Search results for "confinement"
showing 10 items of 213 documents
Confinement-deconfinement transition due to spontaneous symmetry breaking in quantum Hall bilayers
2015
Band-inverted electron-hole bilayers support quantum spin Hall insulator and exciton condensate phases. We investigate such a bilayer in an external magnetic field. We show that the interlayer correlations lead to formation of a helical quantum Hall exciton condensate state. In contrast to the chiral edge states of the quantum Hall exciton condensate in electron-electron bilayers, existence of the counterpropagating edge modes results in formation of a ground state spin-texture not supporting gapless single-particle excitations. This feature has deep consequences for the low energy behavior of the system. Namely, the charged edge excitations in a sufficiently narrow Hall bar are confined, i…
Compressive behavior of short high-strength concrete columns
2010
Abstract The focus of the present paper is the compressive response of short high strength reinforced concrete members. Members have square transverse cross-sections and they are reinforced with longitudinal steel bars and transverse stirrups. A preliminary analysis to check the stability condition of longitudinal bars was made to verify that buckling occurs after yielding in compression. Prescriptions on required diameter and spacing of stirrups are given. In the following, a model is presented which allows us to evaluate the confinement pressures exercised by transverse steel and by longitudinal bars during the loading process taking into account the interaction of the stirrups with the i…
Influence of steel reinforcements on the behavior of compressed high strength R.C. circular columns
2012
Abstract In the present paper the focus is on the compressive response of short high strength reinforced concrete members having circular transverse cross-sections and reinforced with longitudinal steel bars and transverse spirals or hoops. An analytical model is proposed which allows one to estimate the confinement pressures exerted by transverse steel and by longitudinal bars during the loading process, taking into account the interaction of the hoops or spirals with the inner core both in the plane of the transverse steel and in the space between two successive hoops. Yielding of steel spirals or hoops and longitudinal bars including buckling phenomena and damage to the concrete core are…
Efficiency investigation of a negative hydrogen ion beam production with the use of the gasdynamic ECR plasma source
2020
Abstract Negative hydrogen ion sources are of great demand in modern physics as injectors into accelerators and drivers for neutral beam injectors for fusion devices. It has been shown earlier that the use of the gasdynamic ECR discharge provides the opportunity to extract up to 80 mA/cm2 of negative ion current density. We studied experimentally the volumetric negative hydrogen ion production and vacuum ultraviolet emission in a gasdynamic ECR discharge. The high-density plasma was sustained by the pulsed 37 GHz / 100 kW gyrotron radiation in a magnetic configuration consisting of two consecutive simple mirror traps. The future prospects of the volumetric H− source based on the gasdynamic …
Printing Biology for Advanced Synthetic Biosystem
2019
Printing technologies represent a powerful tool for the direct micro- and nano- fabrication of biomolecular structures at the interface between life and materials sciences (Arrabito et al., 2012). Their continuous development over the last years has permitted the onset of man-made biosystems with customizable dimensions (from the micron-scale down to the nanometer scale), composition (organic molecules, DNA, proteins, phospholipids), and relevant functions (molecular interactions, drug screening, cellular biointerfaces, cell-like compartments). In this work, we show the possibility to leverage the fabrication of a wide class of solid-supported or liquid-liquid based synthetic compartments b…
Breakdown of separability due to confinement
2017
A simple system of two particles in a bidimensional configurational space S is studied. The possibility of breaking in S the time-independent Schrodinger equation of the system into two separated one-dimensional one-body Schrodinger equations is assumed. In this paper, we focus on how the latter property is countered by imposing such boundary conditions as confinement to a limited region of S and/or restrictions on the joint coordinate probability density stemming from the sign-invariance condition of the relative coordinate (an impenetrability condition). Our investigation demonstrates the reducibility of the problem under scrutiny into that of a single particle living in a limited domain …
Light harvesting with Ge quantum dots embedded in SiO2 and Si3N4
2014
Cataloged from PDF version of article. Germanium quantum dots (QDs) embedded in SiO2 or in Si3N4 have been studied for light harvesting purposes. SiGeO or SiGeN thin films, produced by plasma enhanced chemical vapor deposition, have been annealed up to 850 degrees C to induce Ge QD precipitation in Si based matrices. By varying the Ge content, the QD diameter can be tuned in the 3-9 nm range in the SiO2 matrix, or in the 1-2 nm range in the Si3N4 matrix, as measured by transmission electron microscopy. Thus, Si3N4 matrix hosts Ge QDs at higher density and more closely spaced than SiO2 matrix. Raman spectroscopy revealed a higher threshold for amorphous-to-crystalline transition for Ge QDs e…
Why does vacuum drive to the loading of halloysite nanotubes? The key role of water confinement.
2019
The filling of halloysite nanotubes with active compounds solubilized in aqueous solvent was investigated theoretically and experimentally. Based on Knudsen thermogravimetric data, we demonstrated the water confinement within the cavity of halloysite. This process is crucial to properly describe the driving mechanism of halloysite loading. In addition, Knudsen thermogravimetric experiments were conducted on kaolinite nanoplates as well as on halloysite nanotubes modified with an anionic surfactant (sodium dodecanoate) in order to explore the influence of both the nanoparticle morphology and the hydrophobic/hydrophilic character of the lumen on the confinement phenomenon. The analysis of the…
Major results from the first plasma campaign of the Wendelstein 7-X stellarator
2017
After completing the main construction phase of Wendelstein 7-X (W7-X) and successfully commissioning the device, first plasma operation started at the end of 2015. Integral commissioning of plasma start-up and operation using electron cyclotron resonance heating (ECRH) and an extensive set of plasma diagnostics have been completed, allowing initial physics studies during the first operational campaign. Both in helium and hydrogen, plasma breakdown was easily achieved. Gaining experience with plasma vessel conditioning, discharge lengths could be extended gradually. Eventually, discharges lasted up to 6 s, reaching an injected energy of 4 MJ, which is twice the limit originally agreed for t…
The assessment of lifestyle changes during the COVID-19 pandemic using a multidimensional scale
2020
Introduction Healthy lifestyles are relevant to several diseases and to maintain individuals’ mental health. Exposure to epidemics and confinement have been consistently associated with psychological consequences, but changes on lifestyle behaviours remain under-researched. Materials and Methods An online survey was conducted among the general population living in Spain during the COVID-19 home-isolation. In addition to demographic and clinical data, participants self-reported changes in seven lifestyle domains. The Short Multidimensional Inventory Lifestyle Evaluation was developed specifically to evaluate changes during the confinement (SMILE-C). Results A total of 1254 individuals comple…