Eliminating Biases in Evaluating Mutual Fund Performance from a Survivorship Free Sample

Poor performing mutual funds are less likely to be observed in the data sets that are typically available. This so-called survivor problem can induce a substantial bias in measures of the performance of the funds and the persistence of this performance. Many studies have recently argued that survivorship bias can be avoided by analyzing a sample that contains returns on each fund up to the period of disappearance using standard techniques. Such data sets are usually referred to as 'survivorship free'. In this paper we show that the use of standard methods of analysis on a 'survivorship free' data-set typically still suffers from a bias and we show how one can easily correct for this using weights based on probit regressions. Using a sample with quarterly returns on U.S. based equity funds, we first of all model how survival probabilities depend upon historical returns, the age of the fund and upon aggregate economy-wide shocks. Subsequently we employ a Monte Carlo study to analyze the size and shape of the survivorship bias in various performance measures that arise when a 'survivorship free database' is used with standard techniques. In particular, we show that survivorship bias induces a spurious U-shape pattern in performance persistence. Finally, we show how a weighting procedure based upon probit regressions can be used to correct for the bias. In this way, we obtain bias-corrected estimates of abnormal performance relative to a one-factor and the Carhart [1997] four-factor model, as well as its persistence. Our results are in accordance with the persistence pattern found by Carhart [1997], and do not support the existence of a hot hand phenomenon in mutual fund performance.

Solvates, salts, and cocrystals : a proposal for a feasible classification system

The design of pharmaceutical cocrystals has initiated widespread debate on the classification of cocrystals. Current attempts to classify multicomponent crystals suffer from ambiguity, which has led to inconsistent definitions for cocrystals and for multicomponent crystals in general. Inspired by the work of Aitipamula et al. (Cryst. Growth Des. 2012, 12, 2147-2152), we present a feasible classification system for all multicomponent crystals. The present classification enables us to analyze and classify multicomponent crystal structures present in the Cambridge Structural Database (CSD). This reveals that all seven classes proposed are relevant in terms of frequency of occurrence. Lists of CSD refcodes for all classes are provided. We identified over 5000 cocrystals in the CSD, as well as over 12 000 crystals with more than two components. This illustrates that the possibilities for alternative drug formulations can be increased significantly by considering more than two components in drug design

LOFAR early-time search for coherent radio emission from GRB 180706A

© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.The nature of the central engines of gamma-ray bursts (GRBs) and the composition of their relativistic jets are still under debate. If the jets are Poynting flux dominated rather than baryon dominated, a coherent radio flare from magnetic re-connection events might be expected with the prompt gamma-ray emission. There are two competing models for the central engines of GRBs; a black hole or a newly formed milli-second magnetar. If the central engine is a magnetar it is predicted to produce coherent radio emission as persistent or flaring activity. In this paper, we present the deepest limits to date for this emission following LOFAR rapid response observations of GRB 180706A. No emission is detected to a 3$\sigma$ limit of 1.7 mJy beam$^{-1}$ at 144 MHz in a two-hour LOFAR observation starting 4.5 minutes after the gamma-ray trigger. A forced source extraction at the position of GRB 180706A provides a marginally positive (1 sigma) peak flux density of $1.1 \pm 0.9$ mJy. The data were time-sliced into different sets of snapshot durations to search for FRB like emission. No short duration emission was detected at the location of the GRB. We compare these results to theoretical models and discuss the implications of a non-detection.Peer reviewedFinal Accepted Versio

Co-crystals of diflunisal and isomeric pyridinecarboxamides – a thermodynamics and crystal engineering contribution

Diflunisal is an anti-inflammatory, non-steroidal drug, class II of the Biopharmaceutical Classification System, which has recently been the subject of renewed interest due to its potential for use in the oral therapy of familial amyloid polyneuropathy. In this study, a thermodynamics based approach is used to investigate binary mixtures (diflunisal + picolinamide and diflunisal + isonicotinamide) in order to identify solid forms that are potentially useful to improve the biopharmaceutical performance of this active pharmaceutical ingredient. Special emphasis is placed on the research of co-crystals and on the influence of structural changes in the pyridinecarboxamide co-former molecules for co-crystal formation with diflunisal. The thermodynamics based methodology described by ter Horst et al. in 2010 indicates that the formation of co-crystals is thermodynamically feasible for both systems. The binary solid–liquid phase diagrams were built and allowed unequivocal identification of the formation of co-crystals of diflunisal with each of the two isomers and also their stoichiometry of 1 : 1, (diflunisal : co-former) in the case of pyridine-2-carboxamide (picolinamide) and (2 : 1) for pyridine-4-carboxamide (isonicotinamide). Two binary eutectic mixtures, potentially relevant for pharmaceutical application, were also identified. Infrared spectroscopy allowed the identification of the acid⋯N-pyridine heterosynthon in the three co-crystals formed by diflunisal with the isomeric pyridinecarboxamides. However, the results clearly differentiated pyridine-2-carboxamide from pyridine-3-carboxamide and pyridine-4-carboxamide, that share similar crystalline arrangements, at least with respect to the supramolecular synthons

Pharmacological aspects of neonatal antidepressant withdrawal

Depression is common in reproductive age women, and continued pharmacologic treatment of depression during pregnancy may be necessary to prevent relapse, which could be harmful for both the fetus and the mother. Although data on drug safety are imperfect and incomplete, the benefits of antidepressant therapy during pregnancy generally outweigh the risks. Neonates who are exposed to antidepressant medications during gestation are at increased risk to have neonatal withdrawal syndrome, although the exact incidence of this complication is unknown because the definition of the syndrome is not clear and withdrawal reactions are probably underreported. Tricyclic antidepressant withdrawal syndrome is most likely related to muscarinergic activity and individual drug half-lives, and selective serotonin reuptake inhibitor withdrawal may be due to a decrease in available synaptic serotonin in the face of down-regulated serotonin receptors, the secondary effects of other neurotransmitters, and biological or cognitive sensitivity. Other factors that influence neonatal toxicity or withdrawal include the normal physiologic changes of pregnancy, the altered activity of CYP450 enzymes during pregnancy, drug-drug transporter (PgP and OCT3) interaction, and the presence of genetic polymorphisms in genes influencing drug metabolism. Further research is necessary

Liposomal amphotericin B for visceral leishmaniasis in human immunodeficiency virus-coinfected patients: 2-year treatment outcomes in Bihar, India

Reports on treatment outcomes of visceral leishmaniasis (VL)-human immunodeficiency virus (HIV) coinfection in India are lacking. To our knowledge, none have studied the efficacy of liposomal amphotericin B in VL-HIV coinfection. We report the 2-year treatment outcomes of VL-HIV-coinfected patients treated with liposomal amphotericin B followed by combination antiretroviral treatment (cART) in Bihar, India

Extended RDF: Computability and Complexity Issues

ERDF stable model semantics is a recently proposed semantics for ERDF ontologies and a faithful extension of RDFS semantics on RDF graphs. In this paper, we elaborate on the computability and complexity issues of the ERDF stable model semantics. Based on the undecidability result of ERDF stable model semantics, decidability under this semantics cannot be achieved, unless ERDF ontologies of restricted syntax are considered. Therefore, we propose a slightly modified semantics for ERDF ontologies, called ERDF #n- stable model semantics. We show that entailment under this semantics is, in general, decidable and also extends RDFS entailment. Equivalence statements between the two semantics are provided. Additionally, we provide algorithms that compute the ERDF #n-stable models of syntax-restricted and general ERDF ontologies. Further, we provide complexity results for the ERDF #nstable model semantics on syntax-restricted and general ERDF ontologies. Finally, we provide complexity results for the ERDF stable model semantics on syntax-restricted ERDF ontologies

Effects of hand orientation on motor imagery - event related potentials suggest kinesthetic motor imagery to solve the hand laterality judgment task

Motor imagery (MI) refers to the process of imagining the execution of a specific motor action without actually producing an overt movement. Two forms of MI have been distinguished: visual MI and kinesthetic MI. To distinguish between these forms of MI we employed an event related potential (ERP) study to measure interference effects induced by hand orientation manipulations in a hand laterality judgement task. We hypothesized that this manipulation should only affect kinesthetic MI but not visual MI. The ERPs elicited by rotated hand stimuli contained the classic rotation related negativity (RRN) with respect to palm view stimuli. We observed that laterally rotated stimuli led to a more marked RRN than medially rotated stimuli. This RRN effect was observed when participants had their hands positioned in either a straight (control) or an inward rotated posture, but not when their hands were positioned in an outward rotated posture. Posture effects on the ERP-RRN have not previously been studied. Apparently, a congruent hand posture (hands positioned in an outward rotated fashion) facilitates the judgement of the otherwise more demanding laterally rotated hand stimuli. These ERP findings support a kinesthetic interpretation of MI involved in solving the hand laterality judgement task. The RRN may be used as a non-invasive marker for kinesthetic MI and seems useful in revealing the covert behavior of MI in e.g. rehabilitation programs

An introduction to description logics and query rewriting

This chapter gives an overview of the description logics underlying the OWL 2 Web Ontology Language and its three tractable profiles, OWL 2 RL, OWL 2 EL and OWL 2 QL. We consider the syntax and semantics of these description logics as well as main reasoning tasks and their computational complexity. We also discuss the semantical foundations for fist-order and datalog rewritings of conjunctive queries over knowledge bases given in the OWL2 profiles, and outline the architecture of the ontology-based data access system Ontop