Estimación bayesiana del modelo de difusión con saltos de Merton Alba Suarez, Miguel Antonio; Alba Acosta, Miguel Ángel; Alba Acosta, David Camilo
Revista mexicana de economía y finanzas = Mexican journal of economics and finance : REMEF,
06/2022, Letnik:
17, Številka:
2
Journal Article
Recenzirano
Odprti dostop
En la literatura existen diferentes aportes en la forma como se puede identificar la evolución de los derivados financieros vía precios de los activos subyacentes. El Modelo de Difusión con Saltos de ...Merton (MDSM) es una de las referencias más importantes para modelar la dinámica estocástica de los rendimientos de los activos en comparación con el modelo de Black y Scholes (B&S). El objetivo principal de este trabajo es realizar un análisis comparativo entre el MDSM y el B&S desde un enfoque bayesiano utilizando métodos Markov-Chain-Monte-Carlo (MCMC).
Las simulaciones aplicadas al registro diario de algunas de las principales acciones que conforman el índice NASDAQ evidenciaron la superioridad en ajuste del MDSM sobre los rendimientos financieros vía MCMC. Algunas recomendaciones y limitaciones de esta investigación surgen en la propuesta adecuada para los valores usados como parámetros para las distribuciones a priori previas a la estimación de las distribuciones posterior para cada parámetro de cada modelo.
El mayor aporte dentro del marco estadístico de esta investigación es ilustrar la efectividad los métodos MCMC para MDSM en yuxtaposición a B&S.
Formaldehyde (FA) involvement in specific economic activities has become one of the major threats for their worker’s health. The risks of exposure to FA include carcinogenic effects and important ...respiratory affections. One of the essential requirements to ensure safe working conditions is the availability of reliable FA monitoring systems. In this work we have developed a semi-continuous integrating optical sensor based on the evanescent field absorption of light by the FA-sensitive cladding of a plastic optical fiber. To this aim, we capitalized on the acid catalyzed FA-Leuco Fuchsin (LF) colorimetric reaction. We have also substantially reduced the costs of the typical fiber optic sensors by using poly(methyl methacrylate) 3D printing filaments as optical waveguides for the first time. The filaments are coated with a LF-doped Nafion® perfluorosulfonated cladding. The FA sensing fibers are interrogated with a custom-built optoelectronic device using dedicated software, tailored to in situ, online unattended atmospheric FA monitoring. Limits of detection from 0.03 to 0.20 ppmv (0.037–0.25 mg m⁻³) for 67–33% relative humidity, respectively, have been achieved for a 15 min sampling time that matches the legal requirements for the FA short term exposure limits, with automatic analyte level-dependent regeneration time. The sensor responds at least up to 5.5 ppmv (6.77 mg m⁻³). The portable prototype has been tested for 4 months at the paper impregnation process unit of a Spanish industry.
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•A fiberoptic colorimetric sensor for airborne formaldehyde monitoring is described.•Formaldehyde detection is based on the Leuco Fuchsin colorimetric reaction.•The sensor uses the evanescent wave absorption of the Leuco Fuchsin−doped cladding.•3D printing filaments are used as waveguides.•The fiberoptic sensor has been successfully tested in a real workplace environment table.
Mechanisms linking occupational heat exposure with chronic diseases have been proposed. However, evidence on occupational heat exposure and cancer risk is limited.
We evaluated occupational heat ...exposure and female breast cancer risk in a large Spanish case-control study. We enrolled 1,738 breast cancer cases and 1,910 frequency-matched population controls. A Spanish job-exposure matrix, MatEmEsp, was used to assign estimates of the proportion of workers exposed (
≥ 25% for at least 1 year) and work time with heat stress (wet bulb globe temperature ISO 7243) for each occupation. We used three exposure indices: ever versus never exposed, lifetime cumulative exposure, and duration of exposure (years). We estimated ORs and 95% confidence intervals (CI), applying a lag period of 5 years and adjusting for potential confounders.
Ever occupational heat exposure was associated with a moderate but statistically significant higher risk of breast cancer (OR 1.22; 95% CI, 1.01-1.46), with significant trends across categories of lifetime cumulative exposure and duration (
= 0.01 and 0.03, respectively). Stronger associations were found for hormone receptor-positive disease (OR ever exposure = 1.38; 95% CI, 1.12-1.67). We found no confounding effects from multiple other common occupational exposures; however, results attenuated with adjustment for occupational detergent exposure.
This study provides some evidence of an association between occupational heat exposure and female breast cancer risk.
Our results contribute substantially to the scientific literature. Further investigations are needed considering multiple occupational exposures.
Mammographic density (MD), the proportion of radiologically dense breast tissue, is a strong risk factor for breast cancer. Our objective is to investigate the influence of occupations and ...occupational exposure to physical, chemical, and microbiological agents on MD in Spanish premenopausal women.
This is a cross-sectional study based on 1362 premenopausal workers, aged 39–50, who attended a gynecological screening in a breast radiodiagnosis unit of Madrid City Council. The work history was compiled through a personal interview. Exposure to occupational agents was evaluated using the Spanish job-exposure matrix MatEmESp. MD percentage was assessed using the validated semi-automated computer tool DM-Scan. The association between occupation, occupational exposures, and MD was quantified using multiple linear regression models, adjusted for age, educational level, body mass index, parity, previous breast biopsies, family history of breast cancer, energy intake, use of oral contraceptives, smoking, and alcohol consumption.
Although no occupation was statistically significantly associated with MD, a borderline significant inverse association was mainly observed in orchard, greenhouse, nursery, and garden workers (β = −6.60; 95% confidence interval (95%CI) = -14.27; 1.07) and information and communication technology technicians (β = −7.27; 95%CI = −15.37; 0.84). On the contrary, a positive association was found among technicians in art galleries, museums, and libraries (β = 8.47; 95%CI = −0.65; 17.60). Women occupationally exposed to fungicides, herbicides, and insecticides tended to have lower MD. The percentage of density decreased by almost 2% for every 5 years spent in occupations exposed to the mentioned agents.
Although our findings point to a lack of association with the occupations and exposures analyzed, this study supports a deeper exploration of the role of certain occupational agents in MD, such as pesticides.
•Influence of occupations/occupational exposures on mammographic density was studied.•We used multiple linear regression models in a cross-sectional study.•In general, no association was observed with the occupations and exposures studied.•Women involved in agricultural sector showed lower mammographic density.•Mammographic density decreased by 2% for every 5 years of exposure to pesticides.
ObjectivesThe association between occupational exposures and mammographic density (MD), a marker of breast cancer risk, has not been previously explored. Our objective was to investigate the ...influence of occupational exposure to chemical, physical and microbiological agents on MD in adult women.MethodsThis is a population-based cross-sectional study based on 1476 female workers aged 45–65 years from seven Spanish breast cancer screening programmes. Occupational history was surveyed by trained staff. Exposure to occupational agents was assessed using the Spanish job-exposure matrix MatEmESp. Percentage of MD was measured by two radiologists using a semiautomatic computer tool. The association was estimated using mixed log-linear regression models adjusting for age, education, body mass index, menopausal status, parity, smoking, alcohol intake, type of mammography, family history of breast cancer and hormonal therapy use, and including screening centre and professional reader as random effects terms.ResultsAlthough no association was found with most of the agents, women occupationally exposed to perchloroethylene (eβ=1.51; 95% CI 1.04 to 2.19), ionising radiation (eβ=1.23; 95% CI 0.99 to 1.52) and mould spores (eβ=1.44; 95% CI 1.01 to 2.04) tended to have higher MD. The percentage of density increased 12% for every 5 years exposure to perchloroethylene or mould spores, 11% for every 5 years exposure to aliphatic/alicyclic hydrocarbon solvents and 3% for each 5 years exposure to ionising radiation.ConclusionsExposure to perchloroethylene, ionising radiation, mould spores or aliphatic/alicyclic hydrocarbon solvents in occupational settings could be associated with higher MD. Further studies are needed to clarify the accuracy and the reasons for these findings.
High mammographic density is one of the main risk factors for breast cancer. Although several occupations have been associated with breast cancer, there are no previous occupational studies exploring ...the association with mammographic density. Our objective was to identify occupations associated with high mammographic density in Spanish female workers.
We conducted a population-based cross-sectional study of occupational determinants of high mammographic density in Spain, based on 1476 women, aged 45–68 years, recruited from seven screening centers within the Spanish Breast Cancer Screening Program network. Reproductive, family, personal, and occupational history data were collected. The latest occupation of each woman was collected and coded according to the 1994 National Classification of Occupations. Mammographic density was assessed from the cranio-caudal mammogram of the left breast using a semi-automated computer-assisted tool. Association between mammographic density and occupation was evaluated by using mixed linear regression models, using log-transformed percentage of mammographic density as dependent variable. Models were adjusted for age, body mass index, menopausal status, parity, smoking, alcohol intake, educational level, type of mammography, first-degree relative with breast cancer, and hormonal replacement therapy use. Screening center and professional reader were included as random effects terms.
Mammographic density was higher, although non-statistically significant, among secondary school teachers (eβ = 1.41; 95%CI = 0.98–2.03) and nurses (eβ = 1.23; 95%CI = 0.96–1.59), whereas workers engaged in the care of people (eβ = 0.81; 95%CI = 0.66–1.00) and housewives (eβ = 0.87; 95%CI = 0.79–0.95) showed an inverse association with mammographic density. A positive trend for every 5 years working as secondary school teachers was also detected (p-value = 0.035).
Nurses and secondary school teachers were the occupations with the highest mammographic density in our study, showing the latter a positive trend with duration of employment. Future studies are necessary to confirm if these results are due to chance or are the result of a true association whose causal hypothesis is, for the moment, unknown.
•Association between occupation and mammographic density in Spain was investigated.•We used mixed linear regression models in a population-based cross-sectional study.•Secondary school teachers and nurses showed the highest mammographic density.•Positive trend with working time was also detected among secondary school teachers.•Night-shift work and stress conditions have been proposed as potential explanations.
El Valor en Riesgo (VaR), se define como la máxima perdida que se puede tener en la inversión de un portafolio con un determinado nivel de confianza, en un periodo determinado, en condiciones ...normales del mercado. Para calcularlo, existen diversas herramientas paramétricas y no paramétricas que se fundamentan en el supuesto de que los rendimientos de los activos siguen una distribución de probabilidad (con frecuencia la distribución Normal). Por su parte las copulas, vistas como funciones de distribución multivariadas, capturan las relaciones de dependencia diferentes a las lineales, ayudando a condensar la volatilidad de los activos multivariados que usualmente presentan comportamientos complejos de dependencia. Este trabajo presenta la implementación de la teoría de copulas bajo estándares del paradigma bayesiano con el objetivo de obtener la distribución de probabilidad que permita una correcta estimación del VaR de un portafolio comprendido por las acciones de Bancolombia y Ecopetrol.
Right ventricular (RV) diastolic dysfunction in patients with a surgically-repaired RV outflow tract (RVOT) obstruction merits further studies. Right atrial (RA) dilation and function may be related ...to (RV) diastolic dysfunction in this setting. The end-diastolic forward flow (EDFF) in the pulmonary artery (PA) has been suggested as a non-invasive marker of poor RV compliance, however, there is controversy regarding its true significance; EDFF quantification may help elucidate this controversy.
to study predictors of RA enlargement and dysfunction in patients with a surgically-repaired RVOT obstruction and its relationship with quantitative EDFF.
In 81 consecutive patients (mean age: 37.5 (±7) years), transthoracic echocardiography (Echo) and cardiac magnetic resonance (CMR) were performed. Echo parameters: RA size (indexed RA area (iRAA)), RA function (RA global strain (RAGS)) and maximum EDFF velocity-time integral (VTI-EDFF) obtained during a whole respiratory cycle. CMR-indexed RA area (imRAA) was also obtained. Patients were divided into three groups according to iRAA, imRAA and RAGS; bivariate analysis was performed. A multivariate model was then applied using variables that were found to be statistically significant in the bivariate analysis.
Upon multivariate analysis, higher VTI-EDFF values and the presence of significant tricuspid regurgitation proved to be independent factors associated with increased iRAA and imRAA and lower RAGS, whereas RV volumes, function and pulmonary regurgitant fraction were not.
VTI-EDFF linearly correlated with the degree of RA dilation and deformation; EDFF quantification as against qualitative assessment may be considered a non-invasive tool for diastolic RV dysfunction.
Key question: what are the determinants of right atrial dilatation in adult patients with congenital heart disease and previous surgical repair of right ventricular outflow obstruction? Key findings: EDFF quantification should be included in the echocardiographic assessment of patients with CHD. Take Home Message: End-diastolic forward flow quantification is determinant of right atrial dilatation and function. Right ventricular diastolic dysfunction is a main determinant of right atrial dilatation and function. Display omitted
Open surgery for thoracoabdominal aortic aneurysms remains one of the most aggressive procedures, with a risk of paraplegia reaching up to 20% in some series. Preconditioning of the spinal ...circulation through prior embolization has been postulated to improve outcomes. We evaluate our initial experience with six patients.
From May 2022 to June 2023, we operated on six patients with type II thoracoabdominal aortic aneurysms after prior embolization of the majority of their intercostal and lumbar arteries in 2–3 sessions separated by one month, prior to open surgery. Ethical considerations: All patients give their informed consent for the procedure and the publication of the results. Disclosures: None.
We encountered no technical or neurological issues during the embolizations. The surgery was notably simpler due to reduced thoracic bleeding. Upon awakening, neurological assessment in all patients revealed no deficits. However, one patient, who required vasoconstrictors for sepsis postoperatively, subsequently developed paraplegia (6 days after the surgery).
Stepwise prior embolization of a significant portion of intercostal and lumbar arteries proves to be of great assistance during surgery. However, we believe it is necessary to reimplant some intercostal arteries to favor spinal cord irrigation. We do not consider indiscriminate embolization of all intercostal arteries advisable, as it significantly reduces irrigation, which can be further compromised by postoperative vasoconstrictors.
La cirugía abierta de los aneurismas de aorta tóraco-abdominales sigue siendo una de las cirugías más agresivas con un riesgo de paraplejia que en algunas series alcanza el 20%. El preacondicionamiento de la circulación medular mediante embolización previa se ha postulado para mejorar resultados. Valoramos nuestra experiencia inicial con seis pacientes.
Desde Mayo 2022 a Junio de 2023 hemos operado a 6 pacientes de aneurisma tóraco-abdominal tipo II, tras embolización previa de la mayor parte de sus arterias intercostales y lumbares en 2-3 sesiones separadas por un mes, previamente a la cirugía abierta.
No tuvimos ningún problema durante las embolizaciones, técnico ni neurológico. La cirugía fue claramente más sencilla dado el menor sangrado durante el tiempo torácico. La valoración neurológica al despertar en todos los pacientes no mostró déficit neurológico alguno, sin embargo un paciente con necesidades posteriores de vasoconstrictor por sepsis presentó posteriormente paraplejia (6 días después de la cirugía).
La embolización previa escalonada de gran parte de intercostales y lumbares resulta de gran ayuda durante la cirugía, no obstante creemos necesaria la reimplantación de alguna intercostal a fin de favorecer la irrigación medular. No creemos prudente la embolización indiscriminada de todas las arterias intercostales, al reducirse drásticamente la irrigación que puede ser empeorada por vasoconstrictores en el postoperatorio. Resumen secundario.
Common variable immunodeficiency is the primary immunodeficiency (CVID) frequently found in adults. Its prevalence is estimated from 1:25,000 to 75,000 alive newborns; there are variations by ethnic ...groups, it is estimated about 50-70% in Caucasian patients. Oral cavity lesions are rarely found in adult patients with CVID, there are reports about lesions on pediatric patients mostly caused by infections.
To describe the orofacial lesions (oral, maxillofacial and neck area) affecting adults with CVID.
A transversal, prospective study was done in patients with CVID attended at Specialties Hospital, CMN SXXI, Mexico City. Patients where examined by the oral and maxillofacial surgeon and clinical findings were reported, then the descriptive analysis of the lesions was done.
We evaluated 26 patients, 16 female and 10 males, average age of 38.6 years. In 18/26 patients we found oral lesions on 7 different types. The most frequent was minor salivary glands hiperplasia (19/26),petechiae (12/26) and herpetic ulcers (7/26). In head and neck, we found 4 different lesions, the most common was lymphadenopathy <2cm (4/26).
The immunologic alterations associated to CVID favors the development of lesions mainly of infectious and probably autoinmune origin that affects the oral cavity and head and neck area.
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