Panniculectomy: an alternative approach to the revision of a difficult stoma.

AIM: We describe a modified abdominoplasty technique as an alternative approach to the revision of a difficult stoma. METHOD: A patient with a retracted colostomy secondary to change in abdominal wall contour following significant weight loss was treated with this technique. The patient had previous colostomy revision with marlex mesh insertion for combined parastomal and massive ventral hernia repair. A preoperatively marked crescent shaped left upper quadrant segment of skin and subcutaneous fat was excised and the defect was approximated in multiple layers. This shifted the stoma opening cephalad and eliminated the cutaneous crease that originally made it difficult to obtain a proper stoma seal. RESULTS: At one year follow up the patient was extremely satisfied with the results and was able to properly pouch the stoma. CONCLUSION: Modified abdominoplasty can be used as an alternative, low morbid approach in dealing with selected patients with difficult stoma problems.

Rat adult hepatocytes in primary pure and mixed monolayer culture. Comparison of the maintenance of mixed function oxidase and conjugation pathways of drug metabolism.

The stabilities of several drug oxidation and conjugation pathways in adult rat hepatocytes were investigated in two systems: a primary pure culture lasting 3 days and a primary mixed culture (hepatocytes co-cultured with epithelial cells) lasting 10 days. The cytochrome P450 content in hepatocytes drastically declined within 48 hr in both culture systems. Cytochrome P450-dependent mixed function oxidase was measured by the O-dealkylation of ethoxyresorufin (EROD) and of pentoxyresorufin (PROD). UPD-glucuronosyl transferase (UDP-GT) activity was measured using 1-naphthol and morphine as substrates. In both culture systems, the activities of enzymes belonging to the 3-methylcholanthrene-inducible family, namely EROD and 1-naphthol UDP-GT, were much better maintained than those of PROD and morphine UDP-GT, which belong to the phenobarbitone-inducible family: in pure cultures, EROD and 1-naphthol UDP-GT activities declined to 60% of initial values within 3 days; in mixed cultures, EROD activity was stable throughout the 10 day culture period, whereas that of 1-naphthol UDP-GT was stable until day 4 but had declined to 70% of the initial value by day 8. In contrast, PROD and morphine UDP-GT activities declined to approx. 30% of the initial values within 2 days in both culture systems, and had dropped to approx. 10% of the initial value within 8 days in mixed culture. Reduced glutathione (GSH) levels fluctuated, but remained high throughout culture. GSH conjugation declined to 40% of initial values within 3 days in pure culture, whereas it remained relatively constant in mixed culture. Comparison of these two culture systems therefore showed that although the inclusion of epithelial cells did prolong hepatocyte viability, there was a change in relative enzyme activities in both systems, suggesting a shift towards a more de-differentiated drug metabolism pattern.

Children's self-report of postoperative pain intensity and treatment threshold: determining the adequacy of medication.

OBJECTIVE: Many studies have shown indirectly that children are undermedicated for postoperative pain. In this study, we used a pain self-report scale to examine this more directly. METHODS: We performed a survey with 63 children who were postoperative from minor, uncomplicated surgery. Using the self-report scale, we determined the pain intensity at time of interview, the worst pain experienced postoperatively, and the intensity of pain that the subject felt to warrant pharmacologic intervention (the "treatment threshold"). A subgroup of 48 children was asked to indicate on the scale the intensities that represented mild, moderate, and severe pain. RESULTS: Mean (SD) pain at time of interview was 1.9 (1.7) on the 0-6 scale. Mean worst postoperative pain was 3.8 (1.8). The mean for treatment threshold was 3.2 (1.8). We found gender differences in regard to the judgments about the intensities representing mild, moderate, and severe pain, with girls rating these lower than did boys. Twenty-five percent of subjects reported pain that was mild, 29% reported moderate pain, and 46% reported severe pain. CONCLUSIONS: We found that 51% of subjects were undermedicated for postoperative pain, being required to suffer pain that was above their treatment threshold. By determining each subject's treatment threshold and estimate of moderate pain, we have better defined the intensity at which pain becomes clinically significant.

Direct observation of the ponderomotive force effects in short-scale-length laser plasmas by frequency-domain interferometry.

We report on single-shot frequency-domain interferometric measurements showing space- and time-resolved ponderomotive electron density profile steepening of a short-scale-length ultraintense laser-produced plasma. The density gradient scale length is varied by applying a time-delayed laser prepulse. The measured absolute position of the critical density surface is found to be in agreement with one-dimensional hydrodynamic simulations for the range of scale lengths studied.

Time-resolved plasma spectroscopy of thin foils heated by a relativistic-intensity short-pulse laser.

Time-resolved K-shell x-ray spectra are recorded from sub-100 nm aluminum foils irradiated by 150-fs laser pulses at relativistic intensities of Ilambda(2)=2 x 10(18) W microm(2)/cm(2). The thermal penetration depth is greater than the foil thickness in these targets so that uniform heating takes place at constant density before hydrodynamic motion occurs. The high-contrast, high-intensity laser pulse, broad spectral band, and short time resolution utilized in this experiment permit a simplified interpretation of the dynamical evolution of the radiating matter. The observed spectrum displays two distinct phases. At early time, < or =500 fs after detecting target emission, a broad quasicontinuous spectral feature with strong satellite emission from multiply excited levels is seen. At a later time, the He-like resonance line emission is dominant. The time-integrated data is in accord with previous studies with time resolution greater than 1 ps. The early time satellite emission is shown to be a signature of an initial large area, high density, low-temperature plasma created in the foil by fast electrons accelerated by the intense radiation field in the laser spot. We conclude that, because of this early time phenomenon and contrary to previous predictions, a short, high-intensity laser pulse incident on a thin foil does not create a uniform hot and dense plasma. The heating mechanism has been studied as a function of foil thickness, laser pulse length, and intensity. In addition, the spectra are found to be in broad agreement with a hydrodynamic expansion code postprocessed by a collisional-radiative model based on superconfiguration average rates and on the unresolved transition array formalism.

X-ray emission of a xenon gas jet plasma diagnosed with Thomson scattering.

We present the results of a benchmark experiment aimed at validating recent calculation techniques for the emission properties of medium and high-Z multicharged ions in hot plasmas. We use space- and time-resolved M-shell x-ray spectroscopy of a laser-produced gas jet xenon plasma as a primary diagnostic of the ionization balance dynamics. We perform measurements of the electron temperature, electron density, and average charge state by recording simultaneous spectra of ion acoustic and electron plasma wave Thomson scattering. A comparison of the experimental x-ray spectra with calculations performed ab initio with a non-local-thermodynamic-equilibrium collisional-radiative model based on the superconfiguration formalism, using the measured plasma parameters, is presented and discussed.

Complete characterization of a plasma mirror for the production of high-contrast ultraintense laser pulses.

Improving the temporal contrast of ultrashort and ultraintense laser pulses is a major technical issue for high-field experiments. This can be achieved using a so-called "plasma mirror." We present a detailed experimental and theoretical study of the plasma mirror that allows us to quantitatively assess the performances of this system. Our experimental results include time-resolved measurements of the plasma mirror reflectivity, and of the phase distortions it induces on the reflected beam. Using an antireflection coated plate as a target, an improvement of the contrast ratio by more than two orders of magnitude can be achieved with a single plasma mirror. We demonstrate that this system is very robust against changes in the pulse fluence and imperfections of the beam spatial profile, which is essential for applications.

L-band x-ray absorption of radiatively heated nickel.

Absorption of L-M and L-N transitions of nickel has been measured using point projection spectroscopy. The x-ray radiation from laser-irradiated gold cavities was used to heat volumetrically nickel foils "tamped with carbon" up to 20 eV. Experimental spectra have been analyzed with calculations based on the spin-orbit split arrays statistical approach and performed for each ionic species Ni5+ to Ni11+. Using a least-squares fit, this method provides an ion distribution broader than at local thermodynamic equilibrium, which is explained by spatial and temporal temperature gradients. A major improvement in the simulation of the absolute value of transmission is obtained with a resolved transition array statistical calculation that reproduces the experimental spectrum with the nominal areal mass density by taking into account the saturation of narrow lines.

Observation of collisionless shocks in laser-plasma experiments.

The propagation in a rarefied plasma (n(e) < or approximately 10(15) cm(-3)) of collisionless shock waves and ion-acoustic solitons, excited following the interaction of a long (tauL approximately 470 ps) and intense (I approximately 10(15) W cm(-2)) laser pulse with solid targets, has been investigated via proton probing techniques. The shocks' structures and related electric field distributions were reconstructed with high spatial and temporal resolution. The experimental results were interpreted within the framework of the nonlinear wave description based on the Korteweg-de Vries-Burgers equation.

Revisiting nonlocal electron-energy transport in inertial-fusion conditions.

Correct modeling of the electron-energy transport is essential for inertial confinement fusion target design. Various transport models have been proposed in order to extend the validity of a hydrodynamical description into weakly collisional regimes, taking into account the nonlocality of the electron transport combined with the effects of self-generated magnetic fields. We have carried out new experiments designed to be highly sensitive to the modeling of the heat flow on the Ligne d'Intégration Laser facility, the prototype of the Laser Megajoule. We show that two-dimensional hydrodynamic simulations correctly reproduce the experimental results only if they include both the nonlocal transport and magnetic fields.

Picosecond time-resolved X-ray absorption spectroscopy of ultrafast aluminum plasmas.

We have used point-projection K-shell absorption spectroscopy to infer the ionization and recombination dynamics of transient aluminum plasmas. Two femtosecond beams of the 100 TW laser at the LULI facility were used to produce an aluminum plasma on a thin aluminum foil (83 or 50 nm), and a picosecond x-ray backlighter source. The short-pulse backlighter probed the aluminum plasma at different times by adjusting the delay between the two femtosecond driving beams. Absorption x-ray spectra at early times are characteristic of a dense and rather homogeneous plasma. Collisional-radiative atomic physics coupled with hydrodynamic simulations reproduce fairly well the measured average ionization as a function of time.

Comparison of laser ion acceleration from the front and rear surfaces of thin foils.

The comparative efficiency and beam characteristics of high-energy ions generated by high-intensity short-pulse lasers (approximately 1-6 x 10(19) W/cm2) from both the front and rear surfaces of thin metal foils have been measured under identical conditions. Using direct beam measurements and nuclear activation techniques, we find that rear-surface acceleration produces higher energy particles with smaller divergence and a higher efficiency than front-surface acceleration. Our observations are well reproduced by realistic particle-in-cell simulations, and we predict optimal criteria for future applications.

Single-shot spectral interferometry with chirped pulses.

We present a method for obtaining time-resolved measurements of the amplitude modulation and the phase shift of a chirped probe pulse interacting with a femtosecond-laser-produced plasma. Based on spectral interferometry, the technique allows for single-shot measurements and keeps the temporal resolution associated with the full bandwidth of the probe pulse. We demonstrate the efficiency of this technique by probing femtosecond-laser breakdown of plastic targets.

Study of the ion-distribution dynamics of an aluminum laser-produced plasma with picosecond resolution.

The ion-distribution dynamics of an expanding aluminum plasma produced by a nanosecond laser pulse at moderate intensity (10(13) W cm(-2)) is studied by point-projection x-ray absorption spectroscopy with unprecedented, picosecond, time resolution. We show that the ionic populations measured as a function of distance to the target and at different probing times differ markedly from those predicted by widely accepted collisional radiative models coupled to hydrodynamic simulations. We discuss the effects of radiation, conduction, and expansion cooling on the spatiotemporal ionic distribution evolution.

Heating of thin foils with a relativistic-intensity short-pulse laser.

K-shell x-ray spectroscopy of sub-100 nm Al foils irradiated by high contrast, spatially uniform, 150 fs, Ilambda (2)=2 x 10(18) W microm(2)/cm(2), laser pulses is obtained with 500 fs time resolution. Two distinct phases occur: At /=500 fs the resonance transitions dominate. Initial satellites arise from a large area, high density, low temperature (approximately 100 eV) plasma created by fast electrons. Thus, contrary to predictions, a short, high intensity laser incident on a thin foil does not create a uniform, hot dense plasma.

Frequency-domain interferometer for measuring the phase and amplitude of a femtosecond pulse probing a laser-produced plasma.

A frequency-domain interferometer for probing the variations of the dielectric constant of a plasma with sub-100- fs temporal resolution and lambda/2000 phase resolution is described. Imaging the plasma on the entrance slit of a spectrograph provides spatial resolution along a diameter of the focal spot. The technique is used to map out the expansion of the critical density surface of a femtosecond laser-produced plasma with subnanometer spatial resolution along the laser axis.

Metabolic activation of the nitroaromatic antiandrogen flutamide by rat and human cytochromes P-450, including forms belonging to the 3A and 1A subfamilies.

The in vitro metabolic activation of flutamide, a nitroaromatic antiandrogen which produces hepatitis in a few recipients, was first studied with male rat liver microsomes. There was no electron spin resonance evidence for the reduction of flutamide by reduced nicotinamide adenine dinucleotide phosphate (NADPH)-cytochrome P-450 reductase into a nitro anion free radical. In contrast, flutamide was oxidatively transformed by cytochrome P-450 into reactive metabolite(s) that covalently bound to microsomal proteins. Covalent binding required oxygen and NADPH, and was decreased by the nucleophile glutathione and by the cytochrome P-450 inhibitors SKF 525-A, piperonyl butoxide and troleandomycin (an inhibitor of the cytochrome P-450 3A subfamily). Covalent binding was increased markedly by pretreatment with dexamethasone (an inducer of the cytochrome P-450 3A subfamily) and moderately by pretreatment with beta-naphthoflavone (an inducer of the 1A family). Covalent binding was immunoinhibited markedly by anticytochrome P-450 3A immunoglobulin G and moderately by anticytochrome P-450 1A immunoglobulin G. Covalent binding was much lower with liver microsomes from female rats (not expressing P-450 3A2). Covalent binding of flutamide also occurred with human liver microsomes (where it was inhibited by troleandomycin), and with yeast microsomes expressing human liver cytochromes P-450 1A1, 1A2 or 3A4. We concluded that flutamide was oxidatively transformed into chemically reactive metabolite(s) by rat and human cytochromes P-450, including forms belonging to the 3A and 1A subfamilies.

Comparison of measured and calculated X-ray and hot-electron production in short-pulse laser-solid interactions at moderate intensities.

Ultrashort pulse laser-solid interaction experiments with 4x10(16) W/cm(2),120 fs, 45 degrees incidence angle, p-polarized pulses are theoretically analyzed with the help of 1(1/2)-dimensional (1(1/2) D) particle-in-cell (PIC) simulations. The laser impinges upon preformed plasmas with a precisely controlled density-gradient scale-length. PIC electron distribution functions are used as an input to 3D Monte Carlo simulations to interpret measured electron distributions and Kalpha radiation emission. Satisfactory agreement between the experimental and simulation results is obtained for the measured absorption coefficient, the energy distribution of the back-scattered hot electrons, the hot-electron temperature in the bulk of the target, and the Kalpha yield, when the preplasma scale-length is varied.

Hot-electron distribution functions in a subpicosecond laser interaction with solid targets of varying initial gradient scale lengths.

We have studied the distribution function of the hot electrons produced during the interaction of a 120-fs, 60-mJ, 800-nm wavelength and a p-polarized laser pulse with bilayered Al/Fe targets. The main pulse interacts with a preformed plasma, obtained with a controlled prepulse, whose density gradient scale length has been measured. The electron distribution function is characterized by means of the Kalpha emission of the two materials of the target as a function of the Al-layer thickness. The low-energy region (<50 keV) of the hot-electron distribution function shows no dependency in shape on the gradient scale length, but only a variation in the total number of the generated electrons. The comparison between the experimental results and the particle-in-cell and Monte Carlo calculations of the electron distribution function and the Kalpha emission is gratifying.