Observation of an exotic narrow doubly charmed tetraquark

Conventional hadronic matter consists of baryons and mesons made of three quarks and quark-antiquark pairs, respectively. The observation of a new type of hadronic state, a doubly charmed tetraquark containing two charm quarks, an anti-u and an anti-d quark, is reported using data collected by the LHCb experiment at the Large Hadron Collider. This exotic state with a mass of about 3875 MeV/c 2 manifests itself as a narrow peak in the mass spectrum of D0D0π + mesons just below the D∗+D0 mass threshold. The near-threshold mass together with a strikingly narrow width reveals the resonance nature of the state.

Crosstalk in Electrical Connectors

Crosstalk electromagnetic interference occurs in on-board electrical wire bundles of aircraft electrical systems under the effect of external electromagnetic fields. Efficient reduction of crosstalk and elimination of their propagation paths in wire bundles can be achieved by shielding the conductors in the bundles and the bundles as a whole without breaks and discontinuities between the shields and housings of electrical connectors. The shielding of conductors in bundles does not eliminate the crosstalk completely, which can propagate through the contacts of electrical connectors. For estimating the influence of electrical connectors on the levels of crosstalk in electrical system circuits, their experimental studies should be carried out. In the course of these experimental studies, the interference voltage induced at the receptor contacts when voltage is applied to the source contacts in the specified frequency band is measured. The results from experimental studies of crosstalk for various types of electrical connectors in a specified frequency band make it possible to evaluate the resonance nature and levels of crosstalk interference levels depending on the relative position of the contacts and frequency.

Second optical harmonic generation by a layered plasmon nanoparticle

The features of second harmonic generation by a spherical nanoparticle with a plasmon shell are theoretically studied. In the framework of the quasistatic perturbation theory, expressions for the oscillating at a doubled frequency induced dipole and quadrupole moments of a particle were obtained. The second harmonic radiation power was calculated, which showed the resonance nature of the dependence of power on the exciting wavelength. Moreover, the positions of the radiation power resonances significantly depend on the dielectric permittivity of the particle core and its size.

Mathematics of a Mantra

This paper aims to examine the enunciation (uccāraṇa-kāla) time intervals for śrīvidyā pañcadaśī, a fifteen seed-syllable mantra (bīja-mantra) related to the homonymous śākta school Śrīvidyā or Traipuradarśaṇa. Following the indications provided in the Yoginīhṛdaya, with Dīpikā commentary by Amṛtānanda, and the Varivasyāraharasya by Bhāskararāya with Prakāśa auto-commentary, the research finds that these durations are not arbitrary at all but rather the result of a rigorous assessment. Moreover, the duration values suggest a specific conceptual goal that the mathematical rigor manifested by the authors seeks to fulfil: the progressive diminution of time intervals in order to achieve an atemporal dimension. The choice of the units of measurement itself is designed to meet this metaphysical and ritual need. By counting the intervals (both relative and overall) of mantra recitation, it is also possible to confirm the resonance nature of the sounds following nasalisations, sounds conceived by the authors as entirely independent of the reciter’s phonatory activity.

Detecting 1-D and 2-D ground resonances with a single-station approach

SUMMARY The vibration modes of the ground have been described both in the 1-D and 2-D case. The 1-D resonance is found on geological structures whose aspect ratio is low, that is on layers with a lateral width much larger than their thickness. A typical example is that of a horizontal soft sediment layer overlying hard bedrock. In this case, the 1-D resonance frequency, traditionally detected by means of the microtremor H/V (horizontal to vertical spectral ratio) technique, depends on the bedrock depth and on the shear wave velocity of the resonating cover layer. The H/V technique is thus used both to map the resonance frequencies in seismic microzonation studies and for stratigraphic imaging. When 2-D resonance occurs, generally on deep and narrow valleys, the whole sedimentary infill vibrates at the same frequency and stratigraphic imaging can no longer be performed by means of the 1-D resonance equation. Understanding the 1-D or 2-D resonance nature of a site is therefore mandatory to avoid wrong stratigraphic and dynamic interpretations, which is in turn extremely relevant for seismic site response assessment. In this paper, we suggest a procedure to address this issue using single-station approaches, which are much more common compared to the multistation synchronized approach presented by research teams in earlier descriptions of the 2-D resonances. We apply the procedure to the Bolzano sedimentary basin in Northern Italy, which lies at the junction of three valleys, for which we observed respectively 1-D-only, 1-D and 2-D, and 2-D-only resonances. We conclude by proposing a workflow scheme to conduct experimental measurements and data analysis in order to assess the 1-D or 2-D resonance nature of a site using a single-station approach.

Computational studies of resonance wave pumping in compliant tubes

The valveless impedance pump is a simple design that allows the producion or amplification of a flow without the requirement for valves or impellers. It is based on fluid-filled flexible tubing, connected to tubing of different impedances. Pumping is achieved by a periodic excitation at an off-centre position relative to the tube ends. This paper presents a comprehensive study of the fluid and structural dynamics in an impedance pump model using numerical simulations. An axisymmetric finite-element model of both the fluid and solid domains is used with direct coupling at the interface. By examining a wide range of parameters, the pump's resonance nature is described and the concept of resonance wave pumping is discussed. The main driving mechanism of the flow in the tube is the reflection of waves at the tube boundary and the wave dynamics in the passive tube. This concept is supported by three different analyses: (i) time-dependent pressure and flow wave dynamics along the tube, (ii) calculations of pressure–flow loop areas along the passive tube for a description of energy conversion, and (iii) an integral description of total work done by the pump on the fluid. It is shown that at some frequencies, the energy given to the system by the excitation is converted by the elastic tube to kinetic energy at the tube outlet, resulting in an efficient pumping mechanism and thus significantly higher flow rate. It is also shown that pumping can be achieved with any impedance mismatch at one boundary and that the outlet configuration does not necessarily need to be a tube.