318 research outputs found

    Visible-light-promoted iridium(III)-catalyzed acceptorless dehydrogenation of N-Heterocycles at room temperature

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    An effective visible-light-promoted iridium(III)catalyzed hydrogen production from N-heterocycles is described. A single iridium complex constitutes the photocatalytic system playing a dual task, harvesting visible-light and facilitating C-H cleavage and H-2 formation at room temperature and without additives. The presence of a chelating C-N ligand combining a mesoionic carbene ligand along with an amido functionality in the Ir-III complex is essential to attain the photocatalytic transformation. Furthermore, the le l complex is also an efficient catalyst for the thermal reverse process under mild conditions, positioning itself as a proficient candidate for liquid organic hydrogen carrier technologies (LOHCs). Mechanistic studies support a light-induced formation of H-2 from the Ir-H intermediate as the operating mode of the iridium complex

    Noncommutative Scalar Field Coupled to Gravity

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    A model for a noncommutative scalar field coupled to gravity is proposed via an extension of the Moyal product. It is shown that there are solutions compatible with homogeneity and isotropy to first non-trivial order in the perturbation of the star-product, with the gravity sector described by a flat Robertson-Walker metric. We show that in the slow-roll regime of a typical chaotic inflationary scenario, noncommutativity has negligible impact.Comment: Revtex4, 6 pages. Final version to appear at Phys. Rev.

    A 9-month Jumping Intervention to Improve Bone Acquisition in Adolescent Male Athletes: The PRO-BONE Study

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    This is the author acepted manuscript. The final version is available via the DOI in this recordAnnual Meeting of the American College of Sports Medicine (ACSM), 29 May - 2 June 2018, Minneapolis, USA. G-21 Thematic Poster - Bone Quality in Athletes and Special Population

    The effect of a high-impact jumping intervention on bone mass, bone stiffness and fitness parameters in adolescent athletes

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    This is the final version. Available on open access from Springer via the DOI in this record.This study demonstrates that a 9-month jumping intervention can improve bone mass gains and physical fitness performance in adolescent males participating in non-osteogenic sports, such as swimming and cycling. PURPOSE: To examine the effect of a jumping intervention on bone mass, bone stiffness and fitness parameters in adolescents involved in different sports. METHODS: Ninety-three adolescent male swimmers (SWI), footballers (FOO) and cyclists (CYC) were randomised to intervention (INT) and sport (INT-SWI = 19, INT-FOO = 15, INT-CYC = 14) or sport only (CON-SWI = 18, CON-FOO = 15, CON-CYC = 12) groups. The 9-month jumping intervention consisted of 3 levels (12 weeks each) of 20 repetitions per set of counter movement jumps (CMJ) using adjustable weight vests (level 1 = 20 CMJ jumps/set, 0 kg, 3 sets/day, 3 times/week; level 2 = 20 CMJ jumps/set, 2 kg, 4 sets/day, 3 times/week; level 3 = 20 CMJ jumps/set, 5 kg, 4 sets/day, 4 times/week). Total body bone mineral content (BMC) at total body less head (TBLH) was measured using dual-energy X-ray absorptiometry and bone stiffness using quantitative ultrasound. Fitness was assessed using the 20-m shuttle run (20mSRT), CMJ and standing long jump (SLJ) tests. RESULTS: INT-SWI had significantly higher increase in BMC legs and bone stiffness compared to CON-SWI (4.2-12.7%). INT-CYC had significantly higher increase in BMC at TBLH and legs and bone stiffness compared to CON-CYC (5.0-12.3%). There were no significant differences between INT-FOO and CON-FOO in any bone outcomes (0.9-3.9%). The increase in CMJ performance was significantly higher in INT-SWI (3.1 cm) and INT-CYC (3.2 cm) compared to CON-SWI and CON-CYC groups, respectively. CONCLUSIONS: A 9-month jumping intervention can improve bone mass, bone stiffness and muscular fitness in adolescent males participating in non-osteogenic sports, such as swimming and cycling. CLINICAL TRIAL REGISTRATION: ISRCTN17982776.European Union Seventh Framework Programme (FP7/2007–2013

    A 9-month jumping intervention to improve bone geometry in adolescent male athletes

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    This is the author accepted manuscript. The final version is available from Lippincott, Williams & Wilkins via the DOI in this record.PURPOSE: Sports have different effects on bone development and effective interventions to improve bone health of adolescent athletes are needed. The purpose of the study was to investigate the effect of a 9-month jumping intervention on bone geometry and metabolism in adolescent male athletes METHODS: Ninety-three adolescent (14.1 years old) male swimmers (SWI), footballers (FOO) and cyclists (CYC) were randomized to an intervention and sport (INT-SWI=19, INT-FOO=15, INT-CYC=14) or sport only (CON-SWI =18, CON-FOO =15, CON-CYC =12) groups. Cross-sectional area (CSA), cross-sectional moment of inertia (CSMI) and section modulus (Z) at the femoral neck were assessed using hip structural analysis, and trabecular texture of the lumbar spine using trabecular bone score (TBS). Bone mineral content (BMC) at femoral neck and lumbar spine was assessed using dual-energy x-ray absorptiometry. Serum N-terminal propeptide of procollagen type I (PINP), isomer of the Carboxi-terminal telopeptide of type 1 collagen (CTX-I), total serum calcium and 25 hydroxyvitamin D [25(OH)D] were analysed. RESULTS: INT-CYC acquired significantly higher lumbar spine BMC (4.6 %) and femoral neck BMC (9.8 %) than CON-CYC. INT-CYC acquired significantly higher CSA (11.0 %), CSMI (10.1 %) and TBS (4.4 %) than CON-CYC. INT-SWI acquired significantly higher femoral neck BMC (6.0 %) and CSMI (10.9 %) than CON-SWI. There were no significant differences between INT-FOO and CON-FOO in any bone outcomes. PINP significantly decreased in CON-SWI, INT-FOO, CON-FOO and CON-CYC. CTX-I significantly decreased in CON-SWI and CON-CYC. 25(OH)D significantly increased in INT-CYC, CON-CYC, INT-FOO and CON-FOO. CONCLUSIONS: A 9-month jumping intervention improved bone outcomes in adolescent swimmers and cyclists, but not in footballers. This intervention might be used by sports clubs to improve bone health of adolescent athletes.The research leading to these results has received funding from the European Union Seventh Framework Programme ([FP7/2007-2013] under grant agreement n°. PCIG13-GA-2013-618496

    Effect of maturational timing on bone health in male adolescent athletes engaged in different sports: The PRO-BONE study

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    This is the author accepted manuscript. the final version is available from Elsevier via the DOI in this recordObjectives: To describe differences in bone outcomes according to biological age in male athletes participating in osteogenic (OS) or non-osteogenic (NOS) sports. Design: Longitudinal (12-months). Methods: 104 adolescents (12–14 years) were measured at baseline and after 1y: OS group (n = 37 football or soccer players) and NOS group (n = 39 swimmers, n = 28 cyclists). Years from peak height velocity (PHV, −2 to +2) was used as a maturational landmark. Bone mineral content (BMC) was assessed using DXA. Hip structural analysis estimated cross-sectional area (CSA), cross-sectional moment of inertia (CSMI) and section modulus (Z) at the femoral neck (FN). Trabecular bone score (TBS) estimated lumbar spine (LS) texture. Quantitative ultrasound measured bone stiffness. Multilevel regression models adjusted by hours of training were fitted. Results: Compared to NOS, OS had significantly greater total body (less head) BMC from PHV to +2 years from PHV (from 9.5% to 11.3%, respectively); LS BMC from −1 years from PHV to PHV (from 9.8% to 9.9%); hip BMC (from 11.6% to 22.9%), FN BMC (from 12.0% to 15.9%), TBS (from 4.2% to 4.8%) and stiffness index (from 11.9% to 23.3%) from −1 years from PHV to +2 years from PHV; and CSA (from 8.4% to 18.8%), Z (from 5.5% to 22.9%) and CSMI (from 10.6% to 23.3%) from −2 years from PHV to +2 years from PHV. There was a significant trend for the between-group differences to increase with biological age except for LS BMC and TBS. Conclusions: These findings underline the differential bone response to different sports throughout the years surrounding PHV in male adolescent athletes. Clinical trial registration: ISRCTN17982776.European Union Seventh Framework ProgrammeUniversity of Castilla-La ManchaUniversity of Granad

    Bone health in children and youth with Cystic Fibrosis: a systematic review and meta-analysis of matched cohort studies

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    This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordObjective To assess the evidence regarding the differences in areal bone mineral density (aBMD) between children and adolescents with cystic fibrosis (CF) compared with their healthy peers, based on data from longitudinal studies. Study design We searched MEDLINE, SPORTDiscus, the Cochrane Library, PEDro (Physiotherapy Evidence Database), and Embase databases. Observational studies addressing the change of aBMD in children with CF and healthy children and adolescents were eligible. The DerSimonian and Laird method was used to compute pooled estimates of effect sizes (ES) and 95% CIs for the change of whole body (WB), lumbar spine (LS), and femoral neck (FN) aBMD. Results Six studies with participants with CF and 26 studies with healthy participants were included in the systematic review and meta-analysis. For the analysis in children with CF, the pooled ES for the change of WB aBMD was 0.29 (95% CI –0.15 to 0.74), for the change of LS aBMD was 0.13 (95% CI –0.16 to 0.41), and for the change of FN aBMD was 0.09 (95% CI –0.39 to 0.57). For the analysis in healthy children, the pooled ES for the change of WB aBMD was 0.37 (95% CI 0.26-0.49), for the change of LS aBMD was 0.13 (95% CI –0.16 to 0.41), and for the change of FN aBMD was 0.52 (95% CI 0.19-0.85). Conclusions aBMD development might not differ between children and adolescents with CF receiving medical care compared with their healthy peers. Further longitudinal studies in a CF population during growth and development are required to confirm our findings

    The Mediating Role of Lean Soft Tissue in the Relationship between Somatic Maturation and Bone Density in Adolescent Practitioners and Non-Practitioners of Sports

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    This study aimed to identify the mediating effect of lean soft tissue (LST) in the association between somatic maturation and areal bone mineral density (aBMD) in adolescents by sex and sport participation. The sample included 558 adolescents (401 males, mean age of 14.0 years) that were practitioners of sports (11 sport modalities, n = 402) and a non-sport group (n = 157). Somatic maturation was assessed by using a validated peak height velocity prediction equation. Dual-energy X-ray absorptiometry (DXA) was used to assess aBMD (upper and lower limbs, spine and total body less head—TBLH) and LST. For both sexes, LST mediated the association between somatic maturation and aBMD at all skeletal sites (mediation percentage ranging from 36.3% to 75.4%). For sport and non-sport groups, the LST also mediated the association between somatic maturation and aBMD at all skeletal sites (mediation percentage ranging from 51.6% to 85.6%). The direct effect was observed in all groups, except for lower limbs and TBLH in the non-sport group. The association between somatic maturation and aBMD was mediated by LST in adolescents of both sexes and regardless of involvement in organized sports. Our findings highlighted the role of improving LST to mitigate the association of somatic maturation with aBMD.São Paulo Research Foundation (FAPESP) (FAPESP Process 2013/06963-5, 2015/13543-8, 2016/06920-2, 2017/09182-5, 2018/24164-6 and 2015/19710-3)FAPESP (2017/27234-2)FAPESP (2016/20354-0)“La Caixa” Foundation within the Junior Leader fellowship programme (ID 100010434; code LCF/BQ/PR19/11700007
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