Divide-and-Conquer Semiclassical Dynamics: A Viable Route for Spectroscopic Calculations of High Dimensional Molecular Systems

The accurate prediction of vibrational spectra has become a very challenging task for theoretical methods. The most relevant stumbling block is represented by the necessity to employ quantum methods, since very often quantum effects, like zero point energy, quantum anharmonicities, and overtones, are not negligible to gain insights into the physics of a molecular system. Unfortunately, quantum mechanical methods are usually affected by the so-called curse of dimensionality problem, which limits their applicability to small and medium sized molecules. A viable alternative is represented by the Semiclassical theory, which is obtained by stationary-phase approximating to the second order of the Feynman Path-Integral representation of the Quantum time evolution operator, and allows to calculate spectral densities. In particular, the Coherent State Representation was shown to be very valid in molecular applications. However, even in this case the curse of dimensionality occurs and the method runs out of steam when the system dimensionality increases to 25-30 degrees of freedom or more. Here, we present a method, called Divide-and-Conquer, able to overcome this issue, and to reproduce spectra of high-dimensional molecular systems, while retaining the typical semiclassical accuracy (20-30 cm-1). The method is tested on simple molecules. Then, it is used to calculate spectra of a C60 model, which is made by 174 degrees of freedom, and of variously sized-water clusters characterized by strong hydrogen-bonding that red shifts the involved OH stretches. Finally, the method is also combined with ab-initio molecular dynamics to abandon the necessity to employ pre-fitted Potential Energy Surfaces, and applied to study supramolecular systems as the protonated glycine dimer and hydrogen-tagged protonated glycine

Divide-and-Conquer Semiclassical Dynamics: A Viable Method for Vibrational Spectra Calculations of High Dimensional and Anharmonic Molecular Systems

The prediction of accurate vibrational frequencies is often necessary for the interpretation of experimental outcomes, especially when sources of strong anharmonic effects such as hydrogen bonding are present. Unfortunately, the most relevant stumbling block to fill in the gap between theory and experiment is usually represented by dimensionality problems, when quantum mechanical effects like Zero Point Energy, quantum anharmonicities, and overtones cannot be neglected. In this circumstance quantum applications are generally limited to small and medium sized molecules. One possible alternative is represented by Semiclassical theory, which allows to recover accurate spectral densities by taking advantage of quantities arising from classical mechanics simulations. [1-5] In particular, here we present a method, called Semiclassical \u201cDivide-and-Conquer\u201d, able to reproduce spectra of high-dimensional molecular systems accurately. [6,7] The method is first validated by performing spectra of small and medium sized molecules, and then it is used to calculate the spectra of benzene and a C 60 model, which is made of 174 degrees of freedom. Then, we show results of variously sized-water clusters characterized by strong hydrogen-bonding that red shifts the involved OH stretches. [8] Finally, the method is combined with ab-initio molecular dynamics to abandon the necessity to employ pre-fitted Potential Energy Surfaces, and applied to study supramolecular systems like the protonated glycine dimer and hydrogen-tagged protonated glycine. [9] [1] W. H. Miller, J. Chem. Phys. 1970, 53, 3578; [2] E. J. Heller, J. Chem. Phys. 1981, 75, 2923; M. F. Herman and E. Kluk, Chem. Phys. 1984, 91, 27. [3] K. G. Kay, J. Chem. Phys. 1994, 101, 2250; W. H. Miller, J. Phys. Chem. A 2001, 105, 2942. [4] A. L. Kaledin and W. H. Miller, J. Chem. Phys. 2003, 118, 7174. [5] R. Conte, A. Aspuru-Guzik, and M. Ceotto, J. Phys. Chem. Lett. 2013, 4, 3407. [6] M. Ceotto, G. Di Liberto, and R. Conte, Phys. Rev. Lett. 2017, 119, 010401. [7] G. Di Liberto, R. Conte, and M. Ceotto, J. Chem. Phys. 2018, 148, 014307. [8] G. Di Liberto, R. Conte, and M. Ceotto, J. Chem. Phys. 2018, 148, 104302. [9] F. Gabas, G. Di Liberto, R. Conte, and M. Ceotto In preparation

Approximate computing design exploration through data lifetime metrics

When designing an approximate computing system, the selection of the resources to modify is key. It is important that the error introduced in the system remains reasonable, but the size of the design exploration space can make this extremely difficult. In this paper, we propose to exploit a new metric for this selection: data lifetime. The concept comes from the field of reliability, where it can guide selective hardening: the more often a resource handles "live" data, the more critical it be-comes, the more important it will be to protect it. In this paper, we propose to use this same metric in a new way: identify the less critical resources as approximation targets in order to minimize the impact on the global system behavior and there-fore decrease the impact of approximation while increasing gains on other criteria

Seasonal Training-Load Quantification in Elite English Premier League Soccer Players

Purpose: To quantify the seasonal training load completed by professional soccer players of the English Premier League. Methods: Thirty players were sampled (using GPS, heart rate, and rating of perceived exertion [RPE]) during the daily training sessions of the 2011–12 preseason and in-season period. Preseason data were analyzed across 6 × 1-wk microcycles. In-season data were analyzed across 6 × 6-wk mesocycle blocks and 3 × 1-wk microcycles at start, midpoint, and end-time points. Data were also analyzed with respect to number of days before a match. Results: Typical daily training load (ie, total distance, high-speed distance, percent maximal heart rate [%HRmax], RPE load) did not differ during each week of the preseason phase. However, daily total distance covered was 1304 (95% CI 434–2174) m greater in the 1st mesocycle than in the 6th. %HRmax values were also greater (3.3%, 1.3–5.4%) in the 3rd mesocycle than in the first. Furthermore, training load was lower on the day before match (MD-1) than 2 (MD-2) to 5 (MD-5) d before a match, although no difference was apparent between these latter time points. Conclusions: The authors provide the 1st report of seasonal training load in elite soccer players and observed that periodization of training load was typically confined to MD-1 (regardless of mesocycle), whereas no differences were apparent during MD-2 to MD-5. Future studies should evaluate whether this loading and periodization are facilitative of optimal training adaptations and match-day performance

Passive drag in young swimmers: Effects of body composition, morphology and gliding position

The passive drag (Dp) during swimming is affected by the swimmer’s morphology, body density and body position. We evaluated the relative contribution of morphology, body composition, and body position adjustments in the prediction of a swimmer’s Dp. This observational study examined a sample of 60 competitive swimmers (31 male and 29 female) with a mean (±SD) age of 15.4 ± 3.1 years. The swimmer’s Dp was measured using an electro-mechanical towing device and the body composition was assessed using a bioelectrical impedance analyser. Body lengths and circumferences were measured in both the standing position and the simulated streamlined position. Partial correlation analysis with age as a control variable showed that Dp was largely correlated (p < 0.05) with body mass, biacromial-and bi-iliac-breadth, streamline chest circumference and breadth. Body mass, Body Mass Index, chest circumference and streamline chest circumference showed a significant and moderate to strong effect (η2 > 0.55) on Dp. Body mass was the best predictor of Dp explaining 69% of the variability. These results indicate that swimmers with lower Dp values were: (i) slimmer, with lower fat and fat-free mass; (ii) thinner, with lower shoulder breadth, chest circumference, and streamline trunk diameters (iii), shorter, with lower streamline height. These findings can be used for talent identification in swimming, with particular reference to the gliding performance

Arm-stroke descriptor variability during 200-M front crawl swimming

The present study aimed to explore the variability of the arm-stroke temporal descriptors between and within laps during middle-distance swimming event using IMMUs. Eight male swimmers performed a 200-m maximum front-crawl in which the inter-lap and intra-lap variability of velocity, stroke rate, stroke-phases duration and arm-coordination index were measured through five units of IMMU. An algorithm computes the 3D coordinates of the wrist by means the IMMU orientation and the kinematic chain of upper arm biomechanical model, and it recognizes the start events of the four arm-stroke phases. Velocity and stroke rate had a mean value of 1.47 ± 0.10 m·s−1 and 32.94 ± 4.84 cycles·min−1, respectively, and a significant decrease along the 200-m (p < 0.001; η2 = 0.80 and 0.47). The end of each lap showed significantly lower stroke rate compared to the start and the middle segment (p < 0.05; η2 = 0.55). No other significant inter-lap and intra-lap differences were detected. The two main findings are: (i) IMMUs technology can be an effective solution to continuously monitor the temporal descriptors during the swimming trial; (ii) swimmers are able to keep stable their temporal technique descriptors in a middle-distance event, despite the decrease of velocity and stroke rate

Evaluation of radiative transfer schemes for mesoscale model data assimilation: a case study

International audienceThe assimilation of Special Sensor Microwave Imager (SSM/I) data into the Mesoscale Model 5 (MM5) allows for improving the weather forecast. However the results suggested an update the Radiative Transfer Equation (RTE) within the three-dimensional variational (3DVAR) algorithm which is tailored for non rainy conditions only. To this purpose, a new RTE algorithm is tested, in order to account for radiometric response in rainy regions. The new brightness temperatures (TB) are estimated by using hydrometeor profiles from the MM5 mesoscale model, running with two different microphysical parameterizations. The goodness of the results is assessed by comparing the new TB with those of the original RTE algorithm in the 3DVAR code and the SSM/I observed data. The results confirm a better reliability of the new RTE compared to the old one

Study of aerobic granular sludge stability in a continuous-flow membrane bioreactor

A granular continuous-flow membrane bioreactor with a novel hydrodynamic configuration was developed to evaluate the stability of aerobic granular sludge (AGS). Under continuous-flow operation (Period I), AGS rapidly lost their structural integrity resulting in loose and fluffy microbial aggregates in which filamentous bacteria were dominant. The intermittent feeding (Period II) allowed obtaining the succession of feast and famine conditions that favored the increase in AGS stability. Although no further breakage occurred, the formation of new granules was very limited, owing to the absence of the hydraulic selection pressure. These results noted the necessity to ensure, on the one hand the succession of feast/famine conditions, and on the other, the hydraulic selection pressure that allows flocculent sludge washout. This preliminary study shows that the proposed configuration could meet the first aspect; in contrast, biomass selection needs to be improved

The effect of acute caffeine ingestion on physical performance in elite European competitive soccer match-play

The present study examined the effect of acute caffeine ingestion (150 mg) on the physical performance of elite European soccer players during official competitive match-play. The current investigation was a parallel-group design that collated data from a cohort of 19 male outfield players from an elite European soccer team (mean ± SD, age 26 ± 4 years; weight 80.5 ± 8.1 kg; height 1.83 ± 0.07 m; body-fat 10.8 ± 0.7%). Players were classified and matched by position and grouped accordingly: centre defender (CD) n = 5, wide defender (WD) n = 3, centre midfield (CM) n = 7, wide forward (WF) n = 2, and centre forward (CF) n = 2. For all performance variables, the mean values were compared in caffeine consumers vs. non consumers using independent-sample t-tests, with significance set at p < .05. Cohen’s d was used to quantify the effect size, and was interpreted as trivial (<0.2), small (0.2-0.5), medium (0.5-0.8), and large (>0.8). For all examined variables, there were trivial or small non-significant (p > .05) trivial or small differences between caffeine consumers and non-consumers. The findings of the present research did not confirm the study hypothesis, once running and accelerometry-based variables did not improve with the caffeine ingestion of 150 mg. Therefore, the caffeine supplement used in this study is not suggested for improving performance in the variables analysed

Daily Distribution of Macronutrient Intakes of Professional Soccer Players From the English Premier League.

The daily distribution of macronutrient intake can modulate aspects of training adaptations, performance and recovery. We therefore assessed the daily distribution of macronutrient intake (as assessed using food diaries supported by the remote food photographic method and 24 h recalls) of professional soccer players (n=6) of the English Premier League during a 7-day period consisting of two match days and five training days. On match days, average carbohydrate (CHO) content of the pre-match (0.05) though such intakes were lower than contemporary guidelines considered optimal for pre-match CHO intake and post-match recovery. On training days, we observed a skewed and hierarchical approach (Plunch (0.6 g.kg(-1))>breakfast (0.3 g.kg(-1))>evening snacks (0.1 g.kg(-1)). We conclude players may benefit from consuming greater amounts of CHO in both the pre-match and post-match meals so as to increase CHO availability and maximize rates of muscle glycogen re-synthesis, respectively. Furthermore, attention should also be given to ensuring even daily distribution of protein intake so as to potentially promote components of training adaptation