90 research outputs found

    Lorentzian Isothermic Surfaces and Bonnet Pairs

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    Lorentzian surfaces in Lorentz three-space are studied using an indefinite version of the quaternions. A classification theorem for Bonnet pairs in Lorentz three-space is obtained

    Lorentzian Isothermic Surfaces in R-j(n)

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    If a time-like surface in R-j(n) is isothermic then there is another, uniquely determined surface which is either anti-conformal or conformal and sign-reversing with the same Gauss map. The choice of mapping depends on whether the shape operator is diagonalizable over R or C

    Shape Operators of Einstein Hypersurfaces in Indefinite Space Forms

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    The possible shape operators for an Einstein hypersurface in an indefinite space form are classified algebraically. If the shape operator A is not diagonalizable then either A2 = 0 or A2 = -b2Id

    Bjorling Problem for Timelike Surfaces in the Lorentz-Minkowski Space

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    We solve the Bjorling problem for timelike surfaces in the Lorentz-Minkowski space through a split-complex representation formula obtained for this kind of surface. Our approach uses the split-complex numbers and natural split-holomorphic extensions. As applications, we show that the minimal timelike surfaces of revolution as well as minimal ruled timelike surfaces can be characterized as solutions of certain adequate Bjorling problems in the Lorentz-Minkowski space

    Clinical Safety-in-Use Study of a New Tampon Design

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    Objective: To confirm the safety of a new experimental Tampax(®) tampon and applicator compared with that of a currently marketed Tampax(®) tampon and applicator using comprehensive gynecological and microbiological assessments. Methods: A 2-month, single-blind, randomized, crossover study was conducted in which each subject served as her own control. Safety was evaluated by comparing potential product-related irritation (using colposcopic examination and subject diary data), assessment of vaginal discharge, vaginal pH, and effects on selected microorganisms (yeast, Escherichia coli ,Staphylococcus aureus and group B streptococci) obtained by vaginal swab cultures after normal menstrual use in the experimental and control groups. Results: In total, 110 women completed the study. There were no significant differences between the groups that used either the experimental or control tampon with regard to prevalence or mean cell density for the selected microorganisms. No differences were observed in the incidence or severity of erythema, in abrasion or ulceration of the cervix, vagina, introitus, vulva or perineum, or in mean vaginal pH and discharge assessments. There were equivalent low incidences of reported symptoms such as discomfort during insertion, wear or removal, and a similar low incidence of burning, stinging or itching during use of either the control or experimental tampon. There was a more favorable overall product rating for the experimental tampon (p = 0.003). Conclusions: This approach provides a combination of gynecological, microbiological and self-reported (diary recall) methodologies in order to assess tampon safety during use more thoroughly than has previously been reported, and it supports a comparable safety profile for the experimental tampon and a currently marketed tampon

    The cost effectiveness of vaccinating against Lyme disease.

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    To determine the cost effectiveness of vaccinating against Lyme disease, we used a decision tree to examine the impact on society of six key components. The main measure of outcome was the cost per case averted. Assuming a 0.80 probability of diagnosing and treating early Lyme disease, a 0.005 probability of contracting Lyme disease, and a vaccination cost of 50peryear,themeancostofvaccinationpercaseavertedwas50 per year, the mean cost of vaccination per case averted was 4,466. When we increased the probability of contracting Lyme disease to 0.03 and the cost of vaccination to 100peryear,themeannetsavingspercaseavertedwas100 per year, the mean net savings per case averted was 3,377. Since few communities have average annual incidences of Lyme disease >0. 005, economic benefits will be greatest when vaccination is used on the basis of individual risk, specifically, in persons whose probability of contracting Lyme disease is >0.01

    Weekly variation in health-care quality by day and time of admission: a nationwide, registry-based, prospective cohort study of acute stroke care.

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    Studies in many health systems have shown evidence of poorer quality health care for patients admitted on weekends or overnight than for those admitted during the week (the so-called weekend effect). We postulated that variation in quality was dependent on not only day, but also time, of admission, and aimed to describe the pattern and magnitude of variation in the quality of acute stroke care across the entire week.Accepted manuscript (12 month embargo

    Significant benefits of AIP testing and clinical screening in familial isolated and young-onset pituitary tumors

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    Context Germline mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene are responsible for a subset of familial isolated pituitary adenoma (FIPA) cases and sporadic pituitary neuroendocrine tumors (PitNETs). Objective To compare prospectively diagnosed AIP mutation-positive (AIPmut) PitNET patients with clinically presenting patients and to compare the clinical characteristics of AIPmut and AIPneg PitNET patients. Design 12-year prospective, observational study. Participants & Setting We studied probands and family members of FIPA kindreds and sporadic patients with disease onset ≤18 years or macroadenomas with onset ≤30 years (n = 1477). This was a collaborative study conducted at referral centers for pituitary diseases. Interventions & Outcome AIP testing and clinical screening for pituitary disease. Comparison of characteristics of prospectively diagnosed (n = 22) vs clinically presenting AIPmut PitNET patients (n = 145), and AIPmut (n = 167) vs AIPneg PitNET patients (n = 1310). Results Prospectively diagnosed AIPmut PitNET patients had smaller lesions with less suprasellar extension or cavernous sinus invasion and required fewer treatments with fewer operations and no radiotherapy compared with clinically presenting cases; there were fewer cases with active disease and hypopituitarism at last follow-up. When comparing AIPmut and AIPneg cases, AIPmut patients were more often males, younger, more often had GH excess, pituitary apoplexy, suprasellar extension, and more patients required multimodal therapy, including radiotherapy. AIPmut patients (n = 136) with GH excess were taller than AIPneg counterparts (n = 650). Conclusions Prospectively diagnosed AIPmut patients show better outcomes than clinically presenting cases, demonstrating the benefits of genetic and clinical screening. AIP-related pituitary disease has a wide spectrum ranging from aggressively growing lesions to stable or indolent disease course

    THE BERNSTEIN PROBLEM FOR TIMELIKE SURFACES

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