6,510 research outputs found
Gender Differences In Responses To Hypothetical Business Ethical Dilemmas By Business Undergraduates
Business leaders are often failing to display ethical behavior in business decisions. This paper examines the gender differences found in undergraduate business students when faced with ethical decision making dilemmas
The treatment of severely comminuted intra-articular fractures of the distal radius
Comminuted fractures of the distal end of the
radius are caused by high-energy trauma and present as
shear and impacted fractures of the articular surface of the
distal radius with displacement of the fragments. The force
of the impact and the position of the hand and carpal bone
determine the pattern of articular fragmentation and their
displacement and the amount and the extent of frequent
concommitant ligament and carpal bone injury. The result
of the osseous lesion in comminuted fractures was termed
"pilon radiale", which emphasizes the amount of damage
to the distal radius and the difficulties to be expected in
restoring the articular congruity. Besides this the additional
injury, either strain of disruption of the ligaments and
the displacement of the carpus and/ or the triangular fibrocartilage
complex will equally influence the functional
outcome. This review will expand on the relevant anatomy,
correct classification and diagnosis of the fracture, diagnostic
tools and operative treatment options. Current treatment
concepts are analysed with regard to actual literature
using the tools of evidence based medicine criteria. A new
classification of severely comminuted distal radius fractures
is proposed using CT data of 250 complex intraarticular
radius fractures. Finally a standardized treatment protocol
using external fixation in combination with minimal
invasive internal osteosynthesis is described
Sonochemical Degradation of Perfluorooctane Sulfonate (PFOS) and Perfluorooctanoate (PFOA) in Landfill Groundwater: Environmental Matrix Effects
Perfluorinated chemicals such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are environmentally persistent and recalcitrant to most conventional chemical and microbial treatment technologies. In this paper, we show that sonolysis is able to decompose PFOS and PFOA present in groundwater beneath a landfill. However, the pseudo first-order rate constant for the sonochemical degradation in the landfill groundwater is reduced by 61 and 56% relative to MilliQ water for PFOS and PFOA, respectively, primarily due to the presence of other organic constituents. In this study, we evaluate the effect of various organic compounds on the sonochemical decomposition rates of PFOS and PFOA. Organic components in environmental matrices may reduce the sonochemical degradation rates of PFOS and PFOA by competitive adsorption onto the bubble−water interface or by lowering the average interfacial temperatures during transient bubble collapse events. The effect of individual organic compounds depends on the Langmuir adsorption constant, the Henry’s law constant, the specific heat capacity, and the overall endothermic heat of dissociation. Volatile organic compounds (VOCs) are identified as the primary cause of the sonochemical rate reduction for PFOS and PFOA in landfill groundwater, whereas the effect of dissolved natural organic matter (DOM) is not significant. Finally, a combined process of ozonation and sonolysis is shown to substantially recover the rate loss for PFOS and PFOA in landfill groundwater
Job Shadowing Experiences as a Teaching Tool: A New Twist on a Tried and True Technique
This article reports an innovative twist on the use of the job shadowing experience as a means not only to provide real-world exposure for the student, but also as a way to generate real-time data from the professionals to be utilized as a basis for class discussion. Reaction from both students and professionals has been overwhelmingly positive
Enhancement of perfluorooctanoate and perfluorooctanesulfonate activity at acoustic cavitation bubble interfaces
Acoustic cavitation driven by ultrasonic irradiation decomposes and mineralizes the recalcitrant perfluorinated surfactants perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA). Pyrolytic cleavage of the ionic headgroup is the rate-determining step. In this study, we examine the sonochemical adsorption of PFOX, where X = S for PFOS and A for PFOA, by determining kinetic order and absolute rates over an initial PFOX concentration range of 20 nM to 200 μM. Sonochemical PFOX kinetics transition from pseudo-first-order at low initial concentrations, [PFOX]_i 40 μM, as the bubble interface sites are saturated. At PFOX concentrations below 100 μM, concentration-dependent rates were modeled with Langmuir−Hinshelwood (LH) kinetics. Empirically determined rate maximums, V_(Max)^(−PFOA) = 2230 ± 560 nM min^−1 and V_(Max)^(−PFOS) = 230 ± 60 nM min^−1, were used in the LH model, and sonochemical surface activities were estimated to be K_(Sono)^(PFOS) = 120000 M^−1 and K_(Sono)^(PFOA) = 28500 M^−1, 60 and 80 times greater than equilibrium surface activities, K_(Eq)^(PFOS) and K_(Eq)^(PFOA). These results suggest enhanced sonochemical degradation rates for PFOX when the bubble interface is undersaturated. The present results are compared to previously reported sonochemical kinetics of nonvolatile surfactants
Reductive defluorination of aqueous perfluorinated alkyl surfactants : effects of ionic headgroup and chain length
Perfluorinated chemicals (PFCs) are distributed throughout the environment. In the case of perfluorinated alkyl carboxylates and sulfonates, they can be classified as persistent organic pollutants since they are resistant to environmentally relevant reduction, oxidation, and hydrolytic processes. With this in mind, we report on the reductive defluorination of perfluorobutanoate, PFBA (C_3F_7CO_2−), perfluorohexanoate, PFHA (C_5F_(11)CO_2−), perfluorooctanoate, PFOA (C_7F_(15)CO_2−), perfluorobutane sulfonate, PFBS (C_4F_9SO_3−), perfluorohexane sulfonate, PFHS (C_6F_(13)SO_3−), and perfluorooctane sulfonate, PFOS (C_8F_(17)SO_3−) by aquated electrons, eaq−, that are generated from the UV photolysis (λ = 254 nm) of iodide. The ionic headgroup (-SO_3− vs -CO_2−) has a significant effect on the reduction kinetics and extent of defluorination (F index = −[F−]_(produced)/[PFC]_(degraded)). Perfluoroalkylsulfonate reduction kinetics and the F index increase linearly with increasing chain length. In contrast, perfluoroalkylcarboxylate chain length appears to have a negligible effect on the observed kinetics and the F index. H/F ratios in the gaseous fluoro-organic products are consistent with measured F indexes. Incomplete defluorination of the gaseous products suggests a reductive cleavage of the ionic headgroup occurs before complete defluorination. Detailed mechanisms involving initiation by aquated electrons are proposed
Observation of high-Tc superconductivity in inhomogeneous combinatorial ceramics
A single-sample synthesis concept based on multi-element ceramic samples can
produce a variety of local products. When applied to cuprate superconductors
(SC), statistical modelling predicts the occurrence of possible compounds in a
concentration range of about 50 ppm. In samples with such low concentrations,
determining which compositions are superconducting is a challenging task and
requires local probes or separation techniques. Here, we report results from
samples with seven components: BaO2, CaCO3, SrCO3, La2O3, PbCO3, ZrO2 and CuO
oxides and carbonates, starting from different grain sizes. The reacted
ceramics show different phases, particular grain growth, as well as variations
in homogeneity and superconducting properties. High-Tc superconductivity up to
118 K was found. Powder x-ray diffraction (XRD) in combination with
energy-dispersive spectroscopy (EDS), scanning transmission electron microscopy
(STEM) can assign Pb1223 and (Sr,Ca,Ba)0.7-1.0CuO2 phases in inhomogeneous
samples milled with 10 mm ball sizes. Rather uniform samples featuring strong
grain growth were obtained with 3 mm ball sizes, resulting in Tc =70 K
superconductivity of the La(Ba,Ca)2Cu3Ox based phase. Scanning SQUID microscopy
(SSM) establishes locally formed superconducting areas at a level of a few
microns in inhomogeneous superconducting particles captured by a magnetic
separation technique. The present results demonstrate a new synthetic approach
for attaining high-Tc superconductivity in compounds without Bi, Tl, Hg, or the
need for high-pressure synthesis
Three-dimensional foam flow resolved by fast X-ray tomographic microscopy
Thanks to ultra fast and high resolution X-ray tomography, we managed to
capture the evolution of the local structure of the bubble network of a 3D foam
flowing around a sphere. As for the 2D foam flow around a circular obstacle, we
observed an axisymmetric velocity field with a recirculation zone, and
indications of a negative wake downstream the obstacle. The bubble
deformations, quantified by a shape tensor, are smaller than in 2D, due to a
purely 3D feature: the azimuthal bubble shape variation. Moreover, we were able
to detect plastic rearrangements, characterized by the neighbor-swapping of
four bubbles. Their spatial structure suggest that rearrangements are triggered
when films faces get smaller than a characteristic area.Comment: 5 pages, 5 figure
APDs as Single-Photon Detectors for Visible and Near-Infrared Wavelenghts down to Hz Rates
For the SPECTRAP experiment at GSI, Germany, detectors with Single-Photon
counting capability in the visible and near-infrared regime are required. For
the wavelength region up to 1100 nm we investigate the performance of 2x2 mm^2
avalanche photo diodes (APDs) of type S0223 manufactured by Radiation
Monitoring Devices. To minimize thermal noise, the APDs are cooled to
approximately -170 deg. C using liquid nitrogen. By operating the diodes close
to the breakdown voltage it is possible to achieve relative gains in excess of
2x10^4. Custom-made low noise preamplifiers are used to read out the devices.
The measurements presented in this paper have been obtained at a relative gain
of 2.2x10^4. At a discriminator threshold of 6 mV the resulting dark count rate
is in the region of 230/s. With these settings the studied APDs are able to
detect single photons at 628 nm wavelength with a photo detection efficiency of
(67+-7)%. Measurements at 1020 nm wavelength have been performed using the
attenuated output of a grating spectrograph with a light bulb as photon source.
With this setup the photo detection efficiency at 1020 nm has been determined
to be (13+-3)%, again at a threshold of 6 mV.Comment: 14 pages, 9 figures, submitted to Journal of Instrumentatio
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