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Abstract: Two series of novel thermally stable second-order nonlinear optical (NLO) and photochromic chromophores have been designed and synthesized. The two series of compounds were based on different combinations of donor groups (pyrrole or thienylpyrrole) which act simultaneously as π-conjugated bridges, together with diazoaryl or diazothiazolyl as acceptor moieties. Their photochromic and electrochemical behavior were characterized, while hyper-Rayleigh scattering (HRS) was employed to evaluate their second-order nonlinear optical properties. The results of these studies have been critically analyzed together with two other related compounds reported earlier from our laboratories in which the thienylpyrrole system was used as the donor group keeping the functionalized diazoaryl as acceptor moiety. The measured molecular first hyperpolarizabilities and the observed photochromic behavior showed strong variations for the different donor systems used (pyrrole or thienylpyrrole) and were also sensitive to the acceptor strength of the diazenehetero(aryl) moiety. The thienylpyrrole based compounds endowed with extended π-conjugated bridges and stronger donor auxiliary effects in comparison to the pyrrole compounds, when coupled to the stronger acceptor diazo(hetero)aryl groups gave rise to significantly larger hyperpolarizabilities (β = 274–415 × 10−30 esu) for an incident wavelength of 1064 nm. These compounds also displayed improved photochromic behavior with very fast response to the visible light stimulus (1.5 s) and fast thermal return to the original forms (2–3 s). [Copyright &y& Elsevier]

Abstract: New N-substituted benzopyranocarbazoles were synthesized and their photochromic properties, under continuous near-UV irradiation, are described. Besides a remarkable sensitiveness to solar light, N-methyl and N-benzyl derivatives give rise to particularly stable coloured open forms. The structure of these photoisomers was characterized through NMR spectroscopy. According to our results, it was possible, after UV irradiation, to accumulate more than 90% of the long-lived TT-isomer. At ambient temperature, coloured TT state was fully photobleachable by visible light and no significant degradation was observed during cycling. This remarkable property opens a range of potential applications for these N-substituted benzopyranocarbazoles in photoswitchable devices. [Copyright &y& Elsevier]

A range of aryl ether linked benzophenones (8) has been conveniently obtained by nucleophilic displacement of fluoride from 4-fluorobenzophenone with a dihydroxy-benzene or-naphthalene. The linked benzophenones were efficiently transformed in two steps to symmetrically linked naphthopyrans (10d–k). The photochromic response of these novel systems under steady state irradiation is characterised by a two stage fading process and their colourability is only marginally improved over the related monomeric analogues (10a–c). [Copyright &y& Elsevier]

The objectives were to examine knee angle-, and gender-specific knee extensor torque output and quadriceps femoris (QF) muscle recruitment during maximal effort, voluntary contractions. Fourteen young adult men and 15 young adult women performed three isometric maximal voluntary contractions (MVC), in a random order, with the knee at 0° (terminal extension), 10°, 30°, 50°, 70°, and 90° flexion. Knee extensor peak torque (PT), and average torque (AT) were expressed in absolute (N m), relative (N m kg-1) and allometric-modeled (N m kg-n) units. Vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) muscle EMG signals were full-wave rectified and integrated over the middle 3 s of each contraction, averaged over the three trials at each knee angle, and normalized to the activity recorded at 0°. Muscle recruitment efficiency was calculated as the ratio of the normalized EMG of each muscle to the allometric-modeled average torque (normalized to the values at 0° flexion), and expressed as a percent. Men generated significantly greater knee extensor PT and AT than women in absolute, relative and allometric-modeled units. Absolute and relative PT and AT were significantly highest at 70°, while allometric-modeled values were observed to increase significantly across knee joint angles 10–90°. VM EMG was significantly greater than the VL and RF muscles across all angles, and followed a similar pattern to absolute knee extensor torque. Recruitment efficiency improved across knee joint angles 10–90° and was highest for the VL muscle. VM recruitment efficiency improved more than the VL and RF muscles across 70–90° flexion. The findings demonstrate angle-, and gender-specific responses of knee extensor torque to maximal-effort contractions, while superficial QF muscle recruitment was most efficient at 90°, and less dependent on gender. [Copyright &y& Elsevier]

• Novel azo dyes based on 5-hydroxyquinoline and their well-known 8HQ analogues were synthesized. • Partially deuteration technique in 13C NMR spectroscopy was used in order to investigate the tautomerization in these azo dyes. • The study of solvatochromism in azo dyes strengthens explanation of tautomerism disclosing the effect of solvent used on these phenomena. • Photochromism phenomena justifies E/Z isomerization in the studied azo dyes. Image, graphical abstract A series of novel substituted-azo dyes 8-(aryldiazenyl)quinolin-5-ol (5a-i) were synthesized by the coupling reaction of 5-hydroxyquinoline with diazotized aniline derivatives in the presence of NaNO 2 in HCl/H 2 O mixture. The study of the spectroscopic and solvatochromic properties were performed by FT-IR, 1H and 13C-NMR and UV-Visible spectroscopies. The tautomerism of these dyes was studied using the deuteration technique and solvatochromic measurements. Photochromic properties of these 5-hydroxyquinoline azo dyes were also examined via E/Z and Z/E photochemical isomerization reactions and compared with the existing 8-hydroxyquinoline analogous. The novel substituted-azo dyes exhibited higher Z/E thermal isomerization rates and have larger absorbance wavelength range than their 8-hydroxyquinoline analogous, making them potential molecular switches. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine superficial quadriceps femoris (QF) EMG and torque at perceived voluntary contraction efforts. Thirty subjects (15 males, 15 females) performed 9, 5 s, sub-maximal contractions at prescribed levels of perceived voluntary effort at points 1-9 on an 11-point scale (0-10), in a random order. Surface electromyograms (EMG) of the vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) muscles, as well as QF peak torque (PT), average torque (AT), and torque coefficient of variation (C.V.), were sampled. The raw EMG signals were full-wave rectified and integrated over the middle three s of each contraction. The sampled EMG signals, and PT and AT at each perceived exertion level were normalized to the average of three maximal voluntary contractions. The normalized EMG and torque values at each perceived exertion level were then compared to equivalent percent values (i.e., 10% at a perceived level of 1). The results demonstrated that at all perceived exertion levels, with the exception of the RF at a level of 2 which was equivalent to 20%, and the VL and RF muscles at a level 1 in which activation was greater than 10%, activation was significantly less than the equivalent percent value at each point on the scale. VM EMG was found to be less than the VL and RF from contraction levels 3-9. PT was shown to be less than the equivalent percent values at contraction levels 6-9. The AT was found to be lower than the expected percent value at perceived effort levels 2-9. Torque C.V. was not found to be different across the range of perceived effort. The major findings of this study suggested that humans over-estimate voluntary QF muscle torque when guided by perceptual sensations. It is also suggested that the produced EMG signals revealed a reliance on the VL muscle for knee extensor torque generation at sub-maximal levels.

Background: 1) To examine the validity and accuracy of the CR-10 scale for evaluating perceived exertion, and 2) to assess gender differences in perceived exertion across different levels of contraction intensity., Experimental Design: cross-sectional, comparative design., Setting: Human Performance and Fatigue Laboratory, Eastern Washington University., Subjects: 30 healthy, college age volunteers (15 males, 15 females)., Measures: All subjects were assessed for isometric torque and perceived exertion of the quadriceps femoris muscles, via the CR-10 scale. One low anchor was applied under resting conditions with the knee flexed to 60 degrees, and a high anchor was applied during a maximal voluntary muscle contraction (MVC). SUBJECTS performed five-second isometric contractions equivalent to 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% of their MVC, in a random order, and were assessed for perceived exertion by visually observing the CR-10 scale. One sample "t"-tests and 95% confidence intervals were calculated for perceived exertion at each relative torque level. A single factor ANOVA with repeated measures was performed across al levels of exercise intensity. Linearity for perceived exertion was assessed via regression analysis., Results: Perceived exertion at each exercise intensity were as follows: 10%: 1.87+/-1.14, 20%: 2.43+/-1.19, 30%: 3.5+/-1.36, 40%: 3.97+/-1.52, 50%: 4.73+/-1.28, 60%: 5.53+/-1.28, 70%: 6.73+/-1.62, 80%: 7.57+/-1.72, and 90%: 8.6+/-1.52. The increase in perceived exertion across the intensity spectrum was found to fit both linear and quadratic trends. There were no gender differences in perceived exertion across all levels of exercise intensity., Conclusions: The findings demonstrate that the CR-10 scale closely approximates perceived exertion of the quadriceps femoris muscles during sub-maximal, static contractions, and is not gender specific.

The pattern of mobility of the mandibular incisor with intrusive loads was consistent with the view that the periodontal tissues are viscoelastic. A significant time-dependency of the response was observed. The pattern of mobility was similar to that reported for axially directed extrusive loads and for horizontal loads.