211 research outputs found
Risk Classification for Claim Counts and Losses Using Regression Models for Location, Scale and Shape
This paper presents and compares different risk classi?cation models for the frequency and severity of claims employing regression models for location, scale and shape. The differences between these models are analyzed through the mean and the variance of the annual number of claims and the costs of claims of the insureds, who belong to different risk classes and interesting results about claiming behaviour are obtained. Furthermore, the resulting a priori premiums rates are calculated via the expected value and standard deviation principles with independence between the claim frequency and severity components assumed
Bonus-Malus Systems with Two Component Mixture Models Arising from Different Parametric Families
Two component mixture distributions defined so that the component distributions do not necessarily arise from the same parametric family are employed for the construction of Optimal Bonus-malus Systems (BMS) with frequency and severity components. The proposed modelling framework is used for the first time in actuarial literature research and includes an abundance of alternative model choices to be considered by insurance companies when deciding on their Bonus-Malus pricing strategies. Furthermore, we advance one step further by assuming that all the parameters and mixing probabilities of the two component mixture distributions are modelled in terms of covariates, extending our previous work in Tzougas, Vrontos and Frangos (2014). Applying Bayes theorem we derive optimal BMS either by updating the posterior probability of the policyholders' classes of risk or by updating the posterior mean and the posterior variance. The resulting tailor-made premiums are calculated via the expected value and variance principles and are compared to those based only on the a posteriori criteria. The use of the variance principle in a Bonus-Malus ratemaking scheme in a way that takes into consideration both the number and the costs of claims based on both the a priori and the a posterior classification criteria has not yet been proposed and can alter the resulting premiums significantly, providing the actuary with useful alternative tariff structures
Essential oils as antibacterial agents against food-borne pathogens: are they really as useful as they are claimed to be ?
Original articleMost studies evaluating the use of essential oils
(EO) as antibacterial agents focus mainly on minimal
inhibitory concentrations (MIC) rather than minimal bactericidal
concentrations (MBC). In this work, we compared
MICs and MBCs of EO from condiment plants commonly
used in Mediterranean Europe, namely Origanum vulgare,
Salvia lavandulaefolia, Salvia officinalis, Salvia sclarea
and Rosmarinus officinalis, aiming to evaluate their
application as disinfecting agents in minimally processed
produce. Outbreaks-related pathogens such as Listeria
monocytogenes, Pseudomonas aeruginosa and Yarrowia
lipolytica were used. Results showed that all EO were able
to reduce bacterial growth in all bacterial strains tested,
particularly O. vulgare. However, fewer EO exhibited
bactericidal activities, and were only effective against one
or two bacterial strains, hence eliminating the possibility to
use them as broad range disinfectants. Furthermore, the
necessary concentrations were too high for food application.
Hence, our work suggests the need to evaluate MBC
rather than MIC and questions EO usefulness in controlling
undesired microorganisms. Overall, and despite the large volume of data published on EO, results obtained were not
very encouraging for a realistic application on produce and
question the viability of EOs as disinfecting agents in foodinfo:eu-repo/semantics/publishedVersio
Dyadic adjustment, family coping, body image, quality of life and psychological morbidity in patients with psoriasis and their partners
Background Psoriasis is an incurable and chronic disease
that includes unpredictable periods of remission and relapse
requiring long-term therapy.
Purpose This paper focuses on the relationship among
family coping, psychological morbidity, body image,
dyadic adjustment and quality of life in psoriatic patients
and their partners.
Method One hundred and one patients with psoriasis and
78 partners comprised the sample. They were regular users
of the Dermatology Service of a Central Northern hospital
in Portugal and a private dermatology clinic. Patients with
psoriasis were assessed on anxiety, depression, body image,
quality of life, dyadic adjustment and family coping.
Partners were assessed on the same measures except body
image and quality of life.
Results A positive relationship among dyadic adjustment,
psychological morbidity and family coping in patients and
their partners was found. Also, patients with lower levels of
quality of life had partners with higher levels of depressive
and anxious symptoms. Better dyadic adjustment predicted
family coping in the psoriatic patient. High levels of dyadic
adjustment in patients and low partners’ trait anxiety
predicted better dyadic adjustment in partners.
Conclusion The results highlight the importance of incorporating
family variables in psychological interventions in
psoriasis’ care, particularly family coping and dyadic
adjustment as well as the need for psychological intervention
to focus both on patients and partners
The design of an optimal Bonus-Malus System based on the Sichel distribution
This chapter presents the design of an optimal Bonus-Malus System (BMS) using the Sichel distribution to model the claim frequency distribution. This system is proposed as an alternative to the optimal BMS obtained by the traditional Negative Binomial model [19]. The Sichel distribution has a thicker tail than the Negative Binomial distribution and it is considered as a plausible model for highly dispersed count data. We also consider the optimal BMS provided by the Poisson-Inverse Gaussian distribution (PIG), which is a special case of the Sichel distribution. Furthermore, we develop a generalised BMS that takes into account both the a priori and a posteriori characteristics of each policyholder. For this purpose we consider the generalised additive models for location, scale and shape (GAMLSS) in order to use all available information in the estimation of the claim frequency distribution. Within the framework of the GAMLSS we propose the Sichel GAMLSS for assessing claim frequency as an alternative to the Negative Binomial Type I (NBI) regression model used by Dionne and Vanasse [9, 10]. We also consider the NBI and PIG GAMLSS for assessing claim frequency
Integrin-Dependent Activation of the JNK Signaling Pathway by Mechanical Stress
Mechanical force is known to modulate the activity of the Jun N-terminal kinase (JNK) signaling cascade. However, the effect of mechanical stresses on JNK signaling activation has previously only been analyzed by in vitro detection methods. It still remains unknown how living cells activate the JNK signaling cascade in response to mechanical stress and what its functions are in stretched cells
International Consensus Based Review and Recommendations for Minimum Reporting Standards in Research on Transcutaneous Vagus Nerve Stimulation (Version 2020).
Given its non-invasive nature, there is increasing interest in the use of transcutaneous vagus nerve stimulation (tVNS) across basic, translational and clinical research. Contemporaneously, tVNS can be achieved by stimulating either the auricular branch or the cervical bundle of the vagus nerve, referred to as transcutaneous auricular vagus nerve stimulation(VNS) and transcutaneous cervical VNS, respectively. In order to advance the field in a systematic manner, studies using these technologies need to adequately report sufficient methodological detail to enable comparison of results between studies, replication of studies, as well as enhancing study participant safety. We systematically reviewed the existing tVNS literature to evaluate current reporting practices. Based on this review, and consensus among participating authors, we propose a set of minimal reporting items to guide future tVNS studies. The suggested items address specific technical aspects of the device and stimulation parameters. We also cover general recommendations including inclusion and exclusion criteria for participants, outcome parameters and the detailed reporting of side effects. Furthermore, we review strategies used to identify the optimal stimulation parameters for a given research setting and summarize ongoing developments in animal research with potential implications for the application of tVNS in humans. Finally, we discuss the potential of tVNS in future research as well as the associated challenges across several disciplines in research and clinical practice
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