| 1. |
- Bartsch, Hans, et al.
(författare)
-
Tvåvingar – Diptera
- 2010
-
Ingår i: Rödlistade arter i Sverige 2010 – The 2010 Red List of Swedish Species. - 9789188506351 ; , s. 393-410
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
|
|
| 2. |
- Brodin, Ulf B
(författare)
-
A ‘3 step’ IRT strategy for evaluation of the use of sum scores in small studies with questionnaires using items with ordered response levels : ‘To make a lot out of nothing’, from the Swedish locution: ‘Att koka soppa på en spik’
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This study is focused on a strategy for a basic evaluation of a questionnaire at an early state (i.e. only a limited sample from the target population is available). Several questionnaires are constructed within the medical research to investigate phenomenon which cannot be explicitly measured (latent variables). In many cases, these questionnaires are applied on a limited sample (less than 100 subjects), without any proper evaluation of its basic characteristic. This thesis presents a ‘3- step’ strategy for evaluation of questionnaires, where only a limited sample is available for the investigation. Only questionnaires, containing items with a common set of answer alternatives, are considered. The answer alternatives are in terms of an ordered scale to measure the underlying, latent, variable. In all cases, the intention is that a sum score will be a relevant measure of the status of a subject. The higher the score, the more of the latent characteristic is attached to the subject. This implies that all items should represent one common dimension. The investigation is carried out in three steps and is focused on whether the following criteria, at least approximately, correspond to the intentions which the researcher was supposed to have in mind, at the construction of the questionnaire: 1. All items cooperate; 2. All items work together towards a common dimension; 3. Non-coherent/irrelevant items, as well as non-coherent answer profiles can be identified; 4. The subjects can be reasonably ranked, based on the sum score, on the latent scale; 5. The sum score can be transformed, via a statistical model, to a relevant interval scaled measure; 6. The set of items covers reasonably the intended population; 7. The item set is sufficient for an estimate of a person’s position on the latent scale; 8. Defined subgroups perceive the questionnaire in the same way; 9. A straight forward sum score is a sufficient measure (sufficient statistic). Otherwise, an elaborated model, with item specific discrimination, is considered. Step 1: Non parametric statistical analysis according to ‘The Mokken scale analysis’ (1 - 4); Step 2: A parametric model according to the Rasch approach (3, 5 - 8); and Step 3: Can further information be gained from an extended model? (9). This strategy was applied on 5 studies, all carried out with the intention to use the sum score as a relevant measure of persons’ status on the underlying latent scale. Each study involves more than one questionnaire. The ’3 – step’ strategy was applied on 13 questionnaires within these 5 studies, where the intention was to use a sum score. Results: Already Step 1 reveals most of the basic weaknesses of the questionnaire, such as weak or contradictory items, deficient correlations between items and a violation of an invariant ordering of the item across low to high scoring persons. These findings are also confirmed in later steps, where further characteristics can be revealed. It also turned out that a well behaved questionnaire according to the ‘Mokken requirements’ is a prerequisite for a reasonable parametric approach. Furthermore, in most cases the number of items appears to be too small and that the item set has an insufficient coverage to reasonably estimate a person measure for all subjects belonging to the intended population. But, the ‘3 steps’ can constitute a comprehensive message for a basic improvement of the questionnaire.
|
|
| 3. |
- Brodin, Ulf, et al.
(författare)
-
The application of Item Response Theory on a teaching strategy profile questionnaire
- 2010
-
Ingår i: BMC Medical Education. - : BioMed Central. - 1472-6920. ; 10:14
-
Tidskriftsartikel (refereegranskat)abstract
- Background In medical education research, various questionnaires are often used to study possible relationships between strategies and approaches to teaching and learning and the outcome of these. However, judging the applicability of such questionnaires or the interpretation of the results is not trivial. Methods As a way to develop teacher thinking, teaching strategy profiles were calculated for teachers in a research intensive department at Karolinska Institutet. This study compares the sum score, that was inherent in the questionnaire used, with an Item Response Theory (IRT) approach. Three teaching dimensions were investigated and the intended sum scores were investigated by IRT analysis. Results Agreements as well as important differences were found. The use of the sum score seemed to agree reasonably with an IRT approach for two of the dimensions, while the third dimension could not be identified neither by a the sum score, nor by an IRT approach, as the items included showed conflicting messages. Conclusions This study emphasizes the possibilities to gain better insight and more relevant interpretation of a questionnaire by use of IRT. A sum score approach should not be taken for granted. Its use has to be thoroughly evaluated.
|
|
| 4. |
- Cederberg, B., et al.
(författare)
-
Tvåvingar
- 2010
-
Ingår i: Rödlistade arter i Sverige 2010. - 9789188506351 ; , s. 185-202
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Abstract is not available
|
|
| 5. |
- Ehnman, Monika, et al.
(författare)
-
Distinct Effects of Ligand-Induced PDGFR alpha and PDGFR beta Signaling in the Human Rhabdomyosarcoma Tumor Cell and Stroma Cell Compartments
- 2013
-
Ingår i: Cancer Research. - 1538-7445. ; 73:7, s. 2139-2149
-
Tidskriftsartikel (refereegranskat)abstract
- Platelet-derived growth factor receptors (PDGFR) alpha and beta have been suggested as potential targets for treatment of rhabdomyosarcoma, the most common soft tissue sarcoma in children. This study identifies biologic activities linked to PDGF signaling in rhabdomyosarcoma models and human sample collections. Analysis of gene expression profiles of 101 primary human rhabdomyosarcomas revealed elevated PDGF-C and -D expression in all subtypes, with PDGF-D as the solely overexpressed PDGFR beta ligand. By immunohistochemistry, PDGF-CC, PDGF-DD, and PDGFR alpha were found in tumor cells, whereas PDGFR beta was primarily detected in vascular stroma. These results are concordant with the biologic processes and pathways identified by data mining. While PDGF-CC/PDGFR alpha signaling associated with genes involved in the reactivation of developmental programs, PDGF-DD/PDGFR beta signaling related to wound healing and leukocyte differentiation. Clinicopathologic correlations further identified associations between PDGFR beta in vascular stroma and the alveolar subtype and with presence of metastases. Functional validation of our findings was carried out in molecularly distinct model systems, where therapeutic targeting reduced tumor burden in a PDGFR-dependent manner with effects on cell proliferation, vessel density, and macrophage infiltration. The PDGFR-selective inhibitor CP-673,451 regulated cell proliferation through mechanisms involving reduced phosphorylation of GSK-3 alpha and GSK-3 beta. Additional tissue culture studies showed a PDGFR-dependent regulation of rhabdosphere formation/cancer cell stemness, differentiation, senescence, and apoptosis. In summary, the study shows a clinically relevant distinction in PDGF signaling in human rhabdomyosarcoma and also suggests continued exploration of the influence of stromal PDGFRs on sarcoma progression. Cancer Res; 73(7); 2139-49. (C)2013 AACR.
|
|
| 6. |
- Lovén, Jakob, et al.
(författare)
-
MYCN-regulated microRNAs repress estrogen receptor-alpha (ESR1) expression and neuronal differentiation in human neuroblastoma.
- 2010
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 107:4, s. 1553-8
-
Tidskriftsartikel (refereegranskat)abstract
- MYCN, a proto-oncogene normally expressed in the migrating neural crest, is in its amplified state a key factor in the genesis of human neuroblastoma (NB). However, the mechanisms underlying MYCN-mediated NB progression are poorly understood. Here, we present a MYCN-induced miRNA signature in human NB involving the activation and transrepression of several miRNA genes from paralogous clusters. Several family members derived from the miR-17 approximately 92 cluster, including miR-18a and miR-19a, were among the up-regulated miRNAs. Expression analysis of these miRNAs in NB tumors confirmed increased levels in MYCN-amplified samples. Specifically, we show that miR-18a and miR-19a target and repress the expression of estrogen receptor-alpha (ESR1), a ligand-inducible transcription factor implicated in neuronal differentiation. Immunohistochemical staining demonstrated ESR1 expression in human fetal sympathetic ganglia, suggesting a role for ESR1 during sympathetic nervous system development. Concordantly, lentiviral restoration of ESR1 in NB cells resulted in growth arrest and neuronal differentiation. Moreover, lentiviral-mediated inhibition of miR-18a in NB cells led to severe growth retardation, outgrowth of varicosity-containing neurites, and induction of neuronal sympathetic differentiation markers. Bioinformatic analyses of microarray data from NB tumors revealed that high ESR1 expression correlates with increased event-free survival in NB patients and favorable disease outcome. Thus, MYCN amplification may disrupt estrogen signaling sensitivity in primitive sympathetic cells through deregulation of ESR1, thereby preventing the normal induction of neuroblast differentiation. Collectively, our findings demonstrate the molecular consequences of abnormal miRNA transcription in a MYCN-driven tumor and offer unique insights into the pathology underlying MYCN-amplified NB.
|
|
| 7. |
- Strondl, Annika, et al.
(författare)
-
Characterisation and control of powder properties for additive manufacturing
- 2014
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Powder characterization and handling in PM are important issues and required powder properties will vary between different component manufacturing processes. By understanding and controlling these, the final material properties for different applications can be improved and become more reliable. In this study, metal powders used in additive manufacturing have been investigated regarding particle size and shape using dynamic image analysis. In parallel, powder flow characteristics have been evaluated with a powder rheometer. Correlations within the results have been found between particle shape and powder flow characteristic that could explain certain effects of the powder processing in the additive manufacturing processes.
|
|
