Institutional change and the evolution of the regulatory state: evidence from the Swiss case

This article examines institutional change in a case that was expected to be particularly resilient but showed considerable structural transformation: the institutionalization of the regulatory state in Switzerland. This process is illustrated through the establishment of independent regulatory agencies (IRAs) in four areas: banking and finance; telecommunications; electricity; and competition. The theoretical framework developed by Streeck, Thelen and Mahoney is used to explore hypotheses about the modes of institutional change, with the methodology of diachronic within-case study. Results confirm only partially the expectations, pointing to layering and displacement as the prevalent modes of change. The concluding part discusses the type and the direction of change as additional explanatory factors.

Real-time MR imaging of myocardial regional function using strain-encoding (SENC) with tissue through-plane motion tracking.

PURPOSE: To implement real-time myocardial strain-encoding (SENC) imaging in combination with tracking the tissue displacement in the through-plane direction. MATERIALS AND METHODS: SENC imaging was combined with the slice-following technique by implementing three-dimensional (3D) selective excitation. Certain adjustments were implemented to reduce scan time to one heartbeat. A total of 10 volunteers and five pigs were scanned on a 3T MRI scanner. Spatial modulation of magnetization (SPAMM)-tagged images were acquired on planes orthogonal to the SENC planes for comparison. Myocardial infarction (MI) was induced in two pigs and the resulting SENC images were compared to standard delayed-enhancement (DE) images. RESULTS: The strain values computed from SENC imaging with slice-following showed significant difference from those acquired without slice-following, especially during systole (P < 0.01). The strain curves computed from the SENC images with and without slice-following were similar to those computed from the orthogonal SPAMM images, with and without, respectively, tracking the tag line displacement in the strain direction. The resulting SENC images showed good agreement with the DE images in identifying MI in infarcted pigs. CONCLUSION: Correction of through-plane motion in real-time cardiac functional imaging is feasible using slice-following. The strain measurements are more accurate than conventional SENC measurements in humans and animals, as validated with conventional MRI tagging.

Smooth transition or permanent exit? Evidence on job prospects of displaced industrial workers

This article examines the job prospects of displaced industrial workers in Switzerland. Based on a survey of 1,203 workers who were dismissed after their manufacturing plants closed down, we analyse the determinants of re-employment, the sector of re-employment and the change in wages. Two years after displacement, a majority of workers were back in employment: 69% were re-employed, 17% un-employed and 11% retired. Amongst re-employed workers, two thirds found a job in manufacturing and one third in services. Contrary to a common belief, low-end services are not the collecting vessel of redundant industrial workers. Displaced workers aged 55 and older seem particularly vulnerable after a plant closes down: over 30% were long-term unemployed, and those older workers who found a new job suffered disproportionate wage losses. Advanced age-and not low education-appears as the primary handicap after mass redundancy.

Linear and nonlinear terrain deformation maps from a reduced set of interferometric SAR images

In this paper, an advanced technique for the generation of deformation maps using synthetic aperture radar (SAR) data is presented. The algorithm estimates the linear and nonlinear components of the displacement, the error of the digital elevation model (DEM) used to cancel the topographic terms, and the atmospheric artifacts from a reduced set of low spatial resolution interferograms. The pixel candidates are selected from those presenting a good coherence level in the whole set of interferograms and the resulting nonuniform mesh tessellated with the Delauney triangulation to establish connections among them. The linear component of movement and DEM error are estimated adjusting a linear model to the data only on the connections. Later on, this information, once unwrapped to retrieve the absolute values, is used to calculate the nonlinear component of movement and atmospheric artifacts with alternate filtering techniques in both the temporal and spatial domains. The method presents high flexibility with respect to the required number of images and the baselines length. However, better results are obtained with large datasets of short baseline interferograms. The technique has been tested with European Remote Sensing SAR data from an area of Catalonia (Spain) and validated with on-field precise leveling measurements.

3D-muodot tuoliaihion muotopuristuksessa

Diplomityössä tutkittiin muotopuristeissa käytettävien viilujen soveltuvuutta yhteistyöyrityksen, VK Valmiskaluste Oy:n, valmistaman lepotuolin materiaaliksi. Tuoliaihion muoto edellytti viilun taivuttamista kahteen suuntaan, eli kyseessä oli ns. 3D-muoto. Muotopuristeita valmistavissa yrityksissä tehtyjen haastattelujen perusteella valittiin viilumateriaalit ja mitattiin niiden murtovenymä. Materiaaleja testattiin puristamalla tuoliaihioita. Aihionmuoto edellytti viilulta vähintään 3,3 %:n venyvyyttä. Koepuristuksetvahvistivat murtovenymätestauksen tulokset, eli tutkitun aihion pintarakenne säilyi ehjänä käyttämällä paperitaustaista viilua tai 3D-muotoihin tarkoitettua 3D-viilua. Kirjallisuusosiossa on selvitetty taivutettavuuteen vaikuttavia tekijöitä ja viilun rakenteen muokkausta taivutettavuuden parantamiseksi .

Paediatric bi-ventricular external assist device based on artificial muscles

Objective: Existing VADs are single-ventricle pumps needing anticoagulation. We developed a bi ventricular external assist device that reproduces the physiological heart muscle movement completely avoiding anticoagulants. Methods: The device has a carbon fibre skeleton fitting a 30-40 kg patient's heart, to which a Nitinol based artificial muscle is connected. The artificial muscle wraps both ventricles. The strength of the Nitinol fibres is amplified by a pivot articulation in contact with the ventricle wall. The fibres are electrically driven and a dedicated control unit has been developed. We assessed hemodynamic performances of this device using a previously described dedicated bench test. Volume ejected and pressure gradient has been measured with afterload ranging from 25 to 50mmHg. Results: With anafterload of 50mmHg the system has an ejection fraction (EF) of 10% on the right side and 8% on the left side. The system is able to generate a systolic ejection of 5,5 ml on the right side and 4,4 ml on the left side. With anafterload of 25mmHg the results are reduced of about 20%. The activation frequency is 80/minute resulting in a total volume displacement of 440 ml/minute on the right side and 352 ml/minute on the left side. Conclusions: The artificial muscle follows Starling's law as the ejected volume increases when afterload increases. These preliminary studies confirmed the possibility of improving the EF of a failing heart using artificial muscle for external cardiac compression. This device could be helpful in weaning CPB and/or for short-term cardio-circulatory support in paediatric population with cardiac failure.

Multi-slice three-dimensional myocardial strain tensor quantification using zHARP.

In this article we propose a novel method for calculating cardiac 3-D strain. The method requires the acquisition of myocardial short-axis (SA) slices only and produces the 3-D strain tensor at every point within every pair of slices. Three-dimensional displacement is calculated from SA slices using zHARP which is then used for calculating the local displacement gradient and thus the local strain tensor. There are three main advantages of this method. First, the 3-D strain tensor is calculated for every pixel without interpolation; this is unprecedented in cardiac MR imaging. Second, this method is fast, in part because there is no need to acquire long-axis (LA) slices. Third, the method is accurate because the 3-D displacement components are acquired simultaneously and therefore reduces motion artifacts without the need for registration. This article presents the theory of computing 3-D strain from two slices using zHARP, the imaging protocol, and both phantom and in-vivo validation.

Trophic resource partitioning and competition between the two sibling bat species Myotis myotis and Myotis blythii

1. Niche theory predicts that the stable coexistence of species within a guild should be associated, if resources are limited, with a mechanism of resource partitioning. Using extensive data on diets, the present study attempts: (i) to test the hypothesis that, in sympatry, the interspecific overlap between the trophic niches of the sibling bat species Myotis myotis and M. blythii-which coexist intimately in their roosts-is effectively lower than the two intraspecific overlaps; (ii) to assess the role played by interspecific competition in resource partitioning through the study of trophic niche displacement between several sympatric and allopatric populations. 2. Diets were determined by the analysis of faecal samples collected in the field from individual bats captured in various geographical areas. Trophic niche overlaps were calculated monthly for all possible intraspecific and interspecific pairs of individuals from sympatric populations. Niche breadth was estimated from: (i) every faecal sample; (ii) all the faecal samples collected per month in a given population (geographical area). 3. In every population, the bulk of the diets of M. myotis and M. blythii consisted of, respectively, terrestrial (e.g. carabid beetles) and grass-dwelling (mostly bush crickets) prey. All intraspecific trophic niche overlaps were significantly greater than the interspecific one, except in Switzerland in May when both species exploited mass concentrations of cockchafers, a non-limiting food source. This clearcut partitioning of resources may allow the stable, intimate coexistence observed under sympatric conditions. 4. Relative proportions of ground-and grass-dwelling prey, as well as niche breadths (either individual or population), did not differ significantly between sympatry and allopatry, showing that, under allopatric conditions, niche expansion does not take place. This suggests that active interspecific competition is not the underlying mechanism responsible for the niche partitioning which is currently observed between M. myotis and M. blythii.

1,2,3,4-Tetrahydrobenzo[h][1,6]naphthyridines as a new family of potent peripheral-to-midgorge-site inhibitors of acetylcholinesterase: synthesis, pharmacological evaluation and mechanistic studies

A series of 1,2,3,4-tetrahydrobenzo[h][1,6]naphthyridines differently substituted at positions 1, 5, and 9 have been designed from the pyrano[3,2-c]quinoline derivative 1, a weak inhibitor of acetylcholinesterase (AChE) with predicted ability to bind to the AChE peripheral anionic site (PAS), at the entrance of the catalytic gorge. Fourteen novel benzonaphthyridines have been synthesized through synthetic sequences involving as the key step a multicomponent Povarov reaction between an aldehyde, an aniline and an enamine or an enamide as the activated alkene. The novel compounds have been tested against Electrophorus electricus AChE (EeAChE), human recombinant AChE (hAChE), and human serum butyrylcholinesterase (hBChE), and their brain penetration has been assessed using the PAMPA-BBB assay. Also, the mechanism of AChE inhibition of the most potent compounds has been thoroughly studied by kinetic studies, a propidium displacement assay, and molecular modelling. We have found that a seemingly small structural change such as a double O → NH bioisosteric replacement from the hit 1 to 16a results in a dramatic increase of EeAChE and hAChE inhibitory activities (>217- and >154-fold, respectively), and in a notable increase in hBChE inhibitory activity (> 11-fold), as well. An optimized binding at the PAS besides additional interactions with AChE midgorge residues seem to account for the high hAChE inhibitory potency of 16a (IC50 = 65 nM), which emerges as an interesting anti-Alzheimer lead compound with potent dual AChE and BChE inhibitory activities.

Korkeakappa-massan suotatuvuus

Työn tarkoituksena oli tutkia korkeakappa-massan suotautuvuutta sekä etsiä uusia analyysimenetelmiä korkeakappa-massan karakterisoimiseksi. Työssä pyrittiin määrittämään tekijöitä, jotka vaikuttavat korkeakappa-massan suotautumiseen. Työn kirjallisessa osassa tarkasteltiin aluksi yleisesti keiton teoriaa, minkä jälkeen käsiteltiin jauhatusta ja tarkemmin korkeakappa-massan hienovaraisempaa jauhatusta eli kuidutusta. Seuraavaksi käsiteltiin suodatusta ja sen teoriaa sekä suodatukseen vaikuttavia tekijöitä. Massan pesusta esitettiin perusteet ja teoriaa. Lopuksi tarkasteltiin massan karakterisointia eri lähestymistavoilla sekä kuitujen perusominaisuuksia. Kokeellisessa osassa verrattiin LTY:n koesuodatuslaitteistolla tehdyillä suodatuskokeilla korkeakappa-massaisen sellukakun suotautuvuutta eri paine-eroilla, suodoksen eri hienoainepitoisuuksilla sekä ennen ja jälkeen sellutehtaallatapahtuneen kuidutuksen. Savonlinnassa sijaitsevalla laitteistolla tehtiin syrjäytystestejä ennen ja jälkeen kuidutusta otetuilla sellumassoilla. Lisäksi ennenja jälkeen kuidutusta otettuja sellumassanäytteitä karakterisoitiin mm. kuituanalysaattorilla, huokoskoko- ja ominaispinta-ala-analyyseillä sekä SEM-kuvilla. Suodatuskokeissa hienoainepitoisuudella ei ollut merkitystä permeabiliteettiin mitattujen suodosvirtausten perusteella. Kuten Darcyn lain perusteella voitiin olettaa, kakun paine-eron kasvaessa permeabiliteetti kasvoi. Vaikutus ei ollut kuitenkaan lineaarinen paine-eroon verrattuna vaan kakun permeabiliteetti kasvoi enemmän tietyllä paine-erovälillä. Tämä paine-eroväli vaihteli hieman riippuen oliko sellumassa otettu ennen vai jälkeen kuidutusta. Lappeenrannassa tehdyissä suodatuskokeissa ei ennen ja jälkeen kuidutusta otetuilla näytteillä ollut selvää eroa permeabiliteeteissa, mutta Savonlinnan syrjäytystesteissä ero syrjäytymisnopeudessa oli selvä. Ennen ja jälkeen kuidutusta otettujen sellumassojen kuituanalysaattorituloksissa ja SEM-kuvissa ei havaittu eroa näytteiden välillä, mutta massojen huokoskoko muuttui kuidutuksen vaikutuksesta.

1,2,3,4-Tetrahydrobenzo[h][1,6]naphthyridines as a new family of potent peripheral-to-midgorge-site inhibitors of acetylcholinesterase: synthesis, pharmacological evaluation and mechanistic studies

A series of 1,2,3,4-tetrahydrobenzo[h][1,6]naphthyridines differently substituted at positions 1, 5, and 9 have been designed from the pyrano[3,2-c]quinoline derivative 1, a weak inhibitor of acetylcholinesterase (AChE) with predicted ability to bind to the AChE peripheral anionic site (PAS), at the entrance of the catalytic gorge. Fourteen novel benzonaphthyridines have been synthesized through synthetic sequences involving as the key step a multicomponent Povarov reaction between an aldehyde, an aniline and an enamine or an enamide as the activated alkene. The novel compounds have been tested against Electrophorus electricus AChE (EeAChE), human recombinant AChE (hAChE), and human serum butyrylcholinesterase (hBChE), and their brain penetration has been assessed using the PAMPA-BBB assay. Also, the mechanism of AChE inhibition of the most potent compounds has been thoroughly studied by kinetic studies, a propidium displacement assay, and molecular modelling. We have found that a seemingly small structural change such as a double O → NH bioisosteric replacement from the hit 1 to 16a results in a dramatic increase of EeAChE and hAChE inhibitory activities (>217- and >154-fold, respectively), and in a notable increase in hBChE inhibitory activity (> 11-fold), as well. An optimized binding at the PAS besides additional interactions with AChE midgorge residues seem to account for the high hAChE inhibitory potency of 16a (IC50 = 65 nM), which emerges as an interesting anti-Alzheimer lead compound with potent dual AChE and BChE inhibitory activities.

Outcome after proximal femoral fractures during primary total hip replacement by the direct anterior approach.

BACKGROUND: The literature suggests that intraoperative fractures of the greater trochanter and the metaphysis are increased with uncemented stems and the direct anterior approach. This study aims to determine the incidence and assess the functional and radiological outcome after such fractures. METHODS: 484 consecutive total hip replacements (THR) (64 ± 12 years) were analyzed. We treated trochanteric fractures conservatively without any further denuding, and secured metaphyseal fissures with cerclages. Postoperative X-rays and at the latest follow-up were compared to assess secondary fracture displacement and stem subsidence. Western Ontario and McMaster Universities Arthritis Index (WOMAC) scores after 1 year were analyzed. For each patient sustaining a fracture, two patients without fractures were matched in terms of age, body mass index and gender. RESULTS: 13 (2.7 %, 5 male, 68 ± 9 years) patients with intraoperative fractures of the greater trochanter (n = 8) or the metaphysis (n = 5) were analyzed. Consolidation was observed in 7/8 patients sustaining a trochanteric fracture while secondary displacement of the fragment occurred in one case. Stem subsidence was observed in 2/5 cases (5 and 7 mm). Patients who sustained a fracture showed a trend towards poorer WOMAC scores at 1 year postoperatively, compared to patients without fractures. A significantly increased joint stiffness was also observed. CONCLUSION: The intraoperative fracture risk in this series of THR through a direct anterior approach was 2.7 %. Trochanteric fractures do heal without primary fixation. Metaphyseal fractures heal well if immediately stabilized with a cerclage.

Translation of polarity cues into asymmetric spindle positioning in "Caenorhabditis elegans"

Abstract: Asymmetric cell division is important to generate tissue diversity. The Caenorhabditis elegans embryo is well suited to study the mechanisms of asymmetric cell division. In wild type one-cell stage embryos, the spindle sets up along the anterior-posterior axis (AP). During anaphase, the spindle elongates. While the anterior spindle pole is relatively immobile, the posterior spindle pole moves towards the posterior cortex during anaphase leading to an asymmetric spindle position. As a result, the first cleavage gives rise to a large anterior blastomere and a smaller posterior one, which differs also in cell fate determinants. This posterior spindle displacement occurs in response to polarity cues set up along the AP axis by the PAR proteins and is due to imbalanced pulling forces acting on the two spindle poles, with net forces acting on the posterior spindle pole being more extensive than those at the anterior one. The project of my thesis was to characterize the involvement of two new components, gpr-1 and gpr-2, in spindle positioning. These genes encode essentially identical proteins containing a GoLoco motif characteristic of proteins interacting with α subunits of heterotrimeric G protein (Gα). In gpr-1/2(RNAi) embryos and in embryos lacking simultaneously two α subunits, goa-1 and gpa-16, (Ga(RNAi) embryos), there is a minimal posterior displacement of the spindle during anaphase, and the first division is equal. I found that the pulling forces acting on the two spindle poles is weak and equal in gpr-1/2(RNAi) and Gα (RNAi) embryos. I found that GPR-1/2 acts downstream of polarity cues for generation of pulling forces. Furthermore, I showed that GPR-1/2 distribution was enriched at the posterior cortex during metaphase whereas GOA-1 and GPA-16 were uniformly distributed at the cell cortex throughout the cell cycle. Gα subunits oscillate between GDP- and GTP-bound forms. Gα signaling is turned on by GDP/GTP exchange catalyzed by guanine nucleotide exchange factors (GEFs) and turned off by hydrolysis of GTP catalyzed by GTPase activating proteins (GAPs). A third class of proteins, the guanine dissociation inhibitors (GDIs), binds the GDP-bound form of Gα subunits and inhibits nucleotide exchange. I found that GPR-1/2 acts as a GDI for GOA-1. Taken together, my findings suggest a model in which differential activation of Gα subunits along the AP axis may translate into generation of differential pulling forces on the anterior and posterior spindle poles, and, thus, asymmetric cell division. Résumé L'embryon du nématode Caenorhabditis elegans est un modèle approprié pour étudier les mécanismes de la division asymétrique. Chez l'embryon précoce, le fuseau mitotique se forme le long de l'axe antéro-postérieur (A/P) et au centre de l'embryon, le pôle antérieur restant relativement immobile alors que le pôle postérieur du fuseau se déplace vers le cortex postérieur au cours de l'anaphase conduisant à une position excentrée du fuseau. 11 en résulte une première division qui génère un blastomère antérieur et postérieur de grande et petite taille respectivement et qui diffèrent en facteurs développementaux. Ce déplacement postérieur se produit en réponse de la polarité établie par la distribution polarisée des protéines PAR et est le résultat de la génération de forces inégales tirant sur les deux pôles du fuseau, les forces agissant sur le pôle postérieur du fuseau étant plus grandes. Le projet de ma thèse était d'identifier la fonction de deux nouveaux constituants, gpr-1 et gpr-2 dans le positionnement asymétrique du fuseau. Ces gènes codent essentiellement pour la même protéine qui contient un motif GoLoco, caractéristique des protéines interagissant avec la sous-unité alpha des protéines G hétérotrimériques. Chez l'embryon gpr-1/2(RNAi) et chez les embryons dépourvus d'activité de deux sous-unités alpha, goa-1 et gpa-16, (Gα(RNAi)), j'ai montré qu'il y avait un déplacement minimal du fuseau vers le pôle postérieur au cours de l'anaphase et la première division est symétrique en raison de forces faibles et égales agissant sur les deux pôles du fuseau. J'ai également montré que gpr-1/2 était requis en aval des signaux établissant la polarité pour générer les forces responsables du positionnement asymétrique du fuseau. De plus, j'ai montré que GPR-1/2 était enrichi au pôle postérieur lors de la métaphase alors que GOA-1 et GPA-16 étaient localisés de façon uniforme au cortex de l'embryon précoce. Gas oscillent entre une forme liée au GDP et une forme liée au GTP. La signalisation des Gas est activée par l'échange GDP/GTP qui est catalysé par des protéines GEFs. La signalisation des Gas est désactivée par l'hydrolyse du GTP qui est catalysée par des protéines GAPs. Une troisième classe de protéines, GDIs lie la forme GDP et inhibe l'échange de nucléotides. J'ai montré que GPR-1/2 agissait comme un GDI pour GOA-1. Mes résultats suggèrent un modèle dans lequel une activation différentielle des Gα le long de l'axe A/P pourrait générer des forces différentielles sur le pôle antérieur et postérieur du fuseau.

A computationally efficient shear deformable beam element for large deformation multibody applications

In this paper, a new two-dimensional shear deformable beam element based on the absolute nodal coordinate formulation is proposed. The nonlinear elastic forces of the beam element are obtained using a continuum mechanics approach without employing a local element coordinate system. In this study, linear polynomials are used to interpolate both the transverse and longitudinal components of the displacement. This is different from other absolute nodal-coordinate-based beam elements where cubic polynomials are used in the longitudinal direction. The accompanying defects of the phenomenon known as shear locking are avoided through the adoption of selective integration within the numerical integration method. The proposed element is verified using several numerical examples, and the results are compared to analytical solutions and the results for an existing shear deformable beam element. It is shown that by using the proposed element, accurate linear and nonlinear static deformations, as well as realistic dynamic behavior, can be achieved with a smaller computational effort than by using existing shear deformable two-dimensional beam elements.

Mekanismien dynamiikan simuloinnissa sovellettavia numeerisia- ja mallinnusmenetelmiä

Koneet voidaan usein jakaa osajärjestelmiin, joita ovat ohjaus- ja säätöjärjestelmät, voimaa tuottavat toimilaitteet ja voiman välittävät mekanismit. Eri osajärjestelmiä on simuloitu tietokoneavusteisesti jo usean vuosikymmenen ajan. Osajärjestelmien yhdistäminen on kuitenkin uudempi ilmiö. Usein esimerkiksi mekanismien mallinnuksessa toimilaitteen tuottama voimaon kuvattu vakiona, tai ajan funktiona muuttuvana voimana. Vastaavasti toimilaitteiden analysoinnissa mekanismin toimilaitteeseen välittämä kuormitus on kuvattu vakiovoimana, tai ajan funktiona työkiertoa kuvaavana kuormituksena. Kun osajärjestelmät on erotettu toisistaan, on niiden välistenvuorovaikutuksien tarkastelu erittäin epätarkkaa. Samoin osajärjestelmän vaikutuksen huomioiminen koko järjestelmän käyttäytymissä on hankalaa. Mekanismien dynamiikan mallinnukseen on kehitetty erityisesti tietokoneille soveltuvia numeerisia mallinnusmenetelmiä. Useimmat menetelmistä perustuvat Lagrangen menetelmään, joka mahdollistaa vapaasti valittaviin koordinaattimuuttujiin perustuvan mallinnuksen. Numeerista ratkaisun mahdollistamiseksi menetelmän avulla muodostettua differentiaali-algebraaliyhtälöryhmää joudutaan muokkaamaan esim. derivoimalla rajoiteyhtälöitä kahteen kertaan. Menetelmän alkuperäisessä numeerisissa ratkaisuissa kaikki mekanismia kuvaavat yleistetyt koordinaatit integroidaan jokaisella aika-askeleella. Tästä perusmenetelmästä johdetuissa menetelmissä riippumattomat yleistetyt koordinaatit joko integroidaan ja riippuvat koordinaatit ratkaistaan rajoiteyhtälöiden perusteella tai yhtälöryhmän kokoa pienennetään esim. käyttämällä nopeus- ja kiihtyvyysanalyyseissä eri kiertymäkoordinaatteja kuin asema-analyysissä. Useimmat integrointimenetelmät on alun perin tarkoitettu differentiaaliyhtälöiden (ODE) ratkaisuunjolloin yhtälöryhmään liitetyt niveliä kuvaavat algebraaliset rajoiteyhtälöt saattavat aiheuttaa ongelmia. Nivelrajoitteiden virheiden korjaus, stabilointi, on erittäin tärkeää mekanismien dynamiikan simuloinnin onnistumisen ja tulosten oikeellisuuden kannalta. Mallinnusmenetelmien johtamisessa käytetyn virtuaalisen työn periaatteen oletuksena nimittäin on, etteivät rajoitevoimat tee työtä, eli rajoitteiden vastaista siirtymää ei tapahdu. Varsinkaan monimutkaisten järjestelmien pidemmissä analyyseissä nivelrajoitteet eivät toteudu tarkasti. Tällöin järjestelmän energiatasapainoei toteudu ja järjestelmään muodostuu virtuaalista energiaa, joka rikkoo virtuaalisen työn periaatetta, Tästä syystä tulokset eivät enää pidäpaikkaansa. Tässä raportissa tarkastellaan erityyppisiä mallinnus- ja ratkaisumenetelmiä, ja vertaillaan niiden toimivuutta yksinkertaisten mekanismien numeerisessa ratkaisussa. Menetelmien toimivuutta tarkastellaan ratkaisun tehokkuuden, nivelrajoitteiden toteutumisen ja energiatasapainon säilymisen kannalta.