526 research outputs found
Helical axis analysis to quantify humeral kinematics during shoulder rotation.
© 2019 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.Information pertaining to the helical axis during humeral kinematics during shoulder rotation may be of benefit to better understand conditions such as shoulder instability. The aim of this study is to quantify the behavior of humeral rotations using helical axis (HA) parameters in three different conditions. A total of 19 people without shoulder symptoms participated in the experiment. Shoulder kinematics was measured with an optoelectric motion capture system. The subjects performed three different full range rotations of the shoulder. The shoulder movements were analyzed with the HA technique. Four parameters were extracted from the HA of the shoulder during three different full-range rotations: range of movement (RoM), mean angle (MA), axis dispersion (MDD), and distance of their center from the shoulder (D). No significant differences were observed in the RoM for each condition between left and right side. The MA of the axis was significantly lower on the right side compared to the left in each of the three conditions. The MDD was also lower for the right side compared to the left side in each of the three conditions.The four parameters proposed for the analysis of shoulder kinematics showed to be promising indicators of shoulder instability.Peer reviewe
Linear divisibility sequences and Salem numbers
We study linear divisibility sequences of order 4, providing a
characterization by means of their characteristic polynomials and finding their
factorization as a product of linear divisibility sequences of order 2.
Moreover, we show a new interesting connection between linear divisibility
sequences and Salem numbers. Specifically, we generate linear divisibility
sequences of order 4 by means of Salem numbers modulo 1
Periodic representations and rational approximations of square roots
In this paper the properties of R\'edei rational functions are used to derive
rational approximations for square roots and both Newton and Pad\'e
approximations are given as particular cases. As a consequence, such
approximations can be derived directly by power matrices. Moreover, R\'edei
rational functions are introduced as convergents of particular periodic
continued fractions and are applied for approximating square roots in the field
of p-adic numbers and to study periodic representations. Using the results over
the real numbers, we show how to construct periodic continued fractions and
approximations of square roots which are simultaneously valid in the real and
in the p-adic field
Identities Involving Zeros of Ramanujan and Shanks Cubic Polynomials
In this paper we highlight the connection between Ramanujan cubic polynomials
(RCPs) and a class of polynomials, the Shanks cubic polynomials (SCPs), which
generate cyclic cubic fields. In this way we provide a new characterization for
RCPs and we express the zeros of any RCP in explicit form, using trigonometric
functions. Moreover, we observe that a cyclic transform of period three
permutes these zeros. As a consequence of these results we provide many new and
beautiful identities. Finally we connect RCPs to Gaussian periods, finding a
new identity, and we study some integer sequences related to SCPs
Groups and monoids of Pythagorean triples connected to conics
We define operations that give the set of all Pythagorean triples a structure
of commutative monoid. In particular, we define these operations by using
injections between integer triples and matrices. Firstly, we
completely characterize these injections that yield commutative monoids of
integer triples. Secondly, we determine commutative monoids of Pythagorean
triples characterizing some Pythagorean triple preserving matrices. Moreover,
this study offers unexpectedly an original connection with groups over conics.
Using this connection, we determine groups composed by Pythagorean triples with
the studied operations
Polynomial sequences on quadratic curves
In this paper we generalize the study of Matiyasevich on integer points over
conics, introducing the more general concept of radical points. With this
generalization we are able to solve in positive integers some Diophantine
equations, relating these solutions by means of particular linear recurrence
sequences. We point out interesting relationships between these sequences and
known sequences in OEIS. We finally show connections between these sequences
and Chebyshev and Morgan-Voyce polynomials, finding new identities
The Biharmonic mean
We briefly describe some well-known means and their properties, focusing on
the relationship with integer sequences. In particular, the harmonic numbers,
deriving from the harmonic mean, motivate the definition of a new kind of mean
that we call the biharmonic mean. The biharmonic mean allows to introduce the
biharmonic numbers, providing a new characterization for primes. Moreover, we
highlight some interesting divisibility properties and we characterize the
semi--prime biharmonic numbers showing their relationship with linear recurrent
sequences that solve certain Diophantine equations
Sodium hydroxide pretreatment as an effective approach to reduce the dye/holes recombination reaction in P-Type DSCs
We report the synthesis of a novel squaraine dye (VG21-C12) and investigate its behavior
as p-type sensitizer for p-type Dye-Sensitized Solar Cells. The results are compared
with O4-C12, a well-known sensitizer for p-DSC, and sodium hydroxide pretreatment
is described as an effective approach to reduce the dye/holes recombination. Various
variable investigation such as dipping time, dye loading, photocurrent, and resulting cell
efficiency are also reported. Electrochemical impedance spectroscopy (EIS) was utilized
for investigating charge transport properties of the different photoelectrodes and the
recombination phenomena that occur at the (un)modified electrode/electrolyte interface
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