Universality of quantum time dilation

Time dilation is a difference in measured time between two clocks that either move with different velocities or experience different gravitational potentials. Both of these effects stem from the theory of relativity and are usually associated with classically defined trajectories, characterized by position, momentum, and acceleration. However, when spatial degrees of freedom are treated in a quantum way and a clock is allowed to be in a coherent superposition of either two momenta or two heights, additional quantum corrections to classical time dilation appear, called kinematic and gravitational quantum time dilations, respectively. We show that similarly to its classical counterpart, kinematic quantum time dilation is universal for any clock mechanism, while gravitational quantum time dilation is not. We also show that although both of these effects reduce to incoherent averaging of different classical time dilation contributions, there exists an additional quantum time dilation effect that has no classical analog and can be extracted from higher-order corrections to the system's Hamiltonian

Quantum time dilation in a gravitational field

According to relativity, the reading of an ideal clock is interpreted as the elapsed proper time along its classical trajectory through spacetime. In contrast, quantum theory allows the association of many simultaneous trajectories with a single quantum clock, each weighted appropriately. Here, we investigate how the superposition principle affects the gravitational time dilation observed by a simple clock – a decaying two-level atom. Placing such an atom in a superposition of positions enables us to analyze a quantum contribution to a classical time dilation manifest in spontaneous emission. In particular, we show that the emission rate of an atom prepared in a coherent superposition of separated wave packets in a gravitational field is different from the emission rate of an atom in a classical mixture of these packets, which gives rise to a quantum gravitational time dilation effect. We demonstrate that this nonclassical effect also manifests in a fractional frequency shift of the internal energy of the atom that is within the resolution of current atomic clocks. In addition, we show the effect of spatial coherence on the atom's emission spectrum

Contact force-sensing versus standard catheters in non-fluoroscopic radiofrequency catheter ablation of idiopathic outflow tract ventricular arrhythmias

Background: Adequate contact between the catheter tip and tissue is important for optimal lesion formation and, in some procedures, it has been associated with improved effectiveness and safety. We evaluated the potential benefits of contact force-sensing (CFS) catheters during non-fluoroscopic radiofrequency catheter ablation (NF-RFCA) of idiopathic ventricular arrhythmias (VAs) originating from outflow tracts (OTs). Methods: A group of 102 patients who underwent NF-RFCA (CARTO, Biosense Webster Inc., Irvine, CA, USA) of VAs from OTs between 2014 to 2018 was retrospectively analyzed. Results: We included 52 (50.9%) patients in whom NF-RFCA was performed using CFS catheters and 50 (49.1%) who were ablated using standard catheters. Arrhythmias were localized in the right and left OT in 70 (68.6%) and 32 (31.4%) patients, respectively. The RFCA acute success rate was 96.1% (n = 98) and long-term success during a minimum 12-month follow-up (mean 51.3 ± 21.6 months) was 85.3% (n = 87), with no difference between CFS and standard catheters. There was no difference in complications rate between CFS (n = 1) and standard catheter (n = 2) ablations. Conclusions: There is no additional advantage of CFS catheters use over standard catheters during NF-RFCA of OT-VAs in terms of procedural effectiveness and safety

Survey of period variations of superhumps in SU UMa-type dwarf novae. VI. The sixth year (2013-2014)

© The Author 2014. Published by Oxford University Press on behalf of the Astronomical Society of Japan. All rights reserved. Continuing the project undertaken by Kato et al. (2009), we collected times of superhump maxima for 56 SU UMa-type dwarf novae mainly observed during the 2013-2014 season and characterized these objects. We detected negative superhumps in VW Hyi and indicated that the low number of normal outbursts in some supercycles can be interpreted as a result of disk tilt. This finding, combined with the Kepler observation of V1504 Cyg and V344 Lyr, suggests that disk tilt is responsible for modulating the outburst pattern in SU UMa-type dwarf novae. We also studied the deeply eclipsing WZ Sge-type dwarf nova MASTER OT J005740.99+443101.5 and found evidence of a sharp eclipse during the phase of early superhumps. The profile can be reproduced by a combination of the eclipse of the axisymmetric disk and the uneclipsed light source of early superhumps. This finding shows the lack of evidence for a greatly enhanced hot spot during the early stage of WZ Sge-type outburst. We detected growing (stage A) superhumps in MN Dra and give a suggestion that some of SU UMa-type dwarf novae situated near the critical condition of tidal instability may show long-lasting stage A superhumps. The large negative period derivatives reported in such systems can be understood as a result of the combination of stage A and B superhumps. Two WZ Sge-type dwarf novae, AL Com and ASASSN-13ck, showed a long-lasting (plateau-type) rebrightening. In the early phase of their rebrightenings, both objects showed a precursor-like outburst, suggesting that the long-lasting rebrightening is triggered by a precursor outburst

Wpływ bariery cieplnej na rozkład temperatur i naprężeń w silniku ZS

The paper presents results of FEM investigations into the effect of thermal barrier coating (TBC) on stress and temperature distributions in the components of naturally aspirated diesel engine. Calculations were performed by means of Abaqus ver. 6.8-3 computer program. The considered coating was plasma sprayed double-layered TBC consisting 0.15 mm thick NiCrAl bond layer and 0.3 mm ZrO2-8%Y2O3 top coat. TBC reduced the maximum temperature of the cylinder head by 15K compared to uncoated metal head, increased temperature of the outlet channel by 10 K and reduced maximum temperatures in inlet and outlet valves by 2 and 1.2 K, respectively. Although maximum temperature of the pis ton head remained the same after deposition of the coating but the range of temperatures at the piston head was reduced by 23.8%. Application o f TBC considerably reduced stresses in acritical region of outlet valve- the interface of stellite hardfacing /valve. The highest thermal stresses in the TBC were in the bondcoat, which confirms the common localization of damages. Stress concentrations were also found in the metal part at the edges of TBC and at the edges of the recess machined in the piston head. The reduction of metal temperatures and thermal gradients in protected components should have some positive effect on the components' durability.W pracy przedstawiono rezultaty badań numerycznych wpływu powłoki typu bariery cieplnej (TBC) na rozkład temperatur i naprężeń w elementach wolnossącego silnika ZS. Obliczenia numeryczne zostały wykonane przy pomocy programu Abaqus wer. 6.8-3. Rozważano natryskaną plazmowo powlokę dwuwarstwową składającą się z warstwy podkładowej o gr. 0,15 mm i warstwy ceramicznej ZrO2-8%Y2O3 o grubości 0,3 mm. TBC obniżyła maksymalną temperaturę głowicy silnika o 15 K w porównaniu do głowicy nie pokrytej powłoką oraz obniżyła maksymalne temperatury zaworów wylotowego i dolotowego o 2 K i 1,2 K, odpowiednio. Wprawdzie maksymalna temperatura tłoka pozostała stała ale obniżył się o 23,8% zakres temperatur na powierzchni tłoka. Zastosowanie powłoki znacznie obniżyło wartość naprężeń w krytycznym miejscu zaworu wylotowego- granicy podłoża i warstwy napawanej stellitem Najwyższa wartość naprężeń TBC występowała w warstwie podkładowej co potwierdziło częstą lokalizację pęknięć. Znaleziono również koncentracje naprężeń na krawędzi TBC i krawędzi wybrania w denku tłoka. Obniżenie temperatur metalu i gradientów temperatur w pokrytych elementach powinno wydłużyć trwałość elementów

Post-critical deformations state of multi-section, multi-stringer thin walled structure, subjected to the torsion. Experimental research and non-linear numerical analysis

Rozważa się trzysegmentową, dziesięciopodłużnicową strukturę cienkościenną o ściankach płaskich, wykonaną z materiału o charakterystyce natychmiastowej przybliżanej modelem materiału idealnie sprężysto-plastycznego. Materiał konstrukcji (poliwęglan) wykazuje efekt dwójłomności wymuszonej w świetle spolaryzowanym. Konstrukcję poddaje się skręcaniu, wskutek czego w obszarze struktury pojawia się stan lokalnej deformacji zakrytycznej segmentów pokrycia, interpretowany w pierwszym przybliżeniu jako pole ciągnień. W wyniku nieliniowej analizy numerycznej, w trakcie której zachowywana jest zgodność ścieżek równowagi otrzymanych na drodze numerycznej oraz badań eksperymentalnych, wyznacza się pole naprężeń, uwzględniające stan giętny i błonowy ustroju.Paper presents results of experimental and numerical research of thin-walled structure reinforced by ten stringers and four frames, subjected to the torsion. The experimental structure was made of the polycarbonate, for which the tensile strength test was carried out and material constants determined. It also characterized by the high optical activity thanks to which it became possible to obtain qualitative information about optical effect distribution in circular polarization conditions. As the result of the torsional load, the post-critical deformations state comes out in all area of the model. Using non-linear numerical analyses, keeping the compliance of equilibrium paths, the stress field considering bending and membrane effects was obtained

Investigations of spheroidisation of tungsten and molybdenum powders in a plasma jet

W artykule przedstawiono wyniki badań sferoidyzacji proszków wolframu i molibdenu w strumieniu plazmy niskotemperaturowej. Określono wpływ zastosowanych parametrów sferoidyzacji na średnią średnicę cząstek proszków i jej rozkład statystyczny. Na tej podstawie dokonano wstępnej optymalizacji mocy plazmy (mocy elektrycznej dostarczonej do palnika plazmowego) oraz długości drogi lotu cząstek proszku. Wykazano, że zmiana mocy plazmy nie wpływa w zasadniczy sposób na wielkość cząstek wolframu, natomiast (w przypadku proszku molibdenu) jej zwiększenie powoduje poczatkowo wzrost, a nastepnie spadek średniej średnicy cząstek. Z kolei zwiększanie długości drogi lotu cząstek w obu przypadkach spowodowało ubytek drobnej frakcji proszku.Investigation results of tungsten and molybdenum powders which were modified in the plasma flame are presented in this paper. The influence of basic parameters applied during spheroidisation on a mean diameter of powders and its statistical distribution was estimated. Plasma power and a distance of powder particles flight were optimised. It was found that a change of plasma power did not influence on a diameter of particles. Moreover increase in the distance of powder particles flight caused the decrease in a fine fraction of powders