265 research outputs found
Factors Related to Average Concentric Velocity of Four Barbell Exercises at Various Loads
The resistance exercise load is the primarily determinant of the average concentric velocity (ACV) during a repetition. It is unknown whether individual factors such as training experience or anthropometrics also influence the ACV. Previous research has shown the ACV during the 1 repetition maximum (1RM) varies between exercises, but it is not clear whether ACV is different between exercises at various percentages of the 1RM. This information could provide practical guidelines for trainees using ACV to select training loads. Therefore, the purpose of this study was to determine whether training age, current training frequency, limb length, height, and relative strength are related to ACV at loads between 35 and 100% of the 1RM for the squat, bench press, deadlift, and overhead press. A secondary purpose was to compare the ACV values between the 4 lifts at each relative load. Fifty-one (18 women and 33 men) completed 2 testing sessions in which the squat, bench press, deadlift, and overhead press ACV were measured during a modified 1RM protocol. Average concentric velocity values were significantly different among the 4 lifts (p \u3c 0.05) at all relative loads between 35 and 100% 1RM except for 55% 1RM (p = 0.112). Generally, compared at the same relative loads, the overhead press exhibited the greatest ACV followed by the squat, bench press, and deadlift (in order). In addition, relative strength level was inversely related to ACV at maximal loads (â„95% 1RM) for the squat, bench press, and deadlift while height was positively related to ACV at moderate loads (55% 1RM) for all lifts (p \u3c 0.05). These results suggest that the load-velocity profile is unique for each of these exercises, and that velocity ranges used for exercise prescription should be specific to the exercise. A trainee\u27s relative strength and height may be a primary influence on the ACV
Formation of ultracold RbCs molecules by photoassociation
The formation of ultracold metastable RbCs molecules is observed in a double
species magneto-optical trap through photoassociation below the
^85Rb(5S_1/2)+^133Cs(6P_3/2) dissociation limit followed by spontaneous
emission. The molecules are detected by resonance enhanced two-photon
ionization. Using accurate quantum chemistry calculations of the potential
energy curves and transition dipole moment, we interpret the observed
photoassociation process as occurring at short internuclear distance, in
contrast with most previous cold atom photoassociation studies. The vibrational
levels excited by photoassociation belong to the 5th 0^+ or the 4th 0^-
electronic states correlated to the Rb(5P_1/2,3/2)+Cs(6S_1/2) dissociation
limit. The computed vibrational distribution of the produced molecules shows
that they are stabilized in deeply bound vibrational states of the lowest
triplet state. We also predict that a noticeable fraction of molecules is
produced in the lowest level of the electronic ground state
Sensitivity and identifiability of hydraulic and geophysical parameters from streaming potential signals in unsaturated porous media
Fluid flow in a charged porous medium generates electric potentials called
streaming potential (SP). The SP signal is related to both hydraulic and
electrical properties of the soil. In this work, global sensitivity analysis
(GSA) and parameter estimation procedures are performed to assess the
influence of hydraulic and geophysical parameters on the SP signals and to
investigate the identifiability of these parameters from SP measurements.
Both procedures are applied to a synthetic column experiment involving a
falling head infiltration phase followed by a drainage phase.GSA is used through variance-based sensitivity indices, calculated using
sparse polynomial chaos expansion (PCE). To allow high PCE orders, we use an
efficient sparse PCE algorithm which selects the best sparse PCE from a
given data set using the Kashyap information criterion (KIC). Parameter
identifiability is performed using two approaches: the Bayesian approach
based on the Markov chain Monte Carlo (MCMC) method and the first-order
approximation (FOA) approach based on the LevenbergâMarquardt algorithm. The
comparison between both approaches allows us to check whether FOA can
provide a reliable estimation of parameters and associated uncertainties for
the highly nonlinear hydrogeophysical problem investigated.GSA results show that in short time periods, the saturated hydraulic conductivity
(Ks) and the voltage coupling coefficient at saturation Csat are the most influential parameters, whereas in long time periods, the
residual water content (Ξs), the Mualemâvan Genuchten parameter
n and the Archie saturation exponent na
become influential, with strong interactions between them. The
Mualemâvan Genuchten parameter α has a very weak
influence on the SP signals during the whole experiment.Results of parameter estimation show that although the studied problem is
highly nonlinear, when several SP data collected at different altitudes
inside the column are used to calibrate the model, all hydraulic (Ks,âΞs,âα,ân)
and geophysical parameters (na,âCsat) can be reasonably estimated from the SP measurements. Further, in
this case, the FOA approach provides accurate estimations of both mean
parameter values and uncertainty regions. Conversely, when the number of SP
measurements used for the calibration is strongly reduced, the FOA approach
yields accurate mean parameter values (in agreement with MCMC results) but
inaccurate and even unphysical confidence intervals for parameters with
large uncertainty regions.</p
A global method for coupling transport with chemistry in heterogeneous porous media
Modeling reactive transport in porous media, using a local chemical
equilibrium assumption, leads to a system of advection-diffusion PDE's coupled
with algebraic equations. When solving this coupled system, the algebraic
equations have to be solved at each grid point for each chemical species and at
each time step. This leads to a coupled non-linear system. In this paper a
global solution approach that enables to keep the software codes for transport
and chemistry distinct is proposed. The method applies the Newton-Krylov
framework to the formulation for reactive transport used in operator splitting.
The method is formulated in terms of total mobile and total fixed
concentrations and uses the chemical solver as a black box, as it only requires
that on be able to solve chemical equilibrium problems (and compute
derivatives), without having to know the solution method. An additional
advantage of the Newton-Krylov method is that the Jacobian is only needed as an
operator in a Jacobian matrix times vector product. The proposed method is
tested on the MoMaS reactive transport benchmark.Comment: Computational Geosciences (2009)
http://www.springerlink.com/content/933p55085742m203/?p=db14bb8c399b49979ba8389a3cae1b0f&pi=1
Double helical conformation and extreme rigidity in a rodlike polyelectrolyte
The ubiquitous biomacromolecule DNA has an axial rigidity persistence length
of ~50 nm, driven by its elegant double helical structure. While double and
multiple helix structures appear widely in nature, only rarely are these found
in synthetic non-chiral macromolecules. Here we describe a double helical
conformation in the densely charged aromatic polyamide
poly(2,2'-disulfonyl-4,4'-benzidine terephthalamide) or PBDT. This double helix
macromolecule represents one of the most rigid simple molecular structures
known, exhibiting an extremely high axial persistence length (~1 micrometer).
We present X-ray diffraction, NMR spectroscopy, and molecular dynamics (MD)
simulations that reveal and confirm the double helical conformation. The
discovery of this extreme rigidity in combination with high charge density
gives insight into the self-assembly of molecular ionic composites with high
mechanical modulus (~1 GPa) yet with liquid-like ion motions inside, and
provides fodder for formation of new 1D-reinforced composites.Comment: Accepted for publication by Nature Communication
Novel LOTUS-domain proteins are organizational hubs that recruit C. elegans Vasa to germ granules
We describe MIP-1 and MIP-2, novel paralogous C. elegans germ granule components that interact with the intrinsically disordered MEG-3 protein. These proteins promote P granule condensation, form granules independently of MEG-3 in the postembryonic germ line, and balance each other in regulating P granule growth and localization. MIP-1 and MIP-2 each contain two LOTUS domains and intrinsically disordered regions and form homo- and heterodimers. They bind and anchor the Vasa homolog GLH-1 within P granules and are jointly required for coalescence of MEG-3, GLH-1, and PGL proteins. Animals lacking MIP-1 and MIP-2 show temperature-sensitive embryonic lethality, sterility, and mortal germ lines. Germline phenotypes include defects in stem cell self-renewal, meiotic progression, and gamete differentiation. We propose that these proteins serve as scaffolds and organizing centers for ribonucleoprotein networks within P granules that help recruit and balance essential RNA processing machinery to regulate key developmental transitions in the germ line
Rebooting an Old Script by New Means: TeledildonicsâThe Technological Return to the âCoital Imperativeâ
Teledildonics, a form of digital-mediated sexual interaction, opens new possibilities for the understanding of sexual activity. At first glance, it disrupts conventional preconditions and assumptions about sexual interaction, by allowing the dimension of touch despite the physical distance between partners and, ultimately, promoting a sexual dimension definitely disconnected from the reproductive model of sexuality. However, by scrutinizing the design and functionality of the devices, as well as the discourses presented by three commercial companiesâLovePalz, Lovense and KiirooâI suggest that this technology reinforces the âcoital imperativeâ, by equating sexual interaction with penetration of the vagina by the penis. Although permitting other formulations, specifically for non-heterosexual couples, the penetrative act remains a presupposition. In spite of structurally disrupting the reproductive model of sex, teledildonics promotes its strongest corollary.info:eu-repo/semantics/publishedVersio
The Problematization of Sexuality among Women Living with HIV and a New Feminist Approach for Understanding and Enhancing Womenâs Sexual Lives
In the context of HIV, womenâs sexual rights and sexual autonomy are important but frequently overlooked and violated. Guided by community voices, feminist theories, and qualitative empirical research, we reviewed two decades of global quantitative research on sexuality among women living with HIV. In the 32 studies we found, conducted in 25 countries and composed mostly of cis-gender heterosexual women, sexuality was narrowly constructed as sexual behaviours involving risk (namely, penetration) and physiological dysfunctions relating to HIV illness, with far less attention given to the fullness of sexual lives in context, including more positive and rewarding experiences such as satisfaction and pleasure. Findings suggest that women experience declines in sexual activity, function, satisfaction, and pleasure following HIV diagnosis, at least for some period. The extent of such declines, however, is varied, with numerous contextual forces shaping womenâs sexual well-being. Clinical markers of HIV (e.g., viral load, CD4 cell count) poorly predicted sexual outcomes, interrupting widely held assumptions about sexuality for women with HIV. Instead, the effects of HIV-related stigma intersecting with inequities related to trauma, violence, intimate relations, substance use, poverty, aging, and other social and cultural conditions primarily influenced the ways in which women experienced and enacted their sexuality. However, studies framed through a medical lens tended to pathologize outcomes as individual âproblems,â whereas others driven by a public health agenda remained primarily preoccupied with protecting the public from HIV. In light of these findings, we present a new feminist approach for research, policy, and practice toward understanding and enhancing womenâs sexual livesâone that affirms sexual diversity; engages deeply with society, politics, and history; and is grounded in womenâs sexual rights
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