Training and Transfer Effect of FluoroSim, an Augmented Reality Fluoroscopic Simulator for Dynamic Hip Screw Guidewire Insertion: A Single-Blinded Randomized Controlled Trial

BACKGROUND: FluoroSim, a novel fluoroscopic simulator, can be used to practice dynamic hip screw (DHS) guidewire insertion in a high-fidelity clinical scenario. Our aim was to demonstrate a training effect in undergraduate medical students who are not familiar with this operation and its simulation. METHODS: Forty-five undergraduate medical students were recruited and randomized to either training (n = 23) or control (n = 22) cohorts. The training cohort had more exposure to FluoroSim (5 attempts each week) over a 2-week period (with a 1-week washout period in between) compared with the control cohort (a single attempt 1 week apart) over a 2-week period. Five real-time objective performance metrics were recorded: (1) tip-apex distance (TAD) (mm), (2) predicted cut-out rate (%), (3) total procedural time (sec), (4) total number of radiographs (n), and (5) total number of guidewire retries (n). RESULTS: At baseline, there was no significant difference in the performance metrics, which confirmed the absence of a selection bias. The intragroup training effect demonstrated a significant improvement in all metrics for the training cohort only. A significant difference between groups was demonstrated as the training cohort significantly outperformed the control cohort in 3 metrics (procedural time [25%], number of radiographs [57%], and number of guidewire retries [100%]; p < 0.001). A learning curve showed an inversely proportional correlation between frequency of attempts and procedural time as well as the number of digital fluoroscopic radiographs that were made, indicating the development of psychomotor skills. There was also an improved baseline of the learning curve after the 1-week washout period, suggesting skill retention. CONCLUSIONS: Skill acquisition with the FluoroSim system was demonstrated with repeat exposure in a safe, radiation-free high-fidelity clinical simulation with actual operating room equipment. The task of DHS guidewire insertion requires cognitive and psychomotor skills that take a variable number of attempts to acquire, as demonstrated on the learning curve. Additional work is required to demonstrate that the skill tested by the FluoroSim is the same skill that is required for intraoperative DHS guidewire insertion. However, use of the FluoroSim provides improvement in skills with extra-clinical training opportunities for orthopaedic trainees. CLINICAL RELEVANCE: FluoroSim has demonstrated validity and training effect. It has the potential to be approved for possible use on patients in the operating room to help surgeons with the operation. Consequently, operating time, accuracy of TAD, and surgical outcomes may all be improved

Injectivity of sections of convex harmonic mappings and convolution theorems

In the article the authors consider the class ${\mathcal H}_0$ of sense-preserving harmonic functions $f=h+\overline{g}$ defined in the unit disk $|z|<1$ and normalized so that $h(0)=0=h'(0)-1$ and $g(0)=0=g'(0)$, where $h$ and $g$ are analytic in the unit disk. In the first part of the article we present two classes $\mathcal{P}_H^0(\alpha)$ and $\mathcal{G}_H^0(\beta)$ of functions from ${\mathcal H}_0$ and show that if $f\in \mathcal{P}_H^0(\alpha)$ and $F\in\mathcal{G}_H^0(\beta)$, then the harmonic convolution is a univalent and close-to-convex harmonic function in the unit disk provided certain conditions for parameters $\alpha$ and $\beta$ are satisfied. In the second part we study the harmonic sections (partial sums) $$s_{n, n}(f)(z)=s_n(h)(z)+\overline{s_n(g)(z)},$$ where $f=h+\overline{g}\in {\mathcal H}_0$, $s_n(h)$ and $s_n(g)$ denote the $n$-th partial sums of $h$ and $g$, respectively. We prove, among others, that if $f=h+\overline{g}\in{\mathcal H}_0$ is a univalent harmonic convex mapping, then $s_{n, n}(f)$ is univalent and close-to-convex in the disk $|z|< 1/4$ for $n\geq 2$, and $s_{n, n}(f)$ is also convex in the disk $|z|< 1/4$ for $n\geq2$ and $n\neq 3$. Moreover, we show that the section $s_{3,3}(f)$ of $f\in {\mathcal C}_H^0$ is not convex in the disk $|z|<1/4$ but is shown to be convex in a smaller disk.Comment: 16 pages, 3 figures; To appear in Czechoslovak Mathematical Journa

Filtration of submicrometer particles by pelagic tunicates

Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 107 (2010): 15129-15134, doi:10.1073/pnas.1003599107.Salps are common in oceanic waters and have higher per individual filtration rates than any other zooplankton filter feeder. Though salps are centimeters in length, feeding via particle capture occurs on a fine, mucous mesh (fiber diameter d ~ 0.1 μm) at low velocity (U = 1.6 ± 0.6 cm s-1, mean ± SD) and is thus a low-Reynolds number (Re ~ 10-3) process. In contrast to the current view that particle encounter is dictated by simple sieving of particles larger than the mesh spacing, a low-Re mathematical model of encounter rates by the salp feeding apparatus for realistic oceanic particle size distributions shows that submicron particles, due to their higher abundances, are encountered at higher rates (particles per time) than larger particles. Data from feeding experiments with 0.5, 1 and 3 μm diameter polystyrene spheres corroborate these results. Though particles larger than 1 μm (e.g. flagellates, small diatoms) represent a larger carbon pool, smaller particles in the 0.1–1 μm range (e.g. bacteria, Prochlorococcus) may be more quickly digestible because they present more surface area, and we find that particles smaller than the mesh size (1.4 μm) can fully satisfy salp energetic needs. Furthermore, by packaging submicrometer particles into rapidly sinking fecal pellets, pelagic tunicates can substantially change particle size spectra and increase downward fluxes in the ocean.This work was supported by the National Science Foundation (OCE-0647723 to LPM and OCE-074464- CAREER to RS) and the WHOI Ocean Life Institute

Ontwikkeling van de HydroRig

De HydroRig is een alternatief vistuig voor de vangst van platvis ter vervanging van de wekkerstimulering in de boomkorvisserij. De noodzaak voor alternatieven komt voort uit ecosysteem kritiek op de boomkor met wekkers en de sterk oplopende brandstofkosten. In Nederland werden er al proeven gedaan aan een vistuig waarbij de boom is vervangen door een vleugel om de stroming op de bodem te beïnvloeden. Het idee van beïnvloeding van de stroming om vangst te verbeteren kwam oorspronkelijk uit de VS in een toepassing op een schelpdierkor. Door middel van bolkappen in het vistuig worden bodemdieren omhoog gedreven om beschikbaar te komen voor vangst. Dit rapport beschrijft de ontwikkeling vanaf 2008 in het VIP project HydroRig een geeft de stadia, van experimenten op zee met een aangepast vleugelprofiel, stromingsberekeningen en proeven in het laboratorium (water-grond goot) van DELTARES te Delft aan zgn. ‘bolkappen’, en toepassing hiervan op zee in verschillende configuraties met vangstmonitoring en onderwaterobservaties op de FD-281. Aan het eind van het project werden door middel van modelproeven in de ‘flume tank’ van IFREMER te Boulogne, Frankrijk nieuwe ontwerpen gemaakt voor een net met de onderpees dichter bij de boom. Gemiddeld werd bij vergelijking met het zusterschip FD-283, ook vissend op schol met een traditioneel boomkortuig en 100 mm maaswijdte, met de HydroRig (FD-281) ca. 21% brandstof bespaard, maar daartegenover stond een ca. 32% lagere besomming. Het vissen met de HydroRig in het commerciële bedrijf stagneert momenteel door de lage scholprijzen, die een belemmering vormen tot verder experimenteren. Toch wordt aanbevolen de proeven met bolkappen en nieuwe netontwerpen te vervolgen en te pogen de visnamigheid op schol te verbeteren, omdat de HydroRig veel minder benthos bijvangt

Glory Oscillations in the Index of Refraction for Matter-Waves

We have measured the index of refraction for sodium de Broglie waves in gases of Ar, Kr, Xe, and nitrogen over a wide range of sodium velocities. We observe glory oscillations -- a velocity-dependent oscillation in the forward scattering amplitude. An atom interferometer was used to observe glory oscillations in the phase shift caused by the collision, which are larger than glory oscillations observed in the cross section. The glory oscillations depend sensitively on the shape of the interatomic potential, allowing us to discriminate among various predictions for these potentials, none of which completely agrees with our measurements

How Accurate is the Use of Contralateral Implant Size as a Template in Bilateral Hemiarthroplasty?

Purpose Accurately predicting implant size for hemiarthroplasties offers an important contribution to theatre efficiency and patients’ intraoperative care. However, pre-operative sizing using templating of implants in hip fracture patients requiring a hemiarthroplasty is often difficult due to non-standard radiographs, absence of a calibration marker, poor marker placement, variable patient position, and in many institutions a lack of templating facilities. In patients who have previously undergone a hemiarthroplasty on the contralateral side, surgeons can use the contralateral implant size for pre-operative planning purposes. However, the accuracy of doing this has not previously been reported. The aim of this study was to investigate the reliability of using an in situ contralateral implant as a predictor of implant size on the contralateral side. Methods A retrospective review of our local neck of femur fracture (NOF) database was undertaken to identify patients who had bilateral hip hemiarthroplasty. Operative records were reviewed to establish the size of prostheses used at operation. Correlation, agreement, and reliability analysis were performed using the least squares, Bland–Altman plot, and intra-class correlation coefficient (ICC) methods, respectively. Results Operative records were identified for 45 patients who had bilateral hemiarthroplasties. There was a difference in implant size used in 58% of cases. Of these 77% required a larger implant on the right. Implant sizes were within 1 mm of the contralateral side in 78% and within 2 mm in 91% of patients. However, in 9% of patients, there was a discrepancy greater than 2 mm with some cases having up to 6 mm discrepancy. Correlation coefficient was 0.83 and the ICC 0.90. Conclusions The findings in this study indicated that using the size of a contralateral implant can be used as a reliable indicator of head size in cases of bilateral hemiarthroplasty. However, the surgeon should remain cautious as there is a one in ten chance of there being a 3 mm or more difference in implant size

On the inconsistency of the Bohm-Gadella theory with quantum mechanics

The Bohm-Gadella theory, sometimes referred to as the Time Asymmetric Quantum Theory of Scattering and Decay, is based on the Hardy axiom. The Hardy axiom asserts that the solutions of the Lippmann-Schwinger equation are functionals over spaces of Hardy functions. The preparation-registration arrow of time provides the physical justification for the Hardy axiom. In this paper, it is shown that the Hardy axiom is incorrect, because the solutions of the Lippmann-Schwinger equation do not act on spaces of Hardy functions. It is also shown that the derivation of the preparation-registration arrow of time is flawed. Thus, Hardy functions neither appear when we solve the Lippmann-Schwinger equation nor they should appear. It is also shown that the Bohm-Gadella theory does not rest on the same physical principles as quantum mechanics, and that it does not solve any problem that quantum mechanics cannot solve. The Bohm-Gadella theory must therefore be abandoned.Comment: 16 page