Impact of Investor's Varying Risk Aversion on the Dynamics of Asset Price Fluctuations

While the investors' responses to price changes and their price forecasts are well accepted major factors contributing to large price fluctuations in financial markets, our study shows that investors' heterogeneous and dynamic risk aversion (DRA) preferences may play a more critical role in the dynamics of asset price fluctuations. We propose and study a model of an artificial stock market consisting of heterogeneous agents with DRA, and we find that DRA is the main driving force for excess price fluctuations and the associated volatility clustering. We employ a popular power utility function, $U(c,\gamma)=\frac{c^{1-\gamma}-1}{1-\gamma}$ with agent specific and time-dependent risk aversion index, $\gamma_i(t)$, and we derive an approximate formula for the demand function and aggregate price setting equation. The dynamics of each agent's risk aversion index, $\gamma_i(t)$ (i=1,2,...,N), is modeled by a bounded random walk with a constant variance $\delta^2$. We show numerically that our model reproduces most of the ``stylized'' facts observed in the real data, suggesting that dynamic risk aversion is a key mechanism for the emergence of these stylized facts.Comment: 17 pages, 7 figure

In situ epitaxial MgB2 thin films for superconducting electronics

A thin film technology compatible with multilayer device fabrication is critical for exploring the potential of the 39-K superconductor magnesium diboride for superconducting electronics. Using a Hybrid Physical-Chemical Vapor Deposition (HPCVD) process, it is shown that the high Mg vapor pressure necessary to keep the MgB$_2$ phase thermodynamically stable can be achieved for the {\it in situ} growth of MgB$_2$ thin films. The films grow epitaxially on (0001) sapphire and (0001) 4H-SiC substrates and show a bulk-like $T_c$ of 39 K, a $J_c$(4.2K) of $1.2 \times 10^7$ A/cm$^2$ in zero field, and a $H_{c2}(0)$ of 29.2 T in parallel magnetic field. The surface is smooth with a root-mean-square roughness of 2.5 nm for MgB$_2$ films on SiC. This deposition method opens tremendous opportunities for superconducting electronics using MgB$_2$

Mio-Pliocene Faunal Exchanges and African Biogeography: The Record of Fossil Bovids

The development of the Ethiopian biogeographic realm since the late Miocene is here explored with the presentation and review of fossil evidence from eastern Africa. Prostrepsiceros cf. vinayaki and an unknown species of possible caprin affinity are described from the hominid-bearing Asa Koma and Kuseralee Members (∼5.7 and ∼5.2 Ma) of the Middle Awash, Ethiopia. The Middle Awash Prostrepsiceros cf. vinayaki constitutes the first record of this taxon from Africa, previously known from the Siwaliks and Arabia. The possible caprin joins a number of isolated records of caprin or caprin-like taxa recorded, but poorly understood, from the late Neogene of Africa. The identification of these two taxa from the Middle Awash prompts an overdue review of fossil bovids from the sub-Saharan African record that demonstrate Eurasian affinities, including the reduncin Kobus porrecticornis, and species of Tragoportax. The fossil bovid record provides evidence for greater biological continuity between Africa and Eurasia in the late Miocene and earliest Pliocene than is found later in time. In contrast, the early Pliocene (after 5 Ma) saw the loss of any significant proportions of Eurasian-related taxa, and the continental dominance of African-endemic taxa and lineages, a pattern that continues today

Telomere disruption results in non-random formation of de novo dicentric chromosomes involving acrocentric human chromosomes

Copyright: © 2010 Stimpson et al.Genome rearrangement often produces chromosomes with two centromeres (dicentrics) that are inherently unstable because of bridge formation and breakage during cell division. However, mammalian dicentrics, and particularly those in humans, can be quite stable, usually because one centromere is functionally silenced. Molecular mechanisms of centromere inactivation are poorly understood since there are few systems to experimentally create dicentric human chromosomes. Here, we describe a human cell culture model that enriches for de novo dicentrics. We demonstrate that transient disruption of human telomere structure non-randomly produces dicentric fusions involving acrocentric chromosomes. The induced dicentrics vary in structure near fusion breakpoints and like naturally-occurring dicentrics, exhibit various inter-centromeric distances. Many functional dicentrics persist for months after formation. Even those with distantly spaced centromeres remain functionally dicentric for 20 cell generations. Other dicentrics within the population reflect centromere inactivation. In some cases, centromere inactivation occurs by an apparently epigenetic mechanism. In other dicentrics, the size of the alpha-satellite DNA array associated with CENP-A is reduced compared to the same array before dicentric formation. Extrachromosomal fragments that contained CENP-A often appear in the same cells as dicentrics. Some of these fragments are derived from the same alpha-satellite DNA array as inactivated centromeres. Our results indicate that dicentric human chromosomes undergo alternative fates after formation. Many retain two active centromeres and are stable through multiple cell divisions. Others undergo centromere inactivation. This event occurs within a broad temporal window and can involve deletion of chromatin that marks the locus as a site for CENP-A maintenance/replenishment.This work was supported by the Tumorzentrum Heidelberg/Mannheim grant (D.10026941)and by March of Dimes Research Foundation grant #1-FY06-377 and NIH R01 GM069514

Middleborns disadvantaged? testing birth-order effects on fitness in pre-industrial finns

Parental investment is a limited resource for which offspring compete in order to increase their own survival and reproductive success. However, parents might be selected to influence the outcome of sibling competition through differential investment. While evidence for this is widespread in egg-laying species, whether or not this may also be the case in viviparous species is more difficult to determine. We use pre-industrial Finns as our model system and an equal investment model as our null hypothesis, which predicts that (all else being equal) middleborns should be disadvantaged through competition. We found no overall evidence to suggest that middleborns in a family are disadvantaged in terms of their survival, age at first reproduction or lifetime reproductive success. However, when considering birth-order only among same-sexed siblings, first-, middle-and lastborn sons significantly differed in the number of offspring they were able to rear to adulthood, although there was no similar effect among females. Middleborn sons appeared to produce significantly less offspring than first-or lastborn sons, but they did not significantly differ from lastborn sons in the number of offspring reared to adulthood. Our results thus show that taking sex differences into account is important when modelling birth-order effects. We found clear evidence of firstborn sons being advantaged over other sons in the family, and over firstborn daughters. Therefore, our results suggest that parents invest differentially in their offspring in order to both preferentially favour particular offspring or reduce offspring inequalities arising from sibling competition

Building Babies - Chapter 16

In contrast to birds, male mammals rarely help to raise the offspring. Of all mammals, only among rodents, carnivores, and primates, males are sometimes intensively engaged in providing infant care (Kleiman and Malcolm 1981). Male caretaking of infants has long been recognized in nonhuman primates (Itani 1959). Given that infant care behavior can have a positive effect on the infant’s development, growth, well-being, or survival, why are male mammals not more frequently involved in “building babies”? We begin the chapter defining a few relevant terms and introducing the theory and hypotheses that have historically addressed the evolution of paternal care. We then review empirical findings on male care among primate taxa, before focusing, in the final section, on our own work on paternal care in South American owl monkeys (Aotus spp.). We conclude the chapter with some suggestions for future studies.Deutsche Forschungsgemeinschaft (HU 1746/2-1) Wenner-Gren Foundation, the L.S.B. Leakey Foundation, the National Geographic Society, the National Science Foundation (BCS-0621020), the University of Pennsylvania Research Foundation, the Zoological Society of San Dieg

Ideal timing to transfer from an acute care hospital to an interdisciplinary inpatient rehabilitation program following a stroke: an exploratory study

BACKGROUND: Timely accessibility to organized inpatient stroke rehabilitation services may become compromised since the demand for rehabilitation services following stroke is rapidly growing with no promise of additional resources. This often leads to prolonged lengths of stays in acute care facilities for individuals surviving a stroke. It is believed that this delay spent in acute care facilities may inhibit the crucial motor recovery process taking place shortly after a stroke. It is important to document the ideal timing to initiate intensive inpatient stroke rehabilitation after the neurological event. Therefore, the objective of this study was to examine the specific influence of short, moderate and long onset-admission intervals (OAI) on rehabilitation outcomes across homogeneous subgroups of patients who were admitted to a standardized interdisciplinary inpatient stroke rehabilitation program. METHODS: A total of 418 patients discharged from the inpatient neurological rehabilitation program at the Montreal Rehabilitation Hospital Network after a first stroke (79% of all cases reviewed) were included in this retrospective study. After conducting a matching procedure across these patients based on the degree of disability, gender, and age, a total of 40 homogeneous triads (n = 120) were formed according to the three OAI subgroups: short (less than 20 days), moderate (between 20 and 40 days) or long (over 40 days; maximum of 70 days) OAI subgroups. The rehabilitation outcomes (admission and discharge Functional Independence Measure scores (FIM), absolute and relative FIM gain scores, rehabilitation length of stay, efficiency scores) were evaluated to test for differences between the three OAI subgroups. RESULTS: Analysis revealed that the three OAI subgroups were comparable for all rehabilitation outcomes studied. No statistical difference was found for admission (P = 0.305–0.972) and discharge (P = 0.083–0.367) FIM scores, absolute (P = 0.533–0.647) and relative (P = 0.496–0.812) FIM gain scores, rehabilitation length of stay (P = 0.096), and efficiency scores (P = 0.103–0.674). CONCLUSION: OAI does not seem to affect significantly inpatient stroke rehabilitation outcomes of patients referred from acute care facilities where rehabilitation services are rapidly initiated after the onset of the stroke and offered throughout their stay. However, other studies considering factors such as the type and intensity of the rehabilitation are required to support those results

Deficiencies in the transfer and availability of clinical trials evidence: A review of existing systems and standards

Background: Decisions concerning drug safety and efficacy are generally based on pivotal evidence provided by clinical trials. Unfortunately, finding the relevant clinical trials is difficult and their results are only available in text-based reports. Systematic reviews aim to provide a comprehensive overview of the evidence in a specific area, but may not provide the data required for decision making. Methods: We review and analyze the existing information systems and standards for aggregate level clinical trials information from the perspective of systematic review and evidence-based decision making. Results: The technology currently used has major shortcomings, which cause deficiencies in the transfer, traceability and availability of clinical trials information. Specifically, data available to decision makers is insufficiently structured, and consequently the decisions cannot be properly traced back to the underlying evidence. Regulatory submission, trial publication, trial registration, and systematic review produce unstructured datasets that are insufficient for supporting evidence-based decision making. Conclusions: The current situation is a hindrance to policy decision makers as it prevents fully transparent decision making and the development of more advanced decision support systems. Addressing the identified deficiencies would enable more efficient, informed, and transparent evidence-based medical decision making

Extended-schedule dose-dense temozolomide in refractory gliomas

This multicenter phase II study conducted by the Spanish Neuro-Oncology Group evaluated the activity of an extended, dose-dense temozolomide regimen in patients with temozolomide-refractory malignant glioma. Adult patients (at least 18 years of age) with WHO grade III or IV glioma and a Karnofsky Performance Status of 60 or higher were treated with temozolomide (85 mg/m2/day) for 21 consecutive days every 28-day cycle until disease progression or unacceptable toxicity. All patients had developed progressive disease either during or less than 3 months after completing previous temozolomide treatment. Forty-seven patients were treated with a median of 2 (range, 1–13) cycles of temozolomide. Before study entry, patients had received a median of 6 cycles of temozolomide: 39 (83%) as part of initial therapy and 23 (49%) as second-line therapy. Three patients (6.4%) had a partial response with durations of 8.0, 3.5, and 3.2 months; 15 patients (31.9%) had stable disease with a median duration of 2.1 months, including 2 patients with stable disease (SD) for greater than 6 months (14 and 16 months). Median time to progression was 2 months, and median overall survival from study entry was 5.1 months. The 6-month progression-free survival rate was 16.7%. The most common hematologic toxicities were lymphopenia, thrombocytopenia, and leukopenia. Lymphopenia occurred in 83% of patients and was grade 3 in 28%, but no opportunistic infections occurred. In conclusion, this extended dose-dense schedule of temozolomide appears to have modest activity in patients refractory to previous treatment with temozolomide and is associated with manageable toxicity

Measurement of the top quark mass using the matrix element technique in dilepton final states

We present a measurement of the top quark mass in pp¯ collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider. The data were collected by the D0 experiment corresponding to an integrated luminosity of 9.7  fb−1. The matrix element technique is applied to tt¯ events in the final state containing leptons (electrons or muons) with high transverse momenta and at least two jets. The calibration of the jet energy scale determined in the lepton+jets final state of tt¯ decays is applied to jet energies. This correction provides a substantial reduction in systematic uncertainties. We obtain a top quark mass of mt=173.93±1.84  GeV