Experimental Demonstration of Stationary Dark-State Polaritons Dressed by Dipole-Dipole Interaction

Dark-state polaritons (DSPs) based on the effect of electromagnetically induced transparency are bosonic quasiparticles, representing the superpositions of photons and atomic ground-state coherences. It has been proposed that stationary DSPs are governed by the equation of motion closely similar to the Schr\"{o}dinger equation and can be employed to achieve Bose-Einstein condensation (BEC) with transition temperature orders of magnitude higher than that of the atomic BEC. The stationary-DSP BEC is a three-dimensional system and has a far longer lifetime than the exciton-polariton BEC. In this work, we experimentally demonstrated the stationary DSP dressed by the Rydberg-state dipole-dipole interaction (DDI). The DDI-induced phase shift of the stationary DSP was systematically studied. Notably, the experimental data are consistent with the theoretical predictions. The phase shift can be viewed as a consequence of elastic collisions. In terms of thermalization to achieve BEC, the $\mu$m$^2$-size interaction cross-section of the DDI can produce a sufficient elastic collision rate for the stationary DSPs. This work makes a substantial advancement toward the realization of the stationary-DSP BEC

Effect of tempering on stretch-flangeability of 980 mpa grade dual-phase steel

In this study, the effect of tempering on the stretch-flangeability is investigated in 980 MPa grade dual-phase steel consisting of ferrite and martensite phases. During tempering at 300 ??C, the strength of ferrite increases due to the pinning of dislocations by carbon atoms released from martensite, while martensite is softened as a consequence of a reduction in its carbon super-saturation. This strength variation results in a considerable increase in yield strength of the steel, without loss of tensile strength. The hole expansion test shows that steel tempered for 20 min (T20 steel) exhibits a higher hole expansion ratio than that of steel without tempering (T0 steel). In T0 steel, severe plastic localization in ferrite causes easy pore formation at the ferrite-martensite interface and subsequent brittle crack propagation through the highly deformed ferrite area during hole expansion testing; this propagation is mainly attributed to the large difference in hardness between ferrite and martensite. When the difference in hardness is not so large (T20 steel), on the other hand, tempered martensite can be considerably deformed together with ferrite, thereby delaying pore formation and hindering crack propagation by crack blunting. Eventually, these different deformation and fracture behaviors contribute to the superior stretch-flangeability of T20 steel

Compensatory UTE/T2W Imaging of Inflammatory Vascular Wall in Hyperlipidemic Rabbits

<div><p>Objectives</p><p>To obtain compensatory ultra-short echo time (UTE) imaging and T2-weighted (T2W) imaging of Watanabe heritable hyperlipidemic (WHHL) rabbits following dextran-coated magnetic nanocluster (DMNC) injection for the effective <i>in vivo</i> detection of inflammatory vascular wall.</p><p>Methods</p><p>Magnetic nanoparticle was synthesized by thermal decomposition and encapsulated with dextran to prepare DMNC. The contrast enhancement efficiency of DMNC was investigated using UTE (repetition time [TR] = 5.58 and TE = 0.07 ms) and T2W (TR = 4000 and TE = 60 ms) imaging sequences. To confirm the internalization of DMNC into macrophages, DMNC-treated macrophages were visualized by cellular transmission electron microscope (TEM) and magnetic resonance (MR) imaging. WHHL rabbits expressing macrophage-rich plaques were subjected to UTE and T2W imaging before and after intravenous DMNC (120 μmol Fe/kg) treatment. <i>Ex vivo</i> MR imaging of plaques and immunostaining studies were also performed.</p><p>Results</p><p>Positive and negative contrast enhancement of DMNC solutions with increasing Fe concentrations were observed in UTE and T2W imaging, respectively. The relative signal intensities of the DMNC solution containing 2.9 mM Fe were calculated as 3.53 and 0.99 in UTE and T2W imaging, respectively. DMNC uptake into the macrophage cytoplasm was visualized by electron microscopy. Cellular MR imaging of DMNC-treated macrophages revealed relative signals of 3.00 in UTE imaging and 0.98 in T2W imaging. <i>In vivo</i> MR images revealed significant brightening and darkening of plaque areas in the WHHL rabbit 24 h after DMNC injection in UTE and T2W imaging, respectively. <i>Ex vivo</i> MR imaging results agreed with these <i>in vivo</i> MR imaging results. Histological analysis showed that DMNCs were localized to areas of inflammatory vascular wall.</p><p>Conclusions</p><p>Using compensatory UTE and T2W imaging in conjunction with DMNC is an effective approach for the noninvasive <i>in vivo</i> imaging of atherosclerotic plaque.</p></div

Intravascular MR imaging of WHHL rabbit after DMNC injection.

<p>Aortic arch (red) and thoracic aorta (green) at 0, 0.25, 2, and 25 h after DMNC injection (0 h: baseline without DMNC injection) were visualized by (a) UTE and (b) T2W imaging. The intravascular signal intensity of (c) UTE and (d) T2W imaging was quantified and plotted versus time.</p

Extracted rabbit aorta was investigated by MR imaging and histological staining.

<p>(a) Extracted aorta was visualized by UTE and T2W imaging. (b) Histological investigation was performed by H&E, PB staining. The rectangle in (a) the <i>ex vivo</i> MR Imaging indicates the area shown in (b).</p

<i>In vitro</i> treatment of macrophages with DMNC.

<p>(a) TEM image of macrophage treated with DMNC (inset: magnified image of selected area). (b) UTE and T2W images and (c) relative signal intensities of macrophages following DMNC treatment (20 μg Fe).</p

Characterization of atherosclerotic plaques.

<p>ORO staining of aorta of (a) WHHL rabbits and (b) normal rabbits. The aortic arch and thoracic aorta of (c) WHHL rabbit and (d) normal rabbit were visualized by T2W imaging. (e) The vessel wall thickness of WHHL and normal rabbits were measured from the MR imaging results (*p<0.0001).</p

Solution MR imaging of DMNC.

<p>(a) UTE and T2W images of DMNC solution, and (b) relative signal intensity versus Fe concentration.</p