Simple technique for the compression of nanojoule pulses from few-cycle laser oscillator to 1.7-cycle duration via nonlinear spectral broadening in diamond.

We report on a simple approach for the compression of few-cycle laser pulses generated in an ultrafast laser oscillator to a duration corresponding to 1.7 cycles of near-infrared light (compression factor of 1.44) by nonlinear spectral broadening in diamond and subsequent dispersion compensation using chirped mirrors. After the spectral broadening, the pulse spectrum spans over almost an octave (580-1000 nm at the -10 dB level). The pulses are compressed by broadband-chirped mirrors and a wedge pair to a duration of 4.5 fs measured by spectral phase interferometry for direct electric-field reconstruction (SPIDER). The properties of the broadened spectrum and their modelling by numerical solution of a 1D nonlinear Schrödinger equation show that the main source of spectral broadening is self-phase modulation, whereas stimulated Raman scattering does not play a significant role.

Coherent phonon dynamics in micro- and nanocrystalline diamond.

We report on the time-resolved coherent anti-Stokes Raman spectroscopy of phonon dephasing in micro- and nanocrystalline diamond films. The dephasing times T(2) were found to be dependent on the morphology of diamond films (average size of crystals and content of nondiamond carbon phase) and changed from 0.7 to 1.72 ps. The dephasing times were found to be temperature independent in the range 10-295 K. In addition to diamond Raman active phonon mode at 1332 cm(-1), we investigated also the dynamics of a broad Raman peak at 1530 cm(-1) which is present in samples with higher content of nondiamond sp(2) hybridized carbon phase. This peak was found to be homogenously broadened with very fast dephasing (T(2)~50 fs).

Nonlinear optical properties of nanocrystalline diamond.

We report on investigation of nonlinear optical phenomena in nanocrystalline diamond prepared by microwave plasma enhanced chemical vapour deposition. We observed the upconverted photoluminescence, the second and the third harmonic generation and Z-scan signal. The value of the third order nonlinear susceptibility was estimated. Our results show that nonlinear optical properties of nanocrystalline diamond have many features of the bulk diamond affected to some extent by the presence of grain boundaries.

Femtosecond luminescence spectroscopy of core states in silicon nanocrystals.

We present a study of ultrafast carrier transfer from highly luminescent states inside the core of silicon nanocrystal (due to quasidirect transitions) to states on the nanocrystal-matrix interface. This transfer leads to a sub-picosecond luminescence decay, which is followed by a slower decay component induced by carrier relaxation to lower interface states. We investigate the luminescence dynamics for two different surface passivation types and we propose a general model describing spectral dependence of ultrafast carrier dynamics. Our results stress the crucial role of the energy distribution of the interface states on surface-related quenching of quasidirect luminescence in silicon nanocrystals. We discuss how to avoid this quenching in order to bring the attractive properties of the quasidirect recombination closer to exploitation.

Systematic study of Mn-doping trends in optical properties of (Ga,Mn)As.

We report on a systematic study of optical properties of (Ga,Mn)As epilayers spanning the wide range of accessible Mn(Ga) dopings. The material synthesis was optimized for each nominal Mn doping in order to obtain films which are as close as possible to uniform uncompensated (Ga,Mn)As mixed crystals. We observe a broad maximum in the mid-infrared absorption spectra whose position exhibits a prevailing blueshift for increasing Mn doping. In the visible range, a peak in the magnetic circular dichroism also shifts with increasing Mn doping. The results are consistent with the description of ferromagnetic (Ga,Mn)As based on the microscopic valence band theory. They also imply that opposite trends seen previously in the optical data on a limited number of samples are not generic and cannot serve as an experimental basis for postulating the impurity band model of ferromagnetic (Ga,Mn)As.

Carrier dynamics in InAs/AlAs quantum dots: lack in carrier transfer from wetting layer to quantum dots.

Structures with self-assembled InAs quantum dots (QDs) embedded in an AlAs matrix have been studied by steady-state and transient photoluminescence. It has been shown that in contrast to InAs/GaAs QD systems carriers are mainly captured by quantum dots directly from the AlAs matrix, while transfer of carriers captured by the wetting layer far away from QDs to the QDs is suppressed. At low temperatures the carriers captured by the wetting layer are localized by potential fluctuations at the wetting layer interface, while at high temperatures the carriers are delocalized but captured by nonradiative centers located in the wetting layer.

Interobserver and intraobserver agreement in the evaluation of CT perfusion in ischemic stroke.

Knowledge of interrater reliability in the evaluation of perfusion computed tomography (CTP) studies is very limited even though the method is widely used in the workup of acute stroke. The aims of this study were to estimate the inter- and intraobserver agreement in the evaluation of CTP data and to evaluate the feasibility of the method. The CTP data of 20 consecutive patients (50% were females) aged 68+/-11 years with different categories of acute ischemic stroke were included in this retrospective analysis. Perfusion studies were evaluated independently by six radiologists on two different occasions. The overall inter- and intraobserver agreement was substantial, showing a capital KA, Cyrillic value of 0.65 (95% confidence interval 0.39-0.91). The time required for the post-processing and interpretation ranged from 37 to 460 seconds. Evaluation of manually post-processed CTP data according to the maximum slope model appears to be reliable. Experience and also a short training period increase the reliability of the method and reduce the time needed for delivery of the results to the treating clinician.

Interplay of bimolecular and Auger recombination in photoexcited carrier dynamics in silicon nanocrystal/silicon dioxide superlattices.

We report results of investigating carrier recombination in silicon nanocrystal/silicon dioxide superlattices. The superlattices prepared by nitrogen-free plasma enhanced chemical vapour deposition contained layers of silicon nanocrystals. Femtosecond transient transmission optical spectroscopy was used to monitor carrier mechanisms in the samples. The three-particle Auger recombination was observed in accord with previous reports. However, under high pump intensities (high photoexcited carrier densities) the bimolecular process dominated the recombination. Detailed analysis of measured data and fitting procedure made it possible to follow and quantify the interplay between the two recombination processes. The bimolecular recombination was interpreted in terms of the trap-assisted Auger recombination.

Composition, structure, and luminescence of montmorillonites saturated with different aggregates of methylene blue.

The distribution of various aggregates (dimers, trimers, and tetramers) of methylene blue (MB) formed in aqueous solution at various concentrations of dye has been calculated using the equilibrium aggregation constants betaq. Two montmorillonite samples with different cation exchange capacities, surface areas, and interlayer distances d001, Na-SWy, and Ca-Cheto, were saturated with methylene blue (MB) solutions with various ratios between monomers and higher aggregates of dye. The total amount of MB in the intercalated montmorillonite samples (MB-SWy and MB-Cheto) increases with increasing concentration of dye in water solutions, i.e., with increasing aggregates/monomers ratio of MB in water solution. In all intercalated montmorillonite samples with methylene blue except guest qth aggregate cations [MBqq+] low contents of Na+ (in MB-SWy) and Ca2+ (in MB-Cheto) cations were also determined. A very good positive correlation between the basal spacing d001 and the MB/montmorillonite molar ratio was revealed for saturated MB-montmorillonite samples. Structural analysis using a combination of diffraction data with molecular modeling revealed the differences in the interlayer arrangement of MB guests in MB-SWy and MB-Cheto intercalates. Also, fluorescence measurements showed the strong effect of the silicate layer charge on the spectroscopic behavior of MB guests intercalated in montmorillonite. Methylene blue exhibits a certain luminescence in MB-SWy samples with cation exchange capacity 0.80 meq g-1 and almost no luminescence in MB-Cheto samples with higher cation exchange capacity 1.50 meq g-1.

Differential expression of the mouse and human Thy-1 gene in embryonal carcinoma cells.

Mouse P19 embryonal carcinoma (EC) cells express on their surfaces a Thy-1 glycoprotein. The expression of Thy-1 at the mRNA and protein levels is down-regulated during differentiation induced by retinoic acid (RA). Thy-1 is also expressed in human NTERA-2 EC cells, but its expression is not down-regulated during RA-induced differentiation. As a first step towards understanding differential regulation of the mouse and human Thy-1 gene in EC cells, we have introduced genomic DNA fragments encompassing the mouse or human Thy-1 gene into NTERA-2 and P19-derived cells and analyzed surface properties of the transfectants. In the transient transfection assay, both mouse and human Thy-1 genes were expressed on cell surfaces at comparable levels. P19-derived stable transfectants exhibited great clonal variations in the expressions of the transfected Thy-1 gene products, which in part reflected copy numbers. There was no simple correlation between the expression of the transfected Thy-1 gene and two stem cell surface markers, TEC-1 and TEC-4. In the course of differentiation induced by RA several clones with a surface phenotype of EC cells exhibited a significant decrease in the expression of the transfected mouse Thy-1, whereas expression of the human Thy-1 was less efficiently down-regulated. The results suggest the presence of multiple cis- and trans-acting elements controlling expression of the mouse and human Thy-1 genes in P19 EC cells and their differentiated derivatives.

The Thy-1 glycoprotein is expressed in mouse embryonal carcinoma cells P19.

Thy-1 is a well characterized glycoprotein known to be variably expressed on the surface of different cell types. Serological analysis of a limited number of teratocarcinoma-derived cell lines suggested that mouse embryonal carcinoma cells do not express Thy-1 and that its expression is associated with the appearance of differentiated cells. In this report we show that monoclonal antibody 1aG4, recognizing Thy-1.2 epitope, binds specifically to P19 embryonal carcinoma cells and their undifferentiated subclones. A number of control experiments confirmed that 1aG4 antibody binds to the Thy-1.2 glycoprotein expressed on the surface of P19 embryonal carcinoma cells and not to the antigen expressed on differentiated derivatives of these cells or to a cross-reactive epitope. Transcriptional activity of the Thy-1 gene in undifferentiated P19 cells was shown by transfection experiments in which transfer of the Thy-1.1 gene into P19 cells resulted in stable expression of the Thy-1.1 antigen on the surface of recipient cells. Direct evidence for the presence of Thy 1 mRNA in P19 cells was obtained by Northern blot analysis with a Thy-1-specific cDNA probe. Treatment of P19 cells with retinoic acid resulted in a decrease in the expression of Thy-1 antigen which preceded changes in morphology of the cells. These data indicate that Thy-1 is a developmentally regulated surface marker of P19 embryonal carcinoma cells which is amenable to direct genetic analysis.

Retinoic acid-induced changes in differentiation-defective embryonal carcinoma RAC65 cells.

RAC65 is a mutant clone of mouse embryonal carcinoma cells, P19, which does not undergo terminal differentiation upon treatment with retinoic acid (RA). RAC65 cells express a truncated RA receptor alpha (RAR alpha) which, however, does not fully explain their defect. Here we show that RAC65 cells exhibit an additional defect in RAR alpha mRNA which may reflect a defect in RNA splicing. The parental and mutant cells also differ in their capacities to bind [3H]RA into nuclear fractions and in expression of cellular RA binding protein (CRABP) mRNA after treatment with RA. The combined data suggest that the defect in RAC65 RAR alpha results in reduced expression of the CRABP gene after RA treatment and, therefore, increased flow of RA into the nucleus.

Reduced phagocytic activity of polymorphonuclear leukocytes in alpha(1,3) fucosyltransferase VII-deficient mice.

Deficiencies in adhesion molecules or their counter-receptors in humans may have severe consequences as exemplified by leukocyte adhesion deficiency (LAD) I or II syndromes. Because such diseases occur with great rarity, animal models are valuable for studying the role of particular adhesion molecules and their natural ligands in immunity. We studied selected immune parameters and general health in mice with a defect in the sialyl-Lewis X antigen (selectin ligand) caused by disruption of the gene encoding alpha(1,3)fucosyltransferase VII (Fuc-TVII). Leukocytes from Fuc-TVII -/- and control mice were tested for adherence to cellophane membranes or polymer particles in vivo and phagocytic activity in vitro. While no difference in adherence was found, the number of neutrophil granulocytes in exudate induced by intraperitoneal injection of polymer beads was reduced in knock-out mice. Moreover, the phagocytic activity in Fuc-TVII -/- mice was significantly reduced. These animals have splenomegaly due to increased hematopoiesis and reduced weight but do not exhibit clinical signs of immunodeficiency. In conclusion, the lack of Fuc-TVII activity leads to several morphological and functional abnormalities without an impact on survival rate.

Risk of seizures after myelography: comparison of iohexol and metrizamide.

A parallel, double-blind, randomized study comparing iohexol and metrizamide--both 180 mg l/ml--in lumbar myelography was carried out in 60 consecutive patients. Eight to 15 ml of contrast medium were administered with the upper level at the middle thoracic column. A detailed neurologic examination was performed before and 24 hr after myelography. EEG recordings--evaluated visually and with fast Fourier transformation analysis--and somatosensory evoked responses were registered before, 6 hr after, and 24 hr after myelography. All patients were observed for adverse reactions for 24-48 hr. Iohexol did not produce any epileptiform activity but epileptiform activity was detected in five patients receiving metrizamide. Iohexol produced significantly less frequent and less severe EEG changes than did metrizamide both at visual evaluation (p less than .0025) and at fast Fourier transformation analysis (p less than .04). No significant changes occurred in the early components of the somatosensory evoked potentials after either contrast medium. Iohexol caused significantly (p less than .002) less frequent and less severe adverse reactions than did metrizamide. The neurologic examination revealed no changes of clinical importance with either contrast agent.

Elevation of the larynx on normal and abnormal cineradiogram.

The relationship between bolus volume (2.5, 5, 10 and 20 ml) and larynx elevation during swallowing was assessed in 10 non-dysphagic and 10 dysphagic individuals without pharyngeal dysfunction. Laryngeal elevation in different types of pharyngeal dysfunction was assessed in 60 non-dysphagic and 75 dysphagic patients. All subjects were examined with liquid barium and cineradiography at 50 frames/s. The laryngeal elevation was measured at the moment when the bolus reached the level of the valleculae and at maximum elevation. Elevation of the larynx, both the initial and maximal, was not influenced by sex, age or presence of dysphagia. Elevation of the larynx at the moment when the bolus reached the valleculae, when expressed in per cent of maximum elevation, was lower with 10 and 20 ml bolus volumes compared with 2.5 ml bolus volume (p < 0.05) in the 10 dysphagic individuals. Pharyngeal dysfunction was associated with significantly lower initial elevation of the larynx, at the moment when the bolus reached the level of the valleculae, although the maximal laryngeal elevation was normal. Initial elevation was 30% lower (p = 0.03) in patients with aspiration of bolus material into the trachea, 22% lower (p = 0.007) in those with defective closure of the laryngeal vestibule without aspiration and 16% lower (p = 0.06) in those with incoordination of the cricopharyngeal muscle compared with patients without dysfunction.

Location of the mandibular canal: comparison of macroscopic findings, conventional radiography, and computed tomography.

Four mandibular specimens were radiographically examined bilaterally to locate the mandibular canal. The following radiographic techniques were used: periapical and panoramic radiography, hypocycloidal tomography, and computed tomography (CT). The distance from the crest of the alveolar process to the superior border of the mandibular canal was measured in millimeters on all radiographs. The specimens were then sectioned, and the location of the mandibular canal (as measured on contact radiographs of the sections) was compared with measurements made on the other radiographs. The results showed that CT gave the most accurate position of the mandibular canal and is therefore probably the best method for preoperative planning of the implant surgery involving the area close to the mandibular canal.

Use of lumbar extension, slump test, physical and neurological examination in the evaluation of patients with suspected herniated nucleus pulposus. A prospective clinical study.

This prospective and consecutive study was designed to evaluate the validity of different clinical tests, e.g. lumbar extension in lying and slump test for patients with suspected herniated nucleus pulposus, in comparison with findings on computed tomography (CT) and/or magnetic resonance imaging (MRI) scan. There were 105 patients who were seen and examined by the senior author (for the sake of the study) at the Orthopaedic Physiotherapy Department, on an average of 5.5 days (range 0-21 days) before CT and/or MRI examination were carried out. There were 36 women and 69 men with an average age of 42.7 +/- 9.8 (range 19-64) years. According to the radiological findings on CT and/or MRI, the patients were divided into three groups: 52 patients with disc hernia, 41 patients with bulging discs and 12 patients without positive findings. The mean values with standard deviations of 25 variables of three diagnostic groups were studied. Multiple comparison adjustment according to Bonferroni showed significant differences for three variables that were of diagnostic value (lumbar range of motion for forward flexion, left side-bending in standing, and pain distribution during extension in standing). The agreement between clinical and radiological findings for type and level of diagnosis of disc herniation was accurate in 72 patients (69%). The diagnostic sensitivity for disc herniation was 82.6% and the specificity 54.7%.

Value of radiography in the management of possible fishbone ingestion.

A retrospective study was performed on 42 consecutive patients to examine the value of radiography in the management of complaints of fishbone ingestion. All patients underwent an oral examination followed by radiographic examination with plain films, barium swallows, barium and water swallows, and an endoscopic examination. All radiographs were reviewed by two unbiased, experienced radiologists. Of the 7 cases with fishbone found at endoscopic examination, only two (29%) bones were seen by the primary radiologist and 5 (71%) by the reviewing radiologists. Except for one case in which all three radiologists detected a fishbone that passed during the examination, and thereby was not found on endoscopy, no fishbones were found at the radiographic examination that were not seen on the endoscopic examination. Thus, radiography added no valuable information but only delayed the endoscopic examination with ensuing removal of the foreign body, which had to be performed regardless of the outcome of the radiographic examination. Therefore, we suggest that patients with a short history of complaints of fishbone ingestion, ie, 48 hours or less, should first be evaluated with oral and endoscopic examination.

Expression of human erythropoietin gene in the mammary gland of a transgenic mouse.

WAP is being recognized as the principal milk protein expressed in pregnant or lactating females of several mammalian species. Recently, it has been shown that the 6.3-kb 5' untranslated region of the rWAP gene is able to control, and almost completely restrict, the expression of the transgene into the mammary gland of the transgenic animal. We cloned the genomic fragment carrying the rWAP gene locus from the rabbit phage genomic library and used the 8.5-kb long 5' untranslated part of the rWAP gene to target the expression of hEPO, cloned from the human phage genomic library, into the mammary gland of the mouse. The vectors, carrying either the hEPO gene or the rWAP-hEPO hybrid gene, were injected into the mouse ova, and 12 transgenic animals were identified by PCR and Southern blot from the progeny of 168 tested littermates. Transgenic mice were viable, fertile and displayed a normal development. Recombinant human erythropoietin was produced in the milk of a transgenic mouse female at a secretion level of 5.3 mIU/ml, as detected by ELISA. Despite the low production of the transgenic glycoprotein in the milk we demonstrate that the hybrid gene can be expressed in the mammary gland of the host animal. Thus, WAP-based recombinant vectors, with additional optimizing modifications, can be useful for production of therapeutic proteins in the transgenic mammals.

[A method of using intraluminal splints in the treatment and prevention of recurrent ileus of the small intestine]. / Metoda intraluminálního dlahování v lécbe a prevenci recidivujícího ileu tenkého streva.

The authors present a group of 23 patients where splints were used in the loops of the small intestine. The group is divided into two sub-groups. The first one comprises patients where the splint was inserted because of relapsing ileus of the small intestine after previous surgical operations. The second sub-group comprises patients where this operation was performed either preventively or as part of a primary operation or as part of a reoperation called for by complications immediately preceding operation. The internal splint is inserted via jejunostomy and through the loops of the small intestine it is guided by means of a sutured Foley catheter which after proper insertion of the splint is left in the caecum. The authors emphasize the importance of effective decompression of the small intestine during the early postoperative period which is made possible by suction of the ileous contents through lateral openings of the inserted probe. After three years' work, using this method, the authors confirm that it gives good results.