7440 research outputs found
Sort by
Coherent modeling of male and female mortality using Lee–Carter in a complex number framework
No full textForecasts of female and male mortality that are conducted independently run the risk of projecting implausible sex differentials and fail to exploit correlations that are known to exist between the sexes. We present a new model for the simultaneous modeling of female and male mortality. The model casts mortality as a complex-valued process where the real and imaginary parts correspond to female and male mortalities, respectively. Calculations proceed similarly to the usual Lee–Carter model, via the singular value decomposition, albeit in complex form. Initial applications suggest that the complex Lee–Carter gives fits that are broadly comparable to independent real fits, while offering the advantage of explicit modeling of the relationship between the sexes. Furthermore, model parameters are informative and easily-interpretable.8 page(s
Optimal reinsurance policies with two reinsurers in continuous time
No full textAn optimal reinsurance problem of an insurer is studied in a continuous-time model, where insurance risk is partly transferred to two reinsurers, one adopting the expected-value premium principle and another one using the variance premium principle. The insurer aims to select an optimal reinsurance arrangement to minimize the probability of ruin. To provide an easy-to-implement solution to the problem, (semi)-explicit expressions for the optimal reinsurance strategies as well as the minimal ruin probabilities are derived for several claims distributions. Numerical studies including a real-data example based on the Danish fire insurance losses are provided to illustrate the solution of the problem. Our empirical results based on the Danish data reveal that the heavy-right-tailedness of claims distributions has a significant impact on the optimal reinsurance strategies and has a quite pronounced impact on the residual risk described by the minimal ruin probability.14 page(s
Cell-based wideband variable-gain amplifier with accurate gain adjustment in 65 nm CMOS technology
No full textDesign of an inductor-less wideband variable-gain amplifier (VGA) using a cell-based strategy is presented. The VGA has a measured gain range of 24 dB, of which 17.3 dB is dB-linear with less than ±0.3 dB gain error. The -3 dB bandwidth is from 2 GHz to 2.2 GHz for the entire dB-linear range. An output 1 dB compression point of 1.8 dBm and a noise figure of 24 dB are measured. Due to the simple structure, the current consumption of the VGA core is only 2.9 mA from a 1.2 V supply, and the size is only 225 μm × 45 μm, excluding pads.3 page(s
Leading learning : the role of school leaders in supporting continuous professional development
No full textIn contemporary school settings, leaders seeking to support professional development are faced with many challenges. These challenges call for educators who can undertake professional learning that is continuous and adaptive to change. As a term, continuous professional development (CPD) reflects many different forms of professional development in face-to-face and online contexts. However, as school leaders seek to facilitate effective CPD, identifying the best model of CPD for each school community remains a challenge. This mixed-methods study sought to understand the contextual factors that influence how school leaders facilitate CPD within their communities. Drawing on data from three school case studies and questionnaire responses from a broader sample of 102 school leaders across 17 schools, the researchers examined leaders’ changing perceptions, the school-based professional development support structures and the ways in which educators employed both structured and unstructured time for professional learning. Findings draw attention to two key areas: first, that leaders increasingly prefer technology-mediated, informal professional learning over more traditional and structured forms; and, second, that leaders are drawing on insights from popular thinkers in education aided by the expanded networks which current technology tools afford.18 page(s
Karagiozis in Australia : exploring principles of social justice in the arts for young children
No full textThis paper examines Karagiozis – Greek shadow puppet theatre for children – as a way to explore how the Arts might support socially just education in the early years. As authors from diverse cultural backgrounds with different experiences of arriving and residing in Australia, we consider themes of social justice identified in a Karagiozis play and an interview with a Greek-Australian Karagiozis puppeteer, drawing on Nussbaum’s (2000) Capability Approach. Layered analysis of the data provides a basis for examining: (1) the potential of Karagiozis for exploring social justice themes with young children; and (2) intersections between social justice themes identified in Karagiozis and circumstances for multicultural groups in the Australian context. This paper builds awareness about the value of employing the Capability Approach as a framework for exploring matters of social justice and contributes to dialogue about the value of the Arts in opening possibilities for young children’s learning and meaning-making about social justice matters in local and global contexts.20 page(s
Carbohydrate ingestion induces sex-specific cardiac vagal inhibition, but not vascular sympathetic modulation, in healthy older women
No full textThe role of vagal function in cardiovascular risk in older women remains unclear. Autonomic modulation following carbohydrate ingestion (CI) and postural stress (PS) were investigated in 14 healthy men and 21 age-matched postmenopausal women (age: 65.0 ± 2.1 vs. 64.1 ± 1.6 years), with normal and comparable insulin sensitivity. Continuous noninvasive finger arterial pressure and ECG were recorded in the lying and the standing positions before and after ingestion of a carbohydrate-rich meal (600 kcal, carbohydrate 78%, protein 13%, and fat 8%). Low-frequency (LF, 0.04–0.15 Hz) and high-frequency (HF, 0.15–0.4 Hz) components (ms²) of heart rate variability (HRV), low-frequency power (mmHg²) of systolic blood pressure variability (SBP LF power), and the sequence method for spontaneous baroreflex sensitivity (BRS, ms/mmHg) were used to quantify autonomic modulation. In response to CI and PS, mean arterial pressure maintained stable, and heart rate increased in women and men in the lying and standing positions. Following CI (60, 90, and 120 min postprandially) in the standing position, SBP LF power increased by 40% in men (P = 0.02), with unchanged HRV parameters; in contrast, in women, HRV HF power halved (P = 0.02), with unaltered SBP LF power. During PS before and after CI, similar magnitude of SBP LF power, HRV, and BRS changes was observed in men and women. In conclusion, CI induces sex-specific vascular sympathetic activation in healthy older men, and cardiac vagal inhibition in healthy older women; this CI-mediated efferent vagal inhibition may suggest differential cardiovascular risk factors in women, irrespective of insulin resistance, and impairment of autonomic control.8 page(s
Data integration and mining for synthetic biology design
No full textOne aim of synthetic biologists is to create novel and predictable biological systems from simpler modular parts. This approach is currently hampered by a lack of well-defined and characterised parts and devices. However, there is a wealth of existing biological information, which can be used to identify and characterise biological parts, and their design constraints in the literature and numerous biological databases. However, this information is spread amongst these databases in many different formats. New computational approaches are required to make this information available in an integrated format that is more amenable to data mining. A tried and tested approach to this problem is to map disparate data sources into a single dataset, with common syntax and semantics, to produce a data warehouse or knowledge base. Ontologies have been used extensively in the life sciences, providing this common syntax and semantics as a model for a given biological domain, in a fashion that is amenable to computational analysis and reasoning. Here, we present an ontology for applications in synthetic biology design, SyBiOnt, which facilitates the modelling of information about biological parts and their relationships. SyBiOnt was used to create the SyBiOntKB knowledge base, incorporating and building upon existing life sciences ontologies and standards. The reasoning capabilities of ontologies were then applied to automate the mining of biological parts from this knowledge base. We propose that this approach will be useful to speed up synthetic biology design and ultimately help facilitate the automation of the biological engineering life cycle.12 page(s
X-ray induced singlet oxygen generation by nanoparticle-photosensitizer conjugates for photodynamic therapy : determination of singlet oxygen quantum yield
No full textSinglet oxygen is a primary cytotoxic agent in photodynamic therapy. We show that CeF₃ nanoparticles, pure as well as conjugated through electrostatic interaction with the photosensitizer verteporfin, are able to generate singlet oxygen as a result of UV light and 8 keV X-ray irradiation. The X-ray stimulated singlet oxygen quantum yield was determined to be 0.79 ± 0.05 for the conjugate with 31 verteporfin molecules per CeF₃ nanoparticle, the highest conjugation level used. From this result we estimate the singlet oxygen dose generated from CeF₃-verteporfin conjugates for a therapeutic dose of 60 Gy of ionizing radiation at energies of 6 MeV and 30 keV to be (1.2 ± 0.7) × 10⁸ and (2.0 ± 0.1) × 10⁹ singlet oxygen molecules per cell, respectively. These are comparable with cytotoxic doses of 5 × 10⁷–2 × 10⁹ singlet oxygen molecules per cell reported in the literature for photodynamic therapy using light activation. We confirmed that the CeF₃-VP conjugates enhanced cell killing with 6 MeV radiation. This work confirms the feasibility of using X- or γ- ray activated nanoparticle-photosensitizer conjugates, either to supplement the radiation treatment of cancer, or as an independent treatment modality.9 page(s
Optical manipulation and spectroscopy of silicon nanoparticles exhibiting dielectric resonances
No full textWe demonstrate that silicon (Si) nanoparticles with scattering properties exhibiting strong dielectric resonances can be successfully manipulated using optical tweezers. The large dielectric constant of Si has a distinct advantage over conventional colloidal nanoparticles in that it leads to enhanced trapping forces without the heating associated with metallic nanoparticles. Further, the spectral features of the trapped nanoparticles provide a unique marker for probing size, shape, orientation and local dielectric environment. We exploit these properties to investigate the trapping dynamics of Si nanoparticles with different dimensions ranging from 50 to 200 nm and aspect ratios between 0.4 and 2. The unique combination of spectral and trapping properties make Si nanoparticles an ideal system for delivering directed nanoscale sensing in a range of potential applications.8 page(s
Hopf comonads on naturally Frobenius map-monoidales
No full textWe study monoidal comonads on a naturally Frobenius map-monoidale M in a monoidal bicategory ℳ. We regard them as bimonoids in the duoidal hom-category ℳ(M, M), and generalize to that setting various conditions distinguishing classical Hopf algebras among bialgebras; in particular, we define a notion of antipode in that context. Assuming the existence of certain conservative functors and the splitting of idempotent 2-cells in ℳ, we show all these Hopf-like conditions to be equivalent. Our results imply in particular several equivalent characterizations of Hopf monoids in braided monoidal categories, of small groupoids, of Hopf algebroids over commutative base algebras, of weak Hopf algebras, and of Hopf monads in the sense of Bruguières and Virelizier.37 page(s