Browsing by Subject "maintenance"

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  • Somerharju, Pentti; Virtanen, Jorma A.; Hermansson, Martin (2020)
    Mammalian cells maintain the complex glycerophospholipid (GPL) class compositions of their various membranes within close limits because this is essential to their well-being or viability. Surprisingly, however, it is still not understood how those compositions are maintained except that GPL synthesis and degradation are closely coordinated. Here, we hypothesize that abrupt changes in the chemical activity of the individual GPL classes coordinate synthesis and degradation as well other the homeostatic processes. We have previously proposed that only a limited number of “allowed” or “optimal” GPL class compositions exist in cellular membranes because those compositions are energetically more favorable than others, that is, they represent local free energy minima (Somerharju et al 2009, Biochim. Biophys. Acta 1788, 12-23). This model, however, could not satisfactorily explain how the “optimal” compositions are sensed by the key homeostatic enzymes, that is, rate-limiting synthetizing enzymes and homeostatic phospholipases. We now hypothesize that when the mole fraction of a GPL class exceeds an optimal value, its chemical activity abruptly increases which (a) increases its propensity to efflux from the membrane thus making it susceptible for hydrolysis by homeostatic phospholipases; (b) increases its potency to inhibit its own biosynthesis via a feedback mechanism; (c) enhances its conversion to another glycerophospholipid class via a novel process termed “head group remodeling” or (d) enhances its translocation to other subcellular membranes. In summary, abrupt change in the chemical activity of the individual GPL classes is proposed to regulate and coordinate those four processes maintaining GPL class homeostasis in mammalian cells.
  • Angelstam, Per; Manton, Michael; Yamelynets, Taras; Fedoriak, Mariia; Albulescu, Andra-Cosmina; Bravo, Felipe; Cruz, Fatima; Jaroszewicz, Bogdan; Kavratishvili, Marika; Munos-Rojas, Jose; Sijtsma, Frans; Washbourne, Carla-Leanne; Agnoletti, Mauro; Dobrynin, Denis; Izakovicova, Zita; Jansson, Nicklas; Kanka, Robert; Kopperoinen, Leena; Lazdinis, Marius; Metzger, Marc; van der Moolen, Bert; Özut, Deniz; Gjorgieska, Dori Pavlovska; Strydmets, Natalie; Tolunay, Ahmet; Turkogly, Turkay; Zagidullina, Asiya (Springer Link, 2020)
    Landscape Ecology 36 (2020)
    Context Maintaining functional green infrastructures (GIs) require evidence-based knowledge about historic and current states and trends of representative land cover types. Objectives We address: (1) the long-term loss and transformation of potential natural forest vegetation; (2) the effects of site productivity on permanent forest loss and emergence of traditional cultural landscapes; (3) the current management intensity; and (4) the social-ecological contexts conducive to GI maintenance. Methods We selected 16 case study regions, each with a local hotspot landscape, ranging from intact forest landscapes, via contiguous and fragmented forest covers, to severe forest loss. Quantitative open access data were used to estimate (i) the historic change and (ii) transformation of land covers, and (iii) compare the forest canopy loss from 2000 to 2018. Qualitative narratives about each hotspot landscape were analysed for similarities (iv). Results While the potential natural forest vegetation cover in the 16 case study regions had a mean of 86%, historically it has been reduced to 34%. Higher site productivity coincided with transformation to non-forest land covers. The mean annual forest canopy loss for 2000–2018 ranged from 0.01 to 1.08%. The 16 case studies represented five distinct social-ecological contexts (1) radical transformation of landscapes, (2) abuse of protected area concepts, (3) ancient cultural landscapes (4) multi-functional forests, and (5) intensive even-aged forest management, of which 1 and 4 was most common. Conclusions GIs encompass both forest naturalness and traditional cultural landscapes. Our review of Pan-European regions and landscapes revealed similarities in seemingly different contexts, which can support knowledge production and learning about how to sustain GIs.
  • Kallonen, Ville (Helsingfors universitet, 2016)
    This research considers factors affecting customer satisfaction and value perception of ERP maintenance and support service. The research strategy is qualitative and it is carried out as a semi-structured interview study. In the study 12 experts working with maintenance and support services for ERP systems are interviewed. The interviewees represent IT vendor sales organization and service managers and the customer-side IT management, service managers and application experts. The theoretical framework of the research is primarily based on DeLone and McLean (2003) IS Success theory and framework of Critical Success Factors for ERP Maintenance Support by Law, Chen and Wu (2009). The theoretical framework is subsequently converted to ten themes which comprise the core of this research. The purpose of the research is to find out what factors affect the satisfaction and value perception of companies using ERP maintenance and support services and what is the effect of the research themes. The research sample is limited; however it provides in-depth insights into similarities and differences between viewpoints of people working in different roles related maintenance and support service. The study also considers how the viewpoints differ when the interviewee is working for an IT vendor or for a customer company IT organization. The conclusion of the research is that the interviewee viewpoints match with that of their counterpart at the customer or the vendor. To improve customer satisfaction, IT vendors should better involve parties representing customer business and end users in management of the service and in definition of service requirements, and not satisfied to collaborate between IT organizations only. Fulfilling contractual and written obligations is critical for realizing service value. IT vendors should be able to be flexible and adjust their service delivery according to customer requirements, regardless of if these requirements are captured in contracts or service level documents. Customers consider the vendor technical competence to be critical for service quality, in addition to which competence in customer business and processes is essential for realizing added value in the service. The physical location of service delivery does not increase the customer’s willingness to pay. The vendor should use efficient processes to minimize the effect of service delivery location and personnel turnover for service quality.