96 research outputs found
Soliton pinning by long-range order in aperiodic systems
We investigate propagation of a kink soliton along inhomogeneous chains with
two different constituents, arranged either periodically, aperiodically, or
randomly. For the discrete sine-Gordon equation and the Fibonacci and
Thue-Morse chains taken as examples, we have found that the phenomenology of
aperiodic systems is very peculiar: On the one hand, they exhibit soliton
pinning as in the random chain, although the depinning forces are clearly
smaller. In addition, solitons are seen to propagate differently in the
aperiodic chains than on periodic chains with large unit cells, given by
approximations to the full aperiodic sequence. We show that most of these
phenomena can be understood by means of simple collective coordinate arguments,
with the exception of long range order effects. In the conclusion we comment on
the interesting implications that our work could bring about in the field of
solitons in molecular (e.g., DNA) chains.Comment: 4 pages, REVTeX 3.0 + epsf, 3 figures in accompanying PostScript file
(Submitted to Phys Rev E Rapid Comm
Effect of melatonin ingestion on physical performance, metabolic responses, and recovery after an intermittent training session
Objectives Fatigue is a limiting factor for sport performance. For this reason, optimal recovery after training is just as critical as the training program itself, if not more. Indeed, there is a need for strategies that can facilitate recovery after training, and one such strategy is the ingestion of supplements like melatonin (MEL). This study aimed to evaluate if MEL intake could improve recovery of athletes after an intermittent training session (ITS). Methods Fifteen elite female athletes (17.4â±â0.4âyears, 76.4â±â5.6âkg, 1.76â±â0.04âm; meanâ±âstandard deviation) participated in two testing campaigns. During each period, they performed a battery of physical and cognitive tests before and after an ITS, as well as after ingesting MEL (6âmg tablet) or placebo in a randomized design. The ITS comprised the modified agility T-test, squat jump, counter movement jump, maximum standing ball-throw velocity test, maximum jump ball-throw velocity test, and 20-m sprint. Oral temperature (OT) and vigilance were evaluated before and after the ITS. Rating of perceived exertion (RPE), blood lactate [La], and glucose [Gl] were recorded after each ITS. Results Short-term performance, recovery of physical performance, and OT were not affected by MEL ingestion after the ITS. Moreover, MEL did not affect cognitive performance or RPE scores after the ITS. However, [La] and [Gl] (pâ<â0.05 for both) were decreased after MEL ingestion. Conclusion: MEL has no effect on the recovery of physical performance but may affect glucose utilization and lactate metabolism during the team-handball training session
Morning melatonin ingestion and diurnal variation of short-term maximal performances in soccer players
Aim Very few studies have investigated the temporal specificity of melatonin (MEL) ingestion upon short-term maximal athletic performances. The aim of the present study was to explore the effect of morning MEL ingestion on cognitive and physical performances measured in the afternoon. Methods Twelve soccer players from a Tunisian squad (17.9 ± 1.3 years, 1.74 ± 0.06 m and 62.0 ± 8.8 kg) participated in the present study. They performed two testing sessions at 08:00 h, 12:00 h and 16:00 h after either MEL (5mg) or placebo (PLA) ingestion, in a randomized order. During each period, the participants performed the following cognitive and physical tests: reaction time and vigilance tests, medicine-ball throw (MBT), five jumps, handgrip strength (HG), and agility tests. Results cognitive and physical performances were significantly higher at 16:00 h compared to 08:00 h during the two conditions (p < 0.05). Moreover, performances of MBT and HG were lower in the morning with MEL in comparison to PLA (p < 0.05). However, MEL ingestion did not affect physical and cognitive performances measured at 12:00 h and 16:00 h. Conclusion morning MEL ingestion has no unfavourable effect on afternoon physical and cognitive performances in soccer players
MucocĂšle sphĂ©noĂŻdale bilatĂ©rale : a propos dâun cas
Les mucocĂšles sphĂ©noĂŻdales sont des formations pseudokystiques expansives, dâĂ©volution lente, qui se dĂ©veloppent au sein de la cavitĂ© sinusienne sphĂ©noĂŻdale. Elles possĂšdent la capacitĂ© dâĂ©roder les parois osseuses et prĂ©sentent une Ă©volution pseudotumorale. Les rapports neuromĂ©ningĂ©s et orbitaires font la gravitĂ© de cette localisation sinusienne la prĂ©sentation clinique qui est souvent dâapparition retardĂ©e par rapport Ă la constitution de la mucocĂšle. Lâimagerie (TDM et IRM) permet le diagnostic positif et le diagnostic diffĂ©rentiel avec certains processus dĂ©veloppĂ©s au niveau de lâĂ©tage moyen de la base du crĂąne. La marsupialisation chirurgicale par voie endoscopique endonasale permet lâeffondrement de la mucocĂšle.Mots-clĂ©s : mucocĂšle, sinus sphĂ©noĂŻda
Far-infrared study of the Jahn-Teller distorted C60 monoanion in C60 tetraphenylphosphoniumiodide
We report high-resolution far-infrared transmission measurements on C(60)-tetraphenylphosphoniumiodide as a function of temperature. In the spectral region investigated (20-650 cm(-1)), we assign intramolecular modes of the C(60) monoanion and identify low-frequency combination modes. The well-known F(1u)(1) and F(1u)(2) modes are split into doublers at room temperature, indicating a D(5d) or D(3d) distorted ball. This result is consistent with a dynamic Jahn-Teller effect in the strong-coupling limit or with a static distortion stabilized by low-symmetry perturbations. The appearance of silent odd modes is in keeping with symmetry reduction of the hall, while activation of even modes is attributed to interband electron-phonon coupling and orientational disorder in the fulleride salt. Temperature dependences reveal a weak transition in the region 125-150 K in both C(60)(-) and counterion modes, indicating a bulk, rather than solely molecular, effect. Anomalous softening (with decreasing temperature) in several modes may correlate with the radial character of those vibrations. [S0163-1829(98)03245-7]
Morning melatonin ingestion and diurnal variation of short-term maximal performances in soccer players
Variation in the provision and practice of implant-based breast reconstruction in the UK: Results from the iBRA national practice questionnaire
Introduction The introduction of biological and synthetic meshes has revolutionised the practice of implant-based breast reconstruction (IBBR) but evidence for effectiveness is lacking. The iBRA (implant Breast Reconstruction evAluation) study is a national trainee-led project that aims to explore the practice and outcomes of IBBR to inform the design of a future trial. We report the results of the iBRA National Practice Questionnaire (NPQ) which aimed to comprehensively describe the provision and practice of IBBR across the UK. Methods A questionnaire investigating local practice and service provision of IBBR developed by the iBRA Steering Group was completed by trainee and consultant leads at breast and plastic surgical units across the UK. Summary data for each survey item were calculated and variation between centres and overall provision of care examined. Results 81 units within 79 NHS-hospitals completed the questionnaire. Units offered a range of reconstructive techniques, with IBBR accounting for 70% (IQR:50â80%) of participating units' immediate procedures. Units on average were staffed by 2.5 breast surgeons (IQR:2.0â3.0) and 2.0 plastic surgeons (IQR:1.0â3.0) performing 35 IBBR cases per year (IQR:20-50). Variation was demonstrated in the provision of novel different techniques for IBBR especially the use of biological (n = 62) and synthetic (n = 25) meshes and in patient selection for these procedures. Conclusions The iBRA-NPQ has demonstrated marked variation in the provision and practice of IBBR in the UK. The prospective audit phase of the iBRA study will determine the safety and effectiveness of different approaches to IBBR and allow evidence-based best practice to be explored
The impact of immediate breast reconstruction on the time to delivery of adjuvant therapy: the iBRA-2 study
Background:
Immediate breast reconstruction (IBR) is routinely offered to improve quality-of-life for women requiring mastectomy, but there are concerns that more complex surgery may delay adjuvant oncological treatments and compromise long-term outcomes. High-quality evidence is lacking. The iBRA-2 study aimed to investigate the impact of IBR on time to adjuvant therapy.
Methods:
Consecutive women undergoing mastectomyâ±âIBR for breast cancer JulyâDecember, 2016 were included. Patient demographics, operative, oncological and complication data were collected. Time from last definitive cancer surgery to first adjuvant treatment for patients undergoing mastectomyâ±âIBR were compared and risk factors associated with delays explored.
Results:
A total of 2540 patients were recruited from 76 centres; 1008 (39.7%) underwent IBR (implant-only [nâ=â675, 26.6%]; pedicled flaps [nâ=â105,4.1%] and free-flaps [nâ=â228, 8.9%]). Complications requiring re-admission or re-operation were significantly more common in patients undergoing IBR than those receiving mastectomy. Adjuvant chemotherapy or radiotherapy was required by 1235 (48.6%) patients. No clinically significant differences were seen in time to adjuvant therapy between patient groups but major complications irrespective of surgery received were significantly associated with treatment delays.
Conclusions:
IBR does not result in clinically significant delays to adjuvant therapy, but post-operative complications are associated with treatment delays. Strategies to minimise complications, including careful patient selection, are required to improve outcomes for patients
Application of the Dimer and Tetramer Models for Interpretation of the IR Spectra of TEA(TCNQ)
An interpretation of the IR polarized spectra of the organic quasi-one--dimensional semiconductor triethylammonium (TCNQ), between 80 and 300 K, is discussed in terms of the dimer and tetramer theories. It is concluded that the dimer model is acceptable only for describing high-T phase of TEA(TCNQ). The tetramer model is more adequate for an interpretation of the IR spectra of the salt within the large temperature range. It is also shown that the phase transition influences distinctly neither vibronic (electron-molecular vibration coupled) modes nor conformity of the experimental spectra with calculated ones according to the dimer or tetramer theory
Temperature dependence of infrared spectral properties of the dimerized quasi 1-d TCNQ salts
Temperature dependence of spectral properties of dimerized TCNQ salts is explained in terms of isolated dimer model. Electron-electron correlation in these compounds is shown to be of major importance. The analysis of Re(1/Ï (Ï)) function, which can be calculated from reflectance data, is claimed to allow determination of temperature dependence of electron-molecular vibrations coupling parameters without ambiguity.Les variations thermiques des propriĂ©tĂ©s spectrales des sels TCNQ construits de dimĂšres sont expliquĂ©es par le modĂšle de dimĂšre isolĂ©. Le rĂŽle important des corrĂ©lations Ă©lectron-Ă©lectron dans ces composĂ©s est soulignĂ©. L'analyse de la fonction Re (1/Ï (Ï)) calculĂ©e en tenant compte de la rĂ©flexion a permis de dĂ©terminer sans ambiguĂŻtĂ© la dĂ©pendance thermique des paramĂštres de couplage Ă©lectron-phonon
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