2,840 research outputs found
Weighted entropy and optimal portfolios for risk-averse Kelly investments
Following a series of works on capital growth investment, we analyse
log-optimal portfolios where the return evaluation includes `weights' of
different outcomes. The results are twofold: (A) under certain conditions, the
logarithmic growth rate leads to a supermartingale, and (B) the optimal
(martingale) investment strategy is a proportional betting. We focus on
properties of the optimal portfolios and discuss a number of simple examples
extending the well-known Kelly betting scheme.
An important restriction is that the investment does not exceed the current
capital value and allows the trader to cover the worst possible losses.
The paper deals with a class of discrete-time models. A continuous-time
extension is a topic of an ongoing study
The Effect of Selective Die Spacer Placement Techniques on the Seatability of Castings
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74992/1/j.1532-849X.1993.tb00382.x.pd
Evidence for a continuous decline in lower stratospheric ozone offsetting ozone layer recovery
Ozone forms in the Earth's atmosphere from the photodissociation of molecular oxygen, primarily in the tropical stratosphere. It is then transported to the extratropics by the Brewer–Dobson circulation (BDC), forming a protective "ozone layer" around the globe. Human emissions of halogen-containing ozone-depleting substances (hODSs) led to a decline in stratospheric ozone until they were banned by the Montreal Protocol, and since 1998 ozone in the upper stratosphere is rising again, likely the recovery from halogen-induced losses. Total column measurements of ozone between the Earth's surface and the top of the atmosphere indicate that the ozone layer has stopped declining across the globe, but no clear increase has been observed at latitudes between 60° S and 60° N outside the polar regions (60–90°). Here we report evidence from multiple satellite measurements that ozone in the lower stratosphere between 60° S and 60° N has indeed continued to decline since 1998. We find that, even though upper stratospheric ozone is recovering, the continuing downward trend in the lower stratosphere prevails, resulting in a downward trend in stratospheric column ozone between 60° S and 60° N. We find that total column ozone between 60° S and 60° N appears not to have decreased only because of increases in tropospheric column ozone that compensate for the stratospheric decreases. The reasons for the continued reduction of lower stratospheric ozone are not clear; models do not reproduce these trends, and thus the causes now urgently need to be established
Massive stars as thermonuclear reactors and their explosions following core collapse
Nuclear reactions transform atomic nuclei inside stars. This is the process
of stellar nucleosynthesis. The basic concepts of determining nuclear reaction
rates inside stars are reviewed. How stars manage to burn their fuel so slowly
most of the time are also considered. Stellar thermonuclear reactions involving
protons in hydrostatic burning are discussed first. Then I discuss triple alpha
reactions in the helium burning stage. Carbon and oxygen survive in red giant
stars because of the nuclear structure of oxygen and neon. Further nuclear
burning of carbon, neon, oxygen and silicon in quiescent conditions are
discussed next. In the subsequent core-collapse phase, neutronization due to
electron capture from the top of the Fermi sea in a degenerate core takes
place. The expected signal of neutrinos from a nearby supernova is calculated.
The supernova often explodes inside a dense circumstellar medium, which is
established due to the progenitor star losing its outermost envelope in a
stellar wind or mass transfer in a binary system. The nature of the
circumstellar medium and the ejecta of the supernova and their dynamics are
revealed by observations in the optical, IR, radio, and X-ray bands, and I
discuss some of these observations and their interpretations.Comment: To be published in " Principles and Perspectives in Cosmochemistry"
Lecture Notes on Kodai School on Synthesis of Elements in Stars; ed. by Aruna
Goswami & Eswar Reddy, Springer Verlag, 2009. Contains 21 figure
Genetic Interactions between Chromosomes 11 and 18 Contribute to Airway Hyperresponsiveness in Mice
We used two-dimensional quantitative trait locus analysis to identify interacting genetic loci that contribute to the native airway constrictor hyperresponsiveness to methacholine that characterizes A/J mice, relative to C57BL/6J mice. We quantified airway responsiveness to intravenous methacholine boluses in eighty-eight (C57BL/6J X A/J) F2 and twenty-seven (A/J X C57BL/6J) F2 mice as well as ten A/J mice and six C57BL/6J mice; all studies were performed in male mice. Mice were genotyped at 384 SNP markers, and from these data two-QTL analyses disclosed one pair of interacting loci on chromosomes 11 and 18; the homozygous A/J genotype at each locus constituted the genetic interaction linked to the hyperresponsive A/J phenotype. Bioinformatic network analysis of potential interactions among proteins encoded by genes in the linked regions disclosed two high priority subnetworks - Myl7, Rock1, Limk2; and Npc1, Npc1l1. Evidence in the literature supports the possibility that either or both networks could contribute to the regulation of airway constrictor responsiveness. Together, these results should stimulate evaluation of the genetic contribution of these networks in the regulation of airway responsiveness in humans
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The cultural grammar of governance: The UK Code of Corporate Governance, reflexivity, and the limits of 'soft' regulation
We identify limits of ‘reflexive governance’ by examining the UK Code of Corporate Governance that is celebrated for its ‘reflexivity’. By placing the historical genesis of the Code within its politico-economic context, it is shown how its scope and penetration is impeded by a shallow, ‘single loop’ of reflexivity. Legitimized by agency theory, the Code is infused by a ‘cultural grammar’ that perpetuates relations of shareholder primacy as it restricts accountability to narrow forms of information disclosure directed exclusively at shareholders. Engagement of a deeper, ‘double loop’ reflexivity allows account to be taken of the historical conditions and theoretical conceptions that shape practices and outcomes of corporate governance. Only then is it possible to disclose, challenge and reform narrow conceptions, boundaries and workings of ‘reflexive governance’
The Role of Individual Variables, Organizational Variables and Moral Intensity Dimensions in Libyan Management Accountants’ Ethical Decision Making
This study investigates the association of a broad set of variables with the ethical decision making of management accountants in Libya. Adopting a cross-sectional methodology, a questionnaire including four different ethical scenarios was used to gather data from 229 participants. For each scenario, ethical decision making was examined in terms of the recognition, judgment and intention stages of Rest’s model. A significant relationship was found between ethical recognition and ethical judgment and also between ethical judgment and ethical intention, but ethical recognition did not significantly predict ethical intention—thus providing support for Rest’s model. Organizational variables, age and educational level yielded few significant results. The lack of significance for codes of ethics might reflect their relative lack of development in Libya, in which case Libyan companies should pay attention to their content and how they are supported, especially in the light of the under-development of the accounting profession in Libya. Few significant results were also found for gender, but where they were found, males showed more ethical characteristics than females. This unusual result reinforces the dangers of gender stereotyping in business. Personal moral philosophy and moral intensity dimensions were generally found to be significant predictors of the three stages of ethical decision making studied. One implication of this is to give more attention to ethics in accounting education, making the connections between accounting practice and (in Libya) Islam. Overall, this study not only adds to the available empirical evidence on factors affecting ethical decision making, notably examining three stages of Rest’s model, but also offers rare insights into the ethical views of practising management accountants and provides a benchmark for future studies of ethical decision making in Muslim majority countries and other parts of the developing world
Kinetics of the hydrogen abstraction ·C2H5 + alkane → C2H6 + alkyl reaction class: an application of the reaction class transition state theory
This paper presents an application of the reaction class transition state theory (RC-TST) to predict thermal rate constants for hydrogen abstraction reactions at alkane by the C2H5 radical on-the-fly. The linear energy relationship (LER), developed for acyclic alkanes, was also proven to hold for cyclic alkanes. We have derived all RCTST
parameters from rate constants of 19 representative
reactions, coupling with LER and the barrier height
grouping (BHG) approach. Both the RC-TST/LER, where
only reaction energy is needed, and the RC-TST/BHG,
where no other information is needed, can predict rate
constants for any reaction in this reaction class with satisfactory accuracy for combustion modeling. Our analysis indicates that less than 50% systematic errors on the average exist in the predicted rate constants using either
the RC-TST/LER or RC-TST/BHG method, while in comparison with explicit rate calculations, the differences
are within a factor of 2 on the average. The results also
show that the RC-TST method is not sensitive to the choice
of density functional theory used
A Link between Prompt Optical and Prompt Gamma-Ray Emission in Gamma-Ray Bursts
The prompt optical emission that arrives with gamma-rays from a cosmic
gamma-ray burst (GRB) is a signature of the engine powering the burst, the
properties of the ultra-relativistic ejecta of the explosion, and the ejecta's
interactions with the surroundings. Until now, only GRB 990123 had been
detected at optical wavelengths during the burst phase. Its prompt optical
emission was variable and uncorrelated with the prompt gamma-ray emission,
suggesting that the optical emission was generated by a reverse shock arising
from the ejecta's collision with the surrounding material. Here we report
prompt optical emission from GRB 041219a. It is variable and correlated with
the prompt gamma-rays, indicating a common origin for the optical light and the
gamma-rays. Within the context of the standard fireball model of GRBs, we
attribute this new optical component to internal shocks driven into the burst
ejecta by variations of the inner engine. The correlated optical emission is a
direct probe of the jet isolated from the medium. The timing of the
uncorrelated optical emission is strongly dependent on the nature of the
medium.Comment: 9 pages, 4 figures. Note: This paper has been accepted for
publication in Nature, but is embargoed for discussion in the popular press
until formal publication in Nature. Resubmit - Added table comparing Swift
and RAPTOR dat
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