Application of the exact regularized point particle method (ERPP) to particle laden turbulent shear flows in the two-way coupling regime

The Exact Regularized Point Particle method (ERPP), which is a new inter-phase momentum coupling ap- proach, is extensively used for the first time to explore the response of homogeneous shear turbulence in presence of different particle populations. Particle suspensions with different Stokes number and/or mass loading are considered. Particles with Kolmogorov Stokes number of order one suppress turbulent kinetic energy when the mass loading is increased. In contrast, heavier particles leave this observable almost un- changed with respect to the reference uncoupled case. Turbulence modulation is found to be anisotropic, leaving the streamwise velocity fluctuations less affected by unitary Stokes number particles whilst it is increased by heavier particles. The analysis of the energy spectra shows that the turbulence modulation occurs throughout the entire range of resolved scales leading to non-trivial augmentation/depletion of the energy content among the different velocity components at different length-scales. In this regard, the ERPP approach is able to provide convergent statistics up to the smallest dissipative scales of the flow, giving the opportunity to trust the ensuing results. Indeed, a substantial modification of the turbu- lent fluctuations at the smallest-scales, i.e. at the level of the velocity gradients, is observed due to the particle backreaction. Small scale anisotropies are enhanced and fluctuations show a greater level of in- termittency as measured by the probability distribution function of the longitudinal velocity increments and by the corresponding flatness

Experimental verification of reciprocity relations in quantum thermoelectric transport

Symmetry relations are manifestations of fundamental principles and constitute cornerstones of modern physics. An example are the Onsager relations between coefficients connecting thermodynamic fluxes and forces, central to transport theory and experiments. Initially formulated for classical systems, these reciprocity relations are also fulfilled in quantum conductors. Surprisingly, novel relations have been predicted specifically for thermoelectric transport. However, whereas these thermoelectric reciprocity relations have to date not been verified, they have been predicted to be sensitive to inelastic scattering, always present at finite temperature. The question whether the relations exist in practice is important for thermoelectricity: whereas their existence may simplify the theory of complex thermoelectric materials, their absence has been shown to enable, in principle, higher thermoelectric energy conversion efficiency for a given material quality. Here we experimentally verify the thermoelectric reciprocity relations in a four-terminal mesoscopic device where each terminal can be electrically and thermally biased, individually. The linear response thermoelectric coefficients are found to be symmetric under simultaneous reversal of magnetic field and exchange of injection and emission contacts. Intriguingly, we also observe the breakdown of the reciprocity relations as a function of increasing thermal bias. Our measurements thus clearly establish the existence of the thermoelectric reciprocity relations, as well as the possibility to control their breakdown with the potential to enhance thermoelectric performanceComment: 7 pages, 5 figure

Turbulent mixing of a slightly supercritical Van der Waals fluid at Low-Mach number

Supercritical fluids near the critical point are characterized by liquid-like densities and gas-like transport properties. These features are purposely exploited in different contexts ranging from natural products extraction/fractionation to aerospace propulsion. Large part of studies concerns this last context, focusing on the dynamics of supercritical fluids at high Mach number where compressibility and thermodynamics strictly interact. Despite the widespread use also at low Mach number, the turbulent mixing properties of slightly supercritical fluids have still not investigated in detail in this regime. This topic is addressed here by dealing with Direct Numerical Simulations (DNS) of a coaxial jet of a slightly supercritical Van der Waals fluid. Since acoustic effects are irrelevant in the Low Mach number conditions found in many industrial applications, the numerical model is based on a suitable low-Mach number expansion of the governing equation. According to experimental observations, the weakly supercritical regime is characterized by the formation of finger-like structures-- the so-called ligaments --in the shear layers separating the two streams. The mechanism of ligament formation at vanishing Mach number is extracted from the simulations and a detailed statistical characterization is provided. Ligaments always form whenever a high density contrast occurs, independently of real or perfect gas behaviors. The difference between real and perfect gas conditions is found in the ligament small-scale structure. More intense density gradients and thinner interfaces characterize the near critical fluid in comparison with the smoother behavior of the perfect gas. A phenomenological interpretation is here provided on the basis of the real gas thermodynamics properties.Comment: Published on Physics of Fluid

An investigation of spray velocity resulting from high-velocity penetration of thin plates by disks

Analysis based on one-dimensional shock wave theory to study maximum velocity of spray emanating from rear surface of thin meteoroid bumpe

Root Zone Sensors for Irrigation Management in Intensive Agriculture

Crop irrigation uses more than 70% of the world’s water, and thus, improving irrigation efficiency is decisive to sustain the food demand from a fast-growing world population. This objective may be accomplished by cultivating more water-efficient crop species and/or through the application of efficient irrigation systems, which includes the implementation of a suitable method for precise scheduling. At the farm level, irrigation is generally scheduled based on the grower’s experience or on the determination of soil water balance (weather-based method). An alternative approach entails the measurement of soil water status. Expensive and sophisticated root zone sensors (RZS), such as neutron probes, are available for the use of soil and plant scientists, while cheap and practical devices are needed for irrigation management in commercial crops. The paper illustrates the main features of RZS’ (for both soil moisture and salinity) marketed for the irrigation industry and discusses how such sensors may be integrated in a wireless network for computer-controlled irrigation and used for innovative irrigation strategies, such as deficit or dual-water irrigation. The paper also consider the main results of recent or current research works conducted by the authors in Tuscany (Italy) on the irrigation management of container-grown ornamental plants, which is an important agricultural sector in Italy

Has the use of computers in radiation therapy improved the accuracy in radiation dose delivery?

Purpose: It is well recognized that computer technology has had a major impact on the practice of radiation oncology. This paper addresses the question as to how these computer advances have specifically impacted the accuracy of radiation dose delivery to the patient. Methods: A review was undertaken of all the key steps in the radiation treatment process ranging from machine calibration to patient treatment verification and irradiation. Using a semi-quantitative scale, each stage in the process was analysed from the point of view of gains in treatment accuracy. Results: Our critical review indicated that computerization related to digital medical imaging (ranging from target volume localization, to treatment planning, to image-guided treatment) has had the most significant impact on the accuracy of radiation treatment. Conversely, the premature adoption of intensity-modulated radiation therapy has actually degraded the accuracy of dose delivery compared to 3-D conformal radiation therapy. While computational power has improved dose calibration accuracy through Monte Carlo simulations of dosimeter response parameters, the overall impact in terms of percent improvement is relatively small compared to the improvements accrued from 3-D/4-D imaging. Conclusions: As a result of computer applications, we are better able to see and track the internal anatomy of the patient before, during and after treatment. This has yielded the most significant enhancement to the knowledge of “in vivo” dose distributions in the patient. Furthermore, a much richer set of 3-D/4-D co-registered dose-image data is thus becoming available for retrospective analysis of radiobiological and clinical responses

3D Visibility Representations of 1-planar Graphs

We prove that every 1-planar graph G has a z-parallel visibility representation, i.e., a 3D visibility representation in which the vertices are isothetic disjoint rectangles parallel to the xy-plane, and the edges are unobstructed z-parallel visibilities between pairs of rectangles. In addition, the constructed representation is such that there is a plane that intersects all the rectangles, and this intersection defines a bar 1-visibility representation of G.Comment: Appears in the Proceedings of the 25th International Symposium on Graph Drawing and Network Visualization (GD 2017

Restricted three-body problem in effective-field-theory models of gravity

One of the outstanding problems of classical celestial mechanics was the restricted 3-body prob- lem, in which a planetoid of small mass is subject to the Newtonian attraction of two celestial bodies of large mass, as it occurs, for example, in the sun-earth-moon system. On the other hand, over the last decades, a systematic investigation of quantum corrections to the Newtonian potential has been carried out in the literature on quantum gravity. The present paper studies the effect of these tiny quantum corrections on the evaluation of equilibrium points. It is shown that, despite the extreme smallness of the corrections, there exists no choice of sign of these corrections for which all qualitative features of the restricted 3-body problem in Newtonian theory remain unaffected. Moreover, first-order stability of equilibrium points is characterized by solving a pair of algebraic equations of fifth degree, where some coefficients depend on the Planck length. The coordinates of stable equilibrium points are slightly changed with respect to Newtonian theory, because the planetoid is no longer at equal distance from the two bodies of large mass. The effect is conceptually interesting but too small to be observed, at least for the restricted 3-body problems available in the solar system.Comment: 20 pages, latex, 8 figure

The Queue-Number of Posets of Bounded Width or Height

Heath and Pemmaraju conjectured that the queue-number of a poset is bounded by its width and if the poset is planar then also by its height. We show that there are planar posets whose queue-number is larger than their height, refuting the second conjecture. On the other hand, we show that any poset of width $2$ has queue-number at most $2$, thus confirming the first conjecture in the first non-trivial case. Moreover, we improve the previously best known bounds and show that planar posets of width $w$ have queue-number at most $3w-2$ while any planar poset with $0$ and $1$ has queue-number at most its width.Comment: 14 pages, 10 figures, Appears in the Proceedings of the 26th International Symposium on Graph Drawing and Network Visualization (GD 2018

OP0205 ULTRASOUND-DETECTED CALCIUM PYROPHOSPHATE CRYSTAL DEPOSITION: WHICH SITES SHOULD BE SCANNED?

Background:In recent years, ultrasonography (US) has emerged as an accurate and reliable tool for the diagnosis of calcium pyrophosphate (CPP) deposition disease (CPPD) in daily practice. Previous studies analyzed the diagnostic value of US findings in different tissues and joints. However, no studies have investigated the optimal US scanning protocol in the diagnosis of CPPD at patient level.Objectives:To assess the diagnostic value of the combinations of OMERACT-defined US findings of CPPD in the upper and lower limbs and to select the best minimal combination of anatomic structures to be scanned for diagnosing CPPD in inter-critical periods.Methods:Patients with a crystal-proven diagnosis of CPPD and age- and sex-matched disease-controls were prospectively enrolled in this cross-sectional, monocentric, case-control study. All subjects underwent a bilateral US examination of 9 hyaline cartilages (HC), 6 fibrocartilages (FC), 5 tendons, 1 joint recess and 1 ligament as follows: shoulder (glenoid FC, humeral HC and acromioclavicular FC), elbow (humeral HC and triceps tendon), wrist (triangular FC, scapho-lunate ligament, volar recess of the radio-lunate joint), hand (HC of the metacarpophalangeal joints from 2nd to 5th finger), hip (acetabular FC and femoral HC), knee (femoral condyles' HC, meniscal FC, patellar and quadriceps tendons), ankle (talar HC, Achilles tendon and plantar fascia). US assessment was carried-out by a rheumatologist blinded to clinical data. CPP deposits were identified as presence/absence, according to the OMERACT definitions [1].Results:Ninety-five patients were enrolled: 45 CPPD patients (age: 72±10.6 years, disease duration: 5.6±7.8 years, female/male ratio: 1.3) and 50 age- and sex-matched disease-controls (18 with rheumatoid arthritis, 13 with osteoarthritis, 10 with psoriatic arthritis and 9 with gout).The FC of the medial and lateral meniscus were the most frequently involved targets of CPP deposits in cases (81.8% and 77.3% of patients, respectively), followed by the triangular FC of the wrist (68.2%), the HC of the femoral condyles (54.5%), the scapho-lunate ligament (52.3%) and the acetabular FC (50.0%). In all these anatomical targets, US findings indicative of CPP deposits were detected in a significantly higher percentage of cases than controls (p<0.01).The US scanning protocols that showed the best balance between sensitivity and specificity, the most sensitive and the most specific were shown in Table 1.Table 1.Diagnostic performances of different US scanning protocolsAnatomical targetsSESPLH+LH-Knee meniscal FC and wrist triangular FC0.86(0.76-0.96)0.86(0.73-0.94)6.35(3.17-12.72)0.13(0.06-0.30)Knee meniscal FC, wrist triangular FC and hip acetabular FC0.93(0.82-0.99)0.82(0.69-0.91)5.19(2.85-9.42)0.08(0.03-0.24)Hip acetabular FC, knee femoral condyles' HC andwrist scapho-lunate ligament0.67(0.51-0.80)0.96(0.86-0.99)16.67(4.22-65.82)0.35(0.23-0.53)LH: likelihood ratio, SE: sensitivity, SP: specificity, US: ultrasonography.In all US scanning protocols, each anatomical target was assessed bilaterally.Figure 1 includes representative pictures showing CPP crystal deposits in different anatomical targets.A: Wrist, longitudinal scan of the triangular FC complex.B: Knee, longitudinal scan of the lateral meniscus.C: Hip, longitudinal scan of the acetabular labrum FC,D: Knee, longitudinal scan of the medial femoral condyle's HC.Arrows: CPP crystal deposits at FC, arrowhead: CPP crystal deposits at HC.Conclusion:Our results suggest that bilateral US assessment of knee, wrist and hip provided acceptable sensitivity and specificity for diagnosing CPPD.References:[1]Filippou G, et al. Identification of calcium pyrophosphate deposition disease (CPPD) by ultrasound: reliability of the OMERACT definitions in an extended set of joints-an international multiobserver study by the OMERACT Calcium Pyrophosphate Deposition Disease Ultrasound Subtask Force. Ann Rheum Dis. 2018;77:1194-9.Disclosure of Interests:Edoardo Cipolletta: None declared, Jacopo Di Battista: None declared, Walter Grassi Speakers bureau: Walter Grassi has received speaking fees from AbbVie, Celgene, Grünenthal, Pfizer and Union Chimique Belge Pharma., Emilio Filippucci Speakers bureau: Emilio Filippucci. has received speaking fees from AbbVie, Bristol-Myers Squibb, Janssen-Cilag, Novartis, Pfizer, Roche and Union Chimique Belge Pharma