492 research outputs found

    From Rational Bubbles to Crashes

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    We study and generalize in various ways the model of rational expectation (RE) bubbles introduced by Blanchard and Watson in the economic literature. First, bubbles are argued to be the equivalent of Goldstone modes of the fundamental rational pricing equation, associated with the symmetry-breaking introduced by non-vanishing dividends. Generalizing bubbles in terms of multiplicative stochastic maps, we summarize the result of Lux and Sornette that the no-arbitrage condition imposes that the tail of the return distribution is hyperbolic with an exponent mu<1. We then extend the RE bubble model to arbitrary dimensions d and, with the renewal theory for products of random matrices applied to stochastic recurrence equations, we extend the theorem of Lux and Sornette to demonstrate that the tails of the unconditional distributions follow power laws, with the same asymptotic tail exponent mu<1 for all assets. Two extensions (the crash hazard rate model and the non-stationary growth rate model) of the RE bubble model provide ways of reconciliation with the stylized facts of financial data. The later model allows for an understanding of the breakdown of the fundamental valuation formula as deeply associated with a spontaneous breaking of the price symmetry. Its implementation for multi-dimensional bubbles explains why the tail index mu seems to be the same for any group af assets as observed empirically. This work begs for the introduction of a generalized field theory which would be able to capture the spontaneous breaking of symmetry, recover the fundamental valuation formula in the normal economic case and extend it to the still unexplored regime where the economic growth rate is larger than the discount growth rate.Comment: Latex 27 pages with 3 eps figur

    Influence of biofilm lubricity on shear-induced transmission of staphylococcal biofilms from stainless steel to silicone rubber

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    In real-life situations, bacteria are often transmitted from biofilms growing on donor surfaces to receiver ones. Bacterial transmission is more complex than adhesion, involving bacterial detachment from donor and subsequent adhesion to receiver surfaces. Here, we describe a new device to study shear-induced bacterial transmission from a (stainless steel) pipe to a (silicone rubber) tube and compare transmission of EPS-producing and non-EPS-producing staphylococci. Transmission of an entire biofilm from the donor to the receiver tube did not occur, indicative of cohesive failure in the biofilm rather than of adhesive failure at the donor-biofilm interface. Biofilm was gradually transmitted over an increasing length of receiver tube, occurring mostly to the first 50cm of the receiver tube. Under high-shearing velocity, transmission of non-EPS-producing bacteria to the second half decreased non-linearly, likely due to rapid thinning of the lowly lubricious biofilm. Oppositely, transmission of EPS-producing strains to the second tube half was not affected by higher shearing velocity due to the high lubricity and stress relaxation of the EPS-rich biofilms, ensuring continued contact with the receiver. The non-linear decrease of ongoing bacterial transmission under high-shearing velocity is new and of relevance in for instance, high-speed food slicers and food packaging

    Association of Tumor Microenvironment with Biological and Chronological Age in Head and Neck Cancer

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    There is often a mismatch between the chronological and biological age of head and neck squamous cell carcinoma (HNSCC) patients. Treatment is based on chronological age, while biological age seems to be a better prognosticator for treatment toleration. This study investigated whether tumor characteristics are associated with chronological and biological age. The relation with survival was also assessed. Prospectively collected data from 164 newly diagnosed HNSCC patients enrolled in the OncoLifeS database were analyzed. Biological age was assessed by a multidomain geriatric assessment. Several immunological markers were tested by immunohistochemistry on tissue microarray sections from the tumor. Disease-free survival (DFS), adjusted for chronological- and biological age, was assessed by univariable and bivariable analyses. In biologically old patients, a lower infiltration of CD163+ macrophages (p = 0.036) as well as CD4+ (p = 0.019) and CD8+ (p = 0.026) lymphocytes was found in the tumor microenvironment. Chronological older patients showed significantly lower PD-L1 combined positive scores (p = 0.030). Advanced tumor stage and perineural growth were related to a worse DFS. None of the immunological markers showed a significant association with DFS. Biological age might have a stronger influence on tumor microenvironment than chronological age. These findings should initiate clinical studies investigating the response to specific treatment regimens (e.g., immunotherapy) according to the biological age.</p

    Association of Tumor Microenvironment with Biological and Chronological Age in Head and Neck Cancer

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    There is often a mismatch between the chronological and biological age of head and neck squamous cell carcinoma (HNSCC) patients. Treatment is based on chronological age, while biological age seems to be a better prognosticator for treatment toleration. This study investigated whether tumor characteristics are associated with chronological and biological age. The relation with survival was also assessed. Prospectively collected data from 164 newly diagnosed HNSCC patients enrolled in the OncoLifeS database were analyzed. Biological age was assessed by a multidomain geriatric assessment. Several immunological markers were tested by immunohistochemistry on tissue microarray sections from the tumor. Disease-free survival (DFS), adjusted for chronological- and biological age, was assessed by univariable and bivariable analyses. In biologically old patients, a lower infiltration of CD163+ macrophages (p = 0.036) as well as CD4+ (p = 0.019) and CD8+ (p = 0.026) lymphocytes was found in the tumor microenvironment. Chronological older patients showed significantly lower PD-L1 combined positive scores (p = 0.030). Advanced tumor stage and perineural growth were related to a worse DFS. None of the immunological markers showed a significant association with DFS. Biological age might have a stronger influence on tumor microenvironment than chronological age. These findings should initiate clinical studies investigating the response to specific treatment regimens (e.g., immunotherapy) according to the biological age.</p

    Effects of a multi-faceted program to increase influenza vaccine coverage among health care workers:A hospital-based cluster randomized controlled trial

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    Background: Immunizing health care workers (HCWs) against influenza has proven to protect their patients. Despite recommentations of the World Health Organization and the Dutch Health Council, influenza vaccine uptake among hospital HCWs remains low in the Netherlands Objectives: To assess the effects of implementing a hospital- based multi-faceted influenza immunization program on vaccine coverage in health care workers (HCW) and on patient morbidity. Methods: We conducted a cluster randomized controlled trial among all eight University Medical Centers (UMC) of The Netherlands during the influenza seasons of 2009- 2010 and 2010-2011. Participants were hospital staff of three intervention (n = 27,900 in 2009), three control (n = 22,451) and two external non-randomized intervention UMCs (n = 16,893), and 3,367 patients admitted to the departments of pediatrics and internal medicine during both influenza epidemics. We offered a vaccination implementation progran to staff of intervention and external UMCs, but not to control UMCs. The primary outcome measure was influenza vaccine coverage among HCW. Secondary outcome measures were work absenteeism and patient morbidity. Results: In 2009, the coverage of seasonal, first pandemic and second pandemic vaccine was 32.3%, 61.7% and 45.8% in the intervention UMCs. Corresponding figures for control UMCs were significantly lower at 20.4%, 38.0%, and 17.8%, respectively (p <0.05). In 2010, the coverage of the seasonal vaccine was 28.6% and 17.8% in intervention and control UMCs, respectively (p <0.05). During their stay, influenza and/or pneumonia was reduced in patients of intervention UMCs compared to control UMCs (work in progress). Rates of HCWs' absenteeism and influenza testing rates during epidemics were higher in intervention than control UMCs. Conclusions: Adoption of the program improved the influenza vaccine coverage among hospital staff. An increase in coverage was associated with decreased patient morbidity from influenza and/or pneumonia

    Viral Hepatitis and Rapid Diagnostic Test Based Screening for HBsAg in HIV-infected Patients in Rural Tanzania.

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    \ud \ud Co-infection with hepatitis B virus (HBV) is highly prevalent in people living with HIV in Sub-Saharan Africa. Screening for HBV surface antigen (HBsAg) before initiation of combination antiretroviral therapy (cART) is recommended. However, it is not part of diagnostic routines in HIV programs in many resource-limited countries although patients could benefit from optimized antiretroviral therapy covering both infections. Screening could be facilitated by rapid diagnostic tests for HBsAg. Operating experience with these point of care devices in HIV-positive patients in Sub-Saharan Africa is largely lacking. We determined the prevalence of HBV and Hepatitis C virus (HCV) infection as well as the diagnostic accuracy of the rapid test device Determine HBsAg in an HIV cohort in rural Tanzania. Prospectively collected blood samples from adult, HIV-1 positive and antiretroviral treatment-naïve patients in the Kilombero and Ulanga antiretroviral cohort (KIULARCO) in rural Tanzania were analyzed at the point of care with Determine HBsAg, a reference HBsAg EIA and an anti-HCV EIA. Samples of 272 patients were included. Median age was 38 years (interquartile range [IQR] 32-47), 169/272 (63%) subjects were females and median CD4+ count was 250 cells/µL (IQR 97-439). HBsAg was detected in 25/272 (9.2%, 95% confidence interval [CI] 6.2-13.0%) subjects. Of these, 7/25 (28%) were positive for HBeAg. Sensitivity of Determine HBsAg was rated at 96% (95% CI 82.8-99.6%) and specificity at 100% (95% CI, 98.9-100%). Antibodies to HCV (anti-HCV) were found in 10/272 (3.7%, 95% CI 2.0-6.4%) of patients. This study reports a high prevalence of HBV in HIV-positive patients in a rural Tanzanian setting. The rapid diagnostic test Determine HBsAg is an accurate assay for screening for HBsAg in HIV-1 infected patients at the point of care and may further help to guide cART in Sub-Saharan Africa

    Molecular imaging to identify patients with metastatic breast cancer who benefit from endocrine treatment combined with cyclin-dependent kinase inhibition

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    BACKGROUND: Adding cyclin-dependent kinase (CDK) inhibitor to endocrine treatment improves outcome in œstrogen receptor (ER) positive metastatic breast cancer, but identifying the subset of patients who benefit is challenging. Response is potentially associated with ER expression heterogeneity. This is because, unlike the primary tumour in the breast that is localized to the organ, the metastatic breast cancer has spread and continues to spread to distant locations in the body such as bones, lungs, liver, axial skeleton, even to the central nervous system like the brain, wherefrom obtaining biopsies are not easy, and also, the metastasised tissues are heterogeneous. Positron emission tomography (PET) with 16α-[18F]fluoro-17β-œstradiol (FES), briefly referred to as FES-PET, allows whole-body ER assessment. We explored whether FES-PET heterogeneity and FES uptake were related to letrozole and palbociclib outcome, in patients with ER positive, metastatic breast cancer. PATIENTS AND METHODS: Patients underwent a baseline FES-PET and 18F-fluorodeoxyglucose (FDG) PET, the FDG-PET served to help identify active sites of breast cancer with contrast-enhanced computed tomography (CT). FES-PET heterogeneity score (% FES positive lesions divided by all lesions on FDG-PET and/or CT) and FES uptake were related to outcome and 8-week FDG-PET response. Circulating tumour DNA (CtDNA) samples for ESR1 mutation analysis were collected at baseline. RESULTS: In 30 patients with 864 metastatic lesions, baseline FES-PET heterogeneity was assessed. In 27 patients with 688 lesions, response was evaluated. Median time to progression (TTP) was 73 weeks (95% confidence interval [CI] 21 to ∞) in 7 patients with 100% FES positive disease, 27 weeks (14-49) in heterogeneous FES positive disease (20 patients), and 15 weeks (9 to ∞) without FES positivity (three patients; log-rank P = 0.30). Geometric mean FES uptake was 2.3 for metabolic progressive patients, 2.5 (Pvs progression = 0.82) for metabolic stable disease, and 3.3 (Pvs progression = 0.40) for metabolic response (Ptrend = 0.21). ESR1 mutations, found in 13/23 patients, were unrelated to FES uptake. CONCLUSION: This exploratory study suggests that FES-PET heterogeneity may potentially identify the subset of ER positive, metastatic breast cancer patients who benefit from letrozole combined with CDK inhibition. CLINICAL TRIAL INFORMATION: NCT02806050
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