230 research outputs found
Tuple decoders for traitor tracing schemes
No full textIn the field of collusion-resistant traitor tracing, Oosterwijk et al. recently determined the optimal suspicion function for simple decoders. Earlier, Moulin also considered another type of decoder: the generic joint decoder that compares all possible coalitions, and showed that usually the generic joint decoder outperforms the simple decoder. Both Amiri and Tardos, and Meerwald and Furon described constructions that assign suspicion levels to c-tuples, where c is the number of colluders. We investigate a novel idea: the tuple decoder, assigning a suspicion level to tuples of a fixed size. In contrast to earlier work, we use this in a novel accusation algorithm to decide for each distinct user whether or not to accuse him. We expect such a scheme to outperform simple decoders while not being as computationally intensive as the generic joint decoder. In this paper we generalize the optimal suspicion functions to tuples, and describe a family of accusation algorithms in this setting that accuses individual users using this tuple-based information
Cancer risk variation in BRCA1/2 mutation families
No full textBRCA1/2 mutation carriers are at a significantly increased risk for breast and ovarian cancer as compared to women in the general population. The cancer risk estimates for mutation carriers show however considerable variation. More accurate, personal risk estimation would be beneficial for counseling and decision making regarding breast cancer screening and preventive surgery. The aim of this thesis was to improve the breast and ovarian cancer risk estimates for BRCA1/2 carriers and their female relatives, by explaining the risk variation and developing subgroup specific risk estimates. Therefore methodology and population characteristics – i.e. mutation status, mutation spectrum, family history, birth cohort – were assessed in families that were referred for genetic testing. The results showed that the reported variation in cancer risk estimates for BRCA1/2 carriers is mainly due to differences in the applied methodology, whereas differences between women have a smaller effect. Non-carriers in BRCA1/2 families appeared to be at a slightly increased risk for breast cancer in their forties as compared to the general population. Differences in the mutation spectrum only partially explained the regional differences among Dutch carriers, and the breast cancer risk did not depend on whether the mutation was paternally or maternally inherited. The breast cancer risk in mutation carriers above age 60 was still significantly increased, and annual screening detected their tumors in a more favorable stage. Application of the above findings will improve risk counselling of BRCA1/2 mutation carriers, and further evaluation of the breast screening protocols in these families is warranted to optimized surveillance
Risk-reducing surgery: Uptake & menopausal consequences
No full textWomen with a BRCA1/2 genetic mutation have an increased risk of developing breast and ovariumcancer. Women with this predisposition are advised to regularly have their breasts examined for breast cancer or to have their breasts preventively removed. With regards to ovarium cancer women are advised to undergo preventive surgery as regular examinations have been found ineffective in detecting cancer in a curable stage. In part 1 of this thesis the factors that influence the decision to undergo preventive surgery in women with a BRCA1/2 mutation was studied. Part 2 studies the alleviation of side effects of the preventive salpingo-oophorectomy by using psychological interventions
Beyond risk-reducing salpingo-oophorectomy: On breast cancer risk and bone health
No full textRisico-reducerende salpingo-oophorectomie (RRSO) is een operatieve eileider- en eierstokverwijdering. RRSO op premenopauzale leeftijd wordt geadviseerd aan vrouwen met een verhoogd eierstokkankerrisico ten gevolge van BRCA1- of BRCA2-kiembaanmutaties. Psychosexuele en fysieke gezondheidseffecten geassocieerd met de natuurlijke menopauze treden waarschijnlijk eerder en heviger op na chirurgische menopauze door premenopauzale RRSO dan na natuurlijke menopauze. Van deze RRSO-geïnduceerde gezondheidseffecten, worden in dit proefschrift het borstkankerrisico en de botgezondheid onderzocht. Eerdere studies rapporteerden een halvering van het borstkankerrisico na RRSO in BRCA1/2- mutatiedraagsters. In onze studie naar de effectiviteit van borstkankerscreening bij BRCA1/2- mutatiedraagsters na premenopauzale RRSO, werd een halvering van het borstkankerrisico niet bevestigd. Sindsdien hebben ook andere studies het bewijs over een RRSO-geïnduceerde borstkankerrisicoreductie in twijfel getrokken en wordt aangenomen dat eerder gerapporteerde risicoreducties het gevolg waren van bias. Meer onderzoek is nodig en tot zolang blijft intensieve borstkankerscreening na RRSO aangewezen. Na de natuurlijke menopauze daalt de botdichtheid en stijgt het fractuurrisico. In een systematische review en meta-analyse over chirurgische menopauze in een algemene populatie, was botdichtheid in vrouwen met een chirurgische menopauze lager dan in premenopauzale leeftijdsgenoten, maar vergelijkbaar met leeftijdsgenoten met een natuurlijke menopauze. In onze studie in vrouwen met een verhoogd eierstokkankerrisico bleek dat botdichtheid en fractuurrisico vijf jaar na premenopauzale RRSO vergelijkbaar waren met de algemene populatie. Wel bleken de botombouwparameters verhoogd. Omdat dit kan wijzen op een verhoogd fractuurrisico op de langere termijn, is een longitudinale studie van dit cohort aangewezen. Dit proefschrift draagt bij aan de zorg voor vrouwen tijdens de counseling en na RRSO
The Relationship between Meaning, Resiliency and Psychosocial Problems in Adolescents
No full textIn dit artikel wordt de samenhang tussen zingeving, resiliency en psychosociale problematiek bij adolescenten onderzocht en variabelen geïdentificeerd die hiermee samenhangen. Dit werd in deze studie onderzocht met een cross-sectioneel onderzoek onder 85 Nederlandse adolescenten in de leeftijd van 12 tot en met 18 jaar. Middels de Child Behavior Checklist (CBCL) werd de psychosociale problematiek gemeten, de Existential Scale of the Purpose in Life Questionnaire (EPIL) mat de zingeving en de nederlandse versie van de Resilience Scale (RS-NL) de resiliency. Met behulp van meervoudige regressie analyse en hiërarchische regressie analyse werden de data geanalyseerd. Er werd een sterk negatief verband gevonden tussen resiliency en psychosociale problematiek (r = -.486, p ≤ .01). Eveneens bleek er een significante negatieve relatie te zijn tussen zingeving en psychosociale problematiek (r = -.822, p ≤ .01). Er werden significante verbanden gevonden tussen de criteriumvariabele psychosociale problematiek en predictorvariabelen geluksgevoel (β = -.221, p = .040) en zingeving (β = -.575, p ≤ .01). Eveneens werden significante verbanden gevonden tussen de criteriumvariabele zingeving en predictorvariabelen geluksgevoel (β = .461, p ≤ .01) en resiliency (β = .432, p ≤ .01).
Bij de moderatie-analyse werd gevonden dat 33% in de variantie van psychosociale problematiek wordt verklaard door resiliency, sekse en leeftijd (F = 9.003, p ≤ .01). Uit de stratificatie bleek dat 56% van de variantie in psychosociale problematiek bij jonge adolescenten verklaard wordt door resiliency. Dit tegenover 9% bij de oudere adolescenten.
De mediatie-analyse toonde dat resiliency in het huidige onderzoek geen significante mediërende rol speelt in het verband tussen zingeving en psychosociale problematiek (S = -1.31 (SE = .15, p = .19).
Geconcludeerd is dat de eerder gevonden samenhang tussen zingeving en resiliency en resiliency en psychosociale problematiek bevestigd is. Interventies bij jongeren met psychosociale problemen met als doel de resiliency en zingeving te verhogen zijn dan ook aanbevolen
A capacity-achieving simple decoder for bias-based traitor tracing schemes
No full textWe investigate alternative suspicion functions for bias-based traitor tracing schemes, and present a practical construction of a simple decoder that attains capacity in the limit of large coalition size . We derive optimal suspicion functions in both the Restricted-Digit Model and the Combined-Digit Model. These functions depend on information that is usually not available to the tracer -- the attack strategy or the tallies of the symbols received by the colluders. We discuss how such results can be used in realistic contexts. We study several combinations of coalition attack strategy versus suspicion function optimized against some attack (another attack or the same). In many of these combinations the usual codelength scaling changes to a lower power of , e.g. . We find that the interleaving strategy is an especially powerful attack. The suspicion function tailored against interleaving is the key ingredient of the capacity-achieving construction
Optimal suspicion functions for Tardos traitor tracing schemes
No full textWe investigate alternative suspicion functions for Tardos traitor tracing schemes. In the simple decoder approach (computation of a score for every user independently) we derive suspicion functions that optimize a performance indicator related to the sufficient code length in the limit of large coalition size . Our results hold for the Restricted-Digit Model as well as the Combined-Digit Model. The scores depend on information that is usually not available to the tracer -- the attack strategy or the tallies of the symbols received by the colluders. We discuss how such results can be used in realistic contexts. We study several combinations of coalition attack strategy vs. suspicion function optimized against some attack (another attack or the same). In many of these combinations the usual scaling is replaced by a lower power of , e.g. . We find that the interleaving strategy is an especially powerful attack, and the suspicion function tailored against interleaving is effective against all considered attacks
Genetic control of tumor development in malformation syndromes
No full textOne of the questions that arises frequently when caring for an individual with a malformation syndrome, is whether some form of tumor surveillance is indicated. In some syndromes there is a highly variable increased risk to develop tumors, while in others this is not the case. The risks can be hard to predict and difficult to explain to affected individuals and their families, and often also to caregivers. The queries arise especially if syndrome causing mutations are also known to occur in tumors. It needs insight in the mechanisms to understand and explain differences of tumor occurrence, and to offer optimal care to individuals with syndromes. Here we provide a short overview of the major mechanisms of the control for tumor occurrences in malformation syndromes.</p
Binary and q-ary Tardos codes, revisited
No full textThe Tardos code is a much studied collusion-resistant fingerprinting code, with the special property that it has asymptotically optimal length m ¿ c^2_0, where c_0 is the number of colluders. In this paper we give alternative security proofs for the Tardos code, working with the assumption that the strongest coalition strategy is position-independent. We employ the Bernstein inequality and Bennett inequality instead of the typically used Markov inequality. This proof technique requires fewer steps and slightly improves the tightness of the bound on the false negative error probability. We present new results on code length optimization, for both small and asymptotically large coalition sizes.
Keywords: Traitor tracing; Tardos fingerprinting; Collusio
- …
