Spectral anomalies and Gouy rotation around the singularity of ultrashort vortex pulses.

Spectral anomalies of femtosecond pulses with orbital angular momentum were studied in the vicinity of singularities. Bessel-Gauss (BG) beams were generated with mode-locked Ti:sapphire oscillators and dispersion-compensated diffractive axicons acting as spiral phase plates (SPPs). High-resolution two-dimensional spectral mapping was performed with a scanning fiber probe. Progressive rotation of the most pronounced features, known as "spectral eyes", in the maps of spectral moments was found at increasing propagation distance. The phenomenon is explained by a wavelength-dependent Gouy phase shift of interfering spectral components in the twisted wavefront. Spatial "spectral switching" was detected for few-cycle pulses. Possible improvements of selectivity are proposed.

Spatio-temporal coherence mapping of few-cycle vortex pulses.

Light carrying an orbital angular momentum (OAM) displays an optical phase front rotating in space and time and a vanishing intensity, a so-called vortex, in the center. Beyond continuous-wave vortex beams, optical pulses with a finite OAM are important for many areas of science and technology, ranging from the selective manipulation and excitation of matter to telecommunications. Generation of vortex pulses with a duration of few optical cycles requires new methods for characterising their coherence properties in space and time. Here we report a novel approach for flexibly shaping and characterising few-cycle vortex pulses of tunable topological charge with two sequentially arranged spatial light modulators. The reconfigurable optical arrangement combines interferometry, wavefront sensing, time-of-flight and nonlinear correlation techniques in a very compact setup, providing complete spatio-temporal coherence maps at minimum pulse distortions. Sub-7 fs pulses carrying different optical angular momenta are generated in single and multichannel geometries and characterised in comparison to zero-order Laguerre-Gaussian beams. To the best of our knowledge, this represents the shortest pulse durations reported for direct vortex shaping and detection with spatial light modulators. This access to space-time coupling effects with sub-femtosecond time resolution opens new prospects for tailored twisted light transients of extremely short duration.

Ultrashort highly localized wavepackets.

The recently introduced concept of radially non-oscillating, temporally stable ultrashort-pulsed Bessel-like beams we referred to as needle beams is generalized to a particular class of highly localized wavepackets (HLWs). Spatio-temporally quasi-nondiffracting pulses propagating along extended zones are shaped from Ti:sapphire oscillator radiation with a spatial light modulator and characterized with spatially resolved second order autocorrelation. Few-cycle wavepackets tailored to resemble circular disks, rings and bars of light represent the closest approximation of linear-optical light bullets known so far. By combining multiple HLWs, complex pulsed nondiffracting patterns are obtained.

Programmable ultrashort-pulsed flying images.

We report the generation of programmable two-dimensional arrangements of ultrashort-pulsed fringe-less Bessel-like beams of extended depth of focus (referred to as needle beams) without truncating apertures. A sub-20-fs Ti:sapphire laser and a liquid-crystal-on-silicon spatial light modulator (LCoS-SLM) of high-fidelity temporal transfer in phase-only operation mode were used in the experiments. Axicon profiles with ultrasmall conical angles were approximated by adapted gray scale distributions. It was demonstrated that digitized image information encoded in amplitudephase maps of the needle beams is propagated over considerably large distances at minimal cross talk without the need for additional relay optics. This experiment represents a physical realization of Saari's proposal of spatio-temporally nondiffracting "flying images" on a few-femtosecond time scale.

Ultrashort-pulsed truncated polychromatic Bessel-Gauss beams.

Spatio-spectral and spatio-temporal transfer and intensity propagation of truncated ultrashort-pulsed Bessel-Gauss beams were investigated. Extended needle-shaped focal zones were generated using a compact setup with a reflective small-angle axicon and self-apodized truncation by an adapted aperture. Spectral maps of Bessel-Gauss beams were analyzed on the basis of higher order statistical moments. Compared to focused pulsed Gaussian beams with their spectrally dependent propagation, an ultrabroadband spatio-spectral transfer function was detected over Rayleigh ranges exceeding 10 cm. These results indicate favorable pseudo-nondiffracting characteristics not only from the point of view of spatial propagation but also with respect to the spectral and temporal stability.

Vacuum-ultraviolet beam array generation by flat micro-optical structures.

Micro-optical structures for VUV laser beam shaping and wave-front sensing were manufactured by thin-film deposition onto CaF2 and transfer by etching. Arrays of Bessel-like F2 laser beams at a wavelength of 157 nm with extremely small conical angles were generated by microaxicon lenses. Beam propagation was studied in simulations and experiments. Apodization by absorbing layers is proposed for beam cleaning.

Ultrashort-pulse wave-front autocorrelation.

Combined spatially resolved collinear autocorrelation and Shack-Hartmann wave-front sensing of femtosecond laser pulses is demonstrated for the first time to our knowledge. The beam is divided into multiple nondiffracting subbeams by thin-film micro-optical arrays. With hybrid refractive-reflective silica/silver microaxicons, wave-front autocorrelation is performed in oblique-angle reflection. Simultaneous two-dimensional detection of local temporal structure and wave-front tilt of propagating few-cycle wave packets is demonstrated.

Spatially resolved small-angle noncollinear interferometric autocorrelation of ultrashort pulses with microaxicon arrays.

Small-angle, noncollinear, first- and second-order interferometric autocorrelation experiments with Ti:sapphire laser pulses of 9-80-fs duration have been performed with microaxicon arrays. Predictions of short-pulse spatial frequency effects were verified by comparison of interference patterns of single elements and matrices. An angular spectrum of Gaussian-shaped axicons was analyzed on the basis of linear refraction. Experimental data indicate contributions to autocorrelation by nonlinear refraction and travel-time differences. The influence of the spectral bandwidth was separated from the pulse-duration-dependent effects. Spatially resolved information about the coherence time was delivered by the multichannel structure.

Generation of femtosecond Bessel beams with microaxicon arrays.

Multiple quasi-Bessel beams are generated by transmission of sub-30-fs pulses from a Ti:sapphire laser through refractive thin-film microaxicon arrays. Time-integrated intensity distributions at several axial positions and for pulse durations of 26 and 12.5 fs reveal significant changes of contrast, envelope function, and spatial frequency spectrum in comparison with continuous wave data. Evidence is presented that strong space-time coupling results in a time-dependent interference zone.

Microlens formation by thin-film deposition with mesh-shaped masks.

Thin-film microlens arrays with high fill factors have been fabricated in a one-step process by shading a vapor beam in a vacuum-deposition apparatus with metallic meshes placed at defined distances to the substrate surface. To generate three-dimensional mask structures with the necessary depth profiles, microgalvanic technology has been applied. Profiles and optical properties of the microlenses have been studied theoretically and experimentally.

Efficient laser operation with nearly diffraction-limited output from a diode-pumped heavily Nd-doped multimode fiber.

Laser performance of a diode-pumped Nd-doped multimode phosphate-glass fiber is reported. The selection of the fundamental mode in a multimode fiber is demonstrated, resulting in laser emission that is close to diffraction limited and that is nearly independent of the pump power. The heavily Nd-doped fibers with core diameters of 100 microm and lengths between 13 and 32 mm deliver as much as 130 mW of cw output power at 1.053 microm. A total efficiency of 31% with respect to launched pump power has been achieved.

Lumenal sites and C terminus accessibility of the skeletal muscle calcium release channel (ryanodine receptor).

The membrane topology of the skeletal muscle ryanodine receptor (RyR1) was investigated using site-directed antibodies directed against amino acid sequences 2804-2930, 4581-4640, 4860-4886, and 4941-5037. Ab(2804-2930) bound with identical affinity to either closed or permeabilized sarcoplasmic reticulum vesicles, confirming the cytoplasmic location of this segment. Ab(4581-4640) did not bind to closed vesicles but bound well to permeabilized vesicles, supporting a lumenal location for this segment. Ab(4860-4886) did not bind to closed vesicles but exhibited weak binding to the permeabilized vesicles, suggesting that a portion of the epitope may be exposed on the lumenal surface. The C-terminal antibody (Ab(4941-5037)) bound weakly to closed vesicles, and binding was not significantly enhanced by permeabilizing vesicles with low concentrations of non-denaturing detergent. However, the C-terminal antibodies bound efficiently to vesicles which were transiently incubated at alkaline pH or subjected to trypsinolysis, conditions where few of the vesicles were permeabilized. These results support a model for the membrane topology of the ryanodine receptor as proposed by Takeshima et al. (Takeshima, H., Nishimura, S., Matsumoto, T., Ishida, H., Kangawa, K., Minamino, N., Matsuo, H., Ueda, M., Hanaoka, M., Hirose, T., and Numa, S. (1989) Nature 339, 439-445). The results also suggest that the native conformation of the C terminus is inaccessible to antibodies.

[Endoscopic ultrasound in TN staging of stomach cancer. A comparison with computerized tomography and conventional ultrasound]. / Endoskopischer Ultraschall im TN-Staging des Magenkarzinoms. Ein Vergleich mit der Computertomographie und der konventionellen Sonographie.

64 patients with histologically proven gastric carcinoma were investigated by endosonography (EUS), computed tomography (CT) and conventional transcutaneous sonography (US). In 50 patients a resection of the stomach was performed and the histological findings were compared with the results of preoperative staging. In all cases EUS was successful in demonstrating the tumour. With CT tumour visualisation was possible in 17 (35.4%), with US in 7 (14.6%) cases. The pT-stage was correctly determined preoperatively by EUS in 40 (81.6%) with CT and US in only 12 (25%) and 4 (8.3%) patients, respectively. The staging accuracy of EUS amounted to 80% in T1-, 81% in T2-, 100% in T3-, and 67% in T4-stage. The sensitivity in demonstrating lymph node metastases was 81.3% for EUS, 25.8% for CT and 9.7% for US. The specificity in this regard was 72.2% for EUS, 83.3% for CT and 100% for EUS. The overall accuracy for determination of pN-stage was 78% for EUS, 47.9% for CT and 41.7% for US. EUS is clearly superior to CT and US in the locoregional TN-staging of gastric carcinoma.

The effects of lipid composition on the binding of lasalocid A to small unilamellar vesicles.

The binding of the carboxylic ionophore lasalocid A (X537A) to small unilamellar phospholipid vesicles of varying composition was examined in an effort to determine what structural features of the phospholipid membrane influence the ionophore-membrane interaction. Apparent dissociation constants (Kapp) were calculated for both the acidic and anionic forms of the ionophore using the change in fluorescence intensity observed for lasalocid A upon addition of phospholipid vesicles. The Kapp for binding to fluid phase dimyristoylphosphatidylcholine (DMPC) vesicles is 46 microM for the anion and 14 microM for the acid. While the phase transition of DMPC had no effect on the Kapp of the anion, an increase was observed in the Kapp of the acid below the phase transition temperature. The Kapp of the anion was not affected by the incorporation of 10% dimyristoylphosphatidylethanolamine (DMPE), but increased slightly upon incorporation of cholesterol. The pKa values of the ionophore were the same in DMPC and DMPC/DMPE membranes. Incorporation of the negative lipids phosphatidylglycerol, phosphatidic acid, or phosphatidylethanolamine (at pH 9.4 where PE carries a negative charge) decreases binding of the anion in accord with the increase in surface potential estimated from Gouy-Chapman theory. The CD spectrum of membrane-bound lasalocid A anion indicated the ionophore to be in an extended acyclic conformation on the membrane surface with the C-1 carboxylate rotated out of the plane of the salicylate ring. The out-of-plane rotation of the carboxylate may be the result of facial binding by the amphiphilic ionophore on the membrane surface or of weak ion pairing to the polar lipid head groups. These results suggest that the primary determinants of binding of the anionic ionophore on the membrane surface are packing density of the polar head groups and membrane surface potential. There is no evidence of strong hydrogen bond formation between the lipid polar head groups and the ionophore as has previously been suggested.

Medical and surgical management of early Q wave myocardial infarction. II. Effects on mortality and global and regional left ventricular function at 10 or more years of follow-up.

To determine the long-term effect of surgical reperfusion on survival and left ventricular function of patients with anterior and inferior Q wave myocardial infarction, 387 patients were followed up for greater than or equal to 10 years after early Q wave infarction. In the anterior infarction group, 102 received conventional therapy and 101 underwent surgical reperfusion. The overall hospital mortality rate in the medically and surgically treated patients was different (16.7% [17 of 102] versus 6.9% [7 of 101], p less than 0.05). The cumulative 13 year actuarial mortality rate widened between the anterior medical and surgical groups (54% versus 31%, p = 0.0003) by the adjusted Cox proportional hazards model. The hospital mortality rate with early reperfusion (that is, less than or equal to 6 h of symptom onset) was 2% (1 of 51), whereas the mortality rate with late reperfusion was 12% (6 of 50). The 13 year actuarial cumulative mortality rate was significantly lower in both the early and late reperfusion groups (30% and 33%, respectively) than in the conventional therapy group (54%, p = 0.0006). The mortality rate in patients receiving surgery after surviving initial medical therapy was 50% (15 of 30). In the survivors of anterior Q wave myocardial infarction, improved global ejection fraction was seen in the patients undergoing early (54 +/- 13%) and late (50 +/- 10%) surgery relative to those receiving conventional therapy (43 +/- 11%, p less than 0.05). Only the early reperfusion group had better regional function of the anterior wall than that of the conventional therapy group. Thus, ventricular function correlated with improved long-term survival. In the patients with inferior Q wave myocardial infarction, the overall hospital mortality rate in the medical and surgical groups was not different (6.1% [6 of 98] versus 4.6% [6 of 86], p = NS). Likewise, the 13 year actuarial cumulative mortality rate was not different between the medical and surgical groups overall (32% versus 30%, p = 0.29) by the adjusted Cox proportional hazards model. The hospital mortality rate in the early reperfusion group was lower than that in the late reperfusion group (2.0% [1 of 49] versus 8.1% [3 of 37], p = NS). The 13 year actuarial cumulative mortality rate was lower in the early surgical group compared with that in the medical group (19% versus 32%, p = 0.04). The late surgical group had a similar 13 year actuarial cumulative mortality rate to that of the medical group (47% versus 32%, respectively, p = 0.47).(ABSTRACT TRUNCATED AT 400 WORDS)

Interaction of the antifolate antibiotic trimethoprim with phosphatidylcholine membranes: a 13C and 31P nuclear magnetic resonance study.

The interaction of the bacterial dihydrofolate reductase inhibitor trimethoprim with small unilamellar 1,2-dimyristoyl-sn-glycero-3-phosphorylcholine vesicles was studied using 13C and 31P NMR spectroscopy. In an effort to determine whether trimethoprim passively permeates the vesicle membrane, an impermeant, anionic complex of the paramagnetic ion Dy3+ was added to the extravesicular compartment. Based on the downfield shift that the Dy3+ complex induces in the [2-13C] resonance of trimethoprim in free solution, membrane permeation and movement of the drug into the intravesicular space can in principle be established from observation of the C2 chemical shift alone. In contrast to what is predicted by a two-compartment model separated by a semipermeable barrier, the presence of vesicles virtually reverses the effect of the shift reagent on the [2-13C] carbon resonance. These results suggest that the majority of the trimethoprim might be sequestered within the vesicle membrane. A saturable decrease in the spin-lattice relaxation time and a saturable increase in the line width at half-height of the [2-13C] resonance as a function of vesicle concentration indicated that trimethoprim does in fact bind to the phospholipid matrix of the membrane bilayer. The KD for the interaction calculated from the relaxation data was 9.7 +/- 0.3 X 10(-4) M at a pH of 7.01 and an ionic strength of 0.015 M. The chemical shift of the [2-13C] resonance is unaffected by interaction with the electroneutral membrane, and the pKa increases by only 0.16 upon binding. These results point to an interfacial location for the pyrimidine moiety. Using the paramagnetic shift reagent Pr3+ and the 31P NMR signal from the phosphodiester groups of the membrane lipids, trimethoprim was shown to displace Pr3+ ions from binding sites on the outer membrane surface as would be expected if the polar pyrimidine ring were located at or near the membrane surface. The extent to which trimethoprim and trimethoprim derivatives modified in the 3'- and 4'-positions interact with the exo face of the membrane is strongly dependent on the type of substituent and whether it is in the 3'- or 4'-position. Van der Waals interactions between the 5-benzyl sidechain and the hydrophobic fatty acid region of the membrane interior appear to be necessary for the polar portion of trimethoprim to compete favorably for the membrane-binding site with the polyvalent Pr3+ ion.(ABSTRACT TRUNCATED AT 400 WORDS)

[Heart rate and visual evoked potentials during figuring arithmetic problems in boys acquired in early childhood with minimal brain damage]. / Untersuchung der Herzschlagrate und des visuell evozierten Potentials während des Rechnens bei Jungen mit frühkindlich erworbenen leichten Hirnschädigungen.

Changes of the pattern reversal EP and heart rate (HR) during calculating were studied on 32 boys with minimal brain damage and a control group (n 27) matched in age, sex and intelligence. The introduction of a reference period and repetition of the calculation period should improve the value of all results and should give simultaneously a first insight in the course of the parameters investigated, during mental loading. Both groups reached the same results in calculating, yet only the brain damaged boys simultaneously showed significant longer latencies of the EP. This result was interpreted as an effect of the higher loading of the damaged subjects. The task-depended increase of the HR was significant in both groups. The HR-level was getting lower with the increasing number of brain damage criteria. The results of intercorrelation between in physiologic parameters and datas of subjective feeling and results of calculating was negative in all cases. These findings were interpreted on the basis of several difficulties to find out clear cut patterns of reaction for different clinical groups.

Rhodamine 123 as a probe of transmembrane potential in isolated rat-liver mitochondria: spectral and metabolic properties.

The spectral and metabolic properties of Rhodamine 123, a fluorescent cationic dye used to label mitochondria in living cells, were investigated in suspensions of isolated rat-liver mitochondria. A red shift of Rhodamine 123 absorbance and fluorescence occurred following mitochondrial energization. Fluorescence quenching of as much as 75% also occurred. The red shift and quenching varied linearly with the potassium diffusion potential, but did not respond to delta pH. These energy-linked changes were accompanied by dye uptake into the matrix space. Concentration ratios, in-to-out, approached 4000:1. A large fraction of internalized dye was bound. At concentrations higher than those needed to record these spectral changes, Rhodamine 123 inhibited ADP-stimulated (State 3) respiration of mitochondria (Ki = 12 microM) and ATPase activity of inverted inner membrane vesicles (Ki = 126 microM) and partially purified F1-ATPase (Ki = 177 microM). The smaller Ki for coupled mitochondria was accounted for by energy-dependent Rhodamine 123 uptake into the matrix. Above about 20 nmol/mg protein (10 microM), Rhodamine 123 caused rapid swelling of energized mitochondria. Effects on electron-transfer reactions and coupling were small or negligible even at the highest Rhodamine 123 concentrations employed. delta psi-dependent Rhodamine 123 uptake together with Rhodamine 123 binding account for the intense fluorescent staining of mitochondria in living cells. Inhibition of mitochondria ATPase likely accounts for the cytotoxicity of Rhodamine 123. At concentrations which do not inhibit mitochondrial function, Rhodamine 123 is a sensitive and specific probe of delta psi in isolated mitochondria.

A technique for direct-vision sternal reentry.

A simple technique in which the retrosternal tissues are dissected from the body of the sternum under direct vision, allowing for relatively quick and safe reentry of the sternum, is presented.