Modeling longevity risks using a principal component approach: A comparison with existing stochastic mortality models

This research proposes a mortality model with an age shift to project future mortality using principal component analysis (PCA). Comparisons of the proposed PCA model with the well-known models—the Lee-Carter model, the age-period-cohort model (Renshaw and Haberman, 2006), and the Cairns, Blake, and Dowd model—employ empirical studies of mortality data from six countries, two each from Asia, Europe, and North America. The mortality data come from the human mortality database and span the period 1970-2005. The proposed PCA model produces smaller prediction errors for almost all illustrated countries in its mean absolute percentage error. To demonstrate longevity risk in annuity pricing, we use the proposed PCA model to project future mortality rates and analyze the underestimated ratio of annuity price for whole life annuity and deferred whole life annuity product respectively. The effect of model risk on annuity pricing is also investigated by comparing the results from the proposed PCA model with those from the LC model. The findings can benefit actuaries in their efforts to deal with longevity risk in pricing and valuation.     

The routes of unity

A model for car following on a closed loop is defined. The stability of the solutions of the model is investigated by considering the evolution of the roots of the corresponding characteristic equation in the complex plane. The solution provides a motivation for investigating the behaviour of the roots of a simple class of algebraic equation.     

Photocaged Quinone Methide Crosslinkers for Light‐Controlled Chemical Crosslinking of Protein–Protein and Protein–DNA Complexes

Small‐molecule crosslinkers are invaluable for probing biomolecular interactions and for crosslinking mass spectrometry. Existing chemical crosslinkers target only a small selection of amino acids, while conventional photo‐crosslinkers target almost all residues non‐specifically, complicating data analysis. Herein, we report photocaged quinone methide (PQM)‐based crosslinkers that target nine nucleophilic residues through Michael addition, including Gln, Arg, and Asn, which are inaccessible to existing chemical crosslinkers. PQM crosslinkers were used in vitro, in Escherichia coli, and in mammalian cells to crosslink dimeric proteins and endogenous membrane receptors. The heterobifunctional crosslinker NHQM could crosslink proteins to DNA, for which few crosslinkers exist. The photoactivatable reactivity of these crosslinkers and their ability to target multiple amino acids will enhance the use of chemical crosslinking for studies of protein–protein and protein–DNA networks and for structural biology.     

EBC-232 and 323: A Structural Conundrum Necessitating Unification of Five In Silico Prediction and Elucidation Methods

Structurally unique halimanes EBC-232 and EBC-323, isolated from the Australian rainforest plant Croton insularis, proved considerably difficult to elucidate. The two diastereomers, which consist an unusual oxo-6,7-spiro ring system fused to a dihydrofuran, were solved by unification and consultation of five in silico NMR elucidation and prediction methods [i.e., ACDLabs, olefin strain energy (OSE), DP4, DU8+ and TD DFT CD]. Structure elucidation challenges of this nature are prime test case examples for empowering future AI learning in structure elucidation.     

New Studies on Humphry Davy: Introduction

This special issue of Ambix brings together eight new studies on Humphry Davy together with an appreciation of the life and work of David Knight, much of whose scholarship was devoted to understanding Davy. Taken together they provide a much richer and more nuanced account of aspects of Davy’s life, showing how he and his work fitted into the very complex and difficult social, cultural and political contexts of the opening decades of the nineteenth century. Taking as our starting point Thomas Carlyle’s 1829 critique of modern science, in this introduction we weld together the themes that emerge from these papers, many of which ground their results in the project to publish Davy’s Letters. This project has provided evidence that helps us critique the disciplinary boundaries that led to Davy becoming seen mostly as a chemist, while his friend Samuel Taylor Coleridge has generally been categorised as a poet. Such boundaries are now breaking down fruitfully as these essays all illustrate in their different ways. A consequence of the new understandings being produced, is that we need to consider anew what constitutes chemistry and chemists, how reputations and commemorations are constructed, the role of audiences (especially women) in developing knowledge and the use of language and literature, which, among other things, are key elements linking chemistry with other parts of society and culture. Davy provides an excellent location by which to address the historical issues involved, giving us an opportunity to balance carefully these and other components (such as human agency) in understanding how knowledge is constructed.     

Enantioselective metal-free reduction of ketones by a user-friendly silane with a reusable chiral additive

1-Hydrosilatrane, a safe and easy-to-handle reducing reagent that can be inexpensively accessed, has been shown to reduce prochiral ketones asymmetrically in the presence of chiral 1,2-aminoalcohols with ees ranging from 8% to 86%. The best result was achieved using ephedrine as the source of chirality, which is readily commercially available. The additive can be recovered through extraction and reused without any erosion of enantioselectivity.     

Stratigraphic analysis of organic materials in wall painting samples using micro-FTIR attenuated total reflectance and a novel sample preparation technique

Wall paintings typically contain low concentrations of organic materials within a largely inorganic matrix and are characterised by their high porosity and long-term exposure to severe environmental conditions. The identification of organic materials within specific paint or plaster layers is challenging and the inherent characteristics of wall painting samples present further complications. Embedding materials (such as epoxy, polyester and acrylic-based resins) used to produce cross-sections often infiltrate porous and leanly bound samples, and compromise the interpretation of Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectra and the qualitative identification of natural organic materials. An alternative method for the preparation of cross-sections of wall painting samples was developed using cyclododecane (C(12)H(24)) as a temporary consolidant and barrier coating to encapsulate the sample, and to provide necessary support to produce a cross-section through microtoming. Impacts of traditional and novel sample preparation techniques on the identification of organic materials with micro-FTIR-ATR were examined for both replica and real wall painting samples.     

Cellulose nanofibrils derived from pulp as a high performance separator for lithium-ion batteries

Cellulose nanofibrils (CNFs) from hardwood bleached kraft pulp (HwBKP) are produced via enzymatic, chemical, and mechanical treatment. A nanoporous structured CNF-based separator is produced, and the electrochemical performance, morphology, and thermal stability analyses are performed in comparison to the commercial polyethylene separator. The results obtained show that the electrolyte-philic CNF separator has capacity retention of 88.6% over 200 cycles and very good ionic conductivity and wettability results due to its high hydrophilic nature. At 140°C, the CNF separator was resilient to heat and remained intact. The CNF separator reflects high thermal resistance and good electrolyte uptake properties that are among the mandatory requirements of a separator hence, a promising contender for use in lithium-ion batteries.     

On SCH and the approachability property

We construct a model of (Very Good Scale). This answers questions of Cummings, Foreman, Magidor and Woodin.

     

Stereoselective isomerisation of N-allyl aziridines into geometrically stable Z enamines by using rhodium hydride catalysis

In the presence of rhodium(I) hydride catalysts, tertiary N-allylamines are known to isomerise into E enamines. In contrast, we have recently found that N-allylaziridines isomerise to form Z enamines. On the basis of literature data, the most likely mechanism of isomerisation would involve a rhodium hydride addition/beta-hydride elimination sequence. We show that the observed selectivity cannot be adequately explained by this pathway and is more consistent with initial CH-activation followed by rearrangement to form a five-membered cyclometallated rhodium intermediate. This intermediate subsequently undergoes reductive elimination to form a C--H bond. The resulting geometrically stable Z enamines are useful building blocks for stereoselective synthesis.