133 research outputs found
Financial liberalization and financial fragility : the experiences of Chile and Indonesia compared
The far-reaching liberalization process introduced in Chile after the overthrow of the Allende regime first met with reasonable success, but in theearly 1980s a foreign-exchange crisis and a banking crisis appeared to mark the end of the experiment. Liberalization was resumed in 1985 and has notbeen plagued by serious crises since. The root of the problem seems to have been an exchange rate policy which had to be abandoned, but not before ithad led economic actors to make the wrong decisions. The lack of prudential supervision of the financial system did the rest. So far, Indonesia has been following much more cautious exchange rate policies in its liberalization drive. Crises on the scale experienced by Chile are not very likely to occur. The lessons provided by the lack of prudential supervision in Chile do not, however, seem to have been taken to heart, or not sufficiently. Even if the Indonesian banks are unlikely to suffer as much as their Chilean opposite numbers from foreign exchange risks, bad loans, in particular resulting fromintra-conglomerate lending, are an increasingly serious prohlem. In dealing with troubled banks the Indonesian authorities have not repeated the mistake of the Chileans to provide a full deposit guarantee. Nonetheless, excellent though the banking rules may look on paper, the implementation leaves muchto be desired and Indonesia probably has not yet seen the end of its banking troubles. Apparently, market imperfections are such that effectiveprudential supervision cannot be dispensed with. Also, it appears that low capital-assetratios in both banks and their clients, as in Chile in the mid-1970s, call for a cautious course in liberalization
Characterising eye movement events with an unsupervised hidden markov model
Eye-tracking allows researchers to infer cognitive processes from eye movements that are classified into distinct events. Parsing the events is typically done by algorithms. Here we aim at developing an unsupervised, generative model that can be fitted to eye-movement data using maximum likelihood estimation. This approach allows hypothesis testing about fitted models, next to being a method for classification. We developed gazeHMM, an algorithm that uses a hidden Markov model as a generative model, has few critical parameters to be set by users, and does not require human coded data as input. The algorithm classifies gaze data into fixations, saccades, and optionally postsaccadic oscillations and smooth pursuits. We evaluated gazeHMMâs performance in a simulation study, showing that it successfully recovered hidden Markov model parameters and hidden states. Parameters were less well recovered when we included a smooth pursuit state and/or added even small noise to simulated data. We applied generative models with different numbers of events to benchmark data. Comparing them indicated that hidden Markov models with more events than expected had most likely generated the data. We also applied the full algorithm to benchmark data and assessed its similarity to human coding and other algorithms. For static stimuli, gazeHMM showed high similarity and outperformed other algorithms in this regard. For dynamic stimuli, gazeHMM tended to rapidly switch between fixations and smooth pursuits but still displayed higher similarity than most other algorithms. Concluding that gazeHMM can be used in practice, we recommend parsing smooth pursuits only for exploratory purposes. Future hidden Markov model algorithms could use covariates to better capture eye movement processes and explicitly model event durations to classify smooth pursuits more accurately
Developing Representations of Compound Stimuli
Classification based on multiple dimensions of stimuli is usually associated with similarity-based representations, whereas uni-dimensional classifications are associated with rule-based representations. This paper studies classification of stimuli and category representations in school-aged children and adults when learning to categorize compound, multi-dimensional stimuli. Stimuli were such that both similarity-based and rule-based representations would lead to correct classification. This allows testing whether children have a bias for formation of similarity-based representations. The results are at odds with this expectation. Children use both uni-dimensional and multi-dimensional classification, and the use of both strategies increases with age. Multi-dimensional classification is best characterized as resulting from an analytic strategy rather than from procedural processing of overall-similarity. The conclusion is that children are capable of using complex rule-based categorization strategies that involve the use of multiple features of the stimuli. The main developmental change concerns the efficiency and consistency of the explicit learning system
Rejoinder by James Berger, Woncheol Jang, Surajit Ray, Luis R. Pericchi and Ingmar Visser
No abstract available
Prior-based Bayesian information criterion
We present a new approach to model selection and Bayes factor determination, based on Laplace expansions (as in BIC), which we call Prior-based Bayes Information Criterion (PBIC). In this approach, the Laplace expansion is only done with the likelihood function, and then a suitable prior distribution is chosen to allow exact computation of the (approximate) marginal likelihood arising from the Laplace approximation and the prior. The result is a closed-form expression similar to BIC, but now involves a term arising from the prior distribution (which BIC ignores) and also incorporates the idea that different parameters can have different effective sample sizes (whereas BIC only allows one overall sample size n). We also consider a modification of PBIC which is more favourable to complex models
Cognitive flexibility training has direct and near transfer effects, but no far transfer effects, preschoolers
The current project studied the direct, near transfer, and far transfer effects of cognitive flexibility training in two experiments with 117 3-year-olds. In both Experiments 1 and 2, children performed three Dimensional Change Card Sorting (DCCS) tasks in a pre-training/training/post-training design. The training consisted of giving corrective feedback in the training DCCS task. In Experiment 2, in addition, three other executive control tasks were administered during pre-training and post-training. Results showed a direct effect of feedback in the training DCCS task and transfer of this effect to the post-training DCCS task after 1 week with different sorting rules and different stimuli. These findings show that preschoolers learned to switch sorting rules in the context of the DCCS task, independent of the specific sorting rules, and that this effect is not transient. No support was found for transfer to the other executive control tasks. A possible explanation is that the feedback mainly improved rule switching, an ability that is specifically required for performing a cognitive flexibility task but not the other executive control tasks
Preparation of UO2, ThO2 and (Th,U)O2 pellets from photochemically-prepared nano-powders
Photochemically-induced preparation of nano-powders of crystalline uranium and/or thorium oxides and their subsequent pelletizing has been investigated. The preparative method was based on the photochemically induced formation of amorphous solid precursors in aqueous solution containing uranyl and/or thorium nitrate and ammonium formate. The EXAFS analyses of the precursors shown that photon irradiation of thorium containing solutions yields a compound with little long-range order but likely "ThO2 like" and the irradiation of uranium containing solutions yields the mixture of U(IV) and U(VI) compounds. The U-containing precursors were carbon free, thus allowing direct heat treatment in reducing atmosphere without pre-treatment in the air. Subsequent heat treatment of amorphous solid precursors at 300-550 C yielded nano-crystalline UO2, ThO2 or solid (Th,U)O2 solutions with high purity, well-developed crystals with linear crystallite size <15 nm. The prepared nano-powders of crystalline oxides were pelletized without any binder (pressure 500 MPa), the green pellets were subsequently sintered at 1300 C under an Ar:H2 (20:1) mixture (UO2 and (Th,U)O2 pellets) or at 1600 C in ambient air (ThO2 pellets). The theoretical density of the sintered pellets varied from 91 to 97%
Robustness of the rule-learning effect in 7-month-old infants: A close, multicenter replication of Marcus et al. (1999)
We conducted a close replication of the seminal work by Marcus and colleagues from 1999, which showed that after a brief auditory exposure phase, 7-month-old infants were able to learn and generalize a rule to novel syllables not previously present in the exposure phase. This work became the foundation for the theoretical framework by which we assume that infants are able to learn abstract representations and generalize linguistic rules. While some extensions on the original work have shown evidence of rule learning, the outcomes are mixed, and an exact replication of Marcus et al.'s study has thus far not been reported. A recent meta-analysis by Rabagliati and colleagues brings to light that the rule-learning effect depends on stimulus type (e.g., meaningfulness, speech vs. nonspeech) and is not as robust as often assumed. In light of the theoretical importance of the issue at stake, it is appropriate and necessary to assess the replicability and robustness of Marcus et al.'s findings. Here we have undertaken a replication across four labs with a large sample of 7-month-old infants (N = 96), using the same exposure patterns (ABA and ABB), methodology (Headturn Preference Paradigm), and original stimuli. As in the original study, we tested the hypothesis that infants are able to learn abstract âalgebraicâ rules and apply them to novel input. Our results did not replicate the original findings: infants showed no difference in looking time between test patterns consistent or inconsistent with the familiarization pattern they were exposed to
Glycan Binding Proteins in Therapeutic Mesenchymal Stem Cell Research
Mesenchymal stem/stromal cells (MSCs) are multipotent adult stem cells that hold enormous therapeutic potential. They are currently in a focus of intense clinical and scientific investigation. MSCs are a promising cell type for various applications in the field of tissue engineering due to their multi-lineage differentiation capacity. Furthermore, one of their most interesting characteristics is that they possess immunomodulatory properties making these cells an attractive candidate for therapy of several immune-mediated disorders. MSCs are of nonembryonic origin and thus provide a less controversial and technically more feasible alternative for ESCs in future therapeutic applications.
Due to their location on the cell surface, glycans are ideal molecules for identification, purification, and characterization of cells for therapeutic purposes. Methods to reliably and proficiently determine both the change in the presence of a specific glycan structures and the changes in the glycome profile of a cell, are needed. Glycan binding proteins in general serve as diagnostic tools in medical and scientific laboratories. High affinity and exquisite specificity are important factors for their successful use.
The aim of this study was to characterize the glycans on the surface of MSCs in order to find novel MSC specific glycan markers. Further goal was to develop antibodies specific for MSC surface glycans, including the novel MSC marker.
As described in the original publications of this study, we first characterized the glycome of MSCs and discovered that certain specific glycan epitopes are present only in MSCs, and not in cells differentiated from them. These epitopes include i antigen, which was further characterized to be a marker for umbilical cord blood derived MSCs. An antibody against the i antigen was generated using recombinant technology. Antibodies recognizing MSC surface glycans were also generated by utilizing hybridoma technology, using whole MSCs in the immunization.
Taken together, these studies provide information of the changes in the glycome profile during MSC differentiation and describe a novel MSC marker. In these studies, we used two different methods to generate anti-glycan antibodies and emphasize the importance of thorough characterization of the binding properties of GBPs. The information of the characteristic glycosylation features of MSCs, and specific markers especially, can be used to isolate and characterize desired, therapeutically advantageous cell populations for distinct applications. Development of better glycan binding proteins will advance the field of cellular therapy and also the glycobiological research in general.Mesenkymaaliset kantasolut (eli mesenkymaaliset stroomasolut) ovat monikykyisiÀ soluja, jotka pystyvÀt erilaistumaan useiksi erilaisiksi solutyypeiksi. Viime aikoina nÀiden solujen tutkimus ja kliininen kÀyttö on herÀttÀnyt paljon huomiota ja kiinnostusta. Mesenkymaalinen kantasolu on lupaava solutyyppi moniin terapeuttisiin sovelluksiin. Erityisesti kudosteknologiset sovellukset kÀyttÀvÀt hyvÀkseen mesenkymaalisten kantasolujen erilaistumiskykyÀ. Yksi mesenkymaalisten kantasolujen kiinnostavimmista piirteistÀ on kuitenkin niiden vaikutus immuunivasteeseen ja mahdollinen kÀyttö immuunivÀlitteisten sairauksien, kuten kÀÀnteishyljintÀreaktion hoidossa.
SekÀ tutkimus- ettÀ terapiakÀyttöön tarkoitetut solut tÀytyy voida tunnistaa, eristÀÀ ja karakterisoida hyvin. Solun pinnalla olevat sokerimolekyylit eli glykaanit tarjoavat tÀhÀn oivan mahdollisuuden. Sokerirakenteista voidaan tarkkailla yksittÀisten glykaanien esiintymisen muutoksia sekÀ pinnan sokeriprofiilin kokonaismuutoksia. TutkimusmenetelmÀt ovat viime vuosina kehittyneet huimasti, mutta vaativat vielÀ jatkuvaa kehitystÀ. Sokerirakenteita sitovat proteiinit (vasta-aineet ja lektiinit) ovat laboratorioissa yleisesti kÀytettyjÀ diagnostisia työkaluja, ja soveltuvat hyvin solun pinnan sokereiden tutkimiseen. Tarkasti mÀÀritetty sitoutumisspesifisyys ja riittÀvÀn hyvÀ sitoutumislujuus ovat merkittÀviÀ tekijöitÀ glykaaneja sitovien proteiinien onnistuneelle kÀytölle sekÀ niiden avulla saatujen tulosten oikeellisuudelle.
TÀmÀn tutkimuksen tarkoituksena oli kartoittaa mesenkymaalisten kantasolujen pinnan sokerirakenteita tavoitteena löytÀÀ spesifinen markkeri sekÀ kehittÀÀ vasta-aineita nÀitÀ rakenteita tunnistamaan. Ensiksi havaitsimme solun pinnan sokeriprofiilin muuttuvan solun erilaistuessa. Keskityimme tarkastelemaan lineaarista poly-LacNAc rakennetta, eli i-antigeenia, jonka mÀÀrÀ solun pinnalla vÀheni huomattavasti solujen erilaistuessa. Tarkempi karakterisointi osoitti i-antigeenin olevan spesifinen markkeri mesenkymaalisille kantasoluille. Kehitimme i-antigeenin tunnistavan vasta-aineen rekombinanttitekniikalla sekÀ mesenkymaalisen solun pinnan sokereille spesifisiÀ vasta-aineita hybridoomatekniikalla.
Jotta soluterapiaa voidaan turvallisesti kehittÀÀ lisÀÀntyviin hoitotarpeisiin, tarvitaan tarkkoja karakterisointimenetelmiÀ ja hyviÀ työkaluja solujen tunnistamiseen ja eristÀmiseen. Tietoa pinnan sokerirakenteiden muutoksista voidaan kÀyttÀÀ eristettÀessÀ haluttuja solupopulaatiota eri terapiasovelluksiin. Sokerirakenteita sitovien proteiinien kehittÀminen edesauttaa sekÀ soluterapian ettÀ glykobiologisen tutkimuksen kehittymistÀ
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