Multiple interactions and AGK rules in pQCD

We review some aspects of multiple interactions in High Energy QCD; we discuss in particular AGK rules and present some results concerning multiple interactions in the context of jet production.Comment: Talk given by MS at 12th International Conference on Elastic and Diffractive Scattering: Forward Physics and QCD, Hamburg, DESY, Germany, 21-25 May 2007. 7pp. Minor change

Lower Extremity Muscle Forces During Loaded Vertical Jumps And The Potential Training Implications

Hexagonal barbell (HB) loaded jumps are often used in training to increase lower extremity power. The effect of external load on lower extremity kinematics and kinetics during jumping has been described, but how individual muscles accommodate to these loads has not. Given the importance of coordinated muscular effort in achieving maximal power output, an understanding of how the lower extremity musculature individually performs during loaded jumps would be advantageous. The purpose of this study is to describe the effect of load on individual muscle forces during the concentric phase of loaded HB jumps. 10 male collegiate athletes (20.4 + 2.4 y; 108.8 + 14.0 kg) performed 5 maximal HB jumps at 0%, 20%, 40% and 60% of their HB deadlift 1-repetition maximum (216.6 + 10.9 kg). Filtered Ground reaction forces (300 Hz) and 3D lower extremity marker trajectories (13 Hz) were input into a 23 DOF musculoskeletal model and muscle forces were estimated with static optimization. Peak muscle force (xBW) was calculated for the gluteus maximum (GMAX), biceps femoris – long head (BFL), rectus femoris (RF), vastus intermedius (VAST), gastrocnemius (GAS), and soleus (SOL). Analysis of variance and LSD post hoc comparisons were used for analysis (p \u3c 0.05). A significant increase in peak muscle force across loads existed for VAST (0%: 7.89 + 0.24 xBW; 20%: 8.22 + 0.28 xBW; 40%: 8.47 + 0.30 xBW; 60%: 8.64 + 0.33 xBW), with significant differences between 0% and 40%, 0% and 60%, and 20% and 60% (all p ≤ 0.015). Significant decreases were noted for RF (0%: 2.50 + 0.13 xBW; 20%: 2.32 + 0.17 xBW; 40%: 2.18 + 0.11 xBW; 60%: 1.98 + 0.20 xBW), with significant differences between 0% and all other conditions, and between 20% and 60% (all p ≤ 0.037). Significant increases were found in GAS across loads (0%: 2.14 + 0.10 xBW; 20%: 2.47 + 0.14 xBW; 40%: 2.72 + 0.12 xBW; 60%: 2.85 + 0.14 xBW), with significance between each load (all p ≤ 0.038). There was no significant difference in GMAX (p = 0.325), BFL (p = 0.369), or SOL (p = 0.122) across loads. Increases in demand were not met with equally distributed increases in peak force output across the lower extremity musculature. The varied effect of load on force output from individual muscles is important information to understand when using loaded jumps as part of training for athletic performance.https://ir.library.illinoisstate.edu/urs2021knr/1002/thumbnail.jp

Bistable defect structures in blue phase devices

Blue phases (BPs) are liquid crystals made up by networks of defects, or disclination lines. While existing phase diagrams show a striking variety of competing metastable topologies for these networks, very little is known as to how to kinetically reach a target structure, or how to switch from one to the other, which is of paramount importance for devices. We theoretically identify two confined blue phase I systems in which by applying an appropriate series of electric field it is possible to select one of two bistable defect patterns. Our results may be used to realise new generation and fast switching energy-saving bistable devices in ultrathin surface treated BPI wafers.Comment: 4 pages, 3 figures. Accepted for publication in Phys. Rev. Let

Inclusive 1-jet Production Cross Section at Small x in QCD: Multiple Interactions

We study corrections due to two Pomeron exchanges to the inclusive 1-jet production cross section in the Regge limit of perturbative QCD for a finite number of colors. By considering deep inelastic scattering on a weakly bound two-nucleon system, we carefully follow the logic of the AGK cutting rules and show, for the single inclusive cross section, that, due to the reggeization of the gluon, modifications of the AGK cutting rules appear. As our main result, we investigate and calculate the jet production vertex in the presence of a two-Pomeron cut correction. Compared to previous studies, we find a novel structure of the jet vertex which has not been considered before. We discuss a few implications of this new piece.Comment: 42 pages, 22 figures, few references and comments added, to appear on JHE

Sulfur Source, Rate, and Methods of Application for Polyethylene-mulched Tomato

Tomato (Lycopersicon esculentum L.) was grown with polyethylene mulch and drip irrigation on a Millhopper fine sandy soil testing very high in P and low in organic matter during two seasons to evaluate the effect of S source, rate, and application methods on plant growth and yield of fruit.  Sulfur rate of 34 and 68 kg S.ha-1 were applied with  preplant (broadcast in the bed), drip (10 weekly drip application), and  by split applications (50% preplant and 50% drip).  In split applications, S sources evaluated were ammonium sulfate and ammonium thiosulfate.  Plant height was increased with S application from 0 to 68 kg S.ha-1 in both studies. However, response on plant dry weight only occurred in spring 1999. Total marketable yield was 17.9 tons.ha-1 with 0 kg S.ha-1 and was increased linearly to 48.1 tons.ha-1 with application of 68 kg S.ha-1 in Spring 1999, but no response to S was obtained in the Spring 1998 study. Measured variables were not affected by S source and methods of application.  Increasing S application from 0  to 68 kg S.ha-1 reduced leaf and plant tissue P concentration 14 and 12% at mid season, 26 and 25% at  late season sampling times, respectively.  S application of 68 kg S.ha-1 reduced soil pH approximately 0.3 unit at the end of the season in both studies.   Key  words:  drip irrigation, sulfur,  fertigation, Lycopersicon esculentu

Human Head-Neck Response to Impact Acceleration: Comparison of Oblique to Combined Frontal and Lateral Response

This paper relates human oblique head-neck kinematics to human frontal and lateral head-neck kinematics for three subjects of varying anthropometry. Head-neck kinematic response to indirect impact acceleration for an oblique test is compared to the superposition of the head/neck behavior of appropriate frontal and lateral tests for the same subject. The results have important implications in terms of the complexity required in the design and validation of omni-directional biofidelic crash test manikins and mathematical models of human head-neck response

A COMPARISON BETWEEN 3D RECONSTRUCTION USING NERF NEURAL NETWORKS AND MVS ALGORITHMS ON CULTURAL HERITAGE IMAGES

In this research, an innovative comparison between 3D reconstructions obtained by means of Artificial Intelligence, in particular NeRF Neural Networks, and by Structure-from-Motion (SfM) and Multi-View-Stereo (MVS) open-source algorithms is proposed. The 3D reconstruction comparison is performed on two test cases, one of cultural interest, one useful only for technical discussion. It is known that the approaches are traditionally used with different objectives and in different contexts but they can however also be used with similar purpose, i.e., 3D reconstruction. In particular, we were interested in evaluating how NeRF reconstructions are accurate from a metric point of view and how the models obtained from the application of NeRF differ from the model obtained from the classical photogrammetry. By analyzing the results in the considered test cases, we show how NeRF networks, although computationally demanding, can be an interesting alternative or complementary methodology, especially in cases where classical photogrammetric techniques do not allow satisfactory results to be achieved. It is therefore suggested to expand efforts in this direction by exploiting, for example, the numerous improvement proposals of the original NeRF network

Direct numerical simulation of supersonic turbulent flows over rough surfaces

We perform direct numerical simulation of supersonic turbulent channel flow over cubical roughness elements, spanning bulk Mach numbers -, both in the transitional and fully rough regime. We propose a novel definition of roughness Reynolds number which is able to account for the viscosity variations at the roughness crest and should be used to compare rough-wall flows across different Mach numbers. As in the incompressible flow regime, the mean velocity profile shows a downward shift with respect to the baseline smooth wall cases, however, the magnitude of this velocity deficit is largely affected by the Mach number. Compressibility transformations are able to account for this effect, and data show a very good agreement with the incompressible fully rough asymptote, when the relevant roughness Reynolds number is used. Velocity statistics present outer layer similarity with the equivalent smooth wall cases, however, this does not hold for the thermal field, which is substantially affected by the roughness, even in the channel core. We show that this is a direct consequence of the quadratic temperature-velocity relation which is also valid for rough walls. Analysis of the heat transfer shows that the relative drag increase is always larger than the relative heat transfer enhancement, however, increasing the Mach number brings data closer to the Reynolds analogy line due to the rising relevance of the aerodynamic heating

Direct numerical simulation of supersonic and hypersonic turbulent boundary layers at moderate-high Reynolds numbers and isothermal wall condition

We study the structure of high-speed zero-pressure-gradient turbulent boundary layers up to friction Reynolds number Reτ ≈ 2000 using direct numerical simulation of the Navier-Stokes equations. Both supersonic and hypersonic conditions with nominal free-stream Mach numbers M∞ = 2, M∞ = 5.86 and heat transfer at the wall are considered. The present simulations extend the database currently available for wall-bounded flows, enabling us to explore high-Reynolds-number effects even in the hypersonic regime. We first analyse the instantaneous fields to characterize the structure of both velocity and temperature fluctuations. In all cases elongated strips of uniform velocity and temperature (superstructures) are observed in the outer portion of the boundary layer, characterized by a clear association between low-/high-speed momentum and high/low temperature streaks. The results highlight important deviations from the typical organization observed in the inner region of adiabatic boundary layers, revealing that the near-wall temperature streaks disappear in strongly non-adiabatic flow cases. We also focus on the structural properties of regions of uniform streamwise momentum (De Silva, Hutchins & Marusic, J. Fluid Mech., vol. 786, 2016, pp. 309.331) observed in turbulent boundary layers, confirming the presence of such zones in the high-speed regime at high Reynolds number and revealing the existence of similar regions for the temperature field. The accuracy of different compressibility transformations and temperature-velocity relations is assessed extending their range of validation to moderate/high Reynolds numbers. Spanwise spectral densities of the velocity and temperature fluctuations at various wall distances have been calculated revealing the energy content and the size of the turbulent eddies across the boundary layer. Finally, we propose a revised scaling for the characteristic length scales, that is based on the local mean shear computed according to the recent theory by Griffin, Fu & Moin [Proc. Natl Acad. Sci. USA, vol. 118 (34)]