singlet o-, m-, and p-Benzynes
- 1995
-
In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 117:27, s. 7186-7194
-
Journal article (peer-reviewed)abstract
- The autoaromatization of (Z)-hex-3-ene-1,5-diyne to the singlet biradical p-benzyne has been reinvestigated by state of the art ab initio methods. Previous CCSD(T)/6-31G(d,p) and CASPT2[0]/ANO[C(5s4p2dlf)/H(3s2p)] calculations estimated the reaction heat at 298 K to be 8-10 and 3.9 +/- 3.2 kcal/mol, respectively. Recent NO- and oxygen-dependent trapping experiments and collision-induced dissociation threshold energy experiments estimate the heat of reaction to be 8.5 +/- 1.0 kcal/mol at 470 K (corrected to 9.5 +/- 1.0 kcal/mol at 298 K) and 8.4 +/- 3.0 kcal/mol at 298 K, respectively. New theoretical estimates at 298 K predict the values at the basis set Limit for the CCSD(T) and CASPT2[gl] methods to be 12.7 +/- 2.0 and 5.4 +/- 2.0 kcal/mol, respectively. The experimentally predicted electronic contribution to the heat of activation is 28.6 kcal/mol. This can be compared with 25.5 and 29.8 kcal/mol from the CASPT2[gl] and the CCSD(T) methods, respectively. The new study has a much larger one-particle basis set for the CCSD(T) method as compared to earlier studies. For the CASPT2 investigation the better suited CASPT2[gl] approximation is utilized. The original CASPT2 method, CASPT2[0], systematically favors open-shell systems relative to closed-shell systems. This was previously corrected empirically. The current study shows that the energy difference between CCSD(T) and CASPT2[gl] at the basis set limit is estimated to be 7 +/- 2 kcal/mol. The study also demonstrates that the estimated heat of reaction is very sensitive to the quality of the basis set. In particular CCSD(T)/6-31G(d,p) approach underestimates the basis set limit of the enthalpy by approximately 5 kcal/mol. Furthermore, the relative energies of the p-, m-, and o-benzynes are computed at the CASPT2[gl] and CCSD(T) levels of theory. These results help to explain the discrepancy between the two methods in the case of the Bergman reaction. The deficiency of the CASPT2 method is mainly attributed to the approximate way in which the dynamic correlation is included by perturbation theory. A similar sized error is attributed to the CCSD(T) method due to the approximate way in which near degeneracy effects are included. This combined CCSD(T) and CASPT2[gl] study indicates that the most recent experimental value of the p-benzyne-o-benzyne energy splitting is overestimated.
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| 19. |
- Lindh, Roland, 1958-, et al.
(author)
-
The reduced multiplication scheme of the Rys quadrature and new recurrence relations for auxiliary function based two‐electron integral evaluation
- 1991
-
In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 95:8, s. 5889-5897
-
Journal article (peer-reviewed)abstract
- The reduced multiplication scheme of the Rys quadrature is presented. The method is based on new ways in which the Rys quadrature can be developed if it is implemented together with the transfer equation applied to the contracted integrals. In parallel to the new scheme of the Rys quadrature improvements are suggested to the auxiliary function based algorithms. The two new methods have very favorable theoretical floating point operation (FLOP) counts as compared to other methods. It is noted that the only significant difference in performance of the two new methods is due to the vectorizability of the presented algorithms. In order to exhibit this, both methods were implemented in the integral program SEWARD. Timings are presented for comparisons with other implementations. Finally, it is demonstrated how the transfer equation in connection with the use of spherical harmonic Gaussians offers a very attractive path to compute the two-electron integrals of such basis functions. It is demonstrated both theoretically and with actual performance that the use of spherical harmonic Gaussians offers a clear advantage over the traditional evaluation of the two-electron integrals in the Cartesian Gaussian basis.
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| 20. |
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| 21. |
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| 22. |
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| 23. |
- Stenutz, Roland, 1968-
(author)
-
The structure and conformation of saccharides determined by experiment and simulation
- 1997
-
Doctoral thesis (other academic/artistic)abstract
- A computer program, CASPER, for sequence determination of oligosaccharides and regular polysaccharides using NMR-data, has been extended to support multiply branched structures. The program has been modified to allow the use of incomplete experimental data since spectral overlap can be a problem even at high fields. The resulting program was tested and used in the structure determination of the capsular polysaccharide from Klebsiella type K52.Four carboxyethyl-substituted sugars, methyl 4-O-[(R)- and (S)-1-carboxyethyl]-a-L-rhamnopyranoside and methyl 6-O-[(R)- and (S)-1-carboxyethyl]-a-D-galactopyranoside have been synthesized. The conformational properties of the latter two have been investigated by both NMR spectroscopy and molecular modelling studies. For the NMR-studies stereospecifically deuterated compounds were prepared.
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| 24. |
- Wilhelmsson, B, et al.
(author)
-
Modeling multicylinder paper drying - Validation of a new simulation program
- 1996
-
In: Tappi Journal. - 0734-1415. ; 79:4, s. 157-167
-
Journal article (peer-reviewed)abstract
- A mathematical model was developed for the drying of paper in a multi-cylinder drying section. The model is based on the unsteady state, one-dimensional heat conduction equation, which is applied to both the cylinder shell and the paper web. No internal mass transfer phenomena were modeled explicitly. Great emphasis ws placed on finding the proper heat and mass transfer coefficients that are integral parts of the boundary conditions. Based on the mathematical model, a simulation program was developed. In order to verify the simulation output nine different industrial paper dryers were surveyed. These produced different paper grades: newsprint, fine paper, fluting, and paperboard. During a survey, temperatures and moisture contents of both paper and drying air as well as the temperature of the cylinder surface were measured. Seven of the nine cases involved steady-state production, whereas in the remaining two cases the basis weight and machine speed were altered considerably. The model applied just as well to lighter paper grades such as newsprint as to heavier grades such as paperboard. The data predicted by the program compared favorably with the measured data in all nine cases.
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| 25. |
- Wilhelmsson, B, et al.
(author)
-
Simulation models of multi-cylinder paper drying
- 1993
-
In: Drying Technology. - : Informa UK Limited. - 1532-2300 .- 0737-3937. ; 11:6, s. 1177-1203
-
Journal article (peer-reviewed)abstract
- The literature on simulation models for multi-cylinder paper dryers is surveyed, 20 such models being reviewed. Models for intraweb heat and mass transfer are treated extensively, a separate chapter being devoted to them. In some of the models the specific physical transfer phenomena are modelled in detail, whereas in other models a more macroscopic approach is adopted. Normally the latter approach requires the incorporation of a large number of empirical constants into the model to describe the complicated heat and mass transfer processes involved and to obtain a reasonable agreement between the model and the measured data. In order to develop the simulation models further without use of an inordinately large number of empirical constants, the different physical phenomena which occur in the dryer must be modelled in greater detail, based both on fundamental theory and on empirical correlations.
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