Effect of Substrate Orientation on Melt Pool during Multi-Layer Deposition in V-Groove with Gas Metal Arc

Thermo-fluid dynamic and experimental approaches are used to investigate the influence of 20\ub0 uphill, downhill and sideway substrate orientation during metal deposition over a previously deposited bead in a V-groove. The computational fluid dynamic model with free surface deformation and metal transfer gives insight into the melt pool flow and causes of defect formation observed on the solidified beads. The experimental metallographs, high-speed images and computational results show good agreement. It is found that the deposition of a second layer on a smooth first layer cooled down to room temperature leads to large changes in melt pool flow pattern at 20\ub0 substrate inclination compared to flat condition. It results in undercut and humps with the uphill orientation and undercut with the side inclination. Therefore, lower angle range is necessary for multilayer gas metal arc deposition for these two last configurations

Physical mechanisms of ESCRT-III-driven cell division.

Living systems propagate by undergoing rounds of cell growth and division. Cell division is at heart a physical process that requires mechanical forces, usually exerted by assemblies of cytoskeletal polymers. Here we developed a physical model for the ESCRT-III-mediated division of archaeal cells, which despite their structural simplicity share machinery and evolutionary origins with eukaryotes. By comparing the dynamics of simulations with data collected from live cell imaging experiments, we propose that this branch of life uses a previously unidentified division mechanism. Active changes in the curvature of elastic cytoskeletal filaments can lead to filament perversions and supercoiling, to drive ring constriction and deform the overlying membrane. Abscission is then completed following filament disassembly. The model was also used to explore how different adenosine triphosphate (ATP)-driven processes that govern the way the structure of the filament is changed likely impact the robustness and symmetry of the resulting division. Comparisons between midcell constriction dynamics in simulations and experiments reveal a good agreement with the process when changes in curvature are implemented at random positions along the filament, supporting this as a possible mechanism of ESCRT-III-dependent division in this system. Beyond archaea, this study pinpoints a general mechanism of cytokinesis based on dynamic coupling between a coiling filament and the membrane

The patterned assembly and stepwise Vps4-mediated disassembly of composite ESCRT-III polymers drives archaeal cell division

ESCRT-III family proteins form composite polymers that deform and cut membrane tubes in the context of a wide range of cell biological processes across the tree of life. In reconstituted systems, sequential changes in the composition of ESCRT-III polymers induced by the AAA-adenosine triphosphatase Vps4 have been shown to remodel membranes. However, it is not known how composite ESCRT-III polymers are organized and remodeled in space and time in a cellular context. Taking advantage of the relative simplicity of the ESCRT-III-dependent division system in Sulfolobus acidocaldarius, one of the closest experimentally tractable prokaryotic relatives of eukaryotes, we use super-resolution microscopy, electron microscopy, and computational modeling to show how CdvB/CdvB1/CdvB2 proteins form a precisely patterned composite ESCRT-III division ring, which undergoes stepwise Vps4-dependent disassembly and contracts to cut cells into two. These observations lead us to suggest sequential changes in a patterned composite polymer as a general mechanism of ESCRT-III-dependent membrane remodeling. </p

The proteasome controls ESCRT-III–mediated cell division in an archaeon

INTRODUCTION: Eukaryotes likely arose from a symbiotic partnership between an archaeal host and an alpha-proteobacterium, giving rise to the cell body and the mitochondria, respectively. Because of this, a number of proteins controlling key events in the eukaryotic cell division cycle have their origins in archaea. These include ESCRT-III proteins, which catalyze the final step of cytokinesis in many eukaryotes and in the archaeon Sulfolobus acidocaldarius. However, to date, no archaeon has been found that harbors homologs of cell cycle regulators, like cyclin-dependent kinases and cyclins, which order events in the cell cycle across all eukaryotes. Thus, it remains uncertain how key events in the archaeal cell cycle, including division, are regulated. RATIONALE: An exception to this is the 20S proteasome, which is conserved between archaea and eukaryotes and which regulates the eukaryotic cell cycle through the degradation of cyclins. To explore the function of the 20S proteasome in the archaeon S. acidocaldarius, we determined its structure by crystallography and carried out in vitro biochemical analyses of its activity with and without inhibition. The impact of proteasome inhibition on cell division and cell cycle progression was examined in vivo by flow cytometry and super-resolution microscopy. Following up with mass spectrometry, we identified proteins degraded by the proteasome during division. Finally, we used molecular dynamics simulations to model the mechanics of this process. RESULTS: Here, we present a structure of the 20S proteasome of S. acidocaldarius to a resolution of 3.7 Å, which we used to model its sensitivity to the eukaryotic inhibitor bortezomib. When this inhibitor was added to synchronous cultures, it was found to arrest cells mid-division, with a stable ESCRT-III division ring positioned at the cell center between the two separated and prereplicative nucleoids. Proteomics was then used to identify a single archaeal ESCRT-III homolog, CdvB, as a key target of the proteasome that must be degraded to enable division to proceed. Examining the localization patterns of CdvB and two other archaeal ESCRT-III homologs, CdvB1 and CdvB2, by flow cytometry and super-resolution microscopy revealed the sequence of events that leads to division. First, a CdvB ring is assembled. This CdvB ring then templates the assembly of the contractile ESCRT-III homologs, CdvB1 and CdvB2, to form a composite division ring. Cell division is then triggered by proteasome-mediated degradation of CdvB, which allows the CdvB1:CdvB2 copolymer to constrict, pulling the membrane with it. During constriction, the CdvB1:CdvB2 copolymer is disassembled, thus vacating the membrane neck to drive abscission, yielding two daughter cells with diffuse CdvB1 and CdvB2. CONCLUSION: This study reveals a role for the proteasome in driving structural changes in a composite ESCRT-III copolymer, enabling the stepwise assembly, disassembly, and contraction of an ESCRT-III–based division ring. Although it is not yet clear how proteasomal inhibition prevents S. acidocaldarius cells from resetting the cell cycle to initiate the next S phase, these data strengthen the case for the eukaryotic cell cycle regulation having its origins in archaea

Divisive structures : Two billions years of biofilament evolution

Our understanding of the functional and regulatory complexity that existed in the eukaryotic progenitor is poor, and investigations have been hindered by our nebulous understanding of where eukaryotes stem from. Recently discovered archaeal lineages with hitherto unseen homology to eukaryotic systems suggest archaea can further our understanding of the eukaryotic cell’s ancestry. However, much of archaeal biology remains largely unexplored. Two eukaryotic systems with archaeal homologues, namely the actin and ESCRT-III protein filament systems, are essential for diverse processes in eukaryotic biology. In this thesis, we show that an archaeal homologue of ESCRT-III divides the cell under proteasomal regulation, a regulatory mechanism central to eukaryotic cell cycle regulation. Additionally, we show how predicted putative profilin and gelsolin homologues regulate the postulated proto-cytoskeleton of Asgard archaea. In investigating the function and regulation of these archaeal systems we demonstrate compelling parallels between archaeal and eukaryotic regulatory strategies which stresses the close evolutionary relationship that exists between these two domains.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 2: Manuscript. Paper 3: Manuscript.</p

Patient participation in end-stage kidney disease care: variation over time and effects of staff-directed interventions - a quasi-experimental study

Abstract Background Among those elements establishing decent quality of care from a patient perspective, opportunities to participate in accord with one’s individual needs and preferences are central. To date, little is known the extent of preference-based patient participation in kidney care, and what facilitates optimal conditions. This study investigated i) preference-based patient participation in kidney care over time, and ii) the effects of interventions designed to enhance person-centred patient participation. Methods A quasi-experimental study was conducted across nine kidney care sites in southeast Sweden. A cohort of 358 patients with stage IV chronic kidney disease (eGRF 15–19 ml/min) or V (eGRF < 15 mL/min) entered the study. Of these, 245 patients (with kidney replacement therapy or intermittent outpatient visits only) completed a survey on patient participation at four time points: every six months from August 2019 to May 2021, patients reported their preferences for and experiences of participation using the validated Patient Preferences for Patient Participation tool, the 4Ps. Between the first and second data collection points, interventions were provided for designated staff to facilitate person-centred participation, using two strategies for two subgroups at three sites each: the managers receiving a bundle of information via e-mail on patient participation in a standard dissemination procedure (three sites), or an additional half-year support program for implementation offered to 1–2 staff per site (three sites), with no intervention for a control group (three sites). The differences in 4Ps data between groups were analysed using multilevel ordinal regression. Results Over time and across all sites, most patients’ experiences of participation fully or almost fully matched their engagement preferences (57%–90%). Still, up to 12% of patient reports indicated that their preferences and experiences were insufficiently matched: in these cases, the patients had preferred to be more involved than they had experienced, for example, in making healthcare plans and setting health-related goals. The interventions did not affect the levels of preference-based participation, but patients in the control group sites had slightly more consistent matches. Conclusions Living with kidney failure necessitates patient engagement, but opportunities to participate in accordance with one’s preferences are not fully provided for all patients. Additional efforts to support a common understanding and to ensure person-centred patient participation is still needed

Långsiktiga effekter? : Personer med funktionsnedsättning och deras etablering på arbetsmarknaden med stöd av Supported Employment – En uppföljning ur arbetstagarperspektiv

Personer med funktionsnedsättning arbetar i lägre utsträckning än personer utan funktionsnedsättning. Att komma in på arbetsmarknaden är svårt och att stadigvarande etablera sig är särskilt problematiskt för de som lever med en intellektuell eller neuropsykiatrisk funktionsnedsättning. Med stöd av Supported employment-metoden erbjuds stöd för att underlätta arbetsmarknadsinträdet. Forskning och uppföljning visar att metoden är relativt snabb och framgångsrik i att bistå personer med funktionsnedsättning till arbete men att det saknas studier som visar om etableringen på arbetsmarknaden är hållbar över tid. Syftet med denna studie är att öka kunskapen om deltagarnas erfarenheter av Supported employment och hållbarheten i arbetssituationen två år efter avslutat stöd. Genom intervjuer med 20 slumpmässigt utvalda deltagare (av 419 aktuella) och deras arbetskonsulenter, varav 14 vid intervjutillfället fortfarande var i arbete, erhålls erfarenheter som pekar på betydelsefulla faktorer för hållbarhet, vilka kategoriseras som a) klientens egenskaper och förhållningssätt, b) arbetskonsulternas betydelse och stöd, c) arbetsgivarnas inställning och attityder samt d) samhällets bemötande. I rapporten ställs och diskuteras studiens resultat och slutsatser i relation till tidigare kunskap på området

Långsiktiga effekter? : Personer med funktionsnedsättning och deras etablering på arbetsmarknaden med stöd av Supported Employment – En uppföljning ur arbetstagarperspektiv

Personer med funktionsnedsättning arbetar i lägre utsträckning än personer utan funktionsnedsättning. Att komma in på arbetsmarknaden är svårt och att stadigvarande etablera sig är särskilt problematiskt för de som lever med en intellektuell eller neuropsykiatrisk funktionsnedsättning. Med stöd av Supported employment-metoden erbjuds stöd för att underlätta arbetsmarknadsinträdet. Forskning och uppföljning visar att metoden är relativt snabb och framgångsrik i att bistå personer med funktionsnedsättning till arbete men att det saknas studier som visar om etableringen på arbetsmarknaden är hållbar över tid. Syftet med denna studie är att öka kunskapen om deltagarnas erfarenheter av Supported employment och hållbarheten i arbetssituationen två år efter avslutat stöd. Genom intervjuer med 20 slumpmässigt utvalda deltagare (av 419 aktuella) och deras arbetskonsulenter, varav 14 vid intervjutillfället fortfarande var i arbete, erhålls erfarenheter som pekar på betydelsefulla faktorer för hållbarhet, vilka kategoriseras som a) klientens egenskaper och förhållningssätt, b) arbetskonsulternas betydelse och stöd, c) arbetsgivarnas inställning och attityder samt d) samhällets bemötande. I rapporten ställs och diskuteras studiens resultat och slutsatser i relation till tidigare kunskap på området