Optimal periodic dividend strategies for spectrally positive L\'evy risk processes with fixed transaction costs

We consider the general class of spectrally positive L\'evy risk processes, which are appropriate for businesses with continuous expenses and lump sum gains whose timing and sizes are stochastic. Motivated by the fact that dividends cannot be paid at any time in real life, we study $\textit{periodic}$ dividend strategies whereby dividend decisions are made according to a separate arrival process. In this paper, we investigate the impact of fixed transaction costs on the optimal periodic dividend strategy, and show that a periodic $(b_u,b_l)$ strategy is optimal when decision times arrive according to an independent Poisson process. Such a strategy leads to lump sum dividends that bring the surplus back to $b_l$ as long as it is no less than $b_u$ at a dividend decision time. The expected present value of dividends (net of transaction costs) is provided explicitly with the help of scale functions. Results are illustrated.Comment: Accepted for publication in Insurance: Mathematics and Economic

On the optimality of joint periodic and extraordinary dividend strategies

In this paper, we model the cash surplus (or equity) of a risky business with a Brownian motion. Owners can take cash out of the surplus in the form of "dividends", subject to transaction costs. However, if the surplus hits 0 then ruin occurs and the business cannot operate any more. We consider two types of dividend distributions: (i) periodic, regular ones (that is, dividends can be paid only at countable many points in time, according to a specific arrival process); and (ii) extraordinary dividend payments that can be made immediately at any time (that is, the dividend decision time space is continuous and matches that of the surplus process). Both types of dividends attract proportional transaction costs, and extraordinary distributions also attracts fixed transaction costs, a realistic feature. A dividend strategy that involves both types of distributions (periodic and extraordinary) is qualified as "hybrid". We determine which strategies (either periodic, immediate, or hybrid) are optimal, that is, we show which are the strategies that maximise the expected present value of dividends paid until ruin, net of transaction costs. Sometimes, a liquidation strategy (which pays out all monies and stops the process) is optimal. Which strategy is optimal depends on the profitability of the business, and the level of (proportional and fixed) transaction costs. Results are illustrated

Clinical measurements versus patient-reported outcomes: analysis of the American Shoulder and Elbow Surgeons physician assessment in patients undergoing reverse total shoulder arthroplasty.

BackgroundThe American Shoulder and Elbow Surgeons (ASES) score is composed of a patient-reported portion and a physician assessment. Although the patient-reported score is frequently used to assess postoperative outcomes after shoulder arthroplasty, no previous studies have used the physician-assessment component. This study evaluated the relationship of the ASES physician-assessment measurements with patient-reported shoulder and general health outcomes.MethodsA retrospective review of a prospectively collected multicenter database was used to analyze patients who underwent primary reverse total shoulder arthroplasty (RTSA) from 2012 to 2015 with a minimum 2-year follow-up. ASES physician-assessment and patient-reported components and 12-Item Short Form Health Survey (SF-12) general health questionnaires were obtained preoperatively and 2 years postoperatively. The relationship between ASES physician measurements with ASES patient-reported outcome (PRO) scores and SF-12 Physical and Mental domain scores was assessed with Pearson correlation coefficients.ResultsIncluded were 74 patients (32 men; mean age, 69.2 years; body mass index, 29.4 kg/m2). Preoperative physician measurements and PRO scores were not significantly correlated. Postoperatively, only the ASES physician-measured active (R = 0.54, P < .01) and passive forward flexion (R = 0.53, P < .01) demonstrated moderate correlation with ASES patient scores. The remaining clinical measurements had no significant correlations with ASES patient or SF-12 scores. During the 2-year period, only improvements in active forward flexion correlated with improvements in ASES patient scores (R = 0.36, P < .01).ConclusionsLittle correlation exists between clinical measurements from the ASES physician component and PROs, including the ASES patient-reported and SF-12 general health surveys, in RTSA patients. Improvement in active forward flexion is the only clinical measurement correlated with PRO improvement at 2 years

Common Raven Impacts on the Productivity of a Small Breeding Population of Snowy Plovers

Common ravens (ravens; Corvus corax), an adaptable, synanthropic generalist, have thrived coincident with increasing human landscape modifications and fragmentation, consequently affecting their prey, which are often sensitive native and protected species. Ravens are a conservation concern for the protected western snowy plover (plover; Charadrius nivosus nivosus), causing low nest and chick survival in some breeding areas along the Pacific coast of North America. We used a long-term dataset from a breeding snowy plover monitoring program in Point Reyes National Seashore (PRNS) to investigate potential impacts of ravens on snowy plover nest and fledging success. Between 2002 and 2020, ravens accounted for 33.7% of all plover nest failures and 40.8% of unexclosed plover nest failures. Raven activity varied by plover breeding site, with more ravens observed per survey hour at Kehoe Beach and the Abbotts Lagoon restoration area, sites that had lower fledge success than other breeding areas. Binomial generalized linear mixed models found that plover nest success was best explained by raven activity (negative relationship) and use of nest exclosures (positive relationship). Our model results on snowy plover fledge success were less apparent, resulting in difficult management planning for this vital rate when using exclosures. Furthermore, nest exclosures were effective in increasing long-term snowy plover nest success in an ecosystem inundated by high raven activity. Evidence from PRNS and other plover breeding sites along the Pacific coast point to long-term negative impacts from ravens

Relación entre contaminación del aire y las infecciones respiratorias agudas, Hospital Nacional PNP Augusto B. Leguia, Rímac - 2013

La investigación realizada se basa en dos grandes problemas que aquejan a la humanidad, la contaminación del aire y las infecciones respiratorias agudas, por lo que se plantea como Problema general ¿Qué relación existe entre la contaminación del aire y las infecciones respiratorias agudas en el Hospital Nacional PNP Augusto B. Leguía, Rímac, 2013? El objetivo de la investigación fue establecer la relación entre la Contaminación del aire y las Infecciones Respiratorias Agudas en el Hospital Nacional PNP Augusto B. Leguía, Rímac, 2013. El diseño de la investigación fue no experimental-transversal de tipo correlacional, se realizó en el Hospital Nacional PNP Augusto B. Leguía del distrito del Rímac que cuenta con un total de 238 trabajadores asistenciales, de donde se extrajo una muestra de 148 trabajadores una vez aplicados los criterios correspondientes. Los datos se obtuvieron a través de dos instrumentos, contaminación del aire e infecciones respiratorias agudas, ambos elaborados por el autor; las respuestas de ambos instrumentos estuvieron de acuerdo a la escala de apreciación tipo Likert. Los datos obtenidos se ingresaron en una base de datos, posteriormente procesados en el paquete estadístico SPSS Versión 21. Los resultados evidencian que existe relación entre la contaminación del aire y las infecciones respiratorias agudas de acuerdo a lo expresado por los trabajadores asistenciales del Hospital Nacional PNP Augusto B. Leguía del distrito del Rímac con un rho de Spearman de 0.171 y con una significancia de p= 0.038

Relación entre contaminación del aire y las infecciones respiratorias agudas, Hospital Nacional PNP Augusto B. Leguia, Rímac - 2013

La investigación realizada se basa en dos grandes problemas que aquejan a la humanidad, la contaminación del aire y las infecciones respiratorias agudas, por lo que se plantea como Problema general ¿Qué relación existe entre la contaminación del aire y las infecciones respiratorias agudas en el Hospital Nacional PNP Augusto B. Leguía, Rímac, 2013? El objetivo de la investigación fue establecer la relación entre la Contaminación del aire y las Infecciones Respiratorias Agudas en el Hospital Nacional PNP Augusto B. Leguía, Rímac, 2013. El diseño de la investigación fue no experimental-transversal de tipo correlacional, se realizó en el Hospital Nacional PNP Augusto B. Leguía del distrito del Rímac que cuenta con un total de 238 trabajadores asistenciales, de donde se extrajo una muestra de 148 trabajadores una vez aplicados los criterios correspondientes. Los datos se obtuvieron a través de dos instrumentos, contaminación del aire e infecciones respiratorias agudas, ambos elaborados por el autor; las respuestas de ambos instrumentos estuvieron de acuerdo a la escala de apreciación tipo Likert. Los datos obtenidos se ingresaron en una base de datos, posteriormente procesados en el paquete estadístico SPSS Versión 21. Los resultados evidencian que existe relación entre la contaminación del aire y las infecciones respiratorias agudas de acuerdo a lo expresado por los trabajadores asistenciales del Hospital Nacional PNP Augusto B. Leguía del distrito del Rímac con un rho de Spearman de 0.171 y con una significancia de p= 0.038

Near-Optimal Evasion of Convex-Inducing Classifiers

Classifiers are often used to detect miscreant activities. We study how an adversary can efficiently query a classifier to elicit information that allows the adversary to evade detection at near-minimal cost. We generalize results of Lowd and Meek (2005) to convex-inducing classifiers. We present algorithms that construct undetected instances of near-minimal cost using only polynomially many queries in the dimension of the space and without reverse engineering the decision boundary.Comment: 8 pages; to appear at AISTATS'201

Proteomic profiling of fatty acid biosynthetic enzymes from oil palm chromoplast

Plant fatty acid metabolism has proven to be amenable to manipulation by conventional breeding, genetic and metabolic engineering to enhance the fatty acid profile. This can be done by engineering palm fruit to synthesise more oleic acid at the expense of palmitic acid. This would produce an oil with greater perceived nutritional quality and higher market value. Although the biochemistry of fatty acid biosynthesis in plants is well described, crosstalk between transcriptional and metabolic controls in regulating fatty acid composition remains poorly understood. Our hypothesis is that phosphorylation is one of the main regulators of acetyl-CoA carboxylase, fatty acid synthase complex and stearoyl-ACP-desaturase in increasing the oleic acid level between oil palm (Elaeis guineensis Jacq. var. Tenera) low and high oleic acid varieties. This study utilised advanced proteomic techniques to isolate, detect and identify chromoplast-based phosphorylated proteins associated with the fatty acid biosynthesis pathway. Sub-organelle isolation using differential centrifugation enriched the chromoplast fraction that contained the fatty acid biosynthetic enzymes before their protein extraction. Gel-based and non-gel based mass spectrometry techniques were then employed to separate and improve the identification of key fatty acid biosynthetic enzymes. Protein expression was analysed using isobaric labelling strategy. Five key enzymes, namely the β-ketoacyl-ACP reductase (EC 1.1.1.100), β-hydroxyacyl-ACP dehydrogenase (EC 4.2.1.58 and 4.2.1.59), 3-enoyl-ACP reductase (EC 1.3.19), β-ketoacyl-ACP synthase (EC 2.3.1.41) and stearoyl-ACP desaturase (EC 1.14.99.6) were identified using GeLC-MS/MS strategy. An additional two subunits of acetyl-CoA carboxylase (EC 6.4.1.2) were identified from the 2DLC-MS/MS strategy. The expression of β-hydroxyacyl-ACP dehydrogenase and β-ketoacyl-ACP synthase was up-regulated in the high oleic acid variety. In contrast, 3-enoyl-ACP reductase was down-regulated in the high oleic acid variety. The existence of other differentially regulated metabolic enzymes associated with fatty acid biosynthesis suggested that the control of fatty acid production, particularly the synthesis of oleic acid, involves more than just the main fatty acid biosynthetic enzymes. Subsequently, the role of phosphorylation in regulating these fatty acid biosynthetic enzymes was investigated using a novel combination of neutral loss-triggered MS3 and Selected Reaction Monitoring. Acetyl-CoA carboxylase and 3-enoyl-ACP reductase were postulated to be phosphorylated in both low oleic acid and high oleic acid-producing oil palms during the fruit maturation stage of 20th week after anthesis. However, other fatty acid biosynthetic enzymes from these oil palm varieties did not show any indication of phosphorylation despite the prediction of phosphoserine-containing peptides. The location of the phosphorylated serine residues in the protein domains of acetyl-CoA carboxylase and 3-enoyl-ACP reductase suggested that phosphorylation could have regulated their enzyme activities. This study has produced a robust method to capture and identify chromoplast-based enzymes that are related to plant fatty acid biosynthesis. The differences in their protein expression levels suggested that fatty acid biosynthetic enzymes were differentially regulated and phosphorylation might be involved in this regulation, at least in the enzyme activity. The outcomes reported in this thesis have significantly improved the knowledge of the possible regulation mechanisms in plant fatty acid biosynthesis. The logical extension of this work in future efforts will be to determine the biological significance of this differential protein expression and to understand the exact role of phosphorylation in the regulation of these enzymes

Recent development in multimedia e-learning technologies

Multimedia and networking technologies have significantly impacted on our daily activities, particularly in terms of how we learn. Nowadays, classroom teaching no longer simply relies on chalk and blackboard as the prime medium for course dissemination. E-learning technologies have made it possible to provide a virtual classroom environment on the Web through supporting teacher-student and student-student communications, course material distribution as well as online student assessments. They provide students with more control over their learning schedule and pace. On top of this, multimedia technologies further offer students different forms of media to match their learning styles, leading to enhancements of their learning effectiveness. This extended introduction discusses the latest e-learning specific multimedia technologies, their research challenges and future trends from both pedagogical and technological perspectives. We also summarize the papers included in this special issue