Optimization Makes Estimation Much More Worse

Mean-variance optimization as a modern portfolio theory is a major model for theoretical purposes, however, in practice portfolio managers don’t have enough interest despite some other ad hoc methods for many reasons such as estimation errors. Recently, the significance of modern portfolio theory has been analyzed that it doesn’t beat the simple naïve 1/N rule not only in many real empirical databases but also in a simulation. By this paper, due to inherent weakness of Sharpe ratio we first express more common use and adjusted measurements such as adjusted expected utility of portfolio under ambiguity aversion to analyze their effects on portfolio optimization after this consideration, because using only sample mean and variance (Sharpe ratio) to evaluate performance value for the portfolio models may be subject to considerable bias. Second, we propose a new model based on the new measurement (adjusting ambiguity Sharpe ratio) to improve portfolio optimization problem. Our result states that by using the new measurement mean- variance optimization beats the naïve rule by applying the adjusted measurement and also the novel model outperforms Markowitz in terms of Sharpe ratio while the interesting is that for adjusting Sharpe ratio inverse result exists. Therefore, our study expresses optimization makes estimation almost worse when we try to use a measurement as an optimization target. Keywords: portfolio selection, optimization, measurement, Sharpe ratio

The Effect of Current Expected Variance of Return on Future Trading Optimal Strategy

Due to the presence of transaction cost, most investors do not keep changing their portfolio to an optimal portfolio over time. This paper adopts a new approach to investigate the linkages between current optimal portfolio variance and the expected future portfolios variances. It is given a closed-form solution for optimal dynamic portfolio selection with trading cost; considering the minimum variance of the utility function as an optimal or selected portfolio by an investor for any period of time based on Gârleanu & Pedersen (2013) framework. Finally, we introduce the multi-period portfolio model based on CRRA preference utility function. Keywords: multiperiod portfolio selection, higher-order moments, CRRA utility function, optimal wealth change

A Novel Approach to Construct Portfolio that Addresses Variance of Utility Function

Many studies in the area of portfolio selection have done based on trade-off among various moments especially between mean and risk of sample returns. Merton (1980) argued that the instability of portfolio weights and sampling errors are due more to estimate the amount of mean. Indeed, it is difficult to estimate the expected return from time series of realized expected return. By this paper, we first answer to this question how to eliminate the wrong effect of mean sample returns instead of ignoring it from calculating portfolio weights and how would be the relation of other moments after this consideration. Second, the substantial evidence from experiments shows that hide information exposes ambiguity aversion to investor’s behavior, and hence decision making under ambiguity for portfolio choice has led to improving tractability of the main features of asset returns. By considering the volatility of utility preferences as ambiguity then individuals prefer to stabilize their utility preferences to maximize their expected utility. Keywords: utility function, portfolio selection, risk aversion, ambiguity aversio

A computational protocol for the study of circularly polarized phosphorescence and circular dichroism in spin-forbidden absorption

We present a computational methodology to calculate the intensity of circular dichroism (CD) in spin-forbidden absorption and of circularly polarized phosphorescence (CPP) signals, a manifestation of the optical activity of the triplet-singlet transitions in chiral compounds. The protocol is based on the response function formalism and is implemented at the level of time-dependent density functional theory. It has been employed to calculate the spin-forbidden circular dichroism and circularly polarized phosphorescence signals of valence n -> pi* and n <- pi* transitions, respectively, in several chiral enones and diketones. Basis set effects in the length and velocity gauge formulations have been explored, and the accuracy achieved when employing approximate (mean-field and effective nuclear charge) spin-orbit operators has been investigated. CPP is shown to be a sensitive probe of the triplet excited state structure. In many cases the sign of the spin-forbidden CD and CPP signals are opposite. For the beta,gamma-enones under investigation, where there are two minima on the lowest triplet excited state potential energy surface, each minimum exhibits a CPP signal of a different sign

Daphnia as an Emerging Epigenetic Model Organism

Daphnia offer a variety of benefits for the study of epigenetics. Daphnia's parthenogenetic life cycle allows the study of epigenetic effects in the absence of confounding genetic differences. Sex determination and sexual reproduction are epigenetically determined as are several other well-studied alternate phenotypes that arise in response to environmental stressors. Additionally, there is a large body of ecological literature available, recently complemented by the genome sequence of one species and transgenic technology. DNA methylation has been shown to be altered in response to toxicants and heavy metals, although investigation of other epigenetic mechanisms is only beginning. More thorough studies on DNA methylation as well as investigation of histone modifications and RNAi in sex determination and predator-induced defenses using this ecologically and evolutionarily important organism will contribute to our understanding of epigenetics

Characterization of two putative potassium channels in Plasmodium falciparum

<p>Abstract</p> <p>Background</p> <p>Potassium channels are essential for cell survival and participate in the regulation of cell membrane potential and electrochemical gradients. During its lifecycle, <it>Plasmodium falciparum </it>parasites must successfully traverse widely diverse environmental milieus, in which K⁺channel function is likely to be critical. Dramatically differing conditions will be presented to the parasite in the mosquito mid-gut, red blood cell (RBC) cytosol and the human circulatory system.</p> <p>Methods</p> <p><it>In silico </it>sequence analyses identified two open-reading frames in the <it>P. falciparum </it>genome that are predicted to encode for proteins with high homology to K⁺channels. To further analyse these putative channels, specific antisera were generated and used in immunoblot and immunofluorescence analyses of <it>P. falciparum</it>-infected RBCs. Recombinant genome methods in cultured <it>P. falciparum </it>were used to create genetic knock outs of each K⁺channel gene to asses the importance of their expression.</p> <p>Results</p> <p>Immunoblot and IFA analyses confirmed the expression of the two putative <it>P. falciparum </it>K⁺channels (PfK1 and PfK2). PfK1 is expressed in all asexual stage parasites, predominantly in late stages and localizes to the RBC membrane. Conversely, PfK2 is predominantly expressed in late schizont and merozoite stage parasites and remains primarily localized to the parasite. Repeated attempts to knockout PfK1 and PfK2 expression by targeted gene disruption proved unsuccessful despite evidence of recombinant gene integration, indicating that <it>pfk1 </it>and <it>pfk2 </it>are apparently refractory to genetic disruption.</p> <p>Conclusion</p> <p>Putative K⁺channel proteins PfK1 and PfK2 are expressed in cultured <it>P. falciparum </it>parasites with differing spatial and temporal patterns. Eventual functional characterization of these channels may reveal future pharmacological targets.</p

Reasons for tubal sterilisation, regret and depressive symptoms

Objective—To examine the associations between sterilisation reasons, regret, and depressive symptoms. Study Design—Black, Hispanic, and non-Hispanic White US women ages 25–45 who participated in the National Survey of Fertility Barriers (NSFB) and reported a tubal sterilisation surgery were included in the sample for this study (n=837). Logistic regression was used to examine how characteristics of the sterilisation surgery (reasons for sterilisation, time since sterilisation, and new relationship since sterilisation) are associated with the odds of sterilisation regret, and linear regression was used to examine associations between sterilisation regret, sociodemographic factors, and depressive symptoms. Results—Findings revealed that 28 percent of U.S. women who have undergone tubal sterilisation report regret. Time since sterilisation and having a reason for sterilisation other than simply not wanting (more) children (e.g., situational factors, health problems, encouragement by others, and other reasons) are associated with significantly higher odds of sterilisation regret. Finally, sterilisation regret is significantly associated with depressive symptoms after controlling for sociodemographic characteristics. Conclusion—Sterilisation regret is relatively common among women who have undergone tubal sterilisation, and regret is linked to elevated, but not necessarily clinical depressive symptoms. The reasons for sterilisation can have important implications for women’s sterilisation regret and associated depressive symptoms

Reasons for tubal sterilisation, regret and depressive symptoms

Objective—To examine the associations between sterilisation reasons, regret, and depressive symptoms. Study Design—Black, Hispanic, and non-Hispanic White US women ages 25–45 who participated in the National Survey of Fertility Barriers (NSFB) and reported a tubal sterilisation surgery were included in the sample for this study (n=837). Logistic regression was used to examine how characteristics of the sterilisation surgery (reasons for sterilisation, time since sterilisation, and new relationship since sterilisation) are associated with the odds of sterilisation regret, and linear regression was used to examine associations between sterilisation regret, sociodemographic factors, and depressive symptoms. Results—Findings revealed that 28 percent of U.S. women who have undergone tubal sterilisation report regret. Time since sterilisation and having a reason for sterilisation other than simply not wanting (more) children (e.g., situational factors, health problems, encouragement by others, and other reasons) are associated with significantly higher odds of sterilisation regret. Finally, sterilisation regret is significantly associated with depressive symptoms after controlling for sociodemographic characteristics. Conclusion—Sterilisation regret is relatively common among women who have undergone tubal sterilisation, and regret is linked to elevated, but not necessarily clinical depressive symptoms. The reasons for sterilisation can have important implications for women’s sterilisation regret and associated depressive symptoms

Nuclear phytochrome a signaling promotes phototropism in Arabidopsis.

Phototropin photoreceptors (phot1 and phot2 in Arabidopsis thaliana) enable responses to directional light cues (e.g., positive phototropism in the hypocotyl). In Arabidopsis, phot1 is essential for phototropism in response to low light, a response that is also modulated by phytochrome A (phyA), representing a classical example of photoreceptor coaction. The molecular mechanisms underlying promotion of phototropism by phyA remain unclear. Most phyA responses require nuclear accumulation of the photoreceptor, but interestingly, it has been proposed that cytosolic phyA promotes phototropism. By comparing the kinetics of phototropism in seedlings with different subcellular localizations of phyA, we show that nuclear phyA accelerates the phototropic response, whereas in the fhy1 fhl mutant, in which phyA remains in the cytosol, phototropic bending is slower than in the wild type. Consistent with this data, we find that transcription factors needed for full phyA responses are needed for normal phototropism. Moreover, we show that phyA is the primary photoreceptor promoting the expression of phototropism regulators in low light (e.g., PHYTOCHROME KINASE SUBSTRATE1 [PKS1] and ROOT PHOTO TROPISM2 [RPT2]). Although phyA remains cytosolic in fhy1 fhl, induction of PKS1 and RPT2 expression still occurs in fhy1 fhl, indicating that a low level of nuclear phyA signaling is still present in fhy1 fhl