Mosaic arthroplasty of the medial femoral condyle in horses - an experimental study.

One Arabian and 5 Hungarian half-bred horses were used to study the macroscopic and microscopic survival of autologous osteochondral grafts in the weight-bearing surface of the medial femoral condyle (MFC). Grafts were harvested from the cranial surface of the medial femoral trochlea (MFT) under arthroscopic control. Three of them were transplanted into the weight-bearing surface of the contralateral MFC using an arthrotomy approach. Three months later this transplantation procedure was repeated on the opposite stifle joints in the same animals, but at that time transplantation was performed arthroscopically. Follow-up arthroscopy was carried out 12 months after the first operations, and biopsies were taken from both the recipient and the donor sites for histological examination. During follow-up arthroscopy, the transplanted areas looked congruent and smooth. Microscopically, the characteristics of hyaline cartilage were present in 5 out of the 10 biopsies examined; however, in the other half of biopsies glycosaminoglycan (GAG) loss and change in the architecture of the transplanted cartilage was observed. In a 16-year-old horse, all grafts broke during harvesting, and thus transplantation was not performed. No radiological signs of osteoarthritic changes were detected 9 to 12 months after the operations in the donor and recipient joints. Clinically, no lameness or effusion was present three months after the transplantations.

Consequences of insecurity in emergency telephone consultations: an experimental study in medical students.

QUESTION UNDER STUDY Handling emergency telephone consultations (ETCs) is a challenging and very important task for doctors. The aims of the study were to document insecurity in medical students during ETCs and to identify the reasons for that insecurity. We hypothesised that insecurity is associated with advising more urgent action (e.g. advice to call for an ambulance) in ETCs. METHODS We used ETCs with simulated patients (SPs), with each student randomly allocated two of four possible cases. After the training, 137 students reported on any insecurity that they had in the various ETC phases. We analysed the reasons for insecurity using descriptive statistics. The association between the students' advice that urgent action was needed and their insecurity was analysed with Spearman rank correlation. RESULTS Overall, 95% of the students felt insecure in at least one phase of their ETC. History taking was the phase in which students felt most insecure (63.1%), followed by the phase of analysing the information given by the patient (44.9%). Perceived insecurity was associated with more urgent advice in one case scenario (abdominal pain; correlation r = 0.46; p <0.01). The other two cases (child with fever; chest pain) also had a positive, but not statistically significant, correlation trend (p <0.12; p <0.08). CONCLUSIONS Insecurity is highly prevalent among medical students in their ETC decision-making. ETC training in medical schools, with a focus on structured history taking and formulating discriminating questions, might help decrease insecurity in ETCs. Medical education should also teach management of insecurity.

Using negotiated budgets for planning and performance evaluation: An experimental study : an experimental study

Budgets are often simultaneously used for the conflicting purposes of planning and performance evaluation. While economic theory suggests that firms should use separate budgets for conflicting purposes this contrasts with existing evidence that firms rarely do so. We address two open questions related to these observations in an experiment. Specifically, we investigate how a planning task that is in conflict with the performance evaluation task affects behavior in budget negotiations and their outcomes. Additionally, we analyze whether a single budget can be effectively used for both purposes compared to two separate budgets. We develop theory to predict that adding a planning task that is in conflict with the superior’s performance evaluation task increases the subordinate’s cooperation in and after the negotiation of a performance evaluation budget. Moreover, we predict that subordinate cooperation increases even more when the superior is restricted to use a single budget for both purposes. Our results broadly support our hypotheses. Specifically, we find that when budgets are used for both planning and performance evaluation, this increases the subordinate’s budget proposals during the negotiation and his performance after the negotiation. These effects tend to be even larger when the superior is restricted to a single budget rather than separate budgets for planning and performance evaluation, particularly with respect to subordinate performance. In our experimental setting, the benefits of increased subordinate cooperation even more than offset the loss in flexibility from the superior’s restriction to a single budget. The results of this study add to the understanding of the interdependencies of conflicting budgeting purposes and contribute to explain why firms often use a single budget for multiple purposes.

Experimental study of electric breakdowns in liquid argon at centimeter scale

In this paper we present results on measurements of the dielectric strength of liquid argon near its boiling point and cathode-anode distances in the range of 0.1 mm to 40 mm with spherical cathode and plane anode. We show that at such distances the applied electric field at which breakdowns occur is as low as 40 kV/cm. Flash-overs across the ribbed dielectric of the high voltage feed-through are observed for a length of 300 mm starting from a voltage of 55 kV. These results contribute to set reference for the breakdown-free design of ionization detectors, such as Liquid Argon Time Projection Chambers (LAr TPC).

Radiation dose reduction in postoperative computed position control of cochlear implant electrodes in lambs - An experimental study

OBJECTIVE Cochlear implants (CI) are standard treatment for prelingually deafened children and postlingually deafened adults. Computed tomography (CT) is the standard method for postoperative imaging of the electrode position. CT scans accurately reflect electrode depth and position, which is essential prior to use. However, routine CT examinations expose patients to radiation, which is especially problematic in children. We examined whether new CT protocols could reduce radiation doses while preserving diagnostic accuracy. METHODS To investigate whether electrode position can be assessed by low-dose CT protocols, a cadaveric lamb model was used because the inner ear morphology is similar to humans. The scans were performed at various volumetric CT dose-indexes CTDIvol)/kV combinations. For each constant CTDIvol the tube voltage was varied (i.e., 80, 100, 120 and 140kV). This procedure was repeated at different CTDIvol values (21mGy, 11mGy, 5.5mGy, 2.8mGy and 1.8mGy). To keep the CTDIvol constant at different tube voltages, the tube current values were adjusted. Independent evaluations of the images were performed by two experienced and blinded neuroradiologists. The criteria diagnostic usefulness, image quality and artifacts (scaled 1-4) were assessed in 14 cochlear-implanted cadaveric lamb heads with variable tube voltages. RESULTS Results showed that the standard CT dose could be substantially reduced without sacrificing diagnostic accuracy of electrode position. The assessment of the CI electrode position was feasible in almost all cases up to a CTDIvol of 2-3mGy. The number of artifacts did not increase for images within this dose range as compared to higher dosages. The extent of the artifacts caused by the implanted metal-containing CI electrode does not depend on the radiation dose and is not perceptibly influenced by changes in the tube voltage. Summarizing the evaluation of the CI electrode position is possible even at a very low radiation dose. CONCLUSIONS CT imaging of the temporal bone for postoperative electrode position control of the CI is possible with a very low and significantly radiation dose. The tube current-time product and voltage can be reduced by 50% without increasing artifacts. Low-dose postoperative CT scans are sufficient for localizing the CI electrode.

Time-order errors and standard-position effects in duration discrimination: An experimental study and an analysis by the sensation-weighting model

Studies have shown that the discriminability of successive time intervals depends on the presentation order of the standard (St) and the comparison (Co) stimuli. Also, this order affects the point of subjective equality. The first effect is here called the standard-position effect (SPE); the latter is known as the time-order error. In the present study, we investigated how these two effects vary across interval types and standard durations, using Hellström’s sensation-weighting model to describe the results and relate them to stimulus comparison mechanisms. In Experiment 1, four modes of interval presentation were used, factorially combining interval type (filled, empty) and sensory modality (auditory, visual). For each mode, two presentation orders (St–Co, Co–St) and two standard durations (100 ms, 1,000 ms) were used; half of the participants received correctness feedback, and half of them did not. The interstimulus interval was 900 ms. The SPEs were negative (i.e., a smaller difference limen for St–Co than for Co–St), except for the filled-auditory and empty-visual 100-ms standards, for which a positive effect was obtained. In Experiment 2, duration discrimination was investigated for filled auditory intervals with four standards between 100 and 1,000 ms, an interstimulus interval of 900 ms, and no feedback. Standard duration interacted with presentation order, here yielding SPEs that were negative for standards of 100 and 1,000 ms, but positive for 215 and 464 ms. Our findings indicate that the SPE can be positive as well as negative, depending on the interval type and standard duration, reflecting the relative weighting of the stimulus information, as is described by the sensation-weighting model.

Apatite as an indicator of fluid salinity: An experimental study of chlorine and fluorine partitioning in subducted sediments

In order to constrain the salinity of subduction zone fluids, piston-cylinder experiments have been conducted to investigate the partitioning behaviour of Cl and F in subducted sediments. These experiments were performed at H2O-undersaturated conditions with a synthetic pelite starting composition containing 800 ppm Cl, over a pressure and temperature range of 2.5–4.5 GPa and 630–900 °C. Repetitive experiments were conducted with 1900 ppm Cl + 1000 ppm F, and 2100 ppm Cl. Apatite represents the most Cl-abundant mineral phase, with Cl concentration varying in the range 0.1–2.82 wt%. Affinity for Cl decreases over the following sequence: aqueous fluid > apatite ⩾ melt > other hydrous minerals (phengite, biotite and amphibole). It was found that addition of F to the Cl-bearing starting composition significantly lowers the Cl partition coefficients between apatite and melt (DClAp–melt) and apatite and aqueous fluid (DClAp–aq). Cl–OH exchange coefficients between apatite and melt (KdCl–OHAp–melt) and apatite and aqueous fluid (KdCl–OHAp–aq) were subsequently calculated. KdCl–OHAp–melt was found to vary from 1 to 58, showing an increase with temperature and a decrease with pressure and displaying a regular decrease with increasing H2O content in melt. Mole fractions of Cl and OH in melt were calculated based on an ideal mixing model for H2O, OH, O, Cl and F. The Cl contents of other hydrous minerals (phengite, biotite and amphibole) fall between 200 and 800 ppm, with resultant Cl partition coefficients from 0.02 to 0.49, appearing independent of the bulk Cl and F content. Preliminary data from this study show that the partitioning behaviour of F is strongly in favour of apatite relative to melt and phengite, with DFAp–melt = 15–51. Apatites from representative eclogite facies metasediments were examined and found to have low Cl contents close to ∼100 ppm. Calculations using our experimentally determined KdCl–OHAp–aq of 0.004 at 2.5 GPa, 630 °C indicate a low salinity character (0.5–2 wt% NaCleq) for the fluid formed during dehydration of subducted oceanic sediment at ∼80 km depth.

Experimental Evaluation of Immediate Recanalization Effect and Recanalization Efficacy of a New Thrombus Retriever for Acute Stroke Treatment In Vivo

BACKGROUND AND PURPOSE: Currently, several new stent retriever devices for acute stroke treatment are under development and early clinical evaluation. Preclinical testing under standardized conditions is an important first step to evaluate the technical performance and potential of these devices. The aim of this study was to evaluate the immediate recanalization effect, recanalization efficacy, thrombus-device interaction, and safety of a new stent retriever intended for thrombectomy in patients with acute stroke. MATERIAL AND METHODS: The pREset thrombectomy device (4 × 20 mm) was evaluated in 16 vessel occlusions in an established swine model. Radiopaque thrombi (10-mm length) were used for visualization of thrombus-device interaction during application and retrieval. Flow-restoration effect immediately after deployment and after 5-minute embedding time before retrieval, recanalization rate after retrieval, thromboembolic events, and complications were assessed. High-resolution FPCT was performed to illustrate thrombus-device interaction during the embedding time. RESULTS: Immediate flow restoration was achieved in 75% of occlusions. An increase or stable percentage of recanalizations during embedding time before retrieval was seen in 56.3%; a decrease, in 12.5%; reocclusion of a previously recanalized vessel, in 18.8%; and no recanalization effect at all, in 12.5%. Complete recanalization (TICI 3) after retrieval was achieved in 93.8%; partial recanalization (TICI 2b), in 6.2%. No distal thromboembolic events were observed. High-resolution FPCT illustrated entrapment of the thrombus between the stent struts and compression against the contralateral vessel wall, leading to partial flow restoration. During retrieval, the thrombus was retained in a straight position within the stent struts. CONCLUSIONS: In this experimental study, the pREset thrombus retriever showed a high recanalization rate in vivo. High-resolution FPCT allows detailed illustration of the thrombus-device interaction during embedding time and is advocated as an add-on tool to the animal model used in this study.