Two phase-matching regimes in high-order harmonic generation.

High-order harmonic generation (HHG) provides scalable sources of coherent extreme ultraviolet radiation with pulse duration down to the attosecond time scale. Efficient HHG requires the constructive interplay between microscopic and macroscopic effects in the generation volume, which can be achieved over a large range of experimental parameters from the driving field properties to those of the generating medium. Here, we present a systematic study of the harmonic yield as a function of gas pressure and medium length. Two regimes for optimum yield are identified, supporting the predictions of a recently proposed analytical model. Our observations are independent on the focusing geometry and, to a large extent, on the pulse duration and laser intensity, providing a versatile approach to HHG optimization.

Superior Photo-thermionic electron Emission from Illuminated Phosphorene Surface.

This work demonstrates that black phosphorene, a two dimensional allotrope of phosphorus, has the potential to be an efficient photo-thermionic emitter. To investigate and understand the novel aspects we use a combined approach in which ab initio quantum simulation tools are utilized along with semiclassical description for the emission process. First by using density functional theory based formalism, we study the band structure of phosphorene. From the locations of electronic bands, and band edges, we estimate the Fermi level and work function. This leads us to define a valid material specific parameter space and establish a formalism for estimating thermionic electron emission current from phosphorene. Finally we demonstrate how the emission current can be enhanced substantially under the effect of photon irradiation. We observe that photoemission flux to strongly dominate over its coexisting counterpart thermionic emission flux. Anisotropy in phosphorene structure plays important role in enhancing the flux. The approach which is valid over a much wider range of parameters is successfully tested against recently performed experiments in a different context. The results open up a new possibility for application of phosphorene based thermionic and photo-thermionic energy converters.

Quantum Optical Signatures in a Strong Laser Pulse after Interaction with Semiconductors.

Electrodynamical processes induced in complex systems like semiconductors by strong electromagnetic fields have traditionally been described using semiclassical approaches. Although these approaches allowed the investigation of ultrafast dynamics in solids culminating in multipetahertz electronics, they do not provide any access to the quantum-optical nature of the interaction, as they treat the driving field classically and unaffected by the interaction. Here, using a full quantum-optical approach, we demonstrate that the subcycle electronic response in a strongly driven semiconductor crystal is imprinted in the quantum state of the driving field resulting in nonclassical light states carrying the information of the interaction. This vital step towards strong-field ultrafast quantum electrodynamics unravels information inaccessible by conventional approaches and leads to the development of a new class of nonclassical light sources.

[Therapy of cardiogenic shock : A success story of German cardiology]. / Therapie des kardiogenen Schocks : Eine Erfolgsgeschichte der deutschen Kardiologie.

In contrast to the situation in the 1960s and 1970s, the mortality risk for patients with myocardial infarction has been clearly reduced, particularly for those with myocardial infarction with cardiogenic shock (MICS). Approximately 5­10 % of patients with a myocardial infarction are affected by a MICS and the mortality risk is between 30 % and 50 %. The primary percutaneous coronary intervention with stent implantation should be carried out as quickly as possible in order to reduce the mortality to around 20 %. This article gives an overview of the currently available options for conservative and fibrinolytic treatment of MICS, of the interventional treatment of cardiogenic shock in the era of intravenous and intracoronary infarct treatment as well as without thrombolysis. In addition, the currently available mechanical support systems and the possibilities for surveillance and monitoring of patients are presented.

Spatial Properties of High-Order Harmonic Beams from Plasma Mirrors: A Ptychographic Study.

Spatial properties of high-order harmonic beams produced by high-intensity laser-matter interactions carry rich information on the physics of the generation process, and their detailed understanding is essential for applications of these light beams. We present a thorough study of these properties in the case of harmonic generation from plasma mirrors, up to the relativistic interaction regime. In situ ptychographic measurements of the amplitude and phase spatial profiles of the different harmonic orders in the target plane are presented, as a function of the key interaction parameters. These measurements are used to validate analytical models of the harmonic spatial phase in different generation regimes, and to benchmark ultrahigh-order Maxwell solvers of particle-in-cell simulation codes.

Detailed Experimental Study of Ion Acceleration by Interaction of an Ultra-Short Intense Laser with an Underdense Plasma.

Ion acceleration from intense (Iλ(2) > 10(18) Wcm(-2) µm(2)) laser-plasma interaction is experimentally studied within a wide range of He gas densities. Focusing an ultrashort pulse (duration ion plasma period) on a newly designed submillimetric gas jet system, enabled us to inhibit total evacuation of electrons from the central propagation channel reducing the radial ion acceleration associated with ponderomotive Coulomb explosion, a mechanism predominant in the long pulse scenario. New ion acceleration mechanism have been unveiled in this regime leading to non-Maxwellian quasi monoenergetic features in the ion energy spectra. The emitted nonthermal ion bunches show a new scaling of the ion peak energy with plasma density. The scaling identified in this new regime differs from previously reported studies.

Dual spectral-band interferometry for spatio-temporal characterization of high-power femtosecond lasers.

We present and demonstrate a technique called RED-SEA TADPOLE for the spatio-temporal characterization of high peak power femtosecond lasers. It retains the basic principle of an existing method, where a scanning monomode fiber is utilized in an interferometric scheme to measure the spectral amplitude and phase at all points across an ultrashort laser beam. We combine this approach with dual spectral-band interferometry, to correct for all phase errors occurring in this interferometer, thus allowing for the simultaneous measurement of the beam wavefront and pulse front in a collimated beam of large diameter. The generic phase correction procedure implemented here can also be extended to other fiber optic device applications sensitive to phase fluctuations.

Optically controlled solid-density transient plasma gratings.

A general approach for optically controlled spatial structuring of overdense plasmas generated at the surface of initially plain solid targets is presented. We demonstrate it experimentally by creating sinusoidal plasma gratings of adjustable spatial periodicity and depth, and study the interaction of these transient structures with an ultraintense laser pulse to establish their usability at relativistically high intensities. We then show how these gratings can be used as a "spatial ruler" to determine the source size of the high-order harmonic beams produced at the surface of an overdense plasma. These results open new directions both for the metrology of laser-plasma interactions and the emerging field of ultrahigh intensity plasmonics.

Optical properties of relativistic plasma mirrors.

The advent of ultrahigh-power femtosecond lasers creates a need for an entirely new class of optical components based on plasmas. The most promising of these are known as plasma mirrors, formed when an intense femtosecond laser ionizes a solid surface. These mirrors specularly reflect the main part of a laser pulse and can be used as active optical elements to manipulate its temporal and spatial properties. Unfortunately, the considerable pressures exerted by the laser can deform the mirror surface, unfavourably affecting the reflected beam and complicating, or even preventing, the use of plasma mirrors at ultrahigh intensities. Here we derive a simple analytical model of the basic physics involved in laser-induced deformation of a plasma mirror. We validate this model numerically and experimentally, and use it to show how such deformation might be mitigated by appropriate control of the laser phase.

Direct observation of density-gradient effects in harmonic generation from plasma mirrors.

High-order harmonics and attosecond pulses of light can be generated when ultraintense, ultrashort laser pulses reflect off a solid-density plasma with a sharp vacuum interface, i.e., a plasma mirror. We demonstrate experimentally the key influence of the steepness of the plasma-vacuum interface on the interaction, by measuring the spectral and spatial properties of harmonics generated on a plasma mirror whose initial density gradient scale length L is continuously varied. Time-resolved interferometry is used to separately measure this scale length.

Short intense laser pulse collapse in near-critical plasma.

It is observed that the interaction of an intense ultrashort laser pulse with a near-critical gas jet results in the pulse collapse and the deposition of a significant fraction of the energy. This deposition happens in a small and well-localized volume in the rising part of the gas jet, where the electrons are efficiently accelerated and heated. A collisionless plasma expansion over ~ 150 µm at a subrelativistic velocity (~ c/3) has been optically monitored in time and space, and attributed to the quasistatic field ionization of the gas associated with the hot electron current. Numerical simulations in good agreement with the observations suggest the acceleration in the collapse region of relativistic electrons, along with the excitation of a sizable magnetic dipole that sustains the electron current over several picoseconds.

Anticorrelation between ion acceleration and nonlinear coherent structures from laser-underdense plasma interaction.

In laser-plasma experiments, we observed that ion acceleration from the Coulomb explosion of the plasma channel bored by the laser is prevented when multiple plasma instabilities, such as filamentation and hosing, and nonlinear coherent structures (vortices or postsolitons) appear in the wake of an ultrashort laser pulse. The tailoring of the longitudinal plasma density ramp allows us to control the onset of these instabilities. We deduced that the laser pulse is depleted into these structures in our conditions, when a plasma at about 10% of the critical density exhibits a gradient on the order of 250 µm (Gaussian fit), thus hindering the acceleration. A promising experimental setup with a long pulse is demonstrated enabling the excitation of an isolated coherent structure for polarimetric measurements and, in further perspectives, parametric studies of ion plasma acceleration efficiency.

Development and characterization of very dense submillimetric gas jets for laser-plasma interaction.

We report on the characterization of recently developed submillimetric He gas jets with peak density higher than 10(21) atoms/cm(3) from cylindrical and slightly conical nozzles of throat diameter of less than 400 µm. Helium gas at pressure 300-400 bar has been developed for this purpose to compensate the nozzle throat diameter reduction that affects the output mass flow rate. The fast-switching electro-valve enables to operate the jet safely for multi-stage vacuum pump assembly. Such gaseous thin targets are particularly suitable for laser-plasma interaction studies in the unexplored near-critical regime.

[Cacoa and dark chocolate in cardiovascular prevention?]. / Kakao und dunkle Schokolade zur kardiovaskulären Prävention?

It has been shown that the consumption of cocoa has a positive influence on a number of cardiovascular surrogate parameters such as arterial vasodilatation and a moderate decrease in blood pressure in humans. In the blood, a decrease in platelet aggregation and an increase in angiogenetic progenitor cells was noted. Furthermore, anti-inflammatory effects, an amelioration of the lipid profile and glucose metabolism was described. An increase of endothelial NO production following the ingestion of the antioxidant cocoa flavanols catechin and epicatechin seems to be the leading mechanism causing these effects. In animal studies of myocardial reperfusion, a decrease in infarct size was noted. In several prospective cohort studies from Europe and the United States, a 50 % reduction of mortality mostly due to a reduction of myocardial infarction was published. Consumption up to about 25 g daily of a flavanol rich dark chocolate (ca. 85 % cocoa content) can be recommended for cardiovascular prevention. In this moderate dosage, the potentially harmful effects due to weight gain and cadmium intake will be minimal. However, controlled randomized trials with well defined clinical endpoints are needed to prove the positive effects described so far. At this point, in time based on the information described in this article, a moderate consumption of flavanol rich cocoa products seems to be effective in the prevention of coronary artery disease and myocardial infarction.

Second-generation real-time three-dimensional echocardiography. Finally on its way into clinical cardiology?

Three-dimensional (3D) echocardiographic imaging has been introduced as a tool to improve the assessment of both morphologic and functional parameters of the cardiovascular system. In the past, data acquisition was limited due to time-consuming sequential acquisition of multiple triggered 2D image planes from 10-60 heart cycles using transesophageal rotational, transthoracic rotational or transthoracic freehand approaches. Recent improvements in the size of matrix array probes and in computing power of modern ultrasound equipment have significantly increased both spatial and temporal resolution of "second-generation" real-time 3D scanners. Although the superiority of 3D echocardiography in the determination of ventricular volume, ventricular mass or valvular orifice area had already been demonstrated in the late 1990s, widespread use in clinical cardiology was limited on account of difficulties in acquisition and post-processing. Clinical use of modern 3D echocardiography is boosted by the marked reduction in acquisition time and the unique possibility of on-line rendering on the ultrasound system. The ability to visualize a virtual 3D surface in real time-although limited to a sector size of about 30 degrees-offers new insights into cardiac pathomorpholgy even in patients with arrhythmias and may in realtime 3D-contrast flow analysis. Analysis of wide-angle 3D datasets (90 by 90 degree pyramidal shape) is possible by combining the 3D information of several [4-7] consecutive heart cycles. 3D datasets including the complete left ventricle provide comprehensive information on ventricular and mitral valve morphology and function. Qualitative and quantitative analyses of regional wall motion at rest and during stress become possible. Combination with 3D color Doppler data allows additional assessment of valvular function as well as determination of flow in the left ventricular outflow tract and across septal defects. The integration and future quantification of these new parameters together with on-line review allows new insights into cardiac function, morphology and synchrony that offer great potentials in the evaluation of right and left ventricular global and regional function, diagnosis of small areas of ischemia, congenital and valvular heart disease and effects of biventricular pacing in dilated heart asynchrony.

[Primary adenocarcinoma of the left atrium mimicking benign myxoma]. / Primäres Adenokarzinom des linken Herzvorhofes. Erst die Histologie führt zur Diagnose Adenokarzinom des Herzens.

Primary tumors of the heart are rare, whereas cardiac metastases, most frequently from adenocarcinomas, occur in up to 20% of malignant tumors. We report about a 61-year-old female patient who was admitted with recurrent stress-induced dizziness, intermittent tachycardia and a fall due to a pre-syncope. Echocardiography showed a left atrial tumor with the typical features of a pediculated myxoma, leading to open heart surgery. However, histopathology revealed a 2.2 x 1.5 cm adenocarcinoma. The subsequent search for a primary tumor, including tumor markers and (18)F-FDG-PET, was unsuccessful, as was a second thorough diagnostic workup half a year later. The tumor was therefore classified as a primary cardiac adenocarcinoma.

Quantitative assessment of right ventricular volumes in severe chronic thromboembolic pulmonary hypertension using transthoracic three-dimensional echocardiography: changes due to pulmonary thromboendarterectomy.

AIMS: Evaluation of a three-dimensional reconstruction method to show the changes of right ventricular volume and systolic function when patients undergo pulmonary thromboendarterectomy for chronic thromboembolic pulmonary hypertension. METHODS AND RESULTS: In the examination of 11 patients (four female, seven male; age 56+/-10 years) before and after pulmonary thromboendarterectomy, end-diastolic and end-systolic right ventricular volumes were determined as a sum total of the calculated volumes of derived parallel slices of the right ventricle. Using a Tomtec workstation and a Vingmed CFM 800 echocardiography device, the acquired data were ECG-and respiration-triggered in the course of transthoracic examination, using step intervals of 5 degrees. The ventricular outline was traced manually on 5mm slices from longitudinal cut planes. For subsequent correction, their area measurements were displayed and the volume cross-checked against the volume from orthogonal cut planes. End-diastolic and end-systolic volumes could be quantified in 11/11 cases before surgery, but data could only be attained for 9/11 patients after surgery, because a limited apical window rendered the postoperative three-dimensional reconstruction impossible in two cases. Before surgery, right ventricular size was larger than normal and systolic function was clearly impaired in all of the patients (end-diastolic volume: 121+/-37 ml; end-systolic volume 91+/-30 ml; ejection fraction 25+/-8%). The decrease in mean pulmonary artery pressure after surgery was significant (47+/-8 vs 26+/-8 mmHg; P<0.05). End-diastolic and end-systolic right ventricular volumes had been reduced (80+/-33 ml and 54+/-31 ml respectively), and the ejection fraction had increased (36+/-9%). CONCLUSIONS: Successfully performed pulmonary thromboendarterectomy leads to a significant reduction of right ventricular chamber size and improvement of systolic function, which can be determined with great precision and quite easily, using transthoracic three-dimensional echocardiography. Published by Elsevier Science Ltd. All rights reserved.

[Quantitative analysis of the left main coronary artery by 3D echocardiography. Role, possibilities and limitations of noninvasive imaging of the left coronary artery]. / Quantitative Analyse des Hauptstammes der linken Koronararterie durch 3D-Echokardiographie. Stellenwert, Möglichkeiten und Grenzen der nicht-invasiven Darstellung der linken Koronararterie.

The left main coronary artery was investigated in 30 patients using a transesophageal approach, and a 3D reconstruction of the 2D databases was performed. Two groups of patients were analyzed. First, patients with calcified aortic stenosis were investigated and the reconstructed data obtained were compared to the left ventricular angiogram of the left coronary artery. Second, the 2D databases of patients with non-calcified aortic valve and aortic anulus were reconstructed using the 3D technique. In group 1 the estimate in size of the left ventricular coronary artery was closely related to the diameter of the left coronary artery as obtained by the coronary angiogram (mean difference 0.08 mm, interval of confidence at 95%, -0.48 and +0.32 mm). In both groups a substantial increase in imaging of the left coronary artery was obtained compared to the standard 2D echocardiographic view (% in group 1, and % in group 2, respectively). Independent of the 3D reconstruction of the left coronary artery in the any-plane mode, an orthogonal imaging of the artery could be obtained in only 15% of patients in group 1 but in 40% of patients in group 2. We conclude that 3D reconstruction of the left coronary artery (LAD) is superior to 2D echocardiography in echo-imaging of the proximal part of the LAD and correlates strongly to the diameters measured in the left coronary angiogram. In patients with major calcification of the aortic anulus and/or a calcified native aortic valve this approach is associated with multiple artifacts in imaging. The rapid technical evolution in this technique including improvement in computer technology and appropriate software may ensure a further important role of 3D echo imaging in noninvasive visualization of the normal and diseased left main coronary artery.

Value of echocardiography in patient follow-up after surgically corrected type A aortic dissection.

BACKGROUND: To identify patients (pts) at risk of late complications, follow-up after surgery for type A aortic dissection is essential. We assessed the value of echocardiography to monitor patients after surgery for type A aortic dissection. METHODS: 80 out of 108 pts operated between 1989 and 1999 for type A aortic dissection survived surgery. 62 pts with at least one TEE, CT or MRI examinations during follow-up were included in this study. All pts had transthoracic echocardiography (TTE), 53 transesophageal echocardiography (TEE), 51 had CT, and 39 had MRI. RESULTS: At the first follow-up, 12 of 48 pts with aortic valve sparing surgery presented with aortic insufficiency >I degrees detected using echocardiography. 16 pts evolved a distal aortic aneurysm of over 5 cm, all seen in TEE, CT and MRI. A distal intimal flap was present in 39 pts and could be seen in TEE, CT and MRI in all patients. A new proximal aortic root dissection took place in 5 pts. Progressive aortic pathology led to reoperation in 9 pts. TEE was especially useful in 2 pts to confirm redissection, in 1 pt to rule out redissection assumed by CT, and in 1 with paraprosthetic blood flow after ascending aortic replacement. MRI led to additional information in 1 patient with false aneurysm of the distal anastomosis and 1 with redissection not seen in TEE 6 month before. CT and MRI were superior to TEE in demonstrating aortic arch pathology, whereas TEE was more effective in showing the flow pattern and residual entry sites. CONCLUSIONS: Echocardiography is an effective and cost-saving diagnostic tool to monitor pts after surgery for type A aortic dissection, and should be the method of choice to ascertain aortic pathology initially after surgery. Follow-up intervals and need for additional CT or MRI should be determined afterwards according to specific pathologies.