Supersolid vortex crystals in Rydberg-dressed Bose-Einstein condensates

We study rotating quasi-two-dimensional Bose-Einstein condensates, in which atoms are dressed to a highly excited Rydberg state. This leads to weak effective interactions that induce a transition to a mesoscopic supersolid state. Considering slow rotation, we determine its superfluidity using quantum Monte Carlo simulations as well as mean field calculations. For rapid rotation, the latter reveal an interesting competition between the supersolid crystal structure and the rotation-induced vortex lattice that gives rise to new phases, including arrays of mesoscopic vortex crystals.

Nonlocal nonlinear optics in cold Rydberg gases

We present an analytical theory for the nonlinear optical response of a strongly interacting Rydberg gas under conditions of electromagnetically induced transparency. Simple formulas for the third-order optical susceptibility are derived and shown to be in excellent agreement with recent experiments. The obtained expressions reveal strong nonlinearities, which in addition are of highly nonlocal character. This property together with the enormous strength of the Rydberg-induced nonlinearities is shown to yield a unique laboratory platform for nonlinear wave phenomena, such as collapse-arrested modulational instabilities in a self-defocusing medium.

Rydberg-induced solitons: three-dimensional self-trapping of matter waves

We propose a scheme for the creation of stable three-dimensional bright solitons in Bose-Einstein condensates, i.e., the matter-wave analog of so-called spatiotemporal "light bullets." Off-resonant dressing to Rydberg nD states is shown to provide nonlocal attractive interactions, leading to self-trapping of mesoscopic atomic clouds by a collective excitation of a Rydberg atom pair. We present detailed potential calculations and demonstrate the existence of stable solitons under realistic experimental conditions by means of numerical simulations.

Rydberg trimers and excited dimers bound by internal quantum reflection

In a combined experimental and theoretical effort we report on two novel types of ultracold long-range Rydberg molecules. First, we demonstrate the creation of triatomic molecules of one Rydberg atom and two ground-state atoms in a single-step photoassociation. Second, we assign a series of excited dimer states that are bound by a so far unexplored mechanism based on internal quantum reflection at a steep potential drop. The properties of the Rydberg molecules identified in this work qualify them as prototypes for a new type of chemistry at ultracold temperatures.

Three-dimensional roton excitations and supersolid formation in Rydberg-excited Bose-Einstein condensates

We study the behavior of a Bose-Einstein condensate in which atoms are weakly coupled to a highly excited Rydberg state. Since the latter have very strong van der Waals interactions, this coupling induces effective, nonlocal interactions between the dressed ground state atoms, which, opposed to dipolar interactions, are isotropically repulsive. Yet, one finds partial attraction in momentum space, giving rise to a roton-maxon excitation spectrum and a transition to a supersolid state in three-dimensional condensates. A detailed analysis of decoherence and loss mechanisms suggests that these phenomena are observable with current experimental capabilities.

Coherent population trapping with controlled interparticle interactions

We investigate coherent population trapping in a strongly interacting ultracold Rydberg gas. Despite the strong van der Waals interactions and interparticle correlations, we observe the persistence of a resonance with subnatural linewidth at the single-particle resonance frequency as we tune the interaction strength. This narrow resonance cannot be understood within a mean-field description of the strong Rydberg-Rydberg interactions. Instead, a many-body density matrix approach, accounting for the dynamics of interparticle correlations, is shown to reproduce the observed spectral features.

Dynamical crystallization in the dipole blockade of ultracold atoms

We describe a method for controlling many-body states in extended ensembles of Rydberg atoms, forming crystalline structures during laser excitation of a frozen atomic gas. Specifically, we predict the existence of an excitation-number staircase in laser excitation of atomic ensembles into Rydberg states. It is shown that such ordered states can be selectively excited by chirped laser pulses, and, via quantum state transfer from atoms to light, be used to create crystalline photonic states.

Breaking the dipole blockade: nearly resonant dipole interactions in few-atom systems

A dipole blockade, in which Rydberg-atom-Rydberg-atom interactions inhibit all but a single collective Rydberg excitation, has been proposed as a mechanism to store and manipulate quantum information in mesoscopic ensembles. We investigate the excitation dynamics of a collection of a few atoms and show that they undergo an unexpected, qualitative change when the number of atoms increases from two to three. In particular, the combined action of three atoms, each of which pairwise would produce a blockade, can break the dipole blockade.

Rydberg atom formation in ultracold plasmas: small energy transfer with large consequences

We present extensive Monte Carlo calculations of electron-impact-induced transitions between highly excited Rydberg states and provide accurate rate coefficients. For moderate energy changes, our calculations confirm the widely applied expressions in P. Mansbach and J. Keck [Phys. Rev. 181, 275 (1969)] but reveal strong deviations at small energy transfer. Simulations of ultracold plasmas demonstrate that these corrections significantly impact the short-time dynamics of three-body Rydberg atom formation. The improved rate coefficients yield quantitative agreement with recent ultracold plasma experiments.

Experimental realization of an exact solution to the Vlasov equations for an expanding plasma

We study the expansion of ultracold neutral plasmas in the regime in which inelastic collisions are negligible. The plasma expands due to the thermal pressure of the electrons, and for an initial spherically symmetric Gaussian density profile, the expansion is self-similar. Measurements of the plasma size and ion kinetic energy using fluorescence imaging and spectroscopy show that the expansion follows an analytic solution of the Vlasov equations for an adiabatically expanding plasma.

Electron-temperature evolution in expanding ultracold neutral plasmas

We have used the free expansion of ultracold neutral plasmas as a time-resolved probe of electron temperature. A combination of experimental measurements of the ion expansion velocity and numerical simulations characterize the crossover from an elastic-collision regime at low initial Gamma(e), which is dominated by adiabatic cooling of the electrons, to the regime of high Gamma(e) in which inelastic processes drastically heat the electrons. We identify the time scales and relative contributions of various processes, and we experimentally show the importance of radiative decay and disorder-induced electron heating for the first time in ultracold neutral plasmas.

Protein expression in the tissues of the cardiovascular system of the rat under selenium deficiency and adequate conditions

We investigate the effects of selenium in tissues of the cardiovascular system. In order to examine the expression of the heart and aorta proteins (part of them) in the homogenate of selenium-deficient (Se(-)) and selenium control rats (Se(+)), two-dimensional electrophoresis was used by means of giga gels (30 x 35 cm). After electrophoresis, the protein expression pattern of the (Se(-)) gel and (Se(+)) gel was compared. The evaluation of the protein difference was implemented by means of a computer program suitable for the analysis of protein separated by the two-dimensional electrophoresis. In this way more than 2000 proteins a gel (heart) were detected and more than 1900 protein spots were detected in the aorta fraction. Ten significant differences were found between the gel of (Se(+)) and (Se(-)) heart homogenate of the rat and more than 15 significant differences between the gel of (Se(+)) and (Se(-)) of the aorta. By means of MALDI-MS-ESI-MS some of these proteins with different expression levels were not determined until now. Of those, three proteins were detected as the alpha myosin heavy chain (alpha-MHC), myosin light chain 1 and 2 (MLC 1 and 2), and the mitochondrial enzyme creatinine kinase. First results suggest that selenium deficiency affects myocardial energy metabolism and contractile proteins.

Antiblockade in Rydberg excitation of an ultracold lattice gas

It is shown that the two-step excitation scheme typically used to create an ultracold Rydberg gas can be described with an effective two-level rate equation, greatly reducing the complexity of the optical Bloch equations. This allows us to efficiently solve the many-body problem of interacting cold atoms with a Monte Carlo technique. Our results reproduce the observed excitation blockade effect. However, we demonstrate that an Autler-Townes double peak structure in the two-step excitation scheme, which occurs for moderate pulse lengths as used in the experiment, can give rise to an antiblockade effect. It is most pronounced for atoms arranged on a lattice. Since the effect is robust against a large number of lattice defects it should be experimentally realizable with an optical lattice created by CO2 lasers.

Cooling by spontaneous decay of highly excited antihydrogen atoms in magnetic traps

An efficient cooling mechanism of magnetically trapped, highly excited antihydrogen (H) atoms is presented. This cooling, in addition to the expected evaporative cooling, results in trapping of a large number of H atoms in the ground state. It is found that the final fraction of trapped atoms is insensitive to the initial distribution of H magnetic quantum numbers. Expressions are derived for the cooling efficiency, demonstrating that magnetic quadrupole (cusp) traps provide stronger cooling than higher order magnetic multipoles. The final temperature of H confined in a cusp trap is shown to depend as approximately 2.2T(n0)n(0)(-2/3) on the initial Rydberg level n0 and temperature T(n0).

New interpretations of measured antihydrogen velocities and field ionization spectra

We present extensive Monte Carlo simulations, showing that cold antihydrogen (H) atoms are produced when antiprotons (p) are gently heated in the side wells of a nested Penning trap. The observed H with high energies, that had seemed to indicate otherwise, are instead explained by a surprisingly effective charge-exchange mechanism. We shed light on the previously measured field-ionization spectrum, and reproduce both the characteristic low-field power law as well as the enhanced H production at higher fields. The latter feature is shown to arise from H toms too deeply bound to be described as guiding center atoms, atoms with internally chaotic motion.

[In-vitro comparison of morphology of current microkeratomes for LASIK]

BACKGROUND

We have performed an in-vitro examination of the morphology of flap thickness and stromal bed after LASIK in porcine eyes.

MATERIALS AND METHODS

Freshly enucleated porcine eyes and synthetic eye models were used for cutting flaps with the microkeratomes Hansatome-Excellus (Bausch&Lomb), M2 single use (Moria), Amadeus (AMO), MK-2000 (Nidek) and Carriazo-Pendular (Schwind). The flap thickness of porcine eyes was determined using a non-contact, confocal optical distance measuring device (CHR 150N, Jurca), in the eye models a mechanical thickness measuring device (Käfler) was used. The morphology of the stromal bed was examined by photography, histology, scanning electron microscopy and confocal optical distance measurements.

RESULTS

The optical/mechanical flap thickness measurements showed an average difference compared to the adjusted thickness of - 3/+ 90 microm (Hansatome-Excellus), + 7/+ 100 microm (M2 single use), - 35/+ 40 microm (Amadeus), - 4/+ 80 microm (MK-2000) and + 11/+ 0 microm (Carriazo-Pendular). Histology showed no mechanical damage and smooth, slightly undulating surfaces with all microkeratomes. In the scanning electron microscopic examination, the stromal surface was found to be homogeneous and smooth for all of the microkeratomes. Average roughness of the ablation surface was 0.27 microm (Hansatome-Excellus), 0.23 microm (M2 single use), 0.21 microm (Amadeus), 0.23 microm (MK-2000) and 0.29 microm (Carriazo-Pendular).

CONCLUSION

The stromal bed showed in all cases only a slightly roughness, which seems to be acceptable for the clinical outcome. However, the more critical point is the large variations in flap thickness compared to the intended thickness.

Angiographic and clinical outcome for the treatment of in-stent restenosis with sirolimus-eluting stent compared to vascular brachytherapy

BACKGROUND

With the use of coronary stents for the treatment of coronary artery disease, in-stent restenosis became a major clinical problem. In this non-randomized study, we examined the use of stent-based delivery of sirolimus (rapamycin) for the treatment of in-stent restenosis in comparison to intracoronary beta-brachytherapy, regarding the clinical effectiveness and the angiographic results for the treatment of in-stent restenosis after 6-9 months.

METHODS AND RESULTS

Between July 2001 and May 2002, 28 patients (65+/-11 years) with instent restenosis were treated with intracoronary brachytherapy. Consecutively, between May 2002 and April 2003, 28 patients (65+/-10 years) with in-stent restenosis were treated with the implantation of a sirolimus-eluting stent (SES). Patients with in-stent restenosis treated by implantation of a SES had significantly lower incidence of in-stent restenosis (1/28 (3.6%) vs 10/28 (36%); p=0.007) and insegment restenosis (4/28 (14%) vs 14/28 (50%); p=0.013) compared to patients treated with brachytherapy. Target lesion and target vessel revascularization rate tended to be lower in the SES group (14 vs 25%) but did not yet reach statistical significance. One patient died in the group treated by implantation of a SES eight months after stenting, one patient suffered from myocardial infarction due to a subtotal in-stent restenosis after brachytherapy. Two patients after brachytherapy underwent surgical revascularization due to recurrent in-stent restenosis similar to the patient with in-stent restenosis after SES implantation.

CONCLUSION

In this study we show the feasibility and safety of the treatment of in-stent restenosis by implantation of sirolimus-eluting stents and demonstrate a lower incidence of recurrent in-stent restenosis as well as lower late luminal loss compared to treatment by intravascular brachytherapy.

Relaxation to nonequilibrium in expanding ultracold neutral plasmas

We investigate the strongly correlated ion dynamics and the degree of coupling achievable in the evolution of freely expanding ultracold neutral plasmas. We demonstrate that the ionic Coulomb coupling parameter Gamma(i) increases considerably in later stages of the expansion, reaching the strongly coupled regime despite the well known initial drop of Gamma(i) to order unity due to disorder-induced heating. Furthermore, we formulate a suitable measure of correlation and show that Gamma(i) calculated from the ionic temperature and density reflects the degree of order in the system if it is sufficiently close to a quasisteady state. At later times, however, the expansion of the plasma cloud becomes faster than the relaxation of correlations, and the system does not reach thermodynamic equilibrium anymore.

[Therapy of malignant ascites in vivo by 211At-labelled microspheres]

AIM

Determination of the biological effect of the alpha emitter (211)At on cellular level as well as the assessment of dosimetric data in a tumour model in vivo.

METHODS

Transplantation of malignant ascitic cells in mice intraperitoneally and estimation of tumour characteristics (doubling time of the cells, mean survival of the animals following an i.p. application of a defined tumour cell number). (211)At labelled human serum albumin microspheres B-20 (MSP) of varying activity were injected into tumour bearing mice intraperitoneally. The effectiveness of the therapy was evaluated by means of determination of the duration of cell cycle arrest as well as the microscopic analysis of the rate of abnormal mitotic cells due to radiation induced damage. Furthermore, dose dependence of survival was evaluated.

RESULTS

Three days following the intraperitoneally application of 8 x 10(6) tumour cells, 50-600 kBq (211)At-MSP were applied into the abdominal cavity. Considering the volume of ascites at this time and the administered activity, dose calculations were performed. An activity of 50 kBq caused a dose of 0.84 Gy. The increase of radiation induced effect on ascitic tumour cells was correlated with the dose. Between the duration of the cell cycle arrest and the administered activity, a directly proportional correlation was found. The mean survival of non-treated animals was 16.9 +/- 3.7 days. The prolongation of the survival was proportional to the activity administered. Using a dosage of 10 Gy, five animals out of 16 survived.

CONCLUSION

Therapy of malignant ascitic cells using (211)At-MSP was effective in vivo. For tumour therapy, the (211)At represents a highly effective alternative to usually applied beta emitters.

Coulomb crystallization in expanding laser-cooled neutral plasmas

We present long-time simulations of expanding ultracold neutral plasmas, including a full treatment of the strongly coupled ion dynamics. Thereby, the relaxation of the expanding laser-cooled plasma is studied, taking into account elastic as well as inelastic collisions. It is demonstrated that, depending on the initial conditions, the ionic component of the plasma may exhibit short-range order or even a superimposed long-range order resulting in concentric ion shells. In contrast to ionic plasmas confined in traps, the shell structures build up from the center of the plasma cloud rather than from the periphery.

Development of a mechanical testing and loading system for trabecular bone studies for long term culture

A highly accurate (+/-3%) mechanical loading and measurement system combined with a trabecular bone diffusion culture-loading chamber has been developed, which provides the ability to study trabecular bone (and possibly) cartilage under controlled culture and loading conditions over long periods of time. The loading device has been designed to work in two main modes, either to apply a specific compressive strain to a trabecular bone cylinder or to apply a specific force and measure the resulting deformation. Presently, precisely machined bone cylinders can be loaded at frequencies between 0.1 Hz to 50 Hz and amplitudes over 7,000 microepsilon. The system allows accurate measurement of many mechanical properties of the tissue in real time, including visco-elastic properties. This paper describes the technical components, reproducibility, precision, and the calibration procedures of the loading system. Data on long term culture and mechanical responses to different loading patterns will be published separately.