Browsing by Subject "STABILITY"

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  • Vuoristo, Sanna; Toivonen, Sanna; Weltner, Jere; Mikkola, Milla; Ustinov, Jarkko; Trokovic, Ras; Palgi, Jaan; Lund, Riikka; Tuuri, Timo; Otonkoski, Timo (2013)
  • Silventoinen, Karri; Volanen, Salla-Maarit; Vuoksimaa, Eero; Rose, Richard J.; Suominen, Sakari; Kaprio, Jaakko (2014)
  • Kisdi, Eva; Geritz, Stefan A.H. (2016)
    We study the joint adaptive dynamics of n scalar-valued strategies in ecosystems where n is the maximum number of coexisting strategies permitted by the (generalized) competitive exclusion principle. The adaptive dynamics of such saturated systems exhibits special characteristics, which we first demonstrate in a simple example of a host-pathogen-predator model. The main part of the paper characterizes the adaptive dynamics of saturated polymorphisms in general. In order to investigate convergence stability, we give a new sufficient condition for absolute stability of an arbitrary (not necessarily saturated) polymorphic singularity and show that saturated evolutionarily stable polymorphisms satisfy it. For the case , we also introduce a method to construct different pairwise invasibility plots of the monomorphic population without changing the selection gradients of the saturated dimorphism.
  • Costa, Clarinda; Liu, Zehua; Martins, João Pedro; Correia, Alexandra; Rahikkala, Antti Tuomas Antero; Li, Wei; Seitsonen, Jani; Ruokolainen, Janne; Hirvonen, Sami-Pekka; Aguiar- Ricardo, Ana; Corvo, M. Luísa; Santos, Hélder A. (2020)
    Here, a continuous two-step glass-capillary microfluidic technique to produce a multistage oral delivery system is reported. Insulin is successfully encapsulated into liposomes, which are coated with chitosan to improve their mucoadhesion. The encapsulation in an enteric polymer offers protection from the harsh gastric conditions. Insulin permeability is enhanced across an intestinal monolayer.
  • Lai, Ru-Yu; Shankar, Ravi; Spirn, Daniel; Uhlmann, Gunther (2017)
    We consider the problem of reconstructing the features of a weak anisotropic background potential by the trajectories of vortex dipoles in a nonlinear Gross-Pitaevskii equation. At leading order, the dynamics of vortex dipoles are given by a Hamiltonian system. If the background potential is sufficiently smooth and flat, the background can be reconstructed using ideas from the boundary and the lens rigidity problems. We prove that reconstructions are unique, derive an approximate reconstruction formula, and present numerical examples.
  • Urraca, Ruben; Antonanzas, Javier; Sanz-Garcia, Andres; Javier Martinez-de-Pison, Francisco (2019)
    Different types of measuring errors can increase the uncertainty of solar radiation measurements, but most common quality control (QC) methods do not detect frequent defects such as shading or calibration errors due to their low magnitude. We recently presented a new procedure, the Bias-based Quality Control (BQC), that detects low-magnitude defects by analyzing the stability of the deviations between several independent radiation databases and measurements. In this study, we extend the validation of the BQC by analyzing the quality of all publicly available Spanish radiometric networks measuring global horizontal irradiance (9 networks, 732 stations). Similarly to our previous validation, the BQC found many defects such as shading, soiling, or calibration issues not detected by classical QC methods. The results questioned the quality of SIAR, Euskalmet, MeteoGalica, and SOS Rioja, as all of them presented defects in more than 40% of their stations. Those studies based on these networks should be interpreted cautiously. In contrast, the number of defects was below a 5% in BSRN, AEMET, MeteoNavarra, Meteocat, and SIAR Rioja, though the presence of defects in networks such as AEMET highlights the importance of QC even when using a priori reliable stations.
  • Lampi, Mirka; Oksanen, Hanna M.; Meier, Florian; Moldenhauer, Evelin; Poranen, Minna M.; Bamford, Dennis H.; Eskelin, Katri (2018)
    Basic and applied virus research requires specimens that are purified to high homogeneity. Thus, there is much interest in the efficient production and purification of viruses and their subassemblies. Advances in the production steps have shifted the bottle neck of the process to the purification. Nonetheless, the development of purification techniques for different viruses is challenging due to the complex biological nature of the infected cell cultures as well as the biophysical and -chemical differences in the virus particles. We used bacteriophage phi 6 as a model virus in our attempts to provide a new purification method for enveloped viruses. We compared asymmetrical flow field-flow fractionation (AF4)-based virus purification method to the well-established ultracentrifugation-based purification of phi 6. In addition, binding of phi 6 virions to monolithic anion exchange columns was tested to evaluate their applicability in concentrating the AF4 purified specimens. Our results show that AF4 enables one-hour purification of infectious enveloped viruses with specific infectivity of similar to 1 x 10(13) PFU/mg of protein and similar to 65-95% yields. Obtained purity was comparable with that obtained using ultracentrifugation, but the yields from AF4 purification were 2-3-fold higher. Importantly, high quality virus preparations could be obtained directly from crude cell lysates. Furthermore, when used in combination with inline light scattering detectors, AF4 purification could be coupled to simultaneous quality control of obtained virus specimen.
  • Popov, Georgi; Bačić, Goran; Mattinen, Miika; Manner, Toni; Lindström, Hannu; Seppänen, Heli; Suihkonen, Sami; Vehkamäki, Marko; Kemell, Marianna; Jalkanen, Pasi; Mizohata, Kenichiro; Räisänen, Jyrki; Leskelä, Markku; Koivula, Hanna Maarit; Barry, Seán T.; Ritala, Mikko (2020)
    Atomic layer deposition (ALD) is a viable method for depositing functional, passivating, and encapsulating layers on top of halide perovskites. Studies in that area have only focused on metal oxides, despite a great number of materials that can be made with ALD. This work demonstrates that, in addition to oxides, other ALD processes can be compatible with the perovskites. We describe two new ALD processes for lead sulfide. These processes operate at low deposition temperatures (45-155 degrees C) that have been inaccessible to previous ALD PbS processes. Our processes rely on volatile and reactive lead precursors Pb(dbda) (dbda = rac-N-2,N-3-di-tertbutylbutane-2,3-diamide) and Pb(btsa)(2) (btsa = bis(trimethylsilyl)amide) as well as H2S. These precursors produce high quality PbS thin films that are uniform, crystalline, and pure. The films exhibit p- type conductivity and good mobilities of 10-70 cm(2) V-1 s(-1). Low deposition temperatures enable direct ALD of PbS onto a halide perovskite CH3NH3PbI3 (MAPI) without its decomposition. The stability of MAPI in ambient air is greatly improved by capping with ALD PbS. More generally, these new processes offer valuable alternatives for PbS-based devices, and we hope that this study will inspire more studies on ALD of non-oxides on halide perovskites.
  • Abu Saleh, Doaa; Niskanen, Jukka; Xue, Yanming; Golberg, Dmitri; Winnik, Francoise M.; Sosnik, Alejandro (2017)
    We report an organic-inorganic hybrid core-shell nanomaterial obtained by conjugation of an amphiphilic monomethoxy-poly(ethylene glycol)-b-poly(epsilon-caprolactone) diblock copolymer to hydroxylated boron nitride nanotubes (BNNTs). The extent of copolymer grafting reached 64% w/w, an exceptionally high value. The hybrid materials exhibit excellent physical stability in water and an outstanding loading capacity (31.3% w/w) for curcumin, a hydrophobic drug. Moreover, they present good compatibility with the Caco2 cell line, a model of intestinal epithelium. Our findings demonstrate the potential of multifunctional hybrid BNNTs to serve as a platform for complex amphiphilic nanoparticle architectures with improved features. (c) 2017 Elsevier Ltd. All rights reserved.
  • Italian CMD Network (2018)
    Background: Dystroglycanopathy (alpha-DG) is a relatively common, clinically and genetically heterogeneous category of congenital forms of muscular dystrophy (CMD) and limb-girdle muscular dystrophy (LGMD) associated with hypoglycosylated alpha-dystroglycan. To date, mutations in at least 19 genes have been associated with alpha-DG. One of them, GMPPB, encoding the guanosine-diphosphate-mannose (GDP-mannose) pyrophosphorylase B protein, has recently been associated with a wide clinical spectrum ranging from severe Walker-Warburg syndrome to pseudo-metabolic myopathy and even congenital myasthenic syndromes. We re-sequenced the full set of known disease genes in 73 Italian patients with evidence of either reduced or nearly absent alpha-dystroglycan to assess genotype-phenotype correlations in this cohort. We used innovative bioinformatic tools to calculate the effects of all described GMPPB mutations on protein function and attempted to correlate them with phenotypic expressions. Results: We identified 13 additional cases from 12 families and defined seven novel mutations. Patients displayed variable phenotypes including less typical pictures, ranging from asymptomatic hyperCKemia, to arthrogryposis and congenital clubfoot at birth, and also showed neurodevelopmental comorbidities, such as seizures and ataxic gait, as well as autism-spectrum disorder, which is seldom described in clinical reports of dystroglycanopathies. We also demonstrated that few mutations recur in the Italian GMPPB-mutated population and that alterations of protein stability are the main effects of GMPPB missense variants. Conclusion: This work adds to the data on genotype-phenotype correlations in alpha-DG and offers new bionformatic tools to provide the conceptual framework needed to understand the complexity of these disorders.
  • Kiviaho, Jenny K.; Linko, Veikko; Ora, Ari; Tiainen, Tony; Järvihaavisto, Erika; Mikkila, Joona; Tenhu, Heikki; Nonappa, [Tuntematon]; Kostiainen, Mauri A. (2016)
    DNA origamis are fully tailored, programmable, biocompatible and readily functionalizable nanostructures that provide an excellent foundation for the development of sophisticated drug-delivery systems. However, the DNA origami objects suffer from certain drawbacks such as low cell-transfection rates and low stability. A great deal of studies on polymer-based transfection agents, mainly focusing on polyplex formation and toxicity, exists. In this study, the electrostatic binding between a brick-like DNA origami and cationic block-copolymers was explored. The effect of the polymer structure on the binding was investigated and the toxicity of the polymer-origami complexes evaluated. The study shows that all of the analyzed polymers had a suitable binding efficiency irrespective of the block structure. It was also observed that the toxicity of polymer-origami complexes was insignificant at the biologically relevant concentration levels. Besides brick-like DNA origamis, tubular origami carriers equipped with enzymes were also coated with the polymers. By adjusting the amount of cationic polymers that cover the DNA structures, we showed that it is possible to control the enzyme kinetics of the complexes. This work gives a starting point for further development of biocompatible and effective polycation-based block copolymers that can be used in coating different DNA origami nanostructures for various bioapplications.
  • Valoppi, Fabio; Lahtinen, Maarit; Bhattarai, Mamata; Kirjoranta, Satu; Juntti, Venla; Peltonen, Leena; Kilpeläinen, Petri O.; Mikkonen, Kirsi S. (2019)
    With the emerging bio-based technologies, the fractionation of complex biomass is essential to obtain value-added functional molecules for material, chemical, and energy production. The refining process of biomasses often requires the use of solvents and hazardous chemicals, whose removal after fractionation decreases the eco-compatibility of the process and increases the cost and time of the refinement. Softwood extracts obtained through the environmentally friendly pressurized hot water extraction are heterogeneous mixtures rich in hemicelluloses and lignin. Here we developed a simple, fast, organic solvent-free, and sustainable method to fractionate softwood extracts using centrifugal forces. The characteristics of each obtained fraction in terms of composition, macromolecular properties (particle size, molar mass, charge), interfacial activity, and stabilization capacity were highly dependent on the centrifugal force and time applied. The hemicellulose and lignin contents in the fractions were balanced by centrifugal forces to obtain functional emulsifiers that efficiently stabilized the oil/water interface. Through fractionation of softwood extracts, we also found that both the hemicelluloses and lignin particles are involved in emulsion interface formation and stabilization. Centrifugation is a scalable concept that can be feasibly and easily introduced into the biorefinery system and used to optimize the composition of biomass fractions for targeted purposes.
  • Siven, Mia; Kovanen, Satu; Siirola, Outi; Hepojoki, Tuomas; Isokirmo, Sari; Laihanen, Niina; Eränen, Tiina; Pellinen, Jukka; Juppo, Anne M. (2017)
    Objectives The study evaluated the quality of compounded sachets and hard gelatine capsules and their feasibility in paediatric drug administration. Methods Commercial tablets were compounded to sachets and capsules in hospital environment, and the uniformity of content and simulated drug dose were determined. Key findings Compounded formulations were successfully obtained for a range of drug substances; dipyridamole, spironolactone, warfarin and sotalol formulations were within acceptable limits for uniformity of content, in most cases. However, some loss of drug was seen. The type and amount of excipients were found to affect uniformity of content; good conformity of capsules was obtained using lactose monohydrate as filler, whereas microcrystalline cellulose was a better choice in sachets. In capsules, content uniformity was obtained for a range of drug doses. If the drug is aimed to be administered through a nasogastric tube, solubility of the drug and excipients should be considered, as they were found to affect the simulated drug dose in administration. Conclusions Compounded sachets and capsules fulfilled the quality requirements in most cases. In compounding, the choice of excipients should be considered as they can affect conformity of the dosage form or its usability in practice. Quality assurance of compounded formulations should be taken into consideration in hospital pharmacies.
  • Sinkkonen, Elina; Elovainio, Marko (2020)
    People's threat perceptions play a role in influencing foreign policies towards perceived adversary countries. Earlier research has identified multiple components shaping mass-level threat perceptions including military power, adversary country's perceived intentions, and national identities. On the individual level, education, use of media, and interest in politics have been shown to influence threat perceptions. However, most studies on perceptions of security threats fail to include both contextual and individual-level explanatory factors and to consider that different national threats may be constructed differently. This research bridges formation of threat perceptions on the individual level to wider societal processes and provides an empirical perspective to understanding threat perceptions among the educated section of the Chinese population. To analyze threat perceptions, students from leading Chinese universities (N = 771) took part in a survey in the autumn of 2011 and spring of 2012. Respondents who followed conventional media were more likely to perceive both the United States and Japan as threatening, and the effect of media consumption was particularly strong with regards to perceived threat from Japan. In addition, each threat perception was significantly associated with threat-specific explanatory factors. Potential explanatory factors of threat perceptions were explored with linear regression models.
  • Augustyn, Bozena; Stepien, Piotr; Poojari, Chetan; Mobarak, Edouard; Polit, Agnieszka; Wisniewska-Becker, Anna; Rog, Tomasz (2019)
    Nanodiscs are suitable tools for studies of membrane proteins (MPs) due to their ability to mimic native biological membranes, and several MP structures are solved in nanodiscs. Among the various cell membrane components, cholesterol (CHL) is known to regulate protein function and its concentration can reach up to 50 mol %. However, studies comprising cholesterol are challenging due to its hydrophobic nature, hence, nanodiscs with only a low cholesterol concentration have been studied. To overcome the problem, cholesterol analogs with high solubility in polar solutions are often used, and one of them is cholesteryl hemisuccinate (CHS). Nevertheless, in molecular dynamics (MD) simulation, this is not an obstacle. In this study, we performed MD simulations of nanodiscs containing neutral phosphatidylcholine (POPC) lipids, negatively charged phosphatidylglycerol (POPG) lipids, CHL, or negatively charged cholesterol analog, CHS. Our simulations show that CHS increases the order of lipids in nanodiscs; the effect is, however, weaker than CHL and even smaller in nanodiscs. Furthermore, CHS gathered around scaffold proteins while cholesterol was uniformly distributed in the nanodiscs. Thus, nanodiscs with CHS are heterogeneous and not equivalent to nanodiscs with CHL. Finally, we also observed the increased concentration of POPG near the scaffold proteins, driven by electrostatic interactions. The MD results are experimentally validated using electron paramagnetic resonance spectroscopy. These results show that nanodiscs are, in fact, complex structures not easily comparable with planar lipid bilayers.
  • Dutta, Bhaskar; Vartiainen, Hannu (2020)
    Farsighted formulations of coalitional formation, for instance, by Harsanyi and Ray and Vohra, have typically been based on the von Neumann-Morgenstern stable set. These farsighted stable sets use a notion of indirect dominance in which an outcome can be dominated by a chain of coalitional "moves" in which each coalition that is involved in the sequence eventually stands to gain. Dutta and Vohra point out that these solution concepts do not require coalitions to make optimal moves. Hence, these solution concepts can yield unreasonable predictions. Dutta and Vohra restricted coalitions to hold common, history-independent expectations that incorporate optimality regarding the continuation path. This paper extends the Dutta-Vohra analysis by allowing for history-dependent expectations. The paper provides characterization results for two solution concepts that correspond to two versions of optimality. It demonstrates the power of history dependence by establishing nonemptyness results for all finite games as well as transferable utility partition function games. The paper also provides partial comparisons of the solution concepts to other solutions.
  • Rantalainen, Ville; Lahti, Jari; Henriksson, Markus; Kajantie, Eero; Eriksson, Johan G.; Räikkönen, Katri (2018)
    Objective To test if the Finnish Defence Forces Basic Intellectual Ability Test scores at 20.1 years predicted risk of organic dementia or Alzheimer disease (AD). Methods Dementia was defined as inpatient or outpatient diagnosis of organic dementia or AD risk derived from Hospital Discharge or Causes of Death Registers in 2,785 men from the Helsinki Birth Cohort Study, divided based on age at first diagnosis into early onset (= 65 years). The Finnish Defence Forces Basic Intellectual Ability Test comprises verbal, arithmetic, and visuospatial subtests and a total score (scores transformed into a mean of 100 and SD of 15). We used Cox proportional hazard models and adjusted for age at testing, childhood socioeconomic status, mother's age at delivery, parity, participant's birthweight, education, and stroke or coronary heart disease diagnosis. Results Lower cognitive ability total and verbal ability (hazard ratio [HR] per 1 SD disadvantage > 1.69, 95% confidence interval [CI] 1.01-2.63) scores predicted higher early-onset any dementia risk across the statistical models; arithmetic and visuospatial ability scores were similarly associated with early-onset any dementia risk, but these associations weakened after covariate adjustments (HR per 1 SD disadvantage > 1.57, 95% CI 0.96-2.57). All associations were rendered non-significant when we adjusted for participant's education. Cognitive ability did not predict late-onset dementia risk. Conclusion These findings reinforce previous suggestions that lower cognitive ability in early life is a risk factor for early-onset dementia.
  • Kisdi, Eva (2015)
    Evolutionary singularities are central to the adaptive dynamics of evolving traits. The evolutionary singularities are strongly affected by the shape of any trade-off functions a model assumes, yet the trade-off functions are often chosen in an ad hoc manner, which may unjustifiably constrain the evolutionary dynamics exhibited by the model. To avoid this problem, critical function analysis has been used to find a trade-off function that yields a certain evolutionary singularity such as an evolutionary branching point. Here I extend this method to multiple trade-offs parameterized with a scalar strategy. I show that the trade-off functions can be chosen such that an arbitrary point in the viability domain of the trait space is a singularity of an arbitrary type, provided (next to certain non-degeneracy conditions) that the model has at least two environmental feedback variables and at least as many trade-offs as feedback variables. The proof is constructive, i.e., it provides an algorithm to find trade-off functions that yield the desired singularity. I illustrate the construction of trade-offs with an example where the virulence of a pathogen evolves in a small ecosystem of a host, its pathogen, a predator that attacks the host and an alternative prey of the predator.
  • Vainio, Markku (SPIE - the international society for optics and photonics, 2020)
    Proceedings of SPIE
    The atmospheric window at 3 to 5 mu m is one of the most important spectral regions for molecular spectroscopy. This region accommodates strong fundamental vibrational spectra of several interesting molecules, including species relevant for air quality monitoring, medical diagnostics, and fundamental research. These applications require excellent spectroscopic sensitivity and selectivity. For example, atmospheric research often needs precise quantification of trace gas fractions of down to the parts-per-trillion level (10(-12)), with the capability of resolving individual spectral features of different molecular compounds. This sets stringent requirements for the light source of the spectrometer in terms of output power, noise, and linewidth. In addition, the wavelength tuning range of the light source needs to be large, preferably over the entire atmospheric window, in order to enable measurements of molecular fingerprints of several compounds. Continuous-wave optical parametric oscillators (CW-OPOs) are one of the few light sources that have the potential of combining all these favorable characteristics. This contribution summarizes our progress in the development of CW-OPOs, with an emphasis on precise frequency control methods for high-resolution molecular spectroscopy. Examples of new applications enabled by the advanced CW-OPO technologies will be presented. These examples include a demonstration of world-record detection sensitivity in trace gas analysis, as well as the first characterization of infrared spectrum of radioactive methane (CH4)-C-14.
  • Sathyanarayanan, Gowtham; Haapala, Markus; Kiiski, Iiro; Sikanen, Tiina (2018)
    We report the development and characterization of digital microfluidic (DMF) immobilized enzyme reactors (IMERs) for studying cytochrome P450 (CYP)-mediated drug metabolism on droplet scale. The on-chip IMERs consist of porous polymer (thiol-ene) monolith plugs prepared in situ by photopolymerization and functionalized with recombinant CYP1A1 isoforms (an important detoxification route for many drugs and other xenobiotics). The DMF devices also incorporate inexpensive, inkjet-printed microheaters for on-demand regio-specific heating of the IMERs to physiological temperature, which is crucial for maintaining the activity of the temperature-sensitive CYP reaction. For on-chip monitoring of the CYP activity, the DMF devices were combined with a commercial well-plate reader, and a custom fluorescence quantification method was developed for detection of the chosen CYP1A1 model activity (ethoxyresorufin-O-deethylation). The reproducibility of the developed assay was examined with the help of ten parallel CYP-IMERs. All CYP-IMERs provided statistically significant difference (in fluorescence response) compared to any of the negative controls (including room-temperature reactions). The average (n = 10) turnover rate was 20.3 +/- 9.0 fmol resorufin per minute. Via parallelization, the concept of the droplet-based CYP-IMER developed in this study provides a viable approach to rapid and low-cost prediction of the metabolic clearance of new chemical entities in vitro.