166 research outputs found
Common Scaling Patterns in Intertrade Times of U. S. Stocks
We analyze the sequence of time intervals between consecutive stock trades of
thirty companies representing eight sectors of the U. S. economy over a period
of four years. For all companies we find that: (i) the probability density
function of intertrade times may be fit by a Weibull distribution; (ii) when
appropriately rescaled the probability densities of all companies collapse onto
a single curve implying a universal functional form; (iii) the intertrade times
exhibit power-law correlated behavior within a trading day and a consistently
greater degree of correlation over larger time scales, in agreement with the
correlation behavior of the absolute price returns for the corresponding
company, and (iv) the magnitude series of intertrade time increments is
characterized by long-range power-law correlations suggesting the presence of
nonlinear features in the trading dynamics, while the sign series is
anti-correlated at small scales. Our results suggest that independent of
industry sector, market capitalization and average level of trading activity,
the series of intertrade times exhibit possibly universal scaling patterns,
which may relate to a common mechanism underlying the trading dynamics of
diverse companies. Further, our observation of long-range power-law
correlations and a parallel with the crossover in the scaling of absolute price
returns for each individual stock, support the hypothesis that the dynamics of
transaction times may play a role in the process of price formation.Comment: 8 pages, 5 figures. Presented at The Second Nikkei Econophysics
Workshop, Tokyo, 11-14 Nov. 2002. A subset appears in "The Application of
Econophysics: Proceedings of the Second Nikkei Econophysics Symposium",
editor H. Takayasu (Springer-Verlag, Tokyo, 2003) pp.51-57. Submitted to
Phys. Rev. E on 25 June 200
Low anti-staphylococcal IgG responses in granulomatosis with polyangiitis patients despite long-term Staphylococcus aureus exposure
Chronic nasal carriage of the bacterium Staphylococcus aureus in patients with the autoimmune disease granulomatosis with polyangiitis (GPA) is a risk factor for disease relapse. To date, it was neither known whether GPA patients show similar humoral immune responses to S. aureus as healthy carriers, nor whether specific S. aureus types are associated with GPA. Therefore, this study was aimed at assessing humoral immune responses of GPA patients against S. aureus antigens in relation to the genetic diversity of their nasal S. aureus isolates. A retrospective cohort study was conducted, including 85 GPA patients and 18 healthy controls (HC). Humoral immune responses against S. aureus were investigated by determining serum IgG levels against 59 S. aureus antigens. Unexpectedly, patient sera contained lower anti-staphylococcal IgG levels than sera from HC, regardless of the patients' treatment, while total IgG levels were similar or higher. Furthermore, 210 S. aureus isolates obtained from GPA patients were characterized by different typing approaches. This showed that the S. aureus population of GPA patients is highly diverse and mirrors the general S. aureus population. Our combined findings imply that GPA patients are less capable of mounting a potentially protective antibody response to S. aureus than healthy individuals
Het Rijksvaccinatieprogramma in Nederland. Ontwikkelingen in 2006
In 2006 several changes were made in the Dutch National Immunisation Programme (NIP): Hepatitis B vaccination at birth was added for children born to mothers positive for hepatitis B surface antigen; a new vaccine for diphtheria, tetanus, pertussis (a-cellular), poliomyelitis and Haemophilus influenzae (DTaP-IPV/Hib) was introduced; vaccination against pneumococcal disease was added at two, three, four and eleven months; risk groups for hepatitis B receive a combined vaccine for DTaP-IPV/Hib and HBV at the same ages; DT-IPV and aP at the age of four years were combined in one vaccine; and new MMR vaccines were introduced. As new information became available in 2006, the desirability to introduce vaccinations in the NIP for the following diseases could be (re)considered: hepatitis B (universal vaccination), rotavirus, varicella and human papillomavirus. For respiratory syncytial virus and meningococcal serogroup B disease no candidate vaccines are available yet. Extension of the programme with available vaccines for hepatitis A, influenza and tuberculosis is not (yet) recommended. The NIP in the Netherlands is effective and safe. However, continued monitoring of the effectiveness and safety of the NIP is important as changes are made regularly. Maintaining high vaccine uptake is vital to prevent (re)emergence of diseases. Furthermore, the programme should be regularly reviewed as new vaccines become available.In 2006 traden verschillende veranderingen op in het Rijksvaccinatieprogramma (RVP) in Nederland: kinderen die geboren worden uit moeders die chronisch geinfecteerd zijn met hepatitis B krijgen vlak na de geboorte een hepatitis B vaccinatie; er is een ander vaccin geintroduceerd voor difterie, kinkhoest (a-cellulair), tetanus, poliomyelitis en Haemophilus influenzae (DaKTP/Hib); vaccinatie tegen pneumokokken is toegevoegd op de leeftijd van 2, drie, vier en elf maanden; risicogroepen voor hepatitis B krijgen op diezelfde leeftijden een combinatievaccin voor DaKTP/Hib en hepatitis B; DTP en aK zijn gecombineerd in een vaccin op vierjarige leeftijd; en er zijn nieuwe BMR vaccins geintroduceerd. Op basis van informatie die in 2006 beschikbaar is gekomen wordt geadviseerd de introductie van vaccinaties voor de volgende ziekten te overwegen: hepatitis B (universele vaccinatie), rotavirus, waterpokken en humaan papillomavirus. Voor respiratoir syncytieel virus en meningokokken B zijn nog geen kandidaatvaccins beschikbaar en uitbreiding van het RVP met beschikbare vaccins voor hepatitis A, influenza en tuberculose wordt nog niet aanbevolen. Het RVP is effectief en veilig, maar voortdurende bewaking hiervan is groot belang, omdat er regelmatig veranderingen optreden. Handhaven van de hoge vaccinatiegraad is essentieel om terugkeer van ziekten te voorkomen. Verder moet regelmatig bekeken worden of het RVP aangepast moet worden aangezien er steeds nieuwe vaccins beschikbaar komen
Hepatitis B screening in the Turkish-Dutch population in Rotterdam, the Netherlands; qualitative assessment of socio-cultural determinants
Background. Hepatitis B is an important health problem in the Turkish community in the Netherlands. Increased voluntary screening is necessary in this community, to detect individuals eligible for treatment and to prevent further transmission of the disease. Methods. We investigated socio-cultural determinants associated with hepatitis B screening in male and female, first and second generation Turkish migrants, by means of Focus Group Discussions. Results. Socio-cultural themes related to hepatitis B screening were identified; these were social norm, social support, sensitivity regarding sexuality, reputation, responsiveness to authority, religious responsibility, cleanliness and religious doctrine regarding health and disease, and the perceived efficacy of Dutch health care services. Motivating factors were the (religious) responsibility for one's health, the perceived obligation when being invited for screening, and social support to get tested for hepatitis B. Perceived barriers were the association of hepatitis B screening with STDs or sexual activity, the perception of low control over one's health, and the perceived low efficacy of the Dutch health care services. Reputation could act as either a motivator or barrier. Conclusion. This study identified relevant socio-cultural themes related to hepatitis B screening, which may serve to customize interventions aimed at the promotion of voluntary hepatitis B screening in the Turkish-Dutch population in the Netherlands
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