Portfolios and the market geometry

A geometric analysis of the time series of returns has been performed in the past and it implied that the most of the systematic information of the market is contained in a space of small dimension. Here we have explored subspaces of this space to find out the relative performance of portfolios formed from the companies that have the largest projections in each one of the subspaces. It was found that the best performance portfolios are associated to some of the small eigenvalue subspaces and not to the dominant directions in the distances matrix. This occurs in such a systematic fashion over an extended period (1990-2008) that it may not be a statistical accident.Comment: 13 pages 12 figure

Regio- and stereoselective synthesis of (Z)-2-Arylsulfanyl allylic alcohols using anhydrous CeCl3 as catalyst under solvent free conditions

AbstractAnhydrous CeCl3 was successfully employed as catalyst for the synthesis of (Z)-2-Arylsulfanyl allylic alcohols from propargylic alcohols and thiols under solvent free conditions. The products were obtained in good to excellent yields

Electrifying green synthesis: recent advances in electrochemical annulation reactions

Electricity originating from renewable resources can be used for highly sustainable and economically attractive applications. With electrons as the mass-free reagent, the use of a stoichiometric amount of oxidants in annulation reactions can be avoided, thereby eliminating the production of waste. Considered as a modern reaction configuration, the availability of electrochemical methods is expanding synthetic applications in the field of organic chemistry. Electrochemical transformations possess many benefits over traditional reagent-based methodologies, such as high functional group tolerance, mild conditions, easy scale up setup, high yields and selective transformations. In this review, we targeted electrochemical annulation reactions involving mediators and mediator-free conditions with generation of new C–C, C–heteroatom and heteroatom–heteroatom bonds, their mechanistic insights, as well as the reactivity of substrates. We also explain the recent use of sacrificial electrodes in annulation reactions

Synthesis of bis(indolyl)methanes using silica gel as an efficient and recyclable surface

AbstractHere we describe a simple, clean, and efficient solvent-free protocol for the synthesis of bis(indolyl)methanes promoted by silica gel. The products were obtained in good to excellent yields through the reaction of indoles with cyclohexanone and a range of aldehydes. The silica gel was easily recovered and utilized for further reactions without loss of activity

A novel approach for micro-antenna fabrication on ZrO2 substrate assisted by laser printing for smart implants

The use of Yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) in medicine has rapidly expanded over the past decade, driven by its advantageous properties, showing potential to overcome titanium alloy in implant fabrication. The release of metal ions and the aesthetic problems of titanium alloy implants are the main reasons for this trend. In addition to meeting expectations regarding its properties, an implant must possess intrinsic capacities such as auto-diagnostic and auto-treatment. Thus, based on the concept of smart implants, this work proposes a hybrid approach for printing a part of the communication system of a zirconia implant by resorting to laser technology, aiming to endow the implant with intrinsic capacities. Therefore, the antenna was designed and then printed on the zirconia surface. The laser was applied as a versatile tool, whether for preparing the surface of the material in a subtractive way, by creating the micro-cavity, or for printing the silver-based antenna in an additive way through laser technology. The silver powder was used as the conductor material of the antenna. The results revealed that the antenna is capable of communicating from inside the body with the outside world without needing to have an exterior antenna attached to the skin.This work has been supported by the FCT (Fundação para a Ciência e Tecnologia -Portugal) in the scope of the projects UID/EEA/04436/2019; Magsense_POCI-01-0247-FEDER-033783, Add.Additive_Manufacturing to Portuguese Industry_POCI-01-0247-FEDER-024533, grant SFRH/BD/ 116554/2016 and the CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico) for the grant 205791/2014-

The use of anhydrous CeCl3 as a recyclable and selective catalyst for the acetalization of aldehydes and ketones

An efficient, clean, chemoselective and solvent-free method for the synthesis of ketone and aldehyde dimethyl acetals was developed using trimethyl orthoformate and commercially available anhydrous CeCl3 as a recyclable catalyst. The method is general and affords the protected carbonyl compounds in good yields and under mild conditions, including aryl and alkyl ketones and activated aldehydes. The catalyst could be utilised directly for 3 cycles, without significant loss of activity

Evolution of the Bianchi I, the Bianchi III and the Kantowski-Sachs Universe: Isotropization and Inflation

We study the Einstein-Klein-Gordon equations for a convex positive potential in a Bianchi I, a Bianchi III and a Kantowski-Sachs universe. After analysing the inherent properties of the system of differential equations, the study of the asymptotic behaviors of the solutions and their stability is done for an exponential potential. The results are compared with those of Burd and Barrow. In contrast with their results, we show that for the BI case isotropy can be reached without inflation and we find new critical points which lead to new exact solutions. On the other hand we recover the result of Burd and Barrow that if inflation occurs then isotropy is always reached. The numerical integration is also done and all the asymptotical behaviors are confirmed.Comment: 22 pages, 12 figures, Self-consistent Latex2e File. To be published in Phys. Rev.

Inconsistency in shoulder arthrometers for measuring glenohumeral joint laxity: a systematic review

There is no consensus on how to measure shoulder joint laxity and results reported in the literature are not well systematized for the available shoulder arthrometer devices. This systematic review aims to summarize the results of currently available shoulder arthrometers for measuring glenohumeral laxity in individuals with healthy or injured shoulders. Searches were conducted on the PubMed, EMBASE, and Web of Science databases to identify studies that measure glenohumeral laxity with arthrometer-assisted assessment. The mean and standard deviations of the laxity measurement from each study were compared based on the type of population and arthrometer used. Data were organized according to the testing characteristics. A total of 23 studies were included and comprised 1162 shoulders. Populations were divided into 401 healthy individuals, 278 athletes with asymptomatic shoulder, and 134 individuals with symptomatic shoulder. Sensors were the most used method for measuring glenohumeral laxity and stiffness. Most arthrometers applied an external force to the humeral head or superior humerus by a manual-assisted mechanism. Glenohumeral laxity and stiffness were mostly assessed in the sagittal plane. There is substantial heterogeneity in glenohumeral laxity values that is mostly related to the arthrometer used and the testing conditions. This variability can lead to inconsistent results and influence the diagnosis and treatment decision-making.This article is a result of the project DILATO (reference 47289) supported by the Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF)

Examining the antecedents of challenge and threat states: The influence of perceived required effort and support availability

To date, limited research has explicitly examined the antecedents of challenge and threat states proposed by the biopsychosocial model. Thus, the aim of the present study was to examine the influence of perceived required effort and support availability on demand/resource evaluations, challenge and threat states, and motor performance. A 2 (required effort; high, low) � 2 (support availability; available, not available) between-subjects design was used with one hundred and twenty participants randomly assigned to one of four experimental conditions. Participants received instructions designed to manipulate perceptions of required effort and support availability before demand/resource evaluations and cardiovascular responses were assessed. Participants then performed the novel motor task (laparoscopic surgery) while performance was recorded. Participants in the low perceived required effort condition evaluated the task as more of a challenge (i.e., resources outweighed demands), exhibited a cardiovascular response more indicative of a challenge state (i.e., higher cardiac output and lower total peripheral resistance), and performed the task better (i.e., quicker completion time) than those in the high perceived required effort condition. However, perceptions of support availability had no significant impact on participants' demand/resource evaluations, cardiovascular responses, or performance. Furthermore, there was no significant interaction effect between perceptions of required effort and support availability. The findings suggest that interventions aimed at promoting a challenge state should include instructions that help individuals perceive that the task is not difficult and requires little physical and mental effort to perform effectively

Chloridodiphen­yl{[1-(1,3-thia­zol-2-yl-κN)ethyl­idene]-4-phenyl­thio­semicarbazidato-κ2 N 1,S}tin(IV) methanol monosolvate

The title compound, [Sn(C6H5)2(C12H11N4S2)Cl]·CH4O, is formed during the reaction between 2-acetyl­thia­zole 4-phenyl­thio­semicarbazone (Hacthptsc) and diphenyl­tin(IV) dichloride in methanol. In the crystal structure, the Sn atom exhibits an octa­hedral geometry with the [N2S] anionic tridentate thio­semicarbazone ligand having chloride trans to the central N and the two phenyl groups trans to each other. The Sn—Cl distance is 2.5929 (6), Sn—S is 2.4896 (6) and Sn—N to the central N is 2.3220 (16) Å. The MeOH mol­ecules link the Sn complexes into one-dimensional chains via N—H⋯O and O—H⋯Cl hydrogen bonds