Two-photon and two-photon-assisted slow light.

We show that light pulses propagating in two-photon absorbing systems may present time delays like slow light produced via coherent population oscillations in one-photon interactions. Two regimes are numerically studied for a simplified two-level system: (a) a light pulse at frequency ω/2 undergoes two-photon absorption (TPA) and is delayed by the absorbing system (two-photon slow light) and (b) a light pulse at frequency ω is delayed in a system prepared by TPA of a light pulse at frequency ω/2 (two-photon-assisted slow light). The study carried out in solutions of dyes and dendrites shows significant delays, low distortion, and good transmission for easily reachable experimental conditions. The working principle can be applied to other media and can be used in telecommunications technology.

Generation of femtosecond paraxial beams with arbitrary spatial distribution.

We present an approach to generate paraxial laser beams with arbitrary spatial distribution in the femtosecond time regime. The proposed technique is based upon a pair of volume phase holographic gratings working in parallel arrangement. It exploits the spatial coherence properties of the incoming laser beam in a compact and robust setup that mitigates angular and spatial chirp. The gratings were recorded in a photopolymerizable glass with a high optical damage threshold and a large optical throughput. Setup performance is studied and experimentally demonstrated by generating Laguerre-Gaussian femtosecond pulses.

Interpretation of colloidal dyeing of polyester fabrics pretreated with ethyl xanthogenate in terms of zeta potential and surface free energy balance.

Data are presented on the adsorption of the colloidal dye Disperse Blue 3 onto polyester fabric (Dacron 54, Stile 777), the fabric being pretreated with different amounts of the surfactant potassium ethyl xanthogenate (PEX). This study has been made by means of both the evolution of the zeta potential of the fiber/dye interface and the behaviour of the surface free energy components of the above systems. The kinetics of adsorption of the process of dyeing, using 10(-4) M of PEX in the pretreatment of the fabric, shows that increasing temperature of adsorption decrease the amount of colloidal dye adsorbed onto the fabric. This fact shows that the principal mechanism involved in this adsorption process is physical in nature. The adsorption isotherms of the colloidal dye onto polyester pretreated with different amounts of PEX, shows that the adsorption of the dye is favored with the increase in the concentration of the surfactant used in the pretreatment. This fact shows that the pretreatment with PEX is a very interesting aspect of interest in textile industry. The zeta potential of the system fabric/surfactant shows that this parameter is negative (about -25 mV) for the untreated fiber and decreases in absolute value for increasing concentration of the surfactant on the fiber, the value of the zeta potential of the system being -5 mV for 10(-2) M of PEX. This behavior can be explained for the chemical reaction nucleophilic attack between the carboxyl groups of polyester, ionized at pH 8, and the thiocarbonyl group of the xanthogenate ion. On the other hand, the zeta potential of the system polyester pretreated with PEX/Disperse Blue 3 at increasing concentrations of the surfactant and the dye shows that this parameter increases its negative value strongly with increasing concentration of the surfactant used in the treatment. This can be explained for the hydrogen bonds between the hydroxy groups of the dye and the S- ions of the thiocarbonyl group of the surfactant preadsorbed onto the fiber.

Simultaneous determination of paracetamol and caffeine by flow injection-solid phase spectrometry using C18 silica gel as a sensing support.

A continuous and simple UV-photometric flow-through biparameter-sensing device has been developed for the simultaneous determination of paracetamol and caffeine at 275 nm. The sensor is based on temporary sequentiation in the arrival of the analytes to the sensing zone by on-line separation using C18 bonded phase beads (the same as that used in the sensing zone) placed into a minicolumn just before the flow cell. The sample containing these compounds is injected into the carrier solution; paracetamol is determined first because it passes through the minicolumn, while caffeine is strongly retained in it. Then, caffeine is conveniently eluted from the precolumn and develops its transitory signal. Using 200 microl of a sample and deionized water as a carrier, the analytical signal showed a very good linearity in the ranges of 10-160 microg ml(-1) and 3.5-50 microg ml(-1) with detection limits of 0.75 and 0.56 microg ml(-1) for paracetamol and caffeine, respectively. If deionized water with the pH adjusted at 12 was used as a carrier solution, these parameters were 25-400 and 4-55 microg ml(-1) with 2.0 and 0.50 microg ml(-1) as the detection limits, respectively. The biparameter optosensor was satisfactorily applied to the simultaneous determination of these two analytes in pharmaceuticals.

Electrokinetic and thermodynamic analysis of the adsorption process of N-cetylpyridinium chloride on polyester fabric.

An electrokinetic and thermodynamic analysis of the adsorption process of N-cetylpyridinium chloride on polyester fabric is described in the present work. The electrokinetic study was performed by means of electrophoretic mobility measurements of the polyester-surfactant system. The most significant result is the increase in electrokinetic potential, zeta, toward more positive values as the surfactant concentration in the dispersion medium is raised. Given the molecular structure of N-cetylpyridinium chloride (N-CP-Cl), which contains a pyridinium group, positively charged, it is feasible that such increase in |zeta| is due to the electrostatic attraction between the carboxyl groups of polyester, ionized at pH 8.5, and the pyridinium group of the surfactant. The uptake of N-CP-Cl by the fiber is experimentally determined at four temperatures: the strong increase in the amount of the surfactant incorporated onto the fiber as the initial concentration of N-CP-Cl is larger shows that the electrostatic attraction between the fiber and the surfactant is the main mechanism of the adsorption of the surfactant onto the fiber. The obtained data on the kinetics and thermodynamics of adsorption of N-cetylpyridinium chloride onto the polyester, standard free energy, enthalpy, and entropy related to the process of adsorption are in accordance with our hypothesis on the mechanisms of adsorption. From a different point of view, the efficient coverage of polyester by N-CP-Cl is also demonstrated by the changes experienced by the surface free energy of polyester upon treatment with N-CP-Cl.

Electrokinetic and Thermodynamic Analysis of the Dyeing Process of Polyamide Fabric with Mordant Black 17.

An electrokinetic and thermodynamic analysis of the dyeing process of polyamide 6.6 (nylon 6.6) by the dye Palatine chrome black (PCB) is described in the present work. The electrokinetic study was performed by means of electrophoretic mobility measurements on bare and dyed fiber. The most significant result is the increase in electrokinetic potential, zeta, toward more negative values as the dye concentration in the dispersion medium is raised. Given the molecular structure of PCB, which contains a sulfonate group per molecule, it is feasible that such increase in |zeta| is due to the adsorption of the negatively charged, dissociated dye entities. The uptake of PCB by the fiber is experimentally determined at two temperatures: the strong increase in the amount of dye incorporated into the fiber as the initial concentration of PCB is larger, and also the fact that higher temperatures favor the dyeing process is an indication of the existence of strong interactions between both interfaces. From a different point of view, the efficient coverage of Nylon by PCB is also demonstrated by the changes experienced by the surface free energy of Nylon upon treatment with PCB. Copyright 2001 Academic Press.

Development of the Abbott AxSYM Free PSA assay: performance characteristics and preliminary clinical evaluation.

The AxSYM Free PSA assay was demonstrated to have good analytical sensitivity and reproducibility. The F/T ratio determinations for 385 men tested during the Prostate Awareness Week who had biopsies due to an elevated total PSA value and/or a suspicious DRE demonstrated that the percentage of free PSA was lower in patients found to have prostate cancer than those that were biopsy negative for the overall group and for all patient categories examined. The optimal strategy for combining PSA values, F/T ratios, DRE and other clinical and diagnostic parameters to improve the early detection of prostate cancer requires additional clinical studies.

Determination of the "reflex range" and appropriate cutpoints for percent free prostate-specific antigen in 413 men referred for prostatic evaluation using the AxSYM system.

OBJECTIVES: Prostate-specific antigen (PSA) exists in the serum in two clinically important molecular forms: free PSA and PSA complexed to alpha 1-antichymotrypsin. Total PSA approximates the sum of the free and complexed forms. Preliminary investigations have illustrated the potential benefits of using percent free PSA to enhance the clinical utility of PSA in distinguishing benign prostate disease from prostate cancer. The current study defines the optimal range of total PSA for measuring percent free PSA (reflex range) and generates appropriate cutpoints for percent free PSA within this range. METHODS: A total of 413 patients, 225 (54%) with benign prostate disease (mean age, 67 years) and 188 (46%) with prostate cancer (mean age, 66 years), who had PSA values between 2.0 and 20.0 ng/mL participated in the investigation. All patients underwent a sextant biopsy to establish the diagnosis. The serum specimens were assayed with the AxSYM PSA assay (total PSA) and AxSYM Free PSA assay (Abbott Laboratories; Abbott Park, IL). Percent free PSA was calculated for all patients. Receiver operating characteristic (ROC) curves were generated for various ranges of total PSA to determine the reflex range that maximized the increase in sensitivity and specificity of percent free PSA over total PSA. Within the optimal range, the ROC curves were utilized to generate cutpoints for percent free PSA to be used in clinical practice. RESULTS: The appropriate reflex range for the utility of percent free PSA was 3.0 to 10.0 ng/mL. The appropriate cutpoint for percent free PSA when the total PSA value was 3.0 to 4.0 ng/mL to achieve 90% sensitivity for the detection of prostate cancer was 0.19. This approach resulted in a biopsy rate of 73% and a cancer detection rate of 44% in men with a total PSA value between 3.0 and 4.0 ng/mL. The appropriate cutpoint for percent free PSA when the total PSA value was 4.1 to 10.0 ng/mL to ensure 95% sensitivity for detection of prostate cancer was 0.24. Within the range of 4.1 to 10.0 ng/mL, this approach resulted in 13% fewer negative biopsies and failure to detect 5% of the cancers. CONCLUSIONS: Percent free PSA should be utilized in patients with a total serum PSA value between 3.0 and 10.0 ng/mL. In patients with a total PSA value between 3.0 and 4.0 ng/mL, percent free PSA enhanced the detection of prostate cancer (improving sensitivity). In patients with a total PSA concentration ranging from 4.1 to 10.0 ng/mL, negative biopsies were eliminated (improving specificity).

Pyrazino[2,3-c]-1,2,6-thiadiazine 2,2-dioxides: a new family of widely tunable, acid-base dye lasers.

Laser emission of different acid-base species of pyrazino[2,3-c]-1,2,6-thiadiazine 2,2-dioxides has been observed. Lasing energy efficiency and spectral and temporal characteristics in dimethyl sulfoxide (DMSO) and acetonitrile, pumped with a N(2) laser (3.7 ns, 0.5 mJ/pulse) in two different two-mirror resonators, have been measured. A very wide tuning range (110 nm) has been determined in the most efficient species, and the triplet-state influence on the species' laser emission was investigated. No photochemical degradation was detected. The deprotonation observed in DMSO in previous spectroscopic measurements did not contribute measurably to laser emission.

Laser-threshold calculations for lasing of acidbase species in proton-transfer media.

An estimate of laser thresholds for both the acid and the base species of dyes undergoing proton-transfer reactions is given. It is seen how the excited-state kinetic constants and proton concentration affect the laser threshold of each species. Calculations of laser threshold for simultaneous lasing of both species are also carried out. The latter is applied to the simultaneous lasing of neutral and acid forms of the 4-Amino-1,7-dimethylpyrido[2,3-c]-1,2,6-thiadiazine 2,2-dioxide in acetonitrile and corroborates the experimental results.

How effective is outdoor-based training in improving management behaviors: a health care application.

This study explores the impact of an outdoor-based training program on management behaviors at a major regional medical center. Sixteen managers attended a combination high and low "ropes" training course given in three phases over a one-year period. This program was designed to increase trust and improve communications within the hospital. A number of group measures from previous research are examined, including trust, group awareness, group effectiveness, self-esteem, and bonding of the group. Empirical evaluations of these items were done prior to training and three months after training. Scales that tapped both interpersonal relations and communications were developed from interviews with previous participants, and were evaluated prior to training and six months after training. Behavioral observations were also used to evaluate the effectiveness of the program. Results indicate that the outdoor-based training program was effective in improving certain key behaviors within the group. While stressing the need for future research, this study strongly supports the further use of outdoor-based training programs in health care settings.

Envelope mirror: a new concept of focusing reflecting optics.

A mathematical method of finding a surface that focuses a finite size source has been developed. We show its use solving two particularly simple cases in which we compare the energy efficiency of the new surface to the classical elliptical cavities. In the examples given, the new designs are frequently advantageous.

[Plasma histamine level in the pulmonary vein immediately following the bolus injection of high-dose heparin in the right atrium. A study carried out during aortocoronary bypass surgery]. / Plasmahistaminspiegel in der Vena pulmonalis unmittelbar nach Bolusinjektion einer hohen Heparindosis in den rechten Vorhof. Eine Untersuchung während aortokoronaren Bypass-Operationen.

This study demonstrates a very rapid and short-lasting elevation of plasma histamine concentrations after heparin injection prior to cannulation for extracorporeal circulation during cardiac surgery. Plasma histamine concentrations increased significantly for less than 1 min following bolus injection of heparin into the right atrium. Blood samples were taken from the distal pulmonary vascular bed, i.e. the pulmonary vein. The design of the study enabled us to observe the development of plasma histamine concentrations within very short time intervals and to detect the high peak plasma histamine concentration that may occur, primarily in the pulmonary outstream vessels. Therefore, the histamine found here could originate from intrathoracically located mast cells. It is more likely, however, that the histamine was administered together with the heparin in complex binding, due to purification problems. The amount of histamine found in this study was sufficient to produce mild to severe circulatory effects in all patients receiving a high dose of heparin.

Expression of the gene for preproatriopeptin in the central nervous system of the rat.

Atriopeptin (AP) is a peptide hormone synthesized and secreted by the atria of the heart that participates in the regulation of fluid and electrolyte balance. AP-like materials have been detected immunologically in neurons in the central nervous system of the rat. In this study, we have used a solution hybridization-nuclease protection assay to determine whether the brain of the rat contains RNA coding preproatriopeptin, the atrial biosynthetic precursor of AP, and to study the regional distribution of preproatriopeptin mRNA in the brain. We have found that the brain contains mRNA identical to the atrial messenger RNA for preproatriopeptin. AP mRNA is differentially distributed in the brain; the highest concentration was found in the hypothalamus, followed by the cortex and septum, hippocampus, midbrain, spinal cord, olfactory bulb, striatum, and pons and medulla. Very low levels were found in the cerebellum, while no detectable AP mRNA was observed in retina, anterior pituitary, or rat liver. The presence of AP mRNA in the brain demonstrates that neurons have the capacity to synthesize preproatriopeptin identical to that produced in the heart. Bioactive peptides produced from this precursor may be endogenous central neuromodulators as well as a circulating hormone.

Membrane-murein attachment at the leading edge of the division septum: a second membrane-murein structure associated with morphogenesis of the gram-negative bacterial division septum.

Electron microscopy of plasmolyzed cells of Salmonella typhimurium revealed a continuous zone of membrane-murein attachment at the leading edge of the division septum at all stages of septal invagination. The membrane-murein attachment site had a characteristic ultrastructural appearance and remained as a bacterial birth scar at the new pole of each of the two daughter cells after cell separation. The continuous zone of membrane-murein attachment at the leading septal edge represents the second organelle based on a topologically ordered domain of membrane-murein adhesion to be described at the site of cell division.

[Hemodynamic changes following heparin injection in aortocoronary bypass operations. Sequela of histamine liberation]. / Hämodynamische Veränderungen nach Heparininjektion bei aortokoronaren Bypassoperationen. Folge einer Histaminfreisetzung.

Prior to cannulation for extracorporeal circulation, 375 Units of Heparin/kg body weight were applied to 22 patients (group 1) into the right atrium. A few minutes later, characteristic changes in haemodynamics were observed. In a second group of 10 patients, the same amount of heparin was injected directly into the ascending aorta to avoid the passage of an undiluted bolus of heparin through the pulmonary vessels. In this group, the haemodynamic effects of heparin seemed to be slightly weakened. Immediately after administration of heparin, a significant increase of plasma histamine was measured (in 12 patients of group 1). This might be the main reason for the heparin-dependent haemodynamic effects.

Blood vessel invasion and axillary lymph node involvement as prognostic indicators for human breast cancer.

Blood vessel invasion and axillary lymph node involvement were examined in 175 breast cancer patients. The incidence of blood vessel invasion was 35%. The presence of blood vessel invasion was highly associated with early disease recurrence. The association of poor prognosis with blood vessel invasion was independent of clinical stage, menopausal status, node status, tumor size, or postsurgical treatment. Those patients with blood vessel invasion and two or more positive nodes were at extremely high risk for early recurrence (70% recurrence by two years compared with 15% recurrence in the remainder of the patients). Thus, blood vessel invasion is a useful indicator of early recurrence in patients with primary breast cancer and, in combination with node status, is a prognostic indicator with high discriminatory power.